Preparation method of high-conductivity lithium iron phosphate cathode material

A technology of lithium iron phosphate and phosphoric acid solution, which is applied in the direction of battery electrodes, chemical instruments and methods, circuits, etc., can solve the problems that it is difficult to enter the interior of particles in large quantities, the performance cannot be fundamentally improved, and the electrochemical performance is good. Achieve the effects of reducing raw material costs, improving electrochemical performance, and reducing production costs

Inactive Publication Date: 2013-08-14
HUNAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, most of the pure phase FePO 4 , to prepare doped and carbon-encapsulated LiFePO by adding doping elements and carbon sources when mixed with Li sources 4 /C; these doping elements and carbon sources are surrounded by FePO 4 The periphery, in the subsequent heat treatment forms LiFePO 4 In the process of /C, it is difficult for the inside of the core to enter the

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] (1) Separately configure H with a mass concentration of 75% 3 PO 4 solution, 1.5mol / L Fe(NO 3 ) 3 solution, 6mol / L NaOH solution.

[0019] (2) The above H 3 PO 4 solution and Fe(NO 3 ) 3 The solution is mixed at a molar ratio of 1:1, and then the doping compound MgO is added at a ratio of Mg:Fe atomic molar ratio of 0.02:0.98. 4 The mass ratio is 8% and 0.12% respectively, adding pyrolysis carbon source polyvinyl alcohol and carbonization accelerator H 3 BO 3 . After stirring for 30 minutes, add it into the reaction kettle together with NaOH solution, stir at a speed of 800 r / min, control the pH to 1.5, and react at 80°C for 5 hours. Afterwards, the precipitate was filtered and washed with distilled water and ethanol until the pH was 7, and dried to obtain the precursor Fe 0.98 Mg 0.02 PO 4 / C (i.e. carbon-coated Fe 0.98 Mg 0.02 PO 4 ).

[0020] (3) The lithium source material LiOH and the Fe prepared in the previous step 0.98 Mg 0.02 PO 4 / C is mixe...

Embodiment 2

[0030] (1) Configure 80% of H respectively 3 PO 4 solution, 2.0mol / L Fe(NO 3 ) 3 Solution, 8mol / L NaOH solution;

[0031] (2) The above H 3 PO 4 solution and Fe(NO 3 ) 3 The solution is mixed at a molar ratio of 1:1, and the doping compound Cr 2 o 3 Add it into the mixed solution, stir for 30min, add it into the reaction kettle together with the NaOH solution, press the FePO 4 The mass ratio is 7% and 0.10% respectively, adding pyrolysis carbon source epoxy resin and carbonization accelerator B to the mixed solution 2 o 3 . Stir at a rate of 1000r / min, control the pH value to 1.6, and react at 80°C for 5h; then filter the precipitate and wash it with distilled water and ethanol until the pH is 7, and dry to obtain the precursor Fe 0.97 Cr 0.02 PO 4 / C.

[0032] (3) The lithium source material Li 2 CO 3 and the precursor Fe obtained in the previous step 0.97 Cr 0.02 PO 4 / C is mixed at a molar ratio of 0.52:1, and LiFe 0.97 Cr 0.02 PO 4 The mass ratio of ...

Embodiment 3

[0035] (1) Configure 70% of H respectively 3 PO 4 solution, 1.8mol / L FeCl 3 Solution, 6mol / L NaOH solution;

[0036] (2) The above H 3 PO 4 solution and FeCl 3 The solution is mixed at a molar ratio of 1:1, and then the doping compound TiO is added to the mixed solution at a ratio of Ti:Fe atomic molar ratio of 0.02:0.96 2 , together with NaOH solution into the reactor; then press and FePO 4 The mass ratio is 6% and 0.08% respectively, adding pyrolysis carbon source phenolic resin and carbonization accelerator B to the mixing system in the above-mentioned reactor 4 C. After stirring for 30 minutes, stir at a speed of 1000 r / min, control the pH value to 1.5, and react at 80° C. for 5 hours. The precipitate was filtered, washed with distilled water and ethanol until the pH was 7, and dried to obtain the precursor Fe 0.96 Ti 0.02 PO 4 / C.

[0037] (3) The lithium source material LiF and the precursor Fe prepared in the previous step 0.96 Ti 0.02 PO 4 / C mixes the in...

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Abstract

The invention provides a preparation method of a high-conductivity lithium iron phosphate cathode material. The preparation method comprises the steps of: adding a doping compound into phosphoric acid and trivalent ferric salt solution, separately adding a pyrolytic carbon source and a carbonization accelerator in two manners, adding alkaline solution, controlling the pH of the system to be within 1-4, reacting for a period of time, washing and drying so as to obtain a ferric phosphate precursor; and mixing a lithium source, the precursor, the pyrolytic carbon source and the carbonization accelerator, stirring (or ball milling), drying in vacuum, thermally treating and grinding so as to prepare the doped carbon-wrapping lithium iron phosphate. The doping compound, the pyrolytic carbon source and the carbonization accelerator are added when the ferric phosphate precursor is prepared, the electric conductivity of lithium iron phosphate intracells and the electric conductivity among particles are improved, and the electrochemical performance of the lithium iron phosphate intracells is obviously improved at a high rate; and moreover, ferrous iron at high price is not used any more, so that the production cost is greatly lowered.

Description

technical field [0001] The invention relates to a preparation method of a positive electrode material of a lithium ion battery, in particular to a preparation method of a lithium iron phosphate positive electrode material. Background technique [0002] The commonly used cathode active materials for lithium-ion batteries are LiCoO 2 , LiMn 2 o 4 and LiFePO 4 , Among them, because lithium iron phosphate material has many advantages such as stable structure, good thermal stability, low raw material cost, low toxicity, environmental friendliness, good safety performance and good high temperature performance, it is a kind of positive electrode active material with great potential. In particular, its oxidation exothermic temperature exceeds 400°C, and it has excellent thermal stability. [0003] But LiFePO 4 The electronic conductivity is low, only 10 -9 ~10 -10 S / cm, thus the rate performance is poor, which limits its application. Generally, methods such as carbon coating...

Claims

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Application Information

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IPC IPC(8): H01M4/58H01M4/62C01B25/45
CPCY02E60/12Y02E60/10
Inventor 范长岭韩绍昌
Owner HUNAN UNIV
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