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The lattice oxygen redox (LOR) reaction, known for its potential to augment the capacity of layered transition metal oxides in sodium-ion batteries (SIBs), has attracted widespread attention. However, the utilization of the LOR reaction often leads to irreversible release of lattice oxygen, causing damage to the crystal structure and deterioration in electrochemical performance, thereby impeding its practical application. Here, we demonstrate a method to significantly enhance the electrochemical performance of P3-type Na0.6Li0.2Mn0.8O2 cathodes by concurrently applying surface NaBO2 coatings and boron doping. We reveal that the NaBO2 coating efficiently mitigates electrolyte corrosion and side reactions on the electrode surface. In addition, boron doping enhances the involvement of manganese in the redox process, thereby boosting capacity, while inhibiting the irreversible Li migration, thereby stabilizing the crystal structure of the material. The synergistic effect of surface NaBO2 coating and bulk phase boron doping enables 6%B-NLMO to exhibit improved electrochemical performance, achieving a discharge capacity of 98.7 mA h g−1 and 95.8% retention after 100 cycles at 20 mA g−1. This synergistic strategy, employing multiple modification techniques, offers a potential way to improve the performance of anion redox cathode materials. [ABSTRACT FROM AUTHOR]

Lithium cobalt oxide (LiCoO2) is one of the most commercially successful cathode materials and has attracted much attention from researchers since its discovery. However, an increase in cut-off voltage generates problems such as structural damage and detrimental side reactions. Under this premise, a layer of LiTaO3 coating is sputtered on the surface of the LiCoO2 electrode by magnetron sputtering, which aims to inhibit the structural damage and the occurrence of side reactions under high voltage. Meanwhile, the ionic conductor layer of LiTaO3 can also promote the transmission process of Li+ and improve the power density. The results show that the capacity retention rate of the MS-2 h (magnetron sputtering for 2 hours) electrode is 86.6% at 0.5C for 100 cycles in a voltage range of 3.0–4.6 V, and the capacity of 91 mA h g−1 is achieved at 3C. The cycling stability of the electrode is also effectively improved at high temperature, and the capacity retention rate was 40.9% after 100 cycles at 50 °C. This work proves that the coating of LiTaO3 on the electrode surface by magnetron sputtering can effectively inhibit the damage of the electrode structure and the occurrence of side reactions during cycling and can promote the transmission of lithium ions. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) are widely used in the mobile electronics, power, energy storage and other fields due to their excellent electrochemical performance, but their limited service life has resulted in a large number of spent LIBs being discarded. Due to the advantages of high recovery efficiency and mild reaction conditions, the combined pyro-hydrometallurgical process for recovering valuable metal elements from spent LIBs is emerging in line with the principles of green chemistry and has potential for large-scale industrial applications. Here we review current developments in the combined recovery process, aiming to figure out the challenges and future directions for the combined process. In detail, thermal pretreatment methods for collecting the cathode material from spent LIBs, the combined recovery process for treating the cathode material, and the subsequent separation and extraction process are summarized. Furthermore, the practical application of combined recycling schemes is demonstrated. Finally, the development and challenges of the combined process in recycling spent LIBs are revealed. Achieving pollution-free emissions and high-value utilization of spent LIB resources with low-cost treatment are future directions for the combined process. [ABSTRACT FROM AUTHOR]

A two-dimensional covalent organic framework (NTCDI-COF) with rich redox active sites, high stability and crystallinity was designed and prepared. As a cathode material for lithium-ion batteries (LIBs), NTCDI-COF exhibits excellent electrochemical performance with an outstanding discharge capacity of 210 mA h g−1 at 0.1 A g−1 and high capacity retention of 125 mA h g−1 after 1500 cycles at 2 A g−1. A two-step Li+ insertion/extraction mechanism is proposed based on the ex situ characterization and density functional theory calculation. The constructed NTCDI-COF//graphite full cells can realize a good electrochemical performance. [ABSTRACT FROM AUTHOR]

The solvation of cations is one of the important factors that determine the properties of electrolytes. Rational solvation structures can effectively improve the performance of various electrochemical energy storage devices. Water-in-Salt (WIS) electrolytes with a wide electrochemically stable potential window (ESW) have been proposed to realize high cell potential aqueous electrochemical energy storage devices relying on the special solvation structures of cations. The ratio of H2O molecules participating in the primary solvation structure of a cation (a cation hydration ratio) is the key factor for the kinetics and thermodynamics of the WIS electrolytes under an electric field. Here, acetates with different cations were used to prepare WIS electrolytes. And, the effect of different cation hydration ratios on the properties of WIS electrolytes was investigated. Various WIS electrolytes exhibited different physicochemical properties, including the saturated concentration, conductivity, viscosity, pH values and ESW. The WIS electrolytes with a low cation hydration ratio (<100%, an NH4-based WIS electrolyte) or a high cation hydration ratio (>100%, a K-based WIS electrolyte and a Cs-based WIS electrolyte) exhibit more outstanding conductivity or a wide ESW, respectively. SCs constructed from active carbon (AC) and these WIS electrolytes exhibited distinctive electrochemical properties. A SC with an NH4-based WIS electrolyte was characterized by higher capacity and better rate capability. SCs with a K-based WIS electrolyte and a Cs-based WIS electrolyte were characterized by a wider operating cell potential, higher energy density and better ability to suppress self-discharge and gas production. These results show that a WIS electrolyte with a low cation hydration ratio or a high cation hydration ratio is suitable for the construction of power-type or energy-type aqueous SCs, respectively. This understanding provides the foundation for the development of novel WIS electrolytes for the application of SCs. [ABSTRACT FROM AUTHOR]

Zinc ion thermoelectrochemical cells (ZTECs) have emerged as one of the attractive candidates for low-grade heat harvesting and energy storage but are greatly limited by the lack of promising cathode materials with superior rate capability and good durability. Here, we propose a facile strategy for the microstructural engineering of hydrate vanadium oxide by a surfactant to overcome such barriers. Impressively, a large Seebeck coefficient of 6.4 mV K−1, remarkable thermal-induced power density of 1.8 W m−2, and high durability were achieved by optimizing the cathode together with superior energy storage behaviors. Besides, one solid-state ZTEC could achieve a high output voltage of ∼0.83 V and power density of 0.2 W m−2 with an ultralow temperature difference of 5 K. All the findings demonstrate the promising potential of microstructural engineering for electrode materials in the construction of high-performance thermoelectrochemical devices. [ABSTRACT FROM AUTHOR]

Tailoring electrolyte components is an effective solution for building supercapacitors that can provide stable performance at low temperature, where traditional energy storage devices fail to operate. In this work, we propose a novel electrolyte with high low-temperature ion conductivity (2.46 mS cm−1 at −70 °C) by dissolving a low melting point ionic liquid, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (PMImNTf2), into a binary organic solvent of acetonitrile (AN) and methyl butyrate (MB) for low-temperature supercapacitors. Experiments together with theoretical calculations demonstrate that the unique solvation interaction of the ionic liquid with AN and MB can effectively weaken the cation–anion electrostatic attraction of PMImNTf2 and the hydrogen bonding between cations and anions, thus endowing the hybrid electrolyte with low freezing point and viscosity. The symmetric supercapacitors constructed with the hybrid electrolyte and commercial active carbon electrodes operated in a temperature range from 25 °C to −70 °C exhibit enhanced electrochemical performance. More significantly, they exhibit an excellent cycling stability over 6000 cycles at an extremely low temperature of −70 °C. [ABSTRACT FROM AUTHOR]

Mesocrystals have received intense attention in the electrochemical energy storage field owing to their favourable electronic conductivity, high crystallinity and large specific surface area. However, a critical limitation to the wide applications of mesocrystals is the lack of a facile synthesis approach for high-performance mesocrystals. Here, we report a one-step self-assembly solvothermal method to prepare 3D hierarchical highly-ordered Nb3O7F nanowire cluster mesocrystals (denoted NOF-NCMs), of which the diameter of each nanowire is within 10 nm. Through kinetic analysis, NOF-NCMs can be confirmed to provide unique intercalation pseudocapacitance, enabling rapid charge transfer. When used as an anode material, the NOF-NCM electrode displays a high capacity of ∼356.7 mAh g−1 at 800 mA g−1, excellent rate performance and a long cycle life with ∼88.3% capacity retention after 3000 cycles. The improved electrochemical properties of NOF-NCMs are attributed to the unique highly-ordered nanowire cluster architectures. A lithium ion capacitor (LIC) is constructed by using well-prepared NOF-NCMs as an anode and commercial AC as a cathode. The NOF-NCMs//AC LIC can hold a maximum energy density of 74.5 W h kg−1 at 87.5 W kg−1, and has a long cycle lifespan with a 92.5% capacity retention after 3000 cycles and low self-discharge rate, demonstrating a bright candidate for applications in both high-energy and high-power electrochemical energy storage. [ABSTRACT FROM AUTHOR]

The vast increase in the use of post-consumer polyethylene terephthalate (PET) plastic brings with it the challenge of recycling the increase in waste bottles and materials. The degradation of waste PET to its monomers in an environmentally benign solvent is a desirable way to process waste PET. Analysis of solubility parameters has inspired the successful application of biomass-derived γ-valerolactone (GVL) for PET dissolution, and further accelerated the alkaline hydrolysis of waste PET to its monomers. Hydrogen-bonding interactions between PET chains and GVL play a major role in the dissolution. Swelling differential scanning calorimetry (DSC) has indicated that GVL processing PET proceeds through two steps: swelling and dissolving. The optimal dissolving process by swelling DSC showed that waste PET bottle pieces could fully swell at 120 °C in 1 h, then dissolve at 170 °C in 2 min. The maximum solubility of PET in GVL is around 0.25 g·g−1. Here, water was used as an anti-solvent to induce PET to reprecipitate from the hot solution. Due to the virtue of fully pre-swelling and the very fast dissolution, the degradation ratio of PET during the dissolving process was only 5.7%. GVL processing greatly increased the effective surface area of PET, which promoted the following complete alkaline hydrolysis of PET in around 8 min. This study provides an environmentally benign, very fast, and energy efficient pathway for recycling waste PET. [ABSTRACT FROM AUTHOR]

Lithium-ion capacitors (LICs) are emerging as one of the most advanced hybrid energy storage devices. The key challenge in constructing a high-performance LIC is to couple an appropriate capacitive cathode with an intercalation anode, wherein they can match well in internal kinetics and capacity simultaneously. Here, we present a strategy for constructing an advanced LIC using a 3D N-doped hollow carbon microsphere (NHCM-12) anode combined with a hierarchical porous carbon (NHCM-A) cathode, which have both been prepared by the same polyimide precursor without any additional catalyst and template for the first time. Quantitative kinetics analysis and density functional theory (DFT) calculations are performed to demonstrate the surface-dominated Li-storage mechanism, revealing that pyrrolic-N and pyridinic-N are beneficial for stronger Li adsorption compared to quaternary-N. As expected, the fully assembled LIC (NHCM-12//NHCM-A) delivers a maximum energy density of 162 W h kg−1 and exhibits an outstanding lifespan over 5000 cycles with 86.2% capacity retention. Accordingly, our simultaneous manipulation of hierarchical N-doped porous carbon as both anode and cathode materials for energy storage using the same precursor may open an avenue for fabricating other ideal electrode structures. [ABSTRACT FROM AUTHOR]

Fabrication of a stable dendrite-free Li metal anode that accommodates very large volume changes is urgently needed for the development of advanced lithium metal batteries. Herein, an integrated Li/TiN/carbon textile anode (LTNC) is fabricated in which lithium is hosted in a self-supported TiN nanorod array with high surface area, excellent electrical conductivity, and porous structure. The as-prepared LTNC anode achieves outstanding electrochemical performance with a low overpotential of 50 mV and stable cycling for 1000 h at 1 mA cm−2, 1 mA h cm−2, and even at a high current density of 10 mA cm−2 it shows highly stable performance with a low overpotential. When paired with a LiNi0.8Mn0.1Co0.1O2 cathode, the assembled cells display enhanced capacity retention of 85% after 500 cycles at 1C and improved coulombic efficiency. Furthermore, a high capacity of 2.3 mA h cm−2 with a capacity retention of 92% is maintained at 1 mA cm−2 after 100 cycles when the negative to positive electrode capacity ratio is only ∼3.5. This work indicates that the structural engineering of Li metal is highly applicable for lithium metal batteries with high rates and long cycle life. [ABSTRACT FROM AUTHOR]

Beyond conventional hybrid ion capacitors (HICs) based on porous carbon capacitive materials, the introduction of faradaic pseudocapacitance in HICs is an effective method to enhance energy density. Herein, we prepare methylene blue functionalized graphene (MB-X) composites taking advantage of electrostatic and extensive π-conjugated interaction. The test results confirm that the composites have high rate capability and excellent cycle stability on account of the synergistic effect between graphene and MB molecules. In order to improve the safety of HICs, an aqueous electrolyte is a promising candidate as long as the cell voltage can be efficiently increased. Therefore, we skillfully employ aqueous solutions with different pH values as asymmetric electrolytes to assemble HICs, where polyimide acts as the battery material and MB-X serves as the capacitive material. Thanks to the asymmetric electrolytes, the constructed aqueous HICs can operate at a cell voltage of 1.9 V, much larger than the decomposition voltage of water. Moreover, the flexible structure, and reversible and fast redox reactions of both the anode and cathode make the aqueous HICs display a maximum energy density of 48.6 W h kg−1 and a maximum power density of 19 kW kg−1, as well as a long-cycle lifetime with a decay of 0.00172% per cycle. [ABSTRACT FROM AUTHOR]

Aqueous dual-ion batteries, one of the latest battery systems, have attracted considerable attention due to their merits of high safety, low cost and environment friendliness except for their high energy density and power density. However, the conventional employment of inorganic electrode materials usually leads to low power density and high cost. Herein, we present a novel aqueous ammonium dual-ion battery (ADIB) with a maximum operating voltage of 1.9 V, in which green and metal-free organic materials such as n-type polyimide and p-type radical polymers serve as anode and cathode, respectively, and 1 M ammonium sulfate solution acts as the electrolyte. During the charging process, the n-type polyimide can combine with cations, while p-type radical polymers can simultaneously accept anions, whereas the cations and anions can reversibly diffuse back to the electrolyte during the discharging process. This ingenious combination makes an assembled ADIB deliver a high energy density of 51.3 W h kg−1 and a maximum power density of 15.8 kW kg−1 (based on the total active weight of both cathode and anode), along with a good cycling stability with 86.4% capacity retention after 10 000 cycles at a current density of 5 A g−1. [ABSTRACT FROM AUTHOR]

The Na-ion hybrid capacitor (NIC) has exhibited its potential applications for devices that need high energy and power densities with low cost. Nevertheless, due to their “Daniell-type” mechanism, conventional NIC devices require massive electrolytes to provide a good ionic conductivity during charging, which could decrease the packaged energy density. Herein, we report a novel “Rocking-Chair” Na-ion hybrid capacitor (RC-NIC) employing Na-ions as charge carriers, Na3V2O2(PO4)2F@PEDOT as the cathode material and activated carbon (AC) as the anode material. RC-NIC efficiently improves the energy density by minimizing the amount of electrolyte like secondary batteries because Na-ion is de-intercalated from the cathode while it is adsorbed to the anode during charging. The Na3V2O2(PO4)2F@PEDOT//AC (peanut shell derived carbon) RC-NIC delivers high energy density of ∼158 W h kg−1 and power density of ∼7000 W kg−1 based on the total mass of active materials in both electrodes, respectively, in the voltage window of 1.0–4.2 V. This is one of the highest energy densities among the previously reported NICs. This concept provides a new route to build sodium-ion hybrid capacitors that meet dual criteria of battery and supercapacitor characters. [ABSTRACT FROM AUTHOR]

Spinel ZnFe2O4 (ZFO) has recently gained prominence as a fascinating anode for lithium-ion batteries (LIBs) owing to its intrinsic merits. However, serious electrode pulverization and modest electrical conductivity hugely hinder its commercial application. Herein, we describe the deliberate fabrication of a multi-functional yolk–shell hollow architecture, designated as H-ZFO–C@void@C, where hollow ZFO sub-microspheres with an internal well-distributed carbon network were prepared in a template-free manner as a yolk, along with a conductive N-doped carbon nanoshell and functional void interspace. Structural/geometric simulations and experiments confirm that the well-defined internal void and hollow interior of the yolk can efficiently accommodate volumetric expansion over lithiation without breaking the outer nanoshell while ensuring good yolk–shell electronic contact and a thin yet stable solid–electrolyte-interphase film on the outer surface. The conducting nano-carbon shell and continuous internal carbon network prevent the serious aggregation of nano-ZFO subunits, and facilitate convenient charge transfer during repeated lithiation/delithiation processes. Benefiting from the synergetic contributions of these appealing design rationales, our integrated H-ZFO–C@void@C anode delivers a high initial coulombic efficiency of ∼76.8%, a remarkable reversible capacity of ∼775 mA h g−1 at 2000 mA g−1, and long-term cyclability after 500 cycles at a high rate of 1000 mA g−1. More promisingly, our design here offers a competitive metal oxide-based anode structure for advanced LIBs. [ABSTRACT FROM AUTHOR]

A new Li–S battery with a polyaniline–graphene oxide (PANI–GO) membrane sandwiched between a sulfur cathode and a separator shows high cycling stability and enhanced rate performance. The initial specific capacity is 1261 mA h g−1 at 0.5C and the capacity retention is 73.0% after 150 cycles. The excellent electrochemical performance can be attributed to the new cell configuration. Specifically, the PANI–GO membrane can not only effectively mitigate the diffusion of lithium polysulfides to the negative electrode by a chemical interaction between the imine group (–N=) of the quinoid ring and polysulfides, but also improve sulfur utilization due to its conductive networks. [ABSTRACT FROM AUTHOR]

Lithium ion capacitors (LICs), which combine the merits of both lithium ion batteries and supercapacitors, have recently attracted considerable attention. However, LICs generally use different materials and synthesis routes for the cathode and anode, resulting in a complicated process and high production cost, from an energy storage device perspective. In addition, the current collector interface structure design plays a key role in the electrochemical process. Herein, we have designed and fabricated a novel LIC with similar-symmetric architecture in both electrodes. The nitrogen-doped porous carbon microspheres (NPCM) derived from the hierarchical assembly of polyimide nanosheets as the anode material showed excellent lithium storage properties. The cathode material (NPCM-A) obtained by the activation of NPCM led to an ultrahigh specific surface area (2007 m2 g−1) and excellent capacitance characteristics. Benefiting from the unique superstructure and 3D porous array current collectors, the novel LIC achieved a high energy density of 95.08 W h kg−1 and could retain 48.2 W h kg−1 even at a high power density of 15 kW kg−1 on the basis of mass of both electrodes. Moreover, the LIC achieved 80.1% capacity retention after 5000 ultra-long cycles, corresponding to fading of 0.004% per cycle. [ABSTRACT FROM AUTHOR]

There is an urgent need but it is still a huge challenge to integrate high energy and power density with high safety in a single energy storage device. Addressing this issue largely depends on design of new energy storage systems with novel electrode architectures. Herein, a novel electrochemical energy storage device called a quasi-solid-state Na-ion capacitor (QSS-NIC) is designed based on a 3D self-supported Na2Ti3O7 nanoribbon array/graphene foam (NTO/GF) anode and graphene foam (GF) cathode, and a Na-ion conducting gel polymer as the electrolyte and separator, without any binders, conducting additives or metal current collectors. Benefiting from the unique 3D self-supported cathode and anode, the GF//NTO/GF configuration achieves a high energy density of 70.6 W h kg−1 and high power density of 4000 W kg−1 on the basis of the mass of both electrodes, and a prominent cycling stability over 5000 cycles (capacitance retention ∼73.2%). This work successfully demonstrates a proof of concept of QSS-NIC as a high performance energy storage device based on two self-supported electrodes, which could provide a feasible approach to bridge the performance gap between capacitors and Na-ion batteries. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage devices are becoming increasingly more important for reducing fossil fuel energy consumption in transportation and for the widespread deployment of intermittent renewable energy. The applications of different energy storage devices in specific situations are all primarily reliant on the electrode materials, especially carbon materials. Biomass-derived carbon materials are receiving extensive attention as electrode materials for energy storage devices because of their tunable physical/chemical properties, environmental concern, and economic value. In this review, recent developments in the biomass-derived carbon materials and the properties controlling the mechanism behind their operation are presented and discussed. Moreover, progress on the applications of biomass-derived carbon materials as electrodes for energy storage devices is summarized, including electrochemical capacitors, lithium–sulfur batteries, lithium-ion batteries, and sodium-ion batteries. The effects of the pore structure, surface properties, and graphitic degree on the electrochemical performance are discussed in detail, which will guide further rational design of the biomass-derived carbon materials for energy storage devices. [ABSTRACT FROM AUTHOR]

Developing flexible and lightweight energy storage systems for miniaturized electronic equipment and high volumetric performance is arousing increasing interest. For practical applications, the parameters of gravimetric and volumetric performance should both be taken into account and given the same importance. Here, a novel hierarchical structure of free-standing, binder-free electrodes of corrugated NiCo2O4 nanosheets on nitrogen doped graphene/carbon nanotubes (NGN/CNTs) film has been designed for use in high-performance supercapacitors. This unique lightweight electrode structure achieved extremely high electrochemical performance, with a volumetric capacitance of 482.7 F cm−3, a gravimetric capacitance of 2292.7 F g−1 at 5 A g−1, and very long-term cycle stability (125% capacitance retention after 10 000 circles at 30 A g−1). Optimal supercapacitive performance was also achieved in our fabricated asymmetric supercapacitor (ASC) by using NiCo2O4/NGN/CNTs as the cathode and NGN/CNTs as the anode. The device exhibited high gravimetric energy densities of 42.71 W h kg−1 at 775 W kg−1 and of 24.69 W h kg−1 at a high gravimetric power density of 15 485 W kg−1; it even demonstrated a high volumetric energy density of 25.90 W h L−1 and a high volumetric power density of 9389 W L−1. This strategy provides a new method to design flexible high-performance electrodes for a new generation of energy storage applications. [ABSTRACT FROM AUTHOR]

Hierarchical hollow porous architectures with intriguing hetero-interfaces are currently of particular interest in emerging energy-related fields. In this investigation, we report a smart template-free methodology to purposefully fabricate high-quality uniform hollow hetero-NiCo2S4/Co9S8 (NCCS) submicro-spindles with well-dispersed hetero-nanodomains at the nanoscale. High-yield hollow mesocrystal nickel cobalt carbonate spindles are first solvothermally synthesized as the intermediate, and a subsequent shape-preserving conversion into hetero-NCCS submicro-spindles via a hydrothermal anion-exchange reaction occurs. The underlying template-free formation mechanism of the hollow structures is tentatively proposed. When evaluated as a promising electrode for supercapacitors, the resultant hollow mesoporous hetero-NCCS electrode with a mass loading of 5 mg cm−2 delivers a good pseudocapacitance of ∼749 F g−1 at a current rate of 4 A g−1, and holds at approximately 620 F g−1 at 15 A g−1 as a result of intrinsic synergetic contributions from structural/compositional/componental merits. Furthermore, an asymmetric device based on hollow mesoporous hetero-NCCS achieves an encouraging energy density of around 33.5 W h kg−1 at a power density of 150 W kg−1, and exceptional cycling behavior with capacitance degradation of ∼0.007% per cycle over 5000 consecutive cycles at 5 A g−1. Comprehensive investigations unambiguously highlight that the unique hollow mesoporous hetero-NCCS submicro-spindles would be a powerful electrode platform for advanced next-generation supercapacitors. [ABSTRACT FROM AUTHOR]

To improve the energy density of supercapacitors, a new type of electrode material with high electrochemical activity and favorable morphology is extremely desired. Ternary metal sulfides with higher electrochemical capacity and activity than mono-metal sulfides hold great promise in the field of energy storage devices. Herein, an advanced electrode composed of zinc cobalt sulfide nanosheets supported on sandwich-like nitrogen-doped graphene/carbon nanotubes (NGN/CNTs) film has been successfully fabricated through a two-step synthesis. Benefiting from the characteristic features and 3D electrode architectures, the Zn0.76Co0.24S electrode exhibits a high specific capacitance of 2484 F g−1 at 2 A g−1 and excellent cycling stability (almost no capacitance fading after 10 000 cycles at 30 A g−1). This creative nanostructure design of ternary transition metal sulfides could provide a promising prospect for application in energy storage devices. Moreover, an asymmetric supercapacitor was also fabricated by using Zn0.76Co0.24S/NGN/CNTs film as the positive electrode and NGN/CNTs film as the negative electrode, exhibiting a high energy density of 50.2 W h kg−1 at 387.5 W kg−1 and superior cycling stability of 100% initial capacity retention over 2000 cycles. This creative nanostructure design could provide a promising new way to develop high-performance supercapacitors and shed new light on configuring carbon-based ternary transition metal sulfide electrode materials in energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Porous NiCo2O4 nanotubes have been successfully synthesized using a facile and cost-effective electrospinning method and used as a noble-metal-free catalyst for rechargeable Li–O2 batteries. The as-synthesized NiCo2O4 nanotubes possess hollow cavities and porous walls, and were found to significantly improve the electrochemical performance of Li–O2 batteries, by endowing them with a high initial discharge capacity, reduced overpotential as well as good rate capability. Excellent cycling stability over 110 cycles with a highly discharged voltage platform of 2.4 V at 200 mA gc−1 was achieved. By means of FESEM, XRD, Raman spectroscopy and GITT analysis, toroidal-shaped Li2O2 particles were identified as the dominant discharge product and it was revealed that the Li2O2 can be completely decomposed during the charging process, indicating its superior reversibility as an effective bifunctional catalyst for Li–O2 batteries. All the results indicated that the porous NiCo2O4 nanotubes expressed intriguing properties and great potential applications as a noble-metal-free effective bifunctional catalyst for rechargeable Li–O2 batteries. [ABSTRACT FROM AUTHOR]

As electrical energy storage and delivery devices, carbon-based supercapacitors have attracted much attention for advancing the energy-efficient economy. It is important to develop a facile, low-cost and environmentally friendly method of producing novel carbon materials. In this study, we report a scalable synthesis of phosphorus- and nitrogen-co-doped porous carbons using lamellar-structured fish scale. The special lamellar structure of fish scale allows the production of porous carbons with large specific surface areas (up to 1300 m2 g−1) and a high level of mesoporosity. Their inherent organic composition could be adapted with abundant N and P functional groups on the final carbons. Their high levels of porosity and rich surface functionality permit the carbons to exhibit excellent electrochemical performance as electrode materials for supercapacitors. The energy densities of supercapacitors approach 11.7 and 33.1 W h kg−1 in aqueous and IL electrolytes, respectively. [ABSTRACT FROM AUTHOR]

Homogeneous ZnCo2O4 nanoflowers have been synthesized on a 3D layered structure of carbon nanotubes/nitrogen-doped graphene (NGN/CNTs) film by a hydrothermal process and subsequent calcination method. The ZnCo2O4 nanoflowers have an average diameter of 4 μm, and are composed of petals less than 100 nanometers. The as-synthesized ZnCo2O4/NGN/CNT film can be directly used as a flexible electrode with a high specific capacitance of 1802 F g−1 at 1 A g−1 and excellent cycling stability (almost 0% fade after 4000 sustaining charge/discharge at 10 A g−1). These results suggest that the obtained electrode has a promising application prospect in flexible energy conversion/storage devices. In addition, a binder-free asymmetric supercapacitor has been synthesized with the ZnCo2O4/NGN/CNT film as the positive electrode and the NGN/CNT film as the negative electrode. This demonstrates superior energy density (≈37.19 W h kg−1 at 750 W kg−1) and power density (≈14.992 kW kg−1 at 14.16 W h kg−1). [ABSTRACT FROM AUTHOR]

Hybrid sodium-ion capacitors (NICs) have tremendous potential in large-scale energy storage applications due to their low cost, long lifetime and high power. However, it remains a great challenge to find a desirable anode material with fast kinetics and superior cycle life. Here an applicable strategy to in situ grow Na2Ti3O7 on 1D CNTs as an anode material for sodium-ion capacitors is presented. Benefiting from the unique 1D nanostructure and the presence of pseudocapacitive charge storage mechanism, the Na2Ti3O7@CNT electrode exhibits excellent electrochemical performance with high rate capability and superb cycling stability. Moreover, a high performance hybrid NIC is also fabricated by using Na2Ti3O7@CNTs as an anode and activated carbon derived from the outer peanut shell as a cathode, which delivers high energy density (58.5 W h kg−1), high power density (3000 W kg−1), and long term cycle life (retaining ca. 75% of its original capacity at 0.4 A g−1 after 4000 cycles). [ABSTRACT FROM AUTHOR]

In response to the ever-increasing demand for grid-scale energy storage systems, sodium ion batteries (SIBs) working at ambient- or room-temperature are gaining much attention as promising alternatives because of the abundance and low cost of sodium resources. However, their adoption is significantly hampered by several issues, especially in terms of sluggish kinetics and capacity retention during cycling. Herein, flexible Prussian blue analogue FeFe(CN)6/carbon cloth composites are synthesized using low temperature strategies and utilized as a potential host for sodium ion insertion. As a proof of concept, the composites demonstrate excellent electrochemical performance: a reversible specific capacity of 82 mA h g−1 at 0.2C, good rate capability and long term cycling life with 81.2% capacity retention over 1000 cycles. Most significantly, this low-cost, scalable and low-temperature synthesis provides guidance for the design of other flexible materials that could have applications in wearable electronics, energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Hybrid supercapacitors are a very appealing power source with high energy density and power density because they employ both the merits of lithium ion batteries and supercapacitors. To balance such hybrid systems, the rate of the redox component must be substantially comparative to the levels of the double layer process. As far as the insertion-host material TiNb2O7 is concerned, we have used facile step electrode design consisting of the physically assisted template infusion of Ti–Nb sol into the pores of AAO followed by in situ conversion into porous TiNb2O7 nanotubes within the AAO walls under calcination, and finally making those templates dissolve away. Using such an electrode as the battery type anode and a graphene grass electrode as the capacitor type cathode, we successfully constructed a novel hybrid supercapacitor. Within a voltage range of 0–3 V, a high energy density of ∼74 W h kg−1 is achieved and it could remain as much as ∼34.5 W h kg−1 at a power of 7500 W kg−1. The present research sheds new light on the development of energy storage devices with both high energy density and high power density. [ABSTRACT FROM AUTHOR]

In this work, TiN NW supported silicon nanorods (TiN@Si NRs) are produced via direct radio frequency (RF) magnetron sputtering of Si deposition onto the surface of TiN NWs. Due to its superior mechanical stability and electrical conductivity, TiN provides more stable support and better conductive pathways for Si when compared with TiO2. The unique core–shell TiN@Si NR structure has enough void space to accommodate the large volume changes of Si during charge/discharge cycling. The novel 3D architecture electrode demonstrates exceptional electrochemical performances with ultrahigh specific capacity. Comparing with TiO2@Si NRs, TiN@Si NR electrodes exhibit improved cycling performances, which can still retain a capacity of 3258.8 mA h g−1 after 200 cycles at 1 A g−1. It should be noted that the TiN@Si NRs show an excellent rate performance even at a high current density (2256.6 mA h g−1 is realized at 10 A g−1). These results endow the electrodes with high power and long cycling stability. [ABSTRACT FROM AUTHOR]