Defoaming agent, secondary battery electrode sheet slurry, electrode sheet, and secondary battery

Abstract

The application discloses a defoaming agent, a secondary battery pole piece slurry, a pole piece and a secondary battery, and belongs to the secondary battery field.The defoaming agent is applied to the slurry of the secondary battery pole piece, and a structural formula of the defoaming agent is shown as formula (I): wherein R1 and R2 are each independently an alkyl group, and n1 and n2 are each independently a positive integer selected from 1 to 30.The defoaming agent of the application can reduce the bubble quantity of the slurry and improve the pole piece yield rate on the premise that the construction performance of the slurry and the pole piece electrical performance are not influenced.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to an antifoaming agent, secondary battery electrode slurry, electrode, and secondary battery. Background Technology

[0002] During the preparation of secondary battery electrode slurry, numerous factors, including the adsorption and volatility of raw materials, friction from the rotating blades during stirring, side reactions from mixing and hydrolysis, equipment, processes, and the operating environment, can lead to the formation of bubbles in the slurry. The presence of bubbles occupies space in the electrode material, reducing the effective contact area between the active material and the electrolyte, lowering the energy density, and thus reducing the overall performance of the battery. Adding defoamers can reduce the surface tension of the slurry and decrease bubble formation.

[0003] However, while current defoamers reduce the amount of bubbles generated when added to secondary battery electrode slurry, they are difficult to balance the surface tension and adhesion of the slurry, which in turn negatively affects the processing performance of the slurry and the electrical performance of the electrode. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a defoamer and its preparation method, a negative electrode sheet, and a secondary battery. The aim is to solve the problem that it is difficult to balance the surface tension and adhesion of the slurry after the defoamer is added to the secondary battery electrode slurry, which in turn brings negative effects on other processing and electrical properties of the slurry.

[0005] To achieve the above objectives, the present invention proposes an antifoaming agent, which is applied to the slurry of secondary battery electrode sheets. The structural formula of the antifoaming agent is shown in formula (I):

[0006]

[0007] R1 and n2 are each independently alkyl groups, and n1 and n2 are each independently selected from positive integers from 1 to 30.

[0008] In some embodiments, the mass percentage of the defoamer in the non-solvent components of the slurry is represented by A, where 0.01 wt% ≤ A ≤ 0.5 wt%.

[0009] In some embodiments, the slurry includes a binder, which includes at least one of styrene-butadiene rubber, styrene-acrylate rubber, and acrylate rubber.

[0010] In some embodiments, the slurry includes an active material, which includes at least one of artificial graphite, natural graphite, hard carbon, silicon-based active material, mesophase carbon microspheres, transition metal nitrides, and transition metal oxide carbon composite materials.

[0011] In some embodiments, the silicon-based active material includes at least one of nano-silicon, silicon-carbon material, silicon-oxygen material, and silicon-based alloy anode material.

[0012] In some embodiments, the silicon-based active material has a microsphere structure, and the sphericity of the microsphere is represented by B, where 0.88 ≤ B ≤ 1.

[0013] In some embodiments, the mass ratio of the silicon-based active material to the active material is represented by C, and A and C satisfy the following formula: when C < 10 wt%, then 0.01 wt% ≤ A ≤ 0.05 wt%; and / or when 10 wt% ≤ C ≤ 20 wt%, then 0.05 wt% < A ≤ 0.1 wt%; and / or when 20 wt% < C ≤ 50 wt%, then 0.1 wt% < A ≤ 0.5 wt%.

[0014] To achieve the above object, the present invention also provides a secondary battery electrode sheet slurry, and the secondary battery electrode sheet slurry includes the above defoaming agent.

[0015] In some embodiments, in the secondary battery electrode sheet slurry: the mass ratio of the active material, binder, conductive agent, and defoaming agent is: (93 - 96.5) : (1.5 - 4.5) : (1 - 2.5) : (0.01 - 0.5).

[0016] To achieve the above object, the present invention also provides an electrode sheet, including a negative electrode sheet prepared from the above secondary battery electrode sheet slurry.

[0017] In some embodiments, the preparation of the electrode sheet includes heat treatment after coating the secondary battery electrode sheet slurry onto a current collector; and / or the current collector is a copper foil with a thickness of 4 μm to 12 μm; and / or the coating speed is from 10 g / cm 2 to 13 g / cm 2 ; and / or the heat treatment temperature is 75°C to 85°C.

[0018] To achieve the above object, the present invention also provides a secondary battery, and the battery includes the above electrode sheet.

[0019] Advantages of the present invention:

[0020] In the defoaming agent provided by the present invention, the allyl glycidyl ether at the end of the siloxane-modified alkoxylated alkynediol is blocked, which can reduce hydrophilicity and can enter the foam bimolecular film, reducing the local surface tension in the slurry foam film, while the surface tension of the remaining part remains unchanged. This tension difference causes the part with stronger tension to pull the part with weaker tension, resulting in cracks, enabling the gas in the bubble to escape and defoaming, reducing the bubbles in the slurry. Description of the Drawings

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the silicon-based active material in one embodiment of the present invention, showing that the microstructure is spherical.

[0022] Figure 2 This is a scanning electron microscope (SEM) image of a silicon-based active material in one embodiment of the present invention, showing a near-spherical microstructure.

[0023] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0024] To make the technical solutions and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below in conjunction with specific embodiments. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter recorded in the claims.

[0025] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0027] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] During the preparation of secondary battery electrode slurry, numerous factors, including the adsorption and volatility of raw materials, friction from the rotating blades during stirring, side reactions from mixing and hydrolysis, equipment, processes, and the operating environment, can lead to the formation of bubbles in the slurry. The presence of bubbles occupies space in the electrode material, reducing the effective contact area between the active material and the electrolyte, lowering the energy density, and thus reducing the overall performance of the battery. Adding defoamers can reduce the surface tension of the slurry and decrease bubble formation.

[0030] However, while current defoamers reduce the amount of bubbles generated when added to secondary battery electrode slurry, they are difficult to balance the surface tension and adhesion of the slurry, which in turn negatively affects the processing performance of the slurry and the electrical performance of the electrode.

[0031] In view of this, the present invention proposes an antifoaming agent. To achieve the above-mentioned objective, the present invention proposes an antifoaming agent that is applied to the slurry of secondary battery electrode sheets. The structural formula of the antifoaming agent is shown in formula (I):

[0032]

[0033] R1 and n2 are each independently alkyl groups, and n1 and n2 are each independently selected from positive integers from 1 to 30.

[0034] The allyl glycidyl ether end-closure of the siloxane-modified alkoxylated acetylene diol in this application reduces hydrophilicity and allows it to enter the foam bilayer membrane. This reduces the local surface tension in the slurry bubble membrane while the surface tension of the rest remains unchanged. This tension difference causes the stronger tension area to pull the weaker tension area, thereby creating a crack and allowing the gas inside the bubble to escape and defoam, thus reducing the bubbles in the negative electrode slurry.

[0035] In some embodiments, the method for preparing the defoamer includes: mixing allyl glycidyl ether with an acetylenol epoxy compound at a molar ratio of 1:(2-3), adding an alkaline catalyst, reacting at a temperature of 85-95°C and a pressure of 0.4-0.6 MPa to generate a coupling polymer, adding hydrogen-containing silicone oil at a molar ratio of 1:1, adding a chloroplatinic acid catalyst, and reacting at a temperature of 85-95°C to generate siloxane-modified alkoxylated acetylenol.

[0036] In some embodiments, the defoamer accounts for a percentage of the non-solvent components in the slurry by mass, denoted by A, where 0.01 wt% ≤ A ≤ 0.5 wt%. The defoamer in this embodiment can achieve defoaming within this range without affecting the rheological properties of the slurry, and can achieve the effect of reducing bubbles in silicon anode slurries with a smaller addition amount. In some embodiments, A ranges from 0.01 wt% to 0.5 wt%, including 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.4 wt%, 0.44 wt%, and 0.48 wt%.

[0037] In some embodiments, the slurry includes a binder, which includes at least one of styrene-butadiene rubber, styrene-acrylate rubber, and acrylate rubber.

[0038] Styrene-butadiene rubber (SBR) possesses excellent flexibility and bonding strength, but it is sensitive to shear and easily introduces air bubbles during high-speed stirring. Styrene-acrylate rubber, or styrene-acrylate copolymer (PHA), combines the rigidity of styrene with the flexibility of acrylate, making it suitable for high-solids-content negative electrode slurries. It exhibits good electrolyte resistance; however, its hydrophobic segments easily adsorb particles of hydrophobic active substances such as graphite, forming gas-solid interfaces and generating air bubbles. Acrylic rubber (ACM) has excellent high-temperature resistance and electrolyte swelling resistance, but its viscosity is medium to high, resulting in a slow bubble rise rate in the slurry, requiring external force to assist in defoaming. The defoamer in this solution can balance the adhesive strength stability of the binder and the defoaming efficiency in both water-based and organic solvent systems corresponding to the above binders.

[0039] In some embodiments, the defoamer siloxane-modified alkoxylated acetylene diol molecule of this solution is inserted between the molecular chains of the binder styrene-butadiene rubber, styrene-acrylate rubber, and acrylate rubber, thereby weakening the intermolecular hydrogen bonding forces. The synergy between the defoamer and the binder in this solution also reduces drying stress and improves the curling condition of the battery electrode preparation.

[0040] In some embodiments, the slurry includes an active material, which includes at least one of artificial graphite, natural graphite, hard carbon, silicon-based active material, mesophase carbon microspheres, transition metal nitrides, and transition metal oxide carbon composite materials.

[0041] Active materials in electrodes primarily function to store and release lithium ions, and their performance directly affects the battery's electrical performance. Artificial graphite, natural graphite, and hard carbon are typically near-spherical or sheet-like particles with abundant active sites on their surfaces. Nano-silicon, silicon-carbon materials, silicon-oxygen materials, and silicon-based alloy anode materials generally have even smaller particle sizes but higher specific surface area and surface energy, and also contain more active functional groups.

[0042] After adsorbing onto the surface of the active material, defoamer molecules form a thin protective film. This film prevents impurities or by-reaction products in the electrolyte from covering the surface of the active material, thus maintaining its activity and facilitating lithium ion adsorption and deintercalation. Simultaneously, the organosilicon portion of the defoamer molecules interacts with lithium salts or other components in the electrolyte to form a conductive interface layer, thereby enhancing the electrochemical reactivity and electronic conductivity of the active material and improving overall battery performance. Furthermore, during battery charging and discharging, defoamers can alleviate volume changes and structural stress in the active material, reducing pulverization and shedding, thus improving cycle stability and lifespan.

[0043] In some embodiments, the silicon-based active material includes at least one of nano-silicon, silicon-carbon materials, silicon-oxygen materials, and silicon-based alloy anode materials.

[0044] In some embodiments, nano silicon includes ball-milled nano silicon, CVD nano silicon, porous nano silicon, core-shell structured silicon nanoparticles (Si@SiO2), etc.; silicon-carbon composites include core-shell structured Si@C, porous silicon / carbon composites, graphene-coated silicon, carbon nanotube silicon-carbon materials, etc.; silicon-oxygen materials (SiO2) X -Based Materials) include SiO / C composites, multilayer coated SiOx such as SiOx@C@TiO2, and lithium pre-doped SiO2. X Silicon-based alloy anode materials include silicon-tin alloy materials, silicon-aluminum alloy materials, silicon-zinc alloy materials, etc.

[0045] The siloxane segments of the defoamer form a flexible coating layer on the surface of the aforementioned silicon-based active material particles, which buffers the volume expansion stress during charging and discharging, reducing crack generation; at the same time, the defoamer suppresses bubbles in the preparation stage of silicon-containing slurry, avoiding the amplification of the volume effect of silicon by pore defects.

[0046] In some embodiments, the silicon-based active material has a microsphere structure. The sphericity of the microspheres is represented by B, where 0.88 ≤ B ≤ 1. There are pores when the spherical silicon-containing active materials are stacked. When the sphericity B is within the above range, the pores are larger. The siloxane-modified alkoxylated diol contains a hydrophilic structure and has the characteristic of low surface tension, and it has excellent wetting effect even in the case of low porosity. In some embodiments, the sphericity B of the nano-silicon is any value in the range of 0.88 to 1, such as 0.89, 0.9, 0.92, 0.95, 0.98, etc.

[0047] Furthermore, when A and B simultaneously satisfy the following ranges: 0.88 ≤ B ≤ 1, and 0.01 wt% ≤ A ≤ 0.5 wt%, within this proportional range of the dosage of the defoamer and the sphericity of the spherical silicon-containing active material, the defoamer can form a more uniform coating on the surface of the spherical silicon-containing active material. Even in an environment with relatively low pores formed by the stacking of the spherical silicon-containing active material, it can effectively wet the silicon surface, thereby avoiding the agglomeration of the active materials in the negative electrode slurry, making them more evenly dispersed in the slurry, increasing the flexibility, and improving the compaction density, providing a basis for the subsequent electrode performance.

[0048] In some embodiments, the mass ratio of the silicon-based active material to the active material is represented by C. A and C satisfy the following formulas: when C < 10 wt%, then 0.01 wt% ≤ A ≤ 0.05 wt%; and / or, when 10 wt% ≤ C ≤ 20 wt%, then 0.05 wt% < A ≤ 0.1 wt%; and / or, when 20 wt% < C ≤ 50 wt%, then 0.1 wt% < A ≤ 0.5 wt%.

[0049] During the preparation process of the silicon-based material, gas is generated by reacting with hydroxide ions, resulting in bubbles. The slurry with a high silicon content generates more gas, and therefore the dosage of the defoamer needs to be correlated with the mass ratio of silicon in the active material. When the silicon content is relatively low, the foaming tendency of the slurry system is weak, and a small amount of defoamer can inhibit the bubbles, avoiding the decrease in dispersibility or the increase in interfacial impedance caused by excessive addition. As the silicon content increases, the high surface activity of the silicon particles and the significant increase in the slurry viscosity significantly exacerbate the foaming risk. At this time, increasing the dosage of the defoamer in stages can not only effectively break the foam but also avoid the cost waste caused by ineffective overdosage. When the dosage relationship between the defoamer and the silicon content in this solution meets the above ratio, compared with the traditional defoamer, the defoamer in this solution can achieve the effect of reducing bubbles in the silicon slurry with less and more precise addition amounts.

[0050] To solve the above problems, the present invention also proposes a secondary battery electrode sheet slurry, including the above defoamer. Adding the above defoamer makes the slurry have a high wetting degree, increases the flexibility of the electrode sheet in subsequent preparation, improves the curling of the electrode sheet, and is beneficial to preventing the deformation of the internal structure of the battery.

[0051] In some embodiments, the mass ratio of active material, binder, conductive agent, and defoamer in the secondary battery electrode slurry is (93-96.5):(1.5-4.5):(1-2.5):(0.01-0.5). Preferably, the mass ratio of active material, binder, conductive agent, and defoamer is 94.95:3:2:0.05.

[0052] In some embodiments, the conductive agent is at least one of conductive carbon black, acetylene black, carbon nanotubes, carbon fibers, graphene, nano-carbon, and Ketjen black; the solvent is deionized water.

[0053] To address the aforementioned problems, the present invention also proposes an electrode sheet comprising an electrode sheet prepared from the aforementioned slurry.

[0054] In some embodiments, the preparation of the electrode includes coating the slurry onto a current collector followed by heat treatment; the current collector is a copper foil with a thickness of 4 μm to 12 μm; the coating speed is 10 g / cm. 2 ~13g / cm 2 The heat treatment temperature is 75℃~85℃. The electrode prepared by this method has good flexibility, is not easy to curl, and has high wettability, which is conducive to the slippage of silicon material and thus results in high compaction density.

[0055] To address the aforementioned problems, this invention also proposes a secondary battery comprising the aforementioned electrodes. It should be noted that regardless of the conventional selection of electrodes, separators, electrolytes, battery assembly methods, etc., as long as the defoamer of this solution is used in the negative electrode slurry, the battery will possess the beneficial effects claimed by the defoamer.

[0056] Example 1

[0057] I. Preparation of Defoamer

[0058] Allyl glycidyl ether and alkynyl diol epoxy compound were mixed in a molar ratio of 1:2, and sodium hydroxide catalyst was added. The mixture was reacted at 90°C and 0.4 MPa to generate a coupling polymer. Hydrogen-containing silicone oil was added, and the molar ratio of coupling polymer to hydrogen-containing silicone oil was 1:1. The mixture was reacted at 90°C with chloroplatinic acid catalyst to obtain siloxane-modified alkoxylated alkynyl diol.

[0059] II. Preparation of negative electrode sheet

[0060] 1. Preparation of negative electrode sheet: By weight, 85.99 parts of artificial graphite and 8.6 parts of nano-silicon with a sphericity of 0.88 were mixed by dry mixing for 30 minutes. Then, 2.4 parts of styrene-butadiene rubber and 40 parts of deionized water were added and stirred for 60 minutes. Then, 1 part of carbon nanotubes, 2 parts of styrene-butadiene rubber and 40 parts of deionized water were added and stirred for 60 minutes. Finally, 0.01 parts of siloxane-modified alkoxylated acetylene diol were added and stirred for 30 minutes to obtain the negative electrode slurry.

[0061] The above silicon anode slurry was prepared at 12 g / cm³. 2 The coating is applied to a 6µm copper foil at a high speed, and the negative electrode is obtained after baking at 80℃.

[0062] Among them, artificial graphite was purchased from Guangdong Kaijin New Energy Technology Co., Ltd.; nano-silicon was purchased from Shanghai Chaowei Nanotechnology Co., Ltd.; styrene-butadiene rubber was purchased from Shandong Gaoshi Science and Industry Trade Co., Ltd.; and carbon nanotubes were purchased from Defang Nano.

[0063] Example 2

[0064] The adhesive is a styrene-acrylate copolymer (PHA), and the rest are as described in Example 1.

[0065] Example 3

[0066] The adhesive is acrylic rubber (ACM), and the rest are as described in Example 1.

[0067] Example 4

[0068] The amount of siloxane-modified alkoxylated acetylene diol added was 0.46 parts, the amount of nano-silicon added was 55.62 parts, and the rest were as described in Example 1.

[0069] Example 5

[0070] The amount of siloxane-modified alkoxylated acetylene diol added was 0.05 parts, and the rest were as described in Example 1.

[0071] Example 6

[0072] The amount of siloxane-modified alkoxylated acetylene diol added was 0.6 parts, the amount of nano-silicon added was 55.62 parts, and the rest were as described in Example 1.

[0073] Example 7

[0074] The sphericity of the nano-silicon is 0.94, and the rest are as described in Example 5.

[0075] Example 8

[0076] The sphericity of the nano-silicon is 0.98, and the rest are as described in Example 5.

[0077] Example 9

[0078] The sphericity of the nano-silicon is 0.8, and the rest are as described in Example 5.

[0079] Comparative Example 1:

[0080] No defoamer is added to the negative electrode slurry. The negative electrode slurry contains artificial graphite, nano-silicon, carbon nanotubes, and binder in a mass ratio of 86:10:1:3. The rest are as described in Example 5.

[0081] Comparative Example 2:

[0082] The defoamer was modified polydimethylsiloxane (purchased from Foshan Qianyou Chemical Co., Ltd.), and the rest are as described in Example 5.

[0083] Performance testing

[0084] (1) Electrode adhesion test

[0085] First, cut the electrode to be tested into 10cm*10cm pieces, then use special adhesive tape to stick it onto the coating layer of the electrode. Then, fix the electrode and adhesive tape assembly onto the upper and lower clamps of the tensile testing machine. After setting the peel length of the tensile testing machine to 120mm and the peel speed to 100mm / min, start the test to obtain the peel strength curve and obtain the peel strength value, which reflects the bonding performance of the active layer of the electrode.

[0086] (2) Surface tension test

[0087] To measure surface tension using the static pendant drop method, fill a syringe with 3 ml of the negative electrode slurry to be tested, attach the syringe to the equipment, adjust the needle clarity to ensure clear focus, lower the sample stage to its lowest position, establish a pendant drop template, select deionized water as the liquid phase, set the extruded liquid volume to 3 μL, measure the surface tension in mN / m, and repeat three times to obtain the average value.

[0088] (3) Electrode curling test

[0089] Cut a 10cm*10cm negative electrode sheet and place it in a 120℃ oven for 2 hours. Use a ruler to measure the warping height of the four corners of the electrode sheet and take the average value in mm.

[0090] (4) Compacted density test

[0091] The coated electrode sheet is placed on a roller press and subjected to a pressure of 50T for 10 seconds. The thickness of the electrode sheet after rolling is measured. The compaction density is obtained using the formula: Compacted density = Areal density / (Thickness of electrode sheet after rolling - Thickness of current collector), with units of g / cm³. 3 .

[0092] (5) Electrode quality statistics

[0093] 100 electrode sheets are randomly selected from a batch of 1000 sheets on the production line for testing. Each sample is tested for various quality indicators such as adhesion. The number of samples that meet the quality standards is counted, and then the excellence rate is calculated as follows: Excellence rate = (Number of qualified samples / Total number of samples) × 100%.

[0094] The performance test results are recorded in Table 1, where A is the mass percentage of defoamer in the non-solvent components of the electrode slurry, B is the sphericity of the silicon-based active material microspheres, and C is the mass ratio of silicon-based active material to active material in the slurry.

[0095] Table 1.

[0096]

[0097] The data in Table 1 demonstrates that the allyl glycidyl ether end-closure of the siloxane-modified alkoxylated acetylene diol in the defoamer provided by this scheme reduces hydrophilicity and allows it to enter the foam bilayer. This reduces the local surface tension in the slurry bubble membrane while the surface tension of the remaining parts remains unchanged. This tension difference causes the stronger tension areas to pull the weaker tension areas, thereby creating cracks that allow the gas inside the bubbles to escape and defoam, reducing the number of bubbles in the slurry.

[0098] In Examples 1-9, the siloxane-modified alkoxylated acetylenic diol defoamer stabilized the surface tension of the slurry at 45.3–46.95 mN / m, which is lower than that of Comparative Example 1 (49.08 mN / m) without defoamer and Comparative Example 2 (48.71 mN / m) with commercially available defoamer, demonstrating its highly efficient ability to reduce surface tension.

[0099] The yield of this solution is 97.5%–98.99%, while Comparative Example 1 only achieves 96.22%, and commercially available defoamers only achieve 97%, highlighting the crucial role of the defoamer in improving production yield. With 0.01 parts of defoamer added, the peel strength reaches a maximum of 38.56 N / cm, while in Example 6, with 0.6 parts of defoamer added, the peel strength drops to 33.88 N / cm, indicating that adding more than 0.5 wt% of defoamer will lead to severe deterioration of adhesion.

[0100] Referring to Examples 1, 5, and 6, as the amount of defoamer increased, the curling height of the electrode decreased from 15 mm to 2 mm, indicating that a higher dosage significantly improved the flatness of the electrode. Referring to Examples 3 and 4, with increasing incorporation of nano-silicon material and adaptability of the defoamer dosage, significant optimization of curling height and yield was achieved with only a slight decrease in adhesion, demonstrating the compatibility of the defoamer in this scheme with the high-silicon-doped secondary battery electrode slurry system. (See attached instruction manual) Figure 1 With appendix Figure 2The images show scanning electron microscope (SEM) images of nano-silicon with different sphericity on the active layer of the electrode. Referring to Examples 7 and 8, the increased sphericity of the nano-silicon significantly improves the compaction density of the electrode, resulting in better electrical performance.

[0101] Comparative Example 1, without the addition of defoamer, had the highest surface tension of 49.08 mN / m and the lowest electrode yield of 96.22%, reflecting coating defects caused by air bubbles in the slurry. Comparative Example 2, using commercially available defoamer, had a lower peel strength of 35.3 N / cm and severe curling with a curling height of 16 mm, resulting in a yield significantly lower than that of the embodiments in this scheme.

[0102] Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

[0103] The above description is only a part or preferred embodiment of the present invention. Neither the text nor the drawings should limit the scope of protection of the present invention. All equivalent structural transformations made using the content of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A defoamer, characterized in that, The defoamer is applied to the slurry of the secondary battery electrode sheet, and the structural formula of the defoamer is shown in formula (Ⅰ): Equation (Ⅰ), Wherein, R1 and R2 are each independently alkyl, and n1 and n2 are each independently selected from positive integers from 1 to 30.

2. A secondary battery electrode slurry, characterized in that, The secondary battery electrode slurry includes the defoamer as described in claim 1.

3. The secondary battery electrode slurry according to claim 2, characterized in that, The secondary battery electrode slurry also includes active material, binder and conductive agent, and the mass ratio of the active material, the binder, the conductive agent and the defoamer is (93~96.5): (1.5~4.5): (1~2.5): (0.01~0.5).

4. The secondary battery electrode slurry according to claim 2, characterized in that, The mass percentage of the defoamer in the non-solvent components of the slurry is represented by A, where 0.01wt%≤A≤0.5wt%.

5. The secondary battery electrode slurry according to claim 3, characterized in that, The adhesive includes at least one of styrene-butadiene rubber, styrene-acrylate rubber, and acrylate rubber.

6. The secondary battery electrode slurry according to claim 3, characterized in that, The active material includes at least one of artificial graphite, natural graphite, hard carbon, silicon-based active material, mesophase carbon microspheres, transition metal nitrides, and transition metal oxide carbon composite materials.

7. The secondary battery electrode slurry according to claim 6, characterized in that, The silicon-based active material includes at least one of nano-silicon, silicon-carbon materials, silicon-oxygen materials, and silicon-based alloy anode materials.

8. The secondary battery electrode slurry according to claim 7, characterized in that, The silicon-based active material has a microsphere structure, and the sphericity of the microsphere is represented by B, where 0.88 ≤ B ≤ 1.

9. The secondary battery electrode slurry according to claim 6, characterized in that, The mass ratio of the silicon-based active material to the total active material is represented by C, and A and C satisfy the following formula: If C < 10 wt%, then 0.01 wt% ≤ A ≤ 0.05 wt%; And / or, if 10wt%≤C≤20wt%, then 0.05wt%<A≤0.1wt%; And / or, if 20wt% < C ≤ 50wt%, then 0.1wt% < A ≤ 0.5wt%.

10. An electrode sheet, characterized in that, Including electrodes prepared from the secondary battery electrode slurry according to any one of claims 2 to 9.

11. The electrode according to claim 10, characterized in that, The preparation of the electrode includes coating the secondary battery electrode slurry onto the current collector and then heat treating it; And / or, the current collector is a copper foil with a thickness of 4μm to 12μm; And / or, the coating amount is 10 g / cm³. 2 ~13g / cm 2 ; And / or, the temperature of the heat treatment is 75°C to 85°C.

12. A secondary battery, characterized in that, The battery includes the electrode as described in claim 10 or 11.

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