Laminated cell and battery

Abstract

The utility model discloses a laminated cell and a battery, the laminated cell is provided with an uppermost pole piece, a middle pole piece group and a lowermost pole piece which are sequentially laminated along the lamination direction, and the laminated cell comprises a main body part and a first tab part connected to the first side of the main body part; the main body part is provided with a first thinned area on the first side, a surface perpendicular to the stacking direction is a projection surface, and the projection of the first thinned area on the projection surface forms a first thinned area; the main body part is provided with a first coating on one surface, far away from the middle pole piece group, of the uppermost pole piece and / or the lowermost pole piece, the projection of the first coating on the projection surface forms a thickened area, and the thickened area is located in the first thinned area. The utility model is applied to the field of secondary batteries.

Description

Technical Field

[0001] The utility model relates to the field of secondary batteries, in particular to a laminated battery core and a battery. Background Art

[0002] While lithium-ion batteries are widely used, they are also subject to increasingly higher requirements from consumers, such as high energy density, high charging speed, and long battery life. Stacking technology has the advantages of high energy density and high safety due to its high volume utilization rate and more stable internal structure. Therefore, it is considered to be one of the most promising technologies in the field of lithium-ion batteries.

[0003] In the current manufacturing process of lithium-ion battery stacking, zebra coating technology is often used in the coating process. At present, the zebra coating process has the problem that it is difficult to achieve zero thinning at the edge, so the thickness is thin. The coating thinning area at the edge of the positive and negative pole pieces corresponds to the edge area of ​​the battery head. Due to the accumulation of thickness differences of all pole pieces, the area close to the head of the battery is often thinner than the main body, which leads to insufficient hot pressing force during the stacking process and the battery formation process. In particular, after the package is soaked in electrolyte, the bonding force between the single-sided positive pole piece and the diaphragm is much smaller than that of the double-sided positive pole piece. At the same time, due to the electron repulsion effect and the tip discharge effect, the current density at the head of the stacked battery cell is greater than that of other parts, and the expansion stress generated during the cycle is much greater than that of the central area. The existence of thickness difference makes it difficult to recover the deformation after the expansion stress is released, which leads to serious lithium deposition at the head and causes lithium deposition on the inner double-sided pole piece, which seriously affects the performance and process development of the stacked battery cell. Utility Model Content

[0004] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model provides a laminated battery core, which can improve battery performance.

[0005] The utility model also provides a battery having the laminated battery core.

[0006] According to the first aspect of the present invention, the laminated battery core has an uppermost electrode sheet, an intermediate electrode sheet group and a lowermost electrode sheet stacked in sequence along a stacking direction, and the laminated battery core includes: a main body and a first electrode ear connected to a first side of the main body;

[0007] The main body has a first thinned area on the first side, a surface perpendicular to the stacking direction is a projection surface, and a projection of the first thinned area on the projection surface forms a first thinned region;

[0008] The main body is provided with a first coating on a side of the uppermost pole piece and / or the lowermost pole piece away from the middle pole piece group, and the projection of the first coating on the projection plane forms a thickened area, and the thickened area is located in the first thinned area.

[0009] According to the stacked battery cell of the first aspect embodiment of the utility model, at least the following beneficial effects are achieved: the coating thickness in the first thinned area is lower than the normal coating thickness, and the thickened area is arranged in the first thinned area, so that the thickness of the first coating layer can make up for the reduced thickness in the first thinned area, and when multiple pole pieces are stacked into a stacked battery cell, the sum of the thickness differences in the thinned areas of each pole piece can be made up by the thickness of the first coating layer, and when the stacked battery cell is hot-pressed, each pole piece is subjected to uniform hot-pressing force, so that the pole pieces can fit tightly, thereby improving the bonding force between the pole pieces and avoiding lithium deposition, thereby improving the cycle performance and safety performance of the battery; the first coating layer is only applied to the topmost pole piece and / or the bottommost pole piece, and the increase in the overall manufacturing process of the stacked battery cell is less; the thickness difference accumulated in the thinned areas of multiple pole pieces is directly eliminated by the thickness of the first coating layer, and the control requirements for the coating accuracy of the first coating layer are lower, and the control is more convenient; the first coating layer is located on the side of the topmost pole piece and / or the bottommost pole piece away from the main body, and the first coating layer improves the bonding force between the original pole piece and the diaphragm without affecting the bonding between the original pole piece and the diaphragm.

[0010] According to some embodiments of the present invention, the main body is provided with a second thinned area on a second side opposite to the first side, the projection of the second thinned area on the projection plane forms a second thinned region, and the thickened region is also located in the second thinned region.

[0011] According to some embodiments of the present invention, the length of the first coating along the direction from the first side to the second side relative to the first side is D, and the pole piece satisfies: <D≤10mm。

[0012] According to some embodiments of the present invention, the main body further comprises an un-thinned area connected to the first thinned area, and the thickness of the un-thinned area along the stacking direction is h. 1 , the thickness of the first thinned area is h 2 , the thickness of the first coating is h 3 , the pole piece satisfies: h 1 >h 2 ,h 1 =h 2 +h 3 .

[0013] According to some embodiments of the present invention, an edge of the first coating on the first side overlaps with an edge of the main body on the first side.

[0014] According to some embodiments of the present invention, the first coating layer is an insulating layer.

[0015] According to some embodiments of the utility model, the intermediate pole piece group includes multiple first pole pieces, the topmost pole piece, all the first pole pieces, and the bottommost pole piece have the same polarity and are all provided with a first pole ear portion, and all the first pole ear portions are stacked along the stacking direction to form the first pole ear portion.

[0016] According to some embodiments of the present utility model, the laminated battery core further includes a second pole ear portion, and the second pole ear portion and the first pole ear portion are both located on the first side of the main body portion;

[0017] or,

[0018] The laminated battery cell also includes a second pole ear portion, which is located on different sides of the main body from the first pole ear portion. The main body is provided with a third thinning zone on the connection side of the second pole ear portion. The projection of the third thinning zone on the projection plane forms a third thinning area, and the thickened area is also located in the third thinning area.

[0019] According to some embodiments of the utility model, the uppermost electrode sheet and the lowermost electrode sheet are coated with a second coating on one side facing the intermediate electrode sheet group, the intermediate electrode sheet group includes a plurality of first electrode sheets and a plurality of second electrode sheets, the first electrode sheets and the second electrode sheets are alternately distributed along the stacking direction, and the second electrode sheets are located at both ends of the intermediate electrode sheet group along the stacking direction, the first electrode sheet has a second coating on both sides along the stacking direction, the second electrode sheet has a third coating on both sides along the stacking direction, the second coating has opposite polarities to the third coating, the main body further has an unthinned area connected to the first thinned area, and the thickness of the unthinned area along the stacking direction is h 1 , the thickness of the first thinned area is h 2 , the thickness of the first coating is h 3 , the pole piece satisfies: h 1 >h 2 ,h 3 =[(CW 1 / PD 1 +CW 2 / PD 2 ) / 1540.25*1000*X]*(1-h 2 / h 1 );

[0020] CW 1 : coating surface density of the second coating layer;

[0021] PD 1: The compacted surface density of the second coating after rolling;

[0022] CW 2 : coating surface density of the third coating;

[0023] PD 2 : The compacted surface density of the third coating after rolling;

[0024] X: the number of stacked pole pieces coated with the third coating.

[0025] The battery according to the embodiment of the second aspect of the utility model includes: the laminated battery core described in the embodiment of the first aspect of the utility model.

[0026] The battery according to the embodiment of the second aspect of the utility model has at least the following beneficial effects: using the stacked battery cell of the embodiment of the first aspect of the utility model is conducive to compensating for the problem of thinness in the head area of ​​the battery cell caused by the thinning area, the battery cell structure is flatter, the formation hot pressing force is more uniform, the bonding force between the pole piece and the diaphragm is significantly increased, and the problem of lithium deposition at the head of the stacked pole piece can be effectively improved, and the cycle performance can be significantly improved.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below with reference to the accompanying drawings and embodiments, wherein:

[0029] Figure 1 This is a schematic diagram of the structure of a laminated battery cell according to an embodiment of the utility model;

[0030] Figure 2 This is a structural schematic diagram of a first implementation mode of a laminated battery cell according to an embodiment of the utility model;

[0031] Figure 3 This is a structural schematic diagram of a second implementation of a laminated battery cell according to an embodiment of the utility model;

[0032] Figure 4 It is a structural schematic diagram of a third implementation mode of a laminated battery cell of an embodiment of the utility model.

[0033] Figure Number:

[0034] The topmost pole piece 100; the first coating 110;

[0035] Intermediate pole piece group 200;

[0036] The bottom pole piece 300;

[0037] Main body 400; first thinned area 410; second thinned area 420; third thinned area 430; fourth thinned area 440; un-thinned area 450;

[0038] The first pole lug portion 500 . DETAILED DESCRIPTION

[0039] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0040] In the description of the present invention, it should be understood that the descriptions involving orientation, such as the orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0041] In the description of the present utility model, "several" refers to one or more, and "multiple" refers to two or more. If there is a description of "first" or "second", it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0042] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0043] It should be noted that the zebra coating technology refers to: continuous coating along the coating direction to form a coating area and an empty foil area with foil alternately distributed along the coating direction, and then a coating area and an adjacent empty foil area are used as a unit. The foil is cut into multiple units, and the empty foil area of ​​each unit is cut to form a false pole ear during the lamination die-cutting, and the single-layer pole piece is formed by die-cutting. However, due to the accuracy of the coating equipment, the coating thickness at both ends of a coating area (close to the empty foil) is often lower than the designed coating thickness, and a thinning area is formed at the edge of the pole piece. After the multiple pole pieces are stacked, the reduced thickness of the thinning area is accumulated, which in turn affects the performance of the battery.

[0044] When the foil is cut to form a pole piece, whether the pole piece has one thinning area or two thinning areas is related to the first cutting method, specifically including the following situations:

[0045] 1. Along the coating direction, the foil has an empty foil area, a coating area and another empty foil area. The first cutting position is located at the center of an empty foil area, the center of the coating area and the center of another empty foil area. Half of the coating area and half of an empty foil area form a unit, and the other half of the coating area and half of another empty foil area form a unit. At this time, a unit has only one thinning area at the connection position of the empty foil area and the coating area, that is, the electrode has only one thinning area, the electrode forms a main body in the coating area, and forms a false pole ear in the empty foil area;

[0046] 2. Along the coating direction, the foil has an empty foil area, a coating area and another empty foil area. The first cutting position is located at the connection position of the coating area and the other empty foil area. After cutting, an empty foil area and the coating area form a unit. One unit has a first thinning area at the connection position of the coating area and an empty foil area, and one unit has a second thinning area at the connection position of the coating area and the other empty foil area, that is, the electrode has two thinning areas. The electrode forms a main part in the coating area and a false electrode ear in the empty foil area.

[0047] Reference Figures 1 to 4 As shown, a laminated battery cell of an embodiment of the utility model has an uppermost electrode sheet 100, an intermediate electrode sheet group 200 and a lowermost electrode sheet 300 sequentially stacked in a stacking direction, and the laminated battery cell includes: a main body 400 and a first pole ear portion 500 connected to a first side of the main body 400; the main body 400 has a first thinned area 410 on the first side, and the surface perpendicular to the stacking direction is a projection surface, and the projection of the first thinned area 410 on the projection surface forms a first thinned area; the main body 400 is at the uppermost electrode sheet 100, the middle electrode sheet group 200 and the lowermost electrode sheet 300 are stacked in a stacking direction, and the laminated battery cell includes: a main body 400 and a first pole ear portion 500 connected to a first side of the main body 400; the main body 400 has a first thinned area 410 on the first side, and the surface perpendicular to the stacking direction is a projection surface, and the projection of the first thinned area 410 on the projection surface forms a first thinned area; A first coating 110 is provided on a side of the layer electrode 100 and / or the bottom electrode 300 away from the middle electrode group 200. The projection of the first coating 110 on the projection plane forms a thickened area, and the thickened area is located in the first thinned area. The stacked battery cell in this embodiment increases the thickness of the first thinned area 410 through the first coating 110 to fill the reduced thickness of the first thinned area 410, thereby reducing the probability of lithium deposition in the stacked battery cell in the first thinned area 410 and improving the cycle performance and safety performance of the battery.

[0048] In this embodiment, the laminated battery cell includes alternately stacked positive and negative electrode sheets, all of which have false pole ears, and in the process of cutting the foil to form the pole sheets, the foil is cut into pole sheets in the first cutting process using the first method, and each pole sheet has only one thinning area, and the pole sheet includes a main body portion and a false pole ear connected to the main body portion. When the main body portion of each pole sheet is stacked and the false pole ears of each pole sheet are stacked, the positive false pole ears are stacked to form the positive pole ear portion, and the negative false pole ears are stacked to form the negative pole ear portion, and the thinning areas of the pole sheets are stacked.

[0049] When the first pole ear portion 500 is provided on the first side of the main body 400, the main body 400 will have a first thinned area 410 on the first side, and the coating thickness of the first thinned area 410 is lower than the coating thickness of the un-thinned area. The main body 400 is provided with a first coating 110 on a side of the uppermost pole piece 100 and the lowermost pole piece 300 away from the middle pole piece group 200, and the thickened area formed by the first coating 110 on the projection surface is located within the first thinned area formed by the first thinned area 410 on the projection surface, so that the thickness difference between the first thinned area 410 and the un-thinned area can be compensated by the thickness of the first coating 110, and then during hot pressing, the existence of the first coating 110 can make the thinned areas of each pole piece tightly connected, and each pole piece is subjected to uniform hot pressing force, so that the pole pieces can fit tightly, thereby improving the adhesion between the pole pieces and avoiding lithium deposition, thereby improving the cycle performance and safety performance of the battery. The first coating 110 may be provided on a side of the uppermost electrode sheet 100 or the lowermost electrode sheet 300 away from the middle electrode sheet group 200; and the first electrode ear 500 may be a positive electrode ear or a negative electrode ear.

[0050] It should be noted that if a compensation layer having the same thinning thickness as that of each thinning area is coated in the thinning area of ​​each pole piece of the intermediate pole piece group 200, the accuracy of the thickness of the compensation layer is extremely high, and the thickness of the compensation layer needs to be precisely controlled to ensure that the thickness of the compensation layer is the same as the thinning thickness of the thinning area of ​​the pole piece. The accuracy of the thickness of the compensation layer is difficult to control, and the manufacturing process is complex. Moreover, when the thickness of the compensation layer exceeds the thinning thickness of the first thinning area, the presence of the compensation layer will also make it impossible for the pole piece to be completely attached to the diaphragm, resulting in a decrease in the bonding force between the pole piece and the diaphragm, which is prone to lithium deposition.

[0051] It is worth understanding that in this embodiment, the first coating 110 is only applied to the topmost electrode sheet 100 and / or the bottommost electrode sheet 300, and there is no need to apply a compensation layer to the thinned area of ​​each electrode sheet of the intermediate electrode sheet group 200. The increase in the overall manufacturing process of the laminated battery cell is less, and the manufacturing is more convenient; the thickness difference accumulated in the thinned areas of multiple electrode sheets is directly eliminated by the thickness of the first coating 110, without the need to eliminate the thickness difference of each thinned area of ​​the electrode sheet separately. The control requirements for the coating accuracy of the first coating 110 are lower, and the control is more convenient. The first coating 110 is located on the side of the topmost electrode sheet 100 and / or the bottommost electrode sheet 300 away from the main body 400. The first coating 110 improves the bonding force between the original electrode sheet and the diaphragm without affecting the bonding between the original electrode sheet and the diaphragm.

[0052] Reference Figure 1 and Figure 2 As shown, in some specific embodiments of the present invention, the main body 400 is provided with a second thinned area 420 on the second side opposite to the first side, and the projection of the second thinned area 420 on the projection plane forms a second thinned region, and the thickened area is also located in the second thinned region.

[0053] In this embodiment, in the process of cutting the foil to form pole pieces, the foil is cut into pole pieces by the second method in the first cutting process, and each pole piece has two thinning areas. The pole piece includes a main body portion and a false pole ear connected to the main body portion. One thinning area is located at the connection position between the main body portion and the false pole ear, and the other thinning area is located on the opposite side of the connection position between the main body portion and the false pole ear. When the main body portion of each pole piece is stacked and the false pole ears of each pole piece are stacked, the positive false pole ears are stacked to form the positive pole ear portion, and the negative false pole ears are stacked to form the negative pole ear portion, and the two thinning areas of the pole piece are stacked separately.

[0054] When the first pole ear portion 500 is provided on the first side of the main body 400, the main body 400 will have a first thinned area 410 on the first side and a second thinned area 420 on the second side relative to the first side. The coating thickness of the first thinned area 410 and the second thinned area 420 is lower than the coating thickness of the non-thinned area. The main body 400 is provided with a first coating 110 on a side of the uppermost pole piece 100 and the lowermost pole piece 300 away from the middle pole piece group 200. The thickened area formed by the first coating 110 on the projection surface is located in the first thinned area 410. In the first thinned area formed on the projection surface, the second thinned area 420 is also located in the second thinned area formed on the projection surface, so that the thickness difference between the first thinned area 410 and the second thinned area 420 compared with the unthinned area can be compensated by the thickness of the first coating 110, and then during hot pressing, the existence of the first coating 110 can make the thinned areas of each pole piece tightly connected, and the hot pressing force of each pole piece is uniform, so that the pole pieces can fit tightly, improve the bonding force between the pole pieces, avoid lithium precipitation, and thus improve the cycle performance and safety performance of the battery. Among them, the first coating 110 can also be provided on the side of the top pole piece 100 or the bottom pole piece 300 away from the middle pole piece group 200.

[0055] In some specific embodiments of the utility model, the first coating 110 can be an insulating layer, which can be insulated while having a thickening effect. It should be noted that when the battery falls, there is a situation where the tab is inserted upside down into the battery cell and a short circuit occurs. By setting the first coating 110 as an insulating layer, the tab will first contact the first coating 110 and be insulated by the first coating 110, which can avoid the short circuit safety problem caused by the tab being inserted upside down during the drop test of the battery cell, and improve the safety performance of the battery cell. In this embodiment, the insulating layer is a ceramic layer.

[0056] In some specific embodiments of the present invention, the length of the first coating 110 along the direction from the first side to the second side relative to the first side is D, and the pole piece satisfies: <D≤10mm。

[0057] Reference Figure 1As shown, in some specific embodiments of the present invention, the main body 400 further has an un-thinned area 450 connected to the first thinned area 410. Along the stacking direction, the thickness of the un-thinned area 450 is h 1 , the thickness of the first thinned area 410 is h 2 , the thickness of the first coating 110 is h 3 , the pole piece meets: h 1 >h 2 ,h 1 =h 2 +h 3 .

[0058] It is worth understanding that in the pole piece: h 1 >h 2 ,h 1 =h 2 +h 3 When the first coating 110 is applied, the thickness of the first thinned area 410 can be just enough to fill the thinned thickness, so that the thickness of the first coating 110 plus the thickness of the first thinned area 410 is equal to the thickness of the un-thinned area 450. During hot pressing, each pole piece is subjected to uniform pressure, so that the pole pieces can fit tightly, thereby improving the bonding force between the pole pieces, avoiding lithium deposition, and thereby improving the cycle performance and safety performance of the battery.

[0059] Reference Figure 1 and Figure 2 As shown, in some specific embodiments of the present invention, the edge of the first coating 110 on the first side overlaps with the edge of the main body 400 on the first side.

[0060] It should be noted that the thinning thickness of the thinned area at the edge of the main body 400 is the largest. When the first coating 110 overlaps the edge of the first side of the main body 400 from the edge of the first side, the first coating 110 has the best thickening effect and can maximize the filling of the thinned thickness of the first thinned area 410, thereby improving the use effect.

[0061] Reference Figure 1 As shown, in some specific embodiments of the present invention, the intermediate pole piece group 200 includes multiple first pole pieces, the topmost pole piece 100, all the first pole pieces, and the bottommost pole piece 300 have the same polarity and are all provided with a first pole ear portion, and all the first pole ear portions are stacked along the stacking direction to form a first pole ear portion 500.

[0062] In this embodiment, the middle pole piece group 200 includes a first pole piece and a second pole piece, the polarity of the second pole piece is opposite to that of the first pole piece, both sides of the first pole piece are coated with polar materials, and the top pole piece 100 and the bottom pole piece 300 are only provided with polar materials on one side facing the middle pole piece group 200, that is, the first pole piece of the middle pole piece group 200 is coated on both sides, and the top pole piece 100 and the bottom pole piece 300 are coated on one side. Among them, the first pole piece can be a positive pole piece or a negative pole piece. In addition, in theory, the polarity of the top pole piece 100 and the bottom pole piece 300 can also be opposite.

[0063] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, in some specific embodiments of the present invention, the stacked battery cell also includes a second pole ear portion, and the second pole ear portion and the first pole ear portion 500 are both located on the first side of the main body 400; or, the stacked battery cell also includes a second pole ear portion, and the second pole ear portion and the first pole ear portion 500 are located on different sides of the main body 400, and the main body 400 is provided with a third thinning area 430 on the connection side of the second pole ear portion, and the projection of the third thinning area 430 on the projection plane forms a third thinning region, and the thickening region is also located in the third thinning region.

[0064] In this embodiment, the first pole piece of the intermediate pole piece group 200, the top pole piece 100 and the bottom pole piece 300 together form a first thinning area 410 or a first thinning area 410 and a second thinning area 420; all second pole pieces of the intermediate pole piece group 200 have second pseudo pole pieces, and when the foil is cut to form second pole pieces in the first cutting method using the first method, each second pole piece has only one thinning area, and all second pseudo pole pieces are stacked to form a second pole piece portion.

[0065] According to the number of thinned areas of the first pole lug, the number of thinned areas of the second pole piece, and the relative position of the first pole lug portion 500 and the second pole lug portion, the following distribution is included:

[0066] 1. When the first pole piece has only one thinned area, the second pole piece has only one thinned area, and the first pole ear portion 500 and the second pole ear portion are both located on the first side of the main body portion 400, the thinned area of ​​the second pole piece will form a first thinned area 410 together with the thinned area of ​​the first pole piece, and will be thickened by the first coating 110 to a thickness close to that of the unthinned area 450, so that the thickness distribution of the main body portion 400 of the pole piece is uniform, which is convenient for hot pressing;

[0067] 2. When the first pole piece has only one thinned area, the second pole piece has only one thinned area, and the first pole ear portion 500 and the second pole ear portion are located on different sides of the main body 400, the thinned area of ​​the second pole piece forms a third thinned area 430 alone, and the projection of the third thinned area 430 on the projection plane forms a third thinned region, and the thickened area formed by the first coating 110 is also located in the third thinned region. The first coating 110 thickens both the first thinned area 410 and the third thinned area 430, so that the thickness distribution of the main body 400 of the pole piece is uniform, which is convenient for hot pressing;

[0068] 3. When the first pole piece has two thinned areas, the second pole piece has only one thinned area, and the first pole ear portion 500 and the second pole ear portion are both located on the first side of the main body portion 400, one thinned area of ​​the second pole piece and one thinned area of ​​the first pole piece together form a first thinned area 410, and another thinned area of ​​the first pole piece forms a second thinned area 420, and the thickened area formed by the first coating 110 is also located in the second thinned area, and the first coating 110 thickens both the first thinned area 410 and the second thinned area 420, so that the thickness distribution of the main body portion 400 of the pole piece is uniform, which is convenient for hot pressing;

[0069] 4. When the first pole piece has two thinned areas, the second pole piece has only one thinned area, and the first pole ear portion 500 is located on the first side of the main body 400, and the second pole ear portion is located on the second side of the main body 400, one thinned area of ​​the first pole piece forms a first thinned area 410, and one thinned area of ​​the second pole piece and another thinned area of ​​the first pole piece together form a second thinned area 420, and the thickened area formed by the first coating 110 is also located in the second thinned area, and the first coating 110 thickens both the first thinned area 410 and the second thinned area 420, so that the thickness distribution of the main body 400 of the pole piece is uniform, which is convenient for hot pressing;

[0070] 5. When the first pole piece has two thinning areas, the second pole piece has only one thinning area, and the first pole ear portion 500 is located on the first side of the main body 400, and the second pole ear portion is located on the third side or the fourth side of the main body 400 adjacent to the first side, one thinning area of ​​the first pole piece forms a first thinning area 410, another thinning area of ​​the first pole piece forms a second thinning area 420, and the thinning area of ​​the second pole piece alone forms a third thinning area 430, and the thickened area formed by the first coating 110 is located in the first thinning area, the second thinning area, and the third thinning area, and the first coating 110 thickens the first thinning area 410, the second thinning area 420, and the third thinning area 430, so that the thickness distribution of the main body 400 of the pole piece is uniform, which is convenient for hot pressing;

[0071] 6. The first pole piece has two thinning areas, the second pole piece has two thinning areas, and the first pole ear portion 500 and the second pole ear portion are both located on the first side of the main body portion 400 or the first pole ear portion 500 is located on the first side of the main body portion 400 and the second pole ear portion is located on the second side of the main body portion 400, one thinning area of ​​the second pole piece and one thinning area of ​​the first pole piece together form a first thinning area 410, another thinning area of ​​the second pole piece and another thinning area of ​​the first pole piece form a second thinning area 420, the thickened area formed by the first coating 110 is located in the first thinning area and the second thinning area, the first coating 110 thickens both the first thinning area 410 and the second thinning area 420, so that the thickness distribution of the main body portion 400 of the pole piece is uniform, which is convenient for hot pressing;

[0072] 7. When the first pole piece has two thinning areas, the second pole piece has two thinning areas, and the first pole ear portion 500 is located on the first side of the main body 400, and the second pole ear portion is located on the third side or the fourth side of the main body 400 adjacent to the first side, one thinning area of ​​the first pole piece forms a first thinning area 410, another thinning area of ​​the first pole piece forms a second thinning area 420, the thinning area of ​​the second pole piece alone forms a third thinning area 430, and another thinning area of ​​the second pole piece forms a fourth thinning area 440, and the thickened area formed by the first coating 110 is located in the first thinning area, the second thinning area, the third thinning area and the fourth thinning area 440, and the first coating 110 thickens the first thinning area 410, the second thinning area 420, the third thinning area 430 and the fourth thinning area 440, so that the thickness distribution of the main body 400 of the pole piece is uniform, which is convenient for hot pressing.

[0073] Reference Figure 1 As shown, in some specific embodiments of the present invention, the uppermost electrode sheet 100 and the lowermost electrode sheet 300 are coated with a second coating on one side facing the middle electrode sheet group 200, the middle electrode sheet group 200 includes a plurality of first electrode sheets and a plurality of second electrode sheets, the first electrode sheets and the second electrode sheets are alternately distributed along the stacking direction, and the second electrode sheets are located at both ends of the middle electrode sheet group 200 along the stacking direction, the first electrode sheets have a second coating on both sides along the stacking direction, the second electrode sheets have a third coating on both sides along the stacking direction, the second coating has opposite polarities to the third coating, the main body 400 further includes an un-thinned area 450 connected to the first thinned area 410, and the thickness of the un-thinned area 450 along the stacking direction is h 1 , the thickness of the first thinning zone is h 2 , the thickness of the first coating 110 is h 3 , the pole piece meets: h 1 >h 2 ,h 3 =[(CW 1 / PD 1 +CW 2 / PD2 ) / 1540.25*1000*X]*(1-h 2 / h 1 );

[0074] CW 1 : coating surface density of the second coating;

[0075] PD 1 : The compacted surface density of the second coating after rolling;

[0076] CW 2 : coating surface density of the third coating;

[0077] PD 2 : compacted surface density of the third coating after rolling;

[0078] X: the number of stacked pole pieces coated with the third coating.

[0079] In this embodiment, the first coating 110 has a thickness h 3 The range is 5mm≤h 3 ≤10mm, the first coating 100 is in a suitable thickness range, so that the first coating 100 can improve the battery cell cycle performance.

[0080] In some specific embodiments of the utility model, the battery according to the embodiment of the second aspect of the utility model includes: the laminated battery cell of the embodiment of the first aspect of the utility model. It is worth understanding that the battery using the laminated battery cell of the embodiment of the first aspect of the utility model is conducive to compensating for the problem of thinness in the head area of ​​the battery cell caused by the thinning area, the battery cell structure is flatter, the formation hot pressing force is more uniform, the bonding force between the pole piece and the diaphragm is significantly increased, and the lithium deposition problem at the head of the laminated pole piece can be effectively improved, and the cycle performance can be significantly improved.

[0081] For ease of understanding, a specific embodiment is used as an example below, and the following content does not constitute a specific limitation to the present invention.

[0082] Example 1

[0083] The first electrode sheet of the intermediate electrode sheet group 200, the top electrode sheet 100 and the bottom electrode sheet 300 are all positive electrode sheets, and the second electrode sheet of the intermediate electrode sheet group 200 is a negative electrode sheet. The positive electrode sheet and the negative electrode sheet each have only one thinning area, and all electrode sheets have false electrode ears, and the false electrode ears of the positive electrode sheet and the negative electrode sheet are located on the same side of the main body, that is, the first side of the main body 400 is provided with a positive electrode ear and a negative electrode ear, and the second side of the main body 400 is opposite to the first side.

[0084] The thickness h of the first coating layer 110 of the positive electrode sheet 3=15mm, and the coating width D of the first coating layer 110 from the first side to the second side is =10mm.

[0085] Example 2

[0086] The difference from Example 1 is that the thickness h of the first coating layer 110 of the positive electrode sheet is 3 =10 mm, and the coating width D of the first coating layer 110 from the first side to the second side is 10 mm.

[0087] Example 3

[0088] The difference from Example 1 is that the thickness h of the first coating layer 110 of the positive electrode sheet is 3 =5mm, and the coating width D of the first coating layer 110 from the first side to the second side is =10mm.

[0089] Example 4

[0090] The difference from Example 1 is that the thickness h of the first coating layer 110 of the positive electrode sheet is 3 =15mm, and the coating width D of the first coating layer 110 from the first side to the second side is =5mm.

[0091] Example 5

[0092] The difference from Example 1 is that the thickness h of the first coating layer 110 of the positive electrode sheet is 3 =10 mm, and the coating width D of the first coating 110 from the first side to the second side =5 mm.

[0093] Example 6

[0094] The difference from Example 1 is that the thickness h of the first coating layer 110 of the positive electrode sheet is 3 =5mm, and the coating width D of the first coating layer 110 from the first side to the second side is 5mm.

[0095] Comparative Example 1

[0096] The difference from Example 1 is that the thickness h of the first coating layer 110 of the positive electrode sheet is 3 =0 mm, and the coating width D of the first coating layer 110 along the direction from the first side to the second side =0 mm.

[0097] After the battery cell is manufactured, the battery is charged and discharged for 1000 times, and then the battery is disassembled. The results are shown in the following table:

[0098] Table 1 Test results of all embodiments and comparative examples

[0099] Case Adhesion force N / m Capacity retention rate % Cycle expansion % Lithium deposition interface Example 1 9.2 95.2％ 9.1％ No lithium precipitation Example 2 7.6 85.9％ 14.2％ No lithium precipitation Example 3 5.3 82.4％ 17.9％ Slight lithium deposition Example 4 8.3 88.6％ 12.8％ No lithium precipitation Example 5 7.1 84.3％ 16.2％ No lithium precipitation Example 6 3.8 79.6％ 18.6％ Moderate lithium precipitation Comparative Example 1 2.3 75.3％ 21.4％ Severe lithium deposition

[0100] Among them, the bonding strength is estimated by using a tensile tester to test the tensile force between the electrode and the diaphragm in the bare battery cell after hot pressing of the stacking.

[0101] It can be seen from the above table that: when the positive electrode is coated with the first coating 110, the bonding force of the battery cell is higher, and the prepared lithium-ion battery can reduce the deformation caused by expansion stress during the cycle, reduce the probability of lithium deposition during the cycle, and make the battery have a lower cycle expansion rate, better cycle performance, and the lithium deposition situation is significantly improved.

[0102] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A laminated battery cell, comprising an uppermost electrode sheet, an intermediate electrode sheet group and a lowermost electrode sheet stacked in sequence along a stacking direction, characterized in that: The laminated battery core comprises: a main body and a first pole ear connected to a first side of the main body; The main body has a first thinned area on the first side, a surface perpendicular to the stacking direction is a projection surface, and a projection of the first thinned area on the projection surface forms a first thinned region; The main body is provided with a first coating on a side of the uppermost pole piece and / or the lowermost pole piece away from the middle pole piece group, and the projection of the first coating on the projection plane forms a thickened area, and the thickened area is located in the first thinned area.

2. The laminated battery cell according to claim 1, characterized in that: The main body is provided with a second thinned area on a second side opposite to the first side, the projection of the second thinned area on the projection plane forms a second thinned region, and the thickened region is also located in the second thinned region.

3. The laminated battery cell according to claim 1, characterized in that: Along the direction from the first side to the second side relative to the first side, the length of the first coating is D, and the pole piece satisfies: <D≤10mm。 4. The laminated battery cell according to claim 1, characterized in that: The first coating layer is an insulating layer.

5. The laminated battery cell according to claim 1, characterized in that: The main body also has an unthinned area connected to the first thinned area. Along the stacking direction, the thickness of the unthinned area is h1, the thickness of the first thinned area is h2, the thickness of the first coating is h3, and the pole piece satisfies: h1>h2, h1=h2+h3.

6. The laminated battery cell according to claim 1, characterized in that: An edge of the first coating layer on the first side overlaps with an edge of the main body on the first side.

7. The laminated battery cell according to claim 1, characterized in that: The intermediate pole piece group includes a plurality of first pole pieces, the topmost pole piece, all the first pole pieces, and the bottommost pole piece have the same polarity and are all provided with a first pole ear portion, and all the first pole ear portions are stacked along the stacking direction to form the first pole ear portion.

8. The laminated battery cell according to claim 1, characterized in that: The laminated battery core further includes a second pole ear portion, wherein the second pole ear portion and the first pole ear portion are both located on the first side of the main body portion; or, The laminated battery cell also includes a second pole ear portion, which is located on different sides of the main body from the first pole ear portion. The main body is provided with a third thinning zone on the connection side of the second pole ear portion. The projection of the third thinning zone on the projection plane forms a third thinning area, and the thickened area is also located in the third thinning area.

9. The laminated battery cell according to claim 1, characterized in that: The uppermost electrode sheet and the lowermost electrode sheet are coated with a second coating on one side facing the intermediate electrode sheet group, the intermediate electrode sheet group includes a plurality of first electrode sheets and a plurality of second electrode sheets, the first electrode sheets and the second electrode sheets are alternately distributed along the stacking direction, and the second electrode sheets are located at both ends of the intermediate electrode sheet group along the stacking direction, the first electrode sheet has a second coating on both sides along the stacking direction, the second electrode sheet has a third coating on both sides along the stacking direction, the second coating has opposite polarity to the third coating, the main body also has an un-thinned area connected to the first thinned area, along the stacking direction, the thickness of the un-thinned area is h1, the thickness of the first thinned area is h2, the thickness of the first coating is h3, and the electrode sheet satisfies: h1>h2, h3=[(CW1 / PD1+CW2 / PD2) / 1540.25*1000*X]*(1-h2 / h1); CW1: coating area density of the second coating; PD1: compacted surface density of the second coating after roller pressing; CW2: coating surface density of the third coating layer; PD2: compacted surface density of the third coating after rolling; X: the number of stacked pole pieces coated with the third coating.

10. A battery, characterized in that: include: The laminated battery cell according to any one of claims 1 to 9.

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