Laminated battery and preparation method thereof

Abstract

The invention relates to the technical field of batteries, in particular to a laminated battery which comprises a shell and an electrode assembly contained in the shell, the electrode assembly comprises a plurality of first pole pieces and two second pole pieces which are laminated in the thickness direction, each second pole piece comprises a current collector, an active substance layer and a functional layer, and the functional layer is arranged in the edge area of the surface of the current collector. The functional layer is arranged to relieve warping of the pole piece in the rolling process due to inconsistent extension tension of the two sides of the single-sided piece, and the functional layer is arranged in the edge area of the surface of the current collector, so that the thickness of the edge of the pole piece is larger, and the edge of the pole piece is subjected to larger pressure during hot-pressing formation, so that the reliability of the pole piece is improved. The warping of the pole piece can be flattened through the step of hot-pressing formation, and lithium is not easy to separate out at the edge. In addition, the invention also discloses a preparation method of the laminated battery.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a laminated battery and a preparation method thereof. Background Art

[0002] While laminated batteries are becoming more and more widely used because they can avoid lithium plating at corners and have high energy density, there is also a demand for further improvement in the energy density of laminated batteries. In order to improve the energy density of laminated batteries, the outermost electrode sheet of the laminated battery cell is usually set to a single-sided sheet. The structure of the single-sided sheet is that one side of the current collector is coated with active material, and the other side of the current collector is not coated with active material, thereby reducing the amount of material that does not participate in the reaction, thereby effectively increasing the content of active materials that effectively participate in the reaction per unit volume or unit mass of the battery, which directly improves the energy density of the battery.

[0003] However, since the single-sided sheet has active materials on one side of the current collector and no active materials on the other side, the stretching tension on both sides of the single-sided sheet is inconsistent during the rolling process of the single-sided sheet, which is prone to warping. Furthermore, after the single-sided sheet is bent, it will cause greater difficulty in processing when stacking the sheets, and when an active material with a large expansion coefficient is used, the adhesion of the single-sided sheet will be weakened due to expansion, which may easily lead to edge lithium deposition.

[0004] Based on this, there is an urgent need to invent a laminated battery and a preparation method thereof to solve the aforementioned technical problems. Summary of the invention

[0005] One of the purposes of the present invention is to provide a laminated battery to address the deficiencies of the prior art, wherein the laminated battery can improve the energy density of the battery and reduce lithium plating at the edge of the battery.

[0006] In order to solve the above technical problems, this application adopts the following technical solutions:

[0007] A laminated battery is provided, comprising a shell and an electrode assembly accommodated in the shell, wherein the electrode assembly comprises a plurality of first pole sheets and two second pole sheets stacked in a thickness direction, wherein all of the first pole sheets are arranged between two of the second pole sheets; the second pole sheet comprises a current collector, an active material layer and a functional layer, wherein the active material layer and the functional layer are respectively arranged on both sides of the current collector in a thickness direction, wherein the functional layer is arranged on a side away from the first pole sheet, and the functional layer is arranged in an edge region of a surface of the current collector.

[0008] Specifically, the material of the functional layer is one or more of a ceramic material, an elastic material, an active substance and a resin material.

[0009] Specifically, the thickness of the functional layer is between 0.5 and 1.5 times the thickness of the active material layer.

[0010] Specifically, the functional layer is provided with a chamfer.

[0011] Specifically, the thickness of the functional layer is 0.1-0.5 mm.

[0012] Specifically, the outer boundary of the edge region coincides with the surface boundary of the current collector, the distance from the inner boundary of the edge region to the surface boundary of the current collector is 0.1 mm to 10 mm, and the functional layer covers the entire edge region.

[0013] Specifically, when the second electrode sheet is a negative electrode sheet, the width of the edge area is greater than the width of the overhang area.

[0014] Specifically, the thickness of the functional layer gradually increases from the inner boundary of the edge region to the inside of the functional layer.

[0015] The beneficial effects of the present invention are as follows: the present application reduces the difference in tension on both sides of the current collector during rolling by setting the functional layer, thereby alleviating the warping of the pole piece due to inconsistent extension tension on both sides of the single-sided piece during rolling, and since the functional layer is set in the edge area of ​​the current collector surface, the thickness at the edge of the pole piece is greater, and when hot pressing is performed, the edge of the pole piece is subjected to greater pressure, and the warping of the pole piece can be smoothed through the hot pressing step, and since the edge of the pole piece is subjected to greater pressure, the bonding strength of the active material is higher, and the active material at the edge of the pole piece is not easily structurally damaged due to the expansion of the active material, resulting in lithium precipitation.

[0016] The second object of the present invention is to provide a method for preparing a laminated battery, which is used to prepare the laminated battery, comprising:

[0017] S1. preparing active material slurry and functional material;

[0018] S2, applying the active material slurry to both sides of the current collector to form a first pole piece;

[0019] S3, applying the active material slurry to one side of the current collector, and connecting the functional material to the other side of the current collector by coating, spraying and bonding to form a second electrode sheet;

[0020] S4, stacking and assembling the first pole piece, the second pole piece and the diaphragm, wherein all the first pole pieces are located between two of the second pole pieces, and packaging them to obtain a packaged battery cell;

[0021] S5, injecting electrolyte into the packaged battery cell and performing steps such as hot pressing, secondary sealing and degassing, and capacity sorting to obtain a finished battery cell.

[0022] Specifically, when the functional substance is connected to the current collector by coating, the step S3 is specifically to fully coat the functional substance on the surface of the current collector and roll it, and then remove the functional substance in the middle of the current collector to form a functional layer with an edge coating structure; and / or when the functional substance is connected to the current collector by spraying, the step S3 is specifically to fully spray the functional substance on the surface of the current collector and roll it, and then remove the functional substance in the middle of the current collector to form a functional layer with an edge coating structure; and / or when the functional substance is connected to the current collector by bonding, the step S3 is specifically to fully bond the functional substance on the surface of the current collector and roll it, and then remove the functional substance in the middle of the current collector to form a functional layer with an edge coating structure.

[0023] Specifically, when the functional substance is connected to the current collector by coating, the step S3 is specifically coating the functional substance on the edge area of ​​the surface of the current collector and rolling it to form a functional layer with an edge coating structure; and / or when the functional substance is connected to the current collector by spraying, the step S3 is specifically spraying the functional substance on the edge area of ​​the surface of the current collector and rolling it to form a functional layer with an edge coating structure; and / or when the functional substance is connected to the current collector by bonding, the step S3 is specifically bonding the functional substance to the edge area of ​​the surface of the current collector and rolling it to form a functional layer with an edge coating structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 This is one of the structural schematic diagrams of the laminated battery of the present invention;

[0026] Figure 2 is a top view of the second pole piece of the present invention;

[0027] Figure 3 This is the second structural schematic diagram of the laminated battery of the present invention.

[0028] Among them: 1-first pole piece; 2-second pole piece; 21-functional layer; 211-chamfer; 22-active material layer; 23-current collector; 3-diaphragm; 100-electrode assembly. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings, but this is not intended to limit the present invention.

[0031] The applicant has found that in order to improve the energy density of the existing laminated batteries, the pole pieces on both sides of the laminated batteries are set as single-sided pieces, that is, pole pieces with active materials on one side of the current collector and no active materials on the other side. The energy density of the battery is improved by eliminating the coating of active materials that do not participate in the reaction on one side.

[0032] However, in actual applications, it was found that since the coating of the active material on one side of the current collector was cancelled, the single-sided sheet was subjected to uneven force during rolling, the extension tension on both sides was inconsistent, and warping was prone to occur. In order to make the electrode sheet subjected to uniform force and reduce the occurrence of warping, it is necessary to apply a new coating on the side of the current collector where the active material coating was cancelled to reduce the impact of the extension tension, or to increase the thickness of the current collector to enhance the strength of the current collector and thus reduce the impact of the extension tension on the current collector. However, the above two settings will reduce the energy density of the battery, which is inconsistent with the original intention of setting up the single-sided sheet.

[0033] The applicant optimized the coating structure that reduces the extension tension and only retained the coating in the portion that is prone to warping, thereby reducing the volume occupied by the coating and improving the energy density of the battery.

[0034] Example 1

[0035] The first aspect of the present invention, as Figure 1-2 As shown, a laminated battery is provided, including a shell and an electrode assembly 100 accommodated in the shell, the electrode assembly 100 includes a plurality of first pole sheets 1 and two second pole sheets 2 stacked in a thickness direction, the first pole sheets 1 and the second pole sheets 2 together form an electrode assembly 100 for electrochemical reaction, wherein all the first pole sheets 1 are arranged between the two second pole sheets 2; the first pole sheet 1 is arranged in the middle of the electrode assembly 100, and the two second pole sheets 2 are respectively arranged at the outermost sides of the electrode assembly 100.

[0036] The second pole piece 2 includes a current collector 23, an active material layer 22 and a functional layer 21, wherein the active material layer 22 and the functional layer 21 are respectively arranged on both sides of the current collector 23 in the thickness direction, wherein the functional layer 21 is arranged on the side away from the first pole piece 1, and the functional layer 21 is arranged in the edge area of ​​the surface of the current collector 23.

[0037] By setting the functional layer 21 in the edge area of ​​the surface of the current collector 23, the difference in the stretching tension on both sides of the second pole piece 2 during rolling is made smaller, which can reduce the warping of the second pole piece 2 during rolling. In addition, since the functional layer 21 is set in the edge area of ​​the surface of the current collector 23 corresponding to the position where the warping of the second pole piece 2 occurs, during the process of hot pressing of the laminated battery, the position where the functional layer 21 is set has a greater thickness and is subjected to a greater pressure during hot pressing. During the hot pressing process, the warped position of the second pole piece 2 can be flattened.

[0038] In order to improve the energy density, the existing batteries have begun to increase the use of silicon materials, and the use of silicon materials makes the battery expand. During the expansion process of the battery, the expansion force will be transmitted from the inside to the outside. Since the second pole piece 2 is arranged on both sides of the electrode assembly 100, it is arranged at the outermost position in the thickness direction. In the horizontal direction perpendicular to the thickness direction, the edge position of the second pole piece 2 is the outermost position. When the battery expands, the expansion force expands from the inside to the outside to the outermost side, and the active material at the outermost position is prone to bonding failure, the structure of the active material layer 22 is destroyed, and even the active material falls off. Therefore, the edge position of the second pole piece 2 is prone to edge lithium deposition, especially when it is set as a single-sided sheet and cannot provide sufficient support for the active material layer 22, the edge lithium deposition becomes more serious. In the present application, by arranging the functional layer 21 at the edge position of the second pole piece 2, the active material layer 22 at the edge position is subjected to greater pressure during the hot pressing of the second pole piece 2, so that the bonding effect of the active material at the edge is better, and it has higher strength to prevent the active material from being structurally damaged when subjected to the expansion force, thereby causing lithium deposition.

[0039] Example 2

[0040] The difference from Example 1 is that the material of the functional layer 21 in this embodiment is one or more of a ceramic material, an elastic material, an active substance and a resin material. When an elastic material is used, it is equivalent to providing a laminated battery with an elastic pressure device, which causes minimal loss in the overall thickness of the laminated battery and improves the energy density of the battery. For ceramic materials, due to their high specific heat capacity, they can conduct heat, reduce temperature rise, improve the thermal stability of the battery cell, and enhance battery safety performance.

[0041] Preferably, the thickness of the functional layer 21 is between 0.5 and 1.5 times the thickness of the active material layer 22. The thickness of the functional layer 21 is closely related to the thickness of the active material layer 22. When the thickness of the functional layer 21 is too small, sufficient pressure cannot be provided during hot pressing, and the active material layer 22 is prone to lithium deposition. When the thickness of the functional layer 21 is too large, the active material layer 22 is subjected to excessive pressure, resulting in lithium ions not being able to be embedded in the active material layer 22 in time, causing lithium deposition.

[0042] Preferably, the functional layer 21 is provided with a chamfer 211 , and the chamfer 211 can reduce stress concentration when the functional layer 21 pressurizes the active material, thereby preventing the active material from being affected.

[0043] Preferably, the thickness of the functional layer 21 is 0.1-0.5 mm. Within this thickness range, the pressure provided by the functional layer 21 is appropriate and the deformation caused to the pole piece will not be too large.

[0044] Preferably, the outer boundary of the edge area coincides with the surface boundary of the current collector 23, and the distance from the inner boundary of the edge area to the surface boundary of the current collector 23 is 0.1 mm to 10 mm. The functional layer 21 covers the entire edge area. The edge area of ​​the functional layer 21 is set within the above range to satisfy the pressurizing effect of the functional layer 21 on the active material layer 22, and will not be too wide to cause a decrease in the energy density of the battery. When compressed within the above width range, the thickness of the functional layer 21 will decrease, and will not affect the thickness of the battery too much.

[0045] Preferably, when the second electrode sheet 2 is a negative electrode sheet, the width of the edge area is greater than the width of the overhang area. When the CB value of the battery is too small, the CB value is the ratio of the positive anode capacity to the cathode capacity. Due to the capacity imbalance, the negative electrode is prone to edge lithium deposition. Therefore, the width of the negative electrode sheet is generally set to be greater than the positive electrode sheet to ensure the capacity balance of the positive and negative electrodes, and the area where the negative electrode sheet exceeds the width of the positive electrode sheet is the overhang area. After multiple cycles, the overhang area may cause lithium deposition due to the accumulation of lithium ions. In the present application, the width of the edge area coated with the functional layer 21 is set to be greater than the width of the overhang area, so that the edge area covers the overhang area, which can provide pressure for the negative electrode active material in the overhang area, thereby improving compaction and preventing excessive accumulation of lithium ions in the overhang area to cause lithium deposition. The present application can reduce lithium deposition in the overhang area.

[0046] like Figure 3As shown, preferably, the thickness of the functional layer 21 gradually increases from the inner boundary of the edge area to the inside of the functional layer 21. Through this arrangement, when the functional layer 21 is pressurized on the active material, a transition is provided between the active material at the compressed position and the active material at the non-compressed position, thereby preventing the connection position between the active material at the compressed position and the active material at the non-compressed position from being damaged due to a sudden change in compaction, resulting in different expansion rates of the active material and causing the structure of the active material layer 22 to be destroyed, thereby causing lithium precipitation.

[0047] Example 3

[0048] A second aspect of the present invention provides a method for preparing a laminated battery, which is used to prepare the laminated battery, comprising:

[0049] S1. preparing active material slurry and functional material;

[0050] S2, applying the active material slurry to both sides of the current collector 23 to form the first pole piece 1;

[0051] S3, applying the active material slurry to one side of the current collector 23, and connecting the functional material to the other side of the current collector 23 by coating, spraying and bonding to form a second electrode sheet 2;

[0052] S4, assembling the first pole piece 1, the second pole piece 2 and the diaphragm 3 by stacking, wherein all the first pole pieces 1 are located between two second pole pieces 2, and encapsulating to obtain an encapsulated battery cell;

[0053] S5. Injecting electrolyte into the packaged battery cell and performing hot pressing, secondary sealing and degassing, and capacity sorting to obtain a finished battery cell.

[0054] Preferably, when the functional substance is connected to the current collector by coating, step S3 specifically comprises: coating the functional substance on the surface of the current collector 23 in an all-round manner and rolling it, and then removing the functional substance in the middle of the current collector 23 to form a functional layer 21 having an edge coating structure; and / or when the functional substance is connected to the current collector by spraying, step S3 specifically comprises: spraying the functional substance on the surface of the current collector 23 in an all-round manner and rolling it, and then removing the functional substance in the middle of the current collector 23 to form a functional layer 21 having an edge coating structure; and / or when the functional substance is connected to the current collector by bonding, step S3 specifically comprises: bonding the functional substance on the surface of the current collector 23 in an all-round manner and rolling it, and then removing the functional substance in the middle of the current collector 23 to form a functional layer 21 having an edge coating structure.

[0055] In order to form a thickness difference in the functional layer 21, it is necessary to remove the functional material in the middle of the current collector 23 so that the thickness of the location with the functional material is larger. When the battery is hot-pressed, since the surface of the entire electrode is pressed down at the same time, the location where the functional layer 21 is provided can provide greater pressure due to its greater thickness.

[0056] The selection of functional substances includes but is not limited to ceramic slurry, low-viscosity accumulation slurry, volatile organic slurry or easy-tear coating. Active substance slurry may also be used. When using active substance slurry, the first pole piece 1 may be selected for processing to obtain the second pole piece 2 to save production steps and improve production efficiency. There are certain restrictions on the functional substance removal area, and at least the coating at the four corners and edges must be retained. At the same time, the boundary of the removal area must be a smooth boundary, such as an ellipse or a chamfered rectangle. The removal method includes but is not limited to wiping with dust-free paper or dust-free cloth dipped in alcohol or other solvents, or laser ablation, or heating volatilization, or tearing, etc. One or more methods.

[0057] The functional layer 21 with the edge coating structure is obtained by removing the slurry in the middle of the current collector 23. The characteristic of this technology is that it has the advantage of uniform compaction. Since both sides of the current collector 23 are fully coated during rolling, the current collector 23 is evenly stressed. During rolling, the functional layer 21 and the active material layer 22 can be evenly compacted. Due to the uniform compaction, a higher compaction density can be achieved, and the rolling thickness of the second pole piece 2 can be guaranteed. The particle compaction effect is consistent with that of the first pole piece 1, avoiding the thickness and energy density loss caused by the excessive low compaction of the second pole piece 2. At the same time, during rolling, the two sides of the current collector 23 are evenly stressed, the stress concentration is small, the foil is not easy to wrinkle, and the material area is not easy to fall off. A thinner current collector 23 can also be selected for the current collector 23 to improve the energy density of the battery.

[0058] Example 4

[0059] The difference from Example 2 is that: when the functional substance is connected to the current collector by coating, step S3 is specifically to coat the functional substance on the edge area of ​​the surface of the current collector 23 and roll it to form a functional layer 21 with an edge coating structure; and / or when the functional substance is connected to the current collector by spraying, step S3 is specifically to spray the functional substance on the edge area of ​​the surface of the current collector 23 and roll it to form a functional layer 21 with an edge coating structure; and / or when the functional substance is connected to the current collector by bonding, step S3 is specifically to bond the functional substance to the edge area of ​​the surface of the current collector 23 and roll it to form a functional layer 21 with an edge coating structure.

[0060] The functional material is coated on the edge area of ​​the surface of the current collector 23 by, but not limited to, partial coating, partial pasting, partial spraying, partial printing, etc., to form a functional layer 21 with an edge coating structure at the edge and four corners of the electrode. The functional material can be a rigid or elastic material.

[0061] This method can save coating materials and reduce costs in the early stage. Since the one-time coating is completed without removing the functional material, coating materials can be saved. The selection of functional materials is more flexible. For example, elastic materials are equivalent to providing an elastic pressure device for the battery cell, which has minimal loss in the overall thickness of the battery cell and increases the force range of the four corners. For ceramic materials, due to their high specific heat capacity, they can conduct heat, reduce temperature rise, improve the thermal stability of the battery cell, and enhance battery safety performance. For adhesive coatings, the operation is simple and the process cost is low.

[0062] Example 5

[0063] Step 1: Stir the required main materials, conductive agents, and binders in a certain proportion to form uniformly dispersed active material slurry and ceramic slurry;

[0064] The specific operation of step 2 is to evenly coat the active material slurry obtained in step 1 on one side of the current collector 23 to obtain a single-sided electrode sheet having a single-sided active material layer 22, and the thickness of the active material layer 22 is 0.2 mm;

[0065] The specific operation of step 3 is to evenly coat the active material slurry obtained in step 1 on the other side of the single-sided electrode sheet obtained in step 2, and roll it to a certain thickness to obtain the first electrode sheet 1 having a double-sided active material layer 22;

[0066] The specific operation of step 4 is to evenly spray the ceramic slurry on the other side of the single-sided electrode obtained in step 2, and roll it to a certain thickness to form a double-sided electrode having an active material layer 22 and a ceramic coating, and the thickness of the ceramic coating is 0.2 mm;

[0067] The specific operation of step 5 is to cut the first pole piece 1 and the double-sided pole piece obtained in steps 3 and 4 into required sizes;

[0068] The specific operation of step 6 is to remove the double-sided electrode obtained in step 5 by peeling off the adhesive tape, remove the coating material in the middle part of the ceramic coating, and only retain the coating material at the edges and four corners, so as to obtain the second electrode 2;

[0069] The specific operation of step 7 is to assemble and fold the second pole piece 2 obtained in step 6, the first pole piece 1 obtained in step 5, the diaphragm 3, and the other polarity pole piece, and perform hot pressing and top sealing welding and other processes to obtain a packaged battery cell;

[0070] The specific operation of step 8 is to obtain a finished battery cell by subjecting the packaged battery cell obtained in step 7 to the steps of liquid injection, aging, hot pressing, secondary sealing and degassing, capacity sorting and the like.

[0071] Example 6

[0072] The difference from Example 5 is that the thickness of the ceramic coating is 0.3 mm.

[0073] Example 7

[0074] The difference from Example 5 is that the thickness of the ceramic coating is 0.1 mm.

[0075] Example 8

[0076] The difference from Example 5 is that the specific operation of step 4 is to evenly spray the active material slurry on the other side of the single-sided electrode obtained in step 2, and roll it to a certain thickness to form a double-sided electrode. The thickness of the active material slurry is 0.2 mm.

[0077] The specific operation of step 6 is to remove the coating material in the middle part of the active material layer 22 by laser ablation from the double-sided electrode obtained in step 5, and only retain the coating material at the edges and four corners to obtain the second electrode 2.

[0078] Example 9

[0079] The difference from Example 5 is that: the specific operation of step 4 is to stick the PE film on the other side of the single-sided electrode sheet obtained in step 2, and roll it to a certain thickness to form a double-sided electrode sheet, and the thickness of the PE film is 0.2 mm;

[0080] The specific operation of step 6 is to remove the middle part of the PE film from the double-sided electrode obtained in step 5 by mechanical scraping, and only retain the PE films at the edges and four corners to obtain the second electrode 2.

[0081] Example 10

[0082] Step 1: Stir the required main materials, conductive agents, and binders in a certain proportion to form uniformly dispersed active material slurry and ceramic slurry;

[0083] The specific operation of step 2 is to evenly coat the active material slurry obtained in step 1 on one side of the current collector 23 to obtain a single-sided electrode sheet having a single-sided active material layer 22, and the thickness of the active material layer 22 is 0.2 mm;

[0084] The specific operation of step 3 is to evenly coat the active material slurry obtained in step 1 on the other side of the single-sided electrode sheet obtained in step 2, and roll it to a certain thickness to obtain the first electrode sheet 1 having a double-sided active material layer 22;

[0085] The specific operation of step 4 is to partially coat the ceramic slurry on the other side of the single-sided electrode obtained in step 2, and roll it to a certain thickness to form a second electrode 2 having an active material layer 22 and a ceramic coating, and the thickness of the ceramic coating is 0.2 mm;

[0086] The specific operation of step 5 is to cut the first pole piece 1 and the second pole piece 2 obtained in steps 3 and 4 into required sizes;

[0087] The specific operation of step 6 is to assemble and fold the second pole piece 2, the first pole piece 1 and the diaphragm 3 obtained in step 5, and the other polar pole piece, and perform hot pressing and top sealing welding and other processes to obtain a packaged battery cell;

[0088] The specific operation of step 7 is to obtain a finished battery cell by subjecting the packaged battery cell obtained in step 6 to the steps of liquid injection, aging, hot pressing, secondary sealing and degassing, capacity sorting and the like.

[0089] Embodiment 11

[0090] The difference from Example 10 is that the specific operation of step 4 is to locally coat the elastic slurry on the other side of the single-sided electrode obtained in step 2, and roll it to a certain thickness to form a second electrode 2 having an active material layer 22 and an elastic coating, and the thickness of the elastic coating is 0.2 mm.

[0091] Example 12

[0092] The difference from Example 11 is that the specific operation of step 4 is to locally coat the active material slurry on the other side of the single-sided electrode sheet obtained in step 2, and roll it to a certain thickness to form a second electrode sheet 2. The thickness of the active material slurry is 0.2 mm.

[0093] Comparative Example 1

[0094] The difference from Example 5 is that the thickness of the ceramic coating is 0.02 mm.

[0095] Comparative Example 2

[0096] The difference from Example 5 is that the thickness of the ceramic coating is 1 mm.

[0097] Comparative Example 3

[0098] Step 1: Stir the required main material, conductive agent and binder in a certain proportion into a uniformly dispersed active material slurry.

[0099] The specific operation of step 2 is to evenly coat the active material slurry obtained in step 1 on one side of the current collector to obtain a single-sided electrode sheet having a single-sided active material layer, and the thickness of the active material layer is 0.2 mm;

[0100] The specific operation of step 3 is to evenly coat the active material slurry obtained in step 1 on the other side of the single-sided electrode sheet obtained in step 2, and roll it to a certain thickness to obtain a first electrode sheet with a double-sided active material layer;

[0101] The specific operation of step 4 is to assemble and fold the single-sided electrode obtained in step 1, the first electrode obtained in step 1, the diaphragm, and the other polarity electrode to obtain a packaged battery cell through hot pressing and top sealing welding.

[0102] The specific operation of step 5 is to obtain a finished battery cell by subjecting the packaged battery cell obtained in step 4 to the steps of liquid injection, aging, hot pressing, secondary sealing and degassing, capacity sorting and the like.

[0103] Performance test method: After 300 cycles at 3C rate, the interface is disassembled to determine the degree of lithium deposition, which is divided into no lithium deposition, slight lithium deposition and severe lithium deposition.

[0104]

[0105]

[0106] By comparing Examples 4 to 6 with Comparative Examples 1 and 2, it can be seen that when the thickness of the functional layer is within the range of the present application, the laminated battery of the present application is not easy to deposit lithium. When the thickness of the functional layer is too small, it cannot provide sufficient pressure during hot pressing, resulting in insufficient adhesion of the active material at the edge. When the functional layer is too thick, the pressure on the active material is too high, resulting in the destruction of the structure of the active material layer and causing lithium deposition.

[0107] From the comparison between Example 4 and Comparative Example 3, it can be seen that the functional layer setting of the present application can reduce lithium deposition at the edge of the single-sided electrode.

[0108] By comparing Example 4 with Examples 8 and 9, it can be seen that the lithium deposition of the stacked batteries is improved after the edge coating structure of the functional layer of the present application is formed.

[0109] The above description shows and describes several preferred embodiments of the present invention, but as before, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept of this article through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A laminated battery, comprising a housing and an electrode assembly (100) contained in the housing, characterized in that: The electrode assembly (100) comprises a plurality of first pole sheets (1) and two second pole sheets (2) stacked in a thickness direction, wherein all of the first pole sheets (1) are arranged between the two second pole sheets (2); The second pole piece (2) comprises a current collector (23), an active material layer (22) and a functional layer (21), wherein the active material layer (22) and the functional layer (21) are respectively arranged on both sides of the current collector (23) in the thickness direction, wherein the functional layer (21) is arranged on a side away from the first pole piece (1), and the functional layer (21) is arranged in an edge region of a surface of the current collector (23).

2. The laminated battery according to claim 1, characterized in that: The material of the functional layer (21) is one or more of a ceramic material, an elastic material, an active substance and a resin material.

3. The laminated battery according to claim 1, characterized in that: The thickness of the functional layer (21) is between 0.5 and 1.5 times the thickness of the active material layer (22).

4. The laminated battery according to claim 1, characterized in that: The functional layer (21) is provided with a chamfer (211).

5. The laminated battery according to claim 1, characterized in that: The thickness of the functional layer (21) is 0.1-0.5 mm.

6. The laminated battery according to claim 1, characterized in that: The outer boundary of the edge region coincides with the surface boundary of the current collector (23), the distance from the inner boundary of the edge region to the surface boundary of the current collector (23) is 0.1 mm to 10 mm, and the functional layer (21) covers the entire edge region.

7. The laminated battery according to claim 1, characterized in that: The thickness of the functional layer (21) gradually increases from the inner boundary of the edge region to the interior of the functional layer (21).

8. A method for preparing a laminated battery, used for preparing the laminated battery according to any one of claims 1 to 8, characterized in that: include: S1. preparing active material slurry and functional material; S2, applying the active material slurry to both sides of the current collector (23) to form a first pole piece (1); S3, coating the active material slurry on one side of the current collector (23), and connecting the functional material to the other side of the current collector (23) by coating, spraying and bonding to form a second pole piece (2); S4, assembling the first pole piece (1), the second pole piece (2) and the diaphragm (3) by stacking them, wherein all the first pole pieces (1) are located between two of the second pole pieces (2), and packaging them to obtain a packaged battery cell; S5, injecting electrolyte into the packaged battery cell and performing steps such as hot pressing, secondary sealing and degassing, and capacity sorting to obtain a finished battery cell.

9. The method for preparing the laminated battery according to claim 8, characterized in that: When the functional substance is connected to the current collector by coating, the step S3 specifically comprises: coating the functional substance on the surface of the current collector (23) in an all-round manner and rolling it, and then removing the functional substance in the middle of the current collector (23) to form a functional layer (21) with an edge coating structure; and / or when the functional substance is connected to the current collector by spraying, the step S3 specifically comprises: spraying the functional substance on the surface of the current collector (23) in an all-round manner and rolling it, and then removing the functional substance in the middle of the current collector (23) to form a functional layer (21) with an edge coating structure; and / or when the functional substance is connected to the current collector by bonding, the step S3 specifically comprises: bonding the functional substance on the surface of the current collector (23) in an all-round manner and rolling it, and then removing the functional substance in the middle of the current collector (23) to form a functional layer (21) with an edge coating structure.

10. The method for preparing a laminated battery according to claim 8, characterized in that: When the functional substance is connected to the current collector by coating, the step S3 specifically comprises coating the functional substance on the edge area of ​​the surface of the current collector (23) and rolling the functional substance to form a functional layer (21) having an edge coating structure; and / or when the functional substance is connected to the current collector by spraying, the step S3 specifically comprises spraying the functional substance on the edge area of ​​the surface of the current collector (23) and rolling the functional layer (21) having an edge coating structure; And / or when the functional substance is connected to the current collector by bonding, the step S3 specifically comprises bonding the functional substance to the edge area of ​​the surface of the current collector (23) and rolling it to form a functional layer (21) having an edge coating structure.

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