CN117110130A

CN117110130A - Method for testing coating integrity of silicon-based material

Info

Publication number: CN117110130A
Application number: CN202311369188.2A
Authority: CN
Inventors: 王闯; 牛凡超
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-10-23
Filing date: 2023-10-23
Publication date: 2023-11-24

Abstract

A method for testing coating integrity of a silicon-based material belongs to the technical field of characterization testing methods. The testing method comprises the following steps: mixing a silicon-based material with a solvent to obtain slurry, wherein the solvent comprises water; placing the slurry in a closed container; immersing a closed container with slurry in the liquid, wherein one end of the closed container is connected with a tension display device; determining the gas production amount of the slurry according to the change of the tension displayed by the tension display device; and determining the coating integrity of the silicon-based material according to the gas yield of the slurry. The testing method provided by the embodiment of the application can simply, conveniently and accurately determine the coating integrity of the silicon-based material.

Description

Method for testing coating integrity of silicon-based material

Technical Field

The application relates to the technical field of characterization test methods, in particular to a test method for coating integrity of a silicon-based material.

Background

With the increasing increase of environmental pollution, the new energy industry is receiving more and more attention. In the new energy industry, battery technology is an important factor in its development.

The development of battery technology requires consideration of various design factors such as capacity, energy density, cycle life, reliability, and the like. The performance of the silicon-based material as an active material is critical to the performance of the battery. In order to improve the performance of the silicon-based material, a coating modification method is an important means for improving the performance of the silicon-based material. For coating-modified silicon-based materials, the coating integrity has a significant impact on the silicon-based material as well as the performance of the battery. Therefore, how to provide a method for testing the coating integrity of a silicon-based material, so as to detect the coating integrity of the silicon-based material more simply and accurately is a technical problem to be solved.

Disclosure of Invention

The present application has been made in view of the above-described problems, and an object thereof is to provide a method for testing the coating integrity of a silicon-based material, which can detect the coating integrity of the silicon-based material more simply and accurately.

In order to achieve the above purpose, the present application provides a method for testing the coating integrity of a silicon-based material.

In a first aspect, a method for testing coating integrity of a silicon-based material is provided, including: mixing the silicon-based material with a solvent to obtain slurry, wherein the solvent comprises water; placing the slurry in a closed container; immersing the closed container with the slurry in liquid, wherein one end of the closed container is connected with a tension display device; determining the gas production amount of the slurry according to the change of the tension displayed by the tension display device; and determining the coating integrity of the silicon-based material according to the gas yield of the slurry.

In the embodiment of the application, the amount of exposed silicon in the silicon-based material varies with the coating integrity. The bare silicon in the silicon-based material reacts with water in the slurry to produce a gas; the more bare silicon, the more readily gas is produced. When the slurry is placed in a closed container, gas generated after the silicon-based material reacts can not escape into the external environment, and adverse effects caused by the generated gas (such as hydrogen) can be reduced. Immersing the sealed container filled with the slurry into the liquid, wherein the sealed container filled with the slurry is subjected to the action of buoyancy. Because the bare silicon of the silicon-based material in the slurry can react with the water in the slurry to generate gas, the buoyancy force applied to the closed container changes, and the tension force displayed by the tension display device changes. The change of the pulling force is equal to the change of the buoyancy, and the change of the buoyancy has a corresponding relation with the volume of the generated gas, so that the gas yield of the slurry can be obtained according to the change of the pulling force. The coating integrity of the silicon-based material can be determined by testing the amount of gas production of the silicon-based material in the slurry. The testing method provided by the embodiment of the application has the advantages of low requirements on the testing device, simplicity and convenience in operation, and capability of detecting the coating integrity of the silicon-based material more simply and accurately.

In one possible embodiment, the change Δf in the tension force _{Tension force} And the gas yield V of the slurry is as follows: ΔF (delta F) _{Tension force} ρgv, where ρ is the density of the liquid and g is the gravitational acceleration. Thus, the gas yield can be calculated according to the change of the tensile force, and the coating integrity of the silicon-based material can be determined according to the gas yield.

In one possible implementation manner, the sealed container with the slurry is immersed in a liquid, and a tension display device is connected to one end of the sealed container, including: and fixing the closed container with the slurry with a bearing device, wherein one end of the bearing device is connected with a tension display device.

The sealed container with the slurry is fixed with the bearing device, so that a connecting piece can be arranged at one end of the bearing device to connect one end of the bearing device with the tension display device. Therefore, the closed container is convenient to be connected with the tension display device through the bearing device, the influence of the connecting piece on the closed container can be reduced, and the risk of gas escaping from the closed container can be reduced.

In one possible implementation, the carrying device comprises a carrying block and a clamping tool for fixing the closed container on the carrying block. Thus, the bearing block and the clamping tool can have simpler structures, and the operation is convenient to carry out.

In one possible implementation, the density of the liquid is less than the density of the closed container; optionally, the liquid comprises silicone oil.

The density of the liquid is less than that of the closed container, so that the closed container is immersed in the liquid, and the buoyancy change is detected by the tension display device. Under the condition that the liquid is silicone oil, the silicone oil can not react with the closed container and the bearing device, so that the buoyancy change can be accurately monitored, and the gas production rate can be accurately detected.

In one possible implementation, the determining the coating integrity of the silicon-based material according to the gas yield of the slurry includes: calculating the gas production rate of the slurry according to the gas production rate of the slurry; and determining the coating integrity of the silicon-based material according to the gas production rate and/or the gas production rate.

The higher the coating integrity of the silicon-based material, the less silicon is exposed, and thus the less gas yield and gas production rate. And the coating integrity of the silicon-based material is conveniently and intuitively reflected through monitoring the gas production rate or the gas production rate.

In one possible implementation, the determining the coating integrity of the silicon-based material according to the gas yield of the slurry includes: and determining the coating integrity of the silicon-based material according to the gas yield of the slurry in 48 hours.

Under the condition of 48 hours, the bare silicon in the silicon-based material is basically completely reacted with water, so that more accurate gas yield is conveniently obtained, and the coating integrity of the silicon-based material is determined according to the gas yield. In addition, in the case of 48 hours, in actual production, the generated gas escapes through the form of bubbling, so that the influence of the generated gas on the slurry coating can be reduced.

In one possible implementation, the determining the coating integrity of the silicon-based material according to the gas yield of the slurry includes: in the case that the gas yield is less than or equal to 0.05ml/g in 48 hours, the coating integrity of the silicon-based material is determined to be more than 99%. In this way, little or no bare silicon is reflected in the silicon-based material, thereby facilitating determination that the coating integrity of the silicon-based material is close to 100%, so that the silicon-based material can be applied to actual production.

In one possible implementation, the gas production is a gas production measured at a temperature T that satisfies: t is more than or equal to 40 ℃ and less than or equal to 55 ℃. Under the condition that the temperature T is not more than 55 ℃, the reaction intensity between the bare silicon and water in the silicon-based material is low, the generated gas amount is not too large, and the risk of air leakage caused by more expansion of the closed container due to too much or too fast generated gas and the like can be reduced; under the condition that the temperature T is not less than 40 ℃, the gas generation rate and the gas production rate are proper, and the gas production rate can be conveniently detected.

In one possible implementation, the temperature T satisfies: t is more than or equal to 40 ℃ and less than or equal to 45 ℃. Thus, the reaction between the bare silicon in the silicon-based material and water is not too severe, the gas generation rate and the gas yield are proper, and the gas yield can be conveniently detected.

In one possible implementation, the slurry further includes a dispersant including sodium carboxymethyl cellulose and styrene-butadiene rubber.

The silicon-based material can be mixed with water to prepare slurry, or can be mixed with water, sodium carboxymethyl cellulose and styrene butadiene rubber to prepare slurry. The silicon-based material, water, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed to prepare slurry, and in the slurry, the volume of gas generated by bare silicon in the silicon-based material is obvious, so that the gas yield is easier to detect. In addition, the components of the slurry are closer to those of the cathode slurry prepared in actual production, and the actual gas production can be reflected better.

In one possible implementation, the mass ratio a of the sodium carboxymethyl cellulose and the styrene-butadiene rubber satisfies: 1: a is more than or equal to 1 and less than or equal to 2:1. In this way, the silicon-based material can be better dispersed in the slurry.

In one possible implementation, the sum C of the mass contents of the sodium carboxymethylcellulose and the styrene-butadiene rubber, based on the total mass of the solvent and the dispersant, satisfies: c is more than or equal to 2wt% and less than or equal to 3wt%. In this way, the silicon-based material can be better dispersed in the slurry.

In one possible implementation, the mass ratio B of the sum of the masses of the solvent and the dispersant to the silicon-based material satisfies: b is more than or equal to 5 and less than or equal to 7:3; alternatively, B satisfies: b is more than or equal to 5 and less than or equal to 6.5:3.5. Under the condition that the mass ratio B of the sum of the solvent and the dispersing agent to the silicon-based material is not more than 2.34, the silicon-based material can be uniformly distributed in the slurry, the reaction between silicon and water is more uniform, and the measured gas yield is more accurate; under the condition that the sum of the mass of the solvent and the dispersant and the mass B of the silicon-based material are not less than 1, the silicon-based material with proper content of the slurry is more suitable in gas yield, and the silicon-based materials with different coating integrality can be better distinguished.

In one possible implementation, the pH of the slurry is 8-9. The environment in the slurry is alkalescent, and in the slurry, the reaction between the bare silicon, hydroxyl and water of the silicon-based material is more facilitated, so that the volume of the generated gas is more obvious.

In one possible implementation, the silicon-based material includes a cladding layer and an inner core, the cladding layer cladding at least a portion of the inner core, the material of the inner core containing elemental silicon. Thus, the coating integrity of the coating layer on the inner core can be tested by a test method to determine whether the coating integrity meets the requirement.

In one possible implementation, the silicon-based material includes at least one of a silicon-carbon composite or a silicon-oxygen composite. The silicon-carbon composite material and the silicon-oxygen composite material have wider application, and the testing method of the embodiment can be applied to the two materials.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a testing method according to an embodiment of the application;

FIG. 2 is a schematic diagram of a testing method according to an embodiment of the application.

Detailed Description

Embodiments of a method for testing the coating integrity of a silicon-based material of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The development of battery technology requires consideration of various design factors such as capacity, energy density, cycle life, reliability, and the like. The performance of the silicon-based material as an active material is critical to the performance of the battery. In order to improve the performance of the silicon-based material, a coating modification method is an important means for improving the performance of the silicon-based material. For cladding modified silicon-based materials, cladding integrity is an important parameter in the performance of the silicon-based material. Under the condition of lower coating integrity, bubbles can be continuously generated in the slurry after the silicon-based material is prepared into the slurry, and the coating effect of the slurry is affected, such as pits and the like, which is not only beneficial to improving the quality of the preparation process, but also is beneficial to improving the safety in the production process.

In order to improve the quality of the preparation process, the production safety and the performance of the prepared battery in the production process, the coating integrity of the silicon-based material is an important step. In a method for testing the coating integrity of a silicon-based material, a Scanning Electron Microscope (SEM) or a Transmission Electron Microscope (TEM) is adopted to observe the morphology of the silicon-based material, and the method can visually characterize the thickness of a coating layer and the coating integrity to a certain extent. However, in this test method, only a part of the silicon-based material, for example, only one or several particles or only a part of the positions of the particles, can be observed, that is, the number of samples that can be tested by the test method is small, the detection efficiency is low, and it is difficult to be represented. In addition, SEM and TEM equipment is expensive and difficult to adapt for large scale applications.

In another test method, the coating integrity of silicon-based materials is tested using X-ray photoelectron spectroscopy (XPS). In the test method, peak fitting can be performed on the curve of the binding energy, and the coating integrity is calculated through a corresponding formula. Although the detection sensitivity of the sample surface of the test method is high, quantitative analysis can be performed, the thickness of a signal source is limited, and larger errors are easily caused; the detection method has low detection efficiency and high requirements on equipment.

In yet another test method, the coating integrity in the silicon-based material is tested by chemical reaction etching in combination with inert atmosphere heat treatment. In the test method, an acidic or alkaline solvent is required to etch the silicon-based material, and an acid-base etchant has a certain use risk; and the heat treatment requires higher energy consumption, the operation complexity is higher, and a certain high-temperature risk exists. Therefore, how to provide a method for testing the coating integrity of a silicon-based material, so as to test the coating integrity of the silicon-based material more simply and accurately is a technical problem to be solved.

In view of the above, the embodiment of the application provides a method for testing the coating integrity of a silicon-based material. In the test method, the silicon-based material is prepared into slurry, and the coating integrity of the silicon-based material is determined by testing the gas yield of the slurry. The test method has low requirements on equipment, is simple and convenient to operate, has higher accuracy, and can simply and accurately test the coating integrity of the silicon-based material.

FIG. 1 is a flow chart of a method for testing the coating integrity of a silicon-based material according to an embodiment of the application. FIG. 2 is a schematic diagram of a testing method according to an embodiment of the application. As shown in connection with fig. 1 and 2, the test method 100 includes the following steps.

Step 110, mixing the silicon-based material with a solvent to obtain a slurry.

The silicon-based material is a solid material. For example, the silicon-based material is a powdery material.

And mixing the silicon-based material with a solvent to obtain slurry containing the silicon-based material. In the case where the coating integrity of the silicon-based material is less than 100%, bare silicon is present on the surface of the silicon-based material. In the slurry environment, the bare silicon reacts with water to produce gas.

The reaction formula for the reaction of silicon with water is as follows: si+2OH ^- +H ₂ O→SiO ₃ ^2- +2H ₂ And ≡. Wherein a certain OH is present in the slurry ^- Thus, the above reaction can be produced.

And 120, placing the slurry in a closed container to obtain the gas yield of the slurry.

The closed container may be a sealed aluminum plastic film. For example, after the slurry is prepared, a certain mass of the slurry is sucked up by using a rubber head dropper and the sucked slurry is dripped into an aluminum plastic film bag, and then the aluminum plastic film bag is subjected to vacuum heat sealing to obtain a sealed aluminum plastic film containing the slurry.

The closed container can be made of other materials as long as the closed container does not react with the slurry. The shape of the sealed container may be rectangular parallelepiped, cylindrical, or other shapes, and embodiments of the present application include, but are not limited to, this.

The slurry is placed in a closed container, and gas generated after the silicon-based material reacts can not escape into the external environment, so that adverse effects caused by the generated gas (such as hydrogen) can be reduced; and then, the coating integrity of the silicon-based material is conveniently determined according to the gas production amount of the slurry in the closed container.

In step 130, the sealed container 21 with the slurry is immersed in the liquid, and the tension display device 22 is connected to one end of the sealed container 21.

In step 140, the gas production of the slurry is obtained according to the change of the tension displayed by the tension display device 22.

The closed vessel 21 is immersed in the liquid, meaning that the closed vessel 21 is completely in the liquid and the slurry in the closed vessel 21 is isolated from the liquid.

One end of the closed container 21 refers to an end of the closed container 21 facing away from the direction of gravity.

As one example, the tension display device 22 is a balance (e.g., analytical balance). In the use process, one end of the analytical balance is provided with a hook, and the closed container is connected with the analytical balance through the hook. The tension displayed by the analytical balance is the difference between the gravity of the closed container and the buoyancy received by the closed container.

In the embodiment of the present application, the tension display device 22 may be other devices, and the embodiment of the present application includes but is not limited to this.

The sealed container 21 containing the slurry is immersed in the liquid, and the sealed container 21 containing the slurry is subjected to the action of the buoyancy. Since the bare silicon of the silicon-based material in the slurry reacts with the water in the slurry to generate gas, the closed vessel 21 expands, and the buoyancy of the expanded closed vessel 21 changes, so that the tension displayed by the tension display device 22 changes. The change of the pulling force is equal to the change of the buoyancy, and the change of the buoyancy has a corresponding relation with the volume of the generated gas, so that the gas yield of the slurry can be obtained according to the change of the pulling force.

And 150, determining the coating integrity of the silicon-based material according to the gas yield of the slurry.

The coating integrity of the silicon-based material can reflect the condition of bare silicon on the surface of the silicon-based material. At a cladding integrity of 100%, the silicon in the silicon-based material is not bare, i.e., there is no bare silicon on the outer surface of the silicon-based material. With a coating integrity of less than 100%, bare silicon is present on the surface of the silicon-based material. The amount of exposed silicon in the silicon-based material varies with the coating integrity of the silicon-based material, and the volume of gas produced varies.

Compared with the method for testing the coating integrity of the silicon-based material by SEM, TEM, XPS, the testing method provided by the embodiment of the application does not need to rely on expensive and complex equipment, has low requirements on the equipment, and is simple and convenient to operate; in addition, the testing method provided by the embodiment of the application can test a large number of samples, and the test result has statistical representativeness, so that the accuracy is higher.

Compared with a test method of combining acid or alkaline reagent etching with inert atmosphere heat treatment, the embodiment of the application does not need to adopt a high-temperature vacuum tube furnace for heat treatment, reduces high-temperature risk, has small required energy consumption and is simple and convenient to operate; the embodiment of the application does not need to etch by an acidic or alkaline solvent, so that the use risk of the acidic or alkaline solvent can be reduced; in addition, the testing method of the embodiment of the application can dynamically monitor the gas production in different time, and compared with the unique value of the specific silicon content obtained by the heat treatment of the etching agent, the testing method of the embodiment of the application can realize dynamic monitoring, thereby having higher accuracy.

In the embodiment of the application, the amount of exposed silicon in the silicon-based material varies with the coating integrity. The bare silicon in the silicon-based material reacts in the slurry to produce a gas; the more bare silicon, the more readily gas is produced. The coating integrity of the silicon-based material can be determined by testing the amount of gas production of the silicon-based material in the slurry. The test method of the embodiment of the application has lower requirement on the test device and is simple and convenient to operate.

In some embodiments, the change in tension ΔF _{Tension force} The gas yield V with the slurry is as follows: ΔF (delta F) _{Tension force} ρgv, where ρ is the density of the liquid and g is the gravitational acceleration.

The gas yield of the slurry is the volume of gas produced by the slurry.

The buoyancy and the tension satisfy the following relation: ΔF (delta F) _{Floating device} =Δmg=ΔF _{Tension force} =pgv. Where Δm is the change in mass of the slurry.

In this embodiment, the amount of gas production may be calculated according to the change in the tensile force, so that the coating integrity of the silicon-based material may be determined according to the amount of gas production.

In some embodiments, the sealed container 21 with the slurry is immersed in the liquid, and a tension display device is connected to one end of the sealed container 21, including: the closed container 21 is fixed with a bearing device, and one end of the bearing device is connected with a tension display device 22.

The carrying means is for carrying the closed vessel 21. As an example, the closed container 21 is a sealed aluminum plastic film in a shape similar to a sheet, the bearing device is an iron block provided with a groove, one end of the bearing device is provided with a through hole, and a copper wire passes through the through hole to be connected with the tension display device 22. Specifically, one end of the copper wire is passed through the through hole, and the other end is screwed into a circular ring shape, and is hung on the Lari display device 22. Wherein, the copper wire can be a copper wire with the diameter of 1mm and the length of 18 cm.

In the case where the load bearing device is provided, the tension display device 22 displays a tension that is the difference between the total weight of the load bearing device and the closed container and the total buoyancy experienced by the load bearing device and the closed container.

Change in tension ΔF _{Tension force} The difference between the currently displayed tension and the initial tension. The initial tension can be measured as follows: after the bearing device bearing the closed container 21 is soaked into the liquid, the bearing device is shaken for several times to remove bubbles, and after the temperature in the liquid is stable, the numerical value displayed by the tension display device 22 is the initial tension.

In embodiments of the present application, the load bearing apparatus may be connected to the tension display apparatus 22 by other connectors besides copper wires, including but not limited to.

The airtight container 21 is fixed to the carrying device so that a connecting member may be provided at one end of the carrying device to connect one end of the carrying device to the tension display device. Therefore, the closed container is convenient to be connected with the tension display device through the bearing device, the influence of the connecting piece on the closed container can be reduced, and the risk of gas escaping from the closed container can be reduced.

In some embodiments, the carrier device comprises a carrier block and a clamping means for securing the closed container to the carrier block. Thus, the bearing block and the clamping tool can have simpler structures, and the operation is convenient to carry out.

As one example, the carrier block is an iron block and the clamping tool is a dovetail clamp. One end of the closed container and one end of the iron block are aligned and secured together by a dovetail clip, and then the carrier is connected to the tension display device 22 by a connector.

In some embodiments, the density of the liquid is less than the density of the closed vessel 21; optionally, the liquid comprises silicone oil.

The density of the liquid is less than the density of the containment vessel, thus facilitating immersion of the containment vessel in the liquid and thereby facilitating detection of the change in buoyancy by the tension display device 22. Under the condition that the liquid is silicone oil, the silicone oil can not react with the closed container 21 and the bearing device, so that the buoyancy change can be accurately monitored, and the gas production rate can be accurately detected.

In some embodiments, determining the cladding integrity of the silicon-based material based on the gas production of the slurry comprises: calculating the gas production rate of the slurry according to the gas production rate of the slurry; and determining the coating integrity of the silicon-based material according to the gas production rate and the gas production amount.

The gas production rate is the ratio of the volume of gas produced to the time the gas is produced. The faster the gas production rate, the more bare silicon.

The gas production rate can be expressed by the gas production per unit time or per unit mass of slurry at a particular time. For example, the gas production rate per unit mass of slurry within 24 hours or 48 hours can be expressed.

The gas production rate can reflect the change of the gas production in a plurality of time periods, and the dynamic monitoring of the gas production is facilitated by measuring the gas production rate; the coating integrity of the silicon-based material is determined by combining the gas production rate and the gas production rate, and can be evaluated by the gas production rate and the gas production rate, so that the coating integrity of the silicon-based material can be intuitively reflected, and the accuracy of the test method can be improved.

In some embodiments, determining the cladding integrity of the silicon-based material based on the gas production of the slurry comprises: and determining the coating integrity of the silicon-based material according to the gas yield of the slurry in 48 hours.

In other embodiments, the coating integrity of the silicon-based material may also be determined by 24 hours of gas production. In the case of 24 hours, the reaction between bare silicon and water is near complete or complete, and more accurate gas production can also be achieved.

In some embodiments, determining the cladding integrity of the silicon-based material based on the gas production of the slurry comprises: in the case that the gas yield is less than or equal to 0.05ml/g in 48 hours, the coating integrity of the silicon-based material is determined to be more than 99%.

In this way, little or no bare silicon is reflected in the silicon-based material, thereby facilitating determination that the coating integrity of the silicon-based material is close to 100%, so that the silicon-based material can be applied to actual production.

The coating integrity of the silicon-based material can be verified by a Transmission Electron Microscope (TEM), and is close to or 100% as determined by the TEM when the gas yield is less than or equal to 0.05ml/g in 48 hours.

In some embodiments, the gas production is gas production measured at a temperature T that satisfies: t is more than or equal to 40 ℃ and less than or equal to 55 ℃. For example, the temperature T is 40 ℃, 45 ℃, 50 ℃, 55 ℃ or any value within the above range.

Under the condition that the temperature T is not more than 55 ℃, the reaction intensity between the bare silicon and water in the silicon-based material is low, the generated gas amount is not too large, and the risk of air leakage caused by more expansion of the closed container due to too much or too fast generated gas and the like can be reduced; under the condition that the temperature T is not less than 40 ℃, the gas generation rate and the gas production rate are proper, and the gas production rate can be conveniently detected.

In some embodiments, the temperature T satisfies: t is more than or equal to 40 ℃ and less than or equal to 45 ℃. For example, T is 40 ℃, 42 ℃, 45 ℃ or any value within the above range.

In this embodiment, the temperature T satisfies the above range, the reaction between the bare silicon in the silicon-based material and water is not too severe, and the rate of gas generation and the gas production rate are suitable, so that the gas production rate can be detected conveniently.

Alternatively, the temperature T is 45 ℃. Under the condition that the temperature is 45 ℃, different silicon-based materials have obvious gas production after reacting with water, so that the coating integrity of the silicon-based materials can be reflected by the gas production accurately.

In some embodiments, the slurry further comprises a dispersant comprising sodium carboxymethyl cellulose and styrene butadiene rubber.

The silicon-based material can be mixed with water to prepare slurry, or can be mixed with water, sodium carboxymethyl cellulose and styrene butadiene rubber to prepare slurry.

The silicon-based material, water, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed to prepare slurry, and in the slurry, the volume of gas generated by bare silicon in the silicon-based material is obvious, so that the gas yield is easier to detect. In addition, the components of the slurry are closer to those of the cathode slurry prepared in actual production, and the actual gas production can be reflected better.

In the embodiment of the application, the slurry can be other dispersing agents, so long as the silicon-based material can be well dispersed in the solvent.

In some embodiments, the mass ratio a of sodium carboxymethyl cellulose to styrene butadiene rubber satisfies: a is more than or equal to 1:1 and less than or equal to 2:1. For example, a is 1,1.1,1.3,1.5,1.8,2 or any value within the above range.

Alternatively, A is 1, at which time the mass ratio of sodium carboxymethylcellulose to styrene-butadiene rubber is 1:1.

Thus, the silicon-based material can be dispersed in the slurry more uniformly.

In some embodiments, the sum C of the mass contents of sodium carboxymethylcellulose and styrene-butadiene rubber, based on the total mass of solvent and dispersant, satisfies: c is more than or equal to 2wt% and less than or equal to 3wt%. In this way, the silicon-based material can be better dispersed in the slurry.

For example, C may be 2wt%,2.4wt%,3wt%, or any value within the above range. Wherein, as an example, the mass content of sodium carboxymethyl cellulose in the solvent may be 1.3wt%, and the mass content of styrene-butadiene rubber in the solvent may be 1.3wt%, and C is 2.6wt%.

In some embodiments, the mass ratio B of the sum of the masses of solvent and dispersant to the mass of silicon-based material satisfies: b is more than or equal to 5 and less than or equal to 7:3. For example, B is 1,1.1,1.3,1.5,1.8,2,2.33,2.34 or any value within the above range.

Under the condition that the mass ratio B of the sum of the solvent and the dispersing agent to the silicon-based material is not more than 7:3, the silicon-based material can be uniformly distributed in the slurry, the reaction between silicon and water is more uniform, and the measured gas yield is more accurate; the sum of the mass of the solvent and the dispersant and the mass B of the silicon-based material is not less than 5:5, the slurry has more proper content of silicon-based materials, so that the gas yield is more proper, and the silicon-based materials with different coating integrality can be better distinguished.

In some embodiments, B satisfies: b is more than or equal to 5 and less than or equal to 6.5:3.5. For example, B is 1.7,1.8,2 or any value within the above range. For example, B is 65:35 and B is a value near 1.857.

In some embodiments, the pH of the slurry is 8 to 9. The environment in the slurry is alkalescent, and in the slurry, the reaction between the bare silicon, hydroxyl and water of the silicon-based material is more facilitated, so that hydrogen is generated.

In some embodiments, the silicon-based material includes a cladding layer that coats at least a portion of the core and an inner core that is of a material that contains elemental silicon. Thus, the coating integrity of the coating layer on the inner core can be tested by a test method to determine whether the coating integrity meets the requirement.

In some embodiments, the silicon-based material comprises at least one of a silicon-carbon composite or a silicon-oxygen composite. The silicon-carbon composite material and the silicon-oxygen composite material have wider application, and the testing method of the embodiment can be applied to the two materials.

Silicon carbon composites include a variety of types. For example, a silicon-carbon composite material with a core-shell structure is prepared by taking silicon as a core and compounding a carbon layer on the surface of silicon particles. For another example, the silicon-carbon composite material with a yolk shell structure uses silicon as a yolk, a carbon layer is used as an eggshell, a certain gap exists between the carbon shell and silicon particles, and a buffer space is reserved for the volume expansion of the silicon.

The silicon oxide composite material comprises silicon oxide/graphite composite material, silicon and silicon dioxide are used as raw materials, the silicon oxide is formed through disproportionation reaction under the high temperature condition, and a layer of carbon is deposited on the surface of the silicon oxide composite material by adopting a vacuum evaporation furnace to form the SiOx/C composite material.

Silicon-based composites in embodiments of the application include, but are not limited to, those described above, for example, composites that may also be used with silicon alloys.

Hereinafter, embodiments of the present application are described. The following examples are illustrative only and are not to be construed as limiting the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Examples (example)

Example 1

In example 1, test was conducted using an experiment 1, the experiment 1 being a silica composite material, the silica composite material being SiO/C, the mass content of carbon being 1.4% based on the total mass of the silica composite material. The specific test procedure is as follows.

(1) The experiment 1, the solvent and the dispersing agent were mixed at a mass ratio of 35:65 to prepare a slurry, wherein the dispersing agent was CMC and SBR at a mass ratio of 1:1. Wherein, in the mixed solution formed by the solvent and the dispersing agent, the mass content of CMC and the mass content of SBR are the same, and are both 1.3 weight percent, and the rest substances in the mixed solution are basically water.

(2) 10g of slurry is weighed for testing, the slurry is added into an aluminum plastic film bag, and the aluminum plastic film bag is vacuumized and heat-sealed.

(3) Shearing off the non-heat-sealed part of the aluminum plastic film bag by scissors, placing the aluminum plastic film bag on an iron block, aligning one ends of the aluminum plastic film bag and the iron block, and clamping the aluminum plastic film bag and the iron block by a dovetail clamp; one end of a copper wire with the diameter of 1mm and the length of 18cm is bound on an iron block, and the other end is twisted into a circle, so that the sample preparation is completed.

(4) Binding the other end of the copper wire on an analytical balance, wherein a hook is arranged on the analytical balance, and the other end of the copper wire is connected with the hook;

(5) The oil bath pot is filled with silicone oil, and the temperature of the oil bath pot is set to be 45 ℃; and transferring the sample to the upper part of the oil bath pot, shaking the sample back and forth and left and right for three times after the sample is completely soaked in the oil bath pot to remove bubbles, measuring initial readings displayed by an analytical balance under the condition that the sample is immersed in silicone oil after the temperature in the oil bath pot is stable, and measuring the readings of the analytical balance for a plurality of times at certain intervals so as to calculate the gas production.

Example 2

Example 2 differs from example 1 in that: example 2 was tested using experiment 2, experiment 2 being a different silicone composite from experiment 1, experiment 2 differing from experiment 1 in that: the carbon content of experiment 2 was higher than that of experiment 1. In experiment 2, the silica composite material was SiO/C, and the mass content of carbon was 2.9% based on the total mass of the silica composite material.

TABLE 1 test results for examples 1-2

The gas production per unit time can be calculated by the following formula: gas production per unit mass= (m 1-m 2)/(ρxm0 xk). Where m1 is the sample mass at 0h, m2 is the sample mass at the test time (e.g., 48 h), ρ is the density of the silicone oil, m0 is the slurry mass, and k is the solids content of the slurry.

Taking the gas production of 48 hours with the experiment number of 1 in example 1 as an example: gas production per unit mass= (113.41-103.21)/(0.9446 ×10.18×0.35) =3.03.

The test method is shown in combination with example 1 and example 2 with a clear differentiation for the different experimental products. In the same period, the gas production per unit mass in example 2 was smaller than that in example 1, thus reflecting that the coating integrity of experiment 2 in example 2 was greater than that of experiment 1.

The carbon content of the experiment product 2 is higher, the carbon content of the experiment product 1 is lower, and the coating of the experiment product 1 is easy to be incomplete, so that the gas yield of the experiment product 1 is more.

In examples 1-2, three tests were performed on each experimental product, and the gas production rate in each test was relatively close, which indicates that the test method has high repeatability and accurate test results.

Example 3

Example 3 differs from example 1 in that: example 3 the test was performed using experiment 3.

Example 4

Example 4 differs from example 1 in that: example 4 the test was performed using experiment 4.

Example 5

Example 5 differs from example 1 in that: example 5 the test was performed using experiment 5.

Example 6

Example 6 differs from example 1 in that: example 6 was tested using experiment 6.

In examples 3 to 6, the experimental products were all silica composite SiO/C, and the mass content of carbon was 3.2% based on the total mass of the silica composite. In examples 3-6, the carbon coating amount of the silicone composite was substantially the same, but the experimental products in examples 3-6 were provided by different suppliers, and thus the coating integrity of the silicone composite may be slightly different. In addition, the process for producing the silicone composite material in examples 3 to 6 is different from the process for producing the silicone composite material in examples 1 to 2, and the silicone composite material has a different carbon content.

Table 2 test results for examples 3-6

As shown in example 3, the mass of the sample was substantially unchanged over time, and the gas yield was 0. Therefore, the gas yield of the experiment product 3 in 48 hours is less than 0.05ml/g, the coating integrity is high, and the experiment product is suitable for being used in actual working conditions.

As shown in examples 3 to 6, experiment 3, experiment 6, experiment 4, and experiment 5 were sequentially performed in order of gas production from small to large, thereby obtaining: the different suppliers vary the level of carbon coated silicon-oxygen composites, although the carbon content is substantially the same, there are some differences in coating integrity. Therefore, the method of the embodiment of the application is also beneficial to screening of proper suppliers so as to screen materials with higher coating integrity. In addition, each experimental product is subjected to multiple tests, the repeatability of the result is high, and the gas yield measured by the test method is accurate, so that the coating integrity of the experimental product and whether the coating integrity is qualified can be accurately determined.

Example 7

Example 7 differs from example 1 in that: the solvents are different.

Examples 8 to 10

Examples 8-10 differ from example 1 in that: the mass ratio of solvent to silicon-based material is different.

Example 11

Example 11 differs from example 1 in that: the mass ratio of CMC to SBR in the solvent is different.

In examples 7 to 11, the test article used was test article 1.

In table 3, a is the mass ratio of CMC to SBR, and B is the sum of the mass of solvent and dispersant, to the mass ratio of silicon-based material.

TABLE 3 test results for examples 7-11

As shown in examples 7 and 11, the gas production reaction was more evident by adding CMC and SBR in addition to water alone, the amount of gas produced was more evident, and the determination of the coating integrity was more accurate. Compared with water, the silicon-based material has better wettability in the mixed solution of CMC and SBR, and the contact between silicon and water is more sufficient, thereby being beneficial to the gas production reaction. In addition, the pH is in the range of 8-9, and the slurry has more hydroxide radicals, so that the gas production reaction is facilitated.

In combination with examples 8-10, the mass ratio of the sum of the solvent and the dispersant to the silicon-based material is 6.5:3.5, and the silicon-based material has proper mass content in the slurry, so that the distribution of the silicon-based material in the slurry is more uniform, and the measured gas yield is more accurate.

As shown in the combination of examples 8 and 11, the mass ratio of CMC to SBR is in the range of 1:1-2:1, which is beneficial to better dissolution of silicon-based materials in slurry.

Examples 12 to 13

Example 12 and example 13 provide two different experimental articles 12 and 13. Examples 12 and 13 provide data on the volume of gas produced by the slurry at different temperatures. The difference between the experiment 12 and the experiment 13 is that: silicone composites are materials supplied by different suppliers. Wherein different suppliers have different coating process levels, which may result in different coating integrity. In experiment 12, the silica composite was SiO/C, and the mass content of carbon was 0.8% based on the total mass of the silica composite. In experiment 13, the silica composite material was SiO/C, and the mass content of carbon was 0.8% based on the total mass of the silica composite material.

TABLE 4 test results for examples 12-13

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As shown in examples 12 to 13, the amount of gas produced gradually increased with increasing temperature, and the sample in example 12 was leaked at 60 ℃. In addition, by combining the data, the temperature is set to be 40-55 ℃, and further, the temperature is set to be 45 ℃, so that the volume of generated gas can be detected reasonably and accurately.

Examples 14 to 15

In examples 14-15, data are presented for testing silicon carbon composites. In examples 14-15, experiment 14 and experiment 15 were different silicon carbon materials. The silicon-carbon materials of examples 14 to 15 were prepared by forming a main structure with carbon as a dispersion matrix and silicon as an active material, and coating the outer surface of the main structure with a carbon coating layer. In experiment 14, the mass content of the carbon-coated layer was 3.2% based on the total mass of the silicon-carbon composite material. In experiment 15, the mass content of the carbon-coated layer was 4.6% based on the total mass of the silicon-carbon composite material.

TABLE 5 test results for examples 14-15

The test methods of the embodiments of the present application, as shown in examples 14-15 and examples 1-6, can be applied to a variety of silicon-based materials.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. The method for testing the coating integrity of the silicon-based material is characterized by comprising the following steps of:

mixing the silicon-based material with a solvent to obtain slurry, wherein the solvent comprises water;

placing the slurry in a closed container;

immersing the closed container with the slurry in liquid, wherein one end of the closed container is connected with a tension display device;

determining the gas production amount of the slurry according to the change of the tension displayed by the tension display device;

and determining the coating integrity of the silicon-based material according to the gas yield of the slurry.

2. The method according to claim 1, wherein the change in tension Δf _{Tension force} And the gas yield V of the slurry is as follows: ΔF (delta F) _{Tension force} ρgv, where ρ is the density of the liquid and g is the gravitational acceleration.

3. The test method according to claim 1, wherein the closed container in which the slurry is placed is immersed in a liquid, and a tension display device is connected to one end of the closed container, comprising:

and fixing the closed container with the slurry with a bearing device, wherein one end of the bearing device is connected with a tension display device.

4. A test method according to claim 3, wherein the carrier means comprises a carrier block and clamping means for securing the closed container to the carrier block.

5. The test method of claim 1, wherein the density of the liquid is less than the density of the closed container.

6. The method of testing according to claim 1, wherein the liquid comprises silicone oil.

7. The method of testing of claim 1, wherein determining the coating integrity of the silicon-based material based on the gas production of the slurry comprises:

calculating the gas production rate of the slurry according to the gas production rate of the slurry;

and determining the coating integrity of the silicon-based material according to the gas production rate and the gas production rate.

8. The method of testing of claim 1, wherein determining the coating integrity of the silicon-based material based on the gas production of the slurry comprises:

and determining the coating integrity of the silicon-based material according to the gas yield of the slurry in 48 hours.

9. The test method according to claim 1, wherein the gas production is a gas production measured at a temperature T that satisfies: t is more than or equal to 40 ℃ and less than or equal to 55 ℃.

10. The test method according to claim 9, wherein the temperature T satisfies: t is more than or equal to 40 ℃ and less than or equal to 45 ℃.

11. The test method of claim 1, wherein the slurry further comprises a dispersant comprising sodium carboxymethyl cellulose and styrene-butadiene rubber.

12. The method according to claim 11, wherein the mass ratio a of the sodium carboxymethyl cellulose and the styrene-butadiene rubber satisfies: a is more than or equal to 1:1 and less than or equal to 2:1.

13. The test method according to claim 11, wherein the sum C of the mass contents of the sodium carboxymethyl cellulose and the styrene-butadiene rubber, based on the total mass of the solvent and the dispersant, satisfies: c is more than or equal to 2wt% and less than or equal to 3wt%.

14. The method according to claim 11, wherein the mass ratio B of the sum of the mass of the solvent and the dispersant to the silicon-based material satisfies: b is more than or equal to 5 and less than or equal to 7:3.

15. The method according to claim 14, wherein the mass ratio B of the sum of the mass of the solvent and the dispersant to the silicon-based material satisfies: b is more than or equal to 5 and less than or equal to 6.5:3.5.

16. The method according to claim 1, wherein the slurry has a PH of 8 to 9.

17. The method of any one of claims 1-16, wherein the silicon-based material comprises a cladding layer and a core, the cladding layer cladding at least a portion of the core, the core material comprising elemental silicon.

18. The method of testing of claim 1, wherein the silicon-based material comprises: at least one of a silicon carbon composite or a silicon oxygen composite.