Functional Polymer Coating For Lithium Metal Anode Protection

Lithium?Li?metal is an ideal anode material.Due to its high theoretical specific capacity and low redox potential,it can significantly increase the energy density of batteries to meet the market demand for high-energy-density batteries.However,the formation of dendritic Li and poor cycling performance have hindered its practical application in rechargeable batteries.Considering the chemical forces between polar functional groups and ions in the electrolyte,we constructed a polymer coating with rich functional groups on the electrode surface as an artificial SEI layer to regulate the electrochemical behavior of ions in the area near the interface between the electrolyte and the electrode,thus realizing the Li deposition without dendrite and improving the cyclic performance of Li metal cathode.?1?Sericin has rich polar functional groups on its polypeptide chain.With the rich lithiophilic sites?-OH,-COOH,and-CO-NH-?and anionphilic sites?-NH₂?,Li ions and anions could be regulated separately for the uniform Li plating and stripping at the electrode/electrolyte interface.Extra-long cycle life and high average Coulombic efficiency of 98%can be obtained in Li/Cu cells with the sericin coated Cu anode.Even under extreme test conditions(10 mA cm^-2 with 5 mAh cm^-2),the sericin functional Li metal anode also shows more superior cycling stability in the symmetric cells.The conformal sericin coating can effectively inhibit the corrosion of air and polysulfides on the Li metal anode,and the Li-S batteries with the sericin coated Li anodes exhibit greatly enhanced rate performance and cycling performance;?2?The high binding energy between Poly?vinyl alcohol??PVA?and Li ion makes the lithiophilic sites?-OH?on the PVA molecular skeleton attract a large amount of Li ions,thereby alleviating the tendency of Li ions to accumulate at the protrusions on the electrode surface and homogenizing the Li-ion flux at the electrode/electrolyte interface,thus the Li ions can be uniformly deposited on the electrode surface.Under the current densities of 1,3,5 and 10 mA cm^-2,the PVA-coated Cu electrodes show extended cycling life and improved CE of 98.1,97.6,97.5 and 97.2%,respectively.Moreover,using the PVA-coated Li as the anode effectively improves the cycling performance of Li-S full cells at a rate of 0.2C or 1C.