Preparation method of pole piece and manufacturing equipment of pole piece

Abstract

The invention relates to the field of batteries, and discloses a preparation method of a pole piece and manufacturing equipment of the pole piece. The preparation method comprises the following steps: providing a current collector coated with active slurry; enabling the current collector to sequentially pass through eight heat treatment spaces to obtain a dried pole piece; the temperatures of the eight heat treatment spaces are 75 + / -2 DEG C, 110 + / -2 DEG C, 115 + / -2 DEG C, 125 + / -2 DEG C, 125 + / -2 DEG C, 125 + / -2 DEG C, 115 + / -2 DEG C and 110 + / -2 DEG C in sequence. The peeling strength of the pole piece is improved by adjusting the heat treatment procedure and temperature of the pole piece, the pole piece is sequentially subjected to eight heat treatment links at the set temperature, the weight loss rate of the dried pole piece is kept below 0.3%, the phenomena of cracking and non-uniformity of a coating on the surface of the pole piece are avoided, and the service life of the pole piece is prolonged. And the peeling strength of the pole piece is obviously improved to 550N / m or more, so that the short-circuit rate of a battery roll core is reduced, and the product yield is improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a method for preparing a pole piece and a pole piece manufacturing device. Background Art

[0002] In recent years, with the continuous innovation and development of science and technology, energy consumption has been increasing, global fossil energy is depleting and supply is tight, and climate change is severe. As countries around the world realize the importance and urgency of developing new energy, the share of new energy vehicles in the market continues to increase.

[0003] Compared with traditional fuel vehicles, new energy vehicles have the characteristics of environmental protection and energy saving, zero emission, low noise, energy recovery, and convenient charging, which greatly reduces the environmental pollution caused by automobile exhaust emissions. Lithium batteries have the characteristics of high energy density, long cycle life, fast charging, and strong high and low temperature adaptability, and have a wide range of application markets.

[0004] In the process of manufacturing battery electrodes, the adhesion of the electrodes in the coating step is measured by the peel strength. If the peel strength of the electrode is too low, material falling will occur, which can easily lead to a short circuit in the core and seriously affect the qualified rate of battery production. Summary of the invention

[0005] In view of this, the purpose of the present application is to provide a method for preparing a pole piece, so that the preparation method can significantly improve the peel strength of the pole piece and at the same time ensure a low weight loss rate;

[0006] Another object of the present application is to provide a pole piece manufacturing device based on the above-mentioned preparation method.

[0007] In order to solve the above technical problem / achieve the above purpose or at least partially solve the above technical problem / achieve the above purpose, as a first aspect of the present application, a method for preparing a pole piece is provided, comprising:

[0008] providing a current collector coated with an active slurry;

[0009] The current collector passes through 8 heat treatment spaces in sequence to obtain a dried electrode sheet; the temperatures of the 8 heat treatment spaces are 75±2°C, 110±2°C, 115±2°C, 125±2°C, 125±2°C, 125±2°C, 115±2°C, and 110±2°C in sequence.

[0010] Optionally, the current collector is in each heat treatment space for 3-5 seconds.

[0011] Optionally, the active slurry includes positive / negative electrode active materials, a conductive agent, a binder and a solvent.

[0012] Further optionally, the viscosity of the active slurry is 8000-12000 MPa.S.

[0013] As a second aspect of the present application, a pole piece manufacturing device is provided, including a transmission device and a heat treatment device, wherein the heat treatment device is arranged on the transmission device and is divided into 8 heat treatment spaces in sequence along the forward direction of the transmission device, and the temperatures of the 8 heat treatment spaces are 75±2°C, 110±2°C, 115±2°C, 125±2°C, 125±2°C, 125±2°C, 115±2°C, and 110±2°C in sequence along the forward direction of the transmission device.

[0014] Optionally, a slurry pump is provided at the front end of the heat treatment process to coat the active slurry on the surface of the current collector.

[0015] The present application improves the peel strength of the electrode by adjusting the heat treatment procedure and temperature of the electrode, so that the electrode passes through 8 heat treatment steps with set temperatures in sequence, so that the weight loss rate of the dried electrode is not only maintained below 0.3%, but also the cracking and unevenness of the electrode surface coating are avoided, and the peel strength of the electrode is significantly increased to above 550N / m, thereby reducing the short circuit rate of the battery core and improving the product quality rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application.

[0017] Figure 1 Shown is a schematic structural diagram of the pole piece manufacturing equipment of the present application. DETAILED DESCRIPTION

[0018] The present application discloses a method for preparing a pole piece and a manufacturing device for a pole piece. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the desired result. 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 this application. The products, processes and applications described in this application have been described through preferred embodiments. Relevant personnel can obviously modify or appropriately change and combine the products, processes and applications described in this article without departing from the content, spirit and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0019] It should be noted that, in this article, if relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" appear, they are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements. At the same time, the embodiments in this application and the features in the embodiments may be combined with each other without conflict.

[0020] The peel strength of the pole piece is an important parameter of the pole piece quality. Conventional improvement measures are to improve the formula of the pole piece active slurry, but it is often unable to take into account the weight loss rate of the pole piece surface coating. The present application takes into account both the weight loss rate and the peel strength by controlling the baking temperature of the coated pole piece. The oven temperature affects the drying speed and degree of the coated pole piece. Too low a temperature will result in insufficient baking of the pole piece, resulting in the pole piece peel strength being too low and falling off. Too high a coating oven temperature will cause cracking and unevenness on the coating surface, and the peel strength will be reduced, which is not conducive to production. Therefore, the optimal oven temperature and oven program are crucial to the pole piece coating production.

[0021] Therefore, in a first aspect of the present application, a method for preparing a pole piece is provided, comprising:

[0022] providing a current collector coated with an active slurry;

[0023] The current collector passes through 8 heat treatment spaces in sequence to obtain a dried electrode sheet; the temperatures of the 8 heat treatment spaces are 75±2°C, 110±2°C, 115±2°C, 125±2°C, 125±2°C, 125±2°C, 115±2°C, and 110±2°C in sequence.

[0024] In some embodiments of the present application, the eight heat treatment spaces are connected to each other to ensure that the coated current collector can smoothly enter the next heat treatment link directly from the previous heat treatment link. In some other embodiments of the present application, the temperatures of the eight heat treatment spaces are 75°C, 110°C, 115°C, 125°C, 125°C, 115°C, and 110°C, respectively.

[0025] In some embodiments of the present application, the time for the current collector in each heat treatment space is 3-5s, such as 3s, 3.5s, 4s, 4.5s, 5s, etc. In some other embodiments of the present application, the time for the current collector in each heat treatment space is the same.

[0026] In certain embodiments of the present application, the active slurry includes positive / negative active materials, conductive agents, binders and solvents. In other embodiments of the present application, the positive active materials include but are not limited to lithium iron phosphate, ternary lithium, layered oxide materials, lithium titanate, etc., the negative active materials include but are not limited to graphite, carbon silicon negative electrode materials, etc., the conductive agents include but are not limited to conductive carbon black (such as acetylene black, carbon fiber, carbon nanotubes, Ketjen black), graphite conductive agents, graphene, etc., wherein the binder includes but is not limited to CMC (sodium carboxymethyl cellulose), SBR (styrene butadiene latex), polyvinylidene fluoride (PVDF), etc., and the current collector is a metal foil, such as aluminum foil, copper foil, etc.

[0027] In certain embodiments of the present application, the viscosity of the active slurry is 8000-12000 MPa.S, for example, 10300 MPa.S.

[0028] In the second aspect of the present application, there is also provided a manufacturing device for a pole piece, comprising a transmission device and a heat treatment device, wherein the heat treatment device is arranged on the transmission device and is sequentially divided into 8 heat treatment spaces along the forward direction of the transmission device, and the temperatures of the 8 heat treatment spaces are 75±2°C, 110±2°C, 115±2°C, 125±2°C, 125±2°C, 125±2°C, 115±2°C, and 110±2°C in the forward direction of the transmission device, respectively. The schematic diagram of the structure is shown in Figure 1 .

[0029] In some embodiments of the present application, the transmission device is a transmission belt, and the heat treatment device is an oven, more specifically, an 8-section oven; the transmission belt runs through the 8 sections of the oven, and transports the coated electrode through the 8 sections of the oven in sequence to perform the above-mentioned 8 temperature heat treatments. In some other embodiments of the present application, the shape and specifications of the 8 heat treatment spaces are completely consistent, so that the heat treatment time of the coated electrode in each heat treatment space can be adjusted by controlling the speed of the conveyor; for example, 8 sections of the oven are used as the heat treatment device, the length of each section of the oven is 1m, and the speed of the transmission belt is 20m / min.

[0030] In certain embodiments of the present application, the manufacturing equipment further includes a slurry pump disposed at the front end of the process of the heat treatment device, for coating the active slurry on the surface of the current collector to form a coated electrode.

[0031] In each group of comparative experiments provided in this application, unless otherwise specified, other experimental conditions, materials, etc. are kept consistent except for the differences indicated in each group, so as to provide comparability. The experimental materials and reagents used in the examples can be obtained from commercial channels unless otherwise specified.

[0032] The following is a further description of a method for preparing a pole piece and a pole piece manufacturing device provided in the present application.

[0033] Embodiment 1:

[0034] use Figure 1 The manufacturing equipment shown is used to dry the pole piece. Taking the negative electrode of a cylindrical / square shell lithium titanate battery as an example, the active slurry includes 90-95% lithium titanate, 2-5% PVDF, 1.5-3% SP, and 1.5-2% CNT. The solvent is dissolved using NMP. The slurry viscosity is 10300 MPa.S. The slurry pump coats the collector to form a coated pole piece, which is transported by a transmission belt through 8 ovens in sequence. The transmission belt speed is 20 m / min, and the oven length is 1 m. The temperatures of ovens 1 to 8 are 75°C, 110°C, 115°C, 125°C, 125°C, 125°C, 115°C, and 110°C, respectively.

[0035] Comparative Example 1:

[0036] The drying was carried out according to the method of Example 1, except that the temperatures of ovens in sections 1-8 were 75°C, 110°C, 115°C, 115°C, 115°C, 115°C, 105°C and 95°C, respectively.

[0037] Comparative Example 2:

[0038] The drying was carried out according to the method of Example 1, except that the temperatures of ovens in sections 1-8 were 75°C, 110°C, 115°C, 110°C, 110°C, 110°C, 105°C and 95°C, respectively.

[0039] Comparative Example 3:

[0040] The drying was carried out according to the method of Example 1, except that the temperatures of ovens in sections 1-8 were 75°C, 110°C, 115°C, 130°C, 130°C, 130°C, 115°C, and 110°C, respectively.

[0041] Comparative Example 4:

[0042] The drying was carried out according to the method of Example 1, except that the temperatures of ovens in sections 1-8 were 75°C, 110°C, 115°C, 135°C, 135°C, 135°C, 115°C, and 110°C, respectively.

[0043] Comparative Example 5:

[0044] Refer to the drying method of Example 1, except that the number of oven sections is adjusted from 8 to 7, the original 5th oven section is deleted, and the oven temperatures are 75°C, 110°C, 115°C, 125°C, 125°C, 115°C, and 110°C, respectively.

[0045] Comparative Example 6:

[0046] Refer to the method of Example 1 for drying, except that the number of oven sections is adjusted from 8 to 9, an additional oven at 125°C is added after the 6th oven, oven numbered 7, and the original 7th and 8th oven numbers are changed to 8th and 9th, and the oven temperatures are 75°C, 110°C, 115°C, 125°C, 125°C, 125°C, 115°C, 110°C, respectively.

[0047] Experimental example:

[0048] Cut out a small disc (pole piece) and weigh the total weight M1, place the weighed small disc in the weight loss instrument, weigh the total weight M2 after the test, and calculate the weight loss rate by the formula = (M1-M2) / M1;

[0049] The peel strength of the electrode piece was measured by a peel strength tester, and the dryness and coating distribution of the electrode piece in the oven were checked at the same time. The results of Example 1 and the comparative examples are shown in Table 1 below;

[0050] Table 1

[0051]

[0052]

[0053] It can be seen intuitively from Table 1 that under the standard that the weight loss rate of each treatment group is less than 0.5%, the coating state of Example 1 is the best, and the peeling strength is as high as 550N / m; the effects of other comparative examples are poor, which fully demonstrates that the number of sections of the oven and the temperature value of each section have a direct impact on the state of the electrode after drying. The improvement strategy of the present application is different from the conventional adjustment through the active slurry formula. It is more convenient and efficient in process, and can directly improve the peeling strength of the electrode coating without changing the slurry formula, and control the weight loss rate to meet the requirements.

[0054] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent 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 application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a pole piece, characterized in that: include: providing a current collector coated with an active slurry; The current collector passes through 8 heat treatment spaces in sequence to obtain a dried electrode sheet; the temperatures of the 8 heat treatment spaces are 75±2°C, 110±2°C, 115±2°C, 125±2°C, 125±2°C, 125±2°C, 115±2°C, and 110±2°C in sequence.

2. The preparation method according to claim 1, characterized in that: The current collector is in each heat treatment space for 3-5 seconds.

3. The preparation method according to claim 1, characterized in that: The active slurry includes positive / negative electrode active materials, a conductive agent, a binder and a solvent.

4. The preparation method according to claim 1 or 3, characterized in that: The viscosity of the active slurry is 8000-12000 MPa.S.

5. A pole piece manufacturing device, characterized in that: It includes a transmission device and a heat treatment device. The heat treatment device is arranged on the transmission device and is divided into 8 heat treatment spaces in sequence along the forward direction of the transmission device. The temperatures of the 8 heat treatment spaces are 75±2℃, 110±2℃, 115±2℃, 125±2℃, 125±2℃, 125±2℃, 115±2℃ and 110±2℃ in sequence along the forward direction of the transmission device.

6. The manufacturing equipment according to claim 5, characterized in that The method also includes arranging a slurry pump at the front end of the heat treatment process to coat the active slurry on the surface of the current collector.

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