CN110371940A - A kind of LiMnPO4Presoma template Li3PO4Tiny balloon and its preparation method and application - Google Patents

Abstract

The invention discloses a LiMnPO ₄ precursor template Li ₃ PO ₄ hollow microsphere and its preparation method and application, belonging to the technical field of positive electrode materials of lithium ion batteries. Fully react in the mixed solvent of glycol and deionized water, the reaction product is subjected to solid _- liquid separation, washing, and drying in sequence to obtain the target product _Li3PO4 hollow microspheres, adjust the amount of diethylene glycol or sodium hydroxide during the reaction, Li ₃ PO ₄ hollow microspheres with a diameter of 100 nm to 5 μm can be obtained, and the application of the prepared hollow microspheres in high-performance lithium-ion battery cathode materials is also disclosed. The invention has simple synthesis process, convenient operation, cheap and easy-to-obtain raw materials, low equipment requirements, and is suitable for industrialized production.

Description

A kind of LiMnPO4 precursor template Li3PO4 hollow microspheres and its preparation method and application

technical field

The invention relates to the technical field of cathode materials for lithium ion batteries, in particular to a _LiMnPO4 precursor template _Li3PO4 hollow microsphere, a preparation method and application thereof _.

Background technique

Compared with other secondary batteries such as lead storage and nickel-cadmium batteries, lithium-ion batteries have the advantages of wide operating temperature, high output voltage, low self-discharge rate, high specific power, and large specific energy. With the continuous improvement of people's needs, lithium-ion batteries are developing towards lighter, safer, higher specific energy and higher specific power. Cathode material is an important part of lithium-ion batteries, and its research and development play a vital role in the overall performance of lithium-ion batteries. Cathode materials can be divided into layered structure, spinel structure, etc. according to the structure. Among them, LiMnPO ₄ cathode material with forsterite structure has the characteristics of low cost, high safety, stable structure, and environmental friendliness. It is a hot positive electrode for current research. one of the materials. However, its ionic and electronic conductivity is very low, resulting in poor rate performance. At present, the migration distance of ions is shortened by nanonizing the grain size of materials, thereby improving the rate performance of materials. However, nano-sized grains will lead to a decrease in the tap density of the positive electrode material and a decrease in the volumetric energy density of the battery. Nano-sized grains have a high specific surface area, and are prone to side reactions when in contact with the electrolyte, resulting in capacity loss and safety issues. In addition, the nano-sized crystal grains are difficult to mix evenly with conductive agents and binders, and the processing technology is poor during battery preparation. These problems with the nano-grain size have seriously hindered the commercial development and practical application of LiMnPO ₄ cathode materials.

The hollow microsphere structure material assembled by nano-grains has the characteristics of high tap density, moderate specific surface area and good processing technology, which can not only exert the size effect of nano-grains, but also avoid the above problems. It is widely used in many fields such as energy storage, biomedicine and chemical catalysis. At present, the preparation methods of positive electrode materials with hollow microsphere morphology include hard template method, Stewald ripening method, etc. Among them, the self-sacrificial template method has the advantages of high efficiency, simple process, and strong structure controllability. When the self-sacrificing template method is used to prepare the LiMnPO ₄ positive electrode material with the shape of hollow microspheres, it is still difficult to control the size of the hollow microspheres, which affects the adjustment of the tap density of the LiMnPO ₄ positive electrode material and the optimization of the volumetric energy density. Therefore, There is an urgent need for a size control scheme of the hollow microsphere precursor template.

Contents of the invention

The object of the present invention is, aiming at the low tap density of LiMnPO ₄ nanometer cathode material, provide a kind of LiMnPO ₄ precursor template Li ₃ PO ₄ hollow microsphere and its preparation method and application, by adjusting diethylene glycol solvent or sodium hydroxide To adjust the size of the Li ₃ PO ₄ hollow microspheres to increase the tap density of the material, so as to solve the problems raised in the above-mentioned background technology.

To achieve the above object, the present invention provides the following technical solutions:

A preparation method of LiMnPO ₄ precursor template Li ₃ PO ₄ hollow microspheres, specifically completed according to the following steps:

S1: Mix diethylene glycol and deionized water to prepare a mixed solvent;

S2: Add sodium hydroxide, lithium salt and phosphate to the mixed solvent in sequence at a stirring speed of 800~1200rpm, so that the concentration of hydroxide ions in the mixed solution is 1~10mol/L, the concentration of lithium ions and phosphate ions 0.1~5mol/L, the molar ratio of lithium ion to phosphate ion is 3: (0.9~1.1);

S3: React for 5-60 minutes under stirring;

S4: The reaction product is sequentially subjected to solid-liquid separation, washing, and drying to obtain Li ₃ PO ₄ hollow microspheres with a diameter of 100 nm to 5 μm.

As a further solution of the present invention: the lithium salt described in step S2 is lithium acetate dihydrate, lithium sulfate monohydrate, lithium chloride, lithium lactate or lithium formate monohydrate, and the phosphate is ammonium dihydrogen phosphate, diammonium hydrogen phosphate or Trisodium Phosphate.

As a further solution of the present invention: the specific operation of the solid-liquid separation in step S4 is as follows: the product is separated by a filtration method to obtain solid precipitation in the product.

As a further solution of the present invention: the specific operation of the washing described in step S4 is as follows: first, the solid precipitate obtained by washing the solid-liquid separation with deionized water is washed 3 to 5 times, and then washed 1 to 2 times with absolute ethanol to obtain A solid precipitated after washing.

As a further solution of the present invention: the specific operation of the drying described in step S4 is as follows: the washed solid precipitate is placed in a vacuum drying oven, and vacuum dried at 50-70° C. for 8-16 hours.

As a precursor template, Li ₃ PO ₄ hollow microspheres can be used to prepare LiMnPO ₄ cathode materials and be used in high-performance lithium-ion batteries.

Compared with prior art, the beneficial effect of the present invention is: By adjusting the amount of diethylene glycol or sodium hydroxide in the reaction, the regulation of the size of the Li ₃ PO ₄ hollow microspheres can be realized. The process is simple, the operation is convenient, the raw material is cheap and easy to obtain, and the equipment requirement is low, so it is suitable for industrial production. The prepared Li ₃ PO ₄ hollow microspheres have adjustable size, regular shape, uniform distribution and good crystallinity.

Description of drawings

Fig. 1 is the XRD patterns of Li ₃ PO ₄ hollow microspheres and LiMnPO ₄ hollow microspheres prepared in Example 1 of the present invention.

2 to 6 are SEM images of Li ₃ PO ₄ hollow microspheres and LiMnPO ₄ hollow microspheres prepared in Example 1 of the present invention at different magnifications.

7-8 are TEM images of Li ₃ PO ₄ hollow microspheres and LiMnPO ₄ hollow microspheres prepared in Example 1 of the present invention.

Fig. 9 is the XRD pattern of Li ₃ PO ₄ hollow microspheres prepared in Example 2 of the present invention.

10-12 are SEM images of Li ₃ PO ₄ hollow microspheres prepared in Example 2 of the present invention at different magnifications.

Fig. 13 is the XRD spectrum of the Li ₃ PO ₄ hollow microspheres prepared in Example 3 of the present invention.

14 to 16 are SEM images of Li ₃ PO ₄ hollow microspheres prepared in Example 3 of the present invention at different magnifications.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1: A method for preparing _Li3PO4 hollow microspheres with a diameter of about ₃ μm, and using this as a precursor template to prepare a _LiMnPO4 positive electrode material with a hollow microsphere shape, specifically as follows:

Prepare a mixed solvent with 5ml of diethylene glycol and 35ml of deionized water. 100 mmol sodium hydroxide, 21 mmol lithium acetate dihydrate and 7 mmol ammonium dihydrogen phosphate were sequentially added to the mixed solvent at a stirring speed of 1000 rpm. Reacted for 30min under stirring. The product was separated by filtration to obtain the solid precipitate in the product, and then the solid precipitate was washed 4 times with deionized water and 1 time with absolute ethanol to obtain the washed solid precipitate and then vacuum-dried at 60°C for 12 hours to obtain a solid precipitate with a diameter of approx. 3 μm Li ₃ PO ₄ hollow microspheres.

The prepared 5mmolLi ₃ PO ₄ hollow microspheres, 5mmol manganous acetate tetrahydrate and 5mmol ammonium sulfate were added to 20ml ethylene glycol and 20ml deionized water to prepare a mixed solvent, and after stirring, they were sealed on a polytetrafluoroethylene-lined stainless steel In the reaction kettle, keep warm at 180°C for 4h and then cool to room temperature. The obtained solid was precipitated, washed four times with deionized water, washed once with absolute ethanol, and dried under vacuum at 60°C for 12 hours to obtain LiMnPO ₄ hollow microspheres with a diameter of about 3 μm.

The Li ₃ PO ₄ hollow microspheres and LiMnPO ₄ hollow microspheres prepared in this experiment were detected by X-ray diffractometer, and the detection results are shown in Fig. 1 . It can be seen from Figure 1 that the products prepared in this experiment are pure Li ₃ PO ₄ phase and pure LiMnPO ₄ phase.

The hollow microspheres prepared in this experiment were observed with a scanning electron microscope, as shown in Figures 2-6. Figures 2-3 are SEM images of Li ₃ PO ₄ hollow microspheres at different magnifications. It can be seen from the figures that the Li ₃ PO ₄ hollow microspheres prepared in this experiment have a diameter of about 3 μm, regular shape and uniform distribution; Figure 4 ~6 is the SEM image of LiMnPO ₄ hollow microspheres at different magnifications. It can be seen from the figure that LiMnPO ₄ inherits the morphology and structure of Li ₃ PO ₄ hollow microspheres, with a diameter of about 3 μm.

The hollow microspheres prepared in this experiment were observed with a transmission electron microscope, as shown in Figures 7-8. Figure 7 is a TEM image of Li ₃ PO ₄ hollow microspheres, and it can be seen from the comparison of light and dark contrast in Figure ₇ that the microspheres prepared by the experiment are hollow microspheres _; The ball has a hollow structure.

Example 2: The preparation method of Li ₃ PO ₄ hollow microspheres with a diameter of about 1.5 μm is specifically completed according to the following steps:

Prepare a mixed solvent with 8ml of diethylene glycol and 32ml of deionized water. 100 mmol sodium hydroxide, 21 mmol lithium acetate dihydrate and 7 mmol ammonium dihydrogen phosphate were sequentially added to the mixed solvent at a stirring speed of 1000 rpm. Reacted for 30min under stirring. The product was separated by filtration to obtain the solid precipitate in the product, and then the solid precipitate was washed 4 times with deionized water and 1 time with absolute ethanol to obtain the washed solid precipitate and then vacuum-dried at 60°C for 12 hours to obtain a solid precipitate with a diameter of approx. 3 μm Li ₃ PO ₄ hollow microspheres.

The Li ₃ PO ₄ hollow microspheres prepared in this experiment were detected by an X-ray diffractometer, and the detection results are shown in FIG. 9 . It can be seen from Figure 9 that the product prepared in this experiment is a pure Li ₃ PO ₄ phase.

The Li ₃ PO ₄ hollow microspheres prepared in this experiment were observed with a scanning electron microscope, and the SEM images at different magnifications are shown in Figures 10-12. It can be seen from the figure that the Li ₃ PO ₄ hollow microspheres prepared in this experiment have a diameter of about 1.5 μm, regular shape and uniform distribution.

Embodiment 3: The preparation method of Li ₃ PO ₄ hollow microspheres with a diameter of about 750nm is specifically completed according to the following steps:

Prepare a mixed solvent with 8ml of diethylene glycol and 32ml of deionized water. At a stirring speed of 1000 rpm, 120 mmol of sodium hydroxide, 21 mmol of lithium acetate dihydrate and 7 mmol of ammonium dihydrogen phosphate were sequentially added to the mixed solvent. Reacted for 30min under stirring. The product was separated by filtration to obtain the solid precipitate in the product, and then the solid precipitate was washed 4 times with deionized water and 1 time with absolute ethanol to obtain the washed solid precipitate and then vacuum-dried at 60°C for 12 hours to obtain a solid precipitate with a diameter of approx. 3 μm Li ₃ PO ₄ hollow microspheres.

The Li ₃ PO ₄ hollow microspheres prepared in this experiment were detected by an X-ray diffractometer, and the detection results are shown in FIG. 13 . It can be seen from Figure 13 that the product prepared in this experiment is a pure Li ₃ PO ₄ phase.

The Li ₃ PO ₄ hollow microspheres prepared in this experiment were observed with a scanning electron microscope, and the SEM images at different magnifications are shown in Figures 14-16. It can be seen from the figure that the Li ₃ PO ₄ hollow microspheres prepared in this experiment have a diameter of about 750nm, regular shape and uniform distribution.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (8)

1. a kind of LiMnPO₄Presoma template Li₃PO₄The preparation method of tiny balloon, which comprises the steps of:

S1: by diethylene glycol (DEG) and deionized water mixed preparing mixed solvent；

S2: being added sequentially in the mixed solvent for sodium hydroxide, lithium salts and phosphate under certain mixing speed, so that mixing is molten It is 0.1 ~ 5mol/L, lithium ion and phosphoric acid that hydroxide ion concentration, which is 1 ~ 10mol/L, lithium ion and phosphorus acid ion concentration, in liquid Radical ion molar ratio is 3:(0.9 ~ 1.1)；

S3: 5 ~ 60min is reacted under stirring；

S4: reaction product is successively separated by solid-liquid separation, washs, dry, obtains the Li of diameter 100nm ~ 5 μm₃PO₄Tiny balloon.

2. a kind of LiMnPO according to claim 1₄Presoma template Li₃PO₄The preparation method of tiny balloon, feature Be, lithium salts described in step S2 be acetic acid dihydrate lithium, sulfuric acid monohydrate lithium, lithium chloride, lithium lactate or Lithium formate hydrate, Phosphate is ammonium dihydrogen phosphate, diammonium hydrogen phosphate or tertiary sodium phosphate.

3. a kind of LiMnPO according to claim 2₄Presoma template Li₃PO₄The preparation method of tiny balloon, feature It is, mixing speed is 800 ~ 1200rpm in step S2.

4. a kind of LiMnPO according to claim 1₄Presoma template Li₃PO₄The preparation method of tiny balloon, feature It is, the concrete operations of separation of solid and liquid described in step S4 are as follows: product is separated using filter method, is obtained in product Solid precipitating.

5. a kind of LiMnPO according to claim 1 or 4₄Presoma template Li₃PO₄The preparation method of tiny balloon, it is special Sign is that the concrete operations of washing described in step S4 are as follows: adopting the solid for being washed with deionized and being separated by solid-liquid separation and obtaining first Precipitating is washed 3 ~ 5 times, then is washed 1 ~ 2 time using dehydrated alcohol, and solid precipitates after being washed.

6. a kind of LiMnPO according to claim 5₄Presoma template Li₃PO₄The preparation method of tiny balloon, feature It is, dry concrete operations described in step S4 are as follows: solid precipitating after washing is placed in a vacuum drying oven, and 50 ~ 8 ~ 16h is dried in vacuo at 70 DEG C.

7. a kind of LiMnPO₄Presoma template Li₃PO₄Tiny balloon, which is characterized in that be as described in claim any one of 1-6 Method be prepared.

8. a kind of LiMnPO according to claim 7₄Presoma template Li₃PO₄Tiny balloon is in high performance lithium ion battery Positive electrode in application.