(Digital Presentation) Thermal Acceleration Model for the Capacity Fade of a Rechargeable Li Ion Battery and Its Validation with 10+ Years of Testing Data

Abstract

Rechargeable Li ion batteries have become not only a major power source for consumer electronics, but also a critical power source for high demanding applications like electrical vehicles, portable military devices and medical devices. Medtronic, one of the leading medical device companies has developed a breakthrough rechargeable Li ion battery technology-OverdriveTM to power implantable neurostimulators such as Intellis and Interstim Micro. OverdriveTM batteries have exceptional stable performance and fast charging capability. Figure 1 shows design verification test of capacity stability under two different discharge rate, C/24 and C/168; charging rate are 2C for both groups. As shown in Figure 1, there is virtually no capacity fade under C/168 discharge rate cycling and only a few percent capacity loss under C/24 rate cycling for more than 10 years of testing at 37oC.It is crucial to have a good acceleration testing model to design a rechargeable battery with reliable performance over 10 years of service and to ensure robust design with foreseeing battery material replacement over time. In the early development stage, we established a thermal acceleration capacity fade model for our OverdriveTM battery based on 2 years of testing as shown in Figure 2. Figure 2 shows capacity fade of Overdrive battery cycling at different temperatures up to 10 years. The trend of additional 8 years of data is consistent with model prediction.This presentation will highlight the performance characteristics of the OverdriveTM battery technology and provide the technical details of thermal acceleration capacity fade model. In addition, we will present how the model has been applied to understand the degradation mechanism of OverdriveTM battery and to improve the battery chemistry. Figure 1