A winding device for lithium battery separator

Abstract

The present invention relates to the field of lithium battery diaphragms, and in particular to a winding device for lithium battery diaphragms, comprising a control processing unit, a cylindrical frame formed by at least two winding components, and a stroke control unit for driving the winding components to reciprocate along the radial direction of the cylindrical frame; wherein a pressure sensor is arranged in the surface layer of the winding components used to form the cylindrical frame, and the control processing unit is electrically connected to the stroke control unit and the pressure sensor. The present invention solves the problem of uneven release of internal stress caused by uneven pressure, and will not cause undesirable phenomena such as diaphragm collapse, deformation, rib burst, wrinkles, etc.

Description

Technical Field

[0001] The invention relates to the field of lithium battery separators, and in particular to a winding device for lithium battery separators. Background Art

[0002] During the manufacturing process of lithium-ion battery separators, there are problems such as uneven stretching and uneven thermal history, which result in uneven residual internal stress in the lithium-ion battery separators. The internal stress begins to release during the winding process of the separator, resulting in separator deformation, edge collapse, deformation, rib bursts, wrinkles and other problems. Regardless of whether the separator is directly cut for the second time or coated, the base film and coated products will be unqualified, resulting in increased manufacturing costs for the company.

[0003] Patent "CN111606096" also introduces a winding method that can reduce undesirable problems such as rib folds. However, this process has the following defects:

[0004] 1. Only using air shafts has poor precision, and the expansion joints will shake and deform under pressure because the bottom airbag is made of soft material. The compression degree of the expansion joints in different directions during the winding process is different, and the roundness of the air shaft body cannot be guaranteed during the final winding operation;

[0005] 2. It is impossible to solve the problem of releasing the stress inside the diaphragm during the rewinding process of the air shaft;

[0006] 3. The thermal conductivity of the lithium-ion battery separator itself is not high, and it is impossible to ensure that the center and inner parts of the winding can reach a uniform temperature quickly and effectively during the aging process. Summary of the invention

[0007] Problem that the invention aims to solve

[0008] The purpose of the present invention is to provide a winding device for a lithium battery separator, which is used to solve the problem that the pressure on the separator cannot be accurately controlled during the winding and rolling process of the lithium battery separator, resulting in incomplete and unbalanced stress release in the separator.

[0009] Solutions for solving problems

[0010] The present invention provides a winding device for a lithium battery separator, comprising a control processing unit, a cylindrical frame surrounded by at least two winding assemblies, and a stroke control unit for driving the winding assemblies to reciprocate along the radial direction of the cylindrical frame;

[0011] Among them, a pressure sensor is arranged in the surface layer of the winding component used to enclose a cylindrical frame, and the control processing unit is electrically connected to the stroke control unit and the pressure sensor.

[0012] Effects of the Invention

[0013] The present invention uses a cylindrical frame surrounded by multiple winding components as the winding core when the diaphragm is wound. Each winding component can independently cooperate with a pressure sensor to realize the advancement or retraction of the winding process to reduce or increase the pressure difference between the diaphragm and the diaphragm, accurately control the pressure borne by the diaphragm, and solve the problem of uneven internal stress release caused by uneven pressure, without causing undesirable phenomena such as diaphragm edge collapse, deformation, rib bursting, and wrinkles. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic structural diagram of the winding device of Example 1.

[0015] Figure 2 This is a schematic structural diagram of the winding device of Example 2.

[0016] Figure numerals: control processing unit-10; winding assembly-20; supporting arc block-21; telescopic member-22; airbag-221; travel screw-222; threaded sleeve-223; circulating water tank-30; stroke control unit-40; telescopic sleeve-50; positioning rod-60. DETAILED DESCRIPTION

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail in conjunction with examples. Before describing, it should be understood that the terms used in the specification and the appended claims should not be interpreted as limited to the general dictionary meaning, but should be interpreted based on the meaning and concept corresponding to the technical aspects of the present invention according to the principle that allows the inventor to appropriately define the terms for the best explanation. Therefore, the description proposed here is only for illustrative purposes and preferred examples, not for limiting the scope of the present invention, therefore, it should be understood that other equivalents and modifications can be made without departing from the spirit and scope of the present invention.

[0018] A winding device for a lithium battery separator, comprising a control processing unit 10, a cylindrical frame surrounded by at least two winding assemblies 20, and a stroke control unit 40 for driving the winding assemblies 20 to reciprocate along the radial direction of the cylindrical frame;

[0019] Among them, a pressure sensor is arranged in the surface layer of the winding component 20 used to enclose a cylindrical frame, and the control processing unit 10 is electrically connected to the stroke control unit 40 and the pressure sensor.

[0020] The control processing unit 10 can be any controller having a CPU processing unit, such as a PLC programmable controller, a PC programmable controller, etc.

[0021] When the lithium battery diaphragm is wound, it is wound around the cylindrical frame as the axis core, and the pressure sensor feeds back the contact pressure value between each winding component 20 and the lithium battery diaphragm to the control processing unit 10 in real time. If the pressure values ​​fed back by the pressure sensors of different winding components 20 are different, the control processing unit 10 can control the stroke control unit 40 to drive the winding component 20 to move or retract radially along the cylindrical frame to increase or decrease the contact pressure between the corresponding winding component 20 and the lithium battery diaphragm, so as to ensure that the pressure on the diaphragm in all directions is consistent, the outer circumference of the cylindrical frame maintains true roundness, and the pressure on the diaphragm is accurately controlled to ensure that the internal stress of the lithium battery diaphragm is released evenly during the winding process.

[0022] After the lithium battery diaphragm is rolled up, the outer diameter of the cylindrical frame can be controlled to decrease by 0-40mm to provide space for the diaphragm to release stress. This accelerates the release of stress inside the diaphragm when the stress is released without hindrance and without force.

[0023] The above-mentioned stroke control unit 40 can be any machine such as an electric telescopic rod, a cylinder, etc. that can realize the smooth movement of the winding assembly 20; taking the electric telescopic rod as an example, the moving end of the electric telescopic rod is fixedly connected to the winding assembly 20. When the control processing unit 10 drives the electric telescopic rod to operate, the displacement of the moving end of the electric telescopic rod along the radial direction of the cylindrical frame will drive the corresponding displacement of the winding assembly 20 to control the contact pressure between the surface of the winding assembly 20 and the lithium-ion battery diaphragm.

[0024] There is no specific limit to the number of the winding assemblies 20. As the number of winding assemblies 20 increases, the accuracy of controlling the pressure on the diaphragm can be further improved. To ensure that the outer circumference true circle degree is improved when the diaphragm is wound around the cylindrical frame as the axis core, the two ends of the adjacent winding assemblies 20 perpendicular to the radial direction of the cylindrical frame are in close contact.

[0025] In order to ensure that the winding assembly 20 maintains a certain hardness when in contact with the lithium ion diaphragm and avoid deformation, the winding assembly 20 can be made of carbon fiber or aluminum. Based on the carbon fiber bond, it has better stability in terms of specific stiffness, specific tensile strength, and thermal stability, and reduces the possibility of edge collapse, deformation, rib burst, and wrinkles caused by the instability of the material itself, deformation of the material under stress, and expansion / contraction of the material due to heating / cooling during winding, transportation, and temperature changes. Therefore, the more preferred material is carbon fiber.

[0026] Specific stiffness = elastic modulus divided by material density. Used to compare materials of different densities.

[0027] Specific tensile strength = tensile strength divided by material density.

[0028] project unit Carbon Fiber aluminum Carbon / Aluminum Comparison density (ρg / cm3 1.6 2.7 59％ Specific stiffness E / ρ 43.8 25.6 171％ Specific tensile strength σ / ρ 647 166 389％ Thermal expansion in. / in. / °F 2 13 15％

[0029] The outer diameter of the cylindrical frame may be 170-210 mm.

[0030] In order to further improve the internal stress release effect of the lithium battery diaphragm, in some embodiments, the above-mentioned winding device also includes a temperature control unit for controlling the temperature inside the cylindrical frame. Different temperature environments are created by the temperature control unit and transmitted to the lithium battery diaphragm through the winding assembly 20. Compared with only controlling the winding environment temperature of the lithium battery diaphragm, the winding center and the inner part can effectively and quickly reach a uniform temperature, thereby improving the internal stress release effect.

[0031] Furthermore, the temperature control unit can control the temperature inside the cylindrical frame to be between 5-10°C or 25-85°C; when the lithium battery separator is being rolled up, the temperature control unit can control the temperature inside the cylindrical frame to be between 5-10°C, thereby realizing low-temperature control of rolling up, freezing the molecular chain link movement of the lithium battery separator after heat processing, and reducing the deformation of the lithium battery separator during force rolling up; after the lithium battery separator is rolled up, the temperature control unit can control the temperature inside the cylindrical frame to be between higher than room temperature and lower than the melting temperature Tm of the lithium battery separator, so as to promote the release of stress in the lithium ion separator. In actual operation, it is mostly between 25-85°C.

[0032] The temperature control unit can control the temperature inside the cylindrical frame between 5-10°C or 25-85°C by temperature conduction through media such as wind, water, and chemicals; in some embodiments, the temperature control unit includes a circulating water tank 30 arranged in the cylindrical frame, and the winding component 20 and the stroke control unit 40 are both engaged with the circulating water tank 30, and the circulating water tank 30 is provided with a quick connector connected to the heat exchange / cooling station; by changing the circulating water tank 30 to communicate with the heat exchange station or the cooling station, water of different temperatures will be poured into the circulating water tank 30 to achieve the purpose of changing the temperature inside the cylindrical frame.

[0033] In some embodiments, a telescopic sleeve 50 is also sleeved around the outer periphery of the cylindrical frame to match the multiple winding assemblies 20; on the one hand, the telescopic sleeve 50 is sleeved to increase the outer roundness of the cylindrical frame surrounded by the winding assemblies 20; on the other hand, if the lithium battery diaphragm needs to be coated or re-slit and rewound after winding, the telescopic sleeve 50 can be tightened or loosened by controlling the diameter of the cylindrical frame, which is convenient for production operation. To ensure the elastic strength, the telescopic sleeve can be made of one or more of telescopic cotton, telescopic rubber, and telescopic flannel.

[0034] In certain embodiments, the winding device of the above-mentioned lithium battery separator also includes a plurality of positioning rods 60, a plurality of guide grooves which are arranged relatively still to the ground and whose groove length direction is parallel to the travel direction of the winding assembly 20, one end of the positioning rod 60 is inserted into the guide groove, and the other end is connected to the winding assembly 20; the positioning rod 60 is constrained in the travel direction by the guide groove, driving the winding assembly 20 to be constrained in the travel direction; the positioning rods 60 can be arranged on both sides of the winding assembly 20 perpendicular to the travel direction, and the axially symmetrical arrangement can increase the stability of the winding assembly 20 during displacement.

[0035] The winding assembly 20 can be any structure that can cooperate with the stroke control unit 40 to achieve stable reciprocating motion. Specifically, based on the consideration of improving displacement accuracy, the winding assembly 20 can include a support arc block 21, a telescopic member 22 whose two ends along the traveling direction are respectively connected to the inner arc surface of the support arc block 21 and the output end of the stroke control unit 40; the end of the positioning rod 60 away from the guide groove is connected to the support arc block 21, and the cylindrical frame is surrounded by the outer arc surfaces of multiple support arc blocks 21.

[0036] The above-mentioned telescopic member 22 includes an airbag 221, and the stroke control unit 40 is an air pump. The air pump pumps air into the airbag 221. Under the guidance of the positioning rod 60, the support arc block 21 can be driven to move radially outward along the cylindrical frame, thereby increasing the resistance pressure between the airbag and the winding diaphragm. When the air pump evacuates the airbag 221, the internal pressure of the airbag 221 decreases, and the hardness decreases. Under the diaphragm winding pressure, the support arc block 21 is retracted.

[0037] In addition, the telescopic member 22 includes a travel screw 222 connected to the output end of the travel control unit 40 and a threaded sleeve 223 threadedly connected to the other end of the travel screw 222; the threaded sleeve 223 is connected to the support arc block 21; the travel control unit 40 can be a servo motor. After starting the servo motor, the travel screw 222 rotates forward or reversely. Under the guidance of the positioning rod 60, the threaded sleeve 223 drives the support arc block 21 to move forward or retract.

[0038] Example 1

[0039] like Figure 1 As shown, a winding device for lithium battery separator includes a control processing unit 10; a travel control unit 40 is an air pump; a cylindrical frame surrounded by four winding components 20, each winding component 20 includes: a supporting arc block 21, and an air bag 221 whose two ends along the travel direction are respectively connected to the inner arc surface of the supporting arc block 21 and the output end of the air pump;

[0040] The cylindrical frame is surrounded by the outer arc surfaces of four support arc blocks 21. In this embodiment, gaps are left between adjacent support arc blocks 21. A pressure sensor (not shown in the figure) is set on the inner layer of the outer arc surface of the support arc block 21, and the control processing unit 10 is electrically connected to the pressure sensor and the air pump.

[0041] A telescopic sleeve 50 is also provided around the periphery of the cylindrical frame;

[0042] A circulating water tank 30 is fixed in the cylindrical frame, and eight guide grooves (not shown in the figure) whose groove directions are parallel to the moving direction of the support arc block 21 are opened on the circulating water tank 30. A positioning rod 60 is inserted in each guide groove, and the other end of the positioning rod 60 is connected to the side of the support arc block 21 perpendicular to the moving direction; the positioning rods 60 connected to the same support arc block 21 are symmetrically arranged.

[0043] When in use, S1, the 9um diaphragm after the first slitting is wound on the telescopic sleeve 50, the circulating water tank 30 is connected to the cold exchange station with a circulating water temperature of 10°C, and the diaphragm is cold-formed while winding to reduce the release of residual internal stress of the diaphragm. The winding specification is (300m*2000M);

[0044] S2, during the winding process, the pressure sensor detects the pressure values ​​of different airbags 221 in real time and transmits them to the control processing unit 10. The control processing unit 10 drives the air pump to inflate or exhaust the airbags 221 according to the pressure value, thereby increasing or decreasing the pressure value, maintaining the equal pressure on the surface of the telescopic sleeve 50, and reducing the deformation of the diaphragm due to the extrusion force;

[0045] S3, after the winding is completed, the airbag 221 is evacuated by the air pump, so that the outer diameter of the telescopic sleeve is reduced by 5mm. At the same time, the circulating water tank 30 is switched to be connected to the heat exchange station with a circulating water temperature of 80°C, and the aging is carried out for 6 hours. When the stress release in the diaphragm is unobstructed and stress is not applied, the stress in the diaphragm is accelerated to be released;

[0046] S4, the expansion sleeve 50 and the wound diaphragm after aging are fixed on the cylindrical frame, the expansion shaft is set at a temperature of 10°C, and secondary slitting and winding are performed.

[0047] Example 2

[0048] like Figure 2 As shown, the difference from Example 1 is that:

[0049] The travel control unit 40 is a servo motor;

[0050] Each winding assembly 20 includes: a carbon fiber support arc block 21, a traveling screw 222 connected to the output end of the servo motor, and a threaded sleeve 223 screwed to the other end of the traveling screw 222; the threaded sleeve 223 is connected to the support arc block 21; after the servo motor is started, the traveling screw 222 rotates forward or reversely, and under the guidance of the positioning rod 60, the threaded sleeve 223 drives the support arc block 21 to move forward or retract;

[0051] When the diaphragm is rolled up, the circulating water tank 30 is connected to the cooling station with a circulating water temperature of 5°C, and the rolling specification is 2000m*2000M;

[0052] After the diaphragm is rolled up, the expansion sleeve shrinks 30mm accordingly and the internal stress is released by aging at 35℃ for 480h.

[0053] The expansion sleeve 50 and the wound diaphragm after aging are fixed on the cylindrical frame, the expansion shaft is set at a temperature of 5°C, and the secondary slitting and winding are performed.

[0054] Comparative Example 1

[0055] Select conventional 9um products, use 170mm outer diameter paper core, buffer cotton hardness of 20HA, primary slitting tension of 1N, speed of 30m / min, winding specification of 300mm*2000M, aging time of 6h, and conduct tests. After the test, perform secondary slitting and conduct tests.

[0056] Comparative Example 2

[0057] Select conventional 9um products, use 210mm outer diameter paper core, buffer cotton hardness of 80HA, primary slitting tension of 30N, speed of 120m / min, winding specification of 2000mm*2000M, aging time of 480h, and conduct tests. After the test, perform secondary slitting and conduct tests.

[0058] The performance tests of the diaphragms of the above-mentioned Examples 1-2 and Comparative Examples 1-2 were performed according to the following method, and the results are recorded in Table 1:

[0059] Collapse and deformation: hang the aged diaphragm on the support frame, guide the film through the dual-mode film flatness measuring instrument DCM2-T2N2-L1600D-20190845, lay the diaphragm flat on the positioning line, keep one side of the diaphragm coincident with the positioning line, start the clamp, fix the diaphragm, measure the length of 6m, and use the weight standard M = (30*width mm*length m) g. Hang the weight, start the tester, read the value after 15s, select the maximum value of the reading (mm), and judge it as collapsed edge at the edge, otherwise it is judged as deformation.

[0060] Wrinkles and exposed ribs: Determine by visual inspection and touch, protrusions are exposed ribs, and fish-scale-like bumps are wrinkles.

[0061] Table 1

[0062]

[0063]

Claims

1. A winding device for a lithium battery separator, characterized in that: It comprises a control processing unit (10), a cylindrical frame surrounded by at least two winding assemblies (20) as a winding core for winding a lithium battery diaphragm, and a stroke control unit (40) for driving the winding assembly (20) to perform reciprocating motion along the radial direction of the cylindrical frame; Among them, each winding assembly (20) is used to enclose a surface layer of the cylindrical frame and is provided with a pressure sensor. Each pressure sensor feeds back the contact pressure value between each winding assembly (20) and the lithium battery diaphragm to the control processing unit (10) in real time. The control processing unit (10) is electrically connected to the stroke control unit (40) and the pressure sensor. A telescopic sleeve (50) is provided on the outer periphery of the cylindrical frame.

2. The winding device for lithium battery separator according to claim 1, characterized in that: It also includes a temperature control unit for controlling the temperature inside the cylindrical frame.

3. The winding device for lithium battery separator according to claim 2, characterized in that: The temperature control unit comprises a circulating water tank (30) arranged in the cylindrical frame, the winding assembly (20) and the stroke control unit (40) are both engaged with the circulating water tank (30), and the circulating water tank (30) is provided with a quick connector connected to a heat exchange / cooling station.

4. The winding device for lithium battery separator according to claim 2, characterized in that: The temperature control unit can control the temperature inside the cylindrical frame to be between 5-10°C or between 25-85°C.

5. The winding device for lithium battery separator according to claim 1, characterized in that: It also includes a plurality of positioning rods (60) and a plurality of guide grooves which are arranged relatively still to the ground and whose length direction is parallel to the travel direction of the winding assembly (20); one end of the positioning rod (60) is inserted into the guide groove, and the other end is connected to the winding assembly (20).

6. The lithium battery separator winding device according to claim 5, characterized in that: The winding assembly (20) comprises a supporting arc block (21), and a telescopic member (22) whose two ends along the travel direction are respectively connected to the inner arc surface of the supporting arc block (21) and the output end of the travel control unit (40); One end of the positioning rod (60) away from the guide groove is connected to the supporting arc block (21).

7. The lithium battery separator winding device according to claim 6, characterized in that: The telescopic member (22) comprises an air bag (221), and the stroke control unit (40) is an air pump, which controls the air bag (221) to inflate / deflate to drive the supporting arc block (21) to reciprocate in the radial direction of the cylindrical frame.

8. The lithium battery separator winding device according to claim 6, characterized in that: The telescopic member (22) comprises a travel screw (222) connected to the output end of the travel control unit (40) and a threaded sleeve (223) threadedly connected to the other end of the travel screw (222); the threaded sleeve (223) is connected to the support arc block (21).

9. The lithium battery separator winding device according to claim 1, characterized in that: The travel range of the winding component (20) is 0-40 mm.

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