In-situ growth of LiFePO4 with interconnected pores supported on carbon nanotubes via tavorite-olivine phase transition

Abstract

Lithium iron phosphate (LiFePO4) has gained significant attention as a promising cathode material for lithium-ion batteries due to its excellent stability and safety characteristics. However, its relatively low electrical conductivity restricts its practical application in high-power devices. In this study, we propose a novel approach to improve the electrochemical performance of LiFePO4 cathodes by introducing carbon nanotubes (CNT) through an in-situ growth process. Firstly, CNT serve as nucleation sites for the growth of FePO4, which subsequently attaches and grows in situ on CNT, resulting in the precipitation of CNT/FePO4. Subsequently, pre-lithiation is performed to synthesize CNT/LiFePO4OH, which ensures efficient mass transfer and uniform reaction achieved by wet chemical lithiation process. Eventually,The improved lattice perfection of CNT/LiFePO4 is obtained through the tavorite-olivine phase transition at a low crystallization temperature, allowing for more favorable ion diffusion pathways. Furthermore, in conjunction with the uniform incorporation of CNT to enhance the overall conductivity of the composite, the presence of intrinsically interwoven pores entwined amidst a bedrock of LFP nanoparticles is unveiled. These intricately connected pores function as conduits, promoting the seamless diffusion of electrolyte across the composite structure. This, in turn, augments the interfacial engagement between the cathode and electrolyte, propelling a surge in electrochemical reactivity and harnessing a heightened level of electrochemical efficacy, thereby amplifying the overall electrochemical performance and efficiency. Electrochemical tests demonstrate that the CNT/LiFePO4 cathodes exhibit significantly prominent rate capability with 143.0 mAh g-1 at a rate of 20C, and remarkable cycling stability with a retention rate of ∼97.0% under 1000 cycles at 1C. The in-situ growth of CNT/LiFePO4 offers a simple and scalable approach for the modification of LiFePO4 cathodes, enabling the practical utilization of this promising material in high-performance lithium-ion batteries.