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 cell, preparation method thereof and electronic device

[0001] This application claims priority to Chinese Patent Application No. 202411045595.2, filed on July 31, 2024, and Chinese Patent Application No. 202421847565.9, filed on July 31, 2024, the contents of which are incorporated herein by reference in their entirety.

[0002] TECHNICAL FIELD

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

[0004] BACKGROUND

[0005] The lithium primary battery is a high-energy chemical primary battery, commonly known as a lithium battery. It uses metal lithium as the negative electrode, solid salts or salts dissolved in organic solvents as the electrolyte, and metal oxides or other solid or liquid oxidizing agents as the positive active material, and is widely used in many types of intelligent meters, intelligent transportation, intelligent security, or medical devices, etc. With the widespread application of Internet of Things technology, the application environment of users is becoming more and more strict, and the output capability and stability of the battery in extreme environments are increasingly demanding, so the stability of the structure of the battery cell throughout its life is also increasing.

[0006] Extreme environments mainly include high temperature, low temperature, high pressure, strong vibration, etc. These extreme environmental conditions put higher requirements on the performance and reliability of the battery. For example, in a low temperature environment, the battery material needs to have better low temperature performance to avoid the dissolution and shuttle effect of the positive active ions, as well as the side reactions between the electrode material and the electrolyte, in order to maintain the stability and reliability of the battery. In a high pressure environment, the structure of the battery needs to be more solid and safe to prevent the battery from breaking and exploding. In a strong vibration environment, the structure and fixing method of the battery 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, structure and management system, etc.

[0007] TECHNICAL PROBLEM

[0008] Based on the above, on the one hand, the related art discloses setting a carbon material layer inside the battery, thereby reducing the side reactions inside the battery and improving the conductivity, ultimately reducing the internal resistance of the battery. However, the carbon material layer is prone to falling off, has insufficient strength, and has a gap between the electrode. On the other hand, the related art also discloses preparing an electrode layer with good affinity or conductivity, but it requires a special process to be prepared, and the process and material requirements are high, so it cannot be mass-produced.

[0009] Technical solutions

[0010] In a first aspect, embodiments of the present application provide a lithium primary button cell, comprising a battery shell and an electric core assembly located inside the battery shell, the electric core assembly comprising a negative electrode, a negative electrode modification film, a separator and a positive electrode which are sequentially stacked.

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

[0012] In a second aspect, embodiments of the present application provide a method for preparing the lithium primary button cell according to the first aspect, the method comprising: stamping a negative electrode modification film into a negative electrode provided with a concave groove on the surface to form a precursor material;

[0013] sequentially stacking the precursor material, the separator and the positive electrode to obtain an electric core assembly;

[0014] packaging the electric core assembly and the battery shell to obtain the lithium primary button cell. In a third aspect, embodiments of the present application provide an electronic device comprising the lithium primary button cell according to the first aspect.

[0015] Advantages

[0016] The present application provides a lithium primary button cell. Firstly, the present application provides a negative electrode with a concave groove on the surface, so that the negative electrode modification film can be tightly embedded in the concave groove, and has the following effects: ①The coverage tightness, coverage 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 structure of the electric core assembly itself, but also improves the stability of the structure of the electric core assembly in reliability test, for example, the negative electrode and the negative electrode modification film do not shift under long-time vibration, dropping or centrifugal environment test at room temperature or high temperature, thereby enhancing the stability of the negative electrode modification film and the negative electrode under high discharge depth, and ensuring the stability of large current discharge or pulse discharge performance at room temperature and extremely low temperature; ②The negative electrode has a storage space for the negative electrode modification film, which can not only ensure that the negative electrode modification film does not deform during stamping, but also improve the flatness of the entire negative electrode material composite surface.

[0017] Secondly, the negative electrode modification film has the following advantages: ① the negative electrode modification film has a porous structure. On the one hand, due to the influence of the potential, the positive active material will react with part of the trace components in the non-aqueous electrolyte during the reaction process, forming free cations or anions. At the same time, due to the fact that the liquid absorption capacity of the separator is stronger than that of the positive active material, the concentration polarization effect exists, so that the dissolved positive active material ions can shuttle through the separator, thereby causing irreversible side reactions with the negative electrode to form a high-resistance reaction interface. The negative electrode modification film provided by the application contains a large number of mesopores and micropores, which has a strong ion adsorption function, can well adsorb the dissolved positive active ions in the pore structure, and finally effectively inhibits the transfer of the positive active ions to the negative electrode surface to cause side reactions. On the other hand, part of the 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 the SEI, the separator 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, causing ion transmission to be blocked. The porous structure of the negative electrode modification film provided by the application has strong adsorption performance, which can adsorb free electrolyte in the modification film at the end of discharge, thereby reducing the degree of contact between the free electrolyte and the negative electrode, and improving the discharge performance of the battery. At the same time, the pore structure of the negative electrode modification film can be freely controlled according to the raw material selection and processing technology of the film;

[0018] ② the negative electrode modification film is a multifunctional layer. The modification film has good electrical conductivity, can form a near-capacitive structure with the positive electrode layer, and has certain capacitive properties. When the battery is in a relatively low temperature environment, the above capacitive structure can provide a certain amount of charge at the reaction moment, and at the same time, the modification film and the negative electrode produce good contact, and a certain affinity between particles is formed, thereby changing the original passivation layer state, so that when the electron is turned on, the lithium ion can easily pass through the passivation layer, thereby ensuring that the ion can penetrate the passivation layer and shorten the ion conduction, thereby 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 discharge, ensuring that the battery has a large current output capacity. In addition, the negative electrode modification film provided by the application has good affinity with the negative electrode and can modify the passivation layer on the surface of the negative electrode, thereby better protecting the negative electrode from being eroded by the dissolved positive cations;

[0019] ③The negative electrode modification film has high strength and good flexibility, and the tensile strength of the prepared negative electrode sheet is as high as 0.4-0.5 kN / m, which can ensure the integrity of the negative electrode modification film in the process of cutting the electrode sheet, the processability in the process of assembling the battery, and the integrity in the process of packaging the battery. At the same time, due to its good flexibility, it can reduce the stress generated between the negative electrode and the negative electrode modification film during the lamination, avoid uneven lamination and uneven lamination surface, and also does not dissolve and deform after being immersed in the non-aqueous electrolyte and after deep discharge;

[0020] ④The negative electrode modification film has high flatness, and the thickness deviation of the negative electrode modification film is only within 3 μm, thereby reducing the process difficulty of embedding the negative electrode modification film into the surface of the negative electrode, ensuring the flatness of the lamination between the negative electrode modification film and the negative electrode, reducing the gap between the negative electrode modification film and the negative electrode, and finally improving the interface contact performance between the two;

[0021] ⑤The negative electrode modification film is a self-supporting integrated functional film, which can not only reduce the interface resistance of ion conduction, but also avoid introducing other matrix materials to cause side reactions between the matrix materials and the battery system, or cause insufficient effective space of the battery assembly. In addition, the processing process of the negative electrode modification film provided by the present application is simple, the thickness of the negative electrode modification film is not affected by the thickness of the matrix layer, and the overall thickness can be as low as 30 μm. The uniformity of the negative electrode modification film is not affected by the material and flatness of the substrate layer.

[0022] BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a schematic view of the structure of the lithium primary button cell provided by the present application, wherein the positive electrode is directly prepared by punching into a sheet;

[0024] FIG. 2 is a schematic view of the structure of the lithium primary button cell provided by the present application, wherein the positive electrode is prepared by punching a current collecting ring on the surface of the positive electrode active material layer;

[0025] FIG. 3 is a schematic view of the cross-sectional disassembly of the lithium primary button cell provided by the present application;

[0026] FIG. 4 is a partial enlarged view of the circled part in FIG. 3;

[0027] FIG. 5 is a schematic view of the assembly of the precursor material in the lithium primary button cell provided by the present application;

[0028] FIG. 6 is a schematic view of the process of the preparation method of the lithium primary button cell provided by the present application;

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

[0030] Embodiments of the present application

[0031] As shown in FIGS. 1-4, the present application provides a lithium primary button cell applied to electronic devices, comprising a battery shell 10 and an electrode assembly located inside the battery shell 10, the electrode assembly comprising a negative electrode 3, a negative electrode modification film 4, a separator 5, 6 and a positive electrode 7 arranged in sequence; the surface of the negative electrode 3 close to the negative electrode modification film 4 is provided with a concave groove 9, 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, a ring or a regular polygon, or a combination of at least two of them, for example, it can be a circle. The regular polygon includes, for example, a square, a regular pentagon, a regular hexagon, etc. The center of the concave groove 9 coincides with the center of the vertical projection plane 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 adjusting the area ratio of the negative electrode modification film to the negative electrode, the functionality of the negative electrode modification film can be fully utilized. If the area ratio is too low, the functionality of the negative electrode modification film will be weakened due to the decrease of the modification area, for example, the conductivity of the conductive surface will be relatively less improved, and the adsorption area will also decrease, resulting in a lower adsorption capacity for the dissolved positive active ions. On the contrary, if the area ratio is too large, the negative electrode modification film cannot be firmly riveted due to the small distance of the concave edge. In addition, if the area ratio is too large, the functionality of the negative electrode modification film will not be significantly improved, which will also lead to an increase in the process cost.

[0035] The ratio of the depth of the concave groove 9 to the thickness of the negative modification film 4 is (0.3-1.3):1, which can be (0.95-1.05):1, for example, it can be 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, 0.95:1, 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 adjusting the ratio of the depth of the concave groove to the thickness of the negative modification film, the negative modification film and the negative surface are completely flush, and have good physical bonding force. When the depth of the concave groove is too deep, the degree of downward pressure on the upper surface of the negative modification film is small during the flattening process, resulting in poor bonding force between the lower surface of the negative modification film and the negative 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 modification film is too large, the negative modification film will be stretched horizontally during the flattening process due to the insufficient space of the concave groove, and even cause the negative surface to overflow, resulting in unevenness, and also cause the size of the negative and the negative modification film to be too high, affecting the size of the entire battery cell.

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

[0038] By adjusting the thickness of the negative modification film, the functionality of the negative modification film can be met, and the assembly feasibility of the entire battery cell and sufficient capacity design can be ensured. If the thickness is too small, on the one hand, the processing difficulty of the negative modification film will increase, the production cost will increase, and the assembly processing difficulty of the negative modification film during assembly will increase. On the other hand, too thin thickness will reduce the adsorption capacity of the dissolved positive active ions, and vice versa, too thick thickness will occupy the structural design space of the negative, thereby reducing the design capacity of the entire battery cell.

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

[0040] By adjusting the tensile strength of the negative electrode modification film, the negative electrode modification film has excellent mechanical processing performance, including cutting, transportation positioning, leveling, etc. If the tensile strength is too low, it will affect the implementation of the entire processing process, affect the consistency of assembly, and even because the strength of the negative electrode modification film is poor or easily damaged, the adhesion of the negative electrode modification film will decrease with the increase of the discharge depth, otherwise the film will be too large, which will affect the functionality of the negative electrode modification film, such as the decrease of the conductivity and the decrease of the adsorption capacity of the 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 will decrease the content of the conductive component, similarly, the porosity of the negative electrode modification film will also decrease.

[0041] [According to the rules 91 correction 20.01.2026] The areal density of the negative electrode modification film 4 is 40-80g / m 2 , which can be 50-60g / m 2 , for example, it can be 40g / m 2 , 45g / m 2 , 50g / m 2 , 52g / m 2 , 55g / m 2 , 58g / m 2 , 60g / m 2 , 65g / m 2 , 70g / m 2 , 75g / m 2 , 80g / m 2 , etc.

[0042] By adjusting the areal density of the negative electrode modification film, the negative electrode modification film has excellent comprehensive functionality. If the areal density is too low, the film strength will be poor, and the functionality of the negative electrode modification film will decrease rapidly as the reaction of the battery progresses to the end of discharge. Conversely, the porosity of the corresponding negative electrode modification film will decrease, resulting in a decrease in the adsorption capacity of the dissolved positive active ions, and similarly, the negative electrode modification film component contains a higher content of non-conductive binder component, thereby causing the conductivity of the negative electrode modification film to decrease.

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

[0044] By regulating the pore volume of the negative modification film, it can fully play the function of the modification film. The pore volume of the modification film is also affected by the model of the material, the ratio of the components, and the processing method. If the pore volume is too small, it will lead to a decrease in the adsorption capacity of the dissolved positive active ions, mainly in the small amount of adsorption, and it will soon reach the saturation of the adsorption amount. Conversely, it will make the adsorption efficiency of the dissolved positive active ions low.

[0045] The material of the negative 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 or a combination of at least two of titanium dioxide, molybdenum dioxide, aluminum oxide, lithium titanate, or silver oxide. The carbon material includes any one or a combination of at least two of graphene, acetylene black, carbon nanotube, activated carbon, or graphite. The metal conductive particle includes any one or a combination of at least two of copper particles, silver particles, or gold particles. The fluorine-containing particle includes any one or a combination of at least two of lithium fluoride, carbon fluoride, polytetrafluoroethylene, polyvinylidene fluoride, or polyvinyl fluoride copolymer.

[0046] The material of the negative modification film 4 further includes a binder. The binder 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 can 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 adjusting the mass ratio of the active material to the binder, the negative electrode modification film has excellent functionality, such as including electrical conductivity, adsorption, and flexible self-supporting. If the mass ratio is too low, the negative electrode modification film may not be self-supported or have poor film strength, and vice versa, which may result in poor electrical conductivity, low positive active ion adsorption capacity, and reduced proportion of other materials.

[0049] In the preparation method of the negative electrode modification film, the active material and the binder are pressed or extruded to form a film. The film can be prepared without using a solvent or using an inorganic or organic solvent, depending on the process requirements.

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

[0051] 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, so as to match the functionality of the negative electrode modification film 4. This is because ① the stiffness of the glass fiber separator is less than that of the polypropylene separator, which is conducive to the adhesion of the glass fiber separator and the negative electrode modification film; and ② the liquid absorption capacity of the glass fiber separator is greater than that of the negative electrode modification film, which is greater than that of the polypropylene separator, and is greater than that of the positive electrode. Therefore, a certain concentration gradient is formed, and the glass fiber separator is beneficial to the uniform distribution of the electrolyte in the entire battery. At the same time, the glass fiber separator can act as a storage interface for the electrolyte, ensuring the amount of free electrolyte at the end of the battery life, enhancing the ion conduction capacity, and ensuring the pulse capacity of the battery 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 the positive active material and the storage amount of free electrolyte in the negative electrode modification film, and reducing the side reaction between the dissolved positive active ions and the negative electrode.

[0053] The battery case 10 includes a negative electrode bottom cover 2 on the negative electrode 3 side and a positive electrode cover 8 on the positive electrode 7 side. 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.

[0054] The lithium primary button cell further comprises an electrolyte.

[0055] As shown in Figure 6, the application further provides a method for preparing a lithium primary button cell, comprising the following steps:

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

[0057] S102, sequentially stacking the precursor material, a separator and a positive electrode to obtain an electric core assembly;

[0058] S103, packaging the electric core assembly and a battery shell to obtain the lithium primary button cell.

[0059] After the negative electrode modification film is punched into the negative electrode with the concave groove on the surface, the application further comprises a flattening process for the fitting surface between the negative electrode modification film and the concave groove, so as to fully ensure the fitting degree and the fitting flatness of the two.

[0060] After the negative electrode modification film is cut into a specified shape and punched into the negative electrode with the concave groove on the surface, the positioning requires that the center of the vertical projection surface is completely coincident with the center of the concave groove in the negative electrode, and the preliminary flat fitting is completed.

[0061] When the depth of the concave groove is not higher than the thickness of the negative electrode modification film, in the flattening process, the negative electrode modification film is first stressed, and the centers of the projection surfaces are stressed, and the lower surface of the negative electrode modification film is embedded and fitted with the upper surface of the concave groove of the negative electrode, while the air between the two is discharged, so as to achieve the effect of completely flat embedding; when the depth of the concave groove is higher than the thickness of the negative electrode modification film, the negative electrode modification film is equivalent to being placed in the negative electrode concave groove, in the flattening process, the non-concave groove part of the negative electrode is first stressed, and the center part of the concave groove is in a pressure loss or pressure deficiency state, under the continuous action of the downward pressure, the negative electrode is deformed and acts on the center pressure deficiency area, and finally the negative electrode modification film is tightly fitted in the concave groove, and the upper surface is embedded and fitted by the negative electrode, so as to achieve the effect of flat fitting.

[0062] The battery shell comprises a negative electrode bottom cover 2 located at one side of the negative electrode 3 and a positive electrode cover 8 located at one side of the 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.

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

[0064] The separators 5, 6 are inverted U-shaped, and the two sides of the inverted U-shaped are bent towards the positive electrode 7.

[0065] The electrolyte is injected after the sequential stacking.

[0066] The positive electrode cover 8 is finally covered after the electrolyte is injected and the positive electrode sheet is put in, so that the lithium primary button cell is formed through one-time sealing and two-time sealing.

[0067] The positive electrode sheet includes a current collector and a positive electrode active material layer arranged on at least one side of the current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder. The positive electrode active material includes, for example, manganese dioxide, carbon fluoride or iron sulfide. The conductive agent includes, for example, at least one of graphite, carbon nanotube, conductive carbon black or graphene. The binder includes, for example, 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, the conductive agent and the binder through a high-speed mixing device, and then stamping the mixture into a sheet through a forming machine for direct use, or stamping a current collector net on the surface of the positive electrode active material layer or using a current collector ring.

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

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

[0071] The preparation method of the positive electrode sheet includes the following steps:

[0072] The manganese dioxide, the conductive carbon black and the polytetrafluoroethylene emulsion are mixed through a high-speed mixing device at a mass ratio of 1:0.5:0.6, and then dried to obtain a powder. The powder is stamped into a positive electrode sheet and a current collector through a powder forming and ring assembling machine, so that the positive electrode sheet shown in FIG. 1 is obtained.

[0073] Alternatively,

[0074] The manganese dioxide, the conductive carbon black and the polytetrafluoroethylene emulsion are mixed through a high-speed mixing device at a mass ratio of 1:0.5:0.6, and then dried to obtain a powder. The powder is stamped into a positive electrode sheet and a current collector through a powder forming and ring assembling machine, so that the positive electrode sheet shown in FIG. 1 is obtained.

[0075] The above description of the button cell is for the complete description of the technical solution of the present application, and should not be regarded as a limitation of the present application.

[0076] Embodiment 1

[0077] The embodiment provides a lithium primary button cell, as shown in Figures 3-4, which comprises a cell shell 10, and an electrode assembly and an electrolyte in the cell shell 10, the electrode assembly comprising a lithium metal negative electrode 3, a circular planar negative electrode modification film 4, a diaphragm and a manganese dioxide positive electrode 7 which are sequentially stacked; the lithium metal negative electrode 3 is provided with a circular concave groove 9 on the surface close to one side of the circular planar negative electrode modification film 4, and the circular planar negative electrode modification film 4 is tightly embedded in the circular concave groove 9; the cell shell 10 comprises a negative electrode bottom cover 2 on one side of the lithium metal negative electrode 3 and a positive electrode cover 8 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 comprises 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] [Corrected according to Rule 91 on 20.01.2026] 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; the depth ratio 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 0.08mm, the tensile strength is 0.45KN / m, the area density is 55g / m 2 , the pore size is 2-200nm, and the pore volume is 0.3cm 3 / g. The circular planar negative electrode modification film 4 is prepared by pressing film forming of carbon material and polytetrafluoroethylene binder with a mass ratio of 1:0.15.

[0079] The embodiment also provides a preparation method of the lithium primary button cell, which comprises the following steps:

[0080] As shown in Figure 5, a circular concave groove is formed on the surface of the lithium metal negative electrode by using a circular upper die on the negative electrode bottom cover side, then the circular planar negative electrode modification film is stamped in the negative electrode with the circular concave groove on the surface, and the center of the vertical projection surface is required to be completely coincident with the center of the circular concave groove in the negative electrode, and the precursor material is formed after flattening treatment by using a stamping tool; then the diaphragm is stamped into the negative electrode bottom cover, the diaphragm forms a "U" shape, and the non-aqueous electrolyte is injected; then the manganese dioxide positive electrode sheet is put in, and finally the positive electrode cover is covered, and one-time sealing and pressing and secondary sealing are sequentially carried out to obtain the lithium primary button cell.

[0081] Embodiment 2

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

[0083] [Corrected according to Rule 91 on 20.01.2026] The thickness of the circular ring plane negative electrode modification film is 0.05 mm, the tensile strength is 0.4 KN / m, and the area density is 50 g / m 2 . The pore size is 2-200 nm, and the pore volume is 0.3 cm 3 / g. The material of the circular ring plane negative electrode modification film 4 is prepared by pressing film forming including carbon material and polytetrafluoroethylene binder with a mass ratio of 1:0.1, and the others are the same as embodiment 1.

[0084] Embodiment 3

[0085] The difference between this embodiment and embodiment 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 depth ratio of the square concave groove to the thickness of the square plane negative electrode modification film is 0.97:1.

[0086] [Corrected according to Rule 91 on 20.01.2026] The thickness of the square plane negative electrode modification film is 0.10 mm, the tensile strength is 0.5 KN / m, and the area density is 60 g / m 2 . The pore size is 2-200 nm, and the pore volume is 0.3 cm 3 / g. The material of the square plane negative electrode modification film is prepared by pressing film forming including carbon material and polytetrafluoroethylene binder with a mass ratio of 1:0.2, and the others are the same as embodiment 1.

[0087] Embodiment 4

[0088] The difference between this embodiment and embodiment 1 is that the separator is replaced by a double-layer polypropylene separator, and the others are the same as embodiment 1.

[0089] Embodiment 5

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

[0091] Embodiment 6

[0092] This example differs from Example 1 in that the area ratio of the circular planar negative electrode modification film to the negative electrode is 1.2:1, and the other conditions are the same as in Example 1.

[0093] Example 7

[0094] This example differs from Example 1 in that the depth of the circular concave groove to the thickness of the circular planar negative electrode modification film is 0.1:1, and the other conditions are the same as in Example 1.

[0095] Example 8

[0096] This example differs from Example 1 in that the depth of the circular concave groove to the thickness of the circular planar negative electrode modification film is 2:1, and the other conditions are the same as in Example 1.

[0097] Example 9

[0098] [Corrected according to Rule 91 on 20.01.2026] This example differs from Example 1 in that the areal density of the circular planar negative electrode modification film is 30 g / m 2 , and the other conditions are the same as in Example 1.

[0099] Example 10

[0100] [Corrected according to Rule 91 on 20.01.2026] This example differs from Example 1 in that the areal density of the circular planar negative electrode modification film is 90 g / m 2 , and the other conditions are the same as in Example 1.

[0101] Example 11

[0102] This example differs from Example 1 in that the pore volume of the circular planar negative electrode modification film is 0.02 cm 3 / g, and the other conditions are the same as in Example 1.

[0103] Example 12

[0104] This example differs from Example 1 in that the pore volume of the circular planar negative electrode modification film is 0.7 cm 3 / g, and the other conditions are the same as in Example 1.

[0105] Example 13

[0106] This example differs from Example 1 in that the mass ratio of the carbon material active material to the polytetrafluoroethylene binder is 1:0.02, and the other conditions are the same as in Example 1.

[0107] Example 14

[0108] The embodiment differs from Example 1 in that the mass ratio of the carbon material active material to the polytetrafluoroethylene binder is 1:0.4, and the others are the same as Example 1.

[0109] Comparative Example 1

[0110] The comparative example differs from Example 1 in that the negative electrode is directly punched into a flat surface, and no circular flat negative electrode decoration film is provided, and the others are the same as Example 1.

[0111] Comparative Example 2

[0112] The comparative example differs from Example 1 in that the negative electrode is directly punched into a flat surface, and no circular flat negative electrode decoration film is provided, and the separator is replaced with a double-layer polypropylene separator, and the others are the same as Example 1.

[0113] Comparative Example 3

[0114] The comparative example differs from Example 1 in that the negative electrode is directly punched into a flat surface, and a circular flat negative electrode decoration film is provided, and the others are the same as Example 1.

[0115] Comparative Example 4

[0116] The comparative example differs from Example 1 in that the negative electrode is directly punched into a flat surface, and a circular flat negative electrode decoration film is provided, and the separator is replaced with a double-layer polypropylene separator, and the others are the same as Example 1.

[0117] Comparative Example 5

[0118] The comparative example differs from Example 1 in that the negative electrode is directly punched into a flat surface, and the circular flat negative electrode decoration film is replaced with a circular carbon material layer, and the preparation method of the circular carbon material layer is as follows: acetylene black, ethanol, and polyacrylic acid are stirred uniformly to form a slurry, which is transferred and coated on a polypropylene non-woven fabric, and after vacuum baking, it is cut into a circular flat surface, and the others are the same as Example 1.

[0119] Comparative Example 6

[0120] The comparative example differs from Example 1 in that the negative electrode is directly punched into a flat surface, and the circular flat negative electrode decoration film is replaced with a circular carbon material layer, and the preparation method of the circular carbon material layer is as follows: acetylene black, ethanol, and polyacrylic acid are stirred uniformly to form a slurry, which is transferred and coated on a polypropylene non-woven fabric, and after vacuum baking, it is cut into a circular flat surface, and the separator is replaced with a double-layer polypropylene separator, and the others are the same as Example 1.

[0121] Comparative Example 7

[0122] The difference between the present comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and the circular flat 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 stirred uniformly to form a slurry, which is transferred and coated on a steel mesh and a polypropylene non-woven fabric. After vacuum baking, rolling and cutting into a circular flat surface, the other steps are the same as those of Example 1.

[0123] Comparative Example 8

[0124] The difference between the present comparative example and Example 1 is that the negative electrode is directly punched into a flat surface, and the circular flat 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 stirred uniformly to form a slurry, which is transferred and coated on a steel mesh and a polypropylene non-woven fabric. After vacuum baking, rolling and cutting into a circular flat surface, the other steps are the same as those of Example 1.

[0125] Test conditions

[0126] The negative electrode modification film 4 or carbon foil composite layer provided by Examples 1 to 14 and Comparative Examples 1 to 8 is tested for performance, and the test method is as follows:

[0127] Tensile strength: The tensile strength of the film is tested by an electronic separator tensile machine. First, a 100x14mm negative electrode modification film 4 is cut and placed between the upper and lower clamps of the tensile machine, with a clamping distance of 50mm and a pre-tightening force of 0.5N. The machine is started, and the sample is stretched at a constant elongation speed of 10mm / min until it breaks, and the maximum tensile force value during stretching is recorded.

[0128] The lithium primary button cell provided by Examples 1 to 14 and Comparative Examples 1 to 8 is tested, and the test method is as follows:

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

[0130] (2) The background current is 10μA, then the battery is given a constant current pulse discharge of 10mA for 0.5s, and rests for 4.5s. This step is repeated 3 times, and the discharge voltage value is recorded. Then the refrigerator temperature is adjusted to-20℃, and after resting for 4h, the above test steps are repeated three times. Five batteries are tested for each scheme, and the average value is taken, and the voltage deviation is calculated by the formula: test 5 batteries, voltage deviation=(voltage maximum-voltage minimum) / voltage average

[0131] The test results are shown in Tables 1-2:

[0132] Table 1

[0133]

[0134] Table 2

[0135]

[0136] As can be seen from Table 1-Table 2, the tensile strength value of the negative electrode modification film 4 presents a positive correlation with the thickness of the negative electrode modification film, and also presents a positive correlation with the content of polytetrafluoroethylene, and the pore volume and the area density parameters of the negative electrode modification film 4 can also affect the tensile strength value. As can be known from the comparison between Example 1 and Example 4, the glass fiber diaphragm 5 is arranged close to the negative electrode 3, and the polypropylene diaphragm 6 is arranged close to the positive electrode 7, so as to realize the functional matching of the negative electrode modification film 4.

[0137] As can be known from the comparison between Example 1, Example 5-6, the present application controls the area ratio of the circular planar negative electrode modification film and the negative electrode, so that the negative electrode modification film fully plays its functionality.

[0138] As can be known from the comparison between Example 1, Example 7-8, the present application controls the depth of the circular concave groove and the thickness ratio 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] As can be known from the comparison between Example 1, Example 9-10, the present application controls the area density of the circular planar negative electrode modification film, so that the negative electrode modification film has excellent comprehensive functionality.

[0140] As can be known from the comparison between Example 1, Example 11-12, the present application controls the pore volume of the circular planar negative electrode modification film, so that the negative electrode modification film can fully play the functionality of the modification film.

[0141] As can be known from the comparison between Example 1, Example 13-14, the present application controls the mass ratio of the active material and the binder, so that the negative electrode modification film has excellent functionality, such as including conductivity, adsorption and flexible self-supporting.

[0142] As can be known from the comparison between Example 1, Comparative Examples 1-4, the surface of the negative electrode 3 close to the negative electrode modification film 4 side is not provided with a concave groove 9, so that the bonding force between the negative electrode 3 and the negative electrode modification film 4 is poor, and there is a risk of falling off. It is because the negative electrode modification film provided by the present application has good covering tightness with the negative electrode, so that the pulse voltage of the lithium primary button cell has good consistency after a certain depth of discharge and then low-temperature pulse test.

[0143] It can be seen from the comparison of the embodiment 1 and the comparative examples 5-8 that the circular carbon material layer or the circular carbon foil composite layer disclosed in the related art cannot achieve all the technical effects of the negative electrode modification film provided in the present application.

[0144] The present application provides a lithium primary button cell. Firstly, the present application provides a negative electrode modification film which is tightly embedded in a concave groove on the surface of the negative electrode, and has the following effects: ① the negative electrode modification film and the negative electrode can be tightly combined, and the flatness and the central alignment can be improved, which not only ensures the stability of the structure of the cell assembly itself, but also improves the stability of the structure of the cell assembly in the reliability test, for example, the negative electrode modification film and the negative electrode do not shift in the long-time vibration, drop or centrifugal environment test at room temperature or high temperature, thereby enhancing the stability of the negative electrode modification film and the negative electrode at high discharge depth, and ensuring the stability of the large current discharge or pulse discharge performance at room temperature and extremely low temperature; ② the negative electrode has a storage space for the negative electrode modification film, which can prevent the negative electrode modification film from being deformed during the stamping process, and improve the flatness of the entire negative electrode material composite surface.

[0145] Secondly, the negative electrode modification film provided in the present application has the following advantages: ① the negative electrode modification film has a porous structure. On the one hand, during the reaction of the battery, the positive active material reacts with part of the trace components in the non-aqueous electrolyte to form free cations or anions. Due to the liquid absorption capacity of the separator being stronger than that of the positive active material, a concentration polarization effect exists, which makes the dissolved positive active material ions shuttle through the separator and react with the negative electrode to form a high-resistance reaction interface. The negative electrode modification film provided in the present application has abundant mesopores and micropores, which have strong ion adsorption function and can effectively inhibit the transfer of the dissolved positive active ions to the surface of the negative electrode to form a side reaction. On the other hand, part of the components in the non-aqueous electrolyte also react with the negative electrode to form an SEI film. The SEI film is easily broken in the early stage of the cycle of the battery, and in the later stage of the cycle, the interface impedance between the negative electrode and the separator and the positive electrode increases with the consumption of the negative electrode. At this time, if the negative electrode is in contact with too much free electrolyte, a high-resistance interface film is more likely to be formed, which hinders the ion transmission. The porous structure of the negative electrode modification film provided in the present application has strong adsorption performance, which can adsorb the free electrolyte in the modification film at the end of the discharge, thereby reducing the contact between the free electrolyte and the negative electrode, and improving the discharge performance of the battery. At the same time, the pore structure of the negative electrode modification film can be freely controlled according to the selection of the raw material of the film and the processing technology.

[0146] ②The negative electrode modification film is a multifunctional layer. The modification film has good conductivity and can form a near-capacitor structure with the positive electrode layer, thereby having certain capacitor characteristics. When the battery is in a relatively low temperature environment, the above capacitor structure can provide a certain amount of electric charge at the reaction moment, and at the same time, the modification film and the negative electrode form a good contact, and a certain affinity is formed between the particles, thereby changing the original passivation layer state, so that when the electron is conducted, the lithium ion can easily pass through the passivation layer, thereby ensuring that the ion can penetrate the passivation layer and shorten the ion conduction, thereby 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, thereby ensuring that the battery has a large current output capability. In addition, the negative electrode modification film provided by the application has good affinity with the negative electrode and can modify the passivation layer on the surface of the negative electrode, thereby better protecting the negative electrode from being corroded by the dissolved positive electrode cations;

[0147] ③The negative electrode modification film has high strength and good flexibility, and the tensile strength of the prepared negative electrode sheet is as high as 0.4-0.5 kN / m, which can ensure the integrity of the negative electrode modification film during the slitting process of the electrode sheet, the processability during the battery assembly process, and the integrity during the battery packaging. At the same time, due to its good flexibility, when it is laminated with the negative electrode, the stress generated between the two can be reduced, avoiding uneven lamination and uneven lamination surface, and without dissolution, deformation after deep discharge under the infiltration of non-aqueous electrolyte;

[0148] ④The negative electrode modification film has high flatness, and the thickness range of the negative electrode modification film has a deviation of only 3 pm, thereby reducing the process difficulty of embedding the negative electrode modification film to the surface of the negative electrode, ensuring the flatness of the lamination between the negative electrode modification film and the negative electrode, reducing the gap between the negative electrode modification film and the negative electrode, and finally improving the interface contact performance between the two;

[0149] ⑤The negative electrode modification film is a self-supporting integrated functional film, which can not only reduce the interface resistance of ion conduction, but also avoid introducing other matrix materials to cause side reactions between the matrix and the battery system, or cause insufficient effective space of the battery assembly. In addition, the processing technology of the negative electrode modification film provided by the application is simple, and the thickness of the negative electrode modification film is not affected by the thickness of the matrix layer, and the overall thickness can be as low as 30 pm, and the uniformity of the negative electrode modification film is not affected by the material and flatness of the matrix layer.

Claims

1. A lithium primary button cell, comprising a cell shell and an electrode assembly located inside the cell shell, the electrode assembly comprising a negative electrode, a negative electrode modification film, a separator and a positive electrode which are sequentially stacked; a surface of the negative electrode close to the negative electrode modification film is provided with a concave groove, 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 comprises any one or a combination of at least two of a circle, a ring or a regular polygon; The center of the concave groove coincides with the center of the vertical projection plane 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 depth ratio of the concave groove to the thickness of the negative electrode modification film is (0.3-1.3):

1.

4. [Amended according to Rule 91 on 20.01.2026] The lithium primary button cell according to any one of claims 1 to 3, wherein The thickness of the negative electrode modification film is 0.03-0.20 mm; The tensile strength of the negative electrode modification film is 0.1-2 KN / m; The areal density of the negative electrode modification film is 40-80 g / m 2 ; The negative electrode modification film has a pore volume of 0.05 to 0.5 cm3 / g. 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 comprises 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 of any one of claims 1-5, wherein, The separator comprises a glass fiber separator, or a polypropylene separator, or a combination of a glass fiber separator and a polypropylene separator; The number of layers of the separator is 1-3.

7. The lithium primary button cell of any one of claims 1-6, wherein, The cell shell comprises a negative electrode bottom cover located at the side of the negative electrode and a positive electrode cover located at the side of the positive electrode; 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 further comprises an electrolyte. 8.A method for preparing the lithium primary button cell according to any one of claims 1-7, comprising: punching a negative electrode modification film into a negative electrode provided with a concave groove on the surface to form a precursor material; sequentially stacking the precursor material, a separator and a positive electrode to obtain an electrode assembly; packaging the electrode assembly and a cell shell to obtain the lithium primary button cell.

9. The method of claim 8, wherein, After punching the negative electrode modification film into the negative electrode provided with the concave groove on the surface, the method further comprises: flattening the fitting surface between the negative electrode modification film and the concave groove. 10.An electronic device comprising the lithium primary button cell according to any one of claims 1-7.

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