Lithium-metal batteries are attractive for next-generation energy storage because lithium metal offers a very high theoretical capacity. When paired with high-nickel cathodes such as NCM90, they have the potential to achieve high energy density. However, operating such batteries at high charge and discharge rates presents challenges on both sides of the cell.
At the lithium-metal anode, uneven lithium-ion transport can cause non-uniform lithium deposition and the growth of needle-like dendrites. These structures can damage the solid electrolyte interphase (SEI), continuously consume active lithium and electrolyte, and, in severe cases, penetrate the separator and cause internal short circuits.
Separator engineering has therefore been widely investigated as a way to regulate lithium deposition and stabilize lithium-metal anodes. In the present study, however, researchers found that modifying the separator produced an important additional effect: it substantially enhanced the high-rate performance of the cathode on the opposite side of the cell.
To achieve this, researchers led by Professor Sun-Yul Ryou at the Department of Chemical and Biological Engineering, Hanbat National University, Republic of Korea, developed a cellulose-based separator infused with bikitaite zeolite, called CBT. The separator combines the porous structure of cellulose with the ion-transport properties of bikitaite, forming interconnected pathways for lithium-ion movement.
This paper was made available online on May 28, 2026, and was published in Volume 36, Issue 54 of the journal Advanced Functional Materials on July 6, 2026.
The CBT separator exhibited an ionic conductivity of 3.45 × 10⁻³ S cm⁻¹ and a lithium-ion transference number of 0.742. These properties enabled rapid and more uniform lithium-ion transport through the separator, reducing polarization and facilitating electrochemical reactions under demanding high-rate conditions.
“Our results show that battery performance can be improved not only through new cathode and anode materials, but also through separator engineering. 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,” explains Prof. Ryou.
This effect became increasingly evident as the discharge rate increased. At 1C, cells with the CBT and conventional polyethylene separators both delivered approximately 197 mAh g⁻¹. At 2C, the capacities were 187 and 165 mAh g⁻¹, respectively. At 4C, the difference widened substantially: the NCM90 cathode delivered 163 mAh g⁻¹ with CBT compared to 115 mAh g⁻¹ with the conventional separator, corresponding to an improvement of approximately 42%.
At the same time, the separator retained the benefits traditionally sought from separator engineering on the lithium-metal side. Real-time observation of lithium deposition showed no visible dendrite growth in cells equipped with CBT. Instead, lithium formed a smoother, more compact layer and was removed more uniformly during stripping.
The improved ion transport and interfacial stability also translated into long-term electrochemical performance. In Li||NCM90 cells operated under demanding 2C charge and 4C discharge conditions, cells using CBT retained approximately 60% of their capacity after around 2,500 cycles. The cells also retained approximately 68.9% of their initial capacity after 150 cycles at −25 °C. In addition, the CBT separator maintained its structural integrity at 200 °C.
Beyond its electrochemical performance, separator engineering may offer practical advantages for future battery development. Developing entirely new cathode or anode materials often requires substantial changes in material synthesis, electrode processing, scale-up, and manufacturing. In contrast, functional separator modification is already used in commercial battery manufacturing, for example, in ceramic-coated separators.
The present work does not yet demonstrate commercial-scale manufacturing, and further validation in larger cell formats such as pouch or cylindrical cells will be required. Nevertheless, the findings suggest that introducing ion-transport-regulating functionality into the separator could provide a relatively practical route to improving battery performance without changing the fundamental cathode and anode chemistry.
“Functional separators should not be viewed only as barriers that separate the two electrodes or as a means of protecting the lithium-metal anode. By controlling ion transport across the cell, they could become an important design element for simultaneously achieving high energy density and high-rate operation in next-generation batteries,” concludes Prof. Ryou.
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Reference
Title of original paper: Fast Charge–Discharge of LiNi 0.9 Co 0.05 Mn 0.05 Enabled by a Bikitaite-Infused Separator for Li Metal Batteries
Journal: Advanced Functional Materials
DOI: https://doi.org/10.1002/adfm.75036
About Hanbat National University (HBNU)
Hanbat National University (HBNU) is a public university in Daejeon, South Korea, with origins dating back to 1927 as the Hongseong Public High School of Engineering Training. Renamed Hanbat National University in 2023, it has built a strong reputation for engineering, technology, and industry–academia collaboration. The university is recognized for its extensive partnerships with industry and its role in advancing innovation through applied research and technology transfer. HBNU has been selected for several major national higher education initiatives, including industry–academic cooperation and university innovation programs. Guided by its vision of becoming a "Global Standard University of Industrial Innovation," HBNU aims to strengthen its international competitiveness.
https://www.hanbat.ac.kr/eng/
About Professor Sun-Yul Ryou from Hanbat National University
Dr. Sun-Yul Ryou is a Professor in the Department of Chemical and Biological Engineering at Hanbat National University, Republic of Korea. He received his B.S. and Ph.D. degrees from KAIST and conducted postdoctoral research at the University of Münster, Germany. His research focuses on advanced rechargeable batteries, including lithium-metal and silicon anodes, functional separators, electrode materials, and interfacial engineering. He has published more than 120 SCI(E)-indexed papers, with an h-index of 50, and has extensive research experience in materials and interface design for next-generation rechargeable batteries.
Advanced Functional Materials
Experimental study
Not applicable
Fast Charge–Discharge of LiNi0.9Co0.05Mn0.05 Enabled by a Bikitaite-Infused Separator for Li Metal Batteries
6-Jul-2026
The authors declare no conflicts of interest.