Negative electrode for soft-pack cylindrical battery and method for manufacturing the same

Abstract

The application discloses a negative electrode for soft package cylindrical batteries and a preparation method thereof. The negative electrode comprises a foam copper current collector and a negative electrode active material layer coated on the foam copper current collector. The negative electrode active material layer comprises the following components in parts by weight: 95-105 parts of graphite; 1-5 parts of conductive carbon black; 1-5 parts of a binder SBR; 0.5-2.5 parts of a dispersing agent CMC; 0.1-1 part of a wetting aid SFC; 1-5 parts of porous carbon nanomaterial; and 0.1-0.5 part of a surfactant. Compared with the prior art, the negative electrode can effectively solve the problems of poor wettability and low rate performance of the negative electrode of the soft package cylindrical battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a negative electrode for soft-pack cylindrical batteries and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. With the increasing demand for battery performance and shape diversity, soft-pack cylindrical batteries have attracted more and more attention due to their combination of cylindrical battery and soft-pack battery advantages. However, developing high-performance negative electrode materials and structures suitable for soft-pack cylindrical batteries still faces many challenges.

[0003] Traditional lithium ion battery negative electrodes usually use graphite material coated on copper foil current collectors. This structure has the following problems when applied to soft-pack cylindrical batteries: First, flat copper foil is difficult to adapt to the cylindrical shape, and is prone to wrinkles and stress concentration during winding, affecting the safety and cycle performance of the battery; second, the wettability of the traditional negative electrode is poor, making it difficult for electrolyte to quickly and uniformly penetrate into the interior of the electrode in the cylindrical shape, affecting the production efficiency and performance of the battery; third, the lithium ion diffusion path of the conventional negative electrode structure is long, limiting the rate performance and fast charging ability of the battery, which is more prominent in the cylindrical shape.

[0004] To solve these problems, researchers have tried various methods, such as using flexible current collectors, improving the binder system, etc. However, these methods often have poor adaptability, high cost, or are difficult to mass-produce when applied to soft-pack cylindrical batteries. Therefore, developing a negative electrode structure with high performance, good flexibility, and mass producibility, especially for soft-pack cylindrical batteries, remains an important challenge.

[0005] In recent years, three-dimensional porous current collectors have attracted the attention of researchers. Among them, foam metal has become a potential candidate for soft-pack cylindrical battery negative electrodes due to its high porosity, large specific surface area, good electrical conductivity, and flexibility. However, how to effectively distribute the active material uniformly in the pores of the foam metal while ensuring high capacity, good electrical conductivity, excellent wettability, and appropriate flexibility of the electrode remains a technical problem to be solved.

[0006] In addition, the traditional negative electrode preparation process is difficult to adapt to the special structure of three-dimensional porous current collectors, and it is even more difficult to meet the special requirements of soft-pack cylindrical batteries, so new preparation methods need to be developed to fully exploit their advantages. In particular, in terms of wettability, how to achieve rapid and uniform wettability of electrolyte in the cylindrical shape while ensuring high capacity of the electrode is the key to improving the production efficiency and performance of soft-pack cylindrical batteries.

[0007] Therefore, developing a high-performance negative electrode for soft-pack cylindrical batteries based on three-dimensional porous current collectors and designing a preparation process matched therewith have important theoretical significance and practical application value. SUMMARY

[0008] The main purpose of the present application is to provide a negative electrode for soft-pack cylindrical batteries, which can effectively solve the problems of poor wettability and low rate performance of the negative electrode of soft-pack cylindrical batteries.

[0009] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0010] A negative electrode for soft-pack cylindrical batteries, comprising a foam copper current collector and a negative active material layer coated on the foam copper current collector; the negative active material layer comprises the following components in parts by weight:

[0011] Graphite 95-105 parts;

[0012] Conductive carbon black 1-5 parts;

[0013] Binder SBR 1-5 parts;

[0014] Dispersant CMC 0.5-2.5 parts;

[0015] Wetting agent SFC 0.1-1 part;

[0016] Porous carbon nanomaterial 1-5 parts;

[0017] Surfactant 0.1-0.5 parts.

[0018] Among them, the foam copper current collector has a high specific surface area and a three-dimensional network structure, which not only facilitates the wettability of the electrolyte, but also can load more active materials and facilitate the uniform distribution of the active materials, can shorten the transmission path of electrons and ions, reduce the interface resistance, and improve the energy density and rate performance of the battery.

[0019] Among them, the wetting agent SFC is an anionic high molecular emulsion produced by Shanghai Daowin Industry Co., Ltd., in which the anionic macromolecules have an affinity with the electrolyte on the surface of the negative electrode sheet, which can effectively lock the electrolyte, thereby improving the liquid retention performance and wetting performance of the negative electrode.

[0020] Preferably, the density of the foam copper current collector is 0.45-0.65 g / cm³, the porosity is 85-95%, the pore size is 200-500 μm, the specific surface area is 1500-2500 cm² / g, and the thickness is 0.8-1.2 mm.

[0021] Preferably, the graphite is a mixture of artificial graphite and natural graphite, wherein the weight ratio of artificial graphite to natural graphite is (3-4):1.

[0022] Preferably, the porous carbon nanomaterial is a mixture of carbon nanotubes and graphene, wherein the weight ratio of carbon nanotubes to graphene is (1-2):1.

[0023] Preferably, the surfactant is sodium dodecyl benzene sulfonate.

[0024] Preferably, the surfactant is a mixture of ammonium perfluorooctyl sulfonate (PFSA) and C2F5CONH(CH2CH2O) 23 COC2F5, wherein the mass ratio of ammonium perfluorooctyl sulfonate (PFSA) to C2F5CONH(CH2CH2O) 23 COC2F5 is 1:(1-2).

[0025] Preferably, the surface density of the negative electrode active material layer is 20-25 mg / cm².

[0026] Preferably, the area specific capacity of the negative electrode is 6-8 mAh / cm².

[0027] In addition, the present application also provides a preparation method of the above-mentioned negative electrode for soft-pack cylindrical batteries, comprising the following steps:

[0028] (1) performing plasma treatment on the surface of the foamed copper current collector;

[0029] (2) mixing conductive carbon black, CMC and deionized water, and stirring and dispersing at a speed of 2000-3000 rpm at 20-25°C for 80-120 min;

[0030] (3) adding SBR, graphite and porous carbon nanomaterial to the mixture of step (2), and continuing to stir and mix at a speed of 2000-3000 rpm at 20-25°C for 80-120 min;

[0031] (4) adding wetting agent SFC and surfactant to the mixture of step (3), and continuing to stir and mix at a speed of 700-900 rpm at 20-25°C for 60-80 min, controlling the solid content to be 45-50%, to obtain a negative electrode slurry with a viscosity of 2000-3500 mPa·s;

[0032] (5) coating the negative electrode slurry on the surface-treated foamed copper current collector, and using vacuum impregnation method to make the negative electrode slurry fully penetrate into the pores of the foamed copper;

[0033] (6) drying at 110-130°C for 15-25 min;

[0034] (7) The negative electrode after drying is subjected to roll pressing treatment, and the roll pressing pressure is 6-10 MPa, to obtain the negative electrode.

[0035] In the preparation method of the negative electrode, the foam copper current collector is subjected to plasma treatment, so that the surface thereof is modified, the surface roughness and hydrophilicity are increased, the adhesion between the current collector and the active material is enhanced, and the structural stability of the negative electrode is improved; the preparation process of the negative electrode slurry adopts a step-by-step mixing method, the conductive carbon black is first dispersed to form a conductive network, and then the binder and the active material are added, so that a uniform and stable slurry system can be obtained; the vacuum impregnation method is used for coating, so that the negative electrode slurry can fully penetrate into the pores of the foam copper, the contact area between the active material and the current collector is increased, and the loading capacity is improved; the roll pressing can improve the density and conductivity of the negative electrode, and the preferred roll pressing pressure can take into account the density and the integrity of the conductive network.

[0036] Preferably, the vacuum impregnation process in step (5) comprises: immersing the foam copper current collector into the negative electrode slurry, vacuumizing to-0.08 MPa~ -0.1 MPa, keeping for 5-10 min, then slowly releasing the vacuum, and repeating the process for 2-3 times.

[0037] Preferably, the viscosity of the negative electrode slurry in step (4) is 2500-3000 mPa·s.

[0038] Preferably, the method further comprises, after step (7), vacuum drying treatment, the temperature of the vacuum drying is 50-70℃, and the time is 4-8 h.

[0039] Compared with the prior art, the present application has at least the following beneficial effects:

[0040] Compared with the prior art, the present application has at least the following beneficial effects:

[0041] 2) In the composition of the negative active material layer, graphite is used as the main active material, which has high specific capacity and excellent cycle stability; the addition of conductive carbon black can improve the conductivity of the negative electrode, which is beneficial to the electron transfer of the active material; the addition of porous carbon nanomaterials can build a porous conductive network on one hand, providing a high-speed transmission channel for electrons and ions, and improving the conductivity and rate performance of the negative electrode; on the other hand, the introduction of carbon nanomaterials can also inhibit the agglomeration of graphite particles, increase the specific surface area of the negative electrode, and promote the infiltration of electrolyte; SBR and CMC as the binder and dispersant respectively can enhance the adhesion between the graphite particles and the current collector, and make the graphite uniformly dispersed in the negative electrode slurry, prevent agglomeration, and improve the preparation quality of the negative electrode; the introduction of wetting agent SFC and surfactant in the negative active material layer can significantly improve the wettability of the negative electrode to the electrolyte; among them, the wetting agent SFC can reduce the surface tension of the negative electrode, increase the affinity with the electrolyte; the surfactant can greatly reduce the surface tension of the electrolyte, accelerate the penetration of the electrolyte in the negative electrode pores, thereby speeding up the infiltration speed of the negative electrode and shortening the formation time of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The structure of the negative electrode in an embodiment of the present application is shown in the figure.

[0043] In the figure: 1, foam copper current collector; 2, negative active material layer. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0045] Please refer to the accompanying Figure 1 The negative electrode for soft package cylindrical battery provided in the present application comprises a foam copper current collector 1 and a negative active material layer 2 coated on the foam copper current collector 1; the negative active material layer 2 comprises the following components in parts by weight:

[0046] Graphite 95-105 parts;

[0047] Conductive carbon black 1-5 parts;

[0048] Binder SBR 1-5 parts;

[0049] Dispersant CMC 0.5-2.5 parts;

[0050] Wetting agent SFC 0.1-1 part;

[0051] porous carbon nanomaterial 1-5 parts;

[0052] surfactant 0.1-0.5 parts.

[0053] The foam copper current collector 1 has a high specific surface area and a three-dimensional network structure, which is beneficial to the infiltration of electrolyte, can load more active materials and is beneficial to the uniform distribution of active materials, can shorten the transmission path of electrons and ions, reduce the interface resistance, and improve the energy density and rate performance of the battery.

[0054] In an embodiment according to the present application, the density of the foam copper current collector 1 is 0.45-0.65 g / cm³, the porosity is 85-95%, the pore size is 200-500 μm, the specific surface area is 1500-2500 cm² / g, and the thickness is 0.8-1.2 mm. The structural parameters of the foam copper current collector 1 are optimized, and appropriate density, porosity, pore size and specific surface area are selected, which can not only ensure the conductivity and mechanical strength of the current collector, but also provide sufficient penetration channels for the electrolyte and provide a high-load adhesion substrate for the negative active material; the preferred thickness range can make the current collector have appropriate flexibility and be easy to wind into a columnar shape.

[0055] In an embodiment according to the present application, the graphite is a mixture of artificial graphite and natural graphite, and the weight ratio of artificial graphite to natural graphite is (3-4):1. The use of a mixture of artificial graphite and natural graphite can take into account the high specific capacity of artificial graphite and the low cost advantage of natural graphite.

[0056] In an embodiment according to the present application, the porous carbon nanomaterial is a mixture of carbon nanotubes and graphene, and the weight ratio of carbon nanotubes to graphene is (1-2):1. The addition of porous carbon nanomaterial such as carbon nanotubes and graphene in the negative electrode can not only construct a porous conductive network to provide a high-speed transmission channel for electrons and ions and improve the conductivity and rate performance of the negative electrode, but also inhibit the agglomeration of graphite particles, increase the specific surface area of the negative electrode, and promote the infiltration of the electrolyte. Preferably, carbon nanotubes and graphene are used in combination, which can form a line-surface conductive network between the negative active particles, and can play the synergistic advantages of both to obtain better comprehensive effect.

[0057] In an embodiment according to the present application, the surfactant is sodium dodecyl benzene sulfonate. The surface tension of the electrolyte can be greatly reduced, the penetration of the electrolyte in the negative electrode pores can be accelerated, the infiltration speed of the negative electrode can be accelerated, and the formation time of the battery can be shortened.

[0058] In an embodiment according to the present application, the surfactant is ammonium perfluorooctyl sulfonate (PFSA) and C2F5CONH(CH2CH2O)23 A mixture of COC2F5, wherein ammonium perfluorooctane sulfonate (PFSA) and C2F5CONH(CH2CH2O) 23 The mass ratio of COC2F5 is 1: (1-2);wherein, C2F5CONH(CH2CH2O) 23 COC2F5 is 3% perhalogenated amide polyoxyethylene ester. Ammonium perfluorooctane sulfonate and C2F5CONH(CH2CH2O) 23 The combination of COC2F5 can produce a synergistic effect, further enhancing the wettability of the negative electrode. The fluorine-containing group can reduce the surface tension of the electrolyte, and the polyether chain has hydrophilicity, both of which work together to greatly improve the wettability of the electrolyte, speed up the penetration rate of the electrolyte in the negative electrode pores, especially for the hydrophobic negative electrode, the wetting effect is more significant. Therefore, the synergistic effect of the two surfactants can significantly reduce the surface tension of the electrolyte and improve the wettability of the electrolyte on the negative electrode; at the same time, the ether bond in the surfactant has a certain film-forming property, which can form a uniform and dense wetting layer on the surface of the negative electrode, repair the area with poor wettability of the negative electrode, and improve the utilization rate of the negative electrode.

[0059] In an embodiment according to the present application, the face density of the negative electrode active material layer 2 is 20-25 mg / cm². Controlling the face density of the negative electrode active material layer 2 to be 20-25 mg / cm² can ensure sufficient active material load, and at the same time, will not be too dense to hinder the wettability of the electrolyte.

[0060] In an embodiment according to the present application, the area specific capacity of the negative electrode is 6-8 mAh / cm²; high energy density can be achieved.

[0061] In addition, the present application also provides a preparation method of the above-mentioned negative electrode for soft package cylindrical battery, comprising the following steps:

[0062] (1) Plasma treatment is performed on the surface of the foamed copper current collector;

[0063] (2) The conductive carbon black, CMC and deionized water are mixed, and stirred and dispersed at a speed of 2000-3000 rpm at 20-25℃ for 80-120 min;

[0064] (3) SBR, graphite and porous carbon nanomaterials are added to the mixture of step (2), and the stirring and mixing is continued at a speed of 2000-3000 rpm at 20-25℃ for 80-120 min;

[0065] (4) adding a wetting agent SFC and a surfactant to the mixture of step (3), continuing to stir the mixture at a speed of 700-900 rpm for 60-80 min at 20-25℃, and controlling the solid content to be 45-50%, to obtain a negative electrode slurry with a viscosity of 2000-3500 mPa·s;

[0066] (5) coating the negative electrode slurry on the surface-treated foam copper current collector and fully infiltrating the negative electrode slurry into the pores of the foam copper by vacuum impregnation;

[0067] (6) drying at 110-130℃ for 15-25 min;

[0068] (7) roll-pressing the dried negative electrode at a roll-pressing pressure of 6-10 MPa to obtain a negative electrode.

[0069] In the preparation method of the negative electrode, the foam copper current collector is subjected to plasma treatment, so that the surface of the foam copper current collector is modified, the surface roughness and hydrophilicity are increased, the adhesion between the current collector and the active material is enhanced, and the structural stability of the negative electrode is improved; the preparation process of the negative electrode slurry adopts a step-by-step mixing method, the conductive carbon black is first dispersed to form a conductive network, and then the binder and the active material are added, so that a uniform and stable slurry system can be obtained; the vacuum impregnation is used for coating, so that the negative electrode slurry can be fully infiltrated into the pores of the foam copper, the contact area between the active material and the current collector is increased, and the loading capacity is improved; the roll-pressing can improve the density and conductivity of the negative electrode, and the optimal roll-pressing pressure can balance the densification and the integrity of the conductive network.

[0070] In an embodiment according to the present application, the vacuum impregnation process in step (5) comprises: immersing the foam copper current collector into the negative electrode slurry, vacuumizing to -0.08 MPa to -0.1 MPa, maintaining for 5-10 min, and then slowly releasing the vacuum, and repeating the process for 2-3 times. The optimal vacuum degree and duration can ensure the fullness of the impregnation.

[0071] In an embodiment according to the present application, the viscosity of the negative electrode slurry in step (4) is 2500-3000 mPa·s.

[0072] In an embodiment according to the present application, the process further comprises, after step (7), vacuum drying at a temperature of 50-70℃ for 4-8 h; the residual moisture can be removed, the stability of the electrode is improved, the side reactions are reduced, and the service life of the battery is prolonged.

[0073] Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. The reagents or instruments used are not marked with the manufacturer, and are all conventional products that can be obtained from the market.

[0074] Example 1

[0075] The present embodiment is a preparation method of a negative electrode for a soft-pack cylindrical battery, and the specific steps are as follows:

[0076] 1. Pretreatment of the foam copper current collector

[0077] A foam copper with a density of 0.55 g / cm³, a porosity of 90%, a pore size of 300 μm, a specific surface area of 2000 cm² / g, and a thickness of 1.0 mm was selected as the current collector. The surface of the foam copper was treated using oxygen plasma, and the treatment parameters were as follows: power 500 W, treatment time 5 minutes, oxygen flow rate 50 sccm, and pressure 10 Pa.

[0078] 2. Preparation of the negative electrode slurry

[0079] (1) 3 g of conductive carbon black, 1.5 g of CMC, and 95 g of deionized water were mixed and dispersed by stirring at a speed of 2500 rpm for 100 min at 23°C;

[0080] (2) 3 g of SBR, 100 g of graphite (75 g of artificial graphite and 25 g of natural graphite), and 3 g of porous carbon nanomaterial (2 g of carbon nanotubes and 1 g of graphene) were added to the above mixture, and the mixture was continuously stirred at a speed of 2500 rpm for 100 min at 23°C;

[0081] (3) 0.5 g of a wetting agent SFC and 0.3 g of a surfactant (sodium dodecyl benzene sulfonate) were added to the above mixture, and the mixture was continuously stirred at a speed of 800 rpm for 70 min at 23°C to control the solid content to 48%, thereby obtaining a negative electrode slurry with a viscosity of 2800 mPa·s.

[0082] 3. Preparation of the negative electrode

[0083] (1) The negative electrode slurry was coated on the surface-treated foam copper current collector, and the negative electrode slurry was fully penetrated into the pores of the foam copper by vacuum impregnation. In the vacuum impregnation process, the foam copper current collector was immersed in the negative electrode slurry, vacuum was drawn to -0.09 MPa and maintained for 8 min, and then the vacuum was slowly released. The process was repeated 3 times.

[0084] (2) Drying at 120°C for 20 min;

[0085] (3) The dried negative electrode was subjected to roll pressing at a pressure of 8 MPa;

[0086] (4) Vacuum drying at a temperature of 60°C for 6 h, thereby obtaining the negative electrode.

[0087] The negative electrode active material layer of the obtained negative electrode has a surface density of 22.5 mg / cm2, and the area specific capacity of the negative electrode is 7.2 mAh / cm2.

[0088] Example 2

[0089] The difference from Example 1 is that the surfactant is a mixture of ammonium perfluorooctylsulfonate (PFSA) and C2F5CONH(CH2CH2O) 23 COC2F5, with a mass ratio of 1:1.5, and the total amount is 0.3 g.

[0090] The rest is the same as Example 1, which will not be repeated here.

[0091] Example 3

[0092] The difference from Example 1 is that the density of the foamed copper current collector is 0.50 g / cm3, the porosity is 92%, and the pore size is 350 μm.

[0093] The rest is the same as Example 1, which will not be repeated here.

[0094] Example 4

[0095] The difference from Example 1 is that the surfactant is a mixture of ammonium perfluorooctylsulfonate (PFSA) and C2F5CONH(CH2CH2O) 23 COC2F5, with a mass ratio of 1:1.5, and the total amount is 0.3 g; the density of the foamed copper current collector is 0.50 g / cm3, the porosity is 92%, and the pore size is 350 μm.

[0096] The rest is the same as Example 1, which will not be repeated here.

[0097] Comparative Example 1

[0098] The negative electrode preparation method is the same as Example 1, except that a traditional copper foil is used instead of a foamed copper current collector.

[0099] Comparative Example 2

[0100] The negative electrode preparation method is the same as Example 1, except that no porous carbon nanomaterial and surfactant are added.

[0101] Comparative Example 3

[0102] The negative electrode preparation method is the same as Example 1, except that the vacuum impregnation method is not used to make the negative electrode slurry fully penetrate into the pores of the foamed copper.

[0103] The negative electrode and the positive electrode prepared in each of the above examples and comparative examples were matched to prepare a soft-packing cylindrical battery; wherein the positive electrode was prepared using NCM811 positive electrode active material, the separator was PE separator, the positive electrode, the separator and the negative electrode were wound into a roll core, placed in an aluminum plastic film, packaged using a heat sealing machine, injected with electrolyte (1M LiPF6 EC / DMC / EMC=1:1:1), and the soft-packing cylindrical battery was obtained.

[0104] The negative electrode and the battery prepared in each of the examples and comparative examples were subjected to the following electrochemical performance tests, and the test results are shown in Table 1.

[0105] 1. Wettability test: The prepared negative electrode was cut into a square of 5 cm x 5 cm, placed in 50 mL of electrolyte (EC:DMC:EMC=1:1:1, volume ratio), and the time required for the electrolyte to completely wet the negative electrode was recorded.

[0106] 2. Rate performance test: The charge and discharge test was carried out at 0.2C and 5C rates, and the discharge capacity at each rate was recorded.

[0107] 3. Cycle performance test: The 500-cycle charge and discharge test was carried out at 1C rate, and the capacity retention rate was recorded.

[0108] Table 1

[0109]

[0110] The test results of Table 1 are analyzed as follows:

[0111] 1. Comparative analysis of the experimental results of the examples and comparative examples

[0112] 1) Wettability: The wettability time of Examples 1-4 was significantly shorter than that of Comparative Examples 1-3. This indicates that the foam copper current collector structure, the addition of surfactant and the application of vacuum impregnation method of the present application significantly improve the wettability of the negative electrode.

[0113] 2) Rate performance: At 0.2C and 5C rates, the discharge capacity of Examples 1-4 was higher than that of Comparative Examples 1-3. In particular, at 5C high rate, the capacity retention of the examples was significantly better than that of the comparative examples, indicating that the negative electrode structure of the present application is beneficial to improve the rate performance of the battery.

[0114] 3) Cycle performance: The capacity retention rate of Examples 1-4 after 500 cycles was significantly higher than that of Comparative Examples 1-3, indicating that the negative electrode structure of the present application has better cycle stability.

[0115] In summary, by using foam copper current collector, adding porous carbon nanomaterial and surfactant, and using vacuum impregnation method, the problem of poor wettability and low rate performance of the negative electrode of the soft-packing cylindrical battery is successfully solved, and the cycle stability of the battery is improved.

[0116] 2. Comparison of experimental results between embodiments

[0117] Ammonium perfluorooctanesulfonate and C2F5CONH(CH2CH2O) 23 The COC2F5 mixture as surfactant is more effective than sodium dodecyl benzene sulfonate in embodiment 1, significantly improving the wettability and electrochemical performance.

[0118] The higher porosity and larger pore size of the foam copper current collector used in embodiment 3 also brings performance improvement compared to embodiment 1, especially in terms of rate performance.

[0119] Embodiment 4 realizes the optimization of wettability, rate performance and cycle performance by combining the optimized surfactant of embodiment 2 and the improved foam copper structure of embodiment 3, which may be due to the combined effect of the optimized surfactant and foam copper structure, fully embodying the synergistic effect between these factors.

[0120] In summary, by optimizing the foam copper current collector structure, selecting high-efficiency surfactant, adding porous carbon nanomaterials and using vacuum impregnation method, a negative electrode for soft-pack cylindrical battery with excellent wettability, high rate performance and good cycle stability is successfully developed.

[0121] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0122] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A negative electrode for a pouch cylindrical battery, characterized in that, It includes a copper foam current collector and a negative electrode active material layer coated on the copper foam current collector; the negative electrode active material layer comprises the following components in parts by weight: 95-105 parts of graphite; 1-5 parts of conductive carbon black; 1-5 parts of SBR adhesive; Dispersant CMC 0.5-2.5 parts; SFC lubricant 0.1-1 part; 1-5 parts of porous carbon nanomaterials; Surfactant 0.1-0.5 parts; The copper foam current collector has a density of 0.45-0.65 g / cm³, a porosity of 85-95%, a pore size of 200-500 μm, a specific surface area of ​​1500-2500 cm² / g, and a thickness of 0.8-1.2 mm. The surfactant is ammonium perfluorooctyl sulfonate and C2F5CONH(CH2CH2O). 23 A mixture of COC2F5, wherein ammonium perfluorooctyl sulfonate is reacted with C2F5CONH(CH2CH2O). 23 The mass ratio of COC2F5 is 1:(1~2); The method for preparing the negative electrode for the soft-pack cylindrical battery includes: coating the negative electrode slurry onto a surface-treated copper foam current collector, and using a vacuum impregnation method to allow the negative electrode slurry to fully penetrate into the pores of the copper foam; the vacuum impregnation process includes: immersing the copper foam current collector into the negative electrode slurry, drawing a vacuum to -0.08MPa to -0.1MPa, maintaining it for 5-10 minutes, and then slowly releasing the vacuum, repeating this process 2-3 times.

2. The negative electrode for a pouch-type cylindrical battery according to claim 1, characterized in that: The graphite is a mixture of artificial graphite and natural graphite, wherein the weight ratio of artificial graphite to natural graphite is (3~4):

1.

3. The negative electrode for a pouch-type cylindrical battery according to claim 1, characterized in that: The porous carbon nanomaterial is a mixture of carbon nanotubes and graphene, wherein the weight ratio of carbon nanotubes to graphene is (1~2):

1.

4. The negative electrode for a pouch-type cylindrical battery according to claim 1, characterized in that: The areal density of the negative electrode active material layer is 20-25 mg / cm².

5. The negative electrode for a pouch-type cylindrical battery according to claim 1, characterized in that: The specific capacity of the negative electrode is 6-8 mAh / cm².

6. A method for preparing a negative electrode for a pouch-pack cylindrical battery according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Plasma treatment of the surface of the foamed copper current collector; (2) Mix conductive carbon black, CMC and deionized water, and disperse them at 2000-3000 rpm at 20-25℃ for 80-120 min. (3) Add SBR, graphite and porous carbon nanomaterials to the mixture in step (2) and continue to stir and mix at 2000-3000 rpm at 20-25℃ for 80-120 min. (4) Add SFC and surfactant to the mixture in step (3), and continue to stir and mix at 700-900 rpm at 20-25℃ for 60-80 min, controlling the solid content to 45-50%, to obtain a negative electrode slurry with a viscosity of 2000-3500 mPa·s. (5) The negative electrode slurry is coated onto the surface-treated foamed copper current collector, and the negative electrode slurry is fully penetrated into the pores of the foamed copper by vacuum impregnation. (6) Dry at 110-130℃ for 15-25 min; (7) The dried negative electrode is subjected to roller pressing treatment with a roller pressing pressure of 6-10 MPa to obtain the negative electrode.

7. The method for preparing the negative electrode for a pouch-pack cylindrical battery according to claim 6, characterized in that, The vacuum impregnation process in step (5) includes: immersing the foamed copper current collector into the negative electrode slurry, evacuating to -0.08MPa~-0.1MPa, maintaining for 5-10 minutes, and then slowly releasing the vacuum. This process is repeated 2-3 times.

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