Particles and Polymer Binder Interaction: A Controlling Factor in Lithium-Ion Electrode Performance

This paper investigates lithium-ion electrode laminates as polymer composites to explain their performance variation due to changes in formulation. There are three essential components in a positive electrode laminate: active material (AM) particles, acetylene black (AB) particles, and the polymer binder. The high filler content and discrete particle sizes make the electrode laminate a very unique polymer composite. This work introduces a physical model in which AB and AM particles compete for polymer binder, which forms fixed layers of polymer on their surfaces. This competition leads to the observed variations in electrode morphology and performance for different electrode formulations. The electronic conductivities of the cathode laminates were measured and compared to an effective conductivity calculation based on the physical model to probe the interaction among the three components to reveal the critical factors controlling electrode conductivity and electrochemical performance. The data and effective conductivity calculation results agree very well with each other. This developed physical model provides a theoretical guideline for optimization of electrode composition for most polymer binder-based Li-ion battery electrodes. © 2012 The Electrochemical Society.