Hydrothermal fabrication of three-dimensional secondary battery anodes

A generalized hydrothermal strategy for fabricating 3D battery electrodes was developed. Ni inverse opals coated with SnO₂NPs or Co₃O₄ nanoplatelets, as well as SiO₂ inverse opals coated with Fe₃O4 were hydrothermally fabricated. For the Ni@SnO₂ NP electrodes, the Ni inverse opal was fabricated on a tungsten foil. Before PS opal growth, the tungsten substrates were cleaned by ultrasonication in acetone, ethanol, and Millipore water for 30 min each. To enlarge the pore size of the final Ni inverse opal, and to enhance the bonding between PS spheres, the PS opal was sintered at 95°C for 3 h. The Ni inverse opal was cleaned with ethanol and deionized water, and dried in an oven. For the Ni@Co₃O₄ and SiO₂@Fe₃O₄ electrodes, the Ni inverse opal was fabricated on gold-coated glass substrates. This Ni@SnO₂NPs@SiO₂ electrode retains a stable capacity of 615 mA h g even after 45 cycles, while still possessing a good C-rate performance. The Ni@Co₃O₄ and SiO₂@Fe₃ O₄ electrodes also exhibit attractive properties including good C-rate performances and high Coulombic efficiencies. These results show that a hydrothermal strategy is a promising general approach for fabricating mesostructured battery electrodes.