Lithium titanate oxide battery cells for high-power automotive applications - Electro-thermal properties, aging behavior and cost considerations

摘要

Lithium-ion batteries are widely used in transportation applications due to their outstanding performance in terms of energy and power density as well as efficiency and lifetime. Although various cell chemistries exist, most of today's electric vehicles on the market have a high-voltage lithium-ion battery system consisting of cells with a graphite-based anode and a metal-oxide cathode. These cells offer a high specific energy density that enables long driving ranges at moderate costs. For applications where power density is the critical design criterion, cells with lithium titanate oxide-based anode materials can be an alternative. These cells offer further advantages such as improved cycle stability and good charge acceptance even at temperatures below 0 degrees C. This paper presents different applications for high-power batteries in electrified vehicles and compares the requirements for suitable battery cells. After an introduction to lithium titanate oxide as anode material in battery cells, electrical and thermal characteristics are presented. For this reason, measurements were performed with two cells using different cathode active materials and a lithium titanate oxide-based anode. Aging behavior is investigated with lifetime tests performed under high-current cycling conditions at two different ambient temperatures. Differences in the capacity loss rate are shown and lifetime considerations are presented. Furthermore, an incremental capacity analysis is performed at different times in the aging study for a deeper analysis of the aging effects occurring in the two cell types. Finally, cost considerations of lithium titanate oxide based battery cells with different properties are presented. Varied production volumes are considered and production costs are compared with costs of state-of-the-art graphite-based high-energy battery cells.