A Balancing Act: Experimental Insights into the Volume Fraction of Conductive Additive in Lithium-Ion Battery Electrodes

Abstract

Lithium-ion battery electrodes are traditionally comprised of a cathode or anode material, a carbon conductive additive, and a polymeric binder. The conductive additive and binder are traditionally considered electrochemically inactive; however, the organization of the carbon-binder matrix in 3D space significantly alters electrode physical properties such as electrical conductivity and porosity, resulting in changes to electrochemical performance. While many experimental studies have altered the mass fraction and type of conductive additive, this study systematically studies the volume fraction of electrode components. Electrodes composed of lithium titanate (LTO) active material and SuperP conductive additive across six different electrode compositions from 20–70 vol% LTO and three different electrode film thicknesses of approximately 70, 125, and 225 μm were evaluated. Electrode structures were observed via scanning electron microscopy and electronic conductivities were measured with 4-point probe analysis. Notably, electrochemical performance described as different figures of merit are maximized for different electrode compositions. For example, while thin electrodes with maximal volume fractions of LTO achieve superior volumetric energy density, power density is maximized for thicker electrodes with an optimal volume fraction of conductive additive. This study demonstrates the importance of balancing overpotential arising from ohmic drop and concentration polarization.