Monoclinic Li3V2 Research Articles

Observation on the electrochemical reactions of Li3-xNaxV2(PO4)3 (0 ≤ x ≤ 3) as cathode materials for rechargeable batteries

In this work, we propose a facile solid state reaction to prepare Li3-xNaxV2(PO4)3/C (0 ≤ x ≤ 3), which are rarely explored as possible cathode materials in sodium-ion batteries. Their phase composition, surface morphology and electrochemical property are described and compared in detail by using various physical/chemical methods. Seen from phase analysis results, it is known that Li2.5Na0.5V2(PO4)3 is a three-phase mixture (monoclinic Li3V2(PO4)3, rhombohedral Li3V2(PO4)3 and rhombohedral Na3V2(PO4)3). In contrast, Li2NaV2(PO4)3, Li1.5Na1.5V2(PO4)3, LiNa2V2(PO4)3 and Li0.5Na2.5V2(PO4)3 are two-phase mixtures consisting of rhombohedral Na3V2(PO4)3 and rhombohedral Li3V2(PO4)3. Evaluated as cathode materials in half-cells, Li3-xNaxV2(PO4)3/C (0 ≤ x ≤ 3) can deliver the initial reversible capacities of 94.3 mAh g−1 (x = 0.0), 103.6 mAh g−1 (x = 0.5), 115.1 mAh g−1 (x = 1.0), 112.7 mAh g−1 (x = 1.5), 99.6 mAh g−1 (x = 2.0), 94.0 mAh g−1 (x = 2.5) and 91.9 (x = 3.0) mAh g−1, respectively. After 45 cycles, the reversible capacities of 88.9 mAh g−1 (x = 0.0), 88.2 mAh g−1 (x = 0.5), 80.6 mAh g−1 (x = 1.0), 99.6 mAh g−1 (x = 1.5), 87.2 mAh g−1 (x = 2.0), 72.7 mAh g−1 (x = 2.5) and 72.3 mAh g−1 (x = 3.0) can be still kept for these samples. The electrochemical results suggest that Li/Na co-existence in M3V2(PO4)3/C may be beneficial to enhance the electrochemical performance. As a result, Li1.5Na1.5V2(PO4)3/C shows the best sodium storage capability as cathode material in sodium-ion batteries.

Approaching better cycleability of LiCoPO4 by vanadium modification

A series of (1−y)LiCoPO4·yLi3V2(PO4)3 with 0≤y≤1 was prepared via mechanochemically assisted carbothermal reduction at 750°C. Structure and electrochemistry were studied by a complex of physico-chemical methods including XRD, NPD, FTIR, NEXAFS, TEM, EDX STEM, and galvanostatic cycling. It has been shown that only a small amount of V ions incorporates into the LiCoPO4 structure. The other V ions form monoclinic Li3V2(PO4)3. Incorporated V ions are in a mixed oxidation state and predominantly substitute for Co2+. The compensation mechanism for supervalent V ions substitution in LiCoPO4 involves the lithium vacancies formation. The as-prepared (1−y)LiCoPO4·yLi3V2(PO4)3 with low y show the enhanced electrochemical behavior compared to pure LiCoPO4, especially in the 4.0–5.0V range, due to a suitable amount of structural defects, which improve ionic and electronic conductivity, and to the presence of the Li-conductive Li3V2(PO4)3 on the surface of the LiCoPO4 particles promoting the deliverance of the Li ions from the electrolyte to the (010) facet.

Evaluation of the electrochemical behavior and structural reversibility of Li3−xNaxV2(PO4)3/C (0≤x≤3) as anode materials for Na-ion batteries

A series of Li3−xNaxV2(PO4)3/C (0≤x≤3) materials are successfully prepared by a simple solid-state reaction method and used for the first time as anode materials for Na-ion batteries. Powder X-ray diffraction (XRD) results show that the phase structures of Li3−xNaxV2(PO4)3/C evolve along with the change of Li/Na atomic ratio (0≤x≤3). With increasing x in Li3−xNaxV2(PO4)3/C from 0.0 to 3.0, the main phase in as-prepared sample transforms from monoclinic Li3V2(PO4)3 to rhombohedral Li3V2(PO4)3, and finally to rhombohedral Na3V2(PO4)3, which results in different sodium storage behavior and performance between Li3−xNaxV2(PO4)3/C (0≤x≤3) materials. Electrochemical results show that Li3−xNaxV2(PO4)3/C (x=0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) can deliver the initial charge capacities of 21.1, 35.9, 33.8, 41.7, 43.3, 43.9 and 47.7mAhg−1 at a current density of 10mAg−1, respectively. After 45 cycles, the reversible capacities can be kept at 16.9, 45.1, 32.6, 44.6, 43.7, 37.8 and 27.3mAhg−1 for Li3V2(PO4)3/C, Li2.5Na0.5V2(PO4)3/C, Li2NaV2(PO4)3/C, Li1.5Na1.5V2(PO4)3/C, LiNa2V2(PO4)3/C, Li0.5Na2.5V2(PO4)3/C and Na3V2(PO4)3/C, respectively. Furthermore, the structural reversibility of Li3−xNaxV2(PO4)3/C (x=1.0, 2.0, and 3.0) is also observed by in-situ XRD observation during sodiation/de-sodiation process. All these observed evidences indicate that only some of Li3−xNaxV2(PO4)3/C (0≤x≤3) can be used as possible sodium storage materials.

Electrochemical and Structural Investigation of the Mechanism of Irreversibility in Li3V2(PO4)3 Cathodes

Lithium-ion batteries dominate the battery field, particularly for electric and hybrid vehicles. Monoclinic Li3V2(PO4)3 has emerged as one of the most promising candidates for the cathode in lithium-ion batteries, offering better environmental safety and lower cost than competing materials. We have used in situ X-ray absorption spectroscopy to characterize the evolution of the vanadium in a Li3V2(PO4)3 cathode as it is cycled electrochemically. These data demonstrate the presence of significant kinetic effects such that the measured electrochemical behavior does not represent the bulk vanadium. When the cell is cycled between 3 and 4.5 V, there are two distinct vanadium species. When the potential is raised above 4.5 V, a third species is observed, consistent with formation of V5+. XANES data for the cathode after 3–4.8 V cycling are consistent with a severely distorted vanadium site, suggesting that lithium–vanadium antisite mixing may be responsible for the electrochemical irreversibility that is seen a...

Mixing transition-metal phosphates Li3V2−xFex(PO4)3 (0≤x≤2): the synthesis, structure and electrochemical properties

Mixing transition-metal phosphates Li3V2−xFex(PO4)3 (0≤x≤2) were first designed to be a type of intercalated and deintercalated cathodes to obtain high specific capacity for safe Li-ion batteries. Since the residual oxygen in the quartz tube furnace and pellet would oxidize the V3+ to V4+ in the Ar ambience during the sintering process, trace amounts of acetylene black inside and outside the pellet could play a role of deoxidizer to protect V3+ meanwhile ensure Fe3+ not reducing to Fe2+. With the concerted effort of inside and outside acetylene black, monoclinic structure Li3V2−xFex(PO4)3 (0≤x≤2) solid solutions had been successfully fabricated via a two-step synthesis method. X-ray diffractions with Rietveld refinement revealed that V1-sites were the preferred position when Fe3+ ions doped into Li3V2(PO4)3, which means, every V1-site was occupied with the same probability by V3+ and Fe3+ when 0<x<1, and then for V2-site when 1<x<2. X-ray photoelectron spectroscopy result showed the presence of trace amounts of acetylene black had realized the coexist of V3+ and Fe3+ in the Li3M2(PO4)3 framework. When evaluated as cathodes for Li-ion batteries, the pure Li3V2(PO4)3 electrode displayed the highest charge (137.2mAhg−1) and discharge (121.5mAhg−1) capacities in the first cycle, with the increase of Fe3+ content, all the charge and discharge capacities reduced drastically. Furthermore, the EIS results showed that the incorporation of the sluggish Fe3+ ions reduced the electronic conductivity and lithium conductivity, which in turn contributed to the poor electrochemical performance. Although our results did not show Fe3+/Fe2+ electrochemical activity contrary to our expectation, this preliminary study on Li3V2−xFex(PO4)3 (0≤x≤2) have provided a prerequisite for further improving the electrochemical properties by nanosizing and carbon-coating to better use these mixing transition-metal phosphate cathodes in the future.

Application of monoclinic graphene-decorated Li3V2(PO4)3/C nanocrystals as an ultra-high-rate cathode for lithium-ion batteries

A nanocomposite, consisting of conductive graphene intercalated with nanosized Li3V2(PO4)3/C hybrids, was successfully synthesized through a solution route followed by microwave irradiation. XRD results reveal that the crystal structure of graphene modified Li3V2(PO4)3/C remains unchanged. TEM images demonstrate that the Li3V2(PO4)3/C nanoparticles in the composite are well enwrapped by graphene. Compared to the pure Li3V2(PO4)3/C electrode, the graphene-decorated Li3V2(PO4)3/C nanocomposite exhibits an excellent high-rate capability and outstanding cycling stability. In the potential range of 3.0–4.8V, it delivers a high initial discharge capacity of 189mAhg−1 at a low rate of 0.1C, and maintains an initial discharge capacity of 143 at 10C. The superior performance can be attributed to the synergetic effect of the nanosized Li3V2(PO4)3/C particles and the conductive graphene wrapping layers. Therefore, we believe that this strategy can be used for the preparation of other graphene-based cathode or anode materials for high-rate lithium-ion batteries.

Synthesis and performance of xLiVPO4F–yLi3V2(PO4)3 composites as cathode materials for lithium ion batteries

The xLiVPO4F–yLi3V2(PO4)3 composite cathode materials have been synthesized through a soft chemical route with mechanical activation assistance followed by low-temperature calcination. Structural analysis indicates that two phases, i.e. monoclinic Li3V2(PO4)3 and triclinic LiVPO4F coexist in the composites. With the addition of LVP, the average particle size becomes smaller. The prepared composite materials show good electrochemical performance, and especially a good cyclic performance, the most suitable x/y ratio being 1:5 where the sample can deliver a reversible capacity of 139mAhg−1.

Electrochemical characterization for lithium vanadium phosphate with different calcination temperatures prepared by the sol–gel method

Li3V2(PO4)3/C (LVP/C) composite materials were synthesized via a sol–gel method with oxalic acid as the chelating agent and polyethylene glycol (PEG) as the supplementary carbon source. The oxalic acid and PEG serve as double carbon sources. This study focused on the effect of different calcination temperatures on the electrochemical properties of Li3V2(PO4)3. The diffraction peaks for all of the samples are well indexed to monoclinic Li3V2(PO4)3 with a P21/n space group. The TGA data indicate that the residual carbon content of LVP/C-700 is the highest (i.e., 2.31wt.%), and as the calcination temperature increased, the residual carbon content of the material gradually decreased. SEM and TEM analyses indicated that the LVP particles that were calcined at 700°C exhibit a uniform particle size distribution and the carbon coating exhibited a complete and orderly moderate thickness. The LVP/C-700 material exhibits the best electrochemical performance in the voltage range of 3.0 to 4.3V and 0.1C where the initial discharge capacity can reach 128.98mAhg−1. Even after 200cycles, the discharge capacity was 119.31mAhg−1, and the capacity retention rate was 92.49%.

Rhinolith in Right Nasal Cavity

The xLiVPO4F–yLi3V2(PO4)3 composite cathode materials have been synthesized through a soft chemical route with mechanical activation assistance followed by low-temperature calcination. Structural analysis indicates that two phases, i.e. monoclinic Li3V2(PO4)3 and triclinic LiVPO4F coexist in the composites. With the addition of LVP, the average particle size becomes smaller. The prepared composite materials show good electrochemical performance, and especially a good cyclic performance, the most suitable x/y ratio being 1:5 where the sample can deliver a reversible capacity of 139 mA h g−1.

Comparison of phase composition, morphology and electrochemical property for Li3−xNaxV2(PO4)3 (x=0.5, 1.5 and 2.0) as lithium storage cathode materials

Three Li3-xNaxV2(PO4)3 (x=0.5, 1.5 and 2.0) samples are synthesized by a traditional solid-state reaction method in this work. Their phase composition, surface morphology and electrochemical property are described and compared by using various physical/chemical methods. Phase analysis results reveal that Li2.5Na0.5V2(PO4)3 consists of monoclinic Li3V2(PO4)3, rhombohedral Li3V2(PO4)3 and rhombohedral Na3V2(PO4)3. While, both Li1.5Na1.5V2(PO4)3 and LiNa2V2(PO4)3 are the two-phase mixture consisted of rhombohedral Li3V2(PO4)3 and rhombohedral Na3V2(PO4)3. Electrochemical testing results reveal that LiNa2V2(PO4)3 and Li1.5Na1.5V2(PO4)3 can deliver the initial discharge capacities of 101.4mAhg−1 and 108.6mAhg−1 with a long potential plateau at 3.69V, respectively. In contrast, Li2.5Na0.5V2(PO4)3 presents an initial discharge capacity of 111.7mAhg−1 with four potential plateaus. High lithium ion diffusion coefficient in Li2.5Na0.5V2(PO4)3 indicates that the existence of monoclinic Li3V2(PO4)3 phase can improve the ionic conductivity and then be responsible for good electrochemical performance. Besides, in-situ X-ray diffraction observation of LiNa2V2(PO4)3 demonstrates that the phase transition is not fully reversible but quasi-reversible during the lithiation-delithiation process. The partial irreversibility of structural evolution for LiNa2V2(PO4)3 induces the capacity loss upon repeated cycles.

Novel synthesis of LiCoPO4–Li3V2(PO4)3 composite cathode material for Li-ion batteries

LiCoPO4–Li3V2(PO4)3 composite cathode material is synthesized by a chemical lithiation method, with Co3V2O8 as the precursor and oxalic acid as the reductant. XRD result indicates that the composite is composed of olivine-type LiCoPO4 and monoclinic Li3V2(PO4)3. TEM, HRTEM and FFT results show that the LiCoPO4–Li3V2(PO4)3 particles are wrapped with nano-carbon webs, and the crystal particles contain the lattice fringes and diffraction spots of LiCoPO4 and Li3V2(PO4)3. The composite shows the stepped charge–discharge platforms which contain the potential plateaus of LiCoPO4 (~4.8V) and Li3V2(PO4)3 (~3.6, 3.7, 4.1 and 4.5V). During the potential range of 3.0–5.0V, the composite delivers the specific capacities of 163.7, 133.6 and 93.8mAhg−1 at 0.05, 0.5 and 2C rates, respectively, and shows good cycling performance.

PEG-combined liquid phase synthesis and electrochemical properties of carbon-coated Li3V2(PO4)3

The carbon-coated monoclinic Li3V2(PO4)3 (LVP) cathode materials were successfully synthesized by liquid phase method using PEG as reducing agent and carbon source. The effects of relative molecular mass of PEG on the properties of Li3V2(PO4)3/C were evaluated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical performance tests. The SEM images show that smaller size particles are obtained by adding larger and smaller PEGs. The electrochemical cycling of Li3V2(PO4)3/C prepared by both PEG200 and PEG20k has a high initial discharge capacity of 131.1 mA·h/g at 0.1C during 3.0–4.2 V, and delivers a reversible discharge capacity of 123.6 mA·h/g over 30 cycles, which is better than that of other samples. The improvement in electrochemical performance is caused by its improved lithium ion diffusion coefficient for the macroporous morphology, which is verified by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Structural and electrochemical properties of Fe- and Al-doped Li3V2(PO4)3 for all-solid-state symmetric lithium ion batteries prepared by spray-drying-assisted carbothermal method

Li3V2(PO4)3 and Li3V1.9M0.1(PO4)3 (M=Fe, Al) samples were synthesized via spray-drying-assisted carbothermal solid-state reaction, and their structural and electrochemical properties were investigated by XRD, SEM, and galvanostatic charge/discharge. Li3V2(PO4)3, Li3V1.9Fe0.1(PO4)3, and Li3V1.9Al0.1(PO4)3 showed initial discharge capacities of 103.3mAhg−1, 107.6mAhg−1, and 105.6mAhg−1, respectively, in the all-solid-state symmetric batteries with Li1.5Al0.5Ge1.5(PO4)3 solid-state electrolytes at a rate of 7.5mAg−1. The enhanced discharge capacities of Fe and Al-doped Li3V2(PO4)3 could be attributed to the increased electrical conductivity induced by the introduction of Fe3+ or Al3+ trivalent ions into the V3+ sites and to the structural stabilization of the monoclinic Li3V2(PO4)3 by the spray-drying process.

Супервалентное допирование для улучшения электрохимических характеристик LiFePO4

The orthophosphates LiFe0.9M0.1PO4 with the structure of olivine doped with vanadium and titanium were obtained by mechanochemically stimulated solidphase synthesis using high-energy planetary mill AGO-2 and subsequent annealing at 750 °C. It is shown that V- and Ti- ions do not completely substitute for Fe2+ ions in the LiFePO4 structure. The remaining part of these ions involve in the formation of second phase with nashiko-like structure: monoclinic Li3V2(PO4)3 (space group P21/n ) and rhombohedral LiTi2(PO4)3 (space group R-3c). According to TEM, the average size of the particle of nanocomposites is about 100-300 nm. EMF of microanalysis showed that the small particles of secondary phases are segregated at the surface of larger particles of LiFePO4. On the charge-discharge curves of LiFe0.9M0.1PO4 there are plateau corresponding to LiFePO4 and the second phase. The doping with vanadium increases the resistance of the cycling of LiFePO4 and improves its cyclability at high speeds to a greater extent than in the case of doping with titanium.

Enhanced electrochemical performance of Li3V2(PO4)3 structurally converted from LiVOPO4 by graphite nanofiber addition

In this work, the structural conversion of LiVOPO4 to Li3V2(PO4)3 due to the addition of graphene nanofiber (GNF) was investigated, and the resulting materials were found to exhibit enhanced capacity and cyclability. First, LiVOPO4 was synthesized using a solid-state method followed by annealing at 900°C for 12h under nitrogen atmosphere. Then, the conversion from the triclinic LiVOPO4 structure to the monoclinic Li3V2(PO4)3 structure due to the GNF addition was observed. No impurity peak was observed in the X-ray diffraction patterns of LiVOPO4 or Li3V2(PO4)3, and the structural conversion caused no defects to form in the resulting Li3V2(PO4)3 crystallite. Field emission-scanning electron microscope studies clearly demonstrate that larger corroded-structure-like particles formed which were mixed with GNF. This provided both a large active area and fast transport of lithium ions, which afforded enough active sites for simultaneous intercalation of many lithium ions, leading to improved electrochemical properties of the material. Compared with LiVOPO4, the Li3V2(PO4)3–GNF showed better properties, such as an improved lithium ion diffusion coefficient, improved cyclability, and smaller impedance. Furthermore, the optimized Li3V2(PO4)3–GNF (7%) battery showed the best discharge capacity of 181mAhg−1 at 0.1C and lithium ion diffusion coefficient of 6.01×10−9cm2s−1.

Study on structure and electrochemical performance of Tm3+-doped monoclinic Li3V2(PO4)3/C cathode material for lithium-ion batteries

Monoclinic Li3V2-xTmx(PO4)3/C with different Tm3+-doping contents (x=0, 0.01, 0.03, 0.05) have been successfully synthesized for the first time via a conventional solid-state reaction. The effect of Tm3+-doping on the crystalline structure, morphology and electrochemical performance of Li3V2(PO4)3/C has been investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. The same phase-pure monoclinic structure of Tm3+-doped Li3V2(PO4)3/C sample can be obtained from XRD results while the particle size is smaller than that of pristine Li3V2(PO4)3/C. The Li3V1.97Tm0.03(PO4)3/C composite exhibits the most excellent electrochemical performance among all the samples. In the voltage range of 3.0–4.8V, the Li3V1.97Tm0.03(PO4)3/C sample delivers a very high initial discharge capacity of 181.2mAhg−1 at 0.1C, significantly higher than that of pristine Li3V2(PO4)3/C (170.1mAhg−1). Moreover, it can still deliver a discharge capacity of 141mAhg−1 and 123.3mAhg−1 at 5.0 and 10.0C, respectively, and sustain 95.2% and 93.4% of capacity retention after 20 cycles. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results demonstrate that the reversibility of pristine Li3V2(PO4)3/C is enhanced and the charge-transfer resistance is reduced after Tm3+-doping at V sites. These improved electrochemical performance can be contributed to the appropriate addition of Tm3+-doping in Li3V2(PO4)3/C system by enhancing structural stability and electrical conductivity.

Facile Synthesis of hybrid phase Li2NaV2(PO4)3 and its application in lithium ion full cell: Li2NaV2(PO4)3|| Li2NaV2(PO4)3

High performance hybrid phase Li2NaV2(PO4)3 (H-LNVP) composite consist of rhombohedral Li3V2(PO4)3 (60.9%), rhombohedral Na3V2(PO4)3 (31.6%) and monoclinic Li3V2(PO4)3 (7.5%) is successfully synthesized via a sol-gel method. The rhombohedral phase Li2NaV2(PO4)3 (R-LNVP) is also obtained for comparison. The H-LNVP delivers better electrochemical performance, higher Li+ diffusion coefficient and more stable structure than that of R-LNVP duo to the existence of small amount monoclinic Li3V2(PO4)3. For the synthesised H-LNVP, there are 123.3mAhg-1 that can be delivered at 0.5C rate as cathode and 128.4mAhg-1 that can be delivered at 0.2Crate as anode. On this basis, a LNVP||LNVP lithium ion full cell is fabricated, with an output output potential of ∼2.48V and a specific discharge capacity of 99.3mA hg−1.

Preparation and characterization of chlorine doped Li3V2(PO4)3 as high rate cathode active material for lithium secondary batteries.

Monoclinic Li3V2(PO4)2.99Cl0.01 was synthesized using the conventional solid state method and the X-ray diffraction pattern was indexed based on P2(1)/n space group. The sharp cyclic voltammetric curves clearly revealed three lithium extraction/insertion processes at approximately 3.64, 3.72, 4.13, and 4.58 V during the anodic scan and 3.96, 3.58, and 3.48 V during the cathodic scan. Charge/discharge studies showed reduced electrolyte decomposition contribution in the case of the chlorine doped Li3V2(PO4)2.99Cl0.01 sample with an initial capacity of 176 mA h g(-1) at a 0.1 C current rate. The chlorine doped Li3V2(PO4)3 sample showed an increased capacity retention with an increase in current rate, even at a very high C-rate (20 C), than the pristine and carbon coated samples. The pristine and carbon coated Li3V2(PO4)3 samples showed a lower capacity retention of 71% and 84%, respectively, at a current rate of 0.1 C. In contrast, the chlorine doped Li3V,(PO4)3 sample retained 87% of the initial capacity (176 mA h g(-1)) at the same current rate but with a higher coulombic efficiency of 91%. The enhanced capacity retention for the chlorine doped Li3V2(PO4)3 was attributed to the reduction in polarization and decreased charge transfer resistance of the electrode.

Synthesis and electrochemical properties of W-doped Li3V2(PO4)3/C cathode materials for lithium ion batteries

Monoclinic Li3V2−xWx(PO4)3/C (x=0, 0.03, 0.05, 0.07, 0.10) compounds were successfully synthesized by the sol–gel method. X-ray diffraction (XRD) patterns demonstrated that the appropriate addition of tungsten enlarged the unit cell volume of Li3V2(PO4)3, which could provide more space for lithium intercalation/de-intercalation. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the main chemical state of V in the Li3V1.93W0.07(PO4)3/C composite is +3 valence, while the chemical state of W in the Li3V1.93W0.07(PO4)3/C is +5 valence. Scanning electron microscope (SEM) analyses illustrated that the addition of W slightly affected the morphology of samples. Li3V2−xWx(PO4)3/C (x≤0.10) exhibited higher discharge capacity and better cycle stability than the pure one. For the optimal composition of Li3V1.93W0.07(PO4)3/C, the initial discharge capacity was 160.3mAhg−1 and 95.5% capacity retention was observed after 50 cycles at 0.5C rate. Cyclic voltammetry (CV) result revealed the reversibility was enhanced after V3+ substituted by W5+. The enhanced electrochemical performances can be attributed to the smaller particle size, higher surface area and enhanced structural stability during the proper amount of W doping in V sites.

Nanostructured Two-Component Composite Approach for Better High-Rate Capability of Cathode Materials

Many efforts have been made to turn insulating compounds into attractive electrode materials, including nanosizing, carbon nanopainting and metal doping. A new approach to enhance high-rate capability of materials with poor electric conductivity is based on the development of two-component composites comprising of low-conductive and high-conductive electrode materials. Monoclinic Li3V2(PO4)3 is a promising cathode for high-power lithium-ion batteries because of its open three-dimensional framework allowing fast transport of lithium ions. Its theoretical capacity is 132 and 197 mAh×g-1 upon cycling to 4.3 and 4.8 V, respectively. Recently, the enhanced electrochemical performance of nanostructured LiVPO4F/Li3V2(PO4)3 composites has been reported [1]. The aim of the present work was to prepare (1-x)LiMPO4/xLi3V2(PO4)3 (M=Mn,Fe) nanocomposites with 0.05£x£0.50 by mechanochemically assisted solid state synthesis and to investigate their structural features and electrochemical performance. The composites were synthesized by the joint carbothermal reduction of MnO2 (Fe2O3) and V2O5 in the mixtures with Li2CO3 and (NH4)2HPO4 using AGO-2 planetary mill. Crystal structure was studied by X-ray and neutron powder diffraction (NPD) using Rietveld refinement. NPD spectra were obtained at IBR-2 reactor of JINR (Dubna). Particle size and morphology were studied by SEM and TEM. The local structure of the LiFePO4/Li3V2(PO4)3 composites was investigated by Mössbauer spectroscopy. The samples were cycled in Swagelok-type half-cells with Li anode, Whatman GF/C separator and LiPF6-based electrolyte in the 2.0-4.8 V (Mn) and 2.5-4.3(4.8) V (Fe) range at 0.1-10C cycling rates. Additionally, GITT method was applied for the evaluation of Li ionic diffusion coefficient in the composites upon cycling. Two phases were present on XRD and NPD patterns of all samples: orthorhombic LiMPO4 (space group Pnmb) and monoclinic Li3V2(PO4)3 (space group P21/n). The refined cell parameters of LiMPO4 and Li3V2(PO4)3 in the composites slightly deviate from those of pure components (Fig. 1). Mössbauer spectroscopy of the 0.75LiFePO4/0.25Li3V2(PO4)3 composite reveals the presence of tiny amounts of Fe3+ ions. According to SEM and TEM, the average particle size of the composite decreases as compared with pure components, indicating that Li3V2(PO4)3 and LiMPO4 phases hinder the crystal growth of each other. In the 2.5-4.8 V range, Li3V2(PO4)3 exhibits four redox plateaus corresponding to a sequence of phase transitions: Li3V2(PO4)3→Li2.5V2(PO4)3→Li2V2(PO4)3→ Li1V2(PO4)3→V2(PO4)3. On the dQ/dU=f(U) plots of the LiMPO4/Li3V2(PO4)3 composites, some additional peaks are also observed corresponding to two redox pairs: Mn3+/Mn4+ (at 4.4 V) and Fe3+/Fe2+ (at 3.45 V). Charge-discharge profiles of the composites and the variation of specific discharge capacity of the composites vs. cycling rate are shown in Fig. 2. When the voltage cut-off increases to 4.8 V for 0.75LiFePO4/0.25Li3V2(PO4)3, its capacity increases and discharge profile gets a sloping form. The enhancement of high-rate electrochemical performance of LiMPO4 in the composites is considered to be a result of reduction in particle size and the nucleation energy for the formation of the MPO4 phases. GITT measurements confirm the increase of D Li and the improvement of Li diffusion in the composites. Thus, the nanostructured two-component composite approach (combination of low- and high-conductive electrode materials) supported by mechanochemically assisted solid state synthesis is shown to be applicable and very promising. The increase in the number of voltage plateaus and the mean intercalation voltage should be advantageous for improvement of cell performance.[1] N.V. Kosova, E.T. Devyatkina, A.B. Slobodyuk, A.K. Gutakovskii // doi 10.1007/s10008-013-2213-1