Electrode plate, composite additive and preparation method therefor, battery, and electrical apparatus

Abstract

An electrode plate, a composite additive and a preparation method therefor, a battery, and an electrical apparatus. The electrode plate comprises a current collector and a functional film layer disposed on at least one side of the current collector, components of the functional film layer comprising the composite additive. The composite additive comprises a porous material, and an additive disposed in a pore structure of the porous material. Using the described electrode plate to prepare a battery can improve the cycle stability of the battery.

Description

Electrode sheet, composite additive, preparation method thereof, battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202410044397.8 filed on January 11, 2024, entitled “Electrode sheet, composite additive and preparation method thereof, battery and electrical device”, which is incorporated into this application in its entirety by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an electrode sheet, a composite additive and a preparation method thereof, a battery and an electrical device. Background Art

[0004] Secondary batteries are becoming increasingly popular due to their clean and renewable characteristics, and have been widely used in many fields such as consumer electronics, electric vehicles, and energy storage.

[0005] As the application of secondary batteries expands, demands for their cycle stability are becoming increasingly stringent. Conventional technologies often enhance battery performance by adding various functional additives to the electrolyte. However, the addition of additives is often accompanied by side reactions. For example, some additives can improve the positive electrode interface but deteriorate the negative electrode, causing side reactions. Furthermore, conventional solutions only utilize additives close to the electrode, with excess additives in the electrolyte phase. Consequently, the cycle stability of conventional secondary batteries still cannot meet the increasingly stringent demands for secondary battery performance.

[0006] Therefore, traditional technologies still need to be further improved.

[0007] Summary of the Invention

[0008] Based on this, it is necessary to provide an electrode sheet, a composite additive and a preparation method thereof, a battery and an electrical device, aiming to improve the cycle stability performance of the battery.

[0009] In a first aspect of the present application, an electrode sheet is provided, comprising a current collector and a functional film layer provided on at least one side of the current collector, wherein the functional film layer comprises a composite additive;

[0010] The composite additive comprises a porous material and an additive arranged in the pore structure of the porous material.

[0011] In the above-mentioned electrode sheet, the functional film layer on the surface of the current collector contains a composite additive with a specific structure. The additive is placed in the pore structure of the porous material. On the one hand, the position of the additive is directly fixed on the surface of the electrode sheet. On the other hand, combined with the advantages of the pore structure of the porous material, it can promote the infiltration of the electrolyte into the composite additive. With the synergistic effect of various aspects, when the above-mentioned electrode sheet is used to prepare a battery, under the infiltration of the electrolyte, the additive can be gradually released from the pores of the porous material and directly targeted to act on the interface where the electrode sheet contacts the electrolyte, exerting a stable effect, thereby improving the cycle stability of the battery.

[0012] It should be noted that when the above-mentioned additives are solid, they can be stacked, embedded or physically adsorbed in the pore structure. When the above-mentioned additives are liquid, the above-mentioned additives are arranged in the pore structure of the porous material mainly through physical adsorption, mainly utilizing the adsorption principle of the porous material, such as intermolecular forces.

[0013] In some embodiments, the composite additive further includes a polymer film layer, and the polymer film layer is disposed on the surface of the porous material.

[0014] Setting a polymer film layer on the surface of the porous material can restrain the additives in the pore structure. When the electrolyte infiltrates the composite additives on the electrode sheet, the solvent must first infiltrate the polymer film and then enter the pores to infiltrate the additives, which is beneficial to delaying the release of the additives in the pores. In order to enable the additives in the pore structure to be released at an appropriate and uniform speed during repeated charge and discharge, the released additives can exert their effects as much as possible, further improving the cycle stability.

[0015] In some embodiments, the thickness of the polymer film layer is 0.1 μm to 0.6 μm.

[0016] In some embodiments, the thickness of the polymer film layer is 0.1 μm to 0.5 μm.

[0017] The thickness of the polymer film layer is further regulated to extend the sustained release rate of the additive while maintaining good electrolyte wettability of the composite additive in the electrode sheet.

[0018] In some embodiments, the polymer film layer comprises a polymer represented by formula (I):

[0019] wherein R1 and R2 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen group, a substituted or unsubstituted aromatic group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaromatic group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group or a carbonate group, and n is the degree of polymerization.

[0020] In some embodiments, the polymer film layer includes at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyethylene sulfonate or polystyrene.

[0021] The polymer has good oxidation resistance and is difficult to undergo oxidation reaction when the electrochemical oxidation potential of the battery is increased and the charging voltage reaches 4.3V.

[0022] In some embodiments, based on the total mass of the porous material and the additive, the mass of the additive accounts for 10% to 70%.

[0023] In some embodiments, based on the total mass of the porous material and the additive, the mass of the additive accounts for 30% to 70%.

[0024] Adjust the mass ratio of additives to effectively play the role of additives while maintaining good wettability of composite additives.

[0025] In some embodiments, the electrode sheet is a positive electrode sheet, and in the functional film layer, the mass proportion of the composite additive is 0.5% to 3%;

[0026] In some embodiments, the electrode sheet is a negative electrode sheet, and in the functional film layer, the mass proportion of the composite additive is 1% to 5%.

[0027] In some embodiments, the additive includes at least one of a physical adsorption type electrolyte additive or a chemical reaction type electrolyte additive.

[0028] The electrolyte additive is directly fixed on the surface of the electrode sheet, so that it can be gradually released from the pores of the porous material under the infiltration of the electrolyte and directly targeted at the interface between the electrode sheet and the electrolyte, reducing the probability of side reactions and playing a stable role, thereby improving the cycle stability of the battery.

[0029] Furthermore, compared with the technical solution of directly adding electrolyte additives to the electrolyte in traditional technologies, the technical solution of the present application directly fixes the electrolyte additives in the electrode sheet. The electrolyte additives can be gradually released from the pore structure of the porous material and directly targeted at the interface between the electrode sheet and the electrolyte, greatly reducing the probability of the additives entering the electrolyte liquid phase. The amount used is less than the amount directly added to the electrolyte, saving costs while still maintaining excellent results.

[0030] In some embodiments, the porous material includes at least one of an inorganic aerogel, an organic aerogel, a molecular sieve, or an organometallic framework material.

[0031] In some embodiments, the porous material satisfies at least one of the following conditions (1) to (4):

[0032] (1) The inorganic aerogel includes at least one of silica aerogel, titania aerogel, zirconia aerogel, alumina aerogel, magnesia aerogel, vanadium oxide aerogel, boron nitride aerogel or titanium nitride aerogel;

[0033] (2) The organic aerogel includes at least one of polymethyl methacrylate aerogel, polystyrene aerogel, or polyimide aerogel;

[0034] (3) The molecular sieve includes at least one of a microporous silica-alumina molecular sieve, a mesoporous silica-alumina molecular sieve, or a macroporous silica-alumina molecular sieve;

[0035] (4) The organic metal framework material includes at least one of a zeolite imidazole framework, a dimethyl imidazole cobalt, an iron-containing organic metal framework material, a zinc-containing organic metal framework material, or a chromium-containing organic metal framework material.

[0036] In a second aspect of the present application, a composite additive is provided, comprising a porous material and an additive disposed in the pore structure of the porous material.

[0037] Among the above-mentioned composite additives, the additives are directly placed in the pore structure. When used to prepare electrode sheets, the additives can be directly fixed on the surface of the electrode sheets. At the same time, combined with the advantages of the pore structure of the porous material, the infiltration of the electrolyte into the composite additives can be promoted; all aspects work synergistically, and under the infiltration of the electrolyte, the additives can gradually be slowly released from the pores of the porous material and directly target the interface where the electrode sheet contacts the electrolyte, exerting a stable effect, thereby improving the cycle stability of the battery.

[0038] In some embodiments, the composite additive further includes a polymer film layer, and the polymer film layer is disposed on the surface of the porous material.

[0039] In some embodiments, the polymer film layer satisfies at least one of the following conditions (1) to (2):

[0040] (1) The thickness of the polymer film layer is 0.1 μm to 0.6 μm;

[0041] (2) The polymer film layer comprises a polymer represented by formula (I):

[0042] wherein R1 and R2 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen group, a substituted or unsubstituted aromatic group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaromatic group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group or a carbonate group, and n is the degree of polymerization.

[0043] In some embodiments, the porous material satisfies at least one of the following conditions (1) to (3):

[0044] (1) The pore size of the porous material is 0.3 nm to 50 nm;

[0045] (2) The porosity of the porous material is 80% to 99.8%;

[0046] (3) The volume average particle size of the porous material is 1 μm to 6 μm.

[0047] Regulating the porosity of porous materials can further increase the number of pores for adsorbing additives. By regulating the pore size of porous materials, the pore structure space for adsorbing additives can be regulated, thereby controlling the adsorption effect of the pore structure on the additives. Regulating the particle size of porous materials is beneficial to increasing the wetting rate of the electrolyte on the composite additives. These factors are all conducive to improving the sustained release effect of additives in the composite additives.

[0048] A third aspect of the present application provides a battery, comprising the electrode sheet of the first aspect and at least one of the composite additives of the second aspect.

[0049] A fourth aspect of the present application provides an electrical device comprising at least one of the electrode sheet of the first aspect, the composite additive of the second aspect, and the battery of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0051] FIG1 is a schematic diagram of an embodiment of a battery cell;

[0052] Figure 2 is an exploded view of Figure 1;

[0053] FIG3 is a schematic diagram of an embodiment of a battery pack;

[0054] FIG4 is an exploded view of FIG3 ;

[0055] FIG5 is a schematic diagram of an embodiment of an electrical device using a battery as a power source;

[0056] FIG6 is an electron microscope image of the composite additive prepared in Example 1.

[0057] Description of reference numerals:

[0058] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery cell; 41. Shell; 42. Electrode assembly; 43. Cover; 5. Electrical device. DETAILED DESCRIPTION

[0059] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0061] In this application, the term "alkyl" refers to a group formed when an alkane loses a hydrogen, such as methane loses a hydrogen to form a methyl group; "alkenyl or alkynyl" refers to a group formed when an alkene or alkyne loses a hydrogen, such as ethylene loses a hydrogen to form vinyl, and acetylene loses a hydrogen to form ethynyl.

[0062] In the present application, the number of carbon atoms in the "alkyl group having 1 to 5 carbon atoms" may be 1 to 5, including 1, 2, 3, 4, and 5. Non-limiting examples include methane, ethyl, and n-propyl.

[0063] In the present application, the term "substituted or unsubstituted" means that the functional group described after the term may or may not have a substituent.

[0064] In the present application, the halogen group includes chlorine, fluorine, bromine, and iodine.

[0065] In this application, "aryl" refers to a hydrocarbon group containing at least one aromatic ring, including non-fused-ring aromatic groups and fused-ring aromatic groups. A fused-ring aromatic group is a group formed by linking two or more aromatic rings through two common adjacent ring atoms, i.e., a fused ring.

[0066] Aromatic ring refers to a cyclic hydrocarbon compound with aromatic properties: that is, a hydrocarbon compound with a cyclic closed-ring conjugated system.

[0067] In the present application, "heteroaromatic group" refers to a group formed when a hydrocarbon compound containing a heteroatom loses a hydrogen atom and has a cyclic closed-ring conjugated system; further, the type of heteroatom can be N, O, P, S, etc.

[0068] In this application, the term "ring atoms" refers to the number of atoms bonded to form a ring. When a ring is substituted with a substituent, the atoms contained in the substituent are not included in the ring atoms. The term "ring atoms" used below applies unless otherwise specified. For example, a benzene ring has 6 ring atoms, and a naphthalene ring has 10 ring atoms.

[0069] In traditional technologies, various functional additives are often added to the electrolyte to help improve battery performance. However, the addition of additives is often accompanied by side reactions, which limit the effective function of the additives. Research has found that the traditional solution of adding additives to the electrolyte requires the use of a large amount of additives, of which only a portion will be freed to the side close to the electrode to improve the interfacial stability of the electrode, while a portion will remain in the bulk phase of the electrolyte. This part of the additive is unable to play a positive and effective role, not only resulting in a waste of resources, but also causing side reactions, which have an adverse effect on battery performance.

[0070] Some technical solutions use polymer capsules to completely encapsulate the additives and apply them to the electrode. During charge and discharge, the capsules rupture to release the additives, effectively preventing cross-reactions. However, further research has found that while the capsules rupture and release the additives at the moment of charge and discharge, the release rate is relatively rapid, and much of the additive still escapes into the electrolyte.

[0071] Based on this, after a lot of experimental research, the technical solution of this application was obtained.

[0072] One embodiment of the present application provides an electrode sheet, which includes a current collector and a functional film layer arranged on at least one side of the current collector, the functional film layer includes a composite additive; the composite additive includes a porous material and an additive arranged in the pore structure of the porous material.

[0073] In the above-mentioned electrode sheet, the functional film layer on the surface of the current collector contains a composite additive with a specific structure. The additive is placed in the pore structure of the porous material. On the one hand, the position of the additive is directly fixed on the surface of the electrode sheet. On the other hand, combined with the advantages of the pore structure of the porous material, it can promote the infiltration of the electrolyte into the composite additive. With the synergistic effect of various aspects, when the above-mentioned electrode sheet is used to prepare a battery, under the infiltration of the electrolyte, the additive can be gradually released from the pores of the porous material and directly targeted to act on the interface where the electrode sheet contacts the electrolyte, exerting a stable effect, thereby improving the cycle stability of the battery.

[0074] It should be noted that when the above-mentioned additives are solid, they can be stacked, embedded or physically adsorbed in the pore structure. When the above-mentioned additives are liquid, the above-mentioned additives are arranged in the pore structure of the porous material mainly through physical adsorption, mainly utilizing the adsorption principle of the porous material, such as intermolecular forces.

[0075] In some embodiments, the porous material comprises an open-pore structure.

[0076] Open pore structure refers to the pores in porous materials that are connected to the outside world.

[0077] In some embodiments, the composite additive further includes a polymer film layer, which is disposed on the surface of the porous material.

[0078] Setting a polymer film layer on the surface of the porous material can restrain the additives in the pore structure. When the electrolyte infiltrates the composite additives on the electrode sheet, the solvent must first infiltrate the polymer film and then enter the pores to infiltrate the additives, which is beneficial to delaying the release of the additives in the pores. In order to enable the additives in the pore structure to be released at an appropriate and uniform speed during repeated charge and discharge, the released additives can exert their effects as much as possible, further improving the cycle stability.

[0079] It should be noted that the pore structure of the porous material contains additives, which means that at least part of the surface of the additives in the pore structure is exposed to the external environment, which is equivalent to a part of the surface of the porous material. When this part of the surface area is covered by the polymer film layer, it is equivalent to a part of the surface of the additive being also covered by the polymer film layer.

[0080] Furthermore, the inner surface of the pore structure of the porous material can also be covered by a polymer without affecting the effect of the additive.

[0081] In some embodiments, at least 50% of the surface area of ​​the porous material is provided with the polymer film layer.

[0082] In some embodiments, at least 70% of the surface area of ​​the porous material is provided with the polymer film layer.

[0083] In some embodiments, at least 90% of the surface area of ​​the porous material is provided with the polymer film layer.

[0084] In some embodiments, at least 95% of the surface area of ​​the porous material is provided with the polymer film layer.

[0085] In some embodiments, the thickness of the polymer film layer is 0.1 μm to 0.6 μm.

[0086] In this application, the unit "μm" means micrometer.

[0087] In some embodiments, the thickness of the polymer film layer is 0.1 μm to 0.5 μm.

[0088] The thickness of the polymer film layer is further regulated to extend the sustained release rate of the additive while maintaining good electrolyte wettability of the composite additive in the electrode sheet.

[0089] In the above "0.1μm~0.5μm", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm; or a range consisting of any two numerical values, for example, it can be 0.1μm~0.5μm, 0.1μm~0.4μm, 0.1μm~0.3μm, 0.1μm~0.2μm, 0.2μm~0.5μm, 0.3μm~0.5μm.

[0090] In some embodiments, the polymer film layer comprises a polymer represented by formula (I):

[0091] wherein R1 and R2 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen group, a substituted or unsubstituted aromatic group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaromatic group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group or a carbonate group, and n is the degree of polymerization.

[0092] The polymer has good oxidation resistance and can improve the electrochemical oxidation potential of the battery. When the charging voltage reaches 4.3 volts (V), it can still maintain a stable structure and function. That is, the electrochemical oxidation potential of the polymer is greater than or equal to 4.3V.

[0093] Furthermore, the electrochemical oxidation potential test method of the above polymer can adopt the following steps:

[0094] The composite additive containing the polymer film layer was added to the positive electrode active layer to prepare a positive electrode sheet, wherein the current collector was a carbon-coated aluminum foil, and the components in the positive electrode active layer included the composite additive, the positive electrode material NMC811, the conductive agent Super P, and the binder PVDF (polyvinylidene fluoride) in a mass ratio of 0.5:97.5:1:1; the positive electrode sheet had an areal capacity of 3.5 mAh / cm 2 .

[0095] Negative electrode sheet: A lithium foil with a thickness of 50 μm and a copper foil with a thickness of 12 μm are rolled and composited to obtain the negative electrode sheet.

[0096] Electrolyte: Lithium hexafluorophosphate (LiPF6) is dissolved in an organic solvent and stirred evenly to obtain an electrolyte with a lithium salt concentration of 1 mol / L; the organic solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 50:50.

[0097] Separator: A polyethylene film with a thickness of 12 μm was used as the separator.

[0098] The above-mentioned positive electrode sheet, separator, negative electrode sheet and electrolyte are assembled to construct a battery cell, charged at a constant current of 0.5C to 4.3V, discharged at a constant current of 0.5C to 2.8V, and the charging cut-off voltage is 4.3V to obtain a charge and discharge curve. If it can be discharged smoothly to 4.3V, and there is no current jump peak at the cut-off voltage in the charge and discharge curve, it is determined that the polymer has no side reaction at the positive electrode of the battery that causes the battery charging and discharging to be interrupted, and the electrochemical oxidation potential is greater than or equal to 4.3V.

[0099] In some embodiments, R1 and R2 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, a cyano group, a halogen, an aromatic group having 6 to 10 ring atoms, an aromatic group having 6 to 10 ring atoms substituted by a halogen, a heteroaromatic group having 5 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0100] In some embodiments, R1 and R2 are independently selected from any one of H, a chain alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, a cyano group, a halogen, a phenyl group, a phenyl group substituted by a halogen, a pyrrolyl group, a pyrrolone group, a pyrrolyl group substituted by a halogen, a pyrrolone group substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0101] In some embodiments, the cation in the sulfonate group may be NH4 +, at least one of alkali metal ions; further, the alkali metal ions include at least one of potassium ions, lithium ions or sodium ions.

[0102] In some embodiments, R1 and R2 are independently selected from any one of H, a chain alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by a halogen, a cyano group, a halogen, a phenyl group, a phenyl group substituted by a halogen, a pyrrolyl group, a pyrrolone group, a pyrrolyl group substituted by a halogen, a pyrrolone group substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0103] In some embodiments, R1 and R2 are independently selected from any one of H, methyl, ethyl, propyl, methyl substituted by chlorine, ethyl substituted by chlorine, propyl substituted by chlorine, cyano, halogen, phenyl, phenyl substituted by halogen, pyrrol, pyrrolone, pyrrol substituted by halogen, pyrrolone substituted by halogen, sulfonic acid, sulfonate, carboxylic acid, carboxylate, carbonic acid or carbonate.

[0104] In some embodiments, the polymer film layer includes at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyethylene sulfonate, or polystyrene.

[0105] In some embodiments, n is 50 to 1×10 5 Any integer.

[0106] In some embodiments, the number average molecular weight of the polymer may be 2×10 3 ~8×10 5 .

[0107] In some embodiments, based on the total mass of the porous material and the additive, the mass of the additive accounts for 10% to 70%.

[0108] In some embodiments, based on the total mass of the porous material and the additive, the mass of the additive accounts for 30% to 70%.

[0109] The mass ratio of additives is adjusted to effectively play the role of additives while maintaining good electrolyte wettability of the composite additives.

[0110] In the above “10% to 70%”, the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 10%, 11%, 13%, 15%, 17%, 19%, 20%, 21%, 23%, 25%, 27%, 29%, 30%, 31%, 33%, 35%, 37%, 39%, 40%, 41%, 43%, 45%, 47%, 49%, 50%, 51%, 53%, 55%, 57%, 59%, 60%, 61%, 63%, 65%, 67%, 69%, 70%; or a range consisting of any two values. For example, it may be 10% to 70%, 20% to 70%, 30% to 70%, 35% to 70%, 40% to 70%, 45% to 70%, 50% to 70%, 55% to 70%, 60% to 70%, 15% to 60%, 25% to 60%, 35% to 60%, 40% to 60%, 45% to 60%, 50% to 60%, 55% to 60%.

[0111] The above-mentioned additives include electrolyte additives, which can be various additives used to be added to electrolytes in the battery field.

[0112] In some embodiments, on the one hand, from the perspective of state, the above-mentioned additives can be liquid or solid; on the other hand, from the perspective of the action mechanism of the additives, they include at least one of a chemical reaction type electrolyte additive that undergoes a chemical reaction during the battery charging and discharging process or a physical adsorption type electrolyte additive that does not react, such as a film-forming agent, an acid binding agent, etc., which undergo a chemical reaction during the battery charging and discharging process; some additives that improve low-temperature performance and additives that improve high-temperature performance act through their own characteristics and do not undergo chemical reactions during the battery charging and discharging.

[0113] The electrolyte additive is directly fixed on the surface of the electrode sheet, so that it can be gradually released from the pores of the porous material under the infiltration of the electrolyte and directly targeted at the interface between the electrode sheet and the electrolyte, reducing the probability of side reactions and playing a stable role, thereby improving the cycle stability of the battery.

[0114] Furthermore, compared with the technical solution of directly adding electrolyte additives to the electrolyte in traditional technologies, the technical solution of the present application directly fixes the electrolyte additives in the electrode sheet. The electrolyte additives can be gradually released from the pore structure of the porous material and directly targeted at the interface between the electrode sheet and the electrolyte, greatly reducing the probability of the additives entering the electrolyte liquid phase. The amount used is less than the amount directly added to the electrolyte, saving costs while still maintaining excellent results.

[0115] In some embodiments, the additive includes at least one of a film-forming additive, an acid-binding agent, a flame-retardant additive, an overcharge protection additive, an additive for improving low-temperature performance, or an additive for improving high-temperature performance.

[0116] As an example: the above-mentioned additives include lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, methyl trifluoroethyl carbonate, trifluoropropylene carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, vinyl acetate, propane sultone, butane sultone, propene sultone, fluoropropane sultone, vinyl sulfate, dimethylsiloxane, trimethylsilyl trifluoromethanesulfonate, vinyltrimethoxysilane, dimethyl phenylphosphonate, dimethyl benzylphosphonate, acetonitrile, succinonitrile or at least one of ionic liquids.

[0117] In some embodiments, the porous material includes at least one of an inorganic aerogel, an organic aerogel, a molecular sieve, or an organometallic framework material.

[0118] In some embodiments, the inorganic aerogel may include at least one of silica aerogel, titania aerogel, zirconia aerogel, alumina aerogel, magnesia aerogel, vanadium oxide aerogel, boron nitride aerogel, or titanium nitride aerogel.

[0119] In some embodiments, the organic aerogel includes a polymer aerogel; as an example, the organic gel may include at least one of polymethyl methacrylate aerogel, polystyrene aerogel, or polyimide aerogel.

[0120] In some embodiments, the molecular sieve may include at least one of a microporous silica-alumina (SiO 2 / Al 2 O 3 ) molecular sieve, a mesoporous silica-alumina molecular sieve, or a macroporous silica-alumina molecular sieve.

[0121] In some embodiments, the organic metal framework material includes at least one of a zeolite imidazole framework, cobalt dimethyl imidazole, an organic metal framework material containing iron, an organic metal framework material containing zinc, or an organic metal framework material containing chromium.

[0122] In some embodiments, the organometallic framework may include ZIF-8 (C8H 12 N4.Zn, zeolite imidazole framework-8), ZIF-67 (C8H 12 N4.Co, dimethyl imidazole cobalt), MIL-100 (C9H6O6Fe, 1,3,5-pyromellitic acid iron), MIL-101 (C 24 H 16 Cr3FO 15, tris[M-[1,4-benzenedicarboxylic acid (2-)]-chloro-M3-oxotriCr), or MOF-5(Zn4O(C8H6O4)3×(HCON(CH3)2)8(C6H5Cl), zinc, tris[[-[1,4-benzenedicarboxylic acid (2-)-KO1).

[0123] The functional film layer may be an active material layer or other functional film layers.

[0124] In some embodiments, the electrode sheet is a positive electrode sheet.

[0125] In some embodiments, the weight percentage of the composite additive in the functional film layer is 0.5% to 3%.

[0126] In some embodiments, the weight percentage of the composite additive in the functional film layer is 1.5% to 3%.

[0127] In the above-mentioned "0.5% to 3%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%; or a range consisting of any two values, for example, it can be 0.5% to 3%, 0.5% to 2%, 0.5% to 1%, 1% to 3%, 1% to 2%, 2% to 3%.

[0128] In some embodiments, the electrode sheet is a negative electrode sheet.

[0129] In some embodiments, the weight percentage of the composite additive in the functional film layer is 1% to 5%.

[0130] In the above-mentioned "1% to 5%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%; or a range consisting of any two values, for example, it can be 1% to 5%, 1% to 4%, 1% to 3%, 1% to 2%, 2% to 3%.

[0131] Under the infiltration of electrolyte, the additives in the electrode sheet can be gradually released from the pore structure of the porous material and directly targeted at the interface between the electrode sheet and the electrolyte, exerting a stable effect. Even with a small amount, it can still stably improve the cycle performance of the battery and reduce the probability of cross-reaction due to excessive additives being released into the electrolyte.

[0132] In some embodiments, the electrode sheet is a positive electrode sheet, and in the composite additive, the mass of the additive accounts for 10% to 70% based on the total mass of the porous material and the additive.

[0133] In some embodiments, the electrode sheet is a positive electrode sheet, and the additives in the composite additive include at least one of a film-forming additive, an acid binding agent, a flame retardant additive, an overcharge protection additive, an additive for improving low-temperature performance, or an additive for improving high-temperature performance.

[0134] In some embodiments, the electrode sheet is a positive electrode sheet, and the additive in the composite additive includes at least one of lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, methyl trifluoroethyl carbonate, trifluoropropylene carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, vinyl acetate, propane sultone, butane sultone, propene sultone, fluoropropane sultone, vinyl sulfate, dimethylsiloxane, trimethylsilyl trifluoromethanesulfonate, vinyltrimethoxysilane, dimethyl phenylphosphonate, dimethyl benzylphosphonate, acetonitrile, succinonitrile or ionic liquid.

[0135] In some embodiments, the electrode sheet is a negative electrode sheet, and the weight of the composite additive is 30% to 70% based on the total weight of the porous material and the additive.

[0136] In some embodiments, the electrode sheet is a negative electrode sheet, and the additive in the composite additive includes a film-forming additive.

[0137] In some embodiments, the electrode sheets are positive and negative electrode sheets, and the additives in the composite additive include at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, vinyl acetate, propane sultone, butane sultone, propene sultone, fluoropropane sultone, vinyl sulfate, dimethylsiloxane, trimethylsilyl trifluoromethanesulfonate, vinyltrimethoxysilane, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate or lithium tetrafluoroborate.

[0138] In some embodiments, the functional film layer further includes an active material, a conductive agent, and a binder.

[0139] In some embodiments, the electrode sheet is a positive electrode sheet, and the mass proportion of the active material in the functional film layer is 93% to 98.5%.

[0140] In some embodiments, the electrode sheet is a positive electrode, and the active material is a positive electrode active material. The positive electrode active material can be selected from common positive electrode active materials in the art, including but not limited to: positive electrode active materials for lithium ion batteries, positive electrode active materials for sodium ion batteries, and positive electrode active materials for potassium ion batteries.

[0141] The positive electrode active material of a lithium ion battery, the positive electrode active material of a sodium ion battery and the positive electrode active material of a potassium ion battery are hereinafter referred to as lithium ion active material, sodium ion active material or potassium ion active material, respectively.

[0142] Further, as an example, the lithium ion active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to: lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or its modified compounds. Examples of lithium phosphates containing olivine structures may include but are not limited to at least one of lithium iron phosphate (such as LiFePO4, referred to as LFP), lithium manganese phosphate (such as LiMnPO4) or lithium manganese iron phosphate. In any embodiment of the present application, the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO4, x is any number from 0 to 1.

[0143] It can be understood that when x is 0, LiFe x Mn (1-x) PO4 is LiMnPO4 lithium manganese phosphate. When x is 1, LiFe x Mn (1-x) PO4 is LiFePO4 lithium iron phosphate (LFP).

[0144] It should be noted that the lithium content in the positive electrode material exemplified above refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charge and discharge process. That is, the molar subscript of Li in the positive electrode active material in the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0145] For example, LiFe x Mn (1-x) PO4 can be further expressed as Li y Fe x Mn (1-x) PO4, y is 0~1.1.

[0146] For example, for the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x , y is 0.2~1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn or Al, and A is one or more of S, N, F, Cl, Br or I.

[0147] The battery is accompanied by Li intercalation and deintercalation and consumption during the charge and discharge process. The molar content of Li varies when the battery is discharged to different states. The above definition of y includes the molar content of Li under different charge and discharge states of the battery. Furthermore, the battery voltage is usually between 2-5V.

[0148] In some embodiments, the above-mentioned active material includes a high-voltage positive electrode active material; further, the above-mentioned active material includes a nickel-containing active material; for example, it can be at least one of a nickel-containing ternary material, lithium nickel cobalt oxide, lithium nickel manganese oxide or lithium nickel cobalt manganese oxide; more specifically, it can be at least one of lithium nickel manganese cobalt oxide, nickel manganese spinel or nickel-rich lithium manganese oxide.

[0149] As an example, the sodium ion active material may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, or a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium ion battery positive electrode active materials may also be used.

[0150] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr or Cu, and 0<x≤1.

[0151] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce; Y includes at least one of P, S or Si; n represents (YO4) n- valence.

[0152] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y includes at least one of P, S, or Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl or Br.

[0153] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and a class of compounds containing an optional halogen anion. Y includes at least one of P, S or Si, and n represents (YO4) n- valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce, m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl or Br.

[0154] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7)(NFPP), NaM1PO4F or Na3(VO y )2(PO4)2F (3-2y) At least one of .

[0155] M1 is at least one of V, Fe, Mn or Ni, and 0≤y≤1.

[0156] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce. Prussian blue compounds are, for example, Na a M2 b M3 c (CN)6, wherein M2 and M3 are each independently selected from at least one of Ni, Cu, Fe, Mn, Co or Zn, 0<a≤2, 0<b<1, 0<c<1.

[0157] In some embodiments, the electrode sheet is a positive electrode sheet, and the conductive agent accounts for 0.5% to 2% by mass in the functional film layer.

[0158] In some embodiments, the electrode sheet is a positive electrode sheet, and the binder accounts for 0.5% to 2% by mass in the functional film layer.

[0159] In any embodiment of the present application, the conductive agent in the positive electrode sheet may be any commonly used conductive agent in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, or graphene. Specifically, the conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), and graphene, or composite conductive agents thereof.

[0160] In any embodiment of the present application, in the above-mentioned positive electrode sheet, the binder of the binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS) or at least one of fluorine-containing acrylate resin.

[0161] In any embodiment of the present application, the positive electrode sheet can be prepared by the following method: dispersing the above-mentioned components for preparing the positive electrode sheet in an organic solvent to form a positive electrode slurry; coating the positive electrode slurry on the current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0162] In some embodiments, the solid content of the positive electrode slurry is 40 wt % to 80 wt %, and the viscosity at 25° C. is adjusted to 5000 mPa·s to 25000 mPa·s.

[0163] In this application, the unit "mPa·s" refers to millipascal·second.

[0164] In some embodiments, the organic solvent includes but is not limited to: N-methylpyrrolidone.

[0165] In some embodiments, the surface density of the positive electrode sheet is 15 mg / cm 2 ~35mg / cm 2 .

[0166] In this application, the unit "mg / cm 2 ” refers to mg / cm2.

[0167] Areal density of positive electrode active material = mass of positive electrode active material / area of ​​positive electrode sheet.

[0168] In some embodiments, the electrode sheet is a negative electrode sheet, and the mass proportion of the active material in the functional film layer is 85% to 97%.

[0169] In some embodiments, the electrode sheet is a negative electrode sheet, and the active material is a negative electrode active material.

[0170] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0171] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesocarbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials or iron-based materials.

[0172] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal or lithium metal alloys.

[0173] In some embodiments, the electrode sheet is a negative electrode sheet, and the conductive agent accounts for 1% to 5% by mass in the functional film layer.

[0174] In some embodiments, the electrode sheet is a negative electrode sheet, and the binder accounts for 1% to 5% by mass in the functional film layer.

[0175] In any embodiment of the present application, the conductive agent in the negative electrode sheet may be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, or graphene. Specifically, the conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), graphene, and composite conductive agents thereof.

[0176] In some embodiments, in the above-mentioned negative electrode sheet, the binder can be a binder commonly used in the art, which can be selected from at least one of ethylene-vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) or carboxymethyl chitosan (CMCS).

[0177] In any embodiment of the present application, the functional film layer may optionally further include other additives, such as a thickener, such as sodium carboxymethyl cellulose (CMC-Na).

[0178] In any embodiment of the present application, the negative electrode sheet can be prepared by the following method: the above-mentioned components for preparing the negative electrode sheet, such as composite additives, negative electrode active materials, conductive agents, binders and any other components, are dispersed in a solvent to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0179] In some embodiments, the solvent includes but is not limited to water.

[0180] In some embodiments, the solid content of the negative electrode slurry is 30 wt % to 70 wt %, and the viscosity at 25° C. is adjusted to 2000 mPa·s to 10000 mPa·s.

[0181] In some embodiments, the surface density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm 2 ~0.03g / cm 2 .

[0182] In this application, the unit "g / cm 2 ” refers to grams per square centimeter.

[0183] The area density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0184] Furthermore, if the composite additive also includes a polymer film layer, the negative electrode sheet can also be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the porous material, additives, negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, a prefabricated electrode sheet can be obtained, and then the prefabricated electrode sheet is fused and impregnated with a liquid additive or a mixed solvent of additives, and then dried to obtain a negative electrode sheet.

[0185] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector. For example, as the metal foil, the negative electrode sheet may be copper foil, and the positive electrode sheet may be aluminum foil.

[0186] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0187] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy.

[0188] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0189] In one embodiment of the present application, a composite additive is provided. The composite additive includes a porous material and an additive disposed in the pore structure of the porous material.

[0190] Among the above-mentioned composite additives, the additives are directly placed in the pore structure. When used to prepare electrode sheets, the additives can be directly fixed on the surface of the electrode sheets. At the same time, combined with the advantages of the pore structure of the porous material, the infiltration of the electrolyte into the composite additives can be promoted; all aspects work synergistically, and under the infiltration of the electrolyte, the additives can gradually be slowly released from the pores of the porous material and directly target the interface where the electrode sheet contacts the electrolyte, exerting a stable effect, thereby improving the cycle stability of the battery.

[0191] In some embodiments, the porous material comprises an open-pore structure.

[0192] Open pore structure refers to the pores in porous materials that are connected to the outside world.

[0193] In some embodiments, the composite additive further includes a polymer film layer, which is disposed on the surface of the porous material.

[0194] Setting a polymer film layer on the surface of the porous material can restrain the additives in the pore structure. When the electrolyte infiltrates the composite additives on the electrode sheet, the solvent must first infiltrate the polymer film and then enter the pores to infiltrate the additives, which is beneficial to delaying the release of the additives in the pores. In order to enable the additives in the pore structure to be released at an appropriate and uniform speed during repeated charge and discharge, the released additives can exert their effects as much as possible, further improving the cycle stability.

[0195] It should be noted that the pore structure of the porous material contains additives, which means that at least part of the surface of the additives in the pore structure is exposed to the external environment, which is equivalent to a part of the surface of the porous material. When this part of the surface area is covered by the polymer film layer, it is equivalent to a part of the surface of the additive being also covered by the polymer film layer.

[0196] Furthermore, the inner surface of the pore structure of the porous material can also be covered by a polymer without affecting the effect of the additive.

[0197] In some embodiments, at least 50% of the surface area of ​​the porous material is provided with the polymer film layer.

[0198] In some embodiments, at least 70% of the surface area of ​​the porous material is provided with the polymer film layer.

[0199] In some embodiments, at least 90% of the surface area of ​​the porous material is provided with the polymer film layer.

[0200] In some embodiments, at least 95% of the surface area of ​​the porous material is provided with the polymer film layer.

[0201] In some embodiments, the thickness of the polymer film layer is 0.1 μm to 0.6 μm.

[0202] In some embodiments, the thickness of the polymer film layer is 0.1 μm to 0.5 μm.

[0203] The thickness of the polymer film layer is further regulated to extend the sustained release rate of the additive while maintaining good electrolyte wettability of the composite additive in the electrode sheet.

[0204] In the above "0.1μm~0.5μm", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm; or a range consisting of any two numerical values, for example, it can be 0.1μm~0.5μm, 0.1μm~0.4μm, 0.1μm~0.3μm, 0.1μm~0.2μm, 0.2μm~0.5μm, 0.3μm~0.5μm.

[0205] In some embodiments, the polymer film layer comprises a polymer represented by formula (I):

[0206] wherein R1 and R2 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen group, a substituted or unsubstituted aromatic group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaromatic group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group or a carbonate group, and n is the degree of polymerization.

[0207] The polymer has good oxidation resistance and can improve the electrochemical oxidation potential of the battery. When the charging voltage reaches 4.3V, it can still maintain a stable structure and function. That is, the electrochemical oxidation potential of the polymer is greater than or equal to 4.3V.

[0208] Furthermore, the electrochemical oxidation potential test method of the above polymer can adopt the following steps:

[0209] The composite additive containing the polymer film layer was added to the positive electrode active layer to prepare a positive electrode sheet, wherein the current collector was a carbon-coated aluminum foil, and the components in the positive electrode active layer included the composite additive, the positive electrode material NMC811, the conductive agent Super P, and the binder PVDF (polyvinylidene fluoride) in a mass ratio of 0.5:97.5:1:1; the positive electrode sheet had an areal capacity of 3.5 mAh / cm 2 .

[0210] Negative electrode sheet: A lithium foil with a thickness of 50 μm and a copper foil with a thickness of 12 μm are rolled and composited to obtain the negative electrode sheet.

[0211] Electrolyte: Lithium hexafluorophosphate (LiPF6) is dissolved in an organic solvent and stirred evenly to obtain an electrolyte with a lithium salt concentration of 1 mol / L; the organic solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 50:50.

[0212] Separator: A polyethylene film with a thickness of 12 μm was used as the separator.

[0213] The above-mentioned positive electrode sheet, separator, negative electrode sheet and electrolyte are assembled to construct a battery cell, charged at a constant current of 0.5C to 4.3V, discharged at a constant current of 0.5C to 2.8V, and the charging cut-off voltage is 4.3V to obtain a charge and discharge curve. If it can be discharged smoothly to 4.3V, and there is no current jump peak at the cut-off voltage in the charge and discharge curve, it is determined that the polymer has no side reaction at the positive electrode of the battery that causes the battery charging and discharging to be interrupted, and the electrochemical oxidation potential is greater than or equal to 4.3V.

[0214] In some embodiments, R1 and R2 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, a cyano group, a halogen, an aromatic group having 6 to 10 ring atoms, an aromatic group having 6 to 10 ring atoms substituted by a halogen, a heteroaromatic group having 5 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0215] In some embodiments, R1 and R2 are independently selected from any one of H, a chain alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, a cyano group, a halogen, a phenyl group, a phenyl group substituted by a halogen, a pyrrolyl group, a pyrrolone group, a pyrrolyl group substituted by a halogen, a pyrrolone group substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0216] In some embodiments, the cation in the sulfonate group may be NH4 + , at least one of alkali metal ions; further, the alkali metal ions include at least one of potassium ions, lithium ions or sodium ions.

[0217] In some embodiments, R1 and R2 are independently selected from any one of H, a chain alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by a halogen, a cyano group, a halogen, a phenyl group, a phenyl group substituted by a halogen, a pyrrolyl group, a pyrrolone group, a pyrrolyl group substituted by a halogen, a pyrrolone group substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0218] In some embodiments, R1 and R2 are independently selected from any one of H, methyl, ethyl, propyl, methyl substituted by chlorine, ethyl substituted by chlorine, propyl substituted by chlorine, cyano, halogen, phenyl, phenyl substituted by halogen, pyrrol, pyrrolone, pyrrol substituted by halogen, pyrrolone substituted by halogen, sulfonic acid, sulfonate, carboxylic acid, carboxylate, carbonic acid or carbonate.

[0219] In some embodiments, the polymer film layer includes at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyethylene sulfonate, or polystyrene.

[0220] In some embodiments, n is 50 to 1×10 5 Any integer.

[0221] In some embodiments, the number average molecular weight of the polymer may be 2×10 3 ~8×10 5 .

[0222] In some embodiments, based on the total mass of the porous material and the additive, the mass of the additive accounts for 10% to 70%.

[0223] The mass ratio of additives is adjusted to effectively play the role of additives while maintaining good electrolyte wettability of the composite additives.

[0224] In the above “10% to 70%”, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 10%, 11%, 13%, 15%, 17%, 19%, 20%, 21%, 23%, 25%, 27%, 29%, 30%, 31%, 33%, 35%, 37%, 39%, 40%, 41%, 43%, 45%, 47%, 49%, 50%, 51%, 53%, 55%, or a range consisting of any two values, for example, 10% to 70%, 20% to 70%, 30% to 70%, 35% to 70%, 40% to 70%, 45% to 70%, 50% to 70%, 55% to 70%, 60% to 70%, 15% to 60%, 25% to 60%, 35% to 60%, 40% to 60%, 45% to 60%, 50% to 60%, 55% to 60%.

[0225] The above-mentioned additives include electrolyte additives, which can be various additives used to be added to electrolytes in the battery field.

[0226] In some embodiments, on the one hand, from the perspective of state, the above-mentioned additives can be liquid or solid; on the other hand, from the perspective of the action mechanism of the additives, they include at least one of a chemical reaction type electrolyte additive that undergoes a chemical reaction during the battery charging and discharging process or a physical adsorption type electrolyte additive that does not react, such as a film-forming agent, an acid binding agent, etc., which undergo a chemical reaction during the battery charging and discharging process; some additives that improve low-temperature performance and additives that improve high-temperature performance act through their own characteristics and do not undergo chemical reactions during the battery charging and discharging.

[0227] The electrolyte additive is directly fixed on the surface of the electrode sheet, so that it can be gradually released from the pores of the porous material under the infiltration of the electrolyte and directly targeted at the interface between the electrode sheet and the electrolyte, reducing the probability of side reactions and playing a stable role, thereby improving the cycle stability of the battery.

[0228] Furthermore, compared with the technical solution of directly adding electrolyte additives to the electrolyte in traditional technologies, the technical solution of the present application directly fixes the electrolyte additives in the electrode sheet. The electrolyte additives can be gradually released from the pore structure of the porous material and directly targeted at the interface between the electrode sheet and the electrolyte, greatly reducing the probability of the additives entering the electrolyte liquid phase. The amount used is less than the amount directly added to the electrolyte, saving costs while still maintaining excellent results.

[0229] In some embodiments, the additive includes at least one of a film-forming additive, an acid-binding agent, a flame-retardant additive, an overcharge protection additive, an additive for improving low-temperature performance, or an additive for improving high-temperature performance.

[0230] As an example: the above-mentioned additives include lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, methyl trifluoroethyl carbonate, trifluoropropylene carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, vinyl acetate, propane sultone, butane sultone, propene sultone, fluoropropane sultone, vinyl sulfate, dimethylsiloxane, trimethylsilyl trifluoromethanesulfonate, vinyltrimethoxysilane, dimethyl phenylphosphonate, dimethyl benzylphosphonate, acetonitrile, succinonitrile or at least one of ionic liquids.

[0231] In some embodiments, the porous material includes at least one of an inorganic aerogel, an organic aerogel, a molecular sieve, or an organometallic framework material.

[0232] In some embodiments, the inorganic aerogel may include at least one of silica aerogel, titania aerogel, zirconia aerogel, alumina aerogel, magnesia aerogel, vanadium oxide aerogel, boron nitride aerogel, or titanium nitride aerogel.

[0233] In some embodiments, the organic aerogel includes a polymer aerogel; as an example, the organic gel may include at least one of polymethyl methacrylate aerogel, polystyrene aerogel, or polyimide aerogel.

[0234] In some embodiments, the molecular sieve may include at least one of a microporous silica-alumina (SiO 2 / Al 2 O 3 ) molecular sieve, a mesoporous silica-alumina molecular sieve, or a macroporous silica-alumina molecular sieve.

[0235] In some embodiments, the organic metal framework material includes at least one of a zeolite imidazole framework, cobalt dimethyl imidazole, an organic metal framework material containing iron, an organic metal framework material containing zinc, or an organic metal framework material containing chromium.

[0236] In some embodiments, the organometallic framework may include ZIF-8 (C8H 12 N4.Zn, zeolite imidazole framework-8), ZIF-67 (C8H 12 N4.Co, dimethyl imidazole cobalt), MIL-100 (C9H6O6Fe, 1,3,5-pyromellitic acid iron), MIL-101 (C 24 H 16 Cr3FO 15 , tris[M-[1,4-benzenedicarboxylic acid (2-)]-chloro-M3-oxotriCr), or MOF-5(Zn4O(C8H6O4)3×(HCON(CH3)2)8(C6H5Cl), zinc, tris[[-[1,4-benzenedicarboxylic acid (2-)-KO1).

[0237] In some embodiments, the electrode sheet is a positive electrode sheet.

[0238] In some embodiments, the pore size of the porous material is 0.3 nm to 50 nm.

[0239] In this application, the unit "nm" refers to nanometers.

[0240] It can be understood that the pore size of a porous material refers to the diameter of the pores of the porous material.

[0241] In some embodiments, the porous material has a porosity greater than or equal to 80%.

[0242] In some embodiments, the porosity of the porous material is 80% to 99.8%.

[0243] In the above-mentioned "80% to 99.8%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 90%, 91%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.8%; or a range consisting of any two values.

[0244] In some embodiments, the volume average particle size of the porous material is 1 μm to 6 μm.

[0245] Regulating the porosity of porous materials can further increase the number of pore structures for adsorbing additives. By regulating the pore size of porous materials, the pore structure space for adsorbing additives can be regulated, thereby controlling the adsorption effect of the pores on the additives. Regulating the particle size of porous materials is beneficial to increasing the wetting speed of the electrolyte on the composite additives, thereby improving the sustained release effect of the additives.

[0246] In the above “0.3nm~50nm”, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiment and the following point values: In the above “0.3nm~50nm”, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiment and the following point values: 0.3nm, 0.5nm, 0.7nm, 0.8nm, 0. 9nm, 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm; or a range consisting of any two numerical values, for example, it can be 0.3nm~1nm, 1nm~10nm, 10nm~50nm, 10nm~40nm, 10nm~30nm, 10nm~20nm, 20nm~50nm, 20nm~40nm, 20nm~30nm, 30nm~50nm.

[0247] In the above "80% to 99.8%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 80%, 85%, 90%, 95%, 98%, 99%; or a range consisting of any two values, for example, it can be 80% to 99.8%, 85% to 99.8%, 90% to 99.8%, 95% to 99.8%.

[0248] In the above "1μm~6μm", the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 1μm, 2μm, 3μm, 4μm, 5μm, 6μm; or a range consisting of any two values.

[0249] One embodiment of the present application further provides a method for preparing the composite additive, comprising the following steps:

[0250] The additive and the porous material are mixed so that the additive enters the pore structure of the porous material.

[0251] The types of additives and porous materials are the same as above and will not be described in detail here.

[0252] In the preparation method of the composite additive, the mixing step can be performed by a dry mixing method or a wet mixing method, as follows:

[0253] Dry mixing method: Mix the additives and porous materials according to the mass ratio, add them to the mechanical fusion machine, and after dry mixing and fusion, the composite additive can be obtained.

[0254] Wet mixing method: Mix the additive and porous material according to the mass ratio, then add the solvent and stir and mix, and then dry to obtain the composite additive.

[0255] The above-mentioned solvent can be any solvent that does not cause chemical reaction between the additive and the pore material; further, the above-mentioned solvent can dissolve the additive.

[0256] Furthermore, if a polymer film layer is provided on the surface of the porous material, the following preparation steps are further included:

[0257] The product obtained by the dry mixing method or the wet mixing method is dry-mixed and fused or wet-impregnated with a polymer to form a polymer film layer.

[0258] Furthermore, the wet impregnation is performed by mixing a solvent and a polymer to prepare a mixed liquid, and then mixing the above product with the mixed liquid for impregnation.

[0259] In some embodiments, the additive is a liquid or can be dissolved in a solvent to form a solution. A polymer film can be first formed on the surface of the porous material, and then the product and the additive are mixed and fused. During this process, the additive will infiltrate the polymer film into the pore structure of the porous material, and the above-mentioned composite additive can also be prepared. This preparation method is particularly suitable for negative electrode systems.

[0260] One embodiment of the present application further provides a battery, which includes the above-mentioned electrode sheet.

[0261] In some embodiments, the battery is a secondary battery; further, the battery can be a lithium metal secondary battery or a lithium ion secondary battery.

[0262] It can be understood that the battery includes a positive electrode sheet and a negative electrode sheet, and the above-mentioned electrode sheet can be a positive electrode sheet or a negative electrode sheet.

[0263] In some embodiments, the electrode sheet is a positive electrode sheet, and the negative electrode sheet in the battery can adopt various negative electrode sheet systems in the art, which are illustrated here by way of example but are not limited to the following.

[0264] In some embodiments, the battery is a lithium metal secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used for lithium metal batteries as is known in the art.

[0265] In some embodiments, the negative electrode sheet directly adopts a lithium-containing metal sheet.

[0266] In another embodiment, the negative electrode sheet includes a lithium-containing metal layer and a conductive layer stacked together.

[0267] Furthermore, the lithium-containing metal in the lithium-containing metal sheet and the lithium-containing metal layer can be lithium metal, or an alloy formed by lithium metal and other metal or non-metal elements.

[0268] Further, the other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In) or platinum (Pt); the non-metallic elements include at least one of boron (B), carbon (C) or silicon (Si).

[0269] In some embodiments, the conductive layer may be copper foil.

[0270] In any embodiment of the present application, the negative electrode sheet can be prepared by directly pressing a lithium-containing metal sheet to obtain the negative electrode sheet, or by stacking and pressing the lithium-containing metal layer and the conductive layer to obtain the negative electrode sheet.

[0271] In some embodiments, the battery is a lithium-ion secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used in lithium-ion batteries and is well known in the art.

[0272] In some embodiments, the negative electrode sheet includes a current collector and a negative electrode active layer supported on a surface of the current collector.

[0273] The components of the negative electrode active layer include a negative electrode active material.

[0274] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0275] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesocarbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials or iron-based materials.

[0276] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal or lithium metal alloys.

[0277] In any embodiment of the present application, the mass proportion of the negative electrode active material in the negative electrode active layer is 70% to 100%.

[0278] In any embodiment of the present application, the components of the negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0279] In any embodiment of the present application, the negative electrode conductive agent may be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, or graphene. Specifically, the negative electrode conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene, or composite conductive agents thereof.

[0280] The weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.

[0281] The negative electrode binder may be a binder commonly used in the art, and may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) or carboxymethyl chitosan (CMCS).

[0282] The weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.

[0283] In any embodiment of the present application, the negative electrode active layer may further optionally include other additives, such as a thickener, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of the other additives in the negative electrode active layer is 0 to 15 wt%.

[0284] In any embodiment of the present application, the current collector in the negative electrode sheet may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil.

[0285] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0286] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy.

[0287] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0288] In any embodiment of the present application, the negative electrode sheet can be prepared by the following method: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0289] In some embodiments, the solvent includes but is not limited to water.

[0290] In some embodiments, the solid content of the negative electrode slurry is 30 wt % to 70 wt %, and the viscosity at 25° C. is adjusted to 2000 mPa·s to 10000 mPa·s.

[0291] In some embodiments, the surface density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm 2 ~0.03g / cm 2 .

[0292] The area density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0293] In some embodiments, the battery further includes a separator and an electrolyte. Examples of the separator and the electrolyte are described below, including but not limited to the following.

[0294] Electrolyte: Generally, the electrolyte includes electrolyte salt and solvent.

[0295] In some embodiments, the electrolyte salt may be selected from electrolyte salts commonly used in the art, such as lithium ion electrolyte salts.

[0296] As an example, the lithium ion electrolyte salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) or lithium tetrafluorooxalatophosphate (LiTFOP).

[0297] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) or diethyl sulfone (ESE).

[0298] In some embodiments, the concentration of the electrolyte salt in the electrolyte solution is generally 0.5 mol / L to 15 mol / L.

[0299] In this application, the unit "mol / L" means mole per liter.

[0300] Diaphragm: The diaphragm is placed between the positive electrode and the negative electrode.

[0301] The type of the diaphragm of the present application can be any known porous structure diaphragm with good chemical stability and mechanical stability.

[0302] In some embodiments, the separator can be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0303] The thickness of the diaphragm is controlled to be 2 μm to 15 μm; optionally, the thickness of the diaphragm is controlled to be 2 μm to 13 μm.

[0304] The present application has no particular limitation on the shape of the battery, and the shape of the battery of the present application can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 4 of a square structure as an example.

[0305] In some embodiments, referring to FIG2 , the housing may include a shell 41 and a cover 43. Shell 41 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. Shell 41 may have an opening communicating with the receiving cavity, and cover 43 may be positioned over the opening to seal the receiving cavity.

[0306] The positive electrode sheet, separator and negative electrode sheet can be wound or laminated to form an electrode assembly 42, which is encapsulated in the receiving cavity. The number of electrode assemblies 42 included in the battery cell 4 can be one or more, which can be adjusted according to needs.

[0307] The battery includes one or more battery cells 4 .

[0308] The battery may be a battery module or a battery pack; the battery module or battery pack includes at least one battery cell 4. The number of battery cells contained in the battery module may be one or more, and those skilled in the art may select an appropriate number based on the application and capacity of the battery module.

[0309] Figures 3 and 4 illustrate an exemplary battery pack 1. Battery pack 1 includes a battery case and one or more battery cells 4 disposed within the battery case. The battery case comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for the battery cells 4.

[0310] The plurality of battery cells 4 can be arranged in the battery box in any manner.

[0311] The present application also provides an electrical device, which includes the above-mentioned battery.

[0312] Furthermore, in the above-mentioned electrical device, the battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0313] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.

[0314] The above-mentioned electrical devices may be, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc.

[0315] In some embodiments, the mobile device may be a mobile phone or a laptop computer, etc.

[0316] In some embodiments, electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, and the like.

[0317] Figure 5 shows an example of an electric device 5. The electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 5, a battery pack can be used.

[0318] As another example, the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0319] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0320] The following are specific examples.

[0321] The raw materials used in the following examples and comparative examples were all purchased from the market unless otherwise specified.

[0322] Example 1

[0323] (1) Preparation of positive electrode

[0324] S1: Preparation of composite additives

[0325] The porous material (silica aerogel) and the additive (lithium difluorooxalate borate) were mixed in a mass ratio of 30:70 and added into a mechanical fusion machine. After dry mixing for 2 hours (h), the product was mixed with a polymer (polyacrylonitrile, with a number average molecular weight of 5×10 4 ) continue to dry-mix and fuse at a mass ratio of 97:3 to form a polymer film layer to obtain a composite additive.

[0326] Among them, the pore size and porosity of the porous material used in the above steps can be tested by gas adsorption test method. The instrument used is a specific surface area and porosity analyzer. The specific steps are: place the sample to be tested in the sample tube of the instrument, evacuate, immerse the sample tube in liquid nitrogen, fill it with a known amount of gas, measure the equilibrium pressure of the gas after reaching adsorption equilibrium, gradually increase the amount of gas to the system to change the pressure, repeat the operation to obtain the adsorption and desorption isotherm, and calculate the pore size and porosity of the sample to be tested.

[0327] The volume average particle size of the porous material was measured using a Malvern laser particle size analyzer to obtain the volume average particle size.

[0328] Please see Table 1 for specific test results.

[0329] In the above composite additives, based on the total mass of the porous material and the additives, the mass proportion of the additives is recorded as Y1; the thickness of the polymer film layer is recorded as Y2.

[0330] The composite additive slice was placed under a scanning electron microscope and imaged, as shown in Figure 6. Further analysis of the element distribution information marked by the scanning electron microscope showed that the particulate matter in the pore structure contained the elements F and B unique to the additive lithium difluorooxalatoborate, indicating that the additive existed in the pore structure of the porous material.

[0331] Furthermore, an inductively coupled plasma optical emission spectrometer (ICP-OES) can be used to test the ratio of the main components of the composite additive: Y1 can be reversely deduced based on the ratio of characteristic elements of the porous material and the additive, such as silicon and boron.

[0332] Furthermore, the thickness of the polymer film layer can be characterized by transmission electron microscopy testing. Ten sites are selected under the transmission electron microscope and the average value is taken and recorded as Y2.

[0333] The specific parameters are shown in Table 1.

[0334] S2: The composite additive, positive electrode active material (lithium nickel cobalt manganese oxide, NMC811), conductive agent (Super P), and binder (PVDF) are mixed in a mass ratio of 0.5:97.5:1:1, and then NMP is added and stirred evenly to obtain a positive electrode slurry (solid content of 70%); the positive electrode slurry is coated on the surface of the positive electrode current collector carbon-coated aluminum foil, dried to form a functional film layer, and a positive electrode sheet with a surface capacity of 3.5 mAh / cm2 (mAh / cm 2 ).

[0335] Among them, the mass proportion of the composite additives in the functional film layer is recorded as Y3.

[0336] (2) A 50 μm thick lithium foil was selected and rolled and composited with a 12 μm thick copper foil to obtain a negative electrode sheet.

[0337] (3) Preparation of electrolyte

[0338] Lithium hexafluorophosphate (LiPF6) is dissolved in an organic solvent and stirred to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0339] The organic solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 50:50.

[0340] (4) A polyethylene film with a thickness of 12 μm was selected as the separator for lithium-ion batteries.

[0341] (5) Battery assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked and combined, and wrapped with aluminum-plastic film bags to form a stacked dry cell. The configured electrolyte is injected, vacuum-sealed, and allowed to stand at room temperature for 6 hours to obtain a battery for subsequent testing.

[0342] (6) Cyclic performance test

[0343] The above-mentioned battery was electrochemically cycled at room temperature (25 degrees Celsius) using a 0.5C constant current and constant voltage charge and a 0.5C constant current and discharge test conditions. The charge and discharge cutoff voltages were set at 4.3V and 2.8V, respectively. The constant current and constant voltage charge was specifically as follows: when charging at a 0.5C constant current to a cutoff voltage of 4.3V, constant voltage charging was continued at 4.3V until the current dropped to 0.05C, followed by discharge at a 0.5C constant current to 2.8V. One charge and discharge cycle was defined as one cycle. When the capacity decay rate of the battery after discharge reached 80%, the battery life was considered to have ended. The number of cycles at this point was recorded and recorded as Cy80%.

[0344] Please see Table 1 for specific test results.

[0345] Example 2

[0346] Example 2 is basically the same as Example 1, except that the preparation steps of the composite additive in step S1 are different, as follows:

[0347] Provide raw materials: polymer (polyacrylonitrile, number average molecular weight of 5×10 4 ), porous material (silica aerogel) and liquid additive (methyl trifluoroethyl carbonate); wherein, the mass ratio of the porous material (silica aerogel) and the additive (methyl trifluoroethyl carbonate) is 30:70, and the mass ratio of the total mass of the porous material and the additive to the polymer is 97:3.

[0348] First, the polymer and porous material (silica aerogel) were added to a mechanical fusion machine and dry-mixed to obtain a porous material coated with a polymer film. This material was then mixed with a liquid additive (methyl trifluoroethyl carbonate) in a blender until the liquid additive was completely absorbed and penetrated the polymer film into the pore structure of the porous material, resulting in a composite additive. The remaining steps were the same as in Example 1. Specific parameters are shown in Table 1.

[0349] Examples 3 to 6

[0350] Examples 3 to 6 are basically the same as Example 1, with the only difference being that in step S1 of preparing the composite additive, the type or physical property parameters of the porous material are different from those in Example 1. Please see Table 1 for details.

[0351] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0352] Examples 7 to 10

[0353] Examples 7 to 10 are basically the same as Example 1, with the only difference being that in the preparation of the composite additive in step S1, while keeping the total mass of the porous material and the additive the same as that in Example 1, the mass ratio of the porous material (silica aerogel) and the additive is adjusted differently, that is, Y1 is different.

[0354] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0355] Examples 11 to 14

[0356] Examples 11 to 14 are substantially the same as Example 1, with the only difference being that in step S1 , in the preparation of the composite additive, the amount of the polymer is regulated so that the thickness Y2 of the polymer film layer is different from that of Example 1.

[0357] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0358] Examples 15-16

[0359] Examples 15 to 16 are basically the same as Example 1, with the only difference being that in step S1 , in the preparation of the composite additive, the type of polymer is different from that in Example 1.

[0360] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0361] Example 17

[0362] Example 17 is basically the same as Example 1, except that in step S1, in the preparation of the composite additive, no polymer is added and no polymer film layer is formed.

[0363] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0364] Examples 18 to 20

[0365] Examples 18 to 20 are basically the same as Example 1, except that in step S2, while keeping the total mass of the composite additive and the positive electrode active material the same as that in Example 1, the respective masses of the composite additive and the positive electrode active material are changed to make Y3 different from that in Example 1.

[0366] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0367] Example 21

[0368] (1) Preparation of negative electrode sheet

[0369] S1: Step S1 is substantially the same as step S1 in Example 1, except that the additive is replaced with an equal mass of 1,3-propane sultone.

[0370] S2: The composite additive, negative electrode active material (graphite), conductive agent (conductive carbon), and binder (sodium carboxymethyl cellulose) were mixed in a mass ratio of 1:97:1:1, and deionized water was added and stirred evenly to obtain a negative electrode slurry (solid content of 40%); the negative electrode slurry was coated on the surface of the negative electrode current collector copper foil and dried to form a functional film layer to obtain a negative electrode sheet with a surface capacity of 3.85 mAh / cm 2 .

[0371] (2) Preparation of positive electrode

[0372] The positive electrode active material is lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon (SuperP), and binder (polyvinylidene fluoride) were mixed in a mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) solvent was added and stirred until the system became uniform to obtain a positive electrode slurry (solid content of 70%). The positive electrode slurry was coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying to obtain a positive electrode sheet with a surface capacity of 3.5 mAh / cm 2 .

[0373] Steps (3) to (6) are the same as those in Example 1. See Table 1 for the test results.

[0374] Comparative Example 1

[0375] Comparative Example 1 is basically the same as Example 1, except that: in step S2, no composite additive is added, and the positive electrode active material (lithium nickel cobalt manganese oxide, NCM811), the conductive agent (SuperP), and the binder (PVDF) are mixed in a mass ratio of 98:1:1; at the same time, in the preparation of the electrolyte in step (3), the additive lithium difluorooxalatoborate is added, and the mass proportion of the additive in the electrolyte is 1%.

[0376] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0377] Comparative Example 2

[0378] Comparative Example 2 is substantially the same as Comparative Example 1, except that the additive is replaced with methyl trifluoroethyl carbonate.

[0379] The other steps are the same as those in Comparative Example 1. Please see Table 1 for specific parameters.

[0380] Comparative Example 3

[0381] Comparative Example 3 is basically the same as Example 1, except that: in step S1, in the preparation of the composite additive, in the step of dry-mixing the porous material and the additive, the porous material is directly replaced with a polymer of equal mass (polyacrylonitrile, with a number average molecular weight of 5×10 4 ), the ratio of the total mass of the polymer used in the preparation process of the composite additive to the mass of the additive is: 32.1:67.9.

[0382] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0383] Comparative Example 4

[0384] Comparative Example 4 is basically the same as Example 21, except that: in step S1, in the preparation of the composite additive, in the step of dry-mixing the porous material and the additive, the porous material is directly replaced with a polymer of equal mass (polyacrylonitrile, with a number average molecular weight of 5×10 4 ), the ratio of the total mass of the polymer used in the preparation process of the composite additive to the mass of the additive is: 32.1:67.9.

[0385] The other steps are the same as those in Example 21. Please see Table 1 for specific parameters.

[0386] The relevant parameters and performance test results of each embodiment and comparative example are shown in Table 1. In the composite additive, the mass percentage of the additive is recorded as Y1, based on the total mass of the porous material and the additive. The thickness of the polymer film layer is recorded as Y2. The mass percentage of the composite additive in the functional film layer of the positive electrode sheet (or negative electrode sheet) is recorded as Y3.

[0387] Table 1

[0388] Where, “\” indicates that the substance or parameter does not exist. “ZIF-67” stands for dimethylimidazolium cobalt.

[0389] By analyzing the data in Table 1, comparing the data of Examples 1 to 20 and Comparative Examples 1 to 3, and comparing the data of Example 21 and Comparative Example 4, it can be seen that the electrode sheet of the present application can improve the cycle stability of the battery.

[0390] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0391] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make several modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the appended claims, and the specification and drawings may be used to interpret the claims.

Claims

1. An electrode sheet, the electrode sheet comprising a current collector and a functional film layer provided on at least one side of the current collector, the functional film layer comprising a composite additive; The composite additive comprises a porous material and an additive provided in the pore structure of the porous material.

2. The electrode sheet according to claim 1, wherein, The composite additive further comprises a polymer film layer provided on the surface of the porous material.

3. The electrode sheet according to claim 2, wherein, The thickness of the polymer film layer is 0.1 μm to 0.6 μm.

4. The electrode sheet according to claim 2 or 3, wherein, The thickness of the polymer film layer is 0.1 μm to 0.5 μm.

5. The electrode sheet according to any one of claims 2 to 4, wherein, The polymer film layer comprises a polymer represented by formula (I): Wherein, R1 and R2 are each independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen, a substituted or unsubstituted aryl group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaryl group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylic acid ester group, a carbonate group or a carbonate ester group, and n is the degree of polymerization.

6. The electrode sheet according to any one of claims 2 to 4, wherein, The polymer film layer comprises at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyvinyl sulfonate or polystyrene.

7. The electrode sheet according to any one of claims 1 to 6, wherein, Based on the total mass of the porous material and the additive, the mass percentage of the additive is 10% to 70%.

8. The electrode sheet according to any one of claims 1 to 7, wherein, Based on the total mass of the porous material and the additive, the mass percentage of the additive is 30% to 70%.

9. The electrode sheet according to any one of claims 1 to 8, wherein, The electrode sheet is a positive electrode sheet, and in the functional film layer, the mass percentage of the composite additive is 0.5% to 3%.

10. The electrode sheet according to any one of claims 1 to 8, wherein, The electrode sheet is a negative electrode sheet, and in the functional film layer, the mass percentage of the composite additive is 1% to 5%.

11. The electrode sheet according to any one of claims 1 to 10, wherein, The additive comprises at least one of an additive for physically adsorbed electrolyte or an additive for chemically reactive electrolyte.

12. The electrode sheet according to any one of claims 1 to 11, wherein, The porous material comprises at least one of an inorganic aerogel, an organic aerogel, a molecular sieve or a metal-organic framework material.

13. The electrode sheet according to claim 12, wherein, The porous material satisfies at least one of the following conditions (1) to (4): (1) The inorganic aerogel comprises at least one of silica aerogel, titanium dioxide aerogel, zirconium dioxide aerogel, aluminum oxide aerogel, magnesium oxide aerogel, vanadium oxide aerogel, boron nitride aerogel or titanium nitride aerogel; (2) The organic aerogel comprises at least one of polymethyl methacrylate aerogel, polystyrene aerogel or polyimide aerogel; (3) The molecular sieve comprises at least one of a microporous silica-aluminum molecular sieve, a mesoporous silica-aluminum molecular sieve or a macroporous silica-aluminum molecular sieve; (4) The metal-organic framework material comprises at least one of a zeolitic imidazolate framework, cobalt dimethylimidazole, an iron-containing metal-organic framework material, a zinc-containing metal-organic framework material or a chromium-containing metal-organic framework material.

14. A composite additive, the composite additive comprising a porous material and an additive provided in the pore structure of the porous material.

15. The composite additive according to claim 14, wherein, The composite additive further comprises a polymer film layer provided on the surface of the porous material.

16. The composite additive according to claim 15, wherein, The polymer film layer satisfies at least one of the following conditions (1) to (2): (1) The thickness of the polymer film layer is 0.1 μm to 0.6 μm; (2) The polymer film layer comprises a polymer represented by formula (I): Among them, R1 and R2 are each independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen, a substituted or unsubstituted aryl group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaryl group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylic acid ester group, a carbonate group or a carbonate ester group, and n is the degree of polymerization.

17. The composite additive according to any one of claims 14 to 16, wherein, The porous material satisfies at least one of the following conditions (1) to (3): (1) The pore diameter of the porous material is 0.3 nm to 50 nm; (2) The porosity of the porous material is 80% to 99.8%; (3) The volume average particle diameter of the porous material is 1 μm to 6 μm.

18. A battery, the battery comprising at least one of the electrode sheets according to any one of claims 1 to 13 and at least one of the composite additives according to any one of claims 14 to 17.

19. An electrical device, the electrical device comprising at least one of the electrode sheets according to any one of claims 1 to 13, at least one of the composite additives according to any one of claims 14 to 17, and at least one of the batteries according to claim 18.

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