14-08-2018 | | By Nnamdi Anyadike
The announcement in late July that University of Cambridge researchers have discovered a way to make super fast charging devices using niobium tungsten oxides could prove to be as commercially groundbreaking as it is scientifically significant. The ‘holy grail’, as it were, of lithium ion battery development is achieving a substantially reduced charging time that would open the door to a whole swathe of new battery markets including fast recharging electric vehicles (EVs).
This feat would need to be achieved by speeding up the movement of lithium ions in and out of a battery’s electrodes. One approach has been to nano-size the active particles, thereby reducing the distance the ions have to travel. The downside to this approach, however, is that the volume is expanded, which increases costs and material instability. As Kent J. Griffith, at the University of Cambridge and lead project author said, “It’s difficult to make a practical battery with nano-particles. You get a lot more unwanted chemical reactions with the electrolyte, so the battery doesn’t last as long, plus it’s expensive to make.”
Now a team led by Clare Grey from the University of Cambridge, UK with colleagues from Argonne National Laboratory in the US and Diamond Light Source, Harwell Science and Innovation Campus, UK has come up with a solution that could greatly enhance the charging times of nickel cobalt aluminium oxide (NCA) batteries, used for EVs, and lithium cobalt oxide (LCO) cathodes used in mobile phone batteries. Rather than pursue the nano-particle route, Grey and her team investigated niobium tungsten oxides instead.
These materials, they noted, have rigid open crystalline structures. And they reasoned lithium ions could quickly flow within, even when micron-sized particles of the oxides were used instead of nano-particles. The scientists found that lithium ions moved “hundreds of times as fast in these oxides than typical anode materials.” The research was funded in part by the European Union (EU), the Science and Technology Facilities Council, and the Engineering and Physical Sciences Research Council.
Griffith pointed out, “Many battery materials are based on the same two or three crystal structures, but these niobium tungsten oxides are fundamentally different. The oxides are held open by ‘pillars’ of oxygen, which enables lithium ions to move through them in three dimensions.”Although the niobium tungsten oxides materials do not result in higher energy densities when used under typical cycling rates, the researchers found that lithium ions move through the materials at rates that far exceed those of typical electrode materials. And this equates to a much faster-charging battery. In addition to their high lithium transport rates, the niobium tungsten oxides are also simple to make.
The commercial repercussions of this development could be quite staggering. The lithium ion battery market is already growing by leaps and bounds and according to some estimates it could exceed more than $69 billion by 2022, having grown at a CAGR of 16% from 2018. Will Adams, Head of Research for the battery materials, base metals and precious metals markets at Metal Bulletin, sees the electrification of vehicles and the need to store electricity generated by renewable energy sources pointing to huge future demand for lithium-ion batteries.
The automotive industry’s use of lithium-ion batteries alone is on track to grow nine-fold to 650 GWh by 2025, from around 70 GWh in 2017. And with government subsidies and incentives in countries like China, sales of electric vehicles (EVs and e-buses) will rise substantially. This will be aided by a dramatic drop in the cost of the of the EV’s battery pack. According to Metal Bulletin, battery pack costs have fallen to around $200 per kWh in 2018 from around $1,000 per kWh in 2010. However, this is the just the beginning. Elon Musk’s Tesla claims that it is close to reaching a battery cell cost of $100/kWh this year, with its battery pack costs expected to reach that level in 2020.
A $100 kWh price tag for a battery pack is thought to be the tipping point where EV and internal combustion engine (ICE) costs are similar to each other. By then, however, the cheaper running cost of EVs is expected to make them the vehicle of choice. But a fast recharge is essential. Would-be buyers would be unlikely to purchase an EV if they have nowhere to recharge at home, or if an inadequate driving range would restrict their use of the vehicle.
So the prospect of a new fast charge battery based on niobium tungsten oxides is certain to make waves in the market. The next step for the Cambridge led scientists is to find the best cathode and electrolyte materials to accompany niobium tungsten oxide anodes. Excitingly, they suggest there are potentially other materials with structures and properties that are also much like those of niobium tungsten oxides. “We are optimistic that there are other promising materials yet to be discovered,” said Griffith.