Pseudocapacitance has been confirmed to significantly improve the rate capability and cycling durability of electrode materials. However, rational design and controllable synthesis of intercalation pseudocapacitive materials for sodium-ion batteries (SIBs) still remain greatly challenging. Herein, a core−shell TiO 2 -based anode composed of S-, Co-, and N-doped amorphous TiO 2 /C framework cores and ultrathin anatase TiO 2 nanosheet shells (SCN-TC@UT) was synthesized using Ti-based metal−organic frameworks (Ti-MOFs) as self-sacrificing templates coupled with a solvothermal sulfidation process. Thanks to heteroatom doping, integration of carbon species, and 2D nanosheet coating, the kinetic properties of SCN-TC@UT have been significantly improved. As a consequence, the anode achieves ultrahigh capacitive contributions up to 90.9 and 96.3% of the total capacity at scan rates of 5 and 10 mV s −1 and delivers unprecedented 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, 2000, and 18,000 cycles, respectively. Even at an ultrahigh rate of 50 C, the anode can still deliver a capacity of 108 mA h g −1 . This work demonstrates the most efficient TiO 2 -based anode ever reported for SIBs and holds great potential in directing the development of amorphous materials for intercalation pseudocapacitance.

TiO2 is the most promising anode material for lithium-/sodium-ion batteries (LIBs/SIBs) for grid-scale energy storage. However, the use of TiO2 anodes is greatly restricted by the low theoretical capacity, inferior electrical conductivity, and slow ion diffusion. In this study, nitrogen-doped carbon-coated TiO2/TiF3 heterostructure nanoboxes with a hierarchically porous yolk–shell structure were successfully fabricated and demonstrated impressive electrochemical performance when employed as anodes for LIBs and SIBs. Specifically, this anode delivers a high lithium storage capacity of 245 mA h g–1 at 100 mA g–1 after 100 cycles and excellent rate capability up to 5000 mA g–1 with a capacity of 71 mA h g–1. In addition, it also delivers a considerable sodium storage capacity of 112 mA h g–1 at 50 mA g–1 after 100 cycles. The enhanced lithium and sodium storage performance is attributed to the TiO2/TiF3 heterostructure that improves both specific capacity and charge transfer, conductive carbon frameworks, and hierarchically porous yolk–shell structure with open diffusion channels.

No abstract

No abstract

No abstract