The European Green Deal targets net zero CO2 emissions of greenhouse gases in Europe by 2050, specifying zero emissions from new cars by 2035. Electrification of the automotive industry is key to meeting these goals, but rapid advances in energy storage technologies such as lithium-ion batteries are required to realise this. Many new materials combinations for battery electrodes are emerging that can begin to address performance targets, but lifetime issues remain problematic. Hence, there is an urgent need for traceable analytical techniques to decipher structure-behaviour relationships and elucidate degradation and failure mechanisms to improve battery performance by design, rather than empirically.
Quantification of elemental composition, and determination of oxidation and chemical binding states, coordination and phase structure are crucial for an enhanced understanding of battery electrode degradation . Moreover, investigations must be conducted in real-time, allowing aging mechanisms to be linked to battery state of charge (SoC) and state of health (SoH). Currently, degradation studies are performed post mortem, using ex situ methods where the cell is disassembled, leading to chemical modification which can distort the result.
To avoid that, operando methods, where electrode materials are characterised simultaneously during cell charge-discharge, are needed. Whilst some operando methods are available, they are not sufficiently reliable or quantitative to allow confident data interpretation. Moreover, there is a need for new hybrid operando methods, where multiple measurands are synchronously probed during electrochemical cycling, to establish causal links between materials properties and their impact on cell performance. Such advanced measurements bring new challenges as they require special sample environments such as dedicated electrochemical cells with thin probing windows, while ensuring that the electrochemical behaviour remains unperturbed.
Hence, there is a need for establishing a robust, validated metrological framework for operando metrology, that can be transferred to battery developers and demonstrated through industrial case studies.