Surface Engineering Enabling Efficient Upcycling of Highly Degraded Layered Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Energy

Background:

• Direct recycling of cathode materials offers economic and environmental benefits.
• Existing methods struggle with highly degraded layered materials due to rock-salt phase accumulation blocking lithium diffusion.
• This accumulation presents thermodynamic challenges for phase transformation.

Purpose of the Study:

• To develop a surface engineering strategy for direct upcycling of highly degraded cathode materials.
• To reactivate lithium diffusion channels on degraded cathode surfaces.
• To enhance the stability and performance of recycled cathode materials.

Main Methods:

• Employed an acid etching technique for surface modification of degraded cathode materials.
• Selective removal of electrochemically inert rock-salt phases.
• Dissociation of polycrystalline structures into single crystals to reduce relithiation barriers.

Main Results:

• Restored the capacity of degraded LiNi$_{0.5}$Co$_{0.2}$Mn$_{0.3}$O$_{2}$ from 59.7 to 165.4 mAh g$^{-1}$, achieving performance comparable to commercial materials.
• Achieved 80.1% capacity retention at 1 C after 500 cycles in pouch-type full cells.
• Demonstrated the strategy's effectiveness on Ni-rich layered materials and LiCoO$_{2}$.

Conclusions:

• Surface engineering-assisted direct upcycling is a promising approach for highly degraded cathode materials.
• Acid etching effectively removes detrimental surface phases and improves material structure.
• This method enhances electrochemical performance and stability, enabling sustainable battery recycling.