Energy storage device and electric device

Abstract

The application relates to an energy storage device and an electric equipment. The energy storage device comprises a positive pole piece, a diaphragm, a negative pole piece and an electrolyte; the positive pole piece comprises a positive active material; the electrolyte comprises a first type of additive and a second type of additive, wherein the first type of additive comprises an electron-accepting group-substituted nitrogen-containing heterocyclic compound, and the second type of additive comprises a bicyclic sulfate compound; the median particle size of the positive active material is denoted as D50 正 , and the unit is mu m; in the electrolyte, the percentage of the first type of additive in the total mass of the electrolyte is denoted as C1, and the percentage of the second type of additive in the total mass of the electrolyte is denoted as C2; the energy storage device satisfies: the numerical ratio of D50 正 / C2 is 100-250, and the numerical ratio of C2 / C1 is 0.7-1.5.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, specifically to an energy storage device and electrical equipment. Background Technology

[0002] Fossil fuels remain the primary mode of global energy consumption, making energy storage crucial for human development. Energy storage mainly includes physical energy storage and electrochemical energy storage. Among these, electrochemical energy storage has seen the most rapid growth in the past decade or so. Electrochemical energy storage utilizes chemical elements as the energy storage medium, with the charging and discharging process accompanied by chemical reactions or valence changes in the storage medium. Based on the storage device, electrochemical energy storage can be categorized into lithium-ion batteries, lead-acid batteries, lead-carbon batteries, flow batteries, and sodium-sulfur batteries. Lithium-ion batteries and lead-acid batteries are the most widely used electrochemical energy storage technologies in industrial applications.

[0003] With the rapid development of new energy technologies, the requirements for the cycle life and safety performance of energy storage batteries are becoming increasingly stringent. However, from a technical perspective, improving the safety performance of energy storage batteries usually leads to a deterioration in their dynamic performance, making it difficult to achieve a perfect compatibility between high safety performance and high dynamic performance. Summary of the Invention

[0004] To address the aforementioned issues, this application provides an energy storage device with high safety, excellent dynamic performance, and good cycle stability, which can supply power to electrical equipment.

[0005] One aspect of this application provides an energy storage device, comprising: a positive electrode, a diaphragm, a negative electrode, and an electrolyte;

[0006] The positive electrode sheet includes a positive active material;

[0007] The electrolyte includes a first type of additive and a second type of additive, wherein the first type of additive includes nitrogen-containing heterocyclic compounds substituted with electron-withdrawing groups, and the second type of additive includes bicyclic sulfate compounds.

[0008] The median particle size of the positive electrode active material is denoted as D50. 正 The unit is μm;

[0009] In the electrolyte, the percentage of the first type of additive in the total mass of the electrolyte is denoted as C1, and the percentage of the second type of additive in the total mass of the electrolyte is denoted as C2.

[0010] The energy storage device satisfies:

[0011] D50 正 The numerical ratio of C2 to C1 is 100 to 250, and the numerical ratio of C2 to C1 is 0.7 to 1.5.

[0012] Adding electron-withdrawing group-substituted nitrogen-containing heterocyclic compounds as the first-class additive (C1 by mass in the electrolyte) to the electrolyte can improve the heat resistance of the SEI film on the negative electrode side, reduce the heat generated by the decomposition of the SEI film during overcharging, and reduce the heat generated by the reaction between the solvent and lithium graphite after the SEI film decomposes. However, the SEI film formed by this additive is relatively dense, with a large interfacial impedance, resulting in a large negative electrode interfacial impedance and poor kinetic performance on the negative electrode side. Adding bicyclic sulfate compounds as the second-class additive (C2 by mass in the electrolyte) to the electrolyte can form films on the positive and negative electrode surfaces, and the resulting sulfur-containing inorganic lithium salts have high ionic conductivity, resulting in a smaller interfacial impedance on the positive and negative electrode sides, thus improving kinetic performance. However, this additive is prone to hydrolysis and acid production, which attacks the SEI film and can damage the cycle stability of the energy storage device.

[0013] This application utilizes nitrogen-containing heterocyclic compounds with substituted electronic groups and bicyclic sulfate compounds as additives in the electrolyte, and controls the median particle size D50 of the positive electrode active material. 正 The C2 / C1 ratio is between 100 and 250, ensuring minimal oxidation heat generation on the positive electrode side during overcharging. Furthermore, the second type of additive reduces the interfacial impedance of the positive electrode active material, thus guaranteeing good safety and kinetic performance on the positive electrode side. Additionally, controlling the C2 / C1 ratio to 0.7–1.5 improves the thermal stability of the SEI film on the negative electrode side, reducing heat generation during overcharging without worsening the interfacial impedance, thereby ensuring good safety and kinetic performance on the negative electrode side. Ultimately, this synergistic effect enables the energy storage device to possess both high safety and high kinetic performance, low heat generation, and excellent cycle stability.

[0014] In some implementations, the D50 正 The D50 of the positive electrode active material is controlled to be 0.5μm to 1.3μm. Using large-particle positive electrode active material can reduce heat generation from side reactions during overcharging and improve the safety performance of the positive electrode side, but it will deteriorate the cell's kinetic performance. The D50 of the positive electrode active material is controlled to be 0.5μm to 1.3μm, and the D50... 正 The C2 / C1 ratio is 100-250, and the C2 / C1 ratio is 0.7-1.5, which is beneficial to the synergistic effect of the positive electrode on safety and dynamic performance, thereby obtaining an energy storage device with high safety, excellent dynamic performance and good cycle stability.

[0015] In some embodiments, the positive electrode active material is lithium iron phosphate. Lithium iron phosphate has good stability, high safety, long lifespan, large capacity, and light weight. Using lithium iron phosphate as the positive electrode active material is beneficial for synergistically improving the safety and dynamic performance of the energy storage device, resulting in an energy storage device with high safety, excellent dynamic performance, and good cycle stability.

[0016] In some embodiments, the general structural formula of the nitrogen-containing heterocyclic compound substituted with the electron-withdrawing group is shown in formula (I):

[0017]

[0018] In this configuration, each X1 is independently C, CH, and N, Y1 is a halogen, and at least one X1 is C, which is connected to the Y1.

[0019] When nitrogen-containing heterocyclic compounds with electron-withdrawing groups as shown in formula (I) are used as electrolyte additives, they can easily form an SEI film containing electron-withdrawing groups and nitrogen on the negative electrode surface. This type of SEI film is dense and has high thermal stability. During overcharging, the decomposition of the negative electrode SEI film generates little heat, and the reaction between the solvent and the lithium conductive agent after the SEI film decomposes generates little heat.

[0020] In some embodiments, the electron-withdrawing group-substituted nitrogen-containing heterocyclic compound is selected from one or more of 2-fluoropyridine, 2,6-difluoropyridine, 3-fluoropyridine, pentafluoropyridine, 2-fluoropyrazine, 2-fluoropyridazine, and 3-fluoropyridazine. Using these electron-withdrawing group-substituted nitrogen-containing heterocyclic compounds as electrolyte additives facilitates the formation of an electron-withdrawing group and nitrogen-containing SEI film on the negative electrode surface. This type of SEI film is dense and has high thermal stability. During overcharging, the decomposition of the negative electrode SEI film generates less heat, and the reaction between the solvent and the lithium-ion conductive agent after SEI film decomposition also generates less heat, thereby ensuring good safety and kinetic performance on the negative electrode side.

[0021] In some embodiments, C1 is 0.01% to 2%. Using nitrogen-containing heterocyclic compounds with electron-withdrawing groups as electrolyte additives results in a denser SEI film with higher interfacial impedance, which is detrimental to rapid lithium-ion transport. If C1 is too low, the thermal stability of the SEI film on the negative electrode side is poor; if C1 is too high, the interfacial impedance is high, leading to poor kinetic performance. Therefore, controlling C1 to 0.01% to 2%, along with D50... 正 The C2 / C1 ratio is 100-250, and the C2 / C1 ratio is 0.7-1.5, which is beneficial to the safety and dynamic performance of the synergistic negative electrode, resulting in an energy storage device with high safety, excellent dynamic performance and good cycle stability.

[0022] In some embodiments, the general structural formula of the bicyclic sulfate compound is shown in formula (II) below:

[0023]

[0024] R1, R2, R3 and R4 are, respectively, hydrogen, C1 to C10 alkyl or phenyl.

[0025] Using the bicyclic sulfate ester compound shown in formula (II) as an electrolyte additive, it can form a film on the positive and negative electrode surfaces. The resulting sulfur-containing inorganic lithium salt exhibits high ionic conductivity, leading to lower interfacial impedance between the positive and negative electrodes, thereby improving kinetic performance. Compared to other commonly used sulfur additives, the bicyclic sulfate ester compound shown in formula (II) has two sulfate groups, contains a bicyclic structure, and has four easily broken CO bonds, resulting in higher reactivity, higher reduction potential, and lower oxidation potential. It is easier to form a film on the positive and negative electrode surfaces, and the resulting sulfur-containing interfacial film has high ion-conducting ability, increasing the migration rate of lithium ions between the positive and negative electrodes and improving kinetic performance.

[0026] In some embodiments, the bicyclic sulfate compound is selected from one or more compounds shown in formulas (II-1) and (II-2):

[0027]

[0028] When bicyclic sulfate compounds represented by formula (II-1) and / or formula (II-2) are used as electrolyte additives, they can easily form films on the positive and negative electrode surfaces, forming sulfur-rich SEI films. These SEI films have high ionic conductivity, which enhances the migration ability of lithium ions at the positive and negative electrode interfaces, thereby reducing the impedance of the interfacial film at the positive and negative electrodes and improving kinetic performance.

[0029] In some embodiments, C2 is 0.01% to 2%. Using bicyclic sulfate compounds as electrolyte additives can reduce the interfacial impedance between the positive and negative electrodes, thereby improving kinetic performance. However, these additives are prone to hydrolysis and acid production, which attacks the SEI film and can negatively impact the cycle stability of the energy storage device. Excessive C2 easily leads to hydrolysis and the production of HF acid, resulting in deteriorated cycle performance; insufficient C2 results in high interfacial impedance, significantly worsening cell kinetics. Therefore, C2 is controlled at 0.01% to 2%, along with D50... 正 The C2 / C1 ratio is 100-250, and the C2 / C1 ratio is 0.7-1.5, which is beneficial to the safety and dynamic performance of the synergistic negative electrode, resulting in an energy storage device with high safety, excellent dynamic performance and good cycle stability.

[0030] In some embodiments, the electrolyte further includes a third type of additive, which includes one or more of ethylene esters, sulfonates, and nitrile compounds. This third type of additive can form an excellent interfacial protective film on the electrode surface, reducing the reactivity of the electrode active material with the electrolyte and stabilizing the microstructure of the electrode active material, thereby improving the electrochemical performance of the energy storage device. Simultaneously, the formed solid electrolyte membrane has low impedance, which is beneficial for improving the internal kinetic characteristics of the energy storage device. Furthermore, when used in conjunction with the first and second types of additives, the third type of additive can form a film on the surface of the positive electrode active material, inhibiting particle breakage during cycling and reducing the dissolution of metal ions. It can also form an SEI film on the surface of the negative electrode material, inhibiting the reduction reaction and decomposition of the solvent in the electrolyte at the negative electrode interface, while also reducing interfacial impedance, thereby effectively improving the cycle stability of the energy storage device.

[0031] In some embodiments, the third type of additive includes one or more of the following: fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, ethylene sulfite, methylene disulfonate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, adiponitrile, succinate, and 1,3,6-hexanetrionitrile. These third type of additives can form a superior interfacial protective film on the electrode surface, reducing the reactivity between the electrode active material and the electrolyte and stabilizing the microstructure of the electrode active material, thereby improving the electrochemical performance of the energy storage device. Simultaneously, the formed solid electrolyte membrane has low impedance, which is beneficial for improving the internal kinetic characteristics of the energy storage device, thus more effectively enhancing the cycle stability of the energy storage device.

[0032] In some embodiments, the percentage of the third type of additive in the electrolyte by the total mass of the electrolyte is denoted as C3, where C3 is 1% to 4%. Controlling the amount of the third type of additive to 1% to 4% is beneficial to the synergistic effect of the energy storage device on safety and dynamic performance, resulting in an energy storage device with high safety, excellent dynamic performance, and good cycle stability.

[0033] In some embodiments, the sum of C1, C2, and C3 is 1% to 8%. Controlling the sum of the three additives to 1% to 8% is beneficial to the synergistic effect of the safety and dynamic performance of the energy storage device, resulting in an energy storage device with high safety, excellent dynamic performance, and good cycle stability.

[0034] In some embodiments, the electrolyte further includes a solvent and an electrolyte;

[0035] The solvent includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl acetate, ethyl propionate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and ethylene glycol dimethyl ether.

[0036] The electrolyte includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, and lithium perchlorate.

[0037] Using the aforementioned organic solvents as electrolytes results in lower viscosity, which improves the problem of insufficient wetting of the battery cell in the electrolyte, allowing the electrolyte to effectively wet the active materials. The lithium salts mentioned above possess advantages such as high solubility in organic solvents, good oxidation resistance, strong electrochemical stability, and high compatibility with positive and negative electrode materials, exhibiting excellent overall performance. Using these lithium salts as electrolytes is beneficial for synergistically improving the safety and kinetic performance of energy storage devices, resulting in energy storage devices with high safety, excellent kinetic performance, and good cycle stability.

[0038] A second aspect of this application provides an electrical appliance that includes an energy storage device as described above, the energy storage device supplying power to the electrical appliance. Detailed Implementation

[0039] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0042] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0043] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0044] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0045] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0046] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating 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.

[0047] Unless otherwise stated, a singular term may include a plural term and should not be understood as having a quantity of one.

[0048] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0049] In this application, "A and B are independently selected from x, y or z" means that A and B are independent events, and event A does not affect the occurrence of event B. Therefore, when A is selected from x, B can be selected from any one of x, y or z; when A is selected from y, B can be selected from any one of x, y or z; when A is selected from z, B can be selected from any one of x, y or z.

[0050] In this application, "alkyl" can mean straight-chain, branched, and / or cyclic alkyl. The number of carbon atoms in an alkyl group can be 1 to 50, 1 to 30, 1 to 20, 1 to 10, or 1 to 6. Phrases containing this term, such as "C1 to C9 alkyl," refer to alkyl groups containing 1 to 9 carbon atoms, and each time it appears, it can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, or C9 alkyl. Non-limiting examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, cyclohexyl, adamantane, etc.

[0051] In this application, "halogen" refers to elements in Group 7 of the periodic table, including fluorine, chlorine, bromine, iodine, and astatine.

[0052] In this application, the single bond connecting the substituents extends through the corresponding ring, indicating that the substituent can be attached to any position on the ring, for example... R2 is attached to any substituted site on the benzene ring.

[0053] With the rapid development of new energy technologies, the requirements for the cycle life and safety performance of energy storage batteries are becoming increasingly stringent. However, from a technical perspective, improving the safety performance of energy storage batteries usually leads to a deterioration in their dynamic performance, making it difficult to achieve a perfect compatibility between high safety performance and high dynamic performance.

[0054] To address the aforementioned issues, this application provides an energy storage device with high safety, excellent dynamic performance, and good cycle stability, which can supply power to electrical equipment.

[0055] The technical solution is as follows:

[0056] An energy storage device includes: a positive electrode, a separator, a negative electrode, and an electrolyte;

[0057] The positive electrode sheet includes a positive active material;

[0058] The electrolyte includes a first type of additive and a second type of additive, wherein the first type of additive includes nitrogen-containing heterocyclic compounds substituted with electron-withdrawing groups, and the second type of additive includes bicyclic sulfate compounds.

[0059] The median particle size of the positive electrode active material is denoted as D50. 正 The unit is μm;

[0060] In the electrolyte, the percentage of the first type of additive in the total mass of the electrolyte is denoted as C1, and the percentage of the second type of additive in the total mass of the electrolyte is denoted as C2.

[0061] The energy storage device satisfies:

[0062] D50 正 The numerical ratio of C2 to C1 is 100 to 250, and the numerical ratio of C2 to C1 is 0.7 to 1.5.

[0063] To improve the safety performance of energy storage devices, it is necessary to simultaneously enhance the safety performance of both the positive and negative electrode sides. To improve the safety performance of the positive electrode side, it is generally necessary to control the particle size of the positive electrode active material to reduce heat generation from side reactions during overcharging. On the negative electrode side, safety performance is improved by enhancing the thermal stability of the SEI film, reducing heat generation from SEI film decomposition, and minimizing heat generation from the reaction between the solvent and lithium-ionized graphite after SEI film damage. However, both of these safety improvement strategies lead to deterioration of the kinetic performance on both the positive and negative electrode sides, thus worsening the energy efficiency of the battery cell.

[0064] Specifically, adding electron-withdrawing groups to the electrolyte as a first-class additive (C1 by mass percentage in the electrolyte) readily forms an electron-withdrawing group- and nitrogen-containing SEI film on the negative electrode surface. This improves the heat resistance of the SEI film on the negative electrode side, reduces the heat generated by the decomposition of the SEI film during overcharging, and reduces the heat generated by the reaction between the solvent and lithium graphite after SEI film decomposition. However, the SEI film formed by this additive is relatively dense, with a large interfacial impedance, resulting in a high negative electrode interfacial impedance, which is not conducive to the rapid transport of lithium ions and leads to poor kinetic performance on the negative electrode side. Adding bicyclic sulfate compounds as a second-class additive (C2 by mass percentage in the electrolyte) can form films on both the positive and negative electrode surfaces and form sulfur-containing inorganic lithium salts with high ionic conductivity, resulting in a smaller interfacial impedance between the positive and negative electrodes, thus improving kinetic performance. However, this additive is prone to hydrolysis and acid production, which attacks the SEI film and can damage the cycle stability of the energy storage device.

[0065] When D50 正When the ratio of C2 to D50 is small, there are more side reactions in the positive electrode active material particles, resulting in poor safety performance. Furthermore, the higher content of bicyclic sulfate ester additives makes them more prone to hydrolysis, producing HF acid and leading to deterioration in cycle performance. 正 When the C2 / C1 ratio is large, the positive electrode active material particles are larger, resulting in poor kinetic performance. Meanwhile, the content of bicyclic sulfate ester additives is low, leading to higher interfacial impedance and a significant deterioration in cell kinetics. When the C2 / C1 ratio is high, the C1 content is low, resulting in poor thermal stability of the SEI film on the negative electrode side. Furthermore, the high C2 content makes it easier for acid to form and damage the SEI film, which is detrimental to cycling. When the C2 / C1 ratio is low, the C2 content is low, and the C1 content is high, resulting in higher interfacial impedance, which is unfavorable for rapid lithium-ion transport and leads to poor kinetic performance.

[0066] This application utilizes nitrogen-containing heterocyclic compounds with substituted electronic groups and bicyclic sulfate compounds as additives in the electrolyte, and controls the median particle size D50 of the positive electrode active material. 正 The C2 / C1 ratio is 100–250 to ensure minimal oxidation heat generation on the positive electrode side during overcharging. Furthermore, the second type of additive reduces the interfacial impedance of the positive electrode active material, thus ensuring good safety and kinetic performance on the positive electrode side. Additionally, controlling the C2 / C1 ratio to 0.7–1.5 improves the thermal stability of the SEI film on the negative electrode side, reduces heat generation during overcharging, and does not worsen the interfacial impedance on the negative electrode side, thereby ensuring good safety and kinetic performance on the negative electrode side.

[0067] It is evident that this application improves the safety performance of both the negative and positive electrode sides while also taking into account the dynamic performance of both sides, thereby enhancing the cycle performance without deteriorating the cell's dynamic performance. Ultimately, this synergistically enables the energy storage device to possess both high safety and high dynamic performance, with low heat generation and excellent cycle stability.

[0068] Understandably, the median particle size D50 of the positive electrode active material 正 The numerical ratio to C2 is 100 to 250, including but not limited to 100, 120, 130, 150, 180, 200, 220 or 250.

[0069] Understandably, C2 / C1 is 0.7 to 1.5, including but not limited to 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5.

[0070] The positive electrode, diaphragm, negative electrode, and electrolyte in the energy storage device of this application are described below.

[0071] (1) Positive electrode plate:

[0072] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active layer disposed on the surface of the positive current collector;

[0073] The positive electrode active layer includes the positive electrode active material, positive electrode conductive agent, and positive electrode binder as described above.

[0074] In some embodiments, the positive current collector is selected from metal foil or porous metal plate. Preferably, the current collector is metal foil, such as copper foil or aluminum foil, and more preferably aluminum foil.

[0075] In some implementations, the D50 正 The D50 of the positive electrode active material is controlled to be 0.5μm to 1.3μm. Using large-particle positive electrode active material can reduce heat generation from side reactions during overcharging and improve the safety performance of the positive electrode side, but it will deteriorate the cell's kinetic performance. The D50 of the positive electrode active material is controlled to be 0.5μm to 1.3μm, and the D50... 正 The C2 / C1 ratio is 100-250, and the C2 / C1 ratio is 0.7-1.5, which is beneficial to the synergistic effect of the positive electrode on safety and dynamic performance, thereby obtaining an energy storage device with high safety, excellent dynamic performance and good cycle stability.

[0076] Understandably, in this application, the D50 is... 正 Including but not limited to 0.5μm, 0.6μm, 0.68μm, 0.7μm, 0.8μm, 0.9μm, 0.95μm, 1.0μm, 1.1μm, 1.2μm, 1.233μm, or 1.3μm. Further, the D50... 正 The thickness ranges from 0.6 μm to 1.3 μm. Furthermore, the D50... 正 The range is 0.8μm to 1.3μm.

[0077] In some embodiments, the positive electrode active material is lithium iron phosphate. Lithium iron phosphate has good stability, high safety, long lifespan, large capacity, and light weight. Using lithium iron phosphate as the positive electrode active material is beneficial for synergistically improving the safety and dynamic performance of the energy storage device, resulting in an energy storage device with high safety, excellent dynamic performance, and good cycle stability.

[0078] In one embodiment, the positive electrode conductive agent is selected from one or a mixture of several of acetylene black, graphene, carbon nanotubes and conductive carbon black (SP).

[0079] In one embodiment, the positive electrode binder is selected from one or a mixture of several of polyvinylidene fluoride (PVDF), polyimide (PI), polyacrylic acid (PAA), and polytetrafluoroethylene (PTFE).

[0080] In some embodiments, the positive electrode active layer contains, independently, 85% to 98% by mass of the positive electrode active material, 0.2% to 5% by mass of the positive electrode conductive agent, and 1% to 10% by mass of the positive electrode binder.

[0081] Understandably, in the positive electrode active layer, the mass percentage of the positive electrode active material is 85% to 98%, including but not limited to 85%, 90%, 92%, 93%, 94%, 94.5%, or 98%; the mass percentage of the positive electrode conductive agent is 0.2% to 5%, including but not limited to 0.2%, 0.5%, 1%, 2%, 3%, 3.2%, 3.5%, 3.6%, 3.8%, 4.0%, 4.5%, or 5%; and the mass percentage of the positive electrode binder is 1% to 10%, including but not limited to 1%, 2%, 2.3%, 2.5%, 3%, 3.5%, 3.8%, 4.0%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0082] (2) Diaphragm:

[0083] In some embodiments, the diaphragm is made of polypropylene (PP) or polyethylene (PE).

[0084] (3) Negative electrode plate:

[0085] In some embodiments, the negative electrode sheet includes: a negative current collector and at least one negative active layer disposed on the surface of the negative current collector, the negative active layer including a negative active material, a negative conductive agent, and a negative binder. Further, in each of the active layers, the mass percentage of the negative active material is independently 85% to 98%, the mass percentage of the negative conductive agent is independently 0.2% to 5%, and the mass percentage of the negative binder is independently 1% to 10%.

[0086] Understandably, in the negative electrode active layer, the mass percentage of the negative electrode active material is 85% to 98%, including but not limited to 85%, 90%, 92%, 93%, 94%, 94.5%, or 98%; the mass percentage of the negative electrode conductive agent is 0.2% to 5%, including but not limited to 0.2%, 0.5%, 1%, 2%, 3%, 3.2%, 3.5%, 3.6%, 3.8%, 4.0%, 4.5%, or 5%; and the mass percentage of the negative electrode binder is 1% to 10%, including but not limited to 1%, 2%, 2.3%, 2.5%, 3%, 3.5%, 3.8%, 4.0%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0087] In some embodiments, each of the negative electrode conductive agents is selected from at least one of carbon nanotubes, carbon nanofibers, conductive graphite, graphene, acetylene black, and carbon black, which have the advantages of high conductivity and low resistance. Further, the carbon black is selected from at least one of Ketjen black, channel black, furnace black, and hot-dip galvanized black.

[0088] In some embodiments, the negative electrode binder is selected from at least one of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid, and polyacrylate. These binders can better adhere and retain the negative electrode active material on the current collector, enhance the electronic contact between the negative electrode active material and the conductive agent, and between the negative electrode active material and the current collector, and can better perform the effects of dispersion, thickening, suspension, bonding, and facilitating lithium-ion transport. Preferably, the negative electrode binder is sodium carboxymethyl cellulose (CMC), or one or a mixture of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0089] In some embodiments, the negative current collector is selected from metal foil or porous metal plate. Preferably, the current collector is metal foil, such as copper foil or aluminum foil, and more preferably copper foil.

[0090] (4) Electrolyte:

[0091] In some embodiments, the general structural formula of the nitrogen-containing heterocyclic compound substituted with the electron-withdrawing group is shown in formula (I):

[0092]

[0093] In this configuration, each X1 is independently C, CH, and N, Y1 is a halogen, and at least one X1 is C, which is connected to the Y1.

[0094] When nitrogen-containing heterocyclic compounds with electron-withdrawing groups as shown in formula (I) are used as electrolyte additives, they can easily form an SEI film containing electron-withdrawing groups and nitrogen on the negative electrode surface. This type of SEI film is dense and has high thermal stability. During overcharging, the decomposition of the negative electrode SEI film generates little heat, and the reaction between the solvent and the lithium conductive agent after the SEI film decomposes generates little heat.

[0095] In some embodiments, X1 in formula (I) is N, and the nitrogen-containing heterocyclic compound is pyridine.

[0096] In some embodiments, one of X1 in formula (I) is N, and the nitrogen-containing heterocyclic compound is pyrazine, pyridazine, or pyrimidine.

[0097] In some embodiments, Y1 is fluorine, chlorine, bromine, or iodine. Further, Y1 is fluorine.

[0098] In some embodiments, the electron-withdrawing group-substituted nitrogen-containing heterocyclic compound is selected from one or more of 2-fluoropyridine, 2,6-difluoropyridine, 3-fluoropyridine, pentafluoropyridine, 2-fluoropyrazine, 2-fluoropyridazine, and 3-fluoropyridazine. Using these electron-withdrawing group-substituted nitrogen-containing heterocyclic compounds as electrolyte additives facilitates the formation of an electron-withdrawing group and nitrogen-containing SEI film on the negative electrode surface. This type of SEI film is dense and has high thermal stability. During overcharging, the decomposition of the negative electrode SEI film generates less heat, and the reaction between the solvent and the lithium-ion conductive agent after SEI film decomposition also generates less heat, thereby ensuring good safety and kinetic performance on the negative electrode side.

[0099] In some embodiments, C1 is 0.01% to 2%. Using nitrogen-containing heterocyclic compounds with electron-withdrawing groups as electrolyte additives results in a denser SEI film with higher interfacial impedance, which is detrimental to rapid lithium-ion transport. If C1 is too low, the thermal stability of the SEI film on the negative electrode side is poor; if C1 is too high, the interfacial impedance is high, leading to poor kinetic performance. Therefore, controlling C1 to 0.01% to 2%, along with D50... 正 The C2 / C1 ratio is 100-250, and the C2 / C1 ratio is 0.7-1.5, which is beneficial to the safety and dynamic performance of the synergistic negative electrode, resulting in an energy storage device with high safety, excellent dynamic performance and good cycle stability.

[0100] Understandably, C1 is 0.01% to 2%, including but not limited to 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.1%, 1.2%, 1.5%, 1.8% or 2%.

[0101] In some embodiments, the general structural formula of the bicyclic sulfate compound is shown in formula (II) below:

[0102]

[0103] R1, R2, R3 and R4 are, respectively, hydrogen, C1 to C10 alkyl or phenyl.

[0104] Using the bicyclic sulfate ester compound shown in formula (II) as an electrolyte additive, it can form a film on the positive and negative electrode surfaces. The resulting sulfur-containing inorganic lithium salt exhibits high ionic conductivity, leading to lower interfacial impedance between the positive and negative electrodes, thereby improving kinetic performance. Compared to other commonly used sulfur additives, the bicyclic sulfate ester compound shown in formula (II) has two sulfate groups, contains a bicyclic structure, and has four easily broken CO bonds, resulting in higher reactivity, higher reduction potential, and lower oxidation potential. It is easier to form a film on the positive and negative electrode surfaces, and the resulting sulfur-containing interfacial film has high ion-conducting ability, increasing the migration rate of lithium ions between the positive and negative electrodes and improving kinetic performance.

[0105] Understandably, in this application, R1, R2, R3, and R4 are each independently hydrogen, C1-C10 alkyl, or phenyl. Without limitation, R1, R2, R3, and R4 are each independently hydrogen, C1-C10 straight-chain alkyl, C3-C10 branched-chain alkyl, C3-C10 cyclic alkyl, or phenyl. Further, R1, R2, R3, and R4 are each independently hydrogen, C1-C10 straight-chain alkyl, or C3-C10 branched-chain alkyl. Even further, R1, R2, R3, and R4 are each independently hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, or isobutyl.

[0106] In some embodiments, the bicyclic sulfate compound is selected from one or more compounds shown in formulas (II-1) and (II-2):

[0107]

[0108] When bicyclic sulfate compounds represented by formula (II-1) and / or formula (II-2) are used as electrolyte additives, they can easily form films on the positive and negative electrode surfaces, forming sulfur-rich SEI films. These SEI films have high ionic conductivity, which enhances the migration ability of lithium ions at the positive and negative electrode interfaces, thereby reducing the impedance of the interfacial film at the positive and negative electrodes and improving kinetic performance.

[0109] In some embodiments, C2 is 0.01% to 2%. Using bicyclic sulfate compounds as electrolyte additives can reduce the interfacial impedance between the positive and negative electrodes, thereby improving kinetic performance. However, these additives are prone to hydrolysis and acid production, which attacks the SEI film and can negatively impact the cycle stability of the energy storage device. Excessive C2 easily leads to hydrolysis and the production of HF acid, resulting in deteriorated cycle performance; insufficient C2 results in high interfacial impedance, significantly worsening cell kinetics. Therefore, C2 is controlled at 0.01% to 2%, along with D50... 正The C2 / C1 ratio is 100-250, and the C2 / C1 ratio is 0.7-1.5, which is beneficial to the safety and dynamic performance of the synergistic negative electrode, resulting in an energy storage device with high safety, excellent dynamic performance and good cycle stability.

[0110] Understandably, C2 is 0.01% to 2%, including but not limited to 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.1%, 1.2%, 1.5%, 1.8% or 2%.

[0111] In some embodiments, the electrolyte further includes a third type of additive, which includes one or more of ethylene esters, sulfonates, and nitrile compounds. This third type of additive can form an excellent interfacial protective film on the electrode surface, reducing the reactivity of the electrode active material with the electrolyte and stabilizing the microstructure of the electrode active material, thereby improving the electrochemical performance of the energy storage device. Simultaneously, the formed solid electrolyte membrane has low impedance, which is beneficial for improving the internal kinetic characteristics of the energy storage device. Furthermore, when used in conjunction with the first and second types of additives, the third type of additive can form a film on the surface of the positive electrode active material, inhibiting particle breakage during cycling and reducing the dissolution of metal ions. It can also form an SEI film on the surface of the negative electrode material, inhibiting the reduction reaction and decomposition of the solvent in the electrolyte at the negative electrode interface, while also reducing interfacial impedance, thereby effectively improving the cycle stability of the energy storage device.

[0112] In some embodiments, the third type of additive includes one or more of the following: fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, ethylene sulfite, methylene disulfonate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, adiponitrile, succinate, and 1,3,6-hexanetrionitrile. These third type of additives can form a superior interfacial protective film on the electrode surface, reducing the reactivity between the electrode active material and the electrolyte and stabilizing the microstructure of the electrode active material, thereby improving the electrochemical performance of the energy storage device. Simultaneously, the formed solid electrolyte membrane has low impedance, which is beneficial for improving the internal kinetic characteristics of the energy storage device, thus more effectively enhancing the cycle stability of the energy storage device.

[0113] In some embodiments, the percentage of the third type of additive in the electrolyte by the total mass of the electrolyte is denoted as C3, where C3 is 1% to 4%. Controlling the amount of the third type of additive to 1% to 4% is beneficial to the synergistic effect of the energy storage device on safety and dynamic performance, resulting in an energy storage device with high safety, excellent dynamic performance, and good cycle stability.

[0114] Understandably, C3 is 1% to 4%, including but not limited to 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, or 4%.

[0115] In some embodiments, the sum of C1, C2, and C3 is 1% to 8%. Controlling the sum of the three additives to 1% to 8% is beneficial to the synergistic effect of the safety and dynamic performance of the energy storage device, resulting in an energy storage device with high safety, excellent dynamic performance, and good cycle stability.

[0116] In some embodiments, the electrolyte further includes a solvent and an electrolyte;

[0117] The solvent includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl acetate, ethyl propionate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and ethylene glycol dimethyl ether.

[0118] The electrolyte includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, and lithium perchlorate.

[0119] Using the aforementioned organic solvents as electrolytes results in lower viscosity, which improves the problem of insufficient wetting of the battery cell in the electrolyte, allowing the electrolyte to effectively wet the active materials. The lithium salts mentioned above possess advantages such as high solubility in organic solvents, good oxidation resistance, strong electrochemical stability, and high compatibility with positive and negative electrode materials, exhibiting excellent overall performance. Using these lithium salts as electrolytes is beneficial for synergistically improving the safety and kinetic performance of energy storage devices, resulting in energy storage devices with high safety, excellent kinetic performance, and good cycle stability.

[0120] Optionally, the energy storage device described in this application is a battery. Further, the battery is a lithium-ion battery.

[0121] In one embodiment, the battery is selected from one of button cells, pouch cells, prismatic cells, and cylindrical cells.

[0122] This application also provides a method for preparing the energy storage device as described above, comprising the following steps:

[0123] (1) Preparation of the positive electrode sheet:

[0124] The positive electrode active material, positive electrode conductive agent and positive electrode binder are mixed in a solvent, stirred evenly, and then uniformly coated onto the positive electrode current collector. After drying, the positive electrode sheet is obtained.

[0125] (2) Preparation of negative electrode sheet:

[0126] A negative electrode active slurry is provided, wherein the components of the negative electrode active slurry include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder;

[0127] The negative electrode active slurry is coated onto the negative electrode current collector, and after drying, the negative electrode sheet is obtained.

[0128] (3) Preparation of electrolyte:

[0129] The electrolyte, the first type of additive, and the second type of additive are mixed in a solvent to prepare an electrolyte solution. For electrolyte solutions containing a third type of additive, the step of mixing the third type of additive with the solvent is also included.

[0130] (4) Provide a diaphragm.

[0131] (5) Assembly:

[0132] The positive electrode, negative electrode, separator, and electrolyte are assembled into a battery cell.

[0133] This application also provides an electrical device including the energy storage device described above, wherein the energy storage device supplies power to the electrical device. It is understood that the electrical device described in this application has the beneficial effects of the energy storage device described above, which will not be repeated here. Optionally, the electrical device may include an energy storage system composed of multiple energy storage devices described above. Optionally, the electrical device may be a lighting fixture, etc.

[0134] The present application will be described below through specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present application in any way. In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used can be obtained commercially.

[0135] Example 1

[0136] This embodiment provides a lithium battery and its preparation method, as detailed below:

[0137] (1) Preparation of the positive electrode sheet:

[0138] Lithium iron phosphate (LiFePO4), conductive carbon black (SP), and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone (NMP) solvent and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry had a ratio of LiFePO4:PVDF:conductive carbon black of 97.2%:2.3%:0.5%. The positive electrode slurry was coated onto aluminum foil used as a positive electrode current collector. The unit area of ​​the positive electrode slurry was 1540.25 mm². 2The coating weight is 254mg. After drying, cold pressing, slitting and cutting, the positive electrode sheet is obtained.

[0139] (2) Preparation of negative electrode sheet:

[0140] Artificial graphite (anode active material), conductive carbon (SP), thickener (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain a cathode slurry. The cathode slurry was then coated onto the copper foil of the cathode current collector. The unit area of ​​the cathode slurry was 1540.25 mm². 2 The coating weight is 122mg. After drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.

[0141] (3) Preparation of electrolyte:

[0142] In an argon atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are mixed in a mass ratio of 1:1:1. Additives of type I, type II, and type III are added according to the design in Table 1. Then, the dried electrolyte lithium salt lithium hexafluorophosphate is dissolved in the solvent and stirred until completely dissolved and homogeneous. The lithium salt concentration is 1mol / L.

[0143] (4) Preparation of the diaphragm:

[0144] A polyethylene film with a thickness of 16μm was selected as the diaphragm.

[0145] (5) Battery assembly:

[0146] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator in the middle separating the positive and negative electrodes. After winding, the bare cell is assembled into an outer packaging after welding tabs. The prepared electrolyte is then injected, and the cell is encapsulated, left to stand, formed, shaped, and tested for capacity. Finally, a soft-pack lithium-ion battery with a capacity of 3.2Ah is prepared.

[0147] Example 2

[0148] This embodiment is basically the same as Embodiment 1, except that the amount of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0149] Example 3

[0150] This embodiment is basically the same as Embodiment 1, except that the amount of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0151] Example 4

[0152] This embodiment is basically the same as Embodiment 1, except that the D50 of lithium iron phosphate is different, the amount of the second type of additive C2 is different, and the D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0153] Example 5

[0154] This embodiment is basically the same as embodiment 4, except that the types of the first type of additives are different, as shown in Table 1.

[0155] Example 6

[0156] This embodiment is basically the same as embodiment 5, except that the types of the second type of additives are different, as shown in Table 1.

[0157] Example 7

[0158] This embodiment is basically the same as Embodiment 6, except that the dosage of the first type of additive C1 is different, the dosage of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0159] Example 8

[0160] This embodiment is basically the same as Embodiment 6, except that the dosage of the first type of additive C1 is different, the dosage of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0161] Example 9

[0162] This embodiment is basically the same as Embodiment 6, except that the dosage of the first type of additive C1 is different, the dosage of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0163] Example 10

[0164] This embodiment is basically the same as Embodiment 1, except that the D50 of lithium iron phosphate is different. 正 The numerical ratios of / C2 are different, as shown in Table 1.

[0165] Example 11

[0166] This embodiment is basically the same as Embodiment 1, except that the types of the third type of additives are different, as shown in Table 1.

[0167] Example 12

[0168] This embodiment is basically the same as Embodiment 1, except that the D50 of lithium iron phosphate is different. 正 The numerical ratios of / C2 are different, as shown in Table 1.

[0169] Example 13

[0170] This embodiment is basically the same as Embodiment 1, except that the positive electrode active material is lithium manganese iron phosphate.

[0171] Comparative Example 1

[0172] This comparative example is basically the same as Example 1, except that the first type of additive is omitted and the amount of the first additive in Example 1 is supplemented to the third type of additive, as shown in Table 1.

[0173] Comparative Example 2

[0174] This comparative example is basically the same as Example 1, except that the first type of additive is omitted and the amount of the first additive in Example 1 is supplemented to the amount of the second type of additive, as shown in Table 1.

[0175] Comparative Example 3

[0176] This comparative example is basically the same as Example 1, except that the first type of additive is omitted and the amount of the first additive in Example 1 is supplemented to the second and third types of additives, as shown in Table 1.

[0177] Comparative Example 4

[0178] This comparative example is basically the same as Example 1, except that the second type of additive is omitted and the amount of the second additive in Example 1 is supplemented to the amount of the third additive, as shown in Table 1.

[0179] Comparative Example 5

[0180] This comparative example is basically the same as Example 1, except that the second type of additive is omitted and the amount of the second additive in Example 1 is supplemented to the amount of the first type of additive, as shown in Table 1.

[0181] Comparative Example 6

[0182] This comparative example is basically the same as Example 1, except that the second type of additive is omitted and the amount of the second additive in Example 1 is supplemented to the first and third types of additives, as shown in Table 1.

[0183] Comparative Example 7

[0184] This comparative example is basically the same as Example 1, except that the first and second additives are omitted, and the amounts of the first and second additives in Example 1 are supplemented to the third additive, as shown in Table 1.

[0185] Comparative Example 8

[0186] This comparative example is basically the same as Example 1, except that: D50 正 Different, D50 正 The numerical ratios of / C2 are different, as shown in Table 1.

[0187] Comparative Example 9

[0188] This comparative example is basically the same as Example 1, except that the amount of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0189] Comparative Example 10

[0190] This comparative example is basically the same as Example 1, except that the amount of the second type of additive C2 is different, and D50 is different. 正 The numerical ratios of C2 and C1 are different, as detailed in Table 1.

[0191] test:

[0192] (1) Battery overcharge test: Take a fresh battery cell and attach a temperature sensing wire to the surface of the cell to monitor the battery temperature during overcharge. First, perform pretreatment by discharging with a constant current of 1C to 2.5V, then charging with a constant current of 1C to 3.65V, and then charging with a constant voltage of 0.05C to 3.65V. After standing for 5 minutes, charge the cell with a current of 1C until it reaches 5.475V or the charging time reaches 1 hour. After the charging is completed, observe for 1 hour to monitor the battery surface temperature. The results are shown in Table 1.

[0193] (2) Battery cycle test: The battery was charged and discharged at a current of 0.5C in a voltage window of 2.5-3.65V. The energy of each charge and discharge cycle was recorded. The energy efficiency of each cycle was the ratio of the discharge energy to the charging energy. The results are shown in Table 1.

[0194] In addition, the second category of additives in Table 1 are

[0195] Table 1

[0196]

[0197]

[0198] As shown in Table 1, compared with Comparative Examples 1 to 10, the batteries of Examples 1 to 13 of this application generate less heat during overcharging and have better kinetic performance and better cycle performance.

[0199] As can be seen from Comparative Examples 1 to 7 and Example 1, in this application, the first type of additive and the second type of additive are used in combination and work synergistically to improve the thermal stability of the SEI film on the negative electrode side and reduce heat generation during overcharging, while not deteriorating the interface impedance on the negative electrode side. This ensures that the negative electrode side has good safety and kinetic performance, and ultimately the synergistic effect enables the battery to have both high safety and high kinetic performance, low heat generation, and excellent cycle stability.

[0200] As can be seen from Comparative Examples 8 to 10 and Example 1, in this application, controlling D50 正 The C2 / C1 ratio is between 100 and 250 to ensure minimal oxidation heat generation on the positive electrode side during overcharging and to reduce the interfacial impedance of the positive electrode active material, thereby ensuring good safety and kinetic performance on the positive electrode side. Simultaneously, controlling the C2 / C1 ratio to 0.7–1.5 improves the thermal stability of the SEI film on the negative electrode side, reduces heat generation during overcharging, and does not worsen the interfacial impedance on the negative electrode side, thus ensuring good safety and kinetic performance on the negative electrode side. Ultimately, this synergistic effect results in a battery that combines high safety and high kinetic performance, low heat generation, excellent cycle stability, and a D50 rating. 正 If the values ​​of C2 and C2 / C1 are too large or too small, it will be detrimental to the safety and dynamic performance of the synergistic battery.

[0201] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0202] The embodiments described above merely illustrate several implementation methods of this application to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An energy storage device, characterized in that, include: Positive electrode, separator, negative electrode, and electrolyte; The positive electrode sheet includes a positive active material; The electrolyte includes a first type of additive and a second type of additive, wherein the first type of additive includes nitrogen-containing heterocyclic compounds substituted with electron-withdrawing groups, and the second type of additive includes bicyclic sulfate compounds; the general structural formula of the nitrogen-containing heterocyclic compounds substituted with electron-withdrawing groups is shown in formula (I) below: （I）； In this configuration, each X1 is independently C, CH, and N, Y1 is a halogen, and at least one X1 is C, which is connected to the Y1. The bicyclic sulfate compounds are selected from one or more compounds shown in formulas (II-1) and (II-2): (II-1) (II-2); The median particle size of the positive electrode active material is denoted as D50. 正 The unit is μm; In the electrolyte, the percentage of the first type of additive in the total mass of the electrolyte is denoted as C1, and the percentage of the second type of additive in the total mass of the electrolyte is denoted as C2. The energy storage device satisfies: D50 正 The numerical ratio of / C2 is 100~250, and the D50 正 The thickness ranges from 0.5 μm to 1.3 μm, and the numerical ratio of C2 to C1 is 0.7 to 1.

5.

2. The energy storage device according to claim 1, characterized in that, The electron-withdrawing group-substituted nitrogen-containing heterocyclic compound is selected from one or more of 2-fluoropyridine, 2,6-difluoropyridine, 3-fluoropyridine, pentafluoropyridine, 2-fluoropyrazine, 2-fluoropyridazine, and 3-fluoropyridazine.

3. The energy storage device according to claim 1, characterized in that, The positive electrode active material is one or two of lithium iron phosphate, lithium manganese iron phosphate, and lithium nickel cobalt manganese oxide.

4. The energy storage device according to any one of claims 1 to 3, characterized in that, Satisfy one or more of the conditions in (1) to (2): (1) The C1 is 0.01%~2%; (2) The C2 is 0.01%~2%.

5. The energy storage device according to any one of claims 1 to 3, characterized in that, The electrolyte also includes a third type of additive, which includes one or more of ethylene esters, sulfonates, and nitrile compounds.

6. The energy storage device according to claim 5, characterized in that, The third type of additives includes one or more of the following: fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, ethylene sulfite, methylene disulfonate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, adiponitrile, succinate, and 1,3,6-hexanetrionitrile.

7. The energy storage device according to claim 5, characterized in that, In the electrolyte, the percentage of the third type of additive in the total mass of the electrolyte is denoted as C3, where C3 is 1% to 4%.

8. The energy storage device according to claim 7, characterized in that, The sum of C1, C2, and C3 is 1% to 8%.

9. The energy storage device according to any one of claims 1 to 3, characterized in that, The electrolyte also includes a solvent and an electrolyte; The solvent includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl acetate, ethyl propionate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and ethylene glycol dimethyl ether. The electrolyte includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium trifluoromethanesulfonate, and lithium perchlorate.

10. An electrical appliance, characterized in that, The device includes the energy storage device according to any one of claims 1 to 9, wherein the energy storage device supplies power to the electrical equipment.

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