Imagine an electric car with the range of a Tesla Model S but at one-fifth the price. Picture a battery able to charge in seconds and last for days. Or envisage whole city blocks powering themselves overnight from the already set sun. All of this might be possible with the next generation of batteries currently under development.
Lithium-ion batteries represent a landmark technology that has made the current generation of electric vehicles possible and bathed us in all manner of gadgets.
Lithium-ion chemistries have a certain maximum energy density, dictated by those pesky laws of physics, and today’s batteries are not so far from that theoretical maximum.
Yet, whilst day of their demise, may still many years in the future, it is within view, however, as we’ll find out, replacing the Lithium ion battery, may in fact change the world.
All batteries – watch, flashlight, cell phone, car – work basically the same way. Negatively charged electrons are chemically stolen from a metal anode and flow rather desperately toward a positively charged metal cathode at the other end of the circuit. Voltage is a measure of the force pushing the electrons from pole to pole, while current is the number of electrons speeding by a given point. Together these attributes establish the power of a battery. Current can be altered by changing a battery’s size, but voltage is determined (and fixed) by the atomic makeup of the materials used.
All batteries have three main components: two electrodes and an intervening electrolyte. Lithium ion batteries work under the so-called rocking-chair model. Imagine discharging and charging a battery as similar to the back-and-forth motion of a rocking chair. As the chair rocks one way, using its stored energy, lithium ions flow out of one electrode through the electrolyte and into the other electrode. Then as the chair rocks the other way, charging the battery after a day’s use, the reverse happens, emptying the second electrode of lithium ions.
Fundamentally, when you have a battery, every time you use it, it starts to die a little bit. The more you use it, the more it dies and eventually, it becomes unusable. Theoretically speaking, you expect a certain performance from a battery, and you rarely ever get there and one of the main areas of research is to understand this loss and to minimise it. Cracking this problem, maybe at the chemical level, maybe at the physical or maybe at the atomic, will fundamentally change our relationship to electricity and could lead a revolutions in transport, could reverse the impact we’re having on the environment and to liberate the full potential of renewable power.
How we got here…
In the mid 1800’s, French inventor Raymond Gaston Planté created the first rechargeable battery, a delightful combination of sulfuric acid and strips of lead foil.
At first people thought of Planté’s creation as a “box of electricity” or an electric fuel tank. But the metaphor is not apt; you don’t fill a battery with electrons that are sucked out later on, before filling with more electrons. A battery is more like a complicated and finicky chemical pump that exploits what happens when certain materials (mostly metals) are placed together in an electrolyte solution.
The first widely produced batteries were lead acid. Used in early cars, they got the automobile to start as reliably as the horse. By the 1960’s, engineers had developed lighter, single-use alkaline and mercury batteries, making portable transistor radios and two-way communication devices possible. In the 1980’s, compact rechargeable batteries were developed using nickel and cadmium. Originally used by the military and NASA, NiCads eventually reached the consumer market, giving us video cameras, the first laptops, and cordless power tools. The power cells were reliable but suffered from an annoying glitch dubbed the memory effect: If users didn’t fully charge the batteries on initial use, the cells could “remember” only their original partial charge. This was fixed by the development of nickel metal hydride. NiMH packed more power, had less memory effect than NiCads, and recharged faster.
However, scientists had long known that lithium would make an excellent anode; most battery chemical combinations deliver 1.2 to 2 volts, but when paired with the right cathode, lithium atoms practically spew electrons, delivering the highest nominal voltage of any element in the periodic table at over 3.5 volts per cell.
Lithium however tends to explode on contact with air, which made research understandably difficult! The problem was cracked in the 1970#s, by a US scientist by the name of John Goodenough who finally figured out how to tap the electron potential of lithium: combine it with cobalt. Then all it took was a manufacturer willing to spend the money required to safely mass-produce the new batteries, an opportunity grabbed by Sony grabbed in the early 1980s, producing a rechargeable lithium-ion pack for a video camera.
Being the first rechargeable cells to have no memory effect, having four times the energy of NiCads, and twice the energy of nickel-metal-hydride cells, they ushered in a new energy storage era.
Throughout the ’90s, Li-ions enabled a litany of advances in devices that were hungry for more power. Laptops could be made lighter and faster, cell phones could be smaller and the MP3 player was born.
While a flashlight or a car starter places simple demands on a battery, powering a computer or camcorder is much more complicated. These devices contain dozens or even hundreds of individual components, and LCD screens have different voltage and current needs than, say, hard drives or Wi-Fi chips. So voltages are stepped up or down using transformers and other circuits, resulting in enormous losses in efficiency. The more complex a device, the harder the battery has to work.
Current battery technology
Despite all our best endeavours, the truth is that Lithium-ion technology may be approaching its limits. In the last 150 years, battery performance has improved only about eight-fold (or less, depending how it’s measured). Therefore, as the gains have slowed, the race to develop an even better battery has picked up. Of course, kicking the lithium habit won’t be easy. Possible successors like fuel cells have been heralded for decades, but design, implementation, and cost issues have prevented them from reaching the mainstream.
As tech companies push their businesses into making wearable devices like fitness bands, eyeglasses and smart watches, the limitations of battery technology have become the biggest obstacle to sales and greater profits. Consumers are not willing to embrace a product if it works for only a few hours between charges and must be removed to be plugged in.
So the race is on — both to find alternatives to the traditional battery and to discover ways to make battery power last longer.
The future for batteries
To accomplish the feat, researchers are looking to replace the current standard-bearer for rechargeable batteries – lithium-ion – with batteries made of cheaper, more durable materials, including magnesium, aluminium and calcium.
While private companies such as Tesla and Toyota are working to improve on lithium-ion technology, in the United States it’s the government labs that are trying to move technology to the next level.
George Crabtree, a director at the Argonne National Laboratory near Chicago, said that nearly two years into the project, researchers have narrowed down a list of about 100 types of “beyond lithium-ion” batteries to a few of promising concepts that are already in the prototype phase.
For example, one of the areas of most interest is in the field of rechargeable flow batteries, which store energy in a liquid solution of electrolytes that can be pumped through a membrane, to generate power.
The scientists want to use more cost-effective materials such as sulphur – a plentiful byproduct of refining crude oil – to create a battery with five to 10 times more energy than current flow batteries.
Despite their higher density and lower costs, the commercial development of lithium-sulphur batteries has been largely plagued by short cycle life, typically below 80 charge-discharge cycles. In comparison, a conventional lithium-ion battery will usually achieve 500 charge-discharge cycles.
While the number of charge-discharge cycles achieved by lithium-sulphur batteries is not yet high enough to enter the consumer electronics market, applications in aerospace and defence are strong possibilities where energy storage takes precedence over life cycle.
Once the technical challenges are overcome, combined with solar panels and wind farms, big high-density battery packs could help overcome one of the main problems with renewable systems: They can produce energy only when the conditions – sun or wind – are right, not necessarily when the energy is needed, as fossil fuel-fired generators do.
For long-duration storage, flow batteries are the most likely candidates among all current technologies because they can be easily scaled to gargantuan size, they have few moving parts and a long working life. What’s holding them back is cost: Most flow batteries use the element vanadium as an electrolyte and this is extremely expensive.
Ultimately, building a better battery boils down to figuring out a better way to move electrons. However, once we find that magic combination of materials the commercial, environmental and energy benefits will be immeasurable.