A negative electrode material, a carbon frame material and a preparation method thereof

Abstract

The present application relates to a negative electrode material, including a carbon framework material and a negative electrode active substance. The carbon framework material includes a three-dimensional network skeleton. The negative electrode active substance is distributed in the three-dimensional network skeleton of the carbon framework material. The negative electrode active substance includes a carbonaceous material. The carbon framework material has a three-dimensional network skeleton and has strong compressive resistance. By encapsulating and isolating the negative electrode active substance cage in the three-dimensional network skeleton, the porous structure in the skeleton can be used as a buffer layer to fully absorb and weaken the uneven stress released by the lithium insertion and delithiation of the negative electrode active substance. Since the uneven stress is evenly dispersed, the stress superposition effect between the negative electrode active substances is also weakened accordingly. Therefore, the negative electrode expansion rate is reduced macroscopically, thereby improving the cycle storage performance of the battery cell. The present application also relates to a carbon framework material and a preparation method thereof, a negative electrode pole piece and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device.

Description

Technical Field

[0001] The present application relates to the field of secondary batteries, and specifically to a negative electrode material, a carbon frame material and a preparation method thereof, a negative electrode plate and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device. Background Art

[0002] With the development of technology, clean energy such as batteries are gradually replacing traditional fossil energy and providing power for various scenarios. However, whether it is a square aluminum shell battery or a soft pack battery, it will swell during high-temperature storage or in the later stages of cycling. A large number of studies have shown that the expansion of the battery cell mainly comes from the expansion of the negative electrode.

[0003] Therefore, how to reduce the negative electrode expansion rate has become a technical problem that needs to be solved urgently in the battery field. Summary of the invention

[0004] In view of the problems existing in the background technology, the present application provides a negative electrode material, which can reduce the negative electrode expansion rate.

[0005] The negative electrode material provided in the first aspect of the present application includes a carbon framework material and a negative electrode active substance. The carbon framework material includes a three-dimensional network skeleton. The negative electrode active substance is distributed in the three-dimensional network skeleton of the carbon framework material. The negative electrode active substance includes a carbonaceous material.

[0006] In the technical solution of the embodiment of the present application, the carbon framework material has a three-dimensional network skeleton and strong compressive resistance. By encapsulating and isolating the negative electrode active material cage in the three-dimensional network skeleton, the porous structure in the skeleton can be used as a buffer layer to fully absorb and weaken the uneven stress released by the lithium insertion and removal of the negative electrode active material. Since the uneven stress is evenly dispersed, the stress superposition effect between the negative electrode active materials is also weakened accordingly, so the negative electrode expansion rate is reduced macroscopically, thereby improving the cycle storage performance of the battery cell.

[0007] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the mass ratio of the negative electrode active material to the carbon framework material is (86.5-96):(0.5-10).

[0008] In this design, by optimizing the mass ratio of the negative electrode active material to the carbon frame material, it is beneficial to reduce the negative electrode expansion rate and improve the cycle storage performance of the battery cell.

[0009] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein the mass ratio of the negative electrode active material to the carbon framework material is (91.5-95.5):(1-5).

[0010] In this design, by further optimizing the mass ratio of the negative electrode active material to the carbon framework material, it is beneficial to reduce the negative electrode expansion rate while ensuring that the gram capacity of the negative electrode plate is not affected. When the amount of carbon framework material is too large, a too thick skeleton coating will be formed around the negative electrode active material, resulting in a decrease in the lithium insertion and removal ability of the negative electrode active material (such as graphite), which in turn leads to a decrease in the gram capacity of the negative electrode plate. When the amount of carbon framework material is too small, it will not have the effect of reducing the negative electrode expansion rate.

[0011] In some embodiments, according to the first aspect, a third example of the first aspect is proposed, wherein the specific surface area of ​​the carbon frame material is 1000-3200 m 2 / g.

[0012] In this design, by optimizing the specific surface area of ​​the carbon framework material, it is beneficial for the carbon framework material to better cage-encapsulate and isolate the negative electrode active material, and is beneficial for the rapid transfer of charge. If the specific surface area is too small, it is not conducive to cage encapsulation and isolation, nor is it conducive to the rapid transfer of charge. If the specific surface area is too large, the production process is demanding and the production cost is high.

[0013] In some embodiments, according to the first aspect, a fourth example of the first aspect is provided, and the mesoporosity of the carbon framework material is 20%-85%.

[0014] In this design, by optimizing the mesoporosity of the carbon framework material, it is beneficial for the carbon framework material to better cage-encapsulate and isolate the negative electrode active material. If the mesoporosity is too small, the porous structure in the skeleton is mainly micropores, which cannot form a cage-encapsulation isolation for the negative electrode active material. Therefore, if the mesoporosity is too small, the carbon framework material cannot fully play the role of dispersing stress. If the mesoporosity is too large, the production process is demanding and the production cost is high.

[0015] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, the mass density of the carbon frame material is 0.15-0.5 mg / cm -2 .

[0016] In this design, by optimizing the mass density of the carbon frame material, the carbon frame material can reduce the expansion rate of the negative electrode without affecting the negative electrode's gram capacity, and has basically no effect on the overall weight of the battery cell.

[0017] In some embodiments, according to the first aspect, a sixth example of the first aspect is provided, wherein the compressive strength of the carbon frame material is 3-25 MPa.

[0018] In this design, the compressive strength of the carbon frame material is optimized, which helps to reduce the negative electrode expansion rate.

[0019] In some embodiments, according to the first aspect, a seventh example of the first aspect is provided, wherein the carbon framework material is carbon aerogel.

[0020] In this design, carbon aerogel has a three-dimensional network skeleton, large specific surface area, high porosity, low density, light material, and strong compressive resistance. It can evenly disperse the uneven stress released by the negative electrode active material due to lithium desorption and lithium insertion, effectively reduce the negative electrode expansion rate, and thus improve the cycle storage performance of the battery cell.

[0021] In some embodiments, according to the first aspect, an eighth example of the first aspect is provided, wherein the carbonaceous material includes at least one of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0022] The above-mentioned carbonaceous materials will release uneven stress during the process of lithium removal and lithium insertion, resulting in the expansion of the negative electrode. By using carbon framework materials to cage-encapsulate these carbonaceous materials, the expansion rate of the negative electrode is greatly reduced.

[0023] A second aspect of the present application provides a method for preparing a carbon framework material, comprising the following steps:

[0024] mixing aminopolysaccharide, eutectic molten salt and solvent to form a wet gel;

[0025] freeze-drying the wet gel to obtain a xerogel; and

[0026] The dry gel is carbonized to obtain a carbon framework material.

[0027] In the technical solution of the embodiment of the present application, the combined use of amino polysaccharides and eutectic molten salt can form a rich pore structure inside the carbon framework material, improve the pore consistency, and at the same time improve the compressive resistance of the carbon framework material.

[0028] In some embodiments, according to the second aspect, a first example of the second aspect is provided, wherein the eutectic molten salt comprises ZnCl 2 , any two salts from LiCl, KCl, and NaCl.

[0029] In this design, the eutectic molten salt has a low melting point and a wide temperature range, which can promote the development of a large number of micropores and mesopores, especially mesopores, in the carbon body.

[0030] In some embodiments, according to the second aspect, a second example of the second aspect is provided, wherein the mass ratio of the eutectic molten salt to the amino polysaccharide is (1-15):1.

[0031] In this design, by optimizing the mass ratio of eutectic molten salt to amino polysaccharide, it is beneficial to improve the pore richness, pore consistency and compressive resistance of the carbon framework material.

[0032] The third aspect of the present application provides a carbon framework material obtained by the preparation method described in the second aspect of the present application.

[0033] In the technical solution of the embodiment of the present application, the carbon framework material obtained by the preparation method described in the second aspect of the present application has high pore richness, high pore consistency and high compressive resistance.

[0034] The fourth aspect of the present application provides a negative electrode plate, comprising the negative electrode material described in the first aspect of the present application.

[0035] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the negative electrode plate of the present application can reduce the negative electrode expansion rate.

[0036] A fifth aspect of the present application provides a method for preparing a negative electrode sheet, comprising:

[0037] Mixing the negative electrode active material, the carbon framework material, the conductive agent, the binder, and the solvent to obtain a negative electrode slurry; and

[0038] The negative electrode slurry is coated on the negative electrode current collector and dried.

[0039] In the technical solution of the embodiment of the present application, the negative electrode sheet can be obtained by mixing, coating and drying raw materials such as negative electrode active materials and carbon framework materials. The preparation method is simple to operate, highly repeatable, and suitable for large-scale industrial applications.

[0040] The sixth aspect of the present application provides a secondary battery, comprising the negative electrode sheet described in the fourth aspect of the present application or the negative electrode sheet obtained according to the preparation method described in the fifth aspect of the present application.

[0041] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the secondary battery of the present application can reduce the negative electrode expansion rate.

[0042] A seventh aspect of the present application provides a battery module, comprising the secondary battery described in the sixth aspect of the present application.

[0043] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the battery module of the present application can reduce the negative electrode expansion rate.

[0044] The eighth aspect of the present application provides a battery pack, comprising the battery module described in the seventh aspect of the present application.

[0045] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the battery pack of the present application can reduce the negative electrode expansion rate.

[0046] The ninth aspect of the present application provides an electrical device, characterized in that it includes at least one of the secondary battery described in the sixth aspect of the present application, the battery module described in the seventh aspect of the present application, and the battery pack described in the eighth aspect of the present application.

[0047] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the electric device of the present application can reduce the negative electrode expansion rate.

[0048] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0050] Figure 1 Schematic diagram of carbon aerogel cage encapsulation and isolation of graphite active particles. DETAILED DESCRIPTION

[0051] In order to make the invention purpose, technical solution and beneficial technical effect of the present application clearer, the present application is described in detail below in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application, not for limiting the present application.

[0052] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0053] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and the "multiple" in "one or more" means more than two (including two).

[0054] The above-mentioned summary of the invention of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0055] With the development of technology, clean energy such as batteries are gradually replacing traditional fossil energy and providing power for various scenarios. However, whether it is a square aluminum shell battery or a soft pack battery, swelling will occur during high-temperature storage or in the later stages of cycling. A large number of studies have shown that the expansion of the battery cell mainly comes from the expansion of the negative electrode. Therefore, how to reduce the expansion rate of the negative electrode has become a technical problem that needs to be solved urgently in the battery field.

[0056] The researchers found that the root cause of the negative electrode expansion is the irreversible expansion caused by the negative electrode active materials such as lithium intercalation in graphite. This irreversible expansion comes from the uneven stress release of the lithium intercalated and delithiation graphite body. It is this continuous uneven stress release that leads to the destruction of the SEI film and the generation of side reactions, thereby reducing the electrochemical performance of the battery, especially the loss of cycle storage performance.

[0057] In order to solve the problem of negative electrode expansion caused by uneven stress release of negative electrode active materials, the inventors have designed a negative electrode material after in-depth research. The negative electrode material utilizes a three-dimensional network skeleton of a carbon framework material, which has strong compressive resistance. By encapsulating and isolating the negative electrode active material cage in the three-dimensional network skeleton, the porous structure in the skeleton can be used as a buffer layer to fully absorb and weaken the uneven stress released by the lithium insertion and removal of the negative electrode active material. Since the uneven stress is evenly dispersed, the stress superposition effect between the negative electrode active materials is also weakened accordingly, so the negative electrode expansion rate is reduced macroscopically, thereby improving the cycle storage performance of the battery cell.

[0058] The technical solution described in the embodiments of the present application is applicable to negative electrode materials, and is also applicable to carbon frame materials and their preparation processes, negative electrode sheets using negative electrode materials, preparation processes of negative electrode sheets, secondary batteries using negative electrode sheets, battery modules using secondary batteries, battery packs using battery modules, and electrical devices using at least one of secondary batteries, battery modules and battery packs.

[0059] In the first aspect, according to some embodiments of the present application, see Figure 1 The present application provides a negative electrode material including a carbon framework material and a negative electrode active substance. The carbon framework material includes a three-dimensional network skeleton. The negative electrode active substance is distributed in the three-dimensional network skeleton of the carbon framework material. The negative electrode active substance includes a carbonaceous material.

[0060] In the technical solution of the embodiment of the present application, by encapsulating and isolating the negative electrode active material cage in a three-dimensional network skeleton, the porous structure in the skeleton can act as a buffer layer to fully absorb and weaken the uneven stress released by the lithium insertion and delithiation of the negative electrode active material, thereby correspondingly weakening the stress superposition effect between the negative electrode active materials, thereby reducing the negative electrode expansion rate from a macroscopic perspective and improving the cycle storage performance of the battery cell.

[0061] In some specific embodiments, the carbon framework material includes a continuous three-dimensional network skeleton.

[0062] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the mass ratio of the negative electrode active material to the carbon framework material is (86.5-96):(0.5-10).

[0063] In this design, by optimizing the mass ratio of the negative electrode active material to the carbon frame material, it is beneficial to reduce the negative electrode expansion rate and improve the cycle storage performance of the battery cell.

[0064] In some specific embodiments, the mass ratio of the negative electrode active material to the carbon framework material can be, for example, 86.5:10, 87:9.5, 87.5:9, 88:8.5, 88.5:8, 89:7.5, 89.5:7, 90:6.5, 90.5:6, 91:5.5, 91.5:5, 92:4.5, 92.5:4, 93:3.5, 93.5:3, 94:2.5, 94.5:2, 95:1.5, 95.5:1 or 96:0.5.

[0065] In some embodiments, according to the first aspect, a second example of the first aspect is provided, and the mass ratio of the negative electrode active material to the carbon framework material may be (91.5-95.5):(1-5).

[0066] In this design, by further optimizing the mass ratio of the negative electrode active material to the carbon framework material, it is beneficial to reduce the negative electrode expansion rate while ensuring that the gram capacity of the negative electrode plate is not affected. When the amount of carbon framework material is too large, a too thick skeleton coating will be formed around the negative electrode active material, resulting in a decrease in the lithium insertion and removal ability of the negative electrode active material (such as graphite), which in turn leads to a decrease in the gram capacity of the negative electrode plate. When the amount of carbon framework material is too small, it will not have the effect of reducing the negative electrode expansion rate.

[0067] In some embodiments, according to the first aspect, a third example of the first aspect is proposed, wherein the specific surface area of ​​the carbon frame material is 1000-3200 m 2 / g.

[0068] In this design, by optimizing the specific surface area of ​​the carbon framework material, it is beneficial for the carbon framework material to better cage-encapsulate and isolate the negative electrode active material, and is beneficial for the rapid transfer of charge. If the specific surface area is too small, it is not conducive to cage encapsulation and isolation, nor is it conducive to the rapid transfer of charge. If the specific surface area is too large, the production process is demanding and the production cost is high.

[0069] In some specific embodiments, the specific surface area of ​​the carbon frame material may be, for example, 1000 m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g、1400m 2 / g、1500m 2 / g、1600m 2 / g、1700m 2 / g、1800m 2 / g、1900m 2 / g, 2000m 2 / g, 2100m 2 / g, 2200m 2 / g, 2300m 2 / g, 2400m 2 / g, 2500m 2 / g, 2600m 2 / g, 2700m 2 / g、2800m 2 / g、2900m 2 / g、3000m 2 / g、3100m 2 / g or 3200m 2 / g. Optionally, the specific surface area of ​​the carbon framework material may be 1500-3200m 2 / g, 2000-3200m 2 / g or 2500-3200m 2 / g.

[0070] In some embodiments, according to the first aspect, a fourth example of the first aspect is provided, and the mesoporosity of the carbon framework material is 20%-85%.

[0071] In this design, by optimizing the mesoporosity of the carbon framework material, it is beneficial for the carbon framework material to better cage-encapsulate and isolate the negative electrode active material. If the mesoporosity is too small, the porous structure in the skeleton is mainly micropores, which cannot form a cage-encapsulation isolation for the negative electrode active material. Therefore, if the mesoporosity is too small, the carbon framework material cannot fully play the role of dispersing stress. If the mesoporosity is too large, the production process is demanding and the production cost is high.

[0072] In some specific embodiments, the mesoporosity of the carbon framework material may be, for example, 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%. Optionally, the mesoporosity of the carbon framework material may be 50%-85%, 60%-85% or 65%-75%.

[0073] In some embodiments, according to the first aspect, a fifth example of the first aspect is proposed, the mass density of the carbon frame material is 0.15-0.5 mg / cm -2 .

[0074] In this design, by optimizing the mass density of the carbon frame material, the carbon frame material can reduce the expansion rate of the negative electrode without affecting the negative electrode's gram capacity, and has basically no effect on the overall weight of the battery cell.

[0075] In some specific embodiments, the mass density of the carbon frame material may be, for example, 0.15 mg / cm -2 , 0.2mg / cm -2 , 0.25mg / cm -2 , 0.3mg / cm -2 , 0.35mg / cm -2 , 0.4mg / cm -2 , 0.45mg / cm -2 or 0.5mg / cm -2 Optionally, the mass density of the carbon frame material may be 0.15-0.4 mg / cm -2 , 0.15-0.3mg / cm -2 or 0.15-0.25 mg / cm -2 .

[0076] In some embodiments, according to the first aspect, a sixth example of the first aspect is provided, wherein the compressive strength of the carbon frame material is 3-25 MPa.

[0077] In this design, the compressive strength of the carbon frame material is optimized, which helps to reduce the negative electrode expansion rate.

[0078] In some specific embodiments, the compressive strength of the carbon frame material may be, for example, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa or 25 MPa. Optionally, the compressive strength of the carbon frame material may be 10-25 MPa or 15-25 MPa.

[0079] In some embodiments, according to the first aspect, a seventh example of the first aspect is provided, wherein the carbon framework material is carbon aerogel.

[0080] In this design, carbon aerogel has a continuous three-dimensional network skeleton, large specific surface area, high porosity, low density, light material, and strong compressive resistance. It can evenly disperse the uneven stress released by the negative electrode active material due to lithium desorption and lithium insertion, effectively reduce the negative electrode expansion rate, and thus improve the cycle storage performance of the battery cell.

[0081] In some embodiments, according to the first aspect, an eighth example of the first aspect is provided, wherein the carbonaceous material includes at least one of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0082] The above-mentioned carbonaceous materials will release uneven stress during the process of lithium removal and lithium insertion, resulting in the expansion of the negative electrode. By using carbon framework materials to cage-encapsulate these carbonaceous materials, the expansion rate of the negative electrode is greatly reduced.

[0083] A second aspect of the present application provides a method for preparing a carbon framework material, comprising the following steps:

[0084] mixing aminopolysaccharide, eutectic molten salt and solvent to form a wet gel;

[0085] freeze-drying the wet gel to obtain a xerogel; and

[0086] The dry gel is carbonized to obtain a carbon framework material.

[0087] In the technical solution of the embodiment of the present application, the combination of amino polysaccharide and eutectic molten salt can form a rich pore structure inside the carbon framework material, improve the pore consistency, and improve the compressive strength of the carbon framework material. The carbon framework material of the present application is suitable for cage encapsulation and isolation of negative electrode active materials.

[0088] In some embodiments, according to the second aspect, a first example of the second aspect is provided, wherein the eutectic molten salt comprises ZnCl 2 , any two salts from LiCl, KCl, and NaCl.

[0089] In this design, the eutectic molten salt has a low melting point and a wide temperature range, which can promote the development of a large number of micropores and mesopores, especially mesopores, in the carbon body.

[0090] In some embodiments, according to the second aspect, a second example of the second aspect is provided, wherein the mass ratio of the eutectic molten salt to the amino polysaccharide is (1-15):1.

[0091] In this design, by optimizing the mass ratio of eutectic molten salt to amino polysaccharide, it is beneficial to improve the pore richness, pore consistency and compressive resistance of the carbon framework material.

[0092] In some specific embodiments, the mass ratio of the eutectic molten salt to the amino polysaccharide may be, for example, 1: 1, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, 11: 1, 12: 1, 13: 1, 14: 1 or 15: 1. Optionally, the mass ratio of the eutectic molten salt to the amino polysaccharide may be (1-10): 1.

[0093] In some embodiments, according to the second aspect, a third example of the second aspect is proposed, the mass ratio of the two salts in the eutectic molten salt may be (0.8-1.2):1, optionally (0.9-1.1):1, for example, 1:1.

[0094] In some embodiments, according to the second aspect, a fourth example of the second aspect is provided, and the solvent may be water, ethanol or a mixture thereof.

[0095] In some embodiments, according to the second aspect, a fifth example of the second aspect is proposed, wherein the preparation of the wet gel comprises: mixing amino polysaccharide, eutectic molten salt, inorganic acid and solvent. The addition of inorganic acid helps dissolve the amino polysaccharide in the solvent. Optionally, the inorganic acid can be hydrochloric acid, acetic acid or a mixture thereof.

[0096] In some embodiments, mixing can be performed under ultrasonic conditions.

[0097] In some embodiments, according to the second aspect, a sixth example of the second aspect is provided, the freeze-drying temperature may be -50°C to -20°C, for example -50°C to -30°C. The freeze-drying time may be 24-72h, for example 48-72h.

[0098] In some embodiments, according to the second aspect, a seventh example of the second aspect is provided, the temperature of the carbonization treatment may be 600° C.-900° C., such as 600° C., 700° C., 800° C. or 900° C. The carbonization time may be 1-10 h, such as 2-5 h.

[0099] In some embodiments, according to the second aspect, an eighth example of the second aspect is provided, wherein the carbonization treatment is performed under an inert atmosphere, which may be nitrogen, argon, or the like.

[0100] In some embodiments, according to the second aspect, a ninth example of the second aspect is proposed, in which, after the carbonization treatment, the carbon frame material can be soaked in an inorganic acid solution to remove impurities. The inorganic acid solution can be dilute hydrochloric acid, dilute acetic acid, or a mixture thereof. After soaking, the carbon frame material can be washed with water to remove residual inorganic acid and other impurities. After solid-liquid separation, the carbon frame material can be dried.

[0101] The third aspect of the present application provides a carbon framework material obtained by the preparation method described in the third aspect of the present application.

[0102] In the technical solution of the embodiment of the present application, the carbon framework material obtained by the preparation method described in the second aspect of the present application has high pore richness, high pore consistency and high compressive resistance.

[0103] In some embodiments, the carbon framework material has a specific surface area of ​​1000-3200 m 2 In some specific embodiments, the specific surface area of ​​the carbon framework material may be, for example, 1000 m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g、1400m 2 / g、1500m 2 / g、1600m 2 / g、1700m 2 / g、1800m 2 / g、1900m 2 / g, 2000m 2 / g, 2100m 2 / g, 2200m 2 / g, 2300m 2 / g, 2400m 2 / g, 2500m 2 / g, 2600m 2 / g, 2700m 2 / g、2800m 2 / g、2900m 2 / g、3000m 2 / g、3100m 2 / g or 3200m 2 / g. Optionally, the specific surface area of ​​the carbon framework material may be 1500-3200m 2 / g, 2000-3200m 2 / g or 2500-3200m 2 / g.

[0104] In some embodiments, the mesoporosity of the carbon framework material is 20%-85%. In some specific embodiments, the mesoporosity of the carbon framework material may be, for example, 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%. Optionally, the mesoporosity of the carbon framework material may be 50%-85%, 60%-85% or 65%-75%.

[0105] In some embodiments, the mass density of the carbon frame material is 0.15-0.5 mg / cm -2In some specific embodiments, the mass density of the carbon frame material may be, for example, 0.15 mg / cm -2 , 0.2mg / cm -2 , 0.25mg / cm -2 , 0.3mg / cm -2 , 0.35mg / cm -2 , 0.4mg / cm -2 , 0.45mg / cm -2 or 0.5mg / cm -2 Optionally, the mass density of the carbon frame material may be 0.15-0.4 mg / cm -2 , 0.15-0.3mg / cm -2 or 0.15-0.25 mg / cm -2 .

[0106] In some embodiments, the compressive strength of the carbon frame material is 3-25 MPa.

[0107] The fourth aspect of the present application provides a negative electrode plate, comprising the negative electrode material described in the first aspect of the present application.

[0108] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the negative electrode plate of the present application can reduce the negative electrode expansion rate.

[0109] A fifth aspect of the present application provides a method for preparing a negative electrode sheet, comprising:

[0110] Mixing the negative electrode active material, the carbon framework material, the conductive agent, the binder, and the solvent to obtain a negative electrode slurry; and

[0111] The negative electrode slurry is coated on the negative electrode current collector and dried.

[0112] In the technical solution of the embodiment of the present application, the negative electrode sheet can be obtained by mixing, coating and drying raw materials such as negative electrode active materials and carbon framework materials. The preparation method is simple to operate, highly repeatable, and suitable for large-scale industrial applications.

[0113] The mass ratio of the negative electrode active material to the carbon framework material is (86.5-96):(0.5-10). In some specific embodiments, the mass ratio of the negative electrode active material to the carbon framework material may be, for example, 86.5:10, 87:9.5, 87.5:9, 88:8.5, 88.5:8, 89:7.5, 89.5:7, 90:6.5, 90.5:6, 91:5.5, 91.5:5, 92:4.5, 92.5:4, 93:3.5, 93.5:3, 94:2.5, 94.5:2, 95:1.5, 95.5:1 or 96:0.5. Optionally, the mass ratio of the negative electrode active material to the carbon framework material may be (91.5-95.5):(1-5).

[0114] 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).

[0115] The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0116] In some specific embodiments, the negative electrode active material, the carbon framework material, the conductive agent, the binder, the thickener, and the solvent may be mixed to obtain the negative electrode slurry.

[0117] The thickener may be selected from carboxymethyl cellulose and the like.

[0118] The sixth aspect of the present application provides a secondary battery, comprising the negative electrode sheet described in the fourth aspect of the present application or the negative electrode sheet obtained according to the preparation method described in the fifth aspect of the present application.

[0119] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the secondary battery of the present application can reduce the negative electrode expansion rate.

[0120] A seventh aspect of the present application provides a battery module, comprising the secondary battery described in the sixth aspect of the present application.

[0121] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the battery module of the present application can reduce the negative electrode expansion rate.

[0122] The eighth aspect of the present application provides a battery pack, comprising the battery module described in the seventh aspect of the present application.

[0123] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the battery pack of the present application can reduce the negative electrode expansion rate.

[0124] The ninth aspect of the present application provides an electrical device, characterized in that it includes at least one of the secondary battery described in the sixth aspect of the present application, the battery module described in the seventh aspect of the present application, and the battery pack described in the eighth aspect of the present application.

[0125] In the technical solution of the embodiment of the present application, since the negative electrode material of the first aspect of the present application is adopted, the electric device of the present application can reduce the negative electrode expansion rate.

[0126] The present invention will be further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0127] The carbon aerogels and secondary batteries in the following examples and comparative examples were prepared according to the following general preparation method.

[0128] Preparation of carbon aerogel

[0129] 1g of chitosan was dissolved in 100mL of water under continuous stirring, Xg of eutectic molten salt (the mass ratio of the two salts in the eutectic molten salt was 1:1) was added thereto, and the mixture was fully stirred. 6mL of 1mol / L hydrochloric acid was added under ultrasonic conditions to form a chitosan salt gel; the chitosan salt gel was transferred to a freeze dryer and then freeze-dried at -50°C for 48h; the dry gel was treated at high temperature at 800°C in a nitrogen atmosphere for 2h; the product after the high temperature treatment was soaked in dilute hydrochloric acid for 24h to remove impurities, and then washed with deionized water to remove residual hydrochloric acid and other impurities, and a solid product and a filtrate were separated, and the solid product was dried at 80°C to obtain a carbon aerogel material.

[0130] Preparation of secondary batteries

[0131] Preparation of negative electrode sheet: Add negative electrode active material (graphite), carbon aerogel, conductive agent carbon black Super-P, thickener carboxymethyl cellulose (CMC), and binder SBR in a mass ratio of a:b:1.0:1.0:1.5 (where a+b=96.5) to solvent deionized water and mix evenly to form negative electrode slurry; coat the negative electrode slurry on the current collector copper foil and dry it at 85°C, then trim, cut and strip, and then dry it at 110°C under vacuum conditions for 4 hours, weld the pole ears, and make a secondary battery negative electrode sheet that meets the requirements, and take the prepared electrode sheet to measure the negative electrode sheet gram capacity.

[0132] Preparation of positive electrode sheet: 1) Polyvinylidene fluoride (PVDF), positive electrode material LiFePO 4, conductive agent (carbon black SuperP) at a mass ratio of 90:5:5, N-methyl-pyrrolidone (NMP) is used as solvent, the amount of solvent added is adjusted to control the viscosity of the slurry at 100-20000mPa.s., and the slurry is coated on the positive electrode current collector aluminum foil using a coater or sprayer. After drying at 85°C, cold pressing is performed, and then the edges are trimmed, cut into pieces, and strips are cut, and then dried at 85°C under vacuum conditions for 4 hours, and the tabs are welded to make a secondary battery positive electrode sheet that meets the requirements.

[0133] Preparation of electrolyte: A mixture of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) was used as a non-aqueous organic solvent, wherein the mass ratio of each component was EC:PC:DEC=30:30:40, and lithium hexafluorophosphate (LiPF6) was used as a lithium salt to prepare an electrolyte with a concentration of 1M.

[0134] Preparation of secondary battery: Use 12μm polypropylene film as separator, stack the positive electrode, separator and negative electrode in order, so that the separator is in the middle of the positive and negative electrode to play a role of isolation, and then wind it into a square bare cell with a thickness of 8mm, a width of 60mm and a length of 130mm. Put the bare cell into an aluminum foil packaging bag, vacuum bake it at 75℃ for 10h, inject electrolyte, vacuum seal it, and let it stand for 24h, then charge it to 3.65V with a constant current of 0.1C (160mA), then charge it with a constant voltage of 3.65V until the current drops to 0.05C (80mA), and then discharge it to 3.0V with a constant current of 0.1C (160mA), repeat the charge and discharge twice, and finally charge it to 3.8V with a constant current of 0.1C (160mA), and the preparation of secondary battery is completed.

[0135] Example 1-Example 14

[0136] In Examples 1 to 14, the type and amount of the eutectic molten salt and the mass ratio a:b of graphite to carbon aerogel are listed in Table 1 below.

[0137] Comparative Example 1

[0138] A secondary battery was prepared according to the method described in Example 1, except that no carbon aerogel was prepared and used.

[0139] Comparative Example 2-Comparative Example 3

[0140] A carbon aerogel and a secondary battery were prepared according to the method described in Example 1, except that the parameters listed in the following Table 1 were different from those in Example 1.

[0141] Comparative Example 4

[0142] A carbon aerogel and a secondary battery were prepared according to the method described in Example 5, except that the parameters listed in the following Table 1 were different from those in Example 1, and the prepared xerogel was subjected to a high temperature treatment at 620°C.

[0143] Comparative Example 5

[0144] A carbon aerogel and a secondary battery were prepared according to the method described in Example 5, except that the parameters listed in the following Table 1 were different from those in Example 1, and the prepared xerogel was subjected to a high temperature treatment at 700°C.

[0145] Comparative Example 6

[0146] A carbon aerogel and a secondary battery were prepared according to the method described in Example 13, except that the parameters listed in the following Table 1 were different from those in Example 1, and the prepared xerogel was subjected to a high temperature treatment at 750°C.

[0147] Comparative Example 7

[0148] A carbon aerogel and a secondary battery were prepared according to the method described in Example 12, except that the parameters listed in the following Table 1 were different from those in Example 1, and the prepared xerogel was subjected to a high temperature treatment at 900°C.

[0149] Table 1

[0150]

[0151]

[0152] Carbon Aerogel Characterization Test

[0153] 1. Specific surface area test and mesoporosity test

[0154] Isothermal nitrogen adsorption and desorption test is an effective means to analyze the specific surface area and pore size distribution of materials. In this application, the isothermal nitrogen adsorption and desorption test was carried out using the Micromeritics ASAP 2020 fully automatic physical and chemical adsorption instrument to analyze the specific surface area and pore size of the prepared carbon aerogel material. Before the test, the vacuum was drawn at 200°C, the test temperature was 77K, and the adsorbed gas was N 2 The specific surface area and pore size distribution information were obtained according to the BET (Brunauer-Emmett-Teler) NLDFT (nonlocal density functional theory) calculation method.

[0155] 2. Mass density test

[0156] A quantitative amount of carbon aerogel material is placed in a special compaction mold, and the mold is placed on a compaction (mass) density meter. Different pressures are set, and the thickness of the carbon aerogel material powder under different pressures can be read on the device. The compaction (mass) density is calculated using the formula density = mass / volume.

[0157] 4. Compressive strength test

[0158] A certain amount of carbon aerogel material was placed in a ST-Z16 texture analyzer, and the compressive strength of the material was measured by the device.

[0159] Negative electrode characterization

[0160] Gram Capacity Test:

[0161] The prepared negative electrode plate and lithium plate are assembled into a plate-lithium plate semi-button battery and the button capacity is obtained by charging and discharging at a small rate of 0.33C. The capacity is then divided by the mass of the active material of the plate to obtain the gram capacity parameter.

[0162] Electrical performance characterization of secondary batteries

[0163] Cycle performance test:

[0164] The cycle number test conditions are: the secondary battery is subjected to 1C / 1C cycle test at 25°C and 45°C, respectively, the charge and discharge voltage range is 2.8-3.65V, the expansion rate of the battery cell is monitored simultaneously, and the test is stopped when the capacity decays to 80% of the initial discharge capacity (indicated as @80% SOH in Table 2), and the cycle number and expansion rate are recorded. The test results are shown in Table 2 below.

[0165] Table 2

[0166]

[0167]

[0168]

[0169] By comparing Example 1 and Comparative Example 1, it can be seen that no carbon aerogel is added to the negative electrode plate of Comparative Example 1, and the cycle life of the secondary battery of Comparative Example 1 is significantly shorter than that of Example 1, and its expansion rate is significantly larger than that of Example 1. It can be seen that the cage encapsulation and isolation of graphite by carbon aerogel effectively disperses the uneven stress released by the negative electrode plate, weakens the stress superposition effect between graphites, and thus reduces the expansion rate.

[0170] By comparing Example 1 with Comparative Examples 2-3, it can be seen that an excessive amount of carbon aerogel is added to the negative electrode sheet of Comparative Example 2, and only a small amount of carbon aerogel is added to the negative electrode sheet of Comparative Example 3. The gram capacity of the negative electrode sheets of Comparative Examples 2 and 3 is significantly smaller than that of Example 1, the cycle life is significantly shorter than that of Example 1, and the expansion rate is significantly larger than that of Example 1. It can be seen that the amount of carbon aerogel used has a significant effect on the performance parameters of the secondary battery.

[0171] By comparing Example 5 and Comparative Example 4, it can be seen that the specific surface area of ​​the carbon aerogel material prepared in Comparative Example 4 is significantly lower than that in Example 5, the cycle life of the secondary battery in Comparative Example 4 is significantly shorter than that in Example 5, and its expansion rate is significantly larger than that in Example 5. It can be seen that the specific surface area of ​​the carbon aerogel material has a significant effect on the performance parameters of the secondary battery.

[0172] By comparing Example 5 and Comparative Example 5, it can be seen that the mesoporosity of the carbon aerogel material prepared in Comparative Example 5 is significantly lower than that in Example 5, the cycle life of the secondary battery in Comparative Example 5 is significantly shorter than that in Example 5, and its expansion rate is significantly larger than that in Example 5. It can be seen that the mesoporosity of the carbon aerogel material has a significant effect on the performance parameters of the secondary battery.

[0173] By comparing Example 13 and Comparative Example 6, it can be seen that the mass density of the carbon aerogel material prepared in Comparative Example 6 is significantly higher than that in Example 13, the cycle life of the secondary battery in Comparative Example 6 is significantly shorter than that in Example 13, and its expansion rate is significantly larger than that in Example 13. It can be seen that the mass density of the carbon aerogel material has a significant effect on the performance parameters of the secondary battery.

[0174] By comparing Example 12 and Comparative Example 7, it can be seen that the compressive strength of the carbon aerogel material prepared in Comparative Example 7 is significantly lower than that in Example 12, the cycle life of the secondary battery in Comparative Example 7 is significantly shorter than that in Example 12, and its expansion rate is significantly larger than that in Example 12. It can be seen that the compressive strength of the carbon aerogel material has a significant effect on the performance parameters of the secondary battery.

[0175] By comparing Examples 1-10, it can be seen that when different proportions of carbon aerogel are added to the negative electrode material, as the amount of carbon aerogel increases, the expansion of the battery shows a trend of continuous reduction, and the cycle performance continues to improve. However, when the mass ratio of graphite to carbon aerogel is less than 91.5:5, the gram capacity of the negative electrode plate is reduced. This is because when the amount of carbon aerogel is too large, a too thick skeleton coating will be formed around the graphite particles, resulting in a decrease in the ability of graphite to insert and remove lithium, which in turn leads to a decrease in the gram capacity of the negative electrode plate. In summary, carbon aerogel can improve the problem of negative electrode expansion, but the proportion of carbon aerogel added needs to be reasonably controlled to avoid a decrease in the gram capacity of the negative electrode plate.

[0176] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A negative electrode material, It is characterized in that include: A carbon framework material, comprising a three-dimensional network skeleton; the carbon framework material is a carbon aerogel; A negative electrode active material is distributed in the three-dimensional network skeleton of the carbon framework material, and the negative electrode active material includes a carbonaceous material; the mass ratio of the negative electrode active material to the carbon framework material is (91.5-95.5): (1-5).

2. The negative electrode material according to claim 1, It is characterized in that The specific surface area of ​​the carbon framework material is 1000-3200 m 2 / g.

3. The negative electrode material according to claim 1, It is characterized in that The mesoporosity of the carbon framework material is 20%-85%.

4. The negative electrode material according to claim 1, It is characterized in that The mass density of the carbon frame material is 0.15-0.5 mg / cm -2 .

5. The negative electrode material according to claim 1, It is characterized in that The compressive strength of the carbon frame material is 3-25Mpa.

6. The negative electrode material according to claim 1, It is characterized in that The carbonaceous material includes at least one of artificial graphite, natural graphite, hard carbon and soft carbon.

7. A negative electrode sheet, It is characterized in that The negative electrode material comprises the negative electrode material described in any one of claims 1 to 6.

8. A method for preparing a negative electrode sheet, It is characterized in that include: Mixing the negative electrode active material, the carbon framework material, the conductive agent, the binder, and the solvent to obtain a negative electrode slurry; as well as The negative electrode slurry is coated on the negative electrode current collector and dried; in the negative electrode plate, the negative electrode active material is distributed in the three-dimensional network skeleton of the carbon framework material, and the negative electrode active material includes a carbonaceous material; the mass ratio of the negative electrode active material to the carbon framework material is (91.5-95.5): (1-5); Wherein, the carbon framework material is carbon aerogel, and the preparation method of the carbon framework material comprises the following steps: mixing aminopolysaccharide, eutectic molten salt and solvent to form a wet gel; freeze-drying the wet gel to obtain a dry gel; and The dry gel is carbonized to obtain a carbon framework material.

9. The preparation method according to claim 8, It is characterized in that The eutectic molten salt includes ZnCl 2 , any two salts from LiCl, KCl, and NaCl.

10. The preparation method according to claim 8, It is characterized in that The mass ratio of the eutectic molten salt to the amino polysaccharide is (1-15):

1.

11. The preparation method according to any one of claims 8 to 10, It is characterized in that The binder is selected from at least one of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid and carboxymethyl chitosan.

12. A secondary battery, It is characterized in that Including the negative electrode sheet according to claim 7 or the negative electrode sheet obtained by the preparation method according to any one of claims 8-11.

13. A battery module, It is characterized in that Includes the secondary battery as claimed in claim 12.

14. A battery pack, It is characterized in that Comprising the battery module as claimed in claim 13.

15. An electrical device, It is characterized in that The invention comprises at least one of the secondary battery according to claim 12, the battery module according to claim 13 and the battery pack according to claim 14.

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