Search

Abstract: Monoclinic Li3V2−x Al x (PO4)3 with different Al3+ doping contents (x =0, 0.05, 0.08, 0.10 and 0.12) have been prepared by a facile aluminothermal reaction. Aluminum nanoparticles have been used as source for Al3+ and nucleus for Li3V2−x Al x (PO4)3 nucleation as well as reducing agent in the aluminothermal strategy. The products were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and electrochemical methods. The XRD results show that the as-obtained Li3V2−x Al x (PO4)3 has a phase-pure monoclinic structure, irrespective of the Al3+ doping concentration. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) results reveal that the charge-transfer resistance of the Li3V2(PO4)3 is reduced and the reversibility is enhanced after V3+ substituted by Al3+. In addition, The Li3V2−x Al x (PO4)3 phases exhibit better cycling stability than the pristine Li3V2(PO4)3. [Copyright &y& Elsevier]

Abstract Na 3 V 2 (PO 4) 3 is suitable for the rapid migration of Na+ in the electrochemical reaction process due to its open-ended structure of 3D sodium super ionic conductor type, but the low electronic conductivity and large volume deformation during the repeated Na+ extraction/insertion severely limit its rate and cycle performance. Herein, a blackberry-shaped Na 3 V 2 (PO 4) 3 is synthesized for the first time to address both of the problems, and the structure is composed of aggregated carbon-coated nanoparticles attaching to highly conductive 3D porous carbon scaffolds, hence provides efficient pathways for both electrons and ions. For sodium-ion batteries, the blackberry-shaped Na 3 V 2 (PO 4) 3 exhibits high reversible capacity (116 mA h g−1 at 0.2 C), high-rate performance (83 mA h g−1 at 20 C) and long-life stability (94.4% capacity retention after 4500 cycles at 10 C). The excellent electrochemical performance indicates that blackberry-shaped Na 3 V 2 (PO 4) 3 has better application prospects as an advanced cathode material for sodium-ion batteries. Graphical abstract Image 1 Highlights • The blackberry-shaped Na 3 V 2 (PO 4) 3 is dedicated to promoting more efficient e− and Na+ transport. • It is unique in that it addresses the problems of low electronic conductivity and large volume deformation. • It exhibits high reversible rate capacity (116 mA h g−1 at 0.2 C and 83 mA h g−1 at 20 C). • It exhibits ultra-long-life stability (94.4% capacity retention after 4500 cycles at 10 C). [ABSTRACT FROM AUTHOR]

• A high-performance nickel electrode integrated with Co and carbon dots (CD-Co/Ni(OH) 2) has been prepared by cathodic electrodeposition. • The introduction of Co greatly improves the stability of the Ni(OH) 2 electrode, particularly at high current density. • The CDs-Co/Ni(OH) 2 electrode presents a high specific capacitance and an excellent capacitance retention. • The Ni/Zn supercapattery assembled with a zinc flake as negative electrode and a CDs-Co/Ni(OH) 2 electrode as positive electrode exhibits high power density, high energy density and remarkable cycling stability. Nickel hydroxide (Ni(OH) 2) is one of the most valuable electrode materials for supercapacitors. Owing to the low stability and conductivity of Ni(OH) 2 electrode, the preparation of a fast and high-stability Ni(OH) 2 electrode is a significant challenge. Nickel hydroxide integrated with cobalt and carbon dots (CDs-Co/Ni(OH) 2) as a high performance electrode has been prepared by cathodic electrodeposition for supercapattery in this work. Compared with unintegrated Ni(OH) 2 electrode or carbon dots integrated Ni(OH) 2 electrode, the introduction of Co greatly improves the stability of the Ni(OH) 2 electrode, particularly at high current density. The as-obtained CDs-Co/Ni(OH) 2 electrode presents a high specific capacitance of 338.6 mAh/g at 5 A/g and an extraordinary cycling stability with 1000 cycles even under a high current density of 40 A/g (retaining 84.6%). Besides, the CDs-Co/Ni(OH) 2 electrode exhibits an energy density of 281.2 Wh/kg at a power density of 57.2 kW/kg. Such a glorious stable CDs-Co/Ni(OH) 2 electrode may provide significant insight into future multifarious electronics and electrified vehicle applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, α-Ni(OH) 2 with controllable pristine crystal size is directly electrodeposited on a substrate of Ti wire mesh to fabricate the integrated electrode. The nanoscale effects on morphology, microstructure and electrochemical performance of the cathodic deposited α-Ni(OH) 2 are studied. The results show that the morphology of α-Ni(OH) 2 varies from irregular honeycomb-like nanopieces, ball-shaped particles to oval nanoplates as the cathodic deposition current density increases. The nanostructure diversity of the cathodic deposited α-Ni(OH) 2 is due to the different nanosize which directly depends on the cathodic deposition current density. The electrochemical performances of the cathodic deposited α-Ni(OH) 2 increase with the decrease of the pristine crystal size of α-Ni(OH) 2 . The oval α-Ni(OH) 2 nanoplates consisting of nanosheets with a pristine crystal size of 3 ∼ 5 nm × 5 ∼ 7 nm show the ultrahigh specific capacities of ∼348 mAh g −1 and ∼312.5 mAh g −1 at charge/discharge current density of 5 A g −1 and 100 A g −1 , respectively, and over 70% specific capacity still remains after 1000 cycles, while the irregular honeycomb-like α-Ni(OH) 2 consisting of nanosheet with a pristine crystal size of 10 ∼ 15 nm × 15 ∼ 20 nm shows only ∼260 mAh g −1 specific capacity at 5 A g −1 and ∼150 mAh g −1 at 100 A g −1 . The ultrahigh electrochemical performances are attributed to the nanoscale and the defective nanostructure of the cathodic deposited α-Ni(OH) 2 . [ABSTRACT FROM AUTHOR]

The concept of aqueous solution Al-ion battery inspires much enthusiasm in developing a novel chemical power source. In this work, the electrochemical behavior of TiO 2 -NTAs electrode in Al 3+ aqueous solution with different acidity is evaluated. Electrochemical studies showed that both of H + and Al 3+ in aqueous solution are electrochemical active to TiO 2 -NTAs, however, H + is preferential to hydroxylate on the TiO 2 -NTAs surface rather than to intercalate in the TiO 2 -NTAs lattice as compared with Al 3+ under the assistance of Cl − . The surface hydroxylation of TiO 2 -NTAs can retard Al 3+ diffusion in the TiO 2 -NTAs lattice as evidenced by the increase of faradic resistance R F (by EIS) at initial cathodic polarization process, however, the subsequent decrease of R F is due to the conductance improvement of TiO 2 -NTAs with the Al 3+ intercalation. Here it can be concluded that for Al 3+ aqueous solution battery with TiO 2 -NTAs as electrode, the suitable acidity (pH≈3) is required to minimizing the effect of H + . [ABSTRACT FROM AUTHOR]

The titanium dioxide nanotube array (TiO 2 -NTA) is prepared by a two-step anodic oxidation method and annealed at 450 ∘ C subsequently. The Al-inserted TiO 2 -NTA is prepared by polarizing the TiO 2 -NTAs electrode at 0.4 mA for 2 min in 1 mol/L AlCl 3 . The results show that the Al-inserted sample still remains pure anatase TiO 2 phase (by XRD) and keeps intact nanotube array structure (by FE-SEM). The X-ray photoelectron spectroscopy (XPS) analysis indicates that the insertion of Al 3+ into TiO 2 -NTAs facilitates in the reduction of Ti 4+ to Ti 3+ . Electrochemical investigation on the Al 3+ insertion process reveals that presence of Cl − ions plays vital role for the effective insertion and de-insertion of Al 3+ into/from the TiO 2 -NTA. [ABSTRACT FROM AUTHOR]

• A novel hydrogen ion supercapattery was assembled. • N and P co-doped carbon paper was effectively acted as the cathode substrate. • The cyclic stability could be improved by modifying the cathode with Nafion. Hydrogen ion battery is a promising energy storage device due to its advantages of non-pollution, excellent rate capability and feasibility at low temperature. Herein, we assemble a novel rechargeable hydrogen ion supercapattery with the iodine-absorbed carbon paper doped with N and P (I 2 -NP-CP) as the cathode electrode and molybdenum trioxide as the anode electrode. Typically, the I 2 -NP-CP electrode shows the superior rate capability from 1 A g−1 (174.7 mAh g−1, 483.8 F g−1) to 20 A g−1 (111.1 mAh g−1, 307.7 F g−1), mainly ascribed to the strong interaction between iodine and the NP-CP substrate. Furthermore, electrochemical measurement of the I 2 -NP-CP@Nafion//MoO 3 supercapattery manifests that the electrodes exhibit excellent cycling stability, retaining 124.3 mAh g−1 after 500 cycles at 15 A g−1, accounting for 93.2 % of the initial capacity. Although some IO 3 − dissolves in the electrolyte due to the weak chemical interaction between IO 3 − and NP-CP, and cannot be completely reduced to I− during discharge process, it can be improved by modification of electrode with Nafion resin to further better the cycling stability. The excellent electrochemical properties in this study show the possibility for the development of novel rechargeable hydrogen ion supercapattery system. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: A promising supercapacitor material based on graphene/polypyrrole (PPy) has been successfully synthesized via in situ oxidation polymerization of pyrrole monomers in aqueous graphene oxide (GO) solutions, followed by chemical reduction using ethylene glycol (EG). Unlike the commonly employed hydrazine reduction, the moderate EG reductant does not destruct the PPy conjugative structures, thus facilitating utilization of the electroactive conductive polymer. The morphologies and the structures of the as-prepared materials are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectra, and Fourier transform infrared spectroscopy (FTIR). And the electrochemical performance of the fabricated electrodes was evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The EG-RGO/PPy electrode shows large specific capacitance, high rate performance, and good charge–discharge stability as well. The excellent electrochemical capability is mainly accounted for the sound composite construction that improves the effective utilization of electroactive PPy component, accelerates shuttling the charged carriers, and alleviates the swelling/shrinkage of polymer chains. [Copyright &y& Elsevier]

• The pomegranate-like Si@C microspheres were successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization, and acid etching processes. • The distinctive pomegranate-like Si@C structure stabilizes the porous structure of Si particle and improves the electrochemical property. • As high as 84.98% ICE and 100% Coulombic efficiency were obtained for the sample (Si40@C3), which provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling. Si/C materials are considered as the most promising anodes for the next generation lithium ion batteries. However, the Si/C anodes with high Coulombic efficiency are still a challenge. Here, pomegranate-like Si@C microspheres are successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization and acid etching processes. As high as 84.98% initial Coulombic efficiency (ICE) and 100% Coulombic efficiency are obtained for the sample (Si 40 @C3), and the specific capacity still maintained over 620 mAh g−1 with capacity retention of 70.4% over 250 cycles. The excellent electrochemical performance could be attributed to the distinctive pomegranate-like Si@C structure, which either stabilizes the porous structure of Si particle by inhibiting the volume expansion and pulverization or improves the electrochemical property by the appropriate carbon coating layer. This would provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling. [ABSTRACT FROM AUTHOR]

In this work, we successfully synthesized Ni(OH) 2 thin film electrode in situ doped with CNTs/rGO by cathodic electrodeposition on titanium mesh. The doping effects of CNTs and/or rGO, and the technical conditions, are investigated. The doping of CNTs/rGO can greatly improve the electrochemical performance by forming the porous structure and the conductive network in the Ni(OH) 2 thin film. The highest capacity, 429.5 mAh/g at a current density of 5 A/g, is achieved for the electrode with 0.24 mg/cm2 Ni(OH) 2 and codoped with CNTs and rGO, as compared with only 323.9 mAh/g for undoped electrode. Even at 100 A/g, the specific capacity can still remain 347.5 mAh/g (vs. 221.5 mAh/g for the undoped electrode), and after 1000 cycles, the retention rate of the specific capacity is 74.9% as compared with only 42.7% for the undoped electrode. Even with higher loading amounts of 1.92 mg/cm2 Ni(OH) 2 , the specific capacity retention rate of the codoped electrode is still much higher than that of the undoped electrode. The high electrochemical performance can be attributed to the better ion/electron transfer ability of the codoped electrode. In conclusion, by the cathodic electrodeposition and in situ doping of CNTs/rGO, the porous structure and the conductive network in Ni(OH) 2 film can be constructed, which can improve the ion/electron transfer ability, therefore, the high performance film electrode with higher loading amount of Ni(OH) 2 can be prepared. [ABSTRACT FROM AUTHOR]