FUNctionalized POLYmer electrolytes for energy STORagE

Project Information

FUN POLYSTORE

Grant agreement ID: 771777

DOI

10.3030/771777

Project closed

EC signature date 27 April 2018

Start date 1 September 2018

End date 31 August 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 950 732,00

EU contribution

€ 1 950 732,00

Coordinated by

UPPSALA UNIVERSITET
Sweden

Periodic Reporting for period 4 - FUN POLYSTORE (FUNctionalized POLYmer electrolytes for energy STORagE)

Reporting period: 2023-03-01 to 2024-08-31

Summary of the context and overall objectives of the project

This ERC CoG project has treated the development of solid polymer electrolytes for different types of batteries, most notably lithium batteries, but also many “next-generation batteries” which might be implemented in the future. Today’s lithium-ion batteries contain liquid electrolytes, which are reactive, contribute to battery ageing and safety issues. Solid polymer electrolytes are by comparison more safe, and can also lead to implementation of novel electrode materials that can make the energy content higher. This would mean, for example, electric vehicles with longer driving range and generally are more versatile electrification.

The problem is that the electrochemical performance of polymer electrolytes is not good enough. In particular, the ions of the salt are not transported as fast in polymers as they are in liquids. This project has explored one in this context understudied category of polymers as host materials: polycarbonate and polyesters. These have the possibility to surpass other polymer materials (i.e. polyethers), which have been dominating scientific literature until today. One major advantage is that polycarbonates and polyesters can be chemically tailored in a straightforward way, thereby more easily rendering improved properties.

The project has thereby strived to make novel such polymers, make electrolytes from them, and implement these in novel battery devices. To successfully achieve this, improved scientific understanding needs to be achieved regarding how they work, e.g. by combining insights from computational modelling and experiments.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Different polymeric materials have been synthesized and employed as electrolytes in batteries. These range from very flexible polymers to robust polymers. Also different types of salts have been employed to different concentrations, and both lithium- and sodium-based batteries have been fabricated. The materials have also been investigated through different computer simulations in order to understand ionic transport and how the materials react with the battery electrodes.

The main results show that the combination of polyesters and polycarbonates is powerful for achieving well functional polymer electrolytes. Especially are they good at conducting the positive ion, e.g. lithium and sodium, which is important for their functionality with metal electrodes, and thereby with batteries with high energy density. It is also shown that these materials can be tailored to work with a number of different electrode materials, but that care needs to be taken to chemically modify them further so that the do not decompose during operation. Strategies involve for example using novel salt, additives, and chemical modification to the polymers. More mechanically robust polymers have been constructed, which affect the lifetime of the battery in a positive way. Especially promising results were obtained with a specific type of ceramic particle inserted into the polymer electrolyte.

One of the key achievements in the project was to scientifically explore how ions are actually conducted in the polymer matrix, and which properties that are decisive for rendering an effective ionic transport. This varies with the binding strength of the ion to the polymer, how positive and negative ionic movements are correlated to each other, polymer flexibility and the structural design of the polymer design. This give design implementations for the next generation of polymer electrolyte materials.

While the project has discovered many of the reasons for both successful implementation of these materials in batteries, it has also revealed several fundamental short-comings. This, however, provides a good starting point for chemically solving these problems in the future.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The most vital progress within the current project period has been the improved understanding of both stability and ionic transport in these materials, which are also the key properties of any battery electrolyte. By exploring these properties, the possibility of exploiting these novel polymer electrolyte materials in different battery applications have been understood. Specific examples of where the research has moved beyond current state-of-the-art include:
- Degradation pathways of polymers on Li-metal, and novel methods to explore these properties.
- Novel methods for realistically investigating the decomposition of polymer electrolytes with different types of battery cathodes.
- Ideal salt concentration for high sodium-ion conductivity and for electrochemical stability on both anodes and cathodes
- Novel additives and co-salts which improve battery performance
- The relationship between polymer flexibility, polymer structure and ionic transport
- Strategies to decrease interfacial resistances in solid-state batteries
- Mechanically strengthened but yet highly conductive polymers through block-copolymer strategies and cross-linked materials
- The role of polymer polarity for improved ionic transport through ion-ion correlations.
- The utilization of specific ceramic fillers to improve the performance of polymer electrolytes.
- The potential of a novel type of polymer host: polyketones.

The expectation is to exploit these newly obtained findings into the design of new and improved materials.

Schematic of the materials involved in the project, and key properties explored.