Mechanistic insight into the improved Li ion conductivity of solid polymer electrolytes

Polymer based solid electrolytes (SEs) are envisaged as futuristic components of safer solid state energy devices. But the semi-crystalline nature and slow dynamics of the host polymer matrix are found to hamper the ion transport through the solid polymer network and hence solid state devices are st...

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Bibliographic Details
Published in:RSC advances 2019-11, Vol.9 (66), p.38646-38657
Main Authors: Patra, Sudeshna, Thakur, Pallavi, Soman, Bhaskar, Puthirath, Anand B, Ajayan, Pulickel M, Mogurampelly, Santosh, Karthik Chethan, V, Narayanan, Tharangattu N
Format: Article
Language:English
Subjects:
Chain dynamics
Chemistry
Dipoles
Electrolytes
Ion currents
Ion pairs
Ion transport
Ions
Molecular dynamics
Molten salt electrolytes
Polydimethylsiloxane
Polyethylene oxide
Polymers
Silicone resins
Solid electrolytes
Solid state devices
Thermomechanical analysis
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Summary:Polymer based solid electrolytes (SEs) are envisaged as futuristic components of safer solid state energy devices. But the semi-crystalline nature and slow dynamics of the host polymer matrix are found to hamper the ion transport through the solid polymer network and hence solid state devices are still far beyond the scope of practical application. In this study, we unravel the synergistic roles of Li salt (LiClO 4 ) and two different polymers - polyethylene oxide (PEO) and polydimethyl siloxane (PDMS), in the Li ion transport through their solid blend based electrolyte. A detailed study using dielectric spectroscopy and thermo-mechanical analysis is conducted to understand the tunability of the PEO chain dynamics with LiClO 4 and the mechanism of hopping of Li ions by forming ion pairs with oxygen dipoles on the PEO backbone is established. Despite the lack of PDMS's capability to solvate ions and promote ion transport directly, its proper mixing within the PEO host matrix is demonstrated to enhance ion transport due to the influence of PDMS on the segmental dynamics of PEO. A detailed molecular dynamics study supported by experimental validation suggests that even inert polymers can affect the dynamics of the active host matrix and increase ion transport, leading to next generation high ionic conductivity solid matrices, and opens new avenues in designing polymer based transparent electrolytes. The studies shown here prove that both the Li salt and 'inert-polymer' mixing have paramount importance in the tunability of Li ion conductivity in solid electrolytes for batteries.
ISSN:2046-2069
2046-2069
DOI:10.1039/c9ra08003a