Low-temperature aqueous secondary battery using antifreeze additives

Aqueous electrolyte for olivine cathodes enabling sub-zero operation via ethylene glycol antifreeze additives

This technology improves aqueous lithium-ion batteries using olivine-type cathode materials like LiFePO4. By adding 10–20 wt% ethylene glycol (EtG) to the aqueous electrolyte, it lowers the freezing point and maintains ionic conductivity, effectively suppressing electrode polarization and surface resistance at sub-zero temperatures.

Aqueous electrolytes typically suffer from high freezing points, leading to a sharp drop in ionic conductivity in sub-zero environments. This increases electrode resistance and polarization in LiFePO4 cathodes, significantly degrading cycle performance and rate capability.

This technology optimizes the aqueous electrolyte by adding 10–20 wt% of ethylene glycol to a 1M Li2SO4 solution. This extends the operating temperature range below freezing and enhances lithium-ion transport and intercalation/deintercalation kinetics at low temperatures. Suitable for outdoor solar energy storage and backup power for base stations in cold climates, it maintains a discharge capacity of over 90 mAh g-1 after 100 cycles at -10℃.

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Key Features:

• An aqueous lithium secondary battery using an olivine-type composite oxide represented by Chemical Formula 1 as a cathode active material and an aqueous Li2SO4 solution as the electrolyte
• A modified electrolyte containing 10 wt% to 20 wt% ethylene glycol (EtG) as an antifreeze additive
• An ethylene glycol additive that reduces electrode polarization by suppressing the increase in electrode resistance of olivine-type composite oxides at low temperatures
• An aqueous electrolyte based on a 0.1–10 M Li2SO4 solution that serves as the foundation for the modified electrolyte

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