Investigating operating protocols to extend the lifespan of silicon anodes in Li-ion batteries

Abstract

This investigation explores the differentiated electrochemical behavior of silicon (Si) anodes in lithium-ion batteries (LIBs) under different operating protocols defined by specific voltage windows and capacity control strategies. Our investigation reveals distinctive responses of the Si anode to different state of charge (SoC) ranges, translating delivered capacity into significant variations in cycle life. While predominantly mostly lithiated Si anodes at 0.01–0.32 V subjected to voltage-controlled operation with an SoC between 75 % and 100 % exhibit poor cycle life, a similar situation with predominantly mostly delithiated anodes at 0.23–1.5 V and an SoC of 0–25 % also results in inferior cycle performance. Conversely, predominantly partially lithiated Si anodes at 0.01–0.5 V under voltage-controlled conditions with an SoC range of 65–100 % show superior cycle life performance. However, predominantly partially delithiated Si anodes at 0.1–1.5 V, voltage controlled with an SoC of 0–40 %, lead to a cycle life with obvious degradation. Likewise, Si anodes subjected to full lithiation followed by delithiation at 1200 mA h g−1, controlled by delithiation capacity, demonstrate excellent cycle life within a SoC range of 65–100 %. On the contrary, full delithiation followed by lithiation at 1200 mA h g−1 results in less favorable cycle life within an SoC range of 0–35 %. In short, maintaining the lithiation state at a higher level, i.e. a high SoC, throughout the cycle allows Si anodes to maintain low impedance, resulting in outstanding cycle performance. These results provide important insights into tailoring operating parameters to optimize Si anode cycle performance in LIBs.