Solving the 'grand challenge' of battery research

  • 11-Dec-2017 09:57 EST
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Prof. David Greenwood says of future battery development: "We are going to need new alternatives to deliver a step-change."

Research universities are playing an increasingly vital role in advanced automotive battery R&D and manufacturing capability. Among several new partnerships in Europe is the British government’s investment in the multi-faceted Faraday Battery Challenge, which provides links between leading universities and the auto industry.

Helping to meet that Challenge is the recently announced Faraday Battery Institution, created to co-ordinate U.K. academic research in partnership with industry. The Institution brings together seven U.K. universities to accelerate fundamental research in the development of battery technologies, including the University of WarwickImperial College, London; University College London; University of Cambridge; University of Oxford; Newcastle University; and the University of Southampton.

Prof. David Greenwood, Professor of Advanced Propulsion Systems at the University of Warwick's Manufacturing Group, recently spoke with SAE's European Editor Stuart Birch about the new organization.

The Institution is set to explore “novel approaches” to battery development; what are these likely to be and which would be the salient areas?

The central principle of the Faraday Institution is ‘application-inspired fundamental research’. This means the right science and technology experts working together on the future advances that are going to drive innovation towards commercial application.

The initial focus for this investment is the automotive industry, which has an urgent need for low carbon solutions, but other sectors, such as grid, marine, and aerospace, are likely to grow.

The Faraday Institution will work on research programs developed from grand challenges set by industry, so a focus will be on the biggest research issues that are inhibiting progress. The first tranche of research areas covered will be battery degradation, multi-scale modelling, solid state batteries and recycling / circular economy.

An important approach is that these programs will be managed to ensure that investment remains targeted at the areas that show promise for accelerated development. The Institution will intentionally have a broad scope which does not just focus on electrochemistry and materials. These are important, but we need to think about the wider systems and broader engineering, manufacturing and integration which will also have a significant impact on technology development. This means bringing together different disciplines to work on these challenges collaboratively, whether that’s chemists, engineers, mathematicians, economists or physicists.

From a public perspective, lack of energy density, high cost, excessive weight and recharge time, remain the negative aspects of electric vehicle use; are you confident that these can all be successfully and satisfactorily addressed?

We are continually seeing rapid improvements in lithium-ion battery technologies which are used in electric vehicles today. For example, volumetric energy density has doubled in the last 15 years, and costs have fallen by a factor of four within the last 5-10 years. We are seeing these improvements as a result of technology optimization, volume production and wider market dynamics.

Researchers are demonstrating that continued improvements are feasible, both through continued optimization of current systems, development of new chemistries, and whole systems design and integration.

The challenge is that new technologies, which are emerging at a ‘proof-of-concept’ stage, will take at least eight to ten years to make it to the commercial market as fully validated, industrially manufactured products.

The chemistries we are using in electric vehicles today were developed in labs in previous decades. Commercial batteries are the result of a long-term development process to optimize and validate them for industrial scale manufacturing for specific applications.

This is why joined-up research, development and manufacturing scale-up are essential. Fundamental battery innovation is only the first part of the journey. It needs to be followed up by further development to overcome the complex challenges of manufacture for applications which require high standards of quality, robustness, safety and performance.

Does lithium-ion technology have the development potential to solve near to medium term battery challenges – and what of the fuel cell?

Lithium-ion batteries are broadly accepted to be the automotive chemistry of choice for the next eight to ten years due to existing production maturity and the R&D needs of other future alternatives.

There is still much we can do to optimize lithium-ion for automotive applications, such as new formats and structures of cells, new material additions such as silicon composites, or improved prediction of how batteries age and degrade over time. However, again, the cell materials are only part of this story. There is also still great benefit to be gained from improving the manufacturing processes associated with battery cell, module and pack production, which could also significantly reduce costs. The fuel cell is out of scope of the activities of the Faraday Institution, although it is an area where universities and automotive companies are continuing with their R&D programs.

If lithium ion cannot meet the industry’s long term EV needs, what battery high energy density alternatives could be developed in the medium to long term?

The U.K.’s Automotive Council has set ambitious targets for future battery development in order to focus investment in R&D; these cover cost, energy and power density, life, safety, etc. There are still a number of areas where lithium-ion technology can be optimized, as I have explained.

However, if we are to meet the ambitious targets required by the automotive industry, we are going to need new alternatives to deliver a step change.

A number of these alternatives are being investigated for application potential. For example, lithium-sulfur is demonstrating high gravimetric energy density in some applications today but retains issues with safety, cycle life and volumetric energy density.

Solid state batteries are also being investigated and could offer improved safety and energy density but currently, manufacturing methods would prove too expensive for most applications.

It is important to note that alternatives will need to offer more than an improvement in energy density. There are some alternatives, such as lithium air, which demonstrate very high energy density, but may not have the power density which is going to be required for automotive applications.

For example, we may see a situation where different solutions are developed for different automotive markets, depending on whether they are aimed at premium or low cost, or whether range is a defining factor. Sodium-ion is an example of another chemistry which is already being demonstrated in market applications. It offers a lower cost alternative to lithium-ion. It could be an ideal solution for some applications where this is the primary factor as opposed to maximized energy density, e.g. very low cost or light duty vehicles.

Should the auto industry clear its mind of the seemingly endless big battery debate and go for – perhaps – wireless dynamic charging through the road surface? But are such potential solutions too far out to be considered and too problematical with regard to infrastructure?

The automotive industry is leading the way as it has an urgent requirement for new, low carbon solutions which will be an acceptable alternative to conventional engine technology. The legislative imperative that is driving this direction is likely to continue as national and urban policies increasingly target emissions and air quality.

Creating an infrastructure-based solution is very complex. It would require cross-sector co-ordination and wider national investment and intervention. The automotive industry is already developing battery roadmap targets for a 2030 timeframe and infrastructure development will take longer than this so progress needs to continue in the meantime.

Passenger cars are well suited for battery technology solutions as their use tends to allow periods of extended charging at managed times, e.g. overnight, at a workplace, and they provide a solution which is comparatively low cost to implement in the near-term.

However, for heavy duty and commercial vehicles, on-board energy storage will be a much greater challenge. In the longer-term we may see dynamic solutions developing for these applications, such as wireless or catenary and pantograph systems.

The challenge is that dynamic charging needs a real-time power supply and that means using energy at the times when it may be least likely to be available, e.g. at rush hour commutes. Charging trucks wirelessly through-road is likely to need around a megawatt of power per mile. For that, we will need new power generation capacity, high power connections to major road networks. This type of solution is likely to be decades away as it would require major national-scale infrastructure projects.

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