CN115189033A

CN115189033A - Combined film, composite negative electrode strip and preparation method of composite negative electrode strip

Info

Publication number: CN115189033A
Application number: CN202210960988.0A
Authority: CN
Inventors: 张海波; 赵瑞瑞; 彭燕秋; 叶文凯; 彭彦滔
Original assignee: Eve Energy Co Ltd
Current assignee: Eve Energy Co Ltd
Priority date: 2022-08-11
Filing date: 2022-08-11
Publication date: 2022-10-14

Abstract

The invention belongs to the technical field of metal negative electrode preparation, and discloses a combined film, a composite negative electrode strip and a preparation method of the composite negative electrode strip. The release film is configured to be arranged on one side of the metal negative electrode belt, the battery diaphragm is configured to be arranged on one side of the metal negative electrode belt, which is far away from the release film, and the edge of the release film exceeds or is flush with the edge of the metal negative electrode belt; the edges of the battery separator are beyond or flush with the edges of the metal negative strip. The adhesion of the battery separator is greater than that of the release film. And rolling the laminated battery diaphragm, the metal negative electrode belt and the release film, and peeling the release film to form the composite negative electrode belt. The combined film provided by the invention protects, adheres and supports the metal negative electrode strip through the battery diaphragm, and solves the technical difficulty that the rolled metal negative electrode strip cannot be produced due to soft structure and low strength.

Description

Combined film, composite negative electrode belt and preparation method of composite negative electrode belt

Technical Field

The invention relates to the technical field of metal negative electrode preparation, in particular to a combined film, a composite negative electrode strip and a preparation method of the composite negative electrode strip.

Background

The metal negative strip can be used as the negative electrode of a lithium battery, and the thinner lithium strip can enable the battery to achieve higher power density.

When the lithium belt with the thickness of below 50um is produced, a double-roller rolling mode is generally adopted for production, the two sides of the lithium belt are provided with the PET films which are put into a double-roller machine together for rolling to thin the lithium belt, the lithium belt needs to be peeled off from the PET films after rolling is completed, and then the lithium belt is rolled and packaged, and the rolled lithium belt is taken out for use when a battery is manufactured.

However, when the thickness of the lithium ribbon is small, for example, 1 to 20um, the lithium ribbon is too weak to be completely peeled off from the PET film, and the lithium ribbon is broken and deformed, so that the ultra-thin lithium ribbon cannot be produced, and therefore, a battery requiring the ultra-thin lithium ribbon as a negative electrode cannot be produced.

Therefore, a need exists for a composite membrane, a composite negative electrode tape, and a method for making a composite negative electrode tape that addresses the above-mentioned problems.

Disclosure of Invention

It is an object of the present invention to provide a composite film that facilitates the preparation of ultra-thin metal negative electrode strips, and thus facilitates the fabrication of batteries containing the metal negative electrode strips.

In order to achieve the purpose, the invention adopts the following technical scheme:

a composite membrane comprising:

the release film is configured to be arranged on one side of the metal negative electrode belt, and the edge of the release film exceeds or is flush with the edge of the metal negative electrode belt;

the battery diaphragm is arranged on one side, away from the release film, of the metal negative strip, the edge of the battery diaphragm exceeds or is flush with the edge of the metal negative strip, and the adhesion force of the battery diaphragm and the metal negative strip is larger than that of the release film and the metal negative strip.

As a preferable technical scheme of the combined film, the distance from the edge of the battery diaphragm to the edge of the metal negative electrode strip is not more than 4mm.

As a preferable technical scheme of the combined film, the release film is a PET film.

As a preferable technical scheme of the combined membrane, the battery diaphragm is a PP membrane, a PE membrane or a PP and PE composite membrane.

As a preferable technical scheme of the combined membrane, the thickness of the battery diaphragm is 5-40um.

As a preferable technical scheme of the combined membrane, the metal negative electrode strip is a lithium strip, a sodium strip or a potassium strip.

As a preferable technical solution of the above combined membrane, the lithium ribbon is an alloy lithium ribbon.

Another object of the present invention is to provide a composite negative electrode tape, which can realize the preparation of an ultra-thin negative electrode tape, thereby facilitating the manufacture of a battery including the composite negative electrode tape.

a composite negative electrode tape prepared using the combined film of any one of the above, comprising the metal negative electrode tape and the battery separator, the battery separator being laminated and adhered to the metal negative electrode tape, the edge of the battery separator exceeding or being flush with the edge of the metal negative electrode tape.

The invention further aims to provide a preparation method of the composite negative electrode belt, which is simple and convenient to prepare and can realize the preparation of the ultrathin negative electrode belt.

a preparation method of a composite negative electrode belt is used for preparing the composite negative electrode belt and comprises the following steps:

s1, rolling the sequentially laminated release film, the metal negative electrode strip and the battery diaphragm by using a rolling machine to form a sandwich structure;

s2, stripping the release film on the interlayer structure by using a stripping machine to obtain the composite negative electrode strip.

As a preferable technical solution of the above method for preparing the composite negative electrode tape, the interval time between the step S1 and the step S2 is not more than a preset time.

The invention has the beneficial effects that:

according to the combined film, the composite negative electrode belt and the preparation method of the composite negative electrode belt, the release film, the metal negative electrode belt and the battery diaphragm are sequentially stacked and rolled, and the battery diaphragm and the release film can support the metal negative electrode belt, so that the position of the metal negative electrode belt and a roller is kept relatively stable in the rolling process, meanwhile, the metal negative electrode belt can be protected, and the metal negative electrode belt is prevented from being adhered to the roller under pressure; the adhesive force between the release film and the metal negative electrode belt is smaller than that between the battery diaphragm and the metal negative electrode belt; after rolling, the battery diaphragm is used for providing support for the rolled thinned metal negative electrode belt, so that the release film can be torn off slowly, and the structural damage to the ultrathin metal negative electrode belt is greatly reduced; the composite negative electrode strip formed by tearing the release film does not need to peel off the diaphragm so as to keep the structure of the ultrathin lithium strip complete and undamaged, and can be directly used for manufacturing the battery cell, thereby saving the preparation process of the battery cell and improving the preparation efficiency. The combined film provided by the invention protects, adheres and supports the metal negative electrode strip through the battery diaphragm, and solves the technical difficulty that the rolled metal negative electrode strip cannot be produced due to soft structure and low strength.

Drawings

FIG. 1 is a schematic illustration of a prior art method of making a negative strip;

FIG. 2 is a schematic view of a composite film (for preparing an ultra-thin negative electrode tape) provided by an embodiment of the present invention;

FIG. 3 is a front view of a composite negative strip provided by an embodiment of the present invention;

fig. 4 is a side view of a composite negative strip provided by an embodiment of the present invention.

In the figure:

100. a roller;

1. a release film;

2. a battery separator;

3. a metal negative electrode band;

4. compounding a negative electrode belt; 41. an ultra-thin negative band; 42. passing through a roller to form a diaphragm;

5. a second release film;

6. and (4) passing through a roller to form a negative electrode belt.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or may be connected through the use of two elements or the interaction of two elements. The specific meanings of the above terms in the present invention can be understood in a specific case to those of ordinary skill in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature "on," "above" and "over" the second feature may include the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "right", "left", and the like are used based on the orientations and positional relationships shown in the drawings only for convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to be limiting.

In the prior art, as shown in fig. 1, two sides of a metal negative electrode strip 3 are coated with a release film 1 and a second release film 5, and the three are adhered together after being rolled. When the release film 1 and the second release film 5 are peeled, after one of the release film 1 and the second release film 5 is peeled from the rolled negative electrode tape 6, the reliability of the peeling between the other and the rolled negative electrode tape 6 is significantly affected by the tensile strength of the rolled negative electrode tape 6. Illustratively, the metal negative electrode belt 3 is taken as a lithium belt, after the second release film 5 is peeled from one side of the rolled negative electrode belt 6, when the thickness of the rolled negative electrode belt 6 is large (greater than 100 um), the tensile strength of the rolled negative electrode belt 6 is greater than the adhesive force between the release film 1 and the rolled negative electrode belt 6, and the rolled negative electrode belt 6 is separated from the release film 1, so that the rolled negative electrode belt 6 is not scratched or even broken; when the thickness of the negative electrode belt 6 after passing through the roller is small (less than 50 um), the tensile strength of the negative electrode belt 6 after passing through the roller is less than the adhesive force between the release film 1 and the negative electrode belt 6 after passing through the roller, and when the negative electrode belt 6 after passing through the roller is separated from the release film 1, the negative electrode belt 6 after passing through the roller can be firstly strained or even broken, and cannot be completely and stably separated. Specifically, the tensile strength of the lithium tapes with different thicknesses but 100mm widths is listed in table 1 below, and the peeling force between the lithium tapes with 100mm widths and the release film 1 with the same width is also listed, and it is apparent that when the thickness of the lithium tapes is reduced to 30um, the tensile strength is 1.5N, which is lower than the peeling force 1.6N between the lithium tapes and the release film 1, and the lithium tapes are broken when the lithium tapes are separated from the release film 1.

Table 1:

the present embodiment provides a combined film capable of conveniently manufacturing an ultra-thin negative electrode tape 41 having a thickness of 50um or less, and particularly, as shown in fig. 2, the combined film includes a release film 1 and a battery separator 2.

When the ultrathin negative electrode strip 41 is prepared, the metal negative electrode strip 3 is used as a raw material, the release film 1 is configured to be arranged on one side of the metal negative electrode strip 3, the battery diaphragm 2 is configured to be arranged on one side of the metal negative electrode strip 3, which is far away from the release film 1, and the edge of the release film 1 exceeds or is flush with the edge of the metal negative electrode strip 3; the edges of the battery separator 2 are beyond or flush with the edges of the metal negative strip 3. That is to say, the release film 1 and the battery diaphragm 2 are disposed on both sides of the metal negative strip 3, and both completely cover the metal negative strip 3, and when the laminated release film 1, the metal negative strip 3, and the battery diaphragm 2 are subjected to rolling, the release film 1 and the battery diaphragm 2 provide support and protection for both sides of the metal negative strip 3, so that the position of the metal negative strip 3 between the rolling process and the roller 100 is kept relatively stable, and at the same time, the ultra-thin negative strip 41 formed by rolling is prevented from adhering to the roller 100.

After rolling, the metal negative electrode belt 3 is pressed into an ultrathin negative electrode belt 41, and under the action of mechanical occlusion, surface adsorption and chemical bonds in the rolling process, the ultrathin negative electrode belt 41 is adhered to the release film 1, and the battery diaphragm 2 is adhered to the ultrathin negative electrode belt 41. The adhesion of battery diaphragm 2 and ultra-thin negative pole area 41 is greater than the adhesion from type membrane 1 and ultra-thin negative pole area 41, consequently, tearing off the in-process from type membrane 1, ultra-thin negative pole area 41 can firmly adhere on battery diaphragm 2, and battery diaphragm 2 provides the support for ultra-thin negative pole area 41, has greatly reduced the structural damage to ultra-thin negative pole area 41. In the embodiment, the adhesive force between the battery diaphragm 2 and the ultrathin negative electrode strip 41 is in the range of 0.4-20N/25 mm, and the adhesive force between the release film 1 and the ultrathin negative electrode strip 41 is in the range of 0.01-0.4N/25 mm, so that the ultrathin negative electrode strip 41 can be conveniently prepared. For example, the adhesion force between the battery separator 2 having a thickness of 12um and a width of 100mm and the ultra-thin negative electrode tape 41 is 144N, which is significantly greater than the peeling force 1.6N between the lithium tape and the release film 1 provided in table 1, and when the release film 1 is peeled off, the battery separator 2 can well adsorb the ultra-thin negative electrode tape 41, thereby preventing the ultra-thin negative electrode tape 41 from breaking.

As shown in fig. 3-4, the composite negative electrode tape 4 formed by the release film 1 (i.e. the composite structure of the diaphragm 42 and the ultra-thin negative electrode tape 41 after passing through the roller) is torn off, the diaphragm 42 after passing through the roller does not need to be peeled off, so that the structure of the ultra-thin negative electrode tape 41 is always kept intact, the composite negative electrode tape 4 is combined with a positive electrode plate, and the composite negative electrode tape is directly used for manufacturing a finished battery, thereby saving the battery manufacturing process and improving the manufacturing efficiency. The combined film provided by the embodiment solves the technical difficulty that the rolled ultrathin negative electrode strip 41 cannot be produced due to the soft structure and low strength through the protection, adhesion and support of the battery diaphragm 2 to the metal negative electrode strip 3 before rolling (the rolled ultrathin negative electrode strip 41), saves the battery manufacturing process and improves the production efficiency.

In the rolling process, the greater the distance that the battery diaphragm 2 exceeds the edge of the metal negative strip 3, the less easily the metal negative strip 3 is exposed out of the battery diaphragm 2 and is in direct contact with the roller 100, and the less the possibility that the metal negative strip 3 is adhered to the roller 100 is; the smaller the distance that the battery separator 2 exceeds the edge of the metal negative strip 3, the more the metal negative strip 3 easily sticks to the roller 100 beyond the battery separator 2, resulting in production scrap. In this embodiment, the distance that the edge of battery diaphragm 2 surpasses the edge of metal negative pole area 3 is not more than 4mm, can satisfy the production yield. Moreover, on the composite negative electrode strip 4 obtained after the release film 1 is peeled off, the distance of the diaphragm 42 exceeding the ultrathin negative electrode strip 41 after the separator passes through the roller meets the process requirement of the battery structure, reprocessing is not needed, so that the battery can be directly prepared by using the composite negative electrode strip 4, the battery diaphragm 2 exceeds the metal negative electrode strip 3, the short circuit of the positive electrode and the negative electrode of the battery can be avoided, the energy density of the battery prepared by the composite negative electrode strip 4 is further improved, the design space is saved, and the distance of the edge of the diaphragm 42 exceeding the edge of the ultrathin negative electrode strip 41 after the separator passes through the roller can be 1-2mm.

In this embodiment, the release film 1 is preferably a PET film, which has a high tensile strength and is not easily damaged, and can protect the ultrathin negative electrode tape 41 well. The specific preparation and components of the PET film are the prior art and are not described in detail here.

The metal negative electrode strip 3 mentioned in this embodiment may be a lithium strip, a sodium strip, a potassium strip, or the like, and the use of the above-mentioned composite film can facilitate the preparation of ultra-thin lithium strips, sodium strips, potassium strips, or the like, thereby improving the power performance of the battery. For example, lithium, sodium and potassium tapes of 10, 20 or 40um thickness are prepared. Optionally, the lithium ribbon is an alloy lithium ribbon, and particularly, the alloy lithium ribbon comprises a plurality of current collecting layers and lithium layers which are alternately stacked, and the battery manufactured by the alloy lithium ribbon is long in cycle life and small in volume expansion.

Alternatively, the above-mentioned battery separator 2 may be a PP film, a PE film, or a composite film of PP and PE. That is, the battery separator 2 is a finished separator commonly used in the prior art, and can protect the ultrathin negative electrode strip 41 and form the composite negative electrode strip 4 together with the ultrathin negative electrode strip 41, so that the battery can be directly manufactured. The small thickness of the battery diaphragm 2 is beneficial to improving the energy density of the battery, but the manufacturing difficulty is high, and the risk of short circuit of the anode and the cathode is increased. In this embodiment, the battery separator 2 has a thickness of 5-40um, and can be used to prepare and protect the ultra-thin negative electrode strip 41 to form the composite negative electrode strip 4. In the present embodiment, the thickness of the battery separator 2 is preferably one of 5um, 8um, and 10 um.

The embodiment also provides the composite negative electrode strip 4, which is prepared by using the composite film, wherein the composite negative electrode strip 4 comprises a metal negative electrode strip 3 and a battery diaphragm 2, the battery diaphragm 2 and the metal negative electrode strip 3 are stacked and adhered, and the edge of the battery diaphragm 2 exceeds or is flush with the edge of the metal negative electrode strip 3. The composite negative electrode belt 4 is a rolled product, and the battery diaphragm 2 on the composite negative electrode belt is the above post-roll diaphragm 42.

The embodiment also provides a preparation method of the composite negative electrode strip, which is used for preparing the composite negative electrode strip 4 and comprises the following steps:

s1, rolling the sequentially laminated release film 1, the metal negative electrode strip 3 and the battery diaphragm 2 by using a rolling machine to form a sandwich structure. Specifically, a battery diaphragm 2 and a release film 1 are laminated on two sides of a metal negative electrode belt 3, and the metal negative electrode belt 3 is completely coated to form a sandwich belt to be rolled; the interlayer belt is connected between a pair of rollers 100 of the roller press, along with continuous rolling of the roller press, the unwinding mechanism synchronously unwinds the metal negative electrode roll, the battery diaphragm 2 roll and the release film 1 roll, the downstream of the rollers 100 continuously outputs the interlayer structure formed by pressing the interlayer belt, and at the moment, the metal negative electrode belt 3 in the interlayer belt becomes the ultrathin negative electrode belt 41 in the interlayer structure.

In the present embodiment, the roll pressure of the roll 100 of the roll press can be adjusted in the range of 0.5 ton to 10 tons, and increasing the roll pressure enables the production of an ultra-thin negative electrode tape 41 having a smaller thickness, such as a 20um lithium tape, without damaging the interlayer tape. The faster the speed of the belt between the rollers 100, the greater the roll pressure required to produce an ultra-thin negative strip 41 of the same thickness, and a roll pressure in excess of the upper limit (10 tons) will crush the belt, in this embodiment, a speed of between 0.5 and 10 meters per minute.

And S2, stripping the release film 1 on the sandwich structure by using a stripping machine to obtain the composite negative electrode belt 4. Specifically, two sets of winding mechanisms on the stripping machine respectively wind the release film 1 and the composite negative electrode belt 4, so as to realize the stripping of the release film 1 and the composite negative electrode belt. In order to keep the peeling process and the rolling process synchronous and improve the production efficiency, in this embodiment, the winding speed of the peeling machine to the release film 1 and the composite negative electrode belt 4 is the same as the rolling speed.

Optionally, the interval time between step S1 and step S2 is not greater than the preset time. That is, after the roll pressing, the step of peeling the release film 1 is started within a predetermined time (5 min). After the step S1, the composite negative electrode belt 4 and the release film 1 are still adhered together, the adhesion is tighter after passing through the material conveying roller, and the mechanical embedding force and the molecular force between the surfaces are increased along with the passage of time, so that the stripping is less prone to happen. In this embodiment, the operation between steps S1 and S2 is continuous without time interval, so as to improve the production efficiency.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Numerous obvious variations, adaptations and substitutions will occur to those skilled in the art without departing from the scope of the invention. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A composite membrane, comprising:

the release film (1) is configured to be arranged on one side of the metal negative strip (3), and the edge of the release film (1) exceeds or is flush with the edge of the metal negative strip (3);

the battery diaphragm (2) is configured to be arranged on one side, away from the release film (1), of the metal negative strip (3), the edge of the battery diaphragm (2) exceeds or is flush with the edge of the metal negative strip (3), and the adhesion force of the battery diaphragm (2) and the metal negative strip (3) is larger than that of the release film (1) and the metal negative strip (3).

2. The combined membrane according to claim 1, characterised in that the edge of the battery separator (2) exceeds the edge of the metal negative strip (3) by a distance of not more than 4mm.

3. The combination film according to claim 1, wherein the release film (1) is a PET film.

4. The combined membrane according to claim 1, characterised in that the battery separator (2) is a PP membrane, a PE membrane or a composite membrane of PP and PE.

5. The combined membrane according to claim 1, characterised in that the thickness of the battery separator membrane (2) is 5-40um.

6. The combined membrane according to claim 1, characterised in that the metallic negative strip (3) is a lithium, sodium or potassium strip.

7. The composite membrane of claim 6, wherein said lithium ribbon is an alloyed lithium ribbon.

8. A composite negative strip, characterized in that it is produced using a composite membrane according to any one of claims 1 to 7, said composite negative strip comprising said metallic negative strip (3) and said battery separator (2), said battery separator (2) being laminated and bonded to said metallic negative strip (3), the edges of said battery separator (2) exceeding or being flush with the edges of said metallic negative strip (3).

9. A composite negative electrode tape production method for producing the composite negative electrode tape according to claim 8, characterized by comprising the steps of:

s1, rolling a release film (1), a metal negative electrode strip (3) and a battery diaphragm (2) which are sequentially laminated by using a rolling machine to form a sandwich structure;

s2, peeling the release film (1) on the sandwich structure by using a peeling machine to obtain the composite negative electrode belt (4).

10. The method of claim 9, wherein the interval between step S1 and step S2 is not longer than a predetermined time.