Single crystal Ni-rich layered cathodes enabling superior performance in all-solid-state batteries with PEO-based solid electrolytes

Abstract

PEO-based composite electrolytes are very promising in all-solid-state batteries (ASSBs). To achieve ASSBs with high energy density, PEO based composite electrolytes should match high-voltage cathodes, but the stability of the cathode interface is a challenging issue. Herein, we investigate the electrochemical performance of single-crystal LiNi_0.6Mn_0.1Co_0.3O₂ (SC-NMC613) in ASSBs with PEO-based electrolytes, and compare the electrochemical performance of SC-NMC613 with conventional polycrystalline LiNi_0.6Mn_0.1Co_0.3O₂ (PC-NMC613) systematically. The Li⁺ diffusion coefficient of SC-NMC613 is 2–4 times higher than that of PC-NCM613 in ASSBs. SC-NCM613 shows high initial specific capacity (152 mA h g⁻¹) at 0.5C, stable cycling performance (100 cycles, retention of 108.9 mA h g⁻¹), and exceptional rate capability even without surface modification, while PC-NCM613 shows low initial specific capacity (137.5 mA h g⁻¹) at 0.5C, poor cycling performance (100 cycles, retention of 90.1 mA h g⁻¹), and poor rate capability in ASSBs. The severe cycling degradation of PC-NCM613 is mainly attributed to the structural deterioration inside particles and the formation of a rock-salt phase. The SC-NCM613 particles observably alleviate the generation of intergranular cracks and decelerate the formation of the rock-salt phase. SC-NCM cathodes in ASSBs with PEO-based electrolyte are beneficial to the stability of the cathode interface. Therefore, developing single-crystal Ni-rich cathodes represents a promising strategy to achieve ASSBs with both high energy density and power density.