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In this paper, porous CoSe2 nanosheets were prepared by the hydrothermal method. Their unique nanosheet array structure provides abundant active sites and fast ion transport channels, and thus the material exhibit excellent electrochemical performance.

Due to high ionic conductivity and wide electrochemical window, the garnet solid electrolyte is considered as the most promising candidate electrolyte for solid-state lithium metal batteries. However, the high contact impedance between metallic lithium and the garnet solid electrolyte surface seriously hampers its further application. In this work, a Li-(ZnO)x anode is prepared by the reaction of zinc oxide with metallic lithium and in situ coated on the surface of Li6.8La3Zr1.8Ta0.2O12(LLZTO). The anode can be perfectly bound to the surface of LLZTO solid electrolyte, and the anode/electrolyte interfacial resistance was reduced from 2319 to 33.75 Ω·cm2. The Li-(ZnO)0.15|LLZTO|Li-(ZnO)0.15 symmetric battery exhibits a stable Li striping/plating process during charge-discharging at a constant current density of 0.1 mA·cm−2 for 100 h at room temperature. Moreover, a Li-(ZnO)0.15|LLZTO-SPE|LFP full battery, comprised of a polyethylene oxide-based solid polymer electrolyte (SPE) film as an interlayer between LiFePO4 (LFP) cathode and LLZTO solid electrolyte, presents an excellent performance at 60 ℃. The discharge capacity of the full battery reaches 140 mAh·g−1 at 0.1 C and the capacity attenuation is less than 3% after 50 cycles. © 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd.. All rights reserved.

Lithium-rich manganese-based oxides have the advantages of high discharge specific capacity, so they are potential candidates for advanced lithium battery cathode materials. However, they also have drawbacks to be solved such as serious irreversible loss of capacity and voltage decay in the cycling process. Surface coating method was used in this paper to modify the lithium-rich manganese-based oxide (LRMO, Li1.2Mn0.54Ni0.13Co0.13O2) to improve its electrochemical properties. Zirconium-based compounds coated LRMO materials (ZBC@LRMO) were obtained via the reaction of lithium hydroxide with zirconium n-butanol and subsequent thermal treatment at different temperatures. The results of X-ray diffraction and transmission electron microscopy confirm that the crystal structure and composition of the ZBC coating layer vary with the calcination temperature. The coating layer obtained at 600 ℃ is composed of tetragonal ZrO2 and Li2ZrO3. The ZBC@LRMO sample with tetragonal ZrO2 and Li2ZrO3 composite exhibits the best electrochemical performance: the discharge capacity of ZBC@LRMO can reach 296 mAh g−1 at 0.1 C and 120 mAh g−1 at high rate of 5 C.

Design of suitable composite materials and improvement of the corresponding electrochemical properties based on the intercalation–conversion mechanism are still challenging for Li storage devices. ...

Phosphate material LiMnPO4 is popular for its high energy density (697 W·h·kg−1) and safety. When LiMnPO4 crystal grows, the potential barrier along b and c axis is strong, which makes the crystal grow along b axis to form a one-dimensional chain structure. However, the main migration channel of lithium ions in olivine structure is plane (0 1 0). By shortening the growth in the direction of b axis and enhancing the diffusion along the directions of a and c, two-dimensional nanosheets that are more conducive to the migration of lithium ions are formed. The dosage of polyols is the key factor guiding the dispersion of the crystals to the (0 1 0) plane. X-ray diffraction (XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and other means are used to characterize the samples. After experiments, we found that when the ratio of polyol/water was 2:1, the morphology of the synthesized sample was 20–30 nm thick nanosheets, which had the best electrochemical performance. At 0.1C, the discharge specific capacity reaches 148.9 mA·h·g−1, still reaches 144.3 mA·h·g−1 at the 50th cycle. and there is still 112.5 mA·h·g−1 under high rate (5C). This is thanks to the good dispersion of the material in the direction of the crystal plane (0 1 0). This can solve the problem of low conductivity and ionic mobility of phosphate materials.

Synergistic effect improves the electrochemical properties of metal oxide anode materials for lithium ion-batteries. The influence of different ratios of nickel and manganese on the microscopic morphology and the contribution of pseudocapacitance were investigated. The ternary Prussian blue analog NixMny[Fe(CN)6]2(x + y = 3) manufactured by adjusting the ratio of Ni-Mn mixed salt was used to obtain the ternary transition metal oxide. When the ratio of Ni and Mn is 8:2 or 2:8, the synergistic effect of oxide anode materials between the ternary transition metals is strong. The corresponding materials have excellent cycle stability, higher reversible capacity, lower charge transfer resistance and higher proportion of pseudocapacitance contribution. The calcined product is NiFe2O4-FeMnO3, which has a core-shell structure when the ratio of Ni and Mn is 2:8, and the first cycle discharge capacity is 1697.6 mAh/g. It can provide a reversible capacity 536.1 mAh/g after 500 cycles at 500 mA/g. The analysis of electrode dynamics shows that the pseudocapacitance contribution can reach 46.8% at 0.1 mV/s.

A high-efficiency and low-cost Zr-based metal–organic frameworks loaded with Co catalyst for the catalytic transfer hydrogenation of biomass-derived 5-hydroxymethylfurfural (HMF) into 2,5-dihydroxymethylfuran (DHMF) through Meerwein–Ponndorf–Verley reduction was developed. A series of Co/UiO-66-NH2 catalysts were synthesised by wet impregnation and reduction using the KBH4 method and characterized by XRD, ICP-OES, XPS, SEM, TEM, BET and TPD techniques. As expected, Co1.6/UiO-66-NH2 displayed high catalytic transfer hydrogenation activity with 92.6% HMF conversion and 95.9% DHMF selectivity at a relatively mild reaction temperature (100 °C) in the presence of isopropanol that served as both hydrogen donor and reaction solvent. The highly dispersed Co species may effectively regulate the acid–base sites of the catalyst, which could be the main reason for the high hydrogenation activity.

Li-rich transition metal oxides (Li1+XM1–XO2) are known as the next generation of cathode materials for lithium-ion batteries by reason of their high specific capacity. However, oxygen release and ...

The efficient catalysis of the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over non noble-metal catalysts has received great attention in recent years. However, the reaction usually requires harsh conditions, such as high reaction temperature and excessively long reaction time, which limits the application of the non noble-metal catalysts. In this work, a bimetallic Co x -Cu@C catalyst was prepared via the pyrolysis of MOFs, and an 85% DMF yield was achieved under a reaction temperature and time of 160 °C and 3 h, respectively. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) mapping, and other characterization techniques showed that the synthesis method in this paper realized the in situ loading of cobalt into the copper catalyst. The reaction mechanism studies revealed that the cobalt doping effectively enhanced the hydrogenation activity of the copper-based catalyst on the C-O bond at a low temperature. Moreover, the bimetallic Co x -Cu@C catalyst exhibited superior reusability without any loss in the activity when subjected to five testing rounds.

Ni3[Fe(CN)6]2 nano-cubic precursors were prepared by chemical coprecipitation at room temperature with nickel acetate and potassium ferricyanide as raw materials. The corresponding NiFe2O4-NiO@C composites with excellent crystallization were prepared by two-stage oxidation at low temperature. The microstructure and electrochemical behavior of the materials showed that the Prussian blue analog was transformed into metal oxide while the carbon coating was maintained in the two-stage oxidation at low temperature. The existence of the carbon coating reduces the charge transfer impedance to 31.5 Ω. At the current density of 500 mA/g, the reversible capacity of 632.7 mAh/g is maintained after 500 cycles. At the same time, carbon cladding can also enhance the role of pseudocapacitance in the material. At the scanning rate of 0.1 mV/s, the pseudocapacitance account for 54.4% of the total discharge capacity, which is significantly higher than that of uncoated materials.

A appropriate size with three-dimension (3D) channels for lithium diffusion plays an important role in constructing high-performing LiNi0.5Mn1.5O4 (LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li+ intercalation/deintercalation. In this work, an efficient method for designing the hollow LNMO microsphere with 3D channels structure by using polyethylene oxide (PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g−1 at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.

A uniform nickel film could be coated on crown ether-modified carbon nanotubes (c-CNTs) by electroless deposition. The products CNT@Ni and c-CNT@Ni were oxidized and compressed into CNT@Ni@(NiOH)2 and c-CNT@Ni@(NiOH)2 discs, respectively. The areal and volumetric capacitances of CNT@Ni@(NiOH)2 and c-CNT@Ni@(NiOH)2 were compared and c-CNT@Ni@(NiOH)2 showed a lower resistance.

Durability and safety are main factors contributing to the market requirement of lithium-ion batteries (LIBs) in practical applications. The improvement of current collector has been proven as an effective approach to enhance comprehensive performance of LIBs. To achieve a sufficient electrical contact between the current collector and active materials, honeycomb-like surface of aluminum current collector is etched by direct current in sulfuric acid and phosphoric acid mixed solution. At the same time, a dense anodic aluminum oxide film is formed on the surface of aluminum current collector, which can protect LIBs from corrosion and thermal runaway. Experimental results show that the adhesion between the active material and aluminum current collector was improved by 23% after anodization. The corrosion resistance of alumina foil was promoted significantly in ethyl methyl carbonate and ethylene carbonate electrolyte with LiPF6. The corrosion current peak reduces to 0.022 mA/cm2 from 0.267 mA/cm2 after surface treatment. The capacity retention rate of the LiCoO2 electrode with an oxidation-treated aluminum current collector is 6.3% higher than with untreated aluminum foil at 5C after 500 cycles. What’s more, the nail penetration demonstrates that the aluminum current collector we prepared can reduce the temperature of the full batteries surface when the nail pierced, which improved the safety performance of LIBs.

To meet the requirements of high-performance and long lifespan supercapacitors, the development of electrode materials with better performance and stable structure is in high demand. Herein, an urchin-like NiCoP nanoarray coated with a carbon layer hybrid electrode (NiCoP@C-ULAs) has been successfully synthesized on a carbon cloth by an effective and goal-directed approach. The three-dimensional (3D) urchin-like precursor prepared via the solvothermal method integrates fascinating architectures, in which 1D nanospines favor charge transport and 2D ultrathin nanoflakes provide large active sites and short paths for ion diffusion, thus leading to the highest performance among the precursors. Subsequently, carbon coating and phosphorization were employed to synthesize the NiCoP@C-ULAs composite. The resulting NiCoP@C-ULAs exhibited a high specific area (201.9 m2 g−1), small average pore size (4.4 nm), ultrahigh specific capacity (1046 C g−1 at 1 A g−1) and superior rate capability (76.5% retention even at 20 A g−1). Remarkably, the cycling stability was enhanced from 55.1% to 86.3% at 8 A g−1 after 5000 cycles as compared with NiCoP-ULAs. The main reason for the significant improvement in the electrochemical performances is due to the unique structure and the synergistic effect of NiCoP with high specific capacity and the carbon coating with good mechanical stability. Furthermore, the all-solid-state NiCoP@C-ULAs//AC asymmetric supercapacitor delivers a high energy density of 37.1 W h kg−1 at a power density of 792.8 W kg−1 and outstanding cycling stability (91.4% of specific capacity retention after 10 000 cycles). The LEDs could be lit up by the assembled capacitors for several minutes, which suggests that the NiCoP@C-ULA electrodes possess enormous potential as energy storage and conversion devices in future.

Polyimide-based nitrogen-doped ordered mesoporous carbon was successfully synthesised utilising SBA-15 as a hard template. By controlling the molar ratio of 4,4′-oxydianiline to pyromellitic dianhydride during copolymerising and carbonisation, nitrogen-doped ordered mesoporous carbon (NOMCx) with various nitrogen content and pore distribution were obtained. When the molar ratio of 4,4′-oxydianiline to pyromellitic dianhydride was 6, NOMC6 presented the highest content of nitrogen (7.94 wt%) and moderate specific surface area (890 m2 g−1). Accordingly, NOMC6 showed a high specific capacitance of 282 F g−1 at 0.1 A g−1, and excellent cycle stability (no capacitance loss over 10,000 cycles) in 1 M H2SO4. The synthesised ordered mesoporous carbons do not show a significant decrease of capacitive performance in the current density range of 2 to 20 A g−1. Furthermore, a symmetrical supercapacitor consisting of two NOMC6 electrodes exhibited an energy density of 4.77 Wh kg−1 at power density of 500 W kg−1 (1 A g−1).

This study employed a novel modification strategy to overcome the intrinsic poor rate performance, large initial irreversible capacity, and low cycling stability of Li-rich layered oxide (LLO) cath...

In this study, the water-evaporation-induced assembly of a graphene oxide-ammonium metatungstate hydrate multilayer film was developed. After chemical reduction and high-temperature sulfurization, a graphene-WS2 composite nanofilm with microcavities was obtained. When evaluated as an anode material in a lithium-ion battery, the graphene-WS2 sample (precursor graphene oxide/WS2 mass ratio of 1:4) exhibited high initial specific capacity (∼980 mAh g−1 at 0.1 A g−1), optimal cycling performance (∼450 mAh g−1 after 100 cycles at 0.1 A g−1), and superior rate capability (∼300 mAh g−1 at 2 A g−1). The graphene/WS2 mass ratio influenced the contact between WS2 and graphene and the porous nanofilm structure facilitated the kinetics of lithium-ion diffusion.

To meet the demand for high-power-density and long lifespan surpercapacitors (SCs), the Ni–P@Ni HL/CC-1h with a core–shell structure (Ni–P sphere as the core and nanoflake with the Ni and Ni–P heterogeneous layer as shell) was constructed via a facile strategy. The strategy included hydrothermal synthesis of Ni–P spheres with large Ni surface layer on carbon cloth (Ni–P@Ni HL/CC) and subsequent chemical dealloying using HCl as etching solution in order to remove the redundant Ni substances. The morphology, composition, and electrochemical performances of raw Ni–P@Ni HL/CC and the corresponding samples obtained by different dealloying times (0.5, 1, and 2 h) were characterized. Interestingly, the Ni–P@Ni HL/CC-1h presents a unique structure with a nanoflake shell and a porous core, which can provide a large number of exposed active sites, accelerate electrolyte ion diffusion and support ultra-long cycling. Furthermore, the Ni species existing in the outer flake can increase the conductivity and promote the capacitance during the charge–discharge processes. The Ni–P@Ni HL/CC-1h exhibited high specific capacity of 280.8 C g−1 at current density of 1 mA cm−2, high rate retention of 76.2% at 20 mA cm−2. The maximum specific capacity could reach 388.8 C g−1 at 8 mA cm−2, and maintained the 92.6% retention after 3000 cycles. Moreover, the Ni–P@Ni HL/CC-1h//AC all-solid-state asymmetric supercapacitor (ASC) exhibited high specific capacity, 86.0% retention after 10,000 cycles and high energy density of 27.6 Wh kg−1 at power density of 942.8 W kg−1.

Vanadium oxide (VOx) possesses high-potential pseudocapacitive characteristics. But it is still unsatisfactory for supercapacitors because of the poor ionic diffusivity and electrical conductivity of VOx. Nanocrystallization can decrease the distance of ion diffusion, then improve the ionic diffusivity. Suitable carbon coating could heighten conductivity and provide ion pathways. Here we synthetized V6O13@C by a sol-hydrothermal method, then pyrolyze to form VOx@C core-shell nanorod composites. The carbon nanoshells with abundant pores on the surface of vanadium oxide improve the conductivity of the nanorod electrodes and provide sufficient ion pathways. The microstructure and electrochemical measurements reveal the V6O13@C prepared from 0.8 g V2O5 raw material under 700 °C heating possesses optimal performance. As the electrode materials of a symmetric supercapacitor, such VOx@C core-shell nanorods possess a high capacity (545 F g−1 at 0.5 A g−1, 437 F g−1 at 5 A g−1) and satisfactory cyclability (88.3% retention after 2000 cycles at 0.5 A g−1). SEM and TEM show that the V6O13@C consists of uniform-size nanorods whose diameter is 20 nm with a 7-nm-thickness carbon shell layer. The favorable electrochemical performance is stemmed from unique structural features of V6O13@C nanorods. 1D structure of nanorods could significantly cut down the ion migration process as well as improving ion diffusion kinetics. Carbon nanoshell provides the high conductivity for electron, and the pores provide passageway for ion diffusion.

Metal-organic frameworks featuring controllable morphologies and tunable compositions and pore structures are widely used as precursors for supercapacitors electrode materials. A zinc/cobalt-based zeolitic imidazolate framework was utilized as a precursor to synthesize N, S-codoped porous carbon supported CoS2 nanocomposites, using a two-step (carbonization and sulfurization) procedure. The as-prepared materials maintained the rhombic dodecahedral structure of the precursors, and carbon nanotubes were rooted onto the nanocomposite surface. The N, S-codoped porous carbon supported CoS2 nanocomposite hybrid electrode exhibited excellent electrochemical performance: high specific capacitance (635.8 F/g at 1 A/g), good rate capability (544.2 F/g at 10 A/g), and long-term cycling stability (88.0% retained after 2000 cycles). Moreover, the energy density of the N, S-codoped porous carbon-supported CoS2 nanocomposites//activated carbon asymmetric supercapacitor reached 14.1 Wh/kg at the power density of 0.71 kW/kg, and its capacitance remained 92.2% after 2000 cycles in the 0–1.4 V potential range.

An ideal electrocatalyst for the hydrogen evolution reaction of water splitting requires substantial active sites with high catalytic activity, fast electron and mass transfer, low gas adsorption energy, and high stability. However, a single component catalyst usually has only one of the many properties of an ideal electrocatalyst. Herein, for the first time, we synthesize CoxSe/MoSe2 micro-prisms on foam via a hydrothermal and selenization strategy. After selenization, a crystallized CoMoO4 smooth prismatic structure can be converted into a CoxSe/MoSe2 prismatic structure with lamellar morphology. Such synergistic effects lead to CoxSe/MoSe2 superior electrochemical catalytic activity with a 109 mV over-potential at 10 mA cm−2 and 204 mV over-potential at 100 mA cm−2, an appropriate Tafel slope of 90 mV dec−1, and remarkable long-term stability during 20 h of testing for the hydrogen evolution reaction in an alkaline medium. Density-functional calculations reveal the absorption energy of water and Gibbs free-energy of intermediate adsorb hydrogen of CoxSe/MoSe2 is more favorable for hydrogen evolution reaction than single component catalyst. Both experimental and theoretical calculation results reveal that synergistic effect can efficiently reduce energy barrier of both the initial water adsorption step and subsequent H2 generation on binary catalysts, and improve catalytic activity.

Direct methanol fuel cell is emerging as a promising technology for portable power, which has to surmount the hindrance of high cost caused by the use of platinum and platinum-based catalysts to become commercially viable. In this paper, novel Fe–N–C electrocatalysts for the oxygen reduction reaction (ORR) were prepared from the high nitrogen content prepolymer of melamine formaldehyde resin and Iron (II) acetate by carbonization in inert atmosphere. The catalytic activity for ORR and the methanol tolerance of Fe–N–C were detected by the rotating disk electrode and single cell test. For a direct methanol fuel cell system, the maximum output power density reached 38.47 mW cm−2 at 70 °C. We found the ORR activity of the catalyst changed with the pyrolysis temperature. The onset potentials for oxygen reduction almost were 0.5 V (vs. SCE). The catalyst prepared under 700 °C was found to have the highest activity. The ORR were characterized by X-ray diffractometry, which indicating that the activity change was attributed to the active FexN generation and decomposition.

We developed a promising cathode material prepared by effective surface modification of Li-rich layered oxide (LLO) materials, using a Zr-based MOF (UIO-66-F4), as a precursor to produce in-situ MOF-derived ZrO2 (MDZ) coatings. A new method for F doping on LLO was also proposed. The MOF-assisted treatment renders a uniform nanoscale coating of ZrO2 and a porous structure of Li1.2Mn0.54Co0.13Ni0.13O2 hierarchical secondary microsphere. The rate capability, cycling stability, and first coulombic efficiency of LLO were significantly improved by the MOF-assisted treatment. The discharge capacity of the MOF-derived ZrO2 coated LLO (MDZ@LLO) material was 279 and 110.0 mAh g−1 at 0.1 C and 5 C, respectively. The capacity retention increased from 71.1% to 83.8% after 200 cycles at 1 C while the coulombic efficiency increased from 62% to 72% during the first cycle. Keywords: Lithium-ion battery, Lithium-rich layered oxide material, Surface modification, Fluorine doping

In this work, Li-rich layered oxide materials of Li1.2Mn0.54Co0.13Ni0.13O2 nano/micro hierarchical microrods are easily synthesized using a solvothermal method. Li2MnO3, a Li-rich layered oxide with a framework that is consistent with that of the host, is coated onto the surface of Li1.2Mn0.54Co0.13Ni0.13O2 microrods by a facile sol–gel method. Investigations with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM) and galvanostatic charge/discharge reactions reveal that surface-modified Li1.2Mn0.54Co0.13Ni0.13O2 microrods present better rate performance and cycling stability than other samples. The best electrochemical performance of the surface-modified Li1.2Mn0.54Co0.13Ni0.13O2 microrods is obtained with a layer composed of 5 wt% Li2MnO3 (∼10 nm thick), which provides very high discharge capacities of 244 and 159.5 mAh g−1 at C-rates of 1C and 10C, respectively (1C = 200 mAg−1), and excellent cycling stability (after 80 cycles, capacity retention of 96.0% at 1C). The composite's remarkably improved cyclability and rate capability are attributed to the combination of the nano/micro hierarchical microrod structure and the Li2MnO3-modified surface, which reduce structural degradation during electrochemical cycling. Results also show that the Li2MnO3 surface-modified Li1.2Mn0.54Co0.13Ni0.13O2 microrods significantly decelerate voltage decay and improve the initial coulombic efficiency (76.4%).

Solvothermal method is a very common synthetic method in the preparation of catalysts for the hydrogen evolution reaction (HER) of H2O decomposition. Since a certain surfactant can be added to the solvothermal solvent, the crystal particle growth process can be changed to obtain catalysts with different morphologies. We synthesized a series of nickel-manganese oxides (NiMnO) by adding different amounts of Polyethylene glycol (PEG) using the solvothermal method. Structure characterizations exhibit that NiMnO catalyst prepared with different PEG additions have different morphologies. The NiMnO catalyst prepared by adding 3 g of PEG possesses abundant petal-like scales, it brings a large specific surface area, high reaction efficiency, and has the best electrocatalytic activity in alkaline media.