LiFePO4 particle conductive composite strategies for improving cathode rate capability

Abstract

Lithium iron phosphate (LFP) cathodes are one of the most promising candidates to find application in hybrid electric vehicle energy storage system. For this reason advances in the performance of its theoretical capacity at high charge/discharge rates is under continuous development. Most used strategies to improve power performance are the addition to the LFP particles of an electric conductive carbon or polymer, such as poly(3,4-ethylenedioxythiophene) [PEDOT] doped with polystyrene sulfonate (PSS). The data obtained from impedance analysis provide new insight on the role of these additives that not only improve the charge transfer but also favor the lithiation/delithiation processes in the phosphate matrix. Furthermore, PEDOT is capable to reduce the resistances of charge transfer and lithiation reaction inside the phosphate matrix by one order of magnitude in comparison with those achieved with the carbon coating strategy. In this study, the most effective approach has been the addition of PEDOT by a blending method, resulting in a specific capacity of 130 mA h gLFP−1 at 2 C.