Electrochemical device and electronic device

Abstract

The invention relates to an electrochemical device and an electronic device. Specifically, the invention provides an electrochemical device which comprises a shell and a sealing assembly, and the shell is used for accommodating an electrode assembly; the sealing assembly comprises a pole and an annular part, the pole is electrically connected with the electrode assembly, and the annular part is configured to surround the pole; and the annular part comprises an annular metal part and an annular non-metal part, the annular metal part is hermetically connected with the shell, the annular non-metal part is arranged between the pole and the annular metal part and comprises a polymer material, and the polymer material comprises tetrafluoroethylene chain segments. The electrochemical device provided by the invention has improved sealing performance in a high-temperature and high-humidity environment.

Description

Electrochemical devices and electronic devices Technical Field

[0001] The present application relates to the field of energy storage, and in particular to an electrochemical device and an electronic device. Background Art

[0002] Electrochemical devices (e.g., lithium batteries) are one of the key technologies in my country's core basic industries. Due to their high voltage, high specific energy, long life, no memory effect, and no pollution, they play an important role in consumer electronic products (such as automobiles, medical devices, communications products, military industry, aerospace, etc.). With the expansion of the application of lithium batteries, people have put forward higher requirements for lithium-ion batteries, such as lighter and thinner, longer life, etc. However, lithium batteries usually use liquid electrolyte solutions, including organic solvents and lithium salts. When the lithium battery is not fully sealed (leakage rate is less than 1.0×10 -7 When the pressure is high (Pa·cubic decimeter / second), especially in extreme environments such as high temperature and high humidity, the electrolyte is prone to leakage and gas will escape, causing the electrolyte to "dry up" and the battery to fail.

[0003] In view of the above, there is a real need to provide a novel sealing assembly with improved sealing performance under high temperature and high humidity environments, as well as an electrochemical device and an electronic device using the sealing assembly.

[0004] Summary of the Invention

[0005] The present application attempts to solve at least one problem existing in the related art to at least some extent by providing an electrochemical device and an electronic device.

[0006] According to one aspect of the present application, the present application provides an electrochemical device, which includes a shell and a sealing assembly, wherein the shell is used to accommodate an electrode assembly; the sealing assembly includes a pole and an annular component, wherein the pole is electrically connected to the electrode assembly, and the annular component is configured to surround the pole; and the annular component includes an annular metal component and an annular non-metallic component, wherein the annular metal component is sealed with the shell, the annular non-metallic component is between the pole and the annular metal component and includes a polymer material, and the polymer material contains a tetrafluoroethylene segment.

[0007] By using polymer materials as sealing materials, the sealing performance of electrochemical devices is significantly improved, especially the sealing performance under high temperature and high humidity environments, and the structural design of thin electrochemical devices can be realized.

[0008] According to an embodiment of the present application, the molar percentage of fluorine atoms in the polymer material is not less than 37%.

[0009] According to an embodiment of the present application, the melting point or glass transition temperature of the polymer material is greater than 220°C.

[0010] According to an embodiment of the present application, the thermal weight loss of the polymer material at 360° C. is not greater than 1%. According to an embodiment of the present application, based on the mass of the annular non-metallic component, the mass percentage of the polymer material is greater than or equal to 90%.

[0011] According to an embodiment of the present application, the breakdown voltage of the polymer material at 50° C. is not less than 8 kV / 0.1 mm.

[0012] According to an embodiment of the present application, the polymer material further contains at least one of the following polar monomer units: epoxy vinyl ester, maleic anhydride, itaconic anhydride, citraconic anhydride or 5-norbornene-2,3-dicarboxylic anhydride.

[0013] Introducing polar monomer units into polymer materials can enhance the chemical bonding between the polymer material and the metal, further improving the sealing of electrochemical devices in high temperature and high humidity environments.

[0014] According to an embodiment of the present application, the polymer material further comprises at least one of the following monomer units: hexafluoropropylene, perfluoropropylene vinyl ether, or ethylene.

[0015] Introducing mobile monomer units with side chains or using some hydrogen atoms to replace fluorine atoms into polymer materials can reduce the melt viscosity of the polymer materials and enhance their fluidity, thereby further improving the sealing of electrochemical devices in high temperature and high humidity environments.

[0016] According to an embodiment of the present application, the mass swelling rate of the annular non-metallic component is less than or equal to 5%, and the volume swelling rate is less than or equal to 1.5%.

[0017] Controlling the mass swelling ratio and / or volume swelling ratio of the annular non-metallic component within the above range can further improve the sealing performance of the electrochemical device in a high temperature and high humidity environment.

[0018] According to an embodiment of the present application, the electrode assembly includes a tab, the pole is welded to the tab, and the distance between the welding point on the pole and the annular non-metallic component is a millimeter, and 0.05≤a≤0.7.

[0019] According to an embodiment of the present application, 0.1≤a≤0.4.

[0020] Since a high-temperature resistant polymer material is used as the annular non-metallic component, the distance between the welding point on the pole and the annular non-metallic component can be shortened without causing failure of the annular non-metallic component, thereby allowing the use of small-sized poles (for example, for thin batteries).

[0021] According to an embodiment of the present application, the distance between the welding point on the pole and the annular non-metallic component is smaller than the radius of the pole, and the radius of the pole is in the range of 0.1 mm to 2 mm.

[0022] According to an embodiment of the present application, the thickness of the electrochemical device is no greater than 4 mm.

[0023] According to another aspect of the present application, the present application provides an electronic device, which includes the electrochemical device according to the present application.

[0024] The present application significantly improves the sealing performance of electrochemical devices and electronic devices in high temperature and high humidity environments by using a specific annular non-metallic component.

[0025] Additional aspects and advantages of the present application will be described, shown, or explained in part in the following description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following briefly describes the drawings necessary to describe the embodiments of the present application or the prior art to facilitate the description of the embodiments of the present application. Obviously, the drawings described below only represent some of the embodiments of the present application. Those skilled in the art can, without requiring creative effort, derive drawings for other embodiments based on the structures illustrated in these drawings.

[0027] FIG1 shows a front view of a sealing assembly according to an embodiment of the present application.

[0028] FIG2 shows a cross-sectional view of a sealing assembly according to an embodiment of the present application.

[0029] FIG3 shows a top view of a sealing assembly according to an embodiment of the present application.

[0030] FIG4 shows an energy spectrum diagram according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] The embodiments of the present application will be described in detail below. The embodiments of the present application should not be interpreted as limiting the present application.

[0032] In the detailed description and claims, a list of items linked by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can contain a single element or multiple elements. Item B can contain a single element or multiple elements. Item C can contain a single element or multiple elements.

[0033] As used herein, "structural unit" refers to the smallest repeating unit in a polymeric material, which includes the main chain and the side chains.

[0034] As used herein, "segment" refers to the smallest motion unit composed of several structural units.

[0035] As used herein, "monomer unit" refers to a structural unit that is also called a monomer unit when, except for a change in electronic structure, the types of atoms and the number of each type of atoms are exactly the same as those of a monomer.

[0036] Electrochemical devices (e.g., lithium-ion batteries) have been widely used in various fields due to their superior performance. Electrochemical devices generally use liquid electrolytes, which require the electrochemical devices to have good sealing properties to prevent leakage. Electrochemical devices generally include a housing for accommodating an electrode assembly, wherein one electrode (usually the positive electrode) in the electrode assembly is connected to a conductor outside the electrochemical device through a conductive component (i.e., a pole) to power the electronic device. The housing can be formed by a stamping process, with holes reserved for sealing the poles. Since the housing is generally made of a conductive material (e.g., stainless steel) and is connected to another electrode (usually the negative electrode) in the electrode assembly, in order to electronically insulate the positive and negative electrodes and prevent leakage of the electrolyte, the poles and the housing need to be insulated and sealed. Methods for insulating and sealing the poles and the housing include metal-ceramic sealing, which is achieved by pre-sintering the ceramic material at a high temperature to achieve a seal between the housing and the poles. However, with the demand for thinner electrochemical devices, such as when used in consumer electronic products such as smart watches and smart glasses, this sealing process will fail. This is because in the metal-ceramic sealing process, the size of the sealing component is large, the corresponding pole size is large (for example, at least 6mm), and metal-glass sealing materials are usually used as sealing materials. When the electrochemical device becomes thinner, the pole size needs to be reduced accordingly. Since the expansion coefficients of metal and glass are similar, but the expansion coefficients of metal and glass differ from those of the pole (for example, aluminum) by more than 2 times, the mismatch in thermal expansion coefficients will make it difficult for the pole to conduct heat, and the glass near the welding point will easily expand and shatter at high temperatures, thereby destroying its sealing. This problem is particularly prominent in high temperature and high humidity environments.

[0037] In order to solve the above problems, the present application provides an electrochemical device, which includes a shell and a sealing assembly, wherein the shell is used to accommodate an electrode assembly; the sealing assembly includes a pole and an annular component, wherein the pole is electrically connected to the electrode assembly, and the annular component is configured to surround the pole; and the annular component includes an annular metal component and an annular non-metallic component, wherein the annular metal component is sealed with the shell, the annular non-metallic component is between the pole and the annular metal component and includes a polymer material, and the polymer material contains a tetrafluoroethylene segment.

[0038] Figures 1, 2, and 3 respectively illustrate a front view, a cross-sectional view, and a top view of a sealing assembly according to an embodiment of the present application. The sealing assembly is a coaxial structure comprising, from the inside out, a pole 2, an annular non-metallic component 1, and an annular metal component 3. The annular non-metallic component 1 is hermetically bonded to the pole 2 and the annular metal component 3. The annular non-metallic component 3 can be filled between the pole 2 and the annular metal component 3 using any suitable method (e.g., injection molding).

[0039] The tetrafluoroethylene segment has formula 1:

[0040] Where n is 5000 to 100000.

[0041] Although fluorine has a high electronegativity, from the chemical structure of the tetrafluoroethylene chain segment, the dipole moments are offset by each other, so it is a non-polar substance and does not produce obvious orientation forces. In other words, the dispersion force is the main force, which makes the two atoms forming the covalent bond close to each other, the bond length is short, and the bond energy is large, resulting in a higher melting point of the material. At the same time, the high electron density of fluorine causes the closely arranged fluorine atoms to have mutual repulsion and produce a steric effect, so that the molecular chain presents a helical structure conformation instead of the planar zigzag shape commonly seen in saturated polymers, which is conducive to more efficient stacking of molecular chains to form crystals. The reduction in the spacing between stacked chains increases the intermolecular force exponentially, thereby increasing the melting point of the material. As a result, at the instantaneous high temperature of 300°C to 400°C generated when the electrode column is electrically connected to the electrode assembly (for example, welding), the polymer material containing tetrafluoroethylene segments does not carbonize or decompose. Therefore, the present application significantly improves the sealing performance of the electrochemical device, especially the sealing performance under high temperature and high humidity environments, by using a polymer material containing tetrafluoroethylene segments as a sealing material, and can realize the structural design of a thin electrochemical device.

[0042] In some embodiments, the polymer material has a fluorine atomic percentage of no less than 37% by mole. In some embodiments, the polymer material has a fluorine atomic percentage of no less than 40% by mole. In some embodiments, the polymer material has a fluorine atomic percentage of no less than 45% by mole. In some embodiments, the polymer material has a fluorine atomic percentage of no less than 50% by mole.

[0043] In some embodiments, the polymeric material has a melting point or glass transition temperature greater than 220°C.

[0044] In some embodiments, the polymer material has a thermal weight loss of no greater than 1% at 360° C. In some embodiments, the non-metallic material has a thermal weight loss of no greater than 0.5% at 360° C. In some embodiments, the non-metallic material has a thermal weight loss of no greater than 0.2% at 360° C.

[0045] The glass transition temperature, melting point, and weight loss on heat of a material are inherent properties of the material and are related to the strength of the intermolecular forces between the chains in the material. When the material is amorphous, it has a glass transition temperature; when the material is crystalline, it has a melting point.

[0046] In some embodiments, the mass percentage of the polymer material is greater than or equal to 90% based on the mass of the annular non-metallic component. In some embodiments, the mass percentage of the polymer material is greater than or equal to 95% based on the mass of the annular non-metallic component.

[0047] In some embodiments, the polymer material has a breakdown voltage of no less than 8 kV / 0.1 mm at 50° C. In some embodiments, the polymer material has a breakdown voltage of no less than 10 kV / 0.1 mm at 50° C.

[0048] In some embodiments, the insulation resistance of the polymer material at 50°C is not less than 10 12 Ω·cm.

[0049] The breakdown voltage and insulation resistance of polymer materials reflect the insulating properties of the material, which are related to factors such as the symmetry of the molecular chain and the polarity of the groups contained. Tetrafluoroethylene segments, due to their highly symmetrical non-polar nature, have excellent insulating properties. Therefore, polymer materials containing tetrafluoroethylene segments can effectively prevent short circuits between the positive and negative electrodes in electrochemical devices, improving their safety performance.

[0050] In some embodiments, the polymeric material further comprises at least one of the following polar monomer units: epoxy vinyl ester, maleic anhydride, itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride.

[0051] Introducing polar monomer units into polymer materials can enhance the chemical bonding between the polymer and metal. Therefore, polymer materials containing tetrafluoroethylene segments and polar monomer units can be used as sealing materials between the electrode and the annular metal component, preventing electrolyte leakage through the interface between the annular non-metallic component and the annular metal component or the electrode, further improving the sealing of electrochemical devices in high-temperature and high-humidity environments.

[0052] In some embodiments, the polymeric material further comprises at least one of the following monomeric units: hexafluoropropylene, perfluoropropylene vinyl ether, or ethylene.

[0053] Introducing a mobile monomer unit with a branched chain or using some hydrogen atoms to replace fluorine atoms in a polymer material can reduce the melt viscosity of the polymer material, enhance its fluidity, make it easier to process and shape, and reduce defects in the production process of sealing components. From a microscopic perspective, the polymer material can better rivet with the microscopic undulations on the surface of the metal (pole or annular metal component) to form a mechanically interlocking physical riveted structure, thereby further improving the sealing of the electrochemical device in high temperature and high humidity environments. The mobile monomer unit can also cooperate with the conducting monomer unit to further enhance the adhesion of the polymer material, thereby further improving the sealing of the electrochemical device in high temperature and high humidity environments.

[0054] In some embodiments, the polymer material includes at least one of fluororesin, polyimide, or polyphenylene sulfide.

[0055] In some embodiments, the fluororesin includes at least one of polytetrafluoroethylene, perfluoropropylene-tetrafluoroethylene, or ethylene-tetrafluoroethylene copolymer.

[0056] In some embodiments, the mass swelling ratio of the annular non-metallic component is less than or equal to 5%. In some embodiments, the mass swelling ratio of the annular non-metallic component is less than or equal to 3%. In some embodiments, the mass swelling ratio of the annular non-metallic component is less than or equal to 1%.

[0057] In some embodiments, the volumetric swelling ratio of the annular non-metallic component is less than or equal to 1.5%. In some embodiments, the volumetric swelling ratio of the annular non-metallic component is less than or equal to 1%. In some embodiments, the volumetric swelling ratio of the annular non-metallic component is less than or equal to 0.5%.

[0058] Polymer materials will swell in the electrolyte because the electrolyte contains polar organic solvents. When the main chain of the polymer material contains polar groups, the interaction between the organic solvent and the polymer material is greater than the interaction between the molecular chains of the polymer material, causing the polymer material to easily approach the organic solvent and thus swell. The interaction between the organic solvent and the polymer material is also greater than the interaction between the metal and the polymer material, thereby preventing the bonding interface between the polymer material and the metal from being penetrated by solvent molecules, thereby preventing electrolyte leakage. The tetrafluoroethylene segment is easy to crystallize due to its high regularity, and it has a highly symmetrical structure and is a non-polar segment, so it can effectively improve the resistance of the polymer material to electrolyte swelling. When the mass swelling rate and / or volume swelling rate of the annular non-metallic component is within the above range, the electrochemical device has improved sealing in a high temperature and high humidity environment.

[0059] In some embodiments, the electrode assembly includes a tab, the pole is welded to the tab, and the distance between the welding point position on the pole (as shown by the dotted line in Figure 3) and the annular non-metallic component is a millimeter, and 0.05≤a≤0.7. In some embodiments, 0.1≤a≤0.4. In some embodiments, a is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or within the range of any two of the above values. When the distance a value is too small, the laser welding itself has a width, which will cause welding to the annular seal and cause poor packaging; when the distance a value is too large, it means that the welding area is smaller, there is a probability of cold welding, the pole and the tab are not firmly welded, and the structural stability of the battery is reduced.

[0060] Since a high-temperature resistant polymer material is used as the annular non-metallic component, the distance between the welding point on the pole and the annular non-metallic component can be shortened without causing failure of the annular non-metallic component, thereby allowing the use of small-sized poles (for example, for thin batteries).

[0061] In some embodiments, the pole post and the tab are welded together by laser.

[0062] In some embodiments, the distance between the weld point on the pole and the annular non-metallic component is less than the radius of the pole. In some embodiments, the radius of the pole is in the range of 0.1 mm to 2 mm. In some embodiments, the radius of the pole is 0.1 mm, 0.3 mm, 0.5 mm, 0.8 mm, 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, or a range consisting of any two of the foregoing values.

[0063] In some embodiments, the thickness of the electrochemical device is no greater than 4 mm. In some embodiments, the thickness of the electrochemical device is no greater than 3.6 mm. In some embodiments, the thickness of the electrochemical device is no greater than 3 mm. The sealing assembly design of the present application is particularly suitable for thin electrochemical devices having the above thicknesses.

[0064] In the electrochemical device of the present application, the electrode assembly includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode.

[0065] In some embodiments, the positive electrode includes a positive electrode active material layer and a positive electrode current collector.

[0066] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductor.

[0067] In some embodiments, the positive electrode active material may include at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganese oxide, spinel lithium nickel manganese oxide, or lithium titanate.

[0068] In some embodiments, the positive electrode binder may include a binder polymer such as, but not limited to, at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane.

[0069] In some embodiments, any conductive material can be used as the positive electrode conductive agent, as long as it does not cause chemical changes. Examples of positive electrode conductive agents include, but are not limited to, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metal-based materials such as metal powders or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0070] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.

[0071] In some embodiments, the negative electrode includes a negative active material layer and a negative current collector.

[0072] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductor.

[0073] In some embodiments, the negative electrode active material may include a material that reversibly intercalates and deintercalates lithium ions, lithium metal, a lithium metal alloy, or a transition metal oxide. In some embodiments, the negative electrode active material includes at least one of a carbon material or a silicon material, the carbon material includes at least one of graphite and hard carbon, and the silicon material includes at least one of silicon, a silicon oxide, a silicon carbon compound, or a silicon alloy.

[0074] In some embodiments, the negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, polyimide, polyamide-imide, polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, water-based acrylic resin, polyvinyl formal, or styrene-acrylic copolymer resin.

[0075] In some embodiments, any conductive material can be used as the negative electrode conductive material as long as it does not cause chemical changes. In some embodiments, the negative electrode conductive material includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, conductive graphite, or graphene.

[0076] In some embodiments, the negative electrode current collector may be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0077] There is no particular limitation on the material and shape of the isolation membrane used in the electrochemical device of the present application, and it may be any technology disclosed in the prior art. In some embodiments, the isolation membrane includes a polymer or inorganic substance formed from a material that is stable to the electrolyte of the present application. In some embodiments, the isolation membrane may include a substrate layer and a surface treatment layer. In some embodiments, the substrate layer is a non-woven fabric, a film or a composite film having a porous structure. In some embodiments, the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. In some embodiments, the material of the substrate layer includes at least one of a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane.

[0078] In some embodiments, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0079] In some embodiments, the inorganic layer includes inorganic particles and a binder, wherein the inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0080] In some embodiments, the polymer layer comprises a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0081] The electrochemical device of the present application further comprises an electrolyte. The electrolyte that can be used in the present application can be an electrolyte known in the prior art.

[0082] In some embodiments, the electrolyte includes an organic solvent, an electrolyte salt and an optional additive. The organic solvent of the electrolyte according to the present application may be any organic solvent known in the prior art that can be used as a solvent for the electrolyte. There is no restriction on the electrolyte used in the electrolyte according to the present application, and it may be any electrolyte known in the prior art. The additive of the electrolyte according to the present application may be any additive known in the prior art that can be used as an electrolyte additive. In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate. In some embodiments, the organic solvent includes an ether solvent, for example, including at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME). In some embodiments, the electrolyte salt may be a lithium salt, a sodium salt, etc. In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalatoborate) LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB). In some embodiments, the sodium salt includes, but is not limited to, at least one of NaClO4, NaPF6, NaBF4, Na(FSO2)2N, Na(CF3SO2)2N, Na(C2F5SO2)2N, NaCF3SO3, NaSbF6, NaBC4O8, NaFSI, NaTFSI, sodium salts of lower aliphatic carboxylates, NaAlCl4, NaPO2F2, or Na2PO3F.

[0083] In some embodiments, the electrochemical device of the present application includes, but is not limited to, all types of primary batteries, secondary batteries, or capacitors. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical device is a sodium ion battery.

[0084] The present application further provides an electronic device, which includes the electrochemical device according to the present application.

[0085] The electronic devices or devices of the present application are not particularly limited. In some embodiments, the electronic devices of the present application include, but are not limited to, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0086] The preparation process of electrochemical devices and electronic devices is well known to those skilled in the art and is not particularly limited in this application. For example, the battery can be prepared by the following method: the positive electrode and the negative electrode are overlapped via an isolation membrane, and are wound, folded, and the like as needed to form a bare cell. Stainless steel is selected as the packaging shell, and the bare cell is placed inside the packaging shell. The aluminum tabs of the bare cell and the poles in the sealing assembly are laser welded together to achieve electronic conduction between the poles and the bare cell. The steel shell cover and the shell are connected by laser welding to achieve sealing of the battery. There are through holes on the surface of the steel shell, and the electrolyte is injected into the interior of the cell through the through holes. After sufficient infiltration, the cell is activated under certain current and voltage conditions, and the preparation of the battery is completed.

[0087] The preparation of lithium-ion batteries is described below using lithium-ion batteries as an example and in combination with specific embodiments. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0088] Example

[0089] The following describes the performance evaluation of the lithium-ion battery according to the embodiments and comparative examples of the present application.

[0090] 1. Preparation of lithium-ion batteries

[0091] 1. Preparation of negative electrode

[0092] The negative electrode active material graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 0.7, and stirred evenly. The negative electrode slurry was evenly coated on the negative electrode current collector copper foil. The weight of the active material on the electrode sheet was 95g / m 2Then dry it at 110℃ to obtain the negative electrode. After the above steps are completed, the single-sided coating of the negative electrode is completed. After that, the same steps are performed on the back of the negative electrode in the same way to obtain a double-sided coated negative electrode. After the coating is completed, the negative electrode is cold pressed to 1.7g / cm 3 The compaction density is , and the negative electrode is obtained.

[0093] 2. Preparation of positive electrode

[0094] The positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 0.75, and stirred evenly. The positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil. The weight of the active material on the electrode sheet was 180g / m 2 . Dry at 90℃ to obtain the positive electrode sheet. After the above steps are completed, the single-sided coating of the positive electrode sheet has been completed. After that, the same steps are performed on the back of the positive electrode sheet in the same way to obtain a double-sided coated positive electrode sheet. After the coating is completed, the positive electrode sheet is cold pressed to 4.1g / cm 3 The compaction density is , and the positive electrode is obtained.

[0095] 3. Preparation of electrolyte

[0096] In a dry argon atmosphere, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC=30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15M.

[0097] 4. Preparation of electrode assembly

[0098] Polyethylene (PE) with a thickness of 15 μm is selected as the isolation membrane. The positive electrode sheet, isolation membrane, and negative electrode sheet are stacked in order, so that the isolation membrane is placed between the positive and negative electrodes to play an isolation role. Then the stacked electrode sheets and isolation membrane are wound to obtain an electrode assembly.

[0099] 5. Preparation of sealing components

[0100] When a polymer material containing tetrafluoroethylene segments is used as a sealing material, tetrafluoroethylene, a polar monomer and / or a fluidity enhancing monomer are in situ polymerized according to a certain feed ratio to obtain the sealing material.

[0101] A hollow steel piece with a height of 0.5 mm, an outer diameter of 2.4 mm, and an inner diameter of 1.6 mm is made by mechanical stamping and used as an annular metal sheet (annular metal component). Aluminum is used as the pole, which is a cylinder with a diameter of 0.8 mm and a length of 1.2 mm. When using a sealing material that does not contain polar monomer units, the surface of the annular metal sheet and the pole is subjected to a 150-mesh sandblasting treatment. The pole is then placed in the center of the annular metal sheet. According to the settings of the following embodiments or comparative examples, the sealing material is filled into the gap between the two and sintered at a certain temperature for 30 minutes (the specific materials and their sintering temperatures are shown in the table below) to form an annular non-metallic component. It is then naturally cooled to obtain a sealing assembly.

[0102] The model of tetrafluoroethylene PTFE is POLYFLON M-532 from Dakin.

[0103] The model of polytetrafluoroethylene PFA is Dakin's Neoflon AP-231SH.

[0104] The model of ethylene-tetrafluoroethylene copolymer ETFE is NEOFLON EP-506 produced by Dakin Company.

[0105] 6. Packaging of lithium-ion batteries

[0106] The length, width and thickness of the battery cell are respectively 24mm, 19mm and 4.0mm. The electrode assembly is placed inside the bare battery cell, and the aluminum tabs of the battery cell and the poles of the sealing assembly are laser welded. In the embodiments or comparative examples in Tables 1 to 3, the distance between the welding point position on the pole and the annular non-metallic component is 0.3mm. In the embodiment in Table 4, the distance between the welding point position on the pole and the annular non-metallic component is set as required. The bare battery cell is placed inside a stainless steel shell, and the shell cover and the shell are connected by laser welding. A through hole with a diameter of 0.8mm is reserved on the surface of the shell, and 0.8g of electrolyte is injected into the interior of the battery cell through the through hole. After operations such as formation (charging to 3.3V with a constant current of 0.02C, and then charging to 3.6V with a constant current of 0.1C), a soft-pack lithium-ion battery with a battery thickness of 4mm is obtained.

[0107] 2. Test Method

[0108] 1. Energy dispersive spectrum (EDS) test method

[0109] The micromorphology of the doped solid electrolyte samples was analyzed using a Phenom Prox scanning electron microscope, and the distribution of each element in the sample was obtained by EDS energy spectrum testing.

[0110] 2. Test method for volume swelling performance

[0111] The electrolyte composition is as follows: ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC): ethyl propionate (EP) = 30:10:30:30, and the solute is 1 mol / L lithium hexafluorophosphate.

[0112] Weigh 0.2-2g of sample and dry it at 80℃. Soak the sample in 60℃ electrolyte for 7 days (electrolyte mass: sealing material sample mass = 50:1). Then use the density component of Mettler balance to measure the volume of the sample to be tested. The reference medium is deionized water. The density is recorded as ρ0 (g / cm 3 Wipe off the electrolyte on the sample surface, weigh the sample in air and record its mass as Wair, and the mass weighed in the reference medium as Wref. Calculate the volume swelling ratio ΔV of the sample using the following formula: ΔV = 0.99985 × (Wair - Wref) / (ρ0 - 0.0012) × 100%.

[0113] Three parallel samples were tested for each sample, and the average value was taken.

[0114] 3. Test method for mass swelling performance

[0115] The electrolyte composition is as follows: ethylene carbonate (EC): propylene carbonate (PC): diethyl carbonate (DEC): ethyl propionate (EP) = 30:10:30:30, and the solute is 1 mol / L lithium hexafluorophosphate.

[0116] Weigh 0.2-2g of sample and dry it at 80°C. Record the weight as W1. Soak the sample in a 60°C electrolyte for 7 days (electrolyte mass: sealing material sample mass = 50:1). Wipe off the electrolyte on the sample surface and weigh it. Record it as W2. Then, place the sample to be tested in a vacuum oven at 130°C and dry it to constant weight (≥3 hours). Record the weight as W3. Calculate the mass swelling ratio ΔW of the sample using the following formula: ΔW = (W3 - W1) / W1 × 100%.

[0117] Three parallel samples were tested for each sample, and the average value was taken.

[0118] 4. Test method of adhesion

[0119] The test was conducted using the method specified in "4. Nail head retention test" in GBT3098.18-2004.

[0120] Remove the terminal from the battery and apply axial load from one side of the terminal until it is completely ejected. Place the terminal in a fixture with a punch diameter 0.2 mm smaller than the terminal diameter. Apply the load directly to the terminal along its axis without impact until the terminal begins to move against the annular metal component. The test speed should be no less than 7 mm / min and no more than 13 mm / min. Record the maximum load before the terminal begins to move as the adhesion load for that terminal.

[0121] 5. Test method for high temperature and high humidity test pass rate

[0122] The high-temperature, high-humidity test is conducted at an ambient temperature of 65-75°C and a relative humidity of 85-95%. A fully charged lithium-ion battery is placed in a high-temperature, high-humidity environment for seven days. The battery then passes the test if its voltage drop is less than 0.5V. Fifty replicates of each sample are tested, and the pass rate is recorded.

[0123] 3. Test Results

[0124] This application tested the molar percentages of carbon and fluorine in three polymer materials: ethylene-tetrafluoroethylene copolymer ETFE (Dakin's NEOFLON EP-506) contained 43.85% carbon and 56.15% fluorine; ethylene-tetrafluoroethylene copolymer ETFE (Dupont's TEFZEL-200) contained 42.44% carbon and 57.56% fluorine; and the sample of Example 3-1 contained 46.75% carbon and 52.25% fluorine. Figure 4 shows the energy spectra of Examples 1-3.

[0125] Table 1 shows the effect of polymer materials in annular non-metallic components on the high temperature and high humidity test pass rate of lithium-ion batteries.

[0126] Table 1

[0127] The sealing materials used in Comparative Examples 1-1 and 1-2 are polymer materials without tetrafluoroethylene segments, which have low melting points or glass transition temperatures. Furthermore, the sealing material in Comparative Example 1-1 experiences very high thermal weight loss at 360°C, resulting in a very low pass rate for high-temperature and high-humidity testing of lithium-ion batteries. Comparative Example 1-3 uses glass as an annular non-metallic component, which is susceptible to expansion and fracture at the transient high temperatures generated during the welding process between the electrode and the tab, resulting in a low pass rate for high-temperature and high-humidity testing of lithium-ion batteries.

[0128] The sealing material used in Examples 1-1 to 1-5 is a polymer material containing tetrafluoroethylene segments, with a melting point or glass transition temperature greater than 220°C and a thermal weight loss of no more than 1% at 360°C. Using this sealing material as an annular non-metallic component can significantly improve the pass rate of high-temperature and high-humidity testing for lithium-ion batteries.

[0129] In addition, when the mass swelling rate of the annular non-metallic component is no more than 5% and the volume swelling rate is no more than 1.5%, the annular non-metallic component has good sealing performance, which helps to improve the high temperature and high humidity test pass rate of lithium-ion batteries.

[0130] Table 2 shows the effect of polar monomer units in the polymer material of the annular non-metallic component on the high temperature and high humidity test pass rate of lithium-ion batteries. Except for the parameters listed in Table 2, the settings of Examples 2-1 to 2-3 are the same as those of Example 1-1.

[0131] Table 2

[0132] The results show that when the polymer material containing tetrafluoroethylene chain segments further includes polar monomer units, the adhesion between the annular non-metallic component and the pole can be improved, thereby further improving the high temperature and high humidity test pass rate of lithium-ion batteries.

[0133] Table 3 shows the effect of the flowable monomer units in the polymer material of the annular non-metallic component on the high temperature and high humidity test pass rate of the lithium-ion battery. Except for the parameters listed in Table 3, the settings of Examples 3-1 to 3-7 are the same as those of Example 1-1.

[0134] Table 3

[0135] The results show that when the polymer material containing tetrafluoroethylene chain segments further includes a fluid monomer unit, the melt viscosity of the polymer material decreases and the fluidity increases, thereby further improving the high temperature and high humidity test pass rate of the lithium-ion battery.

[0136] When the polymer material containing tetrafluoroethylene chain segments further contains polar monomer units and fluid monomer units, the bonding force between the annular non-metallic component and the metal can be further improved, thereby further improving the high temperature and high humidity test pass rate of lithium-ion batteries.

[0137] Table 4 shows the effect of the distance a between the welding point position on the terminal and the annular non-metallic component on the high temperature and high humidity test pass rate of lithium-ion batteries. Except for the parameters listed in Table 4, the settings of Examples 4-1 to 4-7 are the same as those of Example 3-1.

[0138] Table 4

[0139] The results show that when the distance between the welding point on the pole and the annular non-metallic part is in the range of 0.05mm to 0.7mm, it helps to further improve the high temperature and high humidity test pass rate of lithium-ion batteries.

[0140] References throughout this specification to "an embodiment," "part of an embodiment," "one embodiment," "another example," "an example," "a specific example," or "a portion of an example" mean that at least one embodiment or example in this application includes the specific features, structures, materials, or characteristics described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as, "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "an example," are not necessarily references to the same embodiment or example in this application. In addition, the specific features, structures, materials, or characteristics described herein may be combined in any suitable manner in one or more embodiments or examples.

[0141] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. An electrochemical device comprising a housing and a sealing assembly, wherein: The housing is used to accommodate the electrode assembly; The sealing assembly comprises: A pole, the pole being electrically connected to the electrode assembly; and an annular member configured to surround the pole and comprising: an annular metal component, the annular metal component being sealingly connected to the housing; and An annular non-metallic component is between the pole and the annular metal component and comprises a polymer material containing tetrafluoroethylene segments.

2. The electrochemical device according to claim 1, wherein the polymer material satisfies at least one of the following conditions: (1) The molar percentage of fluorine atoms in the polymer material is not less than 37%; (2) The melting point or glass transition temperature of the polymer material is greater than 220°C; (3) The thermal weight loss of the polymer material at 360°C is not greater than 1%; (4) Based on the mass of the annular non-metallic component, the mass percentage of the polymer material is greater than or equal to 90%; (5) The breakdown voltage of the polymer material at 50°C is not less than 8 kV / 0.1 mm.

3. The electrochemical device according to claim 1, wherein the polymer material further comprises at least one of the following polar monomer units: epoxy vinyl ester, maleic anhydride, itaconic anhydride, citraconic anhydride or 5-norbornene-2,3-dicarboxylic anhydride.

4. The electrochemical device according to any one of claims 1 to 3, wherein the polymer material further comprises at least one of the following monomer units: hexafluoropropylene, perfluoropropylene vinyl ether or ethylene. 5 . The electrochemical device according to claim 1 , wherein the mass swelling rate of the annular non-metallic component is less than or equal to 5%, and the volume swelling rate is less than or equal to 1.5%.

6. The electrochemical device according to claim 1, wherein the electrode assembly comprises a tab, the pole post is welded to the tab, and the distance between the welding point position on the pole post and the annular non-metallic component is a millimeter, and 0.05≤a≤0.

7. The electrochemical device according to claim 6 , wherein 0.1≤a≤0.

4.

8. The electrochemical device according to claim 1, wherein the distance between the welding point position on the electrode column and the annular non-metallic component is smaller than the radius of the electrode column, and the radius of the electrode column is in the range of 0.1 mm to 2 mm.

9. The electrochemical device according to claim 1, wherein the thickness of the electrochemical device is not greater than 4 mm.

10. An electronic device comprising the electrochemical device according to any one of claims 1 to 9.

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