Electrochemical device and electronic device

Abstract

The embodiment of the invention provides an electrochemical device and an electronic device. The electronic device comprises a positive electrode and an electrolyte, the electrolyte comprises a compound in a formula I, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material, the positive electrode active material contains a manganese element and a metal element A, the metal element A comprises at least one of calcium element, sodium element, magnesium element, chromium element or titanium element. Based on the total mass of the positive electrode active material, the mass content of the metal element A is x%, and 0.001 < = x < = 1; based on the total mass of the electrolyte, the mass content of the compound in the formula I is y%, and y / x is greater than or equal to 0.008 and less than or equal to 12000. In the charging and discharging process of the electrochemical device, transition metal of the positive electrode is not easy to dissolve out, and the electrochemical device has good cycle performance and thermal safety performance.

Description

Technical Field

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

[0002] Electrochemical devices such as lithium-ion batteries are widely used in portable electronics, electric vehicles, aerospace, energy storage, and other fields due to their high energy density, excellent cycle performance, safety, environmental friendliness, and lack of memory effect. However, with the continuous expansion of these applications, higher requirements are being placed on the cycle performance and safety performance of electrochemical devices at high temperatures. Summary of the Invention

[0003] The present application can provide an electrochemical device and an electronic device. During the charge and discharge process of the electrochemical device of the present application, the transition metal of the positive electrode is not easily dissolved, and the electrochemical device has good cycle performance and thermal safety performance.

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

[0005] Formula I Among them, R 11 is selected from any one of a hydrogen atom, a halogen atom, a C1-C6 alkyl group which is substituted or unsubstituted by Rx, a C2-C6 alkenyl group which is substituted or unsubstituted by Rx, a C2-C6 alkynyl group which is substituted or unsubstituted by Rx, and a C1-C6 alkoxy group which is substituted or unsubstituted by Rx, wherein R 12 Any one selected from C1~C6 alkyl substituted or unsubstituted by Rx, C2~C6 alkenyl substituted or unsubstituted by Rx, C2~C6 alkynyl substituted or unsubstituted by Rx, C1~C6 alkoxy substituted or unsubstituted by Rx, and Rx is selected from halogen atoms, C2~C5 cycloalkyl or C6~C 12 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, the positive electrode active material comprising manganese and a metal element A, wherein the metal element A comprises at least one of calcium, sodium, magnesium, chromium, or titanium. The mass content of the metal element A is x% based on the total mass of the positive electrode active material, and 0.001≤x≤1. The mass content of the compound of formula I is y% based on the total mass of the electrolyte, and 0.008≤y / x≤12000.

[0006] Based on the above technical solution, the inventors discovered that while manganese in the positive electrode active material can improve the safety performance of secondary batteries and reduce production costs, it is easily dissolved as ions during the charge and discharge process, affecting the cycling performance and thermal safety of the electrochemical device. A metal element A with a mass content of 0.001% to 1% in the positive electrode active material can interact with the compound of Formula I in the electrolyte to effectively reduce the probability of manganese dissolution from the positive electrode, thereby improving the cycling performance and thermal safety of the electrochemical device. When the positive electrode in the electrochemical device of the present application is delithiated, the metal element A can occupy lithium sites, stabilizing the positive electrode structure. Furthermore, because the compound of Formula I contains carbonyl groups and double bonds, it can form a stable SEI (solid electrolyte interface) film at the positive electrode during the formation process, thereby assisting the element A in stabilizing the positive electrode structure. Therefore, the manganese-containing positive electrode active material with a metal element A content of 0.001% to 1% and the compound of Formula I in the electrolyte can work together to improve the cycling performance and thermal safety of the electrochemical device.

[0007] In one embodiment of the present application, the compound of formula I comprises at least one of the following compounds: .

[0008] In one embodiment of the present application, the mass content of the compound of formula I is y% based on the total mass of the electrolyte; the mass content of the titanium element 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 satisfies at least one of the following conditions: (1) 0.08≤y≤15; (2) the 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 X Ti % and X Cr %,X Ti >X Cr ; (5) 0.2≤y / x≤1000.

[0009] Based on the above embodiment, when the 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 the Ti-O bond is higher than that of the Cr-O bond and the stability is stronger, so 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 the present application, the electrolyte further comprises a cyclic carbonate compound, and 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 embodiment, when the electrolyte includes a cyclic carbonate compound, the interface 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 the present application, 0.0025≤y / f≤1.

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

[0014] In one embodiment of the present application, the electrolyte further comprises a sulfur-oxygen double bond compound, and the sulfur-oxygen double bond compound comprises a compound of formula II:

[0015] Formula II Among them, A 11 any one selected from C1-C4 alkylene substituted or unsubstituted by Ry, C2-C4 alkenylene substituted or unsubstituted by Ry, and C1-C6 chain heteroalkylene substituted or unsubstituted by Ry, wherein the number of heteroatoms in the chain heteroalkylene is 1-5, and the heteroatoms in the chain heteroalkylene are selected from at least one of oxygen, nitrogen, phosphorus, and sulfur atoms. When substituted, the substituents Ry are each independently selected from any one of a halogen atom, a C1-C3 alkyl, and a C2-C4 alkenyl.

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

[0017] In one embodiment of the present application, the sulfur-oxygen double bond compound is selected from at least one of methanedisulfonic acid methylene ester, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, ethylene sulfate, 1,3-propanedisulfonic anhydride (CAS No.: 4720-58-5), 2,4-butane sultone (CAS No.: 1121-03-5), and 1,3-propylene glycol cyclic sulfate; based on the total mass of the electrolyte, the mass content of the sulfur-oxygen double bond compound is g%, and g≤5.

[0018] In one embodiment of the present 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] In a second aspect, the present application provides an electronic device comprising the electrochemical device described above. Therefore, the electronic device provided by the present application has good performance.

[0020] Beneficial effects of this application: The present application provides an electrochemical device and an electronic device, the electrochemical device comprising a positive electrode and an electrolyte, the electrolyte comprising a compound of formula I, the positive electrode comprising 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 containing a positive electrode active material, the positive electrode active material comprising manganese and metal element A, the metal element A comprising 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%, and 0.001≤x≤1. In the electrochemical device of the present application, the manganese element in the positive electrode active material can improve the safety performance of the secondary battery and reduce the preparation cost; by regulating the content of the metal element A in the positive electrode active material and combining the metal element A with the compound of formula I in the electrolyte, the dissolution of the manganese element can be suppressed and the structure of the positive electrode can be stabilized, thereby making the electrochemical device have good cycle performance and thermal safety performance. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiment is only a part of the embodiment of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those who do not specify the manufacturer of the reagents or instruments used are conventional products that can be purchased commercially.

[0022] It should be noted that, in the specific embodiments of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries.

[0023] The present application provides an electrochemical device comprising a positive electrode and an electrolyte, wherein the electrolyte comprises a compound of formula I:

[0024] Formula I Among them, R 11 is selected from any one of a hydrogen atom, a halogen atom, a C1-C6 alkyl group which is substituted or unsubstituted by Rx, a C2-C6 alkenyl group which is substituted or unsubstituted by Rx, a C2-C6 alkynyl group which is substituted or unsubstituted by Rx, and a C1-C6 alkoxy group which is substituted or unsubstituted by Rx, wherein R 12 Any one selected from C1~C6 alkyl substituted or unsubstituted by Rx, C2~C6 alkenyl substituted or unsubstituted by Rx, C2~C6 alkynyl substituted or unsubstituted by Rx, C1~C6 alkoxy substituted or unsubstituted by Rx, and Rx is selected from halogen atoms, C2~C5 cycloalkyl or C6~C 12 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. The positive electrode active material includes manganese and a metal element A. The metal element A includes at least one of calcium (Ca), sodium (Na), magnesium (Mg), chromium (Cr), or titanium (Ti). The mass content of the metal element A is x% based on the total mass of the positive electrode active material, and 0.001≤x≤1. The mass content of the compound of formula I is y% based on the total mass of the electrolyte, and 0.008≤y / x≤12000.

[0025] It should be noted that the above-mentioned "positive electrode includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector" means that the positive electrode active material layer can be arranged on one surface of the positive electrode current collector along the thickness direction of itself, or on two surfaces of the positive electrode current collector along the thickness direction of itself. The "surface" here can be the entire area of ​​the positive electrode current collector or a partial area of ​​the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the thickness of the positive electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided positive electrode active material layer is 30μm to 120μm.

[0026] The inventors have discovered that while manganese in the positive electrode active material is beneficial for improving the safety performance of secondary batteries and reducing preparation costs, it is easily dissolved in the form of ions during the charge and discharge process, affecting the cycle performance and thermal safety performance of the electrochemical device. The positive electrode active material contains the above-mentioned content of metal element A and the compound of formula I in the electrolyte. The synergistic effect can greatly improve the interfacial stability of the positive and negative electrodes in the electrochemical device, thereby improving the cycle performance, thermal stability and safety performance of the electrochemical device. The specific principle is as follows: When the positive electrode is delithiated, Metal A can occupy the lithium sites, preventing manganese migration and negative electrode distortion. Furthermore, the compound of Formula I contains carbonyl groups and double bonds, forming a stable SEI film at the positive electrode during the formation process. This helps Metal A stabilize the positive electrode structure and prevents manganese from dissolving. This reduced manganese dissolution not only stabilizes the positive electrode interface but also minimizes damage to the negative electrode interface of the electrochemical device, significantly improving the cycling performance and thermal safety of the entire electrochemical device.

[0027] Specifically, in some embodiments of the present application, the compound of formula I includes at least one of the following compounds: .

[0028] In some embodiments of the present application, in order to further improve the cycle performance and thermal safety performance of the electrochemical device. Based on the total mass of the electrolyte, the mass content of the compound of formula I is y%, 0.01≤y / x≤10000, preferably 0.2≤y / x≤1000, and further 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 consisting 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 consisting of any two of the above values.

[0029] In some embodiments of the present application, the electrolyte further includes a cyclic carbonate compound. The mass content of the cyclic carbonate compound is f%, 5≤f≤50, and preferably 0.0025≤y / f≤1, based on the total mass of the electrolyte. This can further improve the interfacial properties of the electrochemical device, thereby further enhancing the cycling 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.

[0030] In some embodiments of the present application, in order to further improve the cycle performance and thermal safety performance of the electrochemical device, the electrolyte further includes a sulfur-oxygen double bond compound, and the mass content of the sulfur-oxygen double bond compound is g%, g≤5 based on the total mass of the electrolyte. The sulfur-oxygen double bond compound includes a compound of formula II:

[0031] Formula II Among them, A 11 The compound is selected from any one of C1-C4 alkylene groups substituted or unsubstituted with Ry, C2-C4 alkenylene groups substituted or unsubstituted with Ry, and C1-C6 chain heteroalkylene groups substituted or unsubstituted with Ry, wherein the number of heteroatoms in the chain heteroalkylene group is 1-5, and the heteroatoms in the chain heteroalkylene group are selected from at least one of oxygen atoms, nitrogen atoms, phosphorus atoms, and sulfur atoms. When substituted, the substituents Ry are each independently selected from any one of halogen atoms, C1-C3 alkyl groups, and C2-C4 alkenyl groups. Specifically, the sulfur-oxygen double bond-containing compound is selected from at least one of methanedisulfonic acid methylene ester, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, ethylene sulfate, 1,3-propanedisulfonic anhydride, 2-butane sultone, and 1,3-propylene glycol cyclic sulfate.

[0032] In the positive electrode of the present 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 the above-mentioned types of materials are doped with metal element A. In some preferred embodiments of the present application, in order to further improve the cycle performance and safety performance of the electrochemical device, the metal element A doped with the positive electrode active material includes Ti and / or Cr; based on the total mass of the positive electrode active material, the mass content of Ti is X Ti %, the mass content of Cr 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. Since the bond energy of Ti-O bond is higher than that of Cr-O bond and its stability is stronger, the performance is better when the Ti content is high, and the safety performance of electrochemical device at high temperature is better.

[0033] The positive electrode active material layer of the present application also includes a conductive agent and a binder. There are no particular limitations on the conductive agent and binder in the positive electrode active material layer, as long as they can achieve the objectives of the present 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, a metal material, or a conductive polymer. The conductive carbon black may include, but is not limited to, Super P, acetylene black, or Ketjen Black. The carbon nanotubes may include, but is not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCFs) and / or nanocarbon fibers. The metal material may include, but is not limited to, metal powder and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The 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, polyamideimide, polyvinylidene fluoride, polystyrene butadiene copolymer (styrene butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, or potassium hydroxymethyl cellulose. The present application does not particularly limit the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode active material layer. Persons skilled in the art may select the binder according to actual needs, as long as the objectives of the present application can be achieved.

[0034] The present application has no particular restrictions on the thickness and material of the positive electrode current collector, as long as the purpose of the present 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 can include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0035] 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. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and binder in the conductive layer, which may be at least one of the above-mentioned conductive agent and the above-mentioned binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0036] In the present application, the electrochemical device also includes a negative electrode, which includes a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode active material layer arranged on at least one surface of the negative electrode current collector" means that the negative electrode active material layer can be arranged on one surface of the negative electrode current collector along the thickness direction of itself, or on two surfaces of the negative electrode current collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or a composite current collector, etc.

[0037] The negative electrode active material layer of the present application includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate Li4Ti5O 12 , Li-Al alloy or metallic lithium, etc. The negative electrode active material layer of the present application also includes a binder. The present application has no special restrictions on the binder in the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the binder can be at least one of the above-mentioned binders. The negative electrode active material layer of the present application also includes a conductive agent. The present application has no special restrictions on the conductive agent in the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent can be at least one of the above-mentioned conductive agents. The present application has no special restrictions on the mass ratio of the negative electrode active material, the binder and the 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 the present application can be achieved.

[0038] The present application does not particularly limit the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 5 μm to 16 μm. The present application does not particularly limit the thickness of the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the single-sided negative electrode active material layer is 30 μm to 120 μm.

[0039] 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. The present application has no particular restrictions 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. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, and it can be at least one of the above-mentioned conductive agent and the above-mentioned binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the thickness of the conductive layer, as long as the purpose of the present application can be achieved. For example, the thickness of the conductive layer is 1μm to 10μm.

[0040] In the present application, the electrochemical device also includes a diaphragm, which is used to separate the positive electrode and the negative electrode, prevent internal short circuits in the electrochemical device, allow electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process. This application does not particularly limit the diaphragm, as long as it can achieve the purpose of this application. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of diaphragm may include at least one of woven membranes, non-woven membranes, microporous membranes, composite membranes, rolled membranes or spun membranes.

[0041] In the present application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a non-woven fabric or a composite film having 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 film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic material. For example, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on the above-mentioned inorganic particles, and for example, it may include at least one of aluminum oxide, 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. The present application has no particular restrictions on the above-mentioned binder, and for example, it may be at least one of the aforementioned binders. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0042] The electrochemical device of the present application also includes a packaging bag for containing the positive electrode, separator, negative electrode, and electrolyte, as well as other components of the electrochemical device known in the art. This application does not limit these other components. This application does not specifically limit the packaging bag and can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0043] This application does not specifically limit the type of electrochemical device; it may include any device that undergoes an electrochemical reaction. For purposes of this application, electrochemical devices may include, but are 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).

[0044] The preparation process of the electrochemical device of the present application is well known to those skilled in the art and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: stacking the positive electrode, separator and negative electrode in order, and winding, folding and other operations 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 order, 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, guide plates, etc. may also be placed in the packaging bag as needed to prevent pressure rise and overcharging and discharging inside the electrochemical device.

[0045] The second aspect of the present application provides an electronic device, which includes the electrochemical device according to any one of the aforementioned embodiments. Therefore, the electronic device provided by the present application has good performance.

[0046] The present application does not particularly limit the type of electronic device, and the electronic device may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0047] Example Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are by mass.

[0048] Test methods and equipment: Cyclic performance test: The cycling performance of the electrochemical device was evaluated by the capacity retention rate after 1000 cycles at 25°C. A greater capacity retention rate after 1000 cycles at 25°C indicates better cycling performance of the electrochemical device.

[0049] The electrochemical device was placed in a 25°C thermostat 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, then charged at a constant voltage of 0.05C at 4.2V, allowed to stand for 5 minutes, and then discharged at a constant current of 0.2C to 2.8V, allowed to stand for 5 minutes. The initial discharge capacity (C0) of the electrochemical device was measured. The device was then charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 0.05C at 4.2V, allowed to stand for 5 minutes, and then discharged at a constant current of 1C to 2.8V, allowed to stand for 5 minutes. This constituted one charge-discharge cycle. The above charge / discharge cycle was repeated 1000 times, and the discharge capacity (C1) of the electrochemical device after 1000 cycles was measured.

[0050] The capacity retention rate after 1000 cycles at 25°C = C1 / C0×100%. The higher the capacity retention rate after 1000 cycles at 25°C, the better the cycle performance of the electrochemical device. Specific data on the high-temperature cycle performance of the electrochemical devices in the embodiments and comparative examples are shown in Tables 1 to 3.

[0051] Thermal safety performance test: Hot Box Performance Test: The electrochemical device was discharged at a constant current of 0.2C to 2.8V at 25°C, then charged at a constant current of 0.5C to 4.2V. At 4.2V, it was charged to a constant voltage of 0.05C. The device was then placed in a high-temperature furnace at 130°C, 132°C, and 134°C for one hour. After one hour, the electrochemical device was observed to see if it ignited. If it did not ignite, it was considered a pass. The pass rate was recorded as N / 10, meaning that N out of 10 electrochemical devices passed the test. Specific data from the thermal safety performance tests of the electrochemical devices in each Example and Comparative Example are shown in Tables 1-3.

[0052] Hot box performance judgment criteria: Under different temperatures, the higher the temperature without ignition, the better the hot box performance and thermal safety performance; under the same temperature, the higher the pass rate, the better the hot box performance and thermal safety performance. For example, at 132°C, 5 / 10 test results are better than at 132°C, 3 / 10 test results, and at 132°C, 3 / 10 test results are better than at 130°C, 5 / 10 test results.

[0053] Example 1-1 <Preparation of Negative Electrode> The negative electrode active materials, artificial graphite, SBR, and CMC-Na, were mixed in a mass ratio of 98.5:1:0.5. Deionized water was then added as a solvent to form a negative electrode slurry with a solid content of 54 wt%. The mixture was then stirred evenly in a vacuum mixer to obtain a negative electrode slurry. The conductive agent, Super P, and the binder, SBR, were mixed in a mass ratio of 9:1. Deionized water was then added as a solvent to prepare a conductive layer slurry with a solid content of 10 wt%. The conductive layer slurry was evenly coated on one surface of an 8 μm thick copper foil, a negative electrode current collector, and dried at 85°C to form a 2 μm thick conductive layer on one surface of the copper foil. The negative electrode slurry was then coated on the surface of the conductive layer facing away from the copper foil and dried at 85°C to form a 100 μm thick negative electrode active material layer on the surface facing away from the copper foil, resulting in a negative electrode coated on one side with both the conductive layer and the negative electrode active material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode coated on both sides with both the conductive layer and the negative electrode active material layer. After coating, the negative electrode was cold pressed and cut into 76mm×851mm size for later use. The compaction density of the negative electrode active material layer after cold pressing was 1.60g / cm 3 .

[0054] <Preparation of Positive Electrode> The positive electrode active material lithium manganese oxide, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75wt%. After stirring evenly in a vacuum mixer, a positive electrode slurry was obtained. The positive electrode slurry was evenly coated on one surface of a 10μm thick positive electrode current collector aluminum foil and dried at 85°C to obtain a positive electrode with a single-sided positive electrode active material layer coated with a coating thickness of 110μm. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode with a double-sided positive electrode active material layer coated. After coating, the positive electrode was cold pressed and cut into a size of 74mm×867mm for use. The compaction density of the positive electrode active material layer after cold pressing was 2.70g / cm 3The lithium manganate contains Ti element, and the mass content of Ti element is 0.001% based on the total mass of the positive electrode active material. The details can be seen in Table 1.

[0055] <Preparation of Electrolyte> In an argon atmosphere glove box with a water content of less than 10 ppm, a base solvent was prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 ratio by weight. Then, lithium hexafluorophosphate (LiPF6) and the compound of Formula I were added and mixed thoroughly to form an electrolyte. The LiPF6 content was 12.5% ​​by weight based on the total weight of the electrolyte. The content of the compound of Formula I is shown in Table 1. The remainder was the base solvent.

[0056] In addition, the compounds indicated by the codes in the table can be found in the above content of this article for details.

[0057] <Diaphragm> A polyethylene (PE) porous membrane with a thickness of 5 μm was used.

[0058] <Preparation of Electrochemical Device> The prepared positive electrode, separator, negative electrode, and separator were stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes were then wound to form an electrode assembly. After welding the tabs, the electrode assembly was placed in an aluminum-plastic film bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte was then injected. The electrochemical device was then vacuum packaged, allowed to stand, formed (charged at a constant current of 0.02C to 3.5V, then at a constant current of 0.1C to 3.9V), shaped, and tested for capacity.

[0059] Example 1-2 to Example 1-3 The process was the same as Example 1-1 except that the content of the compound of formula I in the preparation of the electrolyte was adjusted according to Table 1. When the content of the compound of formula I was changed, the mass content of the lithium salt remained unchanged.

[0060] Example 1-4 to Example 1-12 Except for adjusting the content of the metal element Ti in the lithium manganate in <Preparation of Positive Electrode> according to Table 1, the rest is the same as Example 1-3.

[0061] Example 1-13 to Example 1-14 The process was the same as in Example 1-12 except that the content of the compound of formula I in the preparation of the electrolyte was adjusted according to Table 1. When the content of the compound of formula I was changed, the mass content of the lithium salt remained unchanged.

[0062] Example 1-15 to Example 1-22 The process was the same as in Example 1-9 except that the content of the compound of formula I in the preparation of the electrolyte was adjusted according to Table 1. When the content of the compound of formula I was changed, the mass content of the lithium salt remained unchanged.

[0063] Example 1-23 to Example 1-27 Except for adjusting the relevant preparation parameters in <Preparation of Electrolyte> according to Table 1, the rest is the same as Example 1-9.

[0064] Example 1-28 to Example 1-31 Except for adjusting the relevant preparation parameters in <Preparation of Positive Electrode> according to Table 1, the rest is the same as Example 1-9.

[0065] Example 1-32 to Example 1-44 Except for adjusting the type and content of the metal element A in the lithium manganese oxide in <Preparation of the positive electrode> and the relevant preparation parameters in <Preparation of the electrolyte> according to Table 1, the rest is the same as Example 1-9.

[0066] Comparative Examples 1 to 7 Except for adjusting the type and content of the metal element A in the lithium manganese oxide in <Preparation of the positive electrode> and the relevant preparation parameters in <Preparation of the electrolyte> according to Table 1, the rest is the same as Example 1-9.

[0067] Table 1

[0068] Note: In the "Metal Element" column, the number in the brackets of the element represents the mass content of the element based on the total mass of the positive electrode active material, in %.

[0069] Example 2-1 to Example 2-10 Except for preparing the electrolyte according to the following method, the rest is the same as Example 1-9: <Preparation of Electrolyte> In an argon atmosphere glove box with a water content of less than 10 ppm, EC and DEC were mixed, and then LiPF6 and the compound of Formula I were added and mixed thoroughly to form an electrolyte. The mass content of LiPF6, based on the total mass of the electrolyte, was 12.5%. The mass contents of the compound of Formula I and DEC are shown in Table 1, with the balance being EC.

[0070] Example 2-11 Except for adjusting the relevant preparation parameters in <Preparation of Electrolyte> according to Table 2, the rest is the same as Example 2-1.

[0071] Example 2-12 Except for adjusting the relevant preparation parameters in <Preparation of Electrolyte> according to Table 2, the rest is the same as Example 2-10.

[0072] Example 2-13 to Example 2-14 Except for adjusting the relevant preparation parameters in <Preparation of Electrolyte> according to Table 2, the rest is the same as Example 2-3.

[0073] Table 2

[0074] Note: In the column “Metal elements and their content x”, the numbers in brackets represent the mass content of the element based on the total mass of the positive electrode active material, in %.

[0075] Example 3-1 to Example 3-5 The process was the same as in Example 1-9, except that a sulfur-oxygen double bond compound was further added in the preparation of the electrolyte and relevant preparation parameters were adjusted according to Table 3. When the mass content of the sulfur-oxygen double bond compound was changed, the content of the lithium salt LiPF6 remained unchanged.

[0076] Example 3-6 to Example 3-12 Except for adjusting the relevant preparation parameters in <Preparation of Electrolyte> according to Table 3, the rest is the same as Example 3-3.

[0077] Table 3

[0078] Note: In the column “Metal elements and their content x”, the numbers in brackets represent the mass content of the element based on the total mass of the positive electrode active material, in %.

[0079] Referring to Table 1, it can be seen from the examples and comparative examples that by controlling the content of the compound of formula I in the electrolyte and controlling the type and content of the 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.

[0080] Referring to Table 2, it can be seen from Examples 2-1 to 2-10, 2-13 to 2-14, and 1-9 that adding 5% to 50% of a cyclic carbonate compound can improve the cycle performance and thermal safety performance of the electrochemical device.

[0081] Referring to Table 3, it can be seen from Examples 3-1 to 3-12 and 1-9 that adding 1% to 5% of a sulfur-oxygen double bond-containing compound can further improve the cycle performance and thermal safety performance of the electrochemical device.

[0082] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such process, method or article.

[0083] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0084] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An electrochemical device, characterized in that It comprises a positive electrode and an electrolyte, wherein the electrolyte comprises a compound of formula I: Formula I Among them, R 11 is selected from any one of a hydrogen atom, a halogen atom, a C1-C6 alkyl group which is substituted or unsubstituted by Rx, a C2-C6 alkenyl group which is substituted or unsubstituted by Rx, a C2-C6 alkynyl group which is substituted or unsubstituted by Rx, and a C1-C6 alkoxy group which is substituted or unsubstituted by Rx, wherein R 12 Any one selected from C1~C6 alkyl substituted or unsubstituted by Rx, C2~C6 alkenyl substituted or unsubstituted by Rx, C2~C6 alkynyl substituted or unsubstituted by Rx, C1~C6 alkoxy substituted or unsubstituted by Rx, and Rx is selected from halogen atoms, C2~C5 cycloalkyl or C6~C 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, wherein the positive electrode active material layer contains a positive electrode active material, wherein the positive electrode active material includes manganese and a metal element A, wherein 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 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, wherein The compound of formula I includes at least one of the following compounds: 。 3. The electrochemical device according to claim 1, wherein The electrochemical device satisfies at least one of the following conditions: （1）0.08≤y≤15； (2) The metal element A includes the titanium element. Based on the total mass of the positive electrode active material, the mass content of the titanium element is X 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 contents of the titanium element and the chromium element are X Ti % and X Cr %,X Ti >X Cr ; (5) 0.2≤y / x≤1000.

4. The electrochemical device according to claim 1, wherein 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%, and 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 butylene carbonate.

7. The electrochemical device according to any one of claims 1 to 6, characterized in that The electrolyte further comprises a sulfur-oxygen double bond compound, wherein the sulfur-oxygen double bond compound comprises a compound of formula II: Formula II Among them, A 11 any one selected from C1-C4 alkylene substituted or unsubstituted by Ry, C2-C4 alkenylene substituted or unsubstituted by Ry, and C1-C6 chain heteroalkylene substituted or unsubstituted by Ry, wherein the number of heteroatoms in the chain heteroalkylene is 1-5, and the heteroatoms in the chain heteroalkylene are selected from at least one of oxygen atoms, nitrogen atoms, phosphorus atoms, and sulfur atoms. When substituted, the substituents Ry are each independently selected from any one of a halogen atom, a C1-C3 alkyl group, and a C2-C4 alkenyl group.

8. The electrochemical device according to claim 7, characterized in that The sulfur-oxygen double bond compound is selected from at least one of methanedisulfonic acid methylene ester, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, ethylene sulfate, 1,3-propanedisulfonic anhydride, 2,4-butane sultone or 1,3-propylene glycol cyclic sulfate; based on the total mass of the electrolyte, the mass content of the sulfur-oxygen double bond compound is g%, g≤5.

9. The electrochemical device according to any one of claims 1 to 6, wherein 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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