Understanding the Role of Charge Carrier Transport in High Performance Silicon-Based Anode Composite for Solid State Lithium-Ion Battery

Solid state lithium metal batteries are promising as the next-generation energy storage system due to their high energy density, thermal stability, and volumetric miniaturization.[1] However, the use of Li metal anode is detrimental in terms of catastrophic dendrite formation and Li deposition in the solid electrolyte layer that causes short-circuit, thereby limits the battery cyclability. Besides, the chemical and mechanical instability of the Li-anode-SE interface, and the low earth abundance of lithium establish the need for alternative high-capacity anode development. In this regard, silicon is a potential alternative due to its high theoretical capacity of 4200 mAh/g and formation of lithium-rich alloy (Li₁₅Si) at low electrode potential (&lt;0.35 V vs. Li/Li⁺). However, one of the main bottlenecks to achieve electrochemically stable and high-performance Si based anode is limited electronic and ionic conductivity of silicon. [2, 3] Despite appreciable advances in achieving stable Si based anode, the influence of the transport properties on the rate capability and long-term stability remains unclear.<br/><br/>In this study, we aim to understand the role of effective ionic and electronic conductivity in modulating the electrochemical performance of Si based anodes. First, we have developed Si-based composite anodes with a sulfide solid electrolyte and carbon additive, which significantly improved the ionic and electronic conductivity of the electrode composite, respectively. By systematically varying the ratio of the ion/ electron conducting phases in the silicon anode composite and relating corresponding cell performance with effective transport coefficients we can estimate the limiting conductivity values. The particle size of silicon is also found to significantly influence the effective transport properties, which in turn modulate the rate performance as well as the long-term stability of these anode composites. This study provides a comprehensive understanding on the role of charge carrier transport in achieving high-performance silicon based anode composites for solid-state batteries.<br/><br/><br/>Reference:<br/><br/>[1] Janek, J.; Zeier, W. G. Nat. Energy 2016, 1, 16141.<br/><br/>[2] Ohta, N.; Kimura, S.; Sakabe, J.; Mitsuishi, K.; Ohnishi, T.; Takada, K. ACS Appl. Energy Mater. 2019, 2, 7005.<br/><br/>[3] Lewis, J.A.; Cavallaro, K. A.; Liu, Y.; McDowell, M. T. Joule 2022, doi.org/10.1016/j.joule.2022.05.016.