📝 SummarXiv

Abstract

Silicon is a promising anode material for next-generation lithium-ion batteries due to its exceptionally high specific capacity (3600 mAh g$^{-1}$), significantly exceeding that of conventional graphite. However, its practical application is hindered by substantial volume expansion (300-400%) during lithiation, leading to mechanical degradation and capacity fade. A graphite-coated silicon core-shell structure has been proposed to mitigate these issues by combining silicon's capacity with graphite's structural stability. Despite this, experimental studies have shown that the usable capacity of such composite electrodes can remain low, often below 40% at 1C, especially under high-rate cycling. In this work, we develop a physics-based electrochemical model to investigate the charge-discharge behaviour, rate limitations, and degradation mechanisms of silicon-graphite core-shell anodes. The model incorporates lithium transport, interfacial kinetics, evolving contact area due to silicon expansion, and a simplified cracking framework to capture loss of active material. Results are validated against key experimental trends and used to explore the effects of particle size, shell thickness, and charge protocol, offering insights into the design of more durable and efficient Si-based composite anodes.