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A significant obstacle in the manufacturing and practical application of Ni‐rich cathode materials is decreasing the manufacturing cost without sacrificing the cycling stability. Here a high‐energy, ultrahigh‐Ni, and nearly Co‐free cathode with outstanding cycling performance is proposed. This promising cathode is enabled by artificially constructing an “outside‐in” interface structure toward LiNi0.94Co0.05Mn0.01O2 (NCM94) cathodes. Combining theoretical prediction and experimental results, it is revealed that high interfacial stability is achieved by a specific surface chemistry with an outside‐in structure composed of an inner organic layer and an outer inorganic layer. Benefiting from the protection effect of the robust outside layer and the strain relieve function of the inside layer, the intrinsic challenges of interfacial reactions, transition metal (TM) dissolution, and micro‐crack propagation have been mitigated for the Ni‐rich cathode. As a result, the “outside‐in” strategy enables superior cycling stability with a 92.7% retention after 200 cycles and an excellent rate capability of 149.1 mAh g−1 at 10 C, achieved by adding only 0.5% of the production cost. This study unlocks the possibilities of achieving outstanding performance for ultrahigh Ni cathode by spending minimum cost through the facile surface chemistry method. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries (LIBs) are increasingly encouraged to enhance their environmental friendliness and safety while maintaining optimal energy density and cost‐effectiveness. Although various electrolytes using greener and safer glyme solvents have been reported, the low charge voltage (usually lower than 4.0 V vs Li/Li+) restricts the energy density of LIBs. Herein, tetraglyme, a less‐toxic, non‐volatile, and non‐flammable ether solvent, is exploited to build safer and greener LIBs. It is demonstrated that ether electrolytes, at a standard salt concentration (1 m), can be reversibly cycled to 4.5 V vs Li/Li+. Anchored with Boron‐rich cathode‐electrolyte interphase (CEI) and mitigated current collector corrosion, the LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode delivers competitive cyclability versus commercial carbonate electrolytes when charged to 4.5 V. Synchrotron spectroscopic and imaging analyses show that the tetraglyme electrolyte can sufficiently suppress the overcharge behavior associated with the high‐voltage electrolyte decomposition, which is advantageous over previously reported glyme electrolytes. The new electrolyte also enables minimal transition metal dissolution and deposition. NMC811||hard carbon full cell delivers excellent cycling stability at C/3 with a high average Coulombic efficiency of 99.77%. This work reports an oxidation‐resilient tetraglyme electrolyte with record‐high 4.5 V stability and enlightens further applications of glyme solvents for sustainable LIBs by designing Boron‐rich interphases. [ABSTRACT FROM AUTHOR]

[Display omitted] Employing layered materials as the cathodes for solid-state batteries (SSBs) is vital in enhancing the batteries' energy density, whereas numerous issues are present regarding the compatibilities between cathode electrode and modified solid electrolyte (ME) in this battery configuration. By investigating the electrochemical performance and interfacial properties of SSBs using various cathodes, the fundamental reason for the poor compatibility between layered cathodes, especially LiCoO 2 with ME is revealed. Because of the Li(solvent)+ intercalation environments formed in the ME, the resultant weak-interacted TFSI- could be adsorbed and destabilized by Co ions on the surface. Besides, the high energy level offsets between LiCoO 2 and ME lead to Li-ion transferring from the bulk electrode to the electrolyte, resulting in a pre-formed interface on the cathode particles before the electric current is applied, affects the formation of effective cathode-electrolyte interface (CEI) film during electrochemical process and deteriorated overall battery performance. From this view, an interlayer is pre-added on the LiCoO 2 surface through an electrostatic adsorption method, to adjust the energy level offsets between the cathode and ME, as well as isolate the direct contact of surface Co ions to TFSI-. The cycling properties of the SSB using modified LiCoO 2 are greatly enhanced, and a capacity retention of 68.72 % after 100 cycles could be achieved, against 8.28 % previously, certifying the rationality of the understanding and the effectiveness of the proposed modification method. We believe this research could provide basic knowledge of the compatibility between layered cathodes and MEs, shedding light on designing more effective strategies for achieving SSBs with high energy density. [ABSTRACT FROM AUTHOR]

Recently, in electric mobilities and stationary energy storage device applications, the development of long‐lasting, low‐cost, and high‐safety lithium‐ion batteries (LIBs) is widely studied. LiFePO4 (LFP) is a core cathode material for LIBs owing to its cost‐effectiveness and high safety. However, it exhibits low electronic conductivity and sluggish Li+ diffusion, hindering the application of LFP cathodes in high‐power battery industries. Herein, a triazole‐motivated electrolyte additive, 1‐(trimethylsilyl)−1H‐benzotriazole (TMSBTA) is presented, for mitigating iron dissolution via HF scavenging, reinforcing the robustness of the solid electrolyte interphase and constructing a cathode–electrolyte interface (CEI) to balance the ion and electron conduction of the CEI on the LFP cathode. Scanning probe microscopy performed in the conductive atomic force microscopy mode indicates that the electronically conductive CEI created by the oxidative decomposition of TMSBTA enables rapid and homogeneous lithiation and delithiation during cycling without morphological changes in the LFP particles. This study elucidates the design principles of the CEI on the LFP cathode and is expected to guide integrated electrolyte additive engineering for LFP‐containing LIBs. [ABSTRACT FROM AUTHOR]

High interfacial resistance between electrodes and solid‐state electrolyte is the major cause for the failure of all‐solid‐state Li‐ion batteries. Spontaneous (electro)chemical reactions and poor Li‐ion diffusion at the interfaces are closely related to this increased impedance. Although introducing a coating layer can mitigate interfacial reactions and structural reconstruction, it may also lead to poor Li‐ion diffusion. Balancing this trade‐off therefore is crucial for the design of coating layer materials. In this study, the impact of the amorphous LiF (a‐LiF) coating layer on interfacial structural reconstruction and Li‐ion diffusion at the LiCoO2/Li6PS5Cl solid‐state interface is explicitly elucidated via machine‐learning‐assisted molecular dynamics (MD) simulations. It is found that the a‐LiF can effectively protect the P‐S tetrahedron local structures in Li6PS5Cl but cannot suppress the formation of side product S2 dimers. It is further discovered that once the a‐LiF coating exceeds a certain critical thickness, emergence of ordered local structures will inhibit Li‐ion diffusion. The simulations propose that the optimal thickness of the coating layer is around 1 nm. Overall, the work provides a microscopic understanding for effects of the a‐LiF coating layer on the structural and kinetic properties of cathode‐solid electrolyte interfaces and can guide the design of interfacial coating materials for solid‐state batteries. [ABSTRACT FROM AUTHOR]

Lithium iron phosphate (LiFePO4 or LFP) is a promising cathode material for lithium-ion batteries (LIBs), but side reactions between the electrolyte and the LFP electrode can degrade battery performance. This study introduces an innovative coating strategy, using atomic layer deposition (ALD) to apply a thin (5 nm and 10 nm) Al2O3 layer onto high-mass loading LFP electrodes. Galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy (EIS) were used to assess the electrochemical performance of coated and uncoated LFP electrodes. The results show that Al2O3 coatings enhance the cycling performance at room temperature (RT) and 40 °C by suppressing side reactions and stabilizing the cathode–electrolyte interface (CEI). The coated LFP retained 67% of its capacity after 100 cycles at 1C and RT, compared to 57% for the uncoated sample. Post-mortem analyses, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were conducted to investigate the mechanisms behind the improved performance. These analyses reveal that Al2O3 coatings are highly effective in reducing LFP electrode degradation during cycling, demonstrating the potential of ALD Al2O3 coatings to enhance the durability and performance of LFP electrodes in LIBs. [ABSTRACT FROM AUTHOR]

Lithium‐excess cation‐disordered rocksalt materials are a promising class of transition metal‐based cathodes that exhibit high specific capacity and energy density. The exceptional performance is achieved through participation of anionic redox in addition to cationic redox reactions in the electrochemistry. However, anionic redox reactions accompanied by oxygen evolution, accelerated electrolyte breakdown, and structural evolution lead to voltage hysteresis and low initial Coulombic efficiency. Herein, an Al2O3 layer with varying thickness has been coated onto a high‐entropy disordered rocksalt oxyfluoride cathode through atomic layer deposition to enhance battery performance. The results indicate that the utilization of a uniform Al2O3 coating improves the capacity retention and rate capability of the cathode, with the performance being strongly dependent on the layer thickness. Further investigation into cathode–electrolyte interfacial reactions reveals that the thin protecting Al2O3 coating can reduce the decomposition of electrolyte on the cathode surface but cannot prevent bulk phase degradation during prolonged cycling. These findings highlight the need for optimized coating design on the disordered rocksalt cathode to improve battery performance. [ABSTRACT FROM AUTHOR]

Lithium-excess, cation-disordered rocksalt (DRX) materials have been subject to intense scrutiny and development in recent years as potential cathode materials for Li-ion batteries. Despite their compositional flexibility and high initial capacity, they suffer from poorly understood parasitic degradation reactions at the cathode-electrolyte interface. These interfacial degradation reactions deteriorate both the DRX material and electrolyte, ultimately leading to capacity fade and voltage hysteresis during cycling. In this work, differential electrochemical mass spectrometry (DEMS) and titration mass spectrometry are combined to quantify the extent of bulk redox and surface degradation reactions for a set of Mn2+/4+-based DRX oxyfluorides during initial cycling with a high-voltage charging cutoff (4.8 V vs Li/Li+). Increasing the fluorine content from 7.5 to 33.75% is shown to diminish oxygen redox and suppresses high-voltage O2 evolution from the DRX surface. Additionally, electrolyte degradation processes resulting in the formation of both gaseous species and electrolyte-soluble protic species are observed. Subsequently, DEMS is paired with a fluoride-scavenging additive to demonstrate that increasing fluorine content leads to increased dissolution of fluorine from the DRX material into the electrolyte. Finally, a suite of ex situ spectroscopy techniques (X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, and solid-state nuclear magnetic resonance spectroscopy) are employed to study the change in DRX composition during charging, revealing the dissolution of manganese and fluorine from the DRX material at high voltages. This work provides insight into the degradation processes occurring at the DRX-electrolyte interface and points toward potential routes of interfacial stabilization.

Reasonable design of cathode-electrolyte interface (CEI) with high electrochemical stability and high ionic conductivity is crucial for improving the electrochemical performance of cathode materials. Herein, lithium difluoro(oxalate)borate (LiDFOB) is used as an efficient electrolyte additive to form a robust, dense, and conductive CEI on LiFePO4 cathode, which significantly enhances the rate capability and cycling stability. Specifically, the introduction of LiDFOB promotes the formation of a fluoride (F)- and boron (B)-rich CEI, effectively enhancing ion transport kinetics. Simultaneously, the generated CEI exhibits excellent stability, efficiently suppressing the continuous decomposition of the electrolyte and structural damage of LiFePO4 cathode over prolonged cycling. Consequently, the LiFePO4 cathode with LiDFOB additive exhibits a highly reversible capacity of 133.4 mAh g−1 at 0.5 C and an excellent capacity retention of 94.4% over 400 cycles, which is superior to LiFePO4 without additive (only 66.1% capacity retention). This work confirms the promising potential of LiDFOB as a multifunctional electrolyte additive and provides new insights for constructing high-performance CEI. [ABSTRACT FROM AUTHOR]

Lithium‐excess cation‐disordered rocksalt materials are a promising class of transition metal‐based cathodes that exhibit high specific capacity and energy density. The exceptional performance is achieved through participation of anionic redox in addition to cationic redox reactions in the electrochemistry. However, anionic redox reactions accompanied by oxygen evolution, accelerated electrolyte breakdown, and structural evolution lead to voltage hysteresis and low initial Coulombic efficiency. Herein, an Al2O3 layer with varying thickness has been coated onto a high‐entropy disordered rocksalt oxyfluoride cathode through atomic layer deposition to enhance battery performance. The results indicate that the utilization of a uniform Al2O3 coating improves the capacity retention and rate capability of the cathode, with the performance being strongly dependent on the layer thickness. Further investigation into cathode–electrolyte interfacial reactions reveals that the thin protecting Al2O3 coating can reduce the decomposition of electrolyte on the cathode surface but cannot prevent bulk phase degradation during prolonged cycling. These findings highlight the need for optimized coating design on the disordered rocksalt cathode to improve battery performance.

Gel polymer electrolytes (GPE) have stimulated the enthusiasm to develop high‐performance quasi‐solid‐state lithium–sulfur (Li–S) batteries, but the incompatibility between non‐polar sulfur cathode and polar GPE has limited its further development. Changing polarity by replacing the non‐polar sulfur cathode to polar organosulfur cathode is expected to improve the cathode‐electrolyte interface compatibility. Inspired by "like compatible like" strategy, a vinyl‐capped hyperbranched polymer network (PEI‐GMA) is developed that serves as a backbone structure for both organosulfur polymer cathode (G/PEI‐GMA@S) and GPE to construct a strong cathode‐electrolyte interface. High interfacial compatibility contributes to accelerating electron/ion conduction for superior transfer kinetics and construction of stable quasi‐solid‐state Li–S batteries. As a result, the internal resistance of the battery is significantly reduced by 60%, and after 400 cycles, the battery capacity retention rate is 91%, with an average decay rate per cycle as low as 0.022%. Meanwhile, the strategy of optimizing both cathodes and electrolytes without design multiple materials makes Li–S batteries more competitive in practical applications. This study emphasizes the importance of moderating relevant polarity for constructing a strong cathode‐electrolyte interface, which provides guiding principles for the electrode and electrolyte design of advanced Li–S batteries. [ABSTRACT FROM AUTHOR]

LiNi0.8Co0.1Mn0.1O2 (NCM811), a Ni-rich layered oxide, is a promising cathode material for high-energy density lithium-ion batteries (LIBs). However, its structural instability, caused by adverse phase transitions and continuous oxygen release, as well as deteriorated interfacial stability due to excessive electrolyte oxidative decomposition, limits its widespread application. To address these issues, a new concept is proposed that surface targeted precise functionalization (STPF) of the NCM811 cathode using a synergistic slurry additive (SSA) approach. This approach involves coating the NCM811 particle surface with 3-aminopropyl dimethoxy methyl silane (3-ADMS), followed by the precise deposition of ascorbic acid via an acid-base interaction. The slurry additives induce the formation of an ultra-thin spinel surface layer and a stable cathode-electrolyte interface (CEI), which enhances the electrochemical kinetics and inhibits crack propagation. The STPF strategy implemented by the SSA approach significantly improves the cyclic stability and rate performance of the NCM811 cathode in both half-cell and full-cell configurations. This work establishes a promising strategy to enhance the structural stability and electrochemical performance of nickel-rich cathodes and provides a feasible route to promote practical applications of high-energy density lithium-ion battery technology. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) have attracted attention due to their potential applications for future energy storage devices. Despite significant attempts to improve the core electrode materials, only some work has been conducted on the chemistry of the interface between the electrolytes and essential electrode materials. Therefore, the different cathode–electrolyte interfaces (CEIs) that form between various cathode materials and liquid electrolytes for SIBs are briefly reviewed, and the requirements of CEI performance in low‐temperature SIBs. Modifying the cathode materials and electrolyte formulas offers an efficient strategy for CEI enhancement. The summary and analysis, given in this article, may serve as a reference for the development of better sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Lithium iron phosphate (LiFePO4 or LFP) is a promising cathode material for lithium-ion batteries (LIBs), but side reactions between the electrolyte and the LFP electrode can degrade battery performance. This study introduces an innovative coating strategy, using atomic layer deposition (ALD) to apply a thin (5 nm and 10 nm) Al2O3 layer onto high-mass loading LFP electrodes. Galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy (EIS) were used to assess the electrochemical performance of coated and uncoated LFP electrodes. The results show that Al2O3 coatings enhance the cycling performance at room temperature (RT) and 40 °C by suppressing side reactions and stabilizing the cathode–electrolyte interface (CEI). The coated LFP retained 67% of its capacity after 100 cycles at 1C and RT, compared to 57% for the uncoated sample. Post-mortem analyses, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were conducted to investigate the mechanisms behind the improved performance. These analyses reveal that Al2O3 coatings are highly effective in reducing LFP electrode degradation during cycling, demonstrating the potential of ALD Al2O3 coatings to enhance the durability and performance of LFP electrodes in LIBs.

Sodium‐ion batteries (SIBs) have attracted attention due to their potential applications for future energy storage devices. Despite significant attempts to improve the core electrode materials, only some work has been conducted on the chemistry of the interface between the electrolytes and essential electrode materials. Therefore, the different cathode–electrolyte interfaces (CEIs) that form between various cathode materials and liquid electrolytes for SIBs are briefly reviewed, and the requirements of CEI performance in low‐temperature SIBs. Modifying the cathode materials and electrolyte formulas offers an efficient strategy for CEI enhancement. The summary and analysis, given in this article, may serve as a reference for the development of better sodium‐ion batteries.

Argyrodite‐type Li6PS5Cl (LPSCl) has attracted much attention as a solid electrolyte for all‐solid‐state batteries (ASSBs) because of its high ionic conductivity and good mechanical flexibility. LPSCl, however, has challenges of translating research into practical applications, such as irreversible electrochemical degradation at the interface between LPSCl and cathode materials. Even for Li‐ion batteries (LIBs), liquid electrolytes have the same issue as electrolyte decomposition due to interfacial instability. Nonetheless, current LIBs are successfully commercialized because functional electrolyte additives give rise to the formation of stable cathode‐electrolyte interphase (CEI) and solid‐electrolyte interphase (SEI) layers, leading to supplementing the interfacial stability between electrolyte and electrode. Herein, inspired by the role of electrolyte additives for LIBs, trimethylsilyl compounds are introduced as solid electrolyte additives for improving the interfacial stability between sulfide‐based solid electrolytes and cathode materials. 2‐(Trimethylsilyl)ethanethiol (TMS‐SH), a solid electrolyte additive, is oxidatively decomposed during charge, forming a stable CEI layer. As a result, the CEI layer derived from TMS‐SH suppresses the interfacial degradation between LPSCl and LiCoO2, thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2, such as superior cycle life over 2000 cycles (85.0% of capacity retention after 2000 cycles). [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) suffer from severe capacity decay as the harmful substances caused by the violent decomposition of electrolyte under high voltages continue to erode the cathodes. Therefore, the design of high-voltage electrolyte and construction of robust cathode-electrolyte interface (CEI) are critical for long-life SIBs. Herein, an electrically coupled composite electrolyte that takes the merits of cross-linked gel polymers and s well-tuned antioxidant additive (4-trifluoromethylphenylboronic acid, TFPBA) is proposed. Through an electrical coupling effect, TFPBA can be anchored by the cross-linked polymer framework to immobilize the PF6-anion and adsorb onto cathode surface spontaneously, both of which promote the formation of a robust CEI layer to facilitate Na+ transportation and suppress subsequent side reactions and corrosive cracking. As a result, the cells integrating high-voltage P2/O3 cathode and well-tailored gel polymer electrolyte achieve stable cycling over 550 cycles within 1.8-4.2 V with a capacity retention of 71.0% and a high-rate discharge capacity of 77.4 mAh g-1 at 5 C. The work paves the way for the development of functionalized quasi-solid electrolyte for practical next generation high-voltage SIBs. [ABSTRACT FROM AUTHOR]

Abstract Argyrodite‐type Li6PS5Cl (LPSCl) has attracted much attention as a solid electrolyte for all‐solid‐state batteries (ASSBs) because of its high ionic conductivity and good mechanical flexibility. LPSCl, however, has challenges of translating research into practical applications, such as irreversible electrochemical degradation at the interface between LPSCl and cathode materials. Even for Li‐ion batteries (LIBs), liquid electrolytes have the same issue as electrolyte decomposition due to interfacial instability. Nonetheless, current LIBs are successfully commercialized because functional electrolyte additives give rise to the formation of stable cathode‐electrolyte interphase (CEI) and solid‐electrolyte interphase (SEI) layers, leading to supplementing the interfacial stability between electrolyte and electrode. Herein, inspired by the role of electrolyte additives for LIBs, trimethylsilyl compounds are introduced as solid electrolyte additives for improving the interfacial stability between sulfide‐based solid electrolytes and cathode materials. 2‐(Trimethylsilyl)ethanethiol (TMS‐SH), a solid electrolyte additive, is oxidatively decomposed during charge, forming a stable CEI layer. As a result, the CEI layer derived from TMS‐SH suppresses the interfacial degradation between LPSCl and LiCoO2, thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2, such as superior cycle life over 2000 cycles (85.0% of capacity retention after 2000 cycles).

Prussian blue analogues (PBAs) cathodes can host diverse monovalent and multivalent metal ions due to their tunable structure. However, their electrochemical performance suffers from poor cycle life associated with chemo‐mechanical instabilities. This study investigates the driving forces behind chemo‐mechanical instabilities in Ni‐ and Mn‐based PBAs cathodes for K‐ion batteries by combining electrochemical analysis, digital image correlation, and spectroscopy techniques. Capacity retention in Ni‐based PBA is 96% whereas it is 91.5% for Mn‐based PBA after 100 cycles at C/5 rate. During charge, the potassium nickel hexacyanoferrate (KNHCF) electrode experiences a positive strain generation whereas the potassium manganese hexacyanoferrate (KMHCF) electrode undergoes initially positive strain generation followed by a reduction in strains at a higher state of charge. Overall, both cathodes undergo similar reversible electrochemical strains in each charge–discharge cycle. There is ~0.80% irreversible strain generation in both cathodes after 5 cycles. XPS studies indicated richer organic layer compounds in the cathode‐electrolyte interface (CEI) layer formed on KMHCF cathodes compared to the KNHCF ones. Faster capacity fades in Mn‐based PBA, compared to Ni‐based ones, is attributed to the formation of richer organic compounds in CEI layers, rather than mechanical deformations. Understanding the driving forces behind instabilities provides a guideline to develop material‐based strategies for better electrochemical performance. [ABSTRACT FROM AUTHOR]

All‐solid‐state batteries (ASSBs) employing Li‐metal anodes and inorganic solid electrolytes are attracting great attention due to high safety and energy density for next‐generation energy storage devices. However, the volume change of cathode active materials can cause contact loss, resulting in charge carrier isolation, heterogeneous current distribution, and poor electrochemical properties in ASSBs. Here, a simple, yet effective, solvent‐free electrode engineering approach with polytetrafluoroethylene (PTFE) as a binder for ASSBs is reported, enabling intimate contact and stable interfaces with the cathode. It is substantiated that the crystallinity of PTFE can be controlled depending on the heat history, and highly crystalline PTFE displays robust mechanical properties. High‐nickel LiNi0.8Mn0.1Co0.1O2 cathode prepared with crystalline PTFE show improved cycle and rate performances in ASSBs. In addition, it is revealed that the intimate contact between cathode particles with a stable cathode electrolyte layer is maintained during cycling by postmortem studies. This simple engineering method can be applied to prepare cathodes with a variety of active materials and solid electrolytes in ASSBs. [ABSTRACT FROM AUTHOR]

Lithium nitrate (LiNO3) has been the most studied electrolyte additive in lithium-sulfur (Li-S) cells, due to its known function of suppressing the shuttle effect in Li-S cells, which provides a significant increase in the cell's coulombic efficiency and cycling stability. Previous studies indicated that LiNO3 participated in the formation of a passive layer on the lithium electrode and thus suppressed the redox shuttle of the dissolved polysulfides. However, the effects of the LiNO3 on the positive electrode materials have rarely been investigated. By combining scanning electron microscopy, element-selective X-ray absorption spectroscopy, and electrochemical characterizations, we performed a comprehensive study of how the LiNO3 altered the properties of the sulfur electrode/electrolyte interface in Li-S cells and thus influenced the cell performance. We found that LiNO3 is a double-edged sword in the Li-S cell: on one hand, it increased the consumption of the active sulfur; on the other hand, it promoted the survival of the carbon matrix constituent in the sulfur electrode. These two competitive effects indicated that a proper moderate concentration of LiNO3 is required to achieve an optimized cell performance.

Lithium nitrate (LiNO3) has been the most studied electrolyte additive in lithium-sulfur (Li-S) cells, due to its known function of suppressing the shuttle effect in Li-S cells, which provides a significant increase in the cell's coulombic efficiency and cycling stability. Previous studies indicated that LiNO3 participated in the formation of a passive layer on the lithium electrode and thus suppressed the redox shuttle of the dissolved polysulfides. However, the effects of the LiNO3 on the positive electrode materials have rarely been investigated. By combining scanning electron microscopy, element-selective X-ray absorption spectroscopy, and electrochemical characterizations, we performed a comprehensive study of how the LiNO3 altered the properties of the sulfur electrode/electrolyte interface in Li-S cells and thus influenced the cell performance. We found that LiNO3 is a double-edged sword in the Li-S cell: on one hand, it increased the consumption of the active sulfur; on the other hand, it promoted the survival of the carbon matrix constituent in the sulfur electrode. These two competitive effects indicated that a proper moderate concentration of LiNO3 is required to achieve an optimized cell performance.

The solid-electrolyte interphase (SEI) is a key element in anode-electrolyte interactions and ultimately contributes to improving the lifespan and fast-charging capability of lithium-ion batteries. The conventional additive vinyl carbonate (VC) generates spatially dense and rigid poly VC species that may not ensure fast Li + transport across the SEI on the anode. Here, a synthetic additive called isosorbide 2,5-dimethanesulfonate (ISDMS) with a polar oxygen-rich motif is reported that can competitively coordinate with Li + ions and allow the entrance of PF 6 - anions into the core solvation structure. The existence of ISDMS and PF 6 - in the core solvation structure along with Li + ions enables the movement of anions toward the anode during the first charge, leading to a significant contribution of ISDMS and LiPF 6 to SEI formation. ISDMS leads to the creation of ionically conductive and electrochemically stable SEI that can elevate the fast-charging performance and increase the lifespan of LiNi 0.8 Co 0.1 (NCM811)/graphite full cells. Additionally, a sulfur-rich cathode-electrolyte interface with a high stability under elevated-temperature and high-voltage conditions is constructed through the sacrificial oxidation of ISDMS, thus concomitantly improving the stability of the electrolyte and the NCM811 cathode in a full cell with a charge voltage cut-off of 4.4 V.0.1 O 2 (NCM811)/graphite full cells. Additionally, a sulfur-rich cathode-electrolyte interface with a high stability under elevated-temperature and high-voltage conditions is constructed through the sacrificial oxidation of ISDMS, thus concomitantly improving the stability of the electrolyte and the NCM811 cathode in a full cell with a charge voltage cut-off of 4.4 V., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

High‐nickel ternary materials have attracted attention as advanced cathode materials for lithium‐ion batteries (LIBs) owing to their high energy density and low cost. However, the side reactions between carbonate‐based electrolytes and cathode materials under high voltages remain the most significant obstacle to the further application of high‐nickel LIBs. To develop superior LIBs, 4‐fluorobenzenesulfonylacetonitrile (FPSAN) is proposed as a new electrolyte additive to enhance the safety of high‐nickel LIBs. The results demonstrate that the easily decomposed FPSAN can form a protective film on the cathode surface, thereby improving the cycling stability and rate performance of the Li/LiNi0.83Co0.11Mn0.06O2 half‐cells. The FPSAN additive can also maintain the spinel shape of the LiNi0.83Co0.11Mn0.06O2 cathode particles. These results indicate that the FPSAN electrolyte additive can facilitate the application of high‐performance LiNi0.83Co0.11Mn0.06O2 cells. [ABSTRACT FROM AUTHOR]

Building a stable cathode-electrolyte interface (CEI) is crucial for achieving high-performance layered metal oxide cathode materials LiNi x Co y Mn 1-x-y O 2 (NCM). In this work, a novel 4-fluorobenzene isocyanate (4-FBC) electrolyte additive that contains isocyanate and benzene ring functional groups is proposed, which can form robust and homogeneous N-rich and benzene ring skeleton CEI film on the cathode surface, leading to significant improvement in the electrochemical performance of lithium-ion batteries. Taking LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) as an example, the NCM523/SiO@Graphite pouch full cells with electrolytes containing a mass fraction of 1% 4-FBC additives demonstrate improved capacity retention after 200 cycles, retaining capacity retention rates of 81.3%, which is much higher than that of 39.1% without additive. The improvement can be ascribed to the mitigation of electrolyte decomposition and inhibition of transition metal ions the dissolution from the cathode material due to the stable CEI film. Moreover, the electrochemical performance enhancement can also be achieved in high voltage and Ni-rich cathode materials, indicating the universality and effectiveness of this strategy for the practical applications of high energy density lithium-ion batteries., (© 2024 Wiley‐VCH GmbH.)

The LiCoO 2 (LCO) cathode is foreseen for extensive commercial applications owing to its high specific capacity and stability. Therefore, there is considerable interest in further enhancing its specific capacity by increasing the charging voltage. However, single-crystal LCO suffers from a significant capacity degradation when charged to 4.5 V due to the irreversible phase transition and unstable structure. Herein, an ultra-small amount (0.5% wt. in the electrode) of multi-functional PIM-1 (a polymer with intrinsic microporosity) additive is utilized to prepare a kind of binder-free electrode. PIM-1 modulates the solvation structure of LiPF 6 due to its unique structure, which helps to form a stable, robust, and inorganic-rich cathod-eelectrolyte interphase (CEI) film on the surface of LCO at a high voltage of 4.5 V. This reduces the irreversible phase transition of LCO, thereby enhancing the cyclic stability and improving the rate performance, providing new perspectives for the electrodes fabrication and improving LCO-based high-energy-density cathodes., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

The electrode–electrolyte interfaces play a critical role in influencing the cyclic stability, Coulombic efficiency, and safety of rechargeable batteries. Although there are many recent efforts for investigating the solid electrolyte interface formed on anodes, much less attention has been paid to examine the cathode–electrolyte interface (CEI) established on cathodes. Understanding of the chemistry, morphology, and structure of CEI layers is still illusive requiring further in‐depth characterization. The cryogenic electron microscopy is used to reveal a 1.1 nm thick CEI layer formed on a flower‐shaped, carbon‐coated Na3V2(PO4)3/C (NVP/C) cathode in ether‐based electrolyte for Na‐ion batteries. The rationally designed NVP/C cathode delivers cyclic stability with a capacity retention of over 88% at 50 mA g−1 after 1600 cycles and an excellent high‐rate capability at up to 3200 mA g−1. These findings may shed new light on the design of CEI layers to achieve high energy and power densities in rechargeable Na‐ion/metal batteries.

Solid‐state electrolytes (SEs) with high anodic (oxidation) stability are essential for achieving all‐solid‐state Li‐ion batteries (ASSLIBs) operating at high voltages. Until now, halide‐based SEs have been one of the most promising candidates due to their compatibility with cathodes and high ionic conductivity. However, the developed chloride and bromide SEs still show limited electrochemical stability that is inadequate for ultrahigh voltage operations. Herein, this challenge is addressed by designing a dual‐halogen Li‐ion conductor: Li3InCl4.8F1.2. F is demonstrated to selectively occupy a specific lattice site in a solid superionic conductor (Li3InCl6) to form a new dual‐halogen solid electrolyte (DHSE). With the incorporation of F, the Li3InCl4.8F1.2 DHSE becomes dense and maintains a room‐temperature ionic conductivity over 10−4 S cm−1. Moreover, the Li3InCl4.8F1.2 DHSE exhibits a practical anodic limit over 6 V (vs Li/Li+), which can enable high‐voltage ASSLIBs with decent cycling. Spectroscopic, computational, and electrochemical characterizations are combined to identify a rich F‐containing passivating cathode‐electrolyte interface (CEI) generated in situ, thus expanding the electrochemical window of Li3InCl4.8F1.2 DHSE and preventing the detrimental interfacial reactions at the cathode. This work provides a new design strategy for the fast Li‐ion conductors with high oxidation stability and shows great potential to high‐voltage ASSLIBs. [ABSTRACT FROM AUTHOR]

Low‐cost and environment‐friendly dual‐ion batteries (DIBs) with fast‐charging characteristics facilitate the development of high‐power energy storage devices. However, the incompatibility between the cathode and electrolyte at high voltage results in low Coulombic efficiency (CE) and short lifespan. Here, the addition of ≈0.5 wt% lithium difluoro(oxalate) borate salt into the electrolyte forms a robust and durable cathode–electrolyte interface (CEI) in situ on the graphite surface, which enables remarkable cycling of the graphite||Li battery with 87.5% capacity retention after 4000 cycles at 5 C and ultrafast rate capability with 88.8% capacity retention under 40 C (4 A g−1), delivering high‐power of 0.4–18.8 kW kg−1 at energy densities of 422.7–318.8 Wh kg−1. Taking advantage of this robust CEI, a graphite||graphite full battery demonstrates high reversible capacities of 97.6, 92.8, 88.7, and 85.4 mAh (g cathode)−1 at current rates of 10, 20, 30, and 40 C, respectively. The full battery also shows a long cycling life of over 6500 cycles with 92.4% capacity retention and an average CE of ≈99.4% at 1 A g−1, which is superior to other dual‐graphite (carbon) batteries in the literature. This work offers an effective interface‐stabilizing strategy on protecting graphite cathodes and a promising approach for developing DIBs with high‐power capability. [ABSTRACT FROM AUTHOR]

• Trace liquid electrolyte was used to enhance high-voltage stability of PEO solid electrolyte. • Liquid electrolyte is preferentially decomposed by cathode, forming CEI layer. • This work provides an innovative way for high-voltage PEO-based solid-state battery. Polyethylene oxide (PEO) is one of the promising substrates for polymer solid electrolyte. However, when coupled with high energy density nickel-rich layered cathode materials, PEO faces the risk of catalytic decomposition by delithium nickel-rich materials. In this work, the in-situ electrochemical passivation strategy is employed to obtain high voltage PEO-based solid-state lithium battery. Trace commercial liquid electrolyte was added on the surface of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) electrode, and liquid electrolyte is prior to PEO electrolyte to react with the cathode during charge/discharge process, leading to the formation of cathode-electrolyte interface (CEI) layer. The CEI layer avoids the direct contact between PEO and NCM811, thus effectively prevents PEO from being decomposed by NCM811 under high voltage. As a result, the optimized NCM811||PEO||Li battery displays enhanced electrochemical performance, especially cycling performance. This simple but effective strategy not only simplifies the manufacturing process, but also has instructional guidance for high-voltage PEO-based battery. [ABSTRACT FROM AUTHOR]

Lithium phosphate (Li3PO4) is a well-known solid electrolyte for lithium-ions. In this study, we analyzed the effects of Li3PO4 coating on the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 (NCM), a nickel-rich cathode. In particular, the coated materials exhibited enhanced cycle stability at high voltages and possessed superior rate capability. Among the cathodes with different coating levels (0.5–3 wt%), the one with 2 wt% of Li3PO4 provided the best rate capability, possibly because it is a moderate coating level at which the formation of an excessive cathode electrolyte interface (CEI) is suppressed. Thus, an optimal coating was achieved such that the inhibition in the ionic conduction by the excessive CEI is avoided, while the thickness of the coating layer, which can hinder the ionic transport as well, is minimal. The coated NCM effectively suppressed the formation of CEI, especially LiOH component with insulating nature, as revealed by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. As a result, the coated NCM retained more than 70% of the relative capacity, while pristine NCM retained only 35.1% relative capacity after cycling at 3.0–4.9 V vs. Li/Li+ for 200 cycles. This study demonstrates that an artificial CEI layer is effective for enhancing the high-voltage stability and rate capability of Ni-rich NCM cathodes. [ABSTRACT FROM AUTHOR]

Considering practical viability, Li-metal battery electrolytes should be formulated by tuning solvent composition similar to electrolyte systems for Li-ion batteries to enable the facile salt-dissociation, ion-conduction, and introduction of sacrificial additives for building stable electrode-electrolyte interfaces. Although 1,2-dimethoxyethane with a high-donor number enables the implementation of ionic compounds as effective interface modifiers, its ubiquitous usage is limited by its low-oxidation durability and high-volatility. Regulation of the solvation structure and construction of well-structured interfacial layers ensure the potential strength of electrolytes in both Li-metal and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811). This study reports the build-up of multilayer solid-electrolyte interphase by utilizing different electron-accepting tendencies of lithium difluoro(bisoxalato) phosphate (LiDFBP), lithium nitrate, and synthetic 1-((trifluoromethyl)sulfonyl)piperidine. Furthermore, a well-structured cathode-electrolyte interface from LiDFBP effectively addresses the issues with NCM811. The developed electrolyte based on a framework of highly- and weakly-solvating solvents with interface modifiers enables the operation of Li|NCM811 cells with a high areal capacity cathode (4.3 mAh cm -2 ) at 4.4 V versus Li/Li + ., (© 2024 Wiley‐VCH GmbH.)

Layered ternary oxide LiNi x Mn y Co 1- x - y O 2 is a promising cathode candidate for high-energy lithium-ion batteries (LIBs). However, the capacity of LIBs is significantly restricted by several factors, including the repeated dissolution-regeneration of the interfacial film at high temperatures, the dissolution of transition metals, and the increase of impedance. Herein, a new precycling strategy in suitable voltage scope at room temperature is proposed to construct a uniform, thermally stable, and insoluble cathode-electrolyte interface (CEI), which helps to maintain stable cycling performances at high temperatures. Specifically, after 5 precycles in the range of 3.85-4.3 V at room temperature, a CEI layer containing numerous inorganic components and oligomers is formed on the surface of LiNi 0.6 Mn 0.2 Co 0.2 O 2 . Subsequently, the harmful side reactions are effectively suppressed, endowing the cell with an excellent capacity retention of 84.67% after 50 cycles at 0.5C and 55 °C, much higher than that of 65.61% under the conventional film-forming process conditions. This work emphasizes the crucial role of the precycling strategy in regulating the characteristics of CEI layer on the surface of cathode electrode, opening up a new avenue for the high-temperature application of positive electrodes of LIBs.

LiNi0.8Co0.1Mn0.1O2 (NCM811) has received widespread attention due to its high discharge specific capacity. However, poor cycling performance and rate capacity limit its large-scale commercial applications. Here, we develop 4,5-Dicyano-1,3-dithiol-2-one (DDO) as a new type additive to enhance the cycling performance and rate capacity of NCM811/Li+ half cell. Electrochemical tests show that the discharge capacity retention rate of cell is 75.59% after 200 cycles with 0.1 wt% DDO-containing electrolyte, while the cell with blank electrolyte is only 15.11%. The initial coulomb efficiency and rate capacity with 0.1 wt% DDO are higher than the blank one. Through scanning electron microscope (SEM) analysis, the particle of NCM811 is smooth and integral after 50th cycled, while the particle ruptures in blank electrolyte. The outstanding electrochemical performance of NCM811 is attributed to the stable and uniform cathode electrolyte interphase (CEI) film formed by DDO. Moreover, X-ray photoelectron spectroscopy (XPS) reveals that DDO prevents the decomposition of carbonate solvents and nickel element dissolution of NCM811. Other tests also confirm that the robust CEI layer can reduce the polarization and internal resistance of the cell during cycles. [ABSTRACT FROM AUTHOR]

High‐capacity Li‐rich layered oxide cathodes along with Si‐incorporated graphite anodes have high reversible capacity, outperforming the electrode materials used in existing commercial products. Hence, they are potential candidates for the development of high‐energy‐density lithium‐ion batteries (LIBs). However, structural degradation induced by loss of interfacial stability is a roadblock to their practical use. Here, the use of malonic acid‐decorated fullerene (MA‐C60) with superoxide dismutase activity and water scavenging capability as an electrolyte additive to overcome the structural instability of high‐capacity electrodes that hampers the battery quality is reported. Deactivation of PF5 by water scavenging leads to the long‐term stability of the interfacial structures of electrodes. Moreover, an MA‐C60‐added electrolyte deactivates the reactive oxygen species and constructs an electrochemically robust cathode‐electrolyte interface for Li‐rich cathodes. This work paves the way for new possibilities in the design of electrolyte additives by eliminating undesirable reactive substances and tuning the interfacial structures of high‐capacity electrodes in LIBs. [ABSTRACT FROM AUTHOR]

Spinel-structured LiNi x Mn 2-x O 4 (LNMO), with low-cost earth-abundant constituents, is a promising high-voltage cathode material for lithium-ion batteries. Even though extensive electrochemical investigations have been conducted on these materials, few studies have explored correlations between their loss in performance and associated changes in microstructure. Here, down to the atomic scale, the structural evolution of these materials is investigated upon the progressive cycling of lithium-ion cells. Transgranular cracking is revealed to be a key feature during cycling; this cracking is initiated at the particle surface and leads to the penetration of electrolytes along the crack path, thereby increasing particle exposure to the electrolyte. The lattice structure on the crack surface shows spatial variances, featuring a top layer of rock-salt, a sublayer of a Mn 3 O 4 -like arrangement, and then a mixed-cation region adjacent to the bulk lattice. The transgranular cracking, along with the emergence of local lattice distortion, becomes more evident with extended cycling. Further, phase transformation at primary particle surfaces and void formation through vacancy condensation is found in the cycled samples. All these features collectively contribute to the performance degradation of the battery cells during electrochemical cycling., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

High nickel cathode material LiNi x Co y Mn 1-x-y O 2 (NCM) (x ≥ 0.6) has represented the most critical material in virtue of outstanding specific capacity and low self-discharge. However, the high surface alkalinity and detrimental interfacial stability lead to the parasitic reaction and a series of phase deterioration. Herein, in situ cross-linking binder molecular chains with a 3D network structure to construct a stable and robust electrode-electrolyte interface, which can maintain the structural integrity and restrain side reactions is designed. Simultaneously, the cross-linked polymer can form stable hydrogen bonds with the pristine binder, greatly enhancing the bonding property. More importantly, the functional groups contained in the cross-linked co-polymers can chemically anchor transition metals, effectively preventing the dissolution of transition metals. Theoretical calculations confirm the feasibility and advancement of the anchoring mechanism, driving excellent structural stability and inhibition of the NiO impurity phase. This work provides a practical strategy to realize the high stability of cathode materials., (© 2023 Wiley‐VCH GmbH.)

Spinel-structured solids were studied to understand if fast Li+ ion conduction can be achieved with Li occupying multiple crystallographic sites of the structure to form a “Li-stuffed” spinel, and if the concept is applicable to prepare a high mixed electronic-ionic conductive, electrochemically active solid solution of the Li+ stuffed spinel with spinel-structured Li-ion battery electrodes. This could enable a single-phase fully solid electrode eliminating multi-phase interface incompatibility and impedance commonly observed in multi-phase solid electrolyte–cathode composites. Materials of composition Li1.25M(III)0.25TiO4, M(III) = Cr or Al were prepared through solid-state methods. The room-temperature bulk Li+-ion conductivity is 1.63 × 10−4 S cm−1 for the composition Li1.25Cr0.25Ti1.5O4. Addition of Li3BO3 (LBO) increases ionic and electronic conductivity reaching a bulk Li+ ion conductivity averaging 6.8 × 10−4 S cm−1, a total Li-ion conductivity averaging 4.2 × 10−4 S cm−1, and electronic conductivity averaging 3.8 × 10−4 S cm−1 for the composition Li1.25Cr0.25Ti1.5O4 with 1 wt. % LBO. An electrochemically active solid solution of Li1.25Cr0.25Mn1.5O4 and LiNi0.5Mn1.5O4 was prepared. This work proves that Li-stuffed spinels can achieve fast Li-ion conduction and that the concept is potentially useful to enable a single-phase fully solid electrode without interphase impedance.

As a kind of potential cathode for sodium-ion batteries (SIBs), P2-type Na 2/3 Ni 1/3 Mn 2/3 O 2 (P2-NNMO) suffers from the dissolution of transition metals and severe side reactions in conventional electrolytes, which greatly deteriorates its electrochemical performance. Herein, an artificial cathode-electrolyte interface (CEI) is in situ constructed on P2-NNMO cathode based on a spontaneous redox reaction between P2-NNMO material and organic solvent tetrahydrofuran (THF). The uniform and robust CEI layer on P2-NNMO cathode (named P2-NNMO-T) mainly comprises organic Na-based species (R-O-Na, R-CO-Na, and R-O 2 CO-Na), and converts from an initial thickness of 2 nm into 4.6 nm after cycling. It can serve as a versatile interlayer to facilitate Na+ transport, shield the attack of electrolyte solvents, and suppress the transition metal dissolution effectively, thus boosting the cycling stability and fast charging capability of P2-NNMO cathodes. More importantly, the concept of in situ CEI construction can be extended to other layered oxides beyond SIBs discussed herein. [Display omitted] • In-situ construction of uniform and robust CEI was achieved through a novel and facile interface engineering approach. • The organic-rich CEI serves as a versatile interlayer to facilitate Na+ transport and shield the attack of electrolyte. • Interfacial organic-rich CEI suppresses the transition metal dissolution effectively. • In-situ CEI construction boosts the cycling stability and fast charging capability of P2-NNMO cathodes. [ABSTRACT FROM AUTHOR]

The development of K-based layered oxide cathodes is essential for boosting the competitiveness of potassium-ion batteries (PIBs) in grid-scale energy storage. However, their service life is dramatically limited by interfacial instability issues, which is still poorly understood. In this work, amorphous FePO 4 (a-FP) is built on K 0.5 Ni 0.1 Mn 0.9 O 2 (KNMO) as the protective skin, whose elasticity for strain relaxation and the K-conducting nature guarantee its integrity during fast and constant K-ion insertion/extraction. The conformal coating leads to a robust interphase on the cathode surface, which qualifies excellent K-transport ability and significantly suppresses the mechanical cracking and transition metal dissolution. Breakthrough in cycle life of the K-based layered cathodes is therefore achieved, which of the amorphous FePO 4 coated K 0.5 Ni 0.1 Mn 0.9 O 2 (KNMO@a-FP) reaches 2500 cycles. The insights gained from the surface protection layer construction and the in-depth analysis of its working mechanism pave the way for further development of K-based layered cathodes with both bulk structural and interfacial stability., (© 2023 Wiley-VCH GmbH.)

Abstract Ni-rich layered oxide (Ni-rich NCM) is a promising advanced cathode material for lithium-ion batteries (LIBs) because of its high specific capacity. However, the high Ni content in the layered structures is associated with poor surface stability, which in turn accelerates the capacity fading of the cell. To improve the interfacial stability of Ni-rich NCM cathode material, we propose poly(thiophene)-based artificial cathode-electrolyte interphase (CEI)-immobilized Ni-rich NCM cathode material, synthesized using a simple and convenient one-step spin-coating process. At room-temperature cycling, cells with thiophene-modified NCM811 cathodes exhibit improved cycling retention (>91.3%), compared those with bare NCM811 (84.2%). The effectiveness of the artificial CEI layer is evident during high-temperature cycling: cells with 36 kDa-NCM811 exhibit a specific capacity retention of 89.4%, whereas those with bare NCM811 exhibit a drastic decrease in the cycling retention capacity (55.1%) at 55 °C. XPS analyses reveal that the improved electrochemical performance of cells with cycled NCM811 cathodes is due to the surface stability of the cathode; the decomposed adducts in the recovered 36 kDa-NCM811 cathodes are less, whereas they are present in considerable amounts in the cycled NCM811 cathode. In addition, it is confirmed that the molecular weight of the polymer used for the artificial CEI-layer formation significantly affects the electrochemical performance of the cell; polymers with low molecular weights are preferred because P3HTs with low molecular weight have high crystallinity with a hard phase, particularly at high temperature, due to their low T g. Highlights • Thiophene-initiated artificial CEI layer is immobilized on Ni-rich NCM cathode. • Artificial CEI layer effectively suppresses electrolyte decomposition on electrode. • NCM modified by artificial CEI layer gives improved high temperature cycling. [ABSTRACT FROM AUTHOR]

In this study, 1-methyl-1-butylpiperidinium bis(trifluoromethanesulfonyl)-imide (PP 14 TFSI)-sulfolane/lithium difluoro(oxalato)borate (LiDFOB) based electrolytes with inherent thermal stability and low flammability are investigated as promising alternatives of conventional LiPF 6 /carbonate electrolyte in high voltage Li/Li 1.15 (Ni 0.36 Mn 0.64 ) 0.85 O 2 cells at elevated temperatures. The safe and stable electrolyte candidates are selected by optimizing relative composition and represent high oxidative stability (higher than 5.2 V vs Li/Li + ) above 55 °C. The Li/Li 1.15 (Ni 0.36 Mn 0.64 ) 0.85 O 2 cells with E60 electrolyte achieved 172.5 and 238.8 mAh g −1 after 50 cycles between 2.0 and 4.6 V at 0.5C at 55 and 70 °C. Moreover, the Li/Li 1.15 (Ni 0.36 Mn 0.64 ) 0.85 O 2 cell with E60 electrolyte obtains a superior discharge capacity of 97.9 mAh g −1 at high rate of 3C at 70 °C. At extremely high temperature of 85 °C, the cell with E60 electrolyte delivers 218.7 mAh g −1 after 50 cycles at 1C. The excellent cycling performance in high voltage Li/Li 1.15 (Ni 0.36 Mn 0.64 ) 0.85 O 2 cells at elevated temperatures is attributed to the intrinsic oxidative stability and the compact and stable cathode-electrolyte interface (CEI) film derived from E60 electrolyte. We believe it a promising candidate that can be safely used for high voltage Li-rich cells at elevated temperature. [ABSTRACT FROM AUTHOR]

Lithium manganese oxide, LiMn2O4 (LMO) is a promising cathode material, but is hampered by significant capacity fade due to instability of the electrode-electrolyte interface, manganese dissolution into the electrolyte and subsequent mechanical degradation of the electrode. In this work, electrochemically-induced strains in composite LMO electrodes are measured using the digital image correlation (DIC) technique and compared with electrochemical impedance spectroscopy (EIS) measurements of surface resistance for different scan rates. Distinct, irreversible strain variations are observed during the first delithiation cycle. The changes in strain and surface resistance are highly sensitive to the electrochemical changes occurring during the first cycle and correlate with prior reports of the removal of the native surface layer and the formation of cathode-electrolyte interface layer on the electrode surface. A large capacity fade is observed with increasing cycle number at high scan rates. Interestingly, the total capacity fade scales proportionately to the strain generated after each lithiation and delithiation cycle. The simultaneous reduction in capacity and strain is attributed to chemo-mechanical degradation of the electrode. The in situ strain measurements provide new insight into the electrochemical-induced volumetric changes in LMO electrodes with progressing cycling and may provide guidance for materials-based strategies to reduce strain and capacity fade. [ABSTRACT FROM AUTHOR]