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Process for preparing lithium iron phosphate composite cathode material

A composite cathode material, phosphate technology, applied in battery electrodes, electrical components, circuits, etc., can solve the problems of difficult to guarantee product performance stability, difficult to distribute amorphous carbon uniformly, and reduced tap density, etc., to improve electronic conductivity. rate, excellent electronic conductivity, and the effect of solving the problems of dispersibility

Active Publication Date: 2013-09-25
HUNAN UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, carbon coating also has the following problems: firstly, it is difficult to uniformly distribute amorphous carbon among the particles, and it is difficult to guarantee the stability of product performance; secondly, the addition of amorphous carbon significantly reduces the tap density, which makes LiFePO 4 The improvement of performance and the increase of tap density cannot be organically unified
When the method of doping with high-valent metal ions is used, the metal ions enter the lattice to improve the LiFePO 4 The crystal structure of LiFePO has substantially improved its electronic conductivity, thereby improving its macroscopic electrochemical performance, but how to make high-valent metal ions accurately enter LiFePO 4 The lithium or iron position of the crystal is currently a problem that is difficult to control

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] Dissolve lithium acetate, ferrous acetate, and ammonium dihydrogen phosphate as synthetic raw materials in a molar ratio of 1:1:1 in deionized water, add 2ml of alcohol, then add cotton wool with 5% of the total mass of synthetic raw materials, and mix under ultrasonic waves Uniform, evaporate at room temperature until the solvent disappears completely, and then carry out carbonization and synthesis in sequence in a high-purity argon atmosphere to obtain a cotton-like LiFePO 4 / C composite cathode material. Among them, the temperature of carbonization and synthesis was controlled at 550°C, and the time was 12h.

[0021] The resulting cotton-like LiFePO 4 When the / C composite cathode material is charged and discharged at 0.2C rate, the first discharge specific capacity at room temperature can reach 159mAh / g; when charged and discharged at 5C rate, the first discharge specific capacity at room temperature can reach 132mAh / g, after 500 cycles After that, the capacity re...

Embodiment 2

[0023] Dissolve lithium gluconate, ferrous acetate, and diammonium hydrogen phosphate as synthetic raw materials in a molar ratio of 1:1:1 in deionized water, add 2ml of alcohol, and then add catkins with a total mass of synthetic raw materials of 6%. Mix well, evaporate at 50°C until the solvent disappears completely, then carbonize and synthesize sequentially in a high-purity nitrogen atmosphere to obtain catkin-like LiFePO 4 / C composite cathode material. Among them, the temperature of carbonization and synthesis was controlled at 650°C, and the time was 18h.

[0024]The resulting cotton-like LiFePO 4 When the / C composite cathode material is charged and discharged at 0.2C rate, the first discharge specific capacity at room temperature can reach 167mAh / g; when charged and discharged at 5C rate, the first discharge specific capacity at room temperature can reach 135mAh / g, after 500 cycles After that, the capacity retention rate was 94.4%.

Embodiment 3

[0026] Lithium formate, ferrous gluconate and ammonium dihydrogen phosphate that are 1:1:1 molar ratio as synthetic raw materials are dissolved in deionized water, add 2ml of alcohol, then add poplar catkins with 5% of the total mass of synthetic raw materials, in ultrasonic Mix evenly under low temperature, evaporate at 40°C until the solvent disappears completely, and then carry out carbonization and synthesis in sequence in a high-purity argon atmosphere to obtain LiFePO with poplar flocculent shape. 4 / C composite cathode material. Among them, the temperature of carbonization and synthesis is controlled at 60°C, and the time is 24h.

[0027] The resulting flocculent LiFePO 4 When the / C composite cathode material is charged and discharged at 0.2C rate, the first discharge specific capacity at room temperature can reach 163mAh / g; when charged and discharged at 5C rate, the first discharge specific capacity at room temperature can reach 133mAh / g, after 500 cycles After tha...

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Abstract

The invention discloses a process for preparing LiFePO4 / C composite cathode material. The process comprises steps of: mixing and dissolving soluble lithium compounds, soluble iron compounds and soluble phosphates in deionized water, wherein the atomic ratio of lithium, iron and phosphorus is 1:1:1; adding natural plant fibres or bio-membranes used as carriers, and dispersing uniformly via ultrasonic; achieving self-assembly of lithium ions, ferrous ions / iron ions and phosphate ions on the carriers via evaporation; and carrying out high temperature carbonizing and synthesizing in inert atmosphere to form a biomorphic LiFePO4 / C composite cathode material using carbon as a carrier and a conductive agent.

Description

technical field [0001] The invention relates to a battery cathode material and its preparation, in particular to a cathode material for a secondary lithium ion battery or a power energy battery and a preparation method thereof. Background technique [0002] Since the advent of lithium-ion batteries in the 1990s, they have been considered ideal for high-capacity, high-power batteries because of their high energy density, good cycle performance, and charge protection capabilities. In lithium-ion batteries, a large amount of cathode material is used, which increases the production cost of lithium-ion batteries. At present, the substances used as cathode materials for lithium-ion batteries are mainly lithium-containing transition metal oxides, including layered LiMO (M=Co, Ni, Mn) and spinel-type LiMn. 2 o 4 . However, due to the price of these materials (LiCoO 2 ), safety (LiNiO 2 ), high temperature electrochemical performance (LiMn 2 o 4 ) and other reasons make them s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/58
CPCY02E60/10
Inventor 陈晗张优良李娜向楷雄胡忠良丁燕鸿
Owner HUNAN UNIV OF TECH