Nanoscale manganous-manganic oxide, preparation method thereof, coated positive electrode material and battery

Abstract

The invention provides nanoscale manganous-manganic oxide and a preparation method thereof, a coated positive electrode material and a battery, and relates to the technical field of new energy. The repose angle of the nanoscale manganous-manganic oxide is 32-48 degrees, the fluidity of the nanoscale manganous-manganic oxide is in a proper range, the product dispersity is relatively good, the nanoscale manganous-manganic oxide can uniformly coat secondary particles of a positive electrode material when the nanoscale manganous-manganic oxide is used for a battery, and the cycle performance and the first coulombic efficiency of the battery prepared from the sintered positive electrode material can be improved.

Description

Technical Field

[0001] The present application relates to the field of new energy technologies, and particularly to nano-manganese tetraoxide, a preparation method thereof, a coated cathode material, and a battery. Background Art

[0002] In order to improve the electrochemical performance of the cathode material, the surface of the secondary particles of the cathode material is coated. However, if the coating material is unevenly coated on the surface of the cathode material, it will instead affect the electrochemical performance of the cathode material. Manganese tetraoxide is one of the coating materials, and its powder fluidity is an important index determining its coating effect. The existing manganese tetraoxide powder does not meet the coating requirements, and uneven coating may occur after coating.

[0003] The angle of repose is a key parameter describing the fluidity and friction characteristics of particulate materials, defined as the maximum angle between the free inclined plane formed by the particles in the natural accumulation state and the horizontal plane. When the material is in the limit state of equilibrium, this angle represents the stability of the material accumulation body. The size of the angle of repose reflects the influence of the internal friction and adhesion between particles at the microscopic level of the material on the physical and chemical properties of fluidity and accumulation characteristics, and is of great significance for applications such as material coating treatment. Summary of the Invention

[0004] The purpose of the present application is to provide a nano-manganese tetraoxide, a preparation method thereof, a coated cathode material, and a battery, aiming to solve the problem that the fluidity of the existing manganese tetraoxide powder is not suitable for coating the cathode material of the battery, resulting in uneven coating on the surface of the cathode material.

[0005] To achieve the above purpose, in the first aspect of the present application, a nano-manganese tetraoxide is provided, and the angle of repose of the nano-manganese tetraoxide is 32° - 48°.

[0006] Optionally, at least one of the following conditions is satisfied:

[0007] a. The angle of repose of the nano-manganese tetraoxide is 35° - 45°;

[0008] b. The mass content of Na in the nano-manganese tetraoxide ≤ 100 ppm; optionally, the mass content of Na in the nano-manganese tetraoxide is 10 ppm - 80 ppm.

[0009] Optionally, when measuring the particle size of the nano-manganese tetraoxide by a scanning electron microscope, at least one of the following conditions is satisfied:

[0010] a. The average particle size Mz of the nano-manganese tetraoxide is 15 nm - 100 nm; optionally, Mz is 50 nm - 95 nm;

[0011] b. The nanoscale manganese tetraoxide is an amorphous powder composed of multiple particles;

[0012] c. The particles of the nanoscale manganese tetraoxide are granular.

[0013] Optionally, when measuring the particle size of the nanoscale manganese tetraoxide by laser diffraction particle size analysis, at least one of the following conditions is satisfied:

[0014] a. The particle size D of the nanoscale manganese tetraoxide 50 ≤500 nm; optionally, the particle size D of the nanoscale manganese tetraoxide 50 is 200 nm - 500 nm;

[0015] b. The particle size D of the nanoscale manganese tetraoxide 0 ≤100 nm; optionally, the average particle size D of the nanoscale manganese tetraoxide 0 is 60 nm - 100 nm;

[0016] c. The particle size D of the nanoscale manganese tetraoxide 5 is 110 nm - 170 nm;

[0017] d. The particle size D of the nanoscale manganese tetraoxide 95 is 600 nm - 1500 nm; optionally, the particle size D of the nanoscale manganese tetraoxide 95 is 900 nm - 1500 nm;

[0018] e. The particle size D of the nanoscale manganese tetraoxide 100 ≤2000 nm; the particle size D of the nanoscale manganese tetraoxide 100 is 1200 nm - 1800 nm;

[0019] f. The particle size distribution K of the nanoscale manganese tetraoxide 95 =(D 95 -D 5 ) / D 50 is 1.9 - 2.6.

[0020] Optionally, at least one of the following conditions is satisfied:

[0021] a. The BET specific surface area of the nanoscale manganese tetraoxide is 14 m 2 / g - 30 m 2 / g; optionally, the BET specific surface area of the nanoscale manganese tetraoxide is 16 m 2 / g - 27 m 2 / g;

[0022] b. The tapped density TD of the nanoscale manganese tetraoxide is 0.5 g / cm 3 - 0.9 g / cm 3; Optionally, the tapped density TD of nano-manganese tetraoxide is 0.6 g / cm 3 -0.8 g / cm 3 ;

[0023] c. The apparent density AD of nano-manganese tetraoxide is 0.25 g / cm 3 -0.45 g / cm 3 .

[0024] The second aspect of the present application also provides a preparation method of nano-manganese tetraoxide, including:

[0025] Mix a mixed solution of a soluble manganese salt and an oxidant and a precipitant solution, and after reaction, perform post-treatment on the slurry after the reaction to obtain nano-manganese tetraoxide.

[0026] Optionally, a mixed solution of a soluble manganese salt and an oxidant and a precipitant solution are introduced into the bottom liquid for reaction; wherein, the bottom liquid includes a precipitant solution and / or a mixed solution of a soluble manganese salt and an oxidant.

[0027] Optionally, at least one of the following conditions is satisfied:

[0028] A. The soluble manganese salt includes a soluble divalent manganese salt; optionally, the divalent manganese salt includes MnCl 2 , MnSO 4 , Mn(NO 3 ) 2 one or more of them; optionally, the average valence state of Mn in the soluble manganese salt ≤ 2.66; optionally, the average valence state of Mn in the soluble manganese salt is 2.0 - 2.2;

[0029] B. The oxidant includes one or more of hydrogen peroxide, sodium persulfate, and ammonium persulfate;

[0030] C. The soluble manganese salt solution and the oxidant solution are formulated into a mixed solution of a soluble manganese salt and an oxidant according to a molar ratio of the oxidant to the soluble manganese salt of 1:(6 - 11); wherein, the manganese ion concentration in the soluble manganese salt solution is 1 mol / L to 3 mol / L; the mass fraction of the oxidant solution is 5 wt% to 35 wt%;

[0031] D. The prepared mixed solution of a soluble manganese salt and an oxidant is placed for 5 min - 60 min and then introduced into the bottom liquid; optionally, the prepared mixed solution of a soluble manganese salt and an oxidant is placed for 10 min - 40 min and then introduced into the bottom liquid;

[0032] E. The precipitant solution is one or more of potassium hydroxide solution, sodium hydroxide solution, and ammonia water; the mass fraction of the precipitant solution is 25 wt% to 45 wt%;

[0033] F. The pH value of the bottom liquid is 6.0 - 12.0;

[0034] G. The flow rate ratio of the mixed solution of soluble manganese salt and oxidant to the precipitant solution is 1:(0.3 - 0.7);

[0035] H. The flow rate of the mixed solution of soluble manganese salt and oxidant is 15% / h - 21% / h of the volume of the reaction kettle;

[0036] I. The reaction temperature is 10°C - 60°C; optionally, the reaction temperature is 40°C - 60°C;

[0037] J. The stirring speed of the reaction is 400 rpm - 1200 rpm; optionally, the stirring speed of the reaction is 700 rpm - 900 rpm;

[0038] K. The reaction stops after the slurry volume reaches 60% - 90% of the volume of the reaction kettle;

[0039] L. The post-treatment includes solid-liquid separation and water washing of the slurry to obtain a washed product, and then drying, crushing and sieving the washed product to obtain nano-scale manganese tetraoxide; the crushing time is 20 min - 40 min.

[0040] In the third aspect of the present application, a coated cathode material is further provided. The cathode material is obtained by sintering the above nano-scale manganese tetraoxide coated on the cathode material; optionally, the dosage of nano-scale manganese tetraoxide is 1 wt% - 5 wt% of the cathode material before coating; optionally, the cathode material is a lithium-ion cathode material and / or a sodium-ion cathode material. Optionally, the lithium-ion cathode material is at least one of lithium cobaltate, lithium-rich manganese-based cathode material, NCM ternary cathode material, lithium manganate, lithium iron phosphate, and lithium vanadium phosphate; the sodium-ion cathode material is at least one of sodium cobaltate, sodium nickelate, sodium manganate, NFM ternary cathode material, sodium vanadium phosphate, sodium iron phosphate, sodium iron sulfate, and Prussian blue cathode material.

[0041] In the fourth aspect of the present application, a battery is further provided, including the above coated cathode material.

[0042] Compared with the prior art, the beneficial effects of the present application include:

[0043] The angle of repose of the nano-sized manganese tetraoxide provided by this application is 32°-48°. The nano-sized manganese tetraoxide has good fluidity and dispersibility. When used in batteries, the nano-sized manganese tetraoxide can be evenly coated on the secondary particles of the cathode material, which can improve the cycle performance and first Coulomb efficiency of the battery prepared from the sintered cathode material. If the fluidity of the nano-sized manganese tetraoxide is too good, the binding force between the cathode material and the coating material will be weakened due to excessive fluidity, and the adhesion will be poor. It is easy to fall off again after coating, resulting in a poor coating effect. If the fluidity of the nano-sized manganese tetraoxide is too poor, it is easy to block the pipeline, and the coating material will form agglomerates on the surface of the cathode material, resulting in a poor coating effect; ultimately affecting the electrochemical performance of the prepared battery.

[0044] The preparation method of the nano-sized manganese tetraoxide provided by this application is to add an oxidant to a soluble manganese salt in advance and mix them. The oxidant will undergo an oxidation-reduction reaction with some divalent manganese ions, causing some divalent manganese to be oxidized to trivalent manganese in advance, which is beneficial to the subsequent oxidation-reduction reaction.

[0045] The cathode material provided by this application can improve the electrochemical performance of the cathode material while taking into account the cost by adjusting the coating amount of the nano-sized manganese tetraoxide.

[0046] The batteries and power-related devices provided by this application have excellent electrochemical performance and service performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of this application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as limiting the scope of this application.

[0048] Figure 1 SEM photograph of the surface of the nano-sized manganese tetraoxide for Example 1;

[0049] Figure 2 SEM photograph of the surface after sintering of the nano-sized manganese tetraoxide for Example 1 coated on the surface of the sodium-ion cathode material;

[0050] Figure 3 SEM photograph of the surface of the nano-sized manganese tetraoxide for Example 2;

[0051] Figure 4 SEM photograph of the surface after sintering of the nano-sized manganese tetraoxide for Example 2 coated on the surface of the sodium-ion cathode material;

[0052] Figure 5 SEM photograph of the surface of the nano-sized manganese tetraoxide for Example 3;

[0053] Figure 6SEM surface photograph after sintering of nano-manganese tetraoxide of Example 3 coated on the surface of a sodium ion cathode material;

[0054] Figure 7 SEM surface photograph of nano-manganese tetraoxide of Comparative Example 2;

[0055] Figure 8 SEM surface photograph after sintering of nano-manganese tetraoxide of Comparative Example 2 coated on the surface of a sodium ion cathode material;

[0056] Figure 9 SEM surface photograph of the cathode material before coating of Blank Group 1. Detailed implementation manners

[0057] As used herein, the terms:

[0058] When an equivalent, concentration, or other value or parameter is expressed as a range, an optional range, or a range defined by a series of upper optional values and lower optional values, it should be understood that all ranges formed by any pairing of any range upper limit or optional value with any range lower limit or optional value are specifically disclosed, regardless of whether the ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0059] In these examples, unless otherwise specified, the parts and percentages are by mass.

[0060] "And / or" is used to indicate that one or both of the stated circumstances may occur. For example, A and / or B includes (A and B) and (A or B).

[0061] The first aspect of the present application provides a nano-manganese tetraoxide, and the angle of repose of the nano-manganese tetraoxide is 32° - 48°, for example, it can be 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48° or any value between 32° - 48°, 35° - 45°, 32° - 36°, 36° - 43°, 43° - 48°; optionally, the angle of repose of the nano-manganese tetraoxide is 35° - 45°.

[0062] The main purpose of coating the surface of the cathode material with nano-manganese tetraoxide is to improve the electrochemical performance. Lithium manganate (LiMn 3 O 4 ) generated after sintering of (Mn 2 O4 ) or sodium manganate (Na 2 MnO 4 ) coated on the surface of the cathode material to form a protective layer has the following advantages: First, lithium manganate (LiMn 2 O 4 ) or sodium manganate (Na 2 MnO 4 ) is not an inert coating layer and can participate in the electrochemical reaction during charge and discharge, without significantly reducing the energy density of the cathode material; Second, the protective layer of lithium manganate (LiMn 2 O 4 ) or sodium manganate (Na 2 MnO 4 ) reduces the direct contact between the main body of the cathode material and the electrolyte, slows down the occurrence of side reactions on the surface, and maintains the structural stability of the material; Third, the introduction of oxygen vacancies inhibits the activation of the Li 2 MnO 3 component, improves the first Coulomb efficiency, and accelerates the diffusion rate of lithium ions during charge and discharge, thereby enhancing the rate performance of the material.

[0063] There are many factors affecting the angle of repose. Generally speaking, it is mainly affected by the following factors: ① Particle shape: Particles are easy to roll, and the angle of repose is small; The frictional resistance of flaky, needle-shaped or irregular particles is large, and the angle of repose is larger; ② Particle size: Fine particles have a large specific surface area and high frictional resistance, and the angle of repose is larger; Coarse particles are easier to roll under the action of gravity, and the angle of repose is smaller; ③ Particle size distribution: For particles with a large particle size difference, fine particles fill the gaps between coarse particles to form a more stable dense structure, and the angle of repose is larger; For particles with a small particle size difference, there are many pores between particles, and they are easy to slide, and the angle of repose is smaller; ④ Surface roughness of particles: The frictional force between rough particles increases, and the angle of repose increases; The opposite is true for smooth particles; ⑤ Material density: Particles with a higher density have fewer pores and are tightly packed, and the angle of repose is larger; Materials with a lower density or porous materials: There are many internal pores, and the particles are easy to slide, and the angle of repose is smaller; ⑥ Hygroscopicity: Materials with a high residual alkali content are exposed to a humid / wet environment, have strong hygroscopicity, and the adhesion force between particles increases, and the angle of repose increases significantly; Materials with a low residual alkali content have weak hygroscopicity, and the increase in the angle of repose is not obvious; ⑦ Electrostatic adsorption: Particles with strong moisture absorption ability are more conductive due to their high water content, which may change the stacking stability and affect the angle of repose.

[0064] The repose angle of the nano-manganese tetraoxide provided in the present application is 32°-48°, and the nano-manganese tetraoxide has good fluidity and dispersibility. When used in batteries, the nano-manganese tetraoxide can be evenly coated on the secondary particles of the positive electrode material, which can improve the cycle performance and the first coulomb efficiency of the battery prepared by the sintered positive electrode material. If the fluidity of the nano-manganese tetraoxide is too good, the binding force between the positive electrode material and the coating material will be weakened due to the good fluidity, the adhesion is poor, and it is easy to fall off again after coating, resulting in a poor coating effect; if the fluidity of the nano-manganese tetraoxide is too poor, the coating material will form agglomerations on the surface of the positive electrode material, resulting in a poor coating effect; at the same time, it is easy to block the pipeline during processing such as pipeline transportation, which ultimately affects the electrochemical performance of the prepared battery.

[0065] When the particle size distribution is not much different, by measuring the repose angle of nano-manganese tetroxide, the flow of the material and the subsequent coating condition can be quickly evaluated without conducting coating and sintering experiments one by one, thus reducing product verification time; it also provides a quality inspection standard for subsequent product development and production.

[0066] When the particle size of nano-manganese tetraoxide is measured by scanning electron microscopy, the average particle size Mz, particle morphology, etc. of nano-manganese tetraoxide can be measured.

[0067] In some embodiments, the average particle size Mz of nano-scale manganese tetraoxide is 15nm-100nm; alternatively, Mz is 50nm-95nm; illustratively, the average particle size Mz of nano-scale manganese tetraoxide can be 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm or any value between 15nm-100nm, 40nm-100nm, 50nm-95nm, 60nm-90nm.

[0068] The measured particle size of the nano-manganese tetraoxide of the present application is relatively small, and the fluidity and dispersibility are good. When used in batteries, the nano-manganese tetraoxide can be evenly coated on the secondary particles of the positive electrode material, which can improve the cycle performance and the first coulombic efficiency of the battery prepared by the sintered positive electrode material.

[0069] In some embodiments, the nano-sized manganese manganese oxide is an amorphous powder consisting of a plurality of particles.

[0070] Granular nano-scale manganese manganese oxide is an amorphous powder with pseudo-agglomeration. The binding force between particles is van der Waals force, which is easy to break up instead of agglomerating into secondary particle balls that are difficult to break up. It has good fluidity and is conducive to coating on the surface of the positive electrode material.

[0071] In some embodiments, the particles of manganese tetraoxide at the nanoscale are granular.

[0072] Compared with large flaky particles or conical particles, small granular particles are more likely to be uniformly coated on the surface of the cathode material, and can be melted onto the surface of the cathode material faster during sintering to form a protective layer.

[0073] When measuring the particle size of the manganese tetraoxide at the nanoscale by laser particle size analysis diffraction method, D 0 represents the minimum particle size of the powder particle size, D 5 represents the 5% cumulative volume particle size of the powder; D 50 represents the 50% cumulative volume particle size of the powder; D 95 represents the 95% cumulative volume particle size of the powder; D 100 represents the maximum particle size of the powder particle size.

[0074] In some embodiments, the particle size D of the manganese tetraoxide at the nanoscale 50 ≤500 nm, for example, it can be any value within the range of ≤100 nm, ≤200 nm, ≤300 nm, ≤400 nm, ≤500 nm or ≤500 nm, 200 nm - 390 nm, 390 nm - 500 nm, 300 nm - 500 nm; further, the particle size D of the manganese tetraoxide at the nanoscale 50 is 200 nm - 500 nm, for example, it can be 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm or 500 nm.

[0075] The angle of repose of the manganese tetraoxide at the nanoscale is 32° - 48°, and when the particle size D 50 is smaller, after the particles are uniformly coated on the surface of the cathode material and sintered, it is more conducive to the melting of the manganese tetraoxide at the nanoscale into the cathode material, improving the cycle performance of the prepared battery.

[0076] In some embodiments, the particle size D of the manganese tetraoxide at the nanoscale 0 ≤100 nm, for example, it can be any value within the range of ≤100 nm, ≤90 nm, ≤80 nm, ≤70 nm, ≤60 nm, ≤50 nm, ≤40 nm, ≤30 nm or ≤20 nm; further, the particle size D of the manganese tetraoxide at the nanoscale 0is 60 nm - 100 nm; for example, it can be 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or any value between 60 nm - 75 nm, 75 nm - 85 nm, 85 nm - 100 nm, 70 nm - 90 nm, 65 nm - 85 nm, 60 nm - 100 nm.

[0077] The minimum particle size D of nano - manganese tetraoxide 0 (i.e., the lower limit value of the particle size) is too large, which may lead to uneven coating and affect the cycling performance of the prepared battery; if D 0 is too large, the fluidity is poor, resulting in poor coating effect; if D 0 is too small, the fluidity is too good, and it is easy to fall off after coating. In addition, the requirements for crushing equipment are too high, resulting in a sharp increase in production costs, and the powder is too fine, easy to generate dust, difficult to collect and handle, and unfriendly to the environment.

[0078] In some embodiments, the particle size D of nano - manganese tetraoxide 5 is 110 nm - 170 nm; for example, it can be 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm or any value between 110 nm - 170 nm, 110 nm - 125 nm, 125 nm - 155 nm, 155 nm - 170 nm, 120 nm - 160 nm, 125 nm - 155 nm.

[0079] In some embodiments, the particle size D of nano - manganese tetraoxide 95 is 600 nm - 1500 nm. For example, it can be 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm or any value between 600 nm - 1500 nm, 600 nm - 900 nm, 900 nm - 1500 nm, 900 nm - 980 nm, 980 nm - 1380 nm, 1380 nm - 1500 nm, 950 nm - 1450 nm, 1000 nm - 1400 nm. Further, the particle size D of nano - manganese tetraoxide 95 is 900 nm - 1500 nm.

[0080] In some embodiments, the particle size D of nano - manganese tetraoxide 100 ≤2000 nm. For example, it can be ≤1200 nm, ≤1300 nm, ≤1400 nm, ≤1500 nm, ≤1600 nm, ≤1700 nm, ≤1800 nm, ≤1900 nm, ≤2000 nm or any value between 1200 nm - 2000 nm. Further, the particle size D of nano - manganese tetraoxide100 is from 1200 nm to 1800 nm, and for example, it can be 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1800 nm, 1200 nm, or any value between 1200 nm - 1400 nm, 1400 nm - 1650 nm, 1650 nm - 1800 nm, 1400 nm - 1800 nm.

[0081] The maximum particle size D of nanoscale manganese tetraoxide 100 (i.e., the upper limit value of the particle size) being too large may lead to uneven coating and it is not easy to completely melt into the cathode material, affecting the cycle performance of the prepared battery; if D 100 is too small, the improvement of the cycle effect is not obvious, but the production cost increases. In addition, if D 100 is too small, it is easy to generate dust, and the powder is too fine, which is not easy to collect and process, and is not environmentally friendly.

[0082] Controlling the minimum particle size D of nanoscale manganese tetraoxide 0 and the minimum particle size D 100 , controlling the particle size difference between the two, making the particle size of the crushed nanoscale manganese tetraoxide more uniform, can avoid overburning or incomplete burning during sintering after coating, and improve the cycle performance and the first Coulomb efficiency.

[0083] In some embodiments, the particle size distribution K of nanoscale manganese tetraoxide 95 =(D 95 -D 5 ) / D 50 is from 1.9 to 2.6, and for example, it can be 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, or any value between 1.9 - 2.6, 1.9 - 2.2, 2.2 - 2.5, 2.5 - 2.6, 2.0 - 2.5, 2.1 - 2.5, 2.2 - 2.5.

[0084] By controlling each particle size D of nanoscale manganese tetraoxide 0 , D 5 , D 50 , D 95 , D 100 and the particle size distribution K 95 , making the nanoscale manganese tetraoxide composed of particles with specific different particle size dimensions and proportions, having a specific particle size distribution, and the material has relatively large fluidity, which is beneficial to the uniform coating of the nanoscale manganese tetraoxide on the surface of the cathode material, and can improve the cycle performance of the battery prepared from the sintered cathode material.

[0085] In some embodiments, the mass content of Na in nano-manganese tetraoxide is ≤ 100 ppm, for example, it can be ≤ 10 ppm, ≤ 20 ppm, ≤ 30 ppm, ≤ 40 ppm, ≤ 50 ppm, ≤ 60 ppm, ≤ 70 ppm, ≤ 80 ppm, ≤ 90 ppm, ≤ 100 ppm or any value of ≤ 100 ppm, or any value between 10 ppm - 80 ppm, 10 ppm - 35 ppm, 35 ppm - 68 ppm, 68 ppm - 100 ppm, 35 ppm - 75 ppm, 20 ppm - 90 ppm. Optionally, the mass content of Na in nano-manganese tetraoxide is 10 ppm - 80 ppm. The low mass content of sodium in the nano-manganese tetraoxide of the present application can reduce the residual alkali on the surface after coating the cathode material, and can improve the cycle performance of the battery after being fabricated into a battery.

[0086] In some embodiments, the BET specific surface area of the nano-manganese tetraoxide is 14 m 2 / g - 30 m 2 / g, for example, it can be 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g, 19 m 2 / g, 20 m 2 / g, 21 m 2 / g, 22 m 2 / g, 23 m 2 / g, 24 m 2 / g, 25 m 2 / g, 26 m 2 / g, 27 m 2 / g, 28 m 2 / g, 29 m 2 / g, 30 m 2 / g or 14 m 2 / g - 30 m 2 / g, 14 m 2 / g - 18 m 2 / g, 18 m 2 / g - 26 m 2 / g, 26 m 2 / g - 30 m 2 / g, 16 m 2 / g - 27 m 2 / g, 17 m 2 / g - 27 m 2 / g, 18 m 2 / g - 26 m 2 / g; optionally, the BET specific surface area of the nano-manganese tetraoxide is 16 m2 / g - 27m 2 / g。

[0087] In some embodiments, the tapped density TD of nanoscale manganese tetraoxide is 0.5 g / cm 3 - 0.9 g / cm 3 , for example, it can be 0.5 g / cm 3 , 0.6 g / cm 3 , 0.7 g / cm 3 , 0.8 g / cm 3 , 0.9 g / cm 3 or any value between 0.5 g / cm 3 - 0.9 g / cm 3 , 0.6 g / cm 3 - 0.8 g / cm 3 , 0.7 g / cm 3 - 0.8 g / cm 3 ; Optionally, the tapped density TD of nanoscale manganese tetraoxide is 0.6 g / cm 3 - 0.8 g / cm 3 .

[0088] In some embodiments, the apparent density AD of nanoscale manganese tetraoxide is 0.25 g / cm 3 - 0.45 g / cm 3 , for example, it can be 0.25 g / cm 3 , 0.30 g / cm 3 , 0.35 g / cm 3 , 0.40 g / cm 3 , 0.45 g / cm 3 or any value between 0.25 g / cm 3 - 0.45 g / cm 3 , 0.30 g / cm 3 - 0.45 g / cm 3 .

[0089] Factors such as BET, TD, and AD characterize the density of the product in different states. If the density difference from the product to be coated is too large, stratification is likely to occur during the mixing coating process, which will affect the final coating effect.

[0090] The second aspect of the present application also provides a preparation method of nanoscale manganese tetraoxide, including:

[0091] Mixing a mixed solution of a soluble manganese salt and an oxidant with a precipitant solution, reacting them, and then performing post-treatment on the slurry after the reaction to obtain nanoscale manganese tetraoxide.

[0092] In some embodiments, a more specific feeding method is as follows: a mixed solution of a soluble manganese salt and an oxidant and a precipitant solution are introduced into the bottom liquid for reaction;

[0093] Among them, the bottom liquid includes a precipitant solution and / or a mixed solution of a soluble manganese salt and an oxidant.

[0094] In the above preparation method, the "mixed solution of a soluble manganese salt and an oxidant" is added as a mixed solution, rather than adding the "soluble manganese salt" and the "oxidant" separately.

[0095] The above slurry refers to a mixture formed by continuously introducing a mixed solution of a soluble manganese salt and an oxidant and a precipitant solution into the bottom liquid for reaction, or a mixture after the reaction ends.

[0096] In the preparation method of nano-level manganese tetraoxide provided by the present application, by adding the oxidant solution to the soluble manganese salt solution in advance and mixing, the oxidant will undergo an oxidation-reduction reaction with some divalent manganese ions, causing some divalent manganese to be oxidized in advance, which is beneficial to the subsequent oxidation-reduction reaction. If the soluble manganese salt solution, the precipitant, and the oxidant solution are added simultaneously during the reaction instead of mixing the soluble manganese salt solution and the oxidant solution in advance, the oxidation rate may decrease, and the physicochemical properties of the generated product may be different or changed.

[0097] In some embodiments, the soluble manganese salt includes a soluble divalent manganese salt; further, the divalent manganese salt includes MnCl 2 , MnSO 4 , Mn(NO 3 ) 2 or one or more of them;

[0098] In some embodiments, the average valence state of Mn in the soluble manganese salt ≤ 2.66; further, the average valence state of Mn in the soluble manganese salt is 2 - 2.2; for example, the average valence state of Mn in the soluble manganese salt can be ≤ 2.66, ≤ 2.5, ≤ 2.4, ≤ 2.3, ≤ 2.2, ≤ 2.1, ≤ 2.0, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.66 or any value between ≤ 2.66, 2.0 - 2.2, 2.0 - 2.66, 2.1 - 2.6, 2.1 - 2.2.

[0099] The "soluble manganese salt" here refers to the "soluble manganese salt" in the "mixed solution of a soluble manganese salt and an oxidant".

[0100] In some embodiments, the oxidant is one or more of hydrogen peroxide, sodium persulfate, and ammonium persulfate.

[0101] The type and concentration of the added oxidant will affect the oxidation rate of divalent manganese ions, may affect the arrangement of manganese ions in the unit cell and thus affect the internal structure of the crystal grains, and ultimately affect the hardness, particle size, etc. of the generated manganese tetraoxide, and finally affect parameters such as the angle of repose of the pulverized nano-manganese tetraoxide. Compared with gas oxidants such as compressed air and oxygen, the above-mentioned oxidants have better dissolution effects, can be fully miscible with soluble manganese salts, have better mixing uniformity, the generated manganese tetraoxide is easy to pulverize, the particles of the prepared nano-manganese tetraoxide have good consistency, and the angle of repose is moderate.

[0102] In some embodiments, a mixed solution of soluble manganese salt and oxidant is prepared by mixing a soluble manganese salt solution and an oxidant solution according to a molar ratio of the oxidant to the soluble manganese salt of 1:(6 - 11); wherein, the manganese ion concentration in the soluble manganese salt solution is 1 mol / L to 3 mol / L; the mass fraction of the oxidant solution is 5 wt% to 35 wt%.

[0103] Exemplarily, the molar ratio of the oxidant to the soluble manganese salt in the mixed solution of soluble manganese salt and oxidant can be 1:6, 1:7, 1:8, 1:9, 1:10, 1:11 or any value between 1:(6 - 11) and 1:(7.0 - 10.5); the manganese ion concentration in the soluble manganese salt solution can be 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L or any value between 1 mol / L and 3 mol / L; the mass fraction of the oxidant solution can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt% or any value between 5 wt% and 35 wt%.

[0104] An appropriate molar ratio of the oxidant to the soluble manganese salt in the mixed solution of soluble manganese salt and oxidant helps to control the oxidation rate of divalent manganese ions and generate manganese tetraoxide that is easy to pulverize and has a suitable angle of repose after pulverization.

[0105] In some embodiments, the prepared mixed solution of soluble manganese salt and oxidant is placed for 5 min - 60 min and then added to the bottom liquid; for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min or any value between 5 min - 60 min, 10 min - 40 min, 20 min - 50 min, 30 min - 60 min; optionally, the prepared mixed solution of soluble manganese salt and oxidant is placed for 10 min - 40 min and then introduced into the bottom liquid.

[0106] The mixed solution of soluble manganese salt and oxidant is acidic and has stronger oxidation ability, which can ensure that some divalent manganese ions are oxidized to trivalent manganese ions, facilitating the subsequent formation of mixed-valence oxide Mn 3 O 4 (containing Mn2+ and Mn3+). If the content of the oxidant in the mixed solution of soluble manganese salt and oxidant is too high or the standing time after preparation is too long, excessive divalent manganese ions will be oxidized, and some manganese dioxide will be generated subsequently; if the content of the oxidant in the oxidant solution and the soluble manganese salt solution is too low or they are directly added to the reaction kettle without mixing, the oxidation effect of the oxidant will decrease in an alkaline environment, the reaction will be incomplete, and the morphology and physical and chemical properties of the generated product may change.

[0107] In some embodiments, the precipitant is one or more of potassium hydroxide solution, sodium hydroxide solution, and ammonia water; the mass fraction of the precipitant solution is 25wt% - 45wt%, for example, it can be 25wt%, 30wt%, 35wt%, 40wt%, 45wt% or any value between 25wt% - 45wt%.

[0108] In some embodiments, the pH value of the bottom liquid is 6.0 - 12.0, for example, it can be 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 or any value between 6.0 - 12.0.

[0109] In some embodiments, the flow rate ratio of the mixed solution of soluble manganese salt and oxidant to the precipitant solution is 1:(0.3 - 0.7), for example, it can be 1:0.3, 1:0.4, 1:0.5, 1:0.6 or any ratio between 1:(0.3 - 0.7).

[0110] By controlling the flow rate ratio of the oxidant to manganese ions and the precipitant during the synthesis process, the molar ratio between the oxidant and manganese ions and the precipitant can be indirectly controlled, and the oxidation rate can be controlled. Specifically, by controlling the above parameters, the oxidation rate of divalent manganese ions in the reaction kettle can be controlled, thereby controlling the proportion of trivalent manganese ions in the total manganese ions. While increasing the oxidation rate, a weak alkaline environment is maintained to avoid the too-fast oxidation rate in a high pH environment with strong alkalinity (pH > 12) that further oxidizes Mn3+ to Mn 4+ , generating MnO 2 or manganate (such as Na 2 MnO 4 ) and other higher-valence manganese oxides or manganates. At the same time, within the above parameter range, the growth and arrangement mode of the crystal grains inside the product particles and the particle size can also be regulated, making it easy to break during post-treatment, and after breaking, nano-sized manganese tetraoxide with a repose angle of 32° - 48° can be obtained.

[0111] In some embodiments, the flow rate of the mixed solution of soluble manganese salt and oxidant is 15% / h - 21% / h of the volume of the reaction kettle. For example, it can be 15% / h, 16% / h, 17% / h, 18% / h, 19% / h, 20% / h, 21% / h or any value between 15% / h - 21% / h.

[0112] By controlling the flow rate of the mixed solution of soluble manganese salt and oxidant added, the concentration of the materials in the reaction kettle and the reaction rate can be controlled, which affects the speed and physicochemical properties of the subsequent generated products.

[0113] In some embodiments, the reaction temperature is 10°C - 60°C; optionally, the reaction temperature is 40°C - 60°C. For example, it can be 10°C, 20°C, 30°C, 40°C, 50°C, 60°C or any value between 10°C - 60°C.

[0114] By controlling the reaction temperature, the reaction rate and the morphology, physicochemical properties of the generated products can be controlled. A higher temperature (≥70°C) may accelerate the deep oxidation to generate MnO 2 , and it is recommended to carry out the reaction at 40°C - 60°C.

[0115] In some embodiments, the stirring speed of the reaction is 400 rpm - 1200 rpm; optionally, the stirring speed of the reaction is 700 rpm - 900 rpm. For example, it can be 400 rpm, 500 rpm, 600 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm or any value between 400 rpm - 1200 rpm.

[0116] By controlling the stirring speed, the concentration uniformity of the components at different positions in the slurry can be controlled to make the oxidation more uniform; meanwhile, the stirring speed has an impact on the particle size of the materials.

[0117] In some embodiments, the reaction is stopped after the volume of the slurry reaches 60% - 90% of the volume of the reaction kettle. For example, it can be 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90% or any value between 60% - 90%.

[0118] By the flow rate of each raw material solution flowing into the reaction kettle in parallel and the volume of the reaction kettle when the reaction is stopped, the reaction time can be indirectly controlled.

[0119] In some embodiments, the post-treatment includes solid-liquid separation of the slurry and washing to obtain a washed product, and then the washed product is dried, crushed and sieved to obtain nanoscale manganese tetroxide. Among them, the crushing equipment can be a pair-roll crusher, a jet mill, etc.

[0120] The third aspect of the present application further provides a coated cathode material, which is obtained by sintering the above-mentioned nanoscale manganese tetroxide-coated cathode material.

[0121] In some embodiments, the amount of nanoscale manganese tetroxide used is 1 wt% - 5 wt% of the cathode material before coating. For example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or any value between 1 wt% - 5 wt%.

[0122] If the usage amount of the nanoscale manganese tetroxide coating is too low, the improvement of the battery performance prepared after sintering is limited; if the usage amount of the coating is too high, there may be problems such as agglomeration of nanoscale manganese tetroxide, uneven coating, and difficulty in completely melting onto the surface of the cathode material after sintering; at the same time, the cost will also increase.

[0123] In some embodiments, the cathode material is a lithium-ion cathode material and / or a sodium-ion cathode material. Optionally, the lithium-ion cathode material is at least one of lithium cobaltate, lithium-rich manganese-based cathode material, NCM ternary cathode material, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, and lithium vanadium phosphate; the sodium-ion cathode material is at least one of sodium cobaltate, sodium nickelate, sodium manganate, NFM ternary cathode material, sodium vanadium phosphate, sodium iron phosphate, sodium iron sulfate, and Prussian blue cathode material.

[0124] The cathode material provided by the present application can improve the electrochemical performance of the cathode material while taking into account the cost by adjusting the usage amount of the nanoscale manganese tetroxide coating.

[0125] The fourth aspect of the present application further provides a battery, including the above-mentioned coated cathode material.

[0126] The following will describe the implementation schemes of the present application in detail with specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0127] Example 1

[0128] Provide a nanoscale manganese tetroxide with the chemical formula Mn 3 O 4 , and its preparation process is as follows:

[0129] ① Raw material preparation: Prepare a sodium hydroxide solution with a mass fraction of 32%, prepare a manganese sulfate solution with a concentration of 2 mol / L, and prepare a hydrogen peroxide (H 2 O 2 ) solution with a mass fraction of 27.5 wt%;

[0130] An oxidant solution is added to a manganese sulfate solution, and after stirring evenly, a mixed solution of soluble manganese salt and oxidant is obtained, where the molar ratio of the oxidant to the soluble manganese salt is 1:9.

[0131] ② Reaction: Deionized water is added to the reaction kettle, and the pH of the bottom liquid is controlled to be 10.4 with sodium hydroxide solution; the temperature is raised to 50 °C, stirring is started, and the stirring speed is 800 rpm. Then, the mixed solution of soluble manganese salt and oxidant and sodium hydroxide solution prepared and left standing for 30 min are introduced. The flow rate of the mixed solution of soluble manganese salt and oxidant is controlled to be 16.5%-17.5% / h of the volume of the reaction kettle, and the mixed solution of soluble manganese salt and oxidant:sodium hydroxide solution is in a flow rate ratio = 1:(0.44 - 0.46). The temperature during the reaction is controlled to be 50 °C until the volume of the slurry reaches 80% of the volume of the reaction kettle, and the synthesis reaction is stopped.

[0132] ③ Press filtration is carried out with deionized water, followed by three times of slurry washing and drying, and then discharging to obtain the washed product.

[0133] ④ The washed product is placed in a common drying oven and dried at 90 °C for 12 h to obtain the dried product.

[0134] ⑤ After the dried product is crushed by a roller crusher for 30 min, nano-manganese tetraoxide material is obtained.

[0135] The nano-manganese tetraoxide material of Example 1 is measured, and the results are shown in Table 1 below; a scanning electron microscope (SEM) is used to take pictures of the finished product to obtain the surface SEM photo, as Figure 1 shown.

[0136] Example 2

[0137] A nano-manganese tetraoxide is provided, and the difference in its preparation method from that of Example 1 lies in:

[0138] ① Raw material preparation: A mixed solution of a soluble manganese salt solution and an oxidant (H 2 O 2 ) solution is prepared, where the molar ratio of the oxidant to the soluble manganese salt is 1:10, and after preparation, it is left standing for 20 min.

[0139] ② Reaction: The pH of the bottom liquid is controlled to be 10.4, the temperature is raised to 55 °C, the stirring speed is 750 rpm, the flow rate of the mixed solution of soluble manganese salt and oxidant is controlled to be 17.5%-18.5% / h of the volume of the reaction kettle, and the mixed solution of soluble manganese salt and oxidant:sodium hydroxide solution is in a flow rate ratio = 1:(0.47 - 0.49). The temperature during the reaction is controlled to be 55 °C.

[0140] ⑤ The crushing equipment is changed to a jet mill.

[0141] The nano-manganese tetraoxide material of Example 2 was photographed using a scanning electron microscope (SEM) to obtain a surface SEM photograph, as Figure 3 shown.

[0142] Example 3

[0143] A nano-level manganese tetraoxide is provided, with the chemical formula Mn 3 O 4 , and its preparation process is as follows:

[0144] ① Raw material preparation: Prepare an ammonia water solution with a mass fraction of 20% as the precipitating agent, use manganese sulfate as the raw material to prepare a manganese salt solution with Mn 2+ of 2 mol / L, and prepare a sodium persulfate solution with a mass fraction of 10 wt%.

[0145] An oxidant solution was added to the manganese chloride solution, and after stirring evenly, a mixed solution of soluble manganese salt and oxidant was obtained, where the molar ratio of the oxidant to the soluble salt was 1:7.5.

[0146] ② Reaction: Add deionized water, a mixed solution of soluble manganese salt solution and oxidant solution to the reaction kettle, use sodium hydroxide solution to control the bottom liquid pH to 6.5, heat up to 60 °C, start stirring, the stirring speed is 700 rpm, and flow in a mixed solution of ammonia water solution, soluble manganese salt solution and oxidant solution, control the flow rate of the mixed solution of soluble manganese salt and oxidant to be 19.5%-20.5% / h of the reaction kettle volume, soluble manganese salt and oxidant mixed solution: sodium hydroxide solution according to the flow ratio = 1:(0.49 - 0.51), control the process temperature between 60 °C until the slurry volume reaches 85% of the reaction kettle volume and stop the synthesis reaction.

[0147] ③ Use deionized water for pressure filtration, slurry washing, air drying, and discharging to obtain the washed product.

[0148] ④ Place the washed product in an ordinary drying oven and dry it at 90 °C for 12 h to obtain the dried product.

[0149] ⑤ After the dried product is crushed by a roll crusher, the nano-manganese tetraoxide material of Example 3 is obtained.

[0150] The nano-manganese tetraoxide material of Example 3 was photographed using a scanning electron microscope (SEM) to obtain a surface SEM photograph, as Figure 5 shown.

[0151] Example 4

[0152] A nano-level manganese tetraoxide is provided, and the difference in its preparation method from that of Example 1 is that:

[0153] ① Raw material preparation: Prepare a mixed solution of a soluble manganese salt solution and an oxidant (H 2 O 2 ). The molar ratio of the oxidant to the soluble manganese salt is 1:12. After preparation, let it stand for 10 min.

[0154] ② Reaction: Control the pH of the bottom liquid to be 11.6, heat up to 60 °C, the stirring speed is 700 rpm, control the flow rate of the mixed solution of the soluble manganese salt and the oxidant to be 18.5%-19.5% / h of the reaction kettle volume, and the mixed solution of the soluble manganese salt and the oxidant: sodium hydroxide solution is in a flow rate ratio = 1:(0.52 - 0.54), and control the temperature during the reaction to be 60 °C.

[0155] ⑤ Change the crushing equipment to a jet mill for crushing for 15 min.

[0156] Example 5

[0157] Provide a nano-sized manganese tetraoxide, and the difference in its preparation method from that of Example 1 is as follows:

[0158] ① Raw material preparation: Prepare a mixed solution of a soluble manganese salt solution and an oxidant (H 2 O 2 ). The molar ratio of the oxidant to the soluble manganese salt is 1:4.

[0159] ② Reaction: Control the pH of the bottom liquid to be 10.1, heat up to 40 °C, control the flow rate of the mixed solution of the soluble manganese salt and the oxidant to be 12.5%-13.5% / h of the reaction kettle volume, and the mixed solution of the soluble manganese salt and the oxidant: sodium hydroxide solution is in a flow rate ratio = 1:(0.29 - 0.31), and control the temperature during the reaction to be 40 °C until the slurry volume reaches 70% of the reaction kettle volume and stop the synthesis reaction.

[0160] ⑤ Change the crushing equipment to a jet mill for crushing twice, and the crushing time for each time is 25 min.

[0161] Example 6

[0162] Provide a nano-sized manganese tetraoxide, and the difference in its preparation method from that of Example 1 is as follows:

[0163] ① Raw material preparation: Prepare a mixed solution of a soluble manganese salt solution and an oxidant (H 2 O 2 ). The molar ratio of the oxidant to the soluble manganese salt is 1:11. After preparation, let it stand for 15 min.

[0164] ② Reaction: Control the pH of the bottom liquid to 11.5, raise the temperature to 55 °C, the stirring speed is 750 rpm, control the flow rate of the mixed solution of soluble manganese salt and oxidant to be 18.0%-19.0% / h of the volume of the reaction kettle, and the mixed solution of soluble manganese salt and oxidant: sodium hydroxide solution is in a flow rate ratio = 1:(0.49 - 0.51), and control the temperature during the reaction to be 55 °C.

[0165] ③ Use deionized water for pressure filtration and pulp washing twice.

[0166] ⑤ Change the crushing equipment to jet mill crushing for 15 min.

[0167] Comparative Example 1

[0168] Provide a nano-level manganese tetraoxide, and the difference in its preparation method from that of Example 1 is as follows:

[0169] ① Raw material preparation: Prepare a mixed solution of a soluble manganese salt solution and an oxidant (H 2 O 2 ), in which the molar ratio of the oxidant to the soluble manganese salt is 1:20, and let it stand for 22 min after preparation.

[0170] ② Reaction: Control the temperature of the bottom liquid to rise to 70 °C, the flow rate of the mixed solution of soluble manganese salt and oxidant is 22.5%-23.5% / h of the volume of the reaction kettle, and the temperature during the reaction is 70 °C.

[0171] Comparative Example 2

[0172] Provide a nano-level manganese tetraoxide, and the difference in its preparation method from that of Example 1 is as follows:

[0173] ① Raw material preparation: Prepare a mixed solution of a soluble manganese salt solution and an oxidant (H 2 O 2 ), in which the molar ratio of the oxidant to the soluble manganese salt is 1:2.8, and use it directly after preparation.

[0174] ② Reaction: Control the temperature of the bottom liquid to rise to 80 °C, the flow rate of the mixed solution of soluble manganese salt and oxidant is 25.5%-26.5% / h of the volume of the reaction kettle, and the temperature during the reaction is 80 °C.

[0175] Take a photo of the nano-manganese tetraoxide material in Comparative Example 2 using a scanning electron microscope (SEM) to obtain a surface SEM photo, as Figure 7 shown.

[0176] Test the physical and chemical parameters of the nano-manganese tetraoxide obtained in Examples 1-6 and Comparative Examples 1-2 respectively, and the test methods are as follows:

[0177] Angle of repose: Also known as the angle of repose, refer to the determination of the angle of repose in 4.5 of "Test Methods for Physical Properties of Dust (GB / T 16913-2008)".

[0178] Particle size of nano-manganese tetraoxide: Take SEM photos through a scanning electron microscope, select the surface SEM photo of nano-manganese tetraoxide with the largest magnification. Based on the scale in this surface SEM photo, take the longest straight-line distance between the two ends of randomly selected particles as the particle size. Measure the particle sizes of multiple particles, and then take the arithmetic mean to obtain the average particle size. In the above measurement, if there is a situation where particles are blocked, assume the unblocked part as a complete particle for measurement. Exemplarily, the magnification of the surface SEM photo can be 50.0K, etc., and the number of multiple particles can be 20, 30, 40, 50, etc.

[0179] D 50 (Average particle size), D 0 、D 5 、D 95 、D 100 : Measured by a laser particle size analyzer (instrument model: Mastersizer3000), refer to the national standard "GB / T 19077-2016 Particle Size Analysis Laser Diffraction Method"; Note: When measuring the particle size by the laser particle size test method, there is a situation where multiple aggregated particles are measured as a single particle, and the test value is larger than the actual value.

[0180] BET (specific surface area): Measured by a fully automatic nitrogen adsorption specific surface area analyzer (instrument model: BELPREP-VACII / BELSORP-MINI-X), refer to the national standard "GB / T 19587-2017 Gas Adsorption BET Method for the Determination of Solid Substances".

[0181] TD (tap density): Measured by a powder tap density tester (model: Dandong BET BT-302), refer to the national standard "GB / T 5162-2021 Determination of Tap Density of Metal Powders" for determination;

[0182] AD (bulk density): Refer to the national standard "GB / T 1479.3-2017 Determination of Bulk Density of Metal Powders Part 3: Vibration Funnel Method";

[0183] Sedimentation test method: At 25 °C, accurately weigh 10.00 g of the sample (accurate to 0.01 g) and put it into a 250 mL beaker; then add about 100 mL of absolute ethanol and stir for 20 min; then transfer the suspension in the beaker to a 100 mL transparent graduated cylinder, control the total volume of the suspension in the graduated cylinder to be 100 mL, and start timing; after 5 min and 15 min, respectively read the natural sedimentation test values of the material (the scale line corresponding to the interface between the supernatant and the turbid liquid in the graduated cylinder).

[0184] Table 1 Physicochemical data of nano-manganese tetraoxide in Examples 1-6 and Comparative Examples 1-2

[0185]

[0186] Note: Mz is the average value calculated after measuring the particle sizes of 30 randomly selected particles.

[0187] In the field of cathode materials, the sedimentation test data of nanomaterials is closely related to the coating performance. By optimizing the dispersibility, particle size distribution, and sediment stability of nanomaterials through sedimentation tests, the coating performance can be significantly improved, thereby improving the electrochemical performance, structural stability, and thermal stability of cathode materials. Under the same test conditions, the smaller the particle size, the more uniform the particle size, and the less agglomeration, the slower the sedimentation rate and the larger the sedimentation test value; conversely, the smaller the sedimentation test data.

[0188] Compared with Examples 1-6, the sedimentation test value of Comparative Example 1 is smaller. It is speculated that the possible reason is that the particle size is smaller and partial agglomeration accelerates the sedimentation rate (the smaller the particle size, the easier it is to agglomerate); the sedimentation test value of Comparative Example 2 is smaller. It is speculated that the possible reason is that the particle size is larger and the particle size uniformity is poor, resulting in a faster sedimentation rate.

[0189] Residual alkali and electrochemical performance test 1

[0190] The nano-manganese tetraoxide materials prepared in Examples 1-6 and Comparative Examples 1-2 were respectively mixed with the sodium-ion cathode material layer oxide (NaNi 0.3 Fe 0.4 Mn 0.3 O 2 ) at a mass ratio of 2 wt%:1, and then subjected to high-speed mixing and sintering. The sintering temperature was 800 °C, the heating rate was 5 °C / min, and the holding time was 12 h. SEM photos of the surface were taken for the coated cathode materials sintered in Examples 1-3 and Comparative Example 2 respectively.

[0191] Figure 1 、 Figure 3 、 Figure 5 、 Figure 7They are the surface SEM images of the nano-manganese tetraoxide prepared in Examples 1-3 and Comparative Example 2 respectively; among them, the magnification of the left figure is smaller, and the magnification of the right figure is larger. It can be seen from the left figure above that both Examples 1-3 and Comparative Example 2 are amorphous powders formed by particle agglomeration; it can be seen from the right figure above that the particles in Examples 1-3 are granular, with relatively uniform particle sizes, and the overall particle size is relatively small; Comparative Example 2 is mainly granular particles, containing a small amount of large flaky particles, and the particle size uniformity is poor.

[0192] Figure 2 , Figure 4 , Figure 6 , Figure 8 They are the surface SEM photos of the sintered nano-manganese tetraoxide prepared in Examples 1-3 and Comparative Example 2 after being coated on the surface of the cathode material. Figure 9 It is the surface SEM photo of the cathode material before coating in Blank Group 1; among them, Figure 2 , Figure 4 , Figure 6 the surfaces of the larger particles are smooth, similar to the surface morphology of the Figure 9 cathode material, that is, the nano-level manganese tetraoxide melts onto the surface of the cathode material during sintering to form a relatively smooth protective layer, and the battery prepared therefrom has good cycle performance; but Figure 8 a large number of tiny particles adhere to the surfaces of the larger cathode material particles in

[0193] First, weigh 2.0 g of the coated cathode material after coating and sintering with the nano-manganese tetraoxide in Examples 1-6 and Comparative Examples 1-2, add 40 mL of deionized water, and magnetically stir for 10 minutes until fully dispersed to obtain a suspension; then seal the suspension and stir it at 500-1000 rpm for 5 minutes, and then centrifuge it at 3000-5000 rpm for 10 minutes, and take the supernatant; then directly measure the pH value of the supernatant using a calibrated pH meter.

[0194] The coated cathode materials after coating and sintering with the nano-manganese tetraoxide in Examples 1-6 and Comparative Examples 1-2 after sintering, and Blank Group 1 (the sodium-ion cathode material of nano-manganese tetraoxide before coating) are processed and assembled into coin cells. The formulation ratio is coated cathode material:PVDF:SP = 90:5:5 (mass ratio); the anode material is a sodium metal sheet; the electrolyte is 1.0 mol / L of NaPF 6 :EC:DMC:EMC = 1:1:1 (volume ratio); the battery model is a CR2032 coin cell.

[0195] The assembled coin-type battery was tested using a Blue Power test system; the electrochemical performance was tested at 25 °C and 2.0 - 4.3 V, with 1C = 150 mAh / g.

[0196] The test results of the electrochemical performance parameters are shown in Table 2.

[0197] Table 2 Test data 1 for the cathode material of NaNi 0.3 Fe 0.4 Mn 0.3 O 2

[0198]

[0199] Note: Example 1 + NFM is the nano-level manganese tetraoxide-coated NaNi 0.3 Fe 0.4 Mn 0.3 O 2 cathode material after sintering of the coated cathode material, and other examples and comparative examples are similar.

[0200] The angle of repose of the nano-level manganese tetraoxide prepared in Examples 1 - 6 of this application is 32° - 48°, and its fluidity and product dispersibility are good. When used in batteries, the nano-manganese tetraoxide can be uniformly coated on the secondary particles of the cathode material (NaNi 0.3 Fe 0.4 Mn 0.3 O 2 ), which can improve the cycle performance and initial Coulombic efficiency of the battery prepared from the sintered coated cathode material.

[0201] Residual alkali on the surface of the cathode material: The residual alkali on the surface of the cathode material is related to the pH value. The higher the pH value, the higher the surface residual alkali. The poor conductivity of the residual alkali will cause the reduction of the 0.1C initial Coulombic efficiency of the cathode material, and when the residual alkali content is too high, it is easy to cause cross-linking of the PVDF colloidal solution in the binder during the preparation of the electrode sheet, affecting the homogenization and coating processes, and ultimately resulting in poor cycle performance of the battery. Therefore, the determination of the residual alkali content is of great significance for the development and application of the cathode material. If the pH value > 11.5 or the total residual alkali > 3%, it indicates that the surface stability of the cathode material is insufficient and further modification is required.

[0202] ​Compared with the blank group 1, the surface residual alkali amount of the coated cathode materials using the nano-manganese tetraoxide of Examples 1-6 and Comparative Examples 1-2 is low (the corresponding pH value decreases). The possible reason is speculated that the use of nano-manganese tetraoxide to coat the sodium-ion cathode material reduces the residual alkali. Compared with Comparative Examples 1-2, the surface residual alkali amount of the coated cathode materials using the nano-manganese tetraoxide of Examples 1-6 in this application is low. The possible reason is speculated that the angle of repose of nano-manganese tetraoxide is in the range of 32°-48°. After coating the sodium-ion cathode material, the coating effect is better. Compared with Examples 5-6, the surface residual alkali amount of the coated cathode materials using the nano-manganese tetraoxide of Examples 1-4 in this application is low. The possible reason is speculated that the angle of repose of nano-manganese tetraoxide is in the range of 35°-45°. After coating the sodium-ion cathode material, the coating effect is better.

[0203] Electrochemical data: Compared with the blank group 1, the batteries prepared with the coated cathode materials using the nano-manganese tetraoxide of Examples 1-6 and Comparative Examples 1-2 show better capacity retention rate at 1C for 100 cycles and initial Coulombic efficiency at 0.1C. The possible reason is speculated that after sintering, the nano-manganese tetraoxide coated cathode material can partially / entirely melt on the surface of the sodium-ion cathode material, isolating the electrolyte and reducing side reactions.

[0204] Compared with Examples 1-6, the batteries prepared by sintering the coated cathode materials using the nano-manganese tetraoxide of Comparative Example 1 show poor capacity retention rate at 1C for 100 cycles and initial Coulombic efficiency at 0.1C. The possible reason is speculated that its particle size is small, and it is easy to fall off or agglomerate after coating, resulting in a poor coating effect; the batteries prepared by sintering the coated cathode materials using the nano-manganese tetraoxide of Comparative Example 2 show poor capacity retention rate at 1C for 100 cycles and initial Coulombic efficiency at 0.1C. The possible reason is speculated that it has large particles in the shape of polyhedral cones or flakes, and the particle size distribution K 95 is large, the angle of repose is too large, and the fluidity is poor, resulting in uneven coating.

[0205] Compared with Comparative Examples 1-2, the batteries prepared by sintering the coated cathode materials using the nano-manganese tetraoxide of Examples 1-3 in this application show better capacity retention rate at 1C for 100 cycles and initial Coulombic efficiency at 0.1C. The possible reason is speculated that the angle of repose of the nano-manganese tetraoxide used for coating is 32°-48°, and the coating effect is better after coating. Compared with Examples 1-3, the batteries prepared by sintering the coated cathode materials using the nano-manganese tetraoxide of Example 4 show a lower capacity retention rate at 1C for 100 cycles and initial Coulombic efficiency at 0.1C. The possible reason is speculated that its D 50is too large, and the coating uniformity is slightly poor; after the nano-manganese tetraoxide-coated cathode material of Example 5 is sintered and made into a battery, the capacity retention rate at 1C for 100 cycles and the initial Coulomb efficiency at 0.1C are low. It is speculated that the possible reason is its D 50 is too small, and the adhesion of the 1C 100-cycle capacity retention rate and 0.1C initial Coulomb efficiency of nano-manganese tetraoxide is poor; the battery prepared by sintering the nano-manganese tetraoxide-coated cathode material of Example 6 shows a low 1C 100-cycle capacity retention rate. It is speculated that the possible reason is that its sodium content is too high and the residual alkali on the surface of the sintered coated cathode material is too high.

[0206] Residual alkali and electrochemical performance test 2

[0207] The nano-manganese tetraoxide material prepared in Example 1 was mixed with a lithium-ion cathode material (LiNi 0.8 Co 0.2 Mn 0.2 O 2 ) at a mass ratio of 2wt%:1, and then sintered at a sintering temperature of 800°C, a heating rate of 5°C / min, and a holding time of 12h.

[0208] First, weigh 2.0 g of the sintered coated cathode material of nano-manganese tetraoxide using Example 1, add 40 mL of deionized water, and stir magnetically for 10 minutes until fully dispersed to obtain a suspension; then seal the suspension and stir it at 500 - 1000 rpm for 5 minutes, and then centrifuge it at 3000 - 5000 rpm for 10 minutes to take the supernatant; then directly measure the pH value of the supernatant using a calibrated pH meter.

[0209] The sintered coated cathode material of nano-manganese tetraoxide using Example 1 and the blank group 2 (the lithium-ion cathode material of nano-manganese tetraoxide before coating) were processed and assembled into a button cell. The formulation ratio was coated cathode material (LiNi 0.8 Co 0.2 Mn 0.2 O 2 ):PVDF:SP = 92.5:5:2.5 (mass ratio); the negative electrode material was a lithium metal sheet; the electrolyte was 1.0 mol / L LiPF 6 , where LiPF 6 :EC:DMC = 1:1:1 (volume ratio); the battery model was a CR2032 button cell.

[0210] The assembled button cell was tested using a blue battery testing system; the electrochemical performance was tested at 25°C and 2.0 - 4.3V, and 1C = 200 mAh / g.

[0211] The test results of the electrochemical performance parameters are shown in Table 3.

[0212] Table 3 shows the test data of the positive electrode material LiNi 0.8 Co 0.2 Mn 0.2 O 2 for Test Data 2

[0213]

[0214] Note: Example 1 + NCM refers to the coated positive electrode material obtained by sintering the nano-level manganese tetroxide-coated positive electrode material of Example 1, LiNi 0.8 Co 0.2 Mn 0.2 O 2 and other examples and comparative examples are similar.

[0215] Residual alkali on the surface of the positive electrode material: Compared with the blank group 2, the amount of residual alkali on the surface of the coated positive electrode material sintered with the nano-manganese tetroxide-coated positive electrode material (LiNi 0.8 Co 0.2 Mn 0.2 O 2 ) of Example 1 is lower. It is speculated that the possible reason is that the angle of repose of nano-manganese tetroxide is in the range of 32° - 48°, and the coating effect is better after coating the lithium-ion positive electrode material.

[0216] Electrochemical data: Compared with the blank group 2, the coated positive electrode material prepared by sintering the nano-manganese tetroxide-coated positive electrode material of Example 1 in this application shows better capacity retention rate at 1C for 100 cycles and initial Coulomb efficiency at 0.1C. It is speculated that the possible reason is that the angle of repose of the nano-manganese tetroxide used for coating is in the range of 32° - 48°, and the coating effect is better after coating.

[0217] Residual Alkali and Electrochemical Performance Test 3

[0218] Mix the nano-manganese tetroxide material prepared in Example 1 with the lithium-ion positive electrode material (LiFePO 4 ) at a mass ratio of 2wt%:1, and then perform high-speed mixing and sintering. The sintering temperature is 400°C, the heating rate is 5°C / min, and the holding time is 12h.

[0219] First, weigh 2.0 g of the sintered coated positive electrode material using the nano-manganese tetroxide of Example 1, add 40 mL of deionized water, and stir magnetically for 10 minutes until fully dispersed to obtain a suspension; then seal the suspension and stir it at 500 - 1000 rpm for 5 minutes, and then centrifuge it at 3000 - 5000 rpm for 10 minutes to take the supernatant; then directly measure the pH value of the supernatant using a calibrated pH meter.

[0220] The coated cathode material after sintering of the nano-manganese tetraoxide of Example 1 and the lithium-ion cathode material of blank group 3 (nano-manganese tetraoxide before coating) were processed and assembled into a button cell. The formulation ratio was coated cathode material (LiFePO 4 ):PVDF:SP = 90:5:5 (mass ratio); the anode material was a lithium metal sheet; the electrolyte was 1.0 mol / L LiPF 6 , where LiPF 6 :EC:DMC = 1:1:1 (volume ratio); the battery model was a CR2032 button cell.

[0221] The assembled button cells were tested using a Blue Power test system; electrochemical performance tests were carried out at 25 °C and 2.0 - 3.75 V, with 1C = 160 mAh / g.

[0222] The test results of the electrochemical performance parameters are shown in Table 4.

[0223] Table 4 Test data of the cathode material LiFePO 4 3

[0224]

[0225] Note: Example 1 + LFP is the coated cathode material after sintering of the nano-level manganese tetraoxide coated cathode material of Example 1 with LiFePO 4 , and other examples and comparative examples are similar.

[0226] Electrochemical data: Compared with blank group 3, the coated cathode material prepared from the nano-manganese tetraoxide coated cathode material (LiFePO 4 ) of Example 1 of the present application showed a better capacity retention rate at 1C for 500 cycles after being made into a battery. It is speculated that the possible reason is that the angle of repose of the nano-manganese tetraoxide used for coating is in the range of 32° - 48°, and the effect after coating is better.

[0227] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A nano-scale manganese tetraoxide, characterized in that: The repose angle of the nano-scale trimanganese tetraoxide is 32°-48°.

2. The nanometer-scale manganese tetraoxide according to claim 1, characterized in that: At least one of the following conditions is met: a. The angle of repose of the nano-manganese tetroxide is 35°-45°; b. The mass content of Na in the nano-sized manganese tetraoxide is ≤100ppm; optionally, the mass content of Na in the nano-sized manganese tetraoxide is 10ppm-80ppm.

3. The nanometer-scale manganese tetraoxide according to claim 1, characterized in that: When the particle size of the nano manganese tetraoxide is measured by scanning electron microscopy, at least one of the following conditions is met: a. The average particle size Mz of the nano-scale manganese tetraoxide is 15nm-100nm; optionally, Mz is 50nm-95nm; b. The nano-manganese oxide is an amorphous powder consisting of multiple particles; c. The nano-sized manganese tetraoxide particles are granular.

4. The nanometer manganese tetraoxide according to claim 1, characterized in that: When the particle size of the nano manganese tetraoxide is measured by laser particle size analysis diffraction method, at least one of the following conditions is met: a. The particle size D of the nano-manganese tetraoxide 50 ≤500nm; Optionally, the particle size D of the nano-manganese tetraoxide 50 200nm-500nm; b. The particle size D0 of the nano-manganese tetroxide is ≤100nm; optionally, the average particle size D0 of the nano-manganese tetroxide is 60nm-100nm; c. The particle size D5 of the nano-manganese tetraoxide is 110nm-170nm; d. The particle size D of the nano-manganese tetraoxide 95 is 600nm-1500nm; Optionally, the particle size D of the nano-manganese tetraoxide 95 900nm-1500nm; e. The particle size D of the nano-manganese tetraoxide 100 ≤2000nm; the particle size D of the nano-manganese tetraoxide 100 1200nm-1800nm; f. The particle size distribution K of the nano-scale manganese tetraoxide 95 =(D 95 -D5) / D 50 It is 1.9-2.

6.

5. The nanometer-scale manganese tetraoxide according to any one of claims 1 to 4, characterized in that: At least one of the following conditions is met: a. The specific surface area of ​​the nano-manganese tetraoxide is 14m 2 / g-30m 2 / g; Optionally, the BET specific surface area of ​​the nano-manganese tetraoxide is 16m 2 / g-27m 2 / g; b. The tap density TD of the nano-manganese tetraoxide is 0.5 g / cm 3 -0.9g / cm 3 Optionally, the tap density TD of the nano-manganese tetraoxide is 0.6 g / cm 3 -0.8g / cm 3 ; c. The bulk density AD of the nano-manganese tetroxide is 0.25 g / cm 3 -0.45g / cm 3 .

6. A method for preparing nano-manganese tetraoxide, characterized in that: include: The mixed solution of the soluble manganese salt and the oxidant and the precipitant solution are mixed and reacted, and the slurry after the reaction is post-treated to obtain nano-scale manganese tetraoxide.

7. The preparation method according to claim 6, characterized in that: Passing the mixed solution of the soluble manganese salt and the oxidant and the precipitant solution into the base liquid for reaction; Wherein, the base liquid includes the precipitant solution and / or a mixed solution of the soluble manganese salt and the oxidant.

8. The preparation method according to claim 7, characterized in that: At least one of the following conditions is met: A. The soluble manganese salt includes a soluble divalent manganese salt; optionally, the divalent manganese salt includes one or more of MnCl2, MnSO4, and Mn(NO3)2; optionally, the average valence of Mn in the soluble manganese salt is ≤2.66; optionally, the average valence of Mn in the soluble manganese salt is 2.0-2.2; B. the oxidant comprises one or more of hydrogen peroxide, sodium persulfate, and ammonium persulfate; C. preparing a mixed solution of the soluble manganese salt and the oxidant according to a molar ratio of the oxidant to the soluble manganese salt of 1:(6-11); wherein the manganese ion concentration in the soluble manganese salt solution is 1 mol / L to 3 mol / L; and the mass fraction of the oxidant solution is 5 wt% to 35 wt%; D. placing the prepared mixed solution of the soluble manganese salt and the oxidant for 5-60 minutes before passing it into the base solution; alternatively, placing the prepared mixed solution of the soluble manganese salt and the oxidant for 10-40 minutes before passing it into the base solution; E. The precipitant solution is one or more of potassium hydroxide solution, sodium hydroxide solution, and ammonia water; the mass fraction of the precipitant solution is 25wt% to 45wt%; F. the pH value of the base solution is 6.0-12.0; G. The flow ratio of the mixed solution of the soluble manganese salt and the oxidant to the precipitant solution is 1:(0.3-0.7); H. the flow rate of the mixed solution of the soluble manganese salt and the oxidant is 15% / h-21% / h of the volume of the reactor; I. The reaction temperature is 10°C-60°C; optionally, the reaction temperature is 40°C-60°C; J. The stirring speed of the reaction is 400rpm-1200rpm; optionally, the stirring speed of the reaction is 700rpm-900rpm; K. the reaction is stopped after the volume of the slurry reaches 60%-90% of the volume of the reactor; L. The post-treatment includes solid-liquid separation and water washing of the slurry to obtain a washed product, and then drying the washed product, crushing and sieving it to obtain nano-scale manganese tetraoxide; the crushing time is 20min-40min.

9. A coated positive electrode material, characterized in that: The positive electrode material is obtained by coating the positive electrode material with the nano-manganese tetroxide according to any one of claims 1 to 5 and then sintering the coated positive electrode material; optionally, the amount of the nano-manganese tetroxide is 1wt%-5wt% of the positive electrode material before coating; optionally, the positive electrode material is a lithium ion battery positive electrode material and / or a sodium ion battery positive electrode material.

10. A battery, characterized in that: Comprising the coated positive electrode material as described in claim 9.

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