Negative pole piece, battery and electric equipment

Abstract

The utility model relates to the technical field of battery materials, in particular to a negative pole piece, a battery and electric equipment. The negative pole piece comprises: a current collector, wherein the current collector comprises a substrate and a microstructure array arranged on at least one surface of the substrate; the active material layer is arranged on the periphery of the microstructure array, and the active material layer comprises a silicon-based active material; wherein the array units of the microstructure array comprise cuboids and / or hemispheres.

Description

Technical Field

[0001] The present application relates to the technical field of battery materials, and in particular to a negative electrode sheet, a battery, and an electrical device. Background Art

[0002] Although silicon-based anode active materials offer high capacity, their application in batteries is limited by poor cycling performance and excessive volume expansion. While one-dimensional structural design of these materials can alleviate these issues to some extent, the battery's kinetic performance and long-term cycling stability remain insufficient. Utility Model Content

[0003] In order to solve the above technical problems, the present application discloses a negative electrode plate, a battery and an electrical device, which can not only solve the expansion problem caused by silicon-based active materials, but also help improve the dynamic performance and long-term cycle stability of the battery.

[0004] In a first aspect, the present application provides a negative electrode plate, the negative electrode plate comprising:

[0005] A current collector, comprising a substrate and a microstructure array provided on at least one surface of the substrate;

[0006] an active material layer, disposed on the periphery of the microstructure array, the active material layer comprising a silicon-based active material;

[0007] Wherein, the array units of the microstructure array include cuboids and / or hemispheres.

[0008] Furthermore, the thickness of the substrate is D, and along a direction perpendicular to the thickness of the substrate, the height of the array unit is H, 1:1≤H / D≤3:1, 10μm≤H≤30μm, 5μm≤D≤30μm.

[0009] Furthermore, when the array unit is a cuboid, the projection length of the cuboid on the plane of the substrate is 8 μm to 60 μm, and the projection width is 8 μm to 60 μm; and / or,

[0010] When the array unit is a hemisphere, the projection diameter of the hemisphere on the plane of the substrate is 10 μm to 60 μm.

[0011] Furthermore, the spacing between adjacent array units is 10 μm to 30 μm.

[0012] Furthermore, the substrate has a first surface and a second surface disposed opposite to each other, the microstructure array is provided on both the first surface and the second surface, and the microstructure array on the first surface is asymmetrically disposed with respect to the microstructure array on the second surface.

[0013] Furthermore, the active material layer has a thickness of 100 nm to 7 μm.

[0014] Furthermore, the substrate is a copper plate, a nickel plate, a titanium plate or a stainless steel plate, the microstructure array is a copper array, a nickel array, a titanium array or a stainless steel array, and the substrate and the microstructure array are made of the same metal.

[0015] Furthermore, the negative electrode plate further includes a carbon coating layer, and the carbon coating layer is arranged on the periphery of the active material layer.

[0016] In a second aspect, the present application provides a battery, comprising the negative electrode plate as described in the first aspect.

[0017] In a third aspect, the present application provides an electrical device, which includes the negative electrode plate as described in the first aspect, or the electrical device includes the battery as described in the second aspect.

[0018] Compared with the prior art, this application has at least the following beneficial effects:

[0019] The negative electrode plate of the embodiment of the present application sets the silicon-based active material on the microstructure array of the current collector, and further optimizes the structure of the microstructure array to set the array unit of the microstructure array as a rectangular parallelepiped and / or a hemisphere. Compared with the cylindrical array unit, on the one hand, it can provide more accommodation space for the volume expansion of the silicon-based active material, and on the other hand, it has a higher current density and electric field strength, which is beneficial to improving the dynamic performance of the battery. On the other hand, it is beneficial to uniformly distribute the expansion stress of the silicon-based active material, thereby improving the long-term cycle stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a schematic structural diagram of the negative electrode sheet according to an embodiment of the present application;

[0022] Figure 2 This is a schematic structural diagram of a current collector in the negative electrode sheet of an embodiment of the present application;

[0023] Figure 3 It is a schematic structural diagram of another current collector in the negative electrode sheet of an embodiment of the present application.

[0024] Description of reference numerals:

[0025] 1. Current collector; 11. Substrate; 12. Microstructure array; 2. Active material layer. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0027] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe this application and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0028] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0029] Furthermore, the terms "installed," "disposed," "provided with," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections, indirect connections through an intermediary, or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0030] Furthermore, the terms "first," "second," etc., are primarily used to distinguish between different devices, elements, or components (which may or may not be of the same type and configuration), and are not intended to indicate or imply the relative importance or quantity of the devices, elements, or components indicated. Unless otherwise specified, "plurality" means two or more.

[0031] Silicon anode materials have a theoretical maximum lithium insertion capacity of 4200 mAh / g, far exceeding current graphite anodes, making them one of the most promising anode materials. However, silicon's inherent conductivity is inferior to graphite, resulting in poor rate performance. Furthermore, silicon's excessive volume expansion during cycling can easily lead to particle fragmentation and damage to the solid electrolyte interface membrane, resulting in rapid capacity decay and limiting its further application.

[0032] Although a cylindrical one-dimensional structure in the shape of nanowires or micrometers can be used to alleviate the problem of volume expansion to a certain extent, compared to a flat structure of the current collector, the above structure has a certain impact on other performance of the battery. In particular, because the shape of the current collector changes, the electric field distribution around it will change differently, ultimately affecting the dynamic performance of the battery. In addition, silicon is a semiconductor, and its poor conductivity is also the main factor limiting its large-scale application.

[0033] Through in-depth analysis of the causes of the above problems, this application proposes a negative electrode plate, a battery and an electrical device, which can effectively solve the volume expansion problem of silicon-based active materials while further promoting the improvement of the battery's dynamic performance and long-term cycle stability.

[0034] In the first aspect, the embodiment of the present application provides a negative electrode sheet, combined with Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of different negative electrode plates in the embodiment of the present application. The negative electrode plate includes:

[0035] The current collector 1 includes a substrate 11 and a microstructure array 12 provided on at least one surface of the substrate 11;

[0036] An active material layer 2 is provided on the periphery of the microstructure array 12, and the active material layer 2 includes a silicon-based active material;

[0037] The array units of the microstructure array 12 include cuboids and / or hemispheres.

[0038] The negative electrode plate of the embodiment of the present application, while setting the silicon-based active material on the microstructure array 12 of the current collector 1, further optimizes the structure of the microstructure array 12 and sets the array unit of the microstructure array 12 to a rectangular parallelepiped and / or a hemisphere. Compared with the cylindrical array unit, on the one hand, it can provide more accommodation space for the volume expansion of the silicon-based active material, and on the other hand, it has a higher current density and electric field strength, which is beneficial to improving the dynamic performance of the battery. On the other hand, it is beneficial to uniformly distribute the expansion stress of the silicon-based active material, thereby improving the long-term cycle stability of the battery.

[0039] First, the present application replaces the flat current collector 1 structure with a current collector 1 having a microstructure array 12, and utilizes the gaps between the array units of the microstructure array 12 to provide more accommodation space for the silicon-based active materials arranged on the periphery of the array units, thereby avoiding rapid attenuation of the battery capacity and improving the long-term stability of the battery.

[0040] Secondly, the present application found that compared with the use of cylinders, the array units of the microstructure array 12 use rectangular parallelepipeds and / or hemispheres, which have higher current density and electric field strength. During the battery charge and discharge cycle, the ions in the electrolyte are driven by the electric field to produce an electrocapillary climb phenomenon. The large electric field strength can make the charge distribution in the electrolyte more uneven, thereby further strengthening the interaction between the electrolyte and the electric field. Since the rectangular parallelepiped and hemispherical array units in the embodiment of the present application have a higher electric field strength, the electrocapillary effect on the electrolyte at various parts of the array unit along its own height direction is also more significant, that is, the faster the electrolyte penetrates from the bottom to the top of the array unit, the faster the ion migration rate and the better the battery's dynamic performance. And since the rectangular parallelepiped and hemispherical array units in the embodiment of the present application have a higher current density, they can better compensate for the adverse effects caused by the weak conductivity of the silicon-based active material itself, thereby further improving the battery's rate performance.

[0041] Furthermore, the electrocapillary action of the electrolyte is faster along the height of the array unit, which means that the rate differences in ion transport at various locations along the height of the array unit are smaller. When silicon-based active material is provided as the negative electrode active material on the periphery of the array unit, the smaller rate differences result in the silicon-based active material expanding to roughly the same degree at various locations, making the overall expansion stress distribution more uniform. Therefore, when the embodiments of the present application use a rectangular and / or hemispherical microstructure array 12, it is more conducive to improving the long-term cycling stability of the battery.

[0042] It is understandable that, taking lithium-ion batteries as an example, silicon-based active materials are important active materials for realizing lithium ion embedding and extraction in the active material layer 2. Therefore, they are the main components in the active material layer 2, and the amount used can be conventional. However, the active material layer 2 can also include other conventional additives to further improve the performance. For example, conventional amounts of conductive agents and other auxiliary agents can be added to the active material layer 2. For example, when the active material layer 2 is only silicon-based active material, its amount is 100wt%; the active material layer 2 can also include 97wt% silicon-based active material and 3wt% conductive agent. These components can be used in conventional amounts, and this application does not limit this.

[0043] In addition, when the array unit of the microstructure array 12 in the embodiment of the present application is a hemisphere, the hemisphere refers to an incomplete sphere formed after cutting a sphere. For example, the hemisphere can be half of a sphere, or it can be a dome-shaped structure formed by cutting a smaller half of a sphere, or it can be a dome-shaped structure formed by cutting more than half of a sphere. The present application does not impose any restrictions on this.

[0044] In addition, the microstructure array 12 is preferably arranged perpendicular to the surface of the substrate 11 .

[0045] Furthermore, the thickness of the substrate 11 is D, and the height of the array unit along the direction perpendicular to the thickness of the substrate 11 is H, 1:1≤H / D≤3:1, 10μm≤H≤30μm, and 5μm≤D≤30μm. Exemplarily, H / D is 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. Exemplarily, H is 10μm, 12μm, 15μm, 20μm, 22μm, 25μm, or 30μm. Exemplarily, D is 5μm, 10μm, 15μm, 20μm, 25μm, or 30μm.

[0046] The height of the array unit is inversely proportional to the current density and directly proportional to the electric field strength. The thickness of the substrate 11 will affect the extent to which the microstructure array 12 improves battery performance, and both the height of the array unit and the thickness of the substrate 11 will affect the overall thickness of the negative electrode sheet. Therefore, in order to take into account the impact on battery dynamics performance, battery rate performance, etc., the embodiment of the present application controls the ratio of the height of the above-mentioned rectangular parallelepiped and / or hemisphere to the thickness of the substrate 11 and the corresponding H and D within the above-mentioned range to better balance the enhancement effect on the electric field strength and current density, as well as the expansion constraint effect on the silicon-based active material.

[0047] In an optional embodiment, as Figure 2 As shown, when the array unit is a cuboid, the projected length of the cuboid on the plane of the substrate 11 is 8μm to 60μm, and the projected width is 8μm to 60μm. The projected length and width of the array unit on the plane of the substrate 11 are proportional to the current density and the electric field strength. In order to take into account the influence of the size of the array unit on the conductivity of the negative electrode sheet and the degree of electrocapillary wetting of the electrolyte, the embodiment of the present application preferably controls the size of the cuboid array unit within the above range. Exemplarily, the projected length of the cuboid on the plane of the substrate 11 is 8μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm or 60μm. The projected width of the cuboid on the plane of the substrate 11 is 8μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm or 60μm.

[0048] In another optional embodiment, as Figure 3As shown, when the array unit is a hemisphere, the projected diameter of the hemisphere on the plane of the substrate 11 is 10μm to 60μm. The projected diameter of the array unit on the plane of the substrate 11 is proportional to the current density and the electric field strength. In order to take into account the influence of the size of the array unit on the conductivity of the negative electrode and the degree of electrocapillary wetting of the electrolyte, the embodiment of the present application preferably controls the size of the hemispherical array unit within the above range. Exemplarily, the projected diameter of the hemisphere on the plane of the substrate 11 is 10μm, 20μm, 30μm, 40μm, 50μm or 60μm.

[0049] Furthermore, the spacing between adjacent array units is 10μm to 30μm. The larger the spacing between adjacent array units, the more conducive it is to alleviating the volume expansion effect of silicon-based active materials, but the smaller the spacing between adjacent array units, the stronger the corresponding electric field strength. This application controls the spacing between adjacent array units to 10μm to 30μm, which can better balance the above two aspects of performance. Exemplarily, the spacing between adjacent array units is 10μm, 12μm, 15μm, 20μm, 25μm, 28μm or 30μm.

[0050] Furthermore, the thickness of the active material layer 2 is 100 nm to 7 μm. When the thickness of the active material layer 2 is controlled within this range, it is beneficial to provide a higher capacity level while ensuring that the sidewall space of the microstructure array 12 effectively constrains the volume expansion of the active material. Exemplarily, the thickness of the active material layer 2 is 100 nm, 500 nm, 1 μm, 2 μm, 3 μm, 5 μm, or 7 μm.

[0051] In the embodiment of the present application, the microstructure array 12 can be arranged only on a single side of the substrate 11, or on both sides. Preferably, the substrate 11 has a first surface and a second surface arranged opposite to each other, and the microstructure array 12 is provided on both the first surface and the second surface. When the microstructure arrays 12 are provided on both sides, the microstructure arrays 12 on the two sides can be arranged asymmetrically (that is, the horizontal projections of the microstructure arrays 12 on the two sides on the substrate 11 are partially staggered or completely staggered), or symmetrically (that is, the horizontal projections of the microstructure arrays 12 on the two sides on the substrate 11 completely overlap). When the microstructure array 12 is set on both sides and asymmetrically, especially when the horizontal projections on the substrate 11 are completely staggered, it has a higher electric field strength and current density, which is beneficial to further improve the dynamic performance and long-term cycle stability of the battery.

[0052] Furthermore, the substrate 11 is a copper plate, nickel plate, titanium plate, or stainless steel plate, and the microstructure array 12 is a copper array, nickel array, titanium array, or stainless steel array, and the substrate 11 and the microstructure array 12 are made of the same metal. The metal current collector 1 described above can provide both good conductivity and good structural support for the silicon-based active material. In particular, when the substrate 11 and the microstructure array 12 are made of the same metal, the bonding force between the metals is stronger, resulting in a more stable structural connection between the substrate 11 and the microstructure array 12.

[0053] Furthermore, the negative electrode plate also includes a carbon coating layer, which is disposed on the periphery of the active material layer 2. The carbon coating layer can effectively prevent direct contact between the active material layer 2 and the electrolyte, reducing the irreversible loss of lithium or sodium sources in the battery while further suppressing volume expansion during the charge and discharge cycle.

[0054] In a second aspect, an embodiment of the present application provides a battery comprising the negative electrode sheet according to the first aspect. The battery may be a lithium secondary battery or a sodium secondary battery.

[0055] In a third aspect, an embodiment of the present application provides an electrical device, which includes the negative electrode plate as described in the first aspect above, or the electrical device includes the battery as described in the second aspect above.

[0056] The negative electrode sheet of the embodiment of the present application will be further described below in conjunction with more specific embodiments.

[0057] Example 1

[0058] This embodiment provides a negative electrode plate, including:

[0059] A copper foil current collector, comprising a substrate and a microstructure array disposed asymmetrically on both sides of the substrate; wherein the array units of the microstructure array are rectangular parallelepipeds, and along a direction perpendicular to the thickness of the substrate, the array units have a height H of 20 μm, a projected length of 30 μm and a width of 30 μm on the substrate plane, a thickness D of 10 μm, and a spacing of 10 μm between adjacent array units;

[0060] The active material layer is arranged on the periphery of the microstructure array. The active material layer is a silicon-based active material layer. The thickness of the active material layer is 2 μm.

[0061] Example 2

[0062] The only difference between this embodiment and embodiment 1 is that the microstructure arrays in this embodiment are arranged on both sides of the substrate and are symmetrically arranged.

[0063] Example 3

[0064] The only difference between this embodiment and embodiment 1 is that the array unit in this embodiment is a hemisphere, and the projection diameter of the array unit on the substrate plane is 40 μm.

[0065] Example 4

[0066] The only difference between this embodiment and embodiment 3 is that the microstructure arrays in this embodiment are arranged on both sides of the substrate and are symmetrically arranged.

[0067] Example 5

[0068] The only difference between this embodiment and embodiment 1 is that the microstructure array in this embodiment is provided on a single surface of the substrate.

[0069] Example 6

[0070] The only difference between this embodiment and embodiment 1 is that the height H of the array unit is 30 μm, the projected length of the array unit on the substrate plane is 60 μm and the width is 40 μm, the thickness D of the substrate is 10 μm, and the spacing between adjacent array units is 30 μm.

[0071] Example 7

[0072] The only difference between this embodiment and embodiment 1 is that the height H of the array unit is 10 μm, the projected length and width of the array unit on the substrate plane are 8 μm and 8 μm, the thickness D of the substrate is 10 μm, and the spacing between adjacent array units is 20 μm.

[0073] Example 8

[0074] The only difference between this embodiment and embodiment 1 is that the height H of the array unit is 30 μm and the thickness D of the substrate is 30 μm.

[0075] Example 9

[0076] The only difference between this embodiment and embodiment 1 is that the negative electrode plate further includes a carbon coating layer provided on the periphery of the active material layer.

[0077] Comparative Example 1

[0078] The only difference between this comparative example and Example 1 is that the microstructure array in this comparative example is a cylinder, and the projected diameter of the cylinder on the substrate plane is 30 μm.

[0079] Comparative Example 2

[0080] The only difference between this comparative example and comparative example 1 is that the microstructure arrays in this embodiment are arranged on both sides of the substrate and are symmetrically arranged.

[0081] The finite element software COMSOL Multiphysics 6.1 was used to simulate the average electric field strength and average current density of the current collectors in the negative electrode sheets of Examples 1 to 4 and Comparative Examples 1 to 2. The results are shown in Table 1 below.

[0082] Table 1 Electrical performance test results of Examples 1 to 4 and Comparative Examples 1 to 2

[0083] Average electric field strength (V / m) <![CDATA[Average current density (A / m 2 )]]> Example 1 3.90 2.34 Example 2 3.61 2.16 Example 3 3.82 2.29 Example 4 3.60 2.16 Comparative Example 1 2.62 1.57 Comparative Example 2 2.43 1.46

[0084] From the comparison in the above table, it can be seen that the electric field intensity and current density of the rectangular array unit or the hemispherical array unit are higher than those of the cylindrical array unit. It can be seen that the rectangular array unit or the hemispherical array unit can make the electrocapillary climbing effect of the electrolyte at various parts in the height direction of the array unit more obvious, which is not only more conducive to improving the dynamic performance of the battery, but also more conducive to making the expansion stress distribution of the negative electrode sheet tend to be uniform, which is beneficial to the long-term cycle stability of the battery and can better compensate for the impact caused by the weak conductivity of the silicon-based active material.

[0085] In addition, by comparing Examples 1 to 4, it can be seen that the asymmetric arrangement of the microstructure array is more conducive to improving the electric field strength and current density than the symmetric arrangement, and thus can better improve the battery kinetic performance and long-term stability.

[0086] The above is a detailed introduction to the technical solutions disclosed in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the technical solutions and core points of the embodiments of the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present application.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate comprises: A current collector, comprising a substrate and a microstructure array provided on at least one surface of the substrate; an active material layer, disposed on the periphery of the microstructure array, the active material layer comprising a silicon-based active material; Wherein, the array units of the microstructure array include cuboids and / or hemispheres.

2. The negative electrode sheet according to claim 1, characterized in that: The thickness of the substrate is D. Along a direction perpendicular to the thickness of the substrate, the height of the array unit is H, 1:1≤H / D≤3:1, 10μm≤H≤30μm, 5μm≤D≤30μm.

3. The negative electrode sheet according to claim 1, characterized in that: When the array unit is a cuboid, the projection length of the cuboid on the plane of the substrate is 8 μm to 60 μm, and the projection width is 8 μm to 60 μm; and / or, When the array unit is a hemisphere, the projection diameter of the hemisphere on the plane of the substrate is 10 μm to 60 μm.

4. The negative electrode sheet according to claim 1, characterized in that: The spacing between adjacent array units is 10 μm to 30 μm.

5. The negative electrode sheet according to claim 1, characterized in that: The substrate has a first surface and a second surface disposed opposite to each other. The microstructure array is disposed on both the first surface and the second surface, and the microstructure array on the first surface is asymmetrically disposed with respect to the microstructure array on the second surface.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The active material layer has a thickness of 100 nm to 7 μm.

7. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The substrate is a copper plate, a nickel plate, a titanium plate or a stainless steel plate, the microstructure array is a copper array, a nickel array, a titanium array or a stainless steel array, and the substrate and the microstructure array are made of the same metal.

8. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The negative electrode plate further includes a carbon coating layer, which is disposed on the periphery of the active material layer.

9. A battery, characterized in that: The battery comprises the negative electrode sheet according to any one of claims 1 to 8.

10. An electrical device, characterized in that: The electrical device includes the negative electrode sheet according to any one of claims 1 to 8, or the electrical device includes the battery according to claim 9.

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