Secondary battery cell, secondary battery, and electric device

Abstract

This application provides a secondary battery cell, a secondary battery, and an electrical device. The secondary battery cell includes an electrolyte, which includes additives, including sulfated ester compounds. The mass fraction w1 of the sulfated ester compounds in the electrolyte, based on the total mass of the electrolyte, satisfies: 0.01% ≤ w1 ≤ 5%. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The coating weight w2 of one side of the positive electrode film layer satisfies: 77.9 g / m³. 2 ≤w2≤159.6g / m 2 This secondary battery cell possesses excellent power performance and high-temperature storage performance.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to a secondary battery cell, a secondary battery, and an electrical device. Background Technology

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace, thus achieving great development.

[0003] In existing technologies, the power performance of secondary battery cells is poor when sulfate ester compounds are used as electrolyte additives. Therefore, there is a need to provide a secondary battery cell whose electrolyte contains sulfate ester compounds and exhibits good power performance. Summary of the Invention

[0004] This application is made in view of the above-mentioned technical problems, and its purpose is to provide a secondary battery cell, a secondary battery, and an electrical device, wherein the secondary battery cell has good power performance and high-temperature storage performance.

[0005] In a first aspect, a secondary battery cell is provided, the secondary battery cell comprising an electrolyte, an additive comprising a cyclic sulfate compound, wherein the mass fraction w1 of the cyclic sulfate compound in the electrolyte, based on the total mass of the electrolyte, satisfies: 0.01% ≤ w1 ≤ 5%; and a positive electrode comprising a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector, wherein the coating weight w2 of one side of the positive electrode film satisfies: 77.9 g / m³. 2 ≤w2≤159.6g / m 2 .

[0006] With the electrolyte including cyclic sulfate compounds, the secondary battery cell of this application can reduce side reactions between the positive electrode active material and the electrolyte and reduce the internal impedance of the secondary battery cell by controlling the mass fraction of the cyclic sulfate compounds and the coating weight of the positive electrode film within appropriate ranges, thereby improving the power performance and high-temperature storage performance of the secondary battery cell.

[0007] In some embodiments, the charging cutoff voltage v of the secondary battery cell at 25°C satisfies: 4.2V≤v≤5V.

[0008] In some embodiments, 4.2V ≤ v ≤ 4.8V.

[0009] In some embodiments, the secondary battery cell includes a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, and the coating weight w3 of one side of the negative electrode film layer satisfies: 47.5 g / m³. 2 ≤w3≤116.9g / m 2 .

[0010] In some embodiments, the cyclic sulfate compound comprises one or more compounds of formula (1) or modified compounds thereof: Wherein, R1 includes one or more methylene groups having 0-2 carbon atoms; R2 includes one or more methylene groups having 0-2 carbon atoms; R3 includes one or more methylene groups having 0-3 carbon atoms, oxygen, and alkoxy groups having 1-6 carbon atoms; R4 includes one or more hydrogen, halogen, alkyl, and alkoxy groups having 1-6 carbon atoms; and R5 includes one or more hydrogen, halogen, alkyl, and alkoxy groups having 1-6 carbon atoms.

[0011] In some embodiments, R4 and / or R5 further include one or more of the compounds of formula (2) as substituents or modified compounds thereof as substituents: R6 includes one or more of methylene with 0-3 carbon atoms and alkoxy with 1-3 carbon atoms; R7 includes one or more of hydrogen, halogen, alkyl with 1-6 carbon atoms and alkoxy with 1-6 carbon atoms; R8 includes one or more of methylene with 0-2 carbon atoms; R6 in formula (2) can be used as a substituent.

[0012] In some embodiments, the cyclic sulfate compounds include one or more of formulas (3) to (7):

[0013] In some embodiments, the electrolyte comprises a solvent, which includes carbonate solvents.

[0014] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, and fluoroethylene carbonate.

[0015] In some embodiments, the electrolyte comprises a lithium salt, wherein the lithium salt comprises LiPF6.

[0016] In some embodiments, the compaction density ρ of the positive electrode sheet satisfies: 2.4 g / cm³ 3 ≤ρ≤3.7g / cm 3 .

[0017] In some embodiments, the thickness h of the positive electrode film layer satisfies: 0.0209mm ≤ h ≤ 0.0753mm.

[0018] In some embodiments, the porosity p of the positive electrode sheet, as measured by the true density method, satisfies: 23% ≤ p ≤ 27%.

[0019] In some embodiments, the positive electrode film layer includes a positive electrode active material, which includes a lithium-containing transition metal oxide.

[0020] In some embodiments, the lithium-containing transition metal oxide comprises Li m1 [Ni a Co b Mn c Q1 e ]O 2-f One or more of the compounds or their modified compounds, wherein Q1 includes one or more of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.8≤m1≤1.2, 0.5≤a≤0.95, 0.05≤b≤0.2, 0<c<0.3, 0≤e<0.3, 0≤f≤0.5.

[0021] In some embodiments, the average particle size D1 of the primary particles containing lithium transition metal oxide satisfies: 1 μm ≤ D1 ≤ 5 μm.

[0022] In some embodiments, the positive electrode active material includes a lithium-containing transition metal phosphate, wherein the lithium-containing transition metal phosphate includes secondary particles formed by the agglomeration of primary particles.

[0023] In some embodiments, the lithium-containing transition metal phosphate includes the molecular formula Li m2 Fe x Mn r P y O j2 Q2 q2 The compound or its modified compound comprises one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.6≤m1≤1.15, 0<x, 0≤r, 0.9≤x+r≤1, 0.95≤y≤1, 3.5≤j2≤4, 0≤q2≤0.1.

[0024] In some embodiments, the average particle size D2 of the primary particles containing lithium transition metal phosphate satisfies: 10nm ≤ D2 ≤ 1000nm.

[0025] In a second aspect, a secondary battery is provided, the secondary battery comprising a secondary battery cell in any of the implementable embodiments of the first aspect.

[0026] Thirdly, an electrical device is provided, the electrical device comprising a secondary battery cell in any of the implementable embodiments of the first aspect, and / or a secondary battery in the second aspect. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a secondary battery.

[0029] Figure 2 This is a schematic diagram of a secondary battery cell. Detailed Implementation

[0030] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the secondary battery cell, secondary battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0031] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] Unless otherwise specified, in this application, the phrase "A and / or B" means "A, B, or both A and B". More specifically, the condition "A and / or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0034] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their technically accepted meanings.

[0037] As mentioned, "charging cut-off voltage" refers to the highest charging voltage reached by a single secondary battery cell during charging at a certain temperature. When a secondary battery cell reaches this voltage, the charging process will stop to prevent overcharging, which could damage the secondary battery cell or cause safety issues.

[0038] If mentioned, "lithium-containing transition metal phosphates" refers to a class of salts that include lithium, transition metals, and phosphate ions. Examples include lithium iron phosphate materials and lithium manganese iron phosphate materials.

[0039] As mentioned, "lithium-containing transition metal oxides" refers to a class of oxides that include lithium and transition metal elements. Structurally, this includes ternary materials with layered structures, such as LiCoO2 and LiNiO2, as well as LiMn2O4 with a spinel structure. Ternary materials refer to lithium transition metal oxides containing three different transition metal elements. It should be understood that ternary materials can also be doped or coated with trace amounts of other transition metal elements; generally, ternary materials doped or coated with other transition metal elements are still considered ternary materials.

[0040] If mentioned, “cyclic sulfate compounds” refers to cyclic compounds that include the -O-SO2-O- group, wherein the -O-SO2-O- group is usually located on the ring of the cyclic compound.

[0041] The embodiments of this application will be described next.

[0042] A secondary battery cell comprises a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process of the secondary battery cell, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of active ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through, thus ensuring the normal conduction of electrochemical reactions within the secondary battery cell.

[0043] Sulfate compounds can decompose at the positive and negative electrodes to form a solid electrolyte interfacial film, helping to reduce side reactions between the electrolyte and the active materials of the positive and negative electrodes, which is beneficial to the storage performance of secondary battery cells. However, when sulfate compounds are used as electrolyte additives, the power performance of secondary battery cells is poor.

[0044] In view of this, embodiments of this application provide a secondary battery cell, a secondary battery, and an electrical device. The electrolyte of the secondary battery cell uses sulfate ester compounds as additives and has good power performance and high-temperature storage performance.

[0045] Next, the secondary battery cell provided in this application will be introduced.

[0046] [Secondary battery cell]

[0047] Firstly, a secondary battery cell is provided, comprising an electrolyte, which includes additives, including cyclic sulfate compounds. The mass fraction w1 of the cyclic sulfate compound in the electrolyte, based on the total mass of the electrolyte, satisfies: 0.01% ≤ w1 ≤ 5%. The secondary battery cell includes a positive electrode, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The coating weight w2 of one side of the positive electrode film layer satisfies: 77.9 g / m³. 2 ≤w2≤159.6g / m 2 .

[0048] The electrolyte uses cyclic sulfates, which can undergo ring-opening decomposition in the electrolyte to generate sulfur-containing polymers. These polymers form a complete and dense interfacial film at the solid-liquid interface between the positive and negative electrodes and the electrolyte. This reduces side reactions between the electrolyte and the active materials of the positive and negative electrodes, thereby reducing electrolyte decomposition and gas generation during storage (especially under high-temperature storage conditions) and improving the storage performance of the secondary battery cell. However, the resulting interfacial impedance is relatively high, increasing the internal impedance of the secondary battery cell and affecting its power performance. The embodiments of this application ensure the integrity and density of the interfacial film by controlling the mass fraction of cyclic sulfates in the electrolyte within the range of 0.01%-5%; simultaneously, by controlling the coating weight of the positive electrode film on one side to 77.9 g / m², the overall interfacial film integrity and density are maintained. 2-159.6g / m 2 Within a certain range, the internal impedance of the secondary battery cell can be reduced. Therefore, the secondary battery cell of this application has good high-temperature storage performance and power performance. The high-temperature storage performance of the secondary battery cell can be 60℃±20℃.

[0049] The mass fraction of cyclic sulfate compounds in the electrolyte can be detected by any means known to those skilled in the art, such as NMR. The coating weight of the positive electrode film can be determined by any means known to those skilled in the art. For example, 30 unit areas can be randomly selected on the electrode to be tested. The mass m1 of the material excluding the current collector on each unit area electrode can be weighed. The unit area is denoted as S0. The coating weight of each unit area electrode is m1 / S0. The coating weight of the positive electrode film can be recorded as (m1 / S0 + m2 / S0 + ... + m30 / S0) / 30.

[0050] m1 can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%. %, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or values ​​within the range obtained by any combination of the above two values. w2 can be 77.9 g / m 2 78g / m 2 79g / m 2 80g / m 2 81g / m 2 82g / m 2 83g / m 2 84g / m 2 85g / m 2 86g / m 2 87g / m 2 88g / m 2 89g / m 2 90g / m 2 95g / m 2 100g / m 2 105g / m 2 110g / m 2 115g / m2 120g / m 2 125g / m 2 130g / m 2 135g / m 2 140g / m 2 145g / m 2 150g / m 2 155g / m 2 156g / m 2 157g / m 2 158g / m 2 159g / m 2 159.6g / m 2 , or its value is within the range obtained by combining any two of the above values.

[0051] In some embodiments, 0.5% ≤ m1 ≤ 2%.

[0052] The higher the content of cyclic sulfate compounds in the electrolyte, the better the integrity and density of the interfacial film. However, a thicker interfacial film results in a higher internal impedance of the secondary battery cell. When the mass fraction of cyclic sulfate compounds is in the range of 0.5%-2%, it ensures both the integrity and density of the interfacial film and helps reduce the internal impedance of the secondary battery cell, thereby improving its power performance.

[0053] In some embodiments, the charging cutoff voltage v of a single secondary battery cell at 25°C satisfies: 4.1V≤v≤5V; optionally, 4.1V≤v≤4.8V.

[0054] For example, v can be 4.1V, 4.2V, 4.3V, 4.4V, 4.5V, 4.6V, 4.7V, 4.8V, or a value within the range obtained by any combination of the above two values.

[0055] Cyclic sulfate compounds, as electrolyte additives, can stably exist in electrolytes at high voltages above 4.1V, improving electrolyte stability under high voltage and reducing side reactions. When the charging cutoff voltage of a secondary battery cell is between 4.1V and 5V, the discharge specific capacity of the secondary battery cell increases, thereby improving its energy density. Therefore, the secondary battery cell provided in this application can achieve a charging cutoff voltage of 4.1V-5V, achieving good power performance and high-temperature storage performance while also maintaining high energy density.

[0056] In some embodiments, the secondary battery cell includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The coating weight w3 of one side of the negative electrode film layer satisfies: 47.5 g / m³. 2 ≤w3≤116.9g / m 2 .

[0057] For example, w3 could be 47.5 g / m 2 48g / m 2 50g / m 2 52g / m 2 54g / m 2 56g / m 2 58g / m 2 60g / m 2 62g / m 2 64g / m 2 66g / m 2 68g / m 2 70g / m 2 72g / m 2 74g / m 2 76g / m 2 78g / m 2 80g / m 2 82g / m 2 84g / m 2 86g / m 2 88g / m 2 90g / m 2 92g / m 2 94g / m 2 96g / m 2 98g / m 2 100g / m 2 102g / m 2 104g / m 2 106g / m 2 108g / m 2 110g / m 2 112g / m 2 114g / m 2 116g / m 2 116.9g / m 2 , or its value is within the range obtained by combining any two of the above values.

[0058] The lower the coating weight of the negative electrode film, the lower the internal impedance of the secondary battery cell. Therefore, by controlling the coating weight of the negative electrode film at 47.5 g / m³, 2 -116.9g / m 2Within this range, it helps to further improve the internal impedance of secondary battery cells and help improve the power performance of secondary battery cells.

[0059] In some embodiments, the cyclic sulfate compounds include one or more compounds of formula (1) or modified compounds thereof:

[0060] Wherein, R1 includes one or more methylene groups having 0-2 carbon atoms; R2 includes one or more methylene groups having 0-2 carbon atoms; R3 includes one or more methylene groups having 0-3 carbon atoms, oxygen, and alkoxy groups having 1-6 carbon atoms; R4 includes one or more hydrogen, halogen, alkyl, and alkoxy groups having 1-6 carbon atoms; and R5 includes one or more hydrogen, halogen, alkyl, and alkoxy groups having 1-6 carbon atoms.

[0061] As shown in formula (1), the cyclic sulfate ester compound has a bicyclic structure. During the ring-opening reaction to form an interfacial film, it can form a polymer with a chain network, which has a better coating effect on the solid interface and can further reduce the side reactions between the electrolyte and the positive and negative electrode active materials. Therefore, by using the cyclic sulfate ester compound with the structure of formula (1), the high-temperature storage performance of secondary battery cells can be further improved.

[0062] In some embodiments, R4 and / or R5 further include one or more of the compounds of formula (2) as substituents or modified compounds thereof as substituents: R6 includes one or more of methylene with 0-3 carbon atoms and alkoxy with 1-3 carbon atoms; R7 includes one or more of hydrogen, halogen, alkyl with 1-6 carbon atoms and alkoxy with 1-6 carbon atoms; R8 includes one or more of methylene with 0-2 carbon atoms; R6 in formula (2) can be used as a substituent.

[0063] Specifically, when the structure shown in formula (2) is used as a substituent, R6 or a group in R6 can be used as a substituent. It can be that one structure shown in formula (2) is connected to R4 or R5 in the structure shown in formula (1), or it can be that two structures shown in formula (2) are used as substituents and connected to R4 and R5 respectively.

[0064] Introducing the group shown in formula (2) into the compound shown in formula (1) can give the sulfate ester compound a tricyclic or tetracyclic structure, allowing the sulfate ester compound to form a more continuous chain-like network structure during the ring-opening process of forming the interfacial film, thereby further improving the coating effect of the interfacial film on the solid interface. Therefore, by using cyclic sulfate ester compounds with the above structure, the high-temperature storage performance of secondary battery cells can be further improved.

[0065] In some embodiments, the cyclic sulfate compounds include one or more of formulas (3) to (7):

[0066] In some embodiments, the electrolyte includes a solvent, which includes carbonate solvents.

[0067] In some embodiments, carbonate solvents include one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, and fluoroethylene carbonate.

[0068] Carbonate solvents help improve the ionic conductivity of the electrolyte, thereby helping to reduce the internal impedance of the secondary battery cell and improve its power performance.

[0069] In some embodiments, the electrolyte comprises a lithium salt, wherein the lithium salt comprises LiPF6.

[0070] LiPF6 has good thermal stability. Therefore, by selecting LiPF6 as the lithium salt, the high-temperature stability of the electrolyte can be improved, the side reactions of the electrolyte at high temperatures can be reduced, and the high-temperature storage performance of the secondary battery cell can be improved.

[0071] In some embodiments, the compaction density ρ of the positive electrode sheet satisfies: 2.4 g / cm³ 3 ≤ρ≤3.7g / cm 3 .

[0072] When the compaction density of the positive electrode is 2.4 g / cm³ 3 -3.7g / cm 3 Within a certain range, as the compaction density of the positive electrode increases, the contact between the particles of the positive electrode active material becomes tighter, the contact area becomes larger, and there are more channels for electron transport, resulting in lower internal impedance of the secondary battery cell. Therefore, controlling the compaction density of the positive electrode within a certain range helps to further reduce the internal impedance of the secondary battery cell and improve its power performance.

[0073] ρ can be 2.4 g / cm³3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 , or its value is within the range obtained by combining any two of the above values.

[0074] In some embodiments, the thickness h of the positive electrode film layer satisfies: 0.0209mm ≤ h ≤ 0.0753mm.

[0075] A thicker positive electrode film is more conducive to the energy density of the rechargeable battery cell, but it also makes it more difficult for the electrolyte to wet the positive electrode, which is detrimental to lithium-ion kinetics and the power performance of the rechargeable battery cell. When the thickness of the positive electrode film is in the range of 0.0209mm-0.0753mm, both the energy density and power performance of the rechargeable battery cell can be balanced.

[0076] For example, h can be 0.0209mm, 0.021mm, 0.024mm, 0.026mm, 0.028mm, 0.03mm, 0.032mm, 0.034mm, 0.036mm, 0.038mm, 0.04mm, 0.042mm, 0.044mm, 0.046mm, 0.048mm, 0.05mm, 0.052mm, 0.054mm, 0.056mm, 0.058mm, 0.06mm, 0.062mm, 0.064mm, 0.066mm, 0.068mm, 0.07mm, 0.072mm, 0.074mm, 0.075mm, 0.0753mm, or a value within the range obtained by any combination of the above two values.

[0077] In some embodiments, the porosity p of the positive electrode sheet, measured by the true density method, satisfies: 23% ≤ p ≤ 27%; optionally, 23.5% ≤ p ≤ 26%.

[0078] When the porosity of the positive electrode sheet measured by the true density method is 23%-27%, the high porosity of the electrode sheet improves the wettability of the electrolyte. The electrolyte provides a conduction path for active ions inside the material, improves the kinetic performance, and thus improves the power performance of the lithium-ion secondary battery cell.

[0079] For example, p can be 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, or a value within the range obtained by any combination of the above two values.

[0080] In some embodiments, the positive electrode film layer includes a positive electrode active material, which includes a lithium-containing transition metal oxide.

[0081] Lithium-containing transition metal oxides exhibit high specific capacity, with a coating weight of 77.9 g / m² on the positive electrode. 2 -159.6g / m 2 Within a certain range, selecting lithium-containing transition metal oxides as positive electrode active materials helps to improve the energy density of secondary battery cells while ensuring good power performance.

[0082] In some embodiments, lithium-containing transition metal oxides include those with the molecular formula Li m1 [Ni a Co b Mn c Q1 e ]O 2-f One or more of the compounds or their modified compounds, wherein Q1 includes one or more of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.8≤m1≤1.2, 0.5≤a≤0.95, 0.05≤b≤0.2, 0<c<0.3, 0≤e<0.3, 0≤f≤0.5.

[0083] When Q1 is Zr, doping and / or coating zirconium elements in lithium-containing transition metals helps to improve the structural stability of the positive electrode active material at high charging cutoff voltages (4.1V-5V), enabling the secondary battery cell to achieve a high charging cutoff voltage and thus improving the power performance of the secondary battery cell.

[0084] In some embodiments, the average particle size D1 of the primary particles containing lithium transition metal oxides satisfies: 1 μm ≤ D1 ≤ 5 μm; optionally, 1.5 μm ≤ D1 ≤ 3 μm.

[0085] D1 can be 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, 3.1μm, 3 0.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm, or their values ​​are within the range obtained by any combination of the above two values.

[0086] In some embodiments, the positive electrode active material includes a lithium-containing transition metal phosphate, which includes secondary particles formed by the agglomeration of primary particles.

[0087] In some embodiments, the average particle size D2 of the primary particles containing lithium transition metal phosphate satisfies: 10nm ≤ D2 ≤ 1000nm; optionally, 100nm ≤ D2 ≤ 500nm.

[0088] Lithium-containing transition metal phosphates have nanoscale primary particles with small average particle size, resulting in shorter and faster lithium-ion transport paths within the material, thus exhibiting excellent kinetic performance. Introducing lithium-containing transition metal phosphates into cathode active materials helps improve lithium-ion kinetics, thereby reducing the internal impedance of secondary battery cells and enhancing their power performance. Furthermore, lithium-containing transition metal phosphates are relatively inexpensive, enabling cost reduction and making them more suitable for commercial production and applications.

[0089] In some embodiments, lithium-containing transition metal phosphates include those with the molecular formula Li m2 Fe x Mn r P y O j2 Q2 q2 One or more of the compounds or their modified compounds, wherein Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.6≤m2≤1.15, 0<x, 0≤r, 0.9≤x+r≤1, 0.95≤y≤1, 3.5≤j2≤4, 0≤q2≤0.1.

[0090] In some embodiments, the mass ratio of lithium-containing transition metal oxide to lithium-containing transition metal phosphate is 2:1 to 30:1; optionally, the mass ratio is 2:1 to 9:1. When the mass ratio of lithium-containing transition metal oxide to lithium-containing transition metal phosphate is 9:1 to 30:1, the lithium-ion secondary battery of this application has good cycle performance and high-temperature storage performance. When the mass ratio of lithium-containing transition metal oxide to lithium-containing transition metal phosphate is 2:1 to 9:1, the lithium-ion secondary battery of this application has high power density.

[0091] Next, using a lithium-ion battery as a specific example, a detailed description of the positive electrode, negative electrode, separator, and electrolyte in a single secondary battery cell will be provided. It should be understood that the lithium-ion battery is only an example, and the solution provided in this application can also be applied to other types of secondary batteries, such as sodium-ion batteries, magnesium-ion batteries, and lithium-sulfur batteries.

[0092] [Negative electrode plate]

[0093] A negative electrode typically includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material.

[0094] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0095] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. 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 (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0096] In one embodiment, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0097] In some embodiments, the negative electrode active material is a silicon-containing material. The silicon-containing material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composites. By selecting a silicon-containing material as the negative electrode active material, it is beneficial to further improve the volumetric energy density of the battery cell 10. Combined with the structural design of the battery cell 10 in the aforementioned embodiments, the battery cell 10 can possess both high energy density and excellent safety performance.

[0098] In one embodiment, the negative electrode film layer further includes an adhesive. The adhesive 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), and carboxymethyl chitosan (CMCS).

[0099] In some embodiments, the negative electrode film layer further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the negative electrode film layer also includes other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0101] In some embodiments, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0102] [Positive electrode plate]

[0103] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a first positive electrode active material and a second positive electrode active material.

[0104] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0105] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In one embodiment, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. During the charging and discharging process, Li undergoes insertion / extraction and consumption, resulting in different molar contents of Li in the positive electrode active material when the battery is discharged to different states. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. In the examples of positive electrode active materials in this application, the molar content of O is only an ideal value; lattice oxygen release causes changes in the molar content of O, and the actual molar content of O will fluctuate.

[0107] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0108] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may also include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, graphene, and carbon nanofibers.

[0109] In some embodiments, the positive electrode sheet can be prepared by forming a positive electrode slurry from the components described above. For example, the positive electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained.

[0110] Electrolyte

[0111] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements. The electrolyte includes electrolyte salts and solvents.

[0112] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0113] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0114] [Isolation Component]

[0115] This application does not impose any particular restrictions on the type of separator. For example, any known porous membrane with good chemical and mechanical stability can be selected.

[0116] In one embodiment, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0117] [Rechargeable Battery]

[0118] This application also provides a secondary battery, including the secondary battery cell described in the above embodiments. A secondary battery can be a single physical module comprising one or more secondary battery cells to provide higher voltage and capacity. When there are multiple secondary battery cells, the multiple secondary battery cells are connected in series, parallel, or mixed via a busbar.

[0119] In some embodiments, the secondary battery can be a battery pack, which includes a housing and individual secondary battery cells, with the individual secondary battery cells or battery modules housed in the housing.

[0120] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0121] In some embodiments, the secondary battery may be located in the energy storage device. The energy storage device includes energy storage containers, energy storage cabinets, etc.

[0122] Figure 1 This is a schematic diagram of a secondary battery according to this application. Figure 2This is a schematic diagram of a secondary battery cell according to this application. Figure 1-2 As shown, the secondary battery 10 may include multiple secondary battery cells 20 to meet different power usage needs.

[0123] The secondary battery 10 may further include a housing with a hollow interior, housing multiple secondary battery cells 20. For example, multiple secondary battery cells 20 may be connected in parallel, series, or a mixed configuration and then placed inside the housing. The housing may include a first housing portion 101 and a second housing portion 102, which are fitted together to form the housing. The shapes of the first housing portion 101 and the second housing portion 102 may be determined by the shape of the components housed within, for example, by the shape of the combination of the multiple secondary battery cells 20 housed within. At least one of the first housing portion 101 and the second housing portion 102 may have an opening. For example, as... Figure 1 As shown, only one of the first housing portion 101 and the second housing portion 102 may be a hollow cuboid with an opening, while the other may be plate-shaped to cover the opening. Taking the second housing portion 102 as a hollow cuboid with one opening and the first housing portion 101 as plate-shaped as an example, the first housing portion 101 covers the opening of the second housing portion 102 to form a housing with a closed chamber, which can be used to accommodate multiple secondary battery cells 20.

[0124] In addition, this application also provides an electrical device that includes the secondary battery described in the foregoing embodiments.

[0125] For example, unlike Figure 1 As shown, the first housing portion 101 and the second housing portion 102 can both be hollow cuboids with one open side each. The openings of the first housing portion 101 and the second housing portion 102 are opposite to each other, and the first housing portion 101 and the second housing portion 102 are interlocked to form a housing with a closed chamber. This chamber can accommodate multiple secondary battery cells 20. The multiple secondary battery cells 20 are connected in parallel, series, or mixed and placed inside the housing formed by the interlocking of the first housing portion 101 and the second housing portion 102.

[0126] In some embodiments, the secondary battery may further include other components. For example, the secondary battery may further include a busbar component, which can be used to realize electrical connections between multiple secondary battery cells 20, such as in parallel, series, or mixed connections. Specifically, the busbar component can realize electrical connections between secondary battery cells 20 by connecting to the electrode terminals of the secondary battery cells 20; or, the busbar component can also realize electrical connections between secondary battery cells 20 by connecting to other components of the secondary battery cells 20. The busbar component can be fixed to corresponding components of the secondary battery cells 20 by welding, for example, by welding to electrode terminals, sealing structures, or housings, etc., and the embodiments of this application are not limited thereto.

[0127] The secondary battery cells 20 can be directly assembled into secondary battery 10, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into secondary battery 10.

[0128] [Electrical appliances]

[0129] This application provides an electrical device, including the battery described in the above embodiments.

[0130] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical devices.

[0131] This application provides an electrical device, which is a vehicle.

[0132] The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. The vehicle's interior can house a motor, a controller, and a secondary battery 10. The controller is used to control the secondary battery 10 to supply power to the motor. For example, the secondary battery 10 can be located at the bottom, front, or rear of the vehicle. The secondary battery 10 can be used for vehicle power supply; for example, it can serve as the vehicle's operating power source for the vehicle's electrical system, such as for the power needs of starting, navigation, and operation. In another embodiment of this application, the secondary battery 10 can not only serve as the vehicle's operating power source but also as the vehicle's drive power source, replacing or partially replacing gasoline or natural gas to provide driving power to the vehicle.

[0133] 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.

[0134] [Examples and Comparative Examples]

[0135] Example 1

[0136] (1) Preparation of positive electrode sheet

[0137] LiN, the positive electrode active material i0.5 Co 0.3 Mn 0.2 O2 (NCM532), polyvinylidene fluoride (PVDF) binder, and super P conductive agent are mixed uniformly in N-methylpyrrolidone (NMP) solvent at a weight ratio of 80:10:10 to prepare a positive electrode slurry. The slurry is then coated on both sides of a current collector aluminum foil, and the positive electrode sheet is obtained through drying, cold pressing, slitting, and cutting. The single-sided coating weight w2 of the positive electrode film is 155.82 g / m². 2 .

[0138] (2) Preparation of negative electrode sheet

[0139] A negative electrode slurry was prepared by uniformly mixing graphite (the negative electrode active material), super P (a conductive agent), sodium carboxymethyl cellulose (CMC-Na) (a thickener), and styrene-butadiene rubber (SBR) (a binder) in deionized water at a weight ratio of 80:15:3:2. The slurry was then coated on both sides of a copper current collector foil, dried, and subjected to cold pressing, slitting, and cutting to produce the negative electrode sheet for a lithium-ion battery. The single-sided coating weight (w3) of the negative electrode film was 97.52 g / m³. 2 .

[0140] (3) Preparation of electrolyte

[0141] In an argon-atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, a non-aqueous solvent, ethylene carbonate (EC), and ethyl methyl carbonate (EMC), were mixed at a mass ratio of 3:7 to obtain a mixed solvent. The additive shown in formula (7) was added to the mixed solvent, and after thorough mixing, 1 M lithium salt LiPF6 was added and stirred until dissolved. The mass fraction w1 of the additive shown in formula (7) was 0.5% based on the total mass of the electrolyte.

[0142] (4) Preparation of secondary battery cells

[0143] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is placed in a housing, electrolyte is injected, and then it is encapsulated to obtain a secondary battery cell. The CB value of the secondary battery cell can be between 1.05 and 1.2. In Example 1, the CB value of the secondary battery is 1.07.

[0144] Examples 2-15, Comparative Examples 1-3

[0145] Compared with Example 1, the difference is that the electrode parameters or electrolyte parameters are different from those in Example 1, as detailed in Table 1.

[0146] Table 1: Product parameters of Examples 1-15 and Comparative Examples 1-3

[0147] In Table 1, "NCM532" represents the positive electrode active material LiN. i0.5 Co 0.3 Mn 0.2 O2; "NCM811" represents the positive electrode active material LiN i0.8 Co 0.1 Mn 0.1 O2; "Ni90Co5Mn5" represents the positive electrode active material LiN i0.9 Co 0.05 Mn 0.05 O2; "NCM333" represents the positive electrode active material LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2; "w1" represents the mass fraction of cyclic sulfate ester compounds in the electrolyte; "w2" represents the coating weight on one side of the positive electrode film; "w3" represents the coating weight on one side of the negative electrode film; "ρ" represents the compaction density of the positive electrode sheet.

[0148] The battery performance of Examples 1-15 and Comparative Examples 1-3 is detailed in Table 2.

[0149] Table 2: Battery performance parameters of Examples 1-15 and Comparative Examples 1-3

[0150] In Table 2, “Charging Cut-off Voltage” represents the maximum charging cut-off voltage of a single secondary battery cell; “DCR” represents the DC impedance of a single secondary battery cell; “Power Density” represents the power density of a single secondary battery cell at 50% SOC in 30 seconds; and “High Temperature Storage Capacity Retention Rate” represents the capacity retention rate of a single secondary battery cell stored at 60°C for 60 days.

[0151] Comparative analysis of the examples and comparative examples shows that the power density and high-temperature storage performance of Examples 1-15 are superior to those of Comparative Examples 1-3. This demonstrates that when the electrolyte includes cyclic sulfate compounds, and the mass fraction of the cyclic sulfate in the electrolyte is in the range of 0.01%-5% and the coating weight on one side of the positive electrode film is 77.9 g / m², the performance is significantly better. 2 -159.6g / m 2 Within a certain range, secondary batteries can simultaneously possess good power performance and high-temperature storage performance.

[0152] The comparison of Examples 1-3 shows that, with a fixed mass fraction of the cyclic sulfate compound, the smaller the coating weight on one side of the positive electrode film, the smaller the DCR of the secondary battery cell, and the better the power performance and high-temperature storage performance. Considering the influence of coating weight on the energy density of the secondary battery cell, appropriately increasing the coating weight within the above-mentioned range can further improve the energy density of the secondary battery cell.

[0153] Based on the comparison of Examples 1 and 4-6, it can be seen that when the compaction density of the positive electrode sheet is 2.4 g / cm³, 3 -3.7g / cm 3 When the range is within a certain range, the internal impedance of the secondary battery cell can be further reduced, thereby improving the power performance of the secondary battery cell.

[0154] Based on the comparison of Examples 1 and 7-8, it can be seen that when the coating weight of the negative electrode film is 47.5 g / m², 2 -116.9g / m 2 When the range is within a certain range, the internal impedance of the secondary battery cell can be further reduced, thereby improving the power performance of the secondary battery cell.

[0155] Based on the comparison of Examples 1 and 9-11, it can be seen that when the coating weight on one side of the positive electrode film is constant, the smaller the mass fraction of the cyclic sulfate compound, the smaller the DCR of the secondary battery cell and the better the power performance, but the high-temperature storage performance is affected.

[0156] Example 12 illustrates the use of a compound of formula (6) as a cyclic sulfate additive.

[0157] Examples 13-15 demonstrate that the solutions of this application are adapted to different positive electrode active materials, all of which can achieve high cutoff voltage, good power performance and high temperature storage performance.

[0158] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0159] 1. Test method for coating weight

[0160] Randomly select 30 unit areas on the electrode to be tested. Take the electrode to be tested from each unit area and weigh the mass of the material on the unit area electrode, excluding the current collector. Sum the mass and divide by 30 to get the coating weight of the electrode to be tested.

[0161] 2. Test methods for the mass content of each component in the electrolyte

[0162] The mass fraction of additives in the electrolyte can be determined using nuclear magnetic resonance spectroscopy (NMR). The specific testing procedure is as follows: Add 500 μL of deuterated reagent to an NMR tube in a nitrogen-filled glove box. Add 100 μL of the non-aqueous electrolyte sample to the NMR tube. Shake the NMR tube to dissolve the non-aqueous electrolyte in the deuterated reagent. The test is performed using an Oxford Instruments X-Pulse benchtop NMR spectrometer. Because the non-aqueous electrolyte is highly sensitive to moisture, both the NMR test and sample preparation are conducted in a nitrogen atmosphere (H₂O content less than 0.1 ppm, O₂ content less than 0.1 ppm). Simultaneously, all instruments used in the test must be pre-washed with pure water and dried in a vacuum environment at 60°C for at least 48 hours. The deuterated reagent was prepared as follows: Deuterated dimethyl sulfoxide (DMSO-d6), deuterated acetonitrile, and trifluoromethylbenzene were dried using a 4A molecular sieve at a temperature above 25°C for at least 3 days, ensuring that the water content of all reagents was less than 3 ppm. A Metrohm 831KF coulometric moisture analyzer was used for moisture testing. Then, 10 mL of dried DMSO-d6 and 300 μL of dried internal standard trifluoromethylbenzene were mixed thoroughly in a nitrogen-filled glove box to obtain the first solution. 10 mL of dried deuterated acetonitrile and 300 μL of dried internal standard trifluoromethylbenzene were then mixed thoroughly to obtain the second solution. The first and second solutions were then mixed thoroughly to obtain the deuterated reagent.

[0163] The reference standard GB / T 9722-2006 specifies the quantitative analysis of solvent content in electrolytes using organic gas chromatography.

[0164] The lithium salt content in the electrolyte is quantitatively analyzed by ion chromatography, according to the reference standard JY / T020-1996.

[0165] 3. Test method for average particle size

[0166] The "LIBMAS Lithium-ion Battery Material Microscopic Intelligent Analysis System" software was used to automatically identify primary particles using AI, draw particle outlines, and obtain particle quantity, number, area, and maximum caliper diameter. 2000 particles were collected, and the average was calculated.

[0167] The average particle size = the sum of the sizes (longest diameters) of all measured particles / the sum of the number of all measured particles.

[0168] 4. Test method for electrode compaction density

[0169] Thirty unit areas are randomly selected from the electrode to be tested. For each unit area, the mass m1 of the material (excluding the current collector) on that unit area electrode is measured. The electrode thickness H1 and the current collector thickness H0 are also measured. The compaction density of each unit area electrode is calculated as m1 / (H1-H0). The sum of the results from these 30 randomly selected unit areas on the electrode to be tested is then divided by 30 to obtain the compaction density of the electrode to be tested.

[0170] 5. Porosity of the positive electrode sheet measured by the true density method

[0171] The determination was performed according to the standard procedure GB / T 24586-2009. The specific test procedure is as follows: Select more than 20 round pieces with good appearance and no powder shedding from the edges using tweezers and place them into the sample cup. Record the number of pieces and calculate the apparent volume. Then, place the sample cup containing the sample into the true density tester, seal the test system, and introduce helium gas according to the procedure. By detecting the gas pressure in the sample chamber and the expansion chamber, and then calculating the true volume according to Bohr's Law (PV = nRT), the porosity of the sample to be tested can be obtained.

[0172] 6. Test method for internal impedance (DCR) of secondary battery cells

[0173] At room temperature, each battery cell under test was charged at a constant current of 0.5C to 3.65V, and then charged at a constant voltage until the current was 0.05C. The battery was then discharged at a constant current of 0.5C for 60 minutes to adjust the battery to 50% SOC, and the voltage of the battery at this time was recorded as U1. The battery was then discharged at a constant current of 4C for 30 seconds, and the voltage at the end of the discharge was recorded as U2 using a 0.1-second sampling time. The DCR of the secondary battery cell under test is calculated as (U1-U2) / 4C.

[0174] 7.30S Test Method for 50% SOC Power Density

[0175] The test cell was placed in a constant temperature chamber at 25°C and left to stand for 2 hours. Once the cell temperature remained at 25°C, the following tests were performed: 1. Charged with a 1 / 3C constant current to 4.5V, then continued with constant voltage charging until the charging current was less than 0.05C. The charging was then stopped. After a 30-minute pause, the cell was discharged with a 1 / 3C constant current to 2.8V, and the discharge capacity was measured. 2. After a 30-minute pause, the cell was charged with a 1 / 3C constant current to 4.5V, then continued with constant voltage charging until the charging current was less than 0.05C. After a 30-minute pause, the cell was discharged with a 1 / 3C constant current to 0.5C0 (C0 is the cell capacity), i.e., adjusted to 50% SOC, and left to stand for 2 hours. Discharge with a current of X1 A for 30 seconds, and record this step capacity as C1. Let it rest for 5 minutes, and then recharge C1 with a current of 1 / 20C. Discharge with a current of X2 A for 30 seconds, and record this step capacity as C2. Let it rest for 5 minutes, and then recharge C2 with a current of 1 / 20C. Repeat the above steps until the final voltage is 2.8±0.05V. At this time, the current is Xn. Calculate the power density using this current.

[0176] Power density = Power (W) / Discharge capacity (Ah) = Discharge voltage (V) * Test current (A) / Discharge capacity (Ah).

[0177] 8. High-temperature storage performance

[0178] At 25℃, the battery was charged at a constant current rate of 1 / 3C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C. After resting for 30 minutes, it was discharged at a constant current rate of 1 / 3C to 2.8V. The initial discharge capacity of the battery was measured. After resting for 30 minutes, the battery was charged at a constant current rate of 1 / 3C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C. The fully charged battery was then placed in a 60℃ oven for 60 days. After the battery was removed from the high-temperature storage for 60 days and allowed to cool naturally to 25℃, it was discharged at a constant current rate of 1 / 3C to 2.8V, then charged at a constant current rate of 1 / 3C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and finally discharged at a constant current rate of 1 / 3C to 2.8V. The discharge capacity of the battery after 60 days of high-temperature storage was measured.

[0179] Battery capacity retention rate (%) after 100 days of high-temperature storage = Discharge capacity after 100 days of high-temperature storage / Initial discharge capacity × 100%.

[0180] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery cell, characterized in that, The secondary battery cell includes: The electrolyte includes additives, said additives including cyclic sulfate compounds, wherein the mass fraction w1 of said cyclic sulfate compounds in the electrolyte, based on the total mass of said electrolyte, satisfies: 0.01% ≤ w1 ≤ 5%; The positive electrode tab comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, a single-sided coating weight w2 of the positive electrode film layer satisfies: 77.9 g / m 2 ≤ w2 ≤ 159.6 g / m 2 .

2. The secondary battery cell according to claim 1, characterized in that, The charging cutoff voltage v of the secondary battery cell at 25°C satisfies: 4.2V≤v≤5V.

3. The secondary battery cell according to claim 2, characterized in that, 4.2V≤v≤4.8V.

4. The secondary battery cell according to any one of claims 1-3, characterized in that, The secondary battery cell includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The coating weight w3 of the negative electrode film layer on one side satisfies: 47.5 g / m³. 2 ≤w3≤116.9g / m 2 .

5. The secondary battery cell according to any one of claims 1-4, characterized in that, The cyclic sulfate compounds include one or more of compounds with the molecular formula (1) or modified compounds thereof: Wherein, R1 includes one or more methylene groups having 0-2 carbon atoms; R2 includes one or more methylene groups having 0-2 carbon atoms; R3 includes one or more methylene groups having 0-3 carbon atoms, oxygen, and alkoxy groups having 1-6 carbon atoms; R4 includes one or more hydrogen, halogen, alkyl, and alkoxy groups having 1-6 carbon atoms; and R5 includes one or more hydrogen, halogen, alkyl, and alkoxy groups having 1-6 carbon atoms.

6. The secondary battery cell according to any one of claims 5, characterized in that, R4 and / or R5 also include one or more of the compounds shown in formula (2) as substituents or their modified compounds as substituents: R6 includes one or more of methylene with 0-3 carbon atoms and alkoxy with 1-3 carbon atoms; R7 includes one or more of hydrogen, halogen, alkyl with 1-6 carbon atoms and alkoxy with 1-6 carbon atoms; R8 includes one or more of methylene with 0-2 carbon atoms; R6 in formula (2) can be used as a substituent.

7. The secondary battery cell according to any one of claims 1-5, characterized in that, The cyclic sulfate compounds include one or more of formulas (3) to (7):

8. The secondary battery cell according to any one of claims 1-7, characterized in that, The electrolyte includes a solvent, which includes carbonate solvents.

9. The secondary battery cell according to claim 8, characterized in that, The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, and fluoroethylene carbonate.

10. The secondary battery cell according to any one of claims 1-9, characterized in that, The electrolyte includes a lithium salt, and the lithium salt includes LiPF6.

11. The secondary battery cell according to any one of claims 1-10, characterized in that, The compaction density ρ of the positive electrode sheet satisfies: 2.4 g / cm³ 3 ≤ρ≤3.7g / cm 3 .

12. The secondary battery cell according to any one of claims 1-11, characterized in that, The thickness h of the positive electrode film layer satisfies: 0.0209mm≤h≤0.0753mm.

13. The secondary battery cell according to any one of claims 1-12, characterized in that, The porosity p of the positive electrode sheet, measured by the true density method, satisfies the following condition: 23% ≤ p ≤ 27%.

14. The secondary battery cell according to any one of claims 1-13, characterized in that, The positive electrode film layer includes a positive electrode active material, which includes a lithium-containing transition metal oxide.

15. The secondary battery cell according to claim 14, characterized in that, The lithium-containing transition metal oxide includes those with the molecular formula Li. m1 [Ni a Co b Mn c Q1 e O 2-f One or more of the compounds or their modified compounds, Where Q1 includes one or more of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.8≤m1≤1.2, 0.5≤a≤0.95, 0.05≤b≤0.2, 0<c<0.3, 0≤e<0.3, 0≤f≤0.

5.

16. The secondary battery cell according to claim 14 or 15, characterized in that, The average particle size D1 of the primary particles of the lithium-containing transition metal oxide satisfies: 1μm≤D1≤5μm.

17. The secondary battery cell according to any one of claims 14-16, characterized in that, The positive electrode active material includes lithium-containing transition metal phosphate, which comprises secondary particles formed by the agglomeration of primary particles.

18. The secondary battery cell according to claim 17, characterized in that, The lithium-containing transition metal phosphate includes those with the molecular formula Li. m2 Fe x Mn r P y O j2 Q2 q2 One or more of the compounds or their modified compounds, Where Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br, 0.6≤m2≤1.15, 0<x, 0≤r, 0.9≤x+r≤1, 0.95≤y≤1, 3.5≤j2≤4, and 0≤q2≤0.

1.

19. The secondary battery cell according to claim 17 or 18, characterized in that, The average particle size D2 of the primary particles of the lithium-containing transition metal phosphate satisfies: 10nm ≤ D2 ≤ 1000nm.

20. A secondary battery, characterized in that, The secondary battery comprises any one of the secondary battery cells according to claims 1-19.

21. An electrical appliance, characterized in that, The electrical device includes a secondary battery cell as described in any one of claims 1-19, and / or the secondary battery as described in claim 20.

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