CN113659123B - Cathode material, preparation method, device and lithium ion battery - Google Patents

Cathode material, preparation method, device and lithium ion battery Download PDF

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CN113659123B
CN113659123B CN202110938869.0A CN202110938869A CN113659123B CN 113659123 B CN113659123 B CN 113659123B CN 202110938869 A CN202110938869 A CN 202110938869A CN 113659123 B CN113659123 B CN 113659123B
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lithium
silica powder
lithium source
coated silica
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CN113659123A (en
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吴云胜
胡晓东
吴泽轶
何晓云
石九菊
蒋勇明
吴亚平
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Sichuan Jinhuineng New Material Co ltd
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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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • 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
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Abstract

The invention discloses a negative electrode material, a preparation method and equipment thereof, and a lithium ion battery, wherein carbon-coated silica powder and an atomized lithium source are uniformly mixed in an inert atmosphere, and the mixing temperature is 190-350 ℃. The lithium source is atomized into liquid drops and is more uniformly mixed with the carbon-coated silica powder, so that Li caused by local excessive lithiation reaction can be effectively avoided 4 SiO 4 、Li 2 SiO 3 、Li x The generation of lithium-rich products such as Si and the like effectively improves the first efficiency of the silicon-oxygen cathode material, effectively inhibits the gas production phenomenon of the water-based slurry, obviously improves the stability of the slurry of the silicon-oxygen cathode material applied to the battery preparation process, improves the applicability, improves the material capacity, ensures that the mixing temperature is higher than the melting point of lithium, ensures the atomized liquid drop shape of the lithium in the mixing process, ensures the uniform mixing and has high process controllability. The preparation process is simplified, the requirements on conditions and equipment are reduced, the cost is reduced, and the preparation method is convenient for large-scale application.

Description

Negative electrode material, preparation method and equipment, and lithium ion battery
Technical Field
The invention relates to the technical field of energy storage electrode materials, in particular to a negative electrode material, a preparation method, equipment and a lithium ion battery.
Background
The currently used mainstream single graphite cathode material has wide application, but the capacity is 360mAh/g and is close to the theoretical gram capacity of 372mAh/g, and the space is difficult to be improvedAnd (5) realizing. The theoretical capacity of silicon in the cathode material is highest, and Li and Si form alloy Li 4.4 Si, the capacity is as high as 4200mAh/g, which is far larger than the theoretical capacity of graphite. However, unlike the intercalation mechanism of graphite, the alloying mechanism of silicon hinders practical application by up to 300% volume effect during charging and discharging.
Compared with simple substance silicon, the silicon monoxide body contains superfine nano silicon crystal clusters, so that the damage of the structure caused by huge volume effect in the lithium desorption and insertion process can be avoided. And SiO present in the bulk 2 The component is used as a natural carrier, not only effectively prevents the agglomeration of nano silicon crystal clusters, but also is used as a buffer medium to reduce the stress released in the process of releasing and inserting lithium ions, and moreover, the silicon monoxide also has higher theoretical specific capacity, so that the silicon monoxide is considered to be one of the most hopeful negative electrode materials.
Despite the above advantages, the first efficiency of SiO is low due to the formation of lithium silicate, lithium silicate and lithium oxide during the first lithium intercalation process, which do not release lithium ions during the subsequent lithium deintercalation process. When the lithium ion battery is matched with the conventional positive electrode system to manufacture a full battery, the limited lithium ions of the positive electrode cannot be effectively removed after being charged and embedded into SiO for the first time, and the high-capacity characteristic of the silicon substrate is difficult to exert. Therefore, it is necessary to research a silicon-oxygen anode material with high efficiency and high capacity for the first time.
The existing method for improving the first efficiency and capacity of the silicon-oxygen anode material comprises the following steps: firstly, adopting two steps, namely firstly mixing carbon-coated silicon oxide with a lithium source solid phase; and then the pre-lithium precursor obtained by mixing is subjected to heat treatment in a vacuum or non-oxidizing atmosphere. The process effectively improves the first efficiency of silicon oxygen preparation. However, since silicon oxide and lithium source are mixed in a solid phase, uniformity is difficult to ensure. And even if the lithium source is subjected to grain size refinement in a ball milling or crushing mode, on one hand, the specific surface of the lithium source is increased, agglomeration is easy to happen, uniform dispersion is not facilitated, and on the other hand, the activity of the refined lithium source is increased, so that safety problems are easy to generate in the using and transferring processes. In addition, the solid phase cannot be uniformly mixed, resulting in over-reaction of lithium and silicon oxide locallyResulting in lithium-rich compounds such as highly reactive Li x Si, and highly water-soluble compounds such as Li 4 SiO 4 、Li 2 SiO 3 The generation of silicate causes the processing problems of gas generation, sedimentation and the like in the later application of the water-based slurry. And secondly, doping gaseous lithium into the original negative electrode material, wherein the lithium supplementing method adopted in the preparation process is to gasify metal lithium or a lithium-containing raw material and a negative electrode material precursor raw material simultaneously under the action of certain negative pressure, and the two gaseous substances are mixed, cooled and deposited. However, li vapor and SiO X The difference in vapor density is large, so that the delamination problem is easily caused during mixing, and thus it is difficult to mix the lithium source and the negative electrode material uniformly during the practical operation of the method, and in order to prepare Li and SiO x Steam needs high temperature and negative pressure, and has high energy consumption, strict requirements on equipment and high cost.
Disclosure of Invention
The technical problems to be solved by the invention are that the existing silica cathode material is low in efficiency and capacity for the first time, the preparation process is complex, the requirements on conditions and equipment are high, the cost is high, the process is not easy to control, and the prepared cathode material has problems in subsequent application.
The invention is realized by the following technical scheme:
a first object of the present invention is to provide a method for preparing an anode material, the method comprising: mixing carbon-coated silica powder and atomized lithium source in inert atmosphere at 190-350 deg.C, 200 deg.C, 210 deg.C, 220 deg.C, 230 deg.C, 240 deg.C, 250 deg.C, 260 deg.C, 270 deg.C, 280 deg.C, 290 deg.C, 310 deg.C, 330 deg.C, and 340 deg.C; preferably 280 ℃ to 320 ℃.
Preferably, the process of uniformly mixing the carbon-coated silica powder and the atomized lithium source in an inert atmosphere is as follows:
and putting the carbon-coated silica powder into a mixing device, stirring, heating to 190-350 ℃ in an inert atmosphere, and doping the carbon-coated silica powder into a lithium source subjected to atomization treatment in the inert atmosphere.
Preferably, the process of atomizing the lithium source is as follows: under the inert atmosphere, the solid lithium source is heated and melted into liquid, and the inert gas drives the liquid lithium source to enter the atomizer to be dispersed and atomized into liquid drops.
Preferably, the atomizing equipment comprises a melting tank and an atomizing nozzle, and two ends of the atomizing nozzle are respectively communicated with the melting tank and the mixing device;
the process of heating and melting a solid lithium source into a liquid under an inert atmosphere comprises the following steps: adding a solid-phase lithium source into a melting tank of an atomizer under the protection of inert gas, and melting at 280-400 ℃ under the conditions that the water content in the melting tank is less than 50ppm and the oxygen content is less than 50 ppm; the melting temperature can be 290 ℃, 310 ℃, 330 ℃, 350 ℃, 370 ℃ and 390 ℃; more preferably from 300 ℃ to 350 ℃.
The process that the liquid lithium source of the inert gas driving liquid enters the atomizer to be dispersed and atomized into a droplet shape is as follows: the melted lithium source enters the atomizing nozzle under the driving of inert gas as atomization to be atomized into liquid drops, and the liquid drops are sprayed into a mixing device to be mixed with carbon-coated silica powder;
the atomization driving pressure is 0.4MPa to 2.0MPa, and may be 0.5MPa, 0.75MPa, 1MPa, 1.25MPa, 1.5MPa, 1.75MPa, 1.8MPa, 1.9MPa, more preferably 0.8MPa to 1.5MPa;
the aperture of the spray hole of the atomizing spray head is 0.1 mm-2.0 mm, and can be 0.2mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, and more preferably 0.2 mm-1.5 mm.
Preferably, after the carbon-coated silica powder and the atomized lithium source are uniformly mixed in an inert atmosphere, the first treatment is also included;
the first treatment is to heat to 600-800 ℃, cool and discharge after 2-8 h, and the temperature can be raised to 610 ℃, 630 ℃, 650 ℃, 670 ℃, 690 ℃, 710 ℃, 730 ℃, 750 ℃, 770 ℃, 790 ℃, more preferably to 650-720 ℃; the time of the first treatment may be 2.1h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h,6.0h, 6.5h, 7.0h, 7.5h, 7.9h, more preferably 3h to 6h;
the temperature rise rate is 0.5 ℃/min to 3 ℃/min, and may be 0.6 ℃/min, 1.0 ℃/min, 1.2 ℃/min, 1.4 ℃/min, 1.6 ℃/min, 1.8 ℃/min, 2.0 ℃/min, 2.2 ℃/min, 2.4 ℃/min, 2.6 ℃/min,2.9 ℃/min, more preferably 1.2 ℃/min to 2.2 ℃/min.
Preferably, the average particle diameter D50 of the carbon-coated silica powder is 2 μm to 7 μm, and may be 2.1 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 6.8 μm, and more preferably 3.5 μm to 5.5 μm; maximum particle diameter D max Less than 25 μm;
the mass ratio of the lithium source to the carbon-coated silica powder is 3.5 to 8.0%, and may be 3.6%, 3.8%, 4.0%, 4.2%, 4.5%, 4.8%, 5.0%, 5.2%, 5.5%, 5.8%, 6.0%, 6.2%, 6.5%, 6.8%, 7.0%, 7.2%, 7.5%, 7.9%, and more preferably 5.0 to 7.0%;
the carbon-coated silica powder is prepared by carrying out carbon coating treatment on a silicon oxide powder and an organic carbon source in an inert gas at 850-950 ℃ to obtain a structure that the carbon coating is coated on the surface of the silicon oxide, wherein the temperature in the carbon coating process can be 850 ℃, 900 ℃ and 950 ℃;
the average particle diameter D50 of the silicon monoxide powder is 2-6 mu m, and the maximum particle diameter D max Is less than 20 μm, and is,
the mass fraction of the carbon coating accounts for 2.5-8.0% of the carbon-coated silica powder, and can be 2.6%, 3.1%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%,6.0%, 6.5%, 7.0%, 7.5%, 7.9%, and more preferably 4.0-6.0%.
Preferably, the lithium source is solid lithium, and the inert atmosphere is one or a mixture of two of helium, argon, neon and xenon, and more preferably argon.
The second purpose of the invention is to provide a negative electrode material prepared by the method.
A third object of the present invention is to provide an apparatus for use in the above-mentioned manufacturing method.
The fourth purpose of the invention is to provide a lithium ion battery, which comprises the anode material.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the preparation method of the cathode material provided by the embodiment of the invention, the carbon-coated silica powder and the atomized lithium source are uniformly mixed in an inert atmosphere, and the mixing temperature is 190-350 ℃. The lithium source is atomized into liquid drops and is more uniformly mixed with the carbon-coated silica powder, so that the Li caused by local over lithiation reaction can be effectively avoided 4 SiO 4 、Li 2 SiO 3 、Li x The generation of lithium-rich products such as Si and the like effectively improves the first efficiency of the silicon-oxygen cathode material, effectively inhibits the gas production phenomenon of the water-based slurry, obviously improves the stability of the slurry of the silicon-oxygen cathode material applied to the battery preparation process, improves the applicability and also improves the material capacity. And the mixing temperature is higher than the melting point of lithium, so that the atomized liquid drops of the lithium are ensured in the mixing process, the uniform mixing is ensured, and the process controllability is high. The preparation process is simplified, the requirements on conditions and equipment are reduced, the cost is reduced, and the preparation method is convenient for large-scale application. And the peak intensity in the XRD ray diffraction pattern of the prepared cathode material is obtained by selecting proper preparation conditions and reasonable mixture ratio of the substances
Figure BDA0003213956870000041
Figure BDA0003213956870000042
The comprehensive performance is optimal.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, 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, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort. In the drawings:
FIG. 1 is an X-ray diffraction chart of a negative electrode material provided in example 1 of the present invention;
FIG. 2 is an X-ray diffraction pattern of a negative electrode material according to comparative example 1 of the present invention;
fig. 3 is a diagram illustrating a first charge and discharge of a negative electrode material provided in embodiment 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not used as limiting the present invention.
The invention concept of the preparation method of the cathode material provided by the invention is as follows:
a preparation method of a cathode material comprises the step of uniformly mixing carbon-coated silica powder and an atomized lithium source in an inert atmosphere, wherein the mixing temperature is 190-350 ℃.
The lithium source is atomized into liquid drops and is more uniformly mixed with the carbon-coated silica powder, so that Li caused by local excessive lithiation reaction can be effectively avoided 4 SiO 4 、Li 2 SiO 3 、Li x The generation of Si and other lithium-rich products effectively improves the first efficiency of the silicon-oxygen cathode material, effectively restrains the gas generation phenomenon of the water-based slurry, obviously improves the stability of the slurry of the silicon-oxygen cathode material in the preparation process of the battery, improves the applicability and also improves the material capacity. And the mixing temperature is higher than the melting point of lithium, so that the atomized liquid drops of the lithium are ensured in the mixing process, the uniform mixing is ensured, and the process controllability is high. The preparation process is simplified, the requirements on conditions and equipment are reduced, the cost is reduced, and the method is convenient for large-scale application.
Further, the process of uniformly mixing the carbon-coated silica powder and the atomized lithium source in an inert atmosphere is as follows: and (3) putting the carbon-coated silica powder into a mixing device, stirring, heating to 190-350 ℃ in an inert atmosphere, and doping the carbon-coated silica powder into a lithium source atomized in the inert atmosphere. The process of atomizing the lithium source comprises the following steps: under the inert atmosphere, the solid lithium source is heated and melted into liquid, and the inert gas drives the liquid lithium source to enter the atomizer to be dispersed and atomized into liquid drops.
Fully stirring the carbon-coated silica powder before mixing, controlling the temperature in the mixing device to be higher than the lithium melting temperature in advance, and controlling the temperature to be 190-350 ℃ so as to provide a temperature basis for subsequent mixing. And the carbon-coated silica powder is always in a stirring state in the mixing process and is uniformly mixed. The process of the lithium source atomization treatment is carried out in an inert atmosphere, so that the activity is reduced, and the oxidation is avoided. The method comprises the steps of heating and melting non-powder lithium sources such as lithium sheets, lithium blocks, lithium ingots and the like into liquid in an inert atmosphere, and then spraying the liquid on the surface of carbon-coated silica powder which is heated to a temperature above the melting point of lithium and is in a stirring motion state through atomization, so that uniform dispersion and mixing of a small amount of lithium sources and the carbon-coated silica powder are realized. The stirring in the mixing process also avoids Si grain growth caused by partial lithiation reaction heat aggregation easily formed in the existing static heat treatment process, and can obviously reduce expansion and improve cycle performance.
Furthermore, the atomizing equipment comprises a melting tank and an atomizing nozzle, and two ends of the atomizing nozzle are respectively communicated with the melting tank and the mixing device; the process of heating and melting the solid lithium source into liquid under the inert atmosphere comprises the following steps: adding a solid-phase lithium source into a melting tank of an atomizer under the protection of inert gas, and melting at 280-400 ℃ under the conditions that the water content in the melting tank is less than 50ppm and the oxygen content is less than 50 ppm; the process that the liquid lithium source of the inert gas driving liquid enters the atomizer to be dispersed and atomized into a droplet shape is as follows: and the melted lithium source enters the atomizing nozzle under the drive of inert gas as atomizing drive to be atomized into a liquid drop shape, and is sprayed into a mixing device to be mixed with carbon-coated silica powder.
The pre-lithiation treatment process is characterized in that the uniform dispersion and lithiation treatment of the lithium source and the carbon-coated silicon monoxide powder are carried out on the same set of equipment, atomization is carried out, the atomized lithium source and the carbon-coated silicon monoxide powder can be sprayed into a mixing device below the atomization spray head, transfer is not needed between pre-lithiation and uniform dispersion, and potential safety hazards caused by contact of the high-activity lithium source with outside air and the like are avoided. Inert gas is used as power for atomization spraying, the process is simple and controllable, external special power equipment is not needed, and equipment required by preparation is simple, safe and convenient. The spraying mode further enhances the mixing effect.
Further, after the carbon-coated silica powder and the atomized lithium source are uniformly mixed in an inert atmosphere, a first treatment is also included; the first treatment is to heat the mixture to 600-800 ℃ for 2-8 h, then cool and discharge the mixture; the temperature rising speed is 0.5-3 ℃/min.
The uniform load mixing of the lithium liquid and the powder and the subsequent stirring dynamic high-temperature heat treatment can effectively avoid Li caused by local excessive lithiation reaction 4 SiO 4 、Li 2 SiO 3 、Li x The generation of lithium-rich products such as Si and the like obviously improves the applicability of water-based slurry adopted in the battery preparation process; meanwhile, the subsequent high-temperature treatment can control the crystal form structure transformation and the grain size, effectively avoids the occurrence of the local excessive lithiation of the lithium source and the carbon-coated silicon monoxide, and more water-insoluble Li 2 Si 2 O 5 The structure is generated, so that excessive lithium-rich compounds are avoided, the gas generation phenomenon of the water-based slurry is effectively inhibited, and the stability of the slurry in the material application process is remarkably improved. And high energy density and long cycle performance of the cathode material are realized.
The following is an explanation with reference to specific examples.
Example 1: preparation method of negative electrode material
Introducing acetylene gas into commercial silicon monoxide powder in a rotary furnace, and performing carbon coating treatment at 850 deg.C to obtain silicon monoxide powder with coating amount of 4.2%, D50 (median particle diameter) of 4.5 μm, and D max (maximum particle size) of 16.4. Mu.m. Then 10kg of carbon-coated silica powder is put into a colter mixer with an atomizer, heating and stirring are started, argon gas is introduced, the temperature of materials in the mixer is controlled to be 280 ℃, the water content is 20ppm, and the oxygen content is 20ppm;
adding 0.6kg of lithium block into a stainless steel melting tank connected with an atomizing nozzle with the diameter of 0.5mm under the protection of argon, starting to heat to 320 ℃, and simultaneously controlling the water content and the oxygen content in the tank to be 10ppm and 10ppm. And after the lithium block is completely melted, adjusting the air inflow of argon, controlling the atomization driving pressure in the melting tank to be 0.8MPa, atomizing and spraying the atomized powder onto the carbon-coated silicon oxide powder which is continuously stirred below. After the molten lithium liquid is atomized, heating the mixer to 680 ℃ under the stirring state at the heating rate of 1 ℃/min, carrying out heat preservation treatment for 3 hours, cooling and discharging. Finally, 9.8kg of powder is obtained, namely the cathode material.
Example 2: preparation method of negative electrode material
Introducing acetylene gas into commercial silicon oxide powder in a rotary furnace, and performing carbon coating treatment at 850 deg.C to obtain silicon oxide powder with coating amount of 2.6%, D50 of 2.5 μm, and D max The silica powder was coated with 8.4 μm carbon. Then 10kg of carbon-coated silica powder is put into a colter mixer with an atomizer, heating and stirring are started, argon is introduced, the temperature of materials in the mixer is controlled to be 200 ℃, the water content is 40ppm, and the oxygen content is 45ppm;
adding 0.6kg of lithium block into a stainless steel melting tank connected with an atomizing nozzle with the diameter of 0.2mm under the protection of argon, starting to heat to 380 ℃, and simultaneously controlling the water content and the oxygen content in the tank body to be 10ppm and 10ppm. And after the lithium block is completely melted, adjusting the air inflow of argon, controlling the atomization driving pressure in the melting tank to be 0.5MPa, atomizing and spraying the atomized powder into the mixer below. After the atomization of the molten lithium liquid is finished, heating the mixer to 780 ℃ at the heating rate of 2.5 ℃/min, carrying out heat preservation treatment for 6h, cooling and discharging. Finally, 9.8kg of powder is obtained, namely the cathode material.
Example 3: preparation method of negative electrode material
Introducing acetylene gas into commercial silicon oxide powder in a rotary furnace, and performing carbon coating treatment at 950 deg.C to obtain silicon oxide powder with coating amount of 7.8%, D50 of 7.5 μm, and D max The silica powder was coated with carbon of 21.3 μm. Then 10kg of carbon-coated silica powder is put into a colter mixer with an atomizer, heating and stirring are started, argon is introduced, the temperature of materials in the mixer is controlled to be 320 ℃, the water content is 20ppm, and the oxygen content is 25ppm;
adding 0.36kg of lithium block into a stainless steel melting tank connected with an atomizing nozzle with the diameter of 1.5mm under the protection of argon, starting to heat to 300 ℃, and simultaneously controlling the water content and the oxygen content in the tank body to be 10ppm and 10ppm. And after the lithium block is completely melted, adjusting the air inflow of argon, controlling the atomization driving pressure inside the melting tank to be 1.5MPa, atomizing and spraying the atomized powder into a mixer below the melting tank. After the atomization of the molten lithium liquid is finished, heating the mixer to 620 ℃ at the heating rate of 1.5 ℃/min, carrying out heat preservation treatment for 2.5h, cooling and discharging. Finally, 9.8kg of powder is obtained, namely the cathode material.
Example 4: preparation method of negative electrode material
Introducing acetylene gas into the silicon monoxide powder in a rotary furnace to carry out carbon coating treatment at 900 ℃ to obtain the silicon monoxide powder with the coating amount of 5.3 percent, the D50 of 5.1 mu m and the D max The silica powder was coated with 16.3 μm carbon. Then 10kg of carbon-coated silica powder is put into a colter mixer with an atomizer, heating and stirring are started, argon gas is introduced, the temperature of materials in the mixer is controlled to be 300 ℃, the water content is 10ppm, and the oxygen content is 25ppm;
adding 0.78kg of lithium block into a stainless steel melting tank connected with an atomizing nozzle with the diameter of 1.0mm under the protection of argon, starting to heat to 320 ℃, and simultaneously controlling the water content and the oxygen content in the tank to 10ppm and 15ppm. And after the lithium block is completely melted, adjusting the air inflow of argon, controlling the atomization driving pressure inside the melting tank to be 1.8MPa, atomizing and spraying the atomized powder into a mixer below. After the molten lithium liquid is atomized, heating the mixer to 700 ℃ at the heating rate of 2 ℃/min, carrying out heat preservation treatment for 7.5h, cooling and discharging. Finally, 9.8kg of powder is obtained, namely the cathode material.
Example 5: preparation method of negative electrode material
Introducing acetylene gas into the silicon oxide powder in a rotary furnace to carry out carbon coating treatment at 900 ℃ to obtain the silicon oxide powder with the coating amount of 4.5 percent and the D50 of 3.8 mu m max The silica powder was coated with carbon of 10.3 μm. Then 10kg of carbon-coated silica powder is put into a colter mixer with an atomizer, heating and stirring are started, argon gas is introduced, and the interior of the mixer is controlledThe material temperature is 300 ℃, the water content is 30ppm, and the oxygen content is 45ppm;
adding 0.07kg of lithium block into a stainless steel melting tank connected with an atomizing nozzle with the diameter of 0.5mm under the protection of argon, starting to heat to 290 ℃, and simultaneously controlling the water content and the oxygen content in the tank body to be 15ppm and 23ppm. And after the lithium block is completely melted, adjusting the air inflow of argon, controlling the atomization driving pressure inside the melting tank to be 1.0MPa, atomizing and spraying the atomized powder into the mixer below. And after the molten lithium liquid is atomized, heating the mixer to 750 ℃ at the heating rate of 0.8 ℃/min, carrying out heat preservation treatment for 5 hours, cooling and discharging. Finally, 9.8kg of powder is obtained, namely the cathode material.
Comparative example 1
Introducing acetylene gas into the silicon monoxide powder in a rotary furnace to carry out carbon coating treatment at 850 ℃ to obtain the silicon monoxide powder with the coating amount of 1.8 percent, the D50 of 4.3 mu m and the D max The silica powder was coated with carbon at 16.4 μm. The other conditions were the same as in example 1.
Comparative example 2
The same conditions as in example 1 were used except that the ratio of the mass of solid lithium to the mass of carbon-coated silica powder was controlled to 10%.
Comparative example 3
The same procedure as in example 1 was repeated except that the mixing temperature inside the mixer was controlled to 150 ℃.
Comparative example 4
The same procedure as in example 1 was repeated except that the atomizing nozzle having a hole diameter of 2.5mm was used.
Comparative example 5
The same conditions as in example 1 were used except that the temperature in the mixer after atomization was adjusted to 550 ℃.
Example 6: performance test of anode material
1. XRD test
XRD tests were performed on the negative electrode materials obtained in example 1 and comparative example 1, and the results are shown in fig. 1 and 2.
The XRD measurement conditions were as follows: target: c μm (K α line) target; measurement range: 10-90 degrees; the scanning mode is as follows: continuous scanning; scanning rate: 0.04 DEG/s; scanning step length: 0.02 degree; tube voltage: 40.0KV; tube current: 30mA.
As can be seen from fig. 1, the negative electrode material obtained in example 1 contained Si and Li in the X-ray diffraction pattern 2 SiO 3 And Li 2 Si 2 O 5 Three crystal structure peaks and Li corresponding to 24.7 DEG 2 Si 2 O 5 Li having peak intensity corresponding to 18.8 DEG 2 SiO 3 Ratio of corresponding peak intensities
Figure BDA0003213956870000071
Figure BDA0003213956870000081
And 24.7 corresponding to Li 2 Si 2 O 5 Ratio of peak intensity to peak intensity of Si at 28.5 DEG
Figure BDA0003213956870000082
Figure BDA0003213956870000083
Indicating that more water-insoluble Li is present in the anode material 2 Si 2 O 5 Structure, and rich in lithium compound Li 2 SiO 3 The amount of the slurry is less, the gas generation phenomenon of the water system slurry can be effectively inhibited, and the stability of the slurry in the application process of the material is obviously improved.
In comparative example 1, the conditions were the same as in example 1 except that the amount of carbon residue from acetylene cracking on the surface of the silica powder was decreased. The coating layer is thinner than in example 1 due to the reduced amount of carbon coating on the surface, resulting in the pre-lithiation agent being atomized sprayed onto the carbon-coated silica surface, which penetrates the surface carbon layer relatively faster into contact with the internal silica bulk, causing local lithiation, resulting in Li enrichment 2 SiO 3 Increase in the content of (b). Thus Li with higher intensity as shown by XRD pattern in fig. 2 2 SiO 3 And lower strength Li 2 Si 2 O 5 Ratio of the two
Figure BDA0003213956870000084
Less than 2.3. Guide railThe resulting slurry was unstable to standing, and gas evolution was observed after 1 day (as shown in Table 2).
Simultaneously taking the materials obtained in the implementation examples 2-5 and the comparative examples 2-5 to carry out XRD test under the same conditions, and recording corresponding Si and Li in each X-ray diffraction pattern 2 SiO 3 And Li 2 Si 2 O 5 The ratio of the peak intensities was calculated. And silicon grain size was calculated using the scherrer equation based on the Si peak half-peak width at 28.5 °. The results are given in table 1 below.
TABLE 1
Figure BDA0003213956870000085
As is clear from Table 1, examples 1 to 5 all satisfied
Figure BDA0003213956870000086
And is provided with
Figure BDA0003213956870000087
Indicating more water insoluble Li in the negative electrode material 2 Si 2 O 5 Structure, and rich in lithium compound Li 2 SiO 3 The amount of the slurry was small, and as can be seen from table 2, the capacity retention ratio was better, and the stability of the aqueous slurry was stronger.
In contrast, in comparative examples 1 and 2,
Figure BDA0003213956870000091
indicating that there is less non-water soluble Li in the anode material 2 Si 2 O 5 Structure, and rich in lithium compound Li 2 SiO 3 The amount of the carbon black particles was large, and it was found from table 2 that the stability of the aqueous slurry was poor and the cycle capacity retention rate was low.
In the case of the comparative example 3,
Figure BDA0003213956870000092
although the ratio is within the optimum range, it is not limited to
Figure BDA0003213956870000093
The stability in the aqueous slurry was poor and the retention rate of the circulating capacity was low in each example.
In the comparative examples 4 and 5,
Figure BDA0003213956870000094
although the ratio is within the optimum range, it is not limited to
Figure BDA0003213956870000095
Figure BDA0003213956870000096
And in the case of comparative example 4,
Figure BDA0003213956870000097
close to the ratio of 2.3, it can be seen from table 2 that, although the gassing time and capacity retention rate exhibited by the stability of the water-washed slurry were still lower than those of the examples, the performance was better than that of the comparative example 1/2/3/5.
Therefore, only when simultaneously satisfied
Figure BDA0003213956870000098
And
Figure BDA0003213956870000099
under two conditions, the prepared cathode material has the best effect.
2. First charge and discharge test
Taking the negative electrode material obtained in the example 1, and mixing the materials in a mass ratio of 75:15:5: and 5, mixing the negative electrode material, SP (conductive carbon black), CMC (sodium carboxymethylcellulose) and SBR emulsion (styrene butadiene rubber), adding water by using a magnetic stirrer, and continuously stirring and uniformly dispersing to obtain slurry. The slurry was then coated on a 10 μm copper foil by a coater and dried at 90 ℃ under vacuum (-0.1 MPa) for 6 hours. Compacting with roller, controlling compaction density at 1.30g/cm3, making into 12mm diameter wafer with a sheet punching machine, vacuum drying at 90 deg.C (-0.1 MPa) for 5 hr, weighing, and calculating active substance weight. A CR2016 type button cell was assembled in a glove box, and 1mol/L of LiPF6 (lithium hexafluorophosphate) was dissolved in EC (ethylene carbonate) and DEC (diethyl carbonate) at a volume ratio of 1. The battery is stood for 12 hours at room temperature, then a constant current charge-discharge test is carried out on a blue test system, the battery is charged to 0.005V at 0.05C, then the battery is discharged to 1.5V at 0.1C, then charge-discharge circulation is carried out for 50 times at 0.2C, and the ratio of the 50 th discharge capacity to the second discharge capacity is calculated to investigate the circulation stability performance.
The first charge-discharge curve is shown in figure 3, and the first charge specific capacity is 1792.7mAh/g, the first discharge specific capacity is 1540.5mAh/g, and the first efficiency is 85.93%.
In addition, the materials obtained in examples 2 to 5 and comparative examples 1 to 5 were respectively taken, and the first discharge specific capacity, the first efficiency and the cycle retention rate were obtained by testing the first discharge specific capacity under the same conditions as shown in table 2 below.
And (3) taking 30g of slurry left after the first charge and discharge test of each example and comparative example, placing the slurry in a beaker, filling the beaker in an aluminum-plastic film bag, sealing, standing, monitoring the shape change of the aluminum-plastic film bag, and monitoring whether the slurry of each example and comparative example generates gas or not, wherein the monitoring period is 7 days. The results are shown in table 2 below.
TABLE 2
Figure BDA0003213956870000101
As can be seen from Table 2, in examples 1-5, the first discharge specific capacity was higher than 1410mAh/g, the first efficiency was above 80%, the cycle retention rate was above 90%, and no gas was generated when the slurry was left for 7 days. Although the first discharge specific capacity and the first efficiency of comparative examples 1 to 4 are not much different from those of the respective examples, the cycle retention rate was at a low level, and gas was generated from the slurry after the slurry was left for a certain period of time. And comparative example 5 is not good in each property. It can be seen that in examples 1-5, the performance of the obtained negative electrode material is optimal by selecting appropriate preparation conditions and appropriate mixture ratio of the materials.
Example 7:
an apparatus was used in the preparation of examples 1-5.
The equipment comprises a mixing device and an atomizer, the atomizing equipment comprises a melting tank and an atomizing nozzle, one end of the atomizing nozzle is communicated with the mixing device, the other end of the atomizing nozzle is communicated with the melting tank, and the mixing device is positioned below the atomizing nozzle;
the mixing device is a coulter mixer or a V-shaped mixer.
Example 8:
a lithium ion battery comprising the negative electrode material prepared in examples 1-5.
The preparation equipment, raw materials, instruments and materials used in the test process, which are mentioned in the examples of the present invention, can be obtained by the market or the prior art.
The preparation process or the test method and the calculation method which are not mentioned in the embodiment of the invention are all known technologies. And will not be described in detail herein.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A preparation method of a negative electrode material is characterized by comprising the following steps: the method comprises the following steps: uniformly mixing carbon-coated silica powder and an atomized lithium source in an inert atmosphere, wherein the mixing temperature is 190-350 ℃;
the average particle diameter D50 of the carbon-coated silica powder is 2-7 mu m, and the maximum particle diameter D max Less than 25 μm;
the mass ratio of the lithium source to the carbon-coated silica powder is 3.5-8.0%;
the carbon-coated silica powder is prepared by carrying out carbon coating treatment on silicon monoxide powder and an organic carbon source in inert gas at 850-950 ℃ to obtain a silicon oxide surface structure coated with a carbon coating;
the average particle diameter D50 of the silicon monoxide powder is 2-6 mu m, and the maximum particle diameter D max Is less than 20 μm, and is,
the mass fraction of the carbon coating accounts for 2.5-8.0% of the carbon-coated silica powder;
the carbon-coated silica powder is carbon-coated silica powder;
peak intensity I in XRD ray diffraction pattern of negative electrode material Li2Si2O5 / I Li2SiO3 ＞2.3、1.80＜I Li2Si2O5 / I Si ＜2.40。
2. The method for preparing the anode material according to claim 1, wherein the method comprises the following steps: the process of uniformly mixing the carbon-coated silica powder and the atomized lithium source in the inert atmosphere comprises the following steps:
putting the carbon-coated silica powder into a mixing device, stirring, heating to 190-350 ℃ under an inert atmosphere, and doping the carbon-coated silica powder into a lithium source atomized under the inert atmosphere.
3. The method for preparing an anode material according to claim 2, wherein: the process of atomizing the lithium source comprises the following steps: under the inert atmosphere, the solid lithium source is heated and melted into liquid, and the inert gas drives the liquid lithium source to enter the atomizer to be dispersed and atomized into liquid drops.
4. The method for preparing the anode material according to claim 3, wherein:
the atomizer comprises a melting tank and an atomizing nozzle, and two ends of the atomizing nozzle are respectively communicated with the melting tank and the mixing device;
the process of heating and melting the solid lithium source into liquid under the inert atmosphere comprises the following steps: adding a solid-phase lithium source into a melting tank of an atomizer under the protection of inert gas, and melting at 280-400 ℃ under the conditions that the water content in the melting tank is less than 50ppm and the oxygen content is less than 50 ppm;
the process that the inert gas drives the liquid lithium source to enter the atomizer for dispersion and atomization into liquid drops is as follows: the melted lithium source enters the atomizing nozzle under the drive of inert gas as atomization driving to be atomized into a liquid drop shape, and is sprayed into a mixing device to be mixed with carbon-coated silica powder;
the atomization driving pressure is 0.4Mpa to 2.0Mpa;
the aperture of the spray hole of the atomizing spray head is 0.1mm-2.0 mm.
5. The method for preparing an anode material according to claim 1, wherein: after the carbon-coated silica powder and the atomized lithium source are uniformly mixed in an inert atmosphere, the first treatment is also included;
the first treatment is to heat the mixture to 600-800 ℃, cool the mixture for 2h-8h and discharge the mixture;
the temperature rise speed is 0.5-3 ℃/min.
6. The method for preparing an anode material according to claim 1, wherein: the lithium source is solid lithium, and the inert atmosphere is one or a mixture of two of helium, argon, neon and xenon.
7. A negative electrode material, which is prepared by the preparation method according to any one of claims 1 to 6.
8. A device for use in the production method according to any one of claims 1 to 6;
the equipment comprises a mixing device and an atomizer, wherein the atomizer comprises a melting tank and an atomizing nozzle, one end of the atomizing nozzle is communicated with the mixing device, the other end of the atomizing nozzle is communicated with the melting tank, and the mixing device is positioned below the atomizing nozzle;
the mixing device is a colter mixer or a V-shaped mixer.
9. A lithium ion battery, characterized by: comprising the anode material according to claim 7.
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