The Gamry Interface 5000 is the latest potentiostat from Gamry Instruments. This full-featured potentiostat/galvanostat is ideally designed for testing batteries, fuel cells and supercapacitors. What makes this potentiostat so unique? A Dual Electrometer. A second electrometer provides the ability to monitor both half cells in a typical three-electrode setup. With this feature, you can monitor both the anode and Read more about What makes the Interface 5000 Unique?[…]
The various parameters that are typically listed in the specifications of potentiostats are explained in this Technical Note originally posted by Gamry Instruments. There are many important factors that pertain to buying a potentiostat, and the old adage “The more the better” really does not apply when researching the potentiostat to fit your experiment. There Read more about Understanding Potentiostat Specs[…]
Purpose of This Note:
This application note discusses electrochemical measurements on lithium ion batteries. Theory and general setup of lithium ion batteries are explained. Important parameters for characterizing batteries are described.
In addition, various experiments on coin cells are performed. They show how to gain information about a battery’s performance, e.g. capacity and voltage limits as well as long time behavior.
Being able to scan rapidly does not insure that the results will be meaningful! The speed of the current measurement circuitry is often the limiting factor!
The key to finding the practical limit for obtaining meaningful fast scan cyclic voltammograms is nearly always finding the speed of the current measurement. Here the researcher has an important role to play: It is the researcher who must select the current range to use for fast cyclic voltammetry. The autoranging capability of many modern computer controlled potentiostats generally cannot be used because the decisions cannot be made and implemented fast enough.
Because of stray (and deliberately added) capacitances, the current measuring circuitry generally becomes slower as the full scale current decreases. Obtaining the fastest scan requires a tradeoff of scan rate, electrode size, analyte concentration, current range, and acceptable noise in the measurement. It is often better to use a less sensitive current scale (larger full scale current) coupled with a larger pre-amplification factor on the ADC, data recorder, or oscilloscope used. Although this approach is likely to increase the noise in the measurement, it does allow a higher scan rate to be realized.
The speed or frequency response of each current range can sometimes be found in the manufacturer’s data sheet under “Current Measurement” or sometimes as a “System Specification” if a specific current range is quoted along with the bandwidth.
This number can be roughly translated into a scan rate by looking at Figure 1.
For DNA Electrochemical Detection on Microfluidic Gene Chip On the microfluidic gene chip, due to high difficulty in temperature changes frequently and products detecting equipment miniaturize, the conventional methods of DNA detection can’t meet the requirements. In this paper, a newly electrochemical method, cyclic voltammetry, basing on a set of special electrodes and the Loop-mediated Read more about Development of a Cyclic Voltammetry Method[…]
Using Digital Staircase Voltammetry
Cyclic Voltammetry (CV) is unarguably the most popular electrochemical technique. It owes its well deserved reputation to its ability to deduce reaction mechanisms with relatively low cost equipment and quick experimentation. Since the very highly cited paper by Nicholson and Shain1 the technique has been the centerpiece of any electrochemical study.
CV involves sweeping the potential linearly between two limits at a given sweep rate while measuring current. The sweep rate chosen can be varied from few microvolts per second to millions of volts per second.
Electrochemical instrumentation has evolved vastly since the days of Nicholson and Shain. Currently, most manufacturers (including Gamry) make digital instruments with digital signal generators. These signal generators approximate the linear sweep with a staircase of variable step sizes and durations.
Cyclic Voltammetry and Leakage Current
Purpose of This Note
This application note is the first part of an overview of electrochemical techniques used to test electrochemical capacitors (ECs). Electrochemical capacitors that are commercially available were tested to explain and discuss the theoretical background of cyclic voltammetry and leakage current measurement.
This application note is part one of 3. Part 2 of this note discusses techniques that are also familiar to battery technologists. Part 3 describes theory and practice of EIS measurements on capacitors.
In contrast to batteries, ECs generally store energy by highly reversible separation of electrical charge while batteries use chemical reactions. ECs consist of two high-surface electrodes immersed in a conductive liquid or polymer called the electrolyte. The electrodes are separated by an ionic-conducting separator that prevents shorts between the two electrodes.
One of the problems that faced early electrochemists interested in current-potential-time relationships in cyclic voltammetry was the complexity of the diffusion equations. Sevcik [ Coll Czech Chem Comm, 13 (1948) 349 ] derived a series approximation for the current-potential curve in CV, but cyclic voltammetry got a big boost as a mechanistic tool from the landmark series of publications by Nicholson and Shain [ Anal Chem, 36 (1964) 706 ].
Nicholson solved the x-dependence of the diffusion equation via Laplace Transforms but was then left with an integral equation for current vs. E. He numerically integrated this equation for various values of sweep rate and kinetic parameters and published ‘working curves’ for others to use without having to repeat the (then) tedious calculations.