Lithium primary button cell and electronic equipment

Abstract

The utility model provides a lithium primary button cell and electronic equipment. The lithium primary button battery comprises a battery shell and a battery cell assembly located in the battery shell, wherein the battery cell assembly comprises a negative electrode, a negative electrode modification film, a diaphragm and a positive electrode which are sequentially stacked; a concave groove is formed in the surface of one side, close to the negative electrode modification film, of the negative electrode, and the negative electrode modification film is tightly embedded in the concave groove. By optimizing the structure of the lithium primary button cell, the lithium primary button cell has excellent discharge performance, stability and reliability.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery materials, and particularly relates to a primary lithium button cell and an electronic device. Background Art

[0002] A primary lithium battery is a high-energy chemical primary battery, commonly known as a lithium battery. It uses metallic lithium as the negative electrode, solid salts or salts dissolved in organic solvents as the electrolyte, and metal oxides or other solid or liquid oxidants as the positive electrode active material, and is widely used in various fields such as smart meters, intelligent transportation, intelligent security, or medical devices. With the wide application of the Internet of Things technology, the application environment of users is becoming more and more strict, and the requirements for the output ability and stability of the battery in extreme environments are getting higher and higher. Therefore, the requirements for the structural stability of the battery cell during its entire life cycle are also increasing.

[0003] Extreme environments mainly include extreme conditions such as high temperature, low temperature, high pressure, and strong vibration. These extreme environmental conditions put forward higher requirements for the performance and reliability of the battery. For example, in a low-temperature environment, the materials of the battery need to have better low-temperature performance to avoid the dissolution phenomenon and shuttle effect of positive electrode active ions, as well as side reactions occurring between the electrode material and the electrolyte, so as to maintain the stability and reliability of the battery. In a high-pressure environment, the structure of the battery needs to be more robust and safe to prevent the battery from cracking 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, it is necessary to optimize and improve in terms of materials, structure, and management systems.

[0004] Based on the above situation, on the one hand, the prior art discloses that a carbon material layer is provided inside the battery, thereby reducing side reactions inside the battery and improving the conductivity, and finally reducing the internal resistance of the battery. However, the carbon material layer has problems such as being prone to falling off, insufficient strength, and having a gap with the electrode. On the other hand, the prior art also discloses that an electrode layer with good affinity or conductivity is prepared, but it can only be obtained by special processes and has high requirements for processes and materials, so it cannot be mass-produced.

[0005] Therefore, in this field, it is urgent to develop a primary lithium button cell system to solve the above problems by further optimizing its structure. Summary of the Utility Model

[0006] Aiming at the deficiencies existing in the prior art, the purpose of the utility model is to provide a primary lithium button cell and an electronic device. By optimizing the structure of the primary lithium button cell, the utility model enables it to have excellent discharge performance, stability, and reliability.

[0007] To achieve this purpose, the utility model adopts the following technical solutions:

[0008] In a first aspect, the present utility model provides a primary lithium button cell. The primary lithium button cell includes a battery housing and a core component located inside the battery housing. The core component includes a negative electrode, a negative electrode modification film, a separator, and a positive electrode that are sequentially stacked.

[0009] 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.

[0010] First of all, by providing a concave groove on the surface of the negative electrode in the present utility model, the negative electrode modification film can be tightly embedded in the concave groove, and has the following effects: ① It can improve the composite tightness, composite flatness and centering alignment between the negative electrode modification film and the negative electrode, which not only ensures the stability of the structure of the core component itself, but also improves the stability of the structure of the core component in the reliability test. For example, in the long-term vibration, drop or centrifugal environment test at normal temperature or high temperature, there will still be no displacement between the negative electrode and the negative electrode modification film, thereby further enhancing the bonding stability between the negative electrode modification film and the negative electrode at a high depth of discharge, and ensuring the stability of its performance in high-current discharge or pulse discharge at normal temperature and extremely low temperature; ② A storage space for containing the negative electrode modification film is reserved inside the negative electrode in advance, which can not only ensure that the negative electrode modification film does not deform during the stamping process, but also improve the flatness of the composite surface of the entire negative electrode material.

[0011] Secondly, the negative electrode modification film provided by the present utility model has the following advantages: ① The negative electrode modification film has a porous structure. On the one hand, during the reaction process of the battery, due to the influence of potential, 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 separator in the battery is stronger than that of the positive electrode active material, the existence of the concentration polarization effect is caused, making it possible for the dissolved positive electrode active material ions to shuttle through the separator and thus react irreversibly with the negative electrode to form a reaction interface with high internal resistance. The negative electrode modification film provided by the present utility model has a strong ion adsorption function due to its rich mesopores and micropores, and can well adsorb the dissolved positive electrode ions in the pore structure, ultimately effectively inhibiting their transfer to the negative electrode surface to occur side reactions. On the other hand, some components in the non-aqueous electrolyte will also react with the negative electrode to form a SEI film. This SEI is easily broken down in the early stage of battery cycling, and in the later stage of cycling, as the negative electrode is continuously consumed, the interfacial impedance between it and the separator and the positive electrode increases. At this time, if the negative electrode contacts too much free electrolyte, it is easier to form a high-impedance interfacial film, resulting in blocked ion transport. The porous structure in the negative electrode modification film provided by the present utility model has a strong adsorption performance, and can adsorb the free electrolyte in the modification film at the end of discharge, thereby reducing the degree of its contact with the negative electrode, and thus improving the discharge performance of the battery. At the same time, the pore structure of the negative electrode modification film can be freely adjusted according to the selection of the film raw material and the processing technology;

[0012] ② The negative electrode modification film is a multi-functional layer. The modification film has good electrical conductivity and can form a near-capacitor structure with the positive electrode layer, thus having certain capacitive characteristics. When the battery is in a relatively low-temperature environment, the above capacitive structure can provide a certain amount of charge instantaneously during the reaction. At the same time, there is a good contact between the modification film and the negative electrode, and a certain affinity will form between the particles, thereby changing the state of the original passivation layer. When the electrons are conducted, the lithium ions can easily pass through the passivation layer, ensuring that the ions can penetrate the passivation layer, shortening the ion conduction, and thus increasing the instantaneous recovery voltage value. At the same time, the modification layer can further improve the ion and electron conduction rates during the discharge process of the battery, ensuring that the battery has the ability to output a large current. In addition, the negative electrode modification film provided by the present utility model 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 eroded by the dissolved positive electrode cations;

[0013] 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 cutting process, the processability during the battery assembly process, and the integrity during battery packaging. At the same time, due to its good flexibility, when it is laminated with the negative electrode, it can reduce the stress between the two, avoid uneven lamination and uneven lamination surface, and will not dissolve or deform under the infiltration of non-aqueous electrolyte and after deep discharge;

[0014] 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 negative electrode modification film and the negative electrode, reduces the gap between the negative electrode modification film and the negative electrode, and finally improves the interface contact performance between the two;

[0015] ⑤ The 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 the introduction of other matrix materials, which may cause side reactions between the negative electrode modification film and the battery system, or lead to insufficient effective space for the battery cell assembly. In addition, the processing technology of the negative electrode modification film provided by the utility model is simple, and its thickness will not be 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 film will not be affected by the material and flatness of the substrate layer.

[0016] As a preferred technical solution of the present invention, 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, and is more preferably a circle.

[0017] In the present invention, the regular polygon exemplarily includes a square, a regular pentagon, a regular hexagon, and the like.

[0018] As a preferred technical solution of the utility model, the center of the concave groove coincides with the center of the vertical projection surface of the negative electrode modification film.

[0019] As a preferred technical solution of the utility model, the area ratio of the negative electrode modification film to the concave groove is 1:1.

[0020] As a preferred technical solution of the present utility model, the area ratio of the negative electrode modification film to the negative electrode is (0.2-0.99):1, preferably (0.3-0.6):1. For example, it can be 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.

[0021] In the present utility model, by regulating the area ratio of the negative electrode modification film to the negative electrode, its functionality can be fully exerted. If the area ratio is too low, the functionality of the negative electrode modification film will be weakened due to the decrease in the area of the modification region. For example, the conductivity improvement of the conductive surface is relatively small, and the adsorption area decreases accordingly, resulting in a decrease in the adsorption capacity for the dissolved positive active ions. On the contrary, if the area is too large, the functionality will not be significantly improved, and the manufacturing cost will also increase because the distance between the concave edges is small, making it impossible to firmly fix the negative electrode modification film well.

[0022] As a preferred technical solution of the present utility model, the depth ratio of the concave groove to the thickness of the negative electrode modification film is (0.3-1.3):1, preferably (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.

[0023] In the present utility model, by adjusting 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 force. When the depth of the concave groove is too deep, during the flattening process, the downward pressure on the upper surface of the negative electrode modification film is small, resulting in weak bonding force, unevenness or insufficient exhaust and the generation of a certain air gap surface between the lower surface of the negative electrode modification film and the negative electrode in the concave groove; when the depth of the concave groove is too shallow and the thickness of the negative electrode modification film is too large, during the flattening process, due to the excessive thickness of the negative electrode modification film and insufficient space in the concave groove, the lateral extension of the negative electrode modification film will occur during flattening downward pressure, and even cause the overflow of the negative electrode surface, resulting in unevenness. In addition, it will also cause the dimensions of the negative electrode and the negative electrode modification film to be too high, affecting the size of the entire battery cell.

[0024] As a preferred technical solution of the present utility model, the thickness of the negative electrode modification film is 0.03 mm - 0.20 mm, preferably 0.05 - 0.10 mm, and can be, 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.

[0025] In the present utility model, by adjusting the thickness of the negative electrode modification film, it can not only meet the functionality of the negative electrode modification film, but also ensure 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, the manufacturing cost will increase, and the assembly processing difficulty of the negative electrode modification film during the assembly process will increase; on the other hand, if the thickness is too thin, the adsorption capacity for the dissolved positive active ions will decrease accordingly. 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.

[0026] As a preferred technical solution of the present utility model, the surface density of the negative electrode modification film is 40 - 80 g / cm 2 ,, preferably 50 - 60 g / cm 2 ,and can be, for example, 40 g / cm 2 、45 g / cm 2 、50 g / cm 2 、52 g / cm 2 、55 g / cm 2 、58 g / cm 2 、60 g / cm 2 、65 g / cm 2 、70 g / cm 2 、75 g / cm 2 、80 g / cm 2etc.

[0027] In the present utility model, by regulating 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. As the battery cell reaction proceeds to the end of discharge, the functionality of the negative electrode modification film decreases rapidly. On the contrary, the porosity of the negative electrode modification film will decrease correspondingly, resulting in a decrease in the adsorption capacity for the dissolved positive active ions. Similarly, it shows that the negative electrode modification film component contains a relatively high content of non-conductive binder component, thereby causing a decrease in the conductivity of the negative electrode modification film.

[0028] As a preferred technical solution of the present utility model, the pore volume of the negative electrode modification film is 0.05 - 0.5 cm 3 / g, preferably 0.15 - 0.33 cm 3 / g. For example, it 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.

[0029] In the present utility model, by regulating the pore volume of the negative electrode modification film, it can give full play to the functionality of the modification film. The pore volume of the modification film 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 for the dissolved positive active ions will decrease, mainly reflected in the too small adsorption amount and quickly reaching the adsorption saturation. On the contrary, the adsorption efficiency for the dissolved positive active ions will become low.

[0030] In the present utility model, the tensile strength of the negative electrode modification film is 0.1 - 2 KN / m, preferably 0.4 - 0.5 KN / m. For example, it can be 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.

[0031] In the present utility model, by regulating the tensile strength of the negative electrode modification film, the negative electrode modification film has excellent mechanical processing properties, including cutting, transfer positioning, leveling and other properties. If the tensile strength is too low, it will affect the implementation of the entire processing process, affect the consistency of assembly, and even due to the poor strength or easy damage of the negative electrode modification film, the adhesion of the negative electrode modification film will decrease as the depth of discharge increases. On the contrary, 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 ability of dissolved positive active ions. Since the method of increasing the tensile strength of the negative electrode modification film includes increasing the content of the binder, the content of the conductive component will decrease accordingly. Similarly, the porosity of the negative electrode modification film will also decrease.

[0032] As a preferred technical solution of the present utility model, the negative electrode modification film includes at least one of an oxide negative electrode modification film, a carbon material negative electrode modification film, a metal-containing conductive particle negative electrode modification film or a fluorine-containing particle negative electrode modification film.

[0033] In the present utility model, the material of the oxide negative electrode modification film includes any one or a combination of at least two of titanium dioxide, molybdenum dioxide, aluminum oxide, lithium titanate or silver oxide, and a binder.

[0034] In the present utility model, the material of the carbon material negative electrode modification film includes any one or a combination of at least two of graphene, acetylene black, carbon nanotubes, activated carbon or graphite, and a binder.

[0035] In the present utility model, the material of the metal-containing conductive particle negative electrode modification film includes any one or a combination of at least two of copper particles, silver particles or gold particles.

[0036] Preferably, the material of the fluorine-containing particle negative electrode modification film includes any one or a combination of at least two of lithium fluoride, carbon fluoride, polytetrafluoroethylene, polyvinylidene fluoride or polyvinyl fluoride copolymer, and a binder.

[0037] Preferably, the binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, ethylene-propylene fluoride copolymer or polyacrylic acid.

[0038] Preferably, the mass ratio of the active material to the binder is 1:(0.03 - 0.3), preferably 1:(0.05 - 0.25), and for example, it can be 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.

[0039] In the present utility model, by regulating the mass ratio of the active material to the binder, the negative electrode modification film has excellent functionality, such as conductivity, adsorption, and flexible self - supportability. If the mass ratio is too low, the negative electrode modification film may not be able to form self - supportingly or may have poor film strength. On the contrary, it will lead to poor conductivity, low positive electrode active ion adsorption capacity, and a reduced proportion of other materials.

[0040] The present utility model exemplarily provides a method for preparing the above - mentioned negative electrode modification film, which includes the following steps:

[0041] The active material and the binder are subjected to film pressing or extrusion molding. During the molding process, it can be prepared without using a solvent, or a certain inorganic or organic solvent can be used for preparation, which is specifically determined according to the process requirements.

[0042] As a preferred technical solution of the present utility model, the separator includes a glass fiber separator and / or a polypropylene separator.

[0043] As a preferred technical solution of the present utility model, the number of layers of the separator is 1 - 3 layers, preferably 2 layers, and for example, it can be 1 layer, 2 layers, or 3 layers.

[0044] As a preferred technical solution of the present utility model, the separator includes a combination of a glass fiber separator and a polypropylene separator.

[0045] In the present utility model, the glass fiber separator is disposed on the side close to the negative electrode, and the polypropylene separator is disposed on the side close to the positive electrode, so as to achieve functional matching with the negative electrode modification film. This is because: ① the stiffness of the glass fiber separator is less than that of the polypropylene separator, which is beneficial to the fitting of the glass fiber separator and the negative electrode modification film; ② the liquid absorption capacity of the glass fiber separator is utilized: the liquid absorption capacity of the glass fiber separator > the liquid absorption capacity of the negative electrode modification film > the liquid absorption capacity of the polypropylene separator > the liquid absorption capacity of the positive electrode. Therefore, a concentration polarization with a certain gradient is formed, and setting the glass fiber is beneficial to the uniform distribution of the electrolyte in the entire battery cell. At the same time, the glass fiber separator can serve as a storage interface for the electrolyte, ensuring the amount of free electrolyte at the end of the battery cell life, enhancing the ion conduction ability, and ensuring the pulse ability of the battery cell 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 phenomenon 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.

[0046] As a preferred technical solution of the present utility model, the battery case includes a negative electrode bottom cover on the negative electrode side and a positive electrode cover on the positive electrode side.

[0047] As a preferred technical solution of the present utility model, the negative electrode bottom cover is provided with a sealing ring, and the sealing ring is disposed at the edge clamping joint of the negative electrode bottom cover and the positive electrode cover.

[0048] As a preferred technical solution of the present utility model, the primary lithium button cell further includes an electrolyte.

[0049] In a second aspect, the present utility model provides a method for manufacturing the primary lithium button cell according to the first aspect, and the method includes the following steps:

[0050] The negative electrode modification film is stamped into the negative electrode with a concave groove on the surface to form a precursor material; then the precursor material, the separator, and the positive electrode are sequentially stacked to obtain a battery cell assembly, and the battery cell assembly and the battery case are encapsulated to obtain the primary lithium button cell.

[0051] Preferably, after the negative electrode modification film is stamped into the negative electrode with a concave groove on the surface, a flattening treatment is further included to fully ensure the fitting degree and fitting flatness between the two.

[0052] In the present utility model, after the negative electrode modification film is cut into a specified shape, it is stamped into the negative electrode with a concave groove on the surface, and the positioning requires that the center of the vertical projection surface thereof completely coincides with the center of the concave groove inside the negative electrode to complete the preliminary flat fitting.

[0053] In the present utility model, when the depth of the concave groove is not higher than the thickness of the negative electrode modification film, during the flattening process, the negative electrode modification film is first pressed, and the centers of the projection surfaces of both are stressed. With the conduction of the stress, 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 at the same time, the air between the two is discharged to achieve a completely flat and embedded 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 concave groove of the negative electrode. During 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 state of pressure loss or underpressure. Under the continuous action of the downward pressure, the negative electrode will be deformed under pressure and act towards the center underpressure area. The final effect is that the negative electrode modification film is closely fitted in the concave groove, and the upper surface is embedded and fitted by the negative electrode's inward aggregation, thereby achieving a flat and fitted effect.

[0054] In the present utility model, the precursor material and the separator are stamped in the negative electrode bottom cover.

[0055] In the present utility model, the separator is in an inverted U shape, and both sides of the inverted U shape are bent towards the positive electrode.

[0056] In the present utility model, after being stacked in sequence, it further includes injecting electrolyte.

[0057] In the present utility model, after injecting the electrolyte, the formed positive electrode sheet is put in, and finally the positive electrode cover is covered, and the battery is subjected to primary sealing pressure and secondary sealing pressure to form a primary lithium button cell.

[0058] In the present utility model, the positive electrode sheet includes a current collector and a positive electrode active material layer provided 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.

[0059] In the present utility model, the positive electrode active material exemplarily includes manganese dioxide, carbon fluoride, or iron sulfide.

[0060] In the present utility model, the conductive agent exemplarily includes at least one of graphite, carbon nanotubes, conductive carbon black, or graphene.

[0061] In the present utility model, the binder exemplarily includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium polyacrylate, polyethylene oxide, or polyacrylonitrile.

[0062] In the present utility model, the forming process of the positive electrode sheet includes mixing the positive electrode active material, the conductive agent, and the binder evenly through a high-speed mixing device, and then stamping them into sheets by a forming machine for direct use, or a current collecting net can be stamped on the surface of the positive electrode active material layer, or used in combination with a current collecting ring.

[0063] In the present utility model, the material of the negative electrode exemplarily includes lithium metal or lithium alloy.

[0064] In a third aspect, the present utility model provides an electronic device, and the electronic device includes the primary lithium button cell according to the first aspect.

[0065] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0066] The present utility model provides a primary lithium button cell. First of all, by providing a concave groove on the surface of the negative electrode, the negative electrode modification film can be tightly embedded in the concave groove, and the following effects are achieved: ① The composite tightness, composite flatness and center alignment degree between the negative electrode modification film and the negative electrode can be improved, which not only ensures the stability of the structure of the cell component itself, but also improves the stability of the structure of the cell component in the reliability test. For example, under the long-term vibration, dropping or centrifugal environment test at normal temperature or high temperature, there will still be no displacement between the negative electrode and the negative electrode modification film, thereby further enhancing the bonding 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 normal temperature and extremely low temperature; ② A storage space for containing the negative electrode modification film is reserved in advance inside the negative electrode, which can not only ensure that the negative electrode modification film does not deform during the stamping process, but also improve the flatness of the entire composite surface of the negative electrode material.

[0067] Secondly, the negative electrode modification film provided by the present utility model has the following advantages: ① The negative electrode modification film has a porous structure. On the one hand, during the reaction process of the battery, due to the influence of potential, 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 separator in the battery is stronger than that of the positive electrode active material, the existence of the concentration polarization effect is caused, and the dissolved positive electrode active material ions may shuttle through the separator and then react with the negative electrode irreversibly to form a reaction interface with high internal resistance. The negative electrode modification film provided by the present utility model has a strong ion adsorption function due to its rich mesopores and micropores, and can well adsorb the dissolved positive electrode active ions in the pore structure, and finally effectively inhibit their transfer to the surface of the negative electrode to occur side reactions. On the other hand, some components in the non-aqueous electrolyte will also react with the negative electrode to form a SEI film. This 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 separator and the positive electrode increases. At this time, if the negative electrode contacts too much free electrolyte, it is easier to form a high-impedance interfacial film, resulting in blocked ion transport. The porous structure in the negative electrode modification film provided by the present utility model has a strong adsorption performance, and can adsorb the free electrolyte in the modification film at the end of discharge, thereby reducing the degree of its contact with the negative electrode, and thus improving the discharge performance of the battery. At the same time, the pore structure of the negative electrode modification film can be freely adjusted according to the selection of the film raw material and the processing technology;

[0068] ②The negative electrode modification film is a multi-functional layer. The modification film has good electrical conductivity and can form a near-capacitance structure with the positive electrode layer, thus having certain capacitance characteristics. When the battery is in a relatively low-temperature environment, the above capacitance structure can provide a certain amount of charge instantaneously during the reaction. At the same time, a good contact is formed between the modification film and the negative electrode, and a certain affinity will be formed between the particles, thereby changing the state of the original passivation layer. When the electrons are conducted, lithium ions can easily pass through the passivation layer, ensuring that the ions can penetrate the passivation layer, shortening the ion conduction, and thus increasing the instantaneous recovery voltage value. At the same time, the modification layer can further improve the ion and electron conduction rates during the discharge process of the battery, ensuring that the battery has the ability to output a large current. In addition, the negative electrode modification film provided by the present invention 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 eroded by the dissolved positive electrode cations;

[0069] ③The 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 - 0.5 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 surfaces, and it will not dissolve or deform under the infiltration of non-aqueous electrolyte and after deep discharge;

[0070] ④The negative electrode modification film has high flatness. The deviation of the thickness range of the negative electrode modification film is only within 3 μm, thereby reducing the process difficulty when the negative electrode modification film is embedded on 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;

[0071] 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, resulting in side reactions with the battery system or insufficient effective space of the battery cell components. In addition, the processing technology of the negative electrode modification film provided by the present invention is simple, its thickness itself is not affected by the thickness of the matrix layer, the overall thickness can be as low as 30 μm, and the uniformity of the negative electrode modification film is not affected by the material and flatness of the substrate layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 is a schematic structural diagram of the primary lithium button cell provided by the present invention, in which the positive electrode is directly prepared by stamping into sheets;

[0073] Figure 2Schematic structural diagram of the primary lithium button cell provided by the present utility model, wherein the positive electrode is obtained by stamping a current collector ring on the surface of the positive electrode active material layer;

[0074] Figure 3 Schematic exploded sectional view of the primary lithium button cell provided by the present utility model;

[0075] Figure 4 is Figure 3 Partial enlarged view of the circled part in

[0076] Figure 5 Assembly schematic diagram of the precursor material in the primary lithium button cell provided by the present utility model;

[0077] 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. Detailed implementation manners

[0078] It should be understood that in the description of the present utility model, the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0079] It should be noted that in the description of the present utility model, unless otherwise clearly defined and limited, the terms "set", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood through specific situations.

[0080] The technical solutions of the present utility model will be further described below with reference to the drawings and through specific implementation manners.

[0081] In the following examples and comparative examples, the primary lithium button cell is a CR2032 type button cell with a diameter of 20 mm and a thickness of 3.2 mm. Among them, 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 uses a non-aqueous electrolyte of lithium perchlorate with a concentration of 0.9 mol / L (where the solvent is composed of propylene carbonate and ethylene glycol dimethyl ether).

[0082] The preparation method of the positive electrode sheet includes the following steps:

[0083] After mixing manganese dioxide, conductive carbon black, and polytetrafluoroethylene emulsion evenly by a high-speed mixing device according to a mass ratio of 1:0.5:0.6, drying to obtain a powder, and then stamping the powder into a positive electrode sheet and assembling a current collector by a powder forming and ring assembling integrated machine, the positive electrode sheet as shown in Figure 1 is obtained;

[0084] Or,

[0085] After mixing manganese dioxide, conductive carbon black, and polytetrafluoroethylene emulsion evenly by a high-speed mixing device according to a mass ratio of 1:0.5:0.6, drying to obtain a powder, then stamping a current collecting ring on the surface of the positive electrode by a forming machine, and stamping a current collecting ring on the surface of the positive electrode by a forming machine, as shown in Figure 2 the positive electrode sheet is obtained.

[0086] The above description of the button cell is only for more completely elaborating the technical solution of the present invention and should not be regarded as a specific limitation to the present invention.

[0087] Example 1

[0088] This example provides a primary lithium button cell, as shown in Figures 3 - 4 , the primary lithium button cell includes a battery case, and a core component and an electrolyte located inside the battery case. The core component includes a lithium metal negative electrode 3, a circular planar negative electrode modification film 4, a separator, and a manganese dioxide positive electrode 7 stacked in sequence; a circular concave groove 9 is provided on the surface of the lithium metal negative electrode 3 close to 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 battery case includes 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. A sealing ring 1 is provided on the negative electrode bottom cover 2, and the sealing ring 1 is provided at the edge clamping joint of the negative electrode bottom cover 2 and the positive electrode cover 8; the separator includes a combination of a glass fiber separator 5 and a polypropylene separator 6. The glass fiber separator 5 is provided on the side close to the lithium metal negative electrode 3, and the polypropylene separator 6 is provided on the side close to the manganese dioxide positive electrode 7.

[0089] Among them, 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.

[0090] The thickness of the circular planar negative electrode modification film 4 is 0.08 mm, the tensile strength is 0.45 KN / m, the areal density is 55 g / cm 2 , the pore diameter is 2 - 200 nm, and the pore volume is 0.3 cm3 / g. The material of the circular planar negative electrode modification film 4 is prepared by laminating a carbon material and a polytetrafluoroethylene binder with a mass ratio of 1:0.15.

[0091] This embodiment also provides a preparation method of the above lithium primary button cell, which includes the following steps:

[0092] As Figure 5 shown, on one side of the negative electrode bottom cover, a circular concave groove is stamped on the surface of the lithium metal negative electrode by using a circular upper mold, and then the circular planar negative electrode modification film is stamped into the negative electrode with a circular concave groove on its surface. The positioning requires that the center of the vertical projection plane coincides exactly with the center of the circular concave groove in the negative electrode. After leveling treatment by stamping copolymerization, a precursor material is formed; then the separator is stamped into the negative electrode bottom cover, and the separator forms a "U" shape, and a non-aqueous electrolyte is injected; then the formed manganese dioxide positive electrode sheet is placed in, and finally the positive electrode cover is covered, and primary pressing and secondary pressing are carried out in sequence to obtain the lithium primary button cell.

[0093] Example 2

[0094] The difference between this embodiment and Embodiment 1 is that the shape of the negative electrode modification film 4 is a circular planar shape, and the shape of the concave groove 9 is a circular ring shape. Among them, the area ratio of the circular planar negative electrode modification film 4 to the circular ring-shaped concave groove 9 is 1:1; the area ratio of the circular planar negative electrode modification film 4 to the negative electrode 3 is 0.3:1; the depth ratio of the circular ring-shaped concave groove 9 to the thickness of the circular planar negative electrode modification film 4 is 0.95:1;

[0095] The thickness of the circular planar negative electrode modification film 4 is 0.05 mm, the tensile strength is 0.4 KN / m, and the surface density is 50 g / cm 2 , the pore diameter is 2 - 200 nm, and the pore volume is 0.3 cm 3 / g. The material of the circular planar negative electrode modification film 4 is prepared by laminating a carbon material and a polytetrafluoroethylene binder with a mass ratio of 1:0.1, and the others are the same as in Embodiment 1.

[0096] Example 3

[0097] The difference between this embodiment and Embodiment 1 is that the shape of the negative electrode modification film 4 is a square planar shape, and the shape of the concave groove 9 is a square. Among them, the area ratio of the square planar negative electrode modification film 4 to the square concave groove 9 is 1:1; the area ratio of the square planar negative electrode modification film 4 to the negative electrode 3 is 0.6:1; the depth ratio of the square concave groove 9 to the thickness of the square planar negative electrode modification film 4 is 0.97:1;

[0098] The thickness of the square planar negative electrode modification film 4 is 0.10 mm, the tensile strength is 0.5 KN / m, and the surface density is 60 g / cm2 with a pore diameter of 2 - 200 nm and a pore volume of 0.3 cm 3 / g. The material of the square planar negative electrode modification film 4 is prepared by pressing a carbon material and a polytetrafluoroethylene binder with a mass ratio of 1:0.2 into a film, and the others are the same as in Example 1.

[0099] Example 4

[0100] The difference between this example and Example 1 is that the separator is replaced with a double - layer polypropylene separator, and the others are the same as in Example 1.

[0101] Example 5

[0102] The difference between this example and Example 1 is that the area ratio of the circular planar negative electrode modification film 4 to the negative electrode 3 is 0.1:1, and the others are the same as in Example 1.

[0103] Example 6

[0104] The difference between this example and Example 1 is that the area ratio of the circular planar negative electrode modification film 4 to the negative electrode 3 is 1.2:1, and the others are the same as in Example 1.

[0105] Example 7

[0106] The difference between this example and Example 1 is that the ratio of the depth of the circular concave groove 9 to the thickness of the circular planar negative electrode modification film 4 is 0.1:1, and the others are the same as in Example 1.

[0107] Example 8

[0108] The difference between this example and Example 1 is that the ratio of the depth of the circular concave groove 9 to the thickness of the circular planar negative electrode modification film 4 is 2:1, and the others are the same as in Example 1.

[0109] Example 9

[0110] The difference between this example and Example 1 is that the surface density of the circular planar negative electrode modification film 4 is 30 g / cm 2 , and the others are the same as in Example 1.

[0111] Example 10

[0112] The difference between this example and Example 1 is that the surface density of the circular planar negative electrode modification film 4 is 90 g / cm 2 , and the others are the same as in Example 1.

[0113] Example 11

[0114] The difference between this example and Example 1 is that the pore volume of the circular planar negative electrode modification film 4 is 0.02 cm 3 / g, and the others are the same as in Example 1.

[0115] Example 12

[0116] The difference between this example and Example 1 is that the pore volume of the circular planar negative electrode modification film 4 is 0.7 cm 3 / g, and the others are the same as in Example 1.

[0117] Comparative Example 1

[0118] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface and no circular planar negative electrode modification film is provided, and the others are the same as in Example 1.

[0119] Comparative Example 2

[0120] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, no circular planar negative electrode modification film is provided, and the separator is replaced with a double-layer polypropylene separator, and the others are the same as in Example 1.

[0121] Comparative Example 3

[0122] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, and a circular planar negative electrode modification film is provided at the same time, and the others are the same as in Example 1.

[0123] Comparative Example 4

[0124] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, and a circular planar negative electrode modification film is provided at the same time, and the separator is replaced with a double-layer polypropylene separator, and the others are the same as in Example 1.

[0125] Comparative Example 5

[0126] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, and the circular planar negative electrode modification film is replaced with a circular carbon material layer. The preparation method of the circular carbon material layer is as follows: acetylene black is stirred evenly with ethanol and polyacrylic acid 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 plane, and the others are the same as in Example 1.

[0127] Comparative Example 6

[0128] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, and the circular planar negative electrode modification film is replaced with a circular carbon material layer. The preparation method of the circular carbon material layer is as follows: acetylene black is stirred evenly with ethanol and polyacrylic acid 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 plane, and the separator is replaced with a double-layer polypropylene separator, and the others are the same as in Example 1.

[0129] Comparative Example 7

[0130] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, and the circular planar negative electrode modification film is replaced with a circular carbon foil composite layer. The preparation method of the circular carbon foil composite layer is as follows: Stir acetylene black, ethanol, and polyacrylic acid evenly to form a slurry, transfer and coat it on a steel mesh and a polypropylene non-woven fabric. After vacuum baking and rolling to be flat, cut it into a circular plane. Others are the same as in Example 1.

[0131] Comparative Example 8

[0132] The difference between this comparative example and Example 1 is that the negative electrode is directly stamped into a flat surface, and the circular planar negative electrode modification film is replaced with a circular carbon foil composite layer. The preparation method of the circular carbon foil composite layer is as follows: Stir acetylene black, ethanol, and polyacrylic acid evenly to form a slurry, transfer and coat it on a steel mesh and a polypropylene non-woven fabric. After vacuum baking and rolling to be flat, cut it into a circular plane, and the separator is replaced with a double-layer polypropylene separator. Others are the same as in Example 1.

[0133] Test conditions

[0134] Perform performance tests on the negative electrode modification films or carbon foil composite layers provided in Examples 1 to 12 and Comparative Examples 1 to 8. The test method is as follows:

[0135] Tensile strength: Use an electronic diaphragm tensile machine to test the tensile strength of the film. First, cut the negative electrode modification film into 100×14 mm, place it between the upper and lower clamps of the tensile machine, with a clamping distance of 50 mm, a pre-tightening force of 0.5 N, start the machine, and stretch the specimen at a constant elongation speed of 10 mm / min until it breaks and record the maximum tensile force value during the stretching process.

[0136] Test the primary lithium button batteries provided in Examples 1 to 12 and Comparative Examples 1 to 8. The test method is as follows:

[0137] (1) First, at room temperature, the discharge program is constant resistance discharge at 0.2 mA for 800 h, and then place the battery in a refrigerator at -30°C for 4 h;

[0138] (2) The background current is 10 μA, and then give the battery a constant current pulse discharge of 10 mA for 0.5 s, and leave it for 4.5 s. This step is repeated 3 times, and record the discharge voltage value; then adjust the refrigerator temperature to -20°C, leave it for 4 h, and then repeat the above test steps 3 times. Test 5 batteries for each scheme, take their average value, and the calculation formula for voltage deviation is: Test 5 batteries, voltage deviation = (maximum voltage - minimum voltage) / average voltage

[0139] The test results are shown in Tables 1 - 2:

[0140] Table 1

[0141]

[0142]

[0143] Table 2

[0144]

[0145]

[0146] It can be seen from Tables 1 - 2 that the tensile strength value of the negative electrode modification film shows a positive correlation with the thickness of the modification film, and the pore volume and surface density parameters of the negative electrode modification film can also affect its tensile strength value. From the comparison between Example 1 and Example 4, it can be known that setting the glass fiber separator on the side close to the negative electrode and setting the polypropylene separator on the side close to the positive electrode can better achieve the functional matching with the negative electrode modification film.

[0147] From the comparison between Example 1, Example 5 - 6, it can be known that the present utility model makes it fully exert its functionality by regulating the area ratio of the circular planar negative electrode modification film to the negative electrode.

[0148] From the comparison between Example 1, Example 7 - 8, it can be known that the present utility model makes the negative electrode modification film completely flush with the negative electrode surface and has a certain good physical bonding force by regulating the ratio of the depth of the circular concave groove to the thickness of the circular planar negative electrode modification film.

[0149] From the comparison between Example 1, Example 9 - 10, it can be known that the present utility model makes the negative electrode modification film have excellent comprehensive functionality by regulating the surface density of the circular planar negative electrode modification film.

[0150] From the comparison between Example 1, Example 11 - 12, it can be known that the present utility model makes it fully exert the functionality of the modification film by regulating the pore volume of the circular planar negative electrode modification film.

[0151] From the comparison between Example 1 and Comparative Examples 1 - 4, it can be known that no concave groove is provided on the surface of the negative electrode close to the negative electrode modification film, resulting in a poor bonding force between the negative electrode and the negative electrode modification film and a risk of detachment. It is precisely because of the good lamination tightness between the negative electrode modification film and the negative electrode provided by the present utility model that the pulse voltages of the primary lithium button battery have good consistency during the pulse test at low temperature after a certain discharge depth.

[0152] As can be seen from the comparison between Example 1 and Comparative Examples 5-8, the use of the circular carbon material layer or circular carbon foil composite layer disclosed in the prior art cannot achieve all the technical effects of the negative electrode modification film provided by the present invention.

[0153] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A lithium primary button battery, characterized in that: The lithium primary button battery comprises a battery shell and a battery core assembly located inside the battery shell, wherein the battery core assembly comprises a negative electrode, a negative electrode modification film, a separator and a positive electrode which are 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, characterized in that: The shape of the concave groove includes any one of a circle, annular ring or regular polygon or a combination of at least two of them.

3. The lithium primary button cell according to claim 1, characterized in that: The center of the concave groove coincides with the center of the vertical projection surface of the negative electrode modification film.

4. The lithium primary button cell according to claim 1, characterized in that: 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.

5. The lithium primary button cell according to claim 1, characterized in that: The ratio of the depth of the concave groove to the thickness of the negative electrode modification film is (0.3-1.3):

1.

6. The lithium primary button cell according to claim 1, characterized in that: The thickness of the negative electrode modification film is 0.03mm-0.20mm; 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.

7. The lithium primary button cell according to claim 1, characterized in that: The negative electrode modification film includes at least one of an oxide negative electrode modification film, a carbon material negative electrode modification film, a negative electrode modification film containing metal conductive particles, or a negative electrode modification film containing fluorine particles.

8. The lithium primary button cell according to claim 1, characterized in that: The diaphragm includes a glass fiber diaphragm and / or a polypropylene diaphragm; The number of layers of the diaphragm is 1-3; The diaphragm includes a combination of a glass fiber diaphragm and a polypropylene diaphragm.

9. The lithium primary button cell according to claim 1, characterized in that: 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.

10. An electronic device, characterized in that: The electronic device comprises a lithium primary button cell according to any one of claims 1 to 9.

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