Formulating a New Electrolyte: Synergy between Low-Polar and Non-polar Solvents in Tailoring the Solid Electrolyte Interface for the Silicon Anode
Siyu Pan, Xuerui Yang, Yao Zhou, Chao Lv, Haotian Deng, Mingjia Guo, Shou-Xiao Chen, Yiyang Hu, Li Deng, Yu Qiao, Jun‐Tao Li, Ling Huang, Yong Yang, Shi‐Gang Sun
Abstract
Currently, lithium-ion batteries (LIBs) are assembled with polar electrolytes; thus, resulting SEI layers are dominated with organics. Herein, a low-polarity electrolyte is formulated with a low-polarity solvent (tetraethyl silicate, TEOS) and a non-polar inert shielding co-solvent (cyclohexane, CYH); solvation behaviors of lithium salt are investigated. The use of such a low-polarity solvent is found to improve the fraction of anions in the solvation sheath of Li+, and the presence of the non-polar co-solvent further shields the reductive decomposition of the solvent on the anode. The resulting SEI layer is relatively rich in LiF and has a 3D cross-linked Si–O network as a skeleton from the decomposition of TEOS molecules, which is more robust to tolerate the damage from the volume expansion of silicon. A Si-nanoparticle-based anode in such a low-polarity electrolyte delivers a capacity as high as 1491 mAh g–1 after 200 cycles, outperforming those in the commercial polar electrolytes.