Negative active material, preparation method thereof, negative electrode sheet and application

Abstract

The application relates to a negative electrode active material and a preparation method thereof, a negative electrode sheet and application, and belongs to the technical field of batteries. The negative electrode active material comprises a core and a coating layer coating at least part of the surface of the core, the core comprises porous carbon, nano-silicon and a silicon oxide compound distributed in at least the pores of the porous carbon, and the silicon oxide compound is embedded in at least the nano-silicon. Compared with a negative electrode sheet containing a traditional silicon-carbon material, the negative electrode sheet containing the negative electrode active material has a higher compaction density, and the specific capacity and the volume energy density of the secondary battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a negative electrode active material, a preparation method thereof, a negative electrode sheet and application. BACKGROUND

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] With the rapid development of portable electronic devices and electric vehicles, the demand for high-energy-density secondary batteries is increasingly urgent, prompting the development of negative electrode materials such as silicon-based materials. Silicon-carbon material is one of the silicon-based materials, and the low tap density of silicon-carbon material still needs to be improved. SUMMARY

[0004] Therefore, the present application provides a negative electrode active material, a preparation method thereof, a negative electrode sheet and application. Compared with the negative electrode sheet containing the traditional silicon-carbon material, the negative electrode sheet containing the negative electrode active material of the present application has a higher tap density, which improves the specific capacity and volumetric energy density of the secondary battery.

[0005] In a first aspect, the present application provides a negative electrode active material, comprising a core and a coating layer at least coating a part of the surface of the core, wherein the core comprises porous carbon, and nano-silicon and silicon oxide compound at least distributed in the pores of the porous carbon, and the silicon oxide compound is at least embedded in the nano-silicon.

[0006] The silicon oxide compound in the above negative electrode active material enhances the structural strength of the porous carbon, improves the tap density of the negative electrode sheet containing the negative electrode active material, and the silicon oxide compound can provide ion channels for the nano-silicon and the porous carbon; the silicon oxide compound is embedded in the nano-silicon, so that the nano-silicon can protect the silicon oxide compound in multiple directions and reduce the acid corrosion of the silicon oxide compound; the coating layer reduces the specific surface area of the negative electrode active material, reduces the side reaction between the core and the electrolyte, and thus improves the specific capacity and volumetric energy density of the secondary battery.

[0007] In some embodiments, the mass percentage of the silicon oxide compound is 0.02%-40%, or 0.02%-20%, based on the mass of the core.

[0008] In some embodiments, the mass percentage of the nano-silicon is 20%-62%, based on the mass of the core.

[0009] In some embodiments, the ratio of the mass of the nano-silicon to the total mass of the porous carbon and the nano-silicon is (0.22-0.67):1.

[0010] In some embodiments, the mass ratio of the nanosilicon to the porous carbon is (0.3-2):1.

[0011] In some embodiments, the particle size of the nanosilicon is 0.02 nm-40 nm.

[0012] In some embodiments, the silicon oxide compound comprises a material with a chemical formula of SiO x , wherein 0

[0013] In some embodiments, the tap density of the negative electrode active material is 0.4 g / cm 3 -2 g / cm 3 .

[0014] In some embodiments, the specific surface area of the negative electrode active material is 0.005 m 2 / g-4 m 2 / g.

[0015] In some embodiments, the coating layer comprises a carbon material.

[0016] In some embodiments, the mass percentage of the coating layer based on the mass of the negative electrode active material is 0.2%-2%.

[0017] In a second aspect of the present application, a preparation method of the negative electrode active material of the first aspect of the present application is provided, comprising the following steps:

[0018] forming the nanosilicon and the silicon oxide compound in the pores of the porous carbon to obtain the inner core;

[0019] forming the coating layer on at least a part of the surface of the inner core.

[0020] The above preparation method is simple and easy to scale up.

[0021] In some embodiments, the step of forming the nanosilicon and the silicon oxide compound in the pores of the porous carbon to obtain the inner core comprises:

[0022] chemically vapor depositing the porous carbon by using a silane-based substance and a reducing gas;

[0023] mixing the product obtained by chemical vapor deposition with a silicon source, a reducing agent and a solvent;

[0024] performing reduction treatment on the mixed material.

[0025] In some embodiments, the porosity of the porous carbon is 40%-90%.

[0026] In some embodiments, the silane-like substance comprises one or more of monosilane, disilane, tetrafluorosilane, silicon trichloride, and chlorosilane.

[0027] In some embodiments, the reducing gas comprises one or more of ethyne, ethene, and methane.

[0028] In some embodiments, the silicon source comprises one or more of tetraethyl orthosilicate, tetrapropyl orthosilicate, and tetrabutyl orthosilicate.

[0029] In some embodiments, the reducing agent comprises one or more of sucrose and glucose.

[0030] In some embodiments, the solvent comprises one or more of ethanol and isopropanol.

[0031] In some embodiments, the volume ratio of the silane-like substance to the reducing gas is (0.2-10000):1.

[0032] In some embodiments, the total flow rate of the silane-like substance and the reducing gas is 100 mL / min-800 mL / min.

[0033] In some embodiments, the process condition of the chemical vapor deposition comprises: a deposition temperature of 300℃-1000℃, and a deposition time of 0.2h-3h.

[0034] In some embodiments, the mass ratio of the silicon source to the reducing agent is (1-10):1.

[0035] In some embodiments, the mass ratio of the silicon source to the solvent is (1-10):1.

[0036] In some embodiments, the process condition of the reduction treatment comprises: a reduction temperature of 400℃-1000℃, and a reduction time of 2h-6h.

[0037] In a third aspect, the present application provides a negative electrode tab, comprising at least one of the negative electrode active material according to the first aspect of the present application and the negative electrode active material prepared by the preparation method according to the second aspect of the present application.

[0038] The negative electrode tab of the present application comprises the negative electrode active material provided by the present application, and thus at least has the same advantages as the negative electrode active material.

[0039] In some embodiments, the negative electrode tab has a compacted density of 0.9g / cm 3 -1.9g / cm 3 .

[0040] In a fourth aspect of the present application, a secondary battery is provided, comprising the negative electrode sheet according to the third aspect of the present application.

[0041] The secondary battery of the present application comprises the negative electrode active material provided by the present application, and thus has at least the same advantages as the negative electrode active material.

[0042] In a fifth aspect of the present application, an electric device is provided, comprising at least one of the negative electrode active material according to the first aspect of the present application, the negative electrode active material prepared by the preparation method according to the second aspect of the present application, the negative electrode sheet according to the third aspect of the present application, and the secondary battery according to the fourth aspect of the present application.

[0043] The electric device of the present application comprises the negative electrode active material provided by the present application, and thus has at least the same advantages as the negative electrode active material.

[0044] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present application will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0045] For better describing and illustrating the embodiments or examples provided by the present application, one or more drawings can be referred to. The additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the disclosed applications, the presently described embodiments or examples, and the best mode presently contemplated of these applications. Moreover, the same reference numbers are used throughout the drawings to represent the same components. In the drawings:

[0046] Figure 1 Structure diagram of the negative electrode active material according to an embodiment of the present application.

[0047] Figure 2 Preparation flowchart of the core according to an embodiment of the present application.

[0048] Figure 3 Schematic diagram of the battery cell according to an embodiment of the present application.

[0049] Figure 4 Schematic diagram of the battery cell according to an embodiment of the present application. Figure 3 Exploded view of the battery cell according to an embodiment of the present application.

[0050] Figure 5 Schematic diagram of the battery module according to an embodiment of the present application.

[0051] Figure 6 Schematic diagram of the battery pack according to an embodiment of the present application.

[0052] Figure 7 Schematic diagram of the battery pack according to an embodiment of the present application. Figure 6Exploded view of the battery pack according to an embodiment of the present application.

[0053] Figure 8 Schematic view of an electric device using the secondary battery according to an embodiment of the present application as a power source.

[0054] Explanation of Reference Numerals:

[0055] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 cover plate; 6 electric device; 7 negative electrode active material; 70 core; 701 porous carbon; 702 nano-silicon; 703 silicon oxide compound; 71 coating layer. DETAILED DESCRIPTION

[0056] Hereinafter, some embodiments of the negative electrode active material and the method for manufacturing the same, the negative electrode sheet, and the application of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of matters well known, repeated descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0057] The "ranges" disclosed in the present application can be defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, either end value can be included or excluded independently, and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is also listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is within the range, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand manner of describing these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to listing the parameter as, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when it is stated that a parameter is an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0058] In the present application, "a plurality of", "a plurality of kinds", and the like, if not specifically limited, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or more than two.

[0059] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0060] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment or implementation of the present application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. Reference herein to "implementation" has a similar understanding.

[0061] Those skilled in the art can understand that in the method of each embodiment or embodiment, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can also include step (c), which means that step (c) can be added to the method in any order, for example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0062] In the present application, the open technical features or technical solutions described by the words "contain", "include", "comprise" and the like, if not otherwise stated, do not exclude additional members from the listed members, which can be considered as providing both a closed feature or solution composed of the listed members, and an open feature or solution including additional members in addition to the listed members. For example, A includes a1, a2 and a3, if not otherwise stated, it can also include other members, or it can not include additional members, which can be considered as providing the feature or solution that "A is composed of a1, a2 and a3", and also providing the feature or solution that "A includes a1, a2 and a3, and also includes other members". In the present application, if not otherwise stated, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0063] In the present application, "optionally", "optional" and "optional" mean optional, i.e. selected from "yes" or "no" two parallel schemes. If there are multiple "optional" in a technical solution, if there is no special description, and there is no contradiction or mutual restriction relationship, each "optional" is independent.

[0064] Silicon-based materials are a kind of negative active materials with high theoretical specific capacity, which include silicon-oxygen materials and silicon-carbon materials. The silicon-oxygen materials have a relatively high compaction density, but are not resistant to acid and have poor kinetics; the silicon-carbon materials have a relatively low compaction density, which cannot meet the demand of high energy density of batteries. How to use the above two kinds of materials together is crucial to improve the volume energy density of secondary batteries. Based on this, the present application provides a negative active material, which includes a core and a coating layer at least coating a part of the surface of the core, the core includes porous carbon and at least nano-silicon and silicon oxide compound distributed in the pores of the porous carbon, and the silicon oxide compound is at least embedded in the nano-silicon; the above-mentioned silicon oxide compound can enhance the structural strength of the porous carbon, thereby improving the compaction density of the negative electrode sheet containing the negative active material, and at the same time, the silicon oxide compound can provide ion channels for the nano-silicon and the porous carbon; the silicon oxide compound is embedded in the nano-silicon, so that the nano-silicon can protect the silicon oxide compound in multiple directions and reduce the acid corrosion of the silicon oxide compound; the coating layer can reduce the specific surface area of the negative active material, reduce the side reaction between the core and the electrolyte, thereby improving the specific capacity and volume energy density of the secondary battery.

[0065] Negative active material

[0066] The present application provides a negative active material, which includes a core and a coating layer at least coating a part of the surface of the core, the core includes porous carbon and at least nano-silicon and silicon oxide compound distributed in the pores of the porous carbon, and the silicon oxide compound is at least embedded in the nano-silicon.

[0067] In the above-mentioned embodiment, the silicon oxide compound enhances the structural strength of the porous carbon, improves the compaction density of the negative electrode sheet containing the negative active material, and at the same time, the silicon oxide compound can provide ion channels for the nano-silicon and the porous carbon; the silicon oxide compound is embedded in the nano-silicon, so that the nano-silicon can protect the silicon oxide compound in multiple directions and reduce the acid corrosion of the silicon oxide compound; the coating layer reduces the specific surface area of the negative active material, reduces the side reaction between the core and the electrolyte, thereby improving the specific capacity and volume energy density of the secondary battery.

[0068] It should be noted that the negative electrode sheet usually has the highest compaction density, and when the actual compaction density of the negative electrode sheet is higher than the highest compaction density, there will be more broken particles of silicon in the negative electrode sheet. In the above-mentioned embodiment, the structural strength of the negative active material is enhanced by using the silicon oxide compound, thereby improving the compaction density of the negative electrode sheet containing the negative active material.

[0069] Figure 1 is a negative active material as an example. Referring to Figure 1 , the negative active material 7 includes a core 70 and a coating layer 71 coating at least part of a surface of the core 70, the core 70 including porous carbon 701 and nano-silicon 702 and silicon oxide compound 703 distributed at least in pores of the porous carbon 701, the silicon oxide compound 703 being at least embedded in the nano-silicon 702.

[0070] In some embodiments, the mass percentage of the silicon oxide compound is 0.02%-40% based on the mass of the core. By controlling the mass percentage of the silicon oxide compound within the above range, the specific capacity and volumetric energy density of the secondary battery can be further improved. It can be understood that the mass percentage of the silicon oxide compound based on the mass of the core includes but is not limited to 0.02%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%. Further, the mass percentage of the silicon oxide compound based on the mass of the core is 0.02%-20%.

[0071] In some embodiments, the mass percentage of the nano-silicon is 20%-62% based on the mass of the core. Thus, the specific capacity and volumetric energy density of the secondary battery can be further improved. And by controlling the mass ratio of the silicon oxide compound to the nano-silicon within a certain range, the secondary battery can exhibit higher specific capacity and volumetric energy density.

[0072] The content of the silicon oxide compound in the core can be tested using an X-ray photoelectron spectrometer (XPS), for example, the negative electrode sheet containing the above-mentioned silicon oxide compound can be disassembled after full charging, and then tested by XPS, and the ratio of Li-Si chemical bonds and Si-O chemical bonds is compared, so as to determine the relative content of the silicon oxide compound and the nano-silicon; the content of the nano-silicon can be quantitatively tested by an inductively coupled plasma emission spectrometer (ICP).

[0073] In some embodiments, the ratio of the mass of the nano-silicon to the total mass of the porous carbon and the nano-silicon is (0.22-0.67):1. It can be understood that the ratio of the mass of the nano-silicon to the total mass of the porous carbon and the nano-silicon includes but is not limited to 0.22:1, 0.25:1, 0.28:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.67:1.

[0074] In some embodiments, the mass ratio of the nanosilicon to the porous carbon is (0.3-2): 1. Controlling the mass ratio of the nanosilicon to the porous carbon in the above range can improve the conductivity of the negative active material, thereby improving the stability of the secondary battery during the cycling process. It can be understood that the mass ratio of the nanosilicon to the porous carbon includes but is not limited to 0.3: 1, 0.5: 1, 0.7: 1, 1: 1, 1.2: 1, 1.5: 1, 1.7: 1, 2: 1.

[0075] In some embodiments, the particle size of the nanosilicon is 0.02 nm-40 nm. Controlling the particle size of the nanosilicon in the above range can shorten the active ion transport path, thereby improving the rate performance of the secondary battery. It can be understood that the particle size of the nanosilicon includes but is not limited to 0.02 nm, 0.05 nm, 0.1 nm, 0.5 nm, 2 nm, 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm.

[0076] Alternatively, the particle size of the nanosilicon can be tested by using a transmission electron microscope (TEM) to take a photo of the cross section of the negative active material, so that the particle size of the nanosilicon can be measured; or an X-ray diffractometer (XRD) can be used to test the above negative active material, and the particle size of the nanosilicon can be calculated according to the characteristic peak of the nanosilicon using the Scherrer formula.

[0077] In some embodiments, the silicon oxide compound includes a material with a chemical formula of SiOx, where 0 x .

[0078] In some embodiments, the tap density of the negative active material is 0.4 g / cm3-2 g / cm3. 3 -2 g / cm3. 3 Controlling the tap density of the negative active material in the above range further improves the specific capacity and the volumetric energy density of the secondary battery. It can be understood that the tap density of the negative active material includes but is not limited to 0.4 g / cm3, 0.6 g / cm3, 0.8 g / cm3, 1 g / cm3, 1.2 g / cm3, 1.4 g / cm3, 1.6 g / cm3, 1.8 g / cm3, 2 g / cm3. 3 3 3 3 3 3 3 3 3 .

[0079] The tap density of the negative active material is a meaning known in the art, and can be measured by using an instrument and a method known in the art, for example, a tap density tester, such as a BT-300 type tap density tester.​​​​​​​​

[0080] In some embodiments, the specific surface area of the negative electrode active material is 0.005 m2 / g-4 m2 / g. 2 2 For example, the specific surface area of the negative electrode active material can be 0.005 m2 / g, 0.05 m2 / g, 0.5 m2 / g, 0.8 m2 / g, 1 m2 / g, 1.5 m2 / g, 2 m2 / g, 2.5 m2 / g, 3 m2 / g, 3.5 m2 / g, 4 m2 / g, or the like. 2 2 2 2 2 2 2 2 2 2 2

[0081] The specific surface area of the negative electrode active material can be tested by nitrogen adsorption-desorption method. For example, the BET specific surface area of the material can be measured by using a specific surface area analyzer (Tri star II), and the test is performed in accordance with the standard GB / T 19587-2004.

[0082] In some embodiments, the coating layer comprises a carbon material. Optionally, the carbon material comprises amorphous carbon.

[0083] In some embodiments, the mass percentage of the coating layer based on the mass of the negative electrode active material is 0.2%-2%.

[0084] Another embodiment of the present application provides a preparation method of the above negative electrode active material, comprising the following steps:

[0085] forming nano-silicon and silicon oxide compounds in the pores of the porous carbon to obtain a core;

[0086] forming a coating layer on at least a part of the surface of the core.

[0087] Thus, the negative electrode active material can be simply prepared, which is beneficial to the large-scale production of the negative electrode active material.

[0088] In some embodiments, in the step of forming nano-silicon and silicon oxide compounds in the pores of the porous carbon to obtain a core, the step comprises:

[0089] chemically vapor depositing the porous carbon by using a silane-based substance and a reducing gas;

[0090] mixing the product obtained by chemical vapor deposition with a silicon source, a reducing agent, and a solvent;

[0091] performing reduction treatment on the mixed material. ​​​​​​​​​​​​

[0092] In the above embodiment, when chemical vapor deposition is performed, the generated nanosilicon can penetrate into the pores of the porous carbon and complete diffusion and reduction; when the obtained mixture is subjected to reduction treatment, the generated silicon oxide compound is filled in the pores of the porous carbon, and the silicon oxide compound is embedded in the nanosilicon and the porous carbon. Thus, the core can be simply prepared.

[0093] In some embodiments, the method further includes: Figure 2 In the step of forming the nanosilicon and the silicon oxide compound in the pores of the porous carbon to obtain the core, the method includes:

[0094] S10. performing chemical vapor deposition on the porous carbon 701 by using a silane-based substance and a reducing gas;

[0095] S20. mixing the product obtained in the step S10 with a silicon source, a reducing agent, and a solvent;

[0096] S30. performing reduction treatment on the mixture obtained in the step S20.

[0097] In the above embodiment, the porous carbon 701 has micropores and macropores, the step S10 causes the generated nanosilicon 702 to be filled in the micropores of the porous carbon 701, and the steps S20 and S30 cause the generated silicon oxide compound to be filled in the macropores of the porous carbon 702.

[0098] In some embodiments, in the step of forming the coating layer on at least a part of the surface of the core, the method includes: coating the core by using a carbon source. Optionally, the carbon source includes one or more of acetylene and pitch.

[0099] In some embodiments, the silane-based substance includes one or more of monosilane, disilane, tetrafluorosilane, silicon trichloride, and chlorosilane.

[0100] In some embodiments, the reducing gas includes one or more of acetylene, ethylene, and methane.

[0101] In some embodiments, the silicon source includes one or more of tetraethyl orthosilicate, tetrapropyl orthosilicate, and tetrabutyl orthosilicate.

[0102] In some embodiments, the reducing agent includes one or more of sucrose and glucose.

[0103] In some embodiments, the solvent includes one or more of ethanol and isopropanol.

[0104] In some embodiments, the volume ratio of the silane-based substance and the reducing gas is (0.2-10000):1. It can be understood that the volume ratio of the silane-based substance and the reducing gas includes but is not limited to: 0.2:1, 10:1, 100:1, 500:1, 1000:1, 2000:1, 3000:1, 4000:1, 5000:1, 6000:1, 7000:1, 8000:1, 9000:1, 10000:1.

[0105] In some embodiments, the total flow rate of the silane-based substance and the reducing gas is 100 mL / min-800 mL / min. It can be understood that the total flow rate of the silane-based substance and the reducing gas includes but is not limited to: 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min, 500 mL / min, 600 mL / min, 700 mL / min, 800 mL / min.

[0106] In some embodiments, the process conditions of chemical vapor deposition include: deposition temperature 300℃-1000℃, deposition time 0.2h-3h. It can be understood that the deposition temperature includes but is not limited to: 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃; the deposition time includes but is not limited to: 0.2h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h.

[0107] In some embodiments, the mass ratio of the silicon source and the reducing agent is (1-10):1. It can be understood that the mass ratio of the silicon source and the reducing agent includes but is not limited to: 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0108] In some embodiments, the mass ratio of the silicon source and the solvent is (1-10):1. It can be understood that the mass ratio of the silicon source and the solvent includes but is not limited to: 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0109] In some embodiments, the process conditions of the reduction treatment include: reduction temperature 400℃-1000℃, reduction time 2h-6h. It can be understood that the reduction temperature includes but is not limited to: 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃; the reduction time includes but is not limited to: 2h, 3h, 4h, 5h, 6h.

[0110] Another embodiment of the present application provides a negative electrode tab, comprising at least one of the above-mentioned negative electrode active material and the negative electrode active material prepared by the above-mentioned preparation method.

[0111] In some embodiments, the negative electrode tab further comprises a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer comprising at least one of the negative active material described above and the negative active material prepared by the method described above.

[0112] As a non-limiting example, the negative current collector has two opposite surfaces in the thickness direction of the negative current collector, and the negative active material layer is disposed on either one or both of the two opposite surfaces of the negative current collector.

[0113] In some embodiments, the negative electrode tab has a compaction density of 0.9 g / cm 3 -1.9 g / cm 3 . Thus, the secondary battery can have a higher volumetric energy density. It should be noted that the negative electrode tab usually has the highest compaction density, and when the actual compaction density of the negative electrode tab is higher than the highest compaction density, there will be more broken particles of silicon in the negative electrode tab. The negative active material described above enhances the structural strength by using a silicon oxide compound, and thus, the use of the negative active material described above in the negative electrode tab improves the compaction density of the negative electrode tab. It should be understood that the compaction density of the negative electrode tab described above includes but is not limited to: 0.9 g / cm 3 , 1 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 .

[0114] In some embodiments, the negative active material layer can further comprise one or more of the following negative active materials in addition to the negative active material described above: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can include one or more of silicon-nitrogen composites and silicon alloys. The tin-based materials can include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative active materials can also be used.

[0115] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0116] In some embodiments, the negative active material layer can further optionally include a binder. The binder can include one or more 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).

[0117] In some embodiments, the negative active material layer can further optionally include a conductive agent. The conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the negative active material layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0119] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-described components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry, coating the negative electrode slurry on at least one side surface of the negative current collector, and drying, cold-pressing, and the like to obtain the negative electrode sheet. The surface of the negative current collector to which the negative electrode slurry is coated can be one surface of the negative current collector or both surfaces of the negative current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s. The coating unit area density of the negative electrode slurry, on a dry weight basis (excluding the solvent), can be 75 g / m 2 -220 g / m 2 . The compacted density of the negative electrode sheet can be 1.0 g / cm 3 -1.8 g / cm 3 .

[0120] In addition, the secondary battery and the electric device according to the present application are described below with appropriate reference to the accompanying drawings.

[0121] In one embodiment of the present application, a secondary battery is provided.

[0122] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and functions to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0123] Positive electrode sheet

[0124] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material.

[0125] As a non-limiting example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode active material layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0126] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base material. Non-limiting examples of the metal material in the positive electrode current collector can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. Non-limiting examples of the polymer material base material in the positive electrode current collector can include one or more of a polypropylene (PP) base material, a polyethylene terephthalate (PET) base material, a polybutylene terephthalate (PBT) base material, a polystyrene (PS) base material, a polyethylene (PE) base material, and the like.

[0127] For the change in Li content in the positive electrode active material, how to limit the subscript of Li in the general formula:

[0128] For a ternary material:

[0129] Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y , x is 0.2-1.2;

[0130] Li x A a (Ni a Co b Mnc ) 1-d M d O 2-y A y , x+a is 0.2-1.2;

[0131] For the lithium manganese iron phosphate material:

[0132] 1) Li a Mn 1-y B y P 1-z C z O 4-n D n , a is 0-1.1;

[0133] 2) Li a A x Mn 1-y B y P 1-z C z O 4-n D n , a+x is 0-1.1;

[0134] The above limitation of x includes the molar content of Li under different charge and discharge states of the battery (usually the battery voltage is between 2V-5V).

[0135] Understandably, the battery will be accompanied by lithium (Li) deintercalation and consumption during charging and discharging, and the content of Li in the positive plate will be different when the battery is discharged to different states. In the enumeration of the positive active material in the present application, the content of Li is the initial state of the material unless otherwise specified. When the positive active material is applied to the positive plate in the battery system, the content of Li in the positive active material contained in the plate will usually change after charging and discharging cycle. Among them, the content of Li can be quantified by molar content, but is not limited thereto. As for "the content of Li is the initial state of the material", the initial state of the material refers to the state before being put into the positive slurry. It can be understood that the new material obtained by properly modifying the listed positive active material is also within the scope of the positive active material, and the foregoing proper modification refers to acceptable modification of the positive active material, and non-limiting examples include coating modification.

[0136] In the enumeration of the positive active material in the present application, the content of oxygen (O) is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be quantified by molar content, but is not limited thereto.

[0137] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.15 Al 0.05 O2.

[0138] In some embodiments, the positive electrode active material layer can also optionally include a binder. As non-limiting examples, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0139] In some embodiments, the positive electrode active material layer can also optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained. The type of the solvent can be selected from, but is not limited to, any of the above-mentioned embodiments, such as N-methyl pyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When coating the positive electrode slurry, the coating unit area density, in terms of dry weight (excluding the solvent), can be 15 mg / cm 2 - 35 mg / cm 2 . The compaction density of the positive electrode tab can be 3.0 g / cm 3 - 3.6 g / cm 3 , optionally 3.3 g / cm 3 - 3.5 g / cm 3 .

[0141] The negative electrode tab

[0142] The negative electrode tab according to the above-mentioned embodiments of the present application.

[0143] The electrolyte

[0144] The electrolyte has the function of conducting ions between the positive electrode tab and the negative electrode tab. The type of the electrolyte is not particularly limited in the present application, and can be selected according to the needs. For example, the electrolyte can be liquid, gel or all-solid.

[0145] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0146] In some embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-bis-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0147] In some embodiments, the solvent can include one or more of ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0148] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0149] In some embodiments, the additive in the electrolyte solution can include, but is not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0150] Separator film

[0151] In some embodiments, the secondary battery further includes a separator film. The type of the separator film is not particularly limited in the present application, and any publicly known porous structure separator film having good chemical stability and mechanical stability can be used.

[0152] In some embodiments, the material of the separator film can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0153] In some embodiments, the thickness of the separator film is 6 pm to 40 pm, and can be 12 pm to 20 pm.

[0154] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be used to make an electrode assembly through a winding process or a stacking process.

[0155] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0156] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, and the like.

[0157] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0158] In the present application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy to each other, and further, generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct the active ions between the positive electrode sheet and the negative electrode sheet.

[0159] The present application does not particularly limit the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, Figure 3 is a battery cell 5 in a square structure as an example.

[0160] In some embodiments, referring to Figure 4The outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator film can form the electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and a person skilled in the art can select according to actual needs.

[0161] The secondary battery can be a battery module 4 or a battery pack 1.

[0162] The battery module includes at least one battery cell. The number of battery cells contained in the battery module can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0163] Figure 5 The battery module 4 is an example. Refer to Figure 5 In the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0164] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0165] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0166] Figure 6 and Figure 7 The battery pack 1 is an example. Refer to Figure 6 and Figure 7 The battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for receiving the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0167] In addition, the application also provides a power utilization device, which comprises the secondary battery provided by the application. The secondary battery can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. The mobile device can be a mobile phone, a notebook computer, etc., for example; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0168] As the power utilization device, the secondary battery can be selected according to the use requirement thereof.

[0169] Figure 8 The power utilization device 6 is an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the secondary battery for the power utilization device, a battery pack or a battery module can be used.

[0170] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a secondary battery can be used as a power supply.

[0171] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0172] Example 1

[0173] (1) Preparation of a negative electrode active material

[0174] (1.1) High-purity monosilane and acetylene were mixed at a volume ratio of 100:1, and then were sent into a reaction system in which porous carbon (porosity 78%) was placed, so that the nanosilicon was infiltrated into the pores of the porous carbon and diffusion and reduction were completed, the total flow rate of the high-purity monosilane and the acetylene was 400 mL / min, the reaction temperature was 500°C, and the reaction time was 30 min;

[0175] (1.2) The product A obtained in step (1.1) was mixed with a mixed solution at a mass ratio of 1:1, and was stirred for 2 h, the mixed solution was formed by tetraethyl orthosilicate, sucrose and ethanol, the mass ratio of the tetraethyl orthosilicate to the sucrose was 5:1, and the mass ratio of the tetraethyl orthosilicate to the ethanol was 3:1;

[0176] (1.3) The product B obtained in step (1.2) is washed and centrifuged, and the precipitate obtained by centrifugation is reduced under an inert gas atmosphere for 4 h, the flow rate of the inert gas is 400 mL / min, and the reduction temperature is 600°C;

[0177] (1.4) The product obtained in step (1.3) is subjected to carbon coating treatment by passing acetylene into the reactor, the volume ratio of acetylene to inert gas is 1:100, and the total flow rate of acetylene and inert gas is 400 mL / min.

[0178] (2) Preparation of negative electrode sheet

[0179] The negative electrode active material prepared in step (1), the conductive agent acetylene black, the thickening agent sodium carboxymethyl cellulose (CMC-Na), and the binder styrene-butadiene rubber (SBR) are added to water in a mass ratio of 96:2:1:1 and uniformly mixed to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on the double-sided surface of a negative electrode current collector copper foil, and after drying at 85°C, cold pressing is performed to prepare a negative electrode sheet, and the compaction density of the negative electrode sheet is 1.5 g / cm 3 .

[0180] (3) Preparation of positive electrode sheet

[0181] The positive electrode active material nickel-cobalt-manganese ternary material (NCM811), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are uniformly mixed in a mass ratio of 97:2:1 and added to a solvent NMP to prepare a positive electrode slurry; the positive electrode slurry is uniformly coated on the double-sided surface of a positive electrode current collector aluminum foil, and after drying at 85°C, cold pressing is performed, followed by die cutting and slitting to prepare a positive electrode sheet.

[0182] (4) Preparation of separator film

[0183] A polyethylene microporous film is used as a porous separator film substrate, and inorganic aluminum oxide powder, polyvinylpyrrolidone, and acetone solvent are uniformly mixed in a weight ratio of 3:1.5:5.5 to prepare a slurry, which is coated on one side of the substrate and dried to obtain a separator film.

[0184] (5) Preparation of electrolyte

[0185] Lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate (volume ratio of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate is 1:2:1) to obtain an electrolyte.

[0186] (6) Preparation of lithium ion battery

[0187] The positive electrode sheet, the negative electrode sheet and the separator film described above are wound to obtain a bare cell, and then a lithium ion battery is prepared through processes such as packaging, liquid injection, formation, and degassing. The capacity of the negative electrode sheet and the capacity of the positive electrode sheet of the battery are 1 (i.e., N / P = 1), and the design rated capacity of the battery is 100 Ah.

[0188] Example 2-10

[0189] The same as Example 1, except that the parameters described in Table 1-2 are different, and the negative electrode active material is replaced with the negative electrode active material prepared in step (1) of the corresponding example in the preparation of the negative electrode sheet in step (2).

[0190] Comparative Example 1

[0191] The same as Example 1, except that steps (1.2) and (1.3) are omitted.

[0192] Comparative Example 2

[0193] The same as Example 2, except that steps (1.2) and (1.3) are omitted.

[0194] Comparative Example 3

[0195] The same as Example 9, except that steps (1.2) and (1.3) are omitted.

[0196] Performance Test

[0197] (1) Compaction density of the negative electrode sheet

[0198] The total thickness of the electrode sheet is measured using a vernier caliper, and the thickness of the current collector is deducted to calculate the coating thickness. According to the coating area density and the coating thickness, the compaction density of the electrode sheet can be calculated.

[0199] (2) Specific capacity of the battery

[0200] At 25°C, the lithium ion battery is charged at a rate of 0.33C to 4.3V, then charged at a constant voltage until the current is 0.05C, and then discharged at a rate of 0.33C to 2.5V. The discharge capacity at this time is recorded as the 0.33C discharge capacity, and the 0.33C discharge specific capacity is obtained by dividing the mass of the negative electrode active material by the 0.33C discharge capacity.

[0201] (3) Rate performance of the battery

[0202] The lithium ion battery was charged at 0.33C rate to 4.3V at 25℃, then charged at constant voltage to 0.05C, rested for 5min, then discharged at 0.33C rate to 2.5V, and the discharge capacity at this time was recorded, which was the 0.33C discharge capacity; rested for 30min, then charged at 1C rate to 4.3V, then charged at constant voltage to 0.05C, rested for 5min, then discharged at 1C rate to 2.5V, and the discharge capacity at this time was recorded, which was the 1C discharge capacity.

[0203] The rate performance of the battery 1C / 0.33C(%) = 1C discharge capacity / 0.33C discharge capacity x 100%.

[0204] Table 1 Product parameters of negative electrode active material and negative electrode plate

[0205]

[0206]

[0207] Table 2 Preparation parameters of negative electrode active material

[0208]

[0209] Table 3 Battery performance

[0210]

[0211]

[0212] From the observation of Tables 1-3, it can be seen that the specific capacity of the secondary battery is low when only nano-silicon is contained in the negative electrode active material, by comparing Example 1, Examples 3-8, Example 10 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 9 with Comparative Example 3. The negative electrode active material containing silicon oxide compound in the core of Examples 1-10, and the silicon oxide compound is at least embedded in the nano-silicon, effectively improves the specific capacity of the secondary battery, and further improves the volume energy density of the secondary battery.

[0213] The above description of each embodiment tends to emphasize the differences between each embodiment, and the same or similar parts can be referred to each other, and for the sake of brevity, the same or similar parts will not be described herein.

[0214] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art, without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A negative electrode active material, characterized by, The core includes porous carbon and at least nano-silicon and silicon oxide compound distributed in pores of the porous carbon, and the silicon oxide compound is at least embedded in the nano-silicon.

2. The negative electrode active material according to claim 1, characterized by The negative electrode active material has one or more of the following characteristics: (1a) The mass percentage of the silicon oxide compound is 0.02%-40% based on the mass of the core; (1b) The mass percentage of the nano-silicon is 20%-62% based on the mass of the core.

3. The negative electrode active material according to claim 1 or 2, characterized by, The mass percentage of the silicon oxide compound is 0.02%-20% based on the mass of the core.

4. The negative electrode active material according to claim 1 or 2, characterized by The negative electrode active material has one or more of the following characteristics: (2a) The mass ratio of the nano-silicon to the total mass of the porous carbon and the nano-silicon is (0.22-0.67):1; (2b) The mass ratio of the nano-silicon to the porous carbon is (0.3-2):

1.

5. The negative electrode active material according to claim 1 or 2, characterized by The particle size of the nano-silicon is 0.02nm-40nm.

6. The negative electrode active material according to claim 1 or 2, characterized by The silicon oxide compound includes a material of the chemical formula SiO x where 0 < x < 2.

7. The negative electrode active material according to claim 1 or 2, characterized by, The negative electrode active material has one or more of the following characteristics: (3a) the tap density of the negative active material is 0.4 g / cm 3 -2 g / cm 3 ; (3b) the specific surface area of the negative active material is 0.005 m 2 / g-4m 2 / g.

8. The negative electrode active material according to claim 1 or 2, characterized by, The coating layer includes a carbon material.

9. The negative electrode active material according to claim 8, characterized by The mass percentage of the coating layer is 0.2%-2% based on the mass of the negative electrode active material.

10. The method of producing the negative electrode active material according to any one of claims 1 to 9, characterized by, The method includes the following steps: Forming the nano-silicon and the silicon oxide compound in pores of the porous carbon to obtain the core; Forming the coating layer on at least a part of the surface of the core.

11. The method of claim 10, wherein, In the step of forming the nano-silicon and the silicon oxide compound in pores of the porous carbon to obtain the core, the method includes: Chemical vapor deposition of the porous carbon by using a silane substance and a reducing gas; Mixing the product obtained by chemical vapor deposition with a silicon source, a reducing agent and a solvent; Reducing the mixed material.

12. The method of claim 11, wherein, The porosity of the porous carbon is 40%-90%.

13. The production method according to claim 11 or 12, characterized by, The preparation method meets one or more of the following conditions: (4a) The silane substance includes one or more of monosilane, disilane, tetrafluorosilane, silicon trichloride and chlorosilane; (4b) The reducing gas includes one or more of acetylene, ethylene and methane; (4c) The silicon source includes one or more of tetraethyl orthosilicate, tripropyl orthosilicate and tetrabutyl orthosilicate; (4d) The reducing agent includes one or more of sucrose and glucose; (4e) The solvent includes one or more of ethanol and isopropanol; (4f) The volume ratio of the silane substance to the reducing gas is (0.2-10000):1; (4g) The total flow rate of the silane substance and the reducing gas is 100mL / min-800mL / min; (4h) The process conditions of the chemical vapor deposition include: deposition temperature 300℃-1000℃, deposition time 0.2h-3h; (4i) The mass ratio of the silicon source to the reducing agent is (1-10):1; (4j) The mass ratio of the silicon source to the solvent is (1-10):1; (4k) The process conditions of the reducing treatment include: reducing temperature 400℃-1000℃, reducing time 2h-6h.

14. A negative electrode sheet characterized by comprising: at least one of the negative electrode active material according to any one of claims 1 to 9 and the negative electrode active material produced by the production method according to any one of claims 10 to 13.

15. The negative electrode sheet according to claim 14, wherein The compacted density of the negative electrode sheet is 0.9 g / cm 3 -1.9 g / cm 3 .

16. A secondary battery characterized by comprising: the negative electrode tab according to any one of claims 14 to 15.

17. An electrical device, comprising: at least one of the negative electrode active material according to any one of claims 1 to 9, the negative electrode active material produced by the production method according to any one of claims 10 to 13, the negative electrode tab according to any one of claims 14 to 15, and the secondary battery according to claim 16.

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