[en] Here we report a Li-metal-free full battery, using interlayer-expanded V_6O_1_3 ultra-thin nanosheets and prelithiated graphite for cathodes and anodes, respectively. This full Li-ion battery exhibits a superior specific capacity of 233 mAh g"−"1 at a current density of 100 mA g"−"1 and 91% capacity retention after 500 cycles. Our first-principle calculations reveal that the interlayer-expansion is induced by the interaction between V_6O_1_3 and water which breaks interlayer V-O bonds and forms hydroxyls. The unique structure provides short lithium-ion diffusion path, excellent charge transport, abundant binding sites and volume flexibility for Li"+ intercalation/deintercalation, thus leading to high capability (280 mAh g"−"1) and cycling performance (capacity retain 96.1% at 2.4 A g"−"1 for 1000 cycles). Using novel prelithiation process, the Li-metal-free full cells with high controllability and performance is expected to contribute significantly to the development of safe, green, and powerful energy storage devices.

[en] Nanodevices based on semiconductor nanoarrays have demonstrated many novel electronic, optical and chemical properties. In this work, two simple and controllable solution-based methods for growing well-aligned ZnO nanoarrays on zinc substrate are reported. Photoluminescence (PL) spectrum results revealed that the ZnO nanoarrays may have potential applications as building blocks for 'bottom-up' designed photonic and electronic device applications. Furthermore, well-aligned ZnS nanotube arrays have been successfully synthesized by employing the ZnO nanorod arrays as the sacrificial template through the thioglycolic acid-assisted solution reaction route

[en] Heteroatom doping has recently been utilized to improve the catalytic performance of transition metal-based electrocatalysts. However, the doping process is inevitably accompanied by the introduction of oxygen, influencing the heteroatom-induced asymmetric spin density over the active sites and leading to inconspicuous promotion in the property. Herein, by wiping off the undesired heteroatom-oxygen bonding, we maximize the heteroatom-induced improvement in oxygen reaction activity of metal site, providing descendant energy barrier and favorable reaction efficiency for zinc-air batteries. The proof-of-concept material delivers a superior half-wave potential of 0.88 V versus reversible hydrogen electrode for oxygen reduction reaction, a small overpotential of 410 mV at the current density of 10 mA cm⁻² for oxygen evolution reaction, and a reversible oxygen electrode index of 0.76 V in electrochemical measurements. Aqueous zinc-air battery with such catalysts delivers an excellent power density of 162.3 mW cm⁻² and superior durability over 635 cycles. Moreover, in consideration of high safety and flexibility of solid-state batteries, all-solid-state zinc-air battery adopting gel electrolyte is assembled and used to illumine an LED wristband, showing great promises for the next-generation energy system. (paper)

[en] Carbon material doped with nitrogen and transition metal is a kind of promising candidate of the platinum for oxygen reduction reaction (ORR) process due to its low cost, efficiency and stability. Here we demonstrate an original type of Fe/N/C catalyst based on pore-in-pore structures (P–P Fe/N/C), showing one of the highest oxygen reduction reaction performances among all reported Fe/N/C-type catalysts (onset potential of 0.995 V, half-wave potential of 0.881 V vs. RHE with a relatively low mass loading of 0.32 mg cm⁻² and long-term durability (97% relative current in 60 000 s operation) in alkaline media. Such outstanding performances can be ascribed to the efficient active sites activated by the encapsulated atomic and subnanoscale iron, and great exposure of these active sites due to the unique pore-in-pore hierarchical construction. Once assembled in lithium–O₂ batteries, a specific capacity of 7250 mA h g⁻¹ at 70 mA g⁻¹ can be obtained by the P–P Fe/N/C catalyst. Moreover, upon cycling, the P–P Fe/N/C electrode can be cycled 150 times with no capacity loss, which is much longer than six cycles of pure Super P air electrode. These results evidently reveal the developed Fe/N/C catalyst holds great promise to serve as an alternative to the conventional Pt-based noble metal catalysts. (paper)

[en] Highlights: • Conventional geo-accumulation index ignores the uncertainty in observation data. • Stochastic geo-accumulation model (SGM) takes this uncertainty into consideration. • SGM has better capacities in uncertainty analysis and risk recognizing. • SGM has a better capacity in synthetic pollution evaluation. -- Abstract: The uncertainties introduced by sampling errors, measurement errors, and sediment heterogeneity in the evaluation of heavy metal pollution in the sediment of Poyang Lake are inevitable. The conventional geo-accumulation index (IGeo) cannot overcome these uncertainties. Thus, a stochastic geo-accumulation model (SGM) is established to solve this problem. In the SGM, the distribution of the heavy metal's concentration is stimulated by maximum entropy principle. Then, a membership vector is designed to quantify the pollution condition of each pollutant. Finally, a synthetic membership vector is generated to represent the comprehensive situation of heavy metal pollution in the sediment. SGM is applied in the evaluation of heavy metal pollution in four wetlands of Poyang Lake. Results show that (i) the SGM exhibits better capabilities in uncertainty analysis, risk recognition, and comprehensive pollution evaluation than the conventional IGeo and Hakanson index (HI) models. (ii) The pollution grade of heavy metals in the sediment of Longkou Wetland is “moderately contaminated,” whereas the pollution categories in Nanjishan, Wucheng, and Baishazhou wetlands are “uncontaminated to moderately contaminated.” (iii) Copper and lead are the key risk factors in Poyang Lake.

[en] Biomass lignin, as a significant renewable resource, is one of the most abundant natural polymers in the world. Here, we report a novel silicon-based material, in which lignin-derived functional conformal network crosslinks the silicon nanoparticles via self-assembly. This newly-developed material could greatly solve the problems of large volume change during lithiation/delithiation process and the formation of unstable solid electrolyte interphase layers on the silicon surface. With this anode, the battery demonstrates a high capacity of ∼3000 mA h g⁻¹, a highly stable cycling retention (∼89% after 100 cycles at 300 mA g⁻¹) and an excellent rate capability (∼800 mA h g⁻¹ at 9 A g⁻¹). Moreover, the feasibility of full lithium-ion batteries with the novel silicon-based material would provide wide range of applications in the field of flexible energy storage systems for wearable electronic devices. (paper)

[en] Sulfur has become one of the most promising positive electrode materials for lithium sulfur batteries due to its high theoretical capacity and high energy density (2500 Wh kg⁻¹). The use of common nonpolar carbon/sulfur composites has proved to be a good way to improve the performance, but they still cannot efficiently trap highly polar lithium polysulfides due to the weak interactions between nonpolar carbon and polar polysulfides. Herein, we report a new strategy of using polar cysteamine groups to trap polar polysulfides, leading to greatly enhanced capacity of ∼920 mAh g⁻¹ at 1 C with a high Coulombic efficiency of ∼99.1%, and a long cycle life of over 600 cycles with a capacity retention higher than 80%. Importantly, in situ UV/Vis spectroscopy was employed to identify intermediates during cycling, which demonstrates the constructed unique polar cysteamine functionalized carbon nanotubes (CNTs) can greatly reduce the production of polysulfides and suppress the shuttle effect. The broken-bond model of linear polysulfane during cycling was further demonstrated by density functional theory calculations. The present strategy of using polar cysteamine-functionalized CNTs to trap soluble intermediates is promising and has significant potential for the development of highly efficient lithium sulfur batteries. (paper)

[en] Hydrogen ions are ideal charge carriers for rechargeable batteries due to their small ionic radius and wide availability. However, little attention has been paid to hydrogen-ion storage devices because they generally deliver relatively low Coulombic efficiency as a result of the hydrogen evolution reaction that occurs in an aqueous electrolyte. Herein, we successfully demonstrate that hydrogen ions can be electrochemically stored in an inorganic molybdenum trioxide (MoO₃) electrode with high Coulombic efficiency and stability. The as-obtained electrode exhibits ultrafast hydrogen-ion storage properties with a specific capacity of 88 mA hg^-1 at an ultrahigh rate of 100 C. The redox reaction mechanism of the MoO₃ electrode in the hydrogen-ion cell was investigated in detail. The results reveal a conversion reaction of the MoO₃ electrode into H_0.88MoO₃ during the first hydrogen-ion insertion process and reversible intercalation/deintercalation of hydrogen ions between H_0.88MoO₃ and H_0.12MoO₃ during the following cycles. This study reveals new opportunities for the development of high-power energy storage devices with lightweight elements. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Highlights: • Stabilize sulfur cathodes by the formation of low-solubility lithium polysulfides. • The resulted cathodes exhibited nearly 100% CE at current rates from 0.2C to 6 C. • The proposed mechanism was clearly revealed by in-situ UV/vis and DFT calculations. The long-chain lithium polysulfides that are soluble in ether-based electrolyte for lithium sulfur battery are regarded as one of reason for their low Coulumbic efficiency and low rate capability. In this work, we reported a new strategy to stabilize sulfur cathodes with alkylene radicals to covalently connect sulfur through the formation of low-solubility lithium polysulfides, which enables high Coulombic efficiencies of 99.9% at 0.2 C, 99.9% at 0.5 C, 100% at 1 C, 100% at 2 C, 100% at 4 C, 100% at 6 C as well as outstanding rate capability with a high capacity of 702 mAh g⁻¹ at 6 C. The proposed mechanism was clearly revealed by in-situ UV/vis spectroscopy, demonstrating that short chain polysulfides as discharge products with low solubility are mainly produced during charging and discharging process. Moreover, DFT calculations confirmed that the bond breakage of the linear sulfur chains preferentially takes place in the center of the linear polysulfane, resulting in the formation of short-chain polysulfides, which could effectively avoid the production of soluble long-chain polysulfide and suppress the shuttling effect for high Coulumbic efficiency and high-rate capability lithium sulfur batteries.

[en] It is highly challenging to explore high–performance bi-functional oxygen electrode catalysts for their practical application in next-generation energy storage and conversion devices. In this work, we synthesize hierarchical N–doped carbon microspheres with porous yolk–shell structure (NCYS) as a metal-free electrocatalyst toward efficient oxygen reduction through a template-free route. The enhanced oxygen reduction performances in both alkaline and acid media profit well from the porous yolk–shell structure as well as abundant nitrogen functional groups. Furthermore, such yolk–shell microspheres can be used as precursor materials to motivate the oxygen reduction activity of oxygen evolution oriented materials to obtain a desirable bi-functional electrocatalyst. To verify its practical utility, Zn–air battery tests are conducted and exhibit satisfactory performance, indicating that this constructed concept for preparation of bi-functional catalyst will afford a promising strategy for exploring novel metal–air battery electrocatalysts. (paper)