Diaphragm preparation apparatus and diaphragm preparation method

Abstract

Disclosed in the present application are a diaphragm preparation apparatus and a diaphragm preparation method. The diaphragm preparation apparatus comprises a first membrane forming structure, which is configured to perform pressing on first fibrous powder so as to obtain a first primary diaphragm; a second membrane forming structure, which is configured to perform pressing on second fibrous powder so as to obtain a second primary diaphragm; a membrane lamination structure, which is arranged downstream of the first membrane forming structure and the second membrane forming structure and is configured to perform pressing on the first primary membrane and the second primary membrane so as to obtain a primary laminated diaphragm; and a diaphragm thinning structure, which is arranged downstream of the membrane lamination structure and is configured to perform roll-pressing and thinning on the primary laminated diaphragm, so as to obtain a target diaphragm with a target thickness.

Description

Diaphragm preparation equipment and preparation method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 15, 2024, with application number 2024100581304. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of membrane preparation equipment, and in particular to a membrane preparation equipment and a preparation method. Background Art

[0003] With the global energy shortage and increasing awareness of environmental protection, the development of new energy has become the most important research direction in the current energy field. Lithium-ion batteries have the advantages of high operating voltage, no memory effect, low self-discharge and long cycle life. They have gradually become a development hotspot in the energy industry and are widely used in various electronic products.

[0004] Lithium-ion battery manufacturing equipment generally includes wet process manufacturing equipment and dry process manufacturing equipment. However, the active material layer on one side of the current collector obtained by the manufacturing equipment is relatively thin and has a single porosity, which cannot meet the requirements of higher performance batteries. Technical issues

[0005] The present application aims to solve the following technical problems: Currently, when it is necessary to prepare a thicker active material layer for an electrode, the wet multi-layer co-coating technology is mostly used to achieve this. However, the wet process is difficult to achieve ultra-thick electrodes due to the existence of a limit crack thickness. At the same time, the coating is prone to mixed flow in the coating gap during coating, and layer mixing is prone to occur between multi-layer coatings. At the same time, the porosity of the active material layer on one side of the current collector prepared by a dry or wet method is single, which limits the charge and discharge performance of the battery. Technical Solutions

[0006] In the first aspect, the present application provides a membrane preparation device, comprising: a first membrane forming structure, used to press a first fiberized powder to obtain a first initial membrane sheet; a second membrane forming structure, used to press a second fiberized powder to obtain a second initial membrane sheet; a membrane combining structure, arranged downstream of the first membrane forming structure and the second membrane forming structure, used to press the first initial membrane sheet and the second initial membrane sheet to obtain an initial combined membrane sheet; a membrane thinning structure, arranged downstream of the membrane combining structure, used to roll and thin the initial membrane sheet to obtain a target membrane sheet of target thickness.

[0007] In the second aspect, the present application provides a method for preparing a membrane, comprising: pressing a first fiberized powder through a first membrane-forming structure to obtain a first initial membrane; pressing a second fiberized powder through a second membrane-forming structure to obtain a second initial membrane; pressing the first initial membrane and the second initial membrane through a membrane-forming structure to obtain an initial membrane; and rolling and thinning the initial membrane through a membrane thinning structure to obtain a target membrane of a target thickness. Beneficial effects

[0008] The first fiberized powder is pressed by the first film-forming structure to obtain a first initial film sheet, and the second fiberized powder is pressed by the second film-forming structure to obtain a second initial film sheet. Then, the first initial film sheet and the second combined film sheet are pressed under the film-forming action of the film-forming structure to obtain an initial combined film sheet, and then thinned by the film thinning structure to obtain the target film after the target is obtained. Here, since the first fiberized powder and the second fiberized powder are fed separately, the components in the first fiberized powder and the second fiberized powder can be used in different proportions, and the first film-forming structure and the second film-forming structure can use different parameters to press the fiberized powder into a film, so that the first initial film sheet and the second touch sheet can have their own thickness and compaction degree, so that the target film obtained by the combined film can have two layers of film, so that the target film can have a thicker thickness, and the two layers of film can have their own porosity, so that the gradient porosity of the target film is achieved, and when prepared into a battery, the energy density and charge and discharge performance of the battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG1 is a schematic structural diagram of a membrane preparation device according to an embodiment of the present application;

[0010] 2 and 3 are schematic diagrams showing the porosity and tortuosity of target membranes produced by the membrane production apparatus in FIG. 1 ;

[0011] FIG4 is a schematic flow chart of a method for preparing a membrane according to an embodiment of the present application.

[0012] Attached photos:

[0013] 100-diaphragm preparation equipment, 11-first vibrating screen, 12-first movable material trough, 20-first film forming structure, 21-first roller, 31-second vibrating screen, 32-second movable material trough, 40-second film forming structure, 41-second roller, 50-film combining structure, 51-film combining roller, 60-diaphragm thinning structure, 61-thinning roller, 70-first trimming structure, 71-first support roller, 72-first trimming knife, 73-first powder suction nozzle, 74-first dust removal box, 80-second trimming structure, 81-second support roller, 82-second trimming knife, 83-second powder suction nozzle, 84-second dust removal box, 90-speed detection device, 200-guide roller, 210-winding structure, 211-automatic monitoring and correcting device, 212-winding air shaft. Modes for Carrying Out the Invention

[0014] In the description of this application, it should be noted that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting this application.

[0015] The present application will be further described in detail below with reference to the accompanying drawings.

[0016] Please refer to FIG. 1 and FIG. 2 , which show a membrane preparation device 100 provided in an embodiment of the present application, including a first membrane forming structure 20 , a second membrane forming structure 40 , a membrane combining structure 50 , and a membrane thinning structure 60 .

[0017] Among them, the first film-forming structure 20 is used to press the first fiberized powder to obtain a first initial film sheet; the second film-forming structure 4 is used to press the second fiberized powder to obtain a second initial film sheet; the film-forming structure 50 is arranged downstream of the first film-forming structure 20 and the second film-forming structure 40, and is used to press the first initial film sheet and the second initial film sheet to obtain an initial film sheet; the film thinning structure 60 is arranged downstream of the film-forming structure 50, and is used to roll and thin the initial film sheet to obtain a target film sheet of target thickness.

[0018] The above-mentioned membrane preparation equipment 100 presses the first fiberized powder material through the first membrane forming structure 20 to obtain a first initial membrane sheet, presses the second fiberized powder material through the second membrane forming structure 40 to obtain a second initial membrane sheet, and then presses the first initial membrane sheet and the second combined membrane sheet under the membrane-forming action of the membrane-forming structure 50 to obtain a preliminary membrane sheet, and then thins it through the roller pressing of the membrane thinning structure 60 to obtain the target membrane sheet we need, wherein, since the first fiberized powder material and the second fiberized powder material are fed separately, the first fiberized powder material The ingredients in the material and the second fiberized powder can be used in different proportions, and the first film-forming structure 20 and the second film-forming structure 40 can use different parameters to press the fiberized powder into a film, so that the first initial film sheet and the second touch film can have their own thickness and compaction degree, so that the target film obtained by the film combination can have two layers of film, so that the target film can have a thicker thickness, and the two layers of film can have their own porosity, so that the gradient porosity of the target film is achieved, and when it is prepared into a battery, the energy density and charge and discharge performance of the battery can be improved.

[0019] Specifically, in this embodiment, the components of the first fiberized powder and the second fiberized powder are set to be the same, but the proportions of the components can be set to be different, so that the prepared target membrane can have a gradient porosity performance.

[0020] The components of the first and second fiberized powders may include, but are not limited to, a combination of an active material, a conductive agent, and a binder, and the fiberized powder is formed by applying shear force to the active material, the conductive agent, and the binder. The active material may be a positive electrode material such as lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, or one or more combinations of graphite and / or silicon oxygen / silicon carbon negative electrode materials; the conductive agent may include, but is not limited to, one or more combinations of conductive carbon black, carbon nanotubes, graphene, etc.; and the binder may include, but is not limited to, one or more combinations of polytetrafluoroethylene, tetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, polyethylene glycol, polyvinyl pyrrolidone, etc.

[0021] Wherein, please refer to Figure 1. In order to facilitate the unloading of the first film forming structure 20, the membrane preparation equipment 100 in this embodiment also includes a first vibrating screen 11 and a first movable material trough 12 arranged below the first vibrating screen 11. The first vibrating screen 11 is used to receive the first fiberized powder and send it to the first movable material trough 12. The first movable material trough 12 is used to receive the first fiberized powder transported by the first vibrating screen 11 and send it to the first film forming structure 20. The first movable material trough 12 can switch between vertical and horizontal states. In this way, after the powder is poured on the first vibrating screen 11, the first vibrating screen 11 vibrates to allow the powder to gradually fall onto the first movable material trough 12 through the first vibrating screen 11. The first movable material trough 12 can be gradually adjusted from a vertical state to a horizontal state to drive the powder to move, so as to gradually sprinkle the powder, and at the same time adjust the speed of powder sprinkling to avoid accumulation or agglomeration of powder, and at the same time adjust the speed of film forming.

[0022] Specifically, the first vibrating screen 11 includes two layers of first screens arranged from top to bottom. The first fiberized powder falls downward from the sieve holes of the first screen, and then falls into the first movable material trough 12, and is sent out by the first movable material trough 12. By providing two layers of first screens in the first vibrating screen 11, the falling speed of the first fiberized powder can be adjusted.

[0023] Similarly, in order to facilitate the unloading of the second film-forming structure 40, the membrane preparation equipment 100 in this embodiment also includes a second vibrating screen 31 and a second movable material trough 32 arranged below the second vibrating screen 31. The second vibrating screen 31 is used to receive the second fiberized powder and send it to the second movable material trough 32. The second movable material trough 32 is used to receive the second fiberized powder transported by the second vibrating screen 31 and send it to the second film-forming structure 20. The second movable material trough 32 can switch between vertical and horizontal states. In this way, after the powder is poured on the second vibrating screen 31, the second vibrating screen 31 vibrates to allow the powder to gradually fall onto the second movable material trough 32 through the second vibrating screen 31. The second movable material trough 32 can be gradually adjusted from a vertical state to a horizontal state to drive the powder to move, so as to gradually sprinkle the powder, and at the same time adjust the speed of powder sprinkling to avoid accumulation or agglomeration of powder, and at the same time adjust the speed of film forming.

[0024] Specifically, the second vibrating screen 31 includes two layers of second screens arranged from top to bottom. The second fiberized powder falls downward from the sieve holes of the second screen, and then falls into the second movable material trough 32, and is sent out by the second movable material trough 32. By providing two layers of first screens in the second vibrating screen 31, the falling speed of the second fiberized powder can be adjusted.

[0025] Please refer to FIG1 . The first film forming structure 20 includes a pair of first rollers 21 arranged opposite to each other, with a roller diameter of d1 and a pressure of t1. The second film forming structure 40 includes a pair of second rollers 41 arranged opposite to each other, with a roller diameter of d2 and a pressure of t2. Specifically, when setting, d2>d1 and t2>t1.

[0026] Since the roller has a first component of force parallel to the extension direction of the diaphragm and a second component of force perpendicular to the direction of the diaphragm when pressing the diaphragm, by setting a second roller 41 with a larger roller diameter and greater pressure, the weight of the second roller 41 can be made larger. At the same time, combined with the pressure applied to the second roller 41, a larger component of force in the vertical direction can be applied to the diaphragm when the powder is pressed into a membrane. In this way, the pressing pressure applied to the second fiberized powder is greater than the pressing pressure applied to the first fiberized powder, thereby achieving the effect that the first initial diaphragm and the second initial diaphragm have different thicknesses and compaction degrees, so as to achieve the effect of presenting a gradient porosity when the membrane is subsequently formed.

[0027] Specifically, in this embodiment, the roller diameters and pressures of the first and second rollers 21 and 41 are set such that 10 cm ≤ d2 ≤ 30 cm, 8 cm ≤ d1 ≤ 28 cm; 1 ton ≤ t2 ≤ 5 tons, and 0.8 tons ≤ t1 ≤ 4.5 tons. For example, d2 can be set to a value such as 10 cm, 15 cm, 20 cm, 25 cm, or 30 cm; d1 can be set to a value such as 8 cm, 10 cm, 15 cm, 20 cm, 25 cm, or 28 cm, without limitation, as long as d2 > d1. t2 can be set to a value such as 1 ton, 2 tons, 3 tons, 4 tons, or 5 tons, and t1 can be set to a value such as 0.8 tons, 1 ton, 2 tons, 3 tons, 4 tons, or 4.8 tons, without limitation, as long as t2 > t1.

[0028] In this way, the first roller 21 and the second roller 41 respectively compact the powder to obtain an initial membrane sheet. At the same time, by setting the second roller 41 with a larger roller diameter and pressure and setting the first roller 21 with a smaller roller diameter and pressure, the thickness and compaction degree of the initially obtained first membrane sheet and the second membrane sheet can be different, so that a membrane sheet with a gradient porosity can be obtained in the final product.

[0029] Please refer to Figure 1. The film-forming structure 50 in this embodiment includes a pair of film-forming rollers 51 arranged opposite to each other, the roller diameter of the film-forming roller 51 is d3, and the pressure is t3; the film thinning structure 60 includes at least one pair of thinning rollers 61 arranged opposite to each other, the roller diameter of the thinning roller 61 is d4, and the pressure is t4; wherein, d4>d3, t4>t3, and d2>d1>d4>d3, t2>t1>t4>t3, that is, the roller diameter and pressure in the powder film-forming stage are greater than the roller diameter and pressure used in the subsequent film-forming and thinning discontinuities, so that the film-forming roller 51 with a smaller roller diameter performs film-forming on the first and second preliminary film sheets with a smaller pressure to obtain a preliminary film sheet, and passes through the roller of the film-forming roller 51. The diaphragm is stretched and lengthened due to the pressure, and the film-forming roller 51 needs a larger linear speed to drive the diaphragm to move and be tensioned. By setting a film-forming roller 51 with a smaller roller diameter and smaller pressure, the film-forming roller 51 can have a larger linear speed, thereby being able to push the initial film formed after film forming to move backward at a faster speed, so as to achieve the effect of improving the production efficiency. Subsequently, the thickness and compaction degree are fine-tuned by the thinning roller 61. Since the diaphragm thinning structure 60 includes at least one pair of thinning rollers 61, that is, the diaphragm thinning structure 60 can be provided with multiple pairs of thinning rollers 61, each thinning roller 61 can adopt a smaller roller diameter and pressure, so as to be able to fine-tune the thickness and compaction degree of the diaphragm. Therefore, by setting d2>d1>d4>d3, t2>t1>t4>t3, the powder can be pressed into a film by the first roller 21 and the second roller 41 with larger roller diameter and pressure, and the thickness and compaction degree can be adjusted in sequence through the subsequent film forming roller 51 and thinning roller 61.

[0030] Specifically, when setting d4, d3, t4 and t3, 7cm≤d4≤25cm, 5cm≤d3≤20cm, 0.6 tons≤t4≤4 tons, and 0.5 tons≤t3≤3.5 tons; for example, d4 can be set to values ​​such as 7cm, 10cm, 12cm, 15cm, 18cm, 20cm or 25cm, and d3 can be set to values ​​such as 5cm, 10cm, 12cm, 15cm, 18cm, 20cm; t4 can be set to values ​​such as 0.6 tons, 1 ton, 2 tons, 3 tons, 4 tons, and t3 can be set to values ​​such as 0.5 tons, 1 ton, 2 tons, 2.5 tons, 3 tons, 3.5 tons, etc., which are not limited here, and it is sufficient to satisfy d2>d1>d4>d3 and t2>t1>t4>t3.

[0031] Furthermore, when setting the temperatures of the first roller 21, the second roller 41, the film-forming roller 51, and the thinning roller 61, according to the different compositions of the first fiber powder and the second fiber powder, the temperature T1 of the first roller 21 and the temperature T2 of the second roller 41 can be equal to the temperature T3 of the film-forming roller 51, or can be set to be greater than the temperature T3 of the film-forming roller 51, so that the first roller 21 and the second roller use a higher temperature to press the fiberized powder into a film, and then slowly adjust the film thickness and compaction degree of the first initial film sheet and the second initial film sheet under the regulation of the film-forming roller 51 at a lower temperature.

[0032] Specifically, T1 and T2 are both set between 0-200°C, and each of the first and second rollers 21 and 41 can be heated at independently controlled temperatures. T3 is set between 0-150°C, and the temperature of each film-forming roller 51 can be independently controlled. In this way, by setting the temperature of each roller in the two oppositely positioned rollers to be independently controllable, the two oppositely positioned rollers can produce different ductility after rolling the membrane on opposite sides of the membrane. The temperature T4 of the thinning roller 61 is set between 0-200°C, and each thinning roller 61 can be independently controlled, with the temperature difference between the two being less than 3°C.

[0033] Furthermore, in order to enable the thinning roller 61 to adjust the thickness and compaction of the initial diaphragm to the required thickness, the diaphragm thinning structure 60 in this embodiment includes three pairs of thinning rollers 61. Since multiple pairs of thinning rollers are used to adjust the thickness and compaction, the pressure and roller diameter used by the thinning roller 61 in this embodiment are smaller than the first roller 21 and the second roller 22, which can meet the needs of adjusting the thickness and compaction.

[0034] Among them, the thickness range of the first initial membrane sheet and the second initial membrane sheet obtained in this embodiment is 0.1-0.5mm; the thickness range of the target membrane sheet is 0.2-1.0mm. After the pressing of the membrane roller 51 and the adjustment of the thinning roller 61, the total thickness of the first initial membrane sheet and the second initial membrane sheet is within the range of 0.2-1.0mm, achieving the target membrane sheet with gradient porosity and ultra-thick thickness effect.

[0035] Further, please refer to Figure 1. In order to ensure the flatness of the edges of the formed diaphragm, the diaphragm preparation equipment 100 of this embodiment also includes a first trimming structure 70 and a second trimming structure 80; the first trimming structure 70 is arranged between the first roller and the film-forming structure 50, and is used to trim the first initial diaphragm; the second trimming structure 80 is used to trim the second initial diaphragm. In this way, through the setting of the first trimming structure 70 and the second trimming structure 80, the edges of the initially formed first initial diaphragm and the initially formed second contact diaphragm are cut so that the edges of the diaphragms before film forming can have a certain flatness, and the first initial diaphragm and the first initial diaphragm can be adjusted to have the same width, so that the edges of the initial diaphragm obtained after subsequent film forming can be directly rolled up after the thickness and compaction are adjusted.

[0036] Specifically, referring to Figure 1, the first trimming structure 70 includes a first support roller 71, a first trimming knife 72, a first powder suction nozzle 73 and a first dust removal box 74. The first support roller 71 is used to support the first initial film sheet, the first trimming knife 72 is used to cut the edge of the first initial film sheet, the first powder suction nozzle 73 is used to suck away the debris and dust generated during the cutting process of the first trimming knife 72, and the first dust removal box 74 is used to collect the debris and dust adsorbed by the powder suction nozzle. In this way, in this step, the first support roller 71 supports and pulls the film sheet, the first trimming knife 72 adjusts the flatness of the initial film sheet, and at the same time, the first powder suction nozzle 73 adsorbs and the dust removal box collects to prevent powder and debris from flying into the environment;

[0037] The second trimming structure 80 includes a second support roller 81, a second trimming knife 82, a second powder suction nozzle 83 and a second dust removal box 84. The second support roller 81 is used to support the second initial film sheet, the second trimming knife 82 is used to cut the edge of the second initial film sheet, the second powder suction nozzle 83 is used to suck away the debris and dust generated during the cutting process of the second trimming knife 82, and the second dust removal box 84 is used to collect the debris and dust adsorbed by the powder suction nozzle. In this step, the film is supported and pulled by the second support roller 81, and the second trimming knife 82 adjusts the flatness of the initial film sheet. At the same time, the adsorption of the second powder suction nozzle 83 and the collection of the dust removal box are used to prevent powder and debris from flying into the environment.

[0038] In addition, please refer to Figure 1. In order to monitor the travel speed of each roller to ensure the forming quality of the diaphragm, the diaphragm preparation equipment 100 also includes a plurality of speed detection devices 90. The plurality of speed detection devices 90 are respectively arranged in the forward direction of a pair of first rollers 11, the forward direction of the second roller 41, the film-combining roller 51 and the forward direction of the thinning roller 61, and are respectively used to monitor the forward speeds of the first roller 11, the second roller 41, the film-combining roller 51 and the film-combining roller 51. In this way, the speed detection device 90 is used to monitor the travel speeds of the first roller, the second roller 41, the film-combining roller 51 and the film-combining roller 51 to adapt to the travel speed of the diaphragm, avoid bulges and wrinkles on the diaphragm, and ensure the forming quality of the diaphragm.

[0039] Furthermore, in order to ensure the normal movement of the membrane, the membrane preparation equipment 100 further includes a plurality of guide rollers 200 to achieve traction, support and reversal of the movement of the first initial membrane, the second initial membrane, the initial combined membrane and the target membrane.

[0040] Furthermore, in order to realize the winding of the target film, the film preparation equipment 100 of this embodiment also includes a winding structure 210, which includes an automatic monitoring and correcting device 211 and a winding air shaft 212. The automatic monitoring and correcting device 211 adjusts the tension of the film to prevent the film from breaking, and the winding air shaft 212 rotates to realize the winding of the target film.

[0041] Among them, when the compaction degree of the membrane is equal to 1.6 g / cc, the porosity of the membranes obtained at different process stages ranges from 32% to 40%, that is, the porosity of the first initial membrane, the second initial membrane, the initial combined membrane and the target membrane ranges from 32% to 40%, and the porosity of the first initial membrane or the second initial membrane, the initial combined membrane and the target membrane increases successively; the tortuosity of the membranes obtained at different process stages ranges from 1.8 to 2.6, that is, the tortuosity of the first initial membrane, the second initial membrane, the initial combined membrane and the target membrane ranges from 1.8 to 2.6, and the tortuosity of the first initial membrane or the second initial membrane, the initial combined membrane and the target membrane decreases successively.

[0042] Comparisons of the porosity and tortuosity of the membranes obtained at different process stages of this embodiment with those obtained by processes in the prior art are shown in FIG2 and FIG3 .

[0043] Among them, the porosity parameters of the diaphragms obtained at different stages of this embodiment are shown in Figure 2, wherein point a is the porosity of the diaphragm prepared by the process in the prior art, point b is the porosity of the initial diaphragm obtained after the first initial diaphragm and the second initial diaphragm are combined by the diaphragm combining roller 51, point c is the porosity of the diaphragm obtained after thinning by a pair of thinning rollers 61, and point d is the porosity of the target diaphragm obtained after thinning by three pairs of thinning rollers 61; the tortuosity parameters of the diaphragms obtained at different stages are shown in Figure 3, wherein point A is the tortuosity of the diaphragm prepared by the process in the prior art, point B is the tortuosity of the initial diaphragm obtained after the first initial diaphragm and the second initial diaphragm are combined by the diaphragm combining roller 51, point C is the tortuosity of the diaphragm obtained after thinning by a pair of thinning rollers 61, and point D is the tortuosity of the target diaphragm obtained after thinning by multiple pairs of thinning rollers 61.

[0044] It can be seen from Figures 2 and 3 that the single-layer membrane prepared by the ordinary dry process has a minimum porosity of 30% and a maximum tortuosity of 2.9.

[0045] A thick electrode sheet synthesized using the film-closing roller 51 and then processed through a conventional thinning process showed a porosity and tortuosity of 32%, with a maximum tortuosity of 2.6. This indicates that the characteristic parameters of the thick film prepared by the film-closing roller 51 are superior to those of the film prepared by the conventional process.

[0046] After the initial membrane was thinned by a pair of thinning rollers 61, the porosity and tortuosity were tested to be 36% and 2, respectively. This shows that after the initial membrane was thinned by the thinning rollers 61, the performance of the resulting membrane was effectively improved.

[0047] The porosity and tortuosity of the target membrane prepared by using multiple pairs of thinning rollers 61 are 40% and 1.8, respectively.

[0048] The above data demonstrates that, after the first and second preliminary membrane sheets are combined by the combining roller 51 of this embodiment and thinned by the thinning roller 61, the resulting membrane exhibits superior porosity and tortuosity. In thick electrodes, the effective porosity and tortuosity of the electrode sheet are important performance parameters for lithium-ion battery electrodes, effectively assessing the rate performance (lithium deposition thickness and rate) and cycle rate of lithium-ion batteries. A greater porosity and a smaller tortuosity are more conducive to improving the electrode sheet's liquid absorption, and are therefore more beneficial for thick-electrode lithium-ion batteries. Therefore, the membrane prepared in this embodiment effectively improves the subsequent electrochemical performance of the battery.

[0049] The above-mentioned diaphragm preparation equipment 100 discharges the first fiberized powder through the first vibrating screen 11 and the first movable material trough 12, and presses it through the first film-forming structure 20 to obtain a first initial diaphragm, discharges the second fiberized powder through the second vibrating screen 31 and the second movable material trough 32, and presses it through the second film-forming structure 40 to obtain a second initial diaphragm, and then presses the first initial diaphragm and the second combined diaphragm under the film-forming action of the film-forming structure 50 to obtain a preliminary diaphragm, and then thins it through the roller of the diaphragm thinning structure 60 to obtain the target thickness target diaphragm we need, wherein, due to the first fiberized powder The powder and the second fiberized powder are fed separately, so that the components in the first fiberized powder and the second fiberized powder can be used in different proportions, and the first film-forming structure 20 and the second film-forming structure 40 can be pressed into films using different parameters, so that the first initial film sheet and the second touch film can have their own thickness and compaction, so that the target film obtained by the final film bonding can have two layers of film, so that the target film can have a thicker thickness, and each layer of film can have its own porosity and compaction to achieve the effect of gradient porosity. When prepared into a battery, the energy density and charge and discharge performance of the battery can be improved.

[0050] The present application further provides a method 300 for preparing a membrane in a second embodiment, as shown in FIG4 , including:

[0051] S1, pressing the first fiberized powder by the first film-forming structure 20 to obtain a first preliminary film sheet;

[0052] S2, pressing the second fiberized powder by the second film-forming structure 40 to obtain a second primary film sheet;

[0053] S3, pressing the first preliminary membrane sheet and the second preliminary membrane sheet together by the membrane-bonding structure 50 to obtain a preliminary bonded membrane sheet;

[0054] S4, the membrane thinning structure 60 performs rolling thinning on the initially assembled membrane to obtain a target membrane with a target thickness.

Claims

1. A diaphragm preparation device, comprising: A first film-forming structure for pressing a first fibrillated powder to obtain a first primary diaphragm; A second film-forming structure for pressing a second fibrillated powder to obtain a second primary diaphragm; A film combining structure disposed downstream of the first film-forming structure and the second film-forming structure for pressing the first primary diaphragm and the second primary diaphragm together to obtain a preliminarily combined diaphragm; A diaphragm thinning structure disposed downstream of the film combining structure for roll-pressing and thinning the preliminarily combined diaphragm to obtain a target diaphragm with a target thickness.

2. The diaphragm preparation device according to claim 1, wherein: The first film-forming structure includes a pair of relatively arranged first rollers with a roller diameter of d1; The second film-forming structure includes a pair of relatively arranged second rollers with a roller diameter of d2; Wherein, d2 > d1.

3. The diaphragm preparation device according to claim 2, characterized in that, 10 cm ≤ d2 ≤ 30 cm, 8 cm ≤ d1 ≤ 28 cm.

4. The diaphragm preparation device according to claim 2 or 3, characterized in that, The pressure of the first roller is t1; The pressure of the second roller is t2; Wherein, t2 > t1.

5. The diaphragm preparation device according to claim 4, characterized in that 1 ton ≤ t2 ≤ 5 tons, 0.8 ton ≤ t1 ≤ 4.5 tons.

6. The diaphragm preparation device according to claim 4, wherein: The film combining structure includes a pair of relatively arranged film combining rollers with a roller diameter of d3 and a pressure of t3; The diaphragm thinning structure includes at least a pair of relatively arranged thinning rollers with a roller diameter of d4 and a pressure of t4; Wherein, d4 > d3, t4 > t3, and d2 > d1 > d4 > d3, t2 > t1 > t4 > t3.

7. The diaphragm preparation device according to claim 6, wherein: 7 cm ≤ d4 ≤ 25 cm, 5 cm ≤ d3 ≤ 20 cm; 0.6 ton ≤ t4 ≤ 4 tons, 0.5 ton ≤ t3 ≤ 3.5 tons.

8. The diaphragm preparation device according to any one of claims 1-3 or any one of claims 5-7, characterized in that, The thickness range of the first primary diaphragm and the second primary diaphragm is 0.1 - 0.5 mm; the thickness range of the target diaphragm is 0.2 - 1.0 mm.

9. The diaphragm preparation device according to any one of claims 1-3 or any one of claims 5-7, characterized in that, The diaphragm preparation device further includes a first vibrating screen and a first movable material trough. The first vibrating screen is used to receive the first fibrillated powder and send it to the first movable material trough. The first movable material trough is used to receive the first fibrillated powder conveyed by the first vibrating screen and send it to the first film-forming structure. The first movable material trough can be switched between a vertical state and a horizontal state.

10. The diaphragm preparation device according to any one of claims 1-3 or any one of claims 5-7, characterized in that, The diaphragm preparation device further includes a second vibrating screen and a second movable material trough. The second vibrating screen is used to receive the second fibrillated powder and send it to the second movable material trough. The second movable material trough is used to receive the second fibrillated powder conveyed by the second vibrating screen and send it to the second film-forming structure. The second movable material trough can be switched between a vertical state and a horizontal state.

11. The diaphragm preparation device according to any one of claims 1-3 or any one of claims 5-7, characterized in that, The diaphragm preparation device further includes a plurality of speed detection devices respectively used to monitor the forward speeds of the first roller, the second roller, the film combining rollers, and the film combining rollers.

12. The diaphragm preparation device according to any one of claims 1-3 or any one of claims 5-7, characterized in that the porosity ranges of the first preliminary diaphragm, the second preliminary diaphragm, the preliminary combined diaphragm and the target diaphragm are 32%-40%, and the porosity of the first preliminary diaphragm or the second preliminary diaphragm, the preliminary combined diaphragm, and the target diaphragm increases in sequence; 13. The diaphragm preparation device according to any one of claims 1-3 or any one of claims 5-7, characterized in that, the tortuosity ranges of the first preliminary diaphragm, the second preliminary diaphragm, the preliminary combined diaphragm and the target diaphragm are 1.8-2.6, and the tortuosity of the first preliminary diaphragm or the second preliminary diaphragm, the preliminary combined diaphragm, and the target diaphragm decreases in sequence.

14. A method for preparing a diaphragm, characterized in that, comprising: compressing the first fibrillated powder through a first film-forming structure to obtain a first preliminary diaphragm; compressing the second fibrillated powder through a second film-forming structure to obtain a second preliminary diaphragm; compressing the first preliminary diaphragm and the second preliminary diaphragm through a film combining structure to obtain a preliminary combined diaphragm; rolling and thinning the preliminary combined diaphragm through a diaphragm thinning structure to obtain a target diaphragm with a target thickness.

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