TiO₂-Coated Interlayer-Expanded MoSe₂/Phosphorus-Doped Carbon Nanospheres for Ultrafast and Ultralong Cycling Sodium...

Based on multielectron conversion reactions, layered transition metal dichalcogenides are considered promising electrode materials for sodium-ion batteries, but suffer from poor cycling performance and rate capability due to their low intrinsic conductivity and severe volume variations. Here, interlayer-expanded MoSe₂/phosphorus-doped carbon hybrid nanospheres coated by anatase TiO₂ (denoted as MoSe₂/P-C@TiO₂) are prepared by a facile hydrolysis reaction, in which TiO₂ coating polypyrrole-phosphomolybdic acid is utilized as a novel precursor followed by a selenization process. Benefiting from synergistic effects of MoSe₂, phosphorus-doped carbon, and TiO₂, the hybrid nanospheres manifest unprecedented cycling stability and ultrafast pseudocapacitive sodium storage capability. The MoSe₂/P-C@TiO₂ delivers decent reversible capacities of 214 mAh g^-1 at 5.0 A g^-1 for 8000 cycles, 154 mAh g^-1 at 10.0 A g^-1 for 10000 cycles, and an exceptional rate capability up to 20.0 A g^-1 with a capacity of ≈175 mAh g^-1 in a voltage range of 0.5-3.0 V. Coupled with a Na₃V₂(PO₄)₃@C cathode, a full cell successfully confirms a reversible capacity of 242.2 mAh g^-1 at 0.5 A g^-1 for 100 cycles with a coulombic efficiency over 99%.