Abstract
Solid state electrolytes are the core components of all-solid-state lithium batteries.It is critical to develop solid state electrolytes with excellent ionic conductivity and
chemical and electrochemical stability in order to successfully switch from
traditional lithium-ion batteries to all-solid-state lithium batteries.
In this thesis, sulfide solid state electrolyte 75Li2S·25P2S5 glass-ceramic was
synthesised by mechanical ball milling and subsequent heat treatment. Under the
conditions with a jar filling factor of 38.6%, a rotation speed of 370 rpm, a ball-topowder ratio of 15:1 and a total milling time of 48 hours, followed by a 3.5-hour
calcination at 260 °C, the 75Li2S·25P2S5 glass-ceramic with an ionic conductivity
of 1.7×10-5 S cm-1 and a high air stability was obtained.
In order to further improve the ionic conductivity and stability of 75Li2S·25P2S5
glass-ceramic, oxide dopants (P2O5 and Li2O) and lithium halide dopants (LiCl,
LiBr and LiI) were introduced, respectively. In the P2O5-doped system,
98(0.75Li2S·0.25P2S5)·2P2O5 glass-ceramic had a 3.6 times higher ionic
conductivity than the undoped electrolyte and an enhanced air stability. In addition,
the structure degradation and morphology changes of 98(0.75Li2S·0.25P2S5)·2P2O5
glass-ceramic were investigated thoroughly. In the Li2O-doped system,
99(0.75Li2S·0.25P2S5)·1Li2O glass-ceramic had not only the highest ionic
conductivity of 1.5 × 10-4 S cm-1
but also the best air stability. Furthermore, various
electrochemical characterisations have revealed that all doped electrolytes are
capable of inhibiting lithium dendrite formation to some extent while maintaining
chemical and electrochemical stability, with 1Li2O outperforming the others. In the
LiX-doped (X = Cl, Br and I) system, the ionic conductivities of LiX-doped
electrolytes have improved to varied degrees as a result of the formation of high
ionic conductivity phases and the positive effect of halogen ions in providing charge
ii
carriers and creating transport channels. Unfortunately, air stability has not
significantly improved.
Date of Award | 10 Dec 2024 |
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Original language | English |
Awarding Institution |
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Supervisor | Simon R Hall (Supervisor) & Jonathan Clayden (Supervisor) |