Small-Molecule Polycyclic Aromatic Hydrocarbons
In article number 2400273, Jeng-Kuei Chang, Elise Yu-Tzu Li, Yu-Sheng Su, and co-workers present geometric variations of pyrene crystals during the electrochemical process in Li-ion batteries. The image illustrates the irreversible structural collapse caused by the vertical expansion of pyrene dimers, leading to the dissolution of pyrene into the electrolyte, a key factor affecting the long-term cycling stability of the anode material.
Lithium-sulfur batteries (LSBs) present a promising alternative to conventional lithium-ion (Li-ion) batteries due to their high energy density and theoretical capacity. However, their practical application is hindered by issues such as poor sulfur utilization, highly soluble lithium polysulfides (LiPSs), and rapid capacity decay. This study introduces an innovative cell configuration using a separator coated with reduced graphene oxide/carbon nanotube (rGO/CNT) microspheres. The rGO/CNT-coated separator aims to enhance electron transfer, confine LiPSs within the cathode region, and mitigate their migration to the anode. In particular, the LSB cell with an rGO/CNT-modified separator delivers an impressive initial capacity of 1482 mAh g−1 and demonstrates a low capacity decay rate of 0.09% per cycle. The highly conductive rGO/CNT-coated separator enhances active material utilization even at high rates, resulting in a significant capacity of 824 mAh g−1 at 4C. Furthermore, the rGO/CNT-modified separator shows an impressive capacity of 895 mAh g−1 under high sulfur loading of 4.8 mg cm−2 with long-term cycling performance. The results demonstrate that the rGO/CNT-coated separator significantly enhances sulfur reutilization, reduces capacity decay, and improves the electrochemical stability of LSBs. This configuration simplifies the manufacturing process and offers a viable solution for the practical application of LSBs.
Graphene, recognized for its impressive strength, flexibility, and conductivity, has garnered significant interest for numerous applications. Within energy storage sector, especially in battery technology, graphene shows promise for improving battery component performance. Graphene/silicon composites in lithium-ion batteries are gaining attention for their potential to overcome some of the challenges associated with silicon as a high-capacity anode material. Here we present an eco-friendly approach to fabricate graphene flakes, utilizing ball milling, ultrasonication, and spray drying to enable efficient mechanical transfer of graphene onto silicon particles. The technique employs a combination of dry/wet exfoliation and self-assembly, effectively eliminating the need for hazardous chemicals. The developed method illustrates the successful integration of silicon within a graphene envelope, resulting in a stable core-shell structure. Characterization techniques, such as scanning electron microscopy, tunneling electron microscopy, X-ray diffraction, and Raman spectroscopy, verify the quality and stability of the composite with graphene. Electrochemical assessments demonstrate that the composite composed of silicon wrapped in graphene has enhanced cycle stability when compared to pure silicon. Cross-sectional analysis of the microstructure reveals reduced volume expansion and improved structural stability of the electrode. This green synthesis method towards fabricating graphene-based composites holds enormous potential for promoting sustainable manufacturing practices.
