Synthesis Of Lithium Iron Phosphate Research Articles

In-situ preparation of silk-cocoon derived carbon and LiFePO4 nanocomposite as cathode material for Li-ion battery

We report a natural fiber template method for the synthesis of lithium iron phosphate carbonized silk cocoon (LFP-CS), as cathode electrode material for lithium-ion batteries. Bombyx-mori silk-cocoons was used as template and heated along with LFP precursor to obtain a carbonized silk carbon network around LFP. The X-ray powder diffraction (XRD) shows a well crystalline single-phase olivine structured LFP-CS nanoparticle. Scanning electron microscope (SEM) and Transmission electron microscopy (TEM) revealed the spherical morphology of LFP nanoparticle, which was absorbed on the surface and sub-surface of the cocoon fibers. The LFP nanoparticles were uniformly dispersed within the layer of carbon sheet, forming conductive carbon network between individual particles. The electrochemical study revealed that the LFP-CS has a capacity of 163 mAh/g at 0.1C and 123 mAh/g at 5C rate with excellent cycle performance. Apparently, conductive carbon network formed could also increase the electrochemical performance of the electrode material.

High-temperature solid-phase synthesis of lithium iron phosphate using polyethylene glycol grafted carbon nanotubes as the carbon source for rate-type lithium-ion batteries

• The presence of PEG effectively solves the problem of agglomeration of CNTs. • LiFePO 4 cathode material synthesized by high-temperature solid-phase method using PEG/CNTs as carbon source, forming uniform tube- net -like 3D conductive network on the surface. • In the synthesis of LiFePO 4 cathode material, PEG plays the role of dispersant, binder and conductive agent. Lithium iron phosphate (LiFePO 4 )/polyethylene glycol (PEG)/carbon nanotubes (CNTs) are successfully synthesized by the high-temperature solid-phase. PEG grafted onto CNTs surface by covalent functionalization. During the high-temperature sintering process, PEG/CNTs form the uniform tube- net -like 3D conductive network, significantly improving electron mobility. Beneficial effects of PEG include: (1). The addition of PEG improves the dispersion of CNTs by increasing the number of surface defects and groups. (2). The cracking PEG forms porous carbon layer uniformly coated around LiFePO 4 to improve its electrical conductivity. (3). As a thermoplastic polymer, PEG becomes a binder at sintering temperatures up to around 70 °C, making the CNTs and LiFePO 4 contact more closely. Compared to LiFePO 4 /CNTs, LiFePO 4 /PEG/CNTs has superior electrochemical performance, as evidenced by improving rate performance (LiFePO 4 /PEG/CNTs discharges 113.5 mAh g −1 at 15C, LiFePO 4 /CNTs discharges 71.6 mAh g −1 at 15C) and high rate cycling retention (capacity retention of 96.6% at 5 C after 300 cycles for LiFePO 4 /PEG/CNTs, capacity retention of 90.6% at 5 C after 300 cycles for LiFePO 4 /CNTs). The architecture of the composite conducting network effectively solves the issue of the poor electron migration of LiFePO 4 .

Electrochemical crystallization for phosphate recovery from an electronic industry wastewater effluent using sacrificial iron anodes

With the circular economy in mind, recovery of iron phosphate, i.e., ferric phosphate or ferrous phosphate, from industrial wastewater is realized and the products recovered could be used in the synthesis of lithium iron phosphate for Li-ion secondary batteries. The formation of iron phosphate highly depends on pH and dissolved oxygen (DO) level. The present study focused on the phosphorus removal and recovery from the industrial wastewater effluent of a semiconductor plant by crystallization of iron phosphate. P recovery as iron phosphate was explored by means of electrochemical crystallization using a sacrificial iron anode under various DO levels (air sparging, mechanical mixing, and N2 purging) and pH values (both initial and fixed pH). Under the nitrogen purging condition, the P removal linearly increased with increasing of the Fe:P molar ratios, reaching 100% when the Fe:P molar ratio equals 1.5, which is the stoichiometric molar ratio of ferrous phosphate. The ferrous phosphate particles quickly settled and the crystalline structure was confirmed as vivianite. The final product obtained at pH 6.0 was composed of 82 wt% of vivianite. The operational cost of the electrochemical process was estimated to be only 23.5% of the costs required by the fluidized chemical crystallization process reported in the literature.

Application of the factorial design of experiments to hydrothermal synthesis of lithium iron phosphate

AbstractThe mathematical model of lithium iron phosphate prepared by hydrothermal method was established by factor experimental design. The effect of individual variables and their interactions were studied by the main effects plot and Interaction plot. The influence of ascorbic acid dosage on the discharge specific capacity was greater than the hydrothermal time and the hydrothermal temperature, and the influence degree of the latter two was equivalent and the interaction effect of hydrothermal time and ascorbic acid dosage has the greatest influence on the discharge specific capacity in three interaction effects. The optimized hydrothermal condition was hydrothermal time of 9 hours, hydrothermal temperature of 210°C and ascorbic acid dosage of 1.5 mmol in the experimental design range, with the initial discharge specific capacity of 0.1 C as 152.5 mAh g−1. The corresponding characterization was performed using electrochemical methods, XRD, SEM, and TEM. This study provided a protocol to factorially design better experiments to achieve excellent battery criterion in the context of lithium iron phosphate preparation.

Performance of Vanadium Doped and Carbon Bamboo/Carbon Black Coated Lithium Iron Phosphate for Battery Cathode

Synthesis of lithium iron phosphate (LiFePO4) via wet chemical followed by a hydrothermal method has been carried out. The preparation of LiFePO4 was begun with the precursor of LiOH, NH4H2PO4, and FeSO4.7H2O mixed stoichiometrically. After the synthesis, LiFePO4 was doped using vanadium and then coated using two types of carbon sources, i.e. carbon black blended with activated carbon pyrolyzed from bamboo, through a solid-state reaction. The materials were mixed using a ball-mill and subsequently characterized using a thermal analyzer (STA) to determine the sintering temperature. The result shows that LiFePO4 formation temperature is at 639°C. The sintering process was performed for 4 hours and the characterization was done using X-ray diffraction (XRD) and electron microscope (SEM) equipped with energy dispersive x-ray spectroscopy (EDX). The electrochemical impedance spectroscopy (EIS) testing was performed to show the conductivity of the formed materials. XRD result showed that LiFePO4/V/C phase has formed with an olivine structure, while the SEM result showed fair distribution and small particle size with some agglomerated microstructures. The EIS results showed that carbon coating on the active material increases the conductivity, whereas the addition of vanadium increases the conductivity of up to 5 wt.% vanadium but decreases at 7 wt.% vanadium.

Recycling of Lithium Iron Phosphate Batteries: Future Prospects and Research Needs

Since the first synthesis of lithium iron phosphate (LFP) as active cathode material for lithium-ion batteries (LIB) in 1996, it has gained a considerable market share and further growth is expected. Main applications are the fast-growing sectors electromobility and to a lesser extend stationary energy storage. Despite increasing return flows, so far, little emphasis has been put on the recycling of LFP batteries due to the low content of high-value metals. In this study, current developments in the LFP battery market are presented. Furthermore, recycling processes for LIBs are reviewed and their applicability for LFP batteries is assessed. Currently, China is the main market for LFP batteries and rapidly increasing return flows are observed. In Europe and the USA, other battery chemistries are predominant. For LFP battery recycling, individually adaptable processes based on mechanical treatment of the cells followed by hydrometallurgical processing of the active cathode material seem to be the most promising approach. However, at present, these processes are only available at pilot scale, the profitability and their environmental performance are questionable. Therefore, further research addressing these challenges is urgently needed.

Improving the Performance of LiFePO4 Cathode Material By: Finding out an Effective Mixing Ratio for Cathode Slurry and Implementing Calendaring Process

The olivine structured lithium iron (II) phosphate (LiFePO4) is a promising cathode material for use in lithium-ion batteries. It has a high operating voltage (~3.4 V vs Li/Li), nontoxic and environmentally benign [1]. Although It has high specific theoretical capacity (~ 170 mAh g− 1), at high ‘C’ rates the discharge capacity decreased exponentially. To get optimum and consistent discharge capacity at different ‘C’ rates, the conductivity has to be improved. Different percentage of PVDF and carbon black were used to prepare slurry mixture of LiFePO4 and then coated on bare aluminum and carbon coated aluminum foil to make the cathode electrodes. Coin cells were made and tested at 1/10 C, 1/5 C, ½ C and 1C rates. Also to compare the effect of binder on cell performance, distinct percentages of water based binder were used. For this experiment each sample cathode electrode were calendared to different densities. A comparison of uncalendered and calendared cathode electrode (with carbon-coated current collector and also non-carbon coated current collector) were made. Before calendaring, material density was 0.8424 gcm-3 at 146 µm thickness of cathode electrode and after calendaring, density increased to 1.59 g/cm-3at 97 µm thickness. Discharge capacity at different “C” rates shows that the calendared electrode provide consistent and better discharge capacity performance than the uncalendered electrode. Electrochemical impedance spectroscopy (EIS) test shows the calendaring of electrode exhibits a large decrease in contact resistance. Reference: [1] Seung-Ah Hong,Su Jin Kim, Kyung Yoon Chung, Myung-Suk Chun, Byung Gwon Lee, Jaehoon Kim, “Continuous synthesis of lithium iron phosphate (LiFePO4) nanoparticles in supercritical water: Effect of mixing tee”, The Journal of Supercritical Fluids, Elsevier, 2013.

Effect of operating parameters on synthesis of lithium iron phosphate (LiFePO4) particles in near- and super-critical water

Hydrothermal synthesis of lithium iron phosphate (LiFePO4) particles in near- and super-critical water was investigated in a batch reactor system. The phase identification and morphology of synthesized LiFePO4 particles were performed by Fourier Transform Infrared (FT-IR), powder X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The effect of operating parameters including temperature (400–450°C), pressure (200, 275 and 350bar) and reaction time (10 and 60min) were examined on particle size, size distribution, purity, crystalline structure, morphology, and electrochemical performance of the synthesized LiFePO4 in the presence of sodium sulphite (Na2SO3) as reducing agent. Highly crystalline LiFePO4 particles were synthesized at near-critical conditions (400°C, 200bar and 60min) with initial discharge capacity of 87mAhg−1 at 0.1 C-rate.

A Low Cost and High Capacity Synthesis of Lithium Iron Phosphate Using a Pulse Combustion Reactor System

We have developed a reactor for continuous synthesis of various metal oxide materials in oxidizing or reducing atmosphere. The capacity of the current pilot reactor version is 2 L of precursor per hour. In the case of synthesis of lithium iron phosphate this corresponds to 100 grams per hour and the procedure is scalable to 100 kilograms per hour. The apparatus is comprised of a pulse combustion type burner, which operates at a frequency of 150 – 240 Hz and a temperature above 1000 °C, a two fluid nozzle for spraying the precursors, and a reactor pipe, where the reaction takes place. The oxidizing and reducing atmosphere is controlled by setting a fuel rich or fuel lean burning. When working with reducing atmosphere the spraying gas is nitrogen, otherwise air or oxygen can be used. The particles are cooled down with air to about 150 °C and collected with an electrostatic precipitator. Here we demonstrate the functioning of the reactor on the example of lithium iron phosphate. The two precursors used consisted of iron nitrate and lithium carbonate, dissolved in nitric acid. The phosphorus source in one case was ammonium dihydrogen phosphate and triethyl phosphate in the other. As the fuel we used either urea combined with sucrose or glycine. All compounds were dissolved in deionized water. When the precursor is heated up, the water evaporates, and the remaining nitrates and organics react. This process is equivalent to solution combustion synthesis. However, changing the composition of the precursor strongly affects the morphology of the produced materials, which means that the reaction in the precursor is as important as the conditions in the reactor. By spraying such precursors into the hot zone of the reactor, which is held at about 800 °C, the formed droplets are each its own microreactor. The water from the droplets evaporates very fast because of the high temperature and good heat transfer in pulse combustion burners; the temperature in the reactor drops to about 700 °C. This leads to a precipitation of precursor salts and hinders the coalescence of droplets. After the salts reach a high enough temperature, the reaction starts so that a lot of gaseous products are produced. In the case of urea precursor, porous spheres with a diameter of 3 – 15 μm are formed; in the case of glycine precursor agglomerates of particles from 50 to 300 nm are formed. The particles in both cases are carbon coated, either due to carbonization of sucrose or an excess of glycine fuel. As synthesized lithium iron phosphate is partly amorphous, mainly because of the very short residence time at a temperature above 500 °C. Heat treatment in an Ar atmosphere at 700 °C for 3 hours yielded phase pure lithium iron phosphate. The as prepared and heat treated materials have been investigated using XRD, SEM, CHNS elemental analysis and ICP. The electrochemical behavior of as prepared and thermally treated materials has been investigated in a lithium half cell.

Microwave Synthesis of LiFePO4 from Iron Carbonyl Complex

Single mode microwave assisted synthesis of Lithium iron phosphate using iron carbonyl complex [Fe2(CO)9], as source of iron is reported in this paper. The suitable synthesis method for the LiFePO4 was designed based on FT-IR and TG-DTA studies of precursors. As prepared samples were characterized using different techniques such as X-ray diffraction, scanning electron microscope, field emission scanning electron microscope, transmission electron microscope, thermo gravimetric analysis, Raman spectroscope and electrochemical measurements. X-ray diffraction revealed that a single phase LiFePO4 powder can be synthesized quickly and easily by microwave processing. The surface analysis of the as prepared samples reveal that, it consist of nano-size particles with porous agglomeration, where the pores serve as channel for lithium supply and assist for augmentation of the electrochemical character of the product. The initial discharge capacities are 154.2, 132.2 and 121mAhg−1 at 0.1C, 0.5C and1C rate respectively. The obtained LiFePO4 has a high electrochemical capacity and good cyclic ability even after 50 cycles, which is attributed to the smaller particle size, porous agglomeration and graphitic carbon content.

Polyol Synthesis of Lithium Iron Phosphate with Carbon Nanotubes: Effect of Dispersion on Crystallinity and Electrochemical Performance

ABSTRACTCarbon nanotubes (CNTs) have been shown to be a viable conductive additive in Li-Ion batteries [1]. By using CNTs battery life, energy, and power capability can all be improved over carbon black, the traditional conductive additive. A significantly smaller weight percentage (5% CNTs) is needed to get the same conductivity as 20% carbon black. Many of the previous efforts found that a combination of conductive additives was most advantageous [2]. Unfortunately many of these efforts did not attend to the unique challenge that dispersing nanotubes presents and used non-optimal methods to disperse CNTs (e.g. ball milling) [3,4]. With poor dispersion a stable and resilient conductive network in the cathode is hard to form with CNTs alone. Here we investigate the formation of LiFePO₄ with CNTs using a polyol process synthesis.

Lithium iron phosphate spheres as cathode materials for high power lithium ion batteries

Electrode materials composed of micrometer- and sub-micrometer-sized spherical particles are of interest for lithium ion batteries (LIBs) because spheres can be packed with higher efficiency than randomly shaped particles and achieve higher volumetric energy densities. Here we describe the synthesis of lithium iron phosphate (LFP) phases as cathode materials with spherical morphologies. Spherical Li3Fe2(PO4)3 particles and LiFePO4 spheres embedded in a carbon matrix are prepared through phase separation of precursor components in confinement. Precursors containing Li, Fe, and P sources, pre-polymerized phenol–formaldehyde (carbon source), and amphiphilic surfactant (F127) are confined in 3-dimensional (colloidal crystal template) or 2-dimensional (thin film) spaces, and form spherical LFP particles upon heat treatment. Spherical Li3Fe2(PO4)3 particles are fabricated by calcining LiFePO4/C composites in air at different temperatures. LiFePO4 spheres embedded in a carbon matrix are prepared by spin-coating the LFP/carbon precursor onto quartz substrates and then applying a series of heat treatments. The spherical Li3Fe2(PO4)3 cathode materials exhibit a capacity of 100 mA h g−1 (83% of theoretical) at 2.5 C rate. LiFePO4 spheres embedded in a carbon matrix have specific capacities of 130, 100, 83, and 50 mA h g−1 at C/2, 2 C, 4 C, and 16 C rates, respectively (PF_600_2), revealing excellent high-rate performance.

Continuous synthesis of lithium iron phosphate (LiFePO4) nanoparticles in supercritical water: Effect of mixing tee

Continuous supercritical hydrothermal synthesis of olivine (LiFePO4) nanoparticles was carried out using mixing tees of three different geometries; a 90° tee (a conventional Swagelok® T-union), a 50° tee, and a swirling tee. The effects of mixing tee geometry and flow rates on the properties of the synthesized LiFePO4, including particle size, surface area, crystalline structure, morphology, and electrochemical performance, were examined. It was found that, when the flow rate increased, the particle size decreased; however, the discharge capacity of the particles synthesized at the high flow rate was lower due to the enhanced formation of Fe3+ impurities. The use of a swirling tee led to smaller-sized LiFePO4 particles with fewer impurities. As a result, a higher discharge capacity was observed with particles synthesized with a swirling tee when compared with discharge capacities of those synthesized using the 90° and 50° tees. After carbon coating, the order of initial discharge capacity of LiFePO4 at a current density of 17mA/g (0.1C) and at 25°C was swirling tee (149mAh/g)>50° tee (141mAh/g)>90° tee (135mAh/g). The carbon-coated LiFePO4 synthesized using the swirling tee delivered 85mAh/g at 20C-rate and at 55°C.

Hydrothermal synthesis of lithium iron phosphate using pyrrole as an efficient reducing agent

Lithium iron phosphate (LiFePO4) is synthesized by a hydrothermal process using pyrrole as an efficient reducing agent and a subsequent calcination. Observations through a scanning electron microscope and a transmission electron microscope (TEM) show that LiFePO4 has a diameter and length of 500nm and 3μm, respectively. The results of TEM and X-ray diffraction confirm that the structure of LiFePO4 is orthorhombic olivine. Raman and X-ray photoelectron spectroscopy results indicate that Fe3+ oxidized from reactant Fe2+ by air reacts with pyrrole, generating polypyrrole (PPy), and reduces to Fe2+. PPy that is generated can also serve as a carbon source in the subsequent calcination. In addition, the electrochemical measurement results show that the energy capacity of calcined LiFePO4/PPy is 153mAhg−1 at 0.2C. Calcined LiFePO4/PPy offers promising cycle-life performance in lithium-ion batteries.

N-Methyl-2-pyrrolidone-assisted solvothermal synthesis of nanosize orthorhombic lithium iron phosphate with improved Li-storage performance

Exploring an efficient and effective way for synthesis of lithium iron phosphate (LiFePO4) with good Li-storage performance is a good way to fully demonstrate their applications for Li-ion batteries. In this contribution, LiFePO4 nanoparticles were synthesized by a facile solvothermal process with water/N-methyl-2-pyrrolidone (NMP) solvent system at a moderate temperature of 180 °C. The product was determined as single-phase orthorhombic LiFePO4, and the presence of crystal growth inhibitor NMP was favourable for the formation of smaller-sized LiFePO4 particles with improved electrochemical properties. After a carbon coating process, the LiFePO4/C sample afforded a reversible capacity of 140 mA h g−1 at 0.5 C, 106 mA h g−1 at 5.0 C at room temperature, and 163 mA h g−1 at 0.5 C, 153 mA h g−1 at 5.0 C at the higher temperature of 60 °C, respectively. The long cycle test at 0.2 C showed that no noticeable capacity fading was observed. The present LiFePO4 obtained by the facile solvothermal process had good thermal and electrochemical stability, which were attributed to facile Li ion diffusion and a good electron transfer pathway in the solvothermal LiFePO4 product.

Synthesis and electrochemical properties of lithium iron phosphate

Original method for synthesis of lithium iron phosphate was developed. The method includes two stages: 1st, synthesis of iron phosphate from a mixture of ammonium dihydrophosphate and metal oxide; and 2nd, synthesis of lithium iron phosphate by thermal lithiation of the product obtained in the 1st stage, with mechanical activation of the precursor in the course of plastic deformation.

Continuous hydrothermal synthesis of lithium iron phosphate particles in subcritical and supercritical water

We have investigated the continuous hydrothermal synthesis of lithium iron phosphate (LiFePO 4) nanoparticles by reacting iron sulfate, phosphoric acid, and lithium hydroxide in a flow system. The effects of temperature, flowrate of water, and reactant concentration on the size and morphology of particles were investigated. In general, particle size increased with temperature and with increasing reactant concentration. Particle morphology, on the other hand, became more regular at high flowrates of water. Possible reasons for this behavior are given, and differences with batch hydrothermal synthesis of LiFePO 4 are highlighted. The different mechanisms in the two methods results in much smaller and more uniform particles being obtained in continuous hydrothermal synthesis than via batch hydrothermal synthesis.

Hydrothermal synthesis of lithium iron phosphate

LiFePO 4 is a potential cathode candidate for the next generation of secondary lithium batteries. The LiFePO 4 was synthesized by a hydrothermal process. Phase-pure material was obtained and the critical synthesis parameters were determined. Iron disorder onto the lithium sites can be eliminated by using temperatures in excess of 175 °C; above this temperature the crystalline unit cell was essentially identical to that of the high temperature material, with a volume of 291.3 ± 0.2 Å 3. The use of a soluble reductant, such as sugar or ascorbic acid, was found to minimize the oxidation of the iron to ferric. The electronic conductivity was enhanced by the deposition of carbon from the sugar, or by the addition of carbon nanotubes to the hydrothermal reactor. The electrochemical behavior of this material showed more than 90% lithium removal on charge and complete capacity retention over 50 cycles.

The Hydrothermal Synthesis of Lithium Iron Phosphate

AbstractWell-crystalline LiFePO4 particles were successfully prepared in the temperature range between 120 and 220°C, and complete ion ordering was obtained above 175°C where the unit cell dimensions were identical to high temperature material. The use of a soluble reductant, such as sugar or ascorbic acid, was found to minimize the oxidation of the iron to ferric. The electronic conductivity was enhanced by the deposition of carbon from the sugar, or by the addition of carbon nanotubes to the hydrothermal reactor when over 90% of the lithium could be de-intercalated electrochemically. We have extended the hydrothermal synthesis method to the Mn, Co and Ni analogs as well as to the mixed phosphates, such as LiMnyFe1-yPO4.