Enhanced microstructure stability of LiNiCoMnO cathode with negative thermal expansion shell for long-life battery.

With high specific energy density, Ni-rich layered LiNiCoMnO (NCM) material has become one promising cathode candidate for advanced lithium-ion batteries (LIBs). However, severe capacity fading induced by microstructure degradation and deteriorated interfacial Li transportation upon repeated cycling makes the commercial application of NCM cathode in dilemma. To address these issues, LiAlSiO (LASO), one unique negative thermal expansion (NTE) composite with high ionic conductivity, is utilized as a coating layer to improve the electrochemical performances of NCM material. Various characterizations demonstrate that LASO modification can endow NCM cathode with significantly enhanced long-term cyclability, through reinforcing the reversibility of phase transition and restraining lattice expansion, as well as depressing microcrack generation during repeated delithiation-lithiation processes. The electrochemical results indicate that LASO-modified NCM cathode can deliver an excellent rate capability of 136 mAh g at a high current rate of 10 C (1800 mA g), larger than that of the pristine cathode (118 mAh g), especially higher capacity retention of 85.4% concerning the pristine NCM cathode (65.7%) over 500 cycles under 0.2 C. This work provides a feasible strategy to ameliorate the interfacial Li diffusion and suppress the microstructure degradation of NCM material during long-term cycling, which can effectively promote the practical application of Ni-rich cathode in high-performance LIBs.