Cathode collector plate, cylindrical battery and electric vehicle

Abstract

The utility model provides a negative collector plate, a cylindrical battery and an electric carrier, and relates to the field of batteries. The negative collector plate is used for the cylindrical battery and comprises a first welding part, a second welding part and a third welding part, the at least one connecting strip is configured to conduct current from the first welding part to a second welding part, and the second welding part is arranged on a bottom cover of the cylindrical battery; wherein each connecting strip comprises a first end and a second end, the first end of each connecting strip is electrically connected with the first welding part, and the second end of each connecting strip is electrically connected with the second welding part; a circuit protection element is arranged between the first end of each connecting strip and the second end of the corresponding connecting strip, and the circuit protection element is configured to disconnect the corresponding connecting strip when the current passing through the corresponding connecting strip is greater than a protection threshold value. The fuse wire is additionally arranged on the negative collector plate, so that no extra space is occupied, the energy density of the battery is not influenced, and the working efficiency of the cylindrical battery is not influenced.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a negative current collector disc, a cylindrical battery, and an electric vehicle. Background Art

[0002] In recent years, cylindrical batteries have attracted much attention due to their high energy density and good rate performance. However, the internal available space of cylindrical batteries is small, which is not convenient for setting large protection devices such as fuses; and cylindrical batteries have the characteristics of small impedance and high energy density, resulting in a large short-circuit current and poor external short-circuit safety, making it difficult to pass safety tests.

[0003] Based on the above facts, in the prior art, the overall safety of cylindrical batteries is improved by reducing the height of the battery core to increase fuses or adding fuses in the positive electrode column. However, these methods will cause a decrease in the energy density of the battery or fire at high temperatures, and cannot effectively balance the working efficiency and safety of the battery. Utility Model Content

[0004] In view of this, the present application discloses a negative current collector disc, a cylindrical battery, and an electric vehicle, which balance the working efficiency while improving the safety of the cylindrical battery.

[0005] In a first aspect, the present application discloses a negative current collector disc for a cylindrical battery, including: a first welding portion configured to be welded to the negative electrode tab of the cylindrical battery; at least one connecting strip configured to conduct current from the first welding portion to a second welding portion, the second welding portion being disposed on the bottom cover of the cylindrical battery; wherein each connecting strip includes a first end and a second end, the first end of each connecting strip is electrically connected to the first welding portion, and the second end of each connecting strip is electrically connected to the second welding portion; a circuit protection element is disposed between the first end and the corresponding second end of each connecting strip, and the circuit protection element is configured to disconnect the corresponding connecting strip when the current passing through the corresponding connecting strip is greater than a protection threshold.

[0006] Optionally, the circuit protection element is a fuse.

[0007] Optionally, when the current passing through the connecting strip is greater than the protection threshold, the fuse melts to disconnect the connection between the first end and the second end of the corresponding connecting strip.

[0008] Optionally, when the cylindrical battery is used for fast charging, the protection threshold is set to the product of the fast charging rate and the battery capacity of the cylindrical battery divided by the number of connecting strips.

[0009] Optionally, the negative current collector disc is circular and the first welding portion is disposed in the edge region of the negative current collector disc.

[0010] Optionally, the cylindrical battery is a lithium battery.

[0011] In a second aspect, the present application also discloses a cylindrical battery, including the negative current collector plate disclosed in the first aspect above.

[0012] In a third aspect, the present application also discloses an electric vehicle, including the cylindrical battery disclosed in the second aspect above, and the cylindrical battery is used to supply power to the electric vehicle.

[0013] A negative current collector plate, a cylindrical battery, and an electric vehicle disclosed in the present application have at least the following beneficial effects:

[0014] (1) By adding a circuit protection element (fuse) on the negative current collector plate, it does not occupy additional space of the battery, has no impact on the energy density of the battery, that is, it does not affect the working efficiency of the cylindrical battery.

[0015] (2) When an external short circuit occurs in the battery, the fuse of the connecting bar is blown, and the ear welding part (corresponding to the first welding part) and the bottom cover welding part (corresponding to the second welding part) are disconnected, and the battery is powered off; in this way, the safety of the cylindrical battery can be improved, and the battery can be prevented from heating up violently, resulting in the battery catching fire and failing.

[0016] (3) By selecting different fuses (or changing properties such as the material / volume of the fuse), the protection threshold can be freely set to maintain the high-rate performance of the cylindrical battery, so that the fuse will not be blown in the fast charging mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following briefly introduces the drawings used in the description of the embodiments of the present application:

[0018] Figure 1 It is a schematic structural diagram of a negative current collector plate provided by an embodiment of the present application.

[0019] In the figure: 1 - the first welding part, 2 - the connecting bar, 3 - the second welding part, 4 - the circuit protection element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the specific embodiments of the present application will be described below with reference to the drawings. The drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings, and other embodiments can also be obtained. Adjustments and improvements made without departing from the concept of the present application all fall within the protection scope of the present application.

[0021] To simplify the drawings, only the parts related to the corresponding embodiments are schematically shown in each drawing, and they do not represent the actual structure of the product as a whole. Additionally, to simplify the drawings for easier understanding, in some drawings, only some of the components with the same structure or function are schematically illustrated, and there may actually be more or fewer components with the same structure or function.

[0022] In this application, unless otherwise clearly specified and defined, ordinal numbers, such as "first", "second", etc., are only used to distinguish and describe related objects, and cannot be understood as indicating or implying the relative importance or order between related objects; moreover, they do not represent the quantity of related objects. "A plurality" includes two or more, and other quantifiers are similar. " / " is used to describe the relationship between related objects, indicating an "or" relationship between related objects. "And / or" is used to describe the relationship between related objects, including any combination relationship between related objects. For example, "a and / or b" includes: "a alone", "b alone", or "a and b". "One or more" or "at least one" among multiple objects refers to any one object or any combination of multiple objects. For example, "one or more of a1, a2, a3" or "at least one of a1, a2, a3" includes: "a1 alone", "a2 alone", "a3 alone", "a1 and a2", "a1 and a3", "a2 and a3", or "a1, a2 and a3".

[0023] Cylindrical batteries are characterized by high energy density and good rate performance, and are widely used in many fields. For example, cylindrical batteries can be used to power electric vehicles, which include but are not limited to electric cars, electric bicycles, and electric scooters; cylindrical batteries can be used in the power battery packs of electric vehicles, and the power battery pack is a battery pack composed of thousands of cylindrical battery cells. Another example is that cylindrical batteries can be used to build an energy storage system, which can be a home or commercial energy storage system, storing electricity from solar panels or other renewable energy sources, so that electricity can be provided during peak electricity consumption periods to reduce the grid load.

[0024] In a cylindrical battery, the setting of the current collector is of great significance. For example, it can be used for current collection and conduction. The current collector is respectively connected to the positive and negative electrodes of the battery, collects electrons from the active material, and conducts them to the external circuit. This enables the electrical energy generated inside the battery to be effectively transmitted to the external load. Another example is that it can provide structural support to keep the electrode material in a stable structure during the charge and discharge process of the battery, which helps reduce the probability of peeling or falling off of the electrode material, thereby extending the battery life. Additionally, the current collector helps to evenly distribute the current inside the battery, reduce the non-uniformity of the current density, and thus avoid local overheating or excessive consumption of the electrode material. Moreover, the current collector can also help conduct and disperse the heat generated during the operation of the battery, prevent local overheating, and improve the safety and performance stability of the battery.

[0025] In a cylindrical battery, two types of current collectors can be provided: a positive current collector and a negative current collector. Among them, the material of the positive current collector can be aluminum, which can be used to collect electrons generated by the positive active material, conduct the current to the positive terminal through the connecting bar, and provide support for the positive active material to improve its stability during the charge and discharge process. The material of the negative current collector can be copper. Similar to the positive current collector, the negative current collector can be used to collect electrons generated by the negative active material, conduct the current to the negative terminal (usually located at the bottom or side of the battery) through the connecting bar, and provide support for the negative active material to improve its stability during the charge and discharge process.

[0026] In terms of the overall structure, a cylindrical battery can include the following components: a battery housing, a positive terminal, a positive current collector, a positive active material, a separator, a negative current collector, a negative active material, and a negative terminal. Among them, the battery housing is used to provide mechanical protection and sealing; the positive current collector is used to collect current; the positive current collector is used to generate current; the negative current collector is used to collect current; the negative active material is used to generate current; the positive terminal is located at the top of the battery and is used to conduct the current of the positive current collector to the external circuit; the negative terminal is located at the bottom of the battery and is used to conduct the current of the negative current collector to the external circuit; the separator is located between the positive and negative electrodes and is used to prevent short circuits caused by direct contact of electrons, but allows ions to flow between the positive and negative electrodes.

[0027] For the safety of cylindrical batteries, an external short-circuit test can be used to evaluate the safety performance and reliability of batteries or battery packs under short-circuit conditions. This test simulates the situation where the external circuit of the battery is accidentally short-circuited, and observes the performance of the battery in this situation, including temperature changes, voltage drops, current changes, and whether there are dangerous phenomena such as explosions and fires. In other words, batteries that fail the test will catch fire and burn. When designing existing cylindrical batteries, from the perspective of saving space, the volume of the battery is reduced as much as possible, resulting in a small internal available space for the cylindrical battery, and it is inconvenient to add larger protective components such as fuses. Moreover, due to the characteristics of low impedance and high energy density, cylindrical batteries have large short-circuit currents and poor external short-circuit safety, making it difficult to pass safety tests.

[0028] In order to solve this problem, three solutions are given in the prior art. The first solution is to reduce the height of the battery cell to increase the fuse. By reducing the height of the battery cell, extra space can be freed up to install the fuse. A fuse is a protective device that can automatically cut off the circuit when the current is too large. Although this structural setting can increase safety and reduce the probability of battery overheating or fire, it will lead to a decrease in energy density: because reducing the height of the battery cell will reduce the amount of active materials in the battery, thereby reducing the total energy density of the battery. In addition, installing the fuse in a limited space and making it compatible and reliable with other components will greatly increase the complexity of the design. The second solution is to add a fuse in the positive column. The fuse is a conductor that will melt when the current exceeds a preset value, which can effectively prevent overcurrent. By installing a fuse inside the positive column of the battery, the safety of the battery can be increased to a certain extent, it will not take up a lot of space and the installation of the fuse is relatively simple compared to the fuse. However, such a design may increase internal resistance: If the fuse is not designed properly, it may increase the internal resistance of the battery and affect battery performance; this may cause the positive pole temperature to be too high: Since the outer shell of a cylindrical battery is generally directly connected to the negative pole, excessive temperature of the positive pole will cause the insulation of the positive pole to fail, and the positive pole will ignite when in contact with the outer shell, causing the battery to catch fire. The third solution is to process the welding part of the pole ear of the collector and set a fuse position. However, this solution will cause the strength of the welding part of the pole ear to decrease, making it easy to break, affecting battery performance.

[0029] Based on the defects existing in the above three solutions of the prior art, the present application improves the structure of the negative electrode collector plate in the cylindrical battery, thereby improving the safety of the cylindrical battery while taking into account its working efficiency, so that it can pass the external short-circuit test.

[0030] Next, the following description will be given with reference to the accompanying drawings.

[0031] Please refer to Figure 1, which shows a schematic structural diagram of a negative current collector plate provided by an embodiment of the present application. As Figure 1 shown, the negative current collector plate for a cylindrical battery includes: a first welding portion 1 configured to be welded to the negative electrode tab of the cylindrical battery; at least one connecting bar 2 configured to conduct current from the first welding portion 1 to a second welding portion 3 provided on the bottom cover of the cylindrical battery; wherein each connecting bar 2 includes a first end and a second end, the first end of each connecting bar 2 is electrically connected to the first welding portion 1, and the second end of each connecting bar 2 is electrically connected to the second welding portion 3; a circuit protection element 4 is provided between the first end and the corresponding second end of each connecting bar 2, and the circuit protection element 4 is configured to disconnect the corresponding connecting bar 2 when the current passing through the corresponding connecting bar 2 is greater than the protection threshold. It should be noted that the number of the first welding portion 1 and the connecting bars 2 can vary according to the actual design of the cylindrical battery, Figure 1 which is only a schematic diagram and does not include the actual dimensions or ratios used.

[0032] To solve the problem that the excessive current during the external short-circuit test causes the battery to heat up violently, resulting in the battery catching fire and failing, in this embodiment, a circuit protection element 4 is provided between the two ends of the connecting bar 2, which can disconnect the first welding portion 1 and the second welding portion 3 when the current passing through the connecting bar 2 is greater than the preset protection threshold.

[0033] During normal operation, that is, when there is no excessive current, the negative electrode tab of the cylindrical battery is connected to the connecting bar 2 of the negative current collector plate through the first welding portion 1, and then connected to the second welding portion 3 on the bottom cover of the cylindrical battery through the connecting bar 2, and flows to the external circuit. At this time, the current passing through the circuit protection element 4 does not exceed the protection threshold, and the connecting bar 2 will not be disconnected.

[0034] When performing an external short-circuit test, the external short circuit will cause the current of the battery to increase sharply, and the excessive current will flow through the connecting bar 2 of the negative current collector plate. The circuit protection element 4 on the connecting bar 2 can be designed as a conductor that melts at a specific current. When the current is excessive (i.e., exceeds the preset protection threshold), the circuit protection element 4 will disconnect the connection between the first end and the second end of the connecting bar 2, cutting off the connecting bar 2, which also makes the first welding portion 1 and the second welding portion 3 no longer connected, and the current no longer flows to the external circuit. In this way, the battery power-off operation can be realized when the current is excessive, thereby avoiding the risks of violent heating and fire caused by excessive current.

[0035] In addition, compared with installing the circuit protection element on the positive collector of the cylindrical battery, operating on the negative collector has the following benefits. First, because the negative collector can be grounded during design, the potential is lower. Setting the circuit protection element on the negative collector has a smaller potential difference, which may reduce the risk of arcs and sparks, thereby improving safety. Correspondingly, the potential of the positive collector is higher. Setting the circuit protection element on the positive collector has a larger potential difference, which may increase the risk of arcs and sparks, and require higher insulation and safety measures, resulting in higher costs. From the perspective of circuit design and layout, it is easier to set the circuit protection element on the negative collector, which is easy to manufacture due to the suppression of the voltage reference point. From the perspective of maintenance and replacement, the safety risk is lower because the point of the negative collector is lower; while the potential of the positive collector is higher, there may be risks of electric shock and short circuit.

[0036] In some embodiments, in order to simplify manufacturing, the circuit protection element 4 can be set at any position of the connecting bar 2, and the circuit protection element 4 only needs to completely disconnect the connecting bar 2 when the current passing through the corresponding connecting bar 2 exceeds the protection threshold.

[0037] In the above embodiments, by adding a circuit protection element to the negative electrode current collecting disk, no additional space of the battery is occupied and there is no effect on the energy density of the battery, that is, it will not affect the working efficiency of the cylindrical battery. At the same time, the safety of the cylindrical battery is increased, so that it can pass the external short-circuit test, effectively taking into account both the working efficiency and safety of the battery.

[0038] In some embodiments, please continue to refer to Figure 1 The circuit protection element 4 is a fuse. When the current passing through the connecting bar 2 is greater than the protection threshold, the fuse is blown to disconnect the first end and the second end of the corresponding connecting bar 2.

[0039] As one of the optional circuit protection elements, the fuse itself occupies a small space and can be melted when the current is too large. It has a higher current capacity and can be designed to withstand a higher current load for a long time to avoid fire or other damage caused by short circuit or overload. Although the fuse will reduce the strength of the connecting strip to a certain extent, the connecting strips are in parallel relationship, and as long as not all of them are broken, it will not affect the normal conduction. In some embodiments, a fuse can also be used instead of a fuse, which can also take into account the working efficiency and safety of the battery, but the fuse performs better in actual working scenarios.

[0040] In the external short circuit test of the battery, very high currents are involved, exceeding the normal operating current of the battery. Fuses are designed to handle higher current loads and provide protection under long-term high current conditions. Moreover, the short circuit test may continue high current for a period of time to test the battery's tolerance. The ability of the fuse to withstand high current for a long time without immediately blowing makes it more suitable for such a test environment. In addition, the fuse can be designed to not produce splashes or cracks when it blows under high current conditions, providing higher safety. This is particularly important for high current short circuit tests to prevent potential harm to test equipment and operators. It can be seen that using fuses as circuit protection elements can increase the probability of cylindrical batteries passing external short circuit tests.

[0041] When a fuse is used as a circuit protection element, the protection threshold of a cylindrical battery can be determined based on the material properties and design parameters of the fuse itself. Since the fuse protects the battery in the form of melting, the melting point of its material determines when the material will melt at high temperatures. Commonly used fuse materials such as tin, lead alloy, copper, silver, etc., all have different melting points. For example, the melting point of tin is about 232°C, and the melting point of lead is about 327°C. Moreover, materials with high conductivity make it easier for current to pass, but they also generate less heat. Therefore, the resistivity of the material also affects the protection threshold. In addition to the fuse material, changes in its geometric dimensions can also change the protection threshold accordingly. For example, the protection threshold can be freely set by changing the cross-sectional area and length of the fuse: the larger the cross-sectional area of ​​the fuse, the larger the current it can carry. A thinner fuse will generate more heat at the same current and will be easier to melt; the length of the fuse affects the resistance and heat dissipation. A shorter fuse has poor heat dissipation and a faster temperature rise, so it will be easier to melt. In addition, the fuse can be further customized by setting the rated current and rated voltage of the fuse so that it can reach the protection threshold required in actual work.

[0042] In some embodiments, when the cylindrical battery is used for fast charging, the protection threshold is set to the product of the fast charging rate and the battery capacity of the cylindrical battery divided by the number of connecting bars.

[0043] Cylindrical batteries can be used for fast charging. To maintain their high rate performance, the protection threshold can be designed as the product of the fast charge rate and the battery capacity of the cylindrical battery divided by the number of connecting strips, so that the fuse will not be triggered during fast charging. The method for setting the protection threshold can refer to the above embodiment and will not be repeated here.

[0044] In some embodiments, the negative electrode current collector is circular and the first welding portion is disposed at the edge region of the negative electrode current collector. Since the battery itself is a cylindrical battery, the negative electrode current collector is correspondingly designed to be circular so as to better match the cylindrical battery. Providing the first welding portion at the edge region of the negative electrode current collector can help to evenly distribute the current and reduce the current density in the central region of the current collector, thereby reducing local overheating and resistance loss. The pole ear is located at the edge position, which can shorten the path of the current from the active material through the current collector to the pole ear, reduce the overall resistance, and improve the battery efficiency.

[0045] In some embodiments, the cylindrical battery is a lithium battery. Exemplarily, the cylindrical battery can be a 4680 battery or a 4695 battery.

[0046] In some embodiments, the negative electrode collector disk disclosed in this application can be used on a 4680 large cylindrical battery configured as a 23Ah ternary battery, 3 connecting strips are set, and the trigger current of the fuse is set to 23A, that is, the above protection threshold is 23A. Compared with the cylindrical battery in the prior art, which has no fuse designed in the collector disk, a negative electrode collector disk with a fuse is used in this technical solution. The battery is subjected to an external short-circuit test in accordance with the national standard GB-T38031-2020. The prior art failed the test, the battery spray valve caught fire, burned violently, and the temperature reached 600°C. However, the battery of this solution smoked when the valve was opened, but no fire occurred, and the battery passed the test. After disassembly, there was no abnormality in the battery cell, and the negative electrode collector disk connecting strip was blown.

[0047] In some embodiments, the negative electrode collector plate disclosed in this application can be used on a 4695 fast-charge large cylindrical battery configured as a 30Ah ternary battery, 6 connecting strips are set, and the trigger current of the fuse is set to 200A, that is, the above protection threshold is 200A. At the same time, Teflon tape, that is, high temperature resistant tape, is attached to the lower side of the first welding portion. Compared with the prior art in which a fuse is set in the positive pole column, a negative electrode collector plate with a fuse is used in this technical solution. According to GB38301 Safety Requirements for Power Batteries for Electric Vehicles (Draft for Comments) (Replacing GB 38031-2020), the battery is subjected to a safety test after a fast charge cycle. The prior art battery fast-charged for 300 cycles without abnormalities, and an external short-circuit test after the cycle was performed. The positive pole of the battery leaked and ignited, and exploded after a short jet of gas, and the battery burned and failed to pass the test. However, this solution has no abnormalities in the battery fast-charge cycle for 300 cycles, and an external short-circuit test after the cycle was performed. The battery did not open the valve, did not smoke, did not catch fire, and passed the test. There was no abnormality when disassembling the battery cell, and the negative collector plate connecting strip was blown.

[0048] Based on similar technical concepts, the present application also discloses a cylindrical battery, including the negative electrode current collector of the above embodiment. The structure of the cylindrical battery can be referred to above, and will not be described here.

[0049] Based on similar technical concepts, the present application also discloses an electric vehicle, including the cylindrical battery of the above embodiment, and the cylindrical battery is used to power the electric vehicle. For the contents related to the electric vehicle and the cylindrical battery for powering the electric vehicle, please refer to the above, and no further description will be given here.

[0050] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. In addition, the above embodiments can be freely combined as needed.

Claims

1. A negative electrode current collector, characterized in that: For cylindrical batteries, including: A first welding portion is configured to be welded to the negative electrode tab of the cylindrical battery; at least one connecting bar configured to conduct current from the first welding portion to a second welding portion, the second welding portion being disposed on the bottom cover of the cylindrical battery; Wherein, each of the connecting strips comprises a first end and a second end, the first end of each of the connecting strips is electrically connected to the first welding portion, and the second end of each of the connecting strips is electrically connected to the second welding portion; A circuit protection element is provided between the first end of each of the connecting bars and the second end of the corresponding connecting bar, and the circuit protection element is configured to disconnect the corresponding connecting bar when the current passing through the corresponding connecting bar is greater than a protection threshold.

2. The negative electrode current collector according to claim 1, characterized in that: The circuit protection element is a fuse.

3. The negative electrode current collecting disk according to claim 2, characterized in that: When the current passing through the connecting bar is greater than the protection threshold, the fuse is blown to disconnect the first end and the second end of the corresponding connecting bar.

4. The negative electrode current collector according to claim 1, characterized in that: When the cylindrical battery is used for fast charging, the protection threshold is set to the product of the fast charging rate and the battery capacity of the cylindrical battery divided by the number of the connecting bars.

5. The negative electrode current collecting disk according to claim 1, characterized in that: The negative electrode current collecting plate is circular and the first welding portion is disposed at an edge region of the negative electrode current collecting plate.

6. The negative electrode current collecting disk according to claim 1, characterized in that: The cylindrical battery is a lithium battery.

7. A cylindrical battery, characterized in that: It comprises the negative electrode current collecting disk as described in any one of claims 1 to 6.

8. An electric vehicle, characterized in that: It comprises a cylindrical battery as described in claim 7, wherein the cylindrical battery is used to supply power to the electric vehicle.

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