A BF3 -Doped MXene Dual-Layer Interphase for a Reliable Lithium-Metal Anode.

ABSTRACT

A dual-layer interphase that consists of an in-situ-formed lithium carboxylate organic layer and a thin BF3 -doped monolayer Ti3 C2 MXene on Li metal is reported. The honeycomb-structured organic layer increases the wetting of electrolyte, leading to a thin solid electrolyte interface (SEI). While the BF3 -doped monolayer MXene provides abundant active sites for lithium homogeneous nucleation and growth, resulting in about 50% reduced thickness of inorganic-rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells is received. The functional BF3  groups, along with the excellent electronic conductivity and smooth surface of the MXene, greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite-free lithium-metal anode. The battery with this dual-layer coated lithium metal as the anode displays greatly improved electrochemical performance. A high capacity-retention of 175.4 mAh g-1 at 1.0 C is achieved after 350 cycles. In a pouch cell with a capacity of 475 mAh, the battery still exhibits a high discharge capacity of 165.6 mAh g-1 with a capacity retention of 90.2% after 200 cycles. In contrast to the fast capacity decay of pure Li metal, the battery using NCA as the cathode also displays excellent capacity retention in both coin and pouch cells. The dual-layer modified surface provides an effective approach in stabilizing the Li-metal anode.