Advanced Semi-interpenetrating polymer networks (sIPN) for Future High-Voltage Alkali-Metal Batteries

TO-105 • PT 1.2863 - 1.2871 • As of 10/2023
Institute of Energy and Climate Research
Ionics in Energy Storage (IEK-12)

Technology

Our advanced technology introduces new solid electrolytes for alkali metal solid-state batteries. In this context, two recent inventions relate to semi-interpenetrating polymer networks (sIPN), a network family used in high-voltage lithium-based battery cells. Here, the solid electrolyte consists of a continuous polymer matrix with embedded alkali metal ions, which enables flow of electric current. The electrolyte mixtures contain different alkali metal salts and a sIPN composed of a crosslinked and non-crosslinked polymer. Such sIPN networks result in improved stability, conductivity, and galvanostatic cycling performance in alkali-metal based secondary battery cells and related devices.

Problem addressed

Decentralized energy storage faces challenges related to safety, energy density, temperature range, and stability. The use of semi-interpenetrating polymer networks (sIPN) and nanocomposites as separators in alkaline metal batteries shows promise in addressing these issues. They are providing the potential for improved charge and discharge stability and increased energy and power density due to their lower gravimetric density compared to oxide and sulfide-based solid electrolytes. However, compatibility between the polymer electrolytes, alkali metal, and positive electrode material is crucial for successful implementation. Poly(ethylene oxide) (PEO) is a commonly used polymer electrolyte, but it exhibits limitations such as oxidative instability and inhomogeneous lithium-ion transport, as well as lithium dendrite formation when lithium metal anodes are utilized. Improvements are needed to enable the commercial use of solid electrolytes over a wide temperature range and with high-voltage electrodes.

Solution

With our inventions, we aim to overcome drawbacks of existing technology by providing improved charge-discharge stability, enhanced conductivity at low temperatures, and reduced dendrite growth. The solvent-free electrolyte comprising the sIPN structure exhibits excellent electrical and mechanical properties, leading to stable charge-discharge characteristics and increased battery lifespan. Additionally, our electrolytes enable reliable electrical performance even at very low temperatures, expanding the thermal operating window of alkali metal batteries. The second invention particularly uses crosslinked polycarbonates as separators, resulting in significantly improved mechanical stability compared to pure polyethylene oxide (PEO) electrolytes. The combination of crosslinked polycarbonates, non-crosslinked PEO, and a dual salt system leads to enhanced electrical properties and reproducibility in batteries. These improvements allow for extended cycle life and operation in a wider temperature range.

Benefits and Potential Use

The new solid electrolytes are particularly suitable for lithium-based batteries, including Li-metal batteries with high current or high voltage electrodes. Their high mechanical strength and compatibility with demanding electrical conditions make them ideal for such applications. Additionally, these electrolytes can be used in fuel cells or capacitors, further improving electrical contacts. The improved mechanical and electrical properties of the electrolytes contribute to the longevity and efficiency of the batteries. Overall, our inventions offer attractive opportunities for potential licensees in the field of advanced lithium-based battery technologies.

Development Status and Next Steps

Forschungszentrum Jülich has extensive expertise in this field and holds several patents. The technology described above has already been initially verified through prototypes and is continuously being developed further. The Institute of Energy and Climate Research (IEK-12) – Ionics in Energy Storage – already cooperates with numerous national and international companies and scientific partners. Forschungszentrum Jülich focuses on energy and cost-efficient devices, suitable for various emerging technologies. We are continuously seeking for cooperation partners and/or licensees in this and adjacent areas of research and applications.

More technologies