High density lithium iron phosphate and method for synthesizing

A technology of lithium iron phosphate and its synthesis method, which is applied in phosphorus compounds, chemical instruments and methods, and electrode manufacturing, and can solve problems such as slow mass transfer speed

Inactive Publication Date: 2009-04-01
BAK INT TIANJIN +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, solid-phase synthesis also has its inherent disadvantages: high-temperature synthesis is a reaction between solid phases, and the mass transfer rate between Li, Fe, and P elements is relatively slow, so long-term roasting (10-20 hours) is required, or even It also needs to be pre-fired, and then secondly roasted after grinding or the mixture is passed through a high-energy mill and mechanically activated to ensure that the product does not appear impurity phases

Method used

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  • High density lithium iron phosphate and method for synthesizing
  • High density lithium iron phosphate and method for synthesizing
  • High density lithium iron phosphate and method for synthesizing

Examples

Experimental program
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Effect test

Embodiment 1

[0025] Weigh Li 2 CO 3 34.7g, NH 4 h 2 PO 4 111.6g, FeC 2 o 4 2H 2 O 180g, Li 2 PO 3 F3.3g, sucrose 19g, after these five kinds of raw materials are mixed evenly by dry method, slowly add in the beaker that 350ml water is housed under stirring state, wait for CO 2 After basically escaping, move it into a 3L ball mill jar for ball milling for 3 hours. Put the slurry mixed by ball milling into a tray, dry it in an oven at 110°C, and ball mill the dry material for 3 hours. The obtained powder is punched by a granulator into 10mm granular, put the granular material into the crucible, heat up to 750°C at 5°C / min in the atmosphere protection furnace, keep the temperature for 6h, stop heating, and naturally cool to room temperature, the protection gas used in the roasting process is N 2 , the calcined material is crushed to 150 mesh by ball milling to obtain lithium iron phosphate product, the tap density of this product is 1.45g / cm 3 . Lithium iron phosphate product, ac...

Embodiment 2

[0027] Weigh LiOH·H 2 O 41.2g, NH 4 h 2 PO 4 112.7g, FeC 2 o 4 2H 2 O 180g, Na 2 PO 3 F2.9g, glucose 16.5g, ethanol 400ml, put the above materials into a 3L ball mill jar, and ball mill and mix for 2h. Put the mixed slurry into a tray, dry it in an oven at 80°C, and then ball mill the dry material for 4 hours. The obtained powder is punched into 10mm granular, put the granular material into the crucible, under N 2 In the atmosphere protection furnace, the temperature was raised to 680°C at 5°C / min, and the temperature was kept constant for 8 hours. The heating was stopped, and it was naturally cooled to room temperature. The roasted product was ground to 150 mesh by ball milling to obtain lithium iron phosphate product. The tap density of this product was 1.38g / cm 3 . The assembly and testing method of the simulated battery is the same as in Example 1, and the measured specific capacity is 135mAh / g.

Embodiment 3

[0029] Weigh LiC 2 h 3 o 2 2H 2 O 91.8g, (NH 4 ) 2 HPO 4 125.4g, FeCO 3 116g, Na 2 PO 3 F7.1g, glucose 16.5g, ethanol 400ml, put the above materials into a 3L ball mill jar, and ball mill and mix for 2h. Put the mixed slurry into a tray, dry it in an oven at 80°C, and then ball mill the dry material for 4 hours. The obtained powder is punched into 10mm granular, put the granular material into the crucible, under N 2 In the atmosphere protection furnace, the temperature was raised to 680°C at a rate of 5°C / min, and the temperature was kept constant for 8 hours. The heating was stopped, and it was naturally cooled to room temperature. The roasted product was ground to 150 mesh by ball milling to obtain lithium iron phosphate product. The tap density of this product was 1.42g / cm 3 . The assembly and testing methods of the simulated battery are the same as in Example 1, and the measured specific capacity is 140mAh / g.

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Abstract

The public invented a high-density lithium iron phosphate and a synthesis method thereof, the molecular expression formula of the high-density lithium iron phosphate is: Li1-x MexFe(PO4)1-1/3xFx (x is not less than or equal to 0.01 and not more than or equal to 0.10), wherein, Me is a cation doped element and is one of Li, Na and Mg. The synthesis method of the high-density lithium iron phosphate comprises the following steps: step 1: lithium salt, ferrous salt, phosphate and a fluxing agent are mixed according to the calculation of the molecular expression formula; step 2: required amount of reductive ferric iron is added, water or ethanol is taken as a dispersion medium, and granules are prepared by milling, drying and re-milling after the drying; step 3: the prepared granules are transferred into an atmosphere protection furnace and the black lithium iron phosphate is prepared after the calcination in the N2 gas environment. The lithium iron phosphate which is synthesized by using the method has the advantages of high specific capacity, high tap density, good cycle performance, good rate property, simple process and low cost, thereby being applicable to industrial mass production.

Description

technical field [0001] The invention relates to a lithium iron phosphate positive electrode material for a lithium ion battery and a synthesis method thereof, in particular to a method for increasing the tap density of the material and improving the particle size distribution of the powder by using a process of adding flux. Background technique [0002] Lithium-ion battery is a green battery that was commercialized in the early 1990s. Because of its advantages such as high working voltage, high specific energy, long cycle life, no memory effect, and no environmental pollution, it has been widely used since its inception. With the continuous expansion of the application field of lithium batteries, the battery cathode materials are also showing a trend of diversification. [0003] In 1997, Goodenough et al first reported LiFePO with olivine structure 4 It can reversibly intercalate and deintercalate lithium ions. It is considered to be an ideal material for lithium-ion batter...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/58H01M4/48H01M4/04C01B25/45
CPCY02E60/10
Inventor 万里城李启孙鸿飞刘玉平
Owner BAK INT TIANJIN
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