CN210535760U - Electrode assembly and secondary battery - Google Patents
Electrode assembly and secondary battery Download PDFInfo
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- CN210535760U CN210535760U CN201921318869.5U CN201921318869U CN210535760U CN 210535760 U CN210535760 U CN 210535760U CN 201921318869 U CN201921318869 U CN 201921318869U CN 210535760 U CN210535760 U CN 210535760U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The utility model provides an electrode subassembly and secondary battery. The electrode assembly includes a first pole piece, a second pole piece, and a separator separating the first pole piece and the second pole piece. The first pole piece comprises a first current collector and a first active material layer, the first current collector comprises a first main body part and a first pole lug, and the first pole lug extends from the first main body part along one longitudinal end. The first main body part comprises a first coating area and a first transition area, and the first transition area is arranged between the first tab and the first coating area; the first active material layer coats the surface in first coating region, and first transition district and first utmost point ear are not coated first active material layer. The second pole piece includes the second mass flow body and second active substance layer, and the second mass flow body includes second main part and second utmost point ear, and the second utmost point ear extends along fore-and-aft one end from the second main part, and the second active substance layer coats in the surface of second main part. The edge of the first transition region remote from the first coating region does not extend beyond the edge of the second active material layer.
Description
Technical Field
The utility model relates to a battery field especially relates to an electrode subassembly and secondary battery.
Background
An electrode assembly of a secondary battery includes a pole piece and a separator, and the pole piece includes a current collector and an active material layer coated on the surface of the current collector. In order to facilitate electrical connection with electrode terminals of the secondary battery, tabs are generally cut out of the current collector. Before cutting the tab, the current collector has a coated region coated with an active material layer and an uncoated region uncoated with an active material layer, and the tab is formed by cutting the uncoated region. In the process of cutting the tab, the cutter is very easy to act on the active substance layer to cause the risk of falling off of the active substance layer, so that the material waste is caused.
SUMMERY OF THE UTILITY MODEL
In view of the problems of the background art, it is an object of the present invention to provide an electrode assembly and a secondary battery,
in order to accomplish the above object, the present invention provides an electrode assembly and a secondary battery.
The electrode assembly includes a first pole piece, a second pole piece, and a separator separating the first pole piece and the second pole piece. The first pole piece comprises a first current collector and a first active material layer, the first current collector comprises a first main body part and a first pole lug, and the first pole lug extends from the first main body part along one longitudinal end. The first main body part comprises a first coating area and a first transition area, and the first transition area is arranged between the first tab and the first coating area; the first active material layer coats the surface in first coating region, and first transition district and first utmost point ear are not coated first active material layer. The second pole piece includes the second mass flow body and second active substance layer, and the second mass flow body includes second main part and second utmost point ear, and the second utmost point ear extends along fore-and-aft one end from the second main part, and the second active substance layer coats in the surface of second main part. In the direction in which the first main body part points to the first tab, the edge of the first transition region far away from the first coating region does not exceed the edge of the second active material layer.
The first pole piece is a positive pole piece, the second pole piece is a negative pole piece, and the edge of the second active material layer exceeds the edge of the first active material layer along the direction that the first main body part points to the first pole lug.
The edge of the first transition area at least exceeds the edge of the first active material layer by 0.5mm along the direction of the first main body part pointing to the first tab.
The first pole piece further comprises an insulating layer, and the insulating layer is at least partially coated on the surface of the first transition area.
The insulation layer includes a first portion applied to a surface of the first transition zone and a second portion extending from the first portion and applied to a surface of the first tab.
The edge of the second part far away from the first part exceeds the edge of the second active material layer along the direction that the first main body part points to the first tab.
The edge of the second part far away from the first part exceeds the edge of the second active material layer by 0.3mm-14mm along the direction that the first main body part points to the first tab.
The insulating layer has a hardness greater than a hardness of the first current collector.
The insulating layer comprises an inorganic filler and a binder, and the weight ratio of the inorganic filler to the binder is 0.4-6.5.
The first tab and the second tab are located on the same side of the electrode assembly in the longitudinal direction. The second active material layer includes a base region and a thinned region extending from the base region, and a thickness of the thinned region is smaller than a thickness of the base region. In the longitudinal direction, the skived zone is attached to the base zone on a side thereof adjacent the second tab. The second pole piece also comprises a third active substance layer, and the third active substance layer is coated on the surface of the second pole piece and connected to the thinning area. The size of the third active material layer is larger than the size of the thinned region in a direction in which the thinned region is directed toward the third active material layer.
The second body portion includes a second coating region and a second transition region disposed between the second tab and the second coating region. The second active material layer is coated on the surface of the second coating region, and the second transition region is not coated with the second active material layer.
The secondary battery includes the electrode assembly.
The utility model has the advantages as follows: this application sets up first transition district on through the mass flow body, can avoid first active substance layer to drop at the in-process that cuts first utmost point ear. Simultaneously, first transition region can also reduce the effort that transmits to first active material layer when secondary battery vibrations, reduces the risk that first active material layer drops. In addition, the overlapping area of the first transition region and the second active material layer can be reduced, the probability that impurities fall into the first transition region and the second active material layer is reduced, and the risks of contact and short circuit of the first transition region and the second active material layer are reduced.
Drawings
Fig. 1 is a schematic view of a secondary battery according to the present invention.
Fig. 2 is a schematic view of a first embodiment of an electrode assembly according to the present invention.
Fig. 3 is a cross-sectional view of the electrode assembly of fig. 2 taken along line a-a.
Fig. 4 is a sectional view of the electrode assembly of fig. 2 taken along line B-B.
Fig. 5 is an enlarged view of the electrode assembly of fig. 4 at block C.
Fig. 6 is an enlarged view of the electrode assembly of fig. 4 at block D.
Fig. 7 is a schematic view of the first pole piece of fig. 4 in an unfolded state.
Fig. 8 is a schematic view of the first current collector of the first pole piece of fig. 7.
Fig. 9 is a schematic view of the first pole piece of fig. 7 during a molding process.
Fig. 10 is a schematic view of the second pole piece of fig. 4 in an unfolded state.
Fig. 11 is a schematic view of a second current collector of the second pole piece of fig. 10.
Fig. 12 is a schematic view of a second embodiment of an electrode assembly according to the present invention.
Fig. 13 is a sectional view of the electrode assembly of fig. 12 taken along line E-E.
Fig. 14 is an enlarged view of the electrode assembly of fig. 13 at block F.
Fig. 15 is a schematic view of the second pole piece of fig. 13 in an expanded state.
Fig. 16 is a schematic view of a third embodiment of an electrode assembly according to the present invention.
Fig. 17 is an enlarged view of the electrode assembly of fig. 16 at block G.
Fig. 18 is a schematic view of the second pole piece of fig. 16 in an expanded state.
Wherein the reference numerals are as follows:
1 first pole piece
11 first current collector
111 first body part
111a first coating zone
111b first transition zone
112 first pole ear
12 first active material layer
13 insulating layer
131 first part
132 second part
2 second pole piece
21 second current collector
211 second body part
211a second coating zone
211b second transition zone
212 second pole ear
22 second active material layer
221 matrix region
222 skived area
23 third active material layer
3 diaphragm
4 electrode assembly
5 casing
6 top cover plate
7 electrode terminal
8 current collecting component
X longitudinal direction
Y transverse direction
In the Z thickness direction
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In the description of the present application, unless explicitly stated or limited otherwise, the terms "first", "second", "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means more than two (including two); the term "coupled", unless otherwise specified or indicated, is to be construed broadly, e.g., "coupled" may be a fixed or removable connection or a connection that is either integral or electrical or signal; "connected" may be directly connected or indirectly connected through an intermediate. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
In the description of the present application, it should be understood that the terms "upper" and "lower" used in the description of the embodiments of the present application are used in a descriptive sense only and not for purposes of limitation. The present application is described in further detail below with reference to specific embodiments and with reference to the attached drawings.
Referring to fig. 1, the secondary battery of the present application includes an electrode assembly 4, a case 5, a top cap plate 6, an electrode terminal 7, and a current collecting member 8.
The electrode assembly 4 is a core member of the secondary battery that realizes the charge and discharge functions. Referring to fig. 2 and 3, the electrode assembly 4 includes a first pole piece 1, a second pole piece 2, and a separator 3, the separator 3 separating the first pole piece 1 and the second pole piece 2.
The electrode assembly 4 may be of a wound structure. Specifically, the first pole piece 1 and the second pole piece 2 are both one, and the first pole piece 1 and the second pole piece 2 are in a strip structure. The first pole piece 1, the separator 3, and the second pole piece 2 are sequentially laminated and wound two or more turns to form an electrode assembly 4. The electrode assembly 4 may be flat.
Alternatively, the electrode assembly 4 may also be of a laminated structure. Specifically, the first pole piece 1 is provided in plurality, the second pole piece 2 is provided in plurality, the plurality of first pole pieces 1 and the plurality of second pole pieces 2 are alternately stacked, and the separator 3 separates the first pole piece 1 and the second pole piece 2.
The housing 5 may have a hexahedral shape or other shapes. The case 5 forms a receiving chamber therein to receive the electrode assembly 4 and the electrolyte. The case 5 is formed with an opening at one end, and the electrode assembly 4 may be placed into the receiving cavity of the case 5 through the opening. The housing 5 may be made of a material of conductive metal, and preferably, the housing 5 is made of aluminum or aluminum alloy.
The top cap plate 6 is disposed on the case 5 and covers the opening of the case 5, thereby sealing the electrode assembly 4 within the case 5. The top cover plate 6 may be a metal plate and is connected to the housing 5 by welding. Two electrode terminals 7 are provided to the top lid plate 6. The number of the current collecting members 8 is two, one current collecting member 8 connects one electrode terminal 7 with the first pole piece 1 of the electrode assembly 4, and the other current collecting member 8 connects the other electrode terminal 7 with the second pole piece 2 of the electrode assembly 4.
The electrode assembly of the present application is described below in various embodiments.
In the first embodiment, referring to fig. 4 to 6, the first pole piece 1 includes a first current collector 11 and a first active material layer 12, the first current collector 11 includes a first main body portion 111 and a first tab 112, and the first tab 112 extends from one end of the first main body portion 111 in the longitudinal direction X. The first active material layer 12 is coated on the surface of the first body portion 111. The first electrode plate 1 may be a positive electrode plate, correspondingly, the first current collector 11 is an aluminum foil, and the first active material layer 12 includes a ternary material, lithium manganate or lithium iron phosphate. The first tab 112 may be plural. After the first pole piece 1 is wound, a plurality of first tabs 112 are stacked and welded to the current collecting member 8.
The second electrode sheet 2 includes a second current collector 21 and a second active material layer 22, the second current collector 21 includes a second main body portion 211 and a second electrode tab 212, the second electrode tab 212 extends from one end of the second main body portion 211 along the longitudinal direction X, and the second active material layer 22 is coated on the surface of the second main body portion 211. The second electrode sheet 2 may be a negative electrode sheet, correspondingly, the second current collector 21 is a copper foil, and the second active material layer 22 includes graphite or silicon. The second tab 212 may be plural. When the second pole piece 2 is wound, a plurality of second pole pieces 212 are stacked together and welded to the current collecting member 8.
In the present embodiment, referring to fig. 2, the first tab 112 and the second tab 212 are located at both sides of the electrode assembly 4 in the longitudinal direction X, respectively.
During use of the battery, lithium ions in the first active material layer 12 pass through the separator 3 and are inserted into the second active material layer 22. In order to ensure that lithium ions can be inserted into the second active material layer 22 as much as possible, reducing the risk of lithium deposition, the second active material layer 22 needs to have a large width. Specifically, both ends of the second active material layer 22 in the longitudinal direction X protrude beyond the first active material layer 12. In other words, in the direction in which the first body portion 111 is directed toward the first tab 112, one edge T2 of the second active material layer 22 near the first tab 112 exceeds one edge of the first active material layer 12 near the first tab 112; in a direction in which the first tab 112 points toward the first body portion 111, the other edge of the second active material layer 22 remote from the first tab 112 exceeds the other edge of the first active material layer 12 remote from the first tab 112.
During the molding process of the first pole piece 1, a first tab 112 needs to be formed on the first current collector 11 by cutting. If cutting is performed along the edge of first active material layer 12, the cutter is likely to act on first active material layer 12 due to process errors, causing the active material in first active material layer 12 to fall off, resulting in waste of material. The active material in first active material layer 12 is relatively expensive, and therefore, cutting along the edge of first active material layer 12 results in a high cost of first pole piece 1.
In order to avoid the cutter from acting on the first active material layer 12, the present application increases the size of the first body portion 111 in the longitudinal direction X to increase the distance between the first active material layer 12 and the first tab 112 in the longitudinal direction X. Specifically, referring to fig. 5 to 9, the first body part 111 includes a first coating region 111a and a first transition region 111b, the first transition region 111b being disposed between the first tab 112 and the first coating region 111 a; the first active material layer 12 is coated on the surface of the first coating region 111a, and the first active material layer 12 is not coated on both the first transition region 111b and the first tab 112.
The dashed line of fig. 9 shows the movement path of the cutter during cutting of the first tab 112. In the process of cutting the first tab 112, a certain distance is kept between the cutter and the first active material layer 12, so that the cutter is prevented from acting on the first active material layer 12 due to process errors, and the active material of the first active material layer 12 is prevented from falling off. Referring to fig. 7 and 8, after the cutting is completed, a first transition region 111b, to which the first active material layer 12 is not applied, is formed on the first main body portion 111.
When the secondary battery vibrates, the current collecting member 8 pulls the first body part 111 through the first tab 112. Without the first transition region 111b, stress concentration occurs at the root portion of the first tab 112, and the portion of the first active material layer 12 near the root portion of the first tab 112 is likely to fall off. By providing the first transition region 111b, the application can reduce the force transmitted to the first active material layer 12, and reduce the risk of the active material in the first active material layer 12 falling off.
When the electrode assembly 4 is wound, the first and second electrode sheets 1 and 2 are laminated together. The surface of the first coating region 111a is coated with the first active material layer 12, and therefore, the gap between the first coating region 111a and the second active material layer 22 of the second pole piece 2 is small; while the first transition region 111b is not coated with the first active material layer 12, the gap between the first transition region 111b and the second active material layer 22 of the second pole piece 2 is large.
Impurities (e.g., metal particles, etc.) are generated during the welding of the first tab 112 to the current collecting member 8, and since the gap between the first transition region 111b and the second active material layer 22 is large, the impurities easily fall into the gap. In the process of charging and discharging, the first pole piece 1 and the second pole piece 2 can expand, and impurities falling into the gap can be extruded during expansion, so that the impurities puncture the diaphragm 3, and short circuit risk is caused.
Preferably, referring to fig. 5, in a direction in which the first main body portion 111 points to the first tab 112, an edge T1 of the first transition region 111b, which is far from the first coating region 111a, does not exceed an edge T2 of the second active material layer 22. This can reduce the overlapping area of the first transition region 111b and the second active material layer 22, thereby reducing the risk of contact and short-circuiting therebetween. At the same time, the present application also reduces the size of the gap between the first transition region 111b and the second active material layer 22 in the longitudinal direction X, thereby reducing the risk of impurities falling into the gap. In addition, in the longitudinal direction X, the edge T1 of the first transition region 111b is shrunk into the second active material layer 22, thereby reducing the risk of the edge T1 adsorbing impurities.
During cutting of the first tab 112, burrs are generated on the edge T1 of the first transition region 111b away from the first coated region 111a, and the burrs easily pierce the separator 3.
During use of the battery, lithium ions in the first active material layer 12 pass through the separator 3 and are inserted into the second active material layer 22. If the burr on the edge T1 of the first transition region 111b comes into contact with the lithium insertion region of the second active material layer 22, a large amount of heat is instantaneously generated, causing an explosion risk. Whereas if the burr on the edge T1 of the first transition region 111b contacts the lithium non-embedded region of the second active material layer 22, heat generation is less and the safety risk is lower.
During use of the battery, lithium ions in the first active material layer 12 freely diffuse to the surroundings, and therefore, the size of the lithium insertion region of the second active material layer 22 is slightly larger than that of the first active material layer in the longitudinal direction X. In order to reduce the safety risk, the edge of the first transition region 111b in the direction of the first main body portion 111 pointing towards the first tab 112 extends at least 0.5mm beyond the edge of the first active material layer 12. In other words, the first transition area 111b has a size equal to or greater than 0.5mm in the longitudinal direction X. At this time, even if the burr on the edge T1 of the first transition region 111b pierces the separator 3, it is in contact with only the lithium non-embedded region of the second active material layer 22, thereby avoiding explosion and reducing the safety risk.
Referring to fig. 5 and 7, the first pole piece 1 further includes an insulating layer 13, and the insulating layer 13 is at least partially coated on the surface of the first transition region 111 b. The insulating layer 13 may be filled into the gap between the first transition region 111b and the second active material layer 22 of the second diode 2, thereby reducing impurities falling into the gap, further reducing the risk of short circuit. Furthermore, the insulating layer 13 is applied to the first transition region 111b, and the first transition region 111b and the second active material layer 22 of the second electrode sheet 2 can be prevented from electrically communicating with each other through metal impurities.
The insulation layer 13 includes a first portion 131 and a second portion 132, the first portion 131 being applied to the surface of the first transition region 111b, the second portion 132 extending from the first portion 131 and being applied to the surface of the first tab 112. Preferably, the first portion 131 completely covers the surface of the first transition region 111 b.
The first portion 131 may be filled into the gap between the first transition region 111b and the second active material layer 22 of the second diode 2, thereby reducing impurities falling into the gap, further reducing the risk of short circuit. Further, coating the first portion 131 on the surface of the first transition region 111b may also prevent the first transition region 111b from being in electrical communication with the second active material layer 22 of the second electrode sheet 2 through metal impurities.
Referring to fig. 9, in the forming process of the first electrode sheet 1, the first active material layer 12 and the insulating layer 13 are coated on the surface of the first current collector 11, and then the first electrode tab 112 is cut. The insulating layer 13 is generally coated with a constant width, and if the second portion 132 is not remained on the first tab 112, the cutter needs to move along the edge of the insulating layer 13 when cutting the first tab 112, which has a high requirement on the cutting precision and is difficult to implement; in addition, after the cutting is completed, the burr on the edge T1 of the first transition area 111b is large, and the membrane 3 is easily pierced.
Therefore, the present application directly applies a cutter to the insulation layer 13 during cutting of the first tab 112. After cutting, the insulating layer 13 forms a first portion 131 remaining on the first transition region 111b and a second portion 132 remaining on the first tab 112. In addition, when the cutter cuts on the insulating layer 13, burrs on the edge T1 of the first transition region 111b can be effectively reduced, thereby reducing the risk of the diaphragm 3 being punctured.
Referring to fig. 5, in a direction in which the first body portion 111 points toward the first tab 112, an edge T3 of the second portion 132, which is away from the first portion 131, exceeds an edge T2 of the second active material layer 22. The second portion 132 may be filled into the gap between the first tab 112 and the second active material layer 22, thereby reducing impurities falling into the gap and reducing the risk of short circuits. Furthermore, the second portion 132 may also reduce the risk of burrs at the edge of the first tab 112 electrically communicating with the second active material layer 22 after puncturing the separator 3.
The first tab 112 is in a plurality and stacked arrangement, and the plurality of first tabs 112 are gathered together and welded to the current collecting member 8. During the process of drawing the first tabs 112, the roots of some of the first tabs 112 near the first transition region 111b are easily bent, resulting in the roots of these first tabs 112 being inserted between the first pole piece 1 and the second pole piece 2, causing a risk of short circuit. The second portion 132 of the present application may support the first tab 112, reducing the risk of bending the root of the first tab 112. In addition, since the edge T3 of the second portion 132 exceeds the edge T2 of the second active material layer 22, even if the first tab 112 is bent at a region where the second portion 132 is not coated, the bent position maintains a certain distance from the second active material layer 22, and the risk of the first tab 112 contacting the second active material layer 22 is low.
In the direction in which the first body portion 111 points toward the first tab 112, the edge T3 of the second portion 132 remote from the first portion 131 exceeds the edge of the second active material layer 22 by 0.3mm to 14 mm. If the dimension of the edge T3 of the second part 132 beyond the edge T2 of the second active material layer 22 is less than 0.3mm, then when the first tab 112 is bent in the region of the uncoated second part 132, the distance between the position of the bend and the second active material layer 22 is smaller, and there is still a risk of the first tab 112 coming into contact with the second active material layer 22. If the dimension of the edge T3 of the second portion 132 beyond the edge T2 of the second active material layer 22 is more than 14mm, the degree of bendability of the first tab 112 is low, and the occupied space is large, affecting the energy density of the secondary battery.
The insulating layer 13 has a hardness greater than that of the first current collector 11. The high-hardness insulating layer 13 can effectively support the first tab 112, and prevent the root portion of the first tab 112 near the first transition region 111b from being bent.
The insulating layer 13 includes an inorganic filler and a binder, and the ratio of the weight of the inorganic filler to the weight of the binder is 4.1 to 9.6. If the ratio is greater than 9.6, the adhesiveness between the inorganic fillers and the adhesive strength between the insulating layer 13 and the first current collector 11 may be insufficient, and the insulating layer 13 may easily fall off when in contact with the electrolyte. If the ratio is less than 4.1, the insulating effect of the insulating layer 13 is difficult to satisfy; moreover, the inorganic filler is less, and cannot play a role in supporting the first tab 112, so that the first tab 112 is easily folded in the winding process of the first pole piece 1. The inorganic filler is selected from boehmite and Al2O3、SiO2And TiO2One or more of them. The binder may be polyvinylidene fluoride.
In this embodiment, referring to fig. 10 and 11, the second active material layer 22 completely covers the second body portion 211. The second pole piece 2 further comprises a third active material layer 23, and the third active material layer 23 is coated on the surface of the second tab 212 and connected to the second active material layer 22. The second active material layer 22 and the third active material layer 23 are integrally molded.
Specifically, graphite, acetylene black as a conductive agent, CMC as a thickening agent, and SBR as a binder may be mixed, deionized water as a solvent is added, and the mixture is stirred to form a negative electrode slurry, and then the negative electrode slurry is coated on the surface of the second current collector 21. The negative electrode slurry is cured to form a negative electrode active material layer, and then the second electrode tab 212 is cut. When cutting, the cutter can directly act on the negative active material layer. After the cutting is completed, the portion of the anode active material layer remaining on the second main body portion 211 is the second active material layer 22, and the portion of the anode active material layer remaining on the second tab 212 is the third active material layer 23. Cutting on the negative electrode active material layer can reduce burrs at the cut portion, reducing the risk of the separator 3 being punctured. In addition, since the active material of the negative electrode active material layer is relatively inexpensive, a part of the negative electrode active material layer can be cut off as it is.
Other embodiments of the electrode assembly of the present application are explained below. For the sake of simplifying the description, only the differences of the other embodiments from the first embodiment will be mainly described below, and the undescribed portions can be understood with reference to the first embodiment.
Referring to fig. 12 to 15, in the second embodiment, the first tab 112 and the second tab 212 are located on the same side of the electrode assembly in the longitudinal direction X.
During the molding of the second pole piece 2, it is usually necessary to cold press the second active material layer 22 to increase the density of the second active material layer 22. At the time of cold pressing, stress concentration is easily generated at the end of the second active material layer 22 near the second tab 212, causing a risk of fracture of the second current collector 21.
Preferably, the second active material layer 22 includes a base region 221 and a thinned region 222 extending from the base region 221, and the thickness of the thinned region 222 is smaller than that of the base region 221. In the longitudinal direction X, the thinned region 222 is connected to the side of the base region 221 near the second pole ear 212. Preferably, the thinned region 222 gradually decreases in thickness in a direction away from the base region 221.
In the present application, by reducing the thickness of the thinned region 222, during the cold pressing of the second pole piece 2, the stress concentration at the edge T4 of the thinned region 222 away from the base region 211 can be reduced, and the second current collector 21 is prevented from being broken.
Referring to fig. 14, in the direction in which the base region 221 is directed toward the thinned region 222, the edge T1 of the first coating region 111a of the first transition region 111b that is far away exceeds the junction of the base region 221 and the thinned region 222, and does not exceed the edge T4 of the thinned region 222 that is far away from the base region 221. If the edge T1 of the first transition region 111b does not extend beyond the junction of the base region 221 and the thinned region 222, it will result in wasted active material in the thinned region 222. Although reducing the thickness of the thinned region 222 increases the gap between the first transition region 111b and the thinned region 222, the application is still satisfactory because the first portion 131 applied to the first transition region 111b can compensate for the safety risk associated with the increased gap.
In the second embodiment, the third active material layer 23 is connected to the thinned region 222. The thickness of the third active material layer 23 is smaller than that of the matrix region 221. When the second tab 212 is cut, the larger the dimension of the third active material layer 23 in the longitudinal direction X, the smaller the dimension of the thinned region 222 in the longitudinal direction X. The present application can reduce the area where the second active material layer 22 overlaps the first transition region 111b by reducing the size of the thinned region 222 to be smaller, reducing the risk of short circuit. By increasing the size of the third active material layer 23, the probability of root bending of the second tab 212 can be reduced, reducing the risk of short-circuiting. In general, the size of the third active material layer 23 is larger than the size of the thinned region 222 in the direction in which the thinned region 222 points toward the third active material layer 23.
Referring to fig. 14, the edge T1 of the first transition region 111b is shrunk into the second active material layer 22 in the longitudinal direction X, and thus, even if the root of the second tab 212 is bent, there is less risk of it coming into contact with the edge T1 of the first transition region 111 b. Therefore, the short circuit risk can be effectively reduced, and the safety performance is improved.
Referring to fig. 16 to 18, the third embodiment may omit the third active material layer 23, compared to the first embodiment. Specifically, the second body portion 211 includes a second coating region 211a and a second transition region 211b, and the second transition region 211b is disposed between the second tab 212 and the second coating region 211 a. The second active material layer 22 is coated on the surface of the second coating region 211a, and the second transition region 211b is not coated with the second active material layer 22.
By providing the second transition region 211b, the cutter can be prevented from acting on the second active material layer 22 due to process errors. The third embodiment can save the second active material layer 22 compared to the first embodiment.
When the secondary battery vibrates, the current collecting member 8 pulls the second body portion 211 through the second tab 212. Without the second transition region 211b, stress concentration occurs at the root of the second tab 212, and the portion of the second active material layer 22 near the root of the second tab 212 is easily peeled off. By providing the second transition region 211b, the present application can reduce the force transmitted to the second active material layer 22, and reduce the risk of the active material in the second active material layer 22 falling off.
Claims (11)
1. An electrode assembly, comprising a first pole piece (1), a second pole piece (2) and a separator (3), the separator (3) separating the first pole piece (1) from the second pole piece (2);
the first pole piece (1) comprises a first current collector (11) and a first active material layer (12), the first current collector (11) comprises a first main body part (111) and a first pole lug (112), and the first pole lug (112) extends from one end of the first main body part (111) along the longitudinal direction (X);
the first body portion (111) comprises a first coating region (111a) and a first transition region (111b), the first transition region (111b) being disposed between the first tab (112) and the first coating region (111 a); the first active material layer (12) is coated on the surface of the first coating area (111a), and the first transition area (111b) and the first tab (112) are not coated with the first active material layer (12);
the second pole piece (2) comprises a second current collector (21) and a second active substance layer (22), the second current collector (21) comprises a second main body part (211) and a second pole lug (212), the second pole lug (212) extends from one end of the second main body part (211) along the longitudinal direction (X), and the second active substance layer (22) is coated on the surface of the second main body part (211);
in the direction in which the first main body part (111) points toward the first tab (112), the edge of the first transition region (111b) facing away from the first application region (111a) does not extend beyond the edge of the second active material layer (22).
2. The electrode assembly according to claim 1, wherein the first pole piece (1) is a positive pole piece, the second pole piece (2) is a negative pole piece, and an edge of the second active material layer (22) exceeds an edge of the first active material layer (12) in a direction in which the first main body portion (111) points toward the first tab (112).
3. The electrode assembly according to claim 2, characterized in that the edge of the first transition zone (111b) exceeds the edge of the first active material layer (12) by at least 0.5mm in the direction in which the first main body portion (111) points toward the first tab (112).
4. The electrode assembly according to any one of claims 1 to 3, wherein the first pole piece (1) further comprises an insulating layer (13), the insulating layer (13) being at least partially applied to the surface of the first transition zone (111 b).
5. The electrode assembly according to claim 4, wherein the insulating layer (13) includes a first portion (131) and a second portion (132), the first portion (131) being applied to the surface of the first transition region (111b), the second portion (132) extending from the first portion (131) and being applied to the surface of the first tab (112).
6. The electrode assembly according to claim 5, wherein an edge of the second portion (132) remote from the first portion (131) exceeds an edge of the second active material layer (22) in a direction in which the first main body portion (111) points toward the first tab (112).
7. The electrode assembly according to claim 6, wherein an edge of the second portion (132) away from the first portion (131) exceeds an edge of the second active material layer (22) by 0.3mm to 14mm in a direction in which the first body portion (111) points toward the first tab (112).
8. The electrode assembly according to claim 4, wherein the insulating layer (13) has a hardness greater than that of the first current collector (11).
9. The electrode assembly of claim 1,
the first tab (112) and the second tab (212) are located on the same side of the electrode assembly in the longitudinal direction (X);
the second active material layer (22) comprises a base region (221) and a thinned region (222) extending from the base region (221), and the thickness of the thinned region (222) is smaller than that of the base region (221);
in the longitudinal direction (X), the thinning region (222) is connected to the side of the base region (221) close to the second tab (212);
the second pole piece (2) further comprises a third active material layer (23), and the third active material layer (23) is coated on the surface of the second pole lug (212) and connected to the thinning area (222);
the size of the third active material layer (23) is larger than the size of the thinned region (222) in the direction in which the thinned region (222) points toward the third active material layer (23).
10. The electrode assembly of claim 1,
the second body portion (211) comprises a second coating region (211a) and a second transition region (211b), the second transition region (211b) being disposed between the second tab (212) and the second coating region (211 a);
a second active material layer (22) is coated on the surface of the second coating region (211a), and the second transition region (211b) is not coated with the second active material layer (22).
11. A secondary battery comprising the electrode assembly according to any one of claims 1 to 10.
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| CN201921318869.5U CN210535760U (en) | 2019-08-14 | 2019-08-14 | Electrode assembly and secondary battery |
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