Composite Electrode Ink Formulation for All Solid-State Batteries

Solid-state batteries employ composite electrodes which contain a solid ion conductor, a solid active material, a conductive additive, and a binder. The electrode microstructure fundamentally differs from electrodes in conventional batteries because the pore region is ion blocking. While there is extensive research on how to integrate a lithium metal with inorganic electrolytes, there is less knowledge on how an electrode can be integrated with an inorganic electrolyte. Solution processing techniques are ideal for scalable manufacturing and rely on creating an ink which combines the solid material, a binder, and solvent. Ink engineering relies on tailoring the fluidics (rheology), aggregation behavior, and stability for a desired coating process. In this work, we systematically probe the role of two ink constituents: the (1) binder, and (2) solvent on electrode microstructure formation. Lithium titanate anodes achieve nearly a 3-4X increase in capacity from 1.5 mAh/g and 3 mAh/g to 9 mAh/g and ≥12 mAh/g when a high viscosity solvent is employed. The binder plays a larger role in dictating performance of the electrode than surface adhesion properties. Inks with well dispersed constituents led to more effective electrodes for charge storage.