RESUMEN
Main obstacles from the shuttle effect and slow conversion rate of soluble polysulfide compromise the sulfur utilization and cycling life for lithium sulfur (Li-S) batteries. In pursuit of a practically viable high performance Li-S battery, a separator configuration (CoS2 /HPGC/interlayer) as efficient polysulfide trapping barrier is reported. This configuration endows great advantages, particularly enhanced conductivity, promoted polysulfide trapping capability, accelerated sulfur electrochemistry, when using the functional interlayer for Li-S cells. Attributed to the above merits, such cell shows excellent cyclability, with a capacity of 846 mAh g-1 after 250 cycles corresponding to a high capacity retention of 80.2% at 0.2 C, and 519 mAh g-1 after 500 cycles at 1C (1C = 1675 mA g-1 ). In addition, the optimized separator exhibits a high initial areal capacity of 4.293 mAh cm-2 at 0.1C. Moreover, with CoS2 /HPGC/interlayer, the sulfur cell enables a low self-discharge rate with a very high capacity retention of 97.1%. This work presents a structural engineering of the separator toward suppressing the dissolution of soluble Li2 Sn moieties and simultaneously promoting the sulfur conversion kinetics, thus achieving durable and high capacity Li-S batteries.
RESUMEN
Pursuing scalable production of porous carbon with facile and environmentally friendly synthesis methodology is a global goal. Herein, a unique hierarchical porous graphitic carbon (HPGC) with outstanding textural characteristics is achieved by a special synergistic activation mechanism, in which the low-temperature molten state of polymorphisms can induce a high-rate liquid phase porous activation. HPGC with high specific surface area (SSA, â¼2571 m2 g-1) and large pore volume (PV, â¼2.21 cm3 g-1) can be achieved, which also possesses the capability to tune textural characteristics (i.e., SSA, PV, pore size distribution, etc.) within a wide range. Furthermore, the pilot-scale production of HPGC is accomplished, which shows similar textural characteristics to the lab-scale HPGC. Due to the unique structure of HPGC and the capability of the textural control, it can be applicable in a variety of energy storage, energy conversion, and catalysis applications. The applications of pilot-scale HPGC products in supercapacitors and lithium sulfur batteries are highlighted in this work. Furthermore, the synergistic activation strategy can be promoted to other alkali-based carbon activation routes, which can open up new possibilities for the activated carbon production and lead to more widespread industrialized applications of HPGC.
RESUMEN
The Magnéli phase Ti8O15 nanowires (NWs) have been grown directly on a Ti substrate by a facile one-step evaporation-deposition synthesis method under a hydrogen atmosphere. The Ti8O15 NWs exhibit an outstanding electrical conductivity at room temperature. The electrical conductivity of a single Ti8O15 nanowire is 20.6 S cm(-1) at 300 K. Theoretical calculations manifest that the existence of a large number of oxygen vacancies changes the band structure, resulting in the reduction of the electronic resistance. The Magnéli phase Ti8O15 nanowires have been used as conductive carbon-free supports to load Pt nanoparticles for direct methanol oxidation reaction (MOR). The Pt/Ti8O15 NWs show an enhanced activity and extremely high durability compared with commercial Pt/C catalysts.