Electrochemically Active Red P/BaTiO 3 ‐Based Protective Layers Suppressing Li Dendrite Growth for Li Metal Batteries

Li metal has been considered a promising anode for high‐energy density batteries because of its high specific capacity. However, uncontrolled Li dendrite growth and severe electrolyte decomposition are detrimental obstacles hindering the practical applications of lithium metal batteries. Herein, electrochemically active red P‐based protective layers are introduced to suppress Li dendrite growth during cycling. Red P particles confined in the protective layer react with Li dendrites, forming Li 3 P, as Li dendrites are penetrating through the protective layer. As a result, Li metal is no longer plated on the Li 3 P surface because Li 3 P is electrically insulating, eventually leading to suppressing Li dendrite growth. Moreover, the red P‐based protective layer is functionalized with dielectric BaTiO 3 nanoparticles to scavenge radicals generated from electrolyte decomposition as well as to improve the mechanical strength of protective layers. The synergy effect of electrochemically active red P and inactive BaTiO 3 gives rise to the improved short‐circuit time of Li metal and the excellent cycle performance and Coulombic efficiency of Li/Li symmetric and Li/LiFePO 4 full cells over 200 cycles, despite the fact that the cell performances are examined with the conventional electrolyte of LiPF 6 in ethylene carbonate/diethyl carbonate that is highly unstable against Li metal.