Apply innovative acoustical measurement techniques to batteries to improve the battery lifecycle
The battery market is growing exponentially, spurred by the quest for alternatives to fossil fuels. Battery-based storage—a potential solution for stationary applications, intermittent renewables, and vehicles from cars to electric scooters and bikes—has emerged as one of the energy industry’s major research and development priorities. The development of electronic systems is also shaping today’s battery market. The Opera2 project was set up to integrate acoustical measurement tools into battery manufacturing processes and supervision systems.
The lifecycle of a battery has three main stages:
- Formation, a crucial stage that renders the materials that make up the battery active before the battery can be charged
- Characterization and factory testing of the charged, ready-to-use battery
- Monitoring during operation (battery management and safety)
During each of these stages, the battery is put through cycles and current, voltage, and temperature are measured to ensure that the battery is operating as intended. Whether they are used during battery manufacturing or during operation, these measurements do have their limitations. This is due to the time lapse between the actual occurrence of the physical phenomena inside the battery and the observation of the phenomena using electrical and thermal measurement techniques. If thermal runaway could be detected early on, then the battery management system could switch off the battery, preventing accidents and enabling manufacturers to issue product recalls.
The good news is that batteries do talk if you have the right tools to listen to them. Acoustical measurement techniques—used to monitor civil engineering works, for example—can provide information about the condition of the materials that make up the structure they are monitoring.
Each of the three Opera2 partner companies, Bio-Logic (project lead), Accuwatt, and Enertecs, covers one or more of the stages in the battery lifecycle. The project was set up to develop a way to apply acoustical measurement methods to batteries so that the internal phenomena affecting battery component manufacturing, characterization, and management could be observed during operation. The project’s clearly-defined objective was to improve each stage in the battery lifecycle by using a characterization method combining electrochemical and acoustical measurement tools developed by the project’s two research partners LEPMI and Liten.
In terms of research, Opera2 enabled several advances:
- Acoustical signals were identified and characterized for different battery technologies and during different phases of battery operation
- A method for analyzing acoustical signals was developed
- Early warning signs for thermal runaway and other abnormal battery behaviors were identified
Before the project, Bio-Logic was already active in laboratory-grade electrochemical testing instrumentation. The project positioned the company to substantially expand its business into the battery manufacturing market with:
- A new research-grade acoustical measurement instrument that included a dedicated electronic circuit that can be integrated into a Bio-Logic potentiostat, plus a software application for users
- A line of commercial-grade cycling benches used in battery testing and a new software application that can manage and display a large number of channels and store and process large volumes of data
The instruments, used to characterize test production batches, currently account for a substantial percentage of Bio-Logic’s sales revenue. Accuwatt confirmed the benefits of using acoustical measurement for safety applications and started integrating the technique into its high-end BMS, which responds to stringent safety specifications (military and aviation).
The acoustical emission testing method, which is an ideal complement to other testing methods, has been tested and validated and is ready to be implemented. The next step will be to promote the method’s capabilities and benefits to industrial customers and support the project partners’ development on the battery market. Major battery manufacturers (Samsung, Sony, Toshiba, Panasonic, etc.) are particularly interested in these kinds of solutions as a way to increase their batteries’ energy densities while continuing to reduce form factors, which potentially makes batteries more hazardous. The work completed under the Opera2 project positioned Bio-Logic to sell equipment to some of these manufacturers.
The project’s research partners, LEPMI and Liten, will continue their investigations. Specifically, additional research is needed to analyze each acoustical signal (frequency and duration) and characterize the signals in terms of battery operation (normal or abnormal). The goal is to create a library of signatures that can then be integrated into instruments developed by Bio-Logic. The Opera2 project did achieve its initial objectives; however, it also created several new opportunities for Bio-Logic. The company is making substantial investments in R&D to increase its products’ testing capacities fourfold (from 500 channels to 2,000 channels). After the project, LEPMI and Liten established new research partnerships in the field of battery testing. These activities are contributing to maintaining a level of scientific excellence that will benefit companies like Bio-Logic and Accuwatt.
French Single Interministerial Fund