CN101844756A - Method for preparing lithium iron phosphate by using steel slag - Google Patents

Abstract

The invention relates to a method for preparing phosphate containing over two metals, in particular to a method for preparing lithium iron phosphate. The method for preparing the lithium iron phosphate by using steel slag comprises the following steps: selecting and using the steel slag containing Fe and P and containing more than two elements of Mn, Ti, Cr, V and Ni, and reducing the steel slag at the temperature of between 1,200 and 1,600 DEG C to obtain Fe-P-based alloy containing doped elements; oxidizing the Fe-P-based alloy containing the doped elements at the temperature of between 500 and 1,000 DEG C to obtain Fe, P and oxides of the doped elements, namely preparing precursors of LiFePO4; adding a lithium source material, a phosphorus source material or a phosphorus-lithium source material into the precursors to make the molar ratio of Li to Fe to P in the mixture equal to 1-1.2: 1: 1, and mixing the material and the precursors uniformly; and roasting the mixture at the temperature of between 500 and 700 DEG C under the protection of nitrogen or argon to obtain a multi-element doped LiFePO4 material.

Description

The method for preparing iron lithium phosphate with slag

Technical field

The present invention relates to a kind of method for production of phosphate salt that contains two or more metals, especially method preparing phosphate iron lithium.

Background technology

Iron lithium phosphate (LiFePO ₄) be a kind of anode material for lithium-ion batteries.At present, LiFePO ₄The preparation method mainly comprise solid sintering technology and hydrothermal method.The general process of solid sintering technology is that lithium source, source of iron and phosphorus source material are mixed with certain stoichiometric ratio, carry out sintering under protection of inert gas, and the certain hour postcooling is to room temperature.Hydrothermal method is that the aqueous solution with water miscible lithium source, source of iron and phosphorus source material mixes by certain stoichiometric ratio, is transferred in the reactor, is incubated a few hours at a certain temperature, obtains LiFePO after the cooling ₄Precipitation.LiFePO ₄Specific conductivity own is lower, and the method for particle surface bag carbon film commonly used improves LiFePO in the production ₄The surface conductivity of particle.But LiFePO ₄It is more that the method for particle surface bag carbon film reduces the particle tap density, increased the cell making process difficulty.

A lot of metal ions are (as Mn ²⁺, Cr ³⁺, Ti ⁴⁺, Zr ⁴⁺, Nb ⁵⁺, V ⁵⁺, W ⁶⁺, Mo ⁶⁺Deng) to LiFePO ₄Have doping effect preferably, a small amount of doping can obviously improve its this cubic conductance, and can avoid the surperficial shortcoming that coats the tap density reduction that causes, is the emphasis of industry research at present.Metallurgical solid refuse slag itself contain many can be to LiFePO ₄Adulterated metal ingredient, but utilize slag to carry out LiFePO ₄The technology of preparation is not seen open report as yet.

Summary of the invention

The object of the present invention is to provide a kind ofly to prepare the method for iron lithium phosphate with slag, the multiple metallic element that utilizes slag itself to contain is realized the multi-element doping to iron lithium phosphate, improves electric conductivity on the basis that does not reduce tap density.

The present invention is achieved in that and a kind ofly prepares the method for iron lithium phosphate with slag, comprises the steps:

Select for use and contain Fe, P, contain the slag of the two or more elements among Mn, Ti, Cr, V, the Ni simultaneously, slag is reduced processing, obtain containing the Fe-P base alloy of doped element at 1200 ℃～1600 ℃;

Fe-P base alloy 500 ℃～1000 ℃ oxide treatment in air that will contain doped element obtain the oxide compound of Fe, P and doped element, promptly prepare LiFePO ₄Presoma;

In presoma, add lithium source material, phosphorus source material or phosphorus lithium source material, make Li in the mixture: Fe: P (mol ratio)=1～1.2: 1: 1, and mix;

Mixture under nitrogen or argon shield, in 500 ℃～700 ℃ roastings, is obtained the LiFePO of multi-element doping ₄Material.

T.Fe in the described slag 〉=18.0%, and 0.5%≤P ₂O ₅≤ 4.0%, and 1.0%≤MnO+TiO ₂+ Cr ₂O ₃+ V ₂O ₅≤ 10.0%.

Reducing medium is except carbon, CO or H in the reduction process of the present invention ₂Outward, reducing gas such as Sweet natural gas, methane also can reach reduction effect.

The present invention has following beneficial effect: the present invention uses slag to prepare LiFePO ₄, made full use of multiple elements such as containing Fe, P, Mn, Ti, Cr in the slag, reach multi-element doping LiFePO ₄Purpose, saved preparation LiFePO greatly ₄Resource, improve LiFePO ₄Electric conductivity, and guarantee LiFePO ₄Tap density.Opened up new direction for the slag high value added utilization in addition.

Embodiment

Embodiment 1:

(1) takes by weighing the steel-making slag powder (the slag main component sees Table 1) of 1000 grams and the powdered carbon of 100 grams and mix, place High Temperature Furnaces Heating Apparatus to handle 2.5 hours, take out and be chilled to room temperature in 1400 ℃ of following roasting reductions.The Fe-P base alloy that contains doped elements such as Mn, Cr after the reduction processing is separated through magnetic separation.(2) the Fe-P base alloy that the magnetic separation separation is obtained 650 ℃ of oxidations 3.4 hours, obtains composite oxides in air ambient.(3) take by weighing 440 gram NH again ₄H ₂PO ₄Carry out mechanically mixing with 98 gram LiOH with the composite oxides of acquisition and handle, make it even.(4) batching that will mix places ceramic crucible, and roasting is 8 hours under 520 ℃, nitrogen protection, cools to room temperature with the furnace, promptly obtains LiFePO ₄Material.

Embodiment 2:

(1) take by weighing 1000 steel-making slag powder (the slag main component sees Table 1) that restrain, place High Temperature Furnaces Heating Apparatus, the feeding flow is 2 liters/minute a CO reducing gas, in 1250 ℃ of roasting reductions reactions 1.8 hours, takes out and is chilled to room temperature.Magnetic separation obtains containing the Fe-P base alloy of an amount of doped element.(2) alloy that magnetic separation is obtained 750 ℃ of following oxidations 2.5 hours, obtains composite oxides in air ambient.(3) take by weighing 690 gram (NH again ₄) ₂HPO ₄Handle with carrying out mechanically mixing with 132 gram LiOH, make it even with the composite oxides that obtain.(4) batching that will mix places ceramic crucible, and roasting is 6 hours under 620 ℃, nitrogen protection, cools to room temperature with the furnace, promptly obtains LiFePO ₄Material.

Embodiment 3:

(1) take by weighing 1000 steel-making slag powder (the slag main component sees Table 1) that restrain, place High Temperature Furnaces Heating Apparatus, the feeding flow is 2 liters/minute H ₂Reducing gas in 1300 ℃ of roasting reduction reactions 1.5 hours, takes out and is chilled to room temperature.Magnetic separation obtains containing the Fe-P base alloy of an amount of doped element.(2) with the alloy that obtains in air ambient 950 ℃ of oxidations 2.5 hours, obtain composite oxides.(3) take by weighing 590 gram NH again ₄H ₂PO ₄With 79 gram Li ₂O carries out the mechanically mixing processing with the composite oxides of acquisition, makes it even.(4) batching that will mix places ceramic crucible, and roasting is 7.5 hours under 570 ℃, argon shield, cools to room temperature with the furnace, promptly obtains LiFePO ₄Material.

Embodiment 4:

(1) takes by weighing the steel-making slag powder (the slag main component sees Table 1) of 1000 grams and the powdered carbon of 100 grams and mix, place High Temperature Furnaces Heating Apparatus to handle 2.0 hours, take out and be chilled to room temperature in 1550 ℃ of following roasting reductions.The Fe-P base alloy that contains doped elements such as Mn, Cr, V after the reduction processing is separated through magnetic separation.(2) the Fe-P base alloy that the magnetic separation separation is obtained 850 ℃ of oxidations 3.0 hours, obtains composite oxides in air ambient.(3) take by weighing a certain amount of NH of 380 grams again ₄H ₂PO ₄With 179 gram Li ₂C ₂O ₄Carry out mechanically mixing with the composite oxides that obtain and handle, make it even.(4) batching that will mix places ceramic crucible, and roasting is 8 hours under 600 ℃, argon shield, cools to room temperature with the furnace, promptly obtains LiFePO ₄Material.

The main chemical constitution (weight %) of table 1 slag

	??CaO	??SiO 2	??Al 2O 3	??MgO	??T.Fe	??P 2O 5	??MnO	??TiO 2	??Cr 2O 3	??V 2O 5	??NiO
												Implement 1	??41.83	??9.30	??1.55	??9.94	??22.87	??2.19	??2.58	??0.63	??0.60	??0.11	??/
Implement 2	??32.43	??10.29	??3.20	??6.25	??30.90	??0.84	??3.38	??0.43	??1.22	??0.24	??0.11
												Implement 3	??36.18	??8.42	??0.80	??8.69	??29.57	??1.59	??1.99	??0.44	??0.15	??0.15	??0.09

	??CaO	??SiO 2	??Al 2O 3	??MgO	??T.Fe	??P 2O 5	??MnO	??TiO 2	??Cr 2O 3	??V 2O 5	??NiO
												Implement 4	??40.26	??12.08	??2.05	??10.86	??19.62	??2.89	??1.66	??1.02	??2.02	??0.18	??/

All the other are the oxide compound and the unavoidable impurities of trace elements such as Nb, Mo, W to slag except that main component in the table 1, and wherein content of elements is all less than 0.2%.

Claims (2)

1. one kind prepares the method for iron lithium phosphate with slag, it is characterized in that, comprises the steps:

Select for use and contain Fe, P, contain the slag of the two or more elements among Mn, Ti, Cr, V, the Ni simultaneously, slag is reduced processing, obtain containing the Fe-P base alloy of doped element at 1200 ℃～1600 ℃;

Fe-P base alloy 500 ℃～1000 ℃ oxide treatment in air that will contain doped element obtain the oxide compound of Fe, P and doped element, promptly prepare LiFePO ₄Presoma;

In presoma, add lithium source material, phosphorus source material or phosphorus lithium source material, make Li in the mixture: Fe: P (mol ratio)=1～1.2: 1: 1, and mix;

Mixture under nitrogen or argon shield, in 500 ℃～700 ℃ roastings, is obtained the LiFePO of multi-element doping ₄Material.

2. as claimed in claim 1ly prepare the method for iron lithium phosphate, it is characterized in that T.Fe in the described slag 〉=18.0%, and 0.5%≤P with slag ₂O ₅≤ 4.0%, and 1.0%≤MnO+TiO ₂+ Cr ₂O ₃+ V ₂O ₅≤ 10.0%.