阅读说明：本技术 氟化物量子点的制备方法 (Preparation method of fluoride quantum dots ) 是由 罗桂 邓多 唐泽勋 商士波 张瑛 于 2019-12-16 设计创作，主要内容包括：本发明提供一种氟化物量子点的制备方法。氟化物量子点的制备方法,包括：将氧化物量子点、氟源、第一表面活性剂混合,加热进行第一反应得到所述氟化物量子点；所述氧化物量子点的制备方法包括：将原料混合,加热进行第二反应得到中间产物,然后将所述中间产物与第一有机溶剂混合,加热进行第三反应得到所述氧化物量子点；所述原料包括过渡金属的氯化物、第二表面活性剂、水和第二有机溶剂。本申请提供的氟化物量子点分散性好,且具有极短的锂离子扩散路径和表面活性。(The invention provides a preparation method of fluoride quantum dots. The preparation method of the fluoride quantum dot comprises the following steps: mixing oxide quantum dots, a fluorine source and a first surfactant, and heating to perform a first reaction to obtain the fluoride quantum dots; the preparation method of the oxide quantum dot comprises the following steps: mixing the raw materials, heating for a second reaction to obtain an intermediate product, mixing the intermediate product with a first organic solvent, and heating for a third reaction to obtain the oxide quantum dots; the raw materials include a chloride of a transition metal, a second surfactant, water, and a second organic solvent. The fluoride quantum dots provided by the application have good dispersibility, and have extremely short lithium ion diffusion paths and surface activity.)

1. A preparation method of fluoride quantum dots is characterized by comprising the following steps:

mixing oxide quantum dots, a fluorine source and a first surfactant, and heating to perform a first reaction to obtain the fluoride quantum dots;

the preparation method of the oxide quantum dot comprises the following steps: mixing the raw materials, heating for a second reaction to obtain an intermediate product, mixing the intermediate product with a first organic solvent, and heating for a third reaction to obtain the oxide quantum dots;

the raw materials include a chloride of a transition metal, a second surfactant, water, and a second organic solvent.

2. The method of claim 1, wherein the fluorine source comprises one or more of hydrofluoric acid, ammonium fluoride, tetrabutylammonium fluoride.

3. The method according to claim 1, wherein the transition metal includes one or more of Fe, Cu, Zn, Sn, Ti, Zr, Nb, Co, Ni, Mn, Bi.

4. The method of claim 1, wherein the first surfactant and the second surfactant each independently comprise one or more of oleic acid, sodium oleate, stearic acid, sodium fatty acid, potassium fatty acid, oleylamine, and octylamine.

5. The method of claim 1, wherein the first organic solvent comprises one or more of octadecene, oleic acid, oleylamine, and n-octylamine.

6. The method of claim 1, wherein the second organic solvent comprises one or more of ethanol, n-hexane, toluene, petroleum ether, tetrachloromethane, trichloromethane, tetrahydrofuran, acetone, octadecene.

7. The method according to claim 1, further comprising, after the first reaction is completed:

dispersing the reaction system of the first reaction into a first solvent, and then extracting and washing by using a second solvent to obtain the fluoride quantum dot;

the first solvent comprises one or more of n-hexane, toluene and pyridine;

the second solvent comprises one or more of methanol, 2-methoxy ethanol, ethanol and acetone.

8. The method according to claim 1, further comprising, after the second reaction is completed:

extracting the reaction system of the second reaction by using water, and removing the second organic solvent to obtain the intermediate product.

9. The method according to claim 1, further comprising, after the third reaction is completed:

mixing the reaction system of the third reaction with a third solvent, and centrifuging to obtain the oxide quantum dots;

the third solvent comprises one or more of methanol, 2-methoxy ethanol, ethanol and acetone.

10. The process according to any one of claims 1 to 9, wherein the first reaction is carried out at a temperature of 160 ℃ to 250 ℃ for a time of 10h to 48 h;

the temperature of the second reaction is 60-90 ℃, and the time is 3-10 h;

the temperature of the third reaction is 280-360 ℃, and the time is 10s-2 h.

Technical Field

The invention relates to the field of lithium ion batteries, in particular to a preparation method of fluoride quantum dots.

Background

Lithium ion batteries have been widely used in various industrial fields due to their high capacity, high platform voltage, no memory effect, and the like. The positive electrode materials of the lithium ion battery are mainly divided into two types, one type is an embedded positive electrode material, such as lithium cobaltate, a ternary material and the like, and the good layered structure of the positive electrode material endows the material with excellent lithium ion conductivity and excellent cycle stability; another class is conversion type materials, e.g. FeF₃，CuF₂Etc. exhibit a high capacity due to their multi-electron reactivity. Because fluorine atoms have high electronegativity, the anion F in the fluoride-converted material is enabled^-The material has higher bond strength and weak electron delocalization capability, so the material is generally an insulator, has lower electron conductivity, and finally shows charge-discharge voltage hysteresis of the material in a macroscopic view, namely a charge-discharge platform has larger voltage difference. The particle size is reduced, the lithium ion diffusion path is shortened, and the disadvantage of poor conductivity can be greatly alleviated.

However, the existing means can only prepare some nano-scale fluoride particles, such as one-dimensional or two-dimensional materials like nanorods, nanowires, etc., and no fluoride zero-dimensional quantum dots are reported.

In view of this, the present application is specifically made.

Disclosure of Invention

The invention aims to provide a preparation method of fluoride quantum dots, so as to solve the problems.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a preparation method of fluoride quantum dots comprises the following steps:

mixing oxide quantum dots, a fluorine source and a first surfactant, and heating to perform a first reaction to obtain the fluoride quantum dots;

the preparation method of the oxide quantum dot comprises the following steps: mixing the raw materials, heating for a second reaction to obtain an intermediate product, mixing the intermediate product with a first organic solvent, and heating for a third reaction to obtain the oxide quantum dots;

the raw materials include a chloride of a transition metal, a second surfactant, water, and a second organic solvent.

The fluoride has strong bonding capability, so that the quantum dot is difficult to directly prepare. According to the method, the oxide quantum dot template is prepared firstly, and then the fluorine source is adopted for etching and replacing, so that the fluoride with the quantum dot size can be obtained on the basis of the original oxide quantum dot.

The oxygen source of the oxide quantum dots is mainly from oxygen in air, and in addition, the oxygen-containing second surfactant also provides part of oxygen.

The quantum dots referred to herein refer to zero-dimensional quantum dots, i.e., material having a size radius that is smaller than its bohr radius (the maximum radius that can be reached by electronic activity) in any dimension, which have very pronounced quantum size confinement and surface effects. Although nanomaterials also have such effects, the energy level differentiation, surface active defects and shortened lithium ion diffusion paths exhibited by quantum dots are completely different.

The chloride of the transition metal has the general formula MCl_xWherein x is a positive integer and is more than or equal to 2 and less than or equal to 6; the chemical general formula of the oxide quantum dots is MO_yWherein y can be a non-integer or a positive integer, and is more than or equal to 1 and less than or equal to 3; the general formula of the fluoride quantum dot is MF_zWherein z is a positive integer and is more than or equal to 2 and less than or equal to 6.

Preferably, the fluorine source comprises one or more of hydrofluoric acid, ammonium fluoride, tetrabutylammonium fluoride;

preferably, the transition metal comprises one or more of Fe, Cu, Zn, Sn, Ti, Zr, Nb, Co, Ni, Mn, Bi.

As for the selection of the fluorine source, the weak acidity and strong oxidizing property can be presented in the reaction system; the selection of the metal mainly considers whether fluoride quantum dots can be obtained; through research, the corresponding fluoride quantum dots are not easy to obtain due to non-transition metals.

Preferably, the first surfactant and the second surfactant each independently comprise one or more of oleic acid, sodium oleate, octadecanoic acid, sodium fatty acid, potassium fatty acid, oleylamine, n-octylamine;

preferably, the first organic solvent comprises one or more of octadecene, oleic acid, oleylamine, n-octylamine;

preferably, the second organic solvent comprises one or more of ethanol, n-hexane, toluene, petroleum ether, tetrachloromethane, trichloromethane, tetrahydrofuran, acetone, octadecene.

The first surfactant and the second surfactant have the main functions of forming bonding with the primarily formed sub-nano crystal nucleus in the reaction by utilizing the carbon chains of the first surfactant and the second surfactant, and delaying or preventing subsequent ions from effectively depositing, so that the growth and the growth of crystals are prevented; the longer the segment of the surfactant, the more remarkable the effect of inhibiting agglomeration.

The selection of the first organic solvent mainly considers the solubility and boiling point of the intermediate product in the first organic solvent, so as to ensure that the reaction system can carry out liquid phase reaction at the required reaction temperature; the choice of the second organic solvent, mainly considering the solubility of the second surfactant, requires that the chloride of the transition metal, the second surfactant, be able to react in a two-phase system consisting of water and the second organic solvent, in which the chloride is soluble and the second surfactant is soluble.

Preferably, the method further comprises, after the first reaction is finished:

dispersing the reaction system of the first reaction into a first solvent, and then extracting and washing by using a second solvent to obtain the fluoride quantum dot;

preferably, the first solvent comprises one or more of n-hexane, toluene, pyridine;

preferably, the second solvent comprises one or more of methanol, 2-methoxyethanol, ethanol, acetone.

The size of the fluoride quantum dots enables an agglomeration-like effect to occur after the reaction is finished, so that the fluoride quantum dots need to be dispersed firstly, and the first solvent is selected mainly in consideration of the dispersion effect. The long-chain molecules are remained in the finished product to influence the conductivity of the material, so that the remained first surfactant needs to be removed through extraction and washing; the choice of the second solvent is mainly made with a view to the effectiveness of the extraction and washing. The solid fluoride quantum dots are separated from other liquids during the extraction process.

Preferably, the second reaction further comprises, after the end of the second reaction:

extracting the reaction system of the second reaction by using water, and removing the second organic solvent to obtain the intermediate product.

The second reaction produces by-products such as sodium chloride, potassium chloride, ammonium chloride, the presence of which affects the subsequent reaction and therefore requires its removal by extraction using water.

Preferably, the third reaction further comprises, after the end of the third reaction:

mixing the reaction system of the third reaction with a third solvent, and centrifuging to obtain the oxide quantum dots;

preferably, the third solvent comprises one or more of methanol, 2-methoxyethanol, ethanol, acetone.

And a system similar to suspension is obtained after the third reaction is finished, the oxide quantum dots can be precipitated by adding a third solvent, and then the oxide quantum dots are obtained by centrifuging, so that the efficiency of subsequent reaction can be improved.

Optionally, the temperature of the first reaction is 160-250 ℃ and the time is 10-48 h;

the temperature of the second reaction is 60-90 ℃, and the time is 3-10 h;

the temperature of the third reaction is 280-360 ℃, and the time is 10s-2 h.

The control of the reaction temperature and time can not only adjust the reaction process, but also control the size of the obtained quantum dots.

Alternatively, the temperature of the first reaction may be any value between 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃ and 160 ℃ to 250 ℃, and the time may be any value between 10h, 12h, 18h, 24h, 30h, 36h, 42h, 48h and 10h to 48 h; the temperature of the second reaction can be any value between 60 ℃, 70 ℃, 80 ℃, 90 ℃ and 60-90 ℃, and the time can be any value between 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h and 3h-10 h; the temperature of the third reaction can be any value between 280 ℃, 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃, 360 ℃ and 280 ℃ to 360 ℃, and the time can be any value between 10s, 30s, 1min, 10min, 30min, 1h, 1.5h, 2h and 10s to 2 h.

The fluoride quantum dot is prepared by using the preparation method of the fluoride quantum dot.

The fluoride quantum dots have small particle size, have extremely short lithium ion diffusion paths, have a large number of defects and exposed ion active channels on the surface, and can effectively improve the electrochemical activity of the material.

The lithium ion battery anode is prepared by using the fluoride quantum dots.

A lithium ion battery comprises the lithium ion battery anode.

Compared with the prior art, the invention has the beneficial effects that:

1. transition metal oxide quantum dots are obtained through the reaction of transition metal chloride and a surfactant, and are used as templates to react with a fluorine source to obtain fluoride quantum dots;

2. the fluoride quantum dot provided by the application has good dispersibility, has a short lithium ion diffusion path and good surface activity, and is suitable for the anode material for the lithium ion battery.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope of the present invention.

FIG. 1 shows FeF prepared in example 1₃A quantum dot HRTEM image;

FIG. 2 shows FeF prepared in example 1₃HRTEM images of quantum dots at different magnifications.

Detailed Description

The terms as used herein:

"prepared from … …" is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of … …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of … …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when the range "1 ~ 5" is disclosed, the ranges described should be construed to include the ranges "1 ~ 4", "1 ~ 3", "1 ~ 2 and 4 ~ 5", "1 ~ 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

In these examples, the parts and percentages are by mass unless otherwise indicated.

"part by mass" means a basic unit of measure indicating a mass ratio of a plurality of components, and 1 part may represent any unit mass, for example, 1g or 2.689 g. If we say that the part by mass of the component A is a part by mass and the part by mass of the component B is B part by mass, the ratio of the part by mass of the component A to the part by mass of the component B is a: b. alternatively, the mass of the A component is aK and the mass of the B component is bK (K is an arbitrary number, and represents a multiple factor). It is unmistakable that, unlike the parts by mass, the sum of the parts by mass of all the components is not limited to 100 parts.

"and/or" is used to indicate that one or both of the illustrated conditions may occur, e.g., a and/or B includes (a and B) and (a or B).

Embodiments of the present invention will be described in detail below with reference to specific examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.