The role of the anions in the growth speed of fractal electrodeposits

Building a stable and fine solid electrolyte interphase (SEI) is quite critical to inhibiting the generation and growth of dendrites in lithium metal batteries. Aluminum hybrid polymers are believed to be the potential materials for artificial SEI films. Herein, the Al-PEG prepolymer is prepared via an alcoholysis reaction of aluminum ethoxide, polyethylene glycol (PEG), and methoxy polyethylene glycol (MPEG). Then, the according artificial SEI (ASEI) films with tunable modulus are obtained via in-situ crosslinking reaction of the above aluminum hybrid prepolymer with the trimer of hexamethylene diisocyanate (THDI). Its lithium ionic conductivity at room temperature, lithium ionic transference number, and Young's modulus after electrolyte soaking are 2.20×10−3Scm−1, 0.79, and 0.4 GPa, respectively. After ASEI coating, the polarization voltage of the Li@ASEI||Li@ASEI cell is about 100 mV at a current density of 5 mA cm−2 for 5 mAh cm−2 and that of the Li||Li cell is 700 mV. After 500 cycles at 30 °C, the capacity retention of Li@ASEI||LFP full cell is 81% at 1C. While that for the according Li||LFP cell is only 48%. Even after 1000 cycles at 2C, Li@ASEI||LFP full cell still has 72% capacity retention.