Electrode sheet, battery, and electric device

Abstract

The present disclosure provides an electrode sheet, a battery, and an electric device. The electrode sheet comprises an electrode sheet body and at least one tab connected to the electrode sheet body. The electrode sheet body comprises a current collector and active materials coated on the surface of the current collector. The electrode sheet body comprises at least two regions in a first direction, and the at least two regions are coated with different active materials. The at least two regions include a distal region distant from the tab, the active material in the distal region comprises secondary particles, and the secondary particles are formed by a plurality of primary particles.

Description

An electrode, a battery, and an electrical device

[0001] This disclosure claims priority to Chinese Patent Application No. 202411187071.7, filed on August 27, 2024, entitled “An electrode, a battery and an electrical device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of battery technology, and more specifically to an electrode, a battery, and an electrical device. Background Technology

[0003] In existing lithium batteries, the material distribution on the electrode surface is uniform. For electrodes led out from the same side of the tab, the electrode closer to the tab has lower impedance, resulting in a higher current density; while the electrode farther from the tab has higher impedance, resulting in a lower current density. Furthermore, the difference in current density and impedance also causes different amounts of heat generation in the electrodes, which in turn affects the cycle life of the battery.

[0004] Therefore, the electrode plates led out from the same side of the tab have obvious problems with uneven current density and temperature distribution. Summary of the Invention

[0005] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. This summary section is not intended to limit the key features and essential technical features of the claimed technical solutions, nor is it intended to determine the scope of protection of the claimed technical solutions.

[0006] This disclosure provides an electrode sheet, including an electrode sheet body and at least one tab connected to the electrode sheet body. The electrode sheet body includes a current collector and an active material coated on the surface of the current collector. The electrode sheet body includes at least two regions in a first direction, and the active materials coated on the at least two regions are different. The at least two regions include a distal region away from the tab, and the active material in the distal region includes secondary particles, wherein the secondary particles are formed by a plurality of primary particles.

[0007] For example, the secondary particles have a porous structure.

[0008] For example, the primary particle has a first size, the secondary particle has a second size, and the ratio of the second size to the first size is a preset ratio, which is greater than or equal to 30.

[0009] For example, when the first size and the second size are expressed in terms of median diameter, the median diameter of the secondary particle ranges from 6 μm to 9 μm, and the median diameter of the primary particle ranges from 70 nm to 130 nm.

[0010] For example, the first direction is the direction extending from the tab to the electrode sheet.

[0011] For example, the length of the distal region along the first direction is 20% to 30% of the length of the electrode body.

[0012] For example, the distal region is the edge region of the electrode body that is furthest from the tab along the first direction.

[0013] For example, the at least two regions also include a proximal region near the tab, wherein the active material of the proximal region comprises particles having a third size.

[0014] For example, in the at least two regions, the particle size of the active material gradually decreases from the proximal region near the tab to the region away from the tab.

[0015] For example, the third size is larger than the first size and smaller than the second size, and when the third size is expressed as median diameter, the median diameter of the particles having the third size ranges from 0.6 μm to 1.2 μm.

[0016] For example, the active material includes a positive electrode active material.

[0017] For example, the positive electrode active material includes lithium iron phosphate.

[0018] For example, the electrode is used to form a battery with a tab on the same side.

[0019] This disclosure also provides a battery comprising the electrode as described in any of the above claims.

[0020] For example, the electrode includes a positive electrode and a negative electrode, and the tabs of the positive electrode and the negative electrode are located on the same side.

[0021] This disclosure also provides an electrical device, including an electrode as described in any of the preceding claims or a battery as described in any of the preceding claims, and an electrical load, wherein the battery provides electrical energy to the electrical load.

[0022] According to the electrode, battery, and electrical device provided in this disclosure, by dividing the electrode sheet led out from the same side of the tab into at least two regions, the at least two regions include a distal region away from the tab, and the active material of the distal region includes secondary particles formed from primary particles, the problem of uneven distribution of current density and electrode impedance in the electrode led out from the same side of the tab can be improved, thereby improving the electrochemical performance of the electrode. Attached Figure Description

[0023] The following drawings, which are incorporated herein by reference as part of this disclosure, are provided for understanding the disclosure. The drawings illustrate embodiments of the disclosure and their descriptions, serving to explain the principles of the disclosure.

[0024] In the attached image:

[0025] Figure 1 is a schematic diagram of the structure of an electrode sheet according to an embodiment of the present disclosure;

[0026] Figure 2 is a schematic diagram of the structure of a battery according to an embodiment of the present disclosure.

[0027] Figure reference numerals: 10, electrode body; 20, electrode tab; 11, proximal region; 12, distal region. Detailed Implementation

[0028] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring this disclosure.

[0029] It should be understood that this disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0031] To fully understand this disclosure, detailed steps and structures will be set forth in the following description to illustrate the technical solutions presented herein. Preferred embodiments of this disclosure are described in detail below; however, other embodiments may also be implemented in addition to these detailed descriptions.

[0032] For batteries with tabs on the same side, when the active material is uniformly distributed, there are significant issues with uneven current density and temperature along the tab extension direction. The area closer to the tab in the electrode sheet has a high current density, while the area farther from the tab has a low current density and high impedance, affecting battery performance.

[0033] To address the aforementioned problems, this disclosure provides an electrode sheet, as shown in FIG1. ​​The electrode sheet includes: an electrode sheet body 10 and at least one tab 20 connected to the electrode sheet body 10. The electrode sheet body 10 includes a current collector and an active material coated on the surface of the current collector. The electrode sheet body 10 includes at least two regions in a first direction, and the active materials coated on the at least two regions are different. The at least two regions include a distal region 12 away from the tab 20. The active material in the distal region 12 includes secondary particles, wherein the secondary particles are formed by a plurality of primary particles.

[0034] For example, the electrode includes a positive electrode or a negative electrode; the electrode body 10 includes a current collector and an active material on the surface of the current collector; the tab 20 is made of a metal material, the single-layer metal material including aluminum foil or copper foil.

[0035] In one embodiment, the electrode is a positive electrode. Taking a lithium-ion battery as an example, the electrode body 10 of the positive electrode of a lithium-ion battery is typically composed of a positive active material (such as lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, ternary materials, etc.), a conductive agent (such as carbon nanotubes, conductive carbon black, graphene, etc.), and a binder (such as polyvinylidene fluoride PVDF, sodium carboxymethyl cellulose, and styrene-butadiene rubber), which is uniformly mixed and stirred into a paste. This paste is then uniformly coated onto both sides of the positive current collector (e.g., aluminum foil), dried under a nitrogen flow to remove organic dispersants, pressed into shape using a roller press, and then cut to the specified size according to design requirements. The tabs 20 of the positive electrode extend from the positive current collector. The tabs 20 of the positive electrode are typically made of aluminum foil, and their length and width can be designed as needed; this disclosure does not limit this. In one embodiment, the electrode is a negative electrode. The negative electrode active material of the negative electrode sheet of a lithium-ion battery mainly includes graphite, silicon-based or lithium titanate, and the negative electrode current collector can be copper foil. The preparation process of the negative electrode sheet is roughly the same as that of the positive electrode sheet, and will not be described in detail here. The tab 20 of the negative electrode sheet is led out from the negative electrode current collector. The tab 20 of the negative electrode sheet is usually made of copper foil, and its length and width can be designed as needed. This disclosure does not limit this.

[0036] The tab 20 and the current collector can be integrally formed, which can be achieved by welding.

[0037] For example, the electrode body 10 includes at least two regions in a first direction, the at least two regions including a proximal region 11 and a distal region 12 located in the first direction. The active materials coated on the at least two regions are different; the active material of the distal region 12 includes secondary particles, wherein the secondary particles are formed from a plurality of primary particles.

[0038] According to the electrode sheet provided in this disclosure, by dividing the electrode sheet led out from the same side of the tab 20 into at least two regions, and the active materials coated on the at least two regions are different, the at least two regions include a distal region 12 away from the tab 20, and the active material of the distal region 12 includes secondary particles formed from primary particles, the problem of uneven current density and electrode impedance distribution in the electrode led out from the same side of the tab 20 can be improved on the side close to the tab 20 and the side far from the tab 20, thereby improving the electrochemical performance of the electrode.

[0039] For example, the secondary particles have a porous structure.

[0040] Because secondary particles have a large number of pores, they can provide pathways for lithium-ion transport, thereby effectively improving the problem of uneven electrode current density distribution.

[0041] In one embodiment, as shown in FIG1, the first direction is the direction extending from the tab 20 to the electrode sheet. The electrode sheet body 10 is sequentially divided into a proximal region 11 and a distal region 12 along the first direction extending from the tab 20 to the electrode sheet. It should be noted that dividing the electrode sheet body 10 into two regions is merely exemplary; the electrode sheet body 10 may also be divided into three, four, or even more regions, and this disclosure does not impose any limitations on this.

[0042] Since the current density and temperature distribution of the electrode are uneven in the direction extending from the tab 20 to the electrode, the direction extending from the tab 20 to the electrode is taken as the first direction. Based on this direction, the region is divided, which can effectively solve the problem of uneven current density and temperature distribution caused by the uniform distribution of the electrode surface material in this direction.

[0043] Furthermore, based on the above-mentioned division of the electrode body 10 into multiple regions along the first direction, the electrode body 10 can be further divided into multiple regions along the second direction, wherein the second direction is perpendicular to or intersects with the first direction.

[0044] In one embodiment, the first direction includes a direction from high current density to low current density of the electrode body 10. The electrode body 10 is divided into multiple regions according to the current density distribution. In one embodiment, the first direction includes a direction from high temperature to low temperature of the electrode body 10. The electrode body 10 is divided into multiple regions according to the temperature distribution.

[0045] For example, the distal region 12 is the edge region of the electrode body 10 that is furthest from the tab 20 along the first direction.

[0046] In one embodiment, as shown in FIG1, the distal region 12 is not only farther from the tab 20 than the proximal region 11, but is also the region farthest from the tab 20 among the multiple regions of the electrode body 10, and is also the edge region of the electrode body 10 on the side away from the tab 20. The proximal region 11 is not only closer to the tab 20 than the distal region 12, but is also the region closest to the tab 20 among the multiple regions of the electrode body 10, and is also the edge region of the electrode body 10 on the side closer to the tab 20.

[0047] For example, the length of the distal region 12 along the first direction is 20% to 30% of the length of the electrode body 10.

[0048] In one embodiment, when the length of the distal region 12 is small, the current density distribution in the distal region 12 is uneven, and the battery impedance is high; when the length of the distal region 12 is large, the battery energy density is low. Therefore, the length of the distal region 12 is 20% to 30% of the length of the electrode body 10. Taking the length of the electrode body 10 as L as an example, the length of the distal region 12 ranges from 0.2L to 0.3L.

[0049] In one embodiment, the length of the distal region 12 is 0.25L and the length of the proximal region 11 is 0.75L.

[0050] In one embodiment, Table 1 shows the test results of battery performance when the length of the distal region 12 is different.

[0051] The battery manufacturing process is as follows:

[0052] (1) Preparation of positive electrode sheet: Mix positive electrode active material, conductive agent (conductive carbon black), solvent (N-methylpyrrolidone), and binder (PVDF), wherein the mass ratio of positive electrode active material, conductive agent, binder and solvent is 100:1.5:2.5:50; prepare a positive electrode slurry with appropriate viscosity, coat it on the positive electrode current collector (aluminum foil), and dry to obtain positive electrode sheet; wherein, for the selection of positive electrode active material and coating position, please refer to Table 1-4;

[0053] (2) Preparation of negative electrode sheet: The negative electrode active material (graphite powder), conductive agent (conductive carbon black), binder (mixture of CMC and SBR), and solvent (water) are mixed to prepare a negative electrode slurry with appropriate viscosity. The mass ratio of positive electrode active material, conductive agent, binder and solvent is 100:0.8:2.5:50. The slurry is coated on the negative electrode current collector (copper foil) and dried to obtain the negative electrode sheet.

[0054] (3) Electrolyte: LiPF6 concentration of 1 mol / L electrolyte (solvent is 15% DMC + 40% EMC + 15% DEC + 30% EC by mass ratio);

[0055] (4) Preparation of lithium-ion batteries: The prepared positive electrode, separator (PP film) and negative electrode are stacked in sequence to assemble a soft pack battery, and the prepared electrolyte is injected. Electrochemical tests are performed, and the results are shown in Table 1-4.

[0056] Electrochemical performance testing:

[0057] (1) Current density difference test between the distal region of the electrode and the tab side (i.e., the proximal region): Five different locations were selected in the proximal and distal regions to test the current density at the corresponding locations and calculate the average value; the current density difference J between the proximal regions of the electrode is the current density difference between the distal region of the electrode and the tab side, as shown in Table 1-4; the current density test of the electrode is a routine test in this field and no specific restrictions are imposed.

[0058] (2) Battery energy density (Wh / L) test: Under 25℃ conditions, each lithium-ion battery was first charged at a 1 / 3C rate and then discharged at a 1 / 3C rate (voltage range of 2.2V-4.2V), and the actual discharge amount was recorded. The product of the actual discharge amount of the battery at 1 / 3C and the average voltage of the battery during discharge is the energy of the battery. The ratio of the energy of the battery to the volume of the battery is the energy density of the battery (Wh / L), as shown in Table 1-4.

[0059] (3) DC internal resistance at 50% SOC (mΩ): Discharge the battery to 50% SOC, let it rest for 2 hours, charge it at 1C for 30 seconds, let it rest for 2 hours, and discharge it at 1C for 30 seconds; calculate the DC internal resistance at 1C rate, as shown in Table 1-4.

[0060] (4) Capacity retention rate (%) after 500 cycles at 45℃: The battery is charged and discharged once at 0.5C / 0.5C to obtain the discharge capacity C1. Then the battery is placed in a 45℃ constant temperature chamber for 0.5C / 0.5C charge and discharge test. The discharge capacity C500 after the 500th cycle is recorded. The capacity retention rate after 500 cycles = C500 / C1*100%, as shown in Table 1-4.

[0061] Table 1 shows the battery performance test results for different lengths of the distal region 12. According to Table 1, when the length of the distal region 12 is in the range of 0.2L to 0.3L, the DC internal resistance is smaller, the energy density is higher, and the battery performance is better. For example, the battery performance is optimal when the length is 0.25L.

[0062] Table 1

[0063] For example, the active material of the distal region 12 includes secondary particles with a porous structure, wherein the secondary particles are formed from a plurality of primary particles.

[0064] In one embodiment, taking lithium iron phosphate as an example, the active material used in the distal region 12 is a secondary particle with a second size, which is formed by agglomeration or sintering of primary particles with a first size. The size of the secondary particle (i.e., the second size) is larger than the size of the primary particle (i.e., the first size), and the size of the secondary particle is at least 30 times the size of the primary particle, typically 50 to 100 times.

[0065] Here, size refers to the particle size of the material. The particle size can be expressed as the median diameter D50, which is the particle size corresponding to 50% of the cumulative particle size distribution of a sample. It can be measured by laser particle size analysis.

[0066] Specifically, when the first and second dimensions are expressed in terms of median diameter, the median diameter of the secondary particles used to form the distal region 12 ranges from 6 μm to 9 μm, and the median diameter of the primary particles used to form the secondary particles ranges from 70 nm to 130 nm.

[0067] Table 2 shows the test results of battery performance when the secondary particles have different sizes. When the primary particles are the same size, but the secondary particles they form have different sizes, according to Table 2, the battery performance is optimal when the median diameter of the secondary particles is in the range of 6μm to 9μm, for example, 7μm.

[0068] Table 2

[0069] In one embodiment, Table 3 shows the test results of battery performance when the size of the primary particles is different. When the size of the secondary particles is the same, but the size of the primary particles used to form the secondary particles is different, according to Table 3, the battery performance is optimal when the median diameter of the primary particles is in the range of 70 nm to 130 nm, for example, 105 μm.

[0070] Table 3

[0071] The secondary lithium iron phosphate particle material is composed of multiple small-diameter primary lithium iron phosphate particles with a large number of pore structures inside. The far-end region 12 adopts a porous electrode structure to provide a pathway for lithium-ion transport. Using materials with small primary particle size reduces battery impedance and effectively improves the problem of uneven current density distribution along the electrode length.

[0072] For example, the active material of the proximal region 11 comprises particles having a third size.

[0073] For example, the particle size of the active material gradually decreases from the proximal region 11 near the tab 20 to the region away from the tab 20. Here, the particle size of the active material is the particle size of a primary particle.

[0074] Since materials with small particle size can reduce battery impedance, the resistance can gradually decrease from the near-end region 11 close to the tab 20 to the region far away from the tab 20, thus solving the problem of uneven current density distribution.

[0075] The third size is larger than the first size and smaller than the second size. When the third size is expressed as median diameter, the median diameter of the particles having the third size ranges from 0.6 μm to 1.2 μm. The particles with the third size can be composed of primary particles or secondary particles; preferably, they are primary particles.

[0076] In one embodiment, the active material used to form the proximal region 11 comprises primary particles with a third size, the median diameter of which ranges from 0.6 μm to 1.2 μm. This size is smaller than the size of the secondary particles used to form the distal region 12 (i.e., the second size), but larger than the size of the primary particles used to form the secondary particles (i.e., the first size). In one embodiment, the active material comprises a positive electrode active material.

[0077] Specifically, the positive electrode active material includes lithium iron phosphate.

[0078] This disclosure also provides a battery including the electrodes described above.

[0079] In one embodiment, as shown in FIG2, the battery includes a battery with tabs 20 on the same side. The electrode plates of the battery with tabs 20 on the same side include a positive electrode plate and a negative electrode plate, and the tabs 20 of the positive electrode plate and the negative electrode plate are located on the same side.

[0080] Since the tabs 20 of the same-side tab 20 battery are distributed at the same end of the battery, the current density in the area near the tab 20 of the electrode body 10 of the same-side tab 20 battery is high, while the current density and impedance in the area far from the tab 20 are low. Therefore, when the above-mentioned electrode is used to form the same-side tab 20 battery, the distal region 12 formed by the secondary particles as active material has a good ion diffusion and electron transport channel. The primary particles used to form the secondary particles reduce the battery impedance and can effectively improve the problem of uneven current distribution in the length direction of the same-side tab 20 battery.

[0081] In one embodiment, each battery consists of one electrode core, and each electrode core consists of 29 positive electrode sheets and 30 negative electrode sheets, wherein the negative electrode excess ratio is 15% and the compaction is 1.60 g / cm³. 3 .

[0082] In one embodiment, Table 4 shows the performance test results of the battery formed using the electrode sheets described above. Schemes 14-15 serve as a control group. Scheme 14 does not use a partitioning method and all samples are coated with secondary particulate material; Scheme 15 does not use a partitioning method and all samples are coated with third-size particles.

[0083] Table 4

[0084] This disclosure also provides an electrical device, including the electrode or battery as described above and an electrical load, wherein the battery provides electrical energy to the electrical load.

[0085] According to the electrode, battery and electrical device provided in this disclosure, the active material in the distal region 12 of the electrode adopts a porous structure formed by secondary particles to provide a pathway for ion transport. The secondary particles are formed by multiple primary particles. The smaller particle size of the primary particles reduces the battery impedance, effectively improves the problem of uneven current distribution on the electrode surface, and improves battery performance.

[0086] This disclosure has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this disclosure to the described embodiments. Furthermore, those skilled in the art will understand that this disclosure is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of this disclosure, all of which fall within the scope of protection claimed by this disclosure. The scope of protection of this disclosure is defined by the appended claims and their equivalents.

Claims

1. An electrode sheet, characterized in that, The electrode includes an electrode body (10) and at least one tab (20) connected to the electrode body (10). The electrode body (10) includes a current collector and an active material coated on the surface of the current collector. The electrode body (10) includes at least two regions in a first direction, and the active materials coated on the at least two regions are different. The at least two regions include a distal region (12) away from the tab (20). The active material in the distal region (12) includes secondary particles, wherein the secondary particles are formed by a plurality of primary particles.

2. The electrode sheet as described in claim 1, characterized in that, The secondary particles have a porous structure.

3. The electrode sheet as described in claim 2, characterized in that, The primary particle has a first size, and the secondary particle has a second size. The ratio of the second size to the first size is a preset ratio, which is greater than or equal to 30.

4. The electrode sheet as described in claim 2, characterized in that, When the first size and the second size are expressed in terms of median diameter, the median diameter of the secondary particle ranges from 6 μm to 9 μm, and the median diameter of the primary particle ranges from 70 nm to 130 nm.

5. The electrode sheet as described in claim 2, characterized in that, The first direction is the direction extending from the tab (20) to the electrode sheet.

6. The electrode sheet as described in claim 5, characterized in that, The length of the distal region (12) along the first direction is 20% to 30% of the length of the electrode body (10).

7. The electrode sheet as described in claim 6, characterized in that, The distal region (12) is the edge region of the electrode body (10) that is furthest from the electrode tab (20) along the first direction.

8. The electrode sheet as described in claim 3, characterized in that, The at least two regions also include a proximal region (11) near the tab (20), wherein the active material of the proximal region (11) comprises particles having a third size.

9. The electrode sheet as described in claim 8, characterized in that, In the at least two regions, the particle size of the active material gradually decreases from the proximal region (11) near the tab (20) to the region away from the tab (20).

10. The electrode sheet as described in claim 9, characterized in that, The third dimension is larger than the first dimension and smaller than the second dimension. When the third dimension is expressed as median diameter, the median diameter of the particles having the third dimension ranges from 0.6 μm to 1.2 μm.

11. The electrode sheet as described in claim 1, characterized in that, The active material includes a positive electrode active material.

12. The electrode sheet as described in claim 11, characterized in that, The positive electrode active material includes lithium iron phosphate.

13. The electrode sheet as described in claim 1, characterized in that, The electrode is used to form a same-side tab (20) battery.

14. A battery, characterized in that, The electrode includes any one of claims 1 to 13.

15. The battery as claimed in claim 14, characterized in that, The electrode includes a positive electrode and a negative electrode, and the tabs (20) of the positive electrode and the negative electrode are located on the same side.

16. An electrical appliance, characterized in that, The device includes the electrode sheet according to any one of claims 1 to 13 or the battery according to claim 14 or 15, and the electrical load, wherein the battery provides electrical energy to the electrical load.

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