Designing Lithiophilic Lithium Metal Surface by a Hybrid Covalent Organic Framework and MXene Coating

With the increasing demand for developing large-energy-density and safe batteries, a reliable lithium metal as an anode becomes more and more important in various lithium metal and solid-state batteries. On the basis of better lithium regulation from MXene, a lithiophilic lithium metal surface is designed by introducing a 2D hybrid coating that consists of a thin covalent organic framework (COF-1) modified MXene layer (denoted as COF-MXene-Li). The abundant lithiophilic boroxine sites on 2D COF-1 attract lithium ions while the MXene further regulates lithium homogeneous nucleation and growth, thus preventing dendrite formation. The coin cell battery paired with LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) as cathode material displays 17% more capacity retention compared with pure lithium metal after 400 cycles at 0.5C.Over 81.4% capacity retention along with 99.96% Coulombic efficiency (CE) of a 1.0 Ah pouch cell versus LiNi_0.8Co_0.15Al_0.05O₂ (NCA) after 250 cycles is received. The assembled 1.6 Ah pouch cell with NMC811 show an energy density of up to 366.7 Wh Kg^-1 and an actual energy density based on the whole cell of up to 339.7 Wh Kg^-1. The improved cycling stability particularly in pouch cells opens broad applications for this hybrid coating modified lithium metal as anode electrode in a variety of large-energy-density battery systems.