Secondary battery, battery module, battery pack, and electric device

Abstract

The application provides a secondary battery, a battery module, a battery pack and a power utilization device. The secondary battery comprises a positive electrode sheet, a negative electrode sheet and a separator arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode film layer containing a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate material and a conjugated carbonyl compound. In the discharging process of the secondary battery, in addition to the discharging platform of the lithium iron phosphate material itself, a relatively low discharging platform provided by the conjugated carbonyl compound is additionally included in the discharging curve, so that in the discharging process, the voltage decreases with the increase of the discharging capacity, and the voltage decreasing trend is relatively gentle, thereby the discharging capacity can be stably increased, and the power performance of the secondary battery can be improved.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools.

[0003] As battery applications become increasingly widespread, the performance requirements for rechargeable batteries are becoming more stringent. To improve rechargeable battery performance, materials such as the positive electrode active material are typically optimized and improved. However, even with current improvements in positive electrode active materials, the power performance of rechargeable batteries still doesn't improve significantly during use. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a secondary battery, a battery module, a battery pack, and an electrical device.

[0005] The first aspect of this application provides a secondary battery, the secondary battery including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode film layer containing a positive electrode active material, the positive electrode active material including lithium iron phosphate material and a conjugated carbonyl compound.

[0006] Therefore, in the secondary battery of this application, lithium iron phosphate material has a higher discharge plateau voltage, thereby enabling the secondary battery to release higher energy. The conjugated carbonyl compound has a lower discharge plateau voltage than lithium iron phosphate material; and under low charge state, the conjugated carbonyl compound can contribute capacity and mitigate voltage decay. At a specific SOC, the maximum discharge power will be increased due to the greater capacity contribution from the plateau region of the conjugated carbonyl compound, resulting in increased current and slower voltage decay, thus improving power performance. The combined use of lithium iron phosphate material and the conjugated carbonyl compound allows the secondary battery, during discharge, to include not only the discharge plateau of the lithium iron phosphate material itself but also a relatively lower discharge plateau provided by the conjugated carbonyl compound. Thus, during discharge, the voltage decreases with increasing discharge capacity, and the voltage decrease trend is relatively gentle, enabling a stable increase in discharge capacity and improving the power performance of the secondary battery.

[0007] In some embodiments, the mass content of the conjugated carbonyl compound is denoted as a%, based on the total mass of the positive electrode active material, with 2% ≤ a% ≤ 13%; alternatively, 3% ≤ a% ≤ 10%.

[0008] Therefore, when the mass content a% of the conjugated carbonyl compound in this application is within the above range, the conjugated carbonyl compound can share a portion of the current during discharge, which can significantly extend the discharge platform of the positive electrode active material, further smoothing the voltage reduction trend, which is beneficial to further improve the power performance of the secondary battery; and the amount of conjugated carbonyl compound added can be coordinated with the amount of lithium replenishment in the negative electrode, thereby effectively improving the electrochemical performance of the secondary battery.

[0009] In some embodiments, in the discharge curve of the positive electrode relative to graphite at a discharge rate of 0.33C, the proportion of the discharge plateau capacity of the lithium iron phosphate material to the total discharge capacity of the positive electrode active material is W1, 80% ≤ W1 ≤ 99%; and / or in the discharge curve of the positive electrode relative to graphite at a discharge rate of 0.33C, the proportion of the discharge plateau capacity of the conjugated carbonyl compound to the total discharge capacity of the positive electrode active material is W2, 1% ≤ W2 ≤ 20%.

[0010] Therefore, this application can adjust the proportion W1 of the discharge plateau capacity of the lithium iron phosphate material relative to the positive electrode active material by adjusting the mass content of the lithium iron phosphate material relative to the positive electrode active material, thus enabling flexible control of the positive electrode active material as needed. Correspondingly, this application can adjust the proportion W2 of the discharge plateau capacity of the conjugated carbonyl compound relative to the positive electrode active material by adjusting the mass content of the conjugated carbonyl compound relative to the positive electrode active material, thus enabling flexible control of the positive electrode active material as needed.

[0011] In some embodiments, the discharge curve of lithium iron phosphate material relative to graphite at a discharge rate of 0.33C has a discharge plateau voltage V1V, where 3.2≤V1≤3.45.

[0012] Therefore, when the lithium iron phosphate material of this application is added to the secondary battery as a component of the positive electrode active material, the lower discharge cutoff voltage of the secondary battery is about 2.5V at 25°C and 2.0V below 10°C. At lower temperatures, it is more conducive to the synergistic effect of the conjugated carbonyl compound, so that the discharge platform of the conjugated carbonyl compound can be further smoothed during the discharge process, improving the power performance of the secondary battery; and it is also conducive to the capacity contribution of the conjugated carbonyl compound, increasing the discharge capacity and improving the discharge capacity retention rate.

[0013] In some embodiments, the discharge curve of the conjugated carbonyl compound relative to graphite at a discharge rate of 0.33C has a discharge plateau voltage V2 V, where 1.9 ≤ V2 ≤ 2.9.

[0014] Therefore, when the compositional distribution of the conjugated carbonyl compound of this application is increased as a positive electrode active material in a secondary battery, the discharge curve can be further smoothed during the discharge process, improving the power performance of the secondary battery; and it is also beneficial for the conjugated carbonyl compound to contribute capacity, increase discharge capacity, and improve discharge capacity retention rate.

[0015] In some embodiments, the conjugated carbonyl compound includes one or more of quinone compounds or their salts, conjugated carboxyl compounds or their salts, diimide salts, dianhydrides, and macarboxylates; optionally, the quinone compound or its salt includes benzoquinone, anthraquinone, phenanthrenequinone, 1,4-dibenzoquinone, 2,3,5,6-tetrachloro-1,4-benzoquinone, 2,5-dimethoxybenzoquinone, 1,3,4-trihydroxyanthraquinone, 1,5-dilithoxyanthraquinone, dipyridobenzoquinone, dithiophenebenzoquinone, difuranobenzoquinone, nonobenzohexaquinone, and 5,7,12,14-pentabenzene. One or more of tetraketones and 2,5-dihydroxybenzoquinone dilithium salts; conjugated carboxyl compounds or their salts include one or more of terephthalic acid, 2,4-dienyl adipic acid, vinyl dibenzoic acid, lithium terephthalate, lithium 2,4-dienyl adipic acid, and lithium vinyl dibenzoate; diimide salts include pyromellitic acid diimide dilithium salt and / or naphthalene tetracarboxylic acid diimide dilithium salt; dianhydrides include one or more of pyromellitic anhydride, naphthalene tetracarboxylic dianhydride, and perylene tetracarboxylic dianhydride; and rose palmite salts include rose palmite dilithium salt and / or rose palmite tetralithium salt. The above-mentioned conjugated carbonyl compounds have low molecular weight and high specific capacity.

[0016] In some embodiments, the negative electrode sheet includes a negative electrode film layer containing a negative electrode active material, which includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and lithium aluminum alloy.

[0017] In some embodiments, the negative electrode sheet further includes a lithium replenishment layer disposed on the negative electrode film layer.

[0018] Therefore, since the conjugated carbonyl compound in this application contains virtually no lithium, it cannot provide a lithium source. Instead, this application can provide a lithium source through a lithium replenishment layer disposed on the negative electrode. Furthermore, the amount of lithium replenishment in the lithium replenishment layer can be correlated with the mass of the conjugated carbonyl compound, ensuring that the replenishment amount is appropriate without being excessive and thus avoiding a burden on the safety of the production process.

[0019] A second aspect of this application also provides a battery module including a secondary battery as described in any embodiment of the first aspect of this application.

[0020] A third aspect of this application also provides a battery pack including a battery module as described in the second aspect of this application.

[0021] The fourth aspect of this application also provides an electrical device, including a secondary battery as described in any embodiment of the first aspect of this application, a battery module as described in the second aspect of this application, or a battery pack as described in the third aspect of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of one embodiment of the secondary battery of this application.

[0024] Figure 2 yes Figure 1 An exploded view of the implementation method of the secondary battery.

[0025] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0026] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0027] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0028] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0029] The accompanying drawings may not be drawn to scale.

[0030] The annotations in the attached figures are explained as follows:

[0031] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module;

[0032] 5. Secondary battery; 51. Housing; 52. Electrode assembly;

[0033] 53. Cover plate;

[0034] 6. Electrical appliances. Detailed Implementation

[0035] The following detailed description discloses embodiments of the secondary battery, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0036] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0040] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0042] Positive electrode active materials include various materials, with lithium iron phosphate (LFP) compounds being widely studied and applied due to their high capacity and good cycle performance. As lithium intercalation compounds and providers of active lithium ions, LFP compounds maintain a relatively long discharge plateau during discharge, which is beneficial for ensuring the power performance of secondary batteries. During charge and discharge, the insertion or extraction of lithium ions may be accompanied by a phase transition in the positive electrode active material, corresponding to a relatively flat potential plateau in the charge-discharge curve. However, at the end of discharge, the plateau drops sharply, leading to a decrease in the power performance of the secondary battery and a deterioration in discharge capacity. LFP compounds undergo a two-phase transition during charge and discharge between orthorhombic and hexagonal lithium iron phosphate. Since these two phases coexist as solid solutions below 200℃, there is no obvious two-phase transition point during charge and discharge. Therefore, LFP compounds have a long and stable charge-discharge voltage plateau; however, the plateau drops sharply at the end of discharge, resulting in a deterioration in power performance.

[0043] In view of this, the inventors improved the positive electrode active material from the perspective of extending the discharge plateau, thereby improving the power performance and discharge capacity of the secondary battery. The technical solution of this application will now be described in detail.

[0044] Secondary batteries

[0045] In a first aspect, this application provides a secondary battery, the secondary battery including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the positive electrode including a positive electrode film layer containing a positive electrode active material, the positive electrode active material including lithium iron phosphate material and a conjugated carbonyl compound.

[0046] Although the mechanism is not fully understood, the inventors have discovered that in the secondary battery of this application, lithium iron phosphate material has a high discharge plateau voltage, thereby enabling the secondary battery to release higher energy. The conjugated carbonyl compound has a lower discharge plateau voltage than lithium iron phosphate material; and in a low state of charge, the conjugated carbonyl compound can contribute capacity and mitigate voltage decay. At a specific state of charge (SOC), the maximum discharge power will be increased due to the greater capacity contribution from the plateau region of the conjugated carbonyl compound, resulting in increased current and slower voltage decay, thus improving power performance. The combined use of lithium iron phosphate material and the conjugated carbonyl compound allows the secondary battery, during discharge, to include not only the discharge plateau of the lithium iron phosphate material itself but also a relatively lower discharge plateau provided by the conjugated carbonyl compound. Therefore, during discharge, the voltage decreases with increasing discharge capacity, and the voltage decrease trend is relatively gentle, resulting in a stable increase in discharge capacity and improving the power performance of the secondary battery. In some embodiments, the SOC is 3% to 20%, and the specific range of SOC is related to the amount of conjugated carbonyl compound added and the specific capacity.

[0047] The discharge plateau voltage of a positive electrode active material is a well-known concept in the art, representing the voltage value corresponding to half the discharge capacity of the positive electrode active material. The discharge plateau voltage can be measured using methods known in the art. As a specific example, a positive electrode sheet can be prepared using the positive electrode active material to be tested, and a test battery can be formed with a counter electrode. The test battery can be fully charged and then fully discharged within the charge / discharge voltage range, and a curve showing the change in discharge capacity relative to voltage (also called a discharge curve) can be plotted. The voltage corresponding to half the discharge capacity is thus obtained, which is the discharge plateau voltage.

[0048] In the test, the counter electrode can be any electrode known in the art as the negative electrode of a secondary battery. For example, the counter electrode can be a lithium metal sheet, a graphite electrode, or, for instance, a graphite counter electrode. The preparation of the positive electrode, the counter electrode, and the test battery can all refer to national standards or industry specifications. Taking the test of the discharge plateau voltage of lithium iron phosphate material as an example: Lithium iron phosphate material, a conductive agent (e.g., conductive carbon black Super P), and a binder (e.g., polyvinylidene fluoride PVDF) are dispersed in the solvent NMP at a weight ratio of 95:3:2 to form a positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained. A negative electrode active material (e.g., graphite, which can be artificial graphite, natural graphite, or a mixture of artificial and natural graphite) is dispersed in deionized water at a weight ratio of 95:2:2:1 to form a negative electrode slurry. The negative electrode slurry is coated onto the surface of a copper foil current collector, dried, and cold-pressed to obtain a negative electrode sheet. The positive and negative electrode sheets are then stacked or wound with a separator to form an electrode assembly. The electrode assembly is placed in an outer packaging, and an electrolyte is added to prepare a test battery. A commonly used electrolyte in the art can be used. For example, equal volumes of ethylene carbonate (EC) and propylene carbonate (PC) are mixed uniformly, and then lithium salt LiPF6 is added to obtain the electrolyte. The concentration of LiPF6 in the electrolyte can be 1 mol / L. For testing the discharge plateau voltage of conjugated carbonyl compounds, a similar method can be used to prepare the test battery.

[0049] In the test, the charge and discharge voltage range is determined by the battery's own characteristics, such as the type of positive electrode active material. As an example, the charge and discharge regime can be as follows: at 25°C, the test battery is charged at a constant current rate of 0.33C to the upper cutoff voltage, then charged at a constant voltage until the current ≤ 0.05C, at which point the battery is fully charged (100% SOC); after resting for 5 minutes, the battery is discharged at a constant current rate of 0.33C to the lower cutoff voltage, at which point the battery is fully discharged (0% SOC); the discharge curve of the battery is plotted to obtain the discharge plateau voltage.

[0050] In some embodiments, the mass content of the conjugated carbonyl compound is denoted as a%, based on the total mass of the positive electrode active material, with a content of 2% ≤ a% ≤ 13%.

[0051] When the mass content a% of the conjugated carbonyl compound is within the above range, during discharge, the conjugated carbonyl compound can share a portion of the current, significantly extending the discharge platform of the positive electrode active material and further smoothing the voltage reduction trend, which is beneficial to further improving the power performance of the secondary battery. Furthermore, the amount of conjugated carbonyl compound added can be coordinated with the amount of lithium replenishment in the negative electrode, thereby effectively improving the electrochemical performance of the secondary battery. Optionally, 3% ≤ a% ≤ 10%; exemplaryly, the mass content a% of the conjugated carbonyl compound can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, or 13%; or any range consisting of any two of the above values.

[0052] In some embodiments, in the discharge curve of the positive electrode relative to graphite at a discharge rate of 0.33C, the proportion of the discharge plateau capacity of the lithium iron phosphate material to the total discharge capacity of the positive electrode active material is W1, where 80% ≤ W1 ≤ 99%.

[0053] This application allows for flexible control of the discharge platform capacity W1 of the lithium iron phosphate material by adjusting the mass content of the lithium iron phosphate material relative to the positive electrode active material. For example, W1 can be 80%, 82%, 85%, 86%, 88%, 90%, 91%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%; or a range of any two of the above values.

[0054] In some embodiments, in the discharge curve of the positive electrode relative to graphite at a discharge rate of 0.33C, the discharge plateau capacity of the conjugated carbonyl compound accounts for W2 of the total discharge capacity of the positive electrode active material, where 1% ≤ W2 ≤ 20%.

[0055] This application allows for flexible control of the discharge plateau capacity W2 of the conjugated carbonyl compound by adjusting the mass content of the conjugated carbonyl compound relative to the positive electrode active material. For example, W2 can be 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 18%, or 20%; or a range of any two of the above values.

[0056] In this application, a negative electrode sheet is prepared using graphite as the negative electrode active material, as described above. A battery under test is then fabricated using both the positive and negative electrode sheets. The discharge curve of the battery under test is measured according to the charge-discharge regime described above. The discharge capacity corresponding to the discharge plateau voltage of the conjugated carbonyl compound in the discharge curve is obtained, and the proportion of this capacity to the total discharge capacity of the positive electrode active material is calculated.

[0057] In some embodiments, the discharge curve of the lithium iron phosphate material relative to graphite at a discharge rate of 0.33C has a discharge plateau voltage V1 V, where 3.2 ≤ V1 ≤ 3.45.

[0058] When lithium iron phosphate material is added to secondary batteries as a component of the positive electrode active material, the lower discharge cutoff voltage of the secondary battery is about 2.5V at 25℃ and 2.0V below 10℃. At lower temperatures, it is more conducive to the synergistic effect of conjugated carbonyl compounds, so that the discharge platform of conjugated carbonyl compounds can be further smoothed during the discharge process, improving the power performance of secondary batteries; and it is also conducive to the capacity contribution of conjugated carbonyl compounds, increasing the discharge capacity and improving the discharge capacity retention rate.

[0059] Lithium iron phosphate materials can be modified by other materials, such as by doping or coating.

[0060] In some embodiments, the conjugated carbonyl compound includes one or more compounds with a conjugated structure, such as quinone compounds or their salts, conjugated carboxyl compounds or their salts, diimide salts, dianhydrides, and macarboxylates.

[0061] The aforementioned conjugated carbonyl compounds have low molecular weights and high specific capacities. One electrochemical redox reaction mechanism involves the following: first, the compound gains an electron to form a free radical anion, and then gains another electron to form a divalent anion; the reverse process involves the loss of two electrons to restore its carbonyl structure. Of course, when the conjugated carbonyl compound has multiple carbonyl groups, it can simultaneously gain multiple electrons to undergo redox reactions.

[0062] By way of example, the quinone compounds or their salts include one or more of benzoquinone, anthraquinone, phenanthrenequinone, 1,4-dibenzoquinone, 2,3,5,6-tetrachloro-1,4-benzoquinone, 2,5-dimethoxybenzoquinone, 1,3,4-trihydroxyanthraquinone, 1,5-dilithiumoxyanthraquinone, dipyridinobenzoquinone, dithiophenobenzoquinone, difuranobenzoquinone, nonobenzohexaquinone, 5,7,12,14-pentaphenyltetraone, and dilithium salt of 2,5-dihydroxybenzoquinone.

[0063] For example, the conjugated carboxyl compound or its salts include one or more of terephthalic acid, 2,4-dienyl adipic acid, vinyl dibenzoic acid, lithium terephthalate, lithium 2,4-dienyl adipic acid, and lithium vinyl dibenzoate.

[0064] For example, the diimide salt includes lithium pyromellitic diimide and / or lithium naphthalenetetracarboxylate diimide.

[0065] For example, the dianhydride compounds include one or more of pyromellitic dianhydride, naphthalenetetracarboxylic dianhydride, and perylenetetracarboxylic dianhydride;

[0066] For example, the macarnitine salt includes dilithium macarnitine and / or tetralithium macarnitine.

[0067] In some embodiments, the discharge curve of the conjugated carbonyl compound relative to graphite at a discharge rate of 0.33C has a discharge plateau voltage V2 V, where 1.9 ≤ V2 ≤ 2.9.

[0068] When the compositional distribution of conjugated carbonyl compounds as positive electrode active materials is increased in secondary batteries, the discharge curve can be further smoothed during discharge, improving the power performance of the secondary battery. Furthermore, it is beneficial for the capacity contribution of conjugated carbonyl compounds, increasing the discharge capacity and improving the discharge capacity retention rate. Conjugated carbonyl compounds can have one discharge plateau voltage or two discharge plateau voltages, where V2V can refer to the average of its discharge plateau voltages. For example, 1.9≤V2≤2.1, 1.9≤V2≤2.3, 1.9≤V2≤2.5, 1.9≤V2≤2.6, 2.0≤V2≤2.5, 2.1≤V2≤2.6, 2.1≤V2≤2.8, or 2.2≤V2≤2.9.

[0069] [Positive electrode plate]

[0070] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0071] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more combinations selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is less than 5% based on the total mass of the positive electrode film.

[0072] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder is less than 5% based on the total mass of the positive electrode film layer.

[0073] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include aluminum foil or aluminum alloy foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of the metal material include one or more combinations selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer substrate may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0074] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0075] [Negative electrode plate]

[0076] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0077] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0078] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and lithium-aluminum alloys, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0079] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more combinations selected from styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic 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, the mass percentage of the negative electrode binder is less than 5% based on the total mass of the negative electrode film layer.

[0080] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more combinations selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is less than 5% based on the total mass of the negative electrode film layer.

[0081] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of other additives is less than 2% based on the total mass of the negative electrode film.

[0082] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include copper foil or copper alloy foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of the metal material include one or more combinations selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer substrate may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0083] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0084] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a protective layer covering the surface of the negative electrode film layer.

[0085] In some embodiments, the negative electrode sheet further includes a lithium replenishment layer disposed on the negative electrode film layer.

[0086] Since conjugated carbonyl compounds contain virtually no lithium, they cannot provide a lithium source. Therefore, this application provides a lithium source by adding a lithium replenishment layer on the negative electrode. Furthermore, the amount of lithium replenishment in the layer can be correlated with the mass of the conjugated carbonyl compound, ensuring that the replenishment amount is appropriate without being excessive and thus not burdening the safety of the production process. For example, the theoretically required lithium content based on the actual mass of the conjugated carbonyl compound added can be used as the 100% lithium replenishment amount. This replenishment amount can provide a sufficient lithium source for the secondary battery without significantly adversely affecting the manufacturing process and production safety.

[0087] The method for lithium replenishment of the negative electrode sheet can employ methods known in the art. For example, the following method can be used: lithium is replenished to the coated and cold-pressed negative electrode sheet using a lithium replenishment device. In the device, a lithium strip conveying structure is used to transport the lithium strip, and a substrate conveying structure is used to transport the negative electrode sheet. The lithium strip and the negative electrode sheet are rolled together, and after rolling, the lithium strip adheres to the surface of the negative electrode sheet, completing the pre-lithiation of the negative electrode. Of course, other methods can also be used for lithium replenishment, which will not be described in detail here.

[0088] Electrolyte

[0089] The electrolyte acts as a conductor of metal ions between the positive and negative electrodes. The electrolyte used in this application can be any electrolyte known in the art for secondary batteries. The electrolyte includes lithium salts and organic solvents.

[0090] As an example, lithium salts may include one or more combinations selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0091] As an example, the organic solvent may include one or more combinations selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0092] The electrolyte of this application can be prepared using methods conventional in the art. For example, additives, solvents, electrolyte salts, etc., can be mixed evenly to obtain the electrolyte. There are no particular restrictions on the order of addition of the materials; for example, additives, electrolyte salts, etc., can be added to a non-aqueous solvent and mixed evenly to obtain a non-aqueous electrolyte.

[0093] In this application, the components and their contents in the electrolyte can be determined according to methods known in the art. For example, they can be determined by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0094] It should be noted that during the electrolyte testing of this application, freshly prepared electrolyte can be used directly, or electrolyte can be obtained from a secondary battery. An exemplary method for obtaining electrolyte from a secondary battery includes the following steps: discharging the secondary battery to the discharge cutoff voltage (for safety, the battery is generally left fully discharged), followed by centrifugation. A suitable amount of the centrifuged liquid is then taken as the non-aqueous electrolyte. Alternatively, the non-aqueous electrolyte can be obtained directly from the secondary battery's filling port.

[0095] [Isolation membrane]

[0096] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0097] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0098] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0099] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0100] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0101] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 1 This is an example of a square-structured secondary battery 5.

[0102] In some embodiments, such as Figure 1 and Figure 2As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be adjusted according to requirements.

[0103] The method for preparing the secondary battery described in this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is then placed in an outer packaging, dried, and injected with an electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0104] In some embodiments of this application, the secondary battery according to this application can be assembled into a battery module. The number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0105] Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0106] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0107] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0108] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0109] Electrical appliances

[0110] Secondly, this application provides an electrical device, which includes at least one of the secondary battery, battery module, and battery pack described in this application. The secondary battery, battery module, and battery pack can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0111] Electrical devices can be equipped with secondary batteries, battery modules, or battery packs depending on their usage requirements.

[0112] Figure 6 This is a schematic diagram of an example electrical device. The electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device, a battery pack 1 or a battery module can be used.

[0113] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0114] Example

[0115] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0116] Example 1

[0117] 1. Preparation of positive electrode sheet

[0118] Aluminum foil with a thickness of 12μm was used as the positive electrode current collector.

[0119] The positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of solvent NMP at a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained.

[0120] 2. Preparation of negative electrode sheet

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

[0122] Artificial graphite (anode active material), styrene-butadiene rubber (SBR) (binder), sodium carboxymethyl cellulose (CMC-Na) (thickener), and carbon black (Super P) (conductive agent) are mixed thoroughly in an appropriate amount of deionized water at a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform anode slurry. The anode slurry is then uniformly coated onto the surface of copper foil (anode current collector), and after drying and cold pressing, the anode sheet is obtained.

[0123] 3. Separating membrane

[0124] Porous polyethylene (PE) membrane is used as the separator.

[0125] 4. Preparation of electrolyte

[0126] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed at a volume ratio of 1:1 to obtain an electrolyte solvent. Then, lithium salt is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0127] 5. Preparation of secondary batteries

[0128] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0129] Example 2

[0130] Examples 2-1 to 2-6 were prepared in a similar manner to Example 1, except that the mass content a) of the conjugated carbonyl compound was adjusted in Examples 2-1 to 2-6.

[0131] Example 3

[0132] The secondary batteries of Examples 3-1 and 3-2 were prepared in a similar manner to those of Example 1. The difference from Example 1 is that the types of conjugated carbonyl compounds in Examples 3-1 and 3-2 were adjusted.

[0133] Example 4

[0134] The secondary batteries of Examples 4-1 to 4-3 were prepared in a similar manner to those of Example 1. The difference from Example 1 is that the amount of lithium added to the negative electrode was adjusted in Examples 4-1 to 4-3.

[0135] Comparative Example 1

[0136] The secondary battery of Comparative Example 1 was prepared in a similar manner to that of Example 1, except that no conjugated carbonyl compound was used in Comparative Example 1.

[0137] The parameters for the embodiments and comparative examples are shown in Table 1.

[0138] Table 1

[0139]

[0140] Test section

[0141] 1. Capacity performance test of secondary batteries

[0142] The secondary batteries prepared in the above embodiments or comparative examples were placed in an environment of 25°C and allowed to stand until the secondary battery temperature was constant at 25°C; they were then charged at a current of 1 / 3C to the charging termination voltage; allowed to stand for 10 minutes; charged at a current of 0.05C to the charging termination voltage; allowed to stand for 10 minutes; and discharged at a current of 1 / 3C to the discharging termination voltage. The discharge capacity of this step was recorded as the battery discharge capacity Cn at 25°C@0.33C.

[0143] The plateau voltage was determined as follows: Discharge curves were obtained based on discharge data, and the plateau voltage of the conjugated carbonyl compound in the lithium iron phosphate system of the corresponding example / comparative example was observed and determined from the discharge curves.

[0144] 2. Low-temperature power test

[0145] The following is a test result of maximum power at -10℃ for 30 seconds at 10% SOC:

[0146] ① Place the secondary battery prepared in the above embodiments or comparative examples in an environment of 25°C and let it stand until the battery temperature reaches a constant 25°C; ② Charge it with a current of 1 / 3C until the charging termination voltage is reached; ③ Let it stand for 10 minutes; ④ Charge it with a current of 0.05C until the charging termination voltage is reached; ⑤ Let it stand for 10 minutes; ⑥ Discharge it with a current of 1 / 3C for 0.8Cn to adjust the battery to a 10% SOC state of charge; ⑦ Place the battery in an environment of -10°C and let it stand until the battery temperature reaches a constant -10°C; ⑧ Discharge it at a specific power for 30 seconds until the discharge is complete. Stop the discharge voltage and record the discharge capacity of this step as C1; ⑨ Let it stand for 5 minutes; ⑩ If the voltage in step ⑧ has reached the discharge termination voltage, record this power as the maximum power; if the discharge termination voltage has not been reached, or the time to reach the discharge termination voltage is less than 30s, charge it with a current of 0.05C to the same capacity as the discharge capacity C1, that is, readjust the battery to 10% SOC state of charge; increase / decrease the power accordingly and repeat step ⑧ to discharge until the battery discharges to the discharge cutoff voltage in 30s, and record the power at this time as the maximum power.

[0147] 3. -10℃ Automotive Cyclic Operating Condition Test (CLTC Test)

[0148] The secondary batteries prepared in the above embodiments or comparative examples were placed in an environment of 25°C and allowed to stand until the battery temperature reached a constant 25°C; they were then charged at a current of 1 / 3C to the charging termination voltage; allowed to stand for 10 minutes; they were then charged at a current of 0.05C to the charging termination voltage; allowed to stand for 10 minutes; the batteries were placed in an environment of -10°C and allowed to stand until the battery temperature reached a constant -10°C; and they were then discharged using the battery CLTC operating condition process to the discharge termination voltage. The discharge capacity at this step was recorded as the actual discharge capacity of the battery at -10°C.

[0149] Calculation of CLTC discharge capacity retention rate of battery cell at -10℃: (actual CLTC discharge capacity at -10℃ / Ah) divided by (discharge capacity at 25℃ / Ah@0.33C) gives the CLTC discharge capacity retention rate of battery cell at -10℃.

[0150] Test Results

[0151] The effects of this application on improving the power and capacity performance of secondary batteries are shown in Table 2.

[0152] Table 2

[0153]

[0154] As shown in Table 2, Comparative Example 1, lacking the addition of a conjugated carbonyl compound, may experience faster capacity decay and poorer power output during discharge. In this application, a conjugated carbonyl compound is added to the lithium iron phosphate cathode active material. The synergistic effect of the two compounds smooths the discharge curve, resulting in a stable increase in discharge capacity and improving the power performance of the secondary battery. Furthermore, Examples 1 to 2-6 demonstrate that the discharge capacity retention rate of the secondary battery improves with increasing conjugated carbonyl compound content. However, the overall discharge capacity is better when the ratio of lithium iron phosphate material to conjugated carbonyl compound is within a specific range (e.g., Examples 1, 2-2, and 2-3).

[0155] As shown in Examples 1 and 4-1 to 4-3, lithium supplementation to the secondary battery system can effectively improve the discharge capacity and power performance of the secondary battery. However, if the lithium supplementation amount is too high, such as greater than 100%, for example, when the lithium supplementation amount is greater than 8 mg / 1540.25 mm... 2 The discharge capacity and power performance will not be improved further.

[0156] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, comprising a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab, the positive electrode tab comprising a positive electrode film layer containing a positive electrode active material, the positive electrode active material comprising a lithium iron phosphate material and a conjugated carbonyl compound, a proportion of a discharge plateau capacity of the conjugated carbonyl compound to a total discharge capacity of the positive electrode active material in a discharge curve of the positive electrode tab at a 0.33 C discharge rate with respect to graphite is W2, 3.5%≤W2≤16.1%; the negative electrode tab comprising a negative electrode film layer containing a negative electrode active material, the negative electrode tab further comprising a lithium supplement layer disposed on the negative electrode film layer.

2. The secondary battery according to claim 1, wherein a mass content of the conjugated carbonyl compound is a%, 2%≤a%≤13% based on a total mass of the positive electrode active material.

3. The secondary battery according to claim 2, wherein 3%≤a%≤10%。 4. The secondary battery according to claim 1 or 2, wherein a proportion of a discharge plateau capacity of the lithium iron phosphate material to a total discharge capacity of the positive electrode active material in a discharge curve of the positive electrode tab at a 0.33 C discharge rate with respect to graphite is W1, 80%≤W1≤99%.

5. The secondary battery according to claim 1, wherein the lithium iron phosphate material has a discharge plateau voltage V1 V in a discharge curve at a 0.33 C discharge rate with respect to graphite, 3.2≤V1≤3.

45.

6. The secondary battery according to claim 1, wherein the conjugated carbonyl compound has a discharge plateau voltage V2 V in a discharge curve at a 0.33 C discharge rate with respect to graphite, 1.9≤V2≤2.

9.

7. The secondary battery according to claim 1, wherein the conjugated carbonyl compound comprises one or more of a quinone compound or a salt thereof, a conjugated carboxyl compound or a salt thereof, a diimide salt, a dianhydride compound, and a purpurate.

8. The secondary battery according to claim 7, wherein the quinone compound or the salt thereof comprises one or more of benzoquinone, anthraquinone, phenanthraquinone, 1,4-diphenylquinonylbenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone, 2,5-dimethoxybenzoquinone, 1,3,4-trihydroxyanthraquinone, 1,5-dilithiooxyanthraquinone, dipyridophenzoquinone, dithienophenzoquinone, difuranophenzoquinone, nonacenehexaquinone, 5,7,12,14-norbornetetracenetetraone, and 2,5-dihydroxybenzoquinonedi-lithium salt.

9. The secondary battery according to claim 7, wherein the conjugated carboxyl compound or the salt thereof comprises one or more of terephthalic acid, 2,4-dienyl adipic acid, vinylbenzoic acid, lithium terephthalate, lithium 2,4-dienyl adipate, and lithium vinylbenzoate.

10. The secondary battery according to claim 7, wherein the diimide salt comprises di-lithium phthalimide and / or di-lithium naphthalimide.

11. The secondary battery according to claim 7, wherein the dianhydride compound comprises one or more of phthalic anhydride, naphthalene tetracarboxylic dianhydride, and perylene tetracarboxylic dianhydride.

12. The secondary battery according to claim 7, wherein the purpurate comprises di-lithium purpurate and / or tetra-lithium purpurate.

13. The secondary battery according to claim 1, wherein the negative electrode active material comprises one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and lithium-aluminum alloy. 14.A battery module comprising the secondary battery according to any one of claims 1 to 13. 15.A battery pack comprising the battery module according to claim 14.

16. An electric device comprising the secondary battery according to any one of claims 1 to 13, the battery module according to claim 14, or the battery pack according to claim 15.

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