Binder formulation and microstructure in very high loading 3D-printed LiFePO4 electrodes

Abstract

3D-printing has emerged as a promising method for the fabrication of high loading electrodes to increase the energy density of the lithium-ion batteries (LIBs). The formulation and preparation of the printing inks, however, are not trivial and have a significant impact on the electrochemical and structural properties of the 3D-printed electrodes. Here, a comprehensive investigation is conducted to quantify the impact of binder formulation on the performance of the 3D-printed lithium iron phosphate (LFP) electrodes with active-material loadings beyond 25 mg/cm2. This is showcased with the commonly used binders of carboxymethyl cellulose (CMC) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and by highlighting their impact on the printability, microstructure, and cycling behavior of the LFP electrodes made thereof. To do so, a combination of the electrochemical and microstructural characterization techniques is employed to reveal the synergistic effect of the CMC and PEDOT:PSS binders on the mechanical integrity, electrical conductivity, tortuosity, and cycling performance of the 3D-printed LFP electrodes. The results underscore the significance of the binder in optimizing the 3D-printing process for the manufacturing of the energy-dense electrodes.