At a recent Shanghai auto expo, the world's largest battery maker unveiled a battery it claimed could power electric aircraft or propel electric vehicles (EVs) beyond 1,000 kilometres on a single charge.
Chinese Amperex Technology Limited (CATL), which makes one-third of the world's EV batteries, shared few details about the technology but said it would start mass production later this year.
It was the latest in a series of big announcements for the industry, which is booming with the global shift to electrification.
Battery design has been likened to a gold rush, as researchers push the boundaries of materials chemistry and develop lighter, longer-lasting, safer, cheaper batteries that charge more quickly.
Better batteries mean more affordable cars, cheaper electricity for the home, and ways of travelling overseas without emitting tonnes of CO2.
"If you think about our electrified lives, if you took away batteries, none of this is possible," said Adam Best, a principal research scientist at CSIRO.
"But people don't think about batteries."
So, here's how battery technology has improved over the past decade, and where it's going in the future.
EVs clocking 1,000km per charge?
Since being developed about 50 years ago, the amount of energy these batteries store per kilogram, known as their specific energy, has incrementally improved.
From consumer electronics in the 1990s, their applications branched out into electric vehicles in 2006, and large-scale grid storage in 2012.
As the number of applications has increased, so have the types of lithium-ion batteries. One may be designed to be cheaper, another to hold more energy, and a third to recharge more quickly.
Although we often talk in general terms about EV batteries, different models and brands use different types, equivalent to the difference between a V8 performance engine and an economical four-cylinder.
Standard-range EVs, for instance, use a lithium-ion battery with a lithium-iron-phosphate (LFP) chemistry, while longer-range vehicles tend to use nickel-cobalt-aluminium, or nickel-cobalt-manganese.
The main measure of how much energy a battery holds is its specific energy, which is measured in watt-hours per kilogram.
Most EV batteries have a specific energy of under 300Wh/kg.
CATL says its new battery almost doubles that figure, with a specific energy of 500Wh/kg.
Unfortunately, the company has not released many other details, including what this battery would cost, how many times it can be recharged, or how much power it can produce (how fast the stored energy can be used).
CATL says the new design will go into mass production later this year and be used in civil aviation and road transport.
If the battery is as good as it claims, it will mean EVs can drive from Sydney to Melbourne on a single charge.
Or, since most people do not need that kind of range, it will mean smaller battery packs and cheaper EVs.
How to make a better battery
There are two elements to better battery design: chemistry and engineering.
Chemistry involves tweaking the component parts of the battery, while engineering is about the shape and structure of the battery itself.
Batteries store energy in the form of chemical potential. As the amount of energy they store goes up, so does the challenge of keeping them stable, Dr Best said.
"You're trying to have something that's electrochemically stable, thermally stable, and chemically stable. It has to be able to conduct ions at a range of different temperatures."
"These materials that have to do so many different things in concert with each other. It's really like a symphony, with all the parts playing its role."
Often, improvements are made by tweaking the materials of the cathode, anode or electrolyte to reduce weight, improve conductivity, or lower cost.
Improving one metric, however, often comes at the cost of another.
For instance, battery makers have developed a sodium-ion battery that does not use lithium and is therefore as much as half the price.
But it has a lower energy density, of about 200Wh/kg.
For its latest battery, CATL appears to have developed a type of highly conductive electrolyte gel, which saves on weight.
In a statement, it says the battery uses "condensed matter" as an electrolyte to improve the conductive performance of the cells, as well as "innovative" anode materials.
"CATL's condensed battery leverages highly conductive biomimetic condensed state electrolytes to construct a micron-level self-adaptive net structure that can adjust the interactive forces among the chains, thus improving the conductive performance of the cells."
What batteries are needed for flight?
The current crop of small aircraft outfitted with electric power systems operate at 250-270Wh/kg of specific energy.
For electric aviation to really take off, experts say this figure will need to be about 400–500Wh/kg.
But high specific energy isn't the only requirement for electric aviation batteries, according to John Fletcher, a professor of engineering at UNSW.
"You need a battery that can deliver power for take-off," he said.
"The kind of ratios of power that you need to take off and the power to cruise are about 3 to 1."
That is, an aviation battery needs to deliver about three times as much power to get a plane in the air as it does to keep it cruising.
Because CATL hasn't given more detail about its new battery, we don't know its power output.
It says it's partnering with several unnamed companies to use the new condensed matter batteries to develop electric passenger aircraft.
Where is battery development going next?
One of the most promising emerging technologies is solid-state batteries, which use a solid electrolyte material instead of the liquid or gel used in conventional lithium-ion batteries.
A solid electrolyte drastically increases the battery's energy density, as well as safety, as it avoids the need for flammable solvents used in liquid electrolytes.
"Solid-state batteries will play a role in getting rid of those liquid phases that can … cause gas and catch fire," CSIRO's Dr Best said.
Late last year, NASA announced it had developed a solid-state battery with an energy density of 500Wh/kg
Meanwhile, SVOLT Energy, a division of China's Great Wall Motors, has created solid-state sulfide battery cells with an energy density of 350–400Wh/kg
There's also a lot of excitement about batteries that use the oxygen in air as a cathode, resulting in energy densities four times that of existing lithium-ion batteries.
In February, researchers at the Illinois Institute of Technology and US Department of Energy's Argonne National Laboratory announced they had developed a lithium-air battery with an energy density of up to 1200Wh/kg.
These batteries were a long way from being made commercially available, Dr Best said.
"The opportunity of lithium-air batteries is immense, but the chemistry of oxygen reacting with lithium is really difficult to control."
"This device would be an immense breakthrough if that was to work."
