In Situ Grown MnO₂ Nanoflower Arrays on Ni Foam (MnO₂@NF) as 3D Lithiophilic Hosts for a Stable Lithium Metal Anode

As the “holy grail” of lithium battery anode materials, the lithium metal anode suffers from several fatal defects, such as infinite volume expansion and uncontrolled dendrite formation. Herein, a three-dimensional (3D) lithiophilic host that comprises MnO₂ nanoflowers in situ grown on Ni foam (MnO₂@NF) is developed into a stable lithium metal anode. The 3D porous structure of Ni foam (NF) can greatly reduce the average current density of the electrode and relieve volume changes during the repeated plating/stripping process, in which the MnO₂ nanoflower arrays endow the 3D framework with high lithiophilicity, leading to a reduced lithium nucleation barrier and uniform lithium nucleation. It is found that the MnO₂ nanoarrays could transform into Ni/Li₂O, which offers abundant lithium deposition sites, homogenizes Li⁺ flux distribution, and ensures fast Li⁺ transfer kinetics. These advantages of MnO₂@NF enable dendrite-free lithium deposition behavior and excellent electrochemical performance. As a consequence, the as-designed MnO₂@NF host delivers a high Coulombic efficiency (CE) of 98.7% for 400 cycles in a half cell under 0.5 mA cm^–2, and an ultralong cycling lifespan of 2000 h with a low-voltage hysteresis of 18 mV is achieved in a symmetrical cell at 1 mA cm^–2. Furthermore, the Li-MnO₂@NF//LiFePO₄ full cell also exhibits enhanced cyclic stability and rate performance, indicating the application prospects of Li-MnO₂@NF as a stable lithium metal anode.