Next-generation lithium-sulfur battery maintains 82% capacity after 1,000 cycles

A research team has developed an innovative technology that dramatically increases the charging speed of lithium-sulfur batteries. The research team used a new nitrogen-doped porous carbon material to address the problem of slow charging speeds that had hindered the commercialization of existing lithium-sulfur batteries.

Lithium-ion batteries are essential for environmentally friendly technologies such as electric vehicles. Although they have the disadvantages of low energy storage capacity and high cost, they are attracting attention as next-generation batteries because they have high energy density and the raw material sulfur is inexpensive. However, commercialization has been extremely difficult because insufficient sulfur utilization during rapid charging reduces battery capacity.

Another problem is the lithium polysulfide produced during the discharge process. These compounds migrate within the battery and reduce its performance. To address this, researchers have developed batteries by incorporating sulfur into porous carbon structures. However, the performance level suitable for practical use has not yet been reached.

To solve these challenges, Professor Jong-sung Yu of the DGIST team synthesized a new highly graphitic porous carbon material doped with nitrogen and applied it to the positive electrode of lithium-sulfur batteries. This technology allows us to maintain high energy capacity even under rapid charging conditions. This research is published in the journal ACS Nano.

The newly developed carbon material was synthesized using a thermal reduction method involving magnesium and the organometallic framework ZIF-8. At high temperatures, magnesium reacts with nitrogen within ZIF-8, making the carbon structure more stable and robust while forming a diverse pore structure. This structure not only allows for higher sulfur loading, but also improves the contact between sulfur and electrolyte, which significantly improves battery performance.

The lithium-sulfur battery developed in this study uses a multifunctional carbon material synthesized by a simple magnesium-assisted thermal reduction method as a sulfur host. Even under fast charging conditions, with a full charge time of just 12 minutes, it achieves a high capacity of 705mAh g⁻¹, which is 1.6 times that of conventional batteries.

Additionally, nitrogen doping on the carbon surface effectively suppressed the migration of lithium polysulfide, and the battery maintained 82% capacity even after 1,000 charge/discharge cycles, demonstrating excellent stability.

During the study, a collaborative team led by Dr. Khalil Amin of Argonne National Laboratory conducted advanced microscopic analysis. Through these analyses, we confirmed that lithium sulfide (Li2S) is formed in a specific orientation within the layered structure of the newly developed carbon material. This discovery demonstrated that nitrogen doping and porous carbon structure enhance the sulfur loading, while the graphitic nature of the carbon promotes the sulfur reaction, thereby increasing the charging rate.

Professor Yu said, “This research focused on improving the charging speed of lithium-sulfur batteries using a simple synthetic method using magnesium. I hope it will accelerate.”