CN106654254A - Lithium battery positive electrode material and preparation method thereof - Google Patents

Abstract

The invention provides a lithium battery cathode material and a preparation method thereof, and relates to the field of lithium ion batteries. A method for preparing a positive electrode material of a lithium battery, comprising: stirring and mixing a first microemulsion containing lithium acetate, manganese acetate and nickel acetate with a second microemulsion containing carbonate to obtain a third microemulsion. Adding water to the third microemulsion, solid-liquid separation and washing to obtain a solid, and calcining the dried solid. A lithium battery positive electrode material is prepared by the above-mentioned preparation method of the lithium battery positive electrode material. Two microemulsions with reactants solubilized separately are mixed. At this time, due to the collision, fusion, separation and recombination between micellar particles, the two reactants are exchanged and transferred in the micelles, causing chemical reactions in the nucleus. Crystal nuclei are produced, and then gradually grow up to obtain nanoscale materials. Its particle size is small, the diffusion rate of lithium ions is large, and the rate performance is good.

Description

A kind of positive electrode material of lithium battery and preparation method thereof

technical field

The invention relates to the field of lithium ion batteries, in particular to a lithium battery cathode material and a preparation method thereof.

Background technique

Lithium-ion battery is a secondary rechargeable battery, which has been widely used at present. Lithium-ion batteries are generally composed of positive electrodes, negative electrodes, diaphragms, electrolytes, and battery casings. The cost of positive electrode materials accounts for more than 40% of the battery, but the specific capacity of positive electrode materials is far lower than that of negative electrode materials. Therefore, Lithium batteries have important application value in research.

Lithium-rich manganese-based cathode material (typical chemical formula is xLi ₂ MnO ₃ -(1-x)LiMO ₂ , where M=a combination of several transition metal elements such as Ni, Co, and Mn), which is α-NaFeO ₂ type hexagonal layered structure (space group R-3m(166)), its discharge capacity is as high as 250mAh g ^-1 , so it has attracted much attention in battery research in recent years. The chemical formula of 0.6Li ₂ MnO ₃ -0.4LiNi _0.5 Mn _0.5 O ₂ , which is widely studied in lithium-rich manganese-based cathode materials, is because it has a high discharge specific capacity and there is no cobalt element in the chemical elements, so safe and non-toxic. However, lithium-rich manganese-based cathode materials also have the disadvantage of poor rate performance, which restricts the industrial application of the above materials.

Contents of the invention

The object of the present invention is to provide a lithium battery positive electrode material and a preparation method thereof, which aims to improve the disadvantage of poor rate performance of the existing lithium-rich manganese-based positive electrode material 0.6Li ₂ MnO ₃ -0.4LiNi _0.5 Mn _0.5 O ₂ .

The invention provides a technical solution:

A method for preparing a positive electrode material of a lithium battery, comprising: stirring and mixing a first microemulsion containing lithium acetate, manganese acetate and nickel acetate with a second microemulsion containing carbonate to obtain a third microemulsion. Adding water into the third microemulsion, obtaining solid through solid-liquid separation and washing, and calcining the dried solid.

A lithium battery positive electrode material is prepared by the above-mentioned preparation method of the lithium battery positive electrode material.

The beneficial effects of the positive electrode material for lithium batteries provided by the embodiments of the present invention and the preparation method thereof are: stirring and mixing the first microemulsion containing lithium acetate, manganese acetate, and nickel acetate with the second microemulsion containing carbonate to obtain a third microemulsion lotion. Two microemulsions with reactants respectively solubilized are mixed. Due to the collision, fusion, separation and recombination between microemulsion particles, the reactants are exchanged and transferred in the microemulsion; chemical reactions in the nucleus are caused, and crystal nuclei are generated. Gradually grow up, and then through drying and calcination of nano-sized particles. Its particle size is small, the diffusion rate of lithium ions is large, and the rate performance is improved.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is the XRD figure of the positive electrode material of lithium battery that the embodiment of the present invention provides;

Fig. 2 is the SEM picture of the solid provided by Example 1 of the present invention;

Fig. 3 is the first charge and discharge curve of the positive electrode material of the lithium battery provided by the first embodiment of the present invention under the voltage range of 2.0-4.8V;

FIG. 4 is a graph of the rate performance of the lithium battery positive electrode material provided in Example 1 of the present invention in the voltage range of 2.0-4.8V.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention, and It should not be considered as limiting the scope of the invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

The lithium battery positive electrode material and the preparation method thereof of the embodiment of the present invention are described in detail below.

The present invention provides a kind of preparation method of lithium battery cathode material, it comprises:

Stirring and mixing the first microemulsion containing lithium acetate, manganese acetate and nickel acetate with the second microemulsion containing carbonate to obtain a third microemulsion. Adding water to the third microemulsion, solid-liquid separation and washing to obtain a solid, and calcining the dried solid.

Preferably, the method for preparing the first microemulsion includes: dissolving lithium acetate, manganese acetate, and nickel acetate in a molar ratio of 1.84-2.00:0.8:0.2 in water to obtain the first water phase. Add the first oil phase, the first surfactant to the first water phase and stir.

It should be noted that, in other embodiments of the present invention, the first oil phase and the first surfactant can be added to the first water phase and stirred to obtain the first emulsion.

In the present invention, the reactants are reacted in the O/W system of the third microemulsion, and the O/W system can be directly formed by adding the first oil phase to the first water phase. Correspondingly, if the first water phase is added to the first oil phase, a W/O system will be formed first, and then an O/W system will be formed after continuous stirring.

In a preferred embodiment of the present invention, the molar ratio of lithium acetate, manganese acetate and nickel acetate is 1.92:0.8:0.2.

Preferably, the volume ratio of the first water phase, the first oil phase, and the first surfactant is 90-95:9-4:1. In a preferred embodiment of the present invention, the volume ratio of the first water phase, the first oil phase, and the first surfactant is 92:7:1. Under this ratio, the dispersion degree of the first microemulsion is the largest and the stability is the highest. , the microemulsion obtained by stirring is the highest.

Preferably, the first microemulsion also includes a small amount of a co-surfactant, and in the present invention, a co-surfactant is usually a short-chain alcohol, hydrogen, fatty alcohol or other weaker amphoteric compounds. The co-surfactant has the function of stabilizing the system, increasing the fluidity of the interfacial film; adjusting the HLB value of the surfactant. In addition, co-surfactants reduce the bending energy required for the formation of the first microemulsion, making microemulsion droplets easier to form.

Preferably, the method for preparing the second microemulsion comprises: dissolving the carbonate in water to obtain a second water phase; adding a second oil phase and a second surfactant to the second water phase and stirring. The volume ratio of the first water phase, the second oil phase and the second surfactant is 90-95:9-4:1. In a preferred embodiment of the present invention, the volume ratio of the first water phase, the first oil phase, and the first surfactant is 92:7:1.

The above-mentioned carbonate is a carbonate that is easily soluble in water, preferably, sodium carbonate is used in this embodiment.

Correspondingly, in a preferred embodiment of the present invention, the second microemulsion also includes a small amount of co-surfactant.

Preferably, the components of the first oil phase and the second oil phase are the same, and both are selected from one of isopropyl myristate and glyceryl caprylate. In other embodiments of the present invention, the first oil phase and the second oil phase may also be C6-C8 linear hydrocarbons and the like.

Preferably, the first surfactant and the second surfactant have the same components, and both are composite surfactants composed of span80 and tween80. In other embodiments of the present invention, the first surfactant and the second surfactant can also be selected from 2-ethylhexyl sodium succinate, cetyltrimethylammonium bromide, polyoxyethylene Ethers, etc.

In the microemulsion system, the surfactant increases the surface activity of the droplets, reduces the interfacial tension of oil and water, prevents the aggregation of droplets, and improves the stability.

Preferably, in the third microemulsion, the molar ratio of the carbonate ions provided by the second microemulsion to the manganese ions provided by the first microemulsion is 0.8:2.00-2.25. In a preferred embodiment of the present invention, the molar ratio of carbonate ions to manganese ions is 0.8:2.16.

Preferably, the high-speed mixing of the first microemulsion and the second microemulsion is carried out in a water bath or an oil bath at 60°C.

Preferably, in the step of adding water to the third microemulsion, the volume of water added is 1-1.2 times the volume of the third microemulsion. Water is added into the third microemulsion to break the emulsion and separate the water phase and the oil phase. After filtration, a solid was obtained, which was washed with water and ethanol, and then dried. In this embodiment, the volume of water added is 1-1.1 times the volume of the third microemulsion.

Preferably, drying of the solid is carried out under vacuum.

In this embodiment, the solid is calcined in air, specifically, calcined at 500°C for 5 hours, at 750°C for 5 hours, and at 900°C for 10 hours. Calcination under the above-mentioned conditions realizes the migration of lithium ions and manganese ions and the decomposition of acetate groups, and synthesizes a lithium battery positive electrode material with a hexagonal layered structure of crystal form α-NaFeO ₂ .

A microemulsion is a single spherical droplet that is transparent or translucent, low viscosity, isotropic and thermodynamically stable. Microemulsion has special advantages such as small particle size, transparency and stability. In this special microenvironment, there are multiple "microreactors" in the microemulsion, which provide an ideal reaction medium for the reaction between substances.

The microemulsion particles in the microemulsion are constantly doing Brownian motion. When different particles collide with each other, the hydrocarbon chains of the surfactant and co-surfactant penetrate into each other. At the same time, the substances in different microemulsion particles enter Material exchange and chemical reaction occur in another particle to make nano-powder lithium battery anode material.

Nano-powder lithium battery cathode material has small particle size, high diffusion rate of lithium ions, and improved rate performance.

The invention provides a lithium battery positive electrode material, which is prepared by the above-mentioned preparation method of the lithium battery positive electrode material.

The lithium battery cathode material provided by the present invention is a lithium-rich manganese-based cathode material (typical chemical formula is xLi ₂ MnO ₃ -(1-x)Li Ni O ₂ , which is an α-NaFeO ₂ -type hexagonal layered structure (space group R- 3m(166)), the discharge specific capacity is as high as 250mAh g ^-1 , so it has attracted much attention in the field of lithium battery cathode materials. The lithium battery cathode material with better rate performance provided by the present invention has the following chemical formula composition: 0.6Li ₂ MnO ₃ - 0.4LiNi _0.5 Mn _0.5 O ₂ , its particle size is small, the diffusion rate of lithium ions is high, and the rate performance is good.

The characteristics and performance of the present invention will be described in further detail below in conjunction with the examples.

Example 1

This embodiment provides a method for preparing a lithium battery positive electrode material, which includes the following steps:

Preparation of the first microemulsion: 92 mmol of lithium acetate, 40 mmol of manganese acetate and 10 mmol of nickel acetate were dissolved in 500 ml of deionized water, stirred and mixed to obtain the first water phase. Take 90ml of the first water phase in a beaker, add 9ml of the first oil phase into the beaker and keep stirring. In this embodiment, the first oil phase is isopropyl myristate. Add 1 ml of the first surfactant into the beaker and keep stirring. In this embodiment, the first surfactant is a composite surfactant of span80 and tween80. Stir the first microemulsion evenly under magnetic stirring.

The preparation of the second microemulsion: get 100mmol sodium carbonate to be dissolved in 500ml deionized water and stir and mix to obtain the second water phase, get the second water phase of 90ml in the beaker, add the second oil phase of 9ml in the beaker and keep stirring, In this example, the second oily phase was isopropyl myristate. Add 1ml of the second surfactant into the beaker and keep stirring. In this embodiment, the second surfactant is a composite surfactant of span80 and tween80. Stir the second microemulsion evenly under magnetic stirring.

The first microemulsion is mixed with the second microemulsion to obtain the third microemulsion. The third microemulsion is moved into a 60°C hydrothermal kettle, stirred at a stirring speed of 500r/min, and a chemical reaction occurs to form a precipitate.

Add 100ml of deionized water to the third microemulsion, shake and mix, and break the third microemulsion. The water phase and the oil phase were separated, and the water phase was filtered to obtain a solid, which was washed three times with deionized water and twice with ethanol, and dried in a vacuum oven at 100° C. for 10 h under vacuum.

The above solid was calcined at 500° C. for 5 hours, 750° C. for 5 hours, and 900° C. for 10 hours to obtain lithium battery cathode material 0.6Li ₂ MnO ₃ -0.4LiNi _0.5 Mn _0.5 O ₂ .

Embodiment two

This embodiment provides a method for preparing a cathode material for a lithium battery, which differs from the method for preparing an anode material for a lithium battery provided in Example 1 in that:

The first aqueous phase was prepared by dissolving 96mmol of lithium acetate, 40mmol of manganese acetate and 10mmol of nickel acetate in 500ml of deionized water and stirring and mixing. The volumes of the first water phase, the first oil phase and the first surfactant in the first microemulsion are 92ml, 7ml and 1ml respectively.

The second aqueous phase was prepared by dissolving 108 mmol of sodium carbonate in 500 ml of deionized water and stirring and mixing. The volumes of the second water phase, the second oil phase and the second surfactant in the second microemulsion are 92ml, 7ml and 1ml respectively.

Embodiment three

This embodiment provides a method for preparing a cathode material for a lithium battery, which differs from the method for preparing an anode material for a lithium battery provided in Example 1 in that:

The first aqueous phase was prepared by dissolving 100 mmol of lithium acetate, 40 mmol of manganese acetate and 10 mmol of nickel acetate in 500 ml of deionized water and stirring and mixing. The volumes of the first water phase, the first oil phase and the first surfactant in the first microemulsion are 95ml, 4ml and 1ml respectively.

The second aqueous phase was prepared by dissolving 112.5 mmol of sodium carbonate in 500 ml of deionized water and stirring and mixing. The volumes of the second water phase, the second oil phase and the second surfactant in the second microemulsion are 95ml, 4ml and 1ml respectively.

Embodiment Four

This embodiment provides a method for preparing a cathode material for a lithium battery, which differs from the method for preparing an anode material for a lithium battery provided in Example 1 in that:

The volumes of the first water phase, the first oil phase and the first surfactant in the first microemulsion are 95ml, 4ml and 1ml respectively.

The volumes of the second water phase, the second oil phase and the second surfactant in the second microemulsion are 92ml, 7ml and 1ml respectively.

Embodiment five

This embodiment provides a method for preparing a cathode material for a lithium battery, which differs from the method for preparing an anode material for a lithium battery provided in Example 1 in that:

Both the first oil phase and the second oil phase are caprylic capric acid glyceride.

Embodiment six

This embodiment provides a method for preparing a cathode material for a lithium battery, which differs from the method for preparing an anode material for a lithium battery provided in Example 1 in that:

Both the first surfactant and the second surfactant are sodium 2-ethylhexyl succinate.

Embodiment seven

This embodiment provides a method for preparing a cathode material for a lithium battery, which differs from the method for preparing an anode material for a lithium battery provided in Example 1 in that:

During the preparation process of the first microemulsion, the first microemulsion also includes a co-surfactant fatty alcohol, specifically, a small amount of fatty alcohol is added to the first water phase and continuously stirred.

Correspondingly, in this embodiment, the second microemulsion also includes a small amount of co-surfactant fatty alcohol.

Test example 1

The lithium battery positive electrode material prepared in Example 1 was tested. Adopt X'pert TROMPD type polycrystalline target X-ray diffractometer (Cu target Kα ray λ=0.15406nm) of Philips Company, Ni filter, tube current is 20mA, tube voltage is 20kV, scanning angle 2θ=10～80 °, scan speed 8°·min ⁻¹ X-ray diffraction was performed on the positive electrode material for lithium battery prepared in Example 1, and the XRD pattern was obtained as shown in Figure 1.

The S-4800 scanning electron microscope of Hitachi, Japan was used to conduct scanning electron microscope analysis on the positive electrode material of the lithium battery in Example 1, and the obtained scanning electron microscope (SEM) results are shown in FIG. 2 .

It can be seen from Fig. 1 that the main diffraction peaks of the lithium battery cathode material in Example 1 can be indexed as α-NaFeO2 type hexagonal layered structure (space group R-3m (166)), but between 21° and 25° There are some weak superlattice peaks that can be indexed as Li ₂ MnO ₃ (space group C2/m), which are caused by the superlattice arrangement of Li ⁺ and Mn ⁴⁺ ions in the transition metal layer, indicating that the synthesized material is Typical Li-rich materials. And the XRD diffraction peaks 006 and 012 are clearly split, indicating that the synthesized material has a good layered structure.

It can be seen from Fig. 2 that the solids in Example 1 are microspheres with good sphericity and uniform size.

The electrochemical performance of lithium battery cathode materials was characterized by using CR2032 button cells. First, mix the active material, conductive agent acetylene black, and binder (PVDF mass fraction 10%) in a mass ratio of 80:13:7, then add an appropriate amount of N-methylpyrrolidone as a solvent, and stir well. The obtained slurry was coated on an aluminum foil and dried at 120° C. for 10 h under vacuum, and then punched out a disc with a diameter of 14 mm with a punching machine, and compacted under 20 MPa to obtain a positive electrode sheet of a button battery. In a glove box filled with argon, metal lithium is used as the negative electrode, 1mol/L LiPF6 is dissolved in a mixed solution of EC-DMC (volume ratio 1:1) as the electrolyte, and Celgard2400 microporous polypropylene membrane is used as the separator. Coin cells were produced in the order of coin cell assembly. In this embodiment, the BTS test system of Shenzhen Neware Company is used to conduct constant current charge and discharge tests at room temperature at 2.0-4.8V, where 1C=200mAh g ^-1 . Figure 3 is the first charge and discharge curve of the button battery at 0.1C, and Figure 4 is the rate performance diagram of the button battery.

It can be seen from Figure 4 that the first charge curve of the lithium battery cathode material provided in Example 1 has a typical plateau at about 4.4V, indicating that the synthesized material is a typical lithium-rich cathode material, and its first discharge specific capacity at 0.1C is 267.8m Ahg ^-1 . It can be seen from Figure 4 that the average discharge specific capacity of the above materials at 0.1C is 269.2mAh g ^-1 , the average discharge specific capacity at 10C is 108.1mAh g ^-1 , the capacity retention rate is 97.4%, and the first time at 0.5C The discharge specific capacity is 205.3mAh g ^-1 , the discharge specific capacity after cycles is 172.3mAh g ^-1 , and the capacity retention rate is 83.9%.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a kind of preparation method of anode material of lithium battery, it is characterised in that it includes：Will be containing lithium acetate, manganese acetate, acetic acid First microemulsion of nickel is mixed to get the 3rd microemulsion with the stirring of the second microemulsion containing carbonate, to the 3rd microemulsion Interior addition water, Jing separation of solid and liquid, washing obtain solid, and the dried solid is calcined.

2. the preparation method of anode material of lithium battery according to claim 1, it is characterised in that prepare first micro emulsion The method of liquid includes, is 1.84-2.00 by mol ratio：0.8：0.2 lithium acetate, the manganese acetate, the nickel acetate are molten The first water phase is obtained in water；The first oil phase, first surface activating agent are added to first water and stir；First water Phase, first oil phase, the volume ratio of the first surface activating agent are 90-95：9-4：1.

3. the preparation method of anode material of lithium battery according to claim 1, it is characterised in that prepare second micro emulsion The method of liquid includes, carbonate is dissolved in into water and obtains the second water phase；The second oil phase, second surface are added to second water to live Property agent is simultaneously stirred；The second water phase, second oil phase, the volume ratio of the second surface activating agent are 90-95：9-4：1.

4. the preparation method of the anode material of lithium battery according to claim 1-3 any one, it is characterised in that first is oily It is mutually identical with the second oil-phase component, and the one kind being selected from isopropyl myristate, Glycerin, mixed triester with caprylic acid capric acid.

5. the preparation method of anode material of lithium battery according to claim 4, it is characterised in that first surface activating agent and Second surface bioactive agent composition is identical, and is the complexed surfactant of span80 and tween80 compositions.

6. the preparation method of anode material of lithium battery according to claim 1, it is characterised in that in the 3rd microemulsion In, the carbanion provided by second microemulsion is with the mol ratio of the manganese ion provided by first microemulsion 0.8：2.00-2.25.

7. the preparation method of anode material of lithium battery according to claim 1, it is characterised in that first microemulsion, Second microemulsion also contains cosurfactant.

8. the preparation method of anode material of lithium battery according to claim 1, it is characterised in that to the 3rd microemulsion In the step of interior addition water, the volume for adding water is 1-1.2 times of the 3rd microemulsion volume.

9. the preparation method of anode material of lithium battery according to claim 1, it is characterised in that the drying solid is true Carry out under empty condition.

10. a kind of anode material of lithium battery, the preparation method system of the anode material of lithium battery by described in any one of claim 1-9 It is standby to form.