Pseudocapacitance-boosted ultrafast and stable Na-storage in NiTe2 coupled with N-doped carbon nanosheets for advanced sodium-ion half/full batteries.

Developing high-rate and durable anode materials for sodium-ion batteries (SIBs) is still a challenge because of the larger ion radium of sodium compared with lithium ion during charge-discharge process. Herein, NiTe2 coupled with N-doping carbon (NiTe2/NC) hexagonal nanosheets have been fabricated through a solvothermal and subsequent carbonisation strategy. This unique hexagonal nanosheet structure offers abundant active sites and contact area to electrolyte, which could shorten the Na+ diffusion path. The heterostructured N-doping carbon improves the electrochemical conductivity and accelerates the kinetics of Na+ transportation. Electrochemical analysis show that charge-discharge process is controlled by the pseudocapacitive behavior thus leads to high-rate capability and long lifespan in half batteries. As expected, high capacities of 311 mA h g-1 to 217 mA h g-1 at 5 A g-1 to 10 A g-1 are maintained after 800 and 1200 cycles, respectively. Furthermore, the full battery equipped with a Na3V2(PO4)2F cathode and NiTe2/NC anode offers a maximum energy density of 104 Wh kg-1 and maximum power density of 9116  W kg-1. The results clearly show that NiTe2/NC hexagonal nanosheet with superior Na storage properties is an advanced new material for energy storage system.