Integrating surface coating and quasi-solid deep eutectic electrolytes for enhanced cycling of micro-Si anodes in Li-ion batteries

Abstract

Microsilicon (μ-Si) anodes exhibit promising capacity and energy density as lithium-ion battery (LIB) anodes. However, their application is affected by large volume changes, surface pulverization, poor interfacial contact, and limited cyclic stability. Here, we report an integrated methodology to protect μ-Si particles by coating the particle surface and integrating the coated Si particles with a quasi-solid-state (gel) electrolyte to achieve high performance and long-term stability. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy showed that the μ-Si particles were successfully coated with a polydopamine (PD) layer via a wet-chemical process to achieve PD@Si. Moreover, a quasi-solid-state electrolyte composed of LiTFSI/N-methylacetamide deep eutectic solvents and acrylate monomers was optimized to accommodate the volume change endured by μ-Si based anode during cycling. The as-prepared quasi-solid-state electrolyte exhibited a high ionic conductivity (1.63 × 10⁻³ S cm⁻¹) at room temperature. Integrating PD@Si with the modified quasi-solid-state electrolyte delivered a superior stability upon cycling, maintaining a high specific capacity of 1000 mA h g⁻¹ in the quasi-solid-state electrolyte at a current density of 1 A g⁻¹ after 100 cycles in a half-cell battery. Furthermore, post-cycling analyses demonstrated that electrode cracking and delaminating were reduced with the co-utilization of coating and quasi-solid-state electrolyte. These results proved that μ-Si microparticle-based electrodes could be applied to high-energy quasi-solid-state batteries.