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Method for preparing composite material of carbon coated lithium ferrous phosphate through iron phosphate

A technology of carbon-coated ferrous phosphate and lithium ferrous phosphate, applied in phosphorus compounds, chemical instruments and methods, inorganic chemistry, etc., can solve the problem of deteriorating the electrochemical performance of lithium ferrous phosphate materials, which cannot guarantee complete reaction and consistent materials Poor performance and other problems, to achieve the effect of good electrochemical performance, good consistency of material batches, and short cycle time

Inactive Publication Date: 2008-05-21
SHANGHAI JIAO TONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Preparation of LiFePO 4 The most commonly used method is the solid-phase method, the solid-phase reaction is basically a solid / solid interface reaction, the reaction interface is small, the preparation process requires long-term ball milling and multiple heat treatments, the cycle is long, the process is complicated, and the cost increases
Even this cannot guarantee that the reaction is complete. During the high-temperature reaction, lithium phosphate Li with a high melting point may be generated. 3 PO 4 and ferrous phosphate Fe 3 (PO 4 ) 2 , the remaining unreacted impurities will deteriorate the electrochemical performance of lithium iron phosphate materials, and cause poor consistency between different batches of materials
The pure liquid phase reaction, such as the sol-gel method, is beneficial to complete the reaction, but the income is small. It is feasible to prepare samples in the laboratory, and the processing cost is high in industrial production.

Method used

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  • Method for preparing composite material of carbon coated lithium ferrous phosphate through iron phosphate
  • Method for preparing composite material of carbon coated lithium ferrous phosphate through iron phosphate

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] (1) Weigh iron phosphate 4 hydrate (FePO 4 4H 2 (2) 0.2mol is 44.578g, ammonium sulfite 0.4mol, add distilled water, the concentration of ammonium sulfite is 1mol / L, then stir for 6 hours, the temperature of stirring is 50 ℃, then filter and clean to obtain amorphous ferrous phosphate Ammonium;

[0022] (2) The obtained amorphous ferrous ammonium phosphate is mixed with 8.392g lithium hydroxide, and under the protection of argon and 5% hydrogen mixed gas, it is treated at 500°C for 2 hours to obtain lithium ferrous phosphate, and 2.375g is weighed Sucrose, sucrose is dissolved in distilled water and mixed with lithium iron phosphate, heated and stirred until evaporated to dryness, and then treated at 650°C for 2 hours under the protection of argon to obtain carbon-coated lithium iron phosphate. figure 1 It is the XRD spectrum pattern of the carbon-coated lithium ferrous phosphate obtained in Example 1, which shows that lithium ferrous phosphate has a good crystal stru...

Embodiment 2

[0024] (1) Weigh ferric phosphate, ammonium sulfite and ammonia water, wherein 4 hydrated ferric phosphate (FePO 4 4H 2 O) 0.2mol is 44.578g, 0.4mol of ammonium sulfite, 0.2mol of ammonia water, add distilled water, the concentration of ammonium sulfite is 1mol / L, then stir for 4 hours, the temperature of stirring is 70°C, then filter and wash to obtain an amorphous state Ferrous ammonium phosphate;

[0025] (2) The obtained amorphous ferrous ammonium phosphate is mixed with 7.389g lithium carbonate and 3.506g sucrose, and distilled water is added to dissolve the sucrose and heat and stir to make the suspension evaporate to dryness, then in argon and 5% hydrogen mixed gas Under protection, it was treated at 700° C. for 1 hour to obtain carbon-coated lithium iron phosphate. figure 2 It is the charge-discharge curve of the carbon-coated lithium ferrous phosphate obtained in Example 2, and the discharge capacity reaches 139mAh / g at 1C.

Embodiment 3

[0027] (1) Weigh iron phosphate, ammonium thiosulfate and ammonia water, in which iron phosphate 2 hydrate (FePO 4 2H 2 (2) 0.2mol i.e. 37.364g, ammonium thiosulfate 0.2mol, ammoniacal liquor 0.1mol, add distilled water, the concentration of ammonium thiosulfate is 0.5mol / L, then stir for 8 hours, the temperature of stirring is room temperature, then filter and clean to obtain non- Crystalline ammonium ferrous phosphate;

[0028] (2) The obtained amorphous ferrous ammonium phosphate was mixed with 20.404g lithium acetate, and under the protection of nitrogen and 5% hydrogen mixed gas, it was treated at 400°C for 3 hours to obtain lithium ferrous phosphate, and 3.506g glucose was weighed, Glucose was dissolved in distilled water and mixed with lithium iron phosphate, heated and stirred until evaporated to dryness, and then treated at 700° C. for 1 hour under nitrogen protection to obtain carbon-coated lithium iron phosphate.

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Abstract

This invention discloses a method for carbon-coated ferrous lithium phosphate composite material from ferric phosphate. The method comprises: (1) reducing Fe3+ of ferric phosphate into Fe2+ by a liquid-phase reducer; (2) reacting with NH4+ in the solution to obtain ferrous ammonium phosphate; (3) reacting with Li source at a high temperature and in inert atmosphere to obtain ferrous lithium phosphate; (4) coating with carbon to obtain carbon-coated ferrous lithium phosphate composite material. The method adopts Fe3+ as the raw material, thus reducing the costs of the raw material and the processing. The obtained composite material has such advantages as high purity and good electrochemical performance, and can be used as the cathode material of Li-ion batteries.

Description

technical field [0001] The invention belongs to the technical field of material preparation, and in particular relates to a method for preparing a carbon-coated lithium iron phosphate composite material with iron phosphate, which is used as a positive electrode material of a lithium ion battery. Background technique [0002] Since the compound of olivine structure was reported in 1997 as a positive electrode material for charge-discharge lithium-ion batteries, lithium iron phosphate (LiFePO 4 ) positive electrode material has outstanding advantages such as abundant raw materials, low cost, high specific capacity, environmental friendliness, non-toxic and harmless, and good thermal stability. A first-generation cathode replacement material for lithium-ion batteries. [0003] Although LiFePO 4 As a positive electrode material, it has many advantages, but there are some problems in the actual application process. One is LiFePO 4 Low electronic conductivity and ion diffusion...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B25/45H01M4/58
CPCY02E60/12Y02E60/10
Inventor 杨军王延强王久林努丽燕娜
Owner SHANGHAI JIAO TONG UNIV
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