Powering up electric batteries

 Government and the private sector in the United States have joined forces in order to both lower the cost and improve the performance of lithium-ion batteries through the Vehicle Technologies Program (VTP) of the U.S. Department of Energy (DOE). 

Over the past few years, as part of the America Reinvestment and Recovery Act, the VTP awarded US$2.4-billion in contracts to new battery and electric-drive component manufacturing and vehicle deployment projects. These include battery and power electronics manufacturing facilities, PHEV, and electric vehicle (EV) demonstration vehicles, as well as education projects. This program is designed to jumpstart U.S. manufacturing capacity and deploy more than 13,000 vehicles and nearly 23,000 Level 2 charging stations across the country. 

One of the projects was awarded in 2009 to FMC Lithium to help cut the cost of lithium-ion batteries from US$1000/kWh in 2009 to $300/kWh by 2014. FMC also had to find ways to improve the performance of the batteries, and increase battery life. “Achieving the DOE technical and cost targets for the PHEV/EV batteries required development and use of new electrode materials. Stabilized lithium metal powder (SLMP) technology provides an independent source of lithium for Li-ion systems, breaks the limitation that all lithium has to come from the cathode and, thus, allows the use of non-lithium providing cathode materials with potentially larger capacities. These new cathode materials are expected to be more overcharge tolerant and could be used with high capacity advanced anodes,” said Marina Yakovleva of FMC Lithium Division, in a review report. 

The VTP has collaborated with private sector partners such as FMC Lithium, Bosch Inc, and Silatronix to develop new conductive polymer binder materials and improve binder/Silicon interface to enable Silicon alloys in Li-ion negative electrodes. Silicon has the highest theoretical Li-ion storage capacity at 4200 mAh/g. However, the material has a limited cycle life, limited energy density and low columbic efficiency. By 2012, this research project hopes to develop new binder functionalities to further improve capacity retention during cycling, develop electrode structures that have high silicon material loading, and achieve 5 mAh/cm2 to meet the EV/PHEV energy density goals. 

The impact of the VTP is reflected in the fact that the batteries in all leading hybrids today contain DOE battery technology. In May 2011 DOE announced the transition from FreedomCAR and Fuel Partnership to the next-generation partnership, called U.S. DRIVE (Driving Research and Innovation for Vehicle efficiency and Energy sustainability). At the heart of the partnership are twelve technical teams that bring together the foremost technical experts from US DRIVE partner organizations to discuss R&D needs, develop goals and technology roadmaps, and evaluate progress toward technical targets. 

In September 2011, DOE and Saft America celebrated the opening of the company’s advanced lithium-ion battery factory in Jacksonville, Florida. The factory, which is supported partly by DOE investments, is expected to produce 370 megawatt hours of battery capacity per year – enough to supply more than 37,000 electric-drive vehicles. 

The project is part of the Recovery Act’s US$2-billion investments in battery and electric drive component manufacturing, supporting 20 battery and 10 component-manufacturing factories. At full scale, these investments will support factories with the capacity to supply more than 500,000 electric drive vehicles annually. These factories are helping build a US domestic electric-drive vehicle industry. By the end of 2015, it is estimated that the United States could produce 20% of the world’s advanced vehicle batteries. These factories, together with battery design improvements, could halve the cost of lithium ion batteries by 2013. 

Automotive Industries (AI) spoke to David Howell, Team Lead for Hybrid and Electric Systems at the U.S. Department of Energy and asked him what have been the major breakthroughs over the past five years. 

Howell: Most breakthroughs have been in developing materials with higher power. But, we also need greater durability in order to extend the life of the battery. A battery capable of  powering a fully electric car for 300 miles needs to provide 1,000 to 1,500 discharge cycles. In order to achieve this, we have made quite a few breakthroughs in terms of energy densities and power, and we have also driven the price down through a combination of technologies including lower cost materials, improved electrode processing, and battery design optimization. 

AI: Is there a dominant battery technology emerging? 

Howell: For the foreseeable future, we will rely on a family of lithium-ion technologies. Some are best for electric vehicle, while others are better for hybrids. So, we are going to have a family of chemistries for a decade or so. The good news is that we are following a number of avenues and pathways in order to find solutions, and we will probably see some more technology and materials breakthroughs. But, we still have a long way to go in battery technology to reduce the cost, size, and weight of vehicle batteries, and increase their durability. 

AI: What materials and systems do you and your private partners think could lower the cost of electric vehicles? 

Howell: For the anode, we are using some kind of graphite-based or carbon-based 
material today. These materials give us around 350 milliamp hours per gram (mAh/g). Newer materials such as silicon alloys can potentially give us 1,000 mAh/g. Quite a few material suppliers are trying to develop that kind of material. On the cathode side, today’s materials are providing us 150 mAh/g. We believe we can double that to 270 to 370 mAh/g. We also want to go to higher voltages. Right now we are using 3,6 to 3,7 volt cells, and want to push that to five volts. In order to significantly increase the capacity of the battery to meet this voltage target we will need new electrolytes. New technologies such as lithium metal-air and lithium-sulfur are providing the voltage and high capacity, but their main problem is cycle-life. We have significant programs in place to increase the durability of batteries using such materials. 

AI: China is also investing heavily in electric vehicles, and has the advantage of a large installed base and government-stimulated market. Do you see the US as being in a technology race with the Chinese? 

Howell: There is a lot of room for both countries to succeed. We believe we have a technological advantage, but you also need to have significant numbers of electric vehicles on the road – and China has that. In fact, there is pretty good collaboration with the Chinese – both nations see a need to work together. 

AI: What, in your opinion, have been the most significant DOE achievements over the past five years? 

Howell: Five years ago we were looking at three major lithium ion chemistries – nickel-metal-cobalt, manganese spinel, and iron phosphate. All three of these seems to be very competitive. A lot of research and development effort was needed. But there has been substantial progress made with all these chemistries which has resulted in much higher performance batteries. There remains much to be done, and we have identified additional areas of research that could significantly advance the performance of lithium ion batteries. 

The most substantial change over the past five years is that we have seen a recovery in American manufacturing. Battery manufacturing facilities are being installed in the United States. It is very exciting to see industry stepping up. We are also seeing very good electric vehicles being introduced to the market, and are very excited about that.