Ultrasmall, Amorphous V2O3 Intimately Anchored on a Carbon Nanofiber Aerogel Toward High-Rate Zinc-Ion Batteries.

When considered as a cathode candidate for aqueous Zn-ion batteries, V2O3 faces several problems, such as inherently unsuitable structure, fast structural degradation, and sluggish charge transport kinetics. In this paper, we report the synthesis of a V2O3 intimately coupled carbon aerogel by a controllable ion impregnation and solid-state reaction strategy using bacterial cellulose and ammonium metavanadate as raw materials. In this newly designed structure, the carbonized carbon fiber network provides fast ion and electron transport channels. More importantly, the cellulose aerogel functions as a dispersing and supporting skeleton to realize the particle size reduction, uniform distribution, and amorphous features of V2O3. These advantages work together to realize adequate electrochemical activation during the initial charging process and shorter transport distance and faster transport kinetics of Zn2+. The batteries based on the V2O3/CNF aerogel exhibit a high-rate performance and an excellent cycling stability. At a current density of 20 A g-1, the V2O3/CNF aerogel delivers a specific capacity of 159.8 mAh g-1, and it demonstrates an exceptionally long life span over 2000 cycles at 12 A g-1. Furthermore, the electrodes with active material loadings as high as 10 mg cm-2 still deliver appreciable specific capacities of 257 mAh g-1 at 0.1 A g-1.

Hierarchical carbon hollow nanospheres coupled with ultra-small molybdenum carbide as sulfiphilic sulfur hosts for lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are an attractive candidate to replace the current state-of-the-art lithium-ion batteries due to their promising theoretical capacity of 1675 mA h g-1 and energy density of 2500 W h kg-1. However, the lithium polysulfide (LiPS) shuttle effect and the slow sulfur redox kinetics seriously decrease the utilization of sulfur and deteriorate battery performance. Here, hierarchical carbon hollow nanospheres containing intimately coupled molybdenum carbide nanocrystals were synthesized as a sulfiphilic sulfur host. The sufficient interior void space accommodates the sulfur and physically confines LiPSs, while the in situ introduced molybdenum carbide nanoparticles can chemically immobilize LiPSs and catalytically accelerate their redox transformations. As a result, the Li-S batteries with this synergistic effect achieve an excellent rate capability of 566 mA h g-1 at 2C and a long cycle stability over 300 cycles at 1C.

Strategies for Designing High-Performance Hydrogen Evolution Reaction Electrocatalysts at Large Current Densities above 1000 mA cm-2.

The depletion of fossil fuels and rapidly increasing environmental concerns have urgently called for the utilization of clean and sustainable sources for future energy supplies. Hydrogen (H2) is recognized as a prioritized green resource with little environmental impact to replace traditional fossil fuels. Electrochemical water splitting has become an important method for large-scale green production of hydrogen. The hydrogen evolution reaction (HER) is the cathodic half-reaction of water splitting that can be promoted to produce pure H2 in large quantities by active electrocatalysts. However, the unsatisfactory performance of HER electrocatalysts cannot follow the extensive requirements of industrial-scale applications, including working efficiently and stably over long periods of time at high current densities (⩾1000 mA cm-2). In this review, we study the crucial issues when electrocatalysts work at high current densities and summarize several categories of strategies for the design of high-performance HER electrocatalysts. We also discuss the future challenges and opportunities for the development of HER catalysts.

sp-sp2 hybrid-conjugated microporous polymer-derived Pd-encapsulated porous carbon materials for lithium-sulfur batteries.

Pd-encapsulated porous carbon materials (Pd-PCMs) were prepared from the coupling polymerization of an aryl halide and aryl alkyne under mild conditions. Combining its porous microstructure and encapsulated Pd nanoparticles, Pd-PCMs with high sulfur loading reach a capacity of 920 mA h g-1 after 200 cycles at 0.3C.

A Nacre-Like Carbon Nanotube Sheet for High Performance Li-Polysulfide Batteries with High Sulfur Loading.

Lithium-sulfur (Li-S) batteries are considered as one of the most promising energy storage systems for next-generation electric vehicles because of their high-energy density. However, the poor cyclic stability, especially at a high sulfur loading, is the major obstacles retarding their practical use. Inspired by the nacre structure of an abalone, a similar configuration consisting of layered carbon nanotube (CNT) matrix and compactly embedded sulfur is designed as the cathode for Li-S batteries, which are realized by a well-designed unidirectional freeze-drying approach. The compact and lamellar configuration with closely contacted neighboring CNT layers and the strong interaction between the highly conductive network and polysulfides have realized a high sulfur loading with significantly restrained polysulfide shuttling, resulting in a superior cyclic stability and an excellent rate performance for the produced Li-S batteries. Typically, with a sulfur loading of 5 mg cm-2, the assembled batteries demonstrate discharge capacities of 1236 mAh g-1 at 0.1 C, 498 mAh g-1 at 2 C and moreover, when the sulfur loading is further increased to 10 mg cm-2 coupling with a carbon-coated separator, a superhigh areal capacity of 11.0 mAh cm-2 is achieved.

A Dual-Function Na2 SO4 Template Directed Formation of Cathode Materials with a High Content of Sulfur Nanodots for Lithium-Sulfur Batteries.

The sulfur content in carbon-sulfur hybrid using the melt-diffusion method is normally lower than 70 wt%, which greatly decreases the energy density of the cathode in lithium-sulfur (Li-S) batteries. Here, a scalable method inspired by the commercialized production of Na2 S is used to prepare a hierarchical porous carbon-sulfur hybrid (denoted HPC-S) with high sulfur content (≈85 wt%). The HPC-S is characterized by the structure of sulfur nanodots naturally embedded in a 3D carbon network. The strategy uses Na2 SO4 as the starting material, which serves not only as the sulfur precursor but also as a salt template for the formation of the 3D carbon network. The HPC-S cathode with such a high sulfur content shows excellent rate performance and cycling stability in Li-S batteries because of the sulfur nanoparticles, the unique carbon framework, and the strong interaction between them. The production method can also be readily scaled up and used in practical Li-S battery applications.

Dual-functional hard template directed one-step formation of a hierarchical porous carbon-carbon nanotube hybrid for lithium-sulfur batteries.

A novel hierarchical porous carbon-carbon nanotube hybrid (HPCC) is prepared using a one-step strategy that uses nickel nanoparticles as the template for pore formation and at the same time, as the catalyst for carbon nanotube (CNT) growth. Such a structure can not only store sulfur in the micro- and mesopores, which restrict the shuttling of polysulfides, but also ensure good electrical conductivity of the whole system due to the incorporation of CNTs. The hierarchical porous structure also ensures fast mass transportation. These factors effectively guarantee the high electrochemical performance of sulfur stored in this carbon in lithium-sulfur batteries.

A Carbon-Sulfur Hybrid with Pomegranate-like Structure for Lithium-Sulfur Batteries.

A carbon-sulfur hybrid with pomegranate-like core-shell structure, which demonstrates a high rate performance and relatively high cyclic stability, is obtained through carbonization of a carbon precursor in the presence of a sulfur precursor (FeS2 ) and a following oxidation of FeS2 to sulfur by HNO3 . Such a structure effectively protects the sulfur and leaves enough buffer space after Fe(3+) removal and, at the same time, has an interconnected conductive network. The capacity of the obtained hybrid is 450 mA h g(-1) under the current density of 5 C. This work provides a simple strategy to design and prepare various high-performance carbon-sulfur hybrids for lithium-sulfur batteries.

N and S co-doped porous carbon spheres prepared using L-cysteine as a dual functional agent for high-performance lithium-sulfur batteries.

Nitrogen and sulfur co-doped porous carbon spheres (NS-PCSs) were prepared using L-cysteine to control the structure and functionalization during the hydrothermal reaction of glucose and the subsequent activation process. As the sulfur hosts in Li-S batteries, NS-PCSs combine strong physical confinement and surface chemical interaction to improve the affinity of polysulfides to the carbon matrix.