Homogeneous deposition of lithium ions enabled by BN coated separator for high-performance lithium-metal batteries

Lithium metal has become one of the most promising anode materials in the field of energy storage due to its ultra-high theoretical capacity, low density and low negative potential. Unfortunately, the uncontrollable growth of lithium dendrites on the surface of lithium metal anodes can cause serious deterioration of battery performance and even cause serious safety problems, which greatly limits the further practical application of lithium metal batteries. In order to regulate the uniform deposition of lithium ions and inhibit the growth of lithium dendrites, we modified the surface of commercial Celgard®2325 battery separator by coated BN nanosheets and compared it with Celgard®2325 and Al2O3 coated separator (Al2O3-Separator). It is found that the structure of the inorganic coating on the surface of the separator affects the morphology of the lithium dendrites. The layered BN coated separator (BN-Separator) has the function of regulating the uniform deposition of lithium ions, which delivers the coulombic efficiency of 84.8% for Li|Cu half-cell after stabilize cycling 80 cycles (Celgard®2325 remains coulombic efficiency of approximately 66.2% after 38 cycles.). In addition, BN coating increases the ionic conductivity of commercial separator from 0.53 mS·cm−1 to 1.03 mS·cm−1, enabling an excellent cyclability of lithium metal batteries with a superior capacity of 159.4 mAh g−1 after 500 cycles at 1C rate and 119.0 mAh g−1 after 200 cycles at 5C rate. This work provides a feasible strategy for the design of separators with dendrite suppression function in lithium metal batteries.