Electrode fabrication for Li-ion: processing, formulations and defects during coating

The chemistry of the constituent electrode/electrolytes determines the electrochemical stability, reversibility and kinetics of the Li insertion/extraction process and hence limits the performance of Li-ion batteries. However, mechanical stability/configuration of the electrodes is equally important for extended cycle life and is largely determined by the electrode processing and fabrication techniques. Inhomogeneous distribution of the binders and active materials on the electrodes resulting from variations in rheological parameters for the slurry/suspension during formulation and additional defects introduced during processing/fabrication not only lead to poor adhesion and subsequent mechanical failure by delamination, but also result in electrode thickness, porosity and density variations which severely affect the chemistry of the insertion process. The purpose of this paper is to: (1) evaluate the various possible electrode defects with different fabrication techniques used for small scale, specialty purpose Li-ion electrode fabrication such as the aqueous/nonaqueous pasting process, and doctor-blade/web-coating methods and (2) examine the origin of defects and role of curing, drying and electrode formulations which affect the adhesion, coating defects and hence influence the subsequent electrochemical characteristics.