Cell testing
By Apoorv Shaligram
A couple of weeks ago, in the comments section of a post on LinkedIn, I came across a question about cell testing and how it varies from academia to industry; about why do we use certain protocols for cell testing in academia but very different ones in industry. While I tried answering it in brief, I realized that there is much more here that probably warranted a blog post on its own. Between travel and work, this post got a bit delayed. But, here are some thoughts I put together on the topic.
How? Yes. But also Why…
Often, on the topic of testing and characterization (batteries or otherwise), people often think about how others do it and how they should follow the standards and protocols used earlier. While this is important from the point of comparing results of different studies (carried out separately, often at different locations across the globe), it should not be at the cost of the objective of the study itself. Testing and characterization protocol is primarily dictated by the answer to the question, “What am I looking for?” … and then by the answer to the question, “Did someone else look for the same thing, and if yes, how did they go about it?”. However, if someone else’s protocol prevents you from achieving the answer to what you are looking for, it is not worthwhile following the protocol for the sake of it. In such a case, one needs to modify existing protocols as per need or even create fresh protocols!
Electrochemical testing for batteries:
Coming to electrochemical testing, in my opinion, there is no such thing as a standard test. If there are, they provide generic data which is in most cases useless for any specific requirement. Testing protocol needs to be decided based on the objectives of study, which often change with the subject of the study itself. Also, this changes vastly from academia to industry as people are looking for very different pieces of information. A few examples of these below:
- Basic tests (materials): Basic materials characterization tests include understanding voltage profiles and charge storage capacity, reversibility of reactions and cycle life, power capabilities etc. These are very generic testing protocols and do not offer any advanced performance related information about the materials being tested.
- Advanced tests (materials): Advanced tests include protocols for studying kinetics of reactions such as titration techniques and asymmetric cycling studies, impact of cycle life on voltage profiles to draw inferences regarding reversibility, studies eliminating the impact of cell polarization by use of three (or more) electrode assembly, studies on kinetics and reversibility of real electrodes (electrodes with real life characteristics where the composition, process, loading and porosity are the subject of testing) etc..
- Cell development: Cell development looks for very different testing as compared to materials characterization, commercial cell manufacturing or battery pack development. These involve studying real electrode kinetics, cell performance under different conditions and under different protocols, and finally tests for developing “standard cell spec sheets”.
- Battery pack development: Battery pack development involves testing for two things: reliability/repeatability and safety. This involves validating cell spec sheets as received from cell manufacturers, testing beyond cell spec sheets for performance under a wider range of operating conditions, testing for results that allow for accurate warranty calculations etc., other than safety tests such as excessive fast charging, overcharging, short-circuit etc.
Thus, testing protocols needs to be designed to collect the intended information, even if it is something completely new. After all, when we try to find new things, the ways to find them sometimes also need to be new… That’s all for now. I wish you all a very happy Deepavali and a prosperous new year!! Cheers…
