Dr Peter Baker, instrument scientist at the ISIS Neutron and Muon Source, and co-investigator on the Faraday Institution’s FutureCat project, explains how fundamental particles can support research in developing better materials for energy storage.

Following the Intergovernmental Panel on Climate Change’s latest climate assessment, it is clear that we urgently need to change a wide range of human activities and rely on significant innovation to reach net zero emissions. At the forefront of this revolution are advances in energy storage, particularly developments in battery technologies that will in turn unlock several sectors of the economy such as electric vehicles (EVs).

The electrification of transport has led to enormous increases in battery cell production around the world. In 2020 alone, the global EV market increased by 40 per cent, with EV registrations estimated to grow from around 3 million in 2020 to 145 million by 2030. Maintaining the supply for this demand presents challenges as the lithium-ion supply chain faces volatility, in part due to its association with cobalt, the price of which jumped 40 per cent in the first half of 2021.

In the context of addressing both climate change and limited natural resources, battery production needs to be done in a sustainable way, firstly by using abundant materials, secondly by extending cell lifetimes, and ultimately heading towards a circular economy. Several related developments will be needed to tackle this difficult and multi-faceted problem.

One necessary direction is to expand our understanding of current battery materials, work out how to optimise them further, and learn how to make new types of batteries based on new materials. The UK’s ISIS Neutron and Muon Source uses these fundamental particles to investigate materials and is used by battery scientists from around the world researching sustainable improvements and alternatives to lithium-ion batteries. Neutrons examine the structures of battery materials and muons are used to measure how fast the ions move through them at the atomic scale.

Because the raw materials they contain are more abundant, sodium-ion and magnesium-ion batteries show promise as cheaper alternatives to lithium-ion technology. Experiments done at the facility showed that sodium and magnesium ions moved in a similar way to lithium ions in the respective cathode materials. While more research is necessary to explore cathode, electrolyte, and anode materials that work effectively together, this represents a promising step towards a realistic alternative option for electric vehicles.

Last year, we also used muons to study the latest cathode materials as they are charged and discharged. Working with researchers from the Faraday Institution, we investigated the performance of a half-cell made with NMC811, a material increasingly used in the cathode of EV batteries due to its competitive price and energy density properties. Future experiments will look at variants of this material with even lower cobalt content, to stabilise the supply chain and cost.

Conducting experiments while a battery cell is charging and discharging also allows us to investigate other processes that occur during operation. We have used muons to look at a new solid-state electrolyte material in a whole cell, which ceases to be rechargeable below a certain voltage. Muons showed that the rate of ionic motion at the atomic level drops significantly at this voltage, which in turn affects how the whole cell functions. This level of information is critical to understanding the exact processes that affect cell function, to find ways to develop better batteries in the future.

The widespread electrification and decarbonisation of different sectors will almost certainly rely on several types of energy storage. As the lifetime environmental impact of EVs has gained wider attention, the make-up of battery materials has also entered the spotlight. Muons are an important tool to understand the atomic level processes that occur within these materials, and employing techniques like muon spin spectroscopy is one way we can enable UK industry and science to take the next steps towards vital innovations. There is no one size fits all solution – however great strides can be made towards finding new materials through collaborations between industry and academia at UK research facilities like the ISIS Neutron and Muon Source.

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