Pole piece, battery cell and electrochemical device

Abstract

The utility model discloses a pole piece, a battery cell and an electrochemical device. The pole piece comprises a current collector, a pole lug and a heat conduction piece, the current collector comprises a first conductive layer, a supporting layer and a second conductive layer which are sequentially stacked, and the supporting layer can reduce the weight of the pole piece and ensure the structural strength of the pole piece. The sides, away from the supporting layer, of the first conductive layer and the second conductive layer are used for coating active substances. The tab is connected to the first conductive layer, and the heat conduction piece is in contact with the tab, so that heat at the joint of the tab and the first conductive layer is conducted out when the battery cell works, the heat is prevented from damaging the pole piece, and the stability of the electrochemical device with the pole piece is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of secondary batteries, in particular to a pole piece, a battery core and an electrochemical device. Background Art

[0002] With the widespread application of new energy batteries, the market has higher and higher requirements for their weight, energy or volume energy density. The composite current collector is a "sandwich" structure, with an inner layer of a polymer high molecular layer (such as PET, PP or PI) and metal conductive layers (such as Al or Cu) on both sides. In order to obtain batteries with higher mass, energy or volume energy density, composite current collectors are usually used to replace conventional metal foil current collectors. For the pole pieces and batteries of composite current collectors, although the weight and energy density are improved, the conductive layer of the composite current collector is thinner than that of conventional metal foil. After the composite current collector is electrically connected to the conductive component, there is a large resistance in the electrical connection area, and a large amount of heat will be generated when the power is turned on. If this heat cannot be conducted out and dissipated in time, it will cause severe heating in the electrical connection area, and even fuse the composite current collector, causing irreversible effects on the battery. Utility Model Content

[0003] The main purpose of the utility model is to provide a pole piece, a battery core and an electrochemical device, aiming to solve the technical problem of heat dissipation in the electrical connection area between the composite current collector and the pole ear.

[0004] In order to achieve the above-mentioned purpose, the utility model provides a pole piece, comprising:

[0005] A current collector, comprising a first conductive layer, a support layer and a second conductive layer which are sequentially stacked, wherein the first conductive layer comprises a first hollow foil area and a first coating area on a side away from the support layer, wherein the first coating area is used to coat a first active material, and the second conductive layer comprises a second hollow foil area and a second coating area on a side away from the support layer, wherein the second coating area is used to coat a second active material;

[0006] A tab, one end of which is connected to the empty foil area of ​​the first conductive layer, and the other end of which extends out of the first conductive layer;

[0007] A heat conducting member is connected to a side of the tab away from the first conductive layer.

[0008] In some embodiments, the thermal conductor also contacts the first conductive layer.

[0009] In some embodiments, the direction of the first conductive layer pointing to the supporting layer is a first direction, the plane perpendicular to the first direction is a projection plane, the thermal conductor forms a first orthographic projection on the projection plane, and the tab forms a second orthographic projection on the projection plane, and the first orthographic projection at least partially covers the second orthographic projection.

[0010] In some embodiments, the thermally conductive member is a thermally conductive tape.

[0011] In some embodiments, the direction in which the first conductive layer points to the supporting layer is a first direction, a dimension D1 of the first conductive layer along the first direction satisfies: 0.1 μm≤D1≤4 μm, and a dimension D2 of the second conductive layer along the first direction satisfies: 0.1 μm≤D2≤4 μm.

[0012] In some embodiments, the polarity of the first conductive layer is different from the polarity of the second conductive layer, and the material used for the support layer is any one of an insulating polymer material and an insulating polymer composite material;

[0013] or,

[0014] The polarity of the first conductive layer is the same as that of the second conductive layer, and the material used for the support layer is any one of a conductive polymer material and a conductive polymer composite material.

[0015] In some embodiments, a direction in which the first conductive layer points toward the supporting layer is a first direction, and a dimension L of the supporting layer along the first direction satisfies: 2 μm≤L≤22 μm.

[0016] The embodiment of the second aspect of the utility model further provides a battery cell, comprising:

[0017] The pole piece described in any of the above embodiments is a positive pole piece or a negative pole piece.

[0018] The third aspect of the present invention further provides an electrochemical device, comprising:

[0019] Battery cells; and

[0020] A shell is used to accommodate the battery cell.

[0021] In some embodiments, the heat conductive member further contacts the housing.

[0022] Compared with the prior art, the beneficial effects of the utility model are:

[0023] In the technical solution of the utility model, the pole piece includes a current collector, a pole ear and a heat conductor. The current collector includes a first conductive layer, a support layer and a second conductive layer which are stacked in sequence, and the support layer can reduce the weight of the pole piece while ensuring the structural strength of the pole piece. The first conductive layer and the second conductive layer are used to coat the active material on the side away from the support layer. The pole ear is connected to the first conductive layer, and the heat conductor contacts the pole ear to conduct the heat at the connection between the pole ear and the first conductive layer when the battery cell is working, so as to prevent the heat from damaging the pole piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0025] Figure 1 It is a schematic structural diagram of the pole piece in the first embodiment of the utility model from a first viewing angle; wherein the polarity of the first conductive layer is the same as the polarity of the second conductive layer, and the pole lug can be connected only to the first conductive layer;

[0026] Figure 2 It is a structural schematic diagram of the pole piece in the first embodiment of the utility model from a second viewing angle;

[0027] Figure 3 The pole piece edge of the first embodiment of the utility model Figure 1 Sectional view cut along the AA direction;

[0028] Figure 4 Schematic diagram of the structure of the pole piece in the second embodiment of the utility model from the first perspective; wherein, the polarity of the first conductive layer is different from the polarity of the second conductive layer, then both the first conductive layer and the second conductive layer need to be connected to the pole lug, and the setting position of the pole lug on the first conductive layer and the second conductive layer can be set according to the requirements;

[0029] Figure 5 It is a structural schematic diagram of a pole piece from a second viewing angle in the second embodiment of the utility model;

[0030] Figure 6 The pole piece of the second embodiment of the utility model is Figure 4 Sectional view cut along the BB direction;

[0031] Figure 7 The pole piece edge of the third embodiment of the utility model Figure 4 A cross-sectional view cut along the BB direction; wherein the support layer is provided with a through hole, and the through hole can accommodate a heat-conducting member so that the heat-conducting member can balance the temperature of the first conductive layer and the second conductive layer;

[0032] Figure 8 A schematic diagram of an electrochemical device in an embodiment of the utility model; wherein the heat conducting member is also in contact with the housing;

[0033] Fig. 9 It is a schematic diagram of the dimensions of the current collector of the pole piece in one embodiment of the utility model.

[0034] Description of Figure Numbers:

[0035] 1-Electrochemical device;

[0036] 10-battery cell;

[0037] 100-pole piece;

[0038] 110 - current collector; 111 - first conductive layer; 112 - support layer; 113 - second conductive layer;

[0039] 120-ear; 130-heat conducting member; 140-active substance;

[0040] 2- Shell;

[0041] X - first direction.

[0042] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0044] The pole piece usually includes a current collector, a pole ear, and an active material coated on the surface of the current collector. In order to improve the energy density of the pole piece, a composite current collector is usually used. That is, the current collector includes a support layer and a conductive layer attached to the surface of the support layer. Since the support layer is a polymer material and the conductive layer is thin, the energy density of the electrochemical device can be significantly improved. However, the applicant found that the pole ear is connected to the conductive layer by welding, and the composite current collector used will generate a large amount of heat at the connection between the pole ear and the conductive layer when power is turned on. If the heat is not discharged in time, it will cause the connection between the pole ear and the conductive layer to heat up severely, and even melt the current collector, which seriously affects the performance of the electrochemical device.

[0045] In view of this, see Figure 1-9In the first aspect of the utility model, a pole piece 100 is provided, which includes a current collector 110, a pole ear 120 and a heat conductor 130. The current collector 110 includes a first conductive layer 111, a support layer 112 and a second conductive layer 113 which are stacked in sequence, and the direction from the first conductive layer 111 to the support layer 112 is the first direction X. The first conductive layer 111 has a first empty foil area and a first coating area, and the pole ear 120 is connected to the first empty foil area by welding, and the first coating area is used to coat the first active substance. The heat conductor 130 contacts the pole ear 120, and preferably, the heat conductor 130 covers the connection between the pole ear 120 and the first empty foil area. The second conductive layer 113 has a second empty foil area and a second coating area, and the second coating area is used to coat the second active substance.

[0046] In some embodiments, see Figure 1-7 In order to make the temperature of the electrode 100 uniform, the heat conductor 130 is also in contact with the first conductive layer 111. The heat conductor 130 covers the electrode 100 and contacts the first conductive layer 111, and can quickly conduct the heat at the connection between the electrode 100 and the first conductive layer 111 to the entire electrode 100, thereby avoiding excessive heat concentration at the electrode ear 120 of the electrode 100, and avoiding the heat causing the temperature of the electrode 100 to be too high or even melting the electrode 100 and affecting the performance of the electrochemical device 1. In some embodiments, the heat conductor can be a thermally conductive tape, and the thermally conductive tape can be a thermal management tape such as tesa TMT 60742, tesa TMT60743, tesa TMT 60744 or 3M8904.

[0047] In some embodiments, the plane perpendicular to the first direction X is a projection plane, the heat conductor 130 forms a first orthographic projection with the projection plane, and the pole tab 120 forms a second orthographic projection on the projection plane. In one embodiment, the first orthographic projection can fully cover the second orthographic projection. That is, the heat conductor 130 can fully cover the surface of the pole tab 120 on the side away from the first conductive layer 111, and in order to prevent the heat conductor 130 from hindering the transmission of lithium ions of the pole piece 100, the heat conductor 130 does not cover the first conductive layer 111. In another embodiment, the first orthographic projection can cover a local position of the second orthographic projection, preferably, the local position is the welding area of ​​the pole tab 120 and the first conductive layer 111. That is, the heat conductor 130 can at least cover the welding point between the pole tab 120 and the first conductive layer 111, and contact the first conductive layer 111, so that the heat conductor 130 can export the heat at the connection between the pole tab 120 and the first conductive layer 111 when power is turned on.

[0048] In some embodiments, the polarity of the first conductive layer 111 may be the same as the polarity of the second conductive layer 113. In one embodiment, the first conductive layer 111 and the second conductive layer 113 may be metal materials with conductive properties. The first conductive layer 111 and the second conductive layer 113 may be copper (the first conductive layer 111 and the second conductive layer 113 are negative polarities), or aluminum (the first conductive layer 111 and the second conductive layer 113 are positive polarities). In another embodiment, the first conductive layer 111 and the second conductive layer 113 may also be carbon-based conductive materials. The materials used in the first conductive layer 111 and the second conductive layer 113 may be the same or different. In a specific embodiment, the polarity of the first conductive layer 111 may be positive, and the polarity of the second conductive layer 113 is also positive. The polarity of the first conductive layer 111 may also be negative, and the polarity of the second conductive layer 113 is also negative. In this embodiment, the first active material coated on the first conductive layer 111 is the same as the second active material coated on the second conductive layer 113, so that the pole piece 100 as a whole is positive or negative. In other embodiments, the support layer 112 has an insulating property, and the polarity of the first conductive layer 111 and the polarity of the second conductive layer 113 may be different, that is, the polarity of the first conductive layer 111 may be positive, and the polarity of the second conductive layer 113 may be negative. The polarity of the first conductive layer 111 may also be negative, and the polarity of the second conductive layer 113 may be positive. In a specific embodiment, the first active material coated on the first conductive layer 111 is different from the second active material coated on the second conductive layer 113, so that the pole piece 100 has the characteristics of both the positive and negative poles. For ease of description, the following is an example in which the first conductive layer 111 is positive and the second conductive layer 113 is negative. In this embodiment, the electrode 100 has a positive electrode ear and a negative electrode ear, the positive electrode ear is welded to the first empty foil area of ​​the first conductive layer 111, and the negative electrode ear is welded to the second empty foil area of ​​the second conductive layer 113. Taking the plane perpendicular to the first direction X as the projection plane, the first empty foil area forms a third orthographic projection on the projection plane, and the second empty foil area forms a fourth orthographic projection on the projection plane. In one embodiment, the position of the third orthographic projection may be overlapped with the position of the fourth orthographic projection. In another embodiment, the position of the third orthographic projection is different from the position of the fourth orthographic projection. Since the positive electrode and the negative electrode are integrated in the same electrode 100, the energy density of the electrochemical device 1 having the electrode 100 can be improved.

[0049] See also Fig. 9In some embodiments, in order to ensure the conductivity of the first conductive layer 111 and the second conductive layer 113 while improving the mass energy density of the electrochemical device 1, the dimension D1 of the first conductive layer 111 along the first direction X satisfies: 0.1 μm ≤ D1 ≤ 4 μm. For example, the dimension of the first conductive layer 111 along the first direction X may be 0.2 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 2.5 μm, 3 μm or 3.5 μm, etc. Preferably, the dimension D1 of the first conductive layer 111 along the first direction X satisfies: 0.4 μm ≤ D1 ≤ 2 μm. For example, the dimension D1 of the first conductive layer 111 along the first direction X may be 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.7 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.2 μm, 1.6 μm or 1.9 μm, etc. The dimension D2 of the second conductive layer 113 along the first direction X satisfies: 0.1 μm ≤ D2 ≤ 4 μm. For example, the dimension D2 of the second conductive layer 113 along the first direction X may be 0.15 μm, 0.2 μm, 0.3 μm, 0.55 μm, 0.6 μm, 0.75 μm, 0.85 μm, 0.95 μm, 1.5 μm, 2.4 μm, 3.2 μm or 3.5 μm, etc. Preferably, the dimension D2 of the second conductive layer 113 along the first direction X satisfies: 0.4 μm ≤ D2 ≤ 2 μm. For example, the dimension D2 of the second conductive layer 113 along the first direction X may be 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.7 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.2 μm, 1.6 μm or 1.9 μm, etc. In one embodiment, the dimension D1 of the first conductive layer 111 along the first direction X may be equal to the dimension D2 of the second conductive layer 113 along the first direction X. In another embodiment, the dimension D1 of the first conductive layer 111 along the first direction X may also be unequal to the dimension D2 of the second conductive layer 113 along the first direction X. Specifically, if the first conductive layer 111 and the second conductive layer 113 have the same polarity, the dimension of the first conductive layer 111 along the first direction X may be equal to the dimension of the second conductive layer 113 along the first direction X. When the polarity of the first conductive layer 111 is different from the polarity of the second conductive layer 113 , the size of the first conductive layer 111 along the first direction X may not be equal to the size of the second conductive layer 113 along the first direction X.

[0050] See also Fig. 9In some embodiments, in order to ensure the volume energy density of the electrochemical device 1 while ensuring the mechanical strength of the support layer 112, the size L of the support layer 112 along the first direction X satisfies: 2μm≤L≤22μm. Exemplarily, the size of the support layer 112 along the first direction X can be 2.4μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 13μm, 14μm, 16μm, 17μm, 19μm, 20μm, 21μm or 21.5μm, etc. Preferably, the dimension L of the support layer 112 along the first direction X satisfies: 4.5 μm ≤ L ≤ 16 μm. For example, the dimension L of the support layer 112 along the first direction X may be 4.8 μm, 5 μm, 5.5 μm, 6.5 μm, 7.5 μm, 8.4 μm, 8.9 μm, 9.6 μm, 10.4 μm, 11 μm, 12.3 μm, 13 μm, 14.7 μm, 15.2 μm or 15.8 μm, etc. In one embodiment, when the polarity of the first conductive layer 111 is different from the polarity of the second conductive layer 113, the support layer 112 may be made of an insulating polymer material or an insulating polymer composite material. In another embodiment, when the polarity of the first conductive layer 111 is the same as the polarity of the second conductive layer 113, the support layer 112 may also be made of a conductive polymer material or a conductive polymer composite material, etc.

[0051] The second aspect of the utility model also provides a battery cell 10, which includes the pole piece 100 described in any of the above embodiments, and the pole piece 100 is divided into a positive pole piece and a negative pole piece according to its polarity. The pole piece 100 can also be a composite pole piece 100 integrating positive polarity and negative polarity. The battery cell 10 also includes a diaphragm, which is arranged between the positive pole piece and the negative pole piece, and is used to insulate and isolate the adjacent positive pole piece and negative pole piece to prevent short circuit. The battery cell 10 has a plurality of positive pole pieces, a plurality of negative pole pieces and a diaphragm. In one embodiment, each positive pole piece, the diaphragm and each negative pole piece are stacked in sequence. In another embodiment, each positive pole piece, the diaphragm and each negative pole piece are stacked and wound in sequence.

[0052] See also Figure 8 The third aspect of the utility model further provides an electrochemical device 1, which includes the battery cell 10 described in any of the above embodiments. The electrochemical device 1 also includes a housing 2, and the battery cell 10 is placed in the housing 2, so that the housing 2 protects the battery cell 10, and at the same time, the housing 2 can also carry electrolyte, so that the battery cell 10 can react with the electrolyte.

[0053] In order to facilitate the heat dissipation of the heat conductive member 130, in some embodiments, the heat conductive member 130 is also in contact with the housing 2. When the power is turned on, the heat at the connection between the tab 120 and the first conductive layer 111 can be conducted to the housing 2 through the heat conductive member 130. Since the housing 2 can usually be in contact with other structures outside the electrochemical device 1, the housing 2 can conduct the heat to the external environment and achieve heat dissipation and cooling during the conduction process.

[0054] In some embodiments, in order to balance the temperature of the entire electrode 100, that is, to make the temperature of each part of the electrode 100 as similar as possible, see Figure 7 , the support layer 112 also has a through hole. Taking the plane perpendicular to the first direction X as the projection plane, the pole ear 120 forms a second orthographic projection on the projection plane, and the through hole forms a fifth orthographic projection on the projection plane, and the second orthographic projection can cover the fifth orthographic projection. The through hole can accommodate the heat conductor 130, and enable the heat conductor 130 to contact the first conductive layer 111 and the second conductive layer 113, so that the temperatures of the first conductive layer 111 and the second conductive layer 113 tend to be the same, thereby ensuring the overall temperature uniformity of the pole piece 100, so that the electrochemical device 1 with the pole piece 100 has better performance. And because the heat conductor 130 is also provided on the side of the pole ear 120 away from the first conductive layer 111, and the heat conductor 130 can contact other structures, the heat of the pole piece 100 can be conducted to the external environment through the heat conductor 130, so as to achieve heat dissipation of the pole piece 100 and the battery cell 10.

[0055] The electrochemical device 1 of the present application is described in detail below through examples and comparative examples.

[0056] Example 1

[0057] Preparation of composite current collector 110: Select a support layer 112 with a thickness (dimension along the first direction X) of 5μm≤L≤10μm. In Example 1, the support layer 112 has a thickness of 5μm, and a first conductive layer 111 with a thickness of 0.9μm≤D1≤2μm and a second conductive layer 113 with a thickness of 0.9μm≤D2≤2μm are formed on its surface by evaporation. In Example 1, the first conductive layer 111 has a thickness of 1μm, and the second conductive layer 113 has a thickness of 1μm. In this embodiment, the support layer 112 is an insulating polymer material, which can be selected from at least one of polymer materials such as polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polyvinylidene fluoride, silicone rubber, polycarbonate, etc. In this embodiment 1, the support layer 112 is made of polyethylene terephthalate (PET for short), and the thickness of the support layer 112 used for the positive electrode sheet and the negative electrode sheet is the same. The conductive layer of the positive electrode sheet uses aluminum metal (that is, the first conductive layer 111 and the second conductive layer 113 both use aluminum metal), and the conductive layer of the negative electrode sheet uses copper metal (the first conductive layer 111 and the second conductive layer 113 both use copper metal). That is, in this embodiment, the first conductive layer 111 and the second conductive layer 113 are metal conductive layers, and when the current collector 110 is a positive electrode current collector, the first conductive layer 111 and the second conductive layer 113 are both made of aluminum metal, and when the current collector 110 is a negative electrode current collector, the first conductive layer 111 and the second conductive layer 113 are both made of copper metal.

[0058] The formation conditions of the evaporation method are as follows: the support layer 112 with surface cleaning treatment is placed in a vacuum coating chamber, and the high-purity metal wire in the metal evaporation chamber is melted and evaporated at a high temperature of 1800°C to 2000°C. The evaporated metal passes through the cooling system in the vacuum coating chamber and is finally deposited on the surface of the support layer 112, thereby forming a conductive layer.

[0059] Preparation of positive electrode sheet: Mix the positive electrode active material lithium cobalt oxide, conductive agent and binder in a mass ratio of 97.6:1.1:1.3, add N-methylpyrrolidone as a solvent, and stir under the action of a vacuum mixer until the solid content is 76wt% and the system is uniform. The positive electrode slurry is evenly coated on one side of the prepared composite current collector 110, and dried at 100°C to obtain a positive electrode sheet with a single-sided positive electrode active material layer; then, the above steps are repeated on the other side of the composite current collector 110 to obtain a positive electrode sheet with a double-sided positive electrode active material layer. After drying at 100°C, cold pressing is performed, and then striping and welding of the pole ear 120, wherein the area where the pole ear 120 is welded is the transfer welding area, and a heat conductive member 130 is set in this area to cover at least a part of the pole ear 120, and a positive electrode sheet with a specification of 68mm×1600mm is obtained for standby use.

[0060] Preparation of negative electrode sheet: Graphite, binder and thickener are mixed in a mass ratio of 97.7:1.4:0.9, deionized water is added and stirred evenly to obtain negative electrode slurry, wherein the solid content of the negative electrode slurry is 49wt%. The negative electrode slurry is evenly coated on one side of the prepared composite current collector 110, dried at 85°C, and the above steps are repeated on the other surface of the composite current collector 110 to obtain a negative electrode sheet with a double-sided negative electrode material layer. Then, cold pressing, cutting, slitting, welding the pole ear 120, and drying under vacuum conditions at 85°C for 1h, wherein the area where the pole ear 120 is welded is the transfer welding area, and a heat conductor 130 is arranged in this area, and the heat conductor 130 covers at least a part of the pole ear 120 to obtain a negative electrode sheet with a specification of 70mm×1620mm for standby use.

[0061] Preparation of electrolyte: In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate, diethyl carbonate and dimethyl carbonate are mixed in a mass ratio of 3:2:5 to obtain an organic solvent. Lithium hexafluorophosphate is added to the organic solvent to obtain an electrolyte, wherein the concentration of the lithium salt is 1 mol / L.

[0062] Preparation of battery cell 10 and electrochemical device 1: The prepared positive electrode sheet, separator and the prepared negative electrode sheet are stacked and wound in sequence to obtain a wound battery cell 10. The battery cell 10 is placed in an aluminum-plastic film packaging bag (i.e., shell 2), and after drying, an electrolyte is injected, and the electrochemical device 1 is obtained through vacuum packaging, standing, formation, degassing, trimming and other processes.

[0063] Example 2

[0064] The difference between Example 2 and Example 1 is that the thickness of the support layer 112 in Example 2 is 6 μm.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that the thickness of the support layer 112 in Example 3 is 7 μm, the thickness of the conductive layer of the positive electrode sheet is 0.8 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 0.8 μm), and the thickness of the conductive layer of the negative electrode sheet is 1.5 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1.5 μm).

[0067] Example 4

[0068] The difference between Example 4 and Example 1 is that the thickness of the conductive layer of the positive electrode sheet in Example 4 is 0.9 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 0.9 μm).

[0069] Example 5

[0070] The difference between Example 5 and Example 1 is that the thickness of the conductive layer of the negative electrode sheet in Example 5 is 1.5 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1.5 μm).

[0071] Example 6

[0072] The difference between Example 6 and Example 2 is that in Example 6, the thickness of the conductive layer of the positive electrode sheet is 1.2 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1.2 μm), and the thickness of the conductive layer of the negative electrode sheet is 0.9 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 0.9 μm).

[0073] Example 7

[0074] The difference between Example 7 and Example 1 is that the thickness of the support layer 112 in Example 7 is 8 μm, and the thickness of the conductive layer of the positive electrode sheet is 1.2 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1.2 μm).

[0075] Example 8

[0076] The difference between Example 8 and Example 1 is that the thickness of the conductive layer of the positive electrode sheet in Example 8 is 0.9 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 0.9 μm), and the thickness of the conductive layer of the negative electrode sheet is 1.2 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1.2 μm).

[0077] Example 9

[0078] The difference between Example 9 and Example 1 is that the thickness of the support layer 112 in Comparative Example 1 is 1 μm.

[0079] Example 10

[0080] The difference between Example 10 and Example 9 is that the thickness of the conductive layer of the positive electrode in Comparative Example 2 is 5 μm.

[0081] Embodiment 11

[0082] The difference between Example 11 and Example 9 is that the thickness of the support layer 112 in Comparative Example 3 is 24 μm, and the thickness of the conductive layer of the negative electrode sheet is 1 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1 μm).

[0083] Example 12

[0084] The difference between Example 12 and Example 3 is that the thickness of the support layer 112 in Comparative Example 4 is 1 μm.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that the current collector in Comparative Example 1 is a common current collector, that is, in this comparative example, the current collector has no supporting layer 112, and only has a conductive layer (equivalent to the current collector having only the first conductive layer 111 or the second conductive layer 113), the conductive layer thickness of the positive electrode sheet is 10 μm, the conductive layer thickness of the negative electrode sheet is 6 μm, and in this comparative example, the thermal conductor 130 is not attached to the side of the tab 120 away from the conductive layer.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Comparative Example 1 is that the thickness of the conductive layer of the positive electrode sheet in Comparative Example 2 is 8 μm, and the thickness of the conductive layer of the negative electrode sheet is 5 μm.

[0089] Comparative Example 3

[0090] The difference between Comparative Example 3 and Example 1 is that the thickness of the support layer 112 in Comparative Example 3 is 10 μm, the thickness of the conductive layer of the positive electrode sheet is 1.2 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 1.2 μm), the thickness of the conductive layer of the negative electrode sheet is 0.9 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 0.9 μm), and in this comparative example, the heat conductive part 130 is not attached to the side of the tab 120 facing away from the conductive layer.

[0091] Comparative Example 4

[0092] The difference between Comparative Example 4 and Example 3 is that the thickness of the conductive layer of the negative electrode sheet is 0.6 μm (the thickness of the first conductive layer 111 and the second conductive layer 113 are both 0.6 μm), and in this comparative example, the heat conducting member 130 is not attached to the side of the tab 120 away from the conductive layer.

[0093] The preparation conditions and corresponding test results of Examples 1-12 and Comparative Examples 1-4 are listed in Table 1 below.

[0094] Cycle performance test:

[0095] The electrochemical device 1 after formation in each embodiment and comparative example is placed in a thermostat at 25°C ± 2°C for 3 hours, charged to 4.45V at a constant current of 0.7C, and then left to stand for 30 minutes after a cut-off rate of 0.05C; then discharged to 3.0V at a constant current of 0.7C, this is a charge and discharge cycle process, and the discharge capacity C1 of the electrochemical device 1 after the first full charge is recorded; then the charge and discharge cycle process is repeated 500 times according to the above method, and the discharge capacity C2 of the full charge after 500 cycles is recorded. Take 3 electrochemical devices 1 in each group, and calculate the average value of the capacity retention rate of the electrochemical device 1. Among them, the capacity retention rate (%) = C2 (mAh) / C1 (mAh) × 100%, and the capacity retention rate is used to characterize the cycle performance.

[0096] Acupuncture test:

[0097] The electrochemical device 1 after formation in each embodiment and comparative example is fully charged, and then charged at a constant voltage until the current drops to 0.05C, and then charging is stopped. A φ8mm high temperature resistant steel needle is used to penetrate the electrochemical device 1 from a direction perpendicular to the electrode plate at a speed of 25mm / s. The penetration position is preferably close to the geometric center of the pierced surface. The steel needle stays in the electrochemical device 1 to observe whether the electrochemical device 1 has combustion or explosion.

[0098] Temperature rise test:

[0099] The electrochemical device 1 after formation in each embodiment and comparative example was placed in a constant temperature box at 25°C±2°C for 3 hours, charged to 4.45V at a constant current of 3C, and then allowed to stand for 30 minutes after a cut-off rate of 0.05C, and then discharged to 3V at a constant current of 1C, and the temperature changes of the positive and negative poles (the positive and negative poles are penetrated through the shell 2, and the positive and negative poles are used to connect the pole ears 120 on multiple pole pieces 100 as a whole and transmit the current to the outside of the shell 2) during the charging process were tested.

[0100] Table 1 Preparation conditions and corresponding test results of Examples 1-8 and Comparative Examples 1-8

[0101]

[0102]

[0103] Referring to Table 1, comparing Example 3 with Example 12, it can be seen that the thickness of the conductive layer of the positive electrode sheet and the thickness of the conductive layer of the negative electrode sheet are the same, and the pole tabs 120 are both provided with heat conductive members 130. The thickness of the support layer 112 in Example 12 is thinner than that of the support layer 112 in Example 3, and the thickness of the support layer 112 in Example 12 is less than 2 μm. The cycle capacity retention rate of the electrochemical device 1 in Example 12 is lower than the cycle capacity retention rate of the electrochemical device 1 in Example 3. The temperature rise values ​​of the positive and negative pole tabs in Example 12 are not much different from the temperature rise values ​​of the positive and negative pole tabs in Example 3. Comparing Example 1 with Example 11, it can be seen that the thickness of the support layer 112 in Example 11 is greater than the thickness of the support layer 112 in Example 1, and the thickness of the support layer 112 in Example 11 is greater than 22 μm. At this time, the cycle capacity retention rate of the electrochemical device 1 in Example 11 is lower than the cycle capacity retention rate of the electrochemical device 1 in Example 1. It can be seen that when the thickness of the support layer 112 is less than 2 μm or greater than 22 μm, the cycle retention rate of the electrochemical device 1 is lower than the cycle retention rate when the thickness of the support layer 112 is in the range of 2 μm≤L≤22 μm.

[0104] Comparing Comparative Example 1 with Comparative Example 3, and Comparative Example 2 with Comparative Example 4, it can be seen that the current collectors in Comparative Example 1 and Comparative Example 2 are conventional current collectors without a support layer 112, and the current collectors 110 in Comparative Example 3 and Comparative Example 4 are composite current collectors 110 with a support layer 112, and the tabs 120 in the four comparative examples are not provided with a heat conductor 130. The electrochemical devices 1 in Comparative Example 1 and Comparative Example 2 did not pass the needle puncture test, while the electrochemical devices 1 in Comparative Example 3 and Comparative Example 4 passed the needle puncture test. It can be seen that the composite current collector 110 with a support layer 112 can increase the safety of the electrochemical device 1.

[0105] By comparing Examples 1-12 and Comparative Examples 1-4, it can be seen that the tabs 120 in Examples 1-12 are all provided with heat conducting members 130, while the tabs 120 in Comparative Examples 1-4 are not provided with heat conducting members 130. The temperature rise values ​​of the positive and negative tabs of the electrochemical device 1 in Examples 1-12 are generally lower than the temperature rise values ​​of the positive and negative tabs of the electrochemical device 1 in Comparative Examples 1-4. It can be seen that the provision of the heat conducting member 130 can effectively reduce the temperature at the tabs 120 of the electrochemical device 1, further improving the safety of the electrochemical device 1.

[0106] Comparing Examples 1-8 with Comparative Examples 3-4, it can be seen that the tabs 120 in Examples 1-8 are all provided with heat conducting members 130, while the tabs 120 in Comparative Examples 3-4 are not provided with heat conducting members 130. The cycle capacity retention rates of the electrochemical devices 1 in Examples 1-8 are generally higher than the cycle capacity retention rates of the electrochemical devices 1 in Comparative Examples 3-4. It can be seen that the provision of the heat conducting member 130 can also improve the current carrying capacity of the pole piece 100.

[0107] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0108] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or", "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0109] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A pole piece, characterized in that: include: A current collector, comprising a first conductive layer, a support layer and a second conductive layer which are sequentially stacked, wherein the first conductive layer comprises a first hollow foil area and a first coating area on a side away from the support layer, wherein the first coating area is used to coat a first active material, and the second conductive layer comprises a second hollow foil area and a second coating area on a side away from the support layer, wherein the second coating area is used to coat a second active material; A tab, one end of which is connected to the first empty foil area, and the other end of which extends out of the first conductive layer; A heat conducting member is connected to a side of the tab away from the first conductive layer.

2. The pole piece according to claim 1, characterized in that: The thermal conductor is also in contact with the first conductive layer.

3. The pole piece according to claim 1, characterized in that: The direction from the first conductive layer to the supporting layer is a first direction, the plane perpendicular to the first direction is a projection plane, the heat conductor forms a first orthographic projection on the projection plane, the tab forms a second orthographic projection on the projection plane, and the first orthographic projection at least partially covers the second orthographic projection.

4. The pole piece according to claim 1, characterized in that: The heat conducting member is a heat conducting tape.

5. The pole piece according to claim 1, characterized in that: The direction of the first conductive layer pointing toward the supporting layer is a first direction, a dimension D1 of the first conductive layer along the first direction satisfies: 0.1 μm≤D1≤4 μm, and a dimension D2 of the second conductive layer along the first direction satisfies: 0.1 μm≤D2≤4 μm.

6. The pole piece according to claim 1, characterized in that: The polarity of the first conductive layer is different from that of the second conductive layer, and the material used for the support layer is any one of an insulating polymer material and an insulating polymer composite material; or, The polarity of the first conductive layer is the same as that of the second conductive layer, and the material used for the support layer is any one of a conductive polymer material and a conductive polymer composite material.

7. The pole piece according to claim 1, characterized in that: The direction from the first conductive layer to the supporting layer is a first direction, and a dimension L of the supporting layer along the first direction satisfies: 2 μm≤L≤22 μm.

8. A battery cell, characterized in that: include: The electrode sheet according to any one of claims 1 to 7 is a positive electrode sheet or a negative electrode sheet.

9. An electrochemical device, characterized in that: include: The battery cell according to claim 8; as well as A shell is used to accommodate the battery cell.

10. The electrochemical device according to claim 9, characterized in that The heat conducting member also contacts the housing.

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