Micrometer‐Sized SiMg<i>_y</i>O<i>_x</i> with Stable Internal Structure Evolution for High‐Performance Li‐Ion Battery Anodes

Abstract

In recent years, micrometer-sized Si-based anode materials have attracted intensive attention in the pursuit of energy-storage systems with high energy and low cost. However, the significant volume variation during repeated electrochemical (de)alloying processes will seriously damage the bulk structure of SiO_x microparticles, resulting in rapid performance fade. This work proposes to address the challenge by preparing in situ magnesium-doped SiO_x (SiMg_y O_x ) microparticles with stable structural evolution against Li uptake/release. The homogeneous distribution of magnesium silicate in SiMg_y O_x contributes to building a bonding network inside the particle so that it raises the modulus of lithiated state and restrains the internal cracks due to electrochemical agglomeration of nano-Si. The prepared micrometer-sized SiMg_y O_x anode shows high reversible capacities, stable cycling performance, and low electrode expansion at high areal mass loading. A 21700 cylindrical-type cell based on the SiMg_y O_x -graphite anode and LiNi_0.8 Co_0.15 Al_0.05 O₂ cathode demonstrates a 1000-cycle operation life using industry-recognized electrochemical test procedures, which meets the practical storage requirements for consumer electronics and electric vehicles. This work provides insights on the reasonable structural design of micrometer-sized alloying anode materials toward realization of high-performance Li-ion batteries.