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

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 degrees 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 degrees C and deliver a specific cathode capacity of 103.85 mAh g-1 at -60 degrees 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 degrees 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 degrees C.image