Full Exploitation of Charge Compensation of O3-type Cathode Toward High Energy Sodium-Ion Batteries by High Entropy Strategy.

O3-type cathodes with sufficient Na content are considered as promising candidates for sodium-ion batteries (SIBs). However, these cathodes suffer from insufficient utilization of the active elements, restraining the delivered capacity. In this work, a high entropy strategy is applied to a typical O3 cathode NaLi0.1Ni0.35Mn0.55O2 (NLNM), forming a high entropy oxide NaLi0.1Ni0.15Cu0.1Mg0.1Ti0.2Mn0.35O2 (Na-HE). Results show that the active elements are fully exploited in Na-HE, with a two-electron reaction by Ni2+/4+ (further extended to Cu redox and even oxygen redox), vastly different from a one-electron reaction of Ni2+/3+ in NLNM. The full utilization of the active elements dramatically improves the output capacity of the cathode (122.6 mAh g-1 of Na-HE versus 81 mAh g-1 of NLNM). Moreover, the detrimental phase transition is well suppressed in Na-HE. The cathode exhibits high capacity retention of 88.7% after 100 cycles at 130 mA g-1, compared to only 36.4% for NLNM. These findings provide new insight for the design of new cathode materials for SIBs with high energy density and robust stability.

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.

Promoted Stability and Reaction Kinetics in Ni-Rich Cathodes via Mechanical Fusing Multifunctional LiZr2(PO4)3 Nanocrystals for High Mass Loading All-Solid-State Lithium Batteries.

Sulfide all-solid-state lithium battery (ASSLB) with nickel-rich layered oxide as the cathode is promising for next-generation energy storage system. However, the Li+ transport dynamic and stability in ASSLB are hindered by the structural mismatches and the instabilities especially at the oxide cathode/sulfide solid electrolyte (SE) interface. In this work, we have demonstrated a simple and highly effective solid-state mechanofusion method (1500 rpm for 10 min) to combine lithium conductive NASICON-type LiZr2(PO4)3 nanocrystals (∼20 nm) uniformly and compactly onto the surface of the single crystallized LiNi0.8Co0.1Mn0.1O2, which can also attractively achieve Zr4+ doping in NCM811 and oxygen vacancies in the LZPO coating without solvent and annealing. Benefiting from the alleviated interface mismatches, sufficient Li+ ion flux through the LZPO coating, promoted structural stabilities for both NCM811 and sulfide SE, strong electronic coupling effect between the LZPO and NCM811, and enlarged (003) d-spacing with enriched Li+ migration channels in NCM811, the obtained LZPO-NCM811 exhibits superior stability (185 mAh/g at 0.1C for 200 cycles) and rate performance (105 mAh/g at 1C for 1300 cycles) with high mass loading of 27 mgNCM/cm2 in sulfide ASSLB. Even with a pronounced 54 mgNCM/cm2, LZPO-NCM811 manifests a high areal capacity of 9.85 mAh/cm2. The convenient and highly effective interface engineering strategy paves the way to large-scale production of various coated cathode materials with synergistic effects for high performance ASSLBs.

Unraveling the Role of Li and Mg Substitution in Layered Sodium Oxide Cathodes for Sodium-Ion Batteries.

Substituting electrochemically active elements such as Li and Mg in P2-type layered sodium oxide is an effective strategy for developing competitive cathode materials for sodium-ion batteries. However, the lack of atomic-level understanding regarding the distribution of substitution positions complicates the comprehension of the roles of substituting atoms and the mechanism of sodium-ion intercalation. In this study, we identified the stable configurations of Na in Na0.75Ni0.3Mn0.7O2 and Na0.75Li0.15Mg0.05Ni0.1Mn0.7O2 materials using the site exclusion method. Through simulating the complete charging process for both materials, the structure evolution of the cathodes during the cycling and the impact of the partial substitution of Ni elements by Li and Mg atoms were comprehensively elucidated. Our findings revealed that Mg atoms effectively regulate the distribution of forces within the materials, essentially serving as supportive pillars within the cathode. Meanwhile, Li atoms efficiently mitigated electron localization, consequently diminishing volume fluctuations during the charging process. More importantly, the substitution with Li and Mg atoms could synergistically reduce the interaction between transition metals and sodium ions, thereby reducing the diffusion energy barrier of Na ions. This study not only enhances the comprehension of substituted metal atoms in P2 layered oxides but also offers new insights for the development of sodium-ion cathode materials.

Ti-Substituted O3-NaNi0.5Mn0.3Ti0.2O2 Material with a Disordered Transition Metal Layer and a Stable Structure.

O3-type NaNi0.5Mn0.5O2 (NNM) is very competitive for sodium-ion batteries (SIBs) due to its high capacity and easy production. Nevertheless, the intricate phase transitions during the charging-discharging significantly impede its practical application. This paper proposes a strategy for successfully synthesizing NaNi0.5Mn0.3Ti0.2O2 (NNMT) by combining coprecipitation and a high-temperature solid-state method. This method introduces Ti elements while retaining the electrochemically active Ni2+ content, thus, the NNMT has a high initial specific capacity of 151.4 mAh g-1 at 1 C. It is demonstrated that introducing Ti4+ leads to the transition metal layers becoming disordered by ex situ XRD, thus mitigating the irreversible phase transition of the material. In addition, Ti4+ does not have an outer electron, which can reduce electron delocalization in the transition metal layer and improve the material's cyclic stability. The NNMT possesses a capacity retention rate of 60.66% after 150 cycles, much higher than the initial NNM's 18.96%. It also exhibits an excellent discharge capacity of 86.8 mAh g-1 at 5 C. In conclusion, the cycling and rate performance of the Ti-substituted NNMT are greatly improved without capacity loss, which offers innovative concepts for the modification means of the SIBs layered oxide cathode materials.

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.

Operando chemo-mechanical evolution in LiNi0.8Co0.1Mn0.1O2 cathodes.

Ni-rich LiNi x Co y Mn z O2 (NCMxyz, x + y + z = 1, x ≥ 0.8) layered oxide materials are considered the main cathode materials for high-energy-density Li-ion batteries. However, the endless cracking of polycrystalline NCM materials caused by stress accelerates the loss of active materials and electrolyte decomposition, limiting the cycle life. Hence, understanding the chemo-mechanical evolution during (de)lithiation of NCM materials is crucial to performance improvement. In this work, an optical fiber with µÎµ resolution is designed to in operando detect the stress evolution of a polycrystalline LiNi0.8Co0.1Mn0.1O2 (P-NCM811) cathode during cycling. By integrating the sensor inside the cathode, the stress variation of P-NCM811 is completely transferred to the optical fiber. We find that the anisotropy of primary particles leads to the appearance of structural stress, inducing the formation of microcracks in polycrystalline particles, which is the main reason for capacity decay. The isotropy of primary particles reduces the structural stress of polycrystalline particles, eliminating the generation of microcracks. Accordingly, the P-NCM811 with an ordered arrangement structure delivered high electrochemical performance with capacity retention of 82% over 500 cycles. This work provides a brand-new perspective with regard to understanding the operando chemo-mechanical evolution of NCM materials during battery operation, and guides the design of electrode materials for rechargeable batteries.

Achieving Stable Cycling Performance in a P2-Type Layered Oxide Cathode through a Synergic Li/Zn Doping for Sodium-Ion Batteries.

It has been suggested that sodium layered transition metal oxides could potentially serve as excellent cathodes for sodium-ion batteries (SIBs) because of their appropriate operating potentials and high capacities. However, the growing reliance on energy requirements has necessitated a higher energy density of SIBs. It has been demonstrated that activating oxygen-related activities for SIBs is a viable method to improve energy density. Herein, we suggest applying the synergy of Li and Zn codoping to activate the anionic redox reactions (ARRs) and improve their reversibility in Na0.75Ni0.3Mn0.7O2. The dual ion doping alleviates the phase transition and inhibits the Na+/vacancy arrangements, consequently improving the rate capacity and cyclic stability. The Na0.75Li0.15Ni0.1Zn0.05Mn0.7O2 delivers a discharge capacity of 134 mA h g-1 and no significant capacity loss at 100 mA g-1 between 2 and 4.5 V after 200 cycles. More importantly, the density functional theory (DFT) calculation proves that the codoping strategy triggers more ARRs compared to single-element doping, thereby providing enhanced capacity. The codoping induced oxygen redox strategies will create a new path for rational design of cathodes to enhance the energy density for SIBs.

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.

Inhibiting Voltage Decay in Li-Rich Layered Oxide Cathode: From O3-Type to O2-Type Structural Design.

Li-rich layered oxide (LRLO) cathodes have been regarded as promising candidates for next-generation Li-ion batteries due to their exceptionally high energy density, which combines cationic and anionic redox activities. However, continuous voltage decay during cycling remains the primary obstacle for practical applications, which has yet to be fundamentally addressed. It is widely acknowledged that voltage decay originates from the irreversible migration of transition metal ions, which usually further exacerbates structural evolution and aggravates the irreversible oxygen redox reactions. Recently, constructing O2-type structure has been considered one of the most promising approaches for inhibiting voltage decay. In this review, the relationship between voltage decay and structural evolution is systematically elucidated. Strategies to suppress voltage decay are systematically summarized. Additionally, the design of O2-type structure and the corresponding mechanism of suppressing voltage decay are comprehensively discussed. Unfortunately, the reported O2-type LRLO cathodes still exhibit partially disordered structure with extended cycles. Herein, the factors that may cause the irreversible transition metal migrations in O2-type LRLO materials are also explored, while the perspectives and challenges for designing high-performance O2-type LRLO cathodes without voltage decay are proposed.

Impact of Transition Metal Layer Vacancy on the Structure and Performance of P2 Type Layered Sodium Cathode Material.

This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na0.6[Ni0.3Ru0.3Mn0.4]O2 (NRM) cathode material. The incorporation of Ru, Ni, and vacancy enhances the structural stability during extensive cycling, increases the operation voltage, and induces a capacity increase while also activating oxygen redox, respectively, in Na0.7[Ni0.2VNi0.1Ru0.3Mn0.4]O2 (V-NRM) compound. Various analytical techniques including transmission electron microscopy, X-ray absorption near edge spectroscopy, operando X-ray diffraction, and operando differential electrochemical mass spectrometry are employed to assess changes in the average oxidation states and structural distortions. The results demonstrate that V-NRM exhibits higher capacity than NRM and maintains a moderate capacity retention of 81% after 100 cycles. Furthermore, the formation of additional lone-pair electrons in the O 2p orbital enables V-NRM to utilize more capacity from the oxygen redox validated by density functional calculation, leading to a widened dominance of the OP4 phase without releasing O2 gas. These findings offer valuable insights for the design of advanced high-capacity cathode materials with improved performance and sustainability in sodium-ion batteries.

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.

Defect-Driven Configurational Entropy in the High-Entropy Oxide Li1.5MO3-δ.

Layered lithiated oxides are promising materials for next generation Li-ion battery cathode materials; however, instability during cycling results in poor performance over time compared to the high capacities theoretically possible with these materials. Here we report the characterizations of a Li1.47Mn0.57Al0.13Fe0.095Co0.105Ni0.095O2.49 high-entropy layered oxide (HELO) with the Li2MO3 structure where M = Mn, Al, Fe, Co, and Ni. Using electron microscopy and X-ray spectroscopy, we identify a homogeneous Li2MO3 structure stabilized by the entropic contribution of oxygen vacancies. This defect-driven entropy would not be attainable in the LiMO2 structure sometimes observed in similar materials as a secondary phase owing to the presence of fewer O sites and a 3+ oxidation state for the metal site; instead, a Li2-γMO3-δ is produced. Beyond Li2MO3, this defect-driven entropy approach to stabilizing novel compositions and phases can be applied to a wide array of future cathode materials including spinel and rock salt structures.

Enabling Quasi-Zero-Strain Behavior of Layered Oxide Cathodes via Multiple-cations Induced Order-to-Disorder Transition.

The chemically pre-intercalated lattice engineering is widely applied to elevate the electronic conductivity, expand the interlayer spacing, and improve the structural stability of layered oxide cathodes. However, the mainstream unitary metal ion pre-intercalation generally produces the cation/vacancy ordered superstructure, which astricts the further improvement of lattice respiration and charge-carrier ion storage and diffusion. Herein, a multiple metal ions pre-intercalation lattice engineering is proposed to break the cation/vacancy ordered superstructure. Taking the bilayer V2O5 as an example, Ni, Co, and Zn ternary ions are simultaneously pre-intercalated into its interlayer space (NiCoZnVO). It is revealed that the Ni─Co neighboring characteristic caused by Ni(3d)-O(2p)-Co(3d) orbital coupling and the Co-Zn/Ni-Zn repulsion effect due to chemical bond incompatibility, endow the NiCoZnVO sample with the cation/vacancy disordered structure. This not only reduces the Li+ diffusion barrier, but also increases the diffusion dimension of Li+ (from one-dimension to two-dimension). Particularly, Ni, Co, and Zn ions co-pre-intercalation causes a prestress, which realizes a quasi-zero-strain structure at high-voltage window upon charging/discharging process. The functions of Ni ion stabilizing the lattice structure and Co or Zn ions activating more Li+ reversible storage reaction of V5+/V4+ are further revealed. The cation/vacancy disordered structure significantly enhances Li+ storage properties of NiCoZnVO cathode.

Zn Doping Strategy to Suppress the Jahn-Teller Effect to Stabilize Mn-Based Layered Oxide Cathode toward High-Performance Potassium Ion Batteries.

In the research report of cathode of potassium ion battery, Mn-based layered structural oxides have attracted the researcher's attention because of its good energy density and high specific rate capacity. However, the Jahn-Teller effect is the main limiting factor for their development. It leads to the expansion and deactivation of Mn-based layered metal oxides during cycling for a long time. Therefore, mitigation of the Jahn-Teller effect is considered a useful measure to enhance the electrochemical capability of Mn-based layered oxide. In this paper, an R3m-type K0.4Mn0.7Co0.25Zn0.05O2 cathode material is designed through a Zn doping strategy. X-ray diffraction techniques and electrochemical tests verified that the Jahn-Teller effect is effectively mitigated. High performance is achieved in the rate capacity test with 113 mAh g-1 at 50 mA g-1. Comparison with similar materials in recent years has demonstrated its superiority, leading rate performance among Mn-based metal oxides reported in recent years. The practical feasibility is verified in the assembled full cell with soft carbon in anode materials and K0.4Mn0.7Co0.25Zn0.05O2 as cathode. In the full cell rate test, 104.8 mAh g-1 discharging capacity is achieved at 50 mA g-1 current density.

Enhancing P2/O3 Biphasic Cathode Performance for Sodium-Ion Batteries: A Metaheuristic Approach to Multi-Element Doping Design.

Sodium-ion batteries (SIBs) have emerged as a compelling alternative to lithium-ion batteries (LIBs), exhibiting comparable electrochemical performance while capitalizing on the abundant availability of sodium resources. In SIBs, P2/O3 biphasic cathodes, despite their high energy, require furthur improvements in stability to meet current energy demands. This study introduces a systematic methodology that leverages the meta-heuristically assisted NSGA-II algorithm to optimize multi-element doping in electrode materials, aiming to transcend conventional trial-and-error methods and enhance cathode capacity by the synergistic integration of P2 and O3 phases. A comprehensive phase analysis of the meta-heuristically designed cathode material Na0.76Ni0.20Mn0.42Fe0.30Mg0.04Ti0.015Zr0.025O2 (D-NFMO) is presented, showcasing its remarkable initial reversible capacity of 175.5 mAh g-1 and exceptional long-term cyclic stability in sodium cells. The investigation of structural composition and the stabilizing mechanisms is performed through the integration of multiple characterization techniques. Remarkably, the irreversible phase transition of P2→OP4 in D-NFMO is observed to be dramatically suppressed, leading to a substantial enhancement in cycling stability. The comparison with the pristine cathode (P-NFMO) offers profound insights into the long-term electrochemical stability of D-NFMO, highlighting its potential as a high-voltage cathode material utilizing abundant earth elements in SIBs. This study opens up new possibilities for future advancements in sodium-ion battery technology.

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.

A Plastic-Crystal Electrolyte Layer Promotes Interfacial Stability of Ni-Rich Oxide Cathode in Li6PS5Cl-Based All-Solid-State Rechargeable Li Batteries.

Unfavorable parasitic reactions between the Ni-rich layered oxide cathode and the sulfide solid electrolyte have plagued the realization of all-solid-state rechargeable Li batteries. The accumulation of inactive by-products (P2Sx, S, POx n- and SOx n-) at the cathode-sulfide interface impedes fast Li-ion transfer, which accounts for sluggish reaction kinetics and significant loss of cathode capacity. Herein, we proposed an easily scalable approach to stabilize the cathode electrochemistry via coating the cathode particles by a uniform, Li+-conductive plastic-crystal electrolyte nanolayer on their surface. The electrolyte, which simply consists of succinonitrile and Li bis(trifluoromethanesulphonyl)imide, serves as an interfacial buffer to effectively suppress the adverse phase transition in highly delithiated cathode materials, and the loss of lattice oxygen and generation of inactive oxygenated by-products at the cathode-sulfide interface. Consequently, an all-solid-state rechargeable Li battery with the modified cathode delivers high specific capacities of 168 mAh g-1 at 0.1 C and a high capacity retention >80 % after 100 cycles. Our work sheds new light on rational design of electrode-electrolyte interface for the next-generation high-energy batteries.

Lanthanum doping and surface Li3BO3 passivating layer enabling 4.8 V nickel-rich layered oxide cathodes toward high energy lithium-ion batteries.

Single crystalline Ni-rich layered oxide cathodes show high energy density and low cost, have been regarded as one of the most promising candidates for next generation lithium-ion batteries (LIBs). Extending the cycling voltage window will significantly improve the energy density, however, suffers from bulk structural and interfacial chemistry degradation, leading to rapidly cycle performance deterioration. Here, we propose a dual-modification strategy to synthesize La doping and Li3BO3 (LBO) coating layers modified LiNi0.8Co0.1Mn0.1O2 (NCM811) by a facile one-step heating treatment processing. In-situ EIS and XRD, ex-situ XPS techniques are applied to demonstrate that the La diffused amorphous domains and Li3BO3 passivating layers dampen the lattice distortion, enhance the interfacial chemistry behavior as well as lithium ion transportation kinetics. Specifically, surface La doping amorphous domains successfully suppress the intense lattice stress and volume changes induced by the phase transitions during lithiation/delithiation, thus avoiding the intergranular crack and enhancing the mechanical stability of the material. Moreover, the LBO layer formed by the consumption of residual lithium prevents successive parasitic reactions at the interface as well as provides rapid Li-ion diffusion channels. Furthermore, the coating layer also diminishes the residual lithium compounds, increasing the atmosphere stability and safety of LIBs. Consequently, the La doping and LBO coating NCM811 exhibits an exceptional initial specific capacity (230.6 mAh/g) at 0.5C under a high cutoff voltage of 4.8 V, and a 73.8 % capacity retention following 100 cycles. In addition, a superior specific capacity of 133.8 mAh/g is provided even at a high current density (4C). Our work paves a promising road to tackle the integral structure deterioration and interfacial instability of Ni-rich cathodes.