CN111710848A - Silica composite negative electrode material, preparation method thereof and lithium ion battery - Google Patents
Silica composite negative electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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Abstract
The invention provides a silicon-oxygen composite negative electrode material, a preparation method thereof and a lithium ion battery. The silicon-oxygen composite negative electrode material comprises nano silicon, silicon oxide and lithium silicate, wherein the lithium silicate contains doping elements. The method comprises the following steps: mixing SiOy with a doping element source to obtain a doped silicon source; and compounding and roasting the doped silicon source and the lithium source to obtain the silicon-oxygen composite negative electrode material. The silicon-oxygen composite negative electrode material provided by the invention can improve the electronic conductivity of lithium silicate by uniformly distributing the doping elements in the lithium silicate, and reduce the capacity loss caused by the inactivation of internal silicon due to poor conductivity of the lithium silicate generated in situ in the material; by controlling the content of the doping element, the conductivity of the lithium silicate can be improved, the silicon coated with the lithium silicate on the surface is activated to exert the capacity, and the capacity reduction caused by introducing excessive doping elements can be avoided.
Description
Technical Field
The invention belongs to the technical field of energy storage materials, relates to a negative electrode material and a preparation method thereof, and a lithium ion battery, and particularly relates to a silica composite negative electrode material and a preparation method thereof, and a lithium ion battery.
Background
Lithium ion batteries have been widely used in portable electronic products and electric vehicles because of their advantages of high operating voltage, long cycle life, no memory effect, low self-discharge, and environmental friendliness. At present, a commercial lithium ion battery mainly adopts a graphite negative electrode material, but the theoretical specific capacity of the lithium ion battery is only 372mAh/g, and the requirement of the future lithium ion battery on high energy density cannot be met. Although the theoretical capacity of the existing Si is up to 4200mAh/g, the expansion of the existing Si is up to 300%, so that the cycle performance is influenced, and the market popularization and the application are restricted. The corresponding silicon-oxygen material has better cycle performance but low first-time efficiency. When the lithium ion battery is charged for the first time, 20-50% of lithium needs to be consumed for SEI film formation, so that the first coulombic efficiency is greatly reduced. Based on this, the most studied method for improving the first effect of the silica material is doping, wherein lithium doping has a relatively obvious effect on improving the first effect of the silica material.
However, the first effect is improved after lithium doping, and the capacity of the silicon oxide material is reduced. Lithium doping consumes the irreversible phase in silicon oxygen and reduces a part of reversible capacity, and the reduced part of reversible capacity is mainly caused by the reduction of the content of effective silicon (silicon capable of exerting capacity) brought by lithium doping reaction. When silicon is tightly wrapped with non-conductive lithium silicate, electrical contact with the outside is lost due to poor conductivity of lithium silicate, and thus the capacity of the silicon cannot be exerted.
The lithium doping can improve the first effect of the silicon-oxygen material and bring a part of capacity loss. Therefore, the method has great significance for later use and commercialization of the silicon-oxygen material while improving the first effect and reducing the loss of the capacity. Especially in the present circumstances, the rear end cell requires a higher energy density to meet the use and development demands. Therefore, it is important to increase the gram volume of the front end material itself.
A method for improving the performance of a silicon negative electrode material of a lithium ion battery comprises the following steps: preparing a negative electrode of the (I) silicon oxide composite material: 1) weighing a certain amount of SiO powder, pouring the SiO powder into deionized water with the mass being 10 times that of SiO, and then adding a certain amount of graphite and glucose; 2) putting the mixed solution into a high-energy ball mill for ball milling; 3) putting the ball-milled precursor material into a tube furnace; 4) taking out the prepared SiO/C composite material, and mixing the SiO/C composite material with acetylene black serving as a conductive agent and PVDF serving as a binder according to a certain proportion; (II) pre-lithiation treatment on the electrode. The method for pre-lithiation treatment comprises the following steps: 1) dissolving a certain amount of nano metal lithium powder in tetrahydrofuran in a vacuum environment, then uniformly spreading the nano metal lithium powder on an electrode film, and pressing for 1-3min by using the pressure of 2-4 MPa; 2) immersing the electrode film in electrolyte, soaking for 1.5-2.5h, cleaning by using DMC solution, and drying to obtain the final electrode material. Although the method can improve the first effect, the capacity loss is serious.
Disclosure of Invention
In view of the above problems in the prior art, the present invention aims to provide a silica composite anode material, a preparation method thereof, and a lithium ion battery. The silicon-oxygen composite negative electrode material provided by the invention has the advantages of high first-time efficiency and long cycle life.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a silicon-oxygen composite anode material, which comprises nano silicon, silicon oxide and lithium silicate, wherein the lithium silicate contains a doping element.
According to the silicon-oxygen composite negative electrode material provided by the invention, the doping element is added into the lithium silicate, so that the electronic conductivity of the lithium silicate can be improved, and the capacity loss caused by the inactivation of internal silicon due to poor conductivity of the lithium silicate generated in situ in the material can be reduced.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
As a preferable technical scheme of the invention, the doping element is a non-metal element.
Preferably, the doping element comprises any one of boron, nitrogen or sulfur or a combination of at least two thereof.
In the invention, the doping elements of the types are adopted, so that the electronic conductivity of the lithium silicate can be better improved, and the capacity loss caused by the inactivation of internal silicon due to poor conductivity of the lithium silicate generated in situ in the material can be reduced.
Preferably, the mass fraction of the doping element is 5% -10%, such as 5%, 6%, 7%, 8%, 9% or 10% and the like, based on 100% of the total mass of the silicon-oxygen composite anode material.
In the invention, the mass fraction of the doping element is controlled within the range of 5-10 wt%, which not only can improve the conductivity of the lithium silicate and activate the silicon coated with the lithium silicate on the surface to exert the capacity, but also can avoid the capacity reduction caused by introducing too much doping element. This helps to increase the reversible capacity of the pre-lithiated material.
In the invention, if the amount of the doping element is too much, the gram capacity of the material discharge is reduced; if the amount of the doping element is too small, the conductivity of lithium silicate cannot be improved, silicon wrapped by lithium silicate cannot be activated, and finally the discharge capacity of the material is reduced.
In a preferred embodiment of the present invention, the nano silicon is dispersed in a silicon oxide, and the lithium silicate is located on a surface of the silicon oxide. Wherein the silicon oxide is a powder material, and the lithium silicate is coated on the surface of the silicon oxide.
Preferably, the silicon oxide has the formula SiOx, where 0 < x < 1.2, e.g. x is 0.2, 0.5, 0.8, 1 or 1.1, etc.
Preferably, the molar ratio of the nano silicon to the silicon oxide is 1:0.05-1:0.9, such as 1:0.05, 1:0.1, 1:0.3, 1:0.6, or 1:0.9, etc.
Preferably, the molar ratio of lithium silicate to silicon oxide is 1:0.08 to 1:2.2, such as 1:0.08, 1:0.1, 1:0.5, 1:1, 1:1.5, 1:2, or 1:2.2, and the like.
In a second aspect, the present invention provides a method for preparing the silicon-oxygen composite anode material according to the first aspect, wherein the method comprises the following steps:
mixing SiOy with a doping element source to obtain a doped silicon source; and
and compounding and roasting the doped silicon source and the lithium source to obtain the silica composite negative electrode material.
The preparation method provided by the invention has the advantages of simple preparation process, low requirement on equipment and easiness in mass production.
In the preparation method provided by the invention, the silicon source is doped, the doped silicon source is modified, and the doped silicon source reacts with the lithium source, so that the product structure containing nano-silicon, silicon oxide and lithium silicate in the first aspect is obtained.
In a preferred embodiment of the present invention, in the silicon source SiOy, 0 < y < 2, for example, y is 0.1, 0.5, 1, 1.5, or 1.9.
Preferably, in the silicon source SiOy, y is 1.
Preferably, the doping element source comprises any one of or a combination of at least two of elemental boron, boron oxide, boric acid, glutamic acid, ammonium sulfate or elemental sulfur.
The amount of the doping element source added may be calculated according to the first aspect with respect to the preference for the doping element content.
Preferably, the method of mixing in the step of mixing SiOy with the source of the doping element is ball milling.
In a preferred embodiment of the present invention, the lithium source is a lithium compound containing no oxygen.
Preferably, the lithium source comprises any one of lithium hydride, alkyl lithium, metallic lithium or lithium amide, or a combination of at least two thereof.
Preferably, the mass ratio of the doped silicon source to the lithium source is 1:0.02-1:0.2, such as 1:0.02, 1:0.05, 1:0.08, 1:0.1 or 1:0.2, etc. In the invention, if the doped silicon source is too much, the pre-lithium degree is low, and the first effect of the material is not obviously improved; if the lithium source is too much, the silicon crystal grains in the material are too large, and the cycling stability of the material is reduced. The excessive lithium source reacts violently with the silicon source and gives off a large amount of heat, so that the size of silicon crystal grains is increased sharply.
Preferably, the method of compounding in the step of compounding and firing the doped silicon source with the lithium source includes at least one of mixing, kneading, fusing, and stirring.
Preferably, the firing is carried out under a protective atmosphere.
Preferably, the protective atmosphere is a non-oxidizing atmosphere.
Preferably, the protective atmosphere includes any one of a hydrogen atmosphere, a nitrogen atmosphere, a helium atmosphere, a neon atmosphere, an argon atmosphere, a krypton atmosphere, or a xenon atmosphere, or a combination of at least two thereof.
Preferably, the temperature of the calcination is 350 ℃ to 800 ℃, such as 350 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, or 800 ℃ and the like.
Preferably, the calcination time is 2h to 8h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, or the like.
As a preferred technical solution of the present invention, the method for preparing the silicon source SiOy comprises:
heating raw materials capable of generating silicon oxide gas under the condition of vacuum pumping or protective atmosphere, cooling and shaping after the silicon oxide gas is generated to obtain the silicon source SiOy.
In a preferred embodiment of the present invention, the silicon oxide gas generating material is Si or SiO2A mixture of (a).
Preferably, the method for preparing SiOy further comprises shaping the obtained product after the cooling.
Preferably, the shaping comprises any one or a combination of at least two of crushing, ball milling or classifying.
Preferably, the heating temperature is 900 ℃ to 1500 ℃, such as 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, 1400 ℃ or 1500 ℃, etc.
Preferably, the protective atmosphere is a non-oxidizing atmosphere.
Preferably, the gas of the protective atmosphere includes any one of a hydrogen atmosphere, a nitrogen atmosphere, a helium atmosphere, a neon atmosphere, an argon atmosphere, a krypton atmosphere, or a xenon atmosphere, or a combination of at least two thereof.
As a further preferable technical scheme of the preparation method, the method comprises the following steps:
for Si and SiO under vacuum condition or protective atmosphere2Heating the mixture at 900-1500 ℃ to generate silicon oxide gas, and then cooling and shaping to obtain SiOy;
mixing the SiOy with a doping element source and carrying out ball milling to obtain a doped silicon source, wherein the doping element source comprises at least one of a boron simple substance, boron oxide, boric acid, glutamic acid, ammonium sulfate and a sulfur simple substance;
compounding the doped silicon source with a lithium source, and roasting at 350-800 ℃ for 2-8 h under a protective atmosphere to obtain the silicon-oxygen composite negative electrode material, wherein the lithium source is a lithium compound without oxygen, and the compounding method comprises at least one of mixing, kneading, fusing and stirring.
In a third aspect, the invention provides a lithium ion battery, which comprises the silicon-oxygen composite negative electrode material of the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) the silicon-oxygen composite negative electrode material provided by the invention can improve the electronic conductivity of lithium silicate by uniformly distributing the doping elements in the lithium silicate, and reduce the capacity loss caused by the inactivation of internal silicon due to poor conductivity of the lithium silicate generated in situ in the material; by controlling the content of the doping element, the conductivity of the lithium silicate can be improved, the silicon coated with the lithium silicate on the surface is activated to exert the capacity, and the capacity reduction caused by introducing excessive doping elements can be avoided. The silica composite negative electrode material provided by the invention can realize the improvement of the reversible capacity of the material after lithium pre-preparation. The electricity-retaining reversible capacity of the silicon-oxygen composite negative electrode material provided by the invention is more than 1500mAh/g, and the first effect is more than 85%.
(2) The preparation method provided by the invention has the advantages of simple preparation process, low requirement on equipment and easiness in mass production.
Drawings
Fig. 1 is a first charge and discharge curve of the silicon-oxygen composite anode material prepared in example 1.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The following are typical but non-limiting examples of the invention:
example 1
In this example, a silicon-oxygen composite anode material was prepared as follows:
(1) taking 1kg of Si powder and 2kg of SiO2Putting the powder into a VC mixer to be mixed for 30min to obtain SiO2And Si; putting the mixture into a vacuum furnace; heating to 1300 ℃ under the negative pressure condition that the vacuum degree is 5Pa, preserving the heat for 18h, generating SiO steam in the furnace, and generating a SiOy block body after rapid condensation (the condensation temperature is 950 ℃); carrying out crushing, ball milling and grading processes on the SiOy block to control the median particle size to be about 6 mu m, so as to obtain an SiOy powder material, wherein y is 1.0;
(2) taking SiOy 1kg, putting the SiOy into a ball milling tank, adding 470g of ammonium sulfate, and carrying out ball milling for 20min to obtain silicon oxide doped (silicon monoxide doped);
(3) taking 1kg of doped silicon oxide and 150g of lithium hydride, placing the doped silicon oxide and the lithium hydride in a high-speed dispersion machine, stirring for 40min, taking out, placing the doped silicon oxide and the lithium hydride in an atmosphere protection furnace, performing heat treatment in a nitrogen atmosphere at the heat treatment temperature of 750 ℃ for 2h, naturally cooling to room temperature, taking out the materials, and obtaining the silicon-oxygen composite negative electrode material after sieving and demagnetizing.
The silicon-oxygen composite anode material prepared in this example includes silicon oxide (SiOx, x ═ 0.5), nano silicon dispersed in the silicon oxide, and lithium silicate on the surface of the silicon oxide, wherein the lithium silicate contains doping elements (nitrogen element and sulfur element). The mass fraction of the doping element is 8%, the molar ratio of the nano silicon to the silicon oxide is 1:0.4, and the molar ratio of the lithium silicate to the silicon oxide is 1:0.5, wherein the total mass of the silicon-oxygen composite negative electrode material is 100%.
The performance test results of the silicon-oxygen composite anode material prepared in the embodiment are shown in table 1.
Example 2
In this example, a silicon-oxygen composite anode material was prepared as follows:
(1) taking 1kg of Si powder and 2kg of SiO2Putting the powder into a VC mixer to be mixed for 30min to obtain SiO2And Si; putting the mixture into an atmosphere protection furnace; in a nitrogen atmosphereHeating to 1400 ℃ and preserving heat for 16h, generating silicon oxide steam in the furnace, and generating SiOy block through rapid condensation (the condensation temperature is 1300 ℃); the SiOy block is subjected to processes such as crushing, ball milling, grading and the like to control the median particle size to be about 6 mu m, so that an SiOy powder material is obtained, wherein y is 1.0;
(2) putting SiOy 1kg into a ball milling tank, adding 60g of boron simple substance, and ball milling for 20min to obtain silicon oxide doped;
(3) taking 1kg of doped silicon oxide and 80g of metal lithium, placing the doped silicon oxide and the metal lithium in a high-speed dispersion machine, stirring for 40min, taking out, placing the doped silicon oxide and the metal lithium in an atmosphere protection furnace, performing heat treatment in a nitrogen atmosphere at the heat treatment temperature of 600 ℃ for 2.5h, naturally cooling to room temperature, taking out the materials, and obtaining the silicon-oxygen composite negative electrode material after sieving and demagnetizing.
The silicon-oxygen composite anode material prepared in this example includes silicon oxide (SiOx, x ═ 0.8), nano silicon dispersed in the silicon oxide, and lithium silicate located on the surface of the silicon oxide, and the lithium silicate contains a doping element (boron element). The mass fraction of the doping elements is 6%, the molar ratio of the nano silicon to the silicon oxide is 1:0.1, and the molar ratio of the lithium silicate to the silicon oxide is 1:1.2, wherein the total mass of the silicon-oxygen composite negative electrode material is 100%.
The performance test results of the silicon-oxygen composite anode material prepared in the embodiment are shown in table 1.
Example 3
In this example, a silicon-oxygen composite anode material was prepared as follows:
(1) 1.5kg of Si powder and 2kg of SiO2Putting the powder into a VC mixer to be mixed for 30min to obtain SiO2And Si; putting the mixture into a vacuum furnace; heating to 900 ℃ under the negative pressure condition of the vacuum degree of 5Pa, preserving the heat for 20h, generating silicon oxide steam in the furnace, and generating an SiOy block through rapid condensation (the condensation temperature is 1300 ℃); the SiOy block is subjected to processes such as crushing, ball milling, grading and the like to control the median particle size to be about 6 mu m, so that an SiOy powder material is obtained, wherein y is 1.0;
(2) taking SiOy 1kg, putting the SiOy into a ball milling tank, adding 77.3g of glutamic acid, and ball milling for 20min to obtain silicon oxide doped;
(3) and (2) putting 1kg of doped silicon oxide and 20g of methyllithium into a high-speed dispersion machine, stirring for 40min, taking out, putting into an atmosphere protection furnace, performing heat treatment under the nitrogen atmosphere, naturally cooling to room temperature, taking out the material, and performing screening and demagnetizing to obtain the silicon-oxygen composite negative electrode material, wherein the heat treatment temperature is 350 ℃ and the heat treatment time is 8 h.
The silicon-oxygen composite anode material prepared in this example includes silicon oxide (SiOx, x ═ 1.0), nano silicon dispersed in the silicon oxide, and lithium silicate located on the surface of the silicon oxide, and the lithium silicate contains a doping element (nitrogen element). The silicon-oxygen composite anode material comprises, by taking the total mass of the silicon-oxygen composite anode material as 100%, 5% of doping elements by mass, 1:0.06 of the molar ratio of the nano silicon to the silicon oxide, and 1:0.08 of the molar ratio of the lithium silicate to the silicon oxide.
The performance test results of the silicon-oxygen composite anode material prepared in the embodiment are shown in table 1.
Example 4
In this example, a silicon-oxygen composite anode material was prepared as follows:
(1) taking 1kg of Si powder and 2kg of SiO2Putting the powder into a VC mixer to be mixed for 30min to obtain SiO2And Si; putting the mixture into an atmosphere protection furnace; heating to 1500 ℃ in argon atmosphere, preserving heat for 15h, generating silicon oxide steam in the furnace, and generating SiOy block after rapid condensation (the condensation temperature is 1300 ℃); the SiOy block is subjected to processes such as crushing, ball milling, grading and the like to control the median particle size to be about 6 mu m, so that an SiOy powder material is obtained, wherein y is 1.0;
(2) taking SiOy 1kg, putting the SiOy into a ball milling tank, adding 100g of sulfur elementary substance, and ball milling for 20min to obtain silicon oxide doped;
(3) taking 1kg of doped silicon oxide and 200g of metal lithium, placing the doped silicon oxide and the metal lithium in a high-speed dispersion machine, stirring for 40min, taking out, placing the doped silicon oxide and the metal lithium in an atmosphere protection furnace, performing heat treatment under the argon atmosphere at the heat treatment temperature of 800 ℃ for 2h, naturally cooling to room temperature, taking out materials, and obtaining the silicon-oxygen composite negative electrode material after sieving and demagnetizing.
The silicon-oxygen composite anode material prepared in this example includes silicon oxide (SiOx, x ═ 0.1), nano silicon dispersed in the silicon oxide, and lithium silicate located on the surface of the silicon oxide, and the lithium silicate contains a doping element (elemental sulfur). The silicon-oxygen composite anode material comprises, by taking the total mass of the silicon-oxygen composite anode material as 100%, the mass fraction of the doping elements is 10%, the molar ratio of the nano silicon to the silicon oxide is 1:0.9, and the molar ratio of the lithium silicate to the silicon oxide is 1: 2.2.
The performance test results of the silicon-oxygen composite anode material prepared in the embodiment are shown in table 1.
Comparative example 1
This comparative example is the same as example 1 except that the procedure of step (2), i.e., the ammonium sulfate doping, was not performed with respect to example 1, and the procedure of step (3) was performed by directly using the SiOy powder material obtained in step (1) instead of the doped silicon oxide in step (3) of example 1, and other procedures, raw materials, and the like were the same as example 1.
The performance test results of the silicon-oxygen composite anode material prepared by the comparative example are shown in table 1.
Test method
The products of each of the examples and comparative examples were subjected to performance testing as follows:
(1) first charge and discharge performance test of electricity
Taking a silicon-oxygen composite negative electrode material product as an active substance, taking SBR and CMC as a binder, adding conductive carbon black, stirring, pulping, coating on a copper foil, and finally drying and rolling to prepare a negative electrode plate, wherein the active substance is as follows: conductive agent: binder 85:15: 10. Using metal lithium sheet as counter electrode, PP as diaphragm, LiPF6The electrolyte solution was EC + DEC + DMC (EC, DEC and DMC in a volume ratio of 1:1:1), and the simulated cell was assembled in an argon-filled glove box. The electrochemical performance of the button cell is tested by adopting a blue 5V/10mA type cell tester, the charging voltage is 1.5V, the discharge is carried out to 0.01V, and the charging and discharging rate is 0.1C.
(2) Cycle testing
Uniformly mixing a silicon-oxygen composite negative electrode material product and graphite according to a mass ratio of 1:9 to obtain an active substance, taking a metal lithium sheet as a counter electrode, taking PP/PE as a diaphragm, and using LiPF6(volume ratio of EC, DEC and DMC is 1)1:1) as electrolyte, assembling a button cell in an argon-filled glove box, testing the electrochemical performance of the cell for 50 weeks by adopting a blue 5V/10mA type cell tester, wherein the charging voltage is 1.5V, the discharging is carried out to 0.01V, and the charging and discharging rate is 0.1C.
Fig. 1 is a first charge-discharge curve of the silicon-oxygen composite negative electrode material prepared in example 1, and it can be seen from the curve that the material has a high reversible capacity.
The test results of examples 1-4 and comparative examples are shown in Table 1 below:
TABLE 1
It can be known from the above examples and comparative examples that the silicon-oxygen composite negative electrode material provided by the examples can improve the electron conductivity of lithium silicate by uniformly distributing the doping elements in the lithium silicate, and reduce the capacity loss caused by the inactivation of internal silicon due to the poor conductivity of the lithium silicate generated in situ in the material; by controlling the content of the doping element, the conductivity of the lithium silicate can be improved, the silicon coated with the lithium silicate on the surface is activated to exert the capacity, and the capacity reduction caused by introducing excessive doping elements can be avoided.
Comparative example 1 does not use a doping element, and thus the capacity loss in the silicon-based material cannot be reduced, and therefore the capacity, efficiency, and cycle of the anode material are inferior to those of example 1.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The silicon-oxygen composite anode material is characterized by comprising nano silicon, silicon oxide and lithium silicate, wherein the lithium silicate contains a doping element.
2. The silicon-oxygen composite anode material as claimed in claim 1, wherein the doping element is a non-metallic element;
preferably, the doping element comprises at least one of boron, nitrogen and sulfur;
preferably, the mass fraction of the doping element is 5-10% based on the total mass of the silicon-oxygen composite anode material being 100%.
3. The silicon oxygen composite anode material according to claim 1 or 2, wherein the nano silicon is dispersed in silicon oxide, and the lithium silicate is located on the surface of the silicon oxide;
preferably, the silicon oxide has the formula SiOx, wherein 0 < x < 1.2;
preferably, the molar ratio of the nano silicon to the silicon oxide is 1:0.05-1: 0.9;
preferably, the molar ratio of lithium silicate to silicon oxide is 1:0.08 to 1: 2.2.
4. A method for preparing a silicon-oxygen composite anode material according to any one of claims 1 to 3, characterized in that the method comprises the following steps:
mixing SiOy with a doping element source to obtain a doped silicon source; and
and compounding and roasting the doped silicon source and the lithium source to obtain the silica composite negative electrode material.
5. The method according to claim 4, wherein 0 < y < 2 in the SiOy;
preferably, in the SiOy, y is 1;
preferably, the doping element source comprises at least one of elemental boron, boron oxide, boric acid, glutamic acid, ammonium sulfate and elemental sulfur;
preferably, the method of mixing in the step of mixing SiOy with the source of the doping element is ball milling.
6. The production method according to claim 4 or 5, characterized in that the lithium source is a lithium compound containing no oxygen;
preferably, the lithium source comprises at least one of lithium hydride, alkyl lithium, metallic lithium, and lithium amide;
preferably, the mass ratio of the doped silicon source to the lithium source is 1:0.02-1: 0.2;
preferably, the method of compounding in the step of compounding and firing the doped silicon source with the lithium source includes at least one of mixing, kneading, fusing, and stirring;
preferably, the firing is carried out under a protective atmosphere;
preferably, the gas of the protective atmosphere comprises at least one of hydrogen, nitrogen, helium, neon, argon, krypton and xenon;
preferably, the roasting temperature is 350-800 ℃;
preferably, the roasting time is 2h-8 h.
7. The production method according to any one of claims 4 to 6, wherein the production method of SiOy comprises:
heating raw materials capable of generating silicon oxide gas under the condition of vacuum pumping or protective atmosphere, generating the silicon oxide gas, and cooling to obtain the silicon source SiOy.
8. The production method according to claim 7, wherein the raw materials capable of generating a silicon oxide gas are Si and SiO2A mixture of (a);
preferably, the SiOy preparation method further comprises shaping the obtained product after the cooling;
preferably, the shaping comprises at least one of crushing, ball milling, and classifying;
preferably, the heating temperature is 900 ℃ to 1500 ℃.
9. The method for preparing according to any one of claims 4 to 8, characterized in that it comprises the steps of:
for Si and SiO under vacuum condition or protective atmosphere2Heating the mixture at 900-1500 ℃ to generate silicon oxide gas, and then cooling and shaping to obtain SiOy;
mixing the SiOy with a doping element source and carrying out ball milling to obtain a doped silicon source, wherein the doping element source comprises at least one of a boron simple substance, boron oxide, boric acid, glutamic acid, ammonium sulfate and a sulfur simple substance;
compounding the doped silicon source with a lithium source, and roasting at 350-800 ℃ for 2-8 h under a protective atmosphere to obtain the silicon-oxygen composite negative electrode material, wherein the lithium source is a lithium compound without oxygen, and the compounding method comprises at least one of mixing, kneading, fusing and stirring.
10. A lithium ion battery comprising the silicon-oxygen composite anode material according to any one of claims 1 to 3.
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