Researchers from Nankai University and the Shanghai Institute of Space Power-Sources have developed a groundbreaking hydrofluorocarbon electrolyte that enables lithium-metal batteries to reach an energy density of 707 Wh/kg. This innovation allows batteries to operate effectively in extreme conditions as low as -70°C, doubling the capacity of current commercial lithium-ion systems. By utilizing a unique fluorine-coordinated chemistry, the team has overcome traditional barriers in lithium salt dissolution, offering a versatile solution for aerospace, deep-space exploration, and electric vehicles operating in ultra-cold environments.
The study, published in the journal Nature, details a strategic shift away from standard carbonate-based electrolytes. Led by Jun Chen, Qing Zhao, and Yong Li, the research team focused on monofluorinated alkane solvents to create a fluorine-coordinated framework. Specifically, the use of 1,3-difluoropropane (DFP) as a core solvent allowed for a lithium salt concentration exceeding 2 mol/L, a feat previously thought impossible with fluorinated hydrocarbons.
The resulting electrolyte exhibits exceptional physical properties, including a low viscosity of 0.95 cP and oxidation stability surpassing 4.9 V. At the extreme temperature of -70°C, the system maintained an ionic conductivity of 0.29 mS/cm. These characteristics translated into high-performance lithium-metal pouch cells that achieved a peak energy density of 707 Wh/kg at room temperature. Even when subjected to harsh cold, the cells retained approximately 400 Wh/kg at -50°C and remained functional at -70°C.
A key advantage of this hydrofluorocarbon-based system is its ability to bypass the common trade-off between high energy density and low-temperature functionality. The researchers noted that weaker lithium-fluorine coordination lowers dissolution barriers, facilitating rapid charge transfer in freezing conditions. Furthermore, the solvent’s superior wetting properties potentially reduce the total amount of electrolyte required. Testing showed a lithium plating/stripping Coulombic efficiency of 99.7% at room temperature, which only slightly decreased to 98.0% at -70°C.
This technological leap has significant implications for industries requiring lightweight, high-capacity power sources in extreme climates. Potential applications range from low-altitude aircraft and embodied robotics to deep-space missions and polar exploration equipment. By establishing a new direction for electrolyte design, the team has provided a viable pathway for the next generation of lithium-metal batteries where weight and thermal resilience are paramount.