CN212659571U

CN212659571U - Bipolar current collector, pole piece and secondary battery

Info

Publication number: CN212659571U
Application number: CN202021539705.8U
Authority: CN
Inventors: 张芹
Original assignee: Shenzhen Haihong New Energy Technology Co ltd
Current assignee: Xiamen Hithium Energy Storage Technology Co Ltd
Priority date: 2020-07-28
Filing date: 2020-07-28
Publication date: 2021-03-05
Anticipated expiration: 2030-07-28

Abstract

The application provides a bipolar current collector, a pole piece and a secondary battery, and belongs to the technical field of secondary batteries. The bipolar current collector comprises an insulating film layer, a positive electrode metal layer and a negative electrode metal layer. The insulating film layer has a first surface and a second surface in a thickness direction. The anode metal layer is arranged on the first surface, and the cathode metal layer is arranged on the second surface. The positive electrode metal layer has a first coating region for coating a positive electrode active material and a first electrode tab region for connecting a positive electrode tab, and the thickness of the first electrode tab region is greater than that of the first coating region. The negative electrode metal layer has a second coating region for coating a negative electrode active material and a second tab region for connecting a negative electrode tab, the second tab region having a thickness greater than that of the second coating region. The bipolar current collector can reduce the possibility of perforation of the insulating film layer, thereby avoiding the short circuit of the anode and the cathode of the secondary battery to a certain extent.

Description

Bipolar current collector, pole piece and secondary battery

Technical Field

The application relates to the technical field of secondary batteries, in particular to a bipolar current collector, a pole piece and a secondary battery.

Background

In the composite current collector, a copper metal layer is usually formed on both sides of a polymer layer for a negative current collector, and an aluminum metal layer is usually formed on both sides of a polymer layer for a positive current collector, and then a pole piece and a secondary battery are prepared.

In order to further improve the energy density of the battery, the prior art provides a bipolar current collector, which forms a copper layer and an aluminum layer on two surfaces of an insulating film layer, respectively, and then the copper layer is used as a negative electrode, and the aluminum layer is used as a positive electrode to prepare a pole piece and a secondary battery. However, in the process of welding the tab, the insulating film layer is easily welded through, thereby causing a problem of short circuit between the copper layer and the aluminum layer.

SUMMERY OF THE UTILITY MODEL

An object of the present application is to provide a bipolar current collector, a pole piece and a secondary battery, which can avoid short circuit between a positive electrode and a negative electrode, and can facilitate the connection between a tab and the current collector to be firmer.

In a first aspect, the present application provides a bipolar current collector comprising an insulating film layer, a positive metal layer, and a negative metal layer. The insulating film layer is provided with a first surface and a second surface along the thickness direction, the positive electrode metal layer is arranged on the first surface, and the negative electrode metal layer is arranged on the second surface. The positive electrode metal layer has a first coating region for coating a positive electrode active material and a first electrode tab region for connecting a positive electrode tab, and the thickness of the first electrode tab region is greater than that of the first coating region. The negative electrode metal layer has a second coating region for coating a negative electrode active material and a second tab region for connecting a negative electrode tab, the second tab region having a thickness greater than that of the second coating region.

The positive metal layer is used as the positive electrode of the current collector, and the negative metal layer is used as the negative electrode of the current collector. When the first pole lug area of the positive pole metal layer is connected with the positive pole lug, the thickness of the first pole lug area is thick, so that the insulating film layer can be prevented from being perforated when the positive pole lug is connected, and the short circuit of the positive pole and the negative pole of the secondary battery can be avoided to a certain extent.

When the second electrode lug area of the negative electrode metal layer is connected with the negative electrode lug, the thickness of the second electrode lug area is thick, so that the insulating film layer can be prevented from being perforated when the negative electrode lug is connected, and the short circuit of the positive electrode and the negative electrode of the secondary battery can be avoided to a certain extent.

In one possible embodiment, the maximum difference in thickness between the first extreme ear region and the first coating region is from 1 to 400nm, and the maximum difference in thickness between the second extreme ear region and the second coating region is from 1 to 600 nm. Optionally, the maximum thickness difference between the first polar ear region and the first coating region is 100-300nm, and the maximum thickness difference between the second polar ear region and the second coating region is 200-500 nm. The overcurrent capacity between the lug and the current collector can be better, and the energy density of the battery is higher.

In one possible embodiment, the thickness of the first coating region is from 20 to 1500nm, and the thickness of the first polar region is from 30 to 2000 nm; the second coating region has a thickness of 30-2500nm and the second polar ear region has a thickness of 50-3000 nm. The first coating area and the second coating area can respectively meet the current collecting capacity of the positive electrode and the negative electrode, and the first electrode lug area and the second electrode lug area can respectively meet the overcurrent capacity of the positive electrode and the negative electrode.

In one possible embodiment, the first coating zone comprises a first sub-zone and a second sub-zone; the first sub-areas are distributed at positions close to the first polar ear areas and positions far away from the first polar ear areas, and the second sub-areas are located between the two first sub-areas; the thickness of the first subregion is consistent with the thickness of the first polar lug region, and the thickness of the first subregion is larger than that of the second subregion. The second coating area comprises third sub-areas and fourth sub-areas, the third sub-areas are distributed at positions close to the second polar ear area and at positions far away from the second polar ear area, and the fourth sub-areas are located between the two third sub-areas; the thickness of the third sub-area is consistent with that of the second pole ear area, and the thickness of the third sub-area is larger than that of the fourth sub-area.

The thickness of first subregion and third subregion is thicker, after having coated the active material layer, on the one hand, can make the joint strength between reinforcing active material layer and the metal level, and on the other hand, when converging to the position that is close to first utmost point ear district of first subregion on the metal level of coating active material layer, the two's overcurrent ability is stronger, can make the electric current that the active material layer produced finally all converge to utmost point ear department, improves the electric conduction ability of pole piece.

In a possible embodiment, the width of the first subregion is 1 to 5 mm. The width of the third subregion is 1-5 mm.

The pole lug area can be effectively connected with the pole lug, the overcurrent capacity between a thicker area and a thinner area in the coating area can be considered under the condition that the overcurrent capacity of the pole lug and the pole lug area is ensured, and the conductive capacity of the pole piece is further improved.

In one possible embodiment, a fifth subregion is also provided between the first subregion and the second subregion, which becomes increasingly thicker in the direction from the second subregion to the first subregion. A sixth subregion is further arranged between the third subregion and the fourth subregion, and the sixth subregion becomes thicker gradually along the direction from the fourth subregion to the third subregion.

The defects of membrane surfaces such as folds, ribs and the like of the metal layer between the two subregions can be avoided, and the region which becomes thicker gradually is coated with an active substance layer, so that the overcurrent capacity of the coating region becomes stronger gradually, the conductive capacity of the pole piece is stronger, and the conductive capacity of each part can be met.

In one possible implementation, the first surface has a first blank area and a first metal area covered by the positive metal layer, the second surface has a second blank area and a second metal area covered by the negative metal layer, a projection of the first tab area of the positive metal layer in the thickness direction of the insulating film layer is located in the second blank area, and a projection of the second tab area of the negative metal layer in the thickness direction of the insulating film layer is located in the first blank area.

Because the back surface of the first pole lug area is a second blank area (without the negative pole metal layer), even if the insulating film layer is perforated when the positive pole lug is connected (for example, welded) with the positive pole metal layer, the positive pole metal layer and the negative pole metal layer are not contacted, the conduction between the positive pole metal layer and the negative pole metal layer can be avoided, and the short circuit of the positive pole and the negative pole is avoided.

Because the back surface of the second pole lug area is a first blank area (without an anode metal layer), even if the insulating film layer is perforated when the cathode pole lug is connected (for example, welded) with the cathode metal layer, the cathode metal layer and the anode metal layer are not contacted, and the conduction between the cathode metal layer and the anode metal layer can be avoided, thereby avoiding the short circuit of the anode and the cathode.

In one possible embodiment, the first blank region and the second blank region are respectively adjacent to both edges of the insulating film layer in a width direction of the insulating film layer.

Therefore, the tabs are arranged on two sides of the bipolar current collector in the width direction, one side of the bipolar current collector is connected with the positive electrode tab, and the other side of the bipolar current collector is connected with the negative electrode tab, so that short circuit between the positive electrode tab and the negative electrode tab is avoided.

In one possible embodiment, the positive electrode metal layer is a metal aluminum layer, and the negative electrode metal layer is a metal copper layer or a metal nickel layer.

In a second aspect, the present application provides a pole piece, including the above-mentioned bipolar current collector, positive active material layer, negative active material layer, positive tab and negative tab. The positive pole active substance layer sets up in first coating district, and the negative pole active substance layer sets up in the second coating district, and anodal utmost point ear is connected in first utmost point ear district, and negative pole utmost point ear is connected in second utmost point ear district.

The connection strength of the positive and negative electrode lugs is higher, and the conduction between the positive metal layer and the negative metal layer can be avoided after the positive and negative electrode lugs are connected.

In a third aspect, the present application provides a secondary battery, which includes a plurality of the above-mentioned pole pieces, and a plurality of diaphragms, wherein a diaphragm is disposed between two adjacent pole pieces, and a positive electrode active material layer and a negative electrode active material layer are disposed on two sides of the diaphragm respectively. The electrical properties of the secondary battery are better.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments are briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive efforts and also belong to the protection scope of the present application.

Fig. 1 is a schematic structural diagram of an electrical core stack provided in an embodiment of the present application;

fig. 2 is a schematic structural diagram of a pole piece provided in an embodiment of the present application;

fig. 3 is a schematic view of a first structure of a bipolar current collector provided in an embodiment of the present application;

fig. 4 is a second structural schematic diagram of a bipolar current collector provided in an embodiment of the present application;

fig. 5 is a schematic diagram of a third structure of a bipolar current collector provided in an embodiment of the present application;

fig. 6 is a fourth schematic structural diagram of a bipolar current collector provided in an embodiment of the present application;

fig. 7 is a fifth structural schematic diagram of a bipolar current collector provided in an embodiment of the present application.

Icon: 10-pole piece; 20-a separator; 30-a bipolar current collector; 40-positive electrode active material layer; 50-negative electrode active material layer; 60-positive pole tab; 70-a negative electrode tab; 31-an insulating thin film layer; 32-positive metal layer; 33-negative metal layer; 311-a first surface; 312 — a second surface; 3111-a first metal region; 3112-first blank region; 3121-a second metal region; 3122-second clear zone; 321-a first coating zone; 322-first extreme ear region; 331-a second coating zone; 332-second polar ear region; 3211-a first subregion; 3212-a second subregion; 3311-third subregion; 3312-fourth subregion; 3213-fifth subregion; 3313-sixth subregion.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

The main part of the secondary battery is a battery cell, and the battery cell can be a battery cell stack (laminated battery) or a battery cell coil (wound battery). Fig. 1 is a schematic structural diagram of an electrical core stack provided in an embodiment of the present application. Referring to fig. 1, the cell stack includes a plurality of pole pieces 10 and a plurality of diaphragms 20, and a diaphragm 20 is disposed between two adjacent pole pieces 10.

Fig. 2 is a schematic structural diagram of a pole piece 10 according to an embodiment of the present application. Referring to fig. 1 and 2, the pole piece 10 includes a bipolar collector 30, a positive active material layer 40, a negative active material layer 50, a positive tab 60, and a negative tab 70. The positive electrode active material layer 40 and the negative electrode active material layer 50 are respectively disposed in the coating regions of the bipolar current collector 30, and the positive electrode tab 60 and the negative electrode tab 70 are respectively attached to the tab regions of the bipolar current collector 30. The positive electrode active material layer 40 and the negative electrode active material layer 50 are provided on both sides of the separator 20.

Fig. 3 is a schematic view of a first structure of a bipolar current collector 30 according to an embodiment of the present disclosure. Referring to fig. 3, the bipolar current collector 30 includes an insulating film layer 31, a positive electrode metal layer 32, and a negative electrode metal layer 33.

In the embodiment of the present application, the insulating film layer 31 has a first surface 311 and a second surface 312 along a thickness direction, the first surface 311 has a first metal region 3111 and a first blank region 3112, and the second surface 312 has a second metal region 3121 and a second blank region 3122. The positive metal layer 32 is disposed on the first metal region 3111, and the negative metal layer 33 is disposed on the second metal region 3121.

In the embodiment of the present application, the insulating film layer 31 is not conductive, and optionally, the material of the insulating film layer 31 may be a polymer insulating layer, for example: films such as polystyrene, polypropylene, polyester, polycarbonate, polytetrafluoroethylene, polyimide, and the like; the material of the insulating film layer 31 may be synthetic fiber insulating paper, for example: aromatic polyamide fiber paper, polyester fiber paper; the material of the insulating film layer 31 may be various kinds of insulating tapes and the like. The positive electrode metal layer 32 and the negative electrode metal layer 33 are respectively arranged on the first surface 311 and the second surface 312 of the insulating film layer 31, so that the conduction of the positive electrode metal layer 32 and the negative electrode metal layer 33 can be avoided.

Alternatively, the positive electrode metal layer 32 is a metal aluminum layer, and the negative electrode metal layer 33 is a metal copper layer or a metal nickel layer. In the embodiment of the present application, the positive metal layer 32 is a metal aluminum layer to conduct the positive current; the negative metal layer 33 is a copper layer to conduct the negative current. In the present application, the positive electrode metal layer 32 is not limited to a metal aluminum layer, and metal layers that can be used as a positive electrode of a current collector are all within the scope of the present application; the negative electrode metal layer 33 is not limited to a metal copper layer, and any metal layer capable of serving as a negative electrode of a current collector is within the scope of the present application.

In the embodiment of the present application, the positive electrode metal layer 32 has a first coating region 321 and a first electrode tab region 322, the positive electrode active material layer 40 is disposed on the first coating region 321, and the positive electrode tab 60 is connected to the first electrode tab region 322. The anode metal layer 33 has a second coating region 331 and a second tab region 332, the anode active material layer 50 is disposed in the second coating region 331, and the anode tab 70 is attached to the second tab region 332. So as to realize the coating of the active material and the connection of the tab.

In the prior art, usually, all aluminum metal layers are formed on the first surface 311 of the insulating film layer 31, all copper metal layers are formed on the second surface 312, and then when the positive electrode tab 60 is welded with the aluminum metal layers or the negative electrode tab 70 is welded with the copper metal layers, the insulating film layer 31 is easily welded through due to high welding temperature, so that the aluminum metal layers and the copper metal layers at the tab welding position are conducted to form a short circuit.

Therefore, in the present application, the projection of the first tab region 322 in the thickness direction of the insulating film layer 31 is located in the second blank region 3122. The projection of the second tab region 332 in the thickness direction of the insulating film layer 31 is located in the first blank region 3112. When the tab region is connected with the tab, even if the tab region and the tab are damaged and perforated by welding or other connection methods, the problem of conduction between the negative electrode metal layer 33 and the positive electrode metal layer 32 cannot occur because no metal is arranged on the back surface of the tab region (the other surface of the film structure corresponding to the tab region), thereby avoiding short circuit between the positive electrode and the negative electrode.

Referring to fig. 3, the negative electrode metal layer 33 is not disposed on the back of the first surface 311 of the insulating film layer 31 where the first tab area 322 is disposed (as shown in fig. 3, the left side of the dotted line 1 is the first tab area 322 on the upper side, the second blank area 3122 on the lower side, the negative electrode metal layer 33 is not disposed on the second blank area 3122, the first blank area 3112 is on the upper side, the positive electrode metal layer 32 is not disposed on the right side of the dotted line 2, and the second tab area 332 is on the lower side).

It should be noted that: the correspondence between the first extreme ear region 322 and the second blank region 3122 is not limited to the correspondence shown in fig. 3. Fig. 4 is a second structural schematic diagram of the bipolar current collector 30 provided in the embodiment of the present application. Referring to fig. 4, a portion of the first tab area 322 near the first coating area 321 may extend toward the first coating area 321, such that the negative metal layer 33 is disposed below the first tab area 322 near the first coating area 321 (as shown in fig. 4, the left portion of the dotted line 3 is located above the first tab area 322, the second blank area 3122 is located below the first tab area and a portion of the second coating area 331 is located above the second blank area 3122, the negative metal layer 33 is not disposed in the second blank area 3122, the first tab area 322 may not be located entirely in the second blank area 3122, and may have a portion of the second coating area 331; the right portion of the dotted line 4 is located below the second tab area 332, the first blank area 3112 and a portion of the first coating area 321 are located above the first blank area 3112, the positive metal layer 32 is not disposed in the first blank area 3112, the second tab area 332 may not be located entirely in the first blank area 3112, there may be a portion of the second coating zone 331).

In other embodiments, fig. 5 is a schematic diagram of a third structure of the bipolar current collector 30 provided in the embodiments of the present application. Referring to fig. 5, a position of the first blank region 3112 near the first coating region 321 may extend partially toward the first coating region 321, such that the width of the first blank region 3112 exceeds the width of the second tab region 332 (as shown in fig. 5, there is a portion of the second blank region 3122 at a position to the right of the dotted line 5, and a portion of the first blank region 3112 at a position to the left of the dotted line 6). This application does not do the restriction to the blank area on two relative surfaces and the position corresponding relation between the utmost point ear district, as long as when utmost point ear is connected, can pass through the setting in blank area, avoid utmost point ear district and the scheme that the metal at this utmost point ear district back switched on all within the protection scope of this application.

In order to form the bipolar current collector 30 structure, optionally, when the positive electrode metal layer 32 is deposited on the first surface 311 of the insulating film layer 31, the first blank region 3112 of the first surface 311 is masked, the positive electrode metal layer 32 is not formed, the first metal layer of the first surface 311 is masked to distinguish porosity or transmittance, so as to form the first coating region 321 and the first tab region 322 with different thicknesses, and then the back metal layer is disposed.

For example: when the metal layer is deposited, a baffle is arranged between the insulating film layer 31 and the metal source, the baffle comprises a shielding part and a hollow part, the baffle at the position corresponding to the first blank area 3112 (or the second blank area 3122) is completely shielded, and the hollow part is not arranged; the ratio of the hollowed-out portions of the baffle plate at the position corresponding to the first tab region 322 (or the second tab region 332) is greater than the ratio of the hollowed-out portions of the baffle plate at the position corresponding to the first coating region 321 (or the second coating region 331), thereby forming the structure of the bipolar current collector 30 shown in fig. 3.

Optionally, the hollowed-out part is of a hole structure, in order to make the processing technology of the baffle simple, a round hole structure can be arranged on the baffle to form the hollowed-out part, the hole diameter of each round hole structure is consistent, the round hole structures at the corresponding first polar lug areas 322 of the baffle are uniformly distributed, the round hole structures at the corresponding first coating areas 321 of the baffle are also uniformly distributed, the number of the round hole structures at the corresponding first polar lug areas 322 of the baffle is greater than that of the round hole structures at the corresponding first coating areas 321 of the baffle, and therefore a metal layer with different thicknesses can be formed.

Of course, the shielding portion corresponding to the first tab region 322 of the baffle plate may also be 0, and all of the shielding portions are hollow portions, that is, the portion corresponding to the first tab region 322 is not provided with the baffle plate, and more metal sources are plated on the insulating film layer 31.

In the embodiment of the present application, the first blank region 3112 and the second blank region 3122 are respectively located on both sides of the insulating film layer 31 in the width direction of the insulating film layer 31. Referring to fig. 3 to 5, in the cross-sectional views of the bipolar current collector 30, the first blank region 3112 is on the right side of the drawing, and the second blank regions 3122 are on the left side of the drawing, and are staggered one above another.

With continuing reference to fig. 1 and fig. 2, after the current collectors shown in fig. 3-fig. 5 are prepared, the left first tab area 322 is completely connected to the positive tab 60, the right second tab area 332 is completely connected to the negative tab 70, then the left positive tab 60 is collected to the positive connection piece, the right negative tab 70 is collected to the negative connection piece, so as to realize tab outlet at two sides, avoid short circuit when the positive tab 70 and the negative tab 70 are collected, and further avoid short circuit of the positive and negative electrodes.

With continued reference to fig. 3-5, in the present embodiment, the first tab region 322 has a thickness greater than the thickness of the first cladding region 321, and the second tab region 332 has a thickness greater than the thickness of the second cladding region 331. The first coating region 321 and the second coating region 331 are mainly for flow guiding, and are thin to achieve flow guiding capability. And the metal layer is thicker at the position of the pole lug area, so that the insulating film layer can be prevented from being perforated when the anode pole lug is connected, and the anode and cathode of the secondary battery can be prevented from being short-circuited from the other layer.

Optionally, the maximum thickness difference between the first polar lug region 322 and the first coating region 321 is 1-400 nm; the maximum difference in thickness between the second tab region 332 and the second coating region 331 is 1-600 nm. The function of the coating area in the metal layer and the function of the tab area can be fully exerted. Further, the maximum thickness difference between the first polar region 322 and the first coating region 321 is 100-300 nm; the maximum thickness difference between the second tab region 332 and the second coating region 331 is 200-500 nm.

The thickness of the first coating region 321 is 20-1500nm, and the thickness of the first polar lug region 322 is 30-2000 nm; the second coating region 331 has a thickness of 30-2500nm and the second polar ear region 332 has a thickness of 50-3000 nm.

In some possible embodiments, the thickness of first coating region 321 is 1000nm, the thickness of first polar ear region 322 is 1300nm, and the difference between the thickness of first polar ear region 322 and first coating region 321 is 300 nm; the second coating region 331 has a thickness of 2000nm, the second polar ear region 332 has a thickness of 2500nm, and the maximum difference between the thicknesses of the second polar ear region 332 and the second coating region 331 is 500 nm. The present application is not limited.

Fig. 6 is a fourth structural schematic diagram of the bipolar current collector 30 provided in the embodiment of the present application. Referring to fig. 2 and 6, the first coating region 321 includes a first subregion 3211 and a second subregion 3212, the first subregion 3211 is a position close to the first tab region 322 and a position far away from the first tab region 322, the second subregion 3212 is located between the two first subregions 3211 (as shown in fig. 2 and 6, the thinner region is the second subregion 3212 and the thicker region is the first subregion 3211 in the positive electrode metal layer 32 coated with the positive electrode active material), the thickness of the first subregion 3211 is the same as that of the first tab region 322, and the thickness of the first subregion 3211 is greater than that of the second subregion 3212.

The positive electrode active material layer 40 is disposed on the second sub-region 3212 and the first sub-regions 3211 on both sides of the second sub-region 3212, so that the positive electrode active material layer 40 and the positive electrode metal layer 32 can be better bonded (when the positive electrode active material layer 40 is coated, as a whole, the positive electrode active material layer is coated not only on the thin positive electrode metal layer 32, but also on the thick positive electrode metal layer 32, and a stress is generated at the thin and thick junction, so that the adhesion of the positive electrode active material layer 40 is better). The thickness of the first sub-region 3211 close to the first tab region 322 is relatively thick, and the positive active material layer 40 is coated, so that the overcurrent capacity between the relatively thin region of the coating region and the relatively thick region of the coating region can be enhanced, thereby improving the conductivity of the whole pole piece 10, reducing the internal resistance of the battery cell, and improving the capacity retention rate of the battery cell 3C.

The second coating region 331 includes a third sub-region 3311 and a fourth sub-region 3312, the third sub-region 3311 is located close to the second pole ear region 332 and is located far from the second pole ear region 332, the fourth sub-region 3312 is located between two third sub-regions 3311, the thickness of the third sub-region 3311 is consistent with that of the second pole ear region 332, and the thickness of the third sub-region 3311 is greater than that of the fourth sub-region 3312.

The negative electrode active material layer 50 is disposed on the fourth sub-region 3312 and the third sub-regions 3311 on both sides of the fourth sub-region 3312, so that the bonding effect between the negative electrode active material layer 50 and the negative electrode metal layer 33 is better (when the negative electrode active material layer 50 is coated, it is coated on not only the thin negative electrode metal layer 33 region but also the thick negative electrode metal layer 33 region as a whole, there is a stress at the boundary between the thin and thick regions, so that the adhesion of the negative electrode active material layer 50 is better). The third sub-region 3311 close to the second tab region 332 is thicker and coated with the negative active material layer 50, so that the overcurrent capacity between the thinner region of the coating region and the thicker region of the coating region can be enhanced, thereby improving the conductivity of the whole pole piece 10, reducing the internal resistance of the battery cell, and improving the capacity retention rate of the battery cell 3C.

Referring to fig. 6, in the embodiment of the present application, the width a of the first sub-region 3211 is 1-5 mm. The width a of the first sub-region 3211 is a distance a between a boundary between the left first sub-region 3211 and the second sub-region 3212 and a boundary between the first sub-region 3211 and the first polar region 322 (see a on the left in fig. 6). The width of the first sub-area 3211 may also be a distance between a boundary between the right first sub-area 3211 and the second sub-area 3212 and a boundary between the first sub-area 3211 and the first blank area 3112 (e.g. a on the right in fig. 6). The left first sub-region 3211 can not only improve the bonding strength between the positive electrode metal layer 32 and the positive electrode active material layer 40, but also improve the overcurrent capacity at the position, and the right first sub-region 3211 is mainly for improving the bonding strength between the positive electrode metal layer 32 and the positive electrode active material layer 40.

The width b of the third sub-region 3311 is 1-5 mm. The width b of the third sub-region 3311 is the distance b (e.g., the right side b in fig. 6) between the borderline of the third sub-region 3311 and the fourth sub-region 3312 on the right and the borderline of the third sub-region 3311 and the second polar ear region 332. The width of the third sub area 3311 may also be the distance between the border of the second blank area 3122 and the third sub area 3311 and the border of the third sub area 3311 and the fourth sub area 3312 to the left (see b to the left in fig. 6). The third sub-region 3311 on the right side can improve not only the bonding force of the anode metal layer 33 and the anode active material layer 50 but also the overcurrent capacity at that position, and the third sub-region 3311 on the left side is mainly for improving the bonding force of the anode metal layer 33 and the anode active material layer 50.

Further, the first sub-region 3211 adjacent to the first tab region 322 and the third sub-region 3311 adjacent to the second tab region 332 are coated with the active material layer, and the active material layer does not need to be completely aligned with the boundary between the thicker region and the thinner region.

Optionally, the width a of the first sub-region 3211 is 2-4mm and the width b of the third sub-region 3311 is 2-4 mm. In some possible embodiments, the width a of the first subregion 3211 is 1mm, 2mm, 3mm, 4mm, or 5 mm; the width b of the third sub-region 3311 is 1mm, 2mm, 3mm, 4mm or 5 mm.

It should be noted that: the width of the first subregion 3211 may or may not be the same as the width of the second subregion 3212; the widths of the two first subregions 3211 may be uniform or nonuniform; the widths of the two third sub-regions 3311 may or may not be uniform. The present application is not limited, and the sub-regions that can form thicker sub-regions to increase the bonding force between the active material layer and the metal layer, or/and increase the overcurrent capability of the metal layer are within the scope of the present application.

In order to realize the above structure, the method is as follows: the ratio of the hollow parts of the baffle plates at the positions corresponding to the first tab region 322 (or the second tab region 332) and the first sub-region 3211 (or the third sub-region 3311) is greater than the ratio of the hollow parts of the baffle plates at the positions corresponding to the second sub-region 3212 (or the fourth sub-region 3312), so as to form the structure of the bipolar current collector 30 shown in fig. 6.

Fig. 7 is a fifth structural schematic diagram of the bipolar current collector 30 according to the embodiment of the present application. Referring to fig. 7, a fifth subregion 3213 is further disposed between the first subregion 3211 and the second subregion 3212, and the fifth subregion 3213 gradually thickens along the direction from the second subregion 3212 to the first subregion 3211. The positive electrode metal layer 32 can be changed from left to right into a thick, gradually thinner, gradually thicker and thicker layer structure, the film surface defects of wrinkles, ribs and the like of the positive electrode metal layer 32 of the current collector can be avoided, the binding force between the negative electrode active material layer 50 and the positive electrode metal layer 32 can be further increased, the conductive capability of the pole piece 10 can be further increased, and the conductive capability of each part of the pole piece 10 can be met.

Referring to fig. 7, a sixth sub-region 3313 is disposed between the third sub-region 3311 and the fourth sub-region 3312, and the sixth sub-region 3313 gradually thickens along a direction from the fourth sub-region 3312 to the third sub-region 3311. The negative electrode metal layer 33 can be changed into a thick, gradually thinner, gradually thicker and thicker layer structure from left to right, membrane surface defects such as folds, ribs and the like of the negative electrode metal layer 33 of the current collector can be avoided, the binding force between the positive electrode active material layer 40 and the negative electrode metal layer 33 can be further increased, the conductive capability of the pole piece 10 can be further increased, and the conductive capability of each part of the pole piece 10 can be met.

Further, the gradual thickening may be such that a surface of the gradually thickened region away from the insulating film layer 31 forms an inclined plane. In order to realize the above structure, the method is as follows: the ratio of the hollow parts of the baffle plates at the positions corresponding to the first polar ear region 322 (or the second polar ear region 332) and the first sub-region 3211 (or the third sub-region 3311) is greater than the ratio of the hollow parts of the baffle plates at the positions corresponding to the second sub-region 3212 (or the fourth sub-region 3312), and the ratio of the hollow parts of the fifth sub-region 3213 (or the sixth sub-region 3313) is gradually increased, so as to form the structure of the bipolar current collector 30 shown in fig. 7.

In other embodiments, the gradually thicker region (the fifth sub-region 3213 or/and the sixth sub-region 3313) may be a region that is formed by forming an arc surface on a surface of the gradually thicker region away from the insulating film layer 31, where the arc surface protrudes toward a direction away from the insulating film layer 31; or a surface of the gradually thickened region which is away from the insulating film layer 31 is formed into an arc surface which is depressed toward the direction close to the insulating film layer 31. The present application is not limited as long as a gradually thicker structure can be formed to satisfy the conductive capability of each portion of the metal layer.

The bipolar current collector 30 and the pole piece 10 provided by the embodiment of the application have the following beneficial effects:

(1) when the tab area is connected (for example, welded) with the tab, even if the insulating film layer 31 is damaged in the connection process, the conduction between the aluminum metal layer and the copper metal layer can be effectively avoided due to the arrangement of the blank area on the back surface of the tab area, so that the short circuit of the anode and the cathode can be effectively avoided.

(2) The thickness of the pole lug area is thicker, so that the insulation film layer 31 is perforated when the pole lugs are connected, conduction between the aluminum metal layer and the copper metal layer is avoided, and short circuit of the anode and the cathode is avoided from another layer.

(3) The thicker sub-area close to the extreme ear area can not only increase the bonding force between the active material layer and the metal layer, but also increase the overcurrent capacity between the thinner metal layer and the thicker metal layer. The thicker sub-region away from the extreme ear region can increase the bonding force between the active material layer and the metal layer.

(4) The thickness from the thinner sub-region to the thicker sub-region is gradually increased, so that the conductive capability of each part of the metal layer can be effectively met, the conductive capability of the pole piece 10 is improved, and the bonding force between the active material layer and the metal layer is better.

The above description is only a few examples of the present application and is not intended to limit the present application, and various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A bipolar current collector is characterized by comprising an insulating film layer, a positive metal layer and a negative metal layer;

the insulating film layer is provided with a first surface and a second surface along the thickness direction, the positive electrode metal layer is arranged on the first surface, and the negative electrode metal layer is arranged on the second surface;

the positive electrode metal layer is provided with a first coating area for coating positive electrode active substances and a first electrode lug area for connecting a positive electrode lug, and the thickness of the first electrode lug area is greater than that of the first coating area;

the negative electrode metal layer is provided with a second coating area for coating a negative electrode active material and a second pole ear area for connecting a negative electrode pole ear, and the thickness of the second pole ear area is greater than that of the second coating area.

2. The bipolar current collector of claim 1, wherein the maximum difference in thickness between the first tab region and the first coated region is 1-400nm, and the maximum difference in thickness between the second tab region and the second coated region is 1-600 nm.

3. The bipolar current collector of claim 2, wherein the first coated region has a thickness of 20-1500nm, and the first tab region has a thickness of 30-2000 nm; the thickness of the second coating region is 30-2500nm, and the thickness of the second polar ear region is 50-3000 nm.

4. The bipolar current collector of claim 1, wherein the first coating region comprises a first sub-region and a second sub-region; the first sub-areas are distributed at positions close to the first polar ear area and positions far away from the first polar ear area, and the second sub-area is positioned between the two first sub-areas; the thickness of the first sub-area is consistent with that of the first polar lug area, and the thickness of the first sub-area is larger than that of the second sub-area;

the second coated region comprises a third subregion and a fourth subregion; the third sub-regions are distributed at positions close to the second polar ear region and at positions far away from the second polar ear region, and the fourth sub-region is positioned between the two third sub-regions; the thickness of the third sub-area is consistent with that of the second pole ear area, and the thickness of the third sub-area is larger than that of the fourth sub-area.

5. The bipolar current collector of claim 4, wherein the width of the first sub-region is 1-5 mm; the width of the third subregion is 1-5 mm.

6. The bipolar current collector of claim 4, wherein a fifth sub-region is further disposed between the first sub-region and the second sub-region, the fifth sub-region gradually becoming thicker along a direction from the second sub-region to the first sub-region; a sixth sub-region is further arranged between the third sub-region and the fourth sub-region, and the sixth sub-region gradually becomes thicker along the direction from the fourth sub-region to the third sub-region.

7. The bipolar current collector of any one of claims 1 to 6, wherein the first surface has a first blank area and a first metal area covered by the positive metal layer, the second surface has a second blank area and a second metal area covered by the negative metal layer, a projection of the first tab area of the positive metal layer in a thickness direction of the insulating film layer is located in the second blank area, and a projection of the second tab area of the negative metal layer in the thickness direction of the insulating film layer is located in the first blank area.

8. The bipolar current collector of claim 7, wherein the first and second blank regions are respectively adjacent to both edges of the insulating film layer in a width direction of the insulating film layer.

9. A pole piece, comprising:

a bipolar current collector as claimed in any one of claims 1 to 8;

a positive electrode active material layer disposed in the first coating region;

a negative electrode active material layer disposed in the second coating region;

the positive electrode lug is connected to the first electrode lug area;

and the negative pole lug is connected to the second lug area.

10. A secondary battery, comprising an electric core, wherein the electric core comprises a plurality of pole pieces according to claim 9, and a plurality of diaphragms, one diaphragm is disposed between two adjacent pole pieces, and the positive electrode active material layer and the negative electrode active material layer are disposed on two sides of the diaphragm respectively.