Mitigating dendrite formation and electrolyte decomposition via functional double layers coating on copper current collector in anode-free lithium metal battery

Anode-free lithium metal batteries (AFLMBs) are promising power sources. However, Li dendrite and dead Li formation hindered it from practical applications. These challenges mainly result from inhomogeneous Li plating and fragile SEI due to the rough bare copper (bare Cu) surface and commonly used carbonate electrolytes. Herein, we designed a two-step modification on the copper surface with synthesized Ag nanoparticles wrapped with polydopamine ([email protected]) and an artificial protection film (APF) to introduce an interface functional double layers. The first layer serves as Li-seeds for uniform Li nucleation and deposition. The latter (PVDF-HFP/LiTFSI) encapsulates the deposited Li to promote the formation of an anion-derived compact SEI film and minimize the inevitable electrolyte decomposition with Li. It is found that the double-layer coating on copper enables homogenous and Li dendrite-free morphology. The anode-free cell with double layer-coated copper and NMC cathode maintains a superior coulombic efficiency (CE) of 98.15% and over 70 cycles at 40% capacity retention (CR) compared to the CE of 96.18% after 25 cycles at 40% CR on the bare Cu under 0.2 mA cm−2. These prominent achievements stem from the synergetic role of the lithiophilic Ag nanoparticles and the generation of an anion-derived robust LiF-rich SEI film. This study offers an alternative approach for current collector surface modification for the feasibility of AFLMBs.