An electrode tab, a preparation method thereof, and a lithium battery

Abstract

This application provides an electrode sheet, its preparation method, and a lithium battery. The electrode sheet includes an electrode active material layer, which comprises a three-dimensional conductive network substrate, an electrode active material loaded on the three-dimensional conductive network substrate, and a binder. The three-dimensional conductive network substrate and the electrode active material satisfy the following relationship: where V is the actual volume of the three-dimensional conductive network substrate, in cm³. 3 m is the mass of the electrode active material in g; D is the D50 particle size of the electrode active material in μm; ρ is the true density of the electrode active material in g / cm³. 3 d represents the thickness of a single carbon atom layer, with a value of 0.334 nm. This three-dimensional conductive network substrate can optimize the conductive network in the electrode sheets, thereby improving the specific capacity, which in turn benefits the battery's energy density and capacity retention.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, specifically to an electrode sheet, its preparation method, and a lithium battery. Background Technology

[0002] With the development of the new energy industry, the market demand for the energy and power of lithium batteries is increasing. Literature reports that the industry improves the energy density and power of lithium batteries by increasing the areal density, compaction density, and mass ratio of the electrode active materials. However, in the traditional electrode sheet production process, the industry generally adds excessive conductive agents to ensure the electronic conductivity of the electrode sheet during battery charging and discharging. Excessive conductive agents inevitably lead to an insufficient content of active material in the electrode sheet, thus inhibiting the battery's energy density. Furthermore, the distribution and morphology of excessive conductive agents in the electrode sheet are difficult to control. Summary of the Invention

[0003] In view of this, this application provides an electrode sheet, a method for preparing the same, and a lithium battery. The electrode sheet has a three-dimensional conductive network substrate, and by controlling the actual volume of the three-dimensional conductive network substrate to satisfy a specific relationship with the electrode active material, the conductive network in the electrode sheet can be optimized, thereby improving the specific capacity, which in turn is beneficial to the energy density of the battery and improves the capacity retention rate of the battery.

[0004] The first aspect of this application provides an electrode sheet, which is a positive electrode sheet or a negative electrode sheet. The electrode sheet includes an electrode active material layer, which includes a three-dimensional conductive network substrate and an electrode active material and a binder loaded on the three-dimensional conductive network substrate. The three-dimensional conductive network substrate and the electrode active material satisfy the following relationship:

[0005]

[0006] Where V is the actual volume of the three-dimensional conductive network substrate, in cm. 3 m is the mass of the electrode active material in g; D is the D50 particle size of the electrode active material in μm; ρ is the true density of the electrode active material in g / cm³. 3 ; d is the thickness of a single carbon atom layer, and the value of d is 0.334 nm.

[0007] Optionally, D is in the range of 0.1 μm to 20 μm.

[0008] Optionally, in the electrode sheet, the V corresponding to every 100g of the electrode active material is 0.01cm. 3 -20cm 3 Within the range.

[0009] Optionally, the true density of lithium cobalt oxide is 5.1 g / cm³. 3 The true density of the ternary material is 4.8 g / cm³. 3 The true density of lithium manganese oxide is 4.2 g / cm³. 3 The true density of lithium iron phosphate is 3.6 g / cm³. 3 The true density of graphite is 2.26 g / cm³. 3 .

[0010] Optionally, the three-dimensional conductive network substrate is a current collector with a three-dimensional network structure.

[0011] Optionally, the electrode sheet further includes a current collector, and the three-dimensional conductive network substrate is located on at least one side surface of the current collector.

[0012] Optionally, the shape of the three-dimensional conductive network substrate includes a cage shape.

[0013] Optionally, at least a portion of the material of the three-dimensional conductive network matrix includes at least one of conductive polymers, metallic materials, and conductive carbon materials.

[0014] Optionally, the electrode active material includes a positive electrode active material or a negative electrode active material; the positive electrode active material includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide layered ternary material, lithium nickel cobalt aluminum oxide layered ternary material, and nickel manganese cobalt aluminum quaternary material; the negative electrode active material includes at least one of graphite, natural graphite, mesophase carbon microspheres, and silicon-carbon negative electrode material.

[0015] Accordingly, a second aspect of this application provides a method for preparing an electrode sheet, comprising the following steps:

[0016] (1) Construct a three-dimensional conductive network matrix;

[0017] (2) A mixture containing electrode active material and binder is formed on the three-dimensional conductive network substrate so that the electrode active material is loaded on the three-dimensional conductive network substrate to obtain an electrode precursor.

[0018] (3) Roll and cut the electrode precursor to obtain the electrode sheet provided in the first aspect of this application.

[0019] Optionally, step (3) may further include placing the electrode precursor on the current collector and then performing the rolling process.

[0020] Optionally, the method for constructing the three-dimensional conductive network substrate includes three-dimensional printing, powder metallurgy, electrodeposition, or etching of the current collector.

[0021] A third aspect of this application provides a lithium battery having the electrode plates provided in the first aspect of this application. Attached Figure Description

[0022] Figure 1A and Figure 1B A simplified schematic diagram of the cross-section of the electrode sheet provided in the embodiments of this application;

[0023] Figure 2 This is a schematic diagram of the structure of the three-dimensional conductive network substrate prepared in Example 1.

[0024] Explanation of reference numerals in the attached figures: 100 - electrode plate; 10 - current collector; 11 - three-dimensional conductive network substrate; 12 - three-dimensional conductive network substrate. Detailed Implementation

[0025] This application provides an electrode sheet, which can be a positive electrode sheet or a negative electrode sheet. The electrode sheet includes an electrode active material layer, which includes a three-dimensional conductive network matrix and an electrode active material and a binder loaded on the three-dimensional conductive network matrix. The three-dimensional conductive network matrix and the electrode active material satisfy the following relationship:

[0026]

[0027] Where V is the actual volume of the three-dimensional conductive network substrate, in cm. 3 m is the mass of the electrode active material in grams; D is the D50 particle size of the electrode active material in micrometers (μm); and ρ is the true density of the electrode active material in g / cm³. 3 ; d is the thickness of a single carbon atom layer, and the value of d is 0.334 nm.

[0028] In this application, a mathematical calculation model is first established for the actual volume of the three-dimensional conductive network substrate. Based on the function of the three-dimensional conductive network substrate, which is a conductive network between electrode active materials, all electrode active materials need to be connected together and shaped. Therefore, the electrode active materials are pre-designed as spheres with a diameter of D. With numerous spheres closely arranged, it can be understood that the material used to form the three-dimensional conductive network substrate is filled into the gaps between the closely arranged spheres, thus forming an interconnected three-dimensional conductive network (i.e., this 3D network can be understood as hollow spheres or other hollow prism-like structures interlocking). Alternatively, a pre-designed three-dimensional network structure can be formed first, and then the electrode active materials (pre-designed as spheres with a diameter of D) can be filled into the gaps of the three-dimensional network structure. Therefore, the above mathematical calculation model can be seen as a composition with spheres of diameter D and their circumscribed regular hexahedrons as the smallest volume units.

[0029] In the above relationship, 6D 2 d×6D represents the surface area of ​​the circumscribed hexahedron (diameter D) of a sphere with a diameter equal to that of the electrode active material D50. 2 This represents the minimum volume of the 3D conductive network structure substrate used to constitute the aforementioned external hollow regular hexahedron (i.e., the minimum volume of the 3D conductive network structure substrate used in the minimum volume unit). D represents the volume of a sphere with a diameter equal to the particle size of the electrode active material D50. 3 It can represent the volume of a solid regular hexahedron with an edge length of D. This can represent the volume of the irregular object remaining after a sphere of diameter D is removed from a solid cube of length D (i.e., the maximum volume of the 3D conductive network structure substrate used in the smallest volume unit). It can be seen that in each smallest volume unit, the smallest unit volume V of the 3D network substrate... i satisfy: Multiply the above relationship by the total number of electrode active material microspheres used. This gives us the relationship between the actual volume of the entire 3D conductive network matrix and the D50 particle size of the electrode active material:

[0030] When the actual volume V of the three-dimensional conductive network substrate is closer to the lower limit defined in the above formula, the amount of conductive agent can be minimized. That is, while ensuring that the electrode has a good conductive path to achieve better rate performance and lower internal resistance, the proportion of active material in the electrode can be maximized. When V is closer to the upper limit of the above formula, the precision required for parameter control in the preparation of the 3D conductive network substrate can be reduced. This improves the production efficiency of the electrode and increases the proportion of active material in the electrode, thereby improving the specific capacity and thus contributing to the energy density and capacity retention of the battery.

[0031] Furthermore, while ensuring that the actual volume of the three-dimensional conductive network matrix satisfies the aforementioned relationship, the specific shape, prism size, and prism connection method of the three-dimensional conductive network matrix can be designed based on the physicochemical properties of the electrode active material used (e.g., particle size, compaction density, etc.). This helps to achieve the directional stacking of electrode active material particles (i.e., defining the stacking method and position of active material particles), thereby helping to design the areal density and compaction density of the electrode sheet and the battery cell. This ensures that the active material of the electrode sheet has high areal density and high compaction density, thereby improving the specific capacity and thus facilitating the energy density of the battery and improving the battery's capacity retention rate.

[0032] In this application, the D50 particle size of the above-mentioned electrode active material refers to the average particle size of the electrode active material, in μm. The specific definition of the above-mentioned D50 particle size includes the following situations: (1) The D50 particle size can be the particle size corresponding to the cumulative volume percentage of the powdered electrode active material reaching 50%; (2) The D50 particle size can be the particle size corresponding to the cumulative quantity percentage of the powdered electrode active material reaching 50%; (3) The D50 particle size can be determined by randomly sampling the powdered electrode active material or electrode sheet, observing the particle size of the electrode active material particles under a scanning electron microscope (SEM) (the number of electrode active material particles in the sample is generally above 500, preferably above 1000), and measuring the particle size corresponding to the cumulative volume percentage or the cumulative quantity percentage of the electrode active material particles reaching 50%.

[0033] When randomly sampling and measuring the D50 particle size of electrode active material particles in an electrode sheet, the testing method includes the following steps: a) Disassemble the fully discharged battery to obtain the electrode sheet, and then cut any position of the coating area with argon ions to obtain a cross-sectional sample of the electrode sheet; b) Place the above-mentioned electrode cross-sectional sample in an SEM for observation, and adjust the SEM voltage and magnification according to actual needs to ensure that enough particles in the above sample can be clearly seen and photographed to obtain SEM images; c) The obtained SEM images can be imported into grayscale adjustment software (such as Geodict) to count the particle size, or the particle size can be directly identified and counted by the naked eye; d) Accumulate 20-30 experiments, and count no less than 500 particles in each experiment. After statistically analyzing the above results, obtain the particle size distribution range and D50 particle size of the electrode active material particles in the electrode sheet.

[0034] In some embodiments of this application, D is in the range of 0.1 μm to 20 μm (i.e., the D50 particle size of the electrode active material is in the range of 0.1 μm to 20 μm). Controlling the D50 particle size of the electrode active material within the above range is beneficial for suppressing side reactions of the electrode active material during battery operation, and also for ensuring that the electrode sheet has a large compaction density, thereby helping to ensure the energy density of the battery.

[0035] In some embodiments of this application, the actual volume V of the three-dimensional conductive network matrix corresponding to every 100g of electrode active material in the electrode sheet is 0.01cm. 3 -20cm 3Within a certain range. For every 100g of electrode active material, controlling the actual volume V of the corresponding three-dimensional conductive network matrix within a suitable range means controlling the mass of electrode active material loaded on each unit volume of the three-dimensional conductive network matrix. This helps to ensure the mass ratio of electrode active material in the electrode sheet and the fabrication feasibility of the electrode sheet, thereby ensuring that the battery has a suitable energy density, high battery capacity, better rate performance, and longer service life.

[0036] The specific structure of the electrode plates in the embodiments of this application is described below. Please refer to [link / reference]. Figure 1A and Figure 1B .

[0037] In some embodiments of this application, the three-dimensional conductive network substrate is a current collector with a three-dimensional network structure. This three-dimensional conductive network substrate can be obtained by etching the current collector. It is understood that, in order to facilitate the support of the electrode active material, the current collector does not have a three-dimensional network structure throughout its entire thickness direction, but rather on the side closest to the electrode active material layer. Specifically, as... Figure 1A As shown, the electrode 100 is composed of a current collector 10 and a three-dimensional conductive network substrate 11 obtained by etching a portion of the current collector substrate. In some specific embodiments, the current collector may include two parts along its thickness direction: one part is solid, and the other part has a three-dimensional network structure; in other words, the current collector includes a solid current collector substrate of a certain thickness and a current collector with a three-dimensional network structure (i.e., a three-dimensional conductive network substrate). In other embodiments, the current collector may include three parts along its thickness direction: a solid middle part and three-dimensional network structures on both sides. Specifically, see [link to documentation]. Figure 1B The electrode sheet 100 is composed of a current collector 10 and three-dimensional conductive network substrates 11 and 12 obtained by etching a portion of the current collector substrate. The three-dimensional conductive network substrates 11 and 12 are located on both sides of the three-dimensional conductive network substrate 11. It can also be understood that the shapes of the three-dimensional conductive network substrates 11 and 12 can be the same or different; all the three-dimensional conductive network substrates are loaded with electrode active materials, and the electrode active materials loaded on the three-dimensional conductive network substrates 11 and 12 can be the same or different.

[0038] In other embodiments of this application, the electrode sheet further includes a current collector, and the three-dimensional conductive network substrate is located on at least one surface of the current collector. In this case, the current collector can be a common solid current collector without a three-dimensional network structure. Specifically, see [link to relevant documentation]. Figure 1AAt this point, the electrode 100 consists of a current collector 10 and a three-dimensional conductive network substrate 11 located on one side of its surface. Further, the three-dimensional conductive network substrate may be provided on one side surface of the current collector, or it may be provided on both sides of the current collector. Specifically, see [link to relevant documentation]. Figure 1B At this point, the electrode sheet 100 includes a current collector 10 and three-dimensional conductive network substrates 11 and 12 located on its two side surfaces, respectively. The shapes of the three-dimensional conductive network substrates 11 and 12 can be the same or different. All of the three-dimensional conductive network substrates are loaded with electrode active materials, and the electrode active materials loaded on the three-dimensional conductive network substrates 11 and 12 can be the same or different. Loading the three-dimensional conductive network substrates loaded with electrode active materials onto the current collector is necessary to ensure the normal operation of the battery.

[0039] In some embodiments of this application, the shape of the three-dimensional conductive network substrate includes a cage shape. The cage-like structure facilitates its integration with the current collector and simplifies the setting of longitudinal and transverse parameters relative to the electrode during the design process of the three-dimensional network substrate. In other embodiments, the cage-like three-dimensional conductive network substrate can also be a three-dimensional foam, an N-hedral mesh, a three-dimensional spherical mesh, or other three-dimensional mesh structures.

[0040] In this embodiment, at least a portion of the material of the three-dimensional conductive network matrix includes at least one of conductive polymers, metallic materials, and conductive carbon materials. The metallic material can be an elemental metal or a metal alloy. In some specific embodiments, the entire material of the three-dimensional conductive network matrix is ​​conductive, specifically at least one of conductive polymers, metallic materials, and conductive carbon materials. In other embodiments, a portion of the material of the three-dimensional conductive network matrix is ​​non-conductive, specifically non-conductive polymers, ceramic materials, etc. In these cases, a conductive agent can be mixed into the material, or a conductive coating can be formed on the surface of the material. The conductive agent can be carbon nanotubes, graphene, fullerene, graphylene, conductive carbon black, Ketjen black, etc. Specifically, when the material is a non-conductive polymer, its surface can be slightly carbonized to make at least a portion of the material in the final three-dimensional conductive network matrix conductive. Furthermore, the outer surface of at least the three-dimensional conductive network matrix is ​​made conductive, allowing for sufficient contact with the electrode active material, thereby forming a highly efficient conductive network in the electrode sheet.

[0041] In this application, the electrode active material includes a positive electrode active material or a negative electrode active material. It is understood that when the electrode sheet is a positive electrode sheet, the electrode active material is a positive electrode active material; when the electrode sheet is a negative electrode sheet, the electrode active material is a negative electrode active material. Positive and negative electrode active materials are commonly used materials in the battery field.

[0042] The positive electrode active material includes, but is not limited to, at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt manganese oxide layered ternary material (NCM), lithium nickel cobalt aluminum oxide layered ternary material (NCA), and lithium nickel manganese cobalt aluminum oxide quaternary material (NCMA). The negative electrode active material includes, but is not limited to, at least one of graphite, natural graphite, mesophase carbon microspheres, and silicon-carbon negative electrode materials. NCM represents lithium nickel cobalt manganese oxide ternary layered material; in some embodiments, its general structural formula can be represented as Li 1+m Ni x Co y Mn 1-x-y O2 (x≥0.33, 0≤y≤0.4, 0≤m≤0.1). NCA represents lithium-nickel-cobalt-aluminum-oxygen ternary layered material; in some embodiments, its general structural formula can be represented as Li 1+m Ni x Co y Al 1-x-y O2 (x≥0.33, 0≤y≤0.4, 0≤m≤0.1). NCMA represents a lithium-nickel-manganese-cobalt-aluminum-oxygen quaternary material; in some embodiments, its general structural formula can be represented as Li 1+m Ni x Co y Mn z Al 1-x-y-z O2(x≥0.33, 0≤y≤0.4, 0≤z≤0.4, 0≤m≤0.1).

[0043] In some specific embodiments of this application, the true density of lithium cobalt oxide can be 5.1 g / cm³. 3 The true density of the above ternary material can be 4.8 g / cm³. 3 The true density of lithium manganese oxide can be 4.2 g / cm³. 3 The true density of lithium iron phosphate can be 3.6 g / cm³. 3 The true density of graphite can be 2.26 g / cm³. 3 .

[0044] Accordingly, this application also provides a method for preparing an electrode sheet, comprising the following steps:

[0045] (1) Construct a three-dimensional conductive network matrix;

[0046] (2) A mixture containing electrode active material and binder is formed on a three-dimensional conductive network matrix so that the electrode active material is loaded on the three-dimensional conductive network matrix to obtain an electrode precursor.

[0047] (3) Roll and cut the electrode precursor to obtain the electrode provided in this application.

[0048] This preparation method is highly controllable, simple to operate, and can be used for large-scale industrial production.

[0049] In some embodiments of this application, step (2) further includes placing the three-dimensional conductive network substrate on the current collector, and then coating the mixture containing the electrode active material and the binder onto the three-dimensional conductive network substrate. In other embodiments, step (3) further includes placing the electrode precursor on the current collector and then rolling it.

[0050] In this application, the method for constructing the three-dimensional conductive network substrate in step (1) includes, but is not limited to, 3D printing, powder metallurgy, electrodeposition, or etching of the current collector. The construction method can be adjusted according to the raw materials used in preparing the three-dimensional conductive network substrate. For example, in some specific embodiments, if the raw material used for the three-dimensional conductive network substrate is a metallic material, it can be prepared using 3D laser selective sintering or powder metallurgy. In some embodiments, if the three-dimensional conductive network substrate is a current collector with a three-dimensional network structure, it is prepared by etching the current collector. When the raw material used for the three-dimensional conductive network substrate is a conductive polymer or a conductive inorganic carbon material, it can be prepared using 3D printing or electrodeposition.

[0051] In some embodiments, when the raw materials used in preparing the three-dimensional conductive network substrate are non-conductive materials (e.g., non-conductive ceramics or non-conductive polymers), the above method further includes a conductivity treatment. This conductivity treatment includes, but is not limited to: before constructing the three-dimensional conductive network substrate, mixing a conductive agent into the raw material and directly preparing the three-dimensional conductive network substrate using 3D printing or electrodeposition; or after obtaining a non-conductive three-dimensional network substrate using 3D printing or electrodeposition, subjecting it to a slight surface carbonization treatment or forming a conductive layer on its surface to obtain the three-dimensional conductive network substrate. The conductive layer is suitable for being disposed on any non-conductive three-dimensional network substrate, and the carbonization treatment is suitable for processing the aforementioned non-conductive three-dimensional network substrate where the raw material is a polymer.

[0052] When the raw materials used to prepare the three-dimensional conductive network matrix are themselves conductive materials (e.g., conductive polymers, conductive inorganic carbon materials, and metallic materials), the three-dimensional conductive network matrix can be directly constructed. Of course, the conductive treatment described above can also be applied to it. The specific conductive treatment method can be determined according to the morphology of the material and the preparation method, which will not be elaborated here.

[0053] In this application, the formation method in step (2) includes coating, which includes drop coating, brush coating, spray coating, dip coating, scraping coating, and spin coating. The specific coating method can be determined according to the mixture of electrode active material and binder. The mixture can be liquid or solid. In some embodiments of this application, the mixture is a liquid mixture containing solvent, which can be formed on the three-dimensional conductive network substrate by drop coating, brush coating, spray coating, dip coating, scraping coating, spin coating, etc. In other embodiments, the mixture is a solid mixture, which can be formed on the three-dimensional conductive network substrate by powder spraying, etc.

[0054] This application also provides a lithium battery with the electrode plates provided in this application. In some embodiments, the positive electrode plate in the lithium battery is the electrode plate provided in this application, and the negative electrode plate is a conventional electrode plate. In some embodiments, the negative electrode plate in the lithium battery is the electrode plate provided in this application, and the positive electrode plate is a conventional electrode plate. In some embodiments, both the positive and negative electrodes in the lithium battery are electrode plates provided in this application.

[0055] The aforementioned batteries have high specific capacity and excellent capacity retention, and also have high energy density.

[0056] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0057] Example 1

[0058] (1) Construction of the 3D Conductive Network Substrate: A 3D conductive network substrate composed of carbon fiber composite material was prepared using 3D printing technology. Specifically, carbon fibers were passed through a tank containing polylactic acid (PLA), and the PLA-coated carbon fibers were passed through holes with a certain pore size to scrape off excess PLA from the carbon fiber surface. The above filaments were 3D printed, and after curing, a 3D network substrate composed of carbon fiber composite material was obtained. The surface of this substrate was then slightly carbonized to obtain a three-dimensional conductive network substrate. The actual volume of this three-dimensional network substrate was 1.13 cm³. 3 .

[0059] (2) Preparation of positive electrode: 100g of LiNi with a D50 of 1μm was prepared. 0.8 Co 0.1 Mn 0.1 (NCM811), true density is 4.8 g / cm³ 3The positive electrode active slurry is obtained by dissolving 0.5g of PVDF5130 binder in N-methylpyrrolidone (NMP) and mixing it evenly. The three-dimensional conductive network substrate is placed on the positive electrode current collector - aluminum foil, and the above positive electrode active slurry is coated on the 3D conductive network substrate. After drying, it is rolled to obtain the positive electrode sheet.

[0060] (3) Preparation of the negative electrode sheet: 100g of graphite negative electrode active material, 1g of thickener, 1g of emulsion, and 2g of conductive carbon black are added to water in a certain order and mixed evenly to obtain a negative electrode active slurry. The above negative electrode active material is uniformly coated on the surface of the negative electrode current collector - copper foil. After drying, it is pressed into a sheet by a roller press to obtain the negative electrode sheet.

[0061] (4) Battery manufacturing

[0062] The positive electrode obtained in step (2) and the negative electrode obtained in step (3) are alternately stacked with a separator to prepare a battery. The positive and negative electrodes are arranged alternately, and adjacent positive and negative electrodes are separated by a separator, resulting in a dry cell. The dry cell is placed in an aluminum-plastic film outer packaging, electrolyte is injected, and then it is vacuum-sealed. After being placed at 60°C for 48 hours, a pressure layer is applied at 60°C, followed by secondary encapsulation, venting, and capacity testing to obtain a stacked soft-pack full battery with a capacity of 2.2 Ah. The resulting battery is denoted as S1.

[0063] Example 2

[0064] Laser etching technology was used to perform 3D network etching on the positive electrode current collector (aluminum foil), resulting in an actual volume of 1.13 cm³ of the three-dimensional conductive network matrix in the current collector substrate. 3 100g of LiNi with a D50 of 1μm was used. 0.8 Co 0.1 Mn 0.1 (NCM811) was dissolved in NMP with 0.5g of binder PVDF5130 and mixed evenly to obtain a positive electrode active slurry. The above positive electrode active slurry was uniformly coated on a three-dimensional conductive network substrate, dried, and then rolled to obtain a positive electrode sheet. The resulting battery is denoted as S2.

[0065] Example 3

[0066] Using 3D printing technology, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT: PSS) conductive polymer was printed into a 3D conductive network matrix, resulting in an actual volume of 1.13 cm³. 3 100g of LiNi with a D50 of 1μm was used. 0.8 Co 0.1 Mn 0.1(NCM811) was dissolved in NMP with 0.5g of binder PVDF5130 and mixed evenly to obtain a positive electrode active slurry. A 3D conductive network substrate was placed on an aluminum foil, and the above positive electrode active slurry was coated on the 3D conductive network substrate. After drying, the 3D conductive network substrate and the aluminum foil were rolled to obtain a positive electrode sheet. The resulting battery is designated as S3.

[0067] Example 4

[0068] Using 3D printing technology, aluminum powder was used as the printing material. A 3D conductive network substrate was printed on the positive current collector-aluminum foil using laser selective sintering. The volume of the 3D network was 1.13 cm³. 3 100g of LiNi with a D50 of 1μm was used. 0.8 Co 0.1 Mn 0.1 (NCM811) was dissolved in NMP with 0.5g of binder PVDF5130 and mixed evenly to obtain a positive electrode active slurry. The positive electrode active slurry was then coated onto a three-dimensional conductive network substrate. After drying, the 3D conductive network substrate and aluminum foil were rolled together to obtain a positive electrode sheet. The resulting battery is designated as S4.

[0069] Example 5

[0070] The preparation process is the same as in Example 3, except that after the three-dimensional conductive network substrate is printed, it is placed in a high-temperature furnace and its surface is slightly carbonized at 200°C. The resulting battery is designated as S5.

[0071] Example 6

[0072] The preparation process is the same as in Example 3, except that carbon nanotubes are added to the PEDOT:PSS conductive polymer raw material for 3D printing, and the mass percentage of carbon nanotubes in the resulting mixture is 20%. The resulting battery is denoted as S6.

[0073] Example 7

[0074] The preparation process is the same as in Example 3, except that graphene is added to the PEDOT:PSS conductive polymer, the raw material for 3D printing, and the mass percentage of graphene in the resulting mixture is 20%. The resulting battery is designated as S7.

[0075] Examples 8-19

[0076] Following the preparation method of Example 7, positive electrode sheets for Examples 8-19 were prepared. The changes in parameters for each positive electrode sheet in Examples 8-19 are summarized in Table 1. Please refer to Table 1. The true density of lithium iron phosphate (LFP) is 3.6 g / cm³. 3 The batteries produced are designated as S8-S19.

[0077] Example 20

[0078] The negative electrode sheet of Example 20 also conforms to the limitations of this application. Specifically, 100g of graphite negative electrode active material (true density 2.26g / cm³) was used. 3 1g of thickener and 1g of emulsion are added to water in a certain order and mixed evenly to obtain a negative electrode active slurry. A three-dimensional conductive network substrate is placed on a negative electrode current collector—copper foil, and the above-mentioned negative electrode active slurry is coated onto the three-dimensional conductive network substrate. After drying, it is rolled to obtain a negative electrode sheet. The above-mentioned negative electrode sheet and positive electrode sheet are assembled into a battery S20. It should be noted that the positive electrode sheet of battery S20 is the positive electrode sheet obtained in Example 7.

[0079] To highlight the beneficial effects of the embodiments of this application, the following comparative examples are provided.

[0080] Comparative Example 1

[0081] The difference from Example 7 is that the actual volume of the obtained three-dimensional conductive network substrate is 0.06 cm³. 3 The resulting battery is denoted as DS1.

[0082] Comparative Example 2

[0083] The difference from Example 7 is that the actual volume of the obtained three-dimensional conductive network substrate is 20 cm³. 3 The resulting battery is designated DS2.

[0084] Comparative Example 3

[0085] The difference from Example 1 is that 100g of LiNi with a D50 of 1μm was used. 0.8 Co 0.1 Mn 0.1 (NCM811) was dissolved in NMP with 0.5 g of binder PVDF5130 to obtain a positive electrode active slurry. After thorough mixing, the above positive electrode active slurry was coated onto a substrate with a volume of 1.13 cm³. 3 The surface of the carbonized carbon fiber composite sheet is placed on aluminum foil, dried, and then rolled to obtain the positive electrode sheet. The resulting battery is designated DS3.

[0086] Comparative Example 4

[0087] The difference from Example 1 is that 100g of LiNi with a D50 of 1μm was used. 0.8 Co 0.1 Mn 0.1(NCM811), 0.5g of binder PVDF5130, and 2.486g of carbon fiber conductive agent (HV) were dissolved together in NMP to obtain a positive electrode active slurry. After uniform mixing, the above positive electrode active slurry was uniformly coated on aluminum foil, dried, and then rolled to obtain a positive electrode sheet. The resulting battery is designated DS4.

[0088] Table 1. Summary of parameters of electrode sheets prepared in each embodiment and comparative example.

[0089]

[0090]

[0091] Electrochemical performance tests were performed on the electrode sheets and batteries prepared in the above embodiments and comparative examples, including the following steps:

[0092] (1) Longitudinal resistivity test of electrode sheets: The longitudinal resistivity of the obtained positive electrode sheets was tested using a longitudinal resistivity meter. The test pressure was set to 25 MPa and the holding time was 30 s. Ten points were tested for each group of electrode sheets and the average value was taken. The obtained data are summarized in Table 2.

[0093] (2) Test of the ultimate compaction density of the electrode sheet: Continuously increase the pressure of the roller press and use a micrometer to test the thickness of the electrode sheet until the thickness of the electrode sheet can no longer be reduced, and obtain the ultimate compaction density of the electrode sheet. The obtained data are summarized in Table 3.

[0094] (3) Battery capacity test: The capacity test steps are as follows: ambient temperature 25℃, 2.2Ah as 1C, (1) charging: 1 / 3C constant current and constant voltage charging to 4.25V / Cell, cut-off current 0.05C, rest for 30min; (2) discharging: 1 / 3C constant current to 2.5V / Cell, rest for 30min; (3) cycle 3 times, record the third discharge capacity as the true capacity of the battery. The test results are summarized in Table 3.

[0095] (4) Battery cycle performance test: Using 2.2Ah as 1C, 1) Charging: 1 / 3C constant current and constant voltage charging to 4.25V / Cell, cut-off current 0.05C, rest for 30min; 2) Discharging: 1 / 3C constant current to 2.5V / Cell, rest for 30min; 3) Cycle 3 times, record the discharge capacity of the 3rd discharge as the battery's true capacity C0; 4) Charging: Using the battery's true capacity C0 as 1C, 1C constant current and constant voltage charging to 4.25V, cut-off current 0.05C; 5) Rest for 30min; 6) Discharging: Using the battery's true capacity C0 as 1C, 1C constant current discharging to 2.5V; 7) Rest for 30min; 8) Cycle 500 times from 4) to 7). (Note: Because the positive electrode active material used in Example 8 is LFP, the upper limit voltage was set to 3.8V and the lower limit voltage to 2.0V during the test). The results are summarized in Table 3.

[0096] Table 2. Longitudinal resistivity and ultimate compaction density of the electrode sheets prepared in the examples and comparative examples.

[0097]

[0098]

[0099] Table 3. Specific capacity and capacity retention of the batteries prepared in the examples and comparative examples.

[0100]

[0101]

[0102] As shown in Table 2, the longitudinal resistivity of the positive electrode with a three-dimensional conductive network substrate (Examples 1-19) is much lower than that of the positive electrode without a three-dimensional conductive network substrate (Comparative Example 3). Furthermore, when the actual volume of the 3D conductive network substrate is within the design specifications, the longitudinal resistivity of the corresponding positive electrode (Examples 1-19) is much lower than that of the positive electrode with an actual volume lower than the design specifications (Comparative Example 1). However, the positive electrode with an actual volume exceeding the design specifications (Comparative Example 2) does not significantly improve resistivity and inevitably leads to a decrease in the mass ratio of the positive electrode active material in the electrode, thus affecting battery performance. The data on the ultimate compaction density of the positive electrode shows that the ultimate compaction density of the positive electrode with a three-dimensional conductive network matrix (Examples 1-19 and Comparative Examples 1-2) is greater than that of the positive electrode without a three-dimensional conductive network matrix (Comparative Example 3). However, when the actual volume of the three-dimensional conductive network matrix exceeds the amount required by the three-dimensional network design rules, the electrode compaction density of the corresponding positive electrode will decrease (Comparative Example 2).

[0103] As can be seen from the data in Table 3, the battery with the electrode sheet having the three-dimensional conductive network structure provided in this application exhibits a relatively balanced performance in terms of specific capacity and capacity retention after cycling. However, when the actual volume of the 3D conductive network structure exceeds the limit specified in this application, it results in a lower specific capacity (battery DS2). When the actual volume of the 3D conductive network structure is lower than the limit specified in this application, it results in a poorer capacity retention (battery DS1). When both the positive and negative electrode sheets of the battery are electrode sheets specified in this application (battery S20), compared to battery S7 using the same positive electrode sheet, battery S20 has a higher capacity retention after 500 cycles, indicating that when both the positive and negative electrode sheets of the battery are electrode sheets specified in this application, its battery cycle capacity retention is better. Furthermore, the data from the example batteries S1-S20 and the comparative batteries DS3-DS3 show that electrode sheets without a three-dimensional conductive network substrate have no advantage in terms of specific capacity, and the battery capacity retention decreases extremely rapidly.

[0104] The above are exemplary embodiments of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. An electrode sheet, characterized in that, The electrode sheet is either a positive electrode sheet or a negative electrode sheet. The electrode sheet includes an electrode active material layer, which comprises a three-dimensional conductive network substrate and an electrode active material and binder loaded on the three-dimensional conductive network substrate. The three-dimensional conductive network substrate has a cage-like shape. The three-dimensional conductive network substrate and the electrode active material satisfy the following relationship: Where V is the actual volume of the three-dimensional conductive network substrate, in cm. 3 m is the mass of the electrode active material, in grams; D is the particle size corresponding to a cumulative volume percentage of 50% for the electrode active material, in millimeters. m, The true density of the electrode active material is expressed in g / cm³. 3 d is 0.334nm; The value of D is in the range of 0.1 μm to 20 μm; In the electrode sheet, the V corresponding to every 100g of the electrode active material is 0.01cm. 3 -20cm 3 Within the range.

2. The electrode sheet according to claim 1, characterized in that, The three-dimensional conductive network substrate is a current collector with a three-dimensional network structure.

3. The electrode sheet according to claim 1, characterized in that, The electrode sheet also includes a current collector, and the three-dimensional conductive network substrate is located on at least one side surface of the current collector.

4. The electrode sheet according to claim 1, characterized in that, At least a portion of the material of the three-dimensional conductive network matrix includes at least one of conductive polymers, metallic materials, and conductive carbon materials.

5. The electrode sheet according to claim 1, characterized in that, The electrode active material includes a positive electrode active material or a negative electrode active material; the positive electrode active material includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxygen layered ternary material, lithium nickel cobalt aluminum oxygen layered ternary material, and lithium nickel manganese cobalt aluminum oxygen quaternary material; the negative electrode active material includes at least one of graphite, mesophase carbon microspheres, and silicon-carbon negative electrode material.

6. A method for preparing an electrode sheet, characterized in that, Includes the following steps: (1) Constructing a three-dimensional conductive network matrix; (2) A mixture containing electrode active material and binder is formed on the three-dimensional conductive network matrix so that the electrode active material and binder are loaded on the three-dimensional conductive network matrix to obtain an electrode precursor; (3) Roll and cut the electrode precursor to obtain the electrode as described in claim 1.

7. The preparation method according to claim 6, characterized in that, Step (3) also includes placing the electrode precursor on the current collector and then performing the rolling process.

8. The preparation method according to claim 7, characterized in that, The methods for constructing a three-dimensional conductive network substrate include 3D printing, powder metallurgy, electrodeposition, or etching of the current collector.

9. A lithium battery, characterized in that, The lithium battery has an electrode sheet as described in any one of claims 1-5, or includes an electrode sheet prepared by the preparation method as described in any one of claims 6-8.

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