CN113307307B - Method for preparing lithium-rich iron manganese of lithium ion battery anode material by dry method - Google Patents
Method for preparing lithium-rich iron manganese of lithium ion battery anode material by dry method Download PDFInfo
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- CN113307307B CN113307307B CN202110531227.9A CN202110531227A CN113307307B CN 113307307 B CN113307307 B CN 113307307B CN 202110531227 A CN202110531227 A CN 202110531227A CN 113307307 B CN113307307 B CN 113307307B
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- C01G49/00—Compounds of iron
- C01G49/0018—Mixed oxides or hydroxides
- C01G49/0027—Mixed oxides or hydroxides containing one alkali metal
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- C01G45/00—Compounds of manganese
- C01G45/12—Manganates manganites or permanganates
- C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
- C01G45/125—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type[MnO3]n-, e.g. Li2MnO3, Li2[MxMn1-xO3], (La,Sr)MnO3
- C01G45/1257—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type[MnO3]n-, e.g. Li2MnO3, Li2[MxMn1-xO3], (La,Sr)MnO3 containing lithium, e.g. Li2MnO3, Li2[MxMn1-xO3
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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Abstract
A method for preparing a lithium-iron-manganese-rich cathode material of a lithium ion battery by a dry method belongs to the field of lithium ion batteries, and provides a preparation method of the lithium-iron-manganese-rich cathode material, which is suitable for industrialization and is environment-friendly. The method is used for overcoming the defects of complex steps, more control conditions and toxic and harmful synthetic raw materials of the existing synthetic method. The method comprises the steps of firstly synthesizing F and M precursor materials by adopting a low-temperature solid phase method, then grinding the two precursor materials together by adopting a dry mixing mode, carrying out mechanochemical action by dry ball milling, and then carrying out calcination treatment to obtain the lithium-rich iron-manganese anode material. Under the charge-discharge multiplying power of 0.2C, the first discharge specific capacity of the material reaches 195mA h g ‑1 The first coulombic efficiency was 80%. The synthesis method adopts a dry method for synthesis, eliminates the participation of toxic and harmful solvents, has rich reserves of used raw materials, low price and simple synthesis process, is a green and simple dry method synthesis route, and is suitable for industrial large-scale production.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and provides a preparation method of a lithium-rich iron-manganese positive electrode material which is suitable for industrialization and is environment-friendly.
Background
The continuous large consumption of fossil fuels and natural resources has caused serious environmental pollution, and more importantly, the consumption of limited natural resources has been increasingly aggravated in recent years to cause energy exhaustion. In order to overcome environmental and energy crisis, it is important to develop battery technology for efficient energy conversion and energy storage devices. Compared with the traditional lead-acid, nickel-cadmium and nickel-hydrogen batteries, the advanced lithium ion battery is widely applied due to the advantages of small volume, high safety, capability of providing the highest specific energy, volume energy density and the like. However, the energy density of commercial lithium ion batteries using intercalation type positive and carbon negative electrodes is approaching the limit (200-220 Wh/kg), and in order to meet the needs of various products, the exploration of electrode materials with higher energy density becomes the target of developing the next generation of rechargeable lithium ion batteries.
The currently commercialized positive electrode material for lithium ion batteries mainly includes lithium cobaltate (LiCoO) having a layered structure 2 ) Spinel structureLithium manganate (LiMn) 2 O 4 ) Olivine-structured lithium iron phosphate (LiFePO) 4 ) And lithium nickel cobalt oxide (LiNi) x Co y O 2 ) Lithium nickel cobalt manganese oxide (LiNi) x Co y Mn z O 2 ) The specific capacity of the lithium-containing oxide is below 200mAh/g, and compared with a carbon negative electrode with the specific capacity stabilized above 350mAh/g, the low energy density of the positive electrode material becomes a main bottleneck for limiting the improvement of the energy density of the lithium ion battery.
The lithium-iron-manganese-rich cathode material only contains two transition metal elements of iron and manganese as a lithium-rich cathode material, has the advantages of high specific capacity (more than 200 mAh/g) and high energy density of the lithium-rich cathode material, has the advantages of low cost, environmental friendliness, rich reserves, safety and the like, and is a lithium ion battery cathode material with great potential. The lithium-rich iron-manganese material is formed by combining two materials with poor electrochemical activity, has the characteristics of the lithium-rich material, high voltage and high capacity, but the material has the corresponding high capacity only at the nanometer level, so the lithium-rich iron-manganese material has higher requirements on the synthesis means and the processing method of the material.
The current successful synthesis method comprises the following steps: coprecipitation-hydrothermal-calcination three-step method, sol-gel method and low-temperature molten salt method. The three synthesis methods all adopt a wet synthesis route, wherein the three steps of coprecipitation-hydrothermal-calcination need to accurately control the pH value for synthesizing the lithium-rich Fe-Mn material, the dropping rate is at hydrothermal conditions, and the like, and the synthesis steps are complicated. The sol-gel method and the molten salt method are simpler methods for preparing the lithium-rich material, and simplify the synthesis process and control conditions. However, the two methods have high requirements on the solubility and the melting point of the metal salt material during bulk phase doping modification. Therefore, it is necessary to search for a synthetic route which is simpler, suitable for industrial production and environmentally friendly.
Disclosure of Invention
The invention aims to solve the defects of complex steps, more control conditions and toxic and harmful synthetic raw materials of the existing synthetic method. Provides a preparation method of a lithium-rich iron manganese anode material which is suitable for industrialization and is environment-friendly. The method comprises the steps of firstly synthesizing F and M precursor materials by adopting a low-temperature solid phase method, then grinding the two precursor materials together by adopting a dry mixing mode, carrying out mechanochemical action by dry ball milling, and then carrying out calcination treatment to obtain the lithium-rich iron-manganese anode material.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for preparing lithium-rich iron manganese of a lithium ion battery anode material by a dry method comprises the following steps:
step 1, mixing lithium hydroxide and ferric nitrate according to 4:1, adding 1-2 ml of distilled water, then carrying out mechanical ball milling for 20-60 mm, adding 1-2 ml of ethanol after ball milling for a period of time, and continuing ball milling for 10-30 min to obtain the reddish brown slurry.
And 2, drying the reddish brown slurry obtained in the step 1 in a vacuum oven for 80-120 ℃, calcining the dried product in a tubular furnace for 300-350 ℃ and 3h. The calcined powder was washed with distilled water several times and dried to obtain solid powder F.
And 4, dry mixing the sample powder F and M obtained in the steps 2 and 3 according to 3:7 and 2:8 respectively, carrying out dry ball milling (480-600 rpm, the time is 16 h), taking out the mixture, dry mixing and grinding, and repeating for three times to obtain brown powder FM.
And 5, calcining the powder FM obtained in the step 4 in a tubular furnace at 400-800 ℃ for 12h, and naturally cooling to room temperature to obtain the lithium-rich iron-manganese anode material.
The invention has the following advantages:
1. the method comprises the steps of firstly synthesizing F and M precursor materials by adopting a low-temperature solid phase method, then mixing the two materials together by adopting dry grinding, then carrying out dry ball milling in a high-energy ball mill for mechanochemical action, repeating the process for three times, and finally carrying out calcination treatment to obtain the high-capacity lithium-iron-manganese-rich cathode material. The method overcomes the defects of complex and fussy synthesis process and more control conditions of a coprecipitation-hydrothermal-calcination three-step method and a sol-gel method.
2. The method is a route for synthesizing the lithium-rich iron-manganese material by a dry method, and dry grinding and dry mixing are adopted in the synthesis process. Does not contain other toxic and harmful solvents, thereby reducing the emission of waste liquid and waste gas and being more environment-friendly.
3. The method has the advantages of simple equipment and simplified synthesis steps, and is easier to realize industrial large-scale production.
4. The raw materials used in the experiment have abundant reserves, low price and environmental protection.
5. The experiment can obtain the iron-manganese anode material with good electrochemical performance by changing the dosage ratio of the raw materials, and when the molar ratio of F to M is 3:7, the initial discharge specific capacity reaches 195mAh g under the charge-discharge multiplying power of 0.2C -1 The first coulombic efficiency was 80%.
Drawings
Fig. 1 is a process flow chart of preparing lithium-rich iron manganese of the anode material of the lithium ion battery.
FIG. 2 is an XRD diagram of lithium-rich iron manganese (two proportions) for preparing a lithium ion battery anode material
FIG. 3 is a first charge-discharge curve diagram of lithium-rich iron-manganese (two proportions) of the anode material for lithium ion battery at 0.2C rate
FIG. 4 is a cycle performance diagram of lithium-rich iron manganese (two proportions) of the anode material for preparing the lithium ion battery at a magnification of 0.2C
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Example 1
0.2mol (8.392 g) of lithium hydroxide and 0.05mol (20.2 g) of ferric nitrate are mixed, 2ml of distilled water is added, then mechanical ball milling is carried out for 60mim, 2ml of ethanol is added, and ball milling is continued for 30min, so as to obtain reddish brown slurry. Drying the reddish brown slurry in a vacuum oven at 100 ℃ for 18h, and calcining the dried product in a tubular furnace at 300 ℃ for 3h. Washing the calcined powder with 150ml of distilled water, and centrifugally drying to obtain F solid powderAnd (3) grinding. 0.1575mol (12.1918 g) of Li 2 CO 3 And 0.15mol (13.041 g) MnO 2 Dissolving the mixture in ethanol, ball-milling at 450rpm for 6h, calcining the ball-milled brick red powder in a tubular furnace at 600 ℃ for 12h, washing the calcined material with water to remove impurities, and drying in an oven to obtain M solid powder as a sample. 0.015mol (1.4218 g) of F solid powder and 0.035mol (4.088 g) of M solid powder were mixed by dry milling, and then milled again after dry high energy ball milling (480 rpm, time 16 h), and this process was repeated three times to obtain brown powder. And calcining in a tubular furnace (650 ℃,12 h), and naturally cooling to room temperature to obtain the lithium-rich iron-manganese anode material.
XRD phase analysis is carried out on the lithium-rich iron manganese anode material, and as shown in figure 2, the prepared sample has alpha-NaFeO 2 The crystal structure belongs to the R-3m space group. Li at 20-25 DEG 2 MnO 3 The superlattice diffraction peak of (4). Mixing the positive electrode active material serving as a positive electrode active material with acetylene black serving as a conductive agent and PVDF (polyvinylidene fluoride) serving as a bonding agent (dissolved in NMP) to prepare a positive electrode sheet, wherein the mass ratio of the positive electrode active material to the conductive agent to the bonding agent is = 80: 10; a lithium sheet is taken as a counter electrode, then a 2032 button cell is assembled to carry out constant-current charge-discharge test, the test voltage is 2-4.8V, the current is 40m A/g, the prepared lithium-rich iron-manganese anode material has the first discharge specific capacity of 195m Ah/g, and still has the reversible discharge specific capacity of 155m Ah/g after 25 cycles (as shown in figures 2 and 3).
Example 2
0.2mol (8.392 g) of lithium hydroxide and 0.05mol (20.2 g) of ferric nitrate are mixed, 2ml of distilled water is added, then mechanical ball milling is carried out for 60mim, 2ml of ethanol is added, and ball milling is continued for 30min, so as to obtain reddish brown slurry. And drying the reddish brown slurry in a vacuum oven at 100 ℃ for 18 hours, calcining the dried product in a tubular furnace at 300 ℃ for 3 hours, washing the calcined powder with 150ml of distilled water, and drying to obtain F solid powder. 0.1575mol (12.1918 g) of Li 2 CO 3 And 0.15mol (13.041 g) MnO 2 Dissolving the mixture in ethanol, ball-milling at 450rpm for 6h, calcining the ball-milled brick red powder in a tubular furnace at 6000 ℃ for 12h, washing the calcined material with water to remove impurities, and drying in an oven to obtain M solid powder as a sample. 0.010mol of(0.9478 g) F solid powder and 0.040mol (4.6727 g) M solid powder were mixed by dry grinding, and then ground again after dry high energy ball milling (480 rpm, 16 h), and this process was repeated three times to obtain brown powder. And calcining in a tubular furnace (650 ℃,12 hours), and naturally cooling to room temperature to obtain the lithium-rich iron-manganese anode material.
XRD phase analysis is carried out on the lithium-rich iron manganese anode material, and as shown in figure 2, the prepared sample has alpha-NaFeO 2 The crystal structure belongs to the R-3m space group. Li at 20-25 DEG 2 MnO 3 The superlattice diffraction peak of (1). Mixing the positive electrode active material serving as a positive electrode active material with acetylene black serving as a conductive agent and PVDF (polyvinylidene fluoride) serving as a bonding agent (dissolved in NMP) to prepare a positive electrode sheet, wherein the mass ratio of the positive electrode active material to the conductive agent to the bonding agent is = 80: 10; a lithium sheet is taken as a counter electrode, then a 2032 button cell is assembled to carry out constant current charge and discharge test, the test voltage is 2-4.8V, the current is 40m A/g, the prepared lithium-rich iron-manganese anode material has the first discharge specific capacity of 192m Ah/g, and still has the reversible discharge specific capacity of 156m Ah/g after 25 cycles (as shown in figures 2 and 3).
Finally, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (3)
1. A method for preparing lithium-rich iron manganese of a lithium ion battery anode material by a dry method is characterized by comprising the following steps:
step 1, mixing lithium hydroxide and ferric nitrate according to a proportion, adding distilled water, then carrying out mechanical ball milling, adding ethanol after ball milling, and continuing ball milling to obtain reddish brown slurry; the molar ratio of lithium hydroxide to ferric nitrate is 4:1;
step 2, completely drying the reddish brown slurry obtained in the step 1, calcining the dried slurry in a tubular furnace for 300 to 350 ℃ for 3 hours, cleaning the powder after heat treatment with distilled water, and drying to obtain solid powder F;
step 3. Mixing Li 2 CO 3 And MnO 2 Mixing and ball-milling according to a molar ratio of 1.1;
step 4, carrying out dry grinding on the sample powder F and the sample powder M obtained in the step 2 and the step 3 according to different proportions, wherein the mixing molar ratio of the sample F and the sample M is 3:7-2:8; performing dry ball milling, taking out the mixture after ball milling for a period of time, performing dry mixing and grinding, and repeating for three times to obtain brown powder FM;
step 5, calcining the powder FM obtained in the step 4 in a tubular furnace, and naturally cooling to room temperature, wherein the calcining temperature range of the tubular furnace is 400-800 ℃, and the calcining time is 12 hours, so as to obtain the lithium-rich iron-manganese cathode material; in the step 2, the drying temperature is 80 to 120 ℃, and the drying time is 16h;
in step 3, the temperature rise rate is 2~4 ℃/min.
2. The method for preparing the lithium-rich iron-manganese alloy for the positive electrode material of the lithium ion battery in the dry method according to claim 1, wherein in the step 1, the ball milling rotation speed is 300 to 400rpm, the first ball milling time is 20 to 60min, and the second ball milling time is 10 to 30min.
3. The method for preparing the lithium-rich iron-manganese alloy cathode material of the lithium ion battery according to the claim 1, wherein in the step 4, the rotation speed of the ball mill is 480 to 600rpm, and the single time is 16h.
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