Tremendous efforts have been devoted to the development of electrode materials, electrolytes, and separators of energy-storage devices to address the fundamental needs of emerging technologies such as electric vehicles, artificial intelligence, and virtual reality. However, binders, as an important component of energy-storage devices, are yet to receive similar attention. Polyvinylidene fluoride (PVDF) has been the dominant binder in the battery industry for decades despite several well-recognized drawbacks, i.e., limited binding strength due to the lack of chemical bonds with electroactive materials, insufficient mechanical properties, and low electronic and lithium-ion conductivities. The limited binding function cannot meet inherent demands of emerging electrode materials with high capacities such as silicon anodes and sulfur cathodes. To address these concerns, in this review we divide the binding between active materials and binders into two major mechanisms: mechanical interlocking and interfacial binding forces. We review existing and emerging binders, binding technology used in energy-storage devices (including lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, and supercapacitors), and state-of-the-art mechanical characterization and computational methods for binder research. Finally, we propose prospective next-generation binders for energy-storage devices from the molecular level to the macro level. Functional binders will play crucial roles in future high-performance energy-storage devices.

Intermediate polysulfides (S , where n = 2-8) play a critical role in both mechanistic understanding and performance improvement of lithium-sulfur batteries. The rational management of polysulfides is of profound significance for high-efficiency sulfur electrochemistry. Here, the key roles of polysulfides are discussed, with regard to their status, behavior, and their correspondingimpact on the lithium-sulfur system. Two schools of thoughts for polysulfide management are proposed, their advantages and disadvantages are compared, and future developments are discussed.

Lithium–sulfur batteries are promising technologies for powering flexible devices due to their high energy density, low cost and environmental friendliness, when the insulating nature, shuttle effect and volume expansion of sulfur electrodes are well addressed. Here, we report a strategy of using foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for binder-free advanced lithium–sulfur batteries through a facile confinement conversion. The carbon nanotubes interpenetrate through the metal-organic frameworks crystal and interweave the electrode into a stratified structure to provide both conductivity and structural integrity, while the highly porous metal-organic frameworks endow the electrode with strong sulfur confinement to achieve good cyclability. These hierarchical porous interpenetrated three-dimensional conductive networks with well confined S8 lead to high sulfur loading and utilization, as well as high volumetric energy density.

Combining the advantages of homogeneous and heterogeneous catalysts,s ingle-atom catalysts (SACs) are bringing new opportunities to revolutionizeO RR catalysis in terms of cost, activity and durability.However,the lack of highperformance SACs as well as the fundamental understanding of their unique catalytic mechanisms call for serious advances in this field. Herein, for the first time,w ed evelop an Ir-N-C single-atom catalyst (Ir-SAC) whichm imics homogeneous iridium porphyrins for high-efficiency ORR catalysis.I na ccordance with theoretical predictions,the as-developed Ir-SAC exhibits orders of magnitude higher ORR activity than iridium nanoparticles with arecord-high turnover frequency (TOF) of 24.3 e À site À1 s À1 at 0.85 Vv s. RHE) and an impressive mass activity of 12.2 Amg À1 Ir ,which far outperforms the previously reported SACs and commercial Pt/C.A tomic structural characterizations and density functional theory calculations reveal that the high activity of Ir-SACi sa ttributed to the moderate adsorption energy of reaction intermediates on the mononuclear iridium ion coordinated with four nitrogen atom sites.

needs while signifi cantly reducing battery cost. For this reason, the combination of lithium and sulfur has been considered as one of the most promising battery chemistries for full electrifi cation of vehicles. [ 3 ] Despite these advantages, Li S batteries have a few critical barriers to be overcome. Besides the insulating properties of sulfur and polysulfi des, Li S batteries also suffer from dramatic (i.e., ≈76%) volume change of sulfur during cycling and shuttling effect of polysulfi des that sulfur species transport back and forth between electrodes. These lead to the destruction of sulfur cathodes and the corrosion of lithium anode resulting in short battery life.In a traditional Li S cell, a typical sulfur electrode consists of three components, i.e., the electrochemically active sulfur material, the conductive carbon additive, and the polymeric binder. [ 4 ] Through the syntheses of nanoarchitectured carbon additives, the electrochemical performance and cycle life of Li S batteries have been successfully improved. [ 5 ] Although signifi cant achievements have been made in designing nanostructured carbon/sulfur composites for cycle life improvement of Li S batteries, these processes are commonly sophisticated, high cost, and not suitable for large-scale manufacturing.The sulfur cathode in traditional lithium-sulfur batteries suffers from poor cyclability due to polysulfi de shuttling effect as well as large volume change during charge/discharge processes. Gum arabic (GA), a low cost, nontoxic, and sustainable natural polymer from Acacia senegal , is adopted as a binder for the sulfur cathode to address these issues. The excellent mechanical properties of GA endow the cathode with high binding strength and suitable ductility to buffer volume change, while the functional groups chemically and physically confi ne sulfur species within the cathode to inhibit the shuttling effect of polysulfi des. Additionally, GA shifts the electrode fabrication process from the organic solvent process to an aqueous process, eliminates the use of toxic organic solvents, and achieves uniformly distributed electrode with lower impedance. A remarkable cycling performance, i.e., 841 mAh g −1 at low current rate of C /5, is achieved throughout 500 cycles due to the bifunctions of the GA binder.

Emerging as a new frontier in heterogeneous catalysis, single-atom site catalysts (SSCs) have sparked enormous attention and bring about new opportunities to oxygen reduction electrocatalysis. Despite considerable progress achieved recently, most of the reported SSCs suffer from either insufficient activity or unsatisfactory stability, which severely retards their practical application. Here, we demonstrate a novel Ru-SSC with appropriate adsorption free energy of OH* (ΔG OH*) to confer excellent activity and low Fenton reactivity to maintain long-term stability. The as-developed Ru-SSC exhibits encouraging oxygen reduction reaction turnover frequency of 4.99 e– s–1 sites–1, far exceeding the state-of-the-art Fe-SSC counterpart (0.816 e– s–1 sites–1), as a result of Ru energy level regulation via spontaneous OH binding. Furthermore, Ru-SSC exhibits greatly suppressed Fenton reactivity, with restrained generation of reactive oxygen species directly observed, thus endowing the Ru-SSC with much more superior stability (only 17 mV negative shift after 20 000 cycles) than the Fe-SSC counterpart (31 mV). The practical application of Ru-SSC is further validated by its excellent activity and stability in a real fuel cell device.

Stringed “tube on cube” hybrid architecture is developed for high-energy-density lithium–sulfur batteries with high sulfur loading and lean electrolyte.

The notorious shuttling behaviors and sluggish conversion kinetics of the intermediate lithium polysulfides (LPS) are hindering the practical application of lithium sulfur (Li−S) batteries. Herein, an ultrafine, amorphous, and oxygendeficient niobium pentoxide nanocluster embedded in microporous carbon nanospheres (A-Nb 2 O 5−x @MCS) was developed as a multifunctional sulfur immobilizer and promoter toward superior shuttle inhibition and conversion catalyzation of LPS. The A-Nb 2 O 5−x nanocluster implanted framework uniformizes sulfur distribution, exposes vast active interfaces, and offers a reduced ion/electron transportation pathway for expedited redox reaction. Moreover, the low crystallinity feature of A-Nb 2 O 5−x manipulates the LPS chemical affinity, while the defect chemistry enhances the intrinsic conductivity and catalytic activity for rapid electrochemical conversions. Attributed to these superiorities, A-Nb 2 O 5−x @MCS delivers good Li−S battery performances, that is, high areal capacity of 6.62 mAh cm −2 under high sulfur loading and low electrolyte/sulfur ratio, superb rate capability, and cyclability over 1200 cycles with an ultralow capacity fading rate of 0.024% per cycle. This work provides a synergistic regulation on crystallinity and oxygen deficiency toward rapid and durable sulfur electrochemistry, holding a great promise in developing practically viable Li−S batteries and enlightening material engineering in related energy storage and conversion areas.