Synthesis and electrochemical properties of P2-Na<Subscript>2/3</Subscript>Ni<Subscript>1/3</Subscript>Mn<Subscript>2/3</Subscript>O<Subscript>2</Subscript>

The pure phase P2-Na_2/3Ni_1/3Mn_2/3O₂ was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g^?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g^?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na_2/3Ni_1/3Mn_2/3O₂ is a potential cathode material for sodium-ion batteries.     

Polymer electrolytes—relaxation and transport properties

Relaxations in polymer electrolytes were studied in poly(ethylene oxide) and epoxidized natural rubbers both filled with lithium perchlorate. Impedance relaxation was investigated over a wide range of salt concentration at room temperature. Imaginary part of impedance as a function of frequency exhibits generally one maximum and one minimum. These two extreme values rule properties in the DC limit. They can be related to transport properties and degree of dissociation. It turns out that DC conductivity is dominantly ruled by transport coefficient.     

Facile and surfactant-free synthesis of SnO<Subscript>2</Subscript>-graphene hybrids as high performance anode for lithium-ion batteries

A facile microwave-assisted ethylene glycol method is developed to synthesize the SnO₂ nanoparticles dispersed on or encapsulated in reduced graphene oxide (SnO₂-rGO) hybrids. The morphology, structure, and composition of SnO₂-rGO are investigated by scanning electron microscopy, transmission electron microscope, thermo-gravimetric analyzer, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical performance of SnO₂-rGO as anode materials for lithium-ion batteries was tested by cyclic voltammetry, galvanostatic charge–discharge cycling, and rate capability test. It is found that the SnO₂ nanoparticles with a uniform distribution have p-type doping effect with rGO nanosheets. The as-prepared SnO₂-rGO hybrids exhibit remarkable lithium storage capacity and cycling stability, and the possible mechanism involved is also discussed. Their capacity is 1222 mAhg^?1 in the first cycle and maintains at 700 mAhg^?1 after 100 cycles. This good performance can be mainly attributed to the unique nanostructure, good structure stability, more space for volume expansion of SnO₂, and mass transfer of Li⁺ during cycling.     

Dinitrile compound containing ethylene oxide moiety with enhanced solubility of lithium salts as electrolyte solvent for high-voltage lithium-ion batteries

A dinitrile compound containing ethylene oxide moiety (4,7-dioxa-1,10-decanedinitrile, NEON) is synthesized as an electrolyte solvent for high-voltage lithium-ion batteries. The introduction of ethylene oxide moiety into the conventional aprotic aliphatic dinitrile compounds improves the solubility of lithium hexafluorophosphate (LiPF₆) used commercially in the lithium-ion battery industry. The electrochemical performances of the NEON-based electrolyte (0.8 M LiPF₆?+?0.2 M lithium oxalyldifluoroborate in NEON:EC:DEC, v:v:v?=?1:1:1) are evaluated in graphite/Li, LiCoO₂/Li, and LiCoO₂/graphite cells. Half-cell tests show that the electrolyte exhibits significantly improved compatibility with graphite by the addition of vinylene carbonate and lithium oxalyldifluoroborate and excellent cycling stability with a capacity retention of 97 % after 50 cycles at a cutoff voltage of 4.4 V in LiCoO₂/Li cell. A comparative experiment in LiCoO₂/graphite full cells shows that the electrolyte (NEON:EC:DEC, v:v:v?=?1:1:1) exhibits improved cycling stability at 4.4 V compared with the electrolyte without NEON (EC:DEC, v:v?=?1:1), demonstrating that NEON has a great potential as an electrolyte solvent for the high-voltage application in lithium-ion batteries.     

Efficient electrochromic device based on sol–gel prepared WO<Subscript>3</Subscript> films

Tungsten oxide (WO₃) films were prepared on indium–tin oxide (ITO) glass by sol–gel method. The influence of annealing temperature on the structural, morphological, optical, electrochemical, and electrochromic properties has been investigated. The film annealed at 250 °C with an amorphous structure exhibits a noticeable electrochromic performance, such as the highest optical modulation of 58.5 % at 550 nm, high electrochemical stability, and excellent reversibility (Q _b/Q _c?=?96.3 %). An electrochromic (EC) device based on WO₃/NiO complementary structure shows improved performance. It exhibits high optical transmittance modulation of 62 % at 550 nm, excellent cycling stability, and relatively fast electrochromic response time (10 s for coloration and 19 s for bleaching).     

The ASACUSA CUSP: an antihydrogen experiment

In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning-Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected.     

Performance enforcement of gel polymer electrolyte for lithium ion battery with co-doping silicon dioxide and zirconium dioxide nanoparticles

In this work, we report a new method to enforce the comprehensive performances of gel polymer electrolyte (GPE) for lithium ion battery. Poly(methyl methacrylate-acrylonitrile-vinyl acetate) [P(MMA-AN-VAc)] is synthesized as polymer matrix. The physical and electrochemical performances of the matrix and the corresponding GPEs, doped with nano-SiO₂ and nano-ZrO₂ particles individually or simultaneously, are investigated by scanning electron microscopy, thermogravimetry, electrochemical impedance spectroscopy, and charge/discharge test. It is found that the membrane co-doped with 5 wt.% nano-SiO₂?+?5 wt.% nano-ZrO₂ and the corresponding GPE combine the advantages of those doped individually with 10 wt.% nano-SiO₂ or 10 wt.% nano-ZrO₂. Accordingly, the comprehensive performances of the membrane and the corresponding GPE, in terms of thermal stability, ionic conductivity, and electrochemical stability on the anode and cathode of lithium ion battery, is enforced by co-doping 5 wt.% nano-SiO₂ and 5 wt.% nano-ZrO₂.     

Flexible carbon nanostructures with electrospun nickel oxide as a lithium-ion battery anode

Carbon nanostructures (CNS) with high electrical conductivity and unique branched structure of carbon nanotubes combined with NiO nanofibers (NFs) were used as anode for lithium-ion batteries. CNS works as a framework substrate for the anodic conversion reaction of nickel oxide (NiO). Electrochemical performance and behavior of CNS/NiO anodes is compared with the conventional carbon (C)/NiO anodes. CNS/NiO NF-based anode retains high specific capacity under different current densities compared to C/NiO anode. Moreover, specific capacity as high as 450 mAh/g for CNS/NiO NF anode is observed compared to only 90 mAh/g for C/NiO NFs using a current density of 500 mA/g after 500 cycles. This improved performance is attributed to the highly conductive network of CNS leading to efficient charge transfer. The high porosity, electrical conductivity as well as the branched and networked nature of CNS reveal to be of critical importance to allow the electrochemical conversion reactions.     

Study on LiFe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript>/C used as cathode materials for lithium-ion batteries with low Sm component

LiFe_1???x Sm _x PO₄/C cathode materials were synthesized though a facile hydrothermal method. Compared with high-temperature solid-phase sintering, the method can allow for the fabrication of low Sm content (2 %), a scarce and expensive rare earth element, while the presence of an optimized carbon coating with large amount of sp²-type carbon sharply increases the material’s electrochemical performance. The high-rate dischargeability at 5 C, as well as the exchange current density, can be increased by 21 and 86 %, respectively, which were attributed to the fine size and the large cell parameter a/c as much. It should be pointed out that the a/c value will be increased for the LiFePO₄ Sm-doped papered by both of the two methods, while the mechanism is different: The value c is increased for the front and the value a is decreased for the latter, respectively.     

A model for dependent default with hyperbolic attenuation effect and valuation of credit default swap

A hyperbolic function is introduced to reflect the attenuation effect of one firm's default to its partner.If two firms are competitors(copartners),the default inten- sity of one firm will decrease(increase)abruptly when the other firm defaults.As time goes on,the impact will decrease gradually until extinct.In this model,the joint distri- bution and marginal distributions of default times are derived by employing the change of measure,and the fair swap premium of a credit default swap(CDS)can be valued.