Secondary battery and electric device

Abstract

The application discloses a secondary battery and an electric device. The secondary battery comprises a negative electrode sheet and an electrolyte. The negative electrode sheet comprises a negative electrode active material, and the negative electrode active material comprises a silicon-based material and graphite. The electrolyte comprises a solvent and an additive. The solvent comprises propylene carbonate, and the additive comprises a fluorobenzene compound and an unsaturated sulfur-containing organic compound. The unsaturated sulfur-containing organic compound comprises a sulfur-containing heterocyclic structure and branched chains connected to the sulfur-containing heterocyclic structure, wherein one or more branched chains contain an unsaturated group, and the sulfur-containing heterocyclic structure has a thioester group or a sulfate group. The application is beneficial to improving the cycle performance of the battery.

Description

Technical Field

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

[0002] Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in military equipment and aerospace and other fields.

[0003] The development of rechargeable batteries has not only driven technological progress within the battery itself but also supported development in various fields. Improving battery life is crucial not only for enhancing battery performance but also for its profound impact on related industries, technological innovation, and sustainable development. Currently, some rechargeable batteries face significant lifespan limitations. Summary of the Invention

[0004] The first aspect of this application provides a secondary battery, including a negative electrode sheet and an electrolyte; the negative electrode sheet includes a negative electrode active material, which includes a silicon-based material and graphite;

[0005] The electrolyte includes a solvent and additives; the solvent includes propylene carbonate, and the additives include fluorobenzene compounds and unsaturated sulfur-containing organic compounds. The unsaturated sulfur-containing organic compounds include sulfur-containing heterocyclic structures and branches connected to the sulfur-containing heterocyclic structures, one or more of which contain unsaturated groups, and the sulfur-containing heterocyclic structures have thioester groups or sulfate groups.

[0006] This application utilizes unsaturated sulfur-containing organic compounds to preferentially form an interfacial film on the negative electrode surface. The fluorine atoms on fluorobenzene compounds, with their strong electronegativity, can connect to the alkyl groups on PC via hydrogen bonds, forming intermolecular interactions and weakening the Li in the solvation structure. + Coordination strength with PC promotes Li + The desolvation effect of PC at the graphite / electrolyte interface reduces the intrusion of PC solvent into the graphite interlayer, which helps improve the problem of PC co-intercalation and graphite stripping. Furthermore, it facilitates the chemisorption of electron-deficient benzene rings in fluorobenzene compounds onto the exposed electron-rich graphite surface via π-π stacking, thereby hindering direct contact between PC and graphite and synergistically enhancing the physical barrier effect with unsaturated sulfur-containing organic compounds. Therefore, this application helps to further improve the problem of PC co-intercalation and graphite stripping, and improve the cycle performance of the battery.

[0007] In some embodiments, the structure of the fluorobenzene compound is shown in Formula 1:

[0008]

[0009]

[0010] In Formula 1, R1-R5 are each independently selected from one of H, halogen, substituted or unsubstituted C1-C10 saturated alkyl, substituted or unsubstituted C2-C10 unsaturated alkyl, aromatic group, carbonyl group, carboxyl group, ester group, nitrile group, and hydroxyl group.

[0011] These fluorobenzene compounds contain fluorine atoms with strong electron-withdrawing capabilities and electron-deficient benzene rings, which facilitate desolvation and enhance the physical barrier effect in synergy with unsaturated sulfur-containing organic compounds. This further improves the problem of PC co-intercalation and graphite stripping, and further enhances the cycle performance of the battery.

[0012] In some implementations, Equation 1 satisfies at least one of the following (i) to (v):

[0013] (i) Substituted or unsubstituted C1-C10 saturated alkyl groups include substituted or unsubstituted C1-C5 saturated alkyl groups;

[0014] (ii) Substituted or unsubstituted C2-C10 unsaturated alkyl groups include substituted or unsubstituted C2-C5 unsaturated alkyl groups;

[0015] (iii) Aromatic groups include phenyl groups;

[0016] (iv) Hydroxyl groups include alkoxy groups;

[0017] (v) Halogens include F.

[0018] Among the aforementioned groups, the steric hindrance is relatively small, which is beneficial for fluorobenzene compounds to promote desolvation and enhance their physical barrier effect in synergistic interaction with unsaturated sulfur-containing organic compounds.

[0019] In some implementations, in Formula 1, R1-R5 are each independently selected from H and F.

[0020] These fluorobenzene compounds do not have the introduction of other functional groups, resulting in less steric hindrance. Furthermore, as the number of fluorine atoms increases, the electronegativity of fluorobenzene compounds increases, which is beneficial for fluorobenzene compounds to better promote desolvation and enhance their physical barrier effect in synergy with unsaturated sulfur-containing organic compounds.

[0021] In some embodiments, the fluorobenzene compounds include one or more compounds having the structures shown in Formulas 1-1 to 1-3:

[0022] Formula 1-1 Formula 1-2 Formula 1-3

[0023] The aforementioned fluorobenzene compounds do not have the introduction of other functional groups, have less steric hindrance, and multiple fluorine atoms can provide stronger electronegativity, which is conducive to fluorobenzene compounds better playing their role in promoting desolvation and enhancing their physical barrier effect in synergy with unsaturated sulfur-containing organic compounds.

[0024] In some embodiments, the unsaturated sulfur-containing organic compounds include one or more of the following formulas 1-3:

[0025] Formula 2 Formula 3 Formula 4

[0026] At least one of R6 and R7 is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and at least one of R8 and R9 is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups. 10 R 11 At least one of the groups is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and the remaining groups are each independently selected from H, halogen, substituted or unsubstituted C1-C10 saturated alkyl groups, substituted or unsubstituted C2-C10 unsaturated alkyl groups, aromatic groups, carbonyl groups, carboxyl groups, ester groups, nitrile groups, and isocyanate groups.

[0027] The aforementioned unsaturated sulfur-containing organic compounds have thioester groups or sulfate groups, as well as unsaturated bonds, exhibiting high reactivity. They can preferentially form an SEI film on the negative electrode surface compared to fluorobenzene compounds. The generated sulfate-containing substances can improve the chemical stability of the interface and act as a physical barrier, reducing the contact between the electrolyte, especially propylene carbonate (PC), and graphite. This helps to improve the problem of PC co-intercalation with graphite and improve the cycle performance of the battery.

[0028] In some embodiments, the unsaturated sulfur-containing organic compound satisfies at least one of the following (i) to (iv):

[0029] (i) Substituted or unsubstituted C2-C10 unsaturated alkyl groups include substituted or unsubstituted C2-C5 unsaturated alkyl groups;

[0030] (ii) Substituted or unsubstituted C1-C10 saturated alkyl groups include substituted or unsubstituted C1-C5 saturated alkyl groups;

[0031] (iii) Aromatic groups include phenyl groups;

[0032] (iv) Halogens include any one of F, Cl, Br, and I.

[0033] Unsaturated sulfur-containing organic compounds containing the above-mentioned groups have low film-forming resistance, which is beneficial for obtaining better kinetic properties.

[0034] In some embodiments, at least one of R6 and R7 is selected from substituted or unsubstituted C2-C5 unsaturated alkyl groups, and at least one of R8 and R9 is selected from substituted or unsubstituted C2-C5 unsaturated alkyl groups. 10 R 11 At least one of the groups is selected from a substituted or unsubstituted C2-C5 unsaturated alkyl group, and the remaining groups are each independently selected from H, substituted or unsubstituted C1-C5 saturated alkyl groups.

[0035] Unsaturated sulfur-containing organic compounds that meet the above conditions have high reactivity, which is beneficial for further improving the problem of co-intercalation of graphite in PC.

[0036] In some embodiments, the thioester compounds include one or more of formulas 2-1, 2-2, 2-3, and 3-1:

[0037] Equation 2-1 Equation 2-2 Equation 2-3 Equation 3-1

[0038] Unsaturated sulfur-containing organic compounds that meet the above conditions have high reactivity, which is beneficial for further improving the problem of co-intercalation of graphite in PC.

[0039] In some embodiments, the content of fluorobenzene compounds is 0.005 wt% to 5 wt% based on the mass of the electrolyte.

[0040] The content of fluorobenzene compounds meets the above conditions, which is conducive to promoting the desolvation of lithium ions at the interface, and also conducive to constructing an effective specific adsorption layer to isolate the exposed graphite from direct contact with PC. The battery has low internal resistance, maintains good kinetic performance, and obtains high cycle performance.

[0041] In some embodiments, the content of fluorobenzene compounds is 0.1 wt% to 2 wt% based on the mass of the electrolyte.

[0042] The content of fluorobenzene compounds meets the above conditions, which further results in lower battery internal resistance and higher cycle performance.

[0043] In some embodiments, the content of unsaturated sulfur-containing organic matter is 0.005 wt% to 5 wt% based on the mass of the electrolyte.

[0044] Meeting the above conditions regarding the content of unsaturated sulfur-containing organic matter is beneficial for constructing a stable and effective interfacial film at the negative electrode, improving the protection of the negative electrode side, reducing excessive side reactions between unsaturated sulfur-containing organic matter and the interface, reducing lithium salt consumption, and improving the cycle performance of the battery.

[0045] In some implementations, the content of unsaturated sulfur-containing organic matter is 0.1 wt% to 2 wt% based on the mass of the electrolyte.

[0046] The content of unsaturated sulfur-containing organic compounds meets the above conditions, which is conducive to the construction of an effective interfacial film, reduces the occurrence of side reactions, and further improves the cycle performance of the battery.

[0047] In some embodiments, the propylene carbonate content is 2 wt% to 50 wt% based on the total mass of the solvent.

[0048] Meeting the above conditions regarding the content of propylene carbonate can improve the low-temperature performance of the battery, such as low-temperature cycle performance, and is beneficial for reducing Li. + The presence of PC reduces the risk of graphite stripping. Furthermore, it facilitates the addition of other lower-viscosity solvents (such as other low-viscosity chain solvents), reducing the overall viscosity of the electrolyte and thus improving the battery's cycle performance.

[0049] In some embodiments, the propylene carbonate content is 5 wt% to 30 wt% based on the total mass of the solvent.

[0050] The content of propylene carbonate meets the above conditions, which helps to reduce electrolyte viscosity, increase ionic conductivity, reduce the risk of graphite stripping, and further improve the cycle performance of the battery.

[0051] In some embodiments, the additive also includes fluoroethylene carbonate.

[0052] Fluorinated ethylene carbonate can form lithium fluoride-containing inorganic SEI and cross-linked polymers, which can play a role in interface repair during battery operation and improve battery cycle performance.

[0053] In some embodiments, the content of fluoroethylene carbonate is 0.5 wt% to 20 wt%, depending on the mass of the electrolyte.

[0054] The content of fluoroethylene carbonate meets the above conditions, which is conducive to the function of interface repair and improves interface stability. Since FEC itself has relatively poor high-temperature stability, it may react with lithium salt (such as LiPF6) to produce acidic substances, which is detrimental to interface stability. The content of fluoroethylene carbonate meets the above conditions, which is conducive to reducing the occurrence of side reactions and better improving the cycle performance of the battery.

[0055] In some embodiments, the solvent also includes ethylene carbonate.

[0056] The content of fluoroethylene carbonate meets the above conditions, which is conducive to better exerting the interface repair function, reducing the occurrence of side reactions, and further improving the cycle performance of the battery.

[0057] In some embodiments, the content of ethylene carbonate is less than 20 wt% based on the total mass of the solvent.

[0058] The content of ethylene carbonate meets the above conditions, which is beneficial to improve ionic conductivity, obtain electrolyte with lower viscosity, and improve the low-temperature performance of the battery.

[0059] In some embodiments, the silicon-based material includes one or more of silicon-carbon materials, elemental silicon, and silicon-oxygen materials.

[0060] One or more of elemental silicon (such as nano-silicon, micron-silicon), silicon-oxygen materials, and silicon-carbon materials can be used as silicon-based materials. These silicon-based materials can be mixed with graphite, such as through physical mixing, and then used as negative electrode active materials.

[0061] In some embodiments, the silicon-carbon material includes porous carbon and nano-silicon deposited within the pores of the porous carbon; and / or, in the silicon-carbon material, the mass ratio of silicon to carbon is 6:4 to 4:6.

[0062] Based on the volume effect verification of silicon-based materials, the interface structure is damaged and reorganized during operation, posing a certain risk to cycle performance. Silicon-carbon materials, in which silicon is deposited in porous carbon, have a certain inhibitory effect on silicon expansion and exhibit superior cycle performance. In silicon-carbon materials, carbon acts as an insulator in the electrolyte contact, reducing the contact of acid byproducts; moreover, silicon-carbon materials have less expansion and are more stable, thus contributing to improved battery cycle performance.

[0063] In some implementations, the content of silicon-based material is 5wt%-90wt%, and the content of graphite is 10wt%-95wt%, depending on the mass of the negative electrode active material.

[0064] Silicon-based materials can dilute graphite, mitigating the incompatibility between the solvent PC and graphite, which is beneficial for improving the cycle performance of batteries compared to pure graphite systems.

[0065] In some embodiments, the electrolyte also includes an electrolyte salt, which includes one or more of LiPF6, LiFSI, LiTFSI, LiBF4, LiBOB, LiDFOB, LiAsF6, and LiClO4.

[0066] The second aspect of this application provides an electrical device including the secondary battery proposed in the first aspect of this application.

[0067] The electrical equipment provided in this application includes the aforementioned secondary battery and has the beneficial effects of the aforementioned secondary battery, which will not be elaborated here.

[0068] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0069] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0070] Figure 1 This is a schematic diagram of a battery according to one embodiment of this application.

[0071] Figure 2 yes Figure 1 An exploded view of a battery according to one embodiment of this application is shown.

[0072] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0073] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0074] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0075] Figure 6 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0076] Explanation of reference numerals in the attached figures:

[0077] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0078] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0079] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0080] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0081] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0082] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. 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 mention that the method may also include step (c) indicates 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.

[0083] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0084] Taking a silicon-based hybrid secondary battery as an example, its negative electrode active material contains silicon-based materials and graphite, and the lifespan of this type of secondary battery is a significant bottleneck. To meet the fast-charging requirements of silicon-based secondary batteries, solvents with high conductivity and low viscosity are needed to ensure sufficient dissociation of lithium salts and rapid lithium-ion transport in the liquid phase. Among the cyclic solvents used for lithium salt dissociation, PC (propylene carbonate) has a lower melting point and viscosity than EC (ethylene carbonate), which is beneficial for low-temperature charge / discharge and rate performance. However, due to the presence of Li... + The co-intercalation of PC leads to graphite stripping and rapid battery life degradation, hindering the widespread application and utilization of PC in pure graphite systems. However, the stripping problem is mitigated in silicon-based hybrid systems. Furthermore, silicon's theoretical specific capacity is more than 10 times that of carbon-based materials like graphite, offering higher energy density for batteries and potentially meeting the growing energy demands of power batteries and electronic devices. Therefore, the use of PC-based electrolytes in silicon-based hybrid systems could be considered.

[0085] However, even with a certain amount of graphite in the silicon-based hybrid system, PC is still prone to Li₂ oxidation during charging. +- PC co-intercalation problem, and PC is difficult to form a robust and effective SEI (Solid Electrolyte Interphase) film. Solventized lithium ions are continuously co-intercalated, the graphite layered structure collapses, the solvent is continuously reduced and decomposed, and thus the cell life deteriorates.

[0086] In addition, DMC (Dimethyl Carbonate) or carboxylic acid ester solvents in chain solvents have lower viscosity, but the redox window of these solvents is narrower than that of EMC (Ethyl Methyl Carbonate) and DEC (Diethyl Carbonate), making them more prone to side reactions and gas generation at the interface.

[0087] In existing technologies, to address the incompatibility between PC and graphite, strategies include using other solvents (such as EC) to partially or completely replace PC, or adding large amounts of film-forming additives to form a better SEI film, thereby reducing Li. + -PC co-embedding, improving Li + Reversible insertion / extraction of lithium ions in graphite electrodes improves cell lifespan. However, for solvent substitution strategies, EC has a higher freezing point and its low-temperature performance is inferior to PC. Adding large amounts of film-forming additives, such as VC (ethylene carbonate) and PS (1,3-propanesulfonate lactone), results in insufficient interfacial film formation to inhibit PC exfoliation from graphite at low concentrations, while higher concentrations lead to high film resistance, affecting reversible lithium ion insertion / extraction and worsening cell lifespan.

[0088] The first aspect of this application provides a secondary battery, including a negative electrode sheet and an electrolyte; the negative electrode sheet includes a negative electrode active material, which includes a silicon-based material and graphite;

[0089] The electrolyte includes a solvent and additives; the solvent includes propylene carbonate, and the additives include fluorobenzene compounds and unsaturated sulfur-containing organic compounds; the unsaturated sulfur-containing organic compounds include sulfur-containing heterocyclic structures and branches connected to sulfur-containing heterocyclic structures, one or more of which contain unsaturated groups, and the sulfur-containing heterocyclic structures have thioester groups or sulfate groups.

[0090] Fluorobenzene compounds are organic compounds in which one or more hydrogen atoms on the benzene ring are replaced by fluorine atoms; in addition, the remaining hydrogen atoms on the benzene ring can also be replaced by other functional groups.

[0091] Unsaturated sulfur-containing organic compounds have a sulfur-containing heterocyclic structure, and one or more branches are attached to the sulfur-containing heterocyclic structure. One or more of the branches should contain unsaturated groups. In addition, the sulfur-containing heterocyclic structure has a thioester group or a sulfate group.

[0092] The types and contents of fluorobenzene compounds and unsaturated sulfur-containing organic compounds in the electrolyte are well-known in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or a fully discharged battery (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0093] This application uses a lithium-ion battery as an example. Unsaturated sulfur-containing organic compounds combine sulfur-containing ester groups and unsaturated bonds, significantly improving their reactivity and enabling rapid film formation on the negative electrode surface. Furthermore, the generated sulfate-containing substances enhance the chemical stability of the interface. In addition, due to the poor conductivity and high interfacial polarization of silicon-based materials, the active unsaturated bonds are beneficial for improving their reactivity and promoting the reaction and film formation of sulfur-containing groups at the negative electrode interface. The SEI film preferentially formed on the negative electrode surface by unsaturated sulfur-containing organic compounds acts as a physical barrier, reducing the contact between the electrolyte, especially propylene carbonate (PC), and graphite, thus mitigating the problem of PC co-intercalation with graphite.

[0094] Because fluorobenzene compounds also undergo reductive decomposition at lower lithium intercalation potentials during charging, and unsaturated sulfur-containing organic compounds have higher reactivity, they can preferentially form films on the negative electrode compared to fluorobenzene compounds, thus effectively suppressing the reductive decomposition of fluorobenzene. In this way, the highly electronegative fluorine atoms on fluorobenzene compounds can be linked to alkyl groups on PC via hydrogen bonds, forming intermolecular interactions and weakening the Li in the solvation structure. + Coordination strength with PC promotes Li +The desolvation effect of PC at the graphite / electrolyte interface reduces the entry of PC solvent into the graphite interlayer, which helps improve the problems of PC co-intercalation and graphite delamination. However, in the early stage of unsaturated sulfur-containing organic compound film formation, there may be some exposed graphite surface, or the SEI film may have pores or local damage. For example, during battery cycling, the SEI film may dynamically change due to volume expansion / contraction or electrolyte decomposition, resulting in local exposure of the graphite surface. These locally exposed graphite surfaces will come into contact with PC, which can easily lead to PC co-intercalation and affect the stability of the negative electrode. In contrast, the benzene ring of fluorobenzene compounds is electron-deficient and can be electrostatically adsorbed onto the electron-rich graphite surface through π-π stacking, thus hindering the direct contact between PC and graphite, which will then be covered by the newly formed SEI film. In addition, the film thickness of additives (such as unsaturated sulfur-containing organic compounds) in the battery is generally on the nanometer scale, and it is difficult to achieve perfect coverage of the negative electrode surface. Therefore, after the unsaturated sulfur-containing organic compound film is formed, fluorobenzene compounds can further improve the problems of PC co-intercalation and graphite delamination by electrostatic adsorption on the graphite surface. In this way, fluorobenzene compounds and unsaturated sulfur-containing organic compounds work synergistically to further enhance the physical barrier effect, which is beneficial to further improve the problems of PC co-intercalation and graphite stripping, thereby improving the cycle performance of the battery.

[0095] In one embodiment of this application, the structure of the fluorobenzene compound is shown in Formula 1:

[0096]

[0097] In Formula 1, R1-R5 are each independently selected from one of H, halogen, substituted or unsubstituted C1-C10 saturated alkyl, substituted or unsubstituted C2-C10 unsaturated alkyl, aromatic group, carbonyl (-C=O), carboxyl (-COOH), ester group (-COOR), nitrile group (-C≡N), and hydroxyl group.

[0098] The fluorobenzene compounds provided in this application are as shown in Formula 1, having a phenyl group and at least one F atom, with the remaining groups R1-R5 each freely selected from the above functional groups. These fluorobenzene compounds contain fluorine atoms with strong electron-withdrawing ability and electron-deficient benzene rings, which are beneficial for promoting desolvation and enhancing the physical barrier effect in synergy with unsaturated sulfur-containing organic compounds, further improving the problem of PC co-intercalation and graphite stripping, and further improving the cycle performance of the battery.

[0099] Furthermore, in the substituted C1-C10 saturated alkyl groups, the substituents may include F.

[0100] Furthermore, in the substituted C2-C10 unsaturated alkyl groups, the substituents may include F.

[0101] Furthermore, in the ester group (-COOR), R can be selected from C1-C5 alkyl groups.

[0102] In one embodiment of this application, Formula 1 satisfies at least one of the following (i) to (v):

[0103] (i) Substituted or unsubstituted C1-C10 saturated alkyl groups include substituted or unsubstituted C1-C5 saturated alkyl groups;

[0104] (ii) Substituted or unsubstituted C2-C10 unsaturated alkyl groups include substituted or unsubstituted C2-C5 unsaturated alkyl groups;

[0105] (iii) Aromatic groups include phenyl groups;

[0106] (iv) Hydroxyl groups include alkoxy groups;

[0107] (v) Halogens include F.

[0108] Saturated alkyl groups can be substituted or unsubstituted C1-C5 saturated alkyl groups with a relatively small number of carbon atoms and less steric hindrance, which is beneficial for fluorobenzene compounds to promote desolvation and enhance the physical barrier effect in synergy with unsaturated sulfur-containing organic compounds.

[0109] Unsaturated alkyl groups can be C2-C5 unsaturated alkyl groups, including substituted or unsubstituted ones, with a relatively small number of carbon atoms and low steric hindrance, which facilitates the desolvation of fluorobenzene compounds and enhances their physical barrier effect in synergistic interaction with unsaturated sulfur-containing organic compounds. As an example, C2-C5 unsaturated alkyl groups can include any one of alkenyl or alkynyl groups.

[0110] Aromatic groups can include phenyl groups. The relatively few cyclic structures of fluorobenzene compounds result in less steric hindrance, which is beneficial for fluorobenzene compounds to promote desolvation and enhance their physical barrier effect in synergistic interaction with unsaturated sulfur-containing organic compounds.

[0111] Hydroxyl groups include alkoxy groups, which can be straight-chain alkoxy groups or branched-chain alkoxy groups. Examples include methoxy, ethoxy, propoxy, and isopropoxy groups.

[0112] Halogens can be any of F, Cl, Br, and I, especially F, which promotes the desolvation of fluorobenzene compounds.

[0113] In one embodiment of this application, in Formula 1, R1-R5 are each independently selected from H and F.

[0114] The fluorobenzene compounds provided in the embodiments of this application are organic compounds in which one or more hydrogen atoms on the benzene ring are replaced by fluorine atoms, and the number of hydrogen atoms replaced on the benzene ring can be any one of 1 to 6.

[0115] These fluorobenzene compounds do not have the introduction of other functional groups, resulting in less steric hindrance. Furthermore, as the number of fluorine atoms increases, the electronegativity of fluorobenzene compounds increases, which is beneficial for fluorobenzene compounds to better promote desolvation and enhance their physical barrier effect in synergy with unsaturated sulfur-containing organic compounds.

[0116] In one embodiment of this application, the fluorobenzene compound includes one or more compounds having the structures shown in Formulas 1-1 to 1-3:

[0117] Formula 1-1 Formula 1-2 Formula 1-3

[0118] These fluorobenzene compounds do not have the introduction of other functional groups, have less steric hindrance, and multiple fluorine atoms can provide stronger electronegativity, which is conducive to fluorobenzene compounds better playing their role in promoting desolvation and enhancing their physical barrier effect in synergy with unsaturated sulfur-containing organic compounds.

[0119] In one embodiment of this application, the unsaturated sulfur-containing organic compound includes one or more of the following formulas 1-3:

[0120] Formula 2 Formula 3 Formula 4

[0121] At least one of R6 and R7 is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and at least one of R8 and R9 is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups. 10 R 11 At least one of the groups is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and the remaining groups are each independently selected from H, halogen, substituted or unsubstituted C1-C10 saturated alkyl groups, substituted or unsubstituted C2-C10 unsaturated alkyl groups, aromatic groups, carbonyl groups (-C=O), carboxyl groups (-COOH), ester groups (-COOR), nitrile groups (-C≡N), and isocyanate groups (-N=C=O).

[0122] In the unsaturated sulfur-containing organic compound shown in Formula 2, at least one of the two groups R6 and R7 is selected from a substituted or unsubstituted C2-C10 unsaturated alkyl group, and the remaining groups may be selected from H, halogen, substituted or unsubstituted C1-C10 saturated alkyl group, substituted or unsubstituted C2-C10 unsaturated alkyl group, aromatic group, carbonyl group, carboxyl group, ester group, nitrile group, and isocyanate group.

[0123] In the unsaturated sulfur-containing organic compound shown in Formula 3, at least one of the two groups R8 and R9 is selected from a substituted or unsubstituted C2-C10 unsaturated alkyl group, and the remaining groups may be selected from H, halogen, substituted or unsubstituted C1-C10 saturated alkyl group, substituted or unsubstituted C2-C10 unsaturated alkyl group, aromatic group, carbonyl group, carboxyl group, ester group, nitrile group, and isocyanate group.

[0124] In the unsaturated sulfur-containing organic compound shown in Formula 4, the two groups R 10 R 11 At least one of the groups is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and the remaining groups may be selected from H, halogen, substituted or unsubstituted C1-C10 saturated alkyl groups, substituted or unsubstituted C2-C10 unsaturated alkyl groups, aromatic groups, carbonyl groups, carboxyl groups, ester groups, nitrile groups, and isocyanate groups.

[0125] In this embodiment, the unsaturated sulfur-containing organic compounds have thioester groups or sulfate groups, as well as unsaturated bonds, and have high reactivity. They can preferentially form an SEI film on the negative electrode surface compared to fluorobenzene compounds. The generated sulfate-containing substances can improve the chemical stability of the interface and act as a physical barrier, reducing the contact between the electrolyte, especially propylene carbonate (PC), and graphite. This helps to improve the problem of PC co-intercalation with graphite and improve the cycle performance of the battery.

[0126] Furthermore, in the substituted C1-C10 saturated alkyl groups, the substituents may include F.

[0127] Furthermore, in the substituted C2-C10 unsaturated alkyl groups, the substituents may include F.

[0128] Furthermore, in the ester group (-COOR), R can be selected from C1-C5 alkyl groups.

[0129] In one embodiment of this application, the unsaturated sulfur-containing organic compound satisfies at least one of the following (i) to (iv):

[0130] (i) Substituted or unsubstituted C2-C10 unsaturated alkyl groups include substituted or unsubstituted C2-C5 unsaturated alkyl groups;

[0131] (ii) Substituted or unsubstituted C1-C10 saturated alkyl groups include substituted or unsubstituted C1-C5 saturated alkyl groups;

[0132] (iii) Aromatic groups include phenyl groups;

[0133] (iv) Halogens include any one of F, Cl, Br, and I.

[0134] Unsaturated alkyl groups can be substituted or unsubstituted C2-C5 unsaturated alkyl groups with relatively short carbon chain lengths, resulting in relatively higher reactivity and facilitating rapid reduction film formation. As an example, unsaturated alkyl groups include any of alkenyl or alkynyl groups. Specifically, they can be any of vinyl, propenyl, butenyl, or pentenyl groups, or isomers of the corresponding alkenyl groups; specifically, they can be any of ethynyl, propynyl, butynyl, or pentynyl groups, or isomers of the corresponding alkynyl groups.

[0135] Saturated alkyl groups can be substituted or unsubstituted C1 to C5 saturated alkyl groups with relatively short carbon chain lengths, resulting in relatively higher reactivity and facilitating rapid reduction and film formation.

[0136] Halogens can be any of F, Cl, Br, and I, especially unsaturated sulfur-containing organic compounds containing fluorine atoms, which can be used to form SEI membranes containing fluorine, thereby optimizing the performance of SEI membranes and improving their stability and ion transport performance.

[0137] In one embodiment of this application, at least one of R6 and R7 is selected from substituted or unsubstituted C2-C5 unsaturated alkyl groups, and at least one of R8 and R9 is selected from substituted or unsubstituted C2-C5 unsaturated alkyl groups. 10 R 11 At least one of the groups is selected from a substituted or unsubstituted C2-C5 unsaturated alkyl group, and each of the remaining groups is independently selected from H, a substituted or unsubstituted C1-C5 saturated alkyl group.

[0138] Formulas 2, 3, and 4 each contain two substituent groups. One substituent group can be selected from unsaturated alkyl groups, or both can be selected from unsaturated alkyl groups. The remaining groups are selected from short-chain alkyl groups or H. They have high reactivity and can preferentially form an SEI film on the negative electrode surface compared to fluorobenzene compounds. The generated sulfate-containing substances can improve the chemical stability of the interface and can play a physical barrier role, reducing the contact between the electrolyte, especially propylene carbonate (PC), and graphite, and further improving the problem of PC co-intercalation with graphite.

[0139] In one embodiment of this application, the thioester compound includes one or more of formulas 2-1, 2-2, 2-3, and 3-1:

[0140] Equation 2-1 Equation 2-2 Equation 2-3 Equation 3-1

[0141] The unsaturated sulfur-containing organic compounds provided above have high reactivity and can preferentially form an SEI film on the negative electrode surface compared to fluorobenzene compounds. The generated sulfate-containing substances can improve the chemical stability of the interface and act as a physical barrier, reducing the contact between the electrolyte, especially propylene carbonate (PC), and graphite, and better improving the problem of PC co-intercalation with graphite.

[0142] In one embodiment of this application, the content of fluorobenzene compounds is 0.005wt%-5wt% based on the mass of the electrolyte.

[0143] In the embodiments of this application, the content of fluorobenzene compounds meets the above conditions, which is beneficial to promote the desolvation of lithium ions at the interface, and also beneficial to construct an effective specific adsorption layer to isolate the exposed graphite from direct contact with PC. The battery has low internal resistance, maintains good kinetic performance, and obtains high cycle performance.

[0144] As an example, based on the mass of the electrolyte, the content of fluorobenzene compounds is 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, 0.009wt%, 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc.

[0145] In one embodiment of this application, the content of fluorobenzene compounds is 0.1wt%-2wt% based on the mass of the electrolyte.

[0146] In this embodiment, the content of fluorobenzene compounds meets the above conditions, thereby achieving a smaller battery internal resistance and higher cycle performance.

[0147] In one embodiment of this application, the content of unsaturated sulfur-containing organic matter is 0.005 wt% to 5 wt% based on the mass of the electrolyte.

[0148] In the embodiments of this application, the content of unsaturated sulfur-containing organic matter meets the above conditions, which is conducive to building a stable and effective interface film at the negative electrode, improving the protection of the negative electrode side, and reducing the side reactions between excessive unsaturated sulfur-containing organic matter and the interface, reducing the consumption of lithium salt, and improving the cycle performance of the battery.

[0149] As an example, based on the mass of the electrolyte, the content of unsaturated sulfur-containing organic matter is 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, 0.009wt%, 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc.

[0150] In one embodiment of this application, the content of unsaturated sulfur-containing organic matter is 0.1wt%-2wt% based on the mass of the electrolyte.

[0151] In the embodiments of this application, the content of unsaturated sulfur-containing organic matter meets the above conditions, which is conducive to the construction of an effective interface film, reduces the occurrence of side reactions, and further improves the cycle performance of the battery.

[0152] In one embodiment of this application, the content of propylene carbonate is 2wt%-50wt% based on the total mass of the solvent.

[0153] In this embodiment, the melting point and viscosity of propylene carbonate are lower than those of ethylene carbonate (EC). The content of propylene carbonate meets the above conditions, which can improve the low-temperature performance of the battery, such as low-temperature cycle performance, and is beneficial for reducing Li-. + The presence of PC reduces the risk of graphite stripping. Furthermore, it facilitates the addition of other lower-viscosity solvents (such as other low-viscosity chain solvents), reducing the overall viscosity of the electrolyte and thus improving the battery's cycle performance.

[0154] As an example, based on the total mass of the solvent, the content of propylene carbonate is 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, etc.

[0155] In one embodiment of this application, the content of propylene carbonate is 5 wt% to 30 wt% based on the total mass of the solvent.

[0156] In this embodiment, the content of propylene carbonate meets the above conditions, which helps to reduce electrolyte viscosity, increase ionic conductivity, reduce the risk of graphite stripping, and further improve the cycle performance of the battery.

[0157] In one embodiment of this application, the additive also includes fluoroethylene carbonate.

[0158] Fluorinated ethylene carbonate (FEC), as an effective additive for silicon-based anodes, can form inorganic SEI containing lithium fluoride and cross-linked polymers. During battery operation, it can play a role in interface repair and improve battery cycle performance.

[0159] In one embodiment of this application, the content of fluoroethylene carbonate is 0.5wt%-20wt% based on the mass of the electrolyte.

[0160] In this embodiment, the content of fluoroethylene carbonate meets the above conditions, which is beneficial to exert the interface repair function and improve the interface stability. Since FEC itself has relatively poor high-temperature stability, it may react with lithium salt (such as LiPF6) to produce acidic substances, which is detrimental to interface stability. However, the content of fluoroethylene carbonate meets the above conditions, which is beneficial to reduce the occurrence of side reactions and better improve the cycle performance of the battery.

[0161] As an example, based on the mass of the electrolyte, the content of fluoroethylene carbonate is 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, etc.

[0162] In one embodiment of this application, the content of fluoroethylene carbonate is 5wt%-15wt% based on the mass of the electrolyte.

[0163] In this embodiment, the content of fluoroethylene carbonate meets the above conditions, which helps to better exert the interface repair function, reduce the occurrence of side reactions, and further improve the cycle performance of the battery.

[0164] In one embodiment of this application, the solvent also includes ethylene carbonate.

[0165] Ethylene carbonate (EC), as a solvent, can dissociate lithium salts and improve the ionic conductivity of the electrolyte, thus enhancing battery cycle performance. Using EC in combination with polycarbonate (PC) helps reduce the exfoliation of graphite by the PC solvent co-intercalation, further improving battery cycle performance.

[0166] In one embodiment of this application, the content of ethylene carbonate is less than 20 wt% based on the total mass of the solvent.

[0167] EC and PC have melting points of 39°C and -48°C, respectively. EC's melting point is significantly higher than PC's. As the content of EC in the electrolyte increases, the viscosity of the electrolyte tends to increase. In the embodiments of this application, the content of ethylene carbonate meets the above conditions, which is beneficial for improving ionic conductivity, obtaining an electrolyte with lower viscosity, and improving the low-temperature performance of the battery.

[0168] As an example, based on the total mass of the solvent, the content of fluoroethylene carbonate is 0.5 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, etc.

[0169] In one embodiment of this application, the content of ethylene carbonate is 1 wt% to 10 wt% based on the total mass of the solvent.

[0170] In this embodiment, the content of ethylene carbonate meets the above conditions, which is beneficial to improve ionic conductivity, obtain an electrolyte with lower viscosity, and further improve the low-temperature performance of the battery.

[0171] In one embodiment of this application, the solvent further includes ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

[0172] In one embodiment of this application, the silicon-based material includes one or more of silicon-carbon materials, elemental silicon, and silicon-oxygen materials.

[0173] In batteries using a hybrid system of silicon-based materials and graphite, the synergistic effect of the aforementioned fluorobenzene compounds and unsaturated sulfur-containing organic compounds helps to improve the problems of PC co-intercalation and graphite stripping, thereby enhancing the cycle performance of the battery. This is of great significance for solving the lifespan bottleneck problem of silicon-based secondary batteries.

[0174] In addition, silicon-based materials are less prone to co-intercalation with PC compared to graphite, and are compatible with PC. By using silicon-based materials mixed with graphite as negative electrode active materials, the overall stability of the negative electrode active materials in the electrolyte can be improved, which is beneficial to improving the cycle performance of the battery.

[0175] Silicon-based materials have a high specific capacity, which is helpful for the fabrication of high-energy-density batteries. In the embodiments of this application, one or more combinations of elemental silicon (such as nano-silicon, micron-silicon), silicon-oxygen materials, and silicon-carbon materials can be used as silicon-based materials. These silicon-based materials are mixed with graphite, and can be used as negative electrode active materials after physical mixing.

[0176] In one embodiment of this application, the silicon-carbon material includes porous carbon and nano-silicon deposited in the pores of the porous carbon; and / or, in the silicon-carbon material, the mass ratio of silicon to carbon is 6:4 to 4:6.

[0177] In silicon-carbon materials, the mass ratio of silicon to carbon is obtained by calculating the ratio of silicon content to carbon content. Methods known in the art can be used to determine the silicon and carbon content in silicon-carbon materials. As an example,

[0178] The silicon content test in silicon-carbon materials includes: determining the silicon content using inductively coupled plasma (ICP), specifically as follows: taking silicon-carbon material as a sample, digesting the sample with aqua regia and hydrofluoric acid HF, and detecting the silicon content after complete digestion.

[0179] Carbon content testing in silicon-carbon materials: Infrared absorption method for carbon-sulfur content analysis, according to GB / T20123-2006 testing standard, specifically as follows: take silicon-carbon material as a sample, completely digest it and measure the carbon content.

[0180] Based on the volume effect verification of silicon-based materials, the interface structure is damaged and reorganized during operation, posing a certain risk to cycle performance. Silicon-carbon materials, in which silicon is deposited in porous carbon, have a certain inhibitory effect on silicon expansion and exhibit superior cycle performance. In silicon-carbon materials, carbon acts as an insulator in the electrolyte contact, reducing the contact of acid byproducts; moreover, silicon-carbon materials have less expansion and are more stable, thus contributing to improved battery cycle performance.

[0181] Furthermore, the mass ratio of silicon to carbon is 5:5, which helps to further improve the cycle performance of the battery.

[0182] In some embodiments of this application, for porous carbon: the proportion of mesopores in porous carbon is greater than 50%, and the proportion of micropores is less than 50%.

[0183] Mesopores and micropores have meanings known in the art. For example, mesopores refer to pores with an average pore size of 2 nm to 10 nm, and micropores refer to pores with an average pore size of 0.2 nm to 2 nm.

[0184] Mesopores and micropores can be determined using methods known in the art. As an example, the method for determining the proportion of mesopores involves using conventional testing instruments to measure the distribution of each pore and statistically obtaining the specific quantity. For instance, using an ASAP2460 physical adsorption analyzer, the porous carbon material sample after drying and degassing is placed in liquid nitrogen, and different test pressures are adjusted to measure the amount of nitrogen adsorbed, and adsorption and desorption isotherms are plotted. The pore shape is determined based on the shape of the hysteresis loop, and the pore distribution is calculated according to different pore models. The BJH model is used to fit the pore size distribution curves of mesopores and macropores, and the DFT model is used to fit the pore size distribution curve of micropores. Particle size distribution, i.e., the particle size-volume distribution map of carbon particles, can be measured using conventional methods in the art, such as using a particle size analyzer to determine the particle size distribution map and then obtaining it statistically. In this application embodiment, laser diffraction particle size analysis is selected for determination, specifically referring to standard GB / T19077-2016 to obtain the particle size distribution map, which is then calculated.

[0185] The number of micropores and mesopores in this porous structure can be controlled to form a porous carbon material with a relatively high specific surface area. This porous carbon material not only allows for easy control of the silicon content formed within the porous structure, but also reserves some volume space to buffer the expansion of silicon material. By limiting the volume expansion of silicon material during lithium insertion / extraction, the cycle performance of the battery can be improved.

[0186] As an example, the proportion of mesopores in porous carbon is greater than 50% and less than 100%, while the proportion of micropores is less than 50% and greater than 0. More specifically, the proportion of mesopores in porous carbon is 51%, 60%, 70%, 80%, 90%, 95%, etc., and the corresponding proportion of micropores in porous carbon is 49%, 40%, 30%, 20%, 10%, 5%, etc.

[0187] In some specific embodiments of this application, based on the mass of the negative electrode active material, the content of silicon carbide material is 5wt%-90wt%, and the content of graphite is 10wt%-95wt%.

[0188] Silicon-based materials can dilute graphite, mitigating the incompatibility between the solvent PC and graphite, which is beneficial for improving the cycle performance of batteries compared to pure graphite systems.

[0189] As an example, based on the mass of the negative electrode active material, the content of silicon carbide is 5wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, etc., and correspondingly, the content of graphite is 95wt%, 90wt%, 85wt%, 80wt%, 75wt%, 70wt%, 65wt%, 60wt%, 55wt%, 50wt%, 45wt%, 40wt%, 35wt%, 30wt%, 25wt%, 20wt%, 15wt%, 10wt%, etc.

[0190] In one embodiment of this application, the content of silicon carbide material is 10wt%-50wt% and the content of graphite is 50wt%-90wt% based on the mass of the negative electrode active material.

[0191] In one embodiment of this application, based on the mass of the negative electrode active material, the content of silicon carbide material is 20wt%-45wt%, and the content of graphite is 55wt%-80wt%.

[0192] In one embodiment of this application, the electrolyte further includes an electrolyte salt, which includes one or more of LiPF6, LiFSI, LiTFSI, LiBF4, LiBOB, LiDFOB, LiAsF6, and LiClO4.

[0193] Furthermore, the electrolyte salt includes one or more of LiPF6 and LiFSI.

[0194] The secondary battery proposed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0195] One embodiment of this application provides a secondary battery. Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0196] [Positive electrode tablets]

[0197] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including the positive active material of the first aspect of this application.

[0198] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0199] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0200] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0201] In some implementations, such as when the battery is a sodium-ion battery, the positive electrode active material may, as an example, include, but is not limited to, at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0202] Examples of the aforementioned layered transition metal oxides include:

[0203] Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 It is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0204] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 It is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0205] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0206] Examples of the aforementioned polyanionic compounds include:

[0207] A 1 f M 3 g (PO4) i O j X 1 3-j A 1 It is one or more of H, Li, Na, K and NH4, M 3 It is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 It is one or more of F, Cl and Br, 0 <f≤4,0<g≤2,1≤i≤3,0≤j≤2;

[0208] Na n M 4 PO4X 2 M 4is one or more selected from Mn, Fe, Co, Ni, Cu and Zn, X 2 is one or more selected from F, Cl and Br, 0<n≤2;

[0209] Na p M 5 q (SO4)3, wherein M 5 is one or more selected from Mn, Fe, Co, Ni, Cu and Zn, 0<p≤2, 0<q≤2;

[0210] Na s Mn t Fe 3-t (PO4)2(P2O7), wherein 0<s≤4, 0≤t≤3, for example, t is 0, 1, 1.5, 2 or 3.

[0211] As examples of the above-mentioned Prussian blue analogs, there can be enumerated, for example:

[0212] A u M 6 v [M 7 (CN)6] w ·xH2O, wherein A is H + , NH4 + , one or more selected from alkali metal cations and alkaline earth metal cations, M 6 and M 7 each independently is one or more selected from transition metal cations, 0<u≤2, 0<v≤1, 0<w≤1, 0<x<6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Ra 2+ , one or more selected from the group consisting of M 6 and M 7 each independently is a cation of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn and W.

[0213] The modified compounds of each of the above materials can be doped modification and / or surface coating modification of the materials.

[0214] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0215] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0216] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0217] [Negative electrode plate]

[0218] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0219] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0220] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0221] In some embodiments, the negative electrode active material is the negative electrode active material described in the first aspect of the embodiments of this application.

[0222] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from 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).

[0223] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0224] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0225] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0226] [Electrolytes]

[0227] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0228] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0229] In some embodiments of this application, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0230] In some embodiments, the solvent may also include one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0231] In some embodiments, the electrolyte may optionally include other additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0232] As an example, additives also include one or more of the following: saturated or unsaturated cyclic carbonates, sulfite compounds, acid anhydrides, nitrile compounds, aromatic compounds, isocyanate compounds, phosphonitrile compounds, phosphite compounds, phosphate compounds, and borate compounds.

[0233] [Isolation membrane]

[0234] In some embodiments, the battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0235] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0236] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0237] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0238] In some implementations, the battery's outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The battery's outer packaging can also be a soft pack, such as a pouch. The soft pack can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0239] This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The battery 5 is a square structure, which serves as an example.

[0240] In some implementations, refer to Figure 2The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0241] In some implementations, the batteries can be assembled into battery modules, and the number of batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0242] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple batteries 5 can be fixed in place using fasteners.

[0243] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of batteries 5 are received.

[0244] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0245] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0246] The second aspect of this application provides an electrical device including the secondary battery proposed in the first aspect of this application.

[0247] This application also provides an electrical device, which includes at least one of the battery, battery module, or battery pack provided in this application. The 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 include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0248] As electrical equipment, batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0249] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density batteries, a battery pack or battery module can be used.

[0250] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0251] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0252] [Lithium-ion battery manufacturing process]

[0253] Example 1

[0254] (1) Preparation of positive electrode:

[0255] An 8μm thick aluminum foil was used as the positive electrode current collector. The positive electrode active material, LiNi, was used. 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 93:2:5. After thorough stirring and mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0256] (2) Preparation of negative electrode sheet:

[0257] The aforementioned silicon-carbon material, graphite, conductive carbon black, and binder polyacrylic acid are mixed in a mass ratio of 2:6:1:1. Deionized water is added and the mixture is stirred thoroughly to form a negative electrode slurry. The silicon-carbon material is composed of porous carbon and nano-silicon deposited inside. The number of mesopores (2nm-10nm) in the porous carbon accounts for more than 50%-60%, and the number of micropores (0.2nm-2nm) accounts for less than 40%-50%. The mass ratio of silicon to carbon in the silicon-carbon material is 5:5. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector copper foil. After drying and cold pressing, a negative electrode sheet is obtained.

[0258] (3) Separating membrane:

[0259] A polyethylene film with a thickness of 12μm was used as the separator.

[0260] (4) Preparation of electrolyte:

[0261] Ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) were mixed, followed by the addition of propylene carbonate (PC) and ethylene carbonate (EC), and the mixture was thoroughly stirred to obtain a solvent. Next, thoroughly dried lithium salt LiPF6 was dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L. Additives, including fluorobenzene compounds, unsaturated sulfur-containing organic compounds, and fluoroethylene carbonate (FEC), were added.

[0262] (5) Assemble the battery:

[0263] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a barrier between the positive and negative electrodes. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product.

[0264] Examples 2-24

[0265] The preparation of the secondary batteries provided in Examples 2-24 is as shown in Example 1, and the specific differences in parameters are shown in Table 1.

[0266] Comparative Example 1

[0267] The secondary battery provided in Comparative Example 1 was prepared as shown in Example 1, except that no additives were added, as detailed in Table 1.

[0268] Comparative Example 2

[0269] The secondary battery provided in Comparative Example 2 was prepared as in Example 1, except that a fluorobenzene compound of Formula 1-1 was used as an additive, as shown in Table 1.

[0270] Comparative Example 3

[0271] The preparation of the secondary battery provided in Comparative Example 3 is as shown in Example 1, except that: the unsaturated sulfur-containing organic compound shown in Formula 2-1 is used as an additive, as shown in Table 1.

[0272] Comparative Example 4

[0273] The secondary battery provided in Comparative Example 4 was prepared as in Example 1, except that FEC was used as an additive, as shown in Table 1.

[0274] Table 1

[0275]

[0276] Note: The structural formulas of the compounds in Table 1 are shown below:

[0277] The fluorobenzene compounds shown in Formula 1-1 are The fluorobenzene compounds shown in Formula 1-2 are The fluorobenzene compounds shown in Formula 1-3 are The unsaturated sulfur-containing organic compound shown in Equation 2-1 is The unsaturated sulfur-containing organic compounds shown in Equation 2-2 are The unsaturated sulfur-containing organic compounds shown in Equation 2-3 are The unsaturated sulfur-containing organic compound shown in Equation 3-1 is

[0278] [Performance Testing]

[0279] I. Testing Methods

[0280] 1. Detection of ionic conductivity:

[0281] The conductivity of the electrolyte was tested using a Shanghai Leici DDSJ-319L conductivity meter. The specific testing method is as follows: First, rinse the conductivity cell and electrodes three times with distilled water, then rinse the conductivity cell and electrodes three times with a small amount of the electrolyte to be tested. Next, pour in the electrolyte to be tested, ensuring the liquid level is 1-2 cm above the platinum electrode in the conductivity cell. Then, place the conductivity cell in a thermostatic bath that has been preheated to the desired temperature and maintain the temperature for 15-20 minutes. Set the "Calibration / Measurement" button to the "Measurement" position, select an appropriate measurement range, and test the conductivity of the electrolyte.

[0282] 2. Detection of additives in electrolyte:

[0283] Referring to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents", the organic components in the electrolyte were qualitatively and quantitatively analyzed by gas chromatography. Batteries that had been fully discharged (discharged to the lower cutoff voltage so that the battery's state of charge was approximately 0% SOC) were disassembled and centrifuged. The centrifuged electrolyte was used as a sample and analyzed using ion chromatography.

[0284] 3. Detection of negative electrode active materials:

[0285] First, the negative electrode sheet was cut into 6mm × 6mm pieces and attached to an ion polishing machine. It was then cut at 7.5kV for 30 minutes, perpendicular to the large surface of the electrode sheet. Following the JY / T010-1996 testing standard, a Sigma300 scanning electron microscope and energy dispersive spectroscopy (EDS) were used for testing and observation. The images showed dark particles as graphite and bright particles as silicon. A single silicon particle was selected for analysis to determine the silicon-carbon elemental content ratio. Then, a large area was selected (the selection area size was defined) for whole-area elemental analysis to obtain the ratio of (graphite + carbon) to silicon. Finally, the mass ratio of graphite / silicon-carbon material was calculated, thus obtaining the percentage content of graphite and silicon-carbon materials.

[0286] 4. Battery internal resistance test:

[0287] At 25°C, the shipped lithium-ion batteries and lithium-ion batteries that have undergone 800 cycles at 25°C are charged to 4.25V at a constant current of 0.533C. Then, they are charged at a constant voltage of 4.25V until the current is less than 0.05C, and then discharged at 0.533C for 60 minutes, adjusting the battery capacity to 50% SOC. The batteries are then placed in a -20°C constant temperature chamber for 30 minutes. The positive and negative probes of a TH2523A AC internal resistance tester are connected to the positive and negative terminals of the battery, respectively, and the internal resistance values ​​are read using the tester. These are recorded as the initial battery internal resistance (mΩ) and the battery internal resistance after 800 cycles (mΩ).

[0288] 5. Room temperature cycling performance:

[0289] 25℃ Cycling: At 25℃, the prepared secondary battery (full cell) was charged to 4.25V at 0.33C, and then discharged to 2.5V at 0.5C. This constitutes one charge-discharge cycle. The discharge capacity at this point is recorded as the initial discharge capacity. The secondary battery was continued to undergo cyclic charge-discharge testing using the above method, and the discharge capacity after each cycle was recorded until the discharge capacity of the secondary battery decreased to 80% of the initial discharge capacity. The number of cycles at this point was recorded.

[0290] 6. High-temperature storage performance:

[0291] At 25°C, the secondary batteries prepared in each embodiment and comparative example were charged at a constant current rate of 0.33C to the charging cutoff voltage of 4.25V, then charged at a constant voltage rate until the current ≤0.05C, and allowed to stand for 5 minutes. They were then discharged at a constant current rate of 0.33C to the discharging cutoff voltage of 2.5V, and allowed to stand for 5 minutes. This constituted one charge-discharge cycle. The batteries were then charged at a constant current rate of 0.33C to the charging cutoff voltage of 4.25V, then charged at a constant voltage rate until the current ≤0.05C. After storing the batteries at 60°C for 100 days, cyclic charge-discharge tests were conducted on the batteries according to the above method, and the capacity retention rate of the lithium-ion batteries after 100 days of storage was calculated.

[0292] II. Test Results

[0293] The batteries provided in each embodiment and comparative example were tested, and the test results are shown in Table 2.

[0294] Table 2

[0295]

[0296] Table 2 shows that the batteries obtained from Comparative Example 1 (without additives), Comparative Example 2 (using only fluorobenzene compounds as additives), Comparative Example 3 (using only unsaturated sulfur-containing organic compounds as additives), and Comparative Example 4 (using only FEC as additives) exhibited poor cycle performance and storage performance, as well as high internal resistance. In contrast, Examples 1-16 of this application, using a combination of fluorobenzene compounds, unsaturated sulfur-containing organic compounds, and FEC as additives, and Examples 17-24, using a combination of fluorobenzene compounds and unsaturated sulfur-containing organic compounds as additives, achieved higher battery cycle performance and storage performance, and lower internal resistance. Furthermore, adjusting the amounts of each additive component and solvent further improves battery cycle performance and storage performance, and reduces battery internal resistance.

[0297] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, It includes a negative electrode sheet and an electrolyte; the negative electrode sheet includes a negative electrode active material, which includes silicon-based materials and graphite; The electrolyte includes a solvent and additives; the solvent includes propylene carbonate, and the additives include fluorobenzene compounds and unsaturated sulfur-containing organic compounds. The unsaturated sulfur-containing organic compound includes a sulfur-containing heterocyclic structure and branched chains connected to the sulfur-containing heterocyclic structure, wherein one or more of the branched chains contain unsaturated groups, and the sulfur-containing heterocyclic structure has a thioester group or a sulfate ester group.

2. The secondary battery according to claim 1, characterized in that, The structure of the fluorobenzene compounds is shown in Formula 1: In Formula 1, R1-R5 are each independently selected from one of H, halogen, substituted or unsubstituted C1-C10 saturated alkyl, substituted or unsubstituted C2-C10 unsaturated alkyl, aromatic group, carbonyl group, carboxyl group, ester group, nitrile group, and hydroxyl group.

3. The secondary battery according to claim 2, characterized in that, In Equation 1, at least one of the following (i) to (v) is satisfied: (i) The substituted or unsubstituted C1-C10 saturated alkyl group includes substituted or unsubstituted C1-C5 saturated alkyl groups; (ii) The substituted or unsubstituted C2-C10 unsaturated alkyl group includes substituted or unsubstituted C2-C5 unsaturated alkyl groups; (iii) The aromatic group includes phenyl; (iv) The hydrocarbon oxygen group includes alkoxy groups; (v) The halogens include F.

4. The secondary battery according to claim 2 or 3, characterized in that, In Formula 1, R1-R5 are each independently selected from H and F.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The fluorobenzene compounds include one or more of the compounds having the structures shown in Formulas 1-1 to 1-3:

6. The secondary battery according to any one of claims 1 to 5, characterized in that, The unsaturated sulfur-containing organic compounds include one or more of the following formulas 1-3: At least one of R6 and R7 is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and at least one of R8 and R9 is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups. 10 R 11 At least one of the groups is selected from substituted or unsubstituted C2-C10 unsaturated alkyl groups, and the remaining groups are each independently selected from H, halogen, substituted or unsubstituted C1-C10 saturated alkyl groups, substituted or unsubstituted C2-C10 unsaturated alkyl groups, aromatic groups, carbonyl groups, carboxyl groups, ester groups, nitrile groups, and isocyanate groups.

7. The secondary battery according to claim 6, characterized in that, The unsaturated sulfur-containing organic compound satisfies at least one of the following (i) to (iv): (i) The substituted or unsubstituted C2-C10 unsaturated alkyl group includes substituted or unsubstituted C2-C5 unsaturated alkyl groups; (ii) The substituted or unsubstituted C1-C10 saturated alkyl group includes substituted or unsubstituted C1-C5 saturated alkyl groups; (iii) The aromatic group includes phenyl; (iv) The halogen includes any one of F, Cl, Br, and I.

8. The secondary battery according to claim 6 or 7, characterized in that, At least one of R6 and R7 is selected from substituted or unsubstituted C2-C5 unsaturated alkyl groups, and at least one of R8 and R9 is selected from substituted or unsubstituted C2-C5 unsaturated alkyl groups. 10 R 11 At least one of the groups is selected from a substituted or unsubstituted C2-C5 unsaturated alkyl group, and the remaining groups are each independently selected from H, substituted or unsubstituted C1-C5 saturated alkyl groups.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The thioester compounds include one or more of formulas 2-1, 2-2, 2-3, and 3-1:

10. The secondary battery according to any one of claims 1 to 9, characterized in that, Based on the mass of the electrolyte, the content of the fluorobenzene compound is 0.005wt%-5wt%.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, Based on the mass of the electrolyte, the content of the fluorobenzene compound is 0.1wt%-2wt%.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, Based on the mass of the electrolyte, the content of the unsaturated sulfur-containing organic matter is 0.005wt%-5wt%.

13. The secondary battery according to any one of claims 1 to 12, characterized in that, Based on the mass of the electrolyte, the content of the unsaturated sulfur-containing organic matter is 0.1 wt% to 2 wt%.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, Based on the total mass of the solvent, the content of propylene carbonate is 2wt%-50wt%.

15. The secondary battery according to any one of claims 1 to 14, characterized in that, Based on the total mass of the solvent, the content of propylene carbonate is 5wt%-30wt%.

16. The secondary battery according to any one of claims 1 to 15, characterized in that, The additives also include fluoroethylene carbonate.

17. The secondary battery according to claim 16, characterized in that, Based on the mass of the electrolyte, the content of the fluoroethylene carbonate is 0.5 wt% to 20 wt%.

18. The secondary battery according to any one of claims 1 to 17, characterized in that, The solvent also includes ethylene carbonate.

19. The secondary battery according to claim 18, characterized in that, Based on the total mass of the solvent, the content of ethylene carbonate is less than 20 wt%.

20. The secondary battery according to any one of claims 1 to 19, characterized in that, The silicon-based material includes one or more of silicon-carbon materials, elemental silicon, and silicon-oxygen materials.

21. The secondary battery according to claim 19, characterized in that, The silicon-carbon material comprises porous carbon and nano-silicon deposited within the pores of the porous carbon; and / or, in the silicon-carbon material, the mass ratio of silicon to carbon is 6:4 to 4:

6.

22. The secondary battery according to any one of claims 1 to 21, characterized in that, Based on the mass of the negative electrode active material, the content of the silicon-based material is 5wt%-90wt%, and the content of the graphite is 10wt%-95wt%.

23. The secondary battery according to any one of claims 1 to 22, characterized in that, The electrolyte also includes electrolyte salts, which include one or more of LiPF6, LiFSI, LiTFSI, LiBF4, LiBOB, LiDFOB, LiAsF6, and LiClO4.

24. An electrical appliance, characterized in that, The secondary battery includes any one of claims 1 to 23.

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