PO4 Sample Research Articles

High-performance Li-ion battery cathode: Mn-doped LiFePO4 via solution combustion synthesis method

The main drawbacks of LiFePO4, namely low electronic conductivity and slow lithium ion diffusion, are overcome by doping through solution combustion synthesis. This study focuses on altering the properties of LiFePO4 cathode material by introducing manganese (Mn) into the Fe site. Using solution combustion synthesis, we successfully created Mn-doped LiFe1-xMnxPO4 samples (where x = 0.04, 0.08, and 0.12) as it provides highly pure and crystalline material with homogeneous incorporation of dopants. Through various analyses including X-ray diffraction (XRD), RAMAN spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDAX, X-ray photoelectron spectroscopy (XPS), BET surface area measurement, charge/discharge tests (CD), stability assessments, and rate performance evaluations, we uncovered insights into the structure, morphology, elemental composition, surface area, and electrochemical properties of the synthesized materials. Notably, the LiFe0.92Mn0.08PO4 sample exhibited an average capacity of 166.34 mAh/g over 100 cycles at a 0.1C rate, slightly below its theoretical capacity of 170 mAh/g.

Study on Performance and mechanism of low-temperature NH3-SCR denitrification over Mn/(Ce, La)PO4 catalysts

Mn/(Ce, La)PO4 was synthesized by hydrothermal method, and NH3-SCR low-temperature denitration catalyst was prepared by changing Mn loading amounts. A series of characterization methods, such as XRD, BET, NH3-TPD, H2-TPR, etc., were used to investigate the effects of different loading amounts on the surface structure, chemical properties and denitrification activity of the catalysts, and the reaction pathways and denitrification mechanism were investigated by Fourier in-situ infrared detection. The results showed that the denitrification rate of the catalysts loaded with 5 % KMnO4 increased from 7.5 % to 83.8 % at 100 °C, and the optimal denitrification temperature was 250 °C, which was 50 °C lower than that of the unloaded catalysts, and the denitrification rate was 97.3 %. The introduction of Mn resulted in the appearance of a large number of amorphous manganese oxides appear on the surface of the catalysts, which promoted the dispersion of the active species Ce7O12. The increase of Brønsted acidic sites on the catalysts surface, the adsorption capacity of NH3 was significantly enhanced, the redox peak area increased, and the acidic sites increased, thus improving the denitrification activity at low temperature. The infrared results showed that the 5 %Mn/(Ce, La)PO4 sample is rich in Brønsted acid sites and strong in Lewis acid sites at the optimal activity temperature of 250 °C, which enhances the adsorption capacity of the catalysts for NH3. After the passage of the NO+O2 reaction, a large number of nitrate species were present on the surface of catalysts, while a large number of NO2 species were adsorbed, and these species promoted the NH3-SCR reaction on the surface of catalyst. The reactive species of the E-R mechanism are NH4+ species, NH3 species and gaseous NO, and the main reactive species of the l-H mechanism are NH4+ species adsorbed by Brønsted acid site, monodentate nitrate species and bidentate nitrate species.

A new sampling method with zirconium‐loaded resin for phosphate oxygen isotope analysis in oligotrophic freshwater systems

The phosphate oxygen isotope ratio ( ) is a useful technique to trace the sources and biogeochemical cycles of phosphorus (P) in aquatic ecosystems. However, has not been widely used in oligotrophic freshwater systems due to technical and methodological difficulties in collecting sufficient phosphate (PO4 ) for the analysis, which sometimes requires hundreds of liters of the water sample. In this study, a new approach (PaS-Zir) was developed for the analysis in oligotrophic freshwater systems using zirconium (Zr)-loaded (ZrIRC) resin, which has a high affinity for PO4 . ZrClO2 was added to Amberlite IRC748 to obtain the ZrIRC resin. The adsorption/desorption experiment using KH2 PO4 with a known value of was conducted to determine the adsorption/desorption properties of the resin and the likelihood of isotopic fractionation. By installing mesh bags filled with the resin, the PaS-Zir approach was used in two rivers with low PO4 concentrations (0.2 and 5.3μmol/L). A conventional sampling method was also performed in the study river with a higher PO4 concentration to validate the efficacy of the PaS-Zir method. The adsorption/desorption experiment demonstrated that the ZrIRC resin possessed a sufficient adsorption capacity (153 μmol/resin-mL) and exhibited little isotopic fractionation during the adsorption/desorption processes. Using the PaS-Zir method, we were able to collect sufficient PO4 samples for the analysis from the rivers within at least 4 days of mesh bag installation. The values (14.2‰ ±0.2‰) obtained using the PaS-Zir method were comparable to those obtained using the conventional method (14.0‰ ±0.03‰). We proved that the PaS-Zir method is applicable to oligotrophic freshwater systems and is generally more efficient than the conventional method. In addition, our method is useful for improving the understanding of the P dynamics of oligotrophic ecosystems because of the extremely low concentration of PO4 commonly found in them, which are often prone to P pollution.

Synthesis of Cathode Active Material LiMn0.5Fe0.5PO4F/C with Sintering Time Variation

Research has been carried out on the synthesis of LiMn0.5Fe0.5PO4F/C, the cathode active materials with variations in sintering time. The process of producing the LiMn0,5Fe0,5PO4F/C as an active material in lithium battery cathodes has been successfully carried out by the first forming host structure and then infiltrating the lithium Li ions and the flour F ions. In this study, the synthesis was carried out with various sintering time, 6 hours, 8 hours and 10 hours. The raw materials used in this study are manganese dioxide (“MnO2”), iron (III) oxide (“Fe2O3”), lithium fluoride (“LiF”) and phosphoric acid (“H3PO4”) as the solvents. The synthesis was carried out at a calcination temperature of 720°C for 8 hours. The first mashed use a milling process for about 180 minutes, and placed into the oven, then mashed using a mortar. Then the Mn0.5Fe0.5PO4 sample was added with LiF, mixed with the milling process, placed into a drying oven and was varied with the sintering time of 6 hours for the first sample, 8 hours for the second sample and 10 hours for the third sample. As to produce LiMn0.5Fe0.5PO4F material, followed by carbon coating, namely tapioca and sugar (8%:4%). All three samples were calcined at a temperature of 720°C for 4 hours. The results of XRD analysis showed that the three samples did not experience a phase of change, however only shows a few differences in intensity. The results of FESEM analysis show that grain growth occurs vertically and horizontally due to the presence of the Mn and Fe, and with an exact enough amount of tapioca function as a carbon source to coat the active material, it help to creates pores in the powder so that the presence of these pores could provide an intercalation pathway for the lithium ions. At the end the results of the EIS analysis showed that the highest conductivity value of this study was 0.62 x 10-5 S/cm.

Magnetic phase transitions in the LiNi0.9 M 0.1PO4 (M = Mn, Co) single crystals

The LiNiPO4, LiNi0.9Mn0.1PO4, and LiNi0.9Co0.1PO4 single crystals are studied with heat capacity and neutron diffraction measurements over the temperature interval (10–30) K. Two peaks are observed on the temperature dependence of heat capacity for LiNiPO4, and LiNi0.9Co0.1PO4 samples. One peak indicates the first order phase transition from an antiferromagnetic commensurate (C) structure to an incommensurate (IC) one upon heating. According to neutron diffraction, in LiNiPO4 the IC ordering is described by the propagation vector k = 2π/b(0, 0.080, 0) at the Néel temperature T N = 20.8 K, and k = 2π/b(0, 0.098, 0) at T N = 20.2(1) K for LiNi0.9Co0.1PO4. A further increase in temperature leads to the second order phase transition to a paramagnetic state at critical temperature T IC = 21.7 K and 21.1 K for LiNiPO4 and LiNi0.9Co0.1PO4, respectively. The C and IC phases coexist over the temperature interval (20.6–20.8) K and (20.2–21.2) K in LiNiPO4 and LiNi0.9Co0.1PO4, respectively. In the LiNi0.9Mn0.1PO4 the magnetic phase transition occurs at T N = 22.7 K, but a magnetic scattering is observed up to 24.6 K.

Rational design of the micron-sized particle size of LiMn0.8Fe0.2PO4 cathode material with enhanced electrochemical performance for Li-ion batteries

Recently, micron-sized LiMn1−xFexPO4 cathode materials have attracted attention due to its better rate capability and higher tap density than the nano-sized ones. However, the influence of the particle size on the energy density of micron-sized LiMn1−xFexPO4 is still unknown. In this paper, we report the optimal particle size of the micron-sized LiMn0.8Fe0.2PO4 with enhanced electrochemical performance as cathode material in lithium-ion batteries (LIBs). The LiMn0.8Fe0.2PO4 sample with the particle size of ∼9.39 μm delivers the initial discharge capacity of 124 mAh g−1 at 0.2 C rate with high capacity retention of 94.35% after 100 cycles, which is higher than that with the particle sizes of ∼2.71 μm, ∼3.74 μm, ∼6.41 μm or ∼16.31 μm. This structure with the specific capacity of 122 mAh g−1 at 0.5 C rate and 106 mAh g−1 at 3 C rate also exhibits excellent rate performances. The improved electrochemical performances are mainly derived from its fast Li+ diffusion, which causes the higher ionic conductivity. The LiMn0.8Fe0.2PO4 sample with the particle sizes of ∼9.39 μm also shows the highest tap density (0.68 g cc−1) among the as-prepared samples. This finding provides a new way to enhance the energy density of other cathode materials.

Synthesis and characterization of Li1-xTbxNiPO4 solid solution as cathode materials for lithium ion battery application

Modified Pechini-type polymerizable precursor method has been used to prepare nanosized Li1-xTbxNiPO4 (x = 0, 0.03, 0.05, and 0.07) solid solutions to obtain homogeneous with controlled stoichiometry and smaller particle size. The reaction temperature was determined by thermogravimetric (TG/DTA) analysis. X-ray diffraction analysis reveals the formation of orthorhombic structure and the calculated crystallite sizes are found to be in the range of 75–89 nm. Morphological, compositional, and vibrational properties were performed by SEM, EDAX, and FTIR, respectively. Conductivity measurements were carried out at room temperature by AC impedance analysis. The Li0.97Tb0.03Ni0.99PO4 sample shows one order of higher conductivity than pure LiNiPO4. Higher concentration of terbium samples such as Li0.95Tb0.05Ni0.99PO4 and Li0.93Tb0.07Ni0.99PO4 lead to decrease of conductivity. The frequency dependency of dielectric permittivity, dielectric loss, and electric modulus of Li1-x TbxNiPO4 solid solutions are studied. The frequency-dependent plot of modulus reveals that the conductivity relaxation is of non-Debye type.

Graphene encapsulated spherical hierarchical superstructures self-assembled by LiFe0.75Mn0.25PO4 nanoplates for high-performance Li-ion batteries

the electrochemical performance of LiFe0.75Mn0.25PO4 material is further enhanced via synergistic strategies including crystal orientation growth, microspherical self-assembly and graphene encapsulation. The crystal orientation growth of LiFe0.75Mn0.25PO4 with plate-like morphology not only reduces the Li-ion transport length, but also enlarges the (010) surface, and leads to the improvement of Li-ion diffusion. The self-assembled spherical hierarchical superstructures can effectively prevent the plane-plane stacks of LiFe0.75Mn0.25PO4 nanoplates during spontaneously aggregating, providing more (010) surface for Li+ insertion/extraction. The graphene encapsulation can build a 3D conductive network as well as stabilize the microspherical aggregations, resulting in superior electronic conductivity and stability. As a consequence of the synergistic effects, the as-obtained LiFe0.75Mn0.25PO4 sample exhibits excellent rate capability (141.1mAhg−1 at 5C, 126.5mAhg−1 at 10C, 107.7mAhg−1 at 20C) and outstanding cyclability (25°C, 94.6% capacity retention after 500 cycles at 1C). The synergistic strategy involving crystal orientation growth, microspherical self-assembly and graphene encapsulation provides a fascinating candidate to obtain superior olivine-type cathode materials with excellent rate capability and cycling stability, and holds the potential to be extended to the controlled preparation of other electrode materials.

Manganese dissolution in lithium-ion positive electrode materials

Understanding the key factors that affects overall performances of a battery is crucial to the lithium-ion battery industry. To this end characterisation methods must be specific, reproducible and representative. As such, an interference free and reproducible analytical method with a low detection limit (50ppb) to evaluate manganese dissolution from lithium-ion battery positive electrodes is presented. Two different electrolytes (1.0M LiClO4 and 1.0M LiPF6 in EC:DMC (1:1)), LiFePO4, two nominally similar LiFe0.3Mn0.7PO4 samples and spinel LiMn2O4 are used for proof of concept. Mn and Fe quantification is performed on material ageing in solely in electrolyte, as well as, in a battery system with and without forced oxidation. It is demonstrated that water and free acid content in the electrolyte, as well as, imposing an oxidative electrochemical potential has a profound effect on manganese based material dissolution and battery performance.

Solvothermal synthesized LiMn1−xFexPO4@C nanopowders with excellent high rate and low temperature performances for lithium-ion batteries

Mixed-carbon coated LiMn1−xFexPO4 (x = 0, 0.2, 0.5, 1) nano-particles are synthesized by a novel solvothermal approach. All of these powders possess a uniform particle size distribution around 150 nm and a carbon coating layer of about 2 nm. The LiMn1−xFexPO4@C samples with a carbon content of 2 wt% have an optimal electrochemical performance. The average voltage platform of LiMn1−xFexPO4@C increases with the increased Mn/Fe ratio, but declines gradually during electrochemical cycling. The LiMn0.5Fe0.5PO4 sample shows a high energy density (568 W h kg−1), good cycleability (97.1%, 100 cycles) and excellent rate capability (120.2 mA h g−1, 20C) at room temperature. Simultaneously, the LiMn0.5Fe0.5PO4 and LiFePO4 samples also show excellent low temperature electrochemical performance with specific capacities of 109.4 and 138.8 mA h g−1 with average discharge voltages of 3.476 V and 3.385 V, respectively, at −12 °C. Even at −20 °C, their discharge specific capacities are 71.7 and 82.3 mA h g−1 at 3C, respectively.

Synthesis and electrochemical properties of LiFe0.95VxNi0.05−xPO4/C cathode material for lithium-ion battery

In this study, crystalline LiFe0.95VxNi0.05−xPO4/C powders are successfully synthesized using the hydrothermal method. Materials characterization and the electrochemical performance of LiFe0.95VxNi0.05−xPO4/C are investigated. The structure, morphology, and electrochemical performances of the prepared samples are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry, and AC impedance. The XRD pattern indicates that the LiFe0.95VxNi0.05−xPO4/C powders are single-phased with an orthorhombic olivine structure. The LiFe0.95V0.05PO4 sample has the highest capacity of 141mAhg−1, which is 6% higher than that of pure LiFePO4 at 0.1C. As the discharge rate increases to 10C, the LiFe0.95V0.04Ni0.01PO4 sample has the highest capacity of 100mAhg−1, which is 18% higher than that of pure LiFePO4. The CV results prove that the LiFe0.95V0.04Ni0.01PO4 cathode has high capacity and good cyclic performance caused by the high lithium-ion diffusion transport, which is improved by Ni and V doping.

A joint experimental and theoretical study on the effect of manganese doping on the structural, electrochemical and physical properties of lithium iron phosphate

Mn doped LiFe1−xMnxPO4 (x = 0, 0.01, 0.03, 0.05, 0.07) cathode materials are synthesized by a carbothermal reduction method. The structure, morphology and electrochemical performance of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman, and charging–discharging tests. It is found that an appropriate amount of Mn doping did not affect the olivine structure and morphology of LiFePO4, but greatly improves its electrochemical performance. Especially, the LiFe0.97Mn0.03PO4 sample exhibits the best electrochemical performance, which shows the maximum discharge capacity of 148.2 mA h g−1 at 0.1 C and a capacity retention ratio of 98% after 60 cycles at various rates. Based on first-principles density functional theory (DFT), the lithium ion migration channels, energy band structures, densities of states, and charge density diffusion of LiFePO4 and LiFe15/16Mn1/16PO4 are calculated to further investigate the influence of Mn doping on the LiFePO4 lattice. The results prove that the higher lithium ion conduction and electronic conductivity of LiFe15/16Mn1/16PO4 are attributed to Mn doping.

Structural, Morphological, Vibrational and Electrical Studies on Zn Doped Nanocrystalline LiNiPO<sub>4</sub>

Olivine structured LiNi1-xZnxPO4 (x=0, 0.05, 0.10, 0.15, 0.20) have been prepared by a polyol method using 1, 2 propanediol as a polyol medium. The XRD results of pure and Zn doped LiNiPO4 sample authenticate the orthorhombic crystal structure with high crystalline nature. The crystallite size is calculated from the Debye Scherer formula and it is found in the range of 55-65nm and 49-55nm for undoped and doped samples respectively. The thermal properties of LiNi1-xZnxPO4 were investigated by thermo gravimetric analysis (TG) and differential thermal analysis. Laser Raman studies confirm that the dopant is entered in to the LiNiPO4 lattice. Morphology of the samples is analyzed through SEM analysis. The higher electrical conductivity is calculated for LiNi0.85Zn0.15PO4 sample compared with other concentrations of dopant and it is found to be 1.08×10-7 S cm-1 at ambient temperature. Dielectric and Modulus studies are also discussed through impedance spectroscopy.

Redox Centers Evolution in Phospho-Olivine Type (LiFe0.5Mn0.5 PO4) Nanoplatelets with Uniform Cation Distribution

In phospho-olivine type structures with mixed cations (LiM1M2PO4), the octahedral M1 and M2 sites that dictate the degree of intersites order/disorder play a key role in determining their electrochemical redox potentials. In the case of LiFexMn1-xPO4, for example, in micrometer-sized particles synthesized via hydrothermal route, two separate redox centers corresponding to Fe(2+)/Fe(3+) (3.5 V vs Li/Li(+)) and Mn(2+)/Mn(3+) (4.1 V vs Li/Li(+)), due to the collective Mn-O-Fe interactions in the olivine lattice, are commonly observed in the electrochemical measurements. These two redox processes are directly reflected as two distinct peak potentials in cyclic voltammetry (CV) and equivalently as two voltage plateaus in their standard charge/discharge characteristics (in Li ion batteries). On the contrary, we observed a single broad peak in CV from LiFe0.5Mn0.5PO4 platelet-shaped (∼10 nm thick) nanocrystals that we are reporting in this work. Structural and compositional analysis showed that in these nanoplatelets the cations (Fe, Mn) are rather homogeneously distributed in the lattice, which is apparently the reason for a synergetic effect on the redox potentials, in contrast to LiFe0.5Mn0.5PO4 samples obtained via hydrothermal routes. After a typical carbon-coating process in a reducing atmosphere (Ar/H2), these LiFe0.5Mn0.5PO4 nanoplatelets undergo a rearrangement of their cations into Mn-rich and Fe-rich domains. Only after such cation rearrangement (via segregation) in the nanocrystals, the redox processes evolved at two distinct potentials, corresponding to the standard Fe(2+)/Fe(3+) and Mn(2+)/Mn(3+) redox centers. Our experimental findings provide new insight into mixed-cation olivine structures in which the degree of cations mixing in the olivine lattice directly influences the redox potentials, which in turn determine their charge/discharge characteristics.

Phase Separations in LiFe1–xMnxPO4: A Random Stack Model for Efficient Cathode Materials

Olivine-type LiFe1-xMnxPO4 compounds were systematically synthesized by a solvothermal method. Synchrotron radiation X-ray absorption spectroscopy combined with first-principles calculations and energy-dispersive Xray spectroscopy measurements show that the as-prepared LiFe1-xMnxPO4 samples contain two different phases: LiFePO4 and LiMnPO4. Actually, due to the crystal field effect, these two structures are randomly stacked and characterized by a pronounced structural distortion of the MO6 (M: Fe or Mn) octahedra. Moreover, increasing the Mn doping concentration, the distortion of the MO6 octahedra increases. Considering the size of LiMnPO4 stacks and the distortion of MO6 octahedra, the best performance occurs at the optimal Mn doping concentration. Among, the different Fe/Mn ratios, the electrochemical tests show that the as-prepared LiFe0.75Mn0.25PO4 sample exhibits the best electrochemical performance. Moreover, in order to optimize electrochemical performances, data point out that the doping procedure may control the size of the LiMnPO4 stacks, but it is also necessary to control the interplay between the increase of the working voltage and the electrical conductivity of LiMnPO4 stacks.

Synthesis and luminescence of Bi0.95Eu0.05PO4 nanocrystals with different morphologies

Bi0.95Eu0.05PO4 nanocrystals with different morphologies were synthesized by precipitation in different solvents. The Bi0.95Eu0.05PO4 samples were characterized by X-ray powder diffraction, scanning electron microscopy (SEM), and luminescence spectroscopy. The X-ray diffraction results reveal that the Bi0.95Eu0.05PO4 samples present a hexagonal phase. The SEM observations demonstrate that the Bi0.95Eu0.05PO4 samples with different morphologies could be obtained in different solvents. The room temperature luminescent properties of Bi0.95Eu0.05PO4 samples were studied using an excitation wavelength of 290 nm. The emission spectra display the bands associated to the 5D0 → 7FJ electronic transitions characteristics of the Eu3+ cations at different positions.

The effect of Fe vacancy defects on the physical and electrochemical characterizations of LiFe0.92PO4: A combined experimental and theoretical study

The LiFe0.92PO4 including Fe vacancy defects was prepared as performance-improved cathode material for lithium-ion battery by a carbothermal reduction method. A combination of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), electrochemical testing, and first-principles calculations was used to determine and rationalize the physical and electrochemical characterizations of LiFe0.92PO4. The XRD, FTIR and XPS results indicated that Fe vacancy defects had been successfully incorporated into the parent olivine phase of LiFe0.92PO4 and did not affect its olivine lattice structure. Especially, the LiFe0.92PO4 sample exhibited a discharge capacity of 69.0 mAh g−1 at 10C and capacity retention ratio of 96% after 100 cycles at various rates, implying excellent rate capability and cycling stability. Moreover, the lithium ion migration channels, energy band structures, densities of states, and charge densities of LiFePO4 and LiFe0.92PO4 were investigated by first-principles calculations. The results suggest that the higher lithium ion conduction and electronic conductivity of LiFe0.92PO4 is attributed to Fe vacancy defects.

LiMn1−xFexPO4 (x = 0, 0.1, 0.2) nanorods synthesized by a facile solvothermal approach as high performance cathode materials for lithium-ion batteries

LiMn1−xFexPO4 nanomaterials at low Fe concentration (x = 0, 0.1, 0.2) for lithium-ion batteries have been synthesized with high yield via a facile solvothermal route in a mixed solvent of water and polyethylene glycol (PEG200). SEM and TEM images reveal that all samples are single crystalline with similar rod-like shapes, and XRD characterizations indicate that the crystal lattices decrease with the increasing concentration of Fe. Electrochemical tests show that the best electrochemical properties can be achieved by substituting 20% of Fe at Mn-site. The as-prepared LiMn0.8Fe0.2PO4 sample delivers a high initial discharge capacity of 165.3 mAh g−1 at 0.05C, which is close to the theoretical capacity of LiMnPO4. Moreover, it also demonstrates excellent cycle performance and remarkable rate capability.

Effects of vanadium substitution on the cycling performance of olivine cathode materials

V-substituted LiFePO4 (LiFe1−xVxPO4, 0 ≤ x ≤ 0.10) powders are prepared via a solution method. The compositions, crystalline structure, morphology of the prepared powders are systemically investigated with inductive couple plasma-option emission spectrometry (ICP-OES), synchrotron radiation X-ray diffraction (s-XRD), X-ray Absorption Spectroscopy (XAS) and field emission-transmission electron microscopy (FE-TEM). Results of s-XRD and Rietveld analysis reveal that olivine phase is observed exclusively for LiFe1−xVxPO4 (x ≤ 0.05) samples, whereas a minor amount of monoclinic Li3V2(PO4)3 is detected in the prepared LiFe0.93V0.07PO4 and LiFe0.90V0.10PO4 samples. It is also found that the lattice parameters of olivine structure and average Li–O and M–O (M = Fe or V) bond lengths slightly increase and decrease with the amount of V substitution, recommending an enhanced lithium diffusivity in the structure. Results of XAS study suggest that V ions occupy octahedral sites (4c) of Fe in LiFePO4 structure with valence of 3+, showing good agreement with shortened M–O bonds determined in Rietveld analysis. As a result of V substitution, LiFe1−xVxPO4, (0 ≤ x ≤ 0.10) cathodes exhibit better electrochemical performance, such as discharge capacity, rate capability, and cycling performance at both room and elevated temperatures.

Effects of titanium incorporation on phase and electrochemical performance in LiFePO4 cathode material

Ti-incorporated LiFe1−xTixPO4 (0≤x≤0.2) samples have been prepared via a two-step solid-state reaction route. The samples have systematically been investigated with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), cyclic voltammetry (CV) and charge/discharge measurements. The incorporation of Ti in LiFePO4 significantly enhances the electrochemical performance; the carbon-coated LiFe0.9Ti0.1PO4 sample shows the best performance. It is confirmed that LiFe1−xTixPO4 with x≤0.05 are of single phase while those with 0.07≤x≤0.2 contain impurity phases: LiTi2(PO4)3 and TiP2O7. The impurities influence not only the electronic conductivity, but also the total specific capacity. Appropriate amount of titanium incorporation is favorable for the improvement in electrochemical performance.