Liewu Li,Qi Yuan,Shenghua Ye,Yonghuan Fu,Xiangzhong Ren,Qianling Zhang,Jianhong Liu
The layered LiCoO2 cathode plays a key role in high-energy-density lithium-ion batteries (LIBs), delivering a capacity of ∼185 mA h g−1 at a high cut-off voltage of 4.5 V (vs. Li/Li+). However, its practical applications in high-voltage LIBs are limited by a severe side reaction and an irreversible structure transition during cycling. Herein, we report a facile surface coating technique to prepare the Li4SiO4-coated LiCoO2 composite (LiCoO2@Li4SiO4) to confront the issue of instability and increase the capacity of the LiCoO2 cathode at 4.5 V. Notably, the LiCoO2@Li4SiO4 electrode exhibits an exceptionally high initial discharge capacity (180.7 mA h g−1 at 0.1 C), a significantly enhanced rate capability (147.2 mA h g−1 at 5 C), and long-term cycling stability (capacity retention of 82.2% after 500 cycles at 2 C). The experimental results demonstrate that the Li4SiO4 coating could effectively reinforce the structural stability of the LiCoO2@Li4SiO4 electrode during cycling. Furthermore, the density functional theory calculation results further confirm that the Li4SiO4 coating facilitates the rapid Li+ diffusion at the LiCoO2@Li4SiO4 electrode. This work provides a potential strategy for interface engineering of the 4.5 V LiCoO2 cathode for high-energy-density LIBs.
Jean Pierre Mwizerwa,Chenlong Gao,Changyong Liu,Wenfei Lu,Menghao Yang,Jun Shen
Constructing a robust, highly Li-ion-conductive surface layer is an effective strategy to improve the interfacial stability of nickel-rich cathodes like LiNi 0 . 8 Co 0 . 1 Mn 0 . 1 O 2 (NCM811). However, existing methods often fail to balance ion/electron conductivity with suppression of surface phase transformations, leading to poor rate capability, cycling stability, and energy density. This work introduces an in-situ solution-phase formed coating of Li 4 SiO 4 (LSO) that creates a continuous ion/electron-conductive network across NCM811 particles. This LSO enhances lithium-ion transport, builds a stable electrode/electrolyte interface, and alleviates mechanical stress during cycling. As a result, NCM811@LSO exhibits improved electrochemical performance, including reduced voltage decay and stable operation at high voltages. The LSO coating suppresses surface degradation, intergranular cracking, and parasitic reactions by shielding active sites and reducing direct electrolyte contact. It also mitigates electrode polarization and localized overcharging during long-term cycling. Full-cell tests using graphite and SiO/C anodes confirm high energy densities, reaching 765 Wh kg −1 in NCM811@LSO//graphite cells. Furthermore, density functional theory (DFT) calculations support the experimental findings, revealing that LSO promotes favorable interfacial chemistry, suppresses internal cracking, inhibits nickel migration, and prevents irreversible phase transformations. Compared to traditional coatings, the multifunctional LSO layer offers superior protection and conductivity, making it a promising approach for developing advanced, high-energy-density lithium-ion batteries.
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