UK report sees step-change improvements in performance of EV batteries as “highly unlikely” through 2020
|Li-ion technology and cost directions through 2030. Click to enlarge.|
Step-change improvements in performance of advanced automotive batteries are “highly unlikely” to occur out through 2020 as there are no “breakthrough” technologies approaching the electronic consumer market—which is where battery chemistry innovations first appear before trickling down to the more demanding automotive market—today, according to a new report commissioned by the UK Committee on Climate Change.
However, next-generation technologies delivering higher specific energy such as nickel cobalt manganese (NCM) and composite cathodes and high-capacity anodes (e.g., silicon) are estimated to be available in a series vehicle around 2020. Higher voltage cathode chemistries are expected to follow, the report concludes.
These developments could take the energy density of lithium-ion cells close to 300 Wh/kg. As the automotive market grows, new cells will be increasingly developed for that market as well as trickling down from the consumer cell market.
The Committee on Climate Change commissioned energy consultancy Element Energy, Li-ion manufacturer Axeon, and Prof. Peter Bruce of EastChem to investigate the future trajectory of batteries cost and performance. The report—Cost and performance of EV batteries—describes the current state of development and cost of batteries, before mapping the future cost and performance of lithium-ion batteries out to 2030. The report also explores the trajectory of battery technology beyond 2030 through the study of lithium-air batteries, currently the most promising post lithium-ion battery.
Following a review of existing battery cost models, the authors developed a bottom-up component-based approach to cost modeling of lithium-ion cells to 2030. The cost model contains cell component and pack component costs, where each is designed to be fit for purpose for a set of vehicles over the period to 2030. Within the cell module there are sub-models related to cell design, material consumption, manufacturing cost, factory throughput and overheads.
The authors identified two main cost drivers: improvement in material properties delivering higher energy densities; and scaling-up in production of large cell formats.
Current costs for a pure EV of ~$800/kWh at pack level translates into a pack cost of $21,000 for a 2012 medium-sized BEV with a range of 150 km (93 miles), the report found. In 2030, under a baseline scenario, this is predicted to drop to $6,400 for a BEV with a range of 250 km (155 miles).
The authors note that batteries for plug-in hybrids (PHEVs) are more constrained by power density, as the smaller packs have higher discharge rates during acceleration. It results in a higher cost per kWh for a PHEV compared to pure battery electric vehicle.
While lithium-air batteries (if successfully deployed) eventually could bring cost savings at the cell level, this saving is reduced by the increased cost of packing arising from the lower cell voltage and the requirement for more air management. Cost modeling in the report suggests that in the long term, the deployment of Li-air would not be expected to bring a significant cost reduction on the pack level compared to the advanced lithium-ion batteries expected to be developed by 2030. However the approximate 50% weight saving which may be expected with Li-air would have other benefits such as reduced chassis weight and better performance.
Based on the observed development times for battery technologies and the current challenges lithium-air cells face, practical lithium-air batteries for automotive applications are not expected before 2030, according to the report.
This report predicts future Li-Air performance between 500-1000 Wh/kg (at cell level—a factor 2-3 improvement over expectations for Li-Ion in 2030). This is based on historical data on the ratio between theoretical and practical energy of other chemistries and is in accordance with expert opinion, according to the authors.
The technology roadmap assumes that lithium-ion chemistries will reach their highest practicable energy density through the development of high voltage cathodes. There are significant and fundamental technical challenges to be overcome before these technologies can be deployed, such as the development of an electrolyte stable at a high voltage.
The cost benefits brought by high production volume of battery packs are highly dependent on the uptake of EVs. Looking at the announced new production capacity, there is a significant risk of over-capacity in the next 5 years if consumers do not take to the technology; this could stall further investment.—