# Ternary Synergistic Electrolyte Enabling Stable Li-Ion Battery Operation Across −40 °C to 60 °C

## TL;DR

A new electrolyte design enables lithium-ion batteries to work reliably from -40°C to 60°C by improving ion transport and interface stability.

## Contribution

A synergistic ternary electrolyte is developed for stable Li-ion battery performance across extreme temperatures.

## Key findings

- The ACE electrolyte achieves low viscosity and high ionic conductivity at -40°C.
- LFP|Gr cells using ACE show zero capacity decay after 500 cycles at 0°C and 94.1% retention after 100 cycles at 45°C.
- XPS and SEM analysis reveal LiDFP and LiFSI collaboratively enhance SEI/CEI interphases with inorganic compounds.

## Abstract

The operational failure of lithium-ion batteries under extreme temperatures (−40~60 °C) stems primarily from electrolyte limitations. While prior efforts improved either low-temperature or high-temperature performance independently, holistic electrolyte design with practical validation remains elusive. Herein, we develop an all-climate electrolyte (ACE) through synergistic coordination of solvent, Li salt, and additive, achieving low viscosity (<10 mPa·s at −40 °C) and high ionic conductivity (7.0 mS cm−1 at −40 °C). Raman and NMR spectra reveal MA and EC co-occupying Li+ solvation sheath while EMC acts as a diluent, enabling rapid ion transport. Consequently, LiFePO4 (LFP)|graphite (Gr) cell delivers unprecedented cyclability: zero capacity decay over 500 cycles at 0 °C, stable operation across −40~60 °C, and 94.1% retention after 100 cycles at 45 °C in Ah-level pouch cells. XPS and SEM analysis demonstrate lithium difluorophosphate (LiDFP) and lithium bis(fluorosulfonyl)imide (LiFSI) collaboratively remodel SEI/CEI interphases, enriching them with LiF, Li3PO4, and Li2SO4. This inorganic-dominant architecture enhances interfacial Li+ kinetics and all-climate stability compared to the baseline electrolyte. Our tripartite electrolyte strategy provides a material-agnostic solution for all-climate energy storage.