Battery pole piece and battery

Abstract

The utility model relates to battery technology field, concretely provides a kind of battery pole piece and battery.The battery pole piece includes current collector and active material layer.Active material layer is arranged on at least one side surface in the thickness direction of current collector, and active material layer includes multiple coating layers stacked along the thickness direction.Coating layer is provided with blind hole on at least one side surface of current collector, and the orifice of blind hole is arranged on the surface away from current collector in the thickness direction of active material layer, and blind hole is through the contact interface of adjacent coating layers in the thickness direction.Blind hole is provided with filling layer inside.The utility model sets up blind hole and filling layer, solves the problem that the interface bonding force of different coating layers in multilayer coated active material layer is low, and ion transmission efficiency is low.Improve the problem that active material layer coating is thicker and prolongs the transmission distance of ion and electron, leads to dynamics slow, internal resistance increases and polarization exacerbates.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a battery electrode and a battery. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries widely used in mobile devices and electric vehicles. They achieve charging and discharging through the insertion and extraction of lithium ions between the positive and negative electrodes. To improve overall performance and meet the demands for high energy density, current technologies employ multi-layer coating with different coating structures on the battery electrodes.

[0003] Multi-layer coated battery electrodes, due to their increased thickness, extend the transport distance for ions and electrons, leading to significant issues with internal resistance and polarization within the cell. Furthermore, the differences in properties between the various coating layers in a multi-layered structure can easily cause interlayer splitting, impaired conductivity, and low capacity, affecting the battery's cycle life and overall lifespan. Summary of the Invention

[0004] The battery electrode and battery provided by the embodiments of the present invention at least solve the problem that the battery performance is affected by the differences in the properties of different coatings in the multi-layer coating structure of the battery electrode.

[0005] In a first aspect, the present invention provides a battery electrode sheet comprising:

[0006] current collector;

[0007] An active material layer is disposed on at least one surface of the current collector in the thickness direction. The active material layer includes a plurality of coatings stacked along the thickness direction. The active material layer on at least one surface of the current collector is provided with blind holes. The openings of the blind holes are disposed on the surface of the active material layer away from the current collector in the thickness direction. The blind holes penetrate the contact interface of adjacent coatings in the thickness direction.

[0008] The blind hole is filled with a filling layer.

[0009] The battery electrode provided by the present invention includes a first filling layer that is away from the surface of the current collector, and a second filling layer disposed opposite to the first filling layer;

[0010] The surface of the first filling layer is flush with the opening of the blind hole; the thickness of the first filling layer accounts for 5% to 15% of the depth of the blind hole; the thickness of the second filling layer accounts for 85% to 95% of the depth of the blind hole.

[0011] The present invention provides a battery electrode sheet, wherein the battery electrode sheet is a negative electrode sheet, the first filling layer of the negative electrode sheet is an adhesive layer, and the second filling layer of the negative electrode sheet is a conductive layer;

[0012] Alternatively, the battery electrode is a positive electrode, the first filling layer of the positive electrode is a binder layer, and the second filling layer of the positive electrode is a lithium replenishment layer.

[0013] The battery electrode provided by this invention has a blind hole depth that accounts for 50% to 90% of the thickness of the active material layer;

[0014] Or / and, the depth of the blind hole is greater than or equal to 40 μm, and the thickness of the active material layer is less than or equal to 180 μm.

[0015] The battery electrode provided by this invention includes an array of blind holes; the maximum outer diameter of the opening of each blind hole is set to 30 μm to 300 μm, the gap width between adjacent openings of blind holes is set to 200 μm to 5000 μm, and the blind holes occupy 0.5% to 30% of the surface area of ​​the active material layer.

[0016] The battery electrode provided by this invention has a mating portion on the surface of the active material layer away from the current collector in the thickness direction; the mating portion is a raised structure or a recessed structure, and the mating portion is used to mate with a corresponding mating portion on another battery electrode of opposite polarity.

[0017] The battery electrode provided by this invention has a mating portion occupying 5% to 20% of the surface area of ​​the active material layer.

[0018] The battery electrode provided by this invention has a mating portion with a size of 1μm to 20μm in the thickness direction of the current collector.

[0019] Secondly, the present invention also provides a battery comprising a positive electrode and a negative electrode stacked together, and a separator disposed between the positive electrode and the negative electrode; wherein the positive electrode and the negative electrode are configured as battery electrodes as described in any of the above embodiments;

[0020] The positive and negative electrode plates on both sides of the diaphragm form a concave-convex mating structure through the mating part.

[0021] The battery provided by this invention has blind holes in the active material layers of the positive electrode and the negative electrode on both sides of the separator arranged opposite each other along the thickness direction.

[0022] The battery electrode and battery provided by the present invention solve the problems of low interfacial bonding and low ion transport efficiency in multi-layered active material layers by setting blind holes and filling layers. This improves the active material layer coating by increasing the thickness, extending the transport distance of ions and electrons, reducing internal resistance, and mitigating polarization. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0024] Figure 1 This is a schematic diagram of the structure of a battery electrode sheet that is not filled during processing, according to an embodiment of the present invention.

[0025] Figure 2 yes Figure 1 The diagram shows the structure of the battery electrode.

[0026] Figure 3 yes Figure 2 The image shows an isometric sectional view of the battery electrode.

[0027] Figure 4 yes Figure 2 The image shows a cross-sectional view of a battery electrode where blind holes are partially filled during processing.

[0028] Figure 5 yes Figure 2 Another cross-sectional view showing the battery electrode partially filled with blind holes during processing.

[0029] Figure 6 This is a schematic diagram of another battery electrode sheet in an embodiment of the present invention, showing an unfilled structure during processing.

[0030] Figure 7 yes Figure 6 The diagram shows the structure of the battery electrode.

[0031] Figure 8 yes Figure 7 The image shows an isometric sectional view of the battery electrode.

[0032] Figure 9 yes Figure 7 The image shows a cross-sectional view of the battery electrode where blind holes were partially filled during processing.

[0033] Figure 10 This is a schematic diagram of the structure of the battery with the positive and negative electrodes in an embodiment of the present invention.

[0034] Figure 11 This is a schematic diagram of the arrangement of the positive electrode, separator, and negative electrode of the battery in an embodiment of the present invention.

[0035] The above figures include the following reference numerals:

[0036] 1. Current collector; 2. Active material layer; 21. First coating layer; 22. Second coating layer; 23. Third coating layer; 24. Contact interface; 3. Blind hole; 31. Orifice; 32. Hole wall; 33. Closed end; 4. Filling layer; 41. First filling layer; 42. Second filling layer; 51. Negative electrode; 52. Positive electrode; 53. Separator; 6. Mating part; 61. Protruding structure; 62. Recessed structure. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0040] Example 1

[0041] Multilayer coated electrode technology can achieve higher energy density batteries by controlling the weight, particle size, specific capacity, and additive ratio of each coating layer to create a vertically distributed coating structure. However, increasing the thickness of the multilayer coated electrode will prolong the transport distance of ions and electrons, introducing increased internal resistance and polarization problems. Differences in the properties of each layer can also easily lead to interlayer splitting, conduction obstruction, and low capacity, which will adversely affect battery performance and lifespan.

[0042] Therefore, Embodiment 1 of this utility model provides a battery electrode, referring to... Figure 1As shown, the battery electrode includes a current collector 1 and an active material layer 2. The active material layer 2 has blind holes 3, and a filling layer 4 is disposed inside the blind holes 3. By creating holes in the multilayer coating structure and setting a suitable filling layer 4, the interlayer splitting problem is solved and the internal resistance is reduced to alleviate polarization. While maintaining high energy density, the conductivity problem caused by the multilayer coating structure is overcome, ion transport efficiency is improved, and the performance of the battery electrode when applied to a battery is optimized.

[0043] Specifically, the thickness direction of the current collector 1 is perpendicular to the extension direction, and the current collector 1 has opposing surfaces on both sides along the thickness direction. An active material layer 2 is disposed on the current collector 1 and located on at least one surface of the current collector 1 along its thickness direction. The active material layer 2 includes multiple coatings; the number of coatings can be two, three, four, or more, and is not limited in this embodiment. The coatings are stacked on the surface of the current collector 1 along its thickness direction. In this embodiment of the invention, the thickness direction of the current collector 1, the thickness direction of the active material layer 2, and the direction in which the multiple coatings are stacked are all in the same direction, and will be described using the thickness direction as an example; further details will not be repeated below.

[0044] When an active material layer 2 is provided on one side of the current collector 1 along the thickness direction, a blind hole 3 is provided on the active material layer 2. When an active material layer 2 is provided on both sides of the current collector 1 along the thickness direction, a blind hole 3 is provided on at least one side of the active material layer 2. Preferably, a blind hole 3 is provided on both sides of the active material layer 2.

[0045] The orifice 31 of the blind hole 3 is located on the surface of the active material layer 2 away from the current collector 1 in the thickness direction. The blind hole 3 is a hole structure that does not penetrate the entire thickness of the object; it extends inward from the surface of the object to a certain depth and then terminates without penetrating to the other side of the surface. Unlike through-hole structures, when the orifice 31 of the blind hole 3 is located on the surface of the active material layer 2 away from the current collector 1, the closed end 33 of the blind hole 3 does not penetrate to the other side of the active material layer but is inside the active material layer 2. Since the active material layer 2 is coated on the surface of the current collector 1, this structure of the blind hole 3 can avoid creating uncoated areas in the current collector 1 due to hole formation. Unlike tabs without active material coating, the uncoated areas exposed by hole formation are scattered and disordered, unable to form a unified current converging path and lacking directional connection with external conductive components, thus failing to achieve the same effective conduction effect as tabs.

[0046] Furthermore, the blind via 3 structure retains a certain thickness of the active material layer 2 at the via formation point, which can reduce the risk of uneven pressure on the electrode during rolling and reduce strip breakage; it also avoids excessive loss of active material, which could affect energy density and cause lithium plating and lithium dendrite formation. Since the via structure is formed by laser equipment, the blind via 3 processing can reduce the power requirements of the laser equipment, reduce the spatial positioning difficulty of laser etching, and avoid penetrating the foil during processing, thus affecting the yield.

[0047] Continuing, when the active material layer 2 comprises multiple coatings, adjacent coatings are connected by a contact interface 24. During battery cycling, the differences in chemical properties of each layer material result in inconsistent volume expansion and contraction. This uneven volume change creates continuous stress at the interlayer contact interface 24. As stress accumulates, it eventually exceeds the interlayer bonding strength limit, causing gaps or even splits in the originally tightly bonded interface. In this embodiment, the blind hole 3 penetrates the contact interface 24 of adjacent coatings in the thickness direction. That is, the closed end 33 of the blind hole 3 is located inside the coating that is closely attached to the current collector 1 in the thickness direction, penetrating the contact interface 24 of any two adjacent coatings. The blind hole 3 provides a buffer space for material deformation, alleviating the tensile force caused by stress concentration between layers. At the same time, the hole-forming process can enhance the physical bonding force of adjacent coatings, reduce the risk of interlayer splitting, and maintain structural stability.

[0048] The blind hole 3 is provided with a filling layer 4. The filling layer 4 includes a first filling layer 41 away from the surface of the current collector 1, and a second filling layer 42 disposed opposite to the first filling layer 41.

[0049] Specifically, refer to Figure 2 and Figure 3 As shown, when the battery electrode is a negative electrode 51 or a positive electrode 52, the first filler layer 41 is an adhesive layer. When the positive and negative electrodes are assembled with the separator 53 into a core, the adhesion between them is insufficient, making them prone to slippage due to external disturbances during production. Simultaneously, during cycling, the positive electrode, negative electrode, and separator 53 will experience varying degrees of volume expansion and contraction due to differences in material properties, creating gaps between them and further exacerbating poor contact. When the first filler layer 41 is an adhesive layer, it enhances the adhesion between the battery electrode and the separator 53, improves the rigidity of the core, and, through the binding effect of tightly bonded layers, suppresses the gaps caused by volume expansion and contraction between the battery electrode and the separator 53, thereby reducing the risk of lithium plating and poor contact.

[0050] Furthermore, when the battery electrode is a positive electrode 52, the first filler layer 41 is a binder layer, and the material of the first filler layer 41 includes polyvinylidene fluoride (PVDF). When the battery electrode is a negative electrode 51, the first filler layer 41 is a binder layer, and the material of the first filler layer 41 is sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). Since the positive electrode is in a high-voltage, strongly oxidizing environment, PVDF possesses excellent oxidation resistance and chemical stability. The negative electrode material is prone to volume expansion during cycling, and CMC and SBR, while acting as binders, also possess good flexibility to adapt to volume changes. The above binder layer materials are only examples; the binder layer materials can also be determined according to actual needs and other conditions, and are not limited to these.

[0051] Furthermore, the surface of the first filler layer 41 is flush with the opening 31 of the blind via 3. This avoids the surface of the first filler layer 41 being lower than the opening 31, forming a depression that would accumulate electrolyte impurities and affect ion transport, while also reducing the contact area between the adhesive layer and the separator 53, thus affecting the bonding effect. Conversely, it avoids the surface of the first filler layer 41 being higher than the opening 31, forming a protrusion that would compress the separator 53 or create gaps during assembly. The flushness of the surface of the first filler layer 41 with the opening 31 of the blind via 3 ensures that the adhesive layer and the separator 53 are fully adhered to enhance interfacial bonding, while also maintaining the flatness of the battery electrode surface, ensuring a smooth ion transport path.

[0052] Specifically, refer to Figure 3 and Figure 4 As shown, the second filling layer 42 and the first filling layer 41 are disposed opposite each other along the thickness direction. In one embodiment, the battery electrode is a positive electrode 52. In the active material layer 2 of the positive electrode 52, the lithium-ion insertion / extraction rates of each layer are inconsistent. When the lithium-ion insertion or extraction rate is faster in some coatings, the active material in that region can quickly participate in the reaction and release capacity. However, in coatings with slower insertion / extraction rates, due to insufficient lithium-ion supply or obstructed extraction, a large amount of active material cannot fully participate in the electrochemical reaction. Ultimately, this results in the actual capacity of the positive electrode 52 being lower than the design value, causing a low-capacity problem.

[0053] The second filling layer 42 of the positive electrode 52 is a lithium replenishment layer. Exemplarily, the lithium replenishment layer can be set to at least one of lithium iron phosphate (LFP), medium nickel ternary 622 (LiNi0.6Co0.2Mn0.2O2), and lithium iron manganese phosphate (LFMP); it can also include at least one of binary lithium compound Li2O, lithium-rich compound Li2NiO2, lithium-rich compound Li5FeO4, and lithium complex Li2S / Co.

[0054] In some implementations, the lithium supplementation layer can also be configured as a combination of multiple materials to achieve complementary performance. For example, lithium nickel cobalt manganese oxide (NCM) can be used as the main body to supplement lithium iron phosphate (LFP), or high-lithium ternary 811 can be used as the main body to supplement medium-nickel ternary 622, or large-particle-size lithium iron phosphate (LFP) can be used as the main body to supplement small-particle-size lithium manganese iron phosphate (LFMP).

[0055] The lithium ions released from the lithium replenishment layer replenish those lost in the reaction, providing a sufficient lithium ion source for coatings with slow insertion / extraction rates. Active materials that were previously underutilized due to insufficient lithium ion supply can participate in the reaction after lithium replenishment, thus solving the low-capacity problem.

[0056] In addition, the second filler layer 42 is a lithium replenishment layer, which can reduce lithium loss in the first cycle, improve the first charge and discharge efficiency, and the stable lithium ion supply can alleviate the uneven reaction of each coating during the cycle, thereby enhancing the cycle capability of the battery.

[0057] In one embodiment, the battery electrode is a negative electrode 51. Due to differences in the material composition or structure of the different coatings of the active material layer 2 of the negative electrode 51, the conductivity of each layer varies slightly. Electrons need to cross each coating to form a continuous conduction path, but uneven conductivity causes electrons to encounter greater transport resistance at the interlayer interfaces. As the number of cycles increases, the conduction obstruction problem accumulates, leading to a continuous increase in overall internal resistance and exacerbating polarization. The large volume variation of the negative electrode material makes the conductivity difference more likely to disrupt the vertical conductive network, resulting in a more prominent conduction obstruction problem compared to the positive electrode with its stable material volume.

[0058] Therefore, the second filling layer 42 of the negative electrode 51 is a conductive layer. Depending on the contact type, the conductive layer can be set as a point contact conductive agent such as conductive graphite or conductive carbon black, a line contact conductive agent such as conductive carbon fiber or carbon nanotube, or a surface contact conductive agent such as graphene.

[0059] In some embodiments, the conductive layer can also be configured as a combination of multiple active materials to achieve complementary performance. For example, graphite can be used as the main active material to supplement hard carbon, combining the high cycle stability and low-temperature performance of hard carbon to compensate for the shortcomings of graphite under extreme conditions. Alternatively, high-capacity graphite can be used as the main active material to supplement fast-charging graphite, retaining the high capacity base while accelerating ion transport. Or, graphite with a large particle size distribution can be used as the main active material to supplement graphite with a small particle size distribution, fully filling the voids and increasing the material packing density. In other embodiments, the conductive layer material can be specifically set according to actual needs, and is not limited to these.

[0060] By setting the conductive layer of the negative electrode 51, a conductive path in the thickness direction can be established, allowing the conductive network that was originally broken or blocked due to differences in conductivity to be reconnected. Electrons can quickly pass through different layers along these newly added conductive paths, effectively reducing the conduction resistance in the thickness direction, reducing internal resistance, alleviating the polarization phenomenon caused by excessive internal resistance, and improving the electrochemical properties of the battery electrode.

[0061] It should be noted that, in some embodiments, to achieve the effect of lithium replenishment or conductivity of the second filling layer 42, the second filling layer 42 may only abut against the hole wall 32 of the blind hole 3 used for the interlayer contact interface 24, and the first filling layer 41 may be disposed inside the blind hole 3 in the area outside the second filling layer 42. In other embodiments, preferably, for ease of filling, the first filling layer 41 and the second filling layer 42 are disposed opposite each other along the thickness direction.

[0062] Specifically, refer to Figure 4 and Figure 9 As shown, the first filling layer 41 and the second filling layer 42 are disposed opposite each other along the thickness direction. The thickness of the first filling layer 41 is h1, the thickness of the second filling layer 42 is h2, and the depth of the blind hole 3 is H, so h1 + h2 = H. In one embodiment of this utility model, the thickness h1 of the first filling layer 41 accounts for 5% to 15% of the depth H of the blind hole 3, h1 ∈ [5%H, 15%H]. The thickness h2 of the second filling layer 42 accounts for 85% to 95% of the depth H of the blind hole 3, h2 ∈ [85%H, 95%H]. This thickness setting facilitates the balance of performance between the first filling layer 41 and the second filling layer 42. If the thickness of the first filling layer 41 is too small, it is difficult to form an effective adhesive force, and it cannot stably connect the battery electrode and the separator 53, thus failing to enhance the interface bonding. If the thickness of the first filling layer 41 is too large, it will encroach on the space of the second filling layer 42, resulting in excessive loss of active material in the active material layer 2, weakening the conductivity of the conductive layer and the lithium replenishment effect of the lithium replenishment layer. The thickness ratio setting ensures that the adhesive layer can play its due bonding role, while also reserving enough space for the conductive layer and the lithium replenishment layer.

[0063] Specifically, after rolling, the depth H of the blind hole 3 accounts for 50% to 90% of the thickness of the active material layer 2, or / and the depth H of the blind hole 3 is greater than or equal to 40 μm, and the thickness of the active material layer 2 is less than or equal to 180 μm. When the proportion of the blind hole 3 depth H is higher than 90%, the processing is more difficult and it is easy to penetrate and expose the foil or damage the foil. When the proportion of the blind hole 3 depth H is lower than 50%, the hole is too shallow and cannot solve the interlayer splitting problem, and it will also affect the space of the filling layer 4.

[0064] Furthermore, referring to Figure 4 and Figure 9 As shown, in some embodiments, the active material layer 2 comprises three layers stacked together. The thickness of each layer after drying is 15 μm to 80 μm, meaning the thickness of the active material layer 2 is less than or equal to 240 μm. After rolling, the thickness of each layer is 10 μm to 60 μm, meaning the thickness of the active material layer 2, D1+D2+D3, is ≤180 μm, and at this point, the depth H of the blind hole 3 is greater than or equal to 40 μm. The reasonable setting of the depth H of the blind hole 3 in this invention helps to increase the surface area of ​​the battery electrode, improve the contact area of ​​the electrolyte, optimize the wetting effect of the battery electrode, and also provide sufficient space for the filler.

[0065] Specifically, refer to Figure 1 and Figure 6 As shown, the blind vias 3 are arranged in an array to evenly distribute the internal stress of the electrode and avoid local stress concentration. To achieve optimal results, a filling layer 4 is provided in each blind via 3. The orderly arrangement of the blind vias 3 allows for uniform wetting of the electrolyte, facilitating the hole-making process and the filling of the filling layer 4.

[0066] When the blind vias 3 are arranged in an array, the gap width W2 between the openings 31 of adjacent blind vias 3 is 200 μm to 5000 μm. The blind vias 3 occupy 0.5% to 30% of the surface area of ​​the active material layer 2. The openings 31 of the blind vias 3 can be square, circular, or irregularly shaped. The maximum outer diameter of the opening 31 is 30 μm to 300 μm; when the opening 31 is circular, its diameter is 30 μm to 300 μm; when the opening 31 is square or rectangular, its diagonal is 30 μm to 300 μm. (Refer to...) Figure 3 and Figure 4 When the aperture 31 shown is square, 21.22μm≤W1≤212.13μm.

[0067] The gap and diameter of the orifice 31 determine the area occupied by the blind hole 3. If the gap width is too small, the area occupied is too large, or the diameter is too large, it will directly affect the mechanical strength of the battery electrode. If the gap width is too large or the area occupied by the blind hole 3 is too small, it will not be conducive to solving the interlayer problem. If the diameter is too small, it will also be not conducive to the filling of the filler layer 4.

[0068] Reference Figure 5As shown, after the filling layer 4 is filled, its shape is determined by the shape formed by the hole wall 32 and the closed end 33 of the blind hole. In some embodiments, the hole wall 32, the hole opening 31, and the closed end 33 of the blind hole 3 can be formed into a prism, cylinder, pyramid, cone, frustum, or other irregular structure. That is, the closed end 33 can be set as a plane, curved surface, irregular surface, or tip; the hole wall 32 can be set as a prism side, cylinder side, pyramid side, cone side, frustum side, or other irregular surface that can connect the hole opening 31 and the closed end 33.

[0069] For the structure of the blind hole 3, it is preferably configured as a constant-diameter structure where the hole wall 32 extends along the thickness direction and has a consistent inner diameter from the orifice 31 to the closed end 33. Compared with the variable-diameter structure, this type of structure has a regular hole wall 32 with a uniform diameter, which can provide a stable and consistent path for electrolyte penetration and ion transport, avoiding the impact of ion diffusion caused by abrupt changes in pore size in the variable-diameter structure. The hole wall 32 is subjected to more uniform stress and is less prone to cracking or collapse due to cyclic stress concentration, resulting in good structural stability. In addition, the constant-diameter structure is simple and controllable to process, easy to fill, and has a lower cost.

[0070] During the use of battery electrodes, stress changes during battery cycling, uneven stacking pressure, and vibration or temperature fluctuations during long-term use can all exacerbate the relative movement between the battery electrodes and the separator 53. After slippage occurs, the originally aligned active areas may become misaligned, leading to poor local contact and significantly increasing interface resistance. Excessive friction caused by slippage can also damage the separator 53, cause active material to detach, and accelerate mechanical damage to the battery electrodes.

[0071] Specifically, refer to Figure 6 , Figure 7 and Figure 8 As shown, a mating portion 6 is also provided on the surface of the active material layer 2 away from the current collector 1 in the thickness direction. The mating portion 6 is a raised structure 61 or a recessed structure 62. The mating portion 6 is used to mate with the corresponding mating portion 6 on the other side of the battery electrode with opposite polarity. When the mating portion 6 of the positive electrode 52 is a raised structure 61, the mating portion 6 of the negative electrode 51 on the other side of the separator 53 that it abuts is set as a recessed structure 62. Correspondingly, when the mating portion 6 of the positive electrode 52 is a recessed structure 62, the mating portion 6 of the negative electrode 51 on the other side of the separator 53 that it abuts is set as a raised structure 61. The relative movement between the electrodes is restricted by the mating relationship of the mating portions 6 of the two battery electrodes with opposite polarities, and the displacement tendency is offset by the structural interlocking, thereby maintaining interface stability.

[0072] Preferably, the mating portion 6 of the negative electrode 51 is configured as a recessed structure 62. The concave negative electrode can increase the electrolyte contact area and reduce the ion transport path.

[0073] The mating portion 6 reduces the tortuosity of the electrode surface layer, facilitates ion diffusion and transport in the thickness direction, and increases the contact surface in the horizontal direction, reserving space for changes in material volume. The mating portion 6 occupies 5% to 20% of the surface area of ​​the active material layer 2. If the area proportion is too small, the restraining effect on slippage is insufficient; if the proportion is too large, it will occupy the blind hole 3 and make assembly inconvenient. The thickness of the coating with the mating portion 6 is D3, where D3 ∈ (0 μm, 80 μm). The depth of the mating portion 6 of the negative electrode 51 obtained by etching is the same as the thickness of the mating portion 6 of the positive electrode 52, accounting for 30% to 70% of the coating thickness D3 with the mating portion 6.

[0074] In the extending direction of the surface of the active material layer 2, the mating portion 6 can be configured as multiple discrete point structures, specifically at least a portion of a sphere, prism, cylinder, pyramid, cone, frustum, or other irregular structure. Alternatively, the mating portion 6 can be configured as a transversely intersecting strip structure that mates with the array of blind holes 3, extending along a straight line, broken line, or curve. Figure 4 The cross-section of the mating part 6 shown can be configured as a square, arc-shaped, or irregular shape with a protrusion or depression on the surface of the active material layer 2 away from the current collector 1. (Refer to...) Figure 4 As shown, the dimensions of the mating portion 6 in the thickness direction of the current collector 1 are 1μm to 20μm; 1μm≤h3≤20μm and 1μm≤h4≤20μm. When the mating portion 6 is set as a strip structure, its width is less than or equal to 150μm.

[0075] The battery electrode provided in Embodiment 1 of this utility model solves the problems of low interfacial bonding and low ion transport efficiency in multi-layered active material layers 2 by setting blind holes 3 and filling layers 4. It also addresses the issues of slow kinetics, increased internal resistance, and intensified polarization caused by a thicker active material layer 2 coating that extends the transport distance of ions and electrons.

[0076] Example 2

[0077] Reference Figure 10 and Figure 11 As shown, Embodiment 2 of this utility model provides a battery. The battery includes a positive electrode 52 and a negative electrode 51 stacked together, and a separator 53 disposed between the positive electrode 52 and the negative electrode 51. The positive electrode 52 and the negative electrode 51 are configured as the battery electrodes provided in Embodiment 1. Therefore, this battery incorporates all the technical effects of the aforementioned battery electrodes. Since the technical effects of the battery electrodes have been described in detail above, they will not be repeated here.

[0078] The positive electrode 52 and negative electrode 51 on both sides of the separator 53 form a concave-convex mating structure through the mating part 6. When the positive and negative electrode sheets are assembled with the separator 53 into a core, the adhesion between them is insufficient, which makes them prone to slippage due to external disturbances during the production process. The interlocking and concave-convex mating part 6 can increase the stability and facilitate shaping during battery electrode assembly.

[0079] The blind holes 3 of the active material layer 2 of the positive electrode 52 and the negative electrode 51 on both sides of the separator 53 are arranged opposite each other along the thickness direction. When the positive electrode 52 and the negative electrode 51 are engaged with each other through the mating parts 6 with concave and convex arrangements, the openings 31 of the blind holes 3 of the positive electrode 52 on both sides of the separator 53 are also arranged opposite to the openings 31 of the blind holes 3 of the negative electrode 51, which is conducive to the rapid diffusion and migration of lithium ions in the lithium replenishment layer.

[0080] In an embodiment of the battery provided in Embodiment 2 of this utility model, the mating portion 6 of the negative electrode 51 is configured as a recessed structure 62, and the mating portion 6 of the positive electrode 52 is configured as a raised structure 61. The recessed negative electrode can increase the electrolyte contact area and reduce the ion transport path. The negative electrode 51 is first filled with blind holes 3 and then etched with mating portion 6, while the positive electrode 52 is first prepared with mating portion 6 and then filled with blind holes 3. The specific preparation method includes the following steps. Exemplarily, this embodiment also provides a specific preparation method that can be implemented, including specific data of coating slurry and filling layer 4, for performance comparison with comparative examples. It should be noted that the following specific data of electrolyte, separator 53, coating slurry, blind holes 3, and filling layer 4 are only one possible implementation method and do not constitute a specific limitation on the battery provided in Embodiment 2.

[0081] Specifically, the preparation of the negative electrode 51 includes:

[0082] Prepare the current collector 1 for the negative electrode 51. The current collector 1 for the negative electrode 51 is a copper foil with a thickness of 4μm to 20μm, or a composite foil. The middle layer of the composite foil is a PET layer.

[0083] Multiple coatings were sequentially applied, dried, and rolled along a direction away from current collector 1. The anodic areal density of each coating was 0.032 mg / mm². 2 ~0.150mg / mm 2 Each coating, after drying, has a thickness of 15μm to 80μm, and the total thickness of the three coatings stacked is less than or equal to 240μm. After roll pressing, each coating has a thickness of 10μm to 60μm, and the total thickness of the three coatings stacked is less than or equal to 180μm.

[0084] The slurry of the first coating 21 near the current collector 1 contains the following components by mass fraction: 97 parts artificial graphite, 1 part conductive agent SP, and 2 parts binder PAA. The solid components account for 51.2% of the total mass of the slurry, and the slurry viscosity is 5247 mPa·s. The areal density of the first coating 21 is 0.10 g / 1540.25 mm. 2 The compaction concentration is 1.64 g / cc, and the coating thickness after roll pressing is approximately 47.5 μm.

[0085] The slurry for the second coating 22 comprises the following components by mass fraction: 97 parts of a mixed graphite composed of artificial and natural graphite, 1 part of conductive agent SP, and 2 parts of binder PAA. The solid components account for 49.6% of the total slurry mass, and the slurry viscosity is 4639 mPa·s. The areal density of the second coating 22 is 0.08 g / 1540.25 mm. 2 The compaction concentration is 1.62 g / cc, and the coating thickness after roll pressing is approximately 40.1 μm.

[0086] The slurry of the third coating 23, located away from the current collector 1, contains the following components by mass fraction: 97 parts natural graphite, 1 part conductive agent SP, and 2 parts binder PAA. The solid components account for 49.1% of the total mass of the slurry, and the slurry viscosity is 4123 mPa·s. The areal density of the third coating 23 is 0.05 g / 1540.25 mm. 2 The coating thickness after rolling is approximately 32.5μm, with a compaction density of 1.60g / cc.

[0087] The negative electrode sheet 51 uses three coatings of artificial graphite, mixed graphite, and natural graphite, respectively. The combination of graphite with different particle sizes and spacing creates favorable channels for lithium ions to diffuse vertically into the material, accelerating ion transport and improving battery charge / discharge efficiency. Furthermore, this vertically arranged, progressively larger particle size better accommodates the pressure conditions of different coatings. Under the same compaction conditions, the use of larger particle size in the bottom layer reduces the likelihood of particle breakage due to pressure from the upper layers, thus improving the overall compaction effect of the electrode sheet.

[0088] After the active material layer 2 is prepared, blind holes 3 are processed by using an embossing roller with barbs on the surface, or by laser etching to obtain blind holes 3. The blind holes 3 are cylindrical, with an opening diameter 31 of 80 μm, a gap of 3 mm, and a depth H of 100 μm.

[0089] The second filler layer 42 is injected into the blind hole 3 by pinhole injection molding and then dried. The second filler layer 42 is a CNT solution with a solid content of 5% and the thickness h2 of the second filler layer 42 is 90 μm.

[0090] The first filler layer 41 is then injected using pinhole injection molding and dried. The first filler layer 41 is a CMC solution with a solid content of 1.5% and a thickness h1 of 10 μm.

[0091] On the surface of the active material layer 2 away from the current collector 1 in the thickness direction, etching is performed in the area other than the blind hole 3 to obtain the recessed mating part 6. The laser etching can be performed using an ultra-short intense laser pulse with a pulse energy of 1-10 μJ, a laser power of 1-10 W, a laser scanning speed of 1-100 mm / s, an etching time of 0.2-10 s, an etching depth of 10 μm, and a mating part 6 width of 80 μm, thus completing the preparation of the negative electrode sheet 51.

[0092] The preparation of positive electrode 52 includes:

[0093] Prepare a current collector 1 for the positive electrode 52. The current collector 1 for the positive electrode 52 is an aluminum foil with a thickness of 8μm to 20μm, or a composite foil. The middle layer of the composite foil is a PET layer.

[0094] Multiple coatings were sequentially applied, dried, and rolled along a direction away from current collector 1. The cathode areal density of each coating was 0.087 mg / mm². 2 ~0.292mg / mm 2 Each coating, after drying, has a thickness of 15μm to 80μm, and the total thickness of the three coatings stacked is less than or equal to 240μm. After roll pressing, each coating has a thickness of 10μm to 60μm, and the total thickness of the three coatings stacked is less than or equal to 180μm.

[0095] The slurry of the first coating 21 near the current collector 1 contains the following components by mass fraction: 97 parts of small-particle-size LFP, 2 parts of conductive agent CNT, and 1 part of binder PVDF. The solid components account for 65.2% of the total mass of the slurry, and the slurry viscosity is 7236 mPa·s. The areal density of the first coating 21 is 0.18 g / 1540.25 mm. 2 The compaction density is 2.65 g / cc, and the coating thickness after roll pressing is approximately 44.1 μm.

[0096] The slurry for the second coating 22 comprises the following components by mass fraction: 97 parts of LFP (a mixture of large and small particle sizes), 1 part of conductive agent SP, and 2 parts of binder PAA. The solid components account for 65.8% of the total slurry mass, and the slurry viscosity is 7814 mPa·s. The areal density of the second coating 22 is 0.12 g / 1540.25 mm. 2 The compaction concentration is 2.62 g / cc, and the coating thickness after roll pressing is approximately 29.7 μm.

[0097] The slurry of the third coating 23, located away from the current collector 1, contains the following components by mass fraction: 98 parts of large-particle-size LFP, 1.5 parts of conductive agent CNT, and 0.5 parts of binder PVDF. The solid components account for 66.2% of the total mass of the slurry, and the slurry viscosity is 8537 mPa·s. The areal density of the third coating 23 is 0.12 g / 1540.25 mm. 2 The coating thickness after rolling is approximately 30.5μm, with a compaction density of 2.55g / cc.

[0098] After the active material layer 2 is prepared, a transfer coating design is used to transfer the coating onto the active material layer 2 using a micro-grooved roller with corresponding light and dark stripes etched in a direction perpendicular to the coating belt. After drying, alternating raised structures 61 are formed. Alternatively, 3D printing technology can be used to prepare mating parts 6 of the raised structures 61 at predetermined positions on the surface. The raised structures 61 are LFPs with a height of 10 μm, the mating parts 6 have a width of 80 μm and a gap of 3 mm, corresponding to the mating parts 6 of the negative electrode sheet 51.

[0099] The blind hole 3 is formed by using an embossing roller with barbs on its surface, or by drilling using laser etching. The blind hole 3 is cylindrical, with an opening diameter of 80 μm, a gap of 3 mm, and a depth H of 80 μm.

[0100] The second filler layer 42 is injected into the blind hole 3 by pinhole injection molding and then dried. The second filler layer 42 is LFO and the thickness h2 of the second filler layer 42 is 72μm.

[0101] The first filler layer 41 is then injected using pinhole injection molding and dried. The first filler layer 41 is a PVDF liquid with a solid content of 2% and a thickness h1 of 8μm, thus completing the preparation.

[0102] In this embodiment 2, the diaphragm 53 is a 7μm thick PP base film. The positive electrode 52, diaphragm 53, and negative electrode 51 are sequentially stacked, with the mating portion 6 of the positive electrode 52 and the mating portion 6 of the negative electrode 51 facing each other and engaging, followed by hot pressing for shaping. The hot pressing time is 3s to 60s, and the hot pressing pressure is less than or equal to 150 tons. After hot pressing, the electrodes are assembled by winding.

[0103] The electrolyte is injected into the dried battery cell. The preparation of the electrolyte includes: mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 to obtain an organic solvent; then adding solute LiPF6 to the organic solvent to dissolve and mix thoroughly to obtain the electrolyte; the concentration of LiPF6 is 1.2 mol / L. After soaking in the electrolyte for 24 hours, the battery cell is manufactured through formation and aging processes, and then packaged to obtain the battery.

[0104] Comparative Example 1

[0105] Comparative Example 1 provides a battery. The only difference between Comparative Example 1 and the battery provided in Example 2 is that the battery electrode in Comparative Example 1 has a mating part 6 but no blind hole 3 and filling layer 4.

[0106] Comparative Example 2

[0107] Comparative Example 2 provides a battery. The only difference between Comparative Example 2 and the battery provided in Example 2 is that the battery electrode in Comparative Example 2 does not have a mating part 6, a blind hole 3, and a filling layer 4.

[0108] Performance Characterization

[0109] The batteries in Example 2, Comparative Example 1, and Comparative Example 2 underwent initial coulombic efficiency testing, internal resistance testing, rate discharge capacity retention testing, and cycle capacity retention testing.

[0110] The first Coulomb efficiency test includes:

[0111] The batteries from Example 2, Comparative Example 1, and Comparative Example 2 were left to stand at 25°C for 30 minutes.

[0112] Charge at a constant current of 0.5C to 3.65V, then charge at a constant voltage until the current is less than 0.05C; record the charging capacity; let stand for 30 minutes.

[0113] Perform constant current discharge at a rate of 1C to 2.0V, and let it stand for 15 minutes. Then perform constant current discharge at 0.1C to 2.0V, and let it stand for 15 minutes. Then perform constant current discharge at 0.01C to 2.0V, and let it stand for 15 minutes. Record the discharge capacity collected in three separate discharges.

[0114] The initial charge capacity and the sum of the three discharge capacities are collected, and the ratio of the total discharge capacity to the initial charge capacity is calculated as the initial coulombic efficiency.

[0115] The internal resistance test includes: constant current charging at a rate of 0.5C for 1.5 hours, followed by resting for 5 minutes; and internal resistance testing using an internal resistance tester.

[0116] Rate discharge capacity retention testing includes:

[0117] C0 is calibrated by constant current charging to 3.65V at a rate of 0.33C; then constant voltage charging is performed until the current is less than 0.05C, and the charge is left to stand for 30 minutes. This process is repeated twice, and the second discharge capacity is selected as the standard capacity C0.

[0118] After standing for 5 minutes, charge at a constant current of 1C to 3.65V, then charge at a constant voltage until the current is less than 0.05C, and let stand for 30 minutes; then discharge at a rate of 2C to the lower voltage limit of 2.0V to obtain the rate discharge capacity.

[0119] Cyclic capacity retention testing includes:

[0120] Let it stand for 5 minutes, then charge it at a constant current rate of 1C to 3.65V, followed by constant voltage charging until the current is less than 0.05C, and let it stand for 30 minutes.

[0121] Perform constant current discharge at a rate of 1C to 2.0V, and then let it stand for 30 minutes.

[0122] Repeat the above steps to complete 800 charge-discharge cycles.

[0123] Table 1 shows the results of the first coulombic efficiency test, internal resistance test, rate discharge capacity retention test, and cycle capacity retention test of the batteries in Example 2, Comparative Example 1, and Comparative Example 2.

[0124] Table 1

[0125]

[0126] As shown in Table 1, in Example 2, after setting the filling layer 4 and the blind via 3, the introduction of the conductive layer and the lithium replenishment layer improved the first-efficiency data and cycle performance compared with Comparative Example 1 and Comparative Example 2, and the internal resistance was reduced, resulting in better performance.

[0127] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0128] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0129] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery electrode, characterized in that, include: current collector(1); An active material layer (2) is disposed on at least one side surface of the current collector (1) in the thickness direction, and the active material layer (2) includes a plurality of coatings stacked in the thickness direction; The active material layer (2) on at least one side surface of the current collector (1) is provided with a blind hole (3), the opening (31) of the blind hole (3) is provided on the surface of the active material layer (2) away from the current collector (1) in the thickness direction, and the blind hole (3) penetrates the contact interface (24) of the adjacent coating in the thickness direction. The blind hole (3) is provided with a filling layer (4).

2. The battery electrode according to claim 1, characterized in that, The filling layer (4) includes a first filling layer (41) away from the surface of the current collector (1) and a second filling layer (42) disposed opposite to the first filling layer (41); The surface of the first filling layer (41) is flush with the opening (31) of the blind hole (3); the thickness of the first filling layer (41) is 5% to 15% of the depth of the blind hole (3); the thickness of the second filling layer (42) is 85% to 95% of the depth of the blind hole (3).

3. The battery electrode according to claim 2, characterized in that, The battery electrode is a negative electrode (51), the first filling layer (41) of the negative electrode (51) is an adhesive layer, and the second filling layer (42) of the negative electrode (51) is a conductive layer. Alternatively, the battery electrode is a positive electrode (52), the first filling layer (41) of the positive electrode (52) is an adhesive layer, and the second filling layer (42) of the positive electrode (52) is a lithium replenishment layer.

4. The battery electrode according to claim 1, characterized in that, The depth of the blind hole (3) is 50% to 90% of the thickness of the active material layer (2); Or / and, the depth of the blind hole (3) is greater than or equal to 40 μm, and the thickness of the active material layer (2) is less than or equal to 180 μm.

5. The battery electrode according to claim 1, characterized in that, The blind holes (3) are arranged in an array; the maximum outer diameter of the opening (31) of the blind holes (3) is set to 30μm to 300μm, the gap width between the openings (31) of adjacent blind holes (3) is set to 200μm to 5000μm, and the blind holes (3) occupy 0.5% to 30% of the surface area of ​​the active material layer (2).

6. The battery electrode according to claim 1, characterized in that, The surface of the active material layer (2) away from the current collector (1) in the thickness direction is also provided with a mating part (6); the mating part (6) is a raised structure (61) or a recessed structure (62), and the mating part (6) is used to mate with the corresponding mating part (6) on the battery electrode with the opposite polarity.

7. The battery electrode according to claim 6, characterized in that, The mating part (6) occupies 5% to 20% of the surface area of ​​the active material layer (2).

8. The battery electrode according to claim 6, characterized in that, The size of the mating part (6) in the thickness direction of the current collector (1) is 1μm to 20μm.

9. A battery, characterized in that, It includes a positive electrode (52) and a negative electrode (51) stacked together, and a separator (53) disposed between the positive electrode (52) and the negative electrode (51); wherein the positive electrode (52) and the negative electrode (51) are configured as battery electrodes as described in any one of claims 1 to 8; The positive electrode (52) and the negative electrode (51) on both sides of the diaphragm (53) form a concave-convex mating structure through the mating part (6).

10. The battery according to claim 9, characterized in that, The blind holes (3) of the active material layer (2) of the positive electrode (52) and the negative electrode (51) on both sides of the diaphragm (53) are arranged opposite each other along the thickness direction.

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