Electrochemical device and electronic apparatus

Abstract

The electrochemical device comprises a current collector, an active material layer and a coating, the coating is arranged on the active material layer, the coating is provided with a first end part and a second end part which are oppositely arranged along the length direction of the current collector, and the first end part and the second end part are arranged along the width direction of the current collector. The coating is provided with a third end part and a fourth end part which are oppositely arranged; the first end part and the second end part are connected to the current collector, and / or the third end part and the fourth end part are connected to the current collector; the coating is provided with at least one through hole. The through holes are formed in the coating, more electrolyte can be infiltrated to the depth of the active material layer, an original fixed diffusion channel with the low diffusion rate is replaced, a faster substance transfer channel is provided, the overall impedance of the electrode plate of the electrochemical device is reduced, meanwhile, the through holes provide a buffer space for strain of the active material layer, and the resistance of the electrode plate of the electrochemical device is improved. Expansion of the pole piece can be reduced, and improvement of long-term cycle life and maintenance of high energy density of an electrochemical device are facilitated.

Description

Electrochemical devices and electronic devices Technical Field

[0001] Some embodiments of the present application relate to the field of electrochemical technology, and more particularly to an electrochemical device and an electronic device. Background Art

[0002] Electrochemical devices are the source of power for electronic devices and are crucial for ensuring their normal operation. With the increasing popularity of electronic devices such as mobile phones and laptops, the capacity requirements for electrochemical devices are also increasing.

[0003] During the charge and discharge process of the electrochemical device, the expansion of the electrochemical device can easily cause the active material layer to pulverize and fall off from the electrode, causing the active material layer to lose electrical contact with the conductive network such as the current collector, ultimately leading to rapid attenuation and deterioration of the electrode capacity.

[0004] Summary of the Invention

[0005] Some embodiments of the present application aim to provide an electrochemical device and an electronic device, which can at least alleviate the expansion of the electrochemical device.

[0006] In order to alleviate the above technical problems, some embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides an electrochemical device comprising a current collector and an active material layer coated on the current collector, the electrochemical device further comprising a coating, the coating being disposed on the active material layer. Along the length direction of the current collector, the coating has a first end and a second end disposed oppositely, and along the width direction of the current collector, the coating has a third end and a fourth end disposed oppositely. The first end and the second end are connected to the current collector, and / or the third end and the fourth end are connected to the current collector. The coating is provided with at least one through-hole, the through-hole being configured to communicate with the active material layer.

[0008] The coating is applied to the surface of the active material layer to reduce the free expansion space of the active material layer, ensuring that the active material layer maintains good contact with the current collector after long-term charge-discharge cycles of the electrochemical device. The creation of through-holes in the coating allows more electrolyte to penetrate deep into the active material layer, replacing the inherently slower solid-phase diffusion channels and providing a faster material transfer pathway, which helps reduce the overall impedance of the electrochemical device's electrode. Furthermore, the through-holes provide a buffer for strain in the active material layer, reducing electrode expansion and contributing to improved long-term cycle life and high energy density of the electrochemical device.

[0009] According to some embodiments of the present application, the active material layer includes a first active material and a second active material, wherein the gram capacity of the first active material is greater than the gram capacity of the second active material. The first active material includes at least one of elemental silicon, a silicon-oxygen compound, a silicon-carbon composite, and a silicon alloy; and / or the second active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, and mesocarbon microbeads. The first active material is silicon, the second active material is carbon, and the mass content of the first active material in the active material layer is 1% to 45%.

[0010] The theoretical gram capacity of silicon is 4200mAh / g, which is greater than the gram capacity of carbon of 372mAh / g. The use of silicon active materials can increase the capacity of the electrode, and filling the silicon active materials with more stable structures with carbon active materials can serve as a volume buffer matrix for the silicon active materials.

[0011] According to some embodiments of the present application, the coating is provided with a plurality of through-holes, and along the thickness direction of the current collector, the coating has a first side and a second side disposed opposite each other. Compared to the first side, the second side is closer to the active material layer; based on the surface area of ​​the first side, the area of ​​the plurality of through-holes accounts for 10% to 30%. The through-hole area within the aforementioned range can impart good dynamics to the coating while maintaining the original mechanical strength of the coating, effectively reducing the occurrence of irreversible plastic strain in the coating after long-term cycling.

[0012] The plurality of through holes are distributed in an array on the coating. The plurality of through holes are spaced apart. The uniform distribution of the array facilitates the electrolyte to penetrate into all locations of the active material layer, facilitating sufficient contact between the active material layer and the electrolyte.

[0013] According to some embodiments of the present application, the through hole satisfies 0<R≤5μm, where R is the radius of the through hole. The micron-scale porous coating can maintain a stable morphology for a long time during the charge and discharge cycle of the electrochemical device, thereby reducing the volume expansion of the electrode.

[0014] According to some embodiments of the present application, the tensile strength of the coating is greater than that of the active material layer. The coating has higher mechanical strength and tensile strength, can withstand greater stress without inducing plastic strain, and is coated on the surface of the active material layer to reduce the free expansion space of the active material layer, thereby ensuring that the active material layer maintains good contact with the current collector after long-term charge and discharge cycles of the electrochemical device.

[0015] According to some embodiments of the present application, along the thickness direction of the current collector, the active material layer has a third surface and a fourth surface arranged opposite to each other; compared with the third surface, the fourth surface is close to the current collector; along the length direction of the current collector, the active material layer includes a first side surface and a second side surface arranged opposite to each other; along the width direction of the current collector, the active material layer includes a third side surface and a fourth side surface arranged opposite to each other; the coating includes a first portion arranged on the third surface; along the length direction of the current collector, the coating includes a first extension portion and a second extension portion arranged opposite to each other; along the width direction of the current collector, the coating includes a third extension portion and a fourth extension portion arranged opposite to each other; the first extension portion includes the first end and extends to the first side surface; the second extension portion includes the second end and extends to the second side surface.

[0016] A corresponding extension portion is provided in each direction of the active material layer so that the coating covers the active material layer, wherein the first extension portion, the second extension portion, the third extension portion and the fourth extension portion can all be connected and fixed to the current collector to limit the expansion of the active material layer.

[0017] According to some embodiments of the present application, the through hole is provided in the first portion, and at least one of the first extension portion, the second extension portion, the third extension portion, and the fourth extension portion is provided with the through hole. Each extension portion may be provided with a through hole to facilitate the electrolyte to penetrate into the active material layer from all directions.

[0018] The coating has a plurality of through holes, including a first through hole and a second through hole; the first through hole is formed in the first portion; and the second through hole is formed in at least one of the first extension portion and the second extension portion. The third extension portion includes the third end and extends to the third side surface; and the fourth extension portion includes the fourth end and extends to the fourth side surface.

[0019] According to some embodiments of the present application, the coating satisfies at least one of the following conditions: (a) the first extension completely covers the first side of the active material layer; (b) the second extension completely covers the second side of the active material layer; (c) the third extension completely covers the third side of the active material layer; (d) the fourth extension completely covers the fourth side of the active material layer. The first, second, third, and fourth extensions are all connected to the current collector.

[0020] According to some embodiments of the present application, the coating satisfies the following conditions: (a) along the length direction of the current collector, the thickness of the first extension portion and the second extension portion are both 0.5 μm to 10 μm; (b) along the width direction of the current collector, the thickness of the third extension portion and the fourth extension portion are both 0.5 μm to 10 μm; (c) along the direction from the coating to the current collector, the thickness of the first portion is 0.5 μm to 10 μm.

[0021] According to some embodiments of the present application, the coating satisfies the following conditions: (a) along the length direction of the current collector, the thickness of the first extension portion and the second extension portion are both 1 μm to 8 μm; (b) along the width direction of the current collector, the thickness of the third extension portion and the fourth extension portion are both 1 μm to 8 μm; (c) along the direction from the coating to the current collector, the thickness of the first portion is 1 μm to 8 μm.

[0022] When designing the coating thickness, the coating needs to have a certain lower limit of thickness to ensure the coating's inhibitory effect on electrode expansion, and also avoid the risk of excessive coating thickness deteriorating the energy density of the electrochemical device. In the embodiments of the present application, the coating thickness can be selected from 0.5 microns to 10 microns, and in some embodiments, 1 micron to 8 microns can be used.

[0023] According to some embodiments of the present application, the axis of the through hole is parallel to the direction from the coating layer to the active material layer to facilitate the entry and exit of the electrolyte.

[0024] According to some embodiments of the present application, in a second aspect, the present application further proposes an electronic device comprising the electrochemical device as described in any of the above embodiments.

[0025] The above description is only an overview of the technical solution of this application. In order to more clearly understand the technical means of this application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of this application more obvious and easy to understand, the specific implementation methods of this application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] One or more embodiments are exemplarily illustrated by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0027] FIG1 is a schematic structural diagram of an electrochemical device according to some embodiments of the present application;

[0028] FIG2 is a cross-sectional view taken along line AA of FIG1 ;

[0029] FIG3 is a schematic structural diagram of a pole piece in some embodiments of the present application;

[0030] FIG4 is an exploded view of a pole piece according to some embodiments of the present application;

[0031] FIG5 a is a schematic cross-sectional view of a pole piece according to some embodiments of the present application;

[0032] FIG5b is an exploded view of FIG5a;

[0033] FIG6 is a schematic diagram of through-hole arrangement in some embodiments of the present application;

[0034] FIG7 is a schematic diagram of through-hole arrangement in some embodiments of the present application;

[0035] FIG8 is a schematic diagram showing the relationship between expansion and cycle number of electrochemical devices according to some embodiments of the present application;

[0036] FIG9 is a schematic diagram showing the relationship between expansion and cycle number of electrochemical devices according to some embodiments of the present application;

[0037] FIG10 is a schematic diagram showing the relationship between the expansion of a pole piece and the number of cycles in some embodiments of the present application;

[0038] FIG11 is a schematic diagram showing the relationship between electrode expansion and energy density loss of an electrochemical device and coating thickness according to some embodiments of the present application;

[0039] FIG12 is a schematic diagram showing the relationship between discharge rate and discharge capacity in some embodiments of the present application;

[0040] FIG13 is a schematic diagram showing the relationship between the SOC state and DCR of an electrochemical device according to some embodiments of the present application;

[0041] FIG14 is a schematic diagram showing the relationship between the SOC state and Rss of an electrochemical device according to some embodiments of the present application;

[0042] FIG15 is a schematic diagram showing the relationship between the number of cycles and the capacity retention rate in some embodiments of the present application;

[0043] FIG16 is a schematic diagram showing the relationship between the number of cycles and the capacity retention rate of some embodiments of the present application.

[0044] In the picture:

[0045] 100. Electrochemical device;

[0046] 10. Negative electrode;

[0047] 11. Current collector; 111. Long side; 112. Wide side; 113. Thickness side;

[0048] 11a, main surface;

[0049] 12. Active material layer;

[0050] 12a, third side; 12b, first side; 12c, third side; 12d, fourth side;

[0051] 13. Coating; 131. Through hole; 131a. First through hole; 131b. Second through hole; 131c. Third through hole; 132. First end; 133. Third end; 134. Fourth end;

[0052] 13a, first portion; 13a1, first surface; 13a2, second surface; 13b, first extension; 13c, third extension;

[0053] 20. Positive electrode;

[0054] 30. Isolation film. DETAILED DESCRIPTION

[0055] In order to facilitate the understanding of the present application, the present application is described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is described as being "connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "upper", "lower", "inside", "outside" and similar expressions used in this specification are for illustrative purposes only.

[0056] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the relevant listed items.

[0057] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other. "Multiple" in this specification means more than two.

[0058] Currently, the most widely used negative electrode active material for lithium-ion electrochemical devices is graphite. The specific capacity of graphite is relatively low (372mAh / g), which is difficult to meet the growing demand for high-capacity lithium-ion electrochemical devices. Silicon reserves are abundant and have a much higher specific capacity than graphite (4200mAh / g, based on Li 22Si4 alloy), so silicon is considered to be the most promising next-generation negative electrode material. The inventors of this application noticed that during the charge and discharge process of the electrochemical device, the lithium insertion and removal reaction of silicon is accompanied by a huge volume change (>300%, based on Li 22 Si4 alloy), which can easily cause the silicon active material to pulverize and fall off from the electrode, causing the active material layer to lose electrical contact with the conductive network such as the current collector, and ultimately leading to rapid attenuation and deterioration of the electrode capacity.

[0059] To alleviate the above-mentioned problems, on the one hand, the embodiments of the present application propose an electrochemical device 100. In the embodiments of the present application, the electrochemical device 100 is the smallest unit constituting the electrochemical device or the electrochemical device module, and is the place where the conversion of electrical energy and chemical energy is specifically realized. Please refer to Figures 1 and 2, which respectively show the structure of the electrochemical device 100 and the cross-section of the electrochemical device 100. The electrochemical device 100 includes a negative electrode sheet 10, a positive electrode sheet 20 and a separator 30. The negative electrode sheet 10 and the positive electrode sheet 20 are arranged at intervals, and the separator 30 is arranged between the negative electrode sheet 10 and the positive electrode sheet 20 to separate the two. The negative electrode sheet 10, a separator 30, the positive electrode sheet 20 and another separator 30 are stacked and wound into a bare cell of the electrochemical device 100; it is worth mentioning that in other embodiments, the bare cell can also be a stacked structure. Taking the negative electrode sheet 10 as an example, the negative electrode sheet 10 includes a current collector 11 , an active material layer 12 and a coating 13 . The active material layer 12 is coated on at least one surface of the current collector 11 , and the coating 13 is disposed on the active material layer 12 .

[0060] Regarding the above-mentioned current collector 11, please refer to Figures 3 and 4. The current collector 11 is a flat strip-shaped structure as a whole, and the thickness of each part is basically the same. The thickness of the current collector 11 is generally between 3 micrometers (μm) and 20 micrometers. The current collector 11 has a long side 111, a wide side 112, and a thickness side 113. The long side 111 is the side extending along the length direction (X direction) of the current collector 11 when it is unfolded and flat. The wide side 112 is the side extending along the width direction (Y direction) of the current collector 11 when it is unfolded and flat. The thickness side 113 is the side extending along the thickness direction (Z direction) of the current collector 11 when it is unfolded and flat. The current collector 11 has two main surfaces 11a, and the two main surfaces 11a are jointly defined by the above-mentioned long side 111 and the wide side 112. The two main surfaces 11a are arranged opposite to each other along the extension direction of the above-mentioned thickness side 113. The active material layer 12 can be coated on both main surfaces 11a. The current collector 11 is a conductive substrate for the electrode. Different materials can be selected as the current collector 11 of the electrode according to different types of the electrode. In this embodiment, a negative electrode 10 is used, and copper foil can be selected as the current collector 11.

[0061] Regarding the active material layer 12, please refer to Figures 4 and 5b. The active material layer 12 is the core material layer of the electrochemical device 100. The active material layer 12 is coated on at least one surface of the current collector 11, for example, on one of the two main surfaces 11a of the current collector 11, or both main surfaces 11a of the current collector 11 are coated with the active material layer 12. The active material layer 12 includes active materials, conductive agents, adhesives, and deionized water. After mixing, the above materials are stirred evenly and coated on the surface of the current collector 11, thereby obtaining the active material layer 12. The specific composition of the active material is actually diverse. In the present application, the active material layer 12 includes a first active material and a second active material, wherein the gram capacity of the first active material is greater than the gram capacity of the second active material.

[0062] In some embodiments, the first active material comprises at least one of the group consisting of elemental silicon, silicon oxides, silicon-carbon composites, and silicon alloys. The second active material comprises at least one of the group consisting of graphite, soft carbon, hard carbon, carbon fibers, and mesocarbon microbeads.

[0063] Specifically, as an example, the first active material is silicon, and the second active material is carbon. The theoretical gram capacity of silicon is 4200 mAh / g, which is greater than the gram capacity of carbon of 372 mAh / g. The use of silicon active material can increase the capacity of the electrochemical device, and the carbon active material with a more stable structure is filled between the silicon active materials, which can serve as a volume buffer matrix for the silicon active material. Among them, the mass fraction of silicon in the active material layer 12 can be selected from 1% to 45%, and the mass content of silicon can be measured by element analysis.

[0064] Regarding the above-mentioned coating 13, please refer to Figures 3 to 5b. The coating 13 is disposed on the surface of the active material layer 12. The coating 13 can partially or completely cover the active material layer 12. The coating 13 is configured to restrict the active material layer 12 to reduce the powdering and shedding of the active material layer 12. The coating 13 can be a high-strength and high-toughness organic coating film. In some embodiments, to ensure the mechanical strength of the coating 13, the coating 13 is a pure polymer, does not contain any active material, and does not provide any charge and discharge capacity. Compared to the active material layer 12, the coating 13 has higher mechanical strength and tensile strength and can withstand greater stress without generating plastic strain. The coating 13 is coated on the surface of the active material layer 12 to reduce the free expansion space of the active material layer 12, thereby ensuring that the active material layer 12 of the electrochemical device 100 can still be in good contact with the current collector 11 after long-term charge and discharge cycles, thereby improving the cycle life of the electrochemical device 100.

[0065] To facilitate the fixation of the coating 13 to the current collector 11, the end of the coating 13 extends beyond the active material layer 12 to facilitate connection with the current collector 11. For example, along the length direction of the current collector 11, the coating 12 includes a first end 132 and a second end (not shown in the figure), and the first end 132 and the second end are both connected to the current collector 11, so that the coating 13 limits the active material layer 12 in the length direction of the current collector 11. In other embodiments, along the width direction of the current collector 11, the coating 12 includes a third end 133 and a fourth end 134, and the third end 133 and the fourth end 134 are both connected to the current collector 11, or the first end 132, the second end, the third end 133 and the fourth end 134 are all connected to the current collector 11, so that the coating 13 can limit the active material layer 12 in both the length direction and the width direction of the current collector 11, thereby alleviating the expansion of the active material layer 12.

[0066] To facilitate the electrolyte's passage through the coating 13 and into the active material layer 12, referring to Figures 3 to 5b, at least one through-hole 131 is defined in the coating 13. The through-hole 131 extends through the coating 13 and is configured to communicate with the active material layer 12. The electrolyte can directly enter the through-hole 131 from the outside of the coating 13 and react with the active material layer 12. The through-hole 131 serves as a material transfer channel for lithium ions, ensuring that the electrolyte can pass through the coating 13 and properly contact the active material layer 12 on the current collector 11, thereby maintaining the normal dynamics of the electrode. In other embodiments, the electrolyte can also directly penetrate the coating 13 to react with the active material layer 12.

[0067] In an embodiment of the present application, the coating 13 is a high-strength organic coating film with a porous structure. Under the premise of ensuring that the electrode has sufficient dynamics, it can suppress the expansion of the electrode and reduce the risk of powdering and demolding of the active material layer 12. The coating 13 tightly covers the surface of the active material layer 12. When the active material layer 12 is embedded with lithium and expands, the coating 13 generates shrinkage stress, thereby reducing the overall expansion of the electrode. The coating 13 can be punched using the industrially mature LDP (laser drilling) technology, and a through hole 131 is opened on the high-strength coating 13, so that the electrolyte can effectively infiltrate the internal active material layer 12 to smoothly complete the electrochemical reaction, thereby improving the risk of kinetic deterioration brought by the high-strength coating 13; therefore, in the present application, an active material layer 12 with a higher silicon mass content (less than 45%) can be used to increase the capacity of the electrochemical device.

[0068] Regarding the above-mentioned through holes 131, the overall shape of the through holes 131 can be cylindrical, truncated cone, prism or prism, etc. On the surface of the coating 13, the through holes 131 are circular, elliptical, rectangular or polygonal, etc. The number of through holes 131 can be set to multiple, and multiple through holes 131 are arranged at intervals. The through holes 131 can be evenly distributed on the coating 13. For example, as shown in FIG6 , multiple through holes 131 are distributed in an array on the coating 13. The uniform distribution is conducive to the electrolyte penetrating from various positions to the active material layer 12, facilitating sufficient contact between the active material layer 12 and the electrolyte. It is worth mentioning that the distribution of the through holes 131 is not limited to the array distribution in this embodiment. In other embodiments, as shown in FIG7 , the through holes 131 can also be distributed in a honeycomb shape on the coating 13.

[0069] Referring to Figures 4 to 5b, there are multiple through-holes 131, with adjacent through-holes 131 remaining independent and disconnected. The inter-hole spacing can be set to be greater than twice the hole radius, which is the distance between the centers of two adjacent through-holes 131. Along the thickness direction of the current collector 11, the coating 13 has a first surface 13a1 and a second surface 13a2, which are positioned opposite each other. The second surface 13a2 is closer to the active material layer 12 than the first surface 13a1. On the first surface 13a1, the area of ​​the multiple through-holes accounts for 10% to 30%. In one embodiment, the cross-sections of the through-holes 131 can be set to be equal, meaning that the porosity of the coating 13 is 10% to 30%. This imparts good dynamics to the coating 13, maintains its original mechanical strength, and effectively reduces irreversible plastic strain in the coating 13 after long-term cycling. Furthermore, the through-holes 131 are micrometer-sized, with a radius of 5 microns or less. The axis of through-hole 131 can be arranged parallel to the thickness direction of current collector 11. Since the outer surface of coating 13 is generally planar, the axis of through-hole 131 is arranged perpendicular to the outer surface of coating 13 to facilitate the entry and exit of electrolyte. In this embodiment, perpendicular refers to the angle between the axis of through-hole 131 and the outer surface of coating 13 being between 80 and 100 degrees. Coating 13 with a micron-scale porous structure can maintain a stable morphology for a long time during the charge and discharge cycles of electrochemical device 100, thereby reducing the volume expansion of the electrode.

[0070] According to some embodiments of the present application, referring to Figures 4 to 5b, along the thickness direction of the current collector 11, the active material layer 12 has a third surface 12a and a fourth surface 12d that are oppositely disposed. Compared to the third surface 12a, the fourth surface 12d is disposed closer to the current collector, and the third surface 12a is disposed away from the current collector 11. Along the length direction of the current collector 11, the active material layer 12 includes a first side surface 12b and a second side surface (not shown in the figures). Along the width direction of the current collector 11, the active material layer 12 also includes a third side surface 12c and a fourth side surface (not shown in the figures). To enable coating 13 to inhibit expansion of active material layer 12 in multiple directions, coating 13 includes a first portion 13a, a first extension 13b connected to first portion 13a, and a second extension (not shown). First portion 13a is disposed on third surface 12a and closely adheres to third surface 12a. First extension 13b extends to first side surface 12b, and second extension extends to second side surface. The first end 132 is disposed on the first extension, and the second end is disposed on the second extension. In other embodiments, active material layer 12 further includes a third extension 13c and a fourth extension (not shown) connected to first portion 13a. Third extension 13c extends to third side surface 12c, and fourth extension extends to fourth side surface. The third end 133 is disposed on the third extension, and the fourth end 134 is disposed on the fourth extension. A corresponding extension portion is provided in each direction of the active material layer 12 so that the coating 13 covers the active material layer 12 , wherein the first end 132 , the second end 133 and the fourth end 134 can all be connected and fixed to the current collector 11 to limit the expansion of the active material layer 12 .

[0071] Through-holes 131 are provided in the first portion 13a, allowing the electrolyte to penetrate the active material layer 12 directly through the through-holes 131 in the first portion 13a. To improve electrolyte penetration efficiency, through-holes 131 include a first through-hole 131a and a second through-hole 131b. The first through-hole 131a is provided in the first portion 13a, and the second through-hole 131b is provided in at least one of the first extension 13b and the second extension. In other embodiments, through-holes 131 also include a third through-hole 131c, and the third through-hole 131c is provided in at least one of the third extension 13c and the fourth extension. When through-holes 131 are provided in the first extension 13b, the second extension 13b, the third extension 13c, and the fourth extension, the electrolyte can enter the active material layer 12 from all directions, allowing the active material layer 12 to be rapidly penetrated.

[0072] The inventors of this application noticed that the thickness of the coating 13 will also affect the technical effect of this application, that is, the thickness of the coating 13 is related to the expansion of the pole piece. The embodiments of this application conduct relevant tests on coatings 13 with thicknesses of 0 microns (no coating 13), 3 microns and 5 microns to obtain the relationship between the thickness of the coating 13 and the expansion of the pole piece.

[0073] Please refer to Figures 8 to 10. Figures 8 and 9 show the relationship between the expansion of the electrochemical device and the number of cycles. L1 represents the test result curve when the thickness is 0 microns, L2 represents the test result curve when the thickness is 3 microns, and L3 represents the test result curve when the thickness is 5 microns. As the number of cycles of the electrochemical device 100 increases, the thickness of the electrochemical device gradually increases, and its expansion rate increases. Figure 10 shows the relationship between the expansion of the negative electrode plate 10 and the number of cycles. As with the electrochemical device, the expansion increases with the number of cycles. Combining Figures 8 to 10 shows that after the addition of coating 13, the expansion rate of the electrochemical device and the electrode plate decreases significantly, and the degree of decrease increases with the thickness of coating 13. As the thickness of coating 13 increases, the load acting on coating 13 due to the expansion of the electrode plate decreases proportionally, resulting in a smaller strain value for coating 13 itself, ultimately suppressing the expansion of the electrode plate as a whole and the entire electrochemical device 100. Theoretical calculation results show that when the coating 13 is in an elastic strain state, the thickness of the coating 13 is inversely proportional to the pole piece expansion percentage, that is, the greater the thickness of the coating 13, the smaller the pole piece expansion percentage.

[0074] Figure 11 shows the relationship between electrode expansion and the energy density loss of the electrochemical device as a function of the thickness of coating 13. As the thickness of coating 13 increases, the electrode expansion decreases, but the energy density loss of electrochemical device 100 also increases. As shown in Figure 11, the thickness of coating 13 can range from 1 micron to 8 microns.

[0075] Please refer to Figures 12 to 14. In this embodiment, the coating 13 with a thickness of 0 μm, 5 μm, and 5 μm + 30% LDP treatment (the area of ​​the through hole 131 accounts for 30% of the surface of one surface of the coating 13) was tested, where L4 is the test result curve when the thickness is 0 μm, L5 is the test result curve when the thickness is 5 μm, and L6 is the test result curve when the thickness is 5 μm + 30% LDP treatment.

[0076] Figure 12 shows the relationship between discharge rate and discharge capacity for coatings of varying thickness. As the discharge rate increases, the discharge capacity of electrochemical device 100 gradually decreases. As shown in Figure 12, after LDP technology is applied to coating 13 to create through-holes 131, the discharge capacity approaches that of the device without coating 13 as the discharge rate increases, effectively improving the deteriorating kinetic parameters of the electrochemical device.

[0077] Figure 13 shows the relationship between the SOC (state of charge) and DCR (high-frequency impedance) of an electrochemical device with different coating thicknesses. As shown in Figure 13 , as the SOC of the electrochemical device decreases, the DCR gradually increases. After LDP technology is used to create through-holes 131, as the SOC of the electrochemical device decreases, its DCR approaches that of the device without coating 13.

[0078] Figure 14 shows the relationship between the SOC and RSS (low-frequency impedance) of an electrochemical device with different coating thicknesses. As the SOC of the electrochemical device decreases, RSS gradually increases. After LDP technology is used to create through-holes 131, as the SOC of the electrochemical device decreases, RSS impedance approaches that of a device without coating 13. Combining Figures 12 to 14 shows that a coating 13 with a thickness of 5 microns and 30% LDP treatment has a discharge capacity approximately the same as that without coating 13, but significantly reduces the impedance of the electrochemical device.

[0079] By adjusting the thickness of the coating 13 and the structural parameters of the through-holes 131, the electrode dynamics and expansion rate can be precisely balanced. With the mature LDP technology, a series of physical parameters such as the morphology, depth, and distribution of the through-holes can be precisely adjusted and controlled, thereby balancing the improvement of the electrode dynamics with the loss of energy density. When designing the thickness of the coating 13, it is necessary to have a certain lower thickness limit for the coating 13 to ensure that the coating 13 has an inhibitory effect on the expansion of the electrode, and to avoid the risk of excessive thickness of the coating 13 deteriorating the energy density of the electrochemical device 100. In conjunction with Figures 8 to 14, it can be seen that the thickness of the coating 13 can be selected from 0.5 microns to 10 microns. In some other embodiments, the thickness of the coating 13 can also be set to 1 micron to 8 microns. Based on the same inventive concept, the thickness of the first extension portion 13b and / or the second extension portion is 0.5 microns to 10 microns, and in some other embodiments, it can also be set to 1 micron to 8 microns; along the width direction of the current collector 11, the thickness of the third extension portion 13c and / or the fourth extension portion is 0.5 microns to 10 microns, and in some other embodiments, it can also be set to 1 micron to 8 microns; along the direction from the coating 13 to the current collector 11, the thickness of the first part 13a is 0.5 microns to 10 microns, and in some other embodiments, it can also be set to 1 micron to 8 microns.

[0080] To determine the relationship between the structural parameters of through-hole 131 and the expansion and dynamic parameters of the electrode, and to determine the optimal structural parameters for through-hole 131, this application conducted relevant testing experiments on the electrode expansion and dynamics under different through-hole 131 structural parameters. The test results are shown in the table below. Where "Rate" represents the charge and discharge rate; a higher "Rate" is preferred; "HL" represents the high and low temperature test; a higher "HL" value is preferred; "DCR" represents the high-frequency impedance test; a lower "DCR" value is preferred; and "Rss" represents the low-frequency impedance test; a lower "Rss" value is preferred.

[0081] Table 1 shows the relationship between the structural parameters of the through hole 131 and the parameters of the cyclic expansion / dynamics of the pole piece.

[0082]

[0083] Table 1 describes the specific effects of the specific parameters of the through hole 131 on the dynamic-related parameters of the electrode. The preferred parameters of the structure of the through hole 131 are determined according to the three types of design: "whether the through hole 131 exists", "whether the through hole 131 penetrates the coating 13" and "the distribution of the through hole 131". The use of through holes 131 with a small aperture and a low area ratio will achieve the best balance between the two requirements of suppressing the expansion of the electrode and maintaining the original dynamics of the electrode. According to Table 1, in this application, the through hole 131 must penetrate the coating 13. In some embodiments, the radius is less than 5 microns, and the area of ​​the through hole 131 on the surface of the coating 13 accounts for 10% to 50%, or 10% to 30%. The lower limit value gives the coating 13 good dynamics, and the upper limit value maintains the original mechanical strength of the coating 13 to reduce the irreversible plastic strain of the coating 13 after long-term cycling. It should be noted that the same level in the table means that the two test values ​​are the same or substantially the same, for example, the difference is less than 0.1%. In this application, the difference refers to the difference obtained by subtracting the small object from the large object, divided by the small object, and multiplied by 100% to obtain a value.

[0084] Figures 15 and 16 show the relationship between the number of cycles and the capacity retention of the electrochemical device 100 at different coating 13 thicknesses. Multiple test experiments were conducted using an uncoated 13 and a 5 mm thick coating 13 treated with 30% LDP. As shown in Figures 15 and 16, the capacity retention gradually decreases with increasing cycle number. The test curves are nearly identical. The capacity retention of the 5 mm thick coating 13 treated with 30% LDP is approximately the same as that of the uncoated 13 as the cycle number increases, and no risk of cycle deterioration has been observed.

[0085] In this application, by providing micron-sized through-holes 131 in coating 13, more electrolyte can penetrate deep into the electrode, replacing the inherently slower solid-phase diffusion channels and providing a faster material transfer path, thereby reducing the overall impedance of the electrode. Furthermore, through-holes 131 provide a buffer for strain in active material layer 12, reducing electrode expansion and facilitating long-term cycle life and high energy density maintenance for electrochemical device 100.

[0086] Based on the same inventive concept, an embodiment of the present application further provides an electronic device, comprising the electrochemical device 100 as described in any of the above embodiments.

[0087] The electrochemical device 100 disclosed in some embodiments of this application can be used, but is not limited to, in electronic devices such as vehicles, ships, or aircraft. A power supply system comprising the electrochemical device 100 disclosed herein can be used to construct the electronic device. This can increase the capacity of the electrochemical device 100 and improve the endurance of the electronic device, while also reducing the impedance of the electrochemical device 100 to meet the fast charging and discharging requirements of the electrochemical device 100.

[0088] Some embodiments of the present application provide an electronic device using an electrochemical device 100 as a power source. The electronic device may include, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, etc. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc. The spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present application as described above. For the sake of simplicity, they are not provided in detail. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrochemical device comprising a current collector and an active material layer coated on the current collector, characterized in that: The electrochemical device further includes a coating disposed on the active material layer; Along the length direction of the current collector, the coating has a first end and a second end that are oppositely disposed, and along the width direction of the current collector, the coating has a third end and a fourth end that are oppositely disposed; The first end and the second end are connected to the current collector, and / or the third end and the fourth end are connected to the current collector; The coating layer is provided with at least one through hole.

2. The electrochemical device according to claim 1, wherein The active material layer includes a first active material and a second active material, wherein the gram capacity of the first active material is greater than the gram capacity of the second active material.

3. The electrochemical device according to claim 2, characterized in that The active material layer satisfies at least one of the following conditions a) and b): a) the first active material comprises at least one of elemental silicon, a silicon-oxygen compound, a silicon-carbon composite, and a silicon alloy; b) The second active material comprises at least one of graphite, soft carbon, hard carbon, carbon fibers and mesocarbon microbeads.

4. The electrochemical device according to claim 2 or 3, characterized in that The first active material may be present in an amount of 1% to 45% by mass based on the mass of the active material layer.

5. The electrochemical device according to claim 1, wherein The coating is provided with a plurality of through holes. Along the thickness direction of the current collector, the coating has a first surface and a second surface arranged opposite to each other. Compared with the first surface, the second surface is closer to the active material layer. On the first surface, the area of ​​the plurality of through holes accounts for 10% to 30%.

6. The electrochemical device according to claim 1, wherein The through hole satisfies 0<R≤5μm, where R is the radius of the through hole.

7. The electrochemical device according to claim 1, wherein The tensile strength of the coating layer is greater than the tensile strength of the active material layer.

8. The electrochemical device according to claim 1, wherein Along the thickness direction of the current collector, the active material layer has a third surface and a fourth surface that are opposite to each other, and the fourth surface is closer to the current collector than the third surface; Along the length direction of the current collector, the active material layer includes a first side surface and a second side surface that are oppositely disposed; Along the width direction of the current collector, the active material layer includes a third side surface and a fourth side surface that are oppositely disposed; The coating includes a first portion disposed on the third surface; Along the length direction of the current collector, the coating further includes a first extension portion and a second extension portion that are oppositely arranged; The first end portion is disposed on the first extending portion, and the first extending portion extends to the first side surface; the second end portion is disposed on the second extending portion, and the second extending portion extends to the second side surface.

9. The electrochemical device according to claim 8, characterized in that The coating is provided with a plurality of through holes, the through holes including a first through hole and a second through hole; the first through hole is provided in the first portion; and the second through hole is provided in at least one of the first extension portion and the second extension portion.

10. The electrochemical device according to claim 8, characterized in that Along the width direction of the current collector, the coating further includes a third extending portion and a fourth extending portion that are oppositely arranged; The third end portion is disposed on the third extending portion, and the third extending portion extends to the third side surface; the fourth end portion is disposed on the fourth extending portion, and the fourth extending portion extends to the fourth side surface.

11. The electrochemical device according to claim 10, characterized in that The through hole further includes a third through hole, and the third through hole is opened in at least one of the third extending portion and the fourth extending portion.

12. The electrochemical device according to claim 10, wherein A thickness of at least one of the first portion, the first extension, the second extension, the third extension, and the fourth extension is 0.5 μm to 10 μm.

13. An electronic device, characterized in that: Comprising the electrochemical device according to any one of claims 1 to 12.

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