As the lithium-sulfur (Li-S) batteries have high theoretical specific capacity and energy density, they are receiving great spotlight as a next-generation battery system that can replace currently commercialized lithium-ion batteries. However, the shuttle phenomenon, which is the elution phenomenon of sulfur-based active materials during the charging and discharging process, is considered to be the biggest obstacle to commercialization. Among the many studies to suppress the shuttle phenomenon, interlayer studies that physically inhibit the diffusion of the active materials by introducing the new film between the cathode and anode are being conducted recently. However, introduction of new layer inevitably inhibits the movement of Li ions, causing slow redox kinetics. In this work, a fundamental problem was solved by synthesizing an interlayer composed of porous carbon nanofibers. The interlayer composed of porous nanofibers minimizes the hinderance of Li-ion diffusion based on enhanced space for Li-ion diffusion, thereby minimizing the inferiority of the rate-limiting characteristics due to the introduction of a new layer. In addition, since the porous nanofiber has a very superior surface area at the same time, it is possible to maximize the role of the catalyst by distributing the electrochemical catalyst in the form of a single atom throughout the area without agglomeration. The high-surface-area porous nanofiber was able to disperse a large number of iron atoms in the form of bonding with nitrogen atoms in a doubly-coordinated form, and in combination with a high pore volume, very improved electrochemical capacity was delivered. In order to thermodynamically prove the improved electrochemical properties, DFT calculations were performed, and it was demonstrated that the iron atom, which coordinates with the nitrogen atom in a doubly-coordinated form, can positively contribute the redox reaction. As a result, the final product CNPCF/Fe-N-C synthesized in this work maintains 95% coulombic efficiency up to 1600 cycles at 3.0 C. In addition, an electrode with a high active material content of 4.2 mg cm-2 delivered a maximum areal capacity of about 2.9 mAh cm-2 when operated at a high temperature of 45°C.

Improving redox kinetics of lithium-sulfur batteries by designing a porous interlayer combined with an electrochemical catalyst in the form of Fe-N<sub>2</sub>

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Improving redox kinetics of lithium-sulfur batteries by designing a porous interlayer combined with an electrochemical catalyst in the form of Fe-N2

Improving redox kinetics of lithium-sulfur batteries by designing a porous interlayer combined with an electrochemical catalyst in the form of Fe-N₂