Three-dimensional mesostructured binder-free nickel-based TiO₂/RGO lithium-ion battery negative electrodes with enhanced volumetric capacity

Realization of high energy density Li-ion anodes is a significant challenge due to the volume changes generally exhibited by such systems during charge and discharge. Here, three-dimensional inverse opal (3D-IO) mesostructured Ni@TiO₂@RGO electrodes were fabricated by templating nickel electrodeposition with self-assembled, three dimensionally ordered polystyrene (PS) opals, followed by atomic layer deposition (ALD) of TiO₂ and spray coating of reduced graphene oxide (RGO). The electrode delivers initial discharge and charge volumetric capacities of 2082 mAh cm^-3 and 1873 mAh cm^-3 at 0.5 C, respectively. The composite electrode exhibits volumetric discharge and charge capacities of 1508 mAh cm^-3 and 1504 mAh cm^-3 at 0.5 C after 200 cycles and good rate capacity up to at least 10 C. The almost unbroken 3D-IO mesostructure after 200 lithiation and delithiation cycles demonstrates the excellent structural stability of the 3D-IO electrode design concept. The enhanced volumetric capacity and structural stability originate from high active materials loading, the short and efficient ion and electron pathways, and the composite structure provided by the nickel electrodeposition, ALD, and RGO spray coating electrode preparation process, as well as that both TiO₂ and RGO participate in lithium storage.