Rice University Researchers Synthesize Flexible MOF Electrolyte for Solid-State Lithium Batteries

Researchers at Rice University have synthesized a flexible metal-organic framework designed to serve as a solid electrolyte for lithium batteries, addressing a persistent mechanical mismatch between rigid solid electrolytes and lithium-metal electrodes. The study, published in the journal Chemical Science and reported by TechXplore (https://techxplore.com/news/2026-09-soft-material-lithium-ions-solid.html), introduces a zinc-based framework named ZnBTCA that combines structural adaptability with high lithium selectivity.

Solid-state batteries replace volatile liquid electrolytes with solid ion conductors to improve thermal stability and energy density. However, conventional solid electrolytes and many metal-organic frameworks (MOFs) rely on rigid aromatic linkers, creating stiff crystalline structures that struggle to maintain conformal contact with expanding and contracting electrodes during charge-discharge cycling.

To improve mechanical compliance, the Rice team—spanning the departments of Chemical and Biomolecular Engineering, Chemistry, Materials Science and Nanoengineering, and the Rice Advanced Materials Institute—built ZnBTCA using a flexible aliphatic linker containing an open carbon-chain backbone. The resulting anionic framework is softer than rigid MOF counterparts and carries an intrinsic negative charge that promotes the selective transport of positively charged lithium ions.

After replacing initial sodium ions within the framework with lithium, the researchers observed that lithium ions accounted for approximately 95% of the mobile charge-balancing ions while preserving framework integrity. Subsequent measurements indicated that lithium ions carried about 79% of the total ionic current through the material.

To assess resistance against dendrite-induced electrical failure, the team incorporated ZnBTCA into a solid electrolyte membrane positioned between two lithium-metal electrodes. Under progressively increased current densities, the test cells maintained stable operation for nearly 300 hours without short-circuiting under the tested conditions.

"MOF electrolytes are often designed primarily around how effectively they transport ions," said lead author Zina Deriche, a graduate student at Rice. "Here, we're showing that the mechanical properties of the framework can also be an important part of the design." Sibani Lisa Biswal, chair of chemical and biomolecular engineering at Rice, noted that ZnBTCA represents the first known MOF electrolyte constructed from an aliphatic linker with a flexible carbon-chain backbone, establishing mechanical elasticity as a viable tuning parameter alongside chemical composition and pore architecture.