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Surface-modified lithium iron phosphate positive electrode material, and preparation method thereof

A lithium iron phosphate and cathode material technology, applied in the field of lithium ion batteries, can solve the problems of expensive metal oxides, adverse effects of high resistance space charge layer electrode performance, and unsuitable for large-scale industrial applications.

Active Publication Date: 2014-11-26
HEFEI GUOXUAN HIGH TECH POWER ENERGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Recently, some research institutes have adopted CeO 2 and RuO 2 materials to modify the surface of materials, but the metal oxides used in this method are very expensive and not suitable for large-scale industrial applications
[0004] More importantly: in the field of all-solid-state lithium-ion batteries, if the positive electrode has a high electronic conductivity and is in contact with a pure ion-conducting electrolyte, a high-resistance space charge layer will be generated, which will adversely affect the performance of the electrode.

Method used

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  • Surface-modified lithium iron phosphate positive electrode material, and preparation method thereof
  • Surface-modified lithium iron phosphate positive electrode material, and preparation method thereof
  • Surface-modified lithium iron phosphate positive electrode material, and preparation method thereof

Examples

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Embodiment 1

[0029] Glycine Bi 5 FeTi 3 o 15 Powder mechanical mixed grinding coated lithium iron phosphate cathode material:

[0030] The lithium iron phosphate cathode material that does not contain any carbon source is used as the coating object, and Bi(NO 3 ) 3 ·5H 2 O, Fe(NO3)3 9H 2 O, tetrabutyl titanate is used as coating raw material.

[0031] The above-mentioned three kinds of salts are prepared into a precursor solution by adding water according to the stoichiometric ratio (this configuration method is a configuration method commonly used in the prior art, which has no effect on the essence of the present invention, and will not be described in detail here), using glycine as a complexing agent, Add glycine to the precursor solution and stir evenly. The molar ratio of the amount of glycine added to the total anion is 1:2. After stirring, place the precursor solution on a heating plate and heat until it burns into powder. After the powder is pre-fired at 750°C for 15 hours, ...

Embodiment 2

[0034] Glycine Bi 5 FeTi 3 o 15 Powder coated lithium iron phosphate cathode material:

[0035] The lithium iron phosphate cathode material that does not contain any carbon source is used as the coating object, and Bi(NO 3 ) 3 ·5H 2 O, Fe(NO3)3 9H 2 O, tetrabutyl titanate is used as coating raw material.

[0036] The above three salts are prepared into a precursor solution by adding water according to the stoichiometric ratio, using glycine as a complexing agent, adding glycine to the precursor solution and stirring evenly. Add the lithium iron phosphate positive electrode material into the precursor solution, heat and evaporate to form a gel, heat and dry at 100°C for 12 hours, and calcinate at 1000°C for 5 hours under a nitrogen atmosphere to obtain the modified lithium iron phosphate positive electrode material, which is prepared into a coated A lithium iron phosphate positive electrode material with a content of 3 wt%.

Embodiment 3

[0038] MnCo 2 o 4 Powder Mechanical Mixing and Coating Coated Lithium Iron Phosphate

[0039] The lithium iron phosphate cathode material is used as the coating object, manganese acetate and cobalt nitrate are used as raw materials, and the precursor solution is configured according to the stoichiometric ratio, and glycine is used as a complexing agent to prepare MnCo by combustion method. 2 o 4 The material is mechanically mixed with 0.5g of lithium iron phosphate positive electrode material after being pre-fired at 800°C, and then sintered at 650°C to prepare a lithium iron phosphate positive electrode material with a coating content of 3wt%.

[0040] The lithium iron phosphate sample, conductive carbon black and polyvinylidene fluoride were uniformly mixed in a mass ratio of 80:10:10 to make a working electrode, and the negative electrode was prepared by buckling metal lithium sheets for testing. It can also improve the electrochemical performance. figure 2 for MnCo 2...

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Abstract

The invention discloses a surface-modified lithium ion phosphate positive electrode material. The surface of the lithium ion phosphate positive electrode material comprises a mixed conductive conductor coating layer with a structural general formula of Bi[4]Bi[(n-3)]Fe[(n-3)]Ti[3]O[(3n+3)], or MnCo[2-x]Fe[x]O[4] or NiFe[2-x]Co[x]O[4], wherein 3<n<7 and 0<=x<=1. Compared with an un-coated lithium ion phosphate positive electrode material, the mixed conductive surface coating material can effectively dissipate electrons and ions during a discharging process, enhance dynamic characteristics of the material and further increase a discharging capacity of the material. Besides, the surface-modified lithium iron phosphate positive electrode material overcomes the defects of small tap density caused by a carbon coated lithium iron phosphate positive electrode material and a double electrode layer caused by a space charge layer in a full solid lithium ion battery, and can achieve the mixed conductive phosphate positive electrode material with relatively large tap density.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a surface-modified lithium iron phosphate cathode material for lithium ion batteries and a preparation method for the cathode material. Background technique [0002] Lithium-rich cathode materials for lithium-ion batteries have become a research hotspot in the field of lithium-ion battery cathodes due to their high energy density and high energy output. Currently used cathode materials for lithium-ion batteries include LiCoO 2 , LiMn 2 o 4 and LiFePO 4 Among them, lithium iron phosphate cathode material is commonly used in power batteries, which has attracted widespread attention because of its wide source and stable cycle life of 2000 times. However, the electronic conductivity of lithium iron phosphate is low, and the 0.2C discharge specific capacity is about 50-96mAhg-1 (J Solid State Electrochem12 (2008) 825-833). In order to improve these short...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/58
CPCH01M4/5825H01M4/62H01M10/0525Y02E60/10
Inventor 饶媛媛王康平曾晖
Owner HEFEI GUOXUAN HIGH TECH POWER ENERGY