Annealing method of current collector, current collector, positive pole piece and battery

Abstract

The embodiment of the invention discloses an annealing method of a current collector, the current collector, a positive pole piece and a battery. The annealing method of the current collector comprises the following steps: carrying out annealing treatment on the current collector; wherein the annealing treatment comprises a heating stage, a heat preservation stage and a cooling stage, the temperature of the heat preservation stage is 150-350 DEG C, the heat preservation time is 1-3 hours, the material of the current collector is metallic aluminum, and the surface density of the annealed current collector is 200-260 g / m < 2 >. According to the invention, by controlling the surface density of the current collector made of metal aluminum and carrying out annealing treatment at the corresponding annealing temperature, grains of the current collector can be recrystallized, and meanwhile, the size of the formed grains is controlled, so that the mechanical property of the aluminum current collector is improved, the stress released when the aluminum current collector is impacted by a heavy object is reduced, and the service life of the current collector is prolonged. And the impact resistance of the battery using the current collector is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an annealing method of a current collector, a current collector, a positive electrode sheet and a battery. BACKGROUND

[0002] Lithium-manganese batteries are particularly suitable for use in scenarios requiring stable power supply, such as medical devices and safety alarm systems, due to their high working voltage, large energy density, wide working temperature range, long service life and other advantages. In order to ensure the safety of lithium-manganese batteries, it is necessary to perform UL1642 safety performance testing on lithium-manganese batteries, which includes heavy impact testing. The testing method of heavy impact testing is as follows: the test sample battery is placed on a flat surface, a rigid impact rod with a diameter of 15.8±0.1 mm is vertically placed above the central axis of the battery (the rod axis is perpendicular to the longitudinal axis of the battery), and a weight of 9.10±0.46 Kg is dropped from a height of 610±25 mm onto the test sample; the standard is that within 6 hours after the test, the battery must meet the following requirements: no fire and no explosion, except for the performance of battery structural components and the composition of electrolyte, the reason that may cause the heavy impact testing to fail is that the impact causes the positive electrode manganese dioxide coating to peel off from the positive electrode current collector, so that the active material particles pierce the separator and cause internal short circuit of the battery. SUMMARY

[0003] Embodiments of the present application provide an annealing method of a current collector, a current collector, a positive electrode sheet and a battery, which can improve the anti-impact capability of the battery.

[0004] In a first aspect, embodiments of the present application provide an annealing method of a current collector, comprising: annealing the current collector; wherein the annealing process comprises a heating stage, a holding stage and a cooling stage, the temperature of the holding stage is 150℃-350℃, the holding time is 1h-3h, the material of the current collector is aluminum, and the surface density of the current collector after annealing is 200g / m 2 -260g / m 2 .

[0005] In an embodiment, the heating rate of the heating stage is 5°C / min-15°C / min; and / or the cooling mode of the cooling stage is furnace cooling to room temperature.

[0006] In an embodiment, the annealing process is performed in a mixed gas atmosphere composed of inert gas and reducing gas.

[0007] In an embodiment, the volume content of the reducing gas in the mixed gas is less than or equal to 5%.

[0008] In an embodiment, the thickness of the current collector after annealing is 0.25mm-0.35mm; and / or The current collector is net-shaped, and the current collector has a mesh, and the width of the mesh after annealing is 0.06mm-0.15mm.

[0009] In a second aspect, embodiments of the present application provide a current collector prepared by the above-mentioned annealing method of the current collector.

[0010] In a third aspect, embodiments of the present application provide a positive electrode tab, comprising: The above-mentioned current collector; A positive active material layer disposed on the surface of the current collector.

[0011] In an embodiment, the thickness of the positive active material layer is 0.4mm-0.45mm.

[0012] In an embodiment, the compaction density of the positive electrode tab is 2.5g / cm3-2.77g / cm3.

[0013] In a fourth aspect, embodiments of the present application provide a battery comprising the above-mentioned current collector or the above-mentioned positive electrode tab.

[0014] In embodiments of the present application, by controlling the area density of the current collector made of aluminum and annealing it at a corresponding annealing temperature, the grains of the current collector can be recrystallized, and the size of the formed grains can be controlled, thereby improving the mechanical properties of the aluminum current collector, reducing the stress released when the aluminum current collector is impacted by a heavy object, and further improving the impact resistance of the battery using the current collector. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is a structural schematic diagram of the current collector provided by the embodiments of the present application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0018] The embodiments of the present application provide an annealing method of a current collector. The following will be described in detail respectively. It should be noted that the sequence of the following embodiment description is not regarded as the limitation of the preferred sequence of the embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish an order. Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range of forms is only for the convenience and brevity, and should not be understood as a hard limitation of the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which is applicable to any range. In addition, whenever a numerical range is indicated in the present text, it means that any cited number (fraction or integer) in the indicated range is included.

[0019] In a first aspect, the embodiments of the present application provide an annealing method of a current collector, comprising: annealing the current collector; The annealing process includes a temperature rising stage, a temperature holding stage and a cooling stage, the temperature of the temperature holding stage is 150-350℃, for example, it can be 150℃, 180℃, 200℃, 220℃, 250℃, 270℃, 300℃, 320℃, 350℃, etc., the temperature holding time is 1-3h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, etc., the material of the current collector is metal aluminum, and the surface density of the current collector after annealing is 200-260g / m 2 -260g / m 2 , for example, it can be 200g / m 2 , 210g / m 2 , 220g / m 2 , 230g / m 2 , 240g / m 2 , 250g / m 2 , 260g / m 2 , etc.

[0020] In the present application, by controlling the surface density of the current collector made of metal aluminum and annealing it at a corresponding annealing temperature, the grains of the current collector can be recrystallized, and the size of the grains formed can be controlled, thereby improving the mechanical properties of the aluminum current collector, reducing the stress released when the aluminum current collector is impacted by a heavy object, and thereby improving the impact resistance of the battery when the aluminum current collector is used in the battery. At the same time, the mechanical strength of the current collector is improved, the surface density of the current collector can be reduced, and the energy density of the battery is improved. Annealing in three stages of heating, holding, and cooling can promote recrystallization of the current collector and control the grain size.

[0021] It can be understood that when the current collector made of metal aluminum is annealed, too high a temperature will cause the grains formed to be coarse and the strength to decrease; and too low a temperature may not be able to fully recrystallize, affecting the performance of the current collector. Too long a holding time will cause the grains of the aluminum current collector to increase, local stress to be generated, tensile strength to decrease, and elongation at break to decrease.

[0022] In an embodiment, the temperature of the holding stage is 245-255°C, for example, it can be 245°C, 246°C, 247°C, 248°C, 249°C, 250°C, 251°C, 252°C, 253°C, 254°C, 255°C, etc. In this way, the size of the grains of the aluminum current collector can be controlled, thereby improving the mechanical properties of the aluminum current collector and reducing the stress released when the aluminum current collector is impacted by a heavy object.

[0023] In an embodiment, the holding time is 1-1.5h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, etc. In this way, the size of the grains of the aluminum current collector can be controlled, and local stress can be reduced, thereby improving the mechanical properties of the aluminum current collector.

[0024] In an embodiment, the heating rate of the heating stage is 5-15°C / min, for example, it can be 5°C / min, 7°C / min, 9°C / min, 10°C / min, 11°C / min, 13°C / min, 15°C / min, etc.

[0025] In an embodiment, the cooling mode of the cooling stage is furnace cooling to room temperature. In this way, the mechanical properties of the aluminum current collector can be improved.

[0026] In an embodiment, the cooling speed of the cooling stage is less than or equal to 5°C / min.

[0027] In an embodiment, the annealing process is carried out in a mixed gas atmosphere composed of an inert gas and a reducing gas. In this way, the oxidation of the aluminum current collector can be inhibited, and the defects on the surface of the aluminum current collector can be repaired.

[0028] In an embodiment, the volume content of the reducing gas in the mixed gas is less than or equal to 5%. In this way, the defects on the surface of the aluminum current collector can be effectively reduced, and the safety of the process can be ensured.

[0029] In an embodiment, the reducing gas is hydrogen.

[0030] In an embodiment, the thickness of the current collector after annealing is 0.25 mm-0.35 mm, for example, it can be 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.30 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, etc. In this way, the mechanical properties of the aluminum current collector can be improved.

[0031] Please refer to Figure 1 In an embodiment, the current collector is mesh-shaped, and the current collector has mesh wires, and the width r of the mesh wires after annealing is 0.06 mm-0.15 mm, for example, it can be 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, etc. In this way, the mechanical properties of the aluminum current collector can be improved.

[0032] Please refer to Figure 1 In an embodiment, the mesh holes of the current collector are rhombic.

[0033] In a second aspect, embodiments of the present application provide a current collector made by the above-mentioned current collector annealing method.

[0034] In a third aspect, embodiments of the present application provide a positive electrode tab, which comprises: the above-mentioned current collector; a positive active material layer disposed on the surface of the current collector.

[0035] It should be noted that the positive electrode tab comprises the above-mentioned current collector and has all the beneficial effects of the above-mentioned current collector, which will not be described here.

[0036] In an embodiment, the thickness of the positive active material layer is 0.4 mm-0.45 mm, for example, it can be 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, etc.

[0037] It can be understood that the thickness of the positive active material layer refers to the thickness between the side surface of the current collector and the side surface of the positive active material layer away from the current collector.

[0038] In an embodiment, the compaction density of the positive electrode tab is 2.5 g / cm3-2.77 g / cm3. In this way, the anti-heavy-impact capability of the positive electrode tab can be improved.

[0039] It can be understood that if the compaction density of the positive electrode tab is too low or too high, the active material layer is more likely to pierce the separator and cause the positive and negative electrodes to contact and catch fire when a heavy impact is applied.

[0040] In a fourth aspect, embodiments of the present application provide a battery comprising the current collector described above or the positive electrode tab described above.

[0041] It should be noted that the battery comprises the current collector or the positive electrode tab described above, and has all the beneficial effects of the current collector or the positive electrode tab described above, which will not be repeated here.

[0042] Embodiment 1 A current collector and an annealing method thereof, comprising: The wire diameter of the mesh is 0.1 mm, the thickness is 0.3 mm, and the area density is 230 g / m 2 The dried current collector (made of aluminum) is placed in a vacuum annealing furnace for annealing. A nitrogen and hydrogen atmosphere is maintained in the annealing furnace (wherein the volume content of nitrogen is 95% and the volume content of hydrogen is 5%). The temperature is first raised to 250°C at a rate of 10°C / min, then held at 250°C for 1 hour, and then cooled to room temperature with the furnace, to obtain an annealed current collector.

[0043] A battery comprising: the annealed current collector described above as the positive current collector of a lithium-manganese battery, to make a lithium-manganese battery, wherein the thickness of the positive active material layer on the positive electrode tab is 0.43 mm, and the compaction density of the positive electrode tab is 2.65 g / cm3.

[0044] Embodiment 2 This embodiment is basically the same as Embodiment 1, except that the heating rate during annealing in this embodiment is 15°C / min.

[0045] Embodiment 3 This embodiment is basically the same as Embodiment 1, except that the heating rate during annealing in this embodiment is 5°C / min.

[0046] Embodiment 4 This embodiment is basically the same as Embodiment 1, except that the holding temperature during annealing in this embodiment is 350°C.

[0047] Embodiment 5 This embodiment is basically the same as Embodiment 1, except that the holding temperature during annealing in this embodiment is 150°C.

[0048] Example 6 This example is basically the same as Example 1, except that the holding time during annealing in this example is 3 h.

[0049] Example 7 This example is basically the same as Example 1, except that the holding time during annealing in this example is 2 h.

[0050] Example 8 This example is basically the same as Example 1, except that the furnace cooling to room temperature during annealing in this example is replaced by air cooling to room temperature.

[0051] Example 9 This example is basically the same as Example 1, except that the nitrogen and hydrogen atmosphere in the annealing furnace during annealing in this example is replaced by an air atmosphere.

[0052] Example 10 This example is basically the same as Example 1, except that the nitrogen and hydrogen atmosphere in the annealing furnace during annealing in this example is replaced by a nitrogen atmosphere.

[0053] Example 11 This example is basically the same as Example 1, except that the areal density of the current collector grid in this example is 260 g / m 2 , and the compacted density of the positive electrode tab is 2.5 g / cm

[0054] Example 12 This example is basically the same as Example 1, except that the areal density of the current collector grid in this example is 200 g / m 2 , and the compacted density of the positive electrode tab is 2.77 g / cm

[0055] Example 13 This example is basically the same as Example 1, except that the wire diameter of the current collector grid in this example is 0.15 mm.

[0056] Example 14 This example is basically the same as Example 1, except that the wire diameter of the current collector grid in this example is 0.06 mm.

[0057] Example 15 This example is basically the same as Example 1, except that the thickness of the current collector grid in this example is 0.35 mm.

[0058] Example 16 This example is basically the same as Example 1, except that the thickness of the current collector grid in this example is 0.25 mm.

[0059] Example 17 This example is basically the same as Example 1, except that in this example, the thickness of the positive active material layer on the positive electrode tab is 0.45 mm, and the compaction density of the positive electrode tab is 2.77 g / cm3.

[0060] Example 18 This example is basically the same as Example 1, except that in this example, the thickness of the positive active material layer on the positive electrode tab is 0.4 mm, and the compaction density of the positive electrode tab is 2.77 g / cm3.

[0061] Comparative Example 1 This comparative example is basically the same as Comparative Example 1, except that in this comparative example, the current collector grid is not annealed.

[0062] Test Example The current collector grids obtained in the examples and comparative examples were tested for elongation at break and tensile strength at break, and the batteries obtained in the examples and comparative examples were tested for weight impact, and the test results are shown in Table 1.

[0063] Method for testing elongation at break and tensile strength at break: a current collector grid with a length of 15 cm and a width of 2.6 mm was taken, and a universal testing machine was used to test the elongation at break thereof, a tensile force was applied at a tensile speed of 100 mm / min until the current collector grid broke, the maximum tensile force at the breaking point was recorded as the tensile strength at break, the length at the breaking point was recorded, and the elongation at break was calculated. Elongation at break = (length at break - initial length) / initial length Method for testing weight impact (referring to UL1642): A battery sample was placed on a flat surface, a rigid impact rod with a diameter of 15.8±0.1 mm was vertically placed above the central axis of the battery (the rod axis was perpendicular to the longitudinal axis of the battery), and a weight of 9.10±0.46 Kg was dropped from a height of 610±25 mm onto the sample; if the battery under test did not explode, catch fire, or emit smoke within 6 hours, it passed the test, and if the battery under test exploded, caught fire, or emitted smoke, it failed the test. Ten batteries of each scheme were taken for weight impact testing, and the number of times the battery under test passed was recorded.

[0064] Table 1 Test Data Table

[0065] From Table 1, it can be seen that: Compared with Examples 2 and 3, the current collector grid of Example 1 has a greater elongation at break and a greater tensile strength at break, and the battery of Example 1 has a greater number of times of passing the weight impact test, which shows that by controlling the heating rate during annealing, the elongation at break and the tensile strength at break of the current collector grid can be controlled, thereby improving the weight impact resistance of the battery.

[0066] Compared with Example 1, Example 4 and Example 5, the breaking elongation and the breaking tensile strength of the current collector of Example 1 are greater, and the number of passing times of the heavy impact test of the battery of Example 1 is greater. It can be seen that by controlling the holding temperature during annealing, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0067] Compared with Example 1, Example 6 and Example 7, the breaking elongation and the breaking tensile strength of the current collector of Example 1 are greater, and the number of passing times of the heavy impact test of the battery of Example 1 is greater. It can be seen that by controlling the holding time during annealing, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0068] Compared with Example 1, Example 8, the breaking elongation and the breaking tensile strength of the current collector of Example 1 are greater, and the number of passing times of the heavy impact test of the battery of Example 1 is greater. It can be seen that by controlling the cooling mode, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0069] Compared with Example 1, Example 9 and Example 10, the breaking elongation and the breaking tensile strength of the current collector of Example 1 are greater, and the number of passing times of the heavy impact test of the battery of Example 1 is greater. It can be seen that by controlling the gas atmosphere in the annealing furnace during annealing, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0070] Compared with Example 1, Example 11 and Example 12, the breaking elongation and the breaking tensile strength of the current collector of Example 11 are greater, and the number of passing times of the heavy impact test of the battery of Example 11 is greater. It can be seen that by controlling the areal density of the current collector, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0071] Compared with Example 1, Example 13 and Example 14, the breaking elongation and the breaking tensile strength of the current collector of Example 1 are greater, and the number of passing times of the heavy impact test of the battery of Example 1 is greater. It can be seen that by controlling the wire diameter of the current collector, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0072] Compared with Example 1, Example 15 and Example 16, the breaking elongation and the breaking tensile strength of the current collector of Example 1 are greater, and the number of passing times of the heavy impact test of the battery of Example 1 is greater. It can be seen that by controlling the thickness of the current collector, the breaking elongation and the breaking tensile strength of the current collector can be controlled, thereby improving the heavy impact resistance of the battery.

[0073] Compared with Comparative Example 1 and Example 18, the battery of Example 1 has more times of passing the heavy impact test, and it can be seen that the compaction density of the positive electrode tab can control the anti-heavy impact ability of the battery.

[0074] Compared with Comparative Example 1, the current collector of Example 1 has greater elongation at break and greater tensile strength at break, and the battery of Example 1 has more times of passing the heavy impact test, and it can be seen that the annealing treatment of the current collector can control the elongation at break and the tensile strength at break of the current collector, thereby improving the anti-heavy impact ability of the battery.

[0075] In summary, by controlling the surface density of the current collector made of metal aluminum and performing targeted annealing treatment, the grains of the current collector can be recrystallized, and the size of the formed grains can be controlled, thereby improving the mechanical properties of the aluminum current collector, reducing the stress released when the aluminum current collector is impacted by a heavy object, and further improving the impact resistance of the battery when the aluminum current collector is applied in the battery.

[0076] The above describes in detail the annealing method of the current collector, the current collector, the positive electrode tab and the battery provided by the embodiments of the present application, and the principles and implementation manners of the present application are described by applying specific examples; the above description of the embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation manner and application range will be changed, and the above description should not be understood as limiting the present application.

Claims

1. An annealing method for a current collector, characterized in that, include: Anneal the current collector; The annealing process includes a heating stage, a holding stage, and a cooling stage. The holding stage has a temperature of 150℃-350℃ and a holding time of 1h-3h. The current collector is made of aluminum, and its surface density after annealing is 200g / m³. 2 -260g / m 2 .

2. The annealing method for the current collector according to claim 1, characterized in that, The heating rate during the heating phase is 5°C / min - 15°C / min; and / or The cooling method during the cooling stage is to cool the furnace to room temperature.

3. The annealing method for the current collector according to claim 1, characterized in that, The annealing process is carried out in a mixed gas atmosphere consisting of inert gas and reducing gas.

4. The annealing method for the current collector according to claim 3, characterized in that, The volume content of the reducing gas in the mixed gas is less than or equal to 5%.

5. The annealing method for the current collector according to any one of claims 1-4, characterized in that, The thickness of the current collector after annealing is 0.25mm-0.35mm; and / or The current collector is mesh-like, and the current collector has mesh wires. The width of the mesh wires after annealing is 0.06mm-0.15mm.

6. A current collector, characterized in that, It is made by the annealing method of the current collector as described in any one of claims 1-5.

7. A positive electrode sheet, characterized in that, include: The current collector as described in claim 6; A positive electrode active material layer is disposed on the surface of the current collector.

8. The positive electrode sheet according to claim 7, characterized in that, The thickness of the positive electrode active material layer is 0.4mm-0.45mm.

9. The positive electrode sheet according to claim 7, characterized in that, The compaction density of the positive electrode sheet is 2.5 g / cm³-2.77 g / cm³.

10. A battery comprising a current collector as described in claim 6, or a positive electrode as described in any one of claims 7-9.

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