Ultrathin hierarchical porous Cu current collector fabricated by anodic oxidation in complexing agent system for stable anode-free Lithium metal batteries

3D porous Cu current collectors, as the host for Li metal deposition in Li metal batteries, shows great potential in inhibiting Li dendrite growth. A method of fabricating ultrathin porous Cu with 3D hierarchical micronanostructures by electrochemically oxidizing of planar Cu in complexing agent electrolytes, at controlled electrolyte temperature, is introduced in this work. When applied as the anode current collector of anode-free Li metal batteries, the micropores inside the 3D porous Cu provide a large amount of Li accommodating space and accelerates the diffusion rate of lithium ions. The uniformly distributed 3D micro/nanopores effectively homogenizes the local electric field and induce homogeneous deposition of Li, thereby inhibiting the growth of Li dendrites and forming stable SEI layers. The hierarchically structured micro/nanoporous Cu current collector presents low nucleation overpotential and stable Li deposition behavior at 0.5 mA cm⁻². Compared with the Cu current collector, the full-cell (Cu//LiFePO₄) capacity retention assembled by this structure is improved from 10.2% to 55.5% at 100 cycles with 0.2 C rate, and the Coulombic efficiency is as high as 98.3%. This work provides a feasible and scalable method to fabricate hierarchical porous Cu for dendrite-free and high-capacity retention anode-free Li metal batteries.