Design of Aqueous Processed Thick LiFePO4 Composite Electrodes for High-Energy Lithium Battery

Small-amplitude oscillatory rheology is used to probe the microstructure present in aqueous composite electrode slurries for lithium batteries. The materials prepared with carboxymethyl cellulose as the thickener displays a solidlike behavior due to the buildup of a three-dimensional network of colloidal carbon black (CB) particles bridged by the polymeric chains. This network is able to support and inhibit the settling of the larger LiFePO4 particles. Thus a homogeneous morphology is achieved in the dried composite electrode and good electrochemical performance is displayed both at low and high rates. Contrarily, hydroxypropylmethyl cellulose is observed to create weaker bonds between the CB particles and the materials prepared with this thickener display a liquidlike behavior. Then, the setting of the LiFePO4 particles results in a concentration gradient, and thus poor electronic wiring and electrochemical performance, unless drying is accelerated by heating. (C) 2008 The Electrochemical Society.