Method for manufacturing a wound electrode core, battery, and electric device

Abstract

The application provides a preparation method of a wound electrode core, a battery and an electric device. The positive electrode sheet precursor is subjected to softening treatment, so that the sum of the compaction density, water content and softening substance content of the positive electrode material layer of the obtained positive electrode sheet meets a specific mathematical relationship, and the risk of fracture of the positive electrode sheet during bending and the risk of leaving a gap between the positive electrode sheet and the negative electrode sheet after winding can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery preparation, in particular to a preparation method of a wound electrode core, a battery and an electric device. BACKGROUND

[0002] At present, commonly used batteries are divided into laminated batteries and wound batteries. Compared with laminated batteries, wound batteries have simple structure, relatively simple production process and high yield, and thus are welcomed by the market. Among them, wound batteries are generally divided into cylindrical or square shapes. In the preparation of square wound batteries, the inner circle winding diameter of the electrode sheet is small, which causes the positive electrode sheet to be prone to breakage when bending, or there is a gap between the wound positive electrode sheet and the negative electrode sheet, and the broken part of the positive electrode sheet or the area far from the negative electrode sheet is prone to metal deposition (for example, lithium deposition) during the charging and discharging process of the battery, thereby causing irreversible capacity loss and even causing the battery to fail. The industry often reduces the area density of the positive electrode sheet to solve the above problems, but this reduces the energy density of the battery and cannot meet the needs of consumers. SUMMARY

[0003] In view of this, the present application provides a preparation method of a wound electrode core, a battery and an electric device. The preparation method softens the positive electrode sheet precursor by softening treatment, so that the relationship between the compaction density of the positive electrode material layer of the obtained positive electrode sheet, the water content and the content of the softening substance satisfies a specific mathematical relationship, which can reduce the risk of breakage of the positive electrode sheet when bending and leaving a gap between the wound positive electrode sheet and the negative electrode sheet.

[0004] The first aspect of the present application provides a preparation method of a wound electrode core, comprising:

[0005] (1) providing a positive electrode sheet precursor to be wound, the positive electrode sheet precursor comprising a current collector and a positive electrode material layer provided on at least one side surface of the current collector;

[0006] softening the positive electrode sheet precursor by using a softening agent to obtain a positive electrode sheet; the softening agent comprises a softening substance;

[0007] The positive electrode sheet satisfies: θ 3 × (10 4 -A) / 10 4 ≤ 15; wherein θ is the compaction density of the positive electrode material layer, unit: g / cm 3 ; A is the sum of the water content and the content of the softening substance of the positive electrode material layer, unit: ppm;

[0008] (2) heating the positive electrode sheet, stacking a negative electrode sheet on the surface of the positive electrode sheet, winding to obtain a wound electrode core.

[0009] In the preparation method, the softening agent is used to soften the positive electrode sheet precursor, so that the compaction density, water content and content of the softening agent of the positive electrode material layer of the obtained positive electrode sheet meet a special mathematical relationship, the flexibility of the positive electrode sheet can be adjusted more appropriately, thereby reducing the risk of fracture of the positive electrode sheet during winding, and the gap between the positive electrode sheet and the negative electrode sheet in the formed battery after winding can be avoided, and the production yield of the wound battery can be significantly improved. The preparation method has simple steps and strong process reliability, and can realize large-scale industrial production.

[0010] The second aspect of the embodiments of the present application provides a battery comprising a wound electrode core prepared by the preparation method provided in the first aspect of the embodiments of the present application. The wound electrode core of the battery has no fracture of the positive electrode sheet, and the adhesion between the positive electrode sheet and the negative electrode sheet is high. The wound battery is not prone to problems such as metal precipitation during long-term charge-discharge cycle process, and the electrochemical performance of the battery is good.

[0011] The third aspect of the embodiments of the present application provides a power consumption device comprising the battery provided in the second aspect of the embodiments of the present application. Since the power consumption device is powered by the battery provided in the embodiments of the present application, the market competitiveness of the power consumption device is high. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Process flow chart of the preparation method of the wound electrode core provided in an embodiment of the present application;

[0013] Figure 2 Process flow chart of the preparation method of the wound electrode core provided in another embodiment of the present application;

[0014] Figure 3 Process schematic diagram of the preparation method of the wound electrode core provided in an embodiment of the present application, in which the softening agent is used to treat the positive electrode sheet precursor and heating treatment is performed;

[0015] Figure 4 Process schematic diagram of the preparation method of the wound electrode core provided in another embodiment of the present application, in which the softening agent is used to treat the positive electrode sheet precursor and heating treatment is performed. DETAILED DESCRIPTION

[0016] In order to solve the problems of easy fracture of the inner circle positive electrode sheet and easy gap between the positive electrode sheet and the negative electrode sheet in the existing production process of the wound battery, please refer to the process flow in Figure 1 , the embodiments of the present application provide a preparation method of a wound battery core, comprising:

[0017] S01, providing a positive electrode sheet precursor to be wound, the positive electrode sheet precursor comprising a current collector and a positive electrode material layer arranged on at least one side surface of the current collector;

[0018] softening the positive electrode plate precursor to obtain the positive electrode plate; the softening agent comprises a softening substance;

[0019] The positive electrode plate satisfies: calculated by the numerical value of each parameter, θ 3 ×(10 4 -A) / 10 4 ≤15; wherein, the θ is the compaction density of the positive electrode material layer, unit: g / cm 3 ; the A is the sum of the water content and the content of the softening substance of the positive electrode material layer, unit: ppm.

[0020] In the embodiments of the present application, the compaction density of the positive electrode material layer = the surface density of the positive electrode plate / the thickness of the positive electrode material layer, and the surface density of the positive electrode plate is the total mass of the positive electrode material layer / the surface area of the positive electrode material layer. In the embodiments of the present application, the water content of the positive electrode material layer is measured by a trace moisture tester. Specifically, at 25℃±2℃, the material of the positive electrode material layer is taken into the trace moisture tester to test its water content, and the result is the water content of the positive electrode material layer. In the embodiments of the present application, the content of the softening substance of the positive electrode material layer is: the amount of the softening substance / the surface density of the positive electrode plate; then, the A of the positive electrode material layer = the water content + the content of the softening substance.

[0021] In the embodiments of the present application, when the opposite two surfaces of the positive electrode plate precursor both have the positive electrode material layer, the opposite two surfaces of the positive electrode plate precursor can be sequentially subjected to the above-mentioned softening treatment, or the opposite two surfaces of the positive electrode plate precursor can be simultaneously subjected to the softening treatment.

[0022] It can be understood that, in order to ensure the structural stability of the positive electrode plate precursor / positive electrode plate, the positive electrode material layer generally comprises a positive electrode material and a binder. In some embodiments of the present application, the positive electrode material layer has a binder. In the embodiments of the present application, the binder is a binder commonly known in the art for the positive electrode plate, and exemplarily, the above-mentioned binder comprises but is not limited to polyvinylidene fluoride (PVDF) and the like, and the present application does not have any limitation on the content of the binder in the positive electrode material layer, and a person skilled in the art can select according to actual needs.

[0023] In the embodiments of the present application, when the opposite two surfaces of the current collector both have the positive electrode material layer, the positive electrode material layers on the opposite two sides of the current collector both need to satisfy θ 3 ×(10 4 -A) / 10 4≤15; wherein the θ and A of each positive electrode material layer can be the same or different. As is known, for a wound core, it comprises one positive electrode tab and one negative electrode tab, wherein the positive electrode tab and the negative electrode tab are both in a strip shape, and a plurality of positive electrode material layers and a plurality of negative electrode material layers are arranged on the surfaces of the current collectors respectively, and there is a space between adjacent positive electrode material layers and a space between adjacent negative electrode material layers; or the positive electrode tab and the negative electrode tab are both electrode tabs with fixed sizes obtained by cutting (that is, one side surface of the positive electrode tab has only one positive active material layer, and the negative electrode tab is the same). In the embodiments of the present application, the same side surface of the single positive electrode tab comprises a plurality of positive electrode material layers arranged at intervals, and the θ and A of the plurality of positive electrode material layers can be the same or different. In the embodiments of the present application, if the positive electrode tab is an electrode tab with a fixed size obtained by cutting, when the plurality of positive electrode tabs are wound, the θ and A of each positive electrode tab can be the same or different.

[0024] S02, heating the positive electrode tab, and stacking a negative electrode tab on the surface of the positive electrode tab to obtain a wound core.

[0025] In the preparation method of the embodiments of the present application, the softening substance can improve the flexibility of the positive electrode material layer without damaging the structural stability of the positive electrode material layer. When the relationship between the A and the compaction density θ of the positive electrode material layer meets the above-mentioned limitation, the positive electrode material layer (or the positive electrode tab) has a certain flexibility, so that in step S02, the positive electrode tab is heated to soften the binder in the positive electrode material layer, further improving the flexibility of the positive electrode material layer, thereby reducing the risk of fracture of the positive electrode tab during winding, especially reducing the risk of fracture of the positive electrode tab with high compaction density and poor adhesion with the negative electrode tab, to successfully prepare a wound core without fractured tabs, and the positive electrode tab has high adhesion with the negative electrode tab, thereby improving the product yield of the wound core.

[0026] In the embodiments of the present application, θ 3 × (10 4 -A) / 10 4 may be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, etc. If the value of θ 3 × (10 4 -A) / 10 4 is greater than 15, the A value of the positive electrode material layer is too low and / or the compaction density of the positive electrode material layer is too high, resulting in insufficient flexibility and / or excessive toughness of the positive electrode tab, which may be fractured during subsequent winding, and / or there is a visible gap between the positive electrode tab and the negative electrode tab.

[0027] In some embodiments of the present application, the water content of the positive electrode material layer is in the range of 0-1500 ppm. In this way, the water content of the positive electrode sheet and the battery cell in the subsequent production process can be controlled within a suitable range, improving product yield and facilitating the performance of the battery. For example, the water content of the positive electrode material layer can be, but is not limited to, 0, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, etc. At this time, in some specific embodiments, 0 < A ≤ 2500 ppm. At this time, it is beneficial to the flexibility of the positive electrode sheet and the removal of water and softening agent in the subsequent preparation process, thereby facilitating the performance of the final battery. For example, A can be, but is not limited to, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2300 ppm, 2500 ppm, etc.

[0028] In some embodiments of the present application, 2.5 g / cm 3 ≤ θ ≤ 3.0 g / cm 3 . For example, θ can be, but is not limited to, 2.50 g / cm 3 , 2.55 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.70 g / cm 3 , 2.80 g / cm 3 , 2.90 g / cm 3 , 2.95 g / cm 3 , 3.00 g / cm 3 , etc. Controlling the higher compaction density of the positive electrode material layer can obtain a positive electrode material layer with higher surface density, thereby facilitating the improvement of the energy density of the final battery. In the present application, a single positive electrode sheet includes multiple positive electrode material layers, and the compaction density of each positive electrode material layer can be the same or different, which can be determined according to actual application needs. In some specific embodiments, the compaction density of each positive electrode material layer in the positive electrode sheet is independently in the range of 2.5 g / cm 3 -3.0 g / cm 3 . It should be noted that, since the compaction density of the positive electrode material layer is already in a higher range between the heat roller treatment in step S02, the compaction density of the positive electrode material layer in the final finished electrode core and the finished battery is also in the above range.

[0029] In some embodiments of the present application, the areal density of the positive electrode material layer is in the range of 300 g / m 2 - 600 g / m 2 . In this way, a battery with a higher energy density can be obtained, and the risk of breakage of the positive electrode tab during winding is also smaller, so that the energy density and production yield of the final battery can be simultaneously considered. For example, the areal density of the positive electrode material layer can be, but is not limited to, 300 g / m 2 , 320 g / m 2 , 350 g / m 2 , 380 g / m 2 , 400 g / m 2 , 420 g / m 2 , 450 g / m 2 , 480 g / m 2 , 500 g / m 2 , 520 g / m 2 , 550 g / m 2 , 580 g / m 2 , etc. In the embodiments of the present application, the single positive electrode tab includes multiple positive electrode material layers, and the areal density of each positive electrode material layer can be the same or different, which can be determined according to actual application needs. In some specific embodiments, the areal density of each positive electrode material layer in the positive electrode tab is independently in the range of 300 g / m 2 - 600 g / m 2 . Similarly, in the embodiments of the present application, the areal density of the positive electrode material layer is in the above range before / after the heat roller treatment of step S02.

[0030] In some embodiments of the present application, the thickness of the positive electrode material layer is in the range of 100 μm-240 μm. Controlling the thickness of the positive electrode material layer in the above range can further reduce the risk of breakage of the positive electrode tab during winding and the existence of a gap between the positive electrode tab and the negative electrode tab, and can also make the capacity of the final battery higher and the internal resistance smaller, further improving the market competitiveness of the final battery. In the embodiments of the present application, the thickness of the above positive electrode material layer can be, but is not limited to, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, etc. Similarly, the thickness of the multiple positive electrode material layers in the single positive electrode tab can be the same or different. In some specific embodiments, the thickness of each positive electrode material layer in the positive electrode tab is independently in the range of 100 μm-240 μm. Similarly, in the embodiments of the present application, the thickness of the positive electrode material layer is in the above range before / after the heat roller treatment of step S02.

[0031] In some embodiments of the present application, the softening substance includes, but is not limited to, at least one of acetone, xylene, 1,3,5-trichlorobenzene, polyethylene glycol, dimethyl methylphosphonate, polypropylene glycol, diethylene glycol butyl ether, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. The above-mentioned substances have good permeability to the positive active material layer, can quickly soften the positive electrode sheet precursor, and thus can not only soften the positive electrode sheet precursor but also improve the production efficiency of the wound core.

[0032] In some embodiments of the present application, the softening agent further includes a solvent, wherein the solvent includes at least one of N-methylpyrrolidone, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, and ethyl propionate. The above-mentioned solvent can dissolve the aforementioned softening substance to form a softening agent, so that the softening substance can fully penetrate the entire positive material layer, improve the flexibility of the positive electrode sheet precursor at each position, and thus further reduce the risk of fracture of the positive electrode sheet (especially the positive electrode sheet with high compaction density) during winding and low adhesion to the negative electrode sheet. In some specific embodiments, the softening agent simultaneously includes the aforementioned softening substance (specifically, the specific material of the softening substance) and the aforementioned solvent (specifically, the specific material of the solvent). At this time, the softening agent has strong mutual solubility with the binder in the positive material layer, can reduce the binding performance of the binder based on the principle of similar compatibility, so as to achieve a certain softening effect without damaging the structural stability of the positive material layer. In addition, the softening agent can be volatilized during the heating process of the positive electrode sheet in step S02, so as to not only soften the positive electrode sheet precursor but also sufficiently reduce the influence of the softening agent on the performance of the final battery, so as to ensure the performance of the battery.

[0033] In the embodiments of the present application, please refer to Figure 3 Generally, the opposite two side surfaces of the positive electrode sheet precursor each include a plurality of positive material layers, and the softening agent is used to treat the plurality of positive material layers on the opposite two side surfaces of the positive electrode sheet. For a strip-shaped positive electrode sheet precursor, the softening agent can be used to treat the plurality of positive material layers on the opposite two side surfaces of the positive electrode sheet.

[0034] In some embodiments of the present application, the volume of the softening substance accounts for 0.5%-10.0% of the total volume of the softening agent. In this way, the positive electrode sheet precursor can be softened, and the softening substance can be sufficiently volatilized under the action of the heating roller in step S02, so as to reduce the residual amount of the softening agent (specifically, the residual amount of the softening substance and the solvent) in the core, which is beneficial to the performance of the final battery. Exemplarily, the volume of the softening substance can account for 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, etc. of the total volume of the softening agent.

[0035] In some embodiments of the present application, the softening agent is used in an amount of 0.05% to 1% of the mass of the positive electrode material layer. This softens the positive electrode material layer, reduces the risk of fracture of the final positive electrode sheet during the winding process, and improves the adhesion between the positive electrode sheet and the negative electrode sheet after winding. Furthermore, the softening agent is easily volatilized during the hot rolling process in step S02. Furthermore, even if the softening agent is not completely volatilized by the hot rolling process, the residual amount in the positive electrode sheet is low, which will not affect the subsequent battery performance. Illustratively, the mass amount of the softener can be, but is not limited to, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95%, 1.00%, etc. of the mass of the positive electrode material layer.

[0036] In some embodiments of the present application, the specific process of treating the positive electrode sheet precursor with a softener includes but is not limited to spraying, coating, placing the positive electrode sheet precursor in an environment with a high concentration of softener to allow the softener to be infiltrated, and the like. The coating process may be to coat the softener on the positive electrode material layer through an anilox roller or a wire roller, or to coat the softener on the positive electrode material layer through dipping or die extrusion coating. Specifically, the above-mentioned placing the positive electrode sheet precursor in an environment with a high concentration of softener includes but is not limited to: (1) passing the positive electrode sheet precursor through a tank filled with softener to allow the softener to infiltrate the positive electrode material layer; (2) atomizing the softener and placing the positive electrode sheet precursor in an environment filled with atomized softener to allow the softener to infiltrate the positive electrode material layer.

[0037] In the embodiment of the present application, when the positive electrode precursor is treated with a softener, spraying, coating or immersion treatment may be performed only once, or multiple spraying, coating or immersion treatments may be performed.

[0038] In some embodiments of the present application, the ambient temperature when the positive electrode sheet precursor is treated with a softener is 5°C-150°C. The ambient temperature refers to the ambient temperature when the positive electrode sheet precursor is treated with a softener, for example, the spraying ambient temperature. The above ambient temperature is conducive to the softener infiltrating and penetrating the positive electrode material layer in a shorter time, so as to soften the positive electrode material layer. Within the above temperature range, the higher the temperature, the more conducive it is to improving the infiltration of the softener into the positive electrode material layer. Exemplarily, the ambient temperature when the positive electrode sheet precursor is treated with a softener can be 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.

[0039] In some embodiments of the present application, the softening agent is attached and absorbed in the positive electrode material layer for 0.5s-60s, and the obtained positive electrode sheet satisfies θ 3 ×(10 4 -A) / 10 4 ≤15. For example, in a spraying process, the softening agent is sprayed on the positive electrode material layer of the positive electrode sheet precursor for 0.5s-60s, and the obtained positive electrode sheet satisfies θ 3 ×(10 4 -A) / 10 4 ≤15, and enters step S02 to perform roll pressing treatment on the positive electrode sheet by using a hot roller. For example, in a process of placing the positive electrode sheet precursor in an environment with high concentration of softening agent to allow the softening agent to infiltrate, the positive electrode sheet precursor is placed in the environment with high concentration of softening agent for 0.5s-60s, and the obtained positive electrode sheet satisfies θ 3 ×(10 4 -A) / 10 4 ≤15.

[0040] In some embodiments of the present application, referring to Figure 2 , the preparation of the positive electrode sheet precursor includes:

[0041] (1) providing a strip-shaped positive electrode current collector;

[0042] (2) forming a strip-shaped positive electrode material layer on the surface of the positive electrode current collector;

[0043] (3) welding tabs on the blank foil to form a positive electrode sheet precursor; or, removing the positive electrode material layer at a predetermined position and exposing the positive electrode current collector at the predetermined position, and welding tabs at the predetermined position to form a positive electrode sheet precursor. In some embodiments of the present application, the laser cleaning process is used to remove the positive electrode material layer at the predetermined position.

[0044] In some embodiments of the present application, in step S02, the positive electrode sheet is subjected to heating treatment, and the heating temperature is 80℃-130℃. In this way, the binder in the positive electrode material layer is softened by heat, further improving the flexibility of the positive electrode sheet, and the above-mentioned temperature does not affect the structural stability of the positive electrode material layer. For example, the heating temperature when the positive electrode sheet is subjected to heating treatment can be but is not limited to 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, etc.

[0045] In some embodiments of the present application, in step S02, the positive electrode sheet is subjected to heating treatment by using a hot roller. Correspondingly, the surface temperature of the hot roller is in the range of 80℃-130℃. The hot roller can be heated by resistance heating or electromagnetic heating, and the hot roller is connected with a temperature control module to maintain the surface temperature of the hot roller unchanged during long-time continuous roll pressing.

[0046] In some embodiments of the present application, when the positive electrode sheet is heated by the hot roller, the passing speed of the positive electrode sheet is 0.1 m / s-10 m / s. In this way, better heating effect can be achieved to make the binder in the positive electrode material layer soften sufficiently, and high production efficiency can be ensured. For example, the passing speed of the positive electrode sheet can be 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.5 m / s, 1.0 m / s, 2.0 m / s, 3.0 m / s, 4.0 m / s, 5.0 m / s, 6.0 m / s, 7.0 m / s, 8.0 m / s, 9.0 m / s, 10.0 m / s, etc.

[0047] In some embodiments of the present application, when the positive electrode sheet is heated by the hot roller, the tension of the positive electrode sheet is controlled in the range of 0.5 N-200 N. Controlling the tension of the positive electrode sheet is more appropriate, which can ensure that the positive electrode sheet has high flatness before and after heating (for example, without wrinkles, etc.), and the problem of tearing of the positive electrode sheet does not occur, thereby ensuring that the final core has high yield. For example, when the positive electrode sheet is heated by the hot roller, the tension of the positive electrode sheet can be 0.5 N, 1.0 N, 5.0 N, 10.0 N, 20.0 N, 50.0 N, 80.0 N, 100.0 N, 120.0 N, 150.0 N, 180.0 N, 200.0 N, etc.

[0048] In the embodiments of the present application, please refer to Figure 4 The positive electrode sheet can be heated by a single hot roller or by multiple hot rollers. When multiple hot rollers are used to heat the positive electrode sheet, the positive electrode sheet passes through the multiple hot rollers in sequence. The surface of each hot roller can be the same or different (for example, the surface temperature of each hot roller increases in sequence according to the passing order of the positive electrode sheet), and the surface temperature of each hot roller is independently in the range of 80°C-130°C.

[0049] In some embodiments of the present application, the current collector of the positive electrode sheet is welded with a tab, and before the positive electrode sheet is rolled by the hot roller, the welding position of the tab and the current collector is protected. Specifically, a high-temperature-resistant insulating paper can be arranged at the welding position of the tab and the current collector; wherein the material of the high-temperature-resistant insulating paper includes but is not limited to polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), etc.

[0050] In some embodiments of the present application, in step S02, the negative electrode sheet is superimposed on the surface of the positive electrode sheet, and after winding, the wound core is obtained by packaging. In the embodiments of the present application, the packaging process is known to those skilled in the art.

[0051] In some embodiments of the present application, step S02 further comprises stacking a separator between the positive electrode sheet and the negative electrode sheet. That is, in the final electrode core, the separator is located between the positive electrode sheet and the negative electrode sheet. In the embodiments of the present application, the separator in a single electrode core is also in the form of a long strip. The separator can be any separator known in the art, for example, it can be a single-layer separator, a composite separator, etc., which can be selected according to actual application needs.

[0052] The embodiments of the present application also provide a battery comprising the wound electrode core prepared by the preparation method provided by the embodiments of the present application. The battery is a wound battery, which can have high energy density and high reversible capacity.

[0053] The above-mentioned battery can be a liquid battery using electrolyte, or a solid-state battery, or a semi-solid-state battery.

[0054] In some embodiments of the present application, the above-mentioned battery can be a lithium battery, or a sodium battery or other alkali metal battery.

[0055] The embodiments of the present application also provide a power consumption device comprising the battery provided by the embodiments of the present application. Since the power consumption device is powered by the battery provided by the embodiments of the present application, the market competitiveness of the power consumption device is higher.

[0056] In some embodiments of the present application, the above-mentioned power consumption device includes but is not limited to 3C electronic products, power vehicles, etc. The power vehicles include but are not limited to new energy vehicles, electric bicycles, etc. The 3C electronic products include but are not limited to mobile phones, notebook computers, tablet computers, smart watches, wearable electronic devices, etc.

[0057] The technical solutions of the present application are further described in the following embodiments.

[0058] Embodiment 1

[0059] (1) providing a positive electrode sheet precursor, the areal density of the positive electrode sheet precursor being 450 g / m 2 , the compaction density of the positive material layer being 2.65 g / cm 3 , spraying a softening agent on the positive material layer on the opposite surfaces of the positive electrode sheet precursor (first spraying), after standing for 15 s, spraying the softening agent again (second spraying), after standing for 10 s, obtaining a positive electrode sheet. The amount of the softening agent sprayed in the first spraying is 4.5 g / m 2 , and the amount of the softening agent sprayed in the second spraying is 9.0 g / m 2, and the components of the softening agent in the two times of spraying are the same, and the softening agent is an ethylene carbonate / dimethyl carbonate solution of 1,3,5-trichlorobenzene, wherein the volume ratio of 1,3,5-trichlorobenzene (softening substance), ethylene carbonate (solvent) and dimethyl carbonate (solvent) is 5:70:25.

[0060] The water content of the positive electrode sheet is 880 ppm, the content of the softening substance is 1500 ppm, and the value of θ 3 × (10 4 -A) / 10 4 is 14.18.

[0061] (2) The positive electrode sheet is heated by using a hot roller, the surface temperature of the hot roller is 100℃, the roller passing speed is 1 m / s, and then the separator and the negative electrode sheet are sequentially stacked on the surface of the positive electrode sheet, and then a cylindrical winding needle with a diameter of 1.5 mm is used to wind into a 18650 electrode core.

[0062] Example 2

[0063] The difference from Example 1 is that the roller passing speed of the positive electrode sheet is 0.5 m / s.

[0064] Example 3

[0065] The difference from Example 1 is that the surface temperature of the hot roller is 120℃, and the roller passing speed is 1 m / s.

[0066] Example 4

[0067] (1) A positive electrode sheet precursor is provided, the areal density of the positive electrode sheet precursor is 450 g / m 2 , and the compacted density of the positive electrode material layer is 2.65 g / cm 3 . The softening agent is applied on the positive electrode material layer on the opposite surfaces of the positive electrode sheet precursor by using a screen roller with a line number of 200, and the positive electrode sheet is obtained after standing for 30 s. The amount of the softening agent is 13.5 g / m 2 , and the softening agent is an N-methyl pyrrolidone (solvent) solution of dimethyl sulfoxide (softening substance), wherein the volume ratio of dimethyl sulfoxide and N-methyl pyrrolidone is 2:98.

[0068] The water content of the positive electrode material layer is 880 ppm, the content of the softening substance is 1500 ppm, so the value of A is 2380 ppm, and the value of θ 3 × (10 4 -A) / 10 4 is 14.18.

[0069] (2) The positive electrode sheet is heated by a hot roller, the surface temperature of the hot roller is 100℃, the over-roll speed is 1m / s, and then the separator and the negative electrode sheet are stacked on the surface of the positive electrode sheet in sequence, and then a cylindrical winding needle with a diameter of 1.5mm is used to wind into a 18650 electrode core.

[0070] Example 5

[0071] The difference from Example 4 is that the compaction density of the positive electrode material layer is 2.5g / cm 3 , the area density is 425g / m 2 , and the amount of softening agent is adjusted so that the value of A of the positive electrode material layer is 2380ppm, and the value of θ 3 ×(10 4 -A) / 10 4 is 11.90.

[0072] Example 6

[0073] The difference from Example 4 is only that the amount of softening agent is adjusted, and the value of A of the obtained positive electrode material layer is 6000ppm, and the value of θ 3 ×(10 4 -A) / 10 4 is 7.44.

[0074] Example 7

[0075] The difference from Example 6 is that the compaction density of the positive electrode material layer is 3.0g / cm 3 , the area density is 510g / m 2 , and the amount of softening agent is adjusted so that the value of A of the positive electrode material layer is 6000ppm, and the value of θ 3 ×(10 4 -A) / 10 4 is 10.80.

[0076] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0077] Comparative Example 1

[0078] (1) The positive electrode sheet is provided, the area density of the positive electrode sheet is 450g / m 2 , the compaction density of the positive electrode material layer is 2.65g / cm 3 , the water content is 880ppm, and the value of θ 3 ×(10 4 -A) / 10 4 is 16.97.

[0079] (2) The positive electrode sheet was heated by a hot roller, the surface temperature of the hot roller was 80℃, the passing speed of the roller was 1.0 m / s, and then the separator and the negative electrode sheet were stacked on the surface of the positive electrode sheet in sequence, and then the 18650 core was wound by using a cylindrical winding needle with a diameter of 1.5 mm.

[0080] Comparative Example 2

[0081] (1) The positive electrode sheet precursor was provided, the areal density of the positive electrode sheet precursor was 450 g / m 2 , and the compacted density of the positive electrode material precursor was 2.65 g / cm 3 . The softening agent was applied on the positive electrode material layer on the opposite surfaces of the positive electrode sheet precursor by using a screen roller with a line number of 200, and then the positive electrode sheet was obtained after standing for 15 s. The amount of the softening agent was 4.5 g / m 2 , and the softening agent was ethyl carbonate (solvent) solution of 1,3,5-trichlorobenzene (softening substance), wherein the volume ratio of 1,3,5-trichlorobenzene to ethyl carbonate was 5:95.

[0082] The water content of the positive electrode material layer was 880 ppm, and the content of the softening substance was 500 ppm, so A = 1380 ppm, and the value of θ 3 ×(10 4 -A) / 10 4 of the positive electrode sheet was 16.04.

[0083] (2) The positive electrode sheet was heated by a hot roller, the surface temperature of the hot roller was 100℃, the passing speed of the roller was 1 m / s, and then the separator and the negative electrode sheet were stacked on the surface of the positive electrode sheet in sequence, and then the 18650 core was wound by using a cylindrical winding needle with a diameter of 1.5 mm.

[0084] Comparative Example 3

[0085] The difference from Example 1 was that the softening agent was replaced by methyl ethyl carbonate. The value of A was 880 ppm, and the value of θ 3 ×(10 4 -A) / 10 4 was 16.97.

[0086] Performance analysis

[0087] The wound cores prepared in each example and comparative example were disassembled, and whether the positive electrode sheet located in the innermost circle of the core was broken and whether there was a gap visible to the naked eye between the positive electrode sheet and the negative electrode sheet were observed, and the results were summarized in Table 1.

[0088] Table 1

[0089] Is it broken? Is there a gap? Example 1 no no Example 2 no no Example 3 no no Example 4 no no Example 5 no no Example 6 no no Example 7 no no Comparative Example 1 yes yes Comparative Example 2 no yes Comparative Example 3 yes yes

[0090] It can be seen from the data in Table 1 that, after the softening treatment of the positive electrode tab precursor, and when the obtained positive electrode tab satisfies θ 3 ×(10 4 -A) / 10 4 ≤15, the problems of the fracture of the positive electrode tab in the wound core and the existence of the gap between the positive electrode tab and the negative electrode tab can be effectively solved.

[0091] The above is the exemplary embodiments of the present application, it should be noted that, for those skilled in the art, without departing from the principles of the present application, can make several improvements and refinements, these improvements and refinements also regarded as the protection scope of the present application.

Claims

1. A method for preparing a wound pole core, characterized in that: include: (1) providing a positive electrode sheet precursor to be wound, the positive electrode sheet precursor comprising a current collector and a positive electrode material layer disposed on at least one surface of the current collector; At an ambient temperature of 5° C. to 150° C., a softening agent is used to soften the positive electrode sheet precursor to obtain a positive electrode sheet; the softening agent includes a softening substance; The positive electrode sheet satisfies: Calculated by the numerical values ​​of each parameter, θ 3 ×(10 4 -A) / 10 4 ≤15; wherein, θ is the compaction density of the positive electrode material layer, in g / cm 3 ; A is the sum of the water content of the positive electrode material layer and the content of the softening substance, in ppm; (2) The positive electrode sheet is subjected to a heat treatment, and a negative electrode sheet is superimposed on the surface of the positive electrode sheet, and the sheet is wound to obtain a wound electrode core; the heat treatment includes: rolling the positive electrode sheet with a hot roller; wherein the surface temperature of the hot roller is 80°C-130°C; and the tension of the positive electrode sheet when passing through the hot roller is in the range of 0.5N-200N.

2. The preparation method according to claim 1, characterized in that 2.5g / cm 3 ≤θ≤3.0g / cm 3 。 3. The preparation method according to claim 1, characterized in that The water content of the positive electrode material layer is in the range of 0-1500 ppm.

4. The preparation method according to claim 1, characterized in that The softening substance includes at least one of acetone, xylene, 1,3,5-trichlorobenzene, polyethylene glycol, dimethyl methyl phosphate, polypropylene glycol, diethylene glycol butyl ether, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

5. The preparation method according to any one of claims 1 to 4, characterized in that The softener further comprises a solvent; the solvent comprises at least one of nitrogen methyl pyrrolidone, propylene carbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and ethyl propionate; The volume of the softening substance accounts for 0.5%-10.0% of the total volume of the softener.

6. The preparation method according to claim 1, characterized in that The mass amount of the softener is 0.05%-1% of the mass of the positive electrode material layer.

7. A battery, characterized in that: It comprises a wound pole core prepared according to the preparation method according to any one of claims 1-6.

8. An electrical device, characterized in that: The electric device comprises the battery as claimed in claim 7.

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