An ion redistributor for dendrite-free lithium metal anodes

Lithium (Li) metal anodes have attracted considerable interest due to their ultrahigh theoretical gravimetric capacity and very low redox potential. However, the issues of nonuniform lithium deposits (dendritic Li) during cycling are hindering the practical applications of Li metal batteries. Herein, we propose a concept of ion redistributors to eliminate dendrites by redistributing Li ions with Al-doped Li6.75La3Zr1.75Ta0.25O12 (LLZTO) coated polypropylene (PP) separators. The LLZTO with three-dimensional ion channels can act as a redistributor to regulate the movement of Li ions, delivering a uniform Li ion distribution for dendrite-free Li deposition. The standard deviation of ion concentration beneath the LLZTO composite separator is 13 times less than that beneath the routine PP separator. A Coulombic efficiency larger than 98% over 450 cycles is achieved in a Li | Cu cell with the LLZTO-coated separator. This approach enables a high specific capacity of 140 mAh g-1 for LiFePO4 | Li pouch cells and prolonged cycle life span of 800 hours for Li | Li pouch cells, respectively. This strategy is facile and efficient in regulating Li-ion deposition by separator modifications and is a universal method to protect alkali metal anodes in rechargeable batteries.