Improving the Electrochemical Properties of LiFePO4 by Mixed-source-derived Carbon Layer

With the increasing adoption of electric vehicles and the accompanying drive to lower battery costs, lithium iron phosphate (LiFePO4, LFP) has emerged as the most widely used cathode material. The appeal of LFP lies in its reliance on cost-effective elements, such as Fe and P, along with its exceptional safety and cycling stability, attributed to the robust P–O bonds within the (PO4)3–polyanion. However, its practical application has been hindered by its inherently low lithium-ion diffusivity and electronic conductivity, limiting its rate capability. A widely adopted strategy to address this limitation is to coat the surface of LFP particles with a carbon layer, which significantly enhances its electronic conductivity and thereby improves its rate performance. The effectiveness of this carbon coating is highly dependent on the choice of source materials used. In this study, we aimed to optimize the carbon coating by utilizing a composite source of glucose and polystyrene. Furthermore, ferrocene was introduced as an additive to promote the graphitization of the carbon layer and reduce the proportion of disordered carbon, thereby enhancing the quality of the coating. This approach resulted in a significant improvement in the electrochemical performance, with a discharge capacity of approximately 166 mAh·g–1 and a high capacity retention (defined as the 1C discharge capacity relative to the 0.05C discharge capacity) of ~90%. The structural and compositional properties of the carbon coating layer were analyzed using transmission electron microscopy, Raman spectroscopy, and Cs (carbon–sulfur) analysis. The electrochemical performance of the coated LFP was further characterized through impedance measurements and the galvanostatic intermittent titration technique, providing insights into the influence of the carbon coating on cell behavior. These findings underscore the potential of combining composite carbon sources and additives to develop high-quality carbon-coated LFP cathodes, paving the way for enhanced performance in lithium-ion batteries for electric vehicle applications.