Research Projects

In this proposal, we aim to develop crystalline coordination networks (CNs) with single and mixed organic linkers, enabling post-synthetic modifications to achieve new solid-state electrolytes. Our initial strategy involves synthesizing CN-1 using the linker 1H-imidazole-2-carbaldehyde (L1) with Zn²⁺ as inorganic node via a solvothermal method. This network, CN-1, will be chemically modified into two versions, CN-1' and CN-1", by transforming the aldehyde linker to distinct functional groups. Specifically, CN-1’s aldehyde group will be reduced to an alcohol in CN-1' and converted to an imine with alkanolamine in CN-1". Additionally, a mixed-linker approach will be employed to synthesize CN-2 using L1 and imidazole (L2) linkers with Zn²⁺ ion, followed by solvent-assisted linker exchange (SALE) to incorporate bulkier linkers such as benzimidazole. This linker incorporation distorts the crystalline packing, encouraging a phase transition toward a glassy state suited for electrolyte purpose. A major goal is to graft polyethylene oxide (PEO) chains onto the alcohol-based linkers of CN-1' and CN-1", using established organic transformation methods. Various PEO chain lengths (PEO-3, PEO-6, PEO-9) will be attached to increase binding sites for Na⁺ and K⁺ ions, thereby enhancing ion accommodation and mobility. These PEO-modified networks (CN-1'-PEO) will form the basis of solid-state electrolytes, with Na⁺ or K⁺ ions anchored in the PEO chains. To achieve optimal ion incorporation, we will explore sodium and potassium salts, such as NaPF6, KPF6, NaTFSI, KTFSI, NaFSI, and KFSI. To further boost ion conductivity, we aim to transform these modified crystalline networks into glassy or amorphous phases using two techniques: 1. Melt-quenching process: Heating the crystalline CNs to their melting temperature and rapidly cooling to achieve a glassy phase. 2. Mechanochemical ball milling method: Using ball milling to convert crystalline CNs into an amorphous state. These methods will produce glassy phases that retain short-range structural order but lack long-range order, thereby reducing grain boundaries that typically hinder ion conduction. Some CNs (such as, ZIFs) are known to form stable liquid states upon melting and can transform into glass upon rapid cooling; we plan to exploit this behavior to convert crystalline CN-1'-PEO and CN-1"-PEO into superionic glassy electrolytes. The proposed glassy electrolytes are also designed to enhance electrode-electrolyte contact, providing a smooth interface that minimizes issues such as internal resistance, limited ion mobility, and thermal instability. Improved contact is expected to raise conductivity, stability, and battery lifespan, positioning these glassy electrolytes as promising candidates for advanced Na⁺ and K⁺ solid-state battery applications without the need for additives or fillers.