Sodium Ion Conductivity in Superionic IL-Impregnated Metal-Organic Frameworks: Enhancing Stability Through Structural Disorder

Abstract: Metal-organic frameworks (MOFs) are intriguing host materials in composite electrolytes due to their ability for tailoring host-guest interactions by chemical tuning of the MOF backbone. Here, we introduce particularly high sodium ion conductivity into the zeolitic imidazolate framework ZIF-8 by impregnation with the sodium-salt-containing ionic liquid (IL) (Na0.1EMIM0.9)TFSI. We demonstrate an ionic conductivity exceeding 2 × 10−4 S · cm−1 at room temperature, with an activation energy as low as 0.26 eV, i.e., the highest reported performance for room temperature Na+-related ion conduction in MOF-based composite electrolytes to date. Partial amorphization of the ZIF-backbone by ball-milling results in significant enhancement of the composite stability towards exposure to ambient conditions, up to 20 days. While the introduction of network disorder decelerates IL exudation and interactions with ambient contaminants, the ion conductivity is only marginally affected, decreasing with decreasing crystallinity but still maintaining superionic behavior. This highlights the general importance of 3D networks of interconnected pores for efficient ion conduction in MOF/IL blends, whereas pore symmetry is a less stringent condition

Designing Cathodes and Cathode Active Materials for Solid State Batteries

Solid state batteries SSBs currently attract great attention as a potentially safe electrochemical high energy storage concept. However, several issues still prevent SSBs from outperforming today s lithium ion batteries based on liquid electrolytes. One major challenge is related to the design of cathode active materials CAMs that are compatible with the superionic solid electrolytes SEs of interest. This perspective, gives a brief overview of the required properties and possible challenges for inorganic CAMs employed in SSBs, and describes state of the art solutions. In particular, the issue of tailoring CAMs is structured into challenges arising on the cathode , particle , and interface level, related to microstructural, chemo mechanical, and electro chemical interplay of CAMs with SEs, and finally guidelines for future CAM development for SSBs are propose

Metal hydrides for concentrating solar thermal power energy storage

The development of alternative methods for thermal energy storage is important for improving the efficiency and decreasing the cost for Concentrating Solar-thermal Power (CSP). We focus on the underlying technology that allows metal hydrides to function as Thermal Energy Storage (TES) systems and highlight the current state-of-the-art materials that can operate at temperatures as low as room-temperature and as high as 1100 oC. The potential of metal hydrides for thermal storage is explored while current knowledge gaps about hydride properties, such as hydride thermodynamics, intrinsic kinetics and cyclic stability, are identified. The engineering challenges associated with utilising metal hydrides for high-temperature thermal energy storage are also addressed