HMN 2026: How Single-crystalline electrolyte unlocks safer lithium metal batteries

A research team led by Prof. Yoonseob Kim, Associate Professor of the Department of Chemical and Biological Engineering at The Hong Kong University of Science and Technology (HKUST) has reported a significant breakthrough in lithium metal battery (LMB) technology. The team has successfully synthesized a novel single-crystalline 3D borate covalent organic framework (B-COF), which demonstrates exceptional performance as a solid-state electrolyte, thereby enhancing the performance of solid-state lithium batteries.

This advancement promises safer and higher energy density solutions for electric vehicles and large-scale energy storage. The research paper, titled “Single-Crystalline Borate Covalent Organic Frameworks for Solid-State Lithium Metal Batteries,” has been published in Advanced Science.

Traditional LMBs face safety risks from lithium dendrite formation and rapid degradation due to unstable electrolyte interfaces. While Covalent Organic Frameworks (COFs) are promising electrolyte materials due to their porous structure and stability, most existing COFs are polycrystalline, which leads to significant interparticle resistance and limits their performance.

To address this issue, the research team utilized COF-303 as a template to construct a single-crystalline 3D B-COF with highly ordered ion channels. This single-crystalline nature significantly reduces intergrain resistance and facilitates uniform lithium deposition, effectively suppressing dendrite growth.

This work has achieved exceptional ion conductivity and selectivity: It shows a remarkable ionic conductivity of 8.1 mS cm^–1 at room temperature, with a Li⁺ transference number of 0.98 in a quasi-solid-state, ensuring rapid and selective ion movement. The method also has superior interface stability and safety. Supported stable lithium deposition and stripping for more than 2,000 hours in symmetric cells effectively suppresses hazardous dendrite formation.

The cells also boast high efficiency and long-term durability. Full cells utilizing LiFePO₄ cathodes demonstrate robust cycling with 91.8% capacity retention and 99.98% Coulombic efficiency over 600 cycles at 0.5C, delivering an initial capacity of 147 mAh g^–1.

“Our research highlights the promising viability of single-crystalline 3D B-COFs as quasi-solid-state electrolytes. By eliminating the structural disorders found in polycrystalline materials, we have taken a significant step toward realizing high-performance, safe energy storage solutions that are crucial for a greener future,” said Prof. Yoonseob Kim, co-corresponding author of the study.

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