Dual-Layered 3D Composite Skeleton Enables Spatially Ordered Lithium Plating/Stripping for Lithium Metal Batteries with Ultra-Low N/P Ratios

Lithium metal is considered as the ultimate anode for next-generation high energy-density batteries. However, its practical application is still severely hindered by Li dendrite growth as well as infinite volume variation along plating and stripping. Herein, we report a dual-layered, spatially ordered composite skeleton for bottom-up lithium growth by uniformly incorporating Li6.06La3Zr2Al0.2O12 (LLZO) in the upper layer and ZnO in the bottom layer, respectively, in the matrix of carbon fibers (CFs). The well-dispersed ZnO nanoparticles on CFs in the bottom layer function as lithiophilic nucleation sites to homogenize Li nucleation, while LLZO nanoparticles on CFs in the upper layer facilitate Li ion diffusion and distribution for stable lithium growth owing to the high ion conductivity of LLZO. Benefiting from this synergetic effect, the CFs@LLZO//CFs@ZnO composite skeleton can effectively induce Li plating/stripping in a controllable spatially ordered manner, suppressing the volume variation and inhibiting the formation of dendritic lithium. As a result, the symmetric cell using Li|CFs@LLZO//CFs@ZnO||CFs@LLZO//CFs@ZnO|Li presents good cycling stability over 2500 h with a small overpotential of 12 mV at 1 mA cm-2. Notably, under a harsh negative-to-positive N/P ratio of 1, the Li|CFs@LLZO//CFs@ZnO||NCM811 full cell delivers a lifespan of 100 cycles with a capacity fading of only 0.175% per cycle and an average CE of 99.3%.