A novel composite strategy to build a sub-zero temperature stable anode for sodium-ion batteries

Abstract

The extended application of sodium ion batteries (SIBs) to cold climates or high-altitude areas has been severely impeded by the sluggish solid-diffusion process of Na⁺ in the anode material. Herein, we for the first time report CoGa₂S₄ as a novel anode material for SIBs, exhibiting superior full cell performance when coupled with a high-voltage Na_0.7[Mn_0.6Ni_0.2Mg_0.2]O₂ (NMN-2) cathode in a voltage range of 1.0–4.1 V. More importantly, when tested at an ultra-low temperature of −60 °C, CoGa₂S₄ delivers a high reversible capacity close to 100 mA h g⁻¹ upon 1000 cycles at a current density of 1 A g⁻¹. This excellent low-temperature performance is attributed to the fact that after the first discharge process of the CoGa₂S₄ electrode, the Ga-based sulfide loses its electrochemical reaction activity, but fortunately it can serve as a high ionic conductivity medium, facilitating the conversion reaction of cobalt sulfides. The phenomenon that the Ga-based sulfide in CoGa₂S₄ sacrifices the capacity, but allows cobalt sulfides to withstand temperature variation sheds light on designing high performance sub-zero temperature anodes for SIBs.