A compound electrode and a preparation method and application thereof

Abstract

The application discloses a compound electrode and a preparation method and application thereof, and belongs to the technical field of secondary batteries, and solves the problems of complex electrode preparation process and poor electrode performance in the prior art. The compound electrode is composed of a coating and a current collector, wherein the effective component of the coating comprises a compound active substance; and the coating has a vertical arrangement of a micropore network structure; wherein the compound active substance is a combination of at least two kinds of active materials, and the active material is a positive electrode active material or a negative electrode active material. The compound electrode provided by the application is suitable for non-water-sensitive positive and negative electrode materials of lithium / sodium ion batteries, has good widening property, and is beneficial to promoting the development and utilization of super-high specific energy secondary batteries.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and more specifically to a composite electrode, its preparation method, and its application. Background Technology

[0002] The ever-increasing range demands of electric vehicles place increasingly higher requirements on battery performance. A single cathode material is insufficient to meet the stringent requirements of electric vehicles in terms of specific energy, safety, lifespan, and cost. Currently, increasing electrode thickness can increase battery capacity while maintaining the same battery volume, contributing to the development of more compact and efficient battery systems. However, increased electrode thickness can lead to reduced utilization of active materials, further increasing overpotential. Simultaneously, the random and dense packing of electrode materials results in a tortuous porous structure within the electrode, severely hindering electrolyte permeation and increasing ion migration distance, making ion migration a bottleneck in charge transport dynamics in thick electrodes.

[0003] In existing technologies, low-torsion electrodes have been fabricated through electric / magnetic / temperature field induction and template methods, but their complex processes are not conducive to large-scale applications. Furthermore, the introduction of ion-conducting agents into the secondary battery array electrodes still needs to be considered, and the lack of electron distribution between adjacent arrays in secondary batteries leads to poor electrochemical performance of the electrodes. Summary of the Invention

[0004] This invention provides a composite electrode, its preparation method, and its application, to solve the problems of complex electrode preparation processes and poor electrode performance in existing secondary batteries.

[0005] In a first aspect, the present invention provides a composite electrode composed of a coating and a current collector, wherein the effective components of the coating include a composite active substance; and it has a vertically arranged microporous network structure; wherein the composite active substance is a combination of at least two active materials, and the active material is a positive electrode active material or a negative electrode active material.

[0006] As one possible implementation, the positive electrode active material includes nickel-rich layered oxides, lithium-rich layered oxides, high-pressure spinel oxides, and high-pressure polyanionic compounds; the negative electrode active material includes graphite, soft carbon, graphitized carbon, silicon suboxide, silicon carbide, tin, antimony, and phosphorus.

[0007] As one possible implementation, the coating comprises, by weight, the following components: 40-90 parts of the compounded active substance, 3-20 parts of the biphasic conductive agent, 5-20 parts of the solvent, and 0-20 parts of the binder.

[0008] As one possible implementation, the particle size of the compound active material is 10 nm to 50 μm; the compound active material is composed of different active materials through particle gradation, wherein the mass ratio between any two active materials is 0.1 to 10:1 and the particle size ratio is 0.01 to 100:1; and / or, the biphase conductive agent is a conjugated polymer material generated by cyclization reaction of linear polymer materials.

[0009] As one possible implementation, the linear polymer material is one or a combination of several of polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, polyester, and polyvinyl alcohol; and / or, the solvent is one or a combination of several of methylpyrrolidone, N,N-dimethyldiamide, ethyl acetate, sulfolane, dimethyl sulfoxide, acetic acid, deionized water, and acetonitrile; and / or, the binder is one or a combination of several of polyvinylidene fluoride, polyethylene oxide, styrene-butadiene rubber, polytetrafluoroethylene, polyacrylic acid, sodium carboxymethyl cellulose, carboxymethyl cellulose, xanthan gum, sodium alginate, guar gum, and chitosan; and / or, the current collector is one of aluminum foil, copper foil, stainless steel, nickel foil, and carbon foil.

[0010] As one possible implementation method, the cyclization reaction is carried out under the following conditions: temperature 150–300°C, time 5–30 min.

[0011] In a second aspect, the present invention provides a method for preparing a composite electrode, comprising the following steps: mixing the raw material components in proportion to obtain a coating material according to any possible implementation of the first aspect of the formulation of the composite electrode; applying the coating material to the surface of a current collector and drying it to obtain an electrode master sheet; and subjecting the electrode master sheet to high-energy laser treatment to obtain the composite electrode.

[0012] As one possible implementation, the high-energy laser processing is femtosecond laser etching, with the following processing conditions: wavelength of 200–1100 nm, linewidth of 10–50 μm, and power of 500–2000 W.

[0013] Thirdly, the present invention provides an application of the composite electrode described in any possible implementation of the first aspect or the composite electrode prepared by the preparation method described in any possible implementation of the second aspect in a secondary battery.

[0014] Fourthly, the present invention provides a secondary battery in which, when the active material is a positive electrode active material, the composite electrode prepared by the preparation method described in any possible implementation of the first aspect or the preparation method described in any possible implementation of the second aspect serves as its positive electrode; and / or, when the active material is a negative electrode active material, the composite electrode prepared by the preparation method described in any possible implementation of the first aspect or the preparation method described in any possible implementation of the second aspect serves as its negative electrode.

[0015] The composite electrode provided by this invention, by combining electrode materials with different properties, can integrate the advantages of its components, balance and optimize the overall performance of the battery, alleviate volume expansion and structural stress during charging and discharging, thereby improving the battery's energy density, cycle stability, and lifespan. Its composite active materials, through particle gradation, regulate the electrode's electronic conductivity, porosity, and packing density, optimizing the electrode's structure and performance to achieve high energy density, high power density, long cycle life, and high safety. Furthermore, the composite electrode provided by this invention has a vertically aligned microporous network structure in its microstructure, enabling ultrafast ion and electron permeation while maintaining good interfacial contact and a stable electrode structure. Through a hierarchical interactive structural design, it achieves a composite electrode with high load capacity, low tortuosity, and mechanical stability.

[0016] The method for preparing the composite electrode provided by this invention is simple and suitable for industrial production. By laser processing, vertical channels are formed in the electrode, which enhances the mass transfer capacity of the electrode and reduces electronic and ionic resistance, thereby improving the rate performance and discharge areal capacity of the battery, especially under high rate charge and discharge conditions.

[0017] The composite electrode provided by this invention is applicable to non-water-sensitive positive and negative electrode materials for lithium / sodium-ion batteries, and has good scalability, which is conducive to promoting the development and utilization of ultra-high energy density secondary batteries. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The images shown are SEM images of electrodes A and B provided in an embodiment of the present invention, wherein the left image is electrode A and the right image is electrode B.

[0020] Figure 2 The charge and discharge curve of the button cell A provided in an embodiment of the present invention is shown.

[0021] Figure 3 The charge-discharge curve of the button cell B provided in this embodiment of the invention.

[0022] Figure 4 The charge and discharge curve of the button cell C provided in the embodiment of the present invention.

[0023] Figure 5 The charge-discharge curve of the coin cell D provided in the embodiment of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To address the problems of complex electrode fabrication processes and poor electrode performance in existing secondary batteries, this invention provides a fabrication experiment of a composite electrode and performs SEM analysis. The results show that the composite electrode provided by this invention has a vertically arranged microporous network structure, enabling ultrafast ion and electron permeation while maintaining good interfacial contact and a stable electrode structure. Through a hierarchical interactive structure design, the electrode achieves composite thick load, low tortuosity, and mechanical stability.

[0026] Furthermore, this embodiment of the invention provides an experiment on a temperature field-induced directional electrode structure. It can be seen that the process of temperature field-induced electrode preparation involves many steps, which significantly increases the preparation cost and is complex. This invention provides a preparation method that is simple in process and suitable for industrial production.

[0027] Furthermore, this invention provides a performance test of a composite electrode applied in a battery. It shows that it is suitable for non-water-sensitive positive and negative electrode materials in lithium / sodium-ion batteries, exhibiting good scalability and facilitating the development and utilization of ultra-high energy density rechargeable batteries. Moreover, the composite electrode provided by this invention, by combining electrode materials with different properties, can integrate the advantages of its components, balance and optimize the overall performance of the battery, alleviate volume expansion and structural stress during charging and discharging, thereby improving the battery's energy density, cycle stability, and lifespan. The composite active materials, through particle gradation, regulate the electrode's electronic conductivity, porosity, and packing density, optimizing the electrode's structure and performance to achieve high energy density, high power density, long cycle life, and high safety.

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0029] Example 1

[0030] This embodiment provides an experimental method for preparing a composite electrode.

[0031] Electrode coating A is prepared by uniformly mixing positive electrode composite active material, linear polymeric polyacrylonitrile (molecular weight 60,000), solvent N-methylpyrrolidone, and binder polyvinylidene fluoride in a homogenizer at a mass ratio of 80:10:20:10. The positive electrode composite active material is formed by mixing lithium-rich manganese-based oxide (particle size 100-200 nm) and spinel-like phase material in a ball mill at a mass ratio of 1:1 and a particle size ratio of 1:10. Electrode coating A is coated onto current collector aluminum foil with a coating thickness of 1 mm. After standing at room temperature for 5 min, it is transferred to a drying device and treated at 100 °C for 8 h. Then, it is heated to 240 °C for high-temperature cyclization treatment for 30 min. Finally, it is transferred to a femtosecond laser etching device and treated under conditions of wavelength 1030 nm, linewidth 20 μm, and power 1000 W to obtain composite electrode A.

[0032] The positive electrode composite active material was replaced with the same mass of lithium-rich manganese-based oxide, and other conditions were the same as those for the preparation of composite electrode A, to obtain composite electrode A1.

[0033] By replacing the positive electrode composite active material with the same mass of spinel-like phase material, and keeping other conditions the same as for the preparation of composite electrode A, composite electrode A2 was obtained.

[0034] Example 2

[0035] This embodiment provides an experimental method for preparing a composite electrode.

[0036] The wavelength of the transferred material to the femtosecond laser etching equipment was changed to 248nm, and other conditions were the same as those for the preparation of composite electrode A, to obtain composite electrode B.

[0037] Example 3

[0038] This embodiment provides an experimental method for preparing a composite electrode.

[0039] A negative electrode composite active material, linear polymeric polyacrylonitrile (molecular weight 60,000), solvent water, and binder polyacrylic acid were mixed uniformly in a homogenizer at a mass ratio of 80:10:20:10 to obtain electrode coating C. The negative electrode composite active material was formed in a ball mill by mixing nano-silicon (particle size 100-200 nm) and hard carbon material at a mass ratio of 1:3 and a particle size ratio of 1:20. Electrode coating C was coated onto current collector aluminum foil with a coating thickness of 1 mm. After standing at room temperature for 5 min, it was transferred to a drying device and treated at 120 °C for 5 h. Then, it was heated to 200 °C for high-temperature cyclization treatment for 10 min. Finally, it was transferred to a femtosecond laser etching device and treated under conditions of wavelength 1030 nm, linewidth 20 μm, and power 1000 W to obtain composite electrode C.

[0040] The negative electrode composite active material was replaced with the same mass of nano-silicon, and other conditions were the same as those for the preparation of composite electrode C, to obtain composite electrode C1.

[0041] The negative electrode composite active material was replaced with the same mass of hard carbon material, and other conditions were the same as those for the preparation of composite electrode C, to obtain composite electrode C2.

[0042] Example 4

[0043] This embodiment provides an experimental method for preparing a composite electrode.

[0044] The nano-silicon component in the negative electrode composite active material was replaced with SiO material (particle size 3μm), and other conditions were the same as those for the preparation of electrode coating C, to obtain electrode coating D; electrode coating D was coated on current collector aluminum foil with a coating thickness of 500μm, and other conditions were the same as those for the preparation of composite electrode C, to obtain composite electrode D.

[0045] Example 5

[0046] This embodiment provides an experiment for the preparation of an electrode.

[0047] The electrode coating C prepared in Example 3 was coated onto the current collector aluminum foil with a coating thickness of 30 μm. After standing at room temperature for 2 min, it was transferred to a directional freezing device and treated at a cooling rate of 0.5 °C / min for 30 min. Then, it was treated with ultraviolet light at -25 °C for 30 min (UV wavelength 365 nm, intensity 400 mW·cm). -2 The mixture was transferred to a freeze-drying device and treated at 10 Pa pressure for 15 h to obtain the composite electrode E.

[0048] Example 6

[0049] This embodiment provides an experiment for testing the electrochemical performance of a positive electrode.

[0050] A coin cell was assembled using the positive electrode under test as the positive electrode, a lithium metal sheet as the negative electrode, Cegrad 2500 as the separator, and a universal high-voltage positive electrode electrolyte for lithium ions as the electrolyte.

[0051] In this embodiment, the composite electrodes A, A1, A2, and B prepared in Examples 1 and 2 were used as positive electrodes to be tested. Batteries A, A1, A2, and B were assembled and subjected to charge-discharge cycles at a current density of 100 mA / g within a voltage range of 2.0–4.8 V, yielding the following results: Figure 2 The charge / discharge curves and cycle data of batteries A, A1, A2 and B are shown in Table 1.

[0052] Table 1 Electrochemical performance test results

[0053]

[0054] Table 1 shows that battery A has a first-cycle charging capacity of 354.3 mAh / g and a first-cycle discharging capacity of 343.6 mAh / g; button cell B has a first-cycle charging capacity of 321.1 mAh / g and a first-cycle discharging capacity of 311.8 mAh / g; button cell A1 has a first-cycle charging capacity of 410.0 mAh / g and a first-cycle discharging capacity of 405.9 mAh / g; and button cell A2 has a first-cycle charging capacity of 306.4 mAh / g and a first-cycle discharging capacity of 260.5 mAh / g. It can be seen that the capacity performance of composite electrode A and composite electrode B in the secondary battery falls between that of A1 and A2. Combined with... Figure 1 and Figure 2 The comparison shows that the microstructure of electrodes A and B changes, mainly due to the change in wavelength during laser processing affecting the pore width formed by laser etching. This allows for the control of pores in the longitudinal microstructure, thus influencing electrode performance. Meanwhile, according to the cycle retention data in Table 1, the cycle retention of the composite electrodes A and B are 95% and 93% (100 cycles), respectively, effectively improving the cycle life of the electrodes under high capacity conditions.

[0055] Example 7

[0056] This embodiment provides an experiment for testing the electrochemical performance of a negative electrode.

[0057] A coin cell was assembled using the negative electrode under test as the negative electrode, a lithium metal sheet as the counter electrode, Cegrad 2500 as the separator, and a universal lithium-ion negative electrode electrolyte as the electrolyte.

[0058] In this embodiment, the composite electrodes C, C1, C2, and D prepared in Examples 3-4 were used as negative electrodes to be tested. A coin cell C, C1, C2, and D were assembled, and charge-discharge cycles were performed at a current density of 100 mA / g within a voltage range of 0.01–1.5V to obtain the following results: Figure 4 The charge / discharge curves of coin cells C, C1, C2, and D are shown in Table 1.

[0059] Depend on Figure 4 As shown in Table 1, the first-cycle charging capacity of coin cell C is 1633.0 mAh / g, and the first-cycle discharging capacity is 1868.0 mAh / g; the first-cycle charging capacity of coin cell D is 494.0 mAh / g, and the first-cycle discharging capacity is 513.1 mAh / g. The first-cycle charging capacity of coin cell C1 is 3200.0 mAh / g, and the first-cycle discharging capacity is 3584.7 mAh / g; the first-cycle charging capacity of coin cell C2 is 346.0 mAh / g, and the first-cycle discharging capacity is 368 mAh / g. It can be seen that the capacity of electrode C is also between that of C1 and C2. Further cycle testing shows that the capacity retention rate of the composite electrode is significantly improved at high capacities. Meanwhile, compared to battery E, although the temperature field can also induce directional porous structures, the solvent crystallization process is greatly affected by other factors and is difficult to control precisely, resulting in its performance and capacity retention being far inferior to battery C.

[0060] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0061] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A composite electrode, characterized in that, It has a vertically arranged microporous network structure and is composed of a coating and a current collector, wherein the coating comprises, by weight, the following components: The mixture contains 40-90 parts of active substance, 3-20 parts of biphasic conductive agent, 5-20 parts of solvent and 0-20 parts of binder; The compound active material is a combination of at least two active materials, wherein the active material is a positive electrode active material or a negative electrode active material; the different active materials are arranged by particle size distribution to form the compound active material, wherein the mass ratio between any two active materials is 0.1 to 10:1 and the particle size ratio is 0.01 to 100:1; the particle size of the compound active material is 10 nm to 50 μm; The biphase conductive agent is a conjugated polymer material produced by cyclization reaction of linear polymer materials.

2. The composite electrode according to claim 1, characterized in that, The positive electrode active material includes nickel-rich layered oxide, lithium-rich layered oxide, high-pressure spinel oxide, and high-pressure polyanionic compound; The negative electrode active materials include graphite, soft carbon, graphitized carbon, silicon suboxide, silicon carbide, tin, antimony, and phosphorus.

3. The composite electrode according to claim 1, characterized in that, The linear polymer material is one or a combination of several of polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, polyester and polyvinyl alcohol; And / or, the solvent is one or a combination of several of the following: methylpyrrolidone, N,N-dimethyldiamide, ethyl acetate, sulfolane, dimethyl sulfoxide, acetic acid, deionized water, and acetonitrile; And / or, the adhesive is one or a combination of several of the following: polyvinylidene fluoride, polyethylene oxide, styrene-butadiene rubber, polytetrafluoroethylene, polyacrylic acid, sodium carboxymethyl cellulose, carboxymethyl cellulose, xanthan gum, sodium alginate, guar gum, and chitosan; And / or, the current collector is one of aluminum foil, copper foil, stainless steel, nickel foil, and carbon foil.

4. The composite electrode according to claim 1, characterized in that, The cyclization reaction conditions are: temperature 150–300°C, time 5–30 min.

5. A method for preparing a composite electrode, characterized in that, Includes the following steps: The formulation components of the composite electrode according to any one of claims 1 to 4 are mixed evenly in proportion to obtain a coating. The coating is applied to the surface of the current collector and then dried to obtain the electrode master sheet; The electrode mother sheet is subjected to high-energy laser treatment to obtain the composite electrode.

6. The preparation method according to claim 5, characterized in that, The high-energy laser processing is femtosecond laser etching, and the processing conditions are: wavelength of 200-1100nm, linewidth of 10-50μm, and power of 500-2000W.

7. The application of the composite electrode according to any one of claims 1 to 4 or the composite electrode prepared by the preparation method according to any one of claims 5 to 6 in a secondary battery.

8. A secondary battery, characterized in that, When the active material is a positive electrode active material, the composite electrode according to any one of claims 1 to 4 or the composite electrode prepared by the preparation method according to any one of claims 5 to 6 shall be used as its positive electrode. And / or, when the active material is a negative electrode active material, the composite electrode according to any one of claims 1 to 4 or the composite electrode prepared by the preparation method according to any one of claims 5 to 6 shall be used as its negative electrode.

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