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Rare-earth type lithium iron phosphate serving as cathode material of lithium secondary battery and preparation method thereof

A lithium secondary battery, lithium iron phosphate technology, applied in battery electrodes, circuits, electrical components, etc., can solve the three elements that do not meet the chemical dose ratio, the uneven particle size of lithium iron phosphate materials, electrical conductivity and ion diffusion rate Low problems, to achieve the effect of improving electrochemical performance, improving electrical conductivity, and improving electrical conductivity

Active Publication Date: 2012-07-11
HUAWEI TEHCHNOLOGIES CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It mainly has the following deficiencies: 1. Since the lithium, iron, and phosphorus of lithium iron phosphate come from three kinds of materials, uneven mixing often occurs, and the prepared product contains too many impurities, and the ratio of the three elements does not meet The chemical dosage ratio affects the electrochemical performance of the product; 2. The general process time needs at least 20 hours, and a large amount of amine waste gas must be decomposed
3. The particles of the prepared lithium iron phosphate material are not uniform, the particle size distribution range is wide, and the crystal shape is irregular; 4. The material particles synthesized at high temperature are relatively coarse, and it is difficult to control the batch stability of the product; 5. During the sintering process, it is necessary to Extensive use of inert gas to prevent oxidation of ferrous ions
[0005] In addition, compared with mature materials such as lithium cobaltate, lithium manganate and ternary materials, the synthesized pure lithium iron phosphate has very low conductivity and ion diffusion rate, and generally can only be charged and discharged at a small current density. This limits the scope of application of lithium iron phosphate in practice

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] (1) Weigh cerium-rich mixed rare earth materials, ferrous sulfate, lithium carbonate, diammonium hydrogen phosphate and cellulose acetate butyrate at a molar ratio of 2.5:50:25:50:1, and dissolve the cellulose acetate butyrate In acetone, prepare a solution with a weight concentration of cellulose acetate of 42%, and set aside; pour ferrous sulfate, lithium carbonate, diammonium hydrogen phosphate and cerium-rich mixed rare earth materials into a V-type powder mixer and mix for 30 minutes In the powder mixing process, the cellulose acetate dissolved in acetone is gradually sprayed into the powder mixture, so that the cellulose acetate sticks evenly to the mixture particles of the four materials that have been mixed, and the mixture is mixed after the solution is sprayed. Powder for 15 minutes, then take out and dry at 120°C for 30 minutes.

[0031] (2) Put the above-mentioned dried mixture particles into an atmosphere furnace protected by inert gas, keep it warm for 45 ...

Embodiment 2

[0037] The preparation method is the same as that of Example 1, except that the raw materials and the proportioning ratio are slightly adjusted, and the polycerium-rich mixed rare earth, iron phosphate, lithium carbonate and cellulose acetate butyrate are weighed in a molar ratio of 3.3:71.7:35:1;

[0038] The 18650 battery was fabricated by the same method as in Example 1 and then tested.

[0039] Under the ambient temperature of 20±2°C, the above-mentioned 18650 battery was charged and discharged for the first time at 0.2C between 3.65 and 2.0V, and the reversible specific capacity was 157mAh / g, which was 2.6% higher than that of Example 1, and the high-rate discharge performance was also better. , 5C, 20C and 30C discharge specific capacity can reach 95.8%, 84.3% and 77%, and the electric cycle performance is also relatively good. After 10C cycle for 80 times, the specific capacity drops by 1.5%.

Embodiment 3

[0041] The preparation method is the same as that of Example 1, except that the raw materials and the proportioning ratio are slightly adjusted, and the polycerium-rich mixed rare earth, iron phosphate, lithium carbonate and cellulose acetate butyrate are weighed in a molar ratio of 4.2:71.7:36.7:1;

[0042] The 18650 battery was fabricated by the same method as in Example 1 and then tested.

[0043] Under the ambient temperature of 20±2°C, the battery is charged and discharged for the first time at 0.2C between 3.65 and 2.0V, and the reversible specific capacity is 159mAh / g, which is 3.9% higher than that of Example 1. The high-rate discharge performance is also better than that of Example 2. The discharge specific capacity of 5C, 10C, 20C and 30C can reach 95.3%, 88%, 80.1% and 74%, and the electric cycle performance decreases by 5.2% after 50 cycles.

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Abstract

The invention relates to rare-earth type lithium iron phosphate serving as the cathode material of a lithium secondary battery and a preparation method thereof. The rare-earth type lithium iron phosphate contains 100 mole fractions of lithium iron phosphate, 3.9-7.8 mole fractions of rare-earth alloy and 1.1-2.2 mole fractions of cellulose acetate. The preparation method of the rare-earth type lithium iron phosphate comprises the following steps of: putting an iron source compound, a lithium source compound, a phosphorus source compound and a rare-earth material into a powder mixer for powder mixing; in the powder mixing process, gradually spraying cellulose acetate dissolved in acetone to the mixed powder so that cellulose acetate is uniformly stuck on the mixture particles of the four materials, and drying; pre-sintering the dried mixture particles in an atmosphere furnace under inert gas protection; and carrying out heat preservation on the pre-sintered powder in the atmosphere furnace under inert gas protection to obtain the rare-earth type lithium iron phosphate. The rare-earth type lithium iron phosphate provided by the invention has the advantages of good conductive performance, relatively short preparation time and the like.

Description

technical field [0001] The invention belongs to the technical field of electrochemical battery manufacturing, and relates to a positive electrode material used in a lithium battery, in particular to a rare-earth type lithium iron phosphate used as the positive electrode material of a lithium secondary battery and a preparation method thereof. Background technique [0002] Since the appearance of lithium iron phosphate with olivine structure in 1997, lithium iron phosphate has gradually shown some of its unique advantages: 1. Lithium iron phosphate can be used as a new cathode material for lithium batteries, with better high temperature performance and lower specific capacity Not low, especially good safety; 2. Lithium iron phosphate has a wide range of raw materials, cheap prices, and no environmental pollution. Therefore, lithium iron phosphate has been selected by countries all over the world as a new energy material, especially the positive electrode material for vehicle ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/62H01M4/58
CPCY02E60/12Y02E60/10
Inventor 焦德华
Owner HUAWEI TEHCHNOLOGIES CO LTD
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