18-22 July 2016
Hotel Wyndham Grand Axelmannstein, Bad Reichenhall, Germany
Europe/Berlin timezone

Dynamic and Structure of Polymer-Cellulose Composite Electrolyte for Li-ion Battery

19 Jul 2016, 16:50
2h 40m
Hotel Wyndham Grand Axelmannstein, Bad Reichenhall, Germany

Hotel Wyndham Grand Axelmannstein, Bad Reichenhall, Germany

Salzburger Str. 2-6 83453 Bad Reichenhall
Board: 10
Poster Energy storage & transformation Poster Session

Speaker

Mr Pengfei Zhan (Penn State University)

Description

Polymer electrolytes are safer, cleaner, and more flexible than liquid electrolytes that are currently being used in Li batteries. However, polyethylene oxide (PEO) based electrolytes are not stiff enough to prevent dendrite formation, which limits the use of Li metal as an anode. They also do not have high enough conductivity to be practical. In amorphous polymer electrolytes, stiffness and conductivity are inversely related because Li motion is coupled to polymer motion, and any attempt to improve conductivity through faster polymer motion results in decreased stiffness. The crystalline PEO6LiX complex is a tunnel-like polymer/salt structure that promotes fast Li motion. The application is limited because high ion conductivity is only observed with short molecular weight PEO, as the molecular weight increases, growth of crystalline lamellae fold tunnels on themselves and restrict conduction. We show that high aspect ratio nanofillers based on cellulose nanowhiskers promote the formation of tunnel structures. These fillers offer controllable surface chemistry, degree of functionalization and aspect ratio, thus forming an ideal model system. In this work, we fabricate high molecular weight PEO/cellulose nano whiskers nanocomposites. Compared with unfilled electrolytes, room temperature ion conductivity increases up to 1100%. With wide angle x-ray scattering (WAXS), we observe that the structure transitions from amorphous to crystalline as we add cellulose nano whiskers. This is because the interaction between the acidic cellulose surface and polymer chains enhances crystallization. Based on the temperature dependence of conductivity, acidic cellulose nano whiskers reduce the activation energy for Li+ hopping. Using quasi-elastic neutron scattering (QENS), we find that the rotation of PEO6 channels are stabilized when acidic surfaces are present. We believe this is the origin of the low activation energy and high conductivity.

Primary author

Mr Pengfei Zhan (Penn State University)

Co-author

Prof. Janna Maranas (Penn State University)

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