A team led by Professor Cheong Ying Chan at Hong Kong University Of Science And Technology (HKUST) Energy Institute, has proposed a novel cathode design concept for lithium-sulfur (Li-S) battery that substantially improves the performance of this kind of promising next-generation battery. A paper on their work is published in the journal Nature Nanotechnology.

The cathode is composed of uniformly embedded ZnS nanoparticles and Co–N–C single-atom catalyst to form double-end binding sites inside a highly oriented macroporous host, which can effectively immobilize and catalytically convert polysulfide intermediates during cycling, thus eliminating the shuttle effect and lithium metal corrosion.

The ordered macropores enhance ionic transport under high sulfur loading by forming sufficient triple-phase boundaries between catalyst, conductive support and electrolyte. This design prevents the formation of inactive sulfur (dead sulfur).

Our cathode structure shows improved performances in a pouch cell configuration under high sulfur loading and lean electrolyte operation. A 1-A-h-level pouch cell with only 100% lithium excess can deliver a cell specific energy of >300 W h kg⁻¹ with a Coulombic efficiency >95% for 80 cycles.

—Zhao et al.

Design strategy of the macroporous host with double-end binding sites. Credit: HKUST

Li-S batteries can potentially offer an energy density of over 500 Wh/kg, significantly better than Li-ion batteries that reach their limit at 300 Wh/kg. The higher energy density means that the approximate 400 km (250 miles) driving range of an electric vehicle powered by Li-ion batteries can be substantially extended to 600-800 km (373 to 497 miles) if powered by Li-S batteries.

While exciting results on Li-S batteries have been achieved by researchers worldwide, there is still a big gap between lab research and commercialization of the technology on an industrial scale. One key issue is the polysulfide shuttle effect of Li-S batteries that causes progressive leakage of active material from the cathode and lithium corrosion, resulting in a short life cycle for the battery. Other challenges include reducing the amount of electrolyte in the battery while maintaining stable battery performance.

To address these issues, Prof. Zhao’s team collaborated with international researchers to propose a cathode design concept that could achieve good Li-S battery performance.

Their highly oriented macroporous host can uniformly accommodate the sulfur while abundant active sites are embedded inside the host to tightly absorb the polysulfide, eliminating the shuttle effect and lithium metal corrosion.

By bringing up a design principle for a sulfur cathode in Li-S batteries, the joint team increased the batteries’ energy density and made a big step towards the industrialization of the batteries.

We are still in the middle of basic research in this field. However, our novel electrode design concept and the associated breakthrough in performance represent a big step towards the practical use of a next-generation battery that is even more powerful and longer-lasting than today’s lithium-ion batteries.

—Prof. Zhao

Team members from HKUST include Prof. Zhao and his current PhD students ZHAO Chen, ZHANG Leicheng, and former PhD student REN Yuxun (2019 graduate). Other collaborators include researchers from Argonne National Laboratory and Stanford University in the US, Xiamen University in Mainland China, and Imam Abdulrahman Bin Faisal University in Saudi Arabia.

Resources

• Zhao, C., Xu, GL., Yu, Z. et al. (2020) “A high-energy and long-cycling lithium–sulfur pouch cell via a macroporous catalytic cathode with double-end binding sites.” Nat. Nanotechnol. doi: 10.1038/s41565-020-00797-w