Electrolyte and electrochemical device and electronic device using the same

Abstract

The application provides an electrolyte, an electrochemical device and an electronic device using the electrolyte. The electrolyte comprises a compound of formula I. In the compound of formula I, W, X, Y, Z, H and E are independently selected from any one of hydrogen and C1-C6 hydrocarbon groups; R1 is selected from C1-C10 alkylene groups with or without substituents; when R1 has substituents, the substituents are C1-C6 hydrocarbon groups; R2 is selected from C1-C8 halogenated hydrocarbon groups; R3 is selected from ether oxygen alkyl groups; R4 and R5 are independently selected from C1-C3 hydrocarbon groups; and m, n, r, p, h and k are independently integers from 1 to 5000. The electrochemical device provided by the application has relatively optimal electrochemical performance, especially, has relatively optimal cycle life and relatively good liquid locking capacity in a high-voltage system.

Description

Technical Field

[0001] This application belongs to the field of electrochemical technology, and in particular relates to an electrolyte and an electrochemical device and electronic device using the electrolyte. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices and other fields. As the performance requirements for lithium-ion batteries become increasingly stringent, solid-state lithium metal batteries, which combine high energy density and high safety, have become a key development direction for the next generation of lithium-ion batteries. Polymer-based solid electrolytes have good flexibility and excellent thermal stability, but they also have problems such as low ionic conductivity at room temperature and poor oxidation resistance.

[0003] With the development of quasi-solid-state batteries and in-situ solidification technology, gel polymer electrolytes can improve the ionic conductivity of polymer-based solid electrolytes and enhance the safety performance of lithium-ion batteries. On the other hand, gel polymer electrolytes can effectively solve the solid-solid interface contact problem and are conducive to large-scale application.

[0004] However, current quasi-solid-state batteries and in-situ curing technologies suffer from electrochemical decomposition of the electrolyte under higher voltage systems, leading to rapid degradation of battery performance. In addition, current quasi-solid-state batteries and in-situ curing technologies also have the problem of electrolyte leakage. Electrolyte leakage may cause internal short circuits in the battery, increasing the risk of fire and explosion, and may also damage the internal components of electronic devices, leading to equipment failure or malfunction. Summary of the Invention

[0005] The purpose of this application is to provide an electrolyte that has high voltage stability, good cycle performance, and safety. The specific technical solution is as follows:

[0006] The first aspect of this application provides an electrolyte comprising a compound of formula I:

[0007]

[0008] In the compound of formula I, X, Y, Z, H, E and W are each independently selected from hydrogen and any one of C1-C6 hydrocarbon groups;

[0009] R1 is selected from C1-C10 alkylene groups with or without substituents; if R1 has substituents, the substituents are C1-C6 hydrocarbon groups;

[0010] The R2 is selected from C1-C8 alkyl halogens;

[0011] R3 is selected from At least one of the following, wherein q is an integer between 2 and 13; R4 and R5 are respectively selected from C1-C3 hydrocarbon groups; m, n, r, p, h, and k are each independently an integer between 1 and 5000. Here, q being an integer between 2 and 13 refers to the number of repetitions of group R3, and the repeating group can be... At least one of them.

[0012] Compound I, which meets the above characteristics, has a network structure and antioxidant properties. When an electrolyte containing compound I is used in a lithium battery, it has a high ionic conductivity, which can ensure that the battery maintains good cycle performance and good liquid retention capacity under a high voltage environment of 4.5V.

[0013] Among them, the compound of formula I is a gel polymer in macroscopic form, which has a strong liquid-locking ability and can reduce leakage of electrolyte system; in microscopic form, it has a three-dimensional network structure and is rich in haloalkanes, which promotes the conduction of lithium ions and improves the ionic conductivity of electrolyte system.

[0014] In some embodiments of this application, in the compound of formula I, X, Y, Z, H, E and W are each independently selected from hydrogen and methyl. By limiting X, Z, W and Y to the above range, the compound of formula I has better polymerization effect and ion conduction effect.

[0015] In some embodiments of this application, R1 in the compound of formula I is selected from C2-C8 alkylene groups with or without substituents. By limiting R1 to carbon chains within the above range, the electrolyte has better high voltage stability and mechanical strength.

[0016] In some embodiments of this application, R2 is selected from C2-C5 fluoroalkyl groups, which have strong electron-withdrawing groups and higher steric hindrance, making them more conducive to the adsorption and desorption of lithium ions by the polymer, promoting the conduction of lithium ions, and thus further improving the ionic conductivity; at the same time, fluoroalkyl groups have better antioxidant properties, which helps to improve the high voltage stability of the electrolyte system.

[0017] In some embodiments of this application, q in R3 can be an integer between 2 and 9; R4 and R5 are selected from C1-C3 hydrocarbon groups, respectively. Since the carbonyl oxygen and alkyl oxygen in the oxalate group can form a five-membered coordination ring with lithium ions, the electrons of the oxygen in the alkoxy group move towards the lithium ion, which can improve the antioxidant properties of the polymer electrolyte. Simultaneously, it can also promote the dissolution of lithium salts and the transport of lithium ions. Furthermore, by utilizing the non-covalent bond interaction between the oxalate group and solvent molecules, a uniform network structure is formed, locking the solvent molecules within the polymer structure to form uniform and continuous lithium ion transport channels, thereby improving lithium ion conductivity and enhancing the interface.

[0018] In some embodiments of this application, the compound of formula I has at least one of the structures shown in formulas I-1 to I-17:

[0019]

[0020]

[0021]

[0022] In some embodiments of this application, the polymerization precursor of the Formula I compound includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers.

[0023] Fluorinated acrylate monomers have strong electron-withdrawing groups and higher steric hindrance, which are more conducive to the adsorption and desorption of lithium ions by polymers, promote the conduction of lithium ions, and thus further improve the ionic conductivity; at the same time, fluoroalkyl groups have better antioxidant properties, which helps to improve the high-voltage stability of the electrolyte system.

[0024] The carboxylic acid monomers can form a three-dimensional network framework, which can enhance the liquid-locking performance and reduce leakage; and the carboxylic acid ester monomers shown in Formula I have good high pressure stability, which can reduce side reactions in the cycle; and their acrylic acid structure has high conversion rate, avoiding the impact of double bond residue on electrochemical performance.

[0025] Etheroxy-containing monomers have etheroxy groups, and the etheroxy group segments can form coordinate bonds with lithium ions, thereby promoting the migration of lithium ions. Moreover, the structure of the etheroxy-containing monomers shown in Formula I provides good mechanical strength and stability for Formula I compounds and electrolytes containing Formula I compounds.

[0026] Oxalate monomers possess oxalate groups, where the carbonyl and alkyl oxygen atoms can form a five-membered coordination ring with lithium ions. Electrons from the oxygen atom in the alkoxy group migrate towards the lithium ion, enhancing the antioxidant properties of the polymer electrolyte. Simultaneously, it promotes lithium salt dissolution and lithium ion transport. Furthermore, the non-covalent interactions between the oxalate groups and solvent molecules form a uniform network structure, locking solvent molecules within the polymer structure, reducing solvent evaporation or leakage, and enhancing lithium ion transport efficiency by fixing the solvent and creating a uniform network.

[0027] In some embodiments of this application, the fluorinated acrylate monomer is selected from one or more combinations of the structures shown in formulas II-1 to II-6;

[0028]

[0029]

[0030] In some embodiments of this application, the carboxylic acid-containing monomer is selected from one or more combinations of structures shown in formulas III-1 to III-9:

[0031]

[0032] In some embodiments of this application, the ether-oxygen-containing monomer is selected from one or more combinations of the structures shown in IV-1 to IV-2:

[0033] In some embodiments of this application, the oxalate monomer is selected from one or more combinations of the structures shown in V-1 to V-9:

[0034]

[0035]

[0036] In some embodiments of this application, the polymerization precursor of the Formula I compound includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers; based on the mass of the electrolyte, before polymerization of the Formula I compound, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, and the Formula I compound satisfies at least one of the following conditions:

[0037] (5) W1 satisfies: 0.3%-16%; W2 satisfies: 0.75%-32%; W3 satisfies: 0.3%-16%; and W4 satisfies: 0.1%-10%.

[0038] (6)1≤(W2+W3) / (W1+W4)≤9.

[0039] In some embodiments of this application, the polymerization precursor of the Formula I compound includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers; based on the mass of the electrolyte, before polymerization of the Formula I compound, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, wherein W1 satisfies: 0.3%-16%; W2 satisfies: 0.75%-32%; W3 satisfies: 0.3%-16%; and W4 satisfies: 0.1%-10%.

[0040] In some embodiments of this application: In some embodiments of this application, the polymerization precursor of the Formula I compound includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers and oxalate monomers; based on the mass of the electrolyte, before polymerization of the Formula I compound, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, wherein 1≤(W2+W3) / (W1+W4)≤9.

[0041] In some embodiments of this application: when the mass content of fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers and oxalate monomers meets the above range, the monomers can better co-form the network structure of compound I, thereby locking the solvent molecules in the network structure of compound I and reducing the risk of leakage of electrolyte containing compound I.

[0042] In some embodiments of this application, the weight-average molecular weight M of the compound of formula I is... w The weight-average molecular weight is 10,000-800,000; acrylates with a high degree of polymerization are selected as the backbone of Formula I compounds, which effectively reduces the residue of unsaturated double bond monomers in Formula I compounds and enhances the intermolecular interactions within Formula I compounds, thereby improving the stability of the electrolyte system; the weight-average molecular weight is within a suitable range, making it relatively easy for other components in the electrolyte to enter the network structure of Formula I compounds, thus improving the compatibility of Formula I compounds with other components in the electrolyte system; at the same time, the intermolecular interactions within Formula I compounds are relatively strong, the residue of unsaturated double bond monomers is less, the stability is better, and the rapid degradation of battery performance and the risk of leakage are reduced.

[0043] Both etheroxy groups and oxalate groups can form coordination bonds with lithium ions, thereby promoting lithium ion migration. Furthermore, by utilizing the non-covalent interaction between oxalate groups and solvent molecules, a uniform network structure is formed, locking solvent molecules within the network structure of compound I and reducing the risk of leakage.

[0044] In some embodiments of this application, the ionic conductivity of the electrolyte is 1×10⁻⁶. -4 -3.2×10 -3S / cm; Exemplarily, the ionic conductivity of the electrolyte can be 1×10⁻⁴ S / cm, 1.5×10⁻⁴ S / cm, 2×10⁻⁴ S / cm, 2.5×10⁻⁴ S / cm, 3×10⁻⁴ S / cm, 3.5×10⁻⁴ S / cm, 4×10⁻⁴ S / cm, 4.5×10⁻⁴ S / cm, 5×10⁻⁴ S / cm, 6×10⁻⁴ S / cm, 7×10⁻⁴ S / cm, 8×10⁻⁴ S / cm, 9×10⁻⁴ S / cm, 1×10⁻³ S / cm, 1.5×10⁻³ S / cm, 2×10⁻³ S / cm, 2.5×10⁻³ S / cm, 3×10⁻³ S / cm, or a range of any two of the above values. It is understood that the above electrolytes may include a first compound, a lithium salt, and a second compound. Based on the mass of the electrolyte, the mass content of the first compound can be 3%–40%, the mass content of the lithium salt can be 10%–20%, and the mass content of the second compound can be 50%–87%. Higher ionic conductivity can accelerate the migration of lithium ions between the positive and negative electrodes, thereby effectively improving the charge-discharge performance and energy density of the battery.

[0045] In some embodiments of this application, the mass content of the compound of formula I is 3%-40% based on the mass of the electrolyte. Preferably, the mass content of the compound of formula I is 3%-20%. By limiting the mass content of the compound of formula I within the scope of this application, the mass content of the compound of formula I can be matched with the content of other components of the electrolyte, thereby reducing the risk of leakage and providing the electrolyte with higher ionic conductivity.

[0046] In some embodiments of this application, the electrolyte further includes a lithium salt, which comprises one or more combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium hexafluorophosphate, and lithium tetrafluoroborate. The lithium salt provides lithium ions, which, on the one hand, act as bridging centers, further enhancing the compatibility between the compound of Formula I and other components in the electrolyte, thereby making other components in the electrolyte more stable in the compound of Formula I, further reducing the consumption, leakage, and volatilization of other components in the electrolyte system; on the other hand, the lithium salt provides free lithium ions, further improving the ionic conductivity of the electrolyte.

[0047] In some embodiments of this application, the mass content of the lithium salt is 10%-20% based on the mass of the electrolyte. Preferably, the mass content of the lithium salt is 13%-20%. By controlling the mass content of the lithium salt within the scope of this application, on the one hand, some lithium ions act as bridging centers, further deepening the compatibility between the compound of Formula I and other components in the electrolyte, thereby making other components in the electrolyte exist more stably in the compound of Formula I, further reducing the consumption, leakage and volatilization of other components in the electrolyte system; on the other hand, the lithium salt can provide free lithium ions, further improving the ionic conductivity of the electrolyte.

[0048] In some embodiments of this application, the electrolyte further includes a second compound, which includes at least one selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, fluoroethylene carbonate, or difluoroethylene carbonate; based on the mass of the electrolyte, the mass content of the second compound is 50%-87%. Preferably, the mass content of the second compound is 65-85%. By controlling the type and mass content of the second compound in the electrolyte within the scope of this application, the second compound has good compatibility with acrylate groups and halogenated hydrocarbon groups (especially fluoroalkyl groups) in Formula I compounds. Simultaneously, lithium ions can further enhance the compatibility between Formula I compounds and the second compound, thereby making the second compound more stable in Formula I compounds; furthermore, the second compound can further improve the ionic conductivity of the electrolyte.

[0049] In some embodiments of this application, the electrolyte in any of the above embodiments is prepared by the following method: mixing a halogen-containing acrylate monomer, an acrylate-containing monomer, a carboxylic acid-containing monomer, an ether-oxygen-containing monomer, an oxalate monomer, an initiator, a lithium salt, and a second compound uniformly to obtain a precursor solution;

[0050] The precursor solution was subjected to a polymerization reaction to obtain the above-mentioned electrolyte.

[0051] In one embodiment of this application, the polymerization reaction may include an initiation process and a polymerization process. The initiation process may have a reaction temperature of 55°C to 60°C and a reaction time of 0.5 h to 1 h. Exemplarily, the initiation process reaction temperature may be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, or a range of any two of the above values. The initiation process reaction time may be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, or a range of any two of the above values. The polymerization reaction temperature is 40°C to 80°C, and the polymerization reaction time is 6 h to 24 h. For example, the reaction temperature T1 of the polymerization reaction can be 40℃, 42℃, 44℃, 45℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, or a value within any two of the above ranges. For example, the reaction time t1 of the polymerization reaction can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, or a value within any two of the above ranges. Preferably, the reaction time t1 of the polymerization reaction is 10h to 20h.

[0052] In one embodiment of this application, the initiator is selected from at least one of photoinitiators and thermal initiators, preferably from at least one of 2-hydroxy-2-methyl-1-phenylpropanone, methyl benzoylcarbamate, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, azobisisobutyronitrile (AIBN), dimethyl azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide, more preferably from at least one of azobisisobutyronitrile, methyl benzoylcarbamate, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0053] In one embodiment of this application, the second compound is selected from at least one of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), methyl formate (MF), methyl acetate (MA), methyl butyrate (MB), ethyl propionate (EP), methyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), preferably at least one of fluoroethylene carbonate (FEC), propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DC), and methyl methyl carbonate (EMC).

[0054] Exemplarily, the mass content of the initiator can be 0.01%, 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or a value within any two of the above ranges. Preferably, the mass content of the initiator is 0.05% to 1%. In one embodiment of this application, the initiator can be azobisisobutyronitrile (AIBN).

[0055] The electrolyte prepared by the method of this application has high voltage stability and can maintain good cycle performance and good liquid retention ability at high voltage.

[0056] A second aspect of this application provides an electrochemical device comprising a positive electrode and a negative electrode, and an electrolyte as described in any of the foregoing embodiments.

[0057] Applying the above-mentioned electrolyte to a battery allows it to be matched with a silicon-based negative electrode and a high-voltage positive electrode, resulting in high voltage stability and good liquid-locking capability. The voltage of the high-voltage positive electrode can be higher than 4.35V or even 4.4V. In another embodiment of this application, the voltage of the high-voltage positive electrode can be 4.5V.

[0058] In some embodiments of this application, the electrochemical device has at least one of the following features:

[0059] (7) After the electrochemical device is opened, the mass of the electrolyte flowing out under a pressure of 200-400N accounts for less than 1% of the total mass of the electrochemical device;

[0060] (8) After the electrochemical device is opened, it is shielded with a 1500-2500 mesh screen and centrifuged at 3000-3400 rpm for 5-15 minutes. The mass of the electrolyte discharged by centrifugation accounts for less than 1% of the total mass of the electrochemical device.

[0061] In some embodiments of this application, the opening treatment of the electrochemical device can refer to the opening treatment of the electrochemical device in the central region of the electrochemical device along the length direction of the electrochemical device; the central region can be the battery region in the width direction, which is 1 / 4L-1 / 2L away from the two sides of the electrochemical device, where L is the width of the electrochemical device.

[0062] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, which includes at least one lithium cobalt oxide. The positive electrode active material may be a material that has undergone doping modification, surface coating modification, or both doping and surface coating modification of lithium cobalt oxide.

[0063] In some embodiments of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, which includes at least one of pure silicon, silicon-carbon, and graphite. In another embodiment of this application, the negative electrode may also be a lithium metal negative electrode, a carbon-based negative electrode, etc. In one embodiment of this application, the electrochemical device may be a secondary battery, for example, a lithium-ion battery or a lithium metal battery.

[0064] A third aspect of this application provides an electronic device that includes the electrochemical device in any of the foregoing embodiments. The electrochemical device of this application exhibits good high-pressure stability, as well as excellent cycle performance and safety. Therefore, the electronic device provided by this application simultaneously possesses high-pressure stability, good cycle performance, and liquid-locking capability.

[0065] The beneficial effects of this application are:

[0066] This application provides a novel electrolyte, electrochemical device, and electronic device. The electrolyte includes a compound of formula I, which has a network structure and high antioxidant properties. When the electrolyte including the compound of formula I is used in a lithium battery, it has the characteristics of high voltage stability of 4.5V, good liquid retention capacity, and improved cycle performance.

[0067] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0068] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0069] Figure 1 This is a high-voltage cycle capacity retention rate test chart for Embodiment 1 of this application. Detailed Implementation

[0070] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0071] In the following detailed description, numerous specific details are set forth for ease of explanation to provide a thorough understanding of the embodiments of this application. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0072] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0073] In this application, the term "substituted or unsubstituted" can refer to a group that is substituted with one substituent or multiple substituents. When multiple substituents are selected, they can be selected from different substituents. In this application, the same expression means the same thing, and the range of substituents to be selected is as shown above and will not be repeated here.

[0074] In this application, "each independently" means that when there are multiple subjects, they may be the same or different from each other.

[0075] In this application, unless otherwise specified, the description of chemical elements usually includes the concept of isotopes with the same chemical properties. For example, the description of "hydrogen (H)" also includes the concepts of 1H (protium or H) and 2H (deuterium or D) with the same chemical properties; carbon (C) includes 12C, 13C, etc., which will not be elaborated further.

[0076] In this application, the expression Ca-Cb represents that the group has ab carbon atoms. Unless otherwise specified, the number of carbon atoms generally does not include the number of carbon atoms of the substituents.

[0077] In this application, the term "alkyl" may include a branched or straight-chain saturated aliphatic monovalent hydrocarbon group having a specified number of carbon atoms. Examples of C1-C10 alkyl groups include: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.

[0078] In this application, the term "hydrocarbon group" can include a straight-chain or branched saturated aliphatic monovalent hydrocarbon group or an unsaturated aliphatic monovalent hydrocarbon group having a specified number of carbon atoms. Examples of C1-C6 saturated hydrocarbon groups include: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, decyl, undecyl, dodecyl, etc. Unsaturated hydrocarbon groups (C1-C6) can be formed by replacing one or more single bonds in a C1-C6 straight-chain or branched saturated hydrocarbon group with double bonds, etc.

[0079] In this application, the term "halogenated hydrocarbon group" can include a straight-chain or branched saturated aliphatic monovalent hydrocarbon group or an unsaturated aliphatic monovalent hydrocarbon group formed by replacing one or more hydrogen atoms having a specified number of carbon atoms with halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, iodine, etc. Examples of C1-C8 halogenated hydrocarbon groups include trifluoromethyl, 1-fluoroethyl, 1,1-dibromoethyl, etc.

[0080] In this application, the term "alkylene" may include a saturated aliphatic divalent hydrocarbon group having a specified number of carbon atoms. Examples of C1-C10 alkylene groups include methylene, ethylene, propylene, and pentylene.

[0081] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing description of the drawings, are intended to cover non-exclusive inclusion. Unless otherwise stated, the terms used in this application have their commonly understood meanings as understood by one of ordinary skill in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0082] Based on this, the first aspect of this application provides an electrolyte comprising a compound of formula I:

[0083]

[0084] In Formula I, X, Y, Z, H, E, and W are each independently selected from hydrogen and any one of C1-C6 hydrocarbon groups; R1 is selected from C1-C10 alkylene groups with or without substituents; if R1 has a substituent, the substituent is a C1-C6 hydrocarbon group; R2 is selected from C1-C8 haloalkyl groups; R3 is selected from... At least one of the following, wherein q is an integer between 2 and 13; R4 and R5 are respectively selected from C1-C3 hydrocarbon groups; m and n are each independent integers between 1 and 5000.

[0085] For example, X, Y, Z, H, E and W can each be independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl, phenyl, etc.

[0086] For example, in the absence of substituents, R1 can be selected from alkylene groups of methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, and decane; in the presence of substituents, the substituents of R1 can be selected from methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl, phenyl, etc., and the number of substituents can be one or more. When multiple substituents are selected, they can be selected from different substituents.

[0087] For example, R2 can be selected from straight-chain or branched saturated aliphatic monovalent hydrocarbon groups or unsaturated aliphatic monovalent hydrocarbon groups formed by replacing one or more hydrogen atoms in C1-C8 with halogen atoms. Specifically, R2 can be selected from fluoromethyl, chloromethyl, trichloromethyl, 1-fluoroethyl, 1,1-dibromoethyl, 2-chloropropyl, etc.

[0088] For example, m and n can each be independently 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 or 5000, or a value within a range of any two of the above values.

[0089] According to the embodiments of this application, the compound of formula I is a gel polymer in a macroscopic state, which has a strong liquid-locking ability and can reduce leakage of the electrolyte system. In terms of microstructure, the compound of formula I has a three-dimensional network structure and is rich in haloalkanes. This structure promotes the conduction of lithium ions and improves the ionic conductivity of the electrolyte system. In addition, the R1 group selected from C1-C10 alkylene groups and the R2 group selected from C1-C8 haloalkanes attached to the compound of formula I improve the antioxidant capacity and ion migration ability of the electrolyte system.

[0090] R3 attached to compound I can form coordination bonds with lithium ions, thereby promoting lithium ion migration; the cross-linked structure provides good mechanical strength and stability, which helps to maintain the integrity of the electrolyte membrane and prevent internal short circuits in the battery.

[0091] The R4 and R5 attached to the compound of formula I form a structure of suitable spatial size, which helps the polymer to move and promotes lithium ion migration.

[0092] Electrolytes that meet the above characteristics have high voltage stability and can maintain good cycling performance and good liquid retention capacity at high voltages.

[0093] In some embodiments of this application, in Formula I, X, Y, Z, H, E and W are each independently selected from hydrogen and methyl. By limiting X and Y to the above range, the compound of Formula I has better polymerization effect and ion conduction effect.

[0094] In some embodiments of this application, R1 is selected from C1-C10 alkylene groups with or without substituents.

[0095] In some embodiments of this application, when R1 has a substituent, the substituent is a C1-C6 hydrocarbon group. By limiting R1 to a carbon chain within the above range, the electrolyte has better high voltage stability and mechanical strength.

[0096] In some embodiments of this application, R2 is selected from C1-C8 halogenated hydrocarbon groups; R2 is preferably a C2-C5 fluoroalkyl group. The R2 structure provides a strong electron-withdrawing group and higher steric hindrance, which is more conducive to the adsorption and desorption of lithium ions by the polymer, promotes the conduction of lithium ions, and thus further improves the ionic conductivity; at the same time, fluoroalkyl groups have better antioxidant properties, which helps to improve the high voltage stability of the electrolyte system.

[0097] In some embodiments of this application, R3 is selected from...

[0098] At least one of the following, where q is an integer between 2 and 13.

[0099] In some embodiments of this application, in Formula I: R1 is selected from C2-C8 alkylene groups with or without substituents.

[0100] In some embodiments of this application, R2 is selected from C2-C5 fluoroalkyl groups; q in R3 is 2-9; and R4 and R5 are selected from C1-C3 hydrocarbon groups, respectively.

[0101] In some embodiments of this application, the compound of formula I has at least one of the structures shown in formulas I-1 to I-17:

[0102]

[0103]

[0104]

[0105] In some embodiments of this application, the compound of formula I includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers.

[0106] In some embodiments of this application, the fluorinated acrylate monomer is selected from one or more combinations of the structures shown in formulas II-1 to II-6;

[0107]

[0108] In some embodiments of this application, the second monomer is selected from one or more combinations of the structures shown in formulas III-1 to III-9:

[0109]

[0110] In some embodiments of this application, the third monomer is selected from one or more combinations of the structures shown in IV-1 to IV-2:

[0111] In some embodiments of this application, the fourth monomer is selected from one or more combinations of the following monomers:

[0112]

[0113]

[0114] In some embodiments of this application, the polymerization precursor of the Formula I compound includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers; based on the mass of the electrolyte, before polymerization of the Formula I compound, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, and the Formula I compound satisfies at least one of the following conditions:

[0115] (5) W1 meets the following criteria: 0.3%-16%; W2 meets the following criteria: 0.75%-32%; W3 meets the following criteria: 0.3%-16%; and W4 meets the following criteria: 0.1%-10%.

[0116] (6)1≤(W2+W3) / (W1+W4)≤9.

[0117] In some embodiments of this application, the polymerization precursor of the Formula I compound includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers; based on the mass of the electrolyte, before polymerization of the Formula I compound, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, wherein W1 satisfies: 0.3%-16%; W2 satisfies: 0.75%-32%; W3 satisfies: 0.3%-16%; and W4 satisfies: 0.1%-10%.

[0118] The polymerization precursor of the compound of formula I includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers; based on the mass of the electrolyte, before polymerization of the compound of formula I, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, wherein 1≤(W2+W3) / (W1+W4)≤9.

[0119] In some embodiments of this application, W1 and W3 may, by way of example, be 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or values ​​within a range of any two of the above values.

[0120] In some embodiments of this application, W2 can be, by way of example, 0.75%, 1%, 2%, 3%, 7%, 8%, 9%, 10%, 14%, 15%, 16%, 20%, 25%, 30%, 32%, or a value within a range of any two of the above values.

[0121] In some embodiments of this application, W4 can be, by way of example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a value within a range of any two of the above values.

[0122] In some embodiments of this application, for example, (W2+W3) / (W1+W4) can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or a value within a range of any two of the above values.

[0123] In some embodiments of this application, the weight-average molecular weight M of the compound of formula I is... w The weight-average molecular weight M of the compound of formula I is 10,000-800,000; for example, the weight-average molecular weight M of the compound of formula I is... w It can be 10000, 20000, 50000, 100000, 200000, 300000, 330000, 350000, 380000, 400000, 450000, 400000, 500000, 600000, 700000, 800000, or a value within the range of any two of the above values.

[0124] Choosing acrylates with a high degree of polymerization as the backbone of Formula I effectively reduces the residual unsaturated double-bonded monomers in Formula I and enhances the intermolecular interactions within the Formula I compound, thereby improving the stability of the electrolyte system. A suitable weight-average molecular weight improves the compatibility of Formula I compound with other components in the electrolyte system. Excessively high weight-average molecular weight increases the difficulty for other components in the electrolyte system to enter Formula I compound; excessively low weight-average molecular weight leads to rapid performance degradation and an increased risk of leakage.

[0125] In some embodiments of this application, the conductivity of the electrolyte is 1×10⁻⁶. -4 -3.2×10 -3 S / cm;

[0126] For example, the conductivity of the electrolyte can be 1×10⁻⁶. -4 S / cm, 5×10 -4 S / cm, 1×10 -3 S / cm, 2×10 - 3 S / cm, 3×10 -3 S / cm, 3.2×10 -3 S / cm can be any value within the range of any two of the above values. It is understood that the electrolyte may include a first compound, a lithium salt, and a second compound. Based on the mass of the electrolyte, the mass content of the first compound can be 3%–40%, the mass content of the lithium salt can be 10%–20%, and the mass content of the second compound can be 50%–87%. Higher conductivity can accelerate the migration of lithium ions between the positive and negative electrodes, thereby effectively improving the battery's charge / discharge performance and energy density.

[0127] In some embodiments of this application, the mass content of the compound of formula I is 3%-40% based on the mass of the electrolyte. Preferably, the mass content of the compound of formula I is 3%-15%. Exemplarily, based on the mass of the electrolyte, the mass content of the compound of formula I can be 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or a value within a range of any two of the above values.

[0128] By limiting the mass content of compound I within the scope of this application, the mass content of compound I can be matched with the content of other components of the electrolyte, thereby reducing the risk of leakage and providing the electrolyte with higher ionic conductivity.

[0129] In some embodiments of this application, the electrolyte comprises a lithium salt, which includes one or more combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium hexafluorophosphate, and lithium tetrafluoroborate. The lithium salt provides lithium ions, which, on the one hand, act as bridging centers, further enhancing the compatibility between the compound of Formula I and other components in the electrolyte, thereby making other components in the electrolyte more stable in the compound of Formula I, further reducing the consumption, leakage, and volatilization of other components in the electrolyte system; on the other hand, the lithium salt provides free lithium ions, further improving the ionic conductivity of the electrolyte.

[0130] In some embodiments of this application, the lithium salt has a mass content of 10%-20% based on the mass of the electrolyte. Preferably, the lithium salt has a mass content of 13%-20%.

[0131] For example, based on the mass of the electrolyte, the mass content of the lithium salt can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or a value within a range of any two of the above values.

[0132] By controlling the mass content of lithium salt within the scope of this application, on the one hand, some lithium ions act as bridging centers, further enhancing the compatibility between the above-mentioned Formula I compound and other components in the electrolyte, thereby making other components in the electrolyte exist more stably in the Formula I compound, further reducing the consumption, leakage and volatilization of other components in the electrolyte system; on the other hand, lithium salt can provide free lithium ions, further improving the ionic conductivity of the electrolyte.

[0133] In some embodiments of this application, the electrolyte further includes a second compound, which includes at least one selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, fluoroethylene carbonate, or difluoroethylene carbonate; based on the mass of the electrolyte, the mass content of the second compound is 50%-87%, preferably 65-85%. Within the scope of this application, by controlling the type and mass content of the second compound in the electrolyte, the second compound exhibits good compatibility with acrylate groups and halogenated hydrocarbon groups (especially fluoroalkyl groups) in Formula I compounds. Simultaneously, lithium ions can further enhance the compatibility between Formula I compounds and the second compound, thereby making the second compound more stable in Formula I compounds; the second compound can also further improve the ionic conductivity of the electrolyte.

[0134] In some embodiments of this application, the electrolyte in any of the above embodiments is prepared by the following method: mixing a halogen-containing acrylate monomer, an acrylate-containing monomer, a carboxylic acid-containing monomer, an ether-oxygen-containing monomer, an oxalate monomer, an initiator, a lithium salt, and a second compound uniformly to obtain a precursor solution;

[0135] The precursor solution was subjected to a polymerization reaction to obtain the above-mentioned electrolyte.

[0136] In one embodiment of this application, the reaction temperature of the initiation process can be 55°C to 60°C, and the reaction time of the initiation process can be 0.5h to 1h. Exemplarily, the reaction temperature of the initiation process can be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, or a range consisting of any two of the above values. The reaction time of the initiation process can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, or a range consisting of any two of the above values.

[0137] The polymerization reaction temperature is 40℃-80℃, and the reaction time is 6h-24h. For example, the polymerization reaction temperature T1 can be 40℃, 42℃, 44℃, 45℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, or a value within any two of the above ranges. For example, the polymerization reaction time t1 can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, or a value within any two of the above ranges. Preferably, the polymerization reaction time t1 is 10h to 20h.

[0138] The electrolyte prepared by the method of this application has high voltage stability and can maintain good cycle performance and good liquid retention ability at high voltage.

[0139] A second aspect of this application provides an electrochemical device comprising a positive electrode and a negative electrode, and an electrolyte as described in any of the foregoing embodiments. When this electrolyte is used in a battery, it can be matched with silicon-based negative electrodes, lithium metal and carbon-based negative electrodes, and high-voltage positive electrodes, wherein the high voltage is higher than 4.5V. The battery provided by this application exhibits good cycle performance and safety while maintaining high-voltage stability.

[0140] In some embodiments of this application, the electrochemical device has at least one of the following features:

[0141] (7) After the electrochemical device is opened, the mass of the electrolyte flowing out under a pressure of 200-400N accounts for less than 1% of the total mass of the battery;

[0142] (8) After the electrochemical device is opened, it is shielded by a 1500-2500 mesh screen and centrifuged at 3000-3400 rpm for 5-15 minutes. The mass of the electrolyte centrifuged out is less than 1% of the total mass of the battery.

[0143] For example, the pressure can be 200N, 220N, 250N, 280N, 300N, 330N, 350N, 380N, 400N, or a value within the range of any two of the above values. The mesh size of the screen can be 1500 mesh, 1800 mesh, 2000 mesh, 2500 mesh, etc. The centrifugal speed can be 3000rpm, 3100rpm, 3200rpm, 3300rpm, 3400rpm, or a value within the range of any two of the above values.

[0144] In one embodiment of this application, "electrochemical device with opening treatment" can refer to opening the electrochemical device in the central region of the electrochemical device along the length direction of the battery; the central region can be the battery region located 1 / 4L-1 / 2L away from the two sides of the battery in the width direction, where L is the width of the electrochemical device.

[0145] In some embodiments of this application, the aforementioned positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, which includes at least one lithium cobalt oxide. The positive electrode active material may be a lithium cobalt oxide that has undergone doping modification, surface coating modification, or both doping and surface coating modification, which can better match the electrolyte and enable the battery to have high voltage stability.

[0146] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0147] The aforementioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or it can be disposed on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector, or it can be a part of the surface of the positive electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0148] The positive electrode material layer of this application also includes a positive electrode conductive agent and a positive electrode binder. This application does not impose any particular limitations on the positive electrode conductive agent and positive electrode binder in the positive electrode material layer, as long as they can achieve the purpose of this application. For example, the positive electrode binder may include, but is not limited to, at least one of polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene-butadiene copolymer (styrene-butadiene rubber), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium carboxymethyl cellulose, or potassium carboxymethyl cellulose. The positive electrode conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. Conductive carbon black may include, but is not limited to, acetylene black or Ketjen black. Carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. Carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The metallic material may include, but is not limited to, metal powder and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application can be achieved. For example, based on the mass of the positive electrode material layer, the mass content of the positive electrode active material is 80% to 98%, the mass content of the positive electrode conductive agent is 0.5% to 10%, and the mass content of the positive electrode binder is 1.5% to 10%.

[0149] This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector can be 8 μm to 15 μm. This application also does not impose any particular limitation on the thickness of the positive electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided positive electrode material layer can be 30 μm to 40 μm.

[0150] Optionally, the positive electrode may further include a conductive layer, which is located between the positive current collector and the positive electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer; it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; they can be at least one of a positive electrode conductive agent and a positive electrode binder. This application does not impose any particular limitation on the mass ratio of the conductive agent to the binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved.

[0151] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The negative electrode material layer includes a negative electrode active material, which includes at least one of pure silicon, silicon carbide, and graphite.

[0152] For example, the negative electrode active material may include silicon-carbon, wherein the silicon content may be 20%-80% by mass.

[0153] In the electrochemical device of this application, the negative electrode active material may include at least one of pure silicon, silicon-carbon, and graphite, which can be well matched with the electrolyte, enabling the electrochemical device to have high voltage stability, superior cycle life, and liquid-locking capability. The aforementioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved.

[0154] The negative electrode material layer of this application also includes a negative electrode conductive agent and a negative electrode binder. This application does not impose any particular limitations on the negative electrode conductive agent and negative electrode binder in the negative electrode material layer, as long as they can achieve the purpose of this application. For example, the negative electrode binder may include, but is not limited to, at least one of lithium polyacrylate, polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene-butadiene copolymer (styrene-butadiene rubber), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium carboxymethyl cellulose, or potassium carboxymethyl cellulose. The negative electrode conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. Conductive carbon black may include, but is not limited to, acetylene black or Ketjen black. Carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. Carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The metallic material may include, but is not limited to, metal powder and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder in the negative electrode material layer. Those skilled in the art can select these components according to actual needs, as long as the purpose of this application is achieved. For example, based on the mass of the negative electrode material layer, the mass content of the negative electrode active material may be 80% to 98%, the mass content of the negative electrode conductive agent may be 0.5% to 10%, and the mass content of the negative electrode binder may be 0.5% to 10%.

[0155] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves the purpose of this application; for example, it may include copper foil, nickel foil, etc. This application does not impose any particular limitation on the thickness of the negative electrode sheet, as long as it achieves the purpose of this application. This application does not impose any particular limitation on the shape and size of the negative electrode sheet, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector is 5 μm to 15 μm. This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it achieves the purpose of this application; for example, the thickness of a single-sided negative electrode material layer is 30 μm to 60 μm.

[0156] Optionally, the negative electrode sheet may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and they can be at least one of a negative electrode conductive agent and a negative electrode binder. This application does not impose any particular limitation on the mass ratio of the conductive agent and binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved.

[0157] In this application, a separator is used to separate the positive and negative electrode plates, preventing internal short circuits in the battery, allowing ions to pass freely, and not affecting the electrochemical charging and discharging process. This application does not impose any particular limitations on the separator, as long as it achieves the purpose of this application. For example, the separator material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the separator type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0158] In this application, the separator may include a substrate and a surface treatment layer. The substrate may be a nonwoven fabric or composite membrane with a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a separator binder. This application does not have any particular limitation on the inorganic particles, and may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not have any particular limitation on the separator binder, and may include at least one of the aforementioned positive electrode binders. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0159] In one embodiment of this application, the diaphragm can be prepared by the following method: Alumina, polyvinylidene fluoride (PVDF), and an organic solvent are mixed uniformly to obtain an inorganic layer slurry; the inorganic layer slurry is coated onto one surface of a substrate and dried to obtain a diaphragm with an inorganic layer coated on one side; then, PVDF is mixed with an organic solvent to obtain a polymer layer slurry; the polymer layer slurry is coated onto the surface of the inorganic layer away from the substrate and dried to obtain a diaphragm with both an inorganic layer and a polymer layer coated on one side; the polymer layer slurry is uniformly coated onto the other surface of the substrate and dried to obtain a diaphragm, wherein one side of the diaphragm is coated with both an inorganic layer and a polymer layer, and the other side is coated only with a polymer layer. In this application, there are no particular limitations on the mass ratio of alumina, polyvinylidene fluoride (PVDF), and the organic solvent, as long as the purpose of this application can be achieved. This application does not impose any particular restrictions on the thickness of the inorganic layer, polymer layer, and substrate, as long as the purpose of this application can be achieved. This application also does not impose any particular restrictions on the selection of organic solvents, as long as the purpose of this application can be achieved, such as N-methylpyrrolidone, dimethyl sulfoxide, etc.

[0160] The battery of this application also includes a packaging bag for containing the positive electrode, negative electrode, separator, and electrolyte, as well as other components known in the art, which are not limited in this application. This application does not impose any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it achieves the purpose of this application. For example, an aluminum-plastic film packaging bag can be used.

[0161] In one embodiment of this application, the electrochemical device can be a secondary battery, such as a lithium-ion battery or a lithium metal battery.

[0162] A third aspect of this application provides an electronic device that includes the electrochemical device in any of the foregoing embodiments. The electrochemical device of this application exhibits high-pressure stability, good cycle performance, and safety. Therefore, the electronic device provided by this application simultaneously possesses high-pressure stability, good cycle performance, and the safety provided by leak-proof operation.

[0163] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. For example, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors.

[0164] Example

[0165] The following describes the implementation of this application in more detail through specific embodiments and comparative examples, but this application is not limited to these embodiments as long as it does not depart from its spirit.

[0166] The test methods used in the following examples and comparative examples are as follows:

[0167] (1) Weight-average molecular weight test:

[0168] The products of the precursor solutions in each embodiment and comparative example were sampled after polymerization for 12 hours to obtain samples. The samples were dissolved in N-methylpyrrolidone (NMP), and the chromatographic elution curves of the samples were tested using ultra-high performance polymer chromatography (ACQUITYAPC). The weight-average molecular weight of the corresponding samples was calculated using styrene as a standard.

[0169] (2) Polymer structure testing:

[0170] Electrolytes and polymers were separated by Soxhlet extraction, and then the basic functional groups of the polymers were determined by infrared spectroscopy.

[0171] (3) Monomer conversion rate test:

[0172] Samples were taken from the products of the precursor solutions in each example and comparative example after polymerization for 16 hours. The samples were dissolved in deuterated dimethyl sulfoxide (tritated DMSO) and the 1H NMR spectra of the samples were tested using a 400 MHz NMR spectrometer (AVANCEIIIHD 400). The monomer conversion rates of the corresponding monomers were calculated.

[0173] (4) Electrolyte ionic conductivity test:

[0174] Stainless steel sheets, separators, and stainless steel sheets are stacked in sequence, injected with the precursor liquids prepared in each example and comparative example, and then encapsulated. After standing for 12 hours, a liquid battery is obtained. Then, it is polymerized at 60°C for 16 hours. After the reaction is complete, a coin cell is obtained.

[0175] The ionic conductivity of the electrolyte was tested using an electrochemical workstation (Solartron 1470E) via AC impedance spectroscopy. The test temperature was 25°C, the frequency range was 1MHz to 100mHz, and the perturbation amplitude was 10mV.

[0176] The ionic conductivity of the electrolyte was measured at room temperature (25°C).

[0177] (5) Cyclic performance test:

[0178] At an ambient temperature of 25°C, the secondary batteries prepared in each embodiment and comparative example were charged at a constant current of 1C to a voltage of 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.05C. The charging capacity at this point was recorded as the first charge capacity of the secondary battery. After resting for 5 minutes, the batteries were discharged at a constant current of 1C to a voltage of 3.0V, and then rested for 5 minutes. This constitutes one charge-discharge cycle, and the discharge capacity at this point was recorded as the first discharge capacity of the secondary battery, which is also the initial capacity of the secondary battery. The secondary batteries were subjected to 200 charge-discharge cycle tests according to the above method, and the discharge capacity of the 200th cycle was recorded.

[0179] The capacity retention rate (%) of a secondary battery after 200 cycles at 25°C = discharge capacity of the 200th cycle / maximum discharge capacity within 5 cycles × 100%.

[0180] (6) Leakage test:

[0181] Take a lithium-ion battery and make an opening along its length at the center line. (The center line is located equidistant from the two edges of the battery in the width direction). After making the opening, cover the battery with a 2000-mesh screen and centrifuge at 3200 rpm for 10 minutes. Calculate the mass of the centrifuged electrolyte as a percentage of the total battery mass. Leakage is marked as follows: less than 1% of the total battery mass (A); 1% to 2% (B); 2% to 5% (C); and more than 5% (D).

[0182] Example 1-1

[0183] <Preparation of the positive electrode>

[0184] Preparation of lithium cobalt oxide cathode material: LiCoO2, acetylene black, and polyvinylidene fluoride (PVDF, weight average molecular weight 5×105) were mixed in a weight ratio of 94:3:3 and added to N-methylpyrrolidone (NMP) solvent. The mixture was stirred evenly under vacuum to obtain a cathode slurry with a solid content of 75wt%. The cathode slurry was uniformly coated on the surface of the cathode current collector aluminum foil and dried at 90℃ to obtain the cathode electrode sheet.

[0185] <Preparation of Negative Electrode Sheets>

[0186] Preparation of silicon-carbon negative electrode sheet: A mixture of silicon and carbon (mass ratio 50:50) is used as the negative electrode active material, Super P as the conductive agent, styrene-butadiene rubber as the binder, and sodium carboxymethyl cellulose (CMC, weight average molecular weight 90,000) as the thickener. The active material, Super P, sodium carboxymethyl cellulose, and styrene-butadiene rubber are mixed in a weight ratio of 95.7:0.5:0.8:3, and deionized water is added. A negative electrode slurry with a solid content of 45 wt% is obtained under vacuum stirring. The active material layer slurry is uniformly coated onto one surface of an 8 μm thick copper foil used as the negative electrode current collector. The coating is dried at 80°C to form the negative electrode active material layer, which is then cold-pressed and slit to obtain the negative electrode sheet.

[0187] <Preparation of the diaphragm>

[0188] Preparation of the separator: Polyethylene (PE) with a thickness of 8 μm and a porosity of 55% was selected as the base membrane. PVDF slurry and inorganic particulate slurry (plate boehmite and Al2O3 in a mass ratio of 70:30) were distributed and coated on both surfaces of the base membrane, and then dried to obtain the separator membrane. The coating thickness on each surface of the separator membrane was 3 μm.

[0189] <Preparation of Electrolytes and Batteries>

[0190] (1) Fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, oxalate monomers, initiator (AIBN), lithium salt (LiPF6) and non-aqueous solvent are mixed evenly to obtain a precursor solution;

[0191] (2) The precursor solution was polymerized at 60°C for 16 h to obtain the electrolyte;

[0192] (3) The positive electrode, separator and negative electrode are stacked in sequence, injected with precursor solution and then encapsulated to obtain a liquid battery. The precursor solution in the liquid battery undergoes a polymerization reaction to obtain the battery.

[0193] Based on the mass of the precursor solution, the mass contents of fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers are as follows: W2 = 4%, W1 = 2%, W3 = 3%, and W4 = 1%. The mass contents of the initiator are 0.25%, the lithium salt is 13.7%, and the fluoroethylene carbonate (FEC) is 5%. The balance is a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC:DEC = 3:7). Inside the battery, the polymerization initiation temperature of compound I is 60°C, the initiation time is 1 hour, the polymerization reaction temperature is 60°C, and the polymerization reaction time is 15 hours.

[0194] The lithium-ion batteries in the following examples or comparative examples differ from those in Examples 1-1 only in that the types of fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers in the precursor solution are adjusted according to Table 1. The performance test results of the lithium-ion batteries in each example and comparative example are shown in Table 1 below.

[0195] Table 1

[0196]

[0197] The lithium-ion batteries in the following examples or comparative examples differ from those in Examples 1-2 only in that the amounts of W1, W2, W3, W4, Formula I compound, lithium salt, and the second compound are adjusted according to Table 2. The performance test results of the lithium-ion batteries in each example and comparative example are shown in Table 2 below.

[0198] Table 2

[0199]

[0200]

[0201] The lithium-ion batteries in Examples 3-1 to 3-3 differ from those in Examples 1-2 only in that the reaction parameters in the polymerization process are adjusted according to Table 3. The performance test results of the lithium-ion batteries in each example are shown in Table 3 below.

[0202] Table 3

[0203]

[0204] Figure 1 Table 1 shows the cycle capacity retention rate test graphs obtained from cycle performance tests of Examples 1-2 and 1-14 of this application. The horizontal axis represents the number of charge-discharge cycles, and the vertical axis represents the capacity retention rate. In Table 1, the monomers added in Comparative Examples 1 and 2, and the carboxylic acid-containing monomer added in Comparative Example 3, have R1 values ​​exceeding the range defined in this application. Comparative Example 4 did not add the monomers added in this application. Therefore, Comparative Examples 1 to 4 cannot obtain the compound of Formula I of this application. Combining the capacity retention rate data and leakage conditions of Comparative Examples 1, 2, and 4 in Table 1, it can be seen that the battery with the compound of Formula I added in this application has a better capacity retention rate and a better liquid-locking ability.

[0205] As shown in Table 2, in Examples 2-1 to 2-9, 1 ≤ (W2+W3) / (W1+W4) ≤ 9. Compared to Comparative Example 5, where (W2+W3) / (W1+W4) is 0.4 and Comparative Example 7, where (W2+W3) / (W1+W4) is 9.4, Examples 2-1 to 2-9 exhibit better cycle capacity retention and better liquid retention. A comparison of Example 2-1 and Comparative Example 6 in Table 2 shows that when the amount of Compound I added is less than 3%, the battery has a risk of leakage; when the amount of Compound I added is greater than 40%, the battery's cycle capacity retention is poor.

[0206] As can be seen from Table 3, compared with Examples 3-1 and 3-2, the weight-average molecular weight M of Comparative Examples 8 and 9 is significantly lower. w If the weight-average molecular weight is not in the range of 10,000-800,000, it can be seen that when the weight-average molecular weight M... w Batteries with excessively large or small molecular weights exhibit poor cycle capacity retention, and their weight-average molecular weight M... w When the weight-average molecular weight M is too small, there is still a serious problem of leakage; combining Examples 3-1, 3-2, and 1-1 to 1-17, it can be seen that when the weight-average molecular weight M w Within the range of 10,000-800,000 cycles, the battery can simultaneously maintain good cycle capacity and reduce the risk of leakage.

[0207] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0208] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The above descriptions are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises a compound of formula I as shown below: In the compound of formula I, X, Y, Z, H, E and W are each independently selected from hydrogen and any one of C1-C6 hydrocarbon groups; R1 is selected from C1-C10 alkylene groups with or without substituents; if R1 has substituents, the substituents are C1-C6 hydrocarbon groups; R2 is selected from C1-C8 haloalkyl groups; R3 is selected from At least one of the following, where q is an integer between 2 and 13; R4 and R5 are selected from C1-C3 hydrocarbon groups, respectively; m, n, r, p, h, and k are each independent integers from 1 to 5000.

2. The electrolyte according to claim 1, characterized in that, The compound of formula I satisfies at least one of the following conditions: (1) X, Y, Z, H, E and W are each independently selected from hydrogen and methyl; (2) R1 is selected from C2-C8 alkylene groups with or without substituents; (3) R2 is selected from C2-C5 fluoroalkyl groups; (4) q is an integer between 2 and 9.

3. The electrolyte according to claim 1, characterized in that, Compounds of Formula I include any one of Formulas I-1 to I-17:

4. The electrolyte according to any one of claims 1-3, characterized in that, The polymerization precursor of the compound of formula I includes fluorinated acrylate monomers, carboxylic acid monomers, ether-oxygenated monomers, and oxalate monomers; based on the mass of the electrolyte, the mass content of the fluorinated acrylate monomer is W1, the mass content of the carboxylic acid monomer is W2, the mass content of the ether-oxygenated monomer is W3, and the mass content of the oxalate monomer is W4, and the compound of formula I satisfies at least one of the following conditions: (5) W1 satisfies: 0.3%-16%; W2 satisfies: 0.75%-32%; W3 satisfies: 0.3%-16%; and W4 satisfies: 0.1%-10%. (6)1≤(W2+W3) / (W1+W4)≤9.

5. The electrolyte according to any one of claims 1-3, characterized in that, The weight-average molecular weight M of the compound of formula I w The range is 10,000-800,000.

6. The electrolyte according to any one of claims 1-3, characterized in that, The electrolyte has an ionic conductivity of 1×10⁻⁶. -4 -3.2×10 -3 S / cm.

7. The electrolyte according to any one of claims 1-3, characterized in that, Based on the mass of the electrolyte, the mass content of the compound of formula I is 3%-40%.

8. The electrolyte according to any one of claims 1-3, characterized in that, The electrolyte further includes a lithium salt, which comprises one or more combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium hexafluorophosphate, and lithium tetrafluoroborate; the lithium salt has a mass content of 10%-20% based on the mass of the electrolyte.

9. The electrolyte according to any one of claims 1-3, characterized in that, The electrolyte further includes a second compound, which includes at least one selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, fluoroethylene carbonate, or difluoroethylene carbonate; and the second compound comprises 50%-87% by mass based on the mass of the electrolyte.

10. An electrochemical device, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte as described in any one of claims 1-9.

11. The electrochemical device according to claim 10, characterized in that, The electrochemical device has at least one of the following characteristics: (7) After the electrochemical device is opened, the mass of the electrolyte flowing out under a pressure of 200-400N accounts for less than 1% of the total mass of the electrochemical device; (8) After the electrochemical device is opened, it is shielded with a 1500-2500 mesh screen and centrifuged at 3000-3400 rpm for 5-15 minutes. The mass of the electrolyte discharged by centrifugation accounts for less than 1% of the total mass of the electrochemical device.

12. An electronic device comprising the electrochemical device according to any one of claims 10 to 11.

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