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.