Coated ternary material mixed with different particle sizes, preparation method thereof and battery

Abstract

The present application relates to the technical field of new energy battery, in particular to a coated ternary material mixed with different particle sizes, a preparation method thereof and a battery; the preparation method comprises the following steps: mixing a nickel-cobalt-manganese precursor and a lithium salt, and then mixing the mixture with a gel solution to obtain a premix; mixing a metal oxide with the gel solution to obtain an oxide coating agent; mixing a carbon source with the gel solution to obtain a carbon coating agent; coating the oxide coating agent on the outside of the premix by using an electrospinning method to obtain an oxide-coated ternary material; coating the carbon coating agent on the outside of the premix by using an electrospinning method to obtain a carbon-coated ternary material; sintering the oxide-coated ternary material and the carbon-coated ternary material; mixing and sintering the sintered oxide-coated ternary material and the sintered carbon-coated ternary material; wherein the particle size of the oxide-coated ternary material is larger than that of the carbon-coated ternary material. The preparation method is simple, has fewer processes, and can shorten the preparation time.

Description

Technical Field

[0001] This invention relates to the field of new energy battery technology, and more specifically, to coated ternary materials with different particle sizes, their preparation methods, and batteries. Background Technology

[0002] Ternary materials are a common material used to prepare the positive electrode of lithium batteries. The particle size of ternary materials has a significant impact on battery performance. Lithium ions need to migrate between the positive and negative electrodes during charging and discharging, and the particle size affects the diffusion path of lithium ions. If the particles are too large, the path for lithium ions from the interior to the surface becomes longer, which may lead to a decrease in high-rate performance. That is, the battery may perform poorly under high-current charging or discharging, such as rapid capacity decay or severe overheating. Conversely, if the particles are too small, although the structure is more stable, the diffusion path is shorter, and the volume change is smaller, which can improve rate performance, the large surface area leads to more side reactions, thus reducing the lifespan of the lithium battery.

[0003] By mixing large-particle-size ternary materials with small-particle-size ternary materials, a 1+1>2 effect can be achieved.

[0004] However, the methods for mixing large-particle-size ternary materials and small-particle-size ternary materials provided by related technologies are complex and time-consuming; and the production capacity is limited by the loose packing of materials, resulting in low production capacity and high cost. Summary of the Invention

[0005] The purpose of this invention is to provide coated ternary materials with different particle sizes, their preparation methods, and batteries. The preparation method of this invention is simple, involves fewer steps, and can shorten the preparation time. The coated ternary materials with different particle sizes prepared by the method of this invention can improve the electronic conductivity of coated ternary materials with different particle sizes, reduce internal resistance, and also improve compaction density and rate performance. The batteries prepared from the coated ternary materials with different particle sizes of this invention have good electrical performance.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing coated ternary materials with different particle sizes, wherein a nickel-cobalt-manganese precursor and a lithium salt are mixed, and then mixed with a gel solution to obtain a premix.

[0008] Metal oxides are mixed with gel solutions to obtain oxide coating agents;

[0009] The carbon source is mixed with the gel solution to obtain a carbon coating agent;

[0010] Oxide-coated ternary materials were prepared by coating an oxide coating agent onto the outside of a premix using electrospinning.

[0011] Carbon-coated ternary materials were prepared by coating a carbon coating agent onto the outside of a premix using electrospinning.

[0012] Sintered oxide-coated ternary materials, carbon-coated ternary materials;

[0013] The ternary material is a mixture of oxide-coated ternary material and carbon-coated ternary material after sintering; wherein the particle size of the oxide-coated ternary material is larger than that of the carbon-coated ternary material.

[0014] In an optional embodiment, a method for preparing an oxide-coated ternary material by coating an oxide coating agent onto the exterior of a premix using electrospinning specifically includes:

[0015] The premix is ​​loaded into the built-in syringe of the electrospinning apparatus, and the oxide coating agent is loaded into the external syringe of the electrospinning apparatus, the external syringe being coaxially fitted onto the outside of the built-in syringe; then, electrospinning coats the premix with the oxide coating agent; and / or,

[0016] A method for preparing carbon-coated ternary materials by coating a carbon coating agent onto the exterior of a premix using electrospinning specifically includes:

[0017] The premix is ​​filled into the built-in syringe of the electrospinning equipment, and the carbon coating agent is filled into the external syringe of the electrospinning equipment. The external syringe is coaxially sleeved on the outside of the built-in syringe; then electrospinning coats the premix with the carbon coating agent.

[0018] In an optional implementation, the inner diameter of the external syringe is 1.0-1.8 mm, and the inner diameter of the internal syringe is 0.3-0.6 mm.

[0019] In an optional embodiment, the voltage required to coat the oxide coating agent onto the premix using electrospinning is less than the voltage required to coat the carbon coating agent onto the premix using electrospinning; and / or,

[0020] The spinning rate for coating an oxide coating agent onto the outside of a premix using electrospinning is lower than the spinning rate for coating a carbon coating agent onto the outside of a premix using electrospinning.

[0021] In an optional embodiment, in the step of coating the premix with an oxide coating agent using electrospinning, the electrospinning voltage is controlled to be 19.20±0.20kV, the plate spacing to be 10~15cm, and the spinning rate to be 0.2±0.1mL / h; and / or,

[0022] In the step of coating the premix with carbon coating agent by electrospinning, the electrospinning voltage is controlled at 20.0±0.20kV, the plate spacing is 15~20cm, and the spinning rate is 0.6±0.2mL / h.

[0023] In an optional embodiment, the steps of sintering oxide-coated ternary materials and carbon-coated ternary materials include: sintering oxide-coated ternary materials and carbon-coated ternary materials respectively; wherein,

[0024] In the step of sintering at least one of oxide-coated ternary materials and carbon-coated ternary materials, the temperature is raised to 400-500℃ at a heating rate of 3-5℃ / min for the first sintering, and then raised to 900-1000℃ at a heating rate of 3-5℃ / min for the second sintering, followed by cooling.

[0025] In an optional embodiment, when sintered oxide-coated ternary materials and sintered carbon-coated ternary materials are mixed, the mass ratio of oxide-coated ternary materials to carbon-coated ternary materials is 1:0.1 to 1:0.3.

[0026] In an optional embodiment, the preparation method of the gel solution includes mixing polyacrylonitrile (PAN) and N,N-dimethylformamide (DMF) and stirring at a temperature of 40±5°C; wherein the mass ratio of polyacrylonitrile (PAN) to N,N-dimethylformamide (DMF) is 6~10%; and / or,

[0027] The preparation method of the nickel-cobalt-manganese precursor includes: dispersing nickel salt, cobalt salt, and manganese salt in water to obtain a salt solution; then adding the salt solution dropwise to a citric acid-alcohol solution until a sol-gel system is formed; drying the colloid of the sol-gel system at 200-220℃ and grinding it into powder; the total metal ion concentration in the salt solution is 0.2-0.5M; the molar ratio of the salt solution to the citric acid-alcohol solution is 1:1 to 1:1.5; and the mass ratio of citric acid to alcohol in the citric acid-alcohol solution is 1:8 to 1:10; and / or,

[0028] At least one of the following: the mass ratio of metal oxide to nickel-cobalt-manganese precursor, and the mass ratio of carbon source to nickel-cobalt-manganese precursor, is 0.2% to 0.5%; and / or,

[0029] Metal oxides include at least one of zirconium oxide, aluminum oxide, titanium oxide, and cobalt oxide; and / or,

[0030] The particle size D50 of oxide-coated ternary materials is 8-12 μm; the particle size D50 of carbon-coated ternary materials is 2-8 μm.

[0031] Secondly, the present invention provides a coated ternary material with mixed particle sizes, prepared by the preparation method of the coated ternary material with mixed particle sizes according to any of the foregoing embodiments; wherein...

[0032] The gaps in the oxide-coated ternary material are filled with carbon-coated ternary material;

[0033] The chemical formula of the coated ternary material with different particle sizes is LiNi x Co y Mn 1-x-y O2.

[0034] Thirdly, the present invention provides a battery in which the raw materials for preparing the positive electrode of the battery include coated ternary materials with different particle sizes mixed in the aforementioned embodiments.

[0035] The preparation method of coated ternary materials with mixed particle sizes according to the present invention has the following beneficial effects: The preparation method provided in the embodiments of the present invention uses electrospinning to prepare large-particle-size oxide-coated ternary materials and small-particle-size carbon-coated ternary materials, and then sintersects and mixes the large-particle-size and small-particle-size ternary materials to obtain coated ternary materials with mixed particle sizes. Since the preparation method of the present invention uses electrospinning to modify the ternary materials, the mechanical friction between the coating agent and the ternary materials is reduced, the operation is simple and easy to obtain, and the preparation time can be shortened, thereby improving production efficiency.

[0036] Furthermore, by coating nickel-cobalt-manganese precursors with carbon coating agents to prepare small-particle-size ternary materials, and then mixing these small-particle-size ternary materials with large-particle-size oxide-coated ternary materials, the electronic conductivity of the coated ternary materials with different particle sizes can be effectively improved and the internal resistance reduced.

[0037] Meanwhile, the preparation method of the present invention can improve the compaction density and ratio performance of the coated ternary materials with different particle sizes, so that the production capacity is not limited by the loose packing of the material; moreover, when mixing ternary materials with different particle sizes, the intensity of friction and extrusion between particles is reduced, which can improve the problem that coated ternary materials with different particle sizes are easily damaged by mechanical stress.

[0038] The coated ternary material with different particle sizes of the present invention has the following beneficial effects: The coated ternary material with different particle sizes provided in the embodiments of the present invention is prepared by the aforementioned preparation method. The coated ternary material with different particle sizes has good electronic conductivity, low internal resistance, and higher compaction density and rate performance. Moreover, when mixing ternary materials with different particle sizes, the intensity of friction and extrusion between particles is reduced, which can improve the problem that the coated ternary material with different particle sizes is easily damaged by mechanical stress.

[0039] The battery of the present invention has the following beneficial effects: the raw materials for preparing the positive electrode of the battery provided in the embodiments of the present invention include the aforementioned coated ternary materials mixed with different particle sizes; since the coated ternary materials mixed with different particle sizes have good electronic conductivity, low internal resistance, and higher compaction density and rate performance, the battery prepared therefrom has good electrical performance. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the built-in syringe and external syringe of the electrospinning device in this invention;

[0042] Figure 2 This is a schematic diagram of the structure of another type of coated ternary material in this invention;

[0043] Figure 3 This is a schematic diagram of the structure of a coated ternary material according to the present invention;

[0044] Figure 4 This is a normal particle size distribution diagram of the coated ternary material with different particle sizes mixed in Example 1 of this invention;

[0045] Figure 5 This is a charge-discharge curve of an experimental example of coated ternary materials with different particle sizes mixed in Example 1 of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0047] Li, a ternary material with small particle size and large specific surface area +Shorter transmission paths support high-rate charging and discharging in short periods, but due to their small particle size and large specific surface area, the slurry is prone to agglomeration during preparation. This leads to a decrease in solid-phase diffusion coefficient and electronic conductivity, as well as an increase in the internal resistance of lithium-ion batteries. To improve the problems associated with small-particle ternary materials and to fully utilize the performance of large-particle ternary materials, doping with small-particle ternary materials can mitigate the agglomeration problem of small-particle materials. It can also reduce the degree of structural instability degradation of large-particle materials at high rates and high voltages, improve compaction density to some extent, and affect battery energy density.

[0048] The related technology provides a method for mixing ternary materials with different particle sizes, which is a solid-phase mixing method. This method includes: preparing large-particle-size precursors and small-particle-size precursors respectively, then mixing the large-particle-size precursors with lithium sources and additives, sintering once, post-processing, coating (doping), and sintering twice, and mixing the small-particle-size precursors with lithium sources and additives, sintering once, post-processing, coating (doping), and sintering twice.

[0049] It is evident that the solid-phase mixing method provided by the relevant technology requires the separate preparation of large-particle-size precursors and small-particle-size precursors, and then the precursors with different particle sizes are separately mixed with lithium sources, additives, etc., sintered, and coated. Therefore, the solid-phase mixing method provided by the relevant technology is complex and time-consuming.

[0050] Furthermore, the inventors also discovered that the compaction density improvement of ternary materials with different particle sizes prepared by the solid-phase mixing method provided by the related technology is limited (less than 3 g / cm³). 3 Production capacity is still limited by the loose packaging of materials, resulting in low production capacity and high preparation costs. Moreover, the ternary materials with different particle sizes prepared by solid-phase mixing method have limited improvement in compaction density. When the particles are mixed, the friction and extrusion are intense, and they are easily damaged by mechanical stress.

[0051] To simplify the preparation process and further improve compaction density, this invention provides a new method for preparing coated ternary materials with different particle sizes.

[0052] The preparation method includes: mixing nickel-cobalt-manganese precursor and lithium salt evenly, and then mixing with gel solution to obtain a premix;

[0053] Metal oxides are mixed with gel solutions to obtain oxide coating agents;

[0054] The carbon source is mixed with the gel solution to obtain a carbon coating agent;

[0055] Oxide-coated ternary materials were prepared by coating an oxide coating agent onto the outside of a premix using electrospinning.

[0056] Carbon-coated ternary materials were prepared by coating a carbon coating agent onto the outside of a premix using electrospinning.

[0057] Sintered oxide-coated ternary materials, carbon-coated ternary materials;

[0058] The ternary material is a mixture of oxide-coated ternary material and carbon-coated ternary material after sintering; wherein the particle size of the oxide-coated ternary material is larger than that of the carbon-coated ternary material.

[0059] The preparation method involves electrospinning to produce large-particle-size oxide-coated ternary materials and small-particle-size carbon-coated ternary materials. These materials are then sintered and blended to obtain coated ternary materials with mixed particle sizes. Since this method eliminates the need for separate preparation of large and small particle-size precursors, and avoids separate sintering and coating of these precursors, and utilizes electrospinning to reduce mechanical interaction between the coating agent and the ternary materials, the method is simpler, has fewer steps, and shortens preparation time. Specifically, this method can utilize the same nickel-cobalt-manganese precursor to directly coat oxides or carbon via electrospinning, forming oxide-coated and carbon-coated ternary materials with different particle sizes. This reduces the steps required to prepare precursors of different particle sizes, significantly reducing preparation steps and shortening preparation time.

[0060] Furthermore, by coating nickel-cobalt-manganese precursors with carbon coating agents to prepare small-particle-size ternary materials, and then mixing these small-particle-size ternary materials with large-particle-size oxide-coated ternary materials, the electronic conductivity of the coated ternary materials with different particle sizes can be effectively improved and the internal resistance reduced.

[0061] Meanwhile, the preparation method of this invention can improve the compaction density and rate performance of coated ternary materials with different particle sizes, so that production capacity is not limited by the loose packing of the material. Moreover, when mixing ternary materials with different particle sizes, the intensity of friction and extrusion between particles is reduced, which can improve the problem of mechanical stress damage.

[0062] The cathode of a battery prepared by the method of the present invention using coated ternary materials with different particle sizes can enable the corresponding battery to have good electrical performance.

[0063] Optionally, the preparation method of the gel solution includes: mixing polyacrylonitrile (PAN) and N,N-dimethylformamide (DMF) and stirring at a temperature of 40±5℃ (e.g., 35℃, 38℃, 40℃, 43℃, 45℃, etc., which are not specifically limited here); wherein the mass ratio of polyacrylonitrile (PAN) to N,N-dimethylformamide (DMF) is 6~10% (e.g., 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc., which are not specifically limited here).

[0064] Optionally, when preparing the gel solution, it is sufficient to stir until it becomes transparent. The specific stirring time is not limited, for example, stirring for 12 hours, 13 hours, 10 hours, etc.

[0065] Optionally, the preparation method of the nickel-cobalt-manganese precursor includes: dispersing nickel salt, cobalt salt and manganese salt in water to obtain a salt solution, then adding the salt solution dropwise to a citric acid-alcohol solution until a sol-gel system is formed, drying the colloid of the sol-gel system at 200~220℃ (e.g., 200℃, 210℃, 220℃, etc.) and grinding it into powder; wherein, the total metal ion concentration in the salt solution is 0.2-0.5M (e.g., 0.2M, 0.3M, 0.4M, 0.5M, etc., which is not specifically limited here), the mass ratio of the salt solution to the citric acid-alcohol solution is 1:1-1:1.5 (e.g., 1:1, 1:1.2, 1:1.5, etc., which is not specifically limited here), and the mass ratio of citric acid to alcohol solution in the citric acid-alcohol solution is 1:8~1:10 (e.g., 1:8, 1:9, 1:10, etc.).

[0066] Optionally, the molar ratio of nickel salt, cobalt salt, and manganese salt must precisely match the stoichiometric ratio of the target ternary material (e.g., Ni:Co:Mn = x:y:z, X+Y+Z=1), without specific limitations here.

[0067] Optionally, at least one of the nickel salt, cobalt salt, and manganese salt can be a sulfate, nitrate, or acetate. That is, the nickel salt can be at least one of nickel sulfate, nickel nitrate, and nickel acetate; the cobalt salt can be at least one of cobalt sulfate, cobalt nitrate, and cobalt acetate; and the manganese salt can be at least one of manganese sulfate, manganese nitrate, and manganese acetate.

[0068] Optionally, the citric acid alcohol solution can be an aqueous solution of citric acid and ethylene glycol, that is, the alcohol solution in the citric acid alcohol solution is ethylene glycol.

[0069] Optionally, the ethylene glycol can be of analytical grade, i.e., with a mass concentration greater than or equal to 99%.

[0070] Optionally, the molar ratio of the nickel-cobalt-manganese precursor to the lithium salt is 1:1 to 1:1.2, for example: 1:1, 1:1.02, 1:1.03, 1:1.04, 1:1.15, 1:1.2, etc., without being specifically limited here.

[0071] Optionally, the lithium salt includes at least one of lithium sulfate, lithium nitrate, lithium acetate, and lithium carbonate.

[0072] Optionally, at least one of the mass ratio of metal oxide to nickel-cobalt-manganese precursor and the mass ratio of carbon source to nickel-cobalt-manganese precursor is 0.2% to 0.5%, for example: 0.2%, 0.3%, 0.4%, 0.5%, etc., without being specifically limited here.

[0073] Optionally, when preparing oxide coating agents and carbon coating agents, the gel solution accounts for 85% to 95% of the total mass of the coating agent (e.g., 85%, 90%, 92%, 95%, etc.); when preparing premixes, the gel solution accounts for 40% to 65% of the total mass of the premixes (e.g., 40%, 50%, 55%, 60%, 65%, etc.).

[0074] Optionally, the mass ratio of the nickel-cobalt-manganese precursor to the gel solution is 1:(1~2), for example: 1:1, 1:2, etc., which is not specifically limited here.

[0075] Optionally, the metal oxide includes at least one of zirconium oxide, aluminum oxide, titanium oxide, and cobalt oxide.

[0076] Optionally, the carbon source includes, but is not limited to, conductive carbon black; wherein the resistivity of the conductive carbon black powder is less than 0.25 Ω·cm.

[0077] Optionally, a method for preparing oxide-coated ternary materials by coating an oxide coating agent onto the exterior of a premix using electrospinning specifically includes: filling the premix into a built-in syringe of an electrospinning apparatus, filling the oxide coating agent into an external syringe of the electrospinning apparatus, and coaxially fitting the external syringe onto the exterior of the built-in syringe (see reference). Figure 1 Then, electrospinning coats the premix with an oxide coating agent.

[0078] Optionally, a method for preparing carbon-coated ternary materials by coating a premix with a carbon coating agent using electrospinning specifically includes: filling the premix into a built-in syringe of an electrospinning apparatus, filling the carbon coating agent into an external syringe of the electrospinning apparatus, and coaxially fitting the external syringe to the outside of the built-in syringe (see reference). Figure 1 Then, electrospinning coats the premix with a carbon coating agent.

[0079] Optionally, the inner diameter of the external syringe is 1.0-1.8mm, such as 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, etc., without specific limitation; the inner diameter of the internal syringe is 0.3-0.6mm, such as 0.3mm, 0.4mm, 0.5mm, 0.6mm, etc., without specific limitation.

[0080] By controlling the working voltage of electrospinning and the spinning speed of the syringe, coated ternary materials with different particle sizes can be prepared.

[0081] In order to make the particle size of the oxide-coated ternary material larger than that of the carbon-coated ternary material, the voltage at which the oxide coating agent is coated onto the outside of the premix using electrospinning is controlled to be less than the voltage at which the carbon coating agent is coated onto the outside of the premix using electrospinning.

[0082] Similarly, in order to make the particle size of the oxide-coated ternary material larger than that of the carbon-coated ternary material, the spinning rate of the oxide coating agent coated on the outside of the premix using electrospinning is controlled to be less than the spinning rate of the carbon coating agent coated on the outside of the premix using electrospinning.

[0083] Optionally, the step of coating the premix with an oxide coating agent by electrospinning is carried out at room temperature (e.g., around 25°C) and air humidity less than 50% (e.g., 20%, 22%, 25%, 28%, 30%). The electrospinning voltage is controlled at 19.20±0.20kV (e.g., 19.00 kV, 19.10 kV, 19.20 kV, 19.30 kV, 19.40 kV), the plate spacing is 10~15cm (e.g., 10cm, 11cm, 12cm, 13cm, 14cm, 15cm), and the spinning rate is 0.2±0.1mL / h (e.g., 0.1 mL / h, 0.2 mL / h, 0.3 mL / h).

[0084] The step of coating the premix with a carbon coating agent by electrospinning is carried out at room temperature (e.g., around 25°C) and air humidity less than 50% (e.g., 20%, 22%, 25%, 28%, 30%). The electrospinning voltage is controlled at 20.0±0.20kV (e.g., 19.80kV, 19.90kV, 20.00kV, 20.10kV, 20.20kV), the plate spacing is 15~20cm (e.g., 15cm, 16cm, 17cm, 18cm, 19cm, 20cm), and the spinning rate is 0.6±0.2mL / h (e.g., 0.4mL / h, 0.5mL / h, 0.6mL / h, 0.7mL / h, 0.8mL / h).

[0085] It should be noted that the spinning rates mentioned above refer to the spinning rates of both the built-in syringe and the corresponding external syringe. The spun fibers produced by the electrospinning equipment can be collected in aluminum foil.

[0086] It should also be noted that by adjusting the working voltage and spinning rate of electrospinning, strip-shaped (filament-shaped) coated ternary materials (such as...) can be prepared. Figure 2 As shown in the figure, NCM refers to lithium nickel cobalt manganese oxide, which can be ground into spherical shapes (such as...). Figure 3 As shown in the figure, NCM refers to lithium nickel cobalt manganese oxide.

[0087] Optionally, the oxide-coated ternary material and the carbon-coated ternary material are sintered separately; in the step of sintering at least one of the oxide-coated ternary material and the carbon-coated ternary material, the temperature is raised to 400-500℃ (e.g., 400℃, 430℃, 450℃, 480℃, 500℃, etc.) at a heating rate of 3-5℃ / min (e.g., 3℃ / min, 4℃ / min, 5℃ / min, etc.) for a first sintering, and then raised to 900-1000℃ (e.g., 900℃, 920℃, 950℃, 970℃, 1000℃, etc.) at a heating rate of 3-5℃ / min (e.g., 3℃ / min, 4℃ / min, 5℃ / min, etc.) for a second sintering, followed by cooling.

[0088] Optionally, when sintered oxide-coated ternary materials and sintered carbon-coated ternary materials are mixed, the mass ratio of oxide-coated ternary materials to carbon-coated ternary materials is 1:0.1 to 1:0.3 (e.g., 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, etc.).

[0089] Optionally, the particle size D50 of the oxide-coated ternary material is 8-12 μm (e.g., 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc.); the particle size D50 of the carbon-coated ternary material is 2-8 μm (e.g., 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, etc.).

[0090] The preparation method of this invention yields oxide-coated ternary materials with mixed particle sizes, the gaps of which are filled with carbon-coated ternary materials. The chemical formula of the mixed-size coated ternary materials is LiNi. x Co y Mn 1-x-y O2.

[0091] The present invention also provides a battery in which the raw materials for preparing the positive electrode include coated ternary materials of different particle sizes obtained by the preparation method of the present invention.

[0092] It should be noted that the specific manufacturing method and structure of the battery are similar to those of related technologies, and will not be elaborated here.

[0093] The present invention will be further described in detail below with reference to the embodiments.

[0094] Example 1

[0095] Preparation of coated ternary materials with different particle sizes

[0096] 1) Dissolve 70g of polyacrylonitrile (PAN) in 1250mL of N,N-dimethylformamide (DMF) (approximately 6wt%) and stir at 40℃ for 12h until transparent to obtain a gel solution.

[0097] 2) Disperse 0.6 mol of nickel nitrate, 0.2 mol of cobalt nitrate, and 0.2 mol of manganese nitrate into 600 mL of deionized water.

[0098] 3) Add the salt solution obtained in step 2) dropwise to the citric acid-ethylene glycol solution (the mass ratio of citric acid to ethylene glycol is 1:10) until a sol system is formed. Dry the sol system at 200°C and then grind it into powder.

[0099] 4) After mixing the precursor and lithium carbonate obtained in step 3) evenly, add them to the gel solution prepared in step 1). The molar ratio of precursor to lithium carbonate is 1:1.2, and the mass ratio of precursor to gel is 1:2. Mix and stir for 30 minutes, and then load it into the built-in syringe (inner diameter 0.3 mm) of two electrospinning devices.

[0100] 5) Mix nano-zirconia and alumina into the gel solution of step 1), wherein the mass ratio of nano-zirconia to precursor is 0.3%, the mass ratio of alumina to precursor is 0.2%, and the total oxide mass accounts for 5% of the gel solution; mix and stir for 30 min, and then load it into the external syringe (inner diameter 1.0 mm) of one of the electrospinning devices.

[0101] 6) Mix the conductive carbon black with the gel solution prepared in step 1), with a mass ratio of 1:10 between the gel solution and the conductive carbon black, wherein the mass ratio of the conductive carbon black to the precursor is 0.5%. Stir for 30 minutes, and then load the mixture into the external syringe (1.0 mm inner diameter) of another electrospinning device.

[0102] 7) Start the high-voltage electrospinning machine (at room temperature and 20% humidity). Process parameters: working voltage 19.20kV, plate spacing 10cm, spinning rate 0.2mL / h, to obtain ternary materials with large particle size and oxide coating on the surface.

[0103] 8) Start the high-voltage electrospinning machine (at room temperature and 20% humidity). Process parameters: working voltage 20.0kV, plate spacing 15cm, spinning rate 0.6mL / h, to obtain ternary materials with small particle size and carbon coating on the surface.

[0104] 9) The obtained spun yarns were sintered separately. The first sintering was carried out by heating the yarn to 450°C at a heating rate of 3°C / min for 4 hours. The second sintering was carried out by heating the yarn to 900°C at a heating rate of 3°C / min for 12 hours. After calcination, the yarns were cooled to room temperature.

[0105] 10) The oxide-coated ternary material and the carbon-coated ternary material were mixed at a mass ratio of 1:0.15; the normal distribution of particle size of the resulting coated ternary materials with different particle sizes is shown in the figure. Figure 4 .

[0106] according to Figure 4 It is evident that the high particle size uniformity (particle size concentration) of the coated ternary materials with different particle sizes is beneficial for achieving uniform coating during battery fabrication and can improve the performance stability of the battery. Moreover, the more concentrated the particle size distribution, the higher the tap density.

[0107] Example 2

[0108] Preparation of coated ternary materials with different particle sizes

[0109] 1) Dissolve 100g of polyacrylonitrile (PAN) in 1500mL of N,N-dimethylformamide (DMF) (approximately 7 wt%) and stir at 40℃ until transparent to obtain a gel solution.

[0110] 2) Disperse 0.5 mol nickel acetate, 0.2 mol cobalt acetate, and 0.3 mol manganese acetate into 700 mL of deionized water.

[0111] 3) Add the salt solution obtained in step 2) dropwise to a citric acid-ethylene glycol aqueous solution (the mass ratio of citric acid to ethylene glycol is 1:10) until a sol system is formed. Dry the sol system at 220°C and then grind it into powder.

[0112] 4) Mix the precursor and lithium acetate obtained in step 3) evenly and then add them to the gel solution prepared in step 1). The mass ratio of precursor to lithium acetate is 1:1.1 and the mass ratio of precursor to gel is 1:1.5. Mix and stir for 35 minutes, and then load it into the built-in syringe (inner diameter 0.6 mm) of two electrospinning devices.

[0113] 5) Mix titanium oxide and aluminum oxide into the gel solution prepared in step 1), wherein the mass ratio of titanium oxide to precursor is 0.2%, the mass ratio of aluminum oxide to precursor is 0.3%, and the total oxide mass accounts for 5% of the gel solution; mix and stir for 35 min, and then load it into the external syringe (inner diameter 1.8 mm) of one of the electrospinning devices.

[0114] 6) Mix the conductive carbon black with the gel solution prepared in step 1), with a mass ratio of conductive carbon black to gel solution of 1:10, wherein the mass ratio of conductive carbon black to precursor is 0.5%. Stir for 30 minutes, and then fill the liquid into the external syringe (inner diameter 1.8 mm) of another electrospinning device.

[0115] 7) Start the high-voltage electrospinning machine (at room temperature and 30% humidity). Process parameters: working voltage 19.00kV, plate spacing 15cm, spinning rate 0.3mL / h, to obtain ternary materials with large particle size and oxide coating on the surface.

[0116] 8) Start the high-voltage electrospinning machine (at room temperature and 30% humidity). Process parameters: working voltage 19.8kV, plate spacing 20cm, spinning rate 0.8mL / h, to obtain ternary materials with small particle size and carbon coating on the surface.

[0117] 9) The obtained spun yarns were sintered separately. The first sintering was carried out by heating the yarn to 5000℃ at a heating rate of 5℃ / min for 3 hours, and the second sintering was carried out by heating the yarn to 1000℃ at a heating rate of 5℃ / min for 11 hours. After calcination, the yarns were cooled to room temperature.

[0118] 10) The oxide-coated ternary material and the carbon-coated ternary material are mixed in a mass ratio of 1:0.2.

[0119] Example 3

[0120] Preparation of coated ternary materials with different particle sizes

[0121] 1) Dissolve 80g of polyacrylonitrile (PAN) in 1060mL of N,N-dimethylformamide (DMF) (approximately 8 wt%) and stir at 42℃ until transparent to obtain a gel solution.

[0122] 2) Disperse 0.3 mol nickel sulfate, 0.3 mol cobalt sulfate, and 0.3 mol manganese sulfate into 500 mL of deionized water.

[0123] 3) Add the salt solution obtained in step 2) dropwise to a citric acid-ethylene glycol aqueous solution (the mass ratio of citric acid to ethylene glycol is 1:8) until a sol system is formed. Dry the solution at 200°C and then grind it into powder.

[0124] 4) Mix the precursor and lithium sulfate obtained in step 3) evenly and then add them to the gel solution prepared in step 1). The mass ratio of precursor to lithium sulfate is 1:1.2 and the mass ratio of precursor to gel is 1:1.2. Mix and stir for 30 minutes, and then load it into the built-in syringe (inner diameter 0.5 mm) of two electrospinning devices.

[0125] 5) Mix nano-zirconia and alumina into the gel solution prepared in step 1), wherein the mass ratio of nano-zirconia to the precursor is 0.4%, the mass ratio of cobalt oxide to the precursor is 0.1%, and the amount of gel solution accounts for 85% of the total mass of the coating agent; mix and stir for 30 minutes, and then load it into the external syringe (inner diameter 1.5 mm) of one of the electrospinning devices.

[0126] 6) Mix the conductive carbon black with the gel solution prepared in step 1), with a mass ratio of conductive carbon black to gel solution of 1:10, wherein the mass ratio of conductive carbon black to precursor is 0.2%. Stir for 30 minutes, and then fill the mixture into the external syringe (inner diameter 1.5 mm) of another electrospinning device.

[0127] 7) Start the high-voltage electrospinning machine (at room temperature and 20% humidity). Process parameters: working voltage 19.40kV, plate spacing 12cm, spinning rate 0.1mL / h, to obtain ternary materials with large particle size and oxide coating on the surface.

[0128] 8) Start the high-voltage electrospinning machine (at room temperature and 20% humidity). Process parameters: working voltage 20.20kV, plate spacing 18cm, spinning rate 0.4mL / h, to obtain ternary materials with small particle size and carbon coating on the surface.

[0129] 9) The obtained spun yarns were sintered separately. The first sintering was carried out by heating the yarn to 480℃ at a heating rate of 4℃ / min for 4 hours, and the second sintering was carried out by heating the yarn to 950℃ at a heating rate of 4℃ / min for 10 hours. After calcination, the yarns were cooled to room temperature.

[0130] 10) The oxide-coated ternary material and the carbon-coated ternary material are mixed in a mass ratio of 1:0.2.

[0131] Test case

[0132] The coated ternary materials with different particle sizes prepared in Example 1 were combined with lithium titanate as the negative electrode to make a 2Ah soft-pack battery for performance testing (the test methods refer to GB 31241-2022 and GB / T 31486-2015). The test results are shown in Table 1.

[0133] The battery manufacturing and testing process includes: positive electrode: binder: conductive agent = 95.7:2:2.3; the positive electrode is a coated ternary material with different particle sizes; the positive electrode slurry has a solid content of 65%; the foil thickness is 14μm; and the coating surface density is 246g / cm³. 3 The ratio of negative electrode: binder: conductive agent is 94:3.0:3.0. The negative electrode is lithium titanate, the solid content of the negative electrode slurry is 55%, and the areal density is 214 g / cm³. 3 The molar ratio of the electrolyte components is DMC:EMC:EC:LiPF6 = 31.5:33.5:17.5:17.5.

[0134] Table 1

[0135]

[0136] The test results in Table 1 show that 96μm is the ultimate compaction depth. Based on the formula: Compacted density = Areal density / (Roller thickness - Foil thickness), the actual compacted density is calculated to be 3.0 g / cm³. 3 The folded effect is shown in Table 1. The formation temperature was 90℃, and the resulting battery test data (charge-discharge curves after 500 cycles) are as follows. Figure 5 .

[0137] Comparative Example 1

[0138] The large-particle-size coated ternary material obtained in step 7) of Example 1 was used to make a 2Ah soft-pack battery with lithium titanate as the negative electrode and its performance was tested (the test method refers to GB 31241-2022 and GB / T 31486-2015). The test results are shown in Table 2.

[0139] The battery manufacturing and testing process includes: positive electrode: binder: conductive agent = 95.7:2:2.3; the positive electrode is a coated ternary material with different particle sizes; the positive electrode slurry has a solid content of 65%; the foil thickness is 14μm; and the coating surface density is 246g / cm³. 3 The ratio of negative electrode: binder: conductive agent is 94:3.0:3.0. The negative electrode is lithium titanate, the solid content of the negative electrode slurry is 55%, and the areal density is 214 g / cm³. 3 The molar ratio of the electrolyte components is DMC:EMC:EC:LiPF6 = 31.5:33.5:17.5:17.5.

[0140] Table 2

[0141]

[0142] The test results in Table 2 show that 108μm is the ultimate compaction depth. Based on the formula: Compacted density = Areal density / (Roller thickness - Foil thickness), the actual compacted density is calculated to be 2.61 g / cm³. 3The folded effect is shown in Table 2. The formation temperature was 90℃, and the resulting battery test data (charge-discharge curves after 500 cycles) are as follows: Figure 5 .

[0143] Comparative Example 2

[0144] The small-particle-size coated ternary material obtained in step 8) of Example 1 was used to make a 2Ah soft-pack battery with lithium titanate as the negative electrode and its performance was tested (the test method refers to GB 31241-2022 and GB / T 31486-2015). The test results are shown in Table 3.

[0145] The battery manufacturing and testing process includes: positive electrode: binder: conductive agent = 95.7:2:2.3; the positive electrode is a coated ternary material with different particle sizes; the positive electrode slurry has a solid content of 65%; the foil thickness is 14μm; and the coating surface density is 246g / cm³. 3 The ratio of negative electrode: binder: conductive agent is 94:3.0:3.0. The negative electrode is lithium titanate, the solid content of the negative electrode slurry is 55%, and the areal density is 214 g / cm³. 3 The molar ratio of the electrolyte components is DMC:EMC:EC:LiPF6 = 31.5:33.5:17.5:17.5.

[0146] Table 3

[0147]

[0148] The test results in Table 3 show that 156μm is the ultimate compaction depth. Based on the formula: Compacted density = Areal density / (Roller thickness - Foil thickness), the actual compacted density is calculated to be 1.73 g / cm³. 3 The folded effect is shown in Table 3. The formation temperature was 90℃, and the resulting battery test data (charge-discharge curves after 500 cycles) are as follows: Figure 5 .

[0149] Based on the above records, and Tables 1, 2, 3, and... Figure 5 It can be seen that the performance of the coated ternary material with different particle sizes prepared in Example 1 is better than that of the ternary material with a single particle size. The positive electrode of the battery prepared from the material of Example 1 has a higher compaction density and better electrical performance.

[0150] In summary, the preparation method of the coated ternary material with different particle sizes of the present invention is simple and involves fewer steps, which can shorten the preparation time. Moreover, the coated ternary material with different particle sizes prepared by the method of the present invention can improve the electronic conductivity of the coated ternary material with different particle sizes, reduce the internal resistance, and also improve the compaction density and rate performance. The battery prepared by the coated ternary material with different particle sizes of the present invention has good electrical performance.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a coated ternary material with mixed particle sizes, characterized in that: A nickel-cobalt-manganese precursor and a lithium salt are mixed, and then mixed with a gel solution to obtain a premix. The gel solution is prepared by mixing polyacrylonitrile and N,N-dimethylformamide and stirring at a temperature of 40±5℃; wherein the mass ratio of polyacrylonitrile to N,N-dimethylformamide is 6~10%. The metal oxide is mixed with the gel solution to obtain an oxide coating agent; The carbon source is mixed with the gel solution to obtain a carbon coating agent; The oxide coating agent is coated onto the outside of the premix by electrospinning, and spherical oxide-coated ternary materials can be obtained after grinding. The carbon coating agent is coated onto the outside of the premix by electrospinning, and spherical carbon-coated ternary materials can be obtained after grinding. Sintering the oxide-coated ternary material and the carbon-coated ternary material; The oxide-coated ternary material and the carbon-coated ternary material are mixed and sintered; wherein the particle size of the oxide-coated ternary material is larger than that of the carbon-coated ternary material, and the particle size D50 of the oxide-coated ternary material is 8-12 μm, while the particle size D50 of the carbon-coated ternary material is 2-8 μm. The method for preparing oxide-coated ternary materials by coating the premix with the oxide coating agent using electrospinning specifically includes: filling the premix into a built-in syringe of an electrospinning device, filling the oxide coating agent into an external syringe of the electrospinning device, the external syringe being coaxially sleeved on the outside of the built-in syringe; and then electrospinning to coat the premix with the oxide coating agent. The method for preparing carbon-coated ternary materials by coating the premix with a carbon coating agent using electrospinning specifically includes: filling the premix into a built-in syringe of an electrospinning device, filling the carbon coating agent into an external syringe of the electrospinning device, the external syringe being coaxially sleeved on the outside of the built-in syringe; and then electrospinning to coat the premix with the carbon coating agent. The voltage required to coat the oxide coating agent onto the outside of the premix using electrospinning is less than the voltage required to coat the carbon coating agent onto the outside of the premix using electrospinning. The spinning rate at which the oxide coating agent is coated onto the premix using electrospinning is less than the spinning rate at which the carbon coating agent is coated onto the premix using electrospinning.

2. The method for preparing coated ternary materials with different particle sizes according to claim 1, characterized in that: The inner diameter of the external syringe is 1.0-1.8 mm, and the inner diameter of the internal syringe is 0.3-0.6 mm.

3. The method for preparing coated ternary materials with different particle sizes according to claim 1, characterized in that: In the step of coating the premix with the oxide coating agent using electrospinning, the electrospinning voltage is controlled at 19.20±0.20kV, the plate spacing is 10~15cm, and the spinning rate is 0.2±0.1mL / h; and / or, In the step of coating the premix with the carbon coating agent by electrospinning, the electrospinning voltage is controlled to be 20.0±0.20kV, the plate spacing is 15~20cm, and the spinning rate is 0.6±0.2mL / h.

4. The method for preparing coated ternary materials with different particle sizes according to any one of claims 1-2, characterized in that: The steps of sintering the oxide-coated ternary material and the carbon-coated ternary material include: sintering the oxide-coated ternary material and the carbon-coated ternary material respectively; wherein... In the step of sintering at least one of the oxide-coated ternary material and the carbon-coated ternary material, the temperature is increased to 400-500℃ at a heating rate of 3-5℃ / min for the first sintering, and then increased to 900-1000℃ at a heating rate of 3-5℃ / min for the second sintering, followed by cooling.

5. The method for preparing coated ternary materials with different particle sizes according to any one of claims 1-2, characterized in that: When the oxide-coated ternary material and the carbon-coated ternary material are mixed and sintered, the mass ratio of the oxide-coated ternary material to the carbon-coated ternary material is 1:0.1 to 1:0.

3.

6. The method for preparing coated ternary materials with different particle sizes according to any one of claims 1-2, characterized in that: The preparation method of the nickel-cobalt-manganese precursor includes: dispersing nickel salt, cobalt salt, and manganese salt in water to obtain a salt solution; then adding the salt solution dropwise to a citric acid-alcohol solution until a sol-gel system is formed; drying the colloid of the sol-gel system at 200-220°C and grinding it into powder; wherein the total metal ion concentration in the salt solution is 0.2-0.5 M, the molar ratio of the salt solution to the citric acid-alcohol solution is 1:1 to 1:1.5, and the mass ratio of citric acid to alcohol in the citric acid-alcohol solution is 1:8 to 1:10; and / or, At least one of the following: the mass ratio of the metal oxide to the nickel-cobalt-manganese precursor, and the mass ratio of the carbon source to the nickel-cobalt-manganese precursor, is 0.2% to 0.5%; and / or, The metal oxide includes at least one of zirconium oxide, aluminum oxide, titanium oxide, and cobalt oxide; and / or, The particle size D50 of the oxide-coated ternary material is 8-12 μm; the particle size D50 of the carbon-coated ternary material is 2-8 μm.

7. A coated ternary material with mixed particle sizes, characterized in that: The ternary material is prepared by the method for preparing coated ternary materials with different particle sizes as described in any one of claims 1-6; wherein, The gaps in the oxide-coated ternary material are filled with the carbon-coated ternary material; The chemical formula of the coated ternary material with different particle sizes is LiNi. x Co y Mn 1-x-y O2.

8. A battery, characterized in that, The raw materials for preparing the positive electrode of the battery include the coated ternary materials with different particle sizes as described in claim 7.

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