Serena Cussen1,Innes McClelland1,Peter Baker2
University of Sheffield1,ISIS Pulsed Neutron and Muon Source2
Serena Cussen1,Innes McClelland1,Peter Baker2
University of Sheffield1,ISIS Pulsed Neutron and Muon Source2
Efficient and sustainable energy storage technologies will form a core element in decarbonising our energy system and batteries are one of those technologies which will enable that transition. Central to this is the development of new materials and methods which, for example, enable stable interfaces to improve power densities or mitigate degradation processes to improve energy densities. This talk details the use of muon spin relaxation spectroscopy as a local probe of diffusion dynamics in battery materials.<br/>In this talk, I will discuss a new <i>operando</i> muon spectroscopy (μSR) method which can be applied to investigate how local Å-length scale diffusion and internal field properties change in the high nickel content cathode NMC811 during cycling. Our design of a new Battery Analysis by Muon (BAM) cell allows monitoring of diffusional properties with highly correlated structural changes in the unit cell during operating conditions.<br/>The nature of μSR as a local probe means it reflects the diffusion rates at specific sites and from a site-to-site basis, in contrast with bulk measurements such as electrochemical impedance spectroscopy (EIS) which provides information on resistive interfaces and long-range charge transfer. In the case of the high nickel content cathode NMC811, we find that Li<sup>+</sup> dynamics increase most rapidly at the beginning of charge, before decreasing above 75% state of charge (SOC). We also interestingly observe a sensitivity of the static field distribution width parameter Δ, obtainable by μSR, to the TM redox activity and resultant TM-O bond length changes, with a correlation between the trends observed in dQ/dV, cyclic voltammetry and Δ. This observed sensitivity to changes in TM-O bond length is particularly intriguing for investigating anion redox in next-generation cathodes, where µSR can provide additional insights into ongoing challenges in stabilising anion redox behaviour.