Non-aqueous electrolytes, secondary batteries, and power consumption devices

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 more particularly to non-aqueous electrolytes, secondary batteries, and power consumption devices. [Background technology]

[0002] Because rechargeable batteries have characteristics such as high capacity and long lifespan, they are widely used in electronic devices such as mobile phones, laptops, electric scooters, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools.

[0003] As the range of battery applications expands, the demands on the performance of rechargeable batteries are also becoming increasingly stringent. To improve the performance of rechargeable batteries, it is common practice to optimize the materials within the battery, such as the electrolyte. The electrolyte, as the conduction medium for metal ions in rechargeable batteries, has a significant impact on their performance.

[0004] However, currently, when improved electrolytes are applied to secondary batteries, the batteries cannot simultaneously improve both their cycle performance and kinetic performance during use. [Overview of the project]

[0005] This application has been made in view of the above-mentioned problems, and its purpose is to provide a non-aqueous electrolyte, a secondary battery, and a power consumption 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] As a result, the present invention controls the mass percentages of the boron-containing lithium salt additive, phosphorus-containing lithium salt additive, and sulfur-containing lithium salt additive to satisfy the above formula, so that both the boron-containing lithium salt additive and the phosphorus-containing lithium salt additive can participate in the formation of the CEI film, resulting in a rich structural composition of the CEI film, a dense and uniform film layer, excellent protective effect on the positive electrode active material, effective reduction of electrolyte decomposition, and ensuring stable electrolyte performance, thereby improving the cycle stability of the secondary battery; furthermore, the relatively low interfacial impedance of the CEI film is advantageous for improving the dynamic performance of the secondary battery. Through the cooperative action of the boron-containing lithium salt additive and the sulfur-containing lithium salt additive, the boron-containing lithium salt additive acts as a passivator on the positive electrode current collector, reducing the risk of corrosion to the positive electrode current collector by the sulfur-containing lithium salt additive, thereby further improving the cycle stability of the secondary battery. The synergistic action of at least two of the boron-containing lithium salt additives, phosphorus-containing lithium salt additives, and sulfur-containing lithium salt additives can improve the conductivity of the electrolyte and further enhance the dynamic performance of the secondary battery. Furthermore, the synergistic action of at least two of the boron-containing lithium salt additives, phosphorus-containing lithium salt additives, and sulfur-containing lithium salt additives can jointly form an SEI film on the surface of the negative electrode active material. The SEI film has a rich structural composition, its layer is dense and uniform, it effectively protects the negative electrode active material, and the interface impedance of the SEI film is relatively low, thus effectively improving the dynamic performance of the secondary battery.

[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 ensures that the boron-containing lithium salt additive forms a sufficient interfacial film on the surface of the positive electrode active material and / or the negative electrode active material. Thereby, good protection is provided for the positive electrode active material and / or the negative electrode active material, and the cycle stability of the secondary battery can be improved. When the mass percentage of the phosphorus-containing lithium salt additive is within the above range, it ensures that the phosphorus-containing lithium salt additive forms a sufficient interfacial film on the surface of the positive electrode active material and / or the negative electrode active material, provides good protection for the positive electrode active material and / or the negative electrode active material, and can improve 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, phosphorus-containing lithium salt additive, and sulfur-containing additive of this application work together to form an SEI film with the negative electrode film-forming additive, improving the structural composition and impedance of the SEI film and enhancing the cycle performance of the secondary battery. On the other hand, as a positive electrode film-forming additive, it protects the positive electrode active material and works in cooperation with the negative electrode film-forming additive to improve the interfacial characteristics of the secondary battery and enhance the cycle performance of the secondary battery.

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

[0013] As a result, the present invention can further improve the structure of the SEI film and enhance the cycle performance of the secondary battery by controlling the mass percentages of the gaseous film-forming additive and the non-gasic 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, the mass percentage of carbon monoxide is C1% based on the total mass of the nonaqueous electrolyte, 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, and optionally 0.1 ≤ C2 / C1 ≤ 40.

[0015] As a result, the present invention can effectively improve the compositional 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 to 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 the carbonate ester additives, sulfur ester additives, and sulfite ester additives, and optionally, the carbonate ester additive comprises cyclic carbonate ester additives and / or linear carbonate ester additives, further comprising one or more of the cyclic carbonate ester additives: vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, and the linear carbonate ester additive comprises ethyl allyl carbonate AEC, diphenyl carbonate DPC, and methyl allyl The sulfate ester additives include one or more of the carbonate MAC and polycarbonate VA, and optionally include cyclic sulfonic acid ester additives and / or hydrocarbon sulfate ester additives, further including one or more of the cyclic sulfonic acid ester additives, 1,3-propanesultone PS, propensultone PES, and 3-fluoro-1,3-propanesultone FPS, and optionally include one or more of the hydrocarbon sulfate ester additives, 1 or more of the vinyl sulfate DTD, diethyl DES, and dimethyl DMS, and optionally include ethylene sulfite ES and / or vinyl ethylene sulfite VES.

[0018] As a result, the non-gaseous film-forming additive of the present invention can form an SEI film on the surface of the negative electrode active material, and the formation of multiple components together on the surface of the SEI film enriches the film layer structure of the SEI film and improves 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 comprising a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte according to any one embodiment of the first aspect of the present application, wherein the positive electrode sheet comprises a positive electrode active material and the negative electrode sheet comprises a negative electrode active material.

[0021] A third aspect of the present application further provides a power consumption device including a secondary battery according to the second aspect of the present application. [Brief explanation of the drawing]

[0022] To more clearly explain the technical concept of the embodiments of this application, the drawings required for the embodiments of this application are briefly introduced below. Clearly, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 2] Figure 1 is an exploded schematic diagram of an embodiment of a secondary battery. [Figure 3] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 5] Figure 4 is an exploded schematic diagram of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment of a power consumption device that includes a secondary battery of the present invention as a power source. The drawing is not necessarily drawn to actual proportions. The symbols are explained below: 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. [Modes for carrying out the invention]

[0023] The following describes in detail embodiments specifically disclosing the electrolyte, secondary battery, and power consumption device of the present application. However, unnecessary details may be omitted. For example, detailed explanations of known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. The accompanying drawings and the following explanation 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 “range” disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting one lower limit and one upper limit, the selected lower limit and upper limit limiting the boundary of a special range. The range thus limited may include or exclude endpoints, and may be any combination; that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Also, if minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are given, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 may all be expected. In this application, unless otherwise stated, the numerical range “a-b” is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" in this specification refers to all real numbers between "0 to 5," and "0 to 5" is an abbreviation for combinations of these numbers. Also, when a parameter is described as an integer greater than or equal to 2 (≧2), it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0026] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly, but it is preferable that they be performed sequentially. For example, when it is mentioned that the above method includes steps (a) and (b), it means that the above method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, when it is mentioned that the above method may further include step (c), it means that step (c) may be added to the above method in any order. For example, the above method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0027] Unless otherwise specified, the terms "equip" and "include" in this application mean open-ended or closed-ended. For example, the terms "equip" and "include" above may mean further "equip" or "include" other components not listed, or "equip" or "include" only the listed components.

[0028] Unless otherwise specified, the term "or" in this application 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] In this application, the terms "multiple" and "multiple types" refer to two or more types.

[0030] With the increasing application and widespread use of secondary batteries, their overall performance is attracting increasing attention. As the supplier 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. During long-term charge-discharge processes, the constant desorption and insertion of lithium ions by the positive electrode material inevitably leads to structural damage of the material itself, and the destruction of lithium insertion sites directly results in irreversible capacity loss. Furthermore, the positive electrode active material becomes more susceptible to side reactions with the electrolyte, further damaging the structure of the material itself. When the positive electrode active material is described as a ternary material, the ternary material contains manganese, cobalt, and nickel elements. Nickel can improve the specific capacity of the material, cobalt can reduce the occupation of cation mixed sites and stabilize the crystal structure of the ternary material, and manganese can reduce material costs and improve the structural stability and safety of the material. However, during the lithium desorption process of the positive electrode active material, nickel is oxidized from +2 to +4 valence, and tetravalent nickel, which has high oxidizing properties, is prone to side reactions with the electrolyte, which destroys the structure of the active material and reduces the battery capacity.

[0031] In light of the above problems, the inventors improved the non-aqueous electrolyte and added a boron-containing lithium salt additive to the non-aqueous electrolyte, taking into consideration the structural stability of the positive electrode active material from the viewpoint of protecting the positive electrode active material. The boron-containing lithium salt additive can form a cathode electrolyte interface (CEI) film on the surface of the positive electrode active material and provide a protective effect to the positive electrode active material. However, further investigation by the inventors revealed that the uniformity of the CEI film formed by the boron-containing lithium salt additive is poor, and it does not provide a good protective effect to the positive electrode active material, potentially leading to significant damage to the positive electrode active material and thus reducing the cycle performance of the secondary battery. Furthermore, while it is conceivable to increase the concentration of the boron-containing lithium salt additive to improve the protective performance of the CEI film, the impedance value of the CEI film formed in this way may become too high, potentially degrading the dynamic performance of the secondary battery.

[0032] After conducting many 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 at the same time, all three can form a dense and uniform CEI film on the surface of the positive electrode active material. The CEI film can play a good protective role for the positive electrode 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. Non-aqueous electrolytes

[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] )]]Boron-containing lithium salts, as lithium salts with a boron atom as the central atom, coordinate to alkoxy groups, o-diphenols, o-hydroxyl groups, carboxylic acids, etc., to form anionic complexes. These anionic complexes mainly have a delocalized π-bond structure, where the negative charge distribution of the central ion is relatively dispersed and the charge is delocalized. Furthermore, they have a large anionic radius, making it difficult for the anion to form strong ion pairs with lithium ions in organic solvents, resulting in relatively good solubility. The more electron-withdrawing groups there are in the anionic complex, the more stable the anionic structure becomes, increasing the solubility of lithium ions in non-aqueous electrolytes, which is advantageous for improving the conductivity of non-aqueous electrolytes. This, in turn, improves the kinetic performance of the non-aqueous electrolyte and is advantageous for improving the kinetic performance of secondary batteries. In addition, at high potentials, boron-containing lithium salts can passivate the positive electrode current collector, providing good protection to the positive electrode current collector. Furthermore, boron-containing lithium salts can form a CEI film on the surface of the positive electrode active material. The formation of the CEI film effectively reduces the sustained oxidative decomposition of the positive electrode active material by the non-aqueous electrolyte, providing good protection to the positive electrode active material, improving the cycle stability of the positive electrode active material, and reducing electrolyte decomposition, thereby ensuring electrolyte stability. In addition, boron-containing lithium salts can form a high-performance solid electrolyte interface (SoliD Electrolyte Interface, SEI film) on the surface of the negative electrode active material. Since the SEI film is insoluble in organic solvents and can stably exist in organic electrolytes, it can effectively reduce the insertion of solvent molecules in the electrolyte into the negative electrode active material, thereby ensuring the structural stability of the negative electrode active material and ultimately improving the cycle performance of the secondary battery.

[0038] Phosphorus-containing lithium salt additives have relatively large anionic groups and high ionic conductivity, making them advantageous for improving the kinetic performance of the electrolyte. Furthermore, phosphorus-containing lithium salt additives can form a CEI film on the surface of the positive electrode active material. This formed CEI film has high lithium ion conductivity, significantly suppressing the sustained decomposition of the electrolyte and reducing the elution of transfer metal ions in the positive electrode active material, thus improving the cycle performance of the secondary battery. Additionally, phosphorus-containing lithium salt additives can form an SEI film on the surface of the negative electrode active material. Because this film has low interfacial impedance, it can significantly improve the battery's cycle performance.

[0039] Sulfur-containing lithium salt additives have high oxidation resistance, high thermal stability, are not sensitive to water in the electrolyte, and are less likely to cause side reactions. Furthermore, because sulfur-containing lithium salt additives have relatively high conductivity, they are advantageous in improving the lithium ion transfer rate and enhancing the kinetic performance of the electrolyte. However, when sulfur-containing lithium salt additives are used alone, they have a corrosive effect on the positive electrode current collector, degrading the electrochemical performance of the secondary battery.

[0040] In this application, by controlling the mass percentages of the boron-containing lithium salt additive, phosphorus-containing lithium salt additive, and 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, and it can exert a good protective effect on the positive electrode active material. Moreover, it can effectively reduce the decomposition of the electrolyte, ensure the stability of the electrolyte performance, thereby improving the cycle stability of the secondary battery. Also, because the interfacial impedance of the CEI film is relatively low, it is beneficial to the improvement of 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 can passivate the positive electrode current collector, reduce the risk of corrosion of the positive electrode current collector by the sulfur-containing lithium salt additive, and further improve the cycle stability of the secondary battery. The synergistic effect of at least two of the boron-containing lithium salt additive, phosphorus-containing lithium salt additive, and sulfur-containing lithium salt additive, especially the synergistic effect of the three, can improve the conductivity of the electrolyte and further improve the kinetic performance of the secondary battery. Also, the synergistic effect of at least two of the boron-containing lithium salt additive, phosphorus-containing lithium salt additive, and sulfur-containing lithium salt additive, especially the synergistic effect of the three, can jointly form an SEI film on the surface of the negative electrode active material. The structural composition of the SEI film is rich, its film layer is dense and uniform, and it can effectively protect the negative electrode active material. Also, because 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 B atoms can bond with oxalic acid ligands containing oxygen, the resulting product has excellent thermal stability, easily forming a high-performance interfacial film on the surface of the positive electrode active material and / or negative electrode active material, thereby ensuring the structural stability of the positive electrode active material and / or negative electrode active material, and further improving the cycle performance of the secondary battery. Of course, B atoms may also bond with halogen atoms, especially fluorine atoms. Fluorine atoms have a strong electron-withdrawing induction effect, high thermal and chemical stability, and high solubility of lithium ions in the electrolyte, thus ensuring the solubility of lithium ions and the conductivity of the electrolyte.

[0043] When lithium tetrafluoroborate (LiBF4) is used in cooperation with organic solvents in the electrolyte, such as carbonate ester solvents or additives, the viscosity of the system consisting of lithium tetrafluoroborate is relatively low, which is advantageous 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 low impedance for charge transfer in secondary batteries, which can significantly improve the low-temperature performance of secondary batteries. Furthermore, because the SEI film is less prone to thermal decomposition and its performance at high temperatures is relatively stable, the high-temperature performance of secondary batteries can also be significantly improved.

[0044] Either lithium bisoxalate borate (LiBOB) or lithium difluoro(oxalato)borate (LiDFOB) has a passivation effect on the positive electrode current collector in the positive electrode sheet, reducing the risk of side reactions with the positive electrode current collector and corroding it, thereby improving the structural stability of the positive electrode sheet. Furthermore, an electrolyte containing either lithium bisoxalate borate (LiBOB) or lithium difluoro(oxalato)borate (LiDFOB) is less likely to generate acidic substances, further reducing the risk of corrosion of the positive electrode current collector. Lithium bisoxalate borate (LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) have good compatibility with the positive electrode active material, are advantageous for lithium ion transfer, and can form a high-performance interfacial film on the surface of the positive electrode active material and / or negative electrode active material, improving the protective performance of the positive electrode active material and / or negative electrode active material.

[0045] When lithium tetrafluoroborate (LiBF4), lithium bisoxalate borate (LiBOB), and lithium difluoro(oxalato)borate (LiDFOB) are used in cooperation, the three can form a CEI film on the surface of the positive electrode active material, and this CEI film can effectively reduce the decomposition of the positive electrode active material by the electrolyte. Furthermore, the three can form an SEI film on the surface of the negative electrode active material, and this SEI film can improve lithium ion transport and reduce the continuous reductive 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 within the above range, it ensures that the boron-containing lithium salt additive sufficiently forms an interfacial film on the surface of the positive electrode active material and / or negative electrode active material, thereby providing good protection to the positive electrode active material and / or negative electrode active material and improving the cycle stability of the secondary battery. Exemplaryly, the mass percentage A1% of the boron-containing lithium salt additive may be in the range of 0.1%, 0.2%, 0.5%, 1%, 2%, or 2.4%, or any two of the above values.

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

[0049] The above phosphorus-containing lithium salt additive is an inorganic lithium phosphate salt that can participate in the formation of a positive electrode film during the initial charging process of a secondary battery, and can form a stable CEI film with low impedance. This CEI film can effectively reduce the oxidative decomposition of the electrolyte, for example, it can effectively reduce side reactions 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. Furthermore, the above phosphorus-containing lithium salt can form a Li on the surface of the negative electrode active material. x PO y F z Furthermore, an SEI film rich in LiF components can be formed. This SEI film has low interfacial impedance and can significantly improve the cycle performance of secondary batteries.

[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, it is possible to ensure 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 to the positive electrode active material and / or the negative electrode active material and improving the cycle stability of the secondary battery. Exemplaryly, the mass percentage A2% of the phosphorus-containing lithium salt additive may be in the range of 0.1%, 0.2%, 0.5%, 1%, 2%, or 2.1%, or any two of the above values.

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

[0053] When the above-mentioned sulfur-containing lithium salt additive, boron-containing lithium salt additive, and 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] The stability of the electrolyte can be ensured if the mass percentage of the sulfur-containing lithium salt additive is within the above range. For example, the mass percentage A3% of the sulfur-containing lithium salt additive may be 0.1%, 0.2%, 0.5%, 1%, 2%, or 2.1%.

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

[0057] When a non-aqueous electrolyte is used in a secondary battery, the negative electrode film-forming additive primarily forms an SEI film on the surface of the negative electrode active material. The SEI film acts as an ion conductor, allowing metal ions to pass through. Metal ions are inserted and removed through the SEI film, enabling charging and discharging of the secondary battery. At the same time, it also acts as an electronic insulator, reducing the risk of electrons passing through. Furthermore, the SEI film is insoluble in organic solvents, can stably exist in organic electrolyte solvents, and solvent molecules can hardly pass through the film. This effectively reduces co-insertion of solvent molecules, thereby reducing the destruction of the negative electrode active material due to co-insertion of solvent molecules and improving the cycle performance and service life of the active material.

[0058] Boron-containing lithium salt additives, phosphorus-containing lithium salt additives, and sulfur-containing additives work together to form an SEI film with the negative electrode film-forming additive, improving the structural composition and impedance of the SEI film and enhancing the cycle performance of the secondary battery. On the other hand, they act as positive electrode film-forming additives, protecting the positive electrode active material and working in cooperation with the negative electrode film-forming additive to improve the interfacial properties of the secondary battery and enhance the cycle performance of the secondary battery. In particular, when the ratio is within the above range, it is possible to ensure the conductivity of the electrolyte while providing good protection to the positive and negative electrode active materials. Selectively, 3 ≤ B / (A1 + A2 + A3) ≤ 50, and exemplary, B / (A1 + A2 + A3) may be in the range of 2, 3, 5, 6, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 40, 45, 50, 55 or 60, or 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 in the range of 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 5%, 6%, or 7%, or any two of the above 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 for the non-aqueous electrolyte, 0.005 ≦ C * D ≦ 20 is satisfied.

[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 on 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 both can reduce mutual consumption and synergistically improve the cycle performance of the secondary battery. In the present application, 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 gaseous film-forming additives include gaseous film-forming additives containing one or more of the following: carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, nitrogen dioxide, dinitrogen trioxide, phosphorus trioxide, and phosphorus pentoxide. The above gaseous film-forming additives can promote the formation of SEI films and improve the structure of SEI films.

[0065] Furthermore, the gaseous film-forming additive contains carbon monoxide and carbon dioxide, and based on the total mass of the non-aqueous electrolyte, the mass percentage of carbon monoxide is C1%, and based on the total mass of the non-aqueous electrolyte, the mass percentage of carbon dioxide is C2%, and the non-aqueous electrolyte satisfies 0.01 ≤ C2 / C1 ≤ 60.

[0066] Carbon dioxide and carbon monoxide can passivate 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. Furthermore, carbon dioxide directly participates in the film formation reaction on the negative electrode active material surface, while carbon monoxide absorbs oxygen gas released from the secondary battery system, generating carbon dioxide and increasing its concentration, thus further contributing to the film formation reaction. The interaction between carbon dioxide and carbon monoxide reduces the risk of side reactions on the active material surface, improving electrolyte stability. By controlling the mass percentage ratio of carbon monoxide to carbon dioxide within the above range, the compositional structure of the SEI film can be effectively improved, thereby improving the cycle stability of the secondary battery. Selectively, 0.1 ≤ C2 / C1 ≤ 40. For example, C2 / C1 may be a range consisting of 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 any two of the above values.

[0067] Furthermore, 10 -6 ≤C1 ≤ 0.1. Selectively, 5 * 10-6 C1 ≤ 0.08 ppm.

[0068] For example, the mass percentage of carbon monoxide C1% 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 -2It may also be in the range consisting of 0.1% or any two of the above numerical values.

[0069] Furthermore, 10 -6 ≤ C2 ≤ 0.5. Optionally, 5 * 10 -6 ≤ C2 ≤ 0.4.

[0070] Exemplarily, the mass percentage C2% of carbon dioxide 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 It may be a percentage (%), 0.5%, or a range consisting of any two of the above values.

[0071] As an example of a non-gaseous film-forming additive, the non-gaseous film-forming additive includes one or more types from among carbonate ester additives, sulfate ester additives, and sulfite ester additives. The non-gaseous film-forming additive can form an SEI film on the surface of the negative electrode active material, and multiple components can be deposited together on the surface of the SEI film, thereby enriching the film layer structure of the SEI film and improving the structural stability of the SEI film.

[0072] Exemplary, carbonate ester additives include cyclic carbonate ester additives and / or linear carbonate ester additives, and optionally, cyclic carbonate ester additives include one or more of vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, and linear carbonate ester additives include one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate VA. Cyclic carbonate ester additives have a higher dielectric constant and can dissolve lithium salts as much as possible, thereby allowing lithium salts to dissociate lithium ions more easily and improving the conductivity of the electrolyte. Linear carbonate ester additives have a relatively low viscosity and can improve the transfer rate of lithium ions.

[0073] For example, the sulfate ester additives include cyclic sulfonic acid ester additives and / or hydrocarbon sulfate ester additives, further comprising one or more of 1,3-propanesultone PS, propensultone PES, and 3-fluoro-1,3-propanesultone FPS, and the hydrocarbon sulfate ester additives include one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS.

[0074] Exemplary examples include sulfite ester additives, which include ethylene sulfite (ES) and / or vinyl ethylene vinyl sulfite (VES).

[0075] In some embodiments, the non-aqueous electrolyte further comprises an organic solvent. The organic solvent may further include at least one or a combination of at least one 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 this application can be prepared according to conventional methods in the art. For example, an electrolyte can be obtained by uniformly mixing additives, a solvent, an electrolyte salt, etc. The order in which each material is added is not particularly limited; for example, a non-aqueous electrolyte can be obtained by adding additives, an electrolyte salt, etc., to a non-aqueous solvent and mixing them uniformly.

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

[0078] When testing the electrolyte of this application, the newly prepared electrolyte may be obtained as 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 its discharge cutoff voltage (generally fully discharging the battery for safety), centrifuging it, and then using an appropriate amount of liquid obtained by centrifuging as the non-aqueous electrolyte. The non-aqueous electrolyte may also be obtained directly from the filling port of the secondary battery. secondary battery

[0079] According to a second aspect, the present invention 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 can be an electrolyte according to any one embodiment of the first aspect of this application. By using the above electrolyte, the cycle performance and dynamic 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 provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is provided on 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, which can be a positive electrode active material used in secondary batteries known in the art. For example, the positive electrode active material may include at least one of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides 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 their respective modified compounds. Examples of lithium-containing phosphates with an olivine structure include at least one of lithium iron phosphate, lithium iron phosphate-carbon composites, lithium manganese phosphate, lithium manganese phosphate-carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate-carbon composites, and their respective modified compounds. The present invention is not limited to these materials, and other conventionally known materials used as positive electrode active materials in secondary batteries can be used. These positive electrode active materials may be used individually or in combination of two or more types.

[0083] In some embodiments, the positive electrode active material is LiNi x Co y M 1-x-yThe material contains O2, where M is 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 boron-containing lithium salt, the B atoms in the boron-containing lithium salt readily bond with the O atoms in the positive electrode active material, reducing the impedance of charge transfer in the positive electrode active material and lowering the diffusion resistance of lithium ions within the bulk of the positive electrode active material. Therefore, when the non-aqueous electrolyte contains appropriate amounts 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, allowing lithium ions in the bulk of the low-cobalt or cobalt-free positive electrode active material to be replenished to the surface in a timely manner, thereby preventing excessive desorption of lithium from the surface of the low-cobalt or cobalt-free positive electrode active material, and thus stabilizing the crystal structure of the low-cobalt or cobalt-free positive electrode active material. Because the crystal structure of the low-cobalt or cobalt-free positive electrode active material is more stable, the probability of problems such as instability of the structural, chemical, or electrochemical properties of the positive electrode active material due to excessive lithium desorption from the surface of the low-cobalt or cobalt-free positive electrode active material, such as irreversible strain and increased lattice defects in the positive electrode active material, can be greatly reduced.

[0084] LiRing x Co y M 1-x-y O2 can be prepared according to conventional methods in this art. An exemplary preparation method involves mixing 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 sintering them. The sintering atmosphere can be an oxygen-containing atmosphere, such as an air atmosphere or an oxygen gas atmosphere. The O2 concentration in the sintering atmosphere is, for example, 70% to 100%. The sintering temperature and sintering time can be adjusted according to the actual conditions.

[0085] For example, a 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). For example, a nickel source includes, but is not limited to, at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate. For example, a cobalt source includes, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate. For example, a manganese source includes, but is not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate. For example, an aluminum source includes, but is not limited to, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate. For example, an element M precursor includes, but is not limited to, at least one of the oxides, nitrate compounds, carbonate compounds, hydroxyl compounds, and acetate compounds of element M. For example, an element N precursor includes, but is not limited to, at least one of the following: ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium bisulfite, ammonium sulfite, ammonium hydrogen sulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0086] In some examples, based on the total mass of the positive electrode film layer, the molecular formula LiNi x Co y M 1-x-y The mass percentage of layered materials that are O2 is 80% to 99%. For example, LiNi x Co y M 1-x-yThe mass percentage of the layered material being 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 of the above values ​​within a range. Optionally, the molecular formula may be LiNi x Co y M 1-x-y The mass percentage of the layered material, which 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 The compound comprises the following, where 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 above positive electrode active material is prone to lithium depletion on the material surface at high voltage, which can lead to phase changes on the surface of the positive electrode active material, Li / Ni mixing, oxygen release, etc. 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 also contains metal cations, such as Al 3+ and Ni 2+ It can bond with other materials, improving the mixing of Li / Ni and the passivation of the aluminum foil. Furthermore, CO2 and CO are well formed on the surface of the negative electrode active material, and simultaneously absorb oxygen gas released from the positive electrode active material at high voltages, thereby improving the cycle life of the secondary battery.

[0088] In some embodiments, the positive electrode film layer may further optionally contain a positive electrode conductive agent. While the type of positive electrode conductive agent is not particularly limited in this application, examples include one or more types 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 film layer may optionally further contain a positive electrode adhesive. In this application, the type of positive electrode adhesive is not particularly limited, but as an example, the positive electrode adhesive may include one or more types selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, copolymer of tetrafluoroethylene-hexafluoropropylene, and fluorine-containing acrylate resins. In some embodiments, the mass percentage of the positive electrode adhesive is 5% or less based on the total mass of the positive electrode film layer.

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

[0091] The positive electrode film layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing a positive electrode active material, a selectable conductive agent, a selectable adhesive, and any other components in a solvent and stirring them uniformly. The solvent may, 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 placed on at least one surface of the negative electrode current collector, the negative electrode film layer containing a negative electrode active material.

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

[0094] In some embodiments, the negative electrode active material can 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 the following: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, 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, this application is not limited to these materials, and other conventional materials used as negative electrode active materials in batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0095] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode adhesive. In this application, the type of 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, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate 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 optionally contain a negative electrode conductive agent. While the type of negative electrode conductive agent is not particularly limited in this application, examples include one or more types selected from superconducting carbon, conductive graphite, acetylene black, carbon black, kecheng 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 film layer may optionally further contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC-Na) or PTC thermistor materials. In some embodiments, the mass percentage of the other additives is 2% or less based on the total mass of the negative electrode film layer.

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

[0099] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a selectable conductive agent, a selectable adhesive, and other selectable auxiliary agents in a solvent and stirring them uniformly. The solvent may, 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 covering the surface of the negative electrode film layer. [Separator]

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

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

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

[0104] In some embodiments, the secondary battery may include an enclosure. This enclosure can be used to seal the electrode assembly and electrolyte.

[0105] In some embodiments, the casing of the secondary battery may be a hard case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a soft 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 this application is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows an exemplary rectangular secondary battery 5.

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

[0108] The method for preparing the secondary battery of the present invention 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, an electrode assembly can be formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly can be placed in an outer casing, dried, and then the electrolyte can be injected. A secondary battery can then be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0109] In some embodiments of the present invention, the secondary battery according to the present invention may be assembled as 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] Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be fixed by fasteners.

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

[0112] In some embodiments, the battery modules may be assembled as 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] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 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, the upper housing 2 being covered by the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery housing in any manner. power consumption equipment

[0114] In a second embodiment, the present application provides a power consumption device comprising 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 consumption device or as an energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, laptop computers, etc.), electric vehicles (e.g., 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.

[0115] The power consumption device can be configured to use a secondary battery, battery module, or battery pack depending on its usage needs.

[0116] Figure 6 is a schematic diagram of an example power consumption device. This power consumption device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack 1 or battery module can be used to meet the high power and high energy density requirements of this power consumption device.

[0117] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices are typically required to be thin and can use rechargeable batteries as their power source. Examples

[0118] The following examples illustrate the contents of the present application in more detail. These examples are used for interpretive purposes only, and it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the contents of the present application. 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 obtained by purchase or synthesis according to conventional methods and are ready for direct use without further processing. Furthermore, all equipment used in the examples can be obtained by purchase. Example 1 1. Preparation of the positive electrode sheet

[0119] A 12 μm thick aluminum foil is used as the positive electrode current collector.

[0120] LiNi 0.65 Co 0.07 Mn 0.28 Carbon black, a conductive agent, and polyvinylidene fluoride (PVDF), an adhesive, were thoroughly mixed in an appropriate amount of solvent NMP in a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. This slurry was then uniformly applied to the surface of aluminum foil, which served as the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained. 2. Preparation of the 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 suitable amount of deionized water as a solvent in a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. This slurry was then uniformly applied to the surface of the copper foil, which served as the negative electrode current collector, and after drying and cold pressing, a negative electrode sheet was obtained. 3. Separator

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

[0124] Under conditions with a water content of less than 10 ppm, ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate, all non-aqueous organic solvents, were mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent. This solvent was then dissolved with additives and other components to prepare an electrolyte with a lithium salt concentration of 1 mol / L. The specific substances contained in the electrolyte are shown in the table below. 5. Preparation of secondary batteries

[0125] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator interposed between the positive and negative electrode sheets to provide isolation. After this, the assembly is wound up to obtain an electrode assembly. The electrode assembly is placed in an outer case, dried, and then the electrolyte is injected. A 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] A secondary battery was prepared using a method similar to that of Example 1, except that the mass percentage A1 of the "boron-containing lithium salt additive" was adjusted. See Table 1 for specific parameters. Examples 2-4 to 2-5

[0127] A secondary battery was prepared using a method similar to that of Example 1, except that the type of "boron-containing lithium salt additive" was adjusted. See Table 1 for specific parameters. Examples 2-6 to 2-8

[0128] A secondary battery was prepared using a method similar to that of Example 1, except that the mass percentage A2 of the "phosphorus-containing lithium salt additive" was adjusted. See Table 1 for specific parameters. Examples 2-9

[0129] A secondary battery was prepared using a method similar to that of Example 1, except that the type of "phosphorus-containing lithium salt additive" was adjusted. See Table 1 for specific parameters. Examples 2-10 to 2-12

[0130] A secondary battery was prepared using a method similar to that of Example 1, except that the mass percentage A3 of the "sulfur-containing lithium salt additive" was adjusted. See Table 1 for specific parameters. Example 2-13

[0131] A secondary battery was prepared using a method similar to that of Example 1, except that the type of "sulfur-containing lithium salt additive" was adjusted. See Table 1 for specific parameters. Comparative Example

[0132] The secondary battery of Comparative Example 1 was prepared in a similar manner to that of Example 1, except that a boron-containing lithium salt additive was not 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 that of Example 1, except that a phosphorus-containing lithium salt additive was not added to Comparative Example 2. See Table 1 for specific parameters.

[0134] The secondary battery of Comparative Example 3 was prepared in a similar manner to that of Example 1, except that a sulfur-containing lithium salt additive was not 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 Example 1, except that the mass percentage of the "boron-containing lithium salt additive" was adjusted and A1 + A2 + A3 > 3. See Table 1 for specific parameters.

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

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

[0138] A secondary battery was prepared in a similar manner to Example 1, except that the type of "negative electrode film-forming additive" was adjusted. 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 formation additive" was adjusted and a gaseous film formation additive was added.

[0140] If the electrolyte contains a gaseous film-forming additive, first add the non-gasificant film-forming additive. After adding the non-gasificant film-forming additive, evacuate the liquid injection machine to a vacuum of -0.07 MPa to -0.1 MPa (vacuum level refers to the difference between the actual pressure and atmospheric pressure) for 0.5 to 3 minutes, and then inject the gaseous film-forming additive. Refer to Tables 2 to 4 for specific parameters. 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, meaning that 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, meaning that C represents the total mass percentage of the gaseous film-forming additive.

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

[0148] B = C + D, meaning that B represents the total mass percentage of the negative electrode film-forming additive. Test section

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

[0150] A newly prepared electrolyte may be obtained, or an electrolyte may be obtained from a secondary battery. Next, the electrolyte components may be measured using one or more methods such as gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), and nuclear magnetic resonance spectroscopy (NMR).

[0151] Following gas chromatography-mass spectrometry (GC-MS) (GB / T-9722-2006 / GB / T6041-2002), a combination of gas chromatography and mass spectrometry is employed. After separating each component in the sample by gas chromatography, each component is subdivided into fragment ions by mass spectrometry and separated by mass-to-charge ratio (m / z) to form a specific mass spectrum to obtain a qualitative analysis of each organic component in the electrolyte. Subsequently, each organic component in the electrolyte is separated in a chromatography column to generate detection signal spectra for each component, and qualitative analysis of the components is performed by adjusting the retention time. Quantitative analysis is then achieved by calibrating the peak area to match the standard, and a quantitative test analysis of the organic components in the electrolyte is obtained.

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

[0153] Qualitative and quantitative analyses of the components in the electrolyte will be performed according to nuclear magnetic resonance spectroscopy (NMR): JY / T0578-2020. 2. Performance testing of secondary batteries 2.1 Cycle performance test of secondary batteries at 45°C

[0154] The secondary battery was charged to 4.3V with a constant current of 1C at 45℃, and constant voltage charging was continued until the current dropped to 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this time was recorded as the first charge capacity. After the secondary battery was left to stand for 5 minutes, it was discharged to 2.8V with a constant current of 1C. This constituted one charge-discharge cycle, and the discharge capacity at this time was recorded as the first discharge capacity. The secondary battery was tested for cycle charge-discharge according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 25℃ = Discharge capacity after 600 cycles / First discharge capacity × 100%. 2.2 Dynamic performance

[0155] 2.1 Remove the rechargeable battery that has been cycled at 45°C, charge it to 3.7V at 0.1C, then disassemble the rechargeable battery in a PRS340 / 11-119-11 brown glove box, remove the positive and negative electrode sheets, clean the electrode sheets with dimethyl carbonate (DMC), and then cut the electrode sheets to 23mm * 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. Use a pipette gun to take 300 microliters of an electrolyte of 1 M LiPF6 EC / EMC / DEC = 3 / 5 / 2, inject it, then package it with a simple sealer and assemble it into a symmetric battery of cathode - cathode & anode - anode. Then, after testing the AC impedance at 25 °C, a frequency of 500 kHz - 30 mHz, and 73 frequency points with a Shanghai Chenhua electrochemical workstation, plot the real part of the impedance on the abscissa and the negative number of the imaginary part on the ordinate. Based on the abscissa 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 Example 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 (Example 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, Examples 3-1 to 3-8 can improve the protective performance for the negative electrode active material by adjusting the amount of negative electrode film-forming additive used. However, as the amount of negative electrode film-forming additive increases, the interfacial impedance of the surface of the negative electrode active material increases, and the dynamic performance decreases slightly.

[0161] Examples 3-9 to 3-22 demonstrate that by adding a gaseous film-forming additive to the electrolyte, the gaseous and non-gasible film-forming additives act synergistically, further improving the protective performance for the negative electrode active material. Furthermore, the interfacial impedance of the SEI film formed on the surface of the negative electrode active material is low, further improving the dynamic performance of the secondary battery.

[0162] While the present application has been described above with reference to preferred embodiments, various improvements are possible, or some of the components may be replaced with equivalents, without departing from the scope of the application. In particular, the technical features mentioned in each embodiment can be combined in any way, provided that there is no structural inconsistency. The present application is not limited to the specific embodiments disclosed above, but includes all embodiments included in the claims.

Claims

1. A non-aqueous electrolyte containing 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 3%, based on the total mass of the non-aqueous electrolyte. The non-aqueous electrolyte satisfies the condition 0 < A1 + A2 + A3 ≤ 3. The phosphorus-containing lithium salt additive is lithium difluorophosphate LiPO ２ F ２ Lithium fluorophosphate Li ２ PO ３ F and lithium phosphate Li ３ PO ４ Includes one or more of the following types: The sulfur-containing lithium salt additive contains one or more of lithium fluorosulfonate LiFSO ３ , lithium sulfate Li ２ SO ４ and lithium sulfamate LiSO ３ NH ２ . Non-aqueous electrolytes.

2. The non-aqueous electrolyte according to claim 1, wherein 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.

3. The boron-containing lithium salt additives are lithium difluoro(oxalato)borate LiDFOB and lithium tetrafluoroborate LiBF ４ and one or more types of lithium bisoxalate borate LiBOB, The non-aqueous electrolyte according to claim 1.

4. The non-aqueous electrolyte further comprises 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. The aforementioned non-aqueous electrolyte satisfies the condition 2 ≤ B / (A1 + A2 + A3) ≤ 60. 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-gasificant 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. The aforementioned non-aqueous electrolyte is 0.005 ≤ C ＊ Satisfying the condition D ≤ 20, The non-aqueous electrolyte according to claim 4.

6. The gaseous film-forming additive includes one or more of the following: carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, nitrogen dioxide, dinitrogen trioxide, phosphorus trioxide, and phosphorus pentoxide. The mass percentage of carbon monoxide is 1% based on the total mass of the nonaqueous electrolyte. The mass percentage of carbon dioxide is 2% based on the total mass of the nonaqueous electrolyte. The non-aqueous electrolyte satisfies the condition 0.01 ≤ C2 / C1 ≤ 60. The non-aqueous electrolyte according to claim 5.

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

5.

8. The non-gaseous film-forming additive includes one or more of the following: carbonate ester additives, sulfate ester additives, and sulfite ester additives. The non-aqueous electrolyte according to any one of claims 5 to 7.

9. 0 < D ≤ 7, The non-aqueous electrolyte according to any one of claims 5 to 7.

10. A positive electrode sheet containing positive electrode active material, A negative electrode sheet containing a negative electrode active material, A non-aqueous electrolyte according to claim 1, comprising: 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. A secondary battery according to claim 10 or 11, Power consumption equipment.

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