Pole piece, battery cell and lithium ion battery

Abstract

The utility model discloses a pole piece, a battery cell and a lithium ion battery. The pole piece comprises a first current collector and a second current collector, the active material layer is arranged on at least one side surface of the first current collector; the second current collector is embedded in the active material layer, and at least part of the active material layer is located between the first current collector and the second current collector; wherein the second current collector is provided with a plurality of through holes, and the first current collector is electrically connected with the second current collector.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium-ion batteries, in particular to a pole piece, a battery core and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries, with their high voltage and high energy density, have become one of the most widely used batteries. With the continuous development of portable electronic devices, the charging speed of lithium-ion batteries, as a power source, needs to be continuously improved to meet the increasing demand.

[0003] As the market demand for fast-charging batteries grows, many lithium battery manufacturers meet the requirements of fast charging by reducing the electrode surface density and the thickness of the current collector. However, reducing the surface density will directly reduce the space occupancy of the electrode active material, thereby losing volume energy density, which means that the capacity of the lithium-ion battery will become smaller. Utility Model Content

[0004] The main purpose of the utility model is to provide a pole piece, aiming to solve the problem that the existing pole piece increases the charging rate while reducing the capacity.

[0005] To achieve the above-mentioned purpose, the present invention provides a pole piece, which includes:

[0006] a first current collector;

[0007] an active material layer, the active material layer being disposed on at least one side of the first current collector;

[0008] a second current collector, wherein the second current collector is embedded in the active material layer, and at least a portion of the active material layer is located between the first current collector and the second current collector;

[0009] The second current collector is provided with a plurality of through holes, and the first current collector is electrically connected to the second current collector.

[0010] In some embodiments, the distance between the upper surface of the first current collector and the lower surface of the second current collector is L, the distance between the upper surface of the second current collector and the upper surface of the active material layer is D, and the relationship between L and D is: L is greater than D.

[0011] In some embodiments, the value of D ranges from 5 to 10 μm.

[0012] In some embodiments, the first current collector includes a first extension portion extending beyond the active material layer along the length direction, the second current collector includes a second extension portion extending beyond the active material layer along the length direction, and the first extension portion is electrically connected to the second extension portion.

[0013] In some embodiments, the second current collector further includes a connecting portion located in the active material layer, the connecting portion is connected to the second extending portion, and the connecting portion is spaced apart and arranged in parallel with the first current collector.

[0014] In some embodiments, the active material layer has two layers, and is respectively disposed on two opposite sides of the first current collector; the second current collector has two layers, and is respectively embedded in the two active material layers.

[0015] In some embodiments, the through hole has a diameter of 0.5-3 mm.

[0016] In some embodiments, the thickness of the second current collector is greater than the thickness of the first current collector.

[0017] The present invention further proposes a battery core, comprising a diaphragm and two pole pieces with opposite polarities located on both sides of the diaphragm; at least one of the two pole pieces is the pole piece described in the aforementioned embodiment.

[0018] The present invention further provides a lithium-ion battery, comprising a housing and the battery cell described in the aforementioned embodiment, wherein the battery cell is disposed in the housing.

[0019] By embedding a second current collector with through-holes within the active material layer, the present invention allows electrons within the active material layer to migrate toward either the first or second current collector. This significantly shortens the electron transmission path, thereby reducing the impedance of the electrode piece and improving the charge and discharge performance of the lithium-ion battery made with the electrode piece. Furthermore, the heat generated during charge and discharge can be quickly transferred to the first and second current collectors, thereby increasing the volumetric specific heat capacity of the electrode piece and reducing the temperature of the resulting lithium-ion battery during charge and discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of an embodiment of a pole piece of the present utility model;

[0021] Figure 2 This is a top view of the second current collector in the pole piece of the present invention;

[0022] Figure 3 This is a cross-sectional view of an embodiment of a pole piece of the present invention.

[0023] Reference numerals:

[0024] 100 , first current collector; 110 , first extension portion; 200 , active material layer; 300 , second current collector; 310 , through hole; 320 , second extension portion; 330 , connection portion. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the schemes in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0027] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element.

[0028] In addition, the descriptions of "first," "second," etc. in this utility model are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this utility model.

[0029] The utility model proposes a pole piece, referring to Figure 1 and Figure 2 , the pole piece includes:

[0030] a first current collector 100;

[0031] An active material layer 200 , which is disposed on at least one side of the first current collector 100 ;

[0032] The second current collector 300 is embedded in the active material layer 200, and at least a portion of the active material layer 200 is located between the first current collector 100 and the second current collector 300;

[0033] The second current collector 300 is provided with a plurality of through holes 310 , and the first current collector 100 is electrically connected to the second current collector 300 .

[0034] Common current collector materials include metal foils, such as copper foil and aluminum foil, as well as composite materials. Different polarity electrodes use different current collector materials. For example, if copper foil is used as the first current collector 100, the resulting electrode is usually a negative electrode, while if aluminum foil is used as the first current collector 100, the resulting electrode is usually a positive electrode.

[0035] The active material layer 200 includes an adhesive, a conductive agent and an active material, wherein the active material can be at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, a ternary system, lithium titanate and other lithium transition metal oxides, usually accounting for 60 to 99.8% of the total mass of the composition; the conductive agent can include at least one of various types of activated carbon, carbon nanotubes, graphene, hollow graphene balls, carbon black, acetylene black, carbon fiber, Ketjen black, etc., usually accounting for 0.5 to 40% of the total mass of the composition; the binder can include at least one of polyvinylidene fluoride, styrene-butadiene rubber, methyl cellulose phosphate, polytetrafluoroethylene, and polyolefin, usually accounting for 0.5 to 40% of the total mass of the composition; the auxiliary additives can include at least one of a dispersant, a flame retardant, ceramic powder, metal powder, a leveling agent, a defoaming agent, a lithium supplement, a filler, etc., usually accounting for 0 to 20% of the total mass of the composition. It is understandable that active material layers 200 can be set on both sides of the first current collector 100. In this case, the materials of the two active material layers 200 can be the same or different. Different materials can be used to make pole pieces with different polarities. The present invention does not impose any restrictions on this.

[0036] The second current collector 300 is provided with a plurality of through holes 310. The shape and number of the through holes 310 can be set according to design requirements. For example, the through holes 310 can be set to cylindrical, prismatic, or other irregular shapes. The second current collector 300 is embedded in the active material layer 200. The manufacturing process is as follows, taking the production of the positive electrode sheet as an example:

[0037] Step 1: Use aluminum foil as the first current collector 100 and the second current collector 300, and punch a plurality of through holes 310 on the second current collector 300 by laser etching;

[0038] Step 2: Perform a coating operation to coat the active material on the first current collector 100;

[0039] Step 3: When the active material in step 2 is not dry, the second current collector 300 is stacked on the active material, and a portion of the second current collector 300 is embedded in the active material;

[0040] Step 4: Perform secondary coating to coat the active material on the second current collector 300 (the active material coated twice together constitutes the active material layer 200 ), and then dry to obtain the positive electrode sheet.

[0041] The provision of the through hole 310 enables more active materials to be provided on the electrode, thereby increasing the capacity of the battery and facilitating the drying of the active materials during a coating operation.

[0042] The first current collector 100 and the second current collector 300 are electrically connected, allowing electrons to flow rapidly across the electrode, achieving normal electrical conduction. Various methods exist for achieving this electrical connection. For example, a conductive member, such as a metal wire, can be added between the second current collector 300 and the first current collector 100; a conductive coating can be applied to the edges of the first and second current collectors 100 and 300; or portions of the first and second current collectors 100 and 300 can be physically connected to establish an electrical connection. This is not a limitation of the present invention.

[0043] By embedding a second current collector 300 having through-holes 310 within the active material layer 200, the present invention allows electrons within the active material layer 200 to migrate toward the first current collector 100 or the second current collector 300. This significantly shortens the electron transmission path, thereby reducing the impedance of the electrode sheet and improving the charge and discharge performance of the lithium-ion battery fabricated with the electrode sheet. Furthermore, the heat generated during charge and discharge can be quickly transferred to the first current collector 100 and the second current collector 300, thereby increasing the volumetric specific heat capacity of the electrode sheet and reducing the temperature of the resulting lithium-ion battery during charge and discharge.

[0044] like Figure 3 As shown, in some embodiments, the distance between the upper surface of the first current collector 100 and the lower surface of the second current collector 300 is L, the distance between the upper surface of the second current collector 300 and the upper surface of the active material layer 200 is D, and the relationship between L and D is: L is greater than D.

[0045] Since the electrons in the active material layer 200 located above the second current collector 300 can usually only move toward the second current collector 300, by controlling L to be greater than D, the second current collector 300 is made closer to the upper surface of the active material layer 200, that is, there are fewer electrons located above the second current collector 300 and more electrons located below the second current collector 300. During the charging and discharging process, the electrons located below the second current collector 300 can choose to move toward the first current collector 100 or the second current collector 300 nearby, thereby reducing the transmission distance of the electrons in the active material layer 200, further reducing the resistance loss, and improving the charging and discharging efficiency of the lithium-ion battery made of the electrode sheet.

[0046] In some embodiments, the value of D ranges from 5 to 10 μm.

[0047] The second current collector 300 may produce burrs during the drilling process. If D is less than 5μm, the active material layer 200 may not be able to completely cover the burrs, which may easily cause the exposed burrs to scratch the diaphragm and form an internal short circuit when the lithium-ion battery is used, posing a major safety hazard. If D is greater than 10μm, there is too much active material layer 200 located above the second current collector 300, and the electron transmission distance is long, which cannot effectively improve the charge and discharge efficiency. Preferably, D is set to 7μm, which shortens the electron transmission distance while ensuring that the active material layer 200 completely covers the burrs that may exist on the second current collector 300, thereby improving the yield rate. It can be understood that when the upper surface of the second current collector 300 is not parallel to the upper surface of the active material layer 200, the minimum distance between the two is used as D, that is, the minimum distance is in the range of 5 to 10μm.

[0048] like Figure 1 and Figure 3 As shown, in some embodiments, the first current collector 100 includes a first extension portion 110 extending outside the active material layer 200 along the length direction, and the second current collector 300 includes a second extension portion 320 extending outside the active material layer 200 along the length direction, and the first extension portion 110 is electrically connected to the second extension portion 320.

[0049] The electrical connection between the first current collector 100 and the second current collector 300 is achieved through the first extension portion 110 and the second extension portion 320. This structure is simple and does not require a complex structure. It is only necessary to ensure that the areas of the first current collector 100 and the second current collector 300 are larger than the active material layer 200. The first extension portion 110 and the second extension portion 320 can be directly connected by welding, or a metal sheet can be placed between them to achieve electrical connection.

[0050] Preferably, the length of the first extension portion 110 and the second extension portion 320 is set to 5 to 6 mm, so that the first extension portion 110 and the second extension portion 320 have sufficient welding space, thereby ensuring welding strength and reducing the probability of separation due to accidents such as collisions.

[0051] like Figure 1 As shown, in some embodiments, the second current collector 300 further includes a connecting portion 330 located in the active material layer 200 , the connecting portion 330 is connected to the second extension portion 320 , and the connecting portion 330 is spaced apart and arranged in parallel with the first current collector 100 .

[0052] By aligning the connection portion 330 of the first current collector 100 and the second current collector 300 in parallel, electrons in the active material layer 200 are evenly transferred to both the first and second current collectors 100 and 300, avoiding current concentration and local overheating caused by excessive local resistance, thereby improving the stability and safety of the electrode sheet. Furthermore, the first and second current collectors 100 and 300 provide support within the electrode sheet. Their parallel arrangement more evenly distributes mechanical stress, reducing the probability of delamination or rupture of the active material layer 200 and enhancing the cycle life and reliability of lithium-ion batteries fabricated from these electrodes.

[0053] In some embodiments, there are two active material layers 200 , which are respectively disposed on two opposite sides of the first current collector 100 , and there are two second current collectors 300 , which are respectively embedded in the two active material layers 200 .

[0054] The two active material layers 200 disposed on both sides of the first current collector 100 can fully utilize the conductive properties of the first current collector 100, significantly increasing the mass energy density of the manufactured lithium-ion battery, thereby extending the service life of the lithium-ion battery.

[0055] In some embodiments, the diameter of the through hole 310 is 0.5-3 mm.

[0056] If the pore diameter is greater than 3 mm, the area occupied by the through-hole 310 increases, resulting in a reduction in the contact area between the active material layer 200 and the current collector. This in turn lengthens the electron transmission path between the active material in the active material layer 200 and the second current collector 300, which can easily reduce the charge and discharge rate of the manufactured lithium-ion battery. Furthermore, an excessively large pore diameter can weaken the mechanical strength of the electrode. If the pore diameter is less than 0.5 mm, the active material cannot easily penetrate the through-hole 310 during secondary coating, resulting in a large number of gaps in the active material layer 200 and reducing the capacity of the manufactured lithium-ion battery. Preferably, the pore diameter is set to 1 mm.

[0057] In some embodiments, the thickness of the second current collector 300 is greater than the thickness of the first current collector 100. Since the second current collector 300 is provided with a plurality of through holes 310, the thickness of the second current collector 300 is controlled to be larger, thereby increasing the strength of the second current collector 300 and reducing the probability of breakage or damage to the second current collector 300.

[0058] The present invention further provides a battery cell comprising a diaphragm and two pole pieces with opposite polarities located on either side of the diaphragm; at least one of the two pole pieces is the pole piece described in the aforementioned embodiments. Because this battery cell utilizes all the technical solutions of all the aforementioned embodiments, it possesses at least all the technical effects provided by the technical solutions of the aforementioned embodiments, and therefore will not be further elaborated upon here.

[0059] The present invention further provides a lithium-ion battery comprising a housing and the battery cell of the aforementioned embodiment, wherein the battery cell is disposed within the housing. It is understood that if the lithium-ion battery is a soft-pack battery, the housing may be made of an aluminum-plastic film; if the lithium-ion battery is a battery requiring a hard housing, such as a steel-cased battery, the housing may be made of a metal or alloy material.

[0060] The above description is only part or preferred embodiments of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural transformations made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A pole piece, characterized in that: include a first current collector; an active material layer, the active material layer being disposed on at least one side of the first current collector; a second current collector, wherein the second current collector is embedded in the active material layer, and at least a portion of the active material layer is located between the first current collector and the second current collector; The second current collector is provided with a plurality of through holes, and the first current collector is electrically connected to the second current collector.

2. The pole piece according to claim 1, characterized in that: The distance between the upper surface of the first current collector and the lower surface of the second current collector is L, the distance between the upper surface of the second current collector and the upper surface of the active material layer is D, and the relationship between L and D is: L is greater than D.

3. The pole piece according to claim 2, characterized in that: The value range of D is 5 to 10 μm.

4. The pole piece according to claim 1, characterized in that: The first current collector includes a first extension portion extending beyond the active material layer along the length direction, and the second current collector includes a second extension portion extending beyond the active material layer along the length direction, wherein the first extension portion is electrically connected to the second extension portion.

5. The pole piece according to claim 4, characterized in that: The second current collector further includes a connecting portion located in the active material layer, the connecting portion is connected to the second extending portion, and the connecting portion is spaced apart and arranged in parallel with the first current collector.

6. The pole piece according to any one of claims 1 to 5, characterized in that: The active material layer has two layers, and is respectively arranged on two opposite sides of the first current collector; the second current collector has two layers, and is respectively embedded in the two active material layers.

7. The pole piece according to any one of claims 1 to 5, characterized in that: The through hole has a diameter of 0.5-3 mm.

8. The pole piece according to any one of claims 1 to 5, characterized in that: The thickness of the second current collector is greater than the thickness of the first current collector.

9. A battery cell, characterized in that: It comprises a diaphragm and two pole pieces with opposite polarities located on both sides of the diaphragm; at least one of the two pole pieces is the pole piece according to any one of claims 1 to 8.

10. A lithium ion battery, characterized in that: The invention comprises a shell and the battery core as claimed in claim 9, wherein the battery core is arranged in the shell.

Images