Aqueous Lithium-Ion Battery of Nano-LiFePO₄ with Antifreezing Agent of Ethyleneglycol for Low-Temperature Operation

Abstract

Low-temperature performance of the rechargeable batteries is limited because of a narrow temperature range of the electrolyte. Despite the aqueous electrolyte having a lower freezing point than the ethelyenecarbonate for conventional lithium-ion batteries, its freezing point is as high as 0 °C. Antifreeze additive of ethylene glycol for aqueous electrolyte solutions is used to improve the low-temperature performance of aqueous rechargeable lithium-ion batteries. The suitable contents of ethylene glycol expand the temperature range of aqueous electrolyte, pursuing a balance between the low freezing point and high ionic conductivity, and thus enhancing their cyclic performance and decreasing the polarization of electrode reactions. Furthermore, the improvement of the lithium-ion intercalation and deintercalation processes in the nano-LiFePO4 material at low temperature is controlled by varying the content of the antifreeze additive to provide a high ionic conductivity of an aqueous electrolyte solution having 1 M of Li2SO4 depending on the temperature, ranging from 0 to −20 °C. In addition, ethylene glycol for aqueous electrolyte solutions can be used to improve high-performance batteries operating at sub-zero temperatures. The aqueous rechargeable lithium-ion batteries having antifreezing additives are beneficial for various extreme operations of electric vehicles, high-altitude drones, submarine, robotics, and aerospace applications.