Porous electrode and manufacturing method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a porous electrode and a manufacturing method and application thereof. The manufacturing method comprises the following steps: a) compounding a pore-forming agent and a one-dimensional carbon material, forming a coating layer on the surface of the one-dimensional carbon material, and then adding the coating layer into electrode slurry to obtain mixed slurry; and b) forming an active material layer on the surface of at least one side of a current collector by using the mixed slurry obtained in the step a), and removing the pore-forming agent to obtain the porous electrode. Compared with the prior art, according to the manufacturing method provided by the invention, the specific material and the pore-forming agent are selected to be compounded and act in the electrode slurry, and specific process steps are matched, so that relatively good overall interaction is realized; the obtained porous electrode has high pore utilization rate on the basis of having good fast charging capacity and low-temperature performance, and it is guaranteed that the electrode still has good dynamics under the high compaction condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, and more particularly to a porous electrode and a manufacturing method and application thereof. BACKGROUND

[0002] At present, lithium ion batteries have been widely used in power batteries and 3C electronic products, but the energy density of lithium ion batteries is slowly improved, which is difficult to meet the growing demand, especially for power batteries. The energy density of power batteries is related to the endurance of electric vehicles. At present, the improvement of the energy density of power batteries is slow, and increasing the charging speed of the battery is another important way to alleviate the range anxiety. In addition, the low-temperature charging and discharging performance of power batteries is also a problem that needs to be solved urgently.

[0003] In order to improve the energy density of lithium ion batteries, increasing the compaction density and the thickness of the electrode is an effective measure, but this strategy also has limitations. High compaction will lead to a decrease in power density and poor electrode wetting, and the thickness of the electrode cannot be increased indefinitely. A thick electrode will result in the active material at the bottom being unable to be utilized.

[0004] Improving the fast-charging capability of lithium ion batteries and reducing the charging time can alleviate the anxiety of insufficient energy density. However, it is difficult to choose between fast-charging capability and high energy density.

[0005] The main measures to improve the fast-charging performance of lithium ion batteries at present include: reducing the thickness of the electrode sheet; using power-type electrode materials (including using amorphous carbon, lithium titanate, expanded graphite, and using smaller particle size materials); using electrolyte with higher ionic conductivity, lower viscosity, and better film-forming properties; using pore-forming agents to leave pores in the electrode, store more electrolyte, improve the electrolyte wetting property, and improve the fast-charging capability and low-temperature performance.

[0006] However, the above methods have their own defects, such as reducing the thickness of the electrode sheet will significantly reduce the energy density, using amorphous carbon, lithium titanate and other materials will increase the cost, and smaller particle size electrode materials may cause a decrease in the initial efficiency. Adding appropriate pores to the electrode can improve the fast-charging performance and low-temperature performance of the battery, but there are many large pores in the high-porosity electrode, and the actual utilization rate is not high. The pores left by the conventional pore-forming agent are mainly large pores, and more electrolyte is needed to fill the large pores, but the electrolyte in the central region is actually redundant, which causes a certain degree of waste and reduces the energy density of the battery. At the same time, the large pores cannot be guaranteed to be interconnected, and the electrolyte has poor wetting effect, so the actual utilization rate of the pores is low. Therefore, while manufacturing a porous electrode to improve the fast-charging capability and low-temperature performance of the battery, the utilization rate of the electrode pores must be considered. SUMMARY

[0007] Therefore, the present application aims to provide a porous electrode, a manufacturing method thereof and an application thereof.

[0008] The present application provides a manufacturing method of a porous electrode, comprising the following steps:

[0009] a) compounding a pore-forming agent with one-dimensional carbon material to form a coating layer on the surface of the one-dimensional carbon material, and then adding the electrode slurry to obtain a mixed slurry;

[0010] b) removing the pore-forming agent after forming an active material layer on at least one side of the surface of the current collector to obtain a porous electrode.

[0011] Preferably, the pore-forming agent in step a) comprises one or more of iodine, sulfur, naphthalene, benzoic acid, 2-methyl alcohol, cinnamic acid, benzyl alcohol, and o-methyl phthalic anhydride.

[0012] Preferably, the one-dimensional carbon material in step a) comprises one or more of carbon nanotubes, carbon fibers, and Ketjen black.

[0013] Preferably, the mass ratio of the pore-forming agent to the one-dimensional carbon material in step a) is (0.2-10):1.

[0014] Preferably, the compounding process in step a) comprises:

[0015] The pore-forming agent and the one-dimensional carbon material are mixed by a ball milling method or a liquid phase method, and then heated under airtight conditions to melt the pore-forming agent and coat the one-dimensional carbon material to form a coating layer, thereby obtaining a pore-forming agent-one-dimensional carbon material composite.

[0016] Preferably, the thickness of the coating layer is 20-500 nm.

[0017] Preferably, the pore-forming agent-one-dimensional carbon material composite is added in an amount of 0.5wt%-2.5wt% of the electrode slurry.

[0018] Preferably, the process of forming the active material layer in step b) comprises:

[0019] The mixed slurry is sequentially coated, dried and rolled on at least one side of the surface of the current collector to form an active material layer.

[0020] Preferably, the rolling pressure is 1g / cm 3 -2g / cm 3 .

[0021] Preferably, the method of removing the pore-forming agent in step b) is vacuum heating.

[0022] And / or, the vacuum degree of the vacuum heating is -0.1 MPa to 0.06 MPa, the temperature is 40℃ to 200℃, and the time is 2h to 12h.

[0023] And / or, after the vacuum heating, the sublimated pore-forming agent is collected and recycled.

[0024] The application also provides a porous electrode prepared by the manufacturing method.

[0025] The application also provides a battery comprising the porous electrode.

[0026] The application provides a porous electrode, a manufacturing method thereof and an application thereof. The manufacturing method comprises the following steps: a) compounding a pore-forming agent with one-dimensional carbon material to form a coating layer on the surface of the one-dimensional carbon material, and then adding the electrode slurry to obtain a mixed slurry; b) removing the pore-forming agent after forming an active material layer on at least one side of the surface of the current collector to obtain a porous electrode. Compared with the prior art, the manufacturing method provided by the application selects specific materials to compound with the pore-forming agent and acts on the electrode slurry, and cooperates with specific process steps to realize overall good interaction; the obtained porous electrode has higher pore utilization rate on the basis of good fast charging capacity and low temperature performance, and ensures that the electrode still has good dynamics under high compaction conditions.

[0027] Meanwhile, the manufacturing method provided by the application has simple process, easy-to-control conditions, easily-obtained raw materials, low cost, small changes to traditional porous electrode production lines and equipment, high production efficiency, and can realize recycling of the pore-forming agent, and has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0029] Figure 1 The flowchart of the manufacturing method of the porous electrode provided by the application;

[0030] Figure 2 The structure schematic diagram of the negative electrode sheet prepared in Comparative Example 2;

[0031] Figure 3A schematic view of the structure of the negative electrode sheet prepared in Example 1;

[0032] Figure 4 A lithium precipitation photograph of Comparative Example 1;

[0033] Figure 5 A lithium precipitation-free photograph of Example 1. DETAILED DESCRIPTION

[0034] In order to make the personnel in the technical field better understand the scheme of the present application, the technical scheme of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] In the description of the present application, "the same chemical composition" should be understood in a broad sense, that is, the main components of the two have consistent chemical composition, or the chemical composition of the two is basically consistent, which can have the error within the range that can be understood by those skilled in the art and within the range that can be allowed in the art or contain impurities within the allowable range.

[0036] In the description of the present application, "A and / or B" can include any one of the following cases: A alone, B alone, A and B, wherein A and B are only used for example, and can be any technical feature connected by "and / or" in the present application.

[0037] Unless otherwise specified, all technical terms used in the present application have the same meaning as that generally understood by those skilled in the art to which the present application belongs. All patents and publications involved in the present application are incorporated by reference in the present application. The term "comprising" or "including" is an open expression, that is, it includes the content indicated in the present application, but does not exclude other aspects.

[0038] Currently, most existing porous electrode manufacturing methods involve creating pores in the electrode using pore-forming agents. Electrode wetting only requires filling the limited space on the surface of the active material with electrolyte. Filling the large pore centers with electrolyte is redundant and leads to a higher overall electrode porosity, resulting in a higher required electrolyte injection coefficient and a decrease in cell energy density. Furthermore, large pores cannot be guaranteed to be interconnected, leading to poor electrolyte wetting and low actual pore utilization. After electrode compaction, closed pores may remain, rendering them completely unusable. Based on this, this invention manufactures a porous electrode with high porosity utilization, enhancing electrolyte retention, shortening ion diffusion paths, and improving fast-charging performance. It also adjusts the thickness of pores on the active material surface, forming one-dimensional through-holes, avoiding electrolyte waste caused by large pores and ineffective porosity due to closed pores. High porosity utilization can still be achieved under high compaction conditions, ensuring sufficient electrode wetting and maintaining good kinetics even under high compaction.

[0039] This invention provides a method for manufacturing a porous electrode, comprising the following steps:

[0040] a) A pore-forming agent is combined with a one-dimensional carbon material to form a coating layer on the surface of the one-dimensional carbon material, and then added to the electrode slurry to obtain a mixed slurry;

[0041] b) After forming an active material layer on at least one side of the current collector with the mixed slurry obtained in step a), the pore-forming agent is removed to obtain a porous electrode.

[0042] See Figure 1 As shown, Figure 1 A flowchart of the porous electrode manufacturing method provided by the present invention.

[0043] The present invention first combines a pore-forming agent with a one-dimensional carbon material to form a coating layer on the surface of the one-dimensional carbon material, and then adds it to the electrode slurry to obtain a mixed slurry.

[0044] In this invention, the pore-forming agent preferably includes one or more of iodine, sulfur, naphthalene, benzoic acid, 2-carboxylic acid, cinnamic acid, benzyl alcohol, and o-methyl phthalic anhydride, more preferably sulfur, naphthalene, or o-methyl phthalic anhydride. This invention does not impose any special restrictions on the source of the pore-forming agent; commercially available products well-known to those skilled in the art can be used. This invention uses the aforementioned materials with low melting points and easy sublimation under vacuum conditions as pore-forming agents. On the one hand, this allows for the formation of a suitable coating layer on the surface of one-dimensional carbon materials through heating and melting, thereby obtaining suitable pores during subsequent porous electrode manufacturing. On the other hand, it facilitates the removal and recovery of the pore-forming agent in conjunction with subsequent vacuum heating steps.

[0045] In the present application, the one-dimensional carbon material preferably comprises one or more of carbon nanotubes, carbon fibers, and Ketjen black, and more preferably carbon nanotubes. The present application does not have special restrictions on the source of the one-dimensional carbon material, and commercially available products known to those skilled in the art can be used. The present application uses the above-mentioned one-dimensional carbon material with a high aspect ratio and a pore-forming agent to form a composite, in which the one-dimensional carbon material itself can act as a conductive additive in the electrode active layer, and the pore-forming agent forms a nanoscale coating layer on the surface of the one-dimensional carbon material by compounding, which is then removed during the subsequent manufacture of the porous electrode, thereby enabling the formation of pores with a nanoscale thickness (20-500 nm) around the periphery of the one-dimensional carbon material. Such pores enable the active material surface within a range of 20-500 nm to be filled with electrolyte without excessive waste. At the same time, the one-dimensional pores extending along the length of the conductive additive avoid the presence of closed pores, further improving the wettability of the electrode.

[0046] In the present application, the mass ratio of the pore-forming agent to the one-dimensional carbon material is preferably (0.2-10):1, and more preferably (2-10):1, and can be specifically 2:1, 7:3, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. The present application uses the above-mentioned pore-forming agent and one-dimensional carbon material in a ratio to facilitate the subsequent formation of a suitable coating layer, further obtaining the desired one-dimensional pores, and enabling the diameter of the one-dimensional pores to be appropriately controlled.

[0047] In the present application, the compounding process can coat the pore-forming agent on the surface of the one-dimensional carbon material to form a coating layer, preferably comprising:

[0048] The pore-forming agent and the one-dimensional carbon material are mixed by ball milling or liquid phase method, and then heated under airtight conditions to melt the pore-forming agent, which is coated on the surface of the one-dimensional carbon material to form a coating layer, thereby obtaining a pore-forming agent-one-dimensional carbon material composite. The ball milling method uses a ball mill known to those skilled in the art, and the one-dimensional carbon material is preferably continuously ball milled at a speed of 200 rpm-500 rpm for 2 h-5 h to achieve uniform mixing of the pore-forming agent and the one-dimensional carbon material. The liquid phase method involves dissolving the pore-forming agent in a suitable solvent (such as carbon disulfide, chloroform, dichloromethane, etc.), adding the one-dimensional carbon material, and stirring for 3 h-5 h until uniform, and then heating to evaporate the solvent to achieve uniform mixing of the pore-forming agent and the one-dimensional carbon material. Subsequently, the mixture is heated (the heating temperature is preferably 40℃-280℃, and the time is preferably 8 h-12 h) under airtight conditions (such as by adding a high-pressure kettle) to melt the pore-forming agent, which is uniformly coated on the surface of the one-dimensional carbon material to form a coating layer.

[0049] In the present application, the thickness of the coating layer is preferably 20-500 nm. In the present application, the thickness of the coating layer is mainly used to control the diameter of the one-dimensional through hole manufactured, which is specifically set according to the requirements of the battery cell. The larger the diameter of the through hole, the more the electrolyte is infiltrated, which is more conducive to fast charging, but the energy density is reduced. The smaller the diameter of the through hole, the more conducive to improving the fast charging capability in the battery cell of the high energy density system.

[0050] After obtaining the pore-forming agent-one-dimensional carbon material composite, the present application adds it to the electrode slurry to obtain a mixed slurry. The present application does not have special restrictions on the type and source of the electrode slurry, and can use commercially available raw materials known to those skilled in the art to perform conventional homogenization. After adding the pore-forming agent-one-dimensional carbon material composite, further homogenization is performed to obtain the mixed slurry. The present application does not have special restrictions on the process of homogenization, and can use the technical means of mechanical stirring known to those skilled in the art. The purpose is to mix the raw materials uniformly.

[0051] The porous electrode obtained by the manufacturing method provided by the present application can be adapted to various battery systems, including but not limited to lithium ion batteries, sodium ion batteries, potassium ion batteries, etc. On this basis, the electrode slurry can be a positive electrode slurry and / or a negative electrode slurry. As a positive electrode slurry, it includes a positive electrode material (including but not limited to one or more of lithium iron phosphate, lithium iron manganese phosphate, ternary positive electrode, lithium cobaltate, lithium manganate, lithium nickel manganate, layered sodium oxide, sodium ion battery polyanion positive electrode, prussian blue analogs, etc.), and also includes conductive agents, binders and other functional additives commonly used in the preparation of positive electrode slurries. As a negative electrode slurry, it includes a negative electrode material (including but not limited to one or more of graphite, silicon-carbon, silicon, hard carbon, soft carbon, mesocarbon microbeads, expanded graphite, tin, germanium, antimony, bismuth, red phosphorus, black scale, etc.), and also includes conductive agents, binders and other functional additives commonly used in the preparation of negative electrode slurries.

[0052] In the present application, the addition amount of the pore-forming agent-one-dimensional carbon material composite is preferably 0.5wt%-2.5wt% of the electrode slurry, and can be specifically 0.5wt%, 0.67wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%. The present application uses the above addition amount, which is conducive to the one-dimensional carbon material after the removal of the pore-forming agent to achieve a better conductive additive effect in the electrode active material, without affecting the overall performance of the electrode sheet.

[0053] After obtaining the mixed slurry, the present application forms an active material layer on at least one side surface of the current collector, removes the pore-forming agent, and obtains a porous electrode.

[0054] In the present application, the current collector can be a positive electrode current collector such as an aluminum foil or a negative electrode current collector such as a copper foil known to those skilled in the art, and the present application does not have special restrictions thereon.

[0055] In the present application, the process of forming the active material layer preferably comprises:

[0056] The mixed slurry is coated, dried and rolled on at least one side surface of the current collector in sequence to form the active material layer.

[0057] In the present application, the coating and drying process can be achieved by using the technical means for preparing electrode sheets known to those skilled in the art, such as the technical means of oven drying after coating the mixed slurry on one side surface of the current collector, and the present application has no special limitation.

[0058] In the present application, the compaction density of the rolling is 1 g / cm 3 ~ 2 g / cm 3 On this basis, the present application can obtain an active material layer of the desired thickness, and at the same time, the present application can also achieve the technical effect that the electrode can retain good kinetic properties under high compaction. After high compaction, the present application removes the pore-forming agent to leave pores in the electrode, and the remaining pores can still penetrate through the entire electrode, with a sufficiently high utilization rate.

[0059] Finally, the present application removes the pore-forming agent from the rolled electrode sheet; the preferred method for removing the pore-forming agent is vacuum heating; the vacuum degree of the vacuum heating is preferably -0.1 MPa ~ 0.06 MPa, the temperature is preferably 40℃ ~ 200℃, and the time is preferably 2h ~ 12h; on this basis, the present application can achieve complete sublimation of the pore-forming agent in the electrode sheet.

[0060] After sublimation of the pore-forming agent, the remaining pores are surrounded on the surface of the one-dimensional carbon material, and the size of the remaining pores can be controlled by the thickness of the pore-forming agent coated on the surface of the one-dimensional carbon material, which can achieve the infiltration of the electrolyte in the range of 20 ~ 500nm on the surface of the active material, without forming micron-sized block-shaped pores, improving the utilization rate of the pores, and the one-dimensional pores formed can reduce the existence of closed pores in the electrode sheet, improving the utilization rate of the pores, and ultimately obtaining the porous electrode of the present application.

[0061] In the present application, after vacuum heating, the sublimated pore-forming agent is preferably collected and recycled. The pore-forming agent is removed by sublimation, and the pore-forming agent can be recovered by cooling the sublimated gas, without changing the composition of the pore-forming agent, and it is easy to collect. After collection, the pore-forming agent can be repeatedly used, and after removal of the pore-forming agent, the electrical conductivity of the one-dimensional carbon material is not affected, and it can still function as a conductive carbon.

[0062] The manufacturing method provided by the application can make the electrode have one-dimensional through holes, is more conducive to electrolyte infiltration, and at the same time, the one-dimensional through holes almost do not have space waste, can avoid the appearance of closed holes caused by particle accumulation to the greatest extent, and the high utilization rate of the pores can also ensure that the electrode has good kinetics under high compaction conditions; at the same time, the manufacturing method provided by the application has simple process, easy-to-control conditions, easy-to-obtain raw materials, low cost, small changes to the traditional porous electrode production line, high production efficiency, and can also realize the recycling of the pore-forming agent, and has a broad application prospect.

[0063] The application further provides a porous electrode prepared by the manufacturing method.

[0064] The porous electrode provided by the application has the following beneficial effects:

[0065] 1. The application increases the electrode pores, is conducive to improving the liquid retention capacity of the electrode, shortens the ion diffusion path, and is conducive to improving the fast charging capacity and low temperature performance of the battery in various thickness electrodes.

[0066] 2. The pores manufactured in the electrode have high utilization rate, can adjust the active material surface electrolyte thickness in the range of 20-500 nm according to actual needs, and can also reduce the closed pores that occur in the electrode tab compaction process, resulting in invalid porosity.

[0067] The application further provides a battery comprising the porous electrode.

[0068] The porous electrode provided by the application can be adapted to various battery systems, including but not limited to lithium ion batteries, sodium ion batteries, potassium ion batteries, etc., and can be applied to any battery system that needs a conductive agent, and can manufacture controllable one-dimensional pores in the electrode.

[0069] Taking a lithium ion battery as an example, the lithium ion battery comprises the porous electrode (which can be used as a positive electrode and / or a negative electrode), a separator, an electrolyte, and other necessary or unnecessary functional elements or packaging components, etc., and a person skilled in the art can make any selection and combination thereof; wherein the separator includes but is not limited to wet PP, PE, and PP separators; the electrolyte is a mixed solvent in which LiPF6 is dissolved in a conventional carbonate solvent and a carboxylate solvent, and usually contains a small amount of additives, and the application does not have special limitations thereon. When the lithium ion battery comprises the porous electrode, whether the lithium ion battery also uses other composite electrodes or not, it can be used as an embodiment of the application.

[0070] The application provides a porous electrode and a manufacturing method and application thereof; the manufacturing method comprises the following steps: a) compounding a pore-forming agent with one-dimensional carbon material to form a coating layer on the surface of the one-dimensional carbon material, and then adding the electrode slurry to obtain a mixed slurry; and b) removing the pore-forming agent after forming an active material layer on at least one side of the surface of the current collector to obtain the porous electrode. Compared with the prior art, the manufacturing method provided by the application selects specific materials to be compounded with the pore-forming agent and to act on the electrode slurry, and cooperates with specific process steps to realize overall good interaction; the obtained porous electrode has higher pore utilization rate on the basis of good fast charging capacity and low temperature performance, and ensures that the electrode still has good kinetics under high compaction conditions.

[0071] Meanwhile, the manufacturing method provided by the application has simple process, easy-to-control conditions, easily-obtained raw materials, low cost, small changes to the traditional porous electrode production line, high production efficiency, and can realize recycling of the pore-forming agent, and has a broad application prospect.

[0072] In order to further illustrate the application, the following examples are used for detailed description. The raw materials used in the following examples of the application are all commercially available; wherein, the used separator is a 5 μm thick PP separator, the used electrolyte is an electrolyte of LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DEC) and methyl ethyl carbonate (EMC) with a mass ratio of 1:1:1; and the preparation method of the sulfur-carbon nanotube composite is as follows:

[0073] The sulfur powder and carbon nanotubes are mixed, and then ball-milled in a ball mill at a speed of 400 rpm for 4 hours; then the ball-milled mixture is heated to 155 DEG C in an autoclave for 10 hours, and the sulfur-coated carbon nanotube composite is obtained after cooling.

[0074] Comparative Example 1

[0075] LiFePO4 positive electrode material and Super P, polyvinylidene fluoride (PVDF) are selected and uniformly mixed in a mass ratio of 96:2:2, and then coated on an aluminum foil current collector after slurry preparation; the coated product is dried in an oven, and then roll-pressed to obtain a positive electrode sheet with a compaction density of 1.62 g / cm 3 Graphite is selected as a negative electrode material, and the graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) and Super P are uniformly mixed in a mass ratio of 97.6:1.2:0.8:0.4, and then coated on a copper foil current collector after slurry preparation; the coated product is dried in an oven, and then roll-pressed to obtain a negative electrode sheet with a compaction density of 1.62 g / cm 3 A 2.5 Ah small soft-pack battery is prepared by the Z-shaped stacking method. The electrolyte is injected into the battery in an argon glove box, and the injection coefficient is 2.6; and the battery is placed at 45 DEG C for 48 hours.

[0076] Comparative Example 2

[0077] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) were mixed uniformly in a mass ratio of 96:2:2, and then coated on an aluminum foil current collector after slurry preparation, dried in an oven, and then roll-pressed to obtain a cathode sheet with a compacted density of 1.62 g / cm 3 Graphite was selected as the active material of the anode, and graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sulfur, and Super P were mixed uniformly in a mass ratio of 97.6:1.2:0.8:0.667:0.4, and then coated on the surface of a copper foil after slurry preparation, dried in an oven, and then roll-pressed to obtain an anode sheet with a compacted density of 1.62 g / cm 3 , and then dried at 100°C for 8 hours under vacuum to remove sulfur in the sheet, to obtain the required anode sheet (see the structural schematic diagram shown in FIG. 2). Figure 2 Figure 2 A porous electrode manufactured by a conventional pore-forming agent method, comprising a current collector (1), an active material (2), closed pores (3), and open macropores (4), wherein the open macropores (4) can be formed by accumulation of active material particles or holes formed after removal of a pore-forming agent; the porosity of the anode sheet in Comparative Example 2 was actually tested to be 36%); a small soft-pack battery with a capacity of 2.5 Ah was prepared by a Z-shaped lamination method. The electrolyte was injected in an argon glove box, and the injection coefficient was 2.6, and the battery was placed at 45°C for 48 hours.

[0078] Example 1

[0079] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) were mixed uniformly in a mass ratio of 96:2:2, and then coated on an aluminum foil current collector after slurry preparation, dried in an oven, and then roll-pressed to obtain a cathode sheet with a compacted density of 1.62 g / cm 3 Graphite was selected as the active material of the anode, and graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sulfur-carbon nanotube composite (sulfur and carbon nanotube in a mass ratio of 7:3), and Super P were mixed uniformly in a mass ratio of 97.6:1.2:0.8:0.667:0.2, and then coated on the surface of a copper foil after slurry preparation, dried in an oven, and then roll-pressed to obtain an anode sheet with a compacted density of 1.62 g / cm 3 , and then dried at 100°C for 8 hours under vacuum to remove sulfur in the sheet (the sublimated gas was recovered after cooling to recycle sulfur), to obtain the required anode sheet (see the structural schematic diagram shown in FIG. 2). Figure 3 Figure 3 A porous electrode obtained by the manufacturing method provided by the present application, in addition to comprising Figure 2 ​​The same structure current collector and active material (not repeated) further includes a one-dimensional carbon material (5) and a through closed hole (6); the negative electrode sheet porosity in the actual test example 1 is 28%; a 2.5 Ah small soft package battery is made by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and it is placed at 45°C for 48 hours.

[0080] Example 2

[0081] LiFePO4 positive electrode material, Super P and polyvinylidene fluoride (PVDF) are selected and uniformly mixed in a mass ratio of 96:2:2, slurry is prepared, and then coated on an aluminum foil current collector, dried in an oven, and then rolled, with a compaction density of 1.62 g / cm 3 The required positive electrode sheet is prepared; the negative electrode selects graphite as the active material, graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio of 9:1), Super P are uniformly mixed in a mass ratio of 97.6:1.2:0.8:2:0.2, slurry is prepared, and then coated on the surface of a copper foil, dried in an oven, and then rolled, with a compaction density of 1.62 g / cm 3 , and then dried at 100°C under vacuum for 8 hours to remove sulfur in the electrode sheet (the sublimed gas is recovered after cooling to recycle sulfur), to prepare the required negative electrode sheet; a 2.5 Ah small soft package battery is made by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and it is placed at 45°C for 48 hours.

[0082] Example 3

[0083] LiFePO4 positive electrode material, Super P, polyvinylidene fluoride (PVDF) and sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio of 7:3) are selected and uniformly mixed in a mass ratio of 96:1.8:2:0.667, slurry is prepared, and then coated on an aluminum foil current collector, dried in an oven, and then rolled, with a compaction density of 1.62 g / cm 3 , and then dried at 100°C under vacuum for 8 hours to remove sulfur in the electrode sheet (the sublimed gas is recovered after cooling to recycle sulfur), to prepare the required positive electrode sheet; the negative electrode selects graphite as the active material, graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), Super P are uniformly mixed in a mass ratio of 97.6:1.2:0.8:0.4, slurry is prepared, and then coated on the surface of a copper foil, dried in an oven, and then rolled, with a compaction density of 1.62 g / cm 3 , to prepare the required negative electrode sheet; a 2.5 Ah small soft package battery is made by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and it is placed at 45°C for 48 hours.

[0084] Example 4

[0085] LiFePO4 cathode material, Super P, polyvinylidene fluoride (PVDF) and sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio of 7:3) were mixed uniformly in a mass ratio of 96:1.8:2:0.667, and then coated on an aluminum foil current collector after slurry preparation. The coated aluminum foil current collector was dried in an oven, and then roll-pressed to obtain a cathode sheet with a compacted density of 1.62 g / cm3. 3 The cathode sheet was dried at 100°C under vacuum for 8 hours to remove sulfur in the cathode sheet (sublimated gas was recovered after cooling to be reused), and then a 2.5 Ah small soft-pack battery was prepared by a Z-shaped stacking method. The electrolyte was injected into the battery in an argon glove box, and the injection coefficient was 2.6. The battery was placed at 45°C for 48 hours. 3 The cathode sheet was dried at 100°C under vacuum for 8 hours to remove sulfur in the cathode sheet (sublimated gas was recovered after cooling to be reused), and then a 2.5 Ah small soft-pack battery was prepared by a Z-shaped stacking method. The electrolyte was injected into the battery in an argon glove box, and the injection coefficient was 2.6. The battery was placed at 45°C for 48 hours.

[0086] Example 5

[0087] LiFePO4 cathode material, Super P, polyvinylidene fluoride (PVDF) and sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio of 7:3) were mixed uniformly in a mass ratio of 96:1.8:2:0.667, and then coated on an aluminum foil current collector after slurry preparation. The coated aluminum foil current collector was dried in an oven, and then roll-pressed to obtain a cathode sheet with a compacted density of 1.62 g / cm3. 3 The cathode sheet was dried at 100°C under vacuum for 8 hours to remove sulfur in the cathode sheet (sublimated gas was recovered after cooling to be reused), and then a 2.5 Ah small soft-pack battery was prepared by a Z-shaped stacking method. The electrolyte was injected into the battery in an argon glove box, and the injection coefficient was 2.6. The battery was placed at 45°C for 48 hours. 3 The cathode sheet was dried at 100°C under vacuum for 8 hours to remove sulfur in the cathode sheet (sublimated gas was recovered after cooling to be reused), and then a 2.5 Ah small soft-pack battery was prepared by a Z-shaped stacking method. The electrolyte was injected into the battery in an argon glove box, and the injection coefficient was 2.6. The battery was placed at 45°C for 48 hours.

[0088] Example 6

[0089] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96:2:2, coated on the aluminum foil current collector after slurry preparation, dried in an oven, then rolled, and the compaction density is 1.62 g / cm 3 The required positive electrode sheet is prepared; the negative electrode selects graphite as the active material, and graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), o-methyl phthalic anhydride-carbon nanotube composite (o-methyl phthalic anhydride and carbon nanotube mass ratio is 7:3), Super P are mixed uniformly in a mass ratio of 97.6:1.2:0.8:0.667:0.2, coated on the copper foil surface after slurry preparation, dried in an oven, then rolled, and the compaction density is 1.62 g / cm 3 , and then dried at 100°C for 8 hours under vacuum to remove o-methyl phthalic anhydride in the electrode sheet (the sublimed gas is recovered after cooling to recycle o-methyl phthalic anhydride), and the required negative electrode sheet is prepared; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and it is placed at 45°C for 48 hours.

[0090] Example 7

[0091] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96:2:2, coated on the aluminum foil current collector after slurry preparation, dried in an oven, then rolled, and the compaction density is 1.62 g / cm 3 The required positive electrode sheet is prepared; the negative electrode selects graphite and mesocarbon microbeads as the active material, and graphite, mesocarbon microbeads, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio is 7:3), Super P are mixed uniformly in a mass ratio of 90:7.6:1.2:0.8:0.667:0.2, coated on the copper foil surface after slurry preparation, dried in an oven, then rolled, and the compaction density is 1.62 g / cm 3 , and then dried at 100°C for 8 hours under vacuum to remove sulfur in the electrode sheet (the sublimed gas is recovered after cooling to recycle sulfur), and the required negative electrode sheet is prepared; a 2.5 Ah small soft package battery is prepared by the Z-shaped stacking method. The electrolyte is injected in an argon glove box, the injection coefficient is 2.6, and it is placed at 45°C for 48 hours.

[0092] Example 8

[0093] LiFePO4 cathode material and Super P, polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 96:2:2, coated on the aluminum foil current collector after slurry preparation, dried in an oven, then rolled, and the compaction density is 1.62 g / cm3 The positive electrode sheet was prepared; the negative electrode selected graphite and hard carbon as the active material, graphite, hard carbon, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio of 7:3), Super P were mixed uniformly according to the mass ratio of 90:7.6:1.2:0.8:0.667:0.2, after slurry preparation, coated on the surface of copper foil, dried in an oven, then rolled, the compaction density was 1.62 g / cm 3 , and dried at 100°C for 8 hours under vacuum to remove sulfur in the electrode sheet (the sublimed gas was recovered after cooling to reuse the sulfur), to obtain the required negative electrode sheet; a 2.5 Ah small soft package battery was prepared by the Z-shaped stacking method. The electrolyte was injected in an argon glove box, the injection coefficient was 2.6, and it was placed at 45°C for 48 hours.

[0094] Example 9

[0095] The LiFePO4 positive electrode material, LiFe 0.6 Mn 0.4 PO4, Super P, polyvinylidene fluoride (PVDF) and sulfur-carbon nanotube composite (sulfur and carbon nanotube mass ratio of 7:3) were mixed uniformly according to the mass ratio of 67.2:28.8:1.8:2:0.667, after slurry preparation, coated on the surface of aluminum foil current collector, dried in an oven, then rolled, the compaction density was 1.62 g / cm 3 , and dried at 100°C for 8 hours under vacuum to remove sulfur in the electrode sheet (the sublimed gas was recovered after cooling to reuse the sulfur), to obtain the required positive electrode sheet; the negative electrode selected graphite as the active material, graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), Super P were mixed uniformly according to the mass ratio of 97.6:1.2:0.8:0.4, after slurry preparation, coated on the surface of copper foil, dried in an oven, then rolled, the compaction density was 1.62 g / cm 3 , to obtain the required negative electrode sheet; a 2.5 Ah small soft package battery was prepared by the Z-shaped stacking method. The electrolyte was injected in an argon glove box, the injection coefficient was 2.6, and it was placed at 45°C for 48 hours.

[0096] The batteries prepared in each example and comparative example were tested for various performances, specifically including:

[0097] Constant current charge and discharge test, charged at the selected rate (4C and 5C), discharged at 0.33C; low temperature DCR test.

[0098] Lithium precipitation risk determination method: all examples, comparative examples of the battery cell at-10 DEG C according to the given step charging (equivalent 1C rate), 0.33C discharge, cycle 50 times, after 24h after the battery disassembled, observe whether there is lithium precipitation on the negative electrode surface. Lithium precipitation area accounts for the entire electrode area 0~5% is low, 5~10% is medium, more than 10% is high.

[0099] Test results are shown in Table 1 and Figures 4-5 Table 1 Figure 4 is the lithium precipitation photo of comparative example 1, Figure 5 is the no lithium precipitation photo of example 1.

[0100] Table 1

[0101]

[0102] From Table 1, the manufacturing method provided by examples 1-9 of the present application has higher cycle retention rate and capacity, lower resistance in normal low temperature DCR test, and low risk of low temperature lithium precipitation compared with comparative examples 1-2, and has better fast charging ability and low temperature performance as a whole, which benefits from the high porosity utilization rate of the porous electrode designed and manufactured by the present application, and the higher porosity utilization rate can ensure that the electrode still has good dynamics under high compaction condition.

[0103] In summary, the present application provides a porous electrode and its manufacturing method and application, which has the following beneficial effects:

[0104] 1、The electrode sheet provided by the present application increases the electrode porosity, which is beneficial to improve the liquid retention capacity of the electrode, shorten the ion diffusion path, and improve the battery fast charging ability and low temperature performance in various thickness electrodes.

[0105] 2、The porosity of the porous electrode manufactured by the present application has high utilization rate, which can adjust the active material surface electrolyte thickness in the range of 20-500nm according to actual needs, and can also reduce the invalid porosity caused by closed pores in the electrode compaction process.

[0106] 3、The present application can make the electrode retain good dynamics under high compaction condition.

[0107] 4、The pore-forming agent in the present application can be reused.

[0108] In the above description of the specification, the description referring to the terms "one embodiment", "another embodiment", and the like means that the particular feature, structure, material, or characteristic being described is included in at least one embodiment of the application. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Moreover, the terminology used has been chosen for the purpose of clarity based on the description provided herein. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the application and, thus, within its scope, possess the essential, characteristic features. Furthermore, the description herein is in the general context of computer-executable instructions, such as program modules being executed by computers. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Moreover, those skilled in the art will appreciate that the functions could be embodied in software, firmware, hardware, or any combination thereof.

[0109] The foregoing description of the disclosed embodiments enables a person skilled in the art to implement or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for manufacturing a porous electrode, characterized in that, Includes the following steps: a) A pore-forming agent is combined with a one-dimensional carbon material to form a coating layer on the surface of the one-dimensional carbon material, and then added to the electrode slurry to obtain a mixed slurry; b) After forming an active material layer on at least one side of the current collector with the mixed slurry obtained in step a), the pore-forming agent is removed to obtain a porous electrode.

2. The manufacturing method according to claim 1, characterized in that, The pore-forming agent mentioned in step a) includes one or more of iodine, sulfur, naphthalene, benzoic acid, 2-oxalool, cinnamic acid, benzyl alcohol, and o-methylphthalic anhydride.

3. The manufacturing method according to claim 1, characterized in that, The one-dimensional carbon material mentioned in step a) includes one or more of carbon nanotubes, carbon fibers, and Ketjen black.

4. The manufacturing method according to claim 1, characterized in that, The mass ratio of the pore-forming agent to the one-dimensional carbon material in step a) is (0.2-10):

1.

5. The manufacturing method according to claim 1, characterized in that, The compounding process described in step a) includes: After mixing the pore-forming agent with a one-dimensional carbon material by ball milling or liquid phase method, the pore-forming agent is heated under closed conditions to melt the pore-forming agent and coat the surface of the one-dimensional carbon material to form a coating layer, thus obtaining a pore-forming agent-one-dimensional carbon material composite. And / or, the thickness of the coating layer is 20nm to 500nm.

6. The manufacturing method according to claim 5, characterized in that, The amount of the pore-forming agent-one-dimensional carbon material composite added is 0.5wt% to 2.5wt% of the electrode slurry.

7. The manufacturing method according to claim 1, characterized in that, The process of forming the active material layer in step b) includes: The mixed slurry is sequentially coated, dried, and rolled on at least one surface of the current collector to form an active material layer; And / or, the compaction density of the roller press is 1 g / cm³. 3 ~2g / cm 3 .

8. The manufacturing method according to claim 1, characterized in that, The method for removing the pore-forming agent described in step b) is vacuum heating; And / or, the vacuum degree of the vacuum heating is -0.1MPa to 0.06MPa, the temperature is 40℃ to 200℃, and the time is 2h to 12h; And / or, after the vacuum heating, the process further includes: collecting the sublimated pore-forming agent for recycling.

9. A porous electrode, characterized in that, It is prepared by the manufacturing method described in any one of claims 1 to 8.

10. A battery, characterized in that, Includes the porous electrode as described in claim 9.

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