Self-Pressure Silicon-Carbon Anodes for Low-External-Pressure Solid-State Li-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• High stack pressure (≥50 MPa) is crucial for solid-state battery (SSB) performance but impractical for commercialization.
• Silicon (Si) anodes offer high capacity but suffer from significant volumetric expansion (up to 300%) during cycling.
• Interfacial instability due to stress is a major bottleneck for practical SSB development.

Purpose of the Study:

• To develop a self-pressure anode for SSBs that operates stably under low external pressure (≤2 MPa).
• To design a composite anode that compensates for Si volume expansion and maintains dynamic solid-solid interfaces.
• To resolve interfacial mechanical and ion transport challenges in SSBs.

Main Methods:

• Fabrication of a self-pressure anode using poly(ethylene oxide) (PEO)/lithium salt-coated carbon nanotubes (CNTs) compressed by shrinking graphene hydrogel.
• Utilizing capillary-driven hydrogel shrinkage to generate internal pressure, counteracting Si expansion.
• Constructing dynamic solid-solid interfaces between anode components and the electrolyte.

Main Results:

• The self-pressure anode enabled stable SSB operation at 0 MPa external pressure with 700 cycles and 79.2% capacity retention in a composite electrolyte.
• A half-cell with a sulfide solid-state electrolyte achieved 700 cycles at a minimal 2 MPa stack pressure.
• Demonstrated simultaneous alleviation of internal and external stress through a prestressed structure.

Conclusions:

• The proposed self-pressure anode design effectively manages stress and maintains interfacial integrity in SSBs.
• This approach significantly reduces the required external pressure for stable SSB operation, paving the way for commercialization.
• The dynamic interfaces ensure sustained ion and electron transport, crucial for long cycle life.