Designing high-chaos mixed-salt electrolytes for enhancing graphite-electrolyte interfacial stability in lithium-ion batteries

Abstract

The interfacial stability between graphite anodes and electrolytes is crucial for the electrochemical performance of lithium-ion batteries, particularly at low temperatures. This study investigates the effect of incorporating four common Solid-Electrolyte Interphase (SEI) components—LiF, LiNO3, Li2O, and Li2CO3—directly into two types of commercial electrolytes: carbonate-based (1.0 M LiPF6-EC/DMC, LP30) and ether-based (1 M LiTFSI-DOL/DME+2 % LiNO3, LDD) both with 5 % FEC (v/v) to create high-chaos mixed-salt electrolytes (LP30-FEC-4S and LDD-FEC-4S). Our findings show that Li/graphite cells exhibit significantly enhanced rate performance in both LP30-FEC-4S and LDD-FEC-4S electrolytes, compared to commercial LP30 and LP57 electrolytes. LiFePO4/graphite full cells using LP30-FEC-4S and LDD-FEC-4S electrolytes also showed excellent electrochemical performance (124.73 mAh g−1 and 119.21 mAh g−1 specific capacities at 0.5C). Remarkably, stable SEIs form rapidly on the graphite anode surfaces in the designed electrolytes even at low temperatures of −10 °C. Moreover, we demonstrate that the Li+ solvation structure is fundamental in determining the overall electrochemical performance. This study suggests that enhancing the mixing entropy of the system by adding multiple lithium salts to a commercial electrolyte is an effective and cost-efficient strategy for improving graphite-electrolyte compatibility.