Continuous Li<sup>+</sup> Coordination Polymer Electrolyte for Fast Li<sup>+</sup> Migration, Stable Electrolyte Interphases, and Safe Quasi-Solid Lithium Metal Batteries
Kaixin Tian, Mingshan Wang, Rui Hu, Xinpeng Li, Xinpeng Li, Yongyong He, Jialin Song, Bo Zhao, Pan Luo, Xing Li, Xing Li, Guozhong Cao
Abstract
The advancement of quasi-solid lithium metal batteries strongly hinges on attaining fast Li + transport, stable electrode/electrolyte interphases, and high safety. The present study reports a high-continuous Li + coordination polymer electrolyte composed of a poly(1,3,5-trioxane) (PTXE) skeleton and mixed solvent of triethyl phosphate (TEP) and fluoroethylene carbonate (FEC). The continuous ether chains (−[C–O] n −) in PTXE coordinated with binary solvents and anions of dual lithium salt (TFSI – and DFOB – ) optimize the solvent structure and establish rapid Li + migration, achieving high Li + conductivity (1.87 mS cm –1 at 25 °C) and Li + transference number (0.64) prior to the liquid electrolyte. Simultaneously, via the synergistic induction and regulation exerted by polymer chain segments on the coordination of solvents and anions around Li +, phosphorus- and fluorine-rich cathodic and anodic electrolyte interphases are formed. Furthermore, flame-retardant TEP significantly improves the thermal stability at high temperature (60 °C) as well as under harsh mechanical testing. The assembly of a lithium metal battery with high loading mass of LiNi 0.6 Co 0.2 Mn 0.2 O 2 (10 mg cm –2 ) and ultrathin Li (50 μm) exhibits a high capacity retention rate of 87.1% with 120 cycles. Furthermore, a large-capacity pouch cell (7 Ah) with Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (40 mg cm –2 ) achieves high reversible capacity (6.58 Ah) with a high energy density of 505 Wh kg –1 .