Enhancing Performance in Polyanionic Cathode Materials

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The increasing threat posed by climate change has made energy storage more important than ever before. Lithium-ion batteries (LIB) have revolutionised portable electronics and have growing impact in electric vehicles. This success is due to their high energy densities which permit small light batteries to power increasingly small and complicated electronic devices. However, new generations of battery materials are required which combine high energy and power densities with low cost and high safety, for applications such as electric vehicles or static energy storage. The need to reduce CO2 emissions prioritises the use of renewable energy sources as opposed to the burning of fossil fuels. The intermittent nature of these renewable energy sources and the need to match supply with demand requires the storage of excess energy generated at peak production so that it may be released at times of peak demand. Electrochemical energy storage represents one of the more attractive solutions to this challenge. Polyoxyanion compounds are receiving considerable interest as alternative cathodes to conventional oxides. The strong binding of the oxygen in polyoxyanions enhances stability and thus safety, compared with layered transition metal oxides and raises the voltage via the inductive effect. The aim of this work is to investigate new polyanion systems, particularly oxalates, including the incorporation of highly electronegative fluorine which is beneficial for improving the electrochemical performance and raising the voltage.In a particularly exciting development, our preliminary studies indicate that in addition to conventional transition metal redox activity, the oxalate group itself may show redox behaviour.By employing a combination of experimental and computational techniques we will be able to obtain a fuller understanding of these materials and develop them towards possible application.In order to achieve this we have assembled a strong team of collaborators. These include academic partners for both computational (DFT) and experimental (Mossbauer and X-ray absorption spectroscopy) studies, together with industrial support from Faradion and Johnson Matthey.Our approach will maximise the opportunity to combine transition metal and oxalate redox and thereby obtain higher capacities, beyond the conventional metal-only redox activity.