High Areal Capacity Si/LiCoO₂ Batteries from Electrospun Composite Fiber Mats

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Silicon nanoparticles are promising anode materials for lithium-ion batteries due to their high theoretical capacity.
• Challenges include large volume expansion during lithiation, leading to poor cycling stability and low practical capacity.
• Existing nanostructured silicon anodes often suffer from low active material loading and density.

Purpose of the Study:

• To develop freestanding nanofiber mat anodes with high silicon loading and improved electrochemical performance.
• To investigate the effect of compaction and interfiber welding on anode structure and stability.
• To evaluate the performance of these anodes in a full cell configuration.

Main Methods:

• Electrospinning of a composite containing silicon nanoparticles, carbon black, and poly(acrylic acid) (PAA) to form freestanding nanofiber mats.
• Compaction of the mats to a high fiber volume fraction (≈0.85).
• Welding of interfiber contacts using methanol vapor treatment.

Main Results:

• The compacted and welded Si/C/PAA anode (40 wt% Si) achieved high capacities of 1484 mAh g^-1 at 0.1 C and 489 mAh g^-1 at 1 C.
• Demonstrated good cycling stability with 73% capacity retention over 50 cycles.
• Achieved high areal and volumetric capacities (4.5 mAh cm^-2 and 750 mAh cm^-3, respectively) due to high material loading and density.
• A full cell with an electrospun Si/C/PAA anode and LiCoO₂ cathode reached a specific energy density of 270 Wh kg^-1.

Conclusions:

• Freestanding, compacted, and welded Si/C/PAA nanofiber mat anodes offer a viable strategy to overcome limitations of traditional silicon anodes.
• The PAA binder's interaction with the SiOx surface and the robust mat structure contribute to excellent performance.
• This approach enables high-performance lithium-ion batteries with high energy density.