Electrochemical device and electronic device including same

Abstract

An electrochemical device capable of improving high-temperature cycle characteristics and high-temperature interval cycle characteristics, and an electronic device including the same are provided. [Solution] The electrochemical device of the present invention includes a positive electrode and an electrolyte solution, the electrolyte solution including ethylene carbonate (EC), propylene carbonate (PC), and succinonitrile (SN). The positive electrode includes a positive electrode active material, the positive electrode active material including metal element A including at least one of Mg, Zr, and Al. When the mass content of SN is a%, the mass content of EC is b%, and the mass content of PC is c%, relative to the mass of the electrolyte solution, and k is k=b / c, a and k satisfy 1.25≦k≦6 and a / k≧0.2. When the mass content of metal element A is x%, relative to the mass of the positive electrode active material, x satisfies 0.01≦x≦1.

Description

[Technical field]

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

[0002] Rechargeable electrochemical devices are considered to be one of the most attractive energy storage systems due to their advantages of high energy density, relatively simple reaction mechanism, high operating voltage, long life, environmental friendliness, etc. Currently, electrochemical devices such as lithium-ion batteries are widely used in various fields such as wearable devices, smartphones, drones, and laptops. Summary of the Invention [Problem to be solved by the invention]

[0003] With the expansion of the application field of electrochemical devices, the market is increasingly demanding for cycle characteristics, especially high temperature cycle characteristics and high temperature interval cycle characteristics, of electrochemical devices such as lithium ion batteries. For example, a laptop computer, which is a commonly used tool for work, is always in a charging state during use, and heat is often generated during the charging and use process. In this process, the laptop computer is first charged to a fully charged state, kept in a fully charged state for several hours, and finally disconnected from the charger to be in a discharged state. In this process, not only is it required that the electrochemical device of the laptop computer has high temperature cycle characteristics (i.e., multiple cycles of "charge-discharge" at high temperature), but there is also a higher demand for high temperature interval cycle characteristics (i.e., multiple cycles of "charge-maintain at full charge for several hours-discharge" at high temperature). In view of this, the present invention is committed to obtaining an electrochemical device having excellent high temperature cycle characteristics and high temperature interval cycle characteristics in order to meet the above demand.

[0004] In view of the above circumstances, an object of the present invention is to provide an electrochemical device capable of improving high-temperature cycle characteristics and high-temperature interval cycle characteristics, and an electronic device including the same.

[0005] According to one aspect of the present invention, there is provided an electrochemical device, the electrochemical device includes a positive electrode and an electrolyte, the electrolyte includes ethylene carbonate (EC), propylene carbonate (PC), and succinonitrile (SN), the positive electrode includes a positive electrode active material, the positive electrode active material includes a metal element A, the metal element A includes at least one of Mg, Zr, and Al, and when the mass content of SN is a%, the mass content of EC is b%, and the mass content of PC is c%, and k is k=b / c, a and k satisfy 1.25≦k≦6 and a / k≧0.2, and when the mass content of the metal element A is x%, the mass content of the positive electrode active material satisfies 0.01≦x≦1.

[0006] According to an embodiment of the present invention, x and k satisfy x / k≦0.4.

[0007] According to an embodiment of the present invention, x and a satisfy 0.001≦x / a≦1.

[0008] According to an embodiment of the present invention, the positive electrode active material includes lithium cobalt oxide.

[0009] According to an embodiment of the present invention, the positive electrode active material includes lithium nickel cobalt manganese oxide.

[0010] According to an embodiment of the present invention, the positive electrode active material includes lithium cobalt oxide and lithium nickel cobalt manganese oxide, and when the ratio of the mass of the lithium cobalt oxide to the mass of the lithium nickel cobalt manganese oxide is g with respect to the mass of the positive electrode active material, g satisfies 1≦g≦9.

[0011] According to an embodiment of the present invention, the positive electrode active material contains lithium cobalt oxide, and when the median diameter Dv50 of the lithium cobalt oxide is mm, m satisfies 8≦m≦20.

[0012] According to the embodiment of the present invention, when the median diameter Dv50 of the positive electrode active material is y μm, y satisfies 2≦y≦25.

[0013] According to an embodiment of the present invention, x and y satisfy 10≦y / x≦900.

[0014] According to an embodiment of the present invention, y and a satisfy 1≦y / a≦36.

[0015] According to an embodiment of the present invention, the electrolyte further contains lithium difluorophosphate (LiPO2F2), and when the mass content of LiPO2F2 is d% with respect to the mass of the electrolyte, d satisfies 0.01≦d≦0.5.

[0016] According to an embodiment of the present invention, x and d satisfy 0.05≦d / x≦25.

[0017] According to an embodiment of the present invention, k and d satisfy 0.001≦d / k≦0.4.

[0018] According to another aspect of the present invention, the present invention further provides an electronic device comprising an electrochemical device according to the embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the present invention will be described in detail with reference to the examples, which should not be construed as limiting the present invention.

[0020] As used herein, the terms "comprise", "include", and "contain" are used in their open, non-limiting sense.

[0021] In addition, amounts, ratios, and other numerical values ​​may be expressed in range format in this specification. It should be understood that such range format is used for convenience and conciseness. The range format should be understood to be flexible and include not only the numerical values ​​expressly specified as range limits, but also all numerical values ​​or subranges contained in the above ranges as if each numerical value and subrange were expressly specified.

[0022] In the detailed description and claims, a list of items connected by the terms "one or more of," "one or more of," "at least one of," or other similar terms means any combination of the listed items. For example, if item A and item B are listed, the short 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 short 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.

[0023] As an important component of an electrochemical device, the electrolyte is used to transport lithium ions between the positive and negative electrodes and achieve the continuous absorption and release of lithium ions in the materials of the positive and negative electrodes to perform the functions of charging and discharging. Therefore, the electrolyte is important for the electrochemical device to obtain excellent high-temperature properties.

[0024] One of the main features of the electrolyte according to the present invention is that the electrolyte simultaneously contains ethylene carbonate (EC), propylene carbonate (PC), and succinonitrile (SN), and when the mass content of succinonitrile is a%, the mass content of ethylene carbonate is b%, the mass content of propylene carbonate is c%, and k is k=b / c, a and k satisfy 1.25≦k≦6 and a / k≧0.2, relative to the mass of the electrolyte.

[0025] The present invention proposes the above electrolyte solution because it has been found that the high voltage resistance and high temperature stability of the electrolyte solution itself can be improved by adding a certain content of ethylene carbonate to the electrolyte solution. However, if the content of ethylene carbonate in the electrolyte solution is too high, gas generation becomes serious, which is disadvantageous to the high temperature interval cycle characteristics. In contrast, propylene carbonate has excellent high temperature stability, and its addition can compensate for the defects of ethylene carbonate. Therefore, by adding both ethylene carbonate and propylene carbonate to the electrolyte solution, the high temperature stability of the electrolyte solution itself can be improved, thereby improving the high temperature interval cycle characteristics and high temperature cycle characteristics of the electrochemical device. In addition, by adding a nitrile compound to the electrolyte solution, the transition metal in the positive electrode active material (e.g., metallic cobalt in lithium cobalt oxide) can be effectively stabilized, the elution of the transition metal can be reduced, and the structure of the positive electrode active material can be stabilized, thereby further improving the cycle stability and high temperature characteristics of the electrochemical device. Here, the effect of adding succinonitrile (SN) to the electrolyte is particularly prominent compared to other nitrile compounds, because the cyano group in the succinonitrile structure coordinates with the metal ions in the positive electrode active material to form a complex, thereby reducing side reactions between the positive electrode active material and the electrolyte and reducing the generation of gas inside the electrochemical device, and the cyano group reacts with water or hydrogen fluoride in the electrolyte to increase the cycle stability of the electrolyte and further improve the high-temperature cycle characteristics of the electrochemical device.

[0026] However, the present invention has found that although propylene carbonate has excellent high-temperature stability, it is prone to first be reduced and decomposed on the surface of graphite, the negative electrode, at the lithium absorption potential, destroying the structure of graphite, affecting the release of active ions, and further affecting the cycle stability of the electrochemical device; and although succinonitrile can effectively stabilize the transition metal in the positive electrode active material, if added in a large amount, it causes an increase in the impedance of the electrochemical device and causes large polarization. Therefore, the present invention adjusts the mass contents of ethylene carbonate, propylene carbonate, and succinonitrile in the electrolyte and their compounding ratio relationship so that a and k satisfy 1.25≦k≦6 and a / k≧0.2, thereby promoting the synergistic effect of the three, and further improving the high-temperature cycle characteristics and high-temperature interval cycle characteristics of the electrochemical device. In some embodiments, k may be, but is not limited to, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6, or a range consisting of any two of the above values. In some embodiments, a / k can be, but is not limited to, 0.2, 0.5, 1, 1.5, or 2, or a range consisting of any two of the foregoing values.

[0027] The positive electrode, as an important component of an electrochemical device, has an important effect on the performance of electrochemical properties. The positive electrode includes a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. The positive electrode active material includes a material that can reversibly absorb and release active ions, such as lithium ions. The positive electrode active material layer may be a single layer or multiple layers, and each layer of the multiple layers of positive electrode active materials may include the same or different positive electrode active materials. In addition, the positive electrode active material layer further includes a binder and / or a conductive agent.

[0028] One main feature of the positive electrode according to the present invention is that the positive electrode active material is doped with a metal element A, the metal element A containing at least one of Mg, Zr, and Al, and when the mass content of the metal element A is x% with respect to the mass of the positive electrode active material, x satisfies 0.01≦x≦1.

[0029] The present invention proposes the above positive electrode because it has been found that the structure of the positive electrode active material can be more stabilized by doping at least one of Mg, Zr, and Al into the positive electrode active material compared to other metal elements. For example, when the positive electrode active material contains active metal cobalt element (Co), element A occupies the lattice gap, and the AO bond formed after the positive electrode releases lithium is stronger than the Co-O bond, thereby delaying the release of oxygen, preventing the elution of Co, and achieving the purpose of stabilizing the structure of the positive electrode active material. In addition, by controlling the mass content of metal element A in the positive electrode active material within the range of 0.01% to 1%, the release of active ions such as lithium ions in the positive electrode active material can be promoted, polarization can be reduced, and the improvement of high-temperature cycle characteristics and high-temperature interval cycle characteristics can be further promoted. In some embodiments, x can be, but is not limited to, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or a range consisting of any two of the foregoing values.

[0030] Furthermore, by using a combination of an electrolyte and a positive electrode having the above-mentioned characteristics, the high-temperature cycle characteristics and high-temperature interval cycle characteristics of the electrochemical device can be further improved because the electrolyte and the positive electrode have a good matching relationship and can mutually promote the volatilization of each other's actions.

[0031] Furthermore, by adjusting the matching of some components in the electrolyte with the positive electrode active material, the high temperature cycle characteristics and high temperature interval cycle characteristics of the electrochemical device can be further improved.

[0032] In some embodiments, the above-mentioned high-temperature characteristics can be further improved by adjusting the relationship between the content x% of the doped element A in the positive electrode active material and the compounding ratio k of ethylene carbonate and propylene carbonate in the electrolyte. The reason is as follows. Propylene carbonate has excellent high-temperature stability, but is easily decomposed at the negative electrode and destroys the structure of the negative electrode. In contrast, ethylene carbonate can be decomposed on the surface of the negative electrode to form a stable SEI film, and the action of propylene carbonate decomposing at the interface of the negative electrode and destroying the negative electrode can be weakened, so that the high-voltage withstand voltage characteristics and high-temperature stability of the electrolyte itself can be improved by using both. On the other hand, the doped element A can stabilize the structure of the positive electrode active material, and by adjusting the relationship between the content of the doped element A and the compounding ratio k of ethylene carbonate and propylene carbonate, the high-voltage withstand voltage characteristics and high-temperature stability of the electrolyte can be improved, and the structural stability of the positive electrode can be improved, and the high-temperature cycle characteristics and high-temperature interval cycle characteristics of the electrochemical device can be further improved. In some embodiments, x and k satisfy x / k≦0.4. In some embodiments, x and k satisfy x / k≦0.3, x / k≦0.2, or x / k≦0.1.

[0033] In some embodiments, the high temperature characteristics can be further improved by adjusting the relationship between the content x% of the doped element A in the positive electrode active material and the content a% of succinonitrile in the electrolyte. This is because the cyano group in the structure of succinonitrile coordinates with the metal ion in the positive electrode active material to form a complex, thereby stabilizing the structure of the positive electrode active material. By adjusting the relationship between the contents of the two, the structure of the positive electrode active material can be well stabilized and the electrolyte has a relatively low impedance. In some embodiments, x and a satisfy 0.001≦x / a≦1. In some embodiments, x / a may be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or may be in a range consisting of any two of the above numerical values, but is not limited thereto.

[0034] When the positive electrode active material particles are primary particles, the median diameter Dv50 of the positive electrode active material refers to the primary particle diameter of the positive electrode active material particles. When the positive electrode active material particles are aggregated to form secondary particles, the median diameter Dv50 of the positive electrode active material refers to the secondary particle diameter of the positive electrode active material particles.

[0035] In some embodiments, when the median diameter Dv50 of the positive electrode active material is y μm, y satisfies 2≦y≦25. In some embodiments, the median diameter Dv50 of the positive electrode active material may be 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, or 25 μm, or may be in a range consisting of any two of the above values, but is not limited thereto. When the median diameter Dv50 of the positive electrode active material is in the above range, it is possible to ensure not only good contact between the positive electrode active material particles, but also to ensure that the contact area between the positive electrode active material and the electrolyte is in an appropriate range, thereby reducing the occurrence of side reactions, avoiding excessive consumption of the electrolyte during the electrochemical cycle, and reducing the risk of the positive electrode active material particles being cracked by cold pressing during the process of preparing the electrode.

[0036] In some embodiments, the active cathode material includes one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium-containing manganese-based materials.

[0037] In some embodiments, the formula of the lithium cobalt oxide may be, but is not limited to, LiCoO2.

[0038] In some embodiments, the formula of the lithium nickel cobalt manganese oxide is LiNi 0.6 Co 0.2 Mn 0.2It may be, but is not limited to, O2.

[0039] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide and lithium nickel cobalt manganese oxide, and when the positive electrode active material simultaneously includes lithium cobalt oxide and lithium nickel cobalt manganese oxide, g satisfies 1≦g≦9, where g is the ratio of the mass of lithium cobalt oxide to the mass of lithium nickel cobalt manganese oxide, relative to the mass of the positive electrode active material. In some embodiments, g may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, or 9, or a range consisting of any two of the above numerical values.

[0040] In some embodiments, the positive electrode active material includes lithium cobalt oxide, and when the median diameter Dv50 of the lithium cobalt oxide is mm, m satisfies 8≦m≦20. By controlling the median diameter of the lithium cobalt oxide within the above range, not only can the infiltration effect of the electrolyte into the positive electrode active material be enhanced, but also the rate of absorption and release of metal ions such as lithium ions in the positive electrode active material can be improved, thereby further improving the electrochemical characteristics of the electrochemical device.

[0041] In some embodiments, the median diameter Dv50 (y μm) of the positive electrode active material and the content x% of the metal element A in the positive electrode active material satisfy 10≦y / x≦900. When y / x is in the above range, the structural stability and thermal stability at high temperatures of the positive electrode active material can be simultaneously improved, and thus the high temperature cycle characteristics and high temperature interval cycle characteristics of the electrochemical device can be further improved. In some embodiments, y and x satisfy 20≦y / x≦800, 20≦y / x≦600, or 50≦y / x≦500.

[0042] In some embodiments, the median diameter Dv50 (y μm) of the positive electrode active material and the mass content a % of succinonitrile in the electrolyte satisfy 1≦y / a≦36. When y / a is in the above range, the complex formation between succinonitrile and the transition metal in the positive electrode active material is further promoted, and the elution of the transition metal is reduced, thereby improving the structural stability and thermal stability at high temperatures of the positive electrode active material, and thus the high temperature cycle characteristic and high temperature interval cycle characteristic of the electrochemical device can be further improved. In some embodiments, y and a satisfy 2≦y / a≦30, 5≦y / a≦20, or 5≦y / a≦15.

[0043] In some embodiments, the electrolyte further comprises lithium difluorophosphate (LiPO2F2), and the addition of lithium difluorophosphate can cause decomposition and reduction on the surface of the negative electrode to form a structure-stable SEI film, which can further improve the high-temperature cycle characteristics and high-temperature interval cycle characteristics of the electrochemical device. This is reflected in that the addition of lithium difluorophosphate can increase the LiF content in the SEI film, which can enhance the stability of the SEI film and further reduce the occurrence of side reactions.

[0044] In some embodiments, when the mass content of LiPO2F2 is d% with respect to the mass of the electrolyte, d satisfies 0.01≦d≦0.5. When the mass content of LiPO2F2 is in the above range, LiPO2F2 can be sufficiently dissolved in the electrolyte, which can significantly improve the high-temperature characteristics of the electrochemical device, ensure the formation of an SEI film with a moderate impedance, and reduce polarization. In some embodiments, d can be, but is not limited to, 0.01, 0.1, 0.2, 0.3, 0.4, or 0.5, or a range between any two of the above values.

[0045] In some embodiments, the mass content d% of LiPO2F2 and the content x% of the metal element A in the positive electrode active material satisfy 0.05≦d / x≦25. When d / x is in the above range, LiPO2F2 has better solubility in the electrolyte, forms a SEI film with low impedance in the negative electrode, and the metal element in the positive electrode active material makes the structure of the positive electrode active material more stable, promotes the release of active ions such as lithium ions in the positive electrode active material, and achieves simultaneous improvement of the cycle stability of the positive electrode and the negative electrode, thereby further improving the high temperature cycle characteristic and high temperature interval cycle characteristic of the electrochemical device. In some embodiments, d / x can be, but is not limited to, 0.05, 0.1, 0.5, 1, 3, 5, 7, 9, 12, 15, 20, or 25, or a range between any two of the above values.

[0046] In some embodiments, the mass content d% of LiPO2F2 and the mixing ratio k of ethylene carbonate and propylene carbonate in the electrolyte satisfy 0.001≦d / k≦0.4. When d / k is in the above range, the electrolyte has lower impedance and better high temperature resistance, and can form a SEI film with lower impedance at the interface of the negative electrode, thereby further improving the high temperature cycle characteristic and high temperature interval cycle characteristic of the electrochemical device. In some embodiments, d / k can be, but is not limited to, 0.001, 0.05, 0.1, 0.2, 0.3, or 0.4, or a range between any two of the above values.

[0047] A substance different from the composition of the positive electrode active material may be attached to the surface of the positive electrode active material. Examples of the surface-attached substance may include, but are not limited to, at least one of alumina, silica, titanium dioxide, zirconia, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; at least one of lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon. By attaching a substance to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, and the service life of the electrochemical device can be increased.

[0048] In the present invention, a positive electrode active material having a substance with a different composition attached to its surface is also referred to as a "positive electrode active material".

[0049] In some embodiments, the shapes of the positive electrode active material particles include, but are not limited to, block-like, polyhedral, spherical, ellipsoidal, plate-like, needle-like, and columnar shapes. In some embodiments, the positive electrode active material particles include primary particles, secondary particles, or a combination thereof. In some embodiments, the primary particles may aggregate to form secondary particles.

[0050] In some embodiments, the binder in the positive electrode active material layer includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, polyvinylidene fluoride, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethyleneoxy-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic acid (ester)-modified styrene butadiene rubber, epoxy resin, or nylon.

[0051] In some embodiments, the conductive agent in the positive electrode active material layer includes, but is not limited to, a carbon-based material, a metal-based 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, and any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, and silver. In some embodiments, the conductive polymer includes a polyphenylene derivative.

[0052] In the present invention, the type of the positive electrode current collector is not particularly limited, and may be any known material that is suitable for use as a positive electrode current collector. Examples of the positive electrode current collector may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating layer, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum. In order to reduce the electronic contact resistance between the positive electrode current collector and the positive electrode active material layer, the surface of the positive electrode current collector may include a conductive assistant. Examples of the conductive assistant may include, but are not limited to, carbon and precious metals such as gold, platinum, and silver.

[0053] The positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material, a binder, or a conductive agent on a current collector. The positive electrode using the positive electrode active material can be produced by a normal method. That is, the positive electrode active material, the binder, and, if necessary, a conductive agent and a thickener are dry-mixed to form a sheet, and the obtained sheet is pressed onto a positive electrode current collector; or, these materials are dissolved or dispersed in a liquid medium to form a slurry, and the slurry is applied to a positive electrode current collector and dried to form a positive electrode active material layer on the current collector. This allows the positive electrode to be obtained. In some embodiments, the liquid medium may include, but is not limited to, N-methylpyrrolidone.

[0054] In some embodiments, the electrolyte further comprises any non-aqueous solvent that can be used as a solvent for an electrolyte known in the prior art.

[0055] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, cyclic ethers, chain ethers, and aromatic fluorine-containing solvents.

[0056] In some embodiments, examples of cyclic carbonates may include, but are not limited to, butylene carbonate.

[0057] In some embodiments, examples of linear carbonate esters may include, but are not limited to, one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate.

[0058] In some embodiments, examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of γ-butyrolactone and γ-valerolactone. In some embodiments, a portion of the hydrogen atoms of the cyclic carboxylic acid ester may be replaced with fluorine.

[0059] In some embodiments, examples of the chain carboxylic acid ester may include, but are not limited to, one or more of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. In some embodiments, some of the hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, examples of the fluorine-substituted chain carboxylic acid ester may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate.

[0060] In some embodiments, examples of cyclic ethers may include, but are not limited to, one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0061] In some embodiments, examples of linear ethers may include, but are not limited to, one or more of dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane, and the like.

[0062] In some embodiments, aromatic fluorine-containing solvents include, but are not limited to, one or more of fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0063] In some embodiments, the electrolyte is not particularly limited, and any electrolyte known in the art can be used.Examples of electrolytes include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, and LiWF7; lithium tungstates such as LiWOF5; lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, and CF3CF2CF2CF2CO2Li; FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, and CF3CF2SO3 Lithium sulfonates such as Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li; lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN(CF3SO2)(C4F9SO2); LiC(FSO2)3, LiC(CF3SO2)3, Li Methylated lithium salts such as C(C2F5SO2)3; lithium (malonato)borate salts such as lithium bis(malonato)borate and lithium difluoro(malonato)borate; lithium (malonato)phosphate salts such as lithium tris(malonato)phosphate, lithium difluorobis(malonato)phosphate, and lithium tetrafluoro(malonato)phosphate; and LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, L Fluorine-containing organic lithium salts such as iBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2; lithium oxalato borates such as lithium difluoro(oxalato)borate, lithium bis(oxalato)borate; lithium oxalatophosphate salts such as lithium tetrafluoro(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, lithium tris(oxalato)phosphate, and the like, but are not limited to these.

[0064] In some embodiments, the electrolyte includes at least one of LiPF6, LiBF4, LiSbF6, F3SO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), and LiN(CF3SO2)2. In the present invention, the content of the electrolyte is not particularly limited as long as it does not impair the effects of the present invention. In some embodiments, the mass content of the electrolyte is 10% to 15% with respect to the mass of the electrolyte. When the mass content of the electrolyte is in the above range, the viscosity of the electrolyte can be set to an appropriate range, making it easier to ensure good electrical conductivity.

[0065] In the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material. The negative electrode active material layer may be a single layer or multiple layers, and each layer of the multiple layers of the negative electrode active material may include the same or different negative electrode active materials. The negative electrode active material is any material that can reversibly absorb and release active ions such as lithium ions. Examples of the negative electrode active material include lithium metal, structured lithium metal, natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and lithiated TiO2-Li4Ti5O with a spinel structure. 12 , or Li-Al, but are not limited to these.

[0066] In the present invention, the type of the negative electrode current collector is not particularly limited, and any known current collector can be used. Examples of the negative electrode current collector include, but are not limited to, aluminum foil, copper foil, nickel foil, stainless steel foil, or nickel-plated steel foil. In some embodiments, the negative electrode current collector is copper foil.

[0067] The negative electrode active material layer may further include a negative electrode binder, a conductive agent, or a thickener. The negative electrode binder can improve the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. The type of the negative electrode binder is not particularly limited, and may be a material that is stable against the electrolyte or the solvent used in the manufacture of the electrode. In some embodiments, the negative electrode binder includes, but is not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic acid (ester)-modified styrene butadiene rubber, epoxy resin, or nylon.

[0068] In some embodiments, the conductive agent includes, but is not limited to, at least one of a carbon-based material, a metal-based material, and a conductive polymer. In some embodiments, the carbon-based material includes at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber. In some embodiments, the metal-based material includes at least one of metal powder, metal fiber, copper, nickel, aluminum, and silver. In some embodiments, the conductive polymer includes a polyphenylene derivative. In some embodiments, the thickener includes sodium carboxymethyl cellulose.

[0069] The negative electrode can be prepared by a preparation method known in the art. For example, a negative electrode active material layer slurry containing a negative electrode active material, a binder, or a conductive agent is applied to a negative electrode current collector, and the slurry is applied to both sides of the negative electrode current collector to form a negative electrode active material layer, thereby obtaining a negative electrode. In some embodiments, the solvent may include, but is not limited to, water.

[0070] In some embodiments, the electrochemical device of the present invention has a separator between the positive electrode and the negative electrode to prevent short circuit. In the present invention, the material and shape of the separator are not particularly limited, and may be any technology disclosed in the prior art as long as it does not impair the effects of the present invention.

[0071] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer includes a porous sheet having excellent liquid retention, or a material in the form of a nonwoven fabric. Examples of the resin or glass fiber separator material may include, but are not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, and the like. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above separator materials may be used alone or in any combination. The substrate layer may be a material formed by laminating the above materials, and examples include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in this order.

[0072] A surface treatment layer is provided on at least one surface of the base layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer made of a mixture of a polymer and an inorganic material. Examples of inorganic materials may include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The form of the inorganic material may include, but is not limited to, a particulate or fibrous form. The polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylic ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0073] The electrochemical device assembly includes an electrode group, a current collecting structure, a case, and a protective element.

[0074] The electrode group may have either a laminated structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, or a structure in which a positive electrode and a negative electrode are wound with a separator interposed therebetween.

[0075] The current collecting structure is a structure that reduces the resistance of the wiring portion and the joint portion. When the electrode group has the above-mentioned laminated structure, a structure formed by bundling the metal core parts of each electrode layer and welding them to a terminal is preferably used. When the electrode group has the above-mentioned wound structure, the internal resistance can be reduced by providing two or more lead structures to each of the positive electrode and the negative electrode and bundling them to a terminal.

[0076] The material of the case is not particularly limited, and may be any material that is stable against the electrolyte used. The case may be made of, but is not limited to, nickel-plated steel, stainless steel, aluminum or aluminum alloy, magnesium alloy, or other metals, or a laminated film of resin and aluminum foil. In some embodiments, the exterior case is made of aluminum or aluminum alloy metal, or a laminated film. The shape of the case is also arbitrary, and may be, for example, any one of a cylindrical shape, a rectangular shape, a laminated type, and a button type.

[0077] The protective element may be a positive temperature coefficient element whose resistance increases when abnormal heat is generated or an excessive current flows, a thermal fuse, a thermistor, a current cutoff valve, etc. The above-mentioned protective element may be selected so that it does not function during normal use at a high current, but it may also be designed in such a way that abnormal heat generation or thermal runaway does not occur even if the protective element is not present.

[0078] The electrochemical device of the present invention includes any device in which an electrochemical reaction occurs, including, but not limited to, a lithium ion battery. In some embodiments, the electrochemical device of the present invention comprises a positive electrode including a positive electrode active material capable of absorbing and releasing active ions, as in any of the above embodiments, a negative electrode including a negative electrode active material capable of absorbing and releasing active ions, and an electrolyte solution as in any of the above embodiments.

[0079] The present invention further provides an electronic device comprising an electrochemical device according to the present invention.

[0080] The application of the electrochemical device of the present invention is not particularly limited, and can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of the present invention can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, mobile phones, portable facsimiles, portable copy machines, portable printers, stereo headsets, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power sources, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting equipment, toys, game machines, watches, power tools, strobes, cameras, large-scale household storage batteries, and lithium ion capacitors.

[0081] Hereinafter, the present invention will be further described with reference to specific examples, taking a lithium ion battery as an example, and those skilled in the art should understand that the preparation methods described in the present invention are only illustrative, and any other suitable preparation methods are within the scope of the present invention.

[0082] 1. Preparation of lithium-ion batteries 1. Preparation of the negative electrode Artificial graphite as the negative electrode active material, styrene butadiene rubber (SBR) as the binder, and sodium carboxymethyl cellulose (CMC) as the thickener were thoroughly mixed with an appropriate amount of deionized water in a weight ratio of 97.4:1.2:1.4 to form a uniform negative electrode slurry. This slurry was applied to copper foil as the negative electrode current collector, dried, and cold pressed to obtain the negative electrode.

[0083] 2. Preparation of the positive electrode Lithium cobalt oxide or lithium nickel cobalt manganese oxide doped with Mg, Zr, or Al, acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were thoroughly mixed in a weight ratio of 96:2:2 with an appropriate amount of N-methylpyrrolidone (NMP) solvent to form a homogeneous positive electrode slurry. This slurry was applied to an aluminum foil as a positive electrode current collector, dried, and cold pressed to obtain a positive electrode.

[0084] 3. Preparation of electrolyte In a glove box with an argon gas atmosphere having a water content of <10 ppm, a certain mass of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly, and LiPF6, a lithium salt that had been thoroughly dried, was dissolved in the non-aqueous solvent to form a base electrolyte. A certain mass of additives (e.g., nitrile compound additives SN and LiPO2F2) were added to the obtained base electrolyte, and the mixture was mixed uniformly to obtain an electrolyte. Here, the mass content of LiPF6 was 12.5% ​​relative to the mass of the electrolyte, the mass contents of EC, PC, SN, and LiPO2F2 are shown in the table of examples, and the remainder was the mass content of DEC in the electrolyte.

[0085] 4. Preparation of the separator A polyethylene (PE) porous polymer film was used as the separator.

[0086] 5. Preparation of Lithium-ion Battery The positive electrode, the separator, and the negative electrode were stacked in order so that the separator was interposed between the positive electrode and the negative electrode to play a role of isolation, and then wound to obtain a cell. The cell was placed in an exterior foil, and the above-prepared electrolyte was injected into the dried cell, followed by vacuum sealing, standing, formation, shaping, and other processes to complete the preparation of a lithium-ion battery. The lithium ion batteries of the Examples and Comparative Examples were prepared by the above-mentioned preparation method, and the following measurements were performed on the lithium ion batteries, the positive electrode active material, and the electrolyte.

[0087] 2.Measurement method 1. High temperature cycle measurement The battery was placed in a thermostatic chamber at 45°C, charged to 4.4V at a constant current of 1.5C, charged to 4.4V at a constant voltage of 0.05C, and discharged to 3.0V at a constant current of 1.0C. This constituted one charge-discharge cycle, and the initial discharge capacity was recorded as C1. After 500 charge-discharge cycles as described above, the discharge capacity after the 500th cycle was recorded as C 500 The cycle capacity retention rate of the lithium-ion battery at 45°C was calculated using the following formula:

[0088]

number

[0089] 2. High temperature interval cycle measurement The battery was placed in a 45°C incubator, charged to 4.4V at a constant current of 0.5C, charged at 4.4V at a constant voltage of 0.05C, maintained for 19.5 hours, and discharged to 3.0V at a constant current of 0.5C. This constituted one charge-discharge cycle, with the initial discharge capacity being A1 and the thickness of the battery in the fully charged state during the first cycle being T1. The charge-discharge cycle was repeated 23 times as described above. After that, the battery was charged to 4.35V at a constant current of 0.5C, charged at 4.35V at a constant voltage of 0.05C, maintained for 19.5 hours, and discharged to 3.0V at a constant current of 0.5C. This constituted one charge-discharge cycle, with the charge-discharge cycle being repeated 113 times as described above. The discharge capacity after the discharge of the last cycle was A1. 136and the thickness of the battery in the fully charged state during the last cycle is T 136 The interval cycle capacity retention rate and thickness increase rate of the lithium ion battery at 45°C were calculated using the following formulas.

[0090]

number

[0091]

number

[0092] 3. Measurement of the median diameter Dv50 of positive electrode active material particles The particle size of the positive electrode active material particles was measured using a Malvern particle size analyzer. The positive electrode material was dispersed in ethanol, which is a dispersant, and ultrasonic waves were applied for 30 minutes. The sample was then placed in the Malvern particle size analyzer and measurements were started. In the volume-based particle size distribution of the positive electrode material, the particle size at which the cumulative volume is 50% from the small diameter side was taken as Dv50 of the positive electrode material.

[0093] 4. Measurement of the content of Mg, Zr, or Al in the positive electrode active material After discharging the lithium ion battery, it was disassembled, and two positions (denoted as positions 1 and 2) of the positive electrode active material layer were randomly selected and measurements were performed as follows. 1) The positive electrode active material in the positive electrode active material layer at position 1 was obtained, and an inductively coupled plasma (ICP) measurement was performed to obtain the content of Mg, Zr, or Al element in the positive electrode active material. 2) Energy dispersive X-ray analysis (EDS) was performed on the positive electrode active material layer at position 2. The measurement area was enlarged 3000 times and EDS measurement was performed on the entire area to obtain the content of Mg, Zr, or Al element in the positive electrode active material. The maximum value of the above two measurement results was taken as the content of Mg, Zr, or Al element in the positive electrode active material.

[0094] 5. Measurement of the content of each component in the electrolyte After discharging the lithium-ion battery, it was disassembled and centrifuged. The liquid obtained after centrifugation was subjected to gas chromatography-mass spectrometry (GC-MS) and ion chromatography (IC) measurements to measure the components and their contents in the electrolyte.

[0095] 3. Measurement results Table 1 shows the effects of the positive electrode active material and the electrolyte on the high temperature cycle characteristics and high temperature interval cycle characteristics of a lithium ion battery. The median diameter Dv50 of the positive electrode active material in the examples in Table 1 is all 15 μm. The positive electrode active materials in Examples 1-2 to 1-7 are lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O2), where the ratio of the mass of lithium cobalt oxide to the mass of lithium nickel cobalt manganese oxide is 3. The positive electrode active material in other examples and Comparative Examples 1-1 to 1-10 is lithium cobalt oxide (LiCoO2).

[0096] As can be seen from the data in Table 1, compared to the comparative examples, when the electrolyte in the examples simultaneously contains EC, PC, and SN, and the contents thereof satisfy 1.25≦k≦6 and a / k≧0.2, and the positive electrode active materials in the examples are all doped with Mg, Zr, or Al elements, and the contents thereof satisfy 0.01≦x≦1, the electrochemical device in the examples has a high capacity retention rate in both the cycle process and the interval cycle process at 45°C, and a low thickness increase rate in the interval cycle process at 45°C.

[0097] In addition, as can be seen from the comparison of Comparative Examples 1-6 and 1-7 with Example 1-1, better high-temperature properties can be obtained by adding SN to the electrolyte. In addition, as can be seen from the comparison of Comparative Examples 1-8 and 1-9 with Examples, better high-temperature properties can be obtained when the contents of EC, PC, and SN in the electrolyte simultaneously satisfy 1.25≦k≦6 and a / k≧0.2.

[0098] As can be seen from the comparison between Comparative Example 1-10 and Example 1, better high-temperature characteristics can be obtained by doping the positive electrode active material with Mg than by doping the positive electrode active material with other metal elements (e.g., Zn). Note that, as can be seen from Examples 1-24 and 1-25, an electrochemical device having similarly excellent high-temperature characteristics can be obtained by doping the positive electrode active material with Al or Zr.

[0099] In addition, as can be seen from the comparison of Examples 1-30 and 1-31 with Example 1-11, when the electrochemical device further satisfies 0.001≦x / a≦1, the high temperature cycle characteristic and the high temperature interval cycle characteristic of the electrochemical device can be further improved. As can be seen from the comparison of Example 1-32 with Examples 1-22, 1-26, and 1-27, when the electrochemical device further satisfies x / k≦0.4, the high temperature cycle characteristic and the high temperature interval cycle characteristic of the electrochemical device can be further improved.

[0100] [Table 1-1] [Table 1-2] [Table 1-3] Tables 2 and 3 show the effect of the median diameter Dv50 of the positive electrode active material on the high temperature cycle characteristics and high temperature interval cycle characteristics of a lithium ion battery. Here, the examples in Tables 2 and 3 are all improvements based on Examples 1-10, and are distinguished from Examples 1-10 only by the parameters shown in Tables 2 and 3.

[0101] [Table 2] As can be seen from Table 2 above, when the electrochemical device further satisfies 2≦y≦25 and 10≦y / x≦900, the high temperature cycle characteristic and high temperature interval cycle characteristic of the electrochemical device can be further improved.

[0102] [Table 3] As can be seen from Table 3 above, when the electrochemical device further satisfies 1≦y / a≦36, the high temperature cycle characteristic and high temperature interval cycle characteristic of the electrochemical device can be further improved. Examples 4-1 to 4-7 in Tables 4 and 5 are improvements based on Example 1-10, Examples 4-8 and 4-9 in Table 4 are improvements based on Example 1-22, and Examples 5-1 and 5-2 in Table 5 are improvements based on Example 1-1. The specific improvement is to add a certain amount of LiPO2F2 to the electrolyte.

[0103] [Table 4] As can be seen from the comparison between Examples 4-1 to 4-7 and Examples 1-10, after LiPO2F2 is further added to the electrolyte, the high temperature cycle characteristics and high temperature interval cycle characteristics of the obtained electrochemical device are both improved. Also, as can be seen from Table 4, when the content d% of LiPO2F2 satisfies 0.01≦d≦0.5 and 0.05≦d / x≦25, the improvement effect on the electrochemical device is more significant.

[0104] [Table 5] As can be seen from the data in Table 5, when the electrochemical device further satisfies 0.001≦d / k≦0.4, the high temperature cycle characteristic and high temperature interval cycle characteristic of the electrochemical device can be further improved.

[0105] Throughout the specification, references to "an embodiment," "some of the embodiments," "one embodiment," "another example," "example," "embodiment," or "some of the examples" mean that at least one embodiment or example of the invention includes the particular feature, structure, material, or characteristic described in that embodiment or example. Thus, the appearances of, for example, "in some embodiments," "in an embodiment," "in another example," "in one example," "in a particular example," or "example" in various places throughout the specification do not necessarily refer to the same embodiment or example of the invention. Furthermore, particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

[0106] Although exemplary embodiments have been described and illustrated, 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. 1. An electrochemical device comprising: A positive electrode and an electrolyte solution, the electrolyte comprises ethylene carbonate, propylene carbonate, and succinonitrile; The positive electrode includes a positive electrode active material, The positive electrode active material contains a metal element A, The metal element A includes at least one of Mg, Zr, and Al, When the mass content of the succinonitrile is a%, the mass content of the ethylene carbonate is b%, the mass content of the propylene carbonate is c%, and k is k=b / c, a and k satisfy 1.25≦k≦6 and a / k≧0.2, and an electrochemical device, wherein, when the mass content of the metal element A is x % with respect to the mass of the positive electrode active material, x satisfies 0.01≦x≦1;

2. The electrochemical device according to claim 1 , wherein x and k satisfy x / k≦0.

4.

3. The electrochemical device according to claim 1 , wherein x and a satisfy 0.001≦x / a≦1.

4. 10. The electrochemical device of claim 1 , wherein the positive electrode active material comprises lithium cobalt oxide.

5. 10. The electrochemical device of claim 1, wherein the positive electrode active material comprises lithium nickel cobalt manganese oxide.

6. The positive electrode active material includes lithium cobalt oxide and lithium nickel cobalt manganese oxide, 2. The electrochemical device according to claim 1, wherein, when a ratio of a mass of the lithium cobalt oxide to a mass of the lithium nickel cobalt manganese oxide is g with respect to a mass of the positive electrode active material, g satisfies 1≦g≦9.

7. 2. The electrochemical device according to claim 1, wherein when the median diameter Dv50 of the positive electrode active material is y μm, y satisfies 2≦y≦25.

8. The electrochemical device according to claim 7 , wherein x and y satisfy 10≦y / x≦900.

9. The electrochemical device according to claim 7 , wherein y and a satisfy 1≦y / a≦36.

10. The electrolyte further comprises lithium difluorophosphate, 2. The electrochemical device according to claim 1, wherein when a mass content of the lithium difluorophosphate is d % with respect to a mass of the electrolyte, d satisfies 0.01≦d≦0.

5.

11. The electrochemical device according to claim 10 , wherein x and d satisfy 0.05≦d / x≦25.

12. The electrochemical device according to claim 10 , wherein k and d satisfy 0.001≦d / k≦0.

4.

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

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