Application of 3D mullite fiber matrix as a lithiophilic interlayer in lithium metal anodes

The lithium (Li) metal anode is an intriguing choice for Li metal batteries because of its considerably high theoretical capacity. However, the commercialization of unimproved lithium metal batteries is impeded due to the severe security issues related to uncontrollable Li dendrite growth. Herein, we fabricated three-dimensional (3D) mullite sheets via a high temperature annealing process in the presence of silica sol and used such sheets as interlayers between Li anodes and separators for assembling cells. As both Al₂O₃ and SiO₂, the two main components of mullite fibers, are lithiophilic, the deposition of Li during charging processes could be regulated and the growth of lithium dendrites and accumulation of dead Li could be efficiently suppressed. In a Li||Cu half-cell, the mullite fiber/Li composite electrode delivers a coulombic efficiency of above 98% under a current density of 1.0 mA cm^-2. For a Li||LiFePO₄ full cell, the same composite electrode exhibited improved capacity retention (>89%, after 800 cycles) and rate capability at 5.0C.