Kirill G. Bramnik

Synchrotron Diffraction Study of Lithium Extraction from LiMn0.6Fe0.4PO4

Electrochemical lithium extraction from LiMn0.6Fe0.4PO4 was revealed to proceed through two two-phase regions in contrast to the mechanism earlier reported. All phases appearing during charging of the cell have the same olivine-like structure with different cell parameters.

Structural investigation of the Na–Fe–Mo–O system

Four new crystalline structures within the Na-Fe-Mo-O system are reported: sodium tetrairon pentamolydate (1), NaFe(4)(MoO(4))(5), alpha-sodium diiron trimolybdate (2), alpha-NaFe(2)(MoO(4))(3), beta-sodium diiron trimolybdate (3), beta-NaFe(2)(MoO(4))(3), trisodium diiron trimolybdate (4), Na(3)Fe(2)(MoO(4))(3). All these structures belong to orthomolybdate class of compound and are described as networks of [FeO(6)] octahedra and [MoO(4)] tetrahedra. They are compared with each other and with other related structures.

The ferrimagnetic structure of Fe2Mo3O12: dependence of Fe–O–O–Fe supersuperexchange couplings on geometry

Abstract The magnetic structure of Fe 2 Mo 3 O 12 was determined by neutron powder diffraction and magnetization studies. The magnetic unit cell is identical with the monoclinic chemical one ( Z =8), and the magnetic space group is P2 1 /a. The magnetic moments are ferromagnetically aligned along the b -axis for each sublattice corresponding to each Fe-site. There are four different Fe-sites, and the magnetic moments are parallel within two of them, but antiparallel to those of the other two sublattices, so that a ferrimagnetic structure results. The dominant antiferromagnetic supersuperexchange couplings are those along Fe–O–O–Fe paths with the two bridging oxygens belonging to one [MoO 4 ]-tetrahedron and forming large Fe–O–O and O–O–Fe angles.

Preparation, crystal structure, and magnetic properties of double perovskites M2MgReO6 (M=Ca, Sr, Ba)

Abstract The complex oxides M2MgReO6 (M=Ca, Sr, Ba) have been synthesized, and their crystal structures were determined by X-ray diffraction powder data analysis. These compounds belong to the A2BB′O6 (M2MgReO6) perovskites with a “rock-salt” type distribution of Re and Mg atoms over the B-cation sublattice, since a big M cation is located in A positions. The magnetic properties of the M2MgReO6 compounds (M=Ca, Sr, Ba) were investigated and an unexpected behavior observed: significant hysteresis effects were detected for all M2MgReO6 oxides at temperatures up to 300 K. These results point at a ferromagnetic component in all of the M2MgReO6 magnetic structures, even at room temperature.

Preparation and crystal structure of a new high-pressure phase (V0.5Re0.5)O2 with rutile-type structure

Abstract The new complex oxide (V0.5Re0.5)O2 has been synthesized under high pressure of 60 kbar at 1000°C, and its crystal structure determined by single crystal X-ray diffraction data analysis (S.G.: P42/mnm, a = 4.6357(4) Å, c = 2.8292(3) Å, V = 60.80(1) Å3). This compound adopts a rutile-type structure with random cat ion distribution on one crystallographic site. The substitution of 50 vanadium by rhenium stabilizes the high temperature form of VO2 at room temperature. The cation ratio of 1 : 1 was confirmed by EDX analysis performed by electron microscopy on the same crystals used for X-ray diffraction.

Preparation, crystal structure and magnetic properties of the high-pressure phase MnReO4 with a wolframite-type structure

The ternary oxide MnReO(4), manganese rhenium oxide, has been synthesized under a high pressure of 5.5 GPa at 1473 K and its crystal structure has been determined by single-crystal X-ray diffraction. MnReO(4) crystallizes in a wolframite-type structure with average bond lengths of Re-O = 1.935 and Mn-O = 2.160 A that are in good agreement with the ionic radii of Re(6+) and Mn(2+). The magnetic properties of MnReO(4) have been studied by SQUID measurements, revealing magnetic ordering below 275 (10) K and a weak ferromagnetic component of the ordered magnetic structure.

Electrochemical intercalation of lithium in ternary metal molybdates M MoO 4 ( M =Cu,Zn)

Ternary oxides with general formula M MoO 4 (where M is a 3 d -transitional metal) were characterized as cathode materials for lithium rechargeable batteries by galvanostatic charge-discharge technique and cyclic voltammetry. The significant capacity fading after the first cycle of lithium insertion/removal takes place for different copper molybdates (standard a-CuMoO 4 and high-pressure modification CuMoO 4 –III) corresponding to the irreversible copper reduction and formation of Li2MoO4 during the first discharge. X-ray powder diffraction data reveal the decomposition of pristine ZnMoO4 by electrochemical reaction, lithium zink oxide with the NaCl-type structure and Li 2 MoO 3 seem to be formed.

A Feasibility Study on the Use of Li4V3O8 as a High Capacity Cathode Material for Lithium‐Ion Batteries

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).

A feasibility study on the use of Li(4)V(3)O(8) as a high capacity cathode material for lithium-ion batteries.

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).

A Feasibility Study on the Use of Li4V3O8as a High Capacity Cathode Material for Lithium-Ion Batteries

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).