WO2023093168A1

WO2023093168A1 - Base membrane of swelling adhesive tape for lithium battery and swelling adhesive tape for lithium battery

Info

Publication number: WO2023093168A1
Application number: PCT/CN2022/115080
Authority: WO
Inventors: 陈鹏; 王升; 褚宬成; 李力; 付晓; 刘乐文; 陈平绪
Original assignee: 东莞澳中新材料科技股份有限公司; 金发科技股份有限公司
Priority date: 2021-11-23
Filing date: 2022-08-26
Publication date: 2023-06-01
Also published as: CN114213983B; CN114213983A

Abstract

Provided in the present invention are a base membrane of a swelling adhesive tape for a lithium battery and a swelling adhesive tape for a lithium battery. The base membrane has a three-dimensional network structure, and the three-dimensional network structure is formed by crosslinking carbon-carbon saturated bonds, wherein some of the carbon atoms of the carbon-carbon saturated bonds are substituted by an ester group chain segment. The swelling adhesive tape for a lithium battery provided by the present invention comprises a base membrane and an adhesive layer composited with the base membrane, wherein the annular initial viscous force of the adhesive layer is not less than 0.1 N/25 mm. The swelling adhesive tape can be expanded at a high rate in the area in an electrolyte, can maintain a certain strength and shape in a three-dimensional direction, does not shrink at high temperatures, and can be widely applied to lithium battery production processes.

Description

Base film of swelling tape for lithium battery and swelling tape for lithium battery

technical field

The invention belongs to the technical field of swelling tapes, and in particular relates to a swelling tape for a lithium battery and a preparation method thereof.

Background technique

Cylindrical lithium batteries have been widely used in production due to their mature manufacturing process, high degree of automation, and convenience for standardized production. When it should be used in daily equipment, it often shakes and vibrates frequently during use, and there is a certain gap between the bare cell of the cylindrical lithium battery and the cylindrical shell. Shaking and vibration can easily cause the relative movement of the bare cell and the shell of the lithium battery, resulting in damage to the electrode sheet, short circuit of the battery, increase in resistance, etc., which affects the performance of the lithium battery and also poses a great safety hazard. Therefore, it is necessary to bond the bare cell and the cylindrical case and fill the gap between them.

At present, most of the base materials used in swelling tapes for lithium batteries swell in the thickness direction, and the swelling ratio in the thickness direction is limited, which cannot effectively fill the gap between the bare lithium battery cell and the cylindrical shell. Patent CN111995957A discloses an oriented polystyrene expansion tape and its preparation method. It is composed of a single-sided release oriented polystyrene film substrate and an acrylic adhesive layer. The expansion rate of the tape in the thickness direction is 400%. , this tape has low temperature resistance, shrinks at high temperature and cannot be used. Disclosed in CN111518481A is a special swelling tape for lithium batteries and its manufacturing process, including a base layer and a pressure-sensitive adhesive layer coated, the base layer containing TPU particles, EVA particles, styrene resin solution and (titanium dioxide) color paste and other substances , the prepared special swelling adhesive tape for lithium batteries can swell and deform in the length and width direction after contacting the electrolyte of lithium ion batteries, and the area becomes larger than 200% of the original area. The swelling tape prepared by this technology cannot effectively fill the lithium battery gap, and during the long-term use of the battery, the mechanics of the swollen base layer decreases and dissolves out of shape. Therefore, it is important to provide a swelling tape that can expand at a high rate in the area in the electrolyte and maintain a certain strength and shape in the three-dimensional direction, and can effectively fill the gap between the bare cell of the lithium battery and the cylindrical shell. Significance and application prospects.

Contents of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide a base film of a swelling tape for a lithium battery and a swelling tape for a lithium battery. The swelling tape can expand at a high rate in the electrolyte, and can It maintains a certain strength and shape, and does not shrink under high temperature, and can be widely used in the production process of lithium batteries.

According to the first aspect of the present invention, there is provided a base film of swelling adhesive tape for lithium batteries, the base film has a three-dimensional network structure, and the above-mentioned three-dimensional network structure is formed by cross-linking carbon-carbon saturated bonds; carbon-carbon saturated The carbon atom portion of the bond is replaced by an ester segment.

Preferably, the molecular structure of the ester group segment is selected from at least one of formate group and acetate group.

The base film provided by the present invention is formed by cross-linking carbon-carbon saturated bonds in structure, and saturated carbon chains are formed after polymerization of polymer monomers, and cross-linking reactions occur between carbon chains to form a three-dimensional network structure. When the basement membrane is soaked in the electrolyte, the organic small molecule solvent of the electrolyte can first enter the network structure of the basement membrane, so that the flexible structure of the cross-linked and stacked saturated carbon chains is stretched, the basement membrane is swollen, and the area is significantly increased. Secondly, because the carbon-carbon saturated chain is only partly replaced by the ester group segment, there is no hindrance effect of a large rigid group, and more organic solvent molecules can be absorbed, and the flexibility of the segment is better, and more sufficient absorption can also occur. Stretching so that the area swells at a greater rate. The degree of crosslinking of the saturated carbon chain is easily adjusted to a suitable range to achieve the ideal swelling effect, so that the three-dimensional network structure can absorb a large number of organic solvent molecules and swell without deformation or dissolution, so that the base film can be soaked in lithium During the process of battery electrolyte, the area swells and increases, and it is folded and thickened in the direction perpendicular to the longitudinal direction of the lithium battery cell, forming a three-dimensional structure with a certain strength, which effectively fills the gap between the cell and the shell. Moreover, the cross-linked three-dimensional network structure of the base film provided by the present invention has uniform and suitable cross-linking nodes, so the base film also has excellent high temperature resistance, and can maintain a high expansion ratio at high temperatures without shrinkage.

The carbon atom part of the carbon atom of the carbon-carbon saturated bond is replaced by an ester group segment, so that the polarity of the saturated carbon chain is improved, and its swelling performance in polar solvents is improved. The electrolyte of lithium batteries contains a large amount of organic ester solvents, and the ester-based segments are easy to absorb the ester solvents in the electrolyte, allowing them to enter a large amount into the three-dimensional network structure of the basement membrane, so that the basement membrane can swell at a high rate. At least one of the formate group and the acetate group is selected to replace the saturated carbon atom, and it is easier to absorb the ester organic solvent electrolyte.

Preferably, calculated by weight percentage, the raw materials used to prepare the base film include: 88% to 99% ethylene-ester copolymer and 0.1% to 10% crosslinking agent; calculated by weight percentage, ethylene-ester copolymer Contains 10% to 80% of ester monomers.

The polyethylene segment is easy to achieve cross-linking. By adjusting the content of ethylene-ester copolymer, cross-linking agent and ester monomer in the ethylene-ester copolymer, the swelling performance of the base film, high temperature resistance, and after soaking in the electrolyte The strength and other properties can be adjusted synergistically. In the present invention, by limiting their proportions, the base film has a suitable degree of crosslinking, maintains a certain strength after long-term immersion in the electrolyte to support and fill the lithium battery gap, and does not shrink in the high-temperature electrolyte. And it has good affinity and swelling performance to the organic electrolyte solution, and the prepared base film can effectively absorb the organic electrolyte solution and swell without dissolving in the electrolyte solution, or reducing the electrolyte solution due to the high degree of crosslinking. The solution enters, reducing the swelling ratio.

Preferably, the ene-ester copolymer is selected from at least one of ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, and ethylene-methacrylate copolymer; more preferably, the ethylene-acrylate copolymer For ethylene ethyl acrylate copolymer.

The above-mentioned base film can swell at a high rate in an electrolyte, which includes but is not limited to solvents such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate that can be used in lithium batteries. The solvent contains electrolyte salts, which may contain one or more of the following: LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiN(C _x F _2x +1SO ₂ )(C _y F _2y +1SO ₂ ) (here, x and y are natural numbers ), LiCl, LiI, lithium dioxalate borate, etc.

Preferably, the swelling ratio of the base film in the length and width direction is 130%-185%, and the swelling ratio in the thickness direction is 150%-250%.

Preferably, the above-mentioned crosslinking agent is a thermal crosslinking agent.

Preferably, the thermal crosslinking agent contains organic peroxides and/or diethylenetriamine.

The thermal crosslinking agent generates free radicals under heating conditions to undergo a free radical reaction to crosslink the polymer.

Preferably, the organic peroxide is selected from 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butylperoxycarbonate-2-ethylhexyl, 1,1 - At least one of di-tert-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl peroxide, benzoyl peroxide, and dicumyl hydroperoxide.

The invention adopts an organic peroxide thermal crosslinking agent. When the organic peroxide undergoes a crosslinking reaction, it is first decomposed by heat to generate a monovalent free radical, which is an initiating group of the crosslinking reaction. Monovalent free radicals capture hydrogen atoms from saturated carbon chains, and the resulting carbon chain free radicals combine with each other to form a crosslinked structure. The process of using the organic peroxide crosslinking agent is simple and introduces less pollutants into the base film.

Preferably, the raw materials used to prepare the base film also include: 0.1% to 2% processing aid; the processing aid contains an opening slipping aid and an antioxidant, and the opening slipping aid and the The antioxidant is compounded according to the mass ratio of 5:2, and the antioxidant includes at least one of the antioxidant 1010 and the antioxidant 168.

According to another aspect of the present invention, there is provided a swelling adhesive tape for lithium batteries, comprising the above-mentioned base film and an adhesive layer compounded with the base film, the annular initial adhesion of the adhesive layer is not less than 0.1N/25mm;

Preferably, the ring-shaped initial adhesion of the adhesive layer is not higher than 8N/25mm.

Preferably, the annular adhesive force can be 5N/25mm, 1N/25mm, 1.5N/25mm, 2N/25mm.

When the ring-shaped initial adhesive force is less than the viscous binding force required for fast winding cells, the tape cannot fix the bare battery cell. , prone to sticking roller problems. The annular initial adhesive force of the limited adhesive layer is not less than 0.1N/25mm, which can not only ensure that it will not bounce off during the process of affixing the lithium battery production process, but also prevent its adhesive force Reduced to facilitate expansion of the basement membrane to fill the gap.

Preferably, the adhesive layer is polyacrylate pressure-sensitive adhesive or hot-melt pressure-sensitive adhesive.

Preferably, the adhesive layer includes 90%-99% polyacrylate pressure-sensitive adhesive or hot-melt pressure-sensitive adhesive, 0-2% curing agent, and 0-10% other additives.

Preferably, the raw materials used to prepare polyacrylate pressure-sensitive adhesives include: at least one of copolymerizable monomers containing crosslinkable functional groups, and alkyl ester monomers, and the alkyl ester monomers are selected from the group consisting of alkyl acrylate monomers At least one of monomers and alkyl methacrylate monomers.

Preferably, the crosslinkable functional group is selected from at least one of hydroxyl group, carboxyl group, isocyanate group and amide group.

Preferably, the curing agent is at least one selected from epoxy compounds, isocyanate compounds, metal chelate compounds, metal alkoxides, metal salts, amine compounds, hydrazine compounds, and aldehyde compounds.

Preferably, the above-mentioned curing agent is an isocyanate curing agent.

Preferably, the polyacrylate pressure-sensitive adhesive is formed by cross-linking the copolymerizable monomer and an alkyl ester monomer; calculated by weight percentage, the polyacrylate pressure-sensitive adhesive contains 2% to 6% of the copolymerizable monomer and alkyl Base ester monomer 92% ~ 97%.

Limit the content of copolymerizable monomers and alkyl monomers of polyacrylate pressure-sensitive adhesives, which can achieve the ring-shaped initial adhesion of the required adhesive layer, and use it in conjunction with the above-mentioned base film to make swelling tapes for use in lithium batteries. In the production process, it can play a good role in bonding the battery cell and the shell in the electrolyte, and in the process of long-term immersion in the electrolyte after the lithium battery is manufactured, the adhesive force of the adhesive layer gradually decreases, which is beneficial It helps to release the stress of the basement membrane, so that the basement membrane has a good expansion effect.

Preferably, the number of carbon atoms in the alkyl group in the alkyl ester monomer is not less than 4.

Preferably, the number of carbon atoms in the alkyl group in the alkyl ester monomer is 6-18.

When the number of carbon atoms in the alkyl ester monomer is less than 4, the polarity of the copolymer formed by the cross-linking of the copolymerizable monomer and the alkyl ester monomer is relatively large, and the glue layer will be dissolved when it is applied to the electrolyte. invalidated. When the number of carbon atoms in the alkyl ester monomer is more than 18, the crosslinking reaction is not easy to occur.

Preferably, the raw material used to prepare the hot-melt pressure-sensitive adhesive is selected from at least one of isoprene rubber, polyisobutylene rubber, butyl rubber, ethylene-propylene rubber, styrene copolymer and tackifying resin; The copolymer does not contain polar groups; the weight-average molecular weight of the styrene copolymer is 300,000-1.5 million; the softening point of the tackifying resin is 100°C-150°C.

Selecting a polymer monomer that does not contain a polar group to make a hot-melt pressure-sensitive adhesive can ensure that it is not easy to dissolve in the electrolyte, and the weight-average molecular weight of the styrene copolymer selected for preparing the hot-melt pressure-sensitive adhesive is 300,000 to 1,500,000 g/mol, and the softening point of the tackifying resin is 100°C to 150°C, which can achieve the ring-shaped initial tack required by the adhesive layer.

According to another aspect of the present invention, there is provided a method for preparing a base film applied to a swelling adhesive tape for a lithium battery, characterized in that it comprises the following steps:

Step 1. Melt and blend the raw materials used to prepare the base film at 80°C to 100°C to obtain a melt, and extrude the melt to obtain material particles of the base film, and the temperature of the melt should not exceed 110°C;

Step 2, preparing the material particles of the base film into a thin film under heating conditions, and the heating temperature is 80°C to 100°C;

Step 3, subjecting the film to high-temperature vulcanization treatment at 130° C. to 180° C. to obtain a base film.

In the preparation method of the above-mentioned base film, according to the selected raw material of the base film, the thermal crosslinking system is designed. In step 1, the raw materials of the base film are melted and blended at 80°C to 100°C, and the temperature of the melt is controlled. If the temperature exceeds 110°C, in step 2, during the process of casting the material particles into a film, the temperature is controlled at 80°C to 100°C, which can ensure that the material will not produce crosslinking during the process of blending and casting into a film, which will affect For the forming of the matrix, after the matrix is formed, a high-temperature vulcanization treatment is carried out at 130°C to 180°C to make the polymer cross-linked. After this treatment, the saturated carbon chains in the base film structure can be uniformly cross-linked to a certain extent, and the temperature resistance of the prepared base film is improved, and can be kept at 120°C without shrinking, and the cross-linked structure enables the base film to withstand electrolyte without dissolution.

Preferably, in step 1, the melt is extruded by an extruder, and the screw aspect ratio of the extruder is 40:1-48:1.

The screw can ensure that the thermal crosslinking agent can be dispersed. Too long screw will generate more shear heat, which will cause the thermal crosslinking agent to be heated and react in advance in the screw, while too short screw will make the heat exchange The linking agent cannot be well dispersed in the polymer, which will affect the uniformity of the subsequent crosslinking reaction. The present invention limits the length-to-diameter ratio of the screw to 40:1-48:1, so that the crosslinking agent can be evenly dispersed in the polymer In addition, it can ensure the temperature of the system so that the thermal crosslinking agent will react in advance due to heat.

In general, the base film of the swelling adhesive tape for lithium batteries provided by the invention and the swelling adhesive tape for lithium batteries have the following advantages:

1. The base film of the swelling tape for lithium batteries provided by the present invention can swell at a high rate in the area direction in the electrolyte, and also swell to a certain extent in the thickness direction, so that three-dimensional deformation can occur after the base film increases in area, It is folded and thickened perpendicular to the longitudinal direction of the lithium battery cell, effectively filling the gap between the cell and the case. And it can still maintain a high expansion rate without shrinking at high temperature, and it will not deform or dissolve after being soaked in the electrolyte for a long time.

2. The present invention selectively designs the preparation process of the swelling tape base film for lithium batteries according to the raw materials of the base film, and can successfully obtain swelling performance and temperature resistance by setting the temperature and the size of the screw in the film-making step. Good basement membrane.

3. The adhesive layer of the swelling adhesive tape for lithium batteries provided by the present invention does not bounce off after adhesive application, and can effectively bond the battery cell and the base film. And it is compatible with the base film. When it is applied in the lithium battery electrolyte, after the base film swells, its adhesive performance will be reduced. Cooperating with the base film swelling, the stress generated by it will be reduced, so that the area of the base film will increase. The swelling and three-dimensional folding can effectively fill the gap of the lithium battery.

4. The invention provides that the base film and the adhesive layer are used together to make the electrolyte swelling-resistant adhesive tape for lithium batteries. The swelling adhesive tape has simple structure and excellent swelling performance, and can be widely used in industrial production of lithium batteries.

Detailed ways

In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the present invention, rather than Full examples.

Example 1

A swelling adhesive tape for a lithium battery comprises a base film and an adhesive layer compounded with the base film.

The above base film applied to the swelling tape for lithium batteries, the raw materials used to prepare the base film include 98.3% ethylene-vinyl acetate copolymer, 1% 2,5-dimethyl-2,5-bis(tert-butyl peroxide) Oxygen) hexane, 0.2% antioxidant 1010, 0.5% opening smooth agent; wherein the content of vinyl acetate monomer in the ethylene-vinyl acetate copolymer is 50%.

Above-mentioned base film is prepared by following method:

Step 1. Melt and blend the raw materials used to prepare the base film with a twin-screw extruder at 100°C to obtain a melt, extrude the melt to obtain material particles of the base film, and control the temperature of the melt to 100°C; The length-to-diameter ratio of the twin-screw extruder screw is 45:1;

Step 2, preparing the material particles of the base film into a thin film under heating conditions, and the heating temperature is 100°C;

Step 3: Perform high-temperature vulcanization treatment on the film at 130° C. to obtain a base film with a thickness of 40 μm.

The adhesive layer above contains 100 parts of polyacrylate pressure-sensitive adhesive and 0.3 part of curing agent. The polyacrylate pressure-sensitive adhesive is composed of 92% 2-ethylhexyl acrylate, 6% hydroxypropyl acrylate, and 2% acrylic acid. The curing agent is toluene diisocyanate.

The above parts and percentages are parts by weight and percentages by weight.

The above-mentioned swelling tape for lithium batteries is prepared in the following manner: a 4 μm adhesive layer is coated by dimple coating, and after drying, it is attached to the surface of the base film to prepare a swelling tape.

Example 2

The above base film applied to the swelling tape for lithium batteries, the raw materials used to prepare the base film include 88% ethylene-vinyl acetate copolymer, 10% 2,5-dimethyl-2,5-bis(tert-butyl peroxide) Oxygen) hexane, 0.5% antioxidant 1010, 1.5% opening smoothing agent; wherein the content of vinyl acetate monomer in the ethylene-vinyl acetate copolymer is 80%, and the above contents are all percentages by weight.

Above-mentioned base film is prepared by following method:

Step 1. Melt and blend the raw materials used to prepare the base film with a twin-screw extruder at 80°C to obtain a melt, extrude the melt to obtain material particles of the base film, and control the temperature of the melt to 100°C; The length-to-diameter ratio of the twin-screw extruder screw is 40:1;

Step 2, preparing the material particles of the base film into a thin film under heating conditions, and the heating temperature is 80°C;

Step 3, subjecting the film to high-temperature vulcanization treatment at 150° C. to obtain a base film.

The above adhesive layer contains 100 parts of polyacrylate pressure-sensitive adhesive and 0.1 part of curing agent. The polyacrylate pressure-sensitive adhesive is composed of 97% 2-ethylhexyl acrylate, 2% hydroxypropyl acrylate, and 1% acrylic acid. The curing agent For toluene diisocyanate.

The above parts and percentages are parts by weight and percentages by weight.

The preparation method and the thickness of the adhesive layer of the swelling adhesive tape for lithium batteries are the same as in Example 1.

Example 3

A base film applied to swelling adhesive tapes for lithium batteries, comprising 99% ethylene-vinyl acetate copolymer, 0.1% dicumyl peroxide, 0.3% antioxidant 168, and 0.6% opening slippery agent; wherein ethylene- The content of the vinyl acetate monomer in the vinyl acetate copolymer is 10%, and the above contents are all percentages by weight.

Above-mentioned base film is prepared by following method:

Step 1. Melt and blend the raw materials used to prepare the base film with a twin-screw extruder at 90°C to obtain a melt, extrude the melt to obtain material particles of the base film, and control the temperature of the melt to 100°C; The length-to-diameter ratio of the twin-screw extruder screw is 48:1;

Step 2, preparing the material particles of the base film into a thin film under heating conditions, and the heating temperature is 90°C;

Step 3, subjecting the film to a high-temperature vulcanization treatment at 180° C. to obtain a base film.

The above adhesive layer contains 100 parts of polyacrylate pressure-sensitive adhesive and 0.1 part of curing agent. The polyacrylate pressure-sensitive adhesive is composed of 95% 2-ethylhexyl acrylate, 4% hydroxypropyl acrylate, and 1% acrylic acid. The curing agent For toluene diisocyanate.

The above parts and percentages are parts by weight and percentages by weight.

Example 4

A base film applied to swelling adhesive tapes for lithium batteries, comprising 98.3% ethylene-ethyl methacrylate copolymer, 1% diisobenzene peroxide, 0.2% antioxidant 168, and 0.5% opening slippery agent; wherein ethylene - The content of the ethyl methacrylate monomer in the ethyl methacrylate copolymer is 50%, and the above contents are all percentages by weight.

Above-mentioned base film is prepared by following method:

Step 1. Melt and blend the raw materials used to prepare the base film with a twin-screw extruder at 90°C to obtain a melt, extrude the melt to obtain material particles of the base film, and control the temperature of the melt to 100°C; The length-to-diameter ratio of the twin-screw extruder screw is 45:1;

The above-mentioned adhesive layer contains 100 parts of hot-melt pressure-sensitive adhesive and 20 parts of other auxiliary agents, and the raw materials used to prepare the hot-melt pressure-sensitive adhesive include 35% styrene-butadiene-styrene block copolymer (SBS), 50% Hydrogenated styrene-butadiene block copolymer (SEBS), 15% polyisobutylene rubber; other additives are hydrogenated C5 petroleum resin (softening point is 110 ° C); the weight average molecular weight of the styrene copolymer is 300,000.

The above parts and percentages are parts by weight and percentages by weight.

Example 5

The base film used in Example 5 and its preparation method are the same as in Example 1.

The above-mentioned adhesive layer contains 100 parts of hot-melt pressure-sensitive adhesive and 30 parts of other additives, and the raw materials used to prepare the hot-melt pressure-sensitive adhesive include 43% styrene-butadiene-styrene block copolymer (SBS), 55% Hydrogenated styrene-butadiene block copolymer (SEBS), 2% polyisobutylene rubber; other additives are hydrogenated C5 petroleum resin (softening point is 100°C); the weight average molecular weight of the styrene copolymer is 1.5 million.

The above parts and percentages are parts by weight and percentages by weight.

Example 6

The base film used in Example 6 and its preparation method are the same as in Example 1.

The above-mentioned adhesive layer contains 100 parts of hot-melt pressure-sensitive adhesive and 30 parts of other auxiliary agents, and the raw materials used to prepare the hot-melt pressure-sensitive adhesive include 35% styrene-butadiene-styrene block copolymer (SBS), 50% Hydrogenated styrene-butadiene block copolymer (SEBS), 15% polyisobutylene rubber; other additives are hydrogenated C5 petroleum resin (softening point is 150°C); the weight average molecular weight of the styrene copolymer is 1 million.

The above parts and percentages are parts by weight and percentages by weight.

Comparative example 1

The difference between Comparative Example 1 and Example 1 is that the content of vinyl acetate monomer in the ethylene-vinyl acetate copolymer is 5%, and the rest are the same as Example 1.

Comparative example 2

The difference between comparative example 2 and embodiment 1 is that the content of vinyl acetate monomer in the ethylene-vinyl acetate copolymer is 90%, and the rest are all the same as embodiment 1.

Comparative example 3

The difference between Comparative Example 3 and Example 1 is that the content of ethylene-vinyl acetate copolymer is 82%, and the crosslinking agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane The content is 16%, 0.5% antioxidant 1010, 1.5% opening smooth agent; All the other are identical with embodiment 1.

Comparative example 4

The difference between Comparative Example 4 and Example 1 is that the content of ethylene-vinyl acetate copolymer is 99.28%, and the crosslinking agent 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane The content is 0.02%. All the other are identical with embodiment 1.

Comparative example 5

The difference between Comparative Example 5 and Example 1 is that the ethylene-vinyl acetate copolymer is replaced by a styrene-vinyl acetate copolymer, and the rest are the same as in Embodiment 1.

Comparative example 6

The difference between Comparative Example 6 and Example 1 is that the polyacrylate pressure-sensitive adhesive is composed of 12% hydroxypropyl acrylate, 80% 2-ethylhexyl acrylate, and 6% acrylic acid. All the other are identical with embodiment 1.

Comparative example 7

The difference between Comparative Example 7 and Example 4 is that the other additives in the hot-melt pressure-sensitive adhesive are hydrogenated C5 petroleum resin (softening point is 80° C.); the weight average molecular weight of the styrene copolymer is 200,000. All the other are identical with embodiment 4.

Comparative example 8

The difference between Comparative Example 8 and Example 1 is that in Step 3 of the preparation method of the base film, the film is vulcanized at 110° C., and the rest are the same as in Example 1.

Comparative example 9

The difference between Comparative Example 9 and Example 1 is that in step 1 of the preparation method of the base film, the length-to-diameter ratio of the twin-screw extruder used is 35:1, and the rest are the same as in Example 1.

Comparative example 10

The difference between Comparative Example 10 and Example 1 is that in step 1 of the preparation method of the base film, the length-to-diameter ratio of the twin-screw extruder used is 55:1, and the rest are the same as in Example 1.

test case 1

Swelling and shape retention ability test of base film

Test method: Cut the base films prepared in Examples 1-4, Comparative Examples 1-5 and Comparative Example 8 into samples with a length of 55mm and a width of 58mm, and soak them in an electrolyte solution at 85°C for 4 hours. Observe its swelling and shape retention ability. According to different forms, it can be divided into the following states:

For a sample that swells significantly and maintains a good shape, calculate its swelling ratio in the length and width direction in the following manner.

Swelling ratio in the longitudinal direction = (length after soaking in electrolyte/55) × 100%

Swelling ratio in the width direction = (width after soaking in electrolyte/58) × 100%

The test results are shown in Table 1:

Table 1 Swelling and shape retention ability test of base film

Among them, in the process of making the base film in ratio 10, due to the large amount of shear heat generated by the excessively long screw, the above-mentioned materials reacted in advance in the screw, unable to be extruded and granulated, and the production of the base film failed.

The above experimental results show that the base film of the hot-melt adhesive tape for lithium batteries provided by the present invention can swell at a higher rate in the high-temperature electrolyte at 85°C, and the base film maintains good strength and shape, and does not shrink due to high temperature , can be suitable for filling the gap between the lithium battery cell and the casing.

test case 2

Ring tack test

The swelling adhesive tapes for lithium batteries prepared in Examples 1-6 and Comparative Examples 6-7 were subjected to ring initial adhesion test, and the test method refers to GB/T31125-2014.

Test case 3

The swelling tapes for the lithium battery cells prepared in Examples 1-6 and Comparative Examples 6-7 were tested for popping, and the test method was as follows:

Make the swelling tape into a roll with a width of 58mm, put the sample into the winding equipment and wind the cylindrical cell, each cell uses a tape with a specification of width x length 58mm x 54mm, and wait for 4 hours after winding to observe the battery Whether the core pops open. According to different forms, it can be divided into the following states:

1. The cylindrical cell remains unchanged and maintains its original shape;

2. The cylindrical cell pops open, and the swelling tape and the cell loosen.

The test results of test case 2 and test case 2 are shown in table 2

Table 2: Ring initial adhesion and pop-up test results of swelling tape for lithium batteries

项目project	环形初粘力/(N/25mm)Ring initial adhesion/(N/25mm)	圆柱电芯状态Cylindrical cell status
实施例1Example 1	0.60.6	圆柱电芯无变化Cylindrical cell no change
实施例2Example 2	2.22.2	圆柱电芯无变化Cylindrical cell no change
实施例3Example 3	1.51.5	圆柱电芯无变化Cylindrical cell no change
实施例4Example 4	0.70.7	圆柱电芯无变化Cylindrical cell no change
实施例5Example 5	2.62.6	圆柱电芯无变化Cylindrical cell no change
实施例6Example 6	1.61.6	圆柱电芯无变化Cylindrical cell no change
对比例6Comparative example 6	0.080.08	溶胀胶带与电芯松开The swelling tape and the cell loosen
对比例7Comparative example 7	0.080.08	溶胀胶带与电芯松开The swelling tape and the cell loosen

Test case 4

The bare cell of the lithium battery was bonded with the swelling tape provided in Examples 1-6 and Comparative Examples 1-8, which swelled under the immersion in the electrolyte of the lithium battery to fill the gap between the cell and the steel case. The prepared lithium battery is evaluated for the performance of the battery drum, and judged by evaluating the voltage, internal resistance and tab of the battery under long-term, high-frequency, large-amplitude, or large-shock vibration environments. The specific method is: for each group of tests, 10 fully charged 4.2V cylindrical lithium batteries are added to the octahedral prism, and the fixed speed is 66RPM. After continuous rotation for 100 minutes, no power supply can be detected or the internal resistance has increased by more than 15%. If the performance is poor, after the battery is disassembled, if the tab of the battery breaks, it is determined that the performance of the swelling tape for lithium batteries is unqualified.

项目project	锂电池滚筒性能不良个数The number of lithium battery rollers with poor performance	锂电池极耳断裂个数The number of broken tabs of lithium battery
实施例1Example 1	00	00
实施例2Example 2	00	00
实施例3Example 3	00	00
实施例4Example 4	00	00
实施例5Example 5	00	00
实施例6Example 6	00	00
对比例1Comparative example 1	11	33
对比例3Comparative example 3	11	33
对比例5Comparative example 5	22	22
对比例6Comparative example 6	22	44
对比例7Comparative example 7	22	11
对比例8Comparative example 8	22	11

The above experimental results show that the combination of the base film and the adhesive layer provided by the present invention can be used to make a swelling adhesive tape for lithium batteries with good performance. The adhesive tape is applied to lithium batteries. In the lithium battery resistance test, it can effectively enhance the impact resistance of lithium batteries during daily use, and avoid damage to the shell and battery cells when the lithium battery is dropped or impacted. The relative movement causes the battery to fail, prolonging the service life and safety factor of the lithium battery.

The above embodiments are only used to illustrate the technical solution of the present invention rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solution of the present invention can be carried out Modification or equivalent replacement without departing from the spirit and scope of the technical solution of the present invention.

Claims

A base film applied to swelling tapes for lithium batteries, characterized in that: the base film has a three-dimensional network structure, and the three-dimensional network structure is cross-linked by carbon-carbon saturated bonds; the carbon-carbon saturated The carbon atom portion of the bond is replaced by an ester segment.
The base film applied to the swelling tape for lithium batteries according to claim 1, characterized in that: the molecular structure of the ester group segment is selected from at least one of formate group and acetate group.
The base film applied to the swelling tape for lithium batteries as claimed in claim 1 is characterized in that: calculated by weight percentage, the raw materials used to prepare the base film include: 88% to 99% ethylene-ester copolymer and 0.1 %-10% cross-linking agent; calculated by weight percentage, the ethylene-ester copolymer contains 10%-80% ester monomer.
Applied to the base film of swelling tape for lithium batteries as claimed in claim 3, wherein the ethylene-ester copolymer is selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methyl At least one of acrylate copolymers.
The base film applied to swelling adhesive tapes for lithium batteries according to claim 3, wherein the crosslinking agent is a thermal crosslinking agent.
The base film applied to swelling adhesive tapes for lithium batteries according to claim 5, wherein the thermal crosslinking agent contains organic peroxides and/or diethylenetriamine.
Applied to the base film of swelling adhesive tape for lithium batteries as claimed in claim 6, wherein said organic peroxide is selected from 2,5-dimethyl-2,5-bis(tert-butyl peroxy) Hexane, tert-butylperoxycarbonate-2-ethylhexyl, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl peroxide, peroxide At least one of benzoyl and dicumyl hydroperoxide.
The base film applied to the swelling tape for lithium batteries as claimed in claim 3, wherein the raw materials used to prepare the base film also include: 0.1% to 2% processing aid; the processing aid contains openings Slip assistant and antioxidant, said slip assistant and said antioxidant are compounded according to a mass ratio of 5:2, and said antioxidant includes at least one of antioxidant 1010 and antioxidant 168 A sort of.
A swelling adhesive tape for a lithium battery, characterized in that it comprises a base film as claimed in any one of claims 1 to 8 and an adhesive layer compounded with the base film, and the annular initial adhesion of the adhesive layer is not less than 0.1 N/25mm.
The swelling adhesive tape for lithium batteries according to claim 9, wherein, calculated by weight percentage, the adhesive layer is polyacrylate pressure-sensitive adhesive or hot-melt pressure-sensitive adhesive.
The swelling adhesive tape for lithium batteries according to claim 10, wherein the raw materials used to prepare the polyacrylate pressure-sensitive adhesive include: copolymerizable monomers containing crosslinkable functional groups, alkyl ester monomers At least one, the alkyl ester monomer is selected from at least one of alkyl acrylate monomers and alkyl methacrylate monomers.
The swelling tape for lithium batteries according to claim 11, wherein the polyacrylate pressure-sensitive adhesive is formed by cross-linking the copolymerizable monomer and the alkyl ester monomer; calculated by weight percentage, The polyacrylate pressure-sensitive adhesive contains 2%-6% of the copolymerizable monomer and 92%-97% of the alkyl ester monomer.
The swelling adhesive tape for lithium batteries according to claim 11, wherein the number of carbon atoms in the alkyl group in the alkyl ester monomer is not less than 4.
The swelling adhesive tape for lithium batteries according to claim 13, characterized in that the number of carbon atoms in the alkyl group in the alkyl ester monomer is 6-18.
The swelling adhesive tape for lithium batteries according to claim 10, wherein the raw materials used to prepare the hot-melt pressure-sensitive adhesive are selected from isoprene rubber, polyisobutylene rubber, butyl rubber, ethylene-propylene rubber, At least one of the styrene copolymers and a tackifying resin; the styrene copolymer does not contain polar groups; the weight average molecular weight of the styrene copolymer is 300,000 to 1,500,000; the tackifying resin Its softening point is from 100°C to 150°C.
The preparation method of the base film that is applied to lithium battery swelling adhesive tape as described in any one of claim 3 or 4, is characterized in that, comprises the following steps:

Step 1. Melt and blend the raw materials used to prepare the base film at 80-100°C to obtain a melt, and extrude the melt to obtain material particles of the base film. The temperature of the melt should not exceed 110°C;

Step 2, preparing the material particles of the base film into a thin film under heating conditions, and the heating temperature is 80-100°C;

Step 3: subjecting the film to high-temperature vulcanization treatment at 130-180° C. to obtain the base film.
The preparation method of base film as claimed in claim 16, characterized in that, in said step 1, said melt is extruded by an extruder, and the screw aspect ratio of said extruder is 40:1～ 48:1.