An integrated dual-gradient host facilitates oriented bottom-up lithium growth in lithium metal anodes.

Integrated gradient hosts, composed of poorly conductive frameworks on copper current collectors, have been extensively explored for the development of Li metal anodes (LMAs). Despite their potential, high Li nucleation overpotentials and slow interface kinetics often lead to inferior performance. Herein, we combine electrospinning and electrodeposition to create an integrated gradient host, namely OPAN/rGO-CuO/Cu. This involves electrodeposition of graphene oxide onto copper foil, reacting to form a lithiophilic rGO-CuO layer, which is then covered with an oxidized polyacrylonitrile (OPAN) nanofiber layer, establishing conductivity and lithiophilicity dual gradients. The insulating OPAN top layer blocks electron transmission to the surface and prevents Li deposition, while the lithiophilic rGO-CuO layer facilitates Li ion transport to the bottom and reduces the nucleation barrier, both of which promote uniform Li deposition from bottom to top. As a result, the battery achieves an average coulombic efficiency of 98.4% over 500 cycles at 1 mA cm, and the symmetric cell sustains an ultra-long cycle life of 1600 h with a minimal polarization voltage of 12 mV. When paired with a LiFePO cathode, the full cell demonstrates a capacity retention of 92.6% after 300 cycles at 1 C, with an average capacity decay rate of just 0.025% per cycle. This innovative approach offers a promising pathway for developing high-performance LMAs.