LiCoO2 Surface Research Articles

Densification of Cathode/Electrolyte Interphase to Enhance Reversibility of LiCoO2 at 4.65V.

For LiCoO2 (LCO) operated beyond 4.55V (vs Li/Li+), it usually suffers from severe surface degradation. Constructing a robust cathode/electrolyte interphase (CEI) is effective to alleviate the above issues, however, the correlated mechanisms still remain vague. Herein, a progressively reinforced CEI is realized via constructing Zr─O deposits (ZrO2 and Li2ZrO3) on LCO surface (i.e., Z-LCO). Upon cycle, these Zr─O deposits can promote the decomposition of LiPF6, and progressively convert to the highly dispersed Zr─O─F species. In particular, the chemical reaction between LiF and Zr─O─F species further leads to the densification of CEI, which greatly reinforces its toughness and conductivity. Combining the robust CEI and thin surface rock-salt layer of Z-LCO, several benefits are achieved, including stabilizing the surface lattice oxygen, facilitating the interface Li+ transport kinetics, and enhancing the reversibility of O3/H1-3 phase transition, etc. As a result, the Z-LCO||Li cells exhibit a high capacity retention of 84.2% after 1000 cycles in 3-4.65V, 80.9% after 1500 cycles in 3-4.6V, and a high rate capacity of 160mAhg-1 at 16 C (1 C=200mAg-1). This work provides a new insight for developing advanced LCO cathodes.

Enhanced interfacial and cycle stability of 4.6 V LiCoO2 cathode achieved by surface modification of KAlF4

Lithium cobalt oxide is one of the most popular cathode materials for lithium-ion batteries. Due to its relatively low capacity, increasing the output voltage is often necessary to release more capacity. However, subjecting cathode materials to high charging potentials inevitably induces surface-side reactions, compromising the integrity of the crystal structure and accelerating capacity degradation. Therefore, the stability of cathode materials at high voltage becomes crucial for lithium-ion batteries. In this study, we employed the ternary compound KAlF4 (KAF) as a surface modification coating for LiCoO2 (LCO). With the optimized ratio (1 wt%) of KAF, coated LCO cathodes exhibited enhanced capacity retention, excellent cycling, and rate stability. In the high voltage range of 3.0–4.6 V, the specific capacity of the initial discharge at a rate of 0.5 C reached 198.30 mA h g−1. Remarkably, the coated LCO retained 91.56 % of its initial capacity after 200 cycles at 0.5 C. Even at a high rate of 5 C, the coated sample retained a discharge capacity of 120.87 mA h g−1, significantly higher than that of bare LCO (80.24 mA h g−1). After a thorough investigation into the structure changes before and after cycling, we elucidated the mechanism of KAF coating in improving the stability of high-voltage LCO cathodes. The results indicated that KAF forms a stable passivation layer on the surface of LCO, which suppresses cracking and corrosion during charging and discharging, eventually stabilizes the crystal structure, and enhances the cycling stability of LCO.

Construction of Sulfone‐Based Polymer Electrolyte Interface Enables the High Cyclic Stability of 4.6 V LiCoO2 Cathode by In Situ Polymerization

AbstractLithium cobalt oxide (LiCoO2) is considered an indispensable cathode material in the realm of consumer electronic batteries due to its high volumetric energy density. However, at a charging cut‐off voltage as high as 4.6 V, significant interfacial side reactions between LiCoO2 and the electrolyte occur, which adversely impact the battery's cycle performance. The surface‐related issues of LiCoO2 at high charge voltages not only constrain its utilization in conventional lithium‐ion batteries with liquid electrolytes but also limit its application in solid‐state batteries. Although traditional coating methods using inert inorganic compounds can partially alleviate this issue, their point‐like coatings fail to completely prevent the surface of LiCoO2 from direct contact with the electrolyte. The exploration of novel surface protection strategies for LiCoO2 remains imperative to address the associated challenges. Herein, introducing a sulfone‐based polymer electrolyte interface is proposed on the surface of LiCoO2 using methyl vinyl sulfone (MVS) through in situ polymerization. Remarkably, LiCoO2 with sulfone‐based polymer electrolyte interface exhibits a capacity retention rate of 83% after 500 cycles when employing a carbonate electrolyte without additives at a charge cut‐off voltage of 4.6 V. Furthermore, the LiCoO2 and polymer electrolyte interface exhibits exceptional cycle stability when paired with polyether solid electrolytes that do not possess high voltage tolerance. Moreover, the incorporation of a polymer electrolyte interface not only enhances the cycle stability of LiCoO2 but also improves its thermal stability. This work presents novel research perspectives for exploring high‐voltage stable LiCoO2.

Scalable Precise Nanofilm Coating and Gradient Al Doping Enable Stable Battery Cycling of LiCoO2 at 4.7 V

AbstractThe quest for smart electronics with higher energy densities has intensified the development of high‐voltage LiCoO2 (LCO). Despite their potential, LCO materials operating at 4.7 V faces critical challenges, including interface degradation and structural collapse. Herein, we propose a collective surface architecture through precise nanofilm coating and doping that combines an ultra‐thin LiAlO2 coating layer and gradient doping of Al. This architecture not only mitigates side reactions, but also improves the Li+ migration kinetics on the LCO surface. Meanwhile, gradient doping of Al inhibited the severe lattice distortion caused by the irreversible phase transition of O3−H1−3−O1, thereby enhanced the electrochemical stability of LCO during 4.7 V cycling. DFT calculations further revealed that our approach significantly boosts the electronic conductivity. As a result, the modified LCO exhibited an outstanding reversible capacity of 230 mAh g−1 at 4.7 V, which is approximately 28 % higher than the conventional capacity at 4.5 V. To demonstrate their practical application, our cathode structure shows improved stability in full pouch cell configuration under high operating voltage. LCO exhibited an excellent cycling stability, retaining 82.33 % after 1000 cycles at 4.5 V. This multifunctional surface modification strategy offers a viable pathway for the practical application of LCO materials, setting a new standard for the development of high‐energy‐density and long‐lasting electrode materials.

Scalable Precise Nanofilm Coating and Gradient Al Doping Enable Stable Battery Cycling of LiCoO2 at 4.7 V.

The quest for smart electronics with higher energy densities has intensified the development of high-voltage LiCoO2 (LCO). Despite their potential, LCO materials operating at 4.7 V faces critical challenges, including interface degradation and structural collapse. Herein, we propose a collective surface architecture through precise nanofilm coating and doping that combines an ultra-thin LiAlO2 coating layer and gradient doping of Al. This architecture not only mitigates side reactions, but also improves the Li+ migration kinetics on the LCO surface. Meanwhile, gradient doping of Al inhibited the severe lattice distortion caused by the irreversible phase transition of O3-H1-3-O1, thereby enhanced the electrochemical stability of LCO during 4.7 V cycling. DFT calculations further revealed that our approach significantly boosts the electronic conductivity. As a result, the modified LCO exhibited an outstanding reversible capacity of 230 mAh g-1 at 4.7 V, which is approximately 28 % higher than the conventional capacity at 4.5 V. To demonstrate their practical application, our cathode structure shows improved stability in full pouch cell configuration under high operating voltage. LCO exhibited an excellent cycling stability, retaining 82.33 % after 1000 cycles at 4.5 V. This multifunctional surface modification strategy offers a viable pathway for the practical application of LCO materials, setting a new standard for the development of high-energy-density and long-lasting electrode materials.

Superior stable high‐voltage LiCoO2 enabled by modification with a layer of lithiated polyvinylidene fluoride‐derived LiF

AbstractHigh‐voltage LiCoO2 (LCO) can deliver a high capacity and therefore significantly boost the energy density of Li‐ion batteries (LIBs). However, its cyclability is still a major problem in terms of commercial applications. Herein, we propose a simple but effective method to greatly improve the high‐voltage cyclability of an LCO cathode by constructing a surface LiF modification layer via pyrolysis of the lithiated polyvinylidene fluoride (Li‐PVDF) coating under air atmosphere. Benefitting from the good film‐forming and strong adhesion ability of Li‐PVDF, the thus‐obtained LiF layer is uniform, dense, and conformal; therefore, it is capable of acting as a barrier layer to effectively protect the LCO surface from direct exposure to the electrolyte, thus suppressing the interfacial side reactions and surface structure deterioration. Consequently, the high‐voltage stability of the LCO electrode is significantly enhanced. Under a high charge cutoff voltage of 4.6 V, the LiF‐modified LCO (LiF@LCO) cathode demonstrates a high capacity of 201 mA h g−1 at 0.1 C and a stable cycling performance at 0.5 C with 80.5% capacity retention after 700 cycles, outperforming the vast majority of high‐voltage LCO cathodes reported so far.

Hybrid Surface Modification and Bulk Doping Enable Spent LiCoO2 Cathodes for High-Voltage Operation.

The emerging market demand for high-energy-density of energy storage devices is pushing the disposal of end-of-life LiCoO2 (LCO) to shift toward sustainable upgrading into structurally stable high-voltage cathode materials. Herein, an integrated bulk and surface commodification strategy is proposed to render spent LCO (S-LCO) to operate at high voltages, involving bulk Mn doping, near surface P gradient doping, and Li3PO4/CoP (LPO/CP) coating on the LCO surface to yield upcycled LCO (defined as MP-LCO@LPO/CP). Benefiting from hybrid surface coating with Li+-conductive Li3PO4 (LPO) and electron conductive CoP (CP) coupled with Mn and P co-doping, the optimized MP-LCO@LPO/CP cathode exhibits enhanced high-voltage performance, delivering an initial discharge capacity of 218.8 mAh g-1 at 0.2 C with excellent capacity retention of 80.9% (0.5 C) after 200 cycles at a cut-off voltage of 4.6V, along with 96.3% of capacity retention over 100 cycles at 4.5V. These findings may afford meaningful construction for the upcycling of commercial S-LCO into next-generation upmarket cathode materials through the elaborate surface and bulk modification design.

A Highly-Fluorinated Lithium Borate Main Salt Empowering Stable Lithium Metal Batteries.

Traditional lithium salts are difficult to meet practical application demand of lithium metal batteries (LMBs) under high voltages and temperatures. LiPF6, as the most commonly used lithium salt, still suffers from notorious moisture sensitivity and inferior thermal stability under those conditions. Here, we synthesize a lithium salt of lithium perfluoropinacolatoborate (LiFPB) comprising highly-fluorinated and borate functional groups to address the above issues. It is demonstrated that the LiFPB shows superior thermal and electrochemical stability without any HF generation under high temperatures and voltages. In addition, the LiFPB can form a protective outer-organic and inner-inorganic rich cathode electrolyte interphase on LiCoO2 (LCO) surface. Simultaneously, the FPB- anions tend to integrate into lithium ion solvation structure to form a favorable fast-ion conductive LiBxOy based solid electrolyte interphase on lithium (Li) anode. All these fantastic features of LiFPB endow LCO (1.9 mAh cm-2)/Li metal cells excellent cycling under both high voltages and temperatures (e.g., 80 % capacity retention after 260 cycles at 60 °C and 4.45 V), and even at an extremely elevated temperature of 100 °C. This work emphasizes the important role of salt anions in determining the electrochemical performance of LMBs at both high temperature and voltage conditions.

A Highly‐Fluorinated Lithium Borate Main Salt Empowering Stable Lithium Metal Batteries

AbstractTraditional lithium salts are difficult to meet practical application demand of lithium metal batteries (LMBs) under high voltages and temperatures. LiPF6, as the most commonly used lithium salt, still suffers from notorious moisture sensitivity and inferior thermal stability under those conditions. Here, we synthesize a lithium salt of lithium perfluoropinacolatoborate (LiFPB) comprising highly‐fluorinated and borate functional groups to address the above issues. It is demonstrated that the LiFPB shows superior thermal and electrochemical stability without any HF generation under high temperatures and voltages. In addition, the LiFPB can form a protective outer‐organic and inner‐inorganic rich cathode electrolyte interphase on LiCoO2 (LCO) surface. Simultaneously, the FPB− anions tend to integrate into lithium ion solvation structure to form a favorable fast‐ion conductive LiBxOy based solid electrolyte interphase on lithium (Li) anode. All these fantastic features of LiFPB endow LCO (1.9 mAh cm−2)/Li metal cells excellent cycling under both high voltages and temperatures (e.g., 80 % capacity retention after 260 cycles at 60 °C and 4.45 V), and even at an extremely elevated temperature of 100 °C. This work emphasizes the important role of salt anions in determining the electrochemical performance of LMBs at both high temperature and voltage conditions.

Boosting the electrochemical performance of LiCoO2 by triple-phase interface via “island-bridge” shaped surface coating

Surface coating as an effective strategy has been extensively utilized to enhance the surface/interface stability of cathode for lithium-ion batteries. As widely recognized, the electrochemical performance of coated cathode is greatly dependent on the properties of coating layer. Rational design on the structure and composition of coating layer becomes crucial. Here, a unique “island-bridge” shaped Zr-based coating layer has been constructed through a facile synthetic protocol. This coating layer composes of several high-crystalline ZrO2 nanoparticles and a thin low-crystalline zirconium hydroxide layer that connects these nanoparticles, forming a typical “island-bridge” structure. The successful formation of such a unique coating layer was demonstrated to be related to the usage amount of Zr source and the calcined temperature. The novel “island-bridge” coating has been successfully applied to modify the surface of LiCoO2, showing excellent capability on improving the electrochemical performance. The unique “island-bridge” structure coating induces the formation of a triple-phase interface, namely island-cathode-bridge interface. Theoretical calculation suggests that such an island-cathode-bridge triple-phase interface can effectively reduce the Li+ diffusion energy, leading to favorable Li+ transportation kinetics and suppressed cathode-electrolyte interface evolution. Furthermore, this “island-bridge” layer can well prevent direct contact between LiCoO2 and electrolyte, enhancing the surface/interface stability, resulting in improved cyclic performance. This work provides new insights into the rational design of surface coating for high-energy density cathodes.

Construction of Uniform LiF Coating Layers for Stable High-Voltage LiCoO2 Cathodes in Lithium-Ion Batteries.

Stabilizing LiCoO2 (LCO) at 4.5 V rather than the common 4.2 V is important for the high specific capacity. In this study, we developed a simple and efficient way to improve the stability of LiCoO2 at high voltages. After a simple sol-gel method, we introduced trifluoroacetic acid (TA) to the surface of LCO via an afterwards calcination. Meanwhile, the TA reacted with residual lithium on the surface of LCO, further leading to the formation of uniform LiF nanoshells. The LiF nanoshells could effectively restrict the interfacial side reaction, hinder the transition metal dissolution and thus achieve a stable cathode-electrolyte interface at high working-voltages. As a result, the LCO@LiF demonstrated a much superior cycling stability with a capacity retention ratio of 83.54% after 100 cycles compared with the bare ones (43.3% for capacity retention), as well as high rate performances. Notably, LiF coating layers endow LCO with excellent high-temperature performances and outstanding full-cell performances. This work provides a simple and effective way to prepare stable LCO materials working at a high voltage.

In-situ cathode coating for all-solid-state batteries by freeze-drying technology

All solid-state batteries (ASSBs) are considered in the next generation of energy storage, but their active material ratio is low and cathode interface reactions are severe.To overcome these two challenges, a layer of fast ion conductor Li3InCl6 is in-situ synthesized to realize uniform coating on LiCoO2 surface by freeze drying technology, which effectively improves active material proportions/ion transportation capability in the cathode, and prevents interfacial degradation between sulfide solid electrolyte and LiCoO2. The resultant Li-anode ASSBs show excellent electrochemical performances, including 7000 cycles at 20 C (9.4 mA/cm2), unprecedented current rates of 70 C and high loading of 15 mAh/cm2 (110 mg/cm2). The ASSB achieved an energy density of 340 Wh/kg. These encouraging results make future practical applications of high-energy-density ASSB with high cathode loadings and fast-charging capabilities possible.

Enhanced all-solid-state battery performance through in-situ construction of interface modification layer

The development of high-performance all-solid-state lithium batteries (ASSLBs) relies on improving the interface stability between layered oxide cathodes and sulfide electrolytes, as well as the structural stability of cathode active materials. While coating technology is considered an effective solution, the fabrication of these coating materials using economically viable and scalable manufacturing processes remains a comprehensive and challenging task. In this study, a combination of first-principles calculations and experiments is employed to propose, for the first time, a simple and scalable aqueous process to in-situ construct an Li3VO4 (LVO) buffer coating on the surface of LiCoO2(LCO) cathode, which exhibits high ionic conductivity, relatively low electronic conductivity, and high oxidation limit. The LVO buffering coating not only facilitates the migration of lithium ions at the interface, effectively suppresses interface side reactions, and reduces interface impedance, but also enhances the mechanical and structural stability of the cathode material. As a result, the LCO/LPSC/Li-In ASSLBs with 2% LVO coating exhibit an initial discharge capacity of up to 145.6 mAh g−1 at room temperature (0.1C), with a capacity retention of 94.89% after 100 cycles. Furthermore, the ASSLBs demonstrate good capacity and cycle stability under extreme testing conditions, including high voltage, high temperature, and low temperature, especially exhibiting an initial discharge capacity of up to 114.9 mAh g−1 at −20 °C.

Enhanced Cathode Performance: The Heterostructure Construction of LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12.

In this study, the heterostructure cathode material LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12 was prepared by coating Li6.4La3Zr1.4Ta0.6O12 on the surface of LiCoO2 through a one-step solid-phase synthesis. The morphology, structure, electrical state, and elemental contents of both pristine and modified materials were assessed through a range of characterization techniques. Theoretical calculations revealed that the LCO@LLZTO material possessed a reduced diffusion barrier compared to LiCoO2, thereby facilitating the movement of Li ions. Electrochemical tests indicated that the capacity retention rate of the modified cathode composites stood at 70.43% following 300 cycles at a 2C rate. This high rate occurred because the Li6.4La3Zr1.4Ta0.6O12 film on the surface enhanced the migration of Li+, and the spinel phase of Co3O4 had better interfacial stability to alleviate the generation of microcracks by inhibiting the phase change from the layered phase to the rock-salt phase, which considerably improved the electrochemical properties.

Surface Lattice Modulation Enables Stable Cycling of High‐Loading All‐solid‐state Batteries at High Voltages

AbstractHalide solid electrolytes, known for their high ionic conductivity at room temperature and good oxidative stability, face notable challenges in all–solid–state Li–ion batteries (ASSBs), especially with unstable cathode/solid electrolyte (SE) interface and increasing interfacial resistance during cycling. In this work, we have developed an Al3+–doped, cation–disordered epitaxial nanolayer on the LiCoO2 surface by reacting it with an artificially constructed AlPO4 nanoshell; this lithium–deficient layer featuring a rock–salt–like phase effectively suppresses oxidative decomposition of Li3InCl6 electrolyte and stabilizes the cathode/SE interface at 4.5 V. The ASSBs with the halide electrolyte Li3InCl6 and a high–loading LiCoO2 cathode demonstrated high discharge capacity and long cycling life from 3 to 4.5 V. Our findings emphasize the importance of specialized cathode surface modification in preventing SE degradation and achieving stable cycling of halide–based ASSBs at high voltages.

Surface Lattice Modulation Enables Stable Cycling of High-Loading All-solid-state Batteries at High Voltages.

Halide solid electrolytes, known for their high ionic conductivity at room temperature and good oxidative stability, face notable challenges in all-solid-state Li-ion batteries (ASSBs), especially with unstable cathode/solid electrolyte (SE) interface and increasing interfacial resistance during cycling. In this work, we have developed an Al3+-doped, cation-disordered epitaxial nanolayer on the LiCoO2 surface by reacting it with an artificially constructed AlPO4 nanoshell; this lithium-deficient layer featuring a rock-salt-like phase effectively suppresses oxidative decomposition of Li3InCl6 electrolyte and stabilizes the cathode/SE interface at 4.5 V. The ASSBs with the halide electrolyte Li3InCl6 and a high-loading LiCoO2 cathode demonstrated high discharge capacity and long cycling life from 3 to 4.5 V. Our findings emphasize the importance of specialized cathode surface modification in preventing SE degradation and achieving stable cycling of halide-based ASSBs at high voltages.

Multifunctional Umbrella: In Situ Interface Film Forming on the High-Voltage LiCoO2 Cathode by a Tiny Amount of Nanoporous Polymer Additives for High-Energy-Density Li-Ion Batteries.

The LiCoO2 (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 4.5V 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 LiPF6 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 4.5V. 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.

A H+/Li+ Ion Exchange Induced Spinel Ion‐Conductive Interphase Stabilizes 4.5 V LiCoO2 in Sulfide‐Based All‐Solid‐State Lithium Battery

AbstractAll‐solid‐state lithium batteries (ASSLIBs) show significant promise as the next‐generation energy technology due to their high energy density and inherent safety. However, the severe interface reactions between solid electrolyte and the high‐voltage cathodes pose a major challenge, particularly at higher charge voltages. Herein, a H3PO4‐triggered H+/Li+ exchange strategy is proposed to covert LiCoO2 (LCO) surface to spinel Co3O4/Li3PO4 ionic‐conductive interphase. This spinel interphase presents a thickness of 15 nm and good affinity with LCO, which provides long‐lasting protection to suppress interfacial parasitic reactions. Besides, both spinel Co3O4 and amorphous Li3PO4 feature high ionic conductivity compared to bulk LCO, thereby facilitating the interfacial ionic transportation. With such modification, ASSLIBs delivers high specific capacity (146.2 mAh g−1 at 0.1 C), outstanding rate performance (116.4 mAh g−1 at 2 C), and long‐term cyclability (350 cycles at 0.5 C) under a cut‐off voltage of 4.3 V versus Li/Li+. Moreover, this robust spinel interphase further improves the stable cycling (168.9 mAh g−1 at 0.1 C for 100 cycles) under elevated cut‐off voltage (4.5 V vs Li/Li+). This finding highlights the H+/Li+ exchange to convert LCO surface to a spinel ionic‐conductive interphase, which poses new insights for interface design in ASSLIBs.

Diffusion-Optimized Long Lifespan 4.6V LiCoO2: Homogenizing Cycled Bulk-To-Surface Li Concentration with Reduced Structure Stress.

Increasing the charging cut-off voltage (e.g., 4.6V) to extract more Li ions are pushing the LiCoO2 (LCO) cathode to achieve a higher energy density. However, an inhomogeneous cycled bulk-to-surface Li distribution, which is closely associated with the enhanced extracted Li ions, is usually ignored, and severely restricts the design of long lifespan high voltage LCO. Here, a strategy by constructing an artificial solid-solid Li diffusion environment on LCO's surface is proposed to achieve a homogeneous bulk-to-surface Li distribution upon cycling. The diffusion optimized LCO not only shows a highly reversible capacity of 212mAhg-1 but also an ultrahigh capacity retention of 80% over 600cycles at 4.6V. Combined in situ X-ray diffraction measurements and stress-evolution simulation analysis, it is revealed that the superior 4.6V long-cycled stability is ascribed to a reduced structure stress leaded by the homogeneous bulk-to-surface Li diffusion. This work broadens approaches for the design of highly stable layered oxide cathodes with low ion-storage structure stress.

Mechanically and Thermally Stable Cathode Electrolyte Interphase Enables High-temperature, High-voltage Li||LiCoO2 Batteries.

The development of high-energy-density Li||LiCoO2 batteries is severely limited by the instability of cathode electrolyte interphase (CEI) at high voltage and high temperature. Here we propose a mechanically and thermally stable CEI by electrolyte designing for achieving the exceptional performance of Li||LiCoO2 batteries at 4.6 V and 70 °C. 2,4,6-tris(3,4,5-trifluorophenyl)boroxin (TTFPB) as the additive could preferentially enter into the first shell structure of PF6 - solvation and be decomposed on LiCoO2 surface at low oxidation potential to generate a LiBx Oy -rich/LiF-rich CEI. The LiBx Oy surface layer effectively maintained the integrity of CEI and provided excellent mechanical and thermal stability while abundant LiF in CEI further improved the thermal stability and homogeneity of CEI. Such CEI drastically alleviated the crack and regeneration of CEI and irreversible phase transformation of the cathode. As expected, the Li||LiCoO2 batteries with the tailored CEI achieved 91.9 % and 74.0 % capacity retention after 200 and 150 cycles at 4.6 and 4.7 V, respectively. Moreover, such batteries also delivered an unprecedented high-temperature performance with 73.6 % capacity retention after 100 cycles at 70 °C and 4.6 V.