Preparation method of positive electrode material, positive electrode material and battery

Abstract

The application provides a preparation method of a positive electrode material, the positive electrode material and a battery. The preparation method comprises the following steps: placing a positive electrode material matrix into a reaction cavity of an atomic layer deposition system, and introducing a low-temperature superconducting nanometer material precursor into the reaction cavity to perform atomic layer deposition, so as to form a low-temperature superconducting nanometer coating layer on the surface of the positive electrode material matrix. The atomic layer deposition technology is adopted to form a dense nanometer superconducting low-temperature superconducting nanometer coating layer on the outer surface of the carbon-coated positive electrode material matrix, so that the problem of poor low-temperature performance of the existing positive electrode material is solved.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and relates to a method for preparing a cathode material, the cathode material, and a battery. Background Technology

[0002] Lithium-ion batteries offer advantages such as low cost, stable charging and discharging, environmental friendliness, and high safety, making them widely used in battery-powered electronic devices such as mobile phones, laptops, and electric vehicles. Lithium-ion batteries typically use carbon materials as the negative electrode and lithium-containing compounds as the positive electrode, achieving charging and discharging through the insertion and extraction of lithium ions. With increasingly stringent performance requirements for lithium-ion batteries, research on positive electrode materials has become a crucial factor limiting the overall performance improvement of lithium-ion batteries.

[0003] CN116692819A discloses a high-density cathode material with a nanoporous structure and its preparation method. A phosphorus source, lithium source, iron source, soluble carbon source, and a pore-forming agent are mixed and spray-dried to obtain lithium iron phosphate intermediate mixed particles. These particles are then sintered in an inert gas atmosphere to obtain the lithium iron phosphate cathode material. This method promotes faster and more efficient insertion and extraction of lithium ions within the particles, thereby improving its electrochemical performance. CN110416506A discloses a method for preparing a modified cathode material. Using electron beam evaporation, a GeSbTe film is grown on a carbon-coated lithium iron phosphate film. After annealing, a modified lithium iron phosphate cathode material, namely a GeSbTe modified carbon-coated lithium iron phosphate film, is obtained. This material exhibits higher electrochemical activity, reduces electrode polarization, and improves the rate performance and high-rate cycling performance of lithium iron phosphate.

[0004] However, the poor low-temperature performance of lithium-ion batteries has always been a problem that needs to be solved in the industry. Batteries made of lithium iron phosphate have high DCR (DC internal resistance) and low discharge capacity at low temperatures, which affects the use of batteries in winter, especially in northern regions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a cathode material, the cathode material itself, and a battery. Atom layer deposition technology is used to coat a carbon-coated cathode material matrix with a dense nano-superconducting low-temperature superconducting nano-coating layer, thereby improving the conductivity of the cathode material at low temperatures and solving the problem of poor low-temperature performance of existing lithium iron phosphate cathode materials.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a cathode material, the method comprising:

[0008] The positive electrode material substrate is placed in a reaction cavity of an atomic layer deposition system, and a low-temperature superconducting nanometer material precursor is simultaneously introduced into the reaction cavity for atomic layer deposition, so as to form a low-temperature superconducting nanometer coating layer on the surface of the positive electrode material substrate.

[0009] The atomic layer deposition technology is used to deposit the low-temperature superconducting nanometer material precursor on the surface of the positive electrode material substrate, so as to form a dense superconducting network on the outer surface of the positive electrode material substrate, effectively avoiding the problem that the material appears to be attenuated in the low-temperature condition, even loses the conductivity, so that the positive electrode material can still maintain a high capacity even in the low-temperature condition, and the discharge DCR is reduced.

[0010] The low-temperature superconducting nanometer material precursor in the application refers to a material with a low critical transition temperature, which has the characteristics of "zero resistance, magnetic resistance" and the like under low-temperature conditions, and is usually divided into single-metal superconducting materials, alloy superconducting materials and compound superconducting materials.

[0011] As a preferred technical solution of the application, the mass ratio of the low-temperature superconducting nanometer material precursor to the positive electrode material substrate is (0.1-1):100, which can be 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100 or 1:100, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0012] As a preferred technical solution of the application, the positive electrode material substrate is a carbon-coated positive electrode material substrate.

[0013] Preferably, the carbon-coated positive electrode material substrate includes any one of a carbon-coated lithium iron phosphate substrate, a carbon-coated lithium vanadium iron phosphate substrate, a carbon-coated lithium manganese iron phosphate substrate, a carbon-coated lithium ferrous manganese phosphate substrate, and a carbon-coated lithium iron sulfate substrate.

[0014] Preferably, the carbon content in the carbon-coated positive electrode material substrate is 0.6-1%, which can be 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0015] Preferably, the specific surface area of the carbon-coated positive electrode material substrate is 9-15 m 2 / g, which can be 9 m 2 / g, 9.5 m 2 / g, 10 m 2 / g, 10.6 m 2 / g, 11 m 2 / g, 11.5 m 2 / g, 12 m 2 / g, 12.5 m 2 / g, 13 m 2 / g, 13.5 m 2 / g, 14 m 2 / g, 14.5 m 2 / g, or 15 m 2 / g, but not only the listed values, other unlisted values within the range are also applicable.

[0016] Preferably, the particle size D 50 of the carbon-coated positive electrode material substrate is 0.8-1.5 μm, for example, it can be 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.4 μm, 1.45 μm, or 1.5 μm, but not only the listed values, other unlisted values within the range are also applicable.

[0017] It should be noted that D 50 in the present application refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% of the carbon-coated positive electrode material substrate.

[0018] Preferably, the carbon-coated positive electrode material substrate has a tap density of 2.3-2.5 g / cm 3 , for example, it can be 2.3 g / cm 3 , 2.32 g / cm 3 , 2.35 g / cm 3 , 2.36 g / cm 3 , 2.38 g / cm 3 , 2.4 g / cm 3 , 2.43 g / cm 3 , 2.45 g / cm 3 , 2.48 g / cm 3 , or 2.5 g / cm 3 , but not only the listed values, other unlisted values within the range are also applicable.

[0019] It should be noted that the tap density in the present application is the tap density of the sample to be measured under the condition that the pressure unit of the tap density instrument is adjusted to 2 tons.

[0020] The preparation method of the carbon-coated positive electrode material substrate in the present application comprises:

[0021] The positive electrode active material, lithium source, solvent and carbon source are mixed, dried, and then calcined under inert atmosphere to obtain the carbon-coated lithium iron phosphate material.

[0022] It should be noted that the carbon-coated positive electrode material can ensure the conductivity of the positive electrode material matrix at room temperature. The positive electrode active material includes at least one of iron phosphate, manganese carbonate, vanadium pentoxide, ferrous manganese phosphate and iron sulfate, but is not limited thereto. The lithium source includes at least one of lithium hydroxide, lithium carbonate and lithium acetate, but is not limited thereto. The solvent includes at least one of deionized water, ethanol and ethylene glycol, but is not limited thereto. The carbon source includes at least one of citric acid, glucose and sucrose, but is not limited thereto.

[0023] As a preferred technical solution of the present application, the low-temperature superconducting nanomaterial precursor includes at least two metal precursors.

[0024] Preferably, at least two metal precursors are simultaneously introduced into the reaction cavity.

[0025] Preferably, the metal precursor includes at least one of niobium metal precursor, titanium metal precursor, aluminum metal precursor, tin metal precursor, zirconium metal precursor, vanadium metal precursor and gallium metal precursor.

[0026] In the present application, two metal precursors are simultaneously introduced into the reaction cavity for atomic layer deposition, and typical but non-limiting combinations include: a combination of niobium metal precursor and titanium metal precursor, a combination of niobium metal precursor and aluminum metal precursor, a combination of niobium metal precursor and tin metal precursor, a combination of titanium metal precursor and aluminum metal precursor, a combination of niobium metal precursor and zirconium metal precursor, a combination of niobium metal precursor and gallium metal precursor, a combination of titanium metal precursor and zirconium metal precursor, a combination of aluminum metal precursor and zirconium metal precursor, a combination of niobium metal precursor, titanium metal precursor and aluminum metal precursor, or a combination of niobium metal precursor, zirconium metal precursor and aluminum metal precursor, etc.

[0027] It should be noted that niobium exhibits superconductor properties at low temperatures, which is the highest among all metals with superconducting properties, and has high stability and corrosion resistance at room temperature, and can form alloys with titanium, aluminum, tin, zirconium, vanadium and gallium at high temperatures, and can be used as one of the metal precursors for preparing low-temperature superconducting nanocoating, effectively improving the low-temperature performance of the positive electrode material. The molar ratio of the niobium metal precursor to other metal sources in the low-temperature superconducting nanocoating is 1:(1-3).

[0028] Preferably, the metal precursor comprises at least one of pentakis(dimethylamino)niobium, trimethyl(pentamethylcyclopentadiene)titanium, trimethylaluminum, trimethyl(phenylacetylide)tin, dimethyldi(cyclopentadienyl)zirconium, di(ethylcyclopentyl)vanadium and triethylgallium.

[0029] It should be noted that the above-mentioned metal precursor used in the present application not only contains metal elements, but also can interact with other metal precursors to form superconducting alloy structures and supplement carbon elements for the positive electrode material.

[0030] As a preferred technical solution of the present application, the temperature of the reaction cavity is 300-500℃, for example, it can be 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, 430℃, 450℃, 480℃, 490℃ or 500℃, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0031] By controlling the temperature in the reaction cavity within the above range, on the one hand, the loss of carbon due to excessive temperature can be avoided, and the conductivity of the positive electrode material can be reduced, on the other hand, the reaction between different metals can be ensured to form an alloy structure to achieve superconducting effect.

[0032] Preferably, the pressure of the reaction cavity is 5-8 mbar, for example, it can be 5 mbar, 5.2 mbar, 5.4 mbar, 5.5 mbar, 5.8 mbar, 6 mbar, 6.3 mbar, 6.5 mbar, 6.8 mbar, 7 mbar, 7.2 mbar, 7.5 mbar, 7.6 mbar, 7.8 mbar or 8 mbar, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0033] As a preferred technical solution of the present application, the preparation method further comprises: introducing inert gas into the reaction cavity for flushing.

[0034] Preferably, the inert gas and the low-temperature superconducting nanomaterial precursor are introduced into the reaction cavity at the same time for flushing.

[0035] The present application introduces inert gas into the reaction cavity to remove unreacted low-temperature superconducting nanomaterial precursors and reaction by-products in the reaction cavity.

[0036] Preferably, the inert gas comprises nitrogen or argon.

[0037] In the second aspect, the present application provides a positive electrode material, which is prepared by the preparation method of the first aspect, and comprises a positive electrode material substrate and a low-temperature superconducting nanocoating layer coated on the outer surface of the positive electrode material substrate.

[0038] As a preferred technical solution of the present application, a carbon coating layer is further arranged between the positive electrode material base and the low-temperature superconducting nanometer coating layer.

[0039] Preferably, the thickness of the low-temperature superconducting nanometer coating layer is 10-30 nm, for example, it can be 10 nm, 12 nm, 14 nm, 15 nm, 16 nm, 18 nm, 20 nm, 22 nm, 25 nm, 26 nm, 28 nm or 30 nm, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0040] Preferably, the low-temperature superconducting nanometer coating layer comprises at least one of NbTi, Nb3Al, Nb3Sn, Nb3Zr, NbV and GaNb.

[0041] In a third aspect, the present application provides a battery comprising a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector, and the two side surfaces of the positive electrode current collector are respectively provided with a positive electrode active layer, and the positive electrode active layer comprises the positive electrode material of the second aspect.

[0042] As a preferred technical solution of the present application, the compaction density of the positive electrode sheet is ≥2.55 g / cm 3 .

[0043] Preferably, the positive electrode active layer further comprises a positive electrode conductive agent, conductive carbon black and a positive electrode binder, and the total mass of the positive electrode material, the positive electrode conductive agent, the conductive carbon black and the positive electrode binder is 100%, and the mass percentage of the positive electrode material is 96-97%, for example, it can be 96%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5%, 96.6%, 96.7%, 96.8%, 96.9% or 97%, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0044] Preferably, the positive electrode current collector comprises an aluminum foil.

[0045] It should be noted that the present application can also arrange a carbon coating layer between the positive electrode current collector and the positive electrode active layer to improve the conductivity of the material, that is, the aluminum foil of the positive electrode current collector in the present application can also use a commercially available carbon-coated aluminum foil, and the present application does not make specific limitations thereto.

[0046] Preferably, the thickness of the positive current collector is 8-14 μm, for example, it can be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm or 14 μm, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0047] It should be noted that the present application does not make specific limitations on the positive electrode conductive agent, and any conductive agent known to those skilled in the art for preparing a positive electrode sheet of a battery can be used, for example, it can be carbon nanotubes or graphene.

[0048] Preferably, the positive electrode binder includes, but is not limited to, one or a combination of at least one of polyvinylidene fluoride, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene.

[0049] Preferably, the negative electrode sheet includes a negative current collector, and both sides of the negative current collector are coated with a negative active layer.

[0050] Preferably, the compaction density of the negative electrode sheet is 1.4-1.45 g / cm 3 , for example, it can be 1.4 g / cm 3 , 1.41 g / cm 3 , 1.415 g / cm 3 , 1.42 g / cm 3 , 1.425 g / cm 3 , 1.43 g / cm 3 , 1.435 g / cm 3 , 1.44 g / cm 3 , 1.445 g / cm 3 or 1.45 g / cm 3 , but is not limited to the listed values, and other values not listed in the range are also applicable.

[0051] Preferably, the negative current collector includes a copper foil.

[0052] Preferably, the thickness of the negative current collector is 4-8 μm, for example, it can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0053] Preferably, the negative active layer includes a negative electrode conductive agent, conductive carbon black, sodium carboxymethyl cellulose and a negative electrode binder.

[0054] It should be noted that the present application does not make specific limitations on the negative electrode conductive agent, and any conductive agent known to those skilled in the art for preparing the negative electrode sheet of the battery can be used, for example, carbon nanotubes or graphene.

[0055] Preferably, the negative electrode binder includes, but is not limited to, a styrene-butadiene rubber binder or a polyacrylate water-based binder.

[0056] In order to help those skilled in the art better understand the overall technical solution and working process of the present application, the present application exemplarily provides a specific preparation method of the battery, which comprises:

[0057] (1) mixing lithium iron phosphate positive electrode material, positive electrode conductive agent, conductive carbon black, positive electrode binder and a first solvent according to a proportion to obtain a positive electrode slurry, mixing negative electrode conductive agent, conductive carbon black, sodium carboxymethyl cellulose, negative electrode binder and a second solvent according to a proportion to obtain a negative electrode slurry;

[0058] (2) providing a positive electrode current collector, dividing the positive electrode slurry into two parts, coating and drying one part of the positive electrode slurry on one side surface of the positive electrode current collector, coating and drying another part of the positive electrode slurry on the other side surface of the positive electrode current collector, and then rolling to obtain a positive electrode sheet;

[0059] (3) providing a negative electrode current collector, dividing the negative electrode slurry into two parts, coating and drying one part of the negative electrode slurry on one side surface of the negative electrode current collector, coating and drying another part of the negative electrode slurry on the other side surface of the negative electrode current collector, and then rolling to obtain a negative electrode sheet;

[0060] (4) baking the positive electrode sheet and the negative electrode sheet respectively, then stacking in the order of negative electrode sheet, diaphragm, positive electrode sheet, diaphragm, negative electrode sheet, and then sequentially performing hot pressing, welding, shell punching, packaging, cell baking and liquid injection to obtain the battery.

[0061] The present application does not make specific limitations on the first solvent and the second solvent used in the preparation process of the battery, and exemplarily, the first solvent and the second solvent each independently include at least one of deionized water, ethanol and ethylene glycol.

[0062] The numerical range described in the present application not only includes the point values exemplified above, but also includes any point values between the above numerical ranges which are not exemplified, and the specific point values included in the range are not listed due to the length and for the purpose of simplicity.

[0063] Compared with the prior art, the present application has the following beneficial effects:

[0064] The application provides a preparation method of a positive electrode material, the positive electrode material and a battery. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 A schematic view of the lithium iron phosphate positive electrode material prepared in Embodiment 1 of the application. DETAILED DESCRIPTION

[0066] The technical solutions of the application will be further described below with reference to the drawings and specific embodiments.

[0067] Embodiment 1

[0068] The embodiment provides a positive electrode material and a preparation method thereof. Figure 1 As shown in the figure, the positive electrode material comprises a carbon-coated lithium iron phosphate base and a low-temperature superconducting nanocoating layer coated on the outer surface of the carbon-coated lithium iron phosphate base, and the thickness of the low-temperature superconducting nanocoating layer is 20 nm. The preparation method comprises the following steps:

[0069] (1) providing a carbon-coated lithium iron phosphate base with a specific surface area of 10.6 m 2 / g, a carbon content of 0.8%, a particle size volume distribution D 50 of 1.1 μm and a compacted density of 2.38 g / cm 3 ;

[0070] (2) placing 500 g of the carbon-coated lithium iron phosphate base into a reaction cavity of an atomic layer deposition system, and simultaneously introducing 2.1 g of trimethyl (pentamethylcyclopentadiene) titanium, 2.9 g of pentakis (dimethylamino) niobium and nitrogen into the reaction cavity, and performing atomic layer deposition under the condition that the temperature of the reaction cavity is 400 ℃ and the pressure is 7 mbar, so as to form a low-temperature superconducting nanocoating layer on the surface of the carbon-coated lithium iron phosphate base.

[0071] The embodiment also uses the above positive electrode material to prepare a battery, wherein the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating layer. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating layer.

[0072] The preparation method of the battery comprises the following steps:

[0073] S1 adds the positive electrode material, carbon nanotube, conductive carbon black, polyvinylidene fluoride binder and N-methyl pyrrolidone into a homogenizing tank according to a mass ratio of 96.9:1:0.3:1.8:56, stirs until the viscosity is 5500-7500 mPa·s, and obtains a positive electrode slurry;

[0074] S2 divides the positive electrode slurry into two parts, coats one part of the positive electrode slurry on one side surface of the carbon-coated aluminum foil and dries, coats the other part of the positive electrode slurry on the other side surface of the carbon-coated aluminum foil and dries, so that the surface density of the two side surfaces of the carbon-coated aluminum foil is 18 mg / cm 2 , obtains a positive electrode sheet, and then rolls the positive electrode sheet to a compacted density of 2.58 g / cm 3 , and cuts into a size of 95.6 mm x 50.2 mm for standby;

[0075] S3 adds the graphite, conductive carbon black, sodium carboxymethyl cellulose, butadiene-styrene rubber binder and deionized water into a homogenizing tank according to a mass ratio of 96.1:1:1.2:1.7:92, stirs until the viscosity is 2000-4000 mPa·s, and obtains a negative electrode slurry;

[0076] S4 divides the negative electrode slurry into two parts, coats one part of the negative electrode slurry on one side surface of the copper foil and dries, coats the other part of the negative electrode slurry on the other side surface of the copper foil and dries, so that the surface density of the two side surfaces of the copper foil is 9 mg / cm 2 , obtains a negative electrode sheet, and then rolls the negative electrode sheet to a compacted density of 1.43 g / cm 3 , and cuts into a size of 100 mm x 55 mm for standby;

[0077] S5 bakes the positive electrode sheet at 100℃ for 12 h, bakes the negative electrode sheet at 85℃ for 12 h, then stacks in the order of negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet, the negative electrode sheet is 18 pieces, the positive electrode sheet is 17 pieces, and then goes through hot pressing, welding, shell punching, packaging, cell baking and liquid injection, to obtain a soft package battery, the liquid injection amount of each cell is 16 g, and the electrolyte is lithium hexafluorophosphate electrolyte.

[0078] Example 2

[0079] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a carbon-coated lithium iron phosphate base and a low-temperature superconducting nanocoating layer coated on the outer surface of the carbon-coated lithium iron phosphate base. The thickness of the low-temperature superconducting nanocoating layer is 10 nm. The preparation method comprises the following steps:

[0080] (1) providing a carbon-coated lithium iron phosphate base with a specific surface area of 9 m 2 / g, a carbon content of 0.6%, and a particle size volume distribution D 500.8 pm, and a compact density of 2.5 g / cm 3 ;

[0081] (2) 500 g of the carbon-coated lithium-iron-vanadium-phosphate substrate is placed into a reaction chamber of an atomic layer deposition system, and 1.9 g of trimethyl (pentamethylcyclopentadiene) titanium, 2.1 g of pentakis(dimethylamino) niobium and nitrogen gas are simultaneously introduced into the reaction chamber, atomic layer deposition is carried out under the condition that the temperature of the reaction chamber is 300°C and the pressure is 5 mbar, so as to form a low-temperature superconducting nano-coating layer on the surface of the carbon-coated lithium-iron-vanadium-phosphate substrate.

[0082] The positive electrode material is also used to prepare a battery in this embodiment, wherein the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating layer. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating layer. The preparation method of the battery is the same as that of Embodiment 1.

[0083] Embodiment 3

[0084] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a carbon-coated lithium-iron-vanadium-phosphate substrate and a low-temperature superconducting nano-coating layer coated on the outer surface of the carbon-coated lithium-iron-vanadium-phosphate substrate. The thickness of the low-temperature superconducting nano-coating layer is 30 nm. The preparation method comprises the following steps:

[0085] (1) providing a carbon-coated lithium-iron-vanadium-phosphate substrate, wherein the specific surface area of the carbon-coated lithium-iron-vanadium-phosphate substrate is 15 m 2 / g, the carbon content is 1%, the particle size volume distribution D 50 is 1.5 pm, and the compact density is 2.3 g / cm 3 ;

[0086] (2) 500 g of the carbon-coated lithium-iron-vanadium-phosphate substrate is placed into a reaction chamber of an atomic layer deposition system, and 1.9 g of trimethyl (pentamethylcyclopentadiene) titanium, 2.1 g of pentakis(dimethylamino) niobium and nitrogen gas are simultaneously introduced into the reaction chamber, atomic layer deposition is carried out under the condition that the temperature of the reaction chamber is 300°C and the pressure is 5 mbar, so as to form a low-temperature superconducting nano-coating layer on the surface of the carbon-coated lithium-iron-vanadium-phosphate substrate.

[0087] The positive electrode material is also used to prepare a battery in this embodiment, wherein the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating layer. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating layer. The preparation method of the battery is the same as that of Embodiment 1.

[0088] Embodiment 4

[0089] The embodiment provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in the step (2), 4.7g of penta (dimethylamino) niobium, 0.3g of trimethylaluminum and nitrogen are simultaneously introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0090] The embodiment also adopts the positive electrode material to prepare a battery, and the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that in the embodiment 1.

[0091] Embodiment 5

[0092] The embodiment provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in the step (2), 4.7g of penta (dimethylamino) niobium, 0.3g of trimethylaluminum and nitrogen are simultaneously introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0093] The embodiment also adopts the positive electrode material to prepare a battery, and the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that in the embodiment 1.

[0094] Embodiment 6

[0095] The embodiment provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in the step (2), 4.7g of penta (dimethylamino) niobium, 0.3g of trimethylaluminum and nitrogen are simultaneously introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0096] The embodiment also adopts the positive electrode material to prepare a battery, and the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that in the embodiment 1.

[0097] Embodiment 7

[0098] The embodiment provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in the step (2), 4.7g of penta (dimethylamino) niobium, 0.3g of trimethylaluminum and nitrogen are simultaneously introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0099] The positive electrode material is used to prepare a battery. The battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that of Embodiment 1.

[0100] Embodiment 8

[0101] The embodiment provides a positive electrode material and a preparation method thereof. The difference from Embodiment 1 is that in step (2), 1.2 g of trimethyl (pentamethylcyclopentadiene) titanium, 2.9 g of trimethyl aluminum, and 0.9 g of trimethyl aluminum are simultaneously introduced into the reaction cavity, and the remaining process parameters and operating conditions are the same as those of Embodiment 1.

[0102] The positive electrode material is used to prepare a battery. The battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that of Embodiment 1.

[0103] Embodiment 9

[0104] The embodiment provides a positive electrode material and a preparation method thereof. The difference from Embodiment 1 is that in step (2), the temperature of the reaction cavity is 270 DEG C, and the remaining process parameters and operating conditions are the same as those of Embodiment 1.

[0105] The positive electrode material is used to prepare a battery. The battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that of Embodiment 1.

[0106] Embodiment 10

[0107] The embodiment provides a positive electrode material and a preparation method thereof. The difference from Embodiment 1 is that in step (2), the temperature of the reaction cavity is 540 DEG C, and the remaining process parameters and operating conditions are the same as those of Embodiment 1.

[0108] The positive electrode material is used to prepare a battery. The battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that of Embodiment 1.

[0109] Embodiment 11

[0110] The embodiment provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in step (2), 0.2 g of trimethyl (pentamethylcyclopentadiene) titanium, 0.23 g of pentakis(dimethylamino) niobium and nitrogen are introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0111] The embodiment also uses the positive electrode material to prepare a battery, and the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that in the embodiment 1.

[0112] Embodiment 12

[0113] The embodiment provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in step (2), 0.2 g of trimethyl (pentamethylcyclopentadiene) titanium, 0.23 g of pentakis(dimethylamino) niobium and nitrogen are introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0114] The embodiment also uses the positive electrode material to prepare a battery, and the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that in the embodiment 1.

[0115] Comparative example 1

[0116] The comparative example provides a lithium iron phosphate positive electrode material, and the difference from the embodiment 1 is that the carbon-coated positive electrode material matrix is not coated with a low-temperature superconducting nanometer coating layer.

[0117] The comparative example also uses the positive electrode material to prepare a battery, and the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that in the embodiment 1.

[0118] Comparative example 2

[0119] The comparative example provides a positive electrode material and a preparation method thereof, and the difference from the embodiment 1 is that in step (2), 0.2 g of trimethyl (pentamethylcyclopentadiene) titanium, 0.23 g of pentakis(dimethylamino) niobium and nitrogen are introduced into the reaction cavity, and the remaining process parameters and operation conditions are the same as those in the embodiment 1.

[0120] The comparative example also uses the above positive electrode material to prepare a battery, wherein the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that of Example 1.

[0121] Comparative Example 3

[0122] The comparative example provides a positive electrode material and a preparation method thereof, and the difference from Example 1 is that in step (2), 5 g of pentakis(dimethylamino) niobium and nitrogen are simultaneously introduced into the reaction cavity, and the remaining process parameters and operating conditions are the same as those of Example 1.

[0123] The comparative example also uses the above positive electrode material to prepare a battery, wherein the battery comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a carbon-coated aluminum foil, and the two side surfaces of the carbon-coated aluminum foil are respectively provided with a positive electrode active coating. The negative electrode sheet comprises a copper foil, and the two side surfaces of the copper foil are respectively provided with a negative electrode active coating. The preparation method of the battery is the same as that of Example 1.

[0124] The batteries in Examples 1 to 12 and Comparative Examples 1 to 3 are respectively tested for discharge capacity at room temperature and low temperature, and the test conditions are as follows: 1 / 3C charging, cut-off voltage 3.65V, 1 / 3C discharging, cut-off voltage 2.5V. The test results are shown in Table 1.

[0125] Table 1

[0126]

[0127]

[0128] As can be seen from Table 1, the batteries in Examples 1 to 10 have higher capacity and lower DCR at room temperature and low temperature, which is mainly due to the fact that the positive electrode material used in the batteries in Examples 1 to 10 is coated with a low-temperature superconducting nanocoating layer, so that the positive electrode material can still ensure high conductivity even at low temperature, thereby improving the capacity retention rate of the material at low temperature.

[0129] Compared with Example 1, the discharge capacity of the batteries in Examples 6 and 7 at low temperature is reduced, which is mainly due to the fact that the metal precursor used in the positive electrode material of Example 1 comprises a niobium metal precursor, which has stronger superconductivity at low temperature and can maintain higher conductivity compared with the tin metal precursor used in Example 6 and the aluminum metal precursor used in Example 7.

[0130] From comparative example 1, example 9 and example 10, it can be seen that the discharge capacity of the battery of example 9 at low temperature is lower than that of example 1, which is mainly due to the fact that the temperature in the reaction cavity is too low during the preparation of the positive electrode material of example 9, so that the two metal source precursors cannot effectively react to form a dense low-temperature superconducting nanocoating layer, thereby causing the low-temperature performance to decrease. The discharge capacity of example 10 at normal temperature and low temperature is lower than that of example 1, which is mainly due to the fact that the temperature in the reaction cavity of example 10 is too high, causing the carbon loss of the positive electrode material to increase, thereby causing the conductivity to decrease.

[0131] As can be seen from Table 1, compared with example 1, the discharge capacity of example 11 at low temperature decreases, and the discharge DCR increases, which is mainly due to the fact that the addition amount of the metal precursor is too low, which cannot form a dense low-temperature superconducting nanocoating layer, thereby reducing the superconducting performance of the positive electrode material at low temperature. The comprehensive electrical performance of example 12 at normal temperature and low temperature is slightly different from that of example 1, but the excess metal precursor is removed by nitrogen, causing the material to be wasted.

[0132] As can be seen from the content of Table 1, the discharge capacity and DCR of example 1 and comparative example 1 at normal temperature are slightly different, but the capacity retention rate and DCR performance of example 1 at low temperature are obviously better than those of comparative example 1, which is mainly due to the fact that the low-temperature superconducting nanocoating layer of TiNb is formed on the surface of the lithium iron phosphate matrix of the positive electrode material of example 1, thereby enhancing the conductivity of the positive electrode material at low temperature.

[0133] As can be seen from comparative example 1, comparative example 2 and comparative example 3, the discharge capacity and DCR at normal temperature are slightly different, but the capacity retention rate and DCR performance of example 1 at low temperature are obviously better than those of comparative example 2 and comparative example 3, which is mainly due to the fact that the positive electrode material of comparative example 2 and comparative example 3 only uses one kind of metal precursor, while example 1 uses two kinds of metal precursors to form an alloy structure with superconducting performance, which is higher than using one kind of metal source in enhancing the conductivity of the positive electrode material at low temperature.

[0134] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for producing a positive electrode material, characterized by, The preparation method comprises the following steps: putting the positive electrode material substrate into a reaction cavity of an atomic layer deposition system, and introducing a low-temperature superconducting nanometer material precursor into the reaction cavity for atomic layer deposition to form a low-temperature superconducting nanometer coating layer on the surface of the positive electrode material substrate; The positive electrode material substrate is a carbon-coated positive electrode material substrate; the carbon content in the carbon-coated positive electrode material substrate is 0.6-1%; the specific surface area of the carbon-coated positive electrode material substrate is 9-15 m 2 / g; the particle size D 50 of the carbon-coated positive electrode material substrate is 0.8-1.5 μm; and the compaction density of the carbon-coated positive electrode material substrate is 2.3-2.5 g / cm 3 . the low-temperature superconducting nanometer material precursor comprises at least two metal precursors; the at least two metal precursors are simultaneously introduced into the reaction cavity; the metal precursors comprise pentakis(dimethylamino) niobium, trimethyl(pentamethylcyclopentadiene) titanium, trimethylaluminum, trimethyl(phenyl ethynyl) tin, dimethylbis(cyclopentadienyl) zirconium, bis(ethylcyclopentyl) vanadium and triethyl gallium.

2. The production method according to claim 1, characterized by, The mass ratio of the low-temperature superconducting nanometer material precursor to the positive electrode material substrate is (0.1-1):

100.

3. The production method according to claim 1 or 2, characterized by, The carbon-coated positive electrode material substrate comprises any one of a carbon-coated lithium iron phosphate substrate, a carbon-coated lithium vanadium phosphate substrate, a carbon-coated lithium manganese iron phosphate substrate, a carbon-coated lithium ferromanganese phosphate substrate and a carbon-coated lithium iron sulfate substrate.

4. The method of claim 1, wherein, The temperature of the reaction cavity is 300-500℃.

5. The preparation method according to claim 1, characterized in that, The pressure of the reaction cavity is 5-8 mbar.

6. The method of claim 1, wherein, The preparation method further comprises introducing an inert gas into the reaction cavity for flushing.

7. The preparation method according to claim 6, characterized in that, The inert gas and the low-temperature superconducting nanometer material precursor are simultaneously introduced into the reaction cavity for flushing.

8. The preparation method according to claim 6, characterized in that, The inert gas comprises nitrogen or argon.

9. A positive electrode material, characterized by, The positive electrode material is prepared by the preparation method in any one of claims 1-8, and the positive electrode material comprises a positive electrode material substrate and a low-temperature superconducting nanometer coating layer coated on the outer surface of the positive electrode material substrate.

10. The positive electrode material of claim 9, wherein, A carbon coating layer is further arranged between the positive electrode material substrate and the low-temperature superconducting nanometer coating layer.

11. The cathode material of claim 10, wherein, The thickness of the low-temperature superconducting nanometer coating layer is 10-30 nm.

12. The cathode material of claim 9, wherein, The low-temperature superconducting nanometer coating layer comprises at least one of NbTi, Nb3Al, Nb3Sn, Nb3Zr, NbV and GaNb.

13. A battery comprising a positive electrode sheet and a negative electrode sheet, characterized by The positive electrode sheet comprises a positive electrode current collector, and the two side surfaces of the positive electrode current collector are respectively provided with a positive electrode active layer; the positive electrode active layer comprises the positive electrode material in any one of claims 9-12.

14. The battery of claim 13, wherein, The compacted density of the positive electrode plate is ≥ 2.55 g / cm 3 .

15. The battery of claim 13, wherein, The positive electrode active layer further comprises a positive electrode conductive agent, conductive carbon black and a positive electrode binder; the total mass of the positive electrode material, the positive electrode conductive agent, the conductive carbon black and the positive electrode binder is 100%, and the mass percentage of the positive electrode material is 96-97%.

16. The battery of claim 15, wherein, The positive electrode current collector comprises an aluminum foil; The thickness of the positive electrode current collector is 8-14 μm.

17. The battery of claim 13, wherein, The negative electrode sheet comprises a negative electrode current collector, and the two side surfaces of the negative electrode current collector are respectively coated with a negative electrode active layer; The compaction density of the negative electrode plate is 1.4-1.45 g / cm 3 .

18. The battery of claim 17, wherein, The negative electrode current collector comprises a copper foil; The thickness of the negative electrode current collector is 4-8 μm.

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