XRD is a facile and basic analytical technique mainly employed to investigate the crystal
structures and phases of materials. There is characteristic relationship between the
wavelength and spacing of the crystal, and Bragg’s law (2dsinθ = nλ) is employed to describe the diffraction from planes with spacing d, where θ is the angle of incidence with
the lattice planes, d is the distance between lattice planes, n is any integer, and λ is the X-ray
wavelength of the beam. In this thesis, A GBC MMA X-ray generator with Cu Kα radiation
(λ = 1.5406 Å) was hired to detect different Zn electrodes at various states and the powders,
such as ZnS and PVB. The Zn electrode or the powder materials are uniformly stacked on a
disk holder, and the holder is placed on the axis of the diffractometer at an angle θ. The
detector rotates around the diffractometer at the corresponding angle 2θ. The current and
working voltage were set at 40 kV and 25 mA, respectively.
3.4.2 Scanning electron microscopy (SEM)
SEM is one of the most commonly used electron microscopes to observe the microscopic
information of the material. It can use a high energy electron beam to scan and collect
images of the target materials. The electrons can interact with the atoms derive from the
samples surface, producing signals that referring to the sample’s surface composition and
topography. In this thesis, the morphology of various Zn electrodes and other materials was
investigated with the field-emission scanning electron microscope (FE-SEM, JEOL JSM-
7500FA). For the preparation Zn electrode samples, Zn electrode would be directly pasted
onto an aluminium holder with black conductive carbon tape or placed in the special cross-
section holder.
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The atomic force microscope (AFM) is one kind of scanning probe microscopes (SPM) and
they are designed to measure local properties, such as height, friction, magnetism, with a
probe. To acquire an image, the SPM raster-scans the probe over a small area of the sample,
measuring the local property simultaneously. In this thesis, a commercial AFM (Asylum
Research MFP-3D) was used to measure the morphology and thickness of the SBS
nanosheets in trapping mode. An Al coated n-silicon probe with resonance frequency of 204-
497 kHz and force constant of 10-130 N m−1 was used in the AFM measurements.
3.4.5 Raman Spectroscopy
Raman spectroscopy as a common spectroscopic technique can observe rotational,
vibrational, and low-frequency modes. Laser light can shift up and down when it interacts
with phonons molecular vibrations, or other kind excitations. The diffenert enegy indicates
information on the vibrational modes, and these vibrational information can suggeste the
chemical bonds and symmetry of molecules. In this thesis, Raman spectroscopy (Jobin Yvon
HR800) employing a 10 mW helium/neon laser at 632.8 nm and Raman spectra of the
targets samples were captured via mapping.
3.4.6 Fourier-transform infrared spectroscopy (FTIR)
FTIR is a useful tool to investigate the infrared spectrum of adsorption or emission from
solid, liquid, or gas. Specially, it can gather high-spectral-resolution signals over a wide
spectral range. Therefore, it would offer significantly wider information than a dispersive
spectrometer. In this thesis, FTIR maps of the interphase between PVB protected Zn
electrode and electrolyte were collected using a PerkinElmer Spotlight 400 equipped with a
mercury cadmium tellurium (MCT) detector, which consists of single point (point mode) and
16-array (image mode) detectors all in one. Maps of 2 × 8 points (~200 × 100 μm2 area) in
reflectance mode were acquired at 4 cm−1 resolution with 16 scans per pixel from 4000 to 400 cm−1. The drop down average true range is determined by a Ge crystal 100 µm in
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diameter. Principal component analysis is one of the most widely used methods for data
reduction and exploratory analysis. In this work, PCA analyses of the selected FTIR regions
corresponding to the 400−4000 cm−1 range were obtained to reveal the uniformity of the functional groups and SEI layer.
3.4.7 X-ray Photoelectron Spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) is kind of a surface-sensitive quantitative
spectroscopic technique. It primarily used to investigate the empirical formula, elemental
composition, chemical states and electronic states of the elements in target material. When it
is underworking, a beam of X-rays is used to interact with the material, and then numbers of
electrons and the kinetic energy produced from the top surface of the material (0−10 nm) are
monitored simultaneously, which could result in the XPS spectrums. In this thesis work, the
XPS analysis of PVB and ZnS layers or Zn electrodes were carried out to characterize the
chemical bonds in samples. These XPS analysis were conducted on a VG Scientific
ESCALAB 2201XL system with aluminium Kα X-ray radiation.
3.4.8. Operando synchrotron XRD
XRD is a useful tool to study the phase structure as mentioned in 3.4.1. The reaction
mechanism of the electrode during cycling is very important to help understand the volume
changes, phase transitions, and structural stability. Ex-situ XRD could be used to study the
discharge or charge products, although the possibly exposure to the air and the uncertain
phase stability of the electrode may lead to unreliable results. In terms of these concerns, in-
operando measurements are an effective tool which reflects the phase transitions in real time during cycling. In this thesis work, a customized CR2032 coin cell was assembled for
conducting the operando synchrotron XRD experiments, and the details of cell assembly can
be found elsewhere. The operando synchrotron XRD experiments of the hybrid Zn batteries
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wavelength of synchrotron radiation was determined to be 0.68899 Å using LaB6 (Standard
Reference Material SRM 660b).
3.4.9. Contact angle measurements
The contact angle is the angle, conventionally measured through the liquid, where a liquid–
vapor interface meets a solid surface. It quantifies the wettability of a solid surface by a
liquid via the Young equation. A given system of solid, liquid, and vapor at a given
temperature and pressure has a unique equilibrium contact angle. In this thesis, the contact
angles of different Zn electrodes with electrolyte were measured on Dataphysics OCA15
optical contact angle system with 1 µL of electrolyte for each test at the temperature of 25 °C.