Optimized Micro-Silicon Structure Enabling Ultrahigh Initial Coulombic Efficiency and Fast Reaction Kinetics for Advanced Lithium-Ion Batteries

Abstract

Micro-silicon (mSi) based anodes have garnered considerable interest due to their potential for high energy density and lower-cost energy storage systems. However, the large volume changes during repetitive lithiation and delithiation can lead to severe fracture and pulverization of mSi particles, ultimately resulting in rapid performance degradation. In this work, we address this problem by doping mSi with germanium (Ge), which improves electrical conductivity, increases lattice spacing, and optimizes Li+ diffusion channels. This method can achieve an initial coulombic efficiency of up to 95% and accelerated reaction kinetics for mSi-based anodes. Specifically, the Si20Ge anode exhibits a reversible capacity of 1109.3 mAh g-1 at the current density of 4 A g-1 after 150 cycles. When integrated into PVDF-based solid-state full cells, the Si20Ge anode, paired with a LiNi0.8Co0.1Mn0.1 (NCM811) cathode, retains 83% of its capacity after 200 cycles at the current density of 1C. This work offers valuable insights into the rational structural design of mSi alloyed anode materials for achieving higher-performance Li-ion batteries.