Large interlayer spacing vanadium oxide nanotubes as cathodes for high performance sodium ion batteries

Sodium ion batteries (SIBs), as a potential alternative to Li-ion batteries (LIBs), have attracted great attention from researchers. Herein, large interlayer spacing ferric ion substituted vanadium oxide nanotubes (Fe-VNTs) are fabricated using dodecylamine as a template via a facile hydrothermal treatment followed by a ferric ion substitution process. The distances between the adjacent layers of VNT, Fe-VNTs and orthorhombic V₂O₅ are 2.7 nm, 1.2 nm and 0.44 nm, respectively. The larger interlamellar spacing results in faster Na⁺ diffusion reaction kinetics, and the insertion of ferric ion into vanadium oxide layers removes the organic templates between the vanadium oxide layers, leading to high conductivity and small electrochemical reaction resistance. Serving as the sodium ion battery cathode, Fe-VNTs display enhanced sodium storage performance over orthorhombic V₂O₅.

Sodium ion batteries (SIBs), as a potential alternative to Li-ion batteries (LIBs), have attracted great attention from researchers.     

Ultradispersed titanium dioxide nanoparticles embedded in a three-dimensional graphene aerogel for high performance sulfur cathodes

Lithium–sulfur (Li–S) batteries are regarded as one of the most promising energy storage technologies, however, their practical application is greatly limited by a series of sulfur cathode challenges such as the notorious “shuttle effect”, low conductivity and large volume change. Here, we develop a facile hydrothermal method for the large scale synthesis of sulfur hosts consisting of three-dimensional graphene aerogel with tiny TiO₂ nanoparticles (5–10 nm) uniformly dispersed on the graphene sheet (GA–TiO₂). The obtained GA–TiO₂ composites have a high surface area of ∼360 m² g⁻¹ and a hierarchical porous structure, which facilitates the encapsulation of sulfur in the carbon matrix. The resultant GA–TiO₂/S composites exhibit a high initial discharge capacity of 810 mA h g⁻¹ with an ultralow capacity fading of 0.054% per cycle over 700 cycles at 2C, and a high rate (5C) performance (396 mA h g⁻¹). Such architecture design paves a new way to synthesize well-defined sulfur hosts to tackle the challenges for high performance Li–S batteries.

GA–TiO₂ composites as a cathode material realize an excellent electrochemical performance in Li–S batteries.     

Porous SnO2 nanostructure with a high specific surface area for improved electrochemical performance

Tin oxide (SnO₂) has been attractive as an alternative to carbon-based anode materials because of its fairly high theoretical capacity during cycling. However, SnO₂ has critical drawbacks, such as poor cycle stability caused by a large volumetric variation during the alloying/de-alloying reaction and low capacity at a high current density due to its low electrical conductivity. In this study, we synthesized a porous SnO₂ nanostructure (n-SnO₂) that has a high specific surface area as an anode active material using the Adams fusion method. From the Brunauer–Emmett–Teller analysis and transmission electron microscopy, the as-prepared SnO₂ sample was found to have a mesoporous structure with a fairly high surface area of 122 m² g⁻¹ consisting of highly-crystalline nanoparticles with an average particle size of 5.5 nm. Compared to a commercial SnO₂, n-SnO₂ showed significantly improved electrochemical performance because of its increased specific surface area and short Li⁺ ion pathway. Furthermore, during 50 cycles at a high current density of 800 mA g⁻¹, n-SnO₂ exhibited a high initial capacity of 1024 mA h g⁻¹ and enhanced retention of 53.6% compared to c-SnO₂ (496 mA h g⁻¹ and 23.5%).

A porous SnO₂ nanostructure as an anode active material showed significantly improved electrochemical performance.     

Ultrathin flexible graphene films with high thermal conductivity and excellent EMI shielding performance using large-sized graphene oxide flakes

As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed. Large-sized graphene oxide flakes and thermal treatment were employed to fabricate lightweight, flexible and highly conductive graphene films. Compared to graphene films made of smaller-sized flakes, the graphene film made of large-sized flakes possesses less defects and more conjugated domains, leading to higher electrical and higher thermal conductivities, as well as higher EMI SE. By compressing four-layer porous graphene films together, a 14 μm-thick graphene film (LG-4) was obtained, possessing EMI SE of 73.7 dB and the specific SE divided by thickness (SSE/t) of 25 680 dB cm² g⁻¹. The ultrahigh EMI shielding property of the LG-4 film originates from the excellent electrical conductivity (6740 S cm⁻¹), as well as multi-layer structure composed of graphene laminates and insulated air pores. Moreover, the LG-4 film shows excellent flexibility and high thermal conductivity (803.1 W m⁻¹ K⁻¹), indicating that the film is a promising candidate for lightweight, flexible thermal conducting film with exceptional EMI shielding performance.

As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed.     

HKUST-1 derived Cu@CuOx/carbon catalyst for base-free aerobic oxidative coupling of benzophenone imine: high catalytic efficiency and excellent regeneration performance

The oxidative coupling of imines to ketazine with molecular oxygen is a green process towards the synthesis of hydrazine or hydrazine hydrate, which could efficiently address the economic and environmental issues of the traditional Raschig or peroxide-ketazine process. Herein, we developed an efficient heterogeneous base-free benzophenone imine oxidative coupling route with O₂ catalyzed by Cu/CuO_x/carbon materials derived from MOFs under mild conditions. Under optimized conditions, the conversion of BI is up to 98.2% and the selectivity of ketamine is 94.9%. This catalyst has excellent structure stability, recycling, and regeneration performance, owing to the carbonization of organic ligands of MOF at high temperature. More importantly, it is confirmed that the metallic Cu core is essential to improve the catalytic performance of the CuO shell in the BI oxidative coupling reaction, due to the promotion of electron transfer in the CuO surface, making dissolved O₂ molecules more easily insert oxygen vacancies. This strategy might open an avenue to the sustainable catalytic synthesis of hydrazine or hydrazine hydrate.

The oxidative coupling of imines to ketazine with molecular oxygen is a green process towards hydrazine hydrate synthesis, which could efficiently address the environmental and economic issues of the traditional Raschig or peroxide-ketazine process.     

Sb nanosheet modified separator for Li–S batteries with excellent electrochemical performance

An air-stable antimony (Sb) nanosheet modified separator (SbNs/separator) has been prepared by coating exfoliated Sb nanosheets (SbNs) successfully onto a pristine separator through a vacuum infiltration method. The as-prepared Li–S batteries using SbNs/separators exhibit much improved electrochemical performance compared to the ones using commercial separators. The coulombic efficiency (CE) of the Li–S battery using the SbNs/separator after the initial cycle is close to 100% at a current density of 0.1 A g⁻¹, and 660 mA h g⁻¹ capacity retained after 100 cycles. The rate capability of Li–S battery using SbNs/separator delivers a reversible capacity of 425 mA h g⁻¹ when the current density increases to 1 A g⁻¹. The improved electrochemical performance is mainly attributed to the following reasons. Firstly, the combination of physical adsorption and chemical bonding between SbNs and lithium polysulfides (LiPSs), which efficiently inhibits the shuttle phenomena of LiPSs. Secondly, the good electronic conductivity of SbNs improves the utilization of the adsorbed LiPSs, which benefits the capacity release of active materials. Lastly, the fast conversion kinetics of intermediate LiPSs caused by the catalytic effect from SbNs further suppresses the shuttle effect of LiPSs. The SbNs/separators exhibit a great potential for the future high-performance Li–S batteries.

Antimony nanosheet modified separator is prepared for high performance Li–S batteries for the first time.     

Polyacetylene carbon materials: facile preparation using AlCl3 catalyst and excellent electrochemical performance for supercapacitors

Polyacetylene (PA) was synthesized for the first time under mild conditions via polymerization of acetylene in n-octane with AlCl₃ as a catalyst, whereby a series of PA-derived carbon materials were obtained. Their composition and structure were characterized and their electrochemical performance was evaluated systematically. It is found that acetylene gas at 1 MPa can polymerize explosively at room temperature under catalysis of AlCl₃, forming acetylene black-like PA and a great amount of H₂, while in the presence of n-octane solvent, acetylene polymerizes smoothly at higher temperature (30 to 300 °C), forming PA with a H(CH CH)_nH structure. A series of PA-derived carbon materials are obtained by treating PA with KOH at 800 °C. The as-synthesizzed PA-100–KOH exhibits a high specific surface area (∼2500 m² g⁻¹), high specific capacitance (241 F g⁻¹ at a current density of 0.1 A g⁻¹ and 143 F g⁻¹ at 5 A g⁻¹), low AC resistance, and good cycling stability with 91.7% maintenance of capacity after 2000 cycles at a current density of 2 A g⁻¹. This paper provides a new method for the facile synthesis of PA and a novel carbon source for supercapacitor electrode materials with excellent electrochemical performance and practical application.

Polyacetylene (PA) was synthesized for the first time under mild conditions via polymerization of acetylene in n-octane with AlCl₃ as a catalyst, whereby a series of PA-derived carbon materials were obtained.     

The investigation of the specific behavior of a cationic block structure and its excellent flocculation performance in high-turbidity water treatment

The fabrication of a cationic polyacrylamide (CPAM) with high efficiency and economy has been highly desired in the field of high-turbidity water treatment. This study introduced an ultrasound (US)-initiated template polymerization (UTP) method to develop a novel cationic templated polyacrylamide (TPAA) with a microblock structure. TPAA was prepared using acrylamide (AM) and sodium (3-acrylamidopropyl)trimethylammonium chloride (ATAC) as the monomers and sodium polyacrylate (NaPAA) as the template. Factors that affected polymerization such as the ultrasound power, ultrasound time, initiator concentration, pH, and m_AM : m_ATAC and n_NaPAA : n_ATAC values were investigated. The properties of the polymers were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance spectroscopy (¹H NMR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results indicated the successful formation of a cationic microblock structure in TPAA. In addition, TPAA displayed favorable thermal decomposition properties and a rough and coarse surface morphology, as shown by analyses using TGA and SEM, respectively. Moreover, a zip (type I) template polymerization mechanism was identified via analyses of the association constant (K_M), conversion (C_v) and polymerization rate (R_p). The flocculation performance of the templated copolymer TPAA was evaluated by treating high-turbidity water. According to the results for the zeta potentials and FTIR spectra of the generated flocs, it was indicated that the cationic microblocks in the templated copolymer could greatly enhance its charge neutralization, patching and bridging ability, and therefore excellent flocculation performance (residual turbidity: 5.8 NTU, D_f: 1.89, floc size d₅₀: 608.404 μm and floc kinetic: 15.86 × 10⁻⁴ s⁻¹) for treating high-turbidity water was achieved.

The fabrication of a cationic polyacrylamide (CPAM) with high efficiency and economy has been highly desired in the field of high-turbidity water treatment.     

Formation mechanism and characterization of porous biomass carbon for excellent performance lithium-ion batteries

Porous biomass carbon derived from corn stalks was prepared via carbonization and activation of CaCl₂. Combined with its microstructure, the formation mechanism and electrochemical properties were analyzed. The addition of CaCl₂ was the key factor to form the porous structure, and the proportion of CaCl₂ had a significant impact on the pores distribution and electrochemical properties. The resulting sample had a specific surface area of 370.6 m² g⁻¹ and an average pore size of 9.65 nm. The sample was circulated at 0.2C for 100 cycles, the specific discharge capacity was 783 mA h g⁻¹. After 60 cycles at different rates, when the current was restored to 0.2C again, the discharge specific capacity quickly recovered. This showed that the sample had excellent rate performance and cycle stability for lithium-ion batteries.

Porous biomass carbon derived from corn stalks was prepared via carbonization and activation of CaCl₂.     

A facile fabrication of sepiolite mineral nanofibers with excellent adsorption performance for Cd2+ ions

In this work, sepiolite mineral nanofibers are facilely prepared by a microwave-hydrogen peroxide method, and the bulk densities of the samples are adopted to evaluate the defibering effect. The samples are systematically characterized through X-ray diffraction, scanning electron microscopy, specific surface area measurement and zeta potential determination, and the adsorptive performance for heavy metal ions in aqueous solution is studied using cadmium ions as the representative. It is found that the specific surface area and cumulative pore volume increase respectively up to 109.21 m² g⁻¹ and 0.234 cm³ g⁻¹ under the microwave power of 400 W, while the zeta potential reaches a maximum when the pH is 5.0. The adsorption efficiency of sepiolite mineral nanofibers for cadmium ions can reach 68.6% as the optimal value. The as-fabricated sepiolite nanofibers can be regarded as a low-cost and environmentally friendly material which is a promising candidate for heavy metal ion removal from industrial wastewater.

In this work, sepiolite mineral nanofibers are facilely prepared by a microwave-hydrogen peroxide method, and the bulk densities of the samples are adopted to evaluate the defibering effect.     

Synthesis of triblock copolymer polydopamine-polyacrylic-polyoxyethylene with excellent performance as a binder for silicon anode lithium-ion batteries

Triblock copolymer polydopamine-polyacrylic-polyoxyethylene (PDA-PAA-PEO) with excellent performance as a binder for silicon anodes was synthesized. Its structure was confirmed by ¹H-NMR, FTIR and UV-vis spectroscopy. Results of electrochemical measurements indicated that a silicon anode based on PDA-PAA-PEO binder exhibited excellent cycle performance with a reversible capacity of 1597 mA h g⁻¹ after 200 cycles at a current density of 0.5 C, much better than that of an electrode based on a polyvinylidene-fluoride binder. Improvement of the cycle performance and reversible capacity for silicon anodes could be attributed to the strong adhesive and high ion conductivity of PDA-PAA-PEO.

Triblock copolymer polydopamine-polyacrylic-polyoxyethylene with strong adhesion as a novel binder enhance the cycle performance of silicon anode.     

Porous 3D flower-like CoAl-LDH nanocomposite with excellent performance for NO2 detection at room temperature

The 3D flower-like CoAl-layered double hydroxide (CoAl-LDH) was successfully prepared using the functional template agent of fluoride ions via a facile one-step hydrothermal route. Various techniques proved that all the samples presented 3D flower-like microstructural morphology. Representatively, the CA-2 sample, which was synthesized with the molar ratio of Co : Al of 3.65 : 1, had considerably abundant pores in its thin nanosheets. The average pore size was 2–4 nm, the specific surface area was equal to 49.45 m² g⁻¹, and the thickness of nanosheets was approximately 3.068 nm. The CA-2 sample showed an excellent response to 0.01–100 ppm NO₂ with ultrafast response/recovery time at room temperature (RT). The detection limit of the sensor even reached 10 ppb. The superior gas sensing performance could be attributed to the synergistic effects of the functional template agent of fluoride ions and specific porous 3D flower-like nanostructure. The current study showed that the 3D flower-like CoAl-LDHs might a promising material in practical detection of NO₂ at RT.

We have synthesized 3D flower-like CoAl-LDHs consisting of ultrathin nanosheets for excellent performance for NO₂ detection at room temperature.     

Performance optimization of freestanding MWCNT-LiFePO4 sheets as cathodes for improved specific capacity of lithium-ion batteries

The typical lithium-ion-battery positive electrode of “lithium-iron phosphate (LiFePO₄) on aluminum foil” contains a relatively large amount of inactive materials of 29 wt% (22 wt% aluminum foil + 7 wt% polymeric binder and graphitic conductor) which limits its maximum specific capacity to 120.7 mA h g⁻¹ (71 wt% LiFePO₄) instead of 170 mA h g⁻¹ (100 wt% LiFePO₄). We replaced the aluminum current-collector with a multi-walled carbon nanotube (MWCNT) network. We optimized the specific capacity of the “freestanding MWCNT-LiFePO₄” positive electrode. Through the optimization of our unique surface-engineered tape-cast fabrication method, we demonstrated the amount of LiFePO₄ active materials can be as high as 90 wt% with a small amount of inactive material of 10 wt% MWCNTs. This translated to a maximum specific capacity of 153 mA h g⁻¹ instead of 120.7 mA h g⁻¹, which is a significant 26.7% gain in specific capacity compared to conventional cathode design. Experimental data of the freestanding MWCNT-LiFePO₄ at a low discharge rate of 17 mA g⁻¹ show an excellent specific capacity of 144.9 mA h g⁻¹ which is close to its maximum specific capacity of 153 mA h g⁻¹. Furthermore, the freestanding MWCNT-LiFePO₄ has an excellent specific capacity of 126.7 mA h g⁻¹ after 100 cycles at a relatively high discharge rate of 170 mA g⁻¹ rate.

We optimized the specific capacity of freestanding MWCNT-LiFePO₄ positive electrode. We demonstrated as high (low) as 90 wt% LiFePO₄ active material (10 wt% MWCNTs inactive material). This corresponded to a maximum specific capacity of 153 mA h g⁻¹.     

Surface modification of a BN/ETDS composite with aniline trimer for high thermal conductivity and excellent mechanical properties

Boron nitride (BN) particles surface-treated with different amounts of aniline trimer (AT) were used to prepare thermally conductive polymer composites with epoxy-terminated dimethylsiloxane (ETDS). For the same weight content of BN, the BN composites surface-treated with AT showed better mechanical strength and thermal conductivity than the pure BN composites. This is because of the intercalation of AT between BN and ETDS, which not only increased the wettability but also provided excellent heat transfer pathways. We determined the optimum surface treatment ratio by varying the amount of AT, and the results are discussed regarding the thermal conductivity, storage modulus, and tensile strength. Finally, we established the optimum AT ratio for BN surface treatment.

Boron nitride (BN) particles surface-treated with different amounts of aniline trimer (AT) were used to prepare thermally conductive polymer composites with epoxy-terminated dimethylsiloxane (ETDS).     

Anchoring carbon layers and oxygen vacancies endow WO3−x/C electrode with high specific capacity and rate performance for supercapacitors

Herein, novel hierarchical carbon layer-anchored WO_3−x/C ultra-long nanowires were developed via a facile solvent-thermal treatment and a subsequent rapid carbonization process. The inner anchored carbon layers and abundant oxygen vacancies endowed the WO_3−x/C nanowire electrode with high conductivity, as measured with a single nanowire, which greatly enhanced the redox reaction active sites and rate performance. Surprisingly, the WO_3−x/C electrode exhibited outstanding specific capacitance of 1032.16 F g⁻¹ at the current density of 1 A g⁻¹ in a 2 M H₂SO₄ electrolyte and maintained the specific capacitance of 660 F g⁻¹ when the current density increased to 50 A g⁻¹. Significantly, the constructed WO_3−x/C//WO_3−x/C symmetric supercapacitors achieved specific capacitance of 243.84 F g⁻¹ at the current density of 0.5 A g⁻¹ and maintained the capacitance retention of 94.29% after 5000 charging/discharging cycles at the current density of 4 A g⁻¹. These excellent electrochemical performances resulted from the fascinating structure of the WO_3−x/C nanowires, showing a great potential for future energy storage applications.

A high-performance supercapacitor electrode comprising hierarchical carbon layer-anchored WO_3−x/C nanowires with inner abundant redox reaction active sites and numerous oxygen vacancies is presented.     

Two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings with excellent anti-corrosion performance

The economic loss and environmental damage caused by metal corrosion is irreversible. Thus, effective methods, such as coating technologies are used to protect metal surfaces from corrosion. In this work, cardanol-based benzoxazine (CB) was synthesized by a solvent-free method using cardanol, paraformaldehyde and n-octylamine. A cardanol-based benzoxazine copper polymer (CBCP) with good mechanical properties was then prepared by CuCl₂ catalysis and can be cured at room temperature. Subsequently, polyimide corrosion inhibitors with a two-dimensional sheet structure (pyromellitic dianhydride polyimide (PDPI) and 1,4,5,8-naphthalene tetracarboxylic dianhydride polyimide (NDPI)) were designed and prepared. Lastly, PDPI or NDPI was mixed with CBCP to obtain two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings. The Tafel curves and electrochemical impedance spectroscopy (EIS) measurements showed composite coatings with good corrosion resistance in different corrosive media. Compared to CBCP coating, the anticorrosion performance of the composite coatings improved obviously, especially the coating obtained with 0.5 wt% PDPI. It exhibits a high polarization resistance (3.874 × 10⁹ Ω), a high protection efficiency (99.99% and 97.98%) and low corrosion rate (3.376 × 10⁻⁶ mm year⁻¹). This work suggested a facile and eco-friendly strategy for preparing bio-based anticorrosive composite coatings from low cost and abundant cardanol and polyimide corrosion inhibitors, which will significantly promote their application in metal anticorrosion.

Room temperature cured two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings were successfully prepared, which exhibited excellent mechanical properties and anticorrosion properties.     

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.     

Diaminopyrene modified reduced graphene oxide as a novel electrode material for excellent performance supercapacitors

In this paper, novel reduced graphene oxide (rGO) composites (DAPrGOs) modified by diaminopyrene (DAP) were successfully synthesized via a facile solvothermal reaction method and used for supercapacitors. Compared with the pristine rGO, the DAPrGO1 electrode showed distinctly better performance (397.63 F g⁻¹vs. 80.29 F g⁻¹ of pristine rGO at 0.5 A g⁻¹) with small charge transfer resistance. When a symmetric device was fabricated using DAPrGO1 as the active material, it also exhibited a high capacitance of 82.70 F g⁻¹ at 0.5 A g⁻¹ with an energy density of 25.84 W h kg⁻¹ at a power density of 375 W kg⁻¹, and even offered a high power density of 7500 W kg⁻¹ (18.71 W h kg⁻¹) at 10 A g⁻¹. Moreover, the device possessed good electrochemical stability up to 20 000 cycles, implying promising applications in energy storage fields.

Schematic illustration of the facile synthesis process of DAPrGOs nanocomposites, Ragone plots and the superior cyclic stability of the assembled DAPrGO1//DAPrGO1 SSS.