Understanding the nature of the passivation layer enabling reversible calcium plating
As for other multivalent systems, the interface between the calcium (Ca) metal anode and the electrolyte is of paramount importance for reversible plating/stripping. Here, we combined experimental and theoretical approaches to unveil the potential solid electrolyte interphase (SEI) components enabling facile Ca plating. Borates compounds, in the form of cross-linked polymers are suggested as divalent conducting component. A pre-passivation protocol with such SEI is demonstrated and allows to broaden the possibility for electrolyte formulation. We also demonstrated a 10-fold increase in Ca plating kinetics by tuning the cation solvation structure in the electrolyte limiting the degree of contact ion pair. ; Funding from the European Union's Horizon 2020 research and innovation program H2020 is acknowledged: European Research Council (ERC-2016-STG, CAMBAT grant agreement no. 715087) and H2020-MSCA-COFUND-2016 (DOC-FAM, grant agreement no. 754397). A. Ponrouch is grateful to the Spanish Ministry for Economy, Industry and Competitiveness Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496) and to Prof. D. Lemordant (Tours University, France) for stimulating discussions. P. Canepa acknowledges funding from the National Research Foundation under his NRFF NRFF12-2020-0012 and the ANR-NRF NRF2019-NRF-ANR073 Na-MASTER. P. Canepa acknowledges the National Supercomputing Centre, Singapore (https://www.nscc.sg). This work has been done in the frame of the Doctoral Degree Program in Materials Science by the Universitat Autònoma de Barcelona. The FTIR experiments were performed at MIRAS beamline at ALBA Synchrotron with the collaboration of ALBA staff. ; Peer reviewed