CN114695847A - Silicon negative electrode material with porous coating layer and preparation method thereof - Google Patents

Silicon negative electrode material with porous coating layer and preparation method thereof Download PDF

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CN114695847A
CN114695847A CN202011602658.1A CN202011602658A CN114695847A CN 114695847 A CN114695847 A CN 114695847A CN 202011602658 A CN202011602658 A CN 202011602658A CN 114695847 A CN114695847 A CN 114695847A
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silicon
ion conductor
fast ion
lithium
powder
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胡盼
贺劲鑫
陈青华
姚林林
房冰
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Lanxi Zhide New Energy Materials 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
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • 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
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

Abstract

The application provides a silicon cathode material with a porous coating layer, which comprises a silicon-based material, a conductive carbon layer and a fast ion conductor layer, and is characterized in that the conductive carbon layer is coated on the surface of the silicon-based material, and the fast ion conductor layer is coated on the surface of the conductive carbon layer; the fast ion conductor layer is of a porous structure. The physical position of the porous fast ion conductor layer is an excellent conductor of lithium ions, an SEI (solid electrolyte interphase) film is stabilized, and the cycle performance of the material is improved; the inner carbon layer is exposed at the positions of the pores, so that the electronic conductivity is increased; meanwhile, expansion space is reserved at the position of the pore, and the expansion of the silicon-based inner core is favorably buffered. The lithium ion battery with high energy density and rapid charge and discharge can be prepared by adopting the cathode material.

Description

Silicon negative electrode material with porous coating layer and preparation method thereof
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a silicon negative electrode material with a porous coating layer and a preparation method thereof.
Background
With the increasingly wide application of lithium batteries in the fields of portable electronic 3C devices, electric vehicles, logistics, ships, aviation and the like, the requirements of people on high energy density and high rate characteristics are more and more clear. The negative electrode material is a key factor determining the characteristics of the lithium battery, and the silicon material, as a negative electrode material having a high specific capacity, has recently become a hot research trend of researchers. At present, silicon cathode materials mainly comprise a silicon simple substance, a silicon carbon material, a silicon oxide material, a silicon alloy, a silicon nanowire and the like, wherein the silicon oxide is widely researched due to the characteristics of relatively small volume effect, low working voltage, good safety and the like. However, the inferior electronic conductivity and ionic conductivity of the silica material greatly affect the exertion of the chemical properties, and therefore, how to improve the electronic conductivity and ionic conductivity of the material and how to further reduce the volume expansion effect are key technical problems for the practical application of the material.
Disclosure of Invention
In view of the above problems, the present application provides a silicon negative electrode material with a porous coating layer, which can effectively improve the electronic conductivity of a silicon monoxide material and improve the ionic conductivity at the same time, so that the application of the material to a fast-charging battery becomes possible.
In one embodiment, the application provides a silicon cathode material with a porous coating layer, which comprises a silicon-based material, a conductive carbon layer and a fast ion conductor layer, wherein the conductive carbon layer is coated on the surface of the silicon-based material, and the fast ion conductor layer is coated on the surface of the conductive carbon layer; the fast ion conductor layer is of a porous structure.
In one embodiment, the present application further provides a preparation method of the silicon anode material, including the following steps:
(1) mixing SiO2Uniformly mixing the powder and the Si powder according to a certain proportion, placing the mixture in a vacuum furnace, keeping the temperature in the furnace at 900-1300 ℃ and the air pressure at 0-5000 Pa, cooling the evaporation product into blocks, crushing and screening to obtain SiOxPowder of；
(2) Placing SiO powder in a Chemical Vapor Deposition (CVD) furnace, keeping the temperature in the furnace at 600-1100 ℃ and the air pressure at 0-5000 Pa, introducing carbon source gas into the furnace, and depositing for 1-5 h to deposit cracked carbon on SiOxSurface, finishing carbon coating to obtain SiOxa/C composite powder;
(3) mixing SiOxUniformly mixing the/C composite powder with a lithium source and/or magnesium powder in a certain proportion, heating the mixture to 500-1000 ℃ in a high-temperature furnace, and introducing argon for protection to obtain lithium-doped and/or magnesium-doped SiOxa/C composite powder.
(4) And (4) mixing the composite powder obtained in the step (3) with the fast ion conductor powder, uniformly dispersing the mixture into pure water, and adding a certain proportion of foaming agent to obtain a mixed solution with a large amount of micro foams. And then spray drying is carried out, and bubbles are broken to form pores in the powder drying process, so as to obtain the silicon cathode material coated by the porous fast ion conductor layer.
The beneficial effect of this application: the silicon cathode material provided by the application has a double-layer coated core-shell structure, wherein the silicon-oxygen is used as an inner core to ensure high specific capacity and low volume change, the conductive carbon layer is used as a first coating layer to improve the electronic conductivity of the material, and the fast ion conductor layer is used as a second coating layer to improve the ionic conductivity of the material. Meanwhile, the fast ion conductor layer is of a porous structure, the conductive carbon layer can be exposed due to pores with certain pore diameters, the problem that the coating of the fast ion conductor layer reduces the electronic conductivity is solved, and the porous structure can further buffer the volume expansion of the silicon material in the charging and discharging processes, so that the material has a longer cycle life and better fast charging performance.
Additional aspects and advantages of embodiments of the present application will be described or shown in detail in the following description or illustrated in the accompanying drawings.
Drawings
FIG. 1 is a schematic diagram illustrating the XPS method for testing the cladding rate of a fast ion conductor layer according to the present invention;
FIG. 2 is an SEM photograph of the silicon negative electrode material prepared in example 1 of the present invention.
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.
In the present application, amounts, ratios, and other numerical values are presented in a range format, with the understanding that such range format is used for convenience and brevity and should be flexibly understood to include not only the numerical values explicitly specified as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified.
In the application, a list of items linked by the term "at least one of" or other similar terms can mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. Item a may comprise a single element or multiple elements and item B may comprise a single element or multiple elements.
In this application, a list of items linked by the term "and/or" or other similar term can mean any combination of the listed items. For example, if items C and D are listed, the phrase "C and/or D" means only C; only D; or C and D. Item C may comprise a single element or multiple elements, and item D may comprise a single element or multiple elements.
In this application, D50 is the particle size corresponding to 50% cumulative volume percent of the material.
The embodiment provides a silicon cathode material with a porous coating layer, which comprises a silicon base material, a conductive carbon layer and a fast ion conductor layer, wherein the conductive carbon layer is coated on the surface of the silicon base material, and the fast ion conductor layer is coated on the surface of the conductive carbon layer; the fast ion conductor layer is of a porous structure. The silicon-based material can ensure the high specific energy characteristic of the battery, the double-layer coating of the conductive carbon layer and the porous fast ion conductor layer can simultaneously improve the electronic conductivity and the ionic conductivity, and the fast ion conductor layer can further buffer the volume expansion.
In some embodiments, the mass ratio of the fast ion conductor layer is 0.1wt% to 10wt%, preferably 0.3 wt% to 5wt%, based on 100% of the total mass of the silicon negative electrode material, if the mass ratio is less than 0.1wt%, the increase of the ionic conductance is not significant, and if the mass ratio is more than 10wt%, the specific capacity of the material is reduced; the thickness of the fast ion conductor layer is 1-20 nm, preferably 3-10 nm, if the thickness is less than 1nm, the increase of the ionic conductance is not obvious, and if the thickness is more than 10nm, the electronic conductivity of the material is seriously influenced.
In some embodiments, the silicon-based material has a chemical formula of SiOx, wherein 0 < x < 2; the particle size of the silicon-based material is D50= 1-20 μm; the silicon-based material also comprises at least one of a lithium compound and a metal magnesium salt, and the doping of Li and Mg metal elements can improve the first coulombic efficiency of the silicon material.
In some embodiments, the fast ion conductor layer has a coating rate of 10 to 90%, preferably 50 to 70%. If the coating rate is more than 90%, the number of pores is too small, the conductivity of the material is poor, the electronic conductivity is not facilitated, and the quick-charging performance of the material is reduced; if the coating rate is less than 10%, the ionic conductivity is affected, too many pores are formed in the fast ionic conductor layer, the structural strength is poor, the expansion of the silicon-based core cannot be effectively relieved, and the cycle life of the material is shortened. The coating rate can be calculated by XPS (X-ray photoelectron spectroscopy) test, and the specific test method is as follows: the surface of the silicon cathode material has three states, namely the solid position of the fast ion conductor layer, the pore position of the exposed carbon layer and the pore position of the exposed silicon-based material core. When the XPS test is adopted, as shown in figure 1, X rays irradiate the surface of the negative electrode material, the pore position of the exposed carbon layer returns a signal of the C element, and the percentage content C of the C element is calculated; and (3) returning signals of Si and O elements to the pore position of the bare silicon-based kernel, and calculating to obtain the percentage content y of the Si element, wherein the Si content in the silicon-based kernel is as follows: o =1: x, and further obtaining the percentage content of the O element at the pore position as x y; the physical position of the fast ion conductor is the difference value between the total surface area of the cathode material and the position of the pore, and the ratio of the physical position to the surface area of the cathode material is the cladding rate A of the fast ion conductor layer, wherein the cladding rate A is calculated by the formula (I):
Figure DEST_PATH_IMAGE001
（Ⅰ）
wherein A represents a coating rate, C represents a C atom percentage content measured by XPS, y represents a Si atom percentage content, and x represents SiOxThe value of x in the formula.
In some embodiments, the silicon-based material contains silicon crystallites which are dispersed and distributed, and the full width at half maximum of a diffraction peak attributed to Si (111) in the range of 2 theta = 28-28.8 degrees is larger than 2.7 degrees and the corresponding size of the silicon crystallite is smaller than 3nm by X-ray diffraction spectrum analysis, at the moment, the silicon crystallites are more similar to amorphous silicon, and the amorphous silicon has isotropy and uniform volume expansion, is not easy to pulverize to generate new surfaces, consumes more electrolyte, and thus shows better cycle performance.
In some embodiments, the conductive carbon of the conductive carbon layer is at least one of hard carbon, soft carbon, carbon black, graphite, carbon fiber; the thickness of the conductive carbon layer is 2-300 nm.
In some embodiments, the fast ion conductor of the fast ion conductor layer is any material having SEI film function, including but not limited to at least one of lithium fluoride, lithium phosphate, lithium metaphosphate, lithium aluminum phosphate, aluminum metaphosphate, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, zirconium oxide, lithium hydroxide, lithium carbonate, aluminum hydroxide, magnesium hydroxide, zinc hydroxide, LiPON, LLZO, LATP, LLTO, PEO and its derivatives, complex lithium salt polymer electrolyte, CMC-Li, PAA-Li, PAN-Li, epoxy resin, phenol resin, urea resin.
The embodiment also provides a preparation method of the silicon anode material, which comprises the following steps:
(1) mixing SiO2Uniformly mixing the powder and the Si powder according to a certain proportion, placing the mixture in a vacuum furnace, keeping the temperature in the furnace at 900-1300 ℃ and the air pressure at 0-5000 Pa, cooling the evaporation product into blocks, crushing and screening to obtain SiOxPowder; the certain proportion is preferably 0.3-4: 1, more preferably 0.6 to 1.5: 1; the crushing is to perform material powder in at least one of ball milling, sand milling, air flow crushing, mechanical crushing and other crushing modesCrushing; the screening is to screen out particles with proper particle size by means of jet mill classification, vibration sieve and the like.
(2) Mixing SiOxPlacing the powder in a Chemical Vapor Deposition (CVD) furnace, keeping the temperature in the furnace at 600-1100 ℃ and the air pressure at 0-5000 Pa, introducing carbon source gas into the furnace, and depositing for 1-5 h to deposit the cracked carbon on SiOxSurface, finishing carbon coating to obtain SiOxa/C composite powder; the carbon source gas is hydrocarbon CyHz(y.ltoreq.4) including, but not limited to, mixtures of one or more of methane, ethane, ethylene, acetylene, propane, propylene, butane.
(3) Mixing SiOxUniformly mixing the/C composite powder with a lithium source and/or magnesium powder in a certain proportion, heating the mixture to 500-1000 ℃ in a high-temperature furnace, and introducing argon for protection to obtain lithium-doped and/or magnesium-doped SiOxa/C composite powder; the lithium source is not particularly limited, and is preferably at least one of metallic lithium, lithium nitride, and lithium hydride; the proportion is preferably 5 to 30 wt%.
(4) Mixing the composite powder obtained in the step (3) with fast ion conductor powder, uniformly dispersing the mixture into pure water, adding a foaming agent in a certain proportion to obtain a mixed solution with a large amount of micro foams, and performing spray drying, wherein bubbles are broken in the powder drying process to form pores, so as to obtain a silicon cathode material coated by a porous fast ion conductor layer; the certain proportion is preferably 0.01-0.1 wt% based on 100% of the total mass of the composite powder; the foaming agent can be at least one selected from calcium carbonate, magnesium carbonate and sodium bicarbonate; the process conditions of spray drying are not particularly limited, and preferably, the air inlet temperature is 180-250 ℃, the air outlet temperature is 100-110 ℃, and the spray pressure is 0.1-1.0 MPa.
Example 1
Mixing SiO2Powder and Si powder are mixed according to the proportion of 1:1, heating the mixture in a vacuum furnace to 1100 ℃, keeping the air pressure at 100Pa, cooling the evaporation product into blocks, crushing and screening to obtain SiO (x = 1) powder with the diameter D50=5 μm.
Heating the SiO powder obtained in the previous step to 950 ℃ in a Chemical Vapor Deposition (CVD) furnace, controlling the vacuum degree in the furnace at 300Pa, and introducing methane with the flow rate of 9L/min and argon with the flow rate of 18L/min for deposition time of 1 h. Methane is cracked at high temperature, pyrolytic carbon is coated on the surface of SiO, and the thickness of the carbon coating is 10 nm.
Mixing SiO/C composite powder with 1.5wt% LiPO3Mixing, adding pure water, uniformly stirring, adding 0.1wt% of calcium carbonate foaming agent, continuously stirring uniformly, spray-drying, and breaking bubbles to form pores in the powder drying process to obtain the porous fast ion conductor layer coated silicon cathode material. Wherein LiPO3The thickness of the coating layer was 5 nm.
Fig. 2 is an SEM image of the silicon cathode material prepared in example 1, and it can be seen that the fast ion conductor layer on the surface of the prepared silicon cathode material has a microporous structure.
1g of the obtained silicon negative electrode material is sampled, washed by absolute ethyl alcohol and dried by air blowing at 105 ℃ to obtain a sample to be detected. Respectively carrying out narrow spectrum scanning on C, Si elements in a sample to be detected by using a Saimer fly Escalab 250 Xi photoelectron spectrometer, fitting a test result to obtain the narrow spectrum scanning peak area of each element, and calculating the atomic number percentage a of each element in the sample according to a formula (II):
Figure 191235DEST_PATH_IMAGE002
（Ⅱ）
wherein a represents the atomic number percentage of each element, n represents the atomic concentration, and S represents the sensitivity factor.
The calculation results are shown in table 1, and the calculated fast ion conductor layer coating rate a is: 100% -27.6% -1.2% -1.2% 1= 70.0%.
Table 1 example 1 atomic number percentage of surface elements of powder sample
Name Atomic %
C 27.6
Si 1.2
The electron conductivity was tested using the following method: the method is characterized in that a four-wire two-terminal method is adopted, the resistance is determined by measuring the voltage and the current at two ends of the resistor to be measured, and the conductivity is calculated by combining the height and the bottom area of the resistor to be measured. Adding a certain amount of powder into a testing mold, slightly shaking and flattening, and then placing a gasket on the mold on a sample; after the sample loading is finished, the die is placed on a working table of an electronic pressure tester, the pressure is increased to 500kg (159MPa) at the speed of 5mm/min, the pressure is kept constant for 60s, and then the pressure is released to 0; when the sample is constant in pressure of 5000 +/-2 kg (about 15-25 s after the pressure is increased to 1 to 5000 kg), the pressure of the sample is recorded, the deformation height of the sample is read, the display value of the resistance tester at the moment is recorded, and the electronic conductivity can be calculated by adopting a formula (III):
Figure DEST_PATH_IMAGE003
（Ⅲ）
where C represents electron conductivity, ρ represents resistivity, S represents a basal area, and R represents resistance.
The silicon negative electrode material prepared in the above example 1 was assembled into a button lithium battery, and its electrochemical performance was tested.
The lithium button cell is assembled in the following way: mixing the prepared silicon negative electrode material powder with a graphite negative electrode (mass ratio of 20: 80) to obtain mixed negative electrode powder, and mixing the mixed negative electrode powder with the graphite negative electrode material powder according to a mass ratio of 95.2: 0.85: 0.15: 1.2: 2.6 mixing the mixed negative electrode powder, SP, CNT, CMC (sodium carboxymethylcellulose) and SBR (styrene butadiene rubber), and continuously stirring for 8h to be pasty by using a magnetic stirrer. The stirred slurry was poured onto a copper foil having a thickness of 9 μm, coated with an experimental coater, and then applied at 8Drying for 6h under the vacuum (-0.1 MPa) condition at the temperature of 5 ℃ to obtain the negative electrode slice. Then, according to the mass ratio of 90: 2: 1: 7, mixing the NCM811 cathode material, SP, CNT and PVDF (polyvinylidene fluoride), adding a proper amount of NMP (N-methyl pyrrolidone) as a solvent, and continuously stirring for 8 hours to be pasty by using a magnetic stirrer. And pouring the stirred slurry onto an aluminum foil with the thickness of 16 mu m, coating the aluminum foil by using an experimental coater, and drying the aluminum foil for 6 hours at the temperature of 85 ℃ under the vacuum (-0.1 MPa) condition to obtain the positive electrode sheet. Rolling the positive and negative electrode plates to 100 μm in sequence on a manual double-roller machine, preparing a wafer with a diameter of 12mm by using a sheet punching machine, drying for 8h at 85 ℃ under a vacuum (-0.1 MPa), weighing, and calculating the weight of the active substance. Assembling a CR2032 button type full cell in a glove box, taking a polypropylene microporous membrane as a diaphragm and 1mol/L LiPF6in EC: DEC =1:1 Vol% with 5.0% FEC as electrolyte.
The lithium ion conductivity was tested using the following method: carrying out charging and discharging test on the prepared button cell by using a blue electricity (LAND) cell test system, standing for 6 hours, discharging to 0.005V at 0.05C, and then discharging to 0.005V at 0.01C; standing for 5min, and charging to 1.5V at constant current of 0.05C; and (5) standing for 5min, repeating the steps twice, and then performing electrochemical impedance spectroscopy test on the power-on by adopting an electrochemical workstation. The frequency range is 0.01 to 105Hz, the voltage amplitude is 0.005V, the last 5 data points are taken as the data points obtained by the test, the linear slope of Z' to the rotating speed w ^ -0.5 under low frequency is obtained, the slope value is a warburg parameter, and the smaller the warburg parameter is under the same test condition, the higher the lithium ion conductivity is.
The cycle performance was evaluated in the following manner: and standing the prepared button full cell at room temperature for 12h, performing constant-current charge-discharge test on a blue-ray test system, and performing charge-discharge at a current of 0.25C with a charge-discharge cutoff voltage of 3.0-4.25V. The capacity retention rate was calculated by multiplying the discharge capacity at the 100 th cycle/the discharge capacity at the 1 st cycle by 100%, and the higher the value, the better the cycle performance was considered.
Rate performance was evaluated in the following manner: and standing the prepared button full cell at room temperature for 12 hours, then carrying out constant-current charge-discharge test on a blue-ray test system, wherein the charge-discharge cutoff voltage is 3.0-4.25V, and firstly carrying out charge-discharge with 0.25C current for 3 times of circulation. Then, the charge and discharge were carried out with 0.5C current, and the cycle was repeated 3 times. And finally, charging and discharging with 1C current, and circulating for 3 times. The capacity retention rate was calculated by multiplying the discharge capacity at the 9 th cycle/the discharge capacity at the 1 st cycle by 100%, and the higher the value, the better the rate performance was considered.
Examples 2 to 6
The other steps and the process parameters are the same as those of the embodiment 1, and the difference is that the thickness of the fast ion conductor coating layer is changed by controlling the addition amount of the fast ion conductor powder; the coating rate of the fast ion conductor coating layer is controlled by the addition amount of the foaming agent. Further, the powder was subjected to the test and the secondary battery evaluation in the same manner as in example 1.
Comparative example 1
The other steps and the process parameters are the same as those of the example 1, and the difference is that no foaming agent is added, and a pore structure is not formed on the fast ion conductor coating layer;
further, the powder was subjected to the test and the secondary battery evaluation in the same manner as in example 1. .
Table 2 shows the test results of each example and comparative example, and the test results of each example and comparative example 1 show that LiPO having a pore structure provided by the present application3The silicon cathode material of the coating layer has high electronic conductivity and ionic conductivity, so that the silicon cathode material has excellent capacity retention rate and rate capability; the test results of the examples show that by controlling the coating rate and the thickness of the fast ion conductor, the silicon anode material with the best cycle and rate performance can be obtained.
TABLE 2 test results of examples and comparative examples
Figure DEST_PATH_IMAGE005
Variations and modifications to the above-described embodiments may occur to those skilled in the art, which fall within the scope and spirit of the above description. Therefore, the above description is not intended to limit the invention, and the invention is not limited to the above disclosed and described embodiments, and modifications and variations of the invention, such as equivalent substitutions of each raw material and addition of auxiliary components, selection of specific modes, etc., made by those skilled in the art within the spirit of the embodiments, should also fall within the scope of the claims of the present invention.

Claims (8)

1. A silicon cathode material with a porous coating layer comprises a silicon-based material, a conductive carbon layer and a fast ion conductor layer, and is characterized in that the conductive carbon layer is coated on the surface of the silicon-based material, and the fast ion conductor layer is coated on the surface of the conductive carbon layer; the fast ion conductor layer is of a porous structure.
2. The silicon negative electrode material of claim 1, wherein the mass of the fast ion conductor layer is 0.1wt% to 10wt% based on 100% of the total mass of the silicon negative electrode material; the thickness of the fast ion conductor layer is 1-20 nm.
3. The silicon negative electrode material as claimed in claim 1, wherein the silicon-based material has a chemical formula of SiOxWherein x is more than 0 and less than 2; the particle size of the silicon-based material is D50= 1-20 μm; the silicon-based material also comprises at least one of a lithium compound and a metal magnesium salt.
4. The silicon negative electrode material of claim 1, wherein the fast ion conductor layer has a coating rate of 10-90%.
5. The silicon negative electrode material of claim 1, wherein the silicon-based material contains silicon crystallites distributed in a dispersed manner, and the half-height width of a diffraction peak attributed to Si (111) is greater than 2.7 ° in the range of 2 θ = 28-28.8 ° as analyzed by X-ray diffraction pattern, and the corresponding size of the silicon crystallites is less than 3 nm.
6. The silicon negative electrode material according to claim 1, wherein the conductive carbon of the conductive carbon layer is at least one of hard carbon, soft carbon, carbon black, graphite, and carbon fiber; the thickness of the conductive carbon layer is 2-300 nm.
7. The silicon negative electrode material of claim 1, wherein the fast ion conductor of the fast ion conductor layer is any material having SEI film function, including but not limited to at least one of lithium fluoride, lithium phosphate, lithium metaphosphate, lithium aluminum phosphate, aluminum metaphosphate, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, zirconium oxide, lithium hydroxide, lithium carbonate, aluminum hydroxide, magnesium hydroxide, zinc hydroxide, LiPON, LLZO, LATP, LLTO, PEO and its derivatives, complex lithium salt polymer electrolyte, CMC-Li, PAA-Li, PAN-Li, epoxy resin, phenol resin, urea resin.
8. A method for preparing the silicon anode material according to any one of claims 1 to 7, comprising the steps of:
(1) mixing SiO2Uniformly mixing the powder and the Si powder according to a certain proportion, placing the mixture in a vacuum furnace, keeping the temperature in the furnace at 900-1300 ℃ and the air pressure at 0-5000 Pa, cooling the evaporation product into blocks, crushing and screening to obtain SiOxPowder;
(2) mixing SiOxPutting the powder into a Chemical Vapor Deposition (CVD) furnace, keeping the temperature in the furnace at 600-1100 ℃ and the air pressure at 0-5000 Pa, introducing carbon source gas into the furnace according to a required proportion, and depositing for 1-5 h to deposit the cracked carbon on SiOxSurface, finishing carbon coating to obtain SiOxa/C composite powder;
(3) mixing SiOxUniformly mixing the/C composite powder with a lithium source and/or magnesium powder in a certain proportion, heating the mixture to 500-1000 ℃ in a high-temperature furnace, and introducing argon for protection to obtain lithium-doped and/or magnesium-doped SiOxa/C composite powder;
(4) and (3) mixing the composite powder obtained in the step (3) with the fast ion conductor powder, uniformly dispersing the mixture into pure water, adding a foaming agent in a certain proportion to obtain a mixed solution with a large amount of micro-foams, and performing spray drying to obtain a silicon cathode material coated by the porous fast ion conductor layer, wherein the air bubbles are broken to form pores in the powder drying process.
CN202011602658.1A 2020-12-30 2020-12-30 Silicon negative electrode material with porous coating layer and preparation method thereof Pending CN114695847A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115911311A (en) * 2022-11-16 2023-04-04 晖阳(贵州)新能源材料有限公司 Quick-charging graphite composite material for lithium ion battery and preparation method thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115911311A (en) * 2022-11-16 2023-04-04 晖阳(贵州)新能源材料有限公司 Quick-charging graphite composite material for lithium ion battery and preparation method thereof

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