This is a first comparison of the sequential design of experiments strategy and global sensitivity analysis for nanomaterials, thus enabling sustainable product and process design in future.

A particular safety issue with Lithium-ion (Li-ion) cells is thermal runaway (TR), which is the exothermic decomposition of cell components creating an uncontrollable temperature rise leading to fires and explosions. The modelling of TR is difficult due to the broad range of cell properties and potential conditions. Understanding the effect that thermophysical and heat transfer characteristics have on the TR abuse model output is essential to develop more accurate and robust TR models. This study uses global sensitivity analysis (GSA) to investigate the effect of the cell parameters on the outcome of TR events. Using a Gaussian Process (GP) surrogate model to calculate the Sobol' indices, it is shown that the emissivity value is the dominant thermo-characteristic throughout the overall abuse scenario. Further analysis, investigating three key TR features shows the conductivity coefficient to be the most important with respect to the maximum temperature reached during TR. Results demonstrate that researchers can confidently estimate some thermo-characteristics but require accurate characterisation of the emissivity and conductivity coefficient to ensure robust predictions. Given the importance of battery technology to aid in global de-carbonisation, these findings are key to increasing their safe design and operation.

Planar wave fronts in autocatalytic chemical systems propagate with a constant wave form and velocity provided that the reactant and autocatalytic species have similar diffusion coefficients. Such waves are also stable to spatial perturbations. Circular or spherical fronts show a constant wave form and a velocity that increases towards the planar wave velocity as the radius increases with time. These are again stable to spatial perturbation if the reactant and autocatalyst have similar diffusivities. However, if the ratio of the diffusion coefficients δ exceeds some critical value δ*≊2.3 a different situation arises. For cylindrical or spherical geometries, unperturbed waves decelerate as they expand if δ≳δ*. For all geometries, the smooth waves may become unstable to spatial perturbation if δ≳δ* although there are some additional requirements. In Cartesian systems, the width of the reaction zone transverse to the direction of propagation must exceed some minimum value W*≊6 (in dimensionless units) and the wave number of the imposed perturbation must be less than kcr,max≊0.15. For circular or spherical waves, the conditions for the growth of perturbations also involves the radius of the wave at the moment the perturbation is applied. A set of expansions based on small curvature and small departures of δ from unity have been derived allowing the instantaneous wave velocity to be written in the form v(θ,φ,τ)=c+v1κ+v2Δtrκ, where the coefficients c, v1, and v2 depend on δ and κ is the instantaneous curvature.

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