The Delithiation Behavior of LiFePO4 Particles with Broad Particle Size Distribution during Chemically Delithiation

LiFePO₄ is the most promising cathode material, especially for electric vehicle (EV) because of its inexpensive cost, superior thermal and structural safety, and non-toxicity. Although LiFePO₄ has been believed to be poor conductor due to its low electronic conductivity and 1D lithium diffusion, nano-sized LiFePO₄ shows the fastest electrochemical reaction during charge and discharge.

To understand these intriguing behaviors, we have to consider delithiation behavior of particles in the electrode which consists of 10¹⁰ ~ 10¹⁷ particles in addition to the transport properties in the material because a particle has a non-monotonic chemical potential^[1]. The non-monotonic chemical potential of single particle in multi-particle electrode leads to characteristic electrochemical behaviors such as a flat potential in voltage curve of the electrode and a sequential phase transformation between particles. Thus, delithiation behaviors in a particle in the electrode should be understood.

In this study, we will explore delithiation behaviors of LiFePO₄ with broad particle size distribution. For this purpose, chemical delithiation and followed centrifuge method were applied to understand the delithiation behavior of LiFePO₄ depending on particle size. This simple method shows phase transformation behaviors more directly. We synthesized LiFePO₄ with broad particle size distribution by solid state reaction. And then, we can easily separate chemically delithiated small and large particles by centrifuge method. In this talk, we will introduce simple centrifuge method and will discuss about delithiation behavior of LiFePO₄ with broad particle size distribution during chemical delithiation.

[1] W. Dreyer et al 2010 The thermodynamic origin of hysteresis in insertion batteries Nature Mat. 9, 448.