Lithium–sulfur (Li–S) batteries hold the promise of the next generation energy storage system beyond state‐of‐the‐art lithium‐ion batteries. Despite the attractive gravimetric energy density (WG), ...the volumetric energy density (WV) still remains a great challenge for the practical application, based on the primary requirement of Small and Light for Li–S batteries. This review highlights the importance of cathode density, sulfur content, electroactivity in achieving high energy densities. In the first part, key factors are analyzed in a model on negative/positive ratio, cathode design, and electrolyte/sulfur ratio, orientated toward energy densities of 700 Wh L−1/500 Wh kg−1. Subsequently, recent progresses on enhancing WV for coin/pouch cells are reviewed primarily on cathode. Especially, the “Three High One Low” (THOL) (high sulfur fraction, high sulfur loading, high density host, and low electrolyte quantity) is proposed as a feasible strategy for achieving high WV, taking high WG into consideration simultaneously. Meanwhile, host materials with desired catalytic activity should be paid more attention for fabricating high performance cathode. In the last part, key engineering technologies on manipulating the cathode porosity/density are discussed, including calendering and dry electrode coating. Finally, a future outlook is provided for enhancing both WV and WG of the Li–S batteries.
The volumetric energy density (WV) of lithium–sulfur batteries is critical for mobile applications. Key factors that dominate WV progress on WV research are analyzed, and technologies for tuning cathode structure are discussed. A “three‐high one‐low (THOL)” strategy is proposed for high WV and gravimetric energy density (WG), and catalytic hosts are important to unlock the sulfur electroactivity.
It is undoubtable that the use of solar energy will continue to increase. Solar cells that convert solar energy directly to electricity are one of the most convenient and important photoelectric ...conversion devices. Though silicon‐based solar cells and thin‐film solar cells have been commercialized, developing low‐cost and highly efficient solar cells to meet future needs is still a long‐term challenge. Some emerging solar‐cell types, such as dye‐sensitized and perovskite, are approaching acceptable performance levels, but their costs remain too high. To obtain a higher performance–price ratio, it is necessary to find new low‐cost counter materials to replace conventional precious metal electrodes (Pt, Au, and Ag) in these emerging solar cells. In recent years, the number of counter‐electrode materials available, and their scope for further improvement, has expanded for dye‐sensitized and perovskite solar cells. Generally regular patterns in the intrinsic features and structural design of counter materials for emerging solar cells, in particular from an electrochemical perspective and their effects on cost and efficiency, are explored. It is hoped that this recapitulative analysis will help to make clear what has been achieved and what still remains for the development of cost‐effective counter‐electrode materials in emerging solar cells.
Low‐cost counter materials for dye‐sensitized and perovskite solar cells are summarized, with a focus on the regular patterns that appear in their intrinsic features and structural design.
The intrinsic instability of organic electrolytes seriously impedes practical applications of high‐capacity metal (Li, Na) anodes. Ion–solvent complexes can even promote the decomposition of ...electrolytes on metal anodes. Herein, first‐principles calculations were performed to investigate the origin of the reduced reductive stability of ion–solvent complexes. Both ester and ether electrolyte solvents are selected to interact with Li+, Na+, K+, Mg2+, and Ca2+. The LUMO energy levels of ion–ester complexes exhibit a linear relationship with the binding energy, regulated by the ratio of carbon atomic orbital in the LUMO, while LUMOs of ion–ether complexes are composed by the metal atomic orbitals. This work shows why ion–solvent complexes can reduce the reductive stability of electrolytes, reveals different mechanisms for ester and ether electrolytes, and provides a theoretical understanding of the electrolyte–anode interfacial reactions and guidance to electrolyte and metal anode design.
The origin of reduced stability: The reason why ion–solvent complexes promote electrolyte decomposition on alkali/alkaline earth metal anodes is probed. The complexed cations can regulate the contribution ratio of carbon atomic orbitals in LUMOs of ion–ester complexes or totally change the atomic contribution in LUMOs of ion–ether complexes to reduce the energy level of the LUMO.
Lithium–sulfur battery possesses a high energy density; however, its application is severely blocked by several bottlenecks, including the serious shuttling behavior and sluggish redox kinetics of ...sulfur cathode, especially under the condition of high sulfur loading and lean electrolyte. Herein, hollow molybdate (CoMoO4, NiMoO4, and MnMoO4) microspheres are introduced as catalytic hosts to address these issues. The molybdates present a high intrinsic electrocatalytic activity for the conversion of soluble lithium polysulfides, and the unique hollow spherical structure could provide abundant sites and spatial confinement for electrocatalysis and inhibiting shuttling, respectively. Meanwhile, it is demonstrated that the unique adsorption of molybdates toward polysulfides exhibits a “volcano‐type” feature with the catalytic performance following the Sabatier principle. The NiMoO4 hollow microspheres with moderate adsorption show the highest electrocatalytic activity, which is favorable for enhancing the electrochemical performance of sulfur cathode. Especially, the S/NiMoO4 composite could achieve a high areal capacity of 7.41 mAh cm−2 (906.2 mAh g−1) under high sulfur loading (8.18 mg cm−2) and low electrolyte/sulfur ratio (E/S, 4 µL mg−1). This work offers a new perspective on searching accurate rules for selecting and designing effective host materials in the lithium–sulfur battery.
Molybdate hollow spheres (CoMoO4, NiMoO4, MnMoO4) are employed as the host materials for Li–S battery, among which NiMoO4 with the moderate adsorption strength shows the highest catalytic efficiency toward sulfur conversion. The resulting S/NiMoO4 composite delivers high gravimetric capacity under high sulfur loading and lean electrolyte usage.
Simultaneously harvesting, converting and storing solar energy in a single device represents an ideal technological approach for the next generation of power sources. Herein, we propose a device ...consisting of an integrated carbon-based perovskite solar cell module capable of harvesting solar energy (and converting it into electricity) and a rechargeable aqueous zinc metal cell. The electrochemical energy storage cell utilizes heterostructural Co
P-CoP-NiCoO
nanometric arrays and zinc metal as the cathode and anode, respectively, and shows a capacity retention of approximately 78% after 25000 cycles at 32 A/g. In particular, the battery cathode and perovskite material of the solar cell are combined in a sandwich joint electrode unit. As a result, the device delivers a specific power of 54 kW/kg and specific energy of 366 Wh/kg at 32 A/g and 2 A/g, respectively. Moreover, benefiting from its narrow voltage range (1.40-1.90 V), the device demonstrates an efficiency of approximately 6%, which is stable for 200 photocharge and discharge cycles.
Understanding the dynamics and underlying mechanism of carbon exchange between terrestrial ecosystems and the atmosphere is one of the key issues in global change research. In this study, we ...quantified the carbon fluxes in different terrestrial ecosystems in China, and analyzed their spatial variation and environmental drivers based on the long‐term observation data of ChinaFLUX sites and the published data from other flux sites in China. The results indicate that gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem productivity (NEP) of terrestrial ecosystems in China showed a significantly latitudinal pattern, declining linearly with the increase of latitude. However, GEP, ER, and NEP did not present a clear longitudinal pattern. The carbon sink functional areas of terrestrial ecosystems in China were mainly located in the subtropical and temperate forests, coastal wetlands in eastern China, the temperate meadow steppe in the northeast China, and the alpine meadow in eastern edge of Qinghai‐Tibetan Plateau. The forest ecosystems had stronger carbon sink than grassland ecosystems. The spatial patterns of GEP and ER in China were mainly determined by mean annual precipitation (MAP) and mean annual temperature (MAT), whereas the spatial variation in NEP was largely explained by MAT. The combined effects of MAT and MAP explained 79%, 62%, and 66% of the spatial variations in GEP, ER, and NEP, respectively. The GEP, ER, and NEP in different ecosystems in China exhibited ‘positive coupling correlation’ in their spatial patterns. Both ER and NEP were significantly correlated with GEP, with 68% of the per‐unit GEP contributed to ER and 29% to NEP. MAT and MAP affected the spatial patterns of ER and NEP mainly by their direct effects on the spatial pattern of GEP.
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We apply the recently proposed quantum extremal surface construction to calculate the Page curve of the eternal Reissner-Nordström black holes in four dimensions ignoring the backreaction ...and the greybody factor. Without the island, the entropy of Hawking radiation grows linearly with time, which results in the information paradox for the eternal black holes. By extremizing the generalized entropy that allows the contributions from the island, we find that the island extends to the outside the horizon of the Reissner-Nordström black hole. When taking the effect of the islands into account, it is shown that the entanglement entropy of Hawking radiation at late times for a given region far from the black hole horizon reproduces the Bekenstein-Hawking entropy of the Reissner-Nordström black hole with an additional term representing the effect of the matter fields. The result is consistent with the finiteness of the entanglement entropy for the radiation from an eternal black hole. This facilitates to address the black hole information paradox issue in the current case under the above-mentioned approximations.
Optical microfibers (MF), as a connection between fiber optics and nanotechnology, can realize enhanced light-matter/environment interactions, which benefit for optical sensing applications. In this ...paper, we introduce the fundamental working mechanisms of MF-based optical sensors and review their recent progress and status. We also discuss the challenges and opportunities of the MF sensors and provide some clues for future work.
Lithium–sulfur battery is recognized as one of the most promising energy storage devices, while the application and commercialization are severely hindered by both the practical gravimetric and ...volumetric energy densities due to the low sulfur content and tap density with lightweight and nonpolar porous carbon materials as sulfur host. Herein, for the first time, conductive CoOOH sheets are introduced as carbon‐free sulfur immobilizer to fabricate sulfur‐based composite as cathode for lithium–sulfur battery. CoOOH sheet is not only a good sulfur‐loading matrix with high electron conductivity, but also exhibits outstanding electrocatalytic activity for the conversion of soluble lithium polysulfide. With an ultrahigh sulfur content of 91.8 wt% and a tap density of 1.26 g cm−3, the sulfur/CoOOH composite delivers high gravimetric capacity and volumetric capacity of 1199.4 mAh g−1‐composite and 1511.3 mAh cm−3 at 0.1C rate, respectively. Meanwhile, the sulfur‐based composite presents satisfactory cycle stability with a slow capacity decay rate of 0.09% per cycle within 500 cycles at 1C rate, thanks to the strong interaction between CoOOH and soluble polysulfides. This work provides a new strategy to realize the combination of gravimetric energy density, volumetric energy density, and good electrochemical performance of lithium–sulfur battery.
Conductive cobalt oxyhydroxide (CoOOH) sheets are prepared as the carbon‐free immobilizer for Li–S batteries for the first time. The S/CoOOH composite exhibits outstanding electrochemical performance resulting from the remarkable conductive framework and electrocatalytic activity contributed by the CoOOH sheets. Moreover, such composite delivers high gravimetric and volumetric energy densities, owing to the high sulfur content and tap density.
Polyaniline‐coated sulfur/conductive‐carbon‐black (PANI@S/C) composites with different contents of sulfur are prepared via two facile processes including ball‐milling and thermal treatment of the ...conductive carbon black and sublimed sulfur, followed by an in situ chemical oxidative polymerization of the aniline monomer in the presence of the S/C composite and ammonium persulfate. The microstructure and electrochemical performance of the as‐prepared composites are investigated systematically. It is demonstrated that the polyaniline, with a thickness of ≈5–10 nm, is coated uniformly onto the surface of the S/C composite forming a core/shell structure. The PANI@S/C composite with 43.7 wt% sulfur presents the optimum electrochemical performance, including a large reversible capacity, a good coulombic efficiency, and a high active‐sulfur utilization. The formation of the unique core/shell structure in the PANI@S/C composites is responsible for the improvement of the electrochemical performance. In particular, the high‐rate charge/discharge capability of the PANI@S/C composites is excellent due to a synergistic effect on the high electrical conductivity from both the conductive carbon black in the matrix and the PANI on the surface. Even at an ultrahigh rate (10C), a maximum discharge capacity of 635.5 mA h per g of sulfur is still retained for the PANI@S/C composite after activation, and the discharge capacity retention is over 60% after 200 cycles.
A polyaniline‐coated sulfur/conductive‐carbon‐black (PANI@S/C) composite presents an exceptional high‐rate charge/discharge capability and a high active‐sulfur utilization due to the unique core/shell structure and a synergistic effect on the electrical conductivity from both the conductive carbon black in the matrix and the PANI on the surface.
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