Rational electrolyte solvent screening for high-energy lithium metal batteries at low temperatures
Zehang Peng, Kui Ding, Meiting Lai, Rui Qiu, Ye Xiao, Junkai Shi, Xiaoxian Guan, Yue‐Peng Cai, Chao Xu, Fei Wang, Qifeng Zheng
Abstract
Weakening the solvation ability has shown great potential in electrolyte solvent design to promote the cycling performance of Li-metal batteries, yet suffers from sluggish kinetics and uncontrolled Li dendrite formation, particularly at low temperatures. Herein, we propose a guideline for rational electrolyte solvent screening, where the restrained electrostatic potential of the coordinated O is proposed as one descriptor to quantify the solvation effect, followed by introducing the dipole moment as a correction descriptor to optimize solvents’ sensitivity to the electric fields and interphase stability. Under the guidance of this screening principle, a class of asymmetric fluorinated ethers is rationally designed, of which the 3,3,3-trifluoropropyl-1-methyl ether with moderate restrained electrostatic potential of the coordinated O and dipole moment is identified to mediate a stable six-membered chelating structure with Li+, significantly promoting Li kinetics and reversibility from 30 to −60 °C. Coupled with its good anodic stability, this single-salt single-solvent electrolyte enables the 50 μm Li | |4.0 mAh cm−2 LiNi0.8Mn0.1Co0.1O2 coin-cells maintaining > 90% capacity after 200 cycles at benign and low temperatures. A practical Li-metal pouch-cell delivers a high specific energy (based on the mass of all components) of 345.3 Wh kg−1 over 40 cycles at −40 °C. Li-metal batteries suffer from sluggish kinetics at low temperatures. Here, authors propose a guideline for rational electrolyte solvent screening and design a class of asymmetric ethers, which bestows the Li metal pouch cell with a high specific energy of 345.3 Wh kg−1 over 40 cycles at −40 °C.