Negative electrode material and preparation method thereof, and lithium ion battery

Abstract

The present application relates to a negative electrode material, a preparation method thereof, and a lithium-ion battery, comprising a silicon-based material containing oxygen and lithium elements. The negative electrode material is tested by a laser particle size analyzer to obtain a particle size D10 with a cumulative volume distribution of 10% and a particle size D90 with a cumulative volume distribution of 90%. The ratio of the mass proportion of lithium elements to the mass proportion of oxygen elements in particles with a particle size less than or equal to D10 in the negative electrode material is recorded as A1, and the ratio of the mass proportion of lithium elements to the mass proportion of oxygen elements in particles with a particle size greater than or equal to D90 in the negative electrode material is recorded as A2, with 0.6≤A1 / A2<1. The present application provides different ratios of lithium content to oxygen content for materials with smaller and larger particle sizes, and the ratio of lithium content to oxygen content in the smaller particle size material is less than the ratio of lithium content to oxygen content in the larger particle size material, so that the negative electrode material can improve storage performance while improving rate performance and cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials, and in particular to negative electrode materials and preparation methods thereof, and lithium ion batteries. Background Art

[0002] As the application of lithium-ion batteries continues to expand and deepen, the requirements for lithium-ion battery performance are also increasing. In particular, in terms of battery energy density, traditional graphite anode materials are no longer sufficient to meet the growing market demand. As a high-capacity anode material, silicon oxide anode materials have attracted much attention in recent years. The specific capacity of silicon oxide anode materials exceeds 2000mAh / g. However, compared with graphite materials, their lower initial coulombic efficiency, poorer conductivity, and poorer cycle and rate performance limit their practical application.

[0003] In order to improve the performance of silicon-oxygen negative electrode materials, existing technical research has shown that lithium doping can significantly improve the first coulombic efficiency of silicon-oxygen negative electrode materials. Silicon-oxygen materials and lithium-containing compounds are usually mixed and heat-treated for lithium doping. However, lithium doping will change the internal structure of the original silicon-oxygen negative electrode material. As the amount of lithium doping increases, the lithium ion transmission capacity of the silicon-oxygen negative electrode material is improved, so that the silicon-oxygen negative electrode material has better rate performance. However, the addition of too much lithium into the silicon-oxygen negative electrode material will cause the specific surface area of the silicon-oxygen negative electrode material to increase, thereby causing the storage performance of the silicon-oxygen negative electrode material to deteriorate when used in batteries. Therefore, traditional lithium doping of silicon-oxygen negative electrode materials cannot take into account the improvement of rate performance and storage performance.

[0004] Therefore, how to simultaneously improve the rate performance and storage performance of silicon-oxygen negative electrode materials is an urgent problem that needs to be solved. Summary of the Invention

[0005] The present application provides a negative electrode material and a preparation method thereof, and a lithium-ion battery, which can improve the rate performance of the negative electrode material while improving the storage performance and cycle performance.

[0006] In a first aspect, an embodiment of the present application provides a negative electrode material, including a silicon-based material, wherein the silicon-based material contains oxygen and lithium, and the negative electrode material is tested by a laser particle size analyzer to obtain a particle size D10 of 10% of the cumulative volume distribution and a particle size D90 of 90% of the cumulative volume distribution;

[0007] The ratio of the mass proportion of lithium elements to the mass proportion of oxygen elements in particles with a particle size less than or equal to D10 in the negative electrode material is recorded as A1, and the ratio of the mass proportion of lithium elements to the mass proportion of oxygen elements in particles with a particle size greater than or equal to D90 in the negative electrode material is recorded as A2, 0.6≤A1 / A2<1.

[0008] In some embodiments, the negative electrode material includes at least one of the following features (1) to (8):

[0009] (1) The ratio of the mass proportion of the lithium element in the negative electrode material to the mass proportion of the oxygen element in the negative electrode material is recorded as A, and A is 0.1 to 0.7;

[0010] (2) A1 is 0.1 to 0.65;

[0011] (3) A2 is 0.15 to 0.7;

[0012] (4) The silicon-based material includes at least one of a silicon-oxygen material and a silicon element;

[0013] (5) The silicon-based material includes at least one of a silicon-oxygen material and a silicon element, and the silicon-oxygen material includes at least one of Li2SiO3, Li2Si2O5 and Li4SiO4;

[0014] (6) The negative electrode material has a particle size D10 of 10% of the cumulative volume distribution of the material particles, 0.1 μm ≤ D10 ≤ 15 μm;

[0015] (7) The negative electrode material has a particle size D90 at which 90% of the cumulative volume distribution of the material particles is 0.5 μm ≤ D90 ≤ 30 μm;

[0016] (8) The negative electrode material has a particle size D50 at which the cumulative volume distribution of the material particles is 50%, and 0.3 μm≤D50≤25 μm.

[0017] In some embodiments, the negative electrode material includes at least one of the following features (1) to (9):

[0018] (1) The negative electrode material further includes a coating layer distributed on at least a portion of the surface of the silicon-based material;

[0019] (2) The negative electrode material further includes a coating layer distributed on at least a portion of the surface of the silicon-based material, and the coating layer is a carbon layer;

[0020] (3) The negative electrode material further includes a coating layer distributed on at least a portion of the surface of the silicon-based material. For negative electrode materials with a particle size smaller than D10, the coating layer has a thickness of 15 nm to 1000 nm.

[0021] (4) The negative electrode material further includes a coating layer distributed on at least a portion of the surface of the silicon-based material. For the negative electrode material having a particle size greater than D90, the coating layer has a thickness of 10 nm to 900 nm.

[0022] (5) The lithium content in the negative electrode material is 0.1 wt% to 20 wt%;

[0023] (6) The specific surface area of the negative electrode material is 0.1m 2 / g~50m 2 / g;

[0024] (7) The oxygen content of the negative electrode material is 15 wt% to 45 wt%;

[0025] (8) The negative electrode material contains a metal element, and the metal element includes at least one of iron, cobalt, nickel and copper;

[0026] (9) The negative electrode material contains a metal element, and the content of the metal element in the negative electrode material is 1 ppm to 5000 ppm.

[0027] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0028] A silicon oxide raw material and a solution containing a metal catalyst are mixed and solid-liquid separated to obtain a precursor, wherein the mass ratio of the metal catalyst to the silicon oxide raw material is (0.00001-0.05):1;

[0029] The precursor and the lithium source are mixed and heat treated to obtain a negative electrode material.

[0030] In some embodiments, the preparation method includes at least one of the following features (1) to (3):

[0031] (1) The solution containing the metal catalyst also includes a surfactant;

[0032] (2) The solution containing the metal catalyst further comprises a surfactant, wherein the surfactant comprises at least one of sodium lauryl sulfate and stearic acid;

[0033] (3) The solution containing the metal catalyst also includes a surfactant, and the mass ratio of the surfactant to the silicon oxide raw material is (0.01-0.2):1.

[0034] In some embodiments, the preparation method includes at least one of the following features (1) to (8):

[0035] (1) The silicon oxide raw material includes SiO y , where 0<y≤2;

[0036] (2) the silicon oxide raw material has a particle size D10 of 10% of the cumulative volume distribution of the material particles, 0.1 μm≤D10≤15 μm;

[0037] (3) the silicon oxide raw material has a particle size D90 at which 90% of the cumulative volume distribution of the material particles is 0.5 μm ≤ D90 ≤ 30 μm;

[0038] (4) the silicon oxide raw material has a particle size D50 at which the cumulative volume distribution of the material particles is 50%, and 0.3 μm≤D50≤25 μm;

[0039] (5) The metal catalyst includes at least one of copper salt, cobalt salt, nickel salt and iron salt;

[0040] (6) The metal catalyst includes at least one of ferric chloride, cobalt chloride, nickel chloride and copper hydroxide;

[0041] (7) The solvent of the solution containing the metal catalyst includes at least one of water and an alcohol solvent;

[0042] (8) The mixing time is 1 hour to 10 hours.

[0043] In some embodiments, before mixing the precursor and the lithium source and performing a heat treatment, the method further includes: mixing the precursor and a carbon source and performing a carbonization treatment.

[0044] In some embodiments, the preparation method includes at least one of the following features (1) to (6):

[0045] (1) The carbon source includes a gaseous carbon source;

[0046] (2) the carbon source comprises a gaseous carbon source, wherein the gaseous carbon source comprises at least one of alkanes, cycloalkanes, alkenes, alkynes and aromatic hydrocarbons;

[0047] (3) The carbon source includes a gaseous carbon source, and the flow rate of the gaseous carbon source is 0.1 L / min to 500 L / min;

[0048] (4) The temperature of the carbonization treatment is 600° C. to 1000° C.;

[0049] (5) The carbonization treatment time is 0.5h to 10h;

[0050] (6) The carbonization treatment is carried out in a protective gas atmosphere, and the protective gas includes at least one of nitrogen, argon and helium.

[0051] In some embodiments, the preparation method includes at least one of the following features (1) to (5):

[0052] (1) The lithium source includes at least one of metallic lithium, lithium hydride, lithium carbonate, lithium hydroxide, lithium borohydride and lithium aluminum hydride;

[0053] (2) The mass ratio of the silicon oxide raw material to the lithium source is 1:(0.05-0.5);

[0054] (3) The temperature of the heat treatment is 400° C. to 900° C.;

[0055] (4) The heat treatment time is 2 hours to 12 hours;

[0056] (5) The heat treatment is carried out in a protective gas atmosphere, and the protective gas includes at least one of nitrogen, argon and helium.

[0057] In a third aspect, a lithium-ion battery comprises the negative electrode material or the negative electrode material prepared according to the preparation method.

[0058] The technical solution of this application has at least the following beneficial effects:

[0059] In this application, the negative electrode material satisfies 0.6≤A1 / A2<1, indicating that the ratio A1 of the mass proportion of lithium element to the mass proportion of oxygen element in the particles with smaller particle size (particle size less than or equal to D10) in the negative electrode material is less than the ratio A2 of the mass proportion of lithium element to the mass proportion of oxygen element in the particles with larger particle size (particle size greater than or equal to D90) in the negative electrode material. The ratio of the mass proportion of lithium element to the mass proportion of oxygen element reflects the pre-lithiation degree of the negative electrode material particles. The pre-lithiation degree of the negative electrode material particles with smaller particle size is low, which can reduce the specific surface area of the negative electrode material, thereby improving the storage performance of the negative electrode material. The pre-lithiation degree of the negative electrode material particles with larger particle size is higher, which is conducive to improving the lithium ion conductivity inside the negative electrode material and improving the rate performance of the material. In addition, the pre-lithiation of the negative electrode material particles with larger particle size is more sufficient, so that the volume expansion of the negative electrode material during the charge and discharge process is smaller, which is conducive to improving the cycle performance of the negative electrode material. However, if the pre-lithiation degree of the negative electrode material particles with smaller particle size is too low, the lithium ion transmission capacity of the negative electrode material particles will be poor. If the pre-lithiation degree of the negative electrode material particles with larger particle size is too high, the specific surface area of the negative electrode material particles will become too large, which is not conducive to the improvement of the storage performance and rate performance of the negative electrode material. Therefore, in the negative electrode material of the present application, particles of different particle sizes have different pre-lithiation degrees, and the ratio of the mass proportion of lithium element to the mass proportion of oxygen element A1 of the particles with smaller particle size and the ratio of the mass proportion of lithium element to the mass proportion of oxygen element A2 of the particles with larger particle size are controlled between 0.6 and 1 (excluding 1), so that the negative electrode material can improve the storage performance while improving the rate performance and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present invention will be further described below with reference to the accompanying drawings and examples.

[0061] Figure 1 Flowchart of the method for preparing the negative electrode material provided in the embodiment of the present application. DETAILED DESCRIPTION

[0062] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0063] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0064] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0065] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0066] The present application provides a negative electrode material, including a silicon-based material, wherein the silicon-based material contains oxygen and lithium elements, and the negative electrode material is tested by a laser particle size analyzer to obtain a particle size D10 of 10% of the cumulative volume distribution and a particle size D90 of 90% of the cumulative volume distribution;

[0067] The ratio of the mass proportion of lithium element to the mass proportion of oxygen element in particles with a particle size less than or equal to D10 in the negative electrode material is recorded as A1, and the ratio of the mass proportion of lithium element to the mass proportion of oxygen element in particles with a particle size greater than or equal to D90 in the negative electrode material is recorded as A2, 0.6≤A1 / A2<1.

[0068] In the above scheme, the negative electrode material in this application satisfies 0.6≤A1 / A2<1, indicating that the ratio A1 of the mass proportion of lithium element to the mass proportion of oxygen element in the particles with smaller particle size (particle size less than or equal to D10) in the negative electrode material is less than the ratio A2 of the mass proportion of lithium element to the mass proportion of oxygen element in the particles with larger particle size (particle size greater than or equal to D90) in the negative electrode material. The ratio of the mass proportion of lithium element to the mass proportion of oxygen element reflects the pre-lithiation degree of the negative electrode material particles. The pre-lithiation degree of the negative electrode material particles with smaller particle size is low, which can reduce the specific surface area of the negative electrode material, thereby improving the storage performance of the negative electrode material. The pre-lithiation degree of the negative electrode material particles with larger particle size is higher, which is conducive to improving the lithium ion conductivity inside the negative electrode material and improving the rate performance of the material. In addition, the pre-lithiation of the negative electrode material particles with larger particle size is more sufficient, so that the volume expansion of the negative electrode material during the charge and discharge process is smaller, which is conducive to improving the cycle performance of the negative electrode material. However, if the pre-lithiation degree of the negative electrode material particles with smaller particle size is too low, the lithium ion transmission capacity of the negative electrode material particles will be poor. If the pre-lithiation degree of the negative electrode material particles with larger particle size is too high, the specific surface area of the negative electrode material particles will become too large, which is not conducive to the improvement of the storage performance and rate performance of the negative electrode material. Therefore, in the same batch of negative electrode materials in the present application, particles of different particle sizes have different pre-lithiation degrees, and the ratio of the mass proportion of lithium element to the mass proportion of oxygen element A1 of the particles with smaller particle size and the ratio of the mass proportion of lithium element to the mass proportion of oxygen element A2 of the particles with larger particle size are controlled between 0.6 and 1 (excluding 1), so that the negative electrode material can improve the storage performance while improving the rate performance and cycle performance.

[0069] In the present application, the particle size of the negative electrode material is measured by a laser particle size analyzer, and it has a symmetrical distribution similar to a normal distribution. In the above-mentioned normal distribution, the particle size at which the cumulative volume distribution of the negative electrode material particles is 10% is recorded as D10, the particle size at which the cumulative volume distribution of the negative electrode material particles is 90% is recorded as D90, and the particle size at which the cumulative volume distribution of the negative electrode material particles is 50% is recorded as D50, also known as the median particle size.

[0070] In some embodiments, the ratio of the mass proportion of lithium element in the negative electrode material to the mass proportion of oxygen element in the negative electrode material is recorded as A, and A is 0.1 to 0.7, and can specifically be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7, etc. Of course, it can also be other values within the above range, which is not limited here.

[0071] In some embodiments, A1 is 0.1 to 0.65, specifically 0.1, 0.2, 0.3, 0.4, 0.5, or 0.65, and may also be other values within the above range, which is not limited herein. Within the above-defined range, it indicates that particles in the negative electrode material with a particle size smaller than D10 have an appropriate degree of pre-lithiation, which can reduce the specific surface area of the negative electrode material while ensuring that the negative electrode material has an appropriate lithium content, thereby improving the storage performance and initial efficiency of the negative electrode material.

[0072] In some embodiments, A2 is 0.15 to 0.7, specifically 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7, and may be other values within the above range, which is not limited herein. Within the above-defined range, it indicates that particles with a particle size greater than D90 in the negative electrode material have an appropriate pre-lithiation degree, which can not only improve the lithium ion conduction efficiency of the negative electrode material, but also enable the negative electrode material to have an appropriate specific surface area, thereby improving the rate performance, cycle performance, and initial efficiency of the negative electrode material.

[0073] In the present application, the negative electrode materials with a particle size less than or equal to D10 and the negative electrode materials with a particle size greater than or equal to D90 were obtained by screening and measuring by a laser particle size analyzer, and the Li content of the negative electrode materials with a particle size less than or equal to D10 and the negative electrode materials with a particle size greater than or equal to D90 was determined by an ICP spectrometer (Agilent 5800VDVICP-OES), and the O content of the negative electrode materials with a particle size less than or equal to D10 and the negative electrode materials with a particle size greater than or equal to D90 was determined by an ONH elemental analyzer, and then the A1 and A2 values were calculated.

[0074] In some embodiments, the silicon-based material includes at least one of a silicon-oxygen material and silicon alone.

[0075] In some embodiments, the lithium element in the negative electrode material exists in the form of a lithium-containing silicon-oxygen material, and the silicon-oxygen material includes but is not limited to at least one of Li2SiO3, Li2Si2O5 and Li4SiO4.

[0076] In some embodiments, 0.1 μm≤D10≤15 μm, and D10 can be, for example, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 10 μm, 13 μm, or 15 μm, etc., and can certainly be other values within the above range, which is not limited here.

[0077] In some embodiments, 0.5 μm≤D90≤30 μm, and D90 can be, for example, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 25 μm, or 30 μm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0078] In some embodiments, 0.3 μm≤D50≤25 μm, specifically 0.3 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0079] In some embodiments, the silicon element includes silicon microcrystals, and the grain size of the silicon microcrystals is less than or equal to 20 nm, for example, it can be 2 nm, 5 nm, 8 nm, 10 nm, 13 nm, 15 nm or 20 nm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0080] In some embodiments, the negative electrode material also includes a coating layer distributed on at least part of the surface of the silicon-based material, and the coating layer is a carbon layer. On the one hand, the presence of the coating layer can reduce the side reactions caused by the electrolyte entering the interior of the negative electrode material, resulting in a decrease in the initial efficiency and capacity of the negative electrode material. On the other hand, the coating layer can alleviate the volume expansion of silicon to a certain extent and reduce the swelling of the negative electrode plate during charging and discharging.

[0081] In some embodiments, the coating layer thickness of the negative electrode material with a particle size less than or equal to D10 is 15nm to 1000nm, specifically 15nm, 50nm, 100nm, 300nm, 500nm, 800nm and 1000nm, etc., and of course it can also be other values within the above range, which is not limited here.

[0082] In some embodiments, the coating layer thickness of the negative electrode material with a particle size greater than or equal to D90 is 10nm to 900nm, specifically 10nm, 50nm, 100nm, 300nm, 500nm, 700nm and 900nm, etc., and of course it can also be other values within the above range, which is not limited here.

[0083] In some embodiments, the lithium content in the negative electrode material is 0.1wt% to 20wt%, specifically 0.1wt%, 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt% and 20wt%, etc. Of course, it can also be other values within the above range, which is not limited here.

[0084] In some embodiments, the specific surface area of the negative electrode material is 0.1 m 2 / g~50m 2 / g, specifically 0.1m 2 / g, 0.5m 2 / g、10m 2 / g, 20m 2 / g、30m 2 / g, 40m 2 / g and 50m 2 / g, etc., and of course, it can also be other values within the above range, which is not limited here.

[0085] In some embodiments, the oxygen content in the negative electrode material is 15wt% to 45wt%, specifically 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt% and 45wt%, etc. Of course, it can also be other values within the above range, which is not limited here.

[0086] In some embodiments, the negative electrode material contains a metal element, and the metal element includes at least one of iron, cobalt, nickel, and copper.

[0087] In some embodiments, the mass content of the metal element in the negative electrode material is 1 ppm to 5000 ppm, specifically 1 ppm, 10 ppm, 100 ppm, 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, and 5000 ppm, etc., and of course other values within the above range are also possible, and are not limited here. Within the above-defined range, the problem of capacity decay caused by excessive metal element content in the negative electrode material can be reduced. The metal element content can be obtained by testing methods such as ion chromatography, composition analysis, or energy dispersive spectroscopy (EDX analysis).

[0088] In some embodiments, the metal element is present in the core and / or the cladding layer.

[0089] The present invention provides a method for preparing a negative electrode material. Figure 1 As shown in FIG, a flow chart for preparing the negative electrode material provided in an embodiment of the present application includes the following steps:

[0090] Step S100, mixing a silicon oxide raw material and a solution containing a metal catalyst, and performing solid-liquid separation to obtain a precursor, wherein the mass ratio of the metal catalyst to the silicon oxide raw material is (0.00001-0.05):1;

[0091] Step S200 , mixing the precursor and the lithium source and performing heat treatment to obtain a negative electrode material.

[0092] In the above scheme, the present application obtains a precursor by mixing a silicon oxide raw material and a solution containing a metal catalyst so that an appropriate amount of metal catalyst is adsorbed on the surface of the silicon oxide raw material. For materials with smaller particle sizes in the silicon oxide raw material, the specific surface area is larger and can adsorb relatively more metal catalysts, while for materials with larger particle sizes in the silicon oxide raw material, the specific surface area is smaller and can adsorb relatively less metal catalysts. In the process of mixing the precursor and the lithium source for heat treatment, for precursors with smaller particle sizes, the pre-lithiation degree of the material during the heat treatment is lower, which can reduce the surface area of the negative electrode material, thereby improving the storage performance of the negative electrode material. For precursors with larger particle sizes, the pre-lithiation degree of the material during the heat treatment is higher, which is beneficial to improving the lithium ion conductivity of the negative electrode material, thereby improving the rate performance of the negative electrode material; and the negative electrode material particles with larger particle sizes are more fully embedded with lithium, so that the volume change of the negative electrode material during the charge and discharge process is smaller, which is beneficial to improving the cycle performance of the negative electrode material. The preparation method of the present application has a simple preparation process. By pre-mixing the silicon oxide raw material with a solution containing a metal catalyst, the mass ratio of the metal catalyst to the silicon oxide raw material is (0.00001-0.05):1. This can ensure that the metal catalysts adsorbed by silicon oxide raw materials of different particle sizes in the negative electrode material products prepared in the same batch are different, and can also reduce the situation where excessive metal catalyst in the precursor affects the subsequent lithium embedding, so that the prepared negative electrode material has both excellent storage performance and good rate performance.

[0093] The preparation method of the present application is described in detail below with reference to the examples:

[0094] In step S100 , a silicon oxide raw material and a solution containing a metal catalyst are mixed and solid-liquid separated to obtain a precursor. The mass ratio of the metal catalyst to the silicon oxide raw material is (0.00001-0.05):1.

[0095] The present application mixes the silicon oxide raw material and the metal catalyst in a liquid phase, so that the metal catalyst is adsorbed on the surface of the silicon oxide raw material through intermolecular adsorption. For silicon oxide raw materials with a larger specific surface area, the adsorption amount of the metal catalyst is greater. Moreover, the surface of the silicon oxide raw material contains hydroxyl functional groups. In a liquid phase environment, the metal ions in the metal catalyst can partially complex with the silicon oxide raw material and thus be adsorbed on the surface of the silicon oxide raw material, which is conducive to the adsorption of the metal catalyst on the surface of the silicon oxide raw material as much as possible.

[0096] In some embodiments, the silicon oxide raw material comprises silicon oxide SiO y , wherein 0<y≤2, silicon oxide is a silicon-oxygen composite containing oxygen atoms and silicon atoms, and the molar ratio of oxygen atoms to silicon atoms is 0 to 2 and does not include 0. It can be Si, SiO 0.2 、SiO 0.5 、SiO 0.8、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 Or SiO2, etc., a compound of two or more substances, or a substance with the chemical formula SiO y Of course, it can also be other values within the above range, and this application does not limit it here.

[0097] In some embodiments, D10 of the silicon oxide raw material is: 0.1 μm≤D10≤15 μm, and D10 can be, for example, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 10 μm, 13 μm or 15 μm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0098] In some embodiments, D90 of the silicon oxide raw material is 0.5 μm≤D90≤30 μm. D90 may be, for example, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 25 μm or 30 μm, etc. Of course, it may also be other values within the above range, which is not limited here.

[0099] In some embodiments, the D50 of the silicon oxide raw material is 0.3 μm≤D50≤25 μm, specifically 0.3 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm and 25 μm, etc. Of course, it can also be other values within the above range, which is not limited here.

[0100] The particle sizes D10, D50 and D90 of the silicon oxide raw material of the present application are limited to the above ranges, which can ensure that an appropriate amount of metal catalyst is adsorbed on the surface of the silicon oxide raw material, thereby improving the storage performance and rate performance of the negative electrode material, and can also improve the compaction density of the negative electrode material prepared from the silicon oxide raw material, thereby improving the processing performance of the negative electrode material.

[0101] In some embodiments, the mass ratio of the metal catalyst to the silicon oxide raw material is (0.00001-0.05):1, which can be specifically 0.00001:1, 0.0001:1, 0.001:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1 and 0.05:1, etc. Of course, it can also be other values within the above range, which is not limited here. Within the above-mentioned limited range, it can not only make the metal catalysts adsorbed by silicon oxide raw materials of different particle sizes in the same batch different, but also reduce the situation where too much metal catalyst in the precursor affects the subsequent lithium embedding, thereby improving the storage performance and rate performance of the negative electrode material. If the amount of metal catalyst added is too small, the metal catalyst adsorbed on the surface of the silicon oxide raw material is too small. In the subsequent lithium embedding process, it is easy to cause the pre-lithium degree of the precursor with a larger particle size to be lower, and the pre-lithium degree of the precursor with a smaller particle size to be higher, which is not conducive to improving the storage performance of the negative electrode material and the lithium ion conductivity. If the amount of metal catalyst added is too much, too much metal catalyst will be adsorbed on the surface of the silicon oxide raw material, resulting in too low a pre-lithiation degree of the precursor with smaller particle size, which is not conducive to improving the lithium ion conductivity and initial efficiency of the negative electrode material.

[0102] In some embodiments, the solution containing the metal catalyst is prepared by the following method: mixing the metal catalyst and a solvent to obtain the solution containing the metal catalyst.

[0103] In some embodiments, the solution containing the metal catalyst further comprises a surfactant, i.e., the metal catalyst, the surfactant, and the solvent are uniformly mixed to obtain a solution containing the metal catalyst. The present application adds a surfactant to the solution containing the metal catalyst and then mixes it with the silicon raw material. The surfactant can reduce the surface energy of the silicon raw material, which is conducive to the adhesion of the metal catalyst to the surface of the silicon material. It is understood that the present application does not limit the method for mixing the metal catalyst, the surfactant, and the solvent. The metal catalyst can be added first, and then the surfactant is added. Alternatively, the metal catalyst and the surfactant can be mixed first and then added to the solvent.

[0104] In some embodiments, the surfactant includes at least one of sodium lauryl sulfate and stearic acid.

[0105] In some embodiments, the mass ratio of the surfactant to the silicon raw material is (0.01-0.2):1, specifically 0.01:1, 0.05:1, 0.08:1, 0.1:1, 0.15:1 or 0.2:1, etc. Of course, it can also be other values within the above range, which is not limited here.

[0106] In some embodiments, the metal catalyst includes at least one of a copper salt, a cobalt salt, a nickel salt, and an iron salt.

[0107] In some embodiments, the metal catalyst comprises at least one of ferric chloride, cobalt chloride, nickel chloride, and copper hydroxide.

[0108] In some embodiments, the solvent includes, but is not limited to, at least one of water, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and amyl alcohol. Wet mixing the components in the solvent can improve the uniformity of the component mixing and facilitate rapid drying.

[0109] In some embodiments, the mixing time is 1 h to 10 h, for example, 1 h, 3 h, 5 h, 7 h, 9 h or 10 h, etc. Of course, it can also be other values within the above range, which is not limited here.

[0110] In some embodiments, methods of solid-liquid separation include but are not limited to filtration and centrifugation.

[0111] In some embodiments, before mixing the precursor and the lithium source and performing a heat treatment, the method further includes: mixing the precursor and a carbon source and performing a carbonization treatment.

[0112] In the above steps, the precursor and the carbon source are mixed and carbonized to achieve carbon coating. During the carbon coating process, the metal elements on the surface of the silicon oxide raw material can induce carbon deposition, providing cracking and bonding reaction sites for the carbon source molecules, which is beneficial to carbon coating on the surface of the metal catalyst and improving the carbon coating efficiency. Therefore, the small-particle precursor with a higher metal element content has a higher carbon coating amount and a thicker coating layer, while the large-particle precursor with a lower metal element content has a lower carbon coating amount and a thinner coating layer.

[0113] In some embodiments, the carbon source includes a gaseous carbon source. The present application achieves carbon coating by adopting a gaseous carbon source. On the one hand, the gaseous carbon source can achieve uniform coating of the precursor. At the same time, during the introduction of the gaseous carbon source, a part of the metal elements on the surface of the precursor will be separated from the silicon oxide material.

[0114] In some embodiments, the gaseous carbon source includes at least one of alkanes, cycloalkanes, alkenes, alkynes and aromatic hydrocarbons. Exemplarily, the gaseous carbon source includes but is not limited to at least one of acetylene, methane, propylene, benzene, ethanol, methanol, ethylene, propane and butane.

[0115] In some embodiments, the flow rate of the gaseous carbon source is 0.1 L / min to 500 L / min, specifically 0.1 L / min, 1 L / min, 10 L / min, 50 L / min, 100 L / min, 200 L / min, 300 L / min, 400 L / min, and 500 L / min, etc., and of course other values within the above range are also possible, which are not limited here. Within the above-mentioned limited range, it can be ensured that the material with smaller particle size forms a thicker carbon coating layer, and the material with larger particle size forms a thinner carbon coating layer, thereby achieving an improvement in the storage performance and rate performance of the negative electrode material.

[0116] In some embodiments, the temperature of the carbonization treatment is 600°C to 1000°C, for example, it can be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, etc. Of course, it can also be other values within the above range, which is not limited here.

[0117] In some embodiments, the carbonization treatment time is 0.5 h to 10 h, specifically 0.5 h, 1 h, 3 h, 5 h, 8 h or 10 h, etc. Of course, it can also be other values within the above range, which is not limited here.

[0118] In some embodiments, the carbonization treatment is performed in a protective gas atmosphere. Specifically, the protective gas atmosphere includes at least one of nitrogen, argon, and helium.

[0119] Step S200 , mixing the precursor and the lithium source and performing heat treatment to obtain a negative electrode material.

[0120] In this step, the precursor and the lithium source are mixed and heat-treated. The thickness of the surface carbon layer of the precursor with a larger particle size is less than the thickness of the surface carbon layer of the precursor with a smaller particle size. During the heat treatment, the lithium element is more likely to enter the precursor with a larger particle size, but it is more difficult to enter the precursor with a smaller particle size. As a result, in the prepared negative electrode material, the content ratio of lithium and oxygen elements in the negative electrode material with a larger particle size is higher, and the pre-lithiation degree is high, which is beneficial to improving the rate performance and cycle performance of the negative electrode material. The content ratio of lithium and oxygen elements in the negative electrode material with a smaller particle size is lower, and the pre-lithiation degree is low, which is beneficial to improving the storage performance of the negative electrode material.

[0121] In some embodiments, the lithium source includes at least one of metallic lithium, lithium hydride, lithium carbonate, lithium hydroxide, lithium borohydride, and lithium aluminum hydride.

[0122] In some embodiments, the mass ratio of the silicon oxide raw material to the lithium source is 1:(0.05-0.5), for example, 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, or 1:0.5, and of course, other values within the above range are also possible and are not limited here. If the amount of lithium source added is too much, the capacity of the negative electrode material will be too low; if the amount of lithium source added is too little, the lithium-oxygen ratio of the negative electrode material will be too low, the lithium ion transport performance of the negative electrode material will be poor, and thus the initial efficiency of the negative electrode material will be too low.

[0123] In some embodiments, the heat treatment temperature is 400°C to 900°C, for example, 400°C, 50°C, 600°C, 700°C, 800°C, or 900°C, and other values within the above range are also possible. Preferably, the heat treatment temperature is 700°C to 900°C.

[0124] In some embodiments, the heat treatment time is 2 hours to 12 hours, specifically 2 hours, 5 hours, 7 hours, 9 hours, 10 hours or 12 hours, etc., and of course other values within the above range are also possible, and are not limited here. Preferably, the heat treatment time is 3 hours to 12 hours.

[0125] In some embodiments, the heat treatment is performed in a protective gas atmosphere, and the protective gas includes at least one of nitrogen, argon, and helium.

[0126] In some embodiments, after the heat treatment, the material obtained by the heat treatment is further subjected to at least one of screening and demagnetization; preferably, after the heat treatment, screening and demagnetization are performed in sequence.

[0127] In some embodiments, the screening method includes at least one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen, and a chain screen, and the screening mesh number is ≥500 mesh. Specifically, the screening mesh number can be 500 mesh, 600 mesh, 700 mesh, 800 mesh, etc. The particle size of the negative electrode material is controlled within the above range, which is beneficial to improving the cycle performance of the negative electrode material.

[0128] In some embodiments, the demagnetization equipment is any one of a permanent magnetic drum magnetic separator, an electromagnetic iron remover, and a pulsating high gradient magnetic separator. The purpose of demagnetization is to ultimately control the magnetic material content of the negative electrode material, reduce the discharge effect of the magnetic material on the lithium-ion battery, and ensure the safety of the battery during use.

[0129] In a third aspect, the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method described in the second aspect.

[0130] The following further describes the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0131] Example 1

[0132] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0133] (1) Dissolve 10 g of FeCl3 and 1 g of sodium lauryl sulfate in 1.2 kg of water. Soak 1 kg of SiO2 (D10 = 3.0 μm, D50 = 5.5 μm, D90 = 9.6 μm) powder in the solution for 3 h. Filter the mixture with suction and dry it at 100 °C.

[0134] (2) placing the material obtained in step (1) in a tubular furnace and heating it to 900° C. under nitrogen protection, introducing acetylene, keeping the temperature for 3 h, and then cooling to obtain a carbon-coated SiO material;

[0135] (3) 100 g of LiH was mixed with the material obtained in step (2), and then placed in a box furnace under nitrogen protection, heated to 800 ° C, kept warm for 4 h, taken out and sieved to obtain the negative electrode material.

[0136] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of the negative electrode material, D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value, are shown in Tables 1 and 2.

[0137] Example 2

[0138] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0139] (1) Dissolve 10 g of FeCl3 and 1 g of sodium lauryl sulfate in 1.2 kg of water. Soak 1 kg of SiO2 (D10 = 2.0 μm, D50 = 5.0 μm, D90 = 11 μm) powder in the solution for 3 h, filter, and dry at 100 °C.

[0140] (2) placing the material obtained in step (1) in a tubular furnace and heating it to 900° C. under nitrogen protection, introducing acetylene, keeping the temperature for 3 h, and then cooling to obtain a carbon-coated SiO material;

[0141] (3) 60 g of LiH was mixed with the material obtained in step (2), and then placed in a box furnace under nitrogen protection, heated to 800 ° C, kept warm for 4 h, taken out and sieved to obtain the negative electrode material.

[0142] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of the negative electrode material, D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value, are shown in Tables 1 and 2.

[0143] Example 3

[0144] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0145] (1) Dissolve 10 g of FeCl3 and 1 g of sodium lauryl sulfate in 1.2 kg of water. Soak 1 kg of SiO2 (D10 = 3.0 μm, D50 = 5.3 μm, D90 = 7.5 μm) powder in the solution for 3 h. Filter the mixture with suction and dry it at 100 °C.

[0146] (2) placing the material obtained in step (1) in a tubular furnace and heating it to 900° C. under nitrogen protection, introducing acetylene, keeping the temperature for 3 h, and then cooling to obtain a carbon-coated SiO material;

[0147] (3) 240 g of LiH was mixed with the material obtained in step (2), and then placed in a box furnace under nitrogen protection, heated to 800° C., kept warm for 4 h, and then taken out and sieved to obtain the negative electrode material.

[0148] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of the negative electrode material, D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value, are shown in Tables 1 and 2.

[0149] Example 4

[0150] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0151] (1) Dissolve 10 g of FeCl3 and 1 g of sodium lauryl sulfate in 1.2 kg of water. Soak 1 kg of SiO2 (D10 = 2.0 μm, D50 = 5.0 μm, D90 = 11 μm) powder in the solution for 3 h, filter, and dry at 100 °C.

[0152] (2) placing the material obtained in step (1) in a tubular furnace and heating it to 900° C. under nitrogen protection, introducing acetylene, keeping the temperature for 3 h, and then cooling to obtain a carbon-coated SiO material;

[0153] (3) 240 g of LiH was mixed with the material obtained in step (2), and then placed in a box furnace under nitrogen protection, heated to 800° C., kept warm for 4 h, and then taken out and sieved to obtain the negative electrode material.

[0154] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of the negative electrode material, D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value, are shown in Tables 1 and 2.

[0155] Example 5

[0156] The difference from Example 1 is that FeCl3 is replaced by cobalt chloride.

[0157] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of the negative electrode material, D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value, are shown in Tables 1 and 2.

[0158] Example 6

[0159] The difference from Example 1 is that sodium lauryl sulfate is replaced by stearic acid.

[0160] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of the negative electrode material, D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value, are shown in Tables 1 and 2.

[0161] Example 7

[0162] The difference from Example 1 is that sodium lauryl sulfate in step (1) is not added.

[0163] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0164] Example 8

[0165] The difference from Example 1 is that the SiO powder has D10=4.5 μm, D50=7.6 μm, and D90=11.9 μm.

[0166] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0167] Example 9

[0168] The difference from Example 1 is that the SiO powder has D10=6.5 μm, D50=9.5 μm, and D90=16.2 μm.

[0169] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0170] Example 10

[0171] The difference from Example 1 is that the SiO powder has D10=10.6 μm, D50=13.0 μm, and D90=25.1 μm.

[0172] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0173] Example 11

[0174] The difference from Example 1 is that the added amount of FeCl3 is 0.01g.

[0175] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0176] Example 12

[0177] The difference from Example 1 is that the added amount of FeCl3 is 20g.

[0178] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0179] Example 13

[0180] The difference from Example 1 is that the added amount of FeCl3 is 50g.

[0181] The negative electrode material prepared in this embodiment includes a silicon-based material and a carbon coating layer distributed on the surface of the silicon-based material. The silicon-based material includes Li2SiO3 and silicon. The measurement parameters of D10, D50, D90, specific surface area, A value, A1 value, A2 value and A1 / A2 value of the negative electrode material are shown in Tables 1 and 2.

[0182] Comparative Example 1

[0183] (1) Dissolve 1 g of sodium lauryl sulfate in 1.2 kg of water. Soak 1 kg of SiO2 (D10 = 3.0 μm, D50 = 5.5 μm, D90 = 9.6 μm) powder in the solution for 3 h. Filter the mixture with suction and dry it at 100 °C.

[0184] (2) placing the material obtained in step (1) in a tubular furnace and heating it to 900° C. under nitrogen protection, introducing acetylene, keeping the temperature for 3 h, and then cooling to obtain a carbon-coated SiO material;

[0185] (3) 100 g of LiH was mixed with the material obtained in step (2), and then placed in a box furnace under nitrogen protection, heated to 800 ° C, kept warm for 4 h, taken out and sieved to obtain the negative electrode material.

[0186] Comparative Example 2

[0187] The difference from Example 1 is that the added amount of FeCl3 is 60g.

[0188] Performance Testing

[0189] (1) The D50, D10 and D90 of the negative electrode material are measured using a laser particle size analyzer. Specifically, the Mastersizer 3000 laser diffraction technology is used to measure the particle size of the negative electrode material. When the laser beam passes through the dispersed particle sample, the particle size measurement is completed by measuring the intensity of the scattered light. The data is then used to analyze and calculate the particle size distribution of the scattering spectrum. There is a symmetrical distribution similar to a normal distribution in the scattering spectrum. In the distribution, D90 is the particle size at which the cumulative volume distribution of the material particles is 90%, D10 is the particle size at which the cumulative volume distribution of the material particles is 10%, and D50 is the particle size at which the cumulative volume distribution of the material particles is 50%, also known as the median particle size. A classifier is used to screen the material for particle size, and negative electrode materials with a particle size less than or equal to D10 and negative electrode materials with a particle size greater than or equal to D90 are screened out.

[0190] (2) The ICP method was used to test the Li content in the negative electrode material. Test method: 0.500 g of the negative electrode material was placed in a clean platinum crucible, and then calcined at 750 ° C for 2 hours in an air atmosphere muffle furnace to completely remove the carbon element; the cooled calcined residue was fully reacted with 4 mL HNO3 and 6 mL HF mixed acid, and then the platinum crucible containing the solution was placed on a 350 ° C hot plate until the solvent was completely evaporated; after the crucible cooled, 6 mL HCl was added and heated until the residue was completely dissolved, and the volume was adjusted to 100 mL plastic volumetric flask; finally, the total Li element content of the negative electrode material was tested using an ICP spectrometer (Agilent 5800VDVICP-OES).

[0191] Oxygen content test method: The total O content of the material was measured using an ONH elemental analyzer. Specifically, the ONH elemental analyzer (ONH-2000) was used. The following steps were performed: 10mg to 13mg of the negative electrode material was weighed and wrapped in nickel foil. The material was then placed in a graphite crucible in the ONH elemental analyzer for testing to determine the total O content in the negative electrode material. The ratio of the total Li content of the negative electrode material to the total O content in the negative electrode material was recorded as the A value.

[0192] (3) Based on the negative electrode materials with a particle size less than or equal to D10 and the materials with a particle size greater than or equal to D90 screened out in (1), the Li content and O content of the negative electrode materials with a particle size less than or equal to D10 and the negative electrode materials with a particle size greater than or equal to D90 are tested according to (2) and the A1 and A2 values are calculated.

[0193] (4) The grain size of the silicon material in the negative electrode material was determined using a PANalytical X'pert PRO X-ray diffractometer. The XRD of the negative electrode material was measured within a scanning range of 9.749° to 41.157°, with a scanning step of 0.013°, a scanning speed of 6.060° / min, a voltage of 40 kV, and a current of 40 mA. The file was opened with Jade 6, background removed and smoothed, and the Si peak within the range of 26° to 30° was fitted. The Scherrer formula was used, D = kλ / βcosθ, where D is the average grain size perpendicular to the Si reflection crystal plane (111), β-(radians) is the widening degree of the half-height width of the diffraction peak of the crystal plane = FWHM*π / 180, k is the Scherrer constant, which is taken as 0.89, θ is the diffraction angle, and λ is the wavelength of the incident X-ray, which is taken as 0.15406 nm. Full width at half maximum (FWHM) is a chromatographic term that refers to the width of a chromatographic peak at half its height. This refers to the distance between the points where a line drawn through the midpoint of the peak, parallel to the base of the peak, intersects the two sides of the peak. Both FHWM and θ can be obtained using XRD.

[0194] The XRD peak was measured using a Panatech X'pert Pro X-ray diffractometer, and then the Si peak in the XRD was fitted and analyzed using Xpert High Score software to calculate the silicon grain size.

[0195] Software instructions and parameter settings:

[0196] 1. Open the X'pert High Score software, click Open, find the file you just saved, and click OK to open the file;

[0197] 2. Go to Ka2: right-click a blank area of the spectrum and click "Strip K-Alpha2", or select "Treatment" - "Strip K-Alpha2" in the toolbar, click "Strip K-Alpha2" in the pop-up dialog box, and then click "Replace";

[0198] 3. Smooth: Right-click a blank area of the spectrum, click "Smooth" in the menu, click "Smooth" in the pop-up dialog box, and then click "Replace"; select Quintic mode;

[0199] 4. Define the background: right-click a blank area of the spectrum, click "Determine Background", click "Background" in the pop-up dialog box, and then click "Accept"; select 20 for Guanularity and 5 for blending factor;

[0200] 5. Peak search: Right-click on the blank area of the spectrum peak, click "Search Peaks", and select the peak search parameters in the pop-up dialog box:

[0201] Minimum significance: 2.0

[0202] Minimum tip width: 0.1

[0203] Maximum tip width: 5

[0204] Peak base width: 10, click "Search Peaks" in the dialog box on the right, and then click "Accept";

[0205] 6. Peak fitting: Right-click a blank area of the spectrum, click "Set Manual Ranges", enter the angle range of "26~30" in the pop-up dialog box, and then click "OK"; right-click a blank area of the spectrum again, click "Fit Profile", and perform the operation several times until the peak data in the "peak list" on the right no longer changes. Record the angle (θ), half-maximum width (FWHM), and peak height of the peak in the range of about 28.4°.

[0206] (5) The specific surface area of the negative electrode material was measured using the American Micromeritics TriStar 3000 specific surface area and pore size analyzer.

[0207] (6) Electrochemical performance test

[0208] 1. First Coulombic efficiency test:

[0209] a. Preparation of lithium-ion batteries: The negative electrode materials prepared in the above examples and comparative examples were used as negative electrode active materials. After being uniformly mixed with conductive carbon black and CMC / SBR in a mass ratio of 75:15:10, the mixture was coated on copper foil to prepare a negative electrode sheet. A metal lithium sheet was used as the positive electrode sheet, and PP / PE was used as the separator to prepare a button battery.

[0210] b. Tested with a BlueDian Xinwei 5V / 10mA battery tester at a voltage of 1.5V and a current of 0.1C. First coulombic efficiency = first charge specific capacity / first discharge specific capacity.

[0211] 2. Cycle performance test:

[0212] a. Preparation of lithium-ion batteries: The negative electrode materials prepared in the above examples and comparative examples were respectively mixed with graphite at a mass ratio of 15:85 to obtain negative electrode active materials. The negative electrode active materials, conductive carbon black, CMC, and SBR were then uniformly mixed at a mass ratio of 92:4:2:2, and coated on copper foil to prepare a negative electrode sheet. A metal lithium sheet was used as the positive electrode sheet, and PP / PE was used as a separator to prepare a button battery.

[0213] b. Tested with a BlueDian Xinwei 5V / 10mA battery tester at 1.5V and 0.1C. 50-cycle retention rate = 50th discharge capacity / first discharge capacity.

[0214] 3. Rate performance test:

[0215] a. Preparation of lithium-ion batteries: The negative electrode materials prepared in the above examples and comparative examples were respectively mixed with graphite at a mass ratio of 15:85 to obtain negative electrode active materials. The negative electrode active materials, conductive carbon black, CMC, and SBR were then uniformly mixed at a mass ratio of 92:4:2:2, and coated on copper foil to prepare a negative electrode sheet. A metal lithium sheet was used as the positive electrode sheet, and PP / PE was used as a separator to prepare a button battery.

[0216] b. Tested with a BlueDian Xinwei 5V / 10mA battery tester, with a voltage of 1.5V and currents of 0.1C and 3C respectively. 3C / 0.1C = 3C discharge capacity / 0.1C discharge capacity.

[0217] 4. Storage performance test:

[0218] a. Preparation of lithium-ion batteries: The negative electrode material and graphite were composited to a capacity of 450 mAh / g as the negative electrode active material. A negative electrode sheet was prepared according to the active material formula: CMC (2200): SP: SWCNT: SBR (BM451B) = 95.1:1.4:1.45:0.05:2.0. The positive electrode used high-nickel NMC product M2-C2 (produced by BTR) and was prepared according to the formula of M2-C2: Solef 5130: Super P: GNLC-05 = 96.6:1.4:1.3:0.7. The positive and negative electrode sheets were then wound to form a 554065 model soft-pack battery cell. The cell then underwent various processes including injection, formation, and capacity grading to form a battery for testing. The battery design parameters are: positive electrode compaction 3.4g / cc, negative electrode compaction 1.65g / cc, negative electrode surface density 200g / m2, and N / P ratio design is 8.2%.

[0219] b. After the cells are divided into different capacities, charge them at 0.5C to 100% SOC. After storing at 60°C for 7 days, discharge them at 0.5C to the lower voltage limit, recording Capacity 1. Charge and discharge the battery for another week, recording the discharged capacity as Capacity 2. Battery Capacity 1 / Initial Capacity = Capacity Retention Rate, Battery Capacity 2 / Initial Capacity = Capacity Recovery Rate, and 1 - Capacity Recovery Rate = Irreversible Capacity Loss Rate.

[0220] Examples 1 to 13 of the present application are denoted as S1 to S13, and Comparative Examples 1 to 2 are denoted as D1 to D2. The results of the above performance tests are as follows:

[0221] Table 1. A value, A1 value, A2 value of each embodiment and comparative example

[0222]

[0223]

[0224] Table 2. Parameters of negative electrode materials of various examples and comparative examples

[0225]

[0226]

[0227] As shown in Tables 1 to 2, the negative electrode materials prepared in Examples 1 to 13 of the present application are negative electrode materials prepared by adding a metal catalyst to a silicon oxide material. The smaller particles and the larger particles in the negative electrode material particles have different pre-lithiation degrees, and the ratio A1 of the mass proportion of lithium element to the mass proportion of oxygen element in the particles with smaller particle size and the ratio A2 of the mass proportion of lithium element to the mass proportion of oxygen element in the particles with larger particle size are controlled between 0.6 and 1 (excluding 1), so that the negative electrode material can improve the storage performance while improving the rate performance and cycle performance.

[0228] No metal catalyst was added in Comparative Example 1. As can be seen from the contents of Table 1, the A1 value and A2 value of the negative electrode material prepared in Comparative Example 1 are both within the specified range of this application, but the A1 / A2 value does not meet the specified range of this application, indicating that no metal catalyst was added in Comparative Example 1, and in the subsequent pre-lithiation process, it is impossible to selectively pre-lithiate silicon oxide raw materials of different particle sizes, resulting in poor storage performance, cycle performance and rate performance of the negative electrode material.

[0229] In Comparative Example 2, excessive metal catalyst was added, resulting in excessive metal catalyst adsorbed on the surface of the silicon oxide raw material, especially on the surface of the small-particle negative electrode material with a larger specific surface area, resulting in a lower pre-lithiation degree of the small-particle negative electrode material, causing A1 / A2 to not meet the specified range of this application, and the storage performance and rate performance of the negative electrode material are poor.

[0230] The applicant declares that the present invention uses the above-described embodiments to illustrate the detailed process equipment and process flow of the present invention. However, the present invention is not limited to the above-described detailed process equipment and process flow, and does not necessarily rely on the above-described detailed process equipment and process flow in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for the raw materials of the present invention's products, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A negative electrode material, characterized in that The negative electrode material comprises a silicon-based material and a coating layer, wherein the silicon-based material contains oxygen and lithium elements, and the coating layer is distributed on at least a portion of the surface of the silicon-based material. The negative electrode material is tested by a laser particle size analyzer to obtain a particle size D10 at 10% of the cumulative volume distribution and a particle size D90 at 90% of the cumulative volume distribution; The ratio of the mass proportion of the lithium element in the negative electrode material to the mass proportion of the oxygen element in the negative electrode material is recorded as A, and A is 0.26~0.

7. The ratio of the mass proportion of the lithium element in the particles with a particle size less than or equal to D10 in the negative electrode material to the mass proportion of the oxygen element is recorded as A1, and A1 is 0.1~0.

65. The ratio of the mass proportion of the lithium element in the particles with a particle size greater than or equal to D90 in the negative electrode material to the mass proportion of the oxygen element is recorded as A2, and A2 is 0.15~0.7, 0.6≤A1 / A2<1.

2. The negative electrode material according to claim 1, characterized in that The negative electrode material includes at least one of the following characteristics (1) to (5): (1) The silicon-based material includes at least one of a silicon-oxygen material and a silicon element; (2) The silicon-based material includes at least one of a silicon oxide material and a silicon element, and the silicon oxide material includes at least one of Li2SiO3, Li2Si2O5 and Li4SiO4; (3) The negative electrode material has a particle size D10 of 10% of the cumulative volume distribution of the material particles, 0.1 μm ≤ D10 ≤ 15 μm; (4) The negative electrode material has a particle size D90 at which 90% of the cumulative volume distribution of the material particles is 0.5 μm ≤ D90 ≤ 30 μm; (5) The negative electrode material has a particle size D50 at which the cumulative volume distribution of the material particles is 50%, and 0.3 μm ≤ D50 ≤ 25 μm.

3. The negative electrode material according to claim 1, characterized in that The negative electrode material includes at least one of the following features (1) to (8): (1) The coating layer is a carbon layer; (2) For negative electrode materials with a particle size smaller than D10, the coating thickness is 15nm~1000nm; (3) For the negative electrode material having a particle size greater than D90, the coating thickness is 10 nm to 900 nm; (4) The lithium content in the negative electrode material is 0.1 wt% to 20 wt%; (5) The specific surface area of the negative electrode material is 0.1m 2 / g~50m 2 / g; (6) The oxygen content of the negative electrode material is 15 wt% to 45 wt%; (7) The negative electrode material contains a metal element, and the metal element includes at least one of iron, cobalt, nickel and copper; (8) The negative electrode material contains a metal element, and the content of the metal element in the negative electrode material is 1 ppm to 5000 ppm.

4. A method for preparing a negative electrode material, characterized in that: The steps include: Mixing a silicon oxide raw material and a solution containing a metal catalyst, and performing solid-liquid separation to obtain a precursor, wherein the mass ratio of the metal catalyst to the silicon oxide raw material is (0.00001-0.05):1; mixing the precursor and a carbon source to perform carbonization treatment; mixing the carbonized product and a lithium source and performing heat treatment to obtain a negative electrode material; The lithium source comprises at least one of metallic lithium, lithium hydride, lithium carbonate, lithium hydroxide, lithium borohydride and lithium aluminum hydride; The mass ratio of the silicon oxide raw material to the lithium source is 1:(0.1-0.5); The solution containing the metal catalyst also includes a surfactant, and the mass ratio of the surfactant to the silicon oxide raw material is (0.01-0.2):

1.

5. The preparation method according to claim 4, characterized in that The surfactant includes at least one of sodium lauryl sulfate and stearic acid.

6. The preparation method according to claim 4, characterized in that The preparation method includes at least one of the following features (1) to (8): (1) The silicon oxide raw material includes SiO y , where 0<y≤2; (2) The silicon oxide raw material has a particle size D10 of 10% of the cumulative volume distribution of the material particles, 0.1 μm ≤ D10 ≤ 15 μm; (3) The silicon oxide raw material has a particle size D90 at which the cumulative volume distribution of the material particles is 90%, and 0.5 μm ≤ D90 ≤ 30 μm; (4) The silicon oxide raw material has a particle size D50 at which the cumulative volume distribution of the material particles is 50%, and 0.3 μm ≤ D50 ≤ 25 μm; (5) The metal catalyst includes at least one of copper salt, cobalt salt, nickel salt and iron salt; (6) The metal catalyst includes at least one of ferric chloride, cobalt chloride, nickel chloride and copper hydroxide; (7) The solvent of the solution containing the metal catalyst includes at least one of water and an alcohol solvent; (8) The mixing time is 1 hour to 10 hours.

7. The preparation method according to claim 4, characterized in that The preparation method includes at least one of the following features (1) to (6): (1) The carbon source includes a gaseous carbon source; (2) The carbon source includes a gaseous carbon source, and the gaseous carbon source includes at least one of alkanes, cycloalkanes, alkenes, alkynes, and aromatic hydrocarbons; (3) The carbon source includes a gaseous carbon source, and the flow rate of the gaseous carbon source is 0.1 L / min to 500 L / min; (4) The temperature of the carbonization treatment is 600°C to 1000°C; (5) The carbonization treatment time is 0.5h~10h; (6) The carbonization treatment is carried out in a protective gas atmosphere, and the protective gas includes at least one of nitrogen, argon and helium.

8. The preparation method according to claim 4, characterized in that The preparation method includes at least one of the following features (1) to (3): (1) The heat treatment temperature is 400°C to 900°C; (2) The heat treatment time is 2h~12h; (3) The heat treatment is carried out in a protective gas atmosphere, and the protective gas includes at least one of nitrogen, argon and helium.

9. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the negative electrode material according to any one of claims 1 to 3 or the negative electrode material prepared by the preparation method according to any one of claims 4 to 8.

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