Optimization of Inactive Material Content in Lithium Iron Phosphate Electrodes for High Power Applications

The electrochemical performance of lithium iron phosphate (LiFePO4) electrodes has been studied to find the optimum content of inactive materials (carbon black + polyvinylidene difluoride [PVDF] polymer binder) and to better understand electrode performance with variation in electrode composition. Trade-offs between inactive material content and electrochemical performance have been characterized in terms of electrical resistance, rate-capability, area-specific impedance (ASI), pulse-power characterization, and energy density calculations. The ASI and electrical conductivity were found to correlate well with ohmic polarization. The results showed that a 80:10:10 (active material: binder: carbon agents) electrode had a higher pulse-power density and energy density at rates above 1C as compared to 90:5:5, 86:7:7 and 70:15:15 formulations, while the 70:15:15 electrode had the highest electrical conductivity of 0.79 S cm(-1). A CB/PVDF ratio of ca. 1.22 was found to be the optimum formulation of inactive material when the LiFePO4 composition was 80 wt%. (C) 2016 Elsevier Ltd. All rights reserved.