Most of the rechargeable batteries found in portable devices like toys, handheld vacuums, and e-bikes rely on lithium-ion technology. However, these batteries can have a limited lifespan and may pose fire hazards if compromised. To tackle these stability and safety concerns, researchers have created a lithium-sulfur (Li-S) battery that incorporates an enhanced iron sulfide cathode. One prototype has shown remarkable stability across 300 charge-discharge cycles, while another continues to deliver power even after being bent or sliced.
Most rechargeable batteries that power portable devices, such as toys, handheld vacuums and e-bikes, use lithium-ion technology. But these batteries can have short lifetimes and may catch fire when damaged. To address stability and safety issues, researchers reporting in ACS Energy Letters have designed a lithium-sulfur (Li-S) battery that features an improved iron sulfide cathode. One prototype remains highly stable over 300 charge-discharge cycles, and another provides power even after being folded or cut.
Sulfur is considered a promising material for lithium-ion batteries due to its low cost and potential to store more energy than lithium-metal oxides and other materials found in conventional ion-based batteries. To enhance the stability of Li-S batteries at elevated temperatures, researchers have previously suggested using a carbonate-based electrolyte to separate the cathode (made of iron sulfide) from the anode (which contains lithium metal). However, as the sulfide in the cathode dissolves into the electrolyte, it leads to the formation of an impermeable precipitate, resulting in a rapid decline in the battery’s capacity. Liping Wang and his team explored the possibility of adding a protective layer between the cathode and electrolyte to minimize this corrosion while maintaining performance and recharging capabilities.
The research team experimented with different polymers to coat the iron sulfide cathodes and discovered that polyacrylic acid (PAA) yielded the best results, successfully maintaining the electrode’s discharge capacity after 300 charge-discharge cycles. Following this, they integrated a PAA-coated iron sulfide cathode into a prototype battery setup, which also featured a carbonate-based electrolyte, a lithium metal foil as the ion source, and a graphite-based anode. They then produced and evaluated both pouch cell and coin cell battery prototypes.
After completing over 100 charge-discharge cycles, Wang and his team noted no significant loss of capacity in the pouch cell. Further tests demonstrated that the pouch cell continued to function effectively even after being folded and cut in half. The coin cell maintained 72% of its charge capacity after 300 cycles. Subsequently, they applied the polymer coating to cathodes made from other metals, developing lithium-molybdenum and lithium-vanadium batteries. These new cells also exhibited stable capacity over 300 charge-discharge cycles. Overall, the findings suggest that coated cathodes could lead to not only safer Li-S batteries with extended lifespans but also efficient batteries utilizing other metal sulfides, according to Wang’s research team.
The authors acknowledge funding from the National Natural Science Foundation of China; the Natural Science Foundation of Sichuan, China; and the Beijing National Laboratory for Condensed Matter Physics.
