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Porous carbons (PCs) have been widely investigated as electrode materials for supercapacitors. However, during the preparation process, intense pore formation reactions result in an amorphous carbon structure, which limits the rate performance of the electrode material. Herein, coal is chosen as a carbon source and making use of different reaction characteristics of vitrinite and inertinite with a KOH activator, an interconnected porous structure carbon material with an abundant graphite microcrystalline structure is obtained; the organic relationships between the ratio of vitrinite and inertinite, carbonization conditions, material structure and capacity performance were researched. At the ratio of vitrinite to inertinite of 1 : 2, the sample shows a specific surface area of 2507 m2 g−1 and its ID1/IG is 1.31, which is lower than that of raw coal (1.36). Due to the synergistic effect of the pore structure and graphite microcrystals, PC-900-40 exhibits an improved specific capacitance of 229.40 F g−1 at a current density of 1.0 A g−1, and even at a high current density of 10.0 A g−1 it delivers a specific capacitance of 170.04 F g−1. The PC-900-40//PC-900-40 symmetrical capacitor retains 96% of its initial capacitance after 20 000 cycles. [ABSTRACT FROM AUTHOR]

Gallium (Ga) electrodes have been used as anodes in Li-ion batteries, due to their low-melting-point and self-healing properties. However, the use of Ga without a binder or a conductive agent together as the anode material is rare. In this study, AlCl3 was added as an additive to the electrolyte formed by [EMIm]Cl and GaCl3. The obtained binder-free Ga particles were used as the anode of the Li-ion battery; the initial specific capacity was 528.2 mA h g−1 and the initial coulombic efficiency was 97.8%. After 100 cycles, the specific capacity of discharge was 441.6 mA h g−1 at 0.1C. Ga particles obtained from ionic liquids can be used to improve the cycling stability of anodes in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Germanium has emerged as a promising Li ion battery anode material due to its high theoretical capacity. The in situ growth of Ge nanowires on current collectors (binder-free electrodes) has attracted much attention owing to their good electrical contact, excellent strain accommodation ability, promising material durability and short Li ion diffusion distance. Herein, we report a facile and efficient technique to synthesize Ge nanowire cluster arrays (Ge NWCAs) on nickel foam through an ultraviolet light (UV) assisted, template-free electrodeposition process from 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([Emim]Tf2N). As a binder-free anode material, a Ge NWCA electrode exhibits a specific capacity of 1612 mA h g−1 and retains 740 mA h g−1 up to 200 cycles at a current rate of 0.2C. The Ge NWCA electrode affords excellent rate capacity at 0.1C–2C and retains specific capacity as high as 959 mA h g−1 at 2C. Furthermore, the specific capacity well recovers to 998 mA h g−1 when the rate is reduced from 2C to 0.1C. UV assisted ionic liquid electrodeposition might open up a new avenue for the synthesis of semiconductor nanostructures. [ABSTRACT FROM AUTHOR]

Achieving appropriate cycling stability for metal sulfides used as anodes in Li-ion batteries remains highly challenging because of structural collapse or low conductivity. Herein, a novel composite was designed as an anode material for Li-ion batteries. This unique architecture has the advantages of a large interface area, numerous channels for Li+ and electron transport, and a porous structure that facilitates electrolyte infiltration and buffers the volume expansion. As expected, this composite exhibits good cycling stability, high reversible capacity, and high rate capability, delivering a high discharge capacity of 1511.6 mA h g−1 and a high first columbic efficiency of 83.27%. The reversible capacities of graphitic-carbon network material (GCNM) electrodes are 1112 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles, and they show superior rate capabilities. This GCNM composite demonstrates great potential for applications in power sources for flexible and lightweight electronic devices. [ABSTRACT FROM AUTHOR]

Vanadium oxide (V2O5), as a potential positive electrode for sodium ion batteries (SIBs), has attracted considerable attention from researchers. Herein, amorphous and crystalline V2O5 cathodes on a graphite paper without a binder and conductive additives have been synthesized via facile anodic electrochemical deposition following different heat treatments. Both the amorphous V2O5 (a-V2O5) cathode and crystalline V2O5 (c-V2O5) cathode show good rate cycling performance and long cycling life. After five rate cycles, the reversible capacities of both the cathodes were almost unchanged at different current densities from 40 to 5120 mA g−1. Long cycling tests with 10 000 cycles were carried out and the two cathodes exhibit excellent cycling stability. The c-V2O5 cathode retains a high specific capacity of 54 mA h g−1 after 10 000 cycles at 2560 mA g−1 and can be charged within 80 s. Interestingly, the a-V2O5 cathode possesses higher reversible capacities than the c-V2O5 cathode at low current densities, whereas it is inversed at high current densities. The c-V2O5 cathode shows faster capacity recovery from 5120 to 40 mA g−1 than the a-V2O5 cathode. When discharged at 80 mA g−1 (long discharge time of 140 min) and charged at 640 mA g−1 (short charge time of 17 min), the a-V2O5 cathode shows a higher discharge capacity than its c-V2O5 counterpart. The different electrochemical performance of a-V2O5 and c-V2O5 cathodes during various electrochemical processes can provide a rational selection of amorphous or crystalline V2O5 cathode materials for SIBs in their practical applications to meet the variable requirements. [ABSTRACT FROM AUTHOR]

Ge nanotube array anodes are prepared by template-assisted electrodeposition from an ionic liquid to obtain superior cycling performance. They show remarkable cycling ability at 0.2 C, with a very high initial discharge capacity of 1641 mA h g−1 and a charge capacity of 1260 mA h g−1. After 250 cycles the capacity retention is 98% relative to that at the 50th cycle. [ABSTRACT FROM AUTHOR]

To circumvent the imbalances of electrochemical kinetics and charge-storage capacity between Li + ion battery anodes and capacitive cathodes in lithium-ion capacitors (LICs), dual carbon based LICs are constructed and investigated extensively. Herein, S, O dual-doped 3D net-like porous carbon (S-NPC) is prepared using waste paper as the carbon source through a facile solvothermal treatment and chemical activation. Benefiting from the combination effect of the rich S,O-doping (about 2.1 at% for S, and 9.0 at% for O), high surface area (2262 m 2 g -1 ) and interconnected porous network structure, the S-NPC-40 material exhibits excellent electrochemical performance as both cathode material and anode material for LICs. S, O doping not only increases the pseudocapacity but also improves the electronic conductivity, which is beneficial to reduce the mismatch between the two electrodes. The S-NPC-40//S-NPC-40 LIC delivers high energy densities of 176.1 and 77.8 W h kg -1 at power densities of 400 and 20 kW kg -1 , respectively, as well as superior cycling stability with 82% capacitance retention after 20 000 cycles at 2 A g -1 . This research provides an efficient method to convert waste paper to porous carbon electrode materials for high performance LIC devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Vanadium oxide (V 2 O 5 ), as a potential positive electrode for sodium ion batteries (SIBs), has attracted considerable attention from researchers. Herein, amorphous and crystalline V 2 O 5 cathodes on a graphite paper without a binder and conductive additives have been synthesized via facile anodic electrochemical deposition following different heat treatments. Both the amorphous V 2 O 5 (a-V 2 O 5 ) cathode and crystalline V 2 O 5 (c-V 2 O 5 ) cathode show good rate cycling performance and long cycling life. After five rate cycles, the reversible capacities of both the cathodes were almost unchanged at different current densities from 40 to 5120 mA g -1 . Long cycling tests with 10 000 cycles were carried out and the two cathodes exhibit excellent cycling stability. The c-V 2 O 5 cathode retains a high specific capacity of 54 mA h g -1 after 10 000 cycles at 2560 mA g -1 and can be charged within 80 s. Interestingly, the a-V 2 O 5 cathode possesses higher reversible capacities than the c-V 2 O 5 cathode at low current densities, whereas it is inversed at high current densities. The c-V 2 O 5 cathode shows faster capacity recovery from 5120 to 40 mA g -1 than the a-V 2 O 5 cathode. When discharged at 80 mA g -1 (long discharge time of 140 min) and charged at 640 mA g -1 (short charge time of 17 min), the a-V 2 O 5 cathode shows a higher discharge capacity than its c-V 2 O 5 counterpart. The different electrochemical performance of a-V 2 O 5 and c-V 2 O 5 cathodes during various electrochemical processes can provide a rational selection of amorphous or crystalline V 2 O 5 cathode materials for SIBs in their practical applications to meet the variable requirements.