High Polymerization Conversion and Stable High-Voltage Chemistry Underpinning an In Situ Formed Solid Electrolyte
Chen Wang, Huanrui Zhang, Shanmu Dong, Zhenglin Hu, Rongxiang Hu, Ziyang Guo, Tao Wang, Guanglei Cui, Liquan Chen
Abstract
In situ polymerization system can provide a compact and compatible interface with minimum polymer electrolyte, which is imperative to address the bottleneck of notorious solid–solid interface issues for high-energy-density solid-state batteries. However, the existing in situ formed solid-state electrolyte still faces many problems, such as low polymerization conversion and inferior high-voltage stability, prohibiting its applications in practical high-voltage lithium-metal batteries. Herein, we present a deep eutectic solvent (DES)-based in situ polymerized solid electrolyte, which is facile and well matched with the commercially available lithium-ion battery technology. The DES precursor is made from a molten mixture of solid powders, containing a synthesized monomer named (2-(((2-oxo-1,3-dioxolan-4-yl) methoxy) carbonylamino))-ethyl methacrylate (CUMA), a succinonitrile (SN) plastic crystal, and two kinds of lithium salts. After in situ ploymerization triggered by free radical, the liquid again turns into a solid composite electrolyte (PDES-CPE) with a superior polymerization conversion of 99.8%. It delivers a promising lithium-ion conductivity (1.07 × 10–3 S/cm with a high lithium-ion transference number of 0.62 at 30 °C) and prominent high-voltage stability (100 cycles with 82.4% capacity retention coupled with 4.6 V LiCoO2 cathode). Through in situ Fourier transform infrared (FTIR) spectroscopy, we reveal a robust interface chemistry with thermodynamically improved high-voltage stability (compared to polyether-based electrolyte). This as-presented strategy makes a big leap to address the interface issues and boost the development of high-energy-density solid-state lithium-metal batteries.