Researchers Develop Zeolite-Infused Separator to Boost Lithium-Metal Battery Fast-Charging

Researchers at Hanbat National University in South Korea have engineered a novel battery separator that significantly improves high-rate charging and discharging capabilities in lithium-metal batteries. As first reported by TechXplore, the technology utilizes a zeolite-infused cellulose material to streamline ion transport across the cell, enhancing output at both the anode and cathode.

Lithium-metal batteries paired with high-nickel cathodes, such as NCM90, are viewed as promising candidates for next-generation energy storage due to their high theoretical energy capacity. However, widespread commercial deployment has been restricted by uneven lithium-ion movement during rapid charging. This erratic flow causes needle-like dendrites to form on the lithium anode, which degrade internal components, consume active lithium, and risk creating short circuits by puncturing traditional separators.

To solve these structural issues, a research team led by Professor Sun-Yul Ryou in the Department of Chemical and Biological Engineering at Hanbat National University created a composite separator designated as CBT. The component integrates porous cellulose with bikitaite zeolite, establishing interconnected channels that facilitate faster, more uniform lithium-ion movement through the membrane.

Laboratory tests revealed that the CBT separator achieved an ionic conductivity of 3.45 × 10⁻³ S cm⁻¹ and a lithium-ion transference number of 0.742. In addition to suppressing dendrite formation on the anode, the separator notably enhanced electrochemical reactions on the high-nickel NCM90 cathode by minimizing polarization under heavy operational loads.

The functional benefits on the cathode side became increasingly pronounced at higher discharge rates. While both the CBT separator and conventional polyethylene separators delivered approximately 197 mAh g⁻¹ at a 1C rate, their performance diverged as discharge speeds increased. At 2C, CBT-equipped cells produced 187 mAh g⁻¹ compared to 165 mAh g⁻¹ for conventional cells. At a 4C rate, the CBT separator delivered 163 mAh g⁻¹ versus 115 mAh g⁻¹ for standard separators, representing an improvement of roughly 42%.

"Our results show that battery performance can be improved not only through new cathode and anode materials, but also through separator engineering," Ryou said, as reported by TechXplore. "What was particularly interesting was that the effect of the modified separator extended beyond the lithium-metal anode and significantly improved the high-rate performance of the NCM90 cathode."

The CBT separator also demonstrated strong longevity and environmental tolerance. In long-term cycle testing under demanding conditions of 2C charging and 4C discharging, Li||NCM90 cells using the CBT separator retained roughly 60% of their initial capacity after approximately 2,500 cycles. When tested at extreme sub-zero temperatures of −25°C (−13°F), the cells maintained 68.9% capacity after 150 cycles. Thermal stability evaluations showed the separator preserved its structural integrity up to 200°C (392°F).

Focusing on separator engineering offers practical manufacturing advantages over developing entirely new cathode or anode materials. Redesigning active electrode materials typically requires extensive adjustments to chemical synthesis, electrode processing, and industrial scaling. By contrast, modifying separators is already a established practice in commercial battery production, such as the application of ceramic coatings.

The research findings were published in the scientific journal Advanced Functional Materials by lead author Isheunesu Phiri alongside Ryou and co-authors. While the initial study demonstrated performance in laboratory settings, further validation in commercial formats, including pouch and cylindrical cells, will be required before potential industrial deployment. Ryou emphasized that functional separators should be treated as active design elements for managing ion transport across high-energy cells rather than static physical barriers.