Positive electrode sheet, battery, and battery pack

Abstract

A positive electrode sheet, a battery, and a battery pack. The positive electrode sheet comprises a current collector, a first positive electrode active substance layer, and a second positive electrode active substance layer. The current collector comprises a first surface and a second surface opposite to the first surface; the first positive electrode active substance layer is separately disposed on the first surface and the second surface of the current collector, and the first positive electrode active substance layer comprises first positive electrode active particles; and the second positive electrode active substance layer is separately disposed on the side of the first positive electrode active substance layer away from the first surface and the second surface.

Description

Positive electrode, battery and battery pack

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on October 30, 2023, with application number 202322924962.3. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a positive electrode sheet, a battery, and a battery pack. Background Art

[0003] As one of the most important electrochemical energy storage devices, lithium-ion batteries have seen their applications expand from consumer electronics and power tools to emerging fields such as new energy electric vehicles, electric ships, electric aircraft, and robotics. These applications require not only higher capacity but also higher energy density. To achieve higher capacity, the electrode thickness has been increased. SUMMARY OF THE INVENTION

[0004] However, this arrangement results in poor electrolyte wetting of the electrode near the current collector, reduced ion transfer channels, and increased transmission resistance.

[0005] In a first aspect, the present application provides a positive electrode sheet, comprising:

[0006] a current collector comprising a first surface and a second surface opposite to the first surface;

[0007] A first positive electrode active material layer is provided on the first side and the second side of the current collector, and the first positive electrode active material layer includes first positive electrode active particles; and

[0008] The second positive electrode active material layer is respectively arranged on the side of the first positive electrode active material layer away from the first surface and the second surface; the second positive electrode active material layer contains second positive electrode active particles; the particle size of the first positive electrode active particles is larger than the particle size of the second positive electrode active particles; the gaps between the multiple first positive electrode active particles are larger than the gaps between the multiple second positive electrode active particles.

[0009] In a second aspect, the present application also provides a battery comprising a positive electrode sheet.

[0010] In a third aspect, the present application also provides a battery pack, comprising a battery. Beneficial effects

[0011] The positive electrode sheet provided by the present application includes at least the following beneficial effects: the positive electrode sheet includes a current collector, a first positive electrode active material layer and a second positive electrode active material layer, the current collector includes a first surface and a second surface opposite to the first surface; the first positive electrode active material layer is respectively arranged on the first surface and the second surface of the current collector, and the first positive electrode active material layer includes first positive electrode active particles; the second positive electrode active material layer is respectively arranged on the side of the first positive electrode active material layer away from the first surface and the second surface; the second positive electrode active material layer contains second positive electrode active particles; the particle size of the first positive electrode active particles is larger than the particle size of the second positive electrode active particles; the gap between multiple first positive electrode active particles is larger than the gap between multiple second positive electrode active particles, which ensures that the ion channel is not blocked while also ensuring that the electron transmission channel is unobstructed, so that the battery will not suffer from poor high-rate charge and discharge performance due to the increase in the thickness of the electrode sheet during the charge and discharge process. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is a schematic structural diagram of a positive electrode sheet provided in an embodiment of the present application.

[0013] FIG2 is a microscopic schematic diagram of a positive electrode sheet provided in an embodiment of the present application.

[0014] FIG3 is a schematic diagram of a partial structure of a current collector provided in an embodiment of the present application.

[0015] FIG4 is a partial microscopic schematic diagram of a current collector provided in an embodiment of the present application.

[0016] Description of reference numerals:

[0017] 100, positive electrode sheet; 10, current collector; 20, first positive electrode active material layer; 201, first positive electrode active particles; 30, second positive electrode active material layer; 301, second positive electrode active particles; 4, first side; 5, second side. Modes for Carrying Out the Invention

[0018] In the description of this application, unless otherwise specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0019] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, with the first feature having a higher horizontal height than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly below and obliquely below the second feature, with the first feature having a lower horizontal height than the second feature.

[0020] In the description of this embodiment, terms such as "upper," "lower," "left," "right," "front," and "rear" are used to refer to positions or locations based on the positions or locations shown in the accompanying drawings. These terms are intended to facilitate description and simplify operation, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and do not have any special meanings.

[0021] Referring to FIG. 1 and FIG. 2 , the present application provides a positive electrode sheet 100 , including:

[0022] The current collector 10 includes a first surface 4 and a second surface 5 opposite to the first surface 4;

[0023] The first positive electrode active material layer 20 is respectively provided on the first surface 4 and the second surface 5 of the current collector 10 . The first positive electrode active material layer 20 includes first positive electrode active particles 201 ; and

[0024] The second positive electrode active material layer 30 is respectively arranged on the side of the first positive electrode active material layer 20 away from the first surface 4 and the second surface 5; the second positive electrode active material layer 30 includes second positive electrode active particles 301; the particle size of the first positive electrode active particles 201 is larger than the particle size of the second positive electrode active particles 301; the gaps between multiple first positive electrode active particles 201 are larger than the gaps between multiple second positive electrode active particles 301.

[0025] The current collector 10 may be, for example, aluminum foil. The first positive electrode active material layer 20 is disposed on the first side 4 and the second side 5 of the current collector 10. The second positive electrode active material layer 30 is disposed on both sides of the first positive electrode active material layer 20 away from the current collector 10, forming a double-sided coated positive electrode sheet.

[0026] The gaps between the plurality of first positive electrode active particles 201 and the gaps between the plurality of second positive electrode active particles serve as ion channels. The first positive electrode active particles 201 have larger particle sizes, resulting in larger ion channels. The second positive electrode active particles 301 have smaller particle sizes, resulting in smaller ion channels. When ions travel from the second positive electrode active material layer 30 through the first positive electrode active material layer 20 and into the current collector 10, the ion transmission path becomes longer. To ensure that the ion transmission rate is not affected, the ion channels in the first positive electrode active material layer 20 are enlarged to ensure that the ion channels are unobstructed.

[0027] In one embodiment of the present application, the first positive active material layer 20 further includes a first conductive agent, and the second positive active material layer 30 further includes a second conductive agent, and the content of the second conductive agent is greater than that of the first conductive agent.

[0028] Referring to Figure 2 , the first positive electrode active particles 201 in the first positive electrode active material layer 20 have a larger particle size and a lower content of the first conductive agent. The second positive electrode active particles 301 in the second positive electrode active material layer 30 have a smaller particle size and a higher content of the second conductive agent. The particle size of the first positive electrode active particles 201 can be 11 μm to 15 μm, and the content of the first conductive agent can be 2% to 4%. The particle size of the second positive electrode active particles 301 is 5 μm to 10 μm, and the content of the second conductive agent is 5% to 8%.

[0029] The first conductive agent and the second conductive agent can help electrons transport among the first positive electrode active material layer 20, the second positive electrode active material layer 30, and the current collector 10. When electrons are transported from the current collector 10 to the second positive electrode active material layer 30, as the electron transport path becomes longer, the resistance encountered increases. To ensure smooth electron transport, the content of the second conductive agent is increased. That is, when electrons are transported from the first positive electrode active material layer 20 to the second positive electrode active material layer 30, since the content of the second conductive agent is greater than that of the first conductive agent, the electrons will not encounter greater resistance due to the longer transport path, thereby ensuring smooth electron transport.

[0030] In one embodiment of the present application, the content of the first conductive agent is 2%-4%, and the content of the second conductive agent is 5%-8%.

[0031] In one embodiment of the present application, the first positive electrode active material layer 20 further includes a first binder layer, and the second positive electrode active material layer 30 further includes a second binder layer, wherein the first positive electrode active particles 201 and the first conductive agent are dispersed in the first binder layer, and the second positive electrode active particles 301 and the second conductive agent are dispersed in the second binder layer.

[0032] In one embodiment of the present application, the first adhesive layer includes first adhesive particles, the second adhesive layer includes second adhesive particles, and the content of the first adhesive particles is greater than the content of the second adhesive particles.

[0033] The first bonding particles mix and connect the first conductive agent and the first positive active particles 201, and are connected to the first side 4 and the second side 5 of the current collector 10. The second bonding particles mix and connect the second conductive agent and the second positive active particles 301, and are connected to both sides of the second positive active material layer 30 away from the current collector 10.

[0034] In one embodiment of the present application, the content of the first adhesion particles is 5%-8%, and the content of the second adhesion particles is 2%-4%.

[0035] In one embodiment of the present application, the particle size of the first positive electrode active particles 201 is 11 um-15 um, and the particle size of the second positive electrode active particles 301 is 5 um-10 um.

[0036] In one embodiment of the present application, the first positive electrode active particles 201 and the second positive electrode active particles 301 are LiNi x Co y Mn (1-x-y) O2 particles, wherein 0.8<x<0.93, 0.05<y<0.1.

[0037] The first positive electrode active particles 201 and the second positive electrode active particles 301 have different particle sizes and are matched with conductive agents in different proportions. While ensuring that the ion channel is not blocked, the electron transmission channel is also unobstructed, so that during the charge and discharge process of the battery, the high-rate charge and discharge performance will not deteriorate due to the increase in the thickness of the electrode.

[0038] Example 1

[0039] The first positive electrode active particles 201 and the second positive electrode active particles 301 are LiNi x Co y Mn (1-x-y) O2 particles, where 0.8 < x < 0.93, and 0.05 < y < 0.1. When the particle size of the first positive electrode active particles 201 is 11 μm, the content of the first conductive agent is 2%, and the content of the first adhesion particles is 5%. Due to the larger particle size of the first positive electrode active particles 201, the gaps between them after rolling are also larger, which means that the ion transmission path is larger.

[0040] When the particle size of the second positive electrode active particles 301 is 5 μm, the content of the second conductive agent is 5%, and the content of the second adhesion particles is 2%. Since the particle size of the second positive electrode active particles 301 is small, the gaps between them after rolling are also small, that is, the ion transmission path is small.

[0041] When ions enter the first positive active material layer 20 from the second positive active material layer 30 , the ion transmission path becomes longer. Since the ion channel of the first positive active material layer 20 is larger, the ion channel is ensured to be unobstructed.

[0042] Electrons enter the second positive electrode active material layer 30 from the first positive electrode active material layer 20 , and the electron transmission path becomes longer. Since the content of the second conductive agent is higher than that of the first conductive agent, the electron channel is ensured to be unobstructed.

[0043] 3 and 4 , the materials of the first positive electrode active particles 201 and the second positive electrode active particles 301 can be the same or different. When the materials of the first positive electrode active particles 201 and the second positive electrode active particles 301 are the same, they are LiNi x Co y Mn (1-x-y) O2 particles, wherein 0.8<x<0.93, 0.05<y<0.1, can be prepared into a positive electrode sheet 100 by the following steps:

[0044] Step S1: providing a first positive electrode active particle 201, a first conductive agent and a first binder layer;

[0045] The first positive electrode active particles 201 have a relatively large particle size, and a relatively low content of the first conductive agent, for example, 11 μm to 15 μm, a first conductive agent content of 2% to 4%, and a first adhesion particle content of 5% to 8%.

[0046] Step S2: mixing the first positive electrode active particles 201 , the first conductive agent, and the first binder layer and applying the mixture to the first surface 4 of the current collector 10 to form the first positive electrode active material layer 20 on the first surface 4 ;

[0047] Step S3: drying the current collector 10 having the first positive electrode active particles 201, the first conductive agent and the first binder layer, for example, once;

[0048] Step S4: providing a second positive electrode active particle 301, a second conductive agent and a second binder layer;

[0049] The second positive electrode active particles 301 have a relatively small particle size and a relatively high content of the second conductive agent, with the particle size of the second positive electrode active particles 301 being 5 μm to 10 μm, the content of the second conductive agent being 5% to 8%, and the content of the second adhesion particles being 2% to 4%.

[0050] Step S5: mixing the second positive electrode active particles 301, the second conductive agent, and the second binder layer and applying the mixture to a surface of the first positive electrode active material layer 20 away from the first surface 4 to form the second positive electrode active material layer 30 on the surface;

[0051] Step S6: drying the entirety of the second positive electrode active particles 301 , the second conductive agent, and the second binder layer, as well as the first positive electrode active particles 201 , the first conductive agent, and the first binder layer. The drying times may be, for example, 2 times.

[0052] The second side 5 of the current collector 10 is coated using the above steps. The steps of coating the second side 5 of the current collector 10 are not repeated here. The formed sample is rolled and cut to form a double-sided coated positive electrode sheet 100.

[0053] Secondly, an embodiment of the present application provides a battery, including a positive electrode sheet 100 and a negative electrode sheet, an electrolyte, a separator, etc., which are wound to form a battery cell, and a battery is formed, which will not be described in detail here.

[0054] On the third aspect, an embodiment of the present application provides a battery pack, including a battery having a positive electrode sheet 100 and a negative electrode sheet, an electrolyte, a diaphragm and other components. Multiple battery arrays are arranged to form a battery pack, which can be used, for example, in consumer electronic products, power tools, new energy electric vehicles, electric ships, electric aircraft or robots and other electronic devices, and the specific application shall prevail.

[0055] The positive electrode sheet provided in the present application includes at least the following working processes or principles: the first positive electrode active material layer 20 is arranged on the first side 4 and the second side 5 of the current collector 10, the second positive electrode active material layer 30 is arranged on the side of the first positive electrode active material layer 20 away from the current collector 10, the particle size of the first positive electrode active particles 201 is larger than the particle size of the second positive electrode active particles 301, the content of the first conductive agent is less than the content of the second conductive agent, so that particles of different sizes are matched with conductive agents of different proportions, and double-sided coating is achieved, while ensuring that the ion channel is not blocked, the electron transmission channel is also guaranteed to be unobstructed, so that during the charging and discharging process of the battery, the high-rate charging and discharging performance will not deteriorate due to the increase in the thickness of the electrode sheet.

Claims

1. A positive electrode sheet, comprising: A current collector (10) comprising a first surface (4) and a second surface (5) opposite to the first surface (4); A first positive electrode active material layer (20) is respectively disposed on the first surface (4) and the second surface (5) of the current collector (10), wherein the first positive electrode active material layer (20) comprises first positive electrode active particles (201); and The second positive electrode active material layer (30) is respectively arranged on the side of the first positive electrode active material layer (20) away from the first surface (4) and the second surface (5); the second positive electrode active material layer (30) comprises second positive electrode active particles (301); the particle size of the first positive electrode active particles (201) is larger than the particle size of the second positive electrode active particles (301); and the gaps between the plurality of the first positive electrode active particles (201) are larger than the gaps between the plurality of the second positive electrode active particles (301).

2. The positive electrode sheet according to claim 1, wherein: The first positive electrode active material layer (20) further includes a first conductive agent, and the second positive electrode active material layer (30) further includes a second conductive agent, wherein the content of the second conductive agent is greater than that of the first conductive agent.

3. The positive electrode sheet according to claim 2, wherein: The content of the first conductive agent is 2%-4%, and the content of the second conductive agent is 5%-8%.

4. The positive electrode sheet according to claim 3, wherein: The first positive electrode active material layer (20) further includes a first binder layer, and the second positive electrode active material layer (30) further includes a second binder layer, wherein the first positive electrode active particles (201) and the first conductive agent are dispersed in the first binder layer, and the second positive electrode active particles (301) and the second conductive agent are dispersed in the second binder layer.

5. The positive electrode sheet according to claim 4, wherein: The first adhesive layer includes first adhesive particles, the second adhesive layer includes second adhesive particles, and the content of the first adhesive particles is greater than the content of the second adhesive particles.

6. The positive electrode sheet according to claim 5, wherein: The content of the first adhesion particles is 5%-8%, and the content of the second adhesion particles is 2%-4%.

7. The positive electrode sheet according to any one of claims 1 to 6, wherein: The particle size of the first positive electrode active particles (201) is 11 um-15 um, and the particle size of the second positive electrode active particles (301) is 5 um-10 um.

8. The positive electrode sheet according to any one of claims 1 to 6, wherein: The first positive electrode active particle (201) and the second positive electrode active particle (301) are LiNi x Co y Mn (1-x-y) O2 particles, wherein 0.8<x<0.93, 0.05<y<0.

1.

9. A battery comprising the positive electrode sheet according to any one of claims 1 to 8.

10. A battery pack comprising a plurality of batteries according to claim 9.

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