Dual-Shielding Solvent Strategy of High Dipole-Moment Monomers for Stabilizing Gel Polymer-Based Lithium Metal Batteries
Xinjia Zhou, Yuzhi Chen, Fengxu Zhen, Yingbin Wu, Weiping Li, Xiangkai Yin, Limin Liu, Shujiang Ding, Wei Yu
Abstract
Gel polymer electrolytes exhibit excellent interfacial compatibility and high ionic conductivity attributed to the incorporation of high dipole-moment solvents. However, these solvents preferentially adsorb onto the anode compared to the polymer, decomposing into an organic-rich layer with sluggish Li-ion transport kinetics. Furthermore, the solvents dominate the solvation structure, intensifying the formation of unstable interfacial layers. Herein, a dual-shielding solvent strategy involving higher dipole-moment monomers is proposed to mitigate the undesirable interfacial effects in in situ gelled polymer electrolytes. High dipole-moment monomers (allylthiourea and 1,1,1,3,3,3-hexafluoroisopropyl acrylate) exhibit enhanced electrostatic adsorption, displacing solvents adsorbed onto the lithium metal. Moreover, the robust dipole–dipole interactions between high dipole-moment monomers and solvents inhibit the coordination of solvents with Li-ions, resulting in anion-dominated solvation structures. This strategy enables the functional monomers and more anions to synergistically form a stable interfacial passivation layer rich in LiF and Li 2 S. Consequently, the symmetric lithium battery can operate stably for 5000 h at a current density of 0.25 mA cm –2, and the LiFePO 4 ||Li battery maintains a 97% capacity retention rate after 2000 cycles at 2 C. This work integrates dipole-moment properties into the design of gel electrolytes, offering a promising strategy for addressing interfacial challenges in lithium metal batteries.