Electrochemical apparatus and electronic apparatus

Abstract

The present application discloses an electrochemical apparatus and an electronic apparatus. The electrochemical apparatus comprises a positive electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode material, the positive electrode material comprises sodium and lithium, and sodium is present in an amount of 0.2% to 3% by weight based on the mass of the positive electrode sheet; the electrolyte comprises sodium and lithium, wherein based on the mass of the electrolyte, sodium is present in an amount of X% by weight, X is 0.07 to 0.95, and lithium is present in an amount of Y%, Y is 0.3 to 0.7, and Y / X is 0.32 to 10. The electrochemical device of the present application has good high- and low-temperature cycle performance and kinetic performance.

Description

Electrochemical devices and electronic devices Technical Field

[0001] This application relates to the field of electrochemistry, and more particularly to an electrochemical device and an electronic device. Background Technology

[0002] Lithium-ion batteries are now widely used in consumer electronics, electric vehicles, and aerospace. Therefore, more stringent performance requirements are placed on lithium-ion batteries, such as excellent low-temperature performance and rapid charge / discharge capabilities. At the material modification level, methods such as transition metal doping, surface coating, and defect correction are generally used to improve the cathode material, but these methods rarely simultaneously enhance both low-temperature performance and rapid charge / discharge capabilities. Regarding electrolyte modification, organic additives are typically added to alter the solvation structure and interfacial stability, thereby improving battery performance. However, the method of adding cations to adjust the solvation structure is rarely used to modify the electrolyte.

[0003] Summary of the Invention

[0004] In view of this, this application provides an electrochemical device and an electronic device.

[0005] The first aspect of this application provides an electrochemical device, including a positive electrode and an electrolyte. The positive electrode includes a positive electrode material comprising sodium and lithium elements, wherein the mass percentage of sodium is 0.2% to 3% based on the mass of the positive electrode. The electrolyte includes sodium and lithium elements, wherein the mass percentage of sodium is X%, where X is 0.07 to 0.95, the mass percentage of lithium is Y%, where Y is 0.3 to 0.7, and the Y / X ratio is 0.32 to 10.

[0006] This application adds sodium to the cathode material and electrolyte. The sodium in the cathode material and the sodium in the electrolyte will jointly participate in the formation of the electrolyte solvation structure and change it, making the desolvation process of lithium ions easier and improving the kinetic performance of the electrochemical device.

[0007] Furthermore, the sodium element in the electrolyte improves the composition of the SEI film in both the positive and negative electrodes, making the SEI film more stable, which is conducive to the passage of lithium ions and reduces side reactions on the surface of the positive electrode material at high temperatures. This improves the high-temperature cycling performance and kinetic performance (charge-discharge rate) of the electrochemical device. Moreover, in the positive electrode material, when sodium ions enter the lithium layer, they widen the interlayer spacing, which is beneficial to lithium ion diffusion and improves the diffusion kinetics of lithium ions in the positive electrode material. This results in good low-temperature cycling performance and kinetic performance (such as charge-discharge rate) of the electrochemical device.

[0008] Based on the first aspect, in some possible implementations, the positive electrode material also includes boron, with the boron content being 0.03% to 0.4% by mass, depending on the mass of the positive electrode sheet.

[0009] This application adds boron to the cathode material and controls the mass ratio of boron to meet the above-mentioned range. Since the boron will coat the surface of the cathode material, the side reactions between the cathode material and the electrolyte are reduced, the surface stability of the cathode material is improved, and the high and low temperature cycle performance and kinetic performance (such as charge and discharge rate) of the electrochemical device are further improved.

[0010] Based on the first aspect, in some possible implementations, when the positive electrode is in a fully discharged state, the mass percentage of lithium is B%, and B is 5.1 to 8%, based on the mass of the positive electrode.

[0011] This application improves the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) of the electrochemical device by controlling the mass ratio of lithium in the cathode material to meet the above range.

[0012] Based on the first aspect, in some possible implementations, when the positive electrode is in a fully discharged state, the mass percentage of sodium is A% based on the mass of the positive electrode, wherein B / A is 1.7 to 40.

[0013] This application further improves the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) of the electrochemical device by controlling the mass ratio of lithium and sodium elements in the cathode material to meet the above range.

[0014] Based on the first aspect, in some possible implementations, when the positive electrode sheet is in a fully discharged state, the positive electrode material also includes manganese, and the mass percentage of manganese is 24% to 31.2% based on the mass of the positive electrode sheet.

[0015] This application improves the stability of the electrochemical device by adding manganese to the cathode material and controlling the mass ratio of manganese to meet the above-mentioned range. The added manganese maintains a stable +4 valence state and will not react with the electrolyte. This further enhances the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate).

[0016] Based on the first aspect, in some possible implementations, when the positive electrode is in a fully discharged state, the positive electrode material also includes nickel, and the mass percentage of nickel is 25.2% to 32.7% based on the mass of the positive electrode.

[0017] This application further improves high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding nickel to the cathode material and controlling the mass ratio of nickel to meet the above range.

[0018] Based on the first aspect, in some possible implementations, the electrolyte also includes PF6. - Based on the quality of the electrolyte, PF6 - The quality percentage is 10% to 16%.

[0019] This application involves adding PF6 to the electrolyte. - And control PF6 - When the mass ratio meets the above range, the high and low temperature cycling performance and dynamic performance (such as charge and discharge rate) are further improved.

[0020] Based on the first aspect, in some possible implementations, the electrolyte also includes FSI. - Based on the mass of the electrolyte, the FSI - The quality percentage ranges from 0.1% to 2%.

[0021] This application involves adding FSI to the electrolyte. - And control FSI - When the mass ratio meets the above range, the high and low temperature cycling performance and dynamic performance (such as charge and discharge rate) are further improved.

[0022] Based on the first aspect, in some possible implementations, when the electrolyte is in a fully discharged state, the electrolyte also includes boron, and the mass percentage of boron is 0.01% to 0.04% based on the mass of the electrolyte.

[0023] This application further improves high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding boron to the electrolyte and controlling the mass ratio of boron to meet the above-mentioned range.

[0024] Based on the first aspect, in some possible implementations, when the electrolyte is in a fully discharged state, the electrolyte also includes aluminum, and the mass percentage of aluminum is 0.003% to 0.015% based on the mass of the electrolyte.

[0025] This application further improves high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding aluminum to the electrolyte and controlling the mass ratio of aluminum to meet the above-mentioned range.

[0026] Based on the first aspect, in some possible implementations, the electrolyte also includes adiponitrile, fluoroethylene carbonate, and vinylene carbonate.

[0027] This application further improves the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding adiponitrile, fluoroethylene carbonate and vinylene carbonate to the electrolyte.

[0028] A second aspect of this application provides an electronic device including the aforementioned electrochemical device, which has good high and low temperature cycling performance and kinetic performance (such as charge and discharge rate), which is beneficial to improving the service life of the electronic device. Detailed Implementation

[0029] The embodiments of this application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. The reagents and materials described in the following embodiments are all commercially available.

[0030] Electrochemical device

[0031] One embodiment of this application provides an electrochemical device, including a housing (such as a packaging bag) for accommodating a positive electrode, a separator, a negative electrode, and an electrolyte, as well as other components known in the field of electrochemistry. This application does not limit the scope of these other components. This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application. For example, an aluminum-plastic film packaging bag can be used. This application does not impose any particular limitation on the type of electrochemical device; it can include any device that performs an electrochemical reaction. The electrochemical device of this application exhibits excellent high and low temperature cycling performance and kinetic performance.

[0032] Positive electrode sheet

[0033] The positive electrode includes a positive current collector and a positive electrode material layer disposed on the positive current collector. The positive current collector can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, including but not limited to current collectors formed by combining the aforementioned conductive foil and polymer substrate.

[0034] The positive electrode material layer includes a positive electrode material, wherein the positive electrode material includes sodium and lithium elements, and the mass percentage of sodium element is 0.2% to 3% based on the mass of the positive electrode sheet. For example, the mass percentage of sodium element can be any value within the range of 0.2%, 1%, 1.02%, 1.04%, 1.08%, 1.09%, 1.1%, 1.17%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, or any value above.

[0035] This application adds sodium to the cathode material and electrolyte. The sodium in the cathode material and the sodium in the electrolyte will jointly participate in the formation of the electrolyte solvation structure and change it, making the desolvation process of lithium ions easier and improving the kinetic performance of the electrochemical device.

[0036] Furthermore, in cathode materials, when sodium ions enter the lithium layer, they expand the interlayer spacing of the lithium layer, which is conducive to the diffusion of lithium ions and improves the diffusion kinetics of lithium ions in the cathode material, thus enabling the electrochemical device to have good low-temperature cycling performance and kinetic performance (such as charge-discharge rate).

[0037] In some embodiments, the positive electrode material further includes boron, with the boron content ranging from 0.03% to 0.4% by mass, based on the mass of the positive electrode sheet. For example, the boron content can be any value within the range of 0.03%, 0.05%, 0.07%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, or any of the above values.

[0038] This application adds boron to the cathode material and controls the mass ratio of boron to meet the above-mentioned range. Since the boron will coat the surface of the cathode material, the side reactions between the cathode material and the electrolyte are reduced, the surface stability of the cathode material is improved, and the high and low temperature cycle performance and kinetic performance (such as charge and discharge rate) of the electrochemical device are further improved.

[0039] In some embodiments, when the positive electrode is in a fully discharged state, the mass percentage of lithium is B%, based on the mass of the positive electrode, and B is 5.1 to 8. For example, B can be any value within the range of 5.1, 5.2, 5.5, 5.8, 6, 6.4, 6.6, 7, 7.2, 7.4, 7.6, 7.8, 8, or any of the above values.

[0040] This application improves the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) of the electrochemical device by controlling the mass ratio of lithium in the cathode material to meet the above range.

[0041] In some embodiments, when the positive electrode is in a fully discharged state, the mass percentage of sodium is A% based on the mass of the positive electrode, where B / A is from 1.7 to 40. For example, B / A can be any value within the range of 1.7, 1.83, 2, 5, 8, 10, 14, 16, 20, 24, 28, 30, 34, 36, 40, or any of the above values.

[0042] This application further improves the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) of the electrochemical device by controlling the mass ratio of lithium and sodium elements in the cathode material to meet the above range.

[0043] In some embodiments, when the positive electrode is in a fully discharged state, the positive electrode material further includes manganese, and the mass percentage of manganese is 24% to 31.2% based on the mass of the positive electrode. For example, the mass percentage of manganese can be any value within the range of 24%, 24.43%, 25%, 26%, 27%, 28%, 29%, 30%, 31.2%, or any value above.

[0044] This application improves the stability of the electrochemical device by adding manganese to the cathode material and controlling the mass ratio of manganese to meet the above-mentioned range. The added manganese maintains a stable +4 valence state and will not react with the electrolyte. This further enhances the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate).

[0045] In some embodiments, when the positive electrode is in a fully discharged state, the positive electrode material further includes nickel, and the mass percentage of nickel is between 25.2% and 32.7% based on the mass of the positive electrode. For example, the mass percentage of nickel can be any value within the range of 25.2%, 26.2%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.7%, or any of the above values.

[0046] This application further improves high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding nickel to the cathode material and controlling the mass ratio of nickel to meet the above range.

[0047] electrolyte

[0048] According to some embodiments of this application, the electrolyte includes an organic solvent, a lithium salt, and optional additives.

[0049] In some embodiments, the electrolyte comprises sodium and lithium, wherein the mass percentage of sodium is X%, where X is from 0.07 to 0.95, and the mass percentage of lithium is Y%, where Y is from 0.3 to 0.7. For example, X can be any value within the range of 0.07, 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or any value above. Similarly, Y can be any value within the range of 0.3, 0.31, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, or any value above.

[0050] Sodium in the electrolyte improves the composition of the SEI film in both the positive and negative electrodes, making the SEI film more stable, which is conducive to the passage of lithium ions. It also reduces side reactions on the surface of the positive electrode material at high temperatures, thereby improving the high-temperature cycling performance and kinetic performance (charge-discharge rate) of the electrochemical device.

[0051] In some embodiments, Y / X is from 0.32 to 10. For example, Y can be any value within the range of 0.32, 0.35, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or any of the above values.

[0052] This application improves the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) of the electrochemical device by controlling the mass ratio of lithium and sodium elements in the electrolyte to meet the above range.

[0053] In some embodiments, the electrolyte also includes PF6. - Based on the quality of the electrolyte, PF6 - The quality percentage is 10% to 16%.

[0054] This application involves adding PF6 to the electrolyte. - And control PF6 - When the mass ratio meets the above range, the high and low temperature cycling performance and dynamic performance (such as charge and discharge rate) are further improved.

[0055] In some embodiments, the electrolyte also includes FSI - Based on the mass of the electrolyte, the FSI - The quality percentage ranges from 0.1% to 2%.

[0056] This application involves adding FSI to the electrolyte. - And control FSI - When the mass ratio meets the above range, the high and low temperature cycling performance and dynamic performance (such as charge and discharge rate) are further improved.

[0057] In some embodiments, when the electrolyte is in a fully discharged state, the electrolyte also includes boron, with the boron content being 0.01% to 0.04% by mass, based on the mass of the electrolyte.

[0058] This application further improves high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding boron to the electrolyte and controlling the mass ratio of boron to meet the above-mentioned range.

[0059] In some embodiments, when the electrolyte is in a fully discharged state, the electrolyte also includes aluminum, with the aluminum content being 0.003% to 0.015% based on the mass of the electrolyte.

[0060] This application further improves high and low temperature cycling performance and kinetic performance (such as charge and discharge rate) by adding aluminum to the electrolyte and controlling the mass ratio of aluminum to meet the above-mentioned range.

[0061] In some embodiments, the additives include adiponitrile, fluoroethylene carbonate, and vinylene carbonate: the additives selected in this application are adiponitrile, fluoroethylene carbonate, and vinylene carbonate, which further improve the high and low temperature cycling performance and kinetic performance (such as charge and discharge rate).

[0062] In some embodiments, 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(oxalateborate)borate LiB(C2O4)2 (LiBOB), or lithium difluorooxalateborate LiBF2(C2O4) (LiDFOB).

[0063] In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate.

[0064] Negative electrode sheet

[0065] The negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on the negative current collector. The negative current collector can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collector, or any composite current collector disclosed in the prior art, including, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The negative electrode material layer includes a negative electrode material, and optionally a conductive agent, a binder, and a thickener.

[0066] The specific type of anode material is not limited and can be selected according to requirements. For example, anode materials include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured Li4Ti5O. 12 At least one of Li-Al alloys.

[0067] The specific type of conductive agent is not limited and can be selected according to requirements. For example, conductive agents include, but are not limited to, conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and at least one of the following:

[0068] The specific type of adhesive is not limited and can be selected according to requirements. As an example, adhesives include, but are not limited to, at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose.

[0069] The specific type of thickener is not limited and can be selected according to needs. As an example, thickeners include, but are not limited to, sodium carboxymethyl cellulose (CMC).

[0070] Separating membrane

[0071] The material and shape of the separator used in the electrochemical device of this application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0072] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be selected.

[0073] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixture of polymer and inorganic material. The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, and the polymer material is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0074] Electronic devices

[0075] The aforementioned electrochemical device is applied to electronic devices to power loads within them. Furthermore, this electrochemical device exhibits excellent high and low temperature cycling performance and kinetic properties, which helps extend the lifespan of the electronic devices. These electronic devices may include, but are not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0076] Example 1

[0077] <Preparation of cathode materials>

[0078] 1. Prepare a mixed solution containing NiSO4 and MnSO4 according to the elemental molar ratio Ni:Mn = 50:50. Mix this solution with the precipitant NaOH solution and the complexing agent ammonia solution. By controlling the reaction time, ammonia concentration, and pH value, the precursor Ni is obtained. 0.5 Mn 0.5 (OH)2.

[0079] 2. The above-mentioned precursor Ni 0.5 Mn 0.5 (OH)2, lithium carbonate and sodium hydroxide are ground and mixed evenly in a certain proportion, and calcined at 850℃ in air atmosphere for 36h at a heating rate of 3℃ / min. Then, the mixture is cooled to room temperature at a rate of 5℃ / min in a mixed atmosphere of N2 and H2. Finally, the cathode material is obtained by crushing and sieving.

[0080] <Preparation of the positive electrode>

[0081] Polyvinylidene fluoride (PVDF) binder, conductive carbon black (Super P) conductive agent, and positive electrode material were mixed uniformly at a weight ratio of 1.5:1.5:97. N-methylpyrrolidone (NMP) was added as a solvent to obtain a positive electrode slurry with a viscosity of 3000 mPas to 6000 mPas. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil current collector and dried at 120°C for 1 hour to obtain a positive electrode sheet with a single-sided coating of a 60 μm thick positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode material layer. The sheet was dried under vacuum at 120°C for 1 hour, and then cold-pressed, cut, and had tabs welded to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm.

[0082] <Preparation of Negative Electrode Sheets>

[0083] A negative electrode material (graphite), a thickener (sodium carboxymethyl cellulose, CMC-Na), and a binder (styrene-butadiene rubber, SBR) were mixed in a weight ratio of 96:2:2. Deionized water was added, and the mixture was stirred until homogeneous to obtain a negative electrode slurry with a solid content of 75 wt%. The negative electrode slurry was uniformly coated onto one surface of a 12 μm thick copper foil current collector and dried at 120 °C to obtain a single-sided negative electrode sheet with a coating thickness of 80 μm. The above steps were repeated on the other surface of the copper foil to obtain a double-sided negative electrode sheet. After drying under vacuum at 120 °C for 1 hour, the sheet was cold-pressed, cut, and slit to obtain a negative electrode sheet with dimensions of 78 mm × 875 mm.

[0084] <Preparation of Electrolyte>

[0085] In an argon-atmosphere glove box with a water content of <10 ppm, propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) were mixed in a 1:1:1 mass ratio. Thoroughly dried lithium salt LiPF6 was then dissolved in the aforementioned non-aqueous solvent, and 2% 1,3-propanesulfonate lactone was added to prepare the electrolyte used in the examples. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 13.7%, and the mass percentage of NaFSI was 1.8%.

[0086] <Preparation of the separating membrane>

[0087] A porous polyethylene (PE) film with a thickness of 7 μm was used as the separator.

[0088] <Preparation of Lithium-ion Pouch Batteries>

[0089] The positive electrode, separator, and negative electrode prepared above are stacked, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound up. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. Following vacuum sealing, settling, formation (with an upper limit voltage of 4.35V, a formation temperature of 85℃, and a settling time of 2 hours), degassing, and edge trimming, a lithium-ion soft-pack battery is obtained.

[0090] Examples 2 to 6

[0091] The difference between Examples 2 to 6 and Example 1 is that the amounts of lithium carbonate and sodium hydroxide in step 2 of the <Preparation of Cathode Material> and the contents of LiPF6 and NaFSI in the electrolyte are adjusted. The other conditions / preparation methods are the same as in Example 1. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0092] Examples 7 and 8

[0093] The difference between Examples 7 and 8 and Example 1 is that the content of manganese and nickel in the hydroxide precursor in step 1 of the <Preparation of Cathode Material> is adjusted. The other conditions / preparation methods are the same as in Example 1. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0094] Examples 9 to 12

[0095] The difference between Examples 9 to 12 and Example 5 is that, after step 2 of the <Preparation of Cathode Material>, the cathode material is mixed with boric acid and then heat-treated in an air atmosphere at 600°C for 12 hours. The remaining conditions / preparation methods are the same as in Example 5. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0096] Examples 13 to 16

[0097] The difference between Examples 13 and 14 and Example 5 is that the amount of LiPF6 or NaFSI added is adjusted in <Preparation of Electrolyte>. The other conditions / preparation methods are the same as in Example 5. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0098] Examples 17 and 18

[0099] The difference between Examples 17 and 18 and Example 5 is that boron and aluminum are added to the electrolyte. The other conditions / preparation methods are the same as in Example 5. The specific preparation parameters can be adjusted accordingly according to Tables 1 and 2.

[0100] Example 19

[0101] The difference between Example 19 and Example 5 is that adiponitrile, fluoroethylene carbonate, and vinylene carbonate are added to the electrolyte. The other conditions / preparation methods are the same as in Example 5. The specific preparation parameters can be adjusted accordingly according to Tables 1 and 2.

[0102] Comparative Example 1 and Comparative Example 2

[0103] The difference between Comparative Examples 1 and 2 and Example 5 is that the amount of sodium hydroxide in step 2 of the <Preparation of Cathode Material> and the content of LiPF6 and NaFSI in the electrolyte are adjusted. The other conditions / preparation methods are the same as in Example 5. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0104] Comparative Example 3

[0105] The difference between Comparative Example 3 and Example 5 is that sodium hydroxide is not added to the positive electrode material. The other conditions / preparation methods are the same as those in Example 6. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0106] Comparative Example 4

[0107] The difference between Comparative Example 4 and Example 5 is that NaFSI is not added to the electrolyte. The other conditions / preparation methods are the same as in Example 5. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0108] Comparative Example 5

[0109] The difference between Comparative Example 5 and Example 5 is that sodium hydroxide is not added to the positive electrode material and NaFSI is not added to the electrolyte. The other conditions / preparation methods are the same as those in Example 5. The specific preparation parameters mentioned above can be adjusted accordingly according to Tables 1 and 2.

[0110] Test methods

[0111] (1) Element content test

[0112] Element content test of positive electrode material: The positive electrode material was dissolved in aqua regia solution (for example, 0.4g of positive electrode material was dissolved in 10ml of aqua regia solution (the volume ratio of aqua regia to deionized water was 1:1, and the volume ratio of concentrated hydrochloric acid to concentrated nitric acid was 3:1). The positive electrode material was then fully digested in a CEM-Mars5 / Mars6 microwave digester, and the volume was adjusted to 100mL. The mass percentage content of elements such as Li, Na, Ni, Mn and B in the solution was tested using an inductively coupled plasma optical emission spectrometer (ICP-OES) system.

[0113] Electrolyte element content test: Weigh 5g of electrolyte and add 10mL of HNO3. Evaporate to about 2mL in an acid-removing apparatus. After slightly cooling, add 10mL of hydrogen peroxide to digest to about 2mL. Dilute to 50mL using a 50mL plastic volumetric flask. Use ICP-OES to test the content of elements such as Li, Na, Mn, and Ni in the solution.

[0114] (2) 5℃ Cyclic Capacity Retention Rate Test (Low Temperature)

[0115] The lithium-ion pouch battery was placed in a 5℃ constant temperature chamber and left to stand for 30 minutes to reach a constant temperature. The battery was then charged at a constant current of 0.5C to 4.35V at 5℃, followed by constant voltage charging to 0.02C at 4.35V. After standing for 5 minutes, it was discharged at a constant current of 0.5C to 2.8V, and then left to stand for another 5 minutes. This discharge capacity was recorded as the first cycle discharge capacity. This charge-discharge cycle was repeated 400 times, and the discharge capacity of the battery in the 400th cycle was recorded as the 400th cycle discharge capacity. The capacity retention rate (%) of the lithium-ion pouch battery after 400 cycles at 5℃ = (400th cycle discharge capacity / first cycle discharge capacity) × 100%.

[0116] (3) 45℃ Cyclic Capacity Retention Rate Test (High Temperature)

[0117] The lithium-ion pouch battery was placed in a 45℃ constant temperature chamber and left to stand for 30 minutes to reach a constant temperature. The battery was then charged at a constant current of 1.5C to 4.35V at 45℃, followed by constant voltage charging to 0.02C at 4.35V. After standing for 5 minutes, it was discharged at a constant current of 2C to 2.8V, and then left to stand for 5 minutes. This discharge capacity was recorded as the first cycle discharge capacity. This charge-discharge cycle was repeated 400 times, and the discharge capacity of the battery in the 400th cycle was recorded as the 400th cycle discharge capacity. The capacity retention rate (%) of the lithium-ion pouch battery after 400 cycles at 45℃ = (400th cycle discharge capacity / first cycle discharge capacity) × 100%.

[0118] (4) 2C / 0.1C test method

[0119] The lithium-ion pouch battery was charged at 25°C with a constant current of 0.7C to 4.35V, then charged at 4.35V with a constant voltage to 0.025C; allowed to rest for 5 minutes, and then discharged at a constant current of 0.1C to 2.8V, and allowed to rest for 5 minutes. The capacity of the 2C constant current discharge was divided by the capacity of the 0.1C constant current discharge; the ratio is the rate factor 2C / 0.1C.

[0120] The test data of Examples 1 to 19 and Comparative Examples 1 to 5 are recorded in Tables 1 and 2.

[0121] Table 1

[0122] Note: " / " in Table 1 indicates that the corresponding substance or parameter does not exist.

[0123] Table 2

[0124] Note: " / " in Table 2 indicates that the corresponding substance or parameter does not exist.

[0125] As can be seen from Tables 1 and 2, compared with Example 1, Examples 2 to 6, by adjusting the amount of lithium carbonate and sodium hydroxide in step 2 of the <Preparation of Cathode Material> and the content of LiPF6 and NaFSI in the electrolyte, enable the electrochemical device to have good high and low temperature cycling performance and kinetic performance (charge and discharge rate).

[0126] Compared with Example 1, Examples 7 and 8 adjusted the content of manganese and nickel in the cathode material. The comparison shows that the content of manganese and nickel in the cathode material has different degrees of influence on the high and low temperature cycling performance and kinetic performance of the electrochemical device of this application.

[0127] Compared with Example 5, in Examples 9 to 12, boric acid was added after step 2 of the <Preparation of Cathode Material>. By comparison, it can be seen that adding boron to the cathode material can further improve the high and low temperature cycle performance and kinetic performance of the electrochemical device of this application, and the effect is even better when the amount of boron added meets the scope of this application.

[0128] Compared with Example 5, Examples 13 and 14 further improved the high and low temperature cycling performance and kinetic performance (charge and discharge rate) of the electrochemical device by adjusting the amount of LiPF6 added in the electrolyte to meet the scope of this application.

[0129] Compared with Example 5, Examples 15 and 16 further improved the high and low temperature cycling performance and kinetic performance (charge and discharge rate) of the electrochemical device by adjusting the amount of NaFSI added to the electrolyte to meet the scope of this application.

[0130] Compared with Example 5, Examples 17 and 18 added boron and aluminum to the electrolyte and controlled their contents to meet the scope of this application, which further improved the high and low temperature cycling performance and kinetic performance (charge and discharge rate) of the electrochemical device.

[0131] Compared with Example 5, Example 19 added adiponitrile, fluoroethylene carbonate and vinylene carbonate to the electrolyte, which further improved the high and low temperature cycling performance and kinetic performance (charge and discharge rate) of the electrochemical device.

[0132] Furthermore, a comparison of Example 5 with Comparative Examples 1 and 2 shows that when the sodium content in the cathode material and the sodium and lithium content in the electrolyte do not meet the scope of this application, the high and low temperature cycling performance and kinetic performance (charge and discharge rate) of the electrochemical device are affected to varying degrees.

[0133] As can be seen from the comparison between Example 5 and Comparative Examples 3 to 5, when the cathode material or electrolyte does not contain sodium, or when neither contains sodium, the high and low temperature cycle capacity retention rate and charge-discharge rate of the electrochemical device are lower than when the cathode material or electrolyte contains sodium. This shows that the sodium in the cathode material and the sodium in the electrolyte have a synergistic effect, which makes the electrochemical device have good high and low temperature cycle performance and kinetic performance.

[0134] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. An electrochemical device comprising a positive electrode and an electrolyte, characterized in that, The positive electrode sheet includes a positive electrode material, which includes sodium and lithium elements, and the mass percentage of sodium elements is 0.2% to 3% based on the mass of the positive electrode sheet. The electrolyte comprises sodium and lithium. Based on the mass of the electrolyte, the mass percentage of sodium is X%, where X is 0.07 to 0.95, the mass percentage of lithium is Y%, where Y is 0.3 to 0.7, and Y / X is 0.32 to 10.

2. The electrochemical device as described in claim 1, characterized in that, The positive electrode material also includes boron, and the mass percentage of boron is 0.03% to 0.4% based on the mass of the positive electrode sheet.

3. The electrochemical device according to claim 1, characterized in that, Based on the mass of the positive electrode sheet, the mass percentage of lithium element is B%, where B is 5.1% to 8%.

4. The electrochemical device according to claim 3, characterized in that, Based on the mass of the positive electrode sheet, the mass percentage of sodium is A%, where B / A is between 1.7 and 40.

5. The electrochemical device according to any one of claims 1 to 4, characterized in that, The positive electrode material also includes manganese, and the mass percentage of manganese is 24% to 31.2% based on the mass of the positive electrode sheet.

6. The electrochemical device according to any one of claims 1 to 4, characterized in that, The positive electrode material also includes nickel, and the mass percentage of nickel is between 25.2% and 32.7% based on the mass of the positive electrode sheet.

7. The electrochemical device according to any one of claims 1 to 4, characterized in that, The electrolyte also includes PF6. - ; and / or, the electrolyte further includes FSI - .

8. The electrochemical device according to any one of claims 1 to 4, characterized in that, The electrolyte has the following characteristics: (1) The electrolyte also includes boron, and the mass percentage of boron is 0.01% to 0.04% based on the mass of the electrolyte; (2) The electrolyte also includes aluminum, and the mass percentage of aluminum is 0.003% to 0.015% based on the mass of the electrolyte.

9. The electrochemical device according to any one of claims 1 to 4, characterized in that, The electrolyte also includes adiponitrile, fluoroethylene carbonate, and vinylene carbonate.

10. An electronic device, characterized in that, Includes the electrochemical device as described in any one of claims 1 to 9.

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