| AVS 62nd International Symposium & Exhibition | |
| Applied Surface Science | Thursday Sessions |
| Session AS+SS-ThA |
| Session: | Advances in 2D Chemical Mapping and Data Analysis |
| Presenter: | Jeffrey Fenton, Medtronic plc |
| Authors: | D. Reifsnyder Hickey, University of Minnesota J. Fenton, Medtronic plc K. Chen, Medtronic plc P. Yurek, Medtronic plc J. Lesser, Medtronic plc G. Jain, Medtronic plc |
| Correspondent: | Click to Email |
Primary lithium batteries with hybrid carbon monofluoride–silver vanadium oxide (CFx–SVO) cathodes have become widely commercialized as power sources in implantable medical devices. Although CFx and SVO have been used separately as cathode materials, CFx–SVO hybrid cathodes have been developed to meet the increased energy-density, power, and longevity requirements specific to multiyear operation at physiological temperature. However, the microstructural basis for the performance characteristics has not been well understood, including chemical changes in the cathode materials as they discharge. This work presents a microstructural study of discharged cathode materials, aimed at identifying chemical and structural characteristics that can be related to the observed battery-performance characteristics. As a result, the relationships established can be used to improve the performance of future medical device technologies. Scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were used to probe the cathodes chemistry and structure. Although a single analytical method cannot give a full picture of the cathode chemistry and microstructure, the combination of these complementary techniques makes it possible to develop a clearer picture of the structural and chemical changes that occur within the cathode as the battery discharges. The discharged cathodes of SVO, CFx, and SVO-CFx hybrid are compared, which demonstrates that the relatively gradual transformation of SVO that occurs in SVO-only cathodes is accelerated in the hybrid cathodes. Several trends will be shown including: (1) SVO loses its crystalline structure and silver content (replaced by lithium) with discharge; (2) CFx converts into carbon and LiF with discharge; (3) and the hybrid cathodes show steady conversion of CFx, accelerated conversion of SVO (as soon as 5% depth of dischage), and the beginning of LiF formation (as early as 10% depth of discharge).