| dc.description.abstract | The present study describes the results on inorganic and organic materials for energy
storage and sensors. It contains eight chapters including introduction, experimental and
summary sections. The first chapter gives a brief overview of energy storage systems, progress
and challenges associated with them along with a few possible solutions to tackle them. The
second chapter explains all the experimental details like chemicals used, syntheses procedures,
instruments used, and various processes and procedures used in this work.
The third chapter demonstrates the ion storage performance of copper phosphosulfide.
As an anode for Li-ion battery, it delivers a high capacity and high cycling stability. The pre activated electrode delivers very high stable capacity. The capacity offered by the
phosphosulfide is higher than that of the corresponding phosphide and sulfide that indicates
the importance of the presence of both P and S in the structure. The mechanism as investigated
by in situ Raman spectroscopy and other ex situ techniques suggest a conversion reaction and
formation of a thick SEI like film on the electrode surface. As prepared material shows good
performance for Mg-ion battery with moderate rate capability. A further improvement in the
capacity and importantly the rate performance is achieved by utilizing a multiwall carbon
nanotube composite. The composite electrode further delivers high cycling stability at high
current rates. Moderate performance is observed for Al-ion battery which may be due to its
high charge to size ratio that makes the insertion / extraction process rather slow.
The fourth chapter utilizes organic carbonyl compounds as electrodes for mono- and
multi-valent metal ion batteries. A layer type, slight off planar polymer is synthesized from
benzoquinone and pyrrole and explored as a universal cathode for Li, Mg, Zn and Al-ion
batteries. Thousands of stable cycles are observed for all these systems even at very high
current rates and show excellent rate performance. For Li-ion battery, the cell performance is
studied at high rates of 10 A g-1 which takes only 22 s to charge and discharge. For Mg-ion
battery, an alternate alloy anode (AZ31) is explored, and 5000 cycles are observed even at a
high current rate of 2 A g-1
. Similarly, for Zn-ion battery, along with good rate performance, a
long-term stability of 20000 cycles is achieved at 2 A g-1
. More importantly, even for a more
difficult Al-ion system, thousands of stable cycles are obtained at high rates of 0.5 and 1 A g-1
with 100% capacity retention. A surface controlled pseudocapacitive contribution to the overall
capacity is responsible for such high performance in all the cases. The off planar geometry is
expected to facilitate ion diffusion process thereby resulting in high rate and high performance.
Ex situ infrared and X-ray photoelectron spectroscopy measurements show functional group
transformation during the ion storage process. Further, an organic dye, vat orange 11 consisting
of three conjugated anthraquinone units is studied for Mg- and Zn-ion batteries. It shows better
performance than that of a single anthraquinone unit highlighting the benefit of conjugation.
Different carbon additives and electrolytes are investigated further to achieve high performance
for Mg-ion battery. A capacity fading is observed for Zn-ion battery due to high solubility of
the dye in the electrolyte.
The fifth chapter explores a few non-nucleophilic electrolytes for Mg-ion batteries with
wide electrochemical stability window. It is observed that Mg(HMDS)2 and AlCl3 in a mixture
of glymes with ionic liquid additive shows high deposition/ dissolution efficiency with low
overpotentials and excellent oxidation stability on a few common substrates. Further, the
electrolyte speciation study is carried out with the help of Raman and 27Al NMR spectroscopy.
A non-aqueous Li-O2 battery is studied using tin phosphosulfide (SnPS3) as air cathode
in the sixth chapter. High cycling performance and low charge-discharge overpotential is
observed for the rGO composite as compared to the pristine material. High electronic
conductivity and high surface area of rGO is believed to enhance the performance and Li2O2 is
obtained as the discharge product.
The seventh chapter investigates the gas sensing applications and photodetection
activity of Cu3PS4. It is very sensitive towards NH3 gas compared to other analyte gases and
can detect as low as 17 ppb with a high response of 160 % for 10 ppm NH3. It shows a fast
response and excellent reversibility under ambient conditions. Good sensing properties for NO2
gas has been observed. Preliminary photodetector studies reveal that the phosphosulfide can be
used for UV-vis photodetection.
The last chapter summarizes the thesis work and gives some future directions to
improve the performance further and design new systems. At the end, two appendixes are given
where an ionic liquid, 1-ethyl-3-vinylimidazoilum bis(fluorosulfonyl)imide (EVImFSI)
containing lithium bis(trifluorosulfonyl)imide (LiTFSI) is used as a wide potential window (~5
V) electrolyte for Li-ion battery and nickel phosphosulfide (NiPS3) is used as electrocatalyst
for electrochemical nitrogen reduction to ammonia (NH3). | en_US |
