Cobalt oxyhydroxide, cobalt trioxide, preparation method thereof and positive electrode material

Abstract

The invention discloses cobalt oxyhydroxide, cobalt trioxide, and a preparation method and a positive electrode material, and relates to the technical field of secondary batteries. The invention provides cobalt oxyhydroxide with a submicron particle morphology, which enables the prepared cobalt trioxide to inherit this morphology, and the surface of the positive electrode material is modified by using the cobalt trioxide in this morphology, which can optimize the surface stability of the active material, improve the surface ion conductivity and electron conductivity of the active material, and thus improve the cycle performance and rate performance of the battery material.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to cobalt oxyhydroxide, cobalt trioxide, and preparation methods thereof and positive electrode materials. Background Art

[0002] With the diversified and vigorous development of the electric vehicle industry, people have put forward higher requirements for the battery life and fast charging and discharging performance of electric drive equipment such as plug-in hybrid / pure electric vehicles. Consumers and the market are most concerned about the energy density, cost and safety of batteries. As the main lithium source in LIB, the cost, energy density and safety of cathode materials determine the cost, energy density and safety of LIB. Ternary layered oxides have the potential for high energy density and are regarded as ideal cathode materials for long-life lithium-ion batteries.

[0003] To meet the increasing demand for endurance, a typical strategy to further improve the energy density / mileage of layered cathode materials is to x Co y Mn z ]O2(NCM) and Li[Ni x Co y Al z ]O2(NCA) gradually replaces Co, Mn and Al with Ni. However, when the Ni content exceeds 80 mol%, the following problems will occur: the parasitic reaction between the secondary particle surface of the material and the electrolyte is aggravated, the high Ni content on the secondary particle surface 4+ There are problems that accelerate the decomposition of organic electrolytes, and the TM ions that serve as the lattice framework dissolve in the electrolyte and migrate to the negative electrode. The above problems will further lead to rapid capacity decay, heat loss and gas precipitation, which will threaten the safety of the battery and severely compress the service life of the material. In addition, the excess lithium introduced during the mixed lithium sintering process will cause residual lithium on the surface of the positive electrode material, which is usually removed by water washing. However, when the Ni content of the bulk structure exceeds 80 mol%, water washing will cause the crystal structure of the material surface to transform into an inert phase, which will harm the electrochemical properties of the positive electrode material.

[0004] In order to solve the above problems, researchers have proposed many modification strategies, mainly including: surface interface engineering, bulk doping, morphology control, surface coating and other modification methods. At present, the method of constructing the Core-Shell structure has achieved great success. Its relatively inert surface can resist the failure of high nickel properties to a large extent. However, the surface of this structure has a relatively inert layer and is thicker, which reduces the energy density of the material to a certain extent. At the same time, it requires certain improvements or redesigns of the material synthesis equipment. Co(OH)2 as a surface coating has been proven to reduce the amount of residual lithium compounds on the surface, and construct a spinel phase on the surface of secondary particles to enhance the surface stability of the material, making the layered nickel-rich lithium transition metal oxide LiNi x Co y Mn z O2 (x>80mol%, x+y+z=1) has enhanced cycle life and safety.

[0005] When submicron-scale CoOOH or Co3O4 is used as the surface coating material, it can have a beneficial effect on the active material in three aspects: (1) Co3O4 is used as a precursor of LiCoO2 and is built on the surface of the positive electrode material. Compared with spherical Co3O4, this submicron-scale layer is more convenient for Li source embedding structure. It can form part of the LCO positive electrode material under certain sintering conditions to provide part of the capacity, and it is easier to consume the residual lithium compounds on the surface of the secondary particles of the material. The water washing step can be eliminated, and the crystal structure of the material surface is protected from water erosion; (2) When it is enriched on the surface of the positive electrode material, it can form a spinel-like structure coated on the surface of the layered structure, which can delay the highly reactive Ni 4+ Direct contact and reaction with the electrolyte. The above two approaches can enhance its surface stability and ultimately increase the service life of the positive electrode material. (3) Compared with Co(OH)2, CoOOH and Co3O4 have higher cobalt content and stronger electronic conductivity, which is more conducive to the improvement of rate performance.

[0006] In summary, the preparation of CoOOH and Co3O4 with special morphologies and their use as coating agents / additives for positive electrode materials is beneficial to improving the surface stability and cycle stability of positive electrode materials.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The purpose of the present invention is to provide cobalt oxyhydroxide, cobalt trioxide and a preparation method thereof and a positive electrode material, aiming to improve the rate performance and service life of the positive electrode material by providing CoOOH with a special morphology.

[0009] The present invention is achieved in that:

[0010] In a first aspect, the present invention provides a cobalt oxyhydroxide, wherein the cobalt oxyhydroxide is a submicron particle, and the length of the submicron particle is 0.1 μm-1 μm.

[0011] In a second aspect, the present invention provides a method for preparing the cobalt oxyhydroxide of the aforementioned embodiment, comprising: subjecting a cobalt salt to a precipitation reaction in the presence of a precipitant, a complexing agent, a surfactant and an oxidant.

[0012] In an optional embodiment, the precipitant is an inorganic alkali, preferably sodium hydroxide; more preferably, when added in the form of a liquid alkali solution during the precipitation process, the concentration of the added liquid alkali solution is controlled to be 8 mol / L-12 mol / L;

[0013] Preferably, the complexing agent is ammonia water; more preferably, when added in the form of an ammonia solution during the precipitation process, the concentration of the added ammonia solution is controlled to be 5 mol / L-10 mol / L;

[0014] Preferably, the surfactant is selected from at least one of polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium oxalate, ethylene glycol and sodium dodecyl sulfate; more preferably, when added in the form of a surfactant solution during the precipitation process, the concentration of the added surfactant solution is controlled to be 1 g / L-150 g / L;

[0015] Preferably, the oxidant is selected from at least one of hydrogen peroxide, potassium permanganate, sodium hypochlorite, ozone and air; more preferably, the oxidant is added in the form of solution or ventilation during the precipitation process, and when the oxidant is hydrogen peroxide, the mass fraction of the added hydrogen peroxide solution is controlled to be 1%-10%; when the oxidant is potassium permanganate, the concentration of the added potassium permanganate solution is controlled to be 0.01 mol / L-0.4 mol / L; when the oxidant is sodium hypochlorite, the concentration of the added sodium hypochlorite solution is controlled to be 1.5-3.6 mol / L;

[0016] Preferably, the cobalt salt is selected from at least one of sulfate, chloride and nitrate; more preferably, when added in the form of a cobalt salt solution during the precipitation process, the concentration of the added cobalt salt solution is controlled to be 1 mol / L-3 mol / L.

[0017] In an optional embodiment, it includes:

[0018] Preparing an aqueous solution containing a precipitant, a complexing agent and a surfactant as a first base liquid;

[0019] The cobalt salt solution, the liquid alkali solution, the ammonia solution, the surfactant solution and the oxidant solution are pumped into the first bottom liquid in parallel to perform a precipitation reaction;

[0020] The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried;

[0021] Preferably, the volume of the first bottom liquid accounts for 20%-60% of the total volume of the reactor, the hydroxide concentration in the first bottom liquid is 0.001mol / L-2.0mol / L, the ammonia concentration is 1g / L-10g / L, and the surfactant concentration is 1g / L-20g / L;

[0022] Preferably, during the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm, the temperature is 20°C-80°C, the concentration of the hydroxide solution is 0.001mol / L-2.0mol / L, and the concentration of ammonia is 1g / L-10g / L; the rate of addition of the cobalt salt solution is 2L / h-16L / h, and when the volume of the slurry in the reactor reaches 45%-55% of the volume of the reactor, the oxidant solution or gas is introduced, and when the addition reaches 85%-95% of the total volume of the reactor, the addition of each solution is stopped;

[0023] Preferably, during the precipitation process, the volumes of the solutions added satisfy: the volume ratio of the ammonia solution to the cobalt salt solution is (0.01-1.0):1; the volume ratio of the surfactant solution to the cobalt salt solution is (0.01-0.5):1; the volume ratio of the oxidant solution to the cobalt salt solution is (0.01-2.5):1.

[0024] In an optional embodiment, it includes:

[0025] preparing an aqueous solution containing a precipitant, a complexing agent and a surfactant as a second base liquid;

[0026] pumping the cobalt salt solution and the oxidant solution into the second bottom solution to perform a precipitation reaction;

[0027] The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried;

[0028] Preferably, the volume of the second bottom liquid accounts for 40%-60% of the total volume of the reactor, in which the hydroxide concentration is 2.0mol / L-5.0mol / L, the ammonia concentration is 0g / L-5g / L, and the concentration of the surfactant is 0.01g / L-10g / L; during the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm and the temperature is 20°C-80°C;

[0029] Preferably, the volume ratio of the added oxidant solution to the cobalt salt solution is (0.01-2.5):1, the addition rate of the cobalt salt solution is 20L / h-40L / h, and the addition is stopped when the total volume of the reactor is 85%-95%.

[0030] In an optional embodiment, an aqueous solution containing a cobalt salt and a surfactant is configured as the third bottom liquid of the reactor;

[0031] Adding a liquid alkali solution, an ammonia solution and an oxidant into a reaction kettle to carry out a precipitation reaction;

[0032] The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried;

[0033] Preferably, the volume of the third bottom liquid accounts for 30%-70% of the total volume of the reactor, in which the concentration of the cobalt salt is 1.0mol / L-3.0mol / L, and the concentration of the surfactant is 0.01g / L-10g / L; during the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm, and the temperature is 20°C-80°C;

[0034] Preferably, the pumping rate of the liquid alkali solution is 5L / h-15L / h, and the ammonia concentration in the reactor is maintained at 0.5g / L-2.5g / L by adjusting the addition rate of the ammonia solution, and the addition is stopped when the addition reaches 85%-95% of the total volume of the reactor;

[0035] Preferably, the oxidant is added in the form of ozone, and the volume flow rate of the oxidant introduced per hour is controlled to be 0.1 times to 0.5 times the total volume of the reactor.

[0036] In an optional embodiment, the washing process includes: washing with water until the Na content in the sample is less than or equal to 1000 ppm, the K content is less than or equal to 1000 ppm, and the anion content is less than or equal to 1000 ppm;

[0037] Preferably, after drying, the moisture content is less than or equal to 0.8%.

[0038] In a third aspect, the present invention provides a method for preparing cobalt trioxide, which is obtained by calcining the cobalt oxyhydroxide of the aforementioned embodiment or the cobalt oxyhydroxide prepared by any of the preparation methods in the aforementioned embodiment;

[0039] Preferably, the calcination is carried out in an air atmosphere, the calcination temperature is 200° C.-500° C., and the calcination time is 2 h-12 h.

[0040] In a fourth aspect, the present invention provides cobalt trioxide, which is prepared by the preparation method of the aforementioned embodiment.

[0041] In a fifth aspect, the present invention provides a positive electrode material, including a positive electrode material substrate, on the surface of which is coated the cobalt tetroxide in the above embodiment.

[0042] The present invention has the following beneficial effects: the present invention provides cobalt hydroxide oxide with submicron particle morphology, which can make the prepared cobalt tetroxide inherit this morphology, and the cobalt tetroxide in this morphology is used to modify the surface of the positive electrode material, which can optimize the surface stability of the active material, improve the surface ion conductivity and electron conductivity of the active material, so as to enhance the cycle performance and rate performance of the battery material.

[0043] It should be added that the method of surface modification of positive electrode materials is as follows: the physical adsorption capacity of the particles can be used to form a coating on the surface of the ternary positive electrode material through dry coating; submicron-sized CoOOH and Co3O4 monomer layers can be vertically embedded in the surface grain boundaries of the layered oxide positive electrode material secondary particles or attached to the surface of the positive electrode material secondary particles in the form of tangents, forming a spatially staggered protective layer in the form of element diffusion during the sintering process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 This is the SEM image of sample PCH1 of Example 1 (50k magnification);

[0046] Figure 2 This is the SEM (50k magnification) of sample PCH2 in Example 2;

[0047] Figure 3 This is the SEM (50k magnification) of sample PCH3 of Example 3;

[0048] Figure 4 This is the SEM (50k magnification) of sample PCH4 of Example 4;

[0049] Figure 5 This is the SEM (50k magnification) of the sample PCH5 of Example 5;

[0050] Figure 6 This is the SEM (50k magnification) of the sample PCH6 of Example 6;

[0051] Figure 7 This is the SEM (50k magnification) of sample PCH7 of comparative example 1. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0053] The present invention utilizes a wet synthesis method of continuous feeding combined with oxidation treatment and a subsequent low-temperature calcination procedure to prepare CoOOH (cobalt oxyhydroxide) and Co3O4 monocyclic precursors of different sizes and forms, which are used as surface coating materials for positive electrode materials to improve the surface stability and cycle stability of the positive electrode materials.

[0054] The present invention provides a method for preparing cobalt tetroxide, the steps of which are as follows:

[0055] S1. Solution configuration

[0056] Prepare cobalt salt solution, precipitant solution, complexing agent solution, surfactant solution and oxidant solution respectively and set aside.

[0057] In some embodiments, the cobalt salt is selected from at least one of sulfate, chloride and nitrate, and the cobalt salt can be any one or more of the above. When a cobalt salt needs to be added during the coprecipitation process, a cobalt salt solution needs to be prepared in advance, and the concentration of the cobalt salt solution can be 1mol / L-3mol / L, such as 1.0mol / L, 1.3mol / L, 1.5mol / L, 1.8mol / L, 2.0mol / L, 2.3mol / L, 2.5mol / L, 2.8mol / L, 3.0mol / L, etc., within this concentration range to better control the precipitation rate and obtain a product with uniform particle size.

[0058] In some embodiments, the precipitant may be an inorganic alkali, preferably sodium hydroxide, but not limited thereto. When a precipitant needs to be added during the coprecipitation process, a liquid alkali solution needs to be prepared in advance, and the concentration of the liquid alkali solution is 8mol / L-12mol / L, such as 8mol / L, 9mol / L, 10mol / L, 11mol / L, 12mol / L, etc., and within this concentration range, the pH value can be more accurately adjusted within the specified range.

[0059] In some embodiments, the complexing agent can be ammonia water, but is not limited thereto. When a complexing agent needs to be added during the coprecipitation process, an ammonia solution needs to be prepared in advance, and the concentration of the ammonia solution is 5mol / L-10mol / L, such as 5mol / L, 6mol / L, 7mol / L, 8mol / L, 9mol / L, 10mol / L, etc.

[0060] In some embodiments, the surfactant is selected from at least one of polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), sodium dodecylbenzenesulfonate (SDBS), sodium oxalate, ethylene glycol and sodium dodecyl sulfate (SDS), and the surfactant can be any one or more of the above. When a surfactant needs to be added during the coprecipitation process, it is necessary to prepare a surfactant solution in advance, and the concentration of the surfactant solution is 1g / L-150g / L, such as 1g / L, 10g / L, 30g / L, 50g / L, 80g / L, 100g / L, 120g / L, 150g / L, etc.

[0061] In some embodiments, the oxidant is selected from at least one of hydrogen peroxide, potassium permanganate, sodium hypochlorite, ozone and air, and the oxidant can be any one or more of the above. When an oxidant needs to be added during the coprecipitation process, an oxidant solution needs to be prepared in advance (except when a gas oxidant is used).

[0062] When different types of oxidants are used, the concentrations of the configured oxidant solutions are slightly different: when the oxidant is hydrogen peroxide, the mass fraction of the added hydrogen peroxide solution is controlled to be 1%-10%, such as 1%, 3%, 5%, 8%, 10%, etc.; when the oxidant is potassium permanganate, the concentration of the added potassium permanganate solution is controlled to be 0.01mol / L-0.4mol / L, such as 0.01mol / L, 0.05mol / L, 0.10mol / L, 0.20mol / L, 0.30mol / L, 0.40mol / L, etc.; when the oxidant is sodium hypochlorite, the concentration of the added sodium hypochlorite solution is controlled to be 1.5-3.6mol / L, such as 1.5mol / L, 2.5mol / L, 3.0mol / L, 3.5mol / L, 3.6mol / L, etc. By controlling the concentration of different oxidant solutions, a better oxidation treatment effect can be achieved, so that the size and morphology of the product are more suitable as a surface modifier for positive electrode materials.

[0063] S2. Prepare the base solution and perform precipitation reaction

[0064] The cobalt salt is subjected to precipitation reaction in the presence of a precipitant, a complexing agent, a surfactant and an oxidant. The reaction modes are divided into the following three types:

[0065] Method (1):

[0066] An aqueous solution containing a precipitant, a complexing agent and a surfactant is prepared in a reaction kettle as the first bottom liquid, and then a cobalt salt solution, a liquid alkali solution, an aqueous ammonia solution, a surfactant solution and an oxidant solution are pumped into the first bottom liquid in parallel to carry out a precipitation reaction. This method uses a method in which all raw materials are pumped in.

[0067] Further, the volume of the first bottom liquid accounts for 20%-60% of the total volume of the reactor (such as 20%, 30%, 40%, 50%, 60%, etc.), the hydroxide concentration in the first bottom liquid is 0.001mol / L-2.0mol / L (such as 0.001mol / L, 0.010mol / L, 0.050mol / L, 0.100mol / L, 0.500mol / L, 1.000mol / L, 1.500mol / L, 2.000mol / L, etc.), the ammonia concentration is 1g / L-10g / L (such as 1g / L, 3g / L, 5g / L, 8g / L, 10g / L, etc.), and the surfactant concentration is 1-20g / L (such as 1g / L, 3g / L, 5g / L, 10g / L, 15g / L, etc.). The concentrations of hydroxide and ammonia are within the above ranges to meet the conditions for cobalt deposition, and the concentrations of surfactant and oxidant are within the above ranges to better adjust the particle size and morphology of the product.

[0068] Furthermore, during the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm, the temperature is 20°C-80°C, the addition rate of the liquid alkali solution is regulated so that the concentration of the hydroxide solution is 0.001mol / L-2.0mol / L, and the addition rate of the ammonia solution is regulated so that the ammonia concentration is 1g / L-10g / L. Within this range, the deposition conditions of cobalt can be met. Specifically, the stirring speed can be 100 rpm, 300 rpm, 500 rpm, 800 rpm, 1000 rpm, etc.; the deposition temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc.; the concentration of the hydroxide solution in the reactor can be 0.001 mol / L, 0.010 mol / L, 0.050 mol / L, 0.100 mol / L, 0.500 mol / L, 1.000 mol / L, 1.500 mol / L, 2.000 mol / L, etc., and the ammonia concentration can be 1 g / L, 3 g / L, 5 g / L, 8 g / L, 10 g / L, etc.

[0069] Furthermore, during the precipitation reaction, the rate of addition of the cobalt salt solution is 2L / h-16L / h. When the volume of the slurry in the reactor reaches 45%-55% of the volume of the reactor, the oxidant solution or gas is introduced, and the addition of each solution is stopped when the total volume of the reactor is 85%-95%. The volume of each solution added during the precipitation process satisfies: the volume ratio of the ammonia solution to the cobalt salt solution is (0.01-1.0): 1; the volume ratio of the surfactant solution to the cobalt salt solution is (0.01-0.5): 1; the volume ratio of the oxidant solution to the cobalt salt solution is (0.01-2.5): 1. The concentration of each solution added refers to the description of S1, and the morphology and size of the prepared hydroxyl zirconium oxide are further regulated by further regulating the rate and amount of addition.

[0070] Specifically, if the volume of the bottom liquid is small, the oxidant solution is introduced when the volume of the slurry in the reactor reaches 45%-55% of the volume of the reactor, so that the volume of the slurry can reach 45%, 50%, 55%, etc.; when the reaction is stopped, the volume of the slurry in the reactor can be 85%, 90%, 95%, etc. The volume ratio of the added ammonia solution to the cobalt salt solution can be 0.01:1, 0.05:1, 0.10:1, 0.30:1, 0.50:1, 0.80:1, 1.00:1, etc.; the volume ratio of the surfactant solution to the cobalt salt solution can be 0.01:1, 0.05:1, 0.10:1, 0.30:1, 0.50:1, etc.; the volume ratio of the oxidant solution to the cobalt salt solution can be 0.01:1, 0.10:1, 0.50:1, 1.00:1, 1.50:1, 2.00:1, 2.50:1, etc.

[0071] Method (2):

[0072] An aqueous solution containing a precipitant, a complexing agent and a surfactant is prepared as the second base liquid; the cobalt salt solution and the oxidant solution are pumped into the second base liquid together to perform a precipitation reaction. This deposition method adds all the surfactants to the base liquid, and only the cobalt salt solution and the oxidant solution are pumped into the deposition process.

[0073] Further, the volume of the second bottom liquid accounts for 40%-60% of the total volume of the reactor, such as 40%, 50%, 60%, etc. In the second bottom liquid, the hydroxide concentration is 2.0mol / L-5.0mol / L (such as 2.5mol / L, 3.0mol / L, 3.5mol / L, 4.0mol / L, etc.), the ammonia concentration is 0-5g / L, and the concentration of the surfactant is 0.01g / L-10g / L (such as 0.01g / L, 1g / L, 2g / L, 5g / L, 7g / L, 10g / L, etc.), and the hydroxide concentration, ammonia concentration and surfactant concentration are preferably controlled within the above ranges to meet the requirements of cobalt deposition and regulate the product morphology. During the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm (such as 100rpm, 300rpm, 500rpm, 800rpm, 1000rpm, etc.), and the temperature is 20-80℃ (such as 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, etc.).

[0074] Further, the volume ratio of the added oxidant solution and the cobalt salt solution is (0.01-2.5):1, such as 0.01:1, 0.10:1, 0.50:1, 1.00:1, 1.50:1, 2.00:1, 2.50:1, etc.; the addition rate of the cobalt salt solution is 20L / h-40L / h, such as 20L / h, 30L / h, 40L / h, etc.; the addition is stopped when the total volume of the reactor is 85%-95%. The concentrations of the oxidant solution and the cobalt salt solution refer to the description of S1.

[0075] Method (3):

[0076] An aqueous solution containing cobalt salt and surfactant is prepared as the third bottom liquid of the reactor; a liquid alkali solution, an ammonia solution and an oxidant are added to the reactor together to perform a precipitation reaction. In this method, cobalt salt is added to the bottom liquid at one time, and a liquid alkali solution, an ammonia solution and an oxidant are added during the deposition process to adjust the deposition conditions and product morphology.

[0077] Further, the volume of the third bottom liquid accounts for 30%-70% of the total volume of the reactor, such as 30%, 40%, 50%, 60%, 70%, etc. In the third bottom liquid, the concentration of the cobalt salt is 1.0mol / L-3.0mol / L, such as 1.0mol / L, 1.5mol / L, 2.0mol / L, 2.5mol / L, 3.0mol / L, etc. In the third bottom liquid, the concentration of the surfactant is 0.01g / L-10g / L, such as 0.01g / L, 0.1g / L, 0.5g / L, 1.0g / L, 5.00g / L, 10.00g / L, etc.

[0078] Further, the pumping rate of the liquid alkali solution is 5L / h-15L / h, such as 5L / h, 7L / h, 10L / h, 11L / h, 12L / h, etc., and the concentration of the liquid alkali is described in S1. The ammonia concentration in the reactor is maintained at 0.5g / L-2.5g / L by regulating the addition rate of the ammonia solution, such as 0.5g / L, 1.0g / L, 1.5g / L, 2.0g / L, 2.5g / L, etc., and the concentration of the ammonia solution is described in S1. When the total volume of the reactor is 85%-95%, the addition is stopped. During the precipitation reaction, the stirring speed is controlled to be 100-1000rpm and the temperature is 20-80°C.

[0079] Furthermore, the oxidant can be added in the form of ozone, and the volume flow rate of the oxidant introduced per hour is controlled to be 0.1-0.5 times the total volume of the reactor, such as 0.10 times, 0.15 times, 0.20 times, 0.40 times, 0.50 times, etc.

[0080] S3, post-processing

[0081] The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried. The solid-liquid separation can be performed by filtering, centrifuging, etc., and then the obtained solid material is washed to remove surface impurities, and then the washing solvent is removed by drying.

[0082] In some embodiments, the washing process includes: washing with water until the Na content in the sample is less than or equal to 1000 ppm, the K content is less than or equal to 1000 ppm, and the anion content is less than or equal to 1000 ppm, so as to fully remove the surface impurity elements. The water content after drying is controlled to be less than or equal to 0.8%, and the drying method is not limited.

[0083] In the embodiment of the present invention, cobalt oxyhydroxide is prepared through steps S1-S3. The cobalt oxyhydroxide is submicron particles. The length of the submicron particles is 0.1 μm-1 μm, such as 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1.0 μm, etc.

[0084] S4. Low temperature calcination

[0085] The cobalt oxyhydroxide obtained in S3 is calcined to convert the cobalt oxyhydroxide into tricobalt tetroxide.

[0086] In some embodiments, calcination is performed under a flowing air atmosphere at a temperature of 200°C-500°C and a calcination time of 2h-12h to obtain uniform cobalt tetroxide. Specifically, the calcination temperature may be 200°C, 300°C, 400°C, 500°C, etc., and the calcination time may be 2h, 5h, 10h, 12h, 15h, etc., and the Co3O4 product may be obtained by grinding after natural cooling.

[0087] It should be noted that the preparation method provided in the embodiment of the present invention changes the surfactant conditions at the wet synthesis end, combines the oxidant and Co 2+ Due to the high catalytic activity, submicron particles / sheets of cobalt hydroxide oxide with a special microstructure are prepared. After low-temperature calcination at the back end, Co3O4 inherits this morphology and synthesizes a monomer-structured Co3O4 precursor.

[0088] The embodiment of the present invention further provides cobalt trioxide, which is prepared by the above-mentioned preparation method provided by the embodiment of the present invention and inherits the submicron particle morphology of cobalt oxyhydroxide.

[0089] The embodiment of the present invention further provides a positive electrode material, including a positive electrode material substrate, on the surface of which is coated cobalt tetroxide provided by the embodiment of the present invention. The surface of the positive electrode material is modified by using cobalt tetroxide provided by the embodiment of the present invention, so as to optimize the microscopic surface stability of the active material, improve its charge and discharge cycle life and rate performance, etc., thereby improving the ionic conductivity and electrical conductivity of the positive electrode material, so as to improve the rate performance and service life of the material.

[0090] The surface modification method can be adopted as follows: (1) Forming a coating on the surface of the ternary positive electrode material by dry coating. The embodiment of the present invention utilizes a wet synthesis method of continuous feeding combined with oxidation treatment and a subsequent low-temperature calcination procedure to prepare CoOOH and Co3O4 monolithic precursors of different sizes and shapes, which can be used as surface coating materials for ternary positive electrode materials to improve the surface stability and cycle stability of the positive electrode materials. (2) Mixing and calcining cobalt tetroxide and layered oxide positive electrode materials. Submicron-sized CoOOH and Co3O4 monomer sheets can be vertically embedded in the surface grain boundaries of the layered oxide positive electrode material secondary particles or attached to the surface of the positive electrode material secondary particles in the form of tangents. During the sintering process, a spatially staggered protective layer is formed in the form of element diffusion. This structure can optimize the microscopic surface stability of the active material to improve its charge and discharge cycle life and rate performance, thereby improving the ionic conductivity and electrical conductivity of the positive electrode material to improve the rate performance and service life of the material.

[0091] It should be noted that, on the positive electrode material side, CoOOH and Co3O4 can be embedded in the grain boundaries (and secondary particle surfaces) of the secondary particles of the polycrystalline nickel-rich layered oxide positive electrode materials or attached to the surface of the single crystal secondary particles due to their special monomeric particles. After heat treatment, they form a protective layer and a conductive layer through element diffusion and physical adsorption. This structure can optimize the microscopic surface stability of the active material to improve its charge and discharge cycle life and rate performance. The experimental results show that the submicron-sized monolithic CoOOH and Co3O4 precursors can provide different electrical performance gains for the positive electrode materials after being coated and added to the surface of the positive electrode materials.

[0092] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0093] Example 1

[0094] This example uses a co-current precipitation-oxidation method to prepare CoOOH and Co3O4 precursors, and the steps are as follows:

[0095] (1) According to the concentration of a certain metal cobalt sulfate solution, the corresponding mass of cobalt sulfate is calculated, and cobalt sulfate is prepared with pure water to prepare a metal cobalt sulfate solution with a concentration of 2 mol / L, which is recorded as solution A.

[0096] (2) Prepare a 10 mol / L sodium hydroxide solution as a precipitant, denoted as solution B.

[0097] (3) Configuration of auxiliary feed ①: According to a certain concentration, calculate the corresponding mass and use pure water to prepare liquid ammonia into an ammonia solution with a concentration of 8 mol / L, which is recorded as C1 solution.

[0098] (4) Configuration of auxiliary feed ②: According to a certain concentration, the corresponding mass is calculated, and PVP (polyvinyl pyrrolidone) is prepared into a mixed solution with a concentration of 100 g / L and CTAB with a concentration of 10 g / L using pure water, which is recorded as C2 solution.

[0099] (5) Preparation of auxiliary feed ③: Sodium hypochlorite was prepared into a solution with a concentration of 3.5 mol / L, which was recorded as C3 solution.

[0100] (6) Add pure water, a certain amount of liquid alkali, ammonia, PVP and CTAB into the reactor to adjust the hydroxide concentration in the bottom liquid to 0.7 mol / L, the ammonia concentration to 2 g / L, the PVP solution concentration to 5 g / L, and the CTAB concentration to 0.5 g / L. Make the bottom liquid in the reactor account for 50% of the total volume of the reactor, start the stirring speed at 800 rpm and the temperature at 60°C.

[0101] (7) Under the conditions in step (6), the A, B, C1, and C2 solutions are simultaneously pumped into the reactor in parallel to carry out precipitation reaction. The rate of addition of the cobalt salt solution is 5 L / h, and the volume ratio of the added auxiliary feed ① to the cobalt salt solution is: V F① / V Co =0.015, the volume ratio of cobalt salt solution to auxiliary feed ② is: V Co / V F② =0.025, the flow rate of solution B is adjusted according to the hydroxide concentration (so that the hydroxide concentration is 0.7 mol / L). When the slurry volume in the reactor reaches 50% of the reactor, C3 solution is introduced, and the volume ratio of auxiliary feed ③ to cobalt salt solution is: V F③ / V Co = 1.6. When the slurry in the reactor reaches 90% of the total space, the reaction is stopped.

[0102] (8) The slurry obtained in step (7) is filtered and washed to remove excess sulfate ions and anion impurities. When Na≤1000ppm, S≤1000ppm, and Cl≤1000ppm in the sample, the sample is dried to obtain a product PCH1.

[0103] (9) The product PCH1 obtained in step (8) is transferred to a tube furnace, calcined at 200 degrees Celsius for 4 hours in an air atmosphere, and ground and sieved to obtain PCO1.

[0104] (10) The product PCH1 was characterized by SEM. Figure 1 The particle size distribution is 0.5-1.5μm. Individual submicron particles are thicker but smaller in lateral size, with uniform distribution and good dispersion.

[0105] Example 2

[0106] This example uses a one-pot method to prepare CoOOH and Co3O4 precursors, and the steps are as follows:

[0107] (1) According to the concentration of a certain metal cobalt chloride salt solution, calculate the corresponding mass of cobalt chloride, and use pure water to prepare the salt into a solution with a concentration of 2.5 mol / L, which is recorded as solution A. Use pure water to prepare potassium permanganate into a solution with a concentration of 0.40 mol / L, which is recorded as solution C3.

[0108] (2) Add pure water, a certain amount of liquid alkali, ammonia water, SDBS and sodium oxalate into the reactor to adjust the hydroxide concentration in the bottom liquid to 3.1 mol / L, the ammonia concentration to 2 g / L, the SDBS concentration to 0.8 g / L and the sodium oxalate concentration to 3.5 g / L. Make the bottom liquid in the reactor account for 50% of the total volume, start the stirring speed at 800 rpm and the temperature at 60°C.

[0109] (3) Under the conditions in step (2), directly pump solution A into the reactor for precipitation reaction. The cobalt salt solution feed rate is 30 L / h. At the same time, pump C3 solution, and the volume ratio of the added auxiliary feed ③C3 to the cobalt salt solution is: V F③ / V Co = 1.24. When the slurry in the reactor reaches 90% of the total space, the reaction is stopped.

[0110] (4) Filter the slurry obtained in step (3), wash and remove excess chloride ion impurities. When Na≤1000ppm, Cl≤1000ppm, and K≤1000ppm in the sample, dry the sample to obtain product PCH2.

[0111] (5) The product PCH2 obtained in step (4) is transferred to a tube furnace, calcined at 300 degrees Celsius for 3 hours in an air atmosphere, and then ground and sieved to obtain PCO2.

[0112] (6) The product PCH2 obtained in step (5) was characterized by SEM. Figure 2 The particle size is 0.1-1μm, and individual submicron particles are thin and blade-shaped with small lateral dimensions, with uniform distribution and good dispersion.

[0113] Example 3

[0114] This embodiment provides a second one-pot method for preparing CoOOH and Co3O4 precursors, and the steps are as follows:

[0115] (1) According to the concentration of a certain metal cobalt nitrate salt solution, calculate the corresponding mass of cobalt nitrate, and use pure water to prepare a cobalt salt solution with a concentration of 1.9 mol / L, which is recorded as solution A;

[0116] (2) preparing a sodium hydroxide solution with a concentration of 10 mol / L as a precipitant, recorded as solution B;

[0117] (3) Configuration of auxiliary feed ①: According to a certain concentration, calculate the corresponding mass, and use pure water to prepare liquid ammonia into an ammonia solution with a concentration of 5 mol / L, which is recorded as C1 solution;

[0118] (4) Auxiliary feed ③: commercial O3, denoted as C3;

[0119] (5) Add solution A accounting for 30% of the volume of the reactor into the reactor, start the stirring and heating program: the stirring speed is 400 rpm, the temperature is 30°C, and the concentration of the PVP solution is adjusted to 10 g / L and the concentration of the DTAB solution is 4 g / L.

[0120] (6) Under the conditions in step (5), the B solution was directly pumped into the reactor for precipitation reaction at a pumping rate of 10 L / h. The C1 solution was simultaneously pumped in to ensure that the ammonia concentration in the reactor was maintained at 1 g / L, and O3 gas was introduced at a volume flow rate of 0.15 of the total volume of the reactor.

[0121] (7) The slurry obtained in step (6) is filtered and washed to remove excess impurities. When the Na content in the sample is ≤1000 ppm, the sample is dried to obtain a product PCH3.

[0122] (8) The product PCH3 obtained in step (7) is transferred to a tubular furnace, calcined at 300 degrees Celsius for 3 hours in an air atmosphere, and then ground and sieved to obtain PCO3.

[0123] (9) The product PCH3 obtained in step (7) was characterized by SEM. Figure 3 The particle size is 0.1-0.5μm, and the individual submicron particles are thin and blade-shaped with small lateral dimensions, and are evenly distributed and well dispersed.

[0124] Example 4

[0125] This embodiment adopts the parallel flow method provided in Example 1 to prepare CoOOH and Co3O4 precursors. Compared with Example 1, the following differences are found:

[0126] (1) The auxiliary solution ③ is 0.4 mol / L potassium permanganate;

[0127] (2) The bottom liquid is prepared as follows: pure water, a certain amount of liquid alkali, ammonia water, CTAB and PVP are added to the reactor to adjust the hydroxide concentration in the bottom liquid to 1.0 mol / L, the ammonia concentration to 2 g / L, the PVP concentration to 15 g / L, and the CTAB concentration to 1.5 g / L. The bottom liquid in the reactor accounts for 40% of the total volume, and the stirring speed is turned on at 850 rpm and the temperature is 60°C.

[0128] (3) The A, B, C1, and C2 solutions are simultaneously pumped into the reactor in a parallel flow manner for precipitation reaction. The rate of addition of the cobalt salt solution is 5 L / h, and the volume ratio of the added auxiliary feed ① to the cobalt salt solution is: V F① / V Co =0.02, the volume ratio of cobalt salt solution to auxiliary feed ② is: V Co / V F② =0.08, the flow rate of solution B is adjusted according to the hydroxide concentration (making the hydroxide concentration 1.0 mol / L). When the slurry volume in the reactor reaches 50% of the reactor, C3 solution is introduced, and the volume ratio of auxiliary feed ③ to cobalt salt solution is: V F③ / V Co = 1.7. When the slurry in the reactor reached 90% of the total space, the reaction was stopped.

[0129] (4) The remaining parameters are consistent with those in Example 1.

[0130] (5) The slurry obtained in step (3) is filtered and washed to remove excess impurities. When Na≤1000ppm and Mn≤1000ppm in the sample, the sample is dried to obtain the product PCH4.

[0131] (6) The product PCH3 obtained in step (5) is transferred to a tube furnace, calcined at 300 degrees Celsius for 3 hours in an air atmosphere, and then ground and sieved to obtain PCO4.

[0132] (7) The product PCH4 obtained in step (6) was characterized by SEM. Figure 4 The particle size is 0.1-0.5μm, and the individual submicron particles are thin and blade-shaped with small lateral dimensions, and are evenly distributed and well dispersed.

[0133] Example 5

[0134] This example adopts the one-pot method provided in Example 3 to prepare CoOOH and Co3O4 precursors, and the steps are as follows:

[0135] (1) According to the concentration of a certain metal cobalt nitrate salt solution, calculate the corresponding mass of cobalt nitrate, and use pure water to prepare a cobalt salt solution with a concentration of 2.0 mol / L, which is recorded as solution A;

[0136] (2) preparing a sodium hydroxide solution with a concentration of 10 mol / L as a precipitant, recorded as solution B;

[0137] (3) Configuration of auxiliary feed ①: According to a certain concentration, calculate the corresponding mass, and use pure water to prepare liquid ammonia into an ammonia solution with a concentration of 5 mol / L, which is recorded as C1 solution;

[0138] (4) Auxiliary feed ③: Use pure water to prepare sodium hypochlorite into a solution with a concentration of 3.5 mol / L, denoted as C3;

[0139] (5) Add solution A accounting for 30% of the volume of the reactor into the reactor, start the stirring and heating program: the stirring speed is 500 rpm, the temperature is 40°C, and the concentration of the PVP solution is adjusted to 15 g / L and the concentration of the DTAB solution is 4 g / L.

[0140] (6) Under the conditions in step (5), directly pump solution B into the reactor for precipitation reaction at a pumping rate of 10 L / h. Simultaneously pump solution C1 into the reactor to make the ammonia concentration in the reactor 1 g / L, and simultaneously introduce solution C3. The volume ratio of auxiliary feed ③ to cobalt salt solution is: V F③ / V Co = 1.7. When the slurry in the reactor reaches 90% of the total space, the reaction is stopped.

[0141] (7) The slurry obtained in step (6) is filtered and washed to remove excess impurities. When the Na content in the sample is ≤1000 ppm, the sample is dried to obtain a product denoted as PCH5.

[0142] (8) The product PCH5 obtained in step (7) is transferred to a tube furnace, calcined at 300 degrees Celsius for 3 hours in an air atmosphere, and then ground and sieved to obtain PCO5.

[0143] (9) The product PCH5 obtained in step (7) was characterized by SEM. Figure 5 The particle size is 0.1-0.5μm, and the individual submicron particles are thin and have small lateral dimensions, with uniform distribution and good dispersion.

[0144] Example 6

[0145] The only difference from Example 4 is that the auxiliary solution ② is configured as a mixed solution of 120 g / L pvp and 13 g / L CTAB, and the volume ratio of the cobalt salt solution to the auxiliary feed ② is: V Co / V F② =0.15. The SEM of the obtained PCH6 sample is shown in Figure 6 .

[0146] Comparative Example 1

[0147] The only difference from Example 1 is that no surfactant and oxidant are added during the process. Figure 7 .

[0148] Experimental Example 1

[0149] Electrochemical performance test:

[0150] (1) The cobalt oxyhydroxide and cobalt trioxide prepared in the example and the comparative example were physically mixed with NCM positive electrode material (Ni:Co:Mn=90:5:5 in molar ratio) and annealed at 770° C. to prepare different modified positive electrode materials.

[0151] (2) The several positive electrode materials prepared in step (1) were mixed into a slurry according to the mass ratio of positive electrode material: conductive carbon: polyvinylidene fluoride (PVDF) = 90:5:5, and a positive electrode sheet (the compaction density of the sheet was 3.0 mg / cm 2 ), a metal lithium sheet was selected as the negative electrode material, and 1M LiPF6 / EC:DMC=1:1 (V%) was used as the electrolyte (where EC is ethylene carbonate and DMC is dimethyl carbonate) to assemble into a CR2025 button cell.

[0152] (3) After activation at 0.05C rate for three cycles, the discharge capacity retention rate was obtained by cycling 100 times at 1C rate. Capacity retention rate after 100 cycles (%) = discharge capacity at the 100th cycle / discharge capacity at the 1st cycle × 100%, and the cycle retention rate of the material was obtained, as shown in Table 1.

[0153] (4) The rate performance test was carried out according to the charge and discharge program of 0.05C*3+0.1C*3+0.2C*3+0.5C*3+1.0C*3+2.0C*3+5.0C*3. The results are shown in Table 2.

[0154] Table 1 Comparison of cycle performance of various positive electrode materials

[0155]

[0156] Table 2 Comparison of rate performance of various positive electrode materials

[0157]

[0158]

[0159] It can be seen from the electrochemical performance data that the electrochemical performance of the positive electrode material obtained by using CoOOH and Co3O4 precursors as surface coatings is better than that of cobalt hydroxide. The smaller the lateral size of the CoOOH and Co3O4 precursor particles and the thinner the primary particles, the higher the cycle performance and the better the rate performance (for example, PCH2, PCH3, PCO2, and PCO3 samples); the thicker the particles, the more reliable heterogeneous phase structure protection layer and fast ion diffusion layer attached to the surface of the particles provide for the positive electrode material, and the better the rate performance (for example, PCH1 and PCO1 samples).

[0160] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A cobalt oxyhydroxide, characterized in that The cobalt oxyhydroxide is in the form of submicron particles, and the length of the submicron particles is 0.1 μm-1 μm.

2. A method for preparing the cobalt oxyhydroxide according to claim 1, characterized in that: include: The cobalt salt is subjected to precipitation reaction in the presence of a precipitant, a complexing agent, a surfactant and an oxidant.

3. The preparation method according to claim 2, characterized in that: The precipitant is an inorganic alkali, preferably sodium hydroxide; more preferably, when added in the form of a liquid alkali solution during the precipitation process, the concentration of the added liquid alkali solution is controlled to be 8 mol / L-12 mol / L; Preferably, the complexing agent is ammonia water; more preferably, when added in the form of an ammonia solution during the precipitation process, the concentration of the ammonia solution added is controlled to be 5 mol / L-10 mol / L; Preferably, the surfactant is selected from at least one of polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium oxalate, ethylene glycol and sodium dodecyl sulfate; more preferably, when added in the form of a surfactant solution during the precipitation process, the concentration of the added surfactant solution is controlled to be 1 g / L-150 g / L; Preferably, the oxidant is selected from at least one of hydrogen peroxide, potassium permanganate, sodium hypochlorite, ozone and air; more preferably, the oxidant is added in the form of solution or ventilation during the precipitation process, and when the oxidant is hydrogen peroxide, the mass fraction of the added hydrogen peroxide solution is controlled to be 1%-10%; when the oxidant is potassium permanganate, the concentration of the added potassium permanganate solution is controlled to be 0.01 mol / L-0.4 mol / L; when the oxidant is sodium hypochlorite, the concentration of the added sodium hypochlorite solution is controlled to be 1.5-3.6 mol / L; Preferably, the cobalt salt is selected from at least one of sulfate, chloride and nitrate; more preferably, when added in the form of a cobalt salt solution during the precipitation process, the concentration of the cobalt salt solution added is controlled to be 1 mol / L-3 mol / L.

4. The preparation method according to claim 3, characterized in that: include: Preparing an aqueous solution containing the precipitant, the complexing agent and the surfactant as the first base liquid; Pumping a cobalt salt solution, a liquid alkali solution, an aqueous ammonia solution, a surfactant solution and an oxidant solution into the first bottom liquid in parallel to perform a precipitation reaction; The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried; Preferably, the volume of the first bottom liquid accounts for 20%-60% of the total volume of the reactor, the hydroxide concentration in the first bottom liquid is 0.001mol / L-2.0mol / L, the ammonia concentration is 1g / L-10g / L, and the surfactant concentration is 1g / L-20g / L; Preferably, during the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm, the temperature is 20°C-80°C, the concentration of the hydroxide solution is 0.001mol / L-2.0mol / L, and the ammonia concentration is 1g / L-10g / L; the addition rate of the cobalt salt solution is 2L / h-16L / h, and when the slurry volume in the reactor reaches 45%-55% of the volume of the reactor, the oxidant solution or gas is introduced, and when the addition reaches 85%-95% of the total volume of the reactor, the addition of each solution is stopped; Preferably, during the precipitation process, the volumes of the added solutions satisfy: the volume ratio of the ammonia solution to the cobalt salt solution is (0.01-1.0):1; the volume ratio of the surfactant solution to the cobalt salt solution is (0.01-0.5):1; the volume ratio of the oxidant solution to the cobalt salt solution is (0.01-2.5):

1.

5. The preparation method according to claim 3, characterized in that: include: preparing an aqueous solution containing the precipitant, the complexing agent and the surfactant as the second base liquid; pumping the cobalt salt solution and the oxidant solution into the second bottom solution to perform a precipitation reaction; The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried; Preferably, the volume of the second bottom liquid accounts for 40%-60% of the total volume of the reactor, in which the hydroxide concentration is 2.0mol / L-5.0mol / L, the ammonia concentration is 0g / L-5g / L, and the concentration of the surfactant is 0.01g / L-10g / L; during the precipitation reaction, the stirring speed is controlled to be 100rpm-1000rpm and the temperature is 20°C-80°C; Preferably, the volume ratio of the added oxidant solution to the cobalt salt solution is (0.01-2.5):1, the addition rate of the cobalt salt solution is 20L / h-40L / h, and the addition is stopped when the total volume of the reactor is 85%-95%.

6. The preparation method according to claim 3, characterized in that: Preparing an aqueous solution containing the cobalt salt and a surfactant as the third bottom liquid of the reaction kettle; Adding a liquid alkali solution, an ammonia solution and an oxidant into a reaction kettle to carry out a precipitation reaction; The slurry obtained by the precipitation reaction is subjected to solid-liquid separation, and the obtained solid material is washed and dried; Preferably, the volume of the third bottom liquid accounts for 30%-70% of the total volume of the reactor, in which the concentration of the cobalt salt is 1.0 mol / L-3.0 mol / L, and the concentration of the surfactant is 0.01 g / L-10 g / L; during the precipitation reaction, the stirring speed is controlled to be 100 rpm-1000 rpm, and the temperature is 20° C.-80° C.; Preferably, the pumping rate of the liquid alkali solution is 5L / h-15L / h, and the ammonia concentration in the reactor is maintained at 0.5g / L-2.5g / L by adjusting the addition rate of the ammonia solution, and the addition is stopped when the addition reaches 85%-95% of the total volume of the reactor; Preferably, the oxidant is added in the form of ozone, and the volume flow rate of the oxidant introduced per hour is controlled to be 0.1 times to 0.5 times the total volume of the reactor.

7. The preparation method according to claim 4, 5 or 6, characterized in that: The washing process includes: washing with water until the Na content in the sample is less than or equal to 1000 ppm, the K content is less than or equal to 1000 ppm, and the anion content is less than or equal to 1000 ppm; Preferably, after drying, the moisture content is less than or equal to 0.8%.

8. A method for preparing cobalt trioxide, characterized in that: Obtained by calcining the cobalt oxyhydroxide according to claim 1 or the cobalt oxyhydroxide prepared by the preparation method according to any one of claims 2 to 7; Preferably, the calcination is carried out in an air atmosphere, the calcination temperature is 200° C.-500° C., and the calcination time is 2 h-12 h.

9. A cobalt trioxide, characterized in that: It is prepared by the preparation method described in claim 8.

10. A positive electrode material, characterized in that: It comprises a positive electrode material substrate, on the surface of which the cobalt tetraoxide according to claim 9 is coated.

Images