Tesla is at the forefront of industrial battery technology research.
Electric cars are accelerating commercially. General Motors has already sold 12,000 models of its Chevrolet Bolt and Daimler announced in September 2017 that it is to invest $1bn to produce electric cars in the US, with Investment bank ING, meanwhile, predicts that European cars will go fully electric by 2035.
‘Batteries are a global industry worth tens of billions of dollars, but over the next 10 to 20 years it will probably grow to many hundreds of billions per year,’ says Gregory Offer, battery researcher at Imperial College London. ‘There is an opportunity now to invest in an industry, so that when it grows exponentially you can capture value and create economic growth.’
The big opportunity for technology disruption lies in extending battery lifetime, says Offer, whose team at Imperial takes market-ready or prototype battery devices into their lab to model the physics and chemistry going on inside, and then figures out how to improve them.
Lithium batteries, the battery technology of choice, are built from layers, each connected to a current connector and theoretically generating equivalent power, which flows out through the terminals. However, improvements in design of packs can lead to better performance and slower degradation.
Lithium batteries need to be adapted for electric vehicle use. Image: Public Domain Pictures
For many electric vehicles, cooling plates are placed on each side of the battery cell, but the middle layers get hotter and fatigue faster. Offer’s group cooled the cell terminals instead, because they are connected to every layer. ‘You want the battery operating warmish, not too hot and not too cold,’ he says.
‘Keeping the temperature like that, we could get more energy out and extend the lifetime three-fold.’ If the expensive Li ion batteries in electric cars can outlive the car, he says their resale value will go up and dramatically alter the economic calculation when purchasing the car. ‘If we can get costs down, we will see more electric vehicles, and reduced emissions and improved air quality,’ Offer says.
Alternatives to lithium ion
Battery systems management and thermal regulation will allow current lithium batteries to be continually improved, but there are fundamental limits to this technology. ‘Lithium ion has a good ten years of improvements ahead,’ Offer predicts. ‘At that point we will hit a plateau and we are going to need technologies like lithium (Li) sulfur.’
Will Batteries Power The World? | The Limits Of Lithium-ion. Video: minutephysics
Li sulfur has a theoretical energy density five times higher than Li ion. In September 2017, US space agency NASA said it will work with Oxis Energy in Oxford, UK, to evaluate its Li sulfur cells for applications where weight is crucial, such as drones, high-altitude aircraft and planetary missions.
However, Li sulfur is not the only challenger to Li ion. Toyota is working to develop solid-state batteries, which use solids like ceramics as the electrolyte. ‘They are based around a class of material that can conduct ions at room temperature as a solid,’ Offer explains. ‘The advantage is that you can then use metallic lithium as the anode. This means there is less parasitic mass, increasing energy density.’
The carbon-fiber structure and Li ion battery motor of one of BMW’s electric cars. Image: Mario Roberto Duran Ortiz
For electric cars, the ultimate technology in terms of energy density is rechargeable metal-air batteries. These work by oxidising metals such as lithium, zinc or aluminium with oxygen from the air. ‘Making a rechargeable air breathing electrode is really hard,’ warns Offer. ‘To get the metal to give up the oxygen over and over again, it’s difficult.’
Development in the area looks promising, with the UK nurturing battery-focused SMEs and forward-thinking research groups in universities. The latest investment plan envisages support that links across research, innovation and scale-up, as championed by Mark Walport, the government’s Chief Scientific Advisor.
The Faraday Challenge – part of the Industrial Strategy Challenge Fund. Video: Innovate UK
Introducing a programme to directly tackle this challenge ‘would drive improved efficiency of translation of UK science excellence into desirable economic outcomes; would leverage significant industrial investment in the form of a “deal” with industry; and would send a strong investment signal globally,’ says Walport.