An electrode, its manufacture and use

Abstract

The application discloses an electrode and a manufacturing method and application thereof. The manufacturing method of the electrode comprises the following steps: S1, coating electrode slurry on the surface of the current collector side by using a wet process; S2, vertically immersing a pore-forming needle made of flexible fiber into the electrode slurry; S3, drying the electrode slurry; S4, when the liquid content in the electrode slurry is 5-10 wt%, pulling out the pore-forming needle, and after the electrode slurry is completely dried, forming an active material layer with vertical pores on the surface of the current collector; and S5, after coating electrode slurry on the surface of the other side of the current collector, repeating the above steps S2-S4, thereby obtaining the electrode. The method can efficiently form an electrode with straight pore structure, greatly improves the production efficiency, and the generated straight pores are flat, which greatly improves the service life and safety of the battery. After being filled with electrolyte, the pores can greatly improve the charging capacity and discharging power of the battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to an electrode, a manufacturing method thereof and application. BACKGROUND

[0002] With lithium ion batteries gradually entering millions of households, people's demand for battery performance is becoming higher and higher, especially in terms of energy density, fast charging capability and high power discharge capability. In order to meet these demands, lithium ion battery designers are constantly exploring new design ideas and technical means.

[0003] In the process of improving the energy density of the battery, the single battery is usually made larger and larger and the electrode is made thicker and thicker. However, this design method also brings a series of problems. Due to the porous structure characteristics of the electrode, the electrolyte needs to enter all the pores and fully soak all the active materials of the electrode to ensure that the lithium ion is fully conducted. When the electrode is increased and thickened, the path of the electrolyte soaking the electrode is increased and the degree of tortuosity is increased, which is not conducive to the transmission of lithium ions, resulting in an increase in the internal resistance of the battery, thereby reducing the fast charging capability and power of the battery, and when the soaking is poor, it will further affect the service life and safety of the battery.

[0004] How to ensure the energy density without reducing the charging capability and power, or even further improve these indicators is the focus of the researchers. The existing technologies mainly have the following several methods:

[0005] 1. Thin electrode design: when designing a fast charging type battery, by adopting a thin electrode design, the transmission path of lithium ions in the electrode can be shortened. However, this method will reduce the proportion of active materials, thereby limiting the energy density of the battery.

[0006] 2. Low compaction density design: by reducing the compaction density of the electrode, the porosity can be increased, thereby reducing the degree of tortuosity of the path of lithium ion transmission. However, this method also leads to a reduction in the proportion of active materials, affecting the energy density of the battery.

[0007] 3. Etching holes on the electrode surface: By mechanical or laser etching holes on the electrode surface, the infiltration channels of electrolyte can be increased, and the transmission efficiency of lithium ions can be improved. However, when using mechanical punching, high pressure is needed to break through the active material on the surface of the electrode, so that the depth of the punched hole is uncontrollable, and the active material around the punched hole is raised due to the extrusion of the active material, affecting the surface flatness and the uniformity of the current distribution in the cycle, which is easy to cause lithium precipitation; On the other side of the punched position, there will be excess material accumulation due to the extrusion effect, resulting in protrusions or falling off. Once the electrode is selected to be punched, metal burrs, foreign particles are easy to produce, which is easy to pierce the diaphragm to cause the end grain or self-discharge defect, and waste the active material. If the size of the punched hole is too large, it will affect the energy density of the battery, and if the size of the punched hole is too small, it will pose a great challenge to the material of the puncher. When laser is selected, the advantages are that the size, position and depth of the punched hole are controllable, but there is still a large heat radiation influence area when high-temperature ablation occurs, and the active material in the heat radiation area is damaged, affecting the electrical performance and energy density, and wasting materials. And the molten bead and slag produced by laser ablation at high temperature, these foreign matters may cause short circuit and self-discharge. Finally, the efficiency of laser ablation is a great defect, and industrialization is extremely difficult.

[0008] 4. 3D printed electrode: 3D printing technology can accurately control the shape and structure of the electrode. Although it does not waste materials, the efficiency of 3D printing is extremely low, the cost of the printing head is extremely high, and large-scale industrialization is extremely difficult.

[0009] CN111370645A discloses a method of forming a hole in a liquid slurry and filling the hole with a filler. Although this method eliminates a large amount of powder loss and improves surface flatness, it still faces several problems in implementation: when a solid filler such as a metal probe is used, the metal probe is tightly wrapped by active materials / binders and other materials after the slurry is dried and solidified, making it difficult to remove without damage. If you try to pull it out with brute force, not only will it cause the active material to fall off, but in some cases, the metal probe may not be able to be pulled out at all due to the tight fit. If a pore former is chosen as the filler, although it should theoretically leave a hole during evaporation, due to the extrusion effect of the liquid slurry, the hole formed after drying is often not an ideal vertical channel, but a winding and tortuous shape. Such pore structure not only is not conducive to the uniform infiltration of electrolyte, but also prolongs the path of electrolyte penetration into the electrode, increases the tortuosity of infiltration, and thus adversely affects the performance of lithium-ion batteries. CN106531961A discloses a method of uniformly distributing grooves on the surface of the active material coating on both sides of the electrode sheet by rolling or cold pressing with a specific boss roller or a specific boss plate. The rolling or cold pressing process can easily cause damage or deformation to the electrode material, especially when a large pressure is used, which can cause more obvious damage or deformation, thereby affecting the electrical conductivity and mechanical strength of the electrode sheet, and thus adversely affecting the performance and life of the battery. Moreover, the compaction density of the boss extrusion area is higher than that of the non-extrusion area, resulting in uneven compaction density of the active material area of the electrode, uneven current density, and difficulty for electrolyte to pass through the extruded area, which is not conducive to the performance of the battery. At the same time, if the pressure is too small, the depth of the groove cannot be guaranteed, which affects the infiltration effect of the electrolyte. CN109817895A discloses an electrode preparation method in which micro-holes are punched on the surface of the electrode coating area by a laser mechanism when the surface of the electrode coating area is in a gel state. Although the laser punching technology can punch micro-holes on the surface of the electrode coating area, heat and stress are generated during the laser punching process, which can easily damage the active material on the surface of the electrode sheet, and the shape of the micro-holes can be easily deformed, thereby affecting the performance of the battery. The evaporation point of the solvent in the coating area is usually below 150°C, while the laser punching temperature of the active material is usually 400-500°C or even higher. Most of the heat generated by the laser is absorbed by the solvent, which is then evaporated. The laser punching process is still unable to avoid high-temperature ablation, generating foreign matter such as beads and slag. In addition, the high cost and complex operation of the laser punching equipment also limit the widespread application of this method in industrial production.

[0010] In summary, the prior art has many limitations in improving the performance of lithium-ion batteries. How to ensure the energy density while not reducing or even improving the charging capacity and power of the battery, improving the industrialization efficiency, and improving the life and safety of the battery, is still a technical problem to be solved in the field of lithium-ion batteries. SUMMARY

[0011] In view of the many limitations of the prior art in improving the performance of lithium-ion batteries, the present invention proposes an innovative solution aimed at providing an electrode with straight hole structure and its manufacturing method. The core goal of this invention is to significantly improve the charging capacity, power performance and electrolyte infiltration rate of the battery while ensuring high energy density, and to improve production efficiency.

[0012] Traditional high compaction density design leads to low porosity of the electrode, while high loading capacity makes the electrode thicker, increases the tortuosity of the pores, and further causes problems such as high internal resistance, low fast charging capacity and limited power performance. In addition, the electrolyte faces difficulties in infiltrating these high tortuosity pores, often requiring a long time to complete the infiltration, which not only may lead to poor battery infiltration, but also reduces production efficiency.

[0013] To solve the above problems, the present invention designs an electrode with straight hole structure. This straight hole structure significantly reduces the tortuosity of the pores, thereby improving the charging capacity and power performance of the battery, and allowing the electrolyte to infiltrate the electrode more quickly and more fully.

[0014] To achieve this innovative design, the present invention proposes a completely new electrode manufacturing method. This method can efficiently form an electrode with straight hole structure, greatly improving production efficiency, and the manufacturing method is different from existing mechanical punching, laser etching or 3D printing technology, avoiding the defects that these technologies may bring, greatly improving the life and safety of the battery. At the same time, the method of the present invention avoids the subtractive method of punching, realizes zero waste of raw materials. In addition, this method also has high controllability and flexibility, which can adjust the size, shape and distribution of the straight holes according to actual needs to further optimize the performance of the battery.

[0015] The following is the specific technical solution of the present invention:

[0016] In a first aspect, the present invention provides a method for manufacturing an electrode, comprising the following steps:

[0017] S1, using a wet process to coat electrode slurry on the surface of the current collector side;

[0018] S2, vertically immerse the pore-forming needle made of flexible fiber into the electrode slurry;

[0019] S3, dry the electrode slurry;

[0020] S4, when the liquid content in the electrode slurry is 5-10wt%, the pore-forming needle is pulled out, and after the electrode slurry is completely dried, an active material layer with vertical pores is formed on the surface of the current collector;

[0021] S5, after the electrode slurry is coated on the surface of the other side of the current collector, the above steps S2-S4 are repeated, and thus an electrode is obtained, which comprises a current collector and active material layers on both sides of the current collector.

[0022] In step S2, since the electrode slurry has fluidity at this time, the pore-forming needle can be easily immersed in the slurry, and due to the action of gravity, it can be distributed in the slurry vertically and according to the design of the number of pores per unit area.

[0023] In step S4, when the liquid content in the electrode slurry is 5-10wt%, the electrode slurry is about to be completely dried at this time, and the electrode still contains a certain amount of solvent. The electrode slurry has a certain flexibility, so that the electrode slurry at this time will not wrap the pore-forming needle, so that the pore-forming needle cannot be pulled out or damaged. At the same time, it will not cause the vertical pores to collapse.

[0024] Further, the vertical cross section of the pore-forming needle can be one or more of a circular shape, a rectangular shape, a diamond shape, a triangular shape, etc., and is preferably a circular shape. When the vertical cross section is a circular shape, the diameter is preferably between 1-500μm.

[0025] According to the positive and negative electrodes of the electrode, a suitable current collector is selected. Generally, when the electrode is a positive electrode, the current collector is preferably an aluminum foil; when the electrode is a negative electrode, the current collector is preferably a copper foil.

[0026] Further, the immersion area of the pore-forming needle is 0.01%-10% (preferably 0.03%-3%) of the area of the electrode slurry. If the proportion is less than 0.01%, the improvement in charging capacity and discharging power is small, and when the proportion is greater than 10%, although the charging capacity and discharging power are improved more, the energy density decreases more. Therefore, the proportion is preferably 0.01%-10%, so that the battery has excellent comprehensive performance.

[0027] Further, the surface of the pore-forming needle has a hydrophobic coating or an oleophobic coating, and the hydrophobic or oleophobic property of the coating is opposite to that of the electrode slurry, so as to facilitate the pulling out of the pore-forming needle.

[0028] Flexible fibers become the material for preparing the pore-forming needle due to their easy operation and the characteristics of not easily damaging the verticality of the pores. In terms of material, one or more of PET, PP, PTFE, etc. engineering plastic fiber, or glass fiber, carbon fiber, etc. high-strength material can be selected.

[0029] Compared with the rigid material made pore-forming needle, the flexible fiber pore-forming needle shows significant advantages in the whole operation process of insertion and extraction. The rigid pore-forming needle must always maintain a strict vertical state during the process of inserting the electrode paste until completely extracting, and ensure the vertical upward movement track when extracting to avoid the adverse effects on the verticality of the hole. However, the electrode paste has fluidity, and its density gradually increases during the drying process, which makes the rigid pore-forming needle face great challenges in overcoming the extrusion of the paste to maintain the vertical posture. In the process of industrial production, the electrode is produced on the assembly line, and when the pore-forming needle is extracted, the electrode continues to move forward, which requires the application of upward and forward forces at the same time, so that the control of the rigid pore-forming needle to maintain the vertical posture is extremely difficult, often leading to the tilting or even collapse of the pore-forming needle, which seriously affects the quality and production efficiency of the product. In contrast, the flexible fiber pore-forming needle can more effectively adapt to the fluidity and density changes of the electrode paste due to its good flexibility and elasticity. In the insertion process, the flexible fiber can deform moderately to reduce the insertion resistance; when extracted, its elastic recovery capability can ensure that the pore-forming needle smoothly and vertically separates from the paste, forming a hole structure with good verticality. This feature makes the flexible fiber pore-forming needle have higher stability and controllability in industrial production, providing a strong guarantee for the accurate preparation of the electrode.

[0030] Further, the immersion depth of the pore-forming needle is adjusted by a number of motion joints. Further, the motion joints can also be used to adjust the relative speed of the pore-forming needle and the electrode paste. The motion joints and the pore-forming needle can be integrated on the pore-forming system.

[0031] Preferably, the pore-forming system has two rows of pore-forming needles, and the motion joints are located at both ends of the pore-forming system and in the middle of the two rows of pore-forming needles.

[0032] In a second aspect, the present application provides an electrode prepared by the method of the first aspect.

[0033] In a third aspect, the present application also provides a battery comprising the electrode of the second aspect.

[0034] In the design of the battery, the present application pays special attention to the problem of lithium ion precipitation to form lithium precipitation at the negative electrode, which may pose a threat to the safety and stability of the battery. To this end, the present application proposes two innovative solutions:

[0035] 1. Punching the positive electrode and keeping the negative electrode intact: In this scheme, the positive electrode is prepared by the method of the first aspect of the present application, and contains a carefully designed vertical hole structure to optimize the lithium ion transmission path. The negative electrode maintains the traditional structure without punching. This design ensures the safety of the battery while also improving the charging efficiency and discharging performance to some extent.

[0036] 2. Both the positive and negative electrodes are punched, and the positive electrode aperture is not smaller than the negative electrode aperture: In this scheme, both the positive and negative electrodes are prepared by the method described in the first aspect of the application, and both contain vertical hole structures. In particular, the aperture of the positive electrode is designed to be greater than or equal to the aperture of the negative electrode, and the hole centers are completely aligned. This design not only ensures the safety and stability of the battery, but also more effectively improves the fast charging capability and power density.

[0037] Compared with the prior art, the present application has the following advantages:

[0038] 1. The method of the present application can efficiently form electrodes with straight hole structures, greatly improving production efficiency, and the straight holes are smooth, have no extrusion effect on active materials, and no high-temperature ablation, thereby greatly improving the life and safety of the battery.

[0039] 2. The present application proposes inserting a pore-forming needle made of flexible fiber during wet coating, and pulling it out during drying, thereby forming vertical holes on the surface of the electrode; after the holes are filled with electrolyte, the infiltration path can be greatly shortened; at the same time, the lithium ion transmission path is also shortened, which can greatly improve the charging capacity and discharging power of the battery.

[0040] 3. The method of the present application avoids subtractive methods such as punching, achieving zero waste of raw materials.

[0041] 4. The method of the present application has high controllability and flexibility, and can adjust the size, shape, depth and distribution of the straight holes according to actual needs to further optimize the performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a structural schematic diagram of an embodiment of the battery cell structure of the present application.

[0043] Figure 2 is a pore-forming principle diagram of the electrode: Figure 2 A is the immersion of the pore-forming needle into the electrode slurry; Figure 2 B is the pulling out of the pore-forming needle from the electrode slurry.

[0044] Figure 3 is a structural schematic diagram of the pore-forming system.

[0045] Figure 4 is a schematic diagram of the surface of the electrode after pore-forming of the present application.

[0046] Figure 5 is a continuous production schematic diagram of an electrode pore-forming of the present application.

[0047] Figure 6 is a structural schematic diagram of the pore-forming needle in the vertical section, wherein Figure 6 A is a circular cross-section, Figure 6 B is a rectangular cross-section,Figure 6 C is a rhombic cross section, and Figure 6 D shows a triangular cross section.

[0048] Figure 7 A cross-sectional view of one embodiment of the electrode in the thickness direction.

[0049] Figure 8 A cross-sectional view of another embodiment of the electrode in the thickness direction.

[0050] Figure 9 A cross-sectional view of another embodiment of the electrode in the thickness direction.

[0051] Figure 10 A cross-sectional view of another embodiment of the electrode in the thickness direction.

[0052] Figure 11 A cross-sectional view of another embodiment of the electrode in the thickness direction.

[0053] BRIEF DESCRIPTION OF DRAWINGS

[0054] 1, cell structure; 2, negative electrode sheet; 3, positive electrode sheet; 21, negative current collector; 22, negative active material layer; 31, positive current collector; 32, positive active material layer; 4, pore-forming system; 41, pore-forming needle; 42, movement joint; 5, current collector; 6, electrode slurry. DETAILED DESCRIPTION

[0055] In order to make the skilled in the art better understand the technical solutions in the present application, the present application will be further described below in conjunction with the drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0056] In the present specification, the relevant description of the number of parts and the proportion, if not specifically stated, refers to the weight.

[0057] In the present specification, the total pore area ratio = number of pores per unit area × area of a single pore.

[0058] In the present specification, "cross-sectional area" refers to the area perpendicular to the thickness direction.

[0059] In the present specification, "vertical cross section" refers to a plane perpendicular to the thickness direction.

[0060] Referring to Figure 1An electric cell structure 1 comprising positive electrode sheets 3 and negative electrode sheets 2 stacked alternately. The electric cell structure has N layers of negative electrode sheets, N-1 layers of positive electrode sheets, and N≥2. Figure 1 When N=2, the electric cell structure 1 comprises 2 layers of positive electrode sheets 3 and 3 layers of negative electrode sheets 2. When N=3, the electric cell structure has 3 layers of positive electrode sheets, 4 layers of negative electrode sheets (not shown), and so on. Figure 1

[0061] The positive electrode sheet 3 comprises a positive electrode current collector 31 and positive electrode active material layers 32 on both sides of the positive electrode current collector 31. The current collector is a foil, which can be a metal such as aluminum, copper, etc. The positive electrode current collector 31 is preferably an aluminum foil. The positive electrode active material layer 32 comprises a positive electrode active material, a conductive agent, and a binder, the positive electrode active material being lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium manganese iron phosphate, lithium-rich manganese, Na x Mn, Fe, Co, Ni, Cu, Zn, Cr, etc. £ is a [M2(CN)6] vacancy. Generally, the thickness of the positive electrode active material layers 32 on both sides of the positive electrode current collector 31 can be different when the positive electrode sheet 3 is not rolled. Preferably, the positive electrode active material layers 32 on both sides of the current collector have the same thickness. The positive electrode sheet can be prepared by a wet process, and the electrode slurry used is a positive electrode active slurry obtained by mixing the positive electrode active material layer with a solvent, the type and amount of the solvent being adjusted according to the formulation of the positive electrode active material layer and the wet process requirements. x M1[M2(CN)6] 1-y y •nH2O (0≤x≤2, 0≤y<1, n>0), where A is an alkali metal such as Na + , K + , etc.; M1 and M2 are different coordination transition metal ions (where M1 coordinates with N and M2 coordinates with C), such as Mn, Fe, Co, Ni, Cu, Zn, Cr, etc.; £ is a [M2(CN)6] vacancy. Generally, the thickness of the positive electrode active material layers 32 on both sides of the positive electrode current collector 31 can be different when the positive electrode sheet 3 is not rolled. Preferably, the positive electrode active material layers 32 on both sides of the current collector have the same thickness. The positive electrode sheet can be prepared by a wet process, and the electrode slurry used is a positive electrode active slurry obtained by mixing the positive electrode active material layer with a solvent, the type and amount of the solvent being adjusted according to the formulation of the positive electrode active material layer and the wet process requirements.

[0062] ​​The negative electrode sheet 2 includes a negative electrode current collector 21 and a negative electrode active material layer 22 on both sides of the negative electrode current collector 21. The current collector is a foil, which can be a metal such as aluminum or copper. The negative electrode current collector 21 is preferably a copper foil. The negative electrode active material layer 22 includes a negative electrode active material, a conductive agent, and a binder, and the negative electrode active material can be one or more of graphite, a silicon material, hard carbon, soft carbon, lithium metal, sodium metal, or other alloying materials. Generally, in the case where the negative electrode sheet 2 is not crimped, the thickness of the negative electrode active material layer 22 on both sides of the negative electrode current collector 21 can differ. Preferably, the thickness of the negative electrode active material layer 22 on both sides of the current collector is the same. The negative electrode sheet can be produced using a wet process, and the electrode slurry used in the wet process is a negative electrode active slurry obtained by mixing a negative electrode active material layer with a solvent. The type and amount of the solvent can be adjusted as needed according to the formulation of the negative electrode active material layer and the wet process.

[0063] Referring to Figures 2-3 , in the process of manufacturing the electrode according to the embodiment, a pore-forming system 4 is used, which has a plurality of pore-forming needles 41 made of flexible fibers, and the arrangement of the pore-forming needles is designed according to the number of pores per unit area on the active material layer. The vertical cross-section of the pore-forming needle made of flexible fibers can be one or more of a circular shape, a rectangular shape, a diamond shape, a triangular shape, and the like (see Figure 6 ), and is preferably a circular shape. When the vertical cross-section is a circular shape, the diameter is preferably between 1 and 500 μm.

[0064] In one example, the surface of the pore-forming needle has a hydrophobic coating or an oleophobic coating, and the hydrophobic or oleophobic property of the coating is opposite to that of the electrode slurry, thereby facilitating the removal of the pore-forming needle later.

[0065] In another example, the pore-forming system has a plurality of motion joints 42 for adjusting the immersion depth of the pore-forming needles, so as to realize the insertion and extraction of the pore-forming needles into the electrode slurry. A typical motion joint is shown in Figure 3 , which is located at both ends of the pore-forming system and at the upper part of the pore-forming needles 41 to be immersed in the electrode slurry. In order to maintain the stability of the pore-forming system, the pore-forming needles 41 are generally designed in two rows, and the motion joints are located at both ends and in the middle of the pore-forming needles 41 in the two rows.

[0066] Referring to Figure 2 , in combination with Figure 3 , the method of manufacturing the electrode according to the embodiment includes the following steps:

[0067] (1) using a wet process, electrode slurry 6 is coated on one side of the current collector 5;

[0068] (2) the pore-forming needles 41 made of flexible fibers are vertically immersed in the electrode slurry 6 (as shown in Figure 2A shown);

[0069] (3) drying the electrode slurry;

[0070] (4) when the liquid content in the electrode slurry is 5-10wt% (at this time the electrode slurry is almost dried), pulling out the pore-forming needle (as shown in Figure 2 B), the active material layer with vertical pores is obtained after the electrode slurry is completely dried, and the surface of the active material layer is shown in Figure 4 ;

[0071] (5) after coating the electrode slurry on the surface of the other side of the current collector, repeating the above steps (2)-(4), the electrode is obtained, which includes the current collector and the active material layers on both sides of the current collector. When the electrode is a positive electrode sheet, the active material layer is a positive electrode active material layer; when the electrode is a negative electrode sheet, the active material layer is a negative electrode active material layer.

[0072] In the pore-forming process of the present application, the pore-forming needle is immersed in a volume equivalent to the volume of the vertical pores, so that by accurately controlling the ratio of the immersion area of the pore-forming needle to the area of the electrode slurry, the total pore area ratio required by design can be achieved.

[0073] The cross-sectional view of the vertical pores in the thickness direction can be designed as needed. Figures 7 to 11 The cross-sectional view of the five specific embodiments of the electrode in the thickness direction of the present application is shown. Among them, Figure 7 the cross-sectional shape of the vertical pores is rectangular, Figure 8 the cross-sectional shape of the vertical pores is triangular, Figures 9-11 and the cross-sectional shape of the vertical pores is conical.

[0074] Referring to Figure 5 , the continuous production of the electrode pore-forming of the present application is shown. Figure 5The motion joints shown in the middle are adjustable up and down, and are named as the first motion joint, the second motion joint, the third motion joint, the fourth motion joint, the fifth motion joint and the sixth motion joint from left to right. The relative position of the adjacent two motion joints is adjusted to control the relative position of the pore-forming needle and the active material layer. For example, in the insertion stage of the pore-forming needle, the first motion joint and the second motion joint are kept in a horizontal position and are lowered in height at the same time, so as to control the depth of the pore-forming needle immersed in the electrode slurry. In the drying stage, only the height of the second motion joint and the third motion joint needs to be kept unchanged, and the forward movement speed of the second motion joint and the third motion joint needs to be consistent with the movement speed of the current collector, so as to keep the pore-forming needle relative to the electrode slurry, so that the vertical holes formed on the electrode slurry are consistent with the shape of the pore-forming needle; during the relative motion, the solvent in the electrode slurry is gradually evaporated by baking. In the extraction stage of the pore-forming needle, when the electrode slurry is almost completely dried, the fifth motion joint and the sixth motion joint are raised in height, and the relative position of the motion joint and the electrode slurry is increased, so that the pore-forming needle is extracted from the electrode slurry, so as to leave vertical holes on the surface of the active material layer. The pore-forming needle is extracted when the electrode slurry is almost completely dried, and at this time, the electrode slurry still contains 5-10wt% of solvent, and the electrode slurry has a certain flexibility, so that the pore-forming needle cannot be extracted or the flexible fiber is damaged, and the vertical hole is not collapsed. The movement speed of the current collector in each stage can be controlled by the roller. By controlling the motion joints as shown in Figure 5 the motion joints, the height of the local part of the pore-forming system can be adjusted, so as to realize the local immersion / extraction of the pore-forming needle in the electrode slurry, control the corresponding hole depth, and realize the continuous production of the electrode pore-forming.

[0075] The lithium ion battery involved in the following examples and comparative examples includes the above-mentioned cell structure: the cell structure has 30 layers of negative electrode sheets and 29 layers of positive electrode sheets; the negative electrode active material layers 22 on both sides of the negative electrode current collector 21 have the same thickness of 50 μm; the positive electrode active material layers 32 on both sides of the positive electrode current collector 31 have the same thickness of 60 μm; the formula of the positive electrode active material layer includes lithium nickel cobalt manganese oxide (NCM811) content 95 parts, conductive agent (conductive carbon black Super-P) 2 parts, and polyvinylidene fluoride 3 parts; the formula of the negative electrode active material layer includes graphite 96 parts, conductive agent (conductive carbon black Super-P) 1 part, carbon nanotube 0.5 part, butylphenyl rubber 1.5 parts, and sodium carboxymethyl cellulose 1 part; the positive electrode current collector is aluminum foil with a thickness of 13 μm; the negative electrode current collector is copper foil with a thickness of 6 μm; the cross-sectional area of the positive electrode active material layer is 97 mm x 296 mm, and the cross-sectional area of the negative electrode active material layer is 100 mm x 300 m. The positive electrode sheets and the negative electrode sheets are laminated. After lamination, the cell structure is subjected to welding, packaging, baking, liquid injection, infiltration, formation, capacity test, appearance detection and other manufacturing processes to obtain the lithium ion battery. In the examples and comparative examples, the preparation of the positive electrode sheet adopts a wet process, and the electrode slurry used is a positive electrode active slurry obtained by mixing the formula of the positive electrode active material layer with N-methyl pyrrolidone, and the addition amount of N-methyl pyrrolidone is 30% of the weight of the slurry; the preparation of the negative electrode sheet also adopts a wet process, and the electrode slurry used is a negative electrode active slurry obtained by mixing the formula of the negative electrode active material layer with water, and the addition amount of water is 50% of the slurry. In the process of preparing the lithium ion battery, except that the preparation of the positive electrode sheet and the negative electrode sheet is different, the other steps of the examples and the comparative examples are completely the same.

[0076] Example 1

[0077] The positive electrode material is prepared into an electrode slurry, and the positive electrode sheet is prepared by using the electrode manufacturing method of the application: the hole depth is equal to 50% of the thickness of the active material layer, the hole radius is 10 μm, the total hole area ratio is 0.03%, and the holes are uniformly distributed on the electrode (1 / mm 2 ).

[0078] The negative electrode material is prepared into an electrode slurry, and the negative electrode sheet is prepared by using the electrode manufacturing method of the application: the hole depth is equal to the thickness of the active material layer,

[0079] The hole diameter of the negative electrode sheet is equal to that of the positive electrode sheet, and the hole centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0080] Example 2

[0081] The positive electrode material is prepared into an electrode slurry, and the positive electrode sheet is prepared by using the electrode manufacturing method of the application: the hole depth is equal to 50% of the thickness of the active material layer, the hole radius is 10 μm, the total hole area ratio is 0.03%, and the holes are uniformly distributed on the electrode (1 / mm2 ).

[0082] The negative electrode material is prepared into an electrode slurry, and a negative electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to 50% of the thickness of the active material layer, the hole diameter of the negative electrode sheet is equal to the hole diameter of the positive electrode sheet, and the hole centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0083] Example 3

[0084] The positive electrode material is prepared into an electrode slurry, and a positive electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to the thickness of the active material layer, the hole radius is 10 μm, the total hole area ratio is 0.01%, and the holes are uniformly distributed on the electrode (0.3 per mm 2 ).

[0085] The negative electrode material is prepared into an electrode slurry, and a negative electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to the thickness of the active material layer, the hole diameter of the negative electrode sheet is equal to the hole diameter of the positive electrode sheet, and the hole centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0086] Example 4

[0087] The positive electrode material is prepared into an electrode slurry, and a positive electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to the thickness of the active material layer, the hole radius is 10 μm, the total hole area ratio is 0.31%, and the holes are uniformly distributed on the electrode (10 per mm 2 ).

[0088] The negative electrode material is prepared into an electrode slurry, and a negative electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to the thickness of the active material layer, the hole diameter of the negative electrode sheet is equal to the hole diameter of the positive electrode sheet, and the hole centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0089] Example 5

[0090] The positive electrode material is prepared into an electrode slurry, and a positive electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to the thickness of the active material layer, the hole radius is 10 μm, the total hole area ratio is 3.14%, and the holes are uniformly distributed on the electrode (100 per mm 2 ).

[0091] The negative electrode material is prepared into an electrode slurry, and a negative electrode sheet is prepared by using the electrode manufacturing method of the present application: the hole depth is equal to the thickness of the active material layer, the hole diameter of the negative electrode sheet is equal to the hole diameter of the positive electrode sheet, and the hole centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0092] Example 6

[0093] The positive electrode material is formulated into an electrode slurry, and a positive electrode sheet is prepared using the electrode manufacturing method of this invention: the pore depth is equal to the thickness of the active material layer, the pore radius is 10 μm, the total pore area ratio is 10%, and the pores are uniformly distributed on the electrode (318 pores / mm). 2 ).

[0094] The negative electrode material is formulated into an electrode slurry, and the negative electrode sheet is prepared using the electrode manufacturing method of the present invention: the pore depth is equal to the thickness of the active material layer, the pore diameter of the negative electrode sheet is equal to the pore diameter of the positive electrode sheet, and the pore centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0095] Example 7

[0096] The positive electrode material is formulated into an electrode slurry, and a positive electrode sheet is prepared using the electrode manufacturing method of this invention: the pore depth is equal to the thickness of the active material layer, the pore radius is 3.1 μm, the total pore area ratio is 0.03%, and the pores are uniformly distributed on the electrode (10 pores / mm). 2 ).

[0097] The negative electrode material is formulated into an electrode slurry, and the negative electrode sheet is prepared using the electrode manufacturing method of the present invention: the pore depth is equal to the thickness of the active material layer, the pore diameter of the negative electrode sheet is equal to the pore diameter of the positive electrode sheet, and the pore centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0098] Comparative Example 1

[0099] The positive electrode material is prepared into an electrode slurry, coated on the surface of the positive electrode current collector, and then dried to form a positive electrode sheet.

[0100] The negative electrode material is prepared into an electrode slurry, coated on the surface of the negative electrode current collector, and then dried to form a negative electrode sheet.

[0101] Comparative Example 2

[0102] The positive electrode material is formulated into an electrode slurry, coated onto the surface of the positive electrode current collector, and then dried to form a positive electrode sheet. Mechanical drilling is used on the active material layers on both sides of the positive electrode sheet, ensuring the hole depth equals the active material layer thickness, the hole radius is 10 μm, the total hole area ratio is 0.03%, and the holes are uniformly distributed on the electrode (1 hole / mm). 2 ).

[0103] The negative electrode material is prepared into an electrode slurry, coated on the surface of the negative electrode current collector, and then dried to form a negative electrode sheet. Mechanical drilling is used on the active material layers on both sides of the negative electrode sheet so that the hole depth is equal to the thickness of the active material layer, the hole diameter of the negative electrode sheet is equal to the hole diameter of the positive electrode sheet, and the center of the holes of the positive and negative electrode sheets are completely aligned.

[0104] Comparative Example 3

[0105] The positive electrode material is prepared into an electrode slurry, coated on the surface of the positive electrode current collector, and then dried to form a positive electrode sheet. The active material layer on both sides of the positive electrode sheet is etched by laser to make the hole depth equal to the thickness of the active material layer, the hole radius is 10 μm, the total hole area ratio is 0.03%, and the holes are uniformly distributed on the electrode (1 / mm 2 )。

[0106] The negative electrode material is prepared into an electrode slurry, coated on the surface of the negative electrode current collector, and then dried to form a negative electrode sheet. The active material layer on both sides of the negative electrode sheet is etched by laser to make the hole depth equal to the thickness of the active material layer, the hole radius of the negative electrode sheet is equal to that of the positive electrode sheet, and the hole centers of the positive electrode sheet and the negative electrode sheet are completely aligned.

[0107] The batteries prepared in the examples and comparative examples are tested to measure their energy density, charge capacity, discharge power, and cycle life, and the results are shown in Table 1.

[0108] Sample Pore radius (pm) Pore depth ratio to electrode thickness (%) Total pore area ratio (%) Energy density (Wh / kg) 25°C, 1C Charging capacity (rate) Discharge power (W) Cycle life, GB / T31484-2015 Battery short circuit number / test number Comparative Example 1 - - 0 260 2 3016 998 cycles @ 80% SOH 0 / 10 Comparative Example 2 10 100 0.03 254.92 2.79 3011 734 cycles @ 80% SOH 9 / 10 Comparative Example 3 10 100 0.03 251.92 2.77 3078 708 cycles @ 80% SOH 8 / 10 Example One 10 100 0.03 259.92 2.8 3101 1175 cycles @ 80% SOH 0 / 10 Example Two 10 50 0.03 259.96 2.7 3078 1043 cycles @ 80% SOH 0 / 10 Example Three 10 100 0.01 259.99 2.05 3033 999 cycles @ 80% SOH 0 / 10 Example Four 10 100 0.31 259.6 3.5 3289 1304 cycles @ 80% SOH 0 / 10 Example Five 10 100 3.14 253.4 4.2 3421 1577 cycles @ 80% SOH 0 / 10 Example Six 10 100 10 231.6 6.1 3714 1665 cycles @ 80% SOH 0 / 10 Example Seven 3.1 100 0.03 259.92 2.75 3098 1156 cycles @ 80% SOH 0 / 10

[0109] The battery is cycled at 1C rate, and the capacity retention rate is attenuated from the initial 100% SOH to 80% SOH. The number of cycles experienced is the cycle life. As can be seen from the results in Table 1, after the electrode is designed according to the application, the cycle life of the battery, the short circuit rate of the battery (i.e., the number of battery short circuits / tested number), and the discharge power are significantly optimized. The increase in the hole diameter and the total hole area ratio of the vertical holes of the electrode can significantly improve the discharge power capacity of the battery, but has no significant effect on the energy density.

Claims

1. A method for manufacturing an electrode, characterized in that, Includes the following steps: S1, using a wet process, applies electrode paste to the surface of the current collector side; S2, vertically immerse the perforation needle made of flexible fiber into the electrode slurry; S3, Dry the electrode slurry; S4, when the liquid content in the electrode slurry is 5-10wt%, the hole-forming needle is pulled out. After the electrode slurry is completely dried, an active material layer with vertical holes is formed on the surface of the current collector. S5. After coating the electrode paste on the surface of the other side of the current collector, repeat the above steps S2-S4 to obtain the electrode, which includes the current collector and active material layers located on both sides of the current collector.

2. The method according to claim 1, characterized in that, The vertical cross-section of the pore-forming needle is one or more of the following shapes: circular, rectangular, rhomboid, and triangular.

3. The method according to claim 2, characterized in that, The vertical cross-section of the pore-forming needle is circular, with a diameter between 1 and 500 μm.

4. The method according to claim 1, characterized in that, The immersion area of ​​the pore-forming needle is 0.01%-10% of the electrode slurry area.

5. The method according to claim 1, characterized in that, The surface of the pore-forming needle has a hydrophobic coating or an oleophobic coating, the hydrophobic or oleophobic properties of which are opposite to those of the electrode paste.

6. The method according to claim 1, characterized in that, The insertion depth of the pore-forming needle is adjusted by the movement joint.

7. The method according to claim 6, characterized in that, The motion joint and the pore needles are integrated on the pore system, which has two rows of pore needles, and the motion joint is located at both ends of the pore system and in the middle of the two rows of pore needles.

8. An electrode, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. A battery, characterized in that, The battery includes the electrodes as described in claim 8.

Images