Secondary battery and electric device

Abstract

The present application discloses a secondary battery and an electric device, the secondary battery including a separator including a base membrane and a coating layer formed on at least one side of the base membrane, the coating layer including an ion exchange resin including a group of at least one of Formula 1 or Formula 2, where the group of Formula 1 is a group of at least one of Formula 1 and Formula 2 is a group of at least one of Formula 2 and Formula 2 is a group of at least one of Formula 1 and Formula 2, and wherein the group of Formula 1 is a group of at least one of Formula 2 and Formula 2 is a group of at least one of Formula 2. R1 and R2 respectively and independently contain functional groups of at least one element of C, H, O or N, R3 contains functional groups of at least two elements of C, H or O, and * represents binding sites of the formula 1 and / or the formula 2 with other groups. Therefore, the secondary battery provided by the invention has relatively high storage performance and cycle performance under high cut-off voltage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, and particularly relates to a secondary battery and a power utilization device. BACKGROUND

[0002] Secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the increasing demand for high energy density lithium ion batteries in the market, in addition to the research and development of new materials, deep exploration and improvement of the energy density of existing materials are also one of the research hotspots, and increasing the charge cut-off voltage is one of the effective ways to improve the energy density of the battery. However, increasing the cut-off voltage will cause the storage performance and cycle performance of the battery to deteriorate. SUMMARY

[0003] In view of the technical problems in the background art, the present application provides a secondary battery, which aims to improve the storage performance and cycle performance of the battery at a high cut-off voltage.

[0004] To achieve the above-mentioned purpose, the first aspect of the present application provides a secondary battery, which comprises a separator film, the separator film comprising:

[0005] a base film;

[0006] a coating layer formed on at least one side of the base film, the coating layer comprising an ion exchange resin, the ion exchange resin comprising a group of at least one of Formula 1 or Formula 2,

[0007]

[0008] wherein R 1 and R 2 each independently contains a functional group of at least one element of C, H, O or N, R 3 contains a functional group of at least two elements of C, H or O, and * represents a binding site of the Formula 1 and / or the Formula 2 with other groups.

[0009] The present application at least includes the beneficial effects as described below: the secondary battery of the present application has higher storage performance and cycle performance at a high cut-off voltage.

[0010] In some embodiments, in Formula 1 and / or Formula 2, R 1 and R 2 each independently contains at least one of H, alkyl, alkenyl or alkylamine.

[0011] In some embodiments, in Formula 2, R 3 contains at least one of alkyl, alkenyl or .

[0012] In some embodiments, the formula 1 comprises at least one of the following groups:

[0013] Thus, the storage performance and cycle performance of the battery under high cut-off voltage can be further improved.

[0014] In some embodiments, the formula 2 comprises at least one of the following groups:

[0015]

[0016] Thus, the storage performance and cycle performance of the battery under high cut-off voltage can be further improved.

[0017] In some embodiments, the ion exchange resin further comprises a resin skeleton, and the resin skeleton comprises at least one of a styrene resin, an acrylic resin, a phenolic resin or an epoxy resin.

[0018] In some embodiments, the loading amount of the ion exchange resin on the base film is 10 -5 g / cm 2 -10 -2 g / cm 2 Thus, the storage performance and cycle performance of the battery under high cut-off voltage can be further improved.

[0019] In some embodiments, the volume average particle size Dv50 of the ion exchange resin is 0.5 μm-20 μm. Thus, the storage performance and cycle performance of the battery under high cut-off voltage can be further improved.

[0020] In some embodiments, the thickness of the separation film is 5 μm-100 μm.

[0021] In some embodiments, the air permeability of the separation film is less than or equal to 10000 s.

[0022] In some embodiments, the ion conductivity of the separation film is greater than or equal to 0.2 mS / cm.

[0023] In some embodiments, the secondary battery comprises a positive electrode sheet, and the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises Li a Ni x Mn 2-x-y Z yO4, wherein 0.9≤a≤2.2, 0.2≤x≤0.7, 0≤y≤0.2, Z comprises at least one of Na, Fe, Si, Ti, P, S, Nb, Mo, Ru, Te, Ce, Ta or W. Thus, the energy density and cycle performance of the battery can be improved.

[0024] In some embodiments, the positive electrode active material satisfies at least one of the following conditions:

[0025] The volume average particle size Dv50 of the positive electrode active material is 1 μm-15 μm;

[0026] The BET specific surface area of the positive electrode active material is less than or equal to 1.5 m 2 / g;

[0027] The tap density of the positive electrode active material is 1.5 g / cm 3 -3 g / cm 3 .

[0028] In some embodiments, the coating on at least one side of the separator film is arranged towards the positive electrode tab. Thus, the storage performance and cycle performance of the battery at high cut-off voltage can be further improved.

[0029] In some embodiments, the charge cut-off voltage of the secondary battery is 4.5 V-4.9 V. Thus, the energy density of the battery can be improved.

[0030] In some embodiments, the secondary battery is a lithium ion battery.

[0031] In the second aspect of the present application, a power consuming device is provided, comprising the secondary battery of the first aspect of the present application. Thus, the power consuming device has high energy density, cycle performance and storage performance.

[0032] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are intended to further assist in understanding the preferred embodiments and can be utilized for constricting the present application. Like reference numerals can be used to indicate like elements in the accompanying drawings. In the drawings:

[0034] Figure 1 is a structural schematic diagram of a separator film according to an embodiment of the present application.

[0035] Figure 2is a schematic view of a battery cell according to an embodiment of the present application.

[0036] Figure 3 is Figure 2 is an exploded view of a battery cell according to an embodiment of the present application.

[0037] Figure 4 is a schematic view of a battery module according to an embodiment of the present application.

[0038] Figure 5 is a schematic view of a battery pack according to an embodiment of the present application.

[0039] Figure 6 is Figure 5 is an exploded view of a battery pack according to an embodiment of the present application.

[0040] Figure 7 is a schematic view of an electric device powered by a battery according to an embodiment of the present application.

[0041] BRIEF DESCRIPTION OF DRAWINGS

[0042] 100 separator; 101 base film; 102 coating; 11 battery cell; 11 housing; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

[0043] The embodiments of the present application will be described in detail below. The following examples are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot be used to limit the protection scope of the present application.

[0044] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It will be explicitly understood that the embodiments described herein can be combined with other embodiments.

[0045] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, i.e., all ranges that fall between the upper and lower limits of the broader range. For example, a range of "60% to 120%" is intended to include any and all sub-ranges between (and including) the upper and lower limits of the broad range. For example, a range of 60% to 120% includes any and all sub-ranges between (and including) the upper and lower limits of the broad range, e.g., 60% to 121%, 61% to 120%, 61% to 121%, 62% to 120%, 62% to 121%, 63% to 120%, 63% to 121%, etc. Also, it is specifically intended that the description above include all subclasses of the specific elements (i.e., any and all combinations of the elements). For example, if a certain parameter is described as comprising elements X, Y, and Z, then it is intended that a method comprising any one of X, Y, or Z falls within the scope of the description. Similarly, if a certain parameter is described as excluding elements X, Y, and Z, then it is intended that a method excluding any one of X, Y, or Z falls within the scope of the description.

[0046] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0047] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not specifically stated otherwise.

[0048] All steps of the present application can be performed in sequence or randomly, preferably in sequence, if not specifically stated otherwise. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0049] With the increasing demand for high energy density lithium ion batteries, in addition to the development of new materials, deep exploration and improvement of the energy density of existing materials is also one of the research hotspots, and increasing the charging cutoff voltage is one of the effective ways to improve the energy density of lithium ion batteries. However, increasing the charging cutoff voltage of the battery has the following problems: at high voltage, the existing electrolyte is easy to oxidize and decompose at the positive electrode interface, and the generated oxidation byproducts increase the internal impedance of the battery, and at high voltage, the positive electrode active material is easy to be corroded by the electrolyte oxidation products, leading to the dissolution of transition metal ions from the positive electrode active material, and the structure of the positive electrode active material collapses, thereby causing irreversible capacity decay, and the deposited transition metal ions in the negative electrode will destroy the SEI film (solid electrolyte interface film), and the cycle performance and storage performance of the battery will be deteriorated.

[0050] The coating on the separator of the secondary battery of the present application comprises ion exchange resin, and the ion exchange resin comprises groups of formula 1 and / or formula 2, which can capture the byproducts generated by the oxidation of the electrolyte at the positive electrode interface at high voltage and the transition metal ions dissolved from the positive electrode active material, thereby avoiding the migration of the generated byproducts and transition metal ions to the negative electrode to destroy the SEI film, thereby improving the cycle performance and storage performance of the battery.

[0051] The secondary battery disclosed in the embodiments of the present application can be used in a power consumption device using a battery as a power source or a variety of energy storage systems using a battery as an energy storage element. The power consumption device can include, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, etc. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric plane toy, etc., and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0052] The first aspect of the present application proposes a secondary battery, referring to Figure 1 , the secondary battery comprises a separator 100, the separator 100 comprises a base film 101 and a coating layer 102, the coating layer 102 is formed on at least one side of the base film 101, the coating layer 102 comprises ion exchange resin, and the ion exchange resin comprises groups of at least one of formula 1 or formula 2,

[0053]

[0054] wherein R 1 and R 2 independently contain a functional group of at least one element of C, H, O or N, R 3 contains a functional group of at least two elements of C, H or O, and * represents the bonding site of the formula 1 and / or the formula 2 with other groups.

[0055] The process of improving the cycle performance and storage performance of the battery at high voltage of the present application is speculated as follows: the coating layer 102 on the separator 100 of the secondary battery of the present application includes ion exchange resin, which includes the group of at least one of the above-mentioned formula 1 or formula 2, the amine group on the group of formula 1 and formula 2 can capture the acidic by-products generated by the oxidation of the electrolyte at the positive electrode interface at high voltage, thereby inhibiting the corrosion of the acidic by-products to the positive electrode active material, reducing the dissolution of transition metal ions in the positive electrode active material, and at the same time, the N in the amine group of formula 1 and formula 2 has a lone pair of electrons, which can interact with the empty orbit of the transition metal ions dissolved from the positive electrode active material to form a bond to inhibit the migration of transition metal to the negative electrode to destroy the SEI film, thereby improving the cycle performance and storage performance of the battery.

[0056] In some embodiments of the present application, in the above-mentioned formula 1 and formula 2, R 1 and R 2 each independently contains at least one of H, alkyl, alkenyl or alkylamine, for example, alkyl includes methyl, ethyl, propyl, etc.; alkenyl includes ethenyl, propenyl, etc.; alkylamine includes methylamine, ethylamine, propylamine, isopropylamine, etc. Thus, when R 1 and R 2 each independently is alkylamine, it not only can capture the acidic by-products generated by the oxidation of the electrolyte at the positive electrode interface at high voltage, thereby inhibiting the corrosion of the acidic by-products to the positive electrode active material, reducing the dissolution of transition metal ions in the positive electrode active material, but also the N in the alkylamine has a lone pair of electrons, which can also interact with the empty orbit of the transition metal ions dissolved from the positive electrode active material to form a bond to inhibit the migration of transition metal to the negative electrode to destroy the SEI film, thereby further improving the cycle performance and storage performance of the battery.

[0057] In some embodiments of the present application, in the above-mentioned formula 2, R 3 contains at least one of alkyl, alkenyl or . For example, alkyl includes methyl, ethyl, propyl, etc.; alkenyl includes ethenyl, propenyl, etc.

[0058] As an example, the formula 1 includes at least one of the following groups:

[0059] Thus, the coating layer 102 on the separator 100 of the secondary battery of the present application includes ion exchange resin containing the above-mentioned composition formula 1, and the amine group in the group shown in formula 1 can not only capture the acidic by-products generated by the oxidation of the electrolyte at the interface of the positive electrode at high voltage, thereby inhibiting the corrosion of the acidic by-products to the positive electrode active material and reducing the elution of transition metal ions in the positive electrode active material, but also the N in the amine group has a lone pair of electrons, which can interact with the empty orbital of the transition metal ions eluted from the positive electrode active material to form a bond and inhibit the migration of the transition metal to the negative electrode to destroy the SEI film, thereby further improving the cycle performance and storage performance of the battery.

[0060] As an example, the formula 2 includes at least one of the following groups:

[0061]

[0062] Thus, the coating layer 102 on the separator 100 of the secondary battery of the present application includes ion exchange resin containing the above-mentioned composition formula 2, and the amine group in the group shown in formula 2 can not only capture the acidic by-products generated by the oxidation of the electrolyte at the interface of the positive electrode at high voltage, thereby inhibiting the corrosion of the acidic by-products to the positive electrode active material and reducing the elution of transition metal ions in the positive electrode active material, but also the N in the amine group has a lone pair of electrons, which can interact with the empty orbital of the transition metal ions eluted from the positive electrode active material to form a bond and inhibit the migration of the transition metal to the negative electrode to destroy the SEI film, thereby further improving the cycle performance and storage performance of the battery.

[0063] In some embodiments of the present application, the ion exchange resin further includes a resin skeleton, and the resin skeleton includes at least one of a styrene resin, an acrylic resin, a phenolic resin or an epoxy resin. Thus, by using the resin skeleton of this composition, it can adsorb the acidic by-products generated by the oxidation of the electrolyte at the interface of the positive electrode at high voltage, thereby further inhibiting the corrosion of the acidic by-products to the positive electrode active material and reducing the elution of transition metal ions in the positive electrode active material.

[0064] In some embodiments of the present application, the loading amount of the ion exchange resin on the base film is 10 -5 g / cm 2 -10 -2 g / cm 2 , for example, 2*10 -5 g / cm 2 -7*10 -3 g / cm 2 , 5*10 -5 g / cm 2 -5*10 -3 g / cm 2 , 10 -4 g / cm 2-2*10 -3 g / cm 2 etc. Thus, the present application controls the loading amount of the ion exchange resin on the base film in the above range, so that the ion exchange resin on the separator film 100 can sufficiently capture electrolyte oxidative acidic by-products and bond transition metal ions, inhibit the corrosion of the electrolyte oxidative acidic by-products to the positive electrode active material and the migration of the transition metal dissolved in the positive electrode active material to the negative electrode to destroy the SEI film after the dissolution, thereby further improving the cycle performance and storage performance of the battery.

[0065] In the present application, the test method of "the loading amount of the ion exchange resin on the base film" includes: weighing the weight of the unit area (1 cm 2 ) of the separator film to be tested, denoted as m1 (g), weighing the weight of the unit area (1 cm 2 ) of the base film, denoted as m2 (g), and the specific gravity of the ion exchange resin in the ion exchange resin slurry accounted for the solid phase component, denoted as n, then the loading amount of the separator film to be tested = (m1-m2)*n (g / cm 2 ), wherein m1 and m2 are each obtained by averaging the values of 20 samples.

[0066] In some embodiments of the present application, the volume average particle size Dv50 of the ion exchange resin is 0.5 μm-20 μm, such as 1 μm-20 μm, 3 μm-17 μm, 5 μm-15 μm, 7 μm-12 μm, 8 μm-10 μm, etc. Thus, the present application controls the volume average particle size of the ion exchange resin in the above range, the ion exchange resin particles are not easy to agglomerate, the formed coating 102 is relatively smooth, and at the same time, the ion exchange resin with the above particle size has a large specific surface area, which is helpful to capture electrolyte oxidative by-products under high pressure and bond transition metal ions dissolved from the positive electrode active material, thereby further improving the cycle performance and storage performance of the battery. In other embodiments of the present application, the volume average particle size Dv50 of the ion exchange resin is 0.8 μm-10 μm.

[0067] In the present application, Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50%, which is determined by using a laser particle size analyzer (such as Malvern Master Size 3000) according to the standard GB / T 19077-2016.

[0068] In some embodiments of the present application, the thickness of the separator film 100 is 5-100 μm, for example, 10-95 μm, 15-90 μm, 20-85 μm, 25-80 μm, 30-75 μm, 35-70 μm, 40-65 μm, 45-60 μm, 50-55 μm, etc. Thus, the separator film with the thickness is used in the present application, which not only facilitates ion transmission and reduces impedance, but also can improve the capacity of the battery.

[0069] In the present application, the thickness of the separator film 100 can be measured by a micrometer. The specific measurement method is as follows: 10 pieces of the separator film to be measured are stacked together, the thickness of the 10 pieces of the separator film at 5 different positions is measured by a micrometer, and the average of 5 measurement results is recorded as the final thickness.

[0070] In some embodiments of the present application, the air permeability of the separator film 100 is less than or equal to 10000 s, for example, 500-10000 s, 1000-9000 s, 2000-8000 s, 3000-7000 s, 4000-6000 s, 4500-5000 s, etc. Thus, the air permeability of the separator film 100 is controlled in the above range in the present application, which can improve the safety performance and cycle life of the battery. In some other embodiments of the present application, the air permeability of the separator film 100 is less than or equal to 5000 s, and further, the air permeability of the separator film 100 is less than or equal to 2000 s.

[0071] In the present application, the test method of the air permeability of the separator film 100 can refer to GB / T 458-2008. For example: the separator film is laid flat, a flat position without oil stains is selected, placed at the air outlet of an air compression cylinder, tightened and fixed, the separator film is fixed after the work station, and the self-weight of the cylinder floating on the liquid is used to compress the air in the cylinder. With the air passing through the sample, the cylinder will fall smoothly. The time required for 100 cc of air to pass through a square inch (6.45 cm 2 ) of the separator film is defined as the air permeability.

[0072] In some embodiments of the present application, the ionic conductivity of the separator film 100 is greater than or equal to 0.2 mS / cm, for example, 0.2-2 mS / cm, 0.3-1.8 mS / cm, 0.4-1.5 mS / cm, 0.5-1.3 mS / cm, 0.7-1.2 mS / cm, 0.8-1 mS / cm, etc. Thus, the ionic conductivity of the separator film is controlled in the above range in the present application, which can improve the charge and discharge rate and cycle life of the battery. In some other embodiments of the present application, the ionic conductivity of the separator film 100 is greater than or equal to 0.4 mS / cm.

[0073] In the present application, the method for testing the ionic conductivity of the separator film includes: obtaining Rs (ohmic resistance) by testing the EIS (electrochemical impedance spectrum) of a symmetric battery containing the separator film, and calculating the ionic conductivity according to the formula p = l / (S*Rs), wherein l is the thickness of the separator film, S is the effective area of the separator film, and p is the ionic conductivity of the separator film.

[0074] As an example, the material of the base film 101 can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0075] In some embodiments of the present application, the secondary battery further includes a positive electrode tab including a positive electrode active material, the positive electrode active material including Li a Ni x Mn 2-x-y Z y O4, wherein 0.2≤x≤0.7, 0≤y≤0.2, and Z includes at least one of Na, Fe, Si, Ti, P, S, Nb, Mo, Ru, Te, Ce, Ta, or W. Thus, the positive electrode active material of this composition has excellent structural stability at high voltage, thereby improving the energy density and cycle performance of the battery.

[0076] In some embodiments of the present application, the positive electrode active material Li a Ni x Mn 2-x-y Z y In the positive electrode active material Li

[0077] It should be noted that in the positive electrode tab, the battery, or the power utilization device, due to the consumption of lithium ions during the formation and cycle processes of the battery, the measured lithium content a in the positive electrode active material can be less than 1. Meanwhile, if a lithium supplement is used in the positive electrode tab and the negative electrode tab, the measured lithium content a in the positive electrode active material can be greater than 1 after the formation and cycle processes of the battery.

[0078] In some embodiments of the present application, the positive electrode active material Li a Ni x Mn 2-x-y Z yIn O4, x can be 0.2≤x≤0.7, for example, 0.25≤x≤0.65, 0.3≤x≤0.6, 0.35≤x≤0.55, 0.4≤a≤0.5, 0.45≤a≤0.5, etc. Thus, the nickel element in the above content in the positive electrode active material can improve the specific capacity of the battery.

[0079] In some embodiments of the present application, the positive electrode active material Li a Ni x Mn 2-x-y Z y In O4, y can be 0≤y≤0.2, for example, 0.01≤y≤0.2, 0.05≤y≤0.2, 0.07≤y≤0.2, 0.1≤y≤0.2, 0.12≤y≤0.2, 0.15≤y≤0.2, 0.17≤y≤0.2, 0.19≤y≤0.2, etc. Thus, the Z element in the above content in the positive electrode active material can effectively improve the structural stability of the positive electrode active material and improve the cycle stability of the battery containing the same.

[0080] In the present application, the elemental composition of the positive electrode active material can be determined by instruments and methods known in the art, for example, by inductively coupled plasma atomic emission spectrometry: instrument standard reference EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry". The sample is treated by chemical method to be digested into solution, atomized into plasma to be excited to emit characteristic spectrum of elements, and the content of elements is qualitatively and quantitatively analyzed according to the wavelength and intensity of the spectrum (which is proportional to the concentration).

[0081] In some embodiments of the present application, the volume average particle size Dv50 of the positive electrode active material is 1 μm-15 μm, for example, the Dv50 of the positive electrode active material can be 2 μm-14 μm, 4 μm-13 μm, 5 μm-12 μm, 6 μm-11 μm, 7 μm-10 μm, 8 μm-9 μm, etc. In other embodiments of the present application, the Dv50 of the positive electrode active material is 5 μm-15 μm.

[0082] In the present application, Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50%, for example, referring to the standard GB / T 19077-2016, using a laser particle size analyzer (for example, Malvern Master Size 3000) for determination.

[0083] In some embodiments of the present application, the BET specific surface area of the positive electrode active material is 1.5 m 2 / g, for example, the BET specific surface area of the positive electrode active material can be 0.2 m 2 / g-1.5 m 2 / g, 0.2 m2 / g-1m 2 / g, 0.3m 2 / g-0.8m 2 / g, 0.3m 2 / g-0.5m 2 / g, etc. In some embodiments of the present application, the BET specific surface area of the positive electrode active material is 0.5m 2 / g-1.3m 2 / g.

[0084] In the present application, the BET specific surface area of the positive electrode active material has the meaning known in the art and can be determined using the instruments and methods known in the art, for example, can be tested according to the following method: according to GB / T 19587-2004 gas adsorption BET method, after the sample is heated and degassed, the adsorption amount of gas on the surface of the solid under different adsorption pressures is determined at a constant low temperature, the monolayer adsorption amount of the sample is obtained based on the BET multilayer adsorption theory and its formula, and thus the specific surface area per unit mass of the solid sample is calculated.

[0085] In some embodiments of the present application, the tap density of the positive electrode active material can be 1.5g / cm 3 -3g / cm 3 , for example, 1.7g / cm 3 -3g / cm 3 , 2g / cm 3 -2.7g / cm 3 , 2.3g / cm 3 -2.5g / cm 3 , etc. In some embodiments of the present application, the tap density of the positive electrode active material can be 1.7g / cm 3 -2.3g / cm 3 .

[0086] In the present application, the tap density refers to the mass per unit volume measured after the powder in the container is vibrated under specified conditions. The determination method of the tap density of the positive electrode active material is as follows:

[0087] The weighed positive electrode active material is loaded into the tap density device cylinder, and the cylinder is fixed on the support. The cam is rotated, the directional rod drives the support to slide up and down, and hits on the anvil. Vibrate 250±15 times per minute for 12 minutes. The volume of the positive electrode active material in the cylinder is measured, and the ratio of the mass of the positive electrode active material to the volume is the tap density of the positive electrode active material.

[0088] The calculation formula of the tap density is: ρbt=m0 / V

[0089] Wherein, ρbt——tap density, g / cm 3

[0090] m0 - mass of the positive electrode active material, g

[0091] V - volume of the positive electrode active material after tamping (volume of the measuring cup), cm 3 .

[0092] Specifically, when the Dv50 and the specific surface area of the positive electrode active material of the present application satisfy the above conditions, the surface side reaction of the positive electrode active material can be slowed down; and when the tap density is within the above range, the processing performance of the positive electrode active material can be improved.

[0093] In some embodiments of the present application, the pH value of the soaking solution of the positive electrode active material is greater than or equal to 10.2, for example, the pH value of the positive electrode active material soaking solution can be 10.2-13, 10.5-13, 11-13, 11.5-13, 12-13, 12.5-13, etc. Controlling the pH value of the positive electrode active material soaking solution within the above range can reduce the occurrence of electrolyte side reactions, inhibit the dissolution of transition metal ions, enhance the structural stability, and prolong the battery life.

[0094] Specifically, the pH value of the soaking solution of the positive electrode active material can be measured by the following method: referring to GB / T 9724-2007 General Test Method for pH Value of Chemical Reagents, the sample is mixed with water in a fixed ratio of 1:9 to form a solution, which is sealed and stirred on a magnetic stirrer for 30 min. After stirring, the conical flask is placed in a 25℃ water bath thermostat pot, and the pH of the mixture is measured after standing for 1.5 h using a pH meter.

[0095] In some embodiments of the present application, the coating 102 on at least one side of the separation film 100 is arranged towards the positive electrode tab. In this way, by forming a coating 102 comprising the above-mentioned ion exchange resin on one side of the separation film 100 close to the positive electrode tab, the amine groups on the groups of formula 1 and / or formula 2 in the ion exchange resin can capture the acidic by-products produced by the oxidation of the electrolyte at the positive electrode interface at high voltage, thereby inhibiting the erosion of the acidic by-products to the positive electrode active material, reducing the dissolution of transition metal ions in the positive electrode active material, and at the same time, the N in the amine groups of formula 1 and formula 2 has a lone pair of electrons, which can interact with the empty orbitals of the transition metal ions dissolved from the positive electrode active material to form a bond and inhibit the migration of transition metal to the negative electrode to damage the SEI film, thereby further improving the cycle performance and storage performance of the battery.

[0096] In some embodiments of the present application, the charge cut-off voltage of the secondary battery is 4.5V-4.9V, for example, 4.6V-4.8V, 4.7V-4.8V, etc. In this way, by increasing the charge cut-off voltage of the secondary battery, the energy density of the battery can be improved.

[0097] In the present application, the "charge cut-off voltage of the secondary battery" refers to the voltage of the battery when it reaches a fully charged state during a prescribed constant current charging. The test method includes charging the battery at 0.2C constant current for 5 hours at 25°C, and the voltage value after reaching a fully charged state is the charge cut-off voltage.

[0098] The secondary battery refers to a battery that can be used continuously by activating the active material through charging after discharging.

[0099] It can be understood that the secondary battery proposed in the present application can be a lithium ion battery.

[0100] Generally, the battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet and serves to isolate. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet.

[0101] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the above-mentioned positive electrode active material.

[0102] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode active material layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0103] In some embodiments of the present application, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0104] In some embodiments of the present application, the positive electrode active material layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylic ester resin.

[0105] In some embodiments of the application, the binder has a mass percentage of 0.5-3%, for example 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or the like, based on the total mass of the positive electrode active material layer.

[0106] In some embodiments of the application, the positive electrode active material layer can optionally further include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0107] In some embodiments of the application, the conductive agent has a mass percentage of 0.8-4%, for example 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or the like, based on the total mass of the positive electrode active material layer.

[0108] In some embodiments of the application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, for example, the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (for example, N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after drying, cold pressing, and the like, a positive electrode sheet can be obtained.

[0109] In the battery, the negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0110] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode active material layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0111] In some embodiments of the application, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0112] In some embodiments of the present application, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can include at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, or a silicon alloy. The tin-based material can include at least one of elemental tin, a tin oxide compound, or a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0113] In some embodiments of the present application, the negative active material layer can further optionally include a conductive agent. The conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0114] In some embodiments of the present application, the negative active material layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0115] In some embodiments of the present application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, and the binder, in a solvent (e.g., deionized water) to form a negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and then performing processes such as drying and cold pressing to obtain the negative electrode sheet.

[0116] In some embodiments of the present application, the mass ratio of the binder in the negative electrode sheet based on the total mass of the negative active material layer is 1% to 3%, such as 1.2% to 2.8%, 1.5% to 2.5%, 1.8% to 2.2%, 2% to 2.2%, etc. Thereby, the shedding of the negative electrode sheet can be reduced, and thus the cycle performance of a battery containing the same can be improved.

[0117] The present application does not have a specific limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0118] In some embodiments of the present application, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0119] In some embodiments of the present application, the electrolyte salt can include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorodioxalate phosphate.

[0120] In some embodiments of the present application, the solvent can include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, butanedisulfone, methyl ethyl sulfone, or diethyl sulfone.

[0121] In some embodiments of the present application, the electrolyte can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0122] The secondary battery of the present application can include a battery cell form, a battery module form, and a battery pack form.

[0123] In some embodiments of the present application, the positive electrode tab, the negative electrode tab, and the separator film can be made into a jelly-roll cell through a jelly-roll process.

[0124] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0125] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0126] The shape of the battery cell of the present application is not particularly limited, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 is a battery cell 1 of a square structure as an example.

[0127] In some embodiments, referring to Figure 3 , the outer package can include a shell 11 and a cover plate 13. The shell 11 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate form an accommodation cavity. The shell 11 has an opening communicating with the accommodation cavity, and the cover plate 13 can be provided on the opening to close the accommodation cavity. The positive electrode tab, the separator film, and the negative electrode tab can form an electrode assembly 10 through a stacking and rolling process. The electrode assembly 10 is packaged in the accommodation cavity. The electrolyte is impregnated in the electrode assembly 10. The number of electrode assemblies 10 contained in the battery cell 1 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0128] In some embodiments, the battery cell can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0129] Figure 4 is a battery module 2 as an example. Referring to Figure 4 In the battery module 2, a plurality of battery cells 1 can be arranged in sequence along the length direction of the battery module 2. Of course, other arbitrary arrangements can also be made. Further, the plurality of battery cells 1 can be fixed by fasteners.

[0130] Optionally, the battery module 2 can also include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0131] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0132] Figure 5 and Figure 6 is a battery pack 3 as an example. Referring to Figure 5 and Figure 6 In the battery pack 3, a battery box and a plurality of battery modules 2 arranged in the battery box can be included. The battery box includes an upper box body 31 and a lower box body 32, and the upper box body 31 can be arranged on the lower box body 32 and form a closed space for accommodating the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0133] In addition, the application also provides a power utilization device, which includes the battery provided by the application. The battery cell, the battery module or the battery pack can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0134] As the power utilization device, the battery cell, the battery module or the battery pack can be selected according to the use requirements thereof.

[0135] Figure 7 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the power utilization device for the secondary battery, the battery pack or the battery module can be used.

[0136] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0137] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0138] Example 1

[0139] (1) Preparation of positive electrode sheet

[0140] LiNi, the positive electrode active material 0.5 Mn 1.5 O4 (Dv50 of 10μm) was mixed with conductive carbon black (Super P) and PVDF (polyvinylidene fluoride) at a weight ratio of 96:2.5:1.5. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto both sides of an aluminum foil and dried to obtain a positive electrode sheet. The loading of the positive electrode active material on one side of the positive electrode sheet was 0.016 g / cm³. 2 .

[0141] (2) Preparation of negative electrode sheet

[0142] Artificial graphite (anode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were thoroughly mixed in deionized water at a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. This slurry was then uniformly coated onto both sides of the copper foil used as the negative electrode current collector. After drying and cold pressing, the negative electrode sheet was obtained. The loading of the negative electrode active material on one side of the negative electrode current collector was 0.007 g / cm³. 2 .

[0143] (3) Preparation of electrolyte

[0144] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents fluoroethylene carbonate (FEC) and methyl trifluoroethyl carbonate (FEMC) were mixed evenly at a mass ratio of 3:7 to obtain an organic solvent. LiPF6 was dissolved in the above solvent and stirred evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0145] (4) Preparation of the separating membrane

[0146] Ion exchange resin (base resin is styrene resin, exchange group is formula 1-1, volume average particle size Dv50 of ion exchange resin is 5 μm), binder polyvinylidene fluoride (PVDF) is dissolved in solvent N-methyl pyrrolidone (NMP), and after being mixed uniformly by fully stirring, ion exchange resin slurry is obtained, and then the ion exchange resin slurry is uniformly coated on one side surface of a polyethylene film base film by a doctor blade method, the loading amount of ion exchange resin on the base film is 5*10 -4 g / cm 2 , and the thickness of the ion exchange resin is 18 μm. The ion exchange resin slurry is naturally dried at 25°C to obtain a separator film with a thickness of 18 μm.

[0147] (5) Preparation of a lithium ion battery

[0148] The positive electrode sheet, the separator film and the negative electrode sheet prepared above are sequentially placed, the separator film is placed between the positive electrode sheet and the negative electrode sheet to play a role of isolation (the coating on the separator film faces the positive electrode sheet), and then the electrode assembly is obtained by laminating the sheets, the electrode assembly is packaged with an aluminum plastic bag, electrolyte is injected, and the capacity formation is carried out after packaging to obtain a laminated battery cell.

[0149] The method for preparing the lithium ion battery in examples 2-19 and comparative examples is the same as that in example 1, except that the ion exchange resin composition, loading amount and particle size used in the preparation of the separator film are different, as shown in Table 1.

[0150] Table 1

[0151]

[0152]

[0153] The cycle performance and full charge storage performance of the batteries obtained in examples 1-19 and comparative examples are characterized, and the batteries after 100 cycles are disassembled, and the content of transition metal ions on the separator film and the negative electrode sheet is tested, and the characterization results are shown in Table 2.

[0154] Characterization means:

[0155] (1) Battery room temperature cycle performance test

[0156] At 25°C, the battery is charged at 0.3C constant current to a voltage of 4.9V, and then charged at 4.9V constant voltage to a current of 0.05C, and then the laminated battery is discharged at 0.5C constant current to a voltage of 3.0V, which is one charge cycle process, and the discharge capacity is the discharge capacity of the first cycle. After the cycle charging test is carried out according to the above method, until the discharge capacity is attenuated to 80% of the initial value, the cycle is ended, and the total cycle number is recorded as the room temperature cycle performance.

[0157] (2) Battery room temperature full charge storage performance test

[0158] The battery was charged at 0.3C constant current to 4.9V at 25°C, and then charged at 4.9V constant voltage to 0.05C current. Then the battery was placed at 25°C, and discharged at 0.5C constant current to 3.0V after every 10 days. Then one full charge and discharge was performed at 25°C, and the discharge capacity value C was extracted. n The battery was charged again and continued to store at 25°C environment. Until the discharge capacity C n decayed to 80% of the initial value, the storage ended. The total duration of storage after full charge at 25°C was the normal temperature full charge storage performance.

[0159] (3) After 100 cycles, the battery was disassembled, and the content of transition metal ions (Ni and Mn) on the separator and the negative electrode sheet was tested: at 25°C, the battery was charged at 0.3C constant current to 4.9V, and then charged at 4.9V constant voltage to 0.05C current, and then the battery was discharged at 0.5C constant current to 3.0V after 5min, which was one cycle process recorded as 1 cycle, and the above method was repeated to 100 cycles, and then the content of transition metal elements (Ni and Mn) in the separator and the negative electrode sheet was measured by inductively coupled plasma atomic emission spectrometry (ICP) according to EPA 6010D-2014.

[0160] Table 2

[0161]

[0162]

[0163] Conclusion, from Table 2, it can be seen that the 25°C cycle life and 25°C full charge storage life of the batteries of Examples 1-19 are obviously better than those of the comparative examples, and the content of transition metal elements (Ni and Mn) on the separator and the negative electrode sheet after disassembly of the batteries of Examples 1-19 is obviously lower than that of the comparative examples, which indicates that by forming a coating layer including a group of at least one of Formula 1 or Formula 2 on the base film, the acidic by-products generated by the oxidation of the electrolyte at the positive electrode interface at high voltage can be captured, thereby inhibiting the corrosion of the acidic by-products on the positive electrode active material, reducing the dissolution of transition metal ions in the positive electrode active material, and at the same time, the groups of Formula 1 and Formula 2 can interact with the empty orbitals of the transition metal ions dissolved from the positive electrode active material to form a bond to inhibit the migration of transition metals to the negative electrode to damage the SEI film, thereby improving the cycle performance and storage performance of the battery.

[0164] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art, without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A secondary battery characterized by comprising: The separator film includes: a base film; a coating layer formed on at least one side of the base film, the coating layer including an ion exchange resin including a group of at least one of Formula 1 or Formula 2, wherein R 1 and R 2 each independently contains a functional group with at least one element of C, H, O or N, R 3 contains a functional group with at least two elements of C, H or O, and * indicates the binding site of said Formula 1 and / or said Formula 2 to other groups.

2. The secondary battery according to claim 1, characterized by R 1 and R 2 each independently contains at least one of H, alkyl, alkenyl or alkylamine.

3. The secondary battery according to claim 1 or 2, characterized by R 3 at least one of an alkyl group, an alkenyl group, or at least one of an alkyl group, an alkenyl group, or 4. The secondary battery according to any one of claims 1 to 3, characterized by, the Formula 1 includes at least one of the following groups:

5. The secondary battery according to any one of claims 1 to 4, characterized by, the Formula 2 includes at least one of the following groups:

6. The secondary battery according to any one of claims 1 to 5, characterized by, the ion exchange resin further includes a resin skeleton including at least one of a styrene resin, an acrylic resin, a phenol resin, or an epoxy resin.

7. The secondary battery according to any one of claims 1-6, characterized by The ion exchange resin is loaded on the base film in an amount of 10 -5 g / cm 2 -10 -2 g / cm 2 .

8. The secondary battery according to any one of claims 1-7, characterized by, a volume average particle diameter Dv50 of the ion exchange resin is 0.5 µm - 20 µm.

9. The secondary battery according to any one of claims 1-8, characterized by, a thickness of the separator film is 5 µm - 100 µm.

10. The secondary battery according to any one of claims 1-9, characterized in that, an air permeability of the separator film is less than or equal to 10,000 s.

11. The secondary battery according to any one of claims 1-10, characterized in that, an ionic conductivity of the separator film is greater than or equal to 0.2 mS / cm.

12. The secondary battery according to any one of claims 1-11, characterized by, includes a positive electrode tab, the positive electrode tab including a positive electrode active material, the positive electrode active material including Li a Ni x Mn 2-x-y Z y O4, wherein 0.9≤a≤2.2, 0.2≤x≤0.7, 0≤y≤0.2, Z includes at least one of Na, Fe, Si, Ti, P, S, Nb, Mo, Ru, Te, Ce, Ta, or W.

13. The secondary battery according to claim 12, characterized by the positive electrode active material satisfies at least one of the following conditions: a volume average particle diameter Dv50 of the positive electrode active material is 1 µm - 15 µm; The BET specific surface area of the positive electrode active material is less than or equal to 1.5 m 2 / g; The tap density of the positive electrode active material is 1.5 g / cm 3 - 3 g / cm 3 .

14. The secondary battery according to claim 12 or 13, characterized by the coating layer on at least one side of the separator film is arranged toward the positive electrode sheet.

15. The secondary battery according to any one of claims 1-14, characterized by, a charge cut-off voltage of the secondary battery is 4.5 V - 4.9 V.

16. The secondary battery according to any one of claims 1-15, characterized by, the secondary battery includes a lithium ion battery.

17. An electrical device, comprising: a secondary battery according to any one of claims 1 - 16. a secondary battery according to any one of claims 1 - 16.

Images