Investigation LiFePO4/C nanomaterials with water-soluble binder for lithium-ion batteries

초록

With the rising demand for energy, energy storage and conversion have become global issues. Among the many types of energy storage devices, lithium-ion batteries (LIBs) have a significant share in the market. Cathodes are the most important component of LIBs because they are directly linked to energy density, cycle life, and cost. Industrially, cathodes are produced by mixing with conductive agents and binders in an organic solvent. The slurry is then coated onto an aluminum current collector. Normally, Polyvinylidene difluoride (PVDF) and 1-Methyl-2-pyrrolidone (NMP) are widely used as binders and solvents, respectively. However, this combination is relatively expensive, toxic, and harmful to the environment. To achieve a sustainable process, the development of a water-based cathode slurry is in demand. In this study, we evaluated an aqueous process using Olivine-type LiFePO4 (LFP) as cathode active material. Although LFP has lower energy density and poor conductivity compared to ternary cathode batteries such as LiNixCoyMnzO2 (x+y+z=1, NCM) and LiNixCoyAlzO2 (x+y+z=1, NCA), it is considered a promising material due to its low cost and high stability. Additionally, LFP is less sensitive to water and moisture than other cathode materials. For this reason, LFP in an aqueous solvent has been extensively investigated with commercial water-soluble binders. However, compatibility issues between cathodes and water solvents have not been completely resolved. In our study, we investigated a suitable water-soluble binder for LFP and evaluated its compatibility with these materials. The LFP samples were prepared using a solvothermal method in a Teflon-lined stainless-steel autoclave and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electrochemical properties were then measured using coin half-cells to compare organic and non-organic systems.