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Abstract: Potassium‐ion batteries (PIBs) are promising energy storage systems because of the abundance and low cost of potassium. The formidable challenge is to develop suitable electrode materials and electrolytes for accommodating the relatively large size and high activity of potassium. Herein, Bi‐based materials are reported as novel anodes for PIBs. Nanostructural design and proper selection of the electrolyte salt have been used to achieve excellent cycling performance. It is found that the potassiation of Bi undergoes a solid‐solution reaction, followed by two typical two‐phase reactions, corresponding to Bi ↔ Bi(K) and Bi(K) ↔ K5Bi4 ↔ K3Bi, respectively. By choosing potassium bis(fluorosulfonyl)imide (KFSI) to replace potassium hexafluorophosphate (KPF6) in carbonate electrolyte, a more stable solid electrolyte interphase layer is achieved and results in notably enhanced electrochemical performance. More importantly, the KFSI salt is very versatile and can significantly promote the electrochemical performance of other alloy‐based anode materials, such as Sn and Sb. [ABSTRACT FROM AUTHOR]

Abstract: The structure and electrochemical characteristics of (La1−x Dy x )0.8Mg0.2Ni3.4Al0.1 (x = 0–0.20) hydrogen storage alloys have been investigated. Dysprosium was adopted as a partial substitution element for lanthanum in order to improve electrochemical properties. The XRD, SEM and EDX results showed that the alloys were composed of (La, Mg)2Ni7, LaNi5 and (La, Mg)Ni2 phases. The introduction of Dy promoted the formation of (La, Mg)2Ni7 phase which possesses high hydrogen storage capacity, and controlling dysprosium content at 0.05 can obtain the maximum (La, Mg)2Ni7 phase abundance in the alloys. The maximum discharge capacity was heightened from 382.5 to 390.2 mAh/g, which was ascribed to (La, Mg)2Ni7 phase abundance increasing from 54.8% to a maximum (60.5%). Also, the biggest discharge capacity retention remained 82.7% after 100 cycles at discharge current density of 300 mA/g. [Copyright &y& Elsevier]

Abstract: With respect to first-principles calculations, the sandwich-type dinuclear organometallic compounds as (C5H5)2TM2 (M = Sc and Ti) can adsorb up to eight hydrogen molecules. The corresponding gravimetric hydrogen-storage capacity is 6.7 wt% for (C5H5)2Ti2 and 6.8 wt% for (C5H5)2Sc2. The multimetallocenes (e.g., CpTi3Cp and CpTi4Cp) complexes can further increase the H2 adsorption capacity to 8.7 wt% and 10.4 wt%, respectively. These sandwich-type organometallocenes proposed in this work are favorable for reversible adsorption and desorption of hydrogen under ambient conditions. These predictions will likely provide a new route for developing novel high-capacity hydrogen-storage materials. [Copyright &y& Elsevier]

SnS 2 @CS, as sulfur host and separator modifier, with high electrical conductivity, high specific surface area and abundant active sites can not only contribute to the fast electron transport to improve the electrochemical activity but also can efficiently adsorb and catalyse polysulfides and improve the utilization of active sulfur. [Display omitted] Lithium-sulfur (Li-S) batteries are considered promising candidates for next-generation advanced energy storage systems due to their high theoretical capacity, low cost and environmental friendliness. However, the severe shuttle effect and weak redox reaction severely restrict the practical application of Li-S batteries. Herein, a functional catalytic material of tin disulfide on porous carbon spheres (SnS 2 @CS) is designed as a sulfur host and separator modifier for lithium-sulfur batteries. SnS 2 @CS with high electrical conductivity, high specific surface area and abundant active sites can not only effectively improve the electrochemical activity but also accelerate the capture/diffusion of polysulfides. Theoretical calculations and in situ Raman also demonstrate that SnS 2 @CS can efficiently adsorb and catalyse the rapid conversion of polysulfides. Based on these advantages, the SnS 2 @CS-based Li-S battery delivers an excellent reversible capacity of 868 mAh/g at 0.5C (capacity retention of 96 %), a high rate capability of 852 mAh/g at 2C, and a durable cycle life with an ultralow capacity decay rate of 0.029 % per cycle over 1000 cycles at 2C. This work combines the design of sulfur electrodes and the modification of separators, which provides an idea for practical applications of Li-S batteries in the future. [ABSTRACT FROM AUTHOR]

The functional combination of riboflavin and activated carbon successfully introduced a significant redox reaction in the activated carbon, increasing the specific capacitance of the material and significantly improving the rate performance. Potential control significantly enhances the cycling stability of AC/VB2. [Display omitted] • AC/VB2 has a low charge/discharge plateau of −0.65 to −0.9 V (vs. Hg/HgO). • AC/VB2 as a negative electrode shows high specific capacitance (419.1 F g−1) and outstanding rate performance. • Potential control significantly enhances the cycling stability of AC/VB2. • An AC/VB2(–)||LDH(+) device delivers a high energy density of 58.5 Wh kg−1 and a high power density of 27,410 W kg−1. Pseudocapacitive materials are used to increase the energy density of supercapacitors, but their rate performance and cycling stability are frequently unsatisfactory. Herein, we report a riboflavin-functionalized activated carbon (AC/VB2) as a negative electrode with high specific capacitance (419.1 F g−1) and outstanding rate performance. The potent combination of VB2 and AC renders VB2 insoluble in alkaline liquids and fully exploits its redox characteristics. VB2 contributes additional redox reactions to AC and its reaction plateau is from −0.65 to −0.9 V (vs. Hg/HgO), favoring the storage of large amounts of energy. Based on the detailed analysis of the surface state of the material during the reaction, a strategy to improve cycling stability by controlling the charge/discharge potential window is proposed, which can effectively inhibit the desorption and overreaction of VB2, thus greatly enhancing cycling stability. The electrode can be operated stably for 100,000 cycles without any decline at high current densities. An AC/VB2(–)||LDH(+, Co-doped Ni(OH) 2) device delivered a high energy density of 58.6 Wh kg−1 at a power density of 686 W kg−1 and a high power density of 27,410 W kg−1 at an energy density of 13.2 Wh kg−1. This work offers a practical manual for making high–energy pseudocapacitive negative electrodes and enhancing their cycling stability. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries have attracted enormous attentions as new-generation energy storage devices due to their high theoretical energy density, high theoretical specific capacity, low cost and environmental friendliness. However, polysulfide shuttle and the growth of lithium dendrites significantly restrain the practical application of the Li-S batteries. In this work, a modified PP separator with nanoscale rod-like α-MnO 2 supported on carbon nanotubes was prepared. The α-MnO 2 @CNT modified separator can effectively inhibit the shuttle of polysulfide, enhance the electrochemical activity and accelerate the transfer of ions and electrons. The density functional theory (DFT) calculations demonstrate that α-MnO 2 @CNT can efficiently adsorb and catalyze the conversion of polysulfides. Due to these advantages, the α-MnO 2 @CNT-based Li-S battery delivers a initial discharge capacity of 1469 mAh g−1 at 0.05 C, 1039 mAh g−1 at 0.5 C and the capacity can still maintain 648 mAh g−1 over 500 cycles at 0.5 C (capacity decay rate of 0.075%). Expressly, the capacity decay rate is only 0.022% after 600 cycles at a high current density of 2 C. The excellent performance could be attributed to the α-MnO 2 @CNT modified separator not only accelerating the transmission of electrons but also effectively inhibiting the shuttle of polysulfides. Moreover, this work provides a better idea for practical applications of lithium-sulfur batteries in the future. [Display omitted] • The synthesized α-MnO 2 is in the shape of nanorods. • The α-MnO 2 @CNT composite has good polysulfide adsorption and catalytic conversion ability. • The α-MnO 2 @CNT modified separator shows an excellent long-term cycling stability and rate performance. [ABSTRACT FROM AUTHOR]

The functional combination of methylene blue and activated carbon successfully introduced a significant redox reaction in the activated carbon, increasing the specific capacitance of the material and significantly improving the rate performance. The methylene blue adsorbed on the surface of activated carbon enables fast proton-coupled electron transfer. [Display omitted] • Anthracite can be activated at low temperature and show large specific surface area. • Oxygen groups could effectively contribute the pseudo-capacitance to AC. • The π-π binding endows AC/MB excellent electrochemical properties. • The optimized AC/MB as positive can deliver ultrahigh energy and power density. • Mathematical simulation can optimize the ratio of positive to negative electrodes. Supercapacitors are desired to deliver high power and energy density concurrently, and the introduction of a redox reaction is an effective strategy to improve their capacitive performance. Herein, methylene blue (MB) with redox was employed to functionalize coal-based activated carbons (ACs) as electrode materials for energy storage. The optimized AC shows a high specific capacitance of 408.1 F g−1 in 6 M KOH, deriving from the contribution of the electrical double-layer capacitance of pores and pseudocapacitance of oxygen groups. Interestingly, pure MB shows no capacitive performance mainly due to its low conductivity, while the optimized composite of AC adsorbed MB (AC/MB) surpasses the pure MB and optimized AC in any capacitive performance, displaying a relationship of mutual promotion based on functional combination. The best AC/MB sample exhibits a high specific capacitance of 431.8 F g−1 at 1 A g−1, and 356.1 F g−1 (82.5%) at an ultrahigh current density of 180 A g−1, implying an excellent rate performance. Aiming to deliver maximum energy density, an accurate universal method is proposed to match the mass ratio of negative to positive. The optimized asymmetric supercapacitor AC/MB(+) || AC(-) delivers an energy density of 11.0 Wh kg−1, a power density up to 15.3 kW kg−1 and a high capacity retention rate of 96.3% after 10,000 cycles, displaying good chemical stability. This work proposes a promising strategy for ultrafast store/release energy at high energy density, and also provides an application direction for AC and MB. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ce-doped MnO 2 was prepared by the potentiostatic electrodeposition strategy. • The assembled flexible Zn//Ce-MnO 2 @CC battery exhibits long cycle-life. • The doped cerium ions could stabilize the structure of the cathode materials. • A H+/Zn2+ co-insertion mechanism of the Mn-based oxides cathode was demonstrated. With the development of flexible electronic devices, power sources' higher safety, lighter, and bending ability have been demanded in recent years. While, aqueous zinc-ion batteries (ZIBs) have gained much attention due to their low cost, rich zinc resources, and high safety. Hence, they have been considered the most promising secondary battery in the near future. However, the practical application of aqueous ZIBs is still impeded by the unsatisfied performance of the cathode materials and the complex manufacturing process. Moreover, the electrochemical energy storage process and mechanism of the cathodes at the flexible ZIBs still remain ambiguous and under discussion, which severely limited the development of the ZIBs. Herein, a Ce doped-MnO 2 binder-free cathode electrode was prepared via a one-step potentiostatic electrodeposition strategy. A flexible ZIB assembled based on the Ce-MnO 2 @CC cathode and a homemade gel electrolyte exhibits a high reversible specific capacity (∼311 mAh g−1), a significant energy density (370 Wh kg−1), an excellent stability performance, and achieves good electrochemical behavior even under different bending conditions. Furthermore, the energy storage mechanism of the flexible ZIBs with Mn-based oxides cathode was monitored by the in-situ Raman, XRD, SEM, and TEM, revealing the reversible insertion/extraction of Zn2+ and H+ during the charge/discharge process. Moreover, the results also demonstrate that the structural shedding, and dissolution of the MnO 2 structure are the major factors in reducing capacity. This research opens up new opportunities for flexible ZIBs in the field of portable and wearable electronics. [ABSTRACT FROM AUTHOR]