Stabilizing Interlayer Repulsion in Layered Sodium-Ion Oxide Cathodes via Hierarchical Layer Modification.

Layered sodium-ion oxides hold considerable promise in achieving high-performance sodium-ion batteries. However, the notorious phase transformation during charging, attributed to increased O2-─O2- repulsion, results in substantial performance decay. Here, a hierarchical layer modification strategy is proposed to stabilize interlayer repulsion. During desodiation, migrated Li+ from the transition metal layer and anchored Ca2+ in sodium sites maintain the cationic content within the sodium layer. Meanwhile, partial oxygen substitution by fluorine and the involvement of oxygen in redox reactions increase the average valence of the oxygen layer. This sustained cation presence and elevated anion valence collectively mitigate increasing O2-─O2- repulsion during sodium extraction, enabling the Na0.61Ca0.05[Li0.1Ni0.23Mn0.67]O1.95F0.05 (NCLNMOF) cathode to retain a pure P2-type structure across a wide voltage range. Unexpected insights reveal the interplay between different doping elements: the robust Li─F bonds and Ca2+ steric effects suppressing Li+ loss. The NCLNMOF electrode exhibits 82.5% capacity retention after 1000 cycles and a high-rate capability of 94 mAh g-1 at 1600 mA g-1, demonstrating the efficacy of hierarchical layer modification for high-performance layered oxide cathodes.

Achieving Superior Cyclability Pouch Cells with Oxygen Vacancy-Moderated P'2/P3 Hybrid Layered Sodium Cathode Materials.

Layered P2-type sodium manganese oxide has emerged as a promising cathode candidate for sodium-ion batteries due to its appealing cost-effectiveness and high discharge voltage. However, its practical capacity within the voltage range of 2.0-4.0 V (vs Na+/Na) is relatively low, and its rate capability is hampered by the adverse charge/vacancy ordering during charge/discharge. In this study, a layered P'2/P3 mixed-phase Na0.8-aMn0.675Ni0.225Li0.1O2-x cathode with high (003) crystal plane intensity was designed by introducing oxygen vacancies to P2-structured materials. Aided by these advantages, the hybrid cathode material demonstrates impressive structural and thermal stability and faster Na-ion diffusion kinetics compared to a regular P2 material. Half-cell shows an initial discharge capacity retention of 101 mA h/g at 12 mA/g and 92.25% retention after 500 cycles at 120 mA/g. In combination with a hard carbon anode, the 0.5 A h pouch cell achieved a prevailing capacity retention of 95.2% after 2600 cycles at 36 mA/g. This work opens new dimensions for layered cathode materials with the aim of achieving superior cyclabilities.

Molybdenum-Doped Cobalt-Free Cathode Realizing the Electrochemical Stability by Enhanced Covalent Bonding.

The doping strategy effectively enhances the capacity and cycling stability of cobalt-free nickel-rich cathodes. Understanding the intrinsic contributions of dopants is of great importance to optimize the performances of cathodes. This study investigates the correlation between the structure modification and their performances of Mo-doped LiNi0.8Mn0.2O2 (NM82) cathode. The role of doped Mo's valence state has been proved functional in both lattice structural modification and electronic state adjustment. Although the high-valence of Mo at the cathode surface inevitably reduces Ni valence for electronic neutrality and thus causes ion mixing, the original Mo valence will influence its diffusion depth. Structural analyses reveal Mo doping leads to a mixed layer on the surface, where high-valence Mo forms a slender cation mixing layer, enhancing structural stability and Li-ion transport. In addition, it is found that the high-valence dopant of Mo6+ ions partially occupies the unfilled 4d orbitals, which may strengthen the Mo─O bond through increased covalency and therefore reduce the oxygen mobility. This results in an impressive capacity retention (90.0% after 200 cycles) for Mo-NM82 cathodes with a high Mo valence state. These findings underscore the valence effect of doping on layered oxide cathode performance, offering guidance for next-generation cathode development.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials.

Sodium-ion batteries (SIBs) as a promising technology for large-scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode-electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra-stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM-CS-GMg) cathode material in which a Mg-free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg-hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered-to-rock-salt phase transition and the resultant microcracks. Besides, the less formation of high-valence TM ions on the surface contributes to a stable cathode-electrolyte interface. The as-prepared NCM-CS-GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Ni-Rich Layered Oxide Cathodes/Sulfide Electrolyte Interface in Solid-State Lithium Battery.

Because of the high specific capacity and low cost, Ni-rich layered oxide (NRLO) cathodes are one of the most promising cathode candidates for the next high-energy-density lithium-ion batteries. However, they face structure and interface instability challenges, especially the battery safety risk caused by using an intrinsic flammable organic liquid electrolyte. In this regard, a solid electrolyte with high safety is of great significance to promote the development of energy storage. Among them, sulfide electrolytes are considered to be the most potential substitutes for liquid electrolytes because of their high ionic conductivity and good processing properties. Nevertheless, the interfacial incompatibility between the sulfide electrolyte and NRLO cathode is the critical challenge for high-performance sulfide all-solid-state lithium batteries (ASSLBs). In this review, we summarize the problems of the Ni-rich cathode/sulfide solid electrolyte interface and the strategies to improve the interface stability. On the basis of these insights, we highlight the scientific problems and technological challenges that need to be resolved urgently and propose several potential directions to further improve the interface stability. The objective of this study is to provide a comprehensive understanding and insightful recommendations for the enhancement of the sulfide ASSLBs with NRLO cathode.

Unexpected Elevated Working Voltage by Na+/Vacancy Ordering and Stabilized Sodium-Ion Storage by Transition-Metal Honeycomb Ordering.

Na+/vacancy ordering in sodium-ion layered oxide cathodes is widely believed to deteriorate the structural stability and retard the Na+ diffusion kinetics, but its unexplored potential advantages remain elusive. Herein, we prepared a P2-Na0.8Cu0.22Li0.08Mn0.67O2 (NCLMO-12 h) material featuring moderate Na+/vacancy and transition-metal (TM) honeycomb orderings. The appropriate Na+/vacancy ordering significantly enhances the operating voltage and the TM honeycomb ordering effectively strengthens the layered framework. Compared with the disordered material, the well-balanced dual-ordering NCLMO-12 h cathode affords a boosted working voltage from 2.85 to 3.51 V, a remarkable ~20 % enhancement in energy density, and a superior cycling stability (capacity retention of 86.5 % after 500 cycles). The solid-solution reaction with a nearly "zero-strain" character, the charge compensation mechanisms, and the reversible inter-layer Li migration upon sodiation/desodiation are unraveled by systematic in situ/ex situ characterizations. This study breaks the stereotype surrounding Na+/vacancy ordering and provides a new avenue for developing high-energy and long-durability sodium layered oxide cathodes.

Architecting O3/P2 layered oxides by gradient Mn doping for sodium-ion batteries.

O3 phase layered oxides are highly attractive cathode materials for sodium-ion batteries because of their high capacity and decent initial Coulombic efficiency. However, their rate capability and long cycling life are unsatisfactory due to the narrow Na+ transfer channel and irreversible phase transitions of O3 phase during sodiation/desodiation process. Constructing O3/P2 multiphase structures has been proven to be an effective strategy to overcome these challenges. In this study, we synthesized bi-phasic structured O3/P2 Na(Ni2/9Fe1/3Cu1/9Mn1/3)1-xMnxO2 (x = 0.01, 0.02, 0.03, 0.04, 0.05) materials through Mn doping during sodiation process. Benefiting from surface P2 phase layer with the enhanced Na+ transfer dynamics and high structural stability, the Na(Ni2/9Fe1/3Cu1/9Mn1/3)0.98Mn0.02O2 (NFCM-M2) cathode delivers a reversible capacity of 139.1 mA h g-1 at 0.1 C, and retains 71.4 % of its original capacity after 300 cycles at 1 C. Our work provides useful guidance for designing multiphase cathodes and offers new insights into the structure-performance correlation for sodium-ion cathode materials.

Reviving Fatigue Surface for Solid-State Upcycling of Highly Degraded Polycrystalline LiNi1-x-yCoxMnyO2 Cathodes.

The ongoing tide of spent lithium-ion batteries (LIBs) urgently calls for high-value output in efficient recycling. Recently, direct regeneration has emerged as a novel recycling strategy but fails to repair the irreversible morphology and structure damage of the highly degraded polycrystalline layered oxide materials. Here, this work carries out a solid-state upcycling study for the severely cracked LiNi1-x-yCoxMnyO2 cathodes. The specific single-crystallization process during calcination is investigated and the surface rock salt phase is recognized as the intrinsic obstacle to the crystal growth of the degraded cathodes due to sluggish diffusion in the heterogeneous grain boundary. Accordingly, this work revives the fatigue rock salt phase by restoring a layered surface and successfully reshapes severely broken cathodes into the high-performance single-crystalline particles. Benefiting from morphological and structural integrity, the upcycled single-crystalline cathode materials exhibit an enhanced capacity retention rate of 93.5% after 150 cycles at 1C compared with 61.7% of the regenerated polycrystalline materials. The performance is also beyond that of the commercial cathodes even under a high cut-off voltage (4.5 V) or high operating temperature (45 °C). This work provides scientific insights for the upcycling of the highly degraded cathodes in spent LIBs.

Interfacial Spinel Local Interlocking Strategy Toward Structural Integrity in P3 Oxide Cathodes.

P3-layered transition oxide cathodes have garnered considerable attention owing to their high initial capacity, rapid Na+ kinetics, and less energy consumption during the synthesis process. Despite these merits, their practical application is hindered by the substantial capacity degradation resulting from unfavorable structural transformations, Mn dissolution and migration. In this study, we systematically investigated the failure mechanisms of P3 cathodes, encompassing Mn dissolution, migration, and the irreversible P3-O3' phase transition, culminating in severe structural collapse. To address these challenges, we proposed an interfacial spinel local interlocking strategy utilizing P3/spinel intergrowth oxide as a proof-of-concept material. As a result, P3/spinel intergrowth oxide cathodes demonstrated enhanced cycling performance. The effectiveness of suppressing Mn migration and maintaining local structure of interfacial spinel local interlocking strategy was validated through depth-etching X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and in situ synchrotron-based X-ray diffraction. This interfacial spinel local interlocking engineering strategy presents a promising avenue for the development of advanced cathode materials for sodium-ion batteries.

Rational Regulation of High-Voltage Stability in Potassium Layered Oxide Cathodes.

Layered oxide cathode materials may undergo irreversible oxygen loss and severe phase transitions during high voltage cycling and may be susceptible to transition metal dissolution, adversely affecting their electrochemical performance. Here, to address these challenges, we propose synergistic doping of nonmetallic elements and in situ electrochemical diffusion as potential solution strategies. Among them, the distribution of the nonmetallic element fluorine within the material can be regulated by doping boron, thereby suppressing manganese dissolution through surface enrichment of fluorine. Furthermore, in situ electrochemical diffusion of fluorine from the surface into the bulk of the materials after charging reduces the energy barrier of potassium ion diffusion while effectively inhibiting irreversible oxygen loss under high voltage. The modified K0.5Mn0.83Mg0.1Ti0.05B0.02F0.1O1.9 layered oxide cathode exhibits a high capacity of 147 mAh g-1 at 50 mA g-1 and a long cycle life of 2200 cycles at 500 mA g-1. This work demonstrates the efficacy of synergistic doping and in situ electrochemical diffusion of nonmetallic elements and provides valuable insights for optimizing rechargeable battery materials.

Comparison Study of a Thermal-Driven Microstructure in a High-Ni Cathode for Lithium-Ion Batteries: Critical Calcination Temperature for Polycrystalline and Single-Crystalline Design.

High-Ni layered oxide cathodes are promising candidates for lithium-ion batteries due to their high energy density. However, their cycle stability is compromised by the poor mechanical durability of the particle microstructure. In this study, we investigate the impact of the calcination temperature on microstructural changes, including primary particle growth and pore evolution, using LiNi0.88Mn0.08Co0.04O2 (N884), with an emphasis on the critical calcination temperature for polycrystalline and single-crystal designs in high-Ni cathodes. As the calcination temperature increases, the primary particles undergo a rectangular growth pattern while the pore population decreases. Beyond a certain critical temperature (in this case, 850 °C), a sudden increase in primary particle size and a simultaneous rapid reduction in the pore population are observed. This sudden microstructure evolution leads to poor cycle retention in N884. In contrast, single-crystal particles, free of grain boundaries, synthesized at this critical temperature exhibit superior cycle retention, underscoring the significance of microstructural design over crystalline quality for achieving long-term cyclability. Our study sheds light on the interplay between calcination temperature and microstructural evolution, proposing the critical temperature as a key criterion for single-crystal synthesis.

Toward the High-Voltage Stability of Layered Oxide Cathodes for Sodium-Ion Batteries: Challenges, Progress, and Perspectives.

Sodium-ion batteries (SIBs) have garnered significant attention as ideal candidates for large-scale energy storage due to their notable advantages in terms of resource availability and cost-effectiveness. However, there remains a substantial energy density gap between SIBs and commercially available lithium-ion batteries (LIBs), posing challenges to meeting the requirements of practical applications. The fabrication of high-energy cathodes has emerged as an efficient approach to enhancing the energy density of SIBs, which commonly requires cathodes operating in high-voltage regions. Layered oxide cathodes (LOCs), with low cost, facile synthesis, and high theoretical specific capacity, have emerged as one of the most promising candidates for commercial applications. However, LOCs encounter significant challenges when operated in high-voltage regions such as irreversible phase transitions, migration and dissolution of metal cations, loss of reactive oxygen, and the occurrence of serious interfacial parasitic reactions. These issues ultimately result in severe degradation in battery performance. This review aims to shed light on the key challenges and failure mechanisms encountered by LOCs when operated in high-voltage regions. Additionally, the corresponding strategies for improving the high-voltage stability of LOCs are comprehensively summarized. By providing fundamental insights and valuable perspectives, this review aims to contribute to the advancement of high-energy SIBs.

Co/Al Co-Substituted Layered Manganese-Based Oxide Cathode for Stable and High-Rate Potassium-Ion Batteries.

Manganese-based layered oxides are promising cathode materials for potassium-ion batteries (PIBs) due to their low cost and high theoretical energy density. However, the Jahn-Teller effect of Mn3+ and sluggish diffusion kinetics lead to rapid electrode deterioration and a poor rate performance, greatly limiting their practical application. Here, we report a Co/Al co-substitution strategy to construct a P3-type K0.45Mn0.7Co0.2Al0.1O2 cathode material, where Co3+ and Al3+ ions occupy Mn3+ sites. This effectively suppresses the Jahn-Teller distortion and alleviates the severe phase transition during K+ intercalation/de-intercalation processes. In addition, the Co element contributes to K+ diffusion, while Al stabilizes the layer structure through strong Al-O bonds. As a result, the K0.45Mn0.7Co0.2Al0.1O2 cathode exhibits high capacities of 111 mAh g-1 and 81 mAh g-1 at 0.05 A g-1 and 1 A g-1, respectively. It also demonstrates a capacity retention of 71.6% after 500 cycles at 1 A g-1. Compared to the pristine K0.45MnO2, the K0.45Mn0.7Co0.2Al0.1O2 significantly alleviates severe phase transition, providing a more stable and effective pathway for K+ transport, as investigated by in situ X-ray diffraction. The synergistic effect of Co/Al co-substitution significantly enhances the structural stability and electrochemical performance, contributing to the development of new Mn-based cathode materials for PIBs.

Greener, Safer and Better Performing Aqueous Binder for Positive Electrode Manufacturing of Sodium Ion Batteries.

P2-type cobalt-free MnNi-based layered oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high reversible capacity and well chemical stability. However, the phase transformations during repeated (dis)charge steps lead to rapid capacity decay and deteriorated Na+ diffusion kinetics. Moreover, the electrode manufacturing based on polyvinylidene difluoride (PVDF) binder system has been reported with severely defluorination issue as well as the energy intensive and expensive process due to the use of toxic and volatile N-methyl-2-pyrrolidone (NMP) solvent. It calls for designing a sustainable, better performing, and cost-effective binder for positive electrode manufacturing. In this work, we investigated inorganic sodium metasilicate (SMS) as a viable binder in conjunction with P2-Na0.67Mn0.55Ni0.25Fe0.1Ti0.1O2 (NMNFT) cathode material for SIBs. The NMNFT-SMS electrode delivered a superior electrochemical performance compared to carboxy methylcellulose (CMC) and PVDF based electrodes with a reversible capacity of ~161 mAh/g and retaining ~83 % after 200 cycles. Lower cell impedance and faster Na+ diffusion was also observed in this binder system. Meanwhile, with the assistance of TEM technique, SMS is suggested to form a uniform and stable nanoscale layer over the cathode particle surface, protecting the particle from exfoliation/cracking due to electrolyte attack. It effectively maintained the electrode connectivity and suppressed early phase transitions during cycling as confirmed by operando XRD study. With these findings, SMS binder can be proposed as a powerful multifunctional binder to enable positive electrode manufacturing of SIBs and to overall reduce battery manufacturing costs.

Slow-Released Cationic Redox Activity Promoted Stable Anionic Redox and Suppressed Jahn-Teller Distortion in Layered Sodium Manganese Oxides.

Manganese-based layered oxides are considered promising cathodes for sodium ion batteries due to their high capacity and low-cost manganese and sodium resources. Triggering the anionic redox reaction (ARR) can exceed the capacity limitation determined by conventional cationic redox. However, the unstable ARR charge compensation and Jahn-Teller distortion of Mn3+ ions readily result in structural degradation and rapid capacity fade. Here, we report a P2-type Na0.8Li0.2Mn0.7Cu0.1O2 cathode that shows a capacity retention of 84.5% at 200 mA/g after 200 cycles. Combining in situ X-ray diffraction and multi other ex situ characterizations, we reveal that the enhanced cycling stability is ascribed to a slow release of cationic redox activity which can well suppress the Jahn-Teller distortion and favor the ARR reversibility. Furthermore, density-functional theory calculations demonstrate that the inhibited interlayer migration and reduced band gap facilitate the stability and kinetic behavior of ARR. These findings provide a perspective for designing high-energy-density cathode materials with ARR activity.

Facilitating Layered Oxide Cathodes Based on Orbital Hybridization for Sodium-Ion Batteries: Marvelous Air Stability, Controllable High Voltage, and Anion Redox Chemistry.

Layered oxides have become the research focus of cathode materials for sodium-ion batteries (SIBs) due to the low cost, simple synthesis process, and high specific capacity. However, the poor air stability, unstable phase structure under high voltage, and slow anionic redox kinetics hinder their commercial application. In recent years, the concept of manipulating orbital hybridization has been proposed to simultaneously regulate the microelectronic structure and modify the surface chemistry environment intrinsically. In this review, the hybridization modes between atoms in 3d/4d transition metal (TM) orbitals and O 2p orbitals near the region of the Fermi energy level (EF) are summarized based on orbital hybridization theory and first-principles calculations as well as various sophisticated characterizations. Furthermore, the underlying mechanisms are explored from macro-scale to micro-scale, including enhancing air stability, modulating high working voltage, and stabilizing anionic redox chemistry. Meanwhile, the origin, formation conditions, and different types of orbital hybridization, as well as its application in layered oxide cathodes are presented, which provide insights into the design and preparation of cathode materials. Ultimately, the main challenges in the development of orbital hybridization and its potential for the production application are also discussed, pointing out the route for high-performance practical sodium layered oxide cathodes.

Effect of Electrochemical Pre-Lithiation on Layered Oxide Cathodes for Anode-Free Lithium-metal Batteries.

Due to high energy density and lower manufacturing cost, anode-free lithium-metal batteries (AFLMBs) are attracting increasing attention. The challenges for developing them lie in inferior Coulombic efficiency and short cycle life due to the highly reactive lithium metal. Herein, an electrochemical pre-lithiation strategy is applied to layered oxide cathodes, specifically LiNiO2 and LiCoO2 , aiming to provide an additional lithium source and understand the effect on the cathode structure for AFLMBs. The mechanism for accommodating the excess Li depends on the structural stability of the cathodes where LiNiO2 forms lithiated Li2 NiO2 with the excess lithium in the crystalline lattice while the excess lithium in LiCoO2 forms a Li2 O phase. More importantly, an optimal amount of Li excess is necessary to maintain decent cycle stability and specific capacity in AFLMB, with 40% excess Li for LiNiO2 and 150% for LiCoO2 . While the pre-lithiation process causes particle pulverization depending on the amount of Li excess, LiCoO2 offers a much better cycle performance than LiNiO2 with a promising capacity retention of 80% after 300 cycles in AFLMB (vs 76% after 100 cycles for 40% Li excess in LiNiO2 ). This study provides a promising avenue for developing tailor-made layered oxide cathodes for AFLMBs.

Regulating Anionic Redox via Mg Substitution in Mn-Rich Layered Oxide Cathodes Enabling High Electrochemical Stability for Sodium-Ion Batteries.

With the limited resources and high cost of lithium-ion batteries (LIBs) and the ever-increasing market demands, sodium-ion batteries (SIBs) gain much interest due to their economical sustainability, and similar chemistry and manufacturing processes to LIBs. As cathodes play a vital role in determining the energy density of SIBs, Mn-based layered oxides are promising cathodes due to their low cost, environmental friendliness, and high theoretical capacity. However, the main challenge is structural instability upon cycling at high voltage. Herein, Mg is introduced into the P2-type Na0.62 Ni0.25 Mn0.75 O2 cathode to enhance electrochemical stability. By combining electrochemical testing and material characterizations, it is found that substituting 10 mol% Mg can effectively alleviate the P2-O2 phase transition, Jahn-Teller distortion, and irreversible oxygen redox. Moreover, structural integrity is greatly improved. These lead to enhanced electrochemical performances. With the optimized sample, a remarkable capacity retention of 92% in the half cell after 100 cycles and 95% in the full cell after 170 cycles can be achieved. Altogether, this work provides an alternative way to stabilize P2-type Mn-based layer oxide cathodes, which in turn, put forward the development of this material for the next-generation SIBs.

Defensive and Ion Conductive Surface Layer Enables High Rate and Durable O3-type NaNi1/3 Fe1/3 Mn1/3 O2 Sodium-Ion Battery Cathode.

Na-based layered transition metal oxides with an O3-type structure are considered promising cathodes for sodium-ion batteries. However, rapid capacity fading, and poor rate performance caused by serious structural changes and interfacial degradation hamper their use. In this study, a NaPO3 surface modified O3-type layered NaNi1/3 Fe1/3 Mn1/3 O2 cathode is synthesized, with improved high-voltage stability through protecting layer against acid attack, which is achieved by a solid-gas reaction between the cathode particles and gaseous P2 O5 . The NaPO3 nanolayer on the surface effectively stabilizes the crystal structure by inhibiting surface parasitic reactions and increasing the observed average voltage. Superior cyclic stability is exhibited by the surface-modified cathode (80.1% vs 63.6%) after 150 cycles at 1 C in the wide voltage range of 2.0 V-4.2 V (vs Na+ /Na). Moreover, benefiting from the inherent ionic conduction of NaPO3 , the surface-modified cathode presents excellent rate capability (103 mAh g-1  vs 60 mAh g-1 ) at 10 C. The outcome of this study demonstrates a practically relevant approach to develop high rate and durable sodium-ion battery technology.

High Entropy-Induced Kinetics Improvement and Phase Transition Suppression in K-Ion Battery Layered Cathodes.

Layered oxides are widely accepted to be promising cathode candidate materials for K-ion batteries (KIBs) in terms of their rich raw materials and low price, while their further applications are restricted by sluggish kinetics and poor structural stability. Here, the high-entropy design concept is introduced into layered KIB cathodes to address the above issues, and an example of high-entropy layered K0.45Mn0.60Ni0.075Fe0.075Co0.075Ti0.10Cu0.05Mg0.025O2 (HE-KMO) is successfully prepared. Benefiting from the high-entropy oxide with multielement doping, the developed HE-KMO exhibits half-metallic oxide features with a narrow bandgap of 0.19 eV. Increased entropy can also reduce the surface energy of the {010} active facets, resulting in about 2.6 times more exposure of the {010} active facets of HE-KMO than the low-entropy K0.45MnO2 (KMO). Both can effectively improve the kinetics in terms of electron conduction and K+ diffusion. Furthermore, high entropy can inhibit space charge ordering during K+ (de)insertion, and the transition metal-oxygen covalent interaction of HE-KMO is also enhanced, leading to suppressed phase transition of HE-KMO in 1.5-4.2 V and better electrochemical stability of HE-KMO (average capacity drop of 0.20%, 200 cycles) than the low-entropy KMO (average capacity drop of 0.41%, 200 cycles) in the wide voltage window.