Moldable, self-healing, highly conductive organic co-crystalline solid electrolytes for safer lithium ion batteries

Non-Technical Summary

For this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, the research groups of Profs. Zdilla and Wunder at Temple University are developing a new class of solid electrolyte separators for lithium-ion batteries. Current lithium-ion battery technology relies on the use of a flammable and potentially explosive liquid electrolyte which has led to battery fires and explosions in mobile devices, electric vehicles, and other applications.

The development of solid, minimally flammable replacements would enhance the safety of these devices. However, many currently investigated solid electrolytes exhibit poor performance or incompatibility with existing battery chemistry. With this award, the principal investigators synthesize and study soft-solid co-crystalline electrolytes (i.e. electrolytes that combine two or more molecular components but form a uniform crystalline structure) to understand the fundamental materials chemistry that could enable higher-power performance and promise compatibility with existing and next-generation battery components.

The researchers also use computational tools to better understand these materials that consist of new combinations of organic framework molecules and lithium-ion sources and characterize their electrochemical properties. The project serves the national interest by developing a fundamental understanding that enables technologies to improve the safety and performance of batteries, an ever-more central component of technology in mobile devices, transportation, and clean energy.

Realization of safe, high-power, high-energy battery technology provides a path toward solar energy storage and decreased use of fossil fuels for transportation, both of which provide greater energy independence for the United States, and a means to decrease carbon footprint for the health of the climate. Further, this research serves to train the next generation of scientists at one of the most diverse schools in the country and serves underrepresented groups with great effect.

Technical Summary.

For this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, the research groups of Profs. Zdilla and Wunder at Temple University develop a new class of solid electrolyte separators for lithium-ion batteries. Progress in battery electrolyte research has been incremental and essentially relegated to modifications of liquid organic systems, solid polymers, and solid ceramics.

The new class of solid electrolytes investigated under this effort has the potential to enable better conductivity than other solid organic electrolytes, while at the same time exhibiting better voltage stability and electrode stability windows than liquids, the current market standard. The researchers investigate the materials’ novel mechanophysical properties from a fundamental research perspective, including a developing a surface liquid layer that facilitates self-healing.

While the concept of a surface liquid-solid equilibrium is known (as in the classic example of water-ice), this property has never been applied to electrolyte materials, and thus represents an opportunity for fundamental insights. The objectives of the research are: 1: Preparation and characterization of ion-matrix cocrystals with optimized conductivity and lithium-ion transference numbers (tLi+).

This is achieved by maximizing the mobility of the cation while minimizing the mobility of the anion, which is achieved by designing matrices that interact strongly with the anion, but not with the cation. 2: Evaluation of electrochemical performance and mechanical/thermal properties. This is achieved using characterization using X-ray diffraction, electrochemical analysis (electrochemical impedance spectroscopy, cyclic voltammetry, linear sweep voltammetry, and cycling studies), thermal analysis (DSC, TGA), and post-mortem analysis by electron microscopy. 3: Modelling the physical properties and mechanism of ion conduction using molecular dynamics and quantum molecular computation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.