Particle Size Of LiFePO4 Research Articles

Influence of the nanogrinding process on the performance of lithium iron phosphate

Wet grinding is one of the most common forms of technology in powder production and preparation. Sand mill is the latest technology of wet grinding, which can effectively reduce the grinding particle size and improve the powder reactivity. LiFePO4 is one of the widely used cathode materials for lithium batteries at present, and the grinding process will affect the product performance. In this paper, parallel type and series type grinding processes were simulated by the single-cylinder system and the double cylinder system, which were studied and compared through the preparation of LiFePO4. It was discovered that the series type grinding process can not only increase the grinding efficiency but also improve the consistency of particle size distribution. LiFePO4 prepared by the series type grinding process has better rate performance and a higher discharge voltage platform. Attributing to the uniform particle size of LiFePO4, the lithium-ion diffusion coefficient was raised, which was proved by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). To sum up, based on the results of this paper, the properties of lithium iron phosphate will be affected by the particle size distribution, which is related to the grinding process. Therefore, in order to obtain the best performance of LiFePO4, it is necessary to choose the appropriate production process. This research work provides references and the basis for the research of powder grinding production technology.

Influence of carbon content, particle size, and partial manganese substitution on the electrochemical performance of LiFexMn1-xPO4/carbon composites

LiFePO4/C and LiFexMn1-xPO4/C (x = 0.7) nanocomposites were successfully synthesized via scalable spray-flame synthesis followed by solid-state reaction. A solution of iron (III) acetylacetonate and tributyl phosphate in toluene was used to produce amorphous, nanosized FePO4⋅H2O in a spray-flame reactor which was then milled with Li2CO3 and glucose to produce a LiFePO4/C composite material in a solid-state reaction. The influence of calcination temperature and carbon content on the properties of the resulting material was investigated using specific surface area measurements (BET), X-ray diffraction (XRD), electron microscopy, and electrochemical characterization. The impact of manganese addition on the electrochemical behavior was analyzed using cyclic voltammetry (CV) and constant-current (CC) measurements. XRD shows that the combination of gas-phase synthesis and subsequent solid-state reaction yields highly pure LiFePO4/C. BET measurement revealed that the particle size of LiFePO4 in the composite depends on the amount of glucose. A discharge capacity of more than 140 mAh/g at C/20 is achieved for LiFePO4/C with a carbon content of 6 wt%. This material supports high charge as well as discharge rates delivering more than 60 mAh/g at 16 C and sustains good cycle stability providing 115 mAh/g at 1 C. The energy density of the olivine increases about 10 % by substituting 30 mol% of iron by manganese while preserving the electrochemical performance of pure LiFePO4/C.

LiFePO4 microcrystals as an efficient heterogeneous Fenton-like catalyst in degradation of rhodamine 6G.

We present a novel heterogeneous Fenton-like catalyst of LiFePO4 (LFP). LFP has been widely used as an electrode material of a lithium ion battery, but we observed that commercial LFP (LFP-C) could act as a good Fenton-like catalyst to decompose rhodamine 6G. The catalytic activity of LFP-C microparticles was much higher than a popular catalyst, magnetite nanoparticles. Furthermore, we found that the catalytic activity of LFP-C could be further increased by increasing the specific surface area. The reaction rate constant of the hydrothermally synthesized LFP microcrystals (LFP-H) is at least 18 times higher than that of magnetite nanoparticles even though the particle size of LFP is far larger than magnetite nanoparticles. The LFP catalysts also exhibited a good recycling behavior and high stability under an oxidizing environment. The effects of the experimental parameters such as the concentration of the catalysts, pH, and the concentration of hydrogen peroxide on the catalytic activity of LFP were also analyzed.

Reducing the particle size of LiFePO4 enabled by yeast

Single-phased LiFePO4 with smaller particle size were successfully prepared via hydrothermal route assisted by yeast acted as both size-reducing agent and carbon sources. The as-synthesized product exhibited excellent electrochemical property and cycling stability, We believe that this promising and facile synthesis-strategy enables other hydrothermally synthesized materials with minimizing particle size.

Effect of Heat-Treatment Condition on the Morphology and Electrochemical Property of LiFePO<sub>4</sub>

Liquid co-precipitation method was applied to produce LiFePO4 cathode materials in which Ferrous carbonate was used as raw material. The morphology and electrochemical property of LiFePO4 were characterized by XRD, scanning electron microscopy (SEM) and charge/discharge test respectively. The results show when the precursor was synthesized at 80°C and then heat treated at 700°C for 5h, the particle size of LiFePO4 was 0.1-1μm and the obtained LiFePO4 shows impressive discharge specific capacity of 155mAh•g-1 at 1C rate.

Effect of multi-walled carbon nanotubes on the thermal stability and surface morphology of LiFePO4 cathode material

A novel network composite cathode was prepared by mixing LiFePO4 particles with multiwalled carbon nanotubes (MWCNTs). LiFePO4 particles were connected by MWCNTs and a polymer binder, polypyrrole-polyethylene glycol (PPy-PEG), to form a three-dimensional network. The surface morphology and thermal stability of the LiFePO4-MWCNT/PPy-PEG composite cathode were investigated by scanning electron microscopy, thermogravimetric analysis and pyrolysis capillary gas chromatography. It was found by scanning electron microscopy that the particle size of LiFePO4 in the LiFePO4-MWCNT sample was smaller than that of the pure LiFePO4 and the structure in the LiFePO4-MWCNT/PPy-PEG sample was more homogeneous than in the LiFePO4-MWCNT/PPy sample. Thermogravimetric analysis indicated that PPy-PEG blend polymer in combination with MWCNTs considerably improves the thermal stability of the final cathode material. Pyrolysis capillary gas chromatography measurements at 500 °C showed a decreased thermal stability of organic species contained in the composite cathode material. The addition of MWCNTs was an effective way to increase homogeneity and thermal stability of the LiFePO4-MWCNT/PPy-PEG cathode material.

Reducing the particle size of LiFePO4 enabled by yeast

Reducing the particle size of LiFePO4 enabled by yeast

Preparation and performance of LiFePO 4 and LiFePO 4/C cathodes by freeze-drying

LiFePO 4 and LiFePO 4/C cathodes were prepared by freeze-drying technology. The as-prepared powders were characterized and capacities of cathodes were investigated. LiFePO 4 and LiFePO 4/C had small particle size and narrow particle size distribution, the particle size of LiFePO 4/C (174.5 nm) was smaller than that of LiFePO 4. The capacity of LiFePO 4/C was higher than that of LiFePO 4 under different ratio, the capacity of fading was not obvious on their cycle performances, both of them had better cycle performance.

Structure optimization and the structural factors for the discharge rate performance of LiFePO 4/C cathode materials

Carbon coating and iron phosphides of high electron conductivity were introduced into the LiFePO 4 materials which were derived via a sol–gel method in order to improve the high discharge rate performance. The start constituents were FeC 2O 4·2H 2O, LiOH·H 2O, NH 4H 2PO 4 and ethylene glycol. Effects of the calcination temperature and the ethylene glycol on the structure and the electrochemical performance of the LiFePO 4 materials were investigated. Structure analyses showed that the addition of ethylene glycol caused an obvious decrease in the particle size of LiFePO 4. Calcination temperature and ethylene glycol jointly affected the formation of iron phosphides. Combining the electrochemical testing, it was found that, at low discharge rate, small particle size and high content of LiFePO 4 were much important for the capacity rather than the iron phosphides, and relative high content of Fe 2P (e.g. 8 wt.%) even worsened the capacity. However, with the increase of the discharge rate, the high electron conductive iron phosphides turned to play important role on the capacity. Fe 2P effectively increased both the reaction and diffusion kinetics and hence enhanced the utilization efficiency of the LiFePO 4 at high discharge rate. Combining relative small particle size, even 2 wt.% of iron phosphides could improve the high rate performance of LiFePO 4/C significantly.

Synthesis of carbon-coated LiFePO 4 nanoparticles with high rate performance in lithium secondary batteries

A novel preparation technique was developed for synthesizing carbon-coated LiFePO 4 nanoparticles through a combination of spray pyrolysis (SP) with wet ball milling (WBM) followed by heat treatment. Using this technique, the preparation of carbon-coated LiFePO 4 nanoparticles was investigated for a wide range of process parameters such as ball-milling time and ball-to-powder ratio. The effect of process parameters on the physical and electrochemical properties of the LiFePO 4/C composite was then discussed through the results of X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), the Brunauer–Emmet–Teller (BET) method and the use of an electrochemical cell of Li|1 M LiClO 4 in EC:DEC = 1:1|LiFePO 4. The carbon-coated LiFePO 4 nanoparticles were prepared at 500 °C by SP and then milled at a rotating speed of 800 rpm, a ball-to-powder ratio of 40/0.5 and a ball-milling time of 3 h in an Ar atmosphere followed by heat treatment at 600 °C for 4 h in a N 2 + 3% H 2 atmosphere. SEM observation revealed that the particle size of LiFePO 4 was significantly affected by the process parameters. Furthermore, TEM observation revealed that the LiFePO 4 nanoparticles with a geometric mean diameter of 146 nm were coated with a thin carbon layer of several nanometers by the present method. Electrochemical measurement demonstrated that cells containing carbon-coated LiFePO 4 nanoparticles could deliver markedly improved battery performance in terms of discharge capacity, cycling stability and rate capability. The cells exhibited first discharge capacities of 165 mAh g −1 at 0.1 C, 130 mAh g −1 at 5 C, 105 mAh g −1 at 20 C and 75 mAh g −1 at 60 C with no capacity fading after 100 cycles.

Electrochemical Properties of LiFePO<sub>4</sub>/C Composite Improved by High Energy Milling

The electrochemical properties of LiFePO4 as a cathode of lithium ion batteries considerably depend on a particle size of LiFePO4 and a condition of carbon coating. In this study, LiFePO4 powders were prepared using ultrasonic spray pyrolysis method, and then LiFePO4/C composites were made by infiltrating sucrose solution into LiFePO4 powders, drying, high-energy milling and annealing. The effects of high-energy milling were analyzed by comparing with electrochemical properties of powders synthesized without high-energy milling. It was found that the milling process drastically reduced the particle size of synthesized powders and electrical conductivity, and improved discharge capacity, cycle stability and rate performance.

Synthesis and electrochemical properties of metals-doped LiFePO 4 prepared from the FeSO 4·7H 2O waste slag

FePO 4· xH 2O precursor was synthesized by using raw materials, FeSO 4·7H 2O waste slag and H 3PO 4, without any purifying process. Crystalline metals-doped LiFePO 4 was prepared by heating an amorphous LiFePO 4. The amorphous LiFePO 4 was obtained via a novel ambient temperature reduction method, using the as-prepared FePO 4· xH 2O, oxalic acid and Li 2CO 3 as raw materials. ICP analysis confirms that a small amount of Ti, Al and Ca deposited in precursor. XRD and Rietveld-refined results show that the metals-doped LiFePO 4 is single olivine-type phase and well crystallized, Ti atoms occupy Li (M1) site, resulting in the formation of cation-deficient solid solution. From SEM and corresponding elemental mapping images, it could be found that the particle size of LiFePO 4 is about 200–500 nm, and the distribution of elements (Fe, P and Ti) is homogeneous. The electrochemical performance of LiFePO 4 cathode was evaluated by galvanostatic charge/discharge test. The results indicate that the metals-doped LiFePO 4, prepared from the FeSO 4·7H 2O waste slag, delivers a capacity of 161, 153, 145, 134 and 112 mAh g −1 at 0.1 C, 0.5 C, 1 C, 2 C and 5 C rate, respectively, and shows an excellent cycling performance at moderate current rates (up to 2 C).

Synthesis and electrochemical properties of olivine-type LiFePO 4/C composite cathode material prepared from a poly(vinyl alcohol)-containing precursor

Olivine structure LiFePO 4/C composite powders are synthesized as cathode materials for Li-ion batteries via a conventional solid-state reaction. Improvement in electrochemical performance has been achieved by using poly(vinyl alcohol) as the carbon sources for the as-prepared materials. The influence of the heat treatment on the physical and the electrochemical properties of LiFePO 4/C materials is investigated. To examine the effect of added carbon content on the properties of materials, a one-step heat treatment has been employed with control of the PVA content in the precursor. Six samples were prepared with 0, 1, 3, 5, 10 and 30 wt.% PVA added to the raw materials. The particle size of LiFePO 4 decreases as the carbon content increases. Materials with medium carbon contents have a small charge-transfer resistance and thus exhibit superior electrochemical performance. Interestingly, for a LiFePO 4/C composite with a low PVA content, an unusual plateau at 4.3 V is observed. It is considered that this is due to the Fe 3+/Fe 4+ redox reaction of Fe 3+ compounds that are present as an impurity. For samples with a high PVA amount, a thicker carbon coating provides an obstacle to improve the electrochemical properties.

Morphological investigation of sub-micron FePO 4 and LiFePO 4 particles for rechargeable lithium batteries

Microstructural variations of amorphous FePO 4 and LiFePO 4 (the latter obtained by chemical lithiation of the former) as a result of the annealing temperature have been studied by Thermogravimetric Analysis (TGA)/Differential Thermal Analysis (DTA), chemical analysis, Brunauer–Emmet–Taylor (BET) and Scanning Electron Microscopy (SEM) techniques. Round-shaped amorphous FePO 4 particles 40–80 nm in size are obtained after heating (at 400 °C) amorphous FePO 4·2H 2O in air (previously prepared by a precipitation route). On further heating at 650 °C, in air, crystalline trigonal FePO 4 of crystallite size <200 nm is formed. Round-shaped amorphous LiFePO 4 particles 40–80 nm in size crystallize by heating at 550 °C in Ar+5%H 2 for 3 h. After thermal treatment, LiFePO 4 particles are interconnected by necks, which resembled a sintering process. The particle size of LiFePO 4 increases with an increase of temperature up to 750 °C, but an abnormal growth is evident at annealing temperatures above 650 °C. DTA analysis showed two exothermic peaks at 547 and 768 °C for FePO 4 due to phase transitions, whereas for LiFePO 4 two exothermic effects at 496 and 567 °C are shown.