Séminaire

Vendredi 12 Mars 2021 à 11h00.

Atomic scale changes and their impact on battery performance

''The majority of the research undertaken in my group focuses on making better batteries to meet the demands of emerging applications. A large proportion of the function of batteries arises from the electrodes, and these are in turn mediated by the atomic-scale perturbations during an electrochemical process (e.g. battery use). A method to both understand battery function and improve their performance is to probe the atomic scale evolution operando, i.e., while an electrochemical process is occurring inside a battery. The result is an atomic level “video” of device function which can be directly correlated to performance parameters such as energy density, lifetime (or degradation), rate capability and safety In my group we use operando neutron powder diffraction, with its sensitivity towards lithium, to literally track the evolution of lithium in electrode materials used in rechargeable lithium-ion batteries – we explore commercial and custom-made cells. In addition, the ability to test smaller samples (e.g. in coin cells) with operando X-ray powder diffraction has allowed us to probe other battery types, such as primary lithium, lithium-sulfur and ambient temperature rechargeable sodium-ion batteries, and other configurations, such as thin film devices. With the information from these experiments we have directly related electrochemical properties such as capacity, battery lifetime and differences in charge/discharge to the content and distribution of lithium or sodium in the electrode crystal structures. We are expanding our footprint in both the analytical techniques we use and the reactions we explore. Recent work has been directed towards realizing operando neutron imaging, operando X-ray absorption spectroscopy and ex situ solid-state NMR allowing us to probe non-crystalline components in devices. We are also investigating formation reactions, i.e., literally watching synthesis of crystalline materials used in batteries, tracking the distribution of electrolytes during processes, and are using batteries to make new materials via the newly discovered electrochemically activated solid state synthesis route. The combination of these techniques and reactions provides a wide scope to explore both fundamental reactions and the mechanisms that are critical in applications. Overall, this talk will provide a flavor of the work being undertaken in my group, emphasizing the opportunities between atomic scale insight and application.''