Sodium–sulfur batteries retain capacity over 2,500 cycles with new aluminum catalyst

Lithium grabs the spotlight, but cheap and abundant sodium has long held the key to large-scale energy storage. There is just one catch. Sodium–sulfur batteries degrade fast. Now, researchers at the Chinese Academy of Sciences (CAS) have cracked a major hurdle that plagued the technology for years, using a metal found in ordinary soda cans. Led by Profs. Wang Hui and Zheng Fangcai at the High Magnetic Field Laboratory in Hefei, the team successfully re-engineered single-atom aluminum to outperform far pricier rare-earth elements. Researchers have developed an efficient aluminum single-atom catalyst to overcome the performance limitations of main-group metal catalysts in sodium-sulfur (Na–S) batteries. “This created an asymmetric structure with three oxygen atoms and one nitrogen atom around each Al atom,” the team wrote in the press release. “The batteries also maintained stable performance over thousands of charge-discharge cycles, showing good potential for long-lasting sodium–sulfur batteries,” it added. This illustrates the synthesis schematic, structural characterization, electron transfer process during Na2S6 adsorption, and the p–p orbital hybridization interaction between Al single atoms and sodium polysulfides. (Image by ZHENG Fangcai) Breaking the symmetry For a long time, the search for long-lasting batteries focused on precious heavy metals like platinum, cobalt, or nickel. Main-group metals like aluminum were cheaper and non-toxic, but fundamentally lazy catalysts. And simply lacked the catalytic punch to manage sodium polysulfides. These volatile compound intermediates shuttle and dissolve from the cathode, draining battery life. The team found the solution in breaking atomic symmetry. Typically, isolated aluminum single atoms sit comfortably surrounded by four oxygen atoms (Al–O4). The Hefei team plucked out a single oxygen atom and swapped it for a nitrogen atom. That single change created an asymmetric Al–O3N coordination structure. Altering the local electron distribution around the central aluminum atom through a single nitrogen substitution created a strong localized electric charge. This charge promoted intense p-p orbital hybridization between the aluminum sites and the sulfur species within the battery cell. As a result, polysulfide shuttling was effectively suppressed, driving immediate improvements in reaction speed and overall electrochemical stability. Performance testing of the cathode The runaway polysulfides were effectively trapped, preventing material loss, while the internal chemical reactions accelerated sharply. In lab tests, the new aluminum-based cathode demonstrated outstanding energy output and long-term durability. It delivered a high storage capacity of 1,196 mAh g⁻¹ after 100 cycles. And even after 2,500 continuous charge-discharge cycles, its performance dropped by a microscopic 0.017% per cycle. This exceptional stability allows the inexpensive aluminum material to easily outperform much costlier transition metal catalysts. “The findings highlight the importance of the local atomic environment in determining the catalytic activity of single-atom catalysts and offer new possibilities for designing efficient catalysts based on main-group metals,” the researchers stated. As grid operators seek safer, cheaper alternatives to lithium for renewable power storage, adjusting the atomic architecture of abundant elements like aluminum offers a clear, scalable path forward. The study was published in the journal Angewandte Chemie. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.