Fine-particle lithium iron phosphate LiFePO4 synthesized by a new low-cost aqueous precipitation technique (original) (raw)
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Chemistry and electrochemistry of lithium iron phosphate
Journal of Solid State Electrochemistry, 2008
We report here several synthesis routes and their respective drawbacks/advantages for the preparation of pure LiFePO 4 . We demonstrate the possibility of using LiFePO 4 for electrochemical applications, with respect that an effective carbon coating was realized onto the smallest particles. Actually, to bypass the weak ionic conductivity of lithium iron phosphate, the thinnest would be the particles; the highest would be the performance under severe electrochemical conditions.
A review of recent developments in the synthesis procedures of lithium iron phosphate powders
Journal of Power Sources, 2009
Olivine structure LiFePO 4 attracted much attention as a promising cathode material for lithium-ion batteries. The overwhelming advantage of iron-based compounds is that, in addition to being inexpensive and naturally abundant, they are less toxic than Co, Ni, and Mn. Its commercial use has already started and there are several companies that base their business on lithium phosphate technology. Still, there is a need for a manufacturing process that produces electrochemically-active LiFePO 4 at a low cost. Therefore the interest in developing new approaches to the synthesis of LiFePO 4 did not fade. Here is presented a review of the synthesis procedures used for the production of LiFePO 4 powders along with the highlights of doped and coated derivatives. Apart from already established conventional routes of preparation, numerous alternative procedures are mentioned.
A study on LiFePO 4 and its doped derivatives as cathode materials for lithium-ion batteries
Journal of Power Sources, 2006
LiFePO 4 , doped LiM x Fe 1−x PO 4 , and Li 1−x M x FePO 4 compounds have been prepared via a sol-gel synthesis method. The physical properties of the as-prepared lithium iron phosphates were characterised by X-ray diffraction, X-ray absorption near-edge spectroscopy (XANES), and magnetic susceptibility. The electrochemical properties lithium iron phosphates were tested by a variety of electrochemical techniques. Lithium iron phosphate electrodes demonstrated a stable discharge capacity of 160-165 mAh g −1 , almost approaching the theoretical capacity. The good electronic conductivity and nanocrystalline could contribute to the unique performance of lithium iron phosphate electrodes. Lithium iron phosphates have a significant potential to be used as a new cathode materials in Li-ion batteries.
A controllable synthesis of flower-like lithium iron phosphate LiFePO4 (LFP) was obtained via a two-stage heating during hydrothermal process. In the first stage, the temperature was held at 105 °C (LFP1), 120 °C (LFP2), 150 °C (LFP3) and 190 °C (LFP4) for 5 h. In the final stage, the temperature was held constant at 400 °C under H2/N2 atmosphere for 4 h. To increase the electrochemical reversibility and electronic conductivity, LFP is treated with polyethylene glycol (PEG) as the templating agent and carbon sources for the as-prepared materials. This is to obtain a modified LFP cathode with optimum electrical contact between the electroactive materials and the carbon-filled electrode matrix which is found to be effective in terms of raising the electrochemical performance of the Li-ion batteries. Results show that as the first-stage temperature increased, the corresponding electrochemical performance of the resulting sample has been increased up to a temperature of 150 °C. Galvanos...
Solid State Ionics, 2014
This paper describes the preparation, characterization and electrochemical study of various iron and lithium iron phosphates. The pristine iron phosphate samples obtained were amorphous materials with various textural properties, in terms of average pore size, pore order and specific surface area. Some solids were mesoporous, featuring high surface area, narrow pore size distribution and high pore volume. Lithium iron phosphates were obtained by chemical lithiation of these iron phosphates, using LiI dissolved in acetonitrile. These materials were amorphous and electrochemically inactive against lithium. Following heating at 550°C, the materials crystallized and showed disparate electrochemical performance in lithium half-cells. This can be ascribed not only to the presence in the samples of impurities of different nature (and inherent to the synthesis method), but also to different textural and morphological properties. In fact, the best electrochemical performance was that of crystallized LiFePO 4 obtained from the mesoporous iron phosphate and consisting of rounded nanoparticles with high surface area and adequate porosity. As a result, a better electrolyte impregnation in the porous structures is highly expected. Furthermore, enhancement of the lithium ion diffusion inside the network is observed. This justifies the potential use of carbon-free mesoporous precursors of LiFePO 4 . However, introduction of a conductive carbon coating onto the phosphate particles and/or removal of the impurities prove necessary for good capacity retention upon cycling.
Improving electrochemical properties of lithium iron phosphate by addition of vanadium
Journal of Power Sources, 2007
The poor conductivity, resulting from the low lithium-ion diffusion rate and low electronic conductivity in the LiFePO 4 phase, has posed a bottleneck for commercial applications. Well-crystallized LiFePO 4-based powders with vanadium addition were synthesized with solution method. The synthesized powders are coated with carbon. The powder containing the well-mixed LiFePO 4 and Li 3 V 2 (PO 4) 3 phases (LFVP) with narrow distributed particle size ranging between 0.5 and 2.5 m exhibits improved electrochemical performance. The small particle size and the presence of the electronically conductive mixed phases can be the reasons why the cells containing LFVP exhibit the high discharge capacity of about 100 mAh g −1 at 10 C, whereas the samples with single phase, such as LiFePO 4 and Li 3 V 2 (PO 4) 3 , have the discharge capacity less than 80 Ah g −1 at the same rate.
ChemInform, 2014
New synthesis routes were employed for the synthesis of three derivatives of iron hydroxo-, fluoro-, and mixed hydroxo-fluoro phosphates LiFePO 4 (OH) x F 1-x where 0≤ x ≤1 with tavorite structure type, and their detail electrochemical activities have been presented. The hydrothermal synthesis of pure hydroxo-derivative, LiFePO 4 OH, using phosphorous acid as a source of phosphate yielded good quality crystals from which the crystal structur e was solved for the first time using SC-XRD (single crystal X-ray diffraction). The fluoro derivative, LiFePO 4 F, was prepared as very fine powder at low temperature in a solvent-less flux-based method employing phosphorous acid and mixed alkali metal nitr ates. A mixed anionic hydroxo-fluoro iron tavorite phase, LiFePO 4 (OH) 0.32 F 0.68 , was also synthesized by a hydrothermal route. The electrochemical performance of the three phases was studied with galvanostatic charge/discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy. All three phases showed facile Li-insertion through the reduction of Fe 3+ to Fe 2+ at an average voltage in the range of 2.4-2.75 volt, through the variation of anion from pure OH to pure F. An increase of 0.35 volt was observed as a result of F substitution in OH position. Also, good cyclability and capacity retention was observed for all three phases and a reversible capacity of more than 90% was achieved for LiFePO 4 F. The results of EIS indicated that lithium ion mobility is highest in the mixed anion.
Electrochimica Acta, 2010
In the field of materials for Lithium ion batteries, the lithium iron phosphate LiFePO 4 has been proven for use as a positive electrode due to its good resistance to thermal degradation and overcharge, safety and low cost. The use of nanostructured materials would improve its efficiency. This work shows the results of the synthesis of nanostructured materials with functional properties for Lithium batteries through aerosol techniques. The Spray Pyrolysis method allows synthesizing nanostructured particles with spherical geometry, not agglomerates, with narrow distribution of particle size and homogeneous composition in respect to a precursor solution. Experimental techniques were focused on the morphological (SEM and TEM), structural (XRD and HRTEM-SAED), chemical (EDS) and electrochemical characterization.
RSC Advances, 2014
New synthesis routes were employed for the synthesis of three derivatives of iron hydroxo-, fluoro-, and mixed hydroxo-fluoro phosphates LiFePO 4 (OH) x F 1Àx where 0 # x # 1 with the tavorite structure type, and their detail electrochemical activities have been presented. The hydrothermal synthesis of the pure hydroxo-derivative, LiFePO 4 OH, using phosphorous acid as a source of phosphate yielded good quality crystals from which the crystal structure was solved for the first time using SC-XRD (single crystal X-ray diffraction). The fluoro derivative, LiFePO 4 F, was prepared as a very fine powder at low temperature in a solvent-less flux-based method employing phosphorous acid and mixed alkali metal nitrates. A mixed anionic hydroxo-fluoro iron tavorite phase, LiFePO 4 (OH) 0.32 F 0.68 , was also synthesized by a hydrothermal route. The electrochemical performance of the three phases was studied with galvanostatic chargedischarge tests, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). All three phases showed facile Li-insertion through the reduction of Fe 3+ to Fe 2+ at an average voltage in the range of 2.4-2.75 V, through the variation of the anion from pure OH to pure F. An increase of 0.35 V was observed as a result of F substitution in the OH position. Also, good cyclability and capacity retention were observed for all three phases and a reversible capacity of more than 90% was achieved for LiFePO 4 F. The results of EIS indicated that lithium ion mobility is highest in the mixed anion.