Synergy and Symbiosis Analysis of Capacity-Contributing Polypyrrole and Carbon-Coated Lithium Iron Phosphate Nanostructures for High-Performance Cathode Materials
Zhen Chen, Yan Wang, Miao Wang, Fubao Yong, Wentao Luo, Min Zhao, Faquan Yu
Abstract
To address the existing problems of commercial inorganic cathodes, including relatively low capacity, poor rate performance, structural instability, and low conductivity, it is critical to introduce a conductive matrix accompanied with electrochemical activity. Conductive polymers have great potential as electrodes with good conductivity, high redox activity, and potential. In this study, carbon-coated lithium iron phosphate (C-LiFePO 4 ) nanoparticles were effectively dispersed in a polypyrrole (PPy) matrix by in situ pulverization. PPy, as an active nanostructure, significantly improves conductivity and accelerates Li + diffusion. To further explore the synergy and symbiosis mechanism of PPy and C-LiFePO 4 (hereinafter called C-LFP in the composite), the nanoparticle dispersion, carburization dependence, and heat treatment preference were investigated. Therefore, a reasonable amount of PPy (25 wt %) hybridization, a moderately wrapped carbon buffer layer (5.3 wt %), and a suitable heat treatment (100 °C) were employed to prepare the (C-LFP) 0.75 (PPy) 0.25 nanocomposite. With a smaller particle size, uniformly dispersed morphology, and good synergy effect between PPy and C-LiFePO 4, (C-LFP) 0.75 (PPy) 0.25 delivers a high discharge capacity (209.1 mAh g –1 at 0.1C), a superior rate capability (86.1 mAh g –1 at 10C), and an outstanding capacity retention (83.5% of the initial values after 500 cycles at 0.5C).