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Layered P2-Na0.67Mn0.67Ni0.33O2 has been considered an attractive cathode material for sodium-ion batteries (SIBs). Nevertheless, it is still burdened with hazardous phase transformation of P2–O2 under high voltage and harmful reactions at the interface of the electrode and electrolyte. These result in unfavorable structural degradation and rapid capacity decay. Herein, a gradient Mg2+ doping approach is proposed to trigger a structural transformation. During the annealing process, the bulk-diffused Mg2+ and surface residual Mg2+ induce the formation of the P2/P3@MgO structure. Consequently, this method combines the merits of the composite phases, bulk doping, and surface modification. In consequence, Na+ diffusion kinetics and electrochemical performances are remarkably enhanced. The cells using P2/P3@MgO show 69.7% capacity retention at 0.2 C within a voltage range of 1.5–4.5 V for 100 cycles, compared with the 42.6% for P2-Na0.67Mn0.67Ni0.33O2. This work offers new insights into further developments of advanced layered oxide cathodes for SIBs.

Solid-state polymer electrolytes (SPEs) are deemed as a class of sought-after candidates for high-safety and high-energy-density solid-state lithium metal batteries, but their low ionic conductivity, narrow electrochemical windows, and severe interfacial deterioration limit their practical implementations. Herein, an organoboron- and cyano-grafted polymer electrolyte (PVNB) was designed using vinylene carbonate as the polymer backbone and organoboron-modified poly(ethylene glycol) methacrylate and acrylonitrile as the grafted phases, which may facilitate Li-ion transport, immobilize the anions, and enlarge the oxidation voltage window; therefore, the well-tailored PVNB exhibits a high Li-ion transference number (t Li+ = 0.86), a wide electrochemical window (>5 V), and a high ionic conductivity (σ = 9.24 × 10–4 S cm–1) at room temperature (RT). As a result, the electrochemical cyclability and safety of the Li|LiFePO4 and Li|LiNi0.8Co0.1Mn0.1O2 cells with in situ polymerization of PVNB are substantially improved by forming the stable organic–inorganic composite cathode electrolyte interphase (CEI) and the Li3N–LiF-rich solid electrolyte interphase (SEI).

High-voltage lithium-rich manganese-based layered oxides (LMLOs) are considered as the most competitive cathode materials for next-generation high-energy-density lithium-ion batteries (LIBs). However, LMLOs still suffer from irreversible lattice oxygen release, uncontrollable interface side reactions, and surface structural degradation. Herein, we propose an integration strategy combining La/Al codoping and Li x CoPO4 nanocoating to improve the electrochemical performance of LMLOs comprehensively. La/Al codoping regulates the electronic structure to enhance the redox activity of anions and cations and inhibit structural degradation. The Li x CoPO4 nanocoating formed by in situ reaction with the surface residual lithium can not only promote Li-ion migration but also reduce interfacial side reactions. The induced Layered@Rocksalt@Li x CoPO4 heterostructure suppresses lattice volume variation and structural degradation during cycling. Under the synergistic effect of the heterostructure interface and well-tuned electronic structure, the capacity retention rate of comodified LMLO materials reaches 80.06% after 500 cycles (2.0–4.65 V) and 75.1% after 340 cycles at 1C under a high cut-off voltage of 4.9 V.

Li-rich layered oxides (LLOs) are considered promising candidates for new high-energy-density cathode materials for next-generation power batteries. However, their large-scale applications are largely hindered by irreversible Li/O loss, structural degradation, and interfacial side reactions during cycling. Herein, we demonstrate an integration strategy that tunes the electronic structure by La/Al codoping and constructs a ferroelectric interface on the LLOs surface through Bi0.5Na0.5TiO3 (BNT) coating. Experimental characterization reveals that the synergistic effect of the ferroelectric interface and the well-tuned electronic structure can not only promote the diffusion of Li+ and hinder the migration of O n– but also suppress the lattice volume changes and reduce interfacial side reactions at high voltages up to 4.9 V vs Li+/Li. As a result, the modified material shows enhanced initial capacities and retention rates of 224.4 mAh g–1 and 78.57% after 500 cycles at 2.0–4.65 V and 231.7 mAh g–1 and 85.76% after 200 cycles at 2.0–4.9 V at 1C, respectively.