Potentiostatic intermittent titration technique for electrodes governed by diffusion and interfacial reaction

The potentiostatic intermittent titration technique (PITT) is one of the widely used methods for determining the diffusion coefficient in electrochemical materials, such as lithium diffusion in lithium-ion battery electrodes. The conventional PITT analysis neglects interfacial resistance and assumes the system is diffusion-controlled. For real electrode systems, however, surface reaction as well as diffusion may be rate-limiting. In this Article, we analyze PITT measurements for material systems with finite surface reaction rates. For small amplitude potential steps, we derive analytic solutions for the measured transient current associated with PITT, taking into account the effects of finite surface reaction rates. Using the analytic solutions, the diffusion coefficient, surface reaction rate, and the exchange current density can be determined simultaneously. An example of lithium diffusion in amorphous silicon thin-film electrodes is used to demonstrate the enhanced PITT approach.