Silicon-based negative electrode active material, secondary battery and electrical device

Abstract

This application provides a silicon-based negative electrode active material that contains an alkali metal element-containing silicate and also contains both Mg and Mn elements.

Description

[Technical Field]

[0001] This application relates to the technology of batteries, and more particularly to silicon-based negative electrode active materials, secondary batteries, and electrical devices. [Background technology]

[0002] In recent years, as the range of applications for secondary batteries has expanded, they are widely used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0003] Silicon-based materials have attracted widespread attention in the industry due to their high capacity, and there is a growing demand for higher electrochemical performance. Therefore, in this field, there is still a need for silicon-based anode active materials with superior performance. [Overview of the project]

[0004] In view of the above issues, this application provides a novel silicon-based negative electrode active material, a secondary battery, and an electrical device, which are described below.

[0005] In a first aspect, the present application provides a silicon-based negative electrode active material comprising an alkali metal element-containing silicate and containing both Mg and Mn elements.

[0006] In the above solution, the silicon-based anode active material contains a combination of Mg element and Mn element. Due to this specific combination, the cycle capacity retention rate of the silicon-based anode active material is improved. The combination of Mg element and Mn element brings an unexpected synergistic effect, and the technical effect achieved by the combination of these two is significantly better than the simple sum of the effects when used separately. Although not limited to the following theory, the Mn element has rich valences and has abundant active sites, which improves the electron conductivity of the anode active material and effectively reduces the direct current internal resistance (DCR). In addition, the Mg element and the silicon oxygen material have the characteristic of high binding strength, form a Mg silicate structure, can reduce the reaction between the active material and the electrolyte, effectively reduce lithium consumption, and effectively improve the cycle capacity retention rate. Therefore, by using the silicon-based anode active material of this application, the secondary battery can achieve both high cycle performance and low internal resistance.

[0007] In some embodiments, the content of the Mg element is greater than the content of the Mn element. Within the above ratio range, the Mg element and the Mn element show an unexpected synergistic effect and further improve the cycle capacity retention rate of the silicon-based anode active material.

[0008] In some embodiments, the mass ratio of the Mg element to the Mn element is 1.7:1 or more, and optionally 2.5:1 to 10:1. By using the anode active material according to the above solution in the battery, the battery has a further improved cycle capacity retention rate.

[0009] In some embodiments, the content of the Mg element is 80 ppm or more, and optionally 100 ppm to 500 ppm. By using the anode active material according to the above solution in the battery, the battery has a further improved cycle capacity retention rate.

[0010] In some embodiments, the content of the Mn element is 200 ppm or less, and optionally 10 ppm to 100 ppm. By using the negative electrode active material according to the above solution in a battery, the battery has a further improved cycle capacity retention rate.

[0011] In some embodiments, the volume average particle diameter D of the silicon-based negative electrode active material

[0015] 50 is 4 μm to 10 μm. By using the negative electrode active material according to the above solution in a battery, the battery has a further improved cycle capacity retention rate.

[0012] In some embodiments, the specific surface area of the silicon-based negative electrode active material is 3 m 2 / g or less, and optionally 0.5 m 2 / g to 2 m 2 / g. By using the negative electrode active material according to the above solution in a battery, the battery has a further improved cycle capacity retention rate.

[0013] In some embodiments, the powder volume resistivity of the silicon-based negative electrode active material at a pressure of 4 MPa is 3 Ω·cm or less, and optionally 0.5 Ω·cm to 1.5 Ω·cm. By using the negative electrode active material according to the above solution in a battery, the battery has a further improved cycle capacity retention rate.

[0014] In some embodiments, the tap density of the silicon-based negative electrode active material at a pressure of 49000 N is 1.4 to 1.8 g / cm 3 and optionally 1.5 to 1.7 g / cm 3 . By using the negative electrode active material according to the above solution in a battery, the battery has a further improved capacity.

[0015] In some embodiments, the alkali metal element-containing silicate includes lithium-containing silicate, and the half-value width of the XRD diffraction peak of the lithium-containing silicate is 2.0° or less, and optionally 0.4° to 1.5°. By using the negative electrode active material according to the above solution in a battery, the battery has a further improved cycle capacity retention rate.

[0016] In some implementations, the alkali metal element-containing silicate includes a lithium-containing silicate, and the crystallite size of the lithium-containing silicate is 20 nm or less. By using the negative electrode active material according to the above implementation in a battery, the battery has an even more improved cycle capacity retention rate.

[0017] In some implementations, at least a portion of the surface of the silicon-based negative electrode active material is covered with a coating layer.

[0018] In a second aspect, the present application relates to a method for producing a silicon-based negative electrode active material as described in any one of the above, To provide raw materials containing Si, O, Mn, and Mg elements, The process involves heating the raw material to form steam using a vapor phase growth method, and then cooling the steam to form a deposit. The process involves crushing the sediment and obtaining the crushing product, The present invention provides a method for producing a silicon-based negative electrode active material, which includes reacting the previous product with an alkali metal source to obtain an alkali metallization product.

[0019] In some implementation plans, the method for producing silicon-based negative electrode active material is as follows: The method further includes coating the alkali metallization product to obtain a product having a coating layer.

[0020] In some implementations, the heating temperature in the operation of heating the raw material to form steam is 1100 to 1550°C.

[0021] In some implementations, the cooling temperature in the operation of cooling the steam to form a deposit is 700-900°C.

[0022] In a third aspect, the present application provides a secondary battery comprising a negative electrode containing the silicon-based negative electrode active material described in any one of the above.

[0023] In a fourth aspect, the present application provides an electrical device including a secondary battery as described in any one of the above.

[0024] Beneficial effects One or more embodiments of this application have one or more beneficial effects.

[0025] (1) The combination of Mg and Mn elements produces an unexpected synergistic effect, and the technical effects achieved by this combination are significantly better than the simple sum of the effects when used separately. (2) Batteries using silicon-based negative electrode active materials have improved DC internal resistance. (3) Batteries using silicon-based negative electrode active materials have an improved cycle capacity retention rate. (4) Batteries that utilize silicon-based negative electrode active materials have a high energy density. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of this application. [Figure 6] This is a schematic diagram of an electrical device in which a secondary battery of one embodiment of this application is used as a power source. [Modes for carrying out the invention]

[0027] In the following, embodiments specifically disclosing the silicon-based negative electrode active material and its manufacturing method, positive electrode sheet, negative electrode sheet, secondary battery, battery module, battery pack, and device of this application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially the same structure may be omitted. This is to avoid making the following explanation unnecessarily verbose in order to make it easy for those skilled in the art to understand. Furthermore, the drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the intent of the claims.

[0028] The “range” disclosed in this application is limited to a lower and upper limit, and a given range is limited by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundary of a special range. Such limited ranges may or may not include endpoint values ​​and can be arbitrarily combined, that is, any lower limit and any upper limit can be combined to form a single range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, the ranges 60-110 and 80-120 are also understood to be predictable. Similarly, if 1 and 2 are listed as the minimum range values ​​and 3, 4, and 5 are listed as the maximum range values, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all predictable. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have already been enumerated herein, and "0 to 5" is merely an abbreviation for combinations of these numbers. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0030] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the method may further include step (c), meaning that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), or other cases.

[0031] Unless otherwise specified, any expressions such as “includes” and “inclusive” used in this application may be open or closed. For example, such expressions as “includes” and “inclusive” may further include or include other components not listed, or may include or include only the listed components.

[0032] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the "A or B" condition: A is true (or exists) but B is false (or does not exist); A is false (or does not exist) but B is true (or exists); or both A and B are true (or exist).

[0033] In this specification, ppm (parts per million) means parts per million. However, when ppm is used to describe the content of Mg or Mn elements, it means parts per million of the mass of Mg or Mn elements in the silicon-based anode active material relative to the mass of the silicon-based anode active material.

[0034] [Secondary battery] A secondary battery is also called a rechargeable battery or a storage battery, and refers to a battery that can be continuously used by activating the active material through charging after the battery is discharged.

[0035] Normally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charge and discharge of the battery, active ions (e.g., sodium ions) reciprocally intercalate and deintercalate between the positive electrode sheet and the negative electrode sheet. The separator is provided between the positive electrode sheet and the negative electrode sheet, mainly serving to prevent the short circuit between the positive electrode and the negative electrode and allowing the active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly serving to conduct the active ions.

[0036] The secondary battery is, for example, a lithium-ion battery. A lithium-ion battery is mainly composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode and the negative electrode are separated by the separator to prevent short circuit, and the electrolyte is impregnated into the positive electrode and the negative electrode to ensure ion conduction. During charging, Li + detaches from the positive electrode, passes through the separator via the electrolyte, and is inserted into the negative electrode, so that the positive electrode becomes a high-potential sodium-deficient state and the negative electrode becomes a low-potential sodium-rich state. Conversely, in the discharge process, Li + detaches from the negative electrode, passes through the separator via the electrolyte, and is inserted into the positive electrode material, so that the positive electrode returns to the sodium-rich state. To maintain the charge balance, the same number of electrons are transmitted through the external circuit during charge and discharge, and by moving between the positive electrode and the negative electrode together with Li + oxidation reaction and reduction reaction occur at the positive electrode and the negative electrode respectively. Lithium ions can reversibly move between the positive electrode and the negative electrode in the electrolyte, and both the positive electrode and the negative electrode are composed of insertion-type materials that enable the reversible insertion and deintercalation of lithium ions.

[0037] A secondary battery is, for example, a sodium-ion battery. A sodium-ion battery mainly consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrodes are separated by a separator to prevent short circuits, and the electrolyte is impregnated into the positive and negative electrodes to ensure ion conductivity. During charging, Na + It detaches from the positive electrode, passes through the separator via the electrolyte, and is inserted into the negative electrode, resulting in the positive electrode becoming a high-potential sodium-deficient state and the negative electrode becoming a low-potential sodium-enriched state. Conversely, in the discharge process, Na + The electrons detach from the negative electrode, pass through the separator via the electrolyte, and are inserted into the positive electrode material, returning the positive electrode to a sodium-enriched state. To maintain the charge balance, the same number of electrons are transferred through the external circuit during charging and discharging, and Na + As sodium ions move between the positive and negative electrodes, oxidation and reduction reactions occur at the positive and negative electrodes, respectively. Sodium ions can reversibly move between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are composed of insertion-type materials that allow for the reversible insertion and removal of sodium ions.

[0038] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, the negative electrode film layer containing a negative electrode active material.

[0039] The negative electrode active material of this application is a silicon-based negative electrode active material that contains an alkali metal element-containing silicate and also contains both Mg and Mn elements.

[0040] In the above design, the silicon-based anode active material contains a combination of Mg and Mn elements, and this specific combination improved the cycle capacity retention rate of the silicon-based anode active material. The combination of Mg and Mn elements produced an unexpected synergistic effect, and the technical effect achieved by this combination is significantly better than the simple sum of the effects when they are used separately. Although not limited to the following theory, Mn has a rich valence state and abundant active sites, improving the electronic conductivity of the anode active material and effectively reducing the DC internal resistance (DCR). In addition, Mg and silicon-oxygen materials have high bonding strength, forming a Mg silicate structure, which can reduce the reaction between the active material and the electrolyte, effectively reducing lithium consumption and effectively improving the cycle capacity retention rate. Therefore, by using the silicon-based anode active material of this application, secondary batteries can achieve both high cycle performance and low internal resistance.

[0041] In some implementations, the alkali metal element includes one or more of Li, Na, and K elements. Selectively, the alkali metal element includes Li. In all of the above implementations, the silicon-based anode active material has been improved. First Kowloon This shows the efficiency and cycle capacity maintenance rate.

[0042] In some implementations, the alkali metal element-containing silicate includes a lithium-containing silicate, and the full width at half maximum of the XRD diffraction peak of the lithium-containing silicate is 2.0° or less, and selectively between 0.4° and 1.5°. In the above implementations, the battery has further improved cycle capacity retention and DC internal resistance (DCR).

[0043] In some implementations, the alkali metal element-containing silicate includes a lithium-containing silicate, and the crystallite size of the lithium-containing silicate is 20 nm or less. In the above implementations, the battery has further improved cycle capacity retention and DC internal resistance (DCR).

[0044] In some implementations, the lithium-containing silicate includes at least one of Li2Si2O5 and Li2SiO3.

[0045] In some implementations, Mg and Mn elements are grown within the silicon-based anode active material, for example, during a vapor phase growth process of the silicon-based anode active material. In some implementations, Mg and Mn elements are grown within the silicon-based anode active material when vapor phase growth occurs together with the silicon-based anode active material.

[0046] In some implementations, silicon in a silicon-based anode active material can exist in the form of multiple silicon phases, including crystalline silicon. Specifically, the silicon phases can be dispersed and uniformly distributed within the matrix.

[0047] In some implementations, the silicon-based anode active material contains at least one of silicon crystal grains or silicon oxygen material crystal grains.

[0048] In some implementations, the magnesium (Mg) content in the silicon-based anode active material is greater than the manganese (Mn) content. Within the above ratio range, the magnesium and manganese elements exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate and DC internal resistance (DCR) of the silicon-based anode active material.

[0049] In some implementations, the silicon-based anode active material has a Mg-to-Mn mass ratio of 1.7:1 or higher. Within this ratio range, the Mg and Mn elements exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate of the anode active material.

[0050] In some implementations, the silicon-based anode active material has a Mg-to-Mn mass ratio of 1.7:1 to 25:1. Within this ratio range, the Mg and Mn elements exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate and DC internal resistance (DCR) of the anode active material.

[0051] In some implementations, the silicon-based anode active material has a Mg-to-Mn mass ratio of 1.7:1 to 20:1. Within this ratio range, the Mg and Mn elements exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate and DC internal resistance (DCR) of the anode active material.

[0052] In some implementations, the silicon-based anode active material has a Mg-to-Mn mass ratio of 1.7:1 to 15:1. Within this ratio range, the Mg and Mn elements exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate and DC internal resistance (DCR) of the anode active material.

[0053] In some implementations, the silicon-based anode active material has a Mg-to-Mn mass ratio of 2.5:1 to 10:1. Within this ratio range, the Mg and Mn elements exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate and DC internal resistance (DCR) of the anode active material.

[0054] In some implementations, the mass ratio of Mg to Mn in the silicon-based anode active material may be 30:1 or less, 20:1 or less, 15:1 or less, 14:1 or less, 13:1 or less, 12:1 or less, or 10:1 or less. In some implementations, the mass ratio of Mg to Mn in the silicon-based anode active material may be 1.7:1 or more, 2:1 or more, 3:1 or more, 4:1 or more, 5:1 or more, or 6:1 or more. The mass ratio of Mg to Mn may be composed of any upper and lower limits mentioned above. Within the above ratio range, Mg and Mn exhibited an unexpected synergistic effect, further significantly improving the cycle capacity retention rate and DC internal resistance (DCR) of the anode active material.

[0055] In some implementations, the mass ratio of Mg element to Mn element in the silicon-based negative electrode active material may be 2.5-5:1, 2.5-10:1, 1.7-10:1, 1.7-14:1, 1.7-15:1, 1.7-20:1, 1.7-25:1, 2.5-10:1, 2.5-14:1, 2.5-15:1, 2.5-20:1, 2.5-25:1, 2-10:1, 3-10:1, 4-10:1, 5-10:1, 5-10:1, 6-12:1, or 6-15:1.

[0056] In some implementations, the Mg element content in the silicon-based anode active material is 80 ppm or higher. Within this content range, the Mg and Mn elements showed an unexpected synergistic effect, significantly improving the cycle capacity maintenance rate of the anode active material.

[0057] In some implementations, the Mg element content in the silicon-based negative electrode active material is 100 ppm to 500 ppm. This further improves the battery. First Kowloon It exhibits efficiency and cycle capacity retention. Within the above content range, the elements Mg and Mn showed an unexpected synergistic effect, significantly improving the cycle capacity retention rate of the anode active material.

[0058] In some implementations, the Mg element content in the silicon-based negative electrode active material is 150 ppm to 400 ppm. This further improves the battery. First Kowloon It exhibits efficiency and cycle capacity retention. Within the above content range, the elements Mg and Mn showed an unexpected synergistic effect, significantly improving the cycle capacity retention rate of the anode active material.

[0059] In some implementations, the Mg element content in the silicon-based negative electrode active material is 150 ppm to 300 ppm. This further improves the battery. First Kowloon It exhibits efficiency and cycle capacity retention. Within the above content range, the elements Mg and Mn showed an unexpected synergistic effect, significantly improving the cycle capacity retention rate of the anode active material.

[0060] In some implementations, the upper limit of the Mg element content in the silicon-based anode active material may be any one value selected from 500 ppm, 400 ppm, 300 ppm, or 200 ppm, and the lower limit of the Mg element content may be any one value selected from 300 ppm, 200 ppm, 150 ppm, 100 ppm, 80 ppm, or 50 ppm. That is, the range of the Mg element content may consist of the aforementioned arbitrary upper and lower limits. Within the above range of content, the Mg and Mn elements showed an unexpected synergistic effect, significantly improving the cycle capacity maintenance rate of the anode active material.

[0061] In some implementations, the Mg element content in the silicon-based negative electrode active material is selectively 150-300 ppm, 100-300 ppm, 100-400 ppm, or 100-500 ppm.

[0062] In some implementations, the Mn element content in the silicon-based negative electrode active material is 200 ppm or less. This results in a battery with an even more improved cycle capacity retention rate.

[0063] In some implementations, the Mn element content in the silicon-based negative electrode active material is 20 ppm to 200 ppm. This results in a battery with an even more improved cycle capacity retention rate.

[0064] In some implementations, the Mn element content in the silicon-based negative electrode active material is 20 ppm to 60 ppm. This results in a battery with an improved cycle capacity retention rate.

[0065] In some implementations, the Mn element content in the silicon-based negative electrode active material is 10 ppm to 100 ppm. This results in a battery with an even more improved cycle capacity retention rate.

[0066] In some implementations, the upper limit of the manganese content in the silicon-based anode active material may be any one value selected from 200 ppm, 100 ppm, 80 ppm, or 60 ppm, and the lower limit of the manganese content may be any one value selected from 20 ppm or 30 ppm. That is, the range of the manganese content may consist of the aforementioned arbitrary upper and lower limits. Within the above content range, the Mg and Mn elements showed an unexpected synergistic effect, further significantly improving the cycle capacity maintenance rate of the anode active material.

[0067] In some implementations, the Mn element content in the silicon-based negative electrode active material is selectively 20-30 ppm, 20-40 ppm, 20-60 ppm, 30-60 ppm, 30-100 ppm, 30-200 ppm, and 20-200 ppm.

[0068] In some implementations, the volume-average particle size D of the silicon-based negative electrode active material v 50 is 4μm to 10μm, and selectively 5μm to 8μm. In the above scheme, the battery has an improved cycle capacity retention rate.

[0069] In some implementations, the volume-average particle size D of the silicon-based negative electrode active material v Particle size 50 is selectively 4 μm or larger, and more selectively 5 μm or larger, thereby reducing the consumption of active ions for film formation at the negative electrode and minimizing side reactions of the electrolyte at the negative electrode. This reduces the irreversible capacity of the secondary battery, improves its cycle performance, and also helps to reduce the amount of binder added to the negative electrode sheet, thereby improving the energy density of the secondary battery. Average particle size D v The particle size 50 is selectively 10 μm or smaller, and more selectively 8 μm or smaller, which shortens the migration path of active ions and electrons within the material particles, increasing the migration speed of ions and electrons. This improves the dynamic performance of secondary batteries, helps prevent rupture of silicon-based negative electrode active materials during charging and discharging, and further improves the cycle performance of secondary batteries.

[0070] In some implementations, the specific surface area of ​​the silicon-based negative electrode active material is 3 m². 2 It is less than / g and selectively 0.5m 2 / g~2m 2 The value is / g. In the above scheme, the battery has an improved cycle capacity retention rate.

[0071] In some implementations, the specific surface area of ​​the silicon-based negative electrode active material is 0.5 m². 2 / g~2m 2 The specific surface area is 0.5 m² / g. 2 By having a specific surface area of ​​2 m² or more, the material particles can have many active sites on their surface, effectively improving the electrochemical performance of the silicon-based negative electrode active material and meeting the requirements for the dynamic performance of the secondary battery. 2 Having a value of less than / g helps reduce side reactions at the negative electrode of the electrolyte, reduces the consumption of active ions for film formation at the negative electrode, reduces the irreversible capacity of the secondary battery, and further improves the cycle performance of the secondary battery.

[0072] In some implementations, the powder volume resistivity of the silicon-based negative electrode active material at a pressure of 4 MPa is 3 Ω·cm or less, and selectively between 0.5 Ω·cm and 1.5 Ω·cm. In the above implementations, the battery has an improved DC internal resistance (DCR).

[0073] In some implementations, the powder volume resistivity of the silicon-based anode active material at a pressure of 4 MPa is 3 Ω·cm or less, and more selectively 1.5 Ω·cm or less. Having the powder volume resistivity of the silicon-based anode active material within this range reduces obstacles to electron movement within the particles, contributing to improved dynamic performance of the silicon-based anode active material, reducing polarization phenomena of the anode, and improving the cycle life of the secondary battery.

[0074] In some implementations, the pressure density of the silicon-based negative electrode active material at a pressure of 49,000 N is 1.4 to 1.8 g / cm³. 3 Therefore, selectively 1.5-1.7 g / cm³ 3Therefore, in the above scheme, the battery has an even more improved energy density.

[0075] In some implementations, the silicon-based anode material contains Si and O elements, and the molar ratio of O to Si elements is greater than 0 and less than 2, selectively 0.2 to 1.8:1, more selectively 0.3 to 1.7:1, more selectively 0.4 to 1.6:1, more selectively 0.6 to 1.5:1, more selectively 0.7 to 1.4:1, more selectively 0.8 to 1.3:1, more selectively 0.9 to 1.2:1, and more selectively 1.0 to 1.1:1.

[0076] In some implementations, at least a portion of the surface of the silicon-based negative electrode active material is covered with a coating layer.

[0077] In some implementations, the coating material comprises one or more of polymers, carbon materials, metallic materials, and metallic compounds. For example, the coating layer comprises one or more of a polymer coating layer, a carbon coating layer, and a metallic compound coating layer. Selectively, the polymer may be one or more selected from polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride, and polyethylene. Selectively, the carbon material may comprise one or more of graphite, mesocarbon microbeads (MCMB), hydrocarbon compound pyrolysis carbon, hard carbon, and soft carbon, where graphite may comprise one or more of natural graphite and artificial graphite. Selectively, the metallic compound may comprise one or more of Ti5Si3, Al2O3, and TiO2. The coating layer can further mitigate the volume expansion effect of the silicon-based anode active material and improve the cycle life of the material. At the same time, the coating layer further protects the silicon-based negative electrode active material, suppresses side reactions of the electrolyte on the material surface, and protects the material surface from erosion by the electrolyte, thereby allowing the silicon-based negative electrode active material to exhibit high capacity and further improving the battery's cycle life.

[0078] In a second aspect, the present application relates to a method for producing a silicon-based negative electrode active material as described in any one of the above, To provide raw materials containing Si, O, Mn, and Mg elements, The process involves heating the raw material to form steam using a vapor phase growth method, and then cooling the steam to form a deposit. The process involves crushing the sediment and obtaining the crushing product, The present invention provides a method for producing a silicon-based negative electrode active material, which includes reacting the previous product with an alkali metal source to obtain an alkali metallization product.

[0079] In some implementation plans, the method for producing silicon-based negative electrode active material is as follows: The method further includes coating the alkali metallization product to obtain a product having a coating layer.

[0080] In some implementations, the Si element in the raw materials may be derived from elemental silicon and silicon oxide, and the O element in the raw materials may be derived from silicon oxide. Here, elemental silicon includes, for example, metallic silicon. Silicon oxide includes, for example, one or more of silicon monoxide (SiO) and silicon dioxide (SiO2). Metallic silicon is, for example, any metallic silicon or industrial silicon as specified in the GB / T 2881-2014 standard. The purity of elemental silicon is, for example, 3N or higher, 4N or higher, 5N or higher, or 6N or higher.

[0081] In some implementations, the Mg element in the raw material may originate from elemental silicon or the Mg element contained in the silicon oxide itself, or it may originate from a magnesium source added to the raw material.

[0082] In some implementations, the Mn element in the raw material may originate from elemental silicon or the Mn element contained in the silicon oxide itself, or it may originate from a manganese source added to the raw material.

[0083] In some implementations, the alkali metal elements in the raw materials may originate from alkali metal elements contained in elemental silicon or silicon oxide itself, or from alkali metal sources added to the raw materials.

[0084] In some implementations, the raw materials contain a magnesium source. At least a portion of the Mg element in the raw materials originates from the magnesium source. The magnesium source may be one or more selected from metallic magnesium and magnesium compounds. Here, the magnesium compound may be one or more selected from magnesium oxides, magnesium carbonates, magnesium hydroxides, magnesium nitrates, and magnesium sulfates.

[0085] In some implementations, the raw materials contain a manganese source. At least a portion of the manganese element in the raw materials originates from the manganese source. The manganese source may be one or more selected from metallic manganese, manganese alloys, and manganese compounds. Here, the manganese compound may be one or more selected from manganese oxides, manganese sulfides, manganese carbonates, manganese hydroxides, manganese acetates, manganese oxalates, manganese nitrates, and manganese sulfates.

[0086] In some implementations, the alkali metal source may be one or more selected from elemental alkali metals, alkali metal alloys, and alkali metal compounds. Here, the alkali metal compound may be one or more selected from alkali metal oxides, alkali metal sulfides, alkali metal carbonates, alkali metal hydroxides, alkali metal acetates, alkali metal oxalates, alkali metal nitrates, and alkali metal sulfates.

[0087] In some implementations, the raw materials containing Si, O, Mg, and Mn elements include elemental silicon, silicon dioxide, a magnesium source, and a manganese source.

[0088] In some implementation plans, the amount of Mg element in the negative electrode active material is adjusted by controlling the type and amount of magnesium source in the raw materials.

[0089] In some implementation plans, the amount of Mn element in the negative electrode active material is adjusted by controlling the type and amount of manganese source in the raw materials.

[0090] In some implementations, the Mg content in the negative electrode active material is adjusted by one or more means, such as mixing silicon oxide powders or metallic silicon powders with varying Mg content, and adjusting the type and amount of magnesium source used.

[0091] In some implementations, the Mn element content in the negative electrode active material is adjusted by one or more means, such as mixing silicon oxide powders or metallic silicon powders with varying Mn element content, and adjusting the type and amount of manganese source used.

[0092] In some implementations, the process of heating the raw materials to form steam is carried out in an inert atmosphere at atmospheric pressure or reduced pressure.

[0093] In some implementations, the operation of cooling the steam to form deposits is carried out in an inert atmosphere at atmospheric pressure or reduced pressure.

[0094] In the above manufacturing method, the inert atmosphere may be a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, or the like. Selectively, the absolute pressure of the inert atmosphere is normal pressure (1 standard atmospheric pressure) or reduced pressure (less than 1 standard atmospheric pressure). Selectively, the absolute pressure of the inert atmosphere is 10 Pa to 950 Pa, and more selectively, 20 Pa to 100 Pa.

[0095] In some implementations, within the pressure range of the inert atmosphere described above, lowering the pressure (i.e., increasing the vacuum) can increase the Mg and Mn element content in the final silicon-based anode active material accordingly.

[0096] In some implementations, the heating temperature in the operation of heating the raw material to form steam is 1100 to 1550°C.

[0097] In some implementations, the cooling temperature in the operation of cooling the steam to form a deposit is 700-900°C.

[0098] In some implementations, by adjusting the cooling temperature during the operation of cooling the vapor to form a deposit, the deposit can obtain a suitable crystalline structure. Selectively, a cooling temperature of 850°C to 1050°C helps to obtain good microcrystal size and appropriate crystallinity in silicon-based anode active materials, resulting in a battery with high cycle performance. If the cooling temperature is lower than 800°C, the crystallinity of the material becomes low. Gil It is possible. If the cooling temperature is higher than 1050°C, the microcrystal size of the material may become too large, potentially affecting the battery's cycle performance.

[0099] In some implementations, increasing the temperature within the above heating temperature range can increase the content of Mg and Mn elements in the final silicon-based anode active material accordingly.

[0100] In some implementations, within the pressure range of the inert atmosphere described above, lowering the pressure, i.e., increasing the vacuum level, can correspondingly increase the content of Mg and Mn elements in the final silicon-based anode active material.

[0101] In some implementations, the sediment crushing operation is performed to achieve a predetermined volume-average particle size (D) of the product. v 50) The method includes performing coarse crushing, fine grinding, and classification operations on the sediment according to the parameters of the specific surface area and to obtain a product that satisfies the predetermined parameters. In some implementations, crushing and classification treatment can be performed on the sediment using any method and device known in the art, such as a grinder or an integrated pneumatic grinder and classifier.

[0102] In some implementations, the method for producing a silicon-based anode active material further includes a coating treatment of the alkali metallization product to obtain a product having a coating layer.

[0103] In some implementations, the coating layer material comprises one or more of polymers, carbon materials, metallic materials, and metallic compounds. For example, the coating layer comprises one or more of a polymer coating layer, a carbon coating layer, and a metallic compound coating layer. Selectively, the polymer may be one or more selected from polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride, and polyethylene. Selectively, the carbon material may comprise one or more of graphite, mesocarbon microbeads (MCMB), hydrocarbon compound pyrolysis carbon, hard carbon, and soft carbon, where graphite may comprise one or more of natural graphite and artificial graphite. Selectively, the metallic compound may comprise one or more of Ti5Si3, Al2O3, and TiO2. The coating layer can further mitigate the volume expansion effect of the silicon-based anode active material and improve the cycle life of the material. At the same time, the coating layer further protects the silicon-based negative electrode active material, suppresses side reactions of the electrolyte on the material surface, and protects the material surface from erosion by the electrolyte, thereby allowing the silicon-based negative electrode active material to exhibit high capacity and further improving the battery's cycle life.

[0104] In some implementations, a liquid-phase coating method is used to coat the surface of the silicon-based anode active material, forming a coating layer. For example, a polymer is dissolved in a predetermined solvent, thoroughly stirred and uniformly mixed with the silicon-based anode active material particles, and then the solvent is evaporated and removed, so that the polymer uniformly coats the surface of the silicon-based anode active material particles.

[0105] In some implementations, a coating layer is formed on the surface of the silicon-based anode active material by chemical vapor deposition (CVA). For example, a hydrocarbon compound gas is introduced into a reactor containing the silicon-based anode active material, and heat treatment is performed in an inert atmosphere to carbonize the hydrocarbon compound, forming a coating layer that covers the surface of the silicon-based anode active material, thereby obtaining a silicon-based anode active material whose surface is covered with a coating layer.

[0106] In some implementations, the coating treatment includes a carbon coating treatment. Selectively, the carbon coating treatment includes placing the pulverized product in a chamber containing a carbon source gas, heating it to 700-1000°C, and maintaining the temperature for 1-6 hours.

[0107] In some implementations, the coating treatment includes a carbon coating treatment. Selectively, the carbon coating treatment includes placing the pulverized product in a chamber containing a carbon source gas, heating it to 800-900°C, and maintaining the temperature for 2-5 hours.

[0108] In some implementations, the alkali metal source may be one or more of the following: elemental alkali metals, alkali metal hydroxides, alkali metal carbonates, alkali metal nitrates, alkali metal aminations, and alkali metal hydrides.

[0109] In some implementations, the alkali metal source may be one or more of metallic lithium, lithium hydroxide, lithium carbonate, lithium nitrate, lithium amide, and lithium hydride.

[0110] For example, a negative electrode current collector has two opposing surfaces in the thickness direction of itself, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0111] In some embodiments, a metal foil or a composite current collector can be used as the negative electrode current collector. For example, copper foil can be used as the metal foil. The composite current collector consists of a polymer material substrate layer and a polymer material substrate. layerThe composite current collector may include a metal layer formed on at least one surface. The composite current collector may be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0112] In some embodiments, the anode film layer may include silicon-based anode active materials known in the art other than those described in this application, which can be selected by those skilled in the art as required by practical needs. Examples include, but are not limited to, artificial graphite, natural graphite, hard carbon, soft carbon, and one or more of other silicon-based and tin-based materials. The aforementioned other silicon-based materials may include one or more of elemental silicon, silicon-oxygen composites different from those described in this application, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin-oxygen compounds, and tin alloys. All of these materials are commercially available.

[0113] In some embodiments, the negative electrode film layer further selectively comprises a binder. For example, the binder may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0114] In some embodiments, the negative electrode film layer further selectively comprises a conductive agent. For example, the conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some embodiments, the negative electrode film layer selectively further comprises other additives such as a thickening agent (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0116] In some embodiments, a negative electrode sheet can be manufactured as follows: Components for manufacturing the above-mentioned negative electrode sheet, such as a silicon-based negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and after processes such as baking and cold pressing, a negative electrode sheet can be obtained.

[0117] [Positive electrode sheet] In some embodiments, the positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material.

[0118] For example, a positive electrode current collector has two opposing surfaces in the thickness direction of itself, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0119] In some embodiments, a metal foil or a composite current collector can be used as the positive electrode current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0120] In some embodiments, the positive electrode film layer selectively further comprises a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic ester resin.

[0121] In some embodiments, the cathode film layer selectively further comprises a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, a positive electrode sheet can be manufactured as follows: Components for manufacturing the positive electrode sheet described above, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after processes such as baking and cold pressing, a positive electrode sheet can be obtained.

[0123] [Cathode active material] In some embodiments, the positive electrode active material can be any positive electrode active material known in the art for secondary batteries.

[0124] For example, the positive electrode active material may include at least one material from among olivine-structured lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, this application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may be used. These positive electrode active materials may be used individually or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (Can also be abbreviated as LiNi) 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (Can also be abbreviated as LiNi) 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (Can also be abbreviated as LiNi) 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (Can also be abbreviated as LiNi) 0.8 Co 0.1 Mn 0.1 O2(NCM 811 (It can also be abbreviated as LiNi) Lithium nickel cobalt aluminum oxide (for example, LiNi 0.85 Co 0.15 Al 0.05It may include, but is not limited to, at least one of O2) and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure include, but is not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0125] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. In this application, the type of electrolyte is not specifically limited and can be selected as needed. For example, the electrolyte may be a liquid, a gel, or all-solid.

[0126] In some embodiments, the electrolyte is a liquid and comprises an electrolyte salt and a solvent.

[0127] In some embodiments, the electrolyte salt is selected from sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium hexafluoroarsenate.

[0128] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0129] In some embodiments, the electrolyte selectively further comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and further additives that can improve specific performance of the battery, such as additives that improve the overcharge performance of the battery, or additives that improve the high-temperature or low-temperature performance of the battery.

[0130] [Separator] In some embodiments, the secondary battery further includes a separator. In this application, the type of separator is not particularly limited, and any known porous separator having good chemical and mechanical stability can be selected.

[0131] In some embodiments, the material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0132] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be assembled into an electrode assembly by a winding process or a lamination process.

[0133] In some embodiments, the secondary battery may include an outer casing. This casing can be used to package the electrode assembly and electrolyte.

[0134] In some embodiments, the casing of the secondary battery may be a rigid case, such as a hard plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft pack, such as a bag-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0135] In this application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a secondary battery 5 with a rectangular structure as an example.

[0136] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround the case 51 to form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening to seal the housing cavity. The positive electrode sheet, negative electrode sheet and separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and a person skilled in the art can select this according to specific practical requirements.

[0137] In some embodiments, the secondary battery is assembled as a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0138] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed in place by fastening members.

[0139] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of secondary batteries 5 are housed.

[0140] In some embodiments, the above-mentioned battery modules are further assembled into a battery pack, the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0141] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box 2 and a lower box 3, and the upper box 2 is covered by the lower box 3 and can form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0142] Furthermore, this application provides an electrical device comprising at least one of the secondary battery, battery module, or battery pack provided herein. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0143] The aforementioned electrical device can be selected as a secondary battery, battery module, or battery pack, depending on its intended use.

[0144] Figure 6 shows an example of an electrical device. This electrical device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the requirements for high power output and high energy density of secondary batteries, this electrical device may use a battery pack or battery module.

[0145] Examples of the present application are described below. The examples described below are illustrative and are for interpretive purposes only, and should not be understood as limiting this application. Where specific techniques or conditions are not specified in the examples, they shall be carried out in accordance with the techniques or conditions described in the literature in the art or in the product descriptions. Unless the manufacturer is specified for the reagents or equipment used, they are all common products that can be purchased commercially.

[0146] 1. Method for producing silicon-based negative electrode active material 1.1 Overview In the following specific embodiments, the method for producing the negative electrode active material will be outlined below.

[0147] 1) A vapor containing Si, O, Mn, and Mg elements was provided, and the vapor was cooled to obtain a deposit. 2) The sediment was crushed to obtain the crushing product. 3) The pulverized product was subjected to carbon coating treatment to obtain a carbon-coated product. 4) The carbon-coated product was subjected to a lithium lithiation reaction with a lithium source, and the product was recovered to obtain the negative electrode active material.

[0148] 1.2 Details In the following specific embodiments, the method for producing the negative electrode active material will be described in detail below.

[0149] 1) Depending on the content of Mg and Mn elements in the target product, raw material compositions containing elemental silicon, silicon oxide, a magnesium source (metallic magnesium), and a manganese source (manganese nitrate) were provided. 2) In a helium atmosphere at an absolute pressure of 30 Pa, the raw material composition was heated to 1300°C by vapor phase growth to form vapor, and the vapor was cooled to 950°C to form deposits. 3) The sediment was collected and crushed into a powder. 4) The powder was placed in the reaction chamber of a vapor phase growth device into which a mixed gas of a carbon source gas (acetylene in a proportion of 20% by volume) and nitrogen gas was introduced, and it was heated to 750°C and held for 2 hours to obtain a carbon-coated product. 5) The carbon-coated product was mixed with a lithium source (lithium amide) in a 100:30 (mass ratio), heated to 650°C, and maintained at a constant temperature for 2 hours to carry out the lithiation reaction. The product was then recovered to obtain the negative electrode active material.

[0150] In the above manufacturing method, negative electrode active materials with varying Mn and Mg content can be obtained by adaptively adjusting the content of magnesium and manganese sources in the raw material mixture according to the composition of the target product. It should be understood that, due to the influence of the purity of elemental silicon and silicon dioxide, some elemental silicon and silicon dioxide already contain a certain amount of Mg and Mn elements. In this case, it is necessary to adaptively adjust the content of magnesium and manganese sources in the raw material mixture according to the components and composition of the target product sample.

[0151] Multiple negative electrode active material samples (hereinafter abbreviated as "samples") with different Mn and Mg content were prepared according to the method described above. Details are shown in Table 1. Examples 1 to 11 (E1 to E1 0 This includes comparative examples 1-3 (D1-D3).

[0152] In the above manufacturing method, silicon-based negative electrode active materials with varying Mg and Mn content can be obtained by adaptively adjusting the content of alkali metal sources, magnesium sources, and manganese sources in the raw material mixture according to the composition of the target product. It should be understood that, due to the influence of the purity of elemental silicon and silicon dioxide, some elemental silicon and silicon dioxide already contain a certain amount of Mg and Mn. In this case, it is necessary to adaptively adjust the content of magnesium sources and manganese sources in the raw material mixture according to the components and composition of the target product sample.

[0153] According to the method described above, several types of silicon-based anode active material samples (hereinafter referred to as "samples") with different Mg and Mn content were prepared and obtained. These samples have the following properties.

[0154] 1) The silicon-based anode active material was a silicon-based anode active material having a carbon coating layer, with the carbon coating layer accounting for 4.2 ± 1% of the content, and the remainder being the silicon-based anode active material. 2) The molar ratio of oxygen (O) to silicon (Si) in the silicon-based negative electrode active material was 1 ± 0.1:1. 3) Based on a silicon-based anode active material of 100%, the Li element content was 7.3 ± 0.5%. 4) Based on 100% silicon-based negative electrode active material, the Mg element content was as shown in Table 1. 5) Based on 100% silicon-based negative electrode active material, the Mn element content was as shown in Table 1. 6) Volume-average particle size D of silicon-based negative electrode active material v The size of particle 50 was 6.5 ± 0.5 μm. 7) The specific surface area of ​​the silicon-based negative electrode active material is 1.6 ± 0.25 m². 2 It was / g. 8) The powder volume resistivity of the silicon-based anode active material at a pressure of 4 MPa was 1 ± 0.1 Ω·cm. 9) The pressure density of the silicon-based anode active material at a pressure of 49,000 N is 1.6 ± 0.1 g / cm³. 3 That was the case. 10) The silicon-based negative electrode active material contained Li2SiO3, and the full width at half maximum of the XRD diffraction peak of Li2SiO3 was 0.7°±0.2°, with a crystallite size of 13±2 nm.

[0155] Table 1 shows silicon-based negative electrode active material samples with different Mg and Mn element content.

[0156] Manufacturing of button-type batteries (1) Manufacturing of the negative electrode sheet: The silicon-based negative electrode active material manufactured above, Super-P (conductive carbon black) as a conductive agent, and PAA (polyacrylic acid) as a binder were thoroughly mixed in an appropriate amount of deionized water in a mass ratio of 85:5:10 to form a uniform negative electrode slurry. The negative electrode slurry was coated onto the surface of the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet. (2) Counter electrode: Metallic lithium sheet. (3) Separator: Polyethylene (PE) film. (4) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. Then, LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. Fluoroethylene carbonate (FEC) was added, and the concentration of LiPF6 was 1 mol / L, and the mass percentage of FEC in the electrolyte was 6%. (5) Manufacturing of button-type batteries: The negative electrode sheet, separator, and counter electrode sheet (metal lithium sheet) described above were stacked in order, and the electrolyte described above was added to obtain a button-type battery.

[0157] Manufacturing of rechargeable batteries A mixture of the silicon-based negative electrode active material and artificial graphite prepared as described above (with a mass ratio of 15%:85%), carbon black (Super P) and carbon nanotubes (CNTs) as conductive agents, styrene-butadiene rubber as a binder, and sodium carboxymethylcellulose as a thickener were thoroughly mixed in an appropriate amount of deionized water in a weight ratio of 96.2%:0.7%:0.1%:1.8%:1.2% to form a negative electrode slurry. The negative electrode slurry was applied to two surfaces of the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0158] LiRing 0.8 Co 0.1 Mn 0.1O2 (NCM811), the conductive agent Super P, and the binder polyvinylidene fluoride were mixed in a weight ratio of 96.5%:1.5%:2%, and an appropriate amount of solvent NMP was added. The mixture was then uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was applied to two surfaces of the aluminum foil of the positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0159] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. Then, LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. Fluoroethylene carbonate (FEC) was added, and the concentration of LiPF6 was 1 mol / L, with FEC accounting for 6% of the mass of the electrolyte.

[0160] Using a PE separator, the positive electrode sheet and negative electrode sheet manufactured above were arranged in sequence with the PE separator so that the separator would separate them, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer casing, dried, and then injected with electrolyte. After going through processes such as vacuum packaging, standing, chemical conversion, and aging, a soft-pack secondary battery was obtained. The battery size was 13.5 cm × 6 cm and the capacity was 4 Ah.

[0161] 2. Analysis and detection methods 2.1 Elemental analysis (e.g., Mn, Mg, Si, and alkali metal elements) The elemental content has a known meaning in this art and may be measured by methods known in this art. After decomposing the silicon-based anode active material by referring to EPA-3052-1996, "Microwave Acid Decomposition of Silicates," the content of the target element can be measured using an ICAP-7000 inductively coupled plasma atomic emission spectrometer (ICP-OES) from Thermo Fisher Scientific, USA, according to EPA 6010D-2014, "Inductively Coupled Plasma Atomic Emission Spectroscopy." The specific measurement method is as follows: A 0.5 g sample of silicon-based anode active material was microwave-decomposed using 10 ml of nitric acid and 10 ml of hydrofluoric acid. After decomposition, the sample was placed in a 50 ml volumetric flask and brought to a constant volume, and the content of the target element was measured using an ICAP-7000 ICP-OES.

[0162] 2.2 Elemental Analysis (Oxygen, Carbon) The elemental content has a meaning known in the art and may be measured by methods known in the art. The carbon content in the silicon-based anode active material may be measured by referring to GB / T 20123-2006 / ISO 15350:2000, and the test instrument may be an HCS-140 infrared carbon-sulfur analyzer.

[0163] The oxygen content can be determined by referring to the general rules for elemental analysis using elemental analyzers, JY / T 017-1996, and the Elementar Rapid OXY Cube oxygen elemental analyzer can be used as the test instrument.

[0164] 2.3 Volume resistivity The volume resistivity of a material has a known meaning in the art and can be measured by known instruments and methods in the art. For example, the volume resistivity of the silicon-based anode active material of this application at a pressure of 4 MPa can be measured by the four-probe method. The measurement method includes placing the silicon-based anode active material powder of this application on a sample stage, applying a pressure of 4 MPa to the powder with a press, and after the pressure stabilizes, reading the volume resistivity of the silicon-based anode active material powder at a pressure of 4 MPa using a resistivity meter.

[0165] 2.4 Compression Density The compressive density of the material has a known meaning in this art and can be measured by instruments and methods known in this art, for example, by referring to the GB / T24533-2009 standard and using an electronic pressure tester such as the UTM7305 electronic pressure tester. Approximately 1 g of sample is accurately weighed, and the base area is 1.327 cm². 2 The material's compressive density can be obtained by placing it in a mold, applying a pressure of 49,000 N to the sample using a pressurizing device, holding it under this pressure for 30 seconds, releasing the pressure, and then measuring the height of the sample, using the formula ρ = m / (1.327 × h). In the formula, ρ represents the compressive density of the material, m represents the mass of the sample, and h represents the height of the sample after the pressure of 49,000 N has been applied, held under this pressure for 30 seconds, and then released.

[0166] 2. 5 Analysis of powder particle size Material D v 10, D v 50, D v 90 has a known meaning in this art and can be measured using methods known in this art. For example, it can be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000), referring to the GB / T 19077-2016 standard.

[0167] D v 10, D v 50, D v90 is physically defined as the particle size corresponding to when the cumulative volume distribution percentage of the silicon-based anode active material reaches 10%, 50%, and 90%, respectively.

[0168] 2. 6 Analysis of specific surface area The specific surface area of ​​a material has a known meaning in this art and can be measured by instruments and methods known in this art. For example, it can be measured using the specific surface area analysis method by nitrogen adsorption, referring to the GB / T 19587-2017 standard for measuring the specific surface area of ​​solids by gas adsorption BET method, and calculated using the BET (Brunauer Emmett Teller) method. Here, the specific surface area analysis by nitrogen adsorption may be performed using the Tri StarII 3020 specific surface area and pore size analyzer from Micromeritics, Inc. in the United States.

[0169] 2. 7 Battery performance measurement (1) Cycle capacity maintenance rate At 25°C and under normal pressure, a button-type battery was discharged at a constant current of 0.1C to 0.005V, then discharged again at 0.04C to 0.005V, and allowed to stand for 5 minutes. The discharge capacity, i.e., the first lithium insertion capacity, was recorded. Subsequently, the battery was charged at a constant current of 0.1C to 1.5V, and allowed to stand for 5 minutes. This constituted one charge-discharge cycle, and the charge capacity, i.e., the first lithium desorption capacity, was recorded. For the button-type battery, 30 charge-discharge cycles were performed according to the above method, and the lithium desorption capacity for each cycle was recorded.

[0170] Cycle capacity retention rate (%) = Lithium desorption capacity at 30 cycles / Lithium desorption capacity at 1 cycle × 100%

[0171] (2) DC resistance of the battery DCR At 25°C, the secondary battery was charged with a constant current of 0.33C to 4.25V, then discharged with a constant current of 1C for 48 minutes to adjust the battery's SOC to 20%, and left to stand for 30 minutes. The battery voltage at this time was recorded as U1. Using a sampling point of 0.1 seconds, the battery was discharged with a constant current of 3C for 30 seconds, and the voltage at the end of discharge was recorded as U2. The initial DCR of the battery was expressed as the discharge DCR when the battery's SOC was 20%, and the initial DCR of the battery was given by (U1-U2) / 3C.

[0172] [Table 1]

[0173] 3. Results and Analysis Table 1 shows the raw materials and composition of silicon-based anode active materials in several embodiments of this application, the content and ratio of Mg and Mn elements in the silicon-based anode active material product, and the performance of batteries using the above silicon-based anode active material as the anode active material. Each of these is examined below.

[0174] (1) Regarding the composition of raw materials The raw material silicon used for samples (E1~E10) was metallic silicon 1 (Si≧99.9wt%, Mg=300ppm, Mn=20ppm).

[0175] The raw material silicon used for samples (D1-D3) was metallic silicon 2 (Si ≥ 99.9 wt%, without Mg or Mn).

[0176] table 1 As can be seen, the Mg and Mn elements in the silicon-based negative electrode active material may come from various sources. a) The Mg element in the silicon-based negative electrode active material may be derived from the raw material, metallic silicon. b) The Mn element in the silicon-based negative electrode active material may be derived from the raw material, metallic silicon. c) The Mg element in the silicon-based negative electrode active material may be derived from an additional magnesium source. d) The Mn element in the silicon-based negative electrode active material may originate from an additional manganese source.

[0177] Those skilled in the art can obtain a silicon-based anode active material having the desired chemical composition by adaptively adjusting the content of Mn and Mg elements in the raw materials according to the desired chemical composition of the silicon-based anode active material. If it is necessary to increase or decrease the content of Mg element in the desired silicon-based anode active material, metallic silicon (or silicon oxide) with a higher or lower Mg content may be used, or the magnesium source added to the raw materials may be increased or decreased. If it is necessary to increase or decrease the content of Mn element in the desired silicon-based anode active material, metallic silicon (or silicon oxide) with a higher or lower Mn content may be used, or the manganese source added to the raw materials may be increased or decreased.

[0178] (2) Synergistic effect of Mn and Mg The initial discharge ratio capacities of the above samples were almost identical, all within the range of 1400 mAh / g ± 50 mAh / g, and the differences between the samples were mainly due to DC. resistance This is reflected in the cycle capacity maintenance rate.

[0179] The experimental data in Table 1 demonstrates that the combination of Mg and Mn in the negative electrode active material of this application produced an unexpected synergistic effect.

[0180] The following is a detailed analysis of Example E1 and Comparative Examples D1, D2, and D3.

[0181] Comparative Example D3, a silicon oxide-based composite, contained neither Mg nor Mn elements, and its cycle capacity retention rate was 80.3%. Comparative Example D1, a silicon oxide-based composite, contained 300 ppm of Mg but no Mn elements, and its cycle capacity retention rate was 83.5%, a slight increase of 3.2% compared to D3. Comparative Example D2, a silicon oxide-based composite, contained 30 ppm of Mn but no Mg elements, and its cycle capacity retention rate was 84.1%, a slight increase of 3.8% compared to D3.

[0182] The silicon oxide composite of Example E1 contained both 300 ppm of Mg and 30 ppm of Mn, and its cycle capacity retention rate was 92.1%, an increase of 11.8% compared to D1. This increase was far greater than the simple sum of the performance improvements from adding Mg or Mn individually (i.e., 3.2% + 3.8% = 7%). Therefore, the above experimental evidence demonstrates that the combination of Mg and Mn indeed produced an unexpected synergistic effect.

[0183] (3) Weight ratio of Mg / Mn in silicon oxide composites The experimental data in Table 1 further demonstrates that the performance of the negative electrode active material was significantly improved when the weight ratio of Mg / Mn was greater than 1.

[0184] In Example E10, the Mg / Mn weight ratio was 0.8:1 (less than 1), and the cycle capacity retention rate of the anode active material was only 85.7%. In Examples E1 to E9, the Mg / Mn weight ratio was 1.7:1 to 25:1 (greater than 1), and the cycle capacity retention rate of the anode active material was 86.9% to 92.1%, which was superior to Example E10. From the above experimental data, it was shown that when the Mg content in the silicon oxide composite was greater than the Mn content, the silicon oxide composite showed a more significant improvement in cycle capacity retention performance.

[0185] (4) Mg / Mn ratio in silicon oxide composites As shown in Examples E1 to E9, when the weight ratio of Mg / Mn was 1.7:1 to 25:1, the cycle capacity retention rate of the negative electrode active material was 86.9% to 92.1%, showing an even further improved cycle capacity retention rate.

[0186] As shown in Examples E1 to E4, when the weight ratio of Mg / Mn was 2.5:1 to 10:1, the cycle capacity retention rate of the negative electrode active material was 91.5% to 92.1%, and the DC internal resistance was 13.9 mΩ to 14.3 mΩ, showing further improved cycle capacity retention rate and DC internal resistance.

[0187] (5) Regarding the content of Mg and Mn elements in silicon oxide composites As shown in Examples E1 to E10, the Mg element content in the silicon oxide composite is 80 ppm or more, for example, 100 ppm to 500 ppm, and the negative electrode active material has improved cycle capacity maintenance rate and DC resistance This was shown.

[0188] As shown in Examples E1 to E9, the Mg element content in the silicon oxide composite is 100 ppm to 500 ppm, and the negative electrode active material exhibits improved cycle capacity maintenance and DC. resistance This was shown.

[0189] As shown in Examples E1 to E10, the Mn element content in the silicon oxide composite was 200 ppm or less, for example, 10 ppm to 100 ppm. The negative electrode active material exhibited improved cycle capacity retention and DC. resistance This was shown.

[0190] As shown in Examples E1 to E9, the Mn element content in the silicon oxide composite was 10 ppm to 100 ppm. The negative electrode active material exhibited improved cycle capacity retention and DC. resistance This was shown.

[0191] From the experimental data above, when silicon oxide-based composites contain either Mn or Mg elements alone, the cycle capacity maintenance rate In only sex Noh It was shown that there was an improvement, but the degree of improvement was not significant. When the silicon oxide composite contains a combination of Mn and Mg elements, the negative electrode active material maintains cycle capacity. rate improvement The effect of achieving both and a reduction in DC resistance.This shows that the improvement was particularly significant, indicating that the Mn and Mg elements produced an unexpected synergistic effect.

[0192] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and all embodiments having substantially the same technical idea and achieving the same function and effect within the scope of the technical solution of this application are included in the technical scope of this application. Furthermore, other forms that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included in the scope of this application, without departing from the gist of this application. [Explanation of Symbols]

[0193] 1 Battery pack 2. Top box 3. Lower box 4 Battery Modules 5 Secondary battery 51 cases 52 Electrode assembly 53 lid plate

Claims

1. A silicon-based negative electrode active material containing an alkali metal element-containing silicate and also containing both Mg and Mn elements.

2. The silicon-based negative electrode active material according to claim 1, wherein the content of the Mg element is greater than the content of the Mn element.

3. The silicon-based negative electrode active material according to any one of claims 1 to 2, wherein the mass ratio of the Mg element to the Mn element is 1.7:1 or greater, and selectively 2.5:1 to 10:

1.

4. The silicon-based negative electrode active material according to any one of claims 1 to 3, wherein the content of the Mg element is 80 ppm or more, and selectively 100 ppm to 500 ppm.

5. The silicon-based negative electrode active material according to any one of claims 1 to 4, wherein the content of the Mn element is 200 ppm or less, and selectively between 10 ppm and 100 ppm.

6. (1) Volume average particle size D of the silicon-based negative electrode active material ｖ 50 is 4 μm to 10 μm, and selectively 5 μm to 8 μm, (2) The specific surface area of ​​the silicon-based negative electrode active material is 3 m² ２ It is less than / g and selectively 0.5m ２ / g~2m ２ The fact that it is / g, (3) The powder volume resistivity of the silicon-based negative electrode active material at a pressure of 4 MPa is 3 Ω·cm or less, and selectively between 0.5 Ω·cm and 1.5 Ω·cm, (4) The pressure density of the silicon-based negative electrode active material at a pressure of 49,000 N is 1.4 to 1.8 g / cm³. ３ Therefore, selectively 1.5 to 1.7 g / cm³ ３ That is, (5) The alkali metal element-containing silicate contains a lithium-containing silicate, and the full width at half maximum of the XRD diffraction peak of the lithium-containing silicate is 2.0° or less, and selectively between 0.4° and 1.5°. (6) The alkali metal element-containing silicate contains a lithium-containing silicate, and the crystallite size of the lithium-containing silicate is 20 nm or less. A silicon-based negative electrode active material according to any one of claims 1 to 5, having one or more of the features of the above.

7. A silicon-based negative electrode active material according to any one of claims 1 to 6, wherein at least a portion of the surface is covered with a coating layer.

8. A method for producing a silicon-based negative electrode active material according to any one of claims 1 to 7, To provide raw materials containing Si, O, Mn and Mg elements, The process involves heating the raw material to form steam using a vapor phase growth method, and then cooling the steam to form a deposit. The process involves crushing the sediment and obtaining the crushing product, A method for producing a silicon-based negative electrode active material, comprising reacting a previous product with an alkali metal source to obtain an alkali metallization product.

9. A coating treatment is performed on an alkali metallization product to obtain a product having a coating layer. The method according to claim 8, further comprising

10. (1) In the operation of heating the raw material to form steam, the heating temperature is 1100 to 1550°C, (2) In the operation of cooling the steam to form a deposit, the cooling temperature is 700 to 900°C, The method according to any one of claims 8 to 9, having one or more of the features of the above.

11. A secondary battery comprising a negative electrode containing a silicon-based negative electrode active material according to any one of claims 1 to 7.

12. An electrical device including a secondary battery as described in claim 11.

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