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

Abstract

Developing high-rate and durable anode materials for sodium-ion batteries (SIBs) is still a challenge because of the larger ion radius of sodium compared with the lithium ion during charge–discharge processes. Herein, NiTe₂ coupled with N-doped carbon (NiTe₂/NC) hexagonal nanosheets has been fabricated through a solvothermal and subsequent carbonisation strategy. This unique hexagonal nanosheet structure offers abundant active sites and contact area to the 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 shows that the charge–discharge process is controlled by the pseudocapacitive behavior thus leading 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, a full battery equipped with a Na₃V₂(PO₄)₂O₂F cathode and a NiTe₂/NC anode offers a maximum energy density of 104 W h kg⁻¹ and a maximum power density of 9116 W kg⁻¹. The results clearly show that the NiTe₂/NC hexagonal nanosheet with superior Na storage properties is an advanced new material for energy storage systems.