Effects of Dispersant on the Conductive Carbon for LiFePO4 Cathode

Carbon-based electrically conductive particles (cECP) are commonly used to reduce interparticle resistance in Li-ion batteries, but cECP tend to flocculate in the dense slurries used to fabricate electrodes. Herein, a novel dispersant limits flocculated cECP particle size and improves cECP dispersion. The increased cECP efficacy allows reduced addition of carbon to the battery, thereby increasing the ratio of active material to conductive material and increasing volumetric energy density. With/without dispersant LiFePO4/ketjenblack cathodes are examined by scanning electron microscopy (SEM), slurry viscosity, electrochemical redox behavior, electrochemical impendence spectroscopy (EIS) and charge/discharge cycling performance. Discharge capacity, durability and resistance are better for the with-dispersant LiFePO4 cathode. EIS shows reduced interfacial impedance and increased cycling performance for the with-dispersant electrode. SEM shows smooth distribution of nano-scale particles of consistent size with dispersant use. Without dispersant, the cECP particles are micro-scale, with high variability in size and location. It is seen that a good cECP dispersant in the initial electrode slurry improves Li-ion battery performance, primarily because of a more cohesive cECP network between the active material particles. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3560222] All rights reserved.