Novel Urea-Based Molecule Functioning as a Solid Electrolyte Interphase Enabler and LiPF<sub>6</sub> Decomposition Inhibitor for Fast-Charging Lithium Metal Batteries
Pan Zhou, Yingchun Xia, Yuhao Wu, Wenhui Hou, Yang Lu, Shuai Shuai Yan, Hangyu Zhou, Weili Zhang, Kai Liu
Abstract
The practical application of lithium metal batteries is impeded by the growth of dendrites and decomposition of electrolytes especially at high temperature in normal carbonate-based electrolytes. Herein, a novel urea-based molecule, 1,3-dimethyl-2-imidazolidinone (DMI), with a high donor number is proposed, which exhibits an extraordinary solubility of LiNO3 of over 5 M. As a result, a sufficient amount of LiNO3 is readily introduced into the carbonate electrolytes with DMI as an additive, and an average coulombic efficiency of 99.1% for lithium plating/stripping is achieved due to a stable solid electrolyte interphase (SEI) rich in inorganic-rich lithium salts. The Li||Li symmetric cell achieves a stable operation for over 2500 h at 0.5 mA cm–2 and 1 mAh cm–2, and a granular shape of deposited Li metal is still preserved even at a high current density of 10 mA cm–2. Besides, the decomposition of LiPF6 is inhibited benefiting from its enhanced dissociation after the addition of DMI/LiNO3 and DMI’s function as a PF5 scavenger. Consequently, the Li||LiFePO4 cell succeeds to achieve an excellent capacity retention of 95.6% after 2200 cycles at a high rate of 5C, and a stable operation is realized at a high temperature of 60 °C even under harsh conditions (45 μm ultrathin Li and ∼1.5 mAh cm–2 LiFePO4). This work enriches the solvents and additives pool for stable and high-performance lithium metal batteries and will shed light on future developments of advanced battery electrolytes.