CN118841509A - Lithium primary button cell, preparation method thereof and electronic equipment - Google Patents
Lithium primary button cell, preparation method thereof and electronic equipment Download PDFInfo
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- CN118841509A CN118841509A CN202411045595.2A CN202411045595A CN118841509A CN 118841509 A CN118841509 A CN 118841509A CN 202411045595 A CN202411045595 A CN 202411045595A CN 118841509 A CN118841509 A CN 118841509A
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- Primary Cells (AREA)
Abstract
The invention provides a lithium primary button cell, a preparation method thereof and electronic equipment. The lithium primary button cell comprises a cell shell and a cell assembly positioned in the cell shell, wherein the cell assembly comprises a negative electrode, a negative electrode modification film, a diaphragm and a positive electrode which are sequentially laminated; the surface of the negative electrode, which is close to one side of the negative electrode modifying film, is provided with a concave groove, and the negative electrode modifying film is tightly embedded in the concave groove. The invention optimizes the structure and the material of the lithium primary button cell, so that the lithium primary button cell has excellent discharge performance, good stability and reliability.
Description
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a lithium primary button battery, a preparation method thereof and electronic equipment.
Background
Lithium primary batteries are a type of high-energy chemical primary battery commonly known as lithium batteries. Which takes metallic lithium as a cathode, solid salts or salts dissolved in an organic solvent as electrolyte, metallic oxide or other solid and liquid oxidants as anode active substances, and the intelligent meter is widely applied to the fields of various intelligent meters, intelligent traffic, intelligent security or medical appliances and the like. With the wide application of the internet of things technology, the application environment of users is more and more strict, and the requirements on the output capacity and the stability of a battery in an extreme environment are higher and higher, so that the requirements on the stability of the structure in the whole life cycle of the battery core are also higher.
The extreme environments mainly comprise extreme conditions such as high temperature, low temperature, high voltage, strong vibration and the like, and the extreme environmental conditions put higher requirements on the performance and reliability of the battery, for example, under the low temperature environment, the materials of the battery are required to have better low temperature performance, the dissolution phenomenon and the shuttle effect of positive active ions are avoided, and side reactions between the electrode materials and the electrolyte are avoided, so that the stability and the reliability of the battery are maintained. Under high pressure environments, the structure of the battery needs to be stronger and safer to prevent the battery from being broken and exploded. Under the strong vibration environment, the structure and the fixing mode of the battery need to be more stable and reliable to prevent the battery from shifting or falling off. Accordingly, in order to accommodate the extreme environments described above, optimization and improvement in materials, construction, and management systems are needed.
Based on the above situation, on one hand, the prior art discloses that a carbon material layer is arranged inside a battery, so that side reactions inside the battery are reduced, the conductivity is improved, and finally the internal resistance of the battery is reduced, but the carbon material layer has the problems of easy falling, insufficient strength and gaps between the carbon material layer and electrodes; on the other hand, the prior art also discloses that an electrode layer with good affinity or conductivity is prepared, but a special process is required for preparation, and the requirements on the process and the materials are high, so that the mass production cannot be realized.
Accordingly, there is a need in the art to develop a lithium primary button cell system that solves the above-mentioned problems by further optimizing its structure.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a lithium primary button cell, a preparation method thereof and electronic equipment. The invention optimizes the structure and the material of the lithium primary button cell, so that the lithium primary button cell has excellent discharge performance, good stability and reliability.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
In a first aspect, the invention provides a lithium primary button cell, which comprises a cell shell and a cell assembly positioned in the cell shell, wherein the cell assembly comprises a negative electrode, a negative electrode modification film, a diaphragm and a positive electrode which are sequentially stacked;
The surface of the negative electrode, which is close to one side of the negative electrode modifying film, is provided with a concave groove, and the negative electrode modifying film is tightly embedded in the concave groove.
Firstly, the concave groove is formed in the surface of the negative electrode, so that the negative electrode modification film can be tightly embedded in the concave groove, and the negative electrode modification film has the following effects: ① The lamination compactness, lamination flatness and centering alignment degree between the cathode modification film and the cathode can be improved, so that the stability of the structure of the battery cell assembly is guaranteed, the stability of the structure of the battery cell assembly in a reliability test is also improved, for example, the cathode and the cathode modification film still cannot shift under the conditions of long-time vibration, drop or centrifugal environment test at normal temperature or high temperature, the lamination stability between the cathode modification film and the cathode under high discharge depth is further enhanced, and the stability of high-current discharge or pulse discharge performance at normal temperature and extremely low temperature is guaranteed; ② The storage space for containing the negative electrode modifying film is reserved in the negative electrode, so that the negative electrode modifying film is prevented from deforming in the stamping process, and the flatness of the composite surface of the whole negative electrode material can be improved.
Secondly, the negative electrode modification film provided by the invention has the following advantages: ① The negative electrode modification film has a porous structure. On one hand, the positive electrode active material reacts with partial trace components of the nonaqueous electrolyte to form free cations or anions due to the potential influence in the reaction process of the battery, and meanwhile, concentration polarization effect exists due to the fact that the liquid absorption capacity of the separator in the battery is stronger than that of the positive electrode active material, so that dissolved positive electrode active material ions possibly pass through the separator, irreversible side reactions occur between the positive electrode active material ions and the negative electrode, and a reaction interface with high internal resistance is formed. The negative electrode modified film provided by the invention has a strong ion adsorption function due to the fact that the negative electrode modified film contains abundant mesopores and micropores, and can well adsorb dissolved positive electrode active ions in a pore structure, and finally, the negative electrode active ions are effectively inhibited from being transferred to the surface of a negative electrode to generate side reactions. On the other hand, some of the components in the nonaqueous electrolyte solution also react with the negative electrode to form an SEI film, which is easily broken down in the early cycle period of the battery, and in the later cycle period, as the negative electrode is continuously consumed, the interface resistance between the negative electrode and the separator and the positive electrode increases, and at this time, the negative electrode can more easily form a high-resistance interface film if being in contact with excessive free electrolyte, so that ion transmission is hindered. The porous structure in the negative electrode modification film provided by the invention has stronger adsorption performance, so that free electrolyte can be adsorbed in the modification film at the end of discharge, and the contact degree between the free electrolyte and the negative electrode is further reduced, thereby improving the discharge performance of the battery. Meanwhile, the pore structure of the negative electrode modified membrane can be freely regulated and controlled according to the raw material model selection and the processing technology of the membrane;
② The negative electrode modification film is a multifunctional layer. The modified film has good conductivity, and can form a structure close to capacitance with the positive electrode layer, so that the modified film has certain capacitance characteristics. When the battery is in a relatively low-temperature environment, the capacitor structure can provide a certain amount of charge instantly during reaction, meanwhile, benign contact is generated between the modification film and the negative electrode, and certain affinity effect is formed between particles, so that the state of an original passivation layer is changed, lithium ions easily penetrate through the passivation layer when electrons are conducted, the ions can penetrate through the passivation layer, ion conduction is shortened, and instant recovery voltage value is improved. Meanwhile, the modification layer can further improve the ion and electron conduction rate of the battery in the discharging process, and the battery is guaranteed to have high current output capacity. In addition, the negative electrode modification film provided by the invention has good affinity with the negative electrode, and can modify the passivation layer on the surface of the negative electrode, so that the negative electrode can be better protected from corrosion of dissolved positive cations;
③ The negative electrode modification film has high strength and good flexibility, and the tensile strength of the prepared negative electrode sheet is up to 0.4-0.5kN/m, so that the integrity of the negative electrode modification film in the process of slitting a pole piece, the processability in the process of assembling a battery and the integrity of the battery in packaging can be ensured. Meanwhile, because the composite material has good flexibility, when the composite material is coated with a negative electrode, the stress generated between the composite material and the negative electrode can be reduced, uneven lamination and uneven lamination surface are avoided, and the composite material is not dissolved and deformed under the infiltration of nonaqueous electrolyte and after deep discharge;
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 3 mu m, so that the process difficulty when the negative electrode modification film is embedded to the surface of a negative electrode is reduced, the attaching flatness between the negative electrode modification film and the negative electrode is ensured, the gap between the negative electrode modification film and the negative electrode is reduced, and the interface contact performance between the negative electrode modification film and the negative electrode is finally improved;
⑤ The cathode modification film is a self-supporting integrated functional film, so that the interface resistance of ion conduction can be reduced, and the side reaction between the cathode modification film and a battery system or the insufficient effective space of a battery core assembly can be avoided due to the introduction of other matrix materials. In addition, the processing technology of the negative electrode modification film provided by the invention is simple, the thickness of the negative electrode modification film is not influenced by the thickness of the substrate layer, the overall thickness can be as low as 30 mu m, and the uniformity degree of the negative electrode modification film is not influenced by the material and the flatness of the substrate layer.
Preferably, 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, preferably a circle.
In the present invention, the regular polygon exemplarily includes a square, a regular pentagon, a regular hexagon, and the like.
Preferably, the center of the concave groove coincides with the center of the vertical projection plane of the negative electrode modification film.
Preferably, 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 preferably (0.2 to 0.99): 1, more preferably (0.3 to 0.6): 1, and may 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, for example.
In the invention, the functionality of the negative electrode modifying film is fully exerted by regulating the area ratio of the negative electrode modifying film to the negative electrode, the functionality of the negative electrode modifying film is weakened due to the fact that the area of the modifying area is reduced when the area ratio is too low, for example, the conductivity of a conductive surface is relatively less improved, the adsorption area is reduced, the adsorption capacity of the dissolved positive electrode active ions is reduced, otherwise, the negative electrode modifying film cannot be well riveted due to the fact that the edge distance of a concave surface is small, in addition, the functionality of the negative electrode modifying film is not obviously improved due to the fact that the area ratio is too large, and the manufacturing cost is increased.
Preferably, the ratio of the depth of the concave groove to the thickness of the negative electrode modification film is (0.3 to 1.3): 1, preferably (0.95 to 1.05): 1, and may 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 or the like.
According to the invention, the depth of the concave groove and the thickness ratio of the negative electrode modifying film are regulated, so that the negative electrode modifying film and the negative electrode surface are completely flush and have good physical binding force, when the depth of the concave groove is too deep, the upper surface of the negative electrode modifying film is stressed to a small degree in the flattening process, and a certain air gap surface is generated due to weak binding force, uneven or insufficient exhaust of the lower surface of the negative electrode modifying film and the negative electrode in the concave groove; when the depth of concave groove is too shallow, and the thickness of negative pole modification membrane is too big, then can be in flattening technological process, because negative pole modification membrane is too thick, the space in concave groove is not enough, can cause the horizontal extension of negative pole modification membrane when the flattening pushes down, leads to the excessive of negative pole face even, leads to the unevenness, in addition also can lead to negative pole and negative pole modification membrane size superelevation, influences the size of whole electric core.
The negative electrode modification film preferably has a thickness of 0.03mm to 0.20mm, more preferably 0.05 mm to 0.10mm, and may 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 or the like.
According to the invention, the thickness of the negative electrode modification film is regulated, so that the functionality of the negative electrode modification film can be met, the assembly feasibility of the whole battery cell can be ensured, and the design of the capacity is enough, on the one hand, the processing difficulty of the negative electrode modification film can be increased when the thickness is too small, the manufacturing cost can be increased, and the assembly processing difficulty of the negative electrode modification film in the assembly process is increased; on the other hand, too thin thickness can lead to the adsorption capacity of the positive electrode active ions to dissolve out to be reduced, otherwise, too thick thickness can occupy the structural design space of the negative electrode, so that the design capacity of the whole battery cell is reduced.
Preferably, the tensile strength of the negative electrode modified film is 0.1 to 2KN/m, preferably 0.4 to 0.5KN/m, and may 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 or the like, for example.
In the invention, the tensile strength of the negative electrode modification film is regulated, so that the negative electrode modification film has excellent machining performance, including cutting, transferring and positioning, leveling and other performances, the tensile strength is too low, the implementation of the whole machining process is influenced, the assembly consistency is influenced, even the problem that the bonding degree of the negative electrode modification film is reduced along with the increase of the discharge depth is caused by poor strength or easy damage of the negative electrode modification film, otherwise, the film is too large, the partial functionality of the negative electrode modification film is influenced, such as the reduction of the electric conductivity and the absorption capacity to dissolved positive electrode active ions are reduced, the content of the conductive component is reduced due to the fact that the tensile strength of the negative electrode modification film is increased, and the porosity of the negative electrode modification film is also reduced.
The negative electrode modifying film preferably has an areal density of 40 to 80g/cm 2, preferably 50 to 60g/cm 2, for example 40g/cm2、45g/cm2、50g/cm2、52g/cm2、55g/cm2、58g/cm2、60g/cm2、65g/cm2、70g/cm2、75g/cm2、80g/cm2 and the like.
In the invention, the surface density of the negative electrode modification film is regulated, so that the negative electrode modification film has excellent comprehensive functionality, the surface density is too low, the poor film strength is shown, and the functionality of the negative electrode modification film is quickly reduced along with the progress of the cell reaction to the end stage of discharge. Conversely, the porosity of the negative electrode modification film is reduced, the adsorption capacity of the dissolved positive electrode active ions is reduced, and the negative electrode modification film component contains a non-conductive binder component with higher content, so that the conductivity of the negative electrode modification film is reduced.
Preferably, the pore volume of the negative electrode modification film is 0.05-0.5cm 3/g, preferably 0.15-0.33cm 3/g, for example 0.05cm3/g、0.08cm3/g、0.1cm3/g、0.12cm3/g、0.15cm3/g、0.18cm3/g、0.2cm3/g、0.22cm3/g、0.25cm3/g、0.28cm3/g、0.3cm3/g、0.33cm3/g、0.35cm3/g、0.4cm3/g、0.45cm3/g、0.5cm3/g and the like.
In the invention, the function of the modified film can be fully exerted by regulating the pore volume of the negative electrode modified film, the pore volume of the modified film is also influenced by the types of materials, the proportion of each component and the processing mode, the adsorption capacity of the dissolved positive electrode active ions is reduced due to the fact that the pore volume is too small, the adsorption capacity is saturated quickly due to the fact that the adsorption capacity is too small, and otherwise, the adsorption efficiency of the dissolved positive electrode active ions is reduced.
Preferably, the material of the negative electrode modification film includes an active material.
Preferably, the active material comprises at least one of an oxide material, a carbon material, metallic conductive particles or fluorine-containing particles, preferably an oxide material and/or a carbon material.
Preferably, the oxide material comprises any one or a combination of at least two of titanium dioxide, molybdenum dioxide, aluminum oxide, lithium titanate or silver oxide.
Preferably, the carbon material comprises any one or a combination of at least two of graphene, acetylene black, carbon nanotubes, activated carbon or graphite.
Preferably, the metal conductive particles include any one or a combination of at least two of copper particles, silver particles, or gold particles.
Preferably, the fluorine-containing particles include any one or a combination of at least two of lithium fluoride, carbon fluoride, polytetrafluoroethylene, polyvinylidene fluoride, or polyvinyl fluoride copolymer.
Preferably, the material of the negative electrode modification film further includes a binder.
Preferably, the binder comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene propylene copolymer or polyacrylic acid.
Preferably, the mass ratio of the active material to the binder is 1 (0.03-0.3), preferably 1 (0.05-0.25), and may be, 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.
In the invention, the negative electrode modification film has excellent functionality, such as conductivity, adsorptivity and flexibility self-supporting property, by regulating the mass ratio of the active material to the binder, and the too low mass ratio can lead to the negative electrode modification film not being self-supporting to be molded or having poor film strength, and conversely can lead to poor conductivity, low adsorption capacity of positive electrode active ions and reduced occupation ratio of other materials.
In the invention, the preparation method of the negative electrode modified film comprises the steps of film pressing molding or extrusion molding of an active material and a binder, wherein the preparation can be carried out without using a solvent in the molding process, or can be carried out by using a certain inorganic or organic solvent, and the preparation is specifically determined according to the process requirements.
Preferably, the separator comprises a glass fiber separator and/or a polypropylene separator.
Preferably, the number of layers of the separator is 1-3, preferably 2, and may be 1,2 or 3, for example.
Preferably, the separator comprises a combination of a glass fiber separator and a polypropylene separator.
In the invention, the glass fiber diaphragm is arranged on the side close to the negative electrode, and the polypropylene diaphragm is arranged on the side close to the positive electrode, so that the functional matching with the negative electrode modification film is realized. The stiffness of the ① glass fiber membrane is smaller than that of the polypropylene membrane, so that the glass fiber membrane is favorably attached to the negative electrode modified membrane; ② Exert the liquid absorbing capacity of the glass fiber membrane: the liquid absorption capacity of the glass fiber diaphragm is greater than that of the negative electrode modification film and greater than that of the polypropylene diaphragm, so that concentration polarization with certain gradient is formed, and the arrangement of glass fibers is beneficial to the uniform distribution of electrolyte of the whole battery cell. Meanwhile, the glass fiber diaphragm can be used as a storage interface of electrolyte, so that the amount of free electrolyte at the end of the service life of the battery cell is ensured, the ionic conductivity is enhanced, and the pulse capability of the battery cell at extremely low temperature is ensured. In addition, it is also possible to reduce the storage amount of the positive electrode interface free electrolyte, thereby reducing the dissolution phenomenon of the positive electrode active material and the storage amount of the free electrolyte in the negative electrode modification film, and reducing the side reaction between the dissolved positive electrode active ions and the negative electrode.
Preferably, the battery case includes a negative bottom cover on a negative side and a positive cover on a positive side.
Preferably, the negative bottom cover is provided with a sealing ring, and the sealing ring is arranged at the edge clamping joint of the negative bottom cover and the positive cover.
Preferably, the lithium primary button cell further comprises an electrolyte.
In a second aspect, the present invention provides a method of preparing a lithium primary button cell according to the first aspect, the method comprising the steps of:
Stamping the negative electrode modification film in a negative electrode with a concave groove on the surface to form a precursor material; and then sequentially stacking the precursor material, the diaphragm and the anode to obtain a battery cell assembly, and packaging the battery cell assembly and the battery shell to obtain the lithium primary button battery.
Preferably, the negative electrode modifying film is stamped in the negative electrode with the concave groove on the surface and then further comprises leveling treatment, so that the laminating degree and laminating flatness of the negative electrode modifying film and the negative electrode are fully ensured.
In the invention, after the negative electrode modifying film is cut into a specified shape, the negative electrode modifying film is stamped in a negative electrode with a concave groove on the surface, and the center of a vertical projection surface of the negative electrode modifying film is required to be completely overlapped with the center of the concave groove in the negative electrode in positioning, so that preliminary smooth lamination is finished.
In the invention, when the depth of the concave groove is not higher than the thickness of the negative electrode modifying film, the negative electrode modifying film is pressed firstly in the leveling process, the centers of projection surfaces of the negative electrode modifying film and the negative electrode modifying film are stressed, the stress is conducted, the lower surface of the negative electrode modifying film is embedded and attached with the upper surface of the concave groove of the negative electrode, and meanwhile, air between the negative electrode modifying film and the negative electrode modifying film is discharged, so that the effect of complete leveling and embedding is achieved; when the depth of concave groove is higher than the thickness of negative electrode modification film, be equivalent to negative electrode modification film and be placed in negative electrode concave groove, in the flattening course of working, the negative electrode is stressed at first at the non-concave groove position of negative electrode, concave groove central part is in the decompression or under-pressure state, under the continuous effect of downforce, the negative electrode can be pressed and deformed, toward the regional effect of central under-pressure, final effect is that negative electrode modification film closely laminates in concave groove, and the upper surface is by negative electrode cohesion gomphosis to this reaches the effect of flattening laminating.
Preferably, the battery case includes a negative bottom cover on a negative side and a positive cover on a positive side.
Preferably, the negative bottom cover is provided with a sealing ring, and the sealing ring is arranged at the edge clamping joint of the negative bottom cover and the positive cover.
Preferably, the lithium primary button cell further comprises an electrolyte.
Preferably, the precursor material and the separator are stamped in the negative bottom cover.
Preferably, the separator is in an inverted U shape, and both sides of the inverted U shape are bent in the direction of the positive electrode.
Preferably, the method further comprises injecting electrolyte after the sequential lamination.
In the invention, after electrolyte is injected, the formed positive plate is put in, and finally, the positive plate cover is covered, and the primary sealing and the secondary sealing are carried out on the battery to form the lithium primary button battery.
In the present invention, the positive electrode sheet includes a current collector and a positive electrode active material layer disposed on at least one side of the current collector, the positive electrode active material layer including a positive electrode active material, a conductive agent, and a binder.
In the present invention, the positive electrode active material illustratively includes manganese dioxide, carbon fluoride, or iron sulfide.
In the present invention, the conductive agent illustratively includes at least one of graphite, carbon nanotubes, conductive carbon black, or graphene.
In the present invention, the binder illustratively includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium polyacrylate, polyethylene oxide, or polyacrylonitrile.
In the invention, the forming process of the positive plate comprises the steps of uniformly mixing a positive active material, a conductive agent and a binder through high-speed mixing equipment, and then stamping the mixture into a plate by a forming machine for direct use, or stamping a current collecting net on the surface of the positive active material layer or matching with a current collecting ring for use.
In the present invention, the material of the negative electrode illustratively includes lithium metal or a lithium alloy.
In a third aspect, the present invention provides an electronic device comprising a lithium primary button cell according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
The invention provides a lithium primary button cell, firstly, the surface of a negative electrode is provided with a concave groove, so that a negative electrode modification film can be tightly embedded in the concave groove, and the lithium primary button cell has the following effects: ① The lamination compactness, lamination flatness and centering alignment degree between the cathode modification film and the cathode can be improved, so that the stability of the structure of the battery cell assembly is guaranteed, the stability of the structure of the battery cell assembly in a reliability test is also improved, for example, the cathode and the cathode modification film still cannot shift under the conditions of long-time vibration, drop or centrifugal environment test at normal temperature or high temperature, the lamination stability between the cathode modification film and the cathode under high discharge depth is further enhanced, and the stability of high-current discharge or pulse discharge performance at normal temperature and extremely low temperature is guaranteed; ② The storage space for containing the negative electrode modifying film is reserved in the negative electrode, so that the negative electrode modifying film is prevented from deforming in the stamping process, and the flatness of the composite surface of the whole negative electrode material can be improved.
Secondly, the negative electrode modification film provided by the invention has the following advantages: ① The negative electrode modification film has a porous structure. On one hand, the positive electrode active material reacts with partial trace components of the nonaqueous electrolyte to form free cations or anions due to the potential influence in the reaction process of the battery, and meanwhile, concentration polarization effect exists due to the fact that the liquid absorption capacity of the separator in the battery is stronger than that of the positive electrode active material, so that dissolved positive electrode active material ions possibly pass through the separator, irreversible side reactions occur between the positive electrode active material ions and the negative electrode, and a reaction interface with high internal resistance is formed. The negative electrode modified film provided by the invention has a strong ion adsorption function due to the fact that the negative electrode modified film contains abundant mesopores and micropores, and can well adsorb dissolved positive electrode active ions in a pore structure, and finally, the negative electrode active ions are effectively inhibited from being transferred to the surface of a negative electrode to generate side reactions. On the other hand, some of the components in the nonaqueous electrolyte solution also react with the negative electrode to form an SEI film, which is easily broken down in the early cycle period of the battery, and in the later cycle period, as the negative electrode is continuously consumed, the interface resistance between the negative electrode and the separator and the positive electrode increases, and at this time, the negative electrode can more easily form a high-resistance interface film if being in contact with excessive free electrolyte, so that ion transmission is hindered. The porous structure in the negative electrode modification film provided by the invention has stronger adsorption performance, so that free electrolyte can be adsorbed in the modification film at the end of discharge, and the contact degree between the free electrolyte and the negative electrode is further reduced, thereby improving the discharge performance of the battery. Meanwhile, the pore structure of the negative electrode modified membrane can be freely regulated and controlled according to the raw material model selection and the processing technology of the membrane;
② The negative electrode modification film is a multifunctional layer. The modified film has good conductivity, and can form a structure close to capacitance with the positive electrode layer, so that the modified film has certain capacitance characteristics. When the battery is in a relatively low-temperature environment, the capacitor structure can provide a certain amount of charge instantly during reaction, meanwhile, benign contact is generated between the modification film and the negative electrode, and certain affinity effect is formed between particles, so that the state of an original passivation layer is changed, lithium ions easily penetrate through the passivation layer when electrons are conducted, the ions can penetrate through the passivation layer, ion conduction is shortened, and instant recovery voltage value is improved. Meanwhile, the modification layer can further improve the ion and electron conduction rate of the battery in the discharging process, and the battery is guaranteed to have high current output capacity. In addition, the negative electrode modification film provided by the invention has good affinity with the negative electrode, and can modify the passivation layer on the surface of the negative electrode, so that the negative electrode can be better protected from corrosion of dissolved positive cations;
③ The negative electrode modification film has high strength and good flexibility, and the tensile strength of the prepared negative electrode sheet is up to 0.4-0.5kN/m, so that the integrity of the negative electrode modification film in the process of slitting a pole piece, the processability in the process of assembling a battery and the integrity of the battery in packaging can be ensured. Meanwhile, because the composite material has good flexibility, when the composite material is coated with a negative electrode, the stress generated between the composite material and the negative electrode can be reduced, uneven lamination and uneven lamination surface are avoided, and the composite material is not dissolved and deformed under the infiltration of nonaqueous electrolyte and after deep discharge;
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 3 mu m, so that the process difficulty when the negative electrode modification film is embedded to the surface of a negative electrode is reduced, the attaching flatness between the negative electrode modification film and the negative electrode is ensured, the gap between the negative electrode modification film and the negative electrode is reduced, and the interface contact performance between the negative electrode modification film and the negative electrode is finally improved;
⑤ The cathode modification film is a self-supporting integrated functional film, so that the interface resistance of ion conduction can be reduced, and the side reaction between the cathode modification film and a battery system or the insufficient effective space of a battery core assembly can be avoided due to the introduction of other matrix materials. In addition, the processing technology of the negative electrode modification film provided by the invention is simple, the thickness of the negative electrode modification film is not influenced by the thickness of the substrate layer, the overall thickness can be as low as 30 mu m, and the uniformity degree of the negative electrode modification film is not influenced by the material and the flatness of the substrate layer.
Drawings
Fig. 1 is a schematic structural view of a lithium primary button cell according to the present invention, in which a positive electrode is directly prepared by punching into a sheet;
fig. 2 is a schematic structural diagram of a lithium primary button cell according to the present invention, in which a positive electrode is prepared by punching a collector ring on a surface of a positive electrode active material layer;
FIG. 3 is a schematic view showing a broken-away section of a lithium primary button cell according to the present invention;
FIG. 4 is an enlarged view of a portion of the encircled portion of FIG. 3;
FIG. 5 is a schematic diagram illustrating the assembly of precursor materials in a lithium primary button cell according to the present invention;
The device comprises a 1-sealing ring, a 2-negative electrode bottom cover, a 3-negative electrode, a 4-negative electrode modification film, a 5-glass fiber diaphragm, a 6-polypropylene diaphragm, a 7-positive electrode, an 8-positive electrode cover and a 9-concave groove.
Detailed Description
The technical scheme of the invention is further described below by combining the attached drawings and the specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
The lithium primary button cell in the following examples and comparative examples was a CR2032 type button cell having a diameter of 20mm and a thickness of 3.2mm, wherein the diameter of the positive electrode sheet was 15.00mm and the thickness was 1.85mm; the diameter of the negative plate is 16.00mm, and the thickness is 0.58mm; the electrolyte adopts a nonaqueous electrolyte of lithium perchlorate with the concentration of 0.9mol/L (wherein the solvent consists of propylene carbonate and ethylene glycol dimethyl ether).
The preparation method of the positive plate comprises the following steps:
Uniformly mixing manganese dioxide, conductive carbon black and polytetrafluoroethylene emulsion according to the mass ratio of 1:0.5:0.6 by high-speed mixing equipment, drying to obtain powder, and stamping into positive plates and assembling current collectors by adopting a powder forming and ring assembling integrated machine to obtain the positive plates shown in figure 1;
Or alternatively
Uniformly mixing manganese dioxide, conductive carbon black and polytetrafluoroethylene emulsion according to the mass ratio of 1:0.5:0.6 by high-speed mixing equipment, drying to obtain powder, and stamping a collector ring on the surface of the positive electrode by a forming machine to obtain the positive electrode sheet shown in figure 2.
The above description of the button cell is only for more complete description of the technical solution of the present invention, and should not be taken as a specific limitation of the present invention.
Example 1
The embodiment provides a lithium primary button cell, as shown in fig. 3-4, the lithium primary button cell comprises a cell shell, and a cell component and electrolyte which are positioned in the cell shell, wherein the cell component comprises a lithium metal negative electrode 3, a round plane negative electrode modification film 4, a diaphragm and a manganese dioxide positive electrode 7 which are sequentially stacked; the surface of the lithium metal anode 3, which is close to one side of the circular plane anode modification film 4, is provided with a circular concave groove 9, and the circular plane anode modification film 4 is tightly embedded in the circular concave groove 9; the battery shell comprises a negative bottom cover 2 positioned at one side of a lithium metal negative electrode 3 and a positive cover 8 positioned at one side of a manganese dioxide positive electrode 7, wherein the negative bottom cover 2 is provided with a sealing ring 1, and the sealing ring 1 is arranged at the edge clamping joint of the negative bottom cover 2 and the positive cover 8; the separator comprises a combination of a glass fiber separator 5 and a polypropylene separator 6, wherein the glass fiber separator 5 is arranged on the side close to the lithium metal cathode 3, and the polypropylene separator 6 is arranged on the side close to the manganese dioxide anode 7.
Wherein, the area ratio of the round plane negative electrode modification film 4 to the round concave groove 9 is 1:1; the area ratio of the round plane negative electrode modification film 4 to the lithium metal negative electrode 3 is 0.45:1; the thickness ratio of the depth of the circular concave groove 9 to the circular planar negative electrode modification film 4 was 0.95:1. The thickness of the round plane negative electrode modification film 4 is 0.08mm, the tensile strength is 0.45KN/m, the surface density is 55g/cm 2, the aperture is 2-200nm, and the pore volume is 0.3cm 3/g. The round plane negative electrode modification film 4 is prepared by film pressing and molding of a carbon material and a polytetrafluoroethylene binder in a mass ratio of 1:0.15.
The embodiment also provides a preparation method of the lithium primary button cell, which comprises the following steps:
As shown in fig. 5, a circular concave groove is formed on the surface of a lithium metal negative electrode by punching through a circular upper die on one side of a negative electrode bottom cover, then a circular plane negative electrode modification film is punched in a negative electrode with the circular concave groove on the surface, the center of a vertical projection surface of the circular plane negative electrode modification film is required to be completely overlapped with the center of the circular concave groove in the negative electrode by positioning, and a precursor material is formed after leveling treatment through a punching tool; stamping the diaphragm into a negative bottom cover, forming a U-shaped diaphragm, and injecting nonaqueous electrolyte; and then putting the formed manganese dioxide positive plate, and finally covering the positive plate cover, and sequentially performing primary sealing and pressing and secondary sealing and pressing to obtain the lithium primary button cell.
Example 2
The difference between this embodiment and embodiment 1 is that the shape of the negative electrode modification film is a circular plane, and the shape of the concave groove is a circular ring, wherein the area ratio of the circular plane negative electrode modification film to the circular concave groove is 1:1; the area ratio of the annular plane negative electrode modification film to the negative electrode is 0.3:1; the thickness ratio of the depth of the annular concave groove to the annular plane negative electrode modification film is 0.95:1.
The thickness of the annular plane negative electrode modification film is 0.05mm, the tensile strength is 0.4KN/m, the surface density is 50g/cm 2, the aperture is 2-200nm, and the pore volume is 0.3cm 3/g. The material of the annular plane negative electrode modification film is prepared by film pressing and molding of a carbon material and a polytetrafluoroethylene binder in a mass ratio of 1:0.1, and the other materials are the same as those in the embodiment 1.
Example 3
The difference between the embodiment and the embodiment 1 is that the shape of the negative electrode modifying 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 modifying film to the square concave groove is 1:1; the area ratio of the square plane negative electrode modifying film to the negative electrode is 0.6:1; the thickness ratio of the depth of the square concave groove to the square plane negative electrode modification film is 0.97:1.
The square plane negative electrode modified film has a thickness of 0.10mm, a tensile strength of 0.5KN/m, an areal density of 60g/cm 2, a pore diameter of 2-200nm and a pore volume of 0.3cm 3/g. The square plane negative electrode modification film is prepared by film pressing and molding of a carbon material and a polytetrafluoroethylene binder in a mass ratio of 1:0.2, and the other materials are the same as in example 1.
Example 4
This example differs from example 1 in that the separator was replaced with a double layer polypropylene separator, all other things being equal to example 1.
Example 5
The difference between this example and example 1 is that the area ratio of the round planar negative electrode modification film to the negative electrode was 0.1:1, and the other is the same as in example 1.
Example 6
The difference between this example and example 1 is that the area ratio of the round planar negative electrode modification film to the negative electrode is 1.2:1, and the other is the same as in example 1.
Example 7
The difference between this example and example 1 is that the thickness ratio of the depth of the circular concave groove to the circular planar negative electrode modifying film is 0.1:1, and the other is the same as example 1.
Example 8
The difference between this example and example 1 is that the ratio of the depth of the circular concave groove to the thickness of the circular planar negative electrode modifying film is 2:1, and the other is the same as example 1.
Example 9
The difference between this example and example 1 is that the surface density of the round planar negative electrode modifying film was 30g/cm 2, and the other points were the same as in example 1.
Example 10
The difference between this example and example 1 is that the surface density of the round planar negative electrode modifying film was 90g/cm 2, and the other points were the same as in example 1.
Example 11
This example differs from example 1 in that the pore volume of the round planar anode modification film was 0.02cm 3/g, and the other was the same as in example 1.
Example 12
This example differs from example 1 in that the pore volume of the round planar anode modification film was 0.7cm 3/g, and the other was the same as in example 1.
Example 13
This example differs from example 1 in that the mass ratio of carbon material active material to polytetrafluoroethylene binder is 1:0.02, all other things being equal to example 1.
Example 14
This example differs from example 1 in that the mass ratio of carbon material active material to polytetrafluoroethylene binder is 1:0.4, all other things being equal to example 1.
Comparative example 1
This comparative example differs from example 1 in that the negative electrode was directly punched into a flat surface, and a circular planar negative electrode finishing film was not provided, all of which were the same as example 1.
Comparative example 2
This comparative example differs from example 1 in that the negative electrode was directly punched into a flat surface, and a circular planar negative electrode finishing film was not provided, and the separator was replaced with a double-layered polypropylene separator, all of which were the same as example 1.
Comparative example 3
The comparative example was different from example 1 in that the negative electrode was directly punched into a flat surface while a circular planar negative electrode finishing film was provided, and the other was the same as example 1.
Comparative example 4
This comparative example differs from example 1 in that the negative electrode was directly punched into a flat surface while providing a circular planar negative electrode finishing film, and the separator was replaced with a double-layered polypropylene separator, all of which were the same as in example 1.
Comparative example 5
The comparative example differs from example 1 in that the negative electrode was directly punched to a flat surface, and the round planar negative electrode modification film was replaced with a round carbon material layer, which was prepared as follows: acetylene black, ethanol and polyacrylic acid are stirred uniformly to form slurry, the slurry is transferred and coated on polypropylene non-woven fabric, and the non-woven fabric is cut into a circular plane after vacuum baking, and the other materials are the same as those in the embodiment 1.
Comparative example 6
The comparative example differs from example 1 in that the negative electrode was directly punched to a flat surface, and the round planar negative electrode modification film was replaced with a round carbon material layer, which was prepared as follows: acetylene black, ethanol and polyacrylic acid are stirred uniformly to form slurry, the slurry is transferred and coated on polypropylene non-woven fabric, the non-woven fabric is cut into a round plane after vacuum baking, and the diaphragm is replaced by a double-layer polypropylene diaphragm, and the other materials are the same as those in the embodiment 1.
Comparative example 7
The difference between the comparative example and the example 1 is that the anode adopts direct stamping to form a flat surface, and the round plane anode decoration film is replaced by a round carbon foil composite layer, and the preparation method of the round carbon foil composite layer is as follows: acetylene black, ethanol and polyacrylic acid are stirred uniformly to form slurry, the slurry is transferred and coated on a steel mesh, and the slurry is coated on polypropylene non-woven fabric, rolled and flattened after vacuum baking, and then cut into a round plane, and the other materials are the same as those in the embodiment 1.
Comparative example 8
The difference between the comparative example and the example 1 is that the anode adopts direct stamping to form a flat surface, and the round plane anode decoration film is replaced by a round carbon foil composite layer, and the preparation method of the round carbon foil composite layer is as follows: acetylene black, ethanol and polyacrylic acid are stirred uniformly to form slurry, the slurry is transferred and coated on a steel mesh, a polypropylene non-woven fabric is subjected to vacuum baking, the slurry is rolled and flattened and then cut into a round plane, and the membrane is replaced by a double-layer polypropylene membrane, wherein the other components are the same as those in the embodiment 1.
Test conditions
The negative electrode modified films or carbon foil composite layers provided in examples 1 to 14 and comparative examples 1 to 8 were subjected to performance tests as follows:
Tensile strength: the tensile strength test of the membrane is carried out by adopting an electronic separator tensile machine, firstly, a negative electrode modified membrane with the thickness of 100 multiplied by 14mm is obtained by cutting, the negative electrode modified membrane is placed between an upper clamp and a lower clamp of the tensile machine, the clamping distance is 50mm, the pretightening force is 0.5N, the machine is started, the sample is stretched at a constant elongation speed of 10mm/min until the sample is broken, and the maximum tensile force value in the stretching process is recorded.
The lithium primary button cells provided in examples 1 to 14 and comparative examples 1 to 8 were tested as follows:
(1) Firstly, at normal temperature, discharging for 800 hours at constant resistance of 0.2mA, and then placing the batteries in a refrigerator at-30 ℃ and-20 ℃ for 4 hours respectively;
(2) The background current is 10 mu A, then the battery is discharged by constant current pulse of 10mA and 0.5s, the battery is left for 4.5s, the step is circulated for 3 times, and the discharge voltage value is recorded; then the temperature of the refrigerator is adjusted to-20 ℃, and after the refrigerator is left for 4 hours, the refrigerator is circulated for three times according to the test steps. The battery test of each scheme is 5, the average value is taken, and the calculation formula of the voltage deviation is as follows: test 5 cells, voltage deviation= (voltage maximum value-voltage minimum value)/voltage average value
The test results are shown in tables 1-2:
TABLE 1
TABLE 2
It can be seen from tables 1 to 2 that the tensile strength value of the negative electrode modified film and the thickness of the modified film show a positive correlation, and simultaneously show a positive correlation with the content of polytetrafluoroethylene, and the pore volume and the areal density parameters of the negative electrode modified film can also influence the tensile strength value thereof. As is clear from a comparison of example 1 and example 4, the glass fiber separator was disposed on the side close to the negative electrode, and the polypropylene separator was disposed on the side close to the positive electrode, so that functional matching with the negative electrode modifying film could be better achieved.
As can be seen from comparison of examples 1 and examples 5-6, the invention can fully exert the functions of the round planar anode modifying film and the anode by regulating the area ratio of the anode modifying film to the anode.
As can be seen from comparison of examples 1 and examples 7-8, the invention enables the cathode modifying film and the cathode surface to be completely flush and have a certain good physical binding force by adjusting the thickness ratio of the depth of the circular concave groove and the circular plane cathode modifying film.
As can be seen from comparison of examples 1 and examples 9-10, the surface density of the round planar negative electrode modification film is regulated, so that the negative electrode modification film has excellent comprehensive functionality.
As can be seen from comparison of examples 1 and examples 11 to 12, the invention can fully exert the functionality of the modified membrane by controlling the pore volume of the round planar anode modified membrane.
As is clear from comparison of examples 1 and examples 13 to 14, the present invention provides the negative electrode modifying film with excellent functionality including, for example, conductivity, adsorptivity and flexible self-supporting property by controlling the mass ratio of the active material to the binder.
As is clear from comparison of examples 1 and comparative examples 1 to 4, the surface of the negative electrode on the side close to the negative electrode modification film was not provided with a concave groove, so that the binding force between the negative electrode and the negative electrode modification film was poor, and there was a risk of falling off. The negative electrode modification film and the negative electrode provided by the invention have good covering compactness, so that the pulse voltage of the lithium primary button cell subjected to the pulse test at a low temperature has good consistency after a certain depth of discharge.
As is clear from comparison of example 1 and comparative examples 5 to 8, the round carbon material layer or the round 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.
The applicant states that the process of the invention is illustrated by the above examples, but the invention is not limited to, i.e. does not mean that the invention must be carried out in dependence on the above process steps. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected raw materials, addition of auxiliary components, selection of specific modes, etc. fall within the scope of the present invention and the scope of disclosure.
Claims (10)
1. The lithium primary button cell is characterized by comprising a cell shell and a cell assembly positioned in the cell shell, wherein the cell assembly comprises a negative electrode, a negative electrode modification film, a diaphragm and a positive electrode which are sequentially laminated;
The surface of the negative electrode, which is close to one side of the negative electrode modifying film, is provided with a concave groove, and the negative electrode modifying film is tightly embedded in the concave groove.
2. The lithium primary button cell of 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, preferably a circle;
preferably, 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 of claim 1 or 2, wherein the area ratio of the negative electrode modification film to the concave groove is 1:1;
Preferably, the area ratio of the negative electrode modification film to the negative electrode is (0.2 to 0.99): 1, preferably (0.3 to 0.6): 1;
Preferably, the ratio of the depth 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.
4. A lithium primary button cell according to any one of claims 1-3, characterized in that the negative electrode modification film has a thickness of 0.03mm-0.20mm, preferably 0.05-0.10mm;
Preferably, the tensile strength of the negative electrode modified film is 0.1-2KN/m, preferably 0.4-0.5KN/m;
Preferably, the surface density of the negative electrode modification film is 40-80g/cm 2, preferably 50-60g/cm 2;
preferably, the pore volume of the negative electrode modification film is 0.05-0.5cm 3/g, preferably 0.15-0.33cm 3/g.
5. The lithium primary button cell of any one of claims 1-4, wherein the material of the negative electrode modification film comprises an active material;
preferably, the active material comprises at least one of an oxide material, a carbon material, metallic conductive particles or fluorine-containing particles, preferably an oxide material and/or a carbon material;
Preferably, the oxide material comprises any one or a combination of at least two of titanium dioxide, molybdenum dioxide, aluminum oxide, lithium titanate or silver oxide;
preferably, the carbon material comprises any one or a combination of at least two of graphene, acetylene black, carbon nanotubes, activated carbon or graphite;
preferably, the metal conductive particles comprise any one or a combination of at least two of copper particles, silver particles or gold particles;
Preferably, the fluorine-containing particles comprise any one or a combination of at least two of lithium fluoride, carbon fluoride, polytetrafluoroethylene, polyvinylidene fluoride or polyvinyl fluoride copolymer;
Preferably, the material of the negative electrode modification film further comprises a binder;
preferably, the binder comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene-propylene copolymer or polyacrylic acid;
preferably, the mass ratio of the active material to the binder is 1 (0.03-0.3), preferably 1 (0.05-0.25).
6. The lithium primary button cell of any one of claims 1-5, wherein the separator comprises a fiberglass separator and/or a polypropylene separator;
preferably, the number of layers of the separator is 1-3, preferably 2;
preferably, the separator comprises a combination of a glass fiber separator and a polypropylene separator.
7. The lithium primary button cell of any one of claims 1-6, wherein the cell housing comprises a negative bottom cover on a negative side and a positive cover on a positive side;
Preferably, the negative bottom cover is provided with a sealing ring, and the sealing ring is arranged at the edge clamping part of the negative bottom cover and the positive cover;
Preferably, the lithium primary button cell further comprises an electrolyte.
8. A method of making a lithium primary button cell according to any one of claims 1-7, comprising the steps of:
Stamping the negative electrode modification film in a negative electrode with a concave groove on the surface to form a precursor material; and then sequentially stacking the precursor material, the diaphragm and the anode to obtain a battery cell assembly, and packaging the battery cell assembly and the battery shell to obtain the lithium primary button battery.
9. The method according to claim 8, wherein the step of pressing the negative electrode finishing film into the negative electrode having the concave groove formed on the surface thereof further comprises leveling treatment;
Preferably, the battery case includes a negative bottom cover at a negative side and a positive cover at a positive side;
Preferably, the negative bottom cover is provided with a sealing ring, and the sealing ring is arranged at the edge clamping part of the negative bottom cover and the positive cover;
Preferably, the lithium primary button cell further comprises an electrolyte;
Preferably, the precursor material and the separator are sequentially punched in the negative bottom cover;
preferably, the diaphragm is in an inverted U shape, and two sides of the inverted U shape are bent towards the direction of the positive electrode;
preferably, the method further comprises injecting electrolyte after the sequential lamination.
10. An electronic device, characterized in that it comprises a lithium primary button cell according to any one of claims 1-7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202411045595.2A CN118841509A (en) | 2024-07-31 | 2024-07-31 | Lithium primary button cell, preparation method thereof and electronic equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202411045595.2A CN118841509A (en) | 2024-07-31 | 2024-07-31 | Lithium primary button cell, preparation method thereof and electronic equipment |
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| Publication Number | Publication Date |
|---|---|
| CN118841509A true CN118841509A (en) | 2024-10-25 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202411045595.2A Pending CN118841509A (en) | 2024-07-31 | 2024-07-31 | Lithium primary button cell, preparation method thereof and electronic equipment |
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| Country | Link |
|---|---|
| CN (1) | CN118841509A (en) |
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- 2024-07-31 CN CN202411045595.2A patent/CN118841509A/en active Pending
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