Optimization of multicomponent aqueous suspensions of lithium iron phosphate (LiFePO_4) nanoparticles and carbon black for lithium-ion battery cathodes

摘要

Addition of polyethyleneimine (PEI) to aqueous LiFePO_4 nanoparticle suspensions improves stability and reduces agglomerate size, which is beneficial to lithium-ion battery cathode manufacturing. This research examines the effect of both PEI concentration and molecular weight (MW) on dispersing LiFePO_4 and Super P C45 in multicomponent aqueous suspensions. It is demonstrated that the optimal conditions for obtaining stable suspensions with minimal agglomerate size are 1.5wt% PEI with MW=2000gmol~(-1) and 5.0wt% PEI with MW=10,000gmol~(-1) for LiFePO_4 and Super P C45, respectively. The mixing sequence also affects rheological properties of these suspensions. It is found that dispersing the LiFePO_4 and Super P C45 separately yielded suspensions with superior properties (Newtonian rheological behavior, smaller agglomerate size, improved settling, etc.). In particular, dispersing the LiFePO_4 prior to the Super P C45 when making the final multicomponent suspension is found to be beneficial, which was evidenced by higher half-cell discharge capacity.