Secondary battery, battery module, battery pack and electric equipment

Abstract

The invention relates to the technical field of batteries, and particularly discloses a secondary battery, a battery module, a battery pack and electric equipment. The secondary battery comprises an electrolyte and a lithium supplement agent; the electrolyte comprises a cyclic sulfonate compound containing an unsaturated double bond; the lithium supplementing agent comprises a first lithium supplementing agent and a second lithium supplementing agent; wherein the first lithium supplement agent is prepared from at least one of Li4FeO5, Li3N and Li2O; and the second lithium supplement agent is prepared from at least one of Li2MnO3, Li6CoO4 and Li2NiO2.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery, a battery module, a battery pack and an electrical device. Background Art

[0002] With the rapid development of new energy technologies, the requirements for the cycle life of energy storage batteries are getting higher and higher. Pre-lithiation technology is an important technical means to compensate for the loss of active lithium in the battery cycle and improve the cycle stability. It is achieved by pre-adding additional lithium sources to the positive or negative electrode materials of the battery to compensate for the capacity loss caused by irreversible lithium ion loss during the first charge of the battery, thereby improving the overall performance of the battery. However, pre-lithiation technology also faces some challenges, such as the generation of gas and heat in the lithium supplement during the formation process, which deteriorates the safety and performance of the battery. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present application is to propose a secondary battery, a battery module, a battery pack and an electrical device, wherein the secondary battery includes a lithium supplement that is easy to generate gas and heat, and the electrolyte contains a cyclic sulfonate compound containing an unsaturated double bond, which can effectively inhibit the gas and heat generation during the operation of the battery, thereby effectively improving the energy efficiency and overcharge safety of the battery.

[0004] In one aspect of the present application, the present application provides a secondary battery. According to an embodiment of the present application, the secondary battery includes an electrolyte and a lithium supplement;

[0005] The electrolyte includes a cyclic sulfonate compound containing an unsaturated double bond;

[0006] The lithium supplement includes a first lithium supplement and a second lithium supplement;

[0007] Wherein, the first lithium supplement comprises at least one of Li4FeO5, Li3N and Li2O;

[0008] The second lithium supplement includes at least one of Li2MnO3, Li6CoO4, and Li2NiO2.

[0009] When the secondary battery contains the above two lithium replenishers, gas and heat generation are likely to occur during operation. The applicant has found that the cyclic sulfonate compound containing unsaturated double bonds can inhibit gas generation, and at the same time, the first lithium replenisher can promote the ring opening of the cyclic sulfonate compound, further polymerize in the overcharge stage, adhere to the surface of the active material, and also reduce the dissolution of manganese, cobalt or nickel from the second lithium replenisher and the damage to the SEI film (solid electrolyte interface film), thereby improving safety performance.

[0010] In some embodiments of the present application, the cyclic sulfonate compound containing an unsaturated double bond includes any one of the structures of Formula 1, Formula 2, and Formula 3;

[0011]

[0012] Wherein, R1, R2, and R3 are independently a hydrogen atom or a saturated alkane having 1 to 10 carbon atoms.

[0013] In some embodiments of the present application, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer is arranged on the positive electrode current collector, the mass proportion of the first lithium replenisher in the positive electrode active material layer is a1, the mass proportion of the second lithium replenisher in the positive electrode active material layer is a2, and the mass proportion of the cyclic sulfonate compound in the electrolyte is b1 that satisfies:

[0014]

[0015] In some embodiments of the present application, the mass proportion b1 of the cyclic sulfonate compound in the electrolyte and the mass proportion a1 of the first lithium supplement in the positive electrode active material layer satisfy:

[0016]

[0017] In some embodiments of the present application, the electrolyte further includes a fluorinated nitrogen-containing heterocyclic compound.

[0018] In some embodiments of the present application, the fluorinated nitrogen-containing heterocyclic compound includes at least one of 2-fluoropyridine, 2-fluoropyrazine, 2,6-difluoropyridine, 3-fluoropyridine, pentafluoropyridine, 2-fluoropyridazine, and 3-fluoropyridazine.

[0019] In some embodiments of the present application, the mass proportion a1 of the first lithium replenisher in the positive electrode active material layer, the mass proportion a2 of the second lithium replenisher in the positive electrode active material layer, and the mass proportion b2 of the fluorinated nitrogen-containing heterocyclic compound in the electrolyte satisfy:

[0020]

[0021] In a second aspect of the present application, the present application provides a battery module. According to an embodiment of the present application, the battery module includes the secondary battery described in the first aspect.

[0022] Therefore, the battery module has all the advantages of the secondary battery, which will not be described in detail here.

[0023] In a third aspect of the present application, the present application provides a battery pack. According to an embodiment of the present application, the battery pack includes the battery module described in the second aspect.

[0024] Therefore, the battery pack has all the advantages of the battery module, which will not be described in detail here.

[0025] In a fourth aspect of the present application, the present application proposes an electric device. According to an embodiment of the present application, the electric device includes at least one of the secondary battery described in the first aspect, the battery module described in the second aspect, and the battery pack described in the third aspect.

[0026] Therefore, the electrical equipment has all the advantages of the secondary battery, battery module or battery pack, which will not be described in detail here.

[0027] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. DETAILED DESCRIPTION

[0028] In one aspect of the present application, the present application provides a secondary battery. According to an embodiment of the present application, the secondary battery includes an electrolyte and a lithium supplement;

[0030] The electrolyte includes a cyclic sulfonate compound containing an unsaturated double bond;

[0031] The lithium supplement includes a first lithium supplement and a second lithium supplement;

[0032] Wherein, the first lithium supplement comprises at least one of Li4FeO5, Li3N and Li2O;

[0033] The second lithium supplement includes at least one of Li2MnO3, Li6CoO4, and Li2NiO2.

[0034] The first lithium supplementer will generate oxygen free radicals during the delithiation process. When it is used in the battery, it is easy to generate a large amount of gas during the formation and delithiation process, which will produce more side reactions and deteriorate the performance such as energy efficiency. The second lithium supplementer is more stable than the first lithium supplementer, but it is easy to dissolve manganese, cobalt or nickel under high pressure during the overcharge process, which will generate heat, and the dissolved metal ions are easy to destroy the negative electrode SEI film, further generating more heat, making it difficult to pass the overcharge safety test. The applicant found that the cyclic sulfonate compounds containing unsaturated double bonds contain S atoms with large electronegativity and strong electron-withdrawing ability, and the charged oxygen free radicals generated by the first lithium supplementer during the formation process will attack the SC bond in the cyclic sulfonate compounds, on the one hand, reducing the activity of oxygen free radicals and reducing the generation of gas, and on the other hand, causing the SC bond to break and the cyclic sulfonate compounds to decompose and open the ring. At the same time, during the overcharge process, the cyclic sulfonate compounds after opening will polymerize into a film attached to the positive electrode surface due to the presence of double bonds, reducing the metal dissolution of the second lithium supplementer during the overcharge process, reducing the generation of heat, and improving the safety performance of the battery.

[0035] According to the embodiments of the present application, the cyclic sulfonate compound can be selected according to actual needs. Those skilled in the art can select according to actual needs. As some specific examples, the cyclic sulfonate compound containing an unsaturated double bond includes any one of the structures of Formula 1, Formula 2, and Formula 3 to better inhibit gas production and overcharge thermal runaway of the secondary battery.

[0036]

[0037]

[0038] Wherein, R1, R2, and R3 are independently hydrogen atoms or saturated alkanes with 1 to 10 carbon atoms. Those skilled in the art can select according to actual needs. As some specific examples, when the cyclic sulfonate compound containing an unsaturated double bond is a structure shown in Formula 1, R1 and R2 can be independently hydrogen atoms or C1-C 10 Saturated alkanes (i.e., C1 saturated alkyl, C2 saturated alkyl, C3 saturated alkyl, C4 saturated alkyl, C5 saturated alkyl, C6 saturated alkyl, C7 saturated alkyl, C8 saturated alkyl, C9 saturated alkyl, C 10 saturated alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, cyclopentyl, isopentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl or n-decyl, for example, R1 and R2 are both hydrogen atoms; or, R1 is a hydrogen atom, and R2 is a C1-C 10 Saturated alkane; or, R1 is C1-C 10 Saturated alkane, R2 is a hydrogen atom; or, R1 and R2 are both C1-C 10When the cyclic sulfonic acid ester compound containing an unsaturated double bond is a structure shown in Formula 2 or Formula 3, R1, R2, and R3 can independently be a hydrogen atom or a C1-C 10 Saturated alkane, for example, R1, R2, and R3 are all hydrogen atoms; or, R1 is a hydrogen atom, and R2 is a C1-C 10 Saturated alkane, R3 is a hydrogen atom; or, R1 is a hydrogen atom, R2 is a C1-C 10 Saturated alkane, R3 is C1-C 10 Saturated alkane; or, R1, R2 are hydrogen atoms, R3 is C1-C 10 Saturated alkane; or, R1 is C1-C 10 Saturated alkane, R2, R3 are both hydrogen atoms; or, R1 is C1-C 10 Saturated alkane, R2 is C1-C 10 Saturated alkane, R3 is a hydrogen atom; or, R1 is C1-C 10 Saturated alkane, R2 is a hydrogen atom, R3 is C1-C 10 Saturated alkane; or, R1, R2, and R3 are all C1-C 10 Saturated alkanes.

[0039] According to an embodiment of the present application, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer is arranged on the positive electrode current collector, the mass proportion a1 of the first lithium replenisher in the positive electrode active material layer, the mass proportion a2 of the second lithium replenisher in the positive electrode active material layer, and the mass proportion b1 of the cyclic sulfonate compound in the electrolyte satisfy:

[0040] This can take into account both the safety performance and the cycle performance of the battery.

[0041] According to some specific embodiments of the present application, It can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc. When its value is small (i.e. less than 0.5), it indicates that the amount of the first lithium supplement or the cyclic sulfonate compound added is small, while the amount of the second lithium supplement is large, which is not enough to form a sufficient protective film during the overcharge process to protect the Ni dissolution on the positive electrode side, resulting in increased heat generation and deterioration of safety performance. When its value is large (i.e. greater than 2), it indicates that the amount of the first lithium supplement and the cyclic sulfonate compound added is large, while the amount of the second lithium supplement is small, which will lead to an increase in the SEI film formation impedance during the cycle, resulting in slower lithium ion migration on the negative electrode side and deterioration of energy efficiency.

[0042] According to an embodiment of the present application, the mass proportion b1 of the cyclic sulfonate compound in the electrolyte and the mass proportion a1 of the first lithium supplement in the positive electrode active material layer satisfy:

[0043] This can suppress the gas generation during battery operation and ensure the battery's cycle performance and safety performance.

[0044] According to some specific embodiments of the present application, It can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, etc. When its value is small (i.e. less than 0.2), it indicates that the first lithium supplement is more, while the content of cyclic sulfonate compounds is less, and the activity of oxygen free radicals generated by the excessive first lithium supplement cannot be effectively suppressed, resulting in more solvent consumption, deterioration of cycle performance, and increased gas production, increased side reactions, and deterioration of energy efficiency. When its value is large (i.e. greater than 1.5), the first lithium supplement is less, while the content of cyclic sulfonate compounds is more, and excessive cyclic sulfonate compounds are further consumed in the later cycle process, increasing the SEI film formation impedance, resulting in slower lithium ion migration on the negative electrode side and deterioration of energy efficiency.

[0045] According to an embodiment of the present application, the electrolyte further includes a fluorinated nitrogen-containing heterocyclic compound.

[0046] The fluorinated nitrogen-containing heterocyclic compound contains N atoms with relatively large electronegativity, which are easily reduced and decomposed at the negative electrode, forming a LiF-containing SEI film on the negative electrode side, increasing the inorganic layer components to enhance the negative electrode interface stability, reducing the damage to the SEI film caused by the gas production of the first lithium replenisher and the metal dissolution of the second lithium replenisher, reducing the heat generation during overcharging, and improving the safety performance of the battery.

[0047] According to the specific embodiments of the present application, the types of fluorinated nitrogen-containing heterocyclic compounds are not particularly limited, and those skilled in the art can select them according to actual needs. As some specific examples, fluorinated nitrogen-containing heterocyclic compounds include but are not limited to 2-fluoropyridine, 2-fluoropyrazine, 2,6-difluoropyridine, 3-fluoropyridine, pentafluoropyridine, 2-fluoropyridazine, and 3-fluoropyridazine.

[0048] According to an embodiment of the present application, the mass proportion a1 of the first lithium replenisher in the positive electrode active material layer, the mass proportion a2 of the second lithium replenisher in the positive electrode active material layer, and the mass proportion b2 of the fluorinated nitrogen-containing heterocyclic compound in the electrolyte satisfy:

[0049] This can suppress the gas generation during battery operation and ensure the battery's cycle performance and safety performance.

[0050] According to some specific embodiments of the present application, It can be 1.5, 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, etc. When its value is small (i.e. less than 1.5), it indicates that the amount of fluorinated nitrogen-containing heterocyclic compound added is large, resulting in thicker SEI film on the negative electrode side, larger interface impedance on the negative electrode side, and worsening energy efficiency. When its value is large (i.e. greater than 10), it indicates that the amount of fluorinated nitrogen-containing heterocyclic compound added is small, which is not enough to protect the negative electrode interface, and the safety performance is deteriorated.

[0051] According to some specific embodiments of the present application, in general, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte conducts ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet to prevent the positive and negative electrodes from short-circuiting while allowing ions to pass through.

[0052] According to some specific embodiments of the present application, the secondary battery is a lithium-ion secondary battery.

[0053] According to some specific embodiments of the present application, the positive electrode plate includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, wherein the positive active material layer includes a positive active material and the above-mentioned lithium supplement, wherein the positive active material is preferably a lithium iron phosphate material.

[0054] According to some specific embodiments of the present application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and other substrates).

[0055] According to some specific embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0056] According to some specific embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0057] According to some specific embodiments of the present application, the positive electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the lithium supplement agent, the conductive agent, and the binder are dispersed in a solvent (such as N-methylpyrrolidone, NMP) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0058] According to some specific embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0059] According to some specific embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one side of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0060] According to some specific embodiments of the present application, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys.

[0061] According to some specific embodiments of the present application, the negative electrode active material layer may further include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0062] According to some specific embodiments of the present application, the negative electrode active material layer may further optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0063] According to some specific embodiments of the present application, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0064] According to some specific embodiments of the present application, the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0065] According to some specific embodiments of the present application, the present application has no particular restrictions on the type of isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected. In some embodiments of the present application, the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene or polyvinylidene fluoride.

[0066] According to some specific embodiments of the present application, the positive electrode sheet, the negative electrode sheet and the isolation film can be made into an electrode assembly through a winding process or a lamination process.

[0067] According to some specific embodiments of the present application, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0068] According to some specific embodiments of the present application, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0069] In a second aspect of the present application, the present application provides a battery module. According to an embodiment of the present application, the battery module includes the secondary battery described in the first aspect.

[0070] According to some specific embodiments of the present application, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0071] In a third aspect of the present application, the present application provides a battery pack. According to an embodiment of the present application, the battery pack is the battery module described in the second aspect.

[0072] According to some specific embodiments of the present application, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0073] In a fourth aspect of the present application, the present application proposes an electric device. According to an embodiment of the present application, the electric device includes at least one of the secondary battery described in the first aspect, the battery module described in the second aspect, and the battery pack described in the third aspect.

[0074] According to some specific embodiments of the present application, the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, an electric airplane toy, and the like, and the spacecraft may include an airplane, a rocket, a space shuttle, a spacecraft, and the like.

[0075] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. Wherein, the concentrated sulfuric acid used below is a concentrated sulfuric acid chemical with a mass fraction of 98%. In addition, if not explicitly stated, all reagents used in the following embodiments are commercially available, or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0076] Example 1

[0077] (1) Preparation of electrolyte: In an argon atmosphere glove box with a moisture content of ≤1ppm, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are uniformly stirred and mixed in a mass ratio of 1:1:1, and dry electrolyte lithium salt lithium hexafluorophosphate is dissolved in the solvent, and the lithium salt concentration is 1 mol / L; then vinylene carbonate, 1,3-propylene sultone (cyclic sulfonate compound), and 2-fluoropyridine (fluorinated nitrogen-containing heterocyclic compound) are added respectively, so that the final mass fractions are 3%, 0.5% (i.e., b1), and 0.8% (i.e., b2), respectively, and stirred and mixed uniformly to obtain an electrolyte;

[0078] (2) Preparation of positive electrode sheet: Mix the positive electrode active materials lithium iron phosphate (LiFePO4), lithium ferrite, lithium nickelate, conductive carbon black, and binder PVDF, with the mass ratio of lithium iron phosphate (LiFePO4), conductive carbon black, and binder PVDF being 94.6:1.2:1.5; then add N-methylpyrrolidone as a solvent to prepare a positive electrode slurry with a solid content of 60wt%, and stir evenly, then evenly coat the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and then dry to obtain a positive electrode active material layer, and after cold pressing, stripping, and cutting, obtain a positive electrode sheet. The single-sided thickness of the positive electrode active material layer is 100μm. Among them, the mass fractions of lithium ferrite and lithium nickelate in the positive electrode active material layer are 1.2% (i.e., a1) and 1.5% (i.e., a2), respectively;

[0079] (3) Preparation of negative electrode sheet: Mix the negative electrode active material artificial graphite, thickener sodium carboxymethyl cellulose, conductive carbon black and binder styrene butadiene rubber latex in a mass ratio of 96:2:1:1, add deionized water, prepare a negative electrode slurry with a solid content of 50wt%, and stir evenly. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and after drying, cold pressing, slitting and cutting, a negative electrode sheet is obtained. The single-sided thickness of the negative electrode active material layer is 70μm;

[0080] (4) Preparation of diaphragm: 16 μm polyethylene film was used as diaphragm;

[0081] (5) Battery assembly: stack the positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wind them into a bare battery cell; after welding the tabs, place the bare battery in an outer packaging shell, dry it, inject the above-mentioned electrolyte, and finally prepare the battery through vacuum packaging, standing, forming, shaping, etc.

[0082] Example 2

[0083] The difference between Example 2 and Example 1 is only that:

[0084] In step 1, the mass percentage of the cyclic sulfonate compound in the electrolyte is 1%; other contents are the same as those in Example 1.

[0085] Example 3

[0086] The difference between Example 3 and Example 1 is only that:

[0087] The mass percentage of the cyclic sulfonate compound in the electrolyte is 1.5%; other contents are the same as those in Example 1.

[0088] Example 4

[0089] The difference between Example 4 and Example 1 is only that:

[0090] The mass proportion of cyclic sulfonate compounds in the electrolyte is 1%; the mass proportion of lithium nickelate in the positive electrode active material layer is 2.3%;

[0091] The other contents are the same as those in Example 1.

[0092] Example 5

[0093] The difference between Example 5 and Example 1 is only that:

[0094] The mass proportion of the cyclic sulfonate compound in the electrolyte is 1%; the mass proportion of lithium ferrite in the positive electrode active material layer is 1.5%;

[0095] The other contents are the same as those in Example 1.

[0096] Example 6

[0097] The difference between Example 6 and Example 1 is only that:

[0098] The mass proportion of cyclic sulfonate compounds in the electrolyte is 1.5%; the mass proportion of lithium nickelate in the positive electrode active material layer is 2.3%;

[0099] The other contents are the same as those in Example 1.

[0100] Example 7

[0101] The difference between Example 7 and Example 1 is only that:

[0102] The mass proportion of the cyclic sulfonate compound in the electrolyte is 1%; the mass proportion of the fluorinated nitrogen-containing heterocyclic compound in the electrolyte is 0.3%; and the other contents are the same as those in Example 1.

[0103] Example 8

[0104] The difference between Example 8 and Example 1 is only that:

[0105] The mass proportion of the cyclic sulfonate compound in the electrolyte is 1%; the mass proportion of the fluorinated nitrogen-containing heterocyclic compound in the electrolyte is 1.5%; the other contents are the same as those in Example 1.

[0106] Example 9

[0107] The difference between Example 9 and Example 1 is only that:

[0108] The mass proportion of cyclic sulfonate compounds in the electrolyte is 1.7%; the mass proportion of lithium ferrite in the positive electrode active material layer is 2%;

[0109] The mass percentage of lithium nickelate in the positive electrode active material layer is 2.3%; other contents are the same as those in Example 1.

[0110] Example 10

[0111] The difference between Example 10 and Example 1 is only that:

[0112] The mass proportion of cyclic sulfonate compounds in the electrolyte is 0.4%; the mass proportion of fluorinated nitrogen-containing heterocyclic compounds in the electrolyte is 2%; the mass proportion of lithium ferrite in the positive electrode active material layer is 2%;

[0113] The mass percentage of lithium nickelate in the positive electrode active material layer is 1.2%; other contents are the same as those in Example 1.

[0114] Embodiment 11

[0115] The difference between Example 11 and Example 1 is that:

[0116] The mass proportion of cyclic sulfonate compounds in the electrolyte is 1.5%; the mass proportion of fluorinated nitrogen-containing heterocyclic compounds in the electrolyte is 0.6%; the mass proportion of lithium ferrite in the positive electrode active material layer is 1%;

[0117] The mass percentage of lithium nickel oxide in the positive electrode active material layer is 5%;

[0118] The other contents are the same as those in Example 1.

[0119] Example 12

[0120] The difference between Example 12 and Example 1 is only that:

[0121] The mass percentage of cyclic sulfonate compounds in the electrolyte is 1.5%; no fluorinated nitrogen-containing heterocyclic compounds are added;

[0122] The mass percentage of lithium nickel oxide in the positive electrode active material layer is 2.3%;

[0123] The other contents are the same as those in Example 1.

[0124] Comparative Example 1

[0125] The difference between Comparative Example 1 and Example 1 is only that:

[0126] The mass proportion of cyclic sulfonate compounds in the electrolyte is 3%; the mass proportion of lithium ferrite in the positive electrode active material layer is 0.8%;

[0127] The other contents are the same as those in Example 1.

[0128] Comparative Example 2

[0129] The difference between Comparative Example 2 and Example 1 is only that:

[0130] The mass percentage of cyclic sulfonate compounds in the electrolyte is 0.8%;

[0131] The mass percentage of lithium ferrite in the positive electrode active material layer is 5%;

[0132] The other contents are the same as those in Example 1.

[0133] Comparative Example 3

[0134] The difference between Comparative Example 3 and Example 1 is only that:

[0135] The mass percentage of cyclic sulfonate compounds in the electrolyte is 0.3%;

[0136] The mass percentage of fluorinated nitrogen-containing heterocyclic compounds in the electrolyte is 1.5%;

[0137] The mass percentage of lithium ferrite in the positive electrode active material layer is 0.5%;

[0138] The mass percentage of lithium nickel oxide in the positive electrode active material layer is 5%;

[0139] The other contents are the same as those in Example 1.

[0140] Comparative Example 4

[0141] The difference between Comparative Example 4 and Example 1 is only that:

[0142] The mass percentage of lithium ferrite in the positive electrode active material layer is 3%;

[0143] The mass percentage of lithium nickel oxide in the positive electrode active material layer is 0.5%;

[0144] The other contents are the same as those in Example 1.

[0145] Comparative Example 5

[0146] The difference between Comparative Example 5 and Example 1 is only that:

[0147] The mass percentage of lithium ferrite in the positive electrode active material layer is 5%;

[0148] The mass percentage of lithium nickel oxide in the positive electrode active material layer is 5%;

[0149] The other contents are the same as those in Example 1.

[0150] Comparative Example 6

[0151] The difference between Comparative Example 6 and Example 1 is only that:

[0152] The mass percentage of cyclic sulfonate compounds in the electrolyte is 1%;

[0153] The mass percentage of fluorinated nitrogen-containing heterocyclic compounds in the electrolyte is 2%;

[0154] The mass proportion of lithium ferrite in the positive electrode active material layer is 1%;

[0155] The mass proportion of lithium nickel oxide in the positive electrode active material layer is 1%;

[0156] The other contents are the same as those in Example 1.

[0157] The batteries prepared in Examples 1-12 and Comparative Examples 1-6 were subjected to charge and discharge cycle tests and overcharge tests, respectively, as follows:

[0158] Charge and discharge cycle test: The above battery is subjected to constant current charge and discharge cycle test on a charge and discharge instrument, the test temperature is 25°C, the charge and discharge rate is 1C (the size of the charge and discharge current is usually expressed by the charge and discharge rate, and the calculation formula of the charge and discharge current is: charge and discharge current = charge and discharge rate * rated capacity of the battery), and the charge and discharge voltage window is 2.5V~3.65V (that is, the battery's charge cut-off voltage is 3.65V, and the battery's discharge cut-off voltage is 2.5V; calculate the capacity retention rate and energy efficiency after 800 cycles, The calculation formula is: Capacity retention rate after the nth cycle = (discharge capacity after the nth cycle / discharge capacity of the first cycle) * 100%; Energy efficiency of the nth cycle = (discharge energy of the nth cycle / charge energy of the nth cycle) * 100%. Among them, a complete charge and discharge is usually called a charge and discharge cycle, that is, the battery is first charged from 2.5V to 3.65V, and then discharged from 3.65V to 2.5V, thus forming a charge and discharge cycle. Cycle N means repeating the above process N times.

[0159] Overcharge test: Take a fresh battery cell and attach a temperature sensor to the surface of the battery cell to monitor the temperature of the battery during overcharge. First, pre-treat the battery cell: discharge to 2.5V with a 1C constant current, then charge to 3.65V with a 1C constant current, and charge to 3.65V with a 0.05C constant voltage. After pre-treating, overcharge the battery cell: let it stand for 5 minutes, charge the battery cell with a 1C current, and charge to 5.475V or end the charging time when it reaches 1 hour. After the charging is completed, observe for 1 hour. During the entire charging process, monitor the temperature changes of the battery cell during the overcharge process through the temperature sensor on the surface of the battery cell.

[0160] The experimental results are shown in Table 1.

[0161] Table 1

[0162]

[0163]

[0164] Table 1

[0165]

[0166]

[0167] The results show that the batteries prepared in Examples 1-12 all exhibit good cycle stability, high energy efficiency and low cell surface temperature during overcharging.

[0168] By analyzing Examples 1-3 and Comparative Examples 1-2, it can be seen that when b1 / a1 is 0.83, the battery has the best capacity retention and energy efficiency performance after 800 cycles. When b1 / a1 decreases, the amount of lithium ferrite added is relatively large and the amount of cyclic sulfonate compounds added is relatively small. The cyclic sulfonate compounds are not enough to inhibit the formation and gas production of lithium ferrite, consume more electrolyte and produce more side reactions, resulting in deterioration of cycle capacity retention and energy efficiency. When b1 / a1 increases, the amount of lithium ferrite added is relatively small and the amount of cyclic sulfonate compounds added is relatively large. More cyclic sulfonate compounds are not needed to reduce the decomposition and gas production of lithium ferrite. Too much cyclic sulfonate compounds will cause the SEI film to form thicker, resulting in slower lithium ion migration and deterioration of energy efficiency during the cycle.

[0169] By analyzing Examples 4-6 and Comparative Examples 3-4, it can be seen that when (a1+b1) / a2 is 1.17, the cycle capacity retention, energy efficiency and safety performance are optimal. When (a1+b1) / a2 is small, the content of lithium ferrite and cyclic sulfonate compounds is relatively less than that of lithium nickelate, while lithium nickelate is relatively more. The decomposition products of cyclic sulfonate compounds during overcharging are insufficient to reduce the coverage on the surface of lithium nickelate, resulting in more Ni dissolving out of lithium nickelate and generating heat, leading to deterioration of safety performance, which is manifested as an increase in the maximum surface temperature when the battery cell is overcharged; when (a1+b1) / a2 is large, the content of lithium ferrite and cyclic sulfonate compounds is relatively high relative to that of lithium nickelate, while lithium nickelate is relatively less. The more decomposition products produced by cyclic sulfonate compounds are further decomposed during the cycle, resulting in an increase in the impedance on the negative electrode side and deterioration of energy efficiency during the cycle.

[0170] By analyzing Examples 7-9 and Comparative Examples 5-6, it can be seen that when (a1+a2) / b2 is 5.38, the safety performance and cycle energy efficiency performance of the battery are optimal. When (a1+a2) / b2 is small, the content of lithium ferrite and lithium nickelate is relatively small relative to the fluorinated nitrogen-containing heterocyclic compound, and the content of fluorinated nitrogen-containing heterocyclic compound is relatively large, which will cause the SEI film formed on the negative electrode surface during formation and later cycles to be thicker, the lithium ion migration rate to slow down, and the energy efficiency to deteriorate; when (a1+a2) / b2 is large, the content of lithium ferrite and lithium nickelate is relatively large relative to the fluorinated nitrogen-containing heterocyclic compound, and the content of fluorinated nitrogen-containing heterocyclic compound is relatively small, and a sufficiently dense SEI film cannot be formed on the negative electrode surface, and the protection of the negative electrode interface cannot be strengthened, resulting in lithium ferrite and lithium nickelate damaging the negative electrode interface and further generating heat, resulting in deterioration of safety performance.

[0171] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0172] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A secondary battery, characterized in that: The secondary battery comprises an electrolyte and a lithium supplement; The electrolyte includes a cyclic sulfonate compound containing an unsaturated double bond; The lithium supplement includes a first lithium supplement and a second lithium supplement; Wherein, the first lithium supplement comprises at least one of Li4FeO5, Li3N and Li2O; The second lithium supplement includes at least one of Li2MnO3, Li6CoO4, and Li2NiO2.

2. The secondary battery according to claim 1, characterized in that: The cyclic sulfonate compound containing an unsaturated double bond includes any one of the structures of Formula 1, Formula 2, and Formula 3; Wherein, R1, R2, and R3 are independently a hydrogen atom or a saturated alkane having 1 to 10 carbon atoms.

3. The secondary battery according to claim 1, characterized in that: The secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer is arranged on the positive electrode current collector, the mass proportion a1 of the first lithium replenisher in the positive electrode active material layer, the mass proportion a2 of the second lithium replenisher in the positive electrode active material layer, and the mass proportion b1 of the cyclic sulfonate compound containing an unsaturated double bond in the electrolyte satisfy:

4. The secondary battery according to claim 3, characterized in that: The mass proportion b1 of the cyclic sulfonate compound containing an unsaturated double bond in the electrolyte and the mass proportion a1 of the first lithium supplement in the positive electrode active material layer satisfy:

5. The secondary battery according to claim 3, characterized in that: The electrolyte also includes a fluorinated nitrogen-containing heterocyclic compound.

6. The secondary battery according to claim 5, characterized in that: The fluorinated nitrogen-containing heterocyclic compound includes at least one of 2-fluoropyridine, 2-fluoropyrazine, 2,6-difluoropyridine, 3-fluoropyridine, pentafluoropyridine, 2-fluoropyridazine, and 3-fluoropyridazine.

7. The secondary battery according to claim 5 or 6, characterized in that: The mass proportion a1 of the first lithium replenisher in the positive electrode active material layer, the mass proportion a2 of the second lithium replenisher in the positive electrode active material layer, and the mass proportion b2 of the fluorinated nitrogen-containing heterocyclic compound in the electrolyte satisfy:

8. A battery module, characterized in that: The battery module comprises the secondary battery according to any one of claims 1 to 7.

9. A battery pack, characterized in that: The battery pack includes the battery module according to claim 8.

10. An electrical device, characterized in that: The electrical equipment comprises at least one of the secondary battery according to any one of claims 1 to 7, the battery module according to claim 8, and the battery pack according to claim 9.

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