Lithium Ion Cell Performance Enhancement Using Aqueous LiFePO4 Cathode Dispersions and Polyethyleneimine Dispersant

Switching manufacturing of composite battery electrodes from an organic system to an aqueous system provides both economic and environmental advantages. However, particle agglomeration of the electrode components and poor wetting of electrode dispersions to the current collectors are inherently introduced. Particle agglomeration can be mitigated by selection of appropriate dispersants. This research examines the effect of dispersant, poly(ethyleneimine) (PEI), on the associated morphology and electrochemical performance of LiFePO4. The addition of PEI reduces the agglomerate size and contributes to a more homogeneous distribution of cathode constituents, which results in a smoother, more uniform cathode surface. The LiFePO4 cathodes with PEI demonstrated a higher Li+ diffusion coefficient (1 x 10(-14) cm(2) s(-1)), better initial capacity (>142 mAh g(-1)), greater capacity retention (similar to 100%), and superior rate performance compared to the cathodes without PEI. When PEI concentration was varied, the LiFePO4 cathode with 2 wt% PEI exhibited the best performance at 167 mAh g(-1) capacity (98% of the theoretical capacity) and 100% retention after 50 cycles when discharged at 0.2C at 25 degrees C in a half cell. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.037302jes] All rights reserved.