Research On Improving The Performance Of Lithium Metal Anode By Hexagonal Boron Nitride(h-BN)

Lithium（Li）metal batteries are the most promising next-generation batteries due to their high energy density.However,there are serious problems such as Li dendrite and interfacial side reaction in the dissolution/deposition process of Li metal anode,which affect the cycling and safety performance of Li ion battery.In this paper,hexagonal boron nitride（h-BN）is used to construct a protective coating at the Li metal/electrolyte interface,which induced uniform Li deposition and then inhibited the growth of Li dendrites.The important findings are as follows:（1）To form a double lithophobic structure（h-BN@Cu）,the lithophobic h-BN coating is prepared on the surface of lithophobic Cu foil by conventional coating method.The h-BN layer ensures the lower adsorption energy and stronger charge transfer capacity in the h-BN/Cu interface,leading to the“h-BN-Li-Cu”sandwich deposition structure.The lithiophobic h-BN induces that the uniform Li deposition and inhibited Li dendrites growth.Moreover,the insulating h-BN acts as an interface protective layer to protect Li metal from the undesirable side reaction with electrolyte.Therefore,the h-BN@Cu electrode exhibits stable CE above 95%at 0.5 m A·cm^-2 and 1 m Ah·cm^-2 for 240 cycles.For the symmetric battery,it shows smooth voltage curve for 600 h at 0.25m A·cm^-2,0.5 m Ah·cm^-2,indicating the cycling stability of Li metal is improved significantly.（2）In order to increase the capacity of Li anode and expand the application areas of h-BN in battery research,the h-BN coating is prepared on the surface of Polypropylene（PP）separator to modified Li anode.The experimental results show that h-BN can reduce the interfacial impedance and improve the wettability between electrolyte with separator,which is beneficial to the migration of Li ions.What’s more,the h-BN@PP can reduce the Li nuclear barrier effectively,resulting in the regulated Li nucleation and inhibited Li dendrites growth on heterogeneous substrate,which can be observed directly by in situ characterization.Benefiting from the h-BN@PP,the Li symmetric battery can cycle stably beyond 2300 h with low voltage hysteresis（13 m V）at 1m A·cm^-2,0.5 m Ah·cm^-2 and over 800 h at a higher current density of 3m A·cm^-2,3 m Ah·cm^-2.In the full battery test that Li metal anode matches with Li Fe PO₄（LFP）cathode,the capacity retention rate in 400 cycles increases from 42.50%to 75.90%when h-BN@PP is used,which shows great superiority compared with the pure PP.