The galvanostatic intermittent titration method (GITT) is a galvanostatic method. During the charging and discharging process, a constant current is applied for each step step, and then the open-circuit voltage change caused by the cut-off current is measured . When a constant current is applied to the electrode material, lithium ions are intercalated into or extracted from the particles, causing a concentration difference between the surface and the interior of the electrode. By measuring the change in voltage over time, we can calculate the rate of change in concentration, which allows us to calculate the diffusion coefficient of lithium ions.
Figure1.1 shows the changes in current and voltage over time in a GITT experiment. The sharp rise or fall in voltage can be explained by a drop in iR when current is applied or turned off. The voltage change with time is related to the lithium ion diffusion. The GITT-based lithium ion diffusion coefficient can be obtained using the following equation:
where, is the time of applying a constant current; mB is the mass of the electrode material; VM is the molar volume of the electrode material; MB is the molar mass of the electrode material; S is the electrode-electrolyte interface area; ΔEs is the step per step voltage change; ΔEt is the change in total voltage under constant current conditions; mBVM/MB is the volume of electrode material.
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