Self-assembled three-dimensional nanosphere Sn-SnO2/Li4Ti5O12 composite thin film anode materials and their application in quasi-solid-state thin film batteries

Three-dimensional Sn-SnO₂/Li₄Ti₅O₁₂ composite thin film anode materials, featuring self-assembled Sn-SnO₂ nanospheres, are effectively fabricated through radio-frequency magnetron sputtering technology followed by a rapid annealing treatment. X-ray diffraction analysis shows that the film predominantly consists of polycrystalline Li₄Ti₅O₁₂, along with minor monocrystalline Sn and SnO₂. Scanning electron microscopy results reveal that post-annealed films exhibit nanospherical particles embedded within the composite surface. Electrochemical impedance spectroscopy demonstrates a charge conductivity of 1.41 × 10^-6 S·cm^-1 for the composite film under optimized conditions (annealing temperature: 850 °C, SnO₂/Li₄Ti₅O₁₂ molar ratio: 0.5). Galvanostatic intermittent titration technique analysis reveals a dynamic Li-ion diffusion coefficient ranging from 2.09 × 10^-13 to 1.23 × 10^-11 cm²·s^-1 in a half-cell configuration. In situ XRD characterization highlights excellent structural reversibility and stability of the film during charge/discharge cycles. The composite film delivers initial discharge specific capacities of 151.11 mAh·g^-1 at 0.1 C and 120.16 mAh·g^-1 at 0.5 C, with capacity retention rates of 94.18% and 85.17%, respectively, after 200 cycles. Subsequently, Li_1.3Al_0.3Ti_1.7(PO₄)₃ and LiFePO₄ are employed to assemble a quasi-solid-state battery, achieving initial specific discharge capacities of 115.29 mAh·g^-1 (0.1 C) and 86.55 mAh·g^-1 (0.5 C), with 85.94% and 80.37% capacity after 200 cycles. This work provides valuable insights for developing high-performance 3D Li-ion thin-film anode materials.