EC-Less High-Entropy Electrolytes Enabling High-Safety and Durable Ni-Rich Lithium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Conventional electrolytes in high-energy-density lithium-ion batteries (LIBs) pose thermal safety risks due to decomposition.
• Ethylene carbonate (EC) is a common electrolyte component but can contribute to thermal instability in LIBs.

Purpose of the Study:

• To develop an ethylene carbonate-less high-entropy electrolyte (EC-less HEE) for enhanced thermal safety in NCM811|Gr pouch cells.
• To investigate the impact of anion-dominated solvation sheaths on electrolyte stability and battery performance.

Main Methods:

• Development of an EC-less HEE with dual anion species (e.g., PF6-, FSI-, TFSI-) forming anion-dominated solvation sheaths.
• Material-level thermal analysis to assess heat accumulation and gas evolution.
• Accelerating Rate Calorimetry (ARC) tests on 1.2 Ah NCM811|Gr pouch cells.

Main Results:

• The EC-less HEE demonstrated a 75.3% reduction in heat generation at the material level.
• Cell-level ARC tests showed a 41 °C increase in thermal failure onset temperature (143 °C to 184 °C) and a 264 °C decrease in maximum thermal runaway temperature (763 °C to 499 °C).
• The EC-less HEE-based pouch cell maintained 87.2% capacity after 1400 cycles, indicating excellent cycling stability.

Conclusions:

• The developed EC-less HEE significantly enhances the thermal safety of high-energy-density LIBs.
• Anion-dominated solvation sheaths with elevated LUMO levels effectively suppress electrolyte reduction at the anode.
• This electrolyte design strategy offers a promising pathway for achieving high-safety and high-performance LIBs.