An optimized 3D polymer alloy interface for durability and safety for Li metal batteries

Abstract Compared with other anode materials, lithium (Li) metal anode is regarded as the “Holy Grail” due to its high theoretical specific capacity and low electrochemical redox potential. However, the poor battery life and serious safety problems caused by the uncontrolled growth of Li dendrites and the extreme instability of the interface during the long-term Li plating/striping process have always been obstacles to the commercialization of Li metal batteries (LMBs). Herein, a modified composite separator (PAP@PP) for stabilizing Li metal anode is prepared by coating polymer alloy matrix (PA) and trace pore regulator (octavinyl polyhedral oligomeric silsesquioxane (OV-POSS)) onto the commercial PP separator. The prepared composite separator combines advantages of the polymer alloy matrix and shows rapid diffusion pathway for electrolyte, thus homogenizing Li ion flux on the Li metal surface and greatly improving the interface properties of the Li metal anode/electrolyte. The symmetric Li/Li batteries with PAP@PP separator shows better cycling stability under higher current density without obvious voltage fluctuations. Scanning electron microscopy (SEM) images also prove that the PAP@PP separator has a better regulating effect on Li deposition. More importantly, the Li/Li4Ti5O12 full batteries show superior C-rate performance, lower capacity decay rate (0.01% per cycle) and steady coulomb efficiency (99.7%) after 300 cycles at 4C. This work provides a simple, effective and suitable mass production method for inhibiting the growth of Li dendrites and improving the cycling stability of LMBs.