Battery monomer, lithium ion battery and power utilization device

Abstract

The embodiment of the invention provides a battery monomer, a lithium ion battery and an electric device. The battery monomer comprises a shell, and an electrode assembly and an electrolyte which are accommodated in the shell; the electrolyte comprises a carboxylic ester solvent, and the ionic conductivity sigma of the electrolyte is greater than or equal to 9mS / cm and less than or equal to 25mS / cm; the shell comprises a pressure relief mechanism, and the area S of the pressure relief mechanism is larger than or equal to 200 mm < 2 > and smaller than or equal to 900 mm < 2 >. The battery monomer has good cycle performance and safety performance.

Description

Technical Field

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

[0002] In recent years, secondary batteries, mainly lithium-ion batteries, have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields, and have thus achieved great development.

[0003] With the development and application of lithium-ion batteries, in addition to pursuing higher electrochemical performance, battery safety performance is equally important. Some components in the electrolyte may have the problem of easy gas production, which affects the cycle performance of lithium-ion batteries and threatens the safety performance of lithium-ion batteries. Therefore, how to improve the safety performance of lithium-ion batteries 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 technical problems, and its purpose is to provide a battery cell, a lithium-ion battery and an electrical device.

[0005] In a first aspect, a battery cell is provided, the battery cell comprising a housing and an electrode assembly and an electrolyte contained in the housing; the electrolyte comprises a carboxylic acid ester solvent, and the ionic conductivity σ of the electrolyte satisfies: 9mS / cm≤σ≤25mS / cm; the housing comprises a pressure relief mechanism, and the area S of the pressure relief mechanism satisfies: 200mm 2 ≤S≤900mm 2 .

[0006] In the embodiment of the present application, in a battery cell using an electrolyte having an ion conductivity in the range of 9 mS / cm-25 mS / cm, the area S of the pressure relief mechanism on the housing is designed to be 200 mm 2 -900mm 2 This area range corresponds to the ionic conductivity, and can timely release the gas in the battery cell when the carboxylic acid ester solvent produces gas, thereby improving the cycle performance of the battery cell and the safety performance of the battery cell.

[0007] In a possible implementation, the carboxylate solvent includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate and ethyl acrylate.

[0008] In a possible implementation, based on the total mass of the electrolyte, the mass fraction W1 of the carboxylic acid ester solvent satisfies: 5wt%≤W1≤80wt%.

[0009] In the embodiments of the present application, by controlling the mass content of the carboxylic ester solvent within a suitable range, it is possible to improve the ionic conductivity of the electrolyte and improve the concentration polarization inside the battery cell, while reducing the risk that the excessive gas generation of the carboxylic ester solvent affects the safety performance and cycle performance of the battery cell.

[0010] In a possible implementation manner, the battery cell is disposed in a box body, and a heat insulation member is provided on the inner wall of the box body opposite to the pressure relief mechanism.

[0011] In the embodiments of the present application, by providing a heat insulation member at a position opposite to the pressure relief mechanism, it is possible to block the gas from directly spraying onto the box body when the battery cell discharges gas to the outside, reducing the risk of excessive temperature in a local area of the box body or damage to the box body, thereby helping to improve the safety performance of the battery cell.

[0012] In a possible implementation manner, the vertical distance L between the heat insulation member and the pressure relief mechanism satisfies: 6 mm ≤ L ≤ 13 mm.

[0013] In a possible implementation manner, 7 mm ≤ L ≤ 11 mm.

[0014] In the embodiments of the present application, by controlling the vertical distance between the heat insulation member and the pressure relief mechanism within a suitable range, it is possible to protect the battery cell and the box body while reducing the influence of an excessive distance between the heat insulation member and the pressure relief mechanism on the energy density of the secondary battery or the battery module.

[0015] In a possible implementation manner, the thickness h of the heat insulation member satisfies: 0.2 mm ≤ h ≤ 3 mm.

[0016] In the embodiments of the present application, by controlling the thickness of the heat insulation member within a suitable range, it is possible to protect the battery cell and the box body while reducing the influence of the heat insulation member on the energy density of the secondary battery or the battery module.

[0017] In a possible implementation manner, the time t for the battery cell to be charged from 10% SOC to 80% SOC satisfies: t ≤ 15 min.

[0018] In the embodiments of the present application, in a battery cell with fast charging capability, by combining the design of the aforementioned electrolyte and the pressure relief mechanism, the fast charging battery cell can have good fast charging cycle performance and safety performance.

[0019] In a possible implementation manner, the capacity C of the battery cell satisfies: 80 Ah ≤ C ≤ 160 Ah.

[0020] In a possible implementation manner, 100 Ah ≤ C ≤ 150 Ah.

[0021] In a possible implementation, the electrode assembly includes a positive electrode tab, the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium transition metal oxide.

[0022] In a possible implementation, the battery cell satisfies at least one of the following (1)-(3): (1) 600 mm 2 ≤S≤900 mm 2 ; (2) 0.8 mm ≤ h ≤ 3 mm; (3) 10% wt ≤ W1 ≤ 40 wt%.

[0023] In a possible implementation, the electrode assembly includes a positive electrode tab, the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

[0024] In a possible implementation, the battery cell satisfies at least one of the following (4)-(6): (4) 200 mm 2 ≤S≤500 mm 2 ; (5) 0.2 mm ≤ h ≤ 1 mm; (6) 30% wt ≤ W1 ≤ 70 wt%.

[0025] In a second aspect, a lithium-ion battery is provided, and the lithium-ion battery includes the battery cell in any possible implementation of the first aspect.

[0026] In a third aspect, an electrical device is provided, and the electrical device includes the battery cell in any possible implementation of the first aspect, and / or the lithium-ion battery in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0028] Figure 1 It is a schematic structural diagram of a battery cell.

[0029] Figure 2 It is a schematic exploded view of a battery cell.

[0030] Figure 3 It is a schematic structural diagram of a lithium-ion battery.

[0031] Figure 4 It is a schematic diagram of a battery cell and a heat insulation member. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Hereinafter, embodiments of the battery cell, lithium ion battery, and electrical device of the present application will be specifically described with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying 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 recited in the claims.

[0033] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] In the description of the present application, it should be noted that unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", etc. is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present application. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0035] If there is no special description, in the present application, the phrase "A and / or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A and / or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0036] Unless otherwise specified, all steps of this application can be carried out 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) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0038] Unless otherwise specified, any undefined terms have their generally recognized meanings in the art.

[0039] Next, embodiments of this application will be introduced.

[0040] In recent years, secondary batteries have been widely used in many fields such as power tools, electronic products, electric vehicles, aerospace, etc. due to their high energy density and long service life, and thus have achieved great development. Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. Among them, the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, which can prevent short circuit between the positive and negative electrodes while allowing active ions to pass through, enabling the normal progress of the electrochemical reaction of the secondary battery.

[0041] Taking a lithium-ion battery as an example, a lithium-ion battery is a typical secondary battery. Since it relies on the chemical reaction of lithium ions being inserted and extracted between the positive and negative electrodes for charge and discharge, a lithium-ion battery is also called a rocking chair battery. During the charging process of a lithium-ion battery, lithium ions are extracted from the positive electrode active material, move through the conduction of the electrolyte to the negative electrode and are embedded in the negative electrode active material; during the discharging process, lithium ions are extracted from the negative electrode active material, move through the conduction of the electrolyte to the positive electrode and are embedded in the positive electrode active material.

[0042] It should be understood that the "lithium insertion" and "insertion" processes described in this application refer to the process in which lithium ions are inserted into the positive electrode active material or the negative electrode active material due to an electrochemical reaction, and the "extraction", "lithium extraction", and "extraction and insertion" processes described in this application refer to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0043] During the charge and discharge process of a lithium-ion battery, there is concentration polarization inside the battery cell. Concentration polarization is caused by the fact that the migration rate of lithium ions participating in the electrochemical reaction is slower than that of electrons in the external circuit. Once the concentration polarization inside the battery cell is too large, it may cause lithium deposition on the negative electrode plate, consuming active lithium ions and thus leading to the attenuation of the battery cell capacity. In severe cases, lithium dendrites are generated, triggering safety problems and deteriorating the cycle performance and safety performance of the battery cell.

[0044] Improving the ionic conductivity of the electrolyte can improve concentration polarization. Generally speaking, the ionic conductivity of the electrolyte can be adjusted by selecting appropriate solvents, electrolyte salts, adjusting the proportion of the solvent, the concentration of the electrolyte salt, etc. For example, an electrolyte using a carboxylate solvent usually has a relatively high ionic conductivity, which can improve the concentration polarization inside the battery cell and is beneficial to the safety performance and cycle performance of the lithium-ion battery. However, it is found that carboxylate solvents are prone to side reactions of film formation with the negative electrode, consuming active lithium ions in the electrolyte and generating gas. Especially in scenarios such as fast charging and high temperature, the gas generation amount further increases, threatening the safety performance and cycle performance of the lithium-ion battery. The gas generation situation of carboxylate solvents can be improved by adding additives to the electrolyte or adjusting the proportion of each component in the electrolyte, so as to reduce the impact of its gas generation on the safety performance and cycle performance of the battery cell. However, the effects of the above means are very limited, and with the sacrifice of the amount of carboxylate solvents used, it cannot meet the increasingly wide range of application requirements (such as fast charging).

[0045] In view of this, the embodiments of the present application provide a battery cell, a lithium-ion battery and an electrical device. The battery cell including a carboxylate solvent has good safety performance and cycle performance.

[0046] Next, the battery cell provided by the present application will be introduced.

[0047] [Battery cell]

[0048] First, a battery cell is provided. The battery cell includes a housing, and an electrode assembly and an electrolyte accommodated in the housing. The electrolyte includes a carboxylate solvent, and the ionic conductivity σ of the electrolyte satisfies: 9 mS / cm ≤ σ ≤ 25 mS / cm. The housing includes a pressure relief mechanism, and the area S of the pressure relief mechanism satisfies: 200 mm 2 ≤ S ≤ 900 mm 2 .

[0049] Carboxylate solvents have relatively high ionic conductivity. When applied to electrolytes, they can effectively increase the ionic conductivity of the electrolytes to be within the range of 9 mS / cm - 25 mS / cm. Specifically, σ can be 9 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, 19 mS / cm, 20 mS / cm, 21 mS / cm, 22 mS / cm, 23 mS / cm, 24 mS / cm, 25 mS / cm, or its value can be within the range obtained from any combination of the above two values. S can be 200 mm 2 、250 mm 2 、300 mm 2 、350 mm 2 、400 mm 2 、450 mm 2 、500 mm 2 、550 mm 2 、600 mm 2 、650 mm 2 、700 mm 2 、750 mm 2 、800 mm 2 、850 mm 2 、900 mm 2 , or its value can be within the range obtained from any combination of the above two values.

[0050] It should be understood that the ionic conductivity of the electrolyte is related to temperature. Unless otherwise specified, the ionic conductivity mentioned in this application refers to the ionic conductivity of the electrolyte measured at 25°C. However, considering the normal errors in the test conditions, the above range of ionic conductivity is not limited to 25°C and can also be the ionic conductivity measured at 20°C - 30°C. The test results within this temperature range have relatively small differences and can be equivalent to the test results at 25°C.

[0051] Figure 1 Fig. shows a schematic structural diagram of a battery cell according to this application. Figure 2 Fig. shows a schematic exploded view of a battery cell according to this application. As Figure 1-2 shown, the battery cell 10 generally includes a housing 11 and an electrode assembly 12 disposed in the housing 11. The electrode assembly 12 includes a positive electrode plate, a separator, and a negative electrode plate. The positive electrode plate, the separator, and the negative electrode plate can be fabricated into the electrode assembly 12 through a winding or stacking process. The housing 11 can include a housing body 111 and an end cap 112. Among them, the housing body 111 is provided with an opening, and the end cap 112 is used to cover the opening to isolate the internal environment of the battery cell 10 from the external environment, forming a closed space for accommodating the electrode assembly 12, the electrolyte, and other components.

[0052] The shape of the end cap 112 can be adapted to the shape of the housing 111. For example, the housing 111 is a cuboid structure, and the end cap 112 is a rectangular plate-like structure adapted to the housing 111. For another example, the housing 111 is Figure 1-2 the cuboid structure shown, and the end cap 112 is a rectangular plate-like structure adapted to the housing 111. The material of the end cap 112 can be various. Exemplarily, the end cap 112 can be made of metal, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cap 112 can be the same as or different from the material of the housing 111. As an example, the material of the end cap 112 is aluminum.

[0053] The pressure relief mechanism 13 is an element or component used to actuate when the internal pressure or temperature of the battery cell 10 reaches a predetermined threshold to release the internal pressure or temperature of the battery cell 10. This predetermined threshold can be adjusted according to different design requirements. For example, this predetermined threshold depends on one or several materials of the positive electrode plate, negative electrode plate, electrolyte, and separator in the battery cell 10. "Actuate" means that the pressure relief mechanism 13 generates an action or is activated to a certain state, so that the internal pressure and temperature of the battery cell 10 are released. The actions generated by the pressure relief mechanism 13 can include but are not limited to: at least a part of the pressure relief mechanism 13 ruptures, breaks, is torn, or opens, etc. When the pressure relief mechanism 13 is actuated, the high-temperature and high-pressure substances inside the battery cell 10 are discharged as emissions from the actuated part. In this way, the battery cell 10 can be depressurized and cooled under controlled pressure or temperature, thereby reducing the risk of potential more serious accidents.

[0054] The emissions from the battery cell 10 mentioned in the embodiments of the present application include but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of the separator, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0055] The pressure relief mechanism 13 is provided on the outer shell 11. It can be as Figure 1 shown, the pressure relief mechanism 13 is provided on the housing 111, or it can be as Figure 2As shown, a pressure relief mechanism 13 is provided on the end cap 112. Taking the setting of the pressure relief mechanism 13 on the end cap 112 as an example, the pressure relief mechanism 13 can be a split structure with the end cap 112, and the pressure relief mechanism 13 is an independent component installed on the end cap 112. For example, the pressure relief mechanism 13 can be components such as an explosion-proof valve, a gas valve, a pressure relief valve or a safety valve installed on the end cap 112, and can specifically adopt pressure-sensitive or temperature-sensitive elements or structures. The pressure relief mechanism 13 can also be an integral structure with the end cap 112. The pressure relief mechanism 13 is a part of the end cap 112. For example, the pressure relief mechanism 13 can be formed by setting a notch on the end cap 112, and the thickness at the notch is significantly smaller than the thickness of other areas of the end cap 112. The notch is the weakest position of the pressure relief mechanism 13. When the gas generated by the battery cell 10 is too much, causing the internal pressure to rise and reach the threshold value, or when the internal reaction of the battery cell 10 generates heat, causing the internal temperature of the battery cell 10 to rise and reach the threshold value, the pressure relief mechanism 13 can rupture at the notch, resulting in the internal and external communication of the battery cell 10, and the gas pressure and temperature are released outward through the crack of the pressure relief mechanism 13, thereby avoiding the explosion of the battery cell 10. As an example, a notch groove is provided on the end cap 112, and the area defined by the notch groove forms the pressure relief mechanism 13. More specifically, the notch groove can be in a ring shape with a notch.

[0056] The area of the pressure relief mechanism 13 refers to the maximum area where the pressure relief mechanism 13 can be used to discharge the emissions of the battery cell 10. For example, for the pressure relief mechanism 13 formed by the notch groove, its area is the area of the region defined by the notch groove. Another example is that for the explosion-proof valve type pressure relief mechanism 13, its area is the cross-sectional area of the channel in the explosion-proof valve through which the emissions of the battery cell 10 can pass.

[0057] Generally speaking, the larger the area of the pressure relief mechanism 13, the easier it is for the pressure relief mechanism 13 to rupture in the case of gas generation or thermal runaway of the battery cell 10, which is more conducive to the rapid discharge of the emissions inside the battery cell 10. However, the larger the area of the pressure relief mechanism 13, the greater the risk of damage in the normal state (static, charge-discharge cycle) of the battery cell 10. Therefore, the design of the area of the pressure relief mechanism 13 usually considers the reliability of the battery cell 10 and the mechanical strength of the pressure relief mechanism 13 itself.

[0058] In this embodiment, the influence of the electrolyte on the pressure relief mechanism 13 is fully considered. Specifically, as mentioned above, carboxylic ester solvents can improve the ionic conductivity of the electrolyte, making it within the range of 9 mS / cm - 25 mS / cm, which is beneficial to reducing the concentration polarization of the battery cell 10 and improving the cycling performance of the battery cell 10. However, the reduction stability of carboxylic ester solvents is poor, and irreversible decomposition reactions to generate gas continuously occur at the interface between the negative active material and the electrolyte, and their reduction products cannot form an effective passivation layer. Therefore, compared with ordinary electrolytes, the gas generation amount of the electrolyte including carboxylic ester solvents and having an ionic conductivity within the above range is relatively high during the cycling of the battery cell 10. For the battery cell 10 using an electrolyte with an ionic conductivity within the range of 9 mS / cm - 25 mS / cm, a pressure relief mechanism 13 with an area in the range of 200 mm 2 - 900 mm 2 is correspondingly designed on the outer casing 11. This area range corresponds to the ionic conductivity and can timely release the gas of the battery cell 10 when carboxylic ester solvents generate gas, reducing the risk of affecting the solid-liquid interface due to excessive gas inside the battery cell 10 and deteriorating the cycling performance of the battery cell 10. At the same time, it also reduces the threat to the safety performance of the battery cell 10 due to excessive gas inside the battery cell 10. Thus, while improving the cycling performance of the battery cell 10, the safety performance of the battery cell 10 is also enhanced.

[0059] In one embodiment, the carboxylic ester solvent includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate, and ethyl acrylate.

[0060] In one embodiment, based on the total mass of the electrolyte, the mass fraction W1 of the carboxylic ester solvent satisfies: 5 wt% ≤ W1 ≤ 80 wt%; optionally, 30 wt% ≤ W1 ≤ 80 wt%.

[0061] Specifically, W1 can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, or its value is within the range obtained by combining any two of the above values. The higher the mass content of the carboxylic ester solvent, the higher the ionic conductivity of the electrolyte. In addition, considering the gas generation problem of carboxylic ester solvents, if the content is too high, even though the high ionic conductivity of the electrolyte helps to improve concentration polarization, when the gas generation amount is so large that it affects the stability of the solid-liquid interface at the negative electrode sheet, it is instead unfavorable to the cycling performance of the battery cell 10. Thus, in this embodiment, by controlling the mass content of the carboxylic ester solvent within the above range, the electrolyte conductivity can be improved while the cycling performance of the battery cell 10 is improved.

[0062] Figure 3 It is a schematic structural diagram of a lithium-ion battery.

[0063] As Figure 3 shown, in one embodiment, the battery cell 10 is disposed in the box body 2, and a heat insulation member 23 is provided on the inner wall of the box body 2 opposite to the pressure relief mechanism 13.

[0064] Specifically, the lithium-ion battery 20 may include one or more battery cells 10, and one or more battery cells 10 are accommodated in the box body 2. The plurality of battery cells 10 may be arranged in one or more columns in the thickness direction. The plurality of battery cells 10 may be combined in parallel, in series, or in a mixed connection.

[0065] The heat insulation member 23 is a component provided on the inner wall of the box body 2 opposite to the pressure relief mechanism 13 and the battery cell 10 for blocking the emissions of the battery cell 10. In one embodiment, the material of the heat insulation member 23 may be mica, carbon fiber, etc. For the lithium-ion battery 20, or a battery module composed of a plurality of battery cells 10, when a battery cell 10 exhausts gas outward, it is likely to cause the local temperature of the inner wall of the box body 2 opposite to the pressure relief mechanism 13 of the battery cell 10 to be too high or the pressure borne to be too large, resulting in damage.

[0066] In this embodiment, by providing the heat insulation member 23, when the battery cell 10 exhausts gas outward, it can block the gas from directly spraying onto the box body 2, reducing the risk of the local area of the box body 2 having too high a temperature or the box body 2 being damaged, thereby helping to improve the safety performance of the lithium-ion battery 20.

[0067] Figure 4 It is a schematic diagram of a battery cell 10 and a heat insulation member 23 of the present application.

[0068] As Figure 4 shown, in one embodiment, the vertical distance L between the heat insulation member 23 and the pressure relief mechanism 13 satisfies: 6 mm ≤ L ≤ 13 mm; optionally, 7 mm ≤ L ≤ 11 mm.

[0069] Specifically, L may be 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, or its value is within the range obtained by combining any two of the above values. A certain distance needs to be maintained between the heat insulation member 23 and the pressure relief mechanism 13: if the distance is too small, the space for the battery cell 10 to discharge gas is insufficient, affecting the safety performance of the battery cell 10; if the distance is too large, the space utilization rate inside the box body 2 of the lithium-ion battery 20 will be reduced, which is not conducive to the energy density of the lithium-ion battery 20.

[0070] Thus, in this embodiment, for the area of the pressure relief mechanism 13 in the foregoing embodiment, by controlling the distance L between the heat insulation member 23 and the pressure relief mechanism 13 within the range of 6 mm - 13 mm, it is possible to improve the safety performance of the battery cell 10 and the lithium-ion battery 20 while reducing the influence of the heat insulation member 23 on the energy density of the lithium-ion battery 20.

[0071] In one embodiment, the thickness h of the heat insulation member satisfies: 0.2 mm ≤ h ≤ 3 mm.

[0072] Specifically, h can be 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm, 3 mm, or its value is within the range obtained by combining any two of the above values. The thickness of the heat insulation member 23 directly affects the heat insulation ability of the heat insulation member 23. The thicker its thickness, the better the heat insulation ability, but the heavier the weight of the heat insulation member 23 and the larger the space occupied inside the box body. At the same time, when the distance L between the heat insulation member 23 and the pressure relief mechanism 13 is relatively large, a relatively thin heat insulation member 23 can be used; when the distance L between the heat insulation member and the pressure relief mechanism 13 is relatively small, a relatively thick heat insulation member can be used to achieve the best heat insulation performance and energy density.

[0073] In this embodiment, for the area of the pressure relief mechanism 13 and the distance L between the heat insulation member 23 and the pressure relief mechanism 13 in the foregoing embodiment, by controlling the thickness of the heat insulation member 23 within a suitable range, it is possible to improve the safety performance of the battery cell 10 and the lithium-ion battery 20 while reducing the influence of the heat insulation member 23 on the energy density of the lithium-ion battery 20.

[0074] In one embodiment, the time t for the battery cell 10 to be charged from 10% SOC to 80% SOC satisfies: t ≤ 20 min.

[0075] Specifically, this means that the battery cell 10 has the fast charging ability to be charged from 10% SOC to 80% SOC in a time less than or equal to 20 min. Fast charging, abbreviated as quick charge, refers to charging the battery to a full charge or a nearly full charge state in a relatively short time. The specific definition of fast charging in the industry in different regions has different standards. Generally speaking, if the battery can be charged to 80% of its full charge capacity within 30 min - 60 min, it is considered to belong to fast charging. Further, a charging time within 20 min can be considered to belong to super fast charging; even further, a charging time less than 15 min can be considered to belong to the range of extreme fast charging (XFC).

[0076] The fast charging process can be a constant current charging process or a stepped charging process. The constant current charging process means charging the battery cell 10 at a fixed charging rate. The charging rate represents the ratio of the charging current to the capacity of the battery cell 10. For example, for a battery supporting 4C charging, the charging current can reach four times the battery capacity. The charging rate can be calculated as the ratio of the charging current to the capacity of the battery cell 10. During the fast charging process of the battery cell 10, the charging rate can also vary. For example, when the charging rate of the battery cell 10 is 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 current density is the equivalent charging rate during the process of the battery cell 10 charging from 10% SOC to 80% SOC. In other words, during 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. During this process, the battery cell 10 may experience a transition from constant current charging to constant voltage charging, and thus, the charging rate is not constant. For example: Start charging the battery cell 10 at room temperature of 25°C, from 10% SOC to 80% SOC, and the charging time is 10 minutes (equivalent charging rate ≥ 4C). This charging process can be: initially charge from 10% SOC to 45% SOC at 5C, then charge from 45% SOC to 50% SOC at 4.6C, 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 ends. The charging time for the battery cell 10 to charge from 0% SOC to 100% SOC at 1C is 60 minutes. Thus, when the measured charging time for the battery cell 10 to charge from 10% SOC to 80% SOC is 10 minutes, the equivalent charging rate for this process can be calculated as: [(80% SOC - 10% SOC) / (100% SOC - 0% SOC)] × [(1C × 60 minutes) / 10 minutes] = 4.2C.

[0077] The electrolyte of the battery cell 10 of the present application is a high-conductivity electrolyte with an ionic conductivity of 9 mS / cm - 25 mS / cm, which can support the rapid migration of a large number of lithium ions in a short time during the charging process of the battery cell 10, that is, it is beneficial to the fast charging performance of the battery cell 10. At the same time, during the fast charging process, the gas generation amount of the carboxylic ester solvent in the electrolyte will further increase. Therefore, the area design of the pressure relief mechanism 13 in the foregoing embodiments also takes into account the fast charging performance of the battery cell 10, and by designing the area of the pressure relief mechanism 13 at 200 mm 2 - 900 mm 2Within the range, it is also possible to enable the battery cell 10 with an electrolyte including a carboxylate solvent to have the above-mentioned fast charging ability while having good cycle performance and safety performance.

[0078] In one embodiment, the capacity C of the battery cell 10 satisfies: 80 Ah ≤ C ≤ 160 Ah; optionally 100 Ah ≤ C ≤ 150 Ah.

[0079] Specifically, C can be 80 Ah, 90 Ah, 100 Ah, 110 Ah, 120 Ah, 130 Ah, 140 Ah, 150 Ah, 160 Ah, or a value within the range obtained by combining any two of the above values. The larger the capacity C of the battery cell 10, the larger the area of the pressure relief mechanism 13 that needs to be set. In this embodiment, by controlling the capacity of the battery cell 10 within a suitable range, it can be adapted to the area of the pressure relief mechanism 13 in the range of 200 mm 2 -900 mm 2 to achieve good safety performance.

[0080] In one embodiment, the electrode assembly 12 includes a positive electrode tab, the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium transition metal oxide.

[0081] Specifically, the positive electrode tab generally includes a positive electrode current collector and a positive electrode film layer provided on at least one side surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material. Lithium transition metal oxides refer to a class of oxides including lithium elements and transition metal elements. Structurally, it includes ternary materials with a layered structure, LiCoO 2 、LiNiO 2 etc., and also includes LiMnO with a spinel structure 2 、LiMn 2 O 4 etc. Ternary materials refer to lithium transition metal oxides including three different transition metal elements. It should be understood that trace amounts of other transition metal elements can also be doped in the ternary materials, and ternary materials doped with other transition metal elements are generally considered to still belong to ternary materials. Lithium transition metal oxides generally have a high specific capacity, which helps to improve the energy density of the battery cell 10.

[0082] In one embodiment, when the positive electrode active material includes a lithium transition metal oxide, the battery cell 10 satisfies at least one of (1)-(3): (1) 600 mm 2 ≤ S ≤ 900 mm 2 ; (2) 0.8 mm ≤ h ≤ 3 mm; (3) 10% wt ≤ W1 ≤ 40 wt%.

[0083] Specifically, for the case where the positive electrode active material includes lithium transition metal oxide, due to the poor thermal stability of lithium transition metal oxide, high-energy oxygen ions may be released during the cycling of the battery cell 10, exacerbating the gas-generation side reaction of the carboxylic acid ester solvent in the electrolyte; moreover, the charging cut-off voltage of the battery cell 10 with the positive electrode active material including lithium transition metal oxide is usually relatively high, for example, 4.25V - 4.5V, and the carboxylic acid ester solvent in the electrolyte is more likely to decompose and generate gas at a relatively high voltage.

[0084] Based on this, for the above-mentioned case where the positive electrode active material includes lithium transition metal oxide, the embodiments of the present application can quickly discharge the gas inside the battery cell 10 by further controlling the area of the pressure relief mechanism 13 within a relatively large range, improving the safety performance and cycling performance of the battery cell 10; by further controlling the thickness of the heat insulation member 23 within a relatively thick range, it can withstand a larger exhaust volume of the battery cell 10, improving the safety performance of the battery cell 10 and the lithium-ion battery 20; by controlling the mass content of the carboxylic acid ester solvent in the electrolyte within a relatively small range, the exhaust volume of the battery cell 10 in this system is reduced.

[0085] In one embodiment, the positive electrode active material includes lithium-containing phosphate.

[0086] Specifically, phosphate refers to a class of salts including lithium element, transition metal element, and phosphate ion. Structurally, it includes lithium iron phosphate, lithium manganese iron phosphate, etc. with olivine structure. Lithium-containing phosphate has good structural stability and can stably undergo electrochemical reactions at high temperatures. Its specific capacity is lower than that of lithium transition metal oxide, but it is helpful for the cycling performance of the battery cell 10.

[0087] In one embodiment, when the positive electrode active material includes lithium-containing phosphate, the battery cell 10 satisfies at least one of (4) - (6): (4) 200mm 2 ≤S≤500mm 2 ; (5) 0.2mm ≤ h ≤ 1mm; (6) 30%wt ≤ W1 ≤ 70wt%.

[0088] Specifically, in the case where the above-mentioned positive electrode active material includes lithium-containing phosphate, the embodiments of the present application can quickly discharge the gas inside the battery cell 10 and reduce the probability of breakage of the pressure relief mechanism 13 under normal conditions of the battery cell 10 by further controlling the area of the pressure relief mechanism 13 within a relatively small range, thereby improving the safety performance and cycle performance of the battery cell 10; by further controlling the thickness of the heat insulation member 23 within a relatively thin range, it can withstand the exhaust of the battery cell 10 while reducing the impact on the energy density of the lithium-ion battery 20; by controlling the mass content of the carboxylic ester solvent in the electrolyte within a relatively large range, the cycle performance and fast charging performance of the battery cell 10 of this system can be improved.

[0089] [Negative electrode plate]

[0090] The negative electrode plate generally includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material.

[0091] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0092] In one embodiment, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as 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.).

[0093] In one embodiment, the negative electrode active material can be a negative electrode active material known in the art for batteries. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0094] In one embodiment, the negative electrode active material is a silicon-containing material. The silicon-containing material includes at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, silicon-containing alloy, or silicon-oxy-carbon composite material. By selecting the silicon-containing material as the negative electrode active material, it is beneficial to further improve the volumetric energy density of the battery cell 10. Combining with the structural design of the battery cell 10 in the foregoing embodiments, the battery cell 10 can have both high energy density and excellent safety performance.

[0095] In one embodiment, the negative electrode film layer further includes a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0096] In one embodiment, the negative electrode film layer further includes a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In one embodiment, the negative electrode film layer further includes other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0098] In one embodiment, the negative electrode plate can be prepared by the following method: forming a negative electrode slurry from the above components for preparing the negative electrode plate. For example, dispersing the negative electrode active material, conductive agent, binder, and any other components in a solvent (e.g., N-methylpyrrolidone) to form a negative electrode slurry. Then, coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0099] [Positive electrode plate]

[0100] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0101] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0102] In one embodiment, the positive current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as 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.).

[0103] In one embodiment, in addition to the lithium transition metal oxides and lithium-containing phosphates already mentioned in the foregoing embodiments, the positive electrode active material may also use positive electrode active materials for batteries well known in the art. As an example, the positive electrode active material may further include at least one of the following materials: a modified compound of a lithium-containing phosphate, a modified compound of a lithium transition metal oxide. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may also be used. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which may also be abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which may also be abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which may also be abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which may also be abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which may also be abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of its modified compounds, etc. Examples of the lithium-containing phosphate may include, but are not limited to, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4)、At least one of the composite material of lithium manganese phosphate and carbon and the composite material of lithium iron manganese phosphate and carbon. During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur. When the battery is discharged to different states, the molar content of Li in the positive electrode active material is different. In the enumeration of the positive electrode active material in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li will change. In the enumeration of the positive electrode active material in this application, the molar content of O is only the ideal state value. The release of oxygen from the lattice will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0104] In one embodiment, the positive electrode film layer further includes 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 fluorinated acrylate resin.

[0105] In one embodiment, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0106] In one embodiment, the positive electrode plate can be prepared in the following manner: The components for preparing the positive electrode plate are respectively formed into a positive electrode slurry. For example, the first positive electrode active material and / or the second 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 processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0107] [Electrolyte]

[0108] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. The electrolyte includes an electrolyte salt and a solvent.

[0109] In one embodiment, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluorooxalate phosphate.

[0110] In one embodiment, in addition to the carboxylic ester solvents already mentioned in the foregoing embodiments, the solvent may also be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, ethylene sulfite, propylene sulfite, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene sulfite, fluoroethylene sulfite, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0111] In one embodiment, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0112] [Separator membrane]

[0113] This application does not particularly limit the type of the separator membrane. For example, any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0114] In one embodiment, the material of the separator membrane may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation. When the separator membrane is a multi-layer composite film, the separator membrane of this application does not contain a PVDF coating.

[0115] In one embodiment, the negative electrode plate, the positive electrode plate and the separator may be made into an electrode assembly by a winding process or a stacking process.

[0116] This application does not particularly limit the shape of the battery cell 10, which may be cylindrical, square or any other shape.

[0117] [Lithium-ion battery]

[0118] The embodiment of this application provides a lithium-ion battery 20, including the battery cell 10 in the foregoing embodiment. The lithium-ion battery 20 may be a single physical module including one or more battery cells 10 to provide a higher voltage and capacity. When there are multiple battery cells 10, the multiple battery cells 10 are connected in series, parallel or in a hybrid connection through a bus bar component.

[0119] In some embodiments, the lithium-ion battery 20 may be a battery pack, including a box body 2 and the battery cell 10, and the battery cell 10 or the battery module is accommodated in the box body 2.

[0120] In some embodiments, the box body 2 can be part of the chassis structure of a vehicle. For example, a part of the box body 2 can form at least a part of the vehicle's floor, or a part of the box body 2 can form at least a part of the cross beams and longitudinal beams of the vehicle.

[0121] In some embodiments, the lithium-ion battery 20 can be located in an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0122] Continuing to refer to Figure 3 , the interior of the box body 2 is a hollow structure, and a plurality of battery cells 10 are accommodated in the box body 2. For example, a plurality of battery cells 10 are placed in the box body 2 after being connected in parallel or in series or in a mixed connection combination. The box body 2 can include a first box body part 21 and a second box body part 22, and the first box body part 21 and the second box body part 22 cover each other to form the box body 2. The shapes of the first box body part 21 and the second box body part 22 can be determined according to the shapes of the components accommodated inside, for example, according to the shape of the combination of a plurality of battery cells 10 accommodated inside, and at least one of the first box body part 21 and the second box body part 22 has an opening. For example, as Figure 3 shown, only one of the first box body part 21 and the second box body part 22 can be a hollow cuboid with an opening, and the other can be plate-shaped to cover the opening. Taking the second box body part 22 as a hollow cuboid with an opening and the first box body part 21 as plate-shaped as an example, then the first box body part 21 covers the opening of the second box body part 22 to form the box body 2 with a closed chamber, and this chamber can be used to accommodate a plurality of battery cells 10.

[0123] For another example, different from Figure 3 shown, the first box body part 21 and the second box body part 22 can both be hollow cuboids and each has an opening surface, the openings of the first box body part 21 and the second box body part 22 are arranged opposite to each other, and the first box body part 21 and the second box body part 22 are buckled with each other to form the box body 2 with a closed chamber, and this chamber can be used to accommodate a plurality of battery cells 10. A plurality of battery cells 10 are placed in the box body 2 formed after the first box body part 21 and the second box body part 22 are buckled with each other after being connected in parallel or in series or in a mixed connection combination.

[0124] In some embodiments, the lithium-ion battery 20 may further include other components. For example, the lithium-ion battery 20 may further include a busbar component, which can be used to achieve electrical connection between multiple battery cells 10, such as parallel connection, series connection, or hybrid connection. Specifically, the busbar component can achieve electrical connection between battery cells 10 by connecting the electrode terminals of the battery cells 10; alternatively, the busbar component can also achieve electrical connection between battery cells 10 by connecting other components of the battery cells 10. The busbar component can be fixed to the corresponding component of the battery cell 10 by welding. For example, it can be fixed to the electrode terminal, the sealing structure, or the housing, etc. The embodiments of the present application are not limited thereto.

[0125] The battery cells 10 can directly form the lithium-ion battery 20, or can first form a battery module, and then multiple battery modules form the lithium-ion battery 20.

[0126] [Power-consuming device]

[0127] The embodiments of the present application provide a power-consuming device, including the lithium-ion battery described in the above embodiments.

[0128] The power-consuming device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or an extended-range electric vehicle, etc.; the spacecraft includes an airplane, a rocket, a space shuttle, and a spaceship, etc.; the electric toy includes a fixed or mobile electric toy. For example, a game console, an electric vehicle toy, an electric ship toy, and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool. For example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact drill, a concrete vibrator, and a planer, etc. The embodiments of the present application do not impose special restrictions on the above power-consuming devices.

[0129] The present application provides a power-consuming device, and the power-consuming device is a vehicle.

[0130] The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or a range-extended vehicle, etc. A motor, a controller and a lithium-ion battery 20 can be arranged inside the vehicle. The controller is used to control the lithium-ion battery 20 to supply power to the motor. For example, the lithium-ion battery 20 can be arranged at the bottom, the front end or the rear end of the vehicle. The lithium-ion battery 20 can be used for power supply of the vehicle. For example, the lithium-ion battery 20 can be used as the operating power source of the vehicle for the vehicle's circuit system, such as for the working power requirements during vehicle starting, navigation and operation. In another embodiment of the present application, the lithium-ion battery 20 can not only be used as the operating power source of the vehicle, but also be used as the driving power source of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0131] Hereinafter, 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 a limitation to the present application. For those where specific technologies or conditions are not indicated in the embodiments, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0132] [Examples and Comparative Examples]

[0133] Example 1

[0134] (1) Preparation of negative electrode sheet

[0135] The negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water according to a mass ratio of 96:1.5:1.5:1.0, and after being fully stirred and mixed evenly, a negative electrode paste is prepared; the negative electrode paste is coated on a negative electrode current collector copper foil, and then through drying, cold pressing, and slitting, a negative electrode sheet is obtained.

[0136] (2) Preparation of positive electrode sheet

[0137] The positive electrode active material LiNi 0.65 Co 0.10 Mn 0.25 O 2 , binder polyvinylidene fluoride (PVDF), and conductive agent (acetylene black) are mixed evenly according to a mass ratio of 97.5:1.5:1, dissolved in a solvent N-methylpyrrolidone (NMP), and after being fully stirred and mixed evenly, a positive electrode paste is prepared; the positive electrode paste is uniformly coated on a positive electrode current collector aluminum foil, and then through drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0138] (3) Preparation of battery cell

[0139] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence and wind them to obtain the electrode assembly 12; place the electrode assembly 12 into the housing 111, add electrolyte, and after processes such as encapsulation, standing, formation, and aging, obtain the battery cell 10.

[0140] In the battery cell 10 of Example 1, the pressure relief mechanism 13 on the outer shell 11 is in the form of a notch, and the area S of the pressure relief mechanism 13 defined by the notch is 560 mm 2 , the concentration of lithium salt in the electrolyte is 1 M, and the lithium salt is LiPF 6 , and the carboxylic ester solvent is specifically methyl acetate, and its mass content W1 = 30%; the ionic conductivity σ of the electrolyte is measured to be 12.8 mS / cm.

[0141] Examples 2 - 5

[0142] Compared with Example 1, the difference lies in that the area of the pressure relief mechanism 13 is different from that in Example 1.

[0143] Examples 6 - 8

[0144] Compared with Example 1, the difference lies in the mass content of the carboxylic ester solvent in the electrolyte, and the measured ionic conductivity of the electrolyte is different from that in Example 1.

[0145] Comparative Example 1

[0146] Compared with Example 1, the area of the pressure relief mechanism 13 in Comparative Example 1 is not within the defined range.

[0147] The product parameters and performance parameters of Examples 1 - 8 and Comparative Example 1 are shown in Table 1.

[0148] Table 1: Product parameters and performance parameters of Examples 1 - 8 and Comparative Example 1

[0149]

[0150]

[0151] In Table 1, "W1" represents the mass fraction of the carboxylic ester solvent in the electrolyte, "σ" represents, "S" represents the area of the pressure relief mechanism 13, "weight loss rate" represents the weight loss rate of the battery cell 10 in the safety test, and "number of cycles" represents the number of cycles of the battery cell 10 under 3C fast charging. The specific test process is shown in the test part later.

[0152] According to the comparative analysis of the examples and the comparative examples, it can be seen that both the examples and the comparative examples use a high-ion-conductivity electrolyte including a carboxylic acid ester solvent, and the battery cell 10 can have good fast-charging cycle performance. However, in the safety test, the weight loss rate of the comparative example is much higher than that of the example, indicating that in the battery cell 10 with high ionic conductivity, by designing a pressure relief mechanism 13 with an area corresponding to the ionic conductivity range, the safety problem of the battery cell 10 using the above electrolyte can be effectively solved, enabling the battery cell 10 to obtain good fast-charging cycle performance and safety performance.

[0153] According to the comparative analysis of Examples 1-5, it can be seen that when the mass fraction of the carboxylic acid ester solvent is constant, the larger the area of the pressure relief mechanism 13, the smaller the weight loss rate, and the better the safety performance of the battery cell 10. This shows the direct influence of the area of the pressure relief mechanism 13 on the safety performance of the battery cell 10.

[0154] According to the comparative analysis of Examples 1, 6-8, it can be seen that when the area of the pressure relief mechanism 13 is constant, the larger the mass fraction of the carboxylic acid ester solvent, the higher the ionic conductivity of the electrolyte, and the better the cycle performance of the battery cell 10, but the weight loss rate during the safety test is larger. This shows the direct influence of the carboxylic acid ester solvent on the cycle performance and safety performance of the battery cell 10.

[0155] The following briefly introduces the test methods for 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 well-known test methods in the art can also be used for testing.

[0156] 1. Test method for the ionic conductivity of the electrolyte

[0157] The test method follows HG / T 4067-2015. Use a conductivity meter to test the conductivity of the electrolyte to be tested: Take about 100 mL of the sample to be tested with a dry, clean and corrosion-resistant sample bottle, seal it and place it in a constant temperature water bath at 25 ± 0.5 °C. When the temperature of the sample to be tested is constant, replace the sample bottle cap with a rubber stopper with electrodes inserted. When the temperature is within the range of 25 ± 0.5 °C, read the data, which is the conductivity of the sample to be tested.

[0158] 2. Test method for the area of the pressure relief mechanism

[0159] Perform a CT scan on the battery cell 10 and test the scanned image. According to the scanned image, the shape and size of the pressure relief mechanism 13 can be measured. For the pressure relief mechanism 13 with a regular shape, its area can be calculated according to the area calculation formula for regular shapes. For the pressure relief mechanism 13 with an irregular shape, it can be approximated to a regular shape on the computer and then its area can be calculated through the area calculation formula for regular shapes.

[0160] 3. Test Method for Mass Content of Carboxylate Solvent in Electrolyte

[0161] Refer to the standard GB / T 9722-2006 to quantitatively analyze the content of carboxylate in the electrolyte by organic gas chromatography analysis method.

[0162] Weigh the battery, and record the mass as M0. Disassemble the battery, pour out the free electrolyte, and take the free electrolyte to test the electrolyte composition. Take out the internal electrode assembly and separate the positive electrode plate, negative electrode plate, separator, and mechanical parts. Immerse and clean the positive electrode plate, negative electrode plate, separator, and mechanical parts with DMC solvent for 24 h to 48 h, and soak repeatedly for more than 3 times. Place the above-mentioned positive electrode plate, negative electrode plate, separator, and mechanical parts in an oven at 100 °C for more than 24 h until completely dried. Weigh the above-mentioned dried positive electrode plate, negative electrode plate, separator, and mechanical parts, and record the mass as M1. Thus, the weight of the electrolyte in the lithium-ion battery d3 = M0 - M1.

[0163] Use an IC ion chromatograph to test the inorganic content in the electrolyte. Weigh a quantitative electrolyte (the dilution concentration is in the middle of the standard curve), make up the volume to 100 mL with ultrapure water, and automatically inject the sample for ion chromatographic detection to test the inorganic ion chromatogram. Compare the corresponding inorganic substances according to the peak position of the chromatogram, calculate the corresponding inorganic ion concentration according to the peak area, and calculate the mass of inorganic substances M2 in the electrolyte through the mass of the electrolyte. Dilute the above-mentioned free electrolyte with acetonitrile by 3 to 10 times to obtain the diluted electrolyte solution to be tested. Use a GC-MS 3100 organic component gas chromatograph to perform a full scan qualitative analysis on the above-mentioned diluted electrolyte solution. The inlet temperature is 250 °C, and the scanning range is 35 μm to 270 μm. After the test is completed, obtain the total ion current chromatogram of each organic substance. Compare the corresponding organic substances according to the peak position of the chromatogram, calculate the percentage content of each organic substance according to the peak area, and calculate the mass of each organic substance according to the mass of organic substances in the electrolyte d3 - M2 and the percentage content of each organic substance. For example, the mass of the carboxylate solvent d1 in the electrolyte can be calculated.

[0164] Finally, calculate the mass content of the first solvent by d1 / d3.

[0165] 4. Test Method for Cycle Performance of Battery Cell

[0166] At 25±5°C, fully charge a battery cell 10 at a constant current of 0.33C until it reaches 10% SOC, then charge it from 10% SOC to 45% SOC at 3.7C, then from 45% SOC to 50% SOC at 3.4C, from 50% SOC to 55% SOC at 3.2C, from 55% SOC to 60% SOC at 2.9C, from 60% SOC to 65% SOC at 2.6C, from 65% SOC to 70% SOC at 2.4C, from 70% SOC to 75% SOC at 2.1C, from 75% SOC to 80% SOC at 1.9C, from 80% SOC to 100% SOC at 0.33C. After standing for 30 minutes, discharge it at 1C to 2.5V, and record the discharge capacity C1. This is one charge-discharge cycle. Perform multiple cycles on the battery cell 10 until the discharge capacity of the battery cell 10 decays to 0.8C1 (i.e., the state of health of the battery reaches 80% SOH), and record the number of cycles.

[0167] 5. Test method for the weight loss rate of the battery cell

[0168] Fully charge a battery cell 10 and weigh it, and record the mass as M0. Heat the battery cell 10 at a heating rate of 5°C / min to 60°C and keep it warm for 5 hours, then keep it at each 5°C increase for 30 minutes until thermal runaway occurs. Weigh the battery cell 10 again after thermal runaway, and record the mass as M1. The weight loss rate of the battery cell 10 = (M1 - M0) / M0.

Claims

1. A battery cell, characterized in that: The battery cell comprises a housing and an electrode assembly and an electrolyte contained in the housing; The electrolyte includes a carboxylate solvent, and the ion conductivity σ of the electrolyte satisfies: 9mS / cm≤σ≤25mS / cm; The housing includes a pressure relief mechanism, and the area S of the pressure relief mechanism satisfies: 200mm 2 ≤S≤900mm 2 .

2. The battery cell according to claim 1, characterized in that: The carboxylate solvent includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate and ethyl acrylate.

3. The battery cell according to claim 1 or 2, characterized in that: Based on the total mass of the electrolyte, the mass fraction W1 of the carboxylic acid ester solvent satisfies: 5wt%≤W1≤80wt%.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The battery cell is arranged in a box body, and a heat insulating member is arranged on the inner wall of the box body opposite to the pressure relief mechanism.

5. The battery cell according to claim 4, characterized in that: A vertical distance L between the heat insulating member and the pressure relief mechanism satisfies: 6 mm ≤ L ≤ 13 mm.

6. The battery cell according to claim 5, characterized in that: 7mm≤L≤11mm.

7. The battery cell according to any one of claims 4 to 6, characterized in that: The thickness h of the thermal insulation element satisfies: 0.2mm≤h≤3mm.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The time t for charging the battery cell from 10% SOC to 80% SOC satisfies: t≤20 min.

9. The battery cell according to any one of claims 1 to 8, characterized in that: The capacity C of the battery cell satisfies: 80Ah≤C≤160Ah.

10. The battery cell according to claim 9, characterized in that: 100Ah≤C≤150Ah.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium transition metal oxide.

12. The battery cell according to claim 11, characterized in that: The battery cell satisfies at least one of the following (1)-(3): (1)600mm 2 ≤S≤900mm 2 ; (2) 0.8mm≤h≤3mm; (3) 10%wt≤W1≤40wt%.

13. The battery cell according to any one of claims 1 to 10, characterized in that: The electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

14. The battery cell according to claim 13, characterized in that: The battery cell satisfies at least one of the following (4)-(6): (4)200mm 2 ≤S≤500mm 2 ; (5) 0.2mm≤h≤1mm; (6) 30%wt≤W1≤70wt%.

15. A lithium ion battery, characterized in that: The lithium-ion battery comprises the battery cell according to any one of claims 1 to 14.

16. An electrical device, characterized in that: The electrical device comprises the battery cell according to any one of claims 1 to 14, and / or the lithium-ion battery according to claim 15.

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