Simulation Model Based Real Time Analysis and Design for Single Secondary Particle

Abstract

When the LiFePO4 (LFP) was developed for an active material of lithium-ion batteries, the specific capacity is 100 ~ 110 mAh g-1, which is not competitive compared to other active materials such as LiCoO2 (LCO) for lithium-ion batteries. Because the electrochemical properties including diffusion coefficient and electric conductivity are relatively low. To overcome the limitations, the carbon was coated at the particle surface and the secondary particle composed of millions of nano-sized primary particles was used, so the 150~160 mAh g-1 was accomplished, which is close to theoretical capacity 170 mAh g-1. This dramatic improvement inspires the importance of particle-level studies.A single particle measurement research of active materials was reported first in 1999, which measures single particle properties by direct contact of tens of micron diameter gold or platinum filament to a single particle. This research has difficulty to cover all of the electrochemical properties of a single particle according to particle design because it takes a lot of time for direct contact between the particles and filaments and dropping particles and filaments even under minute vibrations. Moreover, the gold or platinum filament are expansive and difficult to reuse for other materials.In this study, we developed a simulation model for analysis of electrochemical properties inside of a particle and designing particles. Voltage profiles according to the C-rate obtained by simulation and experiment was compared and the model was verified. And the properties of the particle (State of Lithiation, Overpotential, Potential, Concentration) were analyzed in real time in 1D, 2D and 3D. Finally, the electrochemical performance of particles was evaluated for the design parameters (secondary particle size, Primary particle size, porosity).