How self-discharge can alleviate capacity loss during calendar ageing of charged cells - A. Zulke

Calendar ageing dominates the battery degradation in most EV once those might be parked more than 90% of the time. NCA/Gr-SiOx 21700 cells develop a spoon-shaped profile for the capacity fade as a function of state of charge (SoC) when idle. Cells at 100 % SoC have better capacity retention than cells stored at 80 or 90 % SoC but can develop micro-short circuits when exposed to T ≥ 40 degC. Our analysis supports the proposition of a cathode-driven shuttle mechanism that alleviates LLI. Those are interesting observations given that such commercial batteries are widely employed in electric cars, in which SoCs are typically kept at high levels by their users. In this project, cycling and calendar ageing data is continuously fed into life-estimation models developed in collaboration with Altelium Ltd, the Lancaster-born spin-off that looks at real-time battery monitoring for health forecasting. To submit your questions for our Q&A please tweet us at @batterymodel, email us at battery@imperial.ac.uk, contact us on Slack (link provided in presentation e-mail) or simply leave a comment in the field below.