Positive plate, battery and electric equipment

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a positive plate, a battery and electric equipment, the positive plate comprises a current collector, a first coating and a second coating, the first coating is arranged on at least one side of the current collector, the second coating is arranged on the current collector and along the length direction of the positive plate, and the second coating is arranged on the current collector. The second coating is adjacent to at least one end of the first coating, the first coating comprises first particles, the second coating comprises second particles, and the particle size of the second particles is smaller than that of the first particles; the depth of the second particles embedded into the current collector is reduced, and the occurrence probability of a foil gnawing phenomenon is reduced; further, the depth of the second particles embedded into the current collector is prevented from being increased when the battery cell expands, so that the risk of belt breakage of the positive plate is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and in particular relates to a positive electrode sheet, a battery and an electrical device. Background Art

[0002] As a new type of secondary battery, lithium-ion batteries have the advantages of high energy density and power density, high operating voltage, light weight, small size, long cycle life, good safety, and green environmental protection. They have broad application prospects in portable appliances, power tools, large-scale energy storage, electric transportation power supply, etc.

[0003] As consumer electronics products place increasing demands on battery cell performance, especially increasingly stringent energy density (ED) standards, battery cell design is trending towards the use of materials with high voltage, high compaction density, and high gram capacity. However, these high-performance materials, especially lithium cobalt oxide, often appear in the form of larger particles. In the actual manufacturing process, during the rolling process, due to the height difference between the edge of the coating on the foil and the foil, the local rolling pressure increases abnormally, causing these large particles of lithium cobalt oxide to be embedded in the foil, forming the so-called "eating foil" phenomenon. Furthermore, during the recycling of the battery cell, due to the natural effect of material expansion, these embedded large particles will further deepen their embedding, causing the local foil area to become abnormally weak, which may eventually cause the pole piece to break. Utility Model Content

[0004] The purpose of the present invention is to provide a positive electrode sheet, a battery and an electrical device to address the deficiencies of the prior art, thereby solving the technical problem in the prior art that the thickness of the local foil area of ​​the battery cell becomes thinner after a charging cycle due to the phenomenon of foil gnawing, thereby causing the electrode sheet to break.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a positive electrode sheet comprising a current collector, a first coating and a second coating, wherein the first coating is arranged on at least one side of the current collector, the second coating is arranged on the current collector, and along the length direction of the positive electrode sheet, the second coating is adjacent to at least one end of the first coating, the first coating comprises first particles, the second coating comprises second particles, and the particle size of the second particles is smaller than the particle size of the first particles.

[0007] Preferably, the particle size of the second particles is D2, satisfying the relationship: 0<D2≤20μm.

[0008] Preferably, the particle size D2 of the second particles satisfies the relationship: 1 μm≤D2≤20 μm; or, 0<D2<1 μm, wherein when the particle size D2 of the second particles satisfies the relationship: 1 μm≤D2≤20 μm, the surface of the second particles is smooth.

[0009] Preferably, the particle size of the first particles is D1, which satisfies the relationship: 30 μm≤D1≤70 μm.

[0010] Preferably, the thickness of the first coating layer is H1, and the thickness of the second coating layer is H2, satisfying the relationship:

[0011] Preferably, the length of the second coating layer is L2, which satisfies the relationship: 0<L2≤2μm.

[0012] Preferably, the first particles and the second particles are made of the same material, and both are lithium cobalt oxide; or the first particles are lithium cobalt oxide, and the second particles are carbon particles or inorganic oxides.

[0013] Preferably, when the second coating is provided at one end of the first coating, the second coating is provided on the outermost current collector of the battery cell.

[0014] In a second aspect, the present invention provides a battery, comprising a shell and a battery cell, wherein the shell has a receiving cavity, the battery cell is disposed in the receiving cavity, and the battery cell comprises the positive electrode sheet of the above embodiment.

[0015] In a third aspect, the present invention provides an electrical device comprising the battery of the above embodiment.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0017] The positive electrode sheet of the present invention uses a current collector, a first coating layer, and a second coating layer in combination, wherein the first coating layer and the second coating layer are respectively coated on the current collector, and the second coating layer is adjacent to at least one end of the first coating layer along the length direction of the positive electrode sheet. By applying the coating layer in sections, the particle size of the second particles of the second coating layer is made smaller than the particle size of the first particles of the first coating layer, effectively reducing the particle size of the second particles of the second coating layer, so that during the rolling process, the contact area between the second particles and the current collector is relatively reduced, thereby reducing the increase in local rolling pressure caused by height differences, reducing the depth of the second particles embedded in the current collector, and reducing the probability of foil gnawing. In addition, due to the smaller particle size of the second particles, the squeezing effect of the second particles on the current collector is relatively weak when the battery cell expands, and the depth of the second particles embedded in the current collector is shallow, effectively avoiding deepening the depth of the second particles embedded in the current collector when the battery cell expands, thereby reducing the risk of positive electrode segment breakage.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 This is a schematic structural diagram of the pole piece stacking structure of the present invention.

[0021] Figure 2 This is another structural schematic diagram of the pole piece stacking structure of the present invention.

[0022] Figure 3 This is a schematic structural diagram of the positive electrode sheet of the present utility model.

[0023] The description of the accompanying drawings is as follows:

[0024] 100, battery cell; 101, outermost ring;

[0025] 10. Positive electrode; 11. Current collector; 12. First coating; 13. Second coating;

[0026] 20. Negative electrode;

[0027] 30. Diaphragm;

[0028] a. The length direction of the positive electrode. DETAILED DESCRIPTION

[0029] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of the components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0030] Furthermore, the terms “first,” “second,” etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0031] In this utility model, unless otherwise expressly specified or limited, terms such as "installed," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this utility model based on specific circumstances.

[0032] The following will be combined with the Figures 1 to 3 The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] The electrical equipment of the embodiment of the present utility model includes a battery. The electrical equipment can be a car, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The car can be a fuel car, a gas car, or a new energy car. The new energy car can be a pure electric car, a hybrid car, or an extended-range car, and the like; the spacecraft includes airplanes, rockets, space shuttles, and spacecraft, and the like; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiment of the present application does not impose any special restrictions on the above-mentioned electrical equipment.

[0034] The battery of the present invention includes a housing and a battery cell 100. The housing has a receiving cavity, and the battery cell 100 is disposed within the receiving cavity. The battery cell 100 includes a positive electrode sheet 10, a negative electrode sheet 20, and a separator 30. The positive electrode sheet 10, separator 30, and negative electrode sheet 20 are stacked and wound in sequence to form the battery cell 100.

[0035] See also Figures 1 to 3 The positive electrode sheet 10 of an embodiment of the present invention includes a current collector 11, a first coating layer 12 and a second coating layer 13. The first coating layer 12 is arranged on at least one side of the current collector 11, and the second coating layer 13 is arranged on the current collector 11. Along the length direction a of the positive electrode sheet, the second coating layer 13 is adjacent to at least one end of the first coating layer 12. The first coating layer 12 includes first particles, and the second coating layer 13 includes second particles. The particle size of the second particles is smaller than that of the first particles.

[0036] Compared to the prior art, the positive electrode sheet 10 of the present invention embodiment, through the coordinated use of the current collector 11, the first coating 12, and the second coating 13, is coated on the current collector 11 respectively. The second coating 13 is adjacent to at least one end of the first coating 12 along the length direction of the positive electrode sheet 10. By applying the coating in sections, the particle size of the second particles of the second coating 13 is smaller than the particle size of the first particles of the first coating 12, effectively reducing the particle size of the second particles of the second coating 13. As a result, during the rolling process, the contact area between the second particles and the current collector 11 is relatively reduced, thereby reducing the increase in local rolling pressure caused by height differences, reducing the depth of the second particles embedded in the current collector 11, and reducing the probability of foil gnawing. In addition, due to the smaller particle size of the second particles, the squeezing effect of the second particles on the current collector 11 is relatively weak when the battery cell 100 expands, and the depth of the second particles embedded in the current collector 11 is shallow, effectively avoiding the deepening of the second particles embedded in the current collector 11 when the battery cell 100 expands, thereby reducing the risk of the positive electrode sheet 10 breaking.

[0037] It is understood that the smaller size of the second particles facilitates a more uniform and dense distribution of the second coating 13 on the surface of the current collector 11. The uniform second coating 13 can reduce local stress concentration caused by uneven particle distribution and improve the overall flatness and strength of the electrode after rolling.

[0038] It can be understood that when two first coatings 12 are provided, the first of the two first coatings 12 is provided on one side of the current collector 11, and the other of the two first coatings 12 is provided on the other side of the current collector 11, and one end of the two first coatings 12 or the other end of the two first coatings 12 is located at the outermost circle 101 of the battery cell 100, wherein one end of the two first coatings 12 is aligned and the other end of the two first coatings 12 is staggered.

[0039] In some embodiments, the particle size of the first particle is D1, which satisfies the relationship: 30μm≤D1≤70μm. By setting the particle size D1 of the first particle, the particle size D1 of the first particle cannot be too large or too small. When the particle size D1 of the first particle is too large, the excessive particle size may increase the processing difficulty and cost. When the particle size D1 of the first particle is too small, although the smaller particle size can facilitate the rapid diffusion and embedding and de-embedding process of lithium ions, however, too small a particle size may cause agglomeration or agglomeration problems. Therefore, the particle size D1 of the first particle satisfies the relationship: 30μm≤D1≤70μm. It can reduce the processing difficulty and cost of the first particle while ensuring the diffusion rate of lithium ions, reduce agglomeration and agglomeration phenomena, and improve the preparation quality of the electrode.

[0040] Furthermore, the particle size D1 of the first particles is 30 μm, 32 μm, 35 μm, 39 μm, 40 μm, 41 μm, 43 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 57 μm, 60 μm, 63 μm, 66 μm, 69 μm, or 70 μm, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0041] In some embodiments, the particle size of the second particle is D2, which satisfies the relationship: 0<D2≤20μm. By setting the particle size D2 of the second particle, the particle size D2 of the second particle cannot be too large. If the particle size D2 of the second particle is too large, the depth of the second particle embedded in the current collector 11 is deep, and it is easy to deepen the depth of embedding in the current collector 11 when the battery cell 100 expands subsequently, resulting in the positive electrode sheet 10 being broken. At the same time, since the particle size D2 of the second particle needs to be smaller than the particle size D1 of the first particle, the particle size D2 of the second particle satisfies the relationship: 0<D2≤20μm, which can effectively reduce the depth of the second particle embedded in the current collector 11, reduce the probability of the foil gnawing phenomenon, avoid deepening the depth of the second particle embedded in the current collector 11 when the battery cell 100 expands, and thus reduce the risk of the positive electrode sheet 10 being broken.

[0042] Furthermore, the particle size D2 of the second particles satisfies the relationship: 1 μm ≤ D2 ≤ 20 μm. In this case, the surface of the second particles is smooth, effectively preventing the formation of spikes on the surface of the second particles that may pierce the current collector 11 and increase the risk of the positive electrode sheet 10 breaking.

[0043] Alternatively, the particle size D2 of the second particles satisfies the relationship: 0 < D2 < 1 μm. In this case, since the particle size of the second particles is sufficiently small, the second particles can take any form.

[0044] Specifically, when the particle size D2 of the second particles satisfies the relationship: 1 μm ≤ D2 ≤ 20 μm, the particle size D2 of the second particles is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm. However, the present invention is not limited to the values ​​listed above, and other values ​​within the numerical range are also applicable.

[0045] When the particle size D2 of the second particles satisfies the relationship: 0<D2<1μm, the particle size D2 of the second particles is 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm or 0.95μm. However, the present invention is not limited to the values ​​listed above, and other values ​​within the numerical range are also applicable.

[0046] In some embodiments, the particle size D2 of the second particles in the second coating layer 13 gradually decreases along the direction from the first coating layer 12 to the second coating layer 13. This can effectively reduce the particle size D2 of the second particles at the end of the second coating layer 13 away from the first coating layer 12, further reduce the increase in local rolling pressure caused by height differences, reduce the depth of the second particles embedded in the current collector 11, and reduce the probability of foil gnawing.

[0047] See also Figure 3 In some embodiments, the thickness of the first coating layer 12 is H1, and the thickness of the second coating layer 13 is H2, where the thickness H2 of the second coating layer 13 is less than or equal to the thickness H1 of the first coating layer 12. This effectively prevents the thickness H2 of the second coating layer 13 from being greater than the thickness H1 of the first coating layer 12, thereby preventing the thickness H2 of the second coating layer 13 from becoming too thick, resulting in a large height difference between the edge of the second coating layer 13 and the current collector 11, thereby increasing the depth of the second particles embedded in the current collector 11 and increasing the risk of the positive electrode sheet 10 breaking.

[0048] Furthermore, the thickness H1 of the first coating layer 12 and the thickness H2 of the second coating layer 13 satisfy the relationship: when When the thickness H2 of the second coating layer 13 is greater than the thickness H1 of the first coating layer 12, the thickness H2 of the second coating layer 13 is thicker, resulting in a larger height difference between the edge of the second coating layer 13 and the current collector 11, thereby increasing the depth of the second particles embedded in the current collector 11 and increasing the risk of the positive electrode sheet 10 breaking. Although the thickness H2 of the second coating layer 13 is less than the thickness H1 of the first coating layer 12, which solves the problem of the thickness H2 of the second coating layer 13 being too thick, the thickness H2 of the second coating layer 13 is relatively thin, and the difference between the thickness H2 of the second coating layer 13 and the thickness H1 of the first coating layer 12 is large, resulting in poor surface flatness of the positive electrode sheet 10. Therefore, the thickness H1 of the first coating layer 12 and the thickness H2 of the second coating layer 13 are set to satisfy the relationship: This effectively prevents the thickness H2 of the second coating layer 13 from becoming excessively thick, which could result in a significant height difference between the edge of the second coating layer 13 and the current collector 11. This reduces the depth of the second particles embedded in the current collector 11 and reduces the likelihood of foil nibbling. Furthermore, it effectively avoids a significant difference between the thickness H2 of the second coating layer 13 and the thickness H1 of the first coating layer 12, which could result in poor surface flatness on the positive electrode sheet 10.

[0049] See also Figure 3 In some embodiments, the length of the second coating 13 is L2, satisfying the relationship: 0<L2≤2mm. By setting the length of the second coating 13, the length of the second coating 13 cannot be too long. When the length of the second coating 13 is too long, the second coating 13 occupies more space on the current collector 11, which will compress the space occupied by the first coating 12 on the current collector 11, thereby affecting the energy density of the battery. Therefore, the length of the second coating 13 is set to L2, satisfying the relationship: 0<L2≤2mm, which can effectively reduce the depth of the second particles embedded in the current collector 11 while ensuring the energy density of the battery, reduce the probability of the foil gnawing phenomenon, avoid deepening the depth of the second particles embedded in the current collector 11 when the battery cell 100 expands, and thereby reduce the risk of the positive electrode sheet 10 breaking.

[0050] Furthermore, the length L2 of the second coating layer 13 is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2 mm, but is not limited to the values ​​listed above, and other values ​​within the numerical range are also applicable.

[0051] In some embodiments, the first and second particles are made of the same material, and both are lithium cobalt oxide. By making both the first and second particles lithium cobalt oxide, the depth of the second particles embedded in the current collector 11 can be effectively reduced, reducing the probability of foil nibbling, while also increasing the energy density of the battery cell 100.

[0052] Alternatively, the first particles may be lithium cobalt oxide, and the second particles may be carbon particles or inorganic oxides. Since carbon particles and inorganic oxides typically exhibit a non-sharp morphology at a microscopic level, using carbon particles or inorganic oxides as the second particles can further reduce the depth at which the second particles are embedded in the current collector 11, thereby reducing the likelihood of foil nibbling and preventing the second particles from being embedded deeper in the current collector 11 as the battery cell 100 expands, thereby reducing the risk of the positive electrode sheet 10 breaking.

[0053] See also Figures 1 to 3In this embodiment, the second coating layer 13 can be provided at one end or both ends of the first coating layer 12 .

[0054] Furthermore, when the second coating 13 is provided at one end of the first coating 12, the second coating 13 is provided on the current collector 11 of the outermost ring 101 of the battery cell 100. During the cyclic charge and discharge process, the battery will experience volume expansion and contraction, and this repeated deformation will produce a fatigue effect on the material inside the battery cell 100. The outermost ring 101 of the battery cell 100 is directly subjected to the pressure from the inner ring of the battery cell 100 and the external constraints, which makes the fatigue effect of the outermost ring 101 of the battery cell 100 more obvious. Therefore, when the foil gnawing phenomenon occurs in the outermost ring 101 of the battery cell 100, as time goes by and the number of cycles increases, the outermost ring 101 of the battery cell 100 may gradually accumulate damage, eventually leading to the fracture of the electrode piece. Therefore, providing the second coating 13 at the outermost ring 101 of the battery cell 100 can effectively reduce the probability of the foil gnawing phenomenon at the outermost ring 101 of the battery cell 100, thereby reducing the risk of the outermost ring 101 of the battery cell 101 breaking.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced within the present invention.

Claims

1. A positive electrode sheet, characterized in that: The invention comprises a current collector (11), a first coating (12) and a second coating (13), wherein the first coating (12) is arranged on at least one side of the current collector (11), the second coating (13) is arranged on the current collector (11), and along the length direction (a) of the positive electrode sheet, the second coating (13) is adjacent to at least one end of the first coating (12), the first coating (12) comprises first particles, the second coating (13) comprises second particles, and the particle size of the second particles is smaller than the particle size of the first particles.

2. The positive electrode sheet according to claim 1, wherein: The particle size of the second particles is D2, which satisfies the relationship: 0<D2≤20μm.

3. The positive electrode sheet according to claim 2, wherein: The particle size D2 of the second particle satisfies the relationship: 1 μm≤D2≤20 μm; or, 0<D2<1 μm, wherein, when the particle size D2 of the second particle satisfies the relationship: 1 μm≤D2≤20 μm, the surface of the second particle is smooth.

4. The positive electrode sheet according to claim 1, wherein: The particle size of the first particles is D1, which satisfies the relationship: 30 μm≤D1≤70 μm.

5. The positive electrode sheet according to claim 1, wherein: The thickness of the first coating (12) is H1, and the thickness of the second coating (13) is H2, satisfying the relationship:

6. The positive electrode sheet according to claim 1, wherein: The length of the second coating layer (13) is L2, which satisfies the relationship: 0<L2≤2mm.

7. The positive electrode sheet according to claim 1, wherein: The first particles and the second particles are made of the same material, and both are lithium cobalt oxide; or the first particles are lithium cobalt oxide, and the second particles are carbon particles or inorganic oxides.

8. The positive electrode sheet according to claim 1, wherein: When the second coating layer (13) is provided at one end of the first coating layer (12), the second coating layer (13) is provided on the current collector (11) of the outermost circle (101) of the battery cell (100).

9. A battery, characterized in that: The invention comprises a shell and a battery core (100), wherein the shell has a receiving cavity, the battery core (100) is arranged in the receiving cavity, and the battery core (100) comprises the positive electrode sheet according to any one of claims 1 to 8.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

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