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

Abstract

The use of polyvinylidene difluoride (PVDF) binder dissolved in toxic N-methyl pyrrolidone (NMP) organic solvent needs to be decreased during the manufacturing battery process to improve safety. Therefore, the development of aqueous-based binders for negative and positive electrodes is necessary to make the production environmentally friendly. This study reports the performance of hydrothermal VOPO₄ 2H₂O anode material in combination with aqueous-based binders such as sodium carboxymethylcellulose (CMC), polyacrylic acid (PAA) and their mixture CMC-PAA (1:1 wt%). The aqueous binders are compared to standard PVDF as a reference binder. The cells with aqueous- and PVDF-based electrodes are tested by galvanostatic, cyclic voltammetry, and electrochemical impedance spectroscopy measurements. When the CMC-PAA aqueous binder is used, the electrode displays the most stable electrochemical performances due to a uniform distribution of the VOPO₄ with strong adhesion to the current collector for long-term cycle life. A stable, solid electrolyte interphase layer is formed when the mixture of CMC-PAA is used instead of a standard PVDF-based binder. In addition, these samples display stable cycling life at different rate capabilities due to the facilitated lithium-ion diffusion and electronic conductivity.