Secondary battery, battery module, battery pack and electrical device containing these

Abstract

Secondary battery (5) comprising an electrolyte and a negative electrode, wherein the electrolyte comprises a low-viscosity solvent and the viscosity of the low-viscosity solvent at 25 °C is 0.3 mPa·s to 0.6 mPa·s; the low-viscosity solvent comprises at least one solvent selected from dimethyl carbonate, DMC, ethyl acetate, EA, methyl acetate, MA, and acetonitrile, ACN; the mass fraction of the low-viscosity solvent in the total solvent in the electrolyte is 20% to 80%; the electrolyte comprises cyclic carbonate, and the mass fraction of the cyclic carbonate in the total solvent in the electrolyte is 20% to 40%; the electrolyte comprises an electrolyte salt, and the mass fraction of the electrolyte salt in the electrolyte is 10% to 23%, the negative electrode comprises a current collector of the negative electrode and an active material layer of the negative electrode arranged on at least one surface of the current collector of the negative electrode, the porosity P of the active material layer of the negative electrode is 20% to 60%, the OI value of the active material layer of the negative electrode is 3 to 24, the coating weight CW of the active material layer of the negative electrode is 6.5 mg / cm² 2 up to 19.5 mg / cm² 2 amounts; the active material layer of the negative electrode comprises an active material of the negative electrode, and the active material of the negative electrode comprises synthetic graphite; and OI = C004 / C110, where C004 is the peak area of ​​a characteristic 004 diffraction peak in an X-ray diffraction pattern of the active material layer of the negative electrode and C110 is the peak area of ​​a characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode.

Description

TECHNICAL AREA

[0001] This application relates to the field of secondary batteries and in particular to a secondary battery, a battery module, a battery pack and an electrical device containing these. BACKGROUND

[0002] Due to the increasing demand for clean energy, secondary batteries have been used more frequently in recent years in energy storage systems such as hydroelectric power plants, thermal power plants, wind power plants, and solar power plants, as well as in a variety of other areas including power tools, electric vehicles, military equipment, and aerospace. With the significant expansion of the application areas of secondary batteries, higher demands have also been placed on their rate performance, energy density, and storage capacity (especially their storage capacity at high temperatures).

[0003] To improve battery performance, such as rate performance, the following techniques have been proposed. Patent document CN113097429A describes how the electrochemical device can improve the battery's rate performance without affecting its energy density by adjusting the ratio between the terminal voltages of the active materials of the electrochemical device's negative electrode and the excess coefficients of the electrochemical device (a ratio of the capacitance of a negative electrode to the capacitance of a positive electrode, provided that the negative and positive electrodes have the same area). Patent document CN113036298A describes how the secondary battery achieves both good rate performance and a long lifespan by adjusting the OI values ​​of the first and second active material layers of the negative electrode.Patent document CN111653829A describes how the rate performance and cycle performance of the battery can be improved by adding a film-forming additive to the electrolyte. Patent document CN108847489B describes how battery performance, for example the rate performance, can be improved by improving the negative electrode. SUMMARY Technical Problem

[0004] Although the preceding documents described how battery performance, such as rate performance, was improved through the use of various technical means, the improvements of the preceding technologies relate only to positive electrodes, negative electrodes, and electrolytes, without considering the design of the relationship between electrodes, such as negative electrodes, and the electrolytes to improve the battery's rate performance, cycle performance, and storage capacity. Furthermore, the aforementioned state of the art does not yet significantly (or at all) mitigate the problems of strong internal polarization caused by high charging currents and high internal temperatures (leading to problems such as battery swelling). Technical solution

[0005] The inventors of this application have discovered through intensive studies that the rate performance, cycle performance and storage performance of secondary batteries can be improved by using specific negative electrodes and electrolytes, as well as by designing a specific relationship between the negative electrodes and the electrolytes of the secondary batteries.

[0006] According to a first aspect of this application, a secondary battery is provided which contains an electrolyte and a negative electrode, wherein The electrolyte contains a low-viscosity solvent, an electrolyte salt, and a solvent with a high dielectric constant; the viscosity of the low-viscosity solvent at 25 °C is 0.3 mPa·s to 0.6 mPa·s; the dielectric constant of the high-dielectric-constant solvent is between 30 F / m and 100 F / m, and the mass fraction of the high-dielectric-constant solvent in the total solvent in the electrolyte is more than 20%; and the negative electrode includes a current collector of the negative electrode and an active material layer of the negative electrode, which is arranged on at least one surface of the current collector of the negative electrode; and The secondary battery fulfills the following relational relationship: 1×10−4≤B×C×POI×CW≤1×10−3 where B is the mass fraction of the low-viscosity solvent in the total solvent in the electrolyte; C is the mass fraction of the electrolyte salt in the electrolyte; P is the porosity of the active material layer of the negative electrode; CW is the coating weight of the active material layer of the negative electrode, measured in mg / cm² 2, is; and OI is the orientation index of the active material layer of the negative electrode; and OI = C004 / C110, where C004 is the peak area of ​​a characteristic 004 diffraction peak in an X-ray diffraction pattern of the active material layer of the negative electrode and C110 is the peak area of ​​a characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode.

[0007] In this aspect, the rate performance, cycle performance and storage performance of the secondary battery can be improved by using a specific negative electrode and electrolyte, as well as by designing a specific relationship between the negative electrode and the electrolyte of the battery.

[0008] According to each aspect of this application, the low-viscosity solvent may contain at least one solvent selected from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA), and acetonitrile (ACN). This may improve the rate performance of the secondary battery.

[0009] According to each aspect of this application, the mass fraction B of the low-viscosity solvent in the total solvent in the electrolyte can be 10% to 80% and optionally 20% to 70%. This can improve the rate performance of the secondary battery.

[0010] According to each aspect of this application, the electrolyte salt may contain at least one salt selected from LiPF6, LiBF4, LiN(SO2F)2 (LiFSI), LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), and LiBF2C2O4 (LiDFOB); or the electrolyte salt may contain at least one salt selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3. This may improve performance, for example, the rate performance of the secondary battery.

[0011] According to each aspect of this application, the mass fraction C of the electrolyte salt in the electrolyte can be 10% to 23% and optionally 13% to 20%. This can improve performance, for example, the rate performance of the secondary battery.

[0012] According to each aspect of this application, the solvent with a high dielectric constant can contain cyclic carbonate; optionally, the cyclic carbonate contains at least one cyclic carbonate selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and fluoroethylene carbonate. This can improve performance, for example, the rate performance of the secondary battery.

[0013] According to every aspect of this application, the mass fraction of the high dielectric constant solvent in the total solvent in the electrolyte can be between 20% and 40%. If the mass fraction of the high dielectric constant solvent in the total solvent in the electrolyte is within the aforementioned range, this contributes to improving the rate performance, cycle performance, and storage performance of the secondary battery.

[0014] According to each aspect of this application, the electrolyte may further comprise at least one electrolyte selected from diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate, and ethyl propionate. This may contribute to improving the rate performance, cycle performance, and storage performance of the secondary battery.

[0015] According to each aspect of this application, the electrolyte may further contain a film-forming additive, and the film-forming additive contains at least one additive selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3-propanesultone, lithium difluorophosphate, lithium bisfluorooxalate borate, nitrile compound, and cyclic sulfate, the cyclic sulfate optionally being ethylene sulfate. This can contribute to improving the performance of the secondary battery, such as rate performance, cycle performance, storage performance, and flame-retardant performance.

[0016] According to every aspect of this application, the conductivity of the electrolyte at 25 °C can range from 8 mS / cm to 16 mS / cm. This can contribute to improving the rate performance, cycle performance, and storage performance of the secondary battery.

[0017] According to every aspect of this application, the viscosity of the electrolyte at 25 °C can range from 1 mPa·s to 7 mPa·s. This can contribute to improving the rate performance, cycle performance, and storage performance of the secondary battery.

[0018] According to each aspect of this application, the OI value of the active material layer of the negative electrode can be 3 to 24 and optionally 8 to 24. This can help improve the rate performance, cycle performance, and storage performance of the secondary battery.

[0019] According to every aspect of this application, the coating weight CW of the active material layer of the negative electrode can be 6.5 mg / cm². 2 up to 19.5 mg / cm² 2 and optionally 6.5 mg / cm² 2 up to 13 mg / cm² 2 This can help improve the rate performance, cycle performance, and storage performance of the secondary battery.

[0020] According to every aspect of this application, the porosity P of the active material layer of the negative electrode can be from 20% to 60%. This can help to improve the rate performance, cycle performance, and storage performance of the secondary battery.

[0021] According to each aspect of this application, the active material of the negative electrode may contain at least one material selected from artificial graphite, natural graphite, soft carbon, hard carbon and a silicon-based material, and optionally the silicon-based material may contain at least one material selected from elemental silicon, silicon dioxide, silicon-carbon composite and silicon-based alloy (if the secondary battery is a lithium-ion battery);or the active material of the negative electrode may contain at least one material selected from natural graphite, modified graphite, synthetic graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, iron(III) oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate, and sodium terephthalate (if the secondary battery is a sodium-ion battery). This may help to improve the rate performance, cycle performance, and storage performance of the secondary battery.

[0022] According to each aspect of this application, the mass fraction of the silicon-based material in the total active material of the negative electrode is 0% to 30% and optionally 0% to 10%. This can contribute to improving the rate performance, cycle performance, and storage performance of the secondary battery.

[0023] According to each aspect of this application, the secondary battery may further comprise a positive electrode, wherein the positive electrode comprises an active material of the positive electrode with the molecular formula LiNi x Co y Mn z M 1-x-y-zO2 contains, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5 and x + y + z = 1, optionally 0.5 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.3 and 0 ≤ z ≤ 0.3, and M is at least one selected from Zr, Al, Mg, Sb, Fe, Cu and W (if the secondary battery is a lithium-ion battery), or the positive electrode contains at least one positive electrode active material selected from layered transition metal oxides, polyanionic compounds, Prussian blue compounds, sulfides, nitrides, carbides and titanates (if the secondary battery is a sodium-ion battery). This can help improve the rate performance, cycle performance, and storage performance of the secondary battery.

[0024] According to a second aspect of this application, a battery module is provided that contains the aforementioned secondary battery. The battery module exhibits excellent rate performance, cycle life, and storage performance.

[0025] According to a third aspect of this application, a battery pack is provided that contains the aforementioned battery module. The battery pack exhibits excellent rate performance, cycle life, and storage performance.

[0026] According to a fourth aspect of this application, an electrical device is provided which includes at least one of the aforementioned components, namely the secondary battery, the battery module, or the battery pack. The electrical device exhibits excellent rate performance, cycle performance, and storage performance. Beneficial effects

[0027] This application provides a secondary battery which, through the use of a specific negative electrode and a specific electrolyte, as well as through the design of a specific relationship between the negative electrode and the electrolyte, exhibits excellent rate performance, cycle performance, and storage performance. This application further provides a battery module, a battery pack, and an electrical device containing the aforementioned secondary battery. The battery module, the battery pack, and the electrical device all exhibit excellent rate performance, cycle performance, and storage performance. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application. Fig. Figure 2 is an exploded view of the secondary battery according to the embodiment of this application in Fig. 1. Fig. Figure 3 is a schematic diagram of a battery module according to an embodiment of this application. Fig. Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application. Fig. Figure 5 is an exploded view of the battery pack according to the embodiment of this application in Fig. 4. Fig. Figure 6 is a schematic diagram of an electrical device that uses a secondary battery as a power source in an embodiment of this application. DESCRIPTION OF THE EXECUTION FORMS

[0028] The secondary battery in this application is described in detail below. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of a well-known fact or repeated descriptions of an essentially identical structure have been omitted. This is to avoid unnecessarily convoluted descriptions and to facilitate understanding by a person skilled in the art. Furthermore, the following descriptions and embodiments are intended to enable a person skilled in the art to fully understand this application and are not meant to limit the subject matter described in the claims.

[0029] Unless otherwise stated, all embodiments and optional embodiments of this application may be combined to form a new technical solution.

[0030] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form a new technical solution.

[0031] For the sake of simplicity, only a few numerical ranges are explicitly specified in this application. However, any lower bound can be combined with any upper bound to form an unspecified range, any lower bound can be combined with any lower bound to form an unspecified range, and any upper bound can be combined with any upper bound to form an unspecified range. Furthermore, even if not explicitly stated, any point or individual value between the endpoints of a range is included in the range.Therefore, each point or individual value can be used as its own lower or upper limit, which can be combined with another point or individual value, or combined with another lower or upper limit, to form an area not explicitly recorded.

[0032] When describing this application, it should be noted that “more than” or “less than” includes the current number and that “more” in “one or more” means two or more than two, unless otherwise specified.

[0033] A first embodiment of this application can provide a secondary battery, wherein the secondary battery includes an electrolyte and a negative electrode, wherein The electrolyte contains a low-viscosity solvent, an electrolyte salt, and a solvent with a high dielectric constant; the viscosity of the low-viscosity solvent at 25 °C is 0.3 mPa·s to 0.6 mPa·s; the dielectric constant of the high-dielectric-constant solvent is between 30 F / m and 100 F / m, and the mass fraction of the high-dielectric-constant solvent in the total solvent in the electrolyte is more than 20%; and the negative electrode includes a current collector of the negative electrode and an active material layer of the negative electrode, which is arranged on at least one surface of the current collector of the negative electrode; and The secondary battery fulfills the following relational relationship: 1×10−4≤B×C×POI×CW≤1×10−3 where B is the mass fraction of the low-viscosity solvent in the total solvent in the electrolyte; C is the mass fraction of the electrolyte salt in the electrolyte; P is the porosity of the active material layer of the negative electrode; CW is the coating weight of the active material layer of the negative electrode, measured in mg / cm² 2 , is; and OI is the orientation index of the active material layer of the negative electrode; and OI = C004 / C110, where C004 is the peak area of ​​a characteristic 004 diffraction peak in an X-ray diffraction pattern of the active material layer of the negative electrode and C110 is the peak area of ​​a characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode.

[0034] The secondary battery is a complex electrochemical system, and many of its elements (for example, the type of active materials of the positive and negative electrodes, the composition of the electrolyte, and the internal structure of the battery) have a significant impact on its performance, such as rate power, cycle power, and storage power. The inventors of this application have discovered through intensive studies that, among the components of the secondary battery, the design of the electrolyte and the negative electrode have a major influence on the rate power, cycle power, and storage power of the secondary battery. Specifically, the proportion of a solvent with high kinetics (e.g., a low-viscosity solvent) and the proportion of a solvent with a high dielectric constant (e.g., a high-density solvent) have a significant impact on the battery's performance.a cyclic carbonate), the concentration of the electrolyte salt, the porosity of the active material layer of the negative electrode, the coating weight of the active material layer of the negative electrode and the orientation index of the active material of the negative electrode in the secondary battery have a major influence on the rate performance, the cycle performance and the storage performance.

[0035] Based on this, the inventors of this application improve the rate performance, cycle performance and storage performance of the secondary battery by using a specific negative electrode and a specific electrolyte, as well as by designing a specific relationship between the negative electrode and the electrolyte of the battery.

[0036] In this embodiment, the viscosity of the low-viscosity solvent at 25 °C is 0.3 mPa·s to 0.6 mPa·s. Using such a lower-viscosity solvent improves the electrolyte conductivity, allowing the secondary battery to achieve a higher rate of charge. Furthermore, using a solvent with a high dielectric constant in the electrolyte can ensure a certain degree of solvation of the electrolyte salt, thereby increasing the electrolyte conductivity and contributing to improved rate of charge of the secondary battery. Based on this, the proportion of the high-kinetic solvent (e.g., the low-viscosity solvent) and the proportion of the high-dielectric constant solvent (e.g., the high-viscosity solvent) are determined.The concentration of the electrolyte salt (cyclic carbonate), the porosity of the active material layer of the negative electrode, the coating weight of the active material layer of the negative electrode, and the orientation index of the active material of the negative electrode in the secondary battery are adjusted so that the aforementioned parameters satisfy the aforementioned relational relationship and the rate performance, cycle performance, and storage performance of the secondary battery can be improved. In this case, the secondary battery exhibits low polarization, low internal resistance, and a substantially unchanged battery temperature at high rates (e.g., during fast charging).

[0037] With a view to improving the rate performance of the secondary battery, the aforementioned low-viscosity solvent is preferably used in the secondary battery of this embodiment. In this application, the type of low-viscosity solvent is not particularly restricted, provided that the low-viscosity solvent does not readily cause side reactions in the secondary battery and can improve the rate performance of the secondary battery. For example, the low-viscosity solvent can contain at least one low-viscosity solvent selected from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA), and acetonitrile (ACN).

[0038] With regard to improving the rate performance of the secondary battery, the mass fraction B of the low-viscosity solvent in the total solvent in the electrolyte of the secondary battery in this embodiment can be 10% to 80% and optionally 20% to 70%. Optionally, the mass fraction B of the low-viscosity solvent in the total solvent in the electrolyte can be 10% to 70%, 10% to 60%, 10% to 50%, 20% to 50%, 30% to 70%, 30% to 60%, or 30% to 40%. Optionally, the mass fraction B of the low-viscosity solvent in the total solvent in the electrolyte can be 15%, 25%, 35%, 45%, 55%, 65%, or 75%. As described above, the low-viscosity solvent can improve the rate performance of the secondary battery.However, if the proportion of low-viscosity solvent is too high, the proportion of solvent with a high dielectric constant in the electrolyte may be too low. This impairs the dissociation of the electrolyte salt and reduces the ionic conductivity of the electrolyte, thereby degrading the charging rate of the secondary battery. Conversely, if the proportion of low-viscosity solvent is too low, the effect of improving the charging rate of the secondary battery may be negligible.

[0039] The types of electrolyte salts used in this application are not particularly restricted; any electrolyte salts commonly used in this field may be employed. With a view to improving performance characteristics such as the rate performance of the secondary battery, the electrolyte salt in this embodiment may contain at least one electrolyte selected from LiPF6, LiBF4, LiN(SO2F)2 (LiFSI), LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), and LiBF2C2O4 (LiDFOB); or the electrolyte salt may contain at least one electrolyte salt selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3. LiFSI and LiPF6 are preferably used as lithium salts.

[0040] With a view to improving performance characteristics such as the rate performance of the secondary battery, the mass fraction C of the electrolyte salt in the electrolyte in this embodiment is 10% to 23% and optionally 13% to 20%. Optionally, the mass fraction B of the low-viscosity solvent in the total solvent in the electrolyte can be 10% to 22%, 10% to 20%, 10% to 18%, 10% to 16%, 10% to 14%, 10% to 15%, 11% to 20%, 12% to 18%, 12% to 17%, 12% to 15%, 13% to 20%, 13% to 18%, or 13% to 15%.

[0041] The electrolyte salt can provide active ions such as lithium ions, and an electrolyte with a higher concentration of active ions can improve concentration polarization during fast charging. However, at excessively high concentrations of the electrolyte salt, the electrolyte exhibits a relatively high viscosity, which degrades the charging rate performance. Keeping the electrolyte salt concentration within the aforementioned range contributes to improved charging rate performance of the secondary battery.

[0042] With a view to improving performance characteristics such as the rate performance of the secondary battery, the solvent with high dielectric constant in this embodiment can contain cyclic carbonate, and the cyclic carbonate can contain at least one cyclic carbonate selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and fluoroethylene carbonate.

[0043] The solvent with a high dielectric constant possesses good solvation properties. Therefore, an electrolyte containing a certain amount of this solvent can dissociate the electrolyte salt more effectively, achieving a higher ionic conductivity of the electrolyte and improving the charging rate performance of the secondary battery.

[0044] With regard to improving performance characteristics such as the rate performance of the secondary battery, the mass fraction of the high dielectric constant solvent in the electrolyte can be 20% to 40% in this embodiment. Optionally, the mass fraction of the high dielectric constant solvent in the electrolyte can be 20% to 35%, 20% to 30%, 20% to 25%, 25% to 40%, 25% to 36%, 25% to 32%, 25% to 28%, 30% to 40%, or 30% to 35%. Optionally, the mass fraction of the high dielectric constant solvent in the electrolyte can be 21%, 22%, 23%, 24%, 27%, 28%, 29%, 33%, 34%, 37%, 38%, or 39%.If the mass fraction of the solvent with a high dielectric constant (HdP) in the electrolyte is too low, the electrolyte salt cannot dissociate sufficiently, thus reducing the ionic conductivity of the electrolyte. Conversely, if the mass fraction of the HdP in the electrolyte is excessively high, the viscosity of the electrolyte can increase. Consequently, the penetration of the electrolyte to the positive and negative electrodes can be impaired, reducing the performance of the secondary battery. Maintaining the mass fraction of the HdP within the aforementioned range improves the rate performance, cycle life, and storage capacity of the secondary battery.

[0045] With a view to improving the performance characteristics such as rate performance, cycle performance and storage performance of the secondary battery, the electrolyte in this embodiment may further contain at least one electrolyte selected from diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate and ethyl propionate.

[0046] With a view to improving performance characteristics such as rate performance, cycle performance, and storage capacity of the secondary battery, the electrolyte in this embodiment may additionally contain a film-forming additive. The film-forming additive may contain at least one additive selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3-propanesultone, lithium difluorophosphate, lithium bisfluorooxalate borate, a nitrile compound, and cyclic sulfate, the cyclic sulfate optionally being ethylene sulfate. The film-forming additive may form a low-resistance protective film on the surface of the positive electrode and / or the negative electrode of the secondary battery to reduce side reactions in the battery and thereby improve the rate performance, cycle performance, and storage capacity of the secondary battery.

[0047] With a view to improving performance characteristics such as rate performance, cycle performance, and storage capacity of the secondary battery, the conductivity of the electrolyte at 25 °C in this embodiment can be 8 mS / cm to 16 mS / cm. The conductivity can be 8 mS / cm to 16 mS / cm, 8 mS / cm to 14 mS / cm, 8 mS / cm to 12 mS / cm, 8 mS / cm to 10 mS / cm, 9 mS / cm to 15 mS / cm, 9 mS / cm to 13 mS / cm, 9 mS / cm to 11 mS / cm, 10 mS / cm to 15 mS / cm, or 11 mS / cm to 16 mS / cm.

[0048] With a view to improving performance characteristics such as rate performance, cycle performance, and storage capacity of the secondary battery, the viscosity of the electrolyte at 25 °C in this embodiment can range between 1 mPa·s and 7 mPa·s. The viscosity can be 1 mPa·s to 7 mPa·s, 1 mPa·s to 6 mPa·s, 1 mPa·s to 5 mPa·s, 1 mPa·s to 4 mPa·s, 2 mPa·s to 7 mPa·s, 2 mPa·s to 5 mPa·s, 2 mPa·s to 4 mPa·s, 3 mPa·s to 7 mPa·s, 2 mPa·s to 6 mPa·s, or 2 mPa·s to 6.5 mPa·s.

[0049] With regard to improving performance characteristics such as rate performance, cycle performance, and storage performance of the secondary battery, the OI value of the active material layer of the negative electrode in this embodiment can be 3 to 24 and optionally 8 to 24. Optionally, the OI value of the active material layer of the negative electrode can be 3 to 20, 3 to 18, 3 to 15, 3 to 14, 3 to 10, 3 to 8, 3 to 6, 5 to 22, 5 to 20, 5 to 18, 5 to 10, 5 to 8, 6 to 22, 6 to 18, 6 to 15, 6 to 10, 6 to 8, 7 to 18, 7 to 12, 7 to 10, 7 to 9, 8 to 18, 8 to 14, or 8 to 10.

[0050] A lower OI value promotes the rapid incorporation of lithium ions into the negative electrode. If the OI value of the active material layer of the negative electrode is within the range mentioned above, this contributes to the secondary battery exhibiting excellent rate performance, cycle life, and storage performance.

[0051] A person skilled in the art understands that the OI value of the active material layer of the negative electrode is used to specify an orientation index of the active material layer of the negative electrode, i.e., a degree of anisotropy of the crystal grain arrangement in the active material layer of the negative electrode. In this application, the OI value is defined as the area ratio of the characteristic 004 diffraction peak to the characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode. More precisely, OI = C004 / C110, where C004 is the peak area of ​​the characteristic 004 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode, and C110 is the peak area of ​​the characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode.

[0052] The OI value of the active material layer of the negative electrode can be measured using a known prior art method, for example, the method described in the embodiments of this application.

[0053] During the production of the negative electrode, the OI value of the active material layer of the negative electrode can be controlled by adjusting the following parameters.

[0054] The mean particle size by volume Dv50 of the active material of the negative electrode and the OI target value G OIBoth the active material powder and the active material powder have a specific influence on the OI value of the active material layer of the negative electrode. In general, a higher Dv50 value of the active material of the negative electrode corresponds to a higher OI value of the active material layer of the negative electrode, and a higher target OI value of the active material powder of the negative electrode corresponds to a higher OI value of the active material layer of the negative electrode.

[0055] During battery manufacturing, magnetic field induction technology can be used in a coating or drying process to artificially induce the arrangement of the active material in the negative electrode, thereby changing the OI value of the active material layer. Alternatively, it can be used in a cold pressing process to change the arrangement of the active material in the negative electrode by adjusting the compaction density of the active material layer, thereby controlling the OI value of the active material layer.

[0056] With a view to improving performance characteristics such as rate performance, cycle performance and storage performance of the secondary battery, the coating weight CW of the active material layer of the negative electrode in this embodiment can be 6.5 mg / cm². 2 up to 19.5 mg / cm² 2and optionally 6.5 mg / cm² 2 up to 13 mg / cm² 2 Optionally, the coating weight CW of the active material layer of the negative electrode can be 6.5 mg / cm². 2 up to 18 mg / cm² 2 , 6.5 mg / cm² 2 up to 16 mg / cm² 2 , 6.5 mg / cm² 2 up to 14 mg / cm² 2 , 6.5 mg / cm² 2 up to 12 mg / cm² 2 , 6.5 mg / cm² 2 up to 10 mg / cm² 2 , 7 mg / cm 2 up to 18 mg / cm² 2 , 7 mg / cm 2 up to 16 mg / cm² 2 , 7 mg / cm 2 up to 14 mg / cm² 2 , 7 mg / cm 2 up to 12 mg / cm² 2 , 7 mg / cm 2 up to 10 mg / cm² 2 , 8 mg / cm 2 up to 18 mg / cm² 2 , 8 mg / cm 2 up to 16 mg / cm² 2 , 8 mg / cm 2 up to 14 mg / cm² 2 , 8 mg / cm 2 up to 12 mg / cm² 2 , 8 mg / cm 2 up to 10 mg / cm² 2 , 8.5 mg / cm² 2 up to 18 mg / cm² 2 , 8.5 mg / cm² 2 up to 16 mg / cm² 2, 8.5 mg / cm² 2 up to 14 mg / cm² 2 , 8.5 mg / cm² 2 up to 12 mg / cm² 2 or 8.5 mg / cm² 2 up to 10 mg / cm² 2 Furthermore, and optionally, the coating weight CW of the active material layer of the negative electrode can be 9 mg / cm². 2 , 11 mg / cm 2 , 13 mg / cm 2 , 15 mg / cm 2 , 17 mg / cm 2 or 19 mg / cm² 2 be.

[0057] The coating weight of the active material layer of the negative electrode is the mass of the active material layer applied per unit area. A negative electrode with a lower coating weight exhibits lower diffusion resistance, allowing lithium ions to diffuse more readily into the active material layer and thus improving the charging rate of the secondary battery. However, the proportion of active material in the negative electrode directly influences the energy density of the secondary battery, which is why the coating weight of the active material layer should not be too low. If the coating weight (CW) of the active material layer of the negative electrode is within the aforementioned range, it contributes to improved charging rate, cycle life, and storage capacity of the secondary battery.

[0058] With a view to improving performance characteristics such as rate performance, cycle performance and storage performance of the secondary battery, the porosity P of the active material layer of the negative electrode in this embodiment can be 20% to 60%. Optionally, the porosity P of the active material layer of the negative electrode can be 20% to 55%, 20% to 50%, 20% to 45%, 20% to 40%, 20% to 35%, 25% to 55%, 25% to 50%, 25% to 45%, 25% to 40%, 25% to 35%, 30% to 55%, 30% to 45%, 30% to 43%, 30% to 41%, 30% to 38%, 34% to 55%, 34% to 45%, 36% to 43%, 36% to 41%, or 36% to 48%.

[0059] The porosity P of the active material layer of the negative electrode can be tested as follows: An inert gas with a small molecular diameter, such as helium or nitrogen, is used. The actual volume of the sample under test is accurately measured using a displacement method to determine the porosity of the sample using Bohr's law (PV = nRT). Porosity P = (V11 - V12) / V11 × 100%, where V11 represents the apparent volume of the active material layer of the negative electrode and V12 represents the actual volume of the active material layer of the negative electrode.

[0060] The degree of porosity of the active material layer of the negative electrode influences the diffusion of lithium ions within this layer and thus affects the charging rate of the secondary battery. Generally, higher porosity of the active material layer of the negative electrode corresponds to better electrolyte infiltration and improved charging rate of the secondary battery. However, if the porosity is too high, it can lead to an internal short circuit or self-discharge. Furthermore, excessive porosity of the active material layer of the negative electrode can compromise its mechanical strength.If the porosity of the active material layer of the negative electrode is within the above-mentioned range, this contributes to improving the rate performance, cycle performance and storage performance of the secondary battery, while maintaining the mechanical strength of the active material layer of the negative electrode and preventing the occurrence of internal short circuits or self-discharge.

[0061] With a view to improving performance characteristics such as rate performance, cycle performance and storage performance of the secondary battery, the active material of the negative electrode in this embodiment can contain at least one material selected from synthetic graphite, natural graphite, soft carbon, hard carbon and a silicon-based material, or the active material of the negative electrode can contain at least one material selected from natural graphite, modified graphite, synthetic graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, iron(III) oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate and sodium terephthalate.Optionally, the silicon-based material may contain at least one material selected from elemental silicon, silicon dioxide, silicon-carbon composite, and silicon-based alloy.

[0062] With a view to improving performance characteristics such as rate performance, cycle performance, and storage performance of the secondary battery, the mass fraction of the silicon-based material in the total active material of the negative electrode can be 0% to 30% and optionally 0% to 10% in this embodiment. Optionally, the mass fraction of the silicon-based material in the total active material of the negative electrode can be 0% to 25%, 0% to 20%, 0% to 15%, 0% to 5%, 4% to 20%, 4% to 16%, 4% to 12%, 6% to 13%, 6% to 26%, 6% to 18%, 7% to 13%, 7% to 22%, or 7% to 19%.

[0063] With a view to improving performance characteristics such as rate performance, cycle performance and storage performance of the secondary battery, the positive electrode in this embodiment further includes a positive electrode, and the positive electrode can contain an active material of the positive electrode with the molecular formula LiNi x Co y Mn z M 1-x-y-z The material contains O2, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5 and x + y + z = 1, optionally 0.5 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.3 and 0 ≤ z ≤ 0.3, and M is at least one selected from Zr, Al, Mg, Sb, Fe, Cu and W. Optionally, the active material of the positive electrode can be at least one selected from LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (short NCM) 333 ), LiNi 0,5 Co 0,2 Mn 0,3 O2 (short NCM) 523 ), LiNi 0,5 Co 0,25 Mn 0,25 O2 (short NCM) 211 ), LiNi 0,6 Co 0,2 Mn 0,2 O2 (short NCM) 622 ), LiNi0,8 Co 0,1 Mn 0,1 O (short NCM) 811 ) and modified compounds thereof. If the secondary battery is a sodium-ion secondary battery, the positive electrode may contain at least one positive electrode active material selected from layered transition metal oxides, polyanionic compounds, Prussian blue compounds, sulfides, nitrides, carbides, and titanates. Detailed description of the embodiments of the present application

[0064] A secondary battery, a battery module, a battery pack and an electrical device are described in detail below with reference to the attached drawings.

[0065] One embodiment of this application provides for a secondary battery. The secondary battery can be a lithium-ion battery or a sodium-ion battery. The specific embodiments of this application are described in detail below using a lithium-ion battery as an example.

[0066] A typical lithium-ion battery can contain a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process, lithium ions are stored and released between the positive and negative electrodes. The electrolyte conducts lithium ions between the positive and negative electrodes. The separator is positioned between the positive and negative electrodes to prevent a short circuit between them and to allow the passage of ions. In some cases, for example, when a liquid gel polymer electrolyte is used, the liquid electrolyte can also function as the separator. In such cases, the liquid electrolyte is also considered the electrolyte described in this application.In other words, the electrolyte in this application is not limited to a liquid form. The components of the lithium-ion battery are described in detail below. [Positive electrode]

[0067] The positive electrode can include a positive electrode current collector and an active material layer arranged on at least one surface of the positive electrode current collector. The active material layer can contain an active electrode material and optionally a binder and a conductive agent.

[0068] In one example, the current collector of the positive electrode contains two back-to-back surfaces in the thickness direction. The active material layer of the positive electrode is located on one or both of these back-to-back surfaces of the current collector.

[0069] In some embodiments, the current collector of the positive electrode can be a metal foil or a composite material current collector. For example, an aluminum foil can be used as the metal foil. The composite material current collector can comprise a polymer matrix and a metal layer formed on at least one surface of the polymer matrix. The composite material current collector can be manufactured by depositing a metal material (e.g., aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, or the like) onto a polymer matrix (e.g., matrices of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE)).

[0070] In some embodiments, the active material of the positive electrode may be a known active material for lithium-ion batteries. For example, the active material of the positive electrode may comprise at least one of the following: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and corresponding modified compounds thereof. However, this application is not limited to these materials, and other conventional materials suitable as active materials for lithium-ion batteries may also be used. One of these active materials of the positive electrode may be used alone, or two or more of them may be used in combination. For example, an active material of the positive electrode with the molecular formula LiNi may be used. x Co y Mn z M 1-x-y-zO2 is used, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5 and x + y + z = 1, optionally 0.5 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.3 and 0 ≤ z ≤ 0.3, and M is at least one selected from Zr, Al, Mg, Sb, Fe, Cu and W. Optionally, the active material of the positive electrode can be at least one selected from LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (short NCM) 333 ), LiNi 0,5 Co 0,2 Mn 0,3 O2 (short NCM) 523 ), LiNi 0,5 Co 0,25 Mn 0,25 O2 (short NCM) 211 ), LiNi 0,6 Co 0,2 Mn 0,2 O2 (short NCM) 622 ), LiNi 0,8 Co 0,1 Mn 0,1 O (short NCM) 811) and modified compounds thereof. Examples of olivine-structured lithium-containing phosphates include lithium iron phosphates (for example, LiFePO4 (or LFP for short)), lithium iron phosphate and carbon composites, lithium manganese phosphate (for example, LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0071] If the secondary battery is a sodium-ion battery, the positive electrode may contain at least one active positive electrode material selected from layered transition metal oxides, polyanionic compounds, Prussian blue compounds, sulfides, nitrides, carbides, and titanates. Optionally, the active positive electrode material may include, among others, at least one material selected from NaCrO₂, Na₂Fe₂(SO₄)₃, molybdenum disulfide, tungsten disulfide, vanadium disulfide, titanium disulfide, hexagonal boron nitride, carbon-doped hexagonal boron nitride, titanium carbide, tantalum carbide, molybdenum carbide, silicon carbide, Na₂Ti₃O₇, or Na₂Ti₆O₇. 13 , Na4Ti5O 12 , Li4Ti5O 12 and NaTi2(PO4)3 is selected.

[0072] In some embodiments, the active material layer of the positive electrode may optionally contain a binder. The binder may, for example, include at least one binder selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene propylene terpolymer, vinylidene fluoride-hexafluoropropylene tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0073] In some embodiments, the active material layer of the positive electrode may optionally contain a conductive material. For example, a conductive material commonly used in this field may be employed. The conductive material may contain at least one of the following: superconducting carbon, carbon black, carbon black, Ketjen carbon black, carbon nanotubes, carbon nanorods, graphene, and carbon nanofibers.

[0074] In some embodiments, the positive electrode can be produced using the following method: The components mentioned above, which are used to produce a positive electrode, for example, the active material of the positive electrode, the conductive agent, the binder, and all other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode paste; the positive electrode paste is applied to the current collector of the positive electrode, and subsequently, processes such as drying and cold pressing are carried out to obtain the positive electrode.Alternatively, in another embodiment, the positive electrode can be produced using the following method: The positive electrode paste for forming an active material layer of the positive electrode is applied to a separate carrier, and the film obtained by peeling it from the carrier is laminated onto the current collector of the positive electrode. [Negative electrode]

[0075] The negative electrode comprises a negative electrode current collector and an active material layer arranged on at least one surface of the negative electrode current collector. The active material layer may contain an active electrode material and optionally a binder, a conductive agent, and other additives.

[0076] For example, the current collector of the negative electrode has two back-to-back surfaces in its thickness direction, and the active material layer of the negative electrode is arranged on one or both of the two back-to-back surfaces of the current collector of the negative electrode.

[0077] In some embodiments, the negative electrode current collector can be a metal foil or a composite material current collector. For example, a copper foil can be used as the metal foil. The composite material current collector can comprise a polymer matrix and a metal layer formed on at least one surface of the polymer matrix. The composite material current collector can be manufactured by depositing a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, or the like) onto a polymer matrix (e.g., matrices of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE)).

[0078] In this embodiment, where the secondary battery is a lithium-ion battery, the active material of the negative electrode can be a negative electrode active material well known in the art for lithium-ion batteries. For example, the negative electrode active material can comprise at least one material selected from synthetic graphite, natural graphite, soft carbon, hard carbon, and a silicon-based material. The silicon-based material comprises at least one material selected from elemental silicon, silicon dioxide, a silicon-carbon composite, and a silicon-based alloy. If the negative electrode active material comprises the silicon-based material, the mass fraction of the silicon-based material in the total negative electrode active material is 0% to 30%, and optionally 0% to 10%.However, this application is not limited to these materials; other conventional materials that can be used as active materials for the positive electrode of batteries may also be used. One of these active materials for the negative electrode may be used alone, or two or more of them may be used in combination.

[0079] In the embodiment where the secondary battery is a sodium-ion battery, the active material of the negative electrode can comprise at least one material selected from natural graphite, modified graphite, synthetic graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, iron(III) oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate, and sodium terephthalate. Optionally, the active material of the negative electrode is at least one material selected from natural graphite, modified graphite, synthetic graphite, and graphene.

[0080] In some embodiments, the active material layer of the negative electrode may optionally contain a binder. The binder may be selected from at least one of the following: styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylic acid (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0081] In some embodiments, the active material layer of the negative electrode may optionally contain a conductive material. The conductive material may be selected from at least one of the following: superconducting carbon, carbon black, carbon black, Ketjen carbon black, carbon nanotubes, carbon nanorods, graphene, and carbon nanofibers.

[0082] In some embodiments, the active material layer of the negative electrode may alternatively optionally contain other additives such as a thickening agent (for example, sodium carboxymethylcellulose (CMC-Na)).

[0083] In some embodiments, the negative electrode can be produced using the following method: The components mentioned above, which are used to produce a negative electrode, for example, the active material of the positive electrode, the conductive agent, the binder, and all other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste; the negative electrode paste is applied to the current collector of the negative electrode, and subsequently, processes such as drying and cold pressing are carried out to obtain the negative electrode.Alternatively, in another embodiment, the negative electrode can be produced using the following method: The negative electrode paste for forming an active material layer of the negative electrode is applied to a separate carrier, and the film obtained by peeling it from the carrier is laminated onto the current collector of the negative electrode. [Electrolyte]

[0084] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify any particular restrictions regarding the type of electrolyte, which can be selected as needed. For example, the electrolyte can be in a liquid or gel state.

[0085] Furthermore, the electrolyte in the embodiments of this application may contain an additive. The additive may be an additive commonly used in the art. For example, the additive may contain halogenated alkylene carbonates (such as difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, (condensed) glycerides, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the proportion of the added additive may be 0.1% by weight to 5% by weight, based on the total weight of the electrolyte, or the proportion of the additive may be adjusted by a person skilled in the art as required.

[0086] The electrolyte may contain an electrolyte salt and a solvent.

[0087] In the embodiment in which the secondary battery is a lithium-ion battery, the electrolyte salt may contain at least one electrolyte salt selected from LiPF6, LiBF4, LiN(SO2F)2 (LiFSI), LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB) and LiBF2C2O4 (LiDFOB).

[0088] In the embodiment in which the secondary battery is a sodium-ion battery, the electrolyte salt may contain at least one electrolyte salt selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3 and Na(CH3)C6H4SO3.

[0089] In some embodiments, in addition to the solvents mentioned above, such as the low-viscosity solvent and the solvent with a high dielectric constant, the electrolyte may optionally also contain other solvents commonly used in the industry, for example at least one solvent selected from 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. [Separator]

[0090] In some embodiments, the secondary battery additionally includes a separator. The separator is not limited to a specific type in this application and can be any generally known porous separator with good chemical and mechanical stability. Additionally, the separator should exhibit excellent ion permeability and good moisture retention capacity for the electrolyte.

[0091] In some embodiments, the separator material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The shape of the separator is not restricted; it can be a single-layer thin film or a multi-layer composite thin film. If the separator is a multi-layer composite thin film, all layers can consist of the same or different materials, which does not constitute a particular restriction.

[0092] In some embodiments, the positive electrode, the negative electrode and the separator can be joined together to form an electrode assembly by winding or laminating.

[0093] In some embodiments, the secondary battery may include an outer package. The outer package may be used to package the electrode assembly and the electrolyte.

[0094] In some embodiments, the outer packaging of the secondary battery can consist of a rigid casing, such as a hard plastic casing, an aluminum casing, or a steel casing. Alternatively, the outer packaging of the secondary battery can be a soft casing, such as a soft pouch. The material of the soft casing can be plastic. Examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0095] This application does not specify any particular restrictions regarding the shape of the secondary battery; the secondary battery may be cylindrical, rectangular, or of any other shape. For example, it shows Fig. 1 as an example a secondary battery 5 with prismatic structure.

[0096] With reference to Fig.2. In some embodiments, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and a side plate connected to the base plate, the base plate and the side plate enclosing a receiving cavity. The housing 51 has an opening that communicates with the receiving cavity, and the cover plate 53 may cover the opening to close the receiving cavity. The positive electrode, the negative electrode, and the separator may be wound or laminated together to form an electrode assembly 52. ​​The electrode assembly 52 is housed in the receiving cavity. The electrolyte is infiltrated into the electrode assembly 52. ​​One or more electrode assemblies 52 may be present in the secondary battery 5, and the person skilled in the art may make a selection depending on the actual requirements.

[0097] In some embodiments, secondary batteries can be assembled into a battery module, which may contain one or more secondary batteries. A specific quantity can be selected by a person skilled in the art based on the intended use and capacity of the battery module.

[0098] Fig. Figure 3 shows, as an example, a battery module 4. With reference to Fig. In battery module 4, a plurality of secondary batteries 5 are arranged sequentially along the length of the battery module 4. Of course, the plurality of secondary batteries 5 can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fastened using fastening elements.

[0099] Optionally, the battery module 4 can also contain a housing with a receiving cavity, and the multitude of secondary batteries 5 are housed in the receiving cavity.

[0100] In some embodiments, the aforementioned battery module can be assembled into a battery pack. The battery pack can contain one or more battery modules. A specific quantity can be selected by a person skilled in the art based on the intended use and capacity of the battery module.

[0101] Fig. 4 and Fig. Figure 5 shows a battery pack as an example. Referring to Fig. 4 and Fig. 5. The battery pack 1 can contain a battery box and a plurality of battery modules 4 arranged within the battery box. The battery box consists of an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 to form an enclosed space for the battery module 4. The plurality of battery modules 4 can be arranged within the battery box in any configuration.

[0102] Furthermore, this application provides an electrical device. The electrical device includes at least one of the secondary batteries, battery modules, or battery packs provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. Electrical devices may include, among others, mobile devices (e.g., mobile phones or notebooks), electric vehicles (e.g., battery-powered electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, or electric trucks), electric trains, ships, satellite systems, energy storage systems, and the like.

[0103] The secondary battery, battery module or battery pack can be selected based on the requirements for the use of the electrical device for this purpose.

[0104] Fig. Figure 6 shows an example of an electrical device. This electrical device is a battery-powered electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or similar. To meet the electrical device's requirements for high performance and high energy density of the secondary battery, a battery pack or battery module can be used.

[0105] In another example, the device could be a mobile phone, a tablet computer, a notebook computer, or something similar. Such a device generally needs to be lightweight and thin, and a secondary battery can be used as a power source. Examples

[0106] Examples relating to this application are described in detail below. The examples described below are illustrative and serve only to explain this application; they do not, however, constitute a limitation of this application. Examples whose technical solutions or conditions are not specified are based on technical solutions or conditions described in the technical literature or on the product specification. Unless otherwise stated, the reagents or instruments used are exclusively commercially available products. The following application examples illustrate the use of a lithium-ion battery. Example 1: Production of the lithium-ion battery 1. Production of the electrolyte

[0107] The electrolyte was prepared in a glovebox under an argon atmosphere with a water content of < 10 ppm. Dimethyl carbonate, ethylene carbonate, and diethyl carbonate were first mixed in a 2:3:5 ratio (by mass); 13 wt% LiPF6 was added to the mixed solvent. This completed the preparation of the electrolyte. The amount of the aforementioned lithium salt refers to a percentage calculated based on the total weight of the electrolyte. 2. Production of the positive electrode

[0108] An active positive electrode material (LiNi5Co2Mn3O2), a binder (polyvinylidene fluoride), and a conductive agent (acetylene carbon black) were mixed in a weight ratio of 98:1:1 and dispersed in a solvent (N-methylpyrrolidone, NMP) to produce a positive electrode paste. The resulting paste was applied to a current collector aluminum foil, and subsequent processes such as drying, cold pressing, edge trimming, cutting, and slitting were performed to manufacture the positive electrode of the lithium-ion battery. 3. Production of the negative electrode

[0109] Synthetic graphite as the active material of the negative electrode (its OI value is given in Table 1; also below), carbon black as a conductive agent, CMC as a thickener, and styrene-butadiene rubber (SBR) as a binder were mixed in a weight ratio of 96:2:1:1, dispersed in deionized water, and then stirred with a vacuum mixer to obtain a negative electrode paste. The negative electrode paste was applied to a current collector copper foil, and subsequent processes such as drying, cold pressing, trimming, cutting, and slitting were performed to produce a negative electrode with a coating weight of 8 mg / cm². 2 and to obtain a porosity of 40%. The OI values ​​of the active material layers of the negative electrode were 7 in this example (their OI values ​​are given in Table 1; also below). Testing the porosity P of the active material layer of the negative electrode

[0110] The porosity P of the active material layer of the negative electrode can be tested as follows: An inert gas with a small molecular diameter, such as helium or nitrogen, was used. The actual volume of the sample under test was accurately measured using a displacement method to determine the porosity of the sample using Bohr's law (PV = nRT). Porosity P = (V11 - V12) / V11 × 100%, where V11 represents the apparent volume of the active material layer of the negative electrode and was determined by calculating its length × width × thickness, and V12 represents the actual volume of the negative electrode sheet.The specific test procedure was as follows: A compressed steel cylinder was opened; a pressure relief valve was set so that the pressure was between 0.14 MPa and 0.18 MPa; the negative electrode was formed into a relatively flat and defect-free disc with an area of ​​1.5394 cm². 2 The sample was punched, with the number of samples exceeding 20. The sample was placed in a sample cup, and a true density measuring device (GB / T2790-1995) was used to determine the actual volume V12 of the active material layer of the negative electrode. V11 was measured at 1.5394 cm³. 2 The electrode sheet thickness was obtained. The porosity of the sample to be tested was determined using the following formula: Porosity P = (V11 - V12) / V11 × 100 %. Testing the OI value of the active material layer of the negative electrode

[0111] The orientation index (OI) of the active material layer of the negative electrode was used to represent the orientation index of the active material layer of the negative electrode. The OI of the active material layer of the negative electrode can be calculated from an X-ray diffraction pattern measured with an X-ray powder diffractometer. More precisely, OI = C004 / C110, where C004 was the peak area of ​​a characteristic 004 diffraction peak in an X-ray diffraction pattern of the active material layer of the negative electrode, and C110 was the peak area of ​​a characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode. Specific test procedure: The ambient temperature was controlled to 15 °C to 25 °C and the ambient humidity to 20% to 80%.An electrode sheet with a sample area of ​​at least 30 mm × 30 mm was used. The electrode sheet was carefully attached to one end of a clean microscope slide using double-sided adhesive tape, and the slide was then inserted into a Bruker D8 Discover X-ray powder diffractometer. The scan angle range was set to 50° to 80°, the step size to 0.01°, and the duration of each step to 0.9 s. The system was started to obtain the X-ray diffraction pattern of the active material layer of the negative electrode. Using the DIFFRAC.EVA V4.2.2 software, the peak areas of the 004 crystal plane diffraction peak and the 110 crystal plane diffraction peak of the active material layer of the negative electrode were determined. Subsequently, the OI value of the active material layer of the negative electrode was calculated using the formula OI = C004 / C110. 4. Separator

[0112] A standard polypropylene film was used as a separator. 5. Battery installation

[0113] The aforementioned positive electrode, separator, and negative electrode were wound or laminated sequentially, with the separator positioned between the positive and negative electrodes to create a bare battery core. This bare core was then placed in an outer casing. The prepared electrolyte was injected into the dried core, and subsequent processes such as settling, chemical formation, and shaping were performed to produce the lithium-ion secondary battery. Example 2

[0114] The lithium-ion battery was produced in the same way as in Example 1, except that dimethyl carbonate, ethylene carbonate and diethyl carbonate were mixed in a ratio of 4:3:3 (mass ratio). Example 3

[0115] The lithium-ion battery was manufactured in the same way as in Example 1, except that dimethyl carbonate, ethylene carbonate and diethyl carbonate were mixed in a ratio of 7:3:0 (mass ratio). Examples 4 and 5

[0116] The lithium-ion batteries were manufactured in the same way as in Example 2, except that the percentages of lithium salts were changed to 10 wt.% and 23 wt.% respectively. Examples 6 and 7

[0117] The lithium-ion batteries were manufactured in the same way as in Example 2, except that the orientation index (OI) values ​​of the active material layers of the negative electrode were changed to 3 and 24, respectively. Examples 8 and 9

[0118] The lithium-ion batteries were manufactured in the same way as in Example 2, except that the coating weights of the manufactured negative electrodes were reduced to 6.5 mg / cm². 2 or 13 mg / cm² 2 have been changed. Examples 10 and 11

[0119] The lithium-ion batteries were manufactured in the same way as in Example 2, except that the porosity of the manufactured negative electrodes was changed to 20% and 60%, respectively. Example 12

[0120] The lithium-ion battery was produced in the same way as in Example 2, except that dimethyl carbonate was replaced by ethyl acetate. Example 13

[0121] The lithium-ion battery was manufactured in the same way as in Example 1, except that ethylene sulfate was added in an amount of 1% of the total mass of the electrolyte during the manufacture of the electrolyte. Example 14

[0122] The lithium-ion battery was manufactured in the same way as in Example 2, except that the percentage of a solvent, such as a solvent with a high dielectric constant, in the electrolyte was adjusted as shown in Table 2 below. Example 15

[0123] The lithium-ion battery was manufactured in the same way as in Example 2, except that soft carbon, in an amount of 2% of the total mass of the active material of the artificial graphite negative electrode, was applied to the surface of the active material of the artificial graphite negative electrode. The OI value of the active material layer of the negative electrode was 4 in this example. Example 16

[0124] The lithium-ion battery was manufactured in the same way as in Example 2, except that SiO₂ was used at a proportion of 3% based on the total mass of the active material of the negative electrode, synthetic graphite. The OI value of the active material layer of the negative electrode was 7 in this example. Example 17

[0125] The sodium-ion battery was manufactured in the same way as in Example 1, except that the active material of the positive electrode was replaced by NaCrO2 and the electrolyte salt in the electrolyte was replaced by NaPF6. Comparative examples 1 to 8

[0126] The lithium-ion batteries were manufactured in the same manner as in Example 2, except that the percentages of solvents in the electrolyte, the OI values ​​of the active material layers of the negative electrode, the concentrations of lithium salts, the porosities of the active material layers of the negative electrode, and the coating weights of the active material layers of the negative electrode were adjusted as shown in Tables 1 and 2 below.

[0127] The following describes the testing procedure for the lithium-ion battery. 1. Testing the conductivity of the electrolyte

[0128] An alternating voltage of 1 kHz was applied between two parallel platinum-black electrode sheets. Under the influence of the electric field, charged ions migrated in an electrolyte solution, transferring electrons in the process. This ability to transfer electrons was converted into electrical signals, which were then output. In this way, conductivity was achieved.

[0129] The conductivity of the prepared electrolyte was tested using a Rex Electric Chemical conductivity meter (DDSJ-318). The ambient temperature was maintained at 25 °C and the relative humidity at < 80%. A 40 ml sample of electrolyte was used. The sample was placed in a dry and clean plastic centrifuge tube and incubated in a water bath at 25 °C for 30 minutes. The dried electrode was then inserted vertically into a uniform sample. The instrument was started for testing, and the test was repeated three times, with the three results being averaged. 2. Testing the viscosity of the electrolyte

[0130] At a specific temperature, the shear force acting on a rotor as it rotated at a constant speed in the sample caused a spring to generate a torque, and this torque was proportional to the viscosity, so the viscosity could be determined.

[0131] The viscosity of the finished electrolyte was specifically tested using a Brookfield viscometer (DV-2TLV). The ambient temperature was maintained at 25 °C and the relative humidity at < 80%. A 30 ml sample of electrolyte was used and placed in a water bath at 25 °C for at least 30 minutes. The rotor was inserted into a sample beaker, and the sample was added to a distance of approximately 0.3 cm from the beaker's rim. The connected viscometer was started, a speed of 70 rpm was selected for the tests, 10 data points were recorded, and a mean value was calculated from these points. 3. Review of installment payments

[0132] Rate performance test (performed at 80% SOC charge): The test temperature was set to 35°C, and the lithium-ion battery was charged at x C (x was 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, 3) and then discharged at 1 C, with the charge rate being gradually increased. An anode potential of 0 V was used as the final charge voltage. The maximum charging rates x1 C, x2 C, x3 C, x4 C, x5 C, x6 C, x7 C and x8 C, which could be achieved in the ranges 0% to 10% SOC, 10% to 20% SOC, 20% to 30% SOC, 30% to 40% SOC, 40% to 50% SOC, 50% to 60% SOC, 60% to 70% SOC and 70% to 80% SOC, were determined using the following formula: T(min)=(1x1+1x2+1x3+1x4+1x5+1x6+1x7+1x8)×6, to calculate the charging time (min) required to go from 0% to 80% SOC. 4. Lifespan

[0133] At 45 °C, the lithium-ion batteries were charged to 4.25 V with a constant current of 1 C, then charged at a constant current of 0.05 C at 4.25 V, left to stand for 5 minutes, and then discharged at a constant current of 1 C to a lower limit of the cutoff voltage of 2.8 V. This was the first charge / discharge cycle of the secondary batteries. The discharge capacities determined at this time were recorded as the discharge capacities of the first cycle of the lithium-ion batteries.Under the aforementioned charging and discharging conditions, a cyclic charge-discharge cycle was performed until the lithium-ion batteries reached the cutoff condition of a capacity retention rate of 80%. The number of cycles for the secondary batteries was determined under the condition of an 80% capacity retention rate. 5. Testing storage performance at high temperatures

[0134] At 60 °C, the lithium-ion batteries were charged to a voltage of 4.25 V with a constant current of 1 C and then further charged at a current of 0.05 C while maintaining a voltage of 4.25 V. The volumes of the lithium-ion batteries were measured at this point using the discharge method and recorded as V21. The lithium-ion batteries were then placed in an incubator at 60 °C and removed after 30 days of storage. The volumes of the lithium-ion batteries were measured at this point and recorded as V22. Volume swelling ratio (%) of the lithium-ion battery stored for 100 days at 60 °C = [(V22-V21) / V21] × 100. Table 1 number OI value of inactive material of the negative electrode Mean particle size by volume Dv50 of the active material of the negative electrode (µm) CW dernegativenElektrode(mg / cm 2 ) Compact density of the active material layer of the negative electrode (g / cm²) 3 ) Type of active material of the negative electrode OI value of the active material layer of the negative electrode Comparative example 1 3,2 11,1 8 1,6 Artificial graphite 7 Comparative example 2 3,2 11,1 8 1,6 Artificial graphite 7 Comparative example 3 7,3 15,2 8 1,6 Artificial graphite 40 Comparative example 4 3,2 11,1 30 1,6 Artificial graphite 7 Comparative example 5 3,2 11,1 20 1,6 Artificial graphite 40 Comparative example 6 3,2 11,1 30 1,6 Artificial graphite 7 Comparative example 7 3,2 11,1 8 1,6 Artificial graphite 7 Comparative example 8 3,2 11,1 8 1,6 Artificial graphite 7 Example 1 3,2 11,1 8 1,6 Artificial graphite 7 Example 2 3,2 11,1 8 1,6 Artificial graphite 7 Example 3 3,2 11,1 8 1,6 Artificial graphite 7 Example 4 3,2 11,1 8 1,6 Artificial graphite 7 Example 5 3,2 11,1 8 1,6 Artificial graphite 7 Example 6 2,8 10,8 8 1,6 Artificial graphite 3 Example 7 5,7 13,5 8 1,6 Artificial graphite 24 Example 8 3,2 11,1 6,5 1,6 Artificial graphite 7 Example 9 3,2 11,1 13 1,6 Artificial graphite 7 Example 10 3,2 11,1 8 1,6 Artificial graphite 7 Example 11 3,2 11,1 8 1,6 Artificial graphite 7 Example 12 3,2 11,1 8 1,6 Artificial graphite 7 Example 13 3,2 11,1 8 1,6 Artificial graphite 7 Example 14 3,2 11,1 8 1,6 Artificial graphite 7 Example 15 2,9 10,9 8 1,6 Artificial graphite + 2 wt% soft carbon 4 Example 16 3,2 11,1 8 1,6 Synthetic graphite + 3 wt% SiO₂ 7 Example 17 3,2 11,1 8 1,6 Artificial graphite 7 Table 2 number DMC(EA) / Wt. % Mass fraction of LiPF6(NaPF6) in the electrolyte (wt%) Proportion of solvent with high dielectric constant (wt%) Proportion of other linear carbonate teams in total solvent (wt%) Type of inactive material of the negative electrode OI value of the active material layer of the negative electrode CW dernegativenElektrode(mg / cm 2 ) porosity B*C*POI*CW(× 10 -4 ) Conductivity at 25 °C (mS / cm) Viscosity at 25 °C (mPa·s) Charging capacity from 0% to 80% SOC at 35°C (min) Lifespan at 45 °C (cycles) Volume swelling rate at 60 °C Comparative example 1 0 13 30 70 Artificial graphite 7 8 40 0,00 8,35 3,3 13 1500 5% Comparative example 2 40 3 30 30 Artificial graphite 7 8 40 0,86 6 2 15 820 8% Comparative example 3 40 13 30 30 Artificial graphite 40 8 40 0,65 9,95 2,9 13,5 1400 9% Comparative example 4 40 13 30 30 Artificial graphite 7 30 10 0,93 9,95 2,9 13 1455 11% Comparative example 5 10 5 30 60 Artificial graphite 40 20 10 0,01 6,5 7,6 16 540 6% Comparative example 6 40 13 30 30 Artificial graphite 7 30 40 0,99 9,95 2,9 16 1450 8% Comparative example 7 70 30 30 30 Artificial graphite 7 8 40 15 8,2 8,1 15 600 14% Comparative example 8 40 13 10 50 Artificial graphite 7 8 40 3,71 7,15 2 13 1300 5% Example 1 20 13 30 50 Artificial graphite 7 8 40 1,86 9,08 3 10,8 1580 7% Example 2 40 13 30 30 Artificial graphite 7 8 40 3,71 9,95 2,9 10,2 1730 10 % Example 3 70 13 30 / Artificial graphite 7 8 40 6,50 11,28 2,71 9,6 1880 14 % Example 4 40 10 30 30 Artificial graphite 7 8 40 2,86 8,8 2,6 10,7 1520 9,5 % Example 5 40 23 30 30 Artificial graphite 7 8 40 6,57 8,2 7 11 1510 11% Example 6 40 13 30 30 Artificial graphite 3 8 40 8,67 9,95 2,9 9,5 1550 10,8 % Example 7 40 13 30 30 Artificial graphite 24 8 40 1,08 9,95 2,9 11,2 1570 9,5 % Example 8 40 13 30 30 Artificial graphite 7 6,5 40 4,57 9,95 2,9 9 1510 9,3 % Example 9 40 13 30 30 Artificial graphite 7 13 40 2,29 9,95 2,9 11,2 1550 10,3 % Example 10 40 13 30 30 Artificial graphite 7 8 20 1,86 9,95 2,9 11,5 1550 8,9 % Example 11 40 13 30 30 Artificial graphite 7 8 60 5,57 9,95 2,9 9,4 1750 10,1 % Example 12 40EA) 13 30 30 Artificial graphite 7 8 40 3,71 11,8 2,5 8,5 1500 10 % Example 13 20 13 30 50 Artificial graphite 7 8 40 1,86 9,05 3,05 10,8 1720 6% Example 14 40 13 50 10 Artificial graphite 7 8 40 3,71 10,5 4,5 12 1500 15 % Example 15 40 13 30 30 Artificial graphite +2 wt% soft carbon 4 8 40 6,5 9,95 2,9 9,5 1700 10 % Example 16 40 13 30 30 Artificial graphite +3 wt.% SiO₂ 7 8 40 3,71 9,95 2,9 10,3 1600 10,1 % Example 17 20 13 (NaPF6) 30 50 Artificial graphite 7 8 40 1,86 9,00 3 10,2 1500 9%

[0135] A comparison between examples 1 to 17 and comparison examples 1 to 8 in Table 2 shows that lithium-ion batteries, when they satisfy the above-mentioned relational relationship, exhibit excellent rate performance, excellent cycle performance, and good storage performance at high temperatures.

[0136] The comparison between Example 2 and Example 14, as well as Comparative Example 8, shows that if the proportion of solvents with a high dielectric constant is below the range specified in this application, the rate performance and the cycle performance (in particular the cycle life) of the lithium-ion batteries are significantly reduced. The comparison between Example 2 and Example 14 shows that while solvents with a high dielectric constant can improve the battery's rate performance, if the proportion of solvents with a high dielectric constant exceeds the preferred range of this application (20% to 40%), the rate performance, cycle life, and high-temperature storage performance of the lithium-ion battery in Example 14 are somewhat lower than in Example 2, where the proportion of solvent with a high dielectric constant is within the preferred range of this application.

[0137] It should be noted that this application is not limited to the examples above. The embodiments described above are merely examples. Embodiments whose designs are essentially identical to those of the technical idea and which have the same effects as the technical idea within the scope of protection of the technical solutions of this application all fall within the technical scope of this application. Furthermore, within the scope, without departing from the essence of this application, various modifications conceivable by a person skilled in the art are applied to the embodiments, and other modes constructed by combining some of the components of the embodiments also fall within the scope of protection of this application. ALTERNATIVE EXECUTION FORMS

[0138] Alternative designs are described in the following sections. 1. Secondary battery comprising an electrolyte and a negative electrode, wherein The electrolyte comprises a low-viscosity solvent, an electrolyte salt, and a solvent with a high dielectric constant; the viscosity of the low-viscosity solvent at 25 °C is 0.3 mPa·s to 0.6 mPa·s; the dielectric constant of the high-dielectric-constant solvent is between 30 F / m and 100 F / m, and the mass fraction of the high-dielectric-constant solvent in the total solvent in the electrolyte is more than 20%; and the negative electrode comprises a current collector of the negative electrode and an active material layer of the negative electrode, which is arranged on at least one surface of the current collector of the negative electrode; and The secondary battery fulfills the following relational relationship: 1×10−4≤B×C×POI×CW≤1×10−3 where B is the mass fraction of the low-viscosity solvent in the total solvent in the electrolyte; C is the mass fraction of the electrolyte salt in the electrolyte; P is the porosity of the active material layer of the negative electrode; CW is the coating weight of the active material layer of the negative electrode, measured in mg / cm² 2 , is; and OI is the orientation index of the active material layer of the negative electrode; and OI = C004 / C110, where C004 is the peak area of ​​a characteristic 004 diffraction peak in an X-ray diffraction pattern of the active material layer of the negative electrode and C110 is the peak area of ​​a characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode. 2. Secondary battery according to paragraph 1, wherein the low-viscosity solvent comprises at least one solvent selected from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA) and acetonitrile (ACN). 3. Secondary battery according to paragraph 1 or 2, wherein the mass fraction B of the low-viscosity solvent in the total solvent in the electrolyte is 10% to 80% and optionally 20% to 70%. 4. Secondary battery according to any one of paragraphs 1 to 3, wherein the mass fraction C of the electrolyte salt in the electrolyte is 10% to 23% and optionally 13% to 20%. 5. Secondary battery according to any one of paragraphs 1 to 4, wherein the high dielectric constant solvent comprises cyclic carbonate, the cyclic carbonate optionally comprising at least one cyclic carbonate selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and fluoroethylene carbonate. 6. Secondary battery according to any one of paragraphs 1 to 5, wherein the mass fraction C of the solvent with high dielectric constant in the total solvent in the electrolyte is 20% to 40%. 7. Secondary battery according to any one of paragraphs 1 to 6, wherein the electrolyte further comprises at least one electrolyte selected from diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate and ethyl propionate. 8. Secondary battery according to any one of paragraphs 1 to 7, wherein the electrolyte further comprises a film-forming additive, and the film-forming additive comprises at least one additive selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3-propanesultone, lithium difluorophosphate, lithium bisfluorooxalate borate, nitrile compound and cyclic sulfate, the cyclic sulfate optionally being ethylene sulfate. 9. Secondary battery according to any one of claims 1 to 8, wherein the conductivity of the electrolyte at 25 °C is 8 mS / cm to 16 mS / cm. 10. Secondary battery according to any one of claims 1 to 9, wherein the viscosity of the electrolyte at 25 °C is 1 mPa·s to 7 mPa·s. 11. Secondary battery according to any one of claims 1 to 10, wherein the OI value of the active material layer of the negative electrode is 3 to 24 and optionally 8 to 24. 12. Secondary battery according to any one of claims 1 to 11, wherein the coating weight CW of the active material layer of the negative electrode is 6.5 mg / cm². 2 up to 19.5 mg / cm² 2 and optionally 6.5 mg / cm² 2 up to 13 mg / cm² 2 amounts. 13. Secondary battery according to any one of claims 1 to 12, wherein the porosity P of the active material layer of the negative electrode is 20% to 60%. 14. Secondary battery according to any one of paragraphs 1 to 13, wherein the electrolyte salt comprises at least one electrolyte salt selected from LiPF6, LiBF4, LiN(SO2F)2 (LiFSI), LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB) and LiBF2C2O4 (LiDFOB). 15. Secondary battery according to any one of paragraphs 1 to 13, wherein the electrolyte salt comprises at least one electrolyte salt selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3 and Na(CH3)C6H4SO3. 16. Secondary battery according to any one of paragraphs 1 to 14, wherein the active material of the negative electrode comprises at least one material selected from artificial graphite, natural graphite, soft carbon, hard carbon and a silicon-based material; and the silicon-based material optionally comprises at least one material selected from elemental silicon, silicon oxide, silicon-carbon composite and silicon-based alloy. 17. Secondary battery according to paragraph 15, wherein the active material of the negative electrode comprises at least one material selected from natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, iron oxide, vanadium pentoxide, tin oxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate and sodium terephthalate. 18. Secondary battery according to paragraph 16, wherein the mass fraction of the silicon-based material in the total active material of the negative electrode is 0% to 30% and optionally 0% to 10%. 19. Secondary battery according to one of paragraphs 1 to 14 and paragraph 16 or 18, wherein the secondary battery further comprises a positive electrode, and the positive electrode an active material of the positive electrode with the molecular formula LiNi x Co y Mn z M 1-x-y-zO2 includes, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5 and x + y + z = 1, optionally 0.5 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.3 and 0 ≤ z ≤ 0.3, and M is at least one selected from Zr, Al, Mg, Sb, Fe, Cu and W. 20. Secondary battery according to one of paragraphs 1 to 13 and paragraph 15 or 17, wherein the secondary battery further comprises a positive electrode, and the positive electrode comprises at least one active material of the positive electrode, which is selected from the following active materials of the positive electrode: layered transition metal oxide, polyanionic compound, Prussian blue compound, sulfide, nitride, carbide and titanate. 21. Electrical device comprising the secondary battery according to any one of paragraphs 1 to 20. Reference symbol list: 1 battery pack; 2 upper box body; 3 lower box body; 4 battery modules; 5 Secondary battery; 51 cases; 52 Electrode assembly; and 53 Upper cover assembly. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 113097429A

[0003] CN 113036298A

[0003] CN 111653829A

[0003] CN 108847489B

[0003]

Claims

[1] Secondary battery (5) comprising an electrolyte and a negative electrode, wherein the electrolyte comprises a low-viscosity solvent and the viscosity of the low-viscosity solvent at 25 °C is 0.3 mPa·s to 0.6 mPa·s; the low-viscosity solvent comprises at least one solvent selected from dimethyl carbonate, DMC, ethyl acetate, EA, methyl acetate, MA, and acetonitrile, ACN; the mass fraction of the low-viscosity solvent in the total solvent in the electrolyte is 20% to 80%; the electrolyte comprises cyclic carbonate, and the mass fraction of the cyclic carbonate in the total solvent in the electrolyte is 20% to 40%; the electrolyte comprises an electrolyte salt, and the mass fraction of the electrolyte salt in the electrolyte is 10% to 23%, the negative electrode comprises a current collector of the negative electrode and an active material layer of the negative electrode arranged on at least one surface of the current collector of the negative electrode, the porosity P of the active material layer of the negative electrode is 20% to 60%, the OI value of the active material layer of the negative electrode is 3 to 24, the coating weight CW of the active material layer of the negative electrode is 6.5 mg / cm² 2 up to 19.5 mg / cm² 2 amounts; the active material layer of the negative electrode comprises an active material of the negative electrode, and the active material of the negative electrode comprises synthetic graphite; and OI = C004 / C110, where C004 is the peak area of ​​a characteristic 004 diffraction peak in an X-ray diffraction pattern of the active material layer of the negative electrode and C110 is the peak area of ​​a characteristic 110 diffraction peak in the X-ray diffraction pattern of the active material layer of the negative electrode. [2] Secondary battery (5) according to claim 1, wherein the mass fraction of the low-viscosity solvent in the total solvent in the electrolyte is 20% to 70% and optionally 40% to 70%. [3] Secondary battery (5) according to claim 1 or 2, wherein the cyclic carbonate comprises at least one cyclic carbonate selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and fluoroethylene carbonate. [4] Secondary battery (5) according to any one of claims 1 to 3, wherein the mass fraction of the cyclic carbonate in the total solvent in the electrolyte is 20% to 35%. [5] Secondary battery (5) according to claim 4, wherein the mass fraction of the cyclic carbonate in the total solvent in the electrolyte is 25% to 34%. [6] Secondary battery (5) according to any one of claims 1 to 5, wherein the electrolyte further comprises at least one electrolyte selected from diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate and ethyl propionate. [7] Secondary battery (5) according to any one of claims 1 to 6, wherein the electrolyte further comprises a film-forming component, and the film-forming component comprises at least one component selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3-propanesultone, lithium difluorophosphate, lithium bisfluorooxalate borate, nitrile compound and cyclic sulfate, wherein the cyclic sulfate is optionally ethylene sulfate. [8] Secondary battery (5) according to any one of claims 1 to 7, wherein the conductivity of the electrolyte at 25 °C is 8 mS / cm to 16 mS / cm. [9] Secondary battery (5) according to any one of claims 1 to 8, wherein the viscosity of the electrolyte at 25 °C is 1 mPa·s to 7 mPa·s. [10] Secondary battery (5) according to any one of claims 1 to 9, wherein the coating weight CW of the active material layer of the negative electrode is 6.5 mg / cm² 2 up to 13 mg / cm² 2 amounts. [11] Secondary battery (5) according to any one of claims 1 to 10, wherein the porosity P of the active material layer of the negative electrode is 20% to 55% and optionally 20% to 50%. [12] Secondary battery (5) according to any one of claims 1 to 11, wherein the electrolyte salt comprises at least one electrolyte salt selected from LiPF6, LiBF4, LiN(SO2F)2 (LiFSI), LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB) and LiBF2C2O4 (LiDFOB). [13] Secondary battery (5) according to any one of claims 1 to 12, wherein the charging time required to charge the secondary battery from 0% to 80% SOC is determined by a rate power test performed at 35°C. [14] Secondary battery (5) according to any one of claims 1 to 11, wherein the secondary battery further comprises a positive electrode, and the positive electrode an active material of the positive electrode with the molecular formula LiNi x Co y Mn z M1-x-y-z O2 includes, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5 and x + y + z = 1, optionally 0.5 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.3 and 0 ≤ z ≤ 0.3, and M is at least one selected from Zr, Al, Mg, Sb, Fe, Cu and W. [15] Secondary battery (5) according to any one of claims 1 to 12, wherein the secondary battery further comprises a positive electrode, and the positive electrode comprises at least one positive electrode active material selected from the following positive electrode active materials: layered transition metal oxide, polyanionic compound, Prussian blue compound, sulfide, nitride, carbide and titanate.

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