Bootstrap resampling as a tool for uncertainty analysis in 2-D magnetotelluric inversion modelling

Uncertainty estimation is a vital part of geophysical numerical modelling. There exist a variety of methods aimed at uncertainty estimation, which are often complicated and difficult to implement. We present an inversion technique that produces multiple solutions, based on bootstrap resampling, to create a qualitative uncertainty measure for 2-D magnetotelluric inversion models. The approach is easy to implement, can be used with almost any inversion code, and does not require access to the inversion software's source code. It is capable of detecting the effect of data uncertainties on the model result rather than just analysing the effect of model variations on the model response. To obtain uncertainty estimates for an inversion model, the original data set is resampled repeatedly and alternate data set realizations are created and inverted. This ensemble of solutions is then statistically analysed to determine the variability between the different solutions. The process yields interpretable uncertainty maps for the inversion model and we demonstrate its effectiveness to qualitatively quantify uncertainty in synthetic model tests and a case study.Sebastian Schnaidt, Graham Heinso

Synergistic electrolyte additives for enhancing the performance of high-voltage lithium-ion cathodes in half-cells and full-cells

Herein we address the key challenge towards the practical use of high-voltage lithium-ion cathode materials, i.e., the insufficient stability of the electrolyte towards oxidation. The transition metals in such materials, especially nickel, catalyze the decomposition reaction of the electrolyte, ultimately leading to poor cycling stability and rapid fading of the battery. To tackle this challenge, a new combination of electrolyte additives is introduced, targeting stabilized electrode/electrolyte interfaces and interphases for both the anode and cathode. The results show that the synergistic effect of tris(trimethylsilyl) phosphite (TTSPi) and bis(2,2,2-trifluoroethyl) carbonate (TFEC) can significantly improve the performance of cathode half-cells and also of lithium-ion full-cells with a cell voltage higher than 4.5 V. Cells using both TTSPi and TFEC as additives show greatly enhanced cycling stability, increased capacity, and improved coulombic efficiency, which can be even further improved when adding also lithium bis(oxalato)borate. © 2020 Elsevier B.V. • Design of an electrolyte composition for high-voltage cathodes. • Enhanced performance for 5 V cathodes and graphite anodes. • In-depth analysis of the SEI and CEI in half-cells and full-cells. • Synergistic effect of TTSPi and TFEC for high-voltage cathodes and graphite anodes. • Further improvement by adding also LiBOB. © 2020 Elsevier B.V