Novel battery pole group and lithium ion battery

Abstract

The utility model discloses a novel battery pole group and a lithium ion battery. The novel battery pole group comprises a positive plate, a negative plate and a diaphragm, the diaphragm is arranged between the positive plate and the negative plate; the positive plate comprises a positive current collector, and the left and right ends of the front side of the positive current collector are respectively provided with a positive coating interval for welding a positive lug; each positive electrode coating is coated with a positive electrode lug covering adhesive tape which is pasted in a covering manner at intervals; a positive plate core protection adhesive tape is adhered to the right end core of the positive plate; the negative plate comprises a negative current collector, and the left and right end parts of the front side of the negative current collector are respectively provided with a negative coating interval for welding a negative lug; each negative electrode coating is coated with a negative electrode tab covering adhesive tape at an interval; and after the positive plate, the negative plate and the diaphragm are wound into a battery pole group, the two positive tabs are mutually overlapped and welded together. According to the cylindrical lithium ion battery, the problem of coulombic efficiency abnormity in the circulating process of the cylindrical lithium ion battery can be solved, the diaphragm at the core position is protected, and the safety and reliability of the battery are improved.

Description

Technical Field

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

[0002] Cylindrical lithium-ion batteries have the advantages of high internal space utilization, high energy density, relatively simple structure, easy to achieve high consistency, relatively mature manufacturing process, easy large-scale production, long cycle life, and good storage performance. They have been widely used in electric vehicles, energy storage systems, mobile devices, etc.

[0003] As applications such as electric vehicles and power tools place increasingly higher demands on driving range and effective usage time, the energy density and power density of cylindrical lithium-ion batteries also need to be continuously improved.

[0004] In order to improve the power density of cylindrical lithium-ion batteries, it is a common strategy to adopt a dual positive and dual negative electrode group structure. Usually, the dual positive and dual negative structure of conventional battery pole pieces can be achieved by cutting foil and cutting slurry. However, the cut foil structure (such as Figure 3a As shown in the figure, it is necessary to add another empty foil position in the core of the pole piece. Not only is the production process complicated and difficult to manufacture, but there are also problems such as unstable coating and increased workstations. Conventional winding machines are difficult to achieve. In addition, this empty foil occupies limited battery space, causing unnecessary space waste. Therefore, the dual positive and dual negative structure mostly adopts a cut slurry structure (such as Figure 3b As shown in the figure, however, as the power density and energy density become higher and higher, the silicon content of cylindrical lithium-ion batteries with this structure becomes higher and higher, and the pole pieces become thicker and thicker, which leads to an increase in the expansion of the negative electrode during the battery charge and discharge cycle, and an increase in the stress on the battery core diaphragm during the cycle, which ultimately leads to an increase in the probability of abnormal coulomb efficiency (coulomb efficiency is the ratio of the total energy emitted by the battery to the input energy) during the cycle, and the time of the abnormal coulomb efficiency occurring is also earlier.

[0005] Therefore, there is an urgent need to develop a technology that can solve the above technical problems. Utility Model Content

[0006] The purpose of the utility model is to provide a new type of battery pole group and lithium ion battery in view of the technical defects in the prior art.

[0007] To this end, the utility model provides a novel battery electrode group, characterized in that it includes a positive electrode sheet, a negative electrode sheet and a separator;

[0008] The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet;

[0009] A positive electrode sheet, including a positive electrode current collector;

[0010] A vertically distributed positive electrode coating interval is provided at the left and right ends of the front side of the positive electrode current collector;

[0011] The remaining area of ​​the front side of the positive electrode current collector except for two positive electrode coating intervals is coated with a positive electrode coating;

[0012] The entire rear side of the positive electrode current collector is coated with a positive electrode coating;

[0013] The front side of each positive electrode coating interval of the positive electrode current collector is respectively welded with a vertically distributed positive electrode ear;

[0014] The upper portion of the positive electrode ear protrudes upward from the top of the positive electrode current collector;

[0015] A positive electrode tab covering tape is pasted on each positive electrode coating interval;

[0016] The positive electrode tab covers the upper and lower sides of the tape, protruding from the top and bottom of the positive electrode sheet respectively;

[0017] A vertically distributed positive electrode core protection tape is pasted on the right end core of the positive electrode;

[0018] A negative electrode sheet, including a negative electrode current collector;

[0019] The left and right ends of the front side of the negative electrode current collector are respectively provided with a vertically distributed negative electrode coating interval;

[0020] The remaining area of ​​the front side of the negative electrode current collector except for two negative electrode coating intervals is coated with the negative electrode coating;

[0021] The entire rear side of the negative electrode current collector is coated with a negative electrode coating;

[0022] A vertically distributed negative electrode ear is welded to the front side of each negative electrode coating interval of the negative electrode current collector;

[0023] The lower part of the negative electrode ear protrudes downward from the bottom of the negative electrode current collector;

[0024] A negative electrode tab covering tape is pasted on each negative electrode coating interval;

[0025] When the positive electrode sheet is wound together with the negative electrode sheet and the separator into a battery electrode group, the two positive electrode ears overlap and are welded together.

[0026] In addition, the utility model also provides a lithium-ion battery, which includes the novel battery electrode group as described above.

[0027] It can be seen from the technical solution provided by the above utility model that, compared with the prior art, the utility model provides a new type of battery electrode group and lithium-ion battery, which has a scientific structural design, can improve the abnormal coulomb efficiency problem of cylindrical lithium-ion batteries during the cycle process, protect the diaphragm at the core position of the battery, and improve the safety and reliability of the battery, which has great production practical significance.

[0028] After practical verification, the application of the utility model is helpful to solve the problem of abnormal coulombic efficiency of batteries in cycling, especially in high-rate cycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1a A schematic diagram of the structure of a positive electrode sheet of a first structural form in a novel battery electrode group provided by the utility model;

[0030] Figure 1b A schematic diagram of the structure of a negative electrode sheet in a new type of battery electrode group provided by the utility model;

[0031] Figure 1c A schematic diagram of the structure of a positive electrode sheet of a second structural form in a novel battery electrode group provided by the utility model, in which both the core and the tail are affixed with positive electrode sheet protection tape;

[0032] Figure 2 A schematic diagram of the structure of a novel battery electrode group provided by the utility model obtained by winding;

[0033] Figure 3a A schematic diagram of a double positive and double negative cut foil structure used in conventional battery pole pieces;

[0034] Figure 3b : Schematic diagram of the structure of the positive electrode sheet of the comparative example;

[0035] Figure 3c : Schematic diagram of the structure of the negative electrode sheet of the comparative example;

[0036] Figure 4 : Coulombic efficiency diagram of the battery 1.2C / 4C cycle in the embodiment and the comparative example;

[0037] Figure 5 : Coulombic efficiency diagram of the battery 1.2C / 8C cycle in the embodiment and the comparative example;

[0038] In the figure, 1-positive electrode sheet; 2-negative electrode sheet; 3-positive electrode ear; 4-positive electrode coating coating interval; 5-positive electrode ear covering tape;

[0039] 6-positive electrode core protection tape; 7-negative electrode ear; 8-negative electrode coating interval; 9-negative electrode ear covering tape; 10-battery electrode group. DETAILED DESCRIPTION

[0040] 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 of 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.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0042] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0044] See also Figure 1a to Figure 1c As shown, Figure 2 , the utility model provides a novel battery electrode group, which can improve the abnormal coulombic efficiency in the cycle of cylindrical lithium-ion batteries, and comprises a positive electrode sheet 1, a negative electrode sheet 2 and a separator;

[0045] The diaphragm is disposed between the positive electrode sheet 1 and the negative electrode sheet 2 to separate the positive electrode sheet 1 from the negative electrode sheet 2;

[0046] In the present utility model, the specific implementation is as follows: Figure 1a As shown, the positive electrode sheet 1 adopts a bipolar ear structure;

[0047] A positive electrode sheet 1, comprising a positive electrode current collector 100 (i.e., serving as the main body of the positive electrode sheet);

[0048] A vertically distributed positive electrode coating interval 4 (i.e., a section without positive electrode coating, on which there is no positive electrode coating) is respectively provided at the left and right ends of the front side of the positive electrode current collector 100;

[0049] The remaining area of ​​the front side of the positive electrode current collector 100 except the two positive electrode coating intervals 4 is coated with a positive electrode coating 101;

[0050] The entire rear side of the positive electrode current collector 100 is coated with a positive electrode coating 101;

[0051] A vertically distributed positive electrode ear 3 is welded to the front side of each positive electrode coating spacer 4 of the positive electrode current collector 100;

[0052] The upper portion of the positive electrode tab 3 protrudes upward from the top of the positive electrode current collector 100;

[0053] Each positive electrode coating interval 4 is covered with a positive electrode tab covering tape 5;

[0054] The positive electrode tab covers the upper and lower sides of the tape 5, and protrudes from the top and bottom of the positive electrode sheet 1 respectively;

[0055] The positive electrode tab covering tape 5 also covers the surface of the portion of the positive electrode tab 3 located in front of the positive electrode coating interval 4 (i.e., the tab section);

[0056] The right end core of the positive electrode sheet 1 (i.e. the right end) is pasted with a vertically distributed positive electrode sheet core protection tape 6;

[0057] The upper and lower sides of the positive electrode sheet core protection tape 6 protrude from the top and bottom of the positive electrode sheet 1 respectively;

[0058] In the present utility model, in specific implementation, the novel battery electrode group is a battery electrode group obtained by winding a positive electrode sheet 1, a negative electrode sheet 2 and a separator.

[0059] It should be noted that the winding method adopted by the cylindrical battery electrode group is an existing conventional method for preparing the battery electrode group, which will not be described in detail here.

[0060] In the present utility model, the specific implementation is as follows: Figure 2 As shown, for the positive electrode sheet 1, after the positive electrode sheet 1 is wound together with the negative electrode sheet 2 and the separator into a battery electrode group 10, the two positive electrode ears 3 overlap each other and are welded (ie, welded) together.

[0061] For specific implementation, see Figure 1c As shown, the left end of the positive electrode sheet 1 is also pasted with a vertically distributed positive electrode sheet core protection tape 6;

[0062] The upper and lower sides of the positive electrode sheet core protection tape 6 protrude from the top and bottom of the positive electrode sheet 1 respectively;

[0063] Furthermore, one end of the two positive electrode sheet core protection tapes 6 away from the positive electrode coating interval 4 protrudes from the left and right sides of the positive electrode current collector 100 .

[0064] In specific implementation, the width of the positive electrode core protection tape 6 is 4 to 10 mm;

[0065] A portion of the positive electrode sheet core protection tape 6 covers the positive electrode coating 101 of the positive electrode sheet 1;

[0066] Furthermore, the width of the positive electrode sheet core protection tape 6 covering the positive electrode coating 101 of the positive electrode sheet 1 (ie, the powder covering width) is 2 to 8 mm.

[0067] Furthermore, the material of the positive electrode core protection tape 6 is a polymer material.

[0068] Preferably, the positive electrode core protection tape 6 is made of polyimide (PI).

[0069] It should be noted that, for the utility model, in specific implementation, the positive electrode sheet 1 can adopt a single-pole ear, a double-pole ear or a multi-pole ear structure, and adopt a slurry cutting method, and one or more positive electrode sheet core protection tapes 6 are attached to the right end core of the positive electrode sheet 1.

[0070] For the present utility model, the positive electrode sheet is a cut slurry structure, and the core is affixed with a positive electrode sheet core protection tape 6 (such as Figure 1a Compared with the existing common positive and negative double structures, cutting the slurry can save limited battery space, and the utility model can also solve the problem of abnormal cycle efficiency.

[0071] In the present utility model, the specific implementation is as follows: Figure 1b As shown, the negative electrode sheet 2 adopts a bipolar ear structure;

[0072] A negative electrode sheet 2, including a negative electrode current collector 200;

[0073] The left and right ends (i.e., the tail and the core) of the front side of the negative electrode current collector 200 are respectively provided with a vertically distributed negative electrode coating spacer 8;

[0074] The remaining area of ​​the front side of the negative electrode current collector 200 except the two negative electrode coating intervals 8 is coated with a negative electrode coating 201;

[0075] The entire rear side of the negative electrode current collector 200 is coated with a negative electrode coating 201;

[0076] A vertically distributed negative electrode ear 7 is welded to the front side of each negative electrode coating spacer 8 of the negative electrode current collector 200;

[0077] The lower portion of the negative electrode tab 7 protrudes downward from the bottom of the negative electrode current collector 200;

[0078] A negative electrode tab covering tape 9 is pasted (not pasted in a covering manner) on each negative electrode coating interval 8;

[0079] The negative electrode tab covers the upper and lower sides of the tape 9, protruding from the top and bottom of the negative electrode sheet 2 respectively;

[0080] The negative electrode tab covering tape 9 also covers the surface of the portion of the negative electrode tab 7 located in front of the negative electrode coating interval 8 (i.e., the tab segment);

[0081] For the utility model, based on the above structural design, the new battery electrode group provided by the utility model can not only effectively protect the diaphragm at the core of the battery, thereby improving the problem of abnormal coulomb efficiency in the cycle of common double-positive and double-negative structure cylindrical lithium-ion batteries, but also the electrode group structure is scientific and reasonable, and can use the mature welding, injection and packaging processes of cylindrical batteries, which is convenient for mass production.

[0082] It should be noted that for the battery electrode group, during the charging process, lithium ions are extracted from the positive electrode and embedded in the negative electrode through the electrolyte. During the discharge process, lithium ions are extracted from the negative electrode and re-embedded into the positive electrode. As lithium ions are extracted and embedded between the positive and negative electrodes, the microstructure of the positive and negative electrode materials will change, and their thickness will also change accordingly. For the double positive and double negative cut slurry structure, there is such an area in the core of the electrode group: the positive electrode cut-off point-diaphragm-negative electrode. As the charging and discharging proceeds, the thickness changes of the positive and negative electrodes will exert pressure on the diaphragm. Because the diaphragm used in the battery is very thin, only a few to a dozen microns, the diaphragm will become more and more fragile under the action of stress, and may eventually be damaged, resulting in a micro short circuit inside the battery, which in turn abnormally affects the coulomb efficiency.

[0083] As for the new battery electrode group provided by the utility model, the protective tape used at the core position of the positive electrode (i.e., the positive electrode sheet core protective tape 6) is located at the position of the diaphragm which is most susceptible to external force compression to prevent the diaphragm from being damaged. It can effectively protect the diaphragm at the core position of the battery, thereby effectively improving the problem of abnormal coulomb efficiency during the cycle process and improving the reliability and stability of the battery.

[0084] Based on the novel battery pole group provided by the utility model, the utility model further provides a lithium ion battery, which includes the novel battery pole group as described above (i.e., the battery pole group 10);

[0085] In the present invention, in a specific implementation, the lithium ion battery is a cylindrical lithium ion battery.

[0086] After testing, the cylindrical lithium-ion battery of the utility model using the above structure did not have any abnormal coulomb effect problem in the cycles of various standards.

[0087] In the present invention, in a specific implementation, the cylindrical lithium-ion battery includes a 18650 battery and a 21700 battery.

[0088] In order to more clearly understand the technical solution of the present invention, the technical effects of the present invention are explained below in conjunction with specific embodiments.

[0089] Example

[0090] according to Figure 1a to Figure 1c , Figure 2 as well as Figure 3a to Figure 3c As shown, the positive electrode sheet and the negative electrode sheet used to prepare the new battery electrode group are as follows Figure 1a to Figure 1c As shown;

[0091] The silicon content of the negative electrode slurry used in the negative electrode coating 201 of the negative electrode sheet 2 is 13.5%, and the thickness of the negative electrode sheet 2 is 105 mm.

[0092] Comparative example.

[0093] The battery pole pieces (including positive and negative pole pieces) of the comparative example adopt a conventional double positive and double negative structure (such as Figure 3b , Figure 3c The remaining materials are the same as those of the battery in the embodiment.

[0094] The positive electrode sheet, negative electrode sheet and separator of the embodiment and the comparative example are respectively wound into two battery electrode groups, and the two positive electrode ears in each battery electrode group are welded together to obtain the new battery electrode group of the embodiment of the utility model (such as Figure 2 As shown) and the battery pole group of the comparative example.

[0095] The two battery electrode groups are respectively loaded into a battery shell, and two 21700 cylindrical lithium-ion batteries of a certain model are prepared through processes such as bottom welding, closing, liquid injection, welding caps, sealing, cleaning, and formation.

[0096] Then, the cylindrical lithium ion batteries prepared in the embodiments and comparative examples of the present utility model were subjected to the following test evaluations:

[0097] 1. 1.2C / 4C cycle test.

[0098] In an environment of 25°C, the battery was charged at a rate of 1.2C, discharged at a rate of 4C, and 100% DOD (depth of discharge) for charge and discharge cycles. Figure 4As shown, the coulombic efficiency of the battery of the comparative example began to decrease after 390 cycles, while the battery of the embodiment did not show abnormal coulombic efficiency until the end of the cycle (600 cycles).

[0099] 2. 1.2C / 8C cycle test.

[0100] In an environment of 25°C, the battery was charged at a rate of 1.2C, discharged at a rate of 8C, and 100% DOD (depth of discharge) for charge and discharge cycles. Figure 5 It can be seen that the coulombic efficiency of the battery of the comparative example begins to decrease after the 140th cycle, while the battery of the embodiment has been cycled up to 200 times without any abnormal coulombic efficiency problem.

[0101] The comparative battery has fewer cycles with abnormal coulombic efficiency under 1.2C / 4C cycle and 1.2C / 8C cycle, and is more likely to have abnormal coulombic efficiency in high-rate cycles.

[0102] In summary, by optimizing the electrode group structure, the cylindrical lithium-ion battery prepared by the utility model improves the abnormal coulomb efficiency problem existing in the double positive and double negative structure, improves the cycle life, reliability and safety of the battery, and can have broad application prospects in electric vehicles, power tools, smart homes and other fields.

[0103] Compared with the prior art, the novel battery electrode group and lithium-ion battery provided by the utility model have the following beneficial effects:

[0104] 1. The battery electrode group structure of the utility model is based on the double positive and double negative structure, and further adds two protective tapes with adjustable width, which can effectively protect the diaphragm at the core of the battery and prevent the diaphragm from being damaged by stress during the cycle process.

[0105] 2. The battery electrode group of the utility model can effectively reduce the phenomenon of abnormal coulomb efficiency of the battery during the charge and discharge cycle, greatly improving the reliability, safety and service life of the cylindrical lithium-ion battery.

[0106] 3. The battery electrode group of the utility model is easy to prepare and mass-produced, and can avoid the problems of burrs and edge powder loss in the cut slurry structure, thereby reducing self-discharge.

[0107] 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 new type of battery pole group, characterized in that: It comprises a positive electrode sheet (1), a negative electrode sheet (2) and a separator; The diaphragm is arranged between the positive electrode sheet (1) and the negative electrode sheet (2); A positive electrode sheet (1), comprising a positive electrode current collector (100); A vertically distributed positive electrode coating spacer (4) is respectively provided at the left and right ends of the front side of the positive electrode current collector (100); The remaining area of ​​the front side of the positive electrode current collector (100) except for the two positive electrode coating intervals (4) is coated with a positive electrode coating (101); The entire rear side of the positive electrode current collector (100) is coated with a positive electrode coating (101); A vertically distributed positive electrode ear (3) is welded to the front side of each positive electrode coating interval (4) of the positive electrode current collector (100); The upper portion of the positive electrode ear (3) protrudes upward from the top of the positive electrode current collector (100); A positive electrode tab covering tape (5) is pasted on each positive electrode coating interval (4) in a covering manner; The positive electrode tab covers the upper and lower sides of the tape (5), and protrudes from the top and bottom of the positive electrode sheet (1) respectively; A vertically distributed positive electrode core protection tape (6) is adhered to the right end core of the positive electrode sheet (1); A negative electrode sheet (2), comprising a negative electrode current collector (200); A vertically distributed negative electrode coating spacer (8) is respectively provided at the left and right ends of the front side of the negative electrode current collector (200); The remaining area of ​​the front side of the negative electrode current collector (200) except for the two negative electrode coating intervals (8) is coated with a negative electrode coating (201); The entire rear side of the negative electrode current collector (200) is coated with a negative electrode coating (201); A vertically distributed negative electrode ear (7) is welded to the front side of each negative electrode coating interval (8) of the negative electrode current collector (200); The lower part of the negative electrode ear (7) protrudes downward from the bottom of the negative electrode current collector (200); A negative electrode tab covering tape (9) is pasted on each negative electrode coating interval (8); After the positive electrode sheet (1) is wound together with the negative electrode sheet (2) and the separator into a battery electrode group (10), the two positive electrode ears (3) are overlapped and welded together.

2. The novel battery pole group according to claim 1, characterized in that: The positive electrode tab covering tape (5) also covers the surface of the positive electrode tab (3) located in front of the positive electrode coating space (4); The negative electrode tab covering tape (9) covers the surface of the portion of the negative electrode tab (7) located in front of the negative electrode coating space (8).

3. The novel battery electrode group according to claim 1, characterized in that: The upper and lower sides of the positive electrode sheet core protection tape (6) protrude from the top and bottom of the positive electrode sheet (1) respectively; and / or, The negative electrode tab covers the upper and lower sides of the tape (9) and protrudes from the top and bottom of the negative electrode sheet (2) respectively.

4. The novel battery electrode group according to claim 1, characterized in that: A vertically distributed positive electrode core protection tape (6) is also pasted on the left end of the positive electrode sheet (1); The upper and lower sides of the positive electrode sheet core protection tape (6) protrude from the top and bottom of the positive electrode sheet (1) respectively.

5. The novel battery pole group as claimed in claim 4, characterized in that: One end of the two positive electrode sheet core protection tapes (6) away from the positive electrode coating coating interval (4) protrudes from the left and right sides of the positive electrode current collector (100).

6. The novel battery pole group according to claim 1, characterized in that: The width of the positive electrode core protection tape (6) is 4 to 10 mm.

7. The novel battery pole group according to any one of claims 1 to 6, characterized in that: A portion of the positive electrode sheet core protection tape (6) covers the positive electrode coating (101) of the positive electrode sheet (1).

8. The novel battery pole group as claimed in claim 7, characterized in that: The width of the positive electrode sheet core protection tape (6) covering the positive electrode coating (101) of the positive electrode sheet (1) is 2 to 8 mm.

9. A lithium ion battery, characterized in that: The invention comprises a novel battery electrode group as claimed in any one of claims 1 to 8.

10. The lithium ion battery according to claim 9, characterized in that The lithium ion battery is a cylindrical lithium ion battery.

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