CN113258069B - Negative electrode active material, method for preparing same, negative electrode, and secondary battery - Google Patents

Negative electrode active material, method for preparing same, negative electrode, and secondary battery Download PDF

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CN113258069B
CN113258069B CN202110485035.9A CN202110485035A CN113258069B CN 113258069 B CN113258069 B CN 113258069B CN 202110485035 A CN202110485035 A CN 202110485035A CN 113258069 B CN113258069 B CN 113258069B
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negative electrode
active material
mixed solution
precursor
electrode active
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CN113258069A (en
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孙毅
张宽信
项宏发
梁鑫
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Hefei University of Technology
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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, a preparation method thereof, a negative electrode and a secondary battery.

Description

Negative electrode active material, method for preparing same, negative electrode, and secondary battery
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a negative electrode active material for a secondary battery and a preparation method thereof, and further relates to a negative electrode obtained by using the negative electrode active material, and a secondary battery obtained by using the negative electrode.
Background
A Rechargeable battery (Rechargeable battery) generally refers to a Rechargeable battery or a secondary battery, and refers to a battery that can be continuously used by activating an active material by charging after the battery is discharged. With the development of new energy, the lithium ion battery becomes an ideal electric energy storage system due to the advantages of ultrahigh specific capacity, no memory effect, cleanness and the like; in addition, since the reserves of raw materials are abundant and the prices are lower than those of lithium, the research on sodium ion batteries and potassium ion batteries is also increasing and it is expected to develop as a substitute for lithium ion batteries.
The negative active materials that can currently serve as secondary batteries are mainly alloy type negative electrode materials, metal oxides, and carbon materials. The carbon-based negative electrode material is used more, and in addition, the theoretical specific capacity of the silicon-based negative electrode material is ten times that of the carbon-based negative electrode material, and can reach 4200mAh/g (Li) 22 Si 5 ) And the charge and discharge platform of the silicon is low, so that metal dendrite is not easy to generate in the charge and discharge process, and the phenomenon that a circuit is short-circuited and ignited due to the fact that the metal dendrite grows to puncture a diaphragm is avoided, so that the application of the silicon-based negative electrode material is gradually increased. During the first charge and discharge of the secondary battery, metal ions form a passivation film, called an SEI film (solid electrolyte interface film), on the surface of the negative electrode together with a solvent, trace water, HF, etc., although the SEI film can be used as an electrode materialThis leads to an increase in the yield, but also causes irreversible metal ion loss during the formation of the SEI film, resulting in low first-cycle coulombic efficiency of the battery. In addition, some negative electrode active materials can cause volume expansion due to the intercalation of metal ions during the cycling, especially silicon-based negative electrode materials (up to about 300%), even if the volume expansion rate of the silicon oxide is low, the volume expansion rate is about 160%, and is still higher than that of graphite, and the volume expansion can cause the cracking and decomposition of the negative electrode active materials, so that the cycling stability of the battery is reduced.
At present, aiming at the two problems, the main solution is to pre-metallize the cathode active material, compensate the loss of metal elements and improve the first coulombic efficiency; in addition, the coating layer is formed on the surface of the negative electrode active material to inhibit the volume effect of the negative electrode active material, mainly the carbon coating layer, because the carbon material has excellent conductivity and good plasticity, and the coating layer on the surface of the negative electrode active material can buffer volume expansion and improve conductivity.
However, in the conventional scheme, the pre-metallization and the carbon coating are basically performed in two steps. For example, chinese patent applications with application numbers of 202010885030.0 and 202010725716.3 all realize pre-lithiation by mixing a silicon monoxide powder and a lithium source and then carrying out heat treatment, and finally carrying out carbon coating by CVD (chemical vapor deposition) to obtain a pre-lithiated silicon monoxide negative electrode material with high coulombic efficiency and good cycle stability for the first time; in addition, the Chinese patent application with the application number of 202011383695.8 discloses a preparation method of a silicon-oxygen composite material, wherein in-situ polymerization is performed on the surface of acid-modified silicon oxide to obtain a carbon-coated silicon oxide material, and then the carbon-coated silicon oxide material is subjected to pre-lithiation by using organic lithium. It can be seen that in the current process, the steps of pre-metallization and carbon coating are basically performed separately, the process is complex, the steps are complicated, and the pre-metallization degree of the prepared negative electrode material is not uniform enough and the coating carbon layer is not uniform.
Disclosure of Invention
In view of the above, the present invention provides a negative active material and a preparation method thereof, in which a pre-metallization and carbon coating process can be achieved in one step, the preparation process is greatly simplified, the obtained negative active material has a uniform pre-metallization degree and a uniform coating carbon layer thickness, the negative active material can provide metal element compensation for the first cycle, increase the conductivity of the material and inhibit the volume expansion of the negative active material in the subsequent cycle, and the first coulomb efficiency and the cycle stability of the secondary battery are significantly improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention firstly provides a negative active material, which comprises the following steps:
obtaining a precursor mixed solution, wherein the precursor mixed solution comprises a negative electrode active substance, a pre-metallization additive and a polymeric material;
performing polymerization reaction on the precursor mixed solution to obtain a precursor;
and carbonizing the precursor to obtain the carbon-coated pre-metallized negative electrode material.
Further, the negative active material is selected from a high-capacity carbon negative electrode material or a silicon-based negative electrode material.
Further, the pre-metallization additive is selected from a metal simple substance or a metal compound of an element M, and the element M is selected from Li, na or K.
Further, in the metal compound, the cation is selected from Li + 、Na + Or K + The anion is selected from OH - 、COO - 、F - 、NO 3 - 、H - 、AlH 4 - 、CO 3 2- 、TFSI - At least one of (1).
Further, the polymeric material is selected from at least one of polyethylene glycol dimethacrylate (PEGDA), 1,3-Dioxolane (DOL), polyethylene oxide (PEO), vinylidene fluoride, hexafluoropropylene, vinylidene fluoride, acrylonitrile acrylic acid, ethylene glycol methyl ether methacrylate, vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropoxysilane, hydrogen polysiloxane, trimethyl carbonate, vinyl tri-t-butylperoxysilane, butadiene, styrene, and vinyl chloride.
Further, in the precursor mixed solution, the molar ratio of the metal element to the negative active material in the pre-metallization additive is 1:0.1 to 100, wherein the mass ratio of the polymer material to the negative electrode active substance is 1:0.1 to 50 (the mass ratio of the final carbon in the active material is 2 to 25 percent, preferably 5 to 10 percent).
Further, the precursor mixed solution also comprises an initiator, and the addition amount of the initiator is 0.5-5% of the mass of the polymeric material; the initiator is at least one of azo initiator, organic peroxide initiator and persulfate initiator.
Further, the precursor mixed solution also comprises a solvent, and the mass ratio of the solvent to the polymeric material is 1:0.1 to 100; the solvent is at least one selected from water, ethanol, N-methyl pyrrolidone and dimethyl carbonate.
Further, the carbonization process is characterized by comprising the following specific steps: and (3) carbonizing the precursor for 1 to 12h at 500 to 1000 ℃ under the anaerobic condition.
The invention also provides a negative electrode active material prepared by the preparation method of any one of the above materials.
The present invention further provides an anode comprising the anode active material as described above.
The invention further provides a secondary battery which is a lithium ion battery, a sodium ion battery or a potassium ion battery and contains the negative electrode.
Compared with the prior art, the invention has the following beneficial effects:
the preparation method of the negative active material realizes the pre-metallization and carbon coating of the negative active material by one step, and simplifies the preparation process. Meanwhile, the obtained anode active material is more uniform in metallization and uniform in carbon layer thickness, and the carbon layer coated on the surface of the anode active material improves the conductivity of the material and inhibits the volume expansion of the anode active material while compensating for metal loss.
The first coulombic efficiency and the cycle stability of the secondary battery prepared by the cathode active material are obviously improved.
Drawings
Fig. 1 is a schematic process flow diagram of a method for preparing a negative active material according to the present invention.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the specific embodiments illustrated. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The first aspect of the present invention provides a method for preparing a negative electrode active material, comprising the steps of:
obtaining a precursor mixed solution, wherein the precursor mixed solution comprises a negative electrode active substance, a pre-metallization additive and a polymeric material;
performing polymerization reaction on the precursor mixed solution to obtain a precursor;
and carbonizing the precursor to obtain the carbon-coated pre-metallized negative electrode material.
Aiming at the problems of complicated steps, non-uniform pre-metallization degree, non-uniform carbon layer thickness and the like of the prior pre-metallization and carbon coating process of the cathode active material, the invention innovatively provides a preparation method of the cathode active material, which can realize the pre-metallization and carbon coating process of the cathode active material in one step and greatly simplifies the prior process. According to the invention, a precursor mixed solution is obtained by mixing a polymeric material, a pre-metallization additive and a negative active material, the pre-metallization of the negative active material is more uniform by utilizing the polymerization curing capability of the polymeric material, and the surface of the negative active material is coated with a polymer, the process can be realized by one step, and finally, a coated carbon layer is formed on the surface of the negative active material by carbonization, and the specific process is shown in fig. 1. Specifically, firstly, the solidified colloid is tightly contacted with the negative active material due to the in-situ polymerization of the polymeric material on the surface of the negative active material; secondly, the pre-metallization additive which is uniformly distributed in the low-viscosity polymer material solution can be uniformly dispersed around the negative active material on the molecular layer along with the polymerization and solidification reaction; and thirdly, the polymer colloid wrapped on the surface of the cathode active material is gradually dehydrogenated in the calcining process, oxygen elements are carbonized on the particle surface to form a uniform coating layer which is tightly contacted, meanwhile, the pre-metallization additive which is uniformly dispersed in the polymer colloid reacts with the cathode active material at high temperature to generate an irreversible phase in advance, so that the occurrence of side reactions in the first circle of charging and discharging processes is reduced, and the purposes of compensating the loss of the lithium elements and uniformly metallizing are achieved. In other words, since the negative electrode active material is dispersed in the solution of the polymer material having a low viscosity in the present invention, uniformity at a molecular level can be obtained in a short time, and the pre-metallization additive can be uniformly mixed with the negative electrode active material at a molecular level when forming a gel after curing, thereby achieving the purpose of uniform pre-metallization; and because the polymer material is solidified into gel in situ, elements such as gel dehydrogenation, oxygen and the like are naturally reduced in volume on the surface of the particles during heat treatment, and a uniform carbon layer which is uniformly and closely contacted with the negative active material is formed. The preparation method simplifies the prior process, simultaneously has uniform distribution of metal elements after pre-metallization, provides metal element compensation for the circulation of the secondary battery, and has uniform thickness of the coated carbon layer, thereby improving the conductivity of the cathode active material on one hand, inhibiting the volume expansion of the cathode material on the other hand, and having remarkable progress.
Further, the invention is describedThe negative electrode active material of (a) is not particularly limited, and may be any negative electrode active material applicable to a secondary battery in the art, for example, a carbon-based negative electrode material such as artificial graphite, natural graphite, mesocarbon microbeads, graphene, etc., and since the volume expansion rate of the carbon-based negative electrode material is low and negligible, when prepared by the above preparation method, the improvement of the first coulombic efficiency and the improvement of Li are mainly achieved + Preferably, the negative active material is a high-capacity carbon negative electrode material, and specific examples include, but are not limited to, soft carbon or hard carbon; the negative electrode active material in the invention can also be a silicon-based negative electrode material selected from elemental silicon (such as nano silicon particles and metal silicon), and a silicon oxide material (SiOy, wherein 0<y<2, such as silica), silicon carbon materials (such as SiC), silicon alloys (Si-Y, where Y may be an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element, or combinations thereof, and does not include Si); the negative electrode active material can also be a mixture of a carbon-based negative electrode material and a silicon-based negative electrode material, and the mixing ratio of the carbon-based negative electrode material and the silicon-based negative electrode material can be adjusted according to needs. It is noted that, because silicon-based anode materials have a large volume expansion rate during battery cycling, it is preferable that, in some embodiments of the present invention, the anode active material is selected from silicon-based anode materials. Furthermore, in the silicon-based negative electrode material, because the volume expansion rate of the silicon oxide is relatively low, about 160%, which is far less than that of other silicon-based negative electrode materials, the silicon oxide is widely applied, but the volume expansion rate is still higher than that of many carbon-based negative electrode materials, in addition, the lower intrinsic conductivity of the silicon oxide reduces the electrochemical activity of the electrode, and if the silicon oxide is used as a negative electrode active substance, metal ions not only react with an electrolyte to generate a component serving as an SEI film during the first cycle, but also react with the silicon oxide to generate irreversible compounds such as oxides, silicates and the like, so that the first coulombic efficiency is very low. Therefore, more preferably, in some embodiments of the present invention, the negative active material is an oxideAnd (4) sub-silicon.
Further, the pre-metallization additive is selected from a metal simple substance or a metal compound of an element M, and the element M is selected from Li, na or K. In the invention, the pre-metallization additive is added to compensate for metal ions lost in the first circulation process, and the selection of the pre-metallization additive can be adjusted according to different types of secondary batteries, for example, if the secondary battery is a lithium ion battery, the pre-metallization additive selects a lithium simple substance or a lithium compound, and so on, and the description is omitted here.
Further, in the metal compound, the cation is selected from Li + 、Na + Or K + The anion is selected from OH - 、COO - 、F - 、NO 3 - 、H - 、AlH 4 - 、CO 3 2- 、TFSI - At least one of (1). It is to be understood that the selection of the simple metal and the metal compound in the present invention is not particularly limited, and the simple metal or the metal compound conventionally used in the compensation of the metal element of the secondary battery in the art may be used in the present invention. For example, when prelithiation is desired, the prelithiation additive may be selected from at least one of lithium powder, lithium hydroxide, lithium acetate, lithium bistrifluoromethanesulfonimide, lithium fluoride, lithium nitrate, lithium hydride, lithium aluminum hydride; when pre-sodium treatment is required, the pre-metallization additive can be selected from at least one of sodium metal, sodium hydroxide, sodium acetate and sodium carbonate; when pre-potassification is desired, the pre-metallization additive may be selected from at least one of potassium metal, potassium nitrate, potassium hydroxide, potassium carbonate, and other potassium metal cation-containing compounds.
Further, the polymeric material described in the present invention is not particularly limited, and any polymeric material that can be polymerized under a certain condition (e.g., an initiator, light, heat, or high-energy radiation) in the art can be used in the present invention, and specific examples that may be mentioned include, but are not limited to, at least one of polyethylene glycol dimethacrylate (PEGDA), 1,3-Dioxolane (DOL), polyethylene oxide (PEO), vinylidene fluoride, hexafluoropropylene, vinylidene fluoride, acrylonitrile acrylic acid, ethylene glycol methyl ether methacrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, hydrogen polysiloxane, trimethyl carbonate, vinyltri-t-butylperoxysilane, butadiene, styrene, and vinyl chloride.
Furthermore, the degree of pre-metallization of the negative electrode active material can be adjusted according to the capacity required by the first coulombic efficiency by adjusting the addition amount of the pre-metallization additive, and the degree of uniformity of the pre-metallization or the thickness of the coated carbon layer can be adjusted by adjusting the addition amount of the polymer material, wherein the addition amount of the polymer material is determined according to the addition amount of the negative electrode active material, so that the residual carbon content after the carbonization of the polymer is enough to coat the negative electrode active material and cannot be excessive, otherwise, the exertion of the capacity of the negative electrode active material is influenced. Preferably, in some specific embodiments of the present invention, in the precursor mixed solution, the molar ratio of the metal element to the negative active material in the pre-metallization additive is 1:0.1 to 100, preferably 1:5 to 20, preferably, the mass ratio of the polymer material to the negative electrode active material is 1: (0.1 to 50), and controlling the mass percent of the final carbon in the negative active material to be 2-25%, preferably 5-10%.
Furthermore, since a part of the polymeric material can be self-polymerized by light, heat or high-energy ray radiation without adding an initiator, and a part of the polymeric material can be polymerized under the action of the initiator, the initiator can be optionally added or not added according to the needs. In some specific embodiments of the present invention, the precursor mixed solution further includes an initiator, and the addition amount of the initiator can be adjusted according to the addition amount of the polymeric material, and in some specific embodiments of the present invention, the addition amount of the initiator is 0.5% to 5% of the mass of the polymeric material, and is preferably 1%; the kind of the initiator is not particularly limited, and may be conventionally selected in the art or adjusted according to the kind of the polymeric material, and in some specific embodiments of the present invention, the initiator is selected from at least one of azo-type initiators, which may be mentioned by way of example but not limited to Azobisisobutyronitrile (AIBN), azobisisoheptonitrile (ABVN), azobisisobutyramidine hydrochloride (AIBA), azobisisobutyrimidazoline hydrochloride (AIBI), and the like, organic peroxide initiators which may be mentioned by way of example but not limited to benzoyl peroxide, benzoyl t-butyl peroxide, methyl ethyl ketone peroxide, and the like, persulfate initiators which may be mentioned by way of example but not limited to ammonium persulfate, sodium persulfate, and the like.
Further, according to the type of the polymer material, a part of the polymer material itself may function as a solvent, and therefore, the present invention may select to add or not add a solvent according to the type of the polymer material, in some specific embodiments of the present invention, the precursor mixed solution further includes a solvent, the addition amount of the solvent is not particularly limited, and may be adjusted as needed, specifically, the negative active material is just immersed, so that the negative active material is in a state of being just wrapped by the polymer gel after polymerization and curing, and the thickness of the wrapped carbon layer is more uniform, in some embodiments of the present invention, the mass ratio of the solvent to the polymer material is 1:0.1 to 100; in addition, the kind of the solvent is not particularly limited, and may be adjusted according to other raw materials, so that the pre-metallization additive, the initiator, and the polymeric material may be dissolved, and in some specific embodiments of the present invention, the solvent is selected from at least one of water, ethanol, N-methylpyrrolidone, and dimethyl carbonate.
Further, the foregoing preliminary metallization of the negative electrode active material is further performed, and the polymer layer is coated on the surface of the negative electrode active material, and the organic material is heated and decomposed by carbonizing the polymer to obtain the carbon coating layer, the carbonization process in the present invention is not particularly limited, and it is sufficient to perform the heating and decomposition of the organic material under the air-insulated condition that is conventional in the art, and the specific temperature, time, and the like thereof may be adjusted according to the needs (such as the type and amount of the polymer material in the coating layer, and the like), specifically, the carbonization temperature thereof should ensure that the polymer coated on the surface of the negative electrode active material can be completely carbonized, and therefore, is adjusted according to the polymer type, and the carbonization time should satisfy the shortest time required for complete carbonization of the surface polymer, and therefore, is not particularly limited, and in some specific embodiments of the present invention, the carbonization process is specifically: placing the precursor in an anaerobic condition, and sintering at 500-1000 ℃ for 1-12h, preferably carbonizing at 700 ℃ for 6h; in addition, the anaerobic condition can be realized by introducing a protective atmosphere (such as inert gas or nitrogen) into the carbonization equipment, which is not illustrated here, and in some specific embodiments of the invention, a mixed atmosphere of nitrogen and argon is used.
According to a second aspect of the present invention, there is provided a negative active material prepared by the method according to any one of the first aspect of the present invention, wherein the negative active material has uniform pre-metallization and uniform thickness of the surface-coated carbon layer, so that not only can the loss of metal elements be compensated, but also the conductivity of the material can be improved to suppress the volume expansion of the negative active material.
The third aspect of the invention provides an anode containing the anode active material according to the second aspect of the invention. The negative electrode is formed by coating a negative electrode slurry on a negative electrode current collector and drying and rolling. The addition amount of the negative electrode active material in the negative electrode slurry can be conventional, such as 80wt% -95 wt%, and the negative electrode slurry is mainly added with a binder, a conductive agent and a solvent, and can also be added with an auxiliary agent such as a thickening agent and a dispersing agent according to selection. The binder is used as a component contributing to the negative active material, the conductive agent and the adhesion with the negative current collector, and the conductive agent is used for further improving the conductivity of the negative active material, and any one of them can be selected conventionally in the art, for example, the binder can be selected from polyvinylidene fluoride, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, polyvinyl alcohol, etc., the conductive agent can be selected from carbon powder, conductive fiber or whisker, graphite, etc., and the addition amount thereof can be adjusted according to the conventional addition amount. The solvent in the negative electrode slurry may be water or an organic solvent (e.g., alcohol or NMP), and the amount of the solvent added may be dynamically adjusted according to the desired viscosity of the negative electrode slurry, and is not particularly limited. Since the preparation method of the cathode belongs to the prior art, the details are not repeated here.
A fourth aspect of the invention provides a secondary battery which is a lithium ion battery, a sodium ion battery or a potassium ion battery, and which contains the negative electrode according to the third aspect of the invention. The secondary battery further includes a positive electrode, a separator, and an electrolyte, and may be adjusted according to the kind of the secondary battery, which is not particularly limited herein. It is understood that the assembly of the secondary battery may be performed in a conventional manner in the art, such as in an environment where the water oxygen content is less than 0.1ppm, and will not be described herein. Due to the fact that the anode active material is subjected to pre-metallization and carbon coating, the first coulombic efficiency and the cycle stability of the obtained secondary battery are improved, and the method has obvious progress.
The technical solutions of the present invention will be more clearly and completely described below with reference to specific embodiments, and it should be noted that the following embodiments are merely examples of some preferred embodiments of the present invention.
Example 1
Preparation of negative active material:
dissolving lithium hydroxide, polyethylene glycol dimethacrylate (PEGDA) and Azobisisobutyronitrile (AIBN) initiator in a hydroalcoholic solution (a mixed solution of water and ethanol), adding silica, performing ultrasonic treatment, uniformly stirring, and sealing to obtain a precursor mixed solution, wherein the mass ratio of the PEGDA to the hydroalcoholic solution is 1:5, the molar ratio of the lithium hydroxide to the silica is 1;
carrying out self-polymerization reaction on the precursor mixed solution at the temperature of 80 ℃ for 2h to obtain a precursor;
placing the precursor in Ar/N 2 Sintering in the atmosphere at 700 ℃, with the heating rate of 5 ℃/min and the time of 6h, obtaining the carbon-coated pre-lithiated silicon monoxide, and grinding the carbon-coated pre-lithiated silicon monoxide to a proper particle size as required.
Preparation of a negative electrode:
mixing the negative electrode active material, the binder sodium alginate and the conductive agent SP in a ball milling tank according to the mass ratio of 8.
Preparation of secondary battery:
in a glove box with the water oxygen content less than 0.1ppm, a lithium sheet is used as a counter electrode, and a half cell is assembled by the negative electrode, the electrolyte and the diaphragm in the example 1.
Wherein the electrolyte is prepared by mixing Ethylene Carbonate (EC) and diethyl carbonate (DEC) according to the mass ratio of 1:1 in a glove box with the water oxygen content less than 0.1ppm at room temperature, and adding 1mol/L LiPF 6 Fully mixing and standing for 24 times to obtain the product;
the diaphragm is obtained by punching an alumina-coated polypropylene material into a circular disc with the diameter of 16mm, transferring the circular disc into a vacuum drying box with the temperature of 55 ℃ and carrying out vacuum drying for 24 h.
Example 2
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that the mass ratio of PEGDA to the hydroalcoholic solution was 1:4.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 3
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that the mass ratio of PEGDA to the hydroalcoholic solution was 1:3.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 4
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that the molar ratio of lithium hydroxide to silica was 1.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 5
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that the molar ratio of lithium hydroxide to silica was 1.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 6
Preparation of negative active material:
an anode active material was prepared in the same manner as in example 1, except that the molar ratio of lithium hydroxide to silica was 1:5.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 7
Preparation of negative active material:
an anode active material was prepared in the same manner as in example 1, except that the mass ratio of PEGDA to silica was 1:5.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 8
Preparation of negative active material:
an anode active material was prepared in the same manner as in example 1, except that the mass ratio of PEGDA to silica was 1:4.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 9
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that the mass ratio of PEGDA to silica was 1:3.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 10
Preparation of negative active material:
the negative electrode active material is prepared in the same manner as in example 1, except that a precursor mixed solution is obtained by subjecting lithium powder, DOL and silica to ultrasonic treatment, stirring and mixing uniformly, and then sealing, wherein the molar ratio of the lithium powder to the silica is 1.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 11
Preparation of negative active material:
preparing a negative electrode active material in the same manner as in example 1, except that lithium nitrate, vinyl chloride, DOL and silica are subjected to ultrasonic treatment, stirred, mixed uniformly and then sealed to obtain a precursor mixed solution, wherein the molar ratio of the lithium nitrate to the silica is 1;
and carrying out room-temperature self-polymerization reaction on the precursor mixed solution under the irradiation of an ultraviolet lamp for 2 hours to obtain a precursor.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 12
Preparation of negative active material:
an anode active material was prepared in the same manner as in example 1, except that in this example, hard carbon was used as an anode active material, and the molar ratio of lithium hydroxide to hard carbon was 1:45.
preparing a negative electrode and a secondary battery:
the same as in example 1.
Example 13
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that the negative electrode active material used in this example was nano silicon particles.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Comparative example 1
In this comparative example, the same silica as in example 1 was used as the negative electrode active material, and no treatment was performed.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Comparative example 2
Preparation of negative active material:
a negative electrode active material was prepared in the same manner as in example 1, except that lithium hydroxide was not added to the precursor mixed solution to obtain a carbon-coated silica material.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Comparative example 3
Preparation of negative active material:
mixing a mixture of 1:20 lithium hydroxide and silica were mixed by intensive grinding and then subjected to Ar/N 2 Sintering in a tube furnace under the atmosphere, wherein the temperature is 700 ℃, the heating rate is 5 ℃/min, and the time is 6h. And finally, taking out the sintered sample, and grinding for later use to obtain the pre-lithiated silicon protoxide material.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Comparative example 4
Preparation of negative active material:
mixing the components in a mass ratio of 1:20 lithium hydroxide and silica were mixed by intensive grinding and then subjected to Ar/N 2 Sintering in a tubular furnace under the atmosphere, wherein the temperature is 700 ℃, the heating rate is 5 ℃/min, and the time is 6h. Finally, taking out the sintered sample and grinding the sampleObtaining a prelithiated silica material;
placing the obtained pre-lithiated silica material in a crucible, and introducing an atmosphere C 2 H 2 The temperature rise rate of the gas was 5 ℃/min, the CVD temperature was 700 ℃, and the carbon layer thickness was adjusted by adjusting the CVD time and the amount of gas introduced as in example 1 to obtain carbon-coated prelithiated silicon monoxide.
Preparing a negative electrode and a secondary battery:
the same as in example 1.
Test example 1
The secondary batteries of examples 1 to 13 and comparative examples 1 to 4 were tested using an Arbin BT2000 test system at a charging/discharging voltage ranging from 0.01 to 2.0V, and cycled at 0.1C-rate for 300 cycles (25 ℃), and the test results are shown in Table 1.
TABLE 1 test results of Performance test of secondary batteries in examples 1 to 13 and comparative examples 1 to 4
Figure 977407DEST_PATH_IMAGE001
As can be seen from the test results in table 1, the carbon-coated prelithiated silica prepared by the one-step method of the present invention has high first coulombic efficiency and excellent cycle stability while simplifying the process, compared to the silica treated by at most one of the carbon-coating-only and prelithiation-only methods; compared with the existing step-by-step process of obtaining the carbon coating layer by pre-lithiation and then CVD deposition, the preparation method provided by the invention has the advantages that the coulombic efficiency and the cycle stability are improved for the first time, the carbon coating and the pre-lithiation of the silicon oxide surface are simultaneously carried out by virtue of the one-step process, the thickness of the carbon layer is more uniform, and the lithiation of the silicon oxide is more uniform.
Example 14
Preparation of negative active material:
dissolving sodium acetate, polyethylene glycol dimethacrylate (PEGDA) and Azobisisobutyronitrile (AIBN) initiator in a hydroalcoholic solution (a mixed solution of water and ethanol), adding hard carbon, performing ultrasonic treatment, uniformly stirring, and sealing to obtain a precursor mixed solution, wherein the mass ratio of the PEGDA to the hydroalcoholic solution is 1:5, the molar ratio of the sodium acetate to the hard carbon is 1, the mass ratio of the PEGDA to the hard carbon is 1;
carrying out self-polymerization reaction on the precursor mixed solution at the temperature of 80 ℃ for 2h to obtain a precursor;
placing the precursor in Ar/N 2 Sintering in the atmosphere at 700 ℃, with the heating rate of 5 ℃/min and the time of 6h, obtaining the carbon-coated pre-sodiumized hard carbon, and grinding to a proper granularity as required.
Preparing a negative electrode:
mixing the negative electrode active material, the binder sodium alginate and the conductive agent SP in a ball milling tank according to the mass ratio of 8.
Preparation of secondary battery:
in a glove box with water and oxygen content less than 0.1ppm, a sodium sheet is used as a counter electrode, and an electrolyte is NaPF (EC: DEC =1, 1mol/L 6 ) The diaphragm is made of glass fiber material and punched into a circular sheet with the diameter of 16mm, and the circular sheet and the negative electrode in the embodiment are assembled into a half cell.
Example 15
Preparation of negative active material:
dissolving potassium nitrate, polyethylene glycol dimethacrylate (PEGDA) and Azobisisobutyronitrile (AIBN) initiator in a hydroalcoholic solution (a mixed solution of water and ethanol), adding artificial graphite, performing ultrasonic treatment, uniformly stirring, and sealing to obtain a precursor mixed solution, wherein the mass ratio of the PEGDA to the hydroalcoholic solution is 1:5, the molar ratio of potassium nitrate to the artificial graphite is 1, the mass ratio of the PEGDA to the artificial graphite is 1, and the mass ratio of the AIBN initiator is 1% of the mass of the PEGDA;
carrying out self-polymerization reaction on the precursor mixed solution at the temperature of 80 ℃ for 2h to obtain a precursor;
placing the precursor in Ar/N 2 Sintering in the atmosphere at 700 ℃, with the temperature rise rate of 5 ℃/min and the time of 6h to obtain the carbon-coated pre-potassized artificial graphite which can be ground to a proper particle size as required.
Preparation of a negative electrode:
mixing the negative electrode active material, the binder sodium alginate and the conductive agent SP in a ball milling tank according to the mass ratio of 8.
Preparation of secondary battery:
in a glove box with water and oxygen content less than 0.1ppm, potassium sheet is used as a counter electrode, and electrolyte is KPF (EC: DEC =1, 1mol/L 6 ) The diaphragm is made of glass fiber material and punched into a circular sheet with the diameter of 16mm, and the circular sheet and the negative electrode in the embodiment are assembled into a half cell.
Comparative example 5
In this comparative example, the same hard carbon as in example 14 was used as the negative electrode active material, and no treatment was performed.
Preparing a negative electrode and a secondary battery:
the same as in example 14.
Comparative example 6
The negative active material in this comparative example used the artificial graphite as in example 15 and was not subjected to any treatment.
Preparing a negative electrode and a secondary battery:
the same as in example 15.
Test example 2
The secondary batteries of examples 14 and 15 and comparative examples 5 and 6 were tested using an Arbin BT2000 test system, in which the charging and discharging voltages of the sodium ion battery were in the range of 0.01 to 3.0v and the charging and discharging voltages of the potassium ion battery were in the range of 0.01 to 2.0v, and the battery was cycled at 0.1C magnification for 300 cycles (25 ℃), and the test results are shown in table 2.
TABLE 2 test results of Secondary Battery Performance in examples 14 and 15 and comparative examples 5 and 6
Figure 372616DEST_PATH_IMAGE002
The test results in table 2 show that the negative active material obtained by the preparation method of the present invention can be used for preparing sodium ion batteries and potassium ion batteries, and can also significantly improve the first coulombic efficiency and cycle performance of the sodium ion batteries and the potassium ion batteries, and thus, the present invention has significant progress.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims (10)

1. A method for preparing an anode active material, comprising the steps of:
obtaining a precursor mixed solution, wherein the precursor mixed solution comprises a negative electrode active substance, a pre-metallization additive and a polymeric material, and the polymeric material is selected from at least one of polyethylene glycol dimethacrylate (PEGDA) and 1,3-Dioxolane (DOL); the pre-metallization additive is selected from a metal simple substance or a metal compound of an element M, and the element M is selected from Li, na or K;
performing polymerization reaction on the precursor mixed solution to obtain a precursor;
and carbonizing the precursor to obtain the carbon-coated pre-metallized negative electrode material.
2. The method of claim 1, wherein the negative electrode active material is selected from a high capacity carbon negative electrode material or a silicon-based negative electrode material.
3. The method according to claim 1, wherein the cation in the metal compound is selected from Li + 、Na + Or K + The anion is selected from OH - 、COO - 、F - 、NO 3 - 、H - 、AlH 4 - 、CO 3 2- 、TFSI - At least one of (1).
4. The method according to claim 1, wherein the molar ratio of the metal element to the negative active material in the pre-metallization additive in the precursor mixed solution is 1:0.1 to 100, wherein the mass ratio of the polymer material to the negative electrode active substance is 1:0.1 to 50.
5. The preparation method of claim 1, wherein the precursor mixed solution further comprises an initiator, and the addition amount of the initiator is 0.5-5% of the mass of the polymeric material; the initiator is at least one of azo initiator, organic peroxide initiator and persulfate initiator.
6. The preparation method according to claim 1, wherein the precursor mixed solution further comprises a solvent, and the mass ratio of the solvent to the polymeric material is 1:0.1 to 100; the solvent is at least one selected from water, ethanol, N-methyl pyrrolidone and dimethyl carbonate.
7. The preparation method according to claim 1, wherein the carbonization process comprises: and (3) carbonizing the precursor for 1 to 12h at 500 to 1000 ℃ under the anaerobic condition.
8. A negative electrode active material, characterized in that it is produced by the production method as claimed in any one of claims 1 to 7.
9. A negative electrode comprising the negative electrode active material according to claim 8.
10. A secondary battery which is a lithium ion battery, a sodium ion battery or a potassium ion battery, characterized by comprising the negative electrode according to claim 9.
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