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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]

The stability of high‐energy‐density lithium metal batteries (LMBs) heavily relies on the composition of the solid electrolyte interphase (SEI) formed on lithium metal anodes. In this study, the inorganic‐rich SEI layer was achieved by incorporating bisalts additives into carbonate‐based electrolytes. Within this SEI layer, the presence of LiF, polythionate, and Li3N was observed, generated by combining 1.0 м lithium bis(trifluoromethanesulfonyl)imide in ethylene carbonate: ethyl methyl carbonate:dimethyl carbonate in a 1 : 1 : 1 volume ratio, with the addition of 2 wt% lithium difluorophosphate and 2 wt% lithium difluoro(oxalato)borate additives (EL‐DO). Furthermore, this formulation effectively mitigated corrosion of aluminum current collectors. EL‐DO exhibited outstanding performance, including an average coulombic efficiency of 98.2 % in Li||Cu cells and a stable discharge capacity of approximately 162 mAh g−1 after 200 cycles in a Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) configuration. Moreover, EL‐DO displayed the potential to enhance the performance not only of LMBs but also of lithium‐ion batteries. In the case of Gr||NCM811 cell using EL‐DO, it consistently maintained high discharge capacities, even achieving around 135 mAh g−1 after the 100th cycle, surpassing the performance of other electrolytes. This study underscores the synergistic impact of bisalts additives in elevating the performance of lithium 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]

Lithium-ion batteries play a crucial role in storing energy for renewable sources and electric vehicles, yet face challenges related to insufficient energy density. Elevating the working-voltage of cathodes is promising to boost the energy density of batteries by increasing both the output voltage and capacity of cathode, which however could compromise life cycle and safety. This review provides a comprehensive summary of essential factors governing pathways of cathode-induced thermal runaway, including electrolyte decomposition, phase transitions, and crosstalk-induced reactions. Electrode and electrolyte modifications aimed at mitigating parasitic reactions and preventing crosstalk were also discussed. The review concludes with insights into the future application of these strategies, providing a comprehensive perspective on the realization of high-energy and safe 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]

Solid polymer electrolytes (SPEs) have attracted considerable attention for solid-state lithium-metal batteries (LMBs) with high energy density and enhanced safety for future applications. In this study, an SPE was developed based on a poly(ethyl acrylate) (PEA) polymer matrix with the vinylene carbonate (VC) additive (defined as PEA-VC) for high-voltage solid-state LMBs. Results show that introducing the VC additive into the PEA-based SPE leads to high lithium-ion conductivity (1.57 mS/cm at 22°C), a high lithium-ion transference number (0.73), and a wide electrochemical stability window (up to 4.9 V vs. Li/Li+). The remarkable compatibility of the PEA-VC SPE with lithium metal anodes and high-voltage cathodes was demonstrated in Li//Li symmetric cells (800 h lifetime at a current density of 0.1 mA/cm2 at 22°C) and Li//LiNi0.8Mn0.1Co0.1O2 (NMC811) full cells (with a capacity retention of 77.8% after 100 cycles at 0.2C). The improved stability is attributed to the introduction of the VC additive, which helps form a robust cathode–electrolyte interphase, effectively suppressing parasitic interface side reactions. Overall, this study highlights the role of VC additives in high-voltage and solid-state LMBs, offering a general yet effective approach for addressing the interfacial instability issue through an additive-engineering strategy.

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]

This study focuses on the development of a composite gel polymer electrolyte membrane (CGPEM) as a solution to address safety concerns arising from the reactivity of lithium metal and the formation of dendrites. The CGPEM integrates a solid polymer matrix, solid‐electrolyte LSiPS (Li10SiP2S12), with a plasticizer that countering the performance decline caused by sulfide solid electrolyte (SSE) interactions with the cathode. Poly ethylene oxide (PEO) emerges as a promising polymer matrix due to its flexibility, cost‐effectiveness, eco‐friendliness, solvability for Li‐salt, mechanical processing adaptability, adhesive strength, and ionic conductivity. Conductivity and processability of CGPEM were optimized through meticulous adjustment of liquid plasticizer concentration. The CGPEM′s chemical and electrochemical stability were systematically investigated using in‐situ electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRTs). A lithium metal battery is constructed against a high voltage cathode and newly developed CGPEM. Impressively, the cell exhibited outstanding performance, maintaining a discharge capacity of around 146.22 mAh/g after 200 cycles, retaining 86.38 % of its initial capacity. The formation of a LiF‐rich interface layer near the lithium surface, a vital element in curbing CGPE degradation and dendritic growth, resulted in enhanced overall cell performance. [ABSTRACT FROM AUTHOR]

LiNi0.5Mn1.5O4 (LNMO) with a spinel crystal structure presents a compelling avenue towards the development of economic cobalt-free and high voltage (∼ 5 V) lithium-ion batteries. Nevertheless, the elevated operational voltage of LNMO gives rise to pronounced interfacial interactions between the distorted surface lattices characterized by Jahn–Teller (J–T) distortions and the electrolyte constituents. Herein, a localized crystallized coherent LaNiO3 and surface passivated Li3PO4 layer is deposited on LNMO via a one-step calcination process. As evidenced by transmission electron microscopy (TEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and density functional theory (DFT) calculation, the epitaxial growth of LaNiO3 along the LNMO lattice can effectively stabilize the structure and inhibit irreversible phase transitions, and the Li3PO4 surface coating can prevent the chemical reaction between HF and transition metals without sacrificing the electrochemical activity. In addition, the ionic conductive Li3PO4 and atomic wetting inter-layer enables fast charge transfer transport property. Consequently, the LNMO material enabled by the lattice bonding and surface passivating features, demonstrates high performance at high current densities and good capacity retention during long-term test. The rational design of interface coherent engineering and surface coating layers of the LNMO cathode material offers a new perspective for the practical application of high-voltage lithium-ion batteries. [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]

The ionic liquid (IL)‐based electrolyte comprising 1.2 M lithium bis(fluorosulfonyl)imide (LiFSI) in N‐propyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI) (ILE) has been evaluated as a suitable system for the high‐voltage cathode material LiNi0.5−xMn1.5+xO4 (LNMO) when cycled vs. graphite anodes. The oxidative stability of the ILE was evaluated by linear sweep voltammetry (LSV) and synthetic charge‐discharge profile voltammetry (SCPV) and was found to exceed that of state‐of‐the‐art 1 M LiPF6 in 1 : 1 ethylene carbonate (EC) : diethylcarbonate (DEC) (LP40). Improved cycling performance both at 20 °C and 45 °C was found for LNMO||graphite full cells with the IL electrolyte. X‐ray photoelectron spectroscopy (XPS) analysis showed that robust and predominantly inorganic surface layers were formed on the LNMO cathode using the ILE, which stabilized the electrode. Although the high viscosity of the ILE limits the rate performance at 20 °C, this ILE is a promising alternative electrolyte for use in lithium‐ion batteries (LiBs) with high‐voltage cathodes such as LNMO, especially for use at elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract 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.

Sodium-ion batteries (SIBs) are potential replacements for lithium-ion batteries owing to their comparable energy density and the abundance of sodium. However, the low potential and low stability of their cathode materials have prevented their commercialization. Prussian blue analogs are ideal cathode materials for SIBs owing to the numerous diffusion channels in their 3D structure and their high potential vs. Na/Na+. In this study, we fabricated various Fe-V-incorporated hexacyanoferrates, which are Prussian blue analogs, via a one-step synthesis. These compounds changed their colors from blue to green to yellow with increasing amounts of incorporated V ions. The X-ray photoelectron spectroscopy spectrum revealed that V3+ was oxidized to V4+ in the cubic Prussian blue structure, which enhanced the electrochemical stability and increased the voltage platform. The vanadium ferrocyanide Prussian blue (VFPB1) electrode, which contains V4+ and Fe2+ in the Prussian blue structure, showed Na insertion/extraction potential of 3.26/3.65 V vs. Na/Na+. The cycling test revealed a stable capacity of ~70 mAh g−1 at a rate of 50 mA g−1 and a capacity retention of 82.5% after 100 cycles. We believe that this Fe-V-incorporated Prussian green cathode material is a promising candidate for stable and high-voltage cathodes for SIBs. [ABSTRACT FROM AUTHOR]

Binders are electrochemically inactive components that have a crucial impact in battery ageing although being present in only small amounts, typically 1–3 % w/w in commercial products. The electrochemical performance of a battery can be tailored via these inactive materials by optimizing the electrode integrity and surface chemistry. Polyacrylonitrile (PAN) for LiNi0.5Mn1.5O4 (LNMO) half‐cells is here investigated as a binder material to enable a stable electrode‐electrolyte interface. Despite being previously described in literature as an oxidatively stable polymer, it is shown that PAN degrades and develops resistive layers within the LNMO cathode. We demonstrate continuous internal resistance increase in LNMO‐based cells during battery operation using intermittent current interruption (ICI) technique. Through a combination of on‐line electrochemical mass spectrometry (OEMS) and X‐ray photoelectron spectroscopy (XPS) characterization techniques, the degradation products can be identified as solid on the LNMO electrode surface, and no excessive gas formation seen. The increased resistance and parasitic processes are correlated to side‐reactions of the PAN, possibly intramolecular cyclization, which can be identified as the main cause of the comparatively fast capacity fade. [ABSTRACT FROM AUTHOR]

Organic anode materials have garnered attention for use in rechargeable Li-ion batteries (LIBs) owing to their lightweight, cost-effectiveness, and tunable properties. However, challenges such as high electrolyte solubility and limited conductivity, restrict their use in full-cell LIBs. Here, we report the use of highly crystalline Cl-substituted contorted hexabenzocoronene (Cl-cHBC) as an efficient organic anode for full-cell LIBs. By employing an antisolvent crystallization method, the crystallinity of the Cl-cHBC materials has been significantly enhanced, achieving superior electrochemical performance in a half-cell configuration. Furthermore, when incorporated with the conventional lithium iron phosphate (LFP) cathode, the Cl-cHBC||LFP full-cell delivers a high discharge cell voltage of 3.0 V, surpassing the voltages of conventional lithium-titanium oxide anodes and offering improved power densities. In addition, a full cell with high-voltage lithium cobalt oxide and single-crystal high-nickel-based cathodes demonstrates enhanced electrochemical characteristics, including elevated discharge voltages, stable C-rate performance, and cycle endurance. Thus, the proposed highly crystalline Cl-cHBC anode is a promising next-generation solution for LIB applications.

Commercial LiPF 6 -based electrolytes face limitations in oxidation stability (4.2 V) and water tolerance (10 ppm). While replacing LiPF 6 with lithium bis(trifluoromethane)sulfonimide (LiTFSI) improves water tolerance, it induces Al current collector corrosion above 3.7 V vs. Li/Li + . To address this, lithium cyano(trifluoromethanesulfonyl)imide (LiCTFSI) is proposed here as a non-corrosive, moisture-tolerant alternative. The 2.0 M LiCTFSI/propylene carbonate (PC)-fluoroethylene carbonate (FEC) (7:3 by volume) electrolyte enables LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes to reach 210 mAh g -1 (2.8-4.6 V) with a cycle life of 500. Full cells with NCM811||graphite (2.0 mAh cm -2 ) show 77.8% capacity retention after 500 cycles. Even with 2000 ppm moisture in the electrolyte, full cells maintain high cycling stability, reducing the need for costly dry rooms. The electrolyte's low freezing point and high thermal stability enable the operation from -20 °C to 60 °C, delivering 168 mAh g -1 at -20 °C and retaining 94% capacity after 100 cycles at 60 °C. In contrast, cells with commercial LiPF 6 electrolyte deliver 71 mAh g -1 at -20°C and retain 52.7% after 100 cycles at 60 °C. This novel salt offers a cost-effective solution for developing robust, high-performance batteries suitable for extreme conditions., (© 2024 Wiley‐VCH GmbH.)

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]

Transition metal-based sodium fluoro-perovskite of general formula NaMF3 (M = Fe, Mn, and Co) were investigated as cathode materials for rechargeable Na-ion batteries. Preliminary results indicated Na-ion reversible intercalation but highlighted the need to find optimization strategies to improve conductivity and to modulate the operating voltages within experimentally accessible electrolytes' stability windows, in order to fully exploit their potential as high-voltage cathodes. In this study, we combined experimental and computational techniques to investigate structures, defects, and intercalation properties of the NaFe1-xMnxF3 and NaCo1-xMnxF3 systems. Through the use of a simple solvothermal synthesis, we demonstrated the possibility to modulate the sample's morphology in order to obtain fine and dispersed powder samples. The structural results indicated the formations of two solid solutions with a perovskite structure over the entire compositional range investigated. Atomistic simulations suggested that Na-ion diffusion in these systems was characterized by relatively high migration barriers and it was likely to follow three-dimensional paths, thus limiting the effect of anti-site defects. The correlation between structural and computational data highlighted the possibility to modulate both ionic and electronic conductivity as a function of the composition. [ABSTRACT FROM AUTHOR]

Particle size-tuned platelets of the high-voltage cathode material LiCoPO4 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 LiCoPO4. 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 m2 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. LiCoPO4 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.

Particle size-tuned platelets of the high-voltage cathode material LiCoPO4 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 LiCoPO4. 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 m2 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. LiCoPO4 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.

• 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]

Abstract Garnet‐type solid electrolyte is a promising candidate for the fabrication of high energy all‐solid‐state Li‐ion batteries (ASSLIBs), but its use is hampered by a large interfacial resistance. Herein, we propose a surface modification and subsequent sintering to enhance the interfacial connection between the cathode and the solid electrolyte. The ASSLIB prepared by this method delivered an initial discharge capacity of ∼66 mAh g−1 (80 °C) at a rate of 0.1 C. However, the poor contact between the cathode and electrolyte triggered the increase of the interfacial resistance, which caused severe capacity decay upon cycling. The encapsulation of LiCoO2 particles with LiBO2 using a single‐step sintering process dramatically increased the interfacial contact, resulting in a higher discharge capacity of 116 mAh g−1 with good cycling behavior. Therefore, surface modification of the cathode offers a reduction of resistance and promotes efficient Li‐ion transfer pathways across the cathode/solid‐electrolyte interface.

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]

The development of cathode materials has always been one of the most crucial areas of research in the field of sodium-ion batteries. Sulfate-based polyanionic materials, known for their high working voltage characteristics, have received widespread attention. In this work, a fluoro-sulfate sodium-ion battery cathode material, Na 3 Fe 2 (SO 4 ) 3 F modified with carbon nanotubes, was developed using a low-temperature solid-state annealing method. This Na 3 Fe 2 (SO 4 ) 3 F cathode exhibits an exceptionally high voltage of 3.77 V, excellent discharge capacity (102 mAh/g at 0.1C), and good rate capability. This material broadens the research directions for cathode materials and holds promise as a foundation for the further development of high-performance sodium-ion batteries.

High-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) cathodes suffer from severe capacity degradation during long-term cycling due the manganese dissolution and their high operating voltage (∼4.95 V), which pose serious challenges at the surface or interface. Moreover, both traditional ion-doping and passivation layer coating are difficult to apply consistently to LNMO cathode because of their complicated procedures, especially in large-scale production. To address these issues, a strategy employing HNO 3 /H 2 O 2 leaching in synergy with a sintering process at a mid-temperature of 700 °C was used to achieve selective surface reconstruction. An optimal ratio of reactants was applied to balance the capacity and the cyclic stability of the LNMO cathode. The optimized valence composition of Mn on the material surface mitigates the occurrence of Jahn-Teller distortion, accompanied by a reasonable ratio of ordered and disordered phases and the concentration of oxygen vacancies after sintering, which improves the interface behavior between the electrode and electrolyte. This method delivers a high reversible capacity of 116.5 mAh g -1 after 200 cycles at 0.5 C (1 C = 147 mAh g -1 ) with a capacity retention of 91.30% and 110 mAh g -1 with a remarkably high capacity retention of 86.85% after 500 cycles at 2 C. This balanced approach, utilizing the protective effects of oxidation (O 2 2- ) and the erosive action of acid (H + ), is proposed to achieve regional surface reconstruction of advanced LNMO cathode. This opens up a strategy for improving oxide-based cathode materials with low cost and mass production capability, especially favoring high consistency.

Advanced lithium-ion batteries utilize high upper cut-off voltages up to 4.8 V versus lithium metal to reach extraordinary energy densities. Such a harsh environment challenges the cathode stability and requires the construction of robust cathode electrolyte interphases at their electrochemical interface. Inspired by carbonated beverages with supersaturated CO 2 , here, a surface modification strategy that produces effective passivation layer of low modulus from the weakest link, is proposed CO 2 bubbles preferentially nucleate and grow at rough surfaces, which in oxide cathodes, are also the local regions offering fast degradation pathway. Metal ion exchange on carbonated layer assists the construction of highly elastic interface under the guidance of packing factor. This method enables surface reconstruction at both primary and secondary particle levels for various cathodes exemplified by high-voltage LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) and LiCoO 2 (LCO). Remarkably, with ultra-high upper cut-off voltage of 4.8 V versus Li + /Li, over 235 mAh g -1 discharge capacity, and over 900 W h kg -1 discharge energy at cathode level, ≈90% capacity retention can be obtained for LiNi 0.8 Co 0.1 Mn 0.1 O 2 over 100 cycles at 0.5 C with commercial carbonate electrolytes. This carbonated beverage chemistry is promising for constructing high-quality surface passivation in many extreme-condition applications beyond battery cathodes., (© 2024 Wiley‐VCH GmbH.)

Sodium-ion batteries (SIBs) are potential replacements for lithium-ion batteries owing to their comparable energy density and the abundance of sodium. However, the low potential and low stability of their cathode materials have prevented their commercialization. Prussian blue analogs are ideal cathode materials for SIBs owing to the numerous diffusion channels in their 3D structure and their high potential vs. Na/Na+. In this study, we fabricated various Fe-V-incorporated hexacyanoferrates, which are Prussian blue analogs, via a one-step synthesis. These compounds changed their colors from blue to green to yellow with increasing amounts of incorporated V ions. The X-ray photoelectron spectroscopy spectrum revealed that V3+ was oxidized to V4+ in the cubic Prussian blue structure, which enhanced the electrochemical stability and increased the voltage platform. The vanadium ferrocyanide Prussian blue (VFPB1) electrode, which contains V4+ and Fe2+ in the Prussian blue structure, showed Na insertion/extraction potential of 3.26/3.65 V vs. Na/Na+. The cycling test revealed a stable capacity of ~70 mAh g−1 at a rate of 50 mA g−1 and a capacity retention of 82.5% after 100 cycles. We believe that this Fe-V-incorporated Prussian green cathode material is a promising candidate for stable and high-voltage cathodes for SIBs.

Transition metal-based sodium fluoro-perovskite of general formula NaMF3 (M = Fe, Mn, and Co) were investigated as cathode materials for rechargeable Na-ion batteries. Preliminary results indicated Na-ion reversible intercalation but highlighted the need to find optimization strategies to improve conductivity and to modulate the operating voltages within experimentally accessible electrolytes’ stability windows, in order to fully exploit their potential as high-voltage cathodes. In this study, we combined experimental and computational techniques to investigate structures, defects, and intercalation properties of the NaFe1-xMnxF3 and NaCo1-xMnxF3 systems. Through the use of a simple solvothermal synthesis, we demonstrated the possibility to modulate the sample’s morphology in order to obtain fine and dispersed powder samples. The structural results indicated the formations of two solid solutions with a perovskite structure over the entire compositional range investigated. Atomistic simulations suggested that Na-ion diffusion in these systems was characterized by relatively high migration barriers and it was likely to follow three-dimensional paths, thus limiting the effect of anti-site defects. The correlation between structural and computational data highlighted the possibility to modulate both ionic and electronic conductivity as a function of the composition.

Anhydride additives including maleic anhydride and succinic anhydride are initially selected as additives in the commercial electrolytes for high-voltage lithium-ion batteries with a Si-based anode. The introduction of (ethoxy)pentafluorocyclotriphosphazene as a flame retardant realizes the nonflammability of electrolytes, and the conductivity of electrolytes exceeds 10 mS cm -1 at 25 °C. Maleic anhydride and (ethoxy)pentafluorocyclotriphosphazene jointly contribute to the exceptional performances of 4.45 V LiCoO 2 /Si-graphite pouch cells at 25 °C. The capacity retention at 1C of 300 cycles reaches 78%, and the discharge capacity ratio of 6C/1C is approximately 83%. These results suggest that this nonflammable electrolyte has good application prospect. Scanning electron microscopy and X-ray photoelectron spectroscopy measurements are implemented to analyze the interface properties of electrodes.

Solid-state electrolyte batteries have attracted significant interest as promising next-generation batteries due to their achievable high energy densities and nonflammability. In particular, curable polymer network gel electrolytes exhibit superior ion conductivity and interfacial adhesion with electrodes compared to oxide or sulfide solid electrolytes, bringing them closer to commercialization. However, the limited electrochemical stability of matrix polymers, particularly those based on poly (ethylene oxide) (PEO), presents challenges in achieving stable electrochemical performance in high-voltage lithium metal batteries. Here, these studies report a sulfate additive-incorporated thermally crosslinked gel-type polymer electrolyte (SA-TGPE) composed of a PEO-based polymer matrix and a functional sulfate additive, 1,3-propanediolcyclic sulfate (PCS), which forms stable interfacial layers on electrodes. The electrode-electrolyte interface modified by the PCS enhances the electrochemical stability of the polymer electrolyte, effectively alleviating decomposition of the PEO-based polymer matrix on the cathode. Moreover, it also mitigates side reactions of the Ni-rich NCM cathode and dendrites of lithium metal anode. These studies provide a novel perspective by utilizing interfacial modification through electrolyte additives to resolve the electrochemical instability of PEO-based polymer electrolytes in high-voltage lithium metal batteries., (© 2023 Wiley‐VCH GmbH.)

Garnet‐type solid electrolyte is a promising candidate for the fabrication of high energy all‐solid‐state Li‐ion batteries (ASSLIBs), but its use is hampered by a large interfacial resistance. Herein, we propose a surface modification and subsequent sintering to enhance the interfacial connection between the cathode and the solid electrolyte. The ASSLIB prepared by this method delivered an initial discharge capacity of ∼66 mAh g−1 (80 °C) at a rate of 0.1 C. However, the poor contact between the cathode and electrolyte triggered the increase of the interfacial resistance, which caused severe capacity decay upon cycling. The encapsulation of LiCoO2 particles with LiBO2 using a single‐step sintering process dramatically increased the interfacial contact, resulting in a higher discharge capacity of 116 mAh g−1 with good cycling behavior. Therefore, surface modification of the cathode offers a reduction of resistance and promotes efficient Li‐ion transfer pathways across the cathode/solid‐electrolyte interface. [ABSTRACT FROM AUTHOR]

Recently, P2-type (prismatic site) and O2 (octahedral site)/P2-type materials like Na0.66Fe0.33Mn0.5O2 exhibit favorable capacities more than its theoretical value (173 mAh g−1). However, their low operating potential window ≤ 3 V makes them not desirable for practical applications. Among the sodium (Na) cathodes, the P2-Na-Ni-Mn-O is a significant material because of its high theoretical capacity of ≤ 250 mAh g−1 even if it undergoes severe voltage decay with capacity fade due to stacking faults upon cycling above the cut-off voltage (≥ 4.2 V). En route to evade this problem, we substitute zinc (Zn) cation into the P2-Na-Ni-Mn-O system as structure stabilizer, and this material delivers high initial discharge capacity of 205 mAh g−1 while cycling in the range 1.5 to 4.5 V. The X-ray diffraction pattern, energy dispersive spectroscopy (EDS) with mapping, and XPS results show that Zn2+ befit in to the P2-layer structure of Na-Ni-Mn-O2 without changing its origin. [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 cobalt-free layered oxide cathode of LiNi 0.65 Mn 0.35 O 2 is promising for high-energy-density lithium-ion batteries (LIBs). However, under high-voltage conditions, severe side reactions between the Co-free cathode and electrolyte, as well as grain boundary cracks and pulverization of particles, hinder its practical applications. Herein, an electrolyte regulation strategy is proposed by adding fluoroethylene carbonate (FEC) and LiPO 2 F 2 as electrolyte additives in carbonate-based electrolytes to address the above issues. As a result, a homogeneous and dense organic-inorganic hybrid cathode electrolyte interface (CEI) film is formed on the cathode surface. The CEI film consists of C-F, LiF, Li 2 CO 3 , and Li x PO y F z species, which is proven to be highly conductive and effective in suppressing structure damage and alleviating the interfacial reactions between the cathode and electrolyte. With such a CEI film, the interfacial stability of the Co-free cathode and the high-voltage cycling performance of Li||LiNi 0.65 Mn 0.35 O 2 are greatly improved. A reversible capacity of 155.1 mAh g -1 and a capacity retention of 81.3% over 150 cycles are attained at a 4.8 V charge cutoff voltage with the tamed electrolyte, whereas the cell without the additives only retains 76.1% capacity retention. Therefore, our work demonstrates the synergistic effect of FEC and LiPO 2 F 2 in stabilizing the interface of Co-free cathode materials and provides an alternative strategy for the electrolyte design of high-voltage LIBs.