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Lithium iron phosphate composite cathode material and preparation method thereof

A composite positive electrode material, lithium iron phosphate technology, applied in the direction of battery electrodes, electrical components, electrochemical generators, etc., can solve the problem of no improvement in the migration and diffusion of lithium ions, cannot meet the needs of power batteries, and hinder the migration and diffusion of lithium ions To achieve the effect of shortening the diffusion path of lithium ions, improving the high-rate charge-discharge capability, and improving the performance of high-rate charge-discharge

Active Publication Date: 2016-04-20
李震祺 +1
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Problems solved by technology

However, due to the low lithium ion diffusion rate of lithium iron phosphate (10 -14 ~10 -10 cm 2 / s) and low electronic conductivity (-9 s / cm), so that the actual capacity of lithium iron phosphate is much lower than the theoretical value, and the capacity decay of lithium iron phosphate is more rapid when charging and discharging at a high rate, which cannot meet the needs of power batteries
[0003] At present, researchers often use carbon coating, conductive polymer coating, ion doping and other means to improve the conductivity of lithium iron phosphate. Without any improvement, it will even hinder the migration and diffusion of lithium ions; through ion doping, the electronic conductivity and ion diffusivity can be improved at the same time, but the effect is minimal; with the requirements of power batteries for high energy density and high power density, making It is increasingly important to further improve the conductivity and capacity of lithium iron phosphate

Method used

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  • Lithium iron phosphate composite cathode material and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] A lithium iron phosphate composite positive electrode material is prepared by the following steps:

[0043] Step S1: First, weigh 143.86g of ferrous oxalate and 103.93g of lithium dihydrogen phosphate as raw materials according to the molar ratio of Fe:Li:P = 1:1:1, and mix them by ball milling in ethanol medium 4h, dried at 80°C, cooled naturally, continued ball milling for 2h to mix evenly, then heated at 400°C for 12h in an Ar gas atmosphere furnace, and obtained lithium iron phosphate precursor powder after natural cooling.

[0044] Step S2: Use ultrasonic-assisted Hummers method to prepare graphene oxide, then mix and grind melamine and graphene oxide powder according to the mass ratio of 1:7, then heat in an Ar gas atmosphere furnace at 800°C for 6 hours, and cool naturally to obtain N-doped The n-type graphene dopant body, wherein, the N doping amount is 8% (weight percentage).

[0045]Step S3: Mix the N-doped n-type graphene dopant with the lithium iron phospha...

Embodiment 2

[0048] A lithium iron phosphate composite positive electrode material is prepared by the following steps:

[0049] First ferrous citrate, lithium carbonate, diammonium hydrogen phosphate are according to Fe:Li:P mol ratio is 1:1.02:1 each takes by weighing raw material ferrous citrate 246g, lithium carbonate 37.68g, diammonium hydrogen phosphate 132.06g, Ball milled and mixed in ethanol medium for 4 hours, dried at 80°C, cooled naturally, continued ball milled for 2 hours to mix evenly, then heated at 500°C for 10 hours in an Ar gas atmosphere furnace, and cooled naturally to obtain lithium iron phosphate precursor powder.

[0050] Mix and grind benzenediboronic acid and graphene oxide powder according to the mass ratio of 9:4, heat in an Ar gas atmosphere furnace at 600°C for 8 hours, and cool naturally to obtain a B-doped p-type graphene dopant, wherein, B The doping amount is 9% (weight percentage).

[0051] The B-doped p-type graphene dopant and the lithium iron phosphate...

Embodiment 3

[0054] A lithium iron phosphate composite positive electrode material is prepared by the following steps:

[0055] First ferrous oxalate, lithium carbonate, ammonium dihydrogen phosphate according to the mol ratio of Fe:Li:P is 1:1.05:1 and each takes by weighing raw material ferrous oxalate 143.86g, lithium carbonate 38.79g, ammonium dihydrogen phosphate 115.03g, The three were ball milled and mixed in an ethanol medium for 4 hours, dried at 80°C, cooled naturally, continued to be ball milled for 2 hours to mix evenly, and then heated in an Ar gas atmosphere furnace at 600°C for 8 hours, and cooled naturally to obtain a lithium iron phosphate precursor powder.

[0056] Red phosphorus and graphene oxide powder were mixed and ground at a mass ratio of 1:9, then heated at 700°C for 7 hours in an Ar gas atmosphere furnace, and cooled naturally to obtain a P-doped n-type graphene dopant, wherein P-doped Impurity is 10% (weight percentage).

[0057] The P-doped n-type graphene dop...

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Abstract

The invention provides a lithium iron phosphate composite cathode material and a preparation method thereof. A lithium iron phosphate material is wrapped by or doped with doping type graphene, wherein the wrapping amount or doping amount of doping type graphene is 6-10 wt%. By means of the technical scheme, after the lithium iron phosphate cathode material and doping type graphene are compounded, the electron conductivity of lithium iron phosphate is greatly improved; meanwhile, the lithium ion dispersion speed of the material is increased, and therefore the large-rate charging and discharging performance of lithium iron phosphate is improved, and the low-temperature charging and discharging performance of the material is improved; the material is simple in preparation process and suitable for industrial large-scale production.

Description

technical field [0001] The invention belongs to the technical field of lithium ion battery materials, and in particular relates to a lithium iron phosphate composite cathode material and a preparation method thereof. Background technique [0002] With the promotion of new energy technologies, the application and development of lithium-ion power batteries in new energy vehicles is in full swing. Battery materials are the key factors determining the performance of lithium-ion batteries, and the performance of cathode materials plays a decisive role. Lithium iron phosphate has attracted the attention of technical personnel in the field of power lithium-ion batteries because of its theoretical capacity as high as 170mAh / g, good cycle performance and safety performance. However, due to the low lithium ion diffusion rate of lithium iron phosphate (10 -14 ~10 -10 cm 2 / s) and low electronic conductivity (<10 -9 s / cm), so that the actual capacity of lithium iron phosphate is...

Claims

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Application Information

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IPC IPC(8): H01M4/58H01M4/62H01M10/0525
CPCH01M4/5825H01M4/625H01M10/0525Y02E60/10
Inventor 李震祺刘立君宋翠环
Owner 李震祺
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