A cylindrical lithium-ion battery without tabs

Abstract

The application provides a cylindrical tab-free lithium ion battery, which comprises a shell, a battery core and a cap, the battery core is composed of a positive electrode sheet, a diaphragm and a negative electrode sheet, the end of the positive electrode sheet and the negative electrode sheet is respectively designed as an empty foil area with a reduced width, and the empty foil areas of the positive electrode sheet and the negative electrode sheet form a gap area with a spacing on the surface of the battery core after being wound, and the empty foil areas of the positive electrode sheet and the negative electrode sheet are respectively arranged on the two sides of the gap area; the shell is a layered shell composed of different materials, which comprises a first metal shell area, an insulating connecting area and a second metal shell area arranged in sequence, the empty foil areas of the positive electrode sheet and the negative electrode sheet on the battery core respectively fall into the first metal shell area and the second metal shell area, and the insulating connecting area on the shell falls into the gap area on the battery core. The application can effectively improve the energy density of the battery and ensure the efficient conduction of current and heat under high energy density.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and specifically to a cylindrical tabless lithium-ion battery. Background Technology

[0002] With the continuous advancement of lithium-ion battery technology, batteries that combine high energy density and high safety performance have become a hot topic in current battery research. Lithium-ion batteries can be classified into aluminum-cased batteries, steel-cased batteries, and polymer batteries according to their outer packaging. Traditional steel-cased and aluminum-cased batteries with tabs require a certain height of space between the casing and the cap to accommodate the aluminum and nickel strips led out from the positive and negative electrode plates. This design often sacrifices a significant amount of energy density. Furthermore, the internal heat of the battery can only be conducted through the aluminum and nickel strips inside the cell to the casing, and then through the casing to the outside. This very slow conduction and heat dissipation rate creates a significant risk of thermal runaway. Polymer batteries have a non-metallic casing, and their positive and negative electrodes are also conducted out through tabs.

[0003] In the production process of lithium-ion batteries, the welding of the tabs and the external adhesive protection of the cells can lead to problems such as long production cycles and high production costs. During laser welding, aluminum and nickel strips are prone to sticking to the casing and cap, which can increase the defect rate of welded products.

[0004] Some existing technologies aim to simplify the battery manufacturing process and structure by removing the tabs. However, removing the tabs reduces the reliability of the positive and negative electrode connection and conduction, which often leads to problems such as poor electrode contact, current and heat conduction obstacles, and a decrease in battery capacity instead of an increase. This limits the widespread application of tabless-free battery structures. Summary of the Invention

[0005] This invention addresses the problems in the prior art by proposing a cylindrical tabless lithium-ion battery that can improve energy density, effectively mitigate battery thermal runaway, enhance battery production efficiency, and reduce production costs.

[0006] Specifically, the cylindrical tabless lithium-ion battery proposed in this invention includes a casing, a cylindrical cell inside the casing and composed of a positive electrode, a separator, and a negative electrode wound together, and a cap on the top of the casing. The ends of the positive and negative electrodes are designed as empty foil areas with reduced width, and after winding, the empty foil areas of the positive and negative electrodes form gap areas with spacing on the surface of the cell, and positive electrode empty foil areas and negative electrode empty foil areas are respectively formed on both sides of the gap areas. The casing has shell areas made of different materials, including a first metal shell area, an insulating connection area, and a second metal shell area arranged in sequence. The positive electrode empty foil areas and negative electrode empty foil areas on the cell all fall into the first metal shell area and the second metal shell area respectively, and the insulating connection area on the casing falls into the gap area on the cell.

[0007] The first metal shell area of ​​the outer casing is an aluminum shell, and the second metal shell area is a steel shell.

[0008] The outer casing of the present invention adopts a layered design of different materials, so that the positive and negative electrodes of the battery cell are connected to different positions on the outer casing, and the positive and negative electrode plates are in direct contact with the outer casing to improve the conduction rate of battery current and heat, thereby improving the thermal stability of the battery.

[0009] The cap is a metal cap, and from the center to the edge it is provided with a cap venting area, a cap reinforcing area and a cap sealing area.

[0010] The bottom of the battery cell has an insulating protective layer.

[0011] The bottom surface inside the outer shell is provided with an insulating protective layer.

[0012] The battery cell and the cap are provided with insulation protection, preferably with an insulating gasket.

[0013] Wherein, the gap A between the top of the battery cell and the bottom surface of the cap inside the casing is 0.5 to 6 mm; the ratio between the diameter of the battery cell and the inner diameter of the casing is the fill ratio B, with a specific value of 85% to 99%; the ratio between the width of the empty foil area of ​​the positive electrode sheet and the empty foil area of ​​the negative electrode sheet is the foil width ratio C, with a specific value of 0.1 to 9; the ratio of the sum of the widths of the empty foil areas of the positive electrode sheet and the empty foil areas of the negative electrode sheet to the width of the negative electrode load area is the foil occupancy ratio D, with a specific value of 0.9 ≤ D < 1.

[0014] Furthermore, the gap A is preferably 1.5-6 mm, more preferably 1.5-3 mm.

[0015] Furthermore, the filling ratio B is preferably 87% to 99%, more preferably 88% to 97%.

[0016] Furthermore, the foil width ratio C is preferably 0.3-4, more preferably 1±0.5.

[0017] This invention, through its innovative cylindrical tabless-free structure design, eliminates the space occupied by the original tabs and tab connectors in traditional tab-equipped batteries, effectively improving the battery's energy density. Simultaneously, it eliminates the complex welding process of aluminum and nickel strips in lithium-ion battery manufacturing, shortening the production cycle and reducing the defect rate. Based on the high specific surface area of ​​cylindrical cells and their ability to limit expansion during temperature increases, the structure and dimensions of the cell and casing are optimized, effectively solving the safety problems of lithium-ion batteries that may arise from omitting the tabs, such as poor contact and reduced temperature resistance, ensuring efficient current and heat conduction at high energy densities. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the general structure of a traditional battery with tabs;

[0019] Figure 2 This is a schematic diagram of the positive electrode structure of the present invention;

[0020] Figure 3 This is a schematic diagram of the negative electrode structure of the present invention;

[0021] Figure 4 This is a surface view of the battery cell of the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of the battery cell after winding according to the present invention;

[0023] Figure 6 This is a schematic diagram of the outer casing of the present invention;

[0024] Figure 7 This is a schematic diagram of the structure of the cap of the present invention;

[0025] Figure 8 This is a schematic diagram of the internal structure of the battery of the present invention.

[0026] The above figures include the following reference numerals:

[0027] 1-1 Positive load area, 1-2 Positive foil empty area, 2-1 Negative load area, 2-2 Negative foil empty area, 3-Cell, 3-3 Electrolyte resistant tape, 3-4 Gap area, 3-7 Positive tab, 3-8 Negative tab, 4-Outer shell, 4-1 First metal shell area, 4-2 Second metal shell area, 4-3 Insulation connection area, 5-Cap, 5-1 Cap venting area, 5-2 Cap reinforcement area, 5-3 Cap sealing area, 5-5 Tab connector, 6-1 Space between cell and cap. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more comprehensive description will be provided below, along with preferred embodiments. However, it should be understood that these embodiments are merely for more detailed explanation and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of protection of the invention.

[0029] The typical structural design of a traditional battery with tabs is as follows: Figure 1 As shown, the battery cell 3 is placed inside the casing 4, with a cap 5 at the top. The top of the battery cell 3 has a positive electrode tab 3-7 and a negative electrode tab 3-8 leading out. A tab connector 5-5 needs to be designed on the cap 5 to connect to the positive electrode tab 3-7 and / or the negative electrode tab 3-8. The presence of the two tabs and the tab connector 5-5 significantly occupies the space 6-1 between the battery cell 3 and the cap 5 inside the casing 4, resulting in wasted space and a reduction in battery energy density.

[0030] This invention proposes a cylindrical tabless lithium-ion battery, comprising a casing 4, a cylindrical cell 3 formed by winding positive and negative electrodes separated by a separator within the casing 4, and a cap 5 on the top of the casing 4; wherein the ends of the positive and negative electrodes are designed as narrower empty foil areas, optionally, the ends of the positive and negative electrodes are designed as stepped empty foil areas with narrower widths; after the empty foil areas of the positive and negative electrodes are wound, gap areas 3-4 with spacing are formed on the surface of the cell, and the gaps... The two sides of region 3-4 respectively form positive electrode empty foil region 1-2 and negative electrode empty foil region 2-2; the outer shell 4 of the present invention has shell regions made of different materials, including a first metal shell region 4-1, an insulating connection region 4-3, and a second metal shell region 4-2 arranged in sequence. The positive electrode empty foil region 1-2 and the negative electrode empty foil region 2-2 on the battery cell 3 all fall into the first metal shell region 4-1 and the second metal shell region 4-2 respectively, and the insulating connection region 4-3 on the outer shell 4 falls into the gap region 3-4 on the battery cell 3.

[0031] like Figure 2 As shown, the positive electrode used in the lithium-ion battery of this invention includes a positive electrode loading region 1-1 and a positive electrode empty foil region 1-2. The metal foil of the positive electrode loading region 1-1 is coated with a positive electrode active material. The positive electrode empty foil region 1-2 is the portion of the metal foil without a positive electrode active material coating, such as aluminum foil. The positive electrode empty foil region 1-2 has a smaller width than the positive electrode loading region 1-1. Similarly, as... Figure 3 As shown, the negative electrode used in the lithium-ion battery of the present invention includes a negative electrode loading region 2-1 and a negative electrode empty foil region 2-2. The metal foil of the negative electrode loading region 2-1 is coated with a negative electrode active material, and the negative electrode empty foil region 2-2 is the metal foil portion that is not coated with a negative electrode active material, such as copper foil. The negative electrode empty foil region 2-2 has a smaller width than the negative electrode loading region 2-1.

[0032] The structure of cell 3, formed by winding the positive electrode, separator, and negative electrode, is as follows: Figure 4 , Figure 5 As shown, a positive electrode empty foil area 1-2, a gap area 3-4, and a negative electrode empty foil area 2-2 are sequentially formed on the surface of the cell 3. Among them, 3-3 is an electrolyte-resistant tape to prevent the metal foils of the positive electrode empty foil area 1-2 and the negative electrode empty foil area 2-2 from detaching and loosening; the gap area 3-4 is the gap area between the empty foil areas of the positive and negative electrodes after they are wound, which can prevent the positive and negative electrodes from directly contacting each other and causing a short circuit.

[0033] The casing 4 of the lithium-ion battery of the present invention is as follows Figure 6 As shown, the first metal shell area 4-1, the insulation connection area 4-3, and the second metal shell area 4-2 are arranged in sequence with different materials, which correspond to the positive electrode empty foil area 1-2, the gap area 3-4, and the negative electrode empty foil area 2-2 of the cell 3 in sequence, so that the connection of the positive and negative electrodes of the battery can be transmitted to the outer shell 4 through the empty foil area, and then led out through the outer shell 4, thereby replacing the connection function of the tab.

[0034] like Figure 8 As shown, this connection method not only reduces the number of tabs on the battery cell 3, but also simplifies the design of the tab connector 5-5 on the cap 5, thereby reducing the height of this space 6-1 and increasing the energy density of the battery. The height of the first metal casing area 4-1 is greater than the height of the positive electrode empty foil area 1-2, and the height of the second metal casing area 4-2 is greater than the height of the negative electrode empty foil area 2-2. When the battery cell 3 is placed inside the casing 4, the positive electrode empty foil area 1-2 and the negative electrode empty foil area 2-2 all fall within the range of the first metal casing area 4-1 and the second metal casing area 4-2. The insulating connection area 4-3 is the connection area between the first metal casing area 4-1 and the second metal casing area 4-2. Its material is required to be resistant to electrolyte corrosion and have sealing properties, preferably made of materials such as PP, ABS, or PBT. The height of the insulating connection area 4-3 is greater than the height of the gap area 3-4, therefore the insulating connection area 4-3 on the casing 4 falls within the gap area 3-4 on the battery cell 3.

[0035] To fulfill its receiving function, the outer shell 4 can be made of suitable metal materials for the first metal shell area 4-1 and the second metal shell area 4-2. Considering the hardness and conductivity requirements of the shell, the first metal shell area 4-1 can be made of aluminum (aluminum shell), and the second metal shell area 4-2 can be made of steel (steel shell). Those skilled in the art will understand that the layered structure of the outer shell 4 can be designed as a top-bottom layer connecting different electrodes, or it can be designed without creative effort as a front-back or left-right layered structure to connect different electrodes.

[0036] The cap 5 of the present invention has the following structure: Figure 7As shown, the cap 5 can be divided into three regions from the center to the edge: the cap venting region 5-1, the cap reinforcement region 5-2, and the cap sealing region 5-3. In the manufacturing of lithium-ion batteries, the casing 4 and the cap 5 can be sealed by external force.

[0037] To prevent leakage of the positive and negative electrodes, the bottom of the battery cell 3 needs to be insulated and protected. This includes wrapping the bottom of the battery cell 3 with electrolyte-resistant and insulating tape, insulating and corrosion-resistant treatment of the inner bottom surface of the outer casing 4, and providing insulation protection between the battery cell 3 and the cap 5, preferably with an insulating gasket.

[0038] To further verify the optimization and reliability of battery performance after removing the tabs in the structure of this invention, a series of specific experiments are used as examples to illustrate this.

[0039] The battery used in the experiment consists of a casing 4, a battery cell 3, and a cap 5. The battery cell 3 is composed of positive and negative electrode sheets separated by a separator and then wound together. The positive electrode load region 1-1 includes one or more of lithium cobalt oxide, lithium manganese oxide, ternary lithium, lithium iron phosphate, and lithium-rich manganese oxide. The battery contains one or more of the following: S, SP, GF-2, graphene, and PVDF. The positive electrode uses aluminum foil, and the empty foil area 1-2 of the positive electrode is an empty aluminum foil area. The negative electrode load area 2-1 includes one or more of graphite, hard carbon, and SiO, one or more of CNtS, SP, GF-2, and graphene, one or more of SBR and pAA, and CMC. The negative electrode uses copper foil, and the empty foil area 2-2 of the negative electrode is an empty copper foil area. The separator in the experimental scheme includes one of PP separator and PE separator. The positive electrode, separator, and negative electrode are wound and then processed into a battery cell 3 through electrolyte injection, formation, and sealing processes. When injecting the electrolyte, the battery must be placed under conditions where the dew point is below -55°C, and the formation process must be carried out under conditions where the dew point is below -10°C.

[0040] like Figure 8As shown, after the battery cell 3 is placed in the casing 4, the height of the space 6-1 between the battery cell 3 and the cap 5 is defined as gap A (in mm); the ratio between the diameter of the battery cell 3 and the inner diameter of the casing 4 is the fill ratio B (in %); the width ratio between the empty foil area 1-2 of the positive electrode and the empty foil area 2-2 of the negative electrode is the foil width ratio C; the ratio of the sum of the widths of the empty foil areas 1-2 of the positive electrode and the empty foil area 2-2 of the negative electrode to the width of the negative electrode load area 2-1 is the foil coverage ratio D. To increase the contact between the empty foil areas of the positive and negative electrodes and the casing 4, a higher foil coverage ratio D is generally desired. Therefore, the foil coverage ratio D can be designed to be no less than 0.9. At the same time, it should be noted that in battery design, the width of the negative electrode load area 2-1 is generally set to be slightly larger than the width of the positive electrode load area 1-2 to avoid lithium deficiency and ensure that all lithium is embedded in the negative electrode. Therefore, it is better to define the negative electrode load area 2-1 as the denominator in the calculation formula of the foil coverage ratio D. In the experimental design for this batch of battery models, the foil ratio D is (21.5mm + 21.5mm) / 46mm = 0.935.

[0041] As an example, the battery cell 3 of this invention is manufactured using battery type 18650 material. The standard battery height is 65mm and the diameter is 18mm. The battery parameter designs for different examples are listed in Table 1, and the results of testing the batteries obtained in the experiment are also listed in Table 1.

[0042] The capacity test method reads the discharge capacity of 0.2C. The specific test conditions are as follows: (1) let stand for 5 minutes; (2) 0.5C CC to 4.35V, CV to 0.05C; (3) let stand for 5 minutes; (4) 0.2C DC to 3.0V; (5) end.

[0043] The short circuit test method and specific test conditions are as follows: (1) Test voltage 220V, test internal resistance 10 megohms; (2) If the internal resistance is less than 10 megohms, it is determined to be a short circuit.

[0044] The 130℃ hot box test method and specific test conditions are as follows: (1) Place the battery in the forced-air oven and heat the battery at a rate of 5℃ / min. When the temperature of the oven reaches the range of 130℃±2℃, start timing and stop heating when the battery has been placed inside for 60 minutes; (2) When the oven temperature drops below 50℃, open the oven to check the condition of the battery; (3) As long as the battery does not catch fire or explode, the battery is considered to have passed the test.

[0045] Table 1

[0046]

[0047]

[0048] The above experiments can verify that the performance of the lithium-ion battery of the present invention, such as capacity, safety and temperature resistance, after removing the tabs, will be affected by the degree of filling between the cell 3 and the outer casing 4 and the size of the gap between the cell 3 and the cap 5.

[0049] Analysis of Examples 1-6 and 7-18 confirms that for batteries that normally use metal strips as tabs, the gap between cell 3 and cap 5 must be set to more than 5mm to reduce the short-circuit rate of cell 3 to below 1.5%. However, using the battery of the present invention, the gap between cell 3 and cap 5 can be compressed to 1mm while keeping the battery manufacturing short-circuit rate below 1.5%, which can increase the energy density of the battery by 6.67%.

[0050] Furthermore, Examples 7-18 verified the impact of gap A variation on battery capacity and thermal safety. The battery capacity of the present invention decreases as the value of A increases; as the value of A decreases, the battery thermal safety decreases somewhat, but overall it is better than batteries designed using traditional methods. Specifically, when the value of A is controlled within 1.5-6 mm, the battery safety is basically controlled within the ideal range, and the battery's thermal safety performance is stable. Therefore, the gap A range can be designed to be 0.5-6 mm, preferably 1.5-6 mm. Furthermore, considering the impact of gap A variation on battery capacity, in general, the battery capacity decreases as the gap A value increases. However, compared to the highest battery capacity level of 1860 mAh in the prior art (such as Example 3), the battery capacity performance is better when the value of A is controlled within the range of 1.5-3 mm. Therefore, the gap A range is more preferably 1.5-3 mm.

[0051] Examples 19-23, 10, and 25-33 verified the impact of changes in the fill ratio B on the capacity of lithium-ion batteries and the average temperature rise during IC charging. Specifically, when the fill ratio B is less than 87%, the battery capacity deviates significantly from the highest level of existing battery capacity (e.g., Example 3), and the battery temperature rise is also abnormal. This may be related to the high contact resistance of the empty foil areas of the positive and negative electrodes and the casing 4. Therefore, the fill ratio B can be designed to be 85%-99%, preferably 87%-99%.

[0052] The fill ratio B of the cylindrical tabless lithium-ion battery of the present invention can be designed to be a relatively high value, possibly because (1) the cylindrical cell 3 has a large specific surface area and good heat dissipation; (2) the cylindrical cell 3 disperses the expansion effect along the radius of the cell 3 at higher temperatures, thereby limiting the overall expansion. Therefore, when the fill ratio B reaches 99%, the cylindrical tabless battery can still have better battery capacity and temperature rise performance. Further analysis of the effect of fill ratio B on battery capacity confirms that the battery capacity is better when the fill ratio is 88%-97%, the battery capacity is higher than 1880mAh and the battery temperature rise performance is stable. Therefore, the fill ratio B is better at 88%-97%.

[0053] Examples 34-37, 10, and 39-42 demonstrate that the foil width ratio C of the empty foil regions 1-2 of the positive electrode and 2-2 of the negative electrode in the present invention has a certain impact on the temperature rise and thermal safety performance of lithium-ion batteries. Specifically, when the C value is close to 1, the battery exhibits the best temperature rise and thermal safety performance; when the C value is 0.1 or 9, the failure rate has already reached over 10%. To ensure better battery safety performance, it is generally recommended to control the failure rate in the hot box test to within 10%. Therefore, the foil width ratio C can be designed to be in the range of 0.1-9, preferably 0.3-4, and more preferably 1 ± 0.5.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cylindrical tabless lithium-ion battery, comprising a casing (4), a cylindrical cell (3) placed inside the casing (4) and composed of a positive electrode, a separator, and a negative electrode wound together, and a cap (5) disposed on the top of the casing (4); wherein the ends of the positive electrode and the negative electrode are respectively designed as empty foil areas with reduced width, and the empty foil areas of the positive electrode and the negative electrode are wound together to form a gap area (3-4) with spacing on the surface of the cell (3), and a positive electrode empty foil area (1-2) and a negative electrode are respectively formed on both sides of the gap area (3-4). Empty foil area (2-2); The outer shell (4) has a shell area made of different materials, including a first metal shell area (4-1), an insulating connection area (4-3), and a second metal shell area (4-2) arranged in sequence. The empty foil area (1-2) of the positive electrode plate and the empty foil area (2-2) of the negative electrode plate on the battery cell (3) all fall into the first metal shell area (4-1) and the second metal shell area (4-2) respectively. The insulating connection area (4-3) on the outer shell 4 falls into the gap area (3-4) on the battery cell (3). The gap A between the top of the cell (3) and the bottom of the cap (5) inside the outer shell (4) is 0.5~6mm; the ratio of the diameter of the cell (3) to the inner diameter of the outer shell (4) is the filling ratio B, with a specific value of 85%~99%; the ratio of the width of the empty foil area (1-2) of the positive electrode sheet to the empty foil area (2-2) of the negative electrode sheet is the foil width ratio C, with a specific value of 0.1~9; the ratio of the sum of the widths of the empty foil area (1-2) of the positive electrode sheet to the width of the empty foil area (2-2) of the negative electrode sheet to the width of the negative electrode load area (2-1) is the foil occupancy ratio D, with a specific value of 0.9≤D<1.

2. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The first metal shell area (4-1) of the outer shell (4) is an aluminum shell, and the second metal shell area (4-2) is a steel shell.

3. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The cap (5) is a metal cap, and from the center to the edge it is provided with a cap exhaust area (5-1), a cap reinforcement area (5-2) and a cap sealing area (5-3).

4. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The bottom of the battery cell (3) has an insulating protective layer.

5. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The inner bottom surface of the outer shell (4) is provided with an insulating protective layer.

6. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The battery cell (3) and the cap (5) are provided with insulation protection.

7. The cylindrical tabless lithium-ion battery according to claim 6, characterized in that, An insulating gasket is provided between the battery cell (3) and the cap (5).

8. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The gap A is 1.5-6mm.

9. The cylindrical tabless lithium-ion battery according to claim 8, characterized in that, The gap A is 1.5-3mm.

10. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The filling ratio B is 87%~99%.

11. The cylindrical tabless lithium-ion battery according to claim 10, characterized in that, The filling ratio B is 88%-97%.

12. The cylindrical tabless lithium-ion battery according to claim 1, characterized in that, The foil width ratio C is 0.3-4.

13. The cylindrical tabless lithium-ion battery according to claim 12, characterized in that, The foil width ratio C is 1 ± 0.5.

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