Synthesis Of LiFePO4 Research Articles

Synthesis of LiFePO4 using adenosine triphosphate as a new organic phosphorus source and its solvothermal reaction process

LiFePO4 is prepared by hydrothermal method using phosphoric acid (named as LFP-a) or adenosine triphosphate (LFP-b) as phosphoric sources, respectively. The effects of two phosphorus sources on crystal structure, particle morphology and electrochemical properties of the materials are investigated. Meanwhile, the mechanism of adenosine triphosphate as phosphoric source to synthesis LiFePO4 is proposed. The results show that the phosphorus source has significant influence on the synthesized materials. Compared with LFP-a, LFP-b material has higher crystallinity, better particle uniformity and dispersion. This is the result of the slow release of Li3PO4 in the hydrothermal process of the ATP-dominated precursor solution, and the subsequent reaction is relatively ordered, resulting in excellent electrochemical performance: the reversible capacity at 1 C is 148.24 mAh g−1, 137.01 mAh g−1 after 100 cycles, and the capacity retention rate is 92.4 %. This work provides a reference for the preparation of high-performance LiFePO4 from organophosphorus sources.

Formation kinetics of sol-gel derived LiFePO4 olivine analyzed by reliable non-isothermal approach

The formation kinetics of LiFePO4 Olivine synthesized through sol-gel route has been studied by non-isothermal approach. LiFePO4 precursors were prepared by mixing lithium dihydrogen phosphate (LiH2PO4) and iron (III) citrate (C6H5FeO7) and subsequently calcined in an Argon atmosphere at temperatures ranged from of 300–900 °C to form LiFePO4 products. Thermal behaviors of calcination process were analyzed by thermogravimetry (TGA) and differential scanning calorimetry (DSC) simultaneously, while the mineralogical properties of LiFePO4 were characterized using X-ray diffractometer (XRD). The kinetic parameters were determined by Ozawa–Flynn–Wall (OFW), Kissinger, and Kissinger-Akahira-Sunose (KAS) methods, and the reaction mechanism model was evaluated by Coats–Redfern approach. The results indicated that the reaction model of LiFePO4 formation agreed with the three-dimensional diffusion mechanism. The temperature had an essential role in the synthesis of LiFePO4. The optimum calcination temperature was 700 °C where this condition produced LiFePO4 Olivine with high degree of crystallinity, better lattice parameters and phase purity.

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 .

The influence of the Li+ addition rate during the hydrothermal synthesis of LiFePO4 on the average and local structure.

A hydrothermal method was used to synthesize LiFePO4 to explore the effect of the rate of addition of the Li+ precursor to a mixture of the Fe2+ and PO43- precursors. Both the average and local structures were investigated using powder X-ray diffraction, Mössbauer spectroscopy and X-ray absorption spectroscopy. Slower addition rates led to increased oxidation of Fe2+ to Fe3+ despite purging all solutions constantly, as well as increased defects. The local structure as determined by extended X-ray absorption fine structure displayed far less variation between the samples. The formation of a Li3PO4 impurity appeared to be independent of the Li+ addition rate.

Effect of the Heating Rate to Prevent the Generation of Iron Oxides during the Hydrothermal Synthesis of LiFePO4.

Lithium-ion batteries (LIBs) have gained much interest in recent years because of the increasing energy demand and the relentless progression of climate change. About 30% of the manufacturing cost for LIBs is spent on cathode materials, and its level of development is lower than the negative electrode, separator diaphragm and electrolyte, therefore becoming the “controlling step”. Numerous cathodic materials have been employed, LiFePO4 being the most relevant one mainly because of its excellent performance, as well as its rated capacity (170 mA·h·g−1) and practical operating voltage (3.5 V vs. Li+/Li). Nevertheless, producing micro and nanoparticles with high purity levels, avoiding the formation of iron oxides, and reducing the operating cost are still some of the aspects still to be improved. In this work, we have applied two heating rates (slow and fast) to the same hydrothermal synthesis process with the main objective of obtaining, without any reducing agents, the purest possible LiFePO4 in the shortest time and with the lowest proportion of magnetite impurities. The reagents initially used were: FeSO4, H3PO4, and LiOH, and a crucial phenomenon has been observed in the temperature range between 130 and 150 °C, being verified with various techniques such as XRD and SEM.

Controlled Hydrothermal/Solvothermal Synthesis of High-Performance LiFePO4 for Li-Ion Batteries.

The sluggish Li-ion diffusivity in LiFePO4 , a famous cathode material, relies heavily on the employment of a broad spectrum of modifications to accelerate the slow kinetics, including size and orientation control, coating with electron-conducting layer, aliovalent ion doping, and defect control. These strategies are generally implemented by employing the hydrothermal/solvothermal synthesis, as reflected by the hundreds of publications on hydrothermal/solvothermal synthesis in recent years. However, LiFePO4 is far from the level of controllable preparation, due to the lack of the understanding of the relations between the synthesis condition and the nucleation-and-growth of LiFePO4 . In this paper, the recent progress in controlled hydrothermal/solvothermal synthesis of LiFePO4 is first summarized, before an insight into the relations between the synthesis condition and the nucleation-and-growth of LiFePO4 is obtained. Thereafter, a review over surface decoration, lattice substitution, and defect control is provided. Moreover, new research directions and future trends are also discussed.

Hydrothermal synthesis of LiFePO4 particles with controlled morphology

Lithium iron phosphate was prepared by hydrothermal synthesis using LiOH·H2O, FeSO4·7H2O, (NH4)2HPO4, and aminoterephthalic acid (ATPA) as raw materials. The effects of ATPA concentration on particle morphology and electrochemical property were investigated. The samples were characterized by scanning electronic microscope (SEM), X-ray powder diffraction (XRD), infrared absorption spectroscopy (IR) and elemental analysis. The results showed that the particles exhibit a rod-like morphology in the absence of ATPA. When ATPA is added to the system, the particles crystallize as hexagonal plates. An increase in the ATPA concentration leads to the formation of structures with a more complex hierarchical arrangement of structural elements. The resulting particles are expected to serve as a cathode material for industrial needs in electric vehicles (EVs), hybrid electric vehicles (HEVs), and other mobile or portableelectrical devices.

USING OF ATOMIC LAYER DEPOSITION METHOD FOR OBTAINING THIN FILMS BASED ON LiMn2O4 AND LiFePO4

An approach to the synthesis of LiFePO4 and LiMn2O4 by atomic layer deposition is proposed and successfully implemented. The main regularities of the process are revealed and the method of synthesis realization is proposed. The following reagents were proposed and used: 2,2,6,6-tetramethylheptan-3,5 - dione of manganese, oxygen, iron (II) chloride, trimethyl phosphate, water and lithium tret-butylate. Nitrogen was used as an inert gas for purging the reactor and as a carrier gas. The influence of process parameters on the synthesis of thin films based on LiFePO4 and LiMn2O4 is described. It has been established that the phase composition of the resulting films is influenced by the time of precursor release and the process temperature. It is concluded that the increase in process temperature has a positive effect on the density of thin films of LiFePO4 and LiMn2O4. The optimum deposition temperature of LiFePO4 and LiMn2O4 is 400 ºC. It was shown that it is possible to regulate the content of each element and phase composition in films based on LiFePO4 and LiMn2O4 by changing the time of precursors release. The optimal time for the release of precursors for the synthesis of LiFePO4 and LiMn2O4 is 4 s under the stated conditions. Of great importance is the time of release of oxidizing agents-4 and 6 s for the deposition of LiFePO4 and LiMn2O4, respectively. The correlation of the layer growth rate per cycle was revealed, which was 0.2 nm/cycle for the synthesis of LiFePO4. The film obtained in the process is X-ray amorphous. To obtain the crystal structure, the films were annealed in argon at a temperature of 800 ºC. The mechanism of interaction of precursors with the substrate surface is studied. The influence of substrate activation on the uniformity of film growth is revealed.

Synthesis and Characterization of LiFePO4-PANI Hybrid Material as Cathode for Lithium-Ion Batteries.

This work focuses on the synthesis of LiFePO4–PANI hybrid materials and studies their electrochemical properties (capacity, cyclability and rate capability) for use in lithium ion batteries. PANI synthesis and optimization was carried out by chemical oxidation (self-assembly process), using ammonium persulfate (APS) and H3PO4, obtaining a material with a high degree of crystallinity. For the synthesis of the LiFePO4–PANI hybrid, a thermal treatment of LiFePO4 particles was carried out in a furnace with polyaniline (PANI) and lithium acetate (AcOLi)-coated particles, using Ar/H2 atmosphere. The pristine and synthetized powders were characterized by XRD, SEM, IR and TGA. The electrochemical characterizations were carried out by using CV, EIS and galvanostatic methods, obtaining a capacity of 95 mAhg−1 for PANI, 120 mAhg−1 for LiFePO4 and 145 mAhg−1 for LiFePO4–PANI, at a charge/discharge rate of 0.1 C. At a charge/discharge rate of 2 C, the capacities were 70 mAhg−1 for LiFePO4 and 100 mAhg−1 for LiFePO4–PANI, showing that the PANI also had a favorable effect on the rate capability.

Influence Comparison of Precursors on LiFePO4/C Cathode Structure for Lithium Ion Batteries

<p>Electricity is the most energy demanded in this era. Energy storage devices must be able to store long-term and portable. A lithium ion battery is a type of battery that has been occupied in a secondary battery market. Lithium iron phosphate / LiFePO<sub>4</sub> is a type of cathode material in ion lithium batteries that is very well known for its environmental friendliness and low prices. LiFePO<sub>4</sub>/C powder can be obtained from the solid state method. In this study the variables used were the types of precursors : iron sulfate (FeSO<sub>4</sub>), iron oxalate (FeC<sub>2</sub>O<sub>4</sub>) and FeSO<sub>4</sub>+charcoal. Synthesis of LiFePO<sub>4</sub>/C powder using Li:Fe:P at 1:1:1 %mol. Based on the XRD results, LiFePO<sub>4</sub>/C from FeSO<sub>4</sub>+charcoal shows the LiFePO<sub>4</sub>/C peaks according to the JCPDS Card with slight impurities when compared to other precursors. XRD results of LiFePO<sub>4</sub>/C with precursors of FeSO<sub>4</sub> or FeC<sub>2</sub>O<sub>4</sub> shows more impurities peaks. This LiFePO<sub>4</sub>/C cathode is paired with lithium metal anode, activated by a separator, LiPF<sub>6</sub> as electrolyte. Then this arrangement is assembled become a coin cell battery. Based on the electrochemical results, Initial discharge capacity of LiFePO<sub>4</sub>/C from the FeSO<sub>4</sub> precursor is 19.72 mAh/g, while LiFePO<sub>4</sub>/C with the FeC<sub>2</sub>O<sub>4</sub> precursor can obtain initial discharge capacity of 17.99 mAh/g, and LiFePO<sub>4</sub>/C with FeSO<sub>4</sub>+charcoal exhibit initial discharge capacity of 21.36 mAh/g. This means that the presence of charcoal helps glucose and nitrogen gas as reducing agents.</p>

Effect of Fast Heating and Cooling in the Hydrothermal Synthesis on LiFePO4 Microparticles

Hydrothermal synthesis is a chemical process that has gained much interest in recent years, especially for the synthesis of LiFePO4 since it is a method that requires a relatively low temperature, ...

Alkyl chain length effects of hydroxyl-functionalized imidazolium ionic liquids in the ionothermal synthesis of LiFePO4

LiFePO4 is one of the most promising cathode materials for lithium ion batteries. To investigate the role of the cation in the ionothermal synthesis of LiFePO4, three imidazolium-based ionic liquids, containing hydroxyl-terminated alkyl chains of various lengths, were synthesized using microwave-assisted methods: 1-(3-hydroxypropyl)-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide, 1-(6-hydroxyhexyl)-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide, and 1-(9-hydroxynonyl)-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide. An ionothermal synthesis was attempted with each ionic liquid, using various precursors. The resulting solid products were investigated using powder X-ray diffraction and solid state nuclear magnetic resonance spectroscopy. The yield of LiFePO4 increased with an increase in the hydroxyl-terminated alkyl chain length on the imidazolium.

Spectroscopic characterization of LiFePO4 as cathode material for Li-ion battery prepared in the pulse thermo-acoustic reactor

Lithium iron phosphate (LiFePO4) is a cathode material for the rechargeable-lithium batteries. In this paper is presented a novel method of fabrication carbon-coated LiFePO4 in a pilot reactor built according to the principles of the thermo-acoustic burner of Helmholtz-type. Crystalline powder with a high percentage of LiFePO4 was synthesized by incomplete combustion, i.e. in the reductive atmosphere, and calcined at 700?C for 6 h. The obtained samples were characterized by X-ray diffraction, IR and Raman spectroscopy. The aim of this study was to demonstrate the production of the high-quality lithium-ion cathode material by the incomplete combustion. The synthesis of LiFePO4 is completed during calcination and an ordered structure is attained. Fast synthesis in the reactor (less than 2 s) is achieved due to the reduction in the size of reactant's particles and a huge number of collisions owing to their strong turbulent flow associated with explosive combustion.

The influence of process conditions on the phase composition of the LiFePO4 film obtained by the atomic layer method

The approach to synthesis of LiFePO4 using the atomic layer deposited method (ALD-method) is offered and basic laws of the process revealed. Influence of synthesis conditions, precursors’ nature and the sequence of their introduction into the reactor upon the phase composition and morphology of the formed films was studied. The phase composition of the film obtained with the use of ALD-method was investigated in details using a wide series of physical and chemical methods.

One-Pot Synthesis of LiFePO<sub>4</sub> Nano-Particles Dispersed in N-Containing Melamine-Formaldehyde Carbon Matrix as the Cathode Materials for Large Scale Lithium Ion Batteries

LiFePO4 is considered as the promising cathode material for a large-scale Li batteries used in electrical vehicles (EVs). However, a practical use of LiFePO4 cathode is limited by its low ionic conductivity, resulting in low battery’s power performance. This work, a facile and practical method to promote ionic conductivity and capacity of LiFePO4 was developed by dispersing LiFePO4 nanoparticles into a porous nitrogen-riched carbon matrix by employing one-pot synthesis approach. The N-containing carbon porous matrix was prepared by utilizing melamine-formaldehyde (MF) resin as the N-containing carbon precursor and Pluronic F127 as the porous template. The pseudo capacitive effect attributed from lone-pair electrons into melamine functional group was expected to support Li ion transport. After carbonization at 600 °C, uniform LiFePO4 nanocomposite clusters with an average size of about 50-300 nm were obtained. The influence of the molar ratio between pluronic F127 and melamine-formaldehyde (i.e. F127:MF molar ratio as 0:1, 0.03:1, 0.3:1) on the LiFePO4 nanocomposite’s morphology and crystalline structure was investigated by using scanning electron microscope and X-ray diffraction technique. The results show that increasing F127 concentrations support more porous structure formation, leading to a higher surface area but does not affect the LiFePO4 nanocrystalline structure. According to the highest surface area, the N-doped carbon coated LiFePO4 composite product obtained from the molar ratio of F127:MF as 0.3:1 exhibited highest discharging specific capacity of 158.1 mAh g-1, at a rate of 0.1 C and also shows high cycle stability.

Enhanced performance of LiFePO4 originating from the synergistic effect of graphene modification and carbon coating

LiFePO4@Carbon/reduced graphene oxide (LFP@C/rGO) composites as cathode materials for lithium-ion batteries were prepared by a simple solvothermal method followed with a carbon coating. The characterizations indicated that LiFePO4 particles with pure orthorhombic olivine phase were attached to graphene oxide, which could be reduced in the synthesis of LiFePO4 and constructed a conductive network in the composite. After a post carbon encapsulation, a uniform and thin carbon layer on LiFePO4 was formed and could quickly collect electrons via a shorter pathway around LiFePO4 nanoparticles during the charge/discharge. The results showed LFP@C/rGO composites delivered a discharge specific capacity of 148.3 mAh/g at the rate of 1 C, higher than LiFePO4 only modified with graphene or coated with carbon layers. The discharge capacity of 129 mAh/g can still be maintained when the current density increased to 20 C. Furthermore, LFP@C/rGO manifested a satisfactory lifespan and no capacity fading was observed after 200 cycles at the rate of 10 C. Compared with synthesized LiFePO4@C, LFP@C/rGO composites also exhibited a high capacity of 108 mAh/g at −20 °C at a rate of 1 C. Even after 500 charge/discharge cycles, capacity fading was scarcely seen. Electrochemical tests suggested the unique architecture resulted in a synergistic effect between 3D reduced graphene oxide (rGO) conductive network and carbon coating, which remarkably improved the conductivity of electrode and electrochemical kinetics, contributing to outstanding rate performance and cycle life.

Synthesis of LiFePO4 by In Situ Polymerization Restriction Method for Pouch-Typed Cell

We report a two-step approach to synthesize nanosized LiFePO4C composite by an in situ polymerization restriction method. First step, the Fe2O3@polyaniline is fabricated with in situ polymerization method. Secondly, the as-obtained Fe2O3 coated with polyaniline is mixed with LiH2PO4, followed by carbothermal reduction process. The outer polyaniline shell coating Fe2O3 can restrict the aggregation of particles and serves as carbon-containing precursor. The studies of electrochemical performances were carried out at full cell level. The results show that the assembled pouch-typed full-cells with as-obtained LiFePO4 present excellent rate capability and cycle life.

Effects of heating rate on morphology and performance of lithium iron phosphate synthesized by hydrothermal route in organic-free solution

Flake-like LiFePO4 were hydrothermally synthesized in an organic-free solution at heating rates of 0.5, 1.5, 3, and 5 °C min−1. The heating rate has a marked influence on crystal morphology but scarcely on phase purity. The reason for morphology variations is discussed based upon the solubility of precursors Li3PO4 and Fe3(PO4)2·8H2O. The optimum heating rate for hydrothermal synthesis of LiFePO4 is 3 °C min−1. The as-synthesized material exhibits a high specific capacity, excellent rate capability, good low-temperature performance and Li+ diffusivity after carbon coating, all of which could be ascribed to shortened Li+ diffusion distance and higher crystallization degree of the crystalline.

Environmentally benign and scalable synthesis of LiFePO4 nanoplates with high capacity and excellent rate cycling performance for lithium ion batteries

An economical and scalable synthesis route of LiFePO4 nanoplate precursors is successfully prepared in pure water phase under atmosphere without employing environmentally toxic surfactants or high temperature and high pressure compared with traditional hydrothermal or solvothermal methods, which also involves recycling the filtrate to regenerate LiFePO4 nanoplate precursors and collecting by-product Na2SO4. The LiFePO4 precursors present a plate-like morphology with mean thickness and length of 50–100 and 100–300nm, respectively. After carbon coating, the LiFePO4/C nanoparticles with particle size around 200nm can be observed which exhibit a high discharge capacity of 160mAhg−1 at 0.2C and 107mAhg−1 at 20C. A high capacity retention closed to 91% can be reached after 500 cycles even at a high current rate of 20C with coulombic efficiency of 99.5%. This work suggests a simple, economic and environmentally benign method in preparation of LiFePO4/C cathode material for power batteries that would be feasible for large scale industrial production.

Hierarchy concomitant in situ stable iron(II)−carbon source manipulation using ferrocenecarboxylic acid for hydrothermal synthesis of LiFePO4 as high-capacity battery cathode

The iron precursor of lithium iron phosphate (LiFePO4) is highly prone to oxidation to Fe3+ during the hydrothermal synthesis. The Fe3+ impurities in LiFePO4 restrict the conduction path of Li+ ions in LiFePO4, which negatively affect the cell performance. In this paper, we report that ferrocenecarboxylic acid possessing an extremely stable Fe2+ species and as carbon source has been used successfully to suppress Fe3+ impurities in LiFePO4. The X-ray diffraction results reveal that Li2CO3 first reacts with (NH4)2HPO4 to form Li3PO4 at low temperatures, which above 160°C further reacts with ferrocenecarboxylic acid to give LiFePO4. The infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, and elemental analysis results show that the carbon sources during calcination of LiFePO4 are derived from polymers through sequential [4+2] cycloaddition reactions of cyclopentadiene and 1,3-cyclopentadiene-1-carboxylic acid during decomposition of ferrocenecarboxylic acid. The electron paramagnetic resonance results show that the percentage of Fe3+ in the synthesized LiFePO4 is as low as 0.5 mol%. A plausible reaction mechanism for the hydrothermal synthesis of LiFePO4 is also proposed. The as-synthesized LiFePO4 shows an orthorhombic olivine with a discharge capacity of 158mAhg−1 at a discharge rate of 0.1C. The cell also shows excellent C-rate and cycle-life performances.