Origin of Excellent Charge Storage Properties of Defective Tin Disulphide in Magnesium/Lithium-Ion Hybrid Batteries
Xin Fan, Mike Tebyetekerwa, Yilan Wu, Rohit Ranganathan Gaddam, Xin Zhao
Abstract
Abstract 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.