Jingsheng Xu,Zhiyuan Wang,Runguo Zheng,Hongyu Sun,Yanguo Liu,Junhua You
Ni-rich cathodes especially with Ni content over 90 % are promising next-generation cathode materials for advanced high energy lithium − ion batteries. However, in comparison with Ni ≤ 80 % Ni-rich cathodes, these ultrahigh Ni-rich materials face more severe challenges in terms of harmful H2 − H3 phase transformations and structural degradation during cycling. Herein, we present a robust surface structure composted of defect-rich disordered structures and LiF/Li 2 SiO 3 coating for stabilizing the ultrahigh Ni-rich cathode LiNi 0.96 Co 0.03 Mn 0.01 O 2 (NCM96) by modification with (NH 4 ) 2 SiF 6 . The surface disordered structures including Li/TM mixing, spinel, and rock salt structure play a crucial role in inhibiting the irreversible H2-H3 phase transition and reducing lattice volume changes by lattice coherence effect. Moreover, the disordered surface in collaboration with the co-coating restrains the rapid growth of surface rock salt phase into the bulk, enhancing structural stability. The modified sample NSF-0.5 delivers a capacity of 238 mAh/g at 0.1C and maintains a capacity retention of 88.5 % at 0.5C after 100 cycles in half cell as well as 82.3 % at 1C after 300 cycles in full cell, significantly superior to the NCM96. The findings provide a simple and cost-effective surface modification strategy to enhance the structural stability and electrochemical performance of ultrahigh nickel cathodes for high-energy density LIBs.
The sulfide electrolyte-based all-solid-state batteries with high-nickel layered oxide cathodes face significant challenges due to the narrow electrochemical window of sulfides and severe side reactions caused by direct contact with high-voltage oxide cathode materials such as LiNi 0.9 Mn 0.05 Co 0.05 O 2 (NCM90). Here, we successfully synthesized Li 3 InCl 6 (LIC) halide electrolytes through ball-milling followed by annealing method, achieving the ionic conductivity of 2.0 mS cm −1 at room-temperature. The interface between this electrolyte and NCM90 cathode material without any interface modification is stable. By introducing the LIC electrolyte layer, the NCM90/LIC+Cl1.5/Li-In battery exhibits significantly improved electrochemical performance at different temperatures, particularly in terms of initial discharge capacity. Notably, the battery demonstrates outstanding discharge capacity and cycling stability at low temperatures. Experimental investigations reveal that the introduction of the LIC electrolyte with high oxidation potential facilitates the H2-H3 phase transition in NCM90 during high-voltage operation, which is critical for enhancing the discharge capacity. This work provides fundamental insights into interfacial engineering strategies for high-voltage sulfide-based all-solid-state battery systems.
High-capacity Ni-rich cathodes hold considerable promise in advancing both high-energy Li-ion batteries (LIBs) and all-solid-state Li batteries (ASSLBs). Yet, lattice volume changes induced by the H2–H3 phase transition lead to structural degradation. It has been demonstrated that doping approaches can enhance structural stability. Nevertheless, the selection of an appropriate dopant is of considerable importance for the design of high-performance Ni-rich materials with high-entropy doping. Furthermore, the feasibility of high-entropy doped Ni-rich cathodes in ASSLBs has not been reported to date. In this study, leveraging the chemically competitive doping mechanism of Mg, Al, Ti, Nb, and Mo elements, we propose a high-entropy doped LiNi0.8Co0.1Mn0.05Mg0.01Al0.01Ti0.01Nb0.01Mo0.01O2 (HE-NCM) to stabilize Ni-rich cathodes. In-situ X-ray diffraction confirms that the synergistic effect of multiple dopants in high-entropy doping significantly alleviates the H2–H3 phase transition and reduces lattice volume changes, which contribute to the absence of microcracks and improved bulk/interface stability. In ASSLBs, the HE-NCM@LiNbO3 maintains an outstanding capacity retention of 84.5% even after 1700 cycles, demonstrating the feasibility of high-entropy doped Ni-rich cathodes when matched with a sulfide solid-state electrolyte. The application of high-entropy doping methodology for the development of advanced rechargeable batteries has been shown to provide a novel perspective on the improvement of the structural robustness and interfacial compatibility of Ni-rich cathode materials.
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