Low-temperature aqueous secondary battery using antifreeze additives

Aqueous lithium battery electrolyte capable of sub-zero operation using ethylene glycol as an antifreeze additive

This technology features an aqueous lithium secondary battery using an olivine-type LiFePO4 cathode and a Li2SO4 aqueous electrolyte, modified by adding 10–20 wt% ethylene glycol as an antifreeze agent. Ethylene glycol works to suppress the increase in electrode resistance at low temperatures, thereby reducing polarization.

While aqueous lithium secondary batteries offer advantages in safety and cost, the high freezing point of aqueous electrolytes has historically led to significant degradation in cycle and rate performance at low temperatures. In particular, LiFePO4 faces limitations in large-scale applications in sub-zero environments due to its low electronic and ionic conductivity.

This technology lowers the electrolyte freezing point through the addition of ethylene glycol, expanding the operating temperature range while maintaining ionic conductivity and facilitating smooth lithium-ion intercalation and deintercalation at low temperatures. With a 10 wt% addition, the battery exhibits a discharge capacity of 103 mAh/g after 100 cycles at -5℃, and with a 20 wt% addition, it maintains 90 mAh/g after 100 cycles at -10℃. It can be applied to outdoor energy storage systems in extreme cold, as well as large-scale aqueous batteries for military and aerospace use, ensuring operational reliability in winter without the need for separate heating devices.

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Key Features:

• Modified electrolyte for aqueous lithium secondary batteries using an olivine-type composite oxide cathode active material and a Li2SO4 aqueous electrolyte
• Electrolyte for aqueous secondary batteries that suppresses electrode resistance increase and polarization at low temperatures by including 10 wt% to 20 wt% ethylene glycol as an antifreeze additive
• Configuration using LiFePO4 as the cathode active material and a 0.1–10 M, preferably 1 M, Li2SO4 aqueous solution as the aqueous electrolyte
• Low-temperature operating aqueous lithium secondary battery comprising the modified electrolyte, a cathode, an anode, and a separator, exhibiting a discharge capacity of 90 mAh g-1 after 100 cycles at -10℃

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