Combination Of Spray Pyrolysis Research Articles

Electrochemical performance of Mn 3 O 4 nanorods by N‐doped reduced graphene oxide using ultrasonic spray pyrolysis for lithium storage

The crumpled N-doped reduced graphene oxide wrapped Mn3O4 nanorods (Mn-NrGO) composite are synthesized via a combination of spray pyrolysis and a hydrothermal process for lithium ion batteries. The Mn3O4 nanorods are uniformly dispersed in the conductive matrix of crumpled N-doped reduced graphene oxide, forming a uniform wrapped composite and stopping them from restacking, which synergistically enhanced the Li+ ion conductivity. The well-defined Mn3O4 nanorods, strong interaction between Mn3O4 and NrGO, and highly graphitic properties of Mn-NrGO result in superior reversible capacity, long cycle life, and superior rate performance of approximately 1500 mAh/g at 0.1 C after 100 cycles and >660S mAh/g at 1.0 C after 500 cycles.

Efficient and recyclable photocatalytic degradation of methylene blue dye in aqueous solutions using nanostructured Cd1 − xCoxS films of different doping levels

This study outlines the impact of Co doping on the structures, morphologies, optical, and photochemical activities of nanoporous CdS films for efficient solar energy conversion. A sequence of nanotextured films of cadmium cobalt sulfide (Cd1 − xCoxS; where x = 0, 0.02, 0.04, 0.06, and 0.08) were grown on glass substrates using spray pyrolysis method followed by annealing at 300 °C for 2 h. The grown Cd1 − xCoxS films are of single wurtzite phase and polycrystalline nature. The preferential crystallographic growth of Cd1 − xCoxS nanocrystallites along the (002) is changed to (101) direction for x ≥ 0.06. The crystallite size and lattice parameters are decreased for x ≤ 0.04. Also, the absorption is increased and the optical bandgap is decreased to 2.40 eV at 6% Co-doping. The morphological study reveals the growth of agglomerated pure CdS nanorods. The incorporation of Co increases the density of nanorods, which self-assembled to form nanoporous surface at 2 and 4%. A random distribution of irregular nanorods accompanied by patterned spherical clusters is observed at 6%, which is assembled to a nanoporous pattern at 8%. The photocatalytic performances and reaction kinetics of the films are investigated for methylene blue dye decomposition under sunlight and artificial light illumination. The 6% Co-doped film reached the complete removal after 240 min under sunlight irradiation. This film showed higher stability than pure CdS film for 7 runs. Therefore, the combination of spray pyrolysis and adjustable doping level is a viable way for producing large-scale and reusable photocatalytic films for eco-friendly removal of dyes from industrial wastewater.

Synthesis of LiNi1−xCoxPO4/C nanocomposite cathode for lithium ion batteries by a combination of aerosol and powder technologies

Pure LiNi1−xCoxPO4 (x = 0, 0.2, 0.5, 0.8, 1) was synthesized by spray pyrolysis followed by heat treatment. The X-ray diffraction (XRD) patterns of LiNi1−xCoxPO4 were indexed to olivine structure with a Pnma space group. The peak shift and variation of lattice parameters suggested that LiNi1−xCoxPO4 solid solution was formed. Moreover, LiNi1−xCoxPO4/C (x = 0, 0.2, 0.5, 0.8, 1) nanocomposites were successfully synthesized by a combination of spray pyrolysis and wet ball milling followed by heat treatment. The XRD patterns of all samples were indexed to olivine structure with a Pnma space group. From scanning electron microscopy images, the primary particle sizes of LiNi1−xCoxPO4/C nanocomposites were reduced to the range of approximately 50–100 nm. LiNi0.5Co0.5PO4/C cathode exhibited a higher first discharge capacity and cyclability than those of pure LiNi0.5Co0.5PO4. Cyclic voltammetry data demonstrated that reduction peaks of LiNi0.5Co0.5PO4/C cathode occur at 4.44 V and 4.71 V, which were ascribed to Co3+/Co2+ and Ni3+/Ni2+ reduction couples, respectively. Electrochemical impedance spectroscopy data revealed that the LiNi0.5Co0.5PO4/C cathode had a smaller charge transfer resistance, resulting in a faster redox reaction kinetics for the lithium insertion and extraction, due to reduced particle size and introduced conductive carbon.

Rational design of metal-organic framework-templated hollow NiCo2O4 polyhedrons decorated on macroporous CNT microspheres for improved lithium-ion storage properties

We report three-dimensional (3D) porous microspheres comprising interconnected carbon nanotubes (CNT) decorated with hollow NiCo2O4 polyhedrons (H-NCO/CNT) for high-performance lithium-ion batteries (LIBs). The rationally designed composites are successfully fabricated via the combination of spray-pyrolysis and solution-based methods. The macroporous CNT microsphere obtained by spray pyrolysis acts as a substrate for the growth of the zeolitic imidazolate framework-67 (ZIF-67) in ethanol solution. During ion exchange and subsequent oxidation processes, the ZIF-67 polyhedrons were converted into hollow NiCo2O4 polyhedrons consisting of small crystal domains. Rational design of such composite microspheres offers a highly conductive 3D porous network that simultaneously enables fast ion and electron diffusion deep inside the electrodes during cycling. In addition, the hollow polyhedron interiors can accommodate large volume changes and shorten the transport pathway for the ions and electrons. Owing to these structural advantages, high capacity, long cycle life, and excellent rate capability are achieved from H-NCO/CNT microspheres when applied as LIB anodes; the discharge capacity of H-NCO/CNT microspheres remained at 1673 mA h g−1 after 200 cycles at a current density of 1.0 A g−1. Even when cycled at a high current density of 20.0 A g−1, a high capacity of 639 mA h g−1 could be achieved.

Encapsulation of aluminum nanoparticles within copper oxide matrix for enhancing their reactive properties

Simple and easy spray pyrolysis and subsequent calcination processes were employed in this study to fabricate nanoenergetic materials (nEMs) composed of Al as the fuel and CuO as the oxidizer. Al nanoparticles (NPs) and Cu(NO3)2 as the CuO precursor were first dissolved in ethanol, and then they were pyrolized in the gas phase. After the subsequent calcination process, Cu(NO3)2 and its intermediate matrix covering Al NPs were completely transformed to the CuO matrix by thermal decomposition, and thus, the CuO-encapsulated Al NPs were successfully fabricated. The burn rate of the CuO-encapsulated Al NPs fabricated in this study was found to be much higher than that of Al/CuO composite NPs, which were fabricated for comparison by traditional sonication mixing and subsequent calcination processes. The ignition delay time and total burning time of CuO-encapsulated Al NPs were also much shorter than those of Al/CuO composite NPs. This suggests that the combination of spray pyrolysis and subsequent calcination processes can be a versatile and effective method to form the homogeneous and intimate nEMs composed of fuel materials (i.e., Al NP core) and oxidizers (i.e., CuO matrix) with high reactivity and excellent combustion properties.

Synthesis and Characterization of Li2FeP2O7/C Composite By a Combination of Spray Pyrolysis and Wet Ball Milling Followed By Heat Treatment

Introduction Application of lithium-ion battery has been extended from mobile phones, laptop, and portable electronic devices to large scale electric devices with its improvement of capacity and cycle life. Adapting to the electric vehicle (EV) or energy storage system (ESS) as an electrical power source, there are required cathode materials which are safety, low cost and environmentally benign. Thus far, several studies on crystal structure of poly-anion compounds with Fe (II) as cathode materials for lithium-ion battery have been reported [1, 2]. Furthermore, synthesis of Li2FeP2O7/C composites has been introduced with various synthesis methods, such as solid state reaction [3], sol-gel [4] and splash combustion method [5]. In this study, we have prepared Li2FeP2O7/C composites from lithium dihydrogen phosphate and iron nitrate used as a precursor by a combination of spray pyrolysis and wet ball milling followed by heat treatment, and then investigated their electrochemical properties. Experimental Li2FeP2O7/C composites were prepared by a combination of spray pyrolysis and wet ball milling followed by heat treatment. Stoichiometric amount of lithium dihydrogen phosphate and iron nitrate was dissolved into distilled water. Ascorbic acid was added to the precursor solution as a reduction agent. The precursor solution was introduced to an ultrasonic nebulizer that works at a frequency of 1.7MHz. The sprayed droplets were transported to a laminar flow aerosol reactor by a carrier gas and converted into solid particles through the process of evaporation of a solvent, precipitation of solute drying and thermal decomposition within the reactor. The obtained powders were collected by an electrostatic precipitator. The as-prepared powders were mixed with acetylene black (AB) in ethanol by high-energy planetary ball milling and then annealed at 650°C for 2 h in a 3%H2+ Ar atmosphere. The obtained samples were identified as pure-crystallinity with monoclinic structure by the XRD analysis using Cu-Kα radiation. The electrochemical performance of the samples as cathode materials for lithium battery was investigated by galvanostatic measurements with a coin-type cell (CR2032). The cells were cycled between 2.0 and 4.2 V at different current densities from 0.05 C to 2 C (1C=110 mA g-1) on multichannel battery testers (Hokuto Denko, HJ1010mSM8A). The current density and specific capacity were calculated from the mass of Li2FeP2O7 in the electrode. Results and discussion Fig. 1 shows the XRD patterns of the samples which are prepared by spray pyrolysis with various temperatures and then annealed at 650°C for 2 h. Regardless of spray temperature, all of the XRD patterns are indexed to a monoclinic structure with pure phase of Li2FeP2O7. An electrochemical performance of the Li2FeP2O7, which was prepared at 600°C by spray pyrolysis and then annealed at 650°C for 2 h, was tested at various charge-discharge rates ranging from 0.05 to 2 C, in which five cycles were carried out at each charge-discharge rate. The results were shown in Fig. 2. The cell exhibited a first discharge capacity of 78.6 mAh g-1 at 0.05C and dropped to 23.0 mAh g-1 at 1C rate. The Li2FeP2O7/C composite sample was also tested at the same condition and showed enhanced performance than the bare Li2FeP2O7 sample. The detail results will be reported in the conference. References L. Adam, A. Guesdon, and B. Raveau, J. Solid State Chem., 181, 3110( 2008). S. I. Nishimura, M. Nakamura, R. Natsui, and A. Yamada, J. Am. Chem. Soc., 132, 13596(2010). J. Du, L. Jiao, Q. Wu, Y. Liu, Y. Zhao, L. Guo, Y. Wang, and H. Yuan, Electrochim. Acta, 103, 219(2013). L. Tan, S. Zhang, and C. Deng, J. Power Sources, 275, 6(2015). P. Barpanda, T. Ye, S.-C. Chung, Y. Yamada, S. Nishimura, and A. Yamada, J. Mater. Chem., 22, 13455(2012). Figure 1

Synthesis of Li2FeP2O7/Carbon nanocomposite as cathode materials for Li-ion batteries

A Li2FeP2O7/Carbon (C) nanocomposite was successfully synthesized via a combination of spray pyrolysis and wet ball milling followed by annealing from a precursor solution; in which LiNO3, H3PO4 and Fe(NO3)3·9H2O were stoichiometrically dissolved into distilled water. Ascorbic acid was added to the precursor solution as a reduction agent. The peaks of the Li2FeP2O7/C nanocomposite obtained by X-ray diffraction analysis were indexed to the monoclinic structure with the space group P21/c. The Li2FeP2O7/C nanocomposite cathode delivered a first discharge capacity of 100 mAh g−1 at 0.05 C, which corresponded to 91% of its theoretical capacity. After various higher discharge rates from 0.05 to 2 C in the cycle performance test, a discharge capacity of 93 mAh g−1 was achieved at 0.05 C, which showed an excellent capacity retention (93%) after 29 cycles.

Physical and Electrochemical Characterization of Li2FeP2O7/C Nanocomposites Prepared By a Combination of Spray Pyrolysis and Wet Ball Milling Followed By Heat Treatment

Introduction Since the commercialization of lithium-ion batteries in the 1990s, they have been widely utilized for energy storage in mobile electric devices owing to their large gravimetric and volumetric energy densities. Recently, attention has turned to the use of them as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Large-scale batteries require safety, low-cost, long cycle-life, and high energy and power densities. Furthermore, it is well known that the cathode materials have a significant impact on battery capacity, cycle life, safety and cost. Recently, pyrophosphates (Li2MP2O7, M=transition metal), the polyanion compounds with 3D crystal structure, have come into sight as a new candidate of cathode materials [1, 2]. Thus far, we have investigated the synthesis of LiMPO4/C (M=Fe, Mn and Co) nanocomposites by a combination of aerosol and powder technologies followed by heat treatment, and then reported that the composite electrodes showed a good electrochemical performance [3-5]. In this work, the synthesis of Li2FeP2O7/C nanocomposites has been prepared by a combination of spray pyrolysis (SP) and wet ball milling (WBM) followed by heat treatment and their physical and electrochemical properties have been also studied. Experimental The precursor solution used in this study was prepared by dissolving stoichiometric amounts of LiNO3,H3PO4 and Fe(NO3)3¥9H2O in distilled water and then atomized at a frequency of 1.7MHz using an ultrasonic nebulizer. Ascoribic acid was added into the precursor solution as a reducing agent. The sprayed droplet were transported to a reactor using a 3% H2+N2 gas with a gas flow rate of 4 L min-1 , heated at 800 oC and converted into solid particles. The resulting particles were then milled with acetylene black (AB) in ethanol by high-energy planetary ball milling, and then annealed at 600 oC for 2 h in a 3% H2+N2 atmosphere to obtain the desired material. The crystalline phase of the samples was studied by X-ray diffraction (XRD) analysis using Cu-Kα radiation. The surface morphology of the samples was examined by scanning electron microscopy (SEM) at 8 kV. The electrochemical performance of Li2FeP2O7/C nanocomposite was investigated using coin-type cells (CR2032). A 1 mol dm-3 LiPF6 solution in a solvent mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in 1:1 volume ratio (Tomiyama Pure Chemical Co., Ltd.) was used as the electrolyte. The cathode consisted of 70 wt. % Li2FeP2O7/C, 10 wt. % polyvinylidene fluoride (PVdF) as a binder and 20 wt. % acetylene black. The cells were cycled in a constant current-constant voltage mode at a 0.05 C rate (1 C = 110 mA g−1) to 4.3 V, held at 4.3 V until C/100, and then discharged to 2.0 V at a 0.05C rate. Results and discussion Fig. 1 shows the XRD patterns of the samples prepared by spray pyrolysis (SP) at 800 oC (a) and then annealed at 600 oC for 2 h in a 3%N2+H2 gas atmosphere (b). The XRD pattern of the sample prepared by SP with annealing was indexed to the pure-phase of Li2FeP2O7. Fig. 2a shows the SEM image of Li2FeP2O7 prepared by SP and then annealed at 600 oC. The final sample consists of spherical particles with approximately several micrometers in size. The charge-discharge curves of the Li2FeP2O7/Li cell were shown in Fig. 2b. The discharge capacity at 1st cycle was 64 mAh g-1, which corresponds to 58% of its theoretical capacity (110 mAh g-1). This fact may be due to its low electronic and iron conductivities.The synthesis of Li2FeP2O7/C nanocomposite was carried out using a combination of SP at 800 oC and WBM with heat treatment annealed at 600 oC. Fig. 3 shows the charge-discharge curves of the Li2FeP2O7/C nanocomposite /Li cell. The cell exhibited an initial discharge capacity of 100 mAh g-1, which corresponds to 91% of its theoretical capacity. Also, it shows a discharge capacity of 96 mAh g-1 at 5th cycle. The Li2FeP2O7/C composite cathode exhibited a wide and flat potential plateau at approximately 3.5 V vs Li. These facts may indicate that the WBM process is an effective way to improve the electrochemical properties of Li2FeP2O7 electrode. References L. Adam, A. Guesdon, and B. Raveau, J. Solid State Chem., 181, 3110( 2008). P. Barpanda, T. Ye, S.-C. Chung, Y. Yamada, S. Nishimura, and A. Yamada, J. Mater. Chem., 22, 13455(2012). M. Konarova and I. Taniguchi, J. Power Sources, 195, 3661-3667(2010). Z.Bakenov and I. Taniguchi, Electrochem. Commun., 12, 75-78(2010) T. N. L. Doan and I. Taniguchi, J. Power Sources, 195,5679-5684(2011). Figure 1

Physical and Electrochemical Properties of SiOx/C Composites Prepared by a Combination of Spray Pyrolysis and High Energy Ball Milling

ABSTRACTSpray pyrolysis has been widely used to prepare homogeneous and uniform ceramic powders with high purity. In this study, we are proposing ultrasonic spray pyrolysis followed by heat treatment to produce SiOx/C composite powders, where sucrose was used as a carbon source. Furthermore, high energy ball milling of the as-prepared powders in the presence of acetylene black was conducted to activate its electrochemical properties by reducing the particle size and improving the functionalization of the SiOxcomposite particles. SiOx/C nanocomposite finally obtained at a sucrous concentration of 0.1 mol L-1showed superior electrochemical properties, and the SiOx/C nanocomposite electrode delivered the first discharge and charge capacities of 1252 and 819 mAh g-1, respectively, with an initial columbic efficiency of 65% at a current density of 50 mAh g-1in the potential range from 0.01 to 3 V versus Li/Li+.

Synthesis and characterization of Li2MnP2O7/C composite by a combination of spray pyrolsis and wet ball milling followed by annealing

A Li2MnP2O7/C composite was synthesized by a combination of spray pyrolysis and wet ball milling followed by annealing. The peaks of the Li2MnP2O7/C composite obtained by X-ray diffraction analysis were indexed to the monoclinic structure with the space group P21/c. Field-emission scanning electron microscopy and transmission electron microscopy together with energy-dispersive spectroscopy verified that the Li2MnP2O7/C composite consisted of agglomerates of Li2MnSiO4 primary particles, and that a thin carbon layer was partially formed on the surface of these agglomerates. The Li2MnP2O7/C composite cathode delivered a first discharge capacity of 72mAhg−1 at 0.1C and 60°C, while the theoretical capacity is 110mAhg−1 for the Mn3+/Mn2+ redox reaction. The cathode also showed good cycling performance over 15 cycles.

Surface plasmon resonance caused by gold nanoparticles formed on sprayed TiO2 films

Titania films covered by gold nanoparticles are prepared by combination of spray pyrolysis and spin-coating methods. Proposed combination of techniques is prospective for photovoltaic coatings with plasmonic properties. The prepared TiO2 films with Au nanoparticles demonstrate variation in size of the gold nanocrystallites from 36 to 56nm depending on the concentration of the HAuCl4∙3H2O solution and plasmonic light extinction in the spectral range of 600–650nm. It is shown that gold nanocrystallites enhance Raman scattering from the underlying thin TiO2 film.

Synthesis of Li2MnSiO4/C nanocomposites for lithium battery cathode employing sucrose as carbon source

Li2MnSiO4/C nanocomposites were prepared by a combination of spray pyrolysis and ball milling followed by annealing, employing sucrose as the carbon source. The effect of the concentration of sucrose solution on the physical and electrochemical properties of Li2MnSiO4/C nanocomposites was investigated. X-ray diffraction analysis indicated that the peaks of the Li2MnSiO4/C nanocomposites were indexed to the orthorhombic structure of the Pmn21 space group. Field-emission scanning electron microscopy and transmission electron microscopy verified that the Li2MnSiO4/C nanocomposites finally obtained from 0.1molL−1 sucrose solution were agglomerates of Li2MnSiO4 primary particles less than 100nm in size, and that there are thin carbon layers partially formed on the surface of these agglomerates. A Li2MnSiO4/C nanocomposite electrode with 5wt.% acetylene black was used as a cathode for rechargeable lithium batteries, and electrochemical measurement was carried out using Li|1M LiPF6 in EC:DMC=1:1| Li2MnSiO4/C cells at room and elevated temperatures. The Li2MnSiO4/C nanocomposite electrodes delivered first-discharge capacities of 184mAhg−1 at 0.05C and 115mAhg−1 at 1C. Moreover, it exhibited a first-discharge capacity of 225mAhg−1 at 0.05C and 60°C.

Synthesis and characterization of LiCo1/3Mn1/3Fe1/3PO4/C nanocomposite cathode of lithium batteries with high rate performance

Olivine structured LiCo1/3Mn1/3Fe1/3PO4/C nanocomposites were prepared by a combination of spray pyrolysis at 300 °C and wet ball-milling followed by heat treatment at 500 °C for 4 h in a 3%H2 + N2 atmosphere. The formation of a solid solution between LiCoPO4, LiMnPO4, and LiFePO4 at this composition was confirmed by X-ray diffraction analysis. Scanning electron microscopy and transmission electron microscopy with equipped energy dispersive spectroscopy verified that the LiCo1/3Mn1/3Fe1/3PO4/C nanocomposites were agglomerates of LiCo1/3Mn1/3Fe1/3PO4 primary particles with a geometric mean diameter of 107 nm and a uniform chemical composition, and carbon was well distributed on the surface of the agglomerates. The LiCo1/3Mn1/3Fe1/3PO4/C nanocomposite cathode exhibited a high discharge capacity of 159 mAh g−1 at 0.05 C in the potential range of 2.0–5.0 V, corresponding to 94% of theoretical capacity. The capacity retention was 87% after 50 cycles at a charge–discharge rate of 1 C. Furthermore, the rate capability test showed that the high capacity still was retained even at 5 C and 20 C rate with 106 and 72 mAh g−1, respectively.

Synthesis and electrochemical characterization of Li2FexMn1−xSiO4/C (0≦x≦0.8) nanocomposite cathode for lithium-ion batteries

Abstract Li 2 MnSiO 4 /C nanocomposites were synthesized by a novel synthesis route, i.e., a combination of spray pyrolysis and wet ball milling followed by annealing. X-ray diffraction analysis indicated that the peaks of the Li 2 MnSiO 4 /C nanocomposites were indexed to the orthorhombic structure in Pmn 2 1 space group. Field-emission scanning electron microscopy and transmission electron microscopy together with energy-dispersive spectroscopy verified that the Li 2 MnSiO 4 /C nanocomposites were agglomerates of Li 2 MnSiO 4 primary particles with a geometric mean diameter of 65 nm, and that carbon was well distributed on the surface of these agglomerates. Moreover, Li 2 Fe x Mn 1 − x SiO 4 /C (0 2 Fe x Mn 1 − x SiO 4 /C (0 ≦ x ≦ 0.8) nanocomposites were used as cathode materials for rechargeable lithium batteries, and electrochemical measurements were carried out using Li|1 M LiPF 6 in EC:DMC = 1:1|Li 2 Fe x Mn 1 − x SiO 4 /C cells at room temperature. The Li 2 MnSiO 4 /C nanocomposite electrodes delivered first-discharge capacities of 197 and 130 mAh g − 1 at 0.05 and 1 C, respectively. However, they showed poor cyclability due to the transformation to amorphous Li 2 MnSiO 4 during the first charge. On the other hand, a Li 2 Fe 0.5 Mn 0.5 SiO 4 /C nanocomposite cathode delivered a higher discharge capacity of 149 mAh g − 1 at 1 C, and showed better cyclability than Li 2 MnSiO 4 /C nanocomposites.

Effect of spray pyrolysis temperature on physical and electrochemical properties of LiCoPO4/C nanocomposites

LiCoPO4/C nanocomposites could be prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment. The effect of spray pyrolysis temperature on physical and electrochemical properties of the LiCoPO4/C nanocomposites was investigated in the range of spray pyrolysis temperature from 200 to 500°C. Single phase LiCoPO4 olivine structure could be identified by X-ray diffraction analysis for all samples. Scanning electron microscopy observation showed that all samples consisted of approximately 100nm primary particles. The LiCoPO4/C nanocomposites were used as a cathode active material for lithium batteries, and the electrochemical tests were carried out using the cell Li|1M LiPF6 in EC:DMC=1:1|LiCoPO4/C at various charge/discharge rates in a cutoff potential between 2.5 and 5.0V. The final LiCoPO4/C nanocomposite sample prepared at a spray pyrolysis temperature of 300°C exhibited the best electrochemical performance mainly due to the largest specific surface area, the smallest primary particle size and a well distributed carbon in the composites. The cells exhibited initial discharge capacities of 134mAhg−1 at 0.05°C, 128mAhg−1 at 1C and 88mAhg−1 at 10C.

Synthesis of Li 2FeSiO 4/C nanocomposite cathodes for lithium batteries by a novel synthesis route and their electrochemical properties

Li 2FeSiO 4/C nanocomposites were synthesized by a novel synthesis route, i.e., a combination of spray pyrolysis and wet ball-milling followed by annealing. The effect of process parameters such as spray pyrolysis temperature, ball-milling time, carbon content in the wet ball-milling process and annealing temperature on the physical and electrochemical properties of Li 2FeSiO 4/C nanocomposites was investigated. The final sample was identified as Li 2FeSiO 4 with a P2 1 monoclinic structure by X-ray diffraction analysis. Field-emission scanning electron microscopy and transmission electron microscopy with energy-dispersive spectroscopy verified that the Li 2FeSiO 4/C nanocomposites are agglomerates of Li 2FeSiO 4 primary particles with a geometric mean diameter of 65 nm and that the carbon was well-distributed on the surface of the agglomerates. A Li 2FeSiO 4/C nanocomposite sample was used as an electrode material for rechargeable lithium batteries, and electrochemical measurements were carried out by using Li|1 M LiPF 6 in EC: DMC = 1:1| Li 2FeSiO 4/C cells at room temperature. The Li 2FeSiO 4/C nanocomposite electrode delivered a first discharge capacity of 154 mAh g −1 at 0.05 C, corresponding to 93% of the theoretical value. Furthermore, the cycleability and rate capability of the cells were good.

Synthesis and electrochemical characterization of LiCo xMn 1− xPO 4/C nanocomposites

LiCo x Mn 1− x PO 4/C nanocomposites (0 ≤ x ≤ 1.0) were prepared by a combination of spray pyrolysis at 300 °C and wet ball-milling followed by heat treatment at 500 °C for 4 h in 3% H 2 + N 2 atmosphere. X-ray diffraction analysis indicated that all samples had the single phase olivine structures indexed by orthorhombic Pmna. The lattice parameters linearly decreased with increasing cobalt content, which confirmed the existence of solid solutions. It was clearly seen from the scanning electron microscopy observation that the LiCo x Mn 1− x PO 4/C samples were agglomerates with approximately 100 nm primary particles. The LiCo x Mn 1− x PO 4/C nanocomposites were used as cathode materials for lithium batteries, and electrochemical performance was comparatively investigated with cyclic voltammetry and galvanostatic charge–discharge test using the Liǀ1 M LiPF 6 in EC:DMC = 1:1ǀLiCo x Mn 1− x PO 4/C cells at room temperature. The cells at 0.05 C charge–discharge rate delivered first discharge capacities of 165 mAh g −1 (96% of theoretical capacity) at x = 0, 136 mAh g −1 at x = 0.2, 132 mAh g −1 at x = 0.5, 125 mAh g −1 at x = 0.8 and 132 mAh g −1 (79% of theoretical capacity) at x = 1.0, respectively. While the first discharge capacity increased with the cobalt content at high charge–discharge rates more than 0.5 C due to higher electronic conductivity of LiCoPO 4 in comparison with LiMnPO 4, the cycleability of cell became worse with increasing the amount of cobalt. The existence of Mn 2+ seemed to enhance the cycleability of LiCo x Mn 1− x PO 4/C nanocomposite cathode.

Synthesis of spherical LiMnPO 4/C composite microparticles

Spherical LiMnPO 4/C composite microparticles were prepared by a combination of spray pyrolysis and spray drying followed by heat treatment and examined as a cathode material for lithium batteries. The structure, morphology and electrochemical performance of the resulting spherical LiMnPO 4/C microparticles were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electronic microscopy and standard electrochemical techniques. The final sample was identified as a single phase orthorhombic structure of LiMnPO 4 and spherical powders with a geometric mean diameter of 3.65 μm and a geometric standard deviation of 1.34. The electrochemical cells contained the spherical LiMnPO 4/C microparticles exhibited first discharge capacities of 112 and 130 mAh g −1 at 0.05 C at room temperature and 55 °C, respectively. These also showed a good rate capability up to 5 C at room temperature and 55 °C.

Preparation of LiCoPO 4/C nanocomposite cathode of lithium batteries with high rate performance

LiCoPO 4/C nanocomposites could be successfully prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment. X-ray diffraction analysis confirmed that the LiCoPO 4/C nanocomposites were well crystallized in an orthorhombic structure with Pmna space group. Scanning electron microscopy and transmission electron microscopy with equipped energy dispersive spectroscopy verified that the LiCoPO 4/C nanocomposites were the agglomerates of LiCoPO 4 primary particles with a geometric mean diameter of 87 nm, and the carbon was well distributed on the surface of the agglomerates. The LiCoPO 4/C nanocomposites were used as cathode active materials for lithium batteries, and the electrochemical tests were carried out for the cell Li|1 M LiPF 6 in EC:DMC = 1:1|LiCoPO 4/C at various charge–discharge rates. The cells delivered first discharge capacities of 142 and 109 mAh g −1 at 0.05 and 20 C, respectively. Furthermore, the discharge capacity after 40 cycles corresponded to 87% of initial one at 0.1 C rate. The excellent rate capability of the cells is mainly due to the well distributed carbon on the LiCoPO 4 agglomerates, and a much smaller lithium ion diffusion distance in the electrode.

Cathode performance of LiMnPO 4/C nanocomposites prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment

LiMnPO 4/C nanocomposites could be prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment in the range of spray pyrolysis temperature from 200 to 500 °C. The ordered LiMnPO 4 olivine structure without any impurity phase could be identified by X-ray diffraction analysis for all samples. It could be also confirmed from scanning electron microscopy and transmission electron microscopy observations that the final samples were the LiMnPO 4/C nanocomposites with approximately 100 nm in primary particles size. The LiMnPO 4/C nanocomposite samples were used as cathode active materials for lithium batteries, and the electrochemical tests were carried out for the cell Li|1 M LiPF 6 in EC:DMC = 1:1|LiMnPO 4/C at various charge/discharge rates in three charge modes. As a result, the final sample which was synthesized at 300 °C by spray pyrolysis showed the best electrochemical performance due to the largest specific surface area, the smallest primary particle size and a well distribution of carbon. At galvanostatic charge/discharge rates of 0.05 C, the cell delivered first discharge capacities of 123 and 165 mAh g −1 in correspondence to charge cutoff voltages of 4.4 and 5.0 V, respectively. Furthermore, in a constant current–constant voltage charge mode at 4.4 V, the cells also exhibited initial discharge capacities of 147 mAh g −1 at 0.05 C, 145 mAh g −1 at 0.1 C, 123 mAh g −1 at 1 C and 65 mAh g −1 at 10 C. Moreover, the cells showed fair good cycleability over 100 cycles.