Boosted Li+ transport ensured by high-entropy Prussian blue analogues with tuned PF6− adsorption for stable Li metal anode

Abstract

The inhomogeneous lithium metal (Li) deposition and low lithium ion (Li+) mobility lead to the formation and growth of Li dendrites, which impede the desirable performance of Li metal batteries (LMBs) with high energy density in widely practical applications. Herein, a high-entropy MnCoNiCuZn-Prussian blue analogue (HE-PBA) is utilized to modify the commercial polypropylene separator (PP@HE-PBA), which will form an artificial protective layer on the surface of Li. The polar –CN groups of HE-PBA can enhance the wettability of PP to the electrolyte, while the movement of PF6− anions are flexibly tuned by the appropriate absorption ability and synergistic effect of multiple metal ions in HE-PBA. A high Li+ transference number of 0.69 is achieved, which can relieve the Li+ concentration polarization, regulate the Li+ flow, and realize the uniform Li deposition. With PP@HE-PBA, the Li||Li symmetric cells display durability up to 600 h in the ester-based electrolyte at 1 mA cm−2 for 1 mAh cm−2. Also, the PP@HE-PBA exhibits great potential in LMBs, where the Li4Ti5O12 (LTO) ||Li and sulfated polyacrylonitrile (S-PAN) ||Li batteries deliver superior cycling performance to those without PP@HE-PBA.