Negative electrode material, method for manufacturing the same, and battery

Abstract

This application provides a negative electrode material, a method for manufacturing the same, and a battery, relating to the battery technology. The negative electrode material of this application comprises a silicone core and a coating layer that covers at least part of the surface of the silicone core, and the negative electrode material satisfies the requirement that the B:A ratio is 1 to 100, where A is the mass ratio of oxygen and lithium in the negative electrode material, and B is the atomic ratio of oxygen and silicone obtained by testing the negative electrode material by an X-ray photoelectron spectrometer. The method for manufacturing this negative electrode material includes reacting a carbon-coated pre-lithium-silicone material with an oxidizing agent to obtain the negative electrode material. The B:A ratio in the negative electrode material of this application actually represents the degree of oxidation treatment of the surface layer of the negative electrode material, and the larger the ratio, the higher the degree of surface oxidation, which reduces the reaction between the silicone core and external moisture, reduces the risk of hydrolysis and gas generation, and thereby significantly improves the water resistance of the negative electrode material, improving the initial efficiency and cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and particularly to a negative electrode material, its manufacturing method, and a battery.

Background Art

[0002] Silicone-based negative electrode materials are one of the most promising materials for next-generation lithium-ion battery applications. However, the main reason restricting the widespread application of silicone-based negative electrode materials is that they undergo a huge volume change during the charge and discharge process, that is, the expansion rate is too large. Although the silicone-based negative electrode material has a smaller volume expansion change than a pure silicone negative electrode material, its first efficiency is low. To solve this problem, the pre-lithiation technology is always used to pretreat the silicone-based negative electrode material to form lithium silicate, which not only increases the first efficiency but also causes the solution to rise and exhibit alkalinity due to the hydrolysis of lithium silicate salt. As a result, the pre-lithiated silicone-based negative electrode material has relatively poor processing performance and poor slurry stability during the slurry manufacturing process, bringing inconvenience to production and making large-scale production and use impossible.

[0003] Therefore, how to solve the processing problems of silicone-based negative electrode materials during the slurry manufacturing process is the key to their widespread application.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The objective of this application is to effectively reduce the external dissolution of lithium silicate in the pre-lithiated silicone-based material, reduce the generation of a relatively high pH that destroys the stability of the aqueous slurry, reduce the contact between silicone particles and water in the negative electrode material, reduce the risk of gas generation, and improve the safety performance of the negative electrode material in the battery by controlling the relationship between the degree of pre-lithiation of the negative electrode material and the degree of oxidation of surface-active silicone, and to provide a negative electrode material, its manufacturing method, and a battery. [Means for solving the problem]

[0005] The proposed technology of this application is as follows:

[0006] According to a first aspect, the present application provides a negative electrode material comprising a silicone core and a coating layer that at least a portion of covers the surface of the silicone core. The silicone-based core contains silicone and lithium silicate, and the negative electrode material satisfies the condition that the ratio of B:A is 1 to 100, where A is the mass ratio of oxygen and lithium in the negative electrode material, and B is the atomic ratio of oxygen and silicone obtained by testing the negative electrode material with an X-ray photoelectron spectrometer.

[0007] According to a second aspect, the present application provides a negative electrode material comprising a silicone core and a coating layer that at least partially covers the surface of the silicone core, wherein the silicone core contains silicone and lithium silicate, and the A value of the negative electrode material is 1 to 20, where A is the mass ratio of oxygen to lithium in the negative electrode material.

[0008] According to a third aspect, the present application provides a negative electrode material comprising a silicone core and a coating layer that at least partially covers the surface of the silicone core, wherein the silicone core contains silicone and lithium silicate, and the B value of the negative electrode material is 1 to 100, where B is the atomic ratio of oxygen to silicon elements obtained by testing the negative electrode material with an X-ray photoelectron spectrometer.

[0009] The four In one aspect, the present application further provides a method for manufacturing a negative electrode material as described in the first aspect, which method is The method includes reacting a pre-lithium-containing silicone material having a coating layer with an oxidizing agent to obtain the negative electrode material.

[0010] The Five In one aspect, the present application provides a battery which includes the negative electrode material described in the first aspect. [Effects of the Invention]

[0011] The beneficial effects of this application are as follows:

[0012] The mass ratio A value of oxygen and lithium in the negative electrode material of this application reflects the degree of pre-lithification. A lower A value indicates a higher lithium content in the negative electrode material, a higher degree of pre-lithification, and a greater likelihood of hydrolysis reactions, which increases the pH value of the negative electrode slurry and reduces the processing performance of the negative electrode slurry. The atomic ratio of oxygen and silicon elements on the surface of the negative electrode material was tested using an X-ray photoelectron spectrometer. number The ratio can be obtained, and assuming the silicon atoms remain unchanged, a larger B value indicates a greater number of oxygen atoms on the surface of the anode material, meaning that oxidation reactions occur on the surface and the degree of oxidation increases. The B:A ratio actually represents the relationship between the degree of pre-lithification of the anode material and the degree of oxidation of the surface-active silicone. When the ratio satisfies a certain range, the processing performance of the anode material can be improved. Specifically, the surface-active silicone of the anode material undergoes some oxidation, which can reduce the reaction between the core material and external moisture, decrease the dissolution of lithium silicate into the anode material, increase the pH value in the aqueous anode slurry, and break down the adhesive. On the other hand, by reducing contact between the active silicone and water and reducing the risk of gas generation, the water resistance of the anode material can also be significantly improved.

[0013] The present invention relates to a method for manufacturing a negative electrode material, which improves the oxygen content of the surface layer of the negative electrode material by promoting an in-situ oxidation reaction on the surface of a pre-lithium-containing silicone material using an oxidizing agent, thereby reducing the reaction between the core material and external water and improving the processing performance of the negative electrode material. The present invention relates to a manufacturing method that is simple in process, uses readily available raw materials, and can be used for large-scale production.

[0014] The negative electrode plate of this application employs the above-mentioned negative electrode material. The surface-oxidized negative electrode material significantly delays and suppresses the hydrolysis reaction between the pre-lithium-silicone material inside the coating layer and external moisture, thereby further stabilizing the negative electrode plate. [Brief explanation of the drawing]

[0015] To more clearly explain the technical concepts of the embodiments of this application, the following is a brief introduction to the drawings that may be used in the embodiments. It should be understood that these drawings only show some of the embodiments of this application and should not be considered as limitations on the scope of this application. [Figure 1] This diagram shows the viscosity change of the negative electrode slurry prepared from the negative electrode material of Example 1 of this application, after 1 day and 7 days of standing. [Modes for carrying out the invention]

[0016] Terms used in this specification: "Made from..." is synonymous with "inclusion." The terms "inclusion," "includes," "possesses," "contains," or any other variations used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, product, or apparatus containing the elements described is not necessarily limited to those elements and may include other elements not explicitly listed or elements specific to such composition, step, method, product, or apparatus. The conjunction "consists of..." excludes any elements, steps, or components not specifically mentioned.

[0017] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range limited by a set of preferred upper and lower limits, this should be understood as specifically disclosing all ranges formed by any combination of any upper limit or preferred value and any lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when the range "1 to 5" is disclosed, the described range should be understood to include the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", and so on. When a numerical range is described herein, unless otherwise specified, this range is intended to include its end value and all integers and fractions within that range.

[0018] In these examples, unless otherwise specified, all the parts and percentages are based on mass.

[0019] "Parts by mass" is a basic metric unit representing the mass ratio relationship of multiple components. One part may represent any unit mass, for example, it may be represented as 1 g, or it may be represented as 2.689 g, etc. If the parts by mass of component A is a parts and the parts by mass of component B is b parts, it represents the ratio a:b of the mass of component A to the mass of component B. Or, it represents that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiple factor). It must not be misunderstood that, unlike the number of parts by mass, the sum of the parts by mass of all components is not limited to 100.

[0020] "And / or" is used to indicate that one or both of the described situations may occur. For example, A and / or B includes (A and B) and (A or B).

[0021] The silicone-based anode material containing lithium silicate obtained by prelithiation technology can improve the initial efficiency. However, due to the hydrolysis of lithium silicate among them, after preparing the electrode slurry, it is easy to increase the alkalinity of the slurry. The adhesive in the slurry fails due to the alkaline environment, the stability of the slurry becomes poor, and furthermore, the processing performance of the anode material becomes poor. In addition, the nanosilicon in the silicone-based anode material has very high reaction activity, reacts with water to generate hydrogen gas, and as the alkalinity of the slurry is enhanced, the reaction rate becomes faster. After the lithium silicate in the silicone-based anode material is hydrolyzed, the nanosilicon embedded in the lithium silicate is likely to be exposed, reacts with water to generate gas, further affects the coating process of the anode slurry, and affects the performance of the anode plate.

[0022] Currently, the solution to the processing problems of pre-lithium-containing silicone anode materials or amorphous silicone anode materials involves applying a secondary coating. By using different types of coating layers, the internal material is not exposed to aqueous solutions when producing aqueous slurries, thereby delaying gas generation during the material processing process. However, most conventional secondary coating layers consist mainly of inorganic salts or organic polymer layers, and most of them can only delay gas generation in the slurry. Therefore, it is necessary to improve the coating layer on the surface of the anode material to reduce the dissolution of lithium silicate from inside the silicone material to the outside, and to reduce the contact reaction between the internal nanosilicone and water, thereby further improving the processing performance of the anode material. Even with coating, current silicone anode materials still have certain problems with processing performance.

[0023] A first aspect of this application provides a negative electrode material comprising a silicone core and a coating layer that covers the surface of the silicone core in at least a portion thereof.

[0024] The negative electrode material of this application contains silicone and lithium silicate. More preferably, the lithium silicate contains at least one of Li2SiO3, Li2Si2O5, and Li4SiO4.

[0025] It should be explained that the silicone core of the negative electrode material in this application is a pre-lithified silicone material, specifically a pre-lithified silicone oxygen material, which can guarantee that the negative electrode material has a relatively high initial Coulomb efficiency. Silicone oxygen materials generally have the general formula SiO xIt may also be represented by 0 < x ≦ 2. After prelithiation of the silicone oxygen material to form a silicone-based core, the active oxygen in the material reacts with exogenous lithium to generate a lithium silicate, which may be at least one of, for example, Li2SiO3, Li2Si2O5, and Li4SiO4. On the other hand, the lithium silicate can improve the first efficiency of the anode material by alleviating the active lithium consumed in the process of forming the SEI film in the lithium-ion battery. At the same time, the coating layer on the surface of the silicone-based core can play a certain blocking role against moisture, reduce the chemical reaction between the silicone-based core and water, and improve the processing performance of the anode material.

[0026] The anode material of the present application satisfies that the ratio of B:A is 1 to 100, and may be, for example, 1, 5, 10, 20, 30, 50, 80, 100, or any value between 1 and 100. Here, A is the mass ratio of the oxygen element to the lithium element in the anode material, and B is the atomic ratio of the oxygen element to the silicon element obtained by testing the anode material with an X-ray photoelectron spectrometer.

[0027] In some embodiments of the present application, the A value of the anode material is 1 to 20, and may be, for example, 1, 3, 5, 8, 10, 12, 15, 18, 20, or any value between 1 and 20.

[0028] The A value mainly reflects the content relationship between all the oxygen elements and lithium elements in the anode material of the present application. The lower the A value, the higher the Li content, the higher the degree of prelithiation, and the worse the processing performance of the anode slurry. Therefore, reducing the contact between the silicone-based core and water is the key to improving the processing performance of the slurry. The lithium element in the anode material of the present application mainly comes from Li2O, Li x Si, Li2SiO3, Li2Si2O5, Li4SiO4, etc., and the oxygen element mainly comes from SiO, Li2SiO3, Li2Si2O5, Li4SiO4, etc. of the silicone-based core.

[0029] In some embodiments of this application, the B value of the negative electrode material is 1 to 100, and may be, for example, 1, 5, 10, 20, 30, 50, 70, 90, 100, or any value between 1 and 100.

[0030] To understand this, X-ray photoelectron spectroscopy is a surface analysis technique that can generally test areas with a surface thickness of ≤10 nm of a material. Therefore, the B value obtained from the test mainly represents the atoms of O and Si on the surface of the negative electrode material. number This reflects the ratio. To improve the processing performance of the anode material, it is necessary to reduce contact between lithium silicate, activated silicone, and external water in the silicone-based core. A larger B value indicates a higher degree of oxidation of the activated silicone on the surface of the anode material.

[0031] The B:A ratio actually represents the relationship between the degree of pre-lithification in the anode material and the degree of oxidation of the surface-active silicone. By controlling the B:A value, that is, by simultaneously achieving a certain degree of pre-lithification and a certain degree of oxidation of the surface-active silicone, the anode material of this application can guarantee a relatively high initial efficiency, effectively reduce the active silicone content on the surface of the anode material, reduce contact between the silicone core and external water, and further improve the processing performance of the anode material.

[0032] In some embodiments of this application, the negative electrode material satisfies B>A>1, and the B:A ratio is 2 to 30, which may be, for example, 2, 5, 10, 15, 20, 25, 30, or any value between 2 and 30.

[0033] To make it easier to understand, when the B:A ratio is between 2 and 30, both the degree of pre-lithiation in the anode material and the degree of oxidation of the surface-active silicone are appropriate. This not only does not affect the electrochemical performance of the anode material, but it is also possible to improve the processing performance of the anode material by utilizing a relatively high degree of oxidation to block contact between external substances and the silicone core. For example, if the degree of oxidation of the surface-active silicone of the anode material is constant, and the degree of pre-lithiation is too high, the A value will be too small and the B:A ratio will be too large. However, an excessively high degree of pre-lithiation clearly affects processing performance. Alternatively, if the degree of pre-lithiation is constant and the degree of oxidation of the surface-active silicone is too high, the active silicone content in the anode material will be low. This results in a low initial efficiency of the silicone-based material and is likely to affect the electrochemical performance of the anode material.

[0034] In some embodiments of this application, the atoms of oxygen and lithium obtained by testing the negative electrode material with an X-ray photoelectron spectrometer. number The ratio is C, where the C value is between 1 and 10, and may be, for example, 1, 2, 3, 5, 7, 10, or any value between 1 and 10.

[0035] The surface of the pre-lithiumized silicone core may contain not only activated silicone but also residual Li metal from the pre-lithiumization process, which reacts with external water and affects the processing performance of the anode material. Therefore, the C value is used to determine the atomic ratio of oxygen and lithium elements on the surface of the anode material. number The ratio is representative of the fact that a larger C value indicates a higher degree of surface oxidation of the negative electrode material and less residual Li metal.

[0036] In some embodiments of this application, the negative electrode material satisfies the requirement that the C:A ratio is between 0.5 and 10, and may be any value between 0.5 and 10, for example, 0.5, 1, 2, 3, 5, 7, 9, 10, or any other value between 0.5 and 10.

[0037] The C:A ratio actually represents the relationship between the degree of pre-lithification of the anode material and the degree of oxidation of residual lithium on the surface. When the degree of pre-lithification is determined, if the C:A value is too high, it explains that the lithium metal remaining on the surface has been completely oxidized, and furthermore, it can significantly reduce the influence of residual lithium metal on the processing performance of the anode material. However, if the C:A value is too high, it explains that there are too many oxygen atoms on the surface of the material, and if there are too few lithium atoms, it affects the electrochemical performance of the anode material.

[0038] In some embodiments of this application, the coating layer contains a carbon material. The carbon material coating not only prevents contact between the silicone core and external water, but also improves the conductivity of the negative electrode material.

[0039] In some embodiments of this application, the negative electrode material contains an oxide, the oxide being at least partially present on the surface of the silicone core. In some other embodiments, the oxide forms an oxide layer, the oxide being at least partially present on the surface of the silicone core of the negative electrode material. More preferably, the oxide includes a silicone oxide, the general formula of which is SiO x And here, 0 <x≦2である。

[0040] As can be understood, because the carbon material coating layer on the surface of the negative electrode material is difficult to completely cover the silicone core, if a portion of the silicone core is exposed and in contact with the outside, after the negative electrode material is oxidized, the active silicone on the surface of the exposed silicone core is oxidized to silicone oxide and is prone to forming an oxide layer. At least some of the oxide layer is located on the surface of the silicone core of the negative electrode material, and strictly speaking, some of the formed oxide layer is sandwiched between the silicone core and the carbon coating layer, while other parts of the oxide layer are directly exposed to the air. In some special cases, in addition to silicone oxide, the oxide layer formed by the oxidation treatment may also form lithium-containing oxides due to the Li metal remaining on the surface of the silicone core.

[0041] In some embodiments of this application, the pH value of the negative electrode material is 8 to 11.5, and may be any value between 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, or 8 to 11.5.

[0042] As can be understood, the presence of oxides on the surface of the silicone core of this application results in a certain degree of oxidation, reducing contact between lithium silicate and water in the silicone core and further lowering the pH value of the negative electrode material. On the other hand, if the negative electrode material has a relatively high alkalinity, it destroys the structure of the polymer adhesive in the slurry, causing its crosslinking to fail and further reducing the peeling force of the electrode plate. If the alkalinity is relatively low, it is advantageous to slow down the rate at which the aqueous solvent reacts with the lithium silicate and activated silicone inside the negative electrode material to generate gas, further improving the stability of the electrode plate.

[0043] In some embodiments of this application, the viscosity change of the negative electrode slurry containing the negative electrode material before and after 168 hours of standing is ≤ 3000 mPa·s.

[0044] It should be explained that when manufacturing a negative electrode slurry using the negative electrode material of this application, the negative electrode material has, in addition to the silicone core, an outermost coating layer and an oxide formed by the oxidation of the surface of the silicone core. The two-layer protection of the oxide and the outermost coating layer greatly delays and suppresses the hydrolysis reaction of lithium silicate inside the negative electrode material, preventing excessive consumption of water in the negative electrode slurry. As a result, the negative electrode slurry has relatively good stability during the standing process, and even after being left for 7 days, the viscosity change of the slurry is relatively small and does not exceed 3000 mPa·s.

[0045] A second aspect of this application further provides a method for manufacturing the negative electrode material, which includes reacting a prelithified silicone-based material having a coating layer with an oxidizing agent to obtain the negative electrode material.

[0046] In some embodiments of this application, the oxidizing agent includes at least one of oxygen gas, air, hypochlorous acid, hypochlorite, salts containing ferrous ions, salts containing copper ions, and hydrogen peroxide. Selected oxidizing agents can oxidize the surface layer of the pre-lithiumized silicone material, improve the degree of oxidation, and achieve a desired blend ratio of the three elements lithium, oxygen, and silicon.

[0047] In some embodiments of this application, the reaction time between the prelithified silicone material having a coating layer and the oxidizing agent is 1h to 12h, and may be any value between 1h, 2h, 3h, 5h, 8h, 10h, 12h, or 1h to 12h.

[0048] In some embodiments of this application, the mass ratio of the pre-lithified silicone material having a coating layer to the oxidizing agent is 100:1.5 to 5, and may be any value between 100:1.5, 100:2, 100:3, 100:4, 100:4.5, 100:5, or 100:1.5 to 5.

[0049] In some embodiments of this application, after the reaction with the oxidizing agent is completed, the product after the reaction is completed is heat-treated to obtain a negative electrode material. Furthermore, the heat treatment includes raising the temperature to 400°C to 800°C (for example, 400°C, 500°C, 600°C, 700°C, 800°C or any value between 400°C and 800°C) in an inert gas atmosphere and holding the temperature for 4h to 24h (for example, 4h, 8h, 12h, 15h, 20h, 24h or any value between 4h and 24h).

[0050] To make it easier to understand, by heat-treating a pre-lithium-containing silicone material having a coating layer after the oxidation reaction is complete, the coating effect of the surface coating layer of the silicone material can be further enhanced, and the strength of the negative electrode material can be improved.

[0051] In some embodiments of this application, a method for producing a pre-lithium-containing silicone material having a coating layer includes mixing a silicone material with a carbon source, sintering the mixture to obtain a carbon-coated silicone material, and pre-lithiumizing the carbon-coated silicone material and the lithium source to obtain a pre-lithium-containing silicone material having a coating layer.

[0052] In some embodiments of this application, the application further provides a method for producing a prelithified silicone material having another coating layer, which includes reacting a silicone material with a lithium source to obtain a prelithified silicone material, then mixing the prelithified silicone material with a carbon source and sintering it to obtain a prelithified silicone material having a coating layer.

[0053] In some preferred embodiments, the carbon source includes at least one of alkanes, alkenes, alkynes, natural gas, toluene, glucose, sucrose, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyvinylidene fluoride, and coal tar.

[0054] It should be explained that when silicone-based materials are selected and manufactured, silicone oxygen materials, such as silicon monoxide materials, are always chosen, and when a coating layer is manufactured using a carbon source, a gas-phase coating process, a liquid-phase coating process, or a solid-phase coating process can be selected. Here, the gas-phase coating process always involves chemically vapor-depositing a gas such as methane or acetylene to obtain a carbon coating layer, while the liquid-phase coating process and the solid-phase coating process select non-gasic substances such as glucose or sucrose as the carbon source.

[0055] In some embodiments, if the mass of the carbon-coated silicon monoxide material is taken as 100%, the mass fraction of carbon is 2% to 8%, and may be any value between 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 2% to 8%.

[0056] In some preferred embodiments, when pre-lithiation is performed, the selected lithium source includes at least one of lithium hydride, LiOH, metallic lithium, and lithium-containing organic matter.

[0057] In some embodiments, the mass ratio of the carbon-coated silicon monoxide material to the lithium source is 100:11 to 36, and may be, for example, 100:11, 100:15, 100:20, 100:25, 100:30, 100:36, or any value between 100:11 and 36.

[0058] In some preferred embodiments, the pre-lithiation treatment includes raising the temperature to 500°C to 1000°C (for example, 500°C, 600°C, 800°C, 900°C, 1000°C, or any value between 500°C and 1000°C) in an inert gas atmosphere and holding the temperature for 2 hours to 10 hours (for example, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or any value between 2 hours and 10 hours).

[0059] In specific embodiments, the manufacturing method of this application is: The method involves mixing a silicone-based material with a carbon source, sintering the mixture to obtain a carbon-coated silicone-based material, and then pre-lithifying the carbon-coated silicone-based material with a lithium source to obtain a pre-lithified silicone-based material having a coating layer, wherein the mass ratio of the carbon-coated silicon monoxide material to the lithium source is 100:11 to 36, and the pre-lithification treatment includes raising the temperature to 500°C to 1000°C under an inert gas atmosphere. A negative electrode material is obtained by reacting a prelithium-containing silicone material having a coating layer with an oxidizing agent and then heat-treating the reaction, wherein the oxidizing agent comprises at least one of oxygen gas, air, hypochlorous acid, hypochlorite, salts containing trivalent iron ions, salts containing copper ions, and hydrogen peroxide, the reaction time between the prelithium-containing silicone material having a coating layer and the oxidizing agent is 1 h to 12 h, the mass ratio of the prelithium-containing silicone material having a coating layer to the oxidizing agent is 100:1.5 to 5, and the heat treatment includes raising the temperature to 400°C to 800°C under an inert gas atmosphere and maintaining the temperature for 4 h to 24 h.

[0060] In the above manufacturing method, by promoting an in-situ oxidation reaction on the surface of the pre-lithium-containing silicone material using an oxidizing agent, the oxygen element content on the surface of the anode material can be increased, the reaction between the core material and external water can be reduced, and the processing performance of the anode material can be improved. The manufacturing method of this application is simple in process, the raw materials are readily available, and it can be used for large-scale production.

[0061] A third aspect of this application provides a negative electrode plate comprising the negative electrode material described above.

[0062] In some embodiments of this application, a method for manufacturing a negative electrode plate includes applying a negative electrode slurry containing a negative electrode material onto a negative electrode current collector, rolling it, and drying it to obtain a negative electrode plate.

[0063] Here, the negative electrode slurry can be manufactured according to the slurry manufacturing process for commonly used batteries, and the negative electrode plate can similarly be manufactured according to the normal manufacturing process for battery electrode plates. If the viscosity of the negative electrode slurry is too high or too low, it will affect the electrode plate coating process. If the viscosity is too high, the fluidity will be poor and the coating will be uneven, and if the viscosity is too low, the coating thickness will be insufficient and the surface density requirement of the electrode plate cannot be achieved. Therefore, the negative electrode material of this application can ensure that the viscosity of the negative electrode slurry obtained by manufacturing is within an appropriate viscosity range and guarantee the processing performance of the negative electrode plate.

[0064] A fourth aspect of this application provides a battery, which includes the negative electrode plate.

[0065] The following describes in detail the implementation of this application, connecting specific examples. However, those skilled in the art will understand that the following examples are merely illustrative of this application and should not be considered to limit its scope. Specific conditions not explicitly stated in the examples are carried out according to normal conditions or conditions suggested by the manufacturer. Reagents or equipment used that do not have a manufacturer listed are all commercially available, standard products.

[0066] Example 1 This embodiment provides a negative electrode material, the manufacturing method thereof includes the following:

[0067] (1) Carbon coating of silicon monoxide (SiO) using methane is performed. Specifically, silicon monoxide is added to a rotary kiln, then methane gas is injected, the temperature is raised to 1000°C, and the temperature is maintained for 8 hours to obtain a carbon-coated silicon monoxide material with a carbon content of 2-8%. Then, the carbon-coated silicon monoxide material is mixed with lithium hydride, and the mass ratio of the carbon-coated silicon monoxide material to the lithium hydride is 100:12, where the mass content of lithium element is 11%. The temperature is raised to 600°C under an argon gas atmosphere and the temperature is maintained for 6 hours to obtain a carbon-coated pre-lithium silicon monoxide material, where the mass content of lithium element is 10%.

[0068] (2) Sodium hypochlorite and deionized water were mixed to prepare a sodium hypochlorite solution with a concentration of 0.1 mol / L. The mass ratio of the prelithium-coated silicone material having a coating layer to the sodium hypochlorite was 100:1.5. The carbon-coated prelithium-coated silicon monoxide material obtained in step (1) was dispersed in the sodium hypochlorite solution while stirring, and oxidized for 1 hour.

[0069] (3) The material after oxidation treatment was left in a heat treatment furnace to be heat-treated, the temperature was raised to 600°C, and the temperature was maintained for 4 hours. The material after heat treatment was then crushed to obtain the negative electrode material.

[0070] Example 2 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that sodium hypochlorite in step (2) is replaced with copper chloride, the mass ratio of the prelithium-containing silicone material with a coating layer to copper chloride is 100:5, and the concentration of the prepared solution is 0.2 mol / L.

[0071] Example 3 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that sodium hypochlorite in step (2) is replaced with iron chloride, the mass ratio of the pre-lithium-containing silicone material with a coating layer to iron chloride is 100:3, and the concentration of the prepared solution is 0.1 mol / L.

[0072] Example 4 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the oxidation treatment time in step (2) is changed from 1 hour to 4 hours.

[0073] Example 5 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the oxidation treatment time in step (2) is changed from 1 hour to 12 hours.

[0074] Example 6 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that methane in step (1) is replaced with sucrose.

[0075] Example 7 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that methane in step (1) is replaced with natural gas.

[0076] Example 8 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the temperature after mixing with lithium hydride in step (1) is changed from 600°C to 800°C.

[0077] Example 9 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that lithium hydride in step (1) is replaced with metallic lithium, and the mass ratio of the carbon-coated silicon monoxide material to the metallic lithium is 100:11.

[0078] Example 10 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the incubation time for mixing with lithium hydride in step (1) is changed from 6 hours to 12 hours.

[0079] Example 11 The method for manufacturing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the heat treatment temperature in step (3) is changed from 600°C to 400°C.

[0080] Example 12 The method for manufacturing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the heat treatment temperature in step (3) is changed from 600°C to 800°C.

[0081] Example 13 The method for manufacturing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the heat retention time in step (3) is changed from 4 hours to 12 hours.

[0082] Example 14 The method for manufacturing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the heat retention time in step (3) is changed from 4 hours to 24 hours.

[0083] Example 15 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the difference being that the mass ratio of the carbon-coated silicon monoxide material to the lithium hydride in step (1) is 100:24, and the mass content of the lithium element in the obtained carbon-coated pre-lithium silicon monoxide material is replaced from 10% to 20%.

[0084] Example 16 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the difference being that the mass ratio of the carbon-coated silicon monoxide material to the lithium hydride in step (1) is 100:24, the mass content of the lithium element in the obtained carbon-coated pre-lithium silicon monoxide material is changed from 10% to 20%, and the oxidation treatment time in step (2) is changed from 1h to 4h.

[0085] Example 17 The method for producing the negative electrode material according to this embodiment is the same as in Example 1, the only difference being that the mass ratio of the carbon-coated silicon monoxide material to the lithium hydride in step (1) is 100:36, the mass content of the lithium element in the obtained carbon-coated pre-lithium silicon monoxide material is changed from 10% to 30%, and the oxidation treatment time in step (2) is changed from 1h to 12h.

[0086] Comparative Example 1 This comparative example provides a negative electrode material, the manufacturing method of which includes the following.

[0087] After adding silicon monoxide to a rotary kiln, methane gas is injected, the temperature is raised to 1000°C, and the temperature is maintained for 8 hours to obtain a carbon-coated silicon monoxide material with a carbon content of 2-8%. Then, the carbon-coated silicon monoxide material is mixed with lithium hydride, with a mass ratio of 100:12 between the carbon-coated silicon monoxide material and lithium hydride. The mixture is then raised to 600°C under an argon gas atmosphere and the temperature is maintained for 6 hours to obtain a carbon-coated pre-lithium silicon monoxide material, where the mass content of lithium element is 10%.

[0088] Comparative Example 2 This comparative example provides a negative electrode material, and the difference in its manufacturing method compared to Comparative Example 1 is that the mass content of lithium element in the carbon-coated pre-lithium silicon monoxide material obtained by manufacturing is replaced from 10% to 30%.

[0089] The elemental content and pH value of the negative electrode materials produced in each of the above examples and comparative examples were tested, and the test results are shown in Table 1.

[0090] When testing the mass content of element Li in the negative electrode material, the test method employs complete dissolution ICP measurement. The specific procedure involves completely removing carbon elements by calcining 0.5 g of the negative electrode material in air at 750°C for 2 hours, then completely dissolving it in a mixed acid of HCl / HNO3 / HF, dissolving it to a fixed volume in a 100 mL plastic volumetric flask, and finally measuring it using an ICP spectrometer (Agilent 5800). I The lithium content is tested using CP-OES.

[0091] When testing the mass content of element O in the negative electrode material, the test method involves using an ONH elemental analyzer (ONH~2000). The specific procedure involves placing the weighed negative electrode material into a graphite crucible, then sending it to the ONH elemental analyzer for testing to obtain the mass content of element O in the negative electrode material. The A value was obtained by performing a ratio test between the mass content of element O and the mass content of element Li, which was tested using an ICP spectrometer.

[0092] The atomic counts of Si, Li, and O elements on the surface of the negative electrode material were tested. The test method employed an X-ray photoelectron spectrometer (Thermo Scientific K-Alpha), with Al Kα as the excitation source, a beam spot of 400 μm, a full-spectrum scanning pass energy of 100 eV, and a step size of 1 eV. Finally, the atomic counts of O and Si elements were analyzed using Avantage software based on the full-spectrum scanning data. number The ratio is the B value, and the atomic ratio of O element and Li element. number The ratio was analyzed as the C-value.

[0093] The pH value of the negative electrode material was tested. The test method involved ultrasonically dispersing 5 g of the negative electrode material in 45 g of water, and then measuring the pH using a pH meter.

[0094] The negative electrode materials obtained in Examples 1-17 and Comparative Examples 1-2 were used as negative electrode active materials. They were uniformly mixed in a mass ratio of negative electrode active material: carboxymethylcellulose sodium (CMC): styrene-butadiene rubber (SBR) = 96.5:1.5:2, coated onto a copper foil current collector, dried, and a negative electrode plate was obtained for use.

[0095] First, a button cell test was performed on the obtained electrode plates. The battery was assembled in an argon gas glove box, with a metallic lithium sheet as the negative electrode, a 1 mol / L LiPF6 + ethylene carbonate (EC) + methyl ethyl carbonate (EMC) electrolyte, and a polyethyl / propylene composite microporous membrane as the separator. Electrochemical performance was tested on battery testing equipment, with the battery capacity set to the standard 480 mAh / g, the charge / discharge voltage to 0.01V~1.5V, and the charge / discharge rate to 0.1C. The results of the electrochemical performance test are shown in Table 2.

[0096] Viscosity test of negative electrode slurry: Slurry viscosity is tested using a rheometer, and the kinetic viscosity test (rotation mode) is performed with a shear rate range of 0.1 s. -1 ~300 s -1 The test equipment model numbers are HAAKE MARS60, Anton Paar MCR302, and HAAKE MARS4. Gas generation test of negative electrode slurry: After slurry preparation was completed, 20 g of slurry was weighed and sealed in an aluminum plastic film. Then, it was stored at room temperature for 168 hours, and the volume change before and after storage in the aluminum plastic film was measured by the wastewater method, thereby obtaining the gas generation amount of the slurry. The test results for viscosity and gas generation of the negative electrode slurry are shown in Table 1. Figure 1 shows the shear rate (0.1s) of the negative electrode slurry produced in Example 1 after 1 day and 7 days of standing. -1~300s -1 The change process in ) was shown.

[0097] Table 1 Test results for each example and comparative example JPEG2026525434000005.jpg206170

[0098] Table 2 Electrochemical test results for each example and comparative example JPEG2026525434000006.jpg208159

[0099] According to the results in Tables 1 and 2, this application was able to produce an oxide layer by oxidizing the active Si particles and residual lithium exposed on the surface of the material after treating the pre-lithified silicone oxygen material with an oxidizing agent. In Examples 1 to 17, when the surface was treated with an oxidizing agent and the B:A value was in the range of 1 to 100, the gas generation results were all better than those of Comparative Example 1 and 2.

[0100] Examples 1, 2, and 3 used different oxidizing agents and showed similar test results due to the similar degree of surface treatment. On the other hand, Examples 4 and 5 extended the oxidation treatment time, resulting in a thicker and denser oxide layer. Although the gas generation result was 0, similar to Examples 1-3, the gas volume was reduced to some extent. Examples 6 and 7 replaced the carbon source of the coating layer, which did not significantly affect the gas generation result, but slightly affected the initial efficiency and cycle performance of the capacity. Example 8 changed the pre-lithium reaction temperature, making the reaction stronger and more sufficient, resulting in higher initial efficiency, which did not significantly affect other performance. Example 9 changed the lithium source, and the overall performance was similar to Example 1. Example 10 increased the pre-lithium reaction time, which did not significantly affect the performance. Examples 11, 12, 13, and 14 changed the temperature and time of the heat treatment. When the heat treatment conditions were changed, the outer layer oxidation treatment was destroyed to some extent with increasing temperature and time, which had a certain effect on the gas generation performance. In Example 15, the amount of prelithium was increased, improving the initial efficiency, but this had a certain effect on the gas generation performance, resulting in a weakening of the gas generation performance. In Examples 16 and 17, the amount of prelithium was increased, and at the same time the oxidation reaction time was increased. Overall, the gas generation performance was higher compared to the comparative examples, but it did not reach an optimal level, and a small amount of gas was still generated. In Comparative Example 1, no oxidation treatment was performed, so the initial efficiency of the volume was relatively high in all cases, but the gas generation performance was poor, the pH was high, the slurry viscosity changed significantly, and the processing performance was poor. In Comparative Example 2, the amount of prelithium was greatly increased, resulting in unstable product performance after prelithiation, and the gas generation, volume, and cycle performance were all relatively poor.

[0101] Finally, it should be noted that the above embodiments are merely illustrative of the technical concepts of this application and do not limit them. Although the application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that it is still possible to modify the technical concepts described in the above embodiments or to make equivalent substitutions to some or all of the technical features thereof, and such modifications or substitutions will not cause the essence of the relevant technical concepts to deviate from the scope of the technical concepts of the embodiments of this application.

[0102] As those skilled in the art will understand, some of the embodiments herein include some features included in other embodiments, and others do not include other features, but combinations of features from different embodiments are within the scope of this application and form different embodiments. For example, any one of the claimed embodiments above can be used in any combination. The information disclosed in this background art section is intended solely to enhance the overall understanding of the background art of this application and should not be considered to acknowledge or imply in any way that this information constitutes prior art already known to those skilled in the art.

Claims

1. A negative electrode material comprising a silicone-based core and a coating layer that covers at least a portion of the surface of the silicone-based core, The anode material is characterized in that the silicone-based core contains silicone and lithium silicate, and the anode material satisfies the condition that the ratio of B:A is 1 to 100, where A is the mass ratio of oxygen and lithium in the anode material, and B is the atomic ratio of oxygen and silicone obtained by testing the anode material with an X-ray photoelectron spectrometer.

2. The negative electrode material according to claim 1, characterized in that the negative electrode material contains an oxide, and at least a portion of the oxide is present on the surface of the silicone-based core.

3. The negative electrode material according to claim 2, characterized in that at least a portion of the oxide forms an oxide layer located on the surface of the silicone-based core.

4. The lithium silicate is Li ２ SiO ３ Li ２ Si ２ O ５ Li ４ SiO ４ The negative electrode material according to claim 1, comprising at least one of the following.

5. The negative electrode material according to claim 1, characterized in that the pH value of the negative electrode material is 8 to 11.

5.

6. The negative electrode material according to claim 1, characterized in that the A value of the negative electrode material is 1 to 20.

7. The negative electrode material according to claim 1, characterized in that the B value of the negative electrode material is 1 to 100.

8. The negative electrode material according to claim 1, characterized in that when the negative electrode material satisfies B > A > 1, the ratio of B:A is 2 to 30.

9. The anode material according to claim 1, characterized in that the atomic ratio of oxygen to lithium obtained by testing the anode material by an X-ray photoelectron spectrometer is C, where the C value is 1 to 10.

10. The negative electrode material according to claim 1, characterized in that the viscosity change of the negative electrode slurry containing the aforementioned negative electrode material before and after standing for 168 hours is ≤ 3000 mPa·s.

11. The aforementioned oxide includes silicone oxide, and the general formula for silicone oxide is SiO ｘ The negative electrode material according to claim 2, wherein 0 < x ≤ 2.

12. The negative electrode material according to claim 9, further characterized in that the negative electrode material satisfies the requirement that the ratio of C:A is 0.5 to 10.

13. The anode material according to any one of claims 1 to 12, characterized in that the coating layer contains a carbon material.

14. A method for manufacturing a negative electrode material according to any one of claims 1 to 13, A manufacturing method characterized by comprising reacting a pre-lithium-containing silicone material having a coating layer with an oxidizing agent to obtain the negative electrode material.

15. A battery characterized by comprising the negative electrode material described in any one of claims 1 to 13.

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