Significant Improvement in Stability at High Current Density of LiFePO₄-Based Multidimensional Nanocarbon Composite as a Cathode for Lithium-Ion Batteries

Recently, the widespread use of lithium-ion batteries (LIBs) in various applications, ranging from portable electronics to electric vehicles, has spurred significant efforts to improve their technology. These batteries are favored due to their high energy density, long cycle life, and relatively low self-discharge rates, making them essential in the modern energy landscape. Among the various materials used in LIBs, lithium iron phosphate (LiFePO₄, LFP) stands out as a widely used and promising electrode material. This is primarily due to its outstanding characteristics, which include excellent thermal stability, safety, and long cycle life. Especially, LFP is less prone to thermal runaway due to the stable nature of iron phosphate, reducing the risk of thermal runaway and ensuring safer battery operation, making it a safer choice for high-power applications. Nevertheless, the restricted lithium-ion kinetics of LFP, caused by its one-dimensional lithium-ion diffusion pathway, limits its effectiveness in high-performance LIBs. This structural limitation results in slow lithium-ion transport within the electrode, which in turn contributes to poor electrochemical performance, especially under high current conditions. At high currents, the sluggish lithium-ion movement leads to a decrease in capacity and an overall degradation in electrochemical reaction rates. Our study addresses this critical challenge of diminished electrochemical performance at high cycling rates by synthesizing multidimensional LFP-based carbon composites. By engineering the material at the nanoscale, we aim to overcome the intrinsic limitations of LFP. The incorporation of graphene quantum dots (GQDs) and carbon nanotubes (CNTs) with LFP not only improves the one-dimensional lithium-ion diffusion of the material but also significantly enhances its electrical conductivity. The resulting composite material exhibits superior electrochemical characteristics even under high current densities. The enhanced lithium-ion diffusivity and increased electrical conductivity ensure that the material can maintain high capacity and stable cycling performance under high current densities. This improvement is crucial for applications requiring rapid charge and discharge cycles, such as electric vehicles and grid storage systems. This study highlights the effective approach of electrode material design in improving the performance of lithium-ion batteries. By focusing on the nano-engineering of LFP and its composites, we demonstrate that it is possible to significantly enhance the material's properties and overcome its inherent limitations. Our findings provide valuable insights into the design strategies for next-generation electrode materials, paving the way for more efficient and reliable lithium-ion batteries.<br/><br/>Acknowledgement: This work was supported by the National Research Foundation of Korea (NRF-2021R1A2C1008272). This study was supported by Ministry of Trade, Industry and Energy, KEIT, under the project title "International standard development of evaluation methods for nano-carbon-based high-performance supercapacitors for electric vehicles" (project # 20016144). This work was supported by Korean Ministry of Industry, KEIT, "Setting and Developing Key Technology Standards Strategy and Development for Global Competitiveness on Materials, Parts, and Equipments" (project # 20015943)