Composite current collector lithium ion battery

Abstract

A laminated core is composed of a plurality of lamination units, each lamination unit comprises a layer of positive electrode, a layer of negative electrode and two layers of diaphragms, the positive electrode current collector and the negative electrode current collector are composite current collectors, the positive and negative composite current collectors are of a three-layer structure, the middle layer is an insulating layer and is made of a high polymer material, and the middle layer is made of a high polymer material. The upper and lower layers are metal layers; the thicknesses of the positive and negative composite current collector metal layers are in gradient distribution along the tab direction, and the tab position is the maximum thickness position of the metal layer; and the composite current collector tabs are welded with external tabs after the lamination units are manufactured. Through gradient distribution of the metal layers of the composite current collector, the overcurrent capacity of the composite current collector is improved, the impedance is reduced, the problem of uneven heat production caused by uneven current density distribution of the current collector is solved, meanwhile, the external tab is welded in the manufacturing process of the lamination unit, external tab welding before laser cutting is omitted, and the production efficiency is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium ion batteries, and in particular relates to a composite current collector lithium ion battery. Background Art

[0002] The current collector is one of the key materials in lithium batteries. It not only acts as a carrier of the positive and negative active materials in lithium-ion batteries, but also acts as a collector and transmitter of the electron flow. The composite current collector is a new type of lithium battery material with a sandwich structure of "metal conductive layer-polymer material support layer-metal conductive layer" made of polymer insulating resin material as the "sandwich" layer. Compared with traditional aluminum foil or copper foil, the composite current collector can reduce the cost of the battery and improve the energy density and safety performance of the battery.

[0003] The transmission density of electrons on the current collector is uneven. During the battery charging and discharging process, all electrons are transmitted in the direction of the pole ear. Therefore, the closer to the pole ear, the greater the current density on the current collector. Because the upper and lower metal conductive layers of the composite current collector are thin, the current density distribution on the current collector is uneven, which will cause uneven heat generation in the battery, increase impedance, and affect the battery power performance and service life. In addition, there is an insulating layer in the middle of the composite current collector, and the pole ears of the composite current collector cannot be directly welded. Usually, the external pole ears are welded before laser cutting and then laser cutting. All blank spaces before laser cutting are welded to the external pole ears, which is inefficient. Most of the welded external pole ears are cut off during laser cutting, resulting in a lot of scrap and serious scrap. Utility Model Content

[0004] The utility model provides a composite current collector lithium ion battery. The lithium ion battery core is composed of a plurality of laminated units, including a positive electrode layer, a negative electrode layer and two layers of diaphragms. The positive electrode tabs and the negative electrode tabs of the laminated units are on opposite sides, which solves the problems of uneven current density distribution of the current collector, uneven heat generation and serious scrapping.

[0005] The utility model adopts the following technical scheme: a composite current collector lithium ion battery, the core stack includes a plurality of stacking units, each stacking unit includes a positive electrode sheet 1, a negative electrode sheet 2 and two layers of diaphragms 3, and the positive electrode sheet 1 and the negative electrode sheet 2 have pole ears located on both sides of the stacking unit respectively.

[0006] The current collectors of the positive electrode sheet 1 and the negative electrode sheet 2 are a positive electrode composite current collector and a negative electrode composite current collector; the positive electrode composite current collector and the negative electrode composite current collector are a three-layer structure, the upper and lower layers are a first metal conductive layer 5 and a second metal conductive layer 7, and the middle layer is a first insulating layer 4 and a second insulating layer 6.

[0007] Furthermore, each laminate has two layers of separators 3, which are respectively placed under the positive electrode sheet 1 and the negative electrode sheet 2.

[0008] Furthermore, the first insulating layer 4 and the second insulating layer 6 are made of polymer materials, and the polymer materials include one or more of PP, PI, and PET.

[0009] Furthermore, the first metal conductive layer 5 of the positive electrode composite current collector is aluminum, and the second metal conductive layer 7 of the negative electrode composite current collector is copper.

[0010] Furthermore, the thickness of the first metal conductive layer 5 and the second metal conductive layer 7 is gradiently distributed along the tab direction, and the tab positions of the positive composite current collector and the negative composite current collector are respectively the positions where the thickness of the first metal conductive layer 5 and the second metal conductive layer 7 is maximum.

[0011] In each laminate unit, the positive and negative electrode tabs are distributed on the corresponding two sides, and the thickness gradients of the first metal conductive layer 5 and the second metal conductive layer 7 are in opposite directions. After being superimposed on each other, the overall thickness of the laminate unit is consistent.

[0012] Furthermore, there is an insulating layer in the middle of the composite current collector, so the composite current collectors cannot be directly welded between multiple stacking units. After the stacking units are completed, a layer of external pole ears is welded on the upper and lower metal conductive layers 5 and the outer surface of the metal conductive layer 7 of the composite current collector ears on the stacking platform, which are the positive electrode external pole ear 8 and the negative electrode external pole ear 9 respectively.

[0013] Furthermore, the positive electrode external tab 8 is aluminum foil, and the negative electrode external tab 9 is copper foil. After a plurality of laminated units form a stacked core, the external tabs are welded to each other to complete the welding of the stacked core tabs.

[0014] Compared with the prior art, the utility model adopts the above technical solution and has the following technical effects:

[0015] 1. The composite current collector lithium-ion battery of the utility model improves the current carrying capacity of the composite current collector, reduces impedance, and solves the problems of uneven current density distribution and uneven heat generation of the current collector through the gradient distribution of the composite current collector metal layer.

[0016] 2. The composite current collector lithium-ion battery of the utility model welds the external pole ears during the manufacturing process of the stacked unit, eliminating the welding of the external pole ears before laser cutting, thereby improving production efficiency and reducing scrapping. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view of a laminated unit of a composite current collector lithium-ion battery of the utility model;

[0018] Figure 2 This is a top view of a laminated unit of a composite current collector lithium-ion battery of the utility model;

[0019] Figure 3 This is a cross-sectional view of the positive and negative composite current collector of the utility model;

[0020] Figure 4 This is the welding arrangement diagram of the external pole ear of the utility model;

[0021] Figure 5 This is a core stacking layout diagram of a composite current collector lithium-ion battery of the utility model.

[0022] In the figure: 1. positive electrode sheet; 2. negative electrode sheet; 3. diaphragm; 4. first insulating layer; 5. first metal conductive layer; 6. second insulating layer; 7. second metal conductive layer; 8. positive electrode external lug; 9. negative electrode external lug. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] In one embodiment of the present invention, Figure 1 As shown, the composite current collector lithium-ion battery stack consists of a plurality of stacking units, each of which includes a positive electrode sheet 1, a negative electrode sheet 2 and two separators 3. In each stack, the two separators 3 are placed under the positive electrode sheet 1 and the negative electrode sheet 2, respectively.

[0025] The positive electrode sheet 1 and the negative electrode sheet 2 have their tabs on both sides of the laminated unit, such as Figure 2 shown.

[0026] The current collectors of the positive electrode sheet 1 and the negative electrode sheet 2 are both composite current collectors, namely, the positive composite current collector and the negative composite current collector, such as Figure 3 As shown, both the positive composite current collector and the negative composite current collector have a three-layer structure. The upper and lower layers of the positive composite current collector are both the first metal conductive layer 5, and the middle layer is the first insulating layer 4. The upper and lower layers of the negative composite current collector are both the second metal conductive layer 7, and the middle layer is the second insulating layer 6.

[0027] The first insulating layer 4 and the second insulating layer 6 are both made of polymer materials. In particular, in this embodiment, the polymer material is one or more of PP, PI, and PET.

[0028] The first metal conductive layer 5 of the positive electrode current collector is aluminum metal, and the second metal conductive layer 7 of the negative electrode current collector is copper metal.

[0029] In the positive composite current collector and the negative composite current collector, the thickness of the metal conductive layers 5 and 7 gradually increases along the direction of the pole lug. The pole lug position is the position where the thickness of the metal layer of the current collector is the maximum. Therefore, the greater the current density on the current collector, the thicker the metal conductive layer is and the stronger the current carrying capacity is.

[0030] In the laminated unit, the positive and negative electrode tabs are distributed on the corresponding two sides. Therefore, the thickness gradient directions of the metal conductive layers of the positive composite current collector and the negative composite current collector are opposite. After being superimposed on each other, the overall thickness of the laminated unit is consistent.

[0031] The first insulating layer 4 and the second insulating layer 6 are located between the positive electrode composite current collector and the negative electrode composite current collector, so the composite current collectors between multiple laminated units cannot be directly welded. Figure 4 As shown, on the lamination platform, a layer of external pole tabs is welded to the outer surfaces of the upper and lower metal conductive layers of the positive and negative composite current collector pole tabs, namely, the positive pole external pole tab 8 and the negative pole external pole tab 9.

[0032] After multiple laminated units form a laminated core, Figure 5 As shown, the external pole tabs of multiple laminated units are welded to each other to complete the welding of the stacked core pole tabs.

[0033] In particular, in this embodiment, the positive electrode external tab 8 is aluminum foil, and the negative electrode external tab 9 is copper foil.

[0034] In summary, the utility model improves the current carrying capacity of the composite current collector and reduces the impedance through the gradient distribution of the composite current collector metal layer, thereby solving the problem of uneven heat generation caused by uneven current density distribution of the current collector. At the same time, the external pole ears are welded during the production process of the stacked unit, and the welding of the external pole ears before laser cutting is eliminated, thereby improving production efficiency.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A composite current collector lithium ion battery, characterized in that: The composite current collector lithium-ion battery stack comprises a plurality of stacking units, each stacking unit comprises a positive electrode sheet (1), a negative electrode sheet (2) and a separator (3), the positive electrode sheet (1) and the negative electrode sheet (2) have pole ears located on both sides of the stacking unit respectively; the current collectors of the positive electrode sheet (1) and the negative electrode sheet (2) are positive composite current collectors and negative composite current collectors; the positive composite current collectors and the negative composite current collectors are three-layer structures, the upper and lower layers are a first metal conductive layer (5) and a second metal conductive layer (7), and the middle layer is a first insulating layer (4) and a second insulating layer (6).

2. The composite current collector lithium ion battery according to claim 1, characterized in that: Each laminate has two layers of diaphragms (3), which are respectively placed on the lower layers of the positive electrode sheet (1) and the negative electrode sheet (2).

3. The composite current collector lithium ion battery according to claim 1, characterized in that: The first insulating layer (4) and the second insulating layer (6) are made of polymer materials, including PP, PI, and PET.

4. The composite current collector lithium ion battery according to claim 1, characterized in that: The first metal conductive layer (5) of the positive electrode composite current collector is aluminum, and the second metal conductive layer (7) of the negative electrode composite current collector is copper.

5. The composite current collector lithium ion battery according to claim 1 or 4, characterized in that: The thickness of the first metal conductive layer (5) and the second metal conductive layer (7) are distributed in a gradient along the direction of the tab.

6. The composite current collector lithium ion battery according to claim 5, characterized in that: The positions of the tabs of the positive electrode composite current collector and the negative electrode composite current collector are the positions where the thickness of the first metal conductive layer (5) and the second metal conductive layer (7) is the maximum.

7. The composite current collector lithium ion battery according to claim 5, characterized in that: In each laminate unit, the positive and negative electrode tabs are distributed on two corresponding sides, the first metal conductive layer (5) and the second metal conductive layer (7) have thickness gradients in opposite directions, and after being superimposed on each other, the overall thickness of the laminate unit is consistent.

8. The composite current collector lithium ion battery according to claim 1, characterized in that: A layer of external pole lugs is welded to the outer surfaces of the first metal conductive layer (5) and the second metal conductive layer (7), respectively being a positive pole external pole lug (8) and a negative pole external pole lug (9).

9. The composite current collector lithium ion battery according to claim 8, characterized in that: The positive electrode externally connected tab (8) is made of aluminum foil, and the negative electrode externally connected tab (9) is made of copper foil.

10. The composite current collector lithium ion battery according to claim 9, characterized in that: A plurality of lamination units form a stacked core, and the stacked core tabs are connected to each other by welding the external tabs.

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