Thermal safety edge sealing type pole piece, preparation method thereof and battery

Abstract

The invention belongs to the technical field of battery manufacturing, and relates to a thermal safety edge sealing type pole piece and a preparation method thereof and a battery, the thermal safety edge sealing type pole piece comprises a functional current collector and an active material layer arranged on at least one side surface of the functional current collector, the functional current collector at least comprises a transition layer, and a sealing layer is arranged on the edge end face of the thermal safety edge sealing type pole piece. The sealing layer completely covers the edge end surface of the transition layer; wherein the sealing layer contains a main body material and a functional material, and the functional material comprises at least one of an inorganic salt hydrate, a phenolic compound or a lactic acid polymer. The sealing layer is arranged on the end face of the edge of the pole piece, so that the transition layer in the functional current collector is effectively prevented from being in contact with electrolyte, the structural stability of the pole piece and the cycle performance of the battery are remarkably improved, meanwhile, the functional material is added into the sealing layer, and the thermal safety of the battery is considered.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery manufacturing and relates to a pole piece, and in particular to a thermally safe edge-sealed pole piece, a preparation method thereof, and a battery. Background Art

[0002] Currently, functional current collectors based on polymer membranes are widely used in the battery industry. Compared with traditional current collectors, functional current collectors have the advantages of low cost, light weight, and good internal insulation. These characteristics enable the use of functional current collectors in batteries to significantly reduce battery costs while improving battery energy density and safety.

[0003] To improve the adhesion between the polymer film and the metal layer within the functional current collector, technicians typically place a transition layer between the polymer film and the metal layer. However, during battery cycling, this transition layer comes into contact with and corrodes the electrolyte, reducing the adhesion between the metal layer and the polymer film and even causing delamination. This deteriorates the structural stability of the electrode and ultimately the cycling performance of the resulting battery.

[0004] In addition, when the battery is subjected to thermal abuse, a chain reaction of thermal runaway is prone to occur, causing the battery to heat up rapidly, which means that the thermal safety of the battery needs to be further improved.

[0005] It can be seen that how to prevent the transition layer in the functional current collector from contacting the electrolyte, improve the structural stability of the electrode and the cycle performance of the battery, while taking into account the thermal safety of the battery has become an urgent problem to be solved by technical personnel in this field. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a thermally safe edge-sealed electrode, a preparation method and a battery. By arranging a sealing layer on the edge end face of the electrode, the transition layer in the functional current collector is effectively prevented from contacting the electrolyte, thereby significantly improving the structural stability of the electrode and the cycle performance of the battery. At the same time, functional materials are added to the sealing layer to take into account the thermal safety of the battery.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a thermally safe edge-sealed pole piece, comprising a functional current collector and an active material layer arranged on at least one side surface of the functional current collector, the functional current collector containing at least a transition layer, and the edge end face of the thermally safe edge-sealed pole piece is provided with a sealing layer, and the sealing layer completely covers the edge end face of the transition layer.

[0009] The sealing layer contains a main material and a functional material, and the functional material includes at least one of an inorganic salt hydrate, a phenolic compound or a lactic acid polymer.

[0010] The present invention provides a sealing layer on the edge end face of the electrode and ensures that the sealing layer completely covers the edge end face of the transition layer, that is, the sealing treatment is achieved by fully integrating the sealing layer with the end face of the functional current collector, which effectively avoids the transition layer in the functional current collector from contacting the electrolyte, thereby improving the interface stability between the polymer film and the metal layer and the structural stability of the electrode during the battery cycle, significantly improving the cycle performance of the battery. At the same time, the presence of the sealing layer avoids the internal short circuit problem caused by the overlap of burrs on the edge of the current collector of the positive and negative electrode sheets, thereby improving the safety performance of the battery.

[0011] In addition, the present invention adds specific types of functional materials to the sealing layer, which, on the one hand, improves the crystallinity of the main material, further improves its barrier performance to the electrolyte, promotes the interface stability between the polymer film and the metal layer during the battery cycle, improves the structural stability of the electrode, and thus improves the cycle performance of the battery; on the other hand, when the battery is subjected to thermal abuse, it can effectively alleviate the chain reaction of the original battery thermal runaway, thereby effectively inhibiting the continuation of the battery thermal runaway reaction and the continuous temperature rise of the battery, and ultimately significantly improving the thermal safety of the battery.

[0012] Preferably, the inorganic salt hydrate includes at least one of aluminum sulfate hexahydrate, aluminum sulfate hexadecahydrate, aluminum sulfate octahydrate, trisodium phosphate dodecahydrate, ferrous sulfate monohydrate, ferrous sulfate tetrahydrate, ferrous sulfate pentahydrate or ferrous sulfate heptahydrate.

[0013] Preferably, the phenolic compound includes at least one of p-tert-butylphenol, phloroglucinol, p-hydroxybenzoic acid, bisphenol A or p-nitrophenol.

[0014] Preferably, the lactic acid polymer includes at least one of polylactic acid, polylactic acid-glycolic acid copolymer, polycaprolactone-polylactic acid copolymer or polyethylene glycol-polylactic acid copolymer.

[0015] Preferably, based on the total mass of the sealing layer, the content of the functional material is 0.5-5 wt %.

[0016] Preferably, the main body material comprises at least one of polyolefin, polyurethane or polyamide.

[0017] Preferably, the polyolefin comprises at least one of polyethylene, polypropylene or ethylene-propylene copolymer.

[0018] Preferably, the thickness of the sealing layer is 5-500 μm, more preferably 50-200 μm.

[0019] Preferably, the functional current collector comprises a polymer film and a transition layer, a metal layer and a passivation layer provided on at least one surface of the polymer film, and the transition layer is located between the polymer film and the metal layer.

[0020] Preferably, the material of the polymer film includes at least one of polyolefin, polyester, polyamide, polyimide, polyphenylene ether or polyphenylene sulfide.

[0021] Preferably, the polyolefin includes at least one of polyethylene, polypropylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride or polytetrafluoroethylene.

[0022] Preferably, the polyester comprises at least one of polyethylene terephthalate, polybutylene terephthalate or polyethylene naphthalate.

[0023] Preferably, the difference in number average molecular weight between the material of the polymer film and the main material is ≤50,000 g / mol.

[0024] Preferably, the polymer film includes a base film region and transition regions arranged on both sides of the base film region, and the transition region is located between the base film region and the sealing layer.

[0025] Preferably, the material of the transition zone includes at least three of polyolefin, polyester, polyurethane, polyamide, polyimide, polyphenylene ether, polyphenylene sulfide, inorganic salt hydrate, phenolic compound or lactic acid polymer.

[0026] Preferably, the width of the transition zone is 0.05-1 mm.

[0027] Preferably, the sealing layer is partially sealed or fully sealed at the edge end surface of the pole piece.

[0028] Preferably, when the sealing layer is partially sealed, the width of the sealing layer is greater than or equal to the thickness of the functional current collector, and less than or equal to the total thickness of the pole piece.

[0029] Preferably, when the sealing layer is fully sealed, the sealing layer goes over the edge ridge of the pole piece and overlaps at least one side surface of the pole piece, and the overlap width is ≤1 mm.

[0030] In a second aspect, the present invention provides a method for preparing the thermally safe edge-sealed pole piece as described in the first aspect, the preparation method comprising the following steps:

[0031] (1) preparing a functional current collector comprising at least a transition layer;

[0032] (2) providing an active material layer on at least one side surface of the functional current collector to obtain a pole piece;

[0033] (3) A sealing layer is provided on the edge end face of the pole piece, and the sealing layer contains a main material and a functional material, and the sealing layer is controlled to completely cover the edge end face of the transition layer to obtain the thermally safe edge-sealed pole piece.

[0034] Preferably, the method for setting the sealing layer in step (3) includes precision spraying or slit coating.

[0035] Preferably, the coating liquid temperature used in the precision spraying or slit coating is set to T c , then: T m ≤T c ≤T m +50℃.

[0036] Among them, T m Refers to the highest melting point among the melting points of the main material, the functional material, and the polymer film, in °C.

[0037] In a third aspect, the present invention provides a battery comprising the thermally safe edge-sealed pole piece as described in the first aspect.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention provides a sealing layer on the edge end face of the electrode and ensures that the sealing layer completely covers the edge end face of the transition layer, that is, the sealing treatment is achieved by fully integrating the sealing layer with the end face of the functional current collector, which effectively avoids the transition layer in the functional current collector from contacting the electrolyte, thereby improving the interface stability between the polymer film and the metal layer and the structural stability of the electrode during the battery cycle, significantly improving the cycle performance of the battery, and at the same time, the presence of the sealing layer avoids the internal short circuit problem of the positive and negative electrode sheets caused by the burr overlap of the current collector edge, thereby improving the safety performance of the battery.

[0040] (2) The present invention adds a specific type of functional material to the sealing layer, which, on the one hand, improves the crystallinity of the main material, further improves its barrier performance to the electrolyte, promotes the interface stability between the polymer film and the metal layer during the battery cycle, improves the structural stability of the electrode, and thus improves the cycle performance of the battery; on the other hand, when the battery is subjected to thermal abuse, it can effectively alleviate the chain reaction of the original battery thermal runaway, thereby effectively inhibiting the continuation of the battery thermal runaway reaction and the continuous temperature rise of the battery, and ultimately significantly improving the thermal safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the thermal safety edge-sealed pole piece structure provided by the present invention (partially sealed);

[0042] Figure 2This is a schematic diagram of the thermally safe edge-sealed pole piece structure provided by the present invention (all sealed);

[0043] Figure 3 This is a schematic diagram of the functional current collector structure in the thermally safe edge-sealed pole piece provided by the present invention;

[0044] Figure 4 This is a partial enlarged view of the thermally safe edge-sealed pole piece provided by the present invention.

[0045] Among them: 10-functional aluminum current collector; 11-polymer film; 11a-base film region; 11b-transition region; 12-transition layer; 13-metal layer; 14-passivation layer; 20-active material layer; 30-sealing layer; 30a-main material; 30b-functional material. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] An embodiment of the present invention provides a thermally safe edge-sealed pole piece, comprising a functional current collector and an active material layer arranged on at least one side surface of the functional current collector, the functional current collector containing at least a transition layer, and the edge end surface of the thermally safe edge-sealed pole piece is provided with a sealing layer, and the sealing layer completely covers the edge end surface of the transition layer.

[0048] The sealing layer contains a main material and a functional material, and the functional material includes at least one of an inorganic salt hydrate, a phenolic compound or a lactic acid polymer.

[0049] The present invention provides a sealing layer on the edge end face of the electrode and ensures that the sealing layer completely covers the edge end face of the transition layer, that is, the sealing treatment is achieved by fully integrating the sealing layer with the end face of the functional current collector, which effectively avoids the transition layer in the functional current collector from contacting the electrolyte, thereby improving the interface stability between the polymer film and the metal layer and the structural stability of the electrode during the battery cycle, significantly improving the cycle performance of the battery. At the same time, the presence of the sealing layer avoids the internal short circuit problem caused by the overlap of burrs on the edge of the current collector of the positive and negative electrode sheets, thereby improving the safety performance of the battery.

[0050] In addition, the present invention adds specific types of functional materials to the sealing layer, which, on the one hand, improves the crystallinity of the main material, further improves its barrier performance to the electrolyte, promotes the interface stability between the polymer film and the metal layer during the battery cycle, improves the structural stability of the electrode, and thus improves the cycle performance of the battery; on the other hand, when the battery is subjected to thermal abuse, it can effectively alleviate the chain reaction of the original battery thermal runaway, thereby effectively inhibiting the continuation of the battery thermal runaway reaction and the continuous temperature rise of the battery, and ultimately significantly improving the thermal safety of the battery.

[0051] Specifically, when the battery is subjected to thermal abuse, the functional material will be released from the sealing layer and react with the lithium metal in the negative electrode, thereby weakening the reaction between the lithium metal and the electrolyte and reducing the amount of reducing gas generated thereby. The consumption of lithium metal and the reduction in the amount of reducing gas generated can effectively inhibit the reaction with the oxygen released from its positive electrode, thereby reducing the heat generated by the reaction, inhibiting the thermal runaway of the battery, and ultimately improving the thermal safety of the battery.

[0052] In certain embodiments, the functional current collector is specifically a functional aluminum current collector or a functional copper current collector, and the corresponding thermally safe edge-sealed electrode is specifically a positive electrode or a negative electrode. Because the transition layer in both functional current collectors poses risks of electrolyte contact and thermal safety issues, both are suitable for use in the present invention.

[0053] In certain embodiments, the inorganic salt hydrate includes at least one of aluminum sulfate hexahydrate, aluminum sulfate hexadecahydrate, aluminum sulfate octadecahydrate, trisodium phosphate dodecahydrate, ferrous sulfate monohydrate, ferrous sulfate tetrahydrate, ferrous sulfate pentahydrate, or ferrous sulfate heptahydrate.

[0054] In certain embodiments, the phenolic compound includes at least one of p-tert-butylphenol, phloroglucinol, p-hydroxybenzoic acid, bisphenol A, or p-nitrophenol.

[0055] In certain embodiments, the lactic acid-based polymer includes at least one of polylactic acid, polylactic acid-co-glycolic acid, polycaprolactone-polylactic acid copolymer, or polyethylene glycol-polylactic acid copolymer.

[0056] In some embodiments, the total mass of the sealing layer is used as a calculation basis, and the content of the functional material is 0.5-5wt%, for example, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] By limiting the content of functional materials to a reasonable range, the present invention balances the battery's cycling performance and thermal safety. When the functional material content is less than 0.5wt%, the improvement in the cycling performance and thermal safety of the battery assembled with the pole piece is limited. When the functional material content is higher than 5wt%, defects in the sealing layer are likely to occur, hindering the effective isolation of the transition layer in the pole piece from the external electrolyte, resulting in poor structural stability of the pole piece and, in turn, poor cycling performance of the battery.

[0058] In certain embodiments, the body material includes at least one of polyolefin, polyurethane, or polyamide.

[0059] In certain embodiments, the polyolefin includes at least one of polyethylene, polypropylene, or ethylene-propylene copolymer.

[0060] In some embodiments, the thickness of the sealing layer is 5-500 μm, for example, it can be 5 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm or 500 μm, and more preferably 50-200 μm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0061] By limiting the thickness of the sealing layer to a reasonable range, the present invention balances the sealing performance of the sealing layer with the energy density of the battery. When the sealing layer thickness is less than 5μm, the sealing performance of the sealing layer is poor, causing the transition layer in the functional current collector to contact the electrolyte, which in turn leads to poor interface stability between the polymer film and the metal layer, and thus poor structural stability of the pole piece. When the sealing layer thickness exceeds 500μm, it is not conducive to smooth pole piece processing, increasing production costs and reducing the energy density of the battery.

[0062] In some embodiments, the functional current collector includes a polymer film and a transition layer, a metal layer, and a passivation layer disposed on at least one surface of the polymer film, and the transition layer is located between the polymer film and the metal layer.

[0063] In some embodiments, the polymer film is made of at least one of polyolefin, polyester, polyamide, polyimide, polyphenylene ether, or polyphenylene sulfide, and is used to provide support for the functional current collector.

[0064] In certain embodiments, the polyolefin includes at least one of polyethylene, polypropylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, or polytetrafluoroethylene.

[0065] In certain embodiments, the polyester includes at least one of polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate.

[0066] In some embodiments, the difference in number average molecular weight between the material of the polymer film and the main material is ≤50,000 g / mol, for example, it can be 10 g / mol, 100 g / mol, 1000 g / mol, 10,000 g / mol, 20,000 g / mol, 30,000 g / mol, 40,000 g / mol or 50,000 g / mol, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0067] The present invention specifically limits the main material according to the specific material of the polymer film, ensuring that the number average molecular weights of the two materials are close to each other, improving the hot melt effect and interface stability of the two, and further achieving full fusion between the sealing layer and the polymer film, thereby improving the sealing performance of the sealing layer, and significantly improving the barrier performance of the sealing layer to the electrolyte and the thermal safety of the battery.

[0068] In certain embodiments, the polymer film includes a base film region and transition regions disposed on both sides of the base film region, and the transition regions are located between the base film region and the sealing layer.

[0069] In some embodiments, the material of the transition zone includes at least three of polyolefin, polyester, polyurethane, polyamide, polyimide, polyphenylene ether, polyphenylene sulfide, inorganic salt hydrate, phenolic compound or lactic acid polymer.

[0070] In some embodiments, the width of the transition zone is 0.05-1 mm, for example, it can be 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] In the present invention, the width of the transition zone is crucial for balancing the barrier performance and production cost of the sealing layer. If the width of the transition zone is less than 0.05 mm, it indicates that the sealing layer and the polymer film are not fully integrated, reducing the sealing layer's barrier performance to the electrolyte. If the width of the transition zone is greater than 1 mm, the barrier performance of the sealing layer is not significantly improved, and the production cost is unnecessarily increased.

[0072] In some embodiments, the ratio of the thickness of the transition zone to the thickness of the base film zone is (90-110):100, for example, it can be 90:100, 92:100, 94:100, 96:100, 98:100, 100:100, 102:100, 104:100, 106:100, 108:100 or 110:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0073] In the present invention, the thickness of the transition region and the thickness of the base film region both refer to average thickness.

[0074] In some embodiments, the metal layer is made of aluminum or aluminum alloy, which functions as a conductor.

[0075] In some embodiments, the passivation layer is made of aluminum oxide to prevent further oxidation of the metal layer.

[0076] In some embodiments, the thickness of the polymer film is 1-10 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0077] In some embodiments, the thickness of the transition layer is 2-20 nm, for example, it can be 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0078] By limiting the thickness of the transition layer to a reasonable range, the present invention balances adhesion and bonding stability between the film layers. When the thickness of the transition layer is less than 2nm, the uniformity of the transition layer is poor, resulting in low adhesion between the polymer film and the metal layer. When the thickness of the transition layer is greater than 20nm, it is not conducive to further improving the bonding stability between the polymer film and the metal layer.

[0079] In some embodiments, the thickness of the metal layer is 500-2000 nm, for example, it can be 500 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm or 2000 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0080] By limiting the thickness of the metal layer to a reasonable range, the present invention balances the conductivity of the metal layer with the energy density of the battery. When the thickness of the metal layer is less than 500nm, the conductivity of the metal layer is poor; when the thickness of the metal layer is greater than 2000nm, it is not conducive to further improving the energy density of the battery.

[0081] In some embodiments, the thickness of the passivation layer is 5-100 nm, for example, it can be 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0082] In some embodiments, the sealing layer is partially sealed or fully sealed at the edge end surface of the pole piece.

[0083] In some embodiments, when the sealing layer is partially sealed, the width of the sealing layer is greater than or equal to the thickness of the functional current collector and less than or equal to the total thickness of the pole piece.

[0084] In some embodiments, when the sealing layer is fully sealed, the sealing layer passes over the edge ridge of the pole piece and overlaps at least one side surface of the pole piece, and the overlap width is ≤1mm, for example, it can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0085] The present invention limits the overlap width of the sealing layer on the electrode surface to less than 1 mm, thereby avoiding the loss of energy storage function of part of the electrode material due to excessive overlap of the sealing layer, thereby ensuring that the battery capacity is at a high level.

[0086] An embodiment of the present invention further provides a method for preparing the thermally safe edge-sealed electrode according to any of the above embodiments, the method comprising the following steps:

[0087] (1) preparing a functional current collector comprising at least a transition layer;

[0088] (2) providing an active material layer on at least one side surface of the functional current collector to obtain a pole piece;

[0089] (3) A sealing layer is provided on the edge end face of the pole piece, and the sealing layer contains a main material and a functional material, and the sealing layer is controlled to completely cover the edge end face of the transition layer to obtain the thermally safe edge-sealed pole piece.

[0090] In certain embodiments, the method for preparing the functional current collector in step (1) includes: depositing a transition layer, a metal layer, and a passivation layer in sequence on at least one surface of a polymer film.

[0091] In certain embodiments, the method for providing the active material layer in step (2) comprises sequentially performing slurrying, coating, rolling, and die-cutting.

[0092] In some embodiments, the active material layer in step (2) includes an active material, a binder, and a conductive agent.

[0093] For example, the active material includes lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium titanium oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, transition metal phosphate, sodium-transition metal oxide (Na x MO2, M is a transition metal), any one of sodium iron phosphate, sodium vanadium phosphate, sodium iron sulfate, sodium ferric fluorophosphate, Prussian blue compounds, polyanthraquinone, perylenetetracarboxylic dianhydride, polyaniline, polypyrrole, sodium sulfide or sodium tin, or a combination of at least two thereof, with a content of 90-98wt%, for example, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt% or 98wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0094] Exemplarily, the binder includes any one of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, conductive polymers (such as polyaniline, polypyrrole, etc.), sodium alginate or chitosan, or a combination of at least two of them, with a content of 1-5wt%, for example, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0095] Exemplarily, the conductive agent includes any one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene, silver nanowire, copper nanowire or conductive polymer (such as polyaniline, polypyrrole, etc.) or a combination of at least two, with a content of 1-5wt%, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0096] In some embodiments, the thickness of the active material layer in step (2) is 30-300 μm, for example, 30 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm or 300 μm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0097] In certain embodiments, the method for providing the sealing layer in step (3) includes precision spraying or slit coating.

[0098] In some embodiments, the coating liquid temperature used in the precision spray coating or slit coating is set to T c , then: T m ≤T c ≤T m +50℃, for example, it can be T c =T m 、T m +5℃、T m +10℃、T m +15℃、T m +20℃、T m +25℃、T m +30℃、T m +35℃、T m +40℃、T m +45℃ or T m +50℃, but is not limited to the listed values, other values ​​not listed in this numerical range are also applicable.

[0099] Among them, T m Refers to the highest melting point among the melting points of the main material, the functional material, and the polymer film, in °C.

[0100] The present invention limits the coating liquid temperature to be higher than the highest melting point of the main material, functional material and polymer film, and limits the difference between the two to within 50°C. This not only achieves full fusion of the sealing layer and the end face of the electrode, but also avoids unnecessary damage to the edge of the electrode due to excessively high coating liquid temperature and unnecessary increase in preparation cost.

[0101] An embodiment of the present invention further provides a battery, wherein the battery comprises the thermally safe edge-sealed pole piece described in any of the above embodiments.

[0102] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0103] Example 1

[0104] This embodiment provides a thermally safe edge-sealed pole piece, such as Figure 1 As shown, the thermal safety edge-sealed pole piece includes a functional aluminum current collector 10 and an active material layer 20 disposed on both sides of the functional aluminum current collector 10. Figure 3 As shown, the functional aluminum current collector 10 includes a polymer film 11 and a transition layer 12, a metal layer 13 and a passivation layer 14 arranged on both side surfaces of the polymer film 11, and the transition layer 12 is located between the polymer film 11 and the metal layer 13; the edge end face of the thermal safety edge-sealed pole piece is provided with a sealing layer 30, and the sealing layer 30 completely covers the edge end face of the transition layer 12.

[0105] In this embodiment, the polymer film 11 is made of polyethylene terephthalate (number average molecular weight of 14600 g / mol) with a thickness of 6 μm; the transition layer 12 is made of aluminum oxide with a thickness of 10 nm; the metal layer 13 is made of aluminum with a thickness of 1 μm; and the passivation layer 14 is made of aluminum oxide with a thickness of 5 nm.

[0106] like Figure 4 As shown, the sealing layer 30 contains a main material 30a and a functional material 30b, wherein the main material 30a is polyethylene (number average molecular weight is 20000 g / mol), the functional material 30b is aluminum sulfate 18hydrate, the thickness d1 of the sealing layer 30 is 5 μm, and the content of the functional material 30b in the sealing layer 30 is 3 wt %. The difference between the surface energy of the main material 30a and the polymer film 11 is ≤10 mJ / m 2 The polymer film 11 includes a base film region 11a and transition regions 11b disposed on both sides of the base film region 11a, wherein the transition region 11b is located between the base film region 11a and the sealing layer 30. The material of the transition region 11b is a mixture of polyethylene terephthalate, polyethylene, and aluminum sulfate 18-hydrate, the width d2 is 0.5 mm, and the ratio of the average thickness of the transition region 11b to the average thickness of the base film region 11a is 105:100.

[0107] like Figure 1 As shown, the sealing layer 30 is partially sealed at the edge end face of the pole piece, and the width of the sealing layer 30 is equal to the total thickness of the pole piece, that is, the sealing layer 30 completely covers the end of the pole piece without overlap.

[0108] This embodiment also provides a method for preparing the thermally safe edge-sealed electrode, which specifically includes the following steps:

[0109] (1) Preparation of a functional aluminum current collector 10 containing a transition layer 12:

[0110] (1.1) The polymer film 11 is placed in an evaporation machine, and aluminum oxide is deposited on both sides of the film to form a transition layer 12. The specific process is as follows: high-purity aluminum wire (purity of 99.93wt%) is used as the evaporation source, the evaporation boat is heated to 1500°C, the gas source is oxygen, the flow rate is 80mL / min, and the vacuum degree of the vacuum chamber is 0.1Pa.

[0111] (1.2) A metal layer 13 is deposited on the surface of the transition layer 12 by an evaporation coating process. The specific process is as follows: a high-purity aluminum wire (purity of 99.93 wt%) is used as an evaporation source, the evaporation boat is heated to 1500°C, and the vacuum degree of the vacuum chamber is 0.08 Pa.

[0112] (1.3) The obtained functional aluminum current collector 10 is exposed to air and aged for 24 hours to form a passivation layer 14 made of aluminum oxide on its surface.

[0113] (2) Active material layers 20 are provided on both sides of the functional aluminum current collector 10:

[0114] (2.1) Homogenization: a. Premixing (dry mixing): Add NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) and a conductive agent (carbon nanotubes: Super P = 1:1), stirred for 10 minutes at a vacuum degree of -0.08 MPa and a rotation speed of 500 rpm; b. primary wet mixing: adding polyvinyl pyrrolidone (NMP) to the above mixture and stirring for 30 minutes at a rotation speed of 1500 rpm and a temperature of 40°C; c. secondary wet mixing: adding polyvinylidene fluoride (PVDF) to the above mixture and stirring for 60 minutes at a rotation speed of 2000 rpm; d. defoaming treatment: stirring for 20 minutes at a vacuum degree of -0.095 MPa and a rotation speed of 500 rpm to finally obtain a slurry with a solid content of 65wt% and a viscosity of 4500 cP (25°C), wherein the contents of NCM, conductive agent and PVDF are 96wt%, 2wt% and 2wt%, respectively.

[0115] (2.2) Coating: Using the functional aluminum current collector 10 obtained in step (1) as a base, the slurry obtained in step (2.1) was placed in a coating machine for double-sided coating. The coating speed was controlled to be 25 m / min and the surface density was 23.5 mg / cm 2 ; Drying temperature is: 80℃ (Zone 1) → 110℃ (Zone 2) → 90℃ (Zone 3), wind speed is 12m / s (cross flow hot air).

[0116] (2.3) Rolling: Place the baked electrode obtained in step (2.2) in a roller press for rolling. The line pressure is controlled to be 3000 N / mm and the compaction density is 3.5 g / cm 3 , and obtain a pole piece with a thickness of 200 μm.

[0117] (2.4) Die-cutting: Place the electrode obtained in step (2.3) in a die-cutting machine and cut it into 40 mm × 60 mm samples.

[0118] (3) The sample obtained in step (2.4) is placed in a precision slot extrusion sprayer. Polyethylene and aluminum sulfate 18hydrate are used as raw materials. After being melted at 280°C, the sample is passed through the sprayer die head (the die lip gap is 196 μm) while being kept warm. The edge end face of the sample is sprayed to form a sealing layer 30. The sealing layer 30 is controlled to completely cover the edge end face of the transition layer 12 to obtain a thermally safe edge-sealed electrode.

[0119] Example 2

[0120] This embodiment provides a thermally safe edge-sealed electrode. Except that the functional material 30b is changed to p-hydroxybenzoic acid, the rest of the structure and conditions are the same as those in Example 1, so they are not described here in detail.

[0121] Example 3

[0122] This embodiment provides a thermally safe edge-sealed electrode. Except that the functional material 30b is changed to polylactic acid (number average molecular weight is 20,000 g / mol), the rest of the structure and conditions are the same as those in Example 1, so they are not described here.

[0123] Example 4

[0124] This embodiment provides a thermally safe edge-sealed electrode. Except that the content of the functional material 30b in the sealing layer 30 is changed to 0.5wt%, the rest of the structure and conditions are the same as those in Example 1, and thus will not be described in detail here.

[0125] Example 5

[0126] This embodiment provides a thermally safe edge-sealed electrode. Except that the content of the functional material 30b in the sealing layer 30 is changed to 5wt%, the rest of the structure and conditions are the same as those in Example 1, and thus will not be described in detail here.

[0127] Example 6

[0128] This embodiment provides a thermally safe edge-sealed electrode. Except that the content of the functional material 30b in the sealing layer 30 is changed to 6 wt %, the rest of the structure and conditions are the same as those in Example 1, and thus will not be described in detail here.

[0129] Example 7

[0130] This embodiment provides a thermally safe edge-sealed electrode. Except that the content of the functional material 30b in the sealing layer 30 is changed to 0.2 wt %, the rest of the structure and conditions are the same as those in Example 1, and thus will not be described in detail here.

[0131] Example 8

[0132] This embodiment provides a thermally safe edge-sealed electrode. Except that the main material 30a in the sealing layer 30 is changed to polyurethane (number average molecular weight is 20,000 g / mol) and the functional material 30b is changed to bisphenol A, the rest of the structure and conditions are the same as those in Example 1, so they are not repeated here.

[0133] Example 9

[0134] This embodiment provides a thermally safe edge-sealed electrode. Except that the main material 30a in the sealing layer 30 is changed to polyurethane (number average molecular weight of 20,000 g / mol) and the functional material 30b is changed to ferrous sulfate pentahydrate, the remaining structures and conditions are the same as those in Example 1 and are not further described here.

[0135] Example 10

[0136] This embodiment provides a thermally safe edge-sealed electrode. Except that the main material 30a in the sealing layer 30 is changed to polyurethane (number average molecular weight is 20,000 g / mol) and the functional material 30b is changed to polylactic acid (number average molecular weight is 50,000 g / mol), the remaining structures and conditions are the same as those in Example 1, so they are not repeated here.

[0137] Example 11

[0138] This embodiment provides a thermally safe edge-sealed electrode. Except that the main material 30a in the sealing layer 30 is changed to polyamide (number average molecular weight of 20,000 g / mol) and the functional material 30b is changed to aluminum sulfate hexahydrate, the remaining structures and conditions are the same as those in Example 1 and will not be repeated here.

[0139] Example 12

[0140] This embodiment provides a thermally safe edge-sealed electrode. Except that the main material 30a in the sealing layer 30 is changed to polyamide (number average molecular weight of 20,000 g / mol) and the functional material 30b is changed to p-nitrophenol, the remaining structures and conditions are the same as those in Example 1 and will not be described here.

[0141] Example 13

[0142] This embodiment provides a thermally safe edge-sealed electrode. Except that the main material 30a in the sealing layer 30 is changed to polyamide (number average molecular weight is 20,000 g / mol) and the functional material 30b is changed to polylactic acid (number average molecular weight is 50,000 g / mol), the rest of the structure and conditions are the same as those in Example 1, so they are not repeated here.

[0143] Comparative Example 1

[0144] This comparative example provides a pole piece. Except that the sealing layer 30 is not provided on the edge end surface of the pole piece, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0145] Comparative Example 2

[0146] This comparative example provides a pole piece. Except that the functional material 30 b is not added to the sealing layer 30 , the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0147] Comparative Example 3

[0148] This comparative example provides an electrode. Except that the functional material 30b is changed to phthalate, the rest of the structure and conditions are the same as those in Example 1, so they are not described here in detail.

[0149] Performance testing:

[0150] (1) Adhesion test:

[0151] At room temperature (25°C), take a 20mm wide and 120mm long double-sided tape and stick it on the surface of the stainless steel plate, cut the collector sample with a size of 50mm×125mm (the collector before and after the cycle), and then evenly stick the cut measurement sample on the double-sided tape, and the double-sided tape is located in the center of the test sample, and use a 2kg standard small pressure roller to squeeze it back and forth twice; after the extrusion is completed, take a tape of the same size as the tape on the stainless steel plate, stick it to the sample surface, align it with the tape under the sample, and use a 2kg standard small pressure roller to squeeze it back and forth twice, then fix the prepared sample to the clamping distance of the peel force testing device, stretch it at an angle of 180° and a speed of 100mm / min, and set the width to the tape width. After the test is completed, read the peel force value.

[0152] (2) Cyclic performance and thermal safety performance test:

[0153] (A) Battery assembly: The electrode prepared in the present invention was used as the positive electrode; copper foil (thickness 6 μm) was used as the negative electrode current collector, and artificial graphite was used as the negative electrode active material; a polyethylene diaphragm coated with alumina ceramic (thickness 25 μm) was used as the diaphragm; the electrolyte was 1 mol·L -1A carbonate solution of LiPF6, wherein the carbonate is a mixture of propylene carbonate, ethylene carbonate and ethyl methyl carbonate, with a mass ratio of 1:1:1; using the above materials, a lithium-ion battery is assembled according to the relevant process.

[0154] (B) The battery was cycled for 1000 times at a charge / discharge rate of 1 C, and the battery capacity retention rate after 1000 cycles was recorded, that is, the battery capacity after 1000 cycles / the initial capacity of the battery × 100%.

[0155] (C) Place the battery in an adiabatic accelerating calorimeter and perform an adiabatic temperature rise test on the battery in accordance with the method specified in GB / T36276-2023. Record the battery temperature change curve over time, and determine the thermal trigger temperature (T2) and the maximum thermal runaway temperature (T3) from the curve.

[0156] The test results of the electrodes obtained in Examples 1-13 and Comparative Examples 1-3 are shown in Table 1 below.

[0157] Table 1

[0158]

[0159]

[0160] It can be seen that the present invention provides a sealing layer on the edge end face of the electrode and ensures that the sealing layer completely covers the edge end face of the transition layer, that is, the sealing treatment is achieved by fully integrating the sealing layer with the end face of the functional current collector, which effectively avoids the transition layer in the functional current collector from contacting the electrolyte, thereby improving the interface stability between the polymer film and the metal layer and the structural stability of the electrode during the cycle of the battery, significantly improving the cycle performance of the battery, and at the same time, the presence of the sealing layer avoids the internal short circuit problem of the positive and negative electrode sheets caused by the burr overlap of the current collector edge, thereby improving the safety performance of the battery.

[0161] In addition, the present invention adds specific types of functional materials to the sealing layer, which, on the one hand, improves the crystallinity of the main material, further improves its barrier performance to the electrolyte, promotes the interface stability between the polymer film and the metal layer during the battery cycle, improves the structural stability of the electrode, and thus improves the cycle performance of the battery; on the other hand, when the battery is subjected to thermal abuse, it can effectively alleviate the chain reaction of the original battery thermal runaway, thereby effectively inhibiting the continuation of the battery thermal runaway reaction and the continuous temperature rise of the battery, and ultimately significantly improving the thermal safety of the battery.

[0162] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A thermally safe edge-sealed pole piece, comprising a functional current collector and an active material layer disposed on at least one side of the functional current collector, wherein the functional current collector comprises at least a transition layer, characterized in that: The edge end surface of the thermal safety edge-sealed pole piece is provided with a sealing layer, and the sealing layer completely covers the edge end surface of the transition layer; The sealing layer contains a main material and a functional material, and the functional material includes at least one of an inorganic salt hydrate, a phenolic compound or a lactic acid polymer.

2. The thermally safe edge-sealed pole piece according to claim 1, characterized in that: The inorganic salt hydrate includes at least one of aluminum sulfate hexahydrate, aluminum sulfate hexadecahydrate, aluminum sulfate octahydrate, trisodium phosphate dodecahydrate, ferrous sulfate monohydrate, ferrous sulfate tetrahydrate, ferrous sulfate pentahydrate or ferrous sulfate heptahydrate; and / or, the phenolic compound comprises at least one of p-tert-butylphenol, phloroglucinol, p-hydroxybenzoic acid, bisphenol A or p-nitrophenol; and / or, the lactic acid polymer comprises at least one of polylactic acid, polylactic acid-glycolic acid copolymer, polycaprolactone-polylactic acid copolymer or polyethylene glycol-polylactic acid copolymer; And / or, based on the total mass of the sealing layer as a calculation basis, the content of the functional material is 0.5-5 wt %.

3. The thermally safe edge-sealed pole piece according to claim 2, characterized in that: The main body material includes at least one of polyolefin, polyurethane or polyamide; wherein the polyolefin comprises at least one of polyethylene, polypropylene or ethylene-propylene copolymer; And / or, the thickness of the sealing layer is 5-500 μm, more preferably 50-200 μm.

4. The thermally safe edge-sealed pole piece according to claim 3, characterized in that: The functional current collector includes a polymer film and a transition layer, a metal layer and a passivation layer arranged on at least one side of the polymer film, and the transition layer is located between the polymer film and the metal layer; Wherein, the material of the polymer film includes at least one of polyolefin, polyester, polyamide, polyimide, polyphenylene ether or polyphenylene sulfide; And / or, the polyolefin comprises at least one of polyethylene, polypropylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride or polytetrafluoroethylene; And / or, the polyester includes at least one of polyethylene terephthalate, polybutylene terephthalate or polyethylene naphthalate.

5. The thermally safe edge-sealed pole piece according to claim 4, characterized in that: The difference in number average molecular weight between the material of the polymer film and the main material is ≤50,000 g / mol.

6. The thermally safe edge-sealed pole piece according to claim 5, characterized in that: The polymer film includes a base film area and transition areas arranged on both sides of the base film area, and the transition areas are located between the base film area and the sealing layer; The material of the transition zone includes at least three of polyolefin, polyester, polyurethane, polyamide, polyimide, polyphenylene ether, polyphenylene sulfide, inorganic salt hydrate, phenolic compound or lactic acid polymer; And / or, the width of the transition zone is 0.05-1 mm.

7. The thermally safe edge-sealed pole piece according to claim 6, characterized in that: The sealing layer is partially sealed or fully sealed at the edge end surface of the pole piece; Wherein, when the sealing layer is partially sealed, the width of the sealing layer is greater than or equal to the thickness of the functional current collector and less than or equal to the total thickness of the electrode piece; Alternatively, when the sealing layer is fully sealed, the sealing layer goes over the edge ridge of the pole piece and overlaps at least one side surface of the pole piece, and the overlap width is ≤1 mm.

8. A method for preparing a thermally safe edge-sealed electrode according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) preparing a functional current collector comprising at least a transition layer; (2) providing an active material layer on at least one side surface of the functional current collector to obtain a pole piece; (3) A sealing layer is provided on the edge end face of the pole piece, and the sealing layer contains a main material and a functional material, and the sealing layer is controlled to completely cover the edge end face of the transition layer to obtain the thermally safe edge-sealed pole piece.

9. The preparation method according to claim 8, characterized in that The method for setting the sealing layer in step (3) includes precision spraying or slit coating; Set the coating liquid temperature used in the precision spraying or slit coating to T c , then: T m ≤T c ≤T m +50℃; Among them, T m Refers to the highest melting point among the melting points of the main material, the functional material, and the polymer film, in °C.

10. A battery, characterized in that: The battery comprises the thermally safe edge-sealed pole piece according to any one of claims 1 to 7.

Images