Designing Polyurethane Solid Polymer Electrolytes for High-Temperature Lithium Metal Batteries

Rassmus Andersson,Tony D Flaim,Jennifer See,Jonas Mindemark,Daniel Brandell,Guiomar Hernández

doi:10.1021/acsaem.1c02942

Rassmus Andersson, Tony D Flaim + Show 4 more

Open Access

https://doi.org/10.1021/acsaem.1c02942

Copy DOI

Abstract

Potentially high-performance lithium metal cells in extreme high-temperature electrochemical environments is a challenging but attractive battery concept that requires stable and robust electrolytes to avoid severely limiting lifetimes of the cells. Here, the properties of tailored polyester and polycarbonate diols as the soft segments in polyurethanes are investigated and electrochemically evaluated for use as solid polymer electrolytes in lithium metal batteries. The polyurethanes demonstrate high mechanical stability against deformation at low flow rates and moreover at temperatures up above 100 °C, enabled by the hard urethane segments. The results further indicate transferrable ion transport properties of the pure polymers when incorporated as the soft segments in the polyurethanes, offering designing opportunities of the polyurethane by tuning the soft segment ratio and composition. Long-term electrochemical cycling of polyurethane-containing cells in lithium metal batteries at 80 °C proves the stability at elevated temperatures as well as the compatibility with lithium metal with stable cycling maintained after 2000 cycles.

Highlights

To the increasing demand for high-energydensity Li-ion batteries (LIBs), the need for high-temperature battery operation is likewise on the rise
The key to designing polyurethane solid polymer electrolyte (SPE) with high ionic conductivity is to understand the influence of the soft segment and how it is affecting the transport properties
The choice of soft segment is another factor to consider when designing the polyurethane, as it has been seen that the strength of the interaction between the coordinating groups on the polymer and the cations in the system directly affects the ionic conductivity and transference number (T+), which together describe the ion transport abilities in the system.[17]

Summary

■ INTRODUCTION

To the increasing demand for high-energydensity Li-ion batteries (LIBs), the need for high-temperature battery operation is likewise on the rise. The design of the soft segments in a series of polyurethane and their properties as host materials for SPEs for high-temperature lithium metal batteries have been investigated. The structural influence of the soft segment on the intrinsic ion transport properties and the mechanical stability of the polyurethanes have been investigated along with their temperature dependence. The total ionic conductivity of the polymer electrolyte films was determined by electrochemical impedance spectroscopy (EIS) between the frequencies 1 Hz and 10. The electrolyte films were assembled with stainless steel blocking electrodes in CR2032 coin cells and annealed at 100 °C for 1 h and cooled down to room temperature prior to the experiment to ensure good interfacial contact between the polymer and the stainless-steel electrodes. Galvanostatic cycling tests of the electrolyte films were performed with an ARBIN BT-2043 cycling equipment at 80 °C

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ REFERENCES