Magnetic properties of the submicron carbon-coated LiFe1−xMnxPO4 (x = 0, 0.01, 0.1) systems were ... more Magnetic properties of the submicron carbon-coated LiFe1−xMnxPO4 (x = 0, 0.01, 0.1) systems were investigated using the electron spin resonance (ESR) method. The observed ESR signal consisted of two broad resonance lines with a Lorentzian line shape for all samples. The temperature dependence character of the integral intensity of these lines changed significantly with increasing manganese concentration, indicating a change in the nature of the magnetic interactions between the manganese and iron ions. We suggest that the noticeable capacity loss observed in the LiFe1−xMnxPO4 systems with increasing Mn content can be explained by the random distribution of Mn ions and changes to the type of magnetic ordering in these systems, despite the attractiveness of the electrochemical Mn2+/Mn3+ pair compared with Fe+2/Fe+3.
In the present work, sodium-vanadium fluorophosphates were prepared from the same reagents using ... more In the present work, sodium-vanadium fluorophosphates were prepared from the same reagents using the solid-state and the hydrothermal routes. The differences in phase composition, crystal structure, morphology, particle size distribution, and electrochemical properties of the as-prepared products are discussed.
The mixed sodium-iron ortho-pyrophosphate Na4Fe3(PO4)2P2O7 (NFPP) is a promising Na-containing ca... more The mixed sodium-iron ortho-pyrophosphate Na4Fe3(PO4)2P2O7 (NFPP) is a promising Na-containing cathode material with the highest operating voltage among sodium framework structured materials. It operates both in Na and Li electrochemical cells. When cycled in a hybrid Li/Na cell, a competitive co-intercalation of the Li+ and Na+ ions occurs at the cathode side. The present study shows that this process can be tuned by changing the concentration of the Na+ ions in the mixed Li+/Na+-ion electrolyte and current density. It is shown that if the Na concentration in the electrolyte increases, the specific capacity of NFPP also increases and its high-rate capability is significantly improved.
La 3+ modification of Na 3 V 2 (PO 4) 2 F 3 was performed by the direct mechanochemically assiste... more La 3+ modification of Na 3 V 2 (PO 4) 2 F 3 was performed by the direct mechanochemically assisted solid-state synthesis of the Na 3 V 2−x La x (PO 4) 2 F 3 compositions, and by the LaPO 4 coating of the as-prepared Na 3 V 2 (PO 4) 2 F 3 via the precipitation method. It has been shown that no noticeable substitution of the V 3+ ions by the La 3+ ions occurs in the Na 3 V 2 (PO 4) 2 F 3 structure under the synthesis conditions; meanwhile, the introduction of the La 3+ ions into the reagent mixture leads to the formation of the LaPO 4 phase, and accordingly, an increase in the NaF/VPO 4 ratio. The latter results in the formation of the Na 3 PO 4 and Na 3 VF 6 surface impurity phases, which possess high ionic and electronic conductivity, respectively, and significantly enhances the electrical conductivity and the cycling performance of the composite cathode material both in Na and Li cells, while simple surface modification of Na 3 V 2 (PO 4) 2 F 3 by LaPO 4 via precipitation does not.
Pristine Na 3 FePO 4 CO 3 (NFPC) with the monoclinic structure and the P2 1 /m space group was pr... more Pristine Na 3 FePO 4 CO 3 (NFPC) with the monoclinic structure and the P2 1 /m space group was prepared by hydrothermal synthesis at 120 °C. To increase the conductivity of NFPC, it was ballmilled with carbon using a SPEX 8000 mill. Crystal and local structure, morphology, thermal stability, conductivity and electrochemical properties of NFPC and NFPC/C composites were studied by XRD, DSC/TG, FTIR, Mӧssbauer spectroscopy, 23 NMR spectroscopy, magnetic measurements, SEM, EIS and galvanostatic cycling. It has been shown that the as-prepared NFPC is stable below 500 °C and then decomposes to Fe 3 O 4 and Na 3 PO 4. Ball milling of NFPC with and without carbon leads to its partial decomposition with the formation of nanosized superparamagnetic Fe 3 O 4 particles and a significant structural disordering, though the crystal symmetry maintains unchanged. Due to high sensitivity of NFPC to air, pristine sample contains some portion of the Fe 3+ ions; it increases after ball milling. As a result, all samples are able to cycle starting both with charge and discharge. NFPC shows high stability upon cycling with the specific discharge capacity close to the theoretical one (96 mA·h·g-1 for one-electron reaction). Though the capacity of the NFPC/C composites is slightly lower at low cycling rate than that of pristine NFPC, they show better high-rate performance due to improved conductivity via the formation of the highly conductive carbon matrix. As-established low lattice volume variation upon (de)intercalation of the sodium ions along with realization of a single-phase mechanism is responsible for a long cycle life of the NFPC/C cathode material.
Na2FeP2O7 sodium iron pyrophosphate with a triclinic symmetry (the space group P-1) has been prep... more Na2FeP2O7 sodium iron pyrophosphate with a triclinic symmetry (the space group P-1) has been prepared by mechanochemically assisted solid state synthesis. Electrochemical performance of the pristine Na2FeP2O7, NaFeP2O7 prepared by chemical oxidation with NO2BF4 and NaLiFeP2O7 obtained by non-oxidative Na+/Li+ ion exchange with LiBr were studied by galvanostatic cycling in a Li cell with Li as an anode and LiPF6 dissolved in EC+DMC as an electrolyte. XRD, EDX, Mössbauer and NMR spectroscopy studies showed that all the samples were active upon cycling in Li cells which resulted in exchange of one ~Na+ for one Li+ per f.u. to produce a new mixed phase NaLiFeP2O7 with the same triclinic structure as Na2FeP2O7 and good electrochemical performance.
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT Although being commercially realized, lithium-ion batteries are still the object of inte... more ABSTRACT Although being commercially realized, lithium-ion batteries are still the object of intense study aimed of further improving their electrochemical characteristics. The charge-discharge processes strongly depend on the crystal and electronic structure of the intercalation lithium-transition metal oxides used as cathode materials. Last years a great deal of attention was devoted to preparation of these compounds with unusual ordering (structural, magnetic, charge) and electronic state of transition metal ions, and a structure more stable to intercalation/deintercalation of lithium ions at discharge/charge processes, preventing a structural distortion and, thus, providing better electrochemical behavior.
ABSTRACT LiCo1-yFeyPO4 solid solutions (0≤y≤1) were prepared by mechanochemically assisted carbot... more ABSTRACT LiCo1-yFeyPO4 solid solutions (0≤y≤1) were prepared by mechanochemically assisted carbothermal reduction of Co3O4 and Fe2O3. Mechanical activation was performed using a high-energy planetary mill AGO-2. The samples were characterized in detail by X-ray powder diffraction (XRD) using Rietveld refinement, Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), galvanostatic cycling and galvanostatic intermittent titration technique (GITT). According to XRD, all samples are single-phase solid solutions, crystallized in an orthorhombic structure (S.G. Pnma). The cell volume of LiCo1-yFeyPO4 linearly increases vs. Fe content. All Fe ions are in the 2+ oxidation state and are octahedrally coordinated. The LiCo1-yFeyPO4 solid solutions show improved electrochemical performance as compared with LiCoPO4. Based on the data from XRD and GITT, the improvement is attributed to the enhanced Li+ diffusion due to the enlargement of 1D diffusion channels in the polyanion structure of LiCoPO4 and the reduced cell volume change in the material during the Li extraction-insertion process. Besides, a systematic decrease in the average potential of the Co2+/Co3+ redox pair is observed with the increased Fe content, leading to the reaction termination within the electrochemical window of the conventionally available electrolytes. In situ synchrotron diffraction shows that upon charging of LiCo0.5Fe0.5PO4, a two-phase mechanism of Li (de)intercalation at the Fe2+/Fe3+ and Co2+/Co3+ redox stages changes to a solid solution-like mechanism, contrary to the pristine LiFePO4 and LiCoPO4 materials.
The recent launching of production of hybrid and electric vehicles made great demands on lithium-... more The recent launching of production of hybrid and electric vehicles made great demands on lithium-ion batteries (LIBs). One of the promising approaches to the optimization of their properties is in the development of new blended composite electrode materials consisting of two (or more) active components in order to use the advantages of the both of them [1]. Due to a unique combination of properties, the mixed materials show some advantages over the individual components. This includes the longer lifetime, the decreased capacity fading upon the cycling, lower price, the improved thermal stability, more acceptable profiles of charge-discharge curves and operating voltage, etc. For instance, the cathode materials with a layered structure (LiCoO 2
ABSTRACT A soft mechanochemical synthesis approach was applied to prepare some fi ne particulate ... more ABSTRACT A soft mechanochemical synthesis approach was applied to prepare some fi ne particulate lithium-containing compounds with a spinel (LiMn2-xMxO4, Li4Ti5O12), layered (LiNi1-x-yCoxMnyO2, LiV3O8) and framework structure (LiFePO4, Li2FeSiO4, LiTi2(PO4)3). It consists of the fast formation of amorphous or low-crystalline precursors during mechanical activation of LiOH (or Li2CO3) with corresponding anhydrous oxides of d-metals, solid hydroxides, crystal hydrates and acidic salts in highly energetic planetary mills and transformation of these precursors into nanostructured fi nal products under 'soft' heating conditions (lower temperatures and shorter time of treatment) after removal of water molecules, hydroxide groups and other volatile compounds. Most of as-prepared materials show good electrochemical properties as cathodes, anodes or solid electrolytes for lithium-ion batteries.
Journal of Metastable and Nanocrystalline Materials, 2003
ABSTRACT Mechanical activation in highly energetic planetary mills is used to prepare 3 V (Li1+xV... more ABSTRACT Mechanical activation in highly energetic planetary mills is used to prepare 3 V (Li1+xV3O8), 4 V (LiCoO2 and LiMn2O4) and 5 V (substituted LiMn2O4) cathode materials for rechargeable lithium batteries. It is shown that Li1+xV3O8 and LiMn2O4 can be prepared by direct mechanochemical synthesis while the others by subsequent brief heat treatment of activated mixtures at moderate temperatures. In many cases the use of hydroxides as initial reagents is preferable ('soft mechanochemical synthesis'). The advantages of mechanical activation for preparation of multicomponent cathode materials (doped LiCoO2 and LiMn2O4) are demonstrated. The as-prepared materials are characterized by high dispersion and structural disordering providing higher discharge rates and better stability under cycling. The mechanochemical method ensures the decrease of production time and energy expenses, simplification of the process and, as a result, lower material cost, thus being more energy-efficient and ecologically clean as compared with conventional technologies.
Nanosized LiCoO2 and LiMn2O4 were prepared by preliminary mechanical activation of the mixtures o... more Nanosized LiCoO2 and LiMn2O4 were prepared by preliminary mechanical activation of the mixtures of Li2CO3 with Co3O4 and Li2CO3 with MnO or MnO2 in the presence of carbon in high-energy planetary mill and annealed at 750-800{degree sign}C in air. Added carbon inhibits the particles' interaction during mechanical activation and their growth during annealing. The final products are free from carbon due to its oxidation and evaporation. They are characterized by the domain structure and show high specific discharge capacity and good cycleability.
LiFePO4 and LiFePO4/C composites were prepared by mechanical activation process using Fe3+ precur... more LiFePO4 and LiFePO4/C composites were prepared by mechanical activation process using Fe3+ precursor (Fe2O3) in comparison with Fe2+ precursor (FeC2O4•2H2O). The reaction mechanism, phase composition, particle size and electrochemical performance of as-prepared materials were examined by thermal analysis, X-ray diffraction, Mössbauer spectroscopy, SEM, TEM, and galvanostatic cycling. The LiFePO4/C composites were prepared by pyrolysis of suitable organic compounds during synthesis and by in situ incorporation of carbon powder. It has been shown that using carbothermal method, a phase-homogeneous nanosized LiFePO4 is formed at temperatures ≥700°C with specific discharge capacity ~150 mAh/g at C/10 rate.
The surface chemistry of the Al2O3-coated LiCoO2 prepared under heat treatment at 80800° C was s... more The surface chemistry of the Al2O3-coated LiCoO2 prepared under heat treatment at 80800° C was studied by SEM, XRD, IR, XPS and NMR spectroscopy combined with electrochemical testing. It is shown that the particle bulk is free from dopant. XPS Al2s core ...
Mechanical activation (MA) has been used to prepare high dispersed lithium-transition metal catho... more Mechanical activation (MA) has been used to prepare high dispersed lithium-transition metal cathode materials and inorganic solid lithium-ion electrolytes for rechargeable lithium batteries. It has been shown that materials with low-dimensional (submicron) particles ...
The cathode materials of the composition LiNi1 − 2x Co x Mn x O2 (x = 0.1, 0.2. 0.33) synthesized... more The cathode materials of the composition LiNi1 − 2x Co x Mn x O2 (x = 0.1, 0.2. 0.33) synthesized from the Ni, Co, Mn mixed hydroxides and LiOH by using mechanical activation method are studied. It is shown that all synthesized compounds have layered structure described by the space group R-3m. With the decreasing of the nickel content the
This short review reports on the synthesis of nanosized electrode materials for lithium-ion bat t... more This short review reports on the synthesis of nanosized electrode materials for lithium-ion bat teries by mechanical activation (MA) and studies of their properties. Different structural types of compounds were considered, namely, compounds with a layered (LiNi 1-x-y Co x Mn y O 2), spinel (LiMn 2 O 4 , Li 4 Ti 5 O 12), and framework (LiFePO 4 , LiTi 2 (PO 4) 3) structures. The compounds also differed in electronegativity, which varied from 10-4 S cm-1 for LiCoO 2 to 10-9 S cm-1 for LiFePO 4. The preliminary MA of mixtures of reagents in energy intensive mechanoactivators led to the formation of highly reactive precursors, and annealing of the latter formed nanosized products (the mean particle size is 50-200 nm). The local structure of the synthe sized compounds and the composition of their surface were studied by spectral methods. An increase in the dispersity and defect concentration, especially in the region of the surface, improved some electrochemical characteristics. It increased the stability during cycling (LiMn 2 O 4 , at 3 V) and the regions of the formation of solid solutions during cycling (Li 4 Ti 5 O 12 , LiFePO 4), led to growth of surface Li-ion conductivity (LiTi 2 (PO 4) 3), etc. The mechanochemical approach was also used for the synthesis of core-shell type com posite materials (LiFePO 4 /C, LiCoO 2 /MeO x) and materials based on two active electrode components (LiCoO 2 /LiMn 2 O 4).
The possibility for hydrothermal processes to take place under the action of mechanical pulses th... more The possibility for hydrothermal processes to take place under the action of mechanical pulses that arise in mechanical activators is considered for the system: a solid substance-water. Experimental data are presented on the mechanochemical synthesis of gidenbergite, tobermorite and other hydrosilicates that are usually produced according to the autoclave technology.
Single-phase LiVPO 4 F and LiVPO 4 F/Li 3 V 2 (PO 4) 3 nanostructured composite cathode materials... more Single-phase LiVPO 4 F and LiVPO 4 F/Li 3 V 2 (PO 4) 3 nanostructured composite cathode materials were prepared by heating of the VPO 4 +LiF mechanochemically activated mixture to 700°C and subsequent quick or slow cooling to room temperature, respectively. The formation of the composites was proved by a combination of different physico-chemical methods, including XRD, FTIR, 6 Li and 31 P NMR, SEM, TEM, and HRTEM. It has been shown that in the composites LiVPO 4 F and Li 3 V 2 (PO 4) 3 nanocrystals well inset into each other resulting in the nanodomain composite formation. Charge-discharge curves of the composites have a sloping profile both in the high-voltage (3.0-4.5 V) and in the lowvoltage (1.3-2.5 V) ranges, noticeably different from plateaus for a phase-pure LiVPO 4 F, thus indicating a probable change of a two-phase regime of lithium intercalation for a singlephase one. Enhanced rate capability of the LiVPO 4 F/ Li 3 V 2 (PO 4) 3 composites is associated with their microstructure and high ionic conductivity of Li 3 V 2 (PO 4) 3 .
Magnetic properties of the submicron carbon-coated LiFe1−xMnxPO4 (x = 0, 0.01, 0.1) systems were ... more Magnetic properties of the submicron carbon-coated LiFe1−xMnxPO4 (x = 0, 0.01, 0.1) systems were investigated using the electron spin resonance (ESR) method. The observed ESR signal consisted of two broad resonance lines with a Lorentzian line shape for all samples. The temperature dependence character of the integral intensity of these lines changed significantly with increasing manganese concentration, indicating a change in the nature of the magnetic interactions between the manganese and iron ions. We suggest that the noticeable capacity loss observed in the LiFe1−xMnxPO4 systems with increasing Mn content can be explained by the random distribution of Mn ions and changes to the type of magnetic ordering in these systems, despite the attractiveness of the electrochemical Mn2+/Mn3+ pair compared with Fe+2/Fe+3.
In the present work, sodium-vanadium fluorophosphates were prepared from the same reagents using ... more In the present work, sodium-vanadium fluorophosphates were prepared from the same reagents using the solid-state and the hydrothermal routes. The differences in phase composition, crystal structure, morphology, particle size distribution, and electrochemical properties of the as-prepared products are discussed.
The mixed sodium-iron ortho-pyrophosphate Na4Fe3(PO4)2P2O7 (NFPP) is a promising Na-containing ca... more The mixed sodium-iron ortho-pyrophosphate Na4Fe3(PO4)2P2O7 (NFPP) is a promising Na-containing cathode material with the highest operating voltage among sodium framework structured materials. It operates both in Na and Li electrochemical cells. When cycled in a hybrid Li/Na cell, a competitive co-intercalation of the Li+ and Na+ ions occurs at the cathode side. The present study shows that this process can be tuned by changing the concentration of the Na+ ions in the mixed Li+/Na+-ion electrolyte and current density. It is shown that if the Na concentration in the electrolyte increases, the specific capacity of NFPP also increases and its high-rate capability is significantly improved.
La 3+ modification of Na 3 V 2 (PO 4) 2 F 3 was performed by the direct mechanochemically assiste... more La 3+ modification of Na 3 V 2 (PO 4) 2 F 3 was performed by the direct mechanochemically assisted solid-state synthesis of the Na 3 V 2−x La x (PO 4) 2 F 3 compositions, and by the LaPO 4 coating of the as-prepared Na 3 V 2 (PO 4) 2 F 3 via the precipitation method. It has been shown that no noticeable substitution of the V 3+ ions by the La 3+ ions occurs in the Na 3 V 2 (PO 4) 2 F 3 structure under the synthesis conditions; meanwhile, the introduction of the La 3+ ions into the reagent mixture leads to the formation of the LaPO 4 phase, and accordingly, an increase in the NaF/VPO 4 ratio. The latter results in the formation of the Na 3 PO 4 and Na 3 VF 6 surface impurity phases, which possess high ionic and electronic conductivity, respectively, and significantly enhances the electrical conductivity and the cycling performance of the composite cathode material both in Na and Li cells, while simple surface modification of Na 3 V 2 (PO 4) 2 F 3 by LaPO 4 via precipitation does not.
Pristine Na 3 FePO 4 CO 3 (NFPC) with the monoclinic structure and the P2 1 /m space group was pr... more Pristine Na 3 FePO 4 CO 3 (NFPC) with the monoclinic structure and the P2 1 /m space group was prepared by hydrothermal synthesis at 120 °C. To increase the conductivity of NFPC, it was ballmilled with carbon using a SPEX 8000 mill. Crystal and local structure, morphology, thermal stability, conductivity and electrochemical properties of NFPC and NFPC/C composites were studied by XRD, DSC/TG, FTIR, Mӧssbauer spectroscopy, 23 NMR spectroscopy, magnetic measurements, SEM, EIS and galvanostatic cycling. It has been shown that the as-prepared NFPC is stable below 500 °C and then decomposes to Fe 3 O 4 and Na 3 PO 4. Ball milling of NFPC with and without carbon leads to its partial decomposition with the formation of nanosized superparamagnetic Fe 3 O 4 particles and a significant structural disordering, though the crystal symmetry maintains unchanged. Due to high sensitivity of NFPC to air, pristine sample contains some portion of the Fe 3+ ions; it increases after ball milling. As a result, all samples are able to cycle starting both with charge and discharge. NFPC shows high stability upon cycling with the specific discharge capacity close to the theoretical one (96 mA·h·g-1 for one-electron reaction). Though the capacity of the NFPC/C composites is slightly lower at low cycling rate than that of pristine NFPC, they show better high-rate performance due to improved conductivity via the formation of the highly conductive carbon matrix. As-established low lattice volume variation upon (de)intercalation of the sodium ions along with realization of a single-phase mechanism is responsible for a long cycle life of the NFPC/C cathode material.
Na2FeP2O7 sodium iron pyrophosphate with a triclinic symmetry (the space group P-1) has been prep... more Na2FeP2O7 sodium iron pyrophosphate with a triclinic symmetry (the space group P-1) has been prepared by mechanochemically assisted solid state synthesis. Electrochemical performance of the pristine Na2FeP2O7, NaFeP2O7 prepared by chemical oxidation with NO2BF4 and NaLiFeP2O7 obtained by non-oxidative Na+/Li+ ion exchange with LiBr were studied by galvanostatic cycling in a Li cell with Li as an anode and LiPF6 dissolved in EC+DMC as an electrolyte. XRD, EDX, Mössbauer and NMR spectroscopy studies showed that all the samples were active upon cycling in Li cells which resulted in exchange of one ~Na+ for one Li+ per f.u. to produce a new mixed phase NaLiFeP2O7 with the same triclinic structure as Na2FeP2O7 and good electrochemical performance.
New Trends in Intercalation Compounds for Energy Storage, 2002
ABSTRACT Although being commercially realized, lithium-ion batteries are still the object of inte... more ABSTRACT Although being commercially realized, lithium-ion batteries are still the object of intense study aimed of further improving their electrochemical characteristics. The charge-discharge processes strongly depend on the crystal and electronic structure of the intercalation lithium-transition metal oxides used as cathode materials. Last years a great deal of attention was devoted to preparation of these compounds with unusual ordering (structural, magnetic, charge) and electronic state of transition metal ions, and a structure more stable to intercalation/deintercalation of lithium ions at discharge/charge processes, preventing a structural distortion and, thus, providing better electrochemical behavior.
ABSTRACT LiCo1-yFeyPO4 solid solutions (0≤y≤1) were prepared by mechanochemically assisted carbot... more ABSTRACT LiCo1-yFeyPO4 solid solutions (0≤y≤1) were prepared by mechanochemically assisted carbothermal reduction of Co3O4 and Fe2O3. Mechanical activation was performed using a high-energy planetary mill AGO-2. The samples were characterized in detail by X-ray powder diffraction (XRD) using Rietveld refinement, Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), galvanostatic cycling and galvanostatic intermittent titration technique (GITT). According to XRD, all samples are single-phase solid solutions, crystallized in an orthorhombic structure (S.G. Pnma). The cell volume of LiCo1-yFeyPO4 linearly increases vs. Fe content. All Fe ions are in the 2+ oxidation state and are octahedrally coordinated. The LiCo1-yFeyPO4 solid solutions show improved electrochemical performance as compared with LiCoPO4. Based on the data from XRD and GITT, the improvement is attributed to the enhanced Li+ diffusion due to the enlargement of 1D diffusion channels in the polyanion structure of LiCoPO4 and the reduced cell volume change in the material during the Li extraction-insertion process. Besides, a systematic decrease in the average potential of the Co2+/Co3+ redox pair is observed with the increased Fe content, leading to the reaction termination within the electrochemical window of the conventionally available electrolytes. In situ synchrotron diffraction shows that upon charging of LiCo0.5Fe0.5PO4, a two-phase mechanism of Li (de)intercalation at the Fe2+/Fe3+ and Co2+/Co3+ redox stages changes to a solid solution-like mechanism, contrary to the pristine LiFePO4 and LiCoPO4 materials.
The recent launching of production of hybrid and electric vehicles made great demands on lithium-... more The recent launching of production of hybrid and electric vehicles made great demands on lithium-ion batteries (LIBs). One of the promising approaches to the optimization of their properties is in the development of new blended composite electrode materials consisting of two (or more) active components in order to use the advantages of the both of them [1]. Due to a unique combination of properties, the mixed materials show some advantages over the individual components. This includes the longer lifetime, the decreased capacity fading upon the cycling, lower price, the improved thermal stability, more acceptable profiles of charge-discharge curves and operating voltage, etc. For instance, the cathode materials with a layered structure (LiCoO 2
ABSTRACT A soft mechanochemical synthesis approach was applied to prepare some fi ne particulate ... more ABSTRACT A soft mechanochemical synthesis approach was applied to prepare some fi ne particulate lithium-containing compounds with a spinel (LiMn2-xMxO4, Li4Ti5O12), layered (LiNi1-x-yCoxMnyO2, LiV3O8) and framework structure (LiFePO4, Li2FeSiO4, LiTi2(PO4)3). It consists of the fast formation of amorphous or low-crystalline precursors during mechanical activation of LiOH (or Li2CO3) with corresponding anhydrous oxides of d-metals, solid hydroxides, crystal hydrates and acidic salts in highly energetic planetary mills and transformation of these precursors into nanostructured fi nal products under 'soft' heating conditions (lower temperatures and shorter time of treatment) after removal of water molecules, hydroxide groups and other volatile compounds. Most of as-prepared materials show good electrochemical properties as cathodes, anodes or solid electrolytes for lithium-ion batteries.
Journal of Metastable and Nanocrystalline Materials, 2003
ABSTRACT Mechanical activation in highly energetic planetary mills is used to prepare 3 V (Li1+xV... more ABSTRACT Mechanical activation in highly energetic planetary mills is used to prepare 3 V (Li1+xV3O8), 4 V (LiCoO2 and LiMn2O4) and 5 V (substituted LiMn2O4) cathode materials for rechargeable lithium batteries. It is shown that Li1+xV3O8 and LiMn2O4 can be prepared by direct mechanochemical synthesis while the others by subsequent brief heat treatment of activated mixtures at moderate temperatures. In many cases the use of hydroxides as initial reagents is preferable ('soft mechanochemical synthesis'). The advantages of mechanical activation for preparation of multicomponent cathode materials (doped LiCoO2 and LiMn2O4) are demonstrated. The as-prepared materials are characterized by high dispersion and structural disordering providing higher discharge rates and better stability under cycling. The mechanochemical method ensures the decrease of production time and energy expenses, simplification of the process and, as a result, lower material cost, thus being more energy-efficient and ecologically clean as compared with conventional technologies.
Nanosized LiCoO2 and LiMn2O4 were prepared by preliminary mechanical activation of the mixtures o... more Nanosized LiCoO2 and LiMn2O4 were prepared by preliminary mechanical activation of the mixtures of Li2CO3 with Co3O4 and Li2CO3 with MnO or MnO2 in the presence of carbon in high-energy planetary mill and annealed at 750-800{degree sign}C in air. Added carbon inhibits the particles' interaction during mechanical activation and their growth during annealing. The final products are free from carbon due to its oxidation and evaporation. They are characterized by the domain structure and show high specific discharge capacity and good cycleability.
LiFePO4 and LiFePO4/C composites were prepared by mechanical activation process using Fe3+ precur... more LiFePO4 and LiFePO4/C composites were prepared by mechanical activation process using Fe3+ precursor (Fe2O3) in comparison with Fe2+ precursor (FeC2O4•2H2O). The reaction mechanism, phase composition, particle size and electrochemical performance of as-prepared materials were examined by thermal analysis, X-ray diffraction, Mössbauer spectroscopy, SEM, TEM, and galvanostatic cycling. The LiFePO4/C composites were prepared by pyrolysis of suitable organic compounds during synthesis and by in situ incorporation of carbon powder. It has been shown that using carbothermal method, a phase-homogeneous nanosized LiFePO4 is formed at temperatures ≥700°C with specific discharge capacity ~150 mAh/g at C/10 rate.
The surface chemistry of the Al2O3-coated LiCoO2 prepared under heat treatment at 80800° C was s... more The surface chemistry of the Al2O3-coated LiCoO2 prepared under heat treatment at 80800° C was studied by SEM, XRD, IR, XPS and NMR spectroscopy combined with electrochemical testing. It is shown that the particle bulk is free from dopant. XPS Al2s core ...
Mechanical activation (MA) has been used to prepare high dispersed lithium-transition metal catho... more Mechanical activation (MA) has been used to prepare high dispersed lithium-transition metal cathode materials and inorganic solid lithium-ion electrolytes for rechargeable lithium batteries. It has been shown that materials with low-dimensional (submicron) particles ...
The cathode materials of the composition LiNi1 − 2x Co x Mn x O2 (x = 0.1, 0.2. 0.33) synthesized... more The cathode materials of the composition LiNi1 − 2x Co x Mn x O2 (x = 0.1, 0.2. 0.33) synthesized from the Ni, Co, Mn mixed hydroxides and LiOH by using mechanical activation method are studied. It is shown that all synthesized compounds have layered structure described by the space group R-3m. With the decreasing of the nickel content the
This short review reports on the synthesis of nanosized electrode materials for lithium-ion bat t... more This short review reports on the synthesis of nanosized electrode materials for lithium-ion bat teries by mechanical activation (MA) and studies of their properties. Different structural types of compounds were considered, namely, compounds with a layered (LiNi 1-x-y Co x Mn y O 2), spinel (LiMn 2 O 4 , Li 4 Ti 5 O 12), and framework (LiFePO 4 , LiTi 2 (PO 4) 3) structures. The compounds also differed in electronegativity, which varied from 10-4 S cm-1 for LiCoO 2 to 10-9 S cm-1 for LiFePO 4. The preliminary MA of mixtures of reagents in energy intensive mechanoactivators led to the formation of highly reactive precursors, and annealing of the latter formed nanosized products (the mean particle size is 50-200 nm). The local structure of the synthe sized compounds and the composition of their surface were studied by spectral methods. An increase in the dispersity and defect concentration, especially in the region of the surface, improved some electrochemical characteristics. It increased the stability during cycling (LiMn 2 O 4 , at 3 V) and the regions of the formation of solid solutions during cycling (Li 4 Ti 5 O 12 , LiFePO 4), led to growth of surface Li-ion conductivity (LiTi 2 (PO 4) 3), etc. The mechanochemical approach was also used for the synthesis of core-shell type com posite materials (LiFePO 4 /C, LiCoO 2 /MeO x) and materials based on two active electrode components (LiCoO 2 /LiMn 2 O 4).
The possibility for hydrothermal processes to take place under the action of mechanical pulses th... more The possibility for hydrothermal processes to take place under the action of mechanical pulses that arise in mechanical activators is considered for the system: a solid substance-water. Experimental data are presented on the mechanochemical synthesis of gidenbergite, tobermorite and other hydrosilicates that are usually produced according to the autoclave technology.
Single-phase LiVPO 4 F and LiVPO 4 F/Li 3 V 2 (PO 4) 3 nanostructured composite cathode materials... more Single-phase LiVPO 4 F and LiVPO 4 F/Li 3 V 2 (PO 4) 3 nanostructured composite cathode materials were prepared by heating of the VPO 4 +LiF mechanochemically activated mixture to 700°C and subsequent quick or slow cooling to room temperature, respectively. The formation of the composites was proved by a combination of different physico-chemical methods, including XRD, FTIR, 6 Li and 31 P NMR, SEM, TEM, and HRTEM. It has been shown that in the composites LiVPO 4 F and Li 3 V 2 (PO 4) 3 nanocrystals well inset into each other resulting in the nanodomain composite formation. Charge-discharge curves of the composites have a sloping profile both in the high-voltage (3.0-4.5 V) and in the lowvoltage (1.3-2.5 V) ranges, noticeably different from plateaus for a phase-pure LiVPO 4 F, thus indicating a probable change of a two-phase regime of lithium intercalation for a singlephase one. Enhanced rate capability of the LiVPO 4 F/ Li 3 V 2 (PO 4) 3 composites is associated with their microstructure and high ionic conductivity of Li 3 V 2 (PO 4) 3 .
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Papers by Nina Kosova