Performance and aging analysis of high-power lithium titanate oxide cells for low-voltage vehicle applications

Bank, Thomas; Sauer, Dirk Uwe (Thesis advisor); Jossen, Andreas (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Book, Dissertation / PhD Thesis

In: Aachener Beiträge des ISEA 160
Page(s)/Article-Nr.: 1 Online-Ressource : Illustrationen, Diagramme

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

Partial electrification of vehicles with conventional combustion engines is an effective method to enhance efficiency and reduce CO2 emissions. One way of adding a so-called mild hybridization to existing vehicle architectures is to extend the conventional 12V vehicle electrical system by a 48V voltage level that contains a 48V lithium-ion battery. A promising anode material for such a battery is lithium titanate oxide (LTO), which possesses several outstanding material properties including high-power capability, inherent safety and excellent lifetime performance. Extensive scientific studies on mass-produced LTO-based cells are rare, resulting in a lack of essential information on performance and aging behavior. Based on characteristic 48V battery operating conditions this thesis addresses this knowledge gap. It assesses the suitability of an LTO-based cell type for low voltage vehicle systems by reporting essential performance and aging characteristics. The investigated LTO-based cells show excellent power capability and cycle stability, even at high ambient temperatures and high current rates, and meet the vehicle relevant lifetime requirements of 200,000 km. The calendar aging behavior is strongly dependent on temperature and state of charge. This can be attributed to both reversible capacity effects caused by an overhang of the electrodes as well as irreversible aging mechanisms such as (passivating) surface layer formation and gas formation.