Composite porous material and preparation method thereof, negative electrode sheet and battery

Abstract

The present application relates to the field of battery technology, and specifically to a composite porous material and a preparation method thereof, a negative electrode sheet and a battery. The composite porous material comprises: a first mesoporous material, which is a carbon material derived from a metal organic framework material, and has a first mesoporous structure; and a microporous material, which is filled in the first mesoporous structure of the first mesoporous material. When the composite porous material of the present invention is arranged in the middle area of ​​the negative electrode sheet, it can not only improve the dynamic performance of the battery cell, but also improve the disadvantage that the middle part of the battery cell is prone to lack of liquid.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a composite porous material and a preparation method thereof, a negative electrode sheet and a battery. Background Art

[0002] At present, in order to solve the problem of electric vehicle range, improving energy density is an important direction for the development of lithium-ion batteries. Therefore, more and more battery manufacturers are designing batteries with higher and higher surface density of pole pieces. For thick pole pieces, in order to ensure high loading while ensuring the diffusion speed of lithium ions and full utilization of active materials, it is more important to design and optimize the microstructure of the electrode. In addition, in the existing structure, due to the insufficient anode dynamics, the battery cell will cause edge decomposition during overcharging in cycle storage, affecting the energy efficiency of the battery cell and the quality and safety of the battery cell. Moreover, during the cycle of the battery cell, the middle part of the battery cell is prone to lack of liquid, which affects the stability and cycle performance of the battery. Summary of the invention

[0003] In view of this, the present invention provides a composite porous material and a preparation method thereof, a negative electrode sheet and a battery. When the composite porous material of the present invention is arranged in the middle area of ​​the negative electrode sheet, it can not only improve the dynamic performance of the battery cell, but also improve the disadvantage that the middle part of the battery cell is prone to lack of liquid.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a composite porous material, the composite porous material comprising:

[0006] a) a first mesoporous material, the first mesoporous material is a carbon material derived from a metal organic framework material, and the first mesoporous material has a first mesoporous structure;

[0007] b) a microporous material, wherein the microporous material is filled in the first mesoporous structure of the first mesoporous material.

[0008] Preferably, the pore diameter of the first mesoporous structure is 2-50 nm.

[0009] Preferably, the porosity of the first mesoporous material is 40% to 80%.

[0010] In an embodiment of the present invention, the metal organic framework material includes at least one of a ZIF metal organic framework material, a UIO metal organic framework material, and a MIL metal organic framework material.

[0011] Preferably, the particle size D of the microporous material is 50 5~10 nm.

[0012] Preferably, the microporous material has a microporous structure, and the pore size of the microporous structure is less than or equal to 2 nm.

[0013] Preferably, the porosity of the microporous material is 10% to 40%.

[0014] In an embodiment of the present invention, the microporous material includes at least one of silicon dioxide, aluminum hydroxide, and magnesium hydroxide.

[0015] Preferably, the filling volume of the microporous material accounts for 20% to 30% of the total volume of the first mesoporous structure.

[0016] Preferably, the mass percentage of the microporous material to the first mesoporous material is 20% to 50%.

[0017] In a second aspect, the present invention provides a method for preparing the composite porous material, comprising the following steps:

[0018] Carrying out a carbonization treatment on the metal organic framework material to obtain a first mesoporous material;

[0019] The first mesoporous material, the microporous material, the template agent and the solvent are mixed and reacted to obtain a composite porous material.

[0020] Preferably, the temperature of the carbonization treatment is 350-850° C., and the time of the carbonization treatment is 1-10 h.

[0021] In an embodiment of the present invention, the template agent includes at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, tetrapropylammonium hydroxide, and hexadecyltrimethylammonium bromide.

[0022] In an embodiment of the present invention, the solvent includes water and / or an organic solvent.

[0023] In a third aspect, the present invention provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein along the width direction of the negative electrode sheet, the negative electrode active material layer comprises a middle region and edge regions disposed on both sides of the middle region;

[0024] The middle region includes a composite porous material and a first negative electrode active material; the composite porous material is the composite porous material mentioned above and / or a composite porous material prepared by the above preparation method.

[0025] Preferably, in the middle region, the mass ratio of the composite porous material to the first negative electrode active material is (1-2): (92-98).

[0026] In an embodiment of the present invention, the middle region further includes a first conductive agent, a first adhesive and a first thickener.

[0027] Preferably, in the middle region, the mass ratio of the composite porous material, the first negative electrode active material, the first conductive agent, the first binder, and the first thickener is (1-2): (92-98): (0.1-2): (0.1-2): (0.1-2).

[0028] In one embodiment provided by the present invention, the edge region includes a second mesoporous material, a second negative electrode active material, a second conductive agent, a second binder and a second thickener; the second mesoporous material is a carbon material derived from a metal organic framework material, or a transition metal oxide.

[0029] Preferably, in the edge region, the mass ratio of the second mesoporous material, the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is (1-2): (92-98): (0.1-2): (0.1-2): (0.1-2).

[0030] In another embodiment provided by the present invention, the edge region includes a second negative electrode active material, a second conductive agent, a second binder, and a second thickener.

[0031] Preferably, in the edge region, the mass ratio of the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is (94-98): (0.1-2): (0.1-2): (0.1-2).

[0032] In a fourth aspect, the present invention provides a battery comprising the above-mentioned negative electrode sheet.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The composite porous material of the present invention includes a first mesoporous material and a microporous material filled in the pores of the first mesoporous material. Among them, the first mesoporous material is a carbon material derived from a metal organic framework material, and its morphology does not collapse after high-temperature carbonization. The first mesoporous material has a high specific surface area, a large pore volume, an adjustable pore size and a controllable morphology. The high specific surface area can increase the reaction active sites, improve the contact between the electrolyte and the active substance, and increase the transmission rate of lithium ions; at the same time, the first mesoporous material can provide a large number of active sites, greatly improve the electron transmission rate, reduce the interface contact resistance, accelerate the charge transfer, improve the electronic conductivity and improve the surface reaction kinetics, thereby greatly improving the capacity and cycle life of the battery cell and other kinetic properties.

[0035] Microporous materials can reduce the surface tension of the electrode, improve the wetting and infiltration ability of the electrolyte on the electrode, and improve the safety of the battery cell; the particle size of the microporous material is smaller than the pore size of the mesoporous material. After the microporous material is filled into the mesoporous structure of the first mesoporous material, the pore size and pore structure inside the mesoporous structure can be regulated, which can change the interaction between the electrode material and the electrolyte and improve the efficiency and selectivity of the reaction.

[0036] Therefore, when the composite porous material of the present invention is arranged in the middle area of ​​the negative electrode sheet, it can not only improve the dynamic performance of the battery cell, but also improve the disadvantage that the middle part of the battery cell is prone to lack of liquid.

[0037] 2. Further preferably, a second mesoporous material is provided at the edge region of the negative electrode active material layer. The second mesoporous material is a carbon material derived from a metal organic framework material or a transition metal oxide. The second mesoporous material has a high porosity characteristic and diffuses faster than a microporous material. By disposing the second mesoporous material at the edge of the negative electrode sheet, the kinetic performance of the battery cell can be improved, the edge analysis can be reduced, and the cycle performance and safety performance of the battery cell can be further improved.

[0038] 3. In the prior art, the conventional method for making holes in electrodes is to add a binder and a pore-forming agent to the slurry and sinter it at a temperature of 350°C to 850°C. During the high-temperature calcination process, the binder and pore-forming agent in the slurry will decompose and volatilize at high temperature, leaving holes in the electrode to form an electrode with a porous structure.

[0039] The composite porous material of the present invention itself has a rich porous structure. When preparing the electrode sheet, the composite porous material can be directly added to the negative electrode slurry to prepare the electrode sheet with a porous structure, making the preparation method of the electrode sheet with a porous structure more convenient and simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the top view of the negative electrode sheet.

[0041] Figure 2 Schematic diagram of the cross section of the negative electrode sheet.

[0042] Figure 3 This is a SEM image of the organic framework material ZIF-8 synthesized in Example 1. The left image is a SEM image at a scale of 2 μm, the right image is a SEM image at a scale of 200 nm, and the right image is an enlarged image of the left image.

[0043] Figure 4 This is the SEM image of the mesoporous material ZPC after carbonization in Example 1. The left image is a SEM image at a scale of 200 nm, the right image is a SEM image at a scale of 100 nm, and the right image is an enlarged image of the left image. DETAILED DESCRIPTION

[0044] The present invention discloses a composite porous material and a method for preparing the same, a negative electrode sheet and a battery. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all deemed to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0045] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes, and do not indicate or imply relative importance.

[0046] In the description of the present invention, a list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0047] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0048] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0050] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0051] Specifically, the present invention adopts the following technical solutions:

[0052] In a first aspect, the present invention provides a composite porous material, the composite porous material comprising:

[0053] a) a first mesoporous material, the first mesoporous material is a carbon material derived from a metal organic framework material, and the first mesoporous material has a first mesoporous structure;

[0054] b) a microporous material, wherein the microporous material is filled in the first mesoporous structure of the first mesoporous material.

[0055] In the present invention, the composite porous material includes a first mesoporous material and a microporous material filled in its mesoporous structure. The first mesoporous material of the present invention has a unique structure, including a high specific surface area, a large pore volume, an adjustable pore size and a controllable morphology. The high specific surface area can increase the reaction active sites, improve the contact between the electrolyte and the active material, promote the transmission of lithium ions, and improve the dynamics of the battery cell; the first mesoporous material of the present invention is a carbon material derived from a metal organic framework, which has good electrical conductivity (microporous materials such as silicon dioxide are not conductive, and the conductive effect of the microporous material is comprehensive) and has more active sites. The presence of active sites provides a channel for the microporous material to enter, which can increase its entry rate, promote the microporous material to enter the mesoporous structure, and is conducive to a rapid mass transfer process. The active sites of the microporous material and the first mesoporous material interact with each other, and the two act synergistically. The microporous material can reduce the surface tension of the electrode, improve the wetting and infiltration ability of the electrolyte on the electrode, and improve the safety of the battery core; the particle size of the microporous material is smaller than the pore size of the first mesoporous material. After the microporous material is filled into the first mesoporous material, the pore size and pore structure of the first mesoporous material can be regulated to improve the efficiency of the reaction. At the same time, larger reactant molecules are not easy to enter the mesoporous pores, thereby limiting the occurrence of some side reactions in the first mesoporous material, which helps to improve the selectivity of the reaction. Therefore, the composite porous material of the present invention has a larger specific surface area than the mesoporous material, enhances the ability to store charge, and can improve electrolyte penetration and promote ion diffusion more than the microporous material.

[0056] Preferably, the pore size of the first mesoporous structure is 2 to 50 nm. Exemplarily, the pore size of the first mesoporous structure is any value among 2 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 25 nm, 26 nm, 28 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any value within the range of any two of the above values.

[0057] Preferably, the porosity of the first mesoporous material is 40% to 80%. Exemplarily, the porosity of the first mesoporous material is any value among 40%, 50%, 60%, 70%, 80%, or any value within the range consisting of any two of the above values.

[0058] In an embodiment of the present invention, the metal organic framework material includes at least one of a ZIF metal organic framework material, a UIO metal organic framework material, and a MIL metal organic framework material. Since the ZIF metal organic framework material has high stability, high porosity, good thermal stability, good chemical stability, and high crystallinity, the metal organic framework material is preferably a ZIF metal organic framework material.

[0059] In an embodiment of the present invention, the ZIF metal organic framework material includes but is not limited to at least one of ZIF-8, ZIF-5, ZIF-7, ZIF-11, ZIF-12, ZIF-60 or ZIF-67. Since ZIF-8 has a good pore structure and a high specific surface area, it is conducive to the microporous material entering the first mesoporous material, and the synthesis conditions are mild and easy to functionalize, so the ZIF metal organic framework material is preferably ZIF-8.

[0060] In an embodiment of the present invention, the UIO metal organic framework material includes but is not limited to at least one of UIO-66, UIO-67, and UIO-68.

[0061] In an embodiment of the present invention, the MIL metal organic framework material includes but is not limited to at least one of MIL-53, MIL-88, MIL-100, MIL-101, and MIL-125.

[0062] Preferably, the particle size D of the microporous material is 50 For example, the particle size D of the microporous material is 5 to 10 nm. 50 It is any value among 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm or any value within the range of any two of the above values. The particle size of the microporous material is nanometer scale. Within this particle size range, the microporous material can be filled into the first mesoporous material.

[0063] Preferably, the microporous material has a microporous structure, and the pore size of the microporous structure is less than or equal to 2 nm. Exemplarily, the pore size of the microporous structure is any value among 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, or any value within the range of values ​​composed of any two of the above values. Within the above pore size range, the microporous material can reduce the surface tension of the electrode, improve the wetting ability and infiltration ability of the electrolyte on the electrode, and improve the safety of the battery cell.

[0064] Preferably, the porosity of the microporous material is 10% to 40%. Exemplarily, the porosity of the microporous material is any value among 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any value within the range consisting of any two of the above values.

[0065] In an embodiment of the present invention, the microporous material includes at least one of silicon dioxide, aluminum hydroxide, and magnesium hydroxide.

[0066] Preferably, the filling volume of the microporous material accounts for 20% to 30% of the total volume of the first mesoporous structure. Exemplarily, the filling volume of the microporous material accounts for any of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% of the total volume of the first mesoporous structure, or any value within the range of any two of the above values. When it is greater than 30%, there will be too few mesoporous structures, and the advantages of the first mesoporous material cannot be reflected; when it is less than 20%, it will lead to insufficient regulation of the pore size of the first mesoporous material by the microporous material.

[0067] Preferably, the mass percentage of the microporous material to the first mesoporous material is 20% to 50%. Exemplarily, the mass percentage of the microporous material to the first mesoporous material is any value of 20%, 25%, 30%, 35%, 40%, 45%, 50% or any value within the range of any two of the above values. When it is less than 20%, the role of the micropores cannot be played, the wetting ability of the electrolyte to the electrode cannot be improved, and the efficiency and selectivity of the reaction cannot be improved. When it is greater than 50%, the mesoporous structure in the first mesoporous material will be filled too full, the role of the mesopores cannot be played, the reaction active sites cannot be increased, the contact between the electrolyte and the active material cannot be improved, the transmission of lithium ions cannot be promoted, and the dynamics of the battery cell cannot be improved.

[0068] In a second aspect, the present invention provides a method for preparing the composite porous material, comprising the following steps:

[0069] Carrying out a carbonization treatment on the metal organic framework material to obtain a first mesoporous material;

[0070] The first mesoporous material, the microporous material, the template agent and the solvent are mixed and reacted to obtain a composite porous material.

[0071] Preferably, the temperature of the carbonization treatment is 350-850°C, and the time of the carbonization treatment is 1-10 h. Exemplarily, the temperature of the carbonization treatment is any one of 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, or any one of the ranges of any two of the above values, and the time of the carbonization treatment is any one of 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, or any one of the ranges of any two of the above values. If the temperature of the carbonization treatment is too low and the time is too short, the metal organic framework material will have a microporous structure and a mesoporous structure cannot be obtained; if the temperature of the carbonization treatment is too high and the time is too long, the structure of the metal organic framework material will collapse.

[0072] The template in the present invention can induce the microporous material to enter the mesoporous structure of the first mesoporous material, playing a role in structural regulation and synergistic induction. In an embodiment of the present invention, the template includes at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), tetrapropylammonium hydroxide, and hexadecyltrimethylammonium bromide.

[0073] In an embodiment of the present invention, the solvent includes water and / or an organic solvent, preferably an organic solvent, such as methanol.

[0074] In the embodiment of the present invention, the amount of the template in the reaction system is a conventional amount, for example, 1 to 5 mol·L -1 .

[0075] In the embodiment of the present invention, the microporous material is prepared by a conventional method for preparing nanomaterials. For example, the preparation method of nano-scale microporous material silicon dioxide is as follows: (1) Take 2 mol·L -1 Urea, 0.2 mol L -1 Hexadecyltrimethylammonium bromide (CTAB) and 1 mol·L -1 Acetic acid was dissolved in distilled water to 100 mL and stirred in a beaker for 4 h until the solution was completely transparent. (2) Add 1.4 mol·L -1Tetraethyl orthosilicate (TEOS), continue stirring for 10 minutes, the solution becomes uniform and translucent. (3). Transfer the above solution into a plastic bottle and seal the container tightly. Heat the container in a 60℃ oven for 4 days. (4). After cleaning, place it in a preheated oven at 60℃ and dry it for 2 days to form microporous silica material for preparation. For example, the preparation method of nano-scale microporous material aluminum hydroxide is as follows: (1). Adjust the concentration of industrial sodium aluminate to 1 mol / L by diluting it with water; (2). Add urea in a molar ratio of 3:1 to aluminum ions and fully dissolve it; (3). In a hydrothermal kettle, perform hydrothermal reaction at 120±5°C for 3 to 5 hours; (4). After natural cooling, filter and wash, and dry at 80°C for 2 hours to obtain aluminum hydroxide microspheres, and the obtained aluminum hydroxide microspheres have uniform and smooth particle size; (5). Recover the filtered solution, add industrial sodium aluminate mother liquor, and adjust its concentration to 1 mol / L; (6). Repeat steps (2) to (5) for cyclic production.

[0076] In a third aspect, the present invention provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein along the width direction of the negative electrode sheet, the negative electrode active material layer comprises a middle region and edge regions disposed on both sides of the middle region;

[0077] The middle region includes a composite porous material and a first negative electrode active material; the composite porous material is the composite porous material mentioned above and / or a composite porous material prepared by the above preparation method.

[0078] In the present invention, a composite porous material is arranged in the middle region, so that the composite porous material can be preferably arranged in the middle of the battery cell. The mesoporous structure of the composite porous material can increase the specific surface area and porosity of the electrode material, increase the contact area between the electrode surface and the electrolyte, and promote the exchange of lithium ions between the electrode material and the electrolyte, thereby improving the discharge capacity and rate performance of the electrode and improving the kinetic performance. By utilizing the characteristics of uniform pore size and large specific surface area of ​​the microporous material, the microporous material in the composite porous material can solve the problem of poor wettability and easy electrolyte shortage in the middle of the battery cell, and can be more fully infiltrated with the electrolyte, improving the difficulty of infiltration in the middle of the battery cell.

[0079] Preferably, in the middle region, the mass ratio of the composite porous material to the first negative electrode active material is (1-2): (92-98). Exemplarily, the mass ratio of the composite porous material to the first negative electrode active material is any value among 1:46, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, 1:98 or any value within the range of any two of the above values. When the mass ratio of the composite porous material to the first negative electrode active material is less than 1:98, the unique role of the composite porous material cannot be exerted, resulting in an insignificant improvement effect; when the mass ratio is greater than 1:46, it is easy to cause poor slurry stability, resulting in the inability to make samples and poor battery performance.

[0080] In an embodiment of the present invention, the middle region further includes a first conductive agent, a first adhesive and a first thickener.

[0081] Preferably, in the middle region, the mass ratio of the composite porous material, the first negative electrode active material, the first conductive agent, the first binder, and the first thickener is (1-2): (92-98): (0.1-2): (0.1-2): (0.1-2). Exemplarily, the mass ratio of the composite porous material, the first negative electrode active material, the first conductive agent, the first binder, and the first thickener is any value in 2:94.5:1.8:0.9:0.8, 1.8:94.7:1.8:0.9:0.8, 1.6:94.9:1.8:0.9:0.8, 1:98:0.1:0.1:0.1, 1.5:95:1:1:1, 2:92:2:2:2, or any value in the range of any two of the above values.

[0082] In one embodiment provided by the present invention, the edge region includes a second mesoporous material, a second negative electrode active material, a second conductive agent, a second binder and a second thickener; the second mesoporous material is a carbon material derived from a metal organic framework material, or a transition metal oxide.

[0083] For conventional pole pieces, the dynamics deficiency of the battery cell is prone to occur in the edge area, resulting in the phenomenon of lithium deposition in the edge area. In the present invention, the second mesoporous material of the present invention is arranged in the edge area. The second mesoporous material has faster diffusion than the microporous material and better dynamic performance, which can ensure that lithium deposition does not occur at the edge of the pole piece. In addition, the wettability of the edge area is sufficient, so it is preferred that the second mesoporous material in the edge area is not filled with microporous material.

[0084] In an embodiment of the present invention, the transition metal oxide comprises titanium dioxide (TiO 2 ), molybdenum trioxide (MoO 3 ), tungsten trioxide (WO 3 ), vanadium pentoxide (V 2O 5 ), niobium pentoxide (Nb 2 O 5 ), ferric oxide (Fe 2 O 3 ), manganese dioxide (MnO 2 )、SnO 2 )

[0085] In an embodiment of the present invention, the second mesoporous material has a second mesoporous structure. Preferably, the pore size of the second mesoporous structure is 2 to 50 nm, and the porosity of the second mesoporous material is 40% to 80%.

[0086] Preferably, in the edge region, the mass ratio of the second mesoporous material, the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is (1-2): (92-98): (0.1-2): (0.1-2): (0.1-2). Exemplarily, the mass ratio of the second mesoporous material, the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is any value in 2:94.5:1.8:0.9:0.8, 1.8:94.7:1.8:0.9:0.8, 1.6:94.9:1.8:0.9:0.8, 1:98:0.1:0.1:0.1, 1.5:95:1:1:1, 2:92:2:2:2, or any value in the range of any two of the above values.

[0087] In another embodiment of the present invention, the edge region includes a second negative electrode active material, a second conductive agent, a second binder, and a second thickener. In this embodiment, the edge region does not include a second mesoporous material.

[0088] Preferably, in the edge region excluding the second mesoporous material, the mass ratio of the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is (94-98): (0.1-2): (0.1-2): (0.1-2). Exemplarily, the mass ratio of the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is any value among 96.5:1.8:0.9:0.8, 98:0.1:0.1:0.1, 96:1:1:1, 94:2:2:2, or any value within the range consisting of any two of the above values.

[0089] Preferably, the unilateral width of the edge region is 3 to 5 mm. Exemplarily, the unilateral width of the edge region is any value among 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or any value within the range of any two of the above values. When the unilateral width of the edge region is less than 3 mm, coating will be difficult; when the unilateral width of the edge region is greater than 5 mm, the wettability of the middle region will be affected.

[0090] In an embodiment of the present invention, when the second mesoporous material is a carbon material derived from a metal organic framework material, its preparation method is the same as that of the first mesoporous material. When the second mesoporous material is a transition metal oxide, its preparation method is a conventional preparation method.

[0091] In an embodiment of the present invention, the first negative electrode active material and the second negative electrode active material are independently selected from natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, transition metal nitrides, etc.

[0092] In an embodiment of the present invention, the first conductive agent and the second conductive agent are independently selected from at least one of conductive carbon black (eg SP), carbon nanotubes, graphene, and carbon nanofibers.

[0093] In an embodiment of the present invention, the first binder and the second binder are independently selected from at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA).

[0094] In an embodiment of the present invention, the first thickener and the second thickener are independently selected from at least one of carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), and sodium alginate (SA).

[0095] The present invention also provides a method for preparing the negative electrode sheet having the edge region including the second mesoporous material, comprising the following steps:

[0096] Mixing the composite porous material, the first negative electrode active material, the first conductive agent, the first binder, the first thickener and the first solvent to obtain a first slurry;

[0097] Mixing a second mesoporous material, a second negative electrode active material, a second conductive agent, a second binder, a second thickener, and a second solvent to obtain a second slurry;

[0098] The first slurry is applied to the middle area of ​​the negative electrode current collector, and the second slurry is applied to the edge area of ​​the current collector. After drying and punching, a negative electrode sheet is obtained.

[0099] The present invention also provides a method for preparing the negative electrode sheet whose edge region does not include the second mesoporous material, comprising the following steps:

[0100] Mixing the composite porous material, the first negative electrode active material, the first conductive agent, the first binder, the first thickener and the first solvent to obtain a first slurry;

[0101] Mixing a second negative electrode active material, a second conductive agent, a second binder, a second thickener, and a second solvent to obtain a second slurry;

[0102] The first slurry is applied to the middle area of ​​the negative electrode current collector, and the second slurry is applied to the edge area of ​​the current collector. After drying and punching, a negative electrode sheet is obtained.

[0103] In an embodiment of the present invention, the coating speed is 30-60 m / s.

[0104] In a fourth aspect, the present invention provides a battery comprising the above-mentioned negative electrode sheet.

[0105] In an embodiment of the present invention, the battery is a lithium ion battery or a sodium ion battery.

[0106] In the embodiment of the present invention, the battery structure includes but is not limited to button batteries, soft-pack batteries, cylindrical batteries, etc.

[0107] The present application has no particular restrictions on the positive electrode sheet, separator, and electrolyte in the battery, and those skilled in the art can select them according to actual needs as long as the purpose of the present application can be achieved.

[0108] The reagents, instruments or materials used in the present invention can be obtained through commercial channels.

[0109] The present invention will be further described below in conjunction with embodiments:

[0110] Embodiment 1:

[0111] 1. Preparation of negative electrode sheet

[0112] The structure of the negative electrode is as follows Figure 1 and Figure 2 As shown, the negative electrode sheet includes a negative electrode current collector 10 and a negative electrode active material layer 20 disposed on two surfaces of the negative electrode current collector;

[0113] Along the width direction of the negative electrode sheet, the negative electrode active material layer 20 includes a middle region 21 and edge regions 22 arranged on both sides of the middle region, and the width of a single side of the edge region is 4 mm;

[0114] The middle region 21 comprises a composite porous material;

[0115] The edge region 22 comprises a mesoporous material.

[0116] The method for preparing the negative electrode sheet comprises the following steps:

[0117] (1) Preparation of mesoporous materials

[0118] Zinc nitrate hexahydrate (0.258 g, 20 mL) methanol solution was poured into 2-methylimidazole (0.263 g, 20 mL) methanol solution and stirred at room temperature for 1 h. The resulting mixed solution was then allowed to stand for 24 h, centrifuged and dried to obtain metal organic framework material ZIF-8 powder. Figure 3 It was shown that ZIF-8 with a cubic structure was successfully synthesized.

[0119] The obtained ZIF-8 powder was heated to 800°C in a tube furnace under a nitrogen atmosphere and kept at this temperature for 2 h to obtain a mesoporous material ZPC with a pore size of 20-24 nm and a porosity of 60%. Figure 4 It shows that the structure of the organic framework material ZIF-8 does not collapse after carbonization.

[0120] (2) Preparation of microporous materials

[0121] Take 2 mol·L -1 Urea, 0.2 mol·L -1 Hexadecyltrimethylammonium bromide (CTAB) and 1 mol·L -1 Acetic acid was dissolved in distilled water to 100 mL and stirred in a beaker for 4 h until the solution was completely transparent. 1.4 mol·L -1 Tetraethyl orthosilicate (TEOS), continue stirring for 10 minutes, the solution becomes uniform and translucent; transfer the above solution to a plastic bottle and seal the container tightly. Heat the container in a 60℃ oven for 4 days; after cleaning, place it in a 60℃ preheated oven and dry it for 2 days to form microporous silica material with a particle size of D 50 The particle size is 5-10 nm, the pore size is 1-2 nm, and the porosity is 20%.

[0122] (3) Preparation of composite porous materials

[0123] The mesoporous material ZPC prepared in step (1) and the microporous material silica prepared in step (2) were mixed in a methanol solvent at a mass ratio of 4:1, and then the template P123 (concentration of 2 mol·L -1 ), and finally synthesize the composite porous material.

[0124] (4) Preparation of negative electrode

[0125] The composite porous material prepared in step (3), graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, sodium carboxymethyl cellulose (CMC) as a thickener, and conductive carbon black (SP) as a conductive agent are mixed in a mass ratio of 2:94.5:1.8:0.9:0.8, deionized water as a solvent is added, and the mixture is ground with agate to obtain a first negative electrode slurry;

[0126] The mesoporous material prepared in step (1), graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, sodium carboxymethyl cellulose (CMC) as a thickener, and conductive carbon black (SP) as a conductive agent are mixed in a mass ratio of 2:94.5:1.8:0.9:0.8, deionized water as a solvent is added, and the mixture is ground with agate to obtain a second negative electrode slurry;

[0127] The first negative electrode slurry and the second negative electrode slurry are uniformly coated on the middle area and the edge area of ​​the negative electrode current collector copper foil respectively, and then baked and punched to obtain the negative electrode sheet.

[0128] 2. Preparation of positive electrode:

[0129] The positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride (PVDF) and the conductive agent conductive carbon black (SP) are mixed in a mass ratio of 97:2:1 and dispersed in a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry is coated on the current collector aluminum foil, and then baked and punched to obtain a positive electrode sheet.

[0130] 3. Preparation of electrolyte:

[0131] The lithium salt lithium hexafluorophosphate (LiPF 6 ) was dissolved in a mixed solvent consisting of ethyl methyl carbonate (EMC), ethylene carbonate (EC), and dimethyl carbonate (DEC) (the mass ratio of the three was 1:0.5:1.5) to obtain LiPF 6 The concentration of the electrolyte is 1 mol / L.

[0132] 4. Battery assembly:

[0133] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence in a glove box, injected with liquid, and assembled into button batteries. Then, after standing for several hours, a cycle test is performed using an electrochemical workstation to test the battery cell's cycle performance and safety performance.

[0134] Embodiment 2:

[0135] The difference between this embodiment and embodiment 1 is that:

[0136] In the preparation of the negative electrode sheet, the metal organic framework material is replaced by UIO66 with a pore size of 5 to 25 nm, and the microporous material is replaced by aluminum hydroxide. The metal organic framework material and the microporous material are prepared by conventional methods.

[0137] Embodiment 3:

[0138] The difference between this embodiment and embodiment 1 is that:

[0139] In the preparation of the negative electrode sheet, the metal organic framework material is replaced by ZIF67 with a pore size of 2 to 50 nm, and the microporous material is replaced by magnesium hydroxide. The metal organic framework material and the microporous material are prepared by conventional methods.

[0140] Embodiment 4:

[0141] The difference between this embodiment and embodiment 1 is that:

[0142] During the preparation of the negative electrode sheet, the sintering temperature of ZIF8 was changed to 850°C; the microporous material was replaced with magnesium hydroxide.

[0143] Embodiment 5:

[0144] The difference between this embodiment and embodiment 1 is that: in the preparation of the negative electrode sheet, the sintering temperature of ZIF8 is changed to 550° C.; and the microporous material is replaced by magnesium hydroxide.

[0145] Embodiment 6:

[0146] The difference between this embodiment and embodiment 1 is that:

[0147] During the preparation of the negative electrode sheet, the sintering temperature of ZIF8 was changed to 350°C; the microporous material was replaced with magnesium hydroxide.

[0148] Embodiment 7:

[0149] The difference between this embodiment and embodiment 1 is that:

[0150] The edge area of ​​the negative electrode active material layer does not include mesoporous materials, and the material composition is: negative electrode active material graphite, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), conductive agent conductive carbon black (SP) according to 96.5:1.8:0.9:0.8.

[0151] Embodiment 8:

[0152] The difference between this embodiment and embodiment 1 is that:

[0153] Replace the mesoporous material in the edge area with other common mesoporous materials, transition metal oxides TiO 2 .

[0154] Embodiment 9:

[0155] The difference between this embodiment and embodiment 1 is that:

[0156] In the preparation of the negative electrode sheet, the mass ratio of the mesoporous material to the microporous material in step (3) was changed to 2:1;

[0157] The mass ratio of the composite porous material, negative electrode active material graphite, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), and conductive agent conductive carbon black (SP) in step (4) is 1.8:94.7:1.8:0.9:0.8.

[0158] Embodiment 10:

[0159] The difference between this embodiment and embodiment 1 is that:

[0160] In the preparation of the negative electrode sheet, the mass ratio of the mesoporous material to the microporous material in step (3) was changed to 13:3;

[0161] The mass ratio of the composite porous material, negative electrode active material graphite, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), and conductive agent conductive carbon black (SP) in step (4) is 1.6:94.9:1.8:0.9:0.8.

[0162] Comparative Example 1:

[0163] This comparative example is different from Example 7 in that:

[0164] The middle area of ​​the negative electrode active material layer does not include the composite porous material, and the material composition is: negative electrode active material graphite, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), conductive agent conductive carbon black (SP) according to 96.5:1.8:0.9:0.8.

[0165] Comparative Example 2:

[0166] This comparative example is different from Example 7 in that:

[0167] The composite porous material in the middle region is replaced by the mesoporous material prepared in step (1), without the microporous material.

[0168] Comparative Example 3:

[0169] This comparative example is different from Example 7 in that:

[0170] The composite porous material in the middle region is replaced by the microporous material prepared in step (2) without the mesoporous material.

[0171] Comparative Example 4:

[0172] This comparative example is different from Example 7 in that:

[0173] Replace the mesoporous MOF material in the middle region with other common mesoporous materials, transition metal oxides ZrO 2 .

[0174] Comparative Example 5:

[0175] This comparative example is different from Example 7 in that:

[0176] In the absence of a template, a mesoporous material, a microporous material and a solvent are mixed to obtain a composite porous material.

[0177] Battery performance test:

[0178] (1) Improve the dynamics test method:

[0179] Cycle life test: The assembled battery is charged to 3.65V at 0.1C constant current and constant voltage at a constant temperature of 25°C, with a cut-off current of 0.05C; then discharged to 2.5V at 0.33C to obtain the discharge capacity of the first cycle. The charge and discharge cycle is continued according to the above steps for 1000 cycles to obtain the discharge capacity of the 1000th cycle. The capacity retention rate = discharge capacity of the Nth cycle / discharge capacity of the first cycle.

[0180] (2) Safety testing methods:

[0181] The battery cells were subjected to a thermal runaway experiment using a 1000W heating plate in a safety laboratory to observe the battery cell status and the time of thermal runaway.

[0182] (3) Battery conductivity test method:

[0183] The battery uses the AC impedance method to add a certain AC voltage to the battery and measure the impedance change of the electrode to measure the electronic conductivity.

[0184] The experimental results are as follows:

[0185] Table 1

[0186]

[0187] Compared with comparative examples 1-5, the batteries of examples 1-10 have significant advantages in capacity retention, safety and conductivity. In particular, compared with the design of the edge area of ​​example 7 being a common slurry, the edge of example 1 is provided with a mesoporous material based on a metal organic framework material, which can improve the dynamic performance of the battery cell and effectively reduce the situation of edge analysis, thereby significantly improving the safety performance of the battery cell.

[0188] Compared with Example 7, since the middle area of ​​Comparative Example 1 is coated with ordinary slurry and no mesoporous material and microporous material are set, the electronic conductivity and surface reaction kinetics are poor, and the situation that the middle part of the battery cell is prone to liquid shortage cannot be improved, resulting in poor battery cell kinetics and safety performance.

[0189] Compared with Example 7, since only mesoporous material is arranged in the middle area of ​​Comparative Example 2, and the pores of the mesoporous material are not filled with microporous material, the pore size and pore structure inside the mesoporous structure cannot be regulated, the reaction efficiency is low, the selectivity is poor, and the electrolyte has poor wetting and infiltration abilities on the electrode, resulting in poor kinetic and safety performance of the battery cell.

[0190] Compared with Example 7, since Comparative Example 3 only has microporous materials in the middle region and no mesoporous materials, there are fewer active reaction sites, and the lithium ion transmission rate and electron transmission rate cannot be improved, resulting in poor kinetic performance and safety performance of the battery cell.

[0191] Compared with Example 7, in Comparative Example 4, since the middle area is set with other common mesoporous materials, the mesoporous material has poor conductivity and few reactive active sites, and the lithium ion transmission rate and electron transmission rate cannot be improved, resulting in poor kinetic performance and safety performance of the battery cell.

[0192] Compared with Example 7, since no template is added in Comparative Example 5, the microporous material cannot be induced to enter the mesoporous structure of the mesoporous material, and the pore size and pore structure inside the mesoporous structure cannot be regulated. The reaction efficiency is low, the selectivity is poor, and the electrolyte has poor wetting and infiltration abilities on the electrode, resulting in poor kinetic and safety performance of the battery cell.

[0193] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite porous material, characterized in that: The composite porous material comprises: a) a first mesoporous material, wherein the first mesoporous material is a carbon material derived from a metal organic framework material, and the first mesoporous material has a first mesoporous structure; the pore size of the first mesoporous structure is 2 to 50 nm; b) a microporous material, wherein the microporous material is filled in the first mesoporous structure of the first mesoporous material; The filling volume of the microporous material accounts for 20% to 30% of the total volume of the first mesoporous structure; and / or the mass percentage of the microporous material to the first mesoporous material is 20% to 50%.

2. The composite porous material according to claim 1, characterized in that: The porosity of the first mesoporous material is 40% to 80%; And / or, the metal organic framework material includes at least one of a ZIF metal organic framework material, a UIO metal organic framework material, and a MIL metal organic framework material.

3. The composite porous material according to claim 1, characterized in that: The particle size D of the microporous material 50 5~10nm; And / or, the microporous material has a microporous structure, and the pore size of the microporous structure is less than or equal to 2 nm; and / or, the porosity of the microporous material is 10% to 40%; And / or, the microporous material includes at least one of silicon dioxide, aluminum hydroxide, and magnesium hydroxide.

4. The method for preparing the composite porous material according to any one of claims 1 to 3, characterized in that: The steps include: Carrying out a carbonization treatment on the metal organic framework material to obtain a first mesoporous material; The first mesoporous material, microporous material, template agent and solvent are mixed and reacted to obtain a composite porous material.

5. The preparation method according to claim 4, characterized in that: The temperature of the carbonization treatment is 350 to 850° C., and the time of the carbonization treatment is 1 to 10 h; And / or, the template agent includes at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, tetrapropylammonium hydroxide, and hexadecyltrimethylammonium bromide; And / or, the solvent includes water and / or an organic solvent.

6. A negative electrode sheet, characterized in that: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and along the width direction of the negative electrode sheet, the negative electrode active material layer comprises a middle region and edge regions disposed on both sides of the middle region; The middle region includes a composite porous material and a first negative electrode active material; The composite porous material is the composite porous material according to any one of claims 1 to 3 and / or the composite porous material prepared by the preparation method according to any one of claims 4 to 5.

7. The negative electrode sheet according to claim 6, characterized in that: In the middle region, the mass ratio of the composite porous material to the first negative electrode active material is (1-2): (92-98); And / or, the middle region also includes a first conductive agent, a first binder and a first thickener, and in the middle region, the mass ratio of the composite porous material, the first negative electrode active material, the first conductive agent, the first binder and the first thickener is (1-2): (92-98): (0.1-2): (0.1-2): (0.1-2).

8. The negative electrode sheet according to claim 7, characterized in that: The edge region includes a second mesoporous material, a second negative electrode active material, a second conductive agent, a second binder, and a second thickener; the second mesoporous material is a carbon material derived from a metal organic framework material, or a transition metal oxide; in the edge region, the mass ratio of the second mesoporous material, the second negative electrode active material, the second conductive agent, the second binder, and the second thickener is (1-2): (92-98): (0.1-2): (0.1-2): (0.1-2); or, The edge region includes a second negative electrode active material, a second conductive agent, a second binder and a second thickener; in the edge region, the mass ratio of the second negative electrode active material, the second conductive agent, the second binder and the second thickener is (94-98): (0.1-2): (0.1-2): (0.1-2).

9. A battery, characterized in that: The battery comprises the negative electrode sheet according to any one of claims 6 to 8.

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