Holst Centre exists to help the transfer to industrialization of new technologies that could address societal issues and trends. Climate change is perhaps the most pressing issue facing the world today. And it is driving big changes in how we generate and use energy.
A stable renewable energy supply
On the generation front, many countries are looking to switch from fossil fuel-fired power stations to renewable energy resources. For example, in 2016, 86% of the new energy generating capacity installed in the European Union was in the form of renewable energy and wind moved past coal to become the EU's second largest form of power capacity.
The most popular forms of renewable energy currently are wind and solar power. These share a key characteristic: they are entirely dependent on the local conditions. Unlike traditional power stations, you can't just turn wind and solar power on and off when you want to. You only make energy while the wind blows or the sun shines.
Another characteristic of wind and particularly solar is that they can be installed on a much smaller scale. Individual homes and businesses can produce their own electricity, even feeding back excess power to the grid at productive times. But if we have a lot of local energy producers, how will the grid cope if they all have excess electricity to feedback at the same time? Countries like Germany have already had to face negative pricing – effectively paying companies to use electricity. If the volumes of excess electricity get much higher, they could be in danger of crashing the grid.
Clearly, if renewables are going to be a major contributor to energy generation, some form of energy storage is needed to balance out the supply. And if renewable generation is going to be increasingly local, then those energy storage capabilities also need to be local to protect the grid. That means they need to be safe and they need to be compact (specifically have a high capacity to volume ratio).
Taking electric cars further
The same environmental and economic concerns that are driving the adoption of (local) renewable energy are also behind the growing popularity of electric vehicles. These too need compact energy storage solutions to make them feasible, but here it is the capacity per unit weight that is critical.
Of course, electric cars and their batteries already exist. But you need a lot of batteries which limits the vehicles performance and range. They are also slow to charge, meaning electric vehicles typically have to "re-fuel" overnight. What's more, current battery technologies present a small but non-negligible fire risk.
Safe, high-capacity, high-performance batteries
Spurred on by these two trends, Holst Centre decided to explore solutions for compact energy storage. This led to the formation of our research program on thin-film solid state lithium-ion batteries.
Thin-film solid state batteries solve many of the issues around today's batteries. Because the use a solid rather than liquid electrolyte, they are much less likely to leak and catch fire. They can also be charged within minutes.
On the other hand, they have a relatively low capacity. To overcome this, we have developed a novel three-dimensional structure that massively increases the surface area of the films and hence the overall storage density. And we can coat such a surface conformally using spatial atomic layer deposition (sALD) to ensure high performance.
We believe this solution has huge societal potential. In grid applications, it makes local storage a real possibility. Not only would that protect the grid from overload on productive days, it would give individuals much more control over their own energy supply and bills. They would be able to decide whether to sell excess power back to the grid or keep it to reduce the amount of electricity they need to supply at less productive times.
In electric vehicles, the higher energy density of the 3D structure means more storage capacity without damaging the vehicle's performance. That could help push up driving ranges from around 400 km today to something comparable with the 700 km a typical petrol car. And you could be able to "fill up" your electric car as quickly as a petrol car – our goal is 4 minutes for a full charge.
Making energy like plants
Of course, batteries are just one of countless ways that energy can be stored. Looking further ahead, we are already looking at so-called solar fuels: making energy the way plants do to create fluid fuels that have a storage density and are easily transportable.
Ton van Mol
Ton van Mol is Managing Director of Holst Centre / TNO.