Modified styrene-butadiene rubber polymer, negative plate, preparation method of negative plate and lithium ion battery
By introducing active groups into the styrene-butadiene rubber polymer, the adhesion and kinetic properties of the lithium-ion battery negative electrode sheet are improved, solving the problems of battery powder shedding and lithium plating caused by low binder dosage, and improving the energy density and cycle life of the battery.
Patent Information
- Application Number
- CN202511545286.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-28
- Publication Date
- 2025-12-26
AI Technical Summary
Existing lithium-ion battery anode SBR binders have insufficient bonding strength at low dosages, leading to powder shedding and lithium plating during battery fabrication, poor kinetic performance, and interface failure during cycling, failing to meet the requirements for high energy density and long cycle life.
Modified styrene-butadiene rubber polymers are used. By introducing active groups such as carboxyl, ester, cyano or amide groups, the adhesion and kinetic properties of the binder are improved. During cycling, the battery's high-temperature stability and cycle performance are enhanced through intermolecular hydrogen bond self-repair.
It improves the battery's adhesion and lithium-ion transport capacity, enhances the battery's kinetic performance and high-temperature cycling performance, and extends the battery's cycle life.
Smart Images
Figure CN121203084A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of energy storage battery technology, and in particular to a modified styrene-butadiene rubber polymer, a negative electrode sheet, a method for preparing the same, and a lithium-ion battery. Background Technology
[0002] With the continuous development of lithium-ion batteries, the requirements for battery energy density, cycle performance, rate performance, and high and low temperature performance are constantly increasing. Conventional SBR (Selective Bioreactor) for the negative electrode is nearing its limit in terms of binder usage. Insufficient SBR usage leads to low electrode binder strength, resulting in C-corner powder shedding and lithium plating during battery fabrication. Furthermore, conventional SBR lacks ion-conducting capabilities and has poor kinetic performance, offering no significant improvement to fast-charging and low-temperature performance. During cycling, as the negative electrode material expands and contracts during lithium insertion / extraction, interfacial failures easily occur between the binder and the active material, as well as between binders themselves, leading to reduced battery capacity retention in the later stages of cycling. To meet these ever-increasing demands, there is an urgent need to develop binders with high adhesion, high kinetics, and self-healing capabilities to cope with negative electrode expansion and contraction during cycling. Summary of the Invention
[0003] The purpose of this invention is to overcome the shortcomings and defects of the prior art and to provide a modified styrene-butadiene rubber polymer, a negative electrode sheet, a method for preparing the same, and a lithium-ion battery.
[0004] To achieve the above objectives, this application adopts the following solution:
[0005] A modified styrene-butadiene rubber polymer includes a styrene-butadiene rubber polymer and active groups modified on the styrene-butadiene rubber polymer; the active groups include at least one of carboxyl, ester, cyano, or amide groups.
[0006] The modified styrene-butadiene rubber polymer described herein has any one of formulas (I), (II), (III), or (IV).
[0007]
[0008] a, b, and c represent the independent degrees of polymerization of styrene, butadiene, and acrylic acid, respectively.
[0009] The modified styrene-butadiene rubber polymer has a particle size of 50-230 nm and a molecular weight of 30-200 W; preferably, the particle size is 130-140 nm and the molecular weight is 120-180 W.
[0010] The present invention also includes a method for preparing the modified styrene-butadiene rubber polymer, comprising the following steps:
[0011] 1) The first polymerization reaction is carried out in the following steps: the raw materials of emulsifier, styrene, butadiene and the first initiator are mixed in an aqueous solution and then the first polymerization reaction is carried out to obtain the first reaction polymerization intermediate SBR inner layer structure;
[0012] 2) The second polymerization reaction is carried out by the following steps: the first polymerization intermediate, deoxidizer, second initiator, acrylic acid and modified monomer raw materials are subjected to a second polymerization reaction to obtain the product system;
[0013] 3) The product system is subjected to extraction and post-treatment to obtain modified styrene-butadiene rubber polymer.
[0014] In step 1), the molar ratio of styrene to butadiene is 2:8-7:3; preferably 5:5.
[0015] Preferably, in step 1), the temperature of the first polymerization reaction is 30–80°C, and the time of the first polymerization reaction is 1.5–4 h; the first initiator is one of benzoyl peroxide and diisopropyl peroxide; the emulsifier is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyol fatty acid esters.
[0016] Step 2) The acrylic monomer accounts for 1%-6% of the mass of the first polymerization intermediate; preferably 2%; the modified monomer accounts for 1%-6% of the mass of the first polymerization intermediate; preferably 1%.
[0017] Preferably, the modified monomer is one or a mixture of cysteine, 2-amino-2-cyanoacetamide, β-cyano-L-alanine, 3-aminopentanilide, and cysteine; more preferably, it is a mixture of cysteine and 2-amino-2-cyanoacetamide.
[0018] The deoxidizing agent is one or two of sodium formaldehyde sulfoxylate and sodium dithionite dihydrate; the second initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide.
[0019] The present invention also includes an application of the modified styrene-butadiene rubber polymer as an adhesive.
[0020] The present invention also includes a negative electrode sheet, comprising a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the negative electrode binder comprises the modified styrene-butadiene rubber polymer and CMC;
[0021] Preferably, the negative electrode active material is graphite; preferably, the negative electrode conductive agent is carbon black.
[0022] Preferably, the dry weight ratio of the modified styrene-butadiene rubber polymer to CMC is (1-2):(1-2); more preferably, it is 1.5:1.2.
[0023] The present invention also includes a method for preparing the aforementioned negative electrode sheet, comprising the following steps:
[0024] (1) The negative electrode active material and the conductive agent are fed and mixed according to the set ratio. After stirring at low speed, some CMC adhesive and deionized water are added. After mixing thoroughly, the solid content is adjusted for the first time.
[0025] (2) Add CMC adhesive and deionized water to the above mixed slurry again, stir thoroughly, and then perform a second solid content adjustment;
[0026] (3) Add a specific amount of CMC adhesive and deionized water to the mixed slurry obtained in (2) again, mix thoroughly, and then perform a third solid content adjustment; after that, adjust the slurry viscosity to 3000cp by adjusting the amount of deionized water added.
[0027] Preferably, the ratio of CMC adhesive in steps (1), (2), and (3) is 0.6:0.2:0.2;
[0028] (4) Add the SBR to the obtained mixed slurry, stir at low speed, vacuum, and sieve to discharge;
[0029] (5) The obtained negative electrode slurry is coated on the surface of the negative electrode current collector and then rolled into a sheet to obtain a negative electrode sheet.
[0030] The present invention also includes a lithium-ion battery, comprising the aforementioned negative electrode and a positive electrode; preferably, the active material of the positive electrode is one of lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide.
[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0032] This invention provides a method for preparing a high-temperature stable, high-kinetic, and self-healing modified styrene-butadiene rubber polymer (modified SBR) and its application in lithium-ion batteries. The aim is to reduce the amount of binder used while ensuring higher adhesion of the electrode, increase the proportion of main material, and improve the energy density of the battery. At the same time, the introduction of polar monomers can improve the lithium-ion transport capacity of the battery and improve the battery kinetic performance. The intermolecular hydrogen bonds formed can be repeatedly rebuilt and self-healed during the expansion and contraction of the electrode, ensuring the long-term cycle performance of the battery.
[0033] Specifically, the flexible butadiene monomer ensures good wettability of the SBR, resulting in good wetting between it and the main material of the lithium-ion battery anode, enhancing mechanical locking and improving adhesion. Simultaneously, its flexibility improves electrode brittleness, preventing powder shedding and burr formation during pressing, which could lead to battery short circuits. Furthermore, its flexibility prevents lithium plating caused by powder shedding at the C-corner during winding and hot pressing. Meanwhile, the rigid styrene monomer ensures good mechanical strength of the electrode. The introduction of polar functional groups such as carboxyl, ester, and amide groups into the modified SBR can interact with Li... + Coordination, thereby enhancing the SBR's response to Li + The modified SBR enhances the battery's transmission capacity, rate capability, and low-temperature performance. Simultaneously, the amide and cyano groups exhibit excellent high-temperature stability, which benefits the battery's high-temperature cycling and storage performance. The introduction of polar functional groups such as carboxyl and amide groups into the modified SBR promotes the formation of intermolecular hydrogen bonds. These hydrogen bonds can be repeatedly rebuilt and self-repaired during electrode expansion and contraction, thus ensuring a longer cycle life for the battery. Attached Figure Description
[0034] Figure 1 The infrared spectrum of the modified SBR binder (GSBR-5) obtained in Example 5;
[0035] Figure 2 This is a photograph of the negative electrode sheet prepared in Example 5 after being folded three times. Detailed Implementation
[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0037] Comparative Example 1: Fabrication of the negative electrode and lithium-ion battery, the steps are as follows:
[0038] (1) The dry weight ratio (wt%) of graphite, carbon black, CMC and SBR in the negative electrode slurry is 96.3:1.0:1.2:1.5.
[0039] (2) Prepare CMC adhesive solution, wherein the CMC solid content is 1.5% and the solvent is deionized water.
[0040] (3) Add artificial graphite and carbon black according to the set ratio, stir at low speed, add a specific amount of CMC adhesive and deionized water, mix thoroughly, and then perform the first solid content adjustment to adjust the solid content to about 67%.
[0041] (4) Add a specific amount of CMC adhesive and deionized water to the above mixed slurry again, stir thoroughly, and then perform a second solid content adjustment to adjust the solid content to about 61%.
[0042] (5) Add a specific amount of CMC adhesive and deionized water to the mixed slurry obtained in (4) again, mix thoroughly, and then perform a third solid content adjustment; after that, adjust the slurry viscosity to 3000cp by adjusting the amount of deionized water added; the CMC addition ratio in (3), (4), and (5) is 0.6:0.2:0.2;
[0043] (6) Add SBR to the obtained mixed slurry again, stir at low speed, vacuum, and discharge through a 100-mesh sieve.
[0044] The SBR is prepared by mixing sodium dodecylbenzenesulfonate, styrene, butadiene and benzoyl peroxide in an aqueous solution at a mass ratio of 0.2:65:35:0.5 and reacting at 40°C for 2 hours to carry out the first polymerization reaction to obtain the first polymerization intermediate, i.e. the SBR inner layer structure, wherein the molar ratio of styrene to butadiene is 5:5.
[0045] Subsequently, the first reaction polymer intermediate, sodium formaldehyde sulfoxylate, azobisisobutyronitrile, and acrylic acid raw materials were subjected to a second polymerization reaction at 30°C for 2 hours in a mass ratio of 100:0.2:0.5:2 to obtain the product system.
[0046] Finally, the product system was subjected to extraction and post-processing to obtain SBR binder;
[0047] (7) The obtained negative electrode slurry is coated on the surface of the negative electrode current collector, and after being rolled into a sheet, it is assembled together with the lithium iron phosphate positive electrode sheet and the polyethylene separator. After liquid injection and formation, a lithium-ion battery (C1) is obtained.
[0048] Example 1:
[0049] Preparation of modified SBR: Sodium dodecylbenzenesulfonate, styrene, butadiene and benzoyl peroxide were mixed in an aqueous solution at a mass ratio of 0.2:65:35:0.5 and reacted at 40°C for 2 hours to carry out the first polymerization reaction to obtain the first polymerization intermediate, namely the SBR inner layer structure, wherein the molar ratio of styrene to butadiene was 5:5.
[0050] Subsequently, the raw materials comprising the aforementioned first reaction polymer intermediate, sodium formaldehyde sulfoxylate, azobisisobutyronitrile, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, acrylic acid, and the modified monomer 2-amino-2-cyanoacetamide were subjected to a second polymerization reaction at 30°C for 2 hours in a mass ratio of 100:0.2:0.5:0.2:2:1 to obtain the product system.
[0051] Finally, the product system was subjected to extraction and post-processing to obtain modified SBR binder (GSBR-1) with a particle size of 130-140 nm and a molecular weight of 120-180 W.
[0052] The negative electrode and lithium-ion battery were fabricated using a similar procedure to Comparative Example 1, the only difference being the use of a modified SBR binder (GSBR-1) instead of the traditional SBR. After liquefaction formation, a lithium-ion battery (GC1) was obtained.
[0053] Example 2:
[0054] Preparation of modified SBR: Sodium dodecylbenzenesulfonate, styrene, butadiene and benzoyl peroxide were mixed in an aqueous solution at a mass ratio of 0.2:65:35:0.5 and reacted at 40°C for 2 hours to carry out the first polymerization reaction to obtain the first polymerization intermediate, namely the SBR inner layer structure, wherein the molar ratio of styrene to butadiene was 5:5.
[0055] Subsequently, the raw materials comprising the aforementioned polymer intermediate, sodium formaldehyde sulfoxylate, azobisisobutyronitrile, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, acrylic acid, and the modified monomer β-cyano-L-alanine were subjected to a second polymerization reaction at 30°C for 2 hours in a mass ratio of 100:0.2:0.5:0.2:2:1 to obtain the product system.
[0056] Finally, the product system was subjected to extraction and post-treatment to obtain the modified SBR binder (GSBR-2);
[0057] The negative electrode and lithium-ion battery were fabricated using a similar procedure to Comparative Example 1, the only difference being the use of a modified SBR binder (GSBR-1) instead of the traditional SBR. After liquefaction formation, a lithium-ion battery (GC2) was obtained.
[0058] Example 3:
[0059] Preparation of modified SBR: Sodium dodecylbenzenesulfonate, styrene, butadiene and benzoyl peroxide were mixed in an aqueous solution at a mass ratio of 0.2:65:35:0.5 and reacted at 40°C for 2 hours to carry out the first polymerization reaction to obtain the first reaction polymerization intermediate and the SBR inner layer structure, wherein the molar ratio of styrene to butadiene was 5:5.
[0060] Subsequently, the raw materials including the above-mentioned polymer intermediate, sodium formaldehyde sulfoxylate, azobisisobutyronitrile, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, acrylic acid and modified monomer 3-aminopentadienyl nitrile were subjected to a second polymerization reaction at 30°C for 2 hours in a mass ratio of 100:0.2:0.5:0.2:2:1 to obtain the product system.
[0061] Finally, the product system was subjected to extraction and post-treatment to obtain the modified SBR binder (GSBR-3);
[0062] The negative electrode and lithium-ion battery were fabricated using a similar procedure to Comparative Example 1, the only difference being the use of a modified SBR binder (GSBR-3) instead of the traditional SBR. After liquefaction formation, a lithium-ion battery (GC3) was obtained.
[0063] Example 4:
[0064] Preparation of modified SBR: Sodium dodecylbenzenesulfonate, styrene, butadiene and benzoyl peroxide were mixed in an aqueous solution at a mass ratio of 0.2:65:35:0.5 and reacted at 40°C for 2 hours to carry out the first polymerization reaction to obtain the first reaction polymerization intermediate and the SBR inner layer structure, wherein the molar ratio of styrene to butadiene was 5:5.
[0065] Subsequently, the raw materials including the above-mentioned polymer intermediate, sodium formaldehyde sulfoxylate, azobisisobutyronitrile, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, acrylic acid and modified monomer cysteine were subjected to a second polymerization reaction at 30°C for 2 hours in a mass ratio of 100:0.2:0.5:0.2:2:1 to obtain the product system.
[0066] Finally, the product system was subjected to extraction and post-treatment to obtain the modified SBR binder (GSBR-4);
[0067] The negative electrode and lithium-ion battery were fabricated using a similar procedure to Comparative Example 1, the only difference being the use of a modified SBR binder (GSBR-4) instead of the traditional SBR. After liquefaction formation, a lithium-ion battery (GC4) was obtained.
[0068] Example 5:
[0069] Preparation of modified SBR: Sodium dodecylbenzenesulfonate, styrene, butadiene and benzoyl peroxide were mixed in an aqueous solution at a mass ratio of 0.2:65:35:0.5 and reacted at 40°C for 2 hours to carry out the first polymerization reaction to obtain the first reaction polymerization intermediate and the SBR inner layer structure, wherein the molar ratio of styrene to butadiene was 5:5.
[0070] Subsequently, the raw materials comprising the aforementioned first polymer intermediate, sodium formaldehyde sulfoxylate, azobisisobutyronitrile, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, acrylic acid, modified monomer cysteine, and 2-amino-2-cyanoacetamide were subjected to a second polymerization reaction at 30°C for 2 hours in a mass ratio of 100:0.2:0.5:0.2:2:0.5:0.5 to obtain the product system.
[0071] Finally, the product system was subjected to extraction and post-processing to obtain the modified SBR binder (GSBR-5), as shown in infrared spectroscopy. Figure 1As shown; the negative electrode and lithium-ion battery were fabricated using similar steps to Comparative Example 1, the only difference being the use of a modified SBR binder (GSBR-5) instead of the traditional SBR. After liquefaction formation, a lithium-ion battery (GC5) was obtained. The electrode remained in good condition after being folded three times (as shown). Figure 2 ).
[0072] Rate charge / discharge performance test: Rate discharge test: Under room temperature conditions, charge at a constant current of 0.33C to 3.65V, charge at a constant voltage of 3.65V to 0.05C, and then discharge at 3C to 2.5V; Rate charge test: charge at 3C to 3.65V, charge at a constant voltage of 3.65C to 0.05C, and then discharge at 0.33C to 2.5V.
[0073] High and low temperature performance testing: Rate discharge test: At room temperature, charge at a constant current of 0.33C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C for standard capacitance; At room temperature, charge at a constant current of 0.33C to 3.65V, then discharge at -20℃ to 2.0V; At room temperature, charge at a constant current of 0.33C to 3.65V, then discharge at 60℃ to 2.5V.
[0074] High-temperature storage performance test: At room temperature, discharge to 2.5V at 1C and let stand for 10 minutes; charge to 3.65V at 1C constant current and let stand for 10 minutes; charge to 0.05C at 3.65V constant voltage and repeat this charge-discharge cycle 3 times. Finally, fully charge the battery and store it in a 60℃ oven for 30 days. After 30 days of storage, remove the battery and charge and discharge it 3 times at room temperature using the same charge-discharge cycle. Record the residual capacity and recovered capacity after storage.
[0075] High-temperature cycling performance test: At 45℃, discharge at 1C to 2.5V and let stand for 10 minutes; charge at 1C constant current to 3.65V and let stand for 10 minutes; charge at 3.65V constant voltage to 0.05C and repeat this charge and discharge cycle 800 times.
[0076] Table 1 shows the test results of the adhesion of lithium-ion battery electrodes using comparative examples and embodiments with different SBRs.
[0077] Table 1. Test results of lithium-ion battery electrode adhesion in each comparative example and embodiment.
[0078] plan Adhesion Comparative Example 1 25gf / 42mm Example 1 30gf / 42mm Example 2 32gf / 42mm Example 3 31gf / 42mm Example 4 30gf / 42mm Example 5 32gf / 42mm
[0079] Table 1 shows that the electrode adhesion of Examples 2, 3, 4, and 5 is better than that of Comparative Example 1. This indicates that the modified SBR outer layer helps to improve the electrode adhesion.
[0080] The test results of lithium-ion batteries using comparative and example samples with different SBRs are shown in Table 2 below.
[0081] Table 2. Rate test results of lithium-ion batteries in each comparative example and embodiment.
[0082] plan 3C constant current charging ratio / % 3C discharge capacity retention rate Comparative Example 1 82.2 86.5 Example 1 86.4 88.2 Example 2 84.8 87.6 Example 3 86.3 88.4 Example 4 84.2 88.0 Example 5 87.7 88.9
[0083] Table 2 shows that Examples 2, 3, 4, and 5 exhibit better constant current charge ratios and discharge capacities under 3C rate charging and discharging conditions than Comparative Example 1. This indicates that the outer modified SBR facilitates lithium-ion transport, reduces lithium-ion transport impedance, and thus improves the battery's rate charge and discharge performance. Specifically, Example 5 demonstrates higher constant current charge ratios during 3C rate charging and higher discharge capacities during 3C rate discharging than Examples 1 and 4, suggesting that the addition of dual-modified monomers is more beneficial for improving battery rate performance.
[0084] Table 3. High and low temperature test results of lithium-ion batteries in each comparative example and embodiment.
[0085]
[0086]
[0087] Table 3 shows the high and low temperature test results of the lithium-ion batteries in the comparative examples and embodiments. As can be seen from Table 3, the discharge capacity of Examples 2, 3, 4, and 5 under low temperature conditions is superior to that of Comparative Example 1. This indicates that the modified SBR outer layer can improve lithium-ion transport kinetics under low temperature conditions, thereby enhancing the battery's low-temperature discharge capability. Furthermore, the discharge capacity of Examples 2, 3, 4, and 5 under low temperature conditions is superior to that of Comparative Example 1. This indicates that the modified SBR outer layer can improve the battery's high-temperature stability.
[0088] Table 3 shows the residual and recovery results of lithium-ion batteries in each comparative example and embodiment.
[0089] plan Residual capacity retention rate / % Recovery volume retention rate / % Comparative Example 1 93.2 94.2 Example 1 95.5 96.3 Example 2 95.0 95.8 Example 3 95.6 96.5 Example 4 94.7 95.5 Example 5 95.2 96.0
[0090] As shown in Table 3, the residual and recovered capacity retention rates of batteries in Examples 2, 3, 4, and 5 after storage are better than those of the comparative examples. This indicates that the amide and cyano groups in the modified SBR have good high-temperature stability, which helps to form a stable binder network under high temperature and high pressure conditions, thereby improving the high-temperature storage performance of the battery.
[0091] Table 4 shows the cycle test results of the lithium-ion batteries in the comparative examples and embodiments.
[0092] plan Capacity retention rate after 800 cycles at 45℃ / % Comparative Example 1 90.5 Example 1 91.6 Example 2 91.1 Example 3 91.4 Example 4 90.9 Example 5 91.2
[0093] As shown in Table 4, the capacity retention rates of Examples 2, 3, 4, and 5 after 800 cycles in the 2.5-3.65V voltage range are all better than those of the comparative examples. The introduction of polar functional groups such as carboxyl and amide groups in the modified SBR can promote the formation of intermolecular hydrogen bonds. This hydrogen bond effect can be repeatedly rebuilt and self-repaired during the expansion and contraction of the electrode, thereby ensuring that the battery has a longer cycle life.
[0094] As can be seen from the above examples and comparative examples, the addition of modified SBR, including the introduction of polar functional groups such as carboxyl groups, ester groups, and amide groups, can interact with Li + Coordination, thereby enhancing the SBR's response to Li + The modified SBR enhances the battery's transmission capacity, rate capability, and low-temperature performance. Furthermore, the amide and cyano groups within it exhibit excellent high-temperature stability, which benefits the battery's high-temperature cycling and storage performance. Additionally, the introduction of polar functional groups such as carboxyl and amide groups into the modified SBR promotes the formation of intermolecular hydrogen bonds. These hydrogen bonds can be repeatedly rebuilt and self-repaired during electrode expansion and contraction, thus ensuring a longer cycle life for the battery.
[0095] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.
[0096] Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.
[0097] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A modified styrene-butadiene rubber polymer, characterized in that, It includes a styrene-butadiene rubber polymer and active groups modified on the styrene-butadiene rubber polymer; the active groups include at least one of carboxyl, ester, cyano, or amide groups.
2. The modified styrene-butadiene rubber polymer according to claim 1, characterized in that, It has any one of the forms (I), (II), (III) or (IV). a, b, and c represent the independent degrees of polymerization of styrene, butadiene, and acrylic acid, respectively.
3. The modified styrene-butadiene rubber polymer according to claim 2, characterized in that, The particle size is 50-230nm, and the molecular weight is 30-200W; preferably, the particle size is 130-140nm, and the molecular weight is 120-180W.
4. A method for preparing the modified styrene-butadiene rubber polymer according to any one of claims 1-3, characterized in that, Includes the following steps: 1) The first polymerization reaction is carried out in the following steps: the raw materials of emulsifier, styrene, butadiene and the first initiator are mixed in an aqueous solution and then the first polymerization reaction is carried out to obtain the first reaction polymerization intermediate SBR inner layer structure; 2) The second polymerization reaction is carried out by the following steps: the first polymerization intermediate, deoxidizer, second initiator, acrylic acid and modified monomer raw materials are subjected to a second polymerization reaction to obtain the product system; 3) The product system is subjected to extraction and post-treatment to obtain modified styrene-butadiene rubber polymer.
5. The preparation method according to claim 4, characterized in that, In step 1), the molar ratio of styrene to butadiene is 2:8-7:3; preferably 5:
5. Preferably, in step 1), the temperature of the first polymerization reaction is 30–80°C, and the time of the first polymerization reaction is 1.5–4 h; the first initiator is one of benzoyl peroxide ester and diisopropyl peroxide dicarbonate; the emulsifier is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyol fatty acid esters.
6. The preparation method according to claim 4, characterized in that, Step 2) The acrylic monomer accounts for 1%-6% of the mass of the first polymerization intermediate; preferably 2%; the modified monomer accounts for 1%-6% of the mass of the first polymerization intermediate; preferably 1%. The modified monomer is one or a mixture of cysteine, 2-amino-2-cyanoacetamide, β-cyano-L-alanine, 3-aminopentanilide, and cysteine; preferably a mixture of cysteine and 2-amino-2-cyanoacetamide. The deoxidizing agent is one or two of sodium formaldehyde sulfoxylate and sodium dithionite dihydrate; the second initiator is one or more of azobisisobutyronitrile, azobisisobutyronitrile, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide.
7. The application of the modified styrene-butadiene rubber polymer according to any one of claims 1-3, characterized in that, It is used as an adhesive.
8. A negative electrode sheet, characterized in that, It includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the negative electrode binder includes the modified styrene-butadiene rubber polymer as described in any one of claims 1-3 and CMC; Preferably, the negative electrode active material is graphite; preferably, the negative electrode conductive agent is carbon black. Preferably, the dry weight ratio of the modified styrene-butadiene rubber polymer to CMC is (1-2):(1-2); more preferably, it is 1.5:1.
2.
9. A method for preparing the negative electrode sheet according to claim 8, characterized in that, Includes the following steps: (1) The negative electrode active material and the conductive agent are fed and mixed according to the set ratio. After stirring at low speed, some CMC adhesive and deionized water are added. After mixing thoroughly, the solid content is adjusted for the first time. (2) Add CMC adhesive and deionized water to the above mixed slurry again, stir thoroughly, and then perform a second solid content adjustment; (3) Add a specific amount of CMC adhesive and deionized water to the mixed slurry obtained in (2) again, mix thoroughly, and then perform a third solid content adjustment; after that, adjust the slurry viscosity to 3000cp by adjusting the amount of deionized water added. Preferably, the ratio of CMC adhesive in steps (1), (2), and (3) is 0.6:0.2:0.2; (4) Add the SBR to the obtained mixed slurry, stir at low speed, vacuum, and sieve to discharge; (5) The obtained negative electrode slurry is coated on the surface of the negative electrode current collector and then rolled into a sheet to obtain a negative electrode sheet.
10. A lithium-ion battery, characterized in that, It includes the negative electrode sheet as described in claim 8, and the positive electrode sheet; preferably, the active material of the positive electrode sheet is one of lithium iron phosphate, lithium manganese iron phosphate, and lithium cobalt oxide.