Interlayer Modification of Pseudocapacitive Vanadium Oxide and Zn(H2 O)n 2+ Migration Regulation for Ultrahigh Rate and Durable Aqueous Zinc-Ion Batteries.

The interlayer modification and the intercalation pseudocapacitance have been combined in vanadium oxide electrode for aqueous zinc-ion batteries. Intercalation pseudocapacitive hydrated vanadium oxide Mn1.4 V10 O24 ·12H2 O with defective crystal structure, interlayer water, and large interlayer distance has been prepared by a spontaneous chemical synthesis method. The inserted Mn2+ forms coordination bonds with the oxygen of the host material and strengthens the interaction between the layers, preventing damage to the structure. Combined with the experimental data and DFT calculation, it is found that Mn2+ refines the structure stability, adjusts the electronic structure, and improves the conductivity of hydrated vanadium oxide. Also, Mn2+ changes the migration path of Zn2+ , reduces the migration barrier, and improves the rate performance. Therefore, Mn2+ -inserted hydrated vanadium oxide electrode delivers a high specific capacity of 456 mAh g-1 at 0.2 A g-1 , 173 mAh g-1 at 40 A g-1 , and a capacity retention of 80% over 5000 cycles at 10 A g-1 . Furthermore, based on the calculated zinc ion mobility coefficient and Zn(H2 O)n 2+ diffusion energy barrier, the possible migration behavior of Zn(H2 O)n 2+ in vanadium oxide electrode has also been speculated, which will provide a new reference for understanding the migration behavior of hydrated zinc-ion.

Carbon fabric supported 3D cobalt oxides/hydroxide nanosheet network as cathode for flexible all-solid-state asymmetric supercapacitor.

Owing to a lack of electroactive sites and poor conductivity, Co oxides/hydroxides nanosheet network electrodes usually show low experimental capacity, hardly meeting the demand for high energy density needed for an asymmetric supercapacitor. Herein, we demonstrate a surface capacity enhancement of a 3D cobalt oxides/hydroxides nanosheet network cathode through a simple cyclic voltammetry electro-deposition method. By optimizing the electro-deposition parameters, the as-prepared Co oxides/hydroxides nanosheet network electrode delivers a significantly high capacity of 427 C g-1 at the current density of 1 A g-1 and excellent rate ability of 79.8% at the current density of 10 A g-1, as well as outstanding cycling life. A detailed voltammetric analysis using the power-law relationship and Trasatti's method shows that both the large surface area, high pore volume and polycrystalline nature contribute to the enhancement of the surface capacity. In addition, the assembled asymmetric all-solid-state supercapacitor also presents a volume energy density of 2.78 mW h cm-3 at a power density of 14 mW cm-3 and excellent cycling stability. In addition, our prepared asymmetric supercapacitor shows super flexibility and was used to light up a heart-shaped logo. This work may provide valuable insights into the design and fabrication of electrode materials with improved capacity and rate ability.

Impacts of Mn ion in ZnSe passivation on electronic band structure for high efficiency CdS/CdSe quantum dot solar cells.

Surface passivation in quantum dot-sensitized solar cells (QDSSCs) plays a very important role in preventing surface charge recombination and thus enhancing the power conversion efficiency (PCE). ZnSe passivation with dopant in CdS/CdSe co-sensitized QDSSCs has been demonstrated as an effective way to improve the PCE. In the present study, a series of characterizations revealed that a Mn-doped ZnSe passivation layer can not only reduce surface charge recombination, but also enhance light harvesting. By means of density functional theory calculation along with a systematic study of electronic band structure, it has been found that the valence band of ZnSe moves upward on Mn-ion doping which leads to acceleration of charge separation and broader light absorption range. The impact of the Mn ion on charge recombination and light harvesting has been interpreted reasonably and the PCE of CdS/CdSe co-sensitized QDSSCs with Mn-doped ZnSe passivation layer is as high as 6.46%, which is 1.5 times that of the solar cell without the passivation layer.

Improved lithium-ion battery anode capacity with a network of easily fabricated spindle-like carbon nanofibers.

A novel network of spindle-like carbon nanofibers was fabricated via a simplified synthesis involving electrospinning followed by preoxidation in air and postcarbonization in Ar. Not only was the as-obtained carbon network comprised of beads of spindle-like nanofibers but the cubic MnO phase and N elements were successfully anchored into the amorphous carbon matrix. When directly used as a binder-free anode for lithium-ion batteries, the network showed excellent electrochemical performance with high capacity, good rate capacity and reliable cycling stability. Under a current density of 0.2 A g-1, it delivered a high reversible capacity of 875.5 mAh g-1 after 200 cycles and 1005.5 mAh g-1 after 250 cycles with a significant coulombic efficiency of 99.5%.