Storing The Change
Cheaper and better batteries are set to revolutionise the concept of energy storage. Here is the tech spark that triggered the illuminating possibility of clean energy.
A Brief History Of The Lithium Ion Battery
1980 John B Goodenough and Koichi Mizushima develop lithium cobalt oxide as a new cathode material for high energy density batteries1991 Sony brings out the world’s first commercial lithium-ion battery. The li-ion is smaller than a nickel-metal hydride battery, but has higher capacity.1994 Motorola’s MicroTAC Elite becomes first mobile phone to use a li-ion battery2006 Sony announces worldwide recall of its li-ion batteries, following reports of over-heating and fires2008 Tesla Roadster became the first serial production all-electric car to use li-ion batteries2017 Tesla announces it will build a 100-MW energy storage facility in South Australia—the largest such project in the world, billed to power over 30,000 homes
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When Chetan Maini rolled out Reva, India’s first electric car, in 2001, he used 250-kg lead-acid batteries that ran for about 80 km and took eight hours to charge. Today, the best lithium ion (li-ion) batteries, he says, could take you, for the same weight of batteries, roughly 600 km, last five times longer and charge in less than an hour. “It’s still going to cost a lot more, of course, and yet it’s no small transition. And it’s been getting better every year,” says Bangalore-based Maini. Better, because the cost of li-ion batteries has come down almost eight per cent every year, on an average, in the past 15 years.
The next generation of batteries—and people are looking beyond li-ion—could potentially offer more energy density and possibly fix some of those niggles seen in consumer devices, the fires especially. And, while new battery technology doesn’t exactly roll out into the market as quickly as new mobile phone models do, the pace, from a chemistry point of view, has been dramatic. If it weren’t so, points out one expert, we would still be stuck with nickel-cadmium. And, yes, we wouldn’t be talking about the iPhone X, or smartphones in the first place.
“The fundamental change has been in terms of cost reduction. We were talking about $500 per kilowatt hour (kWh) some years ago; today we talk about $250 per kWh. So the cost has halved in just four or five years,” says Venkat Srinivasan of the Argonne National Laboratory in the US, where he heads the Collaborative Centre for Energy Storage Science. “Countries are now talking about having aggressive targets because they feel this is within reach. It doesn’t sound like fusion or something that is always 20 years away.”
The cost of lithium-ion batteries has come down by almost eight per cent every year, on an average, over the past 15 years.
The way energy density of batteries has more than doubled in the past 15 years is dramatic. Clearly, the advent of lithium-based technology has had a fundamental influence on consumer electronic devices. And not just devices. This January, electric car maker Tesla completed a 20 megawatt (MW) grid-connected battery storage facility in southern California, where a methane gas spill shut off supply to gas-powered peaker plants (the ones that kick in during peak energy consumption hours). The battery facility, which charges during non-peak hours and supplies electricity when demand peaks, was billed as the largest li-ion battery storage project in the world at the time, with enough energy to power 2,500 homes all day. It comprises 396 Tesla PowerPacks, each of them, going by Tesla’s website, about 7 feet tall, 3 feet wide, four feet long and weighing 1.6 tonnes—all of this sitting on 1.5 acres (to give a comparison on equally modern terms, a little more than half the floor space at Google’s Council Bluffs data centre). Tesla is now going to set up a 100-MW energy storage facility in South Australia, which can power over 30,000 homes.
Of course, batteries differ depending on their function. But, in general, where is battery technology headed?
The Chemistry Roadmap
Lithium metal has long been used in batteries for consumer electronics, like the old wristwatch or camera cells. But these batteries couldn’t be recharged. The lithium-ion cell, which used a lithium compound instead of the metal and could be recharged, was invented in the 1980s.
An ion is an electrically charged atom that has lost or gained an electron. Inside a battery, ions are moving from one electrode to another through the electrolyte, while electrons are moving through the outer circuit, supplying electricity. When the li-ion cell is charging, lithium ions move from the positive electrode to the negative and they go the opposite way when the cell is discharging.
As researchers explain, there are really only two ways you can increase the energy density of a battery. You could increase the voltage or increase capacity, i.e., the number of lithium or any other ions the material can hold—much the same as saying how many electrons it can hold. The more electrons you hold for the same weight or volume, the more energy the battery is going to have. In the li-ion cell, this latter part, experts say, would mean looking for something beyond graphite for the anode. Like silicon, which can hold 10 times more lithium. But how to get it to work is the key question.
“These two are what I consider to be improvements for existing li-ion batteries that are going to make it better and better. The next part of the roadmap is what I would call a dramatic change in technology,” says Srinivasan. Some of this goes back to that old problem—the lithium metal battery that could never be recharged. There has been a resurgence in this area with the research community using new advances in materials sciences to explore lithium. Much of his research, Srinivasan says, is now in this area.
“If lithium metal becomes successful, it will open the doors for some new chemistries to start coming in,” he says. There is lithium-sulphur and then, probably even better, lithium-oxygen. “We think we can increase the energy density pretty dramatically with sulphur compared to today’s lithium-ions, but to make sulphur work, you have to get lithium metal to work. That’s why lithium metal is an important part of our future. Oxygen becomes the next big thing.”
But back to li-ion. Why some of these batteries explode is now largely known—it’s because dendrites, or tiny whiskers, form if a cell charges too quickly and could cause a short circuit.
“While there is surging demand and widespread government support for li-ion technology as an environmentally clean option in renewable power projects, li-ion and their newer counterparts have significant safety concerns,” says Prashant K. Jain of the University of Illinois. While the potential solution is to replace the flammable organic electrolyte in these batteries with a solid electrolyte, the hitch is that solid electrolytes suffer from poor ionic conductance. “But a phenomenon known as super-ionicity can allow fast, efficient transport of li-ions during battery charging and discharging operations.”
Super-ionic solids are called so because their ions can move exceptionally fast as if they were moving in a liquid. Jain’s lab is working on copper selenide as a potential candidate for the problem. “We found that the nanoclusters of copper selenide exhibit super-ionicity at room temperature. Additionally, copper selenide is also an earth abundant mineral,” says Jain.
Earlier this year, much excitement followed news of a breakthrough by John Goodenough, the 94-year-old co-inventor of the li-ion battery, and his team at the Cockrell School of Engineering, Texas. They used a glass electrolyte instead of a liquid electrolyte like the li-ion cell. The cells, as the researchers demonstrated, have at least thrice as much energy density as li-ion batteries today. However, advances in battery technology typically take a long while to reach the market.
Storage Of The Future
While much of the talk about energy density relates immediately to electronics and transportation, it could possibly also have an impact on the electricity grid systems, given that costs are going down. But if one were to look only at costs and cycle life, experts say, there are some interesting questions being probed. “Like water-based chemistries using new materials,” says Srinivasan of Argonne. “Could we do something that is not lead acid? We have been seeing some interesting new advances in that area also. I am actually very excited about what could happen to grid storage.”
Sun Mobility wants to produce robotic stations where you can swap a battery and move on—in as much time as at a petrol pump.
Even as things stand, the falling cost of batteries alone could see new business models emerging in distributed generation and storage. “I think economically what we are going to see is in places like India, if you are saying am I going to build a grid or think about distributed generation…well, guess what, it’s looking competitive,” he says.
For a single consumer, Prashant Jain of Illinois points out, solar generation and storage are already cost-competitive in several places like California, which have ample sunny days. “To implement energy storage on the grid scale (serving an entire network of consumers), there is a need for technologies or technology advances (batteries, flow batteries or compressed air) that involve cheaper materials (reducing capital costs), longer lifetime, and higher power conversion efficiencies. These factors need improvement before the cost of storage can be economically justified, relative to current utility prices,” says Jain.
In India, at least in transportation, some innovative business models are on the anvil. Chetan Maini, the country’s electric vehicle car pioneer, is working on one such. In 2010, he sold his company Reva Electric to automobile maker Mahindra. Over the past year, he has set up Sun Mobility, a venture that promises to rethink how we look at batteries for electric vehicles. The logic on which this is premised is simple: if you were to take the battery out of the equation, an electric car would cost just as much as a petrol one. So, Sun Mobility wants to produce smart batteries and robotic stations where you don’t recharge, but swap a battery and drive on—in just about as much time as you would spend today in a petrol pump. “Such a solution isn’t available today and we are creating this globally to make electric vehicles viable,” he says.
At the moment, Sun is focussing on three-wheelers and buses in partnership with Ashok Leyland. “Today, if you separate the battery from vehicles, you can make it work…at today’s renewable energy pricing. It’s not like we have to wait 10 years. In 10 years, it’s only going to get better,” says Maini. He reminds you that the world’s first electric car was made over 120 years ago and there were more electric cars in 1900 than gasoline-run ones.
“There is a point at which things come together,” says Maini. Energy costs are coming down on renewables, so are battery prices and the cost of electronics—all of which, he says, means that suddenly electric cars can match the performance or, in the case of Tesla, outperform gasoline vehicles. “Climate change is a large issue for consumers and you have this whole connectivity and shared mobility, which didn’t exist. These factors are coming together for the first time,” he says.
“You can actually make business sense of these today,” says Maini. “You can connect the dots. There is nothing missing.”
Source: outlookindia
