Sodium intercalation into α- and β-VOSO4

Received: 12.02.2019. Accepted: 19.03.2019. Published: 29.03.2019.Na-ion battery is one of the best alternatives to Li-ion battery. Abundance of sodium on earth is three orders of magnitude higher than lithium, which should make Na-ion battery technology cheaper. But alkaline-ion battery prices, which tend to increase because of the massive world demand, also depend on the choice of electrode materials. Therefore, cost-effective electrode development remains an important subject of research because this will allow Na-ion battery to be even more competitive. Electrochemical performances of anhydrous VOSO4 as electrode for Na-ion battery are reported in this letter. Two anhydrous phases of vanadyl sulfate have been studied. The first one, α-VOSO4, shows that up to 0.8 sodium per formula unit (Na/f.u.) can be intercalated in this phase, and a reversible intercalation of 0.4 Na/f.u. has been observed with a strong polarization. The second one, β-VOSO4, can intercalate up to 0.9 Na/f.u. with a reversible inter- calation of 0.4 Na/f.u. leading to a reversible capacity of 64 mAh/g

Sodium intercalation into α- and β-VOSO4

Received: 12.02.2019. Accepted: 19.03.2019. Published: 29.03.2019.Na-ion battery is one of the best alternatives to Li-ion battery. Abundance of sodium on earth is three orders of magnitude higher than lithium, which should make Na-ion battery technology cheaper. But alkaline-ion battery prices, which tend to increase because of the massive world demand, also depend on the choice of electrode materials. Therefore, cost-effective electrode development remains an important subject of research because this will allow Na-ion battery to be even more competitive. Electrochemical performances of anhydrous VOSO4 as electrode for Na-ion battery are reported in this letter. Two anhydrous phases of vanadyl sulfate have been studied. The first one, α-VOSO4, shows that up to 0.8 sodium per formula unit (Na/f.u.) can be intercalated in this phase, and a reversible intercalation of 0.4 Na/f.u. has been observed with a strong polarization. The second one, β-VOSO4, can intercalate up to 0.9 Na/f.u. with a reversible inter- calation of 0.4 Na/f.u. leading to a reversible capacity of 64 mAh/g

Interface modification of clay and graphene platelets reinforced epoxy nanocomposites: a comparative study

The interface between the matrix phase and dispersed phase of a composite plays a critical role in influencing its properties. However, the intricate mecha-nisms of interface are not fully understood, and polymer nanocomposites are no exception. This study compares the fabrication, morphology, and mechanical and thermal properties of epoxy nanocomposites tuned by clay layers (denoted as m-clay) and graphene platelets (denoted as m-GP). It was found that a chemical modification, layer expansion and dispersion of filler within the epoxy matrix resulted in an improved interface between the filler mate-rial and epoxy matrix. This was confirmed by Fourier transform infrared spectroscopy and transmission electron microscope. The enhanced interface led to improved mechanical properties (i.e. stiffness modulus, fracture toughness) and higher glass transition temperatures (Tg) compared with neat epoxy. At 4 wt% m-GP, the critical strain energy release rate G1c of neat epoxy improved by 240 % from 179.1 to 608.6 J/m2 and Tg increased from 93.7 to 106.4 �C. In contrast to m-clay, which at 4 wt%, only improved the G1c by 45 % and Tg by 7.1 %. The higher level of improvement offered by m-GP is attributed to the strong interaction of graphene sheets with epoxy because the covalent bonds between the carbon atoms of graphene sheets are much stronger than silicon-based clay

Sodium intercalation into α- and β-VOSO4

International audienceNa-ion battery is one of the best alternatives to Li-ion battery. Abundance of sodium on earth is three orders of magnitude higher than lithium, which should make Na-ion battery technology cheaper. But alkaline-ion battery prices, which tend to increase because of the massive world demand, also depend on the choice of electrode materials. Therefore, cost-effective electrode development remains an important subject of research because this will allow Na-ion battery to be even more competitive. Electrochemical performances of anhydrous VOSO4 as electrode for Na-ion battery are reported in this letter. Two anhydrous phases of vanadyl sulfate have been studied. The first one, α-VOSO4, shows that up to 0.8 sodium per formula unit (Na/f.u.) can be intercalated in this phase, and a reversible intercalation of 0.4 Na/f.u. has been observed with a strong polarization. The second one, β-VOSO4, can intercalate up to 0.9 Na/f.u. with a reversible intercalation of 0.4 Na/f.u. leading to a reversible capacity of 64 mAh/g

Magnetic properties of LiNi0.5Mn1.5O4 spinels prepared by wet chemical methods

International audienceWe present the magnetic properties of LiNi0.5Mn1.5O4 spinels prepared by the sol–gel and pyrolysis techniques. Structural properties show that the material synthesized by pyrolysis method exhibit an ordered spinel structure. Characterization methods include SQUID magnetometry and ESR spectroscopy. Magnetic measurements have evidenced the ferromagnetic ordering below T c 1⁄4 129 K in LiNi0.5Mn1.5O4. Results show that actually no impurity phase is detected in LiNi0.5Mn1.5O4, thus the ferrimagnetic behavior is attributed to an intrinsic property of this material. The magnetic order in this case is trivially a collinear ferrimagnetic ordering in which both the Ni sublattice and the Mn sublattice are ferromagnetic. ESR measurements show a two-component signal with a complex shape. The dominant band is assigned to Mn4+ ions that are the only paramagnetic entities in this compound

Structure and insertion properties of disordered and ordered LN0.5Mn1.5O4 spinels prepared by wet chemistry

International audienceWe present the synthesis, characterization, and electrode behavior of LiNi0.5Mn1.5O4 spinels prepared by the wet-chemical method via citrate precursors. The phase evolution was studied as a function of nickel substitution and upon intercalation and deintercalation of Li ions. Characterization methods include X-ray diffraction, SEM, Raman, Fourier transform infrared, superconducting quantum interference device, and electron spin resonance. The crystal chemistry of LiNi0.5Mn1.5O4 appears to be strongly dependent on the growth conditions. Both normal-like cubic spinel [Fd3m space group (SG)] and ordered spinel (P4(1)32 SG) structures have been formed using different synthesis routes. Raman scattering and infrared features indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Ni,Mn)-O bonds. Scanning electron microscopy (SEM) micrographs show that the particle size of the LiNi0.5Mn1.5O4 powders ranges in the submicronic domain with a narrow grain-size distribution. The substitution of the 3d(8) metal for Mn in LiNi0.5Mn1.5O4 oxides is beneficial for its charge-discharge cycling performance. For a cut-off voltage of 3.5-4.9 V, the electrochemical capacity of the Li//LiNi0.5Mn1.5O4 cell is ca. 133 mAh/g during the first discharge. Differences and similarities between LiMn2O4 and LiNi0.5W1.5O4 oxides are discussed