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Preparation method of lithium iron phosphate

A technology of lithium iron phosphate and iron phosphate salt, which is applied in chemical instruments and methods, phosphorus compounds, inorganic chemistry, etc., can solve problems that affect the intercalation and extraction of Li atoms, the inability to form electronic conductors, and reduce the packing density of materials. Avoid uneven carbon doping, improve electrochemical performance, and require simple equipment

Inactive Publication Date: 2013-02-20
南京弘毅伯泰数字技术有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the problem is that due to the poor conductivity of lithium iron phosphate itself, conductive carbon materials need to be added during post-processing, which significantly reduces the bulk density of the material.
[0021] In addition to the above shortcomings, the existing methods also have the following deficiencies: In LiFePO 4 structure, due to the PO between the octahedra 4 The tetrahedron restricts the change of the lattice volume, which affects the intercalation and extraction of Li atoms during the charge and discharge process, making LiFePO 4 The ion diffusion rate is low; since there is no continuous FeO 6 The co-edge octahedral network cannot form an electronic conductor, and the conduction of electrons can only be carried out through Fe-O-Fe, making LiFePO 4 low electronic conductivity

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0048] Ferrous sulfate (FeSO 4 ·7H 2 O, analytically pure) as iron source, ammonium dihydrogen phosphate (NH 4 h 2 PO 4 ) is the phosphorus source, Li 2 CO 3 source of lithium. FeSO 4 ·7H 2 O 5.558g dissolved in 20ml deionized water, NH 4 h 2 PO 4 Dissolve 4.6g in 20ml of deionized water, filter, and slowly drop the ferrous sulfate solution into the ammonium dihydrogen phosphate solution to generate NH 4 FePO 4 The precursor is precipitated, filtered, washed, and dried at 80°C for 24 hours; then the precursor is dissolved in an ethanol solution containing oleic acid surfactant under ultrasonic conditions, and the amount of oleic acid is 25% of the weight of the precursor, filtered, and dried; Take Li 2 CO 3 0.74g, ball milled, and roasted at 800°C for 15h at a constant temperature with the ferric phosphate precursor coated with surfactant (N 2 atmosphere), cooling to obtain LiFePO 4 Cathode material. In this example FeSO 4 ·7H 2 O: NH 4 h 2 PO 4 : Li 2 C...

Embodiment 2

[0050] Ferric nitrate and ferrous nitrate (Fe(NO 3 ) 3 9H 2 O and Fe(NO 3 ) 2 ·6H 2 O, analytically pure) as iron source, potassium dihydrogen phosphate (KH 2 PO 4 ) is a phosphorus source, and LiOH is a lithium source. Take Fe(NO 3 ) 3 and Fe(NO 3 ) 2 6.06g and 2.70g were dissolved in 30ml deionized water, KH 2 PO 4 Dissolve 8.16g in 30ml deionized water, filter, and slowly drop ferric nitrate and ferrous nitrate solution into potassium dihydrogen phosphate solution to generate KFePO 4 The precursor was precipitated, filtered, washed, and dried at 80°C for 24 hours; then the precursor was dissolved in an ethanol solution containing ammonium oleate under ultrasonic conditions, and the amount of ammonium oleate was 10% of the mass of the precursor, filtered, and dried; LiOH 0.24g, ball milled, roasted at 1200°C with the ferric phosphate precursor coated with surfactant for 7h (N 2 atmosphere), cooling to obtain LiFePO 4 Cathode material. In this example Fe(NO 3...

Embodiment 3

[0052] With ferric chloride (FeCl 3 , analytically pure) as iron source, lithium phosphate (Li 3 PO 4 ) is a phosphorus source, and LiOH is a lithium source. FeCl 3 1.62g dissolved in 20ml deionized water, Li 3 PO 4 Dissolve 2.32g in 20ml of deionized water, filter, and slowly drop the ferric chloride solution into the lithium phosphate solution to generate LiFePO 4 The precursor is precipitated, filtered, washed, and dried at 90°C for 20 hours; then the precursor is dissolved in an ethanol solution containing linoleic acid under ultrasonic conditions, and the amount of linoleic acid is 40% of the weight of the precursor, filtered, and dried; Take 0.24g of LiOH, ball mill, roast at 400°C with the ferric phosphate precursor coated with surfactant at constant temperature for 20h (argon atmosphere), and cool to obtain LiFePO 4 Cathode material. In this example FeCl 3 : Li 3 PO 4 The molar ratio between :LiOH is 1:2:1.

[0053] Compared with the conventional method, the...

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Abstract

The invention relates to a preparation method of lithium ion phosphate. The method comprises the following steps of: preparing an iron phosphate salt precursor by utilizing reverse precipitation of soluble iron salts and phosphate; cladding the ion phosphate salt precursor by using a surfactant; and then mixing with a lithium source and roasting together to prepare a carbon-doped LiFePO4 powder material with evenly distributed particles and small particle size. The preparation method disclosed by the invention has the advantages of low reaction temperature, mild reaction conditions, short technological flow, simple equipment requirement, environment friendliness and the like.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for preparing lithium iron phosphate. Background technique [0002] Lithium iron phosphate has the characteristics of high specific capacity, good cycle performance, stable electrochemical performance, and low price. It is the preferred material for a new generation of power lithium batteries. [0003] Since it was reported in the 1990s that lithium iron phosphate with an olivine structure can reversibly intercalate and remove lithium, research on lithium iron phosphate has been increasing. [0004] At present, the main preparation methods of lithium iron phosphate are as follows: [0005] 1. High-temperature solid-phase method, that is, iron salts, lithium compounds and phosphates are mixed and reacted in a high-temperature environment. The product prepared by this method has poor performance, coarse particle size and uneven particle size dis...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B25/45
Inventor 朱叙国罗昔贤
Owner 南京弘毅伯泰数字技术有限公司
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