From left to right, Sibani Lisa Biswal, Zina Deriche and Stavroula Alina Kampouri.
Photo Credit: Courtesy of Rice University
Scientific Frontline: Extended "At a Glance" Summary: ZnBTCA Metal-Organic Framework
The Core Concept: ZnBTCA is a relatively soft, flexible metal-organic framework (MOF) designed to selectively transport lithium ions within solid-state batteries.
Key Distinction/Mechanism: Unlike many MOF electrolytes built from rigid aromatic linkers, ZnBTCA utilizes a flexible aliphatic linker with a carbon-chain backbone, making the framework mechanically adaptable while its negatively charged structure promotes the efficient movement of positively charged lithium ions.
Major Frameworks/Components:
- Metal-Organic Framework (MOF): A porous crystalline material constructed from metal atoms (zinc) connected by organic molecules.
- Aliphatic Linker: A flexible molecular building block that provides the material's mechanical softness.
- Solid Electrolyte Membrane: The material is incorporated into a membrane to replace flammable liquid electrolytes.
Future Application: ZnBTCA has the potential to improve the safety and energy density of solid-state batteries by maintaining close contact with electrode surfaces and preventing short circuits caused by uneven lithium growth.
Why It Matters: This development demonstrates that mechanical flexibility, alongside chemical composition and pore structure, can be utilized as a critical design tool for improving the performance and viability of solid-state battery technologies.
For solid-state batteries, moving lithium ions efficiently is only part of the challenge—how the material behaves mechanically can matter too.
Rice University researchers in the departments of Chemical and Biomolecular Engineering, Chemistry, and Materials Science and Nanoengineering, and at the Rice Advanced Materials Institute, have developed a relatively soft, flexible material that can selectively transport lithium ions—offering a new approach to porous solid electrolytes that combine efficient ion movement with better mechanical adaptability inside a battery.
The material, called ZnBTCA, is a metal-organic framework, or MOF: a type of porous crystalline material built from metal atoms connected by organic molecules. MOFs contain tiny, ordered channels that can be tailored to move or hold specific molecules and ions, making them attractive candidates for battery electrolytes. Many MOFs explored as battery electrolytes are built from relatively rigid aromatic linkers. ZnBTCA takes a different approach: it uses a flexible aliphatic linker that makes the framework itself softer and more mechanically adaptable. The material is also built from relatively abundant, low-cost components, including zinc and an inexpensive aliphatic linker.
“MOF electrolytes are often designed primarily around how effectively they transport ions,” said first author Zina Deriche, a graduate student in chemical and biomolecular engineering at Rice. “Here, we’re showing that the mechanical properties of the framework can also be an important part of the design.”
Solid-state batteries replace the flammable liquid electrolytes used in conventional lithium-ion batteries with solid materials, potentially improving safety and energy density. For many MOF electrolytes, however, their relatively rigid crystalline structures can make it harder to maintain close contact with electrode surfaces. The challenge is to preserve efficient, selective lithium-ion transport while making the material more mechanically adaptable.
The Rice team designed ZnBTCA with both challenges in mind. Its flexible molecular building blocks make it relatively soft, while its negatively charged structure favors the movement of positively charged lithium ions through its channels.
“What is exciting is that the same material brings together two useful properties,” said Stavroula Alina Kampouri, a corresponding author of the study and assistant professor of chemical and biomolecular engineering, chemistry, and materials science and nanoengineering. “Its flexible building blocks make the framework softer and more adaptable, while its negatively charged structure promotes selective lithium-ion transport. Bringing these properties together gives us a new way to design MOF electrolytes by considering how ions move and how the material behaves mechanically at the same time.”
After exchanging sodium ions in the material for lithium, the researchers found that about 95% of the mobile charge-balancing ions were lithium, while the framework remained structurally intact. Tests also showed that lithium ions carried about 79% of the ionic current through the material.
Short-circuiting is an important concern in lithium-metal batteries, where uneven lithium growth during repeated charging and discharging can eventually create unwanted electrical pathways through the electrolyte. The team incorporated ZnBTCA into a solid electrolyte membrane and placed it between two lithium-metal electrodes. The cells operated stably for nearly 300 hours as the researchers progressively increased the current, with no evidence of short-circuiting under the conditions tested.
The results suggest that mechanical flexibility could become another design tool for researchers developing MOF electrolytes, alongside factors such as chemical composition, pore structure, and charge.
“To our knowledge, ZnBTCA is the first MOF electrolyte built from an aliphatic linker with a flexible carbon-chain backbone,” said Sibani Lisa Biswal, chair of chemical and biomolecular engineering, the William M. McCardell Professor in Chemical Engineering, and professor of materials science and nanoengineering. “What this work shows is that we can think beyond just the chemistry and pore structure of these materials. Mechanical flexibility can also become a design tool for developing MOF electrolytes for solid-state batteries.”
Funding: This research was supported by a GEM Fellowship as well as the National Science Foundation under grant no. 2404376. This work was done in part using resources of the Shared Equipment Authority at Rice.
Published in journal: Chemical Science
Authors: Zina Deriche, Vallabha Rao Rikka, Isaac Metcalf, Ahad Hussain Javed, Satya Prakash Suman, Moneer Alenezi, Aditya Mohite, Sibani Lisa Biswal, and Stavroula Kampouri
Source/Credit: Rice University | Alexandra Becker
Edited by: Scientific Frontline
Reference Number: ms092926_01