CN111384386A - Negative electrode active material and preparation method thereof - Google Patents
Negative electrode active material and preparation method thereof Download PDFInfo
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 13
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- 239000006182 cathode active material Substances 0.000 abstract description 9
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- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a negative active material and a preparation method thereof. The preparation method of the negative active material includes the steps of: the method comprises the following steps: (1) preparing required raw materials, and dissolving a polymer monomer in a solvent to form a solution; (2) dispersing a metal compound in the solution to form a mixed solution; (3) and dispersing the mixed solution on the surface of the active material particles to obtain the negative electrode active material. The invention can improve the lithium ion channel on the surface of the cathode active material, inhibit the generation of lithium dendrite and by-products, and improve the electrical property, stability and safety of the battery; the preparation method of the cathode active material has the advantages of simple process, simple and convenient operation and high yield, and is suitable for large-scale industrial production.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a negative active material and a preparation method thereof.
Background
Among the existing secondary batteries, lithium ion batteries have great advantages in the aspects of development space, service life, electrical performance and the like, and have considerable competitiveness. At present, the market of power batteries developing at a high speed puts higher requirements on lithium ion batteries: higher energy density, better cycle life, better high and low temperature charge and discharge performance, safety performance and the like, so that the research on the electrode material of the lithium ion battery needs to be further deepened and perfected as an important component of the lithium ion battery and a key factor influencing the electrical performance of the battery.
Silicon as a novel negative electrode active material shows high capacity, and the lithium extraction voltage of the material is low, so that the silicon is considered as the most promising alternative carbon material to become the negative electrode material of the next generation lithium ion battery. However, when silicon is used as a negative electrode active material, a large volume effect exists in the charging and discharging process, which easily causes electrode fracture and pulverization, resistance increase and cycle performance drop suddenly, and severely limits the utilization and commercialization process of the silicon negative electrode material.
At present, researches on silicon cathode active materials mainly comprise the steps of preparing a silicon-carbon composite material by mixing and pyrolyzing silicon powder and a carbon source, and simultaneously depositing silicon and amorphous silicon dioxide by using a vapor phase method, but the silicon cathode active materials improved by the method still have low first charge-discharge efficiency, are still sensitive to water, and have no obvious improvement on safety and stability.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a negative active material and a method for preparing the same, in order to overcome the above-mentioned disadvantages and drawbacks of the background art.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a negative electrode active material includes a silicon-containing active material particle and a polymer layer coated on the active material particle, in which a metal compound is further dispersed.
The design idea of the technical scheme is that the metal compound dispersed in the polymer can construct and improve a lithium ion channel on the surface of the negative active material, and improve the lithium ion transmission capability of the negative active material, so that the problem of electric property reduction caused by polymer coating is avoided, the generation of lithium dendrites and byproducts can be inhibited, and the stability and safety of the negative active material applied to a battery are improved; meanwhile, the polymer layer has certain deformation capacity and elasticity, and the polymer is used for coating the silicon-containing active substance particles, so that the expansion effect of the silicon-containing active substance particles in the lithium intercalation and lithium release processes is ensured to be under the coating control of the polymer layer, and the phenomena of electrode fracture and pulverization, battery cycle performance reduction, battery bulge and the like, which are caused by the expansion effect, of battery performance reduction and unsafe phenomenon are prevented.
Preferably, in the above aspect, the mass of the polymer layer accounts for 0.05% to 15% of the total mass of the negative electrode active material. The design idea is that the mass fraction of the polymer layer is limited to 0.05-15%, so that the problems that the coating protection capability of the silicon-containing active material particles is reduced due to the fact that the polymer layer is too thin and too small in mass, and the difficulty in building a lithium ion channel on the surface of the negative active material is increased and the elasticity of the polymer layer is reduced due to the fact that the polymer layer is too thick and too high in mass can be solved.
Preferably, the metal compound accounts for 0.05-25% of the total mass of the negative electrode active material. The design idea is that the mass fraction of the metal compound is limited to 0.05-25%, so that the problems that the distribution is too dispersed due to too low content of the metal compound, a lithium ion channel is difficult to form effectively, the electrochemical performance of a negative active material is reduced, and the elasticity of a polymer layer is reduced due to too high content of the metal compound can be solved.
Preferably, in the above embodiment, the metal compound is a metal oxide or a metal salt.
Preferably, the metal element in the metal compound is one or more of Li, Mg, Al, Na and Ca. The idea of the design is that the five elements are alkaline earth metal elements, and the problem of the decrease of the electrochemical performance of the negative electrode active material can be avoided by adding the compound of the five elements into the polymer layer.
Preferably, the monomer of the polymer layer is a carbon-containing compound having a main chain carbon atom number of not more than 6. The idea of the design is that a compound with a short main chain (the number of carbon atoms is not more than 6) is used as a monomer of the polymer layer, so that the success rate of coating the silicon-containing active substance particles by the polymer layer and the elasticity of the polymer layer after successful coating can be ensured, the protection effect of the polymer layer on the silicon-containing active substance particles under the expansion effect is further improved, and the cycle performance and the safety of the battery are improved.
Preferably, the carbon-containing compound monomer is one or more of acrylic acid, sodium acrylate, lithium acrylate and aromatic hydrocarbon. The idea of the design is that the polymer layer formed by using the above substances as monomers can reduce or even avoid the performance reduction of the negative active material after coating the silicon-containing active material particles.
Preferably, the silicon-containing active material particles comprise a silicon oxide represented by the formula SiOxThe expressed silicon oxide and the carbon material layer covered on the silicon oxide, x is more than or equal to 0.5 and less than or equal to 1.7. The idea of the design is that since the carbon material has high reversible specific capacity and conductivity, the specific capacity and conductivity of the silicon-containing active material particles can be improved by coating the silicon oxide with the carbon material layerThereby improving the electrical properties of the negative active material and the battery to which it is applied.
Preferably, the silicon oxide further comprises one or more elements of Li, Mg and Al, and the mass of the elements accounts for A, wherein A is more than 0 and less than 20 percent of the total mass of the negative electrode active material.
Preferably, the carbon material layer is hard carbon, covers the surface of the silicon oxide by more than 30%, and has a total carbon content of 0.01% < B < 30% in the total mass of the negative electrode active material, wherein B is the ratio of the total carbon content of the carbon material layer to the total mass of the negative electrode active material.
The preparation method of the anode active material in the technical scheme comprises the following steps:
(1) preparing required raw materials, and dissolving a polymer monomer in a solvent to form a solution;
(2) dispersing a metal compound in the solution to form a mixed solution;
(3) and dispersing the mixed solution on the surface of the active material particles to obtain the negative electrode active material.
In the above-described aspect, the dispersion operation in the step (3) is preferably performed by spraying the mixed solution on the surface of the active material particles or dipping the active material particles in the mixed solution.
Compared with the prior art, the invention has the advantages that:
(1) the cathode active material can improve the lithium ion channel on the surface of the cathode active material, improve the lithium ion transmission capability of the cathode active material, inhibit the generation of lithium dendrite and byproducts, avoid the problems of electrode fracture and pulverization and the like caused by the expansion effect, and improve the stability and safety of the cathode active material after being applied to a battery.
(2) The preparation method of the cathode active material has the advantages of simple process, simple and convenient operation and high yield, and is suitable for large-scale industrial production.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural view of a negative electrode active material of example 1 of the invention;
FIG. 2 is a scanning electron microscope photograph of example 1 of the present invention;
fig. 3 is a schematic diagram showing XRD test results of example 1, example 2 and comparative example 1 of the present invention.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
the negative active material of the embodiment includes a silicon-containing active material particle, a polyacrylic acid and lithium polyacrylate layer coated on the silicon-containing active material particle, and Al dispersed in the polyacrylic acid and lithium polyacrylate layer2O3(ii) a Wherein the silicon-containing active material particles comprise SiOxParticles, coated on SiOxA hard carbon layer on the particles. The structure of the negative active material is shown in fig. 1, and its scanning electron micrograph is shown in fig. 2.
The method for preparing the anode active material of the present embodiment includes the steps of:
(1) preparing required raw materials, and dissolving acrylic acid and lithium acrylate in a solvent to form a solution;
(2) mixing Al2O3Dispersing in the solution to form a mixed solution;
(3) and (3) spraying and dispersing the mixed solution on the surface of active substance particles, and drying to remove the solvent to obtain the negative electrode active material.
The preparation method of the active substance particles comprises the following steps:
(1) silicon powder and silicon dioxide are mixed according to the proportion of 1: 1, heating under low pressure under the protection of inert gas, and depositing on a top deposition plate to obtain SiOxAgglomerating the components, crushing the agglomerates by jaw crushing, jet milling and ball milling to obtain SiOxAnd (3) granules.
(2) And carrying out chemical vapor deposition on the SiOx particles by using hydrocarbon gas to form a hard carbon layer on the surface of the SiOx particles so as to obtain the active material particles.
Example 2:
the negative active material of the embodiment includes silicon-containing active material particles, a polypropylene layer coated on the silicon-containing active material particles, and AlCl3 dispersed in the polypropylene layer; wherein the silicon-containing active material particles comprise SiOxParticles and coating on SiOxA hard carbon layer on the particles.
The method for preparing the anode active material of the present embodiment includes the steps of:
(1) preparing required raw materials, and dissolving acrylic acid in a solvent to form a solution;
(2) mixing AlCl3Dispersing in the solution to form a mixed solution;
(3) and (3) dipping the active material particles in the mixed solution, taking out, drying and removing the solvent to obtain the negative electrode active material.
The preparation method of the active substance particles comprises the following steps:
(1) silicon powder and silicon dioxide are mixed according to the proportion of 1: 1, heating under low pressure under the protection of inert gas, and depositing on a top deposition plate to obtain SiOxAgglomerating the components, crushing the agglomerates by jaw crushing, jet milling and ball milling to obtain SiOxAnd (3) granules.
(2) Will be at the topThe SiOxThe particles are subjected to chemical vapor deposition using a hydrocarbon gas to form a hard carbon layer on the surface, resulting in active material particles.
Comparative example 1:
the negative electrode active material of the present comparative example includes silicon-containing active material particles; the silicon-containing active material particles comprise SiOx particles and hard carbon layers covering the SiOx particles.
The method for preparing the negative active material of the present comparative example includes the steps of:
(1) silicon powder and silicon dioxide are mixed according to the proportion of 1: 1, heating under low pressure under the protection of inert gas, depositing on a top deposition plate to obtain an agglomeration of the SiOx component, crushing the agglomeration by jaw crushing, jet milling and ball milling to obtain the SiOx particles.
(2) And carrying out chemical vapor deposition on the SiOx particles by using hydrocarbon gas to form a hard carbon layer on the surface of the SiOx particles so as to obtain the active material particles.
After the negative active materials of example 1, example 2 and comparative example 1 were prepared into negative electrodes and then prepared into batteries, the results of the relevant tests were as follows:
the results of XRD testing of the three batteries are shown in FIG. 3.
The three groups of batteries were subjected to capacity test by charging and discharging at 0.1C, and the results are shown in table 1. The test results show that although the capacity of the materials in the embodiment 1 and the embodiment 2 is reduced to a certain extent, the first charge-discharge efficiency is improved to a different extent compared with that of the comparative example 1, the electrical property of the materials is improved, and the expected design expectation is met.
TABLE 1 Capacity test results
| capacity/mAh/g | First charge and discharge efficiency/％ | |
| Example 1 | 1298.0 | 74.3％ |
| Example 2 | 1270.1 | 74.0％ |
| Comparative example 1 | 1502.9 | 71.3％ |
The three groups of batteries were subjected to a cycle test by charging and discharging at a charging temperature of 0.1C, and the results are shown in table 2. The test results show that although the capacity decreases rapidly in examples 1 and 2, the cycle retention rate is better than that in comparative example 1 after 50 cycles. The present invention demonstrates that the electrical properties of the material are improved, meeting the expected design expectations.
TABLE 2 comparative results of the electrical cycling test (capacity retention rate)
| Number of |
10 | 20 | 30 | 50 |
| Example 1 | 98.2％ | 98.0％ | 97.9％ | 97.8％ |
| Example 2 | 98.6％ | 98.4％ | 98.4％ | 98.3％ |
| Comparative example 1 | 99.7％ | 99.2％ | 98.3％ | 96.5％ |
The above three groups of batteries were subjected to safety and abuse tests for examples 1, 2 and comparative example 1 under the conditions shown in table 3, in which the numbers represent the severity of battery runaway (1: no smoke; 2: smoke but no open flame; 3, open flame; 4, explosion); the results show that both example 1 and example 2 exhibit superior safety characteristics in short circuit, overcharge, compression and needle prick tests than comparative example 1, meeting expected design expectations.
Table 3 material preparation battery safety test results
| Short circuit | Overcharge | Extrusion | Acupuncture and moxibustion | |
| Example 1 | 1 | 1 | 2 | 2 |
| Example 2 | 1 | 1 | 2 | 2 |
| Comparative example 1 | 2 | 2 | 3 | 3 |
Claims (10)
1. A negative electrode active material is characterized by comprising silicon-containing active material particles and a polymer layer coated on the silicon-containing active material particles, wherein a metal compound is dispersed in the polymer layer.
2. The negative electrode active material according to claim 1, wherein the polymer layer accounts for 0.05 to 15% by mass of the total mass of the negative electrode active material.
3. The negative electrode active material according to claim 1, wherein the metal compound is present in an amount of 0.05 to 25% by mass based on the total mass of the negative electrode active material.
4. The anode active material according to claim 1, wherein the metal element in the metal compound is one or more of Li, Mg, Al, Na, and Ca.
5. The negative electrode active material of any one of claims 1 to 4, wherein the monomer of the polymer layer is a carbon-containing compound having a number of main chain carbon atoms of not more than 6.
6. The negative electrode active material of claim 5, wherein the carbon-containing compound is one or more of acrylic acid, sodium acrylate, lithium acrylate, and aromatic hydrocarbon.
7. The negative electrode active material of any of claims 1 to 4, wherein the silicon-containing active material particles comprise a silicon oxide represented by the formula SiOxThe expressed silicon oxide and the carbon material layer covered on the silicon oxide, x is more than or equal to 0.5 and less than or equal to 1.7.
8. The negative electrode active material according to any one of claims 1 to 4, wherein the silicon oxide further contains one or more elements selected from Li, Mg and Al, and the proportion of the elements by mass to the total mass of the silicon-containing active material particles is A, and 0 < A < 20%.
9. A method for preparing the negative active material of claim 1, comprising the steps of:
(1) preparing required raw materials, and dissolving a polymer monomer in a solvent to form a solution;
(2) dispersing a metal compound in the solution to form a mixed solution;
(3) and dispersing the mixed solution on the surface of the active material particles to obtain the negative electrode active material.
10. The method according to claim 9, wherein the dispersing operation in the step (3) is to spray-disperse the mixed solution on the surface of the active material particles or to dip the active material particles in the mixed solution.
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