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The inherently intermittent and regional nature of renewable energy generation drives the growth of large-scale electrical energy storage systems. Aqueous Zn-based batteries matched with conversion-type cathodes have attracted increasing attention owing to their cost effectiveness, abundant reserves, intrinsic safety, and relatively long lifetime. Halogens with unique electron configurations possess an abundance of chemical valence states, high redox potential, and relatively high theoretical capacity and have shown great promise as cathode materials. However, many intractable challenges need to be resolved, such as the shuttle effect and slow kinetics. In this review, redox mechanisms and fundamental challenges associated with aqueous zinc–halogen batteries are summarized first. Subsequently, the research issues and progress related to halogen cathode materials are discussed. Finally, we present a forward-looking perspective for promising aqueous zinc–halogen batteries. By furnishing a nuanced understanding of recent advancements and challenges in this field, the review aspires to offer valuable guidance to researchers, ultimately facilitating the practical application of aqueous zinc–halogen batteries. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries (LSBs) have received intensive attention in recent years due to their high theoretical energy density derived from the lithiation of sulfur. In the discharge process, sulfur transforms into lithium polysulfides (LiPSs) that dissolve in liquid electrolytes and then into insoluble Li2S precipitated on the electrode surface. The electronically and ionically insulating Li2S leads to two critical issues, including the sluggish reaction kinetics from LiPSs to Li2S and the passivation of the electrode. In this regard, controlling the Li2S deposition is significant for improving the performance of LSBs. In this perspective, we have summarized the recent achievements in regulating the Li2S deposition to enhance the performance of LSBs, including the solution-mediated growth of Li2S, sulfur host enhanced nucleation and catalysis induced kinetic improvement. Moreover, the challenges and possibilities for future research studies are discussed, highlighting the significance of regulating the Li2S deposition to realize the high electrochemical performance and promote the practical uses of LSBs. [ABSTRACT FROM AUTHOR]

Uncontrollable lithium (Li) dendrite growth and continuous side reactions with a carbonate-based electrolyte seriously restrict the use of Li metal anodes. We report a very tough multifunctional artificial protective (MAP) layer formed on a Li metal anode that is ultra-stable in the normally used commercial carbonate electrolyte. The MAP layer is prepared by the in situ photopolymerization of pentaerythritol tetraacrylate (PETEA) and poly(ethylene glycol)diacrylate (PEGDA) in a framework of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) incorporated with graphene oxide (GO). There are two aspects to the functionality of this MAP layer. It has excellent compatibility with the carbonate electrolyte because of the similar chemical structure of the ester group, giving it a high ionic conductivity, and induces the formation of a unique solid electrolyte interphase (SEI) containing organic components and LiF, which has a good chemical stability with the carbonate liquid electrolyte to suppress Li dendrite growth and side reactions. A symmetric battery with the MAP coated Li (MAP-Li) anode steadily cycles for over 1100 h at 1 mA cm−2 in a carbonate liquid electrolyte. The work provides a way to obtain a stable Li metal anode in a practical carbonate electrolyte. [ABSTRACT FROM AUTHOR]

Volumetric and areal capacitance are as important as gravimetric capacitance for small energy storage devices. However, achieving both a high volumetric and a high areal capacitance is still a big challenge. Here we report a dense redox organic molecules/graphene network, in which highly redox active sodium anthraquinone-2-sulfonate (AQS) molecules are anchored on interconnected and highly conductive graphene sheets by noncovalent π–π interactions to form high-performance supercapacitors (SCs). The AQS/graphene (AQS/G) has a high volumetric specific capacitance of up to 650 F cm−3 and an excellent rate capability (422 F cm−3 even at 30 A g−1), as well as a good cycling stability. A maximum areal specific capacitance of 13.3 F cm−2 is achieved at a high mass loading of 32 mg cm−2 (200 μm in thickness), which is amongst the highest values recorded for organic-based materials for SCs. An asymmetric SC constructed with AQS/G and RuO2/graphene delivers a maximum volumetric energy density of 44 W h L−1. This outstanding performance is attributed to the excellent electron conduction and ion transport provided by the dense but interconnected graphene network. This work suggests a new way for organic-based high-performance electrode materials to be used in electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

The density and ion channel abundancy of an electrode material must be elaborately balanced to achieve a high volumetric energy density for any energy storage devices. As a typical example, graphene shows great potential in different energy storage devices but its low density and ion diffusion barrier effect limit its practical uses. In the present work, H2O2 etching was introduced into the hydrothermal assembly of graphene oxide (GO) to decrease the lateral size of GO and create in-plane holes, and after a capillary drying process, a high-density holey graphene monolith (HHGM) with numerous and interconnected ion transporting channels was obtained. The smaller sheet size leads to a more densified assembly while in-plane holes are beneficial to ion transportation in the HHGM, which well balance the high density and fast ion diffusion in the electrode. As a result, the HHGM shows an impressive rate performance, coupled with a high volumetric capacitance. [ABSTRACT FROM AUTHOR]

The shuttling of dissolved polysulfide intermediates and their sluggish reaction kinetics largely reduce the cycle life and sulfur utilization of lithium–sulfur (Li–S) batteries. In this study, low-cost bacterial cellulose was used as the precursor for interconnected carbon networks and a supporting framework for impregnated molybdate ions. After freeze-drying and solid-state thermal reactions, necklace-like molybdenum carbide embedded in interconnected N-doped carbon nanofibers (MoC@N-CNF) was obtained to be used as a high sulfur loading host. On the one hand, the interconnected conductive carbon network enables fast electron and ion transport, and on the other hand, the embedded sulfiphilic MoC efficiently immobilizes polysulfides and catalytically promotes their redox conversion. Therefore, the as-prepared electrode coupled with the lithium polysulfide catholyte exhibits good cycling stability with a low capacity decay of 0.084% per cycle at 1C for 350 cycles and a high rate capability of 799 mA h g−1 at 2C. Moreover, a high areal capacity of 12.3 mA h cm−2 with an areal sulfur loading of 10 mg cm−2 at 0.1C is also achieved. [ABSTRACT FROM AUTHOR]

Porous carbons with a high specific surface area (SSA) have been widely investigated as anodes for sodium-ion batteries (SIBs). Despite their high initial capacity, they are not ideal anodes due to the very low initial coulombic efficiency (ICE) derived from the uncontrollable irreversible reactions of the large carbon surface with the electrolyte resulting in SEI formation. In this study, an ion-conducting SnS–SnS2 hybrid coating is designed that thoroughly coats the outer surface of the porous carbon to prevent contact of the electrolyte with the inner pore surface, while allowing the diffusion of sodium ions to the inside. With an SnS–SnS2 hybrid coating, a commercial activated carbon with a high SSA of 1960 m2 g−1 shows a significant increase in ICE from 15.7% to 68.6%, and at the same time, high capacity and high rate capability are achieved. The capacities reach 380 and 110 mA h g−1 at the current densities of 0.05 and 5 A g−1, respectively. The unique design of the ion-conducting coating suggests an effective way to modify a high surface area porous carbon into a high-performance anode for metal ion batteries, not limited to SIBs. [ABSTRACT FROM AUTHOR]

It is a huge challenge for high-tap-density electrodes to achieve high volumetric energy density but without compromising the ionic transportation. Herein, we prepared compact Li4Ti5O12 (LTO) microspheres consisting of densely packed primary nanoparticles. The real space distribution of lithium ions inside the compact LTO was revealed by using scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) to identify the function of grain boundaries for lithium ion transportation during lithiation. The as-prepared LTO microspheres possess a high tap density (1.23 g cm−3) and an ultra-small specific surface area (2.40 m2 g−1). Impressively, the compact LTO microspheres present excellent electrochemical performance. At high rates of 5C, 10C and 20C, the LTO microspheres show a specific capacity of 146.6, 138.2 and 111 mA h g−1, respectively. The capacity retention remains at 97.8% at 5C after 500 cycles. The STEM-EELS results indicate that the lithiation reaction of LTO is firstly initiated at grain boundaries during the high rate lithiation process and then diffuses to the bulk area. The abundant grain boundaries in compact LTO microspheres can form a highly efficient conductive network to preferentially transport the ions, which contributes to high volumetric and gravimetric energy density simultaneously. [ABSTRACT FROM AUTHOR]

Lithium metal is the most promising anode for next-generation rechargeable lithium batteries but Li dendrite growth and the resulting safety issues resulting from the non-uniform Li deposition hinder its practical use. Considering the high cost and complication of the currently reported approaches to suppress the Li dendrite growth, in this study we have modified a low-cost commercial three-dimensional (3D) Cu foam into a high-performance host for stable Li deposition by the growth of Cu2S nanowires (NWs) inside the Cu framework. The Cu2S NWs were grown by a simple and scalable chemical approach, and they reduce the local current density and homogenize the Li ion distribution because of the increased contact area of the 3D Cu2S NWs/Cu with the electrolyte. They also enable the formation of a protective solid electrolyte interphase (SEI) film containing Li2S2/Li2S. The prepared 3D Cu2S NWs/Cu current collector enables dendrite-free Li deposition/stripping and gives a stable cycling performance with a high coulombic efficiency (95.5% for more than 150 cycles at 2 mA cm−2). Full cells with LiFePO4 as the cathode also exhibit improved cycling stability and improved coulombic efficiency, showing the potential of this host in the use of stable Li metal anodes. [ABSTRACT FROM AUTHOR]

People use polymers as materials for preparing separation media or containers. It is necessary to have a molecular level profound knowledge of gas transport in e bulk and interface regimes of different polymers, but few researchers have done a molecular level study of the bulk and interface behavior of gases in several types of non-homologen polymers thoroughly or developed expressions to correlate gas transport properties with cavity size distribution and chain oscillation flexibility. Therefore, in this work, molecular dynamics (MD) simulation was employed to study the transport of methane and n-butane molecules in the bulk and interface region of polyethylene (PE), poly(4-methyl-2-pentyne) (PMP) and polydimethylsiloxane (PDMS). Penetrant diffusivity, solubility and permeability in the bulk were studied first. The subdiffusion behavior of gas molecules is explored to obtain the mechanisms behind penetrant transport. Both penetrants have much smaller diffusivities in PE than in PMP and PDMS, and they have larger diffusivities in PDMS than in PMP. PE has lower accessible cavity fraction (ACF) and average oscillation amplitudes (AOAs) of the chains than PDMS and PMP. PE also has much smaller solubilities and permeabilities of both penetrants than PDMS and PMP. Though the permeabilities of both penetrants in PDMS are higher than the corresponding values in PMP, PMP has a higher selectivity of n-butane over methane than PDMS. Nonequilibrium MD simulation was performed to study the interface property and gas transport in the interface region. Equations to predict penetrant diffusivity and permeability from the accessible cavity fraction (ACF) and average amplitude of chain oscillation were developed successfully. Penetrant diffusivity and permeability are proportional to the value of ACF to the power of one third and that of ACF to the power of four thirds, respectively. [ABSTRACT FROM AUTHOR]

A liquid Na–K alloy is adsorbed onto a super-aligned carbon nanotube membrane (denoted CM) at room temperature, which is driven by capillary force, fabricating a flexible CM@NaK membrane. The anode directly using the CM@NaK membrane exhibits a smooth electrode–electrolyte (liquid–liquid) interface, contributing to fast ion transport and a dendrite-free stripping/plating process. [ABSTRACT FROM AUTHOR]

Sulfur-functionalized graphene monoliths with a high sulfur fraction (16.8 wt%) were prepared to demonstrate a high capacity (∼400 mA h g−1 at 0.1 A g−1) and ultrafast (∼120 mA h g−1 at 5 A g−1) sodium ion storage. The reversible reaction of –C–Sx–C– with sodium ions contributes to the extra capacity while a 3D graphene network guarantees high rate capability. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) show brilliant performance in separating gas impurities, but few researchers have performed an in-depth exploration of the bulk and interface behavior of penetrants and ILs thoroughly. In this research, we have performed a study on both molecular dynamics (MD) simulation and quantum chemical (QC) calculation to explore the transport of acetylene and ethylene in the bulk and interface regions of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]–[BF4]). The diffusivity, solubility and permeability of gas molecules in the bulk were researched with MD simulation first. The subdiffusion behavior of gas molecules is induced by coupling between the motion of gas molecules and the ions, and the relaxation processes of the ions after the disturbance caused by gas molecules. Then, QC calculation was performed to explore the optical geometry of ions, ion pairs and complexes of ions and penetrants, and interaction potential for pairs and complexes. Finally, nonequilibrium MD simulation was performed to explore the interface structure and properties of the IL–gas system and gas molecule behavior in the interface region. The research results may be used in the design of IL separation media. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are considered promising low-cost alternatives to prevailing lithium-ion batteries (LIBs). The inherently sluggish kinetics of their anode materials, however, poses a great challenge to the SIBs' rate capabilities. This work reports the synthesis of novel MoS2/Carbon (MoS2/C) microspheres with three-dimensional (3D) architecture as an anode for SIBs using a facile hydrothermal strategy. The MoS2/C electrode delivers a reversible capacity of 498 mA h g−1 at 100 mA g−1, which stabilizes at 450 mA h g−1 after 100 cycles. Even at 4 A g−1, the electrode maintains a high reversible capacity above 310 mA h g−1 after 600 cycles, demonstrating its superior rate capability and long-term cyclic stability. Quantitative kinetics analysis reveals a pseudocapacitance-dominated Na+ storage mechanism, especially at high current densities. Furthermore, density functional theory (DFT) calculations show that the Na transport rates are faster through the MoS2/C heterointerface, due to a low diffusion energy barrier, than along the MoS2/MoS2 bilayers. [ABSTRACT FROM AUTHOR]

Developing high-performance flexible film-like electrodes is still a primary task for the practical applications of wearable/portable planar supercapacitors. In this work, a facile and effective approach, i.e., stacking up layers of polyaniline (PANI)/carbon nanotube (CNT) composite networks inside air-laid papers, is proposed to fabricate highly flexible paper electrodes with large areal capacitance and superior rate capability. The layer-by-layer deposition of PANI/CNT networks endows the fabricated paper electrodes with high loading and uniform distribution of PANI; meanwhile, the good electrical conductivity and porous structure of these introduced PANI/CNT networks guarantee sufficient paths for electron movement and ion transportation in the electrodes. Consequently, when 4 layers of PANI/CNT networks (with optimal PANI content) are stacked inside papers, the areal capacitance of the prepared electrode is as high as 1506 mF cm−2 at a charge/discharge current of 10 mA cm−2 and 1298 mF cm−2 at 100 mA cm−2; the electrode also exhibits high flexibility and good cycling stability (with 82% capacitance retention after 11 500 charge/discharge cycles). These merits make our PANI/CNT/papers promising candidates for flexible planar supercapacitor electrodes. Besides, this work is believed to provide a new thought for producing high-loading and high-energy wearable/portable energy storage devices. [ABSTRACT FROM AUTHOR]

The ability to judiciously utilize gel-polymer electrolytes (GPEs) that replace liquid electrolytes is widely recognized as an attractive route to solving the safety concerns of Li-ion batteries (LIBs). In this context, novel LiNi0.8Co0.15Al0.05O2 (NCA)/graphite GPE and NCA/graphite–Si/C GPE batteries with high energy density and excellent electrochemical and safety performances are developed via in situ polymerization of pentaerythritol tetraacrylate (PETEA) in a liquid electrolyte. Notably, the capacity retention of NCA/graphite and NCA/graphite-Si/C GPE batteries after 200 cycles at the discharge rate of 5C is 92.5% and 81.2%, respectively, which are much larger than those implementing liquid electrolytes (i.e., only 55.9% and 51.4%, respectively). Interestingly, the GPE batteries also displayed considerably lower gas production, especially the graphite-Si/C anode battery, and did not undergo a violent combustion during the nail penetration test compared to the liquid electrolyte batteries. The markedly enhanced performances noted above can be attributed to the three-dimensional framework of the GPE which promoted the formation of a very tight protective film on the surface of the electrodes during cycling, thereby inhibiting the cyclable Li consumption and side reactions with the electrolyte. Furthermore, such a protective film effectively retained the structural integrity of the electrodes during the cycling process and reduced the heat reactions between the electrodes and electrolyte. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have gained significant attention as precursors for the fabrication of porous hybrid materials due to their highly controllable composition, structure and pore size. However, at present, MOF-derived materials have rarely been investigated as anode materials for sodium-ion batteries. In this work, we report the fabrication of a Ni-doped Co/CoO/N-doped carbon (NC) hybrid using bimetallic Ni–Co-ZIF as the starting precursor. The resulting Ni-doped Co/CoO/NC hybrid is highly microporous with a high specific surface area of 552 m2 g−1. When employed as an anode material for sodium-ion batteries, the Ni-doped Co/CoO/NC hybrid exhibited both good rate performance with a high discharge capacity of 218 mA h g−1 at a high current density of 500 mA g−1 and good cycling stability, as a high discharge capacity of 218.7 mA h g−1 can be retained after 100 cycles at 500 mA g−1, corresponding to a high capacity retention of 87.5%. The excellent electrochemical performance of the Ni-doped Co/CoO/NC hybrid for SIBs may be attributed to the synergistic effects of various factors, including: (i) the presence of a carbon matrix which provides protection against aggregation and pulverization during sodiation/desodiation; (ii) the highly microporous nature along with the presence of a few mesopores which facilitates better insertion/de-insertion of Na+ ions; (iii) the Ni-doping which introduces defect sites into the atomic structure of CoO via partial substitution, thus enhancing the conductivity of the cobalt oxide (CoO) component and hence, the overall hybrid material, and (iv) the N-doping which promotes a faster migration speed of sodium ions (Na+) across the carbon layer by creating defect sites, thereby improving the conductivity of the carbon frameworks in the hybrid material. [ABSTRACT FROM AUTHOR]

Lithium ion batteries (LIBs) with high power density, extended life time, and enhanced safety properties are promising energy storage devices for pure/hybrid electric vehicles and grid energy storage. Conventional graphite anodes suffer from limited rate capability and great safety concerns. Thus the development of efficient electrode materials with long cycle stability, excellent rate capability and enhanced safety is crucial for high-power LIBs. Spinel Li4Ti5O12 (LTO) has emerged as a competitive anode material for high-power LIBs due to its high safety, excellent high rate capability and extremely long cycling stability. However, the severe gas generation and associated swelling observed in soft-pack batteries during charge/discharge cycles and storage, which are accelerated under elevated temperatures, become a main obstacle to the large-scale application of LTO-based LIBs. Further understanding on the severe gassing behavior in LTO-based LIBs is quite necessary since it not only seriously deteriorates their power density and cycling stability, but also leads to great safety concerns. To date, there are some research reports that specifically refer to the gassing behavior of LTO electrodes. However, there is no critical review that concentrates exclusively on the gassing of LTO-based batteries. Hence, this review aims to provide an up-to-date and comprehensive summary of the gassing behavior in LTO-based LIBs. Details will be given specifically on the influencing factors, possible gassing mechanisms, and state-of-the art remedies. An insight into the future research of LTO-based battery development is given. [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) has attracted great interest as a promising anode material for lithium (Li) ion batteries (LIBs) and sodium (Na) ion batteries (SIBs). However, the key factors that dictate the Li-ion and Na-ion storage and transportation in TiO2 remain unclear. Herein, we report a facile hydrolysis route to crafting a variety of high tap-density TiO2 spheres with controllable size and hierarchical pores. The Li-ion and Na-ion storage properties based on these TiO2 spheres were systematically investigated. The pore distribution and the size of TiO2 spheres were found to exert profound influence on the Li-ion and Na-ion storage and transportation. The Li-ion storage and transportation in dense TiO2 spheres was dependent mainly upon the micropore distribution and volume and independent of the size of spheres. In contrast, the excellent Na-ion storage and transportation in TiO2 spheres was enabled by the loose structure with a large macroscopic pore volume and shortened Na-ion diffusion length. High tap-density TiO2 spheres (1.06 g cm−3) with superior Li-ion and Na-ion storage properties were produced, exhibiting a Li-ion storage specific capacity of 189 mA h g−1 at 1C and a high capacity retention of 88.1% after 100 cycles, and a Na-ion storage specific capacity of 184 mA h g−1 at 1C and capacity retention of 90.5% after 200 cycles. The ability to understand the critical factors controlling the Li-ion and Na-ion storage in high tap-density TiO2 spheres enables their implementation for practical applications in Li-ion and Na-ion batteries. [ABSTRACT FROM AUTHOR]

Retraction of 'Comparing gas transport in three polymers via molecular dynamics simulation' by Luke R. Anderson et al., Phys. Chem. Chem. Phys., 2018, 20, 22123–22133, https://doi.org/10.1039/C8CP02829J. [ABSTRACT FROM AUTHOR]

A novel hierarchical porous carbon–carbon nanotube hybrid (HPCC) is prepared using a one-step strategy that uses nickel nanoparticles as the template for pore formation and at the same time, as the catalyst for carbon nanotube (CNT) growth. Such a structure can not only store sulfur in the micro- and mesopores, which restrict the shuttling of polysulfides, but also ensure good electrical conductivity of the whole system due to the incorporation of CNTs. The hierarchical porous structure also ensures fast mass transportation. These factors effectively guarantee the high electrochemical performance of sulfur stored in this carbon in lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]

Supercapacitors are important energy storage devices capable of delivering energy at a very fast rate. With the increasing interest in portable and wearable electronic equipment, various flexible supercapacitors (FSCs) and flexible electrodes (FEs) have been investigated widely and constantly in recent years. Currently-developed FEs/FSCs exhibit myriad physical forms and functional features and form a complicated and extensive system. Herein, we summarize the recent results about FEs/FSCs and present this review by categories. According to different micro-structures and macroscopic patterns, the existing FEs/FSCs can be divided into three types: fiber-like FEs/FSCs; paper-like FEs/FSCs; and three-dimensional porous FEs (and corresponding FSCs). Subsequently each type of the FEs/FSCs is further sub-classified based on their construction rules, and mechanical and electrochemical properties. To our best knowledge, this is the first time such a hierarchical and detailed classification strategy has been propose. We believe it will be beneficial for researchers around the world to understand FEs/FSCs. In addition, we bring up some fresh ideas for the future development of wearable energy storage devices. [ABSTRACT FROM AUTHOR]

A supercapacitor that possesses excellent performance in a wide temperature range is constructed with a partially graphitized porous carbon (PGPC) as the electrode material and tetraethylammonium tetrafluoroborate/propylene carbonate (Et4NBF4/PC) as the electrolyte. The PGPC-based electrode shows a very consistent performance in a wide temperature range of −20 to 50 °C. At working temperatures as high as 50 °C and as low as −20 °C, it delivers specific capacitances of ∼148 and ∼135 F g−1, respectively, and the supercapacitors exhibit high energy densities of ∼46 and ∼43 W h kg−1. In particular, the low-temperature capacitive performance and rate capability of PGPC are much better than those of the normally used activated carbon and among the best ones ever-reported for carbon-based supercapacitors. More significantly, the PGPC-based supercapacitor shows excellent cycling performance at all tested working temperatures, with a capacitance retention of ∼98% after 1000 cycles at 5 A g−1 even when the working temperature decreases to −20 °C. [ABSTRACT FROM AUTHOR]

A novel nitrogen-doped porous graphene material (NPGM) was prepared by freeze-drying a graphene/melamine–formaldehyde hydrogel and subsequent thermal treatment. The use of melamine–formaldehyde resin as a cross-linking agent and nitrogen source enhances the nitrogen content. NPGM possesses a hierarchical porous structure, a large Brunauer–Emmett–Teller surface area (up to 1170 m2 g−1), and a considerable nitrogen content (5.8 at%). NPGM displays a discharge capacity of 672 mA h g−1 at a current density of 100 mA g−1 when used as an anode material for lithium ion batteries, much higher than that observed for a nitrogen-free graphene porous material (450 mA h g−1). The NPGM electrode also possesses superior cycle stability. No capacity loss was observed even after 200 charge/discharge cycles at a current density of 400 mA g−1. The enhanced electrochemical performance is attributed to nitrogen doping, high specific surface area, and the three-dimensional porous network structure. [ABSTRACT FROM AUTHOR]

The capacity of manganese dioxide (MnO2) deteriorates with cycling due to the irreversible changes induced by the repeated lithiation and delithiation processes. To overcome this drawback, MnO2/nitrogen-doped graphene hybrid aerogels (MNGAs) were prepared via a facile redox process between KMnO4 and carbon within nitrogen-doped graphene hydrogels. The three-dimensional nitrogen-doped graphene hydrogels were prepared and utilized as matrices for MnO2 deposition. The MNGAs-120 obtained after a deposition time of 120 min delivered a very high discharge capacity of 909 mA h g−1 after 200 cycles at a current density of 400 mA g−1, in sharp contrast to only 280 and 70 mA h g−1 delivered from nitrogen-doped graphene aerogels and MnO2. This discharge capacity is superior to that of the previously reported MnO2/carbon based hybrid materials. This material also exhibited an excellent rate capability and cycling performance. Its superior electrochemical performance can be ascribed to the synergistic interaction between uniformly dispersed MnO2 particles with high capacity and the conductive three-dimensional nitrogen-doped graphene network with a large surface area and an interconnected porous structure. [ABSTRACT FROM AUTHOR]

A high output flexible piezoelectric generator based on a highly oriented BaTiO3 film self-assembled using an interfacial strategy is reported. We have successfully controlled the morphology and orientation of BaTiO3 particles and obtained a BaTiO3 film using a facile interfacial self-assembled method. The BaTiO3 film is transferred onto an ITO coated PET substrate and packaged with PDMS (polydimethylsiloxane) to form a flexible piezoelectric energy harvesting device. The interfacial assembling strategy can effectively increase the volume fraction of active piezoelectric materials in composite films. The BaTiO3 film-based piezoelectric generator was demonstrated to harvest wind energy by employing a windmill and the output power was large enough to light a LCD. [ABSTRACT FROM AUTHOR]

A hybrid of holey graphene and Mn3O4 is prepared by a one-step process, in which the formation of a holey structure is accompanied with Mn3O4 nanoparticles through a high temperature reaction between graphene oxide sheets and KMnO4. Holey graphene and Mn3O4 collaboratively attributed to the enhanced catalytic activity and efficiency towards the oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

Cyanoethyl polyvinyl alcohol (PVA-CN)-based gel polymer electrolyte (GPE) is a high-performance electrolyte for lithium-ion batteries (LIBs), which is in situ synthesized from a stable monomer without using additional initiators. Unfortunately, the gelation mechanism of PVA-CN is still unclear. Furthermore, for general GPEs prepared by in situ polymerization, the electrode–GPE interface in batteries remains to be further optimized. Here we present the gelation mechanism of the PVA-CN-based GPE and fabricate an electrode–GPE interface with less resistance during battery formation. The cross-linkable PVA-CN-based organogel is formed via in situ cationic polymerization of the cyano resin initiated by PF5, a strong Lewis acid produced by the thermo-decomposition of LiPF6. It is interesting to find that the battery formation process completed in the precursor solution instead of gel can greatly reduce the interfacial resistance of graphite–GPE and benefit the formation of a more stable solid electrolyte interface (SEI) on the anode, which contributes to a dramatic improvement in battery performance. This work gives useful guidance towards designing new GPE materials and promoting their practical application in LIBs. [ABSTRACT FROM AUTHOR]

This study presents a method to optimize the mass transport and electron transfer of metal oxides in electrochemical processes by using a three-dimensional (3D) porous graphene macroassembly (GM) as a framework. A simple method, pressurized infiltration, is reported to realize uniform dispersion of metal oxide nanoparticles on the graphene skeleton in the GM. The obtained GM–NiO hybrid shows significantly improved performance in electrochemical catalytic processes and energy storage applications. When used as the active material in nonenzymic sensors, it shows a low detection limit towards glucose while maintaining high sensitivity. It also shows a high capacitance of about 727 F g−1 and maintains high rate performance when used as the electrode material for supercapacitors. More importantly, this method may be sufficiently versatile for the hybridization of different kinds of noncarbon materials with GM to promote their practical applications. [ABSTRACT FROM AUTHOR]