Lithium secondary battery and electrical apparatus

Abstract

A lithium secondary battery and an electrical apparatus. The battery comprises an electrolyte, the electrolyte containing a carboxylic ester compound, and based on the mass of the electrolyte, the mass percentage A of the carboxylic ester compound is not less than 30% and not greater than 70%. The battery satisfies the expression: 0.7≤A×(T+L) / H≤7.7, A being the mass percentage of the carboxylic ester compound based on the mass of the electrolyte, T being the thickness of a battery housing in a direction perpendicular to a connecting line of the positive electrode and the negative electrode of the battery, in millimeters, L being the length of the battery housing in a direction parallel to the connecting line of the positive and negative electrodes of the battery, in millimeters, and H being the height of the battery housing in a direction parallel to the direction of gravity when the battery is placed on the ground, in millimeters. The lithium secondary battery, by means of improving the electrolyte, reduces an amount of gas production in a lithium secondary battery circulation process and a storage process, thus comprehensively improving the performance of the lithium secondary battery.

Description

Lithium secondary battery and power-consuming device

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311582292.X, filed on November 23, 2023, entitled “A Lithium Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the technical field of lithium batteries, and in particular to a lithium secondary battery and an electrical device. Background Art

[0004] In recent years, the application of lithium-ion batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the rapid development of lithium-ion batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance. Improving battery power performance, cycle life, and storage life has always been an industry goal. However, due to side reactions of the electrolyte at the anode and cathode interfaces, the overall performance of the battery cells has been poor.

[0005] Summary of the Invention

[0006] The present application is made in view of the above-mentioned problems, and its purpose is to provide a lithium secondary battery, which aims to improve the electrolyte and electrolyte infiltration by improving the electrolyte, thereby reducing the gas production during the circulation and storage process of the lithium secondary battery and comprehensively improving the performance of the lithium secondary battery.

[0007] To achieve the above-mentioned object, a first aspect of the present application provides a lithium-ion secondary battery, the battery comprising an electrolyte, the electrolyte comprising a carboxylate compound, and the mass percentage A of the carboxylate compound, based on the mass of the electrolyte, is not less than 30% and not more than 70%;

[0008] The battery satisfies: 0.7≤A×(T+L) / H≤7.7,

[0009] Wherein, A is the mass percentage of the carboxylate compound based on the mass of the electrolyte; T is the thickness of the battery casing in a direction perpendicular to the line connecting the positive and negative electrodes of the battery, in millimeters; L is the length of the battery casing in a direction parallel to the line connecting the positive and negative electrodes of the battery, in millimeters; H is the height of the battery casing in a direction parallel to the direction of gravity when the battery is placed on the ground, in millimeters.

[0010] The carboxylate compounds contained in the electrolyte provided herein have low viscosity, facilitating rapid electrolyte resorption and improving electrolyte wetting. However, carboxylate compounds have poor reduction stability, and excessive amounts can easily cause reduction side reactions at the negative electrode, worsening battery storage gassing. Therefore, when the battery size and carboxylate compound content satisfy the relationship of 0.7 ≤ A × (T + L) / H ≤ 7.7, both battery gassing and electrolyte wetting can be balanced, comprehensively improving battery cycle performance.

[0011] In any embodiment, the carboxylate compound includes a compound having a structure shown in Formula I,

[0012] Wherein, R1 and R2 each independently include at least one of a C1-C6 alkyl group and a C1-C6 halogenated alkyl group.

[0013] In any embodiment, the carboxylate compound includes at least one of ethyl acetate, methyl acetate, methyl formate, methyl propionate, ethyl propionate, and propyl propionate.

[0014] The carboxylic acid ester solvents mentioned above have a low viscosity, which can better improve the ionic conductivity of the electrolyte and better improve the wetting problem of the electrolyte.

[0015] In any embodiment, the electrolyte contains a high-viscosity solvent with a viscosity greater than 0.6 cP at 25° C., and the mass percentage of the high-viscosity solvent is 10%-40% based on the mass of the electrolyte. Optionally, the mass percentage of the high-viscosity solvent is 20%-30%.

[0016] In any embodiment, the dielectric constant of the high-viscosity solvent is ≥60. Optionally, the high-viscosity solvent includes at least one of ethylene carbonate (EC) and propylene carbonate (PC).

[0017] By controlling the content of the high-viscosity solvent within the above range, the gas production and electrolyte infiltration of the battery can be better taken into account, thereby comprehensively improving the cycle performance of the battery.

[0018] In any embodiment, the battery comprises an anode membrane, wherein the thickness of the anode membrane is 50-100 μm, optionally, the thickness of the anode membrane is 70-80 μm.

[0019] In any embodiment, the battery comprises a cathode membrane, wherein the thickness of the cathode membrane is 70-130 μm, optionally wherein the thickness of the cathode membrane is 100-120 μm.

[0020] In any embodiment, the battery comprises a separator, and the thickness of the separator is 5-20 μm, optionally, the thickness of the separator is 5-12 μm.

[0021] In any embodiment, the relationship between the thickness C of the separator and the thickness D of the cathode membrane is 5%≤C / D≤20%.

[0022] Increasing the separator thickness to a certain extent facilitates electrolyte wetting of the electrode and allows for faster electrolyte reabsorption when squeezed out. However, increasing the thickness of the electrode increases the resistance to lithium ion transmission, which deteriorates the battery's DC resistance (DCR) to a certain extent. Therefore, when the thickness of the anode, cathode, and separator meet the above relationship, the battery's room temperature cycling performance and DCR can be better improved.

[0023] In any embodiment, the electrolyte contains lithium salt, and the mass percentage of the lithium salt is 8%-20% based on the mass of the electrolyte.

[0024] In any embodiment, the lithium salt includes at least one of LiPF6, LiFSI, and LiTFSI.

[0025] When the lithium salt concentration is high, the electrolyte kinetics is better and the DCR is lower. However, excessive lithium salt content will lead to higher electrolyte viscosity, which is not conducive to electrolyte resorption and leads to poor room temperature cycling performance of the battery. Therefore, when the lithium salt content meets the above range, the battery's DCR and room temperature cycling performance can be better improved.

[0026] In any embodiment, the electrolyte further comprises at least one of an additive X and an additive Y, and based on the mass of the electrolyte, the mass percentage of the additive X is 0.1% to 1%, and the mass percentage of the additive Y is 2% to 6%, wherein the additive X comprises at least one of a cyclic sulfonate and a cyclic sulfate, and the cyclic sulfonate and the cyclic sulfate contain a sulfate group, a sulfite group, and / or a sulfonic acid group, and / or the additive Y comprises at least one of a cyclic carbonate containing an unsaturated bond, and the cyclic carbonate containing an unsaturated bond contains a carbonic acid group.

[0027] In any embodiment, the additive X includes at least one of 1,3-propane sultone (PS), 1,3-propene sultone (PES), butyl sultone (BS), methylene methanedisulfonate (MMDS), and diethylene glycol disulfate (DTD).

[0028] When the electrolyte contains the above-mentioned additive X, the gas generation during battery storage can be better reduced.

[0029] In any embodiment, the additive Y is vinylene carbonate (VC).

[0030] Additive Y is a commonly used SEI film-forming additive. Its film-forming stability effectively reduces interfacial side reactions, thereby enhancing battery cycle performance. Furthermore, VC and additive X exhibit a synergistic effect, further improving the battery's room-temperature lifespan.

[0031] A second aspect of the present application provides an electrical device comprising the lithium secondary battery of the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0033] FIG2 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0034] FIG3 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0035] FIG4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG3 ;

[0036] FIG5 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0037] Description of reference numerals: 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0038] Below, the embodiments of the lithium secondary battery, its formation method and the electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0039] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0041] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0043] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0044] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0045] Lithium-ion batteries are increasingly used in modern society. They are widely used due to their advantages such as low price, high safety and long life, but their energy density is relatively low. In order to improve the energy density of batteries, thick coating, high pressure density and larger batteries are usually adopted, but these will make it more difficult for the electrolyte to infiltrate. If the electrolyte is not fully infiltrated during the cycle, it may affect the transmission of lithium ions and thus affect the life of the battery. By using some new solvents to reduce the viscosity of the electrolyte, the infiltration can be improved, but these new solvents often have other side effects, and the higher the dosage, the more obvious the side effects. The present application achieves the purpose of having better dynamics and high temperature performance through electrolyte formula design and battery design.

[0046] [Lithium secondary battery]

[0047] To achieve the purpose, the first aspect of the present application provides a lithium ion secondary battery, the battery comprising an electrolyte, the electrolyte comprising a carboxylate compound, and the mass percentage A of the carboxylate compound based on the mass of the electrolyte is not less than 30% and not more than 70%;

[0048] The battery satisfies: 0.7≤A×(T+L) / H≤7.7,

[0049] Where A is the mass percentage of the carboxylate compound based on the mass of the electrolyte; T is the thickness of the battery casing perpendicular to the line connecting the positive and negative electrodes of the battery, in millimeters; L is the length of the battery casing parallel to the line connecting the positive and negative electrodes of the battery, in millimeters; H is the height of the battery casing parallel to the direction of gravity when the battery is placed on the ground, in millimeters. In some embodiments, the mass percentage A of the carboxylate compound is 30%, 40%, 50%, 60%, 70%, or a range consisting of any two of the foregoing values, or any value within such a range.

[0050] In some embodiments, A×(T+L) / H is 0.7, 1, 1.4, 1.8, 2.3, 2.8, 3.2, 3.6, 4.5, 5, 5.5, 6, 7, 7.7, or a range consisting of any two of the above points or any value within the range.

[0051] The present application has no particular restrictions on the shape of the secondary battery, which can be cylindrical, square, or any other shape. For example, Figures 1 and 2 show a secondary battery with a square structure as an example, with a thickness T, length L, and height H as shown in the figures.

[0052] In some embodiments, when the positive and negative electrodes of the battery are at the same end of the battery casing, an exemplary structure of a prismatic battery is shown in Figure 1. When the battery shown in Figure 1 is placed on the ground in the manner shown in the figure, with the positive and negative electrodes facing upward, the direction parallel to the direction of gravity is the height H of the battery casing, the direction parallel to the line connecting the positive and negative electrodes of the battery is the length L of the battery casing, and the direction perpendicular to the line connecting the positive and negative electrodes of the battery is the thickness T of the battery casing.

[0053] In some embodiments, when the positive and negative electrodes of the battery are at opposite ends of the battery casing, an exemplary structure of a prismatic battery is shown in Figure 2. When the battery shown in Figure 2 is placed on the ground in the manner shown in the figure, with the positive and negative electrodes facing the sides, the direction parallel to the direction of gravity is the height H of the battery casing, the direction parallel to the line connecting the positive and negative electrodes of the battery is the length L of the battery casing, and the direction perpendicular to the line connecting the positive and negative electrodes of the battery is the thickness T of the battery casing.

[0054] Due to the influence of gravity, the electrolyte in the battery tends to settle at the bottom of the battery. Over time, the electrolyte continues to spread upward and infiltrate the electrode, filling the gaps between the cathode and anode and the pores of the electrode, thereby acting as a bridge for lithium ion transmission. During the battery cycle, as charging and discharging proceed, the electrode continuously expands and contracts, and the electrolyte is continuously squeezed out and reabsorbed. If the viscosity of the electrolyte is high and it is squeezed out and not reabsorbed in time, it may cause a lack of electrolyte between the cathode and anode, or in the pores of the electrode, and fail to form an effective lithium ion transmission path, resulting in rapid battery capacity decay.

[0055] The carboxylate compounds contained in the electrolyte provided herein have low viscosity, facilitating rapid electrolyte resorption and improving electrolyte wetting. However, carboxylate compounds have poor reduction stability, and excessive amounts can easily cause reduction side reactions at the negative electrode, worsening battery storage gassing. Therefore, when the battery size and carboxylate compound content satisfy the relationship of 0.7 ≤ A × (T + L) / H ≤ 7.7, both battery gassing and electrolyte wetting can be balanced, comprehensively improving battery cycle performance.

[0056] In some embodiments, the carboxylate compound includes a compound having a structure shown in Formula I,

[0057] Wherein, R1 and R2 each independently include at least one of a C1-C6 alkyl group and a C1-C6 halogenated alkyl group.

[0058] In some embodiments, in Formula I, R1 and R2 each independently include at least one of a C1-C5 alkyl group and a C1-C5 haloalkyl group.

[0059] In some embodiments, in Formula I, R1 and R2 each independently include at least one of a C1-C4 alkyl group and a C1-C4 haloalkyl group.

[0060] In some embodiments, in Formula I, R1 and R2 each independently include at least one of a C1-C3 alkyl group and a C1-C3 haloalkyl group.

[0061] In some embodiments, in Formula I, R1 and R2 each independently include at least one of a C1-C2 alkyl group and a C1-C2 haloalkyl group.

[0062] In some embodiments, the carboxylate compound includes at least one of ethyl acetate, methyl acetate, methyl formate, methyl propionate, ethyl propionate, and propyl propionate.

[0063] The carboxylic acid ester solvents mentioned above have a low viscosity, which can better improve the ionic conductivity of the electrolyte and better improve the wetting problem of the electrolyte.

[0064] In some embodiments, the electrolyte comprises a high-viscosity solvent having a viscosity greater than 0.6 cP at 25° C., wherein the mass percentage of the high-viscosity solvent is 10% to 40% based on the mass of the electrolyte. "Viscosity" as used herein refers to the resistance of a fluid to flow (test methods may refer to GB / T 2794).

[0065] In some embodiments, the mass percentage of the high viscosity solvent is 20%-30%. In some embodiments, based on the mass of the electrolyte, the mass percentage of the high viscosity solvent is 10%, 15%, 20%, 25%, 30%, 35%, 40%, or a range or any value consisting of any two of the above points.

[0066] In some embodiments, the high viscosity solvent has a dielectric constant ≥60.

[0067] The "dielectric constant," also known as permittivity or relative permittivity, is a key parameter used to characterize the electrical properties of dielectric or insulating materials. It is often represented by ε. It is the ratio of the capacitance of a capacitor containing the same material as the dielectric to the capacitance in a vacuum. It indicates the dielectric's relative ability to store electrostatic energy in an electric field (test methods can be found in ASTM D150).

[0068] In some embodiments, the high viscosity solvent includes at least one of ethylene carbonate (EC) and propylene carbonate (PC).

[0069] By controlling the content of the high-viscosity solvent within the above range, the gas production and electrolyte infiltration of the battery can be better taken into account, thereby comprehensively improving the cycle performance of the battery.

[0070] In some embodiments, the electrolyte contains lithium salt, and the mass percentage of the lithium salt is 8%-20% based on the mass of the electrolyte.

[0071] In some embodiments, based on the mass of the electrolyte, the mass percentage of the lithium salt is 8%, 10%, 12%, 14%, 16%, 18%, 20%, or a range consisting of any two of the above points or any value within the range.

[0072] In some embodiments, the lithium salt includes at least one of LiPF6, LiFSI, and LiTFSI.

[0073] When the lithium salt concentration is high, the electrolyte kinetics is better and the DCR is lower. However, excessive lithium salt content will lead to higher electrolyte viscosity, which is not conducive to electrolyte resorption and leads to poor room temperature cycling performance of the battery. Therefore, when the lithium salt content meets the above range, the battery's DCR and room temperature cycling performance can be better improved.

[0074] In some embodiments, the electrolyte further comprises at least one of an additive X and an additive Y, and based on the mass of the electrolyte, the mass percentage of the additive X is 0.1% to 1%, and the mass percentage of the additive Y is 2% to 6%, wherein the additive X comprises at least one of a cyclic sulfonate and a cyclic sulfate, and the cyclic sulfonate and the cyclic sulfate contain a sulfate group, a sulfite group, and / or a sulfonic acid group, and / or the additive Y comprises at least one of a cyclic carbonate containing an unsaturated bond, and the cyclic carbonate containing an unsaturated bond contains a carbonic acid group.

[0075] In some embodiments, the mass percentage of the additive X is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range consisting of any two of the above points or any value within the range.

[0076] In some embodiments, the mass percentage of the additive Y is 2%, 3%, 4%, 5%, 6%, or a range consisting of any two of the above points or any value within the range.

[0077] In some embodiments, the additive X includes at least one of 1,3-propane sultone (PS), 1,3-propene sultone (PES), butyl sultone (BS), methylene methanedisulfonate (MMDS), and diethylene glycol disulfate (DTD).

[0078] When the electrolyte contains the above-mentioned additive X, the gas generation during battery storage can be better reduced.

[0079] In some embodiments, the additive Y is vinylene carbonate (VC).

[0080] Additive Y is a commonly used SEI film-forming additive. Its film-forming stability effectively reduces interfacial side reactions, thereby enhancing battery cycle performance. Furthermore, VC and additive X exhibit a synergistic effect, further improving the battery's room-temperature lifespan.

[0081] In some embodiments, the electrolyte further comprises ethyl methyl carbonate (EMC).

[0082] EMC can improve low-temperature performance and prevent the electrolyte from solidifying at low temperatures.

[0083] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0084] In some embodiments, the battery comprises an anode membrane, wherein the thickness of the anode membrane is 50-100 μm. In some embodiments, the thickness of the anode membrane is 70-80 μm.

[0085] In some embodiments, the thickness of the anode membrane is 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or a range consisting of any two of the above points or any value within the range.

[0086] In some embodiments, the battery comprises a cathode membrane, wherein the cathode membrane has a thickness of 70-130 μm.

[0087] In some embodiments, the cathode membrane has a thickness of 100-120 μm.

[0088] In some embodiments, the thickness of the cathode membrane is 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, or a range or any value consisting of any two of the above points.

[0089] In some embodiments, the battery comprises a separator, wherein the separator has a thickness of 5-20 μm. In some embodiments, the separator has a thickness of 5-12 μm.

[0090] In some embodiments, the thickness of the separator is 5 μm, 10 μm, 15 μm, 20 μm, or a range consisting of any two of the above points or any value.

[0091] In some embodiments, the relationship between the thickness C of the separator and the thickness D of the cathode membrane is 5%≤C / D≤20%.

[0092] In some embodiments, the relationship between the thickness C of the diaphragm and the thickness D of the cathode diaphragm is 5%≤C / D≤18%, 5%≤C / D≤16%, 5%≤C / D≤14%, 5%≤C / D≤14%, 5%≤C / D≤12%, 5%≤C / D≤10%, 5%≤C / D≤8%, and 5%≤C / D≤6%.

[0093] The electrolyte seeps upward from the bottom of the battery, often first soaking the separator and then flowing out to the electrode. Increasing the separator thickness to a certain extent facilitates electrolyte penetration into the electrode and allows for faster electrolyte reabsorption when squeezed out. However, increasing the electrode thickness increases lithium ion transport resistance, which can degrade the battery's DCR. Therefore, when the thickness of the anode, cathode, and separator meet the above relationship, the battery's room temperature cycling performance and DCR can be significantly improved.

[0094] [Positive electrode]

[0095] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0096] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0097] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0099] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0100] In some embodiments, the positive electrode film layer may further include a conductive agent. For 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.

[0101] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0102] [Negative electrode]

[0103] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

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

[0105] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0107] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0108] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0110] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0111] [Isolation film]

[0112] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0114] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0115] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0116] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0117] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG3 shows a secondary battery 5 having a square structure as an example.

[0118] In some embodiments, referring to Figure 4, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0119] [Electrical devices]

[0120] In addition, the present application also provides an electrical device, which includes the lithium secondary battery provided by the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0121] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0122] Figure 5 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0123] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0124] Example

[0125] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0126] 1. Preparation method

[0127] Example 1

[0128] 1.1 Preparation of positive electrode sheet:

[0129] The positive electrode active materials lithium iron phosphate, polyvinylidene fluoride (PVDF), and carbon black (SP) were mixed with the solvent N-methylpyrrolidone in a mass ratio of 97:2:1, and stirred to obtain a uniformly dispersed positive electrode slurry. The positive electrode slurry was evenly coated on both surfaces of the aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet with a thickness of 105 μm.

[0130] 1.2 Preparation of negative electrode sheet:

[0131] The negative electrode active material (artificial graphite): carbon black (SP): styrene-butadiene rubber (SBR): sodium hydroxymethyl cellulose (CMC-Na) is mixed with deionized water as a solvent in a mass ratio of 97:0.5:1.5:1, a pore-forming agent is added, and a uniformly dispersed negative electrode slurry is obtained by stirring. The negative electrode slurry is evenly coated on both surfaces of the copper foil, and after drying, cold pressing, and cutting, a negative electrode sheet is obtained. The thickness of the negative electrode sheet is 73 μm.

[0132] 1.3 Isolation film:

[0133] A polyethylene film was used as the separator, and the thickness of the separator was 7 μm.

[0134] 1.4 Preparation of electrolyte:

[0135] In an argon atmosphere glove box, 25% ethylene carbonate (EC), 50% ethyl acetate (EA), 7.5% ethyl methyl carbonate (EMC), 13% lithium hexafluorophosphate (LiPF6), 0.5% 1,3-propane sultone, and 4% vinylene carbonate were mixed and dissolved, based on the total mass of the electrolyte, to obtain an electrolyte.

[0136] 1.5 Preparation of lithium-ion secondary batteries:

[0137] The positive electrode sheet, the negative electrode sheet and the separator are made into an electrode assembly through a winding process or a lamination process, and placed in a shell made of an aluminum shell, an aluminum-plastic film, etc. After the above-mentioned electrolyte is injected, the battery is allowed to stand at high temperature, formed, and divided into volumes, the battery of Example 1 is obtained. The length L of the battery is 362 mm, the thickness T is 47 mm, and the height H is 89 mm.

[0138] Examples 2 to 7

[0139] The battery preparation methods in Examples 2 to 7 are basically similar to those in Example 1, but the type or mass percentage of the carboxylic acid ester compound in the electrolyte is changed. The specific parameters are shown in Table 1-3-3.

[0140] Examples 8 to 12

[0141] The battery preparation methods in Examples 8 to 12 are basically similar to those in Example 1, except that the type or mass percentage of the high-viscosity solvent in the electrolyte is changed. The specific parameters are shown in Tables 1-3.

[0142] Examples 13 to 16

[0143] The battery preparation methods in Examples 13 to 16 are basically similar to those in Example 1, but the battery size and the value of A×(T+L) / H are changed. The specific parameters are shown in Tables 1-3.

[0144] Examples 17 to 22

[0145] The battery preparation methods in Examples 17 to 22 are basically similar to those in Example 1, except that the type or mass percentage of the lithium salt in the electrolyte is changed. The specific parameters are shown in Tables 1-3.

[0146] Examples 23 to 34

[0147] The battery preparation methods in Examples 23 to 34 are basically similar to those in Example 1, except that the types or mass percentages of additives in the electrolyte are changed. The specific parameters are shown in Tables 1-3.

[0148] Examples 35 to 38

[0149] The battery preparation methods in Examples 35 to 38 are basically similar to those in Example 1, but the thickness of the anode membrane is changed. The specific parameters are shown in Tables 1-3.

[0150] Examples 39 to 42

[0151] The battery preparation methods in Examples 39 to 42 are basically similar to those in Example 1, but the thickness of the cathode membrane is changed. The specific parameters are shown in Tables 1-3.

[0152] Examples 43 to 46

[0153] The battery preparation methods in Examples 43 to 46 are basically similar to those in Example 1, but the thickness of the separator is changed. The specific parameters are shown in Tables 1-3.

[0154] Comparative Examples 1 to 3

[0155] The battery preparation methods in Comparative Examples 1 to 3 are basically similar to those in Example 1, except that the type or mass percentage of the low-viscosity solvent in the electrolyte is changed. The specific parameters are shown in Tables 1-3.

[0156] Comparative Examples 4 to 6

[0157] The battery preparation methods in Examples 4 to 6 are basically similar to those in Example 1, except that the type or mass percentage of the high-viscosity solvent in the electrolyte is changed. The specific parameters are shown in Tables 1-3.

[0158] Comparative Examples 7-8

[0159] The battery preparation methods in Comparative Examples 7 to 8 are basically similar to those in Example 1, but the battery size and the value of A×(T+L) / H are changed. The specific parameters are shown in Tables 1-3.

[0160] Comparative Examples 9 to 11

[0161] The battery preparation methods in Comparative Examples 9 to 11 are basically similar to those in Example 1, except that the type or mass percentage of the lithium salt in the electrolyte is changed. The specific parameters are shown in Tables 1-3.

[0162] Comparative Examples 12 to 17

[0163] The battery preparation methods in Comparative Examples 12 to 17 are basically similar to those in Example 1, except that the types or mass percentages of the additives in the electrolyte are changed. The specific parameters are shown in Tables 1-3.

[0164] Comparative Examples 18-19

[0165] The battery preparation methods in Comparative Examples 18 to 19 are basically similar to those in Example 1, but the thickness of the anode membrane is changed. The specific parameters are shown in Table 1-3.

[0166] Comparative Examples 20-21

[0167] The battery preparation methods in Comparative Examples 20-21 are basically similar to those in Example 1, but the thickness of the cathode membrane is changed. The specific parameters are shown in Tables 1-3.

[0168] Comparative Examples 22-23

[0169] The battery preparation methods in Comparative Examples 22 to 23 are basically similar to those in Example 1, but the thickness of the separator is changed. The specific parameters are shown in Tables 1-3.

[0170] 2. Performance Testing Method

[0171] (1) Determination of 25℃ cycle performance

[0172] At 25°C, the batteries of each Example and Comparative Example were charged at a constant current of 0.5C to a voltage upper limit of 3.8V, then charged at a constant voltage to a current of 0.05C. The batteries were allowed to rest for 5 minutes and then discharged at a constant current of 1 / 3C to 2.0V. This constituted the first charge-discharge cycle of the battery, and the discharge capacity at this time was recorded as the discharge capacity of the first cycle, D1. The batteries were subjected to cyclic charge and discharge tests according to the above method, and the capacity Dn at the nth cycle was recorded. The capacity retention rate was then calculated as Dn / D1. The number of cycles at which the capacity retention rate reached 80% was recorded.

[0173] (2) DCR test

[0174] At 25°C, charge the battery at a constant current of 0.5C to a voltage limit of 3.8V. Then, charge it at a constant voltage to a current of 0.05C. Then, discharge it at 0.5C for 1 hour to 50% SOC, recording the voltage at this point as U1. Then, discharge it at 4C for 30 seconds, recording the voltage at this point as U2. DCR = (U1 - U2) / 4C.

[0175] (3) Storage gas production test

[0176] At 25°C, charge the battery at a constant current of 0.5C to the upper voltage limit of 3.8V, then charge it at a constant voltage to a current of 0.05C. Then, measure the battery volume (V0) using the water displacement method. Then, store the battery at 60°C for 30 days. Remove the battery and place it at 25°C for 2 hours. After returning to room temperature, measure the volume (V2) using the water displacement method. The volume growth rate is V2 / V1-1.

[0177] 3. Analysis of test results of various embodiments and comparative examples

[0178] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in Table 3 below.

[0179] Table 1 Preparation parameters

[0180] Table 2 Preparation parameters

[0181] Table 3 Preparation parameters and performance test results

[0182] The lithium secondary batteries prepared in Examples 1 to 46 all have good performance, including lower DCR, better cycle performance, lower storage gas generation, etc.

[0183] As can be seen from Examples 1 to 7, when preparing the electrolyte of a lithium secondary battery, using a variety of different types of carboxylic acid ester compounds (such as ethyl acetate, methyl acetate, methyl formate) or using different contents of carboxylic acid ester compounds (such as 30%, 40%, 50%, 60%, 70%) can make the prepared lithium secondary battery have better performance, including lower DCR, better cycle performance, lower storage gas production, etc.

[0184] In Comparative Examples 1 and 2, when preparing the electrolyte of the lithium secondary battery, the carboxylic acid ester compound with a content exceeding the range (for example, 0%, 80%) is used. The overall performance of the lithium secondary battery prepared therefrom is poor, for example, a high DCR, poor cycle performance, or high storage gas generation.

[0185] As can be seen from Examples 1 and 8 to 12, when preparing the electrolyte for a lithium secondary battery, using a variety of different types of high-viscosity solvents (e.g., ethylene carbonate, propylene carbonate), or using different contents of high-viscosity solvents (e.g., 10%, 20%, 25%, 30%, 40%), can make the prepared lithium secondary batteries have better performance, including lower DCR, better cycle performance, lower storage gas production, etc.

[0186] In Comparative Examples 3 to 4, when preparing the electrolyte for the lithium secondary battery, a high-viscosity solvent with a content exceeding the range (for example, 0%, 50%) was used. The lithium secondary batteries prepared therefrom had poor overall performance, such as a high DCR, poor cycle performance, or high storage gas production.

[0187] It can be seen from Examples 1 and 13 to 16 that when preparing lithium secondary batteries, using a variety of different battery sizes so that the range of A×(T+L) / H is within the range of 0.7 to 7.7 can make the prepared lithium secondary batteries have better performance, including lower DCR, better cycle performance, lower storage gas production, etc.

[0188] In Comparative Examples 5 to 6, when preparing lithium secondary batteries, when the range of A×(T+L) / H exceeds the range of 0.7 to 7.7 (for example, 0.5, 8), the comprehensive performance of the prepared lithium secondary batteries is poor, for example, DCR is high, cycle performance is poor, or storage gas production is high.

[0189] It can be seen from Examples 1 and 17 to 22 that when preparing the electrolyte for a lithium secondary battery, using a variety of different types of lithium salts (such as LiPF6, LiFSI, LiTFSI) or using different contents of lithium salts (such as 8%, 10%, 13%, 15%, 20%) can make the prepared lithium secondary battery have better performance, including lower DCR, better cycle performance, lower storage gas production, etc.

[0190] In Comparative Examples 7 to 8, when preparing the electrolyte for the lithium secondary battery, a lithium salt with a content exceeding the range (e.g., 5%, 25%) was used. The lithium secondary batteries prepared therefrom had poor overall performance, such as a high DCR, poor cycle performance, or high storage gas production.

[0191] As can be seen from Examples 1 and 23 to 30, when preparing the electrolyte for a lithium secondary battery, using a variety of different types of additives X (e.g., 1,3-propane sultone, 1,3-propenyl lactone, butane sultone, methylene methanedisulfonate, vinyl sulfate), or using different contents of additive X (e.g., 0.1%, 0.3%, 0.5%, 0.6%, 1%), can enable the prepared lithium secondary battery to have better performance, including lower DCR, better cycle performance, lower storage gas generation, etc.

[0192] In Comparative Examples 9 to 10, when preparing the electrolyte of the lithium secondary battery, the additive X with a content exceeding the range (for example, 0%, 1.5%) was used. The comprehensive performance of the lithium secondary batteries prepared therefrom was poor, for example, a high DCR, poor cycle performance, or high storage gas generation.

[0193] It can be seen from Examples 1 and 31 to 34 that when preparing the electrolyte of a lithium secondary battery, the additive Y is vinylene carbonate, and different contents of the additive Y (for example, 2%, 3%, 4%, 5%, 6%) can make the prepared lithium secondary battery have better performance, including lower DCR, better cycle performance, lower storage gas production, etc.

[0194] In Comparative Examples 11 to 12, when preparing the electrolyte of the lithium secondary battery, the additive Y with a content exceeding the range (for example, 1%, 8%) was used, and the lithium secondary batteries prepared therefrom had poor overall performance, for example, high DCR, poor cycle performance, or high storage gas generation.

[0195] It can be seen from Examples 1 and 35 to 46 that when preparing lithium secondary batteries, the use of anode membranes of various thicknesses (e.g., 50 μm, 70 μm, 73 μm, 80 μm, 100 μm), cathode membranes (e.g., 70 μm, 105 μm, 120 μm, 130 μm), and separators (e.g., 5 μm, 6 μm, 7 μm, 12 μm, 20 μm) can all make the prepared lithium secondary batteries have better performance, including lower DCR, better cycle performance, lower storage gas production, etc.

[0196] In Comparative Examples 13 to 18, when preparing lithium secondary batteries, anode membranes (for example, 110 μm, 40 μm), cathode membranes (for example, 140 μm, 60 μm), and separators (for example, 22 μm, 3 μm) with thicknesses outside the range were used. The overall performance of the lithium secondary batteries prepared therefrom was poor, for example, high DCR, poor cycle performance, or high storage gas production.

[0197] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A lithium ion secondary battery, wherein: The battery includes an electrolyte, the electrolyte includes a carboxylic acid ester compound, and based on the mass of the electrolyte, the mass percentage A of the carboxylic acid ester compound is not less than 30% and not more than 70%; The battery satisfies: 0.7≤A×(T+L) / H≤7.7, Wherein, A is the mass percentage of the carboxylic acid ester compound based on the mass of the electrolyte; T is the thickness of the battery casing in a direction perpendicular to the line connecting the positive and negative electrodes of the battery, in millimeters; L is the length of the battery casing in a direction parallel to the line connecting the positive and negative electrodes of the battery, in millimeters; H is the height of the battery casing in a direction parallel to the direction of gravity when the battery is placed on the ground, in millimeters.

2. The secondary battery according to claim 1, wherein The carboxylate compounds include compounds with the structure shown in Formula I, Wherein, R1 and R2 each independently include at least one of a C1-C6 alkyl group and a C1-C6 halogenated alkyl group.

3. The secondary battery according to claim 1 or 2, wherein: The carboxylic acid ester compound includes at least one of ethyl acetate, methyl acetate, methyl formate, methyl propionate, ethyl propionate, and propyl propionate.

4. The secondary battery according to any one of claims 1 to 3, wherein: The electrolyte contains a high-viscosity solvent, and the viscosity of the high-viscosity solvent at 25° C. is greater than 0.6 cP; The dielectric constant of the high viscosity solvent is ≥60, or Based on the mass of the electrolyte, the mass percentage of the high-viscosity solvent is 10%-40% or 20%-30%.

5. The secondary battery according to claim 4, wherein The high viscosity solvent includes at least one of ethylene carbonate (EC) and propylene carbonate (PC).

6. The secondary battery according to any one of claims 1 to 5, wherein: The battery comprises an anode membrane, wherein the thickness of the anode membrane is 50-100 μm, and optionally, the thickness of the anode membrane is 70-80 μm.

7. The secondary battery according to any one of claims 1 to 6, wherein: The battery comprises a cathode membrane, wherein the thickness of the cathode membrane is 70-130 μm, and optionally, the thickness of the cathode membrane is 100-120 μm.

8. The secondary battery according to any one of claims 1 to 7, wherein: The battery comprises a separator, wherein the separator has a thickness of 5-20 μm, and optionally, the separator has a thickness of 5-12 μm.

9. The secondary battery according to claim 7 or 8, wherein: The relationship between the thickness C of the separator and the thickness D of the cathode membrane is 5%≤C / D≤20%.

10. The secondary battery according to any one of claims 1 to 9, wherein: The electrolyte contains lithium salt, and the mass percentage of the lithium salt is 8%-20% based on the mass of the electrolyte.

11. The secondary battery according to claim 10, wherein The lithium salt includes at least one of LiPF6, LiFSI, and LiTFSI.

12. The secondary battery according to any one of claims 1 to 11, wherein the electrolyte further comprises at least one of an additive X and an additive Y, and based on the mass of the electrolyte, the mass percentage of the additive X is 0.1% to 1%, and the mass percentage of the additive Y is 2% to 6%, The additive X comprises at least one of a cyclic sulfonate and a cyclic sulfate, wherein the cyclic sulfonate and the cyclic sulfate contain a sulfate group, a sulfite group, and / or a sulfonic acid group, and / or The additive Y includes at least one of the cyclic carbonates containing unsaturated bonds, and the cyclic carbonates containing unsaturated bonds contain carbonic acid groups.

13. The secondary battery according to claim 12, wherein: The additive X includes at least one of 1,3-propane sultone (PS), 1,3-propene sultone (PES), butyl sultone (BS), methylene dimethyl methoxide (MMDS), and diethyl thiosulfate (DTD).

14. The secondary battery according to claim 12 or 13, wherein: The additive Y is vinylene carbonate (VC).

15. An electrical device comprising the lithium ion secondary battery according to any one of claims 1 to 14.

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