Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device. The electronic device comprises a positive electrode and an electrolyte. The electrolyte comprises a compound of formula I. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, and the positive electrode active material comprises manganese and a metal element A, wherein the metal element A includes at least one of calcium, sodium, magnesium, chromium, or titanium. On the basis of the total mass of the positive electrode active material, the mass content of the metal element A is x%, where 0.001≤x≤1; and on the basis of the total mass of the electrolyte, the mass content of the compound of formula I is y%, where 0.008≤y / x≤12,000. During the charging and discharging process of the electrochemical device, the transition metal of the positive electrode is not easily dissolved, and thus the electrochemical device has good cycle performance and thermal safety performance.

Description

An electrochemical device and an electronic device Technical Field

[0001] This application relates to the field of energy storage, and in particular to an electrochemical device and an electronic device. Background Technology

[0002] Electrochemical devices such as lithium-ion batteries are widely used in portable electronic products, electric vehicles, aerospace, and energy storage due to their advantages such as high energy density, good cycle performance, safety, environmental friendliness, and lack of memory effect. Currently, with the continuous expansion of application areas, higher requirements are being placed on the cycle performance and safety performance at high temperatures of electrochemical devices. Summary of the Invention

[0003] This application can provide an electrochemical device and an electronic device. In the charging and discharging process, the transition metal of the positive electrode of the electrochemical device of this application is not easily dissolved, and the electrochemical device has good cycle performance and thermal safety performance.

[0004] In a first aspect, this application provides an electrochemical device comprising a positive electrode and an electrolyte, the electrolyte comprising a compound of formula I:

[0005] Among them, R 11 Selected from any one of hydrogen atoms, halogen atoms, C1-C6 alkyl groups (with or without Rx substitution), C2-C6 alkenyl groups (with or without Rx substitution), C2-C6 alkynyl groups (with or without Rx substitution), and C1-C6 alkoxy groups (with or without Rx substitution), R 12 It is selected from any one of the following: C1-C6 alkyl groups (with or without Rx substitution), C2-C6 alkenyl groups (with or without Rx substitution), C2-C6 alkynyl groups (with or without Rx substitution), and C1-C6 alkoxy groups (with or without Rx substitution), wherein Rx is selected from a halogen atom, a C2-C5 cycloalkyl group, or a C6-C6 cycloalkyl group. 12 The positive electrode comprises any of the aromatic groups. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, which includes manganese and a metal element A. Metal element A includes at least one of calcium, sodium, magnesium, chromium, or titanium. Based on the total mass of the positive electrode active material, the mass content of metal element A is x%, 0.001≤x≤1; based on the total mass of the electrolyte, the mass content of compound I is y%, 0.008≤y / x≤12000.

[0006] Based on the above technical solution, the inventors discovered that although manganese in the positive electrode active material is beneficial for improving the safety performance of secondary batteries and reducing manufacturing costs, it is easily dissolved in ionic form during charge and discharge, affecting the cycle performance and thermal safety performance of the electrochemical device. Metal element A, with a mass content between 0.001% and 1% in the positive electrode active material, can cooperate with compound I in the electrolyte to effectively reduce the dissolution probability of manganese in the positive electrode, thereby improving the cycle performance and thermal safety performance of the electrochemical device. When the positive electrode in the electrochemical device of this application undergoes delithiation, metal element A can occupy lithium sites, stabilizing the positive electrode structure; moreover, because compound I contains carbonyl and double bond structures, it can form a stable SEI film (i.e., solid electrolyte interface film) at the positive electrode during formation, thereby assisting element A in stabilizing the positive electrode structure. Therefore, the combined effect of manganese-containing positive electrode active material with a metal element A content between 0.001% and 1% and compound I in the electrolyte can improve the cycle performance and thermal safety performance of the electrochemical device.

[0007] In one embodiment of this application, the compound of formula I includes at least one of the following compounds:

[0008] In one embodiment of this application, the mass content of compound I is y% based on the total mass of the electrolyte; and the mass content of titanium is X% based on the total mass of the positive electrode active material. Ti The mass content of chromium is X%. Cr The electrochemical device must satisfy at least one of the following conditions: (1) 0.08 ≤ y ≤ 15; (2) Metal element A includes titanium, and the mass content of titanium is X based on the total mass of the positive electrode active material. Ti %, 0.001≤X Ti ≤0.5; (3) Metal element A includes chromium. Based on the total mass of the positive electrode active material, the mass content of chromium is X. Cr %, 0.001≤X Cr ≤0.5; (4) Metal element A includes titanium and chromium. Based on the total mass of the positive electrode active material, the mass contents of titanium and chromium are respectively X Ti % and X Cr %, X Ti >X Cr (5) 0.2 ≤ y / x ≤ 1000.

[0009] Based on the above implementation scheme, when metal element A is titanium or chromium, the cycle performance and safety performance of the electrochemical device will be better; especially titanium, because the bond energy of Ti-O bond is higher than that of Cr-O bond and the stability is stronger, the performance is better when the titanium content is high and the thermal safety performance of the electrochemical device is better.

[0010] In one embodiment of this application, the electrolyte further includes a cyclic carbonate compound, wherein the mass content of the cyclic carbonate compound is f%, based on the total mass of the electrolyte, and 5 ≤ f ≤ 50%.

[0011] Based on the above implementation scheme, when the electrolyte includes cyclic carbonate compounds, the interfacial performance of the electrochemical device can be better improved, thereby further enhancing the cycle performance and thermal safety performance of the electrochemical device.

[0012] In one embodiment of this application, 0.0025 ≤ y / f ≤ 1.

[0013] In one embodiment of this application, the cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate, or butene carbonate.

[0014] In one embodiment of this application, the electrolyte further includes a sulfur-oxygen double bond compound, which includes compounds of formula II:

[0015] Among them, A 11 It is selected from any one of C1-C4 alkylene groups that are Ry-substituted or unsubstituted, C2-C4 alkenyl groups that are Ry-substituted or unsubstituted, and C1-C6 heteroalkyl groups that are Ry-substituted or unsubstituted, wherein the number of heteroatoms in the heteroalkyl group is 1 to 5, and the heteroatoms in the heteroalkyl group are selected from at least one of oxygen atom, nitrogen atom, phosphorus atom or sulfur atom. When substituted, each substituent Ry is independently selected from any one of halogen atom, C1-C3 alkyl group or C2-C4 alkenyl group.

[0016] Based on the above implementation scheme, when the electrolyte includes sulfur-containing oxygen double bond compounds, the cycle performance and thermal safety performance of the electrochemical device can be further improved.

[0017] In one embodiment of this application, the sulfur-containing double-bond compound is selected from at least one of methylene methane disulfonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, propenyl-1,3-sulfonate lactone, ethylene sulfate, 1,3-propanedisulfonic anhydride (CAS No.: 4720-58-5), 2,4-butanesulfonate (CAS No.: 1121-03-5), and 1,3-propanediol cyclosulfate; the mass content of the sulfur-containing double-bond compound is g%, g≤5, based on the total mass of the electrolyte.

[0018] In one embodiment of this application, the positive electrode active material includes at least one of lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese phosphate, lithium iron manganese phosphate, or lithium-rich manganese-based materials.

[0019] Secondly, this application provides an electronic device that includes the aforementioned electrochemical device. Therefore, the electronic device provided by this application has excellent performance.

[0020] The beneficial effects of this application are:

[0021] This application provides an electrochemical device and an electronic device. The electrochemical device includes a positive electrode and an electrolyte. The electrolyte includes a compound of formula I. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, which includes manganese and a metal element A. The metal element A includes at least one of calcium, sodium, magnesium, chromium, or titanium. Based on the total mass of the positive electrode active material, the mass content of metal element A is x%, where 0.001 ≤ x ≤ 1. In the electrochemical device of this application, the manganese in the positive electrode active material can improve the safety performance of the secondary battery and reduce the manufacturing cost. By controlling the content of metal element A in the positive electrode active material and using metal element A in combination with the compound of formula I in the electrolyte, the dissolution of manganese can be inhibited, and the structure of the positive electrode can be stabilized, thereby enabling the electrochemical device to have good cycle performance and thermal safety performance. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0023] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries in this application are not limited to lithium-ion batteries.

[0024] This application provides an electrochemical device comprising a positive electrode and an electrolyte, wherein the electrolyte comprises a compound of formula I:

[0025] Among them, R 11 Selected from any one of hydrogen atoms, halogen atoms, C1-C6 alkyl groups (with or without Rx substitution), C2-C6 alkenyl groups (with or without Rx substitution), C2-C6 alkynyl groups (with or without Rx substitution), and C1-C6 alkoxy groups (with or without Rx substitution), R 12It is selected from any one of the following: C1-C6 alkyl groups (with or without Rx substitution), C2-C6 alkenyl groups (with or without Rx substitution), C2-C6 alkynyl groups (with or without Rx substitution), and C1-C6 alkoxy groups (with or without Rx substitution), wherein Rx is selected from a halogen atom, a C2-C5 cycloalkyl group, or a C6-C6 cycloalkyl group. 12 The positive electrode comprises any one of the aromatic groups. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, which includes manganese and a metal element A. Metal element A includes at least one of calcium (Ca), sodium (Na), magnesium (Mg), chromium (Cr), or titanium (Ti). Based on the total mass of the positive electrode active material, the mass content of metal element A is x%, 0.001≤x≤1; based on the total mass of the electrolyte, the mass content of compound I is y%, 0.008≤y / x≤12000.

[0026] It should be noted that the aforementioned "positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector" means that the positive active material layer can be disposed on one surface of the positive current collector along its own thickness direction, or on two surfaces of the positive current collector along its own thickness direction. Here, "surface" can refer to the entire area of ​​the positive current collector or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the thickness of the positive active material layer, as long as the purpose of this application is achieved; for example, the thickness of a single-sided positive active material layer can be from 30 μm to 120 μm.

[0027] The inventors discovered that while manganese in the positive electrode active material is beneficial for improving the safety performance of secondary batteries and reducing manufacturing costs, it is prone to dissolving as ions during charge and discharge, affecting the cycle performance and thermal safety of the electrochemical device. The positive electrode active material containing the aforementioned amount of metal element A, in synergy with the compound of formula I in the electrolyte, can significantly improve the interfacial stability of the positive and negative electrodes in the electrochemical device, thereby enhancing the cycle performance, thermal stability, and safety performance of the electrochemical device. The specific principle is as follows:

[0028] When lithium is delithiated from the positive electrode, metal element A can occupy the lithium site, making it difficult for manganese to migrate and reducing the likelihood of distortion in the positive electrode. Furthermore, the compound of formula I contains carbonyl groups and double bonds, which can form a stable SEI film at the positive electrode during formation, assisting metal element A in stabilizing the positive electrode structure and making it less prone to manganese dissolution. This reduced manganese dissolution contributes to a more stable positive electrode interface and also prevents damage to the negative electrode interface of the electrochemical device, significantly improving the overall cycle performance and thermal safety of the electrochemical device.

[0029] Specifically, in some embodiments of this application, the compound of formula I includes at least one of the following compounds:

[0030] In some embodiments of this application, to further improve the cycle performance and thermal safety performance of the electrochemical device, the mass content of the compound of Formula I is y% based on the total mass of the electrolyte, 0.01≤y / x≤10000, preferably 0.2≤y / x≤1000, and more preferably 1≤y / x≤125; for example, y / x can be 0.008, 0.01, 0.08, 0.1, 0.2, 1, 10, 100, 125, 300, 1000, 3000, 10000, 12000, etc., or within the range of any two of the above values. Specifically, y can be 0.008, 0.002, 0.08, 0.6, 1, 8, 10, 12, 15, 24, etc., or within the range of any two of the above values.

[0031] In some embodiments of this application, the electrolyte further includes a cyclic carbonate compound. Based on the total mass of the electrolyte, the mass content of the cyclic carbonate compound is f%, 5 ≤ f ≤ 50, preferably 0.0025 ≤ y / f ≤ 1. This can further improve the interfacial performance of the electrochemical device, thereby further enhancing the cycle performance and thermal safety performance of the electrochemical device. Specifically, the cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate, or butylene carbonate.

[0032] In some embodiments of this application, to further improve the cycle performance and thermal safety performance of the electrochemical device, the electrolyte also includes a sulfur-containing oxygen double bond compound. Based on the total mass of the electrolyte, the mass content of the sulfur-containing oxygen double bond compound is g%, g≤5. The sulfur-containing oxygen double bond compound includes compounds of formula II:

[0033] Among them, A 11 The compound is selected from any one of C1-C4 alkylene groups (substituted or unsubstituted with Ry), C2-C4 alkenyl groups (substituted or unsubstituted with Ry), and C1-C6 heteroalkyl groups (substituted or unsubstituted with Ry), wherein the number of heteroatoms in the heteroalkyl group is 1-5, and the heteroatoms in the heteroalkyl group are selected from at least one of oxygen, nitrogen, phosphorus, or sulfur atoms. When substituted, the substituent Ry is independently selected from any one of halogen atoms, C1-C3 alkyl groups, or C2-C4 alkenyl groups. Specifically, the sulfur-oxygen double bond compound is selected from at least one of methylene disulfonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, propenyl-1,3-sulfonate lactone, ethylene sulfate, 1,3-propanedisulfonic anhydride, 2-butanesulfonate lactone, and 1,3-propanediol cyclosulfate.

[0034] In the positive electrode of this application, the positive electrode active material can be at least one of lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese phosphate, lithium iron manganese phosphate, or lithium-rich manganese-based materials. It should be noted that all of the above-mentioned materials are doped with metal element A. In some preferred embodiments of this application, to further improve the cycle performance and safety performance of the electrochemical device, the metal element A doped in the positive electrode active material includes Ti and / or Cr; the mass content of Ti is X based on the total mass of the positive electrode active material. Ti %, Cr mass content is X Cr %, the two preferably have at least one of the following relationships: (1) X Ti >X Cr (2) 0.001 ≤ X Ti ≤0.2, (3)0.001≤X Cr ≤0.5. Because the bond energy of Ti-O bond is higher than that of Cr-O bond, it is more stable. Therefore, the performance is better when the Ti content is higher, and the safety performance of the electrochemical device is better at high temperatures.

[0035] The positive electrode active material layer of this application also includes a conductive agent and a binder. This application does not impose any particular limitations on the conductive agent and binder in the positive electrode active material layer, as long as they can achieve the purpose of this application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The aforementioned conductive carbon black may include, but is not limited to, Super P, acetylene black, or Ketjen black. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder may include, but is not limited to, at least one of polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene-butadiene copolymer (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose, sodium carboxymethyl cellulose, or potassium carboxymethyl cellulose. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode active material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0036] This application does not impose any particular restrictions on the thickness and material of the positive electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, preferably 6μm to 18μm; the material of the positive electrode current collector may include aluminum foil, aluminum alloy foil or composite current collector (e.g., aluminum-carbon composite current collector), etc.

[0037] Optionally, the positive electrode may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode active material layer. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent and binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0038] In this application, the electrochemical device further includes a negative electrode, which comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The aforementioned "negative electrode active material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode active material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or only a part of it; this application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the negative electrode current collector, as long as the purpose of this application is achieved, for example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors, etc.

[0039] The negative electrode active material layer of this application includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO₂, etc. x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12The negative electrode active material layer of this application includes at least one of the following: Li-Al alloy or metallic lithium. The negative electrode active material layer also includes a binder. This application does not impose any particular limitation on the binder in the negative electrode active material layer, as long as it achieves the purpose of this application. For example, the binder can be at least one of the aforementioned binders. The negative electrode active material layer of this application also includes a conductive agent. This application does not impose any particular limitation on the conductive agent in the negative electrode active material layer, as long as it achieves the purpose of this application. For example, the conductive agent can be at least one of the aforementioned conductive agents. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, binder, and conductive agent in the negative electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved.

[0040] This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector can be from 5 μm to 16 μm. This application also does not impose any particular limitation on the thickness of the negative electrode active material layer, as long as it achieves the purpose of this application. For example, the thickness of the single-sided negative electrode active material layer can be from 30 μm to 120 μm.

[0041] Optionally, the negative electrode may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode active material layer. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent to the binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the thickness of the conductive layer, as long as the purpose of this application is achieved; for example, the thickness of the conductive layer can be from 1 μm to 10 μm.

[0042] In this application, the electrochemical device also includes a diaphragm, which separates the positive and negative electrodes, prevents short circuits within the electrochemical device, allows electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process. This application does not impose any particular limitation on the diaphragm, as long as it achieves the purpose of this application. For example, the diaphragm material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the diaphragm type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0043] In this application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a nonwoven fabric or composite membrane with a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a binder. This application does not have any particular limitation on the aforementioned inorganic particles, and may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not have any particular limitation on the aforementioned binders, and may include at least one of the aforementioned binders. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0044] The electrochemical device of this application also includes a packaging bag for containing the positive electrode, diaphragm, negative electrode, and electrolyte, as well as other components known in the art in the electrochemical device. This application does not limit the aforementioned other components. This application does not have any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0045] This application does not impose any particular limitation on the type of electrochemical device, which may include any device in which an electrochemical reaction occurs. In this application, the electrochemical device may include, but is not limited to: lithium metal secondary batteries, lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, or lithium-ion polymer secondary batteries (lithium-ion polymer batteries), etc.

[0046] The preparation process of the electrochemical device of this application is well known to those skilled in the art, and this application has no particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the packaging bag as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0047] A second aspect of this application provides an electronic device that includes the electrochemical device in any of the foregoing embodiments. Therefore, the electronic device provided by this application has good performance.

[0048] This application does not specifically limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0049] Example

[0050] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0051] Test methods and equipment:

[0052] Cyclic performance test:

[0053] The cycling performance of an electrochemical device is evaluated by the capacity retention rate after 1000 cycles at 25°C. A higher capacity retention rate after 1000 cycles at 25°C indicates better cycling performance of the electrochemical device.

[0054] The electrochemical device was placed in a 25°C constant temperature chamber and allowed to stand for 30 minutes to reach a constant temperature. The device was then charged at a constant current of 0.2C to 4.2V at 25°C, followed by a constant voltage charge to 0.05C at 4.2V, and allowed to stand for 5 minutes. It was then discharged at a constant current of 0.2C to 2.8V, and allowed to stand for 5 minutes. The initial discharge capacity C0 of the electrochemical device was measured. Next, it was charged at a constant current of 1C to 4.2V, followed by a constant voltage charge to 0.05C at 4.2V, and allowed to stand for 5 minutes. Finally, it was discharged at a constant current of 1C to 2.8V, and allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. This charge / discharge cycle was repeated 1000 times, and the discharge capacity C1 after 1000 cycles was measured.

[0055] The capacity retention rate after 1000 cycles at 25°C is calculated as C1 / C0 × 100%. The higher the capacity retention rate after 1000 cycles at 25°C, the better the cycling performance of the electrochemical device. Specific data on the high-temperature cycling performance of the electrochemical devices in each embodiment and comparative example are shown in Tables 1 to 3.

[0056] Thermal safety performance test:

[0057] Hot box performance test: The electrochemical device was discharged at 25°C with a constant current of 0.2C to 2.8V, then charged at a constant current of 0.5C to 4.2V, and finally charged at a constant voltage of 0.05C at 4.2V. It was then placed in a high-temperature furnace at 130°C, 132°C, and 134°C for 1 hour. After 1 hour, the electrochemical device was observed to see if it ignited; if not, it was considered to have passed. The pass rate was recorded as N / 10, indicating that out of 10 electrochemical devices tested, N passed the test. Specific data on the thermal safety performance tests of the electrochemical devices in each embodiment and comparative example are shown in Tables 1-3.

[0058] Hot box performance evaluation criteria: Under different temperatures, the higher the temperature at which the fire does not ignite, the better the hot box performance and the better the thermal safety performance; under the same temperature, the higher the pass rate, the better the hot box performance and the better the thermal safety performance. For example, a test result of 5 / 10 at 132℃ is better than a test result of 3 / 10 at 132℃, and a test result of 3 / 10 at 132℃ is better than a test result of 5 / 10 at 130℃.

[0059] Example 1-1

[0060] <Preparation of the negative electrode>

[0061] The negative electrode active materials, artificial graphite, SBR, and CMC-Na, were mixed in a mass ratio of 98.5:1:0.5, and then deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 54 wt%. The slurry was then stirred evenly in a vacuum mixer. The conductive agent Super P and the binder SBR were mixed in a mass ratio of 9:1, and then deionized water was added as a solvent to prepare a conductive layer slurry with a solid content of 10 wt%. The conductive layer slurry was uniformly coated onto one surface of an 8 μm thick copper foil used as a negative electrode current collector and dried at 85°C, forming a 2 μm thick conductive layer on one surface of the copper foil. Then, the negative electrode slurry was coated onto the surface of the conductive layer away from the copper foil and dried at 85°C, forming a 100 μm thick negative electrode active material layer on the same surface. This yielded a negative electrode with a single-sided conductive layer and a negative electrode active material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode with a double-sided conductive layer and a negative electrode active material layer. After coating, the negative electrode is cold-pressed and cut into 76mm × 851mm dimensions for later use. The compaction density of the negative electrode active material layer after cold pressing is 1.60 g / cm³. 3 .

[0062] <Preparation of the positive electrode>

[0063] Lithium manganese oxide (CMO), Super P (STO), and polyvinylidene fluoride (PVDF) (PVDF) were mixed in a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. The mixture was then stirred evenly in a vacuum mixer to obtain the CMO slurry. This slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil current collector and dried at 85°C to obtain a single-sided coated CMO with a 110 μm thick active material layer. The above steps were then repeated on the other surface of the aluminum foil to obtain a double-sided coated CMO. After coating, the CMO was cold-pressed and cut into 74 mm × 867 mm dimensions for later use. The compaction density of the cold-pressed active material layer was 2.70 g / cm³. 3 The lithium manganese oxide mentioned above contains Ti, and based on the total mass of the positive electrode active material, the mass content of Ti is 0.001%, as detailed in Table 1.

[0064] <Preparation of Electrolyte>

[0065] In an argon-atmospheric glove box with a water content of less than 10 ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 1:1 mass ratio to prepare a base solvent. Lithium hexafluorophosphate (LiPF6) and compound I were then added and mixed thoroughly to obtain the electrolyte. Based on the total mass of the electrolyte, the mass content of LiPF6 was 12.5%, the mass content of compound I is shown in Table 1, and the remainder was the base solvent.

[0066] In addition, the compounds referred to by the codes in the table can be found in the above content of this article.

[0067] <Septum>

[0068] A porous polyethylene (PE) membrane with a thickness of 5 μm was used.

[0069] <Preparation of Electrochemical Devices>

[0070] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the electrochemical device is obtained through vacuum sealing, settling, formation (0.02C constant current charging to 3.5V, then 0.1C constant current charging to 3.9V), shaping, and capacity testing.

[0071] Examples 1-2 to Examples 1-3

[0072] Except for adjusting the content of Formula I compound in <Preparation of Electrolyte> according to Table 1, the rest is the same as in Example 1-1. When the content of Formula I compound changes, the mass content of lithium salt remains unchanged.

[0073] Examples 1-4 to Examples 1-12

[0074] Except for adjusting the content of the metal element Ti in lithium manganese oxide according to Table 1 in <Preparation of the cathode>, the rest is the same as in Examples 1-3.

[0075] Examples 1-13 to Examples 1-14

[0076] Except for adjusting the content of Formula I compound in <Preparation of Electrolyte> according to Table 1, the rest is the same as in Examples 1-12. When the content of Formula I compound changes, the mass content of lithium salt remains unchanged.

[0077] Examples 1-15 to Examples 1-22

[0078] Except for adjusting the content of Formula I compound in <Preparation of Electrolyte> according to Table 1, the rest is the same as in Examples 1-9. When the content of Formula I compound changes, the mass content of lithium salt remains unchanged.

[0079] Examples 1-23 to Examples 1-27

[0080] Except for adjusting the relevant preparation parameters in Table 1 for <Preparation of Electrolyte>, the rest is the same as in Examples 1-9.

[0081] Examples 1-28 to Examples 1-31

[0082] Except for adjusting the relevant preparation parameters in Table 1 for <Preparation of the Cathode>, the rest is the same as in Examples 1-9.

[0083] Examples 1-32 to Examples 1-44

[0084] Except for adjusting the type and content of metal element A in lithium manganese oxide in <Preparation of the positive electrode> according to Table 1, and the relevant preparation parameters in <Preparation of the electrolyte>, the rest are the same as in Examples 1-9.

[0085] Comparative Examples 1 to 7

[0086] Except for adjusting the type and content of metal element A in lithium manganese oxide in <Preparation of the positive electrode> according to Table 1, and the relevant preparation parameters in <Preparation of the electrolyte>, the rest are the same as in Examples 1-9.

[0087] Table 1 Note: In the "Metallic Elements" column, the number in parentheses represents the mass content of that element based on the total mass of the positive electrode active material, in percentages.

[0088] Examples 2-1 to 2-10

[0089] Except for the preparation of the electrolyte as follows, the rest is the same as in Examples 1-9:

[0090] <Preparation of Electrolyte>

[0091] In an argon-atmospheric glove box with a water content of less than 10 ppm, EC and DEC were mixed, and then LiPF6 and compound I were added. After thorough mixing, an electrolyte was obtained. Based on the total mass of the electrolyte, the mass content of LiPF6 was 12.5%, the mass contents of compound I and DEC are shown in Table 1, and the balance was EC.

[0092] Example 2-11

[0093] Except for adjusting the relevant preparation parameters in Table 2 <Preparation of Electrolyte>, the rest is the same as in Example 2-1.

[0094] Example 2-12

[0095] Except for adjusting the relevant preparation parameters in Table 2 <Preparation of Electrolyte>, the rest is the same as in Examples 2-10.

[0096] Examples 2-13 to 2-14

[0097] Except for adjusting the relevant preparation parameters in Table 2 for <Preparation of Electrolyte>, the rest is the same as in Examples 2-3.

[0098] Table 2 Note: In the "Metallic Elements and Their Content x" column, the number in parentheses represents the mass content of that element based on the total mass of the positive electrode active material, in percentages.

[0099] Examples 3-1 to 3-5

[0100] Except for the addition of a sulfur-containing oxygen double bond compound and the adjustment of relevant preparation parameters according to Table 3 in the <Electrolyte Preparation> section, the rest is the same as in Examples 1-9. The content of lithium salt LiPF6 remains unchanged when the mass content of the sulfur-containing oxygen double bond compound changes.

[0101] Examples 3-6 to 3-12

[0102] Except for adjusting the relevant preparation parameters in Table 3 for <Preparation of Electrolyte>, the rest is the same as in Examples 3-3.

[0103] Table 3 Note: In the "Metallic Elements and Their Content x" column, the number in parentheses represents the mass content of that element based on the total mass of the positive electrode active material, in percentages.

[0104] Referring to Table 1, as can be seen from the examples and comparative examples, by controlling the presence of Formula I compounds in the electrolyte and controlling the type and content of metal element A in the positive electrode active material within the scope of this application, the cycle performance and thermal safety performance of the electrochemical device can be improved.

[0105] Referring to Table 2, it can be seen from Examples 2-1 to 2-10, Examples 2-13 to 2-14 and Examples 1-9 that adding 5% to 50% of cyclic carbonate compounds can improve the cycle performance and thermal safety performance of electrochemical devices.

[0106] Referring to Table 3, it can be seen from Examples 3-1 to 3-12 and Examples 1-9 that adding 1% to 5% of sulfur-containing oxygen double bond compounds can further improve the cycle performance and thermal safety performance of the electrochemical device.

[0107] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0108] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0109] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device, characterized in that, It includes a positive electrode and an electrolyte, wherein the electrolyte comprises a compound of formula I: Among them, R 11 Selected from any one of hydrogen atoms, halogen atoms, C1-C6 alkyl groups (with or without Rx substitution), C2-C6 alkenyl groups (with or without Rx substitution), C2-C6 alkynyl groups (with or without Rx substitution), and C1-C6 alkoxy groups (with or without Rx substitution), R 12 It is selected from any one of the following: C1-C6 alkyl groups (with or without Rx substitution), C2-C6 alkenyl groups (with or without Rx substitution), C2-C6 alkynyl groups (with or without Rx substitution), and C1-C6 alkoxy groups (with or without Rx substitution), wherein Rx is selected from a halogen atom, a C2-C5 cycloalkyl group, or a C6-C6 cycloalkyl group. 12 Any of the aromatic groups; The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, which includes manganese and metal element A. Metal element A includes at least one of calcium, sodium, magnesium, chromium, or titanium. Based on the total mass of the positive electrode active material, the mass content of the metal element A is x%, 0.001≤x≤1; Based on the total mass of the electrolyte, the mass content of the compound of formula I is y%, and 0.008≤y / x≤12000.

2. The electrochemical device according to claim 1, characterized in that, The compound of formula I includes at least one of the following compounds:

3. The electrochemical device according to claim 1, characterized in that, The electrochemical device must satisfy at least one of the following conditions: (1)0.08≤y≤15； (2) The metal element A includes the titanium element, and the mass content of the titanium element is X based on the total mass of the positive electrode active material. Ti %, 0.001≤X Ti ≤0.5; (3) The metal element A includes the chromium element, and the mass content of the chromium element is X based on the total mass of the positive electrode active material. Cr %, 0.001≤X Cr ≤0.5; (4) The metal element A includes the titanium element and the chromium element. Based on the total mass of the positive electrode active material, the mass content of the titanium element and the chromium element are respectively X. Ti % and X Cr %, X Ti >X Cr ; (5) 0.2 ≤ y / x ≤ 1000.

4. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes cyclic carbonate compounds, and the mass content of the cyclic carbonate compounds is f%, based on the total mass of the electrolyte, with 5 ≤ f ≤ 50%.

5. The electrochemical device according to claim 4, characterized in that, 0.0025≤y / f≤1.

6. The electrochemical device according to claim 4, characterized in that, The cyclic carbonate compound includes at least one of ethylene carbonate, propylene carbonate, or butene carbonate.

7. The electrochemical device according to any one of claims 1 to 6, characterized in that, The electrolyte also includes sulfur-containing oxygen double bond compounds, including compounds of formula II: Among them, A 11 The substituent is selected from any one of C1-C4 alkylene groups that are Ry-substituted or unsubstituted, C2-C4 alkenyl groups that are Ry-substituted or unsubstituted, and C1-C6 heteroalkyl groups that are Ry-substituted or unsubstituted, wherein the number of heteroatoms in the heteroalkyl group is 1-5, and the heteroatoms in the heteroalkyl group are selected from at least one of oxygen, nitrogen, phosphorus or sulfur atoms. When substituted, each substituent Ry is independently selected from any one of halogen atom, C1-C3 alkyl group or C2-C4 alkenyl group.

8. The electrochemical device according to claim 7, characterized in that, The sulfur-containing oxygen double bond compound is selected from at least one of methylene methane disulfonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, propenyl-1,3-sulfonate lactone, ethylene sulfate, 1,3-propanedisulfonic anhydride, 2,4-butanesulfonate lactone, or 1,3-propanediol cyclosulfonate; based on the total mass of the electrolyte, the mass content of the sulfur-containing oxygen double bond compound is g%, g≤5.

9. The electrochemical device according to any one of claims 1 to 6, characterized in that, The positive electrode active material includes at least one of lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium manganese phosphate, lithium iron manganese phosphate, or lithium-rich manganese-based materials.

10. An electronic device, characterized in that, It includes the electrochemical device according to any one of claims 1 to 9.

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