ИСТИНА

The aqueous electrode processing for the metal-ion batteries has recently received significant consideration, since it can reduce the cost and environmental impact of the battery manufacturing process. The key point of this technology is development of water-soluble and water-dispersible polymer binders that should provide proper characteristics of the electrode slurries in the aqueous environment. Although several water-processable binders have been proposed in literature, the fundamental approaches for proper selection of the binder are not yet well established. In this study, we compared the performance of lithium iron phosphate cathodes formulated with various aqueous-processed polymer binders. The electrodes were prepared with single-walled carbon nanotubes as an electrically conducting component. The performance of the polymer binders was dependent on such parameters as electrical conductivity and adhesive properties of the binder, ability of the binder to stabilize carbon nanotubes dispersion as well as stability of the binder to the electrolytes. Among the studied binders, electrically conducting polymers provided the lowest impedance and best rate performance of the battery cells. It was related to the fact that conducting binder reduced bulk electrical resistance of the cathode active layer as well as interfacial resistance between the cathode layer and aluminum current collector. To further improve the performance of the cathodes, we have employed modified current collector coated with thin layer of carbon. The carbon coating significantly reduced the interfacial resistance at the cathode/current collector interface. As a result, the rate performance of the cathode became less dependent on the conductive property of the binder, so that electrically insulating binders provided almost as high capacitive characteristics as electrically conducting polymers. Thus, the use of electrically conducting binder is not essential when the cathode/current collector interface is optimized. In this case, industrially available and cheaper water-soluble polymers (e.g. polyvinylpyrrolidone or polyacrylic acid copolymers) can be used instead.