Hot-pressed PVDF-based Difunctional Protective Layer for Lithium Metal Anodes

Lithium metal has been considered a promising anode for next-generation batteries due to its high specific energy (3860 mA.h/g) and lowest redox potential (-3.04 V vs. SHE). However,the poor electrochemical stability of lithium metal results in limited cycle life and short-circuit due to lithium dendritic growth. Poor environmental stability of lithium metal also increases production difficulty and cost. Improving the interface stability of lithium metal anode is considered as an important approach to optimize battery performance. Herein,a dual-functional polyvinylidene fluoride (PVDF) protective layer is fabricated on lithium anode surface using a simple hot-pressing method,effectively promoting air stability to 120 min and increasing cycle life of the symmetrical battery to 1200 h. In addition,by introducing SnO2 nanoparticles,an inorganic-organic composite protective layer is constructed. The composite protective layer induces lithium nucleation sites by in-situ alloying, which greatly reduces lithium plating overpotential to 0.007 V and facilitates better cyclability of lithium metal anodes. The full-cell with this protective layer shows a long cycle life of 200 cycles with a capacity retention rate higher than 90% and a high discharge capacity of 127 mA.h/g at a current rate of 3C. The strategy proposed in this work for the dual-function interface protective layer can effectively improve the air stability and electrochemical performance of lithium metal anode.