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

Abstract

The present application provides a silicon-based negative electrode active material, the silicon-based negative electrode active material including an alkaline earth metal element-containing silicate, and the silicon-based negative electrode active material simultaneously containing K and Fe. In one embodiment, the content of the K element is greater than the content of Fe. In one embodiment, the mass ratio of the K element to the Fe element is 8:1 or more, optionally 10:1 to 36:1. In one embodiment, the content of the K element is 400 ppm or more, optionally 800 ppm to 2000 ppm.

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and in particular to silicon-based negative electrode active materials, secondary batteries, and power consuming devices. [Background technology]

[0002] In recent years, as the application range of secondary batteries becomes increasingly wider, secondary batteries are widely used in energy storage power supply systems such as hydroelectric power plants, thermal power plants, wind power plants, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0003] Silicon-based materials are considered to be one of the promising anode active materials due to their high capacity. With the remarkable development of secondary batteries, the demands on their electrochemical performance are increasing. Therefore, there is still a need in the art for silicon-based anode active materials with better performance. Summary of the Invention [Means for solving the problem]

[0004] In view of the above problems, the present application provides a novel silicon-based negative electrode active material, a secondary battery, and a power consuming device, each of which is described below.

[0005] According to a first aspect, the present application provides a silicon-based negative electrode active material, the silicon-based negative electrode active material including an alkaline earth metal element-containing silicate, and the silicon-based negative electrode active material simultaneously containing K and Fe elements.

[0006] In the above solution, the silicon-based negative electrode active material contains a combination of K and Fe, and this particular combination improves the initial coulombic efficiency and kinetic performance of the silicon-based negative electrode active material. The combination of K and Fe exhibits an unexpected synergistic effect, and the technical effect achieved by combining the two elements is significantly superior to the simple addition of each element. Without being limited by the following theory, the inclusion of Fe improves the active ion and electron conductivity during the active ion (lithium ion) absorption / desorption process of the negative electrode active material, suppresses the increase in negative electrode impedance during cycling, and improves the rate performance of the material. At the same time, the potassium silicate produced by the reaction of K with the silicon-oxygen material is beneficial for improving the capacity of the negative electrode active material, thereby improving the initial coulombic efficiency of secondary batteries. Therefore, by using the negative electrode active material of the present application, secondary batteries can simultaneously achieve relatively high initial coulombic efficiency and good rate performance while maintaining a relatively high energy density.

[0007] In some embodiments, the content of the K element is greater than the content of the Fe element, and within this ratio range, the K element and the Fe element exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the silicon-based negative electrode active material.

[0008] In some embodiments, the mass ratio of the K element to the Fe element is 8:1 or more, and optionally 10:1 to 36:1, in which case the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0009] In some embodiments, the content of the K element is 400 ppm or more, and preferably 800 ppm to 2000 ppm, and the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0010] In some embodiments, the content of the Fe element is 500 ppm or less, preferably 30 ppm to 400 ppm, and the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0011] In some embodiments, the volume average particle diameter D v 50 is 4 μm-10 μm, and optionally 5 μm-8 μm. In the above solution, the silicon-based negative electrode active material has improved dynamic performance.

[0012] In some embodiments, the specific surface area of ​​the silicon-based negative electrode active material is 6 m 2 / g or less, and selectively 3m 2 / g-5m 2 / g. In this solution, the silicon-based negative electrode active material has improved initial coulombic efficiency.

[0013] In some embodiments, the silicon-based negative electrode active material has a powder volume resistivity of 6 Ω cm or less, and optionally 0.5 Ω cm to 4.5 Ω cm, under a pressure of 4 MPa, which provides improved dynamic performance.

[0014] In some embodiments, the silicon-based negative electrode active material has a compaction density of 1.4-1.8 g / cm under a pressure of 49000 N. 3 and selectively 1.5-1.7g / cm 3 In addition, in the above solution, the silicon-based negative electrode active material has improved energy density.

[0015] In some embodiments, the alkaline earth metal element-containing silicate comprises a magnesium-containing silicate, and the magnesium-containing silicate has a half-width of 0.50° or less. In such embodiments, the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0016] In some embodiments, the alkaline earth metal element-containing silicate comprises a magnesium-containing silicate, and the magnesium-containing silicate has a crystal grain size of 21 nm or less. In such embodiments, the silicon-based negative electrode active material has improved capacity and ionic conductivity.

[0017] In some embodiments, at least a portion of the surface of the silicon-based negative electrode active material has a coating layer.

[0018] According to a second aspect, the present application provides a method for producing the silicon-based negative electrode active material according to any one of the above aspects, providing a raw material containing Si element, O element, K element, Fe element and alkaline earth metal element; using a vapor deposition process to heat the source material to form a vapor and then cool the vapor to form a deposit; and grinding the sediment to obtain a ground product.

[0019] In some embodiments, the method for producing a silicon-based negative electrode active material includes: The method further includes subjecting the ground product to a coating treatment to obtain a product having a coating layer.

[0020] In some embodiments, the heating temperature for heating the feedstock to form steam is 1100-1550°C.

[0021] In some embodiments, the cooling temperature for cooling the vapor to form the deposit is 700-900°C.

[0022] According to a third aspect, the present application provides a secondary battery including a negative electrode, the negative electrode including the silicon-based negative electrode active material described above.

[0023] According to a fourth aspect, the present application provides a power consumption device including the secondary battery according to any one of the above claims. [Effects of the Invention]

[0024] One or more embodiments of the present application have one or more of the following beneficial effects: (1) The K element and the Fe element have an unexpected synergistic effect, and the technical effect obtained by combining the two is significantly superior to the simple addition of the two elements. (2) silicon-based negative electrode active materials have improved first coulombic efficiency; (3) Silicon-based negative electrode active materials have improved dynamic performance; (4) Silicon-based negative electrode active materials have a relatively high energy density. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 2] FIG. 1 is an exploded view of a secondary battery according to an embodiment of the present application. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consumption device powered by a secondary battery according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the silicon-based negative electrode active material and its manufacturing method, positive electrode plate, negative electrode plate, secondary battery, battery module, battery pack, and device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and repeated description of actually identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate easy understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0027] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the following ranges are also contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. Unless otherwise specified, the numerical range "ab" in this application is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise stated, all embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed 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, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0030] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0031] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0032] In this specification, ppm (parts per million) means parts per million. However, when ppm is used to describe the content of K or Fe, it refers to the mass of K or Fe in the silicon-based negative electrode active material as parts per million of the mass of the silicon-based negative electrode active material.

[0033] [Secondary battery] A secondary battery is also called a rechargeable battery or storage battery, and is a battery that can be continuously used by activating the active material through charging after discharging the battery.

[0034] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process of the battery, active ions (e.g., sodium ions) are absorbed and desorbed by moving back and forth between the positive electrode plate and the negative electrode plate. The separator, installed between the positive electrode plate and the negative electrode plate, primarily serves to prevent short-circuiting between the positive and negative electrodes and allows the active ions to pass through. The electrolyte primarily serves to conduct the active ions between the positive and negative electrode plates.

[0035] An example of a secondary battery is 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 and negative electrodes are separated by a separator to prevent short circuits, and the electrolyte permeates the positive and negative electrodes to ensure ion conduction. When charging, Li + Li is released from the positive electrode, penetrates the separator through the electrolyte, and is absorbed into the negative electrode, putting the positive electrode in a high-potential lithium-deficient state and the negative electrode in a low-potential lithium-rich state. + The electrons are released from the negative electrode, penetrate the separator through the electrolyte, and are absorbed into the positive electrode material, restoring the positive electrode to a lithium-rich state. To maintain charge balance, the same number of electrons are transferred through an external circuit during the charge and discharge process, and Li + Lithium ions migrate between the positive and negative electrodes together with the lithium ions, causing oxidation and reduction reactions at the positive and negative electrodes, respectively. Lithium ions can reversibly migrate between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are made of an absorption-type material that can reversibly absorb and desorb lithium ions.

[0036] The secondary battery is, for example, a sodium ion battery. The sodium ion battery is mainly composed 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 permeates the positive and negative electrodes to ensure ion conduction. During charging, Na + is released from the positive electrode, penetrates the separator through the electrolyte, and is absorbed by the negative electrode, putting the positive electrode in a high-potential sodium-deficient state and the negative electrode in a low-potential sodium-rich state. + The sodium is released from the negative electrode, penetrates the separator through the electrolyte, and is absorbed into the positive electrode material, restoring the positive electrode to a sodium-rich state. To maintain the charge balance, the same number of electrons are transferred through an external circuit during the charge and discharge process, and the sodium is absorbed into the positive electrode material. + Sodium ions migrate between the positive and negative electrodes together with the electrolyte, causing oxidation and reduction reactions at the positive and negative electrodes, respectively. Sodium ions can reversibly migrate between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are made of an absorption-type material that allows reversible absorption and desorption of sodium ions.

[0037] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0038] The negative electrode active material of the present application is a silicon-based negative electrode active material, which includes an alkaline earth metal element-containing silicate, and the silicon-based negative electrode active material simultaneously contains K and Fe elements.

[0039] In the above solution, the silicon-based negative electrode active material contains a combination of K and Fe, and this particular combination improves the initial coulombic efficiency and cycle capacity retention of the silicon-based negative electrode active material. The combination of K and Fe exhibits an unexpected synergistic effect, and the technical effect achieved by combining the two is significantly superior to the simple addition of either element. Without being limited by the following theory, potassium silicate, produced by the reaction of K with silicon dioxide, reduces lithium consumption during the initial charge / discharge process and improves the capacity of the negative electrode active material, thereby improving the initial coulombic efficiency of secondary batteries. At the same time, Fe improves the conductivity of active ions and electrons during the negative electrode active material's absorption / desorption of active ions (lithium ions), reducing the negative electrode impedance during cycling, thereby effectively improving the rate performance of the battery. The combination of Fe and K improves ionic conductivity and also moderates some of the internal expansion of the material. Therefore, by employing the negative electrode active material of the present application, the secondary battery can simultaneously achieve both a relatively higher initial coulombic efficiency and good rate performance, on the premise that it has a relatively higher energy density.

[0040] In some embodiments, the silicon-based negative electrode active material includes a silicon-based negative electrode active material. The silicon in the silicon-based negative electrode active material may exist in the form of multiple silicon phases, including crystalline silicon. Specifically, the silicon phases may be uniformly distributed and occluded / embedded in a matrix including the silicon-based negative electrode active material. In other words, the silicon phases may be uniformly dispersed in the matrix. The silicon phase is a group formed by a set of one or more silicon crystals, and there may be a single group or two or more groups.

[0041] In some embodiments, the K and Fe elements grow in the silicon-based negative electrode active material, for example, during vapor deposition of the silicon-based negative electrode active material. In some embodiments, the K and Fe elements grow in the silicon-based negative electrode active material during co-vapor deposition with the silicon-based negative electrode active material.

[0042] In some embodiments, the silicon-based negative electrode active material has a composite structure in which one or more nanocrystals are dispersed in a silicon-oxygen material matrix, such as a structure in which Si crystal grains and silicate crystal grains are dispersed in a silicon-oxygen material matrix.

[0043] In some embodiments, the content of the K element is greater than the content of the Fe element, and within this ratio range, the K element and the Fe element exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the silicon-based negative electrode active material.

[0044] In some embodiments, the silicon-based negative electrode material has a K to Fe mass ratio of 8:1 or greater, where K and Fe exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0045] In some embodiments, the silicon-based negative electrode material has a K to Fe mass ratio of 10:1 to 36:1, where K and Fe exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0046] In some embodiments, the silicon-based negative electrode material has a K to Fe mass ratio of 20:1 to 32:1, where K and Fe exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0047] In some embodiments, the mass ratio of K to Fe in the silicon-based negative electrode material may be 60:1 or less, optionally 50:1 or less, optionally 40:1 or less, optionally 30:1 or less, optionally 25:1 or less, optionally 20:1 or less, or optionally 15:1 or less. In some embodiments, the mass ratio of K to Fe in the silicon-based negative electrode material may be 8:1 or more, optionally 10:1 or more, optionally 12:1 or more, optionally 13:1 or more, optionally 16:1 or more, or optionally 18:1 or more. The mass ratio of K to Fe may be within any of the upper and lower limits described above. Within the above ratio range, K and Fe exhibit an unexpected synergistic effect, further significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0048] In some embodiments, the mass ratio of K to Fe in the silicon-based negative electrode material is optionally 21-26:1, more preferably 21-27:1, more preferably 20-27:1, more preferably 20-32:1, more preferably 13-32:1, more preferably 13-34:1, more preferably 13-54:1, more preferably 16-54:1, more preferably 16-30:1, and more preferably 18-25:1.

[0049] In some embodiments, the content of K in the silicon-based negative electrode material is 400 ppm or more. Within this content range, K and Fe exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0050] In some embodiments, the content of K in the silicon-based negative electrode material is 800 ppm to 2000 ppm. This allows the negative electrode active material to have improved first cycle efficiency and kinetic performance. Within this content range, K and Fe exhibit an unexpected synergistic effect, significantly improving the first cycle coulombic efficiency and kinetic performance of the negative electrode active material.

[0051] In some embodiments, the content of K in the silicon-based negative electrode material is 800 ppm to 1800 ppm. This allows the negative electrode active material to have improved first cycle efficiency and kinetic performance. Within this content range, K and Fe exhibit an unexpected synergistic effect, significantly improving the first cycle coulombic efficiency and kinetic performance of the negative electrode active material.

[0052] In some embodiments, the content of K in the silicon-based negative electrode material is 1200 ppm to 1600 ppm. This allows the negative electrode active material to have improved first cycle efficiency and kinetic performance. Within this content range, K and Fe exhibit an unexpected synergistic effect, significantly improving the first cycle coulombic efficiency and kinetic performance of the negative electrode active material.

[0053] In some embodiments, the upper limit of the K content may be selected from 2000 ppm, 1800 ppm, 1600 ppm, 1500 ppm, 1400 ppm, 1300 ppm, 1200 ppm, and 1000 ppm, and the lower limit of the K content may be selected from 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, and 1200 ppm. That is, the K content range may be any of the upper and lower limits described above. Within the above content range, K and Fe exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0054] In some embodiments, the content of K element in the silicon-based negative electrode material is optionally 400 ppm-1600 ppm, 800 ppm-1600 ppm, 1300-1600 ppm, more optionally 700-1400 ppm, more optionally 800-1500 ppm, more optionally 900-1600 ppm, and more optionally 1000-1500 ppm.

[0055] In some embodiments, the silicon-based negative electrode material contains 500 ppm or less of Fe, which results in improved first cycle efficiency and kinetic performance of the negative electrode active material.

[0056] In some embodiments, the content of Fe in the silicon-based negative electrode material is 30 ppm to 500 ppm, which results in improved first cycle efficiency and kinetic performance of the negative electrode active material.

[0057] In some embodiments, the content of Fe in the silicon-based negative electrode material is 30 ppm to 400 ppm, which results in improved first cycle efficiency and kinetic performance of the negative electrode active material.

[0058] In some embodiments, the upper limit of the Fe content in the silicon-based negative electrode material may be selected from the group consisting of 500 ppm, 400 ppm, 300 ppm, 260 ppm, 200 ppm, 170 ppm, 150 ppm, 130 ppm, 100 ppm, 80 ppm, and 60 ppm, and the lower limit of the Fe content may be selected from the group consisting of 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, and 100 ppm. That is, the Fe content range may be any of the upper and lower limit values. Within the above content range, K and Fe exhibit an unexpected synergistic effect, significantly improving the initial coulombic efficiency and kinetic performance of the negative electrode active material.

[0059] In some embodiments, the content of Fe element in the silicon-based negative electrode material is optionally 15-500 ppm, 15-300 ppm, 15-150 ppm, 15-80 ppm, 15-60 ppm, 20-260 ppm, 20-150 ppm, 20-100 ppm, 20-80 ppm, 20-60 ppm, 30-200 ppm, 30-100 ppm, 35 -400ppm, 35-300ppm, 35-200ppm, 35-100ppm, 35-80ppm, 35-60ppm, 40-170ppm, 40-130ppm, 40-100ppm, 40-80ppm, 45-100ppm, 60-300ppm, 60-150ppm, 80-500ppm, 90-300ppm, 100-260ppm.

[0060] In some embodiments, the silicon-based negative electrode active material has a volume average particle size Dv50 of 4 μm-10 μm, preferably 5 μm-8 μm, and has improved initial coulombic efficiency and kinetic performance.

[0061] In some embodiments, the volume average particle diameter D v The average particle size D is preferably 4 μm or more, and more preferably 5 μm or more, which can reduce the film formation and consumption of active ions at the negative electrode and reduce the side reaction of the electrolyte at the negative electrode, thereby reducing the initial coulomb efficiency of the secondary battery and improving the cycle performance of the secondary battery. It can also reduce the amount of adhesive added to the negative electrode plate, which is advantageous for improving the energy density of the secondary battery. v 50 is preferably 10 μm or less, more preferably 8 μm or less, which shortens the migration path of active ions and electrons in the material particles and increases the migration speed of ions and electrons, thereby improving the dynamic performance of the secondary battery and preventing the silicon-based negative electrode active material from exploding during charging and discharging, which is advantageous for further improving the cycle performance of the secondary battery.

[0062] In some embodiments, the specific surface area of ​​the silicon-based negative electrode active material is 6 m 2 / g or less, and selectively 3m2 / g-5m 2 / g. In this solution, the silicon-based negative electrode active material has improved initial coulombic efficiency and cycle capacity retention.

[0063] In some embodiments, the specific surface area of ​​the silicon-based negative electrode active material is 3 m 2 / g-6m 2 / g. The specific surface area is selectively 3m 2 / g or more can provide more active sites on the surface of the material particles, effectively improving the electrochemical performance of the silicon-based negative electrode active material and meeting the requirements for the dynamic performance of secondary batteries. 2 / g or less, which is advantageous in reducing the side reactions of the electrolyte at the negative electrode and further reduces the consumption of active ions in the film formation at the negative electrode, thereby reducing the initial coulomb efficiency of the secondary battery and improving the cycle performance of the secondary battery.

[0064] In some embodiments, the silicon-based negative electrode active material has a powder volume resistivity of 6 Ω cm or less, and preferably 0.5 Ω cm to 4.5 Ω cm, under a pressure of 4 MPa. In these embodiments, the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0065] In some embodiments, the volume resistivity of the silicon-based negative electrode active material powder under a pressure of 4 MPa is 6 Ω·cm or less, and more preferably 4.5 Ω·cm or less. Having the volume resistivity of the silicon-based negative electrode active material powder within this range reduces the inhibition of electron movement within the particles, which is beneficial for improving the dynamic performance of the silicon-based negative electrode active material and reducing negative electrode polarization, thereby improving the cycle life of secondary batteries. The volume resistivity of the powder can be reduced by performing a surface treatment on the silicon-based negative electrode active material.

[0066] In some embodiments, the silicon-based negative electrode active material has a compaction density of 1.4-1.8 g / cm under a pressure of 49000 N.3 and selectively 1.5-1.7g / cm 3 In addition, in the above solution, the silicon-based negative electrode active material has improved energy density.

[0067] In some embodiments, the alkaline earth metal element-containing silicate comprises a magnesium-containing silicate, and the magnesium-containing silicate has a half-width of 0.50° or less. In such embodiments, the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0068] In some embodiments, the alkaline earth metal element-containing silicate comprises a magnesium-containing silicate, and the magnesium-containing silicate has a crystal grain size of 21 nm or less. In such embodiments, the silicon-based negative electrode active material has improved initial coulombic efficiency and kinetic performance.

[0069] In some embodiments, the XRD pattern of the silicon-based negative electrode active material has a first diffraction peak at a diffraction angle 2θ of 26°-30°, with a half-width of 0.8°-3.2°, a second diffraction peak at a diffraction angle 2θ of 46°-50°, with a half-width of 1.0°-4.2°, and a third diffraction peak at a diffraction angle 2θ of 54°-58°, with a half-width of 0.8°-4.5°. In the above embodiments, the negative electrode active material has these three diffraction peaks with half-widths within the above ranges, indicating good crystallite size and appropriate crystallinity, which results in relatively high capacity performance and initial coulombic efficiency, and the negative electrode active material maintains relatively high structural stability and is less susceptible to cracking during charge-discharge cycling, thereby improving the cycle life of the battery.

[0070] In some embodiments, the silicon-based negative electrode material contains Si and O, and the molar ratio of O to Si is greater than 0 and less than 2, preferably 0.2-1.8:1, more preferably 0.3-1.7:1, more preferably 0.4-1.6:1, more preferably 0.6-1.5:1, more preferably 0.7-1.4:1, more preferably 0.8-1.3:1, more preferably 0.9-1.2:1, and more preferably 1.0-1.1:1.

[0071] In some embodiments, the alkaline earth metal element includes one or more of Mg, Be, Ca, and Ba. In these embodiments, the silicon-based negative electrode active material exhibits improved first cycle efficiency and kinetic performance.

[0072] In some embodiments, the alkaline earth metal element comprises Mg. In the above embodiments, the silicon-based negative electrode active materials all exhibit improved first cycle efficiency and kinetic performance.

[0073] In some embodiments, at least a portion of the surface of the silicon-based negative electrode active material has a coating layer.

[0074] In some embodiments, at least a portion of the surface of the silicon-based negative electrode active material is coated with a coating layer.

[0075] In some embodiments, the coating layer material may include one or more of a polymer, a carbon material, a metal material, and a metal compound. For example, the coating layer may include one or more of a polymer coating layer, a carbon coating layer, and a metal compound coating layer. Optionally, the polymer may be selected from one or more of polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride, and polyethylene. Optionally, the carbon material may include one or more of graphite, mesocarbon microbeads (MCMB), pyrolytic carbon of hydrocarbon compounds, hard carbon, and soft carbon, where graphite may be one or more of natural graphite and artificial graphite. Optionally, the metal compound may include one or more of Ti5Si3, Al2O3, and TiO2. The coating layer may further mitigate the volume expansion effect of the silicon-based negative electrode active material and improve the cycle life of the material. At the same time, the coating layer also provides protection to the silicon-based negative electrode active material, suppressing side reactions of the electrolyte on the material surface and protecting the material surface from erosion by the electrolyte, thereby allowing the silicon-based negative electrode active material to exhibit a relatively high capacity and further improving the cycle life of the battery.

[0076] According to a second aspect, the present application provides a method for producing the silicon-based negative electrode active material according to any one of the above aspects, providing a raw material containing Si element, O element, K element, Fe element and alkaline earth metal element; using a vapor deposition process to heat the source material to form a vapor and then cool the vapor to form a deposit; and grinding the sediment to obtain a ground product.

[0077] In some embodiments, the method for producing a silicon-based negative electrode active material includes: The method further includes subjecting the ground product to a coating treatment to obtain a product having a coating layer.

[0078] In some embodiments, the Si element in the raw material may be derived from elemental silicon and silicon oxide, and the O element in the raw material may be derived from silicon oxide. Here, the elemental silicon includes, for example, metallic silicon. The silicon oxide includes, for example, one or more of silicon suboxide (SiO) and silicon dioxide (SiO2). The metallic silicon is, for example, any one of metallic silicon or industrial silicon specified in standard GB / T 2881-2014. The purity of the elemental silicon is, for example, 3N or more, 4N or more, 5N or more, or 6N or more.

[0079] In some embodiments, the K element in the raw material may be derived from the K element contained in elemental silicon or silicon oxide itself, or from a potassium source added to the raw material.

[0080] In some embodiments, the Fe element in the raw material may be derived from the Fe element contained in elemental silicon or silicon oxide itself, or from an iron source added to the raw material.

[0081] In some embodiments, the alkaline earth metal element in the raw material may be derived from the alkaline earth metal element contained in elemental silicon or silicon oxide itself, or may be derived from an alkaline earth metal source added to the raw material.

[0082] In some embodiments, the potassium source may be selected from one or more of potassium oxide, potassium hydroxide, potassium chloride, and potassium silicate.

[0083] In some embodiments, the iron source may be selected from one or more of metallic iron, iron alloys, and iron compounds, where the iron compounds may be selected from one or more of iron oxides, iron sulfides, iron carbonates, iron hydroxides, iron acetates, iron oxalates, iron nitrates, and iron sulfates.

[0084] In some embodiments, the alkaline earth metal source may be selected from one or more of an alkaline earth metal, an alkaline earth metal alloy, and an alkaline earth metal compound, wherein the alkaline earth metal compound may be selected from one or more of an alkaline earth metal oxide, an alkaline earth metal sulfide, an alkaline earth metal carbonate, an alkaline earth metal hydroxide, an alkaline earth metal acetate, an alkaline earth metal oxalate, an alkaline earth metal nitrate, and an alkaline earth metal sulfate.

[0085] In some embodiments, the source material containing Si, O, K, Fe, and alkaline earth metal elements includes elemental silicon, silicon dioxide, a potassium source, an iron source, and an alkaline earth metal source.

[0086] In some embodiments, the content of K element in the silicon oxide composite is adjusted by adjusting the type and amount of potassium source in the raw materials.

[0087] In some embodiments, the Fe content in the silicon oxide-based composite is adjusted by one or more means, such as mixing silicon oxide powders or metal silicon powders with different Fe contents, and adjusting the type and amount of iron source added.

[0088] In some embodiments, the heating of the feedstock to form the vapor is carried out in an inert atmosphere at atmospheric or reduced pressure.

[0089] In some embodiments, the cooling of the vapor to form the deposit is carried out in an inert atmosphere at atmospheric or reduced pressure.

[0090] In the above manufacturing method, the inert atmosphere may be a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, etc. Optionally, the absolute pressure of the inert atmosphere is normal pressure (1 atmosphere) or decompression (less than 1 atmosphere). Optionally, the absolute pressure of the inert atmosphere is 10 Pa-950 Pa, and more optionally, 20 Pa-100 Pa.

[0091] In some embodiments, by decreasing the pressure (i.e., increasing the degree of vacuum) within the above inert atmosphere pressure range, the contents of K and Fe in the final silicon-based negative electrode active material can be correspondingly increased.

[0092] In some embodiments, the heating temperature for heating the feedstock to form steam is 1100-1550°C.

[0093] In some embodiments, the cooling temperature for cooling the vapor to form the deposit is 700-900°C.

[0094] In some embodiments, the cooling temperature during the cooling of the vapor to form the deposit can be adjusted to obtain a suitable crystal structure for the deposit. Optionally, the cooling temperature is 850°C-1050°C, which is beneficial for the silicon-based negative electrode active material to obtain a good crystallite size and suitable crystallinity, thereby providing the silicon-based negative electrode active material with a relatively high initial coulombic efficiency and cycle performance. If the cooling temperature is lower than 800°C, the crystallinity of the material may be too low, which may affect the initial coulombic efficiency of the material. If the cooling temperature is higher than 1050°C, the crystallite size of the material may be too large, which may affect the cycle performance of the material.

[0095] In some embodiments, the temperature can be increased within the above heating temperature range to correspondingly increase the contents of K and Fe in the final silicon-based negative electrode active material.

[0096] In some embodiments, within the above-mentioned inert atmosphere pressure range, by decreasing the pressure, i.e., increasing the degree of vacuum, the contents of K and Fe in the final silicon-based negative electrode active material can be correspondingly increased.

[0097] In some embodiments, the operation of crushing the sediment includes subjecting the sediment to rough crushing, fine crushing, and classification based on preset product volume average particle size (Dv50) and specific surface area parameters to obtain a product that meets the preset parameters. In some embodiments, the sediment can be crushed and classified using any method and device known in the art, such as a grinder or an airflow crushing-classifying combined machine.

[0098] In some embodiments, the method for preparing a silicon-based negative electrode active material further includes a step of performing a coating treatment on the pulverized product to obtain a product having a coating layer.

[0099] In some embodiments, the coating layer material may include one or more of a polymer, a carbon material, a metal material, and a metal compound. For example, the coating layer may include one or more of a polymer coating layer, a carbon coating layer, and a metal compound coating layer. Optionally, the polymer may be selected from one or more of polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride, and polyethylene. Optionally, the carbon material may include one or more of graphite, mesocarbon microbeads (MCMB), pyrolytic carbon of hydrocarbon compounds, hard carbon, and soft carbon, where graphite may be one or more of natural graphite and artificial graphite. Optionally, the metal compound may include one or more of Ti5Si3, Al2O3, and TiO2. The coating layer may further mitigate the volume expansion effect of the silicon-based negative electrode active material and improve the cycle life of the material. At the same time, the coating layer also provides protection to the silicon-based negative electrode active material, suppressing side reactions of the electrolyte on the material surface and protecting the material surface from erosion by the electrolyte, thereby allowing the silicon-based negative electrode active material to exhibit a relatively high capacity and further improving the cycle life of the battery.

[0100] In some embodiments, a liquid-phase coating method is used to coat the surface of the silicon-based negative electrode active material to form a coating layer, for example, a polymer is dissolved in a certain solvent, and the polymer is thoroughly mixed with the silicon-based negative electrode active material particles by stirring, and then the solvent is evaporated to remove the polymer, so that the polymer is uniformly coated on the surface of the silicon-based negative electrode active material particles.

[0101] In some embodiments, a coating layer is formed on the surface of the silicon-based negative electrode active material by chemical vapor deposition, for example, by introducing a hydrocarbon compound gas into a reactor containing the silicon-based negative electrode active material and performing heat treatment under an inert atmosphere to carbonize the hydrocarbon compound and form a coating layer on the surface of the silicon-based negative electrode active material, thereby obtaining a silicon-based negative electrode active material having a coating layer on its surface.

[0102] In some embodiments, the coating process includes a carbon coating process, which optionally includes placing the ground product in a chamber containing a carbon source gas, heating the ground product to 700-1000°C, and maintaining the temperature for 1-6 hours.

[0103] In some embodiments, the coating process includes a carbon coating process, which optionally includes placing the ground product in a chamber containing a carbon source gas, heating the ground product to 800-900°C, and maintaining the temperature for 2-5 hours.

[0104] In some embodiments, the alkaline earth metal source may be one or more of an alkaline earth metal, an alkaline earth metal hydroxide, an alkaline earth metal carbonate, an alkaline earth metal nitrate, an alkaline earth metal amide, or an alkaline earth metal hydride.

[0105] In some embodiments, the alkaline earth metal source may be one or more of magnesium metal, magnesium hydroxide, magnesium carbonate, magnesium nitrate, magnesium amide, and magnesium hydride.

[0106] As an example, the negative electrode current collector has two surfaces facing each other in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. For example, copper foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0108] In some embodiments, the negative electrode film layer may further include a silicon-based negative electrode active material known in the art other than the present application, and those skilled in the art may select one or more of these materials according to actual needs. Examples include, but are not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, other silicon-based materials, and tin-based materials. The other silicon-based materials may include one or more of elemental silicon, silicon-oxygen complexes other than those described in the present application, silicon-carbon complexes, silicon-nitrogen complexes, and silicon alloys. The tin-based materials may include one or more of elemental tin, stannic acid compounds, and tin alloys. All of these materials are commercially available.

[0109] In some embodiments, the negative electrode membrane layer optionally further includes an adhesive, for example, the adhesive may be selected from at least one of 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).

[0110] In some embodiments, the negative electrode film layer may further optionally include a conductive agent, for example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the negative electrode membrane layer further optionally includes other auxiliary agents, such as a thickener (e.g., carboxymethylcellulose sodium (CMC-Na)).

[0112] In some embodiments, the negative electrode plate may be manufactured in the following manner: The components for manufacturing the negative electrode plate, such as the silicon-based negative electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied onto a negative electrode current collector, and the negative electrode plate is obtained after processes such as drying and cold pressing.

[0113] [Positive electrode plate] In some embodiments, the positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0114] As an example, the positive electrode current collector has two surfaces facing each other in the thickness direction thereof, and the positive electrode film layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0115] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base 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, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0116] In some embodiments, the positive electrode membrane layer optionally further includes an adhesive. For example, the adhesive 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 acrylate resin.

[0117] In some embodiments, the positive electrode film layer optionally further includes 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.

[0118] In some embodiments, the positive electrode plate may be manufactured in the following manner: Components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then applied onto a positive electrode current collector, and the positive electrode plate is obtained after processes such as drying and cold pressing.

[0119] [Cathode active material] In some embodiments, the positive electrode active material may be any positive electrode active material for secondary batteries known in the art.

[0120] For example, the positive electrode active material may include at least one of lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), 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 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0121] [Electrolytes] The electrolyte serves to conduct ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, and it may be selected according to needs. For example, the electrolyte may be liquid, gel, or all-solid.

[0122] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0123] In some embodiments, the electrolyte salt is selected from sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium hexafluoroarsenate.

[0124] In some embodiments, the solvent may be selected from at least one of 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, ethyl methyl sulfone, and diethyl sulfone.

[0125] In some embodiments, the electrolyte solution further optionally contains additives. For example, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve some battery performance, such as an additive that improves the overcharge performance of the battery, or an additive that improves the high-temperature or low-temperature performance of the battery.

[0126] [Separator] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known porous separator with good chemical stability and mechanical stability may be selected.

[0127] In some embodiments, the separator may be made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0128] In some embodiments, the positive and negative electrodes and the separator can be fabricated into an electrode assembly by a winding or lamination process.

[0129] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0130] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0131] The present application does not particularly limit the shape of the secondary battery, and the secondary battery may be cylindrical, rectangular, or any other shape. For example, Fig. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application, and Fig. 2 is an exploded view of a secondary battery according to an embodiment of the present application.

[0132] In some embodiments, referring to FIG. 2 , the exterior body of the secondary battery may include a case 51 and a top cover assembly 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, where the bottom plate and side plates together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the top cover assembly 53 may cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An 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 this can be selected by those skilled in the art according to specific actual needs.

[0133] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0134] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, the battery module 4 may include a plurality of secondary batteries 5 arranged in order along the longitudinal direction of the battery module 4. Of course, the batteries may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0135] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0136] In some embodiments, the battery modules may be assembled into a battery pack, and the battery pack may include one or more battery modules, the specific number of which may be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0137] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 may be provided with a lid on the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0138] The present application also provides a power consuming device, the power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming 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.), electric trains, ships, satellites, energy storage systems, etc.

[0139] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0140] 6 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density of the secondary battery of the power consuming device, a battery pack or battery module can be employed.

[0141] The following examples of the present application are described. The examples described below are illustrative and are used only to interpret the present application and should not be understood as limitations on the present application. Unless specific techniques or conditions are specified in the examples, they are carried out according to the techniques or conditions described in literature in the field or according to the product instructions. Unless the manufacturer is specified, the reagents or equipment used are all commercially available products.

[0142] Silicon-based negative electrode active material 1. Method for manufacturing silicon-based negative electrode active material 1.1 Overview In the specific embodiment below, the outline of the method for producing a silicon-based negative electrode active material is as follows.

[0143] 1) providing a vapor containing elements Si, O, K, Fe, and Mg, and cooling the vapor to obtain a deposit; 2) crushing the sediment to obtain a crushed product; 3) The pulverized product was subjected to a carbon coating treatment to obtain a carbon-coated product.

[0144] 1.2 Details In the following specific embodiment, a method for producing a silicon-based negative electrode active material will be described in detail as follows.

[0145] 1) providing a raw material composition according to the contents of K, Fe, and Mg elements in the target product, the raw material composition including elemental silicon, silicon oxide, a potassium source (potassium carbonate), an iron source (iron nitrate), and an alkaline earth metal source (metallic magnesium); 2) in a helium atmosphere at an absolute pressure of 30 Pa, the raw material composition is heated to 1300°C to form a vapor, and then the vapor is cooled to 900°C to form a deposit, by vapor deposition; 3) Collect the sediment and grind it into powder; 4) The powder was placed in the reaction chamber of a vapor deposition apparatus, and a mixture of carbon source gas (acetylene) and nitrogen gas was introduced into the reaction chamber, with the acetylene content being 20% ​​by volume. The mixture was heated to 750°C and held for 2 hours to obtain a carbon-coated product, which was then collected to obtain the negative electrode active material.

[0146] In the above manufacturing method, the contents of the alkaline earth metal source, potassium source, and iron source in the raw material mixture can be adaptively adjusted according to the composition of the target product, thereby obtaining negative electrode active materials with various Fe and K contents. It should be understood that, depending on the purity of the silicon element and silicon dioxide, some silicon element and silicon dioxide will already contain a certain amount of K element and Fe element, and in this case, the contents of the potassium source and iron source in the raw material mixture should be adaptively adjusted according to the component composition of the sample target product.

[0147] In the above manufacturing method, the contents of the alkaline earth metal source, potassium source, and iron source in the raw material mixture can be adaptively adjusted according to the composition of the target product, thereby obtaining silicon-based negative electrode active materials with various K and Fe contents. It should be understood that, depending on the purity of the silicon element and silicon dioxide, some silicon element and silicon dioxide will already contain a certain amount of K and Fe, and in this case, the contents of the potassium source and iron source in the raw material mixture should be adaptively adjusted according to the component composition of the sample target product.

[0148] According to the above method, a plurality of silicon-based negative electrode active material samples (hereinafter simply referred to as samples) having different K and Fe contents were produced and obtained. These samples have the following properties.

[0149] 1) The negative electrode active material is a silicon-based negative electrode active material having a carbon coating layer, wherein the content of the carbon coating layer is 4.2±0.2%; 2) The molar ratio of silicon element to oxygen element in the silicon-based negative electrode active material is 1±0.1; 3) The content of Mg element is 7.5±0.5% for 100% silicon-based negative electrode active material, 4) For 100% silicon-based negative electrode active material, the K content is shown in Table 1. 5) For 100% silicon-based negative electrode active material, the Fe content is shown in Table 1. 6) The volume average particle diameter Dv50 of the negative electrode active material is 6.5±0.5 μm, 7) The specific surface area of ​​the negative electrode active material is 5±0.2m 2 / g, 8) The volume resistivity of the powder of the negative electrode active material under a pressure of 4 MPa is 4±0.1 Ω·cm; 9) The silicon-based negative electrode active material has a compaction density of 1.6±0.1 g / cm under a pressure of 49000 N. 3 is.

[0150] Button battery manufacturing (1) Preparation of negative electrode plate: The silicon-based negative electrode active material prepared above, the conductive agent Super-P (conductive carbon black), and the adhesive styrene butadiene rubber were mixed in a mass ratio of 85:5:10 in an appropriate amount of deionized water with sufficient stirring to form a uniform negative electrode slurry. The negative electrode slurry was then applied to the surface of a negative electrode current collector copper foil, dried, and cold-pressed to obtain a negative electrode plate.

[0151] (2) Counter electrode: metallic lithium sheet.

[0152] (3) Separator: Polyethylene (PE) film.

[0153] (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, and LiPF6 was then uniformly dissolved in the solution to obtain an electrolyte. Fluoroethylene carbonate (FEC) was then added, where the concentration of LiPF6 was 1 mol / L and the mass proportion of FEC in the electrolyte was 6%.

[0154] (5) Manufacture of button battery: The above negative electrode plate, separator, and counter electrode of metallic lithium sheet were stacked in this order, and the above electrolyte was added to obtain a button battery.

[0155] Full battery manufacturing The resulting silicon-based anode active material and artificial graphite mixture (15%:85% by weight), conductive carbon black (Super P), carbon nanotubes (CNTs), styrene-butadiene rubber adhesive, and sodium carboxymethyl cellulose thickener were mixed in a weight ratio of 96.2%:0.7%:0.1%:1.8%:1.2% with sufficient stirring in an appropriate amount of deionized water solvent to form anode slurry. The anode slurry was applied to both surfaces of anode copper foil current collector, dried, and cold-pressed to obtain anode plates.

[0156] LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent Super P, and adhesive polyvinylidene fluoride were mixed in a weight ratio of 96.5%:1.5%:2%, and an appropriate amount of NMP solvent was added and stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was then applied to both surfaces of a positive electrode current collector aluminum foil, dried, and cold-pressed to obtain a positive electrode plate.

[0157] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte solution, to which fluoroethylene carbonate (FEC) was added. The concentration of LiPF6 was 1 mol / L, and the mass proportion of FEC in the electrolyte solution was 6%.

[0158] The positive and negative electrode plates prepared above were sequentially arranged using a PE separator, and the separator was positioned in the center between the positive and negative electrode plates to provide isolation. These were then wound to obtain an electrode assembly. The electrode assembly was placed in an outer casing, dried, and then an electrolyte was injected. After vacuum packaging, standing, chemical formation, aging, and other processes, a secondary battery was obtained.

[0159] II. Analysis and detection methods 2.1. Elemental analysis (e.g., K, Fe, Si, and alkaline earth metal elements) The element content has a meaning known in the art and can be measured by methods known in the art. Silicon-based negative electrode active materials are decomposed in accordance with EPA-3052-1996 "Microwave Acid Decomposition Method for Silicates," and the target element content is measured using a Thermo Fisher Scientific ICAP-7000 inductively coupled plasma optical emission spectrometer (ICP-OES) in accordance with EPA 6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectroscopy." Specifically, a 0.5 g sample of silicon-based negative electrode active material is microwave-decomposed using 10 mL of nitric acid and 10 mL of hydrofluoric acid. The decomposition solution is then transferred to a 50 mL volumetric flask and the target element content is measured using an ICAP-7000 ICP-OES.

[0160] 2.2. Elemental analysis (oxygen element, carbon element) The content of the element has a meaning known in the art and can be measured by a method known in the art. The carbon content of the silicon-based negative electrode active material can be tested in accordance with GB / T 20123-2006 / ISO 15350:2000, and the testing equipment can be an HCS-140 infrared carbon / sulfur analyzer.

[0161] The oxygen content can be determined by referring to JY / T 017-1996 General Methods for Elemental Analyzers, and the test equipment can be Elementar's rapid OXY cube oxygen elemental analyzer.

[0162] 2.3. Volume resistivity The volume resistivity of a material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, the four-point probe method can be used to test the volume resistivity of the powder of the silicon-based negative electrode active material of the present application under a pressure of 4 MPa. The test method includes adding the silicon-based negative electrode active material powder of the present application to a sample table, applying a pressure of 4 MPa to the powder with a press, and after the pressure has stabilized, reading the volume resistivity of the silicon-based negative electrode active material powder under a pressure of 4 MPa with a resistivity meter.

[0163] 2.4.Consolidation density The compaction density of a material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, referring to GB / T24533-2009, it can be measured using an electronic pressure tester, such as the UTM7305 type electronic pressure tester. A sample is accurately weighed to about 1 g, and the sample has a base area of ​​1.327 cm. 2 In addition to the mold, a pressure device is used to apply a pressure of 49000 N to the sample and hold it at this pressure for 30 seconds before releasing the pressure, and then measuring the height of the sample, the compacted density of the material can be obtained by the formula ρ=m / (1.327×h), where ρ represents the compacted density of the material, m represents the mass of the sample, and h represents the height after the pressure of 49000 N is applied and held at this pressure for 30 seconds before the pressure is released from the sample.

[0164] 2.5, Powder particle size analysis The Dv10, Dv50, and Dv90 of a material have meanings known in the art and can be measured by methods known in the art, for example, by referring to standard GB / T 19077-2016 and using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0165] The physical definitions of Dv10, Dv50, and Dv90 are the particle sizes corresponding to the cumulative volume distribution percentages of the silicon-based negative electrode active material reaching 10%, 50%, and 90%, respectively.

[0166] 2.6, Specific surface area analysis The specific surface area of ​​a material has a meaning known in the art and can be measured using instruments and methods known in the art, for example, by measuring the specific surface area of ​​a solid material with reference to GB / T 19587-2017 gas adsorption BET method, testing using the nitrogen gas adsorption specific surface area analytical test method, and calculating using the BET (Brunauer Emmett Teller) method, where the nitrogen gas adsorption specific surface area analytical test can be performed using a Tri Star II 3020 specific surface area and pore analyzer from Micromeritics, USA.

[0167] 2.7 Battery performance test (1) First Coulomb Efficiency At 25°C and atmospheric pressure, the button battery was discharged at a constant current of 0.1C to 0.005V, then discharged at a constant current of 0.04C to 0.005V, and then allowed to stand for 5 minutes. The discharge capacity was recorded, i.e., the first cycle lithium absorption capacity. The button battery was then charged at a constant current of 0.1C to 1.5V, and then allowed to stand for 5 minutes. This constitutes one cycle of charge and discharge. The charge capacity was recorded, i.e., the first cycle lithium desorption capacity. The button battery was subjected to 30 cycle charge and discharge tests according to the above method, and the lithium desorption capacity was recorded for each cycle.

[0168] Initial coulombic efficiency (%) = Lithium desorption capacity at the first cycle / Lithium absorption capacity at the first cycle × 100% Cycle capacity retention (%) = Lithium desorption capacity at 30th cycle / Lithium desorption capacity at 1st cycle × 100% (2) Battery DC resistance (DCR) At 25°C, the battery is charged at a constant current of 0.33C up to 4.25V, then discharged at a constant current of 1C for 48 minutes to adjust the battery to 20% SOC. The battery voltage at this time is designated U1. The battery is then discharged at a constant current of 3C for 30 seconds, and the end-of-discharge voltage is designated U2 with a 0.1-second sampling interval. The initial DCR of the battery is represented by the discharge DCR at 20% SOC, and the initial DCR of the battery is calculated as (U1 - U2) / 3C.

[0169] [Table 1-1] [Table 1-2] 3. Results and Discussion Table 1 shows the ingredients and compositions of the raw materials for silicon-based negative electrode active materials in some examples of the present application, the contents and content ratios of K and Fe in the silicon-based negative electrode active material products, and the battery performance of silicon-based negative electrode active materials based on the above silicon-based negative electrode active materials. Each of these is described below.

[0170] (1) Composition of raw materials The raw silicon element used for the samples (E1-E16) is metallic silicon 1 (Si≧99.9 wt%, K=200 ppm, Fe=20 ppm).

[0171] The raw material silicon element used in sample (D1) is metallic silicon 2 (Si≧99.9 wt%, not containing K or Fe).

[0172] As can be seen from Table 1, the K and Fe elements in the silicon-based negative electrode active material may be derived from multiple sources: a) The K element in the silicon-based negative electrode active material may be derived from the raw material metal silicon, b) The Fe element in the silicon-based negative electrode active material may be derived from raw material metal silicon, c) The K element in the silicon-based negative electrode active material may be derived from an additionally added potassium source; d) The Fe element in the silicon-based negative electrode active material may be derived from an additionally added iron source.

[0173] Those skilled in the art can adaptively adjust the contents of Fe and K in the raw materials according to the target chemical composition of the silicon-based negative electrode active material, ultimately obtaining a silicon oxide-based compound having the target chemical composition. When it is necessary to increase / decrease the K content in the target silicon oxide-based compound, metal silicon (or silicon oxide) with a higher / lower K content may be used, or the amount of potassium source additionally added to the raw materials may be increased / decreased. When it is necessary to increase / decrease the Fe content in the target silicon oxide-based compound, metal silicon (or silicon oxide) with a higher / lower Fe content may be used, or the amount of iron source additionally added to the raw materials may be increased / decreased.

[0174] (2) The simultaneous inclusion of K and Fe elements significantly improves the first Coulomb efficiency and kinetic performance. The silicon-based negative electrode active material of Comparative Example D1 did not contain K or Fe, and its initial Coulombic efficiency was 65.32% and its DC internal resistance was 583.68 mΩ. The silicon-based negative electrode active materials of Examples E1-E16 simultaneously contained K and Fe, and their initial Coulombic efficiency was higher (71.42%-76.32%) and their DC internal resistance was lower (505.86-515.07 mΩ), significantly improved compared to D1. As can be seen from the above, the simultaneous inclusion of K and Fe resulted in significant improvements in initial Coulombic efficiency and kinetic performance.

[0175] (3) K / Fe ratio in silicon-based negative electrode active materials As shown in Examples E2-E14, when the weight ratio of K / Fe was 10 to 36:1, the initial coulombic efficiency of the negative electrode active material was 71.76%-76.32%, and the DC internal resistance was 505.86 mΩ-515.07 mΩ, showing further improved initial coulombic efficiency and kinetic performance.

[0176] As shown in Examples E3-E14, when the weight ratio of K / Fe was 12:1 to 36:1, the initial coulombic efficiency of the negative electrode active material was 71.82%-76.32%, and the DC internal resistance was 505.856 mΩ-515.072 mΩ, indicating further improved initial coulombic efficiency and kinetic performance.

[0177] As shown in Examples E6-E13, when the weight ratio of K / Fe was 20:1 to 32:1, the initial coulombic efficiency of the negative electrode active material was 73.23%-76.32%, and the DC internal resistance was 510.976 mΩ-514.56 mΩ, indicating further improved initial coulombic efficiency and kinetic performance.

[0178] (4) Content of K and Fe in silicon-based negative electrode active materials As shown in Examples E1 to E16, when the content of K element in the silicon-based negative electrode active material is 800 ppm or more, for example, 800 ppm to 1520 ppm, the negative electrode active material exhibits improved initial coulombic efficiency and improved kinetic performance.

[0179] As shown in Examples E1 to E16, the content of Fe element in the silicon-based negative electrode active material is 100 ppm or less, for example, 35 ppm to 100 ppm, and the negative electrode active material exhibits improved first coulombic efficiency and improved kinetic performance.

[0180] As shown in Examples E6 to E13, when the content of K element in the silicon-based negative electrode active material is 1200 ppm to 1500 ppm, the negative electrode active material exhibits improved first coulombic efficiency and improved kinetic performance.

[0181] As shown in Examples E6 to E13, the content of Fe element in the silicon-based negative electrode active material is 45 ppm to 64 ppm, and the negative electrode active material exhibits improved first coulombic efficiency and improved kinetic performance.

[0182] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments and other methods configured by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0183] 1: battery pack, 2: upper housing, 3: lower housing, 4: battery module, 5: secondary battery, 51: case, 52: electrode assembly, 53: top cover assembly.

Claims

1. A silicon-based negative electrode active material, the silicon-based negative electrode active material including a silicate containing an alkaline earth metal element, and the silicon-based negative electrode active material simultaneously containing a K element and an Fe element.

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

3. The silicon-based negative electrode active material according to claim 1 , wherein a mass ratio of the K element to the Fe element is 8:1 or more, and optionally 10:1 to 36:

1.

4. The silicon-based negative electrode active material according to claim 1 , wherein the content of the K element is 400 ppm or more, and optionally 800 ppm to 2000 ppm.

5. The silicon-based negative electrode active material according to claim 1 , wherein the content of the Fe element is 500 ppm or less, and optionally 30 ppm to 400 ppm.

6. (1) The volume average particle diameter D of the silicon-based negative electrode active material ｖ 50 is 4 μm-10 μm, and optionally 5 μm-8 μm; (2) The specific surface area of ​​the silicon-based negative electrode active material is 6 m ２ / g or less, and optionally 3m ２ / g-5m ２ / g, (3) The volume resistivity of the powder of the silicon-based negative electrode active material under a pressure of 4 MPa is 6 Ω cm or less, and optionally 0.5 Ω cm to 4.5 Ω cm; (4) The silicon-based negative electrode active material has a compaction density of 1.4-1.8 g / cm under a pressure of 49000 N. ３ and optionally 1.5-1.7 g / cm ３ The characteristic that (5) The alkaline earth metal element-containing silicate includes a magnesium-containing silicate, and the half-width of the magnesium-containing silicate is 0.60° or less, and optionally 0.35°-0.55°; (6) The silicon-based negative electrode active material according to any one of claims 1 to 5, wherein the silicate containing an alkaline earth metal element includes a magnesium-containing silicate, and the magnesium-containing silicate has a crystal grain size of 21 nm or less, and optionally 12 nm to 18 nm.

7. The silicon-based negative electrode active material according to claim 1 , wherein at least a portion of the surface of the silicon-based negative electrode active material has a coating layer.

8. Providing a raw material containing Si element, O element, K element, Fe element, and alkaline earth metal element; using a vapor deposition process to heat the source material to form a vapor and then cool the vapor to form a deposit; and pulverizing the deposit to obtain a pulverized product.

9. The method according to claim 8, further comprising subjecting the ground product to a coating treatment to obtain a product having a coating layer.

10. (1) In the operation of heating the raw material to form steam, the heating temperature is 1100-1550°C; (2) The method according to any one of claims 8 to 9, wherein in the operation of cooling the vapor to form a deposit, the cooling temperature is 700-900°C.

11. A secondary battery comprising a negative electrode, the negative electrode comprising the silicon-based negative electrode active material according to claim 1 .

12. A power consuming device comprising the secondary battery of claim 11.

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