Nonaqueous electrolyte, secondary battery and power consuming device

Abstract

The present application provides a non-aqueous electrolyte, a secondary battery, and an electric power consumption device. The non-aqueous electrolyte contains at least two of a boron-containing lithium salt additive, a phosphorus-containing lithium salt additive, and a sulfur-containing lithium salt additive. The mass percentage of the boron-containing lithium salt additive is A1% based on the total mass of the non-aqueous electrolyte, the mass percentage of the phosphorus-containing lithium salt additive is A2% based on the total mass of the non-aqueous electrolyte, and the mass percentage of the sulfur-containing lithium salt additive is A3% based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte satisfies 0 < A1 + A2 + A3 ≦ 3. The present application can improve the cycle performance and kinetic performance of the secondary battery.

Description

[Technical field]

[0001] This application relates to the field of batteries, and in particular to non-aqueous electrolytes, secondary batteries and power consuming devices. [Background technology]

[0002] 2. Description of the Related Art Secondary batteries have characteristics such as high capacity and long life, and are therefore widely used in electronic devices such as mobile phones, laptops, electric scooters, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools.

[0003] As the application range of batteries becomes wider and wider, the requirements for the performance of secondary batteries become more and more stringent. In order to improve the performance of secondary batteries, it is common to optimize the materials in the secondary battery, such as electrolytes. As a conductive medium for metal ions in secondary batteries, electrolytes have a non-negligible effect on the performance of secondary batteries.

[0004] However, currently, when an improved electrolyte is applied to a secondary battery, the secondary battery cannot simultaneously improve the cycle performance and dynamic performance during use. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and has an object to provide a non-aqueous electrolyte, a secondary battery, and a power consuming device.

[0006] A first aspect of the present application provides a non-aqueous electrolyte for a secondary battery. The non-aqueous electrolyte contains at least two of a boron-containing lithium salt additive, a phosphorus-containing lithium salt additive, and a sulfur-containing lithium salt additive. The mass percentage of the boron-containing lithium salt additive is A1% based on the total mass of the non-aqueous electrolyte, the mass percentage of the phosphorus-containing lithium salt additive is A2% based on the total mass of the non-aqueous electrolyte, and the mass percentage of the sulfur-containing lithium salt additive is A3% based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte satisfies 0 < A1 + A2 + A3 ≤ 3, and optionally 0.01 ≤ A1 + A2 + A3 ≤ 2.

[0007] Thus, the present application provides that the mass percentage of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive and the sulfur-containing lithium salt additive is controlled to satisfy the above formula, so that the boron-containing lithium salt additive and the phosphorus-containing lithium salt additive can participate in the formation of the CEI film, the CEI film has a rich structural composition, its film layer is dense and uniform, and can play a good protective role on the positive electrode active material, and can effectively reduce the decomposition of the electrolyte, ensure the electrolyte performance is stable, and improve the cycle stability of the secondary battery; and the interface impedance of the CEI film is relatively low, which is favorable for improving the dynamic performance of the secondary battery. Through the cooperation of the boron-containing lithium salt additive and the sulfur-containing lithium salt additive, the boron-containing lithium salt additive can play a passivation role on the positive electrode current collector, and can reduce the risk of corrosion of the positive electrode current collector caused by the sulfur-containing lithium salt additive, thereby further improving the cycle stability of the secondary battery. The cooperation of at least two of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive and the sulfur-containing lithium salt additive can improve the conductivity of the electrolyte, and further improve the dynamic performance of the secondary battery. In addition, the cooperation of at least two of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive and the sulfur-containing lithium salt additive can form an SEI film on the surface of the negative electrode active material, and the SEI film has a rich structural composition, a dense and uniform film layer, which effectively protects the negative electrode active material, and the interface impedance of the SEI film is relatively low, so that the dynamic performance of the secondary battery can be effectively improved.

[0008] In any embodiment, the non-aqueous electrolyte satisfies at least one of conditions (1) to (3). (1) 0 < A1 ≤ 2.4. (2) 0 < A2 ≤ 2.1. (3) 0 < A3 ≤ 2.1. When the mass percentage of the boron-containing lithium salt additive is within the above range, it is ensured that the boron-containing lithium salt additive sufficiently forms an interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, thereby providing good protection for the positive electrode active material and / or the negative electrode active material and improving the cycle stability of the secondary battery. When the mass percentage of the phosphorus-containing lithium salt additive is within the above range, it is ensured that the phosphorus-containing lithium salt additive sufficiently forms an interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, thereby providing good protection for the positive electrode active material and / or the negative electrode active material and improving the cycle stability of the secondary battery. When the content of the sulfur-containing lithium salt additive is within the above range, the stability of the electrolyte can be ensured.

[0009] In any embodiment, the boron-containing lithium salt additive includes one or more of lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bisoxalate borate LiBOB, and / or the phosphorus-containing lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium fluorophosphate Li2PO3F, and lithium phosphate Li3PO4, and / or the sulfur-containing lithium salt additive includes one or more of lithium fluorosulfonate LiFSO3, lithium sulfate Li2SO4, and lithium sulfamate LiSO3NH2.

[0010] In any embodiment, the non-aqueous electrolyte further includes a negative electrode film-forming additive configured to form an interfacial film on the surface of the negative electrode active material. The mass percentage of the negative electrode film-forming additive is B% based on the total mass of the non-aqueous electrolyte, and the non-aqueous electrolyte satisfies 2 ≤ B / (A1 + A2 + A3) ≤ 60, and optionally, 3 ≤ B / (A1 + A2 + A3) ≤ 50.

[0011] As a result, the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive, and the sulfur-containing additive of the present application act together to, on the one hand, form an SEI film together with the negative electrode film-forming additive, improve the structural composition and impedance of the SEI film, and improve the cycle performance of the secondary battery, and, on the other hand, act as a positive electrode film-forming additive to protect the positive electrode active material and cooperate with the negative electrode film-forming additive to improve the interfacial properties of the secondary battery, thereby improving the cycle performance of the secondary battery.

[0012] In an optional embodiment, the negative electrode film-forming additive includes a gaseous film-forming additive and / or a non-gaseous film-forming additive, and optionally, the negative electrode film-forming additive includes a gaseous film-forming additive and a non-gaseous film-forming additive, the mass percentage of the gaseous film-forming additive is C% based on the total mass of the non-aqueous electrolyte, the mass percentage of the non-gaseous film-forming additive is D% based on the total mass of the non-aqueous electrolyte, and the non-aqueous electrolyte has a mass percentage of 0.005≦C * D≦20, selectable 0.01≦C * The condition D≦15 is satisfied.

[0013] As a result, the present application can further improve the structure of the SEI film and improve the cycle performance of the secondary battery by controlling the mass percentages of the gaseous film-forming additive and the non-gaseous film-forming additive to be within the above range.

[0014] In any embodiment, the gaseous film-forming additive comprises one or more of carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, nitrogen dioxide, dinitrogen trioxide, phosphorus trioxide, and phosphorus pentoxide, and optionally the gaseous film-forming additive comprises carbon monoxide and carbon dioxide, wherein the mass percentage of carbon monoxide is C1% based on the total mass of the non-aqueous electrolyte, and the mass percentage of carbon dioxide is C2% based on the total mass of the non-aqueous electrolyte, and the non-aqueous electrolyte satisfies 0.01≦C2 / C1≦60, and optionally 0.1≦C2 / C1≦40.

[0015] As a result, the present application makes it possible to effectively improve the composition structure of the SEI film and improve the cycle stability of the secondary battery by controlling the ratio of the mass percentages of carbon monoxide and carbon dioxide to be within the above range.

[0016] In any embodiment, 10 -6 ≦C1≦0.1 and / or 10 -6 ≦C2≦0.5.

[0017] In any embodiment, the non-gaseous film forming additive comprises one or more of a carbonate ester additive, a sulfate ester additive, and a sulfite ester additive, and optionally the carbonate ester additive comprises a cyclic carbonate ester additive and / or a linear carbonate ester additive, and further, the cyclic carbonate ester additive comprises one or more of vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, and the linear carbonate ester additive comprises one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, and methyl allyl carbonate DPC. The additives include one or more of carbonate MAC and polycarbonate VA, and optionally the sulfate ester additives include cyclic sulfonate ester additives and / or hydrocarbyl sulfate ester additives, and further, the cyclic sulfonate ester additives include one or more of 1,3-propane sultone PS, propene sultone PES, 3-fluoro-1,3-propane sultone FPS, the hydrocarbyl sulfate ester additives include one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS, and optionally the sulfite ester additives include ethylene sulfite ES and / or vinyl ethylene sulfite VES.

[0018] As a result, the non-gaseous film-forming additive of the present application can form an SEI film on the surface of the negative electrode active material, and by forming a film of multiple components together on the surface of the SEI film, it is possible to enrich the film layer structure of the SEI film and improve the structural stability of the SEI film.

[0019] In any embodiment, 0 <D≦7である。

[0020] A second aspect of the present application further provides a secondary battery including a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte according to any one of the embodiments of the first aspect of the present application, wherein the positive electrode sheet includes a positive electrode active material, and the negative electrode sheet includes a negative electrode active material.

[0021] A third aspect of the present application further provides a power consuming device including a secondary battery according to the second aspect of the present application. [Brief description of the drawings]

[0022] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces drawings required in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on the drawings without any creative efforts. [Figure 1] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Diagram 2] FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1. [Diagram 3] FIG. 1 is a schematic diagram of an embodiment of a battery module of the present application. [Figure 4] FIG. 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Diagram 5] 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of an embodiment of a power consumption device including a secondary battery of the present application as a power source. The drawings are not necessarily drawn to scale. The symbols are as follows: 1 battery pack; 2 upper housing; 3 lower housing; 4 battery module; 5 secondary battery; 51 case; 52 electrode assembly; 53 cover plate; 6 power consumption device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the electrolyte, secondary battery, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of known matters and duplicated description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate understanding by those skilled in the art. Note that the accompanying 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.

[0024] The "ranges" disclosed in this application are defined in the form of lower and upper limits, where a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, when ranges of 60-120 and 80-110 are recited for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, when minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are recited, ranges of 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 may all be contemplated. In this application, unless otherwise stated, the numerical range "a-b" is represented by the abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, with "0-5" being an abbreviation for combinations of these numerical values. Furthermore, expressing a parameter as an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions. Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0026] Unless otherwise stated, all steps in the present application may be performed in sequence or randomly, but are preferably performed in sequence. For example, the method includes steps (a) and (b) and may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when it is stated that the method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0027] Unless otherwise specified, the terms "comprise" and "include" used herein mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" may refer to further "comprising" or "including" other components not listed, or to "comprising" or "including" only the listed components.

[0028] In this application, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, 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).

[0029] As used herein, the terms "plurality" and "multiple types" refer to two or more types.

[0030] With the application and popularity of secondary batteries, their comprehensive performance has attracted more and more attention. As a provider of lithium insertion compounds and active lithium ions, the stability of the material structure of the positive electrode active material directly affects the overall performance of lithium-ion batteries. In the long-term charge and discharge process, the structure of the material itself is inevitably destroyed in the process of the positive electrode material constantly desorbing / inserting lithium ions, and the destruction of the lithium insertion sites directly leads to irreversible capacity loss. In addition, the positive electrode active material is more likely to undergo side reactions with the electrolyte, which further destroys the structure of the material itself. The positive electrode active material is described as a ternary material, which includes manganese, cobalt and nickel elements. The nickel element can improve the specific capacity of the material, the cobalt element can reduce the cation mixed site occupation and stabilize the crystal structure of the ternary material, and the manganese element can reduce the material cost and improve the structural stability and safety of the material. However, during the lithium desorption process of the positive electrode active material, the nickel element is oxidized from +2 to +4, and the tetravalent nickel, which has high oxidizability, is prone to side reactions with the electrolyte, which destroys the structure of the active material and reduces the battery capacity.

[0031] In view of the above problems, the inventors have improved the non-aqueous electrolyte and added a boron-containing lithium salt additive to the non-aqueous electrolyte in consideration of protecting the positive electrode active material and ensuring the structural stability of the positive electrode active material. The boron-containing lithium salt additive forms a cathode solid electrolyte interface (CEI film) on the surface of the positive electrode active material, and can protect the positive electrode active material. However, the inventors have further studied and found that the CEI film formed by the boron-containing lithium salt additive has poor film uniformity and does not provide good protection for the positive electrode active material, which may cause the positive electrode active material to be significantly damaged, thereby reducing the cycle performance of the secondary battery. In addition, in order to improve the protection performance of the CEI film, it is possible to increase the concentration of the boron-containing lithium salt additive, but the impedance value of the CEI film formed in this way is too high, which may deteriorate the dynamic performance of the secondary battery.

[0032] After conducting numerous studies, the inventors of the present application surprisingly found that when the non-aqueous electrolyte contains a boron-containing lithium salt additive, a phosphorus-containing lithium salt additive, and a sulfur-containing lithium salt additive simultaneously, all three can form a dense and uniform CEI film on the surface of the cathode active material. The CEI film can exert a good protective effect on the cathode active material, and due to the low impedance of the CEI film, the cycle performance and kinetic performance of the secondary battery can be comprehensively improved. Next, the technical solution of the present application will be described in detail. Nonaqueous electrolyte

[0033] According to a first aspect, the present application provides a non-aqueous electrolyte. The non-aqueous electrolyte is an important component of a secondary battery and plays a role in transporting metal ions such as lithium ions between the positive electrode sheet and the negative electrode sheet of the secondary battery.

[0034] The non-aqueous electrolyte contains at least two of a boron-containing lithium salt additive, a phosphorus-containing lithium salt additive, and a sulfur-containing lithium salt additive. Based on the total mass of the non-aqueous electrolyte, the mass percentage of the boron-containing lithium salt additive in the total mass of the electrolyte is A1%, the mass percentage of the phosphorus-containing lithium salt additive in the total mass of the electrolyte is A2% based on the total mass of the non-aqueous electrolyte, and the mass percentage of the sulfur-containing lithium salt additive in the total mass of the electrolyte is A3% based on the total mass of the non-aqueous electrolyte, and the non-aqueous electrolyte satisfies 0 < A1 + A2 + A3 ≤ 3.

[0035] Optionally, the non-aqueous electrolyte contains a boron-containing lithium salt additive, a phosphorus-containing lithium salt additive, and a sulfur-containing lithium salt additive.

[0036] Although the mechanism is not clear, when the non-aqueous electrolyte of the present application is applied to a secondary battery, the cycle performance and kinetic performance of the secondary battery can be improved simultaneously. The inventors speculate that the reaction mechanism is as follows.

[0037] The boron-containing lithium salt is a lithium salt with a B atom as the central atom, and is coordinated with an alkoxy group, o-diphenol, o-hydroxy group, carboxylic acid, etc. to form an anion complex. The anion complex mainly has a delocalized π bond structure, the negative charge distribution of the central ion is relatively dispersed, the charge is delocalized, and the anion radius is large, so that the anion is unlikely to form a strong ion pair with the lithium ion in an organic solvent, and its solubility is relatively good. The more electron-withdrawing groups there are in the anion complex, the more stable the anion structure becomes, and the higher the solubility of the lithium ion in the non-aqueous electrolyte becomes, which is favorable for improving the conductivity of the non-aqueous electrolyte, and thus the dynamic performance of the non-aqueous electrolyte is improved, which is favorable for improving the dynamic performance of the secondary battery. In addition, at high potentials, the boron-containing lithium salt can passivate the positive electrode current collector and provide good protection for the positive electrode current collector. In addition, the boron-containing lithium salt can form a CEI film on the surface of the positive electrode active material, and the formation of the CEI film can effectively reduce the sustained oxidative decomposition of the positive electrode active material against the non-aqueous electrolyte, play a good protective role on the positive electrode active material, improve the cycle stability of the positive electrode active material, reduce the decomposition of the electrolyte, and ensure the stability of the electrolyte. In addition, the boron-containing lithium salt can also form a solid electrolyte interface film (SoliD Electrolyte Interface, SEI film) with excellent performance on the surface of the negative electrode active material. The SEI film is insoluble in organic solvents and can be stably present in the organic electrolyte solution, which can effectively reduce the insertion of the solvent molecules in the electrolyte solution into the negative electrode active material, thereby ensuring the structural stability of the negative electrode active material and improving the cycle performance of the secondary battery.

[0038] The phosphorus-containing lithium salt additive has a relatively large anion group and high ionic conductivity, which is advantageous for further improving the dynamic performance of the electrolyte. In addition, the phosphorus-containing lithium salt additive can form a CEI film on the surface of the positive electrode active material, and the formed CEI film has high lithium ion conductivity, which significantly inhibits the continuous decomposition of the electrolyte and reduces the elution of transferred metal ions in the positive electrode active material, thereby improving the cycle performance of the secondary battery. In addition, the phosphorus-containing lithium salt additive can also form an SEI film on the surface of the negative electrode active material, which has a low interface impedance, thereby significantly improving the cycle performance of the battery.

[0039] The sulfur-containing lithium salt additive has high oxidation resistance, high thermal stability, is not sensitive to water in the electrolyte, and is unlikely to cause side reactions. In addition, the sulfur-containing lithium salt additive has a relatively high electrical conductivity, which is advantageous for improving the lithium ion transfer rate and the dynamic performance of the electrolyte. However, when the sulfur-containing lithium salt additive is used alone, it has a corrosive effect on the positive electrode current collector, which deteriorates the electrochemical performance of the secondary battery.

[0040] In the present application, by controlling the mass percentages of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive, and the sulfur-containing lithium salt additive to satisfy the above formula, both the boron-containing lithium salt additive and the phosphorus-containing lithium salt additive can participate in the formation of the CEI film, the structural composition of the CEI film is rich, its film layer is dense and uniform, it can exert a good protective effect on the positive electrode active material, and effectively reduce the decomposition of the electrolyte, ensuring the stability of the electrolyte performance. Thereby improving the cycle stability of the secondary battery. Also, since the interfacial impedance of the CEI film is relatively low, it is advantageous for improving the kinetic performance of the secondary battery. Due to the synergistic effect between the boron-containing lithium salt additive and the sulfur-containing lithium salt additive, the boron-containing lithium salt additive has a passivation effect on the positive electrode current collector, reducing the risk of corrosion of the positive electrode current collector by the sulfur-containing lithium salt additive, and further improving the cycle stability of the secondary battery. Through the synergistic effect of at least two of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive, and the sulfur-containing lithium salt additive, especially the synergistic effect of the three, the conductivity of the electrolyte can be improved, and the kinetic performance of the secondary battery can be further improved. Also, through the synergistic effect of at least two of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive, and the sulfur-containing lithium salt additive, especially the synergistic effect of the three, an SEI film can be formed on the surface of the negative electrode active material together. The structural composition of the SEI film is rich, its film layer is dense and uniform, it can effectively protect the negative electrode active material, and also, since the interfacial impedance of the SEI film is relatively low, the kinetic performance of the secondary battery can be effectively improved. Optionally, 0 < A1 + A2 + A3 ≤ 2. Exemplarily, A1 + A2 + A3 may be 0.5, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, or 3.

[0041] In some embodiments, the boron-containing lithium salt additive includes one or more of lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bisoxalate borate LiBOB.

[0042] Since the B atom can be bonded with an oxygen-containing oxalic acid ligand, the product after bonding has excellent thermal stability, and is easy to form an interface film with excellent performance on the surface of the positive electrode active material and / or the negative electrode active material, thereby ensuring the structural stability of the positive electrode active material and / or the negative electrode active material, and further improving the cycle performance of the secondary battery. Of course, the B atom may be bonded with a halogen atom, particularly a fluorine atom, which has a strong electron-attracting induction effect, high thermal stability and chemical stability, and high solubility of lithium ions in the electrolyte, thereby ensuring the solubility of lithium ions and the conductivity of the electrolyte.

[0043] When lithium tetrafluoroborate LiBF4 is used in combination with an organic solvent in the electrolyte, such as a carbonate ester solvent or additive, the viscosity of the system made of lithium tetrafluoroborate is relatively low, which is favorable for the release of lithium ions, thereby improving the conductivity of the electrolyte. The SEI film formed by lithium tetrafluoroborate has a relatively uniform thickness, good kinetic activity, and small impedance of charge transfer in the secondary battery, which can significantly improve the low-temperature performance of the secondary battery; the SEI film is not easily thermally decomposed, and its performance at high temperatures is relatively stable, which can significantly improve the high-temperature performance of the secondary battery.

[0044] Any one of lithium bis(oxalato)borate LiBOB and lithium difluoro(oxalato)borate LiDFOB has a passivation effect on the positive electrode current collector in the positive electrode sheet, and can reduce the risk of corroding the positive electrode current collector by a side reaction with the positive electrode current collector, and can improve the structural stability of the positive electrode sheet. In addition, an electrolyte containing any one of lithium bis(oxalato)borate LiBOB and lithium difluoro(oxalato)borate LiDFOB is less likely to generate acidic substances, and can further reduce the risk of corroding the positive electrode current collector. Lithium bis(oxalato)borate LiBOB and lithium difluoro(oxalato)borate LiDFOB have good compatibility with the positive electrode active material, are favorable for the transfer of lithium ions, and can form an interface film with excellent performance on the surface of the positive electrode active material and / or the negative electrode active material, thereby improving the protection performance for the positive electrode active material and / or the negative electrode active material.

[0045] When lithium tetrafluoroborate LiBF4, lithium bis(oxalato)borate LiBOB and lithium difluoro(oxalato)borate LiDFOB are used in combination, they can form a CEI film on the surface of the positive electrode active material, which can effectively reduce the decomposition of the positive electrode active material in the electrolyte. They can also form an SEI film on the surface of the negative electrode active material, which can improve the transport of lithium ions and reduce the continuous reduction decomposition of the electrolyte, thereby improving the cycle stability of the secondary battery.

[0046] In some embodiments, 0 <A1≦2.4である。

[0047] When the mass percentage of the boron-containing lithium salt additive is in the above range, the boron-containing lithium salt additive can ensure that the boron-containing lithium salt additive sufficiently forms an interface film on the surface of the positive electrode active material and / or the negative electrode active material, and can provide good protection for the positive electrode active material and / or the negative electrode active material, thereby improving the cycle stability of the secondary battery. Exemplarily, the mass percentage A1% of the boron-containing lithium salt additive can be 0.1%, 0.2%, 0.5%, 1%, 2% or 2.4%, or a range consisting of any two of the above values.

[0048] In some embodiments, the phosphorus-containing lithium salt additive comprises one or more of lithium difluorophosphate LiPO2F2, lithium fluorophosphate Li2PO3F, and lithium phosphate Li3PO4.

[0049] The phosphorus-containing lithium salt additive is an inorganic lithium phosphate salt, which can participate in the film formation of the positive electrode during the initial charging process of the secondary battery, and can form a stable and low impedance CEI film. The CEI film can effectively reduce the oxidative decomposition of the electrolyte, for example, the side reaction between the carbonate ester solvent in the electrolyte and the surface of the positive electrode active material, thereby ensuring the structural stability of the electrolyte and mitigating the destruction of the positive electrode active material, and improving the cycle performance of the secondary battery. In addition, the phosphorus-containing lithium salt can form Li x PO y F z It is possible to form an SEI film rich in LiF and LiF components. The SEI film has a low interface impedance and can significantly improve the cycle performance of a secondary battery.

[0050] In some embodiments, 0 <A2≦2.1である。

[0051] When the mass percentage of the phosphorus-containing lithium salt additive is within the above range, the phosphorus-containing lithium salt additive can be ensured to sufficiently form an interface film on the surface of the positive electrode active material and / or the negative electrode active material, and can provide good protection for the positive electrode active material and / or the negative electrode active material, thereby improving the cycle stability of the secondary battery. Exemplarily, the mass percentage A2% of the phosphorus-containing lithium salt additive may be 0.1%, 0.2%, 0.5%, 1%, 2% or 2.1%, or a range consisting of any two of the above values.

[0052] In some embodiments, the sulfur-containing lithium salt additive comprises one or more of lithium fluorosulfonate LiFSO3, lithium sulfate Li2SO4, and lithium sulfamate LiSO3NH2.

[0053] When the sulfur-containing lithium salt additive, the boron-containing lithium salt additive and the phosphorus-containing lithium salt additive are used together, the conductivity and stability of the electrolyte can be significantly improved.

[0054] In some embodiments, 0 <A3≦2.1である。

[0055] When the mass percentage of the sulfur-containing lithium salt additive is within the above range, the stability of the electrolyte can be ensured. For example, the mass percentage A3% of the sulfur-containing lithium salt additive can be 0.1%, 0.2%, 0.5%, 1%, 2% or 2.1%.

[0056] In some embodiments, the non-aqueous electrolyte further includes a negative electrode film-forming additive, the negative electrode film-forming additive is configured to form an interfacial film on a surface of the negative electrode active material, a mass percentage of the negative electrode film-forming additive is B % based on a total mass of the non-aqueous electrolyte, and the non-aqueous electrolyte satisfies 2≦B / (A1+A2+A3)≦60.

[0057] When the non-aqueous electrolyte is applied to the secondary battery, the negative electrode film-forming additive mainly forms an SEI film on the surface of the negative electrode active material, and the SEI film can pass metal ions as an ion conductor, and the metal ions can be inserted and removed through the SEI film to realize the charging and discharging of the secondary battery, but at the same time, it can also reduce the risk of electrons passing as an electronic insulator. In addition, the SEI film is insoluble in organic solvents, can be stably present in the organic electrolyte solvent, and the solvent molecules can hardly pass through the layer film, effectively reducing the co-insertion of the solvent molecules, and can reduce the destruction of the negative electrode active material caused by the co-insertion of the solvent molecules, thereby improving the cycle performance and service life of the active material.

[0058] The boron-containing lithium salt additive, the phosphorus-containing lithium salt additive and the sulfur-containing additive act together to form an SEI film together with the negative electrode film-forming additive, improve the structural composition and impedance of the SEI film, and improve the cycle performance of the secondary battery; on the other hand, they act as a positive electrode film-forming additive to protect the positive electrode active material, and cooperate with the negative electrode film-forming additive to improve the interface characteristics of the secondary battery, thereby improving the cycle performance of the secondary battery. In particular, when the ratio is within the above range, the conductivity of the electrolyte is ensured and good protection effect can be achieved for the positive and negative electrode active materials. Alternatively, 3≦B / (A1+A2+A3)≦50, and for example, B / (A1+A2+A3) may be 2, 3, 5, 6, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 40, 45, 50, 55 or 60, or a range consisting of any two of the above values.

[0059] In some embodiments, 0.005≦B≦7. Exemplarily, the mass percentage B% of the negative electrode film-forming additive may be 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 5%, 6%, or 7%, or a range consisting of any two of the above numerical values.

[0060] In some embodiments, the negative electrode film-forming additive includes a gaseous film-forming additive and / or a non-gaseous film-forming additive. Optionally, the negative electrode film-forming additive includes a gaseous film-forming additive and a non-gaseous film-forming additive. Based on the total mass of the non-aqueous electrolyte, the mass percentage of the gaseous film-forming additive is C%, and based on the total mass of the non-aqueous electrolyte, the mass percentage of the non-gaseous film-forming additive is D%, and the non-aqueous electrolyte satisfies 0.005 ≦ C * D ≦ 20.

[0061] The gaseous film-forming additive can promote the formation of a stable SEI film on the surface of the active material by the electrolyte. The SEI film mainly contains lithium carbonate, its performance is more stable, it can achieve effective passivation of the surface of the negative electrode active material, and can improve the power and cycle life of the secondary battery.

[0062] The non-gaseous film-forming additive can form an SEI film on the surface of the negative electrode active material together with the gaseous film-forming additive. The film layer structure of the SEI film is dense and uniform. The combined use of the two can reduce mutual consumption and synergistically improve the cycle performance of the secondary battery. By controlling the mass percentages of the gaseous film-forming additive and the non-gaseous film-forming additive to be within the above ranges, the structure of the SEI film can be further improved, and the cycle performance of the secondary battery can be enhanced. Optionally, 0.01 ≦ C * D ≦ 15. Exemplarily, C * D can be 0.05, 0.01, 0.02, 0.05, 0.1, 0.12, 0.15, 0.2, 0.3, 0.35, 0.4, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18 or 20, or a range consisting of any two of the above numerical values.

[0063] In some embodiments, 0 < D ≦ 7. Optionally, 0 < D ≦ 6. Exemplarily, the mass percentage D% of the non-gaseous film-forming additive can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6% or 7%, or a range consisting of any two of the above numerical values.

[0064] Examples of the gaseous film-forming additive include one or more of carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, nitrogen dioxide, dinitrogen trioxide, phosphorus trioxide, and phosphorus pentoxide. The gaseous film-forming additive can promote the formation of the SEI film and improve the structure of the SEI film.

[0065] Further, the gaseous film-forming additive contains carbon monoxide and carbon dioxide, wherein the mass percentage of carbon monoxide is C1% based on the total mass of the nonaqueous electrolyte, and the mass percentage of carbon dioxide is C2% based on the total mass of the nonaqueous electrolyte, and the nonaqueous electrolyte satisfies 0.01≦C2 / C1≦60.

[0066] Carbon dioxide and carbon monoxide can realize the passivation of the surface of the negative electrode active material, form a lithium carbonate-rich SEI film, and improve the power and cycle life of the secondary battery. In addition, carbon dioxide is directly involved in the film formation reaction on the surface of the negative electrode active material, and carbon monoxide absorbs oxygen gas released from the secondary battery system to generate carbon dioxide, and improves the concentration of carbon dioxide, so that carbon dioxide can further participate in the film formation reaction on the surface of the negative electrode active material. The interaction between carbon dioxide and carbon monoxide can reduce the risk of the electrolyte causing a side reaction on the active material surface, and improve the stability of the electrolyte. By controlling the mass percentage ratio of carbon monoxide to carbon dioxide to be in the above range, the composition structure of the SEI film can be effectively improved, and the cycle stability of the secondary battery can be improved. Optionally, 0.1≦C2 / C1≦40. Illustratively, C2 / C1 may be 0.01, 00.01, 0.02, 0.05, 0.1, 0.12, 0.15, 0.2, 0.3, 0.35, 0.4, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 25, 28, 30, 32, 35, 38, 30, 42, 45, 50, 55, 58, or 60, or a range consisting of any two of the above values.

[0067] Furthermore, 10 -6 ≦C1≦0.1. Selectable, 5 * 10-6 ≦C1≦0.08 ppm.

[0068] For example, the mass percentage C1% of carbon monoxide is 10 -4 %, 2 * 10 -4 %, 5 * 10 -4 %, 8 * 10 -4 %, 10 -3 %, 1.5 * 10 -3 %, 2 * 10 -3 %, 2.5 * 10 -3 %, 3 * 10 -3 %, 3.5 * 10 -3 %, 4 * 10 -3 %, 4.5 * 10 -3 %, 5 * 10 -3 %, 5.5 * 10 -3 %, 6 * 10 -3 %, 7 * 10 -3 %, 7.5 * 10 -3 %, 8 * 10 -3 %, 8.5 * 10 -3 %, 9 * 10 -3 %, 9.5 * 10 -3 %, 10 -2 %, 2 * 10 -2 %, 3 * 10 -2 %, 4 * 10 -2 %, 5 * 10 -2 %, 6 * 10 -2 %, 7 * 10 -2 %, 8 * 10 -2 %, 9 * 10 -2%, or 0.1%, or a range consisting of any two of the above values.

[0069] Furthermore, 10 -6 ≦C2≦0.5. Selectable, 5 * 10 -6 ≦C2≦0.4.

[0070] For example, the mass percentage of carbon dioxide C2% is 10 -4 %, 5 * 10 -4 %, 8 * 10 -4 %, 10 -3 %, 2 * 10 -3 %, 2.5 * 10 -3 %, 3 * 10 -3 %, 3.5 * 10 -3 %, 4 * 10 -3 %, 4.5 * 10 -3 %, 5 * 10 -3 %, 5.5 * 10 -3 %, 6 * 10 -3 %, 7 * 10 -3 %, 7.5 * 10 -3 %, 8 * 10 -3 %, 8.5 * 10 -3 %, 9 * 10 -3 %, 9.5 * 10 -3 %, 10 -2 %, 2 * 10 -2 %, 5 * 10 -2 %, 6 * 10 -2 %, 8 * 10 -2 %, 10 -1 %, 1.1 * 10 -1 %, 1.2 * 10-1 %, 1.5 * 10 -1 %, 1.8 * 10 -1 %, 2 * 10 -1 %, 2.2 * 10 -1 %, 2.5 * 10 -1 %, 2.8 * 10 -1 %, 3 * 10 -1 %, 3.2 * 10 -1 %, 3.8 * 10 -1 %, 4 * 10 -1 %, 4.2 * 10 -1 %, 4.5 * 10 -1 %, 4.8 * 10 -1 %, or 0.5%, or a range consisting of any two of the values ​​above.

[0071] Examples of non-gaseous film-forming additives include one or more of carbonate ester additives, sulfate ester additives, and sulfite ester additives. The non-gaseous film-forming additives form an SEI film on the surface of the negative electrode active material, and multiple components are formed on the surface of the SEI film together, which can enrich the film layer structure of the SEI film and improve the structural stability of the SEI film.

[0072] Exemplarily, the carbonate ester additive includes a cyclic carbonate ester additive and / or a linear carbonate ester additive, and optionally, the cyclic carbonate ester additive includes one or more of vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, and the linear carbonate ester additive includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA. The cyclic carbonate ester additive has a higher dielectric constant and dissolves the lithium salt as much as possible, so that the lithium salt can more easily dissociate lithium ions and improve the conductivity of the electrolyte. The linear carbonate ester additive has a relatively low viscosity and can improve the transfer rate of lithium ions.

[0073] Illustratively, the sulfate ester additives include cyclic sulfonate ester additives and / or hydrocarbyl sulfate ester additives, and further, the cyclic sulfonate ester additives include one or more of 1,3-propane sultone PS, propene sultone PES, and 3-fluoro-1,3-propane sultone FPS, and the hydrocarbyl sulfate ester additives include one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS.

[0074] Illustratively, sulfite additives include ethylene sulfite ES and / or vinyl ethylene vinyl sulfite VES.

[0075] In some embodiments, the non-aqueous electrolyte further comprises an organic solvent, which may further comprise at least one or a combination of a plurality of solvents selected from ethylene carbonate EC, propylene carbonate PC, ethyl methyl carbonate EMC, diethyl carbonate DEC, dimethyl carbonate DMC, dipropyl carbonate DPC, methyl propyl carbonate MPC, ethyl propyl carbonate EPC, butylene carbonate BC, methyl formate MF, methyl acetate MA, ethyl acetate EA, propyl acetate PA, methyl propionate MP, ethyl propionate EP, propyl propionate PP, methyl butyrate MB, ethyl butyrate EB, 1,4-butyrolactone GBL, sulfolane SF, dimethyl sulfone MSM, methyl ethyl sulfone EMS, and diethyl sulfone ESE.

[0076] The electrolyte of the present application can be prepared according to a conventional method in the field. For example, additives, a solvent, an electrolyte salt, etc. can be mixed uniformly to obtain an electrolyte. The order of addition of each material is not particularly limited, and for example, additives, electrolyte salt, etc. can be added to a non-aqueous solvent and mixed uniformly to obtain a non-aqueous electrolyte.

[0077] In the present application, each component and its content in the electrolyte solution can be measured according to a method known in the art, for example, gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0078] In addition, when testing the electrolyte of the present application, a freshly prepared electrolyte may be obtained as it is, or the electrolyte may be obtained from a secondary battery. One exemplary method for obtaining the electrolyte from a secondary battery includes the steps of discharging the secondary battery to a discharge cut-off voltage (for safety reasons, the battery is generally fully discharged), centrifuging, and then using an appropriate amount of the liquid obtained by the centrifugation as the nonaqueous electrolyte. The nonaqueous electrolyte may be obtained directly from the electrolyte inlet of the secondary battery. secondary battery

[0079] According to a second aspect, the present application further provides a secondary battery.

[0080] The secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The separator is provided between the positive electrode sheet and the negative electrode sheet. The electrolyte may be any one of the electrolytes according to the first aspect of the present application. By employing the electrolyte, the cycle performance and kinetic performance of the secondary battery can be improved. [Positive electrode sheet]

[0081] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, for example, the positive electrode current collector has two opposing surfaces in a thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two opposing surfaces of the positive electrode current collector.

[0082] The positive electrode film layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material used in a secondary battery known in the art. For example, the positive electrode active material may include at least one of lithium transition metal oxides, lithium-containing phosphates having an olivine structure, and modified compounds thereof. Examples of lithium transition metal oxides may include at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium-containing phosphates having an olivine structure may include at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof. The present application is not limited to these materials, and other conventionally known materials used as positive electrode active materials for secondary batteries may be used. These positive electrode active materials may be used alone or in combination of two or more.

[0083] In some embodiments, the positive electrode active material is LiNi x Co y M 1-x-yO2, where M is any one selected from Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0≦y≦1, 0≦x<1, and x+y+z≦1. When used in combination with a positive electrode active material and a boron-containing lithium salt, the B atoms in the boron-containing lithium salt are easily bonded to the O atoms in the positive electrode active material, thereby reducing the impedance of the charge transfer of the positive electrode active material and reducing the diffusion resistance of lithium ions in the bulk of the positive electrode active material. Therefore, when the non-aqueous electrolyte contains an appropriate content of lithium tetrafluoroborate and lithium difluoro(oxalato)borate, the low-cobalt or cobalt-free positive electrode active material can have a significantly improved lithium ion diffusion rate, and the lithium ions in the bulk of the low-cobalt or cobalt-free positive electrode active material can be timely replenished to the surface, which can prevent excessive lithium from being desorbed from the surface of the low-cobalt or cobalt-free positive electrode active material, thereby stabilizing the crystal structure of the low-cobalt or cobalt-free positive electrode active material. Since the crystal structure of the low-cobalt or cobalt-free positive electrode active material is more stable, the probability of problems such as the structural, chemical or electrochemical properties of the positive electrode active material becoming unstable due to excessive lithium desorption occurring on the surface of the low-cobalt or cobalt-free positive electrode active material, for example, the probability of problems such as irreversible distortion and increased lattice defects in the positive electrode active material occurring can be significantly reduced.

[0084] LiNi x Co y M 1-x-y O2 can be prepared according to conventional methods in the art. An exemplary preparation method is to mix a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, an M element precursor, and an N element precursor, and then sintering. The sintering atmosphere can be an oxygen-containing atmosphere, for example, an air atmosphere or an oxygen gas atmosphere. The O2 concentration of the sintering atmosphere is, for example, 70% to 100%. The sintering temperature and sintering time can be adjusted according to the actual situation.

[0085] By way of example, the lithium source includes, but is not limited to, at least one of lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), lithium acetate (CH3COOLi), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium nitrate (LiNO3). By way of example, the nickel source includes, but is not limited to, at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate. By way of example, the cobalt source includes, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate. By way of example, the manganese source includes, but is not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate. By way of example, the aluminum source includes, but is not limited to, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate. By way of example, the M element precursor includes, but is not limited to, at least one of an oxide, a nitrate compound, a carbonate compound, a hydroxide compound, and an acetate compound of the M element. By way of example, the N element precursor includes, but is not limited to, at least one of ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium hydrogen carbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium hydrogen sulfate, ammonium hydrogen sulfite, ammonium sulfite, ammonium hydrogen sulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0086] In some embodiments, the molecular formula is LiNi x Co y M 1-x-y The mass percentage of the layered material that is O2 is 80% to 99%. For example, the molecular formula is LiNi x Co y M 1-x-yThe mass percentage of the layered material that is O2 may be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any range therein. Optionally, the molecular formula is LiNi x Co y M 1-x-y The mass percentage of the layered material that is O2 may be 85%-99%, 90%-99%, 95%-99%, 80%-98%, 85%-98%, 90%-98%, 95%-98%, 80%-97%, 85%-97%, 90%-97%, or 95%-97%.

[0087] In some embodiments, the positive electrode active material has the molecular formula LiNi x Co y M 1-x-y In the formula, M represents one or more of Mn, Fe, Mg, Al, Cu, and Ti, and x≧0.5, 0≦y≦0.2, and x+y≦1. The lithium deficiency state of the material surface of the positive electrode active material at high voltage is likely to cause phase change, Li / Ni mixing, oxygen release, etc. on the surface of the positive electrode active material, and the boron-containing lithium salt additive, phosphorus-containing lithium salt additive, and sulfur-containing lithium salt additive can passivate the surface of the positive electrode active material and can also be used to passivate metal cations, such as Al. 3+ and Ni 2+ and can combine with each other to improve the mixing of Li / Ni and the passivation of aluminum foil. Furthermore, CO2 and CO can form a good film on the surface of the negative electrode active material and simultaneously absorb the oxygen gas released from the positive electrode active material at high voltage, thereby improving the cycle life of the secondary battery.

[0088] In some embodiments, the positive electrode film layer may further include a selective positive electrode conductive agent. In the present application, the type of the positive electrode conductive agent is not particularly limited, but for example, the positive electrode conductive agent may include one or more combinations selected from superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is 5% or less based on the total mass of the positive electrode film layer.

[0089] In some embodiments, the positive electrode membrane layer may further include a positive electrode adhesive. In the present application, the type of the positive electrode adhesive is not particularly limited, but for example, the positive electrode adhesive may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. In some embodiments, the mass percentage of the positive electrode adhesive is 5% or less based on the total mass of the positive electrode membrane layer.

[0090] In some embodiments, the positive electrode current collector may be a metal foil piece or a composite current collector. Examples of the metal foil piece include aluminum foil or aluminum alloy foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or more combinations selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, and the polymeric material base layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0091] The positive electrode membrane layer is usually formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). [Negative electrode sheet]

[0092] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0093] For example, the negative electrode current collector has two surfaces opposing each other in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0094] In some embodiments, the negative electrode active material may be a negative electrode active material used in batteries known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and lithium aluminum alloy. The silicon-based material may be at least one selected from elemental silicon, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials used as negative electrode active materials in batteries may be used. Only one of these negative electrode active materials may be used alone, or two or more may be used in combination.

[0095] In some embodiments, the negative electrode film layer may further include a negative electrode adhesive. In the present application, the type of the negative electrode adhesive is not particularly limited, but as an example, the negative electrode adhesive may include one or more combinations selected from styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMMA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode adhesive is 5% or less based on the total mass of the negative electrode film layer.

[0096] In some embodiments, the negative electrode film layer may further include a selective negative electrode conductive agent. In the present application, the type of the negative electrode conductive agent is not particularly limited, but for example, the negative electrode conductive agent may include one or more combinations selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is 5% or less based on the total mass of the negative electrode film layer.

[0097] In some embodiments, the negative electrode membrane layer may further include other optional auxiliary agents. For example, the other auxiliary agents may include thickeners such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other auxiliary agents is 2% or less based on the total mass of the negative electrode membrane layer.

[0098] In some embodiments, the negative electrode current collector may be a metal foil piece or a composite current collector. Examples of the metal foil piece include copper foil and copper alloy foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or more combinations selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, and the polymeric material base layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0099] The negative electrode membrane layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional adhesive, and other optional auxiliary agents in a solvent and stirring uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0100] The negative electrode sheet does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet further includes a protective layer coated on the surface of the negative electrode film layer. [Separator]

[0101] In some embodiments, the secondary battery further includes a separator. The type of the separator of the present application is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0102] In some embodiments, the separator is made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, but is not particularly limited thereto. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, but is not particularly limited thereto.

[0103] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be prepared into an electrode assembly by a winding process or a stacking process.

[0104] In some embodiments, the secondary battery can include an exterior packaging, which can be used to seal the electrode assembly and electrolyte.

[0105] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft package, such as a bag-type soft package. The material of the soft package may be plastic. Examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0106] The shape of the secondary battery of the present application is not particularly limited, and may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows an exemplary secondary battery 5 having a rectangular structure.

[0107] In some embodiments, as shown in FIG. 1 and FIG. 2, the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are surrounded to form a chamber. The case 51 has an opening communicating with the chamber, and the cover plate 53 covers the opening to close the chamber. The positive electrode sheet, the negative electrode sheet and the separator may form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed in the chamber. The electrode assembly 52 is infiltrated with an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be adjusted according to needs.

[0108] The method of preparing the secondary battery of the present application is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, a positive electrode sheet, a separator, and a negative electrode sheet can be formed into an electrode assembly by a winding process or a lamination process, and the electrode assembly can be placed in an outer casing, dried, and then an electrolyte can be injected, and a secondary battery can be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0109] In some embodiments of the present application, the secondary battery of the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0110] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, the multiple secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by a fastener.

[0111] Optionally, the battery module 4 further includes a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0112] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0113] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Fig. 4 and 5, the battery pack 1 may include a battery housing and a plurality of battery modules 4 provided in the battery housing. The battery housing includes an upper housing 2 and a lower housing 3, and the upper housing 2 is covered by the lower housing 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery housing in any manner. power consumption equipment

[0114] In a second aspect, the present application provides a power consuming device including at least one of the secondary battery, battery module, and battery pack of the present application. The secondary battery, battery module, and battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0115] A power consuming device can select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0116] 6 is a schematic diagram of an example power consuming device 6, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack 1 or a battery module can be employed to meet the high power and high energy density demands of the power consuming device.

[0117] Other examples of power consuming devices may be mobile phones, tablet computers, notebook computers, etc. Such power consuming devices are usually required to be thin and may employ secondary batteries as their power source. Working Example

[0118] The following examples will more specifically explain the contents of the present disclosure. These examples are merely used for explanatory purposes, and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the contents of the present disclosure. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass, and all reagents used in the examples can be purchased or synthesized according to conventional methods and can be used directly without the need for further processing. In addition, all devices used in the examples can be purchased. Example 1 1. Preparation of Positive Electrode Sheet

[0119] As the positive electrode current collector, an aluminum foil having a thickness of 12 μm is used.

[0120] Positive electrode active material LiNi 0.65 Co 0.07 Mn 0.28 The conductive agent, carbon black, and adhesive, polyvinylidene fluoride (PVDF), were thoroughly mixed in a weight ratio of 97.5:1.4:1.1 in an appropriate amount of NMP solvent and stirred to form a uniform positive electrode slurry. The positive electrode slurry was then uniformly applied to the surface of an aluminum foil, which was a positive electrode current collector, and the resulting material was dried and cold pressed to obtain a positive electrode sheet. 2. Preparation of Negative Electrode Sheet

[0121] A copper foil with a thickness of 8 μm is used as the negative electrode current collector.

[0122] The negative electrode active material graphite, the adhesive styrene butadiene rubber (SBR), the thickener sodium carboxymethylcellulose (CMC-Na), and the conductive agent carbon black (Super P) were thoroughly mixed in a weight ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of deionized water as a solvent to form a uniform negative electrode slurry. The negative electrode slurry was then uniformly applied to the surface of copper foil as the negative electrode current collector, and dried and cold pressed to obtain a negative electrode sheet. 3. Separator

[0123] A porous polyethylene (PE) film is used as the separator. 4. Preparation of Electrolyte Solution

[0124] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent, and then additives were dissolved in the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L. See the table below for the specific substances contained in the electrolyte. 5. Preparation of Secondary Batteries

[0125] The positive electrode sheet, separator, and negative electrode sheet are stacked in this order, and the separator is interposed between the positive electrode sheet and the negative electrode sheet to perform an isolating function. Then, the stack is wound to obtain an electrode assembly. The electrode assembly is placed in an outer case, dried, and then an electrolyte is injected. The lithium ion battery is obtained through processes such as vacuum sealing, standing, chemical formation, and shaping. Example 2 Examples 2-1 to 2-3

[0126] Except for adjusting the mass percentage A1 of the "boron-containing lithium salt additive", a secondary battery was prepared in a manner similar to that of Example 1. See Table 1 for specific parameters. Examples 2-4 and 2-5

[0127] Except for adjusting the type of "boron-containing lithium salt additive", a secondary battery was prepared in a manner similar to that of Example 1. See Table 1 for specific parameters. Examples 2-6 to 2-8

[0128] Except for adjusting the mass percentage A2 of the "phosphorus-containing lithium salt additive", a secondary battery was prepared in a manner similar to that of Example 1. See Table 1 for specific parameters. Examples 2-9

[0129] Except for adjusting the type of "phosphorus-containing lithium salt additive", a secondary battery was prepared in a manner similar to that of Example 1. See Table 1 for specific parameters. Examples 2-10 to 2-12

[0130] Except for adjusting the mass percentage A3 of the "sulfur-containing lithium salt additive", a secondary battery was prepared in a manner similar to that of Example 1. See Table 1 for specific parameters. Example 2-13

[0131] Except for adjusting the type of "sulfur-containing lithium salt additive", a secondary battery was prepared in a manner similar to that of Example 1. See Table 1 for specific parameters. Comparative Example

[0132] The secondary battery of Comparative Example 1 was similarly prepared in a manner similar to that of Example 1, except that no boron-containing lithium salt additive was added to Comparative Example 1. See Table 1 for specific parameters.

[0133] The secondary battery of Comparative Example 2 was prepared in a similar manner to Example 1, except that no phosphorus-containing lithium salt additive was added to Comparative Example 2. See Table 1 for specific parameters.

[0134] The secondary battery of Comparative Example 3 was similarly prepared in a manner similar to that of Example 1, except that no sulfur-containing lithium salt additive was added to Comparative Example 3. See Table 1 for specific parameters.

[0135] The secondary battery of Comparative Example 4 was prepared in a similar manner to that of Example 1, except that the mass percentage of "boron-containing lithium salt additive" was adjusted and A1+A2+A3>3. Specific parameters are shown in Table 1.

[0136] [Table 1] Example 3 Examples 3-1 to 3-5

[0137] Except for adjusting the mass percentage B of the "negative electrode film-forming additive", a secondary battery was prepared in a similar manner to Example 1. See Tables 2 to 4 for specific parameters. Examples 3-6 to 3-8

[0138] Except for adjusting the type of "negative electrode film forming additive", a secondary battery was prepared in a similar manner to Example 1. See Tables 2 to 4 for specific parameters. Examples 3-9 to 3-15

[0139] A secondary battery was prepared in a similar manner to Example 1, except that the type of "negative electrode film-forming additive" was adjusted and a gaseous film-forming additive was added.

[0140] When the additive in the electrolyte further comprises a gaseous film-forming additive, first add the non-gaseous film-forming additive, and after adding the non-gaseous film-forming additive, evacuate the electrolyte injector at a vacuum level of -0.07MPa to -0.1MPa (vacuum level refers to the difference between the actual pressure and the atmospheric pressure) for 0.5 to 3 minutes, and then inject the gaseous film-forming additive. Specific parameters are shown in Tables 2 to 4. Examples 3-16 to 3-22

[0141] A secondary battery was prepared in a similar manner to Example 1, except that the mass ratio C2 / C1 of carbon monoxide to carbon dioxide in the gaseous film-forming additive was adjusted.

[0142] [Table 2]

[0143] [Table 3]

[0144] [Table 4]

[0145] In Table 4, A=A1+A2+A3, that is, A represents the total mass percentage of the boron-containing lithium salt additive, the phosphorus-containing lithium salt additive, and the sulfur-containing lithium salt additive.

[0146] C=C1+C2, ie, C represents the total mass percentage of the gaseous film-forming additives.

[0147] D=D1+D2+D3, ie, D represents the total mass percentage of the non-gaseous film forming additives.

[0148] B=C+D, that is, B represents the total mass percentage of the negative electrode film-forming additives. Testing part

[0149] 1. Test method for the content of each component in electrolyte

[0150] The electrolyte may be freshly prepared or obtained from a secondary battery, and the electrolyte components may then be measured using one or more of the following methods: gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0151] Gas chromatography-mass spectrometry (GC-MS): According to GB / T-9722-2006 / GB / T6041-2002, gas chromatography and mass spectrometry are combined to separate each component in the sample by gas chromatography, and then each component is divided into fragment ions in mass spectrometry, and separated by mass-to-charge ratio (m / z) to form a specific mass spectrum diagram to obtain the qualitative analysis of each organic component in the electrolyte; then, each organic component in the electrolyte is separated in a chromatography column to generate the detection signal spectrum of each component, and the component is qualified according to the retention time, and the standard is matched and the peak area is calibrated to achieve quantification, and the quantitative test analysis of the organic components in the electrolyte is obtained.

[0152] Ion chromatography (IC): According to JY / T-020, detect and quantify the anions of lithium salt and lithium salt additive in the electrolyte by ion chromatography.

[0153] Nuclear magnetic resonance spectroscopy (NMR): According to JY / T0578-2020, qualitative and quantitative analysis of the components in the electrolyte is obtained. 2. Secondary battery performance test 2.1 Cycle performance test of secondary batteries at 45℃

[0154] The secondary battery was charged at 45°C with a constant current of 1C up to 4.3V, and the constant voltage charging was continued until the current became 0.05C, at which point the secondary battery was fully charged, and the charge capacity at this time was recorded, which is the first charge capacity. The secondary battery was left to stand for 5 minutes, and then discharged at a constant current of 1C down to 2.8V, which is one cycle of charge and discharge, and the discharge capacity at this time was recorded, which is the first discharge capacity. The secondary battery was subjected to a cycle charge and discharge test according to the above method, and the discharge capacity after each cycle was recorded. Capacity retention rate (%) of the secondary battery after 600 cycles at 25°C = discharge capacity after 600 cycles / first discharge capacity × 100%. 2.2 Dynamic performance

[0155] From 2.1, take out the secondary battery cycled at 45°C and charge it at 0.1C to 3.7V. Then, disassemble the secondary battery in a PRS340 / 11-119-11 brown glove box, take out the positive and negative electrode sheets, clean the electrode sheets with dimethyl carbonate (DMC), and then cut the electrode sheets into 23 mm pieces. * 34mm 2Punch out a rectangular sheet of this size, then place it on a dedicated aluminum plastic film in the order of electrode sheet - separator - electrode sheet. Take 300 microliters of an electrolyte of 1 M LiPF6 in EC / EMC / DEC = 3 / 5 / 2 with a pipette gun and inject it. Then, package it with a simple sealing machine and assemble it into a symmetric battery with anode - anode & cathode - cathode. After that, test the AC impedance at 25 °C, a frequency of 500 kHz - 30 mHz, and 73 frequency points with a Shanghai Chenhua electrochemical workstation. Then, plot the real part of the impedance on the x - axis and the negative of the imaginary part on the y - axis. Based on the x - coordinate Rct (charge transfer resistance) corresponding to the valley bottom position in the figure, the quality of the kinetics of the anode and cathode is represented. Test results

[0156] The effects of the present application on the cycle performance and kinetic performance improvement of secondary batteries are shown in Table 5 and Table 6.

[0157]

Table 5

[0158] As can be seen from Table 5, compared with Comparative Examples 1 to 3, in Examples 1 to 2 - 13, when a boron - containing lithium salt additive, a phosphorus - containing lithium salt additive, and a sulfur - containing lithium salt additive are added to the non - aqueous electrolyte and 0 < A1 + A2 + A3 ≤ 3, especially when 0.01 ≤ A1 + A2 + A3 ≤ 2, the three can form good protection on the surfaces of the positive and negative electrode active materials, ensure the stability of the positive and negative electrode active materials, be advantageous for improving the cycle performance of the secondary battery, and the interfacial film formed on the surface of the active material is dense and uniform, and its impedance is relatively small, which is advantageous for improving the kinetic performance of the secondary battery. When A1 + A2 + A3 > 3 (Examples 2 - 3, Example 2 - 8, or Example 2 - 12), the interfacial film formed on the surface of the active material may be too thick, the interfacial impedance becomes high, and the kinetic performance of the secondary battery cannot be improved well.

[0159]

Table 6

[0160] As can be seen from Table 6, in Examples 3-1 to 3-8, the protective performance for the negative electrode active material can be improved by adjusting the amount of the negative electrode film-forming additive used. However, as the amount of the negative electrode film-forming additive used increases, the interfacial impedance of the surface of the negative electrode active material increases, and the dynamic performance is somewhat degraded.

[0161] In Examples 3-9 to 3-22, by adding a gaseous film-forming additive to the electrolyte, the gaseous film-forming additive and the non-gaseous film-forming additive act synergistically, which can further improve the protective performance for the negative electrode active material, and the interface impedance of the SEI film formed on the surface of the negative electrode active material is low, which can further improve the dynamic performance of the secondary battery.

[0162] Although the present application has been described with reference to the preferred embodiments, various improvements may be made without departing from the scope of the present application, or some of the components may be replaced with equivalents. In particular, as long as there is no structural contradiction, the technical features mentioned in each embodiment may be arbitrarily combined. The present application is not limited to the specific embodiments disclosed above, but includes all aspects included in the scope of the claims.

Claims

1. A non-aqueous electrolyte comprising at least two of a boron-containing lithium salt additive, a phosphorus-containing lithium salt additive, and a sulfur-containing lithium salt additive, The mass percentage of the boron-containing lithium salt additive is A1%, based on the total mass of the non-aqueous electrolyte; The mass percentage of the phosphorus-containing lithium salt additive is A2%, based on the total mass of the non-aqueous electrolyte; The mass percentage of the sulfur-containing lithium salt additive is A3%, based on the total mass of the non-aqueous electrolyte; The non-aqueous electrolyte satisfies 0<A1+A2+A3≦3 and optionally 0.01≦A1+A2+A3≦2; Non-aqueous electrolyte.

2. The nonaqueous electrolyte according to claim 1 , wherein the nonaqueous electrolyte satisfies at least one of conditions (1) to (3). (1) 0<A1≦2.

4. (2) 0<A2≦2.

1. (3) 0<A3≦2.

1.

3. The boron-containing lithium salt additive is lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF ４ and lithium bis(oxalato)borate, LiBOB; and / or The phosphorus-containing lithium salt additive is lithium difluorophosphate LiPO ２ F ２ , Lithium fluorophosphate Li ２ P.O. ３ F and lithium phosphate Li ３ P.O. ４ and / or The sulfur-containing lithium salt additive is lithium fluorosulfonate LiFSO ３ , Lithium sulfate Li ２ SO ４ and lithium sulfamate LiSO ３ N.H. ２ One or more of the following may be included: The non-aqueous electrolyte according to claim 1 or 2.

4. The non-aqueous electrolyte further includes a negative electrode film-forming additive configured to form an interfacial film on a surface of the negative electrode active material, the mass percentage of the negative electrode film-forming additive is B % based on the total mass of the nonaqueous electrolyte; The non-aqueous electrolyte satisfies 2≦B / (A1+A2+A3)≦60, and optionally 3≦B / (A1+A2+A3)≦50. The non-aqueous electrolyte according to claim 1 .

5. The negative electrode film-forming additive includes a gaseous film-forming additive and / or a non-gaseous film-forming additive, Optionally, the negative electrode film-forming additive includes a gaseous film-forming additive and a non-gaseous film-forming additive; the mass percentage of the gaseous membrane-forming additive is C%, based on the total mass of the nonaqueous electrolyte; the mass percentage of the non-gaseous film-forming additive is D %, based on the total mass of the non-aqueous electrolyte; The non-aqueous electrolyte has a C ＊ D≦20 and selectably 0.01≦C ＊ D≦15 is satisfied; The non-aqueous electrolyte according to claim 4 .

6. The gaseous film-forming additive includes one or more of carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, nitrogen dioxide, dinitrogen trioxide, phosphorus trioxide, and phosphorus pentoxide; Optionally, the gaseous deposition additive comprises carbon monoxide and carbon dioxide; the mass percentage of carbon monoxide is C1% based on the total mass of the non-aqueous electrolyte; the mass percentage of the carbon dioxide is C2%, based on the total mass of the non-aqueous electrolyte; The non-aqueous electrolyte satisfies 0.01≦C2 / C1≦60, and optionally 0.1≦C2 / C1≦40; The non-aqueous electrolyte according to claim 5 .

7. 10 －６ ≦C1≦0.1, and / or 10 －６ 7. The non-aqueous electrolyte according to claim 6, wherein C2 is 0.

5.

8. The non-gaseous film-forming additive includes one or more of a carbonate additive, a sulfate additive, and a sulfite additive; Optionally, the carbonate ester additive comprises a cyclic carbonate ester additive and / or a linear carbonate ester additive, and further, the cyclic carbonate ester additive comprises one or more of vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, and the linear carbonate ester additive comprises one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA; Optionally, the sulfate ester additive comprises a cyclic sulfonate ester additive and / or a hydrocarbyl sulfate ester additive, and further, the cyclic sulfonate ester additive comprises one or more of 1,3-propane sultone PS, propene sultone PES, and 3-fluoro-1,3-propane sultone FPS, and the hydrocarbyl sulfate ester additive comprises one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS, Optionally, the sulfite additive comprises ethylene sulfite ES and / or vinyl ethylene sulfite VES; The non-aqueous electrolyte according to claim 5 .

9. 0<D≦7; The non-aqueous electrolyte according to claim 5 .

10. A positive electrode sheet including a positive electrode active material; a negative electrode sheet including a negative electrode active material; The non-aqueous electrolyte according to any one of claims 1 to 9, Secondary battery.

11. The molecular formula of the positive electrode active material is LiNi ｘ Co ｙ M １－ｘ－ｙ In the molecular formula, M represents one or more of Mn, Fe, Mg, Al, Cu, and Ti, and x≧0.5, 0≦y≦0.2, and x+y≦1. The secondary battery according to claim 10.

12. The secondary battery according to claim 10 or 11 is provided. Power consuming device.

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