Competitive Coordination of Ternary Anions Enabling Fast Li‐Ion Desolvation for Low‐Temperature Lithium Metal Batteries

• Published in: Advanced functional materials 2024-04, Vol.34 (16), p.n/a
• Main Authors: Liang, Ping, Hu, Honglu, Dong, Yang, Wang, Zhaodong, Liu, Kuiming, Ding, Guoyu, Cheng, Fangyi
• Format: Article
• Language: English
• Subjects: Anions; Business competition; competitive coordination; Coordination; Electrolytes; Electrolytic cells; Freezing; Ion currents; Ion migration; Lithium batteries; lithium metal batteries; low‐temperature electrolytes; solid electrolyte interphases; Solid electrolytes; Solvation; solvation structures
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202309858

Lithium metal batteries (LMBs) working at subzero temperatures are plagued by severe restrictions from the increased energy barrier of Li‐ion migration and desolvation. Herein, a competitive coordination strategy based on the ternary‐anion (TA) coupling of PF6−, TFSI−, and NO3− toward Li+ to achieve an anti‐freezing electrolyte with rapid kinetics is proposed. Computational and spectroscopic analyses reveal that the repulsive interaction among three anions and the preponderant coordination of the Li+‐NO3− further weaken the involvement degree of other anions in the Li+ solvation structure. As a result, the formulated TA electrolyte exhibits low binding energy of Li+‐anions (−4.62 eV), Li+ desolvation energy (17.04 kJ mol−1), and high ionic conductivity (3.39 mS cm−1 at −60 °C), simultaneously promoting anion‐derived solid electrolyte interphase on Li anode. Assembled Li||LiNi0.8Co0.1Mn0.1O2 cells employing the TA electrolyte exhibit robust capacity retention of 86.74% over 200 cycles at 25 °C and deliver a specific cathode capacity of 103.85 mAh g−1 at −60 °C. This study will enlighten the rational design of multi‐anion electrolytes to tailor the Li+ solvation/desolvation for advanced low‐temperature LMBs. Competitive coordination among ternary anions (TA) of PF6−, TFSI−, and NO3− weakens their interaction with Li+, leading to rapid charge transfer kinetics and low Li+‐desolvation energy. The formulated electrolyte expands the low‐temperature window to −120 °C and forms anion‐derived solid/cathode‐electrolyte interphase (SEI/CEI) layers, which endows lithium metal batteries with excellent cycling performance under ultralow temperature range from 25 to −60 °C.