Rational Designs for High-Energy Batteries Using the Property of Cohesion
이현욱
UNIST

Nanostructural design renders several breakthroughs for the construction of high-performance materials and devices, including energy-storage systems. Although attempts made toward electrode engineering have improved the existing drawbacks, nanoengineering is still hindered by some issues. To achieve practical applications of lithium-sulfur (Li-S) batteries, it is difficult to attain a high areal capacity with stable cycling. Physical encapsulation via nanostructural design not only can resolve the issue of lithium polysulfide dissolution during the electrochemical cycling but also can offer significant contact resistance, which in turn can decrease the kinetics, particularly at a high sulfur loading. Thus, we demonstrate an electrospun carbon nanofiber (CNF) matrix for a sulfur cathode. This simple design enables a high mass loading of 10.5 mg cm-2 with a high specific capacity and stable cycling. The CNF-sulfur complex can deliver a high areal capacity of greater than 7 mAh cm-2, which is related to the excellent electrical conductivity of one-dimensional species. Moreover, we have observed that the reacted sulfur species have adhered well to the junction of the CNF network with specific wetting angles, which is induced by the cohesive force between the narrow gaps in the matrix that trapped the viscous polysulfides during cycling. The results of this study open new avenues for the design of high-areal-capacity Li-S batteries. In order to fabricate stable lithium and sodium metal anodes, we have demonstrated the cohesive forces on carbon fibers. By facile treatment on the fibers, they contain numerous nanocrevices at surface, which play a role as nanoscale interlayer gaps to host lithium and sodium metal to achieve more stable galvanostatic cycling of the metal deposition than conventional lithium metal foil. This noticeable property is affected by the synergetic effects of the lithiophilic interface and the capillary force induced by the nanogaps of interlayers.