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A kind of lithium iron phosphate composite material and preparation method thereof

A composite material, lithium iron phosphate technology, applied in the direction of structural parts, electrical components, battery electrodes, etc., can solve the problems of high production cost agglomeration, uneven particle size distribution, large internal resistance and other problems in the synthesis process, and achieve good rate performance and cycle The effect of high performance, uniform particle size and low price

Active Publication Date: 2018-11-09
SHENZHEN LIWEI LI ENERGY TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a lithium iron phosphate composite material and a preparation method thereof, aiming at solving the problems of high production cost, serious agglomeration, uneven particle size distribution, large particle size, and The problem of large internal resistance and large polarization

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0045] Take 1 L of high-magnesium-lithium-ratio natural brine lithium with a lithium content of 1100 mg / L, wherein the mass ratio of magnesium to lithium is 45.32, and adjust the pH to 8.0 with 0.05M borax-hydrochloric acid buffer solution. Weigh 151g FePO 4 The powder is treated in 0.01M dilute hydrochloric acid solution for 6 hours, filtered and placed in a container with a cover, injected with a high-magnesium-lithium ratio natural brine lithium prepared with a good pH value, closed the cover, shaken for 10 hours, filtered, washed, and heated at 100°C After drying for 6 hours, FePO was measured 4The lithium ion exchange rate is 26.7mg / g, and the magnesium ion exchange rate is 1.59mg / g. According to the measured amount of lithium and magnesium, add 15.32g of lithium carbonate, so that the molar ratio of lithium and magnesium: iron molar ratio is 1:1, after mixing, sinter at 300°C for 8 hours in a nitrogen atmosphere to obtain doped lithium iron phosphate Material Li 0.99 ...

Embodiment 2

[0048] Take 1 L of high-magnesium-lithium-ratio natural brine lithium with a lithium content of 500 mg / L, wherein the mass ratio of magnesium to lithium is 36, and adjust the pH to 8.5 with 0.08M borax-hydrochloric acid buffer solution. Weigh 151g FePO 4 The powder is treated in 0.05M dilute sulfuric acid solution for 6 hours, filtered and placed in a container with a cover, injected with a high-magnesium-lithium ratio natural brine lithium prepared with a good pH value, closed the cover, shaken for 12 hours, filtered, washed, and heated at 120°C After drying for 4 hours, it was measured that FePO4 had an exchange rate of 23.4 mg / g for lithium ions and 3.18 mg / g for magnesium ions. According to the amount of lithium and magnesium already contained, add 11.4g of lithium hydroxide so that the molar ratio of lithium and magnesium: iron molar ratio is 1:1. After mixing, sinter at 350°C for 6 hours in an argon atmosphere to obtain doped iron phosphate Lithium material Li 0.98 Mg ...

Embodiment 3

[0051] Take 1 L of high-magnesium-lithium-ratio natural brine lithium with a lithium content of 1500 mg / L, wherein the mass ratio of magnesium to lithium is 51.3, and adjust the pH to 8.5 with 0.08M borax-hydrochloric acid buffer solution. Weigh 151g FePO 4 The powder is treated in 0.05M dilute nitric acid solution for 8 hours, filtered and placed in a container with a cover, injected with a high-magnesium-lithium-to-lithium ratio natural brine lithium prepared with a good pH value, closed the cover, shaken for 4 hours, filtered, washed, and heated at 150°C After drying for 2h, FePO 4 The lithium ion exchange rate is 21.9 mg / g, and the magnesium ion exchange rate is 4.77 mg / g. According to the amount of lithium and magnesium already contained, add 34.35g of lithium nitrate so that the molar ratio of lithium and magnesium: iron molar ratio is 1:1. After mixing, sinter at 350°C for 4 hours in a nitrogen atmosphere to obtain a doped lithium iron phosphate material Li 0.97 Mg ...

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Abstract

The invention discloses a lithium iron phosphate composite material and a preparation method thereof. The preparation method comprises the steps that 1, natural lithium-bearing brine resources are used as a lithium source, the usage amount of refined lithium salt is decreased, and the material synthesis cost is lowered; 2, the raw materials are uniformly distributed in the atomic scale through an ion exchange method, crystal lattice matrix rearrangement is achieved easily through short-distance diffusion, the synthesis process energy consumption is low, the synthesis temperature is low, and the synthesis time is short; the size distribution is uniform, polarization is reduced, and the battery rate capacity is improved; 3, the pH value is adjusted through a borax-hydrochloric acid buffer solution to reasonably control the magnesium constituent content, lithium-vacancy magnesium-doped lithium iron phosphate is prepared, a lithium vacancy promoting diffusion transferring of lithium ions inside a crystal is formed, the material hole concentration is increased, and the charging and discharging speed is increased; 4, the preparation method is more excellent compared with other schemes by considering economy and environmental protection, and has the practical significance particularly for synthesizing the composite battery material by extracting lithium from liquid lithium-bearing brine resources with the high magnesium-lithium ratio.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a lithium iron phosphate composite material and a preparation method thereof. Background technique [0002] Lithium iron phosphate is one of the more promising lithium ion cathode materials. Compared with lithium cobalt oxide and other cathode materials, lithium iron phosphate has the advantages of low cost, no pollution, good safety, and good cycle performance. It is an ideal power battery cathode material. , but its poor electrical conductivity greatly limits its wide application. At present, the common method to improve the conductivity of lithium iron phosphate is to coat the surface with conductive materials. The combination of surface coating and bulk phase doping can undoubtedly further improve the electrochemical performance of the material, and the shortcomings of poor electrical conductivity of lithium iron phosphate have been greatly improved. [0003] At present...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/58H01M10/0525
CPCH01M4/5825H01M10/0525Y02E60/10
Inventor 刘立君宋翠环
Owner SHENZHEN LIWEI LI ENERGY TECH CO LTD