Electrode piece, electrode core assembly, secondary battery and electric equipment

Abstract

The utility model relates to an electrode pole piece, a pole core assembly, a secondary battery and electric equipment, the electrode pole piece comprises a current collector, the surface of the current collector is provided with an electrode material layer and an inorganic material layer, the electrode material layer comprises a middle part and a thinned part connected with at least part of the edge of the middle part, the inorganic material layer is connected with the thinned part, and the thickness of at least part of the inorganic material layer is not less than that of the middle part. The electrode plate disclosed by the utility model can effectively prevent lithium precipitation, prolong the cycle life and improve the safety performance.

Description

Technical Field

[0001] The present disclosure relates to an electrode tab, a core assembly, a secondary battery, and an electrical device. Background Art

[0002] In the process of battery manufacturing, the production of electrode tabs is a crucial step, and the quality of the electrode tabs directly affects the performance and lifespan of the battery. The electrode tab is coated with active materials, and during the production process, the coating process is one of the key steps. If the coating at the edge of the electrode tab is thick, problems such as edge bursting during winding and overpressure of the electrode tab will occur, greatly reducing production efficiency and increasing cell quality issues. Therefore, thinning regions are often introduced at both ends of the electrode tab during production, that is, the thickness at the edge of the electrode tab is reduced to be less than the thickness of the middle region of the electrode tab. However, this design easily causes poor adhesion between the positive and negative electrode tabs in the thinning region and between the electrode tab and the separator, resulting in the blocking of the lithium-ion migration path between the positive and negative electrodes, an increase in lithium-ion diffusion impedance, and the problem of lithium deposition easily occurring at the negative electrode near the thinning region during long-term cycling, affecting the service life of the battery. Summary of the Invention

[0003] The purpose of the present disclosure is to provide an electrode tab, a core assembly, a secondary battery, and an electrical device to prevent lithium deposition in the thinning region and improve the service life of the battery.

[0004] To achieve the above purpose, in the first aspect of the present disclosure, an electrode tab is provided. The electrode tab includes a current collector, and the surface of the current collector has an electrode material layer and an inorganic material layer. The electrode material layer includes a middle part and a thinning part connected to at least part of the edge of the middle part. The inorganic material layer is connected to the thinning part, and the thickness of at least part of the inorganic material layer is not lower than the thickness of the middle part.

[0005] Optionally, the width of the inorganic material layer is not lower than the width of the thinning part.

[0006] Optionally, the inorganic material layer includes a covering part and an extending part connected to each other. The covering part is connected to the thinning part and completely covers the surface of the thinning part, and the extending part is connected to the current collector.

[0007] Optionally, the thickness of the covering part is equal to the thickness of the middle part.

[0008] Optionally, the thickness of the extending part gradually decreases from the middle part to the thinning part.

[0009] Optionally, the width ratio of the covering part to the extending part is 1:(0.1 - 2).

[0010] Optionally, the porosity of the inorganic material layer is 5 - 90%.

[0011] In a second aspect of the present disclosure, a pole core assembly is provided, including the electrode pole piece described in the first aspect of the present disclosure.

[0012] In a third aspect of the present disclosure, a secondary battery is provided, including the pole core assembly described in the second aspect of the present disclosure.

[0013] In a fourth aspect of the present disclosure, an electrical device is provided, including the secondary battery described in the third aspect of the present disclosure.

[0014] Through the above technical solutions, an inorganic material layer is provided on the surface of the current collector of the electrode pole piece of the present disclosure, and the thickness of at least a part of the inorganic material layer is not less than the thickness of the middle part of the electrode material layer, which can make the electrode pole pieces fit more closely, thereby ensuring the normal migration of lithium ions between the positive and negative electrode pole pieces, effectively preventing lithium deposition, prolonging the cycle life, and improving the safety performance.

[0015] Other features and advantages of the present disclosure will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific implementation, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0017] Figure 1 is a schematic structural diagram of an electrode pole piece in a specific implementation of the present disclosure.

[0018] Figure 2 is a schematic structural diagram of a pole core assembly in a specific implementation of the present disclosure.

[0019] Figure 3 is a schematic structural diagram of another pole core assembly in a specific implementation of the present disclosure.

[0020] Figure 4 is a schematic structural diagram of an electrode pole piece in the prior art.

[0021] Figure 5 is a schematic structural diagram of a pole core assembly in the prior art.

[0022] DESCRIPTION OF THE REFERENCE NUMERALS

[0023] 1—current collector, 2—electrode material layer, 21—middle part, 22—thinned part, 3—inorganic material layer, 31—covering part, 32—extending part, 4—positive electrode pole piece, 5—negative electrode pole piece. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following will describe the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and understanding the present disclosure, and are not used to limit the present disclosure.

[0025] In the first aspect of the present disclosure, an electrode pole piece is provided. Figure 1 It is a schematic structural diagram of a specific embodiment of the electrode pole piece. Refer to Figure 1 As shown, the electrode pole piece includes a current collector 1. An electrode material layer 2 and an inorganic material layer 3 are provided on the surface of the current collector 1. The electrode material layer 2 includes a middle portion 21 and a thinned portion 22 connected to at least a part of the edge of the middle portion 21. The inorganic material layer 3 is connected to the thinned portion 22, and the thickness of at least a part of the inorganic material layer 3 is not less than the thickness of the middle portion 21. Wherein, the thickness of the inorganic material layer 3 and the thickness of the middle portion 21 respectively refer to the maximum vertical distance between the surface of the inorganic material layer 3 and the middle portion 21 far from the current collector 1 and the surface of the current collector 1 (refer to Figure 1 H in).

[0026] In the electrode pole piece of the present disclosure, an inorganic material layer 3 connected thereto is provided at the thinned portion 22 of the electrode material layer 2, and the thickness of at least a part of the inorganic material layer 3 is not less than the thickness of the middle portion 21 of the electrode material layer 2. The inorganic material layer 3 has the function of ion conduction and electron insulation. In this way, the overall thickness of the thinned area of the pole piece can be made consistent with the middle area of the pole piece, and the pole pieces in the thinned area can be more closely attached, so as to ensure the normal migration of lithium ions between the positive and negative electrode pole pieces. After the pole pieces are closely attached, it can also prevent the gas generated during the cycle from accumulating in this area and hindering the intercalation of lithium ions, prevent lithium deposition from occurring, extend the cycle life, and improve the safety performance.

[0027] In the present disclosure, the shape and size of the electrode material layer 2 are not particularly limited. The middle portion 21 may have a substantially uniform thickness. The thinned portion 22 is usually provided at at least one end of the middle portion 21, and the thickness of the thinned portion 22 gradually decreases from the inside to the outside (i.e., in the direction from the middle portion to the thinned portion). The inorganic material layer 3 is connected to the thinned portion 22 and forms a thickness not less than that of the middle portion 21, that is, the inorganic material layer 3 can cover the surface of the thinned portion 22. By providing the inorganic material layer 3, it is also possible to avoid the material at the edge of the electrode material layer 2 from falling off, ensure the stability of the size and shape of the pole piece, and improve the quality and life of the pole piece.

[0028] The inorganic material layer 3 may have a certain width to completely cover the thinned portion 22. Specifically, refer to Figure 1 , the width W4 of the inorganic material layer 3 is not less than the width W2 of the thinned portion 22. For example, the ratio of the width W4 of the inorganic material layer 3 to the width W2 of the thinned portion 22 may be (1.5~5):1.

[0029] Further, the inorganic material layer 3 may include a connected covering portion 31 and an extending portion 32. Among them, the covering portion 31 is connected to the thinned portion 22 and completely covers the surface of the thinned portion 22. At this time, the width of the covering portion 31 is equal to the width of the thinned portion 22 (i.e., W2), and the extending portion 32 can extend to the surface of the current collector 1 and be connected to the current collector 1.

[0030] At this time, the thickness of the covering portion 31 is not less than the thickness of the middle portion 21. Exemplarily, referring to Figure 1 , the thickness of the covering portion 31 can be equal to the thickness of the middle portion 21 (i.e., the thickness of both is H). Thus, the thickness of the electrode sheet at the thinned portion 22 can be consistent with the middle region of the electrode sheet, making the electrode sheets in the thinned area fit more closely. In addition, the thickness of the extending portion 32 can gradually decrease from the inside to the outside (i.e., from the middle portion to the direction of the thinned portion), forming a thickness gradient similar to that of the thinned portion 22, which is beneficial to avoiding problems such as edge bursting during the winding of the electrode roll and over-pressing of the electrode sheet in the production process of the electrode sheet. In other embodiments, the thickness of the extending portion 32 can also be substantially unchanged.

[0031] The sizes of the covering portion 31 and the extending portion 32 can be designed as needed. Specifically, the ratio of the width W2 of the covering portion 31 to the width W3 of the extending portion 32 can be 1:(0.1 - 2).

[0032] The material of the inorganic material layer 3 can be a porous material, so that the inorganic material layer 3 has an appropriate porosity. Specifically, the porosity of the inorganic material layer 3 can be 5 - 90%, preferably 20 - 70%. When the inorganic material layer 3 has the porosity within the above range, it can provide a stronger liquid retention capacity and extend the cycle life of the battery cell.

[0033] In a specific embodiment, the inorganic material layer 3 can be made of a mixed slurry containing inorganic oxides and a binder-dispersant. Among them, the inorganic oxides can be, for example, one or a mixture of aluminum oxide, zirconium dioxide, titanium dioxide, silicon dioxide, barium titanate, etc.; the particle size D50 of the inorganic oxides is preferably 0.1 - 5 μm; the binder-dispersant can be, for example, one or a mixture of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR). The dosage ratio of the inorganic oxides to the binder-dispersant can be adjusted as needed. For example, the weight ratio of the inorganic oxides to the binder-dispersant can be 100:(2 - 25). Solvents such as deionized water or N-methylpyrrolidone (NMP) can be added during the preparation of the mixed slurry, and the solvent dosage can be adjusted according to the solid content of the slurry determined by the coating effect.

[0034] The electrode sheet of the present disclosure can be prepared as a positive electrode sheet or a negative electrode sheet, which can ensure closer fitting between the sheets. It can not only avoid defects at the edges of the electrode sheets during the battery manufacturing process, improve the overall production efficiency and the consistency of the battery, but also significantly enhance the battery cycle life and the stability during use, providing a reliable guarantee for the efficient and safe use of the battery.

[0035] In a second aspect of the present disclosure, a core component is provided, including the electrode sheet described in the first aspect of the present disclosure. Figure 2 It is a core component of a specific embodiment. Referring to Figure 2 as shown, the core component may include a positive electrode sheet 4, a negative electrode sheet 5 and a separator. The composition method can be laminating or winding. Among them, the positive electrode sheet and / or the negative electrode sheet can be the electrode sheet described in the first aspect of the present disclosure.

[0036] In a third aspect of the present disclosure, a secondary battery is provided, including the core component described in the second aspect of the present disclosure. The specific structure of the secondary battery is not particularly limited, and it may include other common structures in the art, such as electrolyte and packaging shell, etc.

[0037] In a fourth aspect of the present disclosure, an electrical device is provided, including the secondary battery described in the third aspect of the present disclosure. The electrical device is, for example, a power battery module, an energy storage cabinet, etc.

[0038] The present disclosure will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure.

[0039] The raw materials and reagents used in the examples and comparative examples are all commercially available products.

[0040] Example 1

[0041] This example provides a negative electrode sheet. As Figure 1 shown, it includes a current collector 1 and an electrode material layer 2 and an inorganic material layer 3 coated on the surface of the current collector 1; the electrode material layer 2 includes a middle part 21 and a thinned part 22 connected to the two ends of the middle part 21; the inorganic material layer 3 is connected to the thinned part 22.

[0042] The inorganic material layer 3 is formed by coating a slurry prepared by stirring 100 parts by weight of aluminum oxide (particle size D50 is 3 μm), 1.5 parts by weight of CMC, 10 parts by weight of SBR and 90 parts by weight of water; the porosity of the formed inorganic material layer 3 is 35%, which is beneficial for the coating to absorb more electrolyte.

[0043] The width W1 of the middle part 21 of the electrode material layer 2 is 400 mm, the width W2 of the thinned part 22 is 15 mm, and the width W4 of the inorganic material layer 3 is 20 mm; the inorganic material layer 3 includes a connected covering part 31 and an extending part 32. The covering part 31 completely covers the surface of the thinned part 22. The thickness of the covering part 31 is equal to the thickness H of the middle part 21. The thickness of the extending part 32 gradually decreases due to the leveling of the slurry. The width of the covering part 31 is the same as that of the thinned part 22 (i.e., W2), and the width W3 of the extending part 32 is 5 mm.

[0044] Example 2

[0045] This example provides a positive electrode tab, and its structure is the same as Figure 1 similar.

[0046] Among them, the inorganic material layer 3 is prepared by coating a slurry stirred from 100 parts by weight of aluminum oxide (particle size D50 is 3 μm), 2.5 parts by weight of PVDF, and 100 parts by weight of NMP; the porosity of the formed inorganic material layer 3 is 40%.

[0047] The width W2 of the thinned part 22 is 12 mm, and the width W4 of the inorganic material layer 3 is 18 mm; the inorganic material layer 3 includes a connected covering part 31 and an extending part 32. The covering part 31 completely covers the surface of the thinned part 22. The thickness of the covering part 31 is equal to the thickness H of the middle part 21. The thickness of the extending part 32 gradually decreases due to the leveling of the slurry. The width of the covering part 31 is the same as that of the thinned part 22 (i.e., W2), and the width W3 of the extending part 32 is 6 mm.

[0048] Example 3

[0049] The negative electrode tab of Example 1 and the positive electrode tab of Example 2 are prepared into a core assembly, as Figure 2 shown. This core assembly includes a positive electrode tab 4, a negative electrode tab 5, and a separator. It can be seen that the thinned part of the negative electrode tab of this core assembly can be completely attached to the separator and the corresponding positive electrode, ensuring the normal migration of lithium ions. After the tabs are closely attached, it can also prevent the gas generated during the cycle from accumulating in this area and hindering the intercalation of lithium ions, prevent the formation of lithium deposition, extend the cycle life, and improve the safety performance; on the other hand, the inorganic coating on the edge of the tab has a relatively high porosity, which can increase the liquid retention capacity and extend the cycle life.

[0050] Example 4

[0051] This example provides a core assembly, as Figure 3As shown, compared with Example 3, only the tab ends of the positive electrode sheet 4 and the negative electrode sheet 5 have thinned portions, and the thinned portions at the other ends are cut off during the production of the electrode sheets. The inorganic material layer only needs to be coated on the surface of the thinned portions; there is no thinned portion in the same area of the negative electrode sheet 5 corresponding to the area of the inorganic material layer of the positive electrode sheet 4, and there is no thinned portion in the same area of the positive electrode sheet 4 corresponding to the area of the inorganic material layer of the negative electrode sheet 5. Therefore, the electrode sheets and the separator at both ends of the positive and negative electrodes of the electrode core assembly can be closely attached, ensuring the normal migration of lithium ions.

[0052] Comparative Example 1

[0053] In this comparative example, an electrode core assembly was prepared using existing positive and negative electrode sheets. The structure of the electrode sheets is as Figure 4 shown. The thinned areas at both ends of the electrode sheets are not coated with an inorganic material layer. The structure of the electrode core assembly is as Figure 5 shown. It can be seen that gaps are formed at both ends of the electrode core by the thinned area L1×H1 of the positive electrode sheet and the thinned area L2×H2 of the negative electrode sheet.

[0054] Test Example

[0055] Charge-discharge cycle tests were carried out on the electrode core assemblies of Example 3, Example 4, and Comparative Example 1. The test method was as follows: sufficient cycling was carried out using the same charge-discharge regime, that is, constant current charging at 2C to the upper cut-off voltage, followed by a 30-minute rest, and then discharging at 1C to the lower voltage, and such cycle tests were carried out. The test results are listed in Table 1.

[0056] Table 1

[0057]

[0058] As can be seen from Table 1, the electrode sheets of the present disclosure can effectively improve the fitting effect of the edge electrode sheets, thereby preventing the gas generated during the cycling process from accumulating in this area and hindering the intercalation of lithium ions, preventing the generation of lithium deposition, prolonging the cycle life, improving the safety performance, and effectively avoiding the generation of lithium deposition at the edge of the electrode sheet even under high-rate cycling. The existence of the gap in the electrode sheet of Comparative Example 1 will hinder the normal migration of lithium ions, and the gas generated during the cycling process is likely to accumulate in this area. After long-term cycling, especially after high-rate cycling, lithium deposition will occur first in the thinned area, thus affecting the cycle life and safety performance of the battery.

[0059] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0060] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combinations.

[0061] Furthermore, any combinations can be made among the various different embodiments of the present disclosure, as long as they do not violate the idea of the present disclosure, and they should also be regarded as the content disclosed by the present disclosure.

Claims

1. An electrode tab, characterized in that, The electrode tab includes a current collector, and the surface of the current collector has an electrode material layer and an inorganic material layer. The electrode material layer includes a middle part and a thinned part connected to at least part of the edge of the middle part. The inorganic material layer is connected to the thinned part, and the thickness of at least part of the inorganic material layer is not lower than the thickness of the middle part.

2. The electrode sheet according to claim 1, wherein, The width of the inorganic material layer is not lower than the width of the thinned part.

3. The electrode tab according to claim 1, wherein, The inorganic material layer includes a covering part and an extending part connected to each other. The covering part is connected to the thinned part and completely covers the surface of the thinned part, and the extending part is connected to the current collector.

4. The electrode tab according to claim 3, wherein The thickness of the covering part is equal to the thickness of the middle part.

5. The electrode sheet according to claim 3, wherein, The thickness of the extending part gradually decreases from the middle part to the thinned part.

6. The electrode sheet according to claim 3, wherein, The width ratio of the covering part to the extending part is 1:(0.1 - 2).

7. The electrode sheet according to claim 1, wherein, The porosity of the inorganic material layer is 5 - 90%.

8. A pole core component, characterized in that, It includes the electrode tab according to any one of claims 1 - 7.

9. A secondary battery, characterized in that, It includes the electrode core assembly according to claim 8.

10. An electrical device, characterized in that, It includes the secondary battery according to claim 9.

Images