Electrochemical and electronic devices

Abstract

The present invention relates to an electrochemical device and an electronic device. The electrochemical device of the present invention comprises 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 electrical conductivity of the electrolyte is b mS / cm, and the coating weight of one side of one of the positive electrodes is g / 1540.25mm. 2 Then, a and b are related by the equation b≧50.859a 2 -16.044a+8.2071, 0.2≦a≦0.55. The electrochemical device has improved long-term cycle characteristics and high-temperature storage characteristics, while maintaining good rechargeable battery performance and energy efficiency.

Description

[Technical Field]

[0001] The present invention relates to the field of energy storage, and in particular to electrochemical and electronic devices. [Background technology]

[0002] Currently, lithium-ion batteries are widely used in fields such as electric vehicles, home appliances, and energy storage devices. Due to their high energy density and lack of memory effect, lithium-ion batteries have become the mainstream battery in these fields. In particular, the electric vehicle, micropower, and energy storage industries have entered a period of rapid development, bringing broad prospects for the application of lithium-ion batteries. Due to the inherent properties of lithium iron phosphate cathode materials, batteries formed therefrom have high safety, long service life, excellent high-temperature performance, low cost, and environmental friendliness. Therefore, these batteries have significant advantages and application prospects compared to other types of lithium-ion batteries. Despite the relatively long service life of these batteries, as the demand for battery service life in the fields of power batteries and energy storage continues to increase, further improvements in the storage characteristics, cycle characteristics, safety performance, and dynamic performance of lithium-ion batteries at low cost remain of great value.

[0003] In order to improve energy density and reduce costs by reducing the use of components such as current collectors and separators, it is inevitable to increase the coating weight per unit area of ​​the pole pieces and the compression density. However, after increasing the coating weight and compression density, problems such as poor wetting of large-capacity cells, insufficient electrolyte retention, excessively fast cycle decay, lithium deposition during low-temperature charging, lithium deposition in later stages of use, and increased temperature rise due to high resistance arise, resulting in serious shortening of lifespan and safety risks. Summary of the Invention

[0004] The present invention aims to solve the problems existing in the prior art, and provides an electrochemical device having improved long-term cycle characteristics and high-temperature storage characteristics, and capable of maintaining good battery performance and energy efficiency at the same time.

[0005] In a first aspect, the present invention is an electrochemical device including a positive electrode, a negative electrode, a separator, and an electrolytic solution. The electrolytic solution includes a lithium salt, an organic solvent, and an additive. Let the room-temperature electrical conductivity of the electrolytic solution be b mS / cm, and the coating weight on one side of the positive electrode be a g / 1540.25 mm 2 When this is done, a and b satisfy the relational expression b ≥ 50.859a 2 - 16.044a + 8.2071, and provides an electrochemical device where 0.2 ≤ a ≤ 0.55. In the present invention, the room-temperature electrical conductivity is the electrical conductivity obtained by measurement at a temperature within the range of 20°C to 30°C. According to some embodiments of the present invention, the room-temperature electrical conductivity is the electrical conductivity obtained by measurement at 25°C.

[0006] The present invention solves the problems of infiltration failure, insufficient film formation, "diving" during cycling, and too narrow charging window due to improving the coating weight and compression density of the positive electrode material by limiting the relationship between the room-temperature electrical conductivity of the electrolytic solution and the coating weight on one side of the positive electrode. By satisfying the above relationship between the room-temperature electrical conductivity of the electrolytic solution and the coating weight on one side of the positive electrode, an electrochemical device capable of realizing an ultra-high energy density while realizing an excellent service life can be obtained.

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

[0008] According to some embodiments of the present invention, when the mass fraction of the lithium salt with respect to the total mass of the electrolytic solution is c%, when 0.2 ≤ a ≤ 0.4, c and a satisfy the relational expression c ≥ 1707a 3 - 1393.9a 2 + 391.4a - 30.28, and when 0.4 < a ≤ 0.55, satisfy the relational expression 12.5 ≤ c ≤ 16.25. According to some embodiments of the present invention, 0.2 ≤ a ≤ 0.4, c ≥ 1707a3 -1393.9a 2 It is +391.4a - 30.28. According to some other embodiments of the present invention, when the mass fraction of the lithium salt with respect to the total mass of the electrolytic solution is c%, c and a satisfy the relational expressions 0.4 < a ≤ 0.55 and 12.5 ≤ c ≤ 16.25.

[0009] According to some embodiments of the present invention, when the mass fraction of the lithium salt with respect to the total mass of the electrolytic solution is c%, 6.25 ≤ c ≤ 18.75. According to some embodiments of the present invention, 8.75 ≤ c ≤ 16.25. According to some embodiments of the present invention, 12.5 ≤ c ≤ 16.25.

[0010] According to some embodiments of the present invention, the lithium salt is one or more selected from the group consisting of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). According to some embodiments of the present invention, the lithium salt contains LiPF6.

[0011] According to some embodiments of the present invention, the additive contains fluorocarbonate. The fluorocarbonate can form a stable SEI film on the surface of the negative electrode during the formation process of the electrochemical device, can suppress the reduction decomposition of other components in the electrolytic solution on the surface of the negative electrode, thereby playing a role in improving the cycle characteristics of the electrochemical device, and at the same time can suppress the gas generation during storage and cycling.

[0012] According to some embodiments of the present invention, when the mass fraction of the fluorocarbonate relative to the total mass of the electrolyte is d%, d and a satisfy the relationship 10a-3≦d≦4. According to some embodiments of the present invention, 10a-3≦d≦4 and 0.3≦a≦0.55. According to some embodiments of the present invention, the fluorocarbonate is fluoroethylene carbonate. If the mass fraction of fluoroethylene carbonate is too low, the strengthening effect on the SEI on the surface of the negative electrode is not significant, and the improvement in the cycle performance of the electrochemical device is not significant. If the mass fraction of fluoroethylene carbonate is higher than 4%, the fluoroethylene carbonate decomposes to generate more HF, which adversely worsens SEI corrosion, and at the same time, its low electrochemical stability is prone to causing gas generation in the cell.

[0013] According to some embodiments of the present invention, the organic solvent comprises an organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less. According to some further embodiments of the present invention, the mass fraction of the organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less relative to the total mass of the electrolyte solution is 30% or more. An organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less has low viscosity and high dielectric constant, and can significantly improve the wetting performance of the electrolyte solution, improve liquid retention, and improve the quality of SEI film formation.

[0014] According to some embodiments of the present invention, the organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less 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), and ethylene glycol dimethyl ether (DME).

[0015] According to some embodiments of the present invention, the electrolyte further comprises ethylene carbonate (EC), which can further improve the cycle life of the lithium-ion battery and simultaneously suppress gas generation due to decomposition of the electrolyte, thereby improving safety performance and achieving a longer cycle life.

[0016] According to some embodiments of the present invention, the electrolytic solution satisfies at least one of the following conditions: (I) a mass ratio of an organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less to ethylene carbonate is 0.75 to 3; (II) a mass ratio of ethylene carbonate to lithium hexafluorophosphate is 0.031 to 0.343; and (III) a mass ratio of an organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less to lithium hexafluorophosphate is 1.8 to 7.0.

[0017] According to some embodiments of the present invention, the additive comprises an S═O functional group-containing compound, and the S═O functional group-containing compound is at least one selected from the group consisting of 1,3-propane sultone (PS), ethylene sulfate (DTD), methylenemethane disulfonate (MMDS), propene sultone (PES), 4-methyl-1,3,2-dioxathiolane-2,2-dioxide (PCS), and 1,4-butane sultone (BS). According to some embodiments of the present invention, the mass fraction of the S═O functional group-containing compound relative to the total mass of the electrolyte is 0.01% to 3%. According to some embodiments of the present invention, the mass fraction of the S═O functional group-containing compound relative to the total mass of the electrolyte is 0.1% to 3%. When the mass fraction of the S═O functional group-containing compound is less than 0.1%, the effect of the S═O functional group-containing compound on the formation of SEI on the surfaces of the positive and negative electrodes is insufficient, and the improvement in storage and high-temperature storage of the lithium-ion battery is not significant. If the mass fraction of the S=O functional group-containing compound is higher than 3%, the resistance to film formation at the positive and negative electrode interfaces is too high, deteriorating the charge-discharge characteristics, especially at low temperatures.

[0018] According to some embodiments of the present invention, the additive comprises a lithium-containing additive, and the lithium-containing additive is at least one selected from the group consisting of LiPO2F2, LiDFOB, LiBOB, LiBF4, B4Li2O7, Li3BO3, and CF3LiO3S. According to some embodiments of the present invention, the mass fraction of the lithium-containing additive relative to the total mass of the electrolyte is 0.01% to 3%. If the mass fraction of the lithium-containing additive is lower than 0.01%, the lithium-containing additive has insufficient effect on negative electrode passivation, and the improvement in the cycle characteristics of the electrochemical device is not significant. If the mass percentage content of the lithium-containing additive is higher than 3%, the lithium-containing additive does not significantly improve the negative electrode passivation effect, and at the same time, the cost of the electrolyte increases, resulting in a poor cost-effectiveness. However, by continuously increasing the amount of LiFSI or LiTFSI used, the electrical conductivity of the electrolyte can be significantly improved, and the kinetics of the electrochemical device can be improved.

[0019] According to some embodiments of the present invention, the positive electrode comprises: (A) a positive electrode active material layer, and the positive electrode active material layer has a compressed density of 1.7 g / cm 3 ~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 and lithium manganese iron phosphate; (C) the positive electrode includes a positive electrode active material, and particles of the positive electrode active material have a D50 of 0.5 μm to 2.0 μm; and (D) the positive electrode includes a positive electrode active material, and the BET of the positive electrode active material is 8m 2 / g~25m 2 / g.

[0020] According to some embodiments of the present invention, the negative electrode comprises a graphite material. According to some embodiments of the present invention, the graphite material has a BET of 0.9m 2 / g~1.7m 2 / g and (F) the D of the graphite material V(F) the Raman Id / Ig ratio of the graphite material is 0.25 to 0.5; and (H) the graphite material contains one or more of Al, Fe, Cu, Zn, Cr, Si, Na, P, and S. According to some embodiments of the present invention, 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 invention, the graphite material simultaneously satisfies the above conditions (E), (F), (G), and (H).

[0021] In a second aspect, the present invention provides an electronic device comprising the electrochemical device of the first aspect.

[0022] The electrochemical device provided by the present invention can significantly improve the lifespan and safety performance of electrochemical devices (e.g., lithium ion batteries) by optimizing the electrolyte, improving the kinetics of the electrolyte, and reducing the resistance of film formation, thereby reducing costs and providing them with very high cost performance. DETAILED DESCRIPTION OF THE INVENTION

[0023] Examples of the present invention will be described in detail below, but the examples of the present invention should not be construed as limiting the present invention.

[0024] A list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, the shorthand phrase "at least one of A and B" means A only, B only, or A and B. In another example, if items A, B, and C are listed, the shorthand phrase "at least one of A, B, and C" means A only, B only, C only, 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] Through extensive research and experimental verification, the inventors have found that for lithium iron phosphate batteries, increasing the coating weight per unit area and compression density of the electrode pieces in order to improve energy density and reduce costs results in problems such as poor cell wetting, insufficient electrolyte retention, excessively rapid cycle decay, lithium deposition during low-temperature charging, lithium deposition in later use, and increased temperature rise due to high resistance, resulting in serious lifespan shortening and safety risks, and these risks increase significantly as capacity increases.The present invention solves the problems of poor wetting, insufficient film formation, cycle diving, and narrow charging window caused by increasing the coating weight and compression density of the positive electrode material by limiting the relationship between the room-temperature electrical conductivity of the electrolyte and the coating weight on one side of the positive electrode.

[0026] In a first aspect, the present invention provides an 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, the room temperature electrical conductivity of the electrolyte being b mS / cm, and the coating weight of one side of the positive electrode being ag / 1540.25mm 2 Then, a and b are related by the equation b≧50.859a 2 The present invention provides an electrochemical device that satisfies the relationship -16.044a+8.2071, where 0.2≦a≦0.55. In the present invention, the room temperature electrical conductivity is the electrical conductivity obtained by measurement at a temperature in the range of 20°C to 30°C. According to some embodiments of the present invention, the room temperature electrical conductivity is the electrical conductivity obtained by measurement at 25°C. When the room temperature electrical conductivity of the electrolyte and the coating weight on one side of the positive electrode satisfy the above relationship, an electrochemical device that achieves both ultra-high energy density and excellent service life can be obtained.

[0027] According to some embodiments of the invention, b≦20. According to some embodiments of the invention, 8≦b≦20. In some examples, b is 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or a range consisting of any two of these values.

[0028] According to some embodiments of the present invention, when the mass fraction of the lithium salt with respect to the total mass of the electrolytic solution is c%, when 0.2 ≦ a ≦ 0.4, c and a satisfy the relational expression c ≧ 1707a 3 - 1393.9a 2 + 391.4a - 30.28, and when 0.4 < a ≦ 0.55, it satisfies the relational expression 12.5 ≦ c ≦ 16.25. According to some embodiments of the present invention, when 0.2 ≦ a ≦ 0.4, c ≧ 1707a 3 - 1393.9a 2 + 391.4a - 30.28. According to some other embodiments of the present invention, when the mass fraction of the lithium salt with respect to the total mass of the electrolytic solution is c%, c and a satisfy the relational expressions 0.4 < a ≦ 0.55 and 12.5 ≦ c ≦ 16.25. By appropriately increasing the concentration of the lithium salt, it is possible to reduce the problems of increased concentration polarization due to a thick electrode plate, dark spots at the negative electrode interface, and lithium precipitation.

[0029] According to some embodiments of the present invention, when the mass fraction of the lithium salt with respect to the total mass of the electrolytic solution is c%, 6.25 ≦ c ≦ 18.75. According to some embodiments of the present invention, 8.75 ≦ c ≦ 16.25. According to some embodiments of the present invention, 12.5 ≦ c ≦ 16.25.

[0030] According to some embodiments of the present invention, the lithium salt is one or more selected from the group consisting of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). According to some embodiments of the present invention, the lithium salt contains LiPF6.

[0031] According to some embodiments of the present invention, the additive includes a fluorocarbonate, and when the content of the fluorocarbonate is d%, d and a satisfy the relationship 10a-3≦d≦4. According to some embodiments of the present invention, the additive includes a fluorocarbonate, and when the content of the fluorocarbonate is d%, d and a satisfy the relationship 10a-3≦d≦4 and 0.3≦a≦0.55. According to some embodiments of the present invention, the fluorocarbonate is fluoroethylene carbonate (FEC). The addition of fluoroethylene carbonate can form a low-resistance SEI at the negative electrode interface, and can perform good self-repair during use, suppressing lithium deposition and the occurrence of crack spots during cycling, thereby achieving an ultra-long cycle life.

[0032] According to some embodiments of the present invention, the organic solvent includes an organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less, and the mass fraction of the organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less is 30% or more relative to the mass of the electrolyte. According to some embodiments of the present invention, the organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less 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), and ethylene glycol dimethyl ether (DME). The organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less has low viscosity and high dielectric constant, which significantly improves the wetting performance of the electrolyte, improves liquid retention, and improves the quality of the SEI film formation.

[0033] According to some embodiments of the present invention, the electrolyte further comprises ethylene carbonate, which can further improve the cycle life of the lithium-ion battery and simultaneously suppress gas generation due to decomposition of the electrolyte, thereby improving safety performance and achieving a longer cycle life.

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

[0035] According to some embodiments of the present invention, the additive comprises an S=O functional group-containing compound. Addition of the S=O functional group-containing compound can further improve the cycle life of the lithium-ion battery, while simultaneously suppressing gas generation due to decomposition of the electrolyte, improving safety performance, and achieving a longer cycle life. According to some embodiments of the present invention, the mass fraction of the S=O functional group-containing compound relative to the total mass of the electrolyte is 0.01% to 3%. According to some embodiments of the present invention, the mass fraction of the S=O functional group-containing compound relative to the total mass of the electrolyte is 0.1% to 3%. If the mass fraction of the S=O functional group-containing compound is less than 0.1%, the effect of the S=O functional group-containing compound on the formation of SEI on the surfaces of the positive and negative electrodes is insufficient, and the improvement in the storage and high-temperature storage properties of the lithium-ion battery is not significant. If the mass fraction of the S=O functional group-containing compound is greater than 3%, the resistance to film formation at the positive and negative electrode interfaces is too high, resulting in deterioration of charge / discharge characteristics, especially at low temperatures.

[0036] According to some embodiments of the present invention, the S=O functional group-containing compound is at least one selected from the group consisting of 1,3-propane sultone (PS), ethylene sulfate (DTD), methylenemethane disulfonate (MMDS), propene sultone (PES), 4-methyl-1,3,2-dioxathiolane-2,2-dioxide (PCS), and 1,4-butane sultone (BS).

[0037] According to some embodiments of the present invention, the additive comprises at least one of LiPO2F2, LiDFOB, LiBOB, LiBF4, B4Li2O7, Li3BO3, and CF3LiO3S. The addition of such a lithium salt-containing additive can further improve the cycle life of a lithium-ion battery, while simultaneously suppressing gas generation due to electrolyte decomposition, improving safety performance, and achieving a longer cycle life. According to some embodiments of the present invention, the mass fraction of the lithium-containing additive relative to the total mass of the electrolyte is 0.01% to 3%. If the mass fraction of the lithium-containing additive is less than 0.01%, the lithium-containing additive's effect on negative electrode passivation is insufficient, and the improvement in the cycle performance of the electrochemical device is not significant. If the mass percentage content of the lithium-containing additive is higher than 3%, the lithium-containing additive does not significantly improve the negative electrode passivation effect, and at the same time, the cost of the electrolyte increases, resulting in a poor cost-effectiveness. However, by continuing to increase the amount of LiFSI and LiTFSI used, the electrical conductivity of the electrolyte can be significantly improved, thereby improving the kinetics of the electrochemical device.

[0038] According to some embodiments of the present invention, the positive electrode comprises: (A) a positive electrode active material layer, and the positive electrode active material layer has a compressed density of 1.7 g / cm 3 ~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 and lithium manganese iron phosphate; (C) the positive electrode includes a positive electrode active material, and particles of the positive electrode active material have a D50 of 0.5 μm to 2.0 μm; and (D) the positive electrode includes a positive electrode active material, and the BET of the positive electrode active material is 8m 2 / g~25m 2 / g and at least one of the following conditions is satisfied.

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

[0040] According to some embodiments of the present invention, a positive electrode includes a current collector and a positive electrode active material layer disposed on the current collector. In some examples, the current collector includes, but is not limited to, aluminum. In some examples, 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 further includes an adhesive and may optionally further include a conductive material. The adhesive improves adhesion between the positive electrode active material particles and further improves adhesion between the positive electrode active material and the current collector. In some examples, the adhesive includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or the like. In some embodiments, the conductive material includes, but is not limited to, a carbon-based material, a metallic material, a conductive polymer, and a mixture thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metallic material is 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 may be prepared by a preparation method known in the art. For example, the positive electrode may be obtained by mixing an active material, a conductive material, and an adhesive in a solvent to prepare an active material composition, and then coating the active material composition on a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone.

[0042] According to some embodiments of the present invention, the negative electrode comprises a graphite material. According to some embodiments of the present invention, the graphite material has a BET of 0.9m 2 / g~1.7m 2 / g and (F) the D of the graphite material V (F) the Raman Id / Ig ratio of the graphite material is 0.25 to 0.5; and (H) the graphite material contains one or more of Al, Fe, Cu, Zn, Cr, Si, Na, P, and S. According to some embodiments of the present invention, 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 invention, the graphite material simultaneously satisfies the above conditions (E), (F), (G), and (H).

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

[0044] According to some embodiments of the present invention, the negative electrode further comprises a current collector, and the negative electrode active material is located on the current collector. In some examples, the current collector comprises 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 invention may be prepared by methods known in the art. Generally, the negative electrode active material and optional conductive agents (e.g., carbon materials such as carbon black and metal particles), binders (e.g., SBR), and other optional additives (e.g., PTC thermistor materials) are mixed and dispersed in a solvent (e.g., deionized water), uniformly stirred, and then uniformly coated on a negative electrode current collector and dried to obtain a negative electrode having a negative electrode active layer. Next, the negative electrode having the negative electrode active layer is subjected to a lithium replenishment process to obtain the lithium-replenished negative electrode of the present invention. 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 invention further includes a separator. The material and shape of the separator used in the electrochemical device of the present invention are not particularly limited and may be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic material formed of a material stable to the electrolyte solution of the present invention. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, film, or composite film having a porous structure, and the material of the substrate layer is at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, 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 selected and used. A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer obtained by mixing a polymer and an inorganic material. The inorganic layer includes inorganic particles and a binder, the inorganic particles including at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, and the binder including at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer includes a polymer, and the polymer material is at least one selected from the group consisting of polyamide, polyacrylonitrile, acrylic ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0047] In a second aspect, the present invention provides an electronic device comprising the electrochemical device of the first aspect.

[0048] The electronic device or apparatus of the present invention is not particularly limited. In some embodiments, the electronic device of the present invention includes, but is not limited to, a notebook computer, a pen-based computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc, a walkie-talkie, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household storage battery, and a lithium ion capacitor.

[0049] The present invention will be further described below with reference to examples. It should be understood that these examples are used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0050] 1. Preparation of lithium-ion batteries The lithium ion batteries in the examples and comparative examples are all prepared according to the following method.

[0051] 1. Preparation of the positive electrode The cathode active material, lithium iron phosphate (LFP), conductive agent Super P, and binder, polyvinylidene fluoride, were mixed in a weight ratio of 96.3:1.5:2.2, and N-methylpyrrolidone (NMP) was added. The mixture was stirred in a vacuum mixer until the mixture was homogeneous and transparent, yielding a cathode slurry with a solids content of 72 wt%. The cathode slurry was uniformly coated onto aluminum foil, which served as a cathode current collector. The aluminum foil was then dried at 85°C, cold pressed, cut, and dried under vacuum at 85°C for 4 hours to obtain cathode pieces.

[0052] 2. Preparation of negative electrode pieces The negative electrode active material (artificial graphite), conductive agent Super P, thickener (sodium carboxymethylcellulose (CMC)), and binder (styrene butadiene rubber (SBR)) were mixed in a weight ratio of 96.4:1.5:0.5:1.6, and deionized water was added. The mixture was stirred in a vacuum mixer to obtain a negative electrode slurry with a solids content of 54 wt%. The negative electrode slurry was uniformly coated onto a copper foil negative electrode current collector, which was dried at 85°C. The copper foil was then cold-pressed, sliced, and cut, and then dried in a vacuum at 120°C for 12 hours to obtain negative electrode pieces.

[0053] 3. Preparation of electrolyte In a glove box under a dry argon atmosphere, 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, and then additives were added and dissolved. After sufficient stirring, a lithium salt, LiPF6, was added and mixed uniformly to obtain an electrolyte solution.

[0054] 4. Preparation of separator A polyethylene (PE) separator with a thickness of 7 μm was selected.

[0055] 5. Preparation of Lithium-ion Battery The positive electrode, separator, and negative electrode were stacked in this order so that the separator was interposed between the positive and negative electrodes to serve as an insulator. The stack was then wound up to obtain an electrode part. After the tabs were welded, the electrode part was placed in an aluminum laminate exterior foil, and the prepared electrolyte solution was injected into the dried electrode part. After vacuum packaging, standing, formation (charging to 3.3 V at a constant current of 0.02 C, and then further charging to 3.6 V at a constant current of 0.1 C), shaping, capacity measurement, etc., a soft-pack lithium-ion battery (thickness 3.3 mm, width 39 mm, length 96 mm) was obtained.

[0056] 2. Lithium-ion battery testing process 1. Measurement of cycle characteristics of lithium-ion batteries The lithium-ion battery was placed in a thermostatic box at 25°C and left for 30 minutes to reach a constant temperature. The lithium-ion battery was then charged at a constant current of 1 C until the voltage reached 3.65 V, then charged at a constant voltage of 3.65 V until the current reached 0.05 C, and then discharged at a constant current of 1 C until the voltage reached 2.5 V. This constituted one charge-discharge cycle. The initial discharge capacity was defined as 100%, and the charge-discharge cycle was repeated. Measurements were stopped when the discharge capacity had decayed to 65%, and the number of cycles was recorded as an index for evaluating the cycle characteristics of the lithium-ion battery.

[0057] At the same time, the cycle characteristics of the lithium ion battery at 45°C were measured, and the measurement method was the same as that for the measurement of the 25°C cycle characteristics.

[0058] 2. High SOC high temperature storage test of lithium-ion batteries The lithium-ion batteries were placed in a thermostatic box at 25°C and allowed to stand for 30 minutes to reach a constant temperature. They were charged at a constant current of 1C to 3.65V, then charged at a constant voltage until the current reached 0.05C, and then discharged at a constant current of 1C to 2.5V. The discharge capacity was recorded as the initial capacity of the lithium-ion battery. They were then charged at a constant current of 0.5C to 3.65V and again at a constant voltage until the current reached 0.05C. The battery thickness was measured with a micrometer and recorded. The test lithium-ion batteries were then transferred to a thermostatic box at 60°C and stored for 90 days, during which time the battery thickness was measured once every 30 days. The batteries were then transferred to a thermostatic box at 25°C, allowed to stand for 60 minutes, and then discharged at a constant current of 1C to 2.5V. The discharge capacity was recorded as the remaining capacity of the lithium-ion battery. The battery was charged to 3.65 V at a constant current of 1 C, then charged at a constant voltage until the current reached 0.05 C, and then discharged to 2.5 V at a constant current of 1 C. The discharge capacity was recorded as the recoverable capacity of the lithium-ion battery. The battery's THK (thickness), OCV (open circuit voltage), and IMP (resistance) were measured. The recovered discharge capacity was recorded at 2.5 V at 1 C DC, and the remaining storage capacity retention and recoverable capacity retention of the lithium-ion battery were calculated as indicators for evaluating the high-temperature storage characteristics of the lithium-ion battery. Remaining capacity retention rate = (remaining capacity after 90 days of storage - initial cell capacity) / initial cell capacity x 100% Recovered capacity retention rate = (Recoverable capacity after 90 days of storage - initial cell capacity) / initial cell capacity x 100%

[0059] 3. Lithium-ion battery low 0% SOC high temperature storage test The lithium-ion batteries were placed in a thermostatic box at 25°C and allowed to stand for 30 minutes to reach a constant temperature. They were charged at a constant current of 1C to 3.65V, then charged at a constant voltage until the current reached 0.05C, and then discharged at a constant current of 1C to 2.5V. The discharge capacity was recorded as the initial capacity of the lithium-ion battery. The battery thickness was then measured with a micrometer. The test lithium-ion batteries were then transferred to a thermostatic box at 60°C and stored for 90 days, during which time the battery thickness was measured once every 30 days. The batteries were then placed in a thermostatic box at 25°C, allowed to stand for 60 minutes, charged at a constant current of 1C to 3.65V, then charged at a constant voltage until the current reached 0.05C, and then discharged at a constant current of 1C to 2.5V. The discharge capacity was recorded as the recoverable capacity of the lithium-ion battery. The battery's THK (thickness), OCV (open circuit voltage), and IMP (resistance) were measured. The voltage reached 2.5V at 1C DC, and the thickness expansion rate during storage of the lithium-ion battery was recorded and calculated as an index to evaluate the 0% SOC high-temperature storage characteristics of the lithium-ion battery. 0% SOC storage thickness expansion rate = (thickness after 90 days storage - initial cell thickness) / initial cell thickness × 100%

[0060] 4. Lithium-ion battery DC resistance DCR(-10 o C) The lithium-ion battery was placed in a high-temperature / low-temperature box at -10°C and allowed to stand for 4 hours to maintain a constant temperature. It was charged to 3.65 V at a constant current of 0.1 C, then charged at a constant voltage of 3.65 V until the current reached 0.05 C, and then allowed to stand for 10 minutes. It was then discharged to 2.5 V at a constant current of 0.1 C, and the capacity at this step was recorded as the actual discharge capacity (D0). After allowing to stand for 5 minutes, it was charged to 3.65 V at a constant current of 0.1 C, and then charged at a constant voltage of 3.65 V until the current reached 0.05 C (the current was calculated based on the capacity corresponding to D0). After allowing to stand for 10 minutes, it was discharged for 3 hours at a constant current of 0.1 C (the current was calculated based on the capacity corresponding to D0). The voltage (V1) was recorded. It was then discharged for 1 second at a constant current of 1 C (sampled every 100 ms, and the current was calculated based on the cell's nominal capacity). The voltage (V2) was recorded. Next, the direct current resistance (DCR) corresponding to 70% state of charge (SOC) of the cell was calculated using the following formula: 70%SOC DCR=(V2-V1) / 1C

[0061] 5. Energy conversion efficiency RTE (25℃) of lithium-ion batteries The lithium-ion battery was placed in a thermostatic box at 25°C and allowed to stand for 30 minutes to reach a constant temperature. It was discharged at a constant current of 0.5C to 2.5V and then allowed to stand for 15 minutes. It was charged at a constant current of 0.5C to 3.65V, charged at a constant voltage of 3.65V until the current reached 0.05C, allowed to stand for 60 minutes, and then discharged at a constant current of 0.5C to 2.5V. The battery was charged and discharged three times at the above current levels, and the charge and discharge energies were recorded for each cycle. The energy conversion efficiency was calculated from the charge energy Ec and discharge energy Ed of the final cycle. Energy conversion efficiency = Discharge energy Ed / Charge energy Ec x 100%

[0062] 6. Measurement of charging performance of lithium-ion batteries (lithium deposition status) 1) The lithium-ion battery was placed in a high / low temperature box at -10°C and allowed to stand for 30 minutes to allow the battery to reach a constant temperature. 2) After allowing the battery to reach a constant temperature, it was discharged at a constant current of 0.5C to a voltage of 2.5V. 3) After allowing it to stand for 10 minutes, it was charged at a constant current of 0.1C to a voltage of 3.65V, and then charged at a constant voltage of 3.65V until the current reached 0.05C (the charge capacity C1 was recorded). 4) After allowing it to stand for 10 minutes, it was discharged at a constant current of 0.5C to a voltage of 2.5V. After allowing it to stand for 10 minutes, it was discharged at a constant current of 0.025C to a voltage of 2.5V. After allowing it to stand for 10 minutes, it was discharged at a constant current of 0.005C to a voltage of 2.5V. The full discharge capacity of this step was recorded as D1. 5) After leaving it for 10 minutes, it was charged at a constant current of 0.3C up to a voltage of 3.65V, and then charged at a constant voltage of 3.65V until the current reached 0.05C. 6) After leaving it for 10 minutes, it was discharged at a constant current of 0.5C down to a voltage of 2.5V, left for 10 minutes, and then discharged at a constant current of 0.025C down to a voltage of 2.5V. After leaving it for 10 minutes, it was discharged at a constant current of 0.005C down to a voltage of 2.5V. 7) Steps 5) and 6) were repeated 12 times, and the final full discharge capacity was measured as D 12 The amount of lithium deposition was calculated as the basis for judging the charging performance (the lower the amount of lithium deposition, the lighter the degree of lithium deposition, and when the amount of lithium deposition is lower than 0.3, lithium deposition is difficult to see with the naked eye), and the calculation formula for the amount of lithium deposition is as follows: Amount of lithium deposited = (initial charge capacity C1 - final discharge capacity D 12 ) / Initial charge capacity C1

[0063] 7. Normal discharge temperature rise of lithium-ion batteries (25°C) The lithium-ion battery was placed in a thermostatic box at 25°C and allowed to stand for 30 minutes to reach a constant temperature. It was discharged at a constant current of 0.5C to 2.5V and then allowed to stand for 15 minutes. It was charged at a constant current of 0.5C to 3.65V, charged at a constant voltage of 3.65V until the current reached 0.05C, allowed to stand for 60 minutes, and then discharged at a constant current of 6C to 2.5V. The temperature T at the exact center of the outer surface of the cell during the battery discharge process was recorded, and the temperature increase (T-25°C) was calculated.

[0064] 8. Lithium-ion battery charging performance measurement At 25°C, the battery was discharged at 0.5C to 2.5V, charged at a constant current of 1C to 6.5V, and then charged at a constant voltage for another 3 hours, and the change in the cell surface temperature (the passing criterion was that the cell did not ignite, burn, or explode) was monitored.

[0065] 9. Measurement of the electrical conductivity of the electrolyte (25℃) The electrolyte was placed in a constant temperature water bath at 25°C and kept warm for 1 hour. The electrical conductivity at room temperature was measured using an electrical conductivity meter and the data was recorded. (The temperature was kept constant during the test.)

[0066] 10. Surface tension measurement of electrolyte (25℃) The electrolyte was placed in a constant temperature water bath at 25°C and kept warm for 1 hour, and the surface tension was measured at room temperature using a surface tensiometer, and the data was recorded. (The temperature was kept constant during the test.)

[0067] 3. Measurement results 1. The effect of electrolyte conductivity on battery performance Table 1 shows the coating weight on one side of the positive electrode, the parameters of the electrical 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.

[0068] [Table 1-1]

[0069] [Table 1-2]

[0070] [Table 1-3]

[0071] As is clear from the examples and comparative examples in Table 1, the higher the electrical conductivity of the electrolyte, the better the kinetics, the better the cycle characteristics at thicker applications, the lower the resistance, the less lithium deposition there is, the lower the rise in discharge temperature at high currents, the smaller the interfacial tension of the electrolyte, and the easier it is to infiltrate.

[0072] 2. The effect of the relationship between the lithium salt content and the positive electrode coating weight on battery performance Table 2 shows the coating weight on one side of the positive electrode, the parameters of the lithium salt in the electrolyte, and the battery performance data for Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-6.

[0073] [Table 2-1]

[0074] [Table 2-2]

[0075] As is evident from the examples and comparative examples in Table 2, the higher the lithium salt content in the electrolyte (up to 16.25%), the smaller the concentration polarization, the better the kinetics, the less lithium deposition occurs in thick coatings, the slower the SEI decomposition, the less purple spots on the negative electrode, the better the cycle characteristics, the lower the resistance, and the lower the rise in discharge temperature at high currents.

[0076] 3. The effect of fluorocarbonate additives on battery performance Table 3 shows the electrolyte parameters and battery performance data for Examples 3-1 to 3-29.

[0077] [Table 3-1]

[0078] [Table 3-2]

[0079] [Table 3-3]

[0080] As is evident from the examples and comparative examples in Table 3, in the case of thick coating, a moderate increase in the FEC content leads to good cycle characteristics, lower resistance, and a lower rise in discharge temperature at high currents. This is mainly because increasing the FEC leads to the formation of a stable, low-resistance SEI at the anode interface, which reduces the degree of lithium deposition, slows SEI decomposition, and reduces the occurrence of purple spots on the anode.

[0081] 4. The impact of organic solvents with carbon numbers of 5 or less and boiling points of 120°C or less on battery performance Table 4 shows the electrolyte parameters and battery performance data for Examples 4-1 to 4-29 and Comparative Examples 4-1 to 4-4.

[0082] [Table 4-2]

[0083] [Table 4-3]

[0084] [Table 4-3]

[0085] As can be seen from the examples and comparative examples in Table 4, increasing the coating weight significantly deteriorates the cell cycle characteristics, rechargeable battery performance, discharge temperature rise, and energy conversion efficiency. In the case of thick coatings, the addition of a high-kinetics solvent (30 wt% or more) significantly improves the cell cycle characteristics, rechargeable battery performance, and discharge temperature rise. This is primarily because a high coating weight makes electrolyte infiltration extremely difficult, resulting in significant polarization during the charge / discharge process and insufficient formation of the initial SEI film. This leads to constant lithium deposition on the anode surface during cycling, resulting in loss of active lithium and rapid capacity decay. The addition of a high-kinetics solvent, such as EMC, DMC, EA, MA, EP, or DME, ensures sufficient infiltration of the electrode within a short period of time, resulting in the formation of a uniform SEI at the anode interface, reduced polarization, inhibited lithium deposition, slowed SEI decomposition, minimized purplish spots on the anode, improved cycle characteristics, reduced resistance, and significantly reduced discharge temperature rise at high currents.

[0086] 5. Effect of S=O-containing compound additives on battery performance Table 5 shows the electrolyte parameters and battery performance data for Examples 5-1 to 5-11 and Comparative Example 5-1.

[0087] [Table 5-1]

[0088] [Table 5-2]

[0089] As can be seen from the examples and comparative examples in Table 5, the addition of an S=O-containing compound in the case of thick coating significantly improved cycle performance, capacity retention after storage, suppression of gas generation during storage, and safety performance. This is primarily due to the rapid decomposition of the SEI in thick coating, which makes cycle diving more likely and shortens the service life of the cell. The S=O-containing compound can form a protective film with good thermal and chemical stability on the surfaces of the positive and negative electrodes, suppressing side reactions between the electrodes and the electrolyte, thereby achieving excellent cycle stability, storage stability (suppression of gas generation and improved capacity retention), dynamic performance, and safety performance. The combination of a sulfonic acid ester compound with a high-kinetic solvent significantly suppresses gas generation during storage due to the high-kinetic solvent, achieving relatively excellent service life and safety performance while maintaining relatively high kinetics.

[0090] Although illustrative embodiments have been disclosed and described, those skilled in the art should understand that the above-described embodiments are not to be construed as limiting the present invention, and that modifications, substitutions, and alterations to the embodiments are possible without departing from the spirit, principle, and scope of the present invention.

Claims

1. a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte solution contains a lithium salt, an organic solvent, and an additive; The room temperature electrical conductivity of the electrolyte is b mS / cm, and the coating weight of one side of the positive electrode is a g / 1540.25 mm ２ Then, a and b are related by the equation b ≥ 50.859a ２ -16.044a+8.2071 is satisfied, 0.2≦a≦0.55, and b is satisfied 10≦b≦20; the lithium salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; When the mass fraction of the lithium salt with respect to the total mass of the electrolyte solution is c%, c satisfies the relational formula 6.25≦c≦18.75, the organic solvent contains an organic solvent having a carbon number of 5 or less and a boiling point of 120°C or less, and the mass fraction of the organic solvent having a carbon number of 5 or less and a boiling point of 120°C or less with respect to the total mass of the electrolytic solution is 30% or more; the organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less includes at least one of dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl formate, ethyl formate, propyl formate, tetrahydrofuran, 1,3-dioxolane, and ethylene glycol dimethyl ether; the additive comprises one or more selected from the group consisting of fluorocarbonates and S═O functional group-containing compounds; When the additive contains an S═O functional group-containing compound, the mass fraction of the S═O functional group-containing compound relative to the total mass of the electrolyte solution is 0.5% to 3%; The positive electrode includes a positive electrode active material layer, and the positive electrode active material layer has a compressed density of 1.7 g / cm ３ ~2.5g / cm ３ and the positive electrode includes a positive electrode active material, the positive electrode active material including at least one of lithium iron phosphate and lithium manganese iron phosphate; The electrochemical device, wherein the negative electrode comprises a graphite material.

2. the additive comprises a fluorocarbonate; 2. The electrochemical device according to claim 1, wherein d and a satisfy the relationship 10a-3≦d≦4, 0.3≦a≦0.55, where d% is the mass fraction of the fluorocarbonate relative to the total mass of the electrolyte.

3. 10. The electrochemical device of claim 1, wherein the electrolyte further comprises ethylene carbonate.

4. the additive comprises an S=O functional group-containing compound; 2. The electrochemical device according to claim 1, wherein the S═O functional group-containing compound is at least one selected from the group consisting of 1,3-propane sultone, ethylene sulfate, methylenemethane disulfonate, propene sultone, 4-methyl-1,3,2-dioxathiolane-2,2-dioxide, and 1,4-butane sultone.

5. The electrolyte solution is (I) the mass ratio of the organic solvent having 5 or less carbon atoms and a boiling point of 120°C or less 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 5 or less carbon atoms and a boiling point of 120°C or less to lithium hexafluorophosphate is 1.8 to 7.0; The electrochemical device according to claim 1 , wherein at least one of the following conditions is satisfied:

6. The positive electrode (C) the positive electrode includes a positive electrode active material, and the D50 of particles of the positive electrode active material is 0.5 μm to 2.0 μm; (D) The positive electrode contains a positive electrode active material, and the BET of the positive electrode active material is 8m ２ / g~25m ２ / g, and The electrochemical device according to claim 1 , wherein at least one of the following conditions is satisfied:

7. The graphite material is (E) The BET of the graphite material is 0.9 m ２ / g to 1.7m ２ / g, and (F) D of the graphite material Ｖ 50 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, and S; The electrochemical device according to claim 1 , wherein at least one of the following conditions is satisfied:

8. An electronic device comprising the electrochemical device according to any one of claims 1 to 7.

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