Tailoring Solvation Structures via Precise Diluent Engineering for High-Rate 500 Wh kg^-1 Lithium-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium metal batteries (LMBs) offer high energy density potential (>500 Wh kg-1) but face challenges with unstable interphases and slow Li+ transport kinetics, hindering commercialization.
• Current electrolytes struggle to simultaneously provide efficient ion transport and robust interfacial stability, especially under demanding high-rate conditions.

Purpose of the Study:

• To develop a novel electrolyte strategy for LMBs that decouples Li+ solvation from interfacial stabilization.
• To enhance both ion transport kinetics and interfacial stability in high-voltage LMBs.

Main Methods:

• A hybrid diluent strategy was employed using diluted high-concentration electrolytes (DHCEs).
• The strategy combined fluorinated aromatics for Li+ desolvation and transport with fluorinated ethers for oxidative stability and interphase formation.
• Electrolyte performance was evaluated in Li-NCM622 and Li-NCM811 pouch cells under various cycling conditions.

Main Results:

• The hybrid electrolyte demonstrated synergistic effects, enhancing ion transport, increasing voltage tolerance, and stabilizing electrode-electrolyte interfaces.
• A 0.78 Ah Li-NCM622 pouch cell achieved over 300 cycles at 0.33C charge/0.66C discharge.
• A 2.95 Ah Li-NCM811 pouch cell reached an energy density of 518 Wh kg-1/985 Wh L-1 and retained >92% capacity after 107 cycles at 0.2C charge/1C discharge.

Conclusions:

• The developed hybrid diluent strategy offers a scalable and cost-effective approach to address key failure mechanisms in LMBs.
• This electrolyte design provides a viable pathway for practical high-energy and high-rate lithium metal battery applications.