Negative active material, preparation thereof, secondary battery and device

Abstract

The present invention provides a negative active material comprising a silicon-oxygen-metal complex having the formula SiOxMy, where M is a metal ion, 0 < x < 2, 0.01 < y < 0.4, where the metal ion M comprises at least one of a vanadium ion, a molybdenum ion, and a niobium ion, and where the vanadium ion comprises at least one of V2 +, V3 +, V4 +, and V5 +; the molybdenum ions comprise at least one of Mo < 3 + >, Mo < 4 + >, Mo < 5 + > and Mo < 6 + >; the niobium ions comprise one or more of Nb < 3 + >, Nb < 4 + > and Nb < 5 + >. The silicon-oxygen-metal complex contains reduced metal ions, the reduced metal ions have a lower valence state, and meanwhile, an ion transmission channel is widened due to a larger ion radius, so that the electrochemical kinetics of the silicon-oxygen-metal complex is greatly improved, and particularly, the intrinsic conductivity can be remarkably improved.

Description

Technical Field

[0001] The present application relates to the field of materials, and particularly to a negative electrode active material, its preparation, a secondary battery, and a device. Background Art

[0002] The development of electric vehicles has made significant contributions to energy conservation and emission reduction in industrial society. As the core component of electric vehicles, the energy density of power batteries directly affects the driving range of the whole vehicle and the travel experience of users. Currently, the negative electrode materials of power batteries are mainly graphite materials, and their specific capacity has approached the theoretical value of 372 mAh / g. Therefore, finding the next-generation negative electrode materials has become the key to improving the energy density of power batteries. Silicon monoxide SiOx (0 < x < 2) has become the best candidate due to its high theoretical specific capacity, smaller volume expansion compared to elemental silicon, and rich reserves. However, problems such as slow kinetics and unstable SEI film of SiOx materials have seriously affected their commercial applications.

[0003] In this regard, there are methods in the prior art to carbon-coat silicon-based materials to improve their electronic conductivity. For example, multi-walled carbon nanotubes / N-doped carbon are used to coat SiOx, and the equivalent series resistance of the obtained target material is more than 4 times smaller than that of pure SiOx, and at a current density of 800 mA / g, the capacity is 388 mAh / g (Li et al., Electrochimica Acta, 2016, 206, 328 - 336). Patent CN 114464785 A deposits carbon on the surface of silicon monoxide by low-temperature CVD gas phase method and then performs high-temperature disproportionation to obtain a carbon-coated silicon monoxide negative electrode material, and its rate charge capacity reaches 95.6% at 5C. However, carbon coating only optimizes the surface conductivity of silicon-based materials, and their internal intrinsic conductivity has not been improved, and the transport of electrons / ions inside the bulk material is still blocked.

[0004] Therefore, there is an urgent need in the art for a SiOx material with high conductivity, especially a SiOx material with high intrinsic conductivity. Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide a negative electrode active material, including a silicon-oxygen-metal complex having the formula SiO x M y where M is a metal ion, 0 < x < 2, 0.01 < y < 0.4, wherein the metal ion M includes at least one of vanadium ion, molybdenum ion, and niobium ion, and wherein the vanadium ion includes V 2+ 、V 3+ 、V 4+ and V 5+ at least one of; the molybdenum ion includes Mo 3+, Mo 4+ , Mo 5+ and Mo 6+ at least one of; the niobium ions include Nb 3+ , Nb 4+ and Nb 5+ one or more of.

[0006] Excessive metal ion content will affect the capacity of the SiO x M y material, and when the metal ion content is too low, due to the small amount of low-valent metal ions in the material after reduction, the kinetics of the material will deteriorate. Therefore, according to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, the mass content of V 3+ and V 4+ is 90% to 98%. According to an embodiment of the present invention, based on all molybdenum ions in the negative electrode active material, the mass content of Mo 4+ and Mo 5+ is 85% to 95%; according to an embodiment of the present invention, based on all niobium ions in the negative electrode active material, the mass content of Nb 3+ and Nb 4+ is 85% to 95%. According to an embodiment of the present invention, the average particle size of the silicon-oxygen-metal complex particles is 200 nm to 500 nm.

[0007] According to an embodiment of the present invention, the metal ions are located inside the silicon-oxygen-metal complex.

[0008] According to an embodiment of the present invention, 1.5 ≤ x < 2;

[0009] According to an embodiment of the present invention, 0.05 ≤ y ≤ 0.3.

[0010] According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, the mass content of V 3+ is 38% to 85%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, the mass content of V 4+ is 20% to 55%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, the mass content of V 5+ is 2% to 11%.

[0011] According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, the mass content of V 3+ is 40% to 75%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, the mass content of V 4+The mass content is 24% to 50%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, V 5+ The mass content is 2.5% to 10%.

[0012] According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, Mo 4+ The mass content is 80% to 85%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, Mo 5+ The mass content is 12% to 16%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, Mo 6+ The mass content is 2% to 4%.

[0013] According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, Nb 3+ The mass content is 35% to 38%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, Nb 4+ The mass content is 48% to 52%. According to an embodiment of the present invention, based on all vanadium ions in the negative electrode active material, Nb 5+ The mass content is 11% to 15%.

[0014] Another object of the present invention is to provide a method for preparing a negative electrode active material, the method comprising the following steps:

[0015] (S1) Mixing a metal element precursor with tetraethyl orthosilicate to obtain silica particles containing metal ions to be reduced; (S2) Mixing the silica particles containing metal ions to be reduced obtained in step (S1) with reducing metal particles to obtain silicon-oxygen-metal complex particles containing reduced metal ions.

[0016] According to an embodiment of the present invention, in step (S2), a thermite reaction is carried out at a high temperature to obtain silicon-oxygen-metal complex particles containing reduced metal ions. During the hydrolysis process, tetraethyl orthosilicate polycondenses to form silica nanoparticles, and the metal atomic clusters are uniformly wrapped inside the silicon suboxide and form Si-O-M bonds; after reduction, the silica nanospheres are reduced to silicon suboxide, and at the same time, the high-valent metal elements are also reduced to low-valent and connected to the adjacent O-Si bonds. The d-orbital electrons on the outer layer of the low-valent atoms can effectively improve the local electron conduction ability, and at the same time, the larger atomic radius broadens the ion transport channels, greatly improving its electrochemical kinetics.

[0017] According to an embodiment of the present invention, the volume ratio of the metal element precursor to tetraethyl orthosilicate in step (S1) is 1:20 to 1:2, preferably 1:10 to 1:5;

[0018] According to an embodiment of the present invention, the metal element precursor in step (S1) includes at least one of vanadium triisopropoxide, niobium pentaisopropoxide, and molybdenum pentaisopropoxide;

[0019] According to an embodiment of the present invention, the solution in step (S1) contains ethanol and deionized water, wherein the volume ratio of ethanol to deionized water is 10:1 to 5:5, preferably 7:1 to 3:1.

[0020] According to an embodiment of the present invention, the solution in step (S1) contains ammonia water.

[0021] According to an embodiment of the present invention, the ratio of the volume of tetraethyl orthosilicate in the solution in step (S1) to the sum of the volumes of ethanol and deionized water is 1:30 to 1:5, preferably 1:20 to 1:10.

[0022] According to an embodiment of the present invention, the metal ions to be reduced in the method according to the present invention are, for example, V 5+ , Mo 6+ , and Nb 5+ .

[0023] According to an embodiment of the present invention, the reducing metal particles in step (S2) are magnesium powder, and the particle size of the magnesium powder is between 50 mesh and 500 mesh.

[0024] According to an embodiment of the present invention, in step (S2), the metal ions to be reduced react with magnesium powder in a magnesiothermic reaction, and the magnesiothermic reaction is carried out at a temperature of 600 °C to 950 °C, preferably at a temperature of 650 °C to 750 °C.

[0025] Since too little magnesium powder will weaken the reduction degree of silica and be accompanied by fewer pores and higher metal elements, and too much magnesium powder will completely reduce silica to silicon and destroy the spherical morphology, according to an embodiment of the present invention, the weight ratio of the magnesium powder to the silica particles containing the metal ions to be reduced is 0.5:1 to 2:1.

[0026] According to an embodiment of the present invention, in step (S2), silica reacts with magnesium powder to form silicon monoxide.

[0027] According to an embodiment of the present invention, in step (S2), the time of the magnesiothermic reaction is 1 h to 12 h, preferably 2 h to 8 h.

[0028] According to an embodiment of the present invention, in step (S2), the magnesiothermic reaction is carried out in an inert gas atmosphere, and the inert atmosphere is, for example, nitrogen or argon.

[0029] According to an embodiment of the present invention, in step (S2), the weight ratio of magnesium powder to silicon dioxide particles containing metal ions to be reduced is 0.5:1 to 2:1, preferably 0.8:1 to 1.2:1.

[0030] According to an embodiment of the present invention, in step (S3), the pickling is carried out with acids such as dilute hydrochloric acid, dilute nitric acid, dilute hydrofluoric acid, etc., and the pickling time is 0.5 h to 6 h, preferably 2 h to 4 h.

[0031] According to an embodiment of the present invention, the method further includes step (S3): subjecting the silicon-oxygen-metal complex particles containing the reduced metal ions obtained in step (S2) to pickling to obtain the negative electrode active material. According to an embodiment of the present invention, in step (S3), the negative electrode active material is porous silicon-oxygen-metal complex particles containing reduced metal ions, such as V 3+ 、V 4+ of.

[0032] Another object of the present invention is to provide a secondary battery, which includes a negative electrode plate, the negative electrode plate includes a current collector and a negative electrode active material layer provided on the current collector, and the negative electrode active material layer includes the negative electrode active material according to the present invention or the negative electrode active material prepared by the method according to the present invention.

[0033] Another object of the present invention is to provide a device, which includes the secondary battery according to the present invention.

[0034] The silicon-oxygen-metal complex of the present invention contains reduced metal ions, and the reduced metal ions have a lower valence state. For example, the electrons in the d orbital can more effectively improve the local electron conduction ability, and at the same time, the larger ionic radius broadens the ion transport channels, thereby greatly improving its electrochemical kinetics, especially the intrinsic conductivity can be significantly improved. Brief Description of the Drawings

[0036] In order to make the above objects, features and advantages of the present invention more easily understood, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] Figure 1Schematically shows an SEM image of silica particles containing vanadium ions to be reduced according to the present invention;

[0038] Figure 2 Schematically shows an SEM image of silicon-oxygen-metal complex particles containing reduced vanadium ions according to the present invention;

[0039] Figure 3 Schematically shows the resistivity of the negative electrode plate. Detailed embodiments

[0040] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application. All other embodiments obtained by those skilled in the art based on the technical solutions provided by the present application and the given embodiments fall within the scope of protection of the present application.

[0041] Unless otherwise specified, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of the present application). Unless otherwise specified, the various reagents or raw materials used in the present application are commercially available conventional reagents or raw materials.

[0042] The list of items connected by the terms "at least one of", "at least one of", "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, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. 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.

[0043] In the context of the present invention, "silicon-oxygen-metal complex" refers to a silicon-oxygen-metal complex particle having the formula SiO x M y where M is a metal ion, 0 < x < 2, 0.01 < y < 0.4, wherein the metal ion M includes at least one of vanadium ions, molybdenum ions, and niobium ions, and wherein the vanadium ion includes V 2+, V 3+ , V 4+ and V 5+ and at least one of those in V 3+ , Mo 4+ , Mo 5+ and Mo 6+ and at least one of those in Nb 3+ , Nb 4+ and Nb 5+ and one or more of those in

[0044] In the context of the present invention, "metal ions to be reduced" such as "vanadium ions to be reduced", "molybdenum ions to be reduced" and "niobium ions to be reduced" refer to metal ions with the highest valence state, such as V 5+ , Mo 6+ and Nb 5+ .

[0045] In the context of the present invention, "reduced metal ions" such as "reduced vanadium ions", "reduced molybdenum ions" and "reduced niobium ions" refer to metal ions without the highest valence state, such as V 3+ , V 4+ , Mo 3+ , Mo 4+ , Mo 5+ , Nb 3+ and Nb 4+ .

[0046] The following further elaborates on this application in combination with specific embodiments. It should be understood that these specific embodiments are only used to illustrate this application and not to limit the scope of this application.

[0047] I. Negative electrode sheet

[0048] The negative electrode sheet provided by the present invention includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer contains a conductive agent, a binder, and a negative electrode active material according to the present invention. The negative electrode active material has silicon-oxygen-metal complex particles of the formula SiO x M y , where M is a metal ion, 0 < x < 2, 0.01 < y < 0.4. Among them, the metal ion M includes at least one of vanadium ions, molybdenum ions, and niobium ions, and among them, the vanadium ions include V 2+ , V 3+ , V 4+ and V 5+ and at least one of those in 3+ , Mo 4+ , Mo 5+ and Mo 6+at least one of; the niobium ions include Nb 3+ 、Nb 4+ and Nb 5+ and one or more of them.

[0049] In one embodiment, x is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or any interval formed by them.

[0050] In one embodiment, y is, for example, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or any interval formed by them.

[0051] In the negative electrode active material of the present invention, the reduced low-valent metal element is connected to the adjacent O-Si bond in the bulk phase, and the d-orbital electrons in the outer layer of its low-valent atoms can effectively improve the local electron conduction ability. At the same time, the larger atomic radius also broadens the ion transport channels in the crystal, greatly improving its electrochemical kinetics.

[0052] In one embodiment, the metal ions are present inside the silicon-oxygen-metal complex.

[0053] In one embodiment, the metal ions include vanadium ions, and the vanadium ions include at least one of V 3+ and V 4+ and V 5+ .

[0054] In one embodiment, the metal ions include molybdenum ions, and the molybdenum ions include at least one of Mo 3+ 、Mo 4+ and Mo 5+ and Mo 6+ .

[0055] In one embodiment, the metal ions include niobium ions, and the niobium ions include at least one of Nb 3+ and Nb 4+ and Nb 5+ .

[0056] In one embodiment, the conductive agent can be a commonly used conductive agent, including but not limited to: metal-based materials, carbon-based materials, conductive polymers, and mixtures thereof. In some embodiments, the metal-based materials are selected from metal powders, metal fibers, nickel, copper, aluminum, or silver. In some embodiments, the carbon-based materials are selected from natural graphite, artificial graphite, Super P, acetylene black, Ketjen black, carbon black, carbon fiber, or any combination thereof. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0057] In one embodiment, the binder may be a commonly used binder, including but not limited to: polyvinyl alcohol, hydroxypropyl cellulose, sodium carboxymethyl cellulose (CMC), diacetyl cellulose, polymers containing ethylene oxide, carboxylated polyvinyl chloride, polyvinylpyrrolidone, polyurethane, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyvinyl fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0058] In one embodiment, the negative electrode current collector may be a metal foil or a composite current collector, such as copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

[0059] II. Positive electrode sheet

[0060] The materials, compositions and manufacturing methods of the positive electrode that can be used in the examples of the present application include any techniques disclosed in the prior art.

[0061] In one embodiment, the positive electrode includes a current collector and a positive electrode active material layer located on the current collector. In one embodiment, the positive electrode active material includes, but is not limited to: lithium cobaltate (LiCoO 2 ), lithium nickel cobalt manganese (NCM) ternary material, lithium nickel cobalt aluminum (NCA) ternary material, lithium iron phosphate (LiFePO 4 ), lithium manganese iron phosphate (LiMn x Fe 1-x PO 4 ), or lithium manganate (LiMn 2 O 4 ).

[0062] According to a preferred embodiment of the present application, the positive electrode active material is Li[Nb 1-x-y Co x M y O 2 (M = Mn, Al, etc., such as lithium nickel cobalt manganate Li[Nb 1-x-y Co x Mn y O 2 , 1 - x - y ≥ 0.5, lithium nickel cobalt aluminate Li[Nb 1-x-y Co x Al y O 2 , 1 - x - y ≥ 0.5).

[0063] In one embodiment, the positive electrode active material layer further includes a binder, and optionally includes a conductive material. The binder improves the binding between the positive electrode active material particles and also improves the binding between the positive electrode active material and the current collector. In one embodiment, the binder includes: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0064] In one embodiment, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials are selected from metal powders, metal fibers, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0065] In one embodiment, the positive electrode current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0066] III. Separator

[0067] In the embodiments of the present invention, the material and shape of the separator used are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or an inorganic substance formed of a material stable to the electrolyte of the present invention.

[0068] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film, or a composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, and polyethylene terephthalate. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0069] A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer, an inorganic substance layer, or a layer formed by mixing a polymer and an inorganic substance.

[0070] The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of alumina, silica, magnesia, titania, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene alkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0071] The polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene alkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride - hexafluoropropylene).

[0072] In a preferred embodiment according to the present invention, the separator is a polyethylene (PE) separator double - coated with a ceramic layer, where the thickness of the PE layer is in the range of 5 to 20 μm, and the coating thickness of each ceramic layer is in the range of 0 to 5 μm.

[0073] IV. Electrolyte

[0074] In one embodiment, the electrolyte includes a lithium salt and a solvent.

[0075] In one embodiment, the lithium salt includes, but is not limited to: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate.

[0076] In one embodiment, the solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4 - butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0077] In a preferred embodiment according to the present invention, the electrolyte is LiPF 6 / EC + DMC + EMC.

[0078] V. Electrochemical device

[0079] The electrochemical device according to the present invention can be a secondary battery, such as a lithium secondary battery and a sodium secondary battery, including a lithium metal secondary battery, a sodium metal secondary battery, a lithium ion secondary battery, a sodium ion secondary battery, a lithium polymer secondary battery, a sodium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical device of the present application includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0080] The electrochemical device according to the present invention can be applied in electronic devices, including but not limited to, laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, and lithium ion capacitors, etc.

[0081] VI. Tests

[0082] 1. Test of the resistivity of the negative electrode sheet

[0083] Disperse the negative electrode active material, Super P, and sodium carboxymethyl cellulose (CMC) in deionized water according to a mass ratio of 80:10:10, stir evenly, coat it on a Cu foil with a thickness of 6 μm, and place it in a vacuum drying oven at 110 °C for vacuum drying for 2 h to make a working electrode. Roll the middle long strip of the whole electrode sheet to the target compaction density of 0.90 ± 0.05 g / cm 3 , use a Φ14 mm punching machine to cut 4 circular electrode sheets, measure and record the thickness of each electrode sheet. Use the RM2610 electrode resistance test system to conduct resistivity tests, take 3 points for each circular electrode sheet for determination, and after testing, take the average value of the resistivity of 12 points.

[0084] 2. Test of the metal valence state distribution in the negative electrode active material

[0085] Directly stick 2 mg of the powder sample on double-sided carbon conductive adhesive or ordinary double-sided adhesive, and use an Al Kα (photon energy of 1486.6 eV) anode target for testing.

[0086] Examples and Comparative Examples

[0087] Example 1

[0088] (1) Add 4 mL of tetraethyl orthosilicate (TEOs) to an 80 mL mixed solution of ethanol and deionized water (the volume ratio of ethanol to deionized water is 7:1). After stirring for 10 min, add 0.4 mL of vanadium triisopropoxide, and then add 10 mL of ammonia water solution. After stirring at room temperature for 12 h, separate and dry to obtain silica particles containing vanadium ions to be reduced, as Figure 1 shown;

[0089] (2) Mix the above silica particles containing vanadium ions to be reduced and Mg powder evenly at a mass ratio of 1:1. Transfer to a porcelain boat and place it in a tubular furnace under an argon atmosphere. Carry out a magnesiothermic reduction reaction at 680 °C with a holding time of 2 h, and then take it out after cooling to room temperature;

[0090] (3) After pickling with 2 M hydrochloric acid, wash and dry to obtain porous silicon-oxygen-metal complex particles containing reduced vanadium ions, as Figure 2 shown;

[0091] (4) Add the above porous silicon-oxygen-metal complex particles containing reduced vanadium ions, carbon black Super P, and sodium carboxymethyl cellulose CMC to solvent water in a weight ratio of 80:10:10 and mix to obtain a negative electrode slurry. Then, coat the negative electrode slurry on a 6 μm copper foil on one side. The loading amount of the negative electrode active material layer is 1 mg, and then cut it into a specification of 41 mm × 61 mm.

[0092] Examples 2 - 8

[0093] Examples 2 - 8 are carried out with reference to Example 1, with the difference that the metal oxide complex and the temperature of the magnesiothermic reaction are selected according to Table 1.

[0094] Comparative Example 1

[0095] Comparative Example 1 is carried out with reference to Example 1, with the difference that step (1) is carried out as follows:

[0096] Add 4 mL of tetraethyl orthosilicate (TEOs) to an 80 mL mixed solution of ethanol and deionized water (the volume ratio of ethanol to deionized water is 7:1). After stirring for 10 min, then add 10 mL of ammonia water solution. After stirring at room temperature for 12 h, separate and dry to obtain silica particles.

[0097] Table 1

[0098]

[0099] Note: The content of metal ions with different valence states in Table 1 is calculated based on the metal ions of all the same metal elements in the negative electrode active material. For example, V3+ / % refers to the mass content ratio of trivalent vanadium ions in all vanadium ions in the negative electrode active material.

[0100] As can be seen from Table 1, the negative electrode sheet prepared using the negative electrode active material according to the present invention has obtained a lower resistivity.

[0101] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those of ordinary skill in the art will recognize that some modifications and changes can be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims, and these modifications and changes also fall within the scope of protection of the present invention.

Claims

1. A negative electrode active material, which comprises a silicon-oxygen-metal complex having the formula SiO x M y , wherein M is a metal ion, 0 < x < 2, 0.01 < y < 0.4, Wherein, the metal ion M includes at least one of vanadium ion, molybdenum ion and niobium ion, and wherein, The vanadium ions include V 2+ , V 3+ , V 4+ and V 5+ and at least one of them; The molybdenum ions include Mo 3+ , Mo 4+ , Mo 5+ and Mo 6+ and at least one of them; The niobium ions include Nb 3+ , Nb 4+ and Nb 5+ or one or more of them.

2. The negative electrode active material according to claim 1, characterized in that it satisfies at least one of the following conditions: (i) Based on all vanadium ions in the negative electrode active material, the mass contents of V 3+ and V 4+ are 90% to 98%; (ii) Based on all molybdenum ions in the negative electrode active material, the mass content of Mo 4+ and Mo 5+ is 85% to 95%; (iii) Based on all niobium ions in the negative electrode active material, the mass content of Nb 3+ and Nb 4+ is 85% to 95%; (iv) The average particle size of the silicon-oxygen-metal complex particles is 200 nm to 500 nm; (v) The metal ion is located inside the silicon-oxygen-metal complex; (vi) 1.5 ≤ x < 2; (vii) 0.05 ≤ y ≤ 0.

3.

3. The negative electrode active material according to claim 2, characterized in that it satisfies at least one of the following conditions: (i) Based on all vanadium ions in the negative electrode active material, the mass content of V 3+ is 38% to 85%; (ii) Based on all vanadium ions in the negative electrode active material, the mass content of V 4+ is 20% to 55%; (iii) Based on all vanadium ions in the negative electrode active material, the mass content of V 5+ is 2% to 11%.

4. The negative electrode active material according to claim 3, characterized in that it satisfies at least one of the following conditions (i) Based on all vanadium ions in the negative electrode active material, the mass content of V 3+ is 40% to 75%; (ii) Based on all vanadium ions in the negative electrode active material, the mass content of V 4+ is 24% to 50%; (iii) Based on all vanadium ions in the negative electrode active material, the mass content of V 5+ is 2.5% to 10%.

5. The negative electrode active material according to claim 2, characterized in that it satisfies at least one of the following conditions: (i) Based on all vanadium ions in the negative electrode active material, the mass content of Mo 4+ is 80% to 85%; (ii) Based on all vanadium ions in the negative electrode active material, the mass content of Mo 5+ is 12% to 16%; (iii) Based on all vanadium ions in the negative electrode active material, the mass content of Mo 6+ is 2% to 4%.

6. The negative electrode active material according to claim 2, characterized in that it satisfies at least one of the following conditions: (i) Based on all vanadium ions in the negative electrode active material, the mass content of Nb 3+ is 35% to 38%; (ii) Based on all vanadium ions in the negative electrode active material, the mass content of Nb 4+ is 48% to 52%; (iii) Based on all vanadium ions in the negative electrode active material, the mass content of Nb 5+ is 11% to 15%.

7. A method for preparing the negative electrode active material according to any one of claims 1 to 6, characterized in that the method includes the following steps: (S1) Mixing a metal element precursor with tetraethyl orthosilicate to obtain silicon dioxide particles containing metal ions to be reduced; (S2) Mixing the silicon dioxide particles containing the metal ions to be reduced obtained in step (S1) with reducing metal particles to obtain silicon-oxygen-metal complex particles containing reduced metal ions.

8. The method according to claim 7, characterized in that it satisfies at least one of the following: (i) The volume ratio of the metal element precursor to the tetraethyl orthosilicate in step (S1) is 1:20 to 1:2, preferably 1:10 to 1:5; (ii) The metal element precursor in step (S1) includes at least one of vanadium triisopropoxide, niobium pentaisopropoxide and molybdenum pentaisopropoxide; (iii) The reducing metal particles in step (S2) are magnesium powder; (iv) In step (S2), the metal ions to be reduced and the magnesium powder undergo a magnesiothermic reaction at a temperature of 600 °C to 950 °C, preferably at a temperature of 650 °C to 750 °C; (v) The weight ratio of the magnesium powder to the silicon dioxide particles containing the metal ions to be reduced is 0.5:1 to 2:

1.

9. A secondary battery, including a negative electrode sheet, the negative electrode sheet including a current collector and a negative electrode active material layer provided on the surface of the current collector, the negative electrode active material layer including the negative electrode active material according to any one of claims 1 to 6 or the negative electrode active material prepared by the method according to any one of claims 7 to 8.

10. A device, including the secondary battery according to claim 9.

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