8.3.2 Characterization Techniques
A battery assembly consists of three components: cathode, anode, and electrolyte–
separator. The solid polymer electrolyte (polymer nanocomposite) is sandwiched
between the two electrodes and plays the dual role of both electrolytes (for ion
migration) and separator (for physical separation of electrodes to prevent shortcircuit). Thus, the electrolyte plays a key role during the operation of the battery.
Keeping in mind the desirable device for practical application, there are some
requirements or performance parameters that need to be measured experimentally
in any polymer electrolyte cum separator (Sharma and Thakur 2013).
Fourier Transform Infrared Spectroscopy (FTIR)
The salt dissociation capability of the polymer host plays an important role in
deciding the suitable polymer electrolyte with balanced properties. The polymer
host must have high dissolution capability to boost the salt dissociation into cation
and anion and to fulfill the purpose of the fast ionic conductor. The dissociation
capability of the host polymer is indicated by the presence of the polar group of
polymer (ÀO À , C N À , C ¼ O,) and how strongly it gets coordinated with the
cation. Another important point is the less tendency of the chain reorganization so
that complete polymer chain can effectively participate in separating the cation and
anion. Further, the supportive role is played by the salt in deciding the overall
solvation ability. The salt must have bulky anion as they have low lattice energy
and supports in overcoming the coulombic interaction between ions. The mutual
dissolution ability of the polymer and salt leads to the cation migration via the
segmental motion of the polymer chains. Besides the polymer chain and the salt,
solvent also influences the dissolution ability of all participating species. The solvent
must have high dielectric constant and high dipole moment so that the ion association can be hindered. The overall effect of the three key players is the effective
number of free ion carriers for transport and elimination of the ion pair as they do not
participate in the conduction. So, to achieve the balanced properties, the suitable
combination of the polymer, salt, and solvent is a vital requirement for the fast ionic
conductor. The properties of the individual polymer, salt, and solvent are discussed
in the forthcoming section.
Complex Impedance Spectroscopy (CIS)
As ionic conduction decides the performance of an energy storage system, and ionic
conductivity depends on the molecular weight of the polymer, cation–anion size, and
viscosity of polymer chains. The polymer electrolyte, therefore, must possess high
ionic conductivity and negligible electronic conductivity. As the migration of anions
may affect the battery performance, its migration is avoided during the design of any
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A. Arya and A. L. Sharma
A battery assembly consists of three components: cathode, anode, and electrolyte–
separator. The solid polymer electrolyte (polymer nanocomposite) is sandwiched
between the two electrodes and plays the dual role of both electrolytes (for ion
migration) and separator (for physical separation of electrodes to prevent shortcircuit). Thus, the electrolyte plays a key role during the operation of the battery.
Keeping in mind the desirable device for practical application, there are some
requirements or performance parameters that need to be measured experimentally
in any polymer electrolyte cum separator (Sharma and Thakur 2013).
Fourier Transform Infrared Spectroscopy (FTIR)
The salt dissociation capability of the polymer host plays an important role in
deciding the suitable polymer electrolyte with balanced properties. The polymer
host must have high dissolution capability to boost the salt dissociation into cation
and anion and to fulfill the purpose of the fast ionic conductor. The dissociation
capability of the host polymer is indicated by the presence of the polar group of
polymer (ÀO À , C N À , C ¼ O,) and how strongly it gets coordinated with the
cation. Another important point is the less tendency of the chain reorganization so
that complete polymer chain can effectively participate in separating the cation and
anion. Further, the supportive role is played by the salt in deciding the overall
solvation ability. The salt must have bulky anion as they have low lattice energy
and supports in overcoming the coulombic interaction between ions. The mutual
dissolution ability of the polymer and salt leads to the cation migration via the
segmental motion of the polymer chains. Besides the polymer chain and the salt,
solvent also influences the dissolution ability of all participating species. The solvent
must have high dielectric constant and high dipole moment so that the ion association can be hindered. The overall effect of the three key players is the effective
number of free ion carriers for transport and elimination of the ion pair as they do not
participate in the conduction. So, to achieve the balanced properties, the suitable
combination of the polymer, salt, and solvent is a vital requirement for the fast ionic
conductor. The properties of the individual polymer, salt, and solvent are discussed
in the forthcoming section.
Complex Impedance Spectroscopy (CIS)
As ionic conduction decides the performance of an energy storage system, and ionic
conductivity depends on the molecular weight of the polymer, cation–anion size, and
viscosity of polymer chains. The polymer electrolyte, therefore, must possess high
ionic conductivity and negligible electronic conductivity. As the migration of anions
may affect the battery performance, its migration is avoided during the design of any
276
A. Arya and A. L. Sharma