Titanium Substitution Research Articles

Effect of Titanium Substitution in a P2-Na2/3Co0.95Ti0.05O2 Cathode Material on the Structural and Electrochemical Properties.

Worries about lithium supplies have led to the development of research on sodium batteries. Sodium-ion batteries are regarded as the next generation of energy-storage devices thanks to the generous resources of sodium. In spite of that, structural changes in the electrode materials remain the main challenge of this storage technology. NaCoO2 has been widely investigated as a competitive candidate for LiCoO2. It has been found that the electrochemical cycling curves of this material present numerous potential steps as a result of electronic transitions and/or structural ordering. From this standpoint, this paper reports a novel cathode material, Na2/3Co0.95Ti0.05O2, where 5% of cobalt was replaced by titanium, prepared via a facile solid-state route. The sodiation/desodiation mechanism of this layered material was investigated. Na//Na2/3Co0.95Ti0.05O2 exhibits a first initial capacity of 119 mAh/g in the potential window 2-4.2 V with less potential jumps in the potential versus capacity curve compared to NaCoO2. Genuinely, the electrochemistry of this material demonstrated a reversibility upon the insertion/desinertion process with low polarization. In situ synchrotron investigations on Na2/3Co0.95Ti0.05O2 reveal the occurrence of reversible ordered phases. Ex situ magic-angle-spinning NMR disclosed different environments around sodium starting from the pristine state to the end of charge.

Periodic modeling of zeolite Ti-LTA.

We have proposed a combination of density functional theory calculations and interatomic potential-based simulations to study the structural, electronic, and mechanical properties of pure-silica zeolite Linde Type A (LTA), as well as two titanium-doped compositions. The energetics of the titanium distribution within the zeolite framework suggest that the inclusion of a second titanium atom with configurations Ti-(Si)0-Ti, Ti-(Si)1-Ti, and Ti-(Si)2-Ti is more energetically favorable than the mono-substitution. Infra-red spectra have been simulated for the pure-silica LTA, the single titanium substitution, and the configurations Ti-(Si)0-Ti and Ti-(Si)2-Ti, comparing against experimental benchmarks where available. The energetics of the direct dissociation of water on these Lewis acid sites indicate that this process is only favored when two titanium atoms form a two-membered ring (2MR) sharing two hydroxy groups, Ti-(OH)2-Ti, which suggests that the presence of water may tune the distribution of titanium atoms within the framework of zeolite LTA. The electronic analysis indicates charge transfer from H2O to the Lewis acid site and hybridization of their electronic states.

Effects of titanium substitutions for aluminum and tungsten in Co-10Ni-9Al-9W (at%) superalloys

Polycrystalline Co-10Ni-(9 – x)Al-(9 – x)W-2xTi at% (x = 0, 1, 2, 3, 4) alloys with γ(f.c.c.) plus γ′(L12) microstructures are investigated, where the γ′(L12)-formers Al and W are replaced with Ti. Upon aging, the initially cuboidal γ′(L12)-precipitates grow and develop a rounded morphology. After 256h of aging at 1000°C, the precipitates in the 6 and 8at% Ti alloys coalesce and develop an irregular, elongated morphology. After 1000h of aging, replacement of W and Al with Ti increases both the mean radius, <R>, and volume fraction, ϕ, of the γ′(L12)-phase from <R> = 463nm and ϕ = 8% for 2at% Ti to <R> = 722nm and ϕ = 52% for 8at% Ti. Composition measurements of the γ(f.c.c.)-matrix and γ′(L12)-precipitates demonstrate that Ti substitutes for W and Al in the γ′(L12)-precipitates, increases the partitioning of W to γ′(L12), and changes the partitioning behavior of Al from a mild γ′(L12)-former to a mild γ(f.c.c.)-former. The grain boundaries in the aged alloys exhibit W-rich precipitates, most likely μ(Co7W6)-type, which do not destabilize the γ(f.c.c.) plus γ′(L12) microstructure within the grains. Four important benefits accrue from replacing W and Al with Ti: (i) the alloys’ mass density decrease; (ii) the γ′(L12)-solvus temperature increases; (iii) the γ′(L12) volume fraction formed during aging at 1273K (1000°C) increases; and (iv) the 0.2% offset flow stress increases.

Influence of Ti4+ ion substitution on structural, electrical and dielectric properties of Li0.5Fe2.5O4 nanoparticles

The extent study deals with the structural, electrical and dielectric properties of tetravalent Ti4+ ion substituted lithium ferrite nanoparticles synthesized via sol–gel auto combustion technique with chemical formula Li0.5+0.5xTixFe2.5−1.5xO4 (where 0.0 ≤ x ≤ 1.0 in step of 0.2). The synthesized nanoparticles were characterized by X-ray diffraction technique (XRD). The XRD analysis reveals single phase cubic spinel structure of synthesized samples. The crystallite size calculated from Scherrer’s formula and grain size by linear intercept method using field emission scanning electron microscopy (FE-SEM) images, confirms the nanocrystalline nature of the samples. Infrared (IR) spectroscopy shows principle absorption bands for spinel structure. The DC resistivity at room temperature and as a function of temperature was studied using the two-probe technique. DC electrical resistivity of the samples increases with titanium substitution. The frequency dependence of dielectric properties was studied using LCR-Q meter, the dielectric parameters were found to decrease after substitution of titanium ions.

Study of the structural, thermodynamic and cyclic effects of vanadium and titanium substitution in laves-phase AB2 hydrogen storage alloys

The substitution of the high-purity and expensive raw materials vanadium (V) and titanium (Ti) by their low-cost, low-purity alternatives ferrovanadium (FeV) and Ti sponge in Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5 was investigated and the microstructural, thermodynamic and cyclic properties were tested of these compounds. Four different samples were prepared and studied: one material prepared with high-purity V and Ti, a second one prepared with FeV in substitution for V and Fe, a third prepared with Ti sponge in substitution for Ti, and a fourth prepared with FeV and Ti sponge in substitution for V, Fe and Ti. The substitution of Ti with Ti sponge and of V and Fe by FeV had negligible effects on the microstructural properties. 2.0 mass% H were absorbed in both the pristine (high-purity V and Ti) material and after replacing Ti by Ti sponge. Substitution of V by FeV reduced the initial hydrogen absorption capacity to approximately 1.7 mass%. All materials exhibited equilibrium hydrogen absorption and dissociation pressures of ca. 1.5 MPa. They reversibly stored 1.8 mass% H for both the pristine and Ti-substituted samples and 1.6 mass% H after substitution of V and Fe by FeV or after substitution of V, Fe and Ti by FeV and Ti sponge, respectively.Long-term cyclic experiments over 1000 de-/hydrogenation pressure swing cycles were performed for the pristine material and after substitution of V, Fe and Ti by FeV and Ti sponge, respectively. Both materials exhibited similar activation and degradation behavior upon cycling. A reversible capacity of 1.5 mass% H was recorded for the pristine material after 1000 cycles, and 1.4 mass% H were reversibly stored in the material prepared with FeV and Ti sponge subjected to 1000 cycles. The raw material cost to store an equal amount of hydrogen can be reduced by 83% when V and Ti are substituted by FeV and Ti sponge.

Synthesis and characterization of carbon doped TiO2 photocatalysts supported on stainless steel mesh by sol-gel method

This study synthesized pure anatase carbon doped TiO₂ photocatalysts supported on a stainless steel mesh using a sol-gel solution of 8% polyacrylonitrile (PAN)/dimethylformamide (DMF)/TiCl₄. The influence of the pyrolysis temperature and holding time on the morphological characteristics, particle sizes and surface area of the prepared catalyst was investigated. The prepared catalysts were characterized by several analytical methods: high resolution scanning electron microscopy (HRSEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The XRD patterns showed that the supported TiO₂ nanocrystals are typically anatase, polycrystalline and body-centered tetragonal in structure. The EDS and XPS results complemented one another and confirmed the presence of carbon species in or on the TiO₂ layer, and the XPS data suggested the substitution of titanium in TiO₂ by carbon. Instead of using calcination, PAN pyrolysis was used to control the carbon content, and the mesoporosity was tailored by the applied temperature. The supported TiO₂ nanocrystals prepared by pyrolysis at 300, 350, and 400oC for 3 h on a stainless steel mesh were actual supported carbon doped TiO₂ nanocrystals. Thus, PAN/DMF/TiCl₄ offers a facile, robust sol-gel related route for preparing supported carbon doped TiO₂ nanocomposites.

Titanium doping of BiFeO3 ceramics and identification of minor phases by Raman spectroscopy

Titanium substitution can improve the multiferroic properties of bismuth ferrite materials, albeit the structural changes that this dopant produces in the perovskite structure of BiFeO3 are still not well understood. Due to its high sensitivity, Raman spectroscopy can be a useful tool for trailing the dopant incorporation. In this work, we study the Raman spectra of undoped and Ti4+‐doped BiFeO3 ceramics that also contain small amounts of secondary phases – as it is usual for materials of this system. The micro‐Raman study together with a rigorous derivative analysis of the experimental Raman spectra recorded at low temperature (73 K) enables, for the first time, the identification of the Raman bands associated with the BiFeO3 phase together with those belonging to the minor secondary phases. The comparison between the Raman spectra of the undoped and the Ti4+‐doped materials indicates that some of the titanium added to the composition interacts with the secondary phases while only a partial amount of this dopant actually incorporates into the BiFeO3 phase. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Enhancement in magnetic, piezoelectric and ferroelectric properties on substitution of titanium by iron in barium calcium titanate ceramics

Lead free polycrystalline ceramics with compositional formula Ba0.90Ca0.10Ti1–3x/4FexO3 (BCT), (x=0.000, 0.005, 0.010, 0.015 and 0.020) were prepared by the solid state reaction method. The effect of substitution of Fe3+ ion at Ti-site on the ferroelectric and piezoelectric properties of BCT ceramics was studied. Remanant polarisation (Pr) and saturation polarisation (Ps) show an increasing trend while the reverse trend was observed for coercive field (Ec) with Fe3+ substitution. The values of the piezoelectric charge coefficient (d33) and piezoelectric coupling coefficient (kp) was found to increase with increase in Fe content. Ceramic sample with x=0.02 was found to have a maximum value of d33 (130pC/N) and kp (29%). The prepared ceramic samples show magnetic properties as confirmed by recorded MH loops. On substitution of Fe3+ ions, the ferroelectric BCT ceramics show clear transformation of the diamagnetic nature of BCT ceramics to weak ferromagnetism.

Influence of Excess Lithium on the Electrochemical Performance of Li1+Z MnTiO4 Spinel Structure for High Capacity and Long Cycle Life

Spinel based lithium manganese oxide is the most attractive cathodes for lithium-ion battery due to high capacity, low cost, and non-toxic. This material has a theoretical high capacity of 296 mAh g-1 (2 Li+ ions) if Li+ ions are fully inserted/extracted into/from the spinel structure. However, it is well known that when LiMn2O4 is discharged to a low voltage, e.g., 2 V, high spin Mn3+ ions may induce severe Jahn-Teller distortion. Up to date, this material is only used in the 4 V region with a low capacity of 120 mAh g-1. [1, 2] Much effort has been made to enhance the cycle stability of such cathode materials in a wide voltage window (e.g., 2.0-4.8 V). The substitution of titanium for manganese can improve the cycle life of cathode materials but with a decrease in the capacity of material which restrict its usage in a broad application. [2, 3] In this paper, Li1+z MnTiO4 (z = 0, 0.5, and 1) were developed to solve the problems of low capacity and short cycle life. Excess lithium material (z = 0.5 and 1) formed a solid-solution with notation (1-a)LiMn2-x Ti x O4.aLi2Mn y Ti1-y O3, which improve the capacity of material up to 218 mAh g-1, after 60 cycles with a capacity retention of 93 %. The structure and electrochemical properties were investigated carefully through X-ray diffraction, galvanostatic cycling, cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) to understand the mechanism of the improvement in the capacity and cycle stability of material. We also analyzed the effect of impurity phase as a significant factor that affects the electrochemical performance of the cathodes. References Thackeray, M.M. Prog. Solid State Chem. 1997, 25 (1–2), 1-71Wang, S.; Yang, J.; Wu, X.; Li, Y.; Gong, Z.; Wen, W.; Lin, M.; Yang, J.; Yang, Y. J. Power Sources. 2014, 245, 570-578.Chen, R.; Knapp, M.; Yavuz, M.; Heinzmann, R.; Wang, D.; Ren, S.; Trouillet, V.; Lebedkin, S.; Doyle, S.; Hahn, H.; Ehrenberg, H.; Indris, S. J. Phys. Chem. C. 2014, 118 (24), 12608-12616. Figure 1

Kondo-type behavior of theRu4+lattice inLaCu3Ru4O12

Rare $d$-electron-derived heavy-fermion properties of the solid-solution series ${\mathrm{LaCu}}_{3}{\mathrm{Ru}}_{x}{\mathrm{Ti}}_{4\ensuremath{-}x}{\mathrm{O}}_{12}$ were studied for $1\ensuremath{\le}x\ensuremath{\le}4$ by resistivity, susceptibility, specific-heat measurements, and magnetic-resonance techniques. Our results suggest the existence of a coherent Kondo lattice formed by localized Ru $4d$ electrons leading to strongly enhanced effective electron masses. Pure ruthenate $(x=4)$ is a heavy-fermion metal characterized by a resistivity proportional to ${T}^{2}$ at low temperatures $T$. By increasing titanium substitution the coherent Fermi-liquid state is disturbed, yielding single-ion Kondo-type properties as in the paradigm $4f$-based heavy-fermion compound ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Cu}}_{2.05}{\mathrm{Si}}_{2}$ [M. Ocko et al., Phys. Rev. B 64, 195106 (2001)]. In ${\mathrm{LaCu}}_{3}{\mathrm{Ru}}_{x}{\mathrm{Ti}}_{4\ensuremath{-}x}{\mathrm{O}}_{12}$ the heavy-fermion behavior finally breaks down upon crossing the metal-to-insulator transition close to $x=2$.

Heterogeneous hydrogenation of nitroaromatic compounds on gold catalysts: Influence of titanium substitution in MCM-41 mesoporous supports

A series of Ti-modified MCM-41 supports and their respective Au catalysts were prepared and characterized to study the effect of titanium into the support and on the characteristics of the Au surface species for heterogeneous hydrogenation of aromatic nitrocompounds. The systems were characterized by X-ray diffraction, Infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), diffuse reflectance UV–vis (DRUV–vis), N2 adsorption–desorption isotherms, ICP-MS and X-ray photoelectron spectroscopy (XPS). Additionally, these catalysts were tested for the hydrogenation of nitrobenzene in a batch-type reactor using ethanol as the solvent at 25°C. Based on a combined FT-IR and DRUV–vis was possible to conclude that the Ti(IV) is incorporated into the framework of MCM-41 and Ti-containing MCM-41 catalysts were more active than an MCM-41 unmodified catalyst. The Ti(X)-MCM-41 supports prepared with Ti 2.0wt% incorporation showed the best catalytic performance, which was attributed to an optimal number of isolated Ti sites that increased the Au stability on the support surface. For this system, the effect of the H2 pressure, solvent nature and recyclability of the catalyst was also studied. Finally, a quantitative structure property relationship (QSPR) model was obtained for the catalytic activities of para-substituted nitrobenzenes. The multilinear model considered two parametric descriptors: the sigma constant (σ) and the hydrophobic π-constant, which account for the electronic and hydrophobic effect of the substituents.

Crystal structure, phase transitions, and magnetic properties of titanium doped La0.5Sr0.5MnO3 perovskites

The current paper investigates the effect of titanium substitution on the structure as well as the magnetic properties of La0.5Sr0.5Mn1−xTixO3 (0≤x≤0.5) polycrystalline powder. The samples studied crystallize in a distorted perovskite structures of tetragonal (space group I4/mcm) symmetry with octahedral tilting scheme (a0a0c−), leading to the absence of octahedral tilting all along two perovskite main directions and to an out-of-phase along the third direction, or rhombohedral (space group R3¯c) symmetry with octahedral tilting scheme (a−a−a−) yielding to out-of-phase along the three perovskite main directions. As the Ti content increases, a better matching of the (Mn/Ti)–O distances and (Mn/Ti)–O–(Mn/Ti) bond angle occurs. This phenomenon is created by an elongation of the (Mn/Ti)–O distance, as Mn4+ is substituted by the larger ion Ti4+. In the whole compositional range, the symmetry-adapted to atomic displacements, responsible for the out-of-phase tilting of the (Mn/Ti)O6 octahedra, stays active, anticipating tetragonal-to-rhombohedral phase transition. Taking in to account what has been explained above, measurements of magnetic properties show a decrease of magnetic ordering temperature when Ti content increases, which in turn leads to the diminution of the exchange interaction caused by reducing the FM coupling and the replacement of neighboring manganese Mn3+–O–Mn4+ by Mn3+–O–Ti4+ bonds. This phenomenon results in broadening of the paramagnetic to ferromagnetic phase transition range. Further changes in magnetic properties with the increase in Ti concentration are studied.

Heterogeneous distribution of B-site cations in BaZrxTi1−xO3 epitaxial thin films grown on (0 0 1) SrTiO3 by pulsed laser deposition

The isovalent susbstitution of Ti4+ by Zr4+ in BaZrxTi1−xO3 modifies the dielectric character of ferroelectric BaTiO3 yielding different behaviours such as relaxor, polar cluster, etc. The dynamic coupling between BaTiO3 polar nanoregions and BaZrO3 nonpolar ones as well as microstrain between them are thought to be behind such a rich phase diagram. However, these short-range compositonal variations are elusive to detect and this topic is thus rarely addressed. We have grown epitaxial thin films of BaZrxTi1−xO3 on (001)-oriented SrTiO3 substrates by pulsed laser deposition sweeping the entire composition range between BaTiO3 and BaZrO3 in increments of 0.1 in x. Several characterization techniques (AFM, TEM, XRD, Raman spectroscopy) were used for this research in order to understand the morphological and structural properties of the deposited films. Ellipsometric measurements allowed the calculation of the band gap energy of the films. This work demonstrates the existence of a heterogeneous distribution in the substitution of titanium by zirconium yielding relaxor and polar cluster nanoregions.

Structural, electrical and magnetic study of nanocrystalline Ti-substituted Zn–Mn ferrospinels

Titanium substituted Zn–Mn ferrites were prepared by sol–gel route. Formation of single phase cubic spinel structure for all the compositions was confirmed from their X-ray diffraction studies. These ferrite samples existed as uniform and homogenous grain size as observed from scanning electron microscopy technique (SEM). The magnetic studies indicated that, the ferrimagnetic behavior increases with titanium substitution. Dielectric constant and complex impedance were measured as a function of frequency in the range 20Hz–1MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell–Wagner type of interfacial polarization and impedance study reveals that the electrical conduction in the ferrites is by the interior of the grain boundaries. In general, the substitution of titanium plays an important role in changing the structural, magnetic and electrical properties of these ferrites.

Influence of partial substitution of iron oxide by titanium oxide on the structure and activity of iron–cerium mixed oxide catalyst for selective catalytic reduction of NOx with NH3

The influence of partial substitution of iron oxide by titanium oxide on the catalytic activity of iron–cerium mixed oxide catalyst for the selective catalytic reduction (SCR) of NOx with NH3 has been investigated in this paper. The methods of X-ray diffraction (XRD) spectroscopy, N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (NH3/NO-TPD) were used to reveal the effects of titanium substitution on the structure of iron–cerium mixed oxide catalyst. The NH3-SCR activity of Fe0.95Ce0.05Oz is enhanced by partial substitution of iron oxide by titanium oxide, especially under low-temperature condition. This is primarily due to the increase of surface area, pore volume, adsorbed oxygen concentration and reactant adsorption capability. Among a series of Fe0.95−xCe0.05TixOz(x=0, 0.1, 0.15, 0.2, 0.3 and 0.4) catalysts, Fe0.80Ce0.05Ti0.15Oz(Ti/(Fe+Ce+Ti)=0.15) shows the highest NH3-SCR activity. On the other hand, thermal-stability of iron–cerium mixed oxide catalyst is also enhanced by titanium oxide substitution. At higher annealing temperature, the crystal content of Fe2O3 in Fe0.95Ce0.05Oz catalyst is depressed by the introduction of titanium oxide. Large surface area and pore volume can be achieved by Fe0.80Ce0.05Ti0.15Oz even calcined at 500°C for 5h. This catalyst shows the best NOx conversion in the low-temperature range of 100–300°C.

Effect of the substitution of titanium by chrome on the structural, dielectric and optical properties in Ca0.67La0.22Ti(1−x)CrxO3 perovskites

Polycrystalline samples of Ca0.67La0.22Ti(1−x)CrxO3(x = 0 and x = 0.1) (CLT(1−x)Crx) were synthesized by high-temperature solid–state reaction technique. The effect of replacing of titanium by chrome in the B site on the structural and physical properties of our compound was investigated. Using X-ray diffraction, scanning electron microscopy as well as dielectric characterizations and photoluminescence spectroscopy. These compounds crystallize with orthorhombic symmetry. The material is a classical ferroelectric for x = 0 and presents a relaxor behavior for x = 0.1. TC or Tm decreases when chrome is introduced in the lattice of CLT. A high permittivity of around 25,000 at Tm = 551 K for CLT0.9Cr0.1 was found, which opens the way for its possible use for capacitor applications. The observed increase in dielectric loss is explained in terms of changing oxygen vacancy concentration. The photoluminescence (PL) spectra confirm the dielectric measurements and suggested the formation of oxygen vacancies in the CLT(1−x)Crx sample.

Aqueous Ion Battery Systems Using Sodium Vanadium Phosphate Stabilized by Titanium Substitution

Na3V2(PO4)3 is a popular sodium-ion intercalating cathode material. It degrades in aqueous electrolytes, though. By substitution of half of the vanadium with titanium, the related compound, Na2VTi(PO4)3, was obtained. Three distinct sets of experiments were employed to qualify the potential utility of this material in various aqueous ion battery applications, including sodium and zinc ion. High levels of cycle stability were observed in neutral sodium-containing electrolyte, but less-so in zinc-containing electrolyte. At the end, pouch cells were built with both activated carbon and NaTi2(PO4)3 anode materials, demonstrating practical capabilities of systems utilizing these materials.

In Situ Formation of a Cathode–Electrolyte Interface with Enhanced Stability by Titanium Substitution for High Voltage Spinel Lithium‐Ion Batteries

Although LiNi0.5Mn1.5O4 (LNMO) high‐voltage spinel is a promising candidate for a next generation cathode material, LNMO/graphite full cells experience severe capacity fading caused by degradation reactions at electrode/electrolyte interfaces and consequent active Li+ loss in the cells. In this study, it is first reported that in situ formation of a Ti–O enriched cathode/electrolyte interfacial (CEI) layer on a Ti‐substituted LiNi0.5Mn1.2Ti0.3O4 (LNMTO) spinel cathode effectively mitigates electrolyte oxidation and transition metal dissolution, which improves the Coulombic efficiency and cycle life of LNMTO/graphite full cells. The Ti–O enriched CEI layer is produced in situ during an initial cycling of LNMTO as a result of selective Mn and Ni dissolution at its surface, as evidenced by various surface characterizations using X‐ray photoelectron spectroscopy, transmission electron microscopy, time‐of‐flight secondary ion mass spectrometry, Raman spectroscopy, and synchrotron‐based soft X‐ray absorption spectroscopy. The Ti–O enriched CEI has an advantage over traditional LNMO powder coatings, namely the formation of conformal CEI without compromising electronic conduction pathways between cathode particles.

Titanium-Substituted Na0.44MnO2 Nanorods as Cathode Materials for High Performance Sodium-Ion Batteries

A series of titanium-substituted manganese oxides, Na0.44TixMn1-xO2 (x = 0.11, 0.22, 0.33, and 0.44) with the Na0.44MnO2 were prepared by sol-gel methods. The electrochemical characteristics of these compounds, which are different from Na0.44MnO2, were examined in coin-type cells with NaPF6 electrolyte. While the Na0.44Ti0.11Mn0.89O2 and Na0.44Ti0.44Mn0.56O2 delivered lower capacities, the Na0.44Ti0.22Mn0.78O2 showed higher capacities, about 120 mAh g−1. The Ti-substituted materials exhibited excellent capacity retention over one hundred or more cycles, with 71.8% capacity retention over 450 cycles. Titanium substitution eliminates Mn dissolution.

Effect of Ti-doping on the electrochemical performance of lithium vanadium(III) phosphate

Carbon-coated and titanium-substituted lithium vanadium phosphate composites have been successfully prepared through a sol-gel method followed by solid-state reaction under argon. Li3V1.9Ti0.1(PO4)3-C (LVT10PC) and Li3V1.85Ti0.15(PO4)3-C (LVT15PC) were investigated using X-ray powder diffraction, thermal analysis, transmission electron microscopy, cyclic voltammetry, and galvanostatic tests. Different models for the solid solution mechanism in this system are discussed. Electrochemical tests, at a charge-discharge rate of 0.2 C, in the range 2.8–4.4 V show that LVT10PC delivers the highest discharge capacity of 121 mA h g−1 and declines to 115.7 mA h g−1 up to the 60th cycle, corresponding to a 4.4 % loss. At low levels, titanium substitution is found to increase initial discharge capacity compared to the carbon-coated unsubstituted system (LVPC). Further substitution is found to have detrimental effects on initial discharge capacity and cycling behaviour.