Anion‐Dominated Conventional‐Concentrations Electrolyte to Improve Low‐Temperature Performance of Lithium‐Ion Batteries

• Published in: Advanced functional materials 2024-08, Vol.34 (33), p.n/a
• Main Authors: Chen, Nan, Feng, Mai, Li, Chengjie, Shang, Yanxin, Ma, Yue, Zhang, Jinxiang, Li, Yifan, Chen, Guoshuai, Wu, Feng, Chen, Renjie
• Format: Article
• Language: English
• Subjects: Anions; electrolyte; Electrolytes; Electrolytic cells; Freezing; Ion currents; Lithium; lithium difluorophosphate; Lithium-ion batteries; Low temperature; Sheaths; Solvation; solvation structure; Temperature
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202400337

Low temperatures (< −20 °C) significantly diminish lithium‐ion battery performance due to freezing issues within commercial electrolytes and the high energy barrier for Li+ desolvation at the interface. Although high‐concentration electrolytes and localized high‐concentration electrolytes enhance Li+ desolvation kinetics featuring anion‐participated solvation structures, their high viscosity and propensity for Li salt precipitation render them unsuitable for low‐temperature environments. This study introduces an anion‐dominated conventional‐concentrations electrolyte (ACCE) created by incorporating Lithium difluorophosphate(LiPO2F2)into a 1 M Lithium bis((trifluoromethyl)sulfonyl)azanide(LiTFSI) Dimethyl carbonate(DMC)/Fluoroethylene carbonate(FEC)/Methyl acetate(MA) electrolyte solution. LiPO2F2, characterized by its poor solubility and strong binding with Li+, demonstrates a pronounced tendency to integrate into the primary solvation sheath of Li+. Moreover, the synergy between LiTFSI and LiPO2F2 establishes a dual anion configuration, unveiling a dual anion‐driven mechanism. This mechanism significantly diminishes the interaction between Li+ and solvent molecules, resulting in reduced desolvation energy under low temperatures. The ACCE exhibits high ionic conductivity of 1.3 mS cm−1 at −50 °C, enabling stable cycling of Li/NCM811 cells at −50 °C, and further allows 0.75 Ah graphite(Gr)/LiNi0.8Co0.1Mn0.1O2(NCM811) batteries dischargeable at −40 °C. This study presents a practical application potential for poorly soluble lithium salts and provides a new avenue for designing electrolytes suitable for low‐temperature applications. A novel ACCE is proposed, leveraging LiPO2F2’s low solubility and strong binding to Li+, accelerating Li+ de‐solvation process. This forms a LiF‐rich, phosphate‐rich CEI film, enabling lithium‐ion batteries to cycle at −50 °C extremely low temperature.