阅读说明：本技术 一种改善锂离子电池高电压体系热滥用的极片及其制备方法 (Pole piece for improving heat abuse of high-voltage system of lithium ion battery and preparation method thereof ) 是由 谢孔岩 徐昕 彭冲 李俊义 徐延铭 于 2019-11-07 设计创作，主要内容包括：本发明提供了一种改善锂离子电池高电压体系热滥用的极片及其制备方法,所述极片包括集流体、活性物质层、极耳和胶纸,所述活性物质层设置在集流体的两侧表面,并在所述集流体的两端形成空箔区域；所述极耳设置在集流体的一侧表面的空箔区域上；其中,设置有极耳的一端定义为集流体的头部,另一端定义为集流体的尾部；所述胶纸设置在集流体的头部,并覆盖所述极耳。所述极片可以有效改善高电压大容量4.45V体系电芯的140℃热滥用通过率；所述的胶纸全覆盖方法工艺简单,不需要复杂的装置设备,可以节约生产成本和时间；所述的方法在保障安全性的前提下,容量损失少于0.1％,能量密度几乎无损失。(The invention provides a pole piece for improving heat abuse of a high-voltage system of a lithium ion battery and a preparation method thereof, wherein the pole piece comprises a current collector, active substance layers, a tab and adhesive paper, wherein the active substance layers are arranged on the surfaces of two sides of the current collector, and empty foil areas are formed at two ends of the current collector; the tab is arranged on the empty foil area on one side surface of the current collector; wherein, one end provided with the pole ear is defined as the head of the current collector, and the other end is defined as the tail of the current collector; the adhesive tape is arranged at the head of the current collector and covers the lug. The pole piece can effectively improve the 140 ℃ heat abuse passing rate of a high-voltage high-capacity 4.45V system battery cell; the adhesive paper full-covering method has simple process, does not need complex equipment, and can save production cost and time; the method has the capacity loss of less than 0.1 percent and almost no energy density loss on the premise of ensuring the safety.)

1. A pole piece comprises a current collector, active substance layers, a pole lug and adhesive tape, wherein the active substance layers are arranged on the surfaces of two sides of the current collector, and hollow foil areas are formed at two ends of the current collector;

the tab is arranged on the empty foil area on one side surface of the current collector; wherein, one end provided with the pole ear is defined as the head of the current collector, and the other end is defined as the tail of the current collector;

the adhesive tape is arranged at the head of the current collector and covers the lug.

2. The pole piece according to claim 1, wherein if the active material layer is coated on one side surface of the current collector, two empty foil areas are formed on the side surface; if the active material layer is coated on the two side surfaces of the current collector, four empty foil areas are formed on the two side surfaces of the current collector.

3. The pole piece of claim 1, wherein the width of the active material layer and the width of the current collector are equal;

preferably, the thickness of the gummed paper is 10-20 microns;

preferably, the gummed paper is made of polyethylene terephthalate (PET).

4. The pole piece according to any one of claims 1 to 3, wherein the pole piece is a positive pole piece, the positive pole piece comprises a positive pole current collector, a positive pole active substance layer, a positive pole lug and adhesive tape, the positive pole active substance layer is arranged on the two side surfaces of the positive pole current collector, and a hollow foil area is formed at the two ends of the positive pole current collector;

the positive electrode lug is arranged on a hollow foil area on one side surface of the positive electrode current collector; wherein, one end provided with the anode tab is defined as the head of the anode current collector, and the other end is defined as the tail of the anode current collector;

the adhesive tape is arranged at the head of the positive current collector and covers the empty foil areas of the positive electrode lug and the head of the positive current collector.

5. The pole piece of claim 4, wherein the gummed paper covers the positive electrode tab and completely covers the empty foil area on both side surfaces of the positive electrode current collector head;

wherein the positive electrode current collector is selected from aluminum foil;

wherein the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder;

the positive active material layer is prepared by coating positive slurry on the surface of a positive current collector; the positive electrode slurry is prepared by mixing a positive electrode active material, a conductive agent, a binder and N-methyl pyrrolidone.

6. The pole piece according to any one of claims 1 to 3, wherein the pole piece is a negative pole piece, the negative pole piece comprises a negative pole current collector, a negative pole active material layer, a negative pole lug and gummed paper, the negative pole active material layer is arranged on two side surfaces of the negative pole current collector, and a hollow foil area is formed at two ends of the negative pole current collector;

the negative electrode tab is arranged on the empty foil area on one side surface of the negative electrode current collector; wherein, one end provided with a negative pole tab is defined as the head of a negative pole current collector, and the other end is defined as the tail of the negative pole current collector;

the adhesive tape is arranged at the head of the negative current collector and covers the negative electrode tab.

7. The pole piece of claim 6, wherein the negative current collector is selected from the group consisting of copper foil;

wherein the anode active material layer includes an anode active material, a conductive agent, a binder, and a thickener;

the negative electrode active material layer is prepared by coating negative electrode slurry on the surface of a negative electrode current collector; the negative electrode slurry is prepared by mixing a negative electrode active material, a conductive agent, a binder, a thickening agent and deionized water.

8. A method of making a pole piece, the method comprising:

(1) covering adhesive tape on the empty foil area of the positive current collector provided with one end of the positive electrode lug, completely covering the empty foil area on the surfaces of the two sides of the positive current collector provided with one end of the positive electrode lug, and preparing the pole piece.

9. The method of manufacturing according to claim 8, wherein the method further comprises:

(2) and covering adhesive tape on the empty foil area of the negative current collector at one end of the negative electrode lug, wherein the adhesive tape completely covers the surface of the negative electrode lug, and preparing to obtain the pole piece.

10. The production method according to claim 8 or 9, wherein the method comprises the steps of:

(1-1) mixing a positive electrode active material, a conductive agent and a binder, adding N-methyl pyrrolidone, stirring and dispersing to prepare positive electrode slurry; coating positive electrode slurry on the surfaces of two sides of a positive electrode current collector, reserving empty foil areas on two sides of the positive electrode current collector, arranging a positive electrode lug on the empty foil area on the surface of one side of the positive electrode current collector, covering adhesive paper on the empty foil area of the positive electrode current collector at one end provided with the positive electrode lug, and completely covering the adhesive paper on the empty foil areas on the surfaces of two sides of the positive electrode current collector at one end provided with the positive electrode lug to prepare the pole piece;

preferably, the method comprises the steps of:

(2-1) mixing the negative electrode active material, the conductive agent, the binder and the thickening agent, adding deionized water, stirring and dispersing to prepare negative electrode slurry; and coating the negative electrode slurry on the surfaces of two sides of a negative electrode current collector, reserving empty foil areas on the two sides of the negative electrode current collector, arranging a negative electrode lug on the empty foil area on the surface of one side of the negative electrode current collector, and covering adhesive paper on the negative electrode lug to prepare the pole piece.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a pole piece for improving heat abuse of a high-voltage system of a lithium ion battery and a preparation method thereof.

Background

The lithium ion battery has the characteristics of high energy density, high power density, good cycle performance, no memory effect, environmental protection and the like, is widely applied to various electronic products such as mobile phones, mobile cameras, notebook computers, mobile phones and the like, and is expected to become an energy supply system of future electric automobiles.

At present, the safety of the lithium ion battery is one of the biggest obstacles for commercialization of large lithium ion batteries, and the reasons of explosion, fire and the like are all caused by the fact that the thermal abuse of the battery cannot pass. The traditional methods improve the thermal stability of the anode material and the electrolyte by doping coating, all solid-state and other modes, and the methods not only increase the cost of the battery, but also have immature technology and have great influence on the electrical property of the battery core. In view of the above, it is necessary to provide a method for improving thermal abuse of a lithium ion battery.

Disclosure of Invention

The inventor of the application finds that the passing rate of the battery cells of the current high-voltage high-capacity 4.45V system stored in the oven at 140 ℃ for 0.5 hour is low, and the safety of the lithium ion battery is seriously influenced. Although the safety performance can be improved by an electrolyte or the like, the safety is improved and the electrical performance is hardly guaranteed, for example, the safety is improved by sacrificing the energy density of the battery.

In order to overcome the defects in the prior art, in particular to the problem that the current high-voltage high-capacity 4.45V system battery cell cannot pass through after being stored in an oven at 140 ℃ for 0.5 hour, the invention provides a pole piece for improving high-voltage heat abuse of a lithium ion battery and a preparation method thereof, wherein the pole piece can improve the safety of the high-voltage high-capacity 4.45V system battery cell under the condition of ensuring that the electrical property is not lost, the method is to improve the safety of the battery cell by completely covering a layer of adhesive paper on a hollow foil area on the surface of a current collector at one end of a lug (particularly at the end of a positive lug), so that the problem that the high-voltage high-capacity 4.45V system battery cell cannot pass through after being stored in the oven at 140 ℃ for 0.5 hour is solved, and the energy density is almost not lost under the condition that the capacity loss is less.

The purpose of the invention is realized by the following technical scheme:

a pole piece comprises a current collector, active substance layers, a pole lug and adhesive tape, wherein the active substance layers are arranged on the surfaces of two sides of the current collector, and hollow foil areas are formed at two ends of the current collector;

the tab is arranged on the empty foil area on one side surface of the current collector; wherein, one end provided with the pole ear is defined as the head of the current collector, and the other end is defined as the tail of the current collector;

the adhesive tape is arranged at the head of the current collector and covers the lug.

According to the invention, the pole piece can improve the condition of high-voltage heat abuse of the lithium ion battery.

According to the present invention, the length of the active material layer is smaller than that of the current collector, so that a current collector not covered with the active material layer can be formed at both ends of the current collector, which is defined as a hollow foil area.

Exemplarily, if the active material layer is coated on one side surface of the current collector, two empty foil areas are formed on the side surface; if the active material layer is coated on the two side surfaces of the current collector, four empty foil areas are formed on the two side surfaces of the current collector.

According to the present invention, the width of the active material layer and the width of the current collector are equal.

According to the present invention, the thickness of the active material layer and the current collector is not particularly defined, and may be selected as known in the art.

According to the invention, the thickness of the gummed paper is 10-20 microns, for example 15-18 microns, such as 16 microns.

According to the invention, the gummed paper is made of polyethylene terephthalate (PET), and the gummed paper can be purchased from commercial sources.

In the present invention, by introducing the gummed paper at the head of the current collector, it is possible to achieve an improvement in the heat abuse performance with almost no loss of energy density, that is, such an operation does not cause a loss or a reduction in the energy density of the lithium ion battery, which is completely different from the prior art that the safety of the battery is improved by sacrificing the energy density.

According to the invention, no special treatment is carried out on the tail part of the current collector, namely the tail part is not provided with the adhesive paper full coverage, so that on one hand, the energy density of the battery is partially lost due to the adhesive paper full coverage arranged on the tail part, and meanwhile, the phenomena of low capacity and the like are caused. On the other hand, the gummed paper is arranged at the head and the tail of the current collector, so that the thickness of the battery is influenced. More importantly, the inventor finds that in the process of thermal abuse, the thermal shrinkage of the separator at the head of the current collector is more serious (as shown in fig. 4), the thermal shrinkage of the separator can cause internal short circuits inside the battery, and the generated heat can continuously push a series of side reactions to increase the risk of thermal runaway of the battery. Fig. 4 is a result of dissecting the cell after a heat abuse test on fresh (about 50% SOC) and 70% SOC batteries, and disassembling the battery that passed the test, and it was found that the closer to the fold-in, the more severe the separator shrinkage.

According to one embodiment of the present invention, the pole piece may be a positive pole piece, the positive pole piece includes a positive pole current collector, a positive pole active material layer, a positive pole tab and adhesive tapes, the positive pole active material layer is disposed on two side surfaces of the positive pole current collector, and a hollow foil area is formed at two ends of the positive pole current collector;

the positive electrode lug is arranged on a hollow foil area on one side surface of the positive electrode current collector; wherein, one end provided with the anode tab is defined as the head of the anode current collector, and the other end is defined as the tail of the anode current collector;

the adhesive tape is arranged at the head of the positive current collector and covers the empty foil areas of the positive electrode lug and the head of the positive current collector.

And the adhesive paper covers the positive electrode lug and completely covers the empty foil areas on the surfaces of the two sides of the head of the positive electrode current collector.

Wherein the positive electrode current collector is selected from aluminum foil.

Wherein the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.

The positive active material layer is prepared by coating positive slurry on the surface of a positive current collector; the positive electrode slurry is prepared by mixing a positive electrode active material, a conductive agent, a binder and N-methyl pyrrolidone.

According to one embodiment of the present invention, the electrode sheet may be an anode sheet, the anode sheet includes an anode current collector, an anode active material layer, an anode tab and adhesive tape, the anode active material layer is disposed on two side surfaces of the anode current collector, and forms a hollow foil area at two ends of the anode current collector;

the negative electrode tab is arranged on the empty foil area on one side surface of the negative electrode current collector; wherein, one end provided with a negative pole tab is defined as the head of a negative pole current collector, and the other end is defined as the tail of the negative pole current collector;

the adhesive tape is arranged at the head of the negative current collector and covers the negative electrode tab.

Wherein the negative electrode current collector is selected from copper foil.

Wherein the anode active material layer includes an anode active material, a conductive agent, a binder, and a thickener.

The negative electrode active material layer is prepared by coating negative electrode slurry on the surface of a negative electrode current collector; the negative electrode slurry is prepared by mixing a negative electrode active material, a conductive agent, a binder and deionized water.

The invention also provides a preparation method of the pole piece, which comprises the following steps:

(1) covering adhesive tape on the empty foil area of the positive current collector provided with one end of the positive electrode lug, completely covering the empty foil area on the surfaces of the two sides of the positive current collector provided with one end of the positive electrode lug, and preparing the pole piece.

According to the invention, the method further comprises:

(2) and covering adhesive tape on the empty foil area of the negative current collector at one end of the negative electrode lug, wherein the adhesive tape completely covers the surface of the negative electrode lug, and preparing to obtain the pole piece.

According to the invention, the method comprises the following steps:

(1-1) mixing a positive electrode active material, a conductive agent and a binder, adding N-methyl pyrrolidone, stirring and dispersing to prepare positive electrode slurry; coating positive slurry on the surfaces of two sides of a positive current collector, leaving empty foil areas on two sides of the positive current collector, arranging a positive electrode lug on the empty foil area on one side surface, covering adhesive paper on the empty foil area of the positive current collector arranged at one end of the positive electrode lug, and completely covering the adhesive paper on the empty foil areas on the surfaces of the two sides of the positive current collector arranged at one end of the positive electrode lug to prepare the pole piece.

According to the invention, the method comprises the following steps:

(2-1) mixing the negative electrode active material, the conductive agent, the binder and the thickening agent, adding deionized water, stirring and dispersing to prepare negative electrode slurry; and coating the negative electrode slurry on the surfaces of two sides of a negative electrode current collector, reserving empty foil areas on the two sides of the negative electrode current collector, arranging a negative electrode lug on the empty foil area on the surface of one side of the negative electrode current collector, and covering adhesive paper on the negative electrode lug to prepare the pole piece.

The invention has the beneficial effects that:

the invention provides a pole piece for improving heat abuse of a high-voltage system of a lithium ion battery and a preparation method thereof, wherein the pole piece comprises a current collector, active substance layers, a tab and adhesive paper, wherein the active substance layers are arranged on the surfaces of two sides of the current collector, and empty foil areas are formed at two ends of the current collector; the tab is arranged on the empty foil area on one side surface of the current collector; wherein, one end provided with the pole ear is defined as the head of the current collector, and the other end is defined as the tail of the current collector; the adhesive tape is arranged at the head of the current collector and covers the lug. The pole piece can effectively improve the 140 ℃ heat abuse passing rate of a high-voltage high-capacity 4.45V system battery cell; the adhesive paper full-covering method has simple process, does not need complex equipment, and can save production cost and time; the method has the capacity loss of less than 0.1 percent and almost no energy density loss on the premise of ensuring the safety.

Drawings

Fig. 1 is a schematic structural diagram of a positive electrode tab and a negative electrode tab according to embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of the positive electrode plate and the negative electrode plate in comparative example 4 of the present invention.

Wherein, 1 is positive tab, 2 is positive active material, 3 is positive current collector, 4 is gummed paper, 5 is gummed paper, 6 is gummed paper, 7 is negative tab, 8 is negative current collector, and 9 is negative active material.

Fig. 3 is a comparison of the energy densities of the cells of example 1 and comparative example 4.

Fig. 4 shows the results of dissecting the cells after a heat abuse test on fresh (about 50% SOC) and 70% SOC batteries.

Detailed Description

The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.

Example 1

(1) Preparation of positive plate

Mixing the positive active material, the conductive agent, the binder and the lithium salt, adding N-methyl pyrrolidone, stirring and dispersing to prepare positive slurry. In the positive electrode slurry, the solid component contained 98.23 wt% of lithium cobaltate (LiCoO)₂) 0.87 wt% conductive carbon black and 0.9 wt% polyvinylidene fluoride (PVDF). And coating the positive electrode slurry on the surfaces of the two sides of the positive electrode current collector to obtain a positive electrode active substance layer, drying, slitting and preparing a sheet to obtain the pole piece.

The width of the positive current collector in the pole piece is the same with the width on positive active material layer, the length of the positive current collector in the pole piece is greater than the length on positive active material layer, in this embodiment, the length on positive current collector is 1230mm, the length on one side positive active material layer is 1167mm, the length on the other side positive active material layer is 1047mm, and the both ends in positive current collector both sides form empty foil area respectively promptly.

And welding a positive electrode lug on the blank area on one side, and completely covering the blank areas on two sides of the positive electrode current collector at one end of the positive electrode lug by using adhesive paper with the thickness of 16 micrometers respectively.

(2) Preparation of negative plate

Mixing the negative electrode active material, the conductive agent, the binder and the thickening agent, adding deionized water, stirring and dispersing to prepare negative electrode slurry. In the negative electrode slurry, the solid component contained 96.9 wt% of artificial graphite, 1.3 wt% of sodium carboxymethyl cellulose (CMC), 1.3 wt% of styrene-butadiene rubber (SBR); and then coating the negative electrode slurry on a negative electrode current collector (double-sided coating), drying, slitting and preparing a sheet to obtain the negative electrode sheet.

The width of the negative pole mass flow body in the pole piece is the same with the width on negative active material layer, the length of the negative pole mass flow body in the pole piece is greater than the length on negative active material layer, in this embodiment, the length of the negative pole mass flow body is 1230mm, the length on one side negative active material layer is 1164mm, the length on the other side negative active material layer is 1062mm, form empty foil area respectively at the both ends of negative current flow body both sides promptly, set up negative pole utmost point ear on the empty foil area of one of them side surface, cover on negative pole utmost point ear with the adhesive tape that thickness is 16 microns, the preparation obtains the pole piece.

(3) Preparation of the Battery

And (3) preparing the positive plate prepared in the first step and the negative plate prepared in the second step, a diaphragm and an aluminum-plastic film into a battery, then performing the working procedures of liquid injection, aging, formation, sorting and the like, and finally testing the electrochemical performance and the safety performance (mainly thermal abuse) of the battery.

Comparative example 1

The other operation steps are the same as example 1, except that the preparation method of the positive plate is different:

the width of the positive current collector in the pole piece is the same with the width of positive active material layer, the length of the positive current collector in the pole piece is greater than the length of positive active material layer, the length of the positive current collector is 1230mm, the length of the positive active material layer on one side is 1167mm, the length of the positive active material layer on the other side is 1047mm, namely, the two ends of the two sides of the positive current collector form empty foil areas respectively.

And respectively sticking adhesive tapes with the width of 5mm on the edges of the upper surface and the lower surface of the positive pole piece in the width direction of the positive pole piece.

Comparative example 2

The other operation steps are the same as example 1, except that the preparation method of the positive plate is different:

the width of the positive current collector in the pole piece is the same with the width on positive active material layer, the length of the positive current collector in the pole piece is greater than the length on positive active material layer, in this embodiment, the length on positive current collector is 1230mm, the length on one side positive active material layer is 1167mm, the length on the other side positive active material layer is 1047mm, and the both ends in positive current collector both sides form empty foil area respectively promptly.

All the empty foil areas of the positive electrode current collector are completely covered by adhesive paper with the thickness of 16 microns.

Comparative example 3

The other operation steps are the same as example 1, except that the preparation method of the positive plate is different:

the width of the positive current collector in the pole piece is the same with the width on positive active material layer, the length of the positive current collector in the pole piece is greater than the length on positive active material layer, in this embodiment, the length on positive current collector is 1230mm, the length on one side positive active material layer is 1167mm, the length on the other side positive active material layer is 1047mm, and the both ends in positive current collector both sides form empty foil area respectively promptly.

The empty foil areas on the two sides of the positive current collector are respectively and completely covered by adhesive tapes with the thickness of 16 microns, and the edges of the upper surface and the lower surface of the positive pole piece are respectively pasted with the adhesive tapes with the width of 5mm in the width direction of the positive pole piece.

Comparative example 4

The other operation steps are the same as those in the example 1, except that no adhesive paper is arranged in the process of the preparation method of the positive plate.

Test example 1

The electrochemical properties and safety performance (mainly heat abuse) of the batteries prepared in example 1 and comparative examples 1 to 4 were tested.

The test procedure was as follows:

1. cleaning and checking machines, and paying attention to the cleanliness of heat abuse experimental equipment;

2. the voltage, the internal resistance and the thickness of the sampling battery are tested, the basic electrical property of the sampling battery needs to meet the requirements, the appearance of the sample is visually observed, and the battery has no bad phenomena such as damage, virtual seal, short circuit and the like;

3. checking the contact condition of the anode and cathode lugs of the battery and a clamp used for detection to ensure that a channel where the battery to be detected is located works normally;

4. putting the fully charged battery into a baking oven, setting the temperature of the baking oven as a required temperature, and starting a power supply; the temperature was raised from room temperature to a prescribed temperature at a rate of (5. + -. 2) ° C/min. And starting timing when the temperature of the oven reaches the required temperature, keeping the required temperature for a specified time, and taking out the battery after the test is finished. If the test fails, recording the failure mode and the failure time of the battery;

the test results are shown in table 1 below:

table 1 test results of the batteries of example 1 and comparative examples 1 to 4

	Gummed paper covering mode	Capacity of	Passing situation
				Example 1	Full-coverage adhesive paper for head empty foil area at one side of positive electrode tab	Is normal	3/3pass
Comparative example 1	Gummed paper with 5mm width covered on upper and lower edges of anode	Low capacity	3/3pass
				Comparative example 2	All-covering adhesive paper for all empty foil areas of positive electrode	Low capacity	3/3pass
Comparative example 3	Adhesive paper with 5mm wide for positive electrode empty foil area full coverage and positive electrode edge coverage	Low capacity	3/3pass
				Comparative example 4	Non-sticking adhesive paper for producing sheet by conventional process	Is normal	1/3pass

Wherein 1/3pass means that 3 cells were tested and only 1 passed.

The results in table 1 show that only the head part of the adhesive paper with the empty foil is fully covered, so that the safety performance can be improved, and the capacity is almost not lost; after the upper and lower edges of the pole piece are covered by the adhesive paper, although the safety performance can be improved, the capacity is greatly lost.

Fig. 3 is a comparison of energy densities of the batteries prepared in example 1 and comparative example 4, and it can be seen that the battery of example 1 can improve the passage rate of thermal abuse with almost no loss of energy density.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.