Stress-Strain Engineering with Lithium Solid Solution/Lithium Alloy Composite Anodes for Stable Lithium-Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-energy-density lithium metal batteries require stable lithium anodes, but electrochemical-mechanical instability causes rapid failure due to uncontrolled plating and stress.
• Lithium plating leads to electrode swelling, side reactions, and porous deposits, significantly degrading battery performance.

Purpose of the Study:

• To investigate the coupled stress, strain, and volume variation during lithium metal anode cycling.
• To design a stable composite anode that addresses the electrochemical-mechanical instability of lithium metal.

Main Methods:

• In situ investigation of stress, strain, and their spatial distributions during charge/discharge cycling.
• Development of a dual-phase Li-Ag solid-solution/Li22Sn5 alloy composite anode.
• Electrochemical performance testing of NCM622||Li-Ag/Li22Sn5 pouch cells compared to NCM622||Li cells.

Main Results:

• The Li-Ag/Li22Sn5 composite anode demonstrates enhanced Li+ affinity for uniform plating and a rigid scaffold to confine volume expansion.
• NCM622||Li-Ag/Li22Sn5 pouch cells showed significantly lower internal pressure rise during cycling compared to NCM622||Li cells (58% less pressure increase in the 5th cycle).
• A 1.3 Ah laminated pouch cell retained 87% capacity over 100 cycles at an industry-relevant N/P ratio and electrolyte budget.

Conclusions:

• Understanding mechanical-electrochemical coupling is crucial for designing stable lithium metal anodes.
• The dual-phase Li-Ag/Li22Sn5 composite anode offers a practical approach for achieving long-lifespan, high-energy-density lithium metal batteries.