Electrochemical apparatus and electronic apparatus

Abstract

This application relates to an electrochemical apparatus and an electronic apparatus. The electrochemical apparatus of this application includes a positive electrode, a negative electrode, and an electrolyte, the electrolyte includes an additive, the additive includes a first additive M, the first additive M is selected from at least one of a fluorinated carbonate compound or a sulfur-oxygen double bond-containing compound, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a hard carbon material. The electrochemical apparatus of this application has improved high-temperature cycle performance, low-temperature performance, and rate performance, while simultaneously achieving a capacity per gram of negative electrode active material.

Description

[Technical Field]

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

[0002] With the widespread application of electrochemical equipment, a wide variety of battery types have been developed. Sodium-ion batteries are a new type of rechargeable energy storage device, and their basic operating principle is similar to that of lithium-ion batteries. Compared to conventional lithium-ion batteries, they have certain advantages in terms of cost, rate performance, low-temperature performance, and cycle life. Furthermore, sodium-ion batteries offer even higher safety. Currently, sodium-ion batteries are attracting widespread attention and have broad application potential in fields such as electric vehicles and energy storage systems.

[0003] Graphite is a widely used negative electrode active material in lithium-ion batteries. However, the compound formed by graphite and sodium is thermodynamically unstable, and due to the large ionic radius of sodium ions, sodium ions cannot be reversibly inserted into or removed from the graphite layers. Therefore, conventional graphite cannot be used as a negative electrode active material in sodium-ion batteries. Among the many negative electrode active materials for sodium-ion batteries that are awaiting development, hard carbon materials are attracting considerable attention due to their advantages such as high capacity per gram, good rate performance, and good low-temperature and cycle performance. Moreover, the precursors of hard carbon materials have a wide range of sources, including common biomass materials, coal-based materials, asphalt-based materials, and resin materials, all of which can be used as precursors for hard carbon materials. Furthermore, they are inexpensive, and the energy consumption during the heat treatment process of hard carbon materials is lower than that of graphite materials. The cost advantages of raw materials and processing processes help to further improve the cost advantage of sodium-ion batteries.

[0004] Hard carbon materials have relatively large interlayer spacing, which is advantageous for the insertion and deinsertion of sodium ions and can improve the diffusion rate of sodium ions. At the same time, hard carbon materials have a large number of pore defects inside, allowing for a high sodium storage capacity, making them currently the most ideal negative electrode material for sodium-ion batteries. From the perspective of the sodium storage mechanism, most of the sodium storage capacity of hard carbon is filled under low potential, which is close to the sodium deposition potential. This makes it prone to sodium deposition, which not only leads to irreversible decay of capacity but can also cause gas generation and safety problems in electrochemical devices.

[0005] Therefore, there is a need to provide an improved electrochemical apparatus that uses hard carbon as the negative electrode active material. [Overview of the project]

[0006] The purpose of this application is to provide an electrochemical apparatus and an electronic apparatus, the electrochemical apparatus of this application having improved high-temperature cycling performance, low-temperature performance and rate performance, while simultaneously achieving a high capacity per gram of negative electrode active material. The specific technical solutions are as follows.

[0007] In one embodiment, the present application provides an electrochemical apparatus comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte comprises an additive, the additive comprising a first additive M, the first additive M being selected from at least one of fluorinated carbonate compounds or sulfur-oxygen double bond-containing compounds, and the mass percentage content of the first additive M is m% based on the mass of the electrolyte, the negative electrode comprising a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising a hard carbon material, and the hard carbon material having a density of 1300 cm² as measured by Raman spectroscopy. -1 ~1400cm -1 The peak intensity at 1550 cm² is used as the ID, and the hard carbon material is measured at 1550 cm². -1 ~1650cm -1Let IG be the peak intensity at [location], and let d be the ratio of ID / IG, where d is between 1.0 and 1.6, and the range of m / d is between 0.01 and 4.5.

[0008] In some embodiments, the electrochemical apparatus satisfies at least one of the following conditions: (1) the range of m / d is 1.6 to 3.6, and (2) d is 1.2 to 1.4.

[0009] In some embodiments, X-ray diffraction measurements show that the lattice plane spacing d002 of the hard carbon material is in the range of 0.37 nm to 0.41 nm. In some embodiments, the lattice plane spacing d002 is in the range of 0.38 nm to 0.40 nm.

[0010] In some embodiments, the electrochemical apparatus satisfies at least one of the following conditions: (1) the mass percentage content of the fluorinated carbonate compound is 0.05% to 5% based on the mass of the electrolyte, or (2) the mass percentage content of the sulfur-oxygen double bond-containing compound is 0.05% to 4% based on the mass of the electrolyte.

[0011] In some embodiments, the sulfur-oxygen double bond-containing compound comprises at least one of 1,3-propanesultone, propene-1,3-sultone, 1,2-propanesultone, 1,4-butanesultone, or ethylene sulfate, and / or the fluorinated carbonate compound comprises at least one of fluoroethylene carbonate or difluoroethylene carbonate.

[0012] In some embodiments, the hard carbon material has pores inside, with a pore diameter range of 0.6 nm to 2.0 nm, and the pore volume is less than 0.05 g / cc as determined by nitrogen gas adsorption testing.

[0013] In some embodiments, the hard carbon material satisfies at least one of the following conditions: (1) The specific surface area of ​​the hard carbon material is 0.5 m². 2 / g~10m 2 / g (2) The compaction density of the hard carbon material after depressurization under 5 tons is 0.8 g / cc to 1.6 g / cc. (3) Measurement by X-ray diffraction revealed that the hard carbon material had diffraction peaks in the range of 18° to 30°, and the full width at half maximum of the diffraction peaks was 4° to 12°. (4) The Dv50 of the hard carbon material is between 2 μm and 10 μm, and the Dv50 and Dv90 of the hard carbon material satisfy 2 ≤ Dv90 / Dv50 ≤ 5.

[0014] In some embodiments, the negative electrode active material layer satisfies at least one of the following conditions: (1) The porosity range of the negative electrode active material layer is 30% to 60%, (2) The compaction density of the negative electrode active material layer is in the range of 0.8 g / cc to 1.5 g / cc.

[0015] In some embodiments, the electrode sheet capacity per unit area of ​​the negative electrode active material layer is V1, the positive electrode includes a positive electrode active material layer, the electrode sheet capacity per unit area of ​​the positive electrode active material layer is V2, and the range of V1 / V2 is 1.1 to 1.5.

[0016] In some embodiments, the electrochemical device is a sodium-ion battery.

[0017] In another embodiment, the present application provides an electronic apparatus comprising an electrochemical apparatus according to an embodiment of the present application.

[0018] This application describes how to significantly improve the high-temperature cycle characteristics, low-temperature characteristics, and rate characteristics of electrochemical devices (particularly sodium-ion batteries) by using a combination of a hard carbon material and a specific electrolyte, and by controlling the mixing ratio.

[0019] Further aspects and advantages of the embodiments of this application are, in part, described and shown in the following description or become apparent through the implementation of the embodiments of this application. [Modes for carrying out the invention]

[0020] Embodiments of this application are described in detail below. These embodiments should not be construed as limiting this application.

[0021] As used in this application, the term “approximately” is used to describe and explain small changes. When used in conjunction with an event or scenario, the term may refer to an example where the event or scenario occurs exactly, or an example where the event or scenario occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of change of ±10% or less of the numerical value, such as ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.1%, or ±0.05%.

[0022] Furthermore, quantities, ratios, and other numerical values ​​may be presented in range form within this specification. Such range forms are used for convenience and conciseness and should be interpreted flexibly, encompassing not only the numerical values ​​explicitly designated as limits to the range, but also all individual numerical values ​​or subranges contained within that range, and should be understood as general, as if each numerical value and subrange were explicitly designated.

[0023] In the specific embodiments and claims, a list of items connected by “one of,” “one of,” “one type of,” or other similar terms may mean any one of the enumerated items. For example, if items A and B are enumerated, “one of A and B” means either A only or B only. As another example, if items A, B, and C are enumerated, “one of A, B, and C” means either A only, B only, or C only. Item A may include a single component or multiple components. Item B may include a single component or multiple components. Item C may include a single component or multiple components.

[0024] In specific embodiments and claims, a list of items connected by terms such as "at least one of", "at least one", "at least one kind of", or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, "at least one of A and B" means only A, only B, or A and B. As another example, if items A, B, and C are listed, "at least one of A, B, and C" means only A, 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. Item A may include a single component or a plurality of components. Item B may include a single component or a plurality of components. Item C may include a single component or a plurality of components.

[0025] I. Electrochemical device

[0026] In some embodiments, the present application provides an electrochemical device including a positive electrode, a negative electrode, and an electrolyte.

[0027] In some embodiments, the electrolyte includes an additive, the additive includes a first additive M, the first additive M is selected from at least one of a fluorinated carbonate compound or a sulfur-oxygen double bond-containing compound, and based on the mass of the electrolyte, the mass percentage content of the first additive M is m%, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a hard carbon material, and by measurement using Raman spectroscopy, the peak intensity at 1300 cm -1 ~1400 cm -1 of the hard carbon material is designated as ID, the peak intensity at 1550 cm -1 ~1650 cm -1 of the hard carbon material is designated as IG, the ratio of ID / IG is designated as d, d is 1.0 to 1.6, and the range of m / d is 0.01 to 4.5.

[0028] In some embodiments, the range of m / d is 0.01 to 4.5. In some embodiments, the range of m / d is 1.6 to 3.6. In some embodiments, m / d is a value within the range of 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 4.5, or any two of these numbers.

[0029] In some embodiments, m is between 1 and 10. In some embodiments, m is a value within the range of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any two of these numbers.

[0030] In some embodiments, d is between 1.2 and 1.4. In some embodiments, d is a value within the range of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or any two of these numbers.

[0031] On the other hand, if the ID / IG ratio d of the hard carbon material is within the above range, the hard carbon material has a high defect content. These defects may be caused by the disorder and disorder of the microcrystalline structure of the hard carbon material, or by micropore defects within the hard carbon material. The high defect content allows the hard carbon material to have more sodium ion adsorption sites, thereby improving the rapid charge and discharge capacity of the material. Therefore, by applying the hard carbon material of this application as the negative electrode active material of an electrochemical apparatus, the electrochemical apparatus can achieve good dynamic performance.

[0032] On the other hand, embodiments of this application provide an electrolyte compatible with the above-mentioned highly dynamic rigid carbon material. The electrolyte comprises a first additive M, which is selected from at least one of fluorinated carbonate compounds or sulfur-oxygen double bond-containing compounds. During the initial charge-discharge process, a solid electrolyte interface film (i.e., SEI film) is formed on the surface of the negative electrode active material of the sodium-ion battery, and a structurally stable SEI film is key to a stable cycle of sodium ions. By selecting the composition and content of additives in the electrolyte system, the structure of the SEI film can be made uniform, controlled to be dense and thin, blocking the electrolyte and preventing further decomposition, and expanding the actual electrochemical window of the electrolyte. The strong electron-withdrawing effect of the fluorine atom in the fluorinated carbonate compound improves the electron capability of the central atom, which is reduced at a relatively high potential (~0.7V) on the negative electrode surface to produce a stable SEI film, and further prevents the decomposition of carbonate ester compounds on the active material surface. Sulfur-oxygen double bond-containing compound additives have a similar effect. Because the electronegativity of sulfur atoms is higher than that of carbon atoms, they are preferentially reduced on the negative electrode surface compared to carbonate ester compounds with similar structures, forming a stable SEI film rich in sulfur elements. This improves the high and low temperature performance of electrochemical devices and reduces interfacial resistance.

[0033] Furthermore, the inventors of this application have discovered that surface defects and defect content of the hard carbon active material also affect the formation and structural stability of the SEI film. Due to the higher reaction activity of the defects, they can induce the formation of the SEI film and affect its stability. Therefore, the selection of electrolyte additive content in sodium-ion battery systems requires further consideration of the surface defect content of the hard carbon active material. The inventors of this application have discovered that when the range of m / d between the ID / IG ratio d in the Raman spectral spectrum of the hard carbon material and the mass percentage content m% of the first additive M is within the above range, the SEI film formed at this time effectively improves the transfer rate of sodium ions, thereby improving the kinetic performance, low-temperature performance, and cycle performance of the sodium-ion battery, while simultaneously achieving a capacity per gram of the negative electrode active material.

[0034] In some embodiments, the lattice plane spacing d002 of the hard carbon material is in the range of 0.37 nm to 0.41 nm, as measured by X-ray diffraction. In some embodiments, the lattice plane spacing d002 of the hard carbon material is in the range of 0.38 nm to 0.40 nm. In some embodiments, the lattice plane spacing d002 of the hard carbon material is a value within the range of 0.37 nm, 0.38 nm, 0.39 nm, 0.40 nm, 0.41 nm, or any two of these values. When the 002 lattice plane spacing of the hard carbon material is within the above range, a large 002 lattice plane spacing is advantageous for the rapid transport of sodium ions within the hard carbon material, thereby improving the reversible capacity and kinetic performance when the hard carbon material is applied as a negative electrode active material. In some embodiments, the lattice plane spacing d002 is in the range of 0.38 nm to 0.40 nm, which can further improve the kinetic performance of the hard carbon material.

[0035] In some embodiments, the mass percentage content of the fluorinated carbonate compound is 0.05% to 5% based on the mass of the electrolyte. In some embodiments, the mass percentage content of the fluorinated carbonate compound is within the range of 0.05%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 5%, or any two of these values.

[0036] In some embodiments, the mass percentage content of the sulfur-oxygen double bond-containing compound is 0.05% to 4% based on the mass of the electrolyte. In some embodiments, the mass percentage content of the sulfur-oxygen double bond-containing compound is within the range of 0.05%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or any two of these values.

[0037] The inventors of this application have discovered that when the mass percentage content of the fluorinated carbonate compound additive in the electrolyte system is in the range of 0.05% to 5%, and / or the mass percentage content of the sulfur-oxygen double bond-containing compound additive is in the range of 0.05% to 4%, the thickness of the formed SEI film is appropriate and the structure is stable.

[0038] In some embodiments, the sulfur-oxygen double bond-containing compound includes at least one of 1,3-propanesultone, propene-1,3-sultone, 1,2-propanesultone, 1,4-butanesultone, or ethylene sulfate.

[0039] In some embodiments, the fluorinated carbonate compound comprises at least one of fluoroethylene carbonate or difluoroethylene carbonate.

[0040] In some embodiments, the hard carbon material has pores inside, the pore diameter range of 0.6 nm to 2.0 nm, and the pore volume is less than 0.05 g / cc as determined by nitrogen gas adsorption testing.

[0041] In some embodiments, the pore diameter range is within the range of 0.6 nm, 0.8 nm, 1.0 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2.0 nm, or any two of these values.

[0042] In some embodiments, the pore volume is a value within the range of 0.01 g / cc, 0.02 g / cc, 0.03 g / cc, 0.04 g / cc, 0.05 g / cc, or any two of these values.

[0043] The hard carbon material described in this application has an abundant pore structure internally. When a pore structure within the above-mentioned pore diameter range is present in the hard carbon material, sodium ions can be stored in the micropores during the sodium storage process, thereby providing a high reversible capacity. In some embodiments, when used in an electrochemical apparatus with metallic sodium as the counter electrode, the capacity per gram of the hard carbon material is 200 mAh / g to 1000 mAh / g. Therefore, by applying the hard carbon material of this application as the negative electrode active material for a sodium-ion battery, the sodium-ion battery can have a high energy density. When the pore volume is within the above-mentioned range, the pore structure on the material surface or the content of external communication pores is low.

[0044] In some embodiments, the specific surface area of ​​the hard carbon material is 0.5 m². 2 / g~10m 2 It is / g. In some embodiments, the specific surface area of ​​the hard carbon material is 0.5m². 2 / g, 1m 2 / g, 1.5m 2 / g, 2m 2 / g, 2.5m 2 / g, 3m 2 / g, 3.5m 2 / g, 4m 2 / g, 4.5m 2 / g, 5m 2 / g, 5.5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, or a value within the range of any two of these numbers.

[0045] When the specific surface area of ​​the hard carbon material is within the above range, it is possible not only to ensure that the SEI film formed during the initial charging process of the electrochemical apparatus has an area of ​​appropriate size, but also to reduce the amount of adhesive used in the negative electrode active material layer. This reduces the loss of active ions and the internal resistance of the negative electrode active material layer, thereby improving the initial Coulomb efficiency, cycle performance, and safety performance of the electrochemical apparatus.

[0046] In some embodiments, the compaction density of hard carbon material after depressurization at 5 tons is 0.8 g / cc to 1.6 g / cc. In some embodiments, the compaction density of hard carbon material after depressurization at 5 tons is within the range of 0.8 g / cc, 1.0 g / cc, 1.2 g / cc, 1.4 g / cc, 1.6 g / cc, or any two of these values. It can be expected that a suitable particle size distribution of the active material helps to improve the powder compaction density of the material. From the perspective of the active material itself, the density of the active material is mainly caused by the disordered arrangement of the microcrystalline segregation layer and a large number of pore defects within the material. Because of the abundant pore defects for sodium storage within the hard carbon material, the powder compaction density of the hard carbon material is much lower than that of graphite material. If the compaction density of the hard carbon material after depressurization at 5 tons of pressure is within the above range, the hard carbon material has a high powder compaction density.

[0047] In some embodiments, measurements by X-ray diffraction reveal that the hard carbon material has diffraction peaks in the range of 18° to 30°, with a full width at half maximum (FWHM) of the diffraction peaks being 4° to 12°. In some embodiments, the FWHM of the diffraction peaks is within the range of 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, or any two of these values.

[0048] In some embodiments, the Dv50 of the hard carbon material is 2 μm to 10 μm. In some embodiments, the Dv50 of the hard carbon material is a value within the range of 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any two of these values. When the volume-average particle size of the hard carbon material is within the above range, the hard carbon material can have good electrolyte penetration performance, and on the other hand, the hard carbon material can have a small specific surface area, thereby reducing the consumption of active ions due to the formation of an SEI film on the surface of the hard carbon material during the initial charging process. Therefore, by applying the hard carbon material of this application as the negative electrode active material of an electrochemical apparatus, the electrochemical apparatus can achieve both good dynamic performance and high initial Coulomb efficiency. In some embodiments, the Dv50 and Dv90 of the hard carbon material satisfy 2 ≤ Dv90 / Dv50 ≤ 5. In some embodiments, the ratio of Dv50 to Dv90 of the hard carbon material, Dv90 / Dv50, is a value within the range of 2, 3, 4, 5, or any two of these values. When the ratio of Dv50 to Dv90 of the hard carbon material is within the above range, an appropriate particle size distribution helps to improve the compaction density of the active material layer, resulting in tighter contact between particles after cold pressing of the active material layer, effectively improving the porosity of the active material layer. At the same time, the close contact between particles helps to reduce the impedance of the electrode sheets and improve the dynamic performance of the electrochemical apparatus. Furthermore, an appropriate particle size distribution also helps to improve the processing performance of the active material layer, effectively increasing the thickness of the active material layer and further improving the energy density of the electrochemical apparatus.

[0049] In some embodiments, the Dv90 of the hard carbon material is 5 μm to 50 μm. In some embodiments, the Dv90 of the hard carbon material is a value within the range of 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any two of these values.

[0050] In some embodiments, the porosity range of the negative electrode active material layer is 30% to 60%. In some embodiments, the porosity of the negative electrode active material layer is within the range of 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any two of these values.

[0051] In some embodiments, the compaction density range of the negative electrode active material layer is 0.8 g / cc to 1.5 g / cc. In some embodiments, the compaction density of the negative electrode active material layer is within the range of 0.8 g / cc, 0.9 g / cc, 1.0 g / cc, 1.1 g / cc, 1.2 g / cc, 1.3 g / cc, 1.4 g / cc, 1.5 g / cc, or any two of these values.

[0052] In some embodiments, the thickness range of the negative electrode active material layer on one side is 50 μm to 120 μm. In some embodiments, the thickness range of the negative electrode active material layer is 50 μm, 80 μm, 100 μm, 120 μm, or any two of these values.

[0053] In some embodiments, the electrode sheet capacity per unit area of ​​the negative electrode active material layer is denoted as V1, the positive electrode includes a positive electrode active material layer, the electrode sheet capacity per unit area of ​​the positive electrode active material layer is denoted as V2, and the range of V1 / V2 is 1.1 to 1.5. In some embodiments, the range of V1 / V2 is 1.1 to 1.2. In some embodiments, V1 / V2 is a value within the range of 1.1, 1.2, 1.3, 1.4, 1.5, or any two of these values. Because the sodium storage plateau potential of hard carbon materials is close to the sodium deposition potential, any small increase in polarization during the cycling process can cause sodium deposition, thereby leading to capacity loss, gas generation, or safety problems. To further reduce the possibility of sodium deposition, the electrode sheet capacity per unit area of ​​the negative electrode active material layer needs to be slightly higher than the electrode sheet capacity per unit area of ​​the corresponding positive electrode active material layer. In this application, by keeping the ratio of the electrode sheet capacity per unit area of ​​the negative electrode active material layer to the electrode sheet capacity per unit area of ​​the corresponding positive electrode active material layer within the above range, not only are safety issues reduced, but the energy density of the electrochemical apparatus can also be effectively guaranteed.

[0054] In some embodiments, the negative electrode of this application includes a negative electrode current collector. In some embodiments, the negative electrode current collector of this application is not particularly limited and may be a metal foil, a porous metal plate, or a composite current collector. A composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. A composite current collector can be obtained by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a substrate such as a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE). As one example, the negative electrode sheet is a negative electrode sheet for a lithium-ion battery, and the negative electrode current collector may be copper foil. As another example, the negative electrode sheet is a negative electrode sheet for a sodium-ion battery, and the negative electrode current collector may be copper foil or aluminum foil.

[0055] In some embodiments, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer may be provided on one surface of the negative electrode current collector, or on both surfaces of the negative electrode current collector simultaneously. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposing surfaces of the negative electrode current collector.

[0056] In some embodiments, the negative electrode active material layer may optionally contain an adhesive. The adhesive may be selected from at least one of the following: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin, and nylon.

[0057] In some embodiments, the negative electrode active material layer may optionally contain a conductive agent. The conductive agent may be selected from carbon-based materials, metallic materials, conductive polymers, or any combination of the above materials. For example, carbon-based materials may be selected from at least one of natural graphite, artificial graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, and carbon nanofibers. Metallic materials may be selected from metal powders and metal fibers. Conductive polymers may include polyphenylene derivatives.

[0058] In some embodiments, the negative electrode active material layer optionally includes other additives such as thickeners, such as sodium carboxymethylcellulose (CMC-Na).

[0059] The negative electrode in this application can be manufactured according to conventional methods in the art. For example, the hard carbon and any other negative electrode active material, conductive agent, adhesive and thickener are dispersed in a solvent, the solvent of which may be N-methylpyrrolidone (NMP) or deionized water to form a uniform negative electrode slurry, the negative electrode slurry is applied onto a negative electrode current collector, and a negative electrode sheet is obtained through processes such as drying and cold pressing.

[0060] Note that the parameters of each negative electrode active material layer provided in this application all refer to the parameter range of a negative electrode active material layer on a single surface. If a negative electrode active material layer is provided on two surfaces of a negative electrode current collector, if the parameters of the negative electrode active material layer on either one surface satisfy the range for which protection is sought in this application, it shall be deemed to be included in the scope of protection of this application.

[0061] The negative electrode sheet described herein may include additional functional layers other than the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application may further include a conductive undercoat layer (e.g., consisting of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode active material layer and provided on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet of this application may further include a protective layer covering the surface of the negative electrode active material layer.

[0062] In some embodiments, this application provides a method for manufacturing hard carbon, the manufacturing method comprising the following steps: (1) The precursor material is oxidized at 100-500°C for a processing time of 100-400 minutes to obtain the precursor material after oxidation. (2) Pre-carbonization, pre-thermal decomposition and carbonization treatment are performed on the oxidized precursor material to obtain the carbonized material, and classification treatment is performed on the carbonized material to obtain precursor hard carbon materials having corresponding Dv50 and Dv90 values. (3) The precursor hard carbon material is subjected to a surface coating treatment by holding it at 500 to 1100°C for 5 to 15 hours.

[0063] In some embodiments, the precursor material in the method for producing the hard carbon material described above may be a biomass material, a resin material, a sugar-based material, an asphalt-based material, or a coal-based material. The biomass material may include, but is not limited to, lignin, cellulose, straw, coconut shells, walnut shells, etc. The resin material may be a phenolic resin, a furfural resin, an epoxy resin, an amide resin, a fluorine-containing resin, or a chlorine-containing resin. The sugar-based material may be glucose, magnesium gluconate, sodium gluconate, fructose, starch, maltose, and other sugar derivatives and other sugar derivatives.

[0064] In some embodiments, the oxidation treatment temperature is within the range of 100°C, 200°C, 300°C, 400°C, 500°C, or any two of these values. In some embodiments, the oxidation treatment time is within the range of 100 min, 200 min, 300 min, 400 min, or any two of these values.

[0065] In some embodiments, the pre-carbonization temperature is 400 to 700°C, and the pre-carbonization time is 1 to 4 hours. In some embodiments, the pre-carbonization temperature is within the range of 400°C, 500°C, 600°C, 700°C, or any two of these values.

[0066] In some embodiments, the pre-carbonization time is 1 hour, 2 hours, 3 hours, 4 hours, or a value within a range of any two of these numbers.

[0067] In some embodiments, the pre-thermal decomposition temperature is 50 to 200°C. In some embodiments, the pre-thermal decomposition temperature is within the range of 50°C, 80°C, 100°C, 150°C, 180°C, 200°C, or any two of these values.

[0068] In some embodiments, the pre-thermal decomposition time is 5 to 20 hours. In some embodiments, the pre-thermal decomposition time is within the range of 5 hours, 8 hours, 10 hours, 12 hours, 14 hours, 14 hours, 16 hours, 20 hours, or any two of these values.

[0069] In some embodiments, the material after pre-thermal decomposition is subjected to crushing, sieving, and desquamation. In some embodiments, the desquamation method can be washing with an acidic solution, the acidic solution containing hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or a mixture of the aforementioned acids.

[0070] In some embodiments, the carbonization temperature is 800 to 1500°C. In some embodiments, the carbonization temperature is within the range of 800°C, 1000°C, 1200°C, 1300°C, 1400°C, 1500°C, or any two of these values.

[0071] In some embodiments, the carbonization treatment time is 0.5 to 5 hours. In some embodiments, the carbonization treatment time is within the range of 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 5 hours, or any two of these values.

[0072] In some embodiments, pre-carbonization and carbonization treatment are carried out in an inert gas. In some embodiments, the inert gas includes nitrogen gas, helium gas, argon gas, or a mixture of the aforementioned gases.

[0073] In some embodiments, the surface coating method in the manufacturing method of the hard carbon material described above can be high-temperature melt coating with asphalt or a molten resin, spray coating with a soluble resin, or high-temperature coating with a reducing gas. After coating with asphalt, a molten resin, or a soluble resin, it is necessary to perform thermal decomposition again, and the thermal decomposition temperature range is 700°C to 1300°C. The reducing gas can be methane, acetylene, cyclohexane, benzene, toluene, etc.

[0074] The materials, structure, and manufacturing methods of the positive electrode sheet used in the electrochemical apparatus of this application may include any techniques known in the art.

[0075] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and containing positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode active material layer is provided on any one or two of the two opposing surfaces of the positive electrode current collector.

[0076] In some embodiments, the positive electrode active material layer includes a positive electrode active material, the specific type of which is not particularly limited and may be selected according to requirements.

[0077] In some embodiments, the electrochemical device is a sodium-ion battery. The positive electrode active material can be a positive electrode active material known in the art for sodium-ion secondary batteries. For example, the positive electrode active material may include one or more sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0078] As an example, the above sodium transition metal oxide is, for example, Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 It contains one or more of the following: Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≦0.33、0<h≦0.24、0≦k≦0.32、0<l≦0.68、0≦m<0.1、h+k+l+m=l、0≦y<0.2、Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, here, M 2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba, and 0 <z≦0.1、Na a Lib Ni c Mn d Fe e O2, where 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, and b + c + d + e = 1. As an example, the above polyanion compound is, for example, A l f M 3 g (PO4) i OjX 1 3-j , where A 1 is selected from Na and one or more of H, Li, K, and NH4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, and X 1 is one or more of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2, Na n M 4 PO4X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, and X 2 is one or more of F, Cl, and Br, 0 < n ≤ 2, Na p M 5 q (SO4)3, where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2, Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3. For example, t is 0, 1, 1.5, 2, or 3.

[0079] As an example, the above Prussian blue compound is, for example, A 2 u M 6 V [M 7 (CN)6] w .xH2O, where A 2 is Na and H + , NH 4+and one or more selected from among surplus alkali metal cations and alkaline earth metal cations, M 6 and M 7 are each independently selected from one or more of transition metal cations, where 0 < u ≦ 2, 0 < V ≦ 1, 0 < w ≦ 1, 0 < x < 6. For example, A 2 is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Ra 2+ is one or more of these, and M 6 and M 7 are each independently cations of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W. Preferably, A 2 is one or more of Li + , Na + and K + , and M 6 is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni, and Cu, and M 7 is a cation of one or more transition metal elements selected from Mn, Fe, Co, Ni, and Cu.

[0080] In some embodiments, the positive electrode active material layer may optionally contain a conductive agent. By way of example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, and carbon nanofibers.

[0081] In some embodiments, the positive electrode active material layer may optionally contain an adhesive. For example, the conductive agent can be selected from carbon-based materials, metallic materials, conductive polymers, or any combination of the above materials. For example, carbon-based materials may be selected from at least one of natural graphite, artificial graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, and carbon nanofibers. Metallic materials may be selected from metal powders and metal fibers. Conductive polymers may include polyphenylene derivatives.

[0082] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of a metal foil, the positive electrode current collector can be an aluminum foil. A composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may be selected from one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.

[0083] The positive electrode sheet in this application can be manufactured by conventional methods in the art. For example, the positive electrode active material layer is usually formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is usually formed by dispersing the positive electrode active material, any conductive agent, any adhesive, and any other components in a solvent and stirring it uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP).

[0084] The positive electrode sheet of this application may optionally include other additional functional layers besides the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of this application may further include a conductive undercoat layer (e.g., consisting of a conductive agent and an adhesive) sandwiched between the positive electrode current collector and the positive electrode active material layer and provided on the surface of the positive electrode current collector. In some other embodiments, the positive electrode sheet of this application may further include a protective layer that covers the surface of the positive electrode active material layer.

[0085] The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The electrolyte that can be used in the electrochemical device of this application may be an electrolyte known in the prior art. In some embodiments, the electrolyte may include an organic solvent, an electrolyte salt, and optional additives.

[0086] In some embodiments, the electrochemical apparatus is a sodium-ion cell, and the electrolyte salt may include a sodium salt. For example, the sodium salt may be selected from at least one of NaPF6, NaC1O4, NaBC14, NaSO3CF3, and Na(CH3)C6H4SO3. In some embodiments, the concentration of the sodium salt in the electrolyte is about 0.5–3 mol / L, about 0.5–2 mol / L, or about 0.8–1.5 mol / L.

[0087] In some embodiments, the electrochemical device is a lithium-ion battery, and the electrolyte salt may include a lithium salt. In some embodiments, the electrolyte is an inorganic lithium salt such as LiClO4, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, e.g., LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropanedisulfonyliimide lithium, cyclic 1,2-tetrafluoroethanedisulfonyliimide lithium, LiN(CF3SO2)(C4F9SO2), LiC(CF3SO2)3, LiPF4(CF3)2, LiPF4(C Examples of fluorine-containing organolithium salts include, but are not limited to, fluorine-containing organolithium salts such as 2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2, as well as lithium salts containing dicarboxylic acid complexes such as lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0088] Furthermore, the electrolyte may be used alone or two or more simultaneously. For example, in some embodiments, the electrolyte includes a combination of LiPF6 and LiBF4. In some embodiments, the electrolyte is a combination of an inorganic lithium salt such as LiPF6 or LiBF4 and a fluorine-containing inorganic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, or LiN(C2F5SO2)2. In some embodiments, in some aspects, the concentration of the electrolyte is in the range of 0.8 to 3 mol / L, for example, in the range of 0.8 to 2.5 mol / L, 0.8 to 2 mol / L, 1 to 2 mol / L, 0.5 to 1.5 mol / L, 0.8 to 1.3 mol / L, or 0.5 to 1.2 mol / L, for example, 1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0089] In some embodiments, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may also include additives that can improve several aspects of the battery's performance, such as an additive that improves the battery's overcharge performance and an additive that improves the battery's high-temperature or low-temperature performance.

[0090] In addition to the above-mentioned fluorinated carbonate compounds and sulfur-oxygen double bond-containing compounds, the above-mentioned additives may also include, for example, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), and fluoroethylene carbonate. It may contain, but is not limited to, at least one of the following: methyl methyl formate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0091] The above organic solvents may be used individually or two or more simultaneously. Preferably, two or more of the above organic solvents may be used in combination.

[0092] The electrolyte can be manufactured by conventional methods in the art. For example, an electrolyte can be obtained by uniformly mixing an organic solvent, an electrolyte salt, and any additives. The order in which the raw materials are added is not particularly limited; for example, the electrolyte can be obtained by adding the electrolyte salt and any additives to the organic solvent and mixing them uniformly, or by adding the electrolyte salt to the organic solvent first, and then adding any additives to the organic solvent and mixing them uniformly.

[0093] Separator

[0094] The separator is placed between the positive electrode sheet and the negative electrode sheet and primarily serves to prevent short circuits between the positive and negative electrodes while simultaneously allowing the passage of active ions. The separator usable in the electrochemical apparatus of this application can be any known porous structure separator having good chemical and mechanical stability.

[0095] In some embodiments, the separator material is selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these. Preferably, the separator material includes polyethylene and / or polypropylene. The separator may be a single layer film or a multilayer composite film. If the separator is a multilayer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating may be further provided on the separator.

[0096] In some embodiments, the electrode assembly can be manufactured by winding or laminating a positive electrode sheet, a negative electrode sheet, and a separator.

[0097] The electrochemical apparatus of this application further includes an outer casing used to seal the electrode assembly and the electrolyte. In some embodiments, the outer casing may be a hard case, such as a rigid plastic shell, an aluminum shell, or a steel shell, or a soft package, such as a bag-shaped soft package. The material of the soft package is at least one of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0098] This application is not particularly limited to the shape of the electrochemical apparatus, which may be cylindrical, angular, or any other shape. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly by a winding or lamination process. The electrode assembly is sealed within the electrochemical apparatus. The number of electrode assemblies included in the electrochemical apparatus may be one or more, and a person skilled in the art may select them according to the specific practical needs.

[0099] The manufacturing process of electrochemical devices is known to those skilled in the art, and this application does not particularly limit it. For example, a lithium-ion battery or a sodium-ion battery can be manufactured by the following process: the positive electrode and the negative electrode are stacked with a separator in between, and after winding, folding, or other operations as necessary, they are placed in a case, and the electrolyte is injected into the case and sealed. In addition, if necessary, overcurrent prevention elements, conductive plates, etc., can be placed inside the case to prevent pressure rise and overcharging / discharging inside the sodium-ion battery or lithium-ion battery.

[0100] The following describes a method for manufacturing a sodium-ion battery, using a sodium-ion battery as an example and combining specific embodiments. However, those skilled in the art should understand that the manufacturing method described in this application is merely illustrative, and any other suitable manufacturing method is also included within the scope of this application.

[0101] Examples

[0102] The performance evaluation is performed below based on the examples and comparative examples of the sodium-ion battery of this application.

[0103] Manufacturing of sodium-ion batteries

[0104] 1. Manufacturing of the negative electrode

[0105] Manufacturing of hard carbon materials (negative electrode active material)

[0106] The hard carbon materials used in Examples 1-1 to 1-7, Examples 1-15 to 1-20, and Comparative Example 1-1 are manufactured by the following method.

[0107] 100g of high-temperature asphalt, a precursor material with a softening point of approximately 240°C, and 10g of potassium tartrate template agent are placed in a reaction vessel, heated to 250°C and stirred to melt and mix the precursor material and template agent to obtain the mixed precursor material. After cooling to room temperature, the mixed precursor material is crushed to a Dv50 of 8-15 μm to obtain the precursor material powder. Next, the precursor material powder is placed back into the reaction vessel, heated to 200°C and maintained at that temperature, and a mixed gas of oxygen and nitrogen (where the volume percentage of oxygen is 10%) is passed through the reaction vessel at a rate of 200 ml / min for 180 min to perform an oxidation treatment on the precursor material powder. During the oxidation treatment process, the reaction vessel must be kept agitated to obtain the oxidized precursor material.

[0108] The prepared oxidized precursor material is placed in a tubular furnace, heated to 600°C and maintained for 2 hours to perform a pre-carbonization treatment to obtain pre-carbonized material. The heating rate during the treatment process is 2°C / min, and the atmosphere is 10 L / min of nitrogen gas. After crushing the pre-carbonized material, it is placed in a 1 mol / L hydrochloric acid solution, heated to 100°C and stirred for 12 hours to obtain a pre-pyrolysis carbon solution. The pH value of the pre-pyrolysis carbon solution is then determined by multiple washes and extractions. The material is washed to a more neutral pH, then extracted again and dried to obtain pre-pyrolysis carbon. 50g of the pre-pyrolysis carbon is placed in a tubular furnace, heated to 1200°C and maintained for 2 hours to perform carbonization. The heating rate during the process is 4°C / min, and the atmosphere is 10L / min of nitrogen gas. The material after carbonization is obtained, and the material after carbonization is subjected to classification to obtain a precursor hard carbon material with a Dv50 of 5.2μm and a Dv90 of 13.2μm.

[0109] 50 g of the precursor hard carbon material prepared above was placed in a rotary furnace with an internal volume of 1 L, and the temperature was raised to 750°C under a nitrogen atmosphere of 0.5 L / min. Then the atmosphere was changed to an ethylene-argon mixed gas of 0.5 L / min (wherein the volume proportion of ethylene is 10%), and the temperature was maintained for 10 hours to perform a surface coating treatment on the precursor hard carbon material, thereby preparing the desired hard carbon material.

[0110] The hard carbon materials in Examples 1-8 to 1-11 were manufactured by the following method, with coating times of 16h, 8h, 4h, and 2h in the coating process, respectively, while other conditions were the same as those in the manufacturing process of Example 1-1.

[0111] The hard carbon materials in Examples 1-12 to 1-14 were manufactured by the following method, with oxidation treatment times for the precursor powder set to 150 min, 300 min, and 60 min, respectively, while other conditions were the same as those in the manufacturing process of Example 1-1.

[0112] The hard carbon material in Comparative Example 1-2 was manufactured by the following method: the oxidation treatment time of the hard carbon material precursor powder was 60 mins, the coating time in the coating process was 16 hs, and after the coating process was completed, the material was placed back into the tubular furnace, heated to 900°C and held for 2 hs to perform a secondary carbonization treatment. The heating rate was 4°C / min, and the atmosphere was 10 L / min of nitrogen gas. Other conditions were the same as the manufacturing process in Example 1-1.

[0113] The hard carbon material in Comparative Examples 1-3 was manufactured by the following method, with a coating time of 16 hours in the coating process. After the coating process was completed, the material was placed back into the tubular furnace, heated to 1000°C and held for 2 hours for secondary carbonization. The heating rate was 4°C / min, and the atmosphere during the carbonization process was 10 L / min of nitrogen gas. Other conditions were the same as those in the manufacturing process of Example 1-1.

[0114] The hard carbon materials in Examples 2-1 to 2-10 were manufactured by the following method, and the carbonized material was subjected to classification to obtain materials having the corresponding Dv50 and Dv90 values. Other conditions were the same as those in the manufacturing process of Example 1-2.

[0115] B. The hard carbon material (negative electrode active material) prepared above, styrene-butadiene rubber as an adhesive, and sodium carboxymethylcellulose (CMC-Na) are dissolved in deionized water in a weight ratio of 97:1.5:1.5 to form a negative electrode slurry (solid content: 40 wt%). A 10 μm thick aluminum foil is used as the negative electrode current collector, and the negative electrode slurry is applied to the current collector of the negative electrode sheet, with a single-sided coating thickness of 50 μm. It is dried at 85°C, then cold-pressed, cut, and slit, and finally dried under vacuum conditions at 120°C for 12 hours to obtain a negative electrode tab.

[0116] 2. Manufacturing of the positive electrode

[0117] NaNi 7 / 20 Fe 7 / 20 Mn 3 / 10 O2, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) is added as a solvent. The mixture is then uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry (solid content: 72 wt%) is uniformly applied to an aluminum foil, which serves as the positive electrode current collector, to a thickness of 80 μm. It is dried at 85°C, then cold-pressed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to obtain a positive electrode sheet.

[0118] 3. Preparation of the electrolyte

[0119] Ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) are mixed in a mass ratio of 1:1:1 to obtain an organic solvent. NaPF6 is dissolved in the organic solvent, and then fluoroethylene carbonate (FEC) and / or a sulfur-oxygen double bond-containing compound are added and mixed uniformly to obtain an electrolyte. Here, based on the total mass of the electrolyte, the mass percentage content of NaPF6 is 12.5%. Refer to Table 1 for the mass percentage content of fluoroethylene carbonate (FEC) and the sulfur-oxygen double bond-containing compound. Therein, m% is the sum of the mass percentage content of the fluorinated carbonate compound and the sulfur-oxygen double bond-containing compound.

[0120] 4. Manufacturing of separators

[0121] A 7μm thick polyethylene (PE) is used as the separator.

[0122] 5. Manufacturing of sodium-ion batteries

[0123] A positive electrode sheet, a separator, and a negative electrode sheet are stacked in order and wound to obtain an electrode assembly 52. ​​The electrode assembly 52 is placed inside the outer casing, the electrolyte is added, and a sodium-ion battery is obtained through processes such as sealing, standing, chemical formation, and shaping. The design potential range of the sodium-ion battery is 2.0V to 4.53V.

[0124] 2. Method for measuring the performance of sodium-ion batteries

[0125] 1. Method for measuring the ID / IG value of hard carbon materials

[0126] In this application, the ID / IG ratio of a hard carbon material has a meaning known in the art and can be measured by methods known in the art. For example, measurement by Raman spectroscopy is employed, and the surface defect degree of a sample is measured using a micro-laser Raman spectrometer. An area of ​​100m × 100m is selected from the negative electrode active material layer, and particles within that area are scanned using a micro-laser Raman spectrometer (Raman, HRE Volution, HORIBA Scientific Instruments Division). The D peak and G peak of all particles within that area range are obtained, the data is processed using LabSpec software, and the intensities of the D peak and G peak of each particle are obtained as ID and IG, respectively. The laser wavelength of the Raman spectrophotometer may be in the range of 532nm to 785nm. The ID / IG value in this text is the average value of all ID to IG ratios measured within that range. The D peak is generally 1350 ± 50 cm². -1 It appears in the vicinity and is due to a symmetric stretching vibration radial breathing mode of sp2 carbon atoms in the aromatic ring (structural defect), and the G peak is at 1580±50 cm.-1 It appears in the vicinity and is due to stretching vibrations between sp2 carbon atoms. In this application, the value of ID / IG is denoted as d.

[0127] 2. Method for measuring the lattice plane spacing d002 of hard carbon materials

[0128] The X-ray diffraction patterns of hard carbon materials have known significance in this art and are measured using an X-ray powder diffractometer. An X-ray powder diffractometer (XRD, instrument model: BrukerD8ADvANCE) is used to measure the negative electrode active material graphite. The target is CuKα, the voltage and current are 40KV / 40mA, the scanning angle range is 5° to 80°, the scanning step width is 0.00836°, and the time per step is 0.3s. Furthermore, according to Bragg's law, 2dsinθ=λ (where d is the lattice plane spacing), d002=λ / (2sinθ), where θ is the angle at the position of the maximum peak intensity of the 002 peak.

[0129] 3. Method for measuring the content of each component in the electrolyte.

[0130] The components in the electrolyte and their content can be measured according to conventional methods in the art. The components in the electrolyte and their content can be detected, for example, by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), etc. 4. Method for measuring pore size and pore volume of hard carbon materials

[0131] 4. The pore structure on the surface of hard carbon materials can be measured by methods known in the art. For example, it can be obtained by measurement using an ASAP2460 physicoadsometer. Specifically, after taking a sample of negative electrode active material powder and performing drying and degassing pretreatment, an ASAP2460 physicoadsometer is used, the test atmosphere is nitrogen gas, different test pressures are adjusted, and the amount of nitrogen gas adsorbed is measured for each, creating adsorption isotherms and desorption isotherms. The pore shape is determined based on the shape of the hysteresis loop, and by fitting using a DFT model, a pore size distribution curve of the micropores of the active material is obtained, and further information on the content and pore size of externally connected micropores is obtained.

[0132] 5. Method for measuring the particle size of hard carbon materials

[0133] The volume-average particle sizes Dv50 and Dv90 of hard carbon materials have meanings known in the art, indicating that 50% and 90% of the particles in the volume-based particle size distribution of the hard carbon material have particle sizes smaller than these values, respectively, and can be measured by methods known in the art. For example, they can be measured using a laser particle size analyzer (e.g., a Malvern Mastersizer 2000E from the UK) by referring to the GB / T19077-2016 particle size distribution laser diffraction method. Furthermore, the Dv90 / Dv50 ratio can be determined.

[0134] 6. Consolidation density of hard carbon material after depressurization under 5 tons of pressure.

[0135] The measurement standards refer to GB / T24533-2009 "Graphite-based negative electrode materials for lithium-ion batteries". Specifically, a negative electrode active material sample of 1.0000 ± 0.0500 g is weighed and placed in a measuring mold (CARVER #3619 (13 mm)). Next, the negative electrode active material sample is placed in a measuring device, which is a Sanshi Tateyoko UTM7305. The measuring load is 5.0 tons, the pressurization rate is 10 mm / min, the pressurization holding time is 30 s, the depressurization rate is 30 mm / min, and the depressurization holding time is 10 s. The compaction density is measured during depressurization, and the formula for calculating the compaction density is: compaction density = negative electrode active material mass / negative electrode active material load-bearing area / negative electrode active material thickness.

[0136] 7. Method for measuring the specific surface area of ​​hard carbon materials

[0137] The specific surface area of ​​a hard carbon material has a known meaning in the art and can be measured by methods known in the art. For example, the specific surface area of ​​the negative electrode active material is measured using a specific surface area analyzer (Tristar II 3020 M) by nitrogen gas adsorption / desorption.

[0138] 8. Method for measuring the compaction density of the negative electrode active material layer

[0139] The compaction density of the negative electrode active material layer has a meaning known in the art and can be measured by methods known in the art. For example, the weight of the negative electrode sheet (with the negative electrode active material layer coated on both sides of the negative electrode current collector) after treatment of area S is measured using an electronic balance and recorded as W1. The thickness T1 of the negative electrode sheet is measured using a fraction of a millimeter. The negative electrode active material layer is removed using a solvent and dried. The weight of the negative electrode current collector is measured and recorded as W2. The thickness T2 of the negative electrode current collector is measured using a fraction of a millimeter, and the compaction density PD of the negative electrode active material layer on one side of the negative electrode current collector is PD = (W1 - W2) / {(T1 - T2)·S}.

[0140] 9. Method for measuring the porosity of the negative electrode active material layer

[0141] The negative electrode active material layer sample was prepared into a complete disc. Five samples were measured for each example or comparative example, with each sample volume being approximately 0.35 cm³. The porosity of the negative electrode active material layer was measured according to the standard "GB / T 24586-2009 Measurement of apparent density, true density and porosity of iron ore". The measurement gas was helium gas.

[0142] 10. Method for measuring the volume per gram and initial efficiency of the negative electrode active material.

[0143] The capacity per gram and initial efficiency of the negative electrode active material have meanings known in the art and can be measured by methods known in the art. For example, a negative electrode slurry is obtained by mixing a hard carbon material with an appropriate amount of adhesive, conductive agent and solvent and making it homogenized. The negative electrode slurry is applied to the surface of the negative electrode current collector to obtain a negative electrode sheet. A metallic sodium piece is used as the counter electrode, and the negative electrode sheet is assembled with it to manufacture a coin-type battery. A charge-discharge cycle is performed on the coin-type battery, and the measurement mode is constant current discharge - constant voltage discharge - constant current charge. The measured initial desodium capacity is the capacity per gram of the active material, and the initial efficiency is obtained by dividing the initial desodium capacity by the initial sodium storage capacity. Furthermore, charging and discharging is performed on the coin-type battery under a current density of 0.05C in a constant current discharge - constant voltage discharge - constant current charge mode, and the ratio of 0.05C constant current sodium storage capacity / total sodium storage capacity = measured capacity of the constant current discharge portion / (measured capacity of the constant current discharge portion + measured capacity of the constant voltage discharge portion).

[0144] 11. Method for measuring the rate performance of sodium-ion batteries

[0145] Five sodium-ion batteries are selected from each group, and the following steps are used to repeatedly charge and discharge the batteries. The capacity (average value) at each charging stage is statistically calculated, and the CC stage capacity ratio is determined.

[0146] Specifically, first, the sodium-ion battery was left in a 25°C environment for 1 hour. The battery was then charged with a constant current (CC) at a charge rate of 3C until it reached its rated voltage, after which it was switched to constant voltage (CV) charging. When the charging current fell below 0.05C, charging was stopped and the battery was left for 5 minutes. Furthermore, the battery was discharged with a constant current of 0.2C until it reached its rated voltage, and the battery was left for 5 minutes to ensure the integrity of the subsequent charge and discharge process. The formula for calculating the 3C charge capacity retention rate is: 3C charge capacity retention rate = [CC stage charge capacity / (CC + CV) total charge capacity] × 100%.

[0147] 12. Method for measuring the 45°C cycle performance of sodium-ion batteries

[0148] The battery under test is left standing at a measurement temperature of 45°C for 5 minutes. An electrochemical device is charged and discharged with a current of 1.0C within the design voltage range. The first recorded discharge capacity is defined as D0. The above charge-discharge flow is repeated 1000 times, and the final discharge capacity is defined as D1. The capacity decay rate after the 45°C cycle is defined as D1 / D0, and the unit is %.

[0149] 13. Method for measuring the low-temperature charge / discharge performance of sodium-ion batteries

[0150] A sodium-ion battery was charged to its rated voltage at 25°C at 0.02C, then discharged to its rated voltage at 0.02C, and its discharge capacity A0 was recorded. Next, the temperature was lowered to -20°C and kept warm for 1 hour. After that, the sodium-ion battery was charged to its rated voltage at 0.02C at -20°C, then discharged to its rated voltage at 0.02C, and its discharge capacity A1 was recorded.

[0151] The discharge capacity retention rate at -20°C is A1 / A0.

[0152] 14. Method for measuring the electrolyte volume (retention volume) of a sodium-ion battery

[0153] In this application, the electrolyte volume of the electrochemical apparatus, i.e., the liquid retention volume, is obtained by dividing the mass of the electrolyte in the electrochemical apparatus by the 0.2C discharge capacity of the electrochemical apparatus.

[0154] In this application, various parameters relating to the negative electrode active material or the negative electrode active material layer may be measured by sampling during the battery manufacturing process, or by sampling from the manufactured electrochemical apparatus.

[0155] When the above measurement sample is taken from a sodium-ion battery that has undergone multiple charge-discharge cycles, sampling can be performed, for example, by following steps (1) to (3).

[0156] (1) Discharge treatment is performed on the sodium-ion battery (for safety reasons, the battery is usually fully discharged). After disassembling the battery, the negative electrode sheet is removed and immersed in dimethyl carbonate (DMC) for a certain period of time (e.g., 2 to 10 hours). Then the negative electrode sheet is removed and dried at a certain temperature and time (e.g., 60°C for 4 hours). The negative electrode tab is removed and dried at a certain temperature and time (e.g., 60°C for 4 hours), and the negative electrode tab is removed after drying. At this time, samples can be taken from the dried negative electrode sheet and each parameter relating to the negative electrode active material layer of this application can be measured.

[0157] (2) The anode sheet dried in step (1) is fired at a constant temperature and time (for example, 400°C for 2 hours), and an arbitrary area is selected from the anode sheet after firing to sample the anode active material (a sample can be taken by scraping off the powder using a razor).

[0158] (3) The negative electrode active material recovered in step (2) is subjected to sieving (for example, sieving with a 200-mesh sieve) to obtain a sample for measuring each of the negative electrode active material parameters described in this application.

[0159] 3. Measurement results

[0160] Table 1 shows the parameters and measurement data for Examples 1-1 to 1-20 and Comparative Examples 1-1 to 1-3.

[0161] [Table 1] The " / " in JPEG2026522521000002.jpg217168 indicates that the substance in question has not been added.

[0162] A comparison of Examples 1-1 to 1-20 with Comparative Example 1-1 shows that sodium-ion batteries containing fluorinated carbonate compounds and / or sulfur-oxygen double bond-containing compounds in the electrolyte have improved high-temperature cycle performance, low-temperature performance, and rate performance compared to sodium-ion batteries that do not contain fluorinated carbonate compounds and sulfur-oxygen double bond-containing compounds in the electrolyte, while also achieving a good balance in capacity per gram of negative electrode active material.

[0163] A comparison of Examples 1-1 to 1-20 with Comparative Examples 1-2 and 1-3 further shows that when d is between 1.0 and 1.6 and the m / d range is between 0.01 and 4.5, the sodium-ion battery exhibits improved high-temperature cycle performance, low-temperature performance, and rate performance, while simultaneously achieving a good capacity per gram of negative electrode active material. The effect is even better when the m / d range is between 1.6 and 3.6, and / or when d is between 1.2 and 1.4.

[0164] When the lattice plane spacing d002 of the hard carbon material is in the range of 0.37 nm to 0.41 nm, the high-temperature cycle performance, low-temperature performance, and rate performance of the sodium-ion battery can be further improved, while simultaneously achieving a balance between the capacity per gram of the negative electrode active material. The effect is even better when the lattice plane spacing d002 of the hard carbon material is in the range of 0.38 nm to 0.40 nm.

[0165] The parameters and measurement data for Examples 2-1 to 2-10 are shown in Tables 2 and 3, respectively. Except for the parameters in Tables 2 and 3, Examples 2-1 to 2-10 are the same as the settings for Example 1-2.

[0166] [Table 2]

[0167] [Table 3]

[0168] The results show that appropriate particle size composition, specific surface area, compaction density, pore diameter, pore volume, thickness, and porosity parameters of the hard carbon material can be used to obtain a suitable fluid retention range for sodium-ion batteries, further improving the initial efficiency of the negative electrode active material and enhancing the performance of the sodium-ion battery, while simultaneously achieving a balance between the capacity per gram of the negative electrode active material and the overall performance of the battery.

[0169] Throughout this specification, any reference to “several embodiments,” “partial embodiments,” “one embodiment,” “another embodiment,” “example,” “specific example,” or “partial example” means that at least one embodiment or example of this application includes the specific features, structures, materials, or properties described in that embodiment or example. Therefore, any other references to “several embodiments,” “in an example,” “in an embodiment,” “in one embodiment,” “in one example,” “in a specific example,” or “in an example” in this specification do not necessarily refer to the same embodiments or examples in this application. Furthermore, any specific features, structures, materials, or properties described herein may be combined in any suitable manner in one or more embodiments or examples.

[0170] While exemplary embodiments have been shown and described, those skilled in the art should understand that these embodiments should not be construed as limiting this application, and that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principles, and scope of this application.

Claims

1. It includes a positive electrode, a negative electrode, and an electrolyte, The electrolyte contains an additive, the additive contains a first additive M, the first additive M is selected from at least one of a fluorinated carbonate compound or a sulfur-oxygen double bond-containing compound, and the mass percentage content of the first additive M is m% based on the mass of the electrolyte. The aforementioned negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a hard carbon material. Raman spectroscopy measurements revealed that the hard carbon material has a temperature of 1300 cm². －１ ~1400cm －１ The peak intensity at 1550 cm² of the hard carbon material is defined as ID. －１ ~1650cm －１ An electrochemical apparatus characterized in that the peak intensity at is denoted as IG, the ratio of ID / IG as d, d is between 1.0 and 1.6, and the range of m / d is between 0.01 and 4.

5.

2. The electrochemical apparatus satisfies at least one of the following conditions: (1) The range of m / d is 1.6 to 3.6, (2) The electrochemical apparatus according to claim 1, characterized in that d is 1.2 to 1.

4.

3. The electrochemical apparatus according to claim 1, characterized in that, by measurement by X-ray diffraction, the range of the lattice plane spacing d002 of the hard carbon material is 0.37 nm to 0.41 nm.

4. The electrochemical apparatus satisfies at least one of the following conditions: (1) Based on the mass of the electrolyte, the mass percentage content of the fluorinated carbonate compound is 0.05% to 5%, (2) The electrochemical apparatus according to claim 1, characterized in that the mass percentage content of the sulfur-oxygen double bond-containing compound is 0.05% to 4% based on the mass of the electrolyte.

5. The electrochemical apparatus according to claim 3, characterized in that the range of the lattice plane spacing d002 is 0.38 nm to 0.40 nm.

6. The electrochemical apparatus according to claim 1, characterized in that the sulfur-oxygen double bond-containing compound comprises at least one of 1,3-propanesultone, propene-1,3-sultone, 1,2-propanesultone, 1,4-butanesultone, or ethylene sulfate, and / or the fluorinated carbonate compound comprises at least one of fluoroethylene carbonate or difluoroethylene carbonate.

7. The electrochemical apparatus according to claim 1, characterized in that the hard carbon material has pores inside, the pore diameter range of the pores is 0.6 nm to 2.0 nm, and the pore volume of the pores is less than 0.05 g / cc as determined by a nitrogen gas adsorption test.

8. The hard carbon material satisfies at least one of the following conditions: (1) The specific surface area of ​​the hard carbon material is 0.5 m² ２ / g to 10m ２ / g, (2) The compaction density of the hard carbon material after depressurization under 5 tons is 0.8 g / cc to 1.6 g / cc. (3) Measurement by X-ray diffraction shows that the hard carbon material has diffraction peaks in the range of 18° to 30°, and the full width at half maximum of the diffraction peaks is 4° to 12°. (4) The electrochemical apparatus according to claim 1, characterized in that the Dv50 of the hard carbon material is 2 μm to 10 μm, and the Dv50 and Dv90 of the hard carbon material satisfy 2 ≤ Dv90 / Dv50 ≤ 5.

9. The negative electrode active material layer satisfies at least one of the following conditions: (1) The porosity of the negative electrode active material layer is in the range of 30% to 60%, (2) The electrochemical apparatus according to claim 1, characterized in that the compaction density of the negative electrode active material layer is in the range of 0.8 g / cc to 1.5 g / cc.

10. Let V1 be the electrode sheet capacity per unit area of ​​the negative electrode active material layer. The electrochemical apparatus according to claim 1, characterized in that the positive electrode includes a positive electrode active material layer, the electrode sheet capacity per unit area of ​​the positive electrode active material layer is V2, and the range of V1 / V2 is 1.1 to 1.

5.

11. The electrochemical apparatus according to claim 1, characterized in that the electrochemical apparatus is a sodium-ion battery.

12. An electronic apparatus characterized by including an electrochemical apparatus as described in any one of claims 1 to 11.

Images