Negative active material, preparation method thereof, negative pole piece and application

Abstract

The invention relates to a negative active material, a preparation method thereof, a negative pole piece and application, and belongs to the technical field of batteries. The negative electrode active material comprises an inner core and a coating layer at least coating a part of the surface of the inner core, the inner core comprises porous carbon, and nano silicon and a silicon-oxygen compound which are at least distributed in pores of the porous carbon, and the silicon-oxygen compound is at least embedded in the nano silicon. Compared with a negative pole piece containing a traditional silicon-carbon material, the negative pole piece containing the negative active material disclosed by the invention has relatively high 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 field of battery technology, and in particular to a negative electrode active material and a preparation method thereof, a negative electrode sheet and applications. Background Art

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

[0003] With the rapid development of portable electronic devices and electric vehicles, people's demand for high-energy-density secondary batteries is becoming more and more urgent, prompting the development of negative electrode materials with high theoretical specific capacity such as silicon-based materials. Silicon-carbon material is one of the silicon-based materials. Its low compaction density means that the volume energy density of silicon-carbon material still needs to be improved. Summary of the invention

[0004] Based on this, the present application provides a negative electrode active material and 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 compaction density, which improves the specific capacity and volume energy density of the secondary battery.

[0005] In a first aspect of the present application, a negative electrode active material is provided, comprising a core and a coating layer covering at least a portion of the surface of the core, wherein the core comprises porous carbon and nano-silicon and silicon-oxygen compounds distributed at least in the pores of the porous carbon, and the silicon-oxygen compounds are at least embedded in the nano-silicon.

[0006] The silicon oxide compound in the above-mentioned negative electrode active material enhances the structural strength of the porous carbon and improves the compaction density of the negative electrode plate containing the negative electrode active material. The silicon oxide compound can also provide an ion path for nano-silicon and porous carbon. The silicon oxide compound is embedded in the nano-silicon, so that the nano-silicon can protect the silicon oxide compound in all 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 and reduces the side reaction between the core and the electrolyte, thereby improving the specific capacity and volume energy density of the secondary battery.

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

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

[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 nano-silicon to the porous carbon is (0.3-2):1.

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

[0012] In some embodiments, the silicon oxide compound comprises a chemical formula of SiO x of material, wherein 0<x≤2.

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

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

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

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

[0017] The second aspect of the present application provides a method for preparing the negative electrode active material according to the first aspect of the present application, comprising the following steps:

[0018] forming the nano-silicon and the silicon-oxygen compound in the pores of the porous carbon to obtain the core;

[0019] The coating layer is formed on at least a portion of the surface of the core.

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

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

[0022] Performing chemical vapor deposition on the porous carbon by using a silane 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] The mixed materials are subjected to reduction treatment.

[0025] In some embodiments, the porous carbon has a porosity of 40% to 90%.

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

[0027] In some embodiments, the reducing gas includes one or more of acetylene, ethylene, and methane.

[0028] In some embodiments, the silicon source includes one or more of ethyl orthosilicate, propyl orthosilicate, and butyl orthosilicate.

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

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

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

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

[0033] In some embodiments, the process conditions of the chemical vapor deposition include: a deposition temperature of 300° C.-1000° C., and a deposition time of 0.2 h-3 h.

[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 conditions of the reduction treatment include: a reduction temperature of 400° C.-1000° C., and a reduction time of 2 h-6 h.

[0037] In a third aspect of the present application, a negative electrode plate is provided, comprising at least one of the negative electrode active material described in the first aspect of the present application and the negative electrode active material prepared by the preparation method described in the second aspect of the present application.

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

[0039] In some embodiments, the compaction density of the negative electrode plate is 0.9 g / cm 3 -1.9g / cm 3 .

[0040] A fourth aspect of the present application provides a secondary battery, comprising the negative electrode sheet described in the third aspect of the present application.

[0041] The secondary battery of the present application includes 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] The fifth aspect of the present application provides an electrical device, comprising at least one of the negative electrode active material described in the first aspect of the present application, the negative electrode active material prepared by the preparation method described in the second aspect of the present application, the negative electrode plate described in the third aspect of the present application, and the secondary battery described in the fourth aspect of the present application.

[0043] The electric device of the present application includes 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 following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to better describe and illustrate the embodiments or examples provided by the present application, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes of these applications currently understood. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0046] Figure 1 Schematic diagram of the structure of the negative electrode active material according to one embodiment of the present application.

[0047] Figure 2 This is a flow chart of the preparation of the core according to one embodiment of the present application.

[0048] Figure 3 It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0049] Figure 4 for Figure 3 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0050] Figure 5 It is a schematic diagram of a battery module according to one embodiment of the present application.

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

[0052] Figure 7 for Figure 6An exploded view of a battery pack according to an embodiment of the present application is shown.

[0053] Figure 8 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0054] Description of reference numerals:

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

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

[0057] "Scope" disclosed in the present application can be limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or excluding end values, and any end value can be included or not included independently, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 listed, and if the maximum range values ​​3,4 and 5 are also listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation for these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as 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, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0059] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0060] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. The "implementation methods" mentioned herein have a similar understanding.

[0061] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0062] In the present application, in the open technical features or technical solutions described by the words "contain", "include", "comprise", etc., unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2 and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2 and a3" and the feature or solution of "A not only includes a1, a2 and a3, but also includes other members". In the present application, unless otherwise specified, 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 this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0064] Silicon-based materials are negative electrode active materials with high theoretical specific capacity, including silicon-oxygen materials and silicon-carbon materials. The compaction density of silicon-oxygen materials is relatively high, but they are not acid-resistant and have poor kinetic properties; the compaction density of silicon-carbon materials is relatively low and cannot meet people's demand for high energy density of batteries. How to use the above two materials together is crucial to improving the volume energy density of secondary batteries. Based on this, the present application provides a negative electrode active material, which includes a core and a coating layer that covers at least a portion of the surface of the core, the core includes porous carbon and nano-silicon and silicon oxide compounds distributed at least in the pores of the porous carbon, and the silicon oxide compounds are at least embedded in the nano-silicon; the silicon oxide compounds can enhance the structural strength of the porous carbon, thereby improving the compaction density of the negative electrode electrode sheet containing the negative electrode active material, and the silicon oxide compounds can provide ion paths for the nano-silicon and the porous carbon; the silicon oxide compounds are embedded in the nano-silicon, so that the nano-silicon can protect the silicon oxide compounds in all directions and reduce the corrosion of the silicon oxide compounds by acid; the coating layer can reduce the specific surface area of ​​the negative electrode active material and reduce the side reactions between the core and the electrolyte, thereby improving the specific capacity and volume energy density of the secondary battery.

[0065] Negative electrode active material

[0066] An embodiment of the present application provides a negative electrode active material, including a core and a coating layer that covers at least a portion of the surface of the core, the core including porous carbon and nano-silicon and silicon oxide compounds distributed at least in the pores of the porous carbon, and the silicon oxide compounds are at least embedded in the nano-silicon.

[0067] In the above embodiment, the silicon oxide compound enhances the structural strength of the porous carbon, improves the compaction density of the negative electrode plate containing the negative electrode active material, and the silicon oxide compound can provide an ion path for the nano-silicon and the porous carbon at the same time; the silicon oxide compound is embedded in the nano-silicon, so that the nano-silicon can protect the silicon oxide compound in all directions, reducing 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, 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 a maximum compaction density. When the actual compaction density of the negative electrode sheet is higher than the maximum compaction density, more broken particles of silicon in the negative electrode sheet will appear. In the above embodiment, the structural strength of the negative electrode active material is enhanced by using silicon oxide compounds, thereby increasing the compaction density of the negative electrode sheet containing the negative electrode active material.

[0069] Figure 1 is used as an example of a negative electrode active material. Figure 1 The negative electrode active material 7 includes a core 70 and a coating layer 71 that covers at least a portion of the surface of the core. The core 70 includes porous carbon 701 and nano-silicon 702 and silicon oxide 703 that are at least distributed in the pores of the porous carbon 701. The silicon oxide 703 is at least embedded in the nano-silicon 702.

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

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

[0072] The content of silicon oxide compounds in the core can be tested using an X-ray photoelectron spectroscopy analyzer (XPS). For example, the negative electrode plate containing the above silicon oxide compounds can be fully charged and then disassembled, and then the XPS test is performed to compare the Li-Si chemical bond and Si-O chemical bond ratios to determine the relative content of silicon oxide compounds and nano-silicon; the content of nano-silicon can be quantitatively tested using an inductively coupled plasma emission spectrometer (ICP).

[0073] In some embodiments, the ratio of the mass of nano-silicon to the total mass of porous carbon and nano-silicon is (0.22-0.67): 1. It is understood that the ratio of the mass of nano-silicon to the total mass of porous carbon and 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 nano-silicon to porous carbon is (0.3-2):1. Controlling the mass ratio of nano-silicon to porous carbon within the above range can improve the conductivity of the negative electrode active material, thereby improving the stability of the secondary battery during the cycle process. It is understood that the mass ratio of nano-silicon to 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 nano silicon is 0.02nm-40nm. Controlling the particle size of nano silicon within the above range can shorten the active ion transmission path, thereby improving the rate performance of the secondary battery. It is understood that the particle size of nano silicon includes but is not limited to: 0.02nm, 0.05nm, 0.1nm, 0.5nm, 2nm, 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm.

[0076] Optionally, the nano-silicon particle size can be tested by the following method: using a transmission electron microscope (TEM) to take a picture of the cross section of the negative electrode active material, the particle size of the nano-silicon can be measured; or using an X-ray diffractometer (XRD) to test the above-mentioned negative electrode active material, and using the Scherrer formula to calculate the particle size of the nano-silicon based on the characteristic peaks of the nano-silicon.

[0077] In some embodiments, the silicon oxide compound comprises a chemical formula of SiO x of material, wherein 0<x≤2.

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

[0079] The tap density of the negative electrode active material is well known in the art and can be measured using instruments and methods known in the art, for example, it can be conveniently measured using a tap density tester, such as the BT-300 tap density tester.

[0080] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.005 m 2 / g-4m 2 / g. Exemplarily, the specific surface area of ​​the negative electrode active material may be 0.005 m 2 / g, 0.05m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1m 2 / g, 1.5m 2 / g, 2m 2 / g, 2.5m 2 / g, 3m 2 / g, 3.5m 2 / g or 4m 2 / g, etc.

[0081] The specific surface area of ​​the negative electrode active material can be tested by nitrogen adsorption and desorption method. For example, a specific surface area analyzer (Tri star II) can be used to measure the BET specific surface area of ​​the material, referring to GB / T 19587-2004 standard.

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

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

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

[0085] Nano-silicon and silicon-oxygen compounds are formed in the pores of porous carbon to obtain a core;

[0086] A coating layer is formed on at least a portion of the surface of the inner 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, the step of forming nano-silicon and silicon-oxygen compounds in the pores of porous carbon to obtain the inner core comprises:

[0089] Chemical vapor deposition of porous carbon using silane and reducing gas;

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

[0091] The mixed materials are subjected to reduction treatment.

[0092] In the above embodiment, when chemical vapor deposition is performed, the generated nano-silicon can penetrate into the pores of the porous carbon and complete diffusion and reduction; when the mixed material is subjected to reduction treatment, the generated silicon oxide compound fills the pores of the porous carbon, and the silicon oxide compound is embedded in the nano-silicon and the porous carbon. In this way, the core can be simply prepared.

[0093] In some embodiments, in combination Figure 2 The step of forming nano-silicon and silicon-oxygen compounds in the pores of porous carbon to obtain the inner core comprises:

[0094] S10. Chemical vapor deposition of porous carbon 701 using silane substances and reducing gases;

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

[0096] S30. Performing reduction treatment on the material obtained in step S20.

[0097] In the above embodiment, the porous carbon 701 has micropores and macropores. Step S10 fills the generated nano-silicon 702 in the micropores of the porous carbon 701 , and steps S20 and S30 fill the generated silicon oxide compound in the macropores of the porous carbon 702 .

[0098] In some embodiments, the step of forming a coating layer on at least a portion of the surface of the inner core includes: coating the inner core with a carbon source. Optionally, the carbon source includes one or more of acetylene and asphalt.

[0099] In some embodiments, the silane-based material 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 ethyl orthosilicate, propyl orthosilicate, and butyl 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 substance to the reducing gas is (0.2-10000): 1. It is understood that the volume ratio of the silane substance to 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 substance and the reducing gas is 100 mL / min-800 mL / min. It is understood that the total flow rate of the silane 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 of 300°C-1000°C, deposition time of 0.2h-3h. It is understood that the deposition temperature includes but is not limited to: 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C; 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 to the reducing agent is (1-10): 1. It is understood that the mass ratio of the silicon source to 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 to the solvent is (1-10): 1. It is understood that the mass ratio of the silicon source to 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: a reduction temperature of 400°C-1000°C, and a reduction time of 2h-6h. It is understood that the reduction temperature includes but is not limited to: 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C; and 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 plate, comprising at least one of the negative electrode active material and the negative electrode active material prepared by the preparation method.

[0111] In some embodiments, the negative electrode sheet also includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes at least one of the negative electrode active material described above in the present application and the negative electrode active material prepared by the preparation method described above in the present application.

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

[0113] In some embodiments, the compaction density of the negative electrode sheet is 0.9 g / cm 3 -1.9g / cm 3 . Thus, the secondary battery can further have a higher volume energy density. It should be noted that the negative electrode plate usually has a maximum compaction density. When the actual compaction density of the negative electrode plate is higher than the maximum compaction density, more broken particles of silicon in the negative electrode plate will appear. The above-mentioned negative electrode active material utilizes silicon oxide compounds to enhance the structural strength. Therefore, the above-mentioned negative electrode active material is applied to the negative electrode plate to increase the compaction density of the negative electrode plate. It can be understood that the compaction density of the above-mentioned negative electrode plate includes but is not limited to: 0.9g / cm 3 , 1g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 .

[0114] In some embodiments, the negative electrode active material layer may include one or more of the following negative electrode active materials in addition to the negative electrode active material of the present application: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include one or more of a silicon-nitrogen complex and a silicon alloy. The tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used.

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

[0116] In some embodiments, the negative electrode active material layer may further include a binder. The binder may 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 electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0119] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the surface of the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode collector coated with the negative electrode slurry can be on a single surface of the negative electrode collector or on both surfaces of the negative electrode collector. The solid content of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 -220g / m 2 The compaction density of the negative electrode sheet can be 1.0g / cm 3 -1.8g / cm 3 .

[0120] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[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 the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0123] Positive electrode

[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, wherein the positive electrode active material layer includes a positive electrode active material.

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

[0126] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may 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 may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0127] As the Li content in the positive electrode active material changes, how to define the subscript of Li in the general formula:

[0128] For ternary materials:

[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 lithium manganese iron phosphate materials:

[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 definition 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] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charging and discharging process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the enumeration of positive electrode active materials in this application, unless otherwise specified, the content of Li is the initial state of the material. The positive electrode active material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the content of Li in the positive electrode active material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but is not limited to this. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that the new material obtained by appropriate modification on the basis of the listed positive electrode active materials is also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to the acceptable modification method for the positive electrode active material, and non-limiting examples include coating modification.

[0136] In the list of positive electrode active materials in this application, the content of oxygen (O) is only a theoretical state value. 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 measured by molar content, but is not limited to this.

[0137] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional 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. Among them, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. 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 referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.15 Al 0.05 O2.

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

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

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

[0141] Negative electrode

[0142] The negative electrode sheet of the above embodiment of the present application is adopted.

[0143] Electrolytes

[0144] The electrolyte has the function of conducting ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

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

[0146] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

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

[0148] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0149] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0150] Isolation film

[0151] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0152] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0153] In some embodiments, the isolation film has a thickness of 6 μm-40 μm, and optionally 12 μm-20 μm.

[0154] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0155] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

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

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

[0158] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and further, generally speaking, at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0159] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 3 The battery cell 5 is a square structure as an example.

[0160] In some embodiments, reference Figure 4, the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may 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 shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0161] The secondary battery may 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 those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0163] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0164] Optionally, the battery module 4 may further 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 battery modules described above may also be assembled into a battery pack. The number of battery modules contained in the battery pack may be one or more. Those skilled in the art may select a suitable number according to the application and capacity of the battery pack.

[0166] Figure 6 and Figure 7 1 is a battery pack 1 as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0167] In addition, the present application also provides an electrical device, which includes a secondary battery provided by the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, 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 are not limited thereto.

[0168] As an electrical device, a secondary battery can be selected according to its usage requirements.

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

[0170] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0171] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0172] Example 1

[0173] (1) Preparation of negative electrode active materials

[0174] (1.1) High-purity monosilane and acetylene were mixed in a volume ratio of 100:1 and sent together into a reaction system containing porous carbon (porosity 78%), so that nano-silicon penetrated into the pores of the porous carbon and completed diffusion and reduction. The total flow rate of high-purity monosilane and acetylene was 400 mL / min, the reaction temperature was 500° C., and the reaction time was 30 min.

[0175] (1.2) mixing the product A obtained in step (1.1) with a mixed solution in a mass ratio of 1:1, and stirring for 2 hours, wherein the mixed solution is formed by tetraethyl orthosilicate, sucrose and ethanol, the mass ratio of tetraethyl orthosilicate to sucrose is 5:1, and the mass ratio of tetraethyl orthosilicate to ethanol is 3:1;

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

[0177] (1.4) Acetylene is introduced into the reactor to perform carbon coating treatment on the product obtained in step (1.3), wherein 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 (the negative electrode active material prepared in step (1)), conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), and binder styrene butadiene rubber (SBR) are added into water at a mass ratio of 96:2:1:1 and mixed evenly to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on both sides of the negative electrode current collector copper foil, dried at 85°C, and then cold pressed to prepare a negative electrode sheet, 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 mixed evenly in a mass ratio of 97:2:1 and added to the solvent NMP to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the double-side surfaces of the positive electrode current collector aluminum foil, dried at 85°C and then cold pressed, and then die-cut and slit to prepare a positive electrode sheet.

[0182] (4) Preparation of isolation film

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

[0184] (5) Preparation of electrolyte

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

[0186] (6) Preparation of lithium-ion batteries

[0187] The positive electrode sheet, negative electrode sheet and isolation film are wound to obtain a bare cell, and then a lithium-ion battery is obtained through packaging, liquid injection, formation, exhaust and other processes. The capacity of the negative electrode sheet and the capacity of the positive electrode sheet of the battery are 1 (ie, N / P=1), and the designed rated capacity of the battery is 100Ah.

[0188] Embodiment 2-10

[0189] The method is basically the same as Example 1, except that the parameters described in Table 1-2 are different, and when preparing the negative electrode sheet in step (2), the negative electrode active material is replaced by the negative electrode active material prepared in step (1) of the corresponding embodiment.

[0190] Comparative Example 1

[0191] The process is basically the same as Example 1, except that step (1.2) and step (1.3) are omitted.

[0192] Comparative Example 2

[0193] The method is basically the same as Example 2, except that step (1.2) and step (1.3) are omitted.

[0194] Comparative Example 3

[0195] Basically the same as Example 9, except that step (1.2) and step (1.3) are omitted.

[0196] Performance Testing

[0197] (1) Compacted density of negative electrode

[0198] Use a vernier caliper to measure the total thickness of the pole piece, and deduct the thickness of the current collector to calculate the coating thickness. Based on the two parameters of coating surface density and coating thickness, the compaction density of the pole piece can be calculated.

[0199] (2) Battery specific capacity

[0200] At 25°C, the lithium-ion battery was charged to 4.3V at a constant current of 0.33C, then charged to a current of 0.05C at a constant voltage, left to stand for 5 minutes, and then discharged to 2.5V at a constant current of 0.33C. The discharge capacity at this time was recorded, which was the 0.33C discharge capacity. The 0.33C discharge capacity divided by the mass of the negative electrode active material was the 0.33C discharge specific capacity.

[0201] (3) Battery rate performance

[0202] At 25°C, the lithium-ion battery is charged to 4.3V at a constant current of 0.33C, then charged to a current of 0.05C at a constant voltage, allowed to stand for 5 minutes, and then discharged to 2.5V at a constant current of 0.33C, and the discharge capacity at this time is recorded, which is the 0.33C discharge capacity; let it stand for 30 minutes, then the lithium-ion battery is charged to 4.3V at a constant current of 1C, then charged to a current of 0.05C at a constant voltage, allowed to stand for 5 minutes, and then discharged to 2.5V at a constant current of 1C, and the discharge capacity at this time is recorded, which is the 1C discharge capacity.

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

[0204] Table 1 Product parameters of negative electrode active materials and negative electrode sheets

[0205]

[0206]

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

[0208]

[0209] Table 3 Battery performance

[0210]

[0211]

[0212] Observe Tables 1-3, from the comparison of Example 1, Example 3-8, Example 10 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 9 with Comparative Example 3, it can be seen that when there is only nano-silicon in the negative electrode active material, the specific capacity of the secondary battery is low. The negative electrode active material of Examples 1-10 contains silicon oxide compounds in the core, and the silicon oxide compounds are at least embedded in the nano-silicon, which effectively improves the specific capacity of the secondary battery, thereby improving the volume energy density of the secondary battery.

[0213] The above description of various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other, and for the sake of brevity, they will not be repeated herein.

[0214] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode active material, characterized in that: It comprises a core and a coating layer covering at least a part of the surface of the core, wherein the core comprises porous carbon and nano-silicon and silicon-oxygen compounds at least distributed in the pores of the porous carbon, and the silicon-oxygen compounds are at least embedded in the nano-silicon.

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

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

1.

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

5. The negative electrode active material according to claim 1 or 2, characterized in that: The silicon oxide compound comprises a chemical formula of SiO x of material, wherein 0<x≤2.

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

7. The negative electrode active material according to claim 1 or 2, characterized in that: The coating layer includes a carbon material; Optionally, based on the mass of the negative electrode active material, the mass percentage of the coating layer is 0.2%-2%.

8. The method for preparing the negative electrode active material according to any one of claims 1 to 7, characterized in that: The steps include: forming the nano-silicon and the silicon-oxygen compound in the pores of the porous carbon to obtain the core; The coating layer is formed on at least a portion of the surface of the core.

9. The preparation method according to claim 8, characterized in that: The step of forming the nano-silicon and the silicon-oxygen compound in the pores of the porous carbon to obtain the inner core comprises: Performing chemical vapor deposition on 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; Performing reduction treatment on the mixed materials; Optionally, the porosity of the porous carbon is 40%-90%.

10. The preparation method according to claim 9, characterized in that: 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 comprises one or more of acetylene, ethylene and methane; (4c) the silicon source comprises one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; (4d) the reducing agent comprises one or more of sucrose and glucose; (4e) the solvent comprises 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 100 mL / min-800 mL / min; (4h) The process conditions of the chemical vapor deposition include: a deposition temperature of 300° C. to 1000° C. and a deposition time of 0.2 h to 3 h; (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 reduction treatment include: reduction temperature 400°C-1000°C, and reduction time 2h-6h.

11. A negative electrode plate, characterized in that: At least one of the negative electrode active material according to any one of claims 1 to 7 and the negative electrode active material prepared by the preparation method according to any one of claims 8 to 10; Optionally, the compaction density of the negative electrode plate is 0.9 g / cm 3 -1.9g / cm 3 .

12. A secondary battery, characterized in that: Including the negative electrode sheet as described in claim 11.

13. An electrical device, characterized in that: The invention comprises at least one of the negative electrode active material according to any one of claims 1 to 7, the negative electrode active material prepared by the preparation method according to any one of claims 8 to 10, the negative electrode sheet according to claim 11, and the secondary battery according to claim 12.

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