en.Wedoany.com Reported - A research team led by Professors CHEN Zhongwei, LUO Dan, and WANG Dongdong from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has proposed an electrolyte design strategy based on "polarity contrast" to improve the performance of lithium metal batteries under extremely low-temperature conditions. The relevant research findings have been published in the Journal of the American Chemical Society.

In low-temperature environments, lithium metal batteries face issues such as slow ion transport, sluggish lithium-ion desolvation kinetics, and exacerbated interfacial side reactions, leading to capacity decay and reduced cycling stability, which limits their applications in energy storage, electric vehicles, and aerospace. To address these challenges, the research team constructed a stable anion-dominated solvation structure at low temperatures by regulating the ion-dipole interactions between anions and solvents.

The study screened a pair of solvents with "polarity contrast" characteristics: dimethoxymethane (DMM), which has the lowest electrostatic potential maximum (ESPmax), and fluoroethylene carbonate (FEC), which has the highest ESPmax. At low temperatures, the weakened interaction between DMM and bis(fluorosulfonyl)imide anions (FSI⁻) facilitates the entry of anions into the lithium-ion solvation sheath; meanwhile, FEC further anchors FSI⁻ through enhanced ion-dipole interactions, forming a stable anion-dominated solvation environment. Additionally, the enhanced dipole-dipole interaction between DMM and FEC promotes lithium-ion desolvation kinetics. By precisely regulating these interactions, the team achieved an anion coordination transition at low temperatures.

Using this strategy, the electrolyte induced the formation of a lithium fluoride (LiF)-rich solid electrolyte interphase, which contributes to uniform lithium deposition and highly reversible deposition/stripping behavior at low temperatures. Test results show that Li||SPAN full cells using this electrolyte achieved a capacity retention rate of 80% after 150 cycles at -40°C under a high areal capacity of 4.5 mAh cm⁻². Furthermore, ampere-hour-level pouch cells stably cycled 50 times at -20°C, demonstrating good low-temperature cycling stability and capacity retention. CHEN Zhongwei stated that this research reveals a new mechanism for the dynamic evolution of solvation structures under low-temperature conditions and provides a new theoretical foundation and research strategy for designing low-temperature lithium metal battery electrolytes.

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