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Popular topics · Battery test systems

How are 'data of interest' such as capacity, Coulombic efficiency and dQ/dV calculated automatically?

The variable process functions of EC-Lab and BT-Lab calculate values such as capacity, Coulombic efficiency, energy, dQ/dV and ohmic drop from time, current and voltage, online or in post-processing.

Key points

  • Values calculated in the software depend on the sampling rate chosen by the user; values calculated in the instrument depend only on its time base (200 µs on Essential and Premium potentiostats) and are therefore more accurate.
  • Because the instrument runs autonomously, safety and experimental limits are triggered even if the computer or the communication fails.
  • Calculated variables: Q-Q0, Qcharge and Qdischarge reset every cycle, efficiency (Qdischarge/Qcharge), normalised charge x, dQ/dV, ohmic-drop compensation, cycle number, power (E·I) and energy (E·I·t) in CPW, Echarge and Edischarge.
  • Automatic variables are passed to the next technique as limits or parameters; non-automatic ones are for analysis. Variables are added in the Process Data window, where the cycle definition (charge/discharge or discharge/charge order, loop increment) is chosen.
  • BCD (battery capacity determination) finds the actual capacity by galvanostatic discharge; the next technique uses it to calculate automatically the current for the desired C-rate. This increases precision in tests of thousands of cycles.
  • Coulombic efficiency is calculated automatically and plotted against cycle number; the same tools serve silicon-anode batteries, capacity fade, ohmic drop and dQ/dV analysis.

Figures

Basic data flow (E, I, t) versus values of interest calculated in hardware on Bio-Logic instruments (Q, cycle number, dQ/dV, Δmass).
Figure 1. Basic data flow (E, I, t) versus values of interest calculated in hardware on Bio-Logic instruments (Q, cycle number, dQ/dV, Δmass).
Process Data window: adding variables such as dQ/dE and charge/discharge energy and choosing the cycle definition.
Figure 2. Process Data window: adding variables such as dQ/dE and charge/discharge energy and choosing the cycle definition.
Capacity determined by the BCD technique passed to the next technique: the C-rate is corrected automatically.
Figure 3. Capacity determined by the BCD technique passed to the next technique: the C-rate is corrected automatically.
Automatic calculation of Coulombic efficiency plotted against cycle number.
Figure 4. Automatic calculation of Coulombic efficiency plotted against cycle number.

Images: Bio-Logic Science Instruments; taken from the source article.

Related application notes

Related curriculum module: Battery Testing and Characterisation

Related products:BCS-900 Series (BCS-905 / 910 / 915)MPG-200 Series (MPG-2 / MPG-205)BT-Lab® SuiteEC-Lab®
Source: Bio-Logic Learning Center, “Data of interest – work more efficiently.” · Source updated: November 18, 2024
Copyright of the images and the original text belongs to Bio-Logic SAS.

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