A solid-state Matryoshka doll-like microwave method for one-step rapid synthesis of composites of NiSe2 and nitrogen-doped porous carbon for sodium storage

A facile solid-state Matryoshka doll-like microwave strategy is developed to synthesize composites of NixSey and nitrogen-doped porous carbon (N–C). The crystal structures and morphology of NixSey/N–C are investigated with different feeding mass ratios of Ni/Se and at different microwave processing times. Thereinto, NiSe2/N–C is rapidly prepared in just 20 minutes. The physical–chemical properties of NiSe2/N–C are further investigated and the composite has shown good ion/electron transfer kinetics and structural stability for sodium storage. When employed as the anode of sodium ion batteries (SIBs), NiSe2/N–C shows a high reversible capacity of 374.4 mA h g−1 at 0.2 A g−1 and excellent cycling stability, retaining 95% of its initial capacity at 1.0 A g−1 after 2000 cycles. The good electrochemical performance is attributed to the synergistic effect between the highly active NiSe2 nanoparticles and the 3D conductive N–C frameworks, which expedites the charge-transfer rate and improves the reversibility of the charging/discharging reactions. The excellent Na+ storage kinetics of the NiSe2/N–C electrode results from its low adsorption energy of −0.94 eV and low energy barrier of 0.818 eV. This work provides a feasible microwave synthetic strategy to fabricate SIB electrode materials.