Pole piece structure, electrode assembly, electrochemical device, and electronic device

Abstract

The application relates to the technical field of electrochemical energy storage, and specifically discloses a pole piece structure, which comprises a current collector, a first surface and a second surface arranged on opposite sides of the current collector along a first direction, a functional area and an empty foil area arranged on the current collector along a second direction, an active material layer coated on the first surface and the second surface, and a projection of the active material layer on the current collector along the first direction located in the functional area, and a coating layer arranged on a side of the empty foil area away from the functional area along the second direction and at least partially connected with the first surface and the second surface, wherein the first direction is a thickness direction of the current collector. The application also discloses an electrode assembly, an electrochemical device and an electronic device. The pole piece structure is locally wrapped by the coating layer, thereby meeting the safety requirement and eliminating the negative influence of the thickness of the adhesive paper on the energy density.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to electrode structures, electrode assemblies, electrochemical devices and electronic equipment. Background Technology

[0002] In the lithium battery manufacturing process, such as Figure 1 As shown, after the empty foil of the cathode electrode 1' is cut, burrs 2' will be generated at the cut edge. During the winding process of the anode and cathode electrodes, adhesive tape 4' needs to be applied to the cut position of the anode electrode 3' corresponding to the cathode electrode; similarly, adhesive tape also needs to be applied to the cut position of the cathode electrode corresponding to the anode electrode, in order to prevent the burrs at the cut edge from piercing the separator and causing a short circuit. However, the thickness of the adhesive tape occupies space in the battery thickness, reducing the battery energy density. Summary of the Invention

[0003] The technical problem this application aims to solve is: how to address the issue of existing technologies where adhesive tape occupies battery thickness space and reduces battery energy density.

[0004] To address the aforementioned technical problems, this application proposes an electrode structure having a first direction and a second direction that are perpendicular to each other; the electrode structure includes: The current collector has a first surface and a second surface on opposite sides along the first direction; along the second direction, the current collector includes adjacent functional areas and empty foil areas; An active material layer is coated on the first surface and the second surface, and along the first direction, the orthogonal projection of the active material layer on the current collector is located in the functional area; A covering layer is applied to the side of the empty foil area away from the functional area along the second direction, and the covering layer is at least partially connected to the first surface and the second surface; Wherein, the first direction is the thickness direction of the current collector.

[0005] In some embodiments, the covering layer includes a first connecting portion, a second connecting portion, and an arcuate portion; The arc-shaped portion is located on the side of the empty foil area away from the functional area along the second direction; Along the first direction, the first connecting portion and the second connecting portion are spaced apart; the first connecting portion is disposed on the first surface and connected to the arc-shaped portion; the second connecting portion is disposed on the second surface and connected to the arc-shaped portion. Along the first direction, the orthographic projections of the first connecting portion and the second connecting portion onto the current collector are both located in the empty foil area.

[0006] In some embodiments, the thickness H of the coating layer is 5-30 μm; And / or, the radius R of the arcuate portion is 0.1-0.5 mm.

[0007] In some embodiments, the width W of the first connecting portion and the second connecting portion along the second direction is 0.5-3 mm; And / or, the thickness of the first connecting portion and the second connecting portion along the first direction is less than the thickness of the active material layer.

[0008] In some embodiments, the thickness of the active material layer along the first direction is T, satisfying: 0.1≤H / T≤0.6.

[0009] In some embodiments, along the first direction, the thickness of the arcuate portion gradually decreases from the middle to both ends; And / or, along the second direction, the thickness of the first connecting portion gradually decreases from the end away from the functional area to the end closer to the functional area; the thickness of the second connecting portion gradually decreases from the end away from the functional area to the end closer to the functional area.

[0010] In some embodiments, the coating layer is a ceramic coating layer; And / or, the ceramic coating layer is an alumina coating layer or a silicon dioxide coating layer.

[0011] This application also proposes an electrode assembly, including a first electrode, a second electrode, and a diaphragm; the diaphragm is disposed between the first electrode and the second electrode, and the first electrode, the diaphragm, and the second electrode are wound together to form the electrode assembly; the first electrode and the second electrode have opposite polarities; Both the first electrode and the second electrode adopt the electrode structure described in the above embodiments.

[0012] This application also proposes an electrochemical device comprising the electrode assembly described above.

[0013] This application also proposes an electronic device including the electrochemical device described above.

[0014] Compared with the prior art, the electrode structure, electrode assembly, electrochemical device, and electronic device of this application have the following advantages: This application provides a coating layer on the side of the empty foil area of ​​the current collector away from the functional area, and at least partially connects the coating layer to the first and second surfaces of the current collector. This allows burrs exposed at the edge of the empty foil area after cutting to be wrapped inside the coating layer, effectively preventing the risk of short circuit caused by burrs piercing the separator. At the same time, since the coating layer is only attached to the edge of the empty foil area and does not extend to the surface of the active material layer of the functional area, compared with the prior art which requires additional adhesive tape to be pasted on the electrode surface, this structure does not require an adhesive tape layer to be superimposed in the electrode thickness direction (first direction). Therefore, it does not increase the thickness occupied by the functional area and the overall electrode, and significantly saves the internal thickness space of the battery while ensuring the insulation protection effect, thereby improving the volumetric energy density of the battery. Attached Figure Description

[0015] Figure 1 This is a diagram of the existing technology structure of the electrode.

[0016] Figure 2 This is a schematic diagram of the electrode structure described in this application.

[0017] Figure 3 This is a partial schematic diagram of the electrode structure described in this application.

[0018] Figure 4 This is a schematic diagram of another embodiment of the electrode structure described in this application.

[0019] Figure 5 This is a schematic diagram of the electrode assembly described in this application.

[0020] Figure label: 10. Electrode structure; 10a. First electrode; 10b. Second electrode; 20. Diaphragm; 1. Current collector; 11. Functional area; 12. Empty foil area; 101. First surface; 102. Second surface; 2. Active substance layer; 3. Covering layer; 31. First connecting part; 32. Second connecting part; 33. Arc-shaped part; X, the first direction; Y, the second direction. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0023] The specific embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application.

[0024] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" used to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, "first," "second," etc., are not intended to describe corresponding components.

[0026] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0027] Furthermore, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another instance, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0029] In the detailed description and claims, the list of items connected by the term "at least of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A: only B: or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A: or only B: only G: A and B (excluding C): A and C (excluding B): B and C (excluding A): or all of A, B, and C.

[0030] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0031] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0032] In one embodiment, such as Figure 2 As shown, this application proposes an electrode structure having a first direction X and a second direction Y that are perpendicular to each other. It should be noted that the directional terms mentioned in this embodiment, such as the first direction X, the second direction Y, and the third direction Z, are only for the convenience of describing the relative positional relationship between the components, and are not an absolute limitation on the installation orientation of the electrode structure. For example, for ease of explanation, the first direction X is defined as the thickness direction of the electrode structure, and the second direction Y is defined as the length direction of the electrode structure.

[0033] In some implementation methods, please refer to Figure 2 The electrode structure 10 includes a current collector 1, an active material layer 2, and a coating layer 3. The first direction X is the thickness direction of the current collector 1, and the current collector 1 has a first surface 101 and a second surface 102 on opposite sides along the first direction X. Along the second direction Y, the current collector 1 includes adjacent functional regions 11 and empty foil regions 12. The active material layer 2 is coated on the first surface 101 and the second surface 102, and along the first direction X, the orthographic projection of the active material layer 2 onto the current collector 1 is located in the functional region 11. The coating layer 3 covers the side of the empty foil region 12 away from the functional region 11 along the second direction Y, and the coating layer 3 is at least partially connected to the first surface 101 and the second surface 102. Thus, by [the coating layer is located on the side of the empty foil region 12 away from the functional region 11], [the coating layer is positioned in the first direction X]. A coating layer 3 is provided, and the coating layer 3 is at least partially connected to the first surface 101 and the second surface 102 of the current collector 1. This allows the burrs exposed at the edge of the empty foil area 12 after cutting to be wrapped inside the coating layer 3, effectively avoiding the risk of short circuit caused by burrs piercing the separator. At the same time, since the coating layer 3 is only attached to the edge of the empty foil area 12 and does not extend to the surface of the active material layer 2 of the functional area 11, compared with the prior art, which requires additional adhesive tape to be pasted on the electrode surface, this electrode structure 10 does not need to stack an adhesive tape layer in the electrode thickness direction (first direction). Therefore, it does not increase the thickness of the functional area 11 and the overall electrode, and significantly saves the internal thickness space of the battery while ensuring the insulation protection effect, thereby improving the volumetric energy density of the battery.

[0034] In some embodiments, the covering layer 3 includes a first connecting portion 31, a second connecting portion 32, and an arc-shaped portion 33. Specifically, the arc-shaped portion 33 is located on the side of the empty foil area 12 away from the functional area 11 along the second direction Y. Along the first direction X, the first connecting portion 31 and the second connecting portion 32 are spaced apart. The first connecting portion 31 is disposed on the first surface 101 and connected to the arc-shaped portion 33. The second connecting portion 32 is on the second surface 102 and connected to the arc-shaped portion 33. Along the first direction X, the orthographic projections of the first connecting portion 31 and the second connecting portion 32 on the current collector 1 are both located in the empty foil area 12. Thus, by setting the covering layer 3 as an integral wrapping structure composed of the first connecting portion 31, the second connecting portion 32, and the arc-shaped portion 33, wherein the arc-shaped portion 33 directly covers the edge of the empty foil area 12 away from the functional area 11 along the second direction Y, the cut edge can be fully covered. The burrs generated at the edge effectively prevent burrs from piercing the separator. At the same time, the first connecting part 31 and the second connecting part 32 are respectively fixedly connected to the first surface 101 and the second surface 102 of the current collector 1, and their orthogonal projections along the first direction X are both located within the empty foil area 12. This design, on the one hand, enables the coating layer 3 to form a firm bond with the current collector 1, significantly enhancing the anti-peeling ability of the coating layer 3 during winding and bending, and preventing the protection failure due to detachment. On the other hand, since the orthogonal projections of the first connecting part 31 and the second connecting part 32 do not extend to the active material layer 2 area of ​​the functional area 11, the thickness of the coating layer 3 is only superimposed on the edge of the empty foil area 12. This area itself does not participate in the electrochemical reaction and is located at the end of the electrode, so it will not increase the thickness of the functional area 11, nor will it increase the overall thickness after the battery is stacked or wound.

[0035] In addition, the arc-shaped transition of the arc portion 33 can smoothly disperse edge stress, further reducing the risk of local puncture.

[0036] In some implementation methods, please refer to Figure 3 The thickness H of the coating layer 3 is 5-30 μm; this allows for the optimal reduction of the coating layer 3 thickness while ensuring the effectiveness of insulation protection and manufacturability. Because the end thickness of each electrode layer inside the battery is reduced, more thickness allowance can be provided for the active material layer 2 within the same cell casing size, or the overall thickness of the wound cell can be made thinner, ultimately directly and effectively translating into an increase in the battery's volumetric energy density.

[0037] It should be noted that H is 5-30 μm. This thickness ensures that the first connecting portion 31, the second connecting portion 32, and the arc-shaped portion 33 of the covering layer 3 have sufficient structural strength and insulation thickness. Meanwhile, since the height of the metal burrs generated during cutting is typically in the micrometer range, if H is less than 5 μm, the covering layer 3 is too thin. This not only makes it difficult to completely cover and bury the sharp burrs at the edge of the empty foil area 12, increasing the risk of puncture, but also makes the arc-shaped portion 33 prone to cracking or peeling due to stress concentration during winding and bending, reducing long-term reliability. H ≥ 5 μm provides sufficient physical barrier and mechanical toughness, ensuring the integrity of the sheath and the durability of the insulation protection. Furthermore, H of 5-30 μm is much smaller than the total thickness of the adhesive substrate and adhesive layer in traditional adhesive tape application processes (typically 30-140 μm or even thicker). Since the coating layer 3 is only attached to the empty foil area 12 and does not occupy the thickness space of the functional area 11, H is controlled within 30μm, so that after the battery is wound or stacked, the increase in size of the electrode end in the thickness direction (first direction) is compressed to an extremely low level, thereby significantly reducing the waste of redundant space inside the cell caused by the accumulation of edge thickness.

[0038] In some implementation methods, please refer to Figure 3 The radius R of the arc-shaped portion 33 is 0.1-0.5mm. This ensures that the arc-shaped portion 33 has a sufficient radius of curvature to resist winding stress and prevent cracking and peeling. At the same time, it strictly controls the size increment of the electrode end in the first direction X and the second direction Y, so that the coating layer 3 can firmly wrap the cutting burrs without taking up valuable space inside the battery due to the arc-shaped protrusion.

[0039] It should be noted that the radius of the arc-shaped portion 33, as the curved transition structure at the edge of the foil-covered area 12, directly determines the stress concentration at the bend. If R is less than 0.1 mm, the radius of curvature is too small and the bending is too abrupt. When the electrode undergoes winding, bending, and thermal expansion and contraction during subsequent charge-discharge cycles, significant stress concentration will occur on the inner side of the arc-shaped portion 33. This can easily lead to microcracks, fatigue fracture, or even peeling from the surface of the current collector 1 in the coating layer 3, thus losing its function of protecting against burrs. At the same time, an overly sharp arc edge may also cause local high-pressure stress on adjacent diaphragms, increasing the risk of physical damage. Controlling R ≥ 0.1 mm ensures that the arc-shaped portion 33 has a sufficiently smooth curvature transition, effectively dispersing bending stress and significantly improving the long-term structural durability and diaphragm-friendly properties of the coating layer 3. Furthermore, the arc-shaped portion 33 is located at the outermost end of the empty foil area 12 along the second direction Y. The larger its radius, the larger the outward convexity of the arc-shaped portion in the second direction Y, which directly leads to an increase in the lateral (second direction) space occupied by the electrode end. If R exceeds 0.5mm, the outward convex portion will significantly encroach on the reserved gaps between adjacent electrodes and between the electrode and the casing after the battery is wound or stacked. It may even squeeze the separator or opposing electrode at the bend of the wound cell due to excessive accumulated outward convexity, affecting the safe distance. Controlling R ≤ 0.5mm effectively suppresses the outward expansion of the edge and ensures that there is no interference between adjacent components.

[0040] In some implementation methods, please refer to Figure 3 Along the second direction Y, the width W of the first connecting part 31 and the second connecting part 32 is 0.5-3mm; on the one hand, by providing sufficient anchoring area and burr coverage allowance, it is ensured that the coating layer 3 always maintains a firm fit and complete wrapping with the empty foil area 12 under complex electrochemical environment and mechanical stress; on the other hand, the boundary of the coating layer 3 is strictly constrained not to exceed the empty foil area 12, so as to avoid any encroachment or coverage of the active material of the functional area 11.

[0041] It should be noted that if W is less than 0.5 mm, the contact area between the first connecting part 31 and the second connecting part 32 and the current collector 1 is too small, resulting in insufficient bonding force. Under the subsequent electrode winding and bending, long-term immersion in electrolyte, and the thermal stress of charging and discharging, the coating layer 3 is prone to peeling, flaking, or complete detachment, causing the arc-shaped part 33 to lose its fixed support and fall off from the edge of the empty foil area 12, completely failing the protective function. If W exceeds 3 mm, the first connecting part 31 and the second connecting part 32 are very likely to extend beyond the boundary of the empty foil area 12, inevitably reaching the surface of the active material layer 2 in the functional area 11. This results in the covered active material layer 2 being unable to participate in the electrochemical reaction, directly leading to a decrease in the utilization rate of the active material in this area and local capacity loss. At the same time, this extra covering thickness will unnecessarily increase the thickness of the electrode body, failing to save thickness space and improve energy density.

[0042] In some embodiments, the thickness of the first connecting portion 31 and the second connecting portion 32 along the first direction X is less than the thickness of the active material layer 2. Since the empty foil area 12 itself is not coated with the active material layer 2, the surface of the current collector 1 in this area is exposed, and the first connecting portion 31 and the second connecting portion 32 are directly attached to the first surface 101 and the second surface 102 of the empty foil area 12. When the thickness of the connecting portion is less than the thickness of the active material layer 2, it means that the total thickness of the empty foil area 12 and the connecting portions on both sides in the thickness direction (first direction) is less than the total thickness of the functional area 11 and the active material layers on both sides. This fundamentally avoids any net increase in the battery thickness direction space by the coating layer 3, so that after the cell is wound or stacked, the overall thickness is completely determined by the thickness of the active material layer 2, and the coating layer does not generate an additional thickness burden.

[0043] In some implementation methods, please refer to Figure 3 Along the first direction X, the thickness of the active material layer 2 is T, satisfying: 0.1 ≤ H / T ≤ 0.6. This allows the electrode structure to adapt to electrodes with different areal densities and different battery models. When T is large (e.g., for thick electrodes), the upper limit of 0.6 allows H to be moderately thickened to ensure the adhesion strength of the coating layer 3; when T is small (e.g., for thin electrodes), the lower limit of 0.1 ensures that the coating layer 3 is not too thin and fails.

[0044] It should be noted that if H / T is less than 0.1, it means that H is less than one-tenth of T, and the connection part is too thin, like a "film". Under the stress of winding tension, electrolyte swelling and thermal cycling, it is very easy to generate micro-cracks or local perforations. Not only can it not reliably anchor the arc-shaped part 33, but it may also lose its ability to wrap burrs due to local insulation failure. When H / T is greater than 0.6, the electrode end cannot form a sufficient concave space in the thickness direction (first direction), and cannot provide a buffer area for the diaphragm without compression. It is easy for the diaphragm to be deformed or worn due to the "micro-convex" edge at the winding bend.

[0045] In some implementation methods, please refer to Figure 4 Along the first direction X, the thickness of the arc-shaped portion 33 gradually decreases from the middle to both ends; the middle of the arc-shaped portion 33 is the direct wrapping position corresponding to the cutting burrs, and maintaining sufficient thickness in this area can ensure complete burring and insulation of sharp burrs; while gradually decreasing towards both ends until it connects with the thickness of the connecting portion, so that the outer surface of the arc-shaped portion 33 forms a smooth streamlined arc surface, avoiding local "bulges" or abrupt steps that may occur in the uniform thickness design.

[0046] Furthermore, the arc-shaped portion 33, as a curved transition structure at the edge of the foil-covered area 12, forms an interface region where the geometry changes significantly at its connection with the first connecting portion 31 and the second connecting portion 32. If the thickness of the arc-shaped portion 33 is uniform, a distinct right-angle step or abrupt change in cross-section will form at this connection. When the electrode undergoes thermal stress during winding, bending, and charge-discharge cycles, the stress is easily concentrated at these abrupt interfaces, becoming weak points for crack initiation and propagation. The design of gradually reducing the thickness from the middle to both ends allows for a smooth transition between the arc-shaped portion 33 and the first connecting portion 31 and the second connecting portion 32. Bending and tensile stresses can be gently dispersed and transmitted along the thickness gradient direction, significantly reducing the stress peak at the interface. This effectively prevents the coating layer 3 from peeling, cracking, or fatigue fracture during long-term use, greatly enhancing the long-term robustness and service life of the protective structure.

[0047] In some embodiments, if the connection abruptly ends with its full thickness at the end adjacent to the functional area 11, a near-right-angle "thickness step" will be formed between this end and the surface of the current collector 1. When the electrode undergoes winding and bending, electrolyte immersion and swelling, and charge-discharge thermal cycling, the tip of this step will become a region of high stress concentration, easily inducing the coating layer 3 to warp, microcracks to initiate, or even completely delaminate at this interface, thus causing the protective function to fail. Therefore, please refer to... Figure 4 Along the second direction Y, the thickness of the first connecting portion 31 gradually decreases from the end away from the functional region 11 to the end closer to the functional region 11; the thickness of the second connecting portion 32 gradually decreases from the end away from the functional region 11 to the end closer to the functional region 11. Thus, the design of gradually thinning the thickness from the edge side to the functional region 11 side is equivalent to constructing a smooth wedge-shaped slope at the end of the connecting portion, so that the bending stress and thermal stress are gradually released along the Y direction, eliminating stress singularity; at the same time, the gradually thinning end forms a tight adhesion with the exposed current collector surface, which greatly increases the interfacial fracture energy that needs to be overcome during peeling, and significantly improves the long-term anchoring durability and fatigue peeling resistance of the coating layer 3.

[0048] It should be noted that the side of the connector near functional area 11 is the critical transition position between the empty foil area 12 and the active material layer 2. If the thickness of the connector at this point is not gradually reduced, even if its orthographic projection is still within the empty foil area, a height difference or local "micro-protrusions" may still form between the two due to the larger thickness of the adjacent active material layer 2, which will exert additional pressure on the diaphragm after winding and pressing. When the thickness is gradually reduced to near zero, a seamless and flush geometric connection is achieved between the end of the connector and the sidewall of the active material layer 2, ensuring that the entire surface contour from functional area 11 to empty foil area 12 is smooth and streamlined, without any local protrusions higher than the main plane of the active layer.

[0049] In some embodiments, the coating layer 3 is a ceramic coating layer; specifically, the ceramic coating layer is an alumina coating layer or a silica coating layer. Both alumina and silica are high-hardness inorganic ceramic materials, and their mechanical strength and puncture resistance far exceed those of adhesive paper. When the metal burrs generated by the cutting edge of the electrode come into contact with the coating layer 3, the ceramic layer, with its high elastic modulus and compressive strength, can effectively resist the tip of the burr from pressing in and penetrating. Even under winding and pressing or later battery expansion stress, the central area of ​​the arc-shaped portion 33 can still maintain an intact physical barrier, greatly improving the puncture resistance performance; while traditional adhesive paper is prone to creep softening under long-term stress or high temperature, and the protective reliability will be significantly reduced.

[0050] In addition, alumina and silicon dioxide have extremely high thermal decomposition temperatures. Under conditions such as overheating, short circuits, or even thermal runaway that lithium batteries may face, the coating layer 3 will not melt, decompose, or burn, and can continuously maintain its insulation performance. This avoids the secondary safety risks caused by the shrinkage, carbonization, or release of flammable gases of the adhesive paper at high temperatures. At the same time, these two ceramic materials have excellent chemical inertness in the electrolyte. They do not swell, dissolve, or produce side reactions. Even after long-term immersion, they can still maintain dimensional stability and interfacial adhesion, completely eliminating the failure risks of coating layer 3 peeling and lifting caused by adhesive aging, swelling, or delamination of traditional adhesive paper. This significantly extends the cycle life and storage reliability of the battery.

[0051] In summary, the electrode structure proposed in this embodiment provides a coating layer 3 on the side of the empty foil area 12 of the current collector 1 away from the functional area 11, and the coating layer 3 is at least partially connected to the first surface 101 and the second surface 102 of the current collector 1. This allows the burrs exposed at the edge of the empty foil area 12 after cutting to be wrapped inside the coating layer 3, effectively avoiding the risk of short circuit caused by burrs piercing the separator. At the same time, since the coating layer 3 is only attached to the edge of the empty foil area 12 and does not extend to the surface of the active material layer 2 of the functional area 11, compared with the prior art which requires additional adhesive tape to be pasted on the electrode surface, this structure does not require an adhesive tape layer to be superimposed in the electrode thickness direction (first direction). Therefore, it does not increase the thickness of the functional area 11 and the overall electrode, and significantly saves the internal thickness space of the battery while ensuring the insulation protection effect, thereby improving the volumetric energy density of the battery. That is, this embodiment eliminates the negative impact of adhesive tape thickness on energy density while meeting safety requirements.

[0052] In another embodiment, this application also proposes an electrode assembly, please refer to... Figure 5The electrode assembly is a wound structure, including a first electrode 10a, a second electrode 10b, and a separator 20; the separator 20 is disposed between the first electrode 10a and the second electrode 10b, and the first electrode 10a and the second electrode 10b have opposite polarities; if the electrode assembly is a stacked cell, there are multiple first electrode 10a, separators 20, and second electrode 10b, and the multiple first electrode 10a and second electrode 10b are alternately arranged in the first direction X, and a separator 20 is provided between adjacent first electrode 10a and second electrode 10b; if the electrode assembly is a wound cell, the first electrode 10a, second electrode 10b, and second electrode 10b are disposed between adjacent first electrode 10a and second electrode 10b, and the second electrode 10b is ... After the electrode 10a, separator 20 and second electrode 10b are stacked along the first direction X, they are then wound in the second direction Y to form an electrode assembly. Specifically, the first electrode 10a and the second electrode 10b both adopt the electrode structure 10 of the above embodiment. Since the first electrode 10a and the second electrode 10b both adopt all the technical solutions of the above embodiments, they have at least all the beneficial effects brought about by the technical solutions of the above embodiments, that is, they significantly save the internal thickness space of the battery while ensuring the insulation protection effect, thereby improving the volumetric energy density of the battery.

[0053] It should be noted that in some embodiments, the first electrode 10a is an anode electrode and the second electrode 10b is a cathode electrode, in which case the current collector of the first electrode 10a is copper foil and the current collector of the second electrode 10b is aluminum foil; in another embodiment, the first electrode 10a is a cathode electrode and the second electrode 10b is an anode electrode, in which case the current collector of the first electrode 10a is aluminum foil and the current collector of the second electrode 10b is copper foil.

[0054] In the above embodiments, the active material layer of the cathode electrode can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc., and the active material layer of the anode electrode can be carbon-based materials (such as graphite), silicon-based materials, or alloy materials, etc. The battery mainly relies on the movement of metal ions between the anode and cathode electrodes to operate.

[0055] In addition, the diaphragm 20 can be made of PP (polypropylene) or PE (polyethylene), etc. The electrolyte is a material with good ionic conductivity, such as aqueous solutions of acids, alkalis, and salts, organic or inorganic non-aqueous solutions, molten salts, or solid electrolytes.

[0056] In another embodiment, this application also proposes an electrochemical device that includes the electrode assembly described in the above embodiments. Since the electrochemical device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0057] It should be noted that the electrochemical device in this embodiment includes any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy and vice versa. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0058] A battery is a device that converts chemical energy into electrical energy. It contains an electrolyte solution and metal electrodes, and is housed in a cup, tank, or other container (such as a shell) or a portion of a composite container to generate an electric current. Batteries typically have an anode and a cathode. With technological advancements, the term "battery" now generally refers to any small device capable of generating electrical energy, such as a solar cell. The main performance parameters of a battery are electromotive force, capacity, specific energy, and resistance. The principle of a battery: In a chemical battery, chemical energy is directly converted into electrical energy through spontaneous oxidation and reduction reactions within the battery. These reactions occur at the two electrodes.

[0059] Additionally, a rechargeable battery, also known as a rechargeable battery or accumulator, is a battery that can be recharged after being discharged to reactivate its active materials and continue to be used. Utilizing the reversibility of chemical reactions, a new battery can be constructed; that is, after a chemical reaction converts into electrical energy, the electrical energy can be used to repair the chemical system, and then the chemical reaction can be converted back into electrical energy. Therefore, it is called a rechargeable battery.

[0060] In another embodiment, this application also proposes an electronic device, which includes the electrochemical device described in the above embodiments. The specific structure of the electrochemical device is the same as described in the above embodiments. Since the electronic device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0061] The electronic devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This embodiment does not impose any special limitations on the above-mentioned electronic devices.

[0062] The above description is merely a preferred embodiment of this application. It should be noted that, for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application. The basic principles, main features, and advantages of this application have been shown and described above. For those skilled in the art, it is obvious that this application is not limited to the details of the above preferred embodiments. The embodiments should be considered exemplary and non-limiting. The scope of this application is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included within this application.

[0063] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An electrode structure having a first direction (X) and a second direction (Y) that are perpendicular to each other; characterized in that, The electrode structure (10) includes: The current collector (1) has a first surface (101) and a second surface (102) on opposite sides along the first direction (X); along the second direction (Y), the current collector (1) includes an adjacent functional area (11) and an empty foil area (12). An active material layer (2) is coated on the first surface (101) and the second surface (102), and along the first direction (X), the orthogonal projection of the active material layer (2) on the current collector (1) is located in the functional area (11). A covering layer (3) covers the side of the empty foil area (12) away from the functional area (11) along the second direction (Y), and the covering layer (3) is at least partially connected to the first surface (101) and the second surface (102); Wherein, the first direction (X) is the thickness direction of the current collector (1).

2. The electrode structure according to claim 1, characterized in that, The covering layer (3) includes a first connecting part (31), a second connecting part (32), and an arc-shaped part (33). The arc-shaped portion (33) is located on the side of the empty foil area (12) away from the functional area (11) along the second direction (Y); Along the first direction (X), the first connecting portion (31) and the second connecting portion (32) are spaced apart; the first connecting portion (31) is disposed on the first surface (101) and connected to the arc-shaped portion (33); the second connecting portion (32) is connected to the second surface (102) and connected to the arc-shaped portion (33); Along the first direction (X), the orthographic projections of the first connecting part (31) and the second connecting part (32) on the current collector (1) are both located in the empty foil area (12).

3. The electrode structure according to claim 2, characterized in that, The thickness H of the coating layer (3) is 5-30 μm; And / or, the radius R of the arcuate portion (33) is 0.1-0.5 mm.

4. The electrode structure according to claim 2, characterized in that, Along the second direction (Y), the width W of the first connecting portion (31) and the second connecting portion (32) is 0.5-3mm; And / or, the thickness of the first connecting portion (31) and the second connecting portion (32) along the first direction (X) is less than the thickness of the active material layer (2).

5. The electrode structure according to claim 3, characterized in that, Along the first direction (X), the thickness of the active material layer (2) is T, which satisfies: 0.1≤H / T≤0.

6.

6. The electrode structure according to claim 2, characterized in that, Along the first direction (X), the thickness of the arcuate portion (33) gradually decreases from the middle to both ends; And / or, along the second direction (Y), the thickness of the first connecting portion (31) gradually decreases from the end away from the functional area (11) to the end closer to the functional area (11); the thickness of the second connecting portion (32) gradually decreases from the end away from the functional area (11) to the end closer to the functional area (11).

7. The electrode structure according to claim 6, characterized in that, The coating layer (3) is a ceramic coating layer; And / or, the ceramic coating layer is an alumina coating layer or a silicon dioxide coating layer.

8. An electrode assembly, characterized in that, The electrode assembly includes a first electrode (10a), a second electrode (10b), and a diaphragm (20); the diaphragm (20) is disposed between the first electrode (10a) and the second electrode (10b), and the first electrode (10a), the diaphragm (20), and the second electrode (10b) are wound together to form the electrode assembly; the first electrode (10a) and the second electrode (10b) have opposite polarities; Wherein, the first electrode (10a) and the second electrode (10b) both adopt the electrode structure (10) as described in any one of claims 1-7.

9. An electrochemical device, characterized in that, Includes the electrode assembly as described in claim 8.

10. An electronic device, characterized in that, Includes the electrochemical device as described in claim 9.

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