EC-Lab Technical Notes 07: The “compact” Function in the PCGA protocol

Introduction

The study of batteries and cells often requires specific graphic representations which can take a long time to implement. One of the most common graphics in battery testing is the incremental capacity versus Ewe. It is obtained by potentiostatic intermittent Titration Technique (PITT) using the PCGA protocol. It corresponds to the capacity accumulated on each potential step divided by the size of the step (?Q/?V). This type of diagram can be very useful to determine the composition of batteries or intercalated compounds [1, 2] and can be related to the composition x of Li in the case of a LiCoO2 cell. Moreover, PITT is commonly used to determine the diffusion coefficients of compounds in the cell [2]. The compact function can also be used during battery cycling to determine the apparent resistance of the cell when the experiment switches from the OCV period to the galvanostatic period and vice versa.