Boosting Volumetric Capacity of LiFePO₄ Cathode Material for Electric Vehicles via Spray Drying Process

The recent vigorous commercialization of electric vehicles (EVs) has driven an increase in the specification requirements for LIBs used in EVs. These requirements include high energy density, high-rate capability, long cycle life, low raw material cost, and environmental friendliness. In response to these demands, there is significant attention on the continuous development of cathode materials, with lithium iron phosphate (LiFePO₄, LFP) prominently standing out among them due to its relatively low production cost and stability. Despite its advantages, when compared to other cathode material groups, LFP suffers from low electronic conductivity of 10^-9 S cm^-1. Efforts to improve electronic conductivity have focused on nano-sizing LFP particles, with subsequent carbon coating proving effective in further enhancing electronic conductivity and enabling superior rate capability. While nano-sized LFP has successfully enhanced its intrinsic performance, applying nano-sized LFP to EVs brings new challenges. Nano-sizing LFP particles significantly reduces the volumetric capacity within the electrode, resulting in a decrease in practical capacity at the cell level, ultimately limiting the mileage of EVs. Therefore, the development of LFP cathode materials for EVs requires a completely new approach to particle design.<br/>In this study, to fabricate LFP cathode material suitable for EVs, primary particles of LFP precursor at sizes in the hundreds of nanometers were synthesized using the continuous supercritical hydrothermal method. Subsequently, secondary particles of LFP precursor at sizes in the tens of micrometers were manufactured using the spray drying process. Each process is completed in less than 5 minutes, making it the fastest synthesis method for producing LFP precursor and a highly appropriate synthesis method for mass production. Additionally, by incorporating a carbon source during the spray drying process, high internal electronic conductivity paths were established within the secondary particles. To determine the ideal temperature for carbon coating and LFP phase formation, the optimal sintering temperature for carbon-coated granulated LFP (G-LFP@C) was identified. Electrochemical properties, including rate capability and long-term cycling retention at various current densities, showed that G-LFP@C exhibited excellent performance with high volumetric capacity. The details will be discussed at the conference.