Origin of Excellent Charge Storage Properties of Defective Tin Disulphide in Magnesium/Lithium-Ion Hybrid Batteries

摘要

Lithium-ion batteries(LIBs)are excellent electrochemical energy sources,albeit with existing challenges,including high costs and safety concerns.Magnesium-ion batteries(MIBs)are one of the potential alternatives.However,the performance of MIBs is poor due to their sluggish solid-state Mg^(2+) diffusion kinetics and severe electrode polarizability.Rechargeable magnesium-ion/lithium-ion(Mg^(2+)/Li^(+))hybrid batteries(MLHBs)with Mg^(2+) and Li+as the charge carriers create a synergy between LIBs and MIBs with significantly improved charge transport kinetics and reliable safety features.However,MLHBs are yet to reach a reasonable electrochemical performance as expected.This work reports a composite electrode material with highly defective two-dimensional(2D)tin sulphide nanosheets(SnS_(x))encapsulated in three-dimensional(3D)holey graphene foams(HGF)(SnS_(x)/HGF),which exhibits a specific capacity as high as 600 mAh g^(−1) at 50 mA g^(−1) and a compelling specific energy density of~330 Wh kg^(−1).The excellent electrochemical performance surpasses previously reported hybrid battery systems based on intercalation-type cathode materials under comparable conditions.The role played by the defects in the SnS_(x)/HGF composite is studied to understand the origin of the observed excellent electrochemical performance.It is found that it is closely related to the defect structure in SnS_(x),which offers percolation pathways for efficient ion transport and increased internal surface area assessable to the charge carriers.The defective sites also absorb structural stress caused by Mg^(2+) and Li+insertion.This work is an important step towards realizing high-capacity cathode materials with fast charge transport kinetics for hybrid batteries.