CN111554909B - Negative electrode material containing metal-doped silicon-based composite material, preparation method and lithium battery - Google Patents
Negative electrode material containing metal-doped silicon-based composite material, preparation method and lithium battery Download PDFInfo
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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
- H01M4/364—Composites as mixtures
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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
- 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
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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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- 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
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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
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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
- 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
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Abstract
The embodiment of the invention relates to a negative electrode material containing a metal-doped silicon-based composite material, a preparation method and a lithium battery, wherein the negative electrode material has a core-shell structure and sequentially comprises a core, an intermediate layer and a shell from inside to outside; the inner core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal-doped elements and a silicon-based materialxOyWherein x is more than 0 and less than or equal to 10, y is more than or equal to 0 and less than or equal to 10, and M specifically comprises one or more of Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na and B; the form of the metal doping element is a simple substance or an oxide; the intermediate layer is made of the silicon-based material; the shell is a carbon coating layer formed by continuous carbon particles or carbon films; the diameter range of the negative electrode material is 1 um-60 um; in the negative electrode material, the mass ratio of the core: an intermediate layer: outer shell ═ 20%, 95%]：(5％，60％]：(0％，20％]。
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a negative electrode material containing a metal-doped silicon-based composite material, a preparation method and a lithium battery.
Background
The theoretical reversible capacity of silicon serving as a lithium ion battery negative electrode material is up to 4200mAh/g, but the problems of structural collapse of the electrode material, instability of a Solid Electrolyte Interface (SEI) film and the like caused by a huge volume effect in a lithium desorption process of the silicon material cause great reduction of the battery cyclicity. Currently, the modification work for silicon-based materials is continuously carried out. In the literature (H.Li, X.J.Huang, L.Q.Chen, Z.G.Wu, Y Liang, electric chem.and Solid-State Lett., 2,547-549(1999)), Li et al, by using nanoscale silicon particles to prepare the negative electrode material, can reduce the volume effect, improve the cycle performance of the silicon-based negative electrode material, and maintain a higher reversible capacity (1700 mAh/g). Miyachi et al found that the alloy was doped with 25% Fe,Ti or Ni can make SiOXThe first coulombic efficiency is remarkably improved to 84-86%.
However, in the prior art, the problems of volume expansion, poor cycle stability and the like of silicon-based materials still exist in the lithium intercalation and deintercalation process.
Disclosure of Invention
The invention aims to provide a negative electrode material containing a metal-doped silicon-based composite material, a preparation method and a lithium batteryxOyThe middle layer is made of silicon-based materials, and the shell is a carbon coating layer made of continuous carbon particles or carbon films; according to the invention, the generation of an inert phase is inhibited by doping the metal silicon-based material, the first cycle efficiency is improved, the silicon-based material in the middle layer provides a buffer space for volume expansion in the charge-discharge process, and the carbon coating layer on the outermost layer is beneficial to reducing the specific surface area of particles and reducing the generation of an SEI film.
In order to achieve the above object, in a first aspect, the present invention provides a negative electrode material containing a metal-doped silicon-based composite material, where the negative electrode material has a core-shell structure, and sequentially includes a core, an intermediate layer, and a shell from inside to outside;
the inner core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal-doped elements and a silicon-based materialxOyWherein x is more than 0 and less than or equal to 10, y is more than or equal to 0 and less than or equal to 10, and M specifically comprises one or more of Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na and B; the form of the metal doping element is a simple substance or an oxide;
the intermediate layer is made of the silicon-based material;
the shell is a carbon coating layer formed by continuous carbon particles or carbon films;
the diameter range of the negative electrode material is 1 um-60 um;
in the negative electrode material, the mass ratio of the core: an intermediate layer: outer shell [ 4020%, 95% ]: (5%, 4060% ], (0%, 20% ]).
Preferably, the silicon-based material is any one or a combination of silicon, silicon dioxide and silicon monoxide.
Preferably, the carbon source for forming the carbon coating layer includes one or more of toluene, methane, acetylene, glucose, pitch, or a high molecular polymer.
In a second aspect, an embodiment of the present invention provides a preparation method of the negative electrode material containing the metal-doped silicon-based composite material in the first aspect, including:
injecting a silicon-based material and a simple substance or an oxide of a metal doping element into a reactor to form mixed powder, heating the mixed powder to 400-1200 ℃ in a vacuum environment or a protective atmosphere, carrying out heat treatment for 30min-5 h, and grinding the obtained product to form particles with the average particle size of 0.1-50 mu m;
carrying out acid washing or alkali washing treatment on the material surface layer of the obtained particles so as to remove metal doping elements contained in the material surface layer;
and carrying out carbon coating treatment on the product subjected to alkali washing treatment or the product subjected to alkali washing treatment to obtain the negative electrode material containing the metal-doped silicon-based composite material.
Preferably, the alkali washing treatment is to soak the obtained particles with acid liquor and wash the particles with water to neutrality; the acid solution comprises one of hydrochloric acid, nitric acid or phosphoric acid; the alkali liquor comprises one of sodium hydroxide solution and lithium hydroxide solution;
the soaking time of the soaking treatment is 1 hour to 10 hours.
Preferably, the carbon coating treatment specifically adopts one of a gas phase method, a liquid phase method or a solid phase method;
the gas phase process specifically comprises: mixing a protective atmosphere with a carbon coating gas source, and carrying out gas phase coating on the product subjected to acid washing or alkali washing in a Chemical Vapor Deposition (CVD) furnace;
the liquid phase method specifically comprises: uniformly mixing a liquid-phase carbon source with the product or the product after alkali washing treatment, keeping the temperature at 600-1100 ℃ for 1-12 hours, and drying and carbonizing and coating;
the solid phase method specifically comprises: uniformly mixing a solid-phase carbon source and the product subjected to alkali washing treatment, and then preserving heat for 1-12 hours at 600-1100 ℃ for carbonization treatment; or treating the mixed material of the solid-phase carbon source and the product after the alkali washing treatment by adopting a ball mill or a shaping machine to coat the solid-phase carbon source on the surface of the product after the alkali washing treatment, and then preserving the heat at the temperature of 600-1100 ℃ for 1-12 hours to carry out carbonization treatment.
Preferably, the protective atmosphere comprises an inert atmosphere or a nitrogen atmosphere.
Preferably, the silicon-based material is any one or a combination of silicon, silicon dioxide and silicon monoxide.
In a third aspect, an embodiment of the present invention provides a negative electrode plate, including the negative electrode material containing the metal-doped silicon-based composite material according to the first aspect.
In a fourth aspect, an embodiment of the present invention provides a lithium battery, including the negative electrode material containing the metal-doped silicon-based composite material according to the first aspect.
The negative electrode material containing the metal-doped silicon-based composite material provided by the embodiment of the invention has a core-shell structure, and the core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal doped elements with a silicon-based materialxOyThe middle layer is made of silicon-based materials, and the shell is a carbon coating layer made of continuous carbon particles or carbon films; according to the invention, the generation of an inert phase is inhibited by doping the metal silicon-based material, the first cycle efficiency is improved, the silicon-based material in the middle layer provides a buffer space for volume expansion in the charge-discharge process, and the carbon coating layer on the outermost layer is beneficial to reducing the specific surface area of particles and reducing the generation of an SEI film. The metal-doped silicon-based composite material-containing negative electrode material provided by the invention has the characteristics of high first cycle efficiency and high stability, and can be used as a negative electrode material to be applied to a lithium battery.
Drawings
Fig. 1 is a schematic structural diagram of an anode material comprising a metal-doped silicon-based composite material according to an embodiment of the present invention;
FIG. 2 is a flowchart of a method for preparing an anode material comprising a metal-doped silicon-based composite according to an embodiment of the present invention;
fig. 3 is a scanning electron microscope image of the negative electrode material of the metal-doped silicon-based composite material provided in embodiment 1 of the present invention;
fig. 4 is a graph comparing the full cell capacity retention performance of example 1 of the present invention with that of comparative example 1, comparative example 2.
Detailed Description
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
The embodiment of the invention provides a negative electrode material containing a metal-doped silicon-based composite material, which has a core-shell structure, is shown in figure 1, and sequentially comprises an inner core, an intermediate layer and a shell from inside to outside;
the inner core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal-doped elements and a silicon-based materialxOyWherein x is more than 0 and less than or equal to 10, y is more than or equal to 0 and less than or equal to 10, and M specifically comprises one or more of Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na and B; the form of the metal doping element is a simple substance or an oxide;
the middle layer is made of silicon-based materials and is prepared in an acid washing or alkali washing mode in the preparation process. The silicon-based materials of the inner core and the middle layer can be any one or a combination of silicon, silicon dioxide and silicon monoxide.
The shell is a carbon coating layer formed by continuous carbon particles or carbon films; wherein the carbon source for forming the carbon coating layer comprises one or more of toluene, methane, acetylene, glucose, asphalt or high molecular polymer.
The diameter range of the particles of the negative electrode material provided by the invention is 1 um-60 um.
In the anode material, the mass ratio of the core: an intermediate layer: outer shell [ 20%, 95% ]: (5%, 60% ]: (0%, 20% ]).
The anode material containing the metal-doped silicon-based composite material can be prepared by the following method, and the flow chart of the main preparation steps is shown in fig. 2.
wherein, the silicon-based material is any one or combination of more of silicon, silicon dioxide and silicon monoxide; the metal doping elements comprise one or more of Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na and B, and the form of the metal doping elements is a simple substance of metal or an oxide of the metal; the protective atmosphere includes an inert atmosphere or a nitrogen atmosphere.
specifically, or the alkali washing treatment specifically comprises the steps of soaking the obtained particles by using an acid solution, and then washing the particles to be neutral; the acid solution can be one selected from hydrochloric acid, nitric acid or phosphoric acid; the alkali solution can be one selected from sodium hydroxide solution and lithium hydroxide solution. The soaking time of the soaking treatment is 1 hour to 10 hours.
And step 130, performing carbon coating treatment on the product subjected to alkali washing treatment or alkali washing treatment to obtain the negative electrode material containing the metal-doped silicon-based composite material.
Specifically, the carbon coating treatment specifically adopts one of a gas phase method, a liquid phase method or a solid phase method;
the gas phase process specifically comprises: mixing a protective atmosphere with a carbon coating gas source, and carrying out gas phase coating on a product subjected to alkali washing treatment or in a Chemical Vapor Deposition (CVD) furnace;
the liquid phase method specifically comprises: uniformly mixing a liquid-phase carbon source with the product or the product after alkali washing treatment, keeping the temperature at 600-1100 ℃ for 1-12 hours, and drying and carbonizing and coating;
the solid phase method specifically comprises: uniformly mixing a solid-phase carbon source and the product subjected to alkali washing treatment, and then preserving heat for 1-12 hours at 600-1100 ℃ for carbonization treatment; or treating the mixed material of the solid-phase carbon source and the product after the alkali washing treatment by adopting a ball mill or a shaping machine to coat the solid-phase carbon source on the surface of the product after the alkali washing treatment, and then preserving the heat for 1 to 12 hours at the temperature of between 600 and 1100 ℃ to carry out carbonization treatment.
Specifically, the carbon source used for forming the carbon coating layer in the above gas phase method, liquid phase method or solid phase method may be one or more selected from toluene, methane, acetylene, glucose, pitch or high molecular polymer, according to the actual requirements.
The negative electrode material containing the metal-doped silicon-based composite material provided by the embodiment of the invention has a core-shell structure, and the core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal doped elements with a silicon-based materialxOyThe middle layer is made of silicon-based materials, and the shell is a carbon coating layer made of continuous carbon particles or carbon films; according to the invention, the generation of an inert phase is inhibited by doping the metal silicon-based material, the first cycle efficiency is improved, the silicon-based material in the middle layer provides a buffer space for volume expansion in the charge-discharge process, and the carbon coating layer on the outermost layer is beneficial to reducing the specific surface area of particles and reducing the generation of an SEI film. The negative electrode material containing the metal-doped silicon-based composite material provided by the invention has the characteristics of high first cycle efficiency and high stability, and can be used for preparing a negative electrode plate and applied to a lithium battery.
In order to better understand the preparation process and performance characteristics of the negative electrode material containing the metal-doped silicon-based composite material provided by the present invention, the following description is provided with reference to some specific examples.
Example 1
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking the silica powder and the alumina powder according to the proportion of 1:1 mol ratio of 1kg of the mixture was uniformly mixed and injected into the reactor. And carrying out heat treatment on the mixture for 30min at 1200 ℃ under the nitrogen protection atmosphere. Grinding and sieving the obtained product to obtain silicon oxide compound powder containing alumina;
(2) the obtained composite powder was immersed in dilute hydrochloric acid (10%) for 1 hour, washed with distilled water until the filtrate was neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 900 ℃ to completely dry the sample, switching the argon into a mixed gas of argon and methane (the volume ratio is 1:1), continuously heating to 1100 ℃, and heating at 1100 ℃ for 2 hours to obtain the required cathode material.
Fig. 3 is a scanning electron microscope image of the negative electrode material containing the metal-doped silicon-based composite material provided in embodiment 1 of the present invention, and it can be seen from the scanning electron microscope image that although a carbon layer is deposited on the particle surface and covers the intermediate layer, the matte surface formed by removing aluminum oxide by acid cleaning still can exhibit the acid cleaning effect.
The particle size of the material was measured by a malvern laser particle sizer to obtain an average particle size of 8 μm. In the obtained cathode material, the mass fraction of the core is 70%, the mass fraction of the middle layer silicon-based material is 25%, and the balance is a carbon coating layer.
Mixing the prepared negative electrode material with commercial graphite A in proportion to obtain a lithium ion battery negative electrode material with the specific capacity of 450mAh/g, uniformly mixing the obtained lithium ion battery negative electrode material with 2% of carbon black, 2% of cellulose sodium carbonate and 3% of styrene butadiene rubber in a water solvent to obtain battery slurry, coating the battery slurry on a copper foil, drying the battery slurry, cutting the battery slurry into square sheets with the size of 8 x 8mm, drying the square sheets in vacuum at the temperature of 110 ℃ for 12 hours, assembling the lithium sheets into a half battery in a glove box, and evaluating the electrochemical performance of the half battery.
The electrochemical test mode is as follows: the first cycle was 0.1C to 0.005V, 0.05C to 0.005V, 0.02C to 0.005V. The mixture is left for 5s and charged to 1V at 0.1C and cut off, the subsequent cycles are 0.5C to 0.005V, 0.2C to 0.005V, 0.05C to 0.005V, 0.02C to 0.005V, and left for 5s and charged to 1V at 0.5C and cut off.
The discharge in the electrochemical test is a lithium intercalation process corresponding to the charge in the full cell, and the charge in the electrochemical test is a lithium deintercalation process corresponding to the discharge of the full cell.
After the obtained negative electrode material was coated on a copper foil according to the above ratio, a 1Ah pouch cell was assembled with lithium cobaltate as the positive electrode, and the cycle performance at 0.5C was tested. The results of the first week cycle efficiency and 100 week capacity retention are reported in table 1.
Example 2
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silicon powder and magnesium oxide powder according to the proportion of 1: 2 to 1kg of a mixed material, and the mixture was injected into the reactor. And (3) carrying out heat treatment on the mixture for 5 hours at 1100 ℃ under the nitrogen protection atmosphere. Grinding and sieving the product to obtain silicon-based composite powder containing magnesium oxide;
(2) the obtained composite powder was immersed in dilute hydrochloric acid (15%) for 1 hour, washed with distilled water until the filtrate was neutral, and the sample was dried and sieved at 300 f.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 100 ℃ to completely dry the sample, switching the argon into a mixed gas of argon and methane (the volume ratio is 1:1), continuously heating to 1100 ℃, and heating at 1100 ℃ for 4 hours to obtain the required cathode material.
The particle size of the material was measured by a malvern laser particle sizer to give an average particle size of 6 μm. . In the obtained cathode material, the mass fraction of the core is 60%, the mass fraction of the middle layer silicon-based material is 30%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Example 3
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silicon powder and magnesium powder according to the weight ratio of 3: 2 to 1kg of a mixed material, and the mixture was injected into the reactor. And (3) carrying out heat treatment on the mixture for 3 hours at 1100 ℃ under the nitrogen protection atmosphere. Grinding and sieving the product to obtain silicon-based composite powder containing metal magnesium;
(2) after the obtained composite powder was soaked with dilute hydrochloric acid (15%) for 3 hours, it was washed with distilled water until the filtrate was neutral, and the sample was dried and sieved 300.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 100 ℃ to completely dry the sample, switching the argon into a mixed gas of argon and methane (the volume ratio is 2:1), continuously heating to 1000 ℃, and heating at 1000 ℃ for 6 hours to obtain the required cathode material.
The particle size of the material was measured by a malvern laser particle sizer to obtain an average particle size of 12 μm. In the obtained cathode material, the mass fraction of the core is 50%, the mass fraction of the middle layer silicon-based material is 45%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Example 4
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silica fume and zinc powder according to the proportion of 1: 2 to 1kg of a mixed material, and the mixture was injected into the reactor. And carrying out heat treatment on the mixture for 3 hours at 500 ℃ under the argon protection atmosphere. Grinding and sieving the product to obtain metal zinc-containing silicon monoxide composite powder;
(2) after the obtained composite powder is soaked in dilute nitric acid (15%) for 5 hours, the filtrate is washed by distilled water until the filtrate is neutral, and a sample is dried and sieved by a 300-mesh sieve.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 100 ℃ to completely dry the sample, switching the argon into a gas (the volume ratio is 2:1) formed by mixing argon and methane, continuously heating to 600 ℃, and heating at 600 ℃ for 7 hours to obtain the cathode composite material with the multilayer core-shell structure.
The particle size of the material was measured by a malvern laser particle sizer to give an average particle size of 11 μm. In the obtained cathode material, the mass fraction of the core is 55%, the mass fraction of the middle layer silicon-based material is 32%, and the rest is a carbon coating layer.
Example 5
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silica fume and zinc oxide powder according to the proportion of 3: 1 mol ratio of 1kg of the mixture was uniformly mixed and injected into the reactor. And (3) carrying out heat treatment on the mixture for 5 hours at 1100 ℃ under the argon protection atmosphere. Grinding and sieving the product to obtain zinc oxide-containing silicon oxide composite powder;
(2) after the obtained composite powder was soaked with dilute hydrochloric acid (10%) for 2 hours, the filtrate was washed with distilled water until neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 100 ℃ to completely dry the sample, switching argon into a mixed gas of argon and methane (the volume ratio is 2:1), continuously heating to 1000 ℃, and heating at 1000 ℃ for 1 hour to obtain the required cathode material.
The particle size of the material was measured by a malvern laser particle sizer to give a material with an average particle size of 20 μm. In the obtained cathode material, the mass fraction of the core is 90%, the mass fraction of the middle layer silicon-based material is 8%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Example 6
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silicon powder and copper oxide powder according to the proportion of 1: 2 to 1kg of a mixed material, and the mixture was injected into the reactor. And (3) carrying out heat treatment on the mixture for 2 hours at 1100 ℃ under the argon protection atmosphere. Grinding and sieving the product to obtain silicon-based composite powder containing copper oxide;
(2) after the obtained composite powder was soaked with dilute hydrochloric acid (15%) for 4 hours, the filtrate was washed with distilled water until neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And adding 400g of polyvinylpyrrolidone (PVP) into the sample obtained after sieving, adding 5000ml of distilled water, uniformly stirring, drying at 70 ℃ for 12 hours, putting into a tube furnace, and preserving heat at 500 ℃ for 6 hours under nitrogen atmosphere to obtain the required negative electrode material.
The particle size of the material was measured by a malvern laser particle sizer to give a mean particle size of 30 μm. In the obtained cathode material, the mass fraction of the core is 60%, the mass fraction of the middle layer silicon-based material is 35%, and the balance is a carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Example 7
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silicon powder and ferric oxide powder according to the proportion of 4: 1 mol ratio of 1kg of the mixture was uniformly mixed and injected into the reactor. And (3) carrying out heat treatment on the mixture for 5 hours at 1100 ℃ under the nitrogen protection atmosphere. Grinding and sieving the product to obtain silicon-based compound powder containing ferric oxide;
(2) after the obtained composite powder was immersed in dilute hydrochloric acid (10%) for 1 hour, it was washed with distilled water until the filtrate was neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And adding 500g of phenolic resin into the sample obtained after sieving, adding 500ml of ethanol, uniformly stirring, drying at 50 ℃ for 20 hours, putting into a tubular furnace, and keeping the temperature at 900 ℃ for 3 hours under nitrogen atmosphere to obtain the required negative electrode material.
The particle size of the material was measured by a malvern laser particle sizer to give an average particle size of 42 μm. In the obtained cathode material, the mass fraction of the core is 70%, the mass fraction of the middle layer silicon-based material is 10%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Example 8
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silica fume and ferric oxide powder according to the proportion of 1: 2 to 1kg of a mixed material, and the mixture was injected into the reactor. And (3) carrying out heat treatment on the mixture for 5 hours at 600 ℃ under the argon protection atmosphere. Grinding and sieving the product to obtain the metal magnesium-containing silicon monoxide composite powder;
(2) after the obtained composite powder was soaked with dilute hydrochloric acid (10%) for 4 hours, the filtrate was washed with distilled water until neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And adding 400g of phenolic resin into the sieved sample, uniformly mixing, putting the sample into a ball mill, carrying out ball milling for 5 hours at the speed of 300r/min, and heating the ball-milled product at 1000 ℃ for 6 hours to obtain the required negative electrode material.
The particle size of the material was measured by a malvern laser particle sizer to give a material with an average particle size of 20 μm. In the obtained cathode material, the core accounts for 50 mass percent, the middle layer silicon-based material accounts for 40 mass percent, and the balance is the carbon coating layer.
Example 9
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silicon dioxide powder and alumina powder according to the proportion of 1: a mixture of 1kg was uniformly mixed at a molar ratio of 6 and injected into the reactor. And (3) carrying out heat treatment on the mixture for 3 hours at 1100 ℃ under the argon protective atmosphere. Grinding and sieving the product to obtain silicon oxide compound powder containing alumina, wherein part of the product is aluminum silicate;
(2) after the obtained composite powder was soaked in a sodium hydroxide solution (10%) for 10 hours, the filtrate was washed with distilled water until it was neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 100 ℃ to completely dry the sample, switching the argon into a gas (the volume ratio is 2:1) formed by mixing argon and acetylene, continuously heating to 1000 ℃, and heating at 1000 ℃ for 1 hour to obtain the cathode composite material with the multilayer core-shell structure.
The particle size of the material was measured by a malvern laser particle sizer to obtain an average particle size of 33 μm. In the obtained cathode material, the mass fraction of the core is 40%, the mass fraction of the middle layer silicon-based material is 55%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Example 10
The embodiment provides a method for preparing a negative electrode material containing a metal-doped silicon-based composite material, which comprises the following steps:
(1) taking silicon dioxide powder and aluminum powder according to the proportion of 1: 2 was uniformly mixed to 1kg of the mixture to be charged into the reactor. And (3) carrying out heat treatment on the mixture for 1 hour at 1100 ℃ under the nitrogen protection atmosphere. Grinding and sieving the product to obtain silicon-based compound powder containing metal aluminum to form partial aluminum silicate;
(2) after the obtained composite powder was soaked in a sodium hydroxide solution (10%) for 5 hours, the filtrate was washed with distilled water until it was neutral, and the sample was dried and sieved with a 300-mesh sieve.
(3) And (3) putting the sieved sample into a tubular furnace filled with argon, heating to 100 ℃ to completely dry the sample, switching the argon into a mixed gas of argon and methane (the volume ratio is 2:1), continuously heating to 1100 ℃, and heating at 1100 ℃ for 6 hours to obtain the required cathode material.
The particle size of the material was measured by a malvern laser particle sizer to obtain an average particle size of 12 μm. In the obtained cathode material, the mass fraction of the core is 50%, the mass fraction of the middle layer silicon-based material is 45%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Comparative example 1
This comparative example is intended to illustrate the performance levels of the anode materials prepared in the prior art. The method comprises the following steps:
(1) taking the silica powder and the alumina powder according to the proportion of 1:1 is uniformly mixed into 1kg of mixture material, and the mixture material is injected into a reactor. And carrying out heat treatment on the mixture for 30min at 1200 ℃ under the nitrogen protection atmosphere. Grinding and sieving the product to obtain silicon oxide compound powder containing alumina;
(2) the obtained silicon oxide compound powder containing the alumina is sieved, a sample is put into a tube furnace filled with argon gas, the temperature is raised to 900 ℃, then the argon gas is switched to be a mixed gas of the argon gas and acetylene (the volume ratio is 1:1), the temperature is continuously raised to 1100 ℃, and the silicon oxide particles with the carbon coating layer are prepared by heating at 1100 ℃ for 2 hours.
The particle size of the material was measured by a malvern laser particle sizer to obtain an average particle size of 12 μm. In the obtained material, the mass fraction of the metal-doped silicon-based composite material core is 80%, and the balance is a carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Comparative example 2
This comparative example is intended to illustrate the performance levels of the materials prepared by the prior art. The method comprises the following steps:
(1) taking 10kg of silicon oxide powder, and carrying out heat treatment for 30min at the temperature of 1200 ℃ under the condition of protective nitrogen atmosphere. Grinding and sieving the product to obtain silica particles with the average particle size (D50) of 20 mu m;
(2) and putting the sieved sample into a tubular furnace filled with argon, heating to 900 ℃, switching the argon into a mixed gas of argon and acetylene (the volume ratio is 1:1), continuously heating to 1100 ℃, and heating at 1100 ℃ for 2 hours to obtain the silicon monoxide granules with the carbon coating.
The particle size of the material was measured by a malvern laser particle sizer to obtain an average particle size of 12 μm. In the obtained negative electrode material, the mass fraction of the silicon monoxide inner core is 80%, and the balance is the carbon coating layer.
The battery assembly and test were carried out in the same manner as in example 1 above, and the test results of the first-week cycle efficiency and 100-week capacity retention rate are shown in table 1.
Comparative data of electrochemical performance tests of the anode materials prepared in examples 1 to 10 and comparative examples 1 and 2 are shown in table 1 below. Fig. 4 is a graph comparing the full cell capacity retention performance of example 1 of the present invention with that of comparative example 1, comparative example 2.
| Examples | |
100 week capacity maintenance |
| 1 | 84.2％ | 85％ |
| 2 | 83.7％ | 83％ |
| 3 | 84.1％ | 84％ |
| 4 | 82.9％ | 82％ |
| 5 | 83.3％ | 83％ |
| 6 | 82.1％ | 84％ |
| 7 | 83.4％ | 80％ |
| 8 | 84.5％ | 81％ |
| 9 | 83.7％ | 81％ |
| 10 | 84.3％ | 82％ |
| Comparative example 1 | 84.5％ | 65％ |
| Comparative example 2 | 79.2％ | 55％ |
TABLE 1
According to the comparison result, the core-shell structure cathode material prepared by the invention is shown in the comparison between the comparative example 2 and the example 1, the first cycle efficiency of the sample prepared by the example 1 is higher than that of the comparative example 2, and the volume expansion problem exists in the silicon-based material in the charging and discharging process although the silicon-based material is SiO (silicon dioxide)XSuch a material having an amorphous structureMaterial, Li that may form2O and Li4SiO4The matrix can effectively buffer the volume expansion and maintain the structural stability, but inert phase Li is generated when lithium is inserted for the first time2O and Li4SiO4The first irreversible capacity is also increased, reducing the first cycle efficiency. Illustrating that the incorporation of metal oxides can reduce irreversible capacity.
As can be seen by comparing comparative example 1 with example 1, the cycle retention of the sample prepared in example 1 is higher than that of comparative example 1 because, in the course of the invention, the applicants found that excessive doping of the metal or its oxide causes rapid disproportionation of the silicon-based material such as SiOx into Si and SiO2In this process, the volume of the silicon crystal grains increases, the volume effect is intensified in the charge and discharge processes, and the cycle life is reduced. Therefore, in the preparation process, the metal or the oxide of the outer layer of the inner core is removed by adopting the corresponding solvent to form the middle layer, thereby not only reducing the influence of disproportionation on the cycle life, but also providing sufficient space for volume expansion and further improving the cycle stability of the material. Doping with metals or their oxides to suppress the inert phase Li2O and Li4SiO4And (4) generating. Thus the cycling stability of the example 1 sample with an intermediate layer of silicon-based material without metal doping is better compared to example 1.
The negative electrode material containing the metal-doped silicon-based composite material prepared by the method can obtain better first charge-discharge efficiency and higher capacity retention rate.
The negative electrode material containing the metal-doped silicon-based composite material provided by the embodiment of the invention has a core-shell structure, and the core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal doped elements with a silicon-based materialxOyThe middle layer is made of silicon-based materials, and the shell is a carbon coating layer made of continuous carbon particles or carbon films; according to the invention, the generation of an inert phase is inhibited by doping the metal silicon-based material, the first cycle efficiency is improved, the silicon-based material in the middle layer provides a buffer space for the volume expansion in the charge-discharge process, and the carbon coating layer in the outermost layer is beneficial to reducing the specific surface area of particles and reducing the specific surface area of particlesThe SEI film generation is performed. The metal-doped silicon-based composite material-containing negative electrode material provided by the invention has the characteristics of high first cycle efficiency and high stability, and can be used as a negative electrode material to be applied to a lithium battery.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments 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 (10)
1. The negative electrode material containing the metal-doped silicon-based composite material is characterized by having a core-shell structure and sequentially comprising a core, an intermediate layer and a shell from inside to outside;
the inner core specifically comprises a metal-doped silicon-based composite material SiM formed by compounding one or more metal-doped elements and a silicon-based materialxOyWherein x is more than 0 and less than or equal to 10, y is more than or equal to 0 and less than or equal to 10, and M specifically comprises one or more of Mg, Ca, Ba, Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na and B; the form of the metal doping element is a simple substance or an oxide;
the intermediate layer is made of the silicon-based material;
the shell is a carbon coating layer formed by continuous carbon particles or carbon films;
the diameter range of the negative electrode material is 1 um-60 um;
in the negative electrode material, the mass ratio of the core: an intermediate layer: outer shell [ 20%, 95% ]: (5%, 60% ]: (0%, 20% ]).
2. The negative electrode material of claim 1, wherein the silicon-based material is any one or a combination of silicon, silicon dioxide and silicon monoxide.
3. The anode material of claim 1, wherein a carbon source for forming the carbon coating layer comprises one or more of toluene, methane, acetylene, glucose, pitch, or a high molecular polymer.
4. A method for preparing the negative electrode material containing the metal-doped silicon-based composite material as defined in any one of claims 1 to 3, wherein the method comprises:
injecting a silicon-based material and a simple substance or an oxide of a metal doping element into a reactor to form mixed powder, heating the mixed powder to 400-1200 ℃ in a vacuum environment or a protective atmosphere, carrying out heat treatment for 30min-5 h, and grinding the obtained product to form particles with the average particle size of 0.1-50 mu m;
carrying out acid washing or alkali washing treatment on the material surface layer of the obtained particles so as to remove metal doping elements contained in the material surface layer;
and carrying out carbon coating treatment on the product after the acid washing or alkali washing treatment to obtain the negative electrode material containing the metal-doped silicon-based composite material.
5. The preparation method according to claim 4, wherein the alkali washing treatment is specifically a step of soaking the obtained particles with an acid solution or an alkali solution, and then washing the particles with water to neutrality; the acid solution comprises one of hydrochloric acid, nitric acid or phosphoric acid; the alkali liquor comprises one of sodium hydroxide solution and lithium hydroxide solution;
the soaking time of the soaking treatment is 1 hour to 10 hours.
6. The preparation method according to claim 5, wherein the carbon coating treatment is specifically one of a gas phase method, a liquid phase method or a solid phase method;
the gas phase process specifically comprises: mixing a protective atmosphere with a carbon coating gas source, and carrying out gas phase coating on the product subjected to alkali washing treatment in a Chemical Vapor Deposition (CVD) furnace;
the liquid phase method specifically comprises: uniformly mixing a liquid-phase carbon source with the product subjected to acid washing or alkali washing, keeping the temperature at 600-1100 ℃ for 1-12 hours, and drying and carbonizing and coating;
the solid phase method specifically comprises: uniformly mixing a solid-phase carbon source and the product subjected to alkali washing treatment, and then preserving heat for 1-12 hours at 600-1100 ℃ for carbonization treatment; or treating the mixed material of the solid-phase carbon source and the product after the alkali washing treatment by adopting a ball mill or a shaping machine to coat the solid-phase carbon source on the surface of the product after the alkali washing treatment, and then preserving the heat at the temperature of 600-1100 ℃ for 1-12 hours to carry out carbonization treatment.
7. The method of claim 5, wherein the protective atmosphere comprises an inert atmosphere or a nitrogen atmosphere.
8. The preparation method according to claim 5, wherein the silicon-based material is any one or a combination of silicon, silicon dioxide and silicon monoxide.
9. A negative electrode plate, characterized in that the negative electrode plate comprises the negative electrode material containing the metal-doped silicon-based composite material according to any one of claims 1 to 3.
10. A lithium battery comprising a negative electrode material comprising the metal-doped silicon-based composite material according to any one of claims 1 to 3.
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| CN114497470B (en) * | 2020-11-13 | 2024-03-29 | 湖南中科星城石墨有限公司 | Composite material and preparation method and application thereof |
| CN112467122B (en) * | 2020-12-03 | 2023-01-31 | 松山湖材料实验室 | Lithium orthosilicate composite material and preparation method and application thereof |
| CN113690417B (en) * | 2021-08-18 | 2023-05-26 | 蜂巢能源科技有限公司 | Negative electrode composite material and preparation method and application thereof |
| CN114388771A (en) * | 2022-03-07 | 2022-04-22 | 湖北亿纬动力有限公司 | Silicon-based composite negative electrode material, negative electrode pole piece, preparation method of negative electrode pole piece and lithium ion battery |
| CN114665083B (en) * | 2022-03-21 | 2024-07-02 | 深圳市贝特瑞新能源技术研究院有限公司 | Negative electrode material, preparation method thereof and lithium ion battery |
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