CN215896445U

CN215896445U - Positive pole piece, lithium ion battery and power utilization device

Info

Publication number: CN215896445U
Application number: CN202121404379.4U
Authority: CN
Inventors: 谭远高; 郑伟; 王铭雪; 徐春辉; 陈杰; 项海标
Original assignee: Huizhou Liwinon Energy Technology Co Ltd
Current assignee: Huizhou Liwinon Energy Technology Co Ltd
Priority date: 2021-06-23
Filing date: 2021-06-23
Publication date: 2022-02-22
Anticipated expiration: 2031-06-23

Abstract

The utility model provides a positive pole piece, which comprises a positive pole current collector, a positive pole active substance layer and a safety coating; the positive active material layer is coated on at least one surface of the positive current collector; the safety coating coats the empty paper tinsel district of afterbody of the one side of keeping away from naked electric core center at anodal mass flow body. Compared with the prior art, the positive pole piece is additionally provided with the safety coating in the tail empty foil area of the current collector, so that on one hand, the adhesive force between the positive current collector and the aluminum plastic film of the battery shell is improved, and the bare cell and the aluminum plastic film are well attached together without moving in the drop test process; on the other hand, the safety coating can be preferentially contacted with the negative active material layer, so that the contact probability of the positive current collector and the negative active material layer is greatly reduced, and the dangerous short circuit problem of the positive current collector and the negative active material layer is greatly reduced.

Description

Positive pole piece, lithium ion battery and power utilization device

Technical Field

The utility model relates to the field of lithium batteries, in particular to a positive pole piece, a lithium ion battery and an electric device.

Background

The lithium ion battery has the advantages of high specific energy, strong continuous capability, long cycle life, wide working range, short charging time, capability of discharging with large current and the like, and is widely applied to the power fields of electric vehicles and the like and the consumption fields of mobile phones, watches, flat plates, notebooks and the like. With the development of lithium ion batteries in the fields of fast charging, high energy density and the like, the safety problem caused by the battery core becomes the focus of attention of people gradually. Among them, the drop test of lithium ion batteries is one direction in which people pay attention.

In the lithium ion battery drop test, naked electric core can be in the internal drunkenness of plastic-aluminum membrane, the positive plate can take place the dislocation in the naked electric core, positive and negative pole piece takes place the short circuit, one or more in "anodal active coating + negative pole active coating", "anodal active coating + negative current collector", "anodal current collector + negative pole active coating" four kinds of short circuits may appear, wherein "anodal current collector + negative pole active material" short circuit is the most dangerous short circuit, the joule heat of short circuit release is the most, the accumulated heat can finally cause the electric core to initiate a fire and explode.

Generally, in the dropping process of the lithium ion battery, the turning over of the isolating membrane easily causes the short circuit between the positive current collector and the negative material in the battery core to release a large amount of joule heat, and meanwhile, the situation of positive and negative dislocation is easily caused, so that the short circuit between the positive and negative pole pieces of the battery core is also caused, and further, safety accidents are caused.

At present, the safety performance of the lithium ion battery can be improved by improving the electrolyte and the isolating membrane, but the lithium ion battery can not be isolated from the dangerous short circuit of 'positive current collector + negative active material' in the falling process and the aluminum plastic membrane opened by the jump of a naked electric core, the safety risk of the exposure of the electrolyte is particularly in an electric core ending hollow foil area, the short circuit of 'positive current collector + negative active material' is easy to occur when acupuncture occurs, and therefore, the falling test and the acupuncture test of the lithium ion battery are not obviously improved. In view of the above, it is necessary to provide a technical solution to the above problems.

SUMMERY OF THE UTILITY MODEL

One of the objects of the present invention is: the positive pole piece is provided to reduce the dangerous short circuit problem of 'positive current collector + negative active material' which is easy to occur in the falling process of the current lithium ion battery.

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

a positive electrode sheet comprising:

a positive current collector;

the positive active material layer is coated on at least one surface of the positive current collector;

and the safety coating is coated on the tail empty foil area of the side, far away from the center of the naked electric core, of the positive current collector.

Preferably, the positive active material layer includes a first active material layer and a second active material layer, the first active material layer is coated on one surface of the positive current collector away from the center of the bare cell, and the second active material layer is coated on one surface of the positive current collector close to the center of the bare cell; the coating length of the first active material layer is smaller than that of the second active material layer.

Preferably, the security coating is disposed adjacent to the first active material layer.

Preferably, the coating area of the safety coating is extended to the positive current collector on the outermost ring of the positive pole piece from the tail empty foil area.

Preferably, the security coating is applied in a thickness of less than or equal to 12 μm.

Preferably, the coating thickness of the safety coating can be 8-9 μm, 9-10 μm, 10-11 μm, or 11-12 μm.

Preferably, the safety coating is a high molecular organic polymer, and the high molecular organic polymer is any one of polymethyl acrylate and polyacrylic acid.

The utility model also aims to provide a lithium ion battery, which comprises a bare cell formed by winding a positive pole piece, an isolating membrane and a negative pole piece, wherein the positive pole piece is any one of the positive pole pieces.

Preferably, the outermost ring of the bare cell is the positive current collector, and the single surface of the positive current collector of the outermost ring is coated with the safety coating.

It is a further object of the present invention to provide an electric device including the lithium ion battery of any one of the above aspects.

Compared with the prior art, the utility model has the beneficial effects that: according to the positive pole piece, the arrangement of the safety coating is additionally arranged in the tail empty foil area of the current collector, so that on one hand, the adhesive force between the positive current collector and the aluminum plastic film of the battery shell can be improved by utilizing the safety coating, the bare cell and the aluminum plastic film are well attached together without moving in the drop test process, the situation that the positive pole piece and the negative pole piece are staggered when the cell drops is reduced, the risk of short circuit is further reduced, the play of the bare cell in the aluminum plastic film is reduced, the risk that the aluminum plastic film is broken away is reduced, the electrolyte is prevented from being exposed, and the safety performance of the drop process is improved; on the other hand, the safety coating can be preferentially contacted with the negative active material layer, so that the contact probability of the positive current collector and the negative active material layer is greatly reduced, the risk of short circuit is reduced, and the safety performance of the falling process is improved. Therefore, the dangerous short circuit problem of 'anode current collector + cathode active material' easily generated in the falling process of the conventional lithium ion battery is greatly reduced.

Drawings

Fig. 1 is a schematic structural diagram of a positive electrode plate according to the present invention.

In the figure: 1-positive current collector; 2-positive electrode active material layer; 21-a first active material layer; 22-a second active material layer; 3-safety coating.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The standard parts used in the utility model can be purchased from the market, the special-shaped parts can be customized according to the description of the specification and the accompanying drawings, the specific connection mode of each part adopts conventional means such as bolts, rivets, welding and the like mature in the prior art, the machines, the parts and equipment adopt conventional models in the prior art, and the circuit connection adopts the conventional connection mode in the prior art, so that the detailed description is omitted.

Example 1

As shown in fig. 1, a positive electrode plate includes a positive electrode current collector 1, a positive electrode active material layer 2, and a safety coating 3; the positive active material layer 2 is coated on at least one surface of the positive current collector 1; and the safety coating 3 is coated on the tail empty foil area of the side, away from the center of the naked electric core, of the positive current collector 1.

The safety coating 3 is arranged in a tail empty foil area of the positive current collector 1, so that the influence on other performances is small while the needling and falling performances are improved. Compared with the case that the safety coating 3 is arranged between the positive current collector 1 and the positive active material layer 2, on one hand, the increase of the internal resistance of the battery cell can be avoided; on the other hand, the use of an adhesive can be omitted, and a high-molecular organic polymer with high viscosity is directly adopted as the safety coating 3 for coating, so that the problem that the use of the adhesive deteriorates the high-temperature storage performance and the high-temperature cycle performance of the battery cell is avoided.

In addition, in order to improve the drop test performance of the battery, the arrangement of hot melt adhesive is conventionally added at the tail part of the conventional positive current collector, the arrangement of the hot melt adhesive is replaced by a mode of coating the safety coating 3, so that the bonding area of the bare cell and the aluminum-plastic film is larger, the improvement effect on the drop performance is better, the coating thickness can be lower, the influence on the energy density of the cell is smaller, the process is simpler, and the method is more suitable for industrial production and application.

Further, the positive electrode active material layer 2 comprises a first active material layer 21 and a second active material layer 22, the first active material layer 21 is coated on one surface of the positive electrode current collector 1 far away from the center of the bare cell, and the second active material layer 22 is coated on one surface of the positive electrode current collector 1 near the center of the bare cell; the coating length of the first active material layer 21 is smaller than that of the second active material layer 22. The safety coating 3 is provided on the short coating surface, which is more advantageous to avoid the contact between the positive current collector 1 and the negative active material layer.

Further, the safety coat layer 3 is provided adjacent to the first active material layer 21. I.e. after the active substance layer 2 has been applied, the security coating 3 is applied next to the first active substance layer 21.

Further, the coating area of the safety coating 3 is extended to the positive current collector 1 at the outermost ring of the positive pole piece from the tail empty foil area. All set up safety coating 3 at the outermost circle of positive pole piece, can reduce the contact probability of anodal mass flow body 1 and negative pole active material layer by bigger degree, reduce the risk of short circuit.

Further, the security coating 3 is applied in a thickness of 12 μm or less. Generally, the minimum thickness of the hot melt adhesive arranged at the tail part of the positive electrode current collector 1 is only 12 micrometers, and the thickness is larger, so that the dropping performance of the battery is improved, but more energy density is lost. The safety coating 3 adopted by the utility model can be directly coated on the empty foil area at the tail part of the positive current collector 1, the thickness can be below 12 mu m, and compared with the arrangement of the adopted hot melt adhesive, the safety coating 3 disclosed by the utility model improves the falling performance, reduces the energy density loss and has wider practicability.

Further, the coating thickness of the safety coating 3 can be 8-9 μm, 9-10 μm, 10-11 μm, or 11-12 μm. The proper coating thickness of the safety coating 3 can play a role in protection on one hand, and reduce the contact probability of the positive current collector 1 and the negative active material layer; on the other hand, the energy density of the battery is not greatly influenced due to the overlarge thickness, and the conflict between the safety performance of the battery and the energy density is balanced.

Further, the safety coating 3 is a high molecular organic polymer, and the high molecular organic polymer includes any one of polymethyl acrylate and polyacrylic acid. The high molecular organic polymer is a main material of the safety coating 3, can be prepared into slurry and then directly coated on the positive current collector 1, and is more beneficial to controlling the coating thickness of the positive current collector. In addition, the high molecular organic polymers adopted by the utility model are all polymers with higher viscosity, and no adhesive is added into the slurry of the safety coating 3, so that the adhesive force between the positive current collector 1 and the aluminum-plastic film can be improved, the battery cell and the aluminum-plastic film are well attached together without moving, the risk of short circuit is reduced, and the safety performance of the falling process is improved.

The preparation method of the positive pole piece comprises the following steps:

s1, preparing safety coating 3 slurry, then uniformly coating the safety coating 3 slurry on the positive current collector 1 at certain intervals through gravure printing, wherein the coating width and the coating length are subject to specific design specifications, and then drying the coated positive current collector 1 through an oven to obtain the positive current collector 1 with the safety coating 3;

s2, adding lithium cobaltate, conductive carbon black, carbon nanotubes and a binder polyvinylidene fluoride into a stirring tank according to a certain sequence and a certain mass ratio, uniformly mixing at a certain rotating speed and time, uniformly coating the slurry on the positive current collector 1 with the safety coating 3, ensuring that the safety coating 3 is positioned at the tail of the short membrane surface of the positive pole piece (namely, the tail empty foil area of the positive current collector 1 far away from the center of the battery core), and forming a certain gap between the safety coating 3 and the positive active material layer 2 during coating so as to facilitate subsequent processes such as rolling and the like; and then placing the positive plate in an oven for drying, cold pressing, trimming, cutting, slitting, drying for 4 hours at 110 ℃ under a vacuum condition, and welding a tab to obtain the positive plate.

Example 2

A lithium ion battery comprises a naked battery cell formed by winding a positive pole piece, an isolating membrane and a negative pole piece, wherein the positive pole piece is the positive pole piece in embodiment 1.

Further, the outermost circle of the naked electric core is the positive current collector 1, and the single side of the positive current collector 1 of the outermost circle is coated with the safety coating 3.

The preparation method of the lithium ion battery comprises the following steps:

1) the positive electrode sheet was the positive electrode sheet obtained in example 1.

2) The preparation method of the negative pole piece comprises the following steps: mixing graphite, conductive carbon black, thickener carboxymethylcellulose sodium (CMC) and binder Styrene Butadiene Rubber (SBR) according to a mass ratio of 96: 2.0: 1.0: 1.0, preparing slurry, coating the slurry on a current collector copper foil, drying at 90 ℃, cutting edges, cutting pieces, dividing strips, drying for 4 hours at 110 ℃ under a vacuum condition after dividing the strips, and welding tabs to prepare a negative pole piece.

3) The barrier film is a polyolefin barrier film.

4) The preparation method of the electrolyte comprises the following steps: mixing lithium hexafluorophosphate (LiPF)₆) Dissolving the mixture in a mixed solvent composed of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) (the mass ratio of the three is 1: 2: 1) to obtain the electrolyte with the concentration of 1 mol/L.

5) Winding is carried out in a mode that a negative pole piece is arranged on the inner side and a positive pole piece is arranged on the outer side, the outermost circle of the wound battery core is a single-side area coated with the safety coating, and the procedures of top side sealing, liquid injection, formation, capacity grading and the like are carried out after winding is finished, so that the finished lithium ion battery is obtained.

Example 3

An electric device comprising the lithium ion battery of embodiment 2.

The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool and the like. The vehicle can be a fuel oil vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or a range-extended vehicle and the like; spacecraft include aircraft, rockets, space shuttles, and spacecraft, among others; electric toys include stationary or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric airplane toys, and the like; the electric power tools include metal cutting electric power tools, grinding electric power tools, assembly electric power tools, and electric power tools for railways, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators, and electric planers.

Comparative example 1

Different from the embodiment 2, the positive electrode plate of the comparative example is a conventional positive electrode plate, and the tail empty foil area of the current collector is not coated with a safety coating and is of a conventional structure of 'positive electrode current collector + positive electrode active coating'.

The rest is the same as embodiment 2, and the description is omitted here.

Drop tests and needle prick tests were performed on the lithium ion batteries of example 2 and comparative example 1 described above. The test results are shown in table 1 below.

TABLE 1

Group of	Drop test	Acupuncture experiment
			Example 2	10/10	3/10
Comparative example 1	6/10	0/10

According to the test results, the positive pole piece with the structure effectively improves the drop test and the needling test of the lithium ion battery, and improves the safety performance of the lithium ion battery.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the utility model as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A positive electrode sheet, comprising:

a positive current collector;

2. The positive electrode sheet according to claim 1, wherein the positive active material layer comprises a first active material layer and a second active material layer, the first active material layer is coated on one surface of the positive current collector away from the center of the bare cell, and the second active material layer is coated on one surface of the positive current collector close to the center of the bare cell; the coating length of the first active material layer is smaller than that of the second active material layer.

3. The positive electrode sheet according to claim 2, wherein the safety coating is provided adjacent to the first active material layer.

4. The positive electrode sheet according to claim 3, wherein the coating area of the safety coating is extended from the tail empty foil area to the outermost positive electrode current collector of the positive electrode sheet.

5. The positive electrode sheet according to any one of claims 1 to 4, wherein the safety coating is applied to a thickness of 12 μm or less.

6. The positive electrode plate as claimed in claim 5, wherein the safety coating is applied to a thickness of 8 to 12 μm.

7. The positive electrode plate as claimed in any one of claims 1 to 4, wherein the safety coating is a high molecular organic polymer, and the high molecular organic polymer is any one of polymethyl acrylate and polyacrylic acid.

8. A lithium ion battery comprises a bare cell formed by winding a positive pole piece, a separation film and a negative pole piece, and is characterized in that the positive pole piece is the positive pole piece in any one of claims 1 to 7.

9. The lithium ion battery of claim 8, wherein the outermost ring of the bare cell is the positive current collector, and the single side of the positive current collector of the outermost ring is coated with the safety coating.

10. An electric device comprising the lithium ion battery according to any one of claims 8 to 9.