Secondary battery, battery module, battery pack, and power consumption device including the same

Abstract

The present application provides a secondary battery, and a battery module, a battery pack, and a power consuming device each including the secondary battery. The secondary battery includes a positive electrode sheet and a non-aqueous electrolyte, the non-aqueous electrolyte includes a compound represented by formula 1, the mass percentage of the compound represented by formula 1 is A1 (%) relative to the total mass of the non-aqueous electrolyte, the thickness of the positive electrode current collector is H (μm), the breaking elongation of the positive electrode current collector is Q (%), and the compressed density of the positive electrode active material layer is P (g / cm 3 ) and the secondary battery satisfies the following: H is 4 to 14, A1 / H is 0.0015 to 0.20, Q+A1 is 1 to 4, and P / A1 is 2 to 340. According to the present application, a secondary battery using a thinned positive electrode current collector combines low cost, high energy density, high output performance, excellent processing performance, and high safety performance. [Formula 1] TIFF2024524801000012.tif37134

Description

[Technical field]

[0001] The present application relates to the technical field of batteries, and more particularly to a secondary battery, and a battery module, a battery pack, and a power consuming device each including the secondary battery. [Background technology]

[0002] In recent years, secondary batteries have been widely used in many fields, such as energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aviation and space. With the application and popularity of secondary batteries, the demand for their energy density is becoming higher and higher. Since the aluminum foil current collector does not contribute to the capacity of the secondary battery, thinning the aluminum foil current collector not only reduces the cost, but also allows more active material to be accommodated in a limited battery case, so thinning the aluminum foil current collector is one of the most effective measures to increase the energy density of the secondary battery. Thinning the aluminum foil current collector can reduce the cost and improve the energy density of the secondary battery, but thinning the aluminum foil current collector increases the internal resistance of the battery, increases the amount of heat generated, and at the same time, the processing performance of the positive electrode sheet is poor, making it easier to cause explosion problems, so this method is difficult to put into industrial practical use. As a result, current secondary batteries cannot combine low cost, high energy density, high output performance, excellent processing performance, and high safety performance. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present application is to provide a secondary battery, which enables a secondary battery using a thin-walled positive electrode current collector to have low cost, high energy density, high output performance, excellent processing performance, and high safety performance, as well as a battery module, a battery pack, and a power consumption device including the secondary battery. [Means for solving the problem]

[0004] A first aspect of the present application is a secondary battery including a positive electrode sheet and a non-aqueous electrolyte. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector. The non-aqueous electrolyte contains a compound represented by Formula 1, and the mass percentage of the compound represented by Formula 1 is A1 (%) with respect to the total mass of the non-aqueous electrolyte. The thickness of the positive electrode current collector is H (μm), the elongation at break of the positive electrode current collector is Q (%), and the compression density of the positive electrode active material layer is P (g / cm 3 ). Further, the secondary battery satisfies the conditions that H is 4 to 14, A1 / H is 0.0015 to 0.20, Q + A1 is 1 to 4, and P / A1 is 2 to 340, and provides a secondary battery. [Chemical formula] (X and Y each independently represent a fluorine atom, or at least one selected from the group consisting of a partially fluorinated or fully fluorinated C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 alkenyloxy, C2-C10 alkynyloxy, and C6-C8 aryloxy, and at least one of X and Y represents a fluorine atom.)

[0005] As a discovery made by the inventors of the present application, in a secondary battery using a thin positive electrode current collector, the non-aqueous electrolyte contains a compound represented by Formula 1, and the secondary battery satisfies the conditions that A1 / H is 0.0015 to 0.20, Q + A1 is 1 to 4, and P / A1 is 2 to 340. By controlling the relationship between the content A1 (%), the thickness H (μm) of the positive electrode current collector, the elongation at break Q (%) of the positive electrode current collector, and the compression density P (g / cm 3 ), the secondary battery can have low cost, high energy density, high output performance, excellent processability, and high safety performance.

[0006] In any embodiment of the present application, optionally, A1 / H is from 0.002 to 0.05, more optionally from 0.01 to 0.05. This contributes to improving the strength of the positive electrode current collector, improving the processing performance of the positive electrode sheet, reducing and further avoiding the occurrence of rupture, and also contributes to imparting high output performance and high safety performance to the secondary battery.

[0007] In any embodiment of the present application, optionally, Q + A1 is from 1.5 to 3.5, more optionally from 2.0 to 3.5. This contributes to improving the strength of the positive electrode current collector, improving the processing performance of the positive electrode sheet, reducing and further avoiding the occurrence of rupture, and also contributes to imparting high output performance and high safety performance to the secondary battery.

[0008] In any embodiment of the present application, optionally, P / A1 is from 5 to 340, more optionally from 10 to 340. This contributes to enhancing the output performance and safety performance of the secondary battery.

[0009] In any embodiment of the present application, optionally, A1 is from 0.02 to 1.8, more optionally from 0.02 to 0.5. This can improve defects such as deterioration of output performance due to thinning of the positive electrode current collector, increase in safety risks, and deterioration of processing performance.

[0010] In any embodiment of the present application, optionally, Q is from 0.5 to 3.5, more optionally from 1.5 to 3.5. This contributes to the positive electrode current collector having high strength and excellent processing performance, being difficult to rupture, and also contributes to imparting high safety performance to the secondary battery.

[0011] In any embodiment of the present application, optionally, P is from 3.2 to 3.7, more optionally from 3.4 to 3.7. This contributes to enhancing the energy density of the secondary battery.

[0012] In any embodiment of the present application, optionally, the non-aqueous electrolyte further contains a first lithium salt containing lithium hexafluorophosphate. The mass percentage of the lithium hexafluorophosphate is A2 (%) with respect to the total mass of the non-aqueous electrolyte.

[0013] In any embodiment of the present application, optionally, A2 / A1 is 5 to 650, more optionally 15 to 300. This contributes to further improving the capacity retention rate of the secondary battery while improving problems such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive electrode current collector.

[0014] In any embodiment of the present application, optionally, A2 is 6 to 14.

[0015] In any embodiment of the present application, optionally, the non-aqueous electrolyte further contains a first lithium salt containing a combination of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The mass percentage of the lithium hexafluorophosphate is A2 (%) with respect to the total mass of the non-aqueous electrolyte, and the mass percentage of the lithium bis(fluorosulfonyl)imide is A3 (%) with respect to the total mass of the non-aqueous electrolyte. Optionally, A2 is 6 to 14, and A3 is greater than 0 and 5 or less.

[0016] In any embodiment of the present application, optionally, A3 / A2 is 0.8 or less, more optionally 0.05 to 0.3. This contributes to forming an interfacial film with lower resistance. Optionally, A2 / A1 is 5 to 650, more optionally 15 to 300. This contributes to further improving the capacity retention rate of the secondary battery while improving problems such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive electrode current collector.

[0017] In any embodiment of the present application, optionally, the non-aqueous electrolyte further contains a second lithium salt including at least one of lithium tetrafluoroborate, lithium perchlorate, lithium hexafluorophosphate, lithium difluorophosphate, lithium difluoro(bis(oxalato))phosphate, and lithium tetrafluoro(oxalato)phosphate. The total mass content of the second lithium salt in the non-aqueous electrolyte is A4 (%) with respect to the total mass of the non-aqueous electrolyte. Optionally, A4 is 5 or less, and more optionally 2 or less. The second lithium salt can, as an auxiliary lithium salt, further improve the interfacial performance of the positive electrode and / or the negative electrode, or play a role in improving the ionic conductivity and thermal stability of the non-aqueous electrolyte.

[0018] In any embodiment of the present application, optionally, the second lithium salt contains lithium difluorophosphate. Optionally, the mass ratio α of the lithium difluorophosphate to the lithium hexafluorophosphate is 0.01 to 0.15, and more optionally 0.01 to 0.1. Lithium difluorophosphate has high electrochemical stability, improves the ionic conductivity of the non-aqueous electrolyte, improves the properties of the positive electrode interfacial film and / or the negative electrode interfacial film, and contributes to the construction of a stable and low-resistance positive electrode interfacial film and / or negative electrode interfacial film. Thereby, the decomposition of the non-aqueous electrolyte is effectively reduced, and the output performance and safety performance of the secondary battery are further improved.

[0019] In any embodiment of the present application, optionally, the non-aqueous electrolyte further contains a cyclic carbonate compound. The mass percentage of the cyclic carbonate compound is B1 (%) with respect to the total mass of the non-aqueous electrolyte. Optionally, B1 is 0.5 to 20, and more optionally 15 to 18.

[0020] In any embodiment of the present application, optionally, B1 / 20 + A1 is 1 to 3, and more optionally 1 to 2. This contributes to further improving the capacity retention rate of the secondary battery while improving problems such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive electrode current collector.

[0021] In any embodiment of the present application, optionally, the cyclic carbonate contains at least one of ethylene carbonate, propylene carbonate, vinylene carbonate, and vinyl ethylene carbonate.

[0022] In any embodiment of the present application, optionally, the non-aqueous electrolyte further contains fluoroethylene carbonate. The mass percentage of the fluoroethylene carbonate is C1 (%) with respect to the total mass of the non-aqueous electrolyte. Optionally, 0 < C1 ≤ 2.5, and more optionally, 0 < C1 ≤ 2.0. Thereby, the cycle performance of the secondary battery can be effectively improved.

[0023] In any embodiment of the present application, optionally, 0.25 ≤ C1 / A1 ≤ 25, and more optionally, 0.5 ≤ C1 / A1 ≤ 10. This contributes to further improving the cycle performance of the secondary battery while improving problems such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive electrode current collector.

[0024] In any embodiment of the present application, optionally, the non-aqueous electrolyte further contains a dehydration additive containing at least one of hexamethyldisilazane and tris(trimethylsilyl) phosphate. Optionally, the mass percentage of the dehydration additive is 2% or less, and more optionally 0.05% - 1% with respect to the total mass of the non-aqueous electrolyte. This contributes to further improving the output performance, storage performance, and safety performance of the secondary battery.

[0025] In any embodiment of the present application, optionally, both X and Y represent fluorine atoms.

[0026] In any embodiment of the present application, optionally, among X and Y, one represents a fluorine atom, and the other represents at least one selected from the group consisting of partially fluorinated or fully fluorinated C1 - C5 alkyl, C2 - C5 alkenyl, C2 - C5 alkynyl, phenyl, phenoxy, C1 - C5 alkoxy, C2 - C5 alkenyloxy, and C2 - C5 alkynyloxy.

[0027] In any embodiment of the present application, optionally, among X and Y, one represents a fluorine atom, and the other represents at least one selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, vinyl, propenyl, allyl, butadienyl, ethynyl, propynyl, phenyl, methoxy, ethoxy, Propoxy , vinyloxy, propenyloxy, ethynyloxy, propynyloxy, and phenoxy which are partially fluorinated or fully fluorinated.

[0028] The presence of fluorine atoms contributes to the formation of a thinner fluorine-containing positive electrode interface film and / or negative electrode interface film, contributes to the uniform transport of lithium ions, and effectively suppresses the formation of lithium dendrites.

[0029] In any embodiment of the present application, optionally, the compound represented by the formula 1 includes at least one of the following compounds.

Chemical formula

[0030] In any embodiment of the present application, optionally, the positive electrode current collector uses an aluminum foil or an aluminum alloy foil.

[0031] The second aspect of the present application provides a battery module including the secondary battery described in the first aspect of the present application.

[0032] The third aspect of the present application provides a battery pack including one of the secondary battery described in the first aspect of the present application and the battery module described in the second aspect.

[0033] The fourth aspect of the present application provides a power consumption device including at least one of the secondary battery described in the first aspect of the present application, the battery module described in the second aspect, and the battery pack described in the third aspect.

Advantages of the Invention

[0034] Since the battery module, battery pack, and power consumption device of the present application include the secondary battery according to the present application, they have at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0035] To further illustrate the technical solutions of the embodiments of the present application, the drawings used in the embodiments of the present application will be briefly described below. Obviously, the drawings described below are only a part of the embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative efforts.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Description of the Reference Numerals

[0036] In the drawings, the drawings are not necessarily drawn to actual scale. 1 Battery pack 2 Upper box body 3 Lower box body 4 Battery module 5 Secondary battery 51 Case 52 Electrode assembly 53 Cover plate

Embodiments for Carrying Out the Invention

[0037] Hereinafter, embodiments specifically disclosing the secondary battery according to the present application, the battery module, the battery pack, and the power consumption device including the same will be described in detail with appropriate reference to the drawings. However, detailed descriptions more than necessary may be omitted. For example, detailed descriptions of known matters or duplicate descriptions of actually the same structure may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate the understanding of those skilled in the art. Further, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0038] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit, and a predetermined range is limited by selecting the lower limit and the upper limit that define the boundary of the specific range. The range defined in this way may or may not include the end values, and any combination is possible, that is, it is possible to form one range by combining any lower limit value and any upper limit value. For example, when ranges of 60 to 120 and 80 to 110 are given for a specific parameter, it can be understood that ranges of 60 to 110 and 80 to 120 are also expected. Also, when 1 and 2 are given as the minimum range values and 3, 4, and 5 are given as the maximum range values, all of the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are expected. In the present application, unless otherwise specified, the range of "a to b" represents a shortened expression of any combination of real numbers between a and b. Here, both a and b are real numbers. For example, the numerical range of "0 to 5" means that all real numbers between "0 to 5" are included in this specification, and "0 to 5" is a shortened form of the combination of these numerical values. Also, when it is described that a certain parameter is an integer of 2 or more, it is disclosed that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and any embodiments of this application can be combined with each other to form a new technical solution. Moreover, such a technical solution is considered to be included in the disclosure of this application.

[0040] Unless otherwise specified, all technical features and any technical features of this application can be combined with each other to form a new technical solution. Moreover, such a technical solution is considered to be included in the disclosure of this application.

[0041] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, or selectively sequentially. For example, if the method includes steps (a) and (b), it indicates that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, when it is mentioned that the method may further include step (c), it indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), steps (a), (c), and (b), or steps (c), (a), and (b).

[0042] Unless otherwise specified, the terms "comprising", "having", and "including" described in this application are open-ended and may also be closed-ended. For example, the "comprising", "having", and "including" may mean further "comprising", "having", or "including" other components not listed, or only "comprising", "having", or "including" the listed components.

[0043] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the following conditions is satisfied: 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).

[0044] Throughout this specification, the substituents of the compounds are disclosed in groups or ranges. Such a description is explicitly contemplated to include each individual sub-combination of the members of these groups and ranges. For example, the term "C1-C6 alkyl" is explicitly contemplated to disclose C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, and C5-C6 alkyl alone.

[0045] In the present application, the terms "a plurality" and "a plurality of kinds" mean two or more.

[0046] In the present application, the thicknesses of the current collector and the active material layer have the meanings known in the art and can be tested using methods known in the art. For example, it can be measured using a spiral micrometer.

[0047] In the present application, the compression density of the active material layer has the meaning known in the art and can be tested using methods known in the art. The compression density of the active material layer = the areal density of the active material layer / the thickness of the active material layer. The areal density of the active material layer has the meaning known in the art. For example, an electrode sheet after being coated on one side and cold-pressed (if it is an electrode sheet coated on both sides, the active material layer on one side may be wiped off first) is cut into wafers with an area of S0, and its weight is weighed and recorded as M1. Next, the active material layer of the electrode sheet whose weight has been weighed is wiped off, and the weight of the current collector is weighed and recorded as M0. The areal density of the active material layer = (M1 - M0) / S0. Tests can be carried out by adopting methods known in the art.

[0048] In the present application, the elongation at break of the positive electrode current collector means the elongation at break at room temperature.

[0049] The aluminum foil current collector is one of the essential components of a secondary battery. To further increase the energy density of the secondary battery, thinning the aluminum foil current collector remains one of the most effective measures. By thinning the aluminum foil current collector, it is possible to reduce the cost of the secondary battery and improve its energy density. However, this method is difficult to industrialize. The main reasons are as follows. First, when the aluminum foil current collector is thinned, the resistance of the aluminum foil increases, resulting in an increase in the internal resistance of the battery and a decrease in output performance. Second, since aluminum foil is a good heat conductor material, thinning it increases the heat generation amount of the secondary battery, making heat dissipation difficult and increasing the potential risk to the safety of the secondary battery. Third, when the aluminum foil current collector is thinned, its strength decreases. At the same time, to further increase the energy density of the secondary battery, the thinned aluminum foil current collector generally has a high compression density, making the positive electrode sheet prone to being crushed during roll pressing and affecting the processing performance of the positive electrode sheet and the secondary battery.

[0050] In addition, high-power batteries require a large discharge current during use, resulting in a high heat generation amount during discharge and a significant increase in the decomposition reaction of the non-aqueous electrolyte at the interface between the positive and negative electrodes at high temperatures. This causes a significant increase in the resistance at the positive electrode interface and the negative electrode interface, resulting in a decrease in the output performance of the secondary battery. Currently, to obtain a high-power battery, thickening the aluminum foil current collector is one of the common measures.

[0051] Therefore, currently, the method of increasing the energy density of a secondary battery by thinning the positive electrode current collector still faces many difficulties in terms of practical application, such as deterioration of output performance, increase in safety risks, and deterioration of processing performance.

[0052] As a surprising discovery made by the inventors of the present application, by adopting an appropriate non-aqueous electrolyte solution, problems such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive electrode current collector can be solved. As a result, the secondary battery can have low cost, high energy density, high output performance, excellent processing performance, and high safety performance.

[0053] Specifically, an embodiment of the present application provides a secondary battery.

[0054] A secondary battery is also called a rechargeable battery or a storage battery, and is a battery that can continue to be used by activating the active material by charging after discharging. The secondary battery of the present application may be a lithium secondary battery, particularly a lithium ion secondary battery. The secondary battery includes an electrode assembly, a non-aqueous electrolyte solution, and an exterior body. The exterior body encloses the electrode assembly and the non-aqueous electrolyte solution. The electrode assembly usually includes a positive electrode sheet, but may further include a negative electrode sheet and a separator. The separator is provided between the positive electrode sheet and the negative electrode, mainly serves to prevent short circuit between the positive electrode and the negative electrode, and allows lithium ions to pass through. In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be made into an electrode assembly by a winding process or a lamination process.

[0055] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two corresponding surfaces in its own thickness direction, and the positive electrode active material layer is provided on one or both of the two opposing surfaces of the positive electrode current collector. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode active material layer is provided on one or both of the two opposing surfaces of the negative electrode current collector. During charging and discharging of the secondary battery, lithium ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and desorption. The non-aqueous electrolyte includes a lithium salt and an organic solvent, and plays a role of transmitting lithium ions between the positive electrode sheet and the negative electrode sheet.

[0056] In the secondary battery of the present application, the non-aqueous electrolyte contains a compound represented by Formula 1. X and Y are each independently a fluorine atom, or a partially fluorinated or fully fluorinated C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 alkenyloxy, C2-C10 alkynyloxy, C6-C8 aryloxy, and at least one of X and Y represents a fluorine atom.

Chemical formula

[0057] The mass percentage of the compound represented by Formula 1 is A1 (%) with respect to the total mass of the non-aqueous electrolyte, the thickness of the positive electrode current collector is H (μm), the elongation at break of the positive electrode current collector is Q (%), and the compression density of the positive electrode active material layer is P (g / cm 3 )), and the secondary battery satisfies that H is 4-14, A1 / H is 0.0015-0.20, Q+A1 is 1-4, and P / A1 is 2-340.

[0058] In the present application, the thickness H (μm) of the positive electrode current collector satisfies 4 to 14, and optionally, H may be 4 to 13, 4 to 12, 4 to 11, 4 to 10, 4 to 9, or 4 to 8.

[0059] As a discovery made by the inventors of the present application, in a secondary battery using a thin positive electrode current collector, the non-aqueous electrolyte contains a compound represented by Formula 1, and the secondary battery satisfies A1 / H being 0.0015 to 0.20, Q + A1 being 1 to 4, and P / A1 being 2 to 340. By controlling the relationship between the content A1 (%) and the thickness H (μm) of the positive electrode current collector, the elongation at break Q (%) of the positive electrode current collector, and the compression density P (g / cm 3 ) of the positive electrode active material layer, the secondary battery can have low cost, high energy density, high output performance, excellent processing performance, and high safety performance.

[0060] Although the mechanism is unclear, the inventors of the present application presume that there are several reasons as follows.

[0061] First, the molecular structure of the compound represented by Formula 1 contains an oxalate group. The oxalate group is preferentially oxidized on the surface of the positive electrode active material rather than the organic solvent, and the oxidation product has low resistance characteristics, so it contributes to the formation of a low-resistance positive electrode interface film. On the other hand, the B atom in the molecular structure of the compound represented by Formula 1 is also likely to be strongly bonded to inorganic components such as LiF in the positive electrode interface film. Thereby, the transport of lithium ions is accelerated, the internal resistance of the battery is significantly reduced, both high energy density and high output performance are imparted to the secondary battery, and large current discharge is enabled.

[0062] Second, the B-O bond in the molecular structure of the compound represented by Formula 1 can be bonded to Al 3+ to form a passivation film on the surface of the positive electrode current collector. Thereby, the strength of the positive electrode current collector is improved, the processing performance of the positive electrode sheet is improved, the occurrence of rupture is reduced and further avoided, which contributes to the practical application of the thin positive electrode current collector. Al in the molecular structure of the compound represented by Formula 1 3+Since it contains fluorine atoms that can be combined, it improves the strength of the positive electrode sheet, improves the processing performance of the positive electrode sheet, reduces and further avoids the occurrence of rupture, and enables the practical application of the thinned positive electrode current collector.

[0063] Thirdly, the compound represented by Formula 1 itself has high thermal stability and is, for example, superior to ordinary LiPF6, so it contributes to improving the heat resistance of the entire non-aqueous electrolyte. Also, since the compound represented by Formula 1 is less sensitive to moisture than LiPF6, it contributes to improving the water resistance of the non-aqueous electrolyte, reducing the formation of HF, and lowering the acidity of the non-aqueous electrolyte. Therefore, the non-aqueous electrolyte of the present application has high thermal stability and high electrochemical stability, whereby the decomposition of the non-aqueous electrolyte at high temperatures can be reduced and the internal resistance of the battery can be lowered. Further, as can be understood from Joule's law, since the heat generation amount of the secondary battery is directly related to the internal resistance of the battery, when the internal resistance of the battery decreases, the heat generation amount of the secondary battery also decreases. Thereby, the secondary battery has a high energy density, as well as high output performance and high safety performance.

[0064] Fourthly, surprisingly to the present inventors, the anion moiety in the compound represented by Formula 1 is easily oxidized. Therefore, the lithium ions dissociated from its molecular structure become further active lithium ions and may be contributed to a part of the capacity, contributing to further improving the energy density of the secondary battery.

[0065] Therefore, when the non-aqueous electrolyte contains the compound represented by Formula 1, it contributes to forming a passivation film on the surface of the positive electrode current collector to improve the processing performance of the positive electrode sheet and the secondary battery, and also contributes to forming a low-resistance interfacial film on the surface of the positive electrode active material to improve the output performance and safety performance of the secondary battery. Furthermore, it contributes to increasing the number of active lithium ions to provide a part of the capacity. However, as a discovery made by the inventors of the present application through further research, in order to reduce the adverse effects on the output performance, processing performance, and safety performance caused by thinning the positive electrode current collector, and enable the secondary battery to have low cost, high energy density, high output performance, excellent processing performance, and high safety performance, the content of the compound represented by Formula 1 must be appropriately combined with the thickness of the positive electrode current collector, the elongation at break of the positive electrode current collector, and the compression density of the positive electrode active material layer.

[0066] In the present application, the content A1 (%) of the compound represented by Formula 1 and the thickness H (μm) of the positive electrode current collector satisfy that A1 / H is 0.0015 to 0.20. Therefore, the B-O bond in the molecular structure of the compound represented by Formula 1 is better bonded to Al 3+ to form a passivation film with an appropriate thickness on the surface of the positive electrode current collector. This contributes to improving the strength of the positive electrode current collector, improving the processing performance of the positive electrode sheet, reducing, and further avoiding the occurrence of rupture. When A1 / H is less than 0.0015, the positive electrode current collector is too thick, the content of the compound represented by Formula 1 is low, and the compound represented by Formula 1 is Al 3+Since it is insufficient to form a passivation film on the surface of the positive current collector when combined, the processing performance of the positive electrode sheet and the secondary battery deteriorates. When A1 / H is greater than 0.20, the positive current collector is too thin, the content of the compound represented by Formula 1 is high, and as a result, the formed interfacial film is too thick. Thereby, the resistance of the positive electrode interface and / or the resistance of the negative electrode interface increase, the internal resistance and the heat generation amount of the battery increase, and the output performance and safety performance of the secondary battery deteriorate. Optionally, A1 / H is 0.002 to 0.15, 0.002 to 0.1, 0.002 to 0.08, 0.002 to 0.07, 0.002 to 0.06, 0.002 to 0.05, 0.005 to 0.15, 0.005 to 0.1, 0.005 to 0.08, 0.005 to 0.07, 0.005 to 0.06, 0.005 to 0.05, 0.01 to 0.15, 0.01 to 0.1, 0.01 to 0.08, 0.01 to 0.07, 0.01 to 0.06, or 0.01 to 0.05.

[0067] In the present application, the content A1 (%) of the compound represented by Formula 1 and the elongation at break Q (%) of the positive current collector satisfy that Q + A1 is 1 to 4. Therefore, the B-O bond in the molecular structure of the compound represented by Formula 1 is better bonded to Al 3+ to form a passivation film with an appropriate thickness on the surface of the positive current collector. Thereby, it contributes to improving the strength of the positive current collector, improving the processing performance of the positive electrode sheet, reducing and further avoiding the occurrence of rupture. When Q + A1 is less than 1, the compound represented by Formula 1 is Al 3+It is insufficient to form a passivation film on the surface of the positive current collector when combined, and the ductility of the positive current collector is poor, and rupture is likely to occur during roll pressing. As a result, the processing performance of the positive electrode sheet and the secondary battery deteriorates. When Q + A1 is greater than 4, the positive current collector has high ductility and excellent pressure resistance, but is weak against puncture and is easily broken when pressed by a sharp substance (for example, hard carbon particles usually having a sharp shape), and large burrs are likely to occur, increasing the risk of short circuit inside the battery. Thus, the safety performance of the secondary battery is still not effectively improved. Also, when there is too much of the compound represented by Formula 1, the formed interface film is too thick. As a result, the resistance of the positive electrode interface and / or the negative electrode interface increases, and the output performance and safety performance of the secondary battery deteriorate. Optionally, Q + A1 is 1.5 to 4, 1.8 to 4, 2.0 to 4, 2.2 to 4, 2.4 to 4, 2.6 to 4, 2.8 to 4, 3.0 to 4, 1.5 to 3.5, 1.8 to 3.5, 2.0 to 3.5, 2.2 to 3.5, 2.4 to 3.5, 2.6 to 3.5, 2.8 to 3.5, or 3.0 to 3.5.

[0068] In the present application, the content A1 (%) of the compound represented by Formula 1 and the compression density P (g / cm of the positive electrode active material layer 3)(0) satisfies that P / A1 is 2 to 340. Therefore, the compound represented by Formula 1 contributes to forming a low-resistance interfacial film on the surface of the positive electrode active material to reduce the resistance of the positive electrode interface, and the B atom in the molecular structure of the compound represented by Formula 1 contributes to better bonding with the O atom in the positive electrode active material. As a result, the charge transfer resistance of the positive electrode active material and the diffusion resistance of the bulk phase of lithium ions are also reduced, so that the internal resistance and heat generation amount of the battery can be reduced, and the output performance and safety performance of the secondary battery can be improved. When P / A1 is less than 2, the compression density of the positive electrode active material layer is small, the content of the compound represented by Formula 1 is high, and the formed interfacial film is too thick. As a result, the resistance of the positive electrode interface and / or the resistance of the negative electrode interface is high, the internal resistance and heat generation amount of the battery are high, and the output performance and safety performance of the secondary battery deteriorate. When P / A1 is greater than 340, the compression density of the positive electrode active material layer is large, the content of the compound represented by Formula 1 is low, and the compound represented by Formula 1 is insufficient to form a low-resistance interfacial film on the surface of the positive electrode active material, and the charge transfer resistance of the positive electrode active material and the diffusion resistance of the bulk phase of lithium ions are high. As a result, the internal resistance and heat generation amount of the battery increase, and the output performance and safety performance of the secondary battery deteriorate. Optionally, P / A1 is 2 to 200, 2 to 100, 2 to 75, 2 to 50, 2 to 35, 2 to 30, 2 to 25, 2 to 20, 2 to 15, 3.5 to 340, 3.5 to 200, 3.5 to 100, 3.5 to 75, 3.5 to 50, 3.5 to 35, 3.5 to 30, 3.5 to 25, 3.5 to 20, 3.5 to 15, 5 to 340, 5 to 200, 5 to 100, 5 to 75, 5 to 50, 5 to 35, 5 to 30, 5 to 25, 5 to 20, 10 to 340, 10 to 200, 10 to 100, 10 to 75, 10 to 50, 10 to 35, 10 to 30, 10 to 25, or 10 to 20.

[0069] In some embodiments, optionally, the secondary battery satisfies that H is 4 to 14, A1 / H is 0.01 to 0.05, Q + A1 is 1.5 to 3.5, and P / A1 is 10 to 340. More optionally, the secondary battery satisfies that H is 4 to 14, A1 / H is 0.01 to 0.05, Q + A1 is 2.0 to 3.5, and P / A1 is 10 to 340.

[0070] In the present application, at least one of X and Y represents a fluorine atom. The presence of the fluorine atom contributes to the formation of a thinner fluorine-containing positive electrode interface film and / or negative electrode interface film, and thus contributes to the uniform transport of lithium ions and the effective suppression of the formation of lithium dendrites. In some embodiments, one of X and Y represents a fluorine atom, and the other represents at least one selected from the group consisting of C1-C5 alkyl, C2-C5 alkenyl, C2-C5 alkynyl, phenyl, phenoxy, C1-C5 alkoxy, C2-C5 alkenyloxy, and C2-C5 alkynyloxy that is partially or fully fluorinated. Optionally, one of X and Y represents a fluorine atom, and the other represents at least one selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, vinyl, propenyl, allyl, butadienyl, ethynyl, propynyl, phenyl, methoxy, ethoxy, Propoxy , vinyloxy, propenyloxy, ethynyloxy, propynyloxy, and phenoxy that is partially or fully fluorinated.

[0071] In some embodiments, both X and Y represent fluorine atoms.

[0072] As an example, the compound represented by the formula 1 includes at least one of the following compounds.

Chemical formula

[0073] In some embodiments, the positive current collector uses aluminum foil or aluminum alloy foil. Optionally, to improve the corrosion resistance and strength of the positive current collector, aluminum foil with a purity of 99.99% or more is used. As the aluminum alloy foil, in addition to the aluminum element, it further contains at least one element among iron, magnesium, zinc, manganese, and silicon. For example, the aluminum alloy foil may be an Al-Fe alloy foil, an Al-Mn alloy foil, or an Al-Mg alloy foil. The mass percentage of the aluminum element in the aluminum alloy foil is optionally 95% - 99.5%, more optionally 98% - 99.5%.

[0074] In some embodiments, A1 is 0.02 - 1.8. Optionally, A1 is 0.02 - 1.6, 0.02 - 1.4, 0.02 - 1.2, 0.02 - 1.0, 0.02 - 0.8, 0.02 - 0.7, 0.02 - 0.6, 0.02 - 0.5, 0.05 - 1.6, 0.05 - 1.4, 0.05 - 1.2, 0.05 - 1.0, 0.05 - 0.8, 0.05 - 0.7, 0.05 - 0.6, 0.05 - 0.5, 0.1 - 1.6, 0.1 - 1.4, 0.1 - 1.2, 0.1 - 1.0, 0.1 - 0.8, 0.1 - 0.7, 0.1 - 0.6, or 0.1 - 0.5. When the content of the compound represented by Formula 1 is within an appropriate range, a passivation film with an appropriate thickness can be formed on the surface of the positive current collector, and an interfacial film with low resistance can be formed on the surface of the positive active material. Thereby, defects such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive current collector can be improved. Furthermore, the following situations can be effectively avoided. When the content of the compound represented by Formula 1 is too low, the compound represented by Formula 1 is insufficient to combine with Al 3+ to form a passivation film on the surface of the positive current collector. As a result, the processing performance of the positive electrode sheet and the secondary battery deteriorates. When the content of the compound represented by Formula 1 is too high, the resistance of the positive electrode interface and / or the negative electrode interface increases, the internal resistance and heat generation amount of the battery increase, and the output performance and safety performance of the secondary battery deteriorate.

[0075] In some embodiments, Q is from 0.5 to 3.5. Optionally, Q is from 1 to 3.5, from 1.5 to 3.5, from 1.8 to 3.5, from 2.0 to 3.5, from 2.2 to 3.5, from 2.4 to 3.5, from 2.6 to 3.5, from 2.8 to 3.5, or from 3.0 to 3.5. When the elongation at break of the positive electrode current collector is within an appropriate range, the positive electrode current collector has high strength and excellent processability, and is less likely to rupture. Furthermore, the following situations can be effectively avoided. When the elongation at break of the positive electrode current collector is too small, the ductility of the positive electrode current collector is poor, rupture is likely to occur during roll pressing, and the processability of the positive electrode sheet and the secondary battery deteriorates. When the elongation at break of the positive electrode current collector is too large, it is vulnerable to puncture, and when pressed by a sharp substance, it is broken and large burrs are likely to occur, increasing the risk of short circuit inside the battery. As a result, the safety performance of the secondary battery is still not effectively improved.

[0076] In some embodiments, P is from 3.2 to 3.7. Optionally, P is from 3.3 to 3.7, from 3.4 to 3.7, from 3.5 to 3.7, from 3.2 to 3.6, from 3.3 to 3.6, from 3.4 to 3.6, or from 3.5 to 3.6. When the compression density of the positive electrode active material layer is within a high range, it contributes to the improvement of the energy density of the secondary battery.

[0077] In some embodiments, when the thickness H (μm) of the positive electrode current collector is from 11 or more to 14 or less, specifically, H is from 11 to 14, optionally from 12 to 14, or from 12 to 13, the secondary battery satisfies A1 / H being from 0.005 to 0.15, Q + A1 being from 1 to 4, and P / A1 being from 2 to 100. Optionally, the secondary battery satisfies A1 / H being from 0.005 to 0.1, Q + A1 being from 1.5 to 3.5, and P / A1 being from 5 to 75.

[0078] In some embodiments, when the thickness H (μm) of the positive electrode current collector is from 4 or more to 11 or less, optionally 10 or less, 9 or less, 8 or less, specifically, H is from 4 to 11, optionally from 4 to 10, from 4 to 9, or from 4 to 8, the secondary battery satisfies A1 / H being from 0.006 to 0.1, Q + A1 being from 1 to 4, and P / A1 being from 2 to 100. Optionally, it satisfies A1 / H being from 0.01 to 0.05, Q + A1 being from 1.5 to 3.5, and P / A1 being from 5 to 75. [Lithium salt]

[0079] In some embodiments, the non-aqueous electrolyte further comprises a first lithium salt. The first lithium salt is lithium hexafluorophosphate (LiPF6), or a combination of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI). Since lithium hexafluorophosphate has the characteristic of high ionic conductivity, when its content is within an appropriate range, it can improve the ionic conductivity of the entire non-aqueous electrolyte, accelerate the transport of lithium ions, and contribute to increasing the capacity retention rate of the secondary battery. However, lithium hexafluorophosphate has poor thermal stability in a high-temperature environment and decomposes at high temperatures to produce PF5. PF5 reacts with water to form HF that corrodes the positive electrode active material and increases the gas swelling of the battery. When the non-aqueous electrolyte contains both the compound represented by Formula 1 and lithium hexafluorophosphate, the compound represented by Formula 1 can react with lithium hexafluorophosphate to form the compound LiPF4C2O4. Thereby, partial decomposition of lithium hexafluorophosphate and formation of HF are reduced, and the secondary battery has excellent cycle performance. The chemical formula of lithium bis(fluorosulfonyl)imide is F2NO4S2·Li, and the N atom is linked to two electron-withdrawing sulfonyl groups. Thereby, the charge on the N atom is sufficiently delocalized, and lithium bis(fluorosulfonyl)imide has a low lattice energy and is easy to dissociate, so that the ionic conductivity of the non-aqueous electrolyte can be improved and the viscosity of the non-aqueous electrolyte can be reduced. Furthermore, lithium bis(fluorosulfonyl)imide has excellent high-temperature resistance and is difficult to hydrolyze, and can form a thinner, lower-resistance, and higher-thermal-stability interfacial film on the surface of the negative electrode active material. Thereby, the side reaction between the negative electrode active material and the non-aqueous electrolyte is reduced. However, since lithium bis(fluorosulfonyl)imide is likely to corrode the positive electrode current collector, its content should not be too high.

[0080] In some embodiments, optionally, the mass content of the lithium hexafluorophosphate is A2 (%) with respect to the total mass of the non-aqueous electrolyte, and A2 is 6 to 14. More optionally, A2 is 6 to 12, 6 to 10, 8 to 14, 8 to 12, or 8 to 10.

[0081] In some embodiments, optionally, the mass content of the lithium bis(fluorosulfonyl)imide is A3 (%) with respect to the total mass of the non-aqueous electrolyte, and A3 is greater than 0 and 5 or less. More optionally, A3 is 0.1 to 2.5, 0.1 to 2, 0.1 to 1.5, 0.1 to 1, 0.2 to 2.5, 0.2 to 2, 0.2 to 1.5, 0.2 to 1, 0.5 to 2.5, 0.5 to 2, 0.5 to 1.5, or 0.5 to 1.

[0082] In some embodiments, optionally, A3 / A2 is 0.8 or less, more optionally 0.01 to 0.8, 0.05 to 0.8, 0.1 to 0.8, 0.01 to 0.6, 0.05 to 0.6, 0.1 to 0.6, 0.01 to 0.4, 0.05 to 0.4, 0.1 to 0.4, 0.01 to 0.3, 0.05 to 0.3, or 0.1 to 0.3. Thereby, the non-aqueous electrolyte is less likely to hydrolyze, has higher thermal stability, and is also advantageous for forming an interfacial film with lower resistance.

[0083] In some embodiments, A2 / A1 is 5 to 650 with respect to the total mass of the non-aqueous electrolyte. Since lithium hexafluorophosphate has the characteristic of high ionic conductivity, by appropriately combining the content A1 (%) of the compound represented by Formula 1 and the content A2 (%) of lithium hexafluorophosphate, while improving problems such as deterioration of output performance due to thinning of the positive electrode current collector, improvement of safety risks, and deterioration of processing performance, it contributes to further improving the capacity retention rate of the secondary battery. Furthermore, the following situations can be effectively avoided. When the content of lithium hexafluorophosphate is high and the content of the compound represented by Formula 1 is low, since a large amount of PF5 is present in the non-aqueous electrolyte, the decomposition reaction of the non-aqueous electrolyte increases. Also, the interfacial film formed on the positive electrode by the compound represented by Formula 1 has insufficient uniformity and denseness, and cannot stop the corrosion of the positive electrode active material by HF and subsequent series of side reactions. The secondary battery may have a high gas generation amount and heat generation amount, and there is a risk of deteriorating output performance, storage performance, and safety performance. When the content of lithium hexafluorophosphate is low and the content of the compound represented by Formula 1 is high, since the compound represented by Formula 1 is difficult to completely dissociate in the non-aqueous electrolyte and cations and anions are likely to be combined, the ionic conductivity of the non-aqueous electrolyte decreases, and there is a risk of deteriorating the capacity retention rate of the secondary battery. Optionally, A2 / A1 is 5 to 500, 5 to 300, 5 to 250, 5 to 200, 5 to 150, 5 to 100, 5 to 75, 5 to 50, 10 to 500, 10 to 300, 10 to 250, 10 to 200, 10 to 150, 10 to 100, 10 to 75, 10 to 50, 15 to 500, 15 to 300, 15 to 250, 15 to 200, 15 to 150, 15 to 100, 15 to 75, or 15 to 50.

[0084] In some embodiments, the non-aqueous electrolyte may further contain a second lithium salt. The second lithium salt includes at least one of lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium difluorophosphate (LiPO2F2), lithium difluoro (oxalato) phosphate (LiDFOP), and lithium tetrafluoro (oxalato) phosphate (LiTFOP). The second lithium salt can serve as an auxiliary lithium salt to improve the interfacial performance of the positive electrode and / or the negative electrode, or to improve the ionic conductivity or thermal stability of the non-aqueous electrolyte.

[0085] Optionally, the total mass content of the second lithium salt in the non-aqueous electrolyte is A4 (%) with respect to the total mass of the non-aqueous electrolyte, and A4 is 5 or less, more optionally 2 or less.

[0086] Optionally, in some embodiments, the second lithium salt includes lithium difluorophosphate (LiPO2F2), lithium tetrafluoro (oxalato) phosphate (LiTFOP), or a combination thereof, and more optionally includes lithium difluorophosphate (LiPO2F2). Lithium difluorophosphate has high electrochemical stability, improves the ionic conductivity of the non-aqueous electrolyte, improves the properties of the positive electrode interface film and / or the negative electrode interface film, and contributes to producing a stable and low-resistance positive electrode interface film and / or negative electrode interface film, thus effectively reducing the decomposition of the non-aqueous electrolyte and further improving the output performance and safety performance of the secondary battery. Optionally, the mass ratio α of lithium difluorophosphate to lithium hexafluorophosphate is 0.01 to 0.15, more optionally 0.01 to 0.1.

[0087] In some embodiments, optionally, A1 + A2 + A3 + A4 is 10 to 20, more optionally 12 to 16. [Organic solvent]

[0088] In some embodiments, the non-aqueous electrolyte contains an organic solvent. The organic solvent contains at least one of a cyclic carbonate compound, a chain carbonate compound, and a carboxylate compound. Optionally, the cyclic carbonate compound may contain at least one of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and vinyl ethylene carbonate (VEC). Optionally, the chain carbonate compound may contain at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). Optionally, the carboxylate compound may contain at least one of methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).

[0089] Optionally, in some embodiments, the organic solvent contains at least a cyclic carbonate compound and a chain carbonate compound. When the content of a lithium salt such as lithium hexafluorophosphate is high, the viscosity of the non-aqueous electrolyte increases, the ionic conductivity decreases, which is disadvantageous for the transport of lithium ions. On the other hand, since the cyclic carbonate compound has a high dielectric constant, it can improve the ionic conductivity of the non-aqueous electrolyte. Since the chain carbonate compound has a low viscosity, it can decrease the viscosity of the non-aqueous electrolyte. Therefore, when the organic solvent contains both a cyclic carbonate compound and a chain carbonate compound, it contributes to giving the non-aqueous electrolyte appropriate viscosity and ionic conductivity, which is advantageous for the transport of lithium ions.

[0090] Since the cyclic carbonate compound has a high dielectric constant, it can improve the ionic conductivity of the non-aqueous electrolyte. However, it is prone to decomposition reactions and has an adverse effect on the storage performance of the secondary battery. Therefore, its content must be within an appropriate range. In some embodiments, the mass content of the cyclic carbonate compound is B1 (%) with respect to the total mass of the non-aqueous electrolyte, and B1 is greater than 0 and less than or equal to 20. Optionally, B1 is 0.5 - 20, 1 - 20, 2 - 20, 5 - 20, 10 - 20, 12 - 20, 15 - 20, or 15 - 18.

[0091] In some embodiments, the mass content of the linear carbonate compound is B2 (%) with respect to the total mass of the non-aqueous electrolyte, and B2 is 45 - 80. Optionally, B2 is 50 - 80, 55 - 80, 60 - 80, or 60 - 75.

[0092] Since the carboxylate compound has the advantages of low viscosity and high dielectric constant, when used in a non-aqueous electrolyte, it contributes to giving the non-aqueous electrolyte appropriate viscosity and ionic conductivity, and is advantageous for the transport of lithium ions and the improvement of the rate performance of the secondary battery. The carboxylate compound can improve the output performance of the secondary battery, but its antioxidant ability is low and it is prone to decomposition when stored in a highly charged state. Therefore, its content should not be too high. In some embodiments, the mass content of the carboxylate compound is B3 (%) with respect to the total mass of the non-aqueous electrolyte, and B3 is 0 - 15. In some embodiments, B3 may be 0. In some embodiments, optionally, B3 is 2 - 15, 2 - 10, 2 - 8, or 2 - 5.

[0093] The organic solvent of the present application may contain other solvents other than the above cyclic carbonate compound, linear carbonate compound, and carboxylate compound. As an example, the other solvents may include sulfone solvents such as sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0094] In some embodiments, the content A1 (%) of the compound represented by Formula 1 and the content B1 (%) of the cyclic carbonate compound satisfy that B1 / 20 + A1 is 1 to 3, and optionally 1 to 2, 1 to 1.8, 1 to 1.6, or 1 to 1.4. By appropriately combining the content A1 (%) of the compound represented by Formula 1 and the content B1 (%) of the cyclic carbonate compound, while improving problems such as deterioration of output performance due to thinning of the positive current collector, increase in safety risks, and deterioration of processing performance, it contributes to further improving the capacity retention rate of the secondary battery. Furthermore, the following situations can be effectively avoided. When the content of both the compound represented by Formula 1 and the cyclic carbonate compound is high, the internal resistance and gas generation amount of the battery are high, and thus the output performance and storage performance of the secondary battery may be affected. When the content of both the compound represented by Formula 1 and the cyclic carbonate compound is low, the ionic conductivity of the non-aqueous electrolyte is low, and the compound represented by Formula 1 is insufficient to form a passivation film on the surface of the positive current collector and a low-resistance interfacial film on the surface of the positive electrode active material. As a result, the processing performance of the positive electrode sheet deteriorates, and at the same time, the output performance, safety performance, and cycle performance of the secondary battery may also deteriorate. [Additive]

[0095] In some embodiments, the non-aqueous electrolyte may contain additives such as at least one of a cyclic carbonate compound substituted with a halogen, a nitrile compound, a phosphazene compound, an aromatic hydrocarbon, a halogenated aromatic hydrocarbon compound, an isocyanate compound, an anhydride compound, a sulfate ester compound, a sulfite ester compound, a sulfonate ester compound, and a disulfonic acid ester compound. In the present application, the types of these additives are not particularly limited as long as the gist of the present application is not impaired. Optionally, the total mass content of these additives is 5% or less, more optionally 2.5% or less, based on the total mass of the non-aqueous electrolyte.

[0096] Optionally, in some embodiments, the non-aqueous electrolyte may further contain fluoroethylene carbonate (FEC). Its mass content is C1 (%) with respect to the total mass of the non-aqueous electrolyte, and 0 ≦ C1 ≦ 2.5. For example, C1 may be in the range consisting of 0, 0.10, 0.20, 0.50, 0.75, 1.0, 1.25, 1.50, 1.75, 2.0, 2.25, 2.50, or any value therebetween. Optionally, 0 < C1 ≦ 2.5, 0 < C1 ≦ 2.25, 0 < C1 ≦ 2.0, 0 < C1 ≦ 1.75, 0 < C1 ≦ 1.5, 0 < C1 ≦ 1.25, 0 < C1 ≦ 1.0, 0 < C1 ≦ 0.75, or 0 < C1 ≦ 0.5.

[0097] In a secondary battery, fluoroethylene carbonate undergoes a reduction decomposition reaction at a high potential, forms an interfacial film with certain flexibility on the surface of the negative electrode active material, and can also suppress the reduction decomposition of the organic solvent at a low potential and the occlusion of the organic solvent into the negative electrode active material. Therefore, when the non-aqueous electrolyte contains fluoroethylene carbonate, the cycle performance of the secondary battery can be effectively improved. Furthermore, fluoroethylene carbonate has strong resistance to high-voltage oxidation and is advantageous for use in combination with a high-voltage positive electrode active material, which is advantageous for further increasing the energy density of the secondary battery.

[0098] In some embodiments, the content A1 (%) of the compound represented by Formula 1 and the content C1 (%) of fluoroethylene carbonate further satisfy 0.25 ≦ C1 / A1 ≦ 25. Optionally, 0.5 ≦ C1 / A1 ≦ 15, 0.5 ≦ C1 / A1 ≦ 10, 0.5 ≦ C1 / A1 ≦ 5, 0.5 ≦ C1 / A1 ≦ 4, 0.5 ≦ C1 / A1 ≦ 3, 0.5 ≦ C1 / A1 ≦ 2.5, 0.5 ≦ C1 / A1 ≦ 2, 0.5 ≦ C1 / A1 ≦ 1.5, or 0.5 ≦ C1 / A1 ≦ 1.0.

[0099] When the non-aqueous electrolyte contains fluoroethylene carbonate, the cycle performance of the secondary battery can be effectively improved. However, fluoroethylene carbonate is likely to decompose to form HF that destroys the positive electrode interface film and corrodes the positive electrode active material, increasing the heat generation amount and gas generation amount of the secondary battery. On the other hand, the compound represented by Formula 1 can function as a stabilizer for the positive electrode active material. Since the B atom in its structure has the function of interacting with the O atom on the surface of the positive electrode active material, the crystal structure of the positive electrode active material can be stabilized, and the destruction caused by HF to the crystal structure of the positive electrode active material can be reduced. Therefore, using the compound represented by Formula 1 and fluoroethylene carbonate in combination is advantageous for fully exerting the effect of fluoroethylene carbonate in further improving the cycle performance of the secondary battery. Furthermore, by appropriately controlling the relationship between the content A1 (%) of the compound represented by Formula 1 and the content C1 (%) of fluoroethylene carbonate so as to satisfy 0.25 ≤ C1 / A1 ≤ 25, the synergistic effect of the compound represented by Formula 1 and fluoroethylene carbonate can be fully exerted, while improving problems such as deterioration of output performance, increase in safety risks, and deterioration of processing performance due to thinning of the positive electrode current collector, it can contribute to further improving the cycle performance of the secondary battery. Also, because fluoroethylene carbonate has a high dielectric constant, by appropriately controlling the relationship between the content A1 (%) of the compound represented by Formula 1 and the content C1 (%) of fluoroethylene carbonate so as to satisfy 0.25 ≤ C1 / A1 ≤ 25, it is ensured that the cations and anions of the compound represented by Formula 1 form free ions and avoid the binding of cations and anions. While improving the ionic conductivity of the non-aqueous electrolyte and the cycle performance of the secondary battery, the number of active lithium ions can be increased.

[0100] In some embodiments, the non-aqueous electrolyte may further contain a dehydration additive. The dehydration additive can reduce the water content of the non-aqueous electrolyte and a series of side reactions caused by moisture, thereby reducing the gas generation amount and heat generation amount of the secondary battery, and making the storage performance and safety performance of the secondary battery better. Optionally, in some embodiments, the dehydration additive includes hexamethyldisilazane (HMDS), tris(trimethylsilyl) phosphate (TMSP), or a combination thereof. In addition to effectively reducing the moisture content of the non-aqueous electrolyte, these two dehydration additives can react with lithium hexafluorophosphate to form lithium difluorophosphate. This reduces the decomposition of lithium hexafluorophosphate and the formation of HF, while further stabilizing the positive electrode interface film and / or the negative electrode interface film, reducing the resistance of the positive electrode interface and / or the negative electrode interface, and contributing to further improving the output performance, storage performance, and safety performance of the secondary battery.

[0101] In some embodiments, the mass content of the dehydration additive is 2% or less, optionally 0.05% - 1%, and more optionally 0.1% - 1% based on the total mass of the non-aqueous electrolyte.

[0102] The non-aqueous electrolyte of the present application can be manufactured by conventional methods in the art. For example, the organic solvent, the lithium salt, the additive, etc. can be uniformly mixed to obtain a non-aqueous electrolyte. The addition order of each material is not particularly limited. For example, the lithium salt, the additive, etc. can be added to the organic solvent and uniformly mixed to obtain a non-aqueous electrolyte.

[0103] In the present application, each component and its content in the non-aqueous electrolyte can be measured by methods known in the art. For example, it can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), NMR spectrum analysis (NMR), etc.

[0104] When testing the non-aqueous electrolyte of the present application, the non-aqueous electrolyte can be obtained from the secondary battery. As an example of a method for obtaining the non-aqueous electrolyte from the secondary battery, after discharging the secondary battery to a discharge cut-off voltage (generally, for safety, the battery is fully discharged), centrifugation is performed, and then, a step of using an appropriate amount of the liquid obtained by the centrifugation as the non-aqueous electrolyte is included. The non-aqueous electrolyte may be directly obtained from the liquid injection port of the secondary battery.

[0105] In the present application, the positive electrode active material layer contains a positive electrode active material. As the positive electrode active material, a positive electrode active material for a secondary battery known in the art may be used. For example, the positive electrode active material may include at least one of a lithium transition metal oxide, a lithium-containing phosphate having an olivine structure, and a modified compound thereof. Examples of the lithium transition metal oxide 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 a modified compound thereof. Examples of the lithium-containing phosphate 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 a modified compound thereof. The present application is not limited to these materials, and other conventionally known materials that can be used as the positive electrode active material of the secondary battery may be used. These positive electrode active materials may be used alone or in combination of two or more.

[0106] In some embodiments, the positive electrode active material has a molecular formula of Li a Ni b Co c Mn d Al e M f O g A hIt contains a layered material, where M represents a transition metal site doping cation, A represents an oxygen site doping anion, 0.8 ≦ a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 0.2, 0 ≦ g ≦ 2, 0 ≦ h ≦ 2, b + c + d + e + f = 1, and g + h = 2.

[0107] The molecular formula is Li a Ni b Co c Mn d Al e M f O g A h The layered material represented by this formula is selectively modified by M cation doping, A anion doping, or doping with both M cations and A anions. The layered material obtained by doping has a more stable crystal structure, less likely to precipitate lattice oxygen, and less likely to desorb transition metal ions. As a result, a series of side reactions caused thereby can be reduced, and the safety performance, cycle performance, dynamic characteristics, and other electrochemical characteristics of the secondary battery can be improved.

[0108] In some embodiments, M is at least one selected from Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W.

[0109] In some embodiments, A is at least one selected from F, N, P, and S. Optionally, A is selected from F. By being modified by doping with F, Li a Ni b Co c Mn d Al e M f O g A h has a more stable crystal structure, less likely to precipitate lattice oxygen, and less likely to desorb transition metal ions. As a result, the secondary battery has better safety performance, cycle performance, and dynamic characteristics.

[0110] The values of a, b, c, d, e, f, g, and h are for Li a Nib Co c Mn d Al e M f O g A h satisfies keeping electrically neutral.

[0111] In some embodiments, 0 < b < 0.98. Optionally, 0.50 ≤ b < 0.98, 0.55 ≤ b < 0.98, 0.60 ≤ b < 0.98, 0.65 ≤ b < 0.98, 0.70 ≤ b < 0.98, 0.75 ≤ b < 0.98, or 0.80 ≤ b < 0.98.

[0112] In some embodiments, c = 0.

[0113] In some embodiments, 0 < c ≤ 0.20. Optionally, 0 < c ≤ 0.15, 0 < c ≤ 0.10, 0 < c ≤ 0.09, 0 < c ≤ 0.08, 0 < c ≤ 0.07, 0 < c ≤ 0.06, 0 < c ≤ 0.05, 0 < c ≤ 0.04, 0 < c ≤ 0.03, 0 < c ≤ 0.02, or 0 < c ≤ 0.01. Since cobalt has a low content in the earth's crust, is difficult to mine and has a high price, low cobalt or cobalt-free is an inevitable development trend of the cathode active material. However, cobalt greatly contributes to the lithium ion diffusion rate of the cathode active material, and low cobalt or cobalt-free reduces the lithium ion diffusion rate of the cathode active material and affects the cycle performance of the secondary battery. Researchers have focused on improving the lithium ion diffusion rate of low cobalt or cobalt-free cathode active materials, but there is no good solution yet.

[0114] As a surprising discovery made by the inventors of the present application, the B atom in the compound structure represented by Formula 1 is likely to bond with the O atom in the positive electrode active material, reducing the charge transfer resistance of the positive electrode active material, and thus reducing the diffusion resistance of lithium ions within the bulk of the positive electrode active material. Therefore, the low-cobalt or cobalt-free positive electrode active material can significantly improve the diffusion rate of lithium ions. Lithium ions within the bulk of the low-cobalt or cobalt-free positive electrode active material are timely replenished on the surface, avoiding excessive lithium desorption on the surface of the low-cobalt or cobalt-free positive electrode active material, and 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 of the present application becomes more stable, problems such as instability of the structural, chemical, or electrochemical properties of the positive electrode active material due to excessive lithium desorption on the surface of the low-cobalt or cobalt-free positive electrode active material, for example, the occurrence probability of irreversible strain and increased lattice defects of the positive electrode active material, are reduced.

[0115] In some embodiments, d = 0 and 0 < e < 0.50. Optionally, d = 0 and 0 < e ≤ 0.45, d = 0 and 0 < e ≤ 0.40, d = 0 and 0 < e ≤ 0.35, d = 0 and 0 < e ≤ 0.30, d = 0 and 0 < e ≤ 0.25, d = 0 and 0 < e ≤ 0.20, d = 0 and 0 < e ≤ 0.15, or d = 0 and 0 < e ≤ 0.10.

[0116] In some embodiments, e = 0 and 0 < d < 0.50. Optionally, e = 0 and 0 < d ≤ 0.45, e = 0 and 0 < d ≤ 0.40, e = 0 and 0 < d ≤ 0.35, e = 0 and 0 < d ≤ 0.30, e = 0 and 0 < d ≤ 0.25, e = 0 and 0 < d ≤ 0.20, e = 0 and 0 < d ≤ 0.15, or e = 0 and 0 < d ≤ 0.10.

[0117] In some embodiments, 0 < d < 0.50 and 0 < e < 0.50. Optionally, 0 < d ≤ 0.30 and 0 < e ≤ 0.10.

[0118] In some embodiments, g = 2, h = 0.

[0119] In some embodiments, g = 0 and h = 2.

[0120] In some embodiments, 0 < g < 2, 0 < h < 2, and g + h = 2.

[0121] As an example, the layered material of the formula Li a Ni b Co c Mn d Al e M f O g A h includes, but is not limited to, at least one of LiNi 0.7 Mn 0.3 O2, LiNi 0.69 Co 0.01 Mn 0.3 O2, LiNi 0.68 Co 0.02 Mn 0.3 O2, LiNi 0.65 Co 0.05 Mn 0.3 O2, LiNi 0.63 Co 0.07 Mn 0.3 O2, LiNi 0.61 Co 0.09 Mn 0.3 O2.

[0122] Li a Ni b Co c Mn d Al e M f O g A h can be manufactured by ordinary methods in the art. As an example of the manufacturing method, it can be obtained by mixing a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, an M element precursor, and an A element precursor and sintering them. The sintering atmosphere may be an oxygen-containing atmosphere, for example, an air atmosphere or an oxygen gas atmosphere. The O2 concentration in the sintering atmosphere is, for example, 70% - 100%. The sintering temperature and sintering time can be adjusted according to the actual situation.

[0123] As an 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). As an 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. As an 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. As an 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. As an 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. As an example, the precursor of element M includes, but is not limited to, at least one of an oxide, nitrate compound, carbonate compound, hydroxide compound, and acetate compound of element M. As an example, the precursor of element A 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 bicarbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium bisulfate, ammonium bisulfite, ammonium sulfite, ammonium hydrosulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0124] In some embodiments, based on the total mass of the positive electrode active material layer, the content of the layered material with the molecular formula Li a Ni b Co c Mn d Al e M f O g A h is 80% to 99%. For example, with the molecular formula Li a Nib Co c Mn d Al e M f O g A h The content of the layered material of A may be in a range consisting of any value of 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more. Optionally, the molecular formula is Li a Ni b Co c Mn d Al e M f O g A h The content of the layered material of A is 85% - 99%, 90% - 99%, 95% - 99%, 80% - 98%, 85% - 98%, 90% - 98%, 95% - 98%, 80% - 97%, 85% - 97%, 90% - 97%, or 95% - 97%.

[0125] In some embodiments, the positive electrode active material layer may optionally further contain a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is 5% or less based on the total mass of the positive electrode active material layer.

[0126] In some embodiments, the positive electrode active material layer may further selectively include a positive electrode binder. The present application does not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of vinylidene fluoride - tetrafluoroethylene - propylene, a terpolymer of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, a copolymer of tetrafluoroethylene - hexafluoropropylene, and a fluorine - containing acrylate resin. In some embodiments, the mass content of the positive electrode binder is 5% or less based on the total mass of the positive electrode active material layer.

[0127] The positive electrode active material layer is usually obtained by applying a positive electrode slurry onto a positive electrode current collector, drying it, and cold - pressing it. The positive electrode slurry is usually obtained by dispersing a positive electrode active material, a selective conductive agent, a selective binder, and any other components in a solvent and uniformly stirring them. The solvent may be N - methylpyrrolidone (NMP), but is not limited thereto.

[0128] In the present application, the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material may be a negative electrode active material for a secondary battery known in the art. As an example, the negative electrode active material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon - based materials, tin - based materials, and lithium titanate, but is not limited thereto. The silicon - based materials include at least one of elemental silicon, silicon oxide, silicon - carbon composites, silicon - nitrogen composites, and silicon alloy materials, but are not limited thereto. The tin - based materials include at least one of elemental tin, tin oxide, and tin alloy materials, but are not limited thereto. The present application is not limited to these materials, and other conventionally known materials that can be used as the negative electrode active material of a secondary battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0129] In some embodiments, the negative electrode active material layer may optionally further include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total mass of the negative electrode active material layer, the mass content of the negative electrode conductive agent is 5% or less.

[0130] In some embodiments, the negative electrode active material layer may optionally further include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid-based resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total mass of the negative electrode active material layer, the mass content of the negative electrode binder is 5% or less.

[0131] In some embodiments, the negative electrode active material layer may optionally further include other auxiliaries. As an example, the other auxiliaries may include thickeners such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, based on the total mass of the negative electrode active material layer, the mass content of the other auxiliaries is 2% or less.

[0132] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may be at least one selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0133] The negative electrode active material layer is usually obtained by applying a negative electrode slurry onto a negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is usually obtained by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and any other optional auxiliary agent in a solvent and uniformly stirring them. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0134] In the present application, the separator is provided between the positive electrode sheet and the negative electrode sheet, mainly plays a role in preventing short circuit between the positive electrode and the negative electrode, and allows lithium ions to pass through. The present application does not particularly limit the type of the separator, and any known separator having excellent chemical stability and mechanical stability and having a porous structure may be used.

[0135] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multi-layer composite thin film. When the separator is a multi-layer composite thin film, the materials of each layer may be the same or different.

[0136] In some embodiments, the exterior of the secondary battery may be a rigid case such as a hard plastic case, an aluminum case, or a steel case. The exterior of the secondary battery may also be a soft bag such as a bag-type soft bag. The material of the soft bag may be a plastic such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0137] The present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other arbitrary shape. In FIG. 1, a rectangular-structured secondary battery 5 is illustrated.

[0138] In some embodiments, as shown in FIG. 2, the exterior may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and a storage chamber is defined by the bottom plate and the side plates. The case 51 has an opening communicating with the storage chamber, and the cover plate 53 covers the opening to seal the storage chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is enclosed in the storage chamber. The non-aqueous electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be adjusted according to requirements.

[0139] The manufacturing method of the secondary battery of the present application is a known one. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and a non-aqueous electrolyte can be assembled into a secondary battery. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly by a winding process or a lamination process, the electrode assembly is placed in an exterior, dried, and then a non-aqueous electrolyte is injected, and after passing through processes such as vacuum sealing, standing, formation, and shaping, a secondary battery may be obtained.

[0140] In some embodiments of the present application, the secondary battery according to the present application may be incorporated as a battery module. The battery module may include a plurality of secondary batteries, and the specific number can be adjusted according to the use and capacity of the battery module.

[0141] FIG. 3 is a schematic diagram of an example of the battery module 4. As shown in FIG. 3, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged along the longitudinal direction of the battery module 4. Of course, they may be arranged in other forms. Also, the plurality of secondary batteries 5 may be fixed by a fastener.

[0142] Optionally, the battery module 4 may have a housing having a storage space, and the plurality of secondary batteries 5 are accommodated in this storage space.

[0143] In some embodiments, the above battery module may be assembled as a battery pack. The number of battery modules included in the battery pack can be adjusted according to the use and capacity of the battery pack.

[0144] FIGS. 4 and 5 are schematic diagrams of an example of the battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box may include an upper box body 2 and a lower box body 3. The upper box body 2 covers the lower box body 3 to form a sealed space for storing the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any form.

[0145] Embodiments of the present application further provide a power consumption device including at least one of a secondary battery, a battery module, or a battery pack of the present application. The secondary battery, battery module, or battery pack can be used as both a power source of the power consumption device and an energy storage unit of the power consumption device. The power consumption device may be a mobile device (such as a mobile phone, laptop, etc.), an electric vehicle (such as 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.), a train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

[0146] The power consumption device may select a secondary battery, a battery module, or a battery pack according to the requirements of its use.

[0147] FIG. 6 is a schematic diagram of an example of a power consumption device. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the needs of high power and high energy density by the power consumption device, a battery pack or a battery module can be used.

[0148] As another example of the power consumption device, it may be a mobile phone, a tablet computer, a notebook computer, etc. Since the power consumption device is usually required to be lightweight and thin, a secondary battery can be used as a power source. Examples

[0149] The following examples illustrate the content disclosed in the present application more specifically. It is obvious to those skilled in the art that various modifications and changes can be made within the scope of the content disclosed in the present application. Therefore, these examples are only used for illustrative purposes. Unless otherwise specified, all parts, percentages, and ratios reported in the following examples are based on mass. All reagents used in the examples are commercially available or obtained by conventional synthetic methods and can be used directly without further treatment. Also, the equipment used in the examples is available as commercial products.

[0150] The secondary batteries of each of the examples and comparative examples were all manufactured by the following method. Manufacture of the positive electrode sheet

[0151] LiNi which is a positive electrode active material 0.65 Co 0.05 Mn 0.3 O2, carbon black (Super P) which is a conductive agent, and polyvinylidene fluoride (PVDF) which is a binder were sufficiently stirred and mixed in an appropriate amount of a solvent NMP at a mass ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of an aluminum foil which is a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet. The specific ranges of the thickness H (μm), elongation at break Q (%), and compression density P (g / cm 3 ) are shown in Table 1 and Table 3, respectively. Manufacture of the negative electrode sheet

[0152] Graphite which is a negative electrode active material, styrene-butadiene rubber (SBR) which is a binder, sodium carboxymethyl cellulose (CMC-Na) which is a thickener, and carbon black (Super P) which is a conductive agent were sufficiently stirred and mixed in an appropriate amount of deionized water which is a solvent at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of a copper foil which is a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet. Separator

[0153] A porous polyethylene (PE) film was used as the separator. Manufacture of the non-aqueous electrolyte

[0154] The cyclic carbonate compound, the linear carbonate compound, and the carboxylate compound were uniformly mixed to obtain an organic solvent so as to have the compositions shown in Table 1 and Table 3. Then, the compound represented by Formula 1, fluoroethylene carbonate (FEC), lithium hexafluorophosphate (LiPF6), and lithium bis(fluorosulfonyl)imide (LiFSI) were added to the organic solvent and uniformly mixed to obtain a non-aqueous electrolyte. In Table 1 and Table 3, the content of each component is all based on the total mass of the non-aqueous electrolyte, and " / " means that the corresponding component is not added. Manufacture of secondary battery

[0155] The positive electrode sheet, the separator, and the negative electrode sheet were sequentially laminated and wound to obtain an electrode assembly. The electrode assembly was placed in an outer package, dried, injected with a non-aqueous electrolyte, and subjected to processes such as vacuum sealing, standing, formation, and shaping to obtain a secondary battery. Test part (1) Test of the mass energy density of the secondary battery

[0156] At 25 °C, the secondary battery was charged at a constant current of 0.33C to 4.25V, and then charged at a constant voltage until the current reached 0.05C. After the secondary battery was left standing for 5 min, it was discharged at a constant current of 0.33C to 2.8V to obtain the discharge energy. The mass energy density of the secondary battery (Wh / Kg) = discharge energy / mass of the secondary battery. (2) Test of the output performance of the secondary battery

[0157] At 25 °C, the secondary battery was charged at a constant current of 0.1C to 4.25V, and then charged at a constant voltage until the current reached 0.05C. At this time, the secondary battery was in a fully charged state. The secondary battery was discharged at a constant current of 1C for about 30 min to adjust the state of charge of the secondary battery to 50% SOC. At this time, the voltage of the secondary battery was designated as V0. The secondary battery was discharged at a current I1 of 4C for 30 s, scored every 0.1 s, and the voltage at the end of discharge was designated as V1. The internal resistance DCR of the secondary battery = (V0 - V1) / I1. The smaller the internal resistance of the secondary battery, the better the output performance. (3) Test of the hot box safety performance of the secondary battery

[0158] At 25°C, the secondary battery was charged to 4.25V at a constant current of 0.1C, and then charged at a constant voltage until the current reached 0.05C, at which point the secondary battery was fully charged. The fully charged secondary battery was placed in a high-temperature box with excellent sealing properties, heated to 100°C at 5°C / min, and kept at that temperature for 1 hour, then heated to 105°C at 5°C / min and kept at that temperature for 30 minutes. After that, the temperature was raised at a rate of 5°C / min, and kept at that temperature for 30 minutes every time the temperature was raised by 5°C so that the secondary battery would expire, and the maximum temperature T before the secondary battery expired was measured. max The record was . max The higher the value, the better the hot box safety performance of the secondary battery. (4) Testing the cycle performance of secondary batteries

[0159] At 45°C, the secondary battery was charged to 4.25V at a constant current of 1C, and then charged at a constant voltage until the current reached 0.05C, at which point the secondary battery was fully charged. The charge capacity at this time was recorded and used as the charge capacity of the first cycle. After leaving the secondary battery stationary for 5 minutes, it was discharged at a constant current of 1C to 2.8V, which was considered as one cycle of charge and discharge. The discharge capacity at this time was recorded and used as the discharge capacity of the first cycle. The secondary battery was repeatedly charged and discharged using the above method, and the discharge capacity after each cycle was recorded. Capacity retention rate (%) of the secondary battery after 600 cycles at 45°C = discharge capacity after 600 cycles / discharge capacity of the first cycle × 100%. (5) Testing the storage performance of secondary batteries

[0160] At 60°C, the secondary battery was charged to 4.25V at a constant current of 1C, and then charged at a constant voltage until the current reached 0.05C. At this time, the volume of the secondary battery was tested by the drainage method and determined as V0. The secondary battery was placed in a thermostatic box at 60°C and stored for 30 days, and then removed. At this time, the volume of the secondary battery was tested by the drainage method and determined as V1. The volume expansion rate (%) of the secondary battery after storing it at 60°C for 30 days = [(V1-V0) / V0] x 100%.

[0161] Table 1 shows the parameters of the positive electrode sheets and non-aqueous electrolytes of Examples 1-1 to 1-33 and Comparative Examples 1-1 to 1-4. Table 2 shows the results of testing Examples 1-1 to 1-33 and Comparative Examples 1-1 to 1-4 by the above performance test method.

[0162] Table 3 shows the parameters of the positive electrode sheets and non-aqueous electrolytes of Examples 2-1 to 2-32 and Comparative Examples 2-1 to 2-3. Table 4 shows the results of testing Examples 2-1 to 2-32 and Comparative Examples 2-1 to 2-3 according to the above performance test method.

[0163] [Table 1]

[0164] [Table 2]

[0165] [Table 3]

[0166] [Table 4]

[0167] As can be seen from the combined test results of Table 1 and Table 2, in the secondary battery using the thinned positive current collector, the non-aqueous electrolyte contains the compound represented by Formula 1, and its content A1 (%) and the thickness H (μm) of the positive current collector, the elongation at break Q (%) of the positive current collector, and the compression density P (g / cm 3 ) satisfy that A1 / H is 0.0015 to 0.20, Q + A1 is 1 to 4, and P / A1 is 2 to 340, the secondary battery can have high energy density, low internal resistance, high hot box safety performance, high capacity retention rate, and low volume expansion rate.

[0168] As can be seen from the combined test results of Examples 1-1 to 1-10 and Comparative Example 1-2, when A1 / H is less than 0.0015 and / or P / A1 is greater than 340, the compound represented by Formula 1 is 3+ insufficient to form a passivation film on the surface of the positive current collector by binding to Al and to form a low-resistance interfacial film on the surface of the positive electrode active material. As a result, compared with Comparative Example 1-1, thinning the positive current collector does not improve the adverse effects on the output performance and safety performance, and there is a limit to the increase in the capacity retention rate of the secondary battery.

[0169] As can be seen from the combined test results of Examples 1-1 to 1-10 and Comparative Examples 1-3 to 1-4, when Q + A1 is greater than 4, A1 / H is greater than 0.20, and / or P / A1 is less than 2, there is too much of the compound represented by Formula 1, and the resistance of the positive electrode interface and / or the negative electrode interface does not decrease but instead increases. As a result, the internal resistance of the secondary battery increases and the capacity retention rate deteriorates. The compound represented by Formula 1 provides a part of the active lithium ions and can slightly improve the energy density of the secondary battery. However, due to the oxidative decomposition of the anion, the amount of gas generated inside the battery increases, and the hot box safety performance clearly deteriorates.

[0170] As can be seen from the combined test results of Table 3 and Table 4, in a secondary battery using a thinned positive current collector, the non-aqueous electrolyte contains the compound represented by Formula 1, and its content A1 (%) and the thickness H (μm) of the positive current collector, the elongation at break Q (%) of the positive current collector, and the compression density P (g / cm 3 ) satisfy A1 / H being 0.0015 to 0.20, Q + A1 being 1 to 4, and P / A1 being 2 to 340, the secondary battery performance can have high energy density, low internal resistance, high hot box safety performance, high capacity retention rate, and low volume expansion rate.

[0171] As can be seen from the combined test results of Examples 2-1 to 2-9 and Comparative Example 2-2, when A1 / H is less than 0.0015, the compound represented by Formula 1 is 3+It is insufficient to form a passivation film on the surface of the positive current collector and a low-resistance interfacial film on the surface of the positive electrode active material when combined therewith. As a result, compared with Comparative Example 2-1, thinning the positive current collector does not improve the adverse effects on the output performance and safety performance, and there is a limit to the increase in the capacity retention rate of the secondary battery.

[0172] As can be seen from the combined test results of Examples 2-1 to 2-9 and Comparative Example 2-3, when A1 / H is greater than 0.20, P / A1 is less than 2, and Q + A1 is greater than 4, there are too many compounds represented by Formula 1, and the resistance of the positive electrode interface and / or the negative electrode interface does not decrease but instead increases. As a result, the internal resistance of the secondary battery increases and the capacity retention rate deteriorates. The compound represented by Formula 1 provides a part of the active lithium ions and can slightly improve the energy density of the secondary battery. However, due to the oxidative decomposition of the anion, the amount of gas generated inside the battery increases, and the hot box safety performance is significantly deteriorated.

[0173] It should be noted that the present application is not limited to the above embodiments. The above embodiments are merely examples, and any embodiments having substantially the same configuration within the scope of the technical idea of the present application and exhibiting the same operational effects are included in the technical scope of the present application. Also, various modifications conceivable by those skilled in the art within the scope not departing from the gist of the present application and other forms constructed by combining some of the components in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery comprising a positive electrode sheet and a non-aqueous electrolyte, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector, the non-aqueous electrolyte contains a compound represented by Formula 1, The mass percentage of the compound represented by the formula 1 is A1 (%) with respect to the total mass of the non-aqueous electrolyte, the thickness of the positive electrode current collector is H (μm), the elongation at break of the positive electrode current collector is Q (%), and the compression density of the positive electrode active material layer is P (g / cm ３ ), and the secondary battery satisfies that H is 4 to 14, P is 3.2 to 3.5, A1 / H is 0.0015 to 0.20, Q + A1 is 1 to 4, and P / A1 is 7 to 175. the non-aqueous electrolyte further contains a first lithium salt containing lithium hexafluorophosphate, the non-aqueous electrolyte further contains a second lithium salt containing lithium difluorophosphate. A secondary battery. 【Chemical 1】 (X and Y each independently represent a fluorine atom, or at least one selected from the group consisting of partially fluorinated or fully fluorinated C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 alkenyloxy, C2-C10 alkynyloxy, and C6-C8 aryloxy, and at least one of X and Y represents a fluorine atom.)

2. A1 / H is 0.002 to 0.05, and / or Q + A1 is 1.5 to 3.

5. The secondary battery according to Claim 1.

3. A1 is 0.02 to 1.8, and / or Q is 0.5 to 3.

5. The secondary battery according to Claim 1 or 2.

4. The mass percentage of the lithium hexafluorophosphate is A2 (%) with respect to the total mass of the non-aqueous electrolyte, A2 / A1 is 5 to 650, and / or A2 is 6 to 14. The secondary battery according to Claim 1 or 2.

5. The first lithium salt further contains lithium bis(fluorosulfonyl)imide, The mass percentage of the lithium hexafluorophosphate is A2 (%) with respect to the total mass of the non-aqueous electrolyte, and the mass percentage of the lithium bis(fluorosulfonyl)imide is A3 (%) with respect to the total mass of the non-aqueous electrolyte, A2 is 6 to 14, A3 is greater than 0 and 5 or less, and / or A3 / A2 is 0.8 or less, and / or A2 / A1 is 5 to 650. The secondary battery according to Claim 1 or 2.

6. The total mass percentage of the second lithium salt in the non-aqueous electrolyte is A4 (%) with respect to the total mass of the non-aqueous electrolyte, A4 is 5 or less. The secondary battery according to Claim 1 or 2.

7. The mass ratio α of the lithium difluorophosphate to the lithium hexafluorophosphate is 0.01 to 0.

15. The secondary battery according to Claim 6.

8. The non-aqueous electrolyte further contains a cyclic carbonate compound, and the mass percentage of the cyclic carbonate compound is B1 (%) with respect to the total mass of the non-aqueous electrolyte, where B1 is from 0.5 to 20, and / or B1 / 20 + A1 is from 1 to 3. The secondary battery according to claim 1 or 2.

9. The cyclic carbonate compound contains at least one of ethylene carbonate, propylene carbonate, vinylene carbonate, and vinyl ethylene carbonate. The secondary battery according to claim 8.

10. The non-aqueous electrolyte further contains fluoroethylene carbonate, and its mass percentage is C1 (%) with respect to the total mass of the non-aqueous electrolyte, where 0 < C1 ≤ 2.5, and / or 0.25 ≤ C1 / A1 ≤ 25. The secondary battery according to claim 1 or 2.

11. The non-aqueous electrolyte further contains a dehydration additive containing at least one of hexamethyldisilazane and tris(trimethylsilyl) phosphate, and the mass percentage of the dehydration additive is 2% or less with respect to the total mass of the non-aqueous electrolyte. The secondary battery according to claim 1 or 2.

12. X and Y satisfy one of the following conditions (1) to (3). The secondary battery according to claim 1. (1) Both X and Y represent fluorine atoms. (2) Among X and Y, one represents a fluorine atom, and the other represents at least one selected from the group consisting of partially fluorinated or fully fluorinated C1-C5 alkyl, C2-C5 alkenyl, C2-C5 alkynyl, phenyl, phenoxy, C1-C5 alkoxy, C2-C5 alkenyloxy, and C2-C5 alkynyloxy. (3) Among X and Y, one represents a fluorine atom, and the other represents at least one selected from the group consisting of partially fluorinated or fully fluorinated methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, vinyl, propenyl, allyl, butadienyl, ethynyl, propynyl, phenyl, methoxy, ethoxy, propoxy, vinyloxy, propenyloxy, ethynyloxy, propynyloxy, and phenoxy.

13. The compound represented by Formula 1 contains at least one of the following compounds. The secondary battery according to claim 1. 【Chemical 2】

14. The positive electrode current collector uses an aluminum foil or an aluminum alloy foil. The secondary battery according to claim 1.

15. A battery module including the secondary battery according to claim 1.

16. A battery pack including one of the secondary battery according to claim 1 and the battery module according to claim 15.

17. An electric power consuming device including at least one of the secondary battery according to claim 1, the battery module according to claim 15, and the battery pack according to claim 16.

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