Abstract
Thanks to its exceptional performance in terms of high energy and power density as well as long lifespan, the lithium-ion secondary battery is the most relevant electrochemical energy storage technology to meet the requirements for partial or full electrification of vehicles (plug-in hybrids or pure electric vehicles), and thanks to decreasing cost and ongoing technical improvements, it will maintain this role in the near to mid-term future. This study benchmarks eight different (five 21700 and three 18650 format) high-energy cylindrical cells concerning their suitability for automotive applications and aims to give a holistic overview and comparison between them. Therefore, an ante-mortem material analysis, a benchmark of electrical and thermal values as well as a cycle life study were carried out. The results show that even when applying similar concepts like Nickel-rich cathodes with graphite-based anodes, the cells show wide variations in their performance under the same test conditions.
Highlights
The climate and energy framework for the year 2030 set by the European Commission [1] demands at least 40 % cuts in greenhouse gas emissions, 32 % share for renewable energy, and 32.5 % improvement in energy efficiency; all compared to the levels of the year 1990
The goal of the study was to check these cells for their ability to work under automotive operational conditions for an electric vehicles (EV) setup, including space restrictions and performance values, as predefined by two OEM companies
Nanosized carbon black (CB) (labeled by dotted blue circles in Fig. 1 (a)) suitable for spot conduction and typically used for higher energy densities was combined with vapor grown carbon fibers (VGCF) (labeled by red arrows in Fig. 1 (a))
Summary
The climate and energy framework for the year 2030 set by the European Commission [1] demands at least• 40 % cuts in greenhouse gas emissions, • 32 % share for renewable energy, and • 32.5 % improvement in energy efficiency; all compared to the levels of the year 1990. Especially for road transport these goals are ambitious, since by 2017, emissions increased by 23 % compared to 1990 [2]. Electrification of the transport sector is seen as a key solution to reduce the environmental impact of road transport. The lithium-ion secondary (also known as rechargeable) battery (LIB) is now playing and is believed to continue to play a major role in this scenario in the mid-term. A global market of at least 44 million battery electric vehicles (EV) for the year 2030 is prognosticated, not including two-wheelers and micro transport [3].Cylindrical LIB cells have a competitive edge when it comes to traction batteries because they offer high intrinsic safety and flexibility in battery system design, all at reasonable cost [4]. Additionally, some of the highest energy densities of cells currently available on the market can be found in this format. Therefore, they are used in
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