Overcoming Kinetic Limitations of Silicon Anodes Toward Fast-Charging Sulfide-Based All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• All-solid-state batteries (ASSBs) with silicon (Si) anodes promise high energy density and safety.
• Fast charging of Si anodes is limited by unclear short-circuit mechanisms, hindering ASSB development.

Purpose of the Study:

• To investigate the kinetic limitations causing short circuits in Si anodes during fast charging.
• To develop a novel anode structure for high-performance Si-based ASSBs.

Main Methods:

• Probed kinetic limits in Si anodes, distinguishing between charge transfer and Li+ transport.
• Replaced excess conductive carbon with micro-size Li-Al alloy to create an all-electrochemical-active Si anode.
• Fabricated and tested Si||NCM811 ASSBs with the novel anode design.

Main Results:

• Identified slow charge transfer, not Li+ bulk transport, as the kinetic bottleneck.
• The Li-Al alloy enhanced reaction kinetics to 8.1 mA cm⁻², provided extra capacity, and improved mechanical stability.
• Achieved high initial coulombic efficiency (89.3%), high area capacity (6.7 mAh cm⁻²), and stable cycling (80.5% retention over 850 cycles at 1C).

Conclusions:

• The study elucidates the kinetic origin of Li dendrite growth in Si anodes.
• The developed all-electrochemical-active Si anode using Li-Al alloy offers a viable strategy for high-performance ASSBs.