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U.S. quest for 5X battery boost seeks game-changing tech

One year ago this month, the U.S. Department of Energy announced a $120 million plan to develop a technology capable of radically extending battery life, and it set a target date of five years. The research effort is now entering its second year and is making progress.

A team of government, university and private sector researchers is exploring three possible research “concepts” for improving batteries used in the energy grid, for transportation and in consumer electronics. They want a battery that can leap past lithium-ion batteries, a technology developed in the 1970s that remains a mainstay today.

“We want to change the game, basically,” said George Crabtree, a senior scientist at Argonne National Laboratory and a physics professor who is leading the effort. The goal is to develop a battery that can deliver five times the performance, measured in energy density, that’s also five times cheaper, and do it in five years.

“If you do something less, it won’t be transformational,” said Crabtree, referring to what is now called “the 5-5-5 plan.”

In the past decade, lithium-ion performance has been improving at about 5% a year, and 95% of the battery research community remains focused on the technology, said Crabtree. The reason for the continuing research emphasis is because “it is relatively low risk and there is a good chance of getting that incremental improvement,” he said.

The limited amount of research on lithium-ion alternatives also “means that most everything [else] is unexplored,” said Crabtree, who leads the Joint Center for Energy Storage Research project.

A five-fold increase in battery performance could have a major impact. The Chevy Volt hybrid, for instance, uses lithium-ion batteries. While Volt drivers average about 900 miles between fill-ups, gas-free driving — using only the battery — is limited to about 38 miles. A better battery with a range of hundreds of miles would change the potential for electric vehicles. (It also takes 16 minutes of charging time for each mile driven; improving that charging time is part of the research.)

Improved battery storage would make wind and solar power more cost-effective, and the usefulness of extending cell phone battery life would be an obvious boon.

Here are the three main areas that researchers are looking at, according to Crabtree.

A lithium-ion battery today has a single charge that oscillates between the battery’s cathode — the positive electrode — and its anode — the negative electrode. Researchers are considering replacing the lithium with magnesium that has two charges, or aluminum, which has three charges. What does a charge mean? The energy stored is directly proportional to the charge of the working ion, so twice the charge means twice the energy, all other things being equal. In technical terms, energy is charge times voltage. Thus, two ways to increase energy are to increase charge and increase voltage. On paper, at least, this approach could double or triple a battery’s energy density.

With lithium-ion at the cathode, there is a process involved called intercalation that layers in molecules in such a way that they can come together and then reverse. This second research effort investigates replacing the intercalation step with a true chemical reaction. Chemical bonds store more energy than intercalated ions. One process could involve lithium reacting with oxygen. An analogous process is a fuel cell, where hydrogen produces water, except in the case of the battery the chemical process is reversible.

Liquids could be used to replace crystalline anodes and cathodes, which opens up more space for working ions. This approach makes it possible to use different types of materials for energy storage, including organics. The problem is finding a liquid that can support enough working ions. There are several major challenges, including finding a reaction that stores high energy from many tens of thousands of possible reactions. Another challenge is finding a solvent with enough voltage capability.


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