Electrochemical apparatus and electronic apparatus

Abstract

The present invention provides an electrochemical device having high capacity per gram as well as excellent cycle and dynamic properties, and an electronic device including the electrochemical device. [Solution] The present invention provides an electrochemical device, the electrochemical device including a negative electrode, the negative electrode including a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer including a negative electrode active material, the negative electrode active material layer satisfying 0.1≦SA / S002≦0.3, SA is the peak area value of the A peak in an XRD spectrum of the negative electrode active material layer with 2θ in the range of 42.4° to 43.6°, and S002 is the peak area value of the 002 peak in the XRD spectrum of the negative electrode active material layer.

Description

[Technical Field]

[0001] This invention relates to the field of energy storage, and more specifically to electrochemical and electronic devices. [Background technology]

[0002] Electrochemical devices such as lithium-ion batteries have become mainstream in the market due to their outstanding advantages, including high energy density, high safety, no memory effect, and long operating life. With the proliferation of consumer electronics such as laptops, mobile phones, tablet computers, mobile power supplies, and drones, the demands on the electrochemical devices used in them are becoming increasingly stringent. For example, in the case of batteries, not only are lightweight designs required, but also high capacity and long operating life. [Overview of the Initiative] [Problems that the invention aims to solve]

[0003] In lithium-ion batteries, for example, natural graphite, which has a relatively high capacity per gram, is often used as the negative electrode material. However, the large, layered porous structure of natural graphite makes it difficult to achieve both excellent cycle characteristics and dynamic characteristics, thus limiting its application to high-performance electrochemical devices.

[0004] In light of the above circumstances, the objective of this technology is to provide an electrochemical apparatus and an electronic apparatus including said electrochemical apparatus that have a high capacity per gram and excellent cycle characteristics and dynamic characteristics.

[0005] In a first aspect, the present invention provides an electrochemical apparatus including a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material layer satisfying 0.1 ≤ SA / S002 ≤ 0.3, where SA is the peak area value of the A peak in the XRD spectrum of the negative electrode active material layer where 2θ is in the range of 42.4° to 43.6°, and S002 is the peak area value of the 002 peak in the XRD spectrum of the negative electrode active material layer. There is a negative correlation between the value of the peak area of ​​the A peak SA of the negative electrode active material layer and the thickness of the active material layer, indicating that the larger SA is, the thinner the thickness of the negative electrode active material layer becomes, and the easier it is for active metal ions such as lithium ions to be intercalated and released in the negative electrode active material layer, but the energy density of the electrochemical apparatus decreases. The peak area value S002 of the 002 peak in the negative electrode active material layer is related to the amount of adsorbable active metal ions, such as lithium ions, in the negative electrode active material. A larger S002 indicates a greater amount of adsorbable active metal ions, which is advantageous for increasing the energy density of the electrochemical apparatus. However, if S002 is too large, the deformation of the electrochemical apparatus increases. Through diligent research by the inventors of this invention, it was found that controlling SA / S002 within the above range ensures the energy density of the electrochemical apparatus and the normal release of active metal ions from the active material. As a result, the electrochemical apparatus has a high capacity per gram and possesses excellent cycle characteristics and dynamic characteristics.

[0006] According to some embodiments of the present invention, SA satisfies 7000 ≤ SA ≤ 9000. According to some embodiments of the present invention, S002 satisfies 25000 ≤ S002 ≤ 90000. In the present invention, the value of SA is the peak area of ​​the A peak in the XRD spectrum of the negative electrode active material layer when the electrochemical device is in a fully discharged state. The value of S002 is the peak area of ​​the 002 peak in the XRD spectrum of the negative electrode active material layer when the electrochemical device is in a fully discharged state.

[0007] According to some embodiments of the present invention, the full width at half maximum (FWHM) of the A peak is 0.1° to 0.5°. The FWHM of the A peak reflects the thickness of the active material layer; a narrower FWHM indicates a relatively thinner active material layer, which is advantageous for the active material layer to adsorb active metal ions and improve the dynamical properties of the electrochemical apparatus.

[0008] According to some embodiments of the present invention, in the XRD spectrum of the negative electrode active material layer, 2θ has 101 peaks in the range of 43.6° to 46.6°, S101 and S002 satisfy 0.015 ≤ S101 / S002 ≤ 0.035, and S101 is the value of the peak area of ​​101 peaks.

[0009] According to some embodiments of the present invention, the full width at half maximum (FWHM) of the 101 peak is 0.3° to 0.8°. The 101 peak is related to the amount of active metal ions that the active material can absorb. The larger the peak intensity of the 101 peak, the narrower the FWHM becomes, and the greater the amount of active metal ions that can be absorbed. Therefore, controlling the peak intensity and FWHM of the 101 peak within a certain range is advantageous in obtaining a negative electrode active material with a high amount of absorbed active metal ions, and thus increases the volume per gram of the active material.

[0010] According to some embodiments of the present invention, the negative electrode current collector is a copper foil.

[0011] According to some embodiments of the present invention, the negative electrode current collector contains chromium, with a chromium content of 0.008% to 0.020% of the mass of the negative electrode current collector. According to some embodiments of the present invention, the negative electrode current collector contains niobium, with a niobium content of 0.005% to 0.009% of the mass of the negative electrode current collector. According to some embodiments of the present invention, the negative electrode current collector contains sulfur, with a sulfur content of 0.001% to 0.006% of the mass of the negative electrode current collector. By controlling the content of trace elements in the current collector, it is advantageous for the stretching of the negative electrode active material during the process of releasing activated metal ions, further suppressing deformation of the electrochemical apparatus and improving the dynamic and cyclic characteristics of the electrochemical apparatus.

[0012] According to some embodiments of the present invention, when the thickness of the negative electrode active material layer is Hμm, SA and H satisfy 87 ≤ SA / H ≤ 300. In some embodiments, the thickness of the negative electrode active material layer is Hμm, and the weight of the negative electrode active material layer per unit area is Cg / cm 2 If so, C and H are 0.003 ≤ C ≤ 0.01 and 1.0 ≤ 10. 4 The condition ×C / H ≤ 1.7 is satisfied. SA is inversely proportional to the thickness of the active material, and generally, the smaller the active material layer H, the larger the SA, which in terms of electrical performance means that the rate of absorption of active metal ions increases and lithium is less likely to precipitate. However, if the thickness of the active material layer is too small, the active material layer will have the same weight (Cg / cm³). 2 If the same conditions are met, the greater the pressure applied to the electrode pieces, the less likely it is that active metal ions will be absorbed into the active material layer, resulting in a relatively higher internal resistance of the electrochemical apparatus. Therefore, controlling the thickness of the active material layer and the weight of the negative electrode active material layer per unit area within the above ranges is advantageous for controlling the rate of absorption and release of active metal ions, improving the capacity per gram of negative electrode active material, and enhancing the cycle characteristics and dynamic characteristics of the electrochemical apparatus.

[0013] According to some embodiments of the present invention, the negative electrode active material layer satisfies 10 ≤ S004 / S110 ≤ 25, where S004 is the peak area value of the 004 peak in the XRD spectrum of the negative electrode active material layer, and S110 is the peak area value of the 110 peak in the XRD spectrum of the negative electrode active material layer. When the ratio of S004 / S110 is within the above range, the internal resistance when active metal ions are adsorbed into or released from the negative electrode active material becomes relatively small, and the deposition of active metal ions can be reduced, thereby improving the cycle characteristics and dynamic characteristics of the electrochemical apparatus.

[0014] According to some embodiments of the present invention, the negative electrode active material contains natural graphite. In some embodiments, the capacity per gram of the negative electrode active material is 360 mAh / g to 370 mAh / g.

[0015] In some embodiments, the particle size of the negative electrode active material satisfies 1 μm ≤ Dv10 ≤ 10 μm, 3 μm ≤ Dv50 ≤ 18 μm, and 8 μm ≤ Dv90 ≤ 35 μm. When the particle size distribution of the negative electrode active material is within the above ranges, the internal resistance when active metal ions are adsorbed into or released from the negative electrode active material becomes relatively small, ensuring that the deposition of active metal ions is reduced, as well as side reactions with the electrolyte, thereby ensuring that the electrochemical apparatus has relatively excellent cycle characteristics and dynamic characteristics.

[0016] In a second aspect, the present invention provides an electronic apparatus including the electrochemical apparatus of the first aspect.

[0017] The anode of the electrochemical apparatus provided in the present invention, by including a specific anode active material layer, provides the electrochemical apparatus with high capacity, as well as excellent cycle characteristics and dynamic characteristics. [Modes for carrying out the invention]

[0018] The present invention will be further described below with reference to examples. It should be understood that these specific embodiments are used to illustrate the present invention and are not intended to limit the scope of the invention.

[0019] 1. Electrochemical apparatus In a first aspect, the present invention provides an electrochemical apparatus including a negative electrode, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material layer satisfying 0.1 ≤ SA / S002 ≤ 0.3, where SA is the peak area value of the A peak in the XRD spectrum of the negative electrode active material layer where 2θ is in the range of 42.4° to 43.6°, and S002 is the peak area value of the 002 peak in the XRD spectrum of the negative electrode active material layer.

[0020] In this invention, the characteristic peak in the XRD spectrum of the negative electrode active material layer where 2θ is in the range of 25.0° to 27.0° is the 002 peak.

[0021] In some embodiments, SA / S002 is 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, or 0.29, or within the range of any two of these values. There is a negative correlation between the peak area value SA of the A peak of the negative electrode active material layer and the thickness of the active material layer. The larger SA, the thinner the negative electrode active material layer becomes, making it easier for active metal ions to be intercalated and released in the negative electrode active material layer, but the energy density of the electrochemical apparatus decreases. The peak area value S002 of the 002 peak in the negative electrode active material layer is related to the amount of adsorbable active metal ions, such as lithium ions, in the negative electrode active material. A larger S002 indicates a greater amount of adsorbable active metal ions, resulting in a larger capacity per gram of the negative electrode active material, which is advantageous for increasing the energy density of the electrochemical apparatus. However, if S002 is too large, the deformation rate of the electrochemical apparatus increases, affecting its dynamic characteristics. Through diligent research by the inventors of this invention, it was found that controlling SA / S002 within the above range ensures the energy density of the electrochemical apparatus while also ensuring the normal release of active metal ions from the active material. As a result, the electrochemical apparatus exhibits high capacity per gram, as well as excellent cycle characteristics and dynamic characteristics.

[0022] According to some embodiments of the present invention, SA satisfies 7000 ≦ SA ≦ 9000. In some embodiments, SA is 7100, 7300, 7500, 7700, 7900, 8000, 8100, 8300, 8500, 8700, or 8900, or within a range consisting of any two of these numerical values. According to some embodiments of the present invention, S002 satisfies 25000 ≦ S002 ≦ 90000. In some embodiments, S002 is 27000, 30000, 34000, 40000, 45000, 50000, 55000, 60000, 65000, 70000, 75000, 80000, or 85000, or within a range consisting of any two of these numerical values. In the present invention, the value of SA is the value of the peak area of the A peak in the XRD spectrum of the negative electrode active material layer when the electrochemical device is in a fully discharged state. The value of S002 is the value of the peak area of the 002 peak in the XRD spectrum of the negative electrode active material layer when the electrochemical device is in a fully discharged state.

[0023] According to some embodiments of the present invention, the half-value width of the A peak is 0.1° to 0.5°. In some embodiments, the half-value width of the A peak is 0.15°, 0.17°, 0.2°, 0.23°, 0.25°, 0.27°, 0.3°, 0.33°, 0.35°, 0.37°, 0.4°, 0.43°, 0.45°, or 0.47°, or within a range consisting of any two of these numerical values. The half-value width of the A peak reflects the thickness of the active material layer. The narrower the half-value width, the relatively thinner the active material layer, which is advantageous for the active material layer to occlude active metal ions and is advantageous for improving the kinetic characteristics of the electrochemical device.

[0024] According to some embodiments of the present invention, in the XRD spectrum of the negative electrode active material layer, 2θ has a 101 peak within the range of 43.6° to 46.6°, S101 and S002 satisfy 0.015 ≤ S101 / S002 ≤ 0.035, and S101 is the value of the peak area of the 101 peak. In some embodiments, S101 / S002 is 0.017, 0.019, 0.02, 0.021, 0.023, 0.025, 0.027, 0.029, 0.030, 0.031, or 0.033, or within the range consisting of any two of these numerical values.

[0025] According to some embodiments of the present invention, the full width at half maximum of the 101 peak is 0.3° to 0.8°. In some embodiments, the full width at half maximum of the 101 peak is 0.35°, 0.37°, 0.4°, 0.43°, 0.45°, 0.47°, 0.5°, 0.53°, 0.55°, 0.57°, 0.6°, 0.63°, 0.65°, 0.67°, 0.7°, 0.73°, 0.75°, or 0.77°, or within the range consisting of any two of these numerical values. The 101 peak is related to the amount of active metal ions that can be occluded by the active material. The greater the peak intensity of the 101 peak, the narrower the full width at half maximum, and the greater the amount of active metal ions that can be occluded. Therefore, by controlling the peak intensity and full width at half maximum of the 101 peak within a certain range, it is advantageous to obtain a negative electrode active material with a high amount of occluded active metal ions, and the negative electrode active material has a relatively high capacity per gram.

[0026] According to some embodiments of the present invention, the negative electrode current collector is a copper foil.

[0027] According to some embodiments of the present invention, the negative electrode current collector contains chromium, and the chromium content is 0.008% to 0.020% of the mass of the negative electrode current collector, for example, 0.009%, 0.01%, 0.011%, 0.012%, 0.012%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, or 0.019%, or within the range of any two of these values. According to some embodiments of the present invention, the negative electrode current collector contains niobium, and the niobium content is 0.005% to 0.009% of the mass of the negative electrode current collector, for example, 0.0055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, or 0.085%, or within the range of any two of these values. According to some embodiments of the present invention, the negative electrode current collector contains sulfur, and the sulfur content is 0.001% to 0.006% of the mass of the negative electrode current collector, for example, 0.0015%, 0.02%, 0.0025%, 0.003%, 0.0035%, 0.004%, 0.0045%, 0.005%, or 0.0055%, or within the range of any two of these values. By controlling the content of trace elements in the current collector, it is advantageous for the elongation of the negative electrode active material during the process of releasing activated metal ions, further suppresses deformation of the electrochemical apparatus, and improves the dynamic and cyclic characteristics of the electrochemical apparatus.

[0028] According to some embodiments of the present invention, when the thickness of the negative electrode active material layer is Hμm, SA and H satisfy 87 ≤ SA / H ≤ 300. In some embodiments, the thickness of the negative electrode active material layer is Hμm, and the weight of the negative electrode active material layer per unit area is Cg / cm 2 If so, C and H are 0.003 ≤ C ≤ 0.01 and 1.0 ≤ 10. 4 The condition ×C / H ≤ 1.7 is satisfied. SA is inversely proportional to the thickness of the active material, and generally, the smaller the active material layer H, the larger the SA, which in terms of electrical performance means that the rate of intercalation or release of active metal ions increases, making deposition more difficult. However, if the thickness of the active material layer is too small, the active material layer will have the same weight (Cg / cm³). 2If the same conditions are met, the greater the pressure applied to the electrode piece, the less likely it is that active metal ions such as lithium ions will be absorbed into the active material layer, and the internal resistance during absorption will increase. Therefore, controlling the thickness of the active material layer and the weight of the negative electrode active material layer per unit area within the above range is advantageous for controlling the rate of absorption and release of active metal ions, and is advantageous for improving the capacity per gram of negative electrode active material, as well as the dynamic and cyclic characteristics of the electrochemical apparatus.

[0029] According to some embodiments of the present invention, the negative electrode active material layer satisfies 10 ≤ S004 / S110 ≤ 25, where S004 is the peak area value of the 004 peak in the XRD spectrum of the negative electrode active material layer, and S110 is the peak area value of the 110 peak in the XRD spectrum of the negative electrode active material layer. In some embodiments, S004 / S110 is 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24, or within the range of any two of these numbers. The S004 / S110 ratio is related to the particle size of the negative electrode active material. As the particle size of the negative electrode active material decreases, the S004 / S110 ratio decreases accordingly. In this case, the internal resistance when active metal ions are adsorbed into or released from the negative electrode active material becomes relatively small, and the deposition of active metal ions can be reduced. This lowers the internal resistance of the electrochemical apparatus and improves the capacity retention rate under high-rate charge-discharge conditions. When the S004 / S110 ratio satisfies the above range, the electrochemical apparatus has relatively low internal resistance and relatively high capacity retention rate during high-rate charge-discharge, and the electrochemical apparatus has relatively excellent dynamic and cyclic characteristics.

[0030] According to some embodiments of the present invention, the negative electrode active material contains natural graphite. In some embodiments, the capacity per gram of the negative electrode active material is 360 mAh / g to 370 mAh / g.

[0031] In some embodiments, the particle size of the negative electrode active material satisfies 1 μm ≤ Dv10 ≤ 10 μm, 3 μm ≤ Dv50 ≤ 18 μm, and 8 μm ≤ Dv90 ≤ 35 μm. In the present invention, Dv10 indicates that in the volume-based particle size distribution of the negative electrode active material, 10% of the particles have a particle size smaller than this value. Dv50 indicates that in the volume-based particle size distribution of the negative electrode active material, 50% of the particles have a particle size smaller than this value. Dv90 indicates that in the volume-based particle size distribution of the negative electrode active material, 90% of the particles have a particle size smaller than this value.

[0032] In some embodiments, Dv10 is 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, or 9μm, or within the range of any two of these values. In some embodiments, Dv50 is 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, or 17μm, or within the range of any two of these values. In some embodiments, Dv90 is 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, or 34μm, or within the range of any two of these values. As the particle size of the negative electrode active material decreases, the S004 / S110 ratio also decreases accordingly. At this time, the internal resistance when active metal ions are absorbed into or released from the negative electrode active material becomes relatively small, and the deposition of active metal ions is reduced, lowering the internal resistance of the electrochemical apparatus and improving the capacity retention rate during high-rate charging and discharging. However, if the particle size of the negative electrode active material is too small, the specific surface area of ​​the negative electrode active material increases, increasing the contact area with the electrolyte and making side reactions with the electrolyte more likely. This reduces the initial Coulomb efficiency of the electrochemical apparatus in the process of releasing active metal ions for the first time. Therefore, it is necessary to control this within a certain range to ensure that the electrochemical apparatus has excellent performance.

[0033] The electrochemical apparatus of the present invention further includes a positive electrode, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material, a binder and a conductive agent.

[0034] According to some embodiments of the present invention, a metal foil sheet or a composite current collector can be used as the positive electrode current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metallic material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer substrate.

[0035] According to some embodiments of the present invention, the positive electrode active material includes at least one of lithium cobaltate, lithium nickel-manganese cobaltate, lithium nickel-manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganeseate, spinel-type lithium nickel-manganate, and lithium titanate. In some examples, the binder includes an adhesive polymer, the adhesive polymer being at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethylcellulose, lithium carboxymethylcellulose, modified polyvinylidene fluoride, modified SBR rubber, and polyurethane. In some examples, the binder for polyolefins includes at least one of polyethylene, polypropylene, polyolefin esters, polyolefin alcohols, and polyacrylic acid. In some embodiments, the conductive agent includes carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, or carbon fiber; metallic materials such as metal powders or metal fibers such as copper, nickel, aluminum, or silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0036] The electrochemical apparatus of the present invention includes a separator, and the material and shape of the separator used in the electrochemical apparatus of the present invention are not particularly limited and may be those disclosed in any prior art. In some embodiments, the separator includes a polymer or inorganic material made of a material stable with respect to the electrolyte of the present invention.

[0037] For example, the separator may include a base layer and a surface treatment layer. The base layer is a nonwoven fabric, film, or composite film having a porous structure, and the material of the base layer is at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0038] A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material. The inorganic layer contains inorganic particles and a binder, and the inorganic particles are at least one selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, ythrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene oxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, and the polymer material is at least one selected from the group consisting of polyamide, polyacrylonitrile, acrylic acid ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene oxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0039] The electrochemical apparatus of the present invention further comprises an electrolyte. The electrolyte used in the present invention may be an electrolyte known in the prior art.

[0040] According to some embodiments of the present invention, the electrolyte comprises an organic solvent, a lithium salt, and an optional additive. The organic solvent in the electrolyte of the present invention may be any organic solvent used as a solvent for electrolytes known in the prior art. The electrolyte used in the electrolyte of the present invention is not limited and may be any electrolyte known in the prior art. The additive in the electrolyte of the present invention may be any additive used as an additive for electrolytes known in the prior art. In some examples, the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate. In some examples, the organic solvent includes ether solvents, for example, at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME). In some examples, the lithium salt includes at least one of organolithium salts and inorganic lithium salts. In some examples, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalate)borate LiB(C2O4)2 (LiBOB), or lithium difluoro(oxalate)borate LiBF2(C2O4) (LiDFOB). In some examples, the additive includes at least one of fluoroethylene carbonate and adiponitrile.

[0041] According to some embodiments of the present invention, the electrochemical apparatus of the present invention includes, but is not limited to, a lithium-ion battery or a sodium-ion battery. In some embodiments, the electrochemical apparatus is a lithium-ion battery.

[0042] 2.Electronic equipment The present invention further provides an electronic apparatus including an electrochemical apparatus as described in a first aspect of the present invention.

[0043] The electronic equipment or apparatus of the present invention is not particularly limited. In some embodiments, the electronic equipment of the present invention includes, but is not limited to, laptop computers, pen-input computers, mobile computers, e-book players, mobile phones, mobile fax machines, portable copiers, mobile printers, headphone stereos, video recorders, LCD televisions, handheld vacuum cleaners, portable CD players, MiniDiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, strobes, cameras, large household storage batteries, and lithium-ion capacitors.

[0044] The reagents, materials, and equipment used in the following examples and comparative examples are commercially available unless otherwise specified.

[0045] Examples and Comparative Examples

[0046] Preparation of the positive electrode Lithium cobalt oxide (molecular formula LiCoO2), the positive electrode active material, acetylene black, the conductive agent, and polyvinylidene fluoride (abbreviated as PVDF), the binder, were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (abbreviated as NMP) solvent in a weight ratio of 96:2:2 to obtain a homogeneous positive electrode slurry. This slurry was then applied to aluminum foil, which served as the current collector, and after drying, cold rolling, cutting, and welding of tabs, the positive electrode was obtained.

[0047] Preparation of the negative electrode Preparation of negative electrode active material: Natural graphite ore was used, and crushing / ball milling and flotation were performed to obtain natural flaky graphite. The natural flaky graphite was crushed, and powder with a particle size Dv50 of 3 μm to 18 μm was appropriately selected, and then spheroidized to obtain material A. Material A was mixed with a certain amount of coating agent in a mixing ratio of 50:50 to 90:10, and after uniform mixing, it was placed in a high-temperature carbonization furnace and calcined at 1150°C for 4 hours to obtain material B. Material B is graphite used as the negative electrode active material in the experiment, and the coating agent is a mixture of 50% to 90% solvent and 10% to 50% carbon material, the solvent includes toluene, ethanol, quinoline or diethyl ether, and the carbon material includes carbon nanotubes or graphene.

[0048] The negative electrode active material, styrene-butadiene rubber (abbreviated as SBR) as a binder, and sodium carboxymethylcellulose as a thickener were thoroughly mixed in a deionized water solvent in a weight ratio of 95:2:3 to obtain a uniform negative electrode slurry. This slurry was then applied to copper foil current collectors that had been pre-coated with an undercoat layer (carbon black), with an undercoat layer thickness of 1.5 μm. After drying, the coated negative electrodes were cold-rolled, cut, and welded using different roll press pressures.

[0049] In the examples and comparative examples of the present invention, the corresponding peak values ​​and peak areas in the XRD spectrum of the active material layer were adjusted by adjusting the particle size of the pulverized material and the type and content of the coating agent.

[0050] Preparation of electrolyte Under a dry argon atmosphere, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) (weight ratio 1:1:1) were uniformly mixed to form a base solvent. Dried lithium salt LiPF6 was added to the base solvent and uniformly mixed. Further, fluoroethylene carbonate and adiponitrile were added and uniformly mixed to obtain an electrolyte. The mass percentage of fluoroethylene carbonate in the electrolyte was 3%, the mass percentage of adiponitrile was 2%, the mass percentage of LiPF6 was 12.5%, and the remainder was DEC.

[0051] Preparation of separators A polyethylene porous polymer film with a thickness of 7 μm was used as the separator.

[0052] Preparation of lithium-ion batteries The positive electrode, separator, and negative electrode were stacked in this order, the separator was interposed between the positive and negative electrodes, the assembly was wound and placed in an outer foil, the electrolyte prepared above was injected, and a lithium-ion battery was obtained through processes such as vacuum packaging, settling, chemical conversion, and shaping.

[0053] Measurement method

[0054] 1. X-ray powder diffraction (XRD) measurement (002, 101, A) Diffraction peaks of the crystal plane (hereinafter abbreviated as "002 peak, 101 peak, A peak"): The negative electrode active material layer was measured using an X-ray powder diffractometer (XRD, machine model: Bruker D8 ADVANCE), and an XRD measurement curve was obtained. The target was CuKα, the voltage / current was 40KV / 40mA, the scanning angle range was 5°~80°, the scanning step width was 0.00836°, and the time for each step width was 0.3s. The A peak is located in the diffraction angle 2θ range of 42.4°~43.6°, the 002 peak is located in the diffraction angle 2θ range of 25.0°~27.0°, and the 101 peak is located in the diffraction angle 2θ range of 43.6°~46.6°. S002, S101, and SA are the peak area values ​​of each peak obtained by integrating the 002 peak, 101 peak, and A peak, respectively.

[0055] Measurement method for S004 / S110: The (004) plane diffraction line patterns and (110) plane diffraction line patterns in the X-ray diffraction spectrum of the negative electrode active material layer were measured according to the Chinese Machinery Industry Standard JB / T 4220-2011 "Method for measuring the lattice constant of artificial graphite". The test conditions were as follows: CuKα rays were used as X-rays, and CuKα rays were removed by a filter or monochromator. The operating voltage of the X-ray tube was set to (30~35)kV and the operating current to (15~20)mA. The scanning speed of the counter was set to 1 / 4(°) / min. The diffraction peak of the (004) plane (004 peak in the XRD spectrum of the negative electrode active material layer) is located in the diffraction angle 2θ range of 52°~57°, and the diffraction peak of the (110) plane (110 peak in the XRD spectrum of the negative electrode active material layer) is located in the diffraction angle 2θ range of 75°~80°. The peak area value of the 004 peak was calculated by integration and recorded as S004, and the peak area value of the 110 peak was calculated by integration and recorded as S110. This allowed us to calculate the ratio of S004 / S110 in the negative electrode active material layer.

[0056] In this invention, the peak area values ​​of the 002 peak, 101 peak, A peak, 110 peak, and 004 peak in the XRD spectrum of the negative electrode active material layer represent the numerical values ​​of each peak area calculated by the XRD spectrum.

[0057] 2. Measurement of particle size of negative electrode active material A certain amount of the negative electrode active material layer was taken, and the binder and thickener were dissolved and removed using an organic solvent. After drying, the negative electrode active material powder was obtained. 1 g of the negative electrode active material powder was taken, dissolved in water as a dispersant, and treated with ultrasound for 5 minutes, with the ultrasound intensity set to 53 kHz. The mixed suspension was then injected into a Malvern 3000 measuring device, and each sample was measured three times. The average values ​​of the measurement results were taken as Dv10, Dv50, and Dv90.

[0058] 3. Elemental analysis measurement 0.5 g of the uncoated copper foil region of the negative electrode current collector was weighed, and the copper foil was mixed with 10 mL of HNO3 solution. Trace elements in the current collector were dissolved in the solution using microwave decomposition, and the decomposed solution was introduced into an ICP light source. Using an inductively coupled plasma emission spectrometer (ICP-OES) system, the content of different substances was detected by the characteristic radiant energy emitted by the radiative transition when the outer shell electrons of the gas atoms in the sample material were excited and then returned from the excited state to the ground state.

[0059] 4. Measurement of volume per gram

[0060] (1) Preparation of button cell: A positive electrode was prepared using the negative electrode active material prepared in the above example. The prepared positive electrode, lithium sheet, separator, electrolyte, steel sheet, foamed nickel, and button cell case were assembled together to obtain a button cell, which was left to stand for 6 hours before measurement.

[0061] (2) Measurement steps for button batteries: The assembled button batteries were measured using a Landian (LAND) measuring instrument. The measurement steps were as follows: Discharge to a lower voltage limit of 5mV at 0.05C, then discharge to a constant voltage of 50μA at an upper voltage limit of 2.0V, let stand for 5 minutes, charge to an upper voltage limit of 2.0V at 0.1C, let stand for 5 minutes, and record the capacity per gram at this time as the capacity per gram of the negative electrode active material.

[0062] 5. Measuring BETs The specific surface area was measured according to GB / T 19587-2017. A certain amount of the negative electrode active material layer was taken, the binder and thickener were dissolved and removed using an organic solvent, and the negative electrode active material powder was obtained after drying. The specific steps were as follows: 1g to 8g of negative electrode active material (the sample weight occupied at least 1 / 3 of the ball's volume) was weighed, placed in a tube with a 1 / 2-inch ball section (the tube diameter of the ball section was 12mm), pre-treated at 200°C for 2 hours, and then measured using the TriStar3030 measuring instrument (Micromeristics, USA). The adsorption gas used was N2 (purity: 99.999%), and the measurement was performed at 77K. The specific surface area was measured using the BET calculation method.

[0063] 6. Measurement of the degree of lithium deposition on the negative electrode piece. The lithium-ion battery to be measured was taken, left standing at 0°C (the measurement temperature) for 5 minutes, then charged with a constant current of 0.7C to 4.45V, then charged with a constant voltage of 4.45V to 0.05C, left standing for 5 minutes, and then discharged with a constant current of 0.5C to 3.0V, left standing for 5 minutes. After repeating the above charge and discharge operation 10 times, the battery was fully charged, disassembled in a dry room, and the state of the negative electrode was photographed and recorded.

[0064] Determination of the degree of lithium deposition: This was determined by the condition of the negative electrode piece obtained after fully charging and disassembling the battery. If the entire negative electrode piece is golden in color and the gray area is <2%, it is judged that there is no lithium deposition. If most of the negative electrode piece is golden in color, but gray is observed in a small area, and the gray area is 2% to 20%, it is judged that there is slight lithium deposition. If part of the negative electrode piece is gray, but part is golden in color, and the gray area is 20% to 60%, it is judged that there is lithium deposition. If most of the negative electrode piece is gray, and the gray area is >60%, it is judged that there is serious lithium deposition.

[0065] 7. Measurement of DC Resistance (DCR) A lithium-ion battery was charged at 25°C with a constant current of 1.5C to 4.45V, then charged at 4.45V with a constant voltage of 0.05C, and left to stand for 30 minutes. It was then discharged at 0.1C for 10 seconds, and the voltage value was recorded as U1. It was then discharged at 1C for 360 seconds, and the voltage value was recorded as U2. The charge-discharge operation was repeated 5 times. "1C" is the current value at which the lithium-ion battery's capacity was completely discharged within one hour.

[0066] The DC resistance R of a lithium-ion battery at 25°C was calculated using the following formula. R = (U2 - U1) / (1C - 0.1C)

[0067] The DC resistance R of the lithium-ion battery at 0°C was measured using the same steps as described above for measuring the DC resistance R of the lithium-ion battery at 25°C, the only difference being that the operating temperature was set to 0°C.

[0068] Unless otherwise specified, the DCR described in this invention refers to the DC resistance of a lithium-ion battery at a 10% charge state (SOC).

[0069] 8. Measurement of electrochemical impedance spectroscopy (EIS)

[0070] a) Preparation of a three-electrode battery and lithium plating: In accordance with the lithium-ion battery preparation method described above, during the preparation of the lithium-ion battery, a copper wire was connected to the battery as a reference electrode, lithium was plated onto the negative electrode with a current of 20 μA for 6 hours, and the EIS was measured after the lithium plating was completed.

[0071] b) EIS measurement step: A lithium-plated three-electrode battery was connected to a Bio-Logic VMP3B electrochemical workstation manufactured by Biologie, France, for measurement. The measurement frequency range was 30 MHz to 50 kHz, and the amplitude was 5 mV. After collecting the data, the data was analyzed using an impedance complex plane diagram to obtain Rct data.

[0072] 9. Measurement of the cycle expansion rate of lithium-ion batteries The lithium-ion battery to be measured was left standing at 45°C for 5 minutes, and the initial thickness of the battery (PPG0 and MMC0) was recorded. Then, the lithium-ion battery was charged with a constant current of 0.7C to 4.45V, and further charged with a constant voltage of 4.45V to 0.05C, and the thickness of the battery (PPG1 and MMC1) was recorded. After standing for 5 minutes, it was discharged with a constant current of 0.5C to 3.0V, and then left standing for 5 minutes. The above charge and discharge operation was repeated 500 times. For the first 200 cycles, the thickness of the battery was recorded every 50 cycles, and for the next 300 to 500 cycles, the thickness of the battery (PPGx and MMCx, where x represents the cycle number) was recorded every 100 cycles, and the residual capacity after each charge and discharge was also recorded.

[0073] PPG Measurement: For PPG measurement, automated testing was performed using a PPG softpack battery thickness gauge (manufactured by Shenzhen Automate Automation Technology Co., Ltd). The measurement process was as follows: The battery was placed on the lower measurement panel of the instrument, the upper cover was lowered at a constant speed during measurement, and the battery thickness PPGx was measured by a pressure sensor. x was marked according to the number of cycles for the cycle measurement.

[0074] MMC Measurement: For MMC measurement, a micrometer tester (Mitutoyo Japan, model number: MDC-25SX) was used to measure the thickness of the positive electrode tab of the battery. Three locations (MMCax, MMCbx, MMCcx) were measured, with the letters a, b, and c corresponding to different measurement locations, and the subscript x corresponding to the number of measurement cycles. MMCx = (MMCax + MMCbx + MMCcx) / 3, MMC rebound = (MMCx - MMC0) / MMC × 100%.

[0075] The cycle expansion rate of the lithium-ion battery at 45°C is calculated from the recorded battery thickness = [PPGx / (Max(MMCax, MMCbx, MMCcx))-1]×100%, where Max(MMCax, MMCbx, MMCcx) represents the maximum value at the three measurement points.

[0076] 10. Measurement of 2C discharge capacity maintenance rate After leaving the lithium-ion battery at 2°C for 5 minutes, it was charged with a constant current of 0.7C to 4.45V, then charged with a constant voltage of 0.05C at 4.45V, left to stand for 5 minutes, and then discharged with a constant current of 0.5C to 3.0V, left to stand for 5 minutes. The above charge and discharge operations were repeated, and the 0.1C discharge capacity of the lithium-ion battery was recorded, and then the 2C discharge capacity of the lithium-ion battery was recorded. The 2C discharge capacity retention rate of the lithium-ion battery was calculated using the following formula. 2C discharge capacity maintenance rate = 2C discharge capacity / 0.1C discharge capacity x 100%

[0077] Measurement results

[0078] [Table 1] Note: In Table 1, the full width at half maximum (FWHM) of the A peak in each example and comparative example is 0.1°, the FWHM of the 101 peak is 0.3°, the thickness of the negative electrode active material layer is 30 μm, and the weight of the negative electrode active material layer per unit area is 0.003 g / cm². 2 That is the case.

[0079] As shown in Examples 1 to 12, when the negative electrode active material layer satisfies 0.1 ≤ SA / S002 ≤ 0.3, the capacity per gram of the lithium-ion battery is significantly improved, and the cycle expansion rate at 200 cycles and the DC resistance value at 0°C are significantly reduced. The reduction in the cycle expansion rate at 200 cycles indicates that the lithium-ion battery has improved cycle characteristics, and the reduction in the DC resistance value at 0°C indicates that the lithium-ion battery has improved dynamic characteristics. Therefore, the lithium-ion batteries of Examples 1 to 12 have improved cycle characteristics and dynamic characteristics and high capacity per gram. When the negative electrode active material layer satisfies 7000 ≤ SA ≤ 9000 and / or 25000 ≤ S002 ≤ 90000, the lithium-ion battery has superior overall performance.

[0080] The value of the ratio of SA / S002 in Comparative Example 1 is higher than 0.3, the capacity per gram of the lithium-ion battery is relatively low, the cycle expansion rate at 200 cycles is relatively high, and the value of DCR at 0 °C is relatively high. The value of the ratio of SA / S002 in Comparative Example 2 is less than 0.1. The lithium-ion battery has a relatively high capacity per gram, but has a high cycle expansion rate at 200 cycles and a relatively high value of DCR at 0 °C.

[0081]

Table 2

[0082] [[ID=:13]]As shown in Table 2, when the half-value width of the A peak is 0.1° to 0.5°, the half-value width of the 101 peak is 0.3° to 0.8°, 30 μm ≤ H ≤ 80 μm, 87 ≤ SA / H ≤ 300, and C is 0.003 g / cm 2 ~0.01 g / cm 2 and / or 1.0 ≤ 10 4 ×C / H ≤ 1.7 are satisfied, it can further improve the resistance of the lithium-ion battery and the lithium precipitation situation of the negative electrode sheet, contribute to improving the capacity per gram of the lithium-ion battery, and further improve the cycle characteristics and kinetic characteristics of the lithium-ion battery.

[0083]

Table 3

[0084] Examples 26 to 39 show the relationship between the particle size distribution of the negative electrode active material, the BET and S004 / S110 ratio of the negative electrode active material layer, and battery performance. As shown in Table 3, if a lithium-ion battery satisfies the following conditions: 1 μm ≤ Dv10 ≤ 10 μm, 3 μm ≤ Dv50 ≤ 18 μm, 8 μm ≤ Dv90 ≤ 35 μm, a chromium content of 0.008% to 0.02%, a niobium content of 0.005% to 0.009%, a sulfur content of 0.001% to 0.006%, and / or 10 ≤ S004 / S110 ≤ 25, it further improves the DC resistance at 25°C, the lithium deposition status of the negative electrode piece, and the discharge capacity retention rate at high rate (2C), contributing to further improvement of the cycle characteristics and kinetic characteristics of the lithium-ion battery.

[0085] While exemplary embodiments are disclosed and described, those skilled in the art should understand that the embodiments described above cannot be construed as limiting the invention and that the embodiments can be modified, replaced, and altered without departing from the technical spirit, principles, and scope of the invention.

Claims

1. An electrochemical apparatus including a negative electrode, The aforementioned negative electrode includes a negative electrode current collector and a negative electrode active material layer. The aforementioned negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer satisfies 0.1 ≤ SA / S002 ≤ 0.

3. SA is the peak area value of the A peak in the XRD spectrum of the negative electrode active material layer where 2θ is in the range of 42.4° to 43.6°. S002 is the peak area value of the 002 peak in the XRD spectrum of the negative electrode active material layer. The thickness of the negative electrode active material layer is H μm, and the weight of the negative electrode active material layer per unit area is C g / cm². ２ In this case, the electrochemical apparatus satisfies 0.003 ≤ C ≤ 0.01 and 1.0 ≤ 10⁴ × C / H ≤ 1.

7.

2. The electrochemical apparatus according to claim 1, wherein the full width at half maximum of the A peak is 0.1° to 0.5°.

3. In the XRD spectrum of the negative electrode active material layer, 101 peaks are present in the range of 2θ from 43.6° to 46.6°. S101 and S002 satisfy 0.015 ≤ S101 / S002 ≤ 0.035, The electrochemical apparatus according to claim 1, wherein S101 is the value of the peak area of ​​the 101 peak, and / or the full width at half maximum of the 101 peak is 0.3° to 0.8°.

4. The aforementioned negative electrode is (a) The negative electrode current collector is made of copper foil, (b) The negative electrode current collector contains chromium, and the chromium content is 0.008% to 0.020% of the mass of the negative electrode current collector. (c) The negative electrode current collector contains niobium, and the niobium content is 0.005% to 0.009% of the mass of the negative electrode current collector. (d) The negative electrode current collector contains sulfur, and the sulfur content is 0.001% to 0.006% of the mass of the negative electrode current collector. An electrochemical apparatus according to claim 1, satisfying at least one of the following conditions.

5. The negative electrode active material layer satisfies 10 ≤ S004 / S110 ≤ 25. The electrochemical apparatus according to claim 1, wherein S004 is the peak area value of the 004 peak in the XRD spectrum of the negative electrode active material layer, and S110 is the peak area value of the 110 peak in the XRD spectrum of the negative electrode active material layer.

6. The aforementioned negative electrode is (e) The negative electrode active material contains natural graphite, (g) The capacity per gram of the negative electrode active material is 360 mAh / g to 370 mAh / g, (h) The particle size of the negative electrode active material satisfies 1 μm ≤ Dv10 ≤ 10 μm, 3 μm ≤ Dv50 ≤ 18 μm, and 8 μm ≤ Dv90 ≤ 35 μm, An electrochemical apparatus according to claim 1, satisfying at least one of the following conditions.

7. An electronic apparatus comprising an electrochemical apparatus as described in any one of claims 1 to 6.

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