Controllable\nSynthesis of Anatase TiO₂ Nanosheets\nGrown on Amorphous TiO₂/C Frameworks for Ultrafast Pseudocapacitive\nSodium Storage

Abstract

Pseudocapacitance\nhas been confirmed to significantly improve the\nrate capability and cycling durability of electrode materials. However,\nrational design and controllable synthesis of intercalation pseudocapacitive\nmaterials for sodium-ion batteries (SIBs) still remain greatly challenging.\nHerein, a core–shell TiO₂-based anode composed of\nS-, Co-, and N-doped amorphous TiO₂/C framework cores and\nultrathin anatase TiO₂ nanosheet shells (SCN-TC@UT) was\nsynthesized using Ti-based metal–organic frameworks (Ti-MOFs)\nas self-sacrificing templates coupled with a solvothermal sulfidation\nprocess. Thanks to heteroatom doping, integration of carbon species,\nand 2D nanosheet coating, the kinetic properties of SCN-TC@UT have\nbeen significantly improved. As a consequence, the anode achieves\nultrahigh capacitive contributions up to 90.9 and 96.3% of the total\ncapacity at scan rates of 5 and 10 mV s^–1 and delivers\nunprecedented capacities of 211, 201, and 100 mA h g^–1 at 1, 5, and 30 C (1 C=335 mA g^–1) for over 800,\n2000, and 18,000 cycles, respectively. Even at an ultrahigh rate of\n50 C, the anode can still deliver a capacity of 108 mA h g^–1. This work demonstrates the most efficient TiO₂-based\nanode ever reported for SIBs and holds great potential in directing\nthe development of amorphous materials for intercalation pseudocapacitance.