Electrochemical device and electronic apparatus

Abstract

The invention discloses an electrochemical device and electronic equipment. The electrochemical device comprises a positive plate and electrolyte, the electrolyte comprises an additive A, and the additive A is an organic additive containing lone pair electrons; the positive plate comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises an element M; the M element comprises at least one of Cu and Zn; on the basis of the positive electrode active material, the mass percentage content of the M element is tppm, and t is greater than or equal to 1 and less than or equal to 500. The organic additive containing lone pair electrons in the electrolyte can enter an empty orbit inside the M element in the positive electrode active material, can be complexed with the M element to form a complex, and covers the surfaces of metal particles containing the M element to form a metal particle protection film, so that the M element cannot be dissolved into the electrolyte in the charging and discharging process, and the service life of the electrolyte is prolonged. The M element is prevented from forming dendritic crystals on the surface of the negative electrode and puncturing an isolating membrane to cause short circuit.

Description

Electrochemical devices and electronic devices Technical Field

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

[0002] Lithium-ion batteries have attracted widespread attention due to their high energy density, low maintenance, relatively low self-discharge, long cycle life, lack of memory effect, stable operating voltage, and environmental friendliness. They are widely used in portable electronic devices (including mobile phones, laptops, cameras, and other electronic products), power tools, and electric vehicles. However, with the rapid development of technology and the further expansion of market demand, recycling lithium-ion battery materials can effectively save energy, significantly reduce the material cost of lithium-ion battery production, and further address the environmental pollution problem caused by discarded lithium-ion batteries after use. Therefore, how to recycle the lost lithium-ion battery materials generated during the production process and the materials of used lithium-ion batteries has become a technical problem that needs to be solved urgently.

[0003] Summary of the Invention

[0004] To solve the above problems, embodiments of the present application provide an electrochemical device and an electronic device.

[0005] In a first aspect, the present application provides an electrochemical device comprising a positive electrode sheet and an electrolyte; the electrolyte comprises an additive A, which is an organic additive containing lone pair electrons; the positive electrode sheet comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises an M element; the M element comprises at least one of Cu and Zn; based on the positive electrode active material, the mass percentage content of the M element is t ppm, and t satisfies 1≤t≤500.

[0006] In some exemplary embodiments, the additive A includes at least one of a N-containing heterocyclic compound, a phosphite compound, and a nitrile compound.

[0007] In some exemplary embodiments, the N-containing heterocyclic compound includes at least one of a pyridine compound, quinoxaline, isoquinoline, phenolazine, 1,5-naphthyridine, pyrazine, and pyridazine;

[0008] The pyridine compound includes at least one of pyridine, 2-fluoropyridine, 3-fluoropyridine, 4-fluoropyridine, 2,3-difluoropyridine, 2,4-difluoropyridine, 2,5-difluoropyridine, 3,4-difluoropyridine, 2,3,4-trifluoropyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, N-methylpyrrole, 2,6-lutidine, 4-ethylpyridine, 3,5-lutidine, 4,4'-bipyridine, 4-ethynylpyridine, 4-phenylpyridine, and pyrido[3,4-B]pyrazine;

[0009] The phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, triphenyl phosphite, tripropylene phosphite, tripropynyl phosphite, tris(trimethylsilyl)phosphite, dimethyl ethyl phosphite, diethyl cyanomethyl phosphate, and diethyl cyanoethyl phosphate;

[0010] The nitrile compound includes at least one of acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, heptanenitrile, octanonitrile, isobutyronitrile, allyl nitrile, 6-heptynenitrile, cyclohexanecarbonitrile, 2-cyclopentylacetonitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, methylglutaronitrile, 2-propylvaleronitrile, 1,2-bis(cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,3,6-hexanitrile, 1,3,5-cyclohexanetrinitrile, 1,3,5-benzenetrinitrile, 1,2,3-tris(2-cyanoxy)propane, and 3-methoxypropionitrile.

[0011] In some exemplary embodiments, t satisfies 1≤t≤200.

[0012] In some exemplary embodiments, the positive electrode active material includes a lithium iron phosphate compound having an olivine crystal structure. Based on the positive electrode active material, the mass percentage of Fe element in the lithium iron phosphate compound is g%, and g and t satisfy the relationship: 0.025≤t / g≤16.7.

[0013] In some exemplary embodiments, 0.025≤t / g≤6.

[0014] In some exemplary embodiments, based on the positive electrode active material, the mass percentage of Fe element in the lithium iron phosphate compound is g%, and g satisfies 20≤g≤40.

[0015] In some exemplary embodiments, based on the mass of the electrolyte, the mass percentage of the additive A is a%, and a and t satisfy the relationship: 0.5≤t / a≤1000.

[0016] In some exemplary embodiments, 25≤t / a≤100.

[0017] In some exemplary embodiments, based on the mass of the electrolyte, the mass percentage of the additive A is a%, and a satisfies 0.1≤a≤5.

[0018] In some exemplary embodiments, 0.5≤a≤2.2.

[0019] In some exemplary embodiments, the positive electrode sheet further includes a positive electrode current collector, and the positive electrode material layer is provided on the surface of the positive electrode current collector;

[0020] The coating weight of the positive electrode material layer is zg / 1540.25mm 2 , z satisfies 0.22≤z≤0.45.

[0021] In some exemplary embodiments, z and t satisfy the relationship: 220≤t / z≤480.

[0022] In some exemplary embodiments, the electrolyte further includes a non-aqueous organic solvent, wherein the non-aqueous organic solvent includes at least one of a chain carbonate compound and a chain carboxylate compound;

[0023] At 25° C., the viscosity of the chain carbonate compound is ≤0.7 mPa·s, and the viscosity of the chain carboxylate compound is ≤0.7 mPa·s; and

[0024] Based on the mass of the electrolyte, the percentage of the sum of the mass of the chain carbonate compound and the chain carboxylic acid ester compound is b%, and b and z satisfy the relationship: 30≤b / z≤300.

[0025] In some exemplary embodiments, 50≤b / z≤182.

[0026] In some exemplary embodiments, the electrolyte further includes a non-aqueous organic solvent, and the non-aqueous organic solvent includes at least one of a chain carbonate compound and a chain carboxylate compound; based on the mass of the electrolyte, the percentage content of the sum of the mass of the chain carbonate compound and the chain carboxylate compound is b%, and b satisfies 10≤b≤70.

[0027] In some exemplary embodiments, 25≤b≤55.

[0028] In a second aspect, the present application provides an electronic device comprising the electrochemical device as described above.

[0029] Based on the electrochemical devices and electronic devices of the embodiments of the present application, by adding an organic additive containing lone pair electrons to the electrolyte, the organic additive containing lone pair electrons can enter the empty orbit of the M element, and the organic additive containing lone pair electrons and the M element can produce a complex to form a complex covering the surface of the metal particles containing the M element, forming a metal particle protective film, so that the M element cannot dissolve into the electrolyte during the charging and discharging process, and further the M element cannot obtain electrons and precipitate at the negative electrode, thereby preventing the M element from piercing the isolation membrane and causing a short circuit when the negative electrode dendrite grows. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0031] The inventors have discovered that the positive electrode material layer of the recycled electrochemical device often contains a large amount of metal particles, such as copper, zinc and other metal particles. These metal particles include metal particles with low oxidation potential. The metal particles with low oxidation potential are present in the positive electrode material layer. During the charge and discharge process of the electrochemical device, it is easy to cause oxidative dissolution, electrons are obtained on the electrode to cause dendrite growth, and short circuit points are generated in the electrochemical device, etc., affecting the charge and discharge performance and safety performance of the electrochemical device. Based on this, the present application provides an electrochemical device that recycles the materials of the positive electrode material layer of the recycled electrochemical device and introduces an organic additive containing lone pair electrons into the electrolyte of the electrochemical device. The addition of the organic additive containing lone pair electrons can significantly improve the cycle performance, battery cell K value, storage performance, hot box and other performance of the electrochemical device.

[0032] Specifically, the electrochemical device of the present application includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet. The electrolyte includes an additive A, which is an organic additive containing lone pair electrons. The positive electrode sheet includes a positive electrode material layer, which includes a positive electrode active material. The positive electrode active material includes an element M, which includes at least one of Cu and Zn. The mass percentage of the element M is t ppm based on the positive electrode active material, where t satisfies 1≤t≤500.

[0033] Among them, the M element is a metal impurity that cannot be screened out when the positive electrode material layer of the electrochemical device is recycled. The M element exists in the positive electrode material layer of the positive electrode sheet in the form of metal particles. The oxidation potential of the M element during the charging process is lower than the upper limit voltage of the electrochemical device, so that it is easy to oxidize on the electrode during the charging process to generate metal ions that dissolve in the electrolyte. Then, as the electrolyte migrates to the negative electrode, electrons are obtained and metal dendrites are precipitated. The metal dendrites continue to grow during the cycle and may pierce the isolation membrane, causing a short circuit. The present application adds an organic additive containing lone pair electrons to the electrolyte. The organic additive containing lone pair electrons can enter the empty orbit of the M element. The organic additive containing lone pair electrons and the M element can produce a complex to form a complex covering the surface of the metal particles containing the M element, forming a metal particle protective film, so that the M element cannot dissolve into the electrolyte during the charging and discharging process, and then the M element cannot obtain electrons and precipitate on the negative electrode, thereby preventing the M element from growing dendrites on the negative electrode and piercing the isolation membrane to cause a short circuit.

[0034] In some exemplary embodiments, the mass percentage of the element M can be 1 ppm, 10 ppm, 35 ppm, 50 ppm, 70 ppm, 100 ppm, 150 ppm, 200 ppm, 255 ppm, 345 ppm, 425 ppm, 460 ppm, 500 ppm, or any value within a range consisting of any two of the foregoing values. Preferably, t satisfies 1 ≤ t ≤ 200, in which case the electrochemical device has better cycling performance and storage performance.

[0035] In some exemplary embodiments, the additive A includes at least one of a N-containing heterocyclic compound, a pyridine compound, a phosphite compound, and a nitrile compound.

[0036] The N-containing heterocyclic compound includes at least one of quinoxaline, isoquinoline, phenolazine, 1,5-naphthyridine, pyrazine, and pyridazine.

[0037] The pyridine compound includes at least one of pyridine, 2-fluoropyridine, 3-fluoropyridine, 4-fluoropyridine, 2,3-difluoropyridine, 2,4-difluoropyridine, 2,5-difluoropyridine, 3,4-difluoropyridine, 2,3,4-trifluoropyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, N-methylpyrrole, 2,6-lutidine, 4-ethylpyridine, 3,5-lutidine, 4,4'-bipyridine, 4-ethynylpyridine, 4-phenylpyridine, and pyrido[3,4-B]pyrazine.

[0038] The phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, triphenyl phosphite, tripropylene phosphite, tripropynyl phosphite, tris(trimethylsilyl)phosphite, dimethyl ethyl phosphite, diethyl cyanomethyl phosphate, and diethyl cyanoethyl phosphate.

[0039] The nitrile compound includes at least one of acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, heptanenitrile, octanonitrile, isobutyronitrile, allyl nitrile, 6-heptynenitrile, cyclohexanecarbonitrile, 2-cyclopentylacetonitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, methylglutaronitrile, 2-propylvaleronitrile, 1,2-bis(cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,3,6-hexanetrile, 1,3,5-cyclohexanetrinitrile, 1,3,5-benzenetrinitrile, 1,2,3-tris(2-cyanoxy)propane, and 3-methoxypropionitrile.

[0040] In some exemplary embodiments, the positive electrode active material may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese oxide.

[0041] In some exemplary embodiments, the positive electrode active material includes a lithium iron phosphate compound having an olivine crystal structure. Based on the positive electrode active material, the mass percentage of Fe element in the lithium iron phosphate compound is g%, wherein g ranges from 20 to 40, and g and t satisfy the relationship: 0.025≤t / g≤16.7, which can effectively improve the cycle performance and K value performance of the electrochemical device.

[0042] In some exemplary embodiments, t / g can be 0.025, 0.05, 0.15, 0.5, 3.6, 6.8, 10.3, 14.5, 15.3, 16.7, or any value within a range formed by any two of the foregoing values. Preferably, g and t satisfy the relationship: 0.025 ≤ t / g ≤ 6, in which case the electrochemical device has better cycling performance and K value performance.

[0043] In some exemplary embodiments, based on the mass of the electrolyte, the mass percentage of additive A is a%, and a and t satisfy the relationship: 0.5≤t / a≤1000, which can improve the cycle retention rate and storage thickness expansion rate of the electrochemical device.

[0044] In some exemplary embodiments, t / a can be 0.5, 5, 13, 30, 120, 480, 760, 1000, or any value within a range formed by any two of the foregoing values. Preferably, a and t satisfy the relationship: 25≤t / a≤100, in which case the electrochemical device has better cycling performance and storage performance.

[0045] In some exemplary embodiments, based on the mass of the electrolyte, the mass percentage of additive A is a%, and a satisfies 0.1≤a≤5. When the content of additive A is within this range, it can ensure that the electrolyte has a lower impedance and has a better complexation effect with element M, thereby inhibiting the dissolution of element M from the positive electrode material layer and improving the cycle performance and storage performance of the electrochemical device.

[0046] In some exemplary embodiments, a may be 0.1, 0.15, 0.32, 0.5, 1.4, 2.1, 3.6, 4.8, 5, or any value within a range formed by any two of the foregoing values. Preferably, 0.5 ≤ a ≤ 2.2, in which case the electrochemical device has better cycle performance and storage performance.

[0047] In some exemplary embodiments, the positive electrode sheet further includes a positive electrode current collector, a positive electrode material layer is provided on the surface of the positive electrode current collector, and the coating weight of the positive electrode material layer is zg / 1540.25mm 2 , z satisfies 0.22≤z≤0.45. Within the above range, it is easy to control the thickness of the positive electrode material layer and prevent the metal particles including the M element from being too large to squeeze the positive electrode collector and pierce the separator.

[0048] In some exemplary embodiments, z can be 0.22, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any value within a range formed by any two of the above values. Preferably, z satisfies 0.29≤z≤0.36, in which case the electrochemical device has better cycle performance and hot box safety performance.

[0049] In some exemplary embodiments, z and t satisfy the relationship: 220≤t / z≤480. Within the above range, the positive electrode material layer has a verified coating thickness and can prevent metal particles of the M element from piercing the separator.

[0050] In some exemplary embodiments, t / z can be 220, 256, 287, 306, 412, 468, 480, or any value within a range encompassed by any two of the foregoing values. Preferably, z and t satisfy the relationship: 260 ≤ t / z ≤ 360, thereby providing the electrochemical device with improved cycling performance and hot box safety.

[0051] In some exemplary embodiments, the electrolyte further includes a non-aqueous organic solvent, and the non-aqueous organic solvent includes at least one of a chain carbonate compound and a chain carboxylate compound. For example, the chain carbonate compound includes ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2- trifluoro-2-methylethylene ester or trifluoromethylethylene carbonate, etc.; chain carboxylic acid ester compounds include methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerolactone or caprolactone, etc.

[0052] At 25°C, the viscosity of the chain carbonate compound is ≤0.7 mPa·s, and the viscosity of the chain carboxylate compound is ≤0.7 mPa·s. Based on the mass of the electrolyte, the sum of the mass of the chain carbonate compound and the chain carboxylate compound is b%, where b ranges from 10 to 70, and b and z satisfy the relationship: 32≤b / z≤300. This ensures good wettability of the electrolyte at the positive electrode, resulting in excellent cycling performance and rate capability of the electrochemical device.

[0053] In some exemplary embodiments, b / z can be 32, 56, 87, 176, 212, 268, 200, 300, or any value within a range consisting of any two of the foregoing values. In some exemplary embodiments, b% can be 10%, 15%, 30%, 45%, 60%, 70%, or any value within a range consisting of any two of the foregoing values. Preferably, b and z satisfy the relationship: 50 ≤ b / z ≤ 182, and b% ranges from 25% to 55%, resulting in an electrochemical device having improved cycling performance and rate capability.

[0054] The negative electrode sheet also includes a negative electrode current collector, and the negative electrode material layer is arranged on the surface of the negative electrode current collector. Since the negative electrode material layer and the positive electrode material layer both have thickness, poor wetting may occur when the electrolyte contacts the positive electrode material layer and the negative electrode material layer respectively, especially when the electrolyte is consumed during the cycle and cannot be replenished to the interior of the electrode material in time. By using chain carbonates and chain carboxylates with viscosities lower than 0.7 MPa·s, the overall viscosity of the electrolyte can be reduced, the conductivity of the electrolyte can be increased, and the electrolyte can be easily infiltrated into the positive electrode material layer and the negative electrode material layer in time, so that the ion transmission at the positive electrode material layer and the negative electrode material layer is effectively guaranteed.

[0055] The non-aqueous organic solvent also includes at least one of an ether compound or other organic solvents. The ether compound may include but is not limited to at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide or acetonitrile. The specific selection can be based on actual needs.

[0056] The electrolyte further includes a lithium salt, and the lithium salt and additive A are dissolved in a non-aqueous organic solvent. The present embodiment of the present application does not particularly limit the lithium salt. The lithium salt can use any lithium salt known in the art, as long as it can achieve the purpose of the present application. For example, the lithium salt can include at least one of LiTFSI, LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, or LiPO2F2.

[0057] The positive electrode active material layer also includes a positive electrode conductor and a positive electrode binder. The present application embodiment has no particular restrictions on the positive electrode conductor, as long as the purpose of the present application can be achieved. For example, the positive electrode conductor can include at least one of conductive carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers. The positive electrode binder is used to improve the bonding performance between the materials in the positive electrode material layer, and to improve the bonding performance between the positive electrode material layer and the positive electrode current collector. The present application embodiment has no particular restrictions on the positive electrode binder, as long as the purpose of the present application can be achieved. For example, the positive electrode binder includes at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin and nylon.

[0058] The positive electrode current collector of the present application is not particularly limited, and the positive electrode current collector can be any positive electrode current collector known in the art, such as aluminum foil, aluminum alloy foil or composite current collector.

[0059] The embodiments of the present application have no particular restrictions 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 at least one of lithium metal, lithium metal alloy, graphite, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0060] The negative electrode active material layer may further include a negative electrode conductor and / or a negative electrode binder. The embodiments of the present application have no particular restrictions on the negative electrode conductor, as long as the purpose of the present application can be achieved. For example, the negative electrode conductor may include at least one of carbon black, Super P, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers, or carbon nanowires. The embodiments of the present application have no particular restrictions on the negative electrode binder, as long as the purpose of the present application can be achieved. For example, the negative electrode binder may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyacrylate, polyacrylate, polyvinyl pyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0061] The embodiments of the present application have no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the negative electrode current collector may include at least one of copper foil, nickel foil, or a carbon-based current collector.

[0062] The isolation film of the embodiment of the present application includes a substrate layer and a surface treatment layer. The substrate layer may include a polyethylene (PE) film, a polypropylene (PP) film, a polyvinylidene fluoride film or a multilayer composite film thereof. The surface treatment layer is provided on the surface of the substrate layer, and the surface treatment layer includes at least one of an organic coating and an inorganic coating, the organic coating being selected from at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, and sodium carboxymethyl cellulose, and the inorganic coating being selected from at least one of SiO2, Al2O3, CaO, TiO2, ZnO2, MgO, ZrO2, and SnO2.

[0063] The electrochemical device also includes a positive electrode ear, a negative electrode ear, and an outer packaging. After the positive electrode sheet, separator, and negative electrode sheet are stacked in sequence or stacked on one side and wound, the positive electrode sheet is connected to the positive electrode ear and the negative electrode sheet is connected to the negative electrode ear to form an electrode assembly (battery cell). The electrode assembly is arranged in the internal space of the outer packaging, and the positive electrode ear and the negative electrode ear are led out from the internal space of the outer packaging to the external space of the outer packaging so that the positive electrode ear and the negative electrode ear are electrically connected to the external circuit. Then, the electrolyte is injected into the internal space of the outer packaging, and the outer packaging is sealed to obtain the electrochemical device. The outer packaging can be an aluminum-plastic film outer packaging. The outer packaging includes a rigid outer packaging or a flexible outer packaging. The material of the rigid outer packaging is, for example, metal. The material of the flexible outer packaging is, for example, a metal plastic film, such as an aluminum-plastic film, a steel-plastic film, etc.

[0064] The present application also provides an electronic device, which includes the electrochemical device described above. The electronic device of the present application includes, but is not limited to, a laptop computer, an input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, 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, a car, 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, an industrial and commercial energy storage battery, a household energy storage battery, and a lithium-ion capacitor. It is noted that, in addition to being applicable to the electronic devices listed above, the electrochemical device of the present application is also applicable to energy storage power stations, sea transport vehicles, and air transport vehicles. Air transport vehicles include air transport vehicles within the atmosphere and air transport vehicles outside the atmosphere.

[0065] The present application will be further described in detail below with reference to specific embodiments, taking a lithium-ion battery as an example.

[0066] 1. Lithium-ion battery performance test method

[0067] (1) Cycle test:

[0068] At 45°C, the lithium-ion battery was charged at 1C to 3.6V, then discharged at 1C to 2.5V. This cycle was repeated for 1500 cycles, and the capacity retention was recorded. The test was terminated if the capacity retention was less than 50%.

[0069] (2) K value test:

[0070] At 25°C, charge the lithium-ion battery at 0.5C for 32 minutes, then test the lithium-ion battery voltage OCV1. Leave it at 25°C for 48 hours, then test the lithium-ion battery voltage OCVB. The K value (mV / h) of the lithium-ion battery is (OCV1-OCVB) / 48. Test 50 cells in parallel and take the median as the recorded K value.

[0071] (3) 60℃ high temperature storage test process

[0072] The lithium-ion battery was charged at 0.5C constant current to 3.6V at 25°C, then charged at constant voltage to a current of 0.05C. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in a 60°C oven for 90 days, and the thickness at this time was monitored and recorded as d. The thickness expansion rate (%) of the lithium-ion battery after 90 days of storage at 60°C = (d-d0) / d0 × 100%. Testing was terminated if the thickness expansion rate exceeded 50%.

[0073] (4) Test method for rate temperature rise of lithium-ion batteries

[0074] At 25°C, discharge a lithium-ion battery at 0.5C to 2.5V, then charge it at 1C to 3.6V. Then, at a constant temperature of 25°C, discharge it at a rate of 6C. Monitor the surface temperature of the electrode assembly, and record the highest temperature during this process as t. Calculate the 6C rate temperature rise of the lithium-ion battery as t - 25°C.

[0075] (5) Hot box test process

[0076] Charge at 0.5C constant current to 3.6V, then charge at constant voltage to 0.05C at 3.6V, let stand at 25±5℃ for 60min, inspect the appearance and take photos, then increase the temperature at a rate of 5℃ / min±2℃ / min to 140℃±2℃ and maintain for 140min. After the test, inspect the appearance and take photos, monitor the voltage and temperature during the test, test 10 cells in parallel, and pass if there is no fire or smoke. Record the number of cells that pass.

[0077] (6) Viscosity test

[0078] Viscosity test: The electrolyte was placed in a constant temperature water bath at 25°C for at least 30 minutes. A viscometer (Brewfield, DV1MLV) was used with the ULA spindle. The test conditions were set as follows: a range of 20 cP, a speed at a torque range of 10% to 100%, and a test duration of 10 minutes.

[0079] 2. Preparation method of lithium-ion battery

[0080] 1. Preparation of electrolyte

[0081] In an argon atmosphere glove box with a water content of <10ppm, ethylene carbonate (abbreviated as EC) and diethyl carbonate (abbreviated as DEC) were mixed in a mass ratio of 4:6 to obtain a non-aqueous organic solvent, and then the fully dried lithium salt LiPF6 was dissolved in the above non-aqueous organic solvent at a mass percentage of 12.5% ​​to prepare the basic electrolyte in the embodiment.

[0082] Additive A is added to the above basic electrolyte to obtain an electrolyte.

[0083] 2. Preparation of positive electrode

[0084] The recovered positive electrode active material (lithium iron phosphate compound or lithium cobalt oxide with an olivine crystal structure), conductive carbon black, and binder polyvinylidene fluoride (abbreviated as PVDF) were thoroughly stirred and mixed in an appropriate amount of N-methylpyrrolidone (abbreviated as NMP) solvent at a weight ratio of 97.9:0.4:0.5:1.2 to form a uniform positive electrode slurry; the slurry was coated on the positive electrode current collector Al foil, dried, and cold pressed to obtain a positive electrode sheet with a positive electrode compaction density of 2.40 g / cm 2 Among them, the positive electrode active material of Example I-24 and Example I-25 is lithium cobalt oxide, and the positive electrode active material of the other examples is lithium iron phosphate.

[0085] 3. Preparation of isolation membrane

[0086] The substrate layer is a single-layer PE porous polymer film with a thickness of 5 microns and a porosity of 39%. A surface treatment layer is applied to the surface of the substrate layer. The surface treatment layer includes an inorganic coating and an organic coating. The inorganic coating is Al2O3, and the organic coating is polyvinylidene fluoride.

[0087] 4. Preparation of negative electrode sheet

[0088] The negative electrode active material graphite, the binder styrene-butadiene rubber (abbreviated as SBR), and the thickener sodium carboxymethyl cellulose (abbreviated as CMC) are fully stirred and mixed in an appropriate amount of deionized water in a weight ratio of 97.4:1.4:1.2 to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector Cu foil, dried, and cold pressed to obtain a negative electrode sheet. The compaction density of the negative electrode is 1.80g / cm3.

[0089] 5. Preparation of lithium-ion batteries

[0090] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide insulation. The cells are then wound to form a bare battery cell. The positive electrode sheet is connected to the positive tab, and the negative electrode sheet to the negative tab, forming an electrode assembly. The electrode assembly is then placed inside the aluminum-plastic film outer packaging. The positive and negative tabs are then led out of the inner space of the outer packaging to the outer space of the aluminum-plastic film outer packaging, allowing them to electrically connect to the external circuit. Electrolyte is then injected into the inner space of the aluminum-plastic film outer packaging, which is then sealed. After vacuum packaging, resting, formation, and shaping, the lithium-ion battery is complete.

[0091] The lithium-ion batteries of the examples and comparative examples were prepared and tested according to the above method. The relevant parameters of the lithium-ion batteries in each example are shown in Tables 1 to 4.

[0092] Table 1 shows the relevant parameters of Comparative Example I-1 and Examples I-1 to I-25.

[0093] Table 1

[0094]

[0095] In Table 1, it can be seen from Comparative Example I-1 and Examples I-1 to I-25 that when Additive A is added to the electrolyte, and from Examples I-11 to I-25 that when the positive electrode active material includes the element M and the mass percentage of the element M in the positive electrode active material is between 1 ppm and 500 ppm, the addition of Additive A to the electrolyte can effectively improve the 45°C cycle performance and K value performance of the lithium-ion battery. According to Examples I-11 to I-18, preferably, when the mass percentage of the element M in the positive electrode active material is between 1 ppm and 200 ppm, the addition of Additive A to the electrolyte has a better effect on improving the performance of the lithium-ion battery.

[0096] The positive electrode active material is recycled from an electrochemical device and contains Cu and / or Zn metal impurities that cannot be removed by screening. In Examples I-1 to I-26, additive A is added to the electrolyte. Additive A can enter the vacant orbitals of the Cu or Zn metal elements, preventing Cu and / or Zn from dissolving into the electrolyte during charge and discharge, thereby inhibiting their dissolution from the positive electrode material layer and preventing dendrites from growing at the positive electrode from piercing the separator and causing an internal short circuit in the lithium-ion battery.

[0097] Table 2 shows the relevant parameters of Examples II-1 to II-14.

[0098] Table 2

[0099]

[0100] Table 2 shows that, based on Examples II-1 to II-14, adjusting the ratio t / a of Additive A in the electrolyte within the range of 0.5 to 1000 improves the cycle retention rate and storage thickness expansion rate of the lithium-ion battery. Additive A can form a complex with the element M in the positive electrode active material to a certain degree. When t / a is within the range of 25 to 100, the lithium-ion battery exhibits improved cycle performance and storage performance.

[0101] Table 3 shows the relevant parameters of Examples III-1 to III-10 and Comparative Example III-1.

[0102] Table 3

[0103]

[0104] In Table 3, it can be seen from Examples III-1 to III-10 and Comparative Example III-1 that the coating weight of the positive electrode material layer is adjusted to zg / 1540.25mm 2 , keeping z within the range of 0.22 to 0.45 can effectively improve the hot box test pass rate of lithium-ion batteries. A larger z value corresponds to a thicker positive electrode material layer, which prevents the metal particles containing the M element from being too large, squeezing the current collector and piercing the separator. When z is within the range of 0.29 to 0.36, lithium-ion batteries have better cycling performance and hot box safety.

[0105] Table 4 shows the relevant parameters of Examples IV-1 to IV-10 and Comparative Example IV-1.

[0106] Table 4

[0107]

[0108]

[0109] In Table 4, the sum of the mass of the chain carbonate compound and the chain carboxylate compound in the electrolyte is b%. According to Comparative Example IV-1 and Examples IV-1 to IV-10, it can be seen that when chain carbonate compounds and chain carboxylate compounds having a viscosity lower than 0.7 MPa·s are added to the electrolyte, when the sum of the mass of the chain carbonate compound and the chain carboxylate compound in the electrolyte is 15% to 65%, the cycle performance of the lithium-ion battery is improved, and the rate temperature rise of the lithium-ion battery can be reduced. The low viscosity of the chain carbonate compound and the chain carboxylate compound can also reduce the viscosity of the electrolyte, so that the ion transfer between the positive electrode and the negative electrode can be smooth. Moreover, when the thickness of the positive electrode material layer is relatively thick, the electrolyte can penetrate into the inner layer of the positive electrode material layer, so that the electrolyte can penetrate the positive electrode material layer more fully, so that after the electrolyte is consumed during the cycle, the electrolyte can be replenished to the interior of the positive electrode material layer in a timely manner.

[0110] In the description of this application, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0111] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements 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 Including positive electrode and electrolyte; The electrolyte includes additive A, which is an organic additive containing lone pair electrons; The positive electrode sheet includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes an M element; The M element includes at least one of Cu and Zn; Based on the positive electrode active material, the mass percentage content of the M element is t ppm, and t satisfies 1≤t≤500.

2. The electrochemical device according to claim 1, wherein The additive A includes at least one of a N-containing heterocyclic compound, a phosphite compound, and a nitrile compound.

3. The electrochemical device according to claim 2, characterized in that The N-containing heterocyclic compound includes at least one of pyridine compounds, quinoxaline, isoquinoline, phenolazine, 1,5-naphthyridine, pyrazine, and pyridazine; The pyridine compound includes at least one of pyridine, 2-fluoropyridine, 3-fluoropyridine, 4-fluoropyridine, 2,3-difluoropyridine, 2,4-difluoropyridine, 2,5-difluoropyridine, 3,4-difluoropyridine, 2,3,4-trifluoropyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, N-methylpyrrole, 2,6-lutidine, 4-ethylpyridine, 3,5-lutidine, 4,4'-bipyridine, 4-ethynylpyridine, 4-phenylpyridine, and pyrido[3,4-B]pyrazine; The phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, triphenyl phosphite, tripropylene phosphite, tripropynyl phosphite, tris(trimethylsilyl)phosphite, dimethyl ethyl phosphite, diethyl cyanomethyl phosphate, and diethyl cyanoethyl phosphate; The nitrile compound includes at least one of acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, heptanenitrile, octanonitrile, isobutyronitrile, allyl nitrile, 6-heptynenitrile, cyclohexanecarbonitrile, 2-cyclopentylacetonitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, methylglutaronitrile, 2-propylvaleronitrile, 1,2-bis(cyanoethoxy)ethane, 1,4-dicyano-2-butene, 1,3,6-hexanitrile, 1,3,5-cyclohexanetrinitrile, 1,3,5-benzenetrinitrile, 1,2,3-tris(2-cyanoxy)propane, and 3-methoxypropionitrile.

4. The electrochemical device according to claim 1, wherein The positive electrode active material includes a lithium iron phosphate compound having an olivine crystal structure. Based on the positive electrode active material, the mass percentage of Fe element in the lithium iron phosphate compound is g%, 20≤g≤40, and g and t satisfy the relationship: 0.025≤t / g≤16.

7.

5. The electrochemical device according to claim 1, wherein Based on the mass of the electrolyte, the mass percentage of the additive A is a%, and a and t satisfy the relationship: 0.5≤t / a≤1000.

6. The electrochemical device according to claim 1, wherein Based on the mass of the electrolyte, the mass percentage of the additive A is a%, and 0.07≤a≤5.

7. The electrochemical device according to any one of claims 1 to 6, characterized in that The electrochemical device satisfies at least one of the following conditions: (1)1≤t≤200； (2) The positive electrode active material includes a lithium iron phosphate compound having an olivine crystal structure. Based on the positive electrode active material, the mass percentage of Fe element in the lithium iron phosphate compound is g%, and g and t satisfy the relationship: 0.025≤t / g≤6; (3) Based on the mass of the electrolyte, the mass percentage of the additive A is a%, and a and t satisfy the relationship: 25≤t / a≤100; (4) Based on the mass of the electrolyte, the mass percentage of the additive A is a%, and 0.4≤a≤3.

2.

8. The electrochemical device according to claim 1, wherein The positive electrode sheet further includes a positive electrode current collector, and the positive electrode material layer is provided on the surface of the positive electrode current collector; The coating weight of the positive electrode material layer is zg / 1540.25mm 2 , z satisfies 0.22≤z≤0.

45.

9. The electrochemical device according to claim 8, characterized in that z and t satisfy the relationship: 220≤t / z≤480.

10. The electrochemical device according to claim 8, characterized in that The electrolyte further includes a non-aqueous organic solvent, wherein the non-aqueous organic solvent includes at least one of a chain carbonate compound and a chain carboxylate compound; Based on the mass of the electrolyte, the sum of the mass of the chain carbonate compound and the chain carboxylate compound is b%, b satisfies: 10≤b≤70, and b and z satisfy the relationship: 30≤b / z≤300.

11. The electrochemical device according to any one of claims 8 to 10, characterized in that The electrochemical device satisfies at least one of the following conditions: (1)0.29≤z≤0.36； (2)260≤t / z≤360; (3) Based on the mass of the electrolyte, the percentage of the sum of the mass of the chain carbonate compound and the chain carboxylic acid ester compound is b%, and b and z satisfy the relationship: 50≤b / z≤182, 25≤b≤55.

12. An electronic device, characterized in that: The electrochemical device comprises the electrochemical device according to any one of claims 1 to 11.