Lowering the cost and improving the performance of batteries for plug-in electric vehicles requires improving every part of the battery, from underlying chemistry to packaging. To reach the EV Everywhere Grand Challenge goal of making plug-in electric vehicles as affordable and practical as today's conventional vehicles by 2022, the Vehicle Technologies Office supports work to increase researchers' understanding of the fundamental chemistries and materials associated with lithium-ion (Li-ion) and beyond Li-ion batteries. To understand how batteries work in general, see the Energy Basics page on Batteries. To learn how batteries are used in plug-in electric vehicles, visit the Alternative Fuels Data Center's page on batteries.
The Vehicle Technologies Office carries out exploratory battery materials research as part of its Batteries for Advanced Transportation Technologies (BATT) Program, led by a team of national laboratories and universities.
By starting with the fundamental components, researchers can improve current technologies and develop new ones. For existing battery chemistries, they study why and how current battery materials fail using advanced modeling and characterization techniques. Then, based on those results, they propose and test various solutions to alleviate these problems. In particular, the research focuses on improving battery's energy density while ensuring they operate safely, have a long life and a low cost.
In addition, researchers also investigate new and promising materials for future battery chemistries. They research a number of areas that contribute to this body of knowledge:
- Advanced cell chemistries that promise higher energy density than current ones
- Li-ion anodes that are higher capacity than traditional carbon based electrodes
- New electrolytes that are more stable than current ones
- New cathode materials with high voltage and capacity
- Inactive components in the battery that can perform multiple roles
This work helps researchers develop next-generation Li-ion batteries, as well as "beyond Li-ion" technologies such as lithium-sulfur and lithium-air chemistries. Researchers are addressing issues that prevent these technologies from reaching commercialization, including poor cycle life, low power, low efficiencies, and issues with safety. They are investigating a number of potential solutions, including:
- Improving electrolyte / separator combinations so that they result in less dendrite growth when using Li metal anodes (dendrite growth can lead to shorts in the battery)
- Developing advanced material coatings
- Developing new ceramic, polymer, and hybrid structures with high ionic conductivity, low electronic impedance, and high structural stability
Researchers also work to develop advanced diagnostics and analytical methods that can improve the ability to do research. For example, Brookhaven National Laboratory is using X-rays at the National Synchrotron Light Source (NSLS) to study how the structure of Li-ion batteries' cathode materials change during lithium extraction, which is critical for understanding and designing better materials. This research should help scientists better understand how battery materials change as they test or combine them with other types of materials.
As part of this work, Lawrence Berkeley National Laboratory (LBNL) and the Massachusetts Institute of Technology (MIT) run the Materials Project, which allows researchers to use a search engine interface to sort more than 20,000 types of materials. It includes a Lithium Battery Explorer, which allows researchers to search the database for materials that satisfy critical criteria for lithium batteries.
Research previously supported through this program has led to a number of substantial successes:
- Stanford University has developed silicon nanotube electrodes that show potential to eliminate cracking while exhibiting excellent cycling capability.
- LBNL has developed Ti-doped nickel cobalt manganese oxide cathodes that have shown the potential to reach capacities of 225 mAh/g with better cycling at higher voltages than current cathodes.
- Argonne National Lab (ANL) used modeling to predict a specific additive (a 3-oxabicyclohexane-2,4-dione molecule) to protect the battery's anode and then developed it based on the model.
- LBNL developed a self-assembled separator using a wet process that has a lower cost than commercially available separators but still has comparable ionic conductivities. The separator is a major cost component of the battery cell.