N-Doped Carbon-Coated Ni1.8Co1.2Se4 Nanoaggregates Encapsulated in N-Doped Carbon Nanoboxes as Advanced Anode with Outstanding High-Rate and Low-Temperature Performance for Sodium-Ion Half/Full Batteries

Transition metal selenides have been attracting significant attention owing to their high conductivity and theoretical capacity. In this article, the N-doped carbon (NDC)-coated Ni1.8Co1.2Se4 nanoparticles encapsulated in NDC nanoboxes are prepared from the bi-metal organic framework (Ni-3[Co(CN)(6)](2)center dot 6H(2)O, Ni-Co BMOF) after the selenization reaction and carbon coating. When used as an anode material for sodium-ion batteries, the prepared anode material delivers excellent rate performance (211 and 153 mA h g(-1) at ultrahigh current densities of 30 and 50 A g(-1), respectively) and good cycling performance (379.3 mA h g(-1) at 0.5 A g(-1) after 100 cycles). More importantly, it also exhibits superior sodium-ion full cell (SIFC) performance when coupled with a high-voltage Na3V2(PO4)(2)O2F cathode recently self-made by the authors. The fabricated SIFC gives an energy density up to 227 W h kg(-1) and the capacity retention of above 97.6% even after 60 cycles at 0.4 A g(-1) in a voltage range of 1.2-4.3 V at 25 degrees C. Moreover, the low-temperature (from 25 to -25 degrees C) Na-storage performance of the fabricated SIFC is also studied.