2D Solid‐Electrolyte Interphase Built by High‐Concentration Polymer Electrolyte for Highly Reversible Silicon Anodes

• Published in: Advanced energy materials 2024-01, Vol.14 (2), p.n/a
• Main Authors: Wang, Yuxiao, Li, Tianyu, Yang, Xiaofei, Yin, Qianwen, Wang, Shaogang, Zhang, Hongzhang, Li, Xianfeng
• Format: Article
• Language: English
• Subjects: 2D SEI; Anodes; Electrolytes; high‐concentration electrolyte; Lithium-ion batteries; Polymers; Silicon; silicon anodes; solid–state electrolytes; Solvation; solvation structure
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202303189

Silicon anodes with a high capacity of 4200 mAh g−1 and a low potential of 0.3 V (vs Li+/Li) enable lithium‐ion batteries with improved energy density. However, the thickened 3D solid‐electrolyte interphase (SEI) formation on Si particles in the liquid electrolytes consumes the electrolyte/active Si and blocks the Li+/e− transport, resulting in fast capacity fading. Herein, a high‐concentration polymer electrolyte (HCPE) is designed to build 2D SEI on the Si anode surface instead of the particles, which accommodates the volume change and maintains the continuous Li+/e− transport pathways as well. The retarding effect of NO3− lowers the polymerization rate of 1,3‐dioxolane (DOL), enabling 6 m LiFSI dissolution. The high concentration of LiFSI takes part in constructing the solvation structure and pulls the DOL away, reducing the decomposition of DOL and poly‐DOL (PDOL) and inducing the generation of a LiF‐ and Li3N‐rich SEI with high mechanical strength and fast Li+ transport capability. As a result, the cell using HCPE delivers a high capacity of 1765 mAh g−1 at 2C and maintains a high capacity of 2000 mAh g−1 after 100 cycles at 0.2C, which is superior to that of a liquid electrolyte (617 mAh g−1) and a low‐concentration polymer electrolyte (45 mAh g−1). A high‐concentration polymer electrolyte (HCPE) with low flowability and high ionic conductivity is developed by retarding the ring‐opening polymerization of 1,3‐dioxolane (DOL) with a LiNO3 additive. The increased concentration of LiFSI in HCPE reduces the decomposition of DOL and helps induce the formation of a 2D inorganic‐rich solid‐electrolyte interphase, which accommodates the volume change and maintains the continuous Li+/e‐ transport pathways as well.