Preparation Method of a Porous Carbon Composite Lithium Battery Dry Electrode

Abstract

The present invention provides a method for preparing a dry electrode of a porous carbon composite lithium battery. After uniformly mixing an active material, a conductive agent, porous carbon, and a binder, twin-screw extrusion and extrusion granulation are used to respectively prepare a first particle and a second particle, and the mixed particles are obtained by mixing; subsequently, the mixed particles are rolled on a rolling machine to obtain a dry electrode film; by pre-spraying a conductive adhesive on the surface of the foil to form a conductive coating, the dry electrode film is uniformly pasted on the conductive coating foil respectively, heated, and rolled to obtain the dry electrode of the porous carbon composite lithium battery. The preparation process of the present invention does not use solvents, is environmentally friendly, saves production time and equipment costs, and avoids the problem of battery performance deterioration caused by solvents; moreover, the present invention adopts the form of extrusion granulation to more easily control the degree of fibrosis of the binder, and the production process is simple and efficient.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemistry and relates to a preparation method of a dry electrode for a porous carbon composite lithium battery. Background Art

[0002] As a new type of energy storage device, lithium-ion batteries are widely used because of their advantages such as high energy density, wide operating temperature range, long cycle life, and fast charge and discharge. Traditional lithium-ion batteries often use a wet process, preparing a slurry with water or organic solvents for coating. Organic solvents not only cause environmental pollution and high energy consumption, but also lead to excessive water content during the preparation process, resulting in problems such as battery swelling and rapid performance decay during long-term cycling.

[0003] Based on the above problems, many researchers have chosen to use a dry process to prepare electrodes. A mixed powder is composed of active materials, conductive materials, binders, etc., and is extruded and rolled to form a continuous self-supporting dry coating. This coating is pressed with a current collector to form an electrode sheet. Although this dry electrode preparation process is simple, without a drying process, more flexible, environmentally friendly, can effectively save materials, time and labor costs, and avoid the long-term high-temperature and ultra-low vacuum drying and water removal process, while reducing the product energy consumption, it also improves the cycle service life of the product.

[0004] However, in the current dry electrode preparation process, the binder exists in the form of fibers. Since the binder is fibrillated by methods such as spraying and grinding during the preparation process, the fibrillation is difficult, and the high shear force will cause the bonding performance of the binder to decline, partial inactivation of the positive and negative active materials, cracking of the coatings on the surfaces of the positive and negative active materials, etc. Moreover, the high shear force requires high equipment requirements, resulting in high production costs and being not conducive to large-scale production. If the shear force is low, the degree of binder fibrillation is low, which is not sufficient to adhere the active materials and conductive agents, and problems such as powder shedding are likely to occur.

[0005] Therefore, how to provide a preparation method of a dry electrode for a lithium battery with simple operation and excellent performance is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] In view of this, in view of the deficiencies existing in the prior art, the present invention provides a preparation method of a dry electrode for a porous carbon composite lithium battery.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A preparation method of a dry electrode for a porous carbon composite lithium battery, the method specifically includes the following steps:

[0009] 1) The active material, the conductive agent, the porous carbon and the binder are uniformly mixed and divided into two parts. The first part is subjected to a first extrusion granulation by twin-screw extrusion to obtain first particles having a first particle size; the second part is subjected to a second extrusion granulation by twin-screw extrusion to obtain second particles having a second particle size; the first particles and the second particles are mixed in proportion to obtain mixed particles;

[0010] 2) placing the mixed particles on a heated roller compactor for compaction to obtain a dry electrode membrane;

[0011] 3) After spraying conductive glue on the surface of the foil in advance to form a conductive coating, the dry electrode films are evenly pasted on the conductive coating foil, heated, and rolled to obtain the porous carbon composite lithium battery dry electrode.

[0012] Optionally, the mixed particles include the following components, calculated in percentage by mass:

[0013] Active material 80%-99%, conductive agent 0.5%-5%, porous carbon 0.5-2%, binder 1%-10%.

[0014] Furthermore, the active material is at least one of ternary lithium, lithium iron phosphate, lithium manganate, lithium cobaltate and graphite, the conductive agent is at least one of super-P, Ketjen black, carbon nanotubes, and carbon fibers, and the binder is one of polytetrafluoroethylene PTFE, thermoplastic elastomer SEBS, polyethylene PE, polypropylene PP, and polymethyl methacrylate PMMA.

[0015] Optionally, the specific surface area of the porous carbon is 1000-2500m 2 / g, and the porous carbon is one of activated carbon, activated carbon fiber, and carbon aerogel.

[0016] Furthermore, the particle size of the porous carbon is 5-10 μm, the particle size of the first particles is 0.2-1 mm, the particle size of the second particles is 1-5 mm, and the particle size of the mixed particles is 0.5-5 mm.

[0017] Furthermore, the mixing mass ratio of the first particles to the second particles is 1:1-1:10.

[0018] It should be noted that porous carbon is a carbon material with a continuous nanoporous material structure. It has the properties of high specific surface area, high porosity, good conductivity and controllable pore size, and has attracted widespread attention.

[0019] Moreover, the particle size of the porous carbon is controlled within the range of 5-10 μm to avoid the particle size being too large or too small, which is not conducive to bonding.

[0020] Optionally, in step 2), the rolling temperature is 60 - 200 °C, and the rolling pressure is 2 - 10 atmospheres.

[0021] Optionally, in step 3), the rolling temperature is 60 - 200 °C, and the rolling pressure is 2 - 5 atmospheres.

[0022] It should be noted that the purpose of rolling is to improve the density and strength of the electrode film, thereby improving the energy density of the battery; and rolling with foil is to manufacture the battery current collector, which is convenient for subsequent processing and welding.

[0023] Through the above technical solutions, compared with the prior art, a preparation method of a dry electrode for a porous carbon composite lithium battery provided by the present invention has the following excellent effects:

[0024] 1) In the preparation process of the present invention, no solvent is used, which is environmentally friendly, saves production time and equipment costs, and avoids the problem of battery performance deterioration caused by solvents.

[0025] 2) In the present invention, by preparing the first particles and the second particles with different particle sizes into mixed particles and then rolling, a denser dry electrode film can be prepared.

[0026] 3) In the present invention, by compounding porous carbon with lithium battery materials to prepare a dry electrode, the absorption and retention rate of the electrolyte can be improved, thereby improving battery performance and extending the cycle life.

[0027] 4) In the present invention, the form of extrusion granulation is adopted to more easily control the degree of fibrosis of the binder, and the production process is simple and efficient. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0029] Figure 1 It is a scanning electron microscope image of the battery electrode sheet prepared in Example 1.

[0030] Figure 2 It is a scanning electron microscope image of the battery electrode sheet prepared in the comparative example.

[0031] Figure 3 It is the electrode electrical performance diagram of Example 1 and the comparative example. Detailed Embodiments

[0032] Next, in combination with the embodiments of the present invention and the accompanying drawings of the specification, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0033] The embodiment of the present invention discloses a preparation method of a dry electrode of a porous carbon composite lithium battery.

[0034] For a better understanding of the present invention, the following embodiments are used to further specifically illustrate the present invention, but it should not be understood as a limitation of the present invention. For those skilled in the art, some non-essential improvements and adjustments made according to the above-mentioned invention content are also considered to fall within the scope of protection of the present invention.

[0035] Next, in combination with specific embodiments, the technical solutions of the present invention will be further described.

[0036] Embodiment 1

[0037] A preparation method of a dry electrode of a porous carbon composite lithium battery, the method specifically includes the following steps:

[0038] 1) Mix 85 parts of lithium iron phosphate, 3 parts of super-P, 2 parts of activated carbon, and 10 parts of thermoplastic elastomer SEBS evenly, and divide them into two parts. The first part is extruded by a twin-screw extruder and granulated to obtain first particles with a particle size of 0.3 mm; the second part is extruded by a twin-screw extruder and granulated to obtain second particles with a particle size of 3 mm; the first particles and the second particles are mixed evenly according to a mass ratio of 1:1 to obtain mixed particles.

[0039] 2) Place the mixed particles on a rolling machine with upper and lower heating, the rolling temperature is 150 °C, and the rolling pressure is 6 atmospheres to obtain a dry electrode film;

[0040] 3) After pre-spraying a conductive adhesive on the surface of the foil to form a conductive coating, evenly paste the dry electrode film on the conductive coating foil, heat, and roll. The rolling temperature is 180 °C, and the rolling pressure is 3 atmospheres to obtain the dry electrode of the porous carbon composite lithium battery.

[0041] Figure 1 For the scanning electron microscope image of the dry electrode of the porous carbon composite lithium battery prepared by the process of the present invention, from Figure 1 it can be seen that the surface of the electrode sheet is smooth and there are no cracks, which proves that the positive and negative active materials obtained by using the method of the present invention will not be partially inactivated, and the coating on the surface of the positive and negative active materials will not crack.

[0042] Embodiment 2

[0043] A preparation method of a dry electrode for a porous carbon composite lithium battery, the method specifically includes the following steps:

[0044] 1) Mix 90 parts of lithium iron phosphate, 4 parts of Ketjen black, 1 part of carbon aerogel and 5 parts of thermoplastic elastomer SEBS evenly, divide them into two parts, extrude and granulate the first part with a twin-screw extruder to obtain first particles with a particle size of 0.9 mm; extrude and granulate the second part with a twin-screw extruder to obtain second particles with a particle size of 5 mm; mix the first particles and the second particles evenly according to a mass ratio of 1:5 to obtain mixed particles;

[0045] 2) Place the mixed particles on a rolling mill with upper and lower heating, the rolling temperature is 180 °C, and the rolling pressure is 5 atmospheres to obtain a dry electrode film;

[0046] 3) After pre-spraying a conductive adhesive on the surface of the foil to form a conductive coating, evenly paste the dry electrode film on the conductive coating foil respectively, heat and roll, the rolling temperature is 150 °C, and the rolling pressure is 5 atmospheres, then the dry electrode for the porous carbon composite lithium battery is obtained.

[0047] Example 3

[0048] A preparation method of a dry electrode for a porous carbon composite lithium battery, the method specifically includes the following steps:

[0049] 1) Mix 92 parts of lithium iron phosphate, 2 parts of Ketjen black, 1 part of activated carbon fiber and 5 parts of polytetrafluoroethylene PTFE evenly, divide them into two parts, extrude and granulate the first part with a twin-screw extruder to obtain first particles with a particle size of 0.5 mm; extrude and granulate the second part with a twin-screw extruder to obtain second particles with a particle size of 4.5 mm; mix the first particles and the second particles evenly according to a mass ratio of 1:10 to obtain mixed particles;

[0050] 2) Place the mixed particles on a rolling mill with upper and lower heating, the rolling temperature is 170 °C, and the rolling pressure is 5 atmospheres to obtain a dry electrode film;

[0051] 3) After pre-spraying a conductive adhesive on the surface of the foil to form a conductive coating, evenly paste the dry electrode film on the conductive coating foil respectively, heat and roll, the rolling temperature is 160 °C, and the rolling pressure is 5 atmospheres, then the dry electrode for the porous carbon composite lithium battery is obtained.

[0052] To illustrate the effects of the present invention, the inventor provides the following comparative experiments:

[0053] Comparative Example

[0054] 85 parts of lithium iron phosphate, 3 parts of super-P, 2 parts of activated carbon and 10 parts of PVDF were mixed with NMP solvent, and evenly coated on the surface of the foil by a coater, dried at 130 °C, and cold rolled under 1 atmospheric pressure to obtain a wet electrode. For the electrodes obtained by this process method, partial inactivation of the positive and negative active materials occurs, and the coatings on the surfaces of the positive and negative active materials will crack, as Figure 2 shown.

[0055] Batteries were assembled with the electrodes of Example 1 and Comparative Example 1 respectively, and capacity tests were carried out at different discharge currents. As Figure 3 shown, it can be found that the electrode of Example 1 has a higher capacity.

[0056] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a dry electrode for a porous carbon composite lithium battery, characterized in that, The method specifically includes the following steps: 1) Mix the active material, conductive agent, porous carbon, and binder evenly, and divide it into two parts. The first part is subjected to the first extrusion granulation by twin-screw extrusion to obtain the first particles with the first particle size; the second part is subjected to the second extrusion granulation by twin-screw extrusion to obtain the second particles with the second particle size; mix the first particles and the second particles in proportion to obtain mixed particles; the particle size of the first particles is 0.2 - 1 mm, the particle size of the second particles is 1 - 5 mm, and the first particles and the second particles have different particle sizes; 2) Place the mixed particles on a heated rolling machine for rolling to obtain a dry electrode film; 3) After pre-spraying a conductive adhesive on the surface of the foil to form a conductive coating, evenly paste the dry electrode film on the conductive coating foil respectively, heat, and roll to obtain the dry electrode of the porous carbon composite lithium battery.

2. The preparation method of the dry electrode of the porous carbon composite lithium battery according to claim 1, characterized in that The mixed particles include the following components, calculated by mass percentage: Active material 80% - 99%, conductive agent 0.5% - 5%, porous carbon 0.5 - 2%, binder 1% - 10%.

3. The preparation method of the porous carbon composite lithium battery dry electrode according to claim 2, characterized in that, The active material is at least one of ternary lithium, lithium iron phosphate, lithium manganate, lithium cobaltate, and graphite, the conductive agent is at least one of super-P, Ketjen black, carbon nanotubes, and carbon fibers, and the binder is one of polytetrafluoroethylene PTFE, thermoplastic elastomer SEBS, polyethylene PE, polypropylene PP, and polymethyl methacrylate PMMA.

4. The preparation method of the porous carbon composite lithium battery dry electrode according to claim 1, characterized in that, The specific surface area of the porous carbon is 1000 - 2500 m 2 / g, and the porous carbon is one of activated carbon, activated carbon fiber, and carbon aerogel.

5. The preparation method of the dry electrode of the porous carbon composite lithium battery according to claim 4, characterized in that, The particle size of the porous carbon is 5 - 10 μm, and the particle size of the mixed particles is 0.2 - 5 mm.

6. The preparation method of the porous carbon composite lithium battery dry electrode according to claim 5, characterized in that, The mixing mass ratio of the first particles and the second particles is 1:1 - 1:

10.

7. The preparation method of the dry electrode of the porous carbon composite lithium battery according to claim 1, wherein, In step 2), the rolling temperature is 60 - 200 °C, and the rolling pressure is 2 - 10 atmospheres.

8. The preparation method of the porous carbon composite lithium battery dry electrode according to claim 1, wherein, In step 3), the rolling temperature is 60 - 200 °C, and the rolling pressure is 2 - 5 atmospheres.

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