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The Ni‐rich layered oxides with a Ni content of >0.5 are drawing much attention recently to increase the energy density of lithium‐ion batteries. However, the Ni‐rich layered oxides suffer from aggressive reaction of the cathode surface with the organic electrolyte at the higher operating voltages, resulting in consequent impedance rise and capacity fade. To overcome this difficulty, we present here a heterostructure composed of a Ni‐rich LiNi0.7Co0.15Mn0.15O2 core and a Li‐rich Li1.2− x Ni0.2Mn0.6O2 shell, incorporating the advantageous features of the structural stability of the core and chemical stability of the shell. With a unique chemical treatment for the activation of the Li2MnO3 phase of the shell, a high capacity is realized with the Li‐rich shell material. Aberration‐corrected scanning transmission electron microscopy (STEM) provides direct evidence for the formation of surface Li‐rich shell layer. As a result, the heterostructure exhibits a high capacity retention of 98% and a discharge‐voltage retention of 97% during 100 cycles with a discharge capacity of 190 mA h g−1 (at 2.0–4.5 V under C/3 rate, 1C = 200 mA g−1). To develop high‐performance cathodes, a heterostructure composed of Ni‐rich layered oxide core and a lithium‐rich Li1.2−xNi0.2Mn0.6O2 shell is explored. The heterostructure overcomes the critical drawbacks of both the surface electrochemical instability with electrolyte of the core material as well as the voltage decline problem of the shell layer.

Lithium‐rich layered oxide (LRLO) is a promising material for high‐energy‐density lithium‐ion batteries (LIBs), yet its practical application is hindered by the nucleophilic attack of reactive oxygen species (ROS) on carbonate electrolytes, inducing severe interfacial incompatibility. Herein, a LiPF6‐based carbonate electrolyte modified by dual B/P‐containing additives with oxygen scavenging capability is developed to mitigate these issues. The designed electrolyte enables efficient ROS scavenging and in situ formation of a robust cathode/electrolyte interface (CEI) on the LRLO surface. The designed electrolyte not only enhances the reversibility of anionic redox reactions (ARRs) but also suppresses electrolyte decomposition and transition metal dissolution. Electrochemical tests demonstrate that the Li//LRLO cell with a high mass loading of 15 mg cm−2 retains 94.4% of its initial capacity after 200 cycles, while the 4.5 Ah graphite//LRLO pouch cell exhibits a higher energy density of 282.5 Wh kg−1 with stable cycling over 50 cycles. This work offers a viable strategy for interface engineering of LRLO‐based cathodes, paving the way for the development of high‐performance LIBs with long‐term cyclic stability. To inhibit electrolyte decomposition by nucleophilic attack in carbonate electrolyte, LiBOB and LiDFOP with strong oxygen scavenging ability are selected to quench reactive oxygen species and following construct a robust CEI film on the LRLO cathode. The electrochemical performance of the LRLO cathode is largely improved, attributed to decomposition suppression and structural stability, when cycled in C‐BP electrolyte.

Activation of oxygen redox during the first cycle has been reported as the main trigger of voltage hysteresis during further cycles in high‐energy‐density Li‐rich 3d‐transition‐metal layered oxides. However, it remains unclear whether hysteresis only occurs due to oxygen redox. Here, it is identified that the voltage hysteresis can highly correlate to cationic reduction during discharge in the Li‐rich layered oxide, Li1.2Ni0.4Mn0.4O2. In this material, the potential region of discharge accompanied by hysteresis is apparently separated from that of discharge unrelated to hysteresis. The quantitative analysis of soft/hard X‐ray absorption spectroscopies discloses that hysteresis is associated with an incomplete cationic reduction of Ni during discharge. The galvanostatic intermittent titration technique shows that the inevitable energy consumption caused by hysteresis corresponds to an overpotential of 0.3 V. The results unveil that hysteresis can also be affected by cationic redox in Li‐rich layered cathodes, implying that oxygen redox cannot be the only reason for the evolution of voltage hysteresis. Therefore, appropriate control of both cationic and anionic redox of Li‐rich layered oxides will allow them to reach their maximum energy density and efficiency. A key question regarding the real‐world application potential of Li‐rich layered cathodes is whether the low energy efficiency associated with voltage hysteresis can be improved. The incomplete reduction of Ni acts as a main reason for the hysteresis in Li1.2Ni0.4Mn0.4O2, implying that low energy efficiency caused by hysteresis cannot be unraveled only by preventing oxygen redox.

The burgeoning growth in electric vehicles and portable energy storage systems necessitates advances in the energy density and cost‐effectiveness of lithium‐ion batteries (LIBs), areas where lithium‐rich manganese‐based oxide (LLO) materials naturally stand out. Despite their inherent advantages, these materials encounter significant practical hurdles, including low initial Coulombic efficiency (ICE), diminished cycle/rate performance, and voltage fading during cycling, hindering their widespread adoption. In response, we introduce an ionic‐electronic dual‐conductive (IEDC) surface control strategy that integrates an electronically conductive graphene framework with an ionically conductive heteroepitaxial spinel Li4Mn5O12 layer. Prolonged electrochemical and structural analyses demonstrate that this IEDC heterostructure effectively minimizes polarization, mitigates structural distortion, and enhances electronic/ionic diffusion. Density functional theory calculations highlight an extensive Li+ percolation network and lower Li+ migration energies at the layered‐spinel interface. The designed LLO cathode with IEDC interface engineering (LMOSG) exhibits improved ICE (82.9% at 0.1 C), elevated initial discharge capacity (296.7 mAh g−1 at 0.1 C), exceptional rate capability (176.5 mAh g−1 at 5 C), and outstanding cycle stability (73.7% retention at 5 C after 500 cycles). These findings and the novel dual‐conductive surface architecture design offer promising directions for advancing high‐performance electrode materials. An ionic‐electronic dual‐conductor interface engineering with highly connective Li+ percolation networks and reduced Li+ migration energies is developed to comprehensively enable the reversible cationic–anionic redox chemistry in lithium‐rich manganese‐based oxide cathodes. The prolonged electrochemical/structural evolution analysis and theoretical study suggest that architecture design significantly prevents structural distortion and promotes rapid electron and ion diffusion.

Lithium‐rich layered oxides (LLOs) with high energy density and low cost are regarded as promising candidates for the next‐generation cathode materials for lithium‐ion batteries (LIBs). However, there are still some drawbacks of LLOs such as oxygen instability and irreversible structure reconstruction, which seriously limit their electrochemical performance and practical applications. Herein, the high‐valence Ta doping is proposed to adjust the electronic structures of transition metals, which form strong Ta‐O bonds and reduce the covalency of Ni‐O bonds, thereby stabilizing the lattice oxygen and enhancing the structural/thermal stabilities of LLOs during electrochemical cycling. As a result, the optimized Ta‐doped LLO can deliver a capacity retention of 80% and voltage decay of 0.34 mV cycle−1 after 650 cycles at 1C. This study enriches the fundamental understanding of the electronic structure adjustment of LLOs and contributes to the optimization of LLOs for high‐energy LIBs. The high‐valance Ta doping of bulk Li‐rich layered oxides lead to a superior capacity retention of 80% after 650 cycles and a voltage decay of 0.34 mV cycle−1 at 1C, which is attributed to the stabilization of oxygen by strong Ta‐O bonds and the reduction of covalency of Ni‐O bonds.

Lithium-rich nickel-manganese-cobalt (LirNMC) layered material is a promising cathode for lithium-ion batteries thanks to its large energy density enabled by coexisting cation and anion redox activities. It however suffers from a voltage decay upon cycling, urging for an in-depth understanding of the particle-level structure and chemical complexity. In this work, we investigate the Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 particles morphologically, compositionally, and chemically in three-dimensions. While the composition is generally uniform throughout the particle, the charging induces a strong depth dependency in transition metal valence. Such a valence stratification phenomenon is attributed to the nature of oxygen redox which is very likely mostly associated with Mn. The depth-dependent chemistry could be modulated by the particles’ core-multi-shell morphology, suggesting a structural-chemical interplay. These findings highlight the possibility of introducing a chemical gradient to address the oxygen-loss-induced voltage fade in LirNMC layered materials. Lithium-rich layered material deserves in-depth understanding because it has large capacity enabled by both cation and anion activities. Here, authors apply 3D spectro-tomography with nano resolution to reveal the multi-layer morphology and depth-dependent transition metal valence distribution associated with oxygen redox.

The development of lithium rich layered oxide cathode materials with high energy density is one of the keys to improve the range of new energy vehicles. However, there are two bottlenecks in the development of this material: the voltage attenuation caused by structural transformation and the drastic decomposition of electrolyte at high voltage. In this paper, spherical Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 cathode material (LLO) was prepared, and the cycle performance of LLO cathode in LiBOB electrolyte with different content was compared. In addition, the effect of LiBOB electrolyte additives on lithium rich layered oxide materials was investigated. The decomposition path of LiBOB and the composition of stable CEI film were inferred by using computational chemistry and a variety of surface / interface detection methods.

At present, α-NaFeO 2 lithium-rich layered oxides (LLO) as cathode materials for lithium-ion batteries have attracted widespread attention due to their structure and performance characteristics and have become the mainstream research materials for lithium-ion batteries. However, during the charge and discharge process, the irreversible phase transition, cation mixing, and oxygen loss on the surface will lead to the inevitable severe capacity attenuation. Aiming at these problems, researchers have carried out a lot of modification on the material to improve the electrochemical performances without changing the crystal structure. Element doping is one of the commonly used effective strategies. In this work, the recent progress in understanding the influences of dopants in LLO cathode materials were summarized through five types: dopants substituted for transition metal (TM), lithium, oxygen, respectively, and multiple-dopants, the element doping combined with other strategies. In addition, the development trend of element doping in LLO cathode materials was prospected. It is believed that this review can guide researchers on developing ion doping strategies for the LLO cathode materials.

This study provides an effective surface modification method for Li-rich layered oxide (LLO, Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 ) with Al 2 O 3 coating. Strong organic acid TFBDC (2,3,5,6-tetrafluoro-1,4-phthalic acid) accumulates near alkali metal oxide LLO to form uniform Al-TFBDC coating. Al-TFBDC modified LLO is subjected to heat treatment to form Al 2 O 3 coating on the surface of LLO. This uniform coating protects LLO from direct contact with electrolyte and does not block the migration of Li + . Meanwhile, F − is successfully doped into LLO particles. The LLO coated with doping has clear layer structures, and its electrochemical properties have been significantly improved. The rate performance is increased by 66% at 10 C. After 150 cycles, its capacity retention rate is 92.5%, while that of uncoated LLO is only 55.8%. Graphical abstract

Lithium-rich cathode materials have emerged as promising materials for high-energy density lithium-ion cells due to their high specific capacity and high working voltage. In the present work, a comparative study has been made on the thermal stability and electrochemical performance of the lithium-rich cathode material, Li 1.5 Ni 0.25 Mn 0.75 O 2.5 (LNMO, synthesized by a co-precipitation method) with commercially available nickel-rich cathode material, LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC 811). Thermal runaway is a major safety concern hindering the large-scale application of lithium-ion cells in the booming electric vehicle market, and thus the thermal stability of electrode materials has become an important criteria for practical applications. The thermal stability of the cathode materials is investigated by thermogravimetric analysis (TGA). The LNMO cathode material showed better thermal stability in delithiated state than the NMC 811 cathode. A comparative study on the electrochemical performance of both LNMO and NMC 811 cathodes at a working voltage window of 2–4.8 V showed a higher initial discharge capacity (263 mAhg −1 ) for NMC 811 electrode than LNMO electrode (234 mAhg −1 ). However, the cycling and rate performance studies indicate excellent performance for LNMO cathode than NMC 811 at the higher working voltage.