Negative electrode material and preparation method therefor, secondary battery and electric device

Abstract

A negative electrode material and a preparation method therefor, a secondary battery and an electric device. The negative electrode material comprises a porous carbon matrix and a composite material distributed in the pores of the porous carbon matrix, wherein the composite material comprises a C-Si-O bond and a Si-Si bond. By preparing the composite material containing the C-Si-O bond in the pores of the porous carbon matrix, the volume expansion of Si during charging and discharging can be reduced, and the cycle life of the secondary battery is favorably prolonged.

Description

Negative electrode material and preparation method thereof, secondary battery and electric device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present disclosure is based on the Chinese patent application with application number 202410154299.X, application date February 2, 2024, and invention name “Negative electrode material and preparation method thereof, secondary battery and electrical device”, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby incorporated into the present disclosure as a reference. Technical Field

[0003] The present disclosure relates to the field of battery technology, and in particular to a negative electrode material and a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0004] As a green energy system, batteries are widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace and other fields due to their high energy density, long cycle life, high safety and environmental friendliness.

[0005] As an important component of batteries, negative electrode materials are closely related to battery performance. Currently, carbon-based negative electrode technology is very mature. However, the theoretical specific capacity of 372mAh / g can no longer meet people's growing demand for energy density. In this situation, silicon-based negative electrode materials with higher capacity are receiving increasing attention. The current development direction of silicon-based negative electrode materials mainly involves silicon-carbon composite materials. However, silicon-based negative electrode materials have problems with volume expansion and conductivity during the charge and discharge process, resulting in poor battery cycle performance and affecting the use of secondary batteries.

[0006] Summary of the Invention

[0007] The present disclosure is made in view of the above-mentioned problems, and its purpose is to provide a negative electrode material and its preparation method, a secondary battery and an electric device including the secondary battery. The negative electrode material, when used in a secondary battery, enables the battery to have lower volume expansion and improved cycle life.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a negative electrode material, comprising: a porous carbon matrix and a composite material distributed in the pores of the porous carbon matrix; the composite material contains C-Si-O bonds and Si-Si bonds. Since the Si-C bond has a stronger bond energy than the Si-O bond, it is less likely to break during the charge and discharge process. In this way, the Si-C bond can provide tension to Si and limit the volume expansion of Si during the charge and discharge process. The reduced volume expansion of Si can improve the structural stability of the negative electrode material, thereby improving the cycle stability of the secondary battery. On this basis, the composite material is distributed in the pores of the porous carbon matrix, which can provide space for the expansion of the composite material on the one hand, and on the other hand, it can also limit the expansion of the composite material, which can improve the structural stability and integrity of the negative electrode material, thereby further improving the cycle life of the secondary battery.

[0009] In some embodiments, the composite material comprises Si x O y C z , wherein x is 0.3 to 0.4, y is 0.2 to 0.3, and z is 0.4 to 0.5.

[0010] In some embodiments, in the negative electrode material, relative to the total mass of the negative electrode material, the content of silicon is 30% to 40% by mass, the content of oxygen is 10% to 20% by mass, and the content of carbon is 40% to 50% by mass.

[0011] In some embodiments, the pore volume of the porous carbon matrix is ​​0.6 cm 3 / g to 0.98cm 3 / g; and / or, the pore size of the porous carbon matrix is ​​1 nm to 5 nm; and / or, the specific surface area of ​​the porous carbon matrix is ​​1000 m 2 / g to 2000m 2 / g; and / or, the volume particle size distribution Dv50 of the porous carbon matrix is ​​0.5 μm to 5 μm. The pore volume, pore size, specific surface area and particle size distribution Dv50 of the porous carbon matrix are within the above ranges, and can be a composite material Si x O y C z The volume expansion provides a sufficiently large buffer space, thereby improving the stability of the negative electrode material and further improving the cycle stability of the secondary battery.

[0012] In some embodiments, the composite material accounts for 65% to 72% by weight of the negative electrode material.

[0013] In some embodiments, the negative electrode material includes one or more of the following features:

[0014] (1) The volume particle size distribution Dv50 of the negative electrode material is 0.5 μm to 5 μm; the volume particle size distribution Dv50 of the negative electrode material within the above range helps to increase the compaction density of the negative electrode sheet, thereby improving the volume energy density of the battery.

[0015] (2) The specific surface area of ​​the negative electrode material is 0.8m 2 / g to 9m 2 / g; the specific surface area of ​​the negative electrode material is within the above range, which is beneficial to improving the first coulombic efficiency of the secondary battery.

[0016] (3) The compaction density of the negative electrode material at 5 MPa is 1 g / cm 3 Up to 1.5g / cm 3 When the powder compaction density of the negative electrode material is within the above range, it is conducive to forming a reasonable pore structure between the particles of the negative electrode film layer, improving the active ion and electron transmission performance, and thus improving the kinetic performance of the secondary battery.

[0017] (4) The tap density of the negative electrode material is 0.9 g / cm 3 to 1.1 g / cm 3 When the tap density of the negative electrode material is within the above range, it is beneficial to increase the compaction density of the negative electrode film layer and improve the energy density of the secondary battery.

[0018] A second aspect of the present disclosure provides a method for preparing a negative electrode material, comprising the following steps:

[0019] Prepare a porous carbon matrix; and sequentially and cyclically deposit silicon, oxygen, and carbon on the porous carbon matrix. By sequentially and cyclically depositing silicon, oxygen, and carbon on the porous carbon matrix, a composite material containing C-Si-O and Si-Si bonds can be obtained. Because Si-C bonds have stronger bond energy than Si-O bonds, they are less likely to break during the charge and discharge process. Thus, the Si-C bonds can provide tension to the Si, limiting its volume expansion during charge and discharge, thereby improving the structural stability of the negative electrode material and, in turn, the cycle stability of the secondary battery.

[0020] In some embodiments, silicon deposition includes one or more of the following features: using a silicon-containing gas as the silicon source; using an inert gas as the first carrier gas; and performing the deposition at a temperature of 500°C to 750°C for 6 to 24 hours. Depositing silicon under these conditions facilitates the formation of Si-C bonds, which helps reduce expansion of the negative electrode material and improves the cycling stability of the secondary battery.

[0021] In some embodiments, depositing silicon includes performing the deposition at a deposition temperature of 500°C to 650°C.

[0022] In some embodiments, the oxygen deposition process includes one or more of the following features: using an oxygen-containing gas as the source gas; using an inert gas as the second carrier gas; and performing the deposition process at a temperature of 100°C to 400°C for 18 to 36 hours. Through this deposition process, the oxygen deposited on the surface of the silicon within the pores of the porous carbon matrix forms SiO, which can limit the volume expansion of silicon, thereby improving the stability of the composite material and facilitating the cycling stability of the battery.

[0023] In some embodiments, carbon deposition includes one or more of the following features: using a carbon-containing gas as the carbon source; using an inert gas as the third carrier gas; and performing the deposition at a temperature of 400° C. to 500° C. for 4 to 10 hours. Depositing carbon under these conditions facilitates the formation of C-Si bonds.

[0024] In some embodiments, the porous carbon matrix is ​​prepared by at least one of a carbonization method, an activation method, and a template method.

[0025] The third aspect of the present disclosure provides a secondary battery, comprising a negative electrode plate, the negative electrode plate comprising a negative electrode collector and a negative electrode film layer located on at least one surface of the negative electrode collector; the negative electrode film layer comprises the negative electrode material of the first aspect of the present disclosure or the complex electrode material prepared according to the method of the second aspect of the present disclosure.

[0026] In some embodiments, the negative electrode material further comprises lithium silicate.

[0027] The negative electrode film layer in the secondary battery of the present disclosure includes the negative electrode material provided by the present disclosure, which can effectively improve the cycle performance of the secondary battery.

[0028] A fourth aspect of the present disclosure provides an electric device including the secondary battery according to the third aspect of the present disclosure.

[0029] The electric device of the present disclosure includes the secondary battery provided by the present disclosure, and thus has at least the same advantages as the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is an XPS spectrum of a negative electrode material according to an embodiment of the present disclosure;

[0031] FIG2 is an EDS spectrum of a negative electrode material according to an embodiment of the present disclosure;

[0032] FIG3 is an XRD spectrum of a negative electrode material according to an embodiment of the present disclosure;

[0033] FIG4 is a SEM image of a negative electrode material according to an embodiment of the present disclosure;

[0034] FIG5 is a schematic diagram of a battery cell according to an embodiment of the present disclosure;

[0035] FIG6 is an exploded view of the battery cell according to one embodiment of the present disclosure shown in FIG5 ;

[0036] FIG7 is a schematic diagram of a battery module according to an embodiment of the present disclosure;

[0037] FIG8 is a schematic diagram of a battery pack according to an embodiment of the present disclosure;

[0038] FIG9 is an exploded view of the battery pack shown in FIG8 according to an embodiment of the present disclosure;

[0039] FIG. 10 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present disclosure as a power source.

[0040] Description of reference numerals:

[0041] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 top cover assembly DETAILED DESCRIPTION

[0042] Below, the embodiments of the negative electrode material and its preparation method, secondary battery and electric device disclosed in the present invention are described in detail with appropriate reference to the accompanying drawings. However, there may be 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 structures 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 description are provided for those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter described in the claims.

[0043] " scope " disclosed in the present disclosure is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and selected lower limit and upper limit define the boundary of special scope.The scope that this mode limits can be to include end value or not include end value, and can be combined arbitrarily, and promptly any lower limit can form a scope with any upper limit combination.For example, if the scope of 60-120 and 80-110 is listed for specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.In the present disclosure, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, and wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features disclosed herein can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of the present disclosure may be performed sequentially or randomly, preferably sequentially. For example, a method comprising steps (a) and (b) indicates that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, a method further comprising step (c) indicates that step (c) may be added to the method in any order, for example, the method may comprise steps (a), (b), and (c), or may comprise steps (a), (c), and (b), or may comprise steps (c), (a), and (b), etc.

[0047] Unless otherwise specified, the terms used in the present disclosure have the common meanings that are generally understood by those skilled in the art.

[0048] Unless otherwise specified, the numerical values ​​of the parameters mentioned in the present disclosure can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the present disclosure.

[0049] Unless otherwise specified, in the present disclosure, the term "active ions" refers to ions that can be intercalated and extracted back and forth between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0050] In order to improve the volume expansion of silicon-based negative electrode materials, silicon-carbon composite materials are usually formed as negative electrode materials. Although silicon-carbon composite materials can improve volume expansion to a certain extent, it is still not enough. The reason is that the expansion of nano-scale silicon particles is still relatively large, and the total pore volume of the carbon substrate is still not large enough to buffer such a large expansion. If the pore volume of the carbon substrate is infinitely increased, the stability of the carbon substrate will be greatly reduced. Therefore, existing silicon-containing negative electrode materials still need to be improved.

[0051] Based on this, the present disclosure proposes a negative electrode material and a preparation method thereof, as well as a secondary battery and an electrical device using the negative electrode material as a negative electrode material. The present disclosure and preferred implementation methods are described in more detail below.

[0052] In some embodiments, the negative electrode material provided by the embodiments of the present disclosure includes: a porous carbon matrix and a composite material distributed in the pores of the porous carbon matrix; the composite material contains C-Si-O bonds and Si-Si bonds.

[0053] The present disclosure discovered that during the charge and discharge process, Si-C bonds in composite materials used as negative electrode materials are stronger than Si-O bonds, making them less likely to break. This Si-C bond provides tension to the Si, limiting its volume expansion during charge and discharge. This reduced volume expansion improves the structural stability of the negative electrode material, thereby enhancing the cycling stability of the secondary battery.

[0054] Furthermore, the composite material is distributed in the pores of the porous carbon matrix, which can provide space for the expansion of the composite material on the one hand, and on the other hand, limit the expansion of the composite material, thereby improving the structural stability and integrity of the negative electrode material, thereby further improving the cycle performance of the secondary battery.

[0055] The C—Si—O bonds and Si—Si bonds mentioned in the present disclosure can be characterized by X-ray photoelectron spectroscopy.

[0056] In some embodiments, the composite material comprises Si x O y C z , wherein x is 0.3 to 0.4, y is 0.2 to 0.3, and z is 0.4 to 0.5.

[0057] In the present disclosure, the physical phase of the composite material can be obtained by XRD testing. Specifically, the test can be performed using an X-ray diffractometer in accordance with JIS K0131-1996. The test conditions are as follows: the composite material is prepared using a flat plate sample preparation method, CuKα radiation is used as the radiation source, a copper target is used as the anode target, a voltage of 40 kV, a current of 40 mA, an anti-scatter slit of 1 mm, a scanning 2θ angle range of 20° to 80°, a step size of 0.01671°, a step length of 0.24 s per step, and a scanning rate of 4° / min. The testing instrument can be a Bruker D8 Discover X-ray diffractometer.

[0058] In some embodiments, in the negative electrode material, relative to the total mass of the negative electrode material, the content of silicon is 30% to 40% by mass, the content of oxygen is 10% to 20% by mass, and the content of carbon is 40% to 50% by mass.

[0059] The contents of silicon, oxygen, and carbon in the composite materials mentioned in this disclosure can be measured using instruments and methods known in the art. For example, samples can be prepared using an interface polisher and spectrometers can be used to obtain energy spectra, thereby determining the distribution of silicon, oxygen, and carbon.

[0060] The content of Si and C elements in the present disclosure can be tested in the following way. First, the negative electrode material is dissolved in an excess of sodium hydroxide solution. The Si element in the negative electrode material reacts with the sodium hydroxide solution to form silicate. The C and O elements in the negative electrode material are precipitated because they cannot react with the sodium hydroxide solution. After filtration, the content of element Si is obtained by calculating the content of silicate. The above-mentioned precipitate is placed in a special crucible, and an appropriate amount of flux is added and mixed evenly. The sample is burned in oxygen to convert C into CO2, which enters the absorption cell and is converted into a corresponding signal by the detector. This signal is sampled by a computer and converted into a numerical value proportional to the CO2 concentration after linear correction. The values ​​of the entire analysis process are then accumulated. After the analysis is completed, this accumulated value is divided by the weight value in the computer, multiplied by the correction coefficient, and the blank is deducted to obtain the C content in the negative electrode material. The above method can determine the Si content and C content in the negative electrode material, and the remainder is the O content.

[0061] In some embodiments, the volume particle size distribution Dv50 of the porous carbon matrix is ​​0.5 μm to 5 μm, optionally 0.5 μm to 3 μm. In the present disclosure, since the composite material is formed in the pores of the porous carbon matrix, the particle size of the porous carbon matrix is ​​the size of the negative electrode material.

[0062] In the present disclosure, since the composite material is formed in the pores of the porous carbon matrix, the volume particle size distribution Dv50 of the composite material can be obtained to be less than 2 nm based on the volume particle size distribution Dv50 of the porous carbon matrix, and optionally 1 nm to 1.5 nm.

[0063] In some embodiments, the pore volume of the porous carbon matrix is ​​0.6 cm 3 / g to 0.98cm 3 / g; and / or, the specific surface area of ​​the porous carbon matrix is ​​1000m 2 / g to 2000m 2 / g; and / or, the volume particle size distribution Dv50 of the porous carbon matrix is ​​0.5μm to 5μm; and / or, the pore size of the porous carbon matrix is ​​1nm to 5nm, optionally, the pore size of the porous carbon matrix is ​​1.5nm to 3nm.

[0064] The pore volume of the porous carbon matrix is ​​0.68 cm 3 / g to 0.98 cm 3 / g, pore diameter between 1nm and 5nm, and specific surface area between 1000m 2 / g to 2000m 2 / g, and the volume particle size distribution Dv50 is between 0.5μm and 5μm, which can be a composite material Si x O y C zThe volume expansion provides a sufficiently large buffer space, thereby improving the stability of the negative electrode material and further improving the cycle stability of the secondary battery.

[0065] In some embodiments, the composite material accounts for 65% to 72% by weight of the negative electrode material.

[0066] In the present disclosure, the mass proportion of the composite material in the negative electrode material is within the above range, and a suitable number of silicon-carbon bonds and a suitable number of silicon-oxygen bonds can be formed simultaneously, which helps to improve the expansion performance of the negative electrode material.

[0067] In some embodiments, the negative electrode material includes one or more of the following features:

[0068] (1) The volume particle size distribution Dv50 of the negative electrode material is 0.5 μm to 5 μm; the volume particle size distribution Dv50 of the negative electrode material within the above range helps to increase the compaction density of the negative electrode sheet, thereby improving the volume energy density of the battery.

[0069] (2) The specific surface area of ​​the negative electrode material is 0.8m 2 / g to 9m 2 / g; the specific surface area of ​​the negative electrode material is within the above range, which is beneficial to improving the first coulombic efficiency of the secondary battery.

[0070] (3) The compaction density of the negative electrode material at 5 MPa is 1 g / cm 3 Up to 1.5g / cm 3 When the powder compaction density of the negative electrode material is within the above range, it is conducive to forming a reasonable pore structure between the particles of the negative electrode film layer, improving the active ion and electron transmission performance, and thus improving the kinetic performance of the secondary battery.

[0071] (4) The tap density of the negative electrode material is 0.9 g / cm 3 to 1.1 g / cm 3 When the tap density of the negative electrode material is within the above range, it is beneficial to increase the compaction density of the negative electrode film layer and improve the energy density of the secondary battery.

[0072] In this disclosure, the volume distribution particle size of the negative electrode material has a meaning well known in the art, and refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%. It can be measured using instruments and methods known in the art. For example, it can be measured using a laser particle size analyzer in accordance with GB / T 19077-2016. The testing instrument can be a Mastersizer 3000 laser particle size analyzer manufactured by Malvern Instruments Ltd. in the UK.

[0073] In this disclosure, the BET specific surface area of ​​a negative electrode material is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be a Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, Inc., USA.

[0074] In the present disclosure, the compaction density of the negative electrode material is a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured by an electronic pressure tester (for example, a UTM7305 electronic pressure tester) with reference to GB / T 24533-2009. An exemplary test method is as follows: 1 g of sample powder is weighed and added to a container with a bottom area of ​​1.327 cm 2 In the mold, pressurize to 5MPa, maintain pressure for 30s, then release the pressure, maintain for 10s, and then record and calculate the powder compaction density of the material at 5MPa.

[0075] In the present disclosure, the tap density of the negative electrode material has a meaning well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester with reference to GB / T 5162-2006. The test instrument can be a Dandong Baxter BT-301, and the test parameters are as follows: vibration frequency 250±15 times / min, amplitude 3±0.2mm, vibration number 5000 times, and a 25mL graduated cylinder.

[0076] In order to obtain the above-mentioned negative electrode material, in another embodiment of the present disclosure, a method for preparing the negative electrode material is provided, and the method for preparing the negative electrode material comprises the following steps:

[0077] preparing a porous carbon substrate; and

[0078] Silicon, oxygen, and carbon are sequentially and cyclically deposited on the porous carbon substrate.

[0079] The negative electrode material prepared in the present disclosure includes a porous carbon matrix and a composite material distributed in the pores of the porous carbon matrix; the composite material contains C-Si-O bonds and Si-Si bonds.

[0080] Although the mechanism is not yet clear, the present disclosure has discovered that by cyclically depositing silicon, oxygen, and carbon on a porous carbon substrate, a composite material containing C-Si-O and Si-Si bonds can be obtained. Because the Si-C bond has a stronger bond energy than the Si-O bond, it is less likely to break during the charge and discharge process. In this way, the Si-C bond can provide tension to the Si, limiting the volume expansion of the Si during the charge and discharge process. The reduced volume expansion of Si can improve the structural stability of the negative electrode material, thereby improving the cycle stability of the secondary battery.

[0081] On this basis, the composite material is distributed in the pores of the porous carbon matrix, which can provide space for the expansion of the composite material on the one hand, and on the other hand, limit the expansion of the composite material, thereby improving the structural stability and integrity of the negative electrode material, thereby further improving the cycle performance of the secondary battery.

[0082] In some embodiments, the number of cycles of depositing silicon, oxygen, and carbon is 3 to 5, but is not limited thereto.

[0083] In some embodiments, sequentially depositing silicon, oxygen, and carbon on the porous carbon substrate refers to sequentially depositing silicon, oxygen, and carbon on the porous carbon substrate by chemical deposition.

[0084] In some embodiments, the deposition of silicon includes one or more of the following features:

[0085] A silicon-containing gas is used as a silicon source. Optionally, the silicon-containing gas includes at least one of monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. Optionally, the flow rate of the silicon-containing gas is 0.5 L / min to 5 L / min.

[0086] An inert gas is used as the first carrier gas. Optionally, the first carrier gas includes at least one of nitrogen, argon, helium or neon. Optionally, the flow rate of the first carrier gas is 0.5 L / min to 30 L / min.

[0087] The deposition is performed at a temperature of 500° C. to 750° C. for 6 hours to 24 hours.

[0088] In some embodiments, the silicon-containing gas may also be one or more of disilane, halogenated silane, polysilane, polymethylsilane, silole and its derivatives, silanol and its derivatives.

[0089] In some embodiments, the silicon-containing gas and the first carrier gas are each controlled and regulated by a gas flow rate controller. The gas flow rate controller can precisely control the flow rate of the silicon-containing gas to 0.5 L / min to 5 L / min, and the flow rate of the first carrier gas to 0.5 L / min to 30 L / min. Depositing silicon under these conditions facilitates the formation of Si-C bonds, which helps reduce expansion of the negative electrode material and improves the cycling stability of the secondary battery.

[0090] In some embodiments, the deposition of silicon is performed at a deposition temperature of 500° C. to 650° C. Depositing silicon at a deposition temperature of 500° C. to 650° C. is more conducive to forming Si—C bonds.

[0091] In some embodiments, the deposition of oxygen includes one or more of the following features:

[0092] Oxygen-containing gas is used as the gas source; optionally, the flow rate of the oxygen-containing gas is 0.5 L / min to 5 L / min;

[0093] An inert gas is used as the second carrier gas. Optionally, the second carrier gas includes at least one of nitrogen, argon, helium or neon. Optionally, the flow rate of the first carrier gas is 0.1 L / min to 5 L / min.

[0094] The deposition is performed at a deposition temperature of 400° C. to 500° C. for 18 to 36 hours.

[0095] In some embodiments, the oxygen-containing gas may be one or more of oxygen, carbon dioxide, water vapor, methanol, ethanol, n-propanol, isopropanol, butanol, acetone, and butanone. Preferably, the oxygen-containing gas is oxygen.

[0096] In some embodiments, the oxygen-containing gas and the second carrier gas are each controlled and regulated by a gas flow rate controller, which can accurately control the flow rate of the oxygen-containing gas to 0.5 L / min to 5 L / min and the flow rate of the second carrier gas to 0.1 L / min to 5 L / min. Silicon deposition under the above conditions can form SiO2 on the surface of the silicon within the pores of the porous carbon matrix. SiO2 can limit the volume expansion of silicon, thereby improving the stability of the composite material and promoting the cycle stability of the battery.

[0097] In some embodiments, the deposition of carbon includes one or more of the following characteristics:

[0098] Using a carbon-containing gas as a carbon source, optionally, the carbon-containing gas includes a hydrocarbon compound, further optionally, the carbon-containing gas includes at least one of methane, ethane, propane, ethylene or propylene, optionally, the flow rate of the carbon-containing gas is 0.05 L / min to 0.1 L / min;

[0099] Using an inert gas as a third carrier gas, optionally, the third carrier gas includes at least one of nitrogen, argon, helium or neon, and optionally, the flow rate of the third carrier gas is 0.1 L / min to 5 L / min;

[0100] The deposition is performed at a deposition temperature of 400° C. to 500° C. for 4 to 10 hours.

[0101] In some embodiments, the carbon-containing gas may also be alkynes such as acetylene and propyne, or aromatic hydrocarbons such as benzene, toluene, and xylene. In the present disclosure, methane is preferably used as the carbon source.

[0102] In some embodiments, the carbon-containing gas and the third carrier gas are controlled and adjusted by gas flow rate controllers, respectively. Carbon deposition under the above conditions is conducive to the formation of C-Si bonds.

[0103] In some embodiments, the porous carbon matrix is ​​prepared by at least one of carbonization, activation, and template methods, optionally by alkali activation, water vapor activation, or carbon dioxide activation.

[0104] In some embodiments, the carbon precursor for preparing the porous carbon matrix can be one or more of: glucose, fructose, sucrose, maltose, lactose, cyclodextrin, starch, glycogen, cellulose, hemicellulose, lignin, unsaturated polyester resin, epoxy resin, thermoplastic phenolic resin, thermosetting phenolic resin, polyformaldehyde resin, urea-formaldehyde resin, furfural resin, furfural ketone resin, acrylic resin, polyamide, polyimide, and asphalt.

[0105] In some embodiments, carbonization refers to a process of pyrolyzing organic matter into carbonaceous materials at high temperatures, and the formation of a porous structure can be adjusted by controlling the carbonization conditions.

[0106] In some embodiments, the template method refers to using the voids of certain template materials as templates, filling them with carbon precursors, and then removing the template materials after carbonization or activation, leaving behind a porous carbon material.

[0107] In some embodiments, the activation method refers to introducing an oxidant or alkaline substance into the carbonized material to oxidize it or remove part of the carbonaceous material, thereby forming a porous structure. For example, in the present disclosure, a porous carbon matrix can be formed by water vapor activation.

[0108] In some specific embodiments, the method for preparing the negative electrode material includes:

[0109] (1) preparing a porous carbon matrix;

[0110] Specifically, epoxy resin was dissolved in ethanol and stirred for 30 minutes to disperse it evenly. The mixed solution was placed in a reactor and reacted at 180°C for 10 hours to obtain a powder material. The obtained powder material was placed in a muffle furnace and sintered at 900°C for 4 hours under inert gas protection to obtain a composite carbon source material. Water vapor was introduced into the composite carbon source material, and the steam flow was controlled at 0.3 L / min and the water vapor pressure was controlled at 10 MPa. The activation time was 2 hours to 6 hours, and a pore diameter of 0.8 nm to 5 nm and a pore volume of 0.6 cm were formed. 3 / g to 0.98cm 3 / g, carbon particle size is 0.5μm to 3μm, BET is 1000m 2 / g to 2000m 2 / g porous carbon matrix.

[0111] In some embodiments, after water vapor is introduced, the water vapor (H2O) reacts with a portion of the C material to generate CO and H2, which escape to form pores, thereby achieving pore formation by water vapor.

[0112] (2) depositing silicon;

[0113] Using silicon-containing gas as the silicon source and either nitrogen or argon as the carrier gas, vapor deposition is carried out in a rotary kiln, a tubular furnace, or a fluidized bed; wherein the silicon-containing gas includes one or more of monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane, with a flow rate of 0.5 L / min to 5 L / min; the flow rate of the carrier gas is 0.5 L / min to 30 L / min; the vapor deposition temperature of silicon is 500°C to 750°C, and the time is 6 to 24 hours.

[0114] (3) Deposition of oxygen;

[0115] Vapor deposition is carried out in a rotary kiln, a tubular furnace, or a fluidized bed using oxygen as the gas source and nitrogen or argon as the carrier gas; the flow rate of oxygen is 0.5 L / min to 5 L / min; the flow rate of the carrier gas is 0.1-5 / min; the temperature of oxygen vapor deposition is 100°C to 400°C, and the time is 18 to 36 hours.

[0116] (4) carbon deposition;

[0117] Deposition is carried out in a rotary furnace or a tubular furnace using ethylene or propylene as the carbon-containing gas and either nitrogen or argon as the carrier gas; the flow rate of the carbon-containing gas is 0.05 L / min to 0.1 L / min; the flow rate of the carrier gas is 0.1 L / min to 5 L / min; the temperature of carbon vapor deposition is 400°C to 500°C, and the time is 4h to 10h.

[0118] (5) Repeat the above steps (2), (3), and (4) 3 to 5 times.

[0119] The negative electrode material prepared by the present disclosure forms a C-Si-O bond. The presence of the C-Si bond can provide tension to Si to reduce the volume expansion of silicon. Therefore, the structure of the negative electrode material formed is relatively stable and has a long cycle life. In addition, during the first lithium insertion process, the composite material Si x O y C zThe lithium silicate formed around it can buffer the expansion on the one hand, and on the other hand can serve as an inorganic ion conductor to enhance the solid-phase mass transfer of the material, thereby improving the cycle stability of the battery.

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

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

[0122] The term "secondary battery" mentioned herein refers to a battery cell, a battery module, or a battery pack. Each of these is described below.

[0123] Typically, a battery cell consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0124] Positive electrode

[0125] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0126] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0127] 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 and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum 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.).

[0128] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may adopt the positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present disclosure 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. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as 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 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0129] In some embodiments, when the battery cell is a sodium ion battery, the positive electrode active material may be a positive electrode active material known in the art for sodium ion batteries. For example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc.

[0130] As an optional technical solution of the present disclosure, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 <x≤1。

[0131] As an optional technical solution of the present disclosure, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence.

[0132] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0133] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n- Valence state: Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0134] Polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0135] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 <a≤2,0<b<1,0<c<1。

[0136] In some embodiments, the battery's charge and discharge processes are accompanied by Li intercalation and deintercalation, resulting in different molar Li contents at different discharge states. The molar Li contents listed in this disclosure for positive electrode active materials refer to the material's initial state, i.e., the state before addition. When the positive electrode active material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0137] In the list of positive electrode active materials in this disclosure, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0138] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one 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 film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0141] Negative electrode

[0142] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. The negative electrode film layer includes the negative electrode material in the above embodiment or the negative electrode material prepared by the above embodiment.

[0143] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0144] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0145] In some embodiments, when the battery cell is a lithium-ion battery, the negative electrode active material may be the negative electrode material in the above embodiments.

[0146] In some embodiments, the negative electrode material also includes lithium silicate. During the charge and discharge process, lithium silicate is formed around the negative electrode material. This can buffer the expansion on the one hand, and on the other hand, it can act as an inorganic ion conductor to enhance the solid-phase mass transfer of the material, thereby improving the cycle stability of the secondary battery.

[0147] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0148] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0150] In some embodiments, the negative electrode sheet can be prepared by the following method: 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 (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0151] electrolytes

[0152] The electrolyte conducts ions between the positive and negative electrodes. This disclosure does not specifically limit the type of electrolyte, and the electrolyte can be selected based on needs. For example, the electrolyte can be liquid, gel, or solid.

[0153] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0154] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0155] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0156] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include 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, and additives that improve battery high or low temperature performance.

[0157] Isolation film

[0158] In some embodiments, the battery cell further includes a separator. The present disclosure has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0159] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0160] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0161] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0162] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0163] The present disclosure has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG5 shows a battery cell 5 with a square structure as an example.

[0164] In some embodiments, referring to Figure 6, the outer packaging may include a shell 51 and a top cover assembly 53. 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 top cover assembly 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 be formed into 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 specific actual needs.

[0165] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0166] FIG7 shows an example battery module 4. Referring to FIG7 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0167] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0168] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0169] Figures 8 and 9 illustrate an example battery pack 1. Referring to Figures 8 and 9 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0170] In addition, the present disclosure further provides an electrical device, which includes the secondary battery provided by the present disclosure. 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 can include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0171] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0172] Figure 10 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0173] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0174] Example

[0175] The following examples are provided. The examples described below are illustrative and are intended only to explain the present disclosure and are not to be construed as limiting the present disclosure. Where specific techniques or conditions are not specified in the examples, the methods were performed according to those described in the literature in the art or according to the product specifications. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0176] Example 1

[0177] Preparation method of negative electrode material:

[0178] 1) 10 g of phenolic resin was dissolved in an appropriate amount of ethanol and stirred for 30 min to uniformly disperse the phenolic resin. The mixed solution was placed in a reactor and reacted at 180° C. for 10 h to obtain a powder material. The obtained powder material was placed in a muffle furnace under inert gas protection and sintered at 900° C. for 4 h to obtain a composite carbon source material. Water vapor was introduced into the composite carbon source material, and the steam flow was controlled at 0.3 L / min and the water vapor pressure was controlled at 10 MPa. The activation time was 4 h, and a pore diameter of 2 nm and a pore volume of 0.6 cm were formed. 3 / g, particle size distribution Dv50 is 4μm, BET is 1500m 2 / g porous carbon matrix;

[0179] 2) using monosilane as the silicon source and argon as the carrier gas in a tube furnace at 500° C. for 6 hours; wherein the flow rate of the monosilane gas is 3 L / min; the flow rate of the argon gas is 10 L / min;

[0180] 3) using oxygen as the source gas and nitrogen as the carrier gas in a tube furnace at 200° C. for 18 h; wherein the flow rate of oxygen is 2 L / min; the flow rate of nitrogen is 4 L / min;

[0181] 4) using ethylene as the carbon source and argon as the carrier gas in a tube furnace at 450°C for 8 hours; wherein the flow rate of ethylene is 4 L / min; the flow rate of the protective gas argon is 4 L / min;

[0182] 5) The above silicon deposition, oxygen deposition, and carbon deposition processes are cycled three times.

[0183] Anode material performance characterization

[0184] 1. Chemical bond characterization

[0185] The XPS test was performed using an Axis Supra X-ray photoelectron spectrometer. The test conditions were: the energy range was set to 5 eV to 3000 eV, and the energy step was set to 3 eV. The test method was: 2 mg of negative electrode material powder was pasted on the XPS test sample table with ordinary double-sided tape (not double-sided carbon conductive tape).

[0186] 2. Characterization of element distribution

[0187] Cross-sections of negative electrode material particles were prepared using a JEOL IB-09010CP cross-section polisher. The elemental distribution of the negative electrode material was measured using an Oxford Instruments X-Max energy dispersive spectrometer (EDS). The test method was as follows: a sample preparation glue and negative electrode material powder were mixed evenly (the powder weight was approximately five times that of the glue) and then coated onto a 6μm copper foil. The sample was then dried at 60°C for 30 minutes to obtain the test sample. The sample was then cut into 6mm x 6mm pieces using scissors and affixed to the CP sample stage, with the sample protruding no more than 1mm from the stage. The sample was then cut at 7.5kV. EDS testing conditions were: In-lens mode, voltage: 20kV, aperture: 60μm, working distance: 8.5mm, and scanned at three locations.

[0188] 3. Phase characterization

[0189] A Bruker D8 Discover X-ray diffractometer was used for the test in accordance with JIS K 0131-1996. The test conditions were as follows: the negative electrode material was prepared by a flat plate sample preparation method, CuKα rays were used as the radiation source, a copper target was used as the anode target, the voltage was 40 kV, the current was 40 mA, the anti-scattering slit was 1 mm, the scanning 2θ angle range was 20°-80°, the step size was 0.01671°, the duration of each step was 0.24 s, and the scanning rate was 4° / min.

[0190] 4. Morphological characterization

[0191] A Philips XL-30 field emission scanning electron microscope (SEM) was used for morphology testing. The SEM test conditions were as follows: mode: In-lens, voltage: 10 KV, aperture: 30 μm, and working distance: 4.5 mm.

[0192] The XPS spectrum of the negative electrode material prepared in this example is shown in FIG1 . It can be seen from FIG1 that the negative electrode material includes Si—O bonds and Si—C bonds.

[0193] The EDS spectrum of the negative electrode material prepared in this embodiment is shown in FIG2 . As can be seen from FIG2 , the negative electrode material includes three elements: Si, O, and C. In the EDS spectrum of the Si element, the bright spot represents the Si element, in the EDS spectrum of the C element, the bright spot represents the C element, and in the EDS spectrum of the O element, the bright spot represents the O element. It can be seen that the three elements Si, O, and C are evenly distributed in the entire negative electrode material.

[0194] The XRD spectrum of the negative electrode material prepared in this embodiment is shown in Figure 3. As can be seen from Figure 3, the negative electrode material is amorphous, and its XRD spectrum includes an amorphous carbon peak (located at 20° to 30°) and an amorphous C-Si-O peak (located at about 40° to 60°).

[0195] The SEM image of the negative electrode material prepared in this example is shown in FIG4 . As can be seen from FIG4 , the negative electrode material is irregular in shape.

[0196] Preparation of lithium-ion batteries

[0197] Preparation of the negative electrode sheet: The negative electrode materials prepared in Examples 1 to 8, Comparative Example 1, and Comparative Example 2 are mixed with the conductive agent carbon black, carbon nanotubes (CNTs), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) in a weight ratio of 94.5:1:0.375:2.8:1.325, added to deionized water, and mixed and stirred for 1 hour to obtain an active material slurry; the active material slurry is evenly coated on the negative electrode current collector and dried to obtain a negative electrode sheet.

[0198] Preparation of positive electrode: Lithium nickel cobalt manganese oxide (LiNi 0.94 Co 0.03 Mn 0.03 O2), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are added in a mass ratio of 97:1:2, N-methylpyrrolidone is added, and the mixture is mixed and stirred for 2 hours to obtain a positive electrode slurry; then it is evenly coated on the positive electrode collector, and the positive electrode sheet is obtained after drying, cold pressing, and cutting.

[0199] Isolation membrane: A double-sided coated membrane is used as the isolation membrane, wherein the base membrane is a polypropylene film and the coating is 1 micron aluminum oxide + 1 micron polyvinylidene fluoride.

[0200] Electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC) are mixed in a volume ratio of 1:1:1:1 to obtain an organic solvent, and then lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiN(SO2F)2) in a mass ratio of 4:6 are dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0201] The positive electrode sheet, separator, and negative electrode sheet prepared above are wound in sequence to obtain a bare cell; the bare cell is placed in a packaging shell, dried, and then injected with electrolyte, and a lithium-ion battery is obtained through vacuum packaging, standing, forming, shaping, and other processes.

[0202] Lithium-ion battery test methods

[0203] 1. Negative electrode rebound

[0204] 1) Measure the initial thickness T1 of the negative electrode sheet;

[0205] 2) Charge the battery cells to 4.25V at 0.33C0 at 25°C, and charge at 4.25V constant voltage to a current of 0.05C0;

[0206] 3) Disassemble the lithium-ion battery and test the thickness T2 of the negative electrode;

[0207] 4) The rebound of the negative electrode is (T2-T1) / T2.

[0208] 2. Cycle life

[0209] First, perform voltage calibration as follows:

[0210] 1) Leave the battery cell at 25°C for 2 hours to ensure the temperature of the battery cell is 25°C;

[0211] 2) Charge the battery cells to 4.25V at 0.33C0 at 25°C, and charge at 4.25V constant voltage to a current of 0.05C0;

[0212] 3) Let stand for 1 hour;

[0213] 4) Discharge at 0.33C0 to 0.95C0 at 25°C and record the voltage V1 at this time;

[0214] 5) Let stand for 5 minutes;

[0215] 6) Discharge to 2.0V at 0.33C0 at 25°C;

[0216] 7) Let stand for 5 minutes;

[0217] 8) Charge the battery cell at 0.33C0 to 0.97C0 at 25°C and record the voltage V2 at this time;

[0218] 9) Let stand for 2 hours;

[0219] Next, perform the loop test as follows:

[0220] 1) Leave the battery cell at 25°C for 2 hours to ensure the temperature of the battery cell is 25°C;

[0221] 2) Charge the battery cells to voltage V2 at 0.33C0 at 25°C;

[0222] 3) Let it stand for 0.5h;

[0223] 4) Discharge the battery cell at 0.33C0 at 25°C to voltage V1, and record the capacity at this point as Cn;

[0224] 5) Let stand for 0.5h;

[0225] 6) Repeat steps 2) to 5) until the number of loops n reaches 3000.

[0226] The number of cycles corresponding to a capacity retention rate of 80% is taken as the test result.

[0227] Example 2-9: Except for adjusting the parameters according to Table 1, the remaining steps are the same as those of Example 1.

[0228] Comparative Example 1: Except that carbon is not deposited during the process of forming the composite material (ie, step 4 is not performed), the rest is the same as Example 1.

[0229] Comparative Example 2: A porous carbon substrate was prepared in the same manner as in Example 1, and then SiO was directly deposited in the pores of the porous carbon substrate using silicon and silicon dioxide sources as silicon sources and nitrogen as carrier gas at 1300° C. for 6 h.

[0230] The parameters of the negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-2 and the secondary battery performance test results are shown in Table 1 below.

[0231] Table 1:

[0232] It can be seen from the results in Table 1 above that, compared with Comparative Example 1 (no carbon deposition process) and Comparative Example 2 (direct deposition of SiO), the negative electrode materials of Examples 1 to 8 form a composite material containing C-Si-O bonds by sequentially depositing silicon, oxygen, and carbon on a porous carbon matrix, thereby reducing the full charge plate rebound rate of the negative electrode and improving the cycle life of the secondary battery. Among them, for Example 9, it is speculated that due to the small pore size of the porous carbon matrix, the composite material is difficult to deposit in the pore, resulting in a high full charge rebound rate of the negative electrode. For Example 5, it is speculated that due to the large pore size of the porous carbon matrix, the particle size of the composite material formed in the pore is larger, and the composite material with a larger particle size tends to exist in a crystalline form, so that there will be changes in the crystal phase during the cycle, thereby affecting its cycle performance.

[0233] Examples 10-12: Except for adjusting the parameters according to Table 2, the remaining steps are the same as those of Example 1.

[0234] The parameters of the negative electrode materials prepared in Examples 10-12 and the secondary battery performance test results are shown in Table 2 below.

[0235] Table 2:

[0236] The results in Table 2 show that by setting the silicon deposition temperature between 500°C and 750°C, a negative electrode material containing C-Si-O bonds can be formed, thereby reducing the full charge rebound rate of the negative electrode and improving the cycle life of the secondary battery. When the silicon deposition temperature is 900°C, although C-Si-O bonds are also formed, the higher deposition temperature makes the resulting composite material easy to crystallize and the grain size larger. This makes it more prone to cracking and pulverization during cycling, affecting the stability of the SEI film, resulting in greater rebound and poor cycling performance.

[0237] It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present disclosure, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present disclosure. In addition, within the scope of the present disclosure, various modifications that can be imagined by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present disclosure.

Claims

1. A negative electrode material comprising: A porous carbon matrix and a composite material distributed within the pores of the porous carbon matrix; The composite material contains C-Si-O bonds and Si-Si bonds.

2. The negative electrode material according to claim 1, wherein The composite material includes Si x O y C z , wherein x is 0.3 to 0.4, y is 0.2 to 0.3, and z is 0.4 to 0.

5.

3. The negative electrode material according to claim 1 or 2, wherein In the negative electrode material, relative to the total mass of the negative electrode material, the silicon content is 30% to 40% by mass, the oxygen content is 10% to 20% by mass, and the carbon content is 40% to 50% by mass.

4. The negative electrode material according to any one of claims 1 to 3, wherein The pore volume of the porous carbon matrix is 0.6 cm 3 / g to 0.98cm 3 / g; and / or, The pore size of the porous carbon matrix is 1 nm to 5 nm; and / or, The specific surface area of the porous carbon matrix is 1000 m 2 / g to 2000m 2 / g; and / or, The volume particle size distribution Dv50 of the porous carbon matrix is 0.5 μm to 5 μm.

5. The negative electrode material according to any one of claims 1 to 4, wherein In the negative electrode material, the composite material accounts for 65% to 72% by mass.

6. The negative electrode material according to any one of claims 1 to 5, wherein The negative electrode material includes one or more of the following features: (1) The volume particle size distribution Dv50 of the negative electrode material is 0.5 μm to 5 μm; (2) The specific surface area of the negative electrode material is 0.8 m 2 / g to 9m 2 / g; (3) The compaction density of the negative electrode material at 5 MPa is 1 g / cm 3 Up to 1.5g / cm 3 ; (4) The tap density of the negative electrode material is 0.9 g / cm 3 to 1.1 g / cm 3 .

7. A method for preparing a negative electrode material, comprising: preparing a porous carbon matrix; as well as Silicon, oxygen and carbon are sequentially and cyclically deposited on the porous carbon substrate.

8. The method according to claim 7, wherein: The silicon deposition includes one or more of the following features: Using silicon-containing gas as silicon source; Using inert gas as the first carrier gas; The deposition is performed at a temperature of 500° C. to 750° C. for 6 hours to 24 hours.

9. The method according to claim 8, wherein The silicon deposition comprises: The deposition temperature is between 500°C and 650°C.

10. The method according to any one of claims 7 to 9, wherein The oxygen deposition includes one or more of the following features: Using oxygen-containing gas as gas source; Using inert gas as the second carrier gas; The deposition is performed at a deposition temperature of 100° C. to 400° C. for 18 to 36 hours.

11. The method according to any one of claims 7 to 10, wherein The carbon deposition may include one or more of the following characteristics: Using carbon-containing gas as carbon source; Using inert gas as the third carrier gas; The deposition is performed at a deposition temperature of 400° C. to 500° C. for 4 to 10 hours.

12. The method according to any one of claims 7 to 11, wherein: The porous carbon matrix is prepared by at least one of a carbonization method, an activation method, and a template method.

13. A secondary battery comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises the negative electrode material according to any one of claims 1 to 6, or comprises the negative electrode material prepared by the preparation method according to any one of claims 7 to 12.

14. The secondary battery according to claim 13, wherein The negative electrode material further includes lithium silicate.

15. An electrical device comprising the secondary battery according to claim 13 or 14.

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