Method for preparing carbon coated nanometer LiFePO4

A lithium iron phosphate and nano iron phosphate technology, applied in electrical components, battery electrodes, circuits, etc., can solve the problems affecting the large-scale production and application of lithium iron phosphate materials, poor conductivity of lithium iron phosphate cathode materials, Cathode material purity and non-uniform particle size, etc., to achieve the effect of easy implementation, improved ion mobility and electrical conductivity, and wide particle size distribution

Active Publication Date: 2011-11-30
TSINGHUA UNIV
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Problems solved by technology

[0003] However, FeO in the lithium iron phosphate structure 6 Octahedrons share oxygen atoms to form a common-vertex octahedral structure, which leads to a very low conductivity of lithium iron phosphate (10 -9 ~10 -11 s cm -1 ); In addition, the lithium ion migration channel in lithium iron phosphate is a one-dimensional structure, which also leads to its low lithium ion mobility
The two together lead to poor conductivity of lithium iron phosphate cathode material, and the capacity decays rapidly with the increase of charge and discharge rate.
Even so, the properties such as purity and particle size of the obtained positive electrode materials are still uneven, manifested in the fact that the particle size reaches submicron to micron level and the particle size distribution is wide, the carbon film coating is uneven, and the quality consistency of different batches of products is poor. Seriously affected the large-scale production and application of lithium iron phosphate materials

Method used

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  • Method for preparing carbon coated nanometer LiFePO4
  • Method for preparing carbon coated nanometer LiFePO4
  • Method for preparing carbon coated nanometer LiFePO4

Examples

Experimental program
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Embodiment 1

[0027] 1) Take nano-iron phosphate, nano-lithium carbonate and stearic acid according to the ratio of molar ratio Fe:Li:C=1:1:2.5, wherein iron phosphate is 0.005mol. Dissolving stearic acid in ethanol, and then adding nano-iron phosphate and nano-lithium carbonate thereto. The resulting suspension was sonicated for 15 min to obtain a stable and uniform nanofluid. The nanofluid was dried in a constant temperature oven at 80° C. for 30 minutes, and the solvent was removed to obtain a solid particle reaction mixture.

[0028] 2) The obtained solid particle reaction mixture was placed in a tubular reactor, pre-calcined at 300° C. for 1 h in an inert gas Ar atmosphere atmosphere, and calcined at 700° C. for 6 h, wherein the heating rate was 5 K / min. Lithium iron phosphate particles were obtained after natural cooling, which was designated as sample A.

[0029] figure 1 The SEM image of the nano-iron phosphate and the TEM image of the nano-lithium carbonate used in Example 1 sho...

Embodiment 2

[0031] 1) Take nano-iron phosphate, nano-lithium carbonate and vitamin C according to the ratio of molar ratio Fe:Li:C=1:1:5, wherein iron phosphate is 0.005mol. The vitamin C is dissolved in an aqueous solution of acetone containing 50% of acetone, and then nano iron phosphate and nano lithium carbonate are added thereto. The resulting suspension was sonicated for 15 min to obtain a stable and uniform nanofluid. Send the nanofluid into a vacuum desiccator to remove the solvent to obtain a solid particle reaction mixture.

[0032] 2) The obtained solid particle reaction mixture was placed in a tubular reactor, pre-calcined at 300° C. for 1 h in an inert gas Ar atmosphere atmosphere, and calcined at 700° C. for 6 h, wherein the heating rate was 5 K / min. Lithium iron phosphate particles were obtained after natural cooling.

Embodiment 3

[0034] 1) Take nano-iron phosphate, nano-lithium carbonate and oxalic acid according to the ratio of molar ratio Fe:Li:C=1:1:3, wherein iron phosphate is 0.005mol. Dissolving oxalic acid in isopropanol aqueous solution containing 30% isopropanol, and then adding nano iron phosphate and nano lithium carbonate thereto. The resulting suspension was mechanically ground for 15 min to obtain a stable and uniform nanofluid. The nanofluid is sent to a flash evaporator to remove the solvent to obtain a solid particle reaction mixture.

[0035] 2) The obtained solid particle reaction mixture is placed in a tubular reactor, pre-calcined at 300° C. for 1 h in a hydrogen atmosphere, and calcined at 700° C. for 6 h, wherein the heating rate is 10 K / min. Lithium iron phosphate particles were obtained after natural cooling.

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Abstract

The invention discloses a method for preparing carbon coated nanometer LiFePO4 and belongs to the technical field of preparation of a positive pole material of a lithium ion battery. The method comprises the following steps: dissolving or dispersing nanometer iron phosphate, a nanometer lithium salt and a carbon source which are taken in a molar ratio of Fe to Li to C of 1:1: (1-5) to a solvent so as to obtain a stable and uniform nanometer fluid, and then rapidly removing the solvent in the nanometer fluid, thereby obtaining a uniformly mixed solid particle reactant; and roasting the uniformly mixed solid particle reactant in a hydrogen atmosphere, inert gas atmosphere or mixed gas atmosphere composed of hydrogen and inert gas, so as to obtain carbon coated nanometer LiFePO4. The preparation method disclosed by the invention is high in production efficiency and is easy to implement; and the size of the obtained carbon coated nanometer LiFePO4 particle is in a nanometer level and is narrow in distribution, and the carbon film of the particle is uniform, thereby being beneficial to improvements of ion transfer and conductivity and improvement of consistence of lithium ion battery positive pole materials.

Description

technical field [0001] The invention belongs to the technical field of preparation of positive electrode materials of lithium ion batteries, and in particular relates to a method for preparing carbon-coated nanometer lithium iron phosphate. Specifically, it is a method for preparing uniform carbon-coated nano-lithium iron phosphate by a solid phase method. Background technique [0002] Compared with traditional batteries, lithium-ion batteries have obvious advantages in energy density, so they have been widely used in light mobile devices such as notebook computers, digital cameras, and mobile phones. The capacity, conductivity and other properties of the negative electrode material in lithium-ion batteries are much higher than that of the positive electrode material, so the positive electrode material determines the performance of the battery. However, traditional cathode materials such as lithium cobaltate, lithium manganese oxide, etc. have disadvantages such as poor the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/1397
CPCY02E60/122Y02E60/12Y02E60/10
Inventor 刘洋吕阳成骆广生
Owner TSINGHUA UNIV
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