NiCo2Se4 as an anode material for sodium-ion batteries

Exploring new anode materials is critical for the development of Sodium-ion batteries (SIBs). Herein, a binary-metal selenide NiCo2Se4 was synthesized and investigated as a new anode material for SIBs. After compositing with conductive carbon, the NiCo2Se4@C composite delivers a reversible capacity of 603.2 mAh g−1 with a high initial coulombic efficiency of 85.79% at 0.5 A g−1. At an ultrahigh current density of 2 A g−1, a reversible capacity of 377.5 mAh g−1 can still be obtained after 600 cycles. The detailed Na storage mechanism for NiCo2Se4 is revealed. After discharge, Na2Se, Ni and Co nanoparticles are formed and highly dispersed in Na2Se matrix. After recharge, NiCo2Se4 phase can be regenerated with small amount of CoSe2 and NiSe phases. The multi-phase coexistence after recharge is responsible for the initial capacity loss and the excellent cycle performance in subsequent cycles. Keywords: Sodium-ion batteries, Anode, Selenide, Reaction mechanism