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The exploration of efficient and cost-effective cathodes for flexible hybrid supercapacitors (HSCs) and microbial fuel cells (MFCs) is highly desirable but challenging. Benefiting from the strong points of abundant sources, low price and respectable theoretical capacity, nickel cobaltite (NCO) has a wide applicable prospect as a cathode for flexible HSCs and MFCs. Nevertheless, the capacity, rate capability and oxygen reduction reaction (ORR) activity of the NCO are far from ideal due to its intrinsic weak conductivity. Herein, a feasible and valid method is employed to modify NCO nanowires (NWs) as a high performance cathode for flexible HSCs and MFCs via introducing phosphate ions and oxygen defects. Due to the larger surface, more active sites and faster charge transfer, the assembled flexible HSC device delivers a high energy density of 211 W h kg−1, and the MFC device achieves a power density of 3276.1 mW cm−2. This work may shed light on the modulation of phosphate ions and oxygen defects in enhancing the electrochemical performance of metal oxide electrodes, holding great potential for future flexible multifunctional electrodes. [ABSTRACT FROM AUTHOR]

Aqueous Zn–MnO2 batteries have great potential as flexible energy storage devices owing to their low cost, high energy density, safety, and environmental friendliness. However, their development is plagued by the poor cycling stability, and the use of heavy zinc foil as the anode is antithetical to the flexible devices. Herein, we construct a high-performance and stable flexible rechargeable quasi-solid-state Zn–MnO2 battery using MnO2 nanorod arrays and tiny Zn nanoparticles uniformly deposited on N-doped porous carbon cloth as the free-standing cathode and anode, respectively. The 3D porous nitrogen-doped carbon cloth substrate with high electric conductivity and good flexibility serves as an ideal support for guest active materials of MnO2 nanorod arrays and tiny Zn nanoparticles, which can effectively buffer the volume change giving rise to good cycling ability. Significantly, the device is able to deliver a remarkable capacity of 353 mA h g−1 and good cycling stability (93.6% after 1000 cycles) in an aqueous electrolyte. Moreover, when using PVA/ZnCl2/MnSO4 gel as the electrolyte, the as-fabricated quasi-solid-state Zn–MnO2 battery still achieves a high energy density of 440 W h kg−1, high power density of 7.9 kW kg−1 and excellent cycling ability. This work heralds new opportunities in the development of high-performance, low-cost, safe and flexible electronic devices. [ABSTRACT FROM AUTHOR]

Commercial carbon fiber paper (CFP) has been rarely used as an active electrode material for supercapacitors (SCs) due to its poor electrochemical activity and limited surface area. Herein, we report a facile, scalable and effective thermal oxidation method to directly activate CFP as a robust electrode material in SCs. Significantly, the activated CFP electrode exhibits a high areal capacitance of 0.75 F cm−2 at 5 mA cm−2 and excellent rate capability as well as cycling performance. Moreover, an advanced asymmetric supercapacitor (ASC) device with a remarkable energy density of 2.3 mW h cm−3 and outstanding long-term durability is achieved based on the as-obtained activated CFP electrode as the anode. [ABSTRACT FROM AUTHOR]

Flexible lithium-ion batteries (LIBs) have recently attracted increasing attention with the fast development of bendable electronic systems. Herein, a facile and templatefree solvothermal method is presented for the fabrication of hybrid yolk-shell CoS2 and nitrogen-doped graphene (NG) sheets. The yolk-shell architecture of CoS2 encapsulated with NG coating is designed for the dual protection of CoS2 to address the structural and interfacial stability concerns facing the CoS2 anode. The as-prepared composite can be assembled into a film, which can be used as a binder-free and flexible electrode for LIBs that does not require any carbon black conducting additives or current collectors. When evaluating lithium-storage properties, such a flexible electrode exhibits a high specific capacity of 992 mAh g-1 in the first reversible discharge capacity at a current rate of 100 mA g-1 and high reversible capacity of 882 mAh g-1 after 150 cycles with excellent capacity retention of 89.91 %. Furthermore, a reversible capacity as high as 655 mAh g-1 is still achieved after 50 cycles even at a high rate of 5 C due to the yolk-shell structure and NG coating, which not only provide short Li-ion and electron pathways, but also accommodate large volume variation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hollow MoS2 MACCs have been successfully synthesized. [•] Initial discharge capacity of 1545mAhg−1 is obtained at 100mAg−1. [•] Hollow MoS2 MACCs show enhanced cycling stability and rate capability. [•] Amorphous carbon can improve electrochemical performance. [ABSTRACT FROM AUTHOR]

A novel surface phosphate strategy was adopted to dramatically improve the charge transport, ion diffusion, electroactive sites, and cycle stability of mesoporous NiCo 2 O 4 nanowire arrays (NWAs), drastically boosting their electrochemical properties. Consequently, the as-prepared phosphated NiCo 2 O 4 NWA (P-NiCo 2 O 4 NWA) electrode achieved excellent energy storage performance as a bifunctional anode material for both lithium ion batteries (LIBs) and sodium ion batteries (SIBs). When evaluated as an anode for LIBs, this P-NiCo 2 O 4 NWA electrode showed a high reversible capacity up to 1156 mA h g -1 for 1500 cycles at 200 mA g -1 without appreciable capacity attenuation, while in SIBs, the electrode could also deliver an admirable initial capacity as high as 687 mA h g -1 and maintained 83.5% of this after 500 cycles at the same current density. Most important, when the current density increased from 100 to 1000 mA g -1 , the capacity retention was about 63% in LIBs and 54% in SIBs. This work may shed light on the engineering of efficient electrodes for multifunctional flexible energy storage device applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Flexible lithium-ion batteries (LIBs) have recently attracted increasing attention with the fast development of bendable electronic systems. Herein, a facile and template-free solvothermal method is presented for the fabrication of hybrid yolk-shell CoS2 and nitrogen-doped graphene (NG) sheets. The yolk-shell architecture of CoS2 encapsulated with NG coating is designed for the dual protection of CoS2 to address the structural and interfacial stability concerns facing the CoS2 anode. The as-prepared composite can be assembled into a film, which can be used as a binder-free and flexible electrode for LIBs that does not require any carbon black conducting additives or current collectors. When evaluating lithium-storage properties, such a flexible electrode exhibits a high specific capacity of 992 mAh g(-1) in the first reversible discharge capacity at a current rate of 100 mA g(-1) and high reversible capacity of 882 mAh g(-1) after 150 cycles with excellent capacity retention of 89.91%. Furthermore, a reversible capacity as high as 655 mAh g(-1) is still achieved after 50 cycles even at a high rate of 5 C due to the yolk-shell structure and NG coating, which not only provide short Li-ion and electron pathways, but also accommodate large volume variation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The binary infinite dilute diffusion coefficients, D₁₂(∞), of some alkylbenzenes (Ph-C(n), from Ph-H to Ph-C12) from 313 K to 333 K at 15 MPa in supercritical carbon dioxide (scCO2) have been studied by molecular dynamics (MD) simulation. The MD values agree well with the experimental ones, which indicate MD simulation technique is a powerful way to predict and obtain diffusion coefficients of solutes in supercritical fluids. Besides, the local structures of Ph-C(n)/CO2 fluids are further investigated by calculating radial distribution functions and coordination numbers. It qualitatively convinces that the first solvation shell of Ph-C(n) in scCO2 is significantly influenced by the structure of Ph-C(n) solute. Meanwhile, the mean end-to-end distance, the mean radius of gyration and dihedral angle distribution are calculated to gain an insight into the structural properties of Ph-C(n) in scCO2. The abnormal trends of radial distribution functions and coordination numbers can be reasonably explained in term of molecular flexibility. Moreover, the computed results of dihedral angle clarify that flexibility of long-chain Ph-C(n) is the result of internal rotation of C-C single bond (σ(c-c)) in alkyl chain. It is interesting that compared with n-alkane, because of the existence of benzene ring, the flexibility of alkyl chain in Ph-C(n) with same carbon atom number is significantly reduced, as a result, the carbon chain dependence of diffusion behaviors for long-chain n-alkane (n ≥ 5) and long-chain Ph-C(n) (n ≥ 4) in scCO2 are different.