Binders for green next-generation battery electrodes

Currently, most state-of-the-art battery electrodes are processed using organic solvents such as the highly toxic N-methyl-2-pyrrolidone (NMP), which poses health hazards and environmental concerns. This is a direct consequence of using electrode binders, such as polyvinylidene fluoride (PVDF), which are not soluble in water. Some examples of binders that are soluble or insoluble in water are shown in the figure below. This project investigates a promising new family of binders, thought to offer excellent structural stability, high water solubility, high lithium-ion conductivity, facile extraction from natural resources and are environmentally-friendly. Extensive electrochemical testing and advanced characterisation techniques will result in a detailed understanding of how the binders can be used to further the performance of next-generation battery electrodes.

Characterisation by X-ray photoelectron spectroscopy (XPS) will be a particular focus in this project. XPS is a widely-used, highly surface sensitive technique that offers the possibility to gain chemical information about samples including elemental composition, oxidation states, and bonding environments. This is a particularly important technique in the study of battery materials since the interface between electrode and electrolyte is where chemical reactions typically occur. XPS can be used to study this interface to determine how the active material evolves during cycling, reactions of the binder, and solid electrolyte interphase (SEI) layer formation at the electrode surface. While the use of in-house XPS instruments gives high surface sensitivity, synchrotron-based XPS will be used with multiple photon energies to probe depths of up to 30 nm, allowing for the comparison of surface vs. bulk processes for the electrodes.

Keywords: binder, next-generation batteries, water-soluble, environmentally-friendly