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Elevating the working voltage of sodium‐ion batteries is crucial for expanding their application scenarios. However, as the operating voltage of these batteries increases, the interfacial stability of existing electrolytes becomes inadequate to meet the demands of high‐voltage cathode materials. Along with the interaction with cathode interface, electrolyte trends to be decomposed forming an interphase between the cathode and electrolyte, which plays an essential role in the performance of batteries. This review systematically focuses on the reconstruction of cathode‐electrolyte interphase maintaining the interfacial stability via various strategies at high voltage range. The state‐of‐the‐art characterization techniques and modeling approaches associated with cathode‐electrolyte interphase are also discussed. From the perspective of electrolyte design, the interphase reconstruction strategies focus on solvent molecule manipulation, solute ion manipulation, and the regulation of solvation‐ion interaction. By summarizing strategies for constructing a stable CEI on the cathode, this review aims to provide new insights into achieving high‐voltage sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

The traditional liquid electrolytes pose safety hazards primarily attributed to the flammability of organic solvent, whereas solid-state electrolytes can significantly enhance the safety of lithium-ion batteries. Polymer solid electrolytes are being considered as an effective solution due to their excellent flexibility and low cost, but they suffer low ionic conductivity or high interface impedance. Here, the ketone-containing allyl acetoacetate monomers were polymerized within the cellulose membrane via UV photopolymerization to prepare a cellulose-supported poly-allyl acetoacetate polymer electrolyte. The PAAA electrolyte shows the ion conductivity of 1.14 × 10−4 S cm−1 and the electrochemical stability window of 4.5 V. The Li symmetric battery can stably cycle for 1500 h at 0.1 mA cm−2. The LiFeO4‖Li cell achieves a discharge specific capacity of 160 mAh g−1 and demonstrates excellent cycling stability. Matching with Ni-rich cathodes also delivers decent performance. The designed polymer electrolyte with high ionic conductivity offers new ideas and directions for the development of future energy storage technology. [ABSTRACT FROM AUTHOR]

Magnesium‐based batteries have garnered significant attention due to their high energy density, excellent intrinsic safety, and low cost. However, the application process has been hindered by the high Mg2+ ions diffusion barrier in solid‐state structures and solid‐liquid interphase. To address this issue, a hybrid battery technology based on Mg anode and Fe‐based Prussian Blue Analogue cathode doped with functional transition metal ions and N═O bonds is proposed. Combined multiscale experimental characterizations with theoretical calculations, the subtle lattice distortion can create an asymmetric diffusion path for the active ions, which enables reversible extraction with significantly reduced diffusion barriers achieved by synergistic doping. The optimized cathode exhibits a working potential of 2.3 V and an initial discharge capacity of 152 mAh g−1 at 50 mA g−1. With the preferred electrolyte combined with equivalent concentration [Mg2(µ‐Cl)2(DME)4][AlCl4]2 and NaTFSI salt solution, the hybrid system demonstrates superior cycling performance over 200 cycles at a high current density of 200 mA g−1, maintaining ≈100% coulombic efficiency with superior ion dynamic. The findings are expected to be marked an important step in the further application of high‐voltage cathodes for Mg‐based hybrid batteries. [ABSTRACT FROM AUTHOR]

Co‐free spinel LiNi0.5Mn1.5O4 (LNMO) is emerging as a promising contender for designing next generation high‐energy‐density and fast‐charging Li‐ion batteries, due to its high operating voltage and good Li+ diffusion rate. However, further improvement of the Li+ diffusion ability and simultaneous resolution of Mn dissolution still pose significant challenges for their practical application. To tackle these challenges, a simple co‐doping strategy is proposed. Compared to Pure‐LNMO, the extended lattice in resulting LNMO‐SbF sample provides wider Li+ migration channels, ensuring both enhanced Li+ transport kinetics, and lower energy barrier. Moreover, Sb creating structural pillar and stronger TM─F bond together provides a stabilized spinel structure, which stems from the suppression of detrimental irreversible phase transformation during cycling related to Mn dissolution. Benefiting from the synergistic effect, the LNMO‐SbF material exhibits a superior reversible capacity (111.4 mAh g−1 at 5C, and 70.2 mAh g−1 after 450 cycles at 10C) and excellent long‐term cycling stability at high current density (69.4% capacity retention at 5C after 1000 cycles). Furthermore, the LNMO‐SbF//graphite full cell delivers an exceptional retention rate of 96.9% after 300 cycles, and provides a high energy density at 3C even with a high loading. This work provides valuable insight into the design of fast‐charging cathode materials for future high energy density lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

The pursuit of high‐performance energy storage devices has fueled significant advancements in the all‐solid‐state lithium batteries (ASSLBs). One of the strategies to enhance the performance of ASSLBs, especially concerning high‐voltage cathodes, is optimizing the structure of composite polymer electrolytes (CPEs). This study fabricates a high‐oriented framework of Li6.4La3Zr2Al0.2O12 (o‐LLZO) ceramic nanofibers, meticulously addressing challenges in both the Li metal anode and the high‐voltage LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. The as‐constructed electrolyte features a highly efficient Li+ transport and robust mechanical network, enhancing both electron and ion transport, ensuring uniform current density distribution, and stress distribution, and effectively suppressing Li dendrite growth. Remarkably, the Li symmetric cells exhibit outstanding long‐term lifespan of 9800 h at 0.1 mA cm−2 and operate effectively over 800 h even at 1.0 mA cm−2 under 30 °C. The CPEs design results from the formation of a gradient LiF‐riched SEI and CEI film at the Li/electrolyte/NCM811 dual interfaces, enhancing ion conduction and maintaining electrode integrity. The coin‐cells and pouch cells demonstrate prolonged cycling stability and superior capacity retention. This study sets a notable precedent in advancing high‐energy ASSLBs. [ABSTRACT FROM AUTHOR]

With the ever‐increasing demand for low‐cost energy storage systems, sodium‐ion (Na‐ion) batteries have received great attention. However, the large volume change, sluggish reaction kinetics, and unstable electrode/electrolyte interphase during cycling inevitably deteriorate the performance of Na‐ion batteries. Herein, a high‐voltage water‐soluble multifunctional binder with an extraordinary bonding strength is investigated. Such water‐soluble binder not only exhibits an excellent adhesion strength to maintain the mechanical integrity and enhance the Na‐ion diffusion across the interfac but also constructs a robust protective layer to prevent side reactions and improve the cycle durability at high voltages. As a result, a specific capacity of 91.3 mAh g−1 at 10.0C and high capacity retention of 92.3% for 1000 cycles are achieved. A good cycle stability and rate performance between 2.5 and 4.4 V can be observed after pairing with a high‐voltage electrode, and the practical application of the high‐voltage water‐soluble multifunctional binder is further confirmed by a 0.95 Ah Na‐ion pouch cell. [ABSTRACT FROM AUTHOR]

To realize high-energy-density Li metal batteries at low temperatures, a new electrolyte is needed to solve the high-voltage compatibility and fast lithium-ion de-solvation process. A gel polymer electrolyte with a small-molecular-weight polymer is widely investigated by combining the merits of a solid polymer electrolyte (SPE) and liquid electrolyte (LE). Herein, we present a new gel polymer electrolyte (P-DOL) by the lithium difluoro(oxalate)borate (LiDFOB)-initiated polymerization process using 1,3-dioxolane (DOL) as a monomer solvent. The P-DOL presents excellent ionic conductivity (1.12 × 10−4 S cm−1) at −20 °C, with an oxidation potential of 4.8 V. The Li‖LiCoO2 cell stably cycled at 4.3 V under room temperature, with a discharge capacity of 130 mAh g−1 at 0.5 C and a capacity retention rate of 86.4% after 50 cycles. Moreover, a high-Ni-content LiNi0.8Co0.1Mn0.1O2 (NCM811) cell can steadily run for 120 cycles at −20 °C, with a capacity retention of 88.4%. The underlying mechanism of high-voltage compatibility originates from the dense and robust B- and F-rich cathode interface layer (CEI) formed at the cathode interface. Our report will shed light on the real application of Li metal batteries under all-climate conditions in the future. [ABSTRACT FROM AUTHOR]

A novel electrolyte additive, 3, 3, 3‐trifluoropropylmethyldimethoxysilane (TFPMDS), is first proposed to modify both the cathode and the anode of lithium‐ion batteries at the same time. Charging/discharging tests demonstrate that the electrolyte with 1 wt% TFPMDS not only greatly improves the capacity retention of LiNi0.5Mn1.5O4 (LNMO)//Li cell (29.6%→90.8%) and graphite//Li cell (68.1%→98.3%), but also successfully ensures the long‐term cycle stability of LNMO//graphite pouch cell at 4.9 V. Further electrochemical measurements combining with spectroscopic characterization and theoretical calculations indicate that TFPMDS additive displays three principal functions: 1) Be preferentially oxidized to build a robust cathode electrolyte interphase (CEI) enriched in F/Si species with F‐rich nature of strong oxidation‐resistance. 2) Be able to scavenge the hazardous HF, F−, and H+ through its strong binding with these species and thus to protect LNMO at high‐voltage. 3) Be preferentially adsorbed on the graphite surface to form a "framework", and to co‐construct an elastic solid electrolyte interphase (SEI) after the reduction of ethylene carbonate. Importantly, the Si─O group within TFPMDS is especially important for constructing a "molecular bridge" at the CEI/SEI interphase coupling the inorganic and organic species to improve its compatibility, stability, and elasticity. [ABSTRACT FROM AUTHOR]

A solid-solution cathode of LiCoPO4-LiNiPO4 was investigated as a potential candidate for use with the Li4Ti5O12 (LTO) anode in Li-ion batteries. A pre-synthesized nickel–cobalt hydroxide precursor is mixed with lithium and phosphate sources by wet ball milling, which results in the final product, LiNiyCo1−yPO4 (LNCP) by subsequent heat treatment. Crystal structure and morphology of the product were analyzed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Its XRD patterns show that LNCP is primarily a single-phase compound and has olivine-type XRD patterns similar to its parent compounds, LiCoPO4 and LiNiPO4. Synchrotron X-ray absorption spectroscopy (XAS) analysis, however, indicates that Ni doping in LiCoPO4 is unfavorable because Ni2+ is not actively involved in the electrochemical reaction. Consequently, it reduces the charge storage capability of the LNCP cathode. Additionally, ex situ XRD analysis of cycled electrodes confirms the formation of the electrochemically inactive rock salt-type NiO phase. The discharge capacity of the LNCP cathode is entirely associated with the Co3+/Co2+ redox couple. The electrochemical evaluation demonstrated that the LNCP cathode paired with the LTO anode produced a 3.12 V battery with an energy density of 184 Wh kg−1 based on the cathode mass. [ABSTRACT FROM AUTHOR]

Lithium cobalt phosphate (LiCoPO 4), a cathode material for 5 V high-voltage lithium-ion batteries, has limited its practical application due to its low conductivity and ionic diffusion. In this research, a pure-phase LiCoPO 4 with core-shell structure is successfully synthesized by oleylamine-assisted ethanol solvothermal method, and the influence of different solvothermal reaction times on the properties of the material is fully studied. The results show that pure-phase LiCoPO 4 can be prepared by calcination under pure N 2 , and carbon layers (3 nm ∼ 8 nm) with different thickness are formed on the surface of LiCoPO 4 particles synthesized under different solvothermal reaction times (1 h ∼ 18 h). The LiCoPO 4 prepared under the condition of solvothermal reaction time of 12 h has good crystallization properties and morphology characteristics, and the thickness of the carbon layer formed on the surface is about 6 nm. Electrochemical tests show that it has the largest initial discharge capacity, the best performance and the best cycle stability. Adjusting the reaction conditions enables the formation of a suitable thickness of carbon coating on the surface of LiCoPO 4 , which improves the conductivity, ion diffusion and stability of the material in high voltage environments, thereby improving the electrochemical performance of high-voltage LiCoPO 4. The thickness of the carbon layer on the surface of the high-voltage cathode material LiCoPO 4 is regulated by oleylamine, and the electrochemical performance of LiCoPO 4 is enhanced. [Display omitted] • The core-shell carbon-coated LiCoPO 4 is synthesized. • The pure phase LiCoPO 4 is prepared by adjusting the calcination atmosphere. • Uniformly distributed nanostructured LiCoPO 4 is prepared. • LiCoPO 4 particles with different thickness of carbon-layer are synthesized. [ABSTRACT FROM AUTHOR]

Conventional sodium‐based layered oxide cathodes are extremely air sensitive and possess poor electrochemical performance along with safety concerns when operating at high voltage. The polyanion phosphate, Na3V2(PO4)3 stands out as an excellent candidate due to its high nominal voltage, ambient air stability, and long cycle life. The caveat is that Na3V2(PO4)3 can only exhibit reversible capacities in the range of 100 mAh g−1, 20% below its theoretical capacity. Here, the synthesis and characterizations are reported for the first time of the sodium‐rich vanadium oxyfluorophosphate, Na3.2Ni0.2V1.8(PO4)2F2O, a tailored derivative compound of Na3V2(PO4)3, with extensive electrochemical and structural analyses. Na3.2Ni0.2V1.8(PO4)2F2O delivers an initial reversible capacity of 117 mAh g−1 between 2.5 and 4.5 V under the 1C rate at room temperature, with 85% capacity retention after 900 cycles. The cycling stability is further improved when the material is cycled at 50 °C within 2.8–4.3 V for 100 cycles. When paired with a presodiated hard carbon, Na3.2Ni0.2V1.8(PO4)2F2O cycled with a capacity retention of 85% after 500 cycles. Cosubstitution of the transition metal and fluorine in Na3.2Ni0.2V1.8(PO4)2F2O as well as the sodium‐rich structure are the major factors behind the improvement of specific capacity and cycling stability, which paves the way for this cathode in sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Cobalt-free LiNi 0.5 Mn 1.5 O 4 (LNMO) is a promising alternative to the commonly used cobalt-containing positive electrode active materials in lithium-ion batteries (LIBs), owing to its high redox potential, relatively low cost, and low environmental impact. The high cell voltage, however, comes along with several challenges that need to be overcome before the material can be successfully used in commercial cells. Herein, these challenges are addressed by introducing three additives into the liquid organic carbonate-based electrolyte, namely tris(trimethylsilyl)-phosphite (TTSPi), lithium bis(oxalato) borate (LiBOB), and ethyl-(2,2,2-trifluoroethyl) carbonate (TFEC). The optimized electrolyte composition enables superior performance of Li‖LNMO and graphite‖LNMO cells because of the stabilized interphases at both the negative and the positive electrode and, thus, suppressed electrolyte decomposition. This is demonstrated by the substantially reduced gassing upon cycling and shelf-storage. These results are anticipated to contribute to the successful commercialization of LNMO in more sustainable LIBs. [Display omitted] • Stabilized interphases at the positive and negative electrode. • Mitigated transition metal cross-talk. • Reduced gas evolution upon cycling and storage. • Fully aqueous processed graphite‖LiNi 0.5 Mn 1.5 O 4 lithium-ion cells. [ABSTRACT FROM AUTHOR]

Chemical crosstalk in functioning batteries, which describes the shuttling of electrolyte soluble reactive species through the separator and the disruption of the electrode operation is a major concern, which impacts the development of new electrode generation for lithium or sodium ion/metal batteries and therefore needs to be addressed urgently. The accurate depiction of the origin, the dynamics and deleterious effects of crosstalk process upon cycling of the battery, precondition to possible remediation, requires new operando diagnostic solutions. In this work, a powerful crosstalk sensing technique based on the electrochemical trapping of redox shuttles is introduced and applied to the high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode material. Leaching and transport of transition metal species from the LNMO composite electrode and of electrolyte oxidation products could be evidenced, quantified and tracked upon cycling of the LNMO//Li system, unraveling the critical impact of the electrolyte composition and its resistance to oxidation. [Display omitted] • Simple operando crosstalk sensor with minimal electrochemical "footprint". • Real-time tracking and trapping of redox shuttles by electrodeposition. • Quantification of LNMO dissolution at any operating voltage. • Larger dissolution at high voltages and in less oxidation resistant electrolytes. [ABSTRACT FROM AUTHOR]

Highlights: The cycle performance of poly(ethylene oxide) (PEO)-based all-solid-state lithium batteries with LiCoO2 cathode was greatly improved via coating LiCoO2 with high-voltage stable Li3AlF6. At the upper cutoff voltage of 4.2 V, the poor electrochemical performance is mainly originated from the structure collapse of LiCoO2 at the surface instead of the decomposition of PEO. When the voltage reaches 4.5 V or even higher potentials, the intensive electrochemical decomposition of PEO-based solid polymer electrolyte accelerated interfacial degradation. Poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) is considered as a promising solid-state electrolyte for all-solid-state lithium batteries (ASSLBs). Nevertheless, the poor interfacial stability with high-voltage cathode materials (e.g., LiCoO2) restricts its application in high energy density solid-state batteries. Herein, high-voltage stable Li3AlF6 protective layer is coated on the surface of LiCoO2 particle to improve the performance and investigate the failure mechanism of PEO-based ASSLBs. The phase transition unveils that chemical redox reaction occurs between the highly reactive LiCoO2 surface and PEO-based SPE, resulting in structure collapse of LiCoO2, hence the poor cycle performance of PEO-based ASSLBs with LiCoO2 at charging voltage of 4.2 V vs Li/Li+. By sharp contrast, no obvious structure change can be found at the surface of Li3AlF6-coated LiCoO2, and the original layered phase was well retained. When the charging voltage reaches up to 4.5 V vs Li/Li+, the intensive electrochemical decomposition of PEO-based SPE occurs, leading to the constant increase of cell impedance and directly causing the poor performance. This work not only provides important supplement to the failure mechanism of PEO-based batteries with LiCoO2, but also presents a universal strategy to retain structure stability of cathode–electrolyte interface in high-voltage ASSLBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • LL-GCE has high ionic conductivity and Li+ transference number. • LL-GCE possesses favorable anion-rich solvation structures. • LL-GCE generates LiF-rich CEI and SEI layers after cycling. • LL-GCE shows outstanding compatibility with both Li anode and high-voltage cathode. Ether-based polymer electrolyte shows promising potential for application in solid-state lithium batteries owing to its cost-effectiveness, excellent flexibility, and above all, remarkable stability to lithium metal anode. However, it still suffers from challenges related to low ionic conductivity and inferior oxidation resistance. Herein, an ether-based gel composite electrolyte containing Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) ceramics (LL-GCE) is fabricated via an in-situ polymerization method which can guarantee good interface contact with electrodes. The ceramics not only activate the interaction between polymers and lithium salts, resulting in significantly enhanced ionic conductivity (7.9 × 10−4 S cm−1), but also collaborate with poly(1,3-dioxolane) (PDOL) to construct favorable anion-rich solvation configurations, which effectively restrict the anion migration with Li+ transference number significantly increased to 0.83. Furthermore, the regulated solvation structures can passivate the electrode surface with a high content of robust LiF components formed on the electrolyte/electrode interphase. Consequently, the composite electrolyte demonstrates excellent abilities to inhibit Li dendrite growth and match with high-voltage cathodes. For instance, the LiFePO 4 ||Li cell using such electrolyte conveys a capacity of 135.4 mAh/g and the capacity retention is 99.3 % after 250 cycles at 1C. The LiCoO 2 ||Li full cell also shows excellent cycling performance. This work provides an effective strategy to modify ether-based polymer electrolytes and can boost their development in high-performance solid state lithium metal batteries. [ABSTRACT FROM AUTHOR]

• A new flame retardant (3-butenoxy)pentafluorocyclotriphosphazene has been reported. • The mixture of fluorinated cyclotriphosphazenes makes electrolytes nonflammable. • 4.45 V LiCoO 2 /Silicon-Graphite batteries exhibit great performances. The pursuit for high energy density in lithium-ion batteries has driven the blended adoption of high-voltage cathode and high-capacity Silicon-based anode. Unfortunately, the carbonate-based electrolytes fail to be compatible with these electrode materials and the flammable nature of linear carbonates poses safety hazards to electrolytes. Fluorinated cyclotriphosphazenes can enhance the safety level of electrolytes and possesses the function of high-voltage additives. However, it is difficult to directly employ fluorinated cyclotriphosphazenes in high-voltage lithium-ion batteries containing Silicon-based anode. In this work, an alkenyl-functionalized cyclotriphosphazene- (3-butenoxy)pentafluorocyclotriphosphazene is constructed to enhance the compatibility between electrolytes and Silicon-Graphite anode. The mixed use of (3-butenoxy)pentafluorocyclotriphosphazene and (ethoxy)pentafluorocyclotriphosphazene not only makes electrolytes nonflammable but also renders preeminent performances to 4.45 V LiCoO 2 /Silicon-Graphite pouch cells at 25 °C. The capacity retention of the cell at 1C after 150 cycles surpasses 80 %, and the discharge capacity ratio of 8C/1C reaches around 53 %. With scanning electron microscopy and X-ray photoelectron spectroscopy technique, it is verified that the mixed flame retardant can build a robust interface film on the anode, which handles the adverse effects caused by the volume expansion of Silicon-Graphite. [ABSTRACT FROM AUTHOR]

[Display omitted] • LL-GCE has high ionic conductivity and Li+ transference number. • LL-GCE possesses favorable anion-rich solvation structures. • LL-GCE generates LiF-rich CEI and SEI layers after cycling. • LL-GCE shows outstanding compatibility with both Li anode and high-voltage cathode. Ether-based polymer electrolyte shows promising potential for application in solid-state lithium batteries owing to its cost-effectiveness, excellent flexibility, and above all, remarkable stability to lithium metal anode. However, it still suffers from challenges related to low ionic conductivity and inferior oxidation resistance. Herein, an ether-based gel composite electrolyte containing Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) ceramics (LL-GCE) is fabricated via an in-situ polymerization method which can guarantee good interface contact with electrodes. The ceramics not only activate the interaction between polymers and lithium salts, resulting in significantly enhanced ionic conductivity (7.9 × 10−4 S cm−1), but also collaborate with poly(1,3-dioxolane) (PDOL) to construct favorable anion-rich solvation configurations, which effectively restrict the anion migration with Li+ transference number significantly increased to 0.83. Furthermore, the regulated solvation structures can passivate the electrode surface with a high content of robust LiF components formed on the electrolyte/electrode interphase. Consequently, the composite electrolyte demonstrates excellent abilities to inhibit Li dendrite growth and match with high-voltage cathodes. For instance, the LiFePO 4 ||Li cell using such electrolyte conveys a capacity of 135.4 mAh/g and the capacity retention is 99.3 % after 250 cycles at 1C. The LiCoO 2 ||Li full cell also shows excellent cycling performance. This work provides an effective strategy to modify ether-based polymer electrolytes and can boost their development in high-performance solid state lithium metal batteries. [ABSTRACT FROM AUTHOR]

Next‐generation Li‐ion batteries are being developed with high‐voltage cathodes to maximize their energy and power densities. However, the commercialization of high‐voltage cathodes has been delayed due to the degradations of active materials and electrolytes in long‐term cycling. Recent advances have made significant improvements in these issues; however, the corrosion of Al current collector and its effects on battery performances have not been studied in detail despite its importance. In this study, the compositional and morphological evolutions of the passivation layer formed on Al are examined. The ion fluxes of Al3+ and F− through the native oxide layer of Al play a critical role in the formation of the passivation film and the inhibition of further corrosion. However, the continuous diffusion of the ions during long‐term cycling at elevated temperature deteriorates the passivation ability of the film. An artificial diffusion barrier on the surface of Al effectively suppresses the ion fluxes to enhance the cyclability of LiNi0.5Mn1.5O4. This work contributes to improving the stability of the current collector at high voltages and serves as a benchmark for corrosion studies concerning advanced energy storage devices. [ABSTRACT FROM AUTHOR]

Rechargeable Li-ion batteries must be systematically designed using durable, high-performance components to warrant a sustainable redox activity upon charge/discharge cycles. Investigating structure-property relationship is an inevitable part of research strategies concerning electrodes and their interfaces with electrolytes. Here, principles of atomic orbital overlap and molecular orbital in electrodes is applied to discuss the structure-property relationship. For instance, considering molecular orbital diagrams, the debate is over the dominant charge compensation mechanism of electrodes to ascertain to what extent an obtained long-lasting capacity is contingent on either transition metal or oxygen redox reaction. Inter-atomic distances and distortions in symmetry are described as the factors governing the structural integrity of electrodes. Internal reactions are discussed in context of energy band structures of active materials under cycling due to their significance for battery materials development. Chemical and structural stability of conventional cathode families including high-voltage sulfur cathodes are briefly discussed from an electronic structure viewpoint. Additionally, this study accentuates the assessment of electronic structure within ceramic solid electrolytes and their interfaces with the Li-metal anode, along with common cathodes, throughout cycling. Also, it addresses the local variations in electronic structure occurring within the grain boundaries of polycrystalline ceramic electrolytes, which may contribute to internal structural instability. Importance of incorporating electronic structures, apart from chemical composition and crystal structure to design battery materials is highlighted to provide a novel insight into design of new class of materials. • Structure-property in Li-ion batteries are discussed by molecular orbital concepts. • Integrity of electrodes is described using inter-atomic distances and symmetry. • Internal reaction/band structure of active materials under cycling are emphasized. • Chemical and structural stability of conventional cathode families are addressed. • A new insight into design of battery materials is highlighted. [ABSTRACT FROM AUTHOR]

The electrochemical properties of carbon and reduced graphene-coated Na4Ni3(PO4)2P2O7 materials have been evaluated as high-voltage positive electrodes for sodium-ion batteries. Na4Ni3(PO4)2P2O7 exhibits the highest Ni3+/Ni2+ redox potential of 4.8 V vs. Na+/Na with a theoretical capacity of 127 mAh g−1. Here, we report on the synthesis and characterizations of Na4Ni3(PO4)2P2O7-reduced graphene oxide and Na4Ni3(PO4)2P2O7-carbon composites. The high-voltage dimethyl carbonate–based electrolyte has been chosen to explore the electrochemical properties of Na4Ni3(PO4)2P2O7 as a cathode. Carbon-coated Na4Ni3(PO4)2P2O7 composite electrode delivers a stable discharge capacity of 51 mAh g−1 at 0.1 C rate for 40 cycles which corresponds to a reversible intercalation/de-intercalation of 1.3 sodium ions. The structural deformation has been observed during the charge–discharge process beyond the removal of 1.3 Na+ ions and has been confirmed by in situ PXRD measurements. The present results provide a guideline to improve the performances of the high-voltage Na4Ni3(PO4)2P2O7 material for the next generation sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Flexible and low-cost poly(ethylene oxide) (PEO)-based electrolytes are promising for all-solid-state Li-metal batteries because of their compatibility with a metallic lithium anode. However, the low room-temperature Li-ion conductivity of PEO solid electrolytes and severe lithium-dendrite growth limit their application in high-energy Li-metal batteries. Here we prepared a PEO/perovskite Li3/8Sr7/16Ta3/4Zr1/4O3 composite electrolyte with a Li-ion conductivity of 5.4 × 10-5 and 3.5 × 10-4 S cm-1 at 25 and 45 °C, respectively; the strong interaction between the F- of TFSI- (bistrifluoromethanesulfonimide) and the surface Ta5+ of the perovskite improves the Li-ion transport at the PEO/perovskite interface. A symmetric Li/composite electrolyte/Li cell shows an excellent cyclability at a high current density up to 0.6 mA cm-2. A solid electrolyte interphase layer formed in situ between the metallic lithium anode and the composite electrolyte suppresses lithiumdendrite formation and growth. All-solid-state LijLiFePO4 and high-voltage Li|LiNi0.8Mn0.1Co0.1O2 batteries with the composite electrolyte have an impressive performance with high Coulombic efficiencies, small overpotentials, and good cycling stability. [ABSTRACT FROM AUTHOR]

Abstract This paper shows a Ti-doping strategy for improvement of transport and electrochemical properties of P2-type Ni- and Mn-based layered oxides, candidate cathode materials for the high-voltage Na-ion batteries. Pure and Ti-substituted Na 0.67 Ni 0.33 Mn 0.67-y Ti y O 2 (0 ≤ y ≤ 0.33) oxides are synthesized using a standard high temperature solid state method. While Ti does not affect structural parameters of the materials considerably, it induces change of occupancy of both Na-sites, which is found to be beneficial. For higher concentrations of Ti (y ≥ 0.2) both, electronic and ionic components of the electrical conductivity are enhanced, with sodium conductivity remaining about three orders of magnitude higher than the electronic part. Improved conductivity is associated unexpectedly with higher activation energy, and such peculiar behavior seems to be interrelated with disruption of the ordering at Na-sites. As documented, moderate level of Ti-doping enables to design functional layered transition metal oxide cathode materials for Na-ion batteries, exhibiting high voltage and high reversible capacity. Graphical abstract Image 1 Highlights • Na 0.67 Ni 0.33 Mn 0.67-y Ti y O 2 with stabilized structure and improved conduction. • Titanium induces disordering in the Na-sublattice. • Increased energy difference between Na-sites for Ti-doped samples. • Unique behavior with increased both, E a and values of the electrical conductivity. • Na 0.67 Ni 0.33 Mn 0.47 Ti 0.2 O 2 exhibits improved electrochemical properties. [ABSTRACT FROM AUTHOR]

The olivine polymorph LiCoPO 4 was synthesized by solvothermal and a subsequent annealing process. Carbon free, ex-situ carbon coated and in-situ carbon coated materials were prepared. With the addition of citric acid in the solvothermal reaction, a carbon layer was coated via an in-situ approach. To systematically compare the different carbon coating routes, the structure and morphology of the LiCoPO 4 materials were investigated by XRD, Raman, and SEM. HAADF-STEM combined with EDX was applied to analyze the homogeneity of the carbon layer and corresponding antisite defects. Electrochemical properties were analyzed by half-cells measuring cyclic-voltammograms, charge/discharge cycling behavior stability and rate-capability. It was found that the in-situ carbon coated LiCoPO 4 /C exhibited a superior electrochemical performance due to the relatively uniform and complete surface-layer formation. As a result, an appropriate carbon layer improves the electronic and ionic transport properties, ensures fast electron-transfer kinetics at the electrode particle surfaces and suppresses unwanted side reactions with the electrolyte. [ABSTRACT FROM AUTHOR]

Nanorod structures of LiMn 1.8 Ni 0.2 O 4 applicable as active cathode material for Li-ion batteries were synthesized from α-MnOOH and α-MnO 2 initial phases. The LiMn 1.8 Ni 0.2 O 4 spinel nanorods obtained from α-MnOOH using a novel, eco-friendly method showed higher purity than the traditional spinel obtained from α-MnO2. The showed charge capacity that was in the order of 122 mA h g −1 higher than similar active material reported in the literature, and it was able to keep >80% of initial capacity at a charge rate of 5 C. [ABSTRACT FROM AUTHOR]

High-voltage cathode LiMn 1.5 Ni 0.5 O 4 particles with average size of approximately 2 μm were prepared using a two-step process. Low-temperature magnetic measurements indicated them as ferrimagnetic materials with high Neel temperature (146.5 K) and high magnetization (107 emu/g at 4.5 K) that closely approximates the theoretical value of the stoichiometric LiMn 1.5 Ni 0.5 O 4 compound. Because of their high-purity and high crystallinity, their redox signals were observed only around 4.7 V. Their low-rate capacity was sufficiently high (about 140 mAh/g at 0.1 C). Their capacity retention after the 100th cycle was higher than 95%. In spite of the low specific surface area of the LiMn 1.5 Ni 0.5 O 4 particles, they exhibited high reversible capacity even at a high-current rate. Additionally, the in-situ X-ray diffraction was conducted to elucidate the reaction process, which indicated that the electrochemical reaction progresses reversibly with two consecutive two-phase reactions. The lattice parameters of three corresponding phases remained almost unchanged on the reactions (0.8165, 0.8087, and 0.8000 nm). The presence of the intermediate phase might give the relaxation of the structural variation during the electrochemical reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-type gel polymer electrolyte(GPE) is composed of an anolyte and a catholyte. • Dual-type GPE suppressed side reactions at electrodes and lithium dendritic growth. • The Li/LiCoO 2 cell with dual-type GPE showed an excellent cycle life at 0.5 C rate. The most attractive approach for maximizing the energy density of rechargeable lithium batteries is to combine a lithium metal anode with a high-voltage cathode. However, the dendritic formation of lithium at the anode and the highly oxidizing conditions that cause electrolyte decomposition at the cathode have hindered the practical development of lithium metal batteries (LMBs). In this study, we report a dual-type gel polymer electrolyte (GPE) composed of an anolyte and a catholyte that can address the drawbacks of both the anode and cathode sides. The anolyte is a poly(ethylene oxide)-based composite solid polymer electrolyte that is chemically stable with lithium metal and has a high mechanical strength for suppressing lithium dendrite growth. A cross-linked gel polymer electrolyte with high lithium-ion conductivity and oxidative stability was used as the catholyte. The Li/LiCoO 2 cell assembled with a dual-type GPE exhibited a high discharge capacity of 181.1 mAh g−1 (areal capacity: 3.15 mAh cm−2) in the voltage range of 3.0–4.5 V and excellent cycle life, with a capacity retention of 74 % after 700 cycles at 25 °C and 0.5 C rate. Our study proposes a promising electrolyte system for LMBs with high energy density and good cycle life. [ABSTRACT FROM AUTHOR]

The lack of suitable high-voltage cathode materials has hindered the development of rechargeable magnesium batteries (RMBs). Here, mesoporous Na3V2(PO4)3/C (NVP/C) spheres have been synthesized through a facile spray-drying-annealing method, and their electrochemically desodiated phase NaV2(PO4)3/C (ED-NVP/C) has been investigated as an intercalation host for Mg2+ ions. The obtained ED-NVP/C exhibits an average discharge voltage of around 2.5 V (vs. Mg2+/Mg), higher than those of most previously reported cathode materials. In addition, it can deliver an initial discharge capacity of 88.8 mA h g−1 at 20 mA g−1, with good cycling stability. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate that the electrochemical reaction is based on an intercalation mechanism and shows good reversibility. Galvanostatic intermittent titration technique (GITT) data have revealed that the intercalation process involves a two-phase transition. The reported ED-NVP/C cathode material with high working voltage offers promising potential for application in RMBs. [ABSTRACT FROM AUTHOR]

The boron-doped graphene decorated Li 3 V 2 (PO 4 ) 3 composite (Li 3 V 2 (PO 4 ) 3 /B-GS) has been successfully synthesized for the first time using a facile method. The effects of B-GS on the structure, morphology and electrochemical performance of Li 3 V 2 (PO 4 ) 3 cathode are investigated. The results show that the nano-sized Li 3 V 2 (PO 4 ) 3 particles are about 80 nm on an average and are uniformly dispersed on the conducting B-GS. This combined favorable structure is helpful to facilitate the electron and Li + transmission, leading to the excellent rate capability and cycling stability. The improved battery performance indicates that the obtained Li 3 V 2 (PO 4 ) 3 /B-GS composite can be a potential cathode candidate for the application of high-performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Particle size-tuned platelets of the high-voltage cathode material LiCoPO 4 for Li-ion batteries have been synthesized by a simple one-step microwave-assisted solvothermal process using an array of water/ethylene glycol (EG) solvent mixtures. Particle size control was achieved by altering the concentration of the EG co-solvent in the mixture between 0 and 100 vol%, with amounts of 0–80 vol% EG producing single phase, olivine-type LiCoPO 4 . The particle sizes of the olivine materials were significantly reduced from about 1.2 μm × 1.2 μm × 500 nm (0 vol% EG) to 200 nm × 100 nm × 50 nm (80 vol% EG) with increasing EG content, while specific surface areas increased from 2 to 13 m 2 g -1 . The particle size reduction could mainly be attributed to the modified viscosities of the solvent blends. Owing to the soft template effect of EG, the crystals exhibited the smallest dimensions along the [010] direction of the Li diffusion pathways in the olivine crystal structure, resulting in enhanced lithium diffusion properties. The relationship between the synthesis, crystal properties and electrochemical performance was further elucidated, indicating that the electrochemical performances of the as-prepared materials mainly depend on the solvent composition and the respective particle size range. LiCoPO 4 products obtained from reaction media with low and high EG contents exhibited good electrochemical performances (initial discharge capacities of 87–124 mAh g −1 at 0.1 C), whereas materials made from medium EG concentrations (40–60 vol% EG) showed the highest capacities and gravimetric energy densities (up to 137 mAh g −1 and 658 Wh kg −1 at 0.1 C), excellent rate capabilities, and cycle life. [ABSTRACT FROM AUTHOR]

• The surface structure degradation caused by the coexistence of H2 and H3 phases leads to the capacity fading. • The surface reconstruction layer inhibits the increased polarization and alleviates the kinetic barriers to lithium ions. • The pinning effect of the surface reconstruction layer reducing severe lattice shrinkage and bulk fatigue. Single-crystal Ni-rich layered cathodes have become the mainstream commercial lithium ion batteries because of their structural and cyclic stability. In order to obtain a higher energy density, the cut-off voltage (>4.4 V) must be increased. However, the mechanism of capacity fading at high voltages remains unclear. This study proved that the capacity fading of single-crystal Ni-rich layered materials at high voltage is caused by the appearance of fatigued phases due to surface structure degradation. In particular, a structural evolution mechanism based on the premigration of rare earth elements to lithium sites to form reconstruction layers at the atomic scale was proposed in this paper. The introduction of rare earth element Sc leads to a nanoscale reconstruction layer with a pinning effect on the surface of the Ni-rich material, which alleviates the barriers of kinetic to lithium ions in the highly charged state, improves the reversibility phase transition of the H2 to H3 phase, and maintains structural stability. In particular, the Sc-doped cathodes have a superb capacity retention rate of 95.1% after 300 cycles at 5C under the voltage of 4.6 V with a loss of only 0.016% capacity per cycle. This study reveals the intrinsic link between the capacity fading and structural evolution, providing new insights for the research of Ni-rich layered cathode materials with high energy density. [ABSTRACT FROM AUTHOR]

• Na 3 V 2 O 2 (PO 4) 2 F@rGO is the high voltage cathode for aqueous zinc ion batteries. • The electrochemical properties are enhanced in the hybrid electrolyte. • Reaction mechanism is demonstrated by in situ XRD and ex situ XPS, TEM, and SEM. • Soft pack batteries deliver a capacity of 84.1 mAh g−1 at 10C after 1000 cycles. Na 3 V 2 O 2 (PO 4) 2 F is characterized by a high theoretical specific capacity, high-voltage plateaus, large ion diffusion channels, and stable three-dimensional structure, which is a promising cathode candidate for rechargeable aqueous zinc-ion batteries (AZIBs). Nevertheless, the low electronic conductivity hinders its cycling and rate performance. In this work, a facile microwave-assisted solvothermal approach with postheat treatment has successfully produced Na 3 V 2 O 2 (PO 4) 2 F nanoparticles with the dimension of 20–50 nm wrapped by reduced graphene oxide (rGO). The high pseudocapacitive contribution, high diffusion coefficient, low electrochemical impedance, favorable electrode wettability, and stable structure can be obtained by optimizing the chemical components of electrolyte and the content of rGO, facilitating the Zn2+ storage performance. Hence, Na 3 V 2 O 2 (PO 4) 2 F@rGO delivers excellent electrochemical properties such as a high capacity of 127.0 mAh g−1 at 0.5C, a stable capacity of 63.9 mAh g−1 at 30C after 5000 cycles, and a high average voltage plateau of 1.50 V in hybrid aqueous electrolyte (2 M zinc trifluoromethane sulfonate (Zn(OTf) 2) and 4 M lithium trifluoromethane sulfonate (LiOTf)). Furthermore, exceptional cycling performance in the soft-pack batteries with the size of 3 × 3.5 cm2 includes a reversible capacity of 84.1 mAh g−1 at 10C after 1000 cycles. In situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy reveal reversible Zn2+ insertion/extraction process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-crystal NCM111 (SC-NCM) is obtained from a ternary MOF precursor. • SC-NCM can be operated at a high cut-off voltage with good cyclability. • Specific capacity can be boosted at a large operation range of 2.8–4.6 V. • Enhanced performance can be attributed to better microstructural stability. Single-crystal NCMs show properties of good cyclability and high safety, and considers as promising cathode materials for next generation lithium batteries. But industrial production of single-crystal NCMs should overcome problems of lengthy production steps, high production costs and poor consistency. In this work, a Ni-Co-Mn ternary MOF has been developed for NCM cathode materials preparation. The MOF derived precursors show high activity and can be used to prepare single-crystal NCM111 (SC-NCM) in a regular sintering process. As-prepared SC-NCM cathode materials show an average particle size of 400 nm, reveal a polyhedral structure with smooth surface, and can be applied as a high-voltage cathode with excellent cyclability and high specific capacities. Specifically, it is delivery a high discharge capacity of 172 mAh g−1 and maintains 156 mAh g−1 after 50 cycles in a large potential range of 2.8–4.6 V at a high current of 1 C; it also reveals a good capacity retention of 88.3 % after 600 cycles. The enhanced electrochemical performance can be attributed to the SC-NCM reveals a good microstructural stability, which prevents the unexpected structural degradation and microcrack generation during battery cycling. This work provides a new method to synthesis the high-quality single-crystal NCM materials with good electrochemical performance. [ABSTRACT FROM AUTHOR]

High-performance particles of the high-voltage cathode material LiCoPO 4 for Li-ion batteries are synthesized by a simple and rapid one-step microwave-assisted solvothermal route at moderate temperatures (250 °C). Using a variety of water/alcohol 1:1 (v:v) solvent mixtures, including ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TTEG), polyethylene glycol 400 (PEG), and benzyl alcohol (BA), the focus of the study is set on optimizing the electrochemical performance of the material by controlling the particle size and morphology. Scanning electron microscopy studies reveal a strong influence of the co-solvent on the particle size and morphology, resulting in the formation of variations between square, rhombic and hexagonal platelets. According to selected area electron diffraction experiments, the smallest crystal dimension is in the [010] direction for all materials, which is along the lithium diffusion pathways of the olivine crystal structure. The anisotropic crystal orientations with enhanced Li-ion diffusion properties result in high initial discharge capacities and gravimetric energy densities (up to 141 mAh g −1 at 0.1 C and 677 Wh kg −1 for LiCoPO 4 obtained from TEG), excellent rate capabilities, and cycle life for 20 cycles. [ABSTRACT FROM AUTHOR]

LiNaCo 0.5 Fe 0.5 PO 4 F fluoride-phosphate was synthesized via conventional solid-state and novel freeze-drying routes. The crystal structure was refined based on neutron powder diffraction (NPD) data and validated by electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM). The alkali ions are ordered in LiNaCo 0.5 Fe 0.5 PO 4 F and the transition metals jointly occupy the same crystallographic sites. The oxidation state and oxygen coordination environment of the Fe atoms were verified by 57 Fe Mössbauer spectroscopy. Electrochemical tests of the LiNaCo 0.5 Fe 0.5 PO 4 F cathode material demonstrated a reversible activity of the Fe 3+ /Fe 2+ redox couple at the electrode potential near 3.4 V and minor activity of the Co 3+ /Co 2+ redox couple over 5 V vs Li/Li + . The material exhibited the discharge capacity of more than 82% (theo.) regarding Fe 3+ /Fe 2+ in the 2.4÷4.6 V vs Li/Li + potential range. [ABSTRACT FROM AUTHOR]

In this study, nitrogen-doped carbon is coated on LiVPO 4 F electrode for the first time via a simple chemical refluxing process, using ethylenediamine (EDA) as the carbon and nitrogen source. The structure, morphology and microstructure of the as-prepared electrode are characterized by XRD, XPS, Raman spectra, SEM and TEM. The uniform coating of nitrogen-doped carbon improves the electronic conductivity of LiVPO 4 F. As cathode material for lithium-ion batteries, the nitrogen-doped carbon coated LiVPO 4 F composite exhibits superior rate capability and excellent cycle performance over the carbon coated LiVPO 4 F. The electrode delivers an initial discharge capacity of 109.6 mAh g − 1 at high rate of 10 C and 103.1 mAh g − 1 of capacity is retained after 100 cycles. Thus, this novel modification method of nitrogen-doped carbon coating is highly effective and could be widely used to optimize the electronic conductivity of other electrode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

High-voltage cathode material, LiMn 1.5 Ni 0.5 O 4 , was successfully prepared by two-step process: LiMn 1.6 Ni 0.4 O 4 particles were obtained by the solid state reaction of oxalate precursors at high temperature such as 900 °C and then the LiMn 1.6 Ni 0.4 O 4 particles with Li-acetate di-hydrate and Ni-acetate tetra-hydrate were annealed at low temperature. Both spinel phases are ferromagnetic compounds: LiMn 1.5 Ni 0.5 O 4 has higher Neel temperature (127 K) and larger magnetization (97 emu/g at 4.2 K) than LiMn 1.6 Ni 0.4 O 4 does (103 K and 79 emu/g). The obtained LiMn 1.5 Ni 0.5 O 4 particles had low specific surface area, which may reduce the side reaction with the organic electrolyte, and exhibited electrochemical capacity only at high voltage 4.7 V region. In addition, high reversible capacity as well as good cycle performance was attained. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bilayer PEO electrolyte with different lithium salts is constructed. • The design of bilayer electrolytes facilitates interfacial compatibility with the cathode at high voltage. • The assembled ASSLBs have achieved highly improved cycling stability. Poly (ethylene oxide) (PEO) is easily oxidized at the cathode interface when coupled with high voltage cathodes (such as LiCoO 2), leading to rapid capacity fade, limiting its application in high energy density all-solid-state battery. In this work, a bilayer concept is applied to design two PEO electrolyte layers composited with lithium difluoro (oxalato) borate (LiDFOB) and lithium bis(trifluoromethane sulfonyl) imide (LiTFSI), respectively. The thin PEO/LiDFOB layer is introduced by directly dropping the PEO/LiDFOB solution on the LiCoO 2 cathode surface to construct a closely contact interphase. Meanwhile, a stable cathode electrolyte interphase (CEI) containing Li x B x O y and LiF formed during electrochemical cycling realizes the LiCoO 2 /PEO interfacial compatibility. The self-generated PEO/LiTFSI layer towards the anode side provides high ionic conductivity and stabilizes the Li/electrolyte interface. As a result, the assembled cell using the bilayer PEO electrolyte achieves good cycling stability, the capacity retention increases from 15% to 75% after 100 cycles at 0.2C. The enhanced electrochemical performance is also achieved in LiNi 0.6 Co 0.2 Mn 0.2 O 2 /Li cell using this bilayer PEO electrolyte architecture. This work provides a simple strategy to make high-voltage cathode compatible with PEO electrolyte. [ABSTRACT FROM AUTHOR]

High-voltage lithium (Li)-metal batteries with cell-level energy density over 350 Wh kg−1 are promising energy storage systems. However, the aggressive interphase chemistries associated with highly reactive Li-metal anode and high-voltage cathodes impede their practical applications. Herein, we demonstrate the targeted stabilization of solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) in high-voltage Li-metal batteries by asymmetrically sustained-releasing different additives. An asymmetric sustained-release film loaded with lithium bis-(oxalate)borate (LiBOB) and LiNO 3 on each side is investigated as a proof-of-concept. The sustained-releasing of LiBOB and LiNO 3 can maintain a localized concentration at the high-voltage cathode and Li-metal anode fronts respectively, thus forming a stable B-containing CEI and N-containing SEI. As such, issues like dendrites growth, parasitic side reactions and transition metals dissolution under high-voltage are addressed simultaneously. Based on this strategy, the 30 μm Li|LiNi 0.5 Co 0.2 Mn 0.3 O 2 (4.1 mAh cm−2) batteries deliver a capacity retention of 80% after 173 cycles under a cut-off voltage of 4.5 V. [Display omitted] • Asymmetric sustained-release film (ASRF) loading different additives is designed. • The targeted stabilization of CEI and SEI is achieved by the ASRF. • Long-lasting SEI/CEI are formed by solubility-mediated slow releasing of additives. • CEI on high-voltage cathode (4.5 V) is stabilized by sustained-releasing LiBOB. • SEI on Li-metal anode is protected by sustained-releasing LiNO 3. [ABSTRACT FROM AUTHOR]

The citric acid-assisted sol–gel method was used to produce the high-voltage cathodes LiNi 0.5 Mn 1.5 O 4 and LiNi 0.4 Ru 0.05 Mn 1.5 O 4 at 800 °C and 1000 °C final calcination temperatures. High resolution powder diffraction using synchrotron radiation, inductively coupled plasma – optical emission spectroscopy and scanning electron microscopy analyses were carried out to characterize the structure, chemical composition and morphology. X-ray absorption spectroscopy studies were conducted to confirm Ru doping inside the spinel as well as to compare the oxidation states of transition metals. The formation of an impurity Li x Ni 1− x O in LiNi 0.5 Mn 1.5 O 4 powders annealed at high temperatures ( T ≥ 800 °C) can be suppressed by partial substitution of Ni 2+ by Ru 4+ ion. The LiNi 0.4 Ru 0.05 Mn 1.5 O 4 powder synthesized at 1000 °C shows the highest performance regarding the rate capability and cycling stability. It has an initial capacity of ∼139 mAh g −1 and capacity retention of 84% after 300 cycles at C/2 charging–discharging rate between 3.5 and 5.0 V. The achievable discharge capacity at 20 C for a charging rate of C/2 is ∼136 mAh g −1 (∼98% of the capacity delivered at C/2). Since the electrode preparation plays a crucial role on parameters like the rate capability, the influence of the mass loading of active materials in the cathode mixture is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Lithium nickel manganese oxide (LiNi0.5Mn1.5O4) shows promising applications in next-generation Li-ion batteries due to its high working voltage. In this work, submicron LiNi0.5Mn1.5O4 has been synthesized by a facile solid-phase route and its electrochemical performance has been investigated in both half cells and full cells using mesocarbon microbeads as anodes. In LiNi0.5Mn1.5O4–Li cells, LiNi0.5Mn1.5O4 shows excellent rate performance and high-rate cycling stability. At 20 C, LiNi0.5Mn1.5O4 can yield a discharge capacity of 105.8 mAh g−1. After 1400 cycles at 1 C, a discharge capacity of around 80 mAh g−1 can be still delivered. The LiNi0.5Mn1.5O4-limited full cells exhibit a working voltage of around 4.5 V and a discharge capacity of 90.0 mAh g−1 after 120 cycles at 1 C. The excellent electrochemical performance of LiNi0.5Mn1.5O4 can be attributed to a combination of submicron size, durability of Mn3+ at high rates and small-size induced protective film. [Copyright &y& Elsevier]

• A novel poly (vinyl ethylene carbonate)-based dual-salt gel polymer electrolyte is developed by in-situ polymerization technology. • Stable interfacial layer is formed on electrodes by the synergistic effect of LiTFSI and LiBOB. • Li||Li symmetric and high-voltage Li||LiCoO 2 cells with DS-GPE exhibit superior electrochemical performances. Rechargeable lithium metal batteries (LMBs) have been regarded as one of the most promising next-generation energy-storage systems due to their high theoretical energy density. However, the practical application of LMBs is greatly impeded by poor high-voltage tolerance and safety concerns originated from flammable organic carbonate-based liquid electrolytes. Herein, a novel dual-salt gel polymer electrolyte (DS-GPE) is prepared via in situ polymerization of vinyl ethylene carbonate (VEC) and pentaerythritol tetra acrylate (PETEA) monomers in a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) porous structure. The newly developed DS-GPE shows high ionic conductivity (6.9 mS cm−1) at room temperature, adequate Li+ transference number (t Li + = 0.512), outstanding oxidative resistance (5.3 V vs. Li/Li+) and favorable interfacial compatibility. Stable interfacial layers are rich in B-, F-, components on both the Li metal anode and high-voltage LiCoO 2 cathode, realizing excellent cycling stability in Li||Li symmetrical cells, and a capacity retention of 83.42% over 100 cycles with average Coulombic efficiency of 99.86% in Li||LiCoO 2 cell. [ABSTRACT FROM AUTHOR]

Abstract: Structural, morphological and electrochemical characterizations in EC:DMC-LiPF6 of carbon-coated LiMnPO4 and LiMn1−x Fe x PO4 (x = 0.2, 0.3) cathode materials synthesized via a cost-effective procedure based on sol–gel (from partially or totally soluble precursors in water), pyrolysis and ball milling steps are reported. Carbon-coated LiMnPO4 obtained from totally soluble precursors featuring at 0.1 C 125mAhg−1 at 50 °C and 95mAhg−1 at 30 °C, with a capacity fade per cycle of 0.5% at 50 °C and 0.4% at 30 °C, is a very promising material, particularly in consideration of the inexpensive procedure that was pursued for its synthesis. [Copyright &y& Elsevier]

Abstract: The effects of different cell positive cans and separators on first-cycle Coulombic efficiency and long-term cycling stability of a high-voltage spinel cathode are investigated systematically. Compared to stainless steel (SS) positive cans, aluminum (Al)-clad SS-316 positive cans are much more resistant to oxidation at high voltages; therefore, the initial Coulombic efficiency of the batteries with Al-clad can is improved by more than 13%. Among the five separators studied in this work, the polyethylene (PE) separator exhibits the best electrochemical stability. The cells using LiCr0.05Ni0.45Mn1.5O4 as the cathode, an Al-clad positive can, and a PE separator exhibits a first-cycle Coulombic efficiency of about 90% and a capacity fading of only 0.01% per cycle. [Copyright &y& Elsevier]

Abstract: Carboxymethyl cellulose (CMC), a green and low-cost binder, is used to make lithium-ion battery composite electrodes containing the high voltage cathode material Li2MnO3–LiMO2. This combination of materials results in a homogeneous electrode, which is proved by electron microscopy. The results of the electrochemical investigation indicate that CMC operates well at very high voltages (4.8V). Compared to the PVDF binder, the CMC-based electrode shows an improved cycling stability as well as a very promising rate capability. [Copyright &y& Elsevier]

Abstract: LiMn1.5−x M2x Ni0.5−x O4 (M=Co or Cr, 0.0≤ x ≤0.2) compounds were synthesized by the sol–gel method. It is found from X-ray diffraction analysis that single spinel phases are obtained for both Cr3+- and Co3+-substitution, but a small cation mixing between the 8a and 16d sites is found only in the Co3+-substitution case. All of the compounds exhibit M–T curves characteristic of ferromagnetic materials. As the substitution degree is raised, the saturation magnetization at 4.2K decreases and the Curie temperature shifts lower, irrespective of the kind of the substituent. That is, the cation substitution yields a reduction of the ferromagnetism. Additionally, both Cr3+- and Co3+-substitution have a large influence on the electrochemical properties. The Cr3+-substitution induces a rise in the average operating potential without a loss of redox capacity, while both the average operating potential and the redox capacity decrease with an increase in the Co3+-substitution degree. [Copyright &y& Elsevier]

Abstract: In this paper, we report the electrochemical characteristics of a novel cathode material, Li2CoPO4F, prepared by solid-state reactions. The solid-state reaction mechanism involved in synthesizing the Li2CoPO4F also is analyzed in this paper. When cycled between 2.0V and 5.0V during cyclic voltammetry measurements, the Li2CoPO4F samples present one, fully reversible anodic reaction at 4.81V. When cycled between 2.0V and 5.5V, peaks occurring at 4.81V and 5.12V in the first anodic scan evolved to one broad oxidative, mound-like pattern in subsequent cycles. Correspondingly, the X-ray diffraction (XRD) pattern of the Li2CoPO4F electrode discharged from 5.5V to 2.0V is slightly different from the patterns exhibited by a fresh sample and the sample discharged from 5.0V to 2.0V. This difference may correspond to a structural relaxation that appears above 5V. In the constant current cycling measurements, the Li2CoPO4F samples exhibited a capacity as high as 109mAhg−1 and maintained a good cyclability between 2.0V and 5.5V vs. Li/Li+. XRD measurements confirmed that the discharged state is Li2CoPO4F. Combining these XRD results and electrochemical data proved that up to 1mol Li+ is extractable when charged to 5.5V. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cleverly designed asymmetrical electrolyte was fabricated by in-situ polymerized method. • The asymmetrical electrolyte possesses flexibility and high Li+ transference number. • The electrolyte demonstrates good ability in suppressing Li dendrites growth. • The LiCoO 2 /electrolyte/Li cell exhibits superior electrochemical performance. In-situ polymerized gel polymer electrolytes have been considered as the most promising alternative to liquid electrolyte owing to their high ionic conductivity, improved safety, simple and environmentally friendly manufacturing process, and good interfacial compatibility with electrodes. However, their poor mechanical properties are not able to prevent the Li dendrites growth in batteries. Inspired by the composite electrolytes, an asymmetrical gel electrolyte (A-PGCE) consisting of cellulose membrane-supported gel electrolyte and LLZTO-rich layer on one side is fabricated by a facile one-step in-situ polymerization method. The well-designed A-PGCE not only exhibits excellent properties such as superior flexibility, good thermal stability and wide electrochemical window (5.13 V), but also possesses high ionic conductivity (1.25 × 10-3 S cm−1) and Li+ transference number (0.57). Furthermore, the introduced LLZTO-rich layer demonstrates excellent ability in guiding uniform Li+ deposition and suppressing Li dendrite growth, which enables the symmetrical Li-Li cells with such electrolyte to run stably for over 1750 h at 0.1 mA cm−2 and 450 h at 0.2 mA cm−2. Benefiting from these advantages of A-PGCE, the assembled Li metal battery with high-voltage LiCoO 2 (LCO) cathode shows high initial capacity of 157.6 mAh g−1 in the cutoff voltage of 4.3 V, and the capacity retention is 90.7% after 200 cycles at 0.2C, indicating a superior cyclic stability. The cleverly designed asymmetrical A-PGCE shows great potential in boosting the development of lithium metal batteries with high energy density and safety. [ABSTRACT FROM AUTHOR]

[Display omitted] • An asymmetric gel polymer electrolyte (a-GPE) was well-designed via incorporating BTO and h-BNNS into PVDF-HFP nanofiber membrane. • The introduction of BTO and h-BNNS promoted the dissociation of lithium salts and further improved the ionic conductivity and Li-ion transference number. • The a-GPE effectively suppressed lithium dendrites and stabilized the cathodes simultaneously. • The Li/NCM-523 battery with a-GPE showed excellent rate performance and cycling stability. Lithium metal batteries with high-voltage cathodes are promising next-generation high performance energy storage devices. However, the lithium dendrites in lithium metal anodes, the unstable interface between electrolytes and high-voltage cathodes have hampered the application of high-voltage lithium metal batteries. Here, an asymmetric bilayer composite gel polymer electrolyte (GPE) was designed and prepared by introducing barium titanate (BTO) and hexagonal boron nitride nanosheets (h-BNNS) to PVDF-HFP matrix via electrospinning. The layer doped with h-BNNS was toward lithium metal to suppress the growth of lithium dendrites, and the layer doped with BTO was near to LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM-523) cathode to stabilize the cathode electrolyte interface (CEI) simultaneously. The bilayer GPE co-doped with h-BNNS and BTO not only improved the ionic conductivity to 3.77 × 10−3 S cm−1, but also ameliorated the cycle performance of lithium batteries. The Li/NCM-523 battery with asymmetric composite GPE showed excellent rate performance and cycling stability (151 mAh g−1 at 0.5 C, maintain 80% capacity after 170 cycles). Furthermore, the Li/LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM-811) battery with the asymmetric composite GPE exhibited the initial discharge capacity of 186.4 mAh g−1 and 81% of capacity retention after 100 cycles at 0.5 C. This work demonstrates that the asymmetric composite GPE is of promising application value in lithium metal batteries matched with high voltage cathodes. [ABSTRACT FROM AUTHOR]

Abstract: As a new high-voltage cathode candidate for post 4V cathodes, ordered-olivine LiCoPO4 and fluoride phosphate, Li2CoPO4F were synthesized by solid-state reaction. Their structures were identified by neutron diffraction. The 5V discharge profiles were demonstrated using coin-type cells. Two important issues for commercial use, metal dissolution and oxygen release at elevated temperatures, were also tested with an atomic absorption spectrophotometer and differential scanning calorimeter, respectively. [Copyright &y& Elsevier]

• Sudden, rapid capacity fade observed in cells with gel polymer electrolyte. • Cyclic voltammetry suggests good stability between NMC and gel polymer electrolyte. • Li dendrites and instability with gel polymer electrolyte are of primary concern. • Capacity fade due to cathode can be partially overcome with better cathode design. Solid-state lithium metal batteries (SSLMBs) containing polyethylene oxide (PEO)-derived polymer electrolytes and high-voltage (> 4 V vs. Li/Li+) cathode materials suffer from three sources of failure: (1) instability between the polymer electrolyte and cathode at high voltage, (2) instability of the polymer electrolyte with Li metal, and (3) poorly-designed cathodes. In this study, these three sources of failure are deconvoluted by studying Ni-rich LiNi x Mn y Co 1-x-y O 2 (NMC, x ≥ 0.6) cathodes and a gel polymer electrolyte (GPE) derived from PEO. Initial cycling data reveals that rapid capacity fade occurs regardless of whether soft short circuits form due to Li dendrites. Cyclic voltammetry scans on cells featuring a Li metal electrode, GPE, and a NMC811 electrode free of additives suggest that there are no runaway reactions between the GPE and NMC811 up to 4.5 V vs. Li/Li+. Cathode/cathode symmetric cell cycling demonstrates that Li metal reactivity is a prime source of failure, though a poorly-designed cathode leads to subpar performance. A cathode with single-crystal NMC particles was demonstrated to achieve better initial capacity and longer cycle life, indicating room for improvement in SSLMB cathode design. Therefore, the sources of failure as enumerated may be ranked as follows from most to least concerning: 2 > 3 > 1. [ABSTRACT FROM AUTHOR]