What is it?
To reduce the concentration of greenhouse gases in the environment, scientists all over the world are working to find environmentally sound solutions to fuel the world’s ever-growing transportation needs. Cleaner transport that comes in the form of electric cars is powered by battery packs such as lithium-ion and nickel metal hydride, which promise to provide decent range and speed to vehicles. However, people who need their vehicles to run a bit longer and faster, are still looking for the perfect battery blend that can power their rides. Current researchers in battery technology have helped scientists create next-gen lithium-air batteries that have a potential to provide energy densities up to three times that of conventional lithium-ion batteries used generally. Many companies, including IBM and General Motors look forward to get more out of this technology.
Lithium-air (also known as lithium-oxygen) batteries are similar in principle to lithium-ion batteries. They use an organic electrolyte as a negative electrode (lithium metal) and the electrolyte that is air. This technology is very promising for automotive batteries as theoretically, with oxygen as an unlimited cathode reactant, the capacity of the battery is limited by the Li anode. Lithium air batteries are currently under development and but not yet commercially available. Once available these batteries will have a capacity for energy storage that is five to 10 times greater than that of Li-ion batteries.
The Benefits
Lithium-air batteries are able to have higher energy density because of the lighter cathode and the fact that oxygen is freely available in the environment and doesn’t need to be stored in the battery. The technology has the potential to store almost as much energy as a tank of gasoline, and will have a capacity for energy storage that is five to 10 times greater than that of Li-ion batteries. This will help the cars powered by lithium-air batteries to run longer without needing a recharge.
TRENDS
IBM’s lithium-air battery
IBM has announced that it would develop lithium air batteries for the energy grid and for transportation. The goal will be acquired within the next ten years. IBM executives said the company was unlikely to enter the battery business directly but was looking forward for a partnership that would make full use of their hardware and system design expertise with ultra light battery technology. When the lithium-metal electrode is placed in water, lithium ions leak out and react with oxygen dissolved in the water. According to researchers, while lithium-ion batteries have the potential to deliver about 585 watt-hours of electricity per kilogram and lithium-sulfur has a theoretical potential of about 2,600 watt-hours, and lithium-air batteries might reach targets well above 5,000 watt-hours.
GM’s lithium-air battery to improve EV performance
General Motors believes that electrically driven vehicles, offer the best long-term solution for providing sustainable personal transportation. It has begun conducting research into lithium-air batteries, which may revolutionize electric vehicle technology. These batteries skip metal as a cathode and use atmospheric oxygen molecules to bind directly to lithium. This allows them to be extraordinarily energy dense and therefore obtaining a 10 fold energy density improvement. Since the air we breathe contains abundant oxygen levels, a lithium-air battery does not need to store a supply of oxygen inside itself, which makes the battery much lighter and smaller.
MIT’s lithium-air batteries
A team of researchers at MIT has made significant progress on a technology that could lead to batteries with up to three times the energy density of any battery that currently exists. Scientists at MIT have announced that when they substituted nanoparticles of gold and platinum for the standard carbon electrodes in lithium-air cells, they were able to obtain much higher efficiencies. The find was significant enough for MIT to claim that their research could lead to lithium-air batteries with 3 times the energy density of lithium-ion. That alone would be a big step forward.
K.M. Abraham’s lithium-air battery
In the mid-1990s, K.M. Abraham and co-workers demonstrated the first practical non-aqueous Li-air battery with the use of a Li negative electrode anode, a porous carbon positive electrode cathode, and a gel polymer electrolyte membrane that served as both the separator and ion-transporting medium. The credit for developing the world’s first solid-state, rechargeable lithium air battery goes to the Engineers at the University of Dayton Research Institute. It was designed to address the fire and explosion risk of other lithium rechargeable batteries and make way for development of large-size lithium rechargeables for a number of industry applications, including hybrid and electric cars. A cell design utilizing a non-aqueous electrolyte alleviates the parasitic corrosion reactions of the Li anode that plagued past lithium-air batteries based on alkali aqueous electrolytes. The non-aqueous electrolyte-based cell design also overcomes safety concerns of the Li-air system.
Engineering and Physical Sciences Research Council’s lithium-air battery
Researchers in the UK are developing a rechargeable lithium-air battery that could deliver a significant increase in the energy capacity compared to that of currently available lithium-ion cells. The research work, funded by the Engineering and Physical Sciences Research Council, is being led by researchers at the University of St Andrews with partners at Strathclyde and Newcastle. The four-year EPSRC research project is targeting the development of a Li-air cell that is rechargeable and can sustain cycling. The project is focused on understanding more about how the chemical reaction of the battery works and investigating how to improve it. The Engineering and Physical Sciences Research Council (EPSRC) is the UK’s main agency for funding research in engineering and the physical sciences.
Argonne National Laboratory’s lithium-air battery
Researchers at the Center for Transportation Research at Argonne National Laboratory have shown progress in lithium-air battery technology. The center will be developing world-changing lithium-air batteries that have the capacity to store up to five to 10 times the energy of lithium-ion batteries, or almost as much energy as a tank of gasoline of the same size. The laboratory is ideally suited to lead Li-air research and development (R&D) because it has a broad and deep range of experience in the development of Li-ion batteries and also it has an expert staff of scientists and engineers that have led the development of new materials for advanced batteries, including Li-ion batteries and development of a catalyst for fuel cells. Argonne will also maintain existing relationships with start-up companies and other business partners who will be able to collaborate on commercializing the Li-air battery.
Limitations
Existing lithium-air batteries face the problem of the accumulation of solid products of reactions at the cathode, which degrades the contact between the electrolyte and the air stops to flow. The development costs will be extremely high for these batteries. The current li-ion batteries have a charge-discharge cycle between 300-500 which is not yet known for the lithium air batteries. Even with efficient recycling efforts, the auto industry alone would require huge quantities of lithium to power every car world wide, replacing the gasoline engine.And this can be another limitation of using lithium air batteries.
The Impact
Lithium metal-air batteries can store a tremendous amount of energy, in theory, more than 5,000 watt-hours per kilogram. That’s more than ten-times as much as today’s high-performance lithium-ion batteries, and more than another class of energy-storage devices such as hydrogen fuel cells. Instead of containing a second reactant inside the cell, these batteries react with oxygen in the air that’s pulled in as needed, making them lightweight and compact. If lithium air batteries equate petroleum with fast recharge, then there wouldn’t be a need of fossil fuels which is a non renewable energy source.
Image courtesy: MIT
