阅读说明：本技术 长耐久极耳的制备方法以及应用 (Preparation method and application of long-lasting tab ) 是由 吕飞 申津婧 黄伟 冷旭宁 高秀玲 王驰伟 于 2021-01-12 设计创作，主要内容包括：本发明提供了一种长耐久极耳的制备方法以及应用,长耐久极耳包括极耳本体、交联聚乙烯层、极耳胶层,所述的交联聚乙烯层粘接于极耳本体的表面,所述的极耳胶层粘接于交联聚乙烯层的表面。本发明中的交联聚乙烯具有非常好的热稳定性、耐电解液腐蚀性及电化学稳定性,交联聚乙烯层中三维网状分子链结构不仅会抑制电解液中的有机溶剂对粘接处的溶胀,而且在极耳封装时可以防止极耳胶过封,防止发生镍极耳和铝层接触,降低发生电化学腐蚀的风险,从而提高极耳与铝塑膜封装可靠性、电池长期使用可靠性和寿命。(The invention provides a preparation method and application of a long-lasting tab, wherein the long-lasting tab comprises a tab body, a crosslinked polyethylene layer and a tab glue layer, the crosslinked polyethylene layer is adhered to the surface of the tab body, and the tab glue layer is adhered to the surface of the crosslinked polyethylene layer. The crosslinked polyethylene in the invention has very good thermal stability, electrolyte corrosion resistance and electrochemical stability, the three-dimensional reticular molecular chain structure in the crosslinked polyethylene layer can inhibit the swelling of an organic solvent in the electrolyte to a bonding part, and can prevent the over-sealing of tab glue during the packaging of the tab, prevent the contact of a nickel tab and an aluminum layer, reduce the risk of electrochemical corrosion, thereby improving the packaging reliability of the tab and an aluminum plastic film, and the long-term use reliability and service life of the battery.)

1. Long durable utmost point ear, its characterized in that: including utmost point ear body, crosslinked polyethylene layer, utmost point ear glue film, the crosslinked polyethylene layer bond in the surface of utmost point ear body, utmost point ear glue film bond in the surface on crosslinked polyethylene layer.

2. The long durable tab as claimed in claim 1, wherein: the crosslinked polyethylene layer is prepared by crosslinking polyethylene through irradiation or siloxane crosslinking.

3. The long durable tab of claim 2 wherein: the irradiation crosslinking comprises the following steps:

a. extruding and casting polyethylene with the weight-average molecular weight of 10 kg/mol-900 kg/mol in a double-screw extruder to obtain a polyethylene film sheet with the thickness of 0.5 mm-3 mm by casting, wherein the casting temperature is 200-250 ℃, the temperature of a cooling roller is 20-55 ℃, the extrusion rate is 0.1-20 m/min, and the speed of the cooling roller is 5-300 r/min;

b. longitudinally stretching the polyethylene film at high temperature, wherein the longitudinal stretching temperature is 70-130 ℃, and the longitudinal stretching ratio is 2-20, so as to obtain the polyethylene film with the thickness of 3-200 mu m;

c. carrying out irradiation treatment on the polyethylene film obtained after stretching by using high-energy rays at room temperature, wherein the irradiation intensity is 20 Gy/min-200 Gy/min, the total dose is 30 kGy-250 kGy, and the sealing state is required to be kept in the irradiation process so as to prevent polyethylene from being excessively crosslinked;

d. placing the polyethylene film after irradiation in an oven, standing for 0.5-24 h at the temperature of 40-110 ℃;

e. and standing the polyethylene film sheet subjected to high-temperature treatment at normal temperature for a period of time to obtain a crosslinked polyethylene layer, wherein the standing time is 0.5-24 h.

4. The long durable tab as claimed in claim 3, wherein: in the step a, the weight average molecular weight of polyethylene is 20 kg/mol-800 kg/mol, the thickness of a polyethylene casting membrane is 0.5 mm-1.5 mm, the casting temperature is 210-230 ℃, the temperature of a cooling roller is 30-50 ℃, the extrusion rate is 0.1-15 m/min, and the rotating speed of the cooling roller is 5-180 r/min; preferably, in the step b, the longitudinal stretching temperature is 90-130 ℃, the longitudinal stretching ratio is 2-15, and the thickness of the obtained polyethylene film is 5-150 μm; preferably, in the step c, the irradiation intensity is 50 Gy/min-150 Gy/min, the total dose is 40 kGy-250 Gy, preferably, in the step d, the temperature range is 50-90 ℃, the treatment time is 0.5-10 h, and preferably, in the step e, the treatment time is 0.5-10 h of standing at normal temperature.

5. The long durable tab of claim 2 wherein: the siloxane crosslinking comprises the following steps:

(1) in the double-screw extrusion with the length-diameter ratio of more than 30, 100 parts of polyethylene, 0.1-0.3 part of initiator, 0.1-1.2 parts of siloxane grafting agent and 0.4-1.0 part of catalyst are added into an extruder through a metering hopper and then are crosslinked, wherein the crosslinking temperature is 110-180 ℃;

(2) extruding the casting cross-linked polyethylene film by an extruder, wherein the casting temperature is 200-250 ℃, the temperature of a cooling roller is 20-55 ℃, the extrusion speed is 0.1-20 m/min, and the speed of the cooling roller is 5-300 r/min;

(3) and (3) carrying out longitudinal stretching treatment on the crosslinked polyethylene film at a high temperature, wherein the longitudinal stretching temperature is 70-130 ℃, the longitudinal stretching ratio is 2-15, and cooling and shaping to obtain the high-strength high-resistance polyethylene adhesive tape.

6. The long durable tab as claimed in claim 5, wherein: in the step (1), the polyethylene is 100 parts, the initiator is 0.1-0.2 part, the siloxane crosslinking agent is 0.3-0.9 part, the catalyst is 0.4-0.6 part, and the crosslinking temperature is 120-160 ℃, wherein the initiator is at least one of dicumyl peroxide (DCP), dibenzoyl peroxide (BPO), tert-butyl peroxybenzoate (TBPO), di-tert-butyl peroxide and di-tert-butyl peroxide, the siloxane grafting agent is at least one of vinyl trimethoxy silane and methacryloxypropyl trimethoxy silane, and the catalyst is at least one of dimethyl tin dilaurate, dioctyl tin dilaurate and bismuth neodecanoate; preferably, the thickness of the polyethylene film in the step (2) is 0.5 mm-1.5 mm, the casting temperature is 210-230 ℃, the temperature of a cooling roller is 30-50 ℃, the extrusion rate is 0.1-15 m/min, and the rotating speed of the cooling roller is 5 r/min-180 r/min; preferably, in the step (3), the longitudinal stretching temperature is 90-130 ℃, and the longitudinal stretching ratio is 2-12.

7. The method for manufacturing a long durable tab as claimed in any one of claims 1 to 6, wherein: the method comprises the following steps:

the method comprises the following steps: firstly, a crosslinked polyethylene layer is horizontally placed on a copper nickel-plated tab or an aluminum sheet, the gel content is 7.5-90%, and the thickness is 3-100 μm; the crosslinked polyethylene layer is prepared by the irradiation crosslinking or siloxane crosslinking preparation method;

step two: bonding the crosslinked polyethylene layer on the metal sheet in a hot pressing or hot fusion mode, wherein the hot pressing or hot fusion temperature is 160-240 ℃, the time is 4-10 s, and the crosslinked polyethylene layer is 0-5 mm wider than the tab glue layer;

step three: bonding a tab adhesive tape on a cross-linked polyethylene adhesive tape in a hot pressing or hot fusion mode, wherein the hot pressing or hot fusion temperature is 160-240 ℃, the time is 4-10 s, and the width of the tab adhesive tape is 0-5 mm smaller than that of the cross-linked polyethylene layer;

step four: and carrying out cold pressing treatment on the tab for a period of time, wherein the cold pressing temperature is 80-125 ℃, and the time is 4-10 s.

8. The method for manufacturing a long durable tab according to claim 7, wherein: in the first step, the gel content of the crosslinked polyethylene is 12.5-85%, and the thickness is 3-50 μm; preferably, in the second step, the hot-pressing or hot-melting temperature is 180-230 ℃, the time is 5-8 s, and the width of the crosslinked polyethylene layer is 0.5-4 mm larger than that of the tab glue layer; preferably, in the third step, the hot-pressing or hot-melting temperature is 180-230 ℃ and the time is 5-8 s; preferably, in the fourth step, the cold pressing temperature is 90-120 ℃ and the time is 5-8 s.

9. The ternary soft package battery prepared by using the long durable tab of any one of claims 1 to 8, wherein: the battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the capacity of the battery cell is 3 Ah-250 Ah.

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to a preparation method and application of a long-lasting tab.

Background

The soft package battery is one of the important types of lithium ion batteries, and the sealing material of the soft package battery is formed by mutually melting an aluminum-plastic film material and an adhesive tape in a polymer tab under a certain hot pressing process to achieve a sealing effect. Compared with a hard-shell battery package, the battery package has the following advantages: 1. the aluminum plastic film material is light in weight, and is at least 30% lighter than a hard shell battery, so that the specific energy is higher under the same capacity condition; 2. generally, because the heat sealing strength of the aluminum plastic film and the tab is relatively low, when the battery is out of control due to heat, the battery mainly generates bulging cracking and does not generate explosion, so the safety performance is higher; 3. the internal resistance is smaller, which is beneficial to reducing the heat generated by the battery and improving the power of the battery.

The aluminum-plastic film in the soft package battery generally comprises a three-layer structure, including: 1. the outermost nylon layer can improve the corrosion resistance of the aluminum plastic film and has good thermoplasticity; 2. the aluminum layer of the middle layer can isolate impurities such as moisture, oxygen and the like from entering the battery, and has certain mechanical strength; 3. the polypropylene layer at the innermost layer can isolate the electrolyte from contacting the aluminum layer and has electrolyte corrosion resistance. The tabs are typically made of sheet metal and film of copper plated nickel or aluminum. During packaging, the aluminum plastic film is folded in half, so that the polypropylene layer is in butt joint with the tab film, the aluminum plastic film polypropylene layer and the tab adhesive tape are mixed and melted together at a certain temperature (higher than 180 ℃), under a heat sealing pressure and a heat sealing time in a heat sealing process, and after mutual fusion and cooling for a certain time, a sealing effect is finally achieved. However, once the heat sealing process is not well controlled, the over sealing may occur, so that the nickel tab and the aluminum layer are in contact, and electrochemical corrosion may occur, which may cause damage to the aluminum layer, and finally cause serious failure problems such as liquid leakage, gas expansion and swelling.

With the increase of the energy density of the lithium ion battery, higher requirements are put forward on the reliability and durability of the tab and the aluminum plastic film package. The polymer tab film layer and the aluminum plastic film polypropylene are mutually fused and bonded, so that the reliability of the packaging structure and the long-term service life of the battery are greatly influenced.

Therefore, developing a long durable tab suitable for a high energy density lithium ion battery is one of the important bases of a power lithium ion battery.

Disclosure of Invention

In view of the above, the present invention is directed to a long durable tab for a high energy density lithium ion battery, which is beneficial to improving the service life of the tab, the reliability of the tab and an aluminum plastic film packaging structure, and the long service reliability and service life of the battery.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

long durable utmost point ear, including utmost point ear body, crosslinked polyethylene layer, utmost point ear glue film, the crosslinked polyethylene layer bond in the surface of utmost point ear body, utmost point ear glue film bond in the surface on crosslinked polyethylene layer.

Preferably, the crosslinked polyethylene layer is prepared from polyethylene by radiation crosslinking or siloxane crosslinking.

Preferably, the irradiation crosslinking comprises the following steps:

a. extruding and casting polyethylene with the weight-average molecular weight of 10 kg/mol-900 kg/mol in a double-screw extruder to obtain a polyethylene film sheet with the thickness of 0.5 mm-3 mm by casting, wherein the casting temperature is 200-250 ℃, the temperature of a cooling roller is 20-55 ℃, the extrusion rate is 0.1-20 m/min, and the speed of the cooling roller is 5-300 r/min;

b. longitudinally stretching the polyethylene film at high temperature, wherein the longitudinal stretching temperature is 70-130 ℃, and the longitudinal stretching ratio is 2-20, so as to obtain the polyethylene film with the thickness of 3-200 mu m;

c. carrying out irradiation treatment on the polyethylene film obtained after stretching by using high-energy rays at room temperature, wherein the irradiation intensity is 20 Gy/min-200 Gy/min, the total dose is 30 kGy-250 kGy, and the sealing state is required to be kept in the irradiation process so as to prevent polyethylene from being excessively crosslinked;

d. placing the polyethylene film after irradiation in an oven, standing for 0.5-24 h at the temperature of 40-110 ℃;

e. and standing the polyethylene film sheet subjected to high-temperature treatment at normal temperature for a period of time to obtain a crosslinked polyethylene layer, wherein the standing time is 0.5-24 h.

Preferably, in the step a, the weight average molecular weight of the polyethylene is 20 kg/mol-800 kg/mol, the thickness of the polyethylene casting membrane is 0.5 mm-1.5 mm, the casting temperature is 210-230 ℃, the temperature of a cooling roller is 30-50 ℃, the extrusion rate is 0.1-15 m/min, and the rotating speed of the cooling roller is 5 r/min-180 r/min; preferably, in the step b, the longitudinal stretching temperature is 90-130 ℃, the longitudinal stretching ratio is 2-15, and the thickness of the obtained polyethylene film is 5-150 μm; preferably, in the step c, the irradiation intensity is 50 Gy/min-150 Gy/min, the total dose is 40 kGy-250 Gy, preferably, in the step d, the temperature range is 50-90 ℃, the treatment time is 0.5-10 h, and preferably, in the step e, the treatment time is 0.5-10 h of standing at normal temperature.

Preferably, said silicone cross-linking comprises the steps of:

(1) in the double-screw extrusion with the length-diameter ratio of more than 30, 100 parts of polyethylene, 0.1-0.3 part of initiator, 0.1-1.2 parts of siloxane grafting agent and 0.4-1.0 part of catalyst are added into an extruder through a metering hopper and then are crosslinked, wherein the crosslinking temperature is 110-180 ℃; (ii) a

(2) Extruding the casting cross-linked polyethylene film by an extruder, wherein the casting temperature is 200-250 ℃, the temperature of a cooling roller is 20-55 ℃, the extrusion speed is 0.1-20 m/min, and the speed of the cooling roller is 5-300 r/min;

(3) and (3) carrying out longitudinal stretching treatment on the crosslinked polyethylene film at a high temperature, wherein the longitudinal stretching temperature is 70-130 ℃, the longitudinal stretching ratio is 2-15, and cooling and shaping to obtain the high-strength high-resistance polyethylene adhesive tape.

Preferably, in the step (1), the polyethylene is 100 parts, the initiator is 0.1-0.2 part, the siloxane crosslinking agent is 0.3-0.9 part, the catalyst is 0.4-0.6 part, and the crosslinking temperature is 120-160 ℃, wherein the initiator is at least one of dicumyl peroxide (DCP), dibenzoyl peroxide (BPO), tert-butyl peroxybenzoate (TBPO), di-tert-butyl peroxide and di-tert-butyl peroxide, the siloxane grafting agent is at least one of vinyl trimethoxy silane and methacryloxypropyl trimethoxy silane, and the catalyst is at least one of dimethyl tin dilaurate, dioctyl tin dilaurate and bismuth neodecanoate; preferably, in the step (2), the thickness of the polyethylene film is 0.5 mm-1.5 mm, the casting temperature is 210-230 ℃, the temperature of a cooling roller is 30-50 ℃, the extrusion rate is 0.1-15 m/min, and the rotating speed of the cooling roller is 5 r/min-180 r/min; preferably, in the step (3), the longitudinal stretching temperature is 90-130 ℃, and the longitudinal stretching ratio is 2-12.

The second purpose of the invention is to provide a method for preparing a long-lasting pole lug, which comprises the following steps:

the method comprises the following steps: firstly, a crosslinked polyethylene layer is horizontally placed on a copper nickel-plated tab or an aluminum sheet, the gel content is 7.5-90%, and the thickness is 3-100 μm; the crosslinked polyethylene layer is prepared by the irradiation crosslinking or siloxane crosslinking preparation method;

step two: bonding the crosslinked polyethylene layer on the metal sheet in a hot pressing or hot fusion mode, wherein the hot pressing or hot fusion temperature is 160-240 ℃, the time is 4-10 s, and the crosslinked polyethylene layer is 0-5 mm wider than the tab glue layer;

step three: bonding a tab adhesive tape on a cross-linked polyethylene adhesive tape in a hot pressing or hot fusion mode, wherein the hot pressing or hot fusion temperature is 160-240 ℃, the time is 4-10 s, and the width of the tab adhesive tape is 0-5 mm smaller than that of the cross-linked polyethylene layer;

step four: and carrying out cold pressing treatment on the tab for a period of time, wherein the cold pressing temperature is 80-125 ℃, and the time is 4-10 s.

Preferably, in the step one, the gel content of the crosslinked polyethylene is 12.5-85%, and the thickness is 3-50 μm; preferably, in the second step, the hot-pressing or hot-melting temperature is 180-230 ℃, the time is 5-8 s, and the width of the crosslinked polyethylene layer is 0.5-4 mm larger than that of the tab glue layer; preferably, in the third step, the hot-pressing or hot-melting temperature is 180-230 ℃ and the time is 5-8 s; preferably, in the fourth step, the cold pressing temperature is 90-120 ℃ and the time is 5-8 s.

The third purpose of the invention is to provide a ternary soft package battery prepared by using a long durable tab, which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the battery cell capacity is 3 Ah-250 Ah.

Compared with the prior art, the long-lasting pole lug has the following advantages:

the invention firstly hot presses or hot melts a layer of cross-linked polyethylene sheet on the copper nickel-plated or aluminum sheet, and then hot presses or hot melts a layer of tab glue on the cross-linked polyethylene layer. The cross-linked polyethylene which is hot-pressed or fused in the tab has very good thermal stability, electrolyte corrosion resistance and electrochemical stability, the three-dimensional reticular molecular chain structure in the cross-linked polyethylene layer can inhibit the swelling of an organic solvent in the electrolyte to the cross-linked polyethylene layer, the tab glue can be prevented from being over-sealed during the tab packaging, the nickel tab and aluminum layer contact is prevented, the risk of electrochemical corrosion is reduced, and therefore the packaging reliability of the tab and an aluminum plastic film, the long-term use reliability of a battery and the service life of the battery are improved.

Analyzing a specific principle:

the cross-linked polyethylene adhesive tape has a three-dimensional network structure (shown as formula I, formula II and formula III). Chemical bridging chains exist among the molecular chains of the crosslinked polyethylene, and when the temperature rises, the bridging chains among the molecular chains can limit the mutual movement among the molecular chains, so that the temperature resistance and the electrolyte corrosion resistance of the crosslinked polyethylene can be obviously improved. Compared with linear polyethylene, crosslinked polyethylene has the following advantages: (1) the three-dimensional reticular molecular chain structure ensures that the crosslinked polyethylene has very good heat resistance, higher electrolytic corrosion resistance and longer service life, the long-term service temperature is about 90 ℃, and the service life is more than 30 years; (2) the insulation property and the electrochemical stability are more excellent; (3) the bridging chains among the molecular chains in the crosslinked polyethylene three-dimensional network structure enable the crosslinked polyethylene three-dimensional network structure to have strong acid and alkali resistance and electrolyte resistance. The addition of the crosslinked polyethylene layer in the tab can obviously improve the electrolyte aging resistance and service life of the tab, the reliability of the tab and aluminum plastic film packaging structure, the long-term service reliability and service life of the battery and the long-term service stability of the diaphragm.

The melting point of a common tab glue polypropylene layer is 160 ℃, the packaging temperature of a battery core is about 185 ℃, particularly, the packaging head is likely to have a higher temperature when being heated, the polypropylene layer can be obviously melted, and small bubbles appear, namely, the phenomenon is caused by over-melting. The crosslinked polyethylene crosslinked net structure only becomes soft and does not shrink obviously when the temperature reaches 200-300 ℃, so that the risk of over-melting is greatly reduced.

Drawings

For a clearer explanation of the embodiments or prior art solutions of the present invention, the drawings required for the description of the embodiments or prior art will be briefly described below, and the drawings in the following description are only examples of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic view of such a long durable tab;

FIG. 2 is a graph showing the increase of peel force with aging time after the aging of the extreme ear high temperature soaking electrolytes in examples 1 to 3 and comparative example 1;

fig. 3 is a data graph showing changes of tab peeling force with aging time increase obtained by disassembly after 85 ℃, 100% SOC storage for 28 days, 56 days, 84 days after examples 4-6 and comparative example 2 are applied to a lithium ion battery.

Description of reference numerals:

a. a tab body; 2. a crosslinked polyethylene layer; 3. and a tab glue layer.

Detailed Description

Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

The present invention will be described in detail with reference to the following examples and accompanying drawings.

Example 1

The preparation method of the crosslinked polyethylene rubber strip in the embodiment by irradiation crosslinking comprises the following steps: (1) extruding and casting polyethylene with the weight-average molecular weight of 80kg/mol in a double-screw extruder to obtain a polyethylene film sheet with the thickness of 0.8mm, wherein the casting temperature is 230 ℃, the temperature of a cooling roller is 40 ℃, the extrusion rate is 1m/min, and the speed of the cooling roller is 60 r/min; (2) carrying out longitudinal stretching treatment on the polyethylene film at high temperature, wherein the stretching temperature is 100 ℃, the longitudinal (MD) stretching ratio is 10, the thickness of the polyethylene film is 20 microns, and (3) carrying out irradiation treatment on the polyethylene film at room temperature by using high-energy rays, wherein the irradiation intensity is 50Gy/min, and the total dose is 100kGy, and a sealing state needs to be kept during irradiation so as to prevent polyethylene from being excessively crosslinked; (4) placing the polyethylene film after irradiation in an oven at the temperature of 85 ℃, and standing for 2 hours; (5) standing at normal temperature for 4h to obtain a crosslinked polyethylene adhesive tape with a thickness of 20 μm and a gel content of 35.1%.

The preparation method of the long-lasting pole lug comprises the following steps: (1) firstly, a layer of cross-linked polyethylene adhesive tape with the gel content of 35.1 percent and the thickness of 20 mu m is horizontally placed on the copper nickel-plated tab; (2) and (3) bonding the crosslinked polyethylene adhesive tape on the metal sheet in a hot pressing mode, wherein the hot pressing or hot melting temperature is 210 ℃, and the time is 8 s. (3) Adhering the tab glue on a polyethylene glue strip in a hot pressing mode, wherein the hot pressing or hot melting temperature is 21 ℃, the time is 8s, and the width of the crosslinked polyethylene layer is 2mm larger than that of the tab glue; (4) and (5) cold pressing the lug, wherein the cold pressing temperature is 100 ℃, and the time is 8 s.

Example 2

The preparation method of the cross-linked polyethylene adhesive tape silicone cross-linking in the embodiment comprises the following steps: (1) in the double-screw extrusion with the length-diameter ratio of more than 30, adding corresponding materials into an extruder through a polyethylene (100 parts), an initiator dicumyl peroxide (0.1 part), a siloxane grafting agent methacryloxypropyltrimethoxysilane (0.3 part) and a catalyst dilauryl dimethyltin (0.5 part) metering hopper, and then, controlling the crosslinking temperature to be 160 ℃; (2) extruding the tape-casting crosslinked polyethylene film by an extruder, wherein the tape-casting temperature is 220 ℃, the temperature of a cooling roller is 40 ℃, the extrusion speed is 1m/min to 60 r/min; (3) and (3) carrying out longitudinal stretching treatment on the crosslinked polyethylene film at high temperature, wherein the longitudinal stretching temperature is 120 ℃, the longitudinal stretching ratio is 9, and after cooling and shaping, obtaining a crosslinked polyethylene adhesive tape with the thickness of 20 mu m, wherein the gel content of the crosslinked polyethylene adhesive tape is 45.4%. Other conditions were the same as in example 1.

Example 3

The preparation method of the crosslinked polyethylene rubber strip in the embodiment by irradiation crosslinking comprises the following steps: the total dose of irradiation crosslinking is 155kGy, the gel content of the obtained irradiation crosslinked polyethylene adhesive tape is 55.6%, and other conditions are consistent with those of example 1.

Example 4

This example obtained a gel content of 35.1% for a strip of radiation crosslinked polyethylene, otherwise conditions were consistent with example 1.

Preparing a battery: the batteries prepared in the examples and the comparative examples of the invention are soft package batteries, wherein the positive electrode is ternary nickel cobalt lithium manganate (NCM622), the negative electrode is graphite, the cell capacity is 51Ah, and the cut-off voltage is 2.75V-4.25V. The preparation method comprises the following steps of homogenizing, coating, rolling, slitting, punching and the like to obtain a battery core pole piece, combining a diaphragm and the pole piece into a battery core in the lamination process, and then completing the preparation of the soft package battery through welding, packaging, baking, injecting liquid, packaging, standing, forming and capacity grading.

High temperature storage experiment: and fully charging the battery cell after capacity grading, storing for 28 days, 56 days and 84 days at 85 ℃, then disassembling the stored battery cell, and testing the tab stripping force.

Example 5

The gel content of the crosslinked polyethylene strips prepared by silicone crosslinking in this example was 45.4%, otherwise the conditions were the same as in example 4.

Example 6

The gel content of the crosslinked polyethylene tape prepared by irradiation crosslinking in this example was 55.6%, otherwise the same as in example 4 was maintained

Comparative example 1

In this example, the tab was devoid of the first layer of cross-linked polyethylene strip, otherwise identical to example 1.

Comparative example 2

In this example, the tab was devoid of the first layer of cross-linked polyethylene strip, otherwise identical to example 4.

Fig. 1 is a schematic diagram of a long durable tab obtained by the present invention, wherein a is a tab body (copper nickel plated); and b is a crosslinked polyethylene layer which is bonded on the metal sheet in a hot-pressing mode, the width of the crosslinked polyethylene layer is 2mm wider than that of the tab glue, wherein the three-dimensional network structure in the crosslinked polyethylene glue strip enables the electrolyte resistance swelling, the heat resistance and the electrochemical stability of the crosslinked polyethylene layer to be obviously improved, the tab glue can be prevented from being over-sealed during tab packaging, the nickel tab and an aluminum layer are prevented from being contacted, the risk of electrochemical corrosion is reduced, and therefore the packaging reliability of the tab and the aluminum plastic film and the long-term use reliability and service life of the battery are improved. The layer c is a tab glue layer which is bonded on the crosslinked polyethylene layer in a hot pressing mode.

As shown in fig. 2, it can be seen from the change curves of the tab peeling force after the tab of examples 1 to 3 and comparative example 1 is subjected to high temperature soaking electrolytic aging, that when the tab is bonded with the first layer of cross-linked polyethylene adhesive tape, the tab peeling force shows a weak tendency to decrease as the number of days (electrolyte +1000ppm water) for soaking the tab in electrolyte increases at high temperature (85 ℃). In addition, as the gel content of the first layer of the crosslinked polyethylene adhesive tape increases, the tendency of the tab to reduce in peel force becomes weaker. The reason is that the gel content of the crosslinked polyethylene is increased, the density of the crosslinking points of the three-dimensional network structure is obviously increased, so that the mutual movement among molecular chains is more limited, the electrolyte swelling resistance and the aging resistance of the tab bonding part are obviously enhanced, and the falling trend of the tab stripping force is weakened.

As shown in fig. 3, as can be seen from the change data of the tab peeling force obtained by disassembling after applying examples 4 to 6 and comparative example 2 to a lithium ion battery and storing the battery at a 100% SOC for 28 days, 56 days and 84 days, when the tab is bonded with the first layer of cross-linked polyethylene adhesive tape, the tab after disassembling has a weak tendency of reduction with the increase of the high-temperature storage time, but the reduction range is very small, which indicates that the reliability of the packaging at the tab is still very good and the tab has a significant long durability. The electrochemical stability of the crosslinked polyethylene can be obviously realized by the three-dimensional reticular molecular chain in the crosslinked polyethylene, so that the tab bonding is favorably prevented from being oxidized and the structural stability is kept in the high-voltage and electrolyte environments, and the connection reliability and the service life of the tab are favorably improved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.