Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device, the electrochemical device comprising a positive electrode, a negative electrode, a separator and an electrolyte, the electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the room temperature conductivity of the electrolyte is b mS / cm, and the single-sided coating weight of the positive electrode is a g / 1540.25 mm 2 , and the relationship between a and b satisfies: b ≥ 50.859a 2 -16.044a + 8.2071, 0.2 ≤ a ≤ 0.55. This electrochemical device has improved long-term cycling performance and high-temperature storage performance, while maintaining good charge battery performance and energy efficiency.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and particularly to an electrochemical device and an electronic device. Background Art

[0002] Currently, lithium-ion batteries have been widely used in fields such as electric vehicles, consumer electronics, and energy storage devices, and have gradually become the mainstream batteries in the above fields due to their advantages such as high energy density and no memory effect. In particular, the electric vehicle, micro-power, and energy storage industries have entered a rapid development track, providing a vast blue ocean for the application of lithium-ion batteries. Due to the characteristics of the lithium iron phosphate cathode material itself, the battery composed of it has the characteristics of high safety performance, long service life, high high-temperature performance, low cost, and environmental friendliness, and has relatively large advantages and application prospects compared with other types of lithium-ion batteries. Although its relative life is relatively long, as the requirements for the service life of batteries in the power battery and energy storage fields are getting higher and higher, how to further improve the storage performance, cycle performance, safety performance, and kinetic performance of lithium-ion batteries at a relatively low cost still has important value.

[0003] In order to improve the energy density, reduce the use of components such as current collectors and separators to reduce costs, it has become an inevitable choice to increase the coating weight per unit area and the compaction density of the electrode sheet. However, after increasing the coating weight and compaction density, challenges such as poor infiltration of large-capacity battery cells, insufficient liquid retention, too fast cycle attenuation, lithium plating during low-temperature charging, lithium plating during later use, and increased temperature rise due to high impedance will be brought, resulting in serious life reduction and safety risks. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present application provides an electrochemical device, which has improved long-term cycle performance and high-temperature storage performance, while maintaining good charge and discharge performance and energy efficiency.

[0005] In a first aspect, the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte includes a lithium salt, an organic solvent, and an additive. Among them, the room-temperature conductivity of the electrolyte is b mS / cm, and the single-sided coating weight of the positive electrode is a g / 1540.25mm 2 , and the relationship between a and b satisfies: b≥50.859a 2 -16.044a + 8.2071, where 0.2≤a≤0.55. In the present application, the room-temperature conductivity refers to the conductivity measured at a temperature in the range of 20°C to 30°C. According to some embodiments of the present application, the room-temperature conductivity refers to the conductivity measured at 25°C.

[0006] By defining the relationship between the ambient temperature conductivity of the electrolyte and the single-sided coating weight of the positive electrode, this application solves the problems of poor wetting, insufficient film formation, cyclic voltage decay, and narrow charging window caused by increasing the coating weight and tap density of the positive electrode material. When the ambient temperature conductivity of the electrolyte and the single-sided coating weight of the positive electrode satisfy the above relationship, the electrochemical device can achieve excellent service life while realizing ultra-high energy density.

[0007] According to some embodiments of the present application, b ≤ 20.

[0008] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, and the relationship between c and a satisfies: when 0.2 ≤ a ≤ 0.4, c ≥ 1707a 3 -1393.9a 2 +391.4a - 30.28, when 0.4 < a ≤ 0.55, 12.5 ≤ c ≤ 16.25. According to some embodiments of the present application, 0.2 ≤ a ≤ 0.4, c ≥ 1707a 3 -1393.9a 2 +391.4a - 30.28. According to some other embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, and the relationship between c and a satisfies: 0.4 < a ≤ 0.55, 12.5 ≤ c ≤ 16.25.

[0009] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, 6.25 ≤ c ≤ 18.75. According to some embodiments of the present application, 8.75 ≤ c ≤ 16.25. According to some embodiments of the present application, 12.5 ≤ c ≤ 16.25.

[0010] According to some embodiments of the present application, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide (LiFSI), or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). According to some embodiments of the present application, the lithium salt includes LiPF 6 .

[0011] According to some embodiments of the present application, the additive contains fluorinated carbonate. The fluorinated carbonate can form a stable SEI film on the surface of the negative electrode during the formation process of the electrochemical device, inhibit the reduction decomposition of other components in the electrolyte on the surface of the negative electrode, thereby improving the cycle performance of the electrochemical device, and at the same time inhibiting gas generation during storage and cycling.

[0012] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the fluorinated carbonate is d%, and the relationship between d and a satisfies: 10a - 3 ≤ d ≤ 4. According to some embodiments of the present application: 10a - 3 ≤ d ≤ 4, and 0.3 ≤ a ≤ 0.55. According to some embodiments of the present application, the fluorinated carbonate is fluoroethylene carbonate. When the mass fraction of fluoroethylene carbonate is too low, its strengthening effect on the SEI on the negative electrode surface is not significant, and the improvement of the cycle performance of the electrochemical device is not obvious. When the mass fraction of fluoroethylene carbonate is higher than 4%, it will decompose to produce more HF, which will instead exacerbate the corrosion of SEI. At the same time, its low electrochemical stability is likely to cause gas generation in the battery cell.

[0013] According to some embodiments of the present application, the organic solvent includes an organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C. According to some further embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C is ≥ 30%. The organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C has low viscosity and high dielectric constant, which can significantly improve the wetting performance of the electrolyte, improve liquid retention, and improve the SEI film formation quality.

[0014] According to some embodiments of the present application, the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), methyl formate (MF), ethyl formate (EF), propyl formate (PF), tetrahydrofuran (THF), 1,3-dioxolane (1,3-DOL), or dimethoxyethane (DME).

[0015] According to some embodiments of the present application, the electrolyte further includes ethylene carbonate (EC). Adding ethylene carbonate can further improve the cycle life of the lithium-ion battery, while inhibiting the decomposition and gas generation of the electrolyte and improving the safety performance, so as to achieve a longer cycle life.

[0016] According to some embodiments of the present application, the electrolyte satisfies at least one of the following conditions (I) to (III): (I) The mass ratio of the organic solvent with a carbon atom number ≤ 5 and a boiling point less than or equal to 120°C to ethylene carbonate is 0.75 to 3; (II) The mass ratio of ethylene carbonate to lithium hexafluorophosphate is 0.031 to 0.343; (III) The mass ratio of the organic solvent with a carbon atom number ≤ 5 and a boiling point less than or equal to 120°C to lithium hexafluorophosphate is 1.8 to 7.0.

[0017] According to some embodiments of the present application, the additive includes a compound containing S=O functional group, and the compound containing S=O functional group is selected from at least one of 1,3-propane sultone (PS), vinyl sulfate (DTD), methylene disulfonate (MMDS), propylene sultone (PES), 4-methyl vinyl sulfate (PCS) or 1,4-butyl sultone (BS). According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the compound containing S=O functional group is 0.01% to 3%. According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the compound containing S=O functional group is 0.1% to 3%. When the mass fraction of the compound containing S=O functional group is lower than 0.1%, its effect on the formation of SEI on the surface of the positive and negative electrodes is insufficient, and the improvement of the storage and high temperature storage of lithium-ion batteries is not obvious. When the mass fraction of the compound containing S=O functional group is higher than 3%, the film formation impedance at the interface of the positive and negative electrodes is too large, which deteriorates the charging and discharging performance, especially the charging and discharging performance at low temperature.

[0018] According to some embodiments of the present application, the additive includes a lithium-containing additive, wherein the lithium-containing additive is selected from LiPO 2 F 2 、LiDFOB、LiBOB、LiBF 4 , B 4 Li 2 O 7 , Li 3 BO 3 or CF 3 LiO 3 At least one of S. According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium-containing additive is 0.01% to 3%. When the mass fraction of the lithium-containing additive is lower than 0.01%, its effect on the passivation of the negative electrode is insufficient, and the improvement of the cycle performance of the electrochemical device is not obvious. When the mass percentage of the lithium salt compound is higher than 3%, it has no obvious improvement on the passivation effect of the negative electrode, and at the same time increases the cost of the electrolyte, and the cost performance is not high. However, continuing to increase the dosage of LiFSI and LiTFSI can significantly improve the conductivity of the electrolyte and improve the kinetics of the electrochemical device.

[0019] According to some embodiments of the present application, the positive electrode satisfies at least one of the following conditions (A) to (D): (A) the positive electrode includes a positive electrode active material layer, and the compaction density of the positive electrode active material layer is 1.7 g / cm 3 Up to 2.5g / cm 3; (B) The positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate or lithium manganese iron phosphate; (C) The positive electrode includes a positive electrode active material, and the D50 of the particles of the positive electrode active material is 0.5 μm to 2.0 μm; (D) The positive electrode includes a positive electrode active material, and the BET of the positive electrode active material is 8 m 2 / g to 25 m 2 / g.

[0020] According to some embodiments of the present application, the negative electrode includes a graphite material. According to some embodiments of the present application, the graphite material satisfies at least one of the following conditions (E) to (H): (E) The BET of the graphite material is 0.9 m 2 / g to 1.7 m 2 / g; (F) The Dv50 of the graphite material is 12 μm to 20 μm; (G) The Raman Id / Ig of the graphite material is 0.25 to 0.5; (H) The graphite material contains one or more of Al, Fe, Cu, Zn, Cr, Si, Na, P, or S. According to some embodiments of the present application, the graphite material satisfies at least two or at least three of the above conditions (E) to (H). According to some embodiments of the present application, the graphite material simultaneously satisfies the above conditions (E), (F), (G), and (H).

[0021] In a second aspect, the present application provides an electronic device, which includes the electrochemical device of the first aspect.

[0022] The electrochemical device provided by the present application optimizes the electrolyte, improves the electrolyte kinetics, reduces the film formation impedance, can significantly improve the long life and safety performance of the electrochemical device (such as a lithium-ion battery), thereby reducing costs and having a very high cost performance. Detailed Embodiments

[0023] The embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.

[0024] A list of items connected by the phrase "at least one of" may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0025] The applicant has found through research and a large number of experimental verifications that for lithium iron phosphate system batteries, in order to improve the energy density, reduce costs, and increase the coating weight per unit area and the compaction density of the electrode sheet, challenges such as poor electrolyte infiltration, insufficient liquid retention, excessive cycle attenuation, lithium plating during low-temperature charging, lithium plating during later use, and increased temperature rise due to high impedance will occur, resulting in serious life reduction and safety risks. As the capacity increases, the risks are significantly amplified. This application solves the problems of poor infiltration, insufficient film formation, cycle degradation, and narrow charging window caused by increasing the coating weight and compaction density of the positive electrode material by defining the relationship between the ambient temperature conductivity of the electrolyte and the single-sided coating weight of the positive electrode.

[0026] In a first aspect, the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte includes a lithium salt, an organic solvent, and an additive. Among them, the ambient temperature conductivity of the electrolyte is b mS / cm, and the single-sided coating weight of the positive electrode is a g / 1540.25mm 2 , and the relationship between a and b satisfies: b ≥ 50.859a 2 -16.044a + 8.2071, where 0.2 ≤ a ≤ 0.55. In the present application, the ambient temperature conductivity refers to the conductivity measured at a temperature in the range of 20°C to 30°C. According to some embodiments of the present application, the ambient temperature conductivity refers to the conductivity measured at 25°C. When the ambient temperature conductivity of the electrolyte and the single-sided coating weight of the positive electrode satisfy the above relationship, the electrochemical device can achieve excellent service life while realizing ultra-high energy density.

[0027] According to some embodiments of the present application, b ≤ 20. According to some embodiments of the present application, 8 ≤ b ≤ 20. In some embodiments, b is 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or the range formed by any two of them.

[0028] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, and the relationship between c and a satisfies: when 0.2 ≤ a ≤ 0.4, c ≥ 1707a 3 -1393.9a 2 +391.4a - 30.28, when 0.4 < a ≤ 0.55, 12.5 ≤ c ≤ 16.25. According to some embodiments of the present application, 0.2 ≤ a ≤ 0.4, c ≥ 1707a 3 -1393.9a 2+391.4a - 30.28. According to some other embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, and the relationship between c and a satisfies: 0.4 < a ≤ 0.55, 12.5 ≤ c ≤ 16.25. Appropriately increasing the lithium salt concentration can reduce the increased concentration polarization caused by the thick electrode, the black spots at the negative electrode interface, and the problem of lithium deposition.

[0029] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, 6.25 ≤ c ≤ 18.75. According to some embodiments of the present application, 8.75 ≤ c ≤ 16.25. According to some embodiments of the present application, 12.5 ≤ c ≤ 16.25.

[0030] According to some embodiments of the present application, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide (LiFSI), or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). According to some embodiments of the present application, the lithium salt includes LiPF 6 .

[0031] According to some embodiments of the present application, the additive contains fluorinated carbonate, and the content of fluorinated carbonate is d%, and the relationship between d and a satisfies: 10a - 3 ≤ d ≤ 4. According to some embodiments of the present application, the additive contains fluorinated carbonate, and the content of fluorinated carbonate is d%, and the relationship between d and a satisfies: 10a - 3 ≤ d ≤ 4, and 0.3 ≤ a ≤ 0.55. According to some embodiments of the present application, the fluorinated carbonate is fluoroethylene carbonate (FEC). Adding fluoroethylene carbonate can form a low-impedance SEI at the negative electrode interface and perform good self-repair during use, inhibiting the appearance of lithium deposition and black spots during cycling, thereby achieving an ultra-long cycle life.

[0032] According to some embodiments of the present application, the organic solvent includes an organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C, and based on the mass of the electrolyte, the mass fraction of the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C is ≥ 30%. According to some embodiments of the present application, the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), methyl formate (MF), ethyl formate (EF), propyl formate (PF), tetrahydrofuran (THF), 1,3-dioxolane (1,3-DOL), or ethylene glycol dimethyl ether (DME). The organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120°C has low viscosity and high dielectric constant, can significantly improve the wetting performance of the electrolyte, improve the liquid retention, and improve the SEI film formation quality.

[0033] According to some embodiments of the present application, the electrolyte further comprises ethylene carbonate. Adding ethylene carbonate can further improve the cycle life of the lithium-ion battery, while inhibiting the decomposition and gas production of the electrolyte and improving safety performance, thereby achieving a longer cycle life.

[0034] According to some embodiments of the present application, the electrolyte satisfies at least one of the following conditions (I) to (III): (I) the mass ratio of the organic solvent having a carbon number ≤5 and a boiling point less than or equal to 120°C to ethylene carbonate is 0.75 to 3; (II) the mass ratio of ethylene carbonate to lithium hexafluorophosphate is 0.031 to 0.343; (III) the mass ratio of the organic solvent having a carbon number ≤5 and a boiling point less than or equal to 120°C to lithium hexafluorophosphate is 1.8 to 7.0.

[0035] According to some embodiments of the present application, the additive includes a compound containing S=O functional group. Adding a compound containing S=O functional group can further improve the cycle life of the lithium-ion battery, while inhibiting the decomposition and gas production of the electrolyte and improving the safety performance, thereby achieving a longer cycle life. According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the compound containing S=O functional group is 0.01% to 3%. According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the compound containing S=O functional group is 0.1% to 3%. When the mass fraction of the compound containing S=O functional group is lower than 0.1%, its effect on the formation of SEI on the surface of the positive and negative electrodes is insufficient, and the improvement of the storage and high-temperature storage of lithium-ion batteries is not obvious. When the mass fraction of the compound containing S=O functional group is higher than 3%, the film formation impedance at the interface of the positive and negative electrodes is too large, which deteriorates the charging and discharging performance, especially the charging and discharging performance at low temperatures.

[0036] According to some embodiments of the present application, the compound containing an S═O functional group is selected from at least one of 1,3-propane sultone (PS), dithiothreitol (DTD), methylene disulfonate (MMDS), propene sultone (PES), 4-methylvinyl sulfate (PCS) or 1,4-butane sultone (BS).

[0037] According to some embodiments of the present application, the additive includes LiPO 2 F 2 、LiDFOB、LiBOB、LiBF 4 , B 4 Li 2 O 7 , Li 3 BO 3 or CF 3 LiO 3At least one of S. Adding such a lithium salt additive can further improve the cycle life of the lithium-ion battery, while inhibiting the decomposition and gas generation of the electrolyte and improving the safety performance, thereby achieving a longer cycle life. According to some embodiments of the present application, based on the total mass of the electrolyte, the mass fraction of the lithium-containing additive is 0.01% to 3%. When the mass fraction of the lithium-containing additive is less than 0.01%, its influence on the passivation of the negative electrode is insufficient, and the improvement of the cycle performance of the electrochemical device is not obvious. When the mass percentage content of the lithium salt compound is higher than 3%, there is no obvious improvement in its passivation effect on the negative electrode, while increasing the cost of the electrolyte and having a low cost performance. However, for LiFSI and LiTFSI, continuing to increase the dosage can significantly improve the conductivity of the electrolyte and improve the kinetics of the electrochemical device.

[0038] According to some embodiments of the present application, the positive electrode satisfies at least one of the following conditions (A) to (D): (A) The positive electrode includes a positive electrode active material layer, and the compaction density of the positive electrode active material layer is 1.7 g / cm 3 to 2.5 g / cm 3 ; (B) The positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate or lithium manganese iron phosphate; (C) The positive electrode includes a positive electrode active material, and the particle D50 of the positive electrode active material is 0.5 μm to 2.0 μm; (D) The positive electrode includes a positive electrode active material, and the BET of the positive electrode active material is 8 m 2 / g to 25 m 2 / g.

[0039] According to some embodiments of the present application, the positive electrode includes a positive electrode active material layer, and the compaction density of the positive electrode active material layer is 1.7 g / cm 3 to 2.5 g / cm 3 . According to some embodiments of the present application, the positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate or lithium manganese iron phosphate. According to some embodiments of the present application, the positive electrode includes a positive electrode active material, and the particle D50 of the positive electrode active material is 0.5 μm to 2.0 μm. According to some embodiments of the present application, the positive electrode includes a positive electrode active material, and the BET of the positive electrode active material is 8 m 2 / g to 25 m 2 / g.

[0040] According to some embodiments of the present application, the positive electrode includes a current collector and a positive electrode active material layer located on the current collector. In some embodiments, the current collector may include, but is not limited to: aluminum. In some embodiments, the positive electrode active material layer includes at least one of lithium iron phosphate or lithium manganese iron phosphate. The positive electrode active material layer may further include a binder and optionally a conductive material. The binder improves the binding between the positive electrode active material particles and also improves the binding between the positive electrode active material and the current collector. In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc. In some embodiments, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers and mixtures thereof. In some embodiments, the carbon-based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber or any combination thereof. In some embodiments, the metal-based materials are selected from metal powder, metal fiber, copper, nickel, aluminum or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0041] The positive electrode can be prepared by methods well known in the art. For example, the positive electrode can be obtained by the following method: mixing the active material, the conductive material and the binder in a solvent to prepare an active material composition, and coating the active material composition on the current collector. In some embodiments, the solvent may include, but is not limited to: N-methylpyrrolidone.

[0042] According to some embodiments of the present application, the negative electrode includes a graphite material. According to some embodiments of the present application, the graphite material satisfies at least one of the following conditions (E) to (H): (E) the BET of the graphite material is 0.9 m 2 / g to 1.7 m 2 / g; (F) the Dv50 of the graphite material is 12 μm to 20 μm; (G) the Raman Id / Ig of the graphite material is 0.25 to 0.5; (H) the graphite material contains one or several of Al, Fe, Cu, Zn, Cr, Si, Na, P or S. According to some embodiments of the present application, the graphite material satisfies at least two or at least three of the above conditions (E) to (H). According to some embodiments of the present application, the graphite material simultaneously satisfies the above conditions (E), (F), (G), (H).

[0043] According to some embodiments of the present application, the negative electrode further includes a conductive agent and a binder. According to some embodiments of the present application, the conductive agent includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative. According to some embodiments of the present application, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0044] According to some embodiments of the present application, the negative electrode further includes a current collector, and the negative electrode active material is located on the current collector. In some embodiments, the current collector includes: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

[0045] The negative electrode of the present application can be prepared by well-known methods in the art. Generally, the negative electrode active material and optional conductive agents (such as carbon materials like carbon black and metal particles, etc.), binders (such as SBR), other optional additives (such as PTC thermistor materials), etc. are mixed and dispersed in a solvent (such as deionized water), stirred evenly, and then uniformly coated on the negative electrode current collector, and dried to obtain a negative electrode containing a negative electrode active layer. Then, the negative electrode containing the negative electrode active layer is subjected to a lithium supplementation treatment to obtain the lithium-supplemented negative electrode in the present application. Materials such as metal foil or porous metal plate can be used as the negative electrode current collector.

[0046] The electrochemical device of the present application further includes a separator. There are no particular limitations on the material and shape of the separator used in the electrochemical device of the present application, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer, an inorganic substance, etc. formed of a material stable to the electrolyte of the present application. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected. A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer, an inorganic substance layer, or a layer formed by mixing a polymer and an inorganic substance. The inorganic substance layer includes inorganic particles and a binder, and the inorganic particles are selected from at least one of alumina, silica, magnesia, 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 and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene alkoxide, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene alkoxide, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene).

[0047] In a second aspect, the present application provides an electronic device, which includes the electrochemical device of the first aspect.

[0048] The electronic device or apparatus of the present application is not particularly limited. In some embodiments, the electronic device of the present application includes, but is not limited to, a notebook computer, a pen input type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flash, a camera, a large household battery and a lithium ion capacitor, etc.

[0049] The present application will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application.

[0050] I. Preparation of Lithium Ion Battery

[0051] The lithium-ion batteries in the examples and comparative examples were all prepared according to the following method:

[0052] 1. Preparation of the positive electrode sheet

[0053] The positive electrode active material lithium iron phosphate material (LFP), the conductive agent Super P, and the binder polyvinylidene fluoride were mixed according to a weight ratio of 96.3:1.5:2.2, N-methylpyrrolidone (NMP) was added, and the mixture was stirred in a vacuum mixer until the system became homogeneous and transparent to obtain a positive electrode slurry, where the solid content of the positive electrode slurry was 72 wt%; the positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil; the aluminum foil was dried at 85°C, and then after cold pressing, slicing, and slitting, it was dried in a vacuum at 85°C for 4 h to obtain the positive electrode sheet.

[0054] 2. Preparation of the negative electrode sheet

[0055] The negative electrode active material artificial graphite, the conductive agent Super P, the thickening agent sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) were mixed according to a weight ratio of 96.4:1.5:0.5:1.6, deionized water was added, and a negative electrode slurry was obtained under the action of a vacuum mixer, where the solid content of the negative electrode slurry was 54 wt%; the negative electrode slurry was uniformly coated on the negative electrode current collector copper foil; the copper foil was dried at 85°C, and then after cold pressing, slicing, and slitting, it was dried in a vacuum at 120°C for 12 h to obtain the negative electrode sheet.

[0056] 3. Preparation of the electrolyte

[0057] In a dry argon atmosphere glove box, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), etc. were mixed according to the examples and comparative examples, then additives were added, and after dissolution and sufficient stirring, the lithium salt LiPF 6 , was added. After mixing evenly, the electrolyte was obtained.

[0058] 4. Preparation of the separator

[0059] A 7-μm-thick polyethylene (PE) separator was selected.

[0060] 5. Preparation of the lithium-ion battery

[0061] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive and negative electrode sheets to play an insulating role, and then wind them to obtain an electrode assembly; after welding the tabs, place the electrode assembly in an outer packaging aluminum-plastic film, inject the prepared electrolyte into the dried electrode assembly, and through processes such as vacuum packaging, standing, formation (constant current charging at 0.02C to 3.3V, and then constant current charging at 0.1C to 3.6V), shaping, and capacity testing, a soft-pack lithium-ion battery (with a thickness of 3.3 mm, a width of 39 mm, and a length of 96 mm) is obtained.

[0062] II. Testing Process of Lithium-Ion Battery

[0063] 1. Cycling Performance Test of Lithium-Ion Battery

[0064] Place the lithium-ion battery in an incubator at 25°C and let it stand for 30 minutes to reach a constant temperature. Charge the lithium-ion battery at a constant current of 1C until the voltage reaches 3.65V, then charge it at a constant voltage of 3.65V until the current reaches 0.05C, and then discharge it at a constant current of 1C until the voltage reaches 2.5V. This is one charge-discharge cycle. Taking the capacity of the first discharge as 100%, repeat the charge-discharge cycle until the discharge capacity decays to 65%, then stop the test and record the number of cycles, which is used as an index to evaluate the cycling performance of the lithium-ion battery.

[0065] At the same time, test the cycling performance of the lithium-ion battery at 45°C, and the test method is the same as the above 25°C cycling performance test.

[0066] 2. High SOC High Temperature Storage Test of Lithium-Ion Battery

[0067] Place the lithium-ion battery in an incubator at 25°C and let it stand for 30 minutes to reach a constant temperature. Charge it at a constant current of 1C to 3.65V, charge it at a constant voltage until the current reaches 0.05C, and then discharge it at a constant current of 1C to 2.5V, and record the discharge capacity as the initial capacity of the lithium-ion battery. Then charge it at a constant current of 0.5C to 3.65V, charge it at a constant voltage until the current reaches 0.05C, and use a micrometer to test and record the thickness of the battery. Transfer the tested lithium-ion battery to an incubator at 60°C for storage for 90 days. During this period, test and record the battery thickness once every 30 days, and transfer the battery to an incubator at 25°C and let it stand for 60 minutes, then discharge it at a constant current of 1C to 2.5V, and record the discharge capacity as the remaining capacity of the lithium-ion battery. Charge it at a constant current of 1C to 3.65V, charge it at a constant voltage until the current reaches 0.05C, and then discharge it at a constant current of 1C to 2.5V, and record the discharge capacity as the recoverable capacity of the lithium-ion battery. Test the THK (thickness), OCV (open circuit voltage), and IMP (impedance) of the battery. Discharge at 1C DC to 2.5V, record the recovered discharge capacity and calculate the storage residual capacity retention rate and recoverable capacity retention rate of the lithium-ion battery, which are used as indexes to evaluate the high temperature storage performance of the lithium-ion battery.

[0068] Residual capacity retention rate = (Residual capacity after 90 days of storage - Initial capacity of the battery cell) / Initial capacity of the battery cell × 100%

[0069] Recoverable capacity retention rate = (Recoverable capacity after 90 days of storage - Initial capacity of the battery cell) / Initial capacity of the battery cell × 100%

[0070] 3. Low 0% SOC High Temperature Storage Test of Lithium-Ion Batteries

[0071] Place the lithium-ion battery in an incubator at 25°C and let it stand for 30 minutes to reach a constant temperature. Charge it at a constant current of 1C to 3.65V, then charge it at a constant voltage until the current reaches 0.05C, and then discharge it at a constant current of 1C to 2.5V. Record the discharge capacity as the initial capacity of the lithium-ion battery. Then use a micrometer to measure and record the thickness of the battery. Transfer the tested lithium-ion battery to an incubator at 60°C for 90 days of storage. During this period, measure and record the thickness of the battery once every 30 days, and transfer the battery to an incubator at 25°C and let it stand for 60 minutes. Charge it at a constant current of 1C to 3.65V, then charge it at a constant voltage until the current reaches 0.05C, and then discharge it at a constant current of 1C to 2.5V. Record the discharge capacity as the recoverable capacity of the lithium-ion battery. Test the THK (thickness), OCV (open circuit voltage), and IMP (impedance) of the battery. Discharge from 1C DC to 2.5V, record and calculate the expansion rate of the thickness during the storage of the lithium-ion battery, and use it as an index to evaluate the high temperature storage performance of the lithium-ion battery at 0% SOC.

[0072] 0% SOC Storage Thickness Expansion Rate = (Thickness after 90 days of storage - Initial thickness of the battery cell) / Initial thickness of the battery cell × 100%

[0073] 4. DC Impedance DCR (-10°C) of Lithium-Ion Batteries

[0074] Place the lithium-ion battery in a high and low temperature chamber at -10°C and let it stand for 4 hours to reach a constant temperature. Charge it at a constant current of 0.1C to 3.65V, then charge it at a constant voltage of 3.65V until the current reaches 0.05C, and let it stand for 10 minutes. Then discharge it at a constant current of 0.1C to 2.5V, and record the capacity of this step as the actual discharge capacity D0. Subsequently, let it stand for 5 minutes, charge it at a constant current of 0.1C to 3.65V, and charge it at a constant voltage of 3.65V until the current reaches 0.05C (the current is calculated based on the capacity corresponding to D0). Let it stand for 10 minutes, discharge it at a constant current of 0.1C for 3H (the current is calculated based on the capacity corresponding to D0), and record the voltage V1 at this time. Then, discharge it at a constant current of 1C for 1S (sampling every 100ms, the current is calculated based on the capacity marked on the battery cell), and record the voltage V2 at this time. Then calculate the DC impedance (DCR) corresponding to 70% charge state (SOC) of the battery cell. The calculation formula is as follows:

[0075] 70% SOC DCR = (V2 - V1) / 1C

[0076] 5. Lithium-ion battery energy conversion efficiency RTE (25°C)

[0077] Place the lithium-ion battery in an incubator at 25°C and let it stand for 30 minutes to reach a constant temperature. Discharge it at a constant current of 0.5C until the voltage reaches 2.5V, and then let it stand for 15 minutes. Charge it at a constant current of 0.5C to 3.65V, and then charge it at a constant voltage of 3.65V until the current reaches 0.05C. Let it stand for 60 minutes, and then discharge it at a constant current of 0.5C until the voltage reaches 2.5V. Continuously charge and discharge three times according to the above current magnitude, record the charging and discharging energies respectively, and calculate the energy conversion efficiency by taking the charging energy Ec and discharging energy Ed of the last cycle:

[0078] Energy conversion efficiency = Discharge energy Ed / Charging energy Ec × 100%

[0079] 6. Lithium-ion battery charging performance test (lithium plating situation)

[0080] 1) Place the lithium-ion battery in a high and low temperature chamber at -10°C and let it stand for 30 minutes to reach a constant temperature; 2) Discharge the lithium-ion battery that has reached a constant temperature at a constant current of 0.5C until the voltage reaches 2.5V; 3) After standing for 10 minutes, charge it at a constant current of 0.1C to a voltage of 3.65V, and then charge it at a constant voltage of 3.65V until the current reaches 0.05C (record the charging capacity C 1 ); 4) After standing for 10 minutes, discharge it at a constant current of 0.5C until the voltage reaches 2.5V. After standing for 10 minutes, discharge it at a constant current of 0.025C until the voltage reaches 2.5V. After continuing to stand for 10 minutes, discharge it at a constant current of 0.005C until the voltage reaches 2.5V, and record the complete discharge capacity of this step as D 1 ; 5) After standing for 10 minutes, charge it at a constant current of 0.3C to a voltage of 3.65V, and then charge it at a constant voltage of 3.65V until the current reaches 0.05C; 6) After standing for 10 minutes, discharge it at a constant current of 0.5C until the voltage reaches 2.5V. After standing for 10 minutes, discharge it at a constant current of 0.025C until the voltage reaches 2.5V. After continuing to stand for 10 minutes, discharge it at a constant current of 0.005C until the voltage reaches 2.5V; 7) Repeat steps 5) and 6) 12 times, and record the complete discharge capacity of the last time as D 12 . Calculate the amount of lithium plating as the basis for judging the charging performance (the lower the amount of lithium plating, the milder the degree of lithium plating; when the amount of lithium plating is less than 0.3, it is difficult to see lithium plating with the naked eye). The amount of lithium plating is calculated as follows:

[0081] Amount of lithium plating = (First charging capacity C 1 - Last discharge capacity D 12 ) / First charging capacity C 1

[0082] 7. Temperature Rise during Discharge at Room Temperature (25°C) of Lithium-Ion Battery

[0083] Place the lithium-ion battery in an incubator at 25°C and let it stand for 30 minutes to reach a constant temperature. Discharge it at a constant current of 0.5C until 2.5V, and then let it stand for 15 minutes. Charge it at a constant current of 0.5C to 3.65V, then charge it at a constant voltage of 3.65V until the current reaches 0.05C, and let it stand for 60 minutes. Then discharge it at a constant current of 6C until 2.5V, record the temperature T at the center of the outer surface of the battery cell during the discharge process, and calculate the temperature increase value (T - 25°C).

[0084] 8. Charging Performance Test of Lithium-Ion Battery

[0085] Discharge the battery at 0.5C to 2.5V at 25°C, then charge it at a constant current of 1C to 6.5V, and then charge it at a constant voltage for 3 hours, monitoring the temperature change on the surface of the battery cell (the standard is that the battery cell does not catch fire, burn, or explode).

[0086] 9. Conductivity Test of Electrolyte (25°C)

[0087] Place the electrolyte in a constant temperature water bath at 25°C for 1 hour, and use a conductivity meter to measure the conductivity at room temperature and record the data. (Note to keep the temperature constant during the test)

[0088] 10. Surface Tension Test of Electrolyte (25°C)

[0089] Place the electrolyte in a constant temperature water bath at 25°C for 1 hour, and use a surface tension meter to measure the surface tension at room temperature and record the data. (Note to keep the temperature constant during the test)

[0090] III. Test Results

[0091] 1. Influence of Electrolyte Conductivity on Battery Performance

[0092] For the parameters of the single-sided coating weight of the positive electrode, the conductivity of the electrolyte at room temperature (25°C), and the battery performance data of Examples 1-1 to 1-20 and Comparative Examples 1-1 to 1-6, please refer to Table 1.

[0093] Table 1

[0094]

[0095] Note: The room temperature conductivity in the examples and comparative examples in Table 1 is achieved by adjusting the types of solvents, their proportions, and the concentration of lithium salts

[0096] It can be seen from the examples and comparative examples in Table 1 that the higher the conductivity of the electrolyte, the better the kinetics, the better the cycling performance under thick coating, the lower the impedance, the less severe the lithium deposition, the lower the temperature rise during discharge at high current, and the smaller the interfacial tension of the electrolyte, making it easier to achieve wetting.

[0097] 2. Influence of the Relationship between Lithium Salt Content and Positive Electrode Coating Weight on Battery Performance

[0098] For the positive electrode single-sided coating weight, electrolyte lithium salt parameters, and battery performance data of Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-6, see Table 2

[0099] Table 2

[0100]

[0101] It can be seen from the examples and comparative examples in Table 2 that the higher the electrolyte lithium salt content (within 16.25%), the smaller the concentration polarization, the better the kinetics, the milder the degree of lithium deposition under thick coating, the slower the SEI decomposition, the milder the negative electrode purple spots, the better the cycle performance, the lower the impedance, and the lower the discharge temperature rise under high current

[0102] 3. Influence of Fluorinated Carbonate Additives on Battery Performance

[0103] For the electrolyte parameters and battery performance data of Examples 3-1 to 3-29, see Table 3

[0104] Table 3

[0105]

[0106]

[0107] It can be seen from the examples and comparative examples in Table 3 that under thick coating, moderately increasing the FEC content results in better cycle performance, lower impedance, and lower discharge temperature rise under high current. This is mainly due to the formation of a stable low-impedance SEI at the negative electrode interface when increasing FEC, with a milder degree of lithium deposition, slower SEI decomposition, and milder negative electrode purple spots

[0108] 4. Influence of Organic Solvents with C Atom Number ≤ 5 and Boiling Point ≤ 120°C on Battery Performance

[0109] For the electrolyte parameters and battery performance data of Examples 4-1 to 4-29 and Comparative Examples 4-1 to 4-4, see Table 4

[0110] Table 4

[0111]

[0112]

[0113] As can be seen from the examples and comparative examples in Table 4, with the increase of the coating weight, the cycle performance, charge performance, discharge temperature rise, and energy conversion efficiency of the battery cell deteriorate significantly. After introducing a high-kinetic solvent (more than 30 wt%), under thick coating, the cycle performance, charge performance, and discharge temperature rise of the battery cell are significantly improved. This is mainly because when the coating weight is large, it becomes extremely difficult for the electrolyte to infiltrate, and the polarization during charge and discharge is extremely large, which easily causes the initial SEI film to form insufficiently. During the cycle process, lithium is continuously deposited on the surface of the negative electrode, resulting in the loss of active lithium, and thus the capacity decays rapidly. After introducing high-kinetic solvents such as EMC, DMC, EA, MA, EP, and DME, the electrode can be fully infiltrated in a short time, a uniform SEI is formed at the negative electrode interface, the polarization is reduced, lithium deposition is inhibited, the decomposition of SEI becomes slower, the purple spots on the negative electrode are slight, the cycle performance is improved, the impedance is reduced, and the discharge temperature rise under high current is significantly reduced.

[0114] 5. Influence of S=O compound additives on battery performance

[0115] For the parameter and battery performance data of the electrolytes in Examples 4-22 to 5-11 and Comparative Example 5-1, please refer to

[0116] Table 5.

[0117]

[0118] As can be seen from the examples and comparative examples in Table 5, under thick coating, after adding S=O compounds, the cycle performance, capacity retention rate after storage, gas generation inhibition during storage, and safety performance are all significantly improved. This is mainly because, under thick coating, the SEI decomposes relatively fast, and cycle dives are likely to occur, reducing the service life of the battery cell. S=O compounds can form a protective film with good thermal stability and chemical stability on the surfaces of the positive and negative electrodes, inhibit the side reactions between the electrodes and the electrolyte, and achieve excellent cycle stability, storage stability (gas generation inhibition and capacity retention rate improvement), kinetic performance, and safety performance. After sulfonate compounds are combined with high-kinetic solvents, they can significantly inhibit the gas generation during storage brought by high-kinetic solvents, and achieve better service life and safety performance while maintaining relatively high kinetics.

[0119] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on this application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of this application.

Claims

1. An electrochemical device, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte comprises a lithium salt, an organic solvent, and an additive. Wherein, The ambient temperature conductivity of the electrolyte is b mS / cm, and the single-sided coating weight of the positive electrode is a g / 1540.25 mm 2 , and the relationship between a and b satisfies: b ≥ 50.859a 2 -16.044a + 8.2071, where 0.2 ≤ a ≤ 0.55; the organic solvent includes an organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120 °C, and based on the total mass of the electrolyte, the mass fraction of the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120 °C ≥ 30%; The organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120 °C comprises at least one of dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, propyl acetate, ethyl propionate, methyl formate, ethyl formate, propyl formate, tetrahydrofuran, 1,3-dioxolane, or ethylene glycol dimethyl ether.

2. The electrochemical device according to claim 1, Wherein, b≤20。 3. The electrochemical device according to claim 1, Wherein, Based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, and the relationship between c and a satisfies: When 0.2 ≤ a ≤ 0.4, c ≥ 1707a 3 - 1393.9a 2 + 391.4a - 30.28, When 0.4 < a ≤ 0.55, 12.5 ≤ c ≤ 16.

25.

4. The electrochemical device according to claim 1, Wherein, Based on the total mass of the electrolyte, the mass fraction of the lithium salt is c%, 6.25 ≤ c ≤ 18.

75.

5. The electrochemical device according to claim 1, Wherein, The additive contains fluorinated carbonate. Based on the total mass of the electrolyte, the mass fraction of the fluorinated carbonate is d%, and the relationship between d and a satisfies: 10a - 3 ≤ d ≤ 4, 0.3 ≤ a ≤ 0.

55.

6. The electrochemical device according to claim 1, Wherein, The electrolyte further comprises ethylene carbonate.

7. The electrochemical device according to claim 1, Wherein, The additive includes a compound containing an S=O functional group, and the compound containing an S=O functional group is selected from at least one of 1,3-propane sultone, vinylene sulfate, methylene methanedisulfonate, propylene sultone, 4-methyl vinylene sulfate, or 1,4-butane sultone.

8. The electrochemical device according to claim 7, Wherein, Based on the total mass of the electrolyte, the mass fraction of the compound containing an S=O functional group is 0.01% to 3%.

9. The electrochemical device according to claim 1, Wherein, The electrolyte satisfies at least one of the following conditions (I) to (III): (I) The mass ratio of the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120 °C to ethylene carbonate is 0.75 to 3; (II) The mass ratio of ethylene carbonate to lithium hexafluorophosphate is 0.031 to 0.343; (III) The mass ratio of the organic solvent with a carbon atom number ≤ 5 and a boiling point ≤ 120 °C to lithium hexafluorophosphate is 1.8 to 7.

0.

10. The electrochemical device according to claim 1, Wherein, The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethanesulfonyl)imide; The additive includes a lithium-containing additive, and the lithium-containing additive is selected from LiPO 2 F 2 , LiDFOB, LiBOB, LiBF 4 , B 4 Li 2 O 7 , Li 3 BO 3 or CF 3 LiO 3 S, or at least one of them.

11. The electrochemical device according to claim 1, Wherein, The positive electrode satisfies at least one of the following conditions (A) to (D): (A) The positive electrode includes a positive electrode active material layer, and the tap density of the positive electrode active material layer is 1.7 g / cm 3 to 2.5 g / cm 3 ; (B) The positive electrode comprises a positive electrode active material, and the positive electrode active material comprises at least one of lithium iron phosphate or lithium manganese iron phosphate; (C) The positive electrode comprises a positive electrode active material, and the D50 of the particles of the positive electrode active material is 0.5 μm to 2.0 μm; (D) The positive electrode includes a positive electrode active material, and the BET of the positive electrode active material is 8 m 2 / g to 25 m 2 / g.

12. The electrochemical device according to claim 1, Wherein, The negative electrode includes a graphite material, and the graphite material satisfies at least one of the following conditions (E) to (H): (E) The BET of the graphite material is 0.9 m 2 / g to 1.7 m 2 / g; (F) The D of the graphite material V is 12 μm to 20 μm; (G) The Raman Id / Ig of the graphite material is 0.25 to 0.5; (H) The graphite material contains one or more of Al, Fe, Cu, Zn, Cr, Si, Na, P, or S.

13. An electronic device, comprising the electrochemical device according to any one of claims 1 to 12.

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