(Invited) A Doped Mxene Dual Layer for Reliable Lithium Metal Anode

Abstract

To meet the rapidly growing market in electrical vehicles (EVs) and portable electronic devices, a battery with high energy density is required. In order to reach this goal, Li metal, is considered as the most promising candidate as anode. However, the dendrite forming, low Coulombic efficiency (CE), and unstable solid electrolyte interphase (SEI) pose big challenges in applying Li metal in batteries. Here we introduce a dual-layer coated Li metal surface, which consists a lithium carboxylate organic layer and a doped MXene layer. The porous organic layer increases the wetting of electrolyte and forms a thin solid electrolyte interface (SEI). While the doped MXene leads to 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 was received. The functional groups along with the good 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 paired with NMC811 exhibited a high initial CE of 82.1%. A high capacity-retention of 175.4 mAh/g at 1.0 C was achieved after 350 cycles. After long 500 cycles, a reliable capacity was still remained while the cell with un-modified Li metal quickly dropped to below 74.2 mAh/g. In a 475 mAh pouch cell, the battery still exhibited a high discharge capacity of 165.6 mAh/g with a capacity retention of 90.2% after 200 cycles, while the cell with pure Li metal decreased to 80.5%. Keywords: Lithium metal; Battery; Anode; MXene; Doping