Aqueous Binders for Electrochemically Stable VOPO₄ 2H₂O Anodes for Li-Ion Storage.

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Energy

Background:

• Traditional battery manufacturing uses toxic N-methyl pyrrolidone (NMP) solvent with polyvinylidene difluoride (PVDF) binders, posing safety and environmental concerns.
• Developing aqueous-based binders is crucial for environmentally friendly and safer battery production processes.

Purpose of the Study:

• To evaluate the performance of hydrothermal VOPO4·2H2O anode material with aqueous binders: sodium carboxymethylcellulose (CMC), polyacrylic acid (PAA), and a CMC-PAA mixture.
• To compare the electrochemical performance of aqueous binders against the standard PVDF binder.

Main Methods:

• Electrochemical testing including galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy.
• Performance evaluation of VOPO4·2H2O anode material with CMC, PAA, and CMC-PAA aqueous binders versus PVDF.

Main Results:

• The CMC-PAA aqueous binder demonstrated the most stable electrochemical performance, ensuring uniform VOPO4·2H2O distribution and strong adhesion for extended cycle life.
• A stable solid electrolyte interphase (SEI) layer formed with the CMC-PAA binder, unlike with PVDF.
• Stable cycling life at various rates was observed due to improved lithium-ion diffusion and electronic conductivity.

Conclusions:

• Aqueous binders, particularly the CMC-PAA mixture, are effective alternatives to PVDF/NMP for VOPO4·2H2O anodes, enhancing battery safety and sustainability.
• The CMC-PAA binder facilitates the formation of a stable SEI layer, leading to superior long-term cycling stability and rate capability.