Rigid Polyimide Buffering Layer Enabling Silicon Nanoparticles Prolonged Cycling Life for Lithium Storage

Abstract

Structural design is an effective avenue to alleviate the volume expansion of silicon anode. Surface coating and/or encapsulation shows a significant advantage. However, most coating layers show poor mechanical strength, resulting in fast fading electrochemical performance. In this work, commercial silicon nanoparticles coated with polyimide (PI) film have been synthesized by a simple mechanical stirring process. The polyimide polymer film endows silicon with structural characteristics of intrinsic high ionic conductivity, a stable SEI layer, and structure rigidness. The resulting composites display excellent capacity retention with about 1144 mAh g–1 after 430 cycles at 1 A g–1. The LiCoO2/Si@PI-15% full cell displays a high initial capacity of ∼126 mAh g–1 based on the cathode mass. After 50 cycles, it delivers 55 mAh g–1 reversible capacity with an average CE of ∼98% at 140 mA g–1.