Robust Pitch on Silicon Nanolayer-Embedded Graphite for Suppressing Undesirable Volume Expansion

Abstract

A significant volume expansion exhibited by high-capacity active materials upon lithiation has hindered their application as Li-ion battery anode materials. Although tremendous progress has been made in the development of coating methods that improve the stability of high-capacity active materials, suitable coating sources that are both strong and economical to use are yet to be discovered. Pitch is reported here as a promising coating source for high-capacity anodes owing to the high mechanical strength and low-cost process. Using in situ transmission electron microscopy, it is found that pitch can withstand the severe volume expansion that occurs upon Si lithiation owing to its high mechanical strength, originating from the long-range graphitic ordering. Notably, pitch-coated silicon nanolayer-embedded graphite (SG) exhibits superior capacity retention (81.9%) compared to that of acetylene-coated SG (66%) over 200 cycles in a full-cell by effectively mitigating volume expansion, even under industrial electrode density conditions (1.6 g cc(-1)). Thus, this work presents new possibilities for the development of high-capacity anodes for industrial implementation.