A Ternary Fibrous TiO2-Ni3S4-Carbon Composite Derived from Cellulose Substance for Effective Lithium Storage

Ni3S4-based materials are promising candidates for anodes of lithium-ion batteries (LIBs) due to their high theoretical capacities and excellent redox reversibilities. However, the drawbacks, including low intrinsic conductivity, significant volumetric expansion, and polysulfide shuttle effects, hinder their electrochemical performance and limit practical applications. To address these challenges, herein, a ternary fibrous TiO2-Ni3S4-carbon composite using natural cellulose substance as both the carbon source and structural scaffold was synthesized via hydrothermal and sol-gel approaches. The composite exhibits a nanoarchitecture structure, which retains the three-dimensional network structure of the initial cellulose substance; it is composed of uniformly distributed Ni3S4 nanoparticles wrapping around the carbon fibers with the TiO2 nanoplates coating on the outermost surface. Due to the spatially organized TiO2/Ni3S4/carbon ternary configuration, the composite exhibits excellent electrochemical performance when employed as an anodic material for LIBs. Specifically, the TiO2 coating layer acts as a protective layer, suppressing the shuttle effect of polysulfides and stabilizing the solid electrolyte interface (SEI). The synergistic effect of the carbon fiber and the TiO2 coating layer buffers the volume expansion, prevents the pulverization of the active material, and enhances its structural integrity and stability. Additionally, the Ni3S4-TiO2 heterojunction accelerates charge transfer and increases the pseudocapacitive contributions, thereby improving lithium storage performance. Specifically, the TiO2-Ni3S4-carbon anode delivers a reversible discharge capacity of 600.2 mAh g-1 at 1.0 A g-1 after 3000 cycles (70.3% retention). In the full-cell tests, the anode achieves a reversible capacity of 107.4 mAh g-1 after 3000 cycles at 1.0 A g-1 with an energy density of 224.3 Wh kg-1, demonstrating the application potential of the composite as the anodic material of LIBs.