A negative electrode binder and preparation method thereof and electrode sheet

Abstract

The present invention relates to the field of electrode material technology, and in particular to a negative electrode binder and a preparation method thereof and an electrode sheet. According to the weight percentage, the effective ingredients of the negative electrode binder raw material include the following components: 1-40.0 parts of oligobutadiene; 1-50.0 parts of ethoxyethoxyethyl acrylate; 1-40.0 parts of ethylenically unsaturated carboxylic acid substances; 1-50.0 parts of unsaturated water-soluble monomers; 1-60.0 parts of unsaturated oil-soluble monomers; 0.2-20.0 parts of emulsifiers; 0.1-10.0 parts of initiators; 1-40.0 parts of pH regulators. The negative electrode binder provided by the present invention has a main component of a water-based modified acrylic polymer. When applied to a lithium battery, it can not only significantly reduce the DC resistance and AC impedance, improve the fast charging performance of the battery, but also has excellent processing performance and excellent flexibility, and can meet the needs of fast charging technology.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a negative electrode binder and a preparation method thereof and an electrode sheet. Background Art

[0002] The development of lithium battery fast charging technology is currently facing many challenges, which involve material selection, battery structure design, and manufacturing process. In the fast charging process, problems such as lithium dendrite formation, metal deposition, electrode polarization, ohmic heat, interface impedance, and side reactions are still the main bottlenecks in the development of technology. In order to achieve the goal of fast charging without sacrificing battery life, interdisciplinary cooperation and innovation are needed to overcome these difficulties. Among them, the binder in the lithium battery cell plays a pivotal role. It directly affects the DC resistance and AC impedance of the cell, and thus has an important impact on lithium dendrites, metal deposition, and thermal effects. High-impedance binders will cause the deposition rate of lithium ions on the negative electrode surface to exceed the embedding rate during high current charging, thereby triggering the growth of lithium dendrites and the deposition of metallic lithium, which will not only lead to a sharp decline in battery performance, but also bring great safety hazards.

[0003] Traditional styrene-butadiene rubber (SBR) binders have good flexibility, but their conductivity and ion affinity are relatively weak. In contrast, acrylic acid and its modified materials have shown greater application potential in the field of fast charging due to their superior conductivity and ion affinity. However, the brittle and hard characteristics of acrylic materials make their processing difficult, and the edge collapse and powder loss during the production of pole pieces increase the safety risk of batteries.

[0004] Therefore, in order to adapt to the development needs of fast charging technology, battery cell adhesives face the dual challenges of reducing impedance and improving flexibility.

[0005] In view of this, how to provide an adhesive that has both low impedance and good flexibility is a technical problem that needs to be solved urgently. Summary of the invention

[0006] In order to solve the problem that it is difficult for negative electrode binders used for fast charging in the prior art to have both low impedance and good flexibility, the present invention provides a negative electrode binder, which can not only significantly reduce DC resistance and AC impedance and improve the fast charging performance of the battery, but also has excellent flexibility, thereby solving the problem that it is difficult for negative electrode binders used for fast charging in the prior art to have both low impedance and good flexibility.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A negative electrode binder, wherein the effective ingredients of the raw materials include the following components in parts by weight:

[0009] 1-40.0 parts of oligomeric butadiene;

[0010] 1-50.0 parts of ethoxyethoxyethyl acrylate;

[0011] 1-40.0 parts of ethylenically unsaturated carboxylic acid substances;

[0012] 1-50.0 parts of unsaturated water-soluble monomer;

[0013] 1-60.0 parts of unsaturated oil-soluble monomer;

[0014] Emulsifier 0.2~20.0 parts;

[0015] Initiator 0.1~10.0 parts;

[0016] 1 to 40.0 parts of pH regulator;

[0017] The oligobutadiene is a butadiene homopolymer with a vinyl content of 18 to 70%, a molecular weight of 1400 to 8000, and a glass transition temperature of -50 to -96°C.

[0018] Optionally, the ethylenically unsaturated carboxylic acid substance is an ethylenically unsaturated carboxylic acid or an anhydride of an ethylenically unsaturated carboxylic acid.

[0019] Optionally, the ethylenically unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, b-carboxyethyl acrylate, fumaric acid, and maleic acid.

[0020] Optionally, the unsaturated water-soluble monomer is selected from at least one of acrylamide, methacrylamide, N-hydroxyethyl acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, sodium vinyl sulfonate, and sodium p-styrene sulfonate.

[0021] Optionally, the unsaturated oil-soluble monomer is selected from at least one of acrylonitrile, methacrylonitrile, styrene, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate, octyl methacrylate, isodecyl acrylate, isodecyl methacrylate, and phenyl acrylate.

[0022] Optionally, the emulsifier is selected from at least one of anionic emulsifiers and nonionic emulsifiers.

[0023] Optionally, the initiator is selected from at least one of persulfate initiators, hydroperoxide initiators, organic peroxide initiators, diacyl peroxide initiators, azo initiators, and oxidation-reduction initiators.

[0024] Optionally, the pH adjuster is an inorganic base or an organic base.

[0025] Another object of the present invention is to provide a method for preparing the negative electrode binder as described above, comprising the following steps:

[0026] S1: adding oligobutadiene, ethoxyethoxyethyl acrylate, ethylenically unsaturated carboxylic acid substances, unsaturated water-soluble monomers, unsaturated oil-soluble monomers, and emulsifiers to pure water according to the formula amount, stirring to obtain a liquid component, wherein a part of the liquid component is added to a reaction kettle, and another part of the liquid component is added to a premixing kettle;

[0027] S2: preparing an initiator solution by preparing a formulated amount of initiator;

[0028] S3: After deoxygenating the reactor, stirring, heating to 40-100° C., adding the initiator solution and the liquid components in the premixing kettle into the reactor, and heat-insulating the reactor to obtain an aqueous acrylic copolymer glue solution;

[0029] S4: adding a pH adjuster into the reaction kettle to adjust the pH to 4-9 to obtain a negative electrode binder.

[0030] Another object of the present invention is to provide an electrode sheet comprising the negative electrode binder as described above.

[0031] The beneficial effects of the present invention are:

[0032] The negative electrode binder provided by the present invention has a main component of a water-based modified acrylic polymer. When applied to a lithium battery, it can not only significantly reduce the DC resistance and AC impedance and improve the fast charging performance of the battery, but also has excellent processing performance and excellent flexibility, and can meet the needs of fast charging technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0034] Figure 1 is a photograph of the negative electrode sheet prepared in Example 1 of the present invention;

[0035] Figure 2 This is a photo of the flexibility bending test of the negative electrode sheet prepared in Example 1 of the present invention;

[0036] Figure 3 is a comparison chart of the peeling force of negative electrode sheets prepared by the binder in Example 4 of the present invention and the binder in Comparative Example 1;

[0037] Figure 4It is a comparison chart of the cycle performance of soft-pack batteries of negative electrode sheets prepared with the binder in Example 4 of the present invention and the binder in Comparative Example 1. DETAILED DESCRIPTION

[0038] The present invention is now further described in detail. The embodiments described below are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0039] In order to solve the problem that the negative electrode binder used for fast charging in the prior art is difficult to have both low impedance and good flexibility, the present invention provides a negative electrode binder. The active ingredients of the negative electrode binder raw material include the following components in parts by weight:

[0040] 1-40.0 parts of oligomeric butadiene;

[0041] 1-50.0 parts of ethoxyethoxyethyl acrylate;

[0042] 1-40.0 parts of ethylenically unsaturated carboxylic acid substances;

[0043] 1-50.0 parts of unsaturated water-soluble monomer;

[0044] 1-60.0 parts of unsaturated oil-soluble monomer;

[0045] Emulsifier 0.2~20.0 parts;

[0046] Initiator 0.1~10.0 parts;

[0047] 1 to 40.0 parts of pH regulator;

[0048] The oligobutadiene is a butadiene homopolymer having a vinyl content of 18 to 70%, a molecular weight of 1400 to 8000, and a glass transition temperature of -50 to -96°C.

[0049] The negative electrode binder provided by the present invention is a water-based functional binder; oligobutadiene is used as a polymerization monomer, and unlike randomly copolymerized styrene-butadiene rubber, the oligobutadiene is integrated into a polymer chain in an integral manner to form a block structure, thereby giving the polymer binder better strength and flexibility; on the other hand, randomly distributed ethoxyethoxyethyl acrylate and other acrylate monomers can play a role of internal plasticization, and work together with the block oligobutadiene to make the binder present excellent flexibility.

[0050] In addition, the negative electrode binder can significantly reduce the DC / AC impedance of the lithium battery. The amorphous region formed by the randomly distributed ethoxyethoxyethyl acrylate and other carboxyl-containing monomers in the binder can serve as a channel for lithium ion transmission. At the same time, the weak coordination formed between lithium ions and ether oxygen bonds can promote the jumping movement of lithium ions in the chain, thereby increasing the lithium electron transmission rate and improving ion conductivity. In addition, too short ether oxygen bonds have limited promotion of lithium ion movement, while too long ether oxygen bonds will reduce the bonding performance of the polymer binder.

[0051] The negative electrode binder provided by the present invention has a main component of a water-based modified acrylic polymer. When applied to a lithium battery, it can not only significantly reduce the DC resistance and AC impedance and improve the fast charging performance of the battery, but also has excellent processing performance and excellent flexibility, and can meet the needs of fast charging technology.

[0052] In addition, the negative electrode binder has excellent electrochemical stability and can show excellent service life when applied to electrochemical energy storage devices; at the same time, the negative electrode binder has excellent bonding force, and the excellent flexibility can make the binder and the group and the negative electrode active material better fit, and the polar functional group can form a stronger interaction force with the current collector than SBR. In addition, the negative electrode binder is a water-based product, which is green and environmentally friendly and has good economic performance.

[0053] The present invention preferably uses ethoxyethoxyethyl acrylate as a standard raw material with a purity greater than 98%.

[0054] In order to ensure the comprehensive performance of the negative electrode binder, the present invention preferably uses the ethylenically unsaturated carboxylic acid substance as ethylenically unsaturated carboxylic acid or the anhydride of ethylenically unsaturated carboxylic acid.

[0055] Specifically, the preferred ethylenically unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, b-carboxyethyl acrylate, fumaric acid, and maleic acid; correspondingly, the preferred anhydride of the ethylenically unsaturated carboxylic acid is selected from at least one of acrylic anhydride, methacrylic anhydride, itaconic acid anhydride, b-carboxyethyl acrylate anhydride, fumaric acid anhydride, and maleic anhydride.

[0056] The unsaturated water-soluble monomer of the present invention is preferably selected from at least one of acrylamide, methacrylamide, N-hydroxyethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, sodium vinyl sulfonate, and sodium p-styrene sulfonate; the unsaturated oil-soluble monomer is preferably selected from acrylonitrile, methacrylonitrile, styrene, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate, octyl methacrylate, propylene glycol ... At least one of isodecyl acrylate, isodecyl methacrylate, and phenyl acrylate; the emulsifier is preferably selected from at least one of anionic emulsifiers and nonionic emulsifiers; the initiator is preferably selected from at least one of persulfate initiators, hydroperoxide initiators, organic peroxide initiators, diacyl peroxide initiators, azo initiators, and oxidation-reduction initiators; the pH adjuster is preferably an inorganic base or an organic base; specifically, the inorganic base is preferably selected from at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia water; the organic base is preferably an alcoholamine organic base.

[0057] The negative electrode binder provided by the present invention is used for graphite and silicon-carbon negative electrode applications, and is suitable for energy storage devices such as lithium batteries and supercapacitors.

[0058] Another object of the present invention is to provide a method for preparing the negative electrode binder as described above, the preparation method comprising the following steps:

[0059] S1: according to the formula, oligobutadiene, ethoxyethoxyethyl acrylate, ethylenically unsaturated carboxylic acid substances, unsaturated water-soluble monomers, unsaturated oil-soluble monomers, and emulsifiers are added to pure water, stirred to obtain liquid components, wherein a part of the liquid components is added to a reaction kettle, and another part of the liquid components is added to a premixing kettle;

[0060] S2: preparing an initiator solution with a formulated amount of initiator, preferably preparing an initiator solution with a concentration of 0.1 to 12.0 wt.%;

[0061] S3: After deoxygenating the reactor, stirring, heating to 40-100° C., adding the initiator solution and the liquid components in the premixed kettle into the reactor, preferably slowly adding the initiator solution and the liquid components in the premixed kettle into the reactor while reacting, keeping the reaction temperature within a preset range, and after all components are added into the reactor, heat preservation treatment, preferably heat preservation treatment for 30-360 minutes, to obtain an aqueous acrylic copolymer glue solution;

[0062] In this step, a post-treatment agent may be added as needed to eliminate residual monomers; the preferred post-treatment agent of the present invention is at least one selected from ammonium persulfate-sodium metabisulfite, sodium persulfate-FF6, tert-butyl hydroperoxide-sodium bisulfite, and tert-butyl hydroperoxide-FF6.

[0063] S4: adding a pH adjuster to the reaction kettle to adjust the pH to 4-9 to obtain a negative electrode binder with a solid content of 5-40.0 wt.%.

[0064] The preparation method of the negative electrode binder provided by the present invention has a simple preparation process; the prepared negative electrode binder mainly comprises a water-based modified acrylic polymer, which, when applied to a lithium battery, can not only significantly reduce the DC resistance and AC impedance, and improve the fast charging performance of the battery, but also has excellent processing performance and excellent flexibility, and can meet the requirements of fast charging technology.

[0065] Another object of the present invention is to provide an electrode sheet, which includes the negative electrode binder as described above.

[0066] The electrode sheet provided by the present invention adopts a negative electrode binder whose main component is a water-based modified acrylic polymer. When applied to a lithium battery, it can not only significantly reduce the DC resistance and AC impedance and improve the fast charging performance of the battery, but also has excellent processing performance and excellent flexibility, and can meet the needs of fast charging technology.

[0067] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0068] Example 1

[0069] According to the weight percentage, 20.0 parts of oligobutadiene (Crayville Ricon 130, vinyl content 20%, molecular weight 2500, glass transition temperature -86 ° C), 30.0 parts of ethoxyethoxyethyl acrylate, 10.0 parts of acrylic acid, 25.0 parts of hydroxyethyl acrylate, 15.0 parts of acrylonitrile, plus 2.0 parts of sodium lauryl sulfate, 0.8 parts of S-40, all mixed with 300 parts of pure water, and the raw materials and water were dispersed in a mixer to mix into a uniform liquid component, 20% of which was added to the reactor, and 80% was added to the premixing kettle. 1.0 part of the initiator ammonium persulfate was dissolved in pure water to prepare a 2.0 wt.% initiator solution. After nitrogen was introduced to remove oxygen from the reactor, stirring was started, and the liquid components in the reactor were slowly heated to 70°C. Then, the initiator solution and the liquid components in the premixed kettle were slowly added to the reactor while reacting, and the reaction temperature was kept at 70°C. After all components were added to the reactor, 0.4 parts of post-treatment auxiliary agent ammonium persulfate-sodium pyrosulfite were added, and the temperature was kept for 180 minutes to obtain an aqueous acrylic copolymer glue. 5.0 parts of sodium hydroxide were added, and the pH was adjusted to 6.3 to obtain a negative electrode binder with a solid content of 20.0 wt.%.

[0070] According to the weight percentage, the above 10.0 parts of negative electrode binder (2.0 parts by dry weight) are fully stirred and dispersed with 1.5 parts of CMC, 80.0 parts of water and 96.5 parts of fast-charge negative electrode graphite. After adjusting the solid content, the finished negative electrode slurry is obtained, which is coated on a smooth battery-grade copper foil and dried at 75°C to obtain a fast-charge negative electrode sheet with a dense appearance and good consistency. Figure 1 As shown in the figure, the bonding strength between the negative electrode layer and the copper foil is excellent and the flexibility is good. The bending test is as follows Figure 2 As shown. Surface density 160g / m 2 , compacted density 1.6g / cm 3 When the peel strength is tested at 180°, it is 23N / m. The 3.0Ah soft-pack battery prepared with this binder has a DC resistance DCR of 16.6mΩ, a 1C discharge capacity retention rate of 68.3% at -10℃, and a 3C rate discharge capacity of 93.3% at room temperature.

[0071] Example 2

[0072] According to the weight percentage, 10.0 parts of oligobutadiene (Crayville Ricon 142, vinyl content 55%, molecular weight 4100, glass transition temperature -74 ° C), 50.0 parts of ethoxyethoxyethyl acrylate, 8.0 parts of itaconic acid, 15.0 parts of hydroxypropyl acrylate, 5.0 parts of acrylamide, 12.0 parts of styrene, plus 1.5 parts of sodium dodecylbenzene sulfonate, 0.5 parts of T-40, all mixed with 400 parts of pure water, and the raw materials and water were dispersed in a mixer to mix into a uniform liquid component, 10% of which was added to the reactor, and 90% was added to the premixing kettle. 0.8 parts of initiator sodium persulfate was dissolved in pure water to prepare a 1.0 wt.% initiator solution. After nitrogen was introduced to remove oxygen from the reactor, stirring was started, and the liquid components in the reactor were slowly heated to 80°C. Then, the initiator solution and the liquid components in the premixed kettle were slowly added to the reactor while reacting, and the reaction temperature was kept at 80°C. After all components were added to the reactor, 0.2 parts of post-treatment auxiliary agent sodium persulfate-FF6 was added, and the temperature was kept for 90 minutes to obtain an aqueous acrylic copolymer glue. 5.2 parts of lithium hydroxide were added, and the pH was adjusted to 7.1 to obtain a negative electrode binder with a solid content of 15.0 wt.%.

[0073] According to the weight percentage, the above 13.3 parts of binder (2.0 parts by dry weight) were fully stirred and dispersed with 1.5 parts of CMC, 75.0 parts of water and 96.5 parts of silicon-carbon negative electrode material. After adjusting the solid content, the finished negative electrode slurry was obtained, which was coated on a smooth battery-grade copper foil. After drying at 90°C, a silicon-carbon negative electrode sheet with a dense appearance and good consistency was obtained. The bonding strength between the negative electrode layer and the copper foil was excellent, the flexibility was good, and the surface density was 160g / m 2 , compacted density 1.65g / cm 3 When the peel strength is tested at 180°, it is 20N / m. The 3.0Ah soft-pack battery prepared with this binder has a DC resistance DCR of 17.2mΩ, a 1C discharge capacity retention rate of 67.9% at -10℃, and a 3C rate discharge capacity of 92.8% at room temperature.

[0074] Example 3

[0075] According to the weight percentage, 40.0 parts of oligobutadiene (Crayville Ricon 156, vinyl content 70%, molecular weight 1400, glass transition temperature -55 ° C), 5.0 parts of ethoxyethoxyethyl acrylate, 5.0 parts of methacrylic acid, 5 parts of fumaric acid, 15.0 parts of hydroxypropyl methacrylate, 5.0 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5.0 parts of acrylamide, 20.0 parts of butyl acrylate, plus 1.2 parts of sodium oleate, 0.3 parts of S-20, all mixed with 500 parts of pure water, and the raw materials and water were dispersed in a mixer to mix into a uniform liquid component, 30% of which was added to the reactor, and 70% was added to the premixing kettle. 0.5 parts of the initiator potassium persulfate-sodium pyrosulfite was dissolved in pure water to prepare a 1.0 wt.% initiator solution. After nitrogen was introduced to remove oxygen from the reactor, stirring was started, and the liquid components in the reactor were slowly heated to 85°C. Then, the initiator solution and the liquid components in the premixed kettle were slowly added to the reactor while reacting, and the reaction temperature was kept at 85°C. After all components were added to the reactor, 0.4 parts of post-treatment auxiliary agent tert-butyl hydroperoxide-sodium bisulfite was added, and the temperature was kept for 120 minutes to obtain an aqueous acrylic copolymer glue. 4.2 parts of sodium hydroxide were added, and the pH was adjusted to 6.2 to obtain a negative electrode binder with a solid content of 12.0 wt.%.

[0076] According to the weight percentage, the above 16.7 parts of binder (2.0 parts by dry weight) were fully stirred and dispersed with 1.5 parts of CMC, 70.0 parts of water and 96.5 parts of silicon-carbon negative electrode material. After adjusting the solid content, the finished negative electrode slurry was obtained, which was coated on a smooth battery-grade copper foil. After drying at 85°C, a silicon-carbon negative electrode sheet with a dense appearance and good consistency was obtained. The bonding strength between the negative electrode layer and the copper foil was excellent, the flexibility was good, and the surface density was 155g / m 2 , compacted density 1.6g / cm 3 When tested at 180°, the peel strength is 16N / m. The 3.0Ah soft-pack battery prepared with this binder has a DC resistance DCR of 17.8mΩ, an initial efficiency of 85.9%, a 1C discharge capacity retention rate of 66.8% at -10℃, and a 3C rate discharge capacity of 91.9% at room temperature.

[0077] Example 4

[0078] According to weight percentage, 30.0 parts of oligobutadiene (Crayville Ricon 156), 35.0 parts of ethoxyethoxyethyl acrylate, 12.0 parts of acrylic acid, 8.0 parts of hydroxyethyl methacrylate, 5.0 parts of acrylamide, 10.0 parts of isodecyl acrylate, plus 1.8 parts of sodium lauryl sulfate and 0.5 parts of OP-10, are all mixed with 350 parts of pure water, and the raw materials and water are dispersed in a mixer to mix into a uniform liquid component, 25% of which is added to the reactor and 75% is added to the premixing kettle. 0.8 parts of initiator ammonium persulfate are dissolved in pure water to prepare a 1.0 wt.% initiator solution. After nitrogen was introduced to remove oxygen from the reactor, stirring was started, and the liquid components in the reactor were slowly heated to 75°C. Then, the initiator solution and the liquid components in the premixed kettle were slowly added to the reactor while reacting, and the reaction temperature was kept at 75°C. After all components were added to the reactor, 0.3 parts of post-treatment auxiliary agent tert-butyl hydroperoxide-FF6 was added, and the temperature was kept for 150 minutes to obtain an aqueous acrylic copolymer glue. 6.1 parts of sodium hydroxide were added, and the pH was adjusted to 6.7 to obtain a negative electrode binder with a solid content of 20.0 wt.%.

[0079] According to the weight percentage, the above 10.0 parts of binder (2.0 parts by dry weight) were fully stirred and dispersed with 1.5 parts of CMC, 70.0 parts of water and 96.5 parts of silicon-carbon negative electrode material. After adjusting the solid content, the finished negative electrode slurry was obtained, which was coated on a smooth battery-grade copper foil. After drying at 85°C, a silicon-carbon negative electrode sheet with a dense appearance and good consistency was obtained. The bonding strength between the negative electrode layer and the copper foil was excellent, the flexibility was good, and the surface density was 160g / m 2 , compacted density 1.6g / cm 3 When the peel strength is tested at 180°, it is 22N / m. Figure 3 As shown. The 3.0Ah soft pack battery was prepared with this binder, the DC resistance DCR was 16.2mΩ, the -10℃ low temperature 1C discharge capacity retention rate was 67.5%, and the room temperature 3C rate discharge capacity was 92.7%. The soft pack battery 1C room temperature 600 cycles maintained more than 92%, as shown Figure 4 shown.

[0080] Comparative Example 1

[0081] This comparative example uses a conventional binder (Zeon BM-451B, SBR type) with mature market experience for evaluation. The silicon-carbon negative electrode plate can be prepared using the same process as Example 4, but its 180° peel strength is only 12 N / m, which is significantly inferior to the 22 N / m of Example 4 of the present invention, proving that the negative electrode binder provided by the present invention has achieved an improvement of more than 80% in peel strength compared with conventional binders. The 1C room temperature cycle performance of the soft-pack battery prepared with this conventional binder is also significantly inferior to the 92% retention rate of 600 cycles of Example 4 of the present invention, proving that the negative electrode binder provided by the present invention has achieved an improvement of more than 40% in cycle performance. The DC resistance DCR is 22.0mΩ, the -10℃ low temperature 1C discharge capacity retention rate is 63.2%, and the room temperature 3C rate discharge capacity is 88.8%, which is significantly inferior to Example 4.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 2 is that oligobutadiene and ethoxyethoxyethyl acrylate are not added, and the rest are all the same. The obtained binder can be used to prepare a fast-charge negative electrode plate according to the same process, but its peel strength is only 10 N / m, which is much lower than 20 N / m in Example 2; the brittleness of the plate is obvious, and a large number of brittle cracks occur when bending. A 3.0Ah soft-pack battery was prepared using this binder, with a DC resistance DCR of 22.6mΩ, a low-temperature 1C discharge capacity retention rate of 61.2% at -10℃, and a room temperature 3C rate discharge capacity of 88.4%, which is significantly inferior to Example 2.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that oligobutadiene is not added, and the rest is the same. The obtained binder is prepared by the same process to obtain a fast-charge negative electrode plate, but the bonding force between the negative electrode layer and the copper foil is weak, the peel strength is only 7N / m, the flexibility is poor, and the active material on the plate falls off. A 3.0Ah soft-pack battery was prepared using this binder, with a DC resistance DCR of 21.1mΩ, a 1C discharge capacity retention rate of 42.3% at -10℃, and a 3C rate discharge capacity of 69.6% at room temperature, which is significantly inferior to Example 1.

[0086] Comparative Example 4

[0087] The difference between this comparative example and Example 1 is that ethoxyethoxyethyl acrylate is not added, and the rest are all the same. The obtained binder is prepared into a fast-charging negative electrode plate according to the same process, but the bonding force between the negative electrode layer and the copper foil is weak, the peel strength is 13N / m, and the flexibility is poor. A 3.0Ah soft-pack battery is prepared with this binder, and the DC resistance DCR is 23.1mΩ, the 1C discharge capacity retention rate at -10℃ low temperature is 60.3%, and the 3C rate discharge capacity at room temperature is 87.7%, which is significantly inferior to Example 1.

[0088] Comparative Example 5

[0089] The difference between this comparative example and Example 1 is that the oligobutadiene is Crayville Ricon 154, which is a butadiene homopolymer with a vinyl content of 90%, a molecular weight of 5200, and a glass transition temperature of -14°C. The rest are all the same. The obtained binder is prepared by the same process to obtain a fast-charging negative electrode plate, but the bonding force between the negative electrode layer and the copper foil is weak, the peel strength is only 11N / m, and the flexibility is poor. A 3.0Ah soft-pack battery is prepared with this binder, with a DC resistance DCR of 22.2mΩ, a 1C discharge capacity retention rate of 62.4% at -10°C, and a 3C rate discharge capacity of 88.9% at room temperature, which are significantly inferior to those in Example 1.

[0090] Comparative Example 6

[0091] The difference between this comparative example and Example 1 is that the random copolymerized butadiene rubber Zeon BM-451B is used to replace oligobutadiene, and the rest are all the same. The obtained binder is prepared into a fast-charging negative electrode plate according to the same process, but the bonding force between the negative electrode layer and the copper foil is weak, the peel strength is only 9N / m, and the flexibility is poor. A 3.0Ah soft-pack battery is prepared with this binder, and the DC resistance DCR is 23.7mΩ, the 1C discharge capacity retention rate at -10℃ is 60.1%, and the 3C rate discharge capacity at room temperature is 85.8%, which is significantly inferior to Example 1.

[0092] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A negative electrode binder, characterized in that: The active ingredients of the raw materials include the following components in parts by weight: 1-40.0 parts of oligomeric butadiene; 1-50.0 parts of ethoxyethoxyethyl acrylate; 1-40.0 parts of ethylenically unsaturated carboxylic acid substances; 1-50.0 parts of unsaturated water-soluble monomer; 1-60.0 parts of unsaturated oil-soluble monomer; Emulsifier 0.2~20.0 parts; Initiator 0.1~10.0 parts; 1 to 40.0 parts of pH regulator; Wherein, the oligomeric butadiene is a butadiene homopolymer having a vinyl content of 18 to 70%, a molecular weight of 1400 to 8000, and a glass transition temperature of -50 to -96°C; The negative electrode binder is prepared according to the following method: S1: adding oligobutadiene, ethoxyethoxyethyl acrylate, ethylenically unsaturated carboxylic acid substances, unsaturated water-soluble monomers, unsaturated oil-soluble monomers, and emulsifiers to pure water according to the formula amount, stirring to obtain a liquid component, wherein a part of the liquid component is added to a reaction kettle, and another part of the liquid component is added to a premixing kettle; S2: preparing an initiator solution by preparing a formulated amount of initiator; S3: After deoxygenating the reactor, stirring, heating to 40-100° C., adding the initiator solution and the liquid components in the premixing kettle into the reactor, and heat-insulating the reactor to obtain an aqueous acrylic copolymer glue solution; S4: adding a pH adjuster into the reaction kettle to adjust the pH to 4-9 to obtain a negative electrode binder.

2. The negative electrode binder according to claim 1, characterized in that The ethylenically unsaturated carboxylic acid substance is an ethylenically unsaturated carboxylic acid or an anhydride of an ethylenically unsaturated carboxylic acid.

3. The negative electrode binder according to claim 2, characterized in that The ethylenically unsaturated carboxylic acid is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, b-carboxyethyl acrylate, fumaric acid, and maleic acid.

4. The negative electrode binder according to claim 1, characterized in that The unsaturated water-soluble monomer is selected from at least one of acrylamide, methacrylamide, N-hydroxyethyl acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, sodium vinyl sulfonate, and sodium p-styrene sulfonate.

5. The negative electrode binder according to claim 1, characterized in that The unsaturated oil-soluble monomer is selected from at least one of acrylonitrile, methacrylonitrile, styrene, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isooctyl acrylate, octyl methacrylate, isodecyl acrylate, isodecyl methacrylate, and phenyl acrylate.

6. The negative electrode binder according to claim 1, characterized in that The emulsifier is selected from at least one of anionic emulsifiers and nonionic emulsifiers.

7. The negative electrode binder according to claim 1, characterized in that The initiator is selected from at least one of persulfate initiators, hydroperoxide initiators, organic peroxide initiators, diacyl peroxide initiators, azo initiators, and oxidation-reduction initiators.

8. The negative electrode binder according to claim 1, characterized in that The pH adjuster is an inorganic base or an organic base.

9. An electrode sheet, characterized in that: The invention comprises the negative electrode binder as claimed in any one of claims 1 to 8.

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