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Rechargeable aqueous zinc‐ion batteries are considered as promising candidates for safe and green energy storage. Yet, Zn anodes still suffer from serious challenges. Herein, an effective cation‐sieve of polyethersulfone‐modified sulfonated polyether ether ketone is developed as protective coating layer of the Zn anodes. Cation‐only transmission and dense property of the layer can protect the Zn from active water and anions, inhibiting corrosion, hydrogen evolution reaction (HER), and passivation. Zincophilic property of the layer can homogenize Zn2+ flow, and promote uniform plating of Zn. Therefore, protected symmetric Zn||Zn cell can maintain as long as 5600 h with a low polarization at 1.0 mA cm−2 and 0.5 mAh cm−2, and still long as 800 h at 5.0 mA cm−2 and 5.0 mAh cm−2. It is found that not only the dendrites but also the popular existed passivation product of Zn4SO4(OH)6·5H2O can be inhibited effectively. In asymmetric Zn||Ti cells, average Coulombic efficiency can reach 98.2%, suggesting corrosion and HER are restrained effectively. Matched with MnO2 cathode, full cells using coated Zn exhibit much better cycling performance than that using bare Zn. Moreover, Zn4O3(SO4)·7H2O (ZSH)‐assisted reversible conversion mechanism between the ZSH and ZnxHyMnO2 is revealed through operando Raman. [ABSTRACT FROM AUTHOR]

Non‐flow aqueous zinc‐bromine batteries (AZBBs) are highly attractive owing to their lightweight construction and largely reduced cost compared with the flow ones. Yet, their development is restricted by the sluggish reaction kinetics of Br2/Br−, the shuttle of soluble polybromide species (Brn−, n is odd), and the poor stability of Zn‐based anode. Herein, an effective alkaline‐neutral electrolyte decoupling system is constructed to mitigate these issues, where nitrogen‐doped carbon felt with high catalytic activity to Br2/Br− reaction is developed for cathode, a cost‐effective cation exchange membrane (CEM) of polyethersulfone/sulfonated polyether ether ketone (PES/SPEEK‐M) that can stop Brn− is used as separator, and glucose that can inhibit dendrites is introduced as anolyte additive. The constructed flowless AZBB mainly consists of two separate redox couples, including Zn/Zn(OH)42− in alkaline anolyte and Br2/Br− in neutral media, where non‐cations (e.g. OH−, Zn(OH)42−, H2O,  and Brn−) can be restricted to their respective chamber by the PES/SPEEK‐M while cations can pass by. In the optimized system, good electrochemical performance is achieved, mainly including a surprising discharge voltage of 2.01 V, a high average Coulombic efficiency of 96.7%, and a good cycling life of ≈1000 cycles without obvious capacity decay at a fixed charge capacity of 2 mAh cm−2. [ABSTRACT FROM AUTHOR]

In this article, an elementary method, which based on interfacial polymerization of aniline and intermacromolecular force between polyaniline and polyethersulfone, is proposed to construct a whole-polymer membrane electrode (PANI-FME) for flexible supercapacitors. The concentrations of H 2 SO 4 and ammonium persulphate in coagulation bath have great influence on the basic membrane structure, electrical conductivity, and electrochemical performance. The area specific capacity achieves a maximum value of 1465.2 mC cm−2 at the current density of 0.5 mA cm−2. Furthermore, a device of asymmetric supercapacitors by employing the prepared electrode membrane as the positive electrode and the active carbon flexible membrane as negative electrode exhibits a high specific capacity of 585 mC cm−2 at 0.5 mA cm−2, an energy density of 813 mWh m−2, and a power density of 24.95 W m−2. Image 1 • Membrane electrode is prepared based on the interaction between polyethersulfone and polyaniline. • The membrane electrode preserves its function over mechanical deformation. • The capacity of electrode reaches 1465.2 mC cm-2 at current density of 0.5 mA cm-2. • Asymmetric device has superior energy density and power density. [ABSTRACT FROM AUTHOR]

Abstract In this article, mesoporous carbon nanofibers electrode material is reported using polymer/block copolymer blending system as the precursor. The method combines electrospinning process and high temperature carbonization. In the spinning solution, the polymer of polyacrylonitrile is used as precursor, and the block copolymer of polyacrylic acid- b -polyacrylonitrile- b -polyacrylic acid is used as pore forming additive. Abundant pores are formed due to the sacrifice of the thermoplastic chains in the block copolymers during pre-oxidation and thermal annealing process. The effect of block copolymer content in system on electrochemical performance is investigated. The obtained mesoporous carbon nanofibers display a maximum specific capacitance of 256.3 F g−1 in KOH electrolyte when the amount of the block copolymer is 0.6 g. Furthermore, symmetrical supercapacitor assembled with mesoporous carbon nanofibers exhibits a maximum specific capacitance of 22.34 F g−1 and a capacitance retention of 90% after 80, 000 cycles. Highlights • Polymer/block copolymer blending system is designed as precursor of porous carbon fiber. • Effect of block copolymer content on the electrochemical performance is investigated. • The prepared carbon fibers display a maximum specific capacitance of 256.3 F g−1 • The asymmetric supercapacitor shows a capacitance retention of 90% after 80, 000 cycles. [ABSTRACT FROM AUTHOR]

MoO2/Mo2N hybrid nanobelts doped with gold nanoparticles (AuNPMoON) were synthesized via one-step thermal-treatment of MoO3 nanobelts and HAuCl4. AuNPMoON nanobelts with a width of ca. 200 nm and an Au content of 1.08 wt% prepared in the presence of HAuCl4 exhibited a higher specific capacitance of 348 F g−1 than those prepared in the absence of HAuCl4 (21 F g−1) at a current density of 0.5 A g−1. The influence of Au content on the electrochemical performance of AuNPMoON was investigated. For practical application, two types of supercapacitor devices, PANI☋☋AuNPMoON and AC☋☋AuNPMoON, were assembled. The PANI☋☋AuNPMoON device delivered an energy density of 10.64 W h kg−1, which is higher than that of the AC☋☋AuNPMoON device (8.11 W h kg−1). Meanwhile, the specific capacitance retentions were 87.8% and 85.5% for the PANI☋☋AuNPMoON and AC☋☋AuNPMoON devices after 2000 cycles, respectively. [ABSTRACT FROM AUTHOR]

• Cost-effective and eco-friendly CEMs of SPEEK-Ms are developed. • SiO 2 -SPEEK-M possesses high cation exchange ability and low anion permeability. • ZIHC systems using the SiO 2 -SPEEK-M exhibit good electrochemical performance. Herein, a cost-effective cation exchange membrane (CEM), sulfonated polyether ether ketone membrane (SPEEK-M), is prepared through heat sulfuric acid treatment followed by evaporation induced thermal phase separation. Negative charged sulfonic acid functional groups can be grafted on the polymer chains during this process. Exchange of cations, and repulsion of anions are hence realized using this membrane. To further improve the performance of the SPEEK-M, SiO 2 is introduced in. It is found that ionic conductivity is increased to 46.79 mS·cm−1 for the SiO 2 -SPEEK-M from 19.17 mS·cm−1 for the SPEEK-M. Compared with commercial CEMs, such as DuPont N117 and Huamotech, volume expansion of the SPEEK-M is rather small after immersed in water. The membranes are then used as separators in Zn-ion hybrid capacitors (ZIHCs) with decoupled aqueous electrolytes, which includes a Zn foil anode in an alkaline electrolyte, and an activated carbon (AC) cathode in a neutral electrolyte. The electrolyte decoupling strategy maximizes the operating window of this system to 0.5 ∼ 2.2 V. The specific capacity of the AC can reach 390.0C·g−1 at a current density of 0.5 A·g−1. An energy density of 46.2 Wh·kg−1 at a power density of 3416.1 W·kg−1 can be achieved (counting the weight of AC). After gelation of the electrolytes, the growth of Zn dendrite is successfully eliminated, and capacity retention along cycling is increased to 94.3 % using the SiO 2 -SPEEK-M, which is better than that using the commercial DuPont N117 and Huamotech. The raw materials used here to prepare the CEMs are cheap and eco-friendly, which makes the membranes promising candidates as separators for decoupled electrolyte systems. [ABSTRACT FROM AUTHOR]

As a typical pseudo-capacitive electrode material, α-MnO 2 always suffers from low practical capacity and poor stability because of the low conductivity and unavoidable disproportionation reaction. In the work here, high valance Mo (Mo6+) doping followed by chemical reduction treatment is proposed to mitigate these issues. It is found that morphology of the α-MnO 2 can be influenced by Mo-doping, and tunnel size is tuned by the following reduction. Without doping, α-MnO 2 nanorods with good crystallization can be obtained. With the increase of Mo feed ratio, the length of the nanorods is gradually reduced and fine nanoparticles are formed when the Mo/Mn feed mole ratio reaches 1:20 (named as R-1:20). With this feed ratio, a largely increased capacity of 245 C g−1 at 0.5 A g−1 is achieved, much larger than that of the pure α-MnO 2 nanorods (110 C g−1). Yet, there is a certain distortion of the crystal structure, resulting in decline of rate performance. Meanwhile, cycling performance also decays owing to the increase of active sites and hence disproportionation reaction. After reduction treatment, tunnel size of the R-1:20 are slightly enlarged, leading to the improvement of rate performance and cycling stability, and 93% of the initial capacity is maintained after 10,000 cycles. Mo-doping and the following reduction treatment can effectively increase the activity sites, increase the electronic and ionic conductivity, suppress the disproportionation reaction through the adjustment to morphology and tunnel size, and thus improve the charge storage capability of α-MnO 2. [ABSTRACT FROM AUTHOR]

To widen the practical application of supercapacitors in acid electrolyte, carbon/molybdenum nitride (C/Mo x N) nanofibers are synthesized via combination of electrospinning method and thermal treatment in mixed gas atmosphere of N 2 and NH 3 . When the mass fraction of ammonium molybdate of 1.13  wt .% is added in the precursor mixture solution, as-prepared C/Mo x N composite shows the nanofibers of about 200 nm diameter with Mo x N nanoparticles uniformly embedded in the N-doped carbon substrate, and delivers a specific capacitance of 251 F g −1 . Three types of supercapacitor devices of PANI||C/Mo x N, AC||C/Mo x N and C/Mo x N||C/Mo x N are configured in acid electrolyte. The asymmetric supercapacitor of PANI||C/Mo x N shows a maximum energy density of 14.1 Wh kg −1 and power density of 312 W kg −1 , which was larger than those of AC||C/Mo x N device (12 Wh kg −1 , and 325 W kg −1 ) and symmetric supercapacitors of C/Mo x N||C/Mo x N device (4.51 Wh kg −1 , and 250 W kg −1 ). The C/Mo x N||C/Mo x N device exhibits good cycle life of specific capacitance retention of 78.6% at 2 A g −1 after 15, 000 cycles. [ABSTRACT FROM AUTHOR]