Electrode slurry, electrode and preparation method therefor, and battery

Abstract

The present application belongs to the technical field of lithium batteries. Disclosed are an electrode slurry, an electrode and a preparation method therefor, and a battery. The electrode slurry of the present application comprises an active material, a binder and a conductive agent; and a fibrous polymer material is further added, and the thermal decomposition temperature T of the fibrous high polymer material, the baking temperature T1 of a coated electrode sheet before calendaring and the baking temperature T2 of the electrode sheet after calendaring meet the relational expression: T1<T≤T2.

Description

Electrode slurry, electrodes and their preparation methods and batteries

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411929710.2, filed with the Chinese Patent Office on December 25, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of lithium battery technology, and more specifically, to an electrode slurry, an electrode, a method for preparing the same, and a battery. Background Technology

[0004] Consumers are demanding higher energy density from battery products, leading to increased thickness of lithium-ion battery electrodes. While increased electrode thickness significantly increases the proportion of active material, it also causes problems such as increased electrode tortuosity, higher resistance, and deterioration in rate and cycle performance. Creating pores in thicker electrodes can effectively solve these problems.

[0005] Currently, the most common pore-forming technologies for thick electrodes are pore-forming agents and laser pore-forming. Traditional pore-forming agents are gas-generating compounds that form channels during coating and drying, but they will still form closed pores during the subsequent rolling process, resulting in low pore-forming efficiency. Laser pore-forming uses high-energy lasers to ablate the electrode coating at high temperatures to form pores, but it has problems such as high laser energy consumption, slow pore-forming speed, high dust from molten beads splashing, and easy failure of the coating in the pore-forming area. Summary of the Invention

[0006] This application provides an electrode slurry, an electrode, a method for preparing the same, and a battery to solve the problem of low effective porosity of electrode sheets in related technologies.

[0007] In a first aspect, embodiments of this application provide an electrode slurry, which includes an active material, a binder, and a conductive agent; the electrode slurry also contains a fibrous polymer material; the thermal decomposition temperature T of the fibrous polymer material, the baking temperature T1 of the electrode sheet coated with the electrode slurry before rolling, and the baking temperature T2 after rolling satisfy the following relationship: T1<T≤T2.

[0008] Secondly, embodiments of this application provide a method for preparing an electrode, the method comprising: coating the electrode slurry described in the first aspect onto the surface of a current collector, and sequentially performing a first baking, rolling and a second baking to obtain an electrode.

[0009] Thirdly, embodiments of this application provide a battery including electrodes prepared using the preparation method described in the second aspect.

[0010] Furthermore, the electrode is either a positive electrode or a negative electrode; the areal density of the positive electrode is 110–120 g / m³. 2 The areal density of the negative electrode sheet is 60–70 g / m³. 2 .

[0011] The beneficial effects of this application are:

[0012] The present application provides an electrode slurry, an electrode, a method for preparing the same, and a battery. The present application adds a small amount of thermally decomposable fibrous polymer material during the homogenization process, without using additional pore-forming equipment and pore-forming agents. The process is simple and easy to operate, and can increase the proportion of through holes in the porosity of the electrode. Through holes can improve the electrical performance of lithium-ion batteries, such as rate charge-discharge performance and cycle performance. The pore-forming method used in the present application will not damage the electrode structure and will not cause structural failure in the pore-forming area. Attached Figure Description

[0013] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0014] Figure 1 shows a schematic diagram of the structure of the electrode sheet before baking and decomposition in Embodiment 1 of this application;

[0015] Figure 2 shows a schematic diagram of the structure of the electrode sheet after baking and decomposition in Embodiment 1 of this application.

[0016] Figure reference numerals: 1-Fibrous polymer material; 2-Pore. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] In related technologies, thick electrode pore-forming technology mainly uses pore-forming agents and laser pore-forming. Traditional pore-forming agents are gas-generating compounds that form pores during coating and drying. However, during the subsequent rolling process, the rolling pressure will destroy some of the pores and form closed pores, resulting in low pore-forming efficiency.

[0019] To address the aforementioned problem of low effective porosity, this application, after extensive research, employs a novel approach to create pores in the electrode; by improving the electrode slurry, the effective porosity is increased.

[0020] To achieve the above objectives, according to one aspect of this application, an electrode slurry is provided, comprising an active material, a binder, and a conductive agent; the electrode slurry further contains a fibrous polymer material; the thermal decomposition temperature T of the fibrous polymer material, the baking temperature T1 of the electrode sheet coated with the electrode slurry before rolling, and the baking temperature T2 after rolling satisfy the following relationship: T1<T≤T2.

[0021] This application adds a fibrous polymer material with a specific pyrolysis temperature to the electrode slurry. When the electrode slurry is coated and baked, the pyrolysis temperature of the fiber is higher than the baking temperature of the electrode sheet before rolling. This prevents a large number of specific fibers from undergoing pyrolysis during the baking process before rolling. At this time, the specific fibers occupy a certain solid volume and do not form a large number of channels during the baking process. After the baked electrode sheet is rolled, since a large number of channels have not yet been formed, the rolling process will not affect the channels of the baked electrode sheet. However, the pyrolysis temperature of the specific fibers is lower than the baking temperature of the electrode sheet after rolling. This causes a large number of fibers to undergo pyrolysis and generate gas during the baking process after rolling, which then escapes. Therefore, the electrode sheet can form a large number of channels during the baking process. This application, through research, discovered that electrode sheets require a sequential process of coating, drying, rolling, and baking to form the final rolled electrode sheet. By cleverly utilizing the sequence of baking first, then rolling, and finally baking again, and by selecting fibers with specific thermal decomposition temperatures that can generate gas and form a certain volume of space after thermal decomposition, this method ensures that the specific fibers do not decompose during the baking process before rolling, and that the pore structure is not destroyed during rolling. During the baking process after rolling, a large amount of thermal decomposition occurs, and the pores generated by the fiber thermal decomposition are almost entirely preserved. This avoids the phenomenon that the rolling process would damage the pore structure in the active coating. This method increases the effective porosity in the electrode sheet. Increased porosity increases the electrolyte retention capacity, improves ion diffusion efficiency, and is beneficial for enhancing electrochemical performance.

[0022] In some embodiments, T1+10℃≤T≤T2; further, T1+20℃≤T≤T2; and even further, T1+30℃≤T≤T2.

[0023] In some embodiments, T1 is 100–130°C; T is greater than or equal to 130°C and less than or equal to T2; further, T1 is 110–130°C; for example, T1 is 100°C; T is 120–160°C; further, T is 130–160°C; further, T is 140–150°C; for example, T is 130°C; T2 is 150–160°C; further, T2 is 155–160°C; for example, T2 is 150°C. For example, the thermal decomposition temperature T of the fiber can be any value or a range between any two of 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, and 160℃; T1 can be any value or a range between any two of 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, and 130℃; and T2 can be any value or a range between any two of 150℃, 155℃, and 160℃.

[0024] This application selects fibers with the aforementioned thermal decomposition temperature and matches them with appropriate baking temperatures before and after rolling. This minimizes the thermal decomposition rate of the fibers during the baking process before rolling and ensures that all fibers undergo thermal decomposition during the baking process after rolling. If the fiber thermal decomposition temperature is too high, although the thermal decomposition rate can be further reduced during the baking process before rolling, the excessively high temperature, or even higher than the post-baking temperature, may result in a lower thermal decomposition rate during the baking process after rolling, thus reducing the pore formation rate. Conversely, if the fiber thermal decomposition temperature is too low, a large amount of fiber may have already undergone thermal decomposition during the baking process before rolling, creating numerous pores. These pores are then destroyed during rolling, resulting in fewer thermally decomposed fibers during the baking stage after rolling. Because some pores are destroyed during rolling, closed pores are formed, ultimately reducing the effective porosity.

[0025] In some embodiments, the fibrous polymer material is wool fiber and / or polyvinyl chloride fiber.

[0026] The two fibers selected in this application have suitable thermal decomposition temperatures, ensuring that most fibers do not undergo thermal decomposition during the pre-rolling baking process, while the fibers undergo substantial or complete thermal decomposition during the post-rolling baking process. This results in the creation of a large number of pores, and the escape of gases generated during thermal decomposition prevents damage to the pores. These fibers are readily available and inexpensive. Besides the two materials mentioned above, other materials with thermal decomposition temperatures and pre- and post-rolling baking temperatures that satisfy the aforementioned relationship can also be selected.

[0027] In some embodiments, the ratio of the fiber length of the fibrous polymer material to the thickness of the active coating of the electrode is (0.5 to 1.2):1; for example, this ratio is any value among 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2 or any range between the two.

[0028] For example, the thickness of the active material layer of the electrode is 60–85 μm; for example, the fiber length of the fibrous polymer material is 40–100 μm; further, it is 60–90 μm.

[0029] The specific fiber length in this application is selected based on the electrode thickness. When the fiber length is similar to the thickness of the active coating, the fiber can penetrate the active coating, creating a through-channel after thermal decomposition. This allows the electrolyte entering the channel to wet the bottom of the electrode. The method of adding fibers with a specific thermal decomposition temperature to the slurry in this application is more suitable for creating pores in thick electrodes and achieves better results.

[0030] In some embodiments, the molecular weight of the fibrous polymer material is 4W to 6W g / mol.

[0031] The molecular weight of the fiber selected in this application is related to the thermal decomposition temperature. The higher the molecular weight, the higher the thermal decomposition temperature. The molecular weight of the selected fiber is matched with the drying temperature before and after the electrode is rolled, so that fiber decomposition can be achieved at a conventional drying temperature.

[0032] In some embodiments, the fiber diameter of the fibrous polymer material is 60–140 μm; more specifically, it is 100–120 μm.

[0033] The fiber diameter selected in this application is based on considerations of wettability and process. If the diameter is too small, the pores will be too fine, making it difficult for the electrolyte to enter. If the diameter is too large, the electrode will have obvious defects during the coating and drying process. With this diameter and length, the electrode process and electrochemical performance are both good.

[0034] In some embodiments, the fibrous polymer material accounts for 0.5% to 5% by weight in the electrode slurry; 1% to 4%; further 1% to 3%; further 1% to 2%; for example 1.5%.

[0035] In some embodiments, the active material in the electrode slurry accounts for 93% to 97% by weight; the binder in the electrode slurry accounts for 1% to 1.5% by weight; and the conductive agent in the electrode slurry accounts for 1% to 1.5% by weight.

[0036] This application controls the fiber content in the slurry to be between 1% and 4%, which ensures that a predetermined amount of pores can be formed without affecting the electrochemical performance of the electrolyte itself. If the fiber content is too high, it will occupy the space of the main material, reduce the energy density of the battery, and make the dispersion process difficult, resulting in poor dispersion effect in the electrode and a decrease in the electrical performance of the cell. If the fiber content is too low, it will not have a significant effect on improving porosity (electrochemical performance).

[0037] In some embodiments, the electrode is a positive electrode or a negative electrode; the active material is a positive active material or a negative active material.

[0038] The fibers of this application can be added to the negative electrode slurry or the positive electrode slurry, and can be well mixed with the active material without affecting the properties of the slurry itself; in addition to the above, other conventional materials can also be selected for the positive electrode active material and the negative electrode active material of this application.

[0039] In some embodiments, the positive electrode active material is selected from lithium cobalt oxide or ternary materials; the negative electrode active material is selected from graphite; the conductive agent is selected from conductive carbon black and / or carbon nanotubes; and the binder is selected from polyvinylidene fluoride.

[0040] The fibers screened in this application can be well mixed with active materials, binders, and conductive agents without affecting the normal function of these components. Other conventional materials can also be used as conductive agents and binders.

[0041] According to a second aspect of this application, a method for preparing an electrode is provided, the method comprising: coating an electrode slurry onto the surface of a current collector, and sequentially performing a first baking, rolling and a second baking to obtain the electrode.

[0042] The first baking temperature and the second baking temperature of this application must be matched with the selected fiber thermal decomposition temperature. The first baking temperature cannot be higher than the fiber thermal decomposition temperature within a certain range, and the second baking temperature cannot be lower than the fiber thermal decomposition temperature. In this way, the fiber can be thermally decomposed as little as possible during the first baking process, and after being rolled, it can be thermally decomposed as much as possible during the second baking process, thereby generating a large number of effective channels.

[0043] In some embodiments, the temperature of the first baking is 100°C to 130°C; further, it is 110°C to 130°C; the temperature of the second baking is 150°C to 160°C; and further, the temperature of the second baking is 155°C to 160°C.

[0044] This application uses the aforementioned first and second baking temperatures, matched with the selected fiber thermal decomposition temperature. The first baking temperature is lower than or slightly lower than the fiber thermal decomposition temperature, and the fiber thermal decomposition temperature is less than or equal to the second baking temperature. For example, the first baking temperature is selected from any value or a range between 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, and 130℃; the second baking temperature is selected from any value or a range between 150℃, 155℃, and 160℃. When controlling the second baking temperature, this application also considers that the temperature should not be too high to avoid damaging the performance of the active material of the electrode sheet.

[0045] In some embodiments, the first baking time is 1 to 2 hours; the second baking time is 6 to 10 hours; and the rolling pressure speed is 10 to 20 m / min, for example, 15 m / min. The above baking time can be adjusted according to the properties of the active coating.

[0046] In some embodiments, the electrode slurry mixing process includes: mixing active materials, conductive agents, binders and solvents, adding fibrous polymer materials, mixing and stirring to obtain electrode slurry; the stirring time is 3 to 5 hours.

[0047] According to a third aspect of this application, an electrode is provided, which is prepared using the above-described preparation method.

[0048] In some embodiments, the electrode is a positive electrode or a negative electrode; the areal density of the positive electrode is 110–120 g / m³. 2 The areal density of the negative electrode sheet is 60–70 g / m³. 2 .

[0049] This application describes an electrode prepared using a slurry containing a certain amount of specific fibers. This electrode contains a suitable amount of pores, which is beneficial for absorbing electrolyte and carrying out ion exchange, thereby improving the electrochemical performance of the battery.

[0050] This application adds a small amount of thermally decomposed fibrous polymer material during the homogenization process, without using additional pore-forming equipment. The process is simple and easy to operate, and can increase the proportion of through holes in the porosity of the electrode. The pore-forming method used in this application will not damage the electrode structure and will not cause structural failure in the pore-forming area.

[0051] According to a fourth aspect of this application, a battery is provided, including the electrodes described above.

[0052] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0053] All raw materials used in the embodiments of this application are commercially available.

[0054] The abbreviations for raw materials used in the embodiments of this application are explained as follows:

[0055] SP: Conductive carbon black; CNT: Carbon nanotubes; PVDF: Polyvinylidene fluoride; NMP: N-methylpyrrolidone.

[0056] Example 1

[0057] Preparation of battery positive electrode slurry: LiCoO2:SP:CNT:PVDF:wool fiber were added in a mass ratio of 96%:1%:0.5%:1.3%:1.2%; the wool had a molecular weight of 4W-5W g / mol, a diameter of 80-120μm, a length of 40-80μm, and a thermal decomposition temperature of 130-160℃;

[0058] (1) First, mix lithium cobalt oxide and conductive carbon black evenly to form a mixture;

[0059] (2) Dissolve PVDF in NMP and prepare a glue solution with a solid content of 5%;

[0060] (3) Mix the mixture in step (1) and the adhesive in (2) evenly to obtain a mixture;

[0061] (4) Mix the mixture from step (3) and carbon nanotubes (3wt%) evenly to obtain a mixed slurry;

[0062] (5) Mix the slurry and wool fibers in step (4) at 25 rpm for 4 hours to obtain the positive electrode slurry;

[0063] Preparation of positive electrode sheet:

[0064] The above slurry was coated onto a 9μm thick aluminum foil. The coated aluminum foil was first baked in an oven at 120℃, and then cold-pressed to obtain a positive electrode sheet (as shown in Figure 1). The rolled positive electrode sheet was then baked a second time at 165℃ for 8 hours (as shown in Figure 2). The density after drying was 118 g / m³. 2 The cold pressing speed is 15 m / min.

[0065] Example 2

[0066] Preparation of battery positive electrode slurry: LiCoO2:SP:CNT:PVDF:polyvinyl chloride was added in a mass ratio of 96%:1%:0.5%:1.3%:1.2%; the polyvinyl chloride had a molecular weight of 4W-6Wg / mol, a diameter of 100-120μm, a length of 60-100μm, and a thermal decomposition temperature of 130-160℃;

[0067] (1) First, mix lithium cobalt oxide and conductive carbon black evenly to form a mixture;

[0068] (2) Dissolve PVDF in NMP and prepare a glue solution with a solid content of 5%;

[0069] (3) Mix the mixture in step (1) and the adhesive in (2) evenly to obtain a mixture;

[0070] (4) Mix the mixture from step (3) and carbon nanotubes (3wt%) evenly to obtain a mixed slurry;

[0071] (5) The mixed slurry described in step (4) and polyvinyl chloride are mixed and stirred at 25 rpm for 4 hours to obtain the positive electrode slurry.

[0072] The method for preparing the positive electrode is as follows:

[0073] The above slurry was coated onto a 9μm thick aluminum foil, dried for the first time in an oven at 125℃, and then cold-pressed to obtain a positive electrode sheet. The rolled positive electrode sheet was then baked a second time at 160℃ for 8 hours. The density after drying was 118 g / m³. 2 The cold pressing speed is 15 m / min.

[0074] Example 3

[0075] Preparation of battery negative electrode slurry: Graphite:SP:CNT:SBR:wool fiber were added in a mass ratio of 96.5%:0.5%:0.5%:1.3%:1.2%; the wool had a molecular weight of 4W-5W g / mol, a diameter of 80-120μm, a length of 40-80μm, and a thermal decomposition temperature of 130-160℃.

[0076] (1) First, mix graphite and conductive carbon black evenly to form a mixture;

[0077] (2) Dissolve the mixture in (1) in water and add water according to a solid content of 70%;

[0078] (3) Mix the mixture in (2) and carbon nanotubes (6wt%) evenly;

[0079] (4) After mixing the slurry and wool fiber in (3) at 25 rpm for 4 hours, add SBR and stir to obtain negative electrode slurry.

[0080] The method for preparing the negative electrode is as follows:

[0081] The above slurry was coated onto a 6μm thick copper foil, baked for the first time in an oven at 123℃, and then cold-pressed to obtain a negative electrode sheet. The rolled negative electrode sheet was then baked for a second time at 163℃ for 8 hours. The density of the dried negative electrode sheet was 65g / m³. 2 The cold pressing speed is 25 m / min.

[0082] Example 4

[0083] Preparation of battery negative electrode slurry: Graphite:SP:CNT:SBR:polyvinyl chloride was added in a mass ratio of 96.5%:0.5%:0.5%:1.3%:1.2%; the polyvinyl chloride had a molecular weight of 4W-6Wg / mol, a diameter of 100-120μm, a length of 60-100μm, and a thermal decomposition temperature of 130-160℃.

[0084] (1) First, mix graphite and conductive carbon black evenly to form a mixture;

[0085] (2) Dissolve the mixture in (1) in water and add water according to a solid content of 70%;

[0086] (3) Mix the mixture in (2) and carbon nanotubes (6wt%) evenly;

[0087] (4) After mixing the slurry and polyvinyl chloride in (3) at 25 rpm for 4 hours, add SBR to obtain the negative electrode slurry.

[0088] The method for preparing the negative electrode is as follows:

[0089] The above slurry was coated onto a 6μm thick copper foil, and then baked for the first time in an oven at 128℃. After cold pressing, a negative electrode sheet was obtained. The rolled negative electrode sheet was then baked for a second time at 161℃ for 8 hours. The areal density of the negative electrode sheet was 65 g / m³. 2 The cold pressing speed is 25 m / min.

[0090] Example 5

[0091] The difference between Example 5 and Example 1 is that the first baking temperature before rolling is 100°C, and the second baking temperature after rolling is 165°C.

[0092] Example 6

[0093] The difference between Example 6 and Example 1 is that the first baking temperature before rolling is 110°C, and the second baking temperature after rolling is 160°C.

[0094] Example 7

[0095] The difference between Example 7 and Example 2 is that the first baking temperature before rolling is 105°C, and the second baking temperature after rolling is 163°C.

[0096] Example 8

[0097] The difference between Example 8 and Example 2 is that the first baking temperature before rolling is 115°C, and the second baking temperature after rolling is 160°C.

[0098] Example 9

[0099] The difference between Example 9 and Example 1 is that the mass addition ratio of wool in the positive electrode slurry is 2%.

[0100] Example 10

[0101] The difference between Example 10 and Example 1 is that the mass addition ratio of wool in the positive electrode slurry is 3%.

[0102] Example 11

[0103] The difference between Example 11 and Example 1 is that the mass ratio of wool and polyvinyl chloride in the positive electrode slurry is 2% each.

[0104] Example 12

[0105] The difference between Example 12 and Example 1 is that the mass addition ratio of wool in the positive electrode slurry is 0.5%.

[0106] Example 13

[0107] The difference between Example 13 and Example 1 is that the mass addition ratio of wool in the positive electrode slurry is 5%.

[0108] Comparative Example 1

[0109] The difference between Comparative Example 1 and Example 1 is that the first baking temperature was 130°C.

[0110] Comparative Example 2

[0111] The difference between Comparative Example 2 and Example 1 is that the second baking temperature was 130°C.

[0112] Comparative Example 3

[0113] The difference between Comparative Example 3 and Example 3 is that no polymer fibers are added to the slurry;

[0114] Battery negative electrode slurry: graphite:SP:CNT:SBR = 97.7%:0.5%:0.5%:1.3%;

[0115] (1) First, mix graphite and conductive carbon black evenly to form a mixture;

[0116] (2) Dissolve the mixture in (1) in water and add water according to a solid content of 70%;

[0117] (3) Mix the mixture in (2) and carbon nanotubes (6wt%) evenly, and then add SBR to obtain the negative electrode slurry.

[0118] Comparative Example 4

[0119] The difference between Comparative Example 4 and Example 3 is that ammonium bicarbonate was used as the pore-forming agent;

[0120] Preparation of battery negative electrode slurry: Graphite:SP:CNT:SBR:Ammonium bicarbonate = 96.5%:0.5%:0.5%:1.3%:1.2% added;

[0121] (1) First, mix graphite and conductive carbon black evenly to form a mixture;

[0122] (2) Dissolve the mixture in (1) in water and add water according to a solid content of 70%;

[0123] (3) Mix the mixture in (2) and carbon nanotubes evenly, with a carbon nanotube mass fraction of 6%;

[0124] (4) Mix the slurry from (3) with ammonium bicarbonate and stir, then add SBR to obtain the negative electrode slurry.

[0125] Application examples

[0126] The positive electrode sheets prepared in the examples and comparative examples were assembled with conventional negative electrode sheets without polymer fibers, ceramic coated separators (base film thickness 5μm, double-sided ceramic, ceramic thickness 1μm, then double-sided adhesive coating, adhesive layer thickness 1μm), and electrolytes to form batteries with a capacity of 1800mAh. The electrolyte composition was EC:EMC:PP:LiPF6 = 25:10:50:15 by mass.

[0127] The negative electrode sheets prepared in the examples and comparative examples were assembled with conventional positive electrode sheets without polymer fibers, ceramic coated separators (base film thickness 5μm, double-sided ceramic, ceramic thickness 1μm, then double-sided adhesive coating, adhesive layer thickness 1μm), and electrolytes to form batteries with a capacity of 1800mAh; wherein the electrolyte composition was EC:EMC:PP:LiPF6 = 25:10:50:15 (mass ratio); the electrochemical performance of each battery was tested.

[0128] Electrolyte absorption rate test method: The rolled electrode sheets of each embodiment and comparative example are cut into areas of the same size, 1600 mm². 2 The weight was recorded as m0. After rolling, the electrode sheets were soaked in electrolyte (EC:EMC:PP:LiPF6=25:10:50:15, mass ratio) for 4 hours, then removed, air-dried for 30 seconds, and weighed as m2. The liquid absorption rate was (m1-m0) / m0. The test results are shown in Table 1.

[0129] Electrochemical performance testing conditions: The batteries composed of the rolled electrode sheets of each example and comparative example were tested for rate discharge performance at a temperature of 25°C, a charging rate of 1C, and 1C / 3A / 7A / 10A conditions; the test results are shown in Table 2.

[0130] Table 1

[0131] Table 2

[0132] Table 1 shows the test results, indicating that the electrode sheets prepared in Examples 1 to 13 of this application have an electrolyte absorption rate of 9% to 38%, with most exceeding 20% ​​and even 25%. The electrode sheets prepared in Comparative Examples 1 and 2 have an absorption rate of 10% to 12%. Comparative Example 1 has an absorption rate of 12%, which is due to its excessively high first baking temperature before rolling. Excessively high baking temperatures cause the electrode sheet to crack, and temperatures higher than the fiber decomposition temperature cause the fibers to begin decomposing before rolling, forming channels. After rolling, these channels are further destroyed into closed pores, resulting in fewer channels formed by the remaining fibers during the second baking process. This reduces the effective porosity of the electrode sheet, leading to a significant decrease in its electrolyte absorption. Comparative Example 2 has an absorption rate of 10%, which is due to its excessively low second baking temperature, below the fiber thermal decomposition temperature. After rolling, the fiber thermal decomposition rate in the electrode sheet decreases, failing to form a sufficient number of channels, resulting in a significant reduction in the amount of washing liquid.

[0133] In Comparative Example 3, no pore-forming agent was added to the slurry, and the electrode sheet liquid absorption rate reached 8%. In Comparative Example 4, ammonium bicarbonate was used as a pore-forming agent, and the electrode sheet liquid absorption rate reached 13%. The comparison shows that the liquid absorption of the electrode sheet with specific fibers added to the slurry in this application is approximately 1.5 to 2.5 times that of the traditional electrode sheet with ammonium bicarbonate added to the slurry, and approximately 2.3 to 4 times that of the traditional electrode sheet without any pore-forming agent added to the slurry. Clearly, this application can significantly improve the electrode sheet liquid absorption rate by adding specific fibers to the slurry, thereby improving the electrochemical performance of the battery.

[0134] Table 2 shows the test results. The batteries assembled using the electrode sheets prepared in Examples 1-13 of this application, under 1C / 3A / 7A / 10A conditions, exhibited capacity retention rates of 100%, 97.00%–99.80%, 95.4%–97.50%, and 91.20%–95.60%, respectively. Comparative Examples 1-4 showed retention rates of 100%, 97.00%–98.6%, 94.8%–95.9%, and 91.0%–92.8%, respectively. The batteries assembled using electrode sheets with added specific fibers to the slurry, as described in this application, generally exhibited significantly better capacity retention rates at 3A, 7A, and 10A than Comparative Examples 1-4, demonstrating a substantial improvement in battery capacity retention.

[0135] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

Claims

1. An electrode paste, the electrode paste comprising an active material, a binder and a conductive agent; the electrode paste further comprising a fibrous polymer material; wherein the thermal decomposition temperature T of the fibrous polymer material, the baking temperature T1 of the electrode sheet coated with the electrode paste before rolling and the baking temperature T2 after rolling satisfy the following relationship: T1<T≤T2.

2. The electrode paste according to claim 1, wherein, The relationship is: T1+10℃≤T≤T2; preferably: T1+20℃≤T≤T2; and even more preferably: T1+30℃≤T≤T2.

3. The electrode paste according to claim 1 or 2, wherein, The T1 is 100–130°C; preferably, the T1 is 110–130°C. And / or, the T is 120–160°C; preferably, the T is 130–160°C; more preferably, the T is 140–160°C; And / or, the T2 is 150-165°C; preferably, the T2 is 160-165°C.

4. The electrode paste according to any one of claims 1 to 3, wherein, The fibrous polymer material is wool fiber and / or polyvinyl chloride fiber; And / or, the ratio of the fiber length of the fibrous polymer material to the thickness of the active coating of the electrode is (0.5 to 1.2):

1.

5. The electrode paste according to any one of claims 1 to 4, wherein, The molecular weight of the fibrous polymer material is 4W to 6W g / mol; And / or, the thickness of the active material layer of the electrode is 60–85 μm; And / or, the fiber length of the fibrous polymer material is 40–100 μm; preferably 60–90 μm; And / or, the fiber diameter of the fibrous polymer material is 60-140 μm; preferably 100-120 μm.

6. The electrode paste according to any one of claims 1 to 5, wherein, The fibrous polymer material in the electrode slurry accounts for 0.5% to 5% by weight; preferably 1% to 4%; more preferably 1% to 3%; and even more preferably 1% to 2%. And / or, the active material in the electrode slurry accounts for 93% to 97% by weight; the binder in the electrode slurry accounts for 1% to 1.5% by weight; the conductive agent in the electrode slurry accounts for 1% to 1.5% by weight. And / or, the electrode is a positive electrode or a negative electrode; And / or, the active material is a positive electrode active material or a negative electrode active material; Preferably, the positive electrode active material is selected from lithium cobalt oxide or ternary materials; Preferably, the negative electrode active material is selected from graphite; Preferably, the conductive agent is selected from conductive carbon black and / or carbon nanotubes; Preferably, the adhesive is selected from polyvinylidene fluoride.

7. A method for preparing an electrode, the method comprising: The electrode paste is coated onto the surface of the current collector, and then subjected to a first baking, rolling and a second baking in sequence to obtain the electrode; The electrode paste is the electrode paste according to any one of claims 1 to 6.

8. The method for preparing the electrode according to claim 7, wherein, The temperature of the first baking is 100℃~130℃; preferably 110℃~130℃. And / or, the temperature of the second baking is 150℃~165℃; preferably 160℃~165℃; And / or, the first baking time is 1 to 2 hours; And / or, the second baking time is 6 to 10 hours; And / or, the compaction pressure rate is 10-20 m / min; And / or, the mixing process of the electrode slurry includes: mixing the active material, conductive agent, binder and solvent, adding fibrous polymer material, mixing and stirring to obtain the electrode slurry; preferably, the stirring time is 3 to 5 hours.

9. A battery, comprising electrodes; said electrodes are prepared by the electrode preparation method according to claim 7 or 8; preferably, said electrodes are positive electrode sheets or negative electrode sheets; the areal density of said positive electrode sheet is 110-120 g / m³. 2 The areal density of the negative electrode sheet is 60–70 g / m³. 2 .

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