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.
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.
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.
Lithium–sulfur (Li–S) batteries are regarded as the promising next‐generation energy storage device due to the high theoretical energy density and low cost. However, the practical application of Li–S ...batteries is still limited owing to the cycle stability of both the sulfur cathode and lithium anode. In particular, the instability in the bulk and at the surface of the lithium anode during cycling becomes a huge obstacle for the practical application of Li–S battery. Herein, a Li‐rich lithium–magnesium (Li–Mg) alloy is investigated as an anode for Li–S batteries, based on the consideration of improving the stability in the bulk and at the surface of the lithium anode. Our experimental results reveal that the robust passivation layer is formed on the surface of the Li–Mg alloy anode, which is helpful to reduce side reactions, and enable the smooth surface morphology of anode during cycling. Meanwhile, the mixed electron and Li‐ion conducting matrix of the Li‐poor Li–Mg alloy as a porous skeleton structure can also be formed after delithiation, which can guarantee the structural integrity of the anode in the bulk during Li stripping/plating process. Therefore, the Li‐rich Li–Mg alloy is demonstrated to be a very promising anode material for Li–S battery.
A Li‐rich Li–Mg alloy is investigated as an anode for Li–S batteries. The Li–Mg alloy demonstrates versatile functions, including active material, surface stabilizer, supporting, and conducting matrix, which are beneficial to realize good stability in the bulk and at the surface of the alloy anode for Li–S batteries.
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.
For high‐energy lithium–sulfur batteries, the poor volumetric energy density is a bottleneck as compared with lithium–ion batteries, due to the low density of both the sulfur active material and ...sulfur host. Herein, in order to enhance the volumetric energy density of sulfur cathode, a universal approach is proposed to fabricate a compact sulfur cathode with dense materials as sulfur host, instead of the old‐fashioned lightweight carbon nanomaterials. Based on this strategy, heavy lanthanum strontium manganese oxide (La0.8Sr0.2MnO3), with a high theoretical density of up to 6.5 g cm−3, is introduced as sulfur host. Meanwhile, the La0.8Sr0.2MnO3 host also acts as an efficient electrocatalyst to accelerate the diffusion, adsorption, and redox dynamics of lithium polysulfides in the charge–discharge processes. As a result, such S/La0.8Sr0.2MnO3 cathode presents high gravimetric/volumetric capacity and outstanding cycling stability. Moreover, an ultra‐high volumetric energy density of 2727 Wh L−1‐cathode is achieved based on the densification effect with higher density (1.69 g cm−3), which is competitive to the Ni‐rich oxide cathode (1800–2160 Wh L−1) of lithium–ion batteries. The current study opens up a path for constructing high volumetric capacity sulfur cathode with heavy and catalytic host toward practical applications of lithium–sulfur batteries.
Heavy metal oxides are more suitable than light carbon materials to fabricate compact cathode for lithium–sulfur batteries. Specifically, lanthanum strontium manganese oxide nanofibers, with the tap density of 2.59 g cm−3, display efficient catalytic activity toward lithium polysulfides, enhancing the volumetric energy density of sulfur cathode, which can even exceed lithium–ion batteries.
Elemental sulfur possesses an ultra‐high theoretical specific capacity, while the practical application of sulfur in lithium–sulfur (Li–S) batteries is seriously hindered by the sluggish redox ...kinetics and serious shuttle effect. Enhancing the catalytic activity of the sulfur host by a rational structural design is the key to address these issues. Herein, for the first time, concave‐nanocubic (CNC) nickel–platinum (Ni–Pt) alloys bounded by high‐index facets (HIFs) are introduced as the core catalyst of sulfur for Li–S batteries. It is demonstrated that the CNC Ni–Pt alloy crystallites dispersed uniformly on graphene exhibit a high electrochemical activity to drive the conversion from intermediate lithium polysulfides to solid discharged products. Benefiting from the accelerated redox kinetics by HIFs, the cathode delivers a low capacity damping of 0.025% per cycle for 1000 cycles at 1 C rate. In particular, a high reversible capacity of 664.9 mAh g−1‐cathode with cathode as active material can be achieved with high sulfur loading (8.8 mg cm−2) and low electrolyte usage (5 µL mgs−1). This study focuses on improving the catalytic activity of sulfur hosts by modulating the exposed facets of core catalyst and provides a new path for the structure optimizing of host materials in Li–S batteries.
Well‐designed concave‐nanocubic nickel–platinum alloy crystallites with high‐index facets (HIFs), dispersed uniformly on graphene, are prepared as the catalytic host for lithium–sulfur batteries. The HIFs of the alloy nanocrystallites exhibit a high intrinsic electrocatalytic activity for the conversion of intermediate lithium polysulfides and discharged products. Therefore, the sulfur cathode delivers enhanced electrochemical performances.
Colloidally grown nanosized semiconductors yield extremely high‐quality optoelectronic materials. Many examples have pointed to near perfect photoluminescence quantum yields, allowing for ...technology‐leading materials such as high purity color centers in display technology. Furthermore, because of high chemical yield, and improved understanding of the surfaces, these materials, particularly colloidal quantum dots (QDs) can also be ideal candidates for other optoelectronic applications. Given the urgent necessity toward carbon neutrality, electricity from solar photovoltaics will play a large role in the power generation sector. QDs are developed and shown dramatic improvements over the past 15 years as photoactive materials in photovoltaics with various innovative deposition properties which can lead to exceptionally low‐cost and high‐performance devices. Once the key issues related to charge transport in optically thick arrays are addressed, QD‐based photovoltaic technology can become a better candidate for practical application. In this article, the authors show how the possibilities of different deposition techniques can bring QD‐based solar cells to the industrial level and discuss the challenges for perovskite QD solar cells in particular, to achieve large‐area fabrication for further advancing technology to solve pivotal energy and environmental issues.
The possibilities of different deposition techniques which can bring quantum dot (QD)‐based solar cells to the industrial level are assessed. With perovskite QDs showing dramatic improvements in photovoltaics, the discussions on the challenges particularly for perovskite QD solar cells are given in an attempt to achieve large‐area fabrication solving pivotal energy and environmental issues.
Lithium–sulfur (Li–S) battery is regarded as one of the most promising candidates beyond conventional lithium ion batteries. However, the instability of the metallic lithium anode during lithium ...electrochemical dissolution/deposition is still a major barrier for the practical application of Li–S battery. In this work, lanthanum nitrate, as electrolyte additive, is introduced into Li–S battery to stabilize the surface of lithium anode. By introducing lanthanum nitrate into electrolyte, a composite passivation film of lanthanum/lithium sulfides can be formed on metallic lithium anode, which is beneficial to decrease the reducibility of metallic lithium and slow down the electrochemical dissolution/deposition reaction on lithium anode for stabilizing the surface morphology of metallic Li anode in lithium–sulfur battery. Meanwhile, the cycle stability of the fabricated Li–S cell is improved by introducing lanthanum nitrate into electrolyte. Apparently, lanthanum nitrate is an effective additive for the protection of lithium anode and the cycling stability of Li–S battery.
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