PDA modified commercial paper separator engineering with excellent lithiophilicity and mechanical strength for lithium metal batteries

The lithium metal anode has extremely high theoretical specific capacity and most negative electrochemical potential. However, upon cycling, the formed dendrites result in severe safety concerns and poor stability, thus limiting the applications of the material. Herein, we report a novel separator with excellent lithiophilicity and strength obtained via in-situ modification of virgin cellulose paper (CP) with polydopamine (PDA) to effectively stabilize the Li metal anode. The as-obtained PDA-CP separator showed excellent thermal stability and high mechanical strength due to the interaction between PDA and cellulose molecule, and an excellent electrolyte affinity to enable high electrolyte uptake and ionic conductivity. More importantly, in symmetric Li/Li cells with the PDA-CP separator, the Li metal anode was stabilized during repeated stripping/plating processes over 500 cycles (3000 h) at a current density of 0.5 mA cm−2. Further, we achieved excellent cycling stability over 600 cycles at the rate of 5 C by employing Li/PDA-CP/LiFePO4 cells. The results demonstrate the immense potential of PDA-CP as advanced separator and propose an efficient and simple strategy to stabilize Li metal anode for the next-generation high-energy lithium-metal batteries.