# Data of interest – work more efficiently.

Latest updated: April 19, 2021

Introduction

Electrochemistry is not just about time, current & voltage. The variable process is a set of automated EC and BT Lab potentiostat and battery cycler software functions that can save you valuable time in identifying key data of interest such as battery cycle life, Coulombic efficiency, capacity fading, Ohmic drop, and $\mathrm{d}Q/\mathrm{d}E$, etc.

The potentiostat/galvanostat, that inimitable Swiss Army knife of electrochemical research. We would be lost without it. For years the instruments have been used to better understand the mysterious relationships between time, current and voltage; helping us break down scientific boundaries, develop new products – batteries and other innovations in order to optimize circuits amongst a myriad of other applications and uses.

But, in fact, the instruments can be used for so much more and are often under-exploited. BioLogic’s potentiostats (sometimes referred to as electrochemical workstations) and their control software EC-Lab® and BT Lab® have been designed with a huge range of highly advanced functionality that can be used to help you generate data of interest; data such as Efficiency, QDischarge, Qcapacity and capacity that can play a vital role in advancing  your research.

Data of interest for potentiostats and battery cyclers

There are two types of variable process available in BioLogic’s potentiostat and Battery cycler ranges:

 Usual Online and post processed variables Automatic : Limits or parameters injection Non-Automatic: analysis $Q-Q_0$: charge from the beginning of the experiment X $Q_{charge}$ for a charge cycle reinitialized every cycle X Q discharge: Q for a discharge cycle reinitialized every cycle X Efficiency: $Q_{discharge}/Q_{charge}$ X x: normalized charge X dQ/dV: differential capacity X Ohmic drop compensation X Cycle number X X Power: in CPW, calculated by $E\times{I}$ X Energy: in CPW calculated by $E\times{I}\times{t}$ X Energy charge: : $E\times{I}\times{t}$ X

BATTERY APPLICATIONS

Variable process: Identify Battery Cycle Life more quickly and with increased precision

Take the example of battery applications where the automatic variable process is most applicable.  The initial capacity of a battery, capacity fade during use, the capacities at several charge/discharge rates and Cycle Life are all fundamental research values needed at practically every level of the battery-development value chain.  Therefore, one would assume, this information is easy to identify. Unfortunately, this is often not the case.

BioLogic’s EC-Lab®/BT-Lab®  potentiostat and battery cycler interfaces, however, can give you access to this data, quickly and easily via its variable process functionality.

An accurate starting point, an automated process and increased precision. Only on EC-Lab

The starting point is BCD (Battery Capacity Determination) which ascertains the correct, non-arbitrary, capacity of the battery by performing a galvanostatic discharge. Once this figure has been determined, the system will start automatically cycling your battery, calculating the exact current corresponding to an arbitrary C-Rate down to a predetermined cut-off voltage. In an environment where test cycles of 5K (or more) are common, the automated nature of this capacity determination  process not only makes life easier for users working on battery testing but also increases the precision of such results significantly. It is easy to generate such data and we have put together a video tutorial, which can be found at the bottom of this article, to take you through each individual stage of the process.

 Figure 1: illustrates non- automatic post-process data → allows alternative cycle definition, \$\mathrm{d}Q/\mathrm{d}E (only BL) Figure 2: illustrates  automatic capacity determination re-injected in the next technique → allows C-rate automatic correction or new charge limit Figure 3: illustrate automatic Coulombic Efficiency calculation → allows plotting Eff vs cycle number

At a glance…

• Fully automated process for ascertaining battery cycle life data
• Applicable for other key areas such as determining Coulombic Efficiency, specialist battery chemistries such as silicon batteries, capacity fading, Ohmic drop, and dQ/dV
• Only available on BioLogic’s EC/BT-Lab interface