Synergy and Symbiosis Analysis of Capacity-Contributing Polypyrrole and Carbon-Coated Lithium Iron Phosphate Nanostructures for High-Performance Cathode Materials

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-LiFePO4) 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-LiFePO4 (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-LiFePO4, (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).

LiMn0.8Fe0.2PO4/C Nanoparticles via Polystyrene Template Carburizing Enhance the Rate Capability and Capacity Reversibility of Cathode Materials

“…Undoubtedly, the issues of low electronic conductivity and sluggish lithium-ion diffusion must be resolved in order to encourage the practical application of olivine structure LiMnPO 4 materials in the cathode of lithium-ion batteries. , In this regard, various strategies have been reported; for example, the electrical conductivity may be efficiently increased by covering carbon-based compounds, ,, reducing the grain size to nanoscale can promote the diffusion of lithium ions, − forming solid solution stable crystal structure with the help of doped ions can reduce the influence of Jahn–Teller effect, − and selecting the crystal plane direction that facilitates lithium-ion diffusion can optimize the reversible capacity of materials. , …”