الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
A lack of suitable energy storage technologies is
arguably the most significant impediment to a modern
sustainable energy infrastructure. The storage of chemical
energy, in the form of batteries, is a clear solution to the
problem. But, modern battery technologies today fail to
meet the required metrics for the full electric grid and / or
the role of an electric vehicle. There are significent efforts
by scientists and engineers in the follow up and study of
chemicals to find batteries able, in theory, to outperform
current technologies and avoid their safety issues and all
shortcomings on it like Li-ion cells. For instance,
magnesium ion batteries are thought to be a possible
replacement to existing Li-based systems becouse of the
high abundance of the elements (Mg is the fifth-most
abundant metal on earth), which are non-toxic and do not
degrade in air. Magnesium/sulfur (Mg/S) batteries
represent a very promising technology for these
applications because, in theory, they have a higher
theoretical volumetric capacity than lithium/sulfur (Li/S)
batteries (2062 vs 3832 mAh cm-3
) because of the divalent
nature of Mg2+
. Most importantly, magnesium does not
form dendrites through deposition/stripping process, that is
attributed to be the major cause for the safety issue in
lithium ion battery and rechargeable lithium battery.
However, there are two challenges obstructing the
commercial application of the MgS battery, low electronic
conductivity of sulfur (S) and formation of magnesium
polysulfide species that dissolve into the electrolyte during
cycling. Another challenge, the creation of a suitable
electrolyte that does not interact with the magnesium
anode causing non conducting passivation layers on the
surface of Mg which prevents reversibility of the reaction.
To address these issues, the following hypotheses are
proposed for this study:
1. The sulfur (S) is mixed with the carbon (C) to form a
cathode composite with high electronic conductivity.
2. Synthesis and characterisation of polyvinylidene fluoride/
magnesium trifloromethan sulfonate polymer electrolyte
and evaluate its performance with MgS battery.
3. Synthesis and characterisation of halogen free electrolyte
(HFE) with different concentration of succininitrile
(HFE_SN) and evaluate its performance with MgS battery.
4. Introduction of DMSO on the optimised sample of
HFE_SN as a trial to change the interfacial structure at the
Mg anode surface and facilitates the transport of Mg-ions.
The present thesis consists of 6 chapters
Chapter 1 gives the overview of fossil fuels, energy
storage systems, batteries as energy storage system, type of
battery, history of battery, a secondary battery, magnesium
rechargeable battery, next-generation
batteries, magnesium/sulfur battery, halogen free
electrolyte (HFE), and battery characteristics.
Chapter 2 gives literature surveys for the previous works
in this field.
Chapter 3 contains the description of the materials used in
this thesis and its physical and chemical properties as well
as principles, instrumentations and analytical methods
employed in the present study. The physicochemical
techniques employed were scanning electron microscopy
(SEM), X-ray diffractometer (XRD), energy dispersive Xray analysis (EDS), fourier transform infrared
spectroscopy (FTIR), uv-visible absorption spectroscopy
(UV), thermogravimetry analysis (TGA), electrochemical
impedance spectroscopy (EIS), cyclic voltammetry (CV),
and galvanostatic charge-discharge.
Part one of chapter 4, is an attempt of studying synthesis
and characterisation of polyvinylidene fluoride/magnesium
triflate polymer electrolyte for magnesium/sulfur battery
application. Magnesium-ion conducting polymer
electrolytes (PE) based on polyvinylidene fluoride
(PVDF), tetraethylene glycol dimethyl ether (TEGDME)
and SN with magnesium triflate (CF3SO3)2Mg salt was
synthesised by solution casting method. Fourier-transform
infrared spectroscopy (FTIR) shows a composite between
the polymer and the (CF3SO3)2Mg salt forms. X-ray
diffraction (XRD) data reveals that the broad reflections of
the PVDF polymer are reduced with the addition of
(CF3SO3)2Mg, with scanning electron microscopy (SEM)
illustrating changes in the morphology. The ionic
conductivity found to be 2.9x10-5
S cm-1
at room
temperature (RT) and the ionic transfer number ݐశమ= 0.4
and 0.8 at RT and 55 oC, respectively. The assembled MgS
prototype cell with this polymer electrolyte (PE) delivered
very low initial charge and discharge capacity. Protection
layer on the surface of Mg anode and dual electrolyte
introduced to improve the electrochemical performances of
MgS cell.
Part two of chapter 4, is an attempt to studying the role of
succinonitrile (SN) in optimizing the electrochemical
performance of a halogen-free electrolyte (HFE_SN) that
is based on magnesium nitrate (Mg(NO3)2), TEGDME and
Mg(CF3SO3)2 with different concentration of SN.
Introducing a small amount of SN increased the ionic
conductivity values 2.8×10-5
S. cm-1
and ionic
transference number ݐశమ= 0.8 and 0.9 at RT and 55 oC,
respectively of HFE. Low content of SN results in
electrolyte with low overpotential and high stable Mg
stripping/plating. The MgS cell prototype with this
electrolyte delivered a high initial discharge/charge
capacity with concise cycle life. The concept of protecting
the surface of Mg anode with organic and inorganic
interface relatively increases the cycle life of the MgS cell.
Part three of chapter 4, is an attempt to change the
interfacial structure at the Mg anode surface and facilitate
the transport of Mg-ions by introducing different
concentrations of dimethyl sulfoxide (DMSO) on the
optimized sample of HFE_SN (L1). The as-prepared
electrolyte shows high conductivity (b= 4.48 ×10-5
, 6.52
×10-5
and 9.41 ×10-5
S. cm-1
at 303, 323, and 343 K,
respectively) and high ionic transference number ( ݐశమ =
0.91/0.94 at room temperature/55 ºC), for the matrix
containing 0.75 ml of DMSO. Also, the cell with 0.75 ml
of DMSO shows high oxidation stability, very low
overpotential and steady Mg stripping/plating up to 100 h.
Postmortem analysis of magnesium electrodes at different
electrochemical states reveals the role of DMSO in
[
improving Mg-ion passage through HFE by evolving the
anode/electrolyte interface at the Mg surface improving
Mg-ion passage through HFE by evolving the
anode/electrolyte interface at the Mg surface. This
electrolyte is expected to achieve excellent performance
and good cycle stability when applied in the magnesium
battery in future work.