Yeandel, SR;
Scanlon, DO;
Goddard, P;
(2019)
Enhanced Li-ion dynamics in trivalently doped lithium phosphidosilicate Li2SiP2: a candidate material as a solid Li electrolyte.
Journal of Materials Chemistry A
, 7
(8)
pp. 3953-3961.
10.1039/c8ta10788b.
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Abstract
Oxide and sulphide solid electrolyte materials have enjoyed significant interest in the solid-state battery community. Phosphide materials however are relatively unexplored despite the potential for being high lithium containing systems. This work reports on the phosphidosilicate system Li 2 SiP 2 , one of many systems in the Li-Si-P phase diagram. The phosphidosilicates display complex structures and very large unit cells, which present challenges for ab initio simulations. We present the first computational report on the theoretical ionic conductivity and related diffusion mechanisms of the material Li 2 SiP 2 , selected due to it's unusual supertetrahedral framework which is a recurrent motif amongst the phosphidosilicates. Group 13 dopants have also been introduced into Li 2 SiP 2 showing preference for the silicon site over the lithium site, with doping showing extremely low defect incorporation energies of 0.05 eV, with no increase in defect energy up to concentrations of 10% . Furthermore, clustering of has been found to be unfavourable, in line with trends seen in oxide zeolite structures. Ab initio molecular dynamics (AIMD) simulations indicate high ionic conductivity in pure Li 2 SiP 2 of up to 3.19 × 10 -1 S cm -1 at 700 K. Doping with 10% and associated compensating defects leads to higher ionic conductivities at lower temperatures when compared to pure Li 2 SiP 2 . The activation energies to lithium diffusion were found to be low at 0.30 eV and 0.24 eV for pure and 10% doped Li 2 SiP 2 respectively, in line with previous experimental observations of pure Li 2 SiP 2 . Multiple lithium migration pathways have also been extracted, with some mechanisms displaying activation energies as low as 0.05 eV. Furthermore, our calculated intercalation voltages suggest that these materials are stable against lithium metal and therefore could be very attractive in stabilising the electrode/electrolyte interface.
| Type: | Article |
|---|---|
| Title: | Enhanced Li-ion dynamics in trivalently doped lithium phosphidosilicate Li2SiP2: a candidate material as a solid Li electrolyte |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/c8ta10788b |
| Publisher version: | https://doi.org/10.1039/c8ta10788b |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10070844 |
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