Intermediate- and high-temperature Li batteries with enhanced performance enabled by a hollow C-MoS2 nanosphere electrode†

Abstract

With the continuous upsurge in demand for energy storage, batteries are increasingly required to operate at intermediate and high temperatures. Water-in-salt Li-ion batteries (WIS-LIBs) and molten-salt high-temperature Li batteries (MHLBs) possess inherent safety and are commendable facing intermediate and high temperature working conditions, respectively. However, considering the cost-effectiveness, the performance and in-depth working mechanism of the same material for both intermediate- and high-temperature batteries are seldom investigated. Herein, hollow C-MoS₂ nanospheres have been employed as the electrode material for WIS-LIBs at 60 °C and MHLBs at 500 °C. When applied as the anode material in WIS-LIBs at 60 °C, the material exhibits a high specific capacity (128.9 mAh g⁻¹ at 0.5 A g⁻¹), great rate capability, and long cycling stability. This is mainly ascribed to the unique Li⁺ storage in the hollow nanosphere structure, fast ionic transfer and the more favorable formation of a dense SEI film at intermediate temperatures. During the battery operation, MoS₂ undergoes phase transformation to Li₃Mo₆S₈ and Li₄MoO₅ in the initial Li⁺ ion uptake and transforms to MoS₂ and MoO₃ after discharging in WIS-LIBs. When operated at 500 °C, high voltage plateaus and a high discharging specific capacity of 509.51 mAh g⁻¹ at 0.25 A g⁻¹ can be obtained in MHLBs. During galvanostatic discharging, MoS₂ firstly transforms to Li₃Mo₆S₈ and then to metallic Mo. All these results have revealed the excellent electrochemical performance and the working mechanism of the as-synthesized hollow C-MoS₂ nanospheres in both intermediate- and high-temperature batteries. This work can inspire researchers to explore novel and advanced materials for batteries towards harsh working conditions and extend the environmental frontiers of the battery electrode materials studied at present.