A diffusion encouraged core–shell heterostructured Co3Sn2@SnO2 anode towards emerging dual ion batteries with high energy density

Abstract

Lithium dual-ion batteries (LDIBs) are currently receiving great attention as energy-storage systems due to their low cost, environmentally friendly characteristics, and good safety features. Herein, mesoporous Co₃Sn₂ and SnO₂ core–shell heterostructures (Co₃Sn₂@SnO₂ CSHs) were developed as new anode materials for LDIBs using diffusion-based nanocrystal conversion chemistry. LDIBs were configured using the 1 M LiPF₆ electrolyte, Co₃Sn₂@SnO₂ CSH anode, and expanded graphite (obtained by a simple ball milling process; so-called EG) cathode. After 200 cycles, the Co₃Sn₂@SnO₂-EG LDIB delivered a reversible capacity of 90.0 mA h g⁻¹ at 300 mA g⁻¹, a high coulombic efficiency of 93.3%, and an outstanding energy density of 334.5 W h kg⁻¹. These values demonstrate the feasibility of using LDIBs in various energy-related applications. Mechanisms are proposed to explain the intercalation/deintercalation of PF₆⁻ and Li⁺ ions at different charge–discharge voltages and these are validated by Raman spectroscopy, X-ray diffraction, and elemental mapping. Finally, the superior electrochemical performance of the fabricated LDIBs could be attributed to the following reasons: (i) the large number of inner voids and mesopores in the CSHs improved reaction kinetics and structural stability. (ii) The hybrid composites exhibited a significantly high conductivity. (iii) Inactive Co effectively buffered against electrode pulverization and aggregation, thus enhancing the structural integrity of Co₃Sn₂@SnO₂ CSHs during the charge–discharge process. It is expected that these results will provide a new direction for the exploration of Co₃Sn₂@SnO₂ CSHs and probably other transition metal-based composites in LDIB development for scalable energy storage.