Lithium ion battery monomer, lithium ion battery and electric device

Abstract

The invention discloses a lithium ion battery monomer, a lithium ion battery and an electric device, and belongs to the technical field of batteries. The lithium ion battery cell comprises: an electrolyte comprising a carboxylic ester solvent; the electrode assembly comprises a positive pole piece and a negative pole piece, the positive pole piece and the negative pole piece are stacked to form the electrode assembly, the electrode assembly comprises a main body part, a positive pole lug part and a negative pole lug part, and the positive pole lug part and the negative pole lug part protrude out of the main body part; the end cover is provided with a positive electrode terminal and a negative electrode terminal, and the positive electrode terminal and the negative electrode terminal are connected with the positive electrode lug part and the negative electrode lug part respectively; the distance between one end, close to the end cover, of the main body part and the inner side of the end cover is 3mm to 10mm; and the residual space of the lithium ion battery monomer is 0.05 mL / Ah to 0.3 mL / Ah. According to the technical scheme, the fast charging performance, the service life, the reliability and the energy density of the single lithium ion battery can be considered.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a lithium-ion battery cell, a lithium-ion battery, and an electrical device. Background Art

[0002] As environmental pollution becomes increasingly serious, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor related to its development.

[0003] The development of battery technology needs to consider many design factors, such as fast charging performance, energy density, cycle life, capacity, reliability, etc. How to provide a lithium-ion battery cell that takes into account fast charging performance, service life reliability and energy density is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a lithium-ion battery cell, a lithium-ion battery and an electrical device, so as to take into account the fast charging performance, service life, reliability and energy density of the lithium-ion battery cell.

[0005] In a first aspect, a lithium-ion battery cell is provided, comprising: an electrolyte, the electrolyte comprising a carboxylic acid ester solvent; an electrode assembly, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet are stacked to form the electrode assembly, the electrode assembly comprising a main body, a positive electrode ear and a negative electrode ear, the positive electrode ear and the negative electrode ear protruding from the main body; an end cover, the end cover is provided with a positive electrode terminal and a negative electrode terminal, the positive electrode terminal and the negative electrode terminal are respectively connected to the positive electrode ear and the negative electrode ear; wherein the distance between one end of the main body close to the end cover and the inner side of the end cover is 3 mm to 10 mm; the residual space of the lithium-ion battery cell is 0.05 mL / Ah to 0.3 mL / Ah.

[0006] In an embodiment of the present application, a lithium-ion battery cell includes an electrolyte, and the electrolyte includes a carboxylate solvent, which is beneficial to improving the fast charging performance of the lithium-ion battery cell; the addition of the carboxylate solvent leads to more gas production in the lithium-ion battery cell, and since the positive electrode sheet and the negative electrode sheet are stacked to form an electrode assembly, more heat accumulates in the lithium-ion battery cell, thereby aggravating the gas production of the carboxylate solvent, and by setting the residual space of the lithium-ion battery cell to be greater than or equal to 0.05 mL / Ah, there is more space inside the lithium-ion battery cell to accommodate the generated gas, which can reduce the risk of premature failure of the lithium-ion battery cell due to excessive internal pressure of the lithium-ion battery cell, thereby improving the service life of the lithium-ion battery cell; by setting the residual space of the lithium-ion battery cell to be less than or equal to 0.3 mL / Ah, the space utilization rate inside the lithium-ion battery cell can be improved, and the lithium-ion battery cell has a higher energy density. In addition, since the positive pole ear and the negative pole ear occupy a certain space, under the condition of satisfying the above residual space setting, by setting the distance between the end of the main body close to the end cover and the inner side of the end cover to be greater than or equal to 3mm, there is a suitable space inside the lithium-ion battery cell to accommodate the positive pole ear and the negative pole ear, which is convenient for the shaping of the positive pole ear and the negative pole ear and can reduce the risk of the positive pole ear and the negative pole ear being inserted into the main body, thereby reducing the risk of short circuit and improving the reliability of the lithium-ion battery cell; by setting the distance between the end of the main body close to the end cover and the inner side of the end cover to be less than or equal to 10mm, it is beneficial to improve the space utilization rate inside the lithium-ion battery cell, and the lithium-ion battery cell has a higher energy density. Therefore, the embodiment of the present application can take into account the fast charging performance, service life, reliability and energy density of the lithium-ion battery cell.

[0007] In some embodiments, the distance between the end of the main body close to the end cap and the inner side of the end cap is 4 mm to 7 mm. The above arrangement is conducive to further reducing the risk of the positive electrode ear and the negative electrode ear being inserted into the main body, which is conducive to further improving the reliability of the lithium-ion battery cell while also taking into account a higher energy density.

[0008] In some embodiments, the positive electrode sheet includes a positive electrode collector body and a positive electrode tab, wherein the positive electrode tab protrudes from the positive electrode collector body; the positive electrode tab portion includes multiple layers of the positive electrode tabs, and the number of layers of the multiple layers of the positive electrode tabs is 15 to 70.

[0009] In a lithium-ion battery cell including a carboxylic acid ester solvent, the lithium-ion battery cell has good fast charging performance, and in the case of fast charging, the lithium-ion battery cell has a large charging current; by setting the number of layers of the multi-layer positive electrode ear to be greater than or equal to 15, it is beneficial to improve the current capacity of the positive electrode ear part, reduce the overcurrent risk under the condition of a large charging current, and reduce the temperature of the lithium-ion battery cell; by setting the number of layers of the multi-layer positive electrode ear to be less than or equal to 70, it is beneficial to shape the multi-layer positive electrode ear into the positive electrode ear part, reduce the difficulty of processing the positive electrode ear part, and also help reduce the risk of the positive electrode ear part being inserted into the main body due to the excessive thickness of the positive electrode ear part, thereby reducing the risk of short circuit. Therefore, the above-mentioned setting is beneficial to reduce the risk of overcurrent and short circuit, while facilitating the processing of the positive electrode ear part, so that the lithium-ion battery cell can have both high reliability and good processing performance.

[0010] In some embodiments, the thickness of the positive electrode tab is 10 μm to 15 μm.

[0011] By setting the thickness of the positive electrode tab to be greater than or equal to 10 μm, the positive electrode tab has a more appropriate current flow capacity. By setting the thickness of the positive electrode tab to be less than or equal to 15 μm, the positive electrode tab has an appropriate thickness, and the electrode assembly as a whole occupies an appropriate space, which is beneficial to reducing the risk of deterioration of energy density.

[0012] In some embodiments, the negative electrode plate includes a negative electrode current collector body and a negative electrode tab, wherein the negative electrode tab protrudes from the negative electrode current collector body; the negative electrode tab portion includes multiple layers of the negative electrode tabs, and the number of layers of the multiple layers of the negative electrode tabs is 15 to 100.

[0013] In a lithium-ion battery cell including a carboxylic acid ester solvent, the lithium-ion battery cell has good fast charging performance, and in the case of fast charging, the lithium-ion battery cell has a large charging current; by setting the number of layers of the multi-layer negative electrode ear to be greater than or equal to 15, it is beneficial to improve the current capacity of the negative electrode ear part, reduce the risk of overcurrent in the case of a large charging current, and reduce the temperature of the lithium-ion battery cell; by setting the number of layers of the multi-layer negative electrode ear to be less than or equal to 100, it is beneficial to shape the multi-layer negative electrode ear into the negative electrode ear part, reduce the difficulty of processing the negative electrode ear part, and also help to reduce the risk of the negative electrode ear part being inserted into the main body due to the excessive thickness of the negative electrode ear part, thereby reducing the risk of short circuit. Therefore, the above-mentioned setting is beneficial to reduce the risk of overcurrent and short circuit while facilitating the processing of the negative electrode ear part, so that the lithium-ion battery cell can have both high reliability and good processing performance. In addition, since the positive electrode ear has a better current capacity than the negative electrode ear, the number of layers of the multi-layer positive electrode ear can be slightly lower than the number of layers of the multi-layer negative electrode ear.

[0014] In some embodiments, the thickness of the negative electrode tab is 4 μm to 6 μm.

[0015] By setting the thickness of the negative electrode tab to be greater than or equal to 4μm, the negative electrode tab has a more appropriate current flow capacity, and by setting the thickness of the negative electrode current collector to be less than or equal to 6μm, the negative electrode tab has an appropriate thickness, and the electrode assembly as a whole occupies an appropriate space, which is beneficial to reducing the risk of deterioration of energy density.

[0016] In some embodiments, the residual space of the lithium-ion battery cell is 0.05 mL / Ah to 0.2 mL / Ah, which is helpful to further improve the service life of the lithium-ion battery cell.

[0017] In some embodiments, the lithium-ion battery cell includes a first wall and a second wall, the first wall is the surface with the largest surface area, and the second wall is adjacent to the first wall and the end cover; the distance between the electrode assembly and the second wall is 0.1 mm to 1.5 mm.

[0018] By setting the distance between the electrode assembly and the second wall to be greater than or equal to 0.1 mm, it is convenient for gas and heat to flow out from the gap between the electrode assembly and the second wall. When the residual space is 0.05 mL / Ah to 0.3 mL / Ah, the accumulation and aggregation of gas and heat in the electrode assembly can be reduced, thereby reducing the internal pressure of the lithium-ion battery cell, reducing the risk of premature failure of the lithium-ion battery cell due to excessive internal pressure, and helping to improve the service life of the lithium-ion battery cell. In addition, it is convenient to assemble the lithium-ion battery cell while reserving space for the expansion of the electrode assembly. By setting the distance between the electrode assembly and the second wall to be less than or equal to 1.5 mm, there is a suitable distance between the electrode assembly and the second wall, which can reduce the shaking of the electrode assembly in the lithium-ion battery cell, and help to improve the reliability of the lithium-ion battery cell.

[0019] In some embodiments, based on the total mass of the electrolyte, the mass content W of the carboxylate solvent satisfies: 1wt%≤W≤50wt%, the end cover is provided with a pressure relief mechanism, and the actuating pressure P of the pressure relief mechanism satisfies: 0.6MPa≤P≤1.4MPa.

[0020] In a lithium-ion battery cell including a laminated electrode assembly, by setting 1wt%≤W≤50wt%, the lithium-ion battery cell has a more suitable fast-charging performance, and less gas is generated in the lithium-ion battery cell; by setting 0.6MPa≤P≤1.4MPa, while the lithium-ion battery cell has a suitable fast-charging performance, it can reduce the risk of the pressure relief mechanism actuating the valve in advance, and is conducive to the discharge of emissions from the pressure relief mechanism, thereby taking into account both the service life and reliability of the lithium-ion battery cell.

[0021] In some embodiments, based on the total mass of the electrolyte, the mass content W of the carboxylic ester solvent satisfies: 50 wt% < W ≤ 80 wt%, the end cap is provided with a pressure relief mechanism, and the actuation pressure P of the pressure relief mechanism satisfies: 0.65 MPa ≤ P ≤ 1.35 MPa.

[0022] In a lithium-ion battery cell including a laminated electrode assembly, by setting 50 wt% < W ≤ 80 wt%, the lithium-ion battery cell has excellent fast charging performance; by setting 0.65 MPa ≤ P ≤ 1.35 MPa, while the lithium-ion battery cell has excellent fast charging performance, it can not only reduce the risk of premature actuation and valve opening of the pressure relief mechanism, but also facilitate the discharge of emissions from the pressure relief mechanism, and can balance the service life and reliability of the lithium-ion battery cell.

[0023] In some embodiments, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

[0024] In some embodiments, the positive electrode active material further includes titanium. When the electrolyte includes a carboxylic ester solvent, the lithium-ion battery cell has good fast charging ability, and at the same time, a large temperature rise will occur during fast charging; titanium has good electrical conductivity, and including titanium in the positive electrode active material is beneficial to improving the electron conduction ability of the positive electrode active material, reducing the resistance of the positive electrode active material and the lithium-ion battery cell, thereby improving the charge and discharge efficiency of the lithium-ion battery cell and reducing the temperature rise of the lithium-ion battery cell; in addition, it is also beneficial to promote the diffusion of lithium ions, improve the diffusion efficiency of lithium ions, and improve the kinetic performance of the lithium-ion battery cell.

[0025] In some embodiments, based on the total mass of the positive electrode active material, the mass content of the titanium element is 500 ppm to 3000 ppm. When the mass content of the titanium element is within the above range, the lithium-ion battery cell has a lower resistance, and thus during the fast charging process of the lithium-ion battery cell, the lithium-ion battery cell has a lower temperature rise.

[0026] In some embodiments, the lithium-ion battery cell includes a housing, and the end cap is covered with the housing to form a space for accommodating the electrode assembly; the materials of the housing and the end cap include steel, the thickness of the housing is 0.1 mm to 0.5 mm, and / or the thickness of the end cap is 0.1 mm to 0.5 mm. Through the above settings, it is beneficial to make the actuation pressure of the pressure relief mechanism of the lithium-ion battery cell within the range of 0.6 MPa to 1.4 MPa, and the lithium-ion battery cell can balance a long service life and high reliability.

[0027] In some embodiments, the lithium-ion battery cell includes a shell, and the end cover and the shell are combined to form a space for accommodating the electrode assembly; the material of the shell and the end cover includes aluminum, the thickness of the shell is 0.3mm~0.8mm, and / or the thickness of the end cover is 1.2mm~2mm. Through the above arrangement, it is beneficial to make the actuation pressure of the pressure relief mechanism of the lithium-ion battery cell within the range of 0.6MPa~1.4MPa, and the lithium-ion battery cell can have both a longer service life and higher reliability.

[0028] In some embodiments, the thickness of the end cap where the pressure relief mechanism is provided is 0.07 mm to 0.4 mm. In this way, the risk of premature actuation and valve opening of the pressure relief mechanism can be reduced, and the risk of emissions being discharged from locations other than the pressure relief mechanism can also be reduced.

[0029] In some embodiments, the time t for charging the lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤30min. In this way, the lithium-ion battery cell has a shorter fast charging time, and the lithium-ion battery cell can have a better fast charging performance while taking into account a longer service life and reliability.

[0030] In some embodiments, the time t for charging the lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤20 min. In this way, the lithium-ion battery cell has better fast charging performance.

[0031] In some embodiments, the time t for charging the lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤15min. In this way, the lithium-ion battery cell has better fast charging performance.

[0032] In some embodiments, the ionic conductivity of the electrolyte is 9 mS / cm to 25 mS / cm, and / or the viscosity of the electrolyte is 1 mm 2 / s~4mm 2 / s. In this way, the electrolyte has lower viscosity and higher ion conductivity, and the lithium-ion battery cell has better fast charging performance.

[0033] In some embodiments, the ionic conductivity of the electrolyte is 11 mS / cm to 18 mS / cm. In this way, the electrolyte has a higher ionic conductivity, and the lithium-ion battery cell has a better fast charging performance.

[0034] In some embodiments, the viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s. In this way, the electrolyte has a lower viscosity and the lithium-ion battery cell has a better fast charging performance.

[0035] In some embodiments, the carboxylate solvent includes: one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate or ethyl acrylate. By selecting the above carboxylate solvent, the electrolyte has a lower viscosity and a higher ionic conductivity, which is conducive to improving the fast charging performance of the lithium-ion battery monomer.

[0036] In some embodiments, the electrode assembly includes a separator, and a polymer coating is provided on the side of the separator facing the positive electrode plate, the polymer coating includes one or more of fluorine-containing polymers or non-fluorine-containing polymers, the fluorine-containing polymer includes one or more of vinylidene fluoride homopolymers and vinylidene fluoride copolymers, and the non-fluorine polymer includes an acrylate copolymer.

[0037] Compared with other types of solvents, carboxylate solvents tend to produce more gas. In addition, the electrode assembly formed by stacking the positive and negative pole pieces is more likely to cause gas accumulation between the pole pieces, which can easily increase the risk of wrinkling the pole pieces. The polymer coating is beneficial to improving the adhesion between the isolation membrane and the positive pole piece, and can play a certain restraining role on the positive pole piece, reducing the risk of wrinkling the positive pole piece, which is beneficial to improving the electrical properties of the lithium-ion battery cell, such as the cycle life.

[0038] In some embodiments, the weight of the polymer coating is 1 mg / 1540.25 mm 2 Up to 2mg / 1540.25mm 2 This is beneficial to the transmission and diffusion of lithium ions, and the lithium-ion battery cells have better fast charging performance.

[0039] In a second aspect, a lithium-ion battery is provided, comprising the lithium-ion battery cell in the first aspect and any possible implementation manner thereof.

[0040] In a third aspect, an electrical device is provided, comprising the lithium-ion battery described in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0042] Figure 1 A schematic diagram of a lithium-ion battery cell according to an embodiment of the present application; Figure 2 is a schematic diagram of an electrode assembly according to an embodiment of the present application; Figure 3is a schematic diagram of an electrode assembly according to an embodiment of the present application; Figure 4 is a schematic diagram of an electrode assembly according to an embodiment of the present application; Figure 5 A schematic diagram of a positive electrode sheet according to an embodiment of the present application; Figure 6 A schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 7 A schematic diagram of a lithium-ion battery according to an embodiment of the present application; Figure 8 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0043] The embodiments of the lithium-ion battery cell, lithium-ion battery and electrical device of the present application are described in detail with appropriate reference to the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually the same structure may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] The development of battery technology must consider many design factors at the same time, such as fast charging performance, energy density, cycle life, capacity, reliability, etc. Carboxylic acid ester solvents have the characteristics of low viscosity and high ionic conductivity. Their application in electrolytes is beneficial to improving the fast charging performance of lithium-ion battery cells. However, the side reactions of carboxylic acid ester solvents in lithium-ion battery cells are more intense, and the gas production in the lithium-ion battery cells is more, and the pressure in the lithium-ion battery cells increases, which can easily lead to premature failure of the lithium-ion battery cells, which is not conducive to improving the service life of the lithium-ion battery cells; and in the laminated lithium-ion battery cells, due to the structural design of the laminated lithium-ion battery cells, heat is more likely to accumulate in the laminated lithium-ion battery cells, and the temperature of the lithium-ion battery cells increases, which intensifies the gas production of carboxylic acid ester solvents in the lithium-ion battery cells, further resulting in a reduction in the service life of the lithium-ion battery cells.

[0049] In view of this, the present application provides a lithium-ion battery cell, comprising: an electrolyte, the electrolyte comprising a carboxylic acid ester solvent; an electrode assembly, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet are stacked to form the electrode assembly, the electrode assembly comprising a main body, a positive electrode ear and a negative electrode ear, the positive electrode ear and the negative electrode ear protruding from the main body; an end cover, the end cover is provided with a positive electrode terminal and a negative electrode terminal, the positive electrode terminal and the negative electrode terminal are respectively connected to the positive electrode ear and the negative electrode ear; wherein, the distance between an end of the main body close to the end cover and the inner side of the end cover is 3 mm to 10 mm; the residual space of the lithium-ion battery cell is 0.05 mL / Ah to 0.3 mL / Ah.

[0050] In a laminated lithium-ion battery cell including a carboxylic acid ester solvent, by setting the residual space of the lithium-ion battery cell to be greater than or equal to 0.05 mL / Ah, there is more space inside the lithium-ion battery cell to accommodate the generated gas, which can reduce the risk of premature failure of the lithium-ion battery cell due to excessive internal pressure of the lithium-ion battery cell, thereby increasing the service life of the lithium-ion battery cell; by setting the residual space of the lithium-ion battery cell to be less than or equal to 0.3 mL / Ah, the space utilization rate inside the lithium-ion battery cell can be increased, and the lithium-ion battery cell has a higher energy density. In addition, since the positive pole ear and the negative pole ear occupy a certain space, under the condition of satisfying the above residual space setting, by setting the distance between the end of the main body close to the end cover and the inner side of the end cover to be greater than or equal to 3mm, there is a suitable space inside the lithium-ion battery cell to accommodate the positive pole ear and the negative pole ear, which is convenient for the shaping of the positive pole ear and the negative pole ear and can reduce the risk of the positive pole ear and the negative pole ear being inserted into the main body, thereby reducing the risk of short circuit and improving the reliability of the lithium-ion battery cell; by setting the distance between the end of the main body close to the end cover and the inner side of the end cover to be less than or equal to 10mm, it is beneficial to improve the space utilization rate inside the lithium-ion battery cell, and the lithium-ion battery cell has a higher energy density. Therefore, the embodiment of the present application can take into account the fast charging performance, service life, reliability and energy density of the lithium-ion battery cell.

[0051] During the charging process of a lithium-ion battery cell, lithium ions are released from the positive electrode active material, moved and embedded in the negative electrode; while during the discharging process, lithium ions are released from the negative electrode, moved and embedded in the positive electrode active material.

[0052] The lithium-ion battery cells mentioned in this application are secondary batteries.

[0053] The "embedding" process mentioned in this application refers to the process in which lithium ions are embedded in the positive electrode active material or the negative electrode due to an electrochemical reaction. The "extraction" and "de-embedding" processes mentioned in this application refer to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0054] The "actuation" mentioned in this application means that the pressure relief mechanism is in action or activated to a certain state, so that the internal pressure and temperature of the battery cell can be released. The action produced by the pressure relief mechanism may include but is not limited to: the components in the pressure relief mechanism move to form an exhaust channel, at least a part of the pressure relief mechanism ruptures, breaks, is torn or opened, and so on. When the pressure relief mechanism is actuated, the high-temperature and high-pressure substances inside the battery cell will be discharged from the actuated part as emissions. In this way, the battery cell can be depressurized and cooled under controllable pressure or temperature, thereby avoiding potential more serious accidents. Emissions include but are not limited to: electrolyte, dissolved or split positive and negative pole pieces, fragments of separators, high-temperature and high-pressure gases produced by the reaction, flames, and so on.

[0055] The “actuation pressure” mentioned in this application refers to the internal pressure of the battery cell when the pressure relief mechanism is actuated.

[0056] [Lithium-ion battery cells] Figure 1 Schematic diagram of a lithium-ion battery cell according to an embodiment of the present application. The present application embodiment provides a lithium-ion battery cell 20, for example, Figure 1 As shown, the lithium-ion battery cell 20 includes an electrolyte, an electrode assembly 22 , and an end cap 212 .

[0057] The electrolyte includes carboxylate solvents. Carboxylate solvents have low viscosity and high ionic conductivity. The inclusion of carboxylate solvents in the electrolyte is conducive to the transmission of lithium ions, thereby improving the fast charging performance of lithium-ion battery cells. In addition, during the charging and discharging process of lithium-ion battery cells, carboxylate solvents are prone to side reactions with positive electrode active materials and negative electrode active materials, accompanied by the generation of gas.

[0058] As an example, the carboxylate solvent includes a compound having a structure shown in Formula I, Formula I, Wherein, R1 and R2 each independently include at least one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

[0059] As an example, the carboxylate solvent includes one or more of methyl acetate or ethyl acetate.

[0060] The electrode assembly 22 includes a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are stacked to form the electrode assembly 22 .

[0061] The electrode assembly 22 formed by stacking the positive electrode sheets and the negative electrode sheets can be called a laminated electrode assembly, and the lithium-ion battery cell formed by the laminated electrode assembly can be called a laminated lithium-ion battery cell.

[0062] Figure 2 Schematic diagram of an electrode assembly according to an embodiment of the present application. Figure 2 As shown, the electrode assembly 22 includes a plurality of positive electrode sheets 50 and a plurality of negative electrode sheets 60, and the plurality of positive electrode sheets 50 and the plurality of negative electrode sheets 60 are alternately stacked along the X direction. The electrode assembly 22 may also include a separator 70, which is located between the positive electrode sheets 50 and the negative electrode sheets 60 to separate the positive electrode sheets 50 and the negative electrode sheets 60. The electrode assembly 22 may be formed by stacking the positive electrode sheets 50, the separator 70, and the negative electrode sheets 60.

[0063] Figure 3 Schematic diagram of an electrode assembly according to an embodiment of the present application. Figure 3 As shown, the electrode assembly 22 includes a negative electrode sheet 60 and a plurality of positive electrode sheets 50, the negative electrode sheet 60 includes a plurality of negative electrode stacking segments 60a and a plurality of negative electrode bending segments 60b, the negative electrode bending segment 60b is used to connect two adjacent negative electrode stacking segments 60a, and the plurality of positive electrode sheets 50 and the plurality of negative electrode stacking segments 60a are alternately stacked along a first direction X.

[0064] Figure 4 Schematic diagram of an electrode assembly according to an embodiment of the present application. Figure 4 As shown, the electrode assembly 22 includes a positive electrode sheet 50 and a plurality of negative electrode sheets 60. The positive electrode sheet 50 includes a plurality of positive electrode stacking segments 50a and a plurality of positive electrode bending segments 50b. The positive electrode bending segments 50b are used to connect two adjacent positive electrode stacking segments 50a. The plurality of negative electrode sheets 60 and the plurality of positive electrode stacking segments 50a are alternately stacked along a first direction X.

[0065] The residual space of the lithium ion battery cell is 0.05 mL / Ah to 0.3 mL / Ah, for example, 0.05 mL / Ah, 0.08 mL / Ah, 0.1 mL / Ah, 0.15 mL / Ah, 0.2 mL / Ah, 0.25 mL / Ah, 0.3 mL / Ah or any value within the above range.

[0066] In the embodiment of the present application, the residual space can be represented by K. , where V1 represents the internal volume of the lithium-ion battery cell (ml); V2 represents the volume of the electrode assembly (ml); V3 represents the volume of the electrolyte (ml); and C represents the discharge capacity of the lithium-ion battery cell (Ah).

[0067] The size of the residual space can reflect the size of the redundant space inside the lithium-ion battery cell. The larger the residual space is, the more gas inside the lithium-ion battery cell can be accommodated, but correspondingly, the space utilization rate inside the lithium-ion battery cell is reduced.

[0068] Compared with wound lithium-ion battery cells, laminated lithium-ion battery cells have higher space utilization and higher energy density. In addition, compared with lithium-ion battery cells formed by wound electrode assemblies, lithium-ion battery cells formed by laminated electrode assemblies are more likely to accumulate heat, the temperature inside the lithium-ion battery cells is higher, the side reactions of carboxylic acid ester solvents in the lithium-ion battery cells are aggravated, and more gas is produced in the lithium-ion battery cells. By setting the residual space of the lithium-ion battery cell to be greater than or equal to 0.05mL / Ah, there can be more space inside the lithium-ion battery cell to accommodate the generated gas, which can reduce the risk of premature failure of the lithium-ion battery cell due to excessive internal pressure of the lithium-ion battery cell (for example, the pressure relief mechanism in the lithium-ion battery cell is actuated), thereby increasing the service life of the lithium-ion battery cell; by setting the residual space of the lithium-ion battery cell to be less than or equal to 0.3mL / Ah, the space utilization inside the lithium-ion battery cell can be increased, and the lithium-ion battery cell has a higher energy density.

[0069] The electrode assembly 22 includes a main body 220 , a positive electrode ear 221 a and a negative electrode ear 221 b , and the positive electrode ear 221 a and the negative electrode ear 221 b protrude from the main body 220 .

[0070] The distance between one end of the main body 220 close to the end cover 212 and the inner side of the end cover 212 is 3 mm to 10 mm.

[0071] Along the extension direction of the main body 220 (for example Figure 1 In the y direction, the main body 220 has two opposite ends, one end is close to the end cover 212, and the other end is far away from the end cover 212.

[0072] The end cap 212 has two opposite sides along the thickness direction of the end cap 212 , wherein the inner side of the end cap 212 faces the electrode assembly 22 , and the outer side of the end cap 212 faces away from the electrode assembly 22 .

[0073] The distance between one end of the main body 220 close to the end cover 212 and the inner side of the end cover 212 may be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm or any value within the above range.

[0074] In a lithium-ion battery cell, the positive pole ear 221a and the negative pole ear 221b occupy a certain space. The space used to accommodate the positive pole ear 221a and the negative pole ear 221b in the lithium-ion battery cell is related to the reliability and energy density of the lithium-ion battery cell. The space between the end of the main body 220 close to the end cover 212 and the inner side of the end cover constitutes most of the residual space, and the positive pole ear 221a and the negative pole ear 221b are accommodated in the space between the end of the main body 220 close to the end cover 212 and the inner side of the end cover. In addition, when the temperature of the lithium-ion battery cell is high, the residual space is too small, resulting in a high risk of the positive pole ear 221a and the negative pole ear 221b being inserted into the main body 220, thereby causing internal short circuits and thermal runaway.

[0075] When the residual space of the lithium-ion battery cell is set to 0.05mL / Ah to 0.3mL / Ah, by setting the distance between the end of the main body 220 close to the end cover 212 and the inner side of the end cover 212 to be greater than or equal to 3mm, there is a suitable space inside the lithium-ion battery cell to accommodate the positive pole ear 221a and the negative pole ear 221b, which is convenient for the shaping of the positive pole ear 221a and the negative pole ear 221b and can reduce the risk of the positive pole ear 221a and the negative pole ear 221b being inserted into the main body 220, thereby reducing the risk of short circuit and thermal runaway and improving the reliability of the lithium-ion battery cell; by setting the distance between the end of the main body 220 close to the end cover 212 and the inner side of the end cover to be less than or equal to 10mm, it is beneficial to improve the space utilization rate inside the lithium-ion battery cell, and the lithium-ion battery cell has a higher energy density. Therefore, the embodiment of the present application can take into account the fast charging performance, service life, reliability and energy density of the lithium-ion battery cell.

[0076] In some embodiments, the distance between one end of the main body 220 close to the end cap 212 and the inner side of the end cap 212 is 4 mm to 7 mm.

[0077] The above arrangement is helpful to further reduce the risk of the positive electrode ear 221a and the negative electrode ear 221b being inserted into the main body 220, which is helpful to further improve the reliability of the lithium-ion battery cell while also taking into account a higher energy density.

[0078] Figure 5 A schematic diagram of a positive electrode sheet according to an embodiment of the present application, for example, Figure 5 As shown, the positive electrode sheet 50 includes a positive electrode collector body 501 and a positive electrode tab 502 , and the positive electrode tab 502 protrudes from the positive electrode collector body 501 ; the positive electrode tab portion 221 a includes multiple layers of positive electrode tabs 502 , and the number of layers of the multiple layers of positive electrode tabs 502 is 15 to 70.

[0079] The number of layers of the multi-layer positive electrode tab 502 can be 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70 or any value within the above range.

[0080] The end cap 212 may be provided with a positive electrode terminal 2121a, which may be directly or indirectly electrically connected to the positive electrode ear 221a. For example, the lithium-ion battery cell includes a connecting member 23, and the positive electrode ear 221a is electrically connected to the positive electrode terminal 2121a through the connecting member 23.

[0081] In the lithium-ion battery monomer including carboxylic acid ester solvents, the lithium-ion battery monomer has good fast charging performance. In the case of fast charging, the lithium-ion battery monomer has a large charging current; by setting the number of layers of the multi-layer positive electrode ear 502 to be greater than or equal to 15, it is beneficial to improve the current capacity of the positive electrode ear portion 221a, reduce the overcurrent risk in the case of a large charging current, and reduce the temperature of the lithium-ion battery monomer; by setting the number of layers of the multi-layer positive electrode ear 502 to be less than or equal to 70, it is beneficial to shape the multi-layer positive electrode ear 502 into the positive electrode ear portion 221a, reduce the processing difficulty of the positive electrode ear portion 221a, and also help reduce the risk of the positive electrode ear portion 221a being inserted into the main body 220 due to the excessive thickness of the positive electrode ear portion 221a, thereby reducing the risk of short circuit. Therefore, the above-mentioned setting is beneficial to reducing the risk of overcurrent and short circuit, while facilitating the processing of the positive electrode ear portion 221a, so that the lithium-ion battery monomer can have both high reliability and good processing performance.

[0082] In some embodiments, the thickness of the positive electrode tab 502 is 10 μm to 15 μm.

[0083] The thickness of the positive electrode tab 502 may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any value within the above range.

[0084] The thickness of the positive electrode tab 502 is related to the thickness of the positive electrode current collector body 501. As an example, the positive electrode tab 502 is not coated with a positive electrode active material layer, at least a portion of the positive electrode current collector body 501 is coated with a positive electrode active material layer, and the thickness of the single-layer positive electrode tab 502 is the same as the thickness of the positive electrode current collector body 501.

[0085] By setting the thickness of the positive electrode tab 502 to be greater than or equal to 10 μm, the positive electrode tab 502 has a more appropriate current flow capacity. By setting the thickness of the positive electrode tab 502 to be less than or equal to 15 μm, the positive electrode tab 502 has an appropriate thickness, so that the positive electrode tab portion 221a has an appropriate thickness, and the electrode assembly as a whole occupies an appropriate space, which is beneficial to reducing the risk of energy density deterioration.

[0086] Figure 6 Schematic diagram of a negative electrode sheet of an embodiment of the present application. In some embodiments, for example, Figure 6 As shown, the negative electrode sheet 60 includes a negative electrode current collector body 601 and a negative electrode tab 602 , and the negative electrode tab 602 protrudes from the negative electrode current collector body 601 ; the negative electrode tab portion 221 b includes multiple layers of negative electrode tabs 602 , and the number of layers of the multiple layers of negative electrode tabs 602 is 15 to 100.

[0087] The number of layers of the multi-layer negative electrode tab 602 can be 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 100 or any value within the above range.

[0088] In this embodiment, since the positive electrode tab 502 has a better current carrying capacity than the negative electrode tab 602 , the number of layers of the multi-layer positive electrode tab 502 may be slightly lower than the number of layers of the multi-layer negative electrode tab 602 .

[0089] The end cap 212 may be provided with a negative electrode terminal 2121b, which may be directly or indirectly electrically connected to the negative electrode ear 221b. For example, the lithium-ion battery cell includes a connecting member 23, and the negative electrode ear 221b is electrically connected to the negative electrode terminal 2121b through the connecting member 23.

[0090] In the lithium-ion battery monomer including carboxylic acid ester solvents, the lithium-ion battery monomer has good fast charging performance. In the case of fast charging, the lithium-ion battery monomer has a large charging current; by setting the number of layers of the multi-layer negative electrode ear 602 to be greater than or equal to 30, it is beneficial to improve the overcurrent capacity of the negative electrode ear portion 221b, reduce the overcurrent risk in the case of a large charging current, and reduce the temperature of the lithium-ion battery monomer; by setting the number of layers of the multi-layer negative electrode ear 602 to be less than or equal to 80, it is beneficial to shape the multi-layer negative electrode ear 602 into the negative electrode ear portion 221b, reduce the difficulty of processing the negative electrode ear portion 221b, and also help reduce the risk of the negative electrode ear portion 221b being inserted into the main body 220 due to the excessive thickness of the negative electrode ear portion 221b, thereby reducing the risk of short circuit. Therefore, the above-mentioned setting is beneficial to reducing the risk of overcurrent and short circuit, while facilitating the processing of the negative electrode ear portion 221b, so that the lithium-ion battery monomer can have both high reliability and good processing performance.

[0091] In some embodiments, the thickness of the negative electrode tab 602 is 4 μm to 6 μm.

[0092] The thickness of the negative electrode tab 602 may be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or any value within the above range.

[0093] The thickness of the negative electrode tab 602 is related to the thickness of the negative electrode current collector body 601. As an example, the negative electrode tab 602 is not coated with a negative electrode active material layer, at least a portion of the negative electrode current collector body 601 is coated with a negative electrode active material layer, and the thickness of the single-layer negative electrode tab 602 is the same as the thickness of the negative electrode current collector.

[0094] By setting the thickness of the negative electrode tab 602 to be greater than or equal to 4 μm, the negative electrode tab 602 has a more appropriate current flow capacity. By setting the thickness of the negative electrode tab 602 to be less than or equal to 6 μm, the negative electrode tab 602 has an appropriate thickness, so that the negative electrode tab portion 221b has an appropriate thickness, and the electrode assembly as a whole occupies an appropriate space, which is beneficial to reducing the risk of energy density deterioration.

[0095] In a lithium-ion battery cell, at least part of the surface of the positive electrode current collector body 501 is coated with a positive electrode active material layer, and the surface of the positive electrode tab 502 is not coated with a positive electrode active material layer, at least part of the surface of the negative electrode current collector body 601 is coated with a negative electrode active material layer, and the surface of the negative electrode tab 602 is not coated with a negative electrode active material layer. The electrode assembly 22 may include a main body 220 of the electrode assembly, a positive electrode tab 221a, and a negative electrode tab 221b. In the process of preparing the positive electrode sheet 50 and the negative electrode sheet 60 into an electrode assembly, a plurality of positive electrode ears 502 are combined together and formed into a positive electrode ear portion 221a through processes such as shaping, and a plurality of negative electrode ears 602 are combined together and formed into a negative electrode ear portion 221b through processes such as shaping. In addition, the portion of the negative electrode sheet coated with the negative electrode active material layer and the portion of the positive electrode sheet coated with the positive electrode active material layer form the main body 220 of the electrode assembly, and the positive electrode ear portion 221a and the negative electrode ear portion 221b protrude from the main body 220 of the electrode assembly.

[0096] In some embodiments, the residual space of the lithium-ion battery cell is 0.05 mL / Ah to 0.2 mL / Ah, which is helpful to further improve the service life of the lithium-ion battery cell.

[0097] In some embodiments, the lithium-ion battery cell includes a first wall 201 and a second wall 202 , wherein the first wall 201 is the surface with the largest surface area, and the second wall 202 is adjacent to the first wall 201 and the end cover 212 ; the distance between the electrode assembly 22 and the second wall 202 is 0.1 mm to 1.5 mm.

[0098] The distance between the electrode assembly 22 and the second wall 202 can be Figure 1 In the x direction, the distance between the side of the electrode assembly 22 close to the second wall 202 and the inner wall of the second wall 202 .

[0099] The distance between the electrode assembly 22 and the second wall 202 can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm or any value within the above range.

[0100] By setting the distance between the electrode assembly 22 and the second wall 202 to be greater than or equal to 0.1 mm, it is convenient for gas and heat to flow out from the gap between the electrode assembly 22 and the second wall 202. When the residual space is 0.05 mL / Ah to 0.3 mL / Ah, the accumulation and aggregation of gas and heat in the electrode assembly 22 can be reduced, thereby reducing the internal pressure of the lithium-ion battery cell, reducing the risk of premature failure of the lithium-ion battery cell due to excessive internal pressure, and helping to improve the service life of the lithium-ion battery cell. In addition, it is convenient to assemble the lithium-ion battery cell while reserving space for the expansion of the electrode assembly. By setting the distance between the electrode assembly 22 and the second wall 202 to be less than or equal to 1.5 mm, there is a suitable distance between the electrode assembly 22 and the second wall 202, which can reduce the shaking of the electrode assembly 22 in the lithium-ion battery cell, and helping to improve the reliability of the lithium-ion battery cell.

[0101] In some embodiments, the distance between the electrode assembly and the second wall is 0.2 mm to 1.3 mm. This is beneficial to further improve the service life of the lithium-ion battery cell.

[0102] In some embodiments, the end cover 212 is provided with a pressure relief mechanism 213 .

[0103] As an example, the lithium-ion battery cell includes a shell 211 and an end cover 212 . The shell 211 has an opening, and the end cover 212 covers the opening to form a space for accommodating the electrolyte and the electrode assembly 22 .

[0104] In other embodiments, the pressure relief mechanism 213 may also be disposed on any wall of the housing 211 .

[0105] The pressure relief mechanism 213 is used to discharge high-temperature and high-pressure substances in the lithium-ion battery cell 20 .

[0106] As an example, when the internal pressure or temperature of the lithium-ion battery cell 20 reaches a predetermined threshold, it is actuated to release the internal pressure or temperature. When the internal pressure or temperature of the lithium-ion battery cell 20 reaches a predetermined threshold, the pressure relief mechanism 213 performs an action or a weak structure provided in the pressure relief mechanism 213 is destroyed, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies according to different design requirements. The threshold may depend on one or more materials of the positive electrode plate, the negative electrode plate, the electrolyte and the separator in the lithium-ion battery cell.

[0107] As an example, the pressure relief mechanism 213 may be integrally formed with the end cover 212 .

[0108] As an example, the pressure relief mechanism 213 may also be separately provided and connected to the end cover 212 .

[0109] The actuation pressure of the pressure relief mechanism 213 is the internal pressure of the lithium-ion battery cell 20 when the pressure relief mechanism 213 is actuated.

[0110] The actuation pressure of the pressure relief mechanism 213 can be adjusted by changing the material of the end cover 212 and the thickness of the end cover 212 where the pressure relief mechanism 213 is provided.

[0111] In some embodiments, based on the total mass of the electrolyte, the mass content W of the carboxylate solvent satisfies: 1 wt %≤W≤80 wt %.

[0112] Based on the total mass of the electrolyte, the mass content W of the carboxylate solvent can be 1wt%, 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt% or any value within the above range.

[0113] After the lithium-ion battery cells are formed and a certain number of charge and discharge cycles, the carboxylate solvents are consumed to a certain extent, and the quality of the carboxylate solvents decays to a certain extent. After formation, the quality of the carboxylate solvents is consumed by about 1% to 15%. It should be noted that this refers to the consumption of carboxylate solvents in fresh lithium-ion battery cells compared to unformed lithium-ion battery cells. Fresh lithium-ion battery cells can refer to lithium-ion battery cells that have just been assembled on a vehicle. At this time, the vehicle has not yet been driven or has a low mileage. The less mileage the vehicle has, the fresher the lithium-ion battery cells are.

[0114] For example, the mass content of the carboxylic acid ester solvent after formation is approximately in the range of 1wt% to 78wt%.

[0115] In the embodiments of the present application, the battery cell composed of the electrode assembly formed by stacking the positive electrode sheet and the negative electrode sheet is a stacked battery cell. In the stacked battery cell, heat is more likely to accumulate, and the side reactions and gas generation of the carboxylic acid ester solvent in the battery cell are more obvious. By setting the actuation pressure of the pressure relief mechanism within a suitable range, in this way, in the case of increased gas generation and increased pressure in the battery cell due to the addition of the carboxylic acid ester solvent and the structure of the electrode assembly, the risk of premature actuation and valve opening of the pressure relief mechanism of the lithium-ion battery cell can be reduced, which is beneficial to improving the service life of the lithium-ion battery cell; in addition, when the lithium-ion battery cell undergoes thermal runaway, the risk of emissions in the lithium-ion battery cell being discharged from positions other than the pressure relief mechanism can also be reduced, which is beneficial to improving the reliability of the lithium-ion battery cell.

[0116] In some embodiments, based on the total mass of the electrolyte, the mass content W of the carboxylic acid ester solvent satisfies: 1 wt% ≤ W ≤ 50 wt%, and the actuation pressure P of the pressure relief mechanism satisfies: 0.6 MPa ≤ P ≤ 1.4 MPa.

[0117] In a lithium-ion battery cell including a stacked electrode assembly, by setting 1 wt% ≤ W ≤ 50 wt%, the lithium-ion battery cell has relatively suitable fast charging performance and less gas generation in the lithium-ion battery cell; by setting 0.6 MPa ≤ P ≤ 1.4 MPa, while the lithium-ion battery cell has suitable fast charging performance, the risk of premature actuation and valve opening of the pressure relief mechanism can be reduced, and it is beneficial for emissions to be discharged from the pressure relief mechanism, which can balance the service life and reliability of the lithium-ion battery cell.

[0118] In some embodiments, based on the total mass of the electrolyte, the mass content W of the carboxylic acid ester solvent satisfies: 50 wt% < W ≤ 80 wt%, 0.65 MPa ≤ P ≤ 1.35 MPa.

[0119] In a lithium-ion battery cell including a stacked electrode assembly, by setting 50 wt% < W ≤ 80 wt%, the lithium-ion battery cell has excellent fast charging performance; by setting 0.65 MPa ≤ P ≤ 1.35 MPa, while the lithium-ion battery cell has excellent fast charging performance, the risk of premature actuation and valve opening of the pressure relief mechanism can be reduced, and it is beneficial for emissions to be discharged from the pressure relief mechanism, which can balance the service life and reliability of the lithium-ion battery cell.

[0120] In some embodiments, the area of the pressure relief mechanism is 300 mm 2 ~1000 mm 2 .

[0121] The area of the pressure relief mechanism 213 can be the area of the region defined by the pressure relief mechanism 213.

[0122] As an example, the pressure relief mechanism 213 is a notched groove provided on the end cover 212. The area of ​​the pressure relief mechanism 213 is the area of ​​the notched groove.

[0123] In the case where the lithium-ion battery cell includes a lithium-containing phosphate and a laminated electrode assembly, the area of ​​the pressure relief mechanism 213 may be 300 mm 2 , 400mm 2 , 500mm 2 、600mm 2 、700mm 2 , 800mm 2 , 900mm 2 , 1000mm 2 Or any value within the above range.

[0124] In the case where the lithium-ion battery cell includes a laminated electrode assembly, the area of ​​the pressure relief mechanism is greater than or equal to 300 mm 2 , which is conducive to the discharge of emissions from the pressure relief mechanism when thermal runaway occurs in the lithium-ion battery monomer; the area of ​​the pressure relief mechanism is less than or equal to 1000mm 2 , which facilitates the processing of the pressure relief mechanism.

[0125] In some embodiments, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

[0126] In some embodiments, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and modified substances thereof.

[0127] In some embodiments, the positive electrode active material further includes titanium.

[0128] When the electrolyte includes a carboxylic acid ester solvent, the lithium-ion battery cell has a good fast charging capability, and at the same time, the fast charging process is accompanied by a large temperature rise; titanium has good conductivity, and the inclusion of titanium in the positive electrode active material is beneficial to improving the electronic conductivity of the positive electrode active material and reducing the resistance of the positive electrode active material and the lithium-ion battery cell, thereby improving the charging and discharging efficiency of the lithium-ion battery cell and reducing the temperature rise of the lithium-ion battery cell; in addition, it is also beneficial to promote the diffusion of lithium ions, improve the diffusion efficiency of lithium ions, and improve the kinetic performance of lithium-ion battery cells.

[0129] In some embodiments, the mass content of the titanium element is 500 ppm to 3000 ppm based on the total mass of the positive electrode active material.

[0130] Based on the total mass of the positive electrode active material, the mass content of the titanium element can be 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, 2500ppm, 3000ppm or any value within the above range.

[0131] When the mass content of titanium is within the above range, the lithium-ion battery cell has a lower resistance, and thus during the fast charging process of the lithium-ion battery cell, the lithium-ion battery cell has a lower temperature rise.

[0132] In some embodiments, the lithium-ion battery cell includes a shell 211, and the end cover 212 is covered with the shell 211 to form a space for accommodating the electrode assembly 22; the material of the shell 211 and the end cover 212 includes steel, the thickness of the shell 211 is 0.1mm~0.5mm, and / or the thickness of the end cover 212 is 0.1mm~0.5mm.

[0133] The thickness of the shell 211 may be 0.1 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm, 0.5 mm or any value within the above range, and the thickness of the end cover 212 may be 0.1 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm, 0.5 mm or any value within the above range.

[0134] The above arrangement is conducive to making the actuation pressure of the pressure relief mechanism of the lithium-ion battery cell within the range of 0.6MPa to 1.4MPa, and the lithium-ion battery cell can have both a longer service life and higher reliability.

[0135] In some embodiments, the lithium-ion battery cell includes a shell 211, and the end cover 212 is covered with the shell 211 to form a space for accommodating the electrode assembly 22; the shell 211 and the end cover 212 include aluminum, the thickness of the shell 211 is 0.3mm~0.8mm, and / or the thickness of the end cover 212 is 1.2mm~2mm.

[0136] The thickness of the shell 211 may be 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm or any value within the above range, and the thickness of the end cap 212 may be 1.2 mm, 1.3 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm or any value within the above range.

[0137] The above arrangement is conducive to making the actuation pressure of the pressure relief mechanism of the lithium-ion battery cell within the range of 0.6MPa to 1.4MPa, and the lithium-ion battery cell can have both a longer service life and higher reliability.

[0138] In some embodiments, the thickness of the end cover 212 where the pressure relief mechanism 213 is provided is 0.07 mm to 0.4 mm.

[0139] As an example, the pressure relief mechanism 213 is a notch groove provided on the wall of the end cover 212. The thickness of the end cover 212 where the pressure relief mechanism 213 is provided can be the remaining thickness of the wall of the end cover 212.

[0140] The thickness of the end cover 212 where the pressure relief mechanism 213 is provided can be 0.07 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or any value within the above range.

[0141] When the thickness of the end cover 212 where the pressure relief mechanism 213 is provided is greater than or equal to 0.07 mm, it is beneficial to make the valve opening pressure of the pressure relief mechanism 213 greater than or equal to 0.6 MPa, thereby reducing the risk of premature actuation and valve opening of the pressure relief mechanism 213; when the thickness of the end cover 212 where the pressure relief mechanism 213 is provided is less than or equal to 0.4 mm, it is beneficial to make the valve opening pressure of the pressure relief mechanism 213 less than or equal to 1.4 MPa, thereby reducing the risk of emissions being discharged from locations other than the pressure relief mechanism 213.

[0142] In some embodiments, the time t for charging a lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤30 min.

[0143] The time t can be 30 min, 28 min, 25 min, 23 min, 22 min, 20 min, 18 min, 15 min, 14 min, 13 min, 12 min, 11 min, 10 min, 9 min or any value within the above range.

[0144] In this way, the lithium-ion battery cell has a shorter fast charging time, and the lithium-ion battery cell can have a better fast charging performance while taking into account a longer service life and reliability.

[0145] In some embodiments, the time t for charging a lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤20 min. In this way, the lithium-ion battery cell has better fast charging performance.

[0146] In some embodiments, the time t for charging a lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤15min. In this way, the lithium-ion battery cell has better fast charging performance.

[0147] The above charging time is the charging time of lithium-ion battery cells at 25℃~35℃, and the charging time reflects the fast charging capability of lithium-ion battery cells. During the fast charging process of lithium-ion battery cells, the current density (or rate) is usually not constant, but variable.

[0148] In some embodiments, when the lithium-ion battery is charged at a charging rate greater than or equal to 2.8C, the charging time from 10% SOC to 80% SOC is less than or equal to 15 minutes. This rate is the equivalent charging rate of the lithium-ion battery cell in the process of charging from 10% SOC to 80% SOC. In other words, in the process of charging from 10% SOC to 80% SOC, the charging rate may gradually decrease from greater than 2.8C to less than 2.8C. In this process, the lithium-ion battery cell may undergo a transition from constant current charging to constant voltage charging, so the current is not constant. For example: start charging the lithium-ion battery cell at room temperature of 25°C, charge from 10% SOC to 80% SOC, and the charging time is 10 minutes (equivalent charging rate ≥ 4C). The charging process is: initially at 5C from 10% SOC to 45% SOC, then at 4.6C from 45% SOC to 50% SOC, 4.3C from 50% SOC to 55% SOC, 3.9C from 55% SOC to 60% SOC, 3.6C from 60% SOC to 65% SOC, 3.3C from 65% SOC to 70% SOC, 3.1C from 70% SOC to 75% SOC, 2.9C from 75% SOC to 80% SOC, and the charging is completed. The charging time for a lithium-ion battery cell from 0% SOC to 100% SOC at 1C is 60 min. Therefore, when it is measured that the charging time of the lithium-ion battery cell from 10% SOC to 80% SOC is 10 minutes, the equivalent charging rate of the process can be calculated as: [(80% SOC-10% SOC) / (100% SOC-0% SOC)]×[(1C×60 min) / 10min]=4.2C.

[0149] If a lithium-ion battery cell is placed on a charging pile for charging, the time it takes to charge from 10% SOC to 80% SOC can also be directly recorded.

[0150] When the vehicle is charging at a charging pile, the charging curve will be displayed on the charging pile system (the charging curve may be seen on the charging pile display screen, on the mobile phone charging control APP, in the battery monitoring background, etc.). For example, the horizontal axis is the charging time, and the vertical axis is the charging power and charging SOC. The charging power and SOC of the vehicle's battery at different times can be seen from the charging curve, and the charging time of 20% SOC-80% SOC or 10% SOC-80% SOC can also be read from the charging curve.

[0151] In this application, a charging time of less than 15 minutes from 10% SOC to 80% SOC is considered fast charging, and the battery used in the vehicle is a fast charging battery. In addition, if the vehicle or battery manual mentions that the charging time of 10% SOC to 80% SOC is less than 15 minutes, it also belongs to the fast charging battery mentioned in this application.

[0152] In some embodiments, the ionic conductivity of the electrolyte is 9 mS / cm to 25 mS / cm, and / or the viscosity of the electrolyte is 1 mm 2 / s~4mm 2 / s.

[0153] The ionic conductivity of the electrolyte may be 9 mS / cm, 11 mS / cm, 15 mS / cm, 16 mS / cm, 18 mS / cm, 20 mS / cm, 22 mS / cm, 23 mS / cm, 25 mS / cm, or any value within the above range.

[0154] The viscosity of the electrolyte can be 1mm 2 / s, 1.5mm 2 / s, 2mm 2 / s, 2.5mm 2 / s、3mm 2 / s, 4mm 2 / s or any value within the above range.

[0155] When the electrolyte ion conductivity is 9mS / cm~25mS / cm, the electrolyte has a higher ion conductivity, which is conducive to the diffusion and transmission of lithium ions, and the lithium-ion battery cell has better fast charging performance. 2 / s~4mm 2 / s, which is conducive to the diffusion and transmission of lithium ions, and the lithium-ion battery monomer has better fast charging performance.

[0156] In some embodiments, the ion conductivity of the electrolyte is 11 mS / cm to 18 mS / cm. In this way, the electrolyte has a higher ion conductivity, and the lithium-ion battery cell has a better fast charging performance.

[0157] In some embodiments, the viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s. In this way, the electrolyte has a lower viscosity and the lithium-ion battery cell has a better fast charging performance.

[0158] In some embodiments, the ionic conductivity of the electrolyte is 9 mS / cm to 15 mS / cm, and / or the viscosity of the electrolyte is 1.5 mm 2 / s~3mm 2 / s. This is helpful to improve the fast charging performance of lithium-ion battery cells.

[0159] In some embodiments, the carboxylate solvent includes: one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate or ethyl acrylate. By selecting the above carboxylate solvent, the electrolyte has a lower viscosity and a higher ionic conductivity, which is beneficial to improving the fast charging performance of the lithium-ion battery monomer.

[0160] In some embodiments, the carboxylate solvent includes one or more of methyl acetate or ethyl acetate.

[0161] The viscosity and gas generation degree of carboxylic acid ester solvents are related to the chain length of the carboxylic acid ester solvents. Generally speaking, the more carbon atoms in the carboxylic acid ester solvents, the longer the chain length of the carboxylic acid ester solvents, the greater the viscosity of the carboxylic acid ester solvents, and the lower the gas generation degree.

[0162] The molecules of ethyl acetate and methyl acetate have suitable chain lengths. Ethyl acetate and methyl acetate have both low viscosity, which is beneficial to the diffusion and transmission of lithium ions, and a relatively suitable gas production level. By combining with the actuating pressure of the pressure relief mechanism in the embodiment of the present application, the lithium-ion battery cell can have better fast charging performance and better storage performance.

[0163] In some embodiments, the electrolyte further includes an electrolyte salt, and the electrolyte salt includes one or more of LiPF6 or LiFSI.

[0164] As an example, the electrolyte salt includes only LiPF6.

[0165] As another example, the electrolyte salt includes only LiFSI.

[0166] As an example, the electrolyte salt includes LiPF6 and LiFSI. Wherein, as an example, based on the total mass of the electrolyte salt, the mass content of LiFSI can be 2wt%~30wt%. Based on the total mass of the electrolyte, the mass content of LIFSI can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.2wt%, 9wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, 15wt%, 16wt%, 17wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt% or a numerical range between any two of the above.

[0167] In some embodiments, the electrolyte further includes a cyclic carbonate solvent and a linear carbonate solvent, the linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate, and the cyclic carbonate solvent includes one or more of ethylene carbonate or propylene carbonate.

[0168] As an example, carbonate solvents include ethylene carbonate and dimethyl carbonate. Dimethyl carbonate can improve the conductivity of the electrolyte, thereby improving the fast charging performance of lithium-ion battery cells. Ethylene carbonate can form a film on the surface of the negative electrode, reducing the side reaction between the carboxylate solvent and the negative electrode, which is beneficial to improving the cycle life of the lithium-ion battery cells.

[0169] Cyclic carbonates have a higher dielectric constant, which helps to increase the solubility of lithium salts in the electrolyte and thus help to increase the concentration of lithium salts in the electrolyte. Linear carbonate solvents have lower viscosity and electrochemical stability. Lower viscosity is conducive to the rapid migration of lithium ions in the electrolyte, improving the fast charging performance of lithium-ion battery cells; higher dielectric constants are conducive to increasing the solubility of lithium salts in the electrolyte and thus help to increase the concentration of lithium salts in the electrolyte; good electrochemical stability helps to increase the operating voltage range of lithium-ion battery cells, thereby increasing the capacity of lithium-ion battery cells. The combination of carbonate solvents and carboxylate solvents helps to improve the fast charging performance and cycle performance of lithium-ion battery cells.

[0170] In some embodiments, the electrode assembly includes a separator, and a polymer coating is provided on the side of the separator facing the positive electrode plate. The polymer coating includes one or more of fluorine-containing polymers or non-fluorine polymers. The fluorine-containing polymer includes one or more of vinylidene fluoride homopolymers and vinylidene fluoride copolymers, and the non-fluorine polymer includes an acrylate copolymer.

[0171] As an example, the polymer coating includes a fluoropolymer including polyvinylidene fluoride (PVDF).

[0172] As an example, the polymer coating includes a non-fluoropolymer including an acrylate copolymer.

[0173] Compared with other types of solvents, carboxylate solvents tend to produce more gas. In addition, the electrode assembly formed by stacking the positive and negative pole pieces is more likely to cause gas accumulation between the pole pieces, which can easily increase the risk of wrinkling the pole pieces. The polymer coating is beneficial to improving the adhesion between the isolation membrane and the positive pole piece, and can play a certain restraining role on the positive pole piece, reducing the risk of wrinkling the positive pole piece, which is beneficial to improving the electrical properties of the lithium-ion battery cell, such as the cycle life.

[0174] In some embodiments, a polymer coating is disposed on both the side of the separator facing the positive electrode sheet and the side facing the negative electrode sheet.

[0175] In some embodiments, the weight of the polymer coating is 1 mg / 1540.25 mm 2 Up to 2mg / 1540.25mm 2 .

[0176] The weight of the polymer coating can be 1.0 mg / 1540.25 mm 2 , 1.2mg / 1540.25mm 2 、1.5mg / 1540.25mm 2 、1.8mg / 1540.25mm 2 , 2.0mg / 1540.25mm 2 Or any value within the above range.

[0177] In the above embodiment, the weight of the polymer coating satisfies the above range, which is beneficial to the transmission and diffusion of lithium ions, and the lithium-ion battery cell has good fast charging performance.

[0178] In some embodiments, a ceramic coating is further provided on the surface of the isolation membrane.

[0179] As an example, the ceramic coating includes inorganic particles, such as aluminum oxide.

[0180] As another example, the ceramic coating includes inorganic particles and a binder, for example, the inorganic particles include alumina, and the binder includes PVDF.

[0181] In some embodiments, lithium-ion battery cells can be assembled into a battery module. The number of lithium-ion battery cells 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.

[0182] [Positive electrode] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0183] The positive electrode current collector has two opposite surfaces along its thickness direction. The positive electrode film layer can be arranged on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector.

[0184] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0185] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0186] The battery will be accompanied by Li deintercalation and consumption during the charging and discharging process. The molar content of Li in the positive electrode active material is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system. After the charge and discharge cycle, the molar content of Li will change. In the list of positive electrode active materials in this application, the molar content of O is only an ideal state value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0187] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0188] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0189] In one embodiment, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet are formed into a positive electrode slurry. For example, the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry. Then, the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0190] [Negative electrode] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector.

[0191] The negative electrode current collector may be a metal foil or a composite negative electrode current collector. The negative electrode current collector may be a copper foil. The composite negative electrode 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0192] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for a battery known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0193] The negative electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0194] The negative electrode film layer may further optionally include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0195] [Isolator] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The present application has no particular limitation on the type of separator, for example, any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0196] In one embodiment, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0197] [Electrolytes] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present application embodiment has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0198] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0199] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0200] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0201] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and may also include performance additives that can improve certain battery properties, such as improving battery overcharge performance, improving battery high temperature or low temperature performance, etc.

[0202] [Lithium-ion battery] An embodiment of the present application provides a lithium-ion battery, including the lithium-ion battery cell in the above embodiment. Figure 7 FIG. 1 is a schematic diagram of a lithium-ion battery according to an embodiment of the present application. Figure 7 As shown, the lithium-ion battery 5 may include a plurality of lithium-ion battery cells (not shown in the figure).

[0203] The lithium-ion battery cells 20 can directly form the lithium-ion battery 5 , or can first form a battery module, and then multiple battery modules form the lithium-ion battery 5 .

[0204] [Electrical devices] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0205] Figure 8 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. Figure 8 As shown, the present application provides an electrical device 6, including the battery in the above embodiment.

[0206] Optionally, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc. The embodiments of the present application include but are not limited to these.

[0207] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0208] [Example] Example 1 (1) Preparation of positive electrode sheet: The positive electrode active material, binder polyvinylidene fluoride (PVDF), and conductive agent (acetylene black) are mixed in a mass ratio of 96.9:1.1:2, dissolved in solvent N-methylpyrrolidone (NMP), and fully stirred to prepare positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain positive electrode sheets; the thickness of the aluminum foil is 13 μm, and the single-side coating weight is about 0.145 mg / mm 2 The positive electrode active material includes lithium iron phosphate, and the positive electrode active material also includes titanium element. Based on the total mass of the positive electrode active material, the mass content of the titanium element is 2000 ppm.

[0209] (2) Preparation of negative electrode sheets: artificial graphite, a negative electrode active material, sodium carboxymethyl cellulose (CMC-Na), a thickener, styrene-butadiene rubber (SBR), and a conductive agent Super-P are dissolved in deionized water at a mass ratio of 96.9:1.1:1.5:0.5, and the mixture is stirred and mixed to prepare a negative electrode slurry; the negative electrode slurry is coated on both sides of the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet; the thickness of the copper foil is 4.5 μm, and the coating weight on one side is about 0.065 mg / mm 2 .

[0210] (3) Separator: A polyethylene film with a thickness of 13 μm is used. At least one side of the separator facing the positive electrode is provided with a polymer coating, which includes PVDF. The coating weight of the polymer coating is 1.5 mg / 1540.25 mm 2 .

[0211] (4) Preparation of electrolyte: The solvent in the electrolyte includes methyl acetate MA, ethylene carbonate EC and dimethyl carbonate DMC in a mass ratio of 2:3:5, the electrolyte salt in the electrolyte is LiPF6, and the concentration of the electrolyte salt is 1.1 mol / L. Among them, the carboxylate solvent is MA, and the mass content W of the carboxylate solvent is 16.7wt% based on the total mass of the electrolyte.

[0212] (5) Preparation of lithium-ion batteries: stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in order to obtain an electrode assembly; place the electrode assembly in a shell, add the above-prepared electrolyte, and obtain a lithium-ion battery cell after packaging, standing, forming, aging and other processes.

[0213] In Example 1, the distance between the end of the main body close to the end cap and the inner side of the end cap is 3 mm (denoted as L1), the residual space of the lithium-ion battery cell is 0.05 mL / Ah, the distance between the electrode assembly and the second wall is 0.2 mm, the number of layers of the positive electrode tab is 34, the number of layers of the negative electrode tab is 69, and the actuation pressure of the pressure relief mechanism is 0.6 MPa. The material of the end cap and the shell includes an aluminum shell, the thickness of the end cap is 1.5 mm, and the thickness of the shell is 0.6 mm.

[0214] Embodiment 2-4 The difference between Example 2-4 and Example 1 is that the residual space of the lithium-ion battery cell is different, and accordingly, the distance between the end of the main body close to the end cover and the inner side of the end cover varies.

[0215] Embodiment 5-7 The difference between Example 5-7 and Example 2 is that the number of layers of the positive electrode tab and the negative electrode tab is different.

[0216] Example 8 The difference between Example 8 and Example 1 is that the coating weight of the polymer coating is different. In Example 8, the coating weight of the polymer coating is 0.5 mg / 1540.25 mm 2 .

[0217] Example 9 The difference between Example 9 and Example 1 is that the side of the separator facing the positive electrode plate is not provided with a polymer coating.

[0218] Example 10 The difference between Example 10 and Example 1 is that the mass content of titanium element is 200 ppm based on the total mass of the positive electrode active material.

[0219] Embodiment 11 The difference between Example 11 and Example 1 is that the positive electrode active material is not doped with titanium element.

[0220] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the residual space of the lithium-ion battery cell is less than 0.05 mL / Ah.

[0221] Table 1 Test data of Examples 1-7 and Comparative Example 1

[0222] Table 2 Test results of Examples 1 and 8-9

[0223] Table 3 Test results of Examples 1 and 10-11

[0224] In the embodiments of the present application, the service life of the lithium-ion battery cell is reflected by the number of storage days, the reliability is reflected by whether the positive pole ear or the negative pole ear is inserted into the main body, and the overcurrent risk is reflected by whether thermal runaway occurs.

[0225] In combination with Examples 1-6 and Comparative Example 1, the residual space of the lithium-ion battery cell is set to be greater than or equal to 0.05mL / Ah, and the distance between the end of the main body close to the end cover and the inner side of the end cover is greater than or equal to 3mm, which is conducive to increasing the storage days of the lithium-ion battery cell, and the positive pole ear and the negative pole ear are not inserted into the main body, and no thermal runaway occurs, and the lithium-ion battery cell has a longer service life and higher reliability. In addition, the residual space of the lithium-ion battery cell is set to be less than or equal to 0.3mL / Ah, and the lithium-ion battery cell also has a higher energy density; and the lithium-ion battery cell includes a carboxylic acid ester solvent, which is conducive to improving the fast charging performance of the lithium-ion battery cell.

[0226] In combination with Examples 1-4, the residual space of the lithium-ion battery cell is set to 0.05mL / Ah to 0.2mL / Ah, and the lithium-ion battery cell has a longer storage period; the distance between the end of the main body close to the end cover and the inner side of the end cover is set to 4mm to 7mm, and the lithium-ion battery cell has a longer storage period while also facilitating a higher energy density.

[0227] As shown in Example 5, the number of layers of the positive pole tab is greater than or equal to 15, and the number of layers of the negative pole tab is greater than or equal to 15, which is conducive to reducing the risk of thermal runaway, and the lithium-ion battery cell has a good overcurrent capacity; as shown in Examples 6-7, the number of layers of the positive pole tab is less than or equal to 70, and the number of layers of the negative pole tab is less than or equal to 100, and the positive pole tab part and the negative pole tab part will not be inserted into the main body. In addition, the appropriate increase in the number of layers of the positive pole tab and the negative pole tab is also conducive to improving the overcurrent capacity, and at the same time, it is also conducive to reducing the temperature of the lithium-ion battery cell.

[0228] As shown in Examples 1 and 8, the coating weight of the polymer coating is greater than 0.5 mg / 1540.25 mm 2 In this case, the risk of positive electrode wrinkling is reduced; the coating weight of the polymer coating is 1mg / 1540.25mm 2 Up to 2mg / 1540.25mm 2 Under such circumstances, the positive electrode sheet is not easy to wrinkle, and it is also conducive to the transmission of lithium ions, and the battery cell can have better fast charging performance.

[0229] As shown in Examples 1 and 9, by providing a polymer coating on the side of the separator facing the positive electrode sheet, the risk of wrinkling the positive electrode sheet can be reduced.

[0230] As shown in Examples 1 and 10, when the mass content of titanium is greater than 200 ppm based on the total mass of the positive electrode active material, it is beneficial to reduce the internal resistance of the lithium-ion battery cell, thereby helping to reduce the maximum temperature of the first wall of the lithium-ion battery cell; when the mass content of titanium is 500 ppm to 3000 ppm based on the total mass of the positive electrode active material, it is beneficial to reduce the internal resistance of the lithium-ion battery cell, and it is also beneficial to take into account both the gram capacity of the positive electrode active material and the energy density of the lithium-ion battery cell.

[0231] As shown in Examples 1 and 11, the positive electrode active material is doped with titanium, which is beneficial to reducing the internal resistance of the lithium-ion battery cell, thereby helping to reduce the maximum temperature of the first wall of the lithium-ion battery cell.

[0232] Example 12 The difference between Example 12 and Example 1 is that the actuating pressure of the pressure relief mechanism is different.

[0233] Example 13 The difference between Example 13 and Example 1 is that the mass content W of the carboxylic acid ester solvent based on the total mass of the electrolyte is different, and the actuation pressure of the pressure relief mechanism is different.

[0234] In Example 13, the solvent in the electrolyte includes methyl acetate MA, ethyl acetate EA, ethylene carbonate EC and dimethyl carbonate DMC in a mass ratio of 2:5:2:1, and the actuation pressure of the pressure relief mechanism is 0.65 MPa. Based on the total mass of the electrolyte, the mass content W of the carboxylate solvent (the carboxylate solvent in Example 13 is MA and EA) is 58.3wt%.

[0235] Embodiment 14 The difference between Example 14 and Example 13 is that the actuating pressure of the pressure relief mechanism is different.

[0236] Table 4 Test results of Examples 1 and 12-14

[0237] In combination with Examples 1 and 12, when the mass content W of the carboxylic acid ester solvent is in the range of 1wt% to 50wt% based on the total mass of the electrolyte, the actuation pressure of the pressure relief mechanism is set to 0.6Mpa to 1.4MPa, and the pressure relief mechanism of the battery cell does not actuate the valve opening during normal use, and in the event of thermal runaway, the valve can be opened in a directional manner, and the emissions will not be discharged from a position outside the pressure relief mechanism. In combination with Examples 13-14, when the mass content W of the carboxylic acid ester solvent is in the range of 50wt% to 80wt% based on the total mass of the electrolyte, the actuation pressure of the pressure relief mechanism is set to 0.65Mpa to 1.35MPa, and the pressure relief mechanism of the battery cell does not actuate the valve opening during normal use, and in the event of thermal runaway, the valve can be opened in a directional manner, and the emissions will not be discharged from a position outside the pressure relief mechanism.

[0238] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

[0239] The following is a brief introduction to the test methods of the physical and chemical parameters and performance parameters involved in the embodiments of the present application. It should be understood that the following test methods are only examples, and other test methods known in the art may also be used for testing.

[0240] 1. Test method for actuation pressure of pressure relief mechanism Use two plates to clamp the two large faces of the lithium-ion battery cell, and clamp the large faces of the battery cell from both sides (the distance between the two plates is equal to the distance between the two large faces of the battery cell), and inflate the battery cell until the pressure relief mechanism is actuated, at which point the battery cell fails, and record the pressure in the housing of the battery cell (i.e., the actuation pressure of the pressure relief mechanism). When the pressure relief mechanism is actuated, the bulging distance of the two plates is less than or equal to 3 mm (the bulging distance refers to the maximum distance of the plate protrusion, i.e., the distance that any part of the plate moves from the position when clamped to the position after bulging).

[0241] 2. Test method for the area of ​​the pressure relief mechanism The area of ​​the region defined by the pressure relief mechanism is measured. As an example, the pressure relief mechanism is a round notch groove, and the area of ​​the region enclosed by the notch groove is the area of ​​the pressure relief mechanism.

[0242] 3. Test method for residual space of battery cells Residual Space , where V1 represents the internal volume of the battery cell (ml); V2 represents the volume of the electrode assembly (ml); V3 represents the volume of the electrolyte (ml); and C represents the discharge capacity of the battery cell (Ah).

[0243] As an example, the battery cell is disassembled, and the internal volume of the battery cell is measured by the water displacement method; the volume of the electrode assembly is measured; the electrolyte is extracted from the battery cell and the volume of the electrolyte is measured; and the rated capacity of the battery cell is recorded as C.

[0244] 4. Test method for mass content of carboxylic acid ester solvents The content of carboxylic acid ester in the electrolyte was quantitatively analyzed by organic gas chromatography analysis method with reference to standard GB / T9722-2006.

[0245] 5. Test methods for service life or storage time The prepared battery cell was charged to 100% SOC at a rate of 0.1C and stored at 60°C. The internal pressure of the battery cell was monitored online using a barometer. When the cut-off pressure was 0.35 MPa, the number of days stored at 60°C was recorded.

[0246] 6. Maximum temperature of the first wall and thermal runaway test method The lithium-ion battery cell is charged and discharged for the first time at a rate of 1C (i.e., the current value at which the theoretical capacity is completely discharged within 1 hour), specifically including: at 35°C, the battery is charged at a constant current rate of 1C to a voltage of 3.65V, then charged at a constant voltage to a current ≤0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a voltage of 2.5V, and its actual capacity is recorded as C0. Then the battery is charged with constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, 5C0 in sequence to the full battery charge cut-off voltage of 3.65V or 0V negative electrode cut-off potential (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to the discharge cut-off voltage of the battery cell of 2.5V. Record the SOC (State of Charge) at different charge rates to 10%, 20%, 30%, ..., 80% Charge, state of charge, when "SOC=0" means the battery is fully discharged, when "SOC=100%" means the battery is fully charged) the corresponding negative electrode potential, draw the negative electrode potential curve of the charging rate under different SOC states, and after linear fitting, obtain the charging rate corresponding to the negative electrode potential of 0V under different SOC states. This charging rate is the charging window under this SOC state, which are recorded as C(10%SOC), C(20%SOC), C(30%SOC), C(40%SOC), C(50%SOC), C(60%SOC), C(70%SOC), C(80%SOC), and the maximum charging rate under the corresponding charge state, that is, the fast charging window, is obtained.

[0247] Then, the fast charge cycle test was carried out with the lithium plating window obtained from the above test. The specific process was charging at an ambient temperature of 25°C, charging at a constant current of 0.33C to 10% SOC, charging at a constant current of C (10% SOC) to 20% SOC, charging at a constant current of C (20% SOC) to 30% SOC, charging at a constant current of C (30% SOC) to 40% SOC, charging at a constant current of C (40% SOC) to 50% SOC, charging at a constant current of C (50% SOC) to 60% SOC, and charging at a constant current of C (60% SOC). The battery is charged to 70% SOC with a constant current of C (70% SOC) to 80% SOC, charged to 3.65V with a constant current of 0.33C, charged to 0.05C with a constant voltage of 3.65V, left for 30 minutes, and discharged to 2.5V with a constant current of 0.33C. Before testing this process, a temperature sensing line is installed in the middle of the first wall (the wall with the largest surface area) of the battery cell. The temperature of the first wall during the test is measured, and whether there is thermal runaway (if there is no smoke, fire or explosion, thermal runaway has not occurred).

[0248] 7. Test whether interpolation occurs As an example, a lithium-ion battery cell is disassembled to check whether the positive electrode ear or the negative electrode ear is inserted into the main body.

[0249] As another example, observation is performed through computed tomography (CT) testing. A lithium-ion battery cell is placed in a CT scanning device, and an X-ray beam passes through the lithium-ion battery cell from different angles. The detector records the attenuation signal after the X-ray passes through the lithium-ion battery cell, forming multiple two-dimensional projection images. These projection data are processed through a computer algorithm (such as filtered back projection) to generate a three-dimensional structural image inside the lithium-ion battery cell, thereby determining whether there is a phenomenon in which the positive pole ear or the negative pole ear is inserted into the main body.

[0250] 8. Wrinkle test As an example, a lithium-ion battery cell is disassembled to observe whether the electrode piece (such as the positive electrode piece) has bulges, depressions or folds. If so, the electrode piece is wrinkled.

[0251] 9. Test of ionic conductivity of electrolyte The ionic conductivity of the electrolyte can be measured by instruments and methods known in the art. It can be tested using a conductivity tester, such as a DDSJ-318 conductivity meter. For example, the content on page 5 of the industry standard HG / T4067-2015 "Lithium Hexafluorophosphate Electrolyte" can be referred to.

[0252] The detailed test steps are as follows: (1) Densitometer method, also known as arbitration method.

[0253] Set the density meter's measuring temperature to 20°C, inject the sample into the instrument's measuring cell, perform the measurement and read the data.

[0254] (2) Density meter method Take about 100mL of sample in a dry, clean, corrosion-resistant sample bottle, seal it in a constant temperature water bath at 25℃±0.5℃, shake it from time to time, and when the sample temperature is constant, replace the sample bottle cap with a rubber stopper with an electrode, and when the temperature is within the range of 25℃±0.5℃, read the data in the conductivity meter, which is the conductivity of the sample being tested. You can wait for the data to stabilize for at least 10s before recording the test results.

[0255] 10. Test of electrolyte viscosity The viscosity of the electrolyte (also called kinematic viscosity) can be measured by instruments and methods known in the art. It can be tested using a conductivity tester. For example, the industry standard NB / SH / T0870-2013 "Determination of dynamic viscosity and density of petroleum products and calculation of kinematic viscosity by Stabinger viscometer method" can be referred to.

[0256] The specific test is as follows: The viscosity is measured by combining a kinematic viscosity tester and a Pinnitz viscometer. The inner diameter of the Pinnitz viscometer capillary is 0.6 mm. The Pinnitz viscometer is cleaned with anhydrous ethanol and deionized water in turn and placed in an oven for drying. The electrolyte to be tested is loaded into the clean and dry Pinnitz viscometer. The Pinnitz viscometer with electrolyte is immersed in the constant temperature water bath of the kinematic viscosity tester, fixed vertically, and the water bath temperature is set to 25°C. The constant temperature is maintained for 15 minutes. The electrolyte is sucked into the capillary and the liquid level to be tested exceeds the second mark. The electrolyte is allowed to flow freely under the action of gravity. When the liquid level reaches the second mark, the timing starts, and when the liquid level drops to the first mark, the timing stops. Each electrolyte sample is measured three times according to the above test steps, and the flow time is taken as the average of the three tests. The kinematic viscosity of the electrolyte = the viscosity coefficient of the Pinnitz viscometer × the average time for the electrolyte sample to flow through the capillary.

Claims

1. A lithium-ion battery cell, characterized in that: Comprising: An electrolyte, the electrolyte comprising a carboxylate solvent; An electrode assembly, the electrode assembly comprising a positive electrode tab and a negative electrode tab, the positive electrode tab and the negative electrode tab being stacked to form the electrode assembly, the electrode assembly comprising a main body portion, a positive electrode ear portion and a negative electrode ear portion, the positive electrode ear portion and the negative electrode ear portion protruding from the main body portion; An end cap, the end cap being provided with a positive electrode terminal and a negative electrode terminal, the positive electrode terminal and the negative electrode terminal being connected to the positive electrode ear portion and the negative electrode ear portion respectively; Wherein, the distance between one end of the main body portion close to the end cap and the inner side of the end cap is 3 mm to 10 mm; The residual space of the lithium ion battery cell is 0.05 mL / Ah to 0.3 mL / Ah.

2. The lithium-ion battery cell according to claim 1, characterized in that: The distance between one end of the main body portion close to the end cap and the inner side of the end cap is 4 mm to 7 mm.

3. The lithium-ion battery cell according to claim 1, characterized in that: The positive electrode tab comprises a positive electrode current collector main body portion and a positive electrode ear, the positive electrode ear protruding from the positive electrode current collector main body portion; The positive electrode ear portion comprises multiple layers of the positive electrode ear, and the number of layers of the multiple layers of the positive electrode ear is 15 to 70.

4. The lithium-ion battery cell according to claim 3, characterized in that: The thickness of the positive electrode ear is 10 μm to 15 μm.

5. The lithium-ion battery cell according to claim 1, characterized in that: The negative electrode tab comprises a negative electrode current collector main body portion and a negative electrode ear, the negative electrode ear protruding from the negative electrode current collector main body portion; The negative electrode ear portion comprises multiple layers of the negative electrode ear, and the number of layers of the multiple layers of the negative electrode ear is 15 to 100.

6. The lithium-ion battery cell according to claim 5, characterized in that: The thickness of the negative electrode ear is 4 μm to 6 μm.

7. The lithium-ion battery cell according to claim 1, characterized in that: The residual space of the lithium ion battery cell is 0.05 mL / Ah to 0.2 mL / Ah.

8. The lithium-ion battery cell according to claim 1, characterized in that: The lithium ion battery cell comprises a first wall and a second wall, the first wall being the surface with the largest surface area, and the second wall being adjacent to the first wall and the end cap; The distance between the electrode assembly and the second wall is 0.1 mm to 1.5 mm.

9. The lithium-ion battery cell according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass content W of the carboxylate solvent satisfies: 1 wt% ≤ W ≤ 50 wt%, the end cap is provided with a pressure relief mechanism, and the actuation pressure P of the pressure relief mechanism satisfies: 0.6 MPa ≤ P ≤ 1.4 MPa.

10. The lithium-ion battery cell according to claim 1, characterized in that: Based on the total mass of the electrolyte, the mass content W of the carboxylate solvent satisfies: 50 wt% < W ≤ 80 wt%, the end cap is provided with a pressure relief mechanism, and the actuation pressure P of the pressure relief mechanism satisfies: 0.65 MPa ≤ P ≤ 1.35 MPa.

11. The lithium-ion battery cell according to claim 1, characterized in that: The positive electrode tab comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate.

12. The lithium-ion battery cell according to claim 11, characterized in that: The positive electrode active material further comprises titanium element.

13. The lithium-ion battery cell according to claim 12, characterized in that: Based on the total mass of the positive electrode active material, the mass content of the titanium element is 500 ppm to 3000 ppm.

14. The lithium-ion battery cell according to claim 1, characterized in that: The lithium ion battery cell comprises a housing, and the end cap and the housing are covered to form a space for accommodating the electrode assembly; The materials of the housing and the end cap comprise steel, the thickness of the housing is 0.1 mm to 0.5 mm, and / or, the thickness of the end cap is 0.1 mm to 0.5 mm.

15. The lithium-ion battery cell according to claim 1, characterized in that: The lithium ion battery cell comprises a housing, and the end cap and the housing are covered to form a space for accommodating the electrode assembly; The material of the shell and the end cover includes aluminum, the thickness of the shell is 0.3 mm to 0.8 mm, and / or the thickness of the end cover is 1.2 mm to 2 mm.

16. The lithium-ion battery cell according to claim 9, characterized in that: The thickness of the end cover where the pressure relief mechanism is provided is 0.07 mm to 0.4 mm.

17. The lithium-ion battery cell according to claim 1, characterized in that: The time t for charging the lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤30min.

18. The lithium-ion battery cell according to claim 17, characterized in that: The time t for charging the lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤20min.

19. The lithium-ion battery cell according to claim 18, characterized in that: The time t for charging the lithium-ion battery cell from 10% SOC to 80% SOC satisfies: t≤15min.

20. The lithium-ion battery cell according to claim 1, characterized in that: The ionic conductivity of the electrolyte is 9mS / cm to 25mS / cm, and / or the viscosity of the electrolyte is 1mm 2 / s~4mm 2 / s.

21. The lithium-ion battery cell according to claim 20, characterized in that: The ionic conductivity of the electrolyte is 11mS / cm~18mS / cm.

22. The lithium-ion battery cell according to claim 20, characterized in that: The viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s.

23. The lithium-ion battery cell according to claim 1, characterized in that: The carboxylate solvent includes: one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate or ethyl acrylate.

24. The lithium-ion battery cell according to any one of claims 1 to 23, characterized in that: The electrode assembly includes a separator, which is used to separate the positive electrode plate from the negative electrode plate. A polymer coating is provided on the side of the separator facing the positive electrode plate. The polymer coating includes one or more of a fluorine-containing polymer or a non-fluorine-containing polymer. The fluorine-containing polymer includes one or more of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer. The non-fluorine-containing polymer includes an acrylate copolymer.

25. The lithium-ion battery cell according to claim 24, characterized in that: The weight of the polymer coating is 1 mg / 1540.25 mm 2 Up to 2mg / 1540.25mm 2 .

26. A lithium ion battery, characterized in that: Comprising a lithium-ion battery cell according to any one of claims 1-25.

27. An electrical device, characterized in that: The electric device comprises the lithium-ion battery according to claim 26.

Images