Battery Metrics and Real-World Automotive Target Modelling

Abstract

Long term PHEV and EV targets, provided by USABC, highlight the need for batteries with both higher energy and higher power.[1] These mid- and long-range goals provide standardized targets for assessing future battery technology, and are developed with the vehicle in mind. Consequently, they include pack-level and cell-level targets. Conversely, much of the work performed on early-stage technology focuses on one specific component, like the anode or cathode. Half-cell configurations are typically used with Lithium metal, and not a real-world counter electrode. Also, experiments are usually carried out in research cells (coin, Swagelok, etc) which carry high weight and volume overhead in exchange for stability and reproducibility with small electrodes. Thus, extrapolating the experimental performance of a material in a research setting to compare with a cell-level target is difficult. To address this gap, an automotive target modelling tool has been developed and demonstrated on several candidate systems.[2] The model allows comparison of early-stage materials with real-world automotive targets from USABC, including energy density, power density, specific energy, and specific power (Figure 1). It also allows the proposal of hypothetical scenarios to identify the most promising areas of development, as well as potential showstoppers (Figure 2). An in-depth discussion of Ford’s Carbon-Silicon composite anode research will be discussed in the context of automotive target modelling, as will several other battery systems. A discussion on metrics in general will also be presented, as well as the development of a systematic material assessment protocol and “early assessment targets.” Figure 1: Automotive target modelling for several investigated C-Si systems, for Specific Power. Figure 2: Using Automotive target modelling to assess hypothetical scenarios and identify cases where all targets can be met. [1] United States Advanced Battery Consortium, USABC Goals for Advanced Batteries for EVs (2013). [2] M. Karulkar, R. Blaser, R. Kudla, J. Power Sources, 273, 1194-1201 (2015). Figure 1