Ni-rich cathode materials LiNi x Co y Mn1–x–y O2 (x ≥ 0.6) have attracted much attention due to their high capacity and low cost. However, they usually suffer from rapid capacity decay and short cycle life due to their surface/interface instability, accompanied by the high Ni content. In this work, with the Ni0.9Co0.05Mn0.05(OH)2 precursor serving as a coating target, a Li-ion conductor Li2SiO3 layer was uniformly coated on Ni-rich cathode material LiNi0.9Co0.05Mn0.05O2 by a precoating and syn-lithiation method. The uniform Li2SiO3 coating layer not only improves the Li-ion diffusion kinetics of the electrode but also reduces mechanical microstrain and stabilizes the surface chemistry and structure with a strong Si–O covalent bond. These results will provide further in-depth understanding on the surface chemistry and structure stabilization mechanisms of Ni-rich cathode materials and help to develop high-capacity cathode materials for next-generation high-energy-density Li-ion batteries.

LiCoO2, which was first proposed as a cathode in 1980 by Prof. John B. Goodenough, is still one of the most popular commercial cathodes for lithium‐ion batteries. Tremendous efforts have been invested in increasing the capacity of LiCoO2 by charging to high voltage. However, a series of issues, such as structural instability and dramatic side reactions with electrolytes, can emerge as cut‐off voltage above 4.5 V (vs Li/Li+). Here, a surface modification strategy with a multilayer structure is provided, involving a Zn‐rich surface coating layer, rock‐salt phase buffer layer and surface gradient Al doping layer, to overcome the detrimental issues and achieve stable cycling of LiCoO2 at 4.6 V. The complete coating of the modification layer restrains the interfacial side reactions with electrolyte and inhibits the impedance growth. The phenomenon of quasi‐epitaxial growth demonstrates that the multilayer structure significantly reduces the lattice mismatch between host LiCoO2 and surface coating layer and enhances the stability of the Zn‐rich outside layer, which promote the long‐term effectiveness of the modification. Furthermore, the disordered rock‐salt phase layer and Al surface doping also enhance the structural stability. All of these synergistically lead to the stable cycling of LiCoO2 at 4.6 V with a capacity retention of 65.7% after 500 cycles.

A general polymer‐assisted spinodal decomposition strategy is used to prepare hierarchically porous sodium super ionic conductor (NASICON)‐structured polyanion‐type materials (e.g., Na3V2(PO4)3, Li3V2(PO4)3, K3V2(PO4)3, Na4MnV(PO4)3, and Na2TiV(PO4)3) in a tetrahydrofuran/ethanol/H2O synthesis system. Depending on the boiling point of solvents, the selective evaporation of the solvents induces both macrophase separation via spinodal decomposition and mesophase separation via self‐assembly of inorganic precursors and amphiphilic block copolymers, leading to the formation of hierarchically porous structures. The resulting hierarchically porous Na3V2(PO4)3 possessing large specific surface area (≈77 m2 g−1) and pore volume (≈0.272 cm3 g−1) shows a high specific capacity of 117.6 mAh g−1 at 0.1 C achieving the theoretical value and a long cycling life with 77% capacity retention over 1000 cycles at 5 C. This method presented here can open a facile avenue to synthesize other hierarchically porous polyanion‐type materials.

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While the theoretical capacity of LiCoO 2 is as high as 274 mA h g −1 , its practical specific capacity is only about 140 mA h g −1 when it was first applied in lithium-ion batteries. Raising the charging cutoff voltage can effectively enhance the specific capacity of LiCoO 2 . For example, when increasing the cutoff voltage to 4.5 V vs Li + /Li, the specific capacity will increase to 185 mA h g −1 . However, the surface and structure instability of LiCoO 2 under high-voltage operation lead to rapid capacity decay. Various modified strategies have been proposed, such as element doping and surface coating. In this work, we develop a one-step integrated comodification approach to achieve a long cycle life of LiCoO 2 in the range of 3.0−4.5 V. The phosphate surface layer suppresses the side reaction of electrolyte and Co dissolution. Mn doping enhances the structure stability of LiCoO 2 . The capacity retention of a modified LiCoO 2 with a cutoff voltage of 4.5 V is as high as 83.7% even after 700 cycles.