Particle-size effects on the entropy behavior of a Li_xFePO ₄ electrode

The particle-size effects on the thermodynamic properties and kinetic behavior of a Li_xFePO₄ electrode have a direct influence on the electrode properties. Thus, the development of high-performance Li-ion batteries containing a Li_xFePO₄ cathode requires a complete understanding of the reaction mechanism at the atomic/nano/meso scale. In this work, we report electrochemical calorimetric and potentiometric studies on Li_xFePO₄ electrodes with different particle sizes and clarify the particle-size effect on the reaction mechanism based on the entropy change of (de)lithiation. Electrochemical calorimetry results show that a reduction in particle size shrinks the miscibility gap of Li _xFePO₄ while potentiometric measurements demonstrate that the Li_xFePO₄ particles equilibrate into either a kinetically metastable state or a thermodynamically stable state depending on the particle size.