Supporting the green energy transition

Electric car charging at power station

Mengjiang Lin explains how her EPSRC ICASE project could improve energy storage materials to support the green energy transition.

I started my Engineering and Physical Sciences Research Council (EPSRC) Industrial Cooperative Award in Science and Engineering (ICASE) Doctor of Philosophy (DPhil) in December 2021. This was in the Professor Sir Peter Bruce group at the Department of Materials with my industrial partners, Oxford Instruments.

Previously, I completed a Master of Chemistry in chemistry at the University of Oxford. Collaborating with Oxford Instruments on this ICASE project gives my research industrial relevance and allows me to experience the challenges faced in transforming methodologies from the laboratory to industry.

The demand for energy storage devices

The demand for energy storage devices has never been greater. Lithium-ion batteries that have high energy densities and large capacities are enabling the transition from petrol and diesel vehicles to electric vehicles. However, the capacity we can gain from lithium-ion batteries is approaching a ceiling as we maximise the amount of charge we can extract from the transition metals in the cathode.

New approaches to increase capacity are required. One potential mechanism to extend the capacity is to extract this charge from the anions (such as oxygen) in the cathode, this process is called anionic redox. Anionic redox comes with numerous problems such as the formation of molecular oxygen at the surface of the cathode which goes on to react with the electrolyte.

Why electrolytes are important

Electrolytes are not only important for enabling the lifetime of next-generation cathode materials for lithium-ion cells but also play a vital role in preventing unwanted reactions in batteries. Our current understanding of the electrolyte degradation processes during anionic redox is limited due to the complexity of competing degradation processes.

In my project, I use a range of ex-situ analytical techniques on disassembled cell components to explore how molecular oxygen reacts with the electrolyte. In combination with this, I am developing a novel operando benchtop nuclear magnetic resonance (NMR) methodology to look inside the battery cell. This gives us real-time information on when these unwanted side-reactions take place.

Understanding battery materials

Numerous ex-situ studies have been performed to elucidate the complex chemical reactions of Li-ion battery electrolytes. However, the thermodynamic and kinetic pathways inside a battery are affected when it is being used, and many reactive species are involved in the lithium-ion battery electrolytes. Understanding the changes in battery materials as the cell is cycled is therefore crucial in devising strategies to tame the effect of anionic redox on electrolytes, hence improving the overall battery lifetime.

Operando NMR characterisation on batteries allows comprehensive analysis of different states of charge without deconstructing the cell. Moreover, some transient processes, such as self-discharge and relaxation reactions, can be detected that might not be observable in ex-situ studies due to their time-sensitive nature. Therefore, operando benchtop NMR is potentially a key technique for understanding the evolution and degradation of electrolytes in high voltage, high-capacity batteries that undergo anionic redox process.

The X-Pulse benchtop nuclear magnetic resonance (NMR) spectrometer.

The X-Pulse benchtop NMR spectrometer from Oxford Instruments identifies structure, characterises reaction dynamics and measures physical and chemical properties of molecules, compounds and mixtures. X-Pulse is versatile, powerful and can be easily positioned in a lab, making Operando measurements possible.
Credit: Oxford Instrument plc

ICASE experience

As an ICASE student, I have had extensive opportunities to liaise with my industrial supervisors and foster a network between fellow scientists and industrialists during my quarterly visits to Oxford Instruments. With support from Oxford Instruments, I also received direct access to cutting-edge advanced analytical equipment and the world experts who develop these instruments. Oxford Instruments has also given me insight into the marketing and commercialisation of new scientific business ideas. I have also seen how my ideas have directly benefited industrial battery scientist customers of Oxford Instruments.

After completion of my DPhil degree, I would like to pursue a career in a battery-related industry. Therefore, the industrial experience I have gained during this ICASE programme gives me an excellent foundation for this career pathway.

I cannot recommend the ICASE programme enough, especially if you are interested in both academic and industrial research. An ICASE allows you to co-develop both skills relevant to academia and industry, giving you a head start for a future career in either.

Top image:  Credit: deepblue4you, iStock, Getty Images Plus via Getty Images

This is the website for UKRI: our seven research councils, Research England and Innovate UK. Let us know if you have feedback or would like to help improve our online products and services.