Button lithium primary battery and preparation method therefor, and electronic device

Abstract

Provided in the present application are a button lithium primary battery and a preparation method therefor, and an electronic device. The button lithium primary battery comprises a battery casing (10) and a battery cell assembly located inside the battery casing (10), wherein the battery cell assembly comprises a negative electrode (3), a negative-electrode modification membrane (4), separators (5, 6) and a positive electrode (7), which are sequentially stacked; a recess (9) is provided on the surface of the side of the negative electrode (3) that is close to the negative-electrode modification membrane (4); and the negative-electrode modification membrane (4) is tightly embedded in the recess (9). By means of optimizing the structure and the material of the button lithium primary battery in the present application, the button lithium primary battery has an excellent discharge performance, and good levels of stability and reliability.

Description

Lithium primary button battery, preparation method thereof, and electronic device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 31, 2024 with application number 202411045595.2 and the Chinese patent application filed with the China Patent Office on July 31, 2024 with application number 202421847565.9. The entire contents of the above applications are incorporated by reference into this application.

[0002] Technical Field

[0003] The present application relates to the technical field of battery materials, and in particular to a lithium primary button battery, a preparation method thereof, and an electronic device.

[0004] Background Art

[0005] Lithium primary batteries, commonly known as lithium batteries, are high-energy chemical primary cells. They use metallic lithium as the negative electrode, a solid salt or salt dissolved in an organic solvent as the electrolyte, and a metal oxide or other solid or liquid oxidant as the positive active material. They are widely used in a variety of fields, including smart metering, intelligent transportation, smart security, and medical devices. With the widespread adoption of IoT technology, user application environments are becoming increasingly stringent, placing increasing demands on battery output capacity and stability in extreme environments. Consequently, demands for structural stability throughout the battery cell's lifecycle are also increasing.

[0006] Extreme environments mainly include extreme conditions such as high temperature, low temperature, high pressure, and strong vibration. These extreme environmental conditions place higher demands on the performance and reliability of batteries. For example, in low-temperature environments, the battery materials need to have better low-temperature performance to avoid the dissolution and shuttle effect of the positive electrode active ions, as well as the side reactions between the electrode materials and the electrolyte, in order to maintain the stability and reliability of the battery. In high-voltage environments, the battery structure needs to be stronger and safer to prevent the battery from rupturing and exploding. In strong vibration environments, the battery structure and fixing method need to be more stable and reliable to prevent the battery from shifting or falling off. Therefore, in order to adapt to the above extreme environments, optimization and improvement are needed in terms of materials, structures, and management systems.

[0007] Technical issues

[0008] Based on the above situation, on the one hand, the relevant technology discloses setting a carbon material layer inside the battery, thereby reducing the side reactions inside the battery and improving the conductivity, and ultimately reducing the internal resistance of the battery, but the carbon material layer is easy to fall off, lacks strength, and has gaps between the electrodes; on the other hand, the relevant technology also discloses the preparation of an electrode layer with good affinity or conductivity, but it requires a special process to prepare it, and has high requirements for the process and materials, so it cannot be mass-produced.

[0009] Technical Solutions

[0010] In a first aspect, an embodiment of the present application provides a lithium primary button battery, the lithium primary button battery comprising a battery housing and a battery cell assembly located inside the battery housing, the battery cell assembly comprising a negative electrode, a negative electrode modification film, a separator, and a positive electrode stacked in sequence;

[0011] A concave groove is provided on the surface of the negative electrode close to the negative electrode modification film, and the negative electrode modification film is tightly embedded in the concave groove.

[0012] In a second aspect, an embodiment of the present application provides a method for preparing a lithium primary button battery according to the first aspect, the method comprising: punching a negative electrode modification film into a negative electrode having a concave groove on its surface to form a precursor material;

[0013] The precursor material, the separator and the positive electrode are stacked in sequence to obtain a battery core assembly;

[0014] The battery cell assembly and the battery housing are packaged to obtain the lithium primary button battery. In a third aspect, an embodiment of the present application provides an electronic device comprising the lithium primary button battery according to the first aspect.

[0015] Beneficial effects

[0016] The present application provides a lithium primary button battery. First, the present application provides a concave groove on the surface of the negative electrode so that the negative electrode modification film can be tightly embedded in the concave groove, and has the following effects: ① The lamination tightness, lamination flatness and centering alignment between the negative electrode modification film and the negative electrode can be improved, which not only ensures the stability of the battery cell assembly structure itself, but also improves the structural stability of the battery cell assembly in reliability testing. For example, under long-term vibration, drop or centrifugal environment testing at room temperature or high temperature, there is still no displacement between the negative electrode and the negative electrode modification film, thereby enhancing the lamination stability between the negative electrode modification film and the negative electrode at a high discharge depth, and ensuring the stability of its large current discharge or pulse discharge performance at room temperature and extremely low temperature; ② A storage space for the negative electrode modification film is reserved in advance inside the negative electrode, which not only ensures that the negative electrode modification film does not deform during the stamping process, but also improves the flatness of the entire negative electrode material composite surface.

[0017] Secondly, the negative electrode modification membrane provided by the present application has the following advantages: ① The negative electrode modification membrane has a porous structure. On the one hand, due to the influence of the potential during the reaction process of the battery, the positive electrode active material will react with some trace components in the non-aqueous electrolyte to form free cations or anions. At the same time, since the liquid absorption capacity of the diaphragm in the battery is stronger than the liquid absorption capacity of the positive electrode active material, the concentration polarization effect exists, which makes it possible for the dissolved positive electrode active material ions to shuttle through the diaphragm, thereby causing irreversible side reactions with the negative electrode to form a reaction interface with high internal resistance. The negative electrode modification membrane provided by the present application has a strong ion adsorption function because it contains rich mesopores and micropores, which can well adsorb the dissolved positive electrode active ions in the pore structure, and ultimately effectively inhibit their transfer to the negative electrode surface for side reactions. On the other hand, some components in the non-aqueous electrolyte will also react with the negative electrode to form an SEI film. The SEI is easily broken down in the early stage of the battery cycle, and in the later stage of the cycle, as the negative electrode is continuously consumed, the interface impedance between it and the diaphragm and the positive electrode increases. At this time, if the negative electrode is in contact with too much free electrolyte, it will be more likely to form a high-impedance interface film, resulting in obstruction of ion transmission. The porous structure in the negative electrode modified membrane provided in the present application has strong adsorption properties, which can adsorb the free electrolyte in the modified membrane at the end of discharge, thereby reducing the degree of contact with the negative electrode, thereby improving the discharge performance of the battery. At the same time, the pore structure of the negative electrode modified membrane can be freely regulated according to the raw material selection and processing technology of the membrane;

[0018] ②The negative electrode modification film is a multifunctional layer. The modification film has good electrical conductivity and can form a near-capacitor structure with the positive electrode layer, thereby having certain capacitance characteristics. When the battery is in a relatively low temperature environment, the above-mentioned capacitor structure can provide a certain amount of charge at the instant of the reaction. At the same time, a benign contact is generated between the modification film and the negative electrode, and a certain affinity is formed between the particles, thereby changing the original passivation layer state, so that when the electrons are turned on, lithium ions can easily pass through the passivation layer, thereby ensuring that the ions can penetrate the passivation layer, shortening the ion conduction, and thus improving the instantaneous recovery voltage value. At the same time, the modification layer can improve the ion and electron conduction rate of the battery during the discharge process, ensuring that the battery has a large current output capability. In addition, the negative electrode modification film provided in the present application has good affinity with the negative electrode, and can modify the passivation layer on the surface of the negative electrode, so as to better protect the negative electrode from being corroded by the dissolved positive electrode cations;

[0019] ③ The negative electrode modification film has high strength and good flexibility. The tensile strength of the prepared negative electrode sheet is as high as 0.4-0.5kN / m, which can ensure the integrity of the negative electrode modification film during the electrode sheet slitting process, the processability during the battery assembly process, and the integrity during battery packaging. At the same time, due to its good flexibility, it can reduce the stress generated between the two when laminating with the negative electrode, avoiding uneven lamination and uneven lamination surface. It also does not dissolve or deform under the infiltration of non-aqueous electrolytes and after deep discharge.

[0020] ④ The negative electrode modification film has high flatness, and the deviation of the thickness range of the negative electrode modification film is only within 3μm, which reduces the process difficulty when the negative electrode modification film is embedded in the negative electrode surface, ensures the flatness of the fitting between the negative electrode modification film and the negative electrode, reduces the gap between the negative electrode modification film and the negative electrode, and ultimately improves the interface contact performance between the two;

[0021] ⑤ The negative electrode modification membrane is a self-supporting integrated functional membrane, which not only reduces the interfacial resistance of ion conduction, but also avoids the introduction of other matrix materials, which may cause side reactions between them and the battery system, or lead to insufficient effective space for the battery cell components. In addition, the processing technology of the negative electrode modification membrane provided by this application is simple, and its thickness is not affected by the thickness of the matrix layer. The overall thickness can be as low as 30μm, and the uniformity of the negative electrode modification membrane is not affected by the material and flatness of the substrate layer.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic structural diagram of a lithium primary button cell provided in the present application, wherein the positive electrode is directly prepared by stamping into sheets;

[0024] FIG2 is a schematic structural diagram of a lithium primary button battery provided in the present application, wherein the positive electrode is prepared by punching a collector ring on the surface of the positive electrode active material layer;

[0025] FIG3 is a schematic diagram of a cross-sectional disassembly of a lithium primary button battery provided in the present application;

[0026] FIG4 is a partial enlarged view of the circled portion in FIG3 ;

[0027] FIG5 is a schematic diagram of the assembly of precursor materials in the lithium primary button cell provided in this application;

[0028] FIG6 is a schematic flow chart of a method for preparing a lithium primary button battery provided in the present application;

[0029] Among them, 1-sealing ring, 2-negative electrode bottom cover, 3-negative electrode, 4-negative electrode modification film, 5-glass fiber diaphragm, 6-polypropylene diaphragm, 7-positive electrode, 8-positive electrode cover, 9-concave groove, 10-battery shell.

[0030] Modes for Carrying Out the Invention

[0031] As shown in Figures 1-4, the present application provides a lithium primary button battery for use in electronic devices, including a battery housing 10 and a battery cell assembly located inside the battery housing 10, wherein the battery cell assembly includes a negative electrode 3, a negative electrode modification film 4, separators 5, 6 and a positive electrode 7 stacked in sequence; a concave groove 9 is provided on the surface of the negative electrode 3 close to the negative electrode modification film 4, and the negative electrode modification film 4 is tightly embedded in the concave groove 9.

[0032] The shape of the concave groove 9 includes any one of a circle, annular shape, or a regular polygon, or a combination of at least two thereof, and can be, for example, a circle. Examples of the regular polygon include a square, a regular pentagon, a regular hexagon, and the like. The center of the concave groove 9 coincides with the center of the vertical projection of the negative electrode modification film 4. The area ratio of the negative electrode modification film 4 to the concave groove 9 is 1:1.

[0033] The area ratio of the negative electrode modification film 4 to the negative electrode 3 is (0.2-0.99):1, which can be (0.3-0.6):1, for example, 0.2:1, 0.22:1, 0.25:1, 0.28:1, 0.3:1, 0.32:1, 0.35:1, 0.38:1, 0.4:1, 0.42:1, 0.45:1, 0.48:1, 0.5:1, 0.52:1, 0.55:1, 0.58:1, 0.6:1 , 0.65:1, 0.7:1, 0.75:1, 0.78:1, 0.8:1, 0.82:1, 0.85:1, 0.88:1, 0.9:1, 0.925:1, 0.93:1, 0.935:1, 0.94:1, 0.945:1, 0.95:1, 0.955:1, 0.96:1, 0.965:1, 0.97:1, 0.975:1, 0.98:1, 0.985:1, 0.99:1, etc.

[0034] By regulating the area ratio of the negative electrode modification membrane to the negative electrode, its functionality can be fully exerted. If the area ratio is too low, the functionality of the negative electrode modification membrane will be weakened due to the decrease in the area of ​​the modified region. For example, the conductivity of the conductive surface will increase relatively little, and the adsorption area will decrease accordingly, resulting in a lower adsorption capacity for dissolved positive active ions. Conversely, the negative electrode modification membrane will not be well riveted due to the small distance between the concave edges. In addition, if the area is too large, its functionality will not be significantly improved, which will also lead to an increase in process costs.

[0035] The ratio of the depth of the concave groove 9 to the thickness of the negative electrode modification film 4 is (0.3-1.3):1, which can be (0.95-1.05):1, for example, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.90:1, 0.91:1, 0.92:1, 0.93:1, 0.94:1, 0.9 5:1, 0.96:1, 0.97:1, 1:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, 1.2:1, 1.22:1, 1.25:1, 1.28:1, 1.3:1, etc.

[0036] By regulating the ratio of the depth of the concave groove to the thickness of the negative electrode modification film, the negative electrode modification film and the negative electrode surface are completely flush and have good physical bonding. When the depth of the concave groove is too deep, during the leveling process, the downward pressure on the upper surface of the negative electrode modification film is small, resulting in weak bonding between the lower surface of the negative electrode modification film and the negative electrode in the concave groove, unevenness or insufficient exhaust, resulting in a certain air gap surface; when the depth of the concave groove is too shallow and the thickness of the negative electrode modification film is too large, during the leveling process, because the negative electrode modification film is too thick and the space in the concave groove is insufficient, the negative electrode modification film will be stretched laterally during leveling and even overflow of the negative electrode surface will be caused, resulting in unevenness. In addition, the size of the negative electrode and the negative electrode modification film will be too high, affecting the size of the entire battery cell.

[0037] The thickness of the negative electrode modification film 4 is 0.03 mm-0.20 mm, and can be 0.05 mm-0.10 mm, for example, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.20 mm, etc.

[0038] By regulating the thickness of the negative electrode modification film, the functionality of the negative electrode modification film can be met while ensuring the assembly feasibility of the entire battery cell and sufficient capacity design. If the thickness is too small, on the one hand, the processing difficulty of the negative electrode modification film will increase, which will increase the production cost and increase the difficulty of assembling and processing the negative electrode modification film during the assembly process; on the other hand, if the thickness is too thin, the adsorption capacity of the dissolved positive electrode active ions will be reduced. Conversely, if the thickness is too thick, it will occupy the structural design space of the negative electrode, thereby reducing the design capacity of the entire battery cell.

[0039] The tensile strength of the negative electrode modification film 4 is 0.1-2 KN / m, which may be 0.4-0.5 KN / m, for example, 0.1 KN / m, 0.2 KN / m, 0.3 KN / m, 0.4 KN / m, 0.42 KN / m, 0.45 KN / m, 0.48 KN / m, 0.5 KN / m, 0.8 KN / m, 1 KN / m, 1.2 KN / m, 1.5 KN / m, 1.8 KN / m, 2 KN / m, etc.

[0040] By regulating the tensile strength of the negative electrode modification film, the negative electrode modification film has excellent mechanical processing properties, including cutting, transport positioning, leveling and other properties. Too low tensile strength will affect the implementation of the entire processing process and the consistency of assembly. Even because the strength of the negative electrode modification film is poor or it is easy to be damaged, the fit of the negative electrode modification film decreases with the increase of the discharge depth. Conversely, the film will be too large, which will affect some functions of the negative electrode modification film, such as the decrease in conductivity and the adsorption capacity of dissolved positive active ions. Since the way to increase the tensile strength of the negative electrode modification film includes increasing the content of the binder, which leads to a decrease in the content of the conductive component, the porosity of the negative electrode modification film will also decrease.

[0041] The surface density of the negative electrode modification film 4 is 40-80 g / cm 2 , which can be 50-60g / cm 2 , for example, it can be 40g / cm 2 , 45g / cm 2 , 50g / cm 2 , 52g / cm 2 , 55g / cm 2 , 58g / cm 2 、60g / cm 2 、65g / cm 2 , 70g / cm 2 , 75g / cm 2 、80g / cm 2 wait.

[0042] By regulating the surface density of the negative electrode modification film, the film possesses excellent comprehensive functionality. A too low surface density results in poor membrane strength, and as the cell reaction progresses to the end of discharge, the functionality of the negative electrode modification film declines rapidly. Conversely, a too low surface density results in a corresponding decrease in the porosity of the negative electrode modification film, leading to a decrease in the adsorption capacity for dissolved positive electrode active ions. Similarly, the negative electrode modification film contains a high content of non-conductive binder components, which in turn leads to a decrease in the conductivity of the negative electrode modification film.

[0043] The pore volume of the negative electrode modified membrane 4 is 0.05-0.5 cm 3 / g, which can be 0.15-0.33cm 3 / g, for example, 0.05cm 3 / g, 0.08cm 3 / g, 0.1cm 3 / g, 0.12cm 3 / g, 0.15cm 3 / g, 0.18cm 3 / g, 0.2cm 3 / g, 0.22cm 3 / g, 0.25cm 3 / g, 0.28cm 3 / g, 0.3cm 3 / g, 0.33cm 3 / g, 0.35cm 3 / g, 0.4cm 3 / g, 0.45cm 3 / g, 0.5cm 3 / g, etc.

[0044] By regulating the pore volume of the negative electrode modified membrane, the functionality of the modified membrane can be fully exerted. The pore volume of the modified membrane is also affected by the material model, the ratio of each component, and the processing method. If the pore volume is too small, the adsorption capacity of the dissolved positive electrode active ions will decrease, which is mainly reflected in the fact that the adsorption amount is too small and the adsorption amount will soon reach saturation. Otherwise, the adsorption efficiency of the dissolved positive electrode active ions will become low.

[0045] The material of the negative electrode modification film 4 includes an active material. The active material includes at least one of an oxide material, a carbon material, a metal conductive particle or a fluorine-containing particle, for example, an oxide material and / or a carbon material. The oxide material includes any one of titanium dioxide, molybdenum dioxide, aluminum oxide, lithium titanate or silver oxide or a combination of at least two. The carbon material includes any one of graphene, acetylene black, carbon nanotubes, activated carbon or graphite or a combination of at least two. The metal conductive particles include any one of copper particles, silver particles or gold particles or a combination of at least two. The fluorine-containing particles include any one of lithium fluoride, carbon fluoride, polytetrafluoroethylene, polyvinylidene fluoride or a polyvinyl fluoride copolymer or a combination of at least two.

[0046] The material of the negative electrode modification film 4 further includes a binder, which includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene propylene copolymer, or polyacrylic acid.

[0047] The mass ratio of the active material to the binder is 1:(0.03-0.3), which may be 1:(0.05-0.25), for example, 1:0.03, 1:0.05, 1:0.08, 1:0.1, 1:0.12, 1:0.15, 1:0.18, 1:0.2, 1:0.22, 1:0.25, 1:0.28, 1:0.3, etc.

[0048] By regulating the mass ratio of active materials to binders, the negative electrode modification film can have excellent functionality, such as conductivity, adsorption, and flexible self-support. A too low mass ratio may cause the negative electrode modification film to be unable to self-support or have poor membrane strength. Conversely, it will lead to poor conductivity and low positive electrode active ion adsorption capacity, and reduce the proportion of other materials.

[0049] In the preparation method of the negative electrode modified film, the active material and the binder are subjected to compression molding or extrusion molding. During the molding process, the film can be prepared without using a solvent, or using a certain inorganic or organic solvent, depending on the process requirements.

[0050] The diaphragm includes a glass fiber diaphragm 5 and / or a polypropylene diaphragm 6. The number of layers of the diaphragm is 1-3, which can be 2 layers, for example, 1 layer, 2 layers or 3 layers. The diaphragm includes a glass fiber diaphragm 5 and a polypropylene diaphragm 6.

[0051] A combination of 6.

[0052] The glass fiber separator 5 is arranged near the negative electrode 3, and the polypropylene separator 6 is arranged near the positive electrode 7, thereby achieving functional matching with the negative electrode modification membrane 4. This is because: ① the stiffness of the glass fiber separator is lower than that of the polypropylene separator, which facilitates the bonding of the glass fiber separator and the negative electrode modification membrane; ② the liquid absorption capacity of the glass fiber separator is maximized: the liquid absorption capacity of the glass fiber separator > the liquid absorption capacity of the negative electrode modification membrane > the liquid absorption capacity of the polypropylene separator > the liquid absorption capacity of the positive electrode, thus forming a certain gradient of concentration polarization. The provision of glass fiber facilitates the uniform distribution of electrolyte throughout the battery cell. At the same time, the glass fiber separator can serve as an electrolyte storage interface, ensuring the amount of free electrolyte at the end of the battery cell's life, enhancing the ion conductivity, and ensuring the battery cell's pulse capability at extremely low temperatures. In addition, it can also reduce the storage amount of free electrolyte at the positive electrode interface, thereby reducing the dissolution of positive electrode active materials and the storage amount of free electrolyte in the negative electrode modification membrane, and reducing the side reactions between the dissolved positive electrode active ions and the negative electrode.

[0053] The battery housing 10 includes a negative electrode bottom cover 2 located on one side of the negative electrode 3 and a positive electrode cover 8 located on one side of the positive electrode 7. The negative electrode bottom cover 2 is provided with a sealing ring 1, which is provided at the edge of the negative electrode bottom cover 2 and the positive electrode cover 8.

[0054] The lithium primary button cell also includes an electrolyte.

[0055] As shown in FIG6 , the present application also provides a method for preparing a lithium primary button battery, the method comprising the following steps:

[0056] S101, punching a negative electrode modification film into a negative electrode having a concave groove on its surface to form a precursor material;

[0057] S102, stacking the precursor material, the separator and the positive electrode in sequence to obtain a battery cell assembly;

[0058] S103, encapsulating the battery cell assembly and the battery casing to obtain the lithium primary button battery.

[0059] After punching the negative electrode modification film into the negative electrode with the concave groove on the surface, the method further includes leveling the bonding surface between the negative electrode modification film and the concave groove to fully ensure the bonding and bonding flatness of the two.

[0060] After the negative electrode modified film is cut into a specified shape, it is punched into the negative electrode with a concave groove on the surface. The positioning requires that the center of its vertical projection surface completely coincides with the center of the concave groove in the negative electrode to complete the initial flat fitting.

[0061] When the depth of the concave groove is not higher than the thickness of the negative electrode modification film, during the leveling process, the negative electrode modification film is first subjected to pressure, and the center of the projection surface of the two is subjected to force. The force is conducted, and the lower surface of the negative electrode modification film will be embedded and fitted with the upper surface of the concave groove of the negative electrode, and the air between the two will be discharged to achieve a completely flat and fitting effect; when the depth of the concave groove is higher than the thickness of the negative electrode modification film, it is equivalent to the negative electrode modification film being placed in the negative electrode concave groove. During the leveling process, the non-concave groove part of the negative electrode is first subjected to force, and the center part of the concave groove is in a depressurized or under-pressure state. Under the continuous action of the downward pressure, the negative electrode will be compressed and deformed, and act towards the central under-pressure area. The final effect is that the negative electrode modification film is tightly fitted in the concave groove, and the upper surface is cohesively embedded by the negative electrode, thereby achieving a flat and fitting effect.

[0062] The battery housing includes a negative electrode bottom cover 2 located on one side of the negative electrode 3 and a positive electrode cover 8 located on one side of the positive electrode 7. The negative electrode bottom cover 2 is provided with a sealing ring 1, which is provided at the edge clamping position of the negative electrode bottom cover 2 and the positive electrode cover 8.

[0063] The precursor material and the separators 5 and 6 are punched into the negative electrode bottom cover.

[0064] The separators 5 and 6 are in an inverted U shape, with both sides of the inverted U shape bending toward the positive electrode 7 .

[0065] After the stacking is carried out in sequence, the method further includes injecting electrolyte.

[0066] After the electrolyte is injected, the formed positive electrode sheet is placed, and finally the positive electrode cover 8 is covered, and the battery is sealed and pressed once and twice to form a lithium primary button battery.

[0067] The positive electrode sheet includes a current collector and a positive electrode active material layer disposed on at least one side of the current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material illustratively includes manganese dioxide, carbon fluoride, or iron sulfide. The conductive agent illustratively includes at least one of graphite, carbon nanotubes, conductive carbon black, or graphene. The binder illustratively includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium polyacrylate, polyethylene oxide, or polyacrylonitrile.

[0068] The forming process of the positive electrode sheet includes mixing the positive electrode active material, conductive agent and binder uniformly through a high-speed mixing device, and then punching the sheet into a sheet using a forming machine for direct use. A current collecting net can also be punched on the surface of the positive electrode active material layer, or a current collecting ring can be used in combination.

[0069] The material of the negative electrode 3 exemplarily includes lithium metal or lithium alloy.

[0070] In the following examples and comparative examples, the lithium primary button cell is a CR2032 model button cell with a diameter of 20 mm and a thickness of 3.2 mm. The positive electrode sheet has a diameter of 15.00 mm and a thickness of 1.85 mm; the negative electrode sheet has a diameter of 16.00 mm and a thickness of 0.58 mm; and the electrolyte is a non-aqueous electrolyte of lithium perchlorate with a concentration of 0.9 mol / L (the solvent being composed of propylene carbonate and ethylene glycol dimethyl ether).

[0071] The method for preparing the positive electrode sheet comprises the following steps:

[0072] Manganese dioxide, conductive carbon black, and polytetrafluoroethylene emulsion were mixed uniformly in a mass ratio of 1:0.5:0.6 using a high-speed mixing device, and then dried to obtain a powder. The powder was then punched into a positive electrode sheet and assembled into a current collector using a powder forming and ring assembly machine to obtain the positive electrode sheet shown in FIG1 ;

[0073] or,

[0074] Manganese dioxide, conductive carbon black and polytetrafluoroethylene emulsion were mixed uniformly in a mass ratio of 1:0.5:0.6 by a high-speed mixing device, and then dried to obtain a powder. A collecting ring was then stamped on the positive electrode surface using a molding machine to obtain the positive electrode sheet shown in Figure 2.

[0075] The above description of button batteries is intended to fully illustrate the technical solution of the present application and should not be regarded as a limitation of the present application.

[0076] Example 1

[0077] This embodiment provides a lithium primary button battery, as shown in Figures 3 and 4, the lithium primary button battery includes a battery shell 10, and a battery cell assembly and electrolyte located inside the battery shell 10, the battery cell assembly includes a lithium metal negative electrode 3, a circular planar negative electrode modification film 4, a diaphragm and a manganese dioxide positive electrode 7 stacked in sequence; the surface of the lithium metal negative electrode 3 close to the circular planar negative electrode modification film 4 is provided with a circular concave groove 9, and the circular planar negative electrode modification film 4 is tightly embedded in the circular concave groove 9; the battery shell 10 includes a negative electrode bottom cover 2 located on one side of the lithium metal negative electrode 3 and a positive electrode cover 8 located on one side of the manganese dioxide positive electrode 7, the negative electrode bottom cover 2 is provided with a sealing ring 1, and the sealing ring 1 is arranged at the edge clamping position of the negative electrode bottom cover 2 and the positive electrode cover 8; the diaphragm includes a combination of a glass fiber diaphragm 5 and a polypropylene diaphragm 6, the glass fiber diaphragm 5 is arranged on the side close to the lithium metal negative electrode 3, and the polypropylene diaphragm 6 is arranged on the side close to the manganese dioxide positive electrode 7.

[0078] The area ratio of the circular planar negative electrode modification film 4 to the circular concave groove 9 is 1:1; the area ratio of the circular planar negative electrode modification film 4 to the lithium metal negative electrode 3 is 0.45:1; and the ratio of the depth of the circular concave groove 9 to the thickness of the circular planar negative electrode modification film 4 is 0.95:1. The thickness of the circular planar negative electrode modification film 4 is 0.08 mm, the tensile strength is 0.45 KN / m, and the surface density is 55 g / cm 2 , pore diameter is 2-200nm, pore volume is 0.3cm 3 The circular planar negative electrode modification membrane 4 is prepared by compression molding of a carbon material and a polytetrafluoroethylene binder in a mass ratio of 1:0.15.

[0079] This embodiment also provides a method for preparing the above-mentioned lithium primary button battery, which comprises the following steps:

[0080] As shown in Figure 5, a circular concave groove is punched on the surface of the lithium metal negative electrode using a circular upper mold on one side of the negative electrode bottom cover, and then a circular planar negative electrode modification film is punched into the negative electrode with a circular concave groove on the surface. The positioning requires that the center of its vertical projection surface completely coincides with the center of the circular concave groove in the negative electrode. After being leveled using a stamping tool, a precursor material is formed; then the diaphragm is punched into the negative electrode bottom cover, the diaphragm forms a "U" shape, and a non-aqueous electrolyte is injected; then the formed manganese dioxide positive electrode sheet is placed, and finally the positive electrode cover is covered, and the primary sealing and secondary sealing are performed in sequence to obtain the lithium primary button battery.

[0081] Example 2

[0082] The difference between this embodiment and Example 1 is that the shape of the negative electrode modification film is a circular plane, and the shape of the concave groove is a circular ring, wherein the area ratio of the circular plane negative electrode modification film to the circular concave groove 9 is 1:1; the area ratio of the circular plane negative electrode modification film to the negative electrode is 0.3:1; the ratio of the depth of the circular concave groove 9 to the thickness of the circular plane negative electrode modification film is 0.95:1.

[0083] The thickness of the annular planar negative electrode modification film is 0.05 mm, the tensile strength is 0.4 KN / m, and the surface density is 50 g / cm 2 , pore diameter is 2-200nm, pore volume is 0.3cm 3 The material of the annular planar negative electrode modification membrane 4 is prepared by compression molding of a carbon material and a polytetrafluoroethylene binder in a mass ratio of 1:0.1. Other aspects are the same as those of Example 1.

[0084] Example 3

[0085] The difference between this embodiment and Example 1 is that the shape of the negative electrode modification film is a square plane, and the shape of the concave groove is a square, wherein the area ratio of the square plane negative electrode modification film to the square concave groove is 1:1; the area ratio of the square plane negative electrode modification film to the negative electrode is 0.6:1; and the ratio of the depth of the square concave groove to the thickness of the square plane negative electrode modification film is 0.97:1.

[0086] The thickness of the square planar negative electrode modification film is 0.10 mm, the tensile strength is 0.5 KN / m, and the surface density is 60 g / cm 2 , pore diameter is 2-200nm, pore volume is 0.3cm 3 The material of the square planar negative electrode modification membrane is prepared by compression molding of a carbon material and a polytetrafluoroethylene binder in a mass ratio of 1:0.2, and the rest is the same as in Example 1.

[0087] Example 4

[0088] The difference between this embodiment and embodiment 1 is that the diaphragm is replaced with a double-layer polypropylene diaphragm, and the rest is the same as embodiment 1.

[0089] Example 5

[0090] The difference between this embodiment and embodiment 1 is that the area ratio of the circular planar negative electrode modification film to the negative electrode is 0.1:1, and the other aspects are the same as those of embodiment 1.

[0091] Example 6

[0092] The difference between this embodiment and embodiment 1 is that the area ratio of the circular planar negative electrode modification film to the negative electrode is 1.2:1, and the other aspects are the same as those of embodiment 1.

[0093] Example 7

[0094] The difference between this embodiment and embodiment 1 is that the ratio of the depth of the circular concave groove to the thickness of the circular planar negative electrode modification film is 0.1:1, and the rest is the same as embodiment 1.

[0095] Example 8

[0096] The difference between this embodiment and embodiment 1 is that the ratio of the depth of the circular concave groove to the thickness of the circular planar negative electrode modification film is 2:1, and the rest is the same as embodiment 1.

[0097] Example 9

[0098] The difference between this embodiment and embodiment 1 is that the surface density of the circular planar negative electrode modified film is 30 g / cm 2 , and the rest are the same as in Example 1.

[0099] Example 10

[0100] The difference between this embodiment and embodiment 1 is that the surface density of the circular planar negative electrode modified film is 90 g / cm 2 , and the rest are the same as in Example 1.

[0101] Example 11

[0102] The difference between this embodiment and embodiment 1 is that the pore volume of the circular planar negative electrode modified membrane is 0.02 cm 3 / g, and the rest are the same as in Example 1.

[0103] Example 12

[0104] The difference between this embodiment and embodiment 1 is that the pore volume of the circular planar negative electrode modified membrane is 0.7 cm 3 / g, and the rest are the same as in Example 1.

[0105] Example 13

[0106] The difference between this embodiment and embodiment 1 is that the mass ratio of the carbon material active material to the polytetrafluoroethylene binder is 1:0.02, and the rest is the same as embodiment 1.

[0107] Example 14

[0108] The difference between this embodiment and embodiment 1 is that the mass ratio of the carbon material active material to the polytetrafluoroethylene binder is 1:0.4, and the rest is the same as embodiment 1.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface and no circular planar negative electrode modification film is provided. Other aspects are the same as Example 1.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, no circular planar negative electrode modification film is provided, and the diaphragm is replaced with a double-layer polypropylene diaphragm. The rest is the same as Example 1.

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and a circular planar negative electrode modification film is provided. The rest is the same as Example 1.

[0115] Comparative Example 4

[0116] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, a circular planar negative electrode modification film is provided, and the separator is replaced with a double-layer polypropylene separator. The rest is the same as Example 1.

[0117] Comparative Example 5

[0118] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and the circular planar negative electrode modification film is replaced by a circular carbon material layer. The preparation method of the circular carbon material layer is as follows: acetylene black, ethanol and polyacrylic acid are evenly stirred to form a slurry, which is transferred and coated on a polypropylene non-woven fabric. After vacuum baking, it is cut into a circular plane. The rest is the same as Example 1.

[0119] Comparative Example 6

[0120] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and the circular planar negative electrode modification film is replaced by a circular carbon material layer. The preparation method of the circular carbon material layer is as follows: acetylene black, ethanol and polyacrylic acid are evenly stirred to form a slurry, which is transferred and coated on a polypropylene non-woven fabric. After vacuum baking, it is cut into a circular plane, and the diaphragm is replaced with a double-layer polypropylene diaphragm. The rest is the same as Example 1.

[0121] Comparative Example 7

[0122] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and the circular planar negative electrode modification film is replaced by a circular carbon foil composite layer. The preparation method of the circular carbon foil composite layer is as follows: acetylene black, ethanol and polyacrylic acid are evenly stirred to form a slurry, which is transferred and coated on a steel mesh and a polypropylene non-woven fabric. After vacuum baking, it is rolled flat and then cut into a circular plane. The rest is the same as Example 1.

[0123] Comparative Example 8

[0124] The difference between this comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and the circular planar negative electrode modification film is replaced by a circular carbon foil composite layer. The preparation method of the circular carbon foil composite layer is as follows: acetylene black, ethanol and polyacrylic acid are evenly stirred to form a slurry, which is transferred and coated on a steel mesh and a polypropylene non-woven fabric. After vacuum baking, it is rolled flat and then cut into a circular plane, and the diaphragm is replaced with a double-layer polypropylene diaphragm. The rest is the same as Example 1.

[0125] Test conditions

[0126] The negative electrode modified films 4 or carbon foil composite layers provided in Examples 1 to 14 and Comparative Examples 1 to 8 were subjected to performance tests, and the test methods were as follows:

[0127] Tensile strength: An electronic separator tensile testing machine was used to test the tensile strength of the membrane. First, the negative electrode modified membrane 4 was cut into 100×14 mm pieces and placed between the upper and lower clamps of the tensile testing machine with a clamping distance of 50 mm and a preload of 0.5 N. The machine was started and the sample was stretched at a constant elongation rate of 10 mm / min until it broke, and the maximum tensile force during the stretching process was recorded.

[0128] The lithium primary button batteries provided in Examples 1 to 14 and Comparative Examples 1 to 8 were tested using the following test methods:

[0129] (1) First, at room temperature, the discharge procedure is 0.2 mA constant resistance discharge for 800 h, and then the battery is placed in a refrigerator at -30℃ and -20℃ for 4 h respectively;

[0130] (2) The background current is 10μA, and then the battery is discharged with a constant current pulse of 10mA for 0.5s, and left for 4.5s. This step is repeated three times, and the discharge voltage value is recorded; then the refrigerator temperature is adjusted to -20℃, and after leaving for 4h, the above test steps are repeated three times. Five batteries of each scheme are tested, and the average value is taken. The calculation formula of the voltage deviation is: Test 5 batteries, voltage deviation = (maximum voltage - minimum voltage) / average voltage

[0131] The test results are shown in Table 1 and Table 2:

[0132] Table 1

[0133]

[0134] Table 2

[0135]

[0136] As can be seen from Tables 1 and 2, the tensile strength of the negative electrode modification membrane 4 is positively correlated with its thickness and the polytetrafluoroethylene content. Furthermore, the pore volume and areal density of the negative electrode modification membrane 4 also affect its tensile strength. Comparing Examples 1 and 4, it can be seen that positioning the glass fiber separator 5 near the negative electrode 3 and the polypropylene separator 6 near the positive electrode 7 achieves functional compatibility with the negative electrode modification membrane 4.

[0137] From the comparison between Example 1 and Examples 5-6, it can be seen that the present application fully exerts its functionality by regulating the area ratio of the circular planar negative electrode modification film to the negative electrode.

[0138] From the comparison of Example 1 and Examples 7-8, it can be seen that the present application adjusts the depth ratio of the circular concave groove and the thickness of the circular planar negative electrode modification film so that the negative electrode modification film and the negative electrode surface are completely flush and have a certain good physical bonding force.

[0139] From the comparison between Example 1 and Examples 9-10, it can be seen that the present application makes the negative electrode modification film have excellent comprehensive functionality by regulating the surface density of the circular planar negative electrode modification film.

[0140] From the comparison between Example 1 and Examples 11-12, it can be seen that the present application can fully exert the functionality of the modified membrane by regulating the pore volume of the circular planar negative electrode modified membrane.

[0141] From the comparison of Example 1 and Examples 13-14, it can be seen that the present application adjusts the mass ratio of the active material to the binder to make the negative electrode modified film have excellent functionality, such as conductivity, adsorption, and flexible self-support.

[0142] A comparison of Example 1 and Comparative Examples 1-4 shows that the absence of concave grooves 9 on the surface of negative electrode 3 near negative electrode modification film 4 results in poor bonding between negative electrode 3 and negative electrode modification film 4, posing a risk of detachment. It is precisely because of the excellent adhesion between the negative electrode modification film provided by this application and the negative electrode that the pulse voltage of the lithium primary button cell remains highly consistent after a certain depth of discharge, when subjected to a low-temperature pulse test.

[0143] From the comparison of Example 1 and Comparative Examples 5-8, it can be seen that the circular carbon material layer or circular carbon foil composite layer disclosed in the related art cannot achieve all the technical effects of the negative electrode modification membrane provided by the present application.

[0144] The present application provides a lithium primary button battery. First, the present application provides a concave groove on the surface of the negative electrode so that the negative electrode modification film can be tightly embedded in the concave groove, and has the following effects: ① The lamination tightness, lamination flatness and centering alignment between the negative electrode modification film and the negative electrode can be improved, which not only ensures the stability of the battery cell assembly structure itself, but also improves the structural stability of the battery cell assembly in reliability testing. For example, under long-term vibration, drop or centrifugal environment testing at room temperature or high temperature, there is still no displacement between the negative electrode and the negative electrode modification film, thereby enhancing the lamination stability between the negative electrode modification film and the negative electrode at a high discharge depth, and ensuring the stability of its large current discharge or pulse discharge performance at room temperature and extremely low temperature; ② A storage space for the negative electrode modification film is reserved in advance inside the negative electrode, which not only ensures that the negative electrode modification film does not deform during the stamping process, but also improves the flatness of the entire negative electrode material composite surface.

[0145] Secondly, the negative electrode modification membrane provided by the present application has the following advantages: ① The negative electrode modification membrane has a porous structure. On the one hand, due to the influence of the potential during the reaction process of the battery, the positive electrode active material will react with some trace components in the non-aqueous electrolyte to form free cations or anions. At the same time, since the liquid absorption capacity of the diaphragm in the battery is stronger than the liquid absorption capacity of the positive electrode active material, the concentration polarization effect exists, which makes it possible for the dissolved positive electrode active material ions to shuttle through the diaphragm, thereby causing irreversible side reactions with the negative electrode to form a reaction interface with high internal resistance. The negative electrode modification membrane provided by the present application has a strong ion adsorption function because it contains rich mesopores and micropores, which can well adsorb the dissolved positive electrode active ions in the pore structure, and ultimately effectively inhibit their transfer to the negative electrode surface for side reactions. On the other hand, some components in the non-aqueous electrolyte will also react with the negative electrode to form an SEI film. The SEI is easily broken down in the early stage of the battery cycle, and in the later stage of the cycle, as the negative electrode is continuously consumed, the interface impedance between it and the diaphragm and the positive electrode increases. At this time, if the negative electrode is in contact with too much free electrolyte, it will be more likely to form a high-impedance interface film, resulting in obstruction of ion transmission. The porous structure in the negative electrode modified membrane provided in the present application has strong adsorption properties, which can adsorb the free electrolyte in the modified membrane at the end of discharge, thereby reducing the degree of contact with the negative electrode, thereby improving the discharge performance of the battery. At the same time, the pore structure of the negative electrode modified membrane can be freely regulated according to the raw material selection and processing technology of the membrane;

[0146] ②The negative electrode modification film is a multifunctional layer. The modification film has good electrical conductivity and can form a near-capacitor structure with the positive electrode layer, thereby having certain capacitance characteristics. When the battery is in a relatively low temperature environment, the above-mentioned capacitor structure can provide a certain amount of charge at the instant of the reaction. At the same time, a benign contact is generated between the modification film and the negative electrode, and a certain affinity is formed between the particles, thereby changing the original passivation layer state, so that when the electrons are turned on, lithium ions can easily pass through the passivation layer, thereby ensuring that the ions can penetrate the passivation layer, shortening the ion conduction, and thus improving the instantaneous recovery voltage value. At the same time, the modification layer can improve the ion and electron conduction rate of the battery during the discharge process, ensuring that the battery has a large current output capability. In addition, the negative electrode modification film provided in the present application has good affinity with the negative electrode, and can modify the passivation layer on the surface of the negative electrode, so as to better protect the negative electrode from being corroded by the dissolved positive electrode cations;

[0147] ③ The negative electrode modification film has high strength and good flexibility. The tensile strength of the prepared negative electrode sheet is as high as 0.4-0.5kN / m, which can ensure the integrity of the negative electrode modification film during the electrode sheet slitting process, the processability during the battery assembly process, and the integrity during battery packaging. At the same time, due to its good flexibility, it can reduce the stress generated between the two when laminating with the negative electrode, avoiding uneven lamination and uneven lamination surface. It also does not dissolve or deform under the infiltration of non-aqueous electrolytes and after deep discharge.

[0148] ④ The negative electrode modification film has high flatness, and the deviation of the thickness range of the negative electrode modification film is only within 3μm, which reduces the process difficulty when the negative electrode modification film is embedded in the negative electrode surface, ensures the flatness of the fitting between the negative electrode modification film and the negative electrode, reduces the gap between the negative electrode modification film and the negative electrode, and ultimately improves the interface contact performance between the two;

[0149] ⑤ The negative electrode modification membrane is a self-supporting integrated functional membrane, which not only reduces the interfacial resistance of ion conduction, but also avoids the introduction of other matrix materials, which may cause side reactions between them and the battery system, or lead to insufficient effective space for the battery cell components. In addition, the processing technology of the negative electrode modification membrane provided by this application is simple, and its thickness is not affected by the thickness of the matrix layer. The overall thickness can be as low as 30μm, and the uniformity of the negative electrode modification membrane is not affected by the material and flatness of the substrate layer.

Claims

1. A lithium primary button battery, comprising a battery housing and a battery core assembly located inside the battery housing, wherein the battery core assembly comprises a negative electrode, a negative electrode modification film, a separator and a positive electrode stacked in sequence; A concave groove is provided on the surface of the negative electrode close to the negative electrode modification film, and the negative electrode modification film is tightly embedded in the concave groove.

2. The lithium primary button cell according to claim 1, wherein: The shape of the concave groove includes any one of a circle, annular or regular polygon or a combination of at least two of them; The center of the concave groove coincides with the center of the vertical projection surface of the negative electrode modification film.

3. The lithium primary button cell according to claim 1 or 2, wherein: The area ratio of the negative electrode modification film to the concave groove is 1:1; The area ratio of the negative electrode modification film to the negative electrode is (0.2-0.99):1; The ratio of the depth of the concave groove to the thickness of the negative electrode modification film is (0.3-1.3):

1.

4. The lithium primary button cell according to any one of claims 1 to 3, wherein: The thickness of the negative electrode modification film is 0.03mm-0.20mm; The tensile strength of the negative electrode modified film is 0.1-2KN / m; The surface density of the negative electrode modification film is 40-80 g / cm 2 ; The pore volume of the negative electrode modified membrane is 0.05-0.5cm 3 / g.

5. The lithium primary button cell according to any one of claims 1 to 4, wherein: The material of the negative electrode modification film includes an active material and a binder; The active material comprises at least one of an oxide material, a carbon material, a metal conductive particle or a fluorine-containing particle; The binder comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene-propylene copolymer or polyacrylic acid; The mass ratio of the active material to the binder is 1:(0.03-0.3).

6. The lithium primary button cell according to any one of claims 1 to 5, wherein: The diaphragm comprises a glass fiber diaphragm, or a polypropylene diaphragm, or a combination of a glass fiber diaphragm and a polypropylene diaphragm; The number of layers of the separator is 1-3.

7. The lithium primary button cell according to any one of claims 1 to 6, wherein: The battery housing includes a negative electrode bottom cover located on the negative electrode side and a positive electrode cover located on the positive electrode side; The negative electrode bottom cover is provided with a sealing ring, and the sealing ring is arranged at the edge clamping position of the negative electrode bottom cover and the positive electrode cover; The lithium primary button cell also includes an electrolyte.

8. A method for preparing a lithium primary button cell according to any one of claims 1 to 7, comprising: Punching the negative electrode modification film into the negative electrode having a concave groove on the surface to form a precursor material; The precursor material, the separator and the positive electrode are stacked in sequence to obtain a battery core assembly; The battery core assembly and the battery shell are packaged to obtain the lithium primary button battery.

9. The method according to claim 8, wherein: After punching the negative electrode modification film into the negative electrode with the concave groove on the surface, the method further comprises: The bonding surface between the negative electrode modification film and the concave groove is leveled.

10. An electronic device comprising the lithium primary button cell according to any one of claims 1 to 7.

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