Diaphragm and coating device

Abstract

The utility model relates to the technical field of batteries, and discloses a diaphragm and a coating device, the diaphragm comprises a base membrane and coatings, the base membrane extends along a first direction, the base membrane is alternately bent towards two sides of the first direction to form deformation grooves, and the coatings are coated on two side surfaces of the base membrane. The electrode assembly has the beneficial effects that the structure of the base membrane is improved, and when the pole piece expands, the base membrane can release a certain expansion space, so that the deformation of the electrode assembly is avoided, and the stability of the structure of the electrode assembly is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery technology field especially a kind of diaphragm and coating device. BACKGROUND

[0002] Battery includes shell and electrode assembly in shell, electrode assembly includes positive pole, negative pole and diaphragm, wherein diaphragm is used to isolate positive pole and negative pole in electrode assembly, prevent short circuit and protect the internal material of electrode assembly from the influence of external environment and multiple functions, improve the safety, stability and service life of electrode assembly.

[0003] Generally, diaphragm will include base film and will be provided with functional coating such as ceramic coating, boehmite or polyvinylidene fluoride (pvdf) on at least one side of base film, which can further improve other properties of diaphragm.

[0004] However, the internal pole piece of electrode assembly often experiences significant volume expansion in the complex cycle process of charging and discharging. However, the base film of the widely used diaphragm design on the market is often flat on both sides, specifically, the base film of flat structure cannot adaptively release the additional space required by pole piece expansion, resulting in that diaphragm is in a relatively fixed state inside electrode assembly.

[0005] With the increase of charging and discharging times, the extrusion effect of pole piece on diaphragm becomes more and more obvious, and the extrusion increases the pre-tightening force between pole piece and diaphragm, so that the internal resistance of electrode assembly rises significantly, causing capacity attenuation of electrode assembly. More seriously, when diaphragm cannot effectively cope with pole piece expansion, continuous extrusion of pole piece on diaphragm may cause deformation of electrode assembly, affecting the stability of electrode assembly structure. SUMMARY

[0006] The utility model aims at providing a kind of diaphragm and coating device, the structure of base film is improved, when pole piece expands, base film can release certain expansion space, avoid electrode assembly deformation, improve the stability of electrode assembly structure.

[0007] In order to realize the above-mentioned purpose, the utility model provides a kind of diaphragm, including base film and coating, the base film extends along the first direction, the two sides of the base film are alternately bent and formed with deformation groove to the first direction, and the two side surfaces of the base film are coated with the coating.

[0008] Further, the thickness of the base film is 8um-10um.

[0009] Further, the width of the deformation groove along the first direction is W, the flattened length of the deformation groove in the first direction is L, and W:L=1:(1.002-1.014).

[0010] Further, the thickness H of the coating layer is 5-7 um.

[0011] Further, the base film is a polyethylene or polypropylene microporous film.

[0012] Further, the side of the coating layer opposite to the base film is flat.

[0013] Further, the base film is wavy in the first direction.

[0014] The utility model also provides a kind of coating device for making above diaphragm, including unwinding mechanism, winding mechanism, first dressing coating roll, second dressing coating roll and heating cavity, the base film roll is arranged in the unwinding mechanism, and free end is connected with the winding mechanism, the first dressing coating roll, second dressing coating roll are located between the unwinding mechanism and the winding mechanism, and are located in the heating cavity, the first dressing coating roll, second dressing coating roll can be respectively arranged in the two sides of base film and oppositely set, the first dressing coating roll is provided with a plurality of first protrusions along circumference, first recess is provided between adjacent first protrusion, the second dressing coating roll is provided with a plurality of second protrusions along circumference, second recess is provided between adjacent second protrusion, the first protrusion cooperates with the second recess, the second protrusion cooperates with the first recess;

[0015] the axial direction of the first dressing coating roll is provided with first feeding cavity, and the first protrusion is provided with first discharge channel communicated with the first feeding cavity along the radial direction of the first dressing coating roll;The axial direction of the second dressing coating roll is provided with second feeding cavity, and the second protrusion is provided with second discharge channel communicated with the second feeding cavity along the radial direction of the second dressing coating roll.

[0016] Further, the first dressing coating roll can adjust the distance between the second dressing coating roll.

[0017] Further, the first dressing coating roll and the second dressing coating roll are the same structure, and the first dressing coating roll comprises a motor, a connecting plate, a mounting seat and a roller, the motor is fixedly arranged on the connecting plate, the output end of the motor is connected with the roller, the first protrusion and the first recess are arranged on the roller, the axial direction of the roller is provided with the first feeding cavity, the first protrusion is provided with the first discharge channel communicated with the first feeding cavity along the radial direction of the roller, a strip-shaped groove is formed in the connecting plate, the length direction of the strip-shaped groove is perpendicular to the length direction of the base film, a threaded hole corresponding to the strip-shaped groove is formed in the mounting seat, a screw is connected in the threaded hole, and the connecting plate and the mounting seat are connected by the screw.

[0018] The utility model discloses an embodiment diaphragm and coating device compares with prior art, and its beneficial effect lies in: the two sides of base film along first direction are alternately bent and form and have deformation groove, promote diaphragm to be able to expand with the volume of pole piece and correspondingly expand, can release certain expansion space, avoid the pre -tightening force between pole piece and diaphragm too big, avoid electrode assembly deformation, promote the stability of electrode assembly structure. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is the structure schematic diagram of the diaphragm of the utility model embodiment;

[0020] Figure 2 It is the structure schematic diagram of the base film of the diaphragm of the utility model embodiment;

[0021] Figure 3 It is the structure principle diagram of the coating device of the utility model embodiment;

[0022] Figure 4 It is the structure schematic diagram of the first dressing coating roller of the coating device of the utility model embodiment.

[0023] In the drawing, 1, base film;11, deformation groove;2, coating;3, unwinding mechanism;4, winding mechanism;5, first dressing coating roller;500, first protrusion;501, first recess;502, first discharge channel;50, first feeding cavity;51, motor;52, connecting plate;521, strip slot;53, mounting seat;54, winding roller;55, screw;6, second dressing coating roller;60, second feeding cavity;600, second protrusion;601, second recess;602, second discharge channel;X, first direction. DETAILED DESCRIPTION

[0024] The specific implementation of the utility model will be described in further detail below in combination with the drawings and embodiments. The following embodiments are used to illustrate the utility model, but not to limit the scope of the utility model.

[0025] In the description of the utility model, it should be understood that the position relationship or location relationship indicated by the terms "upper", "lower", "front", "rear", "inner", "outer" and the like in the utility model is based on the position relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the devices and elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the utility model.

[0026] In the description of the utility model, it should be understood that the utility model uses the terms "first", "second" and the like to describe various information, but these information should not be limited to these terms, and these terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the utility model, the "first" information can also be referred to as "second" information, and similarly, the "second" information can also be referred to as "first" information.

[0027] As shown in Figures 1 to 4 The utility model preferred embodiment's diaphragm, including base membrane 1 and coating 2, base membrane 1 as core structure, base membrane 1 extends along the first direction X (i.e. length direction), base membrane 1 alternately bends to the both sides of the first direction X and is formed with deformation groove 11, i.e. base membrane 1 is arranged in the shape of wave in the first direction X, promotes diaphragm to be able to expand with the volume of pole piece and correspondingly expand, can release certain expansion space, guarantees the stability and safety inside electrode assembly. At least one side of base membrane 1 is coated with coating 2, in order to promote the close fit between diaphragm and pole piece, and can form uniform contact with pole piece, the side of coating 2 opposite to base membrane 1 is arranged in plane, optimizes the current distribution inside electrode assembly, helps to improve the energy efficiency and cycle life of electrode assembly. Coating can select ceramic coating, boehmite or pvdf and the like coating.

[0028] In some embodiments, referring to Figure 1 The thickness H of base membrane 1 is 8um-10um. Ensure that base membrane 1 can maintain light and thin while providing sufficient structural support, thereby optimizing the overall energy density of the electrode assembly. Such thickness design not only meets the requirements of the electrode assembly for the strength and stability of the diaphragm during charging and discharging cycles, but also helps to reduce the weight and volume of the electrode assembly. Preferably, in the present embodiment, the thickness of base membrane 1 is 9um.

[0029] In some embodiments, referring to Figure 2 In the first direction X, the width of deformation groove 11 is W, satisfying 15um≤W≤25um, and the length of the flattened deformation groove 11 (the flattened deformation groove 11 refers to the state of being straightened in the X direction) is L, W:L=(1.002-1.014). This width range of deformation groove 11 design not only helps to further enhance the structural strength of base membrane 1, but also more effectively adjusts the internal stress changes caused by the expansion of the pole piece during the charging and discharging process of the electrode assembly, ensuring the stability and safety of the electrode assembly. Preferably, in the present embodiment, the width of deformation groove 11 is 20um. Specifically, in order to facilitate the production of base membrane 1, base membrane 1 can be selected from polyethylene or polypropylene microporous membrane.

[0030] In some embodiments, referring to Figure 1The thickness of the coating layer 2 is 5-7 um, in this thickness range, the capacity, energy density and cycle life of the electrode assembly can be improved, and the safety of the electrode assembly is ensured. The over-thick coating layer will increase the internal resistance of the electrode, reduce the utilization rate of the active material, and cause the capacity of the electrode assembly to decrease; and the over-thin coating layer may cause the electrode structure to be unstable, and shorten the cycle life of the electrode assembly. Preferably, in the embodiment, the thickness of the coating layer 2 is 6 um.

[0031] In some embodiments, in order to increase the deformation amount of the base film, refer to Figure 1 、 Figure 2 The base film 1 is provided with a deformation groove 11 on both sides in the first direction X. That is, the base film 1 is arranged in a wave shape in the first direction X.

[0032] The utility model also provides a preparation device of diaphragm, refer to Figure 3 , including unwinding mechanism 3, winding mechanism 4, first coating roller 5, second coating roller 6 and heating cavity, wherein base film 1 is wound in unwinding mechanism 3, and free end is connected with winding mechanism 4, first coating roller 5, second coating roller 6 are located between unwinding mechanism 3 and winding mechanism 4 and are located in heating cavity, first coating roller 5, second coating roller 6 can be respectively arranged on both sides of base film 1 and are oppositely arranged, the line of connecting the axis of first coating roller 5 and second coating roller 6 is perpendicular to the length direction of base film 1, in order to facilitate the coating of both sides of base film 1 to form coating layer 2, first coating roller 5 is provided with a plurality of first protrusions 500 along the circumference, first recess 501 is arranged between adjacent first protrusions 500, second coating roller 6 is provided with a plurality of second protrusions 600 along the circumference, second recess 601 is arranged between adjacent second protrusions 600, the axial direction of first coating roller 5 is provided with first feeding cavity 50, first protrusion 500 is provided with first discharge channel 502 communicated with first feeding cavity 50 along the radial direction of first coating roller 5, the axial direction of second coating roller 6 is provided with second feeding cavity 60, second protrusion 600 is provided with second discharge channel 602 communicated with second feeding cavity 60 along the radial direction of second coating roller 6, wherein first feeding cavity 50 and second feeding cavity 60 are communicated with slurry box through pipeline, and then the both sides of base film 1 are coated to form coating layer 2.

[0033] Specifically, when the diaphragm is produced, the first coating roller 5 and the second coating roller 6 are moved towards each other under the driving of the external driving mechanism, the first protrusion 500 cooperates with the second groove 601, and the second protrusion 600 cooperates with the first groove 501, the flattened base film 1 is pressed and bonded, the surface of the base film 1 forms a uniform deformation groove 11, due to the existence of the heating cavity, the base film 1 is pressed and kept for a certain time in the heating environment (for example, the heating temperature can be about 45℃), the base film 1 is shaped, the first feeding cavity 50 and the second feeding cavity 60 are communicated with the slurry box through the pipeline, and the two sides of the base film 1 are coated through the first discharge channel 502 and the second discharge channel 602 respectively. Between the winding mechanism 4 and the first coating roller 5, a thickness setting doctor blade (not shown in the figure) is further arranged, which is arranged on the two sides of the base film 1, and can scrape off the excess coating material, so that the overall thickness of the diaphragm is uniform. In this embodiment, the overall thickness of the diaphragm is between 13um and 17um. Since the slurry box is a common setting in the coating device, it is not shown in the figure.

[0034] Further, during the production of the diaphragm, the base film 1 near the unwinding mechanism 3 is linear (flat state, the two sides of the base film are horizontal), and the base film 1 near the winding mechanism 4 is in a wave shape (with a deformation groove). In order to make the first coating roller 5 and the second coating roller 6 extrude the base film 1, the two ends of the base film 1 are uniformly stressed, therefore, tension rollers (not shown in the figure) are arranged between the unwinding mechanism 3 and the first coating roller 5, and between the first coating roller 5 and the winding mechanism 4. Specifically, the tension rollers are arranged on the upper and lower sides of the base film 1, which are used to adjust the tension of the two ends of the base film 1 during extrusion, and ensure the stability of diaphragm production.

[0035] Further, in order to facilitate the coating device to apply coating material to diaphragms of different thicknesses, the distance between the first coating roller 5 and the second coating roller 6 can be adjusted. Specifically, referring to Figure 4In the embodiment, the first coating roller 5 and the second coating roller 6 are identical in structure, the first coating roller 5 comprises a motor 51, a connecting plate 52, a mounting base 53 and a roller 54, the mounting base 53 is fixed during installation as a mounting carrier, the motor 51 is fixed on the connecting plate 52, the roller 54 is connected to an output end of the motor 51, the roller 54 is provided with a first protrusion 500 and a first recess 501, a first feeding cavity 50 is formed in an axial direction of the roller 54, a first feeding passage 502 is formed in the first protrusion 500 and communicates with the first feeding cavity 50 in a radial direction of the roller 54, a strip-shaped groove 521 is formed in the connecting plate 52 and is perpendicular to a length direction of the base film 1, a threaded hole corresponding to the strip-shaped groove 521 is formed in the mounting base 53, and a screw 55 is connected in the threaded hole. When the distance between the first coating roller 5 and the side of the base film 1 needs to be adjusted, the screw 55 is unscrewed, the connecting plate 52 is slid along the length direction of the strip-shaped groove 521, the screw 55 is screwed into the threaded hole after the distance is adjusted to a proper distance, and the adjustment mode of the second coating roller 6 is identical to that of the first coating roller 5, which is not described herein. In addition, in some other embodiments, the first coating roller 5 and the second coating roller 6 are connected to output ends of external driving mechanisms (such as air cylinders or modules) and are guided by slide rails or guide rods to drive the first coating roller 5 and the second coating roller 6 to move relatively to extrude the base film 1 to form the deformation groove 11 and coat the base film 1.

[0036] In conclusion, the embodiment of the utility model provides a diaphragm and a coating device for manufacturing the diaphragm, the base film 1 is alternately bent on both sides along the first direction X and is provided with the deformation groove 11, the diaphragm can expand correspondingly along with the volume expansion of the pole piece, a certain expansion space can be released, the pre-tightening force between the pole piece and the diaphragm is prevented from being too large, the electrode assembly is prevented from deforming, and the stability of the electrode assembly structure is improved.

[0037] The above only describes the preferred embodiments of the utility model, and it should be noted that, for ordinary skilled persons in the technical field, some improvements and replacements can be made without departing from the technical principles of the utility model, and these improvements and replacements should also be regarded as the protection scope of the utility model.

Claims

1. A diaphragm, characterized in that: It includes a base film and a coating, wherein the base film extends along a first direction, the base film is alternately bent to both sides of the first direction to form deformation grooves, and the coating is applied to both sides of the base film.

2. The diaphragm as described in claim 1, characterized in that: The thickness of the base film is 8µm-10µm.

3. The diaphragm as described in claim 1, characterized in that: The width of the deformation groove along the first direction is W, and the flattening length of the deformation groove in the first direction is L, where W:L = 1:(1.002-1.014).

4. The diaphragm as described in claim 1, characterized in that: The thickness H of the coating is 5um-7um.

5. The diaphragm as described in claim 1, characterized in that: The base membrane is a polyethylene or polypropylene microporous membrane.

6. The diaphragm as described in claim 1, characterized in that: The coating is planar on one side facing away from the base film.

7. The diaphragm as described in claim 1, characterized in that: The base film is arranged in a wavy shape in the first direction.

8. A coating apparatus for manufacturing a diaphragm according to any one of claims 1-7, characterized in that: The system includes an unwinding mechanism, a winding mechanism, a first coating roller, a second coating roller, and a heating chamber. The base film roll is disposed on the unwinding mechanism, and its free end is connected to the winding mechanism. The first coating roller and the second coating roller are disposed between the unwinding mechanism and the winding mechanism, and are located in the heating chamber. The first coating roller and the second coating roller can be respectively disposed on both sides of the base film and are arranged opposite to each other. The first coating roller has a plurality of first protrusions along its circumference, and a first groove is provided between adjacent first protrusions. The second coating roller has a plurality of second protrusions along its circumference, and a second groove is provided between adjacent second protrusions. The first protrusions cooperate with the second grooves, and the second protrusions cooperate with the first grooves. The first dressing roller has a first feeding chamber in its axial direction, and the first protrusion has a first discharge channel communicating with the first feeding chamber along the radial direction of the first dressing roller; the second dressing roller has a second feeding chamber in its axial direction, and the second protrusion has a second discharge channel communicating with the second feeding chamber along the radial direction of the second dressing coating.

9. The coating apparatus as described in claim 8, characterized in that: The first dressing roller can adjust the distance between itself and the second dressing roller.

10. The coating apparatus as claimed in claim 9, characterized in that: The first dressing coating roller has the same structure as the second dressing coating roller. The first dressing coating roller includes a motor, a connecting plate, a mounting base, and a roller. The motor is fixedly mounted on the connecting plate, and the output end of the motor is connected to the roller. The roller has a first protrusion and a first groove. The roller has a first feed chamber along its axial direction. The first protrusion has a first discharge channel communicating with the first feed chamber along the radial direction of the roller. The connecting plate has a strip groove, the length direction of which is perpendicular to the length direction of the base film. The mounting base has a threaded hole corresponding to the strip groove, and a screw is connected in the threaded hole. The connecting plate and the mounting base are connected by the screw.

Images