CN117981148A

CN117981148A - Electrochemical device and electronic device

Info

Publication number: CN117981148A
Application number: CN202380013365.5A
Authority: CN
Inventors: 侯天昊; 杨建辉
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2023-03-31
Filing date: 2023-03-31
Publication date: 2024-05-03

Abstract

The present application relates to an electrochemical device and an electronic device. Specifically, the present application provides an electrochemical device comprising a case for accommodating an electrode assembly including a tab, and a sealing assembly; the seal assembly includes a pole post welded to the tab to create an electrical connection and an annular member configured to surround the pole post; and the annular component comprises an annular metal component and an annular non-metal component, wherein the annular metal component is in sealing connection with the housing, the annular non-metal component is between the pole and the annular metal component and comprises a polymeric material comprising at least one of a fluororesin, a polyimide, a polyphenylene sulfide or a polyetheretherketone; and the distance between the welding position on the pole and the annular nonmetallic part is a millimeter, and a is more than or equal to 0.05 and less than or equal to 0.7. The electrochemical device of the present application has good sealability and energy density, and has significantly improved yield, which can reduce costs.

Description

Electrochemical device and electronic device

Technical Field

The application relates to the field of energy storage, in particular to an electrochemical device and an electronic device.

Background

Electrochemical devices (e.g., lithium batteries) are one of the key technologies of the core basic industry in China, and play an important role in consumer electronics (such as the fields of automobiles, medical equipment, communication products, military industry, aerospace and the like) due to the characteristics of high voltage, high specific energy, long service life, no memory effect, no pollution and the like. With the expansion of the application of lithium batteries, higher requirements are put on lithium ion batteries, such as lighter and thinner batteries, longer service life, etc. However, lithium batteries typically use liquid electrolyte solutions, including organic solvents and lithium salts. When the lithium battery is not fully sealed (leakage rate is less than 1.0X10 ^-7 Pa.cubic centimeter per second), the electrolyte is easy to leak and gas can escape, resulting in "dry out" of the electrolyte and failure of the battery. In addition, the common sealing process has the problems of higher cost, low yield, larger material loss and the like when being applied to a thin battery.

In view of the foregoing, it is desirable to provide a novel sealing assembly, and an electrochemical device and an electronic device using the same.

Disclosure of Invention

The present application seeks to address at least one of the problems existing in the related art to at least some extent by providing an electrochemical device and an electronic device.

According to one aspect of the present application, there is provided an electrochemical device including a case for accommodating an electrode assembly, the electrode assembly including a tab; the seal assembly includes a pole post welded to the tab to create an electrical connection and an annular member configured to surround the pole post; and the annular component comprises an annular metal component and an annular non-metal component, wherein the annular metal component is in sealing connection with the housing, the annular non-metal component is between the pole and the annular metal component and comprises a polymeric material comprising at least one of a fluororesin, a polyimide, a polyphenylene sulfide or a polyetheretherketone; and the distance between the welding position on the pole and the annular nonmetallic part is a millimeter, and a is more than or equal to 0.05 and less than or equal to 0.7.

By using a specific polymer sealing material and controlling the welding position on the post, the sealing assembly has good sealability, and at the same time, the electrochemical device has good energy density, which can realize structural design of a thin-type electrochemical device. The design of the application can obviously improve the yield of the electrochemical device, reduce the material loss and reduce the cost.

According to an embodiment of the application, the mass of the polymeric material is greater than or equal to 90% based on the mass of the annular nonmetallic part.

According to the embodiment of the application, 0.1.ltoreq.a.ltoreq.0.3.

According to an embodiment of the application, the cross-sectional area of the annular nonmetallic part is S1 mm ², the cross-sectional area of the polar post is S2mm ², and S1 and S2 satisfy: (S1+S2)/S2 is more than or equal to 1.04 and less than or equal to 16.2.

According to embodiments of the present application, 1.3.ltoreq.S1+S2)/S2.ltoreq.4.3.

According to an embodiment of the application, 0.07.ltoreq.S1.ltoreq.7.6.

According to an embodiment of the application, 0.5.ltoreq.S2.ltoreq.1.6.

When the cross sectional areas of the annular nonmetallic part and the polar post meet the relation, the size distribution of the annular nonmetallic part and the polar post is more reasonable, the yield of the electrochemical device can be further improved, and the cost is reduced.

According to an embodiment of the present application, the width of the annular nonmetallic member is W1 mm, and 0.03.ltoreq.W1.ltoreq.1. When W1 is within the above range, the width of the annular nonmetallic member is as small as possible while taking into consideration the insulation property.

According to an embodiment of the application, the annular metal part has a flange edge with a width W2 mm and 0.01.ltoreq.W2.ltoreq.1.6.

When the annular metal part is provided with the flange edge, and the width of the flange edge is in the range, the insulation and welding rate of the annular metal part and the shell can be guaranteed, the yield of the electrochemical device can be further improved, and the cost is reduced.

According to an embodiment of the application, the glass transition temperature of the nonmetallic material is greater than 200 ℃.

According to an embodiment of the application, the non-metallic material has a melting point of greater than 200 ℃.

According to an embodiment of the application, the non-metallic material has a thermal weight loss of not more than 1% at 360 ℃.

When the glass transition temperature, the melting point or the thermal weight loss at 360 ℃ of the nonmetallic material is within the above range, the nonmetallic material is not carbonized or decomposed at the instant high temperature generated by welding the pole and the pole lug, and an excellent sealing effect can be realized.

According to an embodiment of the present application, the non-metallic material has a coefficient of thermal expansion of no greater than 8X 10 ^-5 cm/cm/. Degree.C.

When the thermal expansion coefficient of the nonmetallic material is in the range, the thermal expansion coefficient of the nonmetallic material is not greatly different from that of the polar post, carbonization or decomposition can not occur at the instant high temperature generated by welding the polar post and the polar lug, the yield of the electrochemical device can be improved, the material loss is reduced, and the cost is reduced.

According to an embodiment of the application, the distance between the welding location on the pole and the annular nonmetallic part is smaller than the radius of the pole, which is in the range of 0.1mm to 2 mm.

According to an embodiment of the present application, the thickness of the electrochemical device is not more than 4mm.

According to another aspect of the present application, there is provided an electronic device comprising the electrochemical device according to the present application.

The present application provides a novel sealing assembly having excellent sealability by using a specific annular nonmetallic member and controlling the welding position of a tab and a post, and an electrochemical device and an electronic device using the sealing assembly have significantly improved yield, thereby reducing material loss and cost.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the application.

Drawings

The drawings that are necessary to describe embodiments of the present application or the prior art will be briefly described below in order to facilitate the description of the embodiments of the present application. It is apparent that the drawings in the following description are only a few embodiments of the application. It will be apparent to those skilled in the art that other embodiments of the drawings may be made in accordance with the structures illustrated in these drawings without the need for inventive faculty.

Fig. 1 illustrates a front view of a seal assembly according to an embodiment of the present application.

Fig. 2 illustrates a cross-sectional view of a seal assembly according to an embodiment of the present application.

Fig. 3 illustrates a top view of a seal assembly according to an embodiment of the present application.

Fig. 4 shows a schematic view of a seal assembly in connection with a housing according to an embodiment of the application.

Fig. 5 shows a schematic diagram of a prior art riveting process.

Detailed Description

Embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the application.

In the detailed description and claims, a list of items connected by the term "at least one of" may 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 A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.

Electrochemical devices (e.g., lithium ion batteries) have been widely used in various fields due to their superior performance. Electrochemical devices generally use a liquid electrolyte, which requires good sealability to prevent leakage of the liquid. Electrochemical devices generally include a case for accommodating an electrode assembly, one electrode (typically, a positive electrode) in the electrode assembly being connected to a conductor outside the electrochemical device through a conductive member (i.e., a post), thereby powering the electronic device. The shell can be formed by adopting a stamping forming process, and a hole site of the sealing pole is reserved. Since the housing is typically a conductive material (e.g., stainless steel) and is connected to the other electrode (typically the negative electrode) in the electrode assembly, an insulating and sealing bond is required between the post and the housing in order to electrically insulate the positive and negative electrodes and avoid leakage of electrolyte. The method for insulating, sealing and bonding the pole and the shell mainly comprises the following two steps: a metal-glass seal by sintering a glass material at a high temperature in advance to achieve a seal between the housing and the post; and a rivet seal, which requires more than two layers of plastic insulating gaskets. However, with the demand for thinning electrochemical devices, such as in consumer electronic products including smart watches and smart glasses, both sealing processes may fail. This is because in a metal-glass sealing process, the seal assembly is large in size, the corresponding pole is large in size (e.g., at least 6 mm), and glass is generally used as the sealing material. When the electrochemical device is thinned, it is necessary to correspondingly reduce the size of the electrode post. Because the expansion coefficients of metal and glass are similar, but the expansion coefficients of metal and glass are different by more than 2 times from those of a pole (such as aluminum), the mismatch of the thermal expansion coefficients can lead to the difficulty in heat conduction of the pole, and the ceramic/glass close to a welding position is easy to expand and crack at high temperature, so that the tightness of the ceramic/glass is damaged, the yield is lower, and the production cost is increased. In the riveting sealing process, a multi-layer riveting structure is generally required, which uses a T-shaped polar post, and at least two layers of sealing gaskets are required to ensure the sealing and insulation of the battery. When the electrochemical device is thinned, the thickness of the electrode post cannot be thinned, resulting in excessive space occupied by inactive substances, thereby reducing the energy density of the electrochemical device. Moreover, the riveting sealing process is complex, and the manufacturing cost is high.

In order to solve the above problems, the present application provides an electrochemical device including a case for accommodating an electrode assembly, the electrode assembly including a tab, and a sealing assembly; the seal assembly includes a pole post welded to the tab to create an electrical connection and an annular member configured to surround the pole post; and the annular component comprises an annular metal component and an annular non-metal component, wherein the annular metal component is in sealing connection with the housing, the annular non-metal component is between the pole and the annular metal component and comprises a polymeric material comprising at least one of a fluororesin, a polyimide, a polyphenylene sulfide or a polyetheretherketone; and the distance between the welding position on the pole and the annular nonmetallic part is a millimeter, and a is more than or equal to 0.05 and less than or equal to 0.7.

Fig. 1,2 and 3 show a front view, a cross-sectional view and a top view, respectively, of a seal assembly according to an embodiment of the present application, wherein the seal assembly is of a coaxial structure and comprises a pole 2, an annular nonmetallic part 1 and an annular metallic part 3 from inside to outside. The annular nonmetallic part 1 is hermetically bonded with the pole post 2 and the annular metallic part 3. The annular non-metal part 3 may be filled between the pole 2 and the annular metal part 3 in any suitable manner (e.g. injection moulding process, etc.). The pole 2 is welded to the tab of the electrode assembly, wherein the welding position on the pole is shown by the broken line in fig. 3, and the distance between the welding position and the annular nonmetallic part 1 is a.

The high electron density of fluorine in the fluororesin causes the closely arranged fluorine atoms to have a mutual repulsive force and generate a steric effect, so that the molecular chains are in a spiral structure conformation rather than the planar zigzag shape common in the saturated polymer, which is beneficial to more efficient stacking of the molecular chains to form crystals. The decrease in the spacing distance between the stacked chains multiplies the intermolecular forces and thus increases the melting point of the material. Thus, the fluororesin is not carbonized or decomposed at a high temperature of 300 to 400 ℃ at the moment of welding the tab to the tab, and a sealing effect can be achieved. Likewise, polyimide, polyphenylene sulfide and polyether-ether-ketone also have high temperature resistance, and can be kept stable at high temperature generated by welding, so that sealing effect is realized.

Because of the use of high temperature resistant polymeric materials as the annular nonmetallic components, the distance between the weld locations on the pole and the annular nonmetallic components can be shortened without causing failure of the annular nonmetallic components, thereby allowing the use of small-sized poles (e.g., for thin-type batteries).

In some embodiments, 0.1.ltoreq.a.ltoreq.0.3. In some embodiments, a is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or a range consisting of any two of the foregoing values.

In some embodiments, the mass of the polymeric material is greater than or equal to 90% based on the mass of the annular nonmetallic component. In some embodiments, the mass of the polymeric material is greater than or equal to 95% based on the mass of the annular nonmetallic component.

In some embodiments, the fluororesin comprises at least one of polytetrafluoroethylene or an ethylene-tetrafluoroethylene copolymer.

In some embodiments, the relative molecular mass of polytetrafluoroethylene is in the range of 5000-500000.

In some embodiments, the relative molecular mass of the ethylene-tetrafluoroethylene copolymer is in the range of 5000-500000.

Polytetrafluoroethylene and ethylene-tetrafluoroethylene copolymer contain tetrafluoroethylene chain segments, and dipole moments are offset each other according to the chemical structure of the copolymer, so the copolymer belongs to nonpolar substances, and no obvious orientation force is generated, namely dispersion force is the main acting force, so that the distance between two atoms forming covalent bonds is short, the bond length is short, and the bond energy is large, and the melting point of the material is higher. The use of polytetrafluoroethylene and/or ethylene-tetrafluoroethylene copolymer as the annular nonmetallic member contributes to further improving the yield of the electrochemical device and reducing the cost.

In some embodiments, the polyimide has the structure of formula I, wherein n is selected from 1000 to 200000.

In some embodiments, the polyphenylene sulfide has the structure of formula II, wherein n is selected from 500 to 50000.

In some embodiments, the polyetheretherketone has the structure of formula III, wherein n is selected from 700 to 70000.

In some embodiments, the polymeric material further comprises an inorganic nonmetallic filler.

In some embodiments, the inorganic nonmetallic filler includes at least one of aluminum oxide, silicon oxide, calcium oxide, beryllium oxide, zinc oxide, or silicate.

In some embodiments, the inorganic nonmetallic filler is present in an amount of 0.1% to 10% based on the mass of the polymeric material.

In some embodiments, the annular nonmetallic feature has a cross-sectional area of S1 mm ², the post has a cross-sectional area of S2 mm ², S1 and S2 satisfy: (S1+S2)/S2 is more than or equal to 1.04 and less than or equal to 16.2. In some embodiments, 1.3.ltoreq.S1+S2)/S2.ltoreq.4.3. In some embodiments, 1.5.ltoreq.S1+S2)/S2.ltoreq.4. In some embodiments, 2.ltoreq.S 1 +S2)/S2.ltoreq.3. In some embodiments, (s1+s2)/S2 is 1.04, 1.1, 1.3, 1.5, 2,3, 4.3, 5, 8, 10, 12, 14, 16.2, or a range consisting of any two of the foregoing values.

In some embodiments, 1.3.ltoreq.S1+S2.ltoreq.8.1. In some embodiments, 1.5.ltoreq.S1+S2.ltoreq.8. In some embodiments, 2.ltoreq.S1+S2.ltoreq.6. In some embodiments, 3.ltoreq.S1+S2.ltoreq.5. In some embodiments, s1+s2 is 1.3, 1.5, 2,3, 4, 5, 6, 7, 8, 8.1 or within a range consisting of any two of the above.

In some embodiments, 0.07.ltoreq.S1.ltoreq.7.6. In some embodiments, 0.1.ltoreq.S1.ltoreq.7. In some embodiments, 0.5.ltoreq.S1.ltoreq.5. In some embodiments, 1.ltoreq.S1.ltoreq.3. In some embodiments, S1 is 0.07, 0.1, 0.5, 1,2, 3,4,5, 6,7, 7.6, or a range consisting of any two of the foregoing values.

In some embodiments, 0.5.ltoreq.S2.ltoreq.1.6. In some embodiments, S2 is 0.5, 0.8, 1, 1.2, 1.5, 1.6 or a range consisting of any two of the foregoing values.

In some embodiments, the width of the annular nonmetallic part is W1 mm (as shown in FIG. 3), and 0.03.ltoreq.W1.ltoreq.1. In some embodiments, 0.05.ltoreq.W1.ltoreq.0.8. In some embodiments, 0.1.ltoreq.W1.ltoreq.0.6. In some embodiments, 0.3.ltoreq.W1.ltoreq.0.5. In some embodiments, W1 is 0.03, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range consisting of any two of the foregoing values. When W1 is within the above range, the width of the annular nonmetallic member is as small as possible, whereby the exposed area of the polymer material in the environment can be reduced, thereby contributing to improvement of sealability of the electrochemical device and improvement of yield; and simultaneously, the insulation property can be considered.

In some embodiments, the annular metal component does not have a flange edge. In some embodiments, the annular metal component has a flange edge. As shown in fig. 1-4, the annular metal part 3 has a flange edge 4. When the annular metal component has a flange edge, as shown in fig. 4, the flange edge 4 may be welded to the housing 5 to effect a sealed connection of the seal assembly to the housing.

In some embodiments, the width of the flange edge of the annular metal part is W2 mm (as shown in FIG. 3), and 0.01.ltoreq.W2.ltoreq.1.6. In some embodiments, 0.05.ltoreq.W2.ltoreq.1. In some embodiments, 0.1.ltoreq.W2.ltoreq.0.5. In some embodiments, W2 is 0.01, 0.05, 0.1, 1.2, 1.5, 1.6, or a range consisting of any two of the foregoing values.

Whether the annular metal part has a flange edge or not and the width of the flange edge can be determined according to the structural design. When the annular metal part is provided with the flange edge, and the width of the flange edge is in the range, the insulation and welding rate of the annular metal part and the shell can be ensured, the yield of the electrochemical device can be further improved, and the cost is reduced.

In some embodiments, the non-metallic material has an amorphous state. In some embodiments, the non-metallic material has a glass transition temperature greater than 200 ℃.

In some embodiments, the nonmetallic material has a crystalline state. In some embodiments, the non-metallic material has a melting point greater than 200 ℃.

In some embodiments, the non-metallic material has a thermal weight loss of no greater than 1% at 360 ℃. In some embodiments, the non-metallic material has a thermal weight loss of no greater than 0.5% at 360 ℃. In some embodiments, the non-metallic material has a thermal weight loss of no greater than 0.2% at 360 ℃.

The glass transition temperature, melting point and thermal weight loss of a material are inherent properties of a material, which are related to the magnitude of chain-to-chain intermolecular forces in the material. When the glass transition temperature (amorphous material), the melting point (crystalline material) or the thermal weight loss at 360 ℃ of the non-metal material is in the above range, the non-metal material is not carbonized or decomposed at the instant high temperature generated by welding the polar post and the polar lug, so that the yield of the electrochemical device can be improved, the material loss is reduced, and the cost is reduced.

In some embodiments, the non-metallic material has a coefficient of thermal expansion of no greater than 8X 10 ^-5 cm/cm/DEG C. In some embodiments, the non-metallic material has a coefficient of thermal expansion of no greater than 5X 10 ^-5 cm/cm/DEG C. When the thermal expansion coefficient of the nonmetallic material is within the above range, the thermal expansion coefficient of the nonmetallic material is not greatly different from that of the polar post, carbonization or decomposition can not occur at the instant high temperature generated by welding the polar post and the polar lug, and an excellent sealing effect can be realized.

In some embodiments, the distance between the weld location on the pole and the annular nonmetallic component is less than the radius of the pole. In some embodiments, the radius of the pole is in the range of 0.1mm to 2 mm. In some embodiments, the radius of the post is 0.1mm, 0.3mm, 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm, 1.8mm, 2mm, or a range consisting of any two of the foregoing values.

In some embodiments, the electrochemical device has a thickness of no greater than 4mm. In some embodiments, the electrochemical device has a thickness of no greater than 3.6mm. In some embodiments, the electrochemical device has a thickness of no greater than 3mm. The seal assembly design of the present application is particularly suited for use with thin electrochemical devices having the thickness described above.

In some embodiments, the post and tab are welded together by laser.

In some embodiments, the annular metal component is the same or different material as the housing. In some embodiments, the post is a different material than the housing.

In some embodiments, the housing is a steel material. In some embodiments, the housing is stainless steel. In some embodiments, the housing is aluminum.

In some embodiments, the annular metal component is a steel material. In some embodiments, the annular metal component is stainless steel. In some embodiments, the annular metal component is aluminum.

In some embodiments, the pole is a steel material. In some embodiments, the pole is stainless steel. In some embodiments, the posts are aluminum, and in some embodiments, the posts are molybdenum.

In some embodiments, the housing and annular metal component are steel materials and the post is aluminum. In some embodiments, the housing and annular metal component are aluminum and the post is a steel material.

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

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

In some embodiments, the positive electrode active material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.

In some embodiments, the positive electrode active material may include at least one of lithium cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel type lithium manganate, spinel type lithium nickel manganate, or lithium titanate.

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.

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

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

In some embodiments, the anode includes an anode active material layer and an anode current collector.

In some embodiments, the anode active material layer includes an anode active material, an anode binder, and an anode conductive agent.

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

In some embodiments, the negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, polyimide, polyamideimide, polyvinylidene fluoride, polytetrafluoroethylene, aqueous acrylic resin, polyvinyl formal, or styrene-acrylic copolymer resin.

In some embodiments, any conductive material may be used as the anode 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.

In some embodiments, the negative 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.

The material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application. In some embodiments, the release film may include a substrate layer and a surface treatment layer. In some embodiments, the substrate layer is a nonwoven, film, or 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 nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.

In some embodiments, the surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.

In some embodiments, the inorganic layer includes inorganic particles and a binder, the inorganic particles being selected from at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is at least one selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

In some embodiments, the polymer layer comprises a polymer, and the material of the polymer is selected from at least one of polyamides, polyacrylonitriles, acrylate polymers, polyacrylic acids, polyacrylates, polyvinylpyrrolidone, polyvinyl alkoxide, polyvinylidene fluoride, and poly (vinylidene fluoride-hexafluoropropylene).

The electrochemical device of the present application further includes an electrolyte. The electrolyte that can be used in the present application may be an electrolyte known in the art.

In some embodiments, the electrolyte includes an organic solvent, an electrolyte salt, and optionally an additive. The organic solvent of the electrolyte according to the present application may be any organic solvent known in the art as a solvent of the electrolyte. The electrolyte used in the electrolyte according to the present application is not limited, and may be any electrolyte known in the art. The additive of the electrolyte according to the present application may be any additive known in the art 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), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate. In some embodiments, the organic solvent comprises an ether-type solvent, for example, comprising at least one of 1, 3-Dioxapentacyclic (DOL) and ethylene glycol dimethyl ether (DME). In some embodiments, the electrolyte salt may be a lithium salt, a sodium salt, or the like. In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, lithium salts include, but are not limited to: lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium difluorophosphate (LiPO ₂F₂), lithium bis (trifluoromethanesulfonyl) imide LiN (CF ₃SO₂)₂ (LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO ₂F)₂) (LiFSI), lithium bis (oxalato) borate LiB (C ₂O₄)₂ (LiBOB) or lithium difluorooxalato borate LiBF ₂(C₂O₄) (lidaob).

In some embodiments, the electrochemical devices of the present application include, but are not limited to, all kinds of primary batteries, secondary batteries, or capacitors. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, lithium secondary batteries include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries. In some embodiments, the electrochemical device is a sodium ion battery.

The application still further provides an electronic device comprising an electrochemical device according to the application.

The electronic device or apparatus of the present application is not particularly limited. In some embodiments, the electronic device of the present application includes, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini-compact discs, transceivers, electronic notepads, calculators, memory cards, portable audio recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, gaming machines, watches, power tools, flashlights, cameras, home-use large storage batteries, lithium ion capacitors, and the like.

The processes for preparing the electrochemical device and the electronic device are well known to those skilled in the art, and the present application is not particularly limited. For example, the battery may be prepared by the following method: the positive electrode and the negative electrode are overlapped through the isolating film, and are wound, folded and the like according to the need to prepare the bare cell. Stainless steel is selected as a packaging shell, the bare cell is arranged inside the packaging shell, and an aluminum tab of the bare cell and a pole in the sealing assembly are welded together through laser, so that electronic conduction between the pole and the bare cell is realized. And the steel shell cover and the shell are connected through laser welding, so that the battery is sealed. Through holes are formed in the surface of the steel shell, and electrolyte is injected into the battery cell through the through holes. And (3) activating the battery core under a certain current and voltage condition after full infiltration, so as to finish the preparation of the battery.

The preparation of lithium ion batteries is described below by way of example in connection with specific examples, and those skilled in the art will appreciate that the preparation methods described in the present application are merely examples, and any other suitable preparation methods are within the scope of the present application.

Examples

The following describes performance evaluation of examples and comparative examples of lithium ion batteries according to the present application.

1. Preparation of lithium ion batteries

1. Preparation of negative electrode

Mixing negative electrode active material graphite, conductive carbon black (Super P) and Styrene Butadiene Rubber (SBR) according to a weight ratio of 96:1.5:2.5, adding deionized water as a solvent, preparing into negative electrode slurry with solid content of 0.7, and uniformly stirring. The negative electrode slurry is uniformly coated on a negative electrode current collector copper foil, and the weight of an effective substance on a pole piece is 95g/m ². And then drying at 110 ℃ to obtain the negative electrode plate. After the steps are finished, the single-sided coating of the negative electrode plate is finished. And then, carrying out the same steps on the back surface of the negative electrode plate by a completely consistent method to obtain the negative electrode plate with the double-sided coating. After the coating was completed, the negative electrode sheet was cold pressed to a compacted density of 1.7g/cm ³ to obtain a negative electrode.

2. Preparation of the Positive electrode

The positive electrode active material lithium cobaltate (LiCoO ₂), conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) are mixed according to the weight ratio of 97.5:1.0:1.5, N-methyl pyrrolidone (NMP) is added as a solvent, and the mixture is prepared into positive electrode slurry with the solid content of 0.75, and the mixture is uniformly stirred. The positive electrode slurry is uniformly coated on a positive electrode current collector aluminum foil, and the weight of active substances on a pole piece is 180g/m ². And drying at 90 ℃ to obtain the positive electrode plate. After the steps are finished, the single-sided coating of the positive electrode plate is finished. And then, carrying out the same steps on the back surface of the positive electrode plate by a completely consistent method to obtain the positive electrode plate with the double-sided coating. After coating, cold pressing the positive pole piece to a compaction density of 4.1g/cm ³ to obtain the positive pole.

3. Preparation of electrolyte

In a dry argon atmosphere, the organic solvents of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) are firstly mixed according to the mass ratio EC: EMC: dec=30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF ₆) is added into the organic solvent for dissolution and uniform mixing, so that an electrolyte with the concentration of lithium salt of 1.15M is obtained.

4. Preparation of electrode assemblies

Polyethylene (PE) with the thickness of 15 mu m is selected as an isolating membrane, a positive pole piece, the isolating membrane and a negative pole piece are sequentially stacked, the isolating membrane is positioned between the positive pole piece and the negative pole piece to play a role of isolation, and then the stacked pole piece and the isolating membrane are wound to obtain the electrode assembly.

5. Preparation of seal assembly

The welding process comprises the following steps: a hollow steel member having a height of 0.5mm, an outer diameter of 2.4mm and an inner diameter of 1.6mm was produced by mechanical punching and used as an annular metal sheet (annular metal member). Aluminum was used as the post, which was a cylinder with a diameter of 0.8mm and a length of 1.2 mm. The electrode post was placed in the center of the annular metal sheet, and the sealing material powder was filled into the gap between the two according to the settings of the following examples or comparative examples, and was sintered at a certain temperature for 30 minutes (specific materials and sintering temperatures thereof are shown in the following table) to form an annular nonmetallic part. And then naturally cooling to obtain the sealing assembly.

The riveting process comprises the following steps: fig. 5 shows a seal assembly formed by a staking process that includes a post 502, an inner seal washer 5011, an outer seal washer 5012, and an outer metal washer 503. The preparation method comprises the following steps: firstly, a structural member required by a riveting process is plugged into a pole column hole reserved in a battery shell, the structure of the structure is formed by sequentially arranging a pole column (T-shaped) 502, an outer sealing gasket 5012, the battery shell, a sealing gasket 5011 and an outer metal sealing gasket 503 from outside to inside, and the T-shaped tip area of the pole column is impacted by a stamping mode to form an I-shaped pole column 502, so that the outer sealing gasket and the inner sealing gasket only press the battery shell, and a riveting sealing structure is obtained.

6. Encapsulation of lithium ion battery

The length, width and thickness of the battery cell are respectively as follows: 24mm, 19mm, 4.0mm. The electrode assembly is arranged in the bare cell, the aluminum tab of the cell and the pole of the sealing assembly are welded by laser, and the distance (amm) between the welding position on the pole and the annular nonmetallic part is smaller than the radius of the pole. The bare cell is arranged inside the stainless steel shell and is connected with the shell cover and the shell through laser welding. The surface of the housing was reserved with a through hole of 0.8mm diameter through which 0.8g of electrolyte was injected into the inside of the cell. And performing the operations of formation (0.02C constant current charging to 3.3V and then 0.1C constant current charging to 3.6V) and the like to obtain the soft-package lithium ion battery.

2. Test method

1. Method for testing thermal expansion coefficient

The thermal expansion coefficient of nonmetallic materials was tested according to the standard test method for linear thermal expansion of solid materials by thermomechanical analysis (astm e 831).

2. Method for testing yield of lithium ion battery

In each example or comparative example, 50 groups of samples to be tested were taken, and red permeate was applied to the inner post and outer layer of the housing. After 15 minutes, the surface permeate was removed with ethanol, the pole was removed, and the sealed area was checked for permeate, and permeate was not passed. The yield of samples passing the seal test was calculated.

3. Method for testing energy density of lithium ion battery

And (3) charging the lithium ion battery to a 100% charge state in an environment of room temperature (25+/-2 ℃), and standing for not less than 30 minutes. 0.2C was discharged to 3.0V and discharge energy E (in Wh) was measured. The maximum value in the length-width-height direction of the lithium ion battery is measured by a micrometer or a vernier caliper, and the volume V (in L) is measured. The volumetric energy density (Wh/L) of the lithium ion battery discharge was calculated by the formula:

Volumetric energy density = E/V.

4. Differential Scanning Calorimetry (DSC) test method

Differential Scanning Calorimetry (DSC) tests were performed using a DuPont model 900 thermal analyzer at a heating rate of 10 ℃/min, and the exothermic peak position and glass transition temperature of the samples were recorded.

3. Test results

Table 1 shows the effect of the sealing process, the material of the annular nonmetallic part of the seal assembly, and the distance a between the weld location on the post and the annular nonmetallic part on the energy density and yield of the lithium ion battery.

TABLE 1

Comparative examples 1-1 and 1-2, although a welding process was used to manufacture the seal assembly, glass was used as the annular nonmetallic member, and when the distance between the welding position on the post and the annular nonmetallic member was small, the high temperature generated by welding resulted in the glass being easily expanded and broken, thereby resulting in a low yield and greatly increasing the production cost. In comparative examples 1 to 3, although fluororesin was used as a sealing material, it was used in a caulking process, and when it was used in a thin battery, the energy density of a lithium ion battery was greatly reduced due to the fact that the electrode post occupied a large battery space, and at the same time, the material consumption was large and the cost was high.

Examples 1-1 to 1-5 a sealing member was prepared using a welding process and specific polymer materials (e.g., fluorine resin, polyimide, and polyphenylene sulfide) were used as an annular nonmetallic member, and even if used for a thin battery, welding at a position on a post from 0.05mm to 0.7mm from the annular nonmetallic member did not destroy the sealing effect of the polymer material, thereby significantly improving the yield of lithium ion batteries, reducing the cost while maintaining good energy density.

When the distance a between the welding position on the pole and the annular nonmetallic part is 0.1mm to 0.3mm, the yield of the ion battery can be further improved, the cost is reduced, and meanwhile, the convenience of the manufacturing process is considered.

Table 2 shows the effect of the width W1 of the annular nonmetallic member, the width W2 of the flange side, the cross-sectional area S1 of the annular nonmetallic member, and the cross-sectional area S2 of the post on the yield of the lithium ion battery. Examples 2-1 to 2-8 were identical in arrangement to examples 1-5, except for the parameters listed in Table 2.

TABLE 2

	W1	W2	S1	S2	(S1+S2)/S2	Yield of finished products
							Examples 1 to 6	1	0.1	5.02	0.29	18.78	78％
Example 2-1	0.03	0.4	0.15	1.86	1.08	92％
							Examples 2 to 3	0.1	0.4	0.48	1.53	1.31	98％
Examples 2 to 4	1	0.01	0.42	0.03	15.00	92％
							Examples 2 to 5	1	0.4	5.88	0.36	16.20	88％
Examples 2 to 6	1	0	0.42	0.03	15.00	80％
							Examples 2 to 7	0.02	0.4	0.15	4.52	1.03	74％
Examples 2 to 8	0.75	0.4	5.06	1.54	4.30	96％

The result shows that when (S1+S2)/S2 is in the range of 1.04-16.2, the distribution of the annular nonmetallic parts and the polar posts is more reasonable, the yield of the lithium ion battery can be further improved, and the cost is reduced. When (S1+S2)/S2 is less than or equal to 1.3 and less than or equal to 4.3, the improvement effect is particularly remarkable.

When the annular metal part has a flange edge, the convenience of welding the annular metal part to the housing can be increased. When the width W2 of the flange edge is in the range of 0.01mm to 1.6mm, the insulation and welding rate of the annular metal part and the shell can be guaranteed, and the improvement of the yield of the lithium ion battery and the cost reduction are facilitated.

When the width W1 of the annular nonmetallic part is in the range of 0.03mm to 1mm, the yield of the lithium ion battery is improved, the short circuit of the lithium ion battery can be effectively avoided, the thickness of the battery core is reduced, and the cost is reduced.

Table 3 shows the effect of the material properties of annular nonmetallic components on the yield of lithium ion batteries. Except for the parameters listed in Table 3, the sealed electrode posts were prepared in examples 3-1 to 3-3 using a welding process with a radius of 0.8mm, a welding distance a of 0.1mm, and a cell thickness of 4mm.

TABLE 3 Table 3

"ETFE" refers to an ethylene-tetrafluoroethylene copolymer,

"FEP" refers to perfluoroethylene propylene copolymer.

In comparative example 3-1, polypropylene was used as an annular nonmetallic member, which had a low melting point or glass transition temperature, a large thermal weight loss, and a high thermal expansion coefficient, and was carbonized in a large amount at a high temperature generated by welding to form fine pores, which became a liquid permeation space, so that sealing effect could not be achieved, and it could not be used.

Examples 3-1 to 3-3 different types of polyphenylene sulfide or fluororesin were used as the annular nonmetallic member. When the melting point or glass transition temperature of the material of the annular nonmetallic part is more than 200 ℃, the thermal weight loss at 360 ℃ is not more than 1% and/or the thermal expansion coefficient is not more than 8 multiplied by 10 ^-5 cm/cm/DEG C, the lithium ion battery has significantly improved yield and reduced cost.

Reference throughout this specification to "an embodiment," "a portion of an embodiment," "one embodiment," "another example," "an example," "a particular example," or "a portion of an example" means that at least one embodiment or example of the present application includes the particular feature, structure, material, or characteristic described in the embodiment or example. Thus, descriptions appearing throughout the specification, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "example," which do not necessarily reference the same embodiments or examples in the application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application, and that changes, substitutions and alterations may be made herein without departing from the spirit, principles and scope of the application.

Claims

1. An electrochemical device comprising a housing and a seal assembly, wherein:

The shell is used for accommodating an electrode assembly, and the electrode assembly comprises a tab;

The seal assembly includes:

a post welded to the tab to create an electrical connection; and

An annular member configured to surround the pole, and comprising:

An annular metal part in sealing connection with the housing; and

An annular non-metallic component between the post and the annular metallic component and comprising a polymeric material comprising at least one of a fluororesin, a polyimide, a polyphenylene sulfide, or a polyetheretherketone;

The distance between the welding position on the pole and the annular nonmetallic part is a millimeter, and a is more than or equal to 0.05 and less than or equal to 0.7.

2. The electrochemical device of claim 1, wherein the mass of the polymeric material is greater than or equal to 90% based on the mass of the annular nonmetallic component.

3. The electrochemical device according to claim 2, wherein 0.1.ltoreq.a.ltoreq.0.3.

4. The electrochemical device of claim 2, wherein the annular nonmetallic component has a cross-sectional area of S1 mm ², the polar post has a cross-sectional area of S2 mm ², S1 and S2 satisfy: (S1+S2)/S2 is more than or equal to 1.04 and less than or equal to 16.2.

5. The electrochemical device according to claim 4, wherein 1.3.ltoreq.S1+S2)/S2.ltoreq.4.3.

6. The electrochemical device according to claim 2, wherein 0.07.ltoreq.s1.ltoreq.7.6 and 0.5.ltoreq.s2.ltoreq.1.6.

7. The electrochemical device of claim 2, wherein the annular nonmetallic member has a width of W1 mm, and 0.03+.w1+.1.

8. The electrochemical device of claim 2, wherein the annular metal member has a flange edge with a width W2 mm and 0.01 ∈w2 ∈1.6.

9. The electrochemical device of claim 2, wherein the non-metallic material has a glass transition temperature greater than 200 ℃ or a melting point greater than 200 ℃.

10. The electrochemical device of claim 2, wherein the non-metallic material has a thermal weight loss of no greater than 1% at 360 ℃.

11. The electrochemical device of claim 2, wherein the non-metallic material has a coefficient of thermal expansion of no greater than 8 x 10 ^-5 cm/cm/°c.

12. The electrochemical device of claim 2, wherein a distance between a welding location on the post and the annular nonmetallic component is less than a radius of the post, the radius of the post being in a range of 0.1mm to 2 mm.

13. The electrochemical device of claim 2, having a thickness of no greater than 4mm.

14. An electronic device comprising the electrochemical device according to any one of claims 1-13.