Electrolytes, secondary batteries, and power consumption devices

Abstract

The present application provides an electrolyte, a secondary battery, and a power consumption device. The electrolyte includes a solvent and an additive, the solvent comprising a compound of formula I, the mass ratio of the compound of formula I in the solvent being 35% or more, where R1 and R2 in formula I are each independently selected from a hydrogen atom, a C1-C3 linear alkyl group, and a C2-C3 alkenyl group, and the additive includes a compound of formula II, where R3, R4, and R5 in formula II are each independently selected from a hydrogen atom, a fluorine atom, a phenyl group, a cyano group, a C1-C6 linear alkyl group, a C3-C6 cyclic alkyl group, and a C2-C6 alkenyl group. The present application simultaneously considers good dynamic performance, high-temperature performance, and excellent overcharge prevention performance of the battery. [C1] TIFF2023550220000017.tif55170

Description

[Technical Field]

[0001] This application relates to the technology of batteries, and more particularly to electrolytes, secondary batteries, and power consumption devices. [Background technology]

[0002] In recent years, secondary batteries have been widely applied in various fields, including energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0003] Significant advancements in secondary batteries have led to increased requirements regarding their energy density, cycle performance, and safety performance. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] This application has been made in view of the above-mentioned problems, and aims to provide an electrolyte, a secondary battery, and a power consumption device. A secondary battery using the electrolyte of the present invention can simultaneously consider good kinetic performance, high-temperature performance, and excellent overcharge prevention performance. [Means for solving the problem]

[0005] To achieve the above objective, a first aspect of the present invention provides an electrolyte comprising a solvent and an additive, wherein the solvent comprises a compound of formula I, and the mass ratio of the compound of formula I in the solvent is 35% or more.

[0006] [ka]

[0007] (R1 and R2 are each independently selected from a hydrogen atom, a C1-C3 linear alkyl group, and a C2-C3 alkenyl group.)

[0008] The above additive contains the compound of formula II.

[0009] [Chemical]

[0010] (R3, R4, and R5 are each independently any one selected from a hydrogen atom, a fluorine atom, a phenyl group, a cyano group, a C1-C6 linear alkyl group, a C3-C6 cyclic alkyl group, and a C2-C6 alkenyl group.)

[0011] By including the compound of formula I and the compound of formula II in the electrolyte, the present application can consider good kinetic performance, high-temperature performance, and excellent overcharge prevention performance.

[0012] In any embodiment, the mass ratio of the compound of formula I in the solvent may be 40% to 70%. By setting the mass ratio of the compound of formula I in the solvent within the above range, the present application can ensure that the electrolyte has high conductivity and low viscosity, can be applied to a thick-film coating system, and thereby further improve the kinetic performance of the battery.

[0013] In any embodiment, the mass ratio of the compound of formula II in the electrolyte may be 9% or less, preferably 3% to 5%. By setting the mass ratio of the compound of formula II in the electrolyte within the above range, the present application can further improve the overcharge prevention performance.

[0014] In any embodiment, the compound of formula I may include at least one selected from methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate, and ethyl acrylate. By selecting the above compound, the present application can further improve the kinetic performance.

[0015] In any embodiment, the compound of formula II may include at least one selected from biphenyl, fluorobenzene, and cyclohexylbenzene. By selecting the above compound, the overcharge prevention performance can be further improved.

[0016] In any embodiment, the electrolyte may satisfy a / b ≥ 11, preferably 11 ≤ a / b ≤ 35 (wherein a is the mass ratio of the compound of formula I in the solvent, and b is the mass ratio of the compound of formula II in the electrolyte). By setting a / b within the above range, the kinetic performance and overcharge prevention performance can be further improved.

[0017] In any embodiment, the electrolyte may further contain an electrolyte salt, and the electrolyte salt may contain a compound of formula III, wherein the molar ratio of the compound of formula III in the electrolyte salt is 10% or more, preferably 20% or more.

[0018] [ka]

[0019] (R6 and R7 are independently an F atom and a fluoroalkyl group, and R6 and R7 may be linked together to form a ring.)

[0020] This invention improves the water resistance of the electrolyte and enhances the high-temperature cycle characteristics of the battery by adding the compound of formula III to the electrolyte and setting the molar ratio of the compound of formula III in the electrolyte salt within the above range.

[0021] In any embodiment, the compound of formula III may include at least one selected from lithium bisfluorosulfonylimide and lithium bis(trifluoromethanesulfonyl)imide. By selecting the above compound, the resistance of the electrolyte to water can be further improved, and the high-temperature cycle characteristics of the battery can be improved.

[0022] In any embodiment, the solvent may further contain a carbonate ester, the mass ratio of the carbonate ester in the solvent being 30% or more, preferably 35% to 65%, and more preferably 40% to 50%.

[0023] In any embodiment, the solvent further contains ethylene carbonate, and the mass ratio of ethylene carbonate in the solvent is 30% or more.

[0024] By further including a carbonate ester in the solvent and setting the mass ratio of the carbonate ester in the solvent within the above range, sufficient dissociation of the electrolyte, especially the lithium salt, can be ensured, allowing for stable film formation on the negative electrode, thereby improving the stability of the negative electrode interface.

[0025] In any embodiment, the additive may further include at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1,3-propanesultone (PS), lithium difluorobisoxalatophosphate (LiDFOP), lithium difluorooxalatoborate (LiDFOB), and lithium bisoxalatoborate (LiBOB). By adding the above additive, the cycle characteristics and thermal stability of the battery can be further improved.

[0026] A second aspect of the present application provides a secondary battery containing the electrolyte described in the first aspect. The secondary battery of the present invention can simultaneously consider good kinetic performance, high-temperature performance, and excellent overcharge prevention performance.

[0027] In any embodiment, the secondary battery may include a positive electrode plate, the positive electrode plate may include a positive electrode coating layer, the positive electrode coating layer may include a positive electrode active material, and the positive electrode active material may include a lithium-containing phosphate with an olivine structure. By using a lithium-containing phosphate with an olivine structure as the positive electrode active material, the cycle life can be improved.

[0028] In any embodiment, the secondary battery is 1g / 1000m2 ≤ L ≤ 5 g / 1000 m 2 may be satisfied, preferably 1 g / 1000 m 2 ≤ L ≤ 4 g / 1000 m 2 is satisfied, more preferably 1.5 g / 1000 m 2 ≤ L ≤ 4 g / 1000 m 2 is satisfied. L = M1 / [M2×B×(a + c)] * 1000 (where M1 is the mass of the compound of Formula II, in g, M2 is the mass of the positive electrode active material, in g, B is the specific surface area of the positive electrode active material, in m 2 / g, a is the mass ratio of the compound of Formula I in the above solvent, and c is the molar ratio of the compound of Formula III in the above electrolyte salt). By setting L within the above range, the kinetic performance, high-temperature performance, and overcharge prevention performance of the battery can be further improved.

[0029] In any embodiment, 8 m 2 / g ≤ B ≤ 16 m 2 / g, preferably, 10 m 2 / g ≤ B ≤ 14 m 2 / g. By setting the specific surface area of the positive electrode active material within the above range, the solid-phase diffusion inside the positive electrode plate can be improved, contributing to the improvement of the kinetic performance of the cell.

[0030] In any embodiment, the thickness of the positive electrode coating layer on one side is 0.08 mm or more, preferably 0.09 mm to 0.3 mm.

[0031] The third aspect of the present application provides a power consumption device including the secondary battery described in the second aspect. Since the power consumption device of the present application includes the secondary battery, it has all the beneficial effects of the secondary battery.

Advantages of the Invention

[0032] According to the present invention, good kinetic performance, high-temperature performance, and excellent overcharge prevention performance of the battery can be considered simultaneously.

Brief Description of the Drawings

[0033] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present invention. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of the present invention. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present invention. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present invention. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of the present invention. [Figure 6] This is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to one embodiment of the present invention. [Modes for carrying out the invention]

[0034] Hereinafter, embodiments specifically disclosing the electrolyte, secondary battery, and power consumption device of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary details may be omitted. For example, detailed descriptions of known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid making the following description unnecessarily long and to make it easily understandable to those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0035] The “range” disclosed herein is defined in the form of a lower bound and an upper bound, and a given range is defined by selecting one lower bound and one upper bound, the selected lower and upper bounds define the boundaries of a particular range. The range thus defined may or may not include endpoint values ​​and can be arbitrarily combined, that is, any lower bound and any upper bound can be combined to form a single range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Also, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, all of the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are expected. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed herein, and "0 to 5" is merely an abbreviation for combinations of these numbers. Also, when it is stated that a parameter is an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all embodiments of this application and any other embodiments can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features of this application, as well as any other technical features, can be combined to form new technical proposals.

[0038] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly, preferably in order. For example, the fact that the method includes steps (a) and (b) indicates that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the fact that the method may further include step (c) indicates that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0039] Unless otherwise specified, the terms "include" and "incorporate" in this application may be open or closed. For example, the terms "include" and "incorporate" may mean that other components not listed may be included or incorporated, or that only the listed components may be included or incorporated.

[0040] Unless otherwise specified, the term "or" in this application is inclusive. For example, the expression "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist) all satisfy the condition "A or B."

[0041] This application provides an electrolyte, a secondary battery containing the electrolyte, and a power consumption device containing the secondary battery. The electrolyte, secondary battery, and power consumption device of this application will be described in detail below.

[0042] electrolyte In one embodiment of the present invention, an electrolyte is provided comprising a solvent and an additive, wherein the solvent comprises a compound of formula I, and the mass ratio of the compound of formula I in the solvent is 35% or more.

[0043] [ka]

[0044] (In the formula, R1 and R2 are each independently selected from a hydrogen atom, a C1-C3 linear alkyl group, and a C2-C3 alkenyl group.)

[0045] The above additive contains the compound of formula II.

[0046] [ka]

[0047] (In the formula, R3, R4, and R5 are each independently selected from a hydrogen atom, a fluorine atom, a phenyl group, a cyano group, a C1-C6 linear alkyl group, a C3-C6 cyclic alkyl group, and a C2-C6 alkenyl group.)

[0048] Although the mechanism is not yet clear, the applicant unexpectedly discovered that by using a compound of formula I and a compound of formula II in the electrolyte and setting the content of compound I to a predetermined amount, it is possible to simultaneously consider good kinetic performance, high-temperature characteristics, and excellent overcharge prevention performance of the battery.

[0049] In batteries using lithium iron phosphate (e.g., LiFePO4, also known as LFP) as the positive electrode active material, the most common method to improve energy density is to increase the thickness of the coating on the positive electrode plate to improve the utilization rate of space inside the cell. However, thicker coatings create new problems. Increasing the thickness of the positive electrode coating lengthens the transport pathway for lithium ions within the electrode plate, making lithium ion transport more difficult and requiring further improvement in the conductivity of the electrolyte. This problem becomes increasingly serious as the thickness of the positive electrode coating increases.

[0050] To solve this problem, the applicant discovered that by using a low-viscosity, high-dielectric solvent (for example, the compound of formula I above) in the electrolyte, the conductivity of the electrolyte can be significantly improved, thereby mitigating the current situation where lithium ion transport is difficult due to thick coating. However, the oxidation potential of the compound of formula I is low and greatly affects the overcharge performance of the LFP cell. To reduce safety issues such as thermal runaway in the overcharged state of the battery, the applicant discovered that the safety of the battery can be improved by adding the compound of formula II above as an overcharge prevention additive to the electrolyte. However, the addition of overcharge prevention additives such as the compound of formula II affects the dynamic performance of the battery.

[0051] As a result of diligent research, the applicant has discovered that by adding a specific amount of the compound of formula I to an electrolyte containing the compound of formula II, the kinetic performance and high-temperature performance of the battery can be improved. This allows for the simultaneous consideration of good kinetic performance, high-temperature performance, and overcharge prevention performance through the synergistic effect of the specific amounts of the compound of formula I and the compound of formula II.

[0052] In some embodiments, the compound of formula I above includes methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, and ethyl acrylate. Preferably, the compound of formula I includes at least one selected from methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate, and ethyl acrylate. More preferably, it includes methyl formate and ethyl acetate. These compounds are used as solvents for the electrolyte, and because these compounds have lower viscosity and higher dielectric constant than linear carbonates, adding these compounds to the electrolyte and replacing linear carbonates can effectively improve the conductivity of the electrolyte, thereby further improving the dynamic performance of the battery.

[0053] The solvent of the electrolyte in this application contains the compound of formula I, and the mass ratio of the compound of formula I in the solvent is 35% or more, preferably 40% to 70%, and more preferably 50% to 60%. If the mass ratio of the compound of formula I in the solvent is less than 35%, the conductivity decreases, the initial DCR (Directive Current Resistance) increases, and the dynamic performance of the battery decreases. Therefore, by setting the mass ratio of the compound of formula I in the solvent within the above range, this application ensures that the electrolyte has high conductivity and low viscosity and can be applied to thick coating systems, thereby further improving the dynamic performance of the battery. Furthermore, if the mass ratio of the compound of formula I in the solvent is greater than 70%, it is disadvantageous for overcharge prevention performance.

[0054] Furthermore, in this application, the solvent of the electrolyte may further contain one or more carbonate esters selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC). The mass ratio of the above carbonate esters in the solvent may be 30% or more, preferably 35% to 65%, and more preferably 40% to 50%. Preferably, ethylene carbonate is included, and more preferably, the mass ratio of the ethylene carbonate in the solvent is 30% or more. By including ethylene carbonate in the solvent and setting the mass ratio of ethylene carbonate in the solvent within the above range, sufficient dissociation of the electrolyte, especially the lithium salt, can be ensured, a stable film can be formed on the negative electrode, and thereby the stability of the negative electrode interface can be improved.

[0055] In some embodiments, the electrolyte of the present invention contains the compound of formula II as an additive, and the compound of formula II functions as an overcharge inhibitor. Preferably, the compound of formula II may include at least one selected from biphenyl, fluorobenzene, and cyclohexylbenzene. The present invention can further improve overcharge prevention performance by using the above compound as an overcharge inhibitor. The present invention preferably includes fluorobenzene. When the cell is overcharged, the voltage rises, the overcharge prevention additive polymerizes, and the polymerization forms an insulating film on the electrode surface, increasing the internal resistance of the battery, reducing or cutting off the overcharge current, and improving the safety performance of the battery. On the other hand, a large amount of heat is released, and the fluorobenzene-based substance polymerizes at high voltage to become a fluorine-containing polymer, resulting in better high-temperature resistance. Furthermore, compared to other benzene ring-based substances, fluorobenzene-based substances readily bond with electrons through fluorine substitution, and to some extent can suppress the reduction side reaction of the compound of formula I at the negative electrode.

[0056] Furthermore, the mass ratio of the compound of formula II in the electrolyte is 9% or less, preferably 3% to 8%, more preferably 3% to 7%, even more preferably 3% to 6%, and particularly preferably 3% to 5%. If the content of the compound of formula II is too high, it is detrimental to the conductivity of the electrolyte, and therefore detrimental to the dynamic performance of the battery. If the content of the compound of formula II is too low, it is detrimental to the overcharge prevention performance. By setting the mass ratio of the compound of formula II in the electrolyte within the above range, the present invention can further improve the overcharge prevention performance without affecting the conductivity of the electrolyte.

[0057] In some embodiments, the electrolyte satisfies a / b ≥ 11, preferably 11 ≤ a / b ≤ 35, more preferably 11 ≤ a / b ≤ 33, even more preferably 15 ≤ a / b ≤ 30, and particularly preferably 16 ≤ a / b ≤ 27. a is the mass ratio of the compound of formula I in the solvent, and b is the mass ratio of the compound of formula II in the electrolyte. The present invention can further improve dynamic performance by setting a / b within the above range.

[0058] On the other hand, because LFP material itself is highly absorbent, moisture in the positive electrode plate cannot be completely removed during the cell production process when packaging before electrolyte injection. In subsequent use, moisture in the positive electrode plate gradually diffuses into the electrolyte, causing a side reaction with lithium hexafluorophosphate (LiPF6) in the electrolyte, generating hydrogen fluoride, which destroys the SEI (solid electrolyte interphase) film, reduces the stability of the negative electrode interface, and accelerates cycle decay. The applicant has discovered that using a water-insensitive lithium salt (for example, the compound of formula III below) can reduce the effect of moisture on the electrode plate and avoid side reactions between the lithium salt and water. However, like the compound of formula I, the compound of formula III also has a low oxidation potential, which significantly affects the overcharge performance of the LFP cell. By adding the compound of formula II above to the electrolyte as an overcharge prevention additive, the objective of improving battery safety can be achieved.

[0059] Accordingly, in some embodiments, the electrolyte of the present application comprises an electrolyte salt, which preferably comprises a compound of formula III.

[0060] [ka]

[0061] (R6 and R7 are independently an F atom and a fluoroalkyl group, respectively. The alkyl group of the fluoroalkyl group may be a methyl group, an ethyl group, a propyl group, etc., and the fluoroalkyl group may be a partially fluorinated alkyl group or a fully fluorinated alkyl group, for example lithium bis(trifluoromethanesulfonyl)imide, lithium bis(nonafluorobutanesulfonyl)imide, lithium bis(pentafluoroethanesulfonyl)imide (C4F) 10 LiNO4S2 is one example. Furthermore, R6 and R7 can be linked to form a ring, such as 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium (C3F6LiNO4S2).

[0062] In some embodiments, the compound of formula III preferably comprises at least one selected from lithium bisfluorosulfonylimide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). More preferably, it comprises lithium bisfluorosulfonylimide (LiFSI). The lithium salt is insensitive to moisture and can mitigate the adverse effects of increased moisture due to thickening of the electrode plates. Therefore, by selecting the compound of formula III as the electrolyte salt, the water resistance of the electrolyte can be further improved, and the thermal cycling characteristics of the battery, particularly at 45°C, can be improved.

[0063] The molar ratio of the compound of formula III in the electrolyte salt may be 10% or more, preferably 20% or more, more preferably 30% or more, even more preferably 40%, particularly preferably 50% or more, and also preferably 80% or less, more preferably 75% or less, even more preferably 70% or less, and particularly preferably 60% or less. By setting the molar ratio of the compound of formula III in the electrolyte salt within the above range, the resistance of the electrolyte to water can be improved.

[0064] Furthermore, the electrolyte salt may further contain lithium hexafluorophosphate (LiPF6). While lithium hexafluorophosphate has high oxidation resistance, it has low thermal stability and is prone to decomposition when in contact with water. The electrolyte of this invention contains a lithium salt of the compound of formula III, and these lithium salts have high thermal stability. Therefore, oxidation resistance and thermal stability can be obtained by adding lithium hexafluorophosphate and a lithium salt of the compound of formula III.

[0065] In some embodiments, the electrolyte of the present application may further contain additives such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1,3-propanesultone (PS), lithium difluorobisoxalatophosphate (LiDFOP), lithium difluorooxalatoborate (LiDFOB), and lithium bisoxalatoborate (LiBOB). Vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and 1,3-propanesultone (PS) can function as film-forming additives. When vinylene carbonate (VC) and 1,3-propanesultone (PS) function as film-forming additives, the impedance is high but the film-forming stability is high, while when fluoroethylene carbonate (FEC) and ethylene sulfate (DTD) function as film-forming additives, the impedance is low but the film-forming stability is low. Furthermore, additives such as lithium difluorobisoxalatophosphate (LiDFOP), lithium difluorooxalatoborate (LiDFOB), and lithium bisoxalatoborate (LiBOB) are not sensitive to moisture and can mitigate the adverse effects of increased moisture content caused by thickening the electrode plates. Therefore, by adding these additives, the cycle characteristics and stability of the battery can be further improved.

[0066] In some embodiments, the conductivity of the electrolyte of the present invention at 25°C is 13 mS / cm or higher, and may be, for example, 14 mS / cm to 18 mS / cm, 15 mS / cm to 17 mS / cm, or 16 mS / cm to 17 mS / cm. If the conductivity of the electrolyte is too low, the dynamic performance of the electrolyte will be insufficient; if the coating thickness of the positive electrode plate is too high, the dynamic performance of the battery will be affected; and if the conductivity of the electrolyte is too high, the thermal stability of the electrolyte will be insufficient, and the high-temperature performance of the battery will be affected. When the conductivity of the electrolyte of the present invention at 25°C is within the above range, the dynamic performance of the electrolyte can be improved, as well as the high and low temperature performance and energy density of the battery can be improved.

[0067] secondary battery A second aspect of the present invention provides a secondary battery containing the above-mentioned electrolyte. The secondary battery of the present invention can simultaneously consider good kinetic performance, high-temperature performance, and excellent overcharge prevention performance.

[0068] The secondary battery of this application may be a lithium-ion secondary battery or the like. Typically, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are inserted and removed by reciprocating between the positive and negative electrode plates. The electrolyte plays a role in conducting ions between the positive and negative electrode plates. The separator is interposed between the positive and negative electrode plates and mainly plays a role in preventing short circuits between the positive and negative electrodes, while allowing ions to pass through.

[0069] [Positive electrode plate] The positive electrode plate includes a positive electrode current collector and a positive electrode coating layer provided on at least one surface of the positive electrode current collector, the positive electrode coating layer containing a positive electrode active material.

[0070] For example, the positive electrode current collector has two opposing surfaces in the direction of its own thickness, and the positive electrode coating layer is applied to one or two of the two opposing surfaces of the positive electrode current collector.

[0071] The positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0072] The positive electrode active material may be any positive electrode active material for batteries known in the art. For example, the positive electrode active material may include an olivine-structured lithium-containing phosphate, which can extend the battery's cycle life. The positive electrode active material may further include lithium transition metal oxides and their modified compounds. However, this application is not limited to these materials, and other conventional materials used as positive electrode active materials for batteries may be used. These positive electrode active materials may be used individually or in combination of two or more. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be called LFP)), a lithium iron phosphate-carbon composite, lithium manganese phosphate (e.g., LiMnPO4), a lithium manganese phosphate-carbon composite, lithium iron manganese phosphate, or a lithium iron manganese phosphate-carbon composite. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (May also be called) LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (May also be called) LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (May also be called) LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (May also be called) LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 (May also be called), lithium nickel cobalt aluminum oxide (e.g., LiNi0.85 Co 0.15 Al 0.05 It may contain, but is not limited to, at least one of O2 and modified compounds thereof.

[0073] The above positive electrode coating layer preferably further comprises an adhesive. As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0074] The above positive electrode coating layer preferably further comprises a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0075] In some embodiments, the thickness of the positive electrode coating layer on one side is 0.08 mm or more, preferably 0.09 mm to 0.3 mm.

[0076] In some embodiments, the positive electrode plate may be manufactured by dispersing the above-mentioned components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, and an adhesive, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, applying the positive electrode slurry to a positive electrode current collector, and obtaining the positive electrode plate by performing processes such as drying and cold pressing.

[0077] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode coating layer installed on at least one surface of the negative electrode current collector, the negative electrode coating layer containing a negative electrode active material.

[0078] For example, the negative electrode current collector has two opposing surfaces in the direction of its own thickness, and the negative electrode coating layer is installed on one or two of the two opposing surfaces of the negative electrode current collector.

[0079] The negative electrode current collector may be a metal foil sheet or a composite current collector. For example, copper foil may be used as the metal foil sheet. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0080] The negative electrode active material described above may be any negative electrode active material known in the art for use in batteries. For example, the negative electrode active material may include at least one of the following: artificial graphite, natural graphite, soft carbon, hard carbon, silicon material, tin material, and lithium titanate. The silicon material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin material may be at least one selected from elemental tin, tin oxygen compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials used as negative electrode active materials in batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0081] The above-mentioned negative electrode coating layer preferably further comprises an adhesive. The adhesive may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl methacrylate (PMAA), and carboxymethyl chitosan (CMCS).

[0082] The above-mentioned negative electrode coating layer preferably further comprises a conductive agent. The conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] The negative electrode coating layer preferably further contains other additives such as a thickening agent (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0084] In some embodiments, the negative electrode plate may be manufactured by dispersing the above-mentioned components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, and an adhesive, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, applying the negative electrode slurry to a negative electrode current collector, and obtaining the negative electrode plate by performing processes such as drying and cold pressing.

[0085] [Electrolyte] The electrolyte plays the role of conducting ions between the positive and negative electrodes. The electrolyte used is the one described in the "Electrolyte" section above.

[0086] [Separator] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known separator with a porous structure that is excellent in chemical and mechanical stability can be selected.

[0087] In some embodiments, the material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multilayer composite thin film, and is not particularly limited. If the separator is a multilayer composite thin film, the materials of each layer may be the same or different, and are not particularly limited.

[0088] [Secondary battery] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be formed into an electrode assembly by a winding process or a lamination process.

[0089] In some embodiments, the secondary battery may include an outer casing. This casing may be used to seal the electrode assembly and electrolyte.

[0090] In some embodiments, the casing of the secondary battery may be a hard case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft pack, such as a pouch soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0091] This application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular secondary battery 5 as an example.

[0092] In some embodiments, referring to Figure 2, the exterior may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates defining a housing cavity. The housing 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening to seal the housing cavity. The positive electrode plate, negative electrode plate and separator can be formed into an electrode assembly 52 by a winding or lamination process. The electrode assembly 52 is packaged within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and a person skilled in the art may select according to specific practical needs.

[0093] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0094] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be secured with fasteners.

[0095] Preferably, the battery module 4 may further include a casing having a housing space, in which a plurality of secondary batteries 5 are housed.

[0096] In some embodiments, the battery modules may be further assembled into a battery pack, the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0097] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 5, the battery pack 1 may include a battery housing and a plurality of battery modules 4 installed in the battery housing. The battery housing includes an upper housing 2 and a lower housing 3, and the upper housing 2 may be covered by the lower housing 3 and form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery housing in any manner.

[0098] In some embodiments, the secondary battery of the present invention has a capacity of 1g / 1000m 2 ≤L ≤ 5g / 1000m 2 Satisfying the following conditions, preferably 1g / 1000m 2 ≤L ≤ 4g / 1000m 2 It satisfies the requirements and provides a comfortable 1.5g / 1000m 2 ≤L ≤ 4g / 1000m 2 It satisfies the requirements and provides a comfortable 1.5g / 1000m 2More than 3.5g / 1000m 2 The following is the formula: L = M1 / [M2 × B × (a + c)] * 1000. M1 is the mass of the compound in formula II, in units of g; M2 is the mass of the positive electrode active material, in units of g; and B is the specific surface area of ​​the positive electrode active material, in units of m. 2 / g, where a is the mass ratio of the compound of formula I in the solvent, and c is the molar ratio of the compound of formula III in the electrolyte salt. By setting L within the above range, the kinetic performance, high-temperature performance, and overcharge prevention performance of the battery can be further improved.

[0099] In some embodiments, 8m 2 / g ≤ B ≤ 16m 2 / g, preferably 10m 2 / g ≤ B ≤ 14m 2 The specific surface area of ​​the positive electrode active material is / g. If the specific surface area of ​​the positive electrode active material is too large, side reactions increase, affecting the performance of the battery. If the specific surface area of ​​the positive electrode active material is too small, the transport of lithium ions within the particles is hindered, affecting the performance of the battery. By setting the specific surface area of ​​the positive electrode active material within the above range, solid-phase diffusion inside the positive electrode plate can be improved, contributing to an improvement in the dynamic performance of the cell.

[0100] power consumption equipment A third aspect of the present invention provides a power consumption device including the above-mentioned secondary battery. Because the power consumption device of the present invention includes the above-mentioned secondary battery, it has all the beneficial effects of the secondary battery.

[0101] The above-mentioned secondary battery may be used as a power source for the above-mentioned power consumption device, or as an energy storage unit for the above-mentioned power consumption device. The above-mentioned power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid vehicles, plug-in hybrid vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0102] The above-mentioned power consumption device may be a secondary battery, a battery module, or a battery pack, depending on the needs of its use.

[0103] Figure 6 shows an example of a power consumption device. This power consumption device may be a pure electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. To meet the high power and high energy density needs of the secondary battery of this power consumption device, a battery pack or battery module may be used.

[0104] Other examples of such devices may include mobile phones, tablet PCs, and laptop computers. Since these devices typically require lighter and thinner designs, they can be powered by rechargeable batteries.

[0105] Examples Examples of the present application are described below. The examples described below are illustrative and are for interpretive purposes only, and should not be understood as limiting the present application. Where no specific technical or technical conditions are shown in the examples, they are carried out in accordance with the technical or technical conditions or product instructions described in the literature of the art. Unless the manufacturer is indicated, the reagents or equipment used are all common products available on the market.

[0106] Example 1 Manufacturing of positive electrode plates Lithium iron phosphate (LFP) with an olivine structure, polyvinylidene fluoride (PVDF), and carbon black (SP) were mixed with a solvent in a mass ratio of 97:2.5:0.5, stirred, and uniformly dispersed to obtain a positive electrode slurry. The positive electrode slurry was then uniformly applied to two sides of an aluminum foil, dried, cold-pressed, and cut to obtain a positive electrode plate. Lithium iron phosphate with an olivine structure was used as the positive electrode active material, and its specific surface area was 12 m². 2 The density was / g, and the thickness of the cold-pressed single-layer film was 0.1 mm.

[0107] Manufacturing of negative electrode plates The negative electrode active material (artificial graphite), carbon black (SP), styrene-butadiene rubber (SBR), and carboxymethyl fiber (CMC) were mixed with a solvent in a ratio of 97:0.5:1.5:1, stirred, and uniformly dispersed to obtain a negative electrode slurry. The negative electrode slurry was then uniformly applied to two sides of a copper foil, dried, cold-pressed, and cut to obtain a negative electrode plate. The thickness of the cold-pressed single-layer film plate was 0.07 mm.

[0108] Separator Polyethylene film was used as a separator.

[0109] Manufacturing of electrolyte In a glove box under an argon atmosphere, 35% by mass of ethyl acetate, 30% by mass of ethylene carbonate, and 35% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Next, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 3%. Then, 1 mol / L lithium hexafluorophosphate (LiPF6) was slowly added as the electrolyte salt. The mixture was then stirred until completely dissolved to obtain the electrolyte.

[0110] Manufacturing of lithium-ion rechargeable batteries The positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator placed between the positive and negative electrode plates to serve as a separator. Next, the assembly was wound up to obtain an electrode assembly, which was then placed in an outer casing, dried, and the electrolyte was injected. Subsequently, processes such as formation and settling were carried out to obtain a secondary battery. The final lithium-ion battery contained 1400g of positive electrode active material and 620g of electrolyte.

[0111] Example 2 In the preparation of the electrolyte, 40% by mass of ethyl acetate, 30% by mass of ethylene carbonate, and 30% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0112] Example 3 In the preparation of the electrolyte, 50% by mass of ethyl acetate, 30% by mass of ethylene carbonate, and 20% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0113] Example 4 In the preparation of the electrolyte, 60% by mass of ethyl acetate, 30% by mass of ethylene carbonate, and 10% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0114] Example 5 In the preparation of the electrolyte, 70% by mass of ethyl acetate and 30% by mass of ethylene carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0115] Example 6 In the preparation of the electrolyte, 80% by mass of ethyl acetate and 20% by mass of ethylene carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0116] Example 7 In the preparation of the electrolyte, 50% by mass of methyl formate, 30% by mass of ethylene carbonate, and 20% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0117] Example 8 In the preparation of the electrolyte, 50% by mass of methyl acetate, 30% by mass of ethylene carbonate, and 20% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0118] Example 9 In the preparation of the electrolyte, 50% by mass of propyl acetate, 30% by mass of ethylene carbonate, and 20% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0119] Example 10 In the preparation of the electrolyte, 50% by mass of methyl acrylate, 30% by mass of ethylene carbonate, and 20% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0120] Example 11 In the preparation of the electrolyte, 50% by mass of ethyl acrylate, 30% by mass of ethylene carbonate, and 20% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0121] Example 12 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 1%. Otherwise, the procedure was the same as in Example 3.

[0122] Example 13 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 2%. Otherwise, the procedure was the same as in Example 3.

[0123] Example 14 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 4%. Otherwise, the procedure was the same as in Example 3.

[0124] Example 15 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 5%. Otherwise, the procedure was the same as in Example 3.

[0125] Example 16 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 9%. Otherwise, the procedure was the same as in Example 3.

[0126] Example 17 In the preparation of the electrolyte, biphenyl was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 3%. Otherwise, the procedure was the same as in Example 3.

[0127] Example 18 In the preparation of the electrolyte, cyclohexylbenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 3%. Otherwise, the procedure was the same as in Example 3.

[0128] Example 19 In the preparation of the electrolyte, lithium hexafluorophosphate (LiPF6) at a concentration of 0.5 mol / L and lithium bisfluorosulfonylimide at a concentration of 0.5 mol / L were slowly added as electrolyte salts, and the molar ratio of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide in the electrolyte salt was 50%, each. Otherwise, it was the same as in Example 3.

[0129] Example 20 In the preparation of the electrolyte, lithium hexafluorophosphate (LiPF6) at a concentration of 0.5 mol / L and lithium bis(trifluoromethanesulfonyl)imide at a concentration of 0.5 mol / L were slowly added as electrolyte salts, and the molar ratio of lithium hexafluorophosphate (LiPF6) and lithium bis(trifluoromethanesulfonyl)imide in the electrolyte salt was 50% each. Otherwise, the procedure was the same as in Example 3.

[0130] Example 21 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 3%, and vinylene carbonate was added so that its mass ratio in the resulting electrolyte was 2%. Otherwise, the procedure was the same as in Example 19.

[0131] Example 22 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 3%, and fluoroethylene carbonate was added so that its mass ratio in the resulting electrolyte was 1%. Otherwise, the procedure was the same as in Example 19.

[0132] Example 23 In the preparation of the electrolyte, fluorobenzene was added to the organic solvent mixture so that its mass ratio in the resulting electrolyte was 3%, and ethylene sulfate was added so that its mass ratio in the resulting electrolyte was 1%. Otherwise, the procedure was the same as in Example 19.

[0133] Comparative Example 1 In the preparation of the electrolyte, 30% by mass of ethyl acetate, 30% by mass of ethylene carbonate, and 40% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0134] Comparative Example 2 In the preparation of the electrolyte, 30% by mass of ethylene carbonate and 70% by mass of dimethyl carbonate were mixed to obtain an organic solvent mixture. Otherwise, the procedure was the same as in Example 1.

[0135] Comparative Example 3 In the preparation of the electrolyte, fluorobenzene was not added. Otherwise, it was the same as in Example 3.

[0136] The relevant parameters for Examples 1-23 and Comparative Examples 1-3 are shown in Table 1 below.

[0137] [Table 1A] [Table 1B] [Table 1C] [Table 1D] [Table 1E] [Table 1F]

[0138] Note: In Table 1, The content of each solvent is expressed as the mass ratio of each solvent to the total solvent mass. The content of each additive is expressed as the mass ratio of each additive in the electrolyte. a is the mass ratio of the compound of formula I to the total solvent mass. b is the mass ratio of the compound additive of formula II in the electrolyte. L = M1 / ​​[M2 × B × (a + c)] * 1000 (wherein M1 is the mass of the additive compound in formula II, in units of g; M2 is the mass of the positive electrode active material, in units of g; and B is the specific surface area of ​​the positive electrode active material, in units of m) 2 (where / g, the meaning of a is the same as above, and c is the molar ratio of the electrolyte salt of the compound in formula III in the electrolyte salt.)

[0139] The testing method is as follows:

[0140] (1) Initial DCR (Directive Current Resistance) At room temperature, the batteries of each example and comparative example were charged to 3.65V with a constant current of 0.5C, then charged with a constant voltage to a current of 0.05C, and the batteries were discharged with a constant current of 0.5C for 30 minutes to adjust the batteries to 50% SOC, with the battery voltage at this time being defined as U1. The batteries were then discharged with a constant current of 4C for 30 seconds, with data collected at 0.1-second intervals, and the discharge end voltage was defined as U2. The initial DCR of the battery was expressed as the discharge DCR at 50% SOC, and the initial DCR of the battery was defined as (U1-U2) / 4C.

[0141] (2) High-temperature cycle performance of the battery At 45°C, the batteries of each example and comparative example were charged to 3.65V with a constant current of 1.0C, then charged again with a constant voltage to a current of 0.05C, the batteries were left to stand for 5 minutes, and then discharged to 2.5V with a constant current of 1.0C. This was the first charge-discharge cycle of the battery, and the discharge capacity recorded was considered to be the discharge capacity of the battery's first cycle. Using the above method, the battery underwent 100 charge-discharge cycles, and the discharge capacity of the battery after 100 cycles was recorded. The capacity retention rate (%) of the battery after 100 cycles at 45°C is calculated as follows: (Discharge capacity of the battery after 100 cycles / Discharge capacity of the battery in the first cycle) × 100%.

[0142] (3) Battery overcharge protection performance At 25°C, the batteries of each example and comparative example are charged to 3.65V with a constant current and voltage of 1C, with a cutoff current of 0.05C. Once the batteries are fully charged, they are charged with a constant current of 1C until the voltage reaches 6V, and observed for 1 hour to check whether the batteries ignite and explode. If only smoke is emitted without ignition or explosion, the test is considered passed. If ignition or explosion occurs, the test is considered failed, and the above procedure is repeated 30 times, recording the number of times the test is passed (number of overcharge passes).

[0143] As can be seen from the results above, Examples 1 to 23 all possess excellent kinetic performance, high-temperature performance, and superior overcharge prevention performance, and can achieve good results.

[0144] In contrast, in Comparative Example 1, the desired effect was not obtained because the content of the compound of formula I was not within the scope of the present invention. In particular, the initial DCR increased to 3.6. In Comparative Example 2, the desired effect was not obtained because the compound of formula I was not added. In particular, the initial DCR increased significantly to 6.0, and the battery dynamics became significantly lower. In Comparative Example 3, no promising effect was obtained because the compound of formula II was not added. In particular, the overcharge prevention performance became significantly lower. As can be seen from the above, by using specific amounts of the compound of formula I and the compound of formula II in combination, it is possible to consider good dynamic performance, high-temperature performance, and excellent overcharge prevention performance of the battery.

[0145] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are merely examples, and any embodiment that has substantially the same configuration as the technical idea and exhibits the same effects within the scope of the technical invention of this application is included within the scope of the technical invention of this application. In addition, other forms that combine some of the components of the embodiments by making various modifications to the embodiments that a person skilled in the art could conceive of, without departing from the gist of this application, are also included within the scope of this application. [Explanation of Symbols]

[0146] 1: Battery pack 2: Upper cabinet 3: Lower cabinet 4: Battery module 5: Secondary battery 51: Housing 52: Electrode assembly 53: Top cover assembly

Claims

1. A secondary battery comprising an electrolyte and a positive electrode plate, The positive electrode plate includes a positive electrode coating layer, the positive electrode coating layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure. The electrolyte comprises a solvent and an additive. The solvent contains the compound of formula I, and the mass ratio of the compound of formula I in the solvent is 35% or more. The aforementioned additive comprises the compound of formula II, a is the mass ratio of the compound of formula I in the solvent, b is the mass ratio of the compound of formula II in the electrolyte, A secondary battery in which the electrolyte satisfies 20 ≤ a / b ≤ 30, and the mass ratio of the compound of formula I in the solvent is 50% to 80%. 【Chemistry 1】 (In the formula, R １ , R ２ Each of these is independently selected from a hydrogen atom, a C1-C3 linear alkyl group, and a C2-C3 alkenyl group. 【Chemistry 2】 (In the formula, R ３ , R ４ , R ５ Each of these is independently selected from a hydrogen atom, a fluorine atom, a phenyl group, a cyano group, a C1-C6 linear alkyl group, a C3-C6 cyclic alkyl group, and a C2-C6 alkenyl group.

2. The secondary battery according to claim 1, wherein the mass ratio of the compound of formula II in the electrolyte is 9% or less.

3. The secondary battery according to claim 2, wherein the mass ratio of the compound of formula II in the electrolyte is 3% to 5%.

4. The secondary battery according to any one of claims 1 to 3, wherein the compound of formula I comprises at least one selected from methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate, and ethyl acrylate.

5. The secondary battery according to any one of claims 1 to 4, wherein the compound of formula II comprises at least one of biphenyl, fluorobenzene, and cyclohexylbenzene.

6. The secondary battery according to claim 1, wherein the electrolyte solution comprises an electrolyte salt, and the electrolyte salt comprises a compound of formula III. 【Transformation 3】 (wherein, R ６ , R ７ are each independently an F atom or a fluoroalkyl group, and R ６ , R ７ may also be linked to form a ring.)

7. The secondary battery according to claim 6, wherein the molar ratio of the compound of formula III in the electrolyte salt is 10% or more.

8. The secondary battery according to claim 6, comprising at least one compound selected from lithium bisfluorosulfonylimide and lithium bis(trifluoromethanesulfonyl)imide.

9. The secondary battery according to any one of claims 1 to 8, wherein the solvent further comprises a carbonate ester, and the mass ratio of the carbonate ester in the solvent is 30% or more.

10. The secondary battery according to any one of claims 1 to 8, wherein the solvent further contains ethylene carbonate, and the mass ratio of the ethylene carbonate in the solvent is 30% or more.

11. The secondary battery according to any one of claims 1 to 10, wherein the additive further comprises at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1,3-propanesultone (PS), lithium difluorobisoxalatophosphate (LiDFOP), lithium difluorooxalatoborate (LiDFOB), and lithium bisoxalatoborate (LiBOB).

12. The aforementioned secondary battery is 1g / 1000m ２ ≦L≦5g / 1000m ２ A secondary battery according to claim 1 that satisfies the requirements. L=M1 / [M2×B×(a+c)]*1000 (M1 is the mass of the compound of formula II, and its unit is g.) M2 is the mass of the positive electrode active material, and its unit is grams. B is the specific surface area of ​​the positive electrode active material, and its unit is m. ２ / g, a is the mass ratio of the compound of formula I in the solvent, c is the molar ratio of the compound in formula III in the electrolyte salt.

13. 8m ２ / g ≤ B ≤ 16m ２ The secondary battery according to claim 12, wherein the value is / g.

14. The secondary battery according to any one of claims 12 to 13, wherein the thickness of the positive electrode coating layer on one side is 0.08 mm or more.

15. A power consumption device including a secondary battery according to any one of claims 12 to 14.

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