Constructing N-Doped graphene supported MoS 2 @Ni 3 S 4 for pseudocapacitive sodium-ion storage with high rate and long life

The development of sodium-ion batteries with a high-power density and long life has attracted considerable interest because of their low cost and potential applications. In this work, we constructed N-doped graphene supported pseudocapacitive material consisting of Ni 3 S 4 grains (50 nm) coated by 3–4 layers of MoS 2 (MoS 2 @Ni 3 S 4 /NG) by facile one-step pyrolysis of nickel phthalocyanine. When the electrode was used as an anode for sodium-ion batteries, a pseudocapacitance-dominated storage mechanism was established, and the extrinsic pseudocapacitance could be further enhanced with the structural evolution of MoS 2 @Ni 3 S 4 during the sodiation/desodiation process, contributing to fast kinetics of Na +  storage. The results of impedance analysis indicated that the MoS 2 layers play a vital role in reducing the charge-transfer resistance because the MoS 2 with wider interlayer spacing enables Na +  to intercalate with a lower energy barrier compared with intercalating into Ni 3 S 4 directly. As a result, the electrode exhibits a superior cycle life over 1000 cycles, and an excellent rate capacity of 564 mAh g −1 can be achieved at 0.5 A g −1.