Modified silica negative electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of battery material preparation, and particularly relates to a modified silica negative electrode material and a preparation method and application thereof. The method comprises the steps that a silicon-oxygen negative electrode material SiOx (0 < X < = 2) is mixed with a carbon source and / or a lithium source, heat treatment is carried out, the modified silicon-oxygen negative electrode material is obtained, and the grain size of the modified silicon-oxygen negative electrode material and the heat treatment time are in a linear relation, and the grain size and the heat treatment temperature are in an exponential relation. By making the heat treatment temperature, time and product grain size meet the linear relation and / or the index relation, the technical effect of regulating and controlling the grains of the modified silicon-oxygen negative electrode material can be achieved, and then regulation and control of the electrochemical performance of the modified material are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material preparation, and specifically relates to a modified silicon oxide negative electrode material and its preparation method and application. More specifically, it relates to a carbon-coated silicon oxide negative electrode material and its preparation method and application, a lithiated silicon oxide negative electrode material and its preparation method and application. Background Art

[0002] Lithium-ion batteries have a wide range of applications in the new energy field. As the most widely used negative electrode material in lithium-ion batteries, graphite has a stable voltage platform and long cycle stability characteristics. However, the theoretical capacity of the material is only 372 mAh / g, which cannot meet the human demand for high-energy-density energy storage. Silicon-based negative electrode materials have become one of the most promising negative electrode materials in the future due to their ultra-high specific capacity. However, the volume expansion of pure silicon materials is large, and silicon oxide materials can alleviate the volume expansion problem of the materials to a certain extent due to their special structural characteristics. However, during the process of preparing silicon oxide negative electrode materials from silicon suboxide, heat treatment processes are required, and silicon clusters in the silicon suboxide will fuse, resulting in an increase in the silicon grain size, which affects the cycling performance of the silicon oxide material. Therefore, how to control the growth of silicon grain size during the heat treatment process has become an urgent technical problem to be solved. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the heat treatment conditions cannot be accurately controlled, resulting in the growth of silicon grain size during the heat treatment of silicon suboxide, thereby affecting the electrochemical performance of the silicon oxide negative electrode material. Thus, a modified silicon oxide negative electrode material and its preparation method and application are provided.

[0004] To this end, the present invention provides the following technical solutions.

[0005] In the first aspect of the present invention, a preparation method of a modified silicon oxide negative electrode material is provided. The silicon oxide negative electrode material SiO x (0 < X ≤ 2) is mixed with a carbon source and / or a lithium source, and after heat treatment, a modified silicon oxide negative electrode material is obtained. The grain size of the modified silicon oxide negative electrode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature.

[0006] In the second aspect of the present invention, a preparation method of a carbon-coated silicon oxide negative electrode material is provided, including: taking a silicon oxide negative electrode material and mixing it with a carbon source, and after heat treatment, a carbon-coated silicon oxide negative electrode material is obtained, denoted as SiO x @C(0 < X ≤ 2). The grain size of the carbon-coated silicon oxide negative electrode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature.

[0007] The third aspect of the present invention provides a method for preparing a carbon-coated silicon oxy negative electrode material, comprising: introducing a carbon source into silicon monoxide for a first heat treatment to obtain a carbon-coated silicon oxy negative electrode material, denoted as SiO x @C(0 < X ≤ 2);

[0008] Wherein, the target grain size D1 of the carbon-coated silicon oxy negative electrode material and the grain size N of the silicon monoxide satisfy relationship 1:

[0009]

[0010] Wherein, D1 is the target grain size of the carbon-coated silicon oxy negative electrode material, in nm;

[0011] N is the grain size of the silicon monoxide, in nm;

[0012] H1 is the time of the first heat treatment, in h;

[0013] T1 is the temperature of the first heat treatment, in °C.

[0014] Specifically, during the heat treatment process, the grain size of the carbon-coated silicon oxy negative electrode material has a linear relationship with the heat treatment time when the temperature of the first heat treatment is constant; the grain size of the carbon-coated silicon oxy negative electrode material has an exponential relationship with the temperature of the first heat treatment when the time of the first heat treatment is constant.

[0015] In the relationship 1, N ≤ 3 nm; and / or, H1 ≥ 0.5 h; and / or, 700 °C ≤ T1 ≤ 1000 °C; preferably, 1 h ≤ H1 ≤ 20 h;

[0016] Wherein, the N can be 0.5 nm, 0.8 nm, 1 nm, 1.3 nm, 1.5 nm, 1.7 nm, 2 nm, 2.2 nm, 2.5 nm, 2.8 nm, 3 nm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] Wherein, the H1 can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 30 h, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] Among them, the T1 can be 700°C, 730°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, 1000°C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] The method provided by the present invention can make the deviation between the target grain size and the actually measured grain size of the carbon-coated silicon oxide anode material be ±0.3 nm.

[0020] The carbon source is a hydrocarbon gas;

[0021] Preferably, the carbon source is at least one of alkanes, alkenes, and alkynes;

[0022] Preferably, the carbon source is at least one of methane, ethylene, acetylene, propane, propylene, and propyne;

[0023] Preferably, when performing the first heat treatment, it further includes the step of introducing a protective gas; when preparing the carbon-coated silicon oxide anode material, the protective gas is nitrogen, etc., which can play a role in protecting the device.

[0024] Preferably, the volume ratio of the carbon source to the protective gas is (1 - 40):(60 - 90);

[0025] Preferably, the volume ratio of the carbon source to the protective gas is 15:85;

[0026] Preferably, the specific steps of the first heat treatment include: heating to 700 - 1000°C at a heating rate of 3 - 10°C / min for the first heat treatment;

[0027] Preferably, the time of the first heat treatment ≥0.5 h;

[0028] Preferably, the time of the first heat treatment is 1 - 20 h.

[0029] Among them, the temperature of the first heat treatment can be 700°C, 730°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, 1000°C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] The heating rate of the first heat treatment can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0031] The time of the first heat treatment may be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 30h, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0032] In the fourth aspect of the present invention, a carbon-coated silicon oxide negative electrode material prepared by the above preparation method is provided. The target grain size D1 of the silicon oxide negative electrode material is ≤ 10 nm;

[0033] Preferably, the target grain size D1 of the silicon oxide negative electrode material is ≤ 4 nm.

[0034] The D1 may be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0035] In the carbon-coated silicon oxide negative electrode material, the mass content of carbon in the carbon-coated silicon oxide negative electrode material is 2 - 6%.

[0036] Due to the poor conductivity of silicon oxide materials, carbon coating treatment is usually carried out to improve conductivity. The inventors found in the research that when the grain size of the carbon-coated silicon oxide negative electrode material is too large, a long plateau will appear at the potential of 0.4 - 0.5 V during the lithium insertion process. This plateau indicates that large silicon crystals are formed during the de-lithiation process of the lithium insertion product - silicon-lithium alloy of the silicon oxide material, which hinders the migration of lithium ions and affects the rate performance of the material. Therefore, by controlling the heat treatment process during carbon coating, a grain size that meets the requirements can be obtained, avoiding too large a grain size, and ensuring the rate performance of the material;

[0037] In addition, when the grain size of the carbon-coated silicon oxide negative electrode material is too large, a repeated conversion process between silicon crystals and silicon-lithium alloy will occur during charge and discharge, prompting new interfaces to be repeatedly generated on the material surface, resulting in the consumption of the electrolyte and affecting the cycle performance of the battery. Therefore, by controlling the grain size of the carbon-coated silicon oxide negative electrode material and preventing the silicon grain size from being too large, a long plateau at the potential of 0.4 - 0.5 V during the first de-lithiation process of the material can be avoided, so that the migration of lithium ions on the surface is not affected, and at the same time, the smaller silicon crystals consume less electrolyte during repeated charge and discharge processes.

[0038] In the fifth aspect of the present invention, a preparation method of a lithiated silicon oxide negative electrode material is provided, including: mixing a silicon oxide negative electrode material with a lithium source and performing heat treatment to obtain a lithiated silicon oxide negative electrode material, denoted as Li-SiO x(0 < X ≤ 2), the grain size of the lithiated silicon oxide anode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature. Specifically, the above silicon oxide anode material is a carbon-coated silicon oxide anode material.

[0039] The sixth aspect of the present invention provides a method for preparing a lithiated silicon oxide anode material, including: taking a carbon-coated silicon oxide anode material, mixing it with a lithium source, and performing a second heat treatment to obtain a lithiated silicon oxide anode material, denoted as Li-SiO x @C(0 < X ≤ 2).

[0040] In the present invention, the carbon-coated silicon oxide anode material can be prepared by the above method or obtained commercially. When the carbon-coated silicon oxide anode material meeting the grain size requirements is prepared by the method of the present invention, D1 is D1'.

[0041] Among them, the target grain size of the lithiated silicon oxide anode material and the grain size of the carbon-coated silicon oxide anode material satisfy the relationship 2:

[0042]

[0043] Among them, D2 is the target grain size of the lithiated silicon oxide anode material, with the unit of nm;

[0044] D1' is the grain size of the carbon-coated silicon oxide anode material, with the unit of nm;

[0045] H2 is the time of the second heat treatment, with the unit of h;

[0046] T2 is the temperature of the second heat treatment, with the unit of °C.

[0047] Specifically, during the second heat treatment, the grain size of the lithiated silicon oxide anode material has a linear relationship with the second heat treatment time when the temperature of the second heat treatment is constant; the grain size of the lithiated silicon oxide anode material has an exponential relationship with the second heat treatment temperature when the time of the second heat treatment is constant.

[0048] In the relationship 2, D1' ≤ 10 nm; and / or, H2 ≥ 0.5 h; and / or, 600 °C ≤ T2 ≤ 800 °C; preferably, 2 h ≤ H2 ≤ 8 h;

[0049] Among them, the D1' can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0050] Preferably, D1' ≤ 4 nm.

[0051] The H2 can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0052] Among them, the T2 can be 600°C, 620°C, 650°C, 680°C, 700°C, 730°C, 750°C, 780°C, 800°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0053] The method provided by the present invention can make the deviation between the target grain size and the actually measured grain size of the lithiated silicon-oxygen anode material be ±0.6 nm.

[0054] The lithium source is a reducing lithium source;

[0055] Preferably, the reducing lithium source includes at least one of lithium powder, lithium hydride, lithium amide, and organolithium;

[0056] Preferably, the organolithium includes alkyllithium;

[0057] Preferably, the alkyllithium is at least one of methyllithium, ethyllithium, butyllithium, and biphenylyllithium;

[0058] Preferably, the molar ratio of Si in the carbon-coated silicon-oxygen anode material to Li in the lithium source is 1:(0.1 - 1);

[0059] Preferably, the molar ratio of Si in the carbon-coated silicon-oxygen anode material to Li in the lithium source is 1:0.67;

[0060] Preferably, the specific steps of the second heat treatment include: heating to 600 - 800°C at a heating rate of 3 - 10°C / min for the second heat treatment;

[0061] Preferably, the time of the second heat treatment ≥0.5 h;

[0062] Preferably, the time of the second heat treatment is 2 - 8 h.

[0063] Among them, the temperature of the second heat treatment can be 600°C, 620°C, 650°C, 680°C, 700°C, 730°C, 750°C, 780°C, 800°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0064] The heating rate of the second heat treatment can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0065] The time of the second heat treatment can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0066] The seventh aspect of the present invention provides a lithiated silicon oxide negative electrode material prepared by the above preparation method.

[0067] The target grain size of the lithiated silicon oxide negative electrode material is 3 nm ≤ D2 ≤ 20 nm; where D2 can be 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0068] Preferably, 3 nm ≤ D2 ≤ 6 nm.

[0069] The composition of the lithiated silicon oxide negative electrode material prepared by the above method of the present invention includes lithium silicate, and the lithium silicate is one or more of Li4SiO4, Li2Si3O5, Li2Si2O5, Li8O2(SiO4), or Li6(Si2O7).

[0070] Pre-lithiation of the carbon-coated silicon oxide negative electrode material can improve the first efficiency of the silicon oxide material and reduce the consumption of the electrolyte during the first charge and discharge process. The inventor found during the pre-lithiation process that the conventional method is prone to cause a sharp increase in the grain size, and the large grain size has a greater negative impact on the cycle and rate performance. By controlling the grain size of the negative electrode material after lithiation to a suitable size, both the first Coulombic efficiency of the negative electrode material can be improved, and the rate and cycle performance of the negative electrode material can be ensured.

[0071] The eighth aspect of the present invention provides a negative electrode sheet, which includes the modified silicon oxide negative electrode material prepared by the above preparation method and / or the carbon-coated silicon oxide negative electrode material prepared by the above preparation method and / or the above carbon-coated silicon oxide negative electrode material and / or the lithiated silicon oxide negative electrode material prepared by the above preparation method and / or the above lithiated silicon oxide negative electrode material.

[0072] The ninth aspect of the present invention provides a battery, which includes the negative electrode sheet as described above.

[0073] The tenth aspect of the present invention provides an electrical device, and the electrical device includes the battery as described above.

[0074] The technical solution of the present invention has the following advantages:

[0075] 1. The preparation method of the modified silicon-oxygen anode material provided by the present invention includes: mixing the silicon-oxygen anode material SiO x with a carbon source and / or a lithium source, and performing heat treatment to obtain a modified silicon-oxygen anode material. The grain size of the modified silicon-oxygen anode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature; wherein, (0 < X ≤ 2). By making the heat treatment temperature, time, and product grain size satisfy a linear relationship and / or an exponential relationship, the present invention can achieve the technical effect of regulating the grains of the modified silicon-oxygen anode material, and further achieve the regulation of the electrochemical performance of the modified material.

[0076] 2. The preparation method of the carbon-coated silicon-oxygen anode material provided by the present invention includes performing a first heat treatment by introducing a gaseous carbon source into silicon monoxide to obtain a carbon-coated silicon-oxygen anode material, denoted as SiO x @C. The target grain size D1 of the carbon-coated silicon-oxygen anode material and the grain size N of the silicon monoxide satisfy relationship 1; by making the target grain size of the carbon-coated silicon-oxygen anode material, the grain size of the silicon monoxide, the heat treatment temperature, and the time satisfy a certain relationship, the present invention can achieve the technical effect of regulating the grains of the carbon-coated silicon-oxygen anode material, and further achieve the regulation of the electrochemical performance of the silicon-oxygen anode material. When the target grain size of the carbon-coated silicon-oxygen anode material, the grain size of the silicon monoxide, the heat treatment temperature, and the time satisfy relationship 1, the error between the actual grain size and the target grain size of the carbon-coated silicon-oxygen anode material is small.

[0077] In addition, by studying the relationship between the grain size of silicon monoxide and the temperature and time of heat treatment, and constructing a relationship to regulate the heat treatment process to facilitate obtaining the grain size of the carbon-coated silicon-oxygen anode material that meets the product requirements, the present invention can make the product have good cycle performance and rate performance.

[0078] 3. The preparation method of the lithium - silicon - oxygen negative electrode material provided by the present invention can regulate the grain size of the lithium - silicon - oxygen negative electrode material by controlling the target grain size of the lithium - silicon - oxygen negative electrode material, the carbon - coated silicon - oxygen negative electrode material, the heat - treatment temperature and time to satisfy a specific relational expression, thereby ensuring the performance of the negative electrode material. On the basis that the target grain size of the lithium - silicon - oxygen negative electrode material, the grain size of the carbon - coated silicon - oxygen negative electrode material, the heat - treatment time and temperature satisfy Relational Expression 2, the error between the actual grain size and the target grain size of the obtained lithium - silicon - oxygen negative electrode material is small. And regulating the heat - treatment temperature through the relational expression is convenient for obtaining a lithium - silicon - oxygen negative electrode material that meets the product requirements. This material can not only improve the first - cycle Coulombic efficiency of the negative electrode material but also ensure the rate performance and cycling performance of the negative electrode material. Detailed Embodiments

[0079] The following embodiments are provided to better understand the present invention further. They are not limited to the best - mode embodiment, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other prior arts falls within the protection scope of the present invention.

[0080] For those not specifying specific experimental steps or conditions in the embodiments, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For reagents or instruments not specifying the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0081] Material performance testing methods:

[0082] Testing method for grain size: It is tested by XRD, that is, by calibrating the full - width at half - maximum of the silicon peak at about 28.5° in the test result, and obtaining the grain size through the Scherrer formula. The expression of the Scherrer formula is: D = Kλ / (βcosθ), where K is a constant; λ is the X - ray wavelength; β is the full - width at half - maximum of the diffraction peak; θ is the diffraction angle. In the calculation method of the present invention, the constant K in the above formula takes 0.89.

[0083] Testing method for electrochemical performance: Using a lithium sheet as the counter electrode, using the materials obtained in each embodiment as the negative electrode materials, assembling a button cell with a lithium sheet as the counter electrode, in a constant - temperature box of a 25°C blue - power test cabinet (T - 3002A - 5V 1mA), the battery is left standing for 6 h. The button cell is discharged to 1.0 mV at 0.1C, left standing for 10 min, and then discharged to 1.0 mV at 0.01C, and the discharge capacity D is recorded; it is charged to 1.5V at 0.05C, and the capacity of the button cell at this time is recorded, denoted as the specific capacity C. The first - cycle efficiency is calculated through the following formula:

[0084]

[0085] 100 th Test method for capacity retention rate: Test method for 100th capacity retention rate: Using the materials obtained in each example as the anode material and lithium nickel cobalt manganese oxide LiNi 0.5 Mn 0.3 Co 0.2 O2 (NMC532) as the cathode material to assemble a button-type full cell. In the constant temperature box of a 25°C Blue Electric test cabinet (T-3002A-5V1mA), let it stand for 6 h, discharge at a constant current of 0.1C to 1.0 mV, stand for 10 min, and discharge at a constant current of 0.01C to 1.0 mV; stand for 10 min, charge at a constant current of 0.1C to 1.5V, record the charging capacity E. After 100 cycles, record the charging capacity F. The capacity retention rate is calculated by the following formula:

[0086]

[0087] Examples 1-12

[0088] Examples 1-12 provide a preparation method of a carbon-coated silicon oxide anode material, including the following steps:

[0089] Put amorphous silicon monoxide (i.e., grain size is 0) into a gas-phase high-temperature reaction furnace, introduce acetylene and nitrogen, and heat it at a heating rate of 5°C to the temperature of the first heat treatment for treatment to obtain a carbon-coated silicon oxide material; conduct experiments according to Relationship 1 to make the target grain size, the temperature of the first heat treatment, the time of the first heat treatment, and the grain size of silicon monoxide of the carbon-coated silicon oxide anode material satisfy Relationship 1; among them, the temperature and time of the first heat treatment are shown in Table 1, and the volume ratio of acetylene to nitrogen is 15:85;

[0090]

[0091] D1 is the target grain size of the carbon-coated silicon oxide anode material, with the unit of nm;

[0092] N is the grain size of silicon monoxide, with the unit of nm;

[0093] H1 is the time of the first heat treatment, with the unit of h;

[0094] T1 is the temperature of the first heat treatment, with the unit of °C.

[0095] Test the actual grain size of the carbon-coated silicon oxide anode material according to the above test method and compare it with the target grain size. The results are shown in Table 1.

[0096] Table 1 Performance test results of carbon-coated silicon oxide anode material

[0097]

[0098] As can be seen from the above experimental results, the size error between the measured grains and the target grains of the carbon-coated silicon oxide anode material is small, indicating that the grain size of the carbon-coated silicon oxide anode material product can be regulated by controlling the target grain size, the grain size of silicon suboxide, the heat treatment temperature and time to satisfy the relational expression 1, and the error is small and the accuracy is high.

[0099] Parallel experiment 1

[0100] The purpose of this parallel experiment is to verify the accuracy of the experimental results. The parallel experiment is carried out according to the following conditions. The temperature and time of the first heat treatment are shown in the following table, and the experimental results are shown in the following table. Other conditions and test methods in the experiment refer to the above content.

[0101] Table 2 Test results of parallel experiment of carbon-coated silicon oxide anode material

[0102]

[0103]

[0104] As can be seen from the above results, the differences in the above parallel experiment results are small, indicating that the method of the present invention has high accuracy and good repeatability.

[0105] Examples 13 - 16

[0106] Examples 13 - 16 provide a preparation method of a lithiated silicon oxide anode material, including the following steps:

[0107] Take a carbon-coated silicon oxide anode material with a grain size D1' of 1.5 nm, mix the carbon-coated silicon oxide anode material with lithium hydride according to a Si:Li molar ratio of 1:0.67, and heat-treat it at a heating rate of 6 °C / min to the temperature of the second heat treatment to obtain a lithiated silicon oxide anode material; conduct experiments according to the relational expression 2 to make the target grain size, the second heat treatment temperature, the second heat treatment time, and the grain size of the carbon-coated silicon oxide anode material of the lithiated silicon oxide anode material satisfy the relational expression 2; wherein, the second heat treatment temperature and the second heat treatment time are shown in Table 3;

[0108]

[0109] D2 is the target grain size of the lithiated silicon oxide anode material, in nm;

[0110] D1' is the grain size of the carbon-coated silicon oxide anode material, in nm;

[0111] H2 is the time of the second heat treatment, in h;

[0112] T2 is the temperature of the second heat treatment, in °C;

[0113] The actual grain size of the lithium - silicon - oxygen anode material was tested according to the above - mentioned test method and compared with the target grain size. The results are shown in Table 3.

[0114] Table 3 Performance test results of lithium - silicon - oxygen anode material

[0115]

[0116] It can be seen from the above experimental results that the size error between the measured grains of the lithium - silicon - oxygen anode material and the target grains is small, indicating that the present invention can regulate the grain size of the product lithium - silicon - oxygen anode material by controlling the target grain size, the grain size of the carbon - coated silicon - oxygen anode material, the heat treatment temperature and time to satisfy Relationship 2, with small error and high accuracy.

[0117] Parallel experiment 2

[0118] The purpose of this parallel experiment is to verify the accuracy of the experimental results of the preparation method of the lithium - silicon - oxygen anode material. The parallel experiment was carried out according to the following conditions. The temperature and time of the second heat treatment are shown in the following table, and the experimental results are shown in the following table. Other conditions and test methods in the experiment refer to the above content.

[0119] Table 4 Parallel experiment test results of lithium - silicon - oxygen anode material

[0120]

[0121]

[0122] It can be seen from the above results that the differences in the above - mentioned parallel experiment results are small, indicating that the method of the present invention has high accuracy and good repeatability.

[0123] Obviously, the above - mentioned embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A preparation method of a modified silicon-oxygen anode material, characterized in that, Mix silicon-oxygen anode material SiO x (0 < X ≤ 2) with a carbon source and / or a lithium source, and through heat treatment, a modified silicon-oxygen anode material is obtained. The grain size of the modified silicon-oxygen anode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature.

2. A preparation method of a carbon-coated silicon oxide negative electrode material, characterized in that, Comprising: Mix the silicon-oxygen anode material with a carbon source and perform heat treatment to obtain a carbon-coated silicon-oxygen anode material, denoted as SiO x @C (0 < X ≤ 2), the grain size of the carbon-coated silicon-oxygen anode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature.

3. A preparation method of a carbon-coated silicon oxide negative electrode material, characterized in that, Comprising: A carbon source is introduced into silicon monoxide for a first heat treatment to obtain a carbon-coated silicon oxide negative electrode material, denoted as SiO x @C (0 < X ≤ 2); Wherein, the target grain size D1 of the carbon-coated silicon oxy anode material and the grain size N of the silicon suboxide satisfy relationship 1: D1 = N + H1 × 0.000075e 0.008×T1 Relationship 1 D1 is the target grain size of the carbon-coated silicon oxy anode material, with the unit of nm; N is the grain size of the silicon suboxide, with the unit of nm; H1 is the time of the first heat treatment, with the unit of h; T1 is the temperature of the first heat treatment, with the unit of °C.

4. The preparation method according to claim 3, wherein In the relationship 1, N ≤ 3 nm; and / or H1 ≥ 0.5 h; and / or, 700 °C ≤ T1 ≤ 1000 °C.

5. The preparation method according to claim 3 or 4, characterized in that The carbon source is a hydrocarbon gas; Preferably, the carbon source is at least one of alkanes, alkenes, and alkynes; Preferably, the carbon source is at least one of methane, ethylene, acetylene, propane, propylene, and propyne; Preferably, when performing the first heat treatment, it further includes the step of introducing a protective gas; Preferably, the volume ratio of the carbon source to the protective gas is (1 - 40):(60 - 90); Preferably, the volume ratio of the carbon source to the protective gas is 15:85; Preferably, the specific steps of the first heat treatment include: heating up to 700 - 1000 °C at a heating rate of 3 - 10 °C / min for the first heat treatment; Preferably, the time of the first heat treatment ≥ 0.5 h.

6. The carbon-coated silicon oxide negative electrode material prepared by the preparation method according to any one of claims 3-5, characterized in that The target grain size D1 of the carbon-coated silicon oxy anode material ≤ 10 nm; Preferably, the target grain size D1 of the carbon-coated silicon oxy anode material ≤ 4 nm.

7. The carbon-coated silicon oxide negative electrode material according to claim 6, characterized in that, The mass content of carbon in the carbon-coated silicon oxy anode material is 2 - 6%; 8. A preparation method of a lithium - silicon - oxygen negative electrode material, characterized in that, Comprising: Mix a silicon oxide negative electrode material with a lithium source and perform heat treatment to obtain a lithiated silicon oxide negative electrode material, denoted as Li-SiO x (0 < X ≤ 2). The grain size of the lithiated silicon oxide negative electrode material has a linear relationship with the heat treatment time and an exponential relationship with the heat treatment temperature.

9. A preparation method of a lithium - silicon - oxygen negative electrode material, characterized in that, Comprising: Take a carbon-coated silicon oxide negative electrode material, mix it with a lithium source, and perform a second heat treatment to obtain a lithiated silicon oxide negative electrode material, denoted as Li-SiO x @C, (0 < X ≤ 2); Wherein, the target grain size of the lithiated silicon oxy anode material and the grain size of the carbon-coated silicon oxy anode material satisfy relationship 2: D2 = D1' + H2 × 0.0042e 0.0085×T2 Relationship 2 D2 is the target grain size of the lithiated silicon oxy anode material, with the unit of nm; D1' is the grain size of the carbon-coated silicon oxy anode material, with the unit of nm; H2 is the time of the second heat treatment, with the unit of h; T2 is the temperature of the second heat treatment, with the unit of °C.

10. The preparation method according to claim 9, characterized in that, In the relationship 2, D1' ≤ 10 nm; and / or, H2 ≥ 0.5 h; and / or, 600 °C ≤ T2 ≤ 800 °C; Preferably, D1' ≤ 4 nm.

11. The preparation method according to claim 9 or 10, characterized in that, The lithium source is a reducing lithium source; Preferably, the reducing lithium source includes at least one of lithium powder, lithium hydride, lithium amide, and organolithium; Preferably, the organolithium contains an alkyl lithium; Preferably, the alkyl lithium is at least one of methyl lithium, ethyl lithium, butyl lithium, and biphenyl lithium; Preferably, the molar ratio of Si in the carbon-coated silicon oxy anode material to Li in the lithium source is 1:(0.1 - 1); Preferably, the molar ratio of Si in the carbon-coated silicon oxy anode material to Li in the lithium source is 1:0.67; Preferably, the specific steps of the second heat treatment include: heating up to 600 - 800 °C at a heating rate of 3 - 10 °C / min for the second heat treatment; Preferably, the time of the second heat treatment ≥ 0.5 h.

12. The lithiated silicon-oxygen anode material prepared by the preparation method according to any one of claims 9-11, characterized in that, The target grain size of the lithiated silicon oxy anode material 3 nm ≤ D2 ≤ 20 nm; Preferably, 3 nm ≤ D2 ≤ 6 nm.

13. A negative electrode plate, characterized in that, The negative electrode sheet includes the modified silicon oxide negative electrode material prepared by the preparation method described in claim 1; and / or, the carbon-coated silicon oxide negative electrode material prepared by the preparation method described in claim 2; and / or, the carbon-coated silicon oxide negative electrode material prepared by the preparation method described in any one of claims 3-5; and / or, the carbon-coated silicon oxide negative electrode material described in any one of claims 6-7; and / or, the lithiated silicon oxide negative electrode material prepared by the method described in claim 8; and / or, the lithiated silicon oxide negative electrode material prepared by the preparation method described in any one of claims 9-11; and / or, the lithiated silicon oxide negative electrode material described in claim 12.

14. A battery, characterized in that, The battery includes the negative electrode sheet as described in claim 13.

15. An electrical device, characterized in that, The electrical device includes the battery as described in claim 14.

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