Electrochemical device and electronic device

Abstract

An electrochemical device having both excellent high-temperature cycle characteristics and low-temperature discharge characteristics is provided. In one aspect of the present invention, there is provided an electrochemical device including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, and the volume of the positive electrode active material layer is V1 cm. 3 and the true volume of the positive electrode active material is V2 cm 3 and V1 and V2 satisfy the relationship 0.8≦V2 / V1≦0.92.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry, and particularly to an electrochemical device and an electronic device.

Background Art

[0002] Electrochemical devices (e.g., lithium-ion batteries) are widely applied in various fields. With the development of society, the requirements for the energy density of electrochemical devices are increasing.

[0003] In some technologies, attempts are made to improve the energy density of electrochemical devices by increasing the voltage to release more energy. However, in a high-voltage system, there are a series of new technical problems for electrochemical devices. Taking a lithium-ion battery with lithium cobaltate as the cathode material as an example, on the one hand, if the low-temperature discharge characteristics of the lithium-ion battery are excellent, the high-temperature cycle characteristics will decrease, and if the high-temperature cycle characteristics are improved, the low-temperature discharge characteristics will decrease. Therefore, it is difficult to balance the high-temperature cycle characteristics and the low-temperature discharge characteristics. On the other hand, in a high-voltage system, the surface of lithium cobaltate shows strong oxidizing power and is easy to react with the electrolyte, so the interfacial relationship between the cathode active material and the electrolyte deteriorates. However, when trying to solve the above interfacial relationship problem, it is necessary not only to balance the discharge characteristics at low temperatures but also to ensure the cycle characteristics at high temperatures. Therefore, it is not easy to solve the problem.

[0004] In some related technologies, attempts are made to solve the above problems by coating and modifying the surface of the cathode active material with a metal oxide or other materials. However, the coating material has a certain obstructive effect on the transport of lithium ions, resulting in an increase in the direct current resistance (DCR), a decrease in the rate performance, and a deterioration of the high-temperature and low-temperature discharge characteristics of the lithium-ion battery.

[0005] Therefore, providing an electrochemical device with excellent high-temperature cycle characteristics and low-temperature discharge characteristics is a technical problem that needs to be urgently solved in this field.

Summary of the Invention

[0006] The present invention provides an electrochemical device and an electronic device that can improve the energy density, reduce the reaction between the surface of the positive electrode active material and the electrolytic solution, and improve the cycle characteristics and low-temperature discharge characteristics of the electrochemical device under high voltage and high temperature.

[0007] In some embodiments, the present invention provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolytic solution. The positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the volume of the positive electrode active material layer is V1 cm 3 and the true volume of the positive electrode active material is V2 cm 3 wherein V1 and V2 satisfy 0.8 ≤ V2 / V1 ≤ 0.92.

[0008] In some embodiments, the electrolytic solution further includes at least one of a nitrile-based compound or a carboxylic acid ester compound. The nitrile-based compound accounts for m of the total mass of the electrolytic solution, and m satisfies 0.5% ≤ m ≤ 10%. The carboxylic acid ester compound accounts for n of the total mass of the electrolytic solution, and n satisfies 12% ≤ n ≤ 40%.

[0009] In some embodiments, m, V1, and V2 satisfy 0.006 ≤ m / (V2 / V1) ≤ 0.095.

[0010] In some embodiments, n, V1, and V2 satisfy 0.16 ≤ n / (V2 / V1) ≤ 0.5.

[0011] In some embodiments, the nitrile compound includes at least one of 1,3,6 - hexanetricarbonitrile, succinonitrile, adiponitrile, suberonitrile, glutaronitrile, sebaconitrile, ethylene glycol bis(propionitrile) ether, 1,3,5 - pentanetricarbonitrile, p - methylbenzonitrile, 2,2 - difluorosuccinonitrile, tricyanobenzene, trans - butenedinitrile or trans - hexenedinitrile, and / or The carboxylic acid ester compound includes at least one of ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate or propyl butyrate.

[0012] In some embodiments, the positive electrode active material is Li x M1 y M2 z O2, where x, y, z respectively satisfy 0.95 ≤ x ≤ 1.03, 0.9 ≤ y ≤ 1.05, 0.002 ≤ z ≤ 0.012, M1 includes at least one of Ni, Co or Mn, M2 includes at least one of Al, Mg, Ti, Zr, La, Y, Sc or Ca.

[0013] In some embodiments, the mass content of M2 in the positive electrode active material is 0.1% - 1.5%.

[0014] In some embodiments, the retention coefficient of the electrolyte in the electrochemical device is k mAh / g, and k satisfies 0.001 ≤ k ≤ 0.0022.

[0015] In some embodiments, the positive electrode satisfies at least one of the following (a) - (c). (a) The particle size Dv50 of the particles of the positive electrode active material is 5.0 μm - 20 μm, (b) The BET specific surface area of the positive electrode active material is 0.07 m 2 / g - 0.4 m 2 / g, (c) The compaction density of the positive electrode active material layer is 4.0 g / cm 3 or more.

[0016] In some embodiments, the positive electrode active material includes first particles and second particles, and the particle size of the first particles is larger than that of the second particles.

[0017] Some embodiments of the present invention provide an electronic device including any of the above electrochemical devices.

[0018] The electrochemical device provided in an embodiment of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution. The positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the volume of the positive electrode active material layer is V1 cm 3 and the true volume of the positive electrode active material is V2 cm 3 where V1 and V2 satisfy 0.8 ≦ V2 / V1 ≦ 0.92. In some embodiments of the present invention, since the positive electrode active material layer has higher deposition efficiency and density, when the volume is constant, more energy can be stored, and the space for the electrolytic solution to penetrate into the positive electrode active material can be reduced. Thereby, the reaction between the positive electrode material and the electrolytic solution under high voltage and high temperature can be reduced, and the cycle characteristics and low-temperature discharge characteristics of the electrochemical device under high voltage and high temperature can be improved.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in more detail. The present invention can be achieved in various aspects and should not be construed as being limited to the embodiments described herein. These embodiments are provided to enable a more detailed and complete understanding of the present invention.

[0020] Electrochemical devices such as lithium-ion batteries are widely applied in various fields. In related technologies, the capacity of lithium-ion batteries is improved by increasing the voltage. However, in high-voltage systems, there are many problems. On the one hand, it is difficult to achieve both low-temperature discharge characteristics and high-temperature cycle characteristics. On the other hand, at high voltages, the surface of the positive electrode active material shows relatively strong oxidizing properties, and the electrolyte is easily oxidized.

[0021] To solve at least some of the above problems, in some embodiments of the present invention, an electrochemical device is provided. The electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the volume of the positive electrode active material layer is V1 cm 3 wherein the true volume of the positive electrode active material is V2 cm 3 and V1 and V2 satisfy 0.8 ≦ V2 / V1 ≦ 0.92.

[0022] In some embodiments, the true volume V2 of the positive electrode active material refers to the volume occupied by the positive electrode active material in the positive electrode active material layer. 0.8 ≦ V2 / V1 ≦ 0.92 indicates that the proportion of the positive electrode active material in the positive electrode active material layer is high. The higher the proportion of the positive electrode active material, the higher the deposition efficiency and density of the positive electrode active material layer, and more energy can be stored within the same volume range, and the space of the positive electrode active material can be effectively utilized. Since the proportion of the positive electrode active material is high, the porosity of the positive electrode active material layer is low, and the space for the electrolyte to penetrate into the positive electrode active material is small, which reduces the reaction between the positive electrode active material and the electrolyte at high voltages (for example, 4.45 V or higher) and high temperatures, and is advantageous for improving the cycle characteristics at high voltages and high temperatures. And, since the contact area between the positive electrode active materials is large and the transport path is short, it is advantageous for improving the low-temperature discharge characteristics of the electrochemical device. The volume of the positive electrode active material layer is V1 cm 3The ratio V2 / V1 of the true volume V2 of the positive electrode active material can be controlled by a method such as controlling the roll press pressure, roll press time, or roll press number in the preparation of the positive electrode. In the present invention, the control method is not particularly limited as long as 0.8 ≤ V2 / V1 ≤ 0.92 can be achieved.

[0023] In some embodiments, the electrolytic solution further contains at least one of a nitrile compound or a carboxylic acid ester compound. The nitrile compound occupies m of the total mass of the electrolytic solution, where m satisfies 0.5% ≤ m ≤ 10%, and the carboxylic acid ester compound occupies n of the total mass of the electrolytic solution, where n satisfies 12% ≤ n ≤ 40%. In some embodiments, the nitrile compound can form a protective film on the surface of the positive electrode active material, thereby protecting the surface of the positive electrode active material, improving the cycle characteristics of the positive electrode active material, and preventing the occurrence of redox reactions between the positive electrode active material and the solvent. In some embodiments, the carboxylic acid ester compound can improve the transport efficiency of lithium ions in the electrolytic solution, so that the electrochemical device has excellent low-temperature characteristics while maintaining excellent high-temperature cycle characteristics.

[0024] In some embodiments, m, V1, and V2 satisfy 0.006 ≤ m / (V2 / V1) ≤ 0.095. In some embodiments, m / (V2 / V1) represents the mass distribution coefficient of a certain addition amount of the nitrile compound. If m / (V2 / V1) is less than 0.006, the added nitrile compound is too little to sufficiently protect the surface of the positive electrode active material, so the high-temperature cycle characteristics deteriorate. If m / (V2 / V1) exceeds 0.095, the nitrile compound may reduce the conductivity of the electrolytic solution, thereby affecting the low-temperature discharge characteristics of the electrochemical device.

[0025] In some embodiments, n, V1, and V2 satisfy 0.16 ≦ n / (V2 / V1) ≦ 0.5. n / (V2 / V1) represents the distribution coefficient of the mass of the carboxylic acid ester compound. When n / (V2 / V1) is less than 0.16, the effect of the carboxylic acid ester compound on improving the transport efficiency of lithium ions in the electrolyte is not significant, so the low-temperature discharge characteristics deteriorate. When n / (V2 / V1) exceeds 0.5, the carboxylic acid ester compound may destroy the SEI (solid electrolyte interphase) film on the surface of the positive electrode active material, increasing side reactions and being disadvantageous to the high-temperature cycle characteristics.

[0026] In some embodiments, the nitrile compound contains at least one of 1,3,6 - hexanetricarbonitrile (HTCN), succinonitrile (SN), adiponitrile (ADN), suberonitrile, glutaronitrile, sebaconitrile, ethylene glycol bis(propionitrile) ether (DENE), 1,3,5 - pentanetricarbonitrile, p - methylbenzonitrile, 2,2 - difluorosuccinonitrile, tricyanobenzene, trans - butenedinitrile, or trans - hexenedinitrile.

[0027] In some embodiments, the carboxylic acid ester compound contains at least one of ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, or propyl butyrate.

[0028] In some embodiments, the positive electrode active material is Li x M1 y M2 zIt contains O2, where x, y, and z satisfy 0.90 ≦ x ≦ 1.03, 0.9 ≦ y ≦ 1.05, and 0.002 ≦ z ≦ 0.012 respectively. M1 contains at least one of Ni, Co, or Mn, and M2 contains at least one of Al, Mg, Ti, Zr, La, Y, Sc, or Ca. In some embodiments, the electrochemical device releases a relatively large amount of lithium ions from the cathode active material at high voltage, which is likely to cause the collapse of the lattice of the cathode active material. Therefore, by doping a certain amount of M2 into the cathode active material, the lattice distortion caused by the release of lithium ions can be reduced, the lattice structure can be further stabilized, and it is advantageous for stabilizing the discharge characteristics and cycle characteristics of the electrochemical device at high voltage.

[0029] In some embodiments, the mass content of M2 in the cathode active material is 0.1% - 1.5%. In some embodiments, if the mass fraction of M2 in the cathode active material is less than 0.1%, the content of M2 is relatively low, and there may be no significant improvement effect. If the mass content of M2 in the cathode active material exceeds 1.5%, the capacity of the cathode active material may decrease, and the high-temperature and low-temperature characteristics of the cathode active material may decrease.

[0030] In some embodiments, the retention coefficient of the electrolyte in the electrochemical device is k mAh / g, and k satisfies 0.001 ≦ k ≦ 0.0022. In some embodiments, k being in this range indicates that the amount of electrolyte can sufficiently wet the electrochemical device and there is relatively little waste.

[0031] In some embodiments, the particle size Dv50 of the particles of the cathode active material is 5.0 μm - 20 μm. In some embodiments, if the particle size Dv50 of the particles of the cathode active material is less than 5.0 μm, the cycle characteristics may decrease. If the particle size Dv50 of the particles of the cathode active material exceeds 20 μm, the rate characteristics may decrease.

[0032] In some embodiments, the BET specific surface area of the cathode active material is 0.07 m 2 / g - 0.4 m 2 / g. In some embodiments, if the specific surface area of the positive electrode active material is less than 0.07 m 2 / g, the rate performance may deteriorate. If the specific surface area of the positive electrode active material exceeds 0.4 m 2 / g, the consumption of the electrolyte may be accelerated.

[0033] In some embodiments, the compression density of the positive electrode active material layer is 4.0 g / cm 3 or more. In some embodiments, if the compression density of the positive electrode active material layer is less than 4.0 g / cm 3 , the volume energy density may be too low. In some embodiments, the compression density of the positive electrode active material layer is 4.5 g / cm 3 or less. In some embodiments, if the compression density of the positive electrode active material layer exceeds 4.5 g / cm 3 , the positive electrode current collector may be broken.

[0034] In some embodiments, the positive electrode active material includes first particles and second particles, and the particle size of the first particles is larger than that of the second particles. In some embodiments, by mixing the first particles and the second particles having different particle sizes, it is advantageous to reduce the voids in the positive electrode active material layer and improve the volume energy density.

[0035] In some embodiments, 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. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material may include one or a mixture of more of soft carbon, hard carbon, natural graphite, artificial graphite, silicon, silicon oxide, silicon carbide, lithium titanate, and silicon oxygen composite that can occlude and release lithium ions.

[0036] In some embodiments, the positive electrode current collector may employ an Al foil, and of course, other positive electrode current collectors commonly used in the art may also be employed. In some embodiments, the thickness of the positive electrode current collector may be 1 μm to 20 μm. In some embodiments, the positive electrode active material layer may be coated only on a partial region of the positive electrode current collector. In some embodiments, the thickness of the positive electrode active material layer may be 10 μm to 200 μm. The thickness of the positive electrode active material layer is the thickness of the positive electrode active material layer on one surface of the positive electrode current collector. It should be understood that these are merely examples, and other appropriate thicknesses may also be employed.

[0037] In some embodiments, the separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have excellent effects in preventing short circuits and can improve the stability of the battery by the shutdown effect. In some embodiments, the thickness of the separator is in the range of about 5 μm to 100 μm.

[0038] In some embodiments, the separator is composed of a porous separation membrane made of polypropylene or polyethylene, or a porous membrane made of an inorganic material such as a ceramic non-woven fabric, and the separator may be composed of two or more porous membranes stacked in a laminated structure.

[0039] In some embodiments, the surface of the separator may further include a porous layer provided on at least one surface of the separator. The porous layer includes inorganic particles and a binder, and the inorganic particles are at least one selected from aluminum oxide (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium oxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the pores of the separator have a diameter in the range of about 0.01 μm to 1 μm. The binder of the porous layer is at least one selected from polyvinylidene fluoride, a copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The porous layer on the surface of the separator can enhance the heat resistance, antioxidant property, and electrolyte wettability of the separator, and strengthen the adhesiveness between the separator and the electrode tab.

[0040] In some embodiments of the present invention, the electrochemical device is of a wound type or a stacked type.

[0041] In some embodiments, the electrochemical device includes a lithium-ion battery, but the present invention is not limited thereto. In some embodiments, the electrochemical device may further include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution. The electrolytic solution includes a lithium salt and a non-aqueous solvent. The lithium salt is one or more selected from LiPF6, LiBF4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate. For example, LiPF6 is used as the lithium salt because it can provide high ionic conductivity and improve cycle characteristics.

[0042] The non-aqueous solvent may be a carbonic ester compound, an ether compound, another organic solvent, or a combination thereof. The carbonic ester compound may be a linear carbonic ester compound, a cyclic carbonic ester compound, a fluorocarbonic ester compound, or a combination thereof. Examples of the linear carbonic ester compound are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of the cyclic carbonic ester compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), or combinations thereof. Examples of the fluorocarbonic ester compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethyl ethylene carbonate, or combinations thereof.

[0043] Examples of ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or combinations thereof. Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.

[0044] Examples of the present invention further provide an electronic device including the above-described electrochemical device. The electronic device of the examples of the present invention is not particularly limited and can be applied to any electronic device known in the prior art. In some examples, the electronic device is a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disk, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, an auxiliary bicycle, a bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flash, a camera, a large household battery, and a lithium ion capacitor, etc., but is not limited thereto.

[0045] Hereinafter, in order to explain the present invention in more detail, some examples and comparative examples are given, where a lithium ion battery is taken as an example.

[0046] Preparation of the positive electrode: Lithium cobaltate, acetylene black, and polyvinylidene fluoride were uniformly mixed at a weight ratio of 95:3:2, and the mixture was dispersed in a solvent, stirred, and vacuumed to obtain a positive electrode slurry. Then, by the doctor blade method or the spray coating method, the slurry was uniformly coated on an aluminum foil which is a positive electrode current collector, and the thickness of the aluminum foil may be between 8 μm and 13 μm. Under the above conditions, as long as the positive electrode active material, binder, and conductive material are uniformly dispersed, they may be mixed with the solvent at any ratio. Then, by coating, drying, and compressing with a roller press, a positive electrode active material layer was obtained, and then it was divided into strips and tabs were welded to obtain a positive electrode (also referred to as a positive electrode sheet).

[0047] Preparation of negative electrode: Artificial graphite, sodium carboxymethyl cellulose, and styrene butadiene rubber were uniformly mixed at a weight ratio of 96:2:2 to prepare a negative electrode mixture, and the negative electrode mixture was dispersed in a solvent to form a slurry. The prepared slurry was uniformly coated on a negative electrode current collector, and the thickness of the current collector was between 4 μm and 9 μm. By the doctor blade method or the spray coating method, the slurry was uniformly coated on the current collector, and then dried and compressed with a roller press to obtain a negative electrode active material layer, and then it was divided into strips and tabs were welded to obtain a negative electrode (also referred to as a negative electrode sheet).

[0048] Preparation of electrolyte: In an argon atmosphere glove box with a water content < 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were uniformly mixed at a weight ratio of 1:1:1, LiPF6 was added, and uniformly stirred to form a base electrolyte. Here, the concentration of LiPF6 was 1.15 mol / L. 3% of fluoroethylene carbonate and 2% of 1,3 - propane sultone were added to the total weight of the electrolyte. The electrolyte was set according to the following examples and comparative examples.

[0049] Preparation of lithium - ion battery: The obtained positive electrode, negative electrode, and separator were wound in a specified winding method to form a cell, which was then placed in a packaging bag. Subsequently, the packaging bag was packaged, filled with electrolyte, and formed, and finally the preparation of the battery was completed.

[0050] Comparative Example 1: When the ratio V2 / V1 of the true volume V2 of the positive electrode active material to the volume V1 of the positive electrode active material layer in the positive electrode sheet was 0.75, the compression density was 3.75 g / cm 3 The positive electrode sheet, separator, and negative electrode sheet were wound to form a cell, and then filled with electrolyte. The retention coefficient of the electrolyte was 0.0014. The mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolyte was 0.04. The nitrile compounds were adiponitrile (ADN) and 1,3,6 - hexanetricarbonitrile (HTCN), and the mass ratio of the two was 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate was 0.25. The BET of the positive electrode active material was 0.32 m 2 / g, the Dv50 was 10 μm, and the Al content in the positive electrode active material was 0.6 wt%.

[0051] Comparative Example 2: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet was 0.75, the compression density was 3.75 g / cm 3 The positive electrode sheet, separator, and negative electrode sheet were wound to form a cell, and then filled with electrolyte. The retention coefficient of the electrolyte was 0.0014. The mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolyte was 0, the mass distribution coefficient n / (V2 / V1) of ethyl propionate was 0.25. The BET of the positive electrode active material was 0.32 m 2 / g, the Dv50 was 10 μm, and the Al content in the positive electrode active material was 0.6 wt%.

[0052] Comparative Example 3: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet was 0.75, the compression density was 3.75 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile (ADN) and 1,3,6 - hexanetricarbonitrile (HTCN), the mass ratio of the two is 2:1, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0053] Comparative Example 4: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.75, the compression density is 3.75 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0054] Example 1: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0055] Example 2: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 . Then, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and an electrolytic solution is poured in. The retention coefficient of the electrolytic solution is 0.0014. The mass partition coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.04. The nitrile compounds are adiponitrile (ADN) and 1,3,6 - hexanetricarbonitrile (HTCN), and the mass ratio of the two is 2:1. The mass partition coefficient n / (V2 / V1) of ethyl propionate is 0.25. The BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0056] Example 3: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.83, the compression density is 4.2 g / cm 3 . Then, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and an electrolytic solution is poured in. The retention coefficient of the electrolytic solution is 0.0014. The mass partition coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.04. The nitrile compounds are adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass partition coefficient n / (V2 / V1) of ethyl propionate is 0.25. The BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0057] Example 4: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.80, the compression density is 4.0 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0058] Example 5: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.89, the compression density is 4.5 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0059] Example 6: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the positive electrode sheet, the separator, and the negative electrode sheet are wound into a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the electrolytic solution does not contain carboxylic acid ester, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The BET of the positive electrode active material is 0.5 m 2It is / g, Dv50 is 5 μm, and the content of Al contained in the positive electrode active material was 0.6 wt%.

[0060] Example 7: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 86%, the compression density is 4.3 g / cm 3 Then, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014. The mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.005. The nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 2.5. The BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material was 0.6 wt%.

[0061] Example 8: When the ratio V2 / V1 of the true volume of the active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014. The mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.003. The nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 2.5. The BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material was 0.6 wt%.

[0062] Example 9: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 86%, the compression density is 4.3 g / cm 3It is obtained by winding a positive electrode sheet, a separator, and a negative electrode sheet to form a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.025, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0063] Example 10: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is obtained by winding a positive electrode sheet, a separator, and a negative electrode sheet to form a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 3:1, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0064] Example 11: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then injecting an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 4:1, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0065] Example 12: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then injecting an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 1:1.5, the partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0066] Example 13: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then injecting an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile, Ethylene glycol bis(propionitrile) ether (DENE), and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the three is 2:1:1. The distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25. The BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0067] Example 14: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 , the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and the electrolyte is poured. The retention coefficient of the electrolyte is 0.0014. The distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolyte is 0.075. The nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25. The BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0068] Example 15: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 , the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and the electrolyte is poured. The retention coefficient of the electrolyte is 0.0014. The distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolyte is 0.095. The nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 2.5. The BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0069] Example 16: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, and the mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.10. The nitrile compound is succinonitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 2.5. The BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0070] Example 17: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, and the mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.02. The nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 0.25. The BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0071] Example 18: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the positive electrode sheet, separator, and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014. The mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.003. The nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 0.1. The BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0072] Example 19: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 , the positive electrode sheet, separator, and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014. The mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.04. The nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 0.12. The BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0073] Example 20: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.18, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0074] Example 21: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of the carboxylic acid ester is 0.25, the mass ratio of ethyl propionate to propyl propionate is 1:1, and the BET of the positive electrode active material is 0.32 m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0075] Example 22: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.32, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0076] Example 23: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.38, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0077] Example 24: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3It is obtained by winding a positive electrode sheet, a separator, and a negative electrode sheet to form a cell, and then pouring an electrolytic solution. The holding coefficient of the electrolytic solution is 0.0014, the distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.42, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0078] Example 25: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is obtained by winding a positive electrode sheet, a separator, and a negative electrode sheet to form a cell, and then pouring an electrolytic solution. The holding coefficient of the electrolytic solution is 0.0014, the distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.46, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0079] Example 26: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.50, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0080] Example 27: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.52, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0081] Example 28: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.07m 2 / g, the Dv50 is 20 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0082] Example 29: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.18m 2 / g, the Dv50 is 16 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0083] Example 30: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014. The distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04. The nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25. The BET of the positive electrode active material is 0.34m 2 / g, the Dv50 is 8 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0084] Example 31: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014. The distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04. The nitrile compound is adiponitrile and 1,3,6-hexanetricarbonitrile, and the mass ratio of the two is 2:1. The distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25. The BET is 0.4m 2 / g, the Dv50 is 5 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0085] Example 32: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0008, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0086] Example 33: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.001, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0087] Example 34: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 86%, the compression density is 4.3 g / cm 3It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.002, the distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0088] Example 35: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet into a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0022, the distribution coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, the mass ratio of the two is 2:1, the distribution coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0089] Example 36: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3It is obtained by winding a positive electrode sheet, a separator and a negative electrode sheet to form a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0018, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.6 wt%.

[0090] Example 37: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is obtained by winding a positive electrode sheet, a separator and a negative electrode sheet to form a cell, and then pouring an electrolytic solution. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.15 wt%.

[0091] Example 38: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.25 wt%.

[0092] Example 39: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 and the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.32m 2 / g, the Dv50 is 10 μm, and the content of Al contained in the positive electrode active material is 0.4 wt%.

[0093] Example 40: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the partition coefficient m / (V2 / V1) of the mass of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The partition coefficient n / (V2 / V1) of the mass of ethyl propionate is 0.25, and the BET of the positive electrode active material is 0.5m 2It is / g, Dv50 is 8 μm, and the content of Al contained in the positive electrode active material was 0.6 wt%.

[0094] Example 41: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 0.25, the BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material was 1.2 wt%.

[0095] Example 42: When the ratio V2 / V1 of the true volume of the positive electrode active material to the volume of the positive electrode active material layer in the positive electrode sheet is 0.86, the compression density is 4.3 g / cm 3 It is, the positive electrode sheet, separator and negative electrode sheet are wound to form a cell, and then an electrolytic solution is poured. The retention coefficient of the electrolytic solution is 0.0014, the mass distribution coefficient m / (V2 / V1) of the nitrile compound in the electrolytic solution is 0.04, the nitrile compound is adiponitrile and 1,3,6 - hexanetricarbonitrile, and the mass ratio of the two is 2:1. The mass distribution coefficient n / (V2 / V1) of ethyl propionate is 0.25, the BET of the positive electrode active material is 0.32 m 2 / g, Dv50 is 10 μm, and the content of Al contained in the positive electrode active material was 1.5 wt%.

[0096] Cycle measurement: Eight batteries prepared in each comparative example and example were taken respectively, and the batteries were measured at 45 °C. They were charged at a constant current to the cut-off voltage at a rate of 0.5C, and the cut-off voltage was 4.45 V (or higher). Further, they were charged at a constant voltage of 4.45 V until the current became less than 0.025C, and brought to a fully charged state (100% SOC) at 4.45 V (or a voltage higher than that). After full charge, they were discharged at a rate of 0.5C, and the discharge capacity D0 at this time was recorded as a reference. The above procedure was repeated, and the discharge capacities D1, D2,... after 1 cycle, 2 cycles,... were recorded. Then, the capacity retention rate was calculated by the following formula. Cycle capacity retention rate at the nth cycle = Dn / D0, n = 1, 2, 3, 4, 5... The number of cycles when the cycle capacity retention rate reached 80% was calculated.

[0097] Measurement of low-temperature capacity retention rate: First, the temperature was adjusted to 25 °C, and the battery was discharged to 3.0 V at a rate of 0.2C and left standing for 5 minutes. It was charged at a constant current to 4.45 V at a rate of 0.5C, and then charged at a constant voltage until the current dropped to 0.025C. Thereafter, the battery was left standing at a temperature of 25 °C for 60 min, and then discharged to 3.0 V, and the discharge capacity D at this time was recorded and left standing for 60 min. Then, at 25 °C, it was charged at a constant current to 4.45 V at a rate of 0.5C, and then charged at a constant voltage until the current dropped to 0.025C. The temperature was adjusted to -10 °C, the battery was left standing for 60 minutes, and then discharged at a constant current to 3.0 V at 0.2C. The discharge capacity Da at this time was recorded, and thus the discharge capacity retention rate at 0.2C and -10 °C = Da / D × 100% was obtained.

[0098] Measurement of the weight of the blank aluminum foil wafer: The positive electrode sheet disassembled from the battery was immersed in dimethyl carbonate DMC for cleaning, and the positive electrode sheet was dried. The diameter was 14 mm (wafer area: 154.025 mm 2) A punching machine for small button-type batteries. Twenty wafers are punched out from a blank aluminum foil area in the positive electrode sheet where there is no positive electrode active material layer or the active material layer has been removed, and the total weight is measured. The average mass (unit: milligram) of one wafer is calculated, and the thickness of the wafer is measured, with the average value calculated as h0 μm.

[0099] Calculation of the retention coefficient k value: First, the battery is discharged to 3.0 V, and the discharge capacity of the battery is obtained as D0 mAh. The mass M1 g of the entire battery is measured, and then the battery is disassembled. Each of the positive electrode, negative electrode, separator, and exterior is immersed in dimethyl carbonate and washed for 30 min, and then placed in an oven at 50 °C and dried for 5 h to 8 h. After drying, the total weight M2 g of the positive electrode, negative electrode, separator, and exterior is measured. Thus, the electrolyte mass is A g, A = M1 - M2, and the retention coefficient k of the electrolyte is k = (M1 - M2) / D0.

[0100] Measurement of particle size: The device uses a Malvern laser particle size analyzer, the device number is Masterisizer 2000, the sample amount is 1 g, ultrasonic waves are not used, water is used as the dispersant, and the pump speed is 3000 r / min.

[0101] Take a powder sample of about 1 g of the positive electrode active material and put it into the device for measurement. The device outputs two curves. One is the particle volume distribution curve, and the other is the particle number distribution curve. The two correspond to each other and are only different expression forms of the same distribution. Dv50 refers to the particle diameter corresponding to when the percentage of the volume cumulative particle size distribution of the sample reaches 50%.

[0102] Measurement of BET (specific surface area): The device uses a specific surface area measurement device, and the device number is Micromeritics TristarII3020 in the United States.

[0103] For the positive electrode material, Step 1: Weigh the material (where the positive electrode active material is between 2 g and 12 g), put it into a sample tube, and place the sample tube into the device. Step 2: Perform degassing by turning on the power of the degassing station for vacuum degassing. Step 3: After degassing is completed, move the sample tube to the cooling port outside the heating port, and continue to evacuate while cooling for at least 10 minutes or more. Step 4: After cooling the sample tube to room temperature, backfill it with nitrogen gas for about 30 seconds. After backfilling, confirm that the sample tube has cooled to room temperature. Then, after removing the sample tube at the degassing port, seal the sample tube with a rubber stopper, measure the total mass of the sample in the balance chamber, and subtract the mass of the empty tube from the above total mass to obtain the mass after degassing. Step 5: Analyze it with the software of the device to obtain data.

[0104] Measurement of Compression Density: Step 1: Punch the positive electrode sheet into wafers with a punching machine. The diameter of the punch of the punching machine is d mm. Punch 20 wafers from the area where the positive electrode active material is coated on both sides of the positive electrode sheet. Here, the blank aluminum foil of the wafer has a weight of m0 mg (the measurement process refers to the measurement of the weight of the blank aluminum foil wafer), and a thickness of h0 μm (the measurement process refers to the measurement of the weight of the blank aluminum foil wafer).

[0105] Step 2: Weigh the punched wafers and record the weight m1~m 20 (mg) of each wafer.

[0106] Step 3: Measure the thickness of each wafer, and associate it one-to-one with the measured weight data to make it h1~h 20 / (μm).

[0107] Step 4: Calculate the compression density PD according to the formula: PD n =[(m n -m0) / (π×(d / 2) 2 / (h n -h0)×1000]. PD = [PD1 + PD2 + ··· + PD n / n, where n is a numerical value between (1, 20).

[0108] Measurement of V1 and V2: V1 = S × (H - h), where S is the area of the positive electrode sheet sample taken, all 1540.25 mm 2 and H is the thickness of the electrode tab, and h is the thickness of the current collector. V2 = [M pole - (S × surface density ρ1 of the aluminum foil)] / (true density ρ2 of the positive electrode material), M pole is the weight of the positive electrode sheet under the area S, and the surface density of the aluminum foil is a known parameter calculated from specific processing data. The true density of the positive electrode material is an inherent property of the material.

[0109] The parameters and performance measurement results of each example and comparative example are shown in Table 1.

[0110]

Table 1

[0111] As can be seen from Examples 2 to 5, when other parameters remain unchanged, as the value of V2 / V1 increases from 80% to 89%, the high-temperature cycle characteristics and low-temperature discharge characteristics of the lithium-ion battery are maintained at a relatively good level, but the overall characteristics show a tendency to first increase and then decrease. Therefore, in some examples, by limiting 0.8 ≤ V2 / V1 ≤ 0.92, it is ensured that the lithium-ion battery has relatively good high-temperature cycle characteristics and low-temperature discharge characteristics.

[0112] As can be seen from Example 1 and Example 2, when other conditions are the same, both the high-temperature cycle characteristics and the low-temperature capacity retention rate of Example 2 are superior to those of Example 1. The reason is considered to be that a nitrile-based compound was used in Example 2, while no nitrile-based compound was used in Example 1. Compared with Example 2, since no nitrile-based compound was used in Example 1, the surface of the positive electrode active material could not be sufficiently protected, thereby reducing the high-temperature cycle characteristics and low-temperature characteristics of the lithium-ion battery compared to those of Example 2. As can be seen from Example 1, Examples 7 to 9, Examples 14, 15 and 17, when other parameters remain unchanged, as m / (V2 / V1) increases, the high-temperature cycle characteristics of the lithium-ion battery first gradually increase and then decrease. However, if the value of m / (V2 / V1) is too high, the low-temperature discharge characteristics of the lithium-ion battery begin to deteriorate. Therefore, in some examples, it is limited that 0.006 ≦ m / (V2 / V1) ≦ 0.095.

[0113] As can be seen from Comparative Example 3 and Comparative Example 4, when the value of n / (V2 / V1) is relatively small, the low-temperature discharge characteristics of the lithium-ion battery are poor. As can be seen from Examples 19 to 27, when other parameters remain unchanged, as the value of n / (V2 / V1) increases, the high-temperature cycle characteristics of the lithium-ion battery first decrease and then increase, and the low-temperature discharge characteristics of the lithium-ion battery gradually increase to a relatively good level and then hardly change. The reason is considered to be that the carboxylic acid ester compound is advantageous for improving the transport efficiency of lithium ions in the electrolyte, thereby being advantageous for improving the low-temperature discharge characteristics and improving the high-temperature cycle characteristics within a certain range. If the content of the carboxylic acid ester compound is too high, there is a possibility of destroying the SEI film on the surface of the positive electrode active material under high-temperature and high-voltage conditions, resulting in a decrease in the high-temperature cycle characteristics. Therefore, in some examples, it is limited that 0.16 ≦ n / (V2 / V1) ≦ 0.38.

[0114] As can be seen from Examples 28 to 32, as the BET specific surface area of the positive electrode active material increases, the high-temperature cycle characteristics and low-temperature discharge characteristics of the lithium-ion battery are good within a certain range. Since the lithium-ion batteries within the specific surface area range shown in Examples 24 to 27 all have relatively good high-temperature cycle characteristics and low-temperature discharge characteristics, in some embodiments, the BET specific surface area of the positive electrode active material is limited to be 0.07 m 2 / g to 0.4 m 2 / g. Since the specific surface area is inversely proportional to the particle diameter of the particles of the positive electrode active material, in some embodiments, the particle diameter Dv50 of the particles of the positive electrode active material is limited to be 5.0 μm to 20 μm.

[0115] As can be seen from Examples 33 to 36, as the retention coefficient k increases, the high-temperature cycle characteristics and low-temperature discharge characteristics of the lithium-ion battery both gradually increase to a relatively good level and then hardly change. The reason is that when the retention coefficient k is relatively low, the amount of the electrolyte is insufficient, so that the performance of the lithium-ion battery cannot be fully exerted. When the retention coefficient k is relatively high, the amount of the electrolyte is sufficient. At this time, increasing the electrolyte will not significantly affect the high-temperature cycle characteristics and low-temperature discharge characteristics, but instead may reduce the capacitance per unit mass. Therefore, in some embodiments, it is limited that 0.001 ≦ k ≦ 0.0022.

[0116] As can be seen from Examples 37, 38, 39 and 41, the increase in the mass content of Al in the positive electrode active material results in the high-temperature cycle characteristics and low-temperature discharge characteristics of the lithium-ion battery first increasing and then decreasing. Therefore, in some embodiments, the mass content of M2 in the positive electrode active material is limited to be 0.1% to 1.5%.

[0117] The above description is only an explanation of the preferred embodiments of the present invention and the applied technical principles. What those skilled in the art should understand is that the scope of the present invention is not limited to the technical solutions consisting of specific combinations of the above technical features, but also includes other technical solutions consisting of any combination of the above technical features or equivalent features thereof. For example, a technical solution formed by mutually replacing the above features with technical features having similar functions disclosed in the present invention.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolytic solution, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material, The volume of the positive electrode active material layer is V1 cm ３ and the true volume of the positive electrode active material is V2 cm ３ where V1 and V2 satisfy 0.8 ≤ V2 / V1 ≤ 0.92, the electrolytic solution further contains a nitrile compound and a carboxylic acid ester compound, the nitrile compound occupies m of the total mass of the electrolytic solution, and m satisfies 0.5% ≤ m ≤ 10%, the carboxylic acid ester compound occupies n of the total mass of the electrolytic solution, and n satisfies 12% ≤ n ≤ 40%, m, V1, and V2 satisfy 0.02 ≤ m / (V2 / V1) ≤ 0.075, and n, V1, and V2 satisfy 0.18 ≤ n / (V2 / V1) ≤ 0.5, the nitrile compound includes at least one of 1,3,6 - hexanetricarbonitrile, succinonitrile, adiponitrile, suberonitrile, glutaronitrile, sebaconitrile, ethylene glycol bis(propionitrile) ether, 1,3,5 - pentanetricarbonitrile, p - methylbenzonitrile, 2,2 - difluorosuccinonitrile, tricyanobenzene, trans - butenedinitrile, or trans - hexenedinitrile, and / or the carboxylic acid ester compound includes at least one of ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, or propyl butyrate, characterized in that it is an electrochemical device.

2. the positive electrode active material contains LixM1yM2zO2, x, y, and z respectively satisfy 0.90 ≤ x ≤ 1.03, 0.9 ≤ y ≤ 1.05, and 0.002 ≤ z ≤ 0.012, M1 includes at least one of Ni, Co, or Mn, M2 includes at least one of Al, Mg, Ti, Zr, La, Y, Sc, or Ca, characterized in that it is the electrochemical device according to Claim 1.

3. The mass content of M2 in the positive electrode active material is 0.1% to 1.5%, characterized in that it is the electrochemical device according to Claim 2.

4. The retention coefficient of the electrolytic solution in the electrochemical device is k mAh / g, and k satisfies 0.001 ≤ k ≤ 0.0022, characterized in that it is the electrochemical device according to Claim 1.

5. The positive electrode satisfies at least one of the following (a) to (c), (a) The particle diameter Dv50 of the particles of the positive electrode active material is 5.0 μm to 20 μm, (b) The BET specific surface area of the positive electrode active material is 0.07 m ２ / g to 0.4 m ２ / g, and (c) The compression density of the positive electrode active material layer is 4.0 g / cm ３ or more. The electrochemical device according to claim 1, characterized in that.

6. An electronic device including the electrochemical device according to any one of claims 1 to 5.

Images