Nickel telluride nanoparticles@hollow porous carbon sphere confined within carbon fibers for fast stable sodium storage

For sodium-ion batteries, nickel telluride (NiTe 2 ) is an excellent anode material. However, significant volume changes and slow kinetics compromise its structural stability and its capacity for high-current reactions. To increase sodium storage performance, NiTe 2 nanoparticles are synthesized in situ within hollow porous carbon spheres (NiTe 2 @HPCS) through a “drop-dry” process, vacuum-assisted adsorption, and vapor tellurization. Then, a large number of NiTe 2 @HPCS particles are densely encapsulated in carbon fibers (CFs) via electrospinning and carbonization (NiTe 2 @HPCS/CF). In coin-type half cells, NiTe 2 @HPCS/CF exhibits a high and stable capacity of 432 mAh g −1 after 500 cycles at 1.0 A g −1 . When half cells are operated at 5.0 and 10.0 A g −1 , the lifespan reaches 1000 cycles and the capacities sustain at 332 and 195 mAh g −1 . The cycled electrode materials preserve the intact composite structure, demonstrating remarkable robustness. Kinetic investigation affirms swift electron and Na + conduction within NiTe 2 @HPCS/CF. Furthermore, in Na 3 V 2 (PO 4 ) 3 //NiTe 2 @HPCS/CF full cells, NiTe 2 @HPCS/CF also exhibits favorable cycling stability. At 1.0 and 5.0 A g −1 after 300 and 500 cycles, reversible capacities reach 299 and 172 mAh g −1 , respectively. The outstanding performance is associated with the unique dual carbon encapsulation structure: HPCSs effectively confine NiTe 2 nanoparticles, maintaining their high electrochemical activity and promoting the sodiation/de-sodiation reactions. CFs further reinforce structural stability and electron conduction of NiTe 2 .