Polymer electrolytes

Ion-conducting polymers may be used in place of traditional liquid electrolytes to make solid-state batteries. The solid-state construct effectively eliminates the safety hazard posed by the flammable organic solvents used in liquid-electrolyte cells and offers better high-temperature stability. The biggest challenge with polymer electrolytes is to improve the ionic conductivity of the materials while retaining a high mechanical stability.New host materialsWe work with developing new materials based on ion coordination by carbonyl groups, such as polycarbonates, polyesters and polyethers, to use as host materials in polymer electrolytes. The carbonyl groups offer weaker coordination that, e.g., the commonly utilized oxyethylene coordinating motif, leading to faster Li+movement in the material.

Transport mechanisms

In order to design better host polymers, we need to understand the ion transport mechanisms in detail. We use a combination of experimental (impedance spectroscopy, NMR spectroscopy, IR spectroscopy) and computational (molecular dynamics, DFT) techniques to gain insight into the molecular details of ion coordination and transport. With proper understanding of the phenomena that govern ion movement in the materials, we can also devise strategies to move towards more efficient transport mechanisms.

Movement of a Li+ cation (purple) through a poly(trimethylene carbonate) (PTMC) matrix simulated by molecular dynamics.

Solid-state batteries
The materials we developed are ultimately tested in prototype solid-state battery cells. We test both Li+- and Na+-conducting polymers in Li and Na cells. While one of the aims is to produce materials that allow for battery operation at room temperature, we also try to implement the polymer electrolytes in niches where they have a clear edge over their liquid counterparts, such as in batteries that operate at high temperatures or other extreme conditions.

Cycling of a polycarbonate material in a Na metal cell at 60 °C

Cycling of a polycarbonate material in a Na metal cell at 60 °C

References
Beyond PEO-Alternative host materials for Li+-conducting solid polymer electrolytes. https://uu.diva-portal.org/smash/record.jsf?pid=diva2:1262653

High-performance solid polymer electrolytes for lithium batteries operational at ambient temperature. https://uu.diva-portal.org/smash/record.jsf?pid=diva2:867615

Ion transport in polycarbonate based solid polymer electrolytes: experimental and computational investigations. https://uu.diva-portal.org/smash/record.jsf?pid=diva2:798456

Restricted Ion Transport by Plasticizing Side Chains in Polycarbonate-Based Solid Electrolytes. https://pubs.acs.org/doi/10.1021/acs.macromol.9b01912

Stable Cycling of Sodium Metal All-Solid-State Batteries with Polycarbonate-Based Polymer Electrolytes. https://uu.diva-portal.org/smash/record.jsf?pid=diva2:1354042

Keywords: solid-state batteries, ion transport mechanisms, coordination, molecular dynamics