Silicon carbon composite material and negative electrode plate containing the same

Abstract

The present application relates to a silicon carbon composite material, which is a particle comprising a porous carbon skeleton, a silicon-containing deposition layer, and a carbon-containing coating layer, the silicon-containing deposition layer being in the pores of the porous carbon skeleton, the carbon-containing coating layer being on the silicon-containing deposition layer and / or on the particle surface, and the silicon carbon composite material has an oil absorption value of 35mL / 100g to 80mL / 100g. The silicon carbon composite material of the present application has a high energy density and an improved cycle life. The present application further relates to a negative electrode plate, a secondary battery, a battery module, a battery pack, and a power consumption device comprising the material.

Description

[Technical field]

[0001] The present application relates to the field of lithium battery technology, in particular to a silicon carbon composite material. The present application further relates to a negative plate, a secondary battery, a battery module, a battery pack and a power consuming device comprising the silicon carbon composite material. [Background technology]

[0002] Due to the wide application of lithium-ion secondary batteries in the field of energy storage, the energy density and long-term performance of lithium-ion secondary batteries have attracted much attention in the field, and much work has been done in this field, including the improvement of materials. Silicon carbon composite materials are popular due to their high energy density and other characteristics. However, silicon-based materials have high surface activity and are prone to side reactions after contact with electrolyte, both of which affect the interfacial stability of the electrode plate, so that the capacity of the material is easily attenuated after multiple cycles, and the service life of the material and the battery is shortened.

[0003] Therefore, there is a pressing need in the field for materials with high energy density and long cycle life. Summary of the Invention

[0004] The present application has been made in view of the above problems, and its object is to provide a silicon carbon composite material and a negative electrode plate containing the material. The silicon carbon composite material of the present application has few side reactions and a long cycle life, so that the secondary battery has good energy density and cycle life.

[0005] According to a first aspect of the present application, there is provided a silicon carbon composite material, the silicon carbon composite material being a particle comprising a porous carbon skeleton, a silicon-containing deposition layer, and a carbon-containing coating layer, the silicon-containing deposition layer being present in the pores of the porous carbon skeleton, the carbon-containing coating layer being present on the silicon-containing deposition layer and / or on the particle surface, and the silicon carbon composite material having an oil absorption value of 35mL / 100g to 80mL / 100g. The silicon carbon composite material of the present application can provide a secondary battery with good energy density and cycle life.

[0006] In any embodiment, the silicon carbon composite material has an oil absorption value of 45mL / 100g to 70mL / 100g, optionally 48mL / 100g to 62mL / 100g. By controlling the oil absorption value of the material within the above range, the energy density and cycle life can be further improved.

[0007] In any embodiment, the silicon content of the particle center of the silicon carbon composite is ≧10 wt%, optionally ≧15 wt%, and further optionally 20 wt% to 35 wt%, based on the total weight of the particle, where the silicon content of the particle center is obtained by ion-polishing the material to obtain a particle cross-section, selecting a cross-section whose major axis length is equal to the volume average particle diameter of the particle, and determining the silicon content at the major axis midpoint on the selected cross-section. The silicon carbon composite of the present application is less likely to react with the electrolyte, thereby improving cycle life.

[0008] In any embodiment, the porous carbon skeleton has a through-hole structure and has an oil absorption value of ≧100 mL / 100 g, optionally ≧120 mL / 100 g, further optionally ≧150 mL / 100 g and ≦190 mL / 100 g, optionally the porous carbon skeleton has an oil absorption value of 136 mL / 100 g to 179 mL / 100 g. Such a porous carbon skeleton is advantageous for a silicon deposition layer to be distributed inside the material particles, thereby contributing to improving energy density and cycle life.

[0009] In any embodiment, the silicon carbon composite material comprises 20% to 60% by weight, optionally 30% to 50% by weight, and further optionally 35% to 45% by weight of silicon, based on the total weight of the silicon carbon composite material, which can provide the material with good energy density and cycle performance.

[0010] In any embodiment, the carbon-containing coating layer comprises 3 wt% to 10 wt%, optionally 3.5 wt% to 7 wt%, and further optionally 4 wt% to 6 wt%, based on the total weight of the silicon carbon composite. By controlling the content of the carbon coating layer, the cycle life can be further improved.

[0011] In any embodiment, the oil absorption value X1 of the porous carbon skeleton, the oil absorption value X2 of the silicon carbon composite, the weight percentage Y1 of silicon in the silicon carbon composite, and the weight percentage Y2 of the carbon coating layer are JPEG2025515835000002.jpg22161k is any value between 100 and 250, optionally between 130 and 180. Such silicon carbon composite materials combine good energy density with long cycle life.

[0012] According to a second aspect of the present application there is further provided a silicon carbon composite material, the silicon carbon composite material comprising: i) providing a porous carbon skeleton, the porous carbon skeleton having a through-hole structure and an oil absorption value of > 100 mL / 100 g and < 190 mL / 100 g; ii) performing chemical vapor deposition using a silicon-containing gas source to form a silicon-containing deposition layer in the pores of the porous carbon skeleton to obtain an intermediate material; and step iii) of forming a carbon-containing coating layer on the silicon-containing deposition layer of the intermediate material and / or on the particle surface of the porous carbon skeleton to obtain the particulate silicon-carbon composite material, the carbon-containing coating layer occupying 3% by weight to 10% by weight based on the total weight of the silicon-carbon composite material; Here, the silicon carbon composite material has an oil absorption value of 35 mL / 100 g to 80 mL / 100 g, and provides a secondary battery with good energy density and cycle life.

[0013] In any embodiment, the silicon carbon composite material has an oil absorption value of 45mL / 100g to 70mL / 100g, optionally 48mL / 100g to 62mL / 100g. By controlling the oil absorption value of the material within the above range, the energy density and cycle life can be further improved.

[0014] In any embodiment, the silicon content of the particle center of the silicon carbon composite material is ≧10 wt%, optionally ≧15 wt%, and further optionally 20 wt% to 35 wt%, based on the total weight of the particle, where the silicon content of the particle center is obtained by the following method: selecting a cross section of the particle obtained by ion-polishing the material, the cross section having a major axis length equal to the volume average particle diameter of the particle, and determining the silicon content at the major axis midpoint on the selected cross section. In this way, the cycle life can be further improved.

[0015] In any embodiment, the porous carbon skeleton has an oil absorption value of ≧120 mL / 100 g, optionally ≧150 mL / 100 g, and optionally the porous carbon skeleton has an oil absorption value of between 136 mL / 100 g and 179 mL / 100 g, thus contributing to further improving energy density and cycle life.

[0016] In any embodiment, the silicon carbon composite material comprises 20% to 60% by weight, optionally 30% to 50% by weight, and further optionally 35% to 45% by weight of silicon, based on the total weight of the silicon carbon composite material, which allows the material to have good gram capacity and cycling performance.

[0017] In any embodiment, the carbon-containing coating layer comprises 3.5 wt% to 7 wt%, and optionally 4 wt% to 6 wt%, based on the total weight of the silicon carbon composite. By controlling the content of the carbon coating layer, the cycle life can be further improved.

[0018] In any embodiment, the oil absorption value X1 of the porous carbon skeleton, the oil absorption value X2 of the silicon carbon composite, the weight percentage Y1 of silicon in the silicon carbon composite, and the weight percentage Y2 of the carbon coating layer are JPEG2025515835000003.jpg22161k is any value between 100 and 250, optionally between 130 and 180. Such silicon carbon composite materials combine good energy density with long cycle life.

[0019] According to a third aspect of the present application, there is further provided a negative plate, the negative plate comprising a current collector and a negative material layer disposed on at least one surface of the current collector, the negative material layer comprising the silicon carbon composite material of the present application. The negative plate of the present application has good energy density and cycle performance.

[0020] In any embodiment, the negative electrode layer comprises 5% to 50% by weight, optionally 10% to 30% by weight, and further optionally 15% to 25% by weight of the silicon carbon composite material, based on the total weight of the negative electrode layer, thus further improving the performance of the plate.

[0021] According to a fourth aspect of the present application, there is provided a secondary battery, the secondary battery comprising the silicon carbon composite material according to the first and second aspects of the present application or the negative electrode plate according to the third aspect.

[0022] According to a fifth aspect of the present application, there is provided a battery module, the battery module including the secondary battery according to the fourth aspect of the present application.

[0023] According to a sixth aspect of the present application, there is provided a battery pack, the battery pack including the battery module of the fifth aspect of the present application.

[0024] According to a seventh aspect of the present application, there is provided a power consumption device, the power consumption device including at least one selected from the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect, or the battery pack of the sixth aspect.

[0025] The silicon carbon composite materials of the present application have high energy density and significantly improved cycle life. [Brief description of the drawings]

[0026] [Figure 1] FIG. 2 is an ion-abrasive cross-sectional topographical analysis of a silicon carbon composite particle of one embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Diagram 3] FIG. 3 is an exploded view of the secondary battery shown in FIG. 2 according to an embodiment of the present application. [Figure 4] FIG. 1 is a schematic diagram of a battery module according to an embodiment of the present application. [Diagram 5] FIG. 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 6] FIG. 6 is an exploded view of the battery pack shown in FIG. 5 according to an embodiment of the present application. [Figure 7] 1 is a schematic diagram of a power consuming device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the silicon carbon composite material and its manufacturing method, negative electrode plate, secondary battery, battery module, battery pack and electric device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of structures that are actually the same may be omitted. This is to avoid the following description from becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and do not limit the subject matter described in the claims.

[0028] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also envisaged. It is noted that if 1 and 2 are listed as the minimum range values, and 3, 4, and 5 are listed as the maximum range values, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all envisaged. In this application, unless otherwise specified, a numerical range "a-b" represents a shorthand representation of any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is only a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0029] Unless otherwise stated, all the embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0030] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0031] Unless otherwise stated, all steps in this application may be performed in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b) to mean that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method may further include step (c) as mentioned above to mean that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0032] Unless otherwise specified, the terms "comprise" and "comprises" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may further include or include other ingredients not listed, or may include or include only the listed ingredients.

[0033] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied in the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and A and B are both true (or exist).

[0034] Based on the wide application of lithium-ion secondary batteries in the field of energy storage, the field pays great attention to their energy density and long-term performance, and much work has been done in this field, including the improvement of materials. Silicon carbon composite materials are popular due to their high energy density and other characteristics. However, silicon-based materials have high surface activity and are prone to side reactions after contact with electrolyte, which affects the stability of the electrode plate interface, and thus the capacity of the material is easily attenuated after multiple cycles, shortening the service life of the material and the battery.

[0035] Thus, there is a pressing need in the art for negative electrode active materials having high energy density and long cycle life.The present invention fulfills such need and provides related advantages.

[0036] Silicon Carbon Composites

[0037] In one embodiment of the present application, a silicon carbon composite is proposed, which is a particle comprising a porous carbon skeleton, a silicon-containing deposition layer, and a carbon-containing coating layer, the silicon-containing deposition layer being located in the pores of the porous carbon skeleton, the carbon-containing coating layer being located on the silicon-containing deposition layer and / or on the particle surface, and the silicon carbon composite has an oil absorption value of 35 mL / 100 g to 80 mL / 100 g.

[0038] The silicon carbon composite material of the present application can improve the energy density (e.g., gram capacity) and cycle life of lithium ion secondary batteries. Without wishing to be bound by any theory, this may be because the silicon carbon composite material of the present application, especially the carbon coating layer and the oil absorption value in the above range, can effectively reduce the electrolyte from entering and contacting the silicon-containing deposit layer in the material pores to cause side reactions, thereby significantly improving the cycle life of lithium ion secondary batteries.

[0039] In this specification, the term "oil absorption value" refers to the volume (mL) of 100g of silicon carbon composite material that absorbs organic solvent (e.g., dibutyl phthalate, acrylic ester). The oil absorption value can be measured with reference to the method described in GB / T3780.2-2007. The oil absorption value of a porous material can reflect the openness of the material pores. The higher the oil absorption value of the material, the more open the pores of the material are, and the easier it is for liquid (e.g., electrolyte) or gas (e.g., various gas source gases, such as silane gas for depositing silicon) to penetrate into the material through the pores.

[0040] In some embodiments, the silicon carbon composite material has an oil absorption value of 45mL / 100g to 70mL / 100g, optionally 48mL / 100g to 62mL / 100g. By controlling the oil absorption value of the material within the above range, the cycle life of the lithium ion secondary battery can be further improved.

[0041] In some embodiments, the silicon carbon composite has a particle center silicon content of ≧10 wt.%, optionally ≧15 wt.%, and optionally 20 wt.% to 35 wt.%, based on the total weight of the particle, wherein the particle center silicon content is obtained by ionically grinding the material to obtain a particle cross-section, selecting a cross-section whose major axis length is equal to the volume average particle size of the particle, and determining the silicon content at the major axis midpoint on the selected cross-section.

[0042] In this specification, the silicon content of the particle center refers to the silicon content of the central region inside the material particle (i.e., the region farthest from the particle surface).Compared to the silicon carbon composite material in the conventional technology, when the total silicon content is the same, the material of the present application has a high silicon content in the material particle center.Therefore, compared with the same kind of material in the conventional technology in which the silicon deposition layer mainly exists in a shallow layer, the silicon carbon composite material of the present application is less likely to react with the electrolyte, which is advantageous in improving cycle life.

[0043] In some embodiments, the particle center silicon content value may be an average value of the silicon content at the major axis midpoints on a number of selected cross sections.

[0044] As used herein, "major axis" means the straight line connecting the two most distant points on said cross-section of the particle. If the cross-section is circular, the major axis is the diameter.

[0045] In this specification, "volume average particle size (Dv50)" has a meaning known in the art and can be measured by using instruments and methods known in the art. For example, it can be determined by using a laser particle size analyzer, referring to GB / T 19077-2016 laser diffraction particle size distribution method.

[0046] In this specification, unless otherwise specified, the terms "wt. %, "wt. %, "%" or other similar expressions have the same meaning and all represent percentage by weight.

[0047] The silicon content at any one point within a particle of material can be measured by any suitable method known in the art, for example X-ray spectroscopy (EDS).

[0048] In some embodiments, the porous carbon skeleton has a through-hole structure and has an oil absorption value of ≧100 mL / 100g, optionally ≧120 mL / 100g, and further optionally ≧150 mL / 100g and ≦190 mL / 100g. In some embodiments, optionally, the porous carbon skeleton has an oil absorption value of ≦185 mL / 100g, and further optionally ≦180 mL / 100g. In some embodiments, optionally, the porous carbon skeleton has an oil absorption value of 136 mL / 100g to 179 mL / 100g. The porous carbon skeleton has an oil absorption value in the above range, and the pore patency in the particles is high, which is advantageous for silicon to be deposited inside the particles. In the present application, the silicon-containing deposition layer in the silicon carbon composite can be advantageously distributed throughout the bulk phase of the porous carbon skeleton material particles, and advantageously, the silicon precursor is easier to reach and deposit in the central region of the porous carbon skeleton particles.Compared with the situation in the prior art where silicon is deposited in large amounts on the particle surface, the silicon carbon composite of the present application is less likely to swell and powder particles during charging, which is advantageous for improving the cycle life of the battery.

[0049] As will be appreciated by those skilled in the art, in this application it is desirable for the oil absorption value of the porous carbon skeleton to be as high as possible, however, taking into consideration factors such as the stability of the structure of the porous carbon skeleton itself, the porous carbon skeleton may have an oil absorption value of 190 mL / 100 g or less.

[0050] As used herein, the term "through hole structure" means that the pores in the material particles interpenetrate each other and form a continuous network structure within the material particles.

[0051] In some embodiments, the porous carbon skeleton has a total pore volume of ≥ 1 cm 3 In some embodiments, the porous carbon skeleton has a macropore volume of ≦0.2 cm 3 / g, mesopore volume ≥ 0.5 cm 3 / g, micropore volume ≦0.3 cm 3In some embodiments, the porous carbon skeleton has a molecular weight of 700 m 2 / g~1500 m 2 The specific surface area (BET) of 1000 nm / g is favorable for the deposition of silicon-containing deposits in the central region of the carbon skeleton, resulting in a high particle-centered silicon content, thereby improving the energy density and cycle performance of the material and the battery. In particular, the porous carbon skeleton has many mesopore structures, which is favorable for the uniform distribution of silicon deposits therein, and is favorable for improving the cycle life by providing sufficient space for the volume change during the cycle process of the silicon material.

[0052] In the present application, the porous carbon skeleton can be obtained from raw materials such as agricultural by-products (e.g., coconut shells, rice husks, straw, corn cobs, etc.), synthetic polymers (e.g., phenolic resins, epoxy resins), or natural polymers (e.g., starch, cellulose, lignin), by methods known in the art (e.g., carbonization).

[0053] In some embodiments, the silicon carbon composite material contains 20% to 60% by weight, optionally 30% to 50% by weight, further optionally 35% to 45% by weight, and further optionally 40% by weight of silicon based on the total weight of the silicon carbon composite material. The silicon carbon composite material of the present application contains the above content of silicon, which can ensure the gram capacity of the material and is also advantageous in maintaining the stability of the material structure (e.g., after charging and absorbing lithium, the volume expansion of silicon does not destroy the carbon skeleton structure and powderize), thereby having good cycle performance.

[0054] In some embodiments, the carbon-containing coating layer accounts for 3% to 10% by weight, optionally 3.5% to 7% by weight, further optionally 4% to 6% by weight, further optionally 5% by weight of the total weight of the silicon carbon composite material. The carbon coating layer in the above content range of the silicon carbon composite material of the present application is advantageous for controlling the oil absorption value within an ideal range, reducing the exposure of the pores of silicon already deposited in the material, reducing irreversible consumption due to the reaction between the silicon-containing deposition layer and the electrolyte, and further improving the cycle performance of the material. Without wishing to be bound by any theory, the carbon coating reduces the volume of the silicon carbon composite material that can be penetrated by the electrolyte and reduces the exposure of the silicon-containing deposition layer to the electrolyte, thereby effectively reducing the contact between the electrolyte and the silicon material in the pores, and improving the cycle life.

[0055] In some embodiments, in the silicon carbon composite of the present application, the oil absorption value X1 of the porous carbon skeleton, the oil absorption value X2 of the silicon carbon composite, the weight percentage Y1 of silicon in the silicon carbon composite, and the weight percentage Y2 of the carbon coating layer are: JPEG2025515835000004.jpg22161k is any number between 100 and 250, optionally between 130 and 180.

[0056] Such silicon carbon composites combine good energy density (eg, gram capacity) with long cycle life.

[0057] In some embodiments, the particles of the silicon carbon composite have a size of ≦0.6 cm as measured by nitrogen adsorption. 3 In some embodiments, the particles of the silicon carbon composite have a total pore volume of ≦0.1 cm 3 / g micropore, ≦0.3cm 3 / g mesopores, ≤0.1cm 3The silicon carbon composite material of the present application has a relatively high mesoporous structure content, and the silicon-containing deposition layer is uniformly distributed therein, and such a structure encapsulates silicon in the voids of the carbon skeleton through the carbon coating. The relatively high mesoporous content provides the expansion space for silicon, and the carbon coating prevents the electrolyte from entering the pores and contacting with silicon to cause side reactions, and further improves the cycle life.

[0058] As used herein, "micropores" are pores typically having a pore size smaller than about 2 nanometers, "mesopores" (also called "mesoporous") are pores typically having a pore size between about 2 nanometers and about 50 nanometers in diameter, and "macropores" are pores typically having a pore size greater than about 50 nanometers.

[0059] In some embodiments, the particles of the silicon carbon composite material are sized to be 1 m 2 / g~15m 2 / g, optionally 4m 2 / g~10m 2 / g, and optionally 6.5m 2 / g~7.5m 2 / g, and optionally 7 m 2 / g.

[0060] In some embodiments, the particles of the silicon carbon composite have a volume average particle size Dv50 of 5 μm to 15 μm, optionally 8 μm to 12 μm. In some embodiments, the silicon carbon composite further optionally has a Dv50 of 9.5 μm to 10.5 μm. In some embodiments, optionally, the silicon carbon composite has a Dv50 of 10 μm.

[0061] In another embodiment of the present application, there is provided a silicon carbon composite material, comprising: i) providing a porous carbon skeleton having a through-hole structure, the porous carbon skeleton having a through-hole structure and an oil absorption value of ≧100 mL / 100 g and ≦190 mL / 100 g; ii) forming a silicon-containing deposition layer in the pores of said porous carbon skeleton by chemical vapor deposition to obtain an intermediate material; and (iii) forming a carbon-containing coating layer on the silicon-containing deposition layer of the intermediate material and / or on the particle surfaces of the porous carbon skeleton to obtain the silicon-carbon composite material, the carbon-containing coating layer accounting for 3% by weight to 10% by weight based on the total weight of the silicon-carbon composite material; Here, the silicon carbon composite material has an oil absorption value of 35 mL / 100 g to 80 mL / 100 g. The silicon carbon composite material of the present application can provide a good cycle life to a secondary battery.

[0062] Without wishing to be bound by any theory, the advantage of using a porous carbon skeleton with a high oil absorption as a raw material in the present application is that the pores have a higher openness. Therefore, compared with similar materials without such an oil absorption in the prior art, the carbon skeleton with a high oil absorption in the present application is more advantageous for uniformly and penetratingly depositing silicon in the depths of the pores of the carbon skeleton and evenly to the center of the particles in a vapor phase growth manner. Then, the particle surface is coated with carbon to seal the silicon deposition layer in the voids and significantly reduce the oil absorption of the final material, thereby obtaining a silicon carbon composite material with a low oil absorption. The pore characteristics of the carbon skeleton of the silicon-containing deposition layer in the silicon carbon composite material thus obtained provide space for the volume change that may occur during cycling, and do not substantially affect the structural stability of the material, while the small oil absorption (i.e., low pore openness) of the carbon coating layer and the final material effectively reduces the electrolyte from entering the pores (especially inside the particles) in large amounts to interact with the silicon-containing deposition layer and cause side reactions. In summary, the silicon carbon composite material of the present application can reduce (or avoid) the structural instability caused by silicon expansion inside the material due to the structural characteristics of its raw carbon skeleton and the final material itself, and can reduce the occurrence of side reactions caused by contact between the electrolyte and the silicon material, so that the material of the present application has an improved cycle life.

[0063] As used herein, "chemical vapor deposition (CVD)" refers to the production of a non-volatile coating layer on a heated surface of a substrate (e.g., a porous carbon skeleton) by chemical reaction thereon using a gaseous compound or mixtures thereof.

[0064] In some embodiments, the silicon carbon composite material has an oil absorption value of 45mL / 100g to 70mL / 100g, optionally 48mL / 100g to 62mL / 100g. By controlling the oil absorption value of the material within the above range, the cycle life of the lithium ion secondary battery can be further improved.

[0065] In some embodiments, the silicon content of the particle center of the silicon carbon composite is ≧10 wt%, optionally ≧15 wt%, and further optionally 20 wt% to 35 wt%, based on the total weight of the particle, where the silicon content of the particle center is obtained by ion-polishing the material to obtain a particle cross section, selecting a cross section whose major axis length is equal to the volume average particle diameter of the particle, and determining the silicon content at the major axis midpoint on the selected cross section. The silicon carbon composite particles of the present application have a high silicon content and are less likely to react with the electrolyte, thereby improving cycle life.

[0066] In some embodiments, the porous carbon skeleton has an oil absorption value of ≧120 mL / 100 g, optionally ≧150 mL / 100 g, and optionally, the porous carbon skeleton has an oil absorption value of 136 mL / 100 g to 179 mL / 100 g. Such a porous carbon skeleton is favorable for a silicon deposition layer to be distributed inside the material particles, thereby contributing to improving energy density and cycle life.

[0067] In some embodiments, the silicon carbon composite material comprises 20% to 60% by weight, optionally 30% to 50% by weight, and further optionally 35% to 45% by weight of silicon, which can provide the material with good energy density and cycling performance.

[0068] In some embodiments, the carbon-containing coating layer comprises 3.5% to 7% by weight, optionally 4% to 6% by weight, based on the total weight of the silicon carbon composite. By controlling the content of the carbon coating layer, the cycle life can be further improved.

[0069] In some embodiments, the silicon carbon composite has an oil absorption value X1 of the porous carbon skeleton, an oil absorption value X2 of the silicon carbon composite, a weight percentage Y1 of silicon in the silicon carbon composite, and a weight percentage Y2 of the carbon coating layer. JPEG2025515835000005.jpg22161k is any value between 100 and 250, optionally between 130 and 180. Such silicon carbon composite materials combine good energy density with long cycle life.

[0070] In another embodiment of the present application, there is provided a method for producing a silicon carbon composite material, comprising: i) providing a porous carbon skeleton having a through-hole structure, the porous carbon skeleton having a through-hole structure and an oil absorption value of ≧100 mL / 100 g and ≦190 mL / 100 g; ii) forming a silicon-containing deposition layer in the pores of said porous carbon skeleton by chemical vapor deposition to obtain an intermediate material; and iii) forming a carbon-containing coating layer on the silicon-containing deposit layer of the intermediate material and / or on the surface of the particles of the porous carbon skeleton to obtain the silicon-carbon composite material, wherein the carbon-containing coating layer accounts for 3 wt. % to 10 wt. % based on the total weight of the silicon-carbon composite material; Here, the silicon carbon composite material has an oil absorption value of 35mL / 100g to 80mL / 100g. According to the method of the present application, a silicon carbon composite material having a significantly improved cycle life and good energy density can be produced and obtained.

[0071] In some embodiments, the silicon carbon composite has an oil absorption value from 45 mL / 100 g to 70 mL / 100 g, optionally from 48 mL / 100 g to 62 mL / 100 g.

[0072] In some embodiments, the porous carbon skeleton has an oil absorption value of ≧120 mL / 100 g, optionally ≧150 mL / 100 g, and ≦190 mL / 100 g. In some embodiments, the porous carbon skeleton has an oil absorption value of 136 mL / 100 g to 179 mL / 100 g. Such a carbon skeleton is favorable for the silicon precursor in step ii) to be deposited in large amounts in the interior (and thus in the central region) of the porous carbon skeleton, so that the final material has a good gram capacity and improves the cycling performance of the battery.

[0073] In some embodiments, the chemical vapor deposition in step ii) is carried out in the presence of a silicon-containing gas source. In some embodiments, the silicon-containing gas source may be selected from any silicon-containing gas source commonly used in the art for chemical vapor deposition. In some embodiments, the silicon-containing gas source is selected from at least one of silane, silicon tetrachloride, and optionally silane. In some embodiments, the silicon-containing gas source may be used in a mixture with an inert gas (e.g., nitrogen). In the case of a mixed gas, the content of silane is about 5% by weight to 100% by weight based on the total weight of the mixed gas. In some embodiments, the intake rate of the silicon-containing gas source in step ii) is 2-8 L / min, optionally 3-5 L / min, and further optionally 4 L / min.

[0074] In some embodiments, the chemical vapor deposition in step ii) is performed at a deposition temperature between 300° C. and 800° C. In some embodiments, the chemical vapor deposition in step ii) is performed for 5-15 hours, optionally for 8-12 hours, optionally for 10 hours.

[0075] In some embodiments, the chemical vapor deposition in step ii) is performed under turnover conditions.

[0076] In some embodiments, the method of the present application further comprises, after step ii) and before step iii), subjecting the intermediate material to surface micro-oxidation, said surface micro-oxidation being carried out by introducing at least one of air, carbon dioxide, carbon monoxide and water vapor into the intermediate material at an elevated temperature, the temperature being determinable by one skilled in the art.

[0077] In some embodiments, step iii) is performed by coating or chemical vapor deposition.

[0078] In the case of coating, the coating is, for example, coating a layer of graphite, graphene, hard carbon or soft carbon on the particle surface of the intermediate material. Alternatively, the particle surface of the intermediate material may be sprayed with a coating layer of a precursor material (e.g., asphalt) known in the art, and then carbonized. In some embodiments, the loading amount of the coating layer of the precursor material is 5-15 wt %, optionally 7-9 wt %, and further optionally 8 wt %, based on the total weight of the intermediate material. The coating amount within the above range is advantageous for achieving a good coating effect.

[0079] In some embodiments, the precursor material is asphalt, optionally with a softening point of 200° C. or less, and further optionally with a softening point of 150-160° C. Asphalt with a softening point within this range is more likely to spread over the particle surface during the coating process, contributing to a good coating effect. In the case of chemical vapor deposition, the chemical vapor deposition is carried out in the presence of a carbon-containing gas source. In some embodiments, the carbon-containing gas source may be selected from any carbon-containing gas source commonly used for chemical vapor deposition in the art. In some embodiments, the carbon-containing gas source is selected from at least one of methane, ethane, ethylene, and acetylene.

[0080] Chemical vapor deposition is carried out in reactors known in the art, such as fluidized bed reactors, static bed reactors, and the like.

[0081] In some embodiments, the chemical vapor deposition in step iii) is performed at a temperature between 800° C. and 1200° C. In some embodiments, the chemical vapor deposition in step iii) has an intake rate of the carbon-containing gas source of 1-5 L / min, optionally 1-3 L / min, and further optionally 2 L / min. In some embodiments, the chemical vapor deposition in step iii) is performed for 1-3 hours.

[0082] Negative plate

[0083] In a further embodiment of the present application, there is provided a negative electrode plate, comprising a current collector and a negative electrode material layer disposed on at least one surface of the current collector, the negative electrode material layer comprising the silicon carbon composite material of the present application or the silicon carbon composite material obtainable by the method of the present application.

[0084] In some embodiments, the negative electrode layer contains 5 wt% to 50 wt%, optionally 15 wt% to 25 wt%, and further optionally 20 wt% of the silicon carbon composite material based on the total weight of the negative electrode layer. The negative electrode layer contains a carbon-based negative electrode active material in this content range, so that the secondary battery can achieve both a long cycle life and good energy density.

[0085] In some embodiments, the negative electrode layer further comprises 5 wt% to 50 wt% of a carbon-based negative electrode active material based on the total weight of the negative electrode layer, and the negative electrode layer contains the carbon-based negative electrode active material in this content range, so that the secondary battery can achieve both a long cycle life and good energy density.

[0086] For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0087] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, a copper foil may be used as the metal foil sheet. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0088] The present application is not limited to these materials, and may further use other conventional materials that can be used as negative electrode active materials in batteries.

[0089] In some embodiments, the negative electrode membrane layer optionally further comprises an adhesive, which 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).

[0090] In some embodiments, the negative electrode membrane layer optionally further comprises 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.

[0091] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)).

[0092] In some embodiments, the negative electrode plate may be manufactured by the following method: The above-mentioned components for manufacturing the negative electrode plate, such as the negative electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, and the negative electrode slurry is coated on a negative electrode current collector, followed by processes such as drying and cold pressing to obtain a negative electrode plate.

[0093] Secondary batteries, battery modules, battery packs and power consuming devices

[0094] In a further embodiment of the present application, a secondary battery is provided, the secondary battery including the silicon carbon composite material of the present application or the negative electrode plate of the present application.

[0095] In a further embodiment of the present application, a battery module is provided, the battery module including the secondary battery of the present application.

[0096] In a further embodiment of the present application, a battery pack is provided, the battery pack including the battery module of the present application.

[0097] In a further embodiment of the present application, a power consuming device is provided, the power consuming device including at least one selected from the secondary battery, the battery module, and the battery pack of the present application.

[0098] The secondary battery, battery module, battery pack and power consuming device of the present application will be described below with appropriate reference to the drawings.

[0099] In one embodiment of the present application, a secondary battery is provided.

[0100] In some embodiments, the secondary battery is a lithium ion secondary battery.

[0101] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During charging and discharging of the battery, active ions shuttle between the positive electrode plate and the negative electrode plate, absorbing and releasing them. The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. The separator is installed between the positive electrode plate and the negative electrode plate, and mainly serves to prevent short-circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0102] [Positive plate]

[0103] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including the positive electrode active material of the first aspect of the present application.

[0104] For example, the positive electrode current collector has two opposing surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0105] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, an aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries that is well known in the art. For example, the positive electrode active material may include at least one material selected from the group consisting of lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as 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. Here, examples of lithium transition metal oxides include lithium cobalt oxides (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM 333 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3 O 2 (NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O 2 (NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811 Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O 2Examples of lithium-containing phosphates having an olivine structure include, but are not limited to, lithium iron phosphate (e.g., LiFePO 4 (which may be abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon, but are not limited thereto.

[0107] In some embodiments, the positive electrode membrane layer optionally further comprises an adhesive. For example, the adhesive may comprise at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0108] In some embodiments, the positive electrode membrane layer optionally further comprises a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, by way of example.

[0109] In some embodiments, the positive electrode plate may be manufactured by the following method: The above-mentioned components for manufacturing the positive electrode plate, such as the positive electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, and the positive electrode slurry is coated on a positive electrode current collector, and the positive electrode plate is obtained through processes such as drying and cold pressing.

[0110] [Electrolytes]

[0111] The electrolyte serves to conduct ions between the positive and negative plates. The present application does not specifically limit the type of electrolyte, which can be selected according to need. For example, the electrolyte may be liquid, gel, or all solid.

[0112] In some embodiments, the electrolyte employs an electrolyte solution, the electrolyte solution including an electrolyte salt and a solvent.

[0113] 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(trifluoromethanesulfonate), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0114] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone.

[0115] In some embodiments, the electrolyte solution optionally further includes additives. For example, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve some performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high temperature or low temperature performance of the battery, etc.

[0116] [Separator]

[0117] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any well-known separator with a porous structure having good chemical stability and mechanical stability may be selected.

[0118] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multi-layer composite thin film, and there is no particular limitation. When the separator is a multi-layer composite thin film, the materials of each layer may be the same or different, and there is no particular limitation.

[0119] In some embodiments, the positive and negative plates and the separator may be fabricated into an electrode assembly by a winding or lamination process.

[0120] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0121] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0122] The present application is not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular or any other shape. For example, FIG. 2 shows a secondary battery 5 having a rectangular structure as an example.

[0123] In some embodiments, referring to FIG. 3, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected on the bottom plate, and the bottom plate and the side plate surround the bottom plate to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to actual specific needs.

[0124] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by one skilled in the art based on the application and capacity of the battery module.

[0125] Fig. 4 shows an example of a battery module 4. Referring to Fig. 4, in the battery module 4, the secondary batteries 5 may be arranged in sequence along the vertical direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed by fasteners.

[0126] Optionally, the battery module 4 may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0127] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by one skilled in the art based on the application and capacity of the battery pack.

[0128] 5 and 6 show an example of a battery pack 1. Referring to FIG. 5 and FIG. 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is provided to cover the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any manner.

[0129] The present application further provides a power consuming device, the power consuming device including at least one of the secondary battery, the battery module, or the battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., 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.), an electric train, a ship, a satellite, an energy storage system, etc.

[0130] The power consumption device can be selected as a secondary battery, a battery module, or a battery pack depending on the demands of the usage.

[0131] 7 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the power consuming device's demand for high power and high energy density of secondary batteries.

[0132] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such devices are generally required to be lightweight and may employ a secondary battery as a power source.

[0133] Working Example

[0134] The following describes the examples of the present application. The examples described below are illustrative and are only for interpreting the present application, and should not be understood as limitations on the present application. If no specific techniques or conditions are specified in the examples, they will be performed according to the techniques or conditions described in the technical literature or the product instructions. For reagents or instruments used, those without the manufacturer's name are all common products that can be purchased commercially.

[0135] Example 1

[0136] 1. Fabrication of silicon carbon composites

[0137] Specific surface area 1440m 2 / g, and the oil absorption value is 160 mL / 100 g. The porous carbon skeleton (whose total pore volume is 1.1 cm 3 / g, macropore 0.17cm 3 / g, mesopores 0.65cm 3 / g and micropore size 0.28cm 3 The porous carbon skeleton was heated to 600 °C, silane gas was introduced at 4 L / min, and vapor deposition was carried out for 10 h to obtain an intermediate material after silane deposition, which was then held at 600 °C and CO 2 The gas was introduced and the temperature change of the system was monitored. During that time, the temperature first rose to about 605°C and then dropped. When the temperature dropped below 605°C, CO 2 When the gas introduction was stopped, the surface micro-oxidation of the intermediate material was completed at this time. Finally, acetylene gas was introduced at 2 L / min at 950°C, and vapor phase growth was carried out for 2 hours to obtain a 5% carbon coating layer. Finally, the silicon carbon composite material of the present application was obtained.

[0138] 2. Manufacturing of negative plate

[0139] The silicon carbon composite material produced as described above, graphite, styrene butadiene rubber (SBR) as an adhesive, acrylic acid-acrylonitrile-acrylamide copolymer as an adhesive, Super P as a conductive agent, carbon nanotubes as conductive agents, and sodium carboxymethylcellulose were mixed in a mass ratio of 20:80:0.8:1:1:1:1:0.5 with water as a solvent to produce a negative electrode slurry (solid content about 55%). The negative electrode slurry was applied to a current collector copper foil (loading amount 7.2 mg / cm2). 2 ) was uniformly coated, dried, cold pressed, and slit to obtain a negative electrode plate.

[0140] 3. Manufacturing the positive electrode plate

[0141] A positive electrode slurry (solid content 76%) was produced by mixing lithium nickel cobalt manganese oxide (NCM811), conductive carbon (SP), and adhesive (PVDF) in a mass ratio of 97:1.5:1.5 with methylpyrrolidone (NMP) as a solvent. The positive electrode slurry was applied to a current collector aluminum foil (loading amount 18.7 mg / cm 2 ) was uniformly coated with the powder, and then dried, cold pressed, and slit to obtain a positive electrode plate.

[0142] 4. Battery manufacturing

[0143] LiPF in a mixed solution of ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio 1:1 at room temperature) 6 A solution with a concentration of 1 M was obtained as the electrolyte. The positive and negative plates manufactured as described above were stacked in the order of "positive plate-separator-negative plate" with a polyethylene (PE) separator in a low-humidity, constant-temperature room, wound, and placed in a case, which was then filled with the electrolyte to assemble a lithium-ion secondary battery.

[0144] 5. Oil absorption test

[0145] The method described in the national standard GB / T 3780.2-2007 was used as a reference, and the instrument method A was adopted. The test sample weight was 20g, and dibutyl phthalate (DBP) was used as the reagent.

[0146] 6. X-ray spectroscopy (EDS) testing

[0147] The electrode plate to be measured was cut into a sample measuring 6 mm x 6 mm, placed on a CP sample stage (the sample should protrude within 1 mm from the sample stage), and cut at a voltage of 7.5 KV for approximately 30 min (the time can be appropriately adjusted depending on the material and thickness of the sample) to obtain a sample that had undergone ion polishing.

[0148] The silicon content in the central region of the silicon carbon composite particles was measured according to the method described in GB / T 17359-2012. The electrode plate samples that had undergone the above ion polishing were examined using a field emission scanning electron microscope (Zeiss Sigma300). Four particle cross sections of the silicon carbon composite material with the long axis length equal to the material Dv50 within the electron microscope field were randomly selected, and the silicon content was tested by EDS at the long axis midpoint on each cross section, and the average value was calculated.

[0149] FIG. 1 shows the ion-polished cross-sectional topography analysis of the electrode plate sample, in which four grain cross sections, each with a major axis equal to Dv50, were selected, and the silicon content of the grain center at the major axis center on each selected cross section (the test points correspond to the spectrum diagrams 1-4 shown in FIG. 1, respectively) was tested.

[0150] 7. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP) Test--Silicon Content of Whole Silicon Carbon Composite

[0151] The material sample was placed in a decomposition tank, mixed acid of concentrated nitric acid / hydrofluoric acid was added, and the sample was decomposed in a microwave decomposition device. The silicon content of the decomposed sample solution was tested using an inductively coupled plasma emission spectrometer.

[0152] 8. Material Gram Capacity Test

[0153] Using the method described above, one side of a negative electrode plate was coated, which was then punched out into small slices with a diameter of 14 mm. The battery was then assembled with a separator and a lithium sheet to form a button battery. The gram capacity was then tested using the following method, with calculations based on 1C=600mAh / g.

[0154] The button battery was discharged to 5mV at a rate of 0.05C, further discharged to 5mV at 50μA, and then further discharged to 5mV at 10μA. After leaving the battery stationary for 5min, the battery was charged to 2V at 0.1C. The battery capacity at this time was detected. The ratio of the capacity to the weight of the active material in the plate was calculated to obtain the gram capacity of the active material.

[0155] 9. Cycle life test

[0156] At an ambient temperature of 25°C, the battery was first discharged at a constant current of 0.33C to 2.7V, left for 5 minutes, then charged at a constant current of 0.5C to 4.2V, then charged at a constant voltage of 4.2V to 0.05C, left for 5 minutes, and then discharged at a constant current of 0.33C to 2.7V. This was the first cycle, and the battery capacity at this time was measured and designated as C1. The above steps were repeated until the capacity decreased to 80% of C1, and the number of cycles at this time was designated as the cycle life.

[0157] 10. Volume average particle size (Dv50) test

[0158] Take a clean beaker, add an appropriate amount of the sample to be measured, dropwise add surfactant and then add dispersant, and use 120W / 5min ultrasonic to ensure that the sample is completely dispersed in the dispersant. Use Marvin 3000 laser particle size analyzer to test the particle size distribution characteristics of the sample and obtain Dv50.

[0159] Example 2

[0160] The same manufacturing and testing methods as in Example 1 were used. The difference is that the specific surface area of ​​the porous carbon skeleton is 750 m 2 / g, oil absorption value is 155 mL / 100 g, and total pore volume is 1.02 cm 3 / g, and the macropores are 0.16 cm 3 / g, and the mesopores are 0.6 cm 3 / g, and the micropore size is 0.26 cm 3 / g.

[0161] Example 3

[0162] The same manufacturing and testing methods as in Example 1 were used. The difference is that the specific surface area of ​​the porous carbon skeleton is 1100 m 2 / g, oil absorption value is 158 mL / 100 g, and total pore volume is 1.15 cm 3 / g and macropores of 0.18 cm 3 / g, and the mesopores are 0.68 cm 3 / g, and the micropore size is 0.29 cm 3 / g.

[0163] Example 4

[0164] The same porous carbon skeleton, preparation method and test method as in Example 2 were adopted. The difference was that after obtaining the intermediate material after silane deposition, 8 wt% of softening point asphalt with a softening point of 160°C was added based on the total weight of the intermediate material, mixed uniformly, and carbonized in a nitrogen atmosphere to obtain a silicon carbon composite material with a 5% carbon coating.

[0165] Examples 5-10

[0166] The preparation and testing methods were the same as in Example 1. The difference is that the oil absorption values ​​of the carbon skeletons in Examples 5-10 are different (see Table 2 for details), and the oil absorption values ​​of the silicon carbon composite materials obtained are different. Table 1 below lists the relevant parameters of the carbon skeletons in each of the above examples.

[0167] Table 1 JPEG2025515835000006.jpg55153

[0168] Comparative Example 1-2

[0169] The same preparation and test methods as in Example 1 were adopted. The difference is that Comparative Example 1 was coated with 18% by weight asphalt and carbonized to obtain a silicon carbon composite material with about 10.8% carbon coating and low oil absorption, while Comparative Example 2 was coated with 5% by weight asphalt and the skeleton had too high an oil absorption, resulting in a silicon carbon composite material with about 3% carbon coating and high oil absorption.

[0170] Comparative Example 3

[0171] The same manufacturing and testing methods as in Example 1 were used, with the difference being that the specific surface area of ​​the porous carbon skeleton was 20 m 2 / g, oil absorption value is 80 mL / 100 g, and total pore volume is 0.22 cm 3 / g, and the macropores are 0.07 cm 3 / g, and mesopores are 0.09 cm 3 / g, and the micropore size is 0.06 cm 3 / g.

[0172] Comparative Example 4

[0173] The porous carbon scaffold, preparation method and test method were adopted as in Example 1. The difference is that the obtained silicon carbon composite material did not undergo carbon coating.

[0174] Comparative Example 5

[0175] The same porous carbon skeleton, preparation method and test method as in Example 1 were adopted. The difference was that after obtaining the intermediate material after silane deposition, CO 2 Finally, 2% by weight of asphalt with a softening point of 250°C was added based on the total weight of the intermediate material, mixed uniformly, and carbonized in a nitrogen atmosphere to obtain a silicon carbon composite material with a carbon coating of about 1.2%.

[0176] Comparative Example 6

[0177] 60nm nanometer silicon powder and emulsion asphalt were uniformly mixed and sprayed at 180℃ to produce 10um solidified particles, which were then placed in asphalt with a softening point of 90℃, impregnated with asphalt to densify, and then carbonized at 1150℃ to produce a silicon carbon composite material with a diameter of 10um encapsulating nanometer silicon particles.

[0178] Table 2 shows the above examples and comparative examples.

[0179] Table 2 JPEG2025515835000007.jpg122153

[0180] * The silicon content at the particle center was obtained by the following method: the material was ion-polished to obtain a particle cross section, and a cross section whose major axis length was equal to the volume average particle diameter of the particle was selected from the cross section, and the silicon content at the midpoint of the major axis on the selected cross section was determined. Four cross sections were taken to measure the silicon content at the particle center, and the average value was calculated. The values ​​shown in the table are average values. In the above table, the particle size of the silicon carbon composite material is all around 10 μm.

[0181] JPEG2025515835000008.jpg16161, where X1 is the oil absorption value of the porous carbon skeleton, X2 is the oil absorption value of the silicon carbon composite, Y1 is the total weight percentage of silicon in the silicon carbon composite, and Y2 is the weight percentage of the carbon coating layer.

[0182] As can be seen from Table 2, in the silicon carbon composite of the present application, the porous carbon skeleton has a large oil absorption value, but the final composite has a small oil absorption value, and the silicon distribution in the particles of the silicon carbon composite of the present application is uniform, especially the silicon content in the central region is high, so that it has good overall performance--high gram capacity and long cycle life.

[0183] Examples 11-14

[0184] According to Example 1, the porous carbon skeleton and silicon carbon composite materials prepared therewith shown in Table 3 were adopted to test the performance. Table 3 shows the effect of the overall silicon content in the material on the performance.

[0185] Table 3 JPEG2025515835000009.jpg61153

[0186] As can be seen from Table 3, when the total silicon content in the silicon carbon composite is 20-60 wt%, the amount of silicon carbon composite required for recombination with graphite is moderate, thereby reducing side reactions and improving cycle performance.

[0187] The silicon content in the central region of the silicon carbon composite particle is within the range of the present application, and the carbon skeleton can constrain the expansion of the silicon, which is advantageous for improving the cycle performance.

[0188] Examples 15-19

[0189] Silicon carbon composite materials were prepared using a similar preparation method to that of Example 1, where silicon carbon composite materials with different carbon coating amounts were obtained by controlling the vapor phase growth time of acetylene gas in step 3. Table 4 shows the effect of different carbon coating amounts on the performance.

[0190] Table 4 JPEG2025515835000010.jpg50155

[0191] As can be seen from Table 4, when the silicon carbon composite material of the present application has the above carbon coating amount, it has good energy density and cycle life.

[0192] Table 5 shows the results of tests on the silicon content of the whole particle and the central region of the silicon carbon composite materials in Example 1 (see FIG. 1) of the present application, Comparative Example 3 and Comparative Example 6 (including the measurement of the silicon content (wt%) at the center of the particle of each of four randomly selected cross sections whose major axis length is equal to the particle Dv50, and the calculation of the average value).

[0193] Table 5 JPEG2025515835000011.jpg50153

[0194] As can be seen from Table 5, the silicon content of the particle center of the silicon carbon composite material of Example 1 of the present application is high, and the distribution of the silicon content of the particle center of different particles is more uniform. The low silicon content of the particle center of the material of Comparative Example 3 indicates that when the total silicon content is the same as that of the material of Example 1, the silicon deposition layer is more distributed in the shallow surface layer of the material particles, and as can be seen from Table 2, its gram capacity and cycle life are both low. In Comparative Example 6, the silicon content of the particle center is also high, but because there is no carbon coating layer, its cycle life is poor, as can be seen from Table 2.

[0195] It should be noted that the present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is an example, and any embodiment having substantially the same configuration as the technical idea and achieving the same effect within the scope of the technical proposal of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiment and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application, within the scope of the purpose of the present application. [Explanation of symbols]

[0196] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate

Claims

1. 1. A silicon carbon composite material comprising particles comprising a porous carbon skeleton, a silicon-containing deposition layer, and a carbon-containing coating layer, the silicon-containing deposition layer being in pores of the porous carbon skeleton and the carbon-containing coating layer being on the silicon-containing deposition layer and / or on a surface of the particles, the silicon carbon composite having an oil absorption value of 35 mL / 100 g to 80 mL / 100 g.

2. 2. The silicon carbon composite of claim 1, wherein the silicon carbon composite has an oil absorption value from 45 mL / 100 g to 70 mL / 100 g, optionally from 48 mL / 100 g to 62 mL / 100 g.

3. 3. The silicon carbon composite material of claim 1, wherein the particle center silicon content of the silicon carbon composite is ≧10 wt.%, optionally ≧15 wt.%, and further optionally 20 wt.% to 35 wt.%, based on the total weight of the particle, wherein the particle center silicon content is obtained by ionically grinding the material to obtain a particle cross section, selecting a cross section whose major axis length is equal to the volume average particle size of the particle, and determining the silicon content at the major axis midpoint on the selected cross section.

4. 4. The silicon carbon composite material of any one of claims 1 to 3, wherein the porous carbon skeleton has a through-hole structure and an oil absorption value of ≧100 mL / 100g, optionally ≧120 mL / 100g, further optionally ≧150 mL / 100g and ≦190 mL / 100g, optionally the porous carbon skeleton has an oil absorption value of from 136 mL / 100g to 179 mL / 100g.

5. 5. The silicon carbon composite of claim 1, wherein the silicon carbon composite comprises from 20% to 60% by weight, optionally from 30% to 50% by weight, and further optionally from 35% to 45% by weight, silicon, based on the total weight of the silicon carbon composite.

6. 6. The silicon carbon composite material of any one of claims 1 to 5, wherein the carbon-containing coating layer comprises from 3 wt% to 10 wt%, optionally from 3.5 wt% to 7 wt%, and further optionally from 4 wt% to 6 wt%, based on the total weight of the silicon carbon composite.

7. The oil absorption value X1 of the porous carbon skeleton, the oil absorption value X2 of the silicon carbon composite material, the weight percentage Y1 of silicon in the silicon carbon composite material, and the weight percentage Y2 of the carbon coating layer are 7. The silicon carbon composite material of claims 1 to 6, wherein k is any number between 100 and 250, optionally between 130 and 180.

8. 1. A silicon carbon composite material comprising: i) providing a porous carbon skeleton, the porous carbon skeleton having a through-hole structure and an oil absorption value of > 100 mL / 100 g and < 190 mL / 100 g; ii) performing chemical vapor deposition using a silicon-containing gas source to form a silicon-containing deposition layer in the pores of the porous carbon skeleton to obtain an intermediate material; and (iii) forming a carbon-containing coating layer on the silicon-containing deposition layer of the intermediate material and / or on the particle surfaces of the porous carbon skeleton to obtain the particulate silicon-carbon composite material, wherein the carbon-containing coating layer accounts for 3% by weight to 10% by weight based on the total weight of the silicon-carbon composite material; Here, the silicon carbon composite material has an oil absorption value of 35 mL / 100 g to 80 mL / 100 g.

9. 9. The silicon carbon composite of claim 8, wherein the silicon carbon composite has an oil absorption value from 45 mL / 100 g to 70 mL / 100 g, optionally from 48 mL / 100 g to 62 mL / 100 g.

10. 10. The silicon carbon composite material of claim 8 or 9, wherein the particle center silicon content of the silicon carbon composite is ≧10 wt%, optionally ≧15 wt%, and further optionally 20 wt% to 35 wt%, based on the total weight of the particle, wherein the particle center silicon content is obtained by ionically grinding the material to obtain a particle cross-section, selecting a cross-section whose major axis length is equal to the volume average particle size of the particle, and determining the silicon content at the major axis midpoint on the selected cross-section.

11. 11. The silicon carbon composite material of any one of claims 8 to 10, wherein the porous carbon skeleton has an oil absorption value of ≧120 mL / 100g, optionally ≧150 mL / 100g, optionally the porous carbon skeleton has an oil absorption value of from 136 mL / 100g to 179 mL / 100g.

12. 12. The silicon carbon composite of any one of claims 8 to 11, wherein the silicon carbon composite comprises 20% to 60% by weight, optionally 30% to 50% by weight, and further optionally 35% to 45% by weight of silicon, based on the total weight of the silicon carbon composite.

13. 13. The silicon carbon composite material of any one of claims 8 to 12, wherein the carbon-containing coating layer comprises from 3.5 wt% to 7 wt%, optionally from 4 wt% to 6 wt%, based on the total weight of the silicon carbon composite material.

14. The oil absorption value X1 of the porous carbon skeleton, the oil absorption value X2 of the silicon carbon composite material, the weight percentage Y1 of silicon in the silicon carbon composite material, and the weight percentage Y2 of the carbon coating layer are 14. The silicon carbon composite material of claims 8 to 13, wherein k is any number between 100 and 250, optionally between 130 and 180.

15. 15. A negative electrode plate comprising: a current collector; and a negative electrode material layer disposed on at least one surface of the current collector, the negative electrode material layer comprising the silicon carbon composite material of claim 1.

16. 16. The negative electrode plate of claim 15, wherein the negative electrode layer comprises 5% to 50% by weight, optionally 10% to 30% by weight, and further optionally 15% to 25% by weight of the silicon carbon composite material, based on the total weight of the negative electrode layer.

17. A secondary battery comprising the silicon carbon composite material according to any one of claims 1 to 14 or the negative electrode plate according to any one of claims 15 to 17.

18. A battery module comprising the secondary battery according to claim 17.

19. A battery pack comprising the battery module according to claim 18.

20. A power consuming device comprising at least one selected from the group consisting of the secondary battery according to claim 17, the battery module according to claim 18, and the battery pack according to claim 19.

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