Researchers at Hong Kong University of Science and Technology have developed a new material that could solve one of the biggest problems in lithium metal batteries.

The team has created a single-crystalline 3D borate covalent organic framework that works as a solid-state electrolyte, improving both safety and performance.

Lithium metal batteries are seen as the next step beyond current lithium-ion systems, especially for electric vehicles and large-scale energy storage.

But they have struggled with safety issues, mainly due to the formation of lithium dendrites and unstable interfaces that lead to degradation and short circuits.

Covalent organic frameworks have been explored as potential electrolyte materials because of their porous and stable structures.

However, most existing versions are polycrystalline, which creates resistance at grain boundaries and limits how efficiently ions can move through the material.

To overcome this, the team used COF-303 as a template to build a single-crystalline structure with highly ordered ion channels.

This design reduces intergrain resistance and enables more uniform lithium deposition, helping suppress dendrite formation.

The material’s ordered ion pathways also allow more consistent ion flow across the electrolyte, reducing hotspots and uneven reactions. This could help improve battery lifespan under real-world conditions, where repeated charging cycles often lead to performance loss and safety risks.

Breaking dendrite growth barrier

The new material delivers strong electrochemical performance across several key metrics. It achieves an ionic conductivity of 8.1 mS cm−1 at room temperature and a Li+ transference number of 0.98, allowing fast and selective ion transport within the battery.

The system also shows improved stability. Tests demonstrated stable lithium deposition and stripping for more than 2,000 hours in symmetric cells, indicating long-term operational reliability and reduced safety risks.

In full-cell configurations using LiFePO4 cathodes, the batteries maintained 91.8 percent capacity retention over 600 cycles, with a Coulombic efficiency of 99.98 percent.

The cells delivered an initial capacity of 147 mAh g−1, pointing to consistent performance over extended use.

The work highlights how structural control at the material level can directly impact battery performance.

By eliminating the disorder seen in polycrystalline frameworks, the researchers were able to improve both efficiency and safety in lithium metal systems.

Toward safer energy storage

“Our research highlights the promising viability of single-crystalline 3D B-COFs as quasi-solid-state electrolytes,” said Prof. Yoonseob Kim.

“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.”

The research was conducted in collaboration with Shanghai Jiao Tong University, reflecting growing international efforts to advance next-generation battery technologies.

The findings suggest that single-crystalline COFs could play a key role in enabling practical solid-state lithium metal batteries.

If scaled successfully, the approach could help address long-standing limitations in battery design, particularly in applications that demand both high energy density and long-term stability.