Cobalt carbonate, cobalt tetraoxide, positive electrode material and preparation method

Abstract

The present application provides a cobalt carbonate, cobalt tetroxide, a cathode material and a preparation method thereof, relating to the field of new energy technologies. The pore volume of the cobalt carbonate provided by the present application is 0.01 - 0.10 cm³ / g, with abundant micropores and uniform pore distribution. During the sintering process, the cobalt carbonate shrinks rapidly and uniformly, and the prepared cobalt tetroxide has high density, uniform element distribution, uniform pore distribution, and a pore volume of 0.0010 - 0.0090 cm³ / g. Through the distribution of a large number of micropores and mesopores, the material activity is improved, and the discharge capacity and cycle performance of the battery are enhanced.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to cobalt carbonate, cobalt tetroxide, positive electrode material and preparation method thereof. Background Art

[0002] With the upgrading of electronic devices in the 3C field, especially the significant improvement of the performance of smart phones in various aspects, higher requirements are put forward for the battery capacity, cycle and safety performance of the equipment. The existing technology generally adopts the method of increasing the charging cut-off voltage and increasing the compaction density of the positive electrode material to improve the energy density of lithium-ion batteries and improve their cycle performance, but there are few improvements on the structure and physicochemical indicators of the precursors of the positive electrode materials such as cobalt carbonate and the cobalt tetroxide products prepared therefrom. Summary of the invention

[0003] The purpose of the present application is to provide cobalt carbonate, cobalt tetroxide, a positive electrode material and a preparation method, aiming to improve battery performance by improving the structural properties of the precursor of the positive electrode material such as cobalt carbonate and the cobalt tetroxide prepared therefrom.

[0004] To achieve the above objectives, the present application provides a cobalt tetraoxide having a porous interior, uniform pore distribution, and a porosity distribution fitting R 2 Value>0.9.

[0005] Preferably, the pore size of cobalt trioxide is 1.0 to 4.5 nm;

[0006] Preferably, the specific surface area of ​​cobalt tetraoxide is 1 to 5 m 2 / g;

[0007] Preferably, the tap density of cobalt oxide is 2.6 to 3.0 g / cm 3 ;

[0008] Preferably, the median particle size of cobalt oxide is 14 to 19 μm;

[0009] Preferably, the pore volume is 0.0010 to 0.0090 cm 3 / g.

[0010] Preferably, the cobalt oxide includes a doping element, and the doping element is selected from one or more of Al, Mg, Ni, Mn, La, Zr, Ti, and W;

[0011] Preferably, the doping mass contents of the doping elements are: Al: 0.40-1.20%, Mg: 0.08-0.50%, Ni: 0.10-3.00%, Mn: 0.10-3.00%, La: 0.05-0.30%, Zr: 0.10-0.30%, Ti: 0.05-0.30%, W: 0.10-0.50%;

[0012] Preferably, the pore volume is 0.0013 to 0.0020 cm 3 / g.

[0013] The present application also provides a cobalt carbonate for preparing the above-mentioned cobalt tetroxide, which has a uniform internal pore size and a uniform pore distribution, and the pore volume of the cobalt carbonate is 0.01 to 0.10 cm 3 / g.

[0014] Preferably, the pore size of cobalt carbonate is 1.0 to 4.0 nm;

[0015] Preferably, the specific surface area of ​​cobalt carbonate is 40 to 130 m 2 / g;

[0016] Preferably, the tap density of cobalt carbonate is 1.4 to 2.0 g / cm 3 ;

[0017] Preferably, the median particle size of the cobalt carbonate is 16 to 22 μm.

[0018] The present application also provides a method for preparing cobalt carbonate, comprising:

[0019] The cobalt salt solution and the precipitant solution are added to a reactor containing a base liquid for reaction, the flow rate of the cobalt salt solution increases with the increase of the particle size of the material, the stirring speed of the reactor decreases with the increase of the particle size of the material, and the reaction is continued until the target particle size is reached to obtain a cobalt carbonate slurry;

[0020] The cobalt carbonate slurry is centrifuged and washed to obtain cobalt carbonate.

[0021] Preferably, the cobalt salt solution is selected from a cobalt sulfate solution and / or a cobalt chloride solution; the precipitant solution is selected from an ammonium bicarbonate solution and / or a sodium carbonate solution; and the base solution is selected from an ammonium bicarbonate solution and / or a sodium carbonate solution;

[0022] Preferably, the cobalt concentration in the cobalt salt solution is 90-130 g / L, the concentration of the precipitant solution is 190-230 g / L; the concentration of the base solution is 5-50 g / L;

[0023] Preferably, the cobalt salt solution includes a doping element, the doping element is selected from one or more of Al, Mg, Ni, Mn, La, Zr, Ti, and W, and the doping element exists in the form of sulfate;

[0024] Preferably, the doping mass contents of the doping elements in cobalt carbonate are: Al: 0.26-0.70%, Mg: 0.05-0.33%, Ni: 0.06-2.00%, Mn: 0.06-2.00%, La: 0.03-0.20%, Zr: 0.06-0.20%, Ti: 0.03-0.20%, W: 0.06-0.33%.

[0025] Preferably, the flow rate of the cobalt salt solution is in the range of 2-6% / h of the available volume of the reactor, and the stirring speed of the reactor is in the range of 300-100 r / min;

[0026] Preferably, the target particle size of cobalt carbonate is 16-22 μm.

[0027] The present application also provides a method for preparing cobalt tetroxide, comprising:

[0028] Providing the above-mentioned cobalt carbonate, or the cobalt carbonate prepared by the above-mentioned method for preparing cobalt carbonate;

[0029] Cobalt carbonate is sintered to obtain cobalt tetroxide.

[0030] Preferably, the sintering temperature is 700-850°C.

[0031] Preferably, the cobalt carbonate is preheated before sintering, the preheating temperature is 200-500° C., and the preheating time is 20 min-60 min;

[0032] Preferably, when a rotary kiln is used for sintering, the rotation frequency of the rotary kiln tube is 0.5-1.5 r / min, and the material layer thickness is ≤16 cm.

[0033] The present application also provides a positive electrode material, which is lithium cobalt oxide obtained by calcining the above-mentioned cobalt trioxide and a lithium source;

[0034] Preferably, the molar ratio of the lithium source to cobalt tetroxide is 1 to 1.05;

[0035] Preferably, the calcination temperature is 900-1200° C., and the calcination time is 20-30 hours.

[0036] Compared with the prior art, the beneficial effects of this application include:

[0037] The pore volume of cobalt carbonate provided in this application is 0.01 to 0.10 cm 3 / g, with abundant micropores and uniform pore distribution. Cobalt carbonate shrinks rapidly and evenly during the sintering process. The prepared cobalt tetroxide has uniform distribution of elements and pores, and the pore volume is 0.0010~0.0090cm 3 / g, on the one hand, it can provide a large number of micropores and mesopores, and on the other hand, it can maintain a certain density of the particles. Through the distribution of a large number of micropores and mesopores, the activity of the material is improved, and the discharge capacity and cycle performance of the battery are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a scanning electron microscope morphology image of the cobalt carbonate particles of Example 1;

[0039] Figure 2 This is a scanning electron microscope morphology image of a cross section of the cobalt carbonate particles of Example 1;

[0040] Figure 3 This is a scanning electron microscope morphology image of the cobalt tetroxide of Example 1;

[0041] Figure 4 This is a scanning electron microscope morphology image of the cross section of cobalt tetroxide in Example 1;

[0042] Figure 5 This is a diagram showing the Al component analysis results of the cobalt tetroxide micro-area of ​​Example 1;

[0043] Figure 6 is a scanning electron microscope morphology image of the cobalt carbonate particles of Example 2;

[0044] Figure 7 This is a scanning electron microscope morphology image of cobalt tetroxide in Example 2;

[0045] Figure 8 This is a scanning electron microscope morphology image of the cross section of cobalt tetroxide in Example 2;

[0046] Fig. 9 This is a graph showing the micro-area Ni component analysis results of cobalt tetroxide in Example 2;

[0047] Fig.10 This is a diagram showing the results of micro-area Mn component analysis of cobalt tetroxide in Example 2;

[0048] Fig.11 is a scanning electron microscope morphology image of the cobalt carbonate particles of Example 3;

[0049] Fig.12 This is a scanning electron microscope morphology image of a cross section of the cobalt carbonate particles of Example 3;

[0050] Fig.13 This is a scanning electron microscope morphology image of cobalt tetroxide of Example 3;

[0051] Fig.14 This is a scanning electron microscope morphology image of the cross section of cobalt tetroxide in Example 3;

[0052] Fig.15This is a correlation coefficient diagram of the regional area and pore area of ​​cobalt tetroxide in Example 3;

[0053] Fig.16 This is a diagram showing the Al component analysis results of the micro-area of ​​cobalt tetroxide in Example 3;

[0054] Fig.17 This is a diagram showing the micro-region Mg component analysis results of cobalt tetraoxide in Example 3;

[0055] Fig.18 is a scanning electron microscope morphology image of the cobalt carbonate particles of Example 4;

[0056] Fig.19 This is a scanning electron microscope morphology image of the cobalt tetroxide of Example 4;

[0057] Fig. 20 This is a scanning electron microscope morphology image of the cross section of cobalt tetroxide in Example 4;

[0058] Fig.21 This is a diagram showing the results of micro-area Al component analysis of cobalt tetroxide in Example 4;

[0059] Fig. 22 This is a scanning electron microscope morphology image of the cobalt carbonate particles of Comparative Example 1;

[0060] Fig.23 This is a scanning electron microscope morphology image of cobalt tetroxide of Comparative Example 1;

[0061] Fig.24 This is a scanning electron microscope morphology image of the cross section of the cobalt tetroxide of Comparative Example 1. DETAILED DESCRIPTION

[0062] The present application provides a cobalt tetroxide, which is porous inside, the pore distribution of the cobalt tetroxide is uniform, and the porosity distribution of the cobalt tetroxide is fitted by R 2 Value>0.9, the pore volume of cobalt tetraoxide is 0.0013~0.0020cm 3 / g. Cobalt trioxide is the raw material for preparing lithium cobalt oxide positive electrode materials. Cobalt trioxide is calcined with lithium source to obtain lithium cobalt oxide. The performance of cobalt trioxide determines the performance of lithium cobalt oxide positive electrode materials and is inherited.

[0063] The porosity of the cobalt tetroxide of the present application is 10-45%, and the porosity of cobalt tetroxide = (pore area of ​​the internal cross-section of cobalt tetroxide / cross-section area of ​​cobalt tetroxide) * 100%). The internal porosity of cobalt tetroxide is a range value, and is not limited to a specific value. The porosity of different parts may be different. For example, the porosity can be 10-20%, 20-30%, or 30-45%. In further examples, the porosity can be, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%.

[0064] The porosity distribution fitting R of the cobalt tetraoxide in this application 2 Value>0.9, porosity distribution fitting R 2 It is used to indicate the uniformity of pore distribution. The specific verification steps are as follows:

[0065] Step 1: Treat a single cobalt oxide particle as a sphere, and divide the circle into n (n≥3) concentric circles according to the cross-section circle of the sphere;

[0066] Step 2: Calculate the area of ​​each concentric circle and the difference between the areas of adjacent concentric circles, as well as the pore area of ​​the corresponding area;

[0067] Step 3: Calculate the change x of the cross-sectional area in different regions and the change y of the pore area in the corresponding region;

[0068] Step 4: Establish a linear relationship between x and y and calculate the correlation coefficient R 2 ;

[0069] When R 2 When R 2 When R is between 0.9 and 0.95, the pore distribution is considered to be relatively uniform. 2 When ≥0.95, the pore distribution is considered to be highly uniform;

[0070] When R 2 When <0.9, the pore distribution is considered to be uneven.

[0071] The pore volume of the cobalt tetraoxide in the present application is 0.0010 to 0.0090 cm 3 / g, for example, the pore volume of cobalt tetraoxide can be 0.0010 to 0.0015 cm 3 / g, 0.0013~0.0017cm 3 / g, 0.0015~0.0020cm 3 / g, 0.0016~0.0020cm 3 / g, 0.0020~0.0030cm 3 / g, 0.0030~0.0040cm 3 / g, 0.0040~0.0050cm 3 / g, 0.0050~0.0070cm 3 / g, or 0.0070~0.0090cm 3 In a further example, the pore volume of cobalt tetraoxide can be 0.0013 cm 3 / g, 0.0014cm 3 / g, 0.0015cm 3 / g, 0.0016cm 3 / g, 0.0017cm 3 / g, 0.0018cm 3 / g, 0.0019cm 3 / g, 0.0020cm 3 / g, 0.0025cm 3 / g, 0.0030cm 3 / g, 0.0034cm 3 / g, 0.0039cm 3 / g, 0.0043cm 3 / g, 0.0047cm 3 / g, 0.0052cm 3 / g, 0.0065cm 3 / g, 0.0067cm 3 / g, 0.0071cm 3 / g, 0.0076cm 3 / g, 0.0081cm 3 / g, or 0.0085cm 3 / g.

[0072] The pore distribution of the cobalt trioxide in this application is highly uniform. In the process of synthesizing lithium cobalt oxide positive electrode materials, a large number of uniformly distributed micropores and mesopores provide a permeation path for the reaction process of lithium salts to enter the interior of the particles, thereby improving the reaction activity, improving the development of lithium cobalt oxide crystal cells, improving the stability of the crystal structure, and improving the cycle performance. The appropriate pore volume can improve the electrochemical performance of the material while avoiding a significant reduction in the tap density and the compacted density, so that the material has a good volume energy density.

[0073] Preferably, the pore size of the cobalt oxide is 1.0 to 4.5 nm. For example, the pore size of the cobalt oxide may be 1.0 to 3.0 nm, 2.0 to 4.5 nm, 1.0 to 2.5 nm, or 2.0 to 4.0 nm. In a further example, the pore size of the cobalt oxide may be 1.0 nm, 2.0 nm, 3.0 nm, 4.0 nm, or 4.5 nm.

[0074] A smaller pore size can ensure the presence of a large number of channels inside the particles while ensuring a smaller pore volume, a higher tap density, and an increase in the specific capacity of the material.

[0075] Preferably, the specific surface area of ​​cobalt tetraoxide is 1 to 5 m 2 For example, the specific surface area of ​​cobalt tetraoxide can be 1.0 to 2.0 m 2 / g, 1.5~3.5m 2 / g, 2.0~4.0m 2 / g, or 3.0~5.0m 2 / g. In a further example, the specific surface area of ​​cobalt tetraoxide can be 1.0m 2 / g, 2.0m 2 / g, 3.0m 2 / g, 4.0m 2 / g, or 5.0m 2 / g.

[0076] Appropriate specific surface area can improve material activity.

[0077] Preferably, the tap density of cobalt oxide is 2.6 to 3.0 g / cm 3 For example, the tap density of cobalt oxide can be 2.6 to 2.7 g / cm 3 2.7~3.0g / cm 3 2.7~2.8g / cm 3 , or 2.8~3.0g / cm 3 In a further example, the tap density of cobalt oxide can be 2.6 g / cm 3 , 2.65g / cm 3 , 2.7g / cm 3 , 2.75g / cm 3 , 2.8g / cm 3 , 2.85g / cm 3 , 2.9g / cm 3 , 2.95g / cm 3 , or 3.0g / cm 3 .

[0078] Cobalt tetroxide has a higher tap density, which can increase the compaction density of the positive electrode material lithium cobalt oxide and improve the specific capacity of the material.

[0079] Preferably, the median particle size of the cobalt oxide is 14 to 19 μm. For example, the median particle size of the cobalt oxide may be 14 to 16 μm, 15 to 18 μm, or 17 to 19 μm. In a further example, the median particle size of the cobalt oxide may be 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, or 19 μm.

[0080] Preferably, the cobalt oxide includes a doping element, and the doping element is selected from one or more of Al, Mg, Ni, Mn, La, Zr, Ti, and W.

[0081] Preferably, the doping mass contents of the doping elements are: Al: 0.40-1.20%, Mg: 0.08-0.50%, Ni: 0.10-3.00%, Mn: 0.10-3.00%, La: 0.05-0.30%, Zr: 0.10-0.30%, Ti: 0.05-0.30%, W: 0.10-0.50%.

[0082] The present application also provides a cobalt carbonate, which is a raw material for preparing cobalt tetroxide. The cobalt carbonate is used to prepare the above cobalt tetroxide. The internal pore size of the cobalt carbonate is consistent, that is, the difference between the pore size detected in different growth processes of the cobalt carbonate particles and the pore size at the end of the cobalt carbonate is less than 20%; the pore distribution of the cobalt carbonate is uniform, and the pore volume of the cobalt carbonate is 0.01-0.10cm 3 / g. For example, the pore volume of cobalt carbonate can be 0.01 to 0.04 cm 3 / g, 0.02~0.06cm 3 / g, or 0.05~0.09cm 3 In a further example, the pore volume of cobalt carbonate may be 0.01 cm 3 / g, 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g, or 0.09cm 3 / g.

[0083] Preferably, the pore size of the cobalt carbonate is 1.0 to 4.0 nm. For example, the pore size of the cobalt carbonate may be 1.0 to 3.0 nm, 2.0 to 4.0 nm, or 3.0 to 4.0 nm. In a further example, the pore size of the cobalt carbonate may be 1.0 nm, 2.0 nm, 3.0 nm, or 4.0 nm.

[0084] Preferably, the specific surface area of ​​cobalt carbonate is 40 to 130 m 2 / g. For example, the specific surface area of ​​cobalt carbonate can be 40 to 60 m 2 / g, 50~80m 2 / g, 70~100m 2 / g, or 110~130m 2 / g. In a further example, the specific surface area of ​​cobalt carbonate can be 40m 2 / g, 45m 2 / g, 50m 2 / g, 55m 2 / g, 60m 2 / g, 65m 2 / g, 70m 2 / g, 75m 2 / g, 80m 2 / g, 85m 2 / g, 90m 2 / g, 95m 2 / g、100m 2 / g, 110m 2 / g, 115m 2 / g, 120m 2 / g, or 130m 2 / g.

[0085] Preferably, the tap density of cobalt carbonate is 1.4 to 2.0 g / cm 3 For example, the tap density of cobalt carbonate can be 1.4 to 1.7 g / cm 3 1.6~1.8g / cm 3 , or 1.5~2.0g / cm 3 In a further example, the tap density of cobalt carbonate may be 1.4 g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , or 2.0g / cm 3 .

[0086] Preferably, the median particle size of cobalt carbonate is 16 to 22 μm. For example, the median particle size of cobalt carbonate may be 16 to 18 μm, 17 to 20 μm, or 18 to 22 μm. In a further example, the median particle size of cobalt carbonate may be 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, 21.5 μm, or 22 μm.

[0087] The present application also provides a method for preparing cobalt carbonate, comprising:

[0088] The cobalt salt solution and the precipitant solution are added to a reactor containing a base liquid for reaction, the flow rate of the cobalt salt solution increases with the increase of the particle size of the material, the stirring speed of the reactor decreases with the increase of the particle size of the material, and the reaction is continued until the target particle size is reached to obtain a cobalt carbonate slurry;

[0089] The cobalt carbonate slurry is centrifuged and washed to obtain cobalt carbonate.

[0090] Specifically, the cobalt salt solution is selected from cobalt sulfate solution and / or cobalt chloride solution; the precipitant solution is selected from ammonium bicarbonate solution and / or sodium carbonate solution; the base solution is selected from ammonium bicarbonate solution and / or sodium carbonate solution;

[0091] The cobalt concentration in the cobalt salt solution is 90-130 g / L, for example, it can be (90, 91, 93, 95, 96, 98, 100, 102, 105, 106, 108, 110, 112, 115, 116, 118, 120, 122, 123, 126, 128 or 130) g / L.

[0092] Preferably, the concentration of the precipitant solution is 190-230 g / L; the concentration of the base solution is 5-50 g / L;

[0093] Preferably, the cobalt salt solution includes a doping element, and the doping element is selected from one or more of Al, Mg, Ni, Mn, La, Zr, Ti, and W;

[0094] Preferably, the doping mass contents of the doping elements in the cobalt carbonate are: Al: 0.26-0.70%, Mg: 0.05-0.33%, Ni: 0.06-2.00%, Mn: 0.06-2.00%, La: 0.03-0.20%, Zr: 0.06-0.20%, Ti: 0.03-0.20%, W: 0.06-0.33%;

[0095] In a preferred embodiment, the flow rate of the cobalt salt solution is in the range of 2% to 6% / h of the available volume of the reactor, for example, the flow rate of the cobalt salt solution can be 2% / h, 3% / h, 4% / h, 5% / h, or 6% / h of the available volume of the reactor. The stirring speed of the reactor is in the range of 300 to 100 r / min, for example, (300, 250, 200, 150 or 100) r / min.

[0096] Preferably, the target particle size of cobalt carbonate is 16-22 μm.

[0097] The present application also provides a method for preparing cobalt tetroxide, comprising:

[0098] Providing the above-mentioned cobalt carbonate, or the cobalt carbonate prepared by the above-mentioned method for preparing cobalt carbonate;

[0099] Cobalt carbonate is sintered to obtain cobalt tetroxide.

[0100] Preferably, the sintering temperature is 700-850°C.

[0101] For example, the sintering temperature may be (700, 710, 720, 730, 740, 750, 760, 770, 780, 790, 810, 820, 830, 840, or 850)°C.

[0102] Preferably, the cobalt carbonate is preheated before sintering, the preheating temperature is 200-500° C., and the preheating time is 20-60 minutes. The lower the preheating temperature and the longer the preheating time, the more uniform the shrinkage of the cobalt oxide will be.

[0103] Preferably, when a rotary kiln is used for sintering, the rotary kiln tube has a rotation frequency of 0.5 to 1.5 r / min, and the material layer thickness is ≤16 cm. The thinner the material layer, the more uniform the heating, and the more uniform the pores of the obtained cobalt trioxide.

[0104] The present application also provides a positive electrode material, which is lithium cobalt oxide obtained by calcining the above-mentioned cobalt tetroxide and a lithium source.

[0105] Preferably, the molar ratio of the lithium source to cobalt oxide is 1 to 1.05.

[0106] Preferably, the calcination temperature is 900-1200° C., for example, it can be (900, 910, 920, 930, 940, 950, 960, 970, 980, 990, 1000, 1010, 1020, 1030, 1040, 1050, 1060, 1070, 1080, 1090, 1100, 1110, 1120, 1130, 1140, 1150, 1160, 1170, 1180, 1190 or 1200)° C. The calcination time is 20-30 h, for example, it can be (20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30) h.

[0107] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0108] Example 1

[0109] 1. A cobalt sulfate solution and an aluminum sulfate solution are mixed to prepare an aluminum-doped cobalt salt solution, wherein the cobalt concentration in the solution is 90 g / L, and the molar ratio of cobalt to aluminum in the solution is: Co:Al=1:0.0139, and an ammonium bicarbonate solution with a mass concentration of 190 g / L is prepared as a precipitant solution; an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0110] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base liquid at the same time to react. The flow rate of the cobalt salt solution is 3% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9μm;

[0111] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm;

[0112] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min, and the particle size grew to 17μm;

[0113] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6% / h of the available volume of the reactor, maintain the stirring speed at 150 r / min for the first 6 hours, and then reduce it to 100 r / min, and the particle size grew to 20.5 μm; the aluminum-doped cobalt carbonate of Example 1 was prepared.

[0114] The scanning electron microscope morphology of the cobalt carbonate particles of Example 1 is shown in Figure 1 The scanning electron microscope morphology of the cross section is shown in Figure 2 The cobalt carbonate of Example 1 was tested and found to have a specific surface area of ​​110 m 2 / g, average pore diameter is 1.77nm, pore volume is 0.06cm 3 / g.

[0115] 3. After centrifugal washing, the cobalt carbonate was sintered, with a preheating temperature of 500°C, a residence time of 20 min in the preheating stage, a high-temperature sintering temperature of 800°C, a sintering time of 3 h, a rotary kiln tube rotation frequency of 1.0 r / min, and a material layer thickness of 16 cm to prepare the aluminum-doped cobalt tetroxide of Example 1.

[0116] The scanning electron microscope morphology of the cobalt oxide of Example 1 is shown in Figure 3 The scanning electron microscope morphology of the cross section is shown in Figure 4 The median particle size D50 of the cobalt oxide in Example 1 is 17.02 μm, and the specific surface area is 2.5 m 2 / g, average pore diameter is 1.99nm, pore volume is 0.0015cm 3 / g, tap density is 2.85g / cm 3 , porosity distribution fitting degree R 2 The value is 0.912, and the porosity distribution fitting degree R 2 The calculation method of the value is shown in Example 3. The cobalt tetraoxide in Example 1 was analyzed for Al content in the particle micro-region using an electron probe instrument. The results are as follows: Figure 5 As shown, the Al element is evenly distributed.

[0117] The cobalt trioxide obtained in Example 1 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1060° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 1.

[0118] Example 2

[0119] 1. A cobalt sulfate solution and an aluminum sulfate, nickel sulfate and manganese sulfate solution are mixed to prepare a cobalt salt solution doped with aluminum, nickel and manganese, wherein the cobalt concentration in the solution is 110 g / L, and the molar ratio of aluminum, nickel, manganese and cobalt in the solution is: Co:Al:Ni:Mn=1:0.0139:0.0035:0.0055, and an ammonium bicarbonate solution with a mass concentration of 190 g / L is prepared as a precipitant solution; an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0120] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base solution at the same time to react. The flow rate of the cobalt salt solution is 3% / h of the available volume of the reactor. The stirring speed is maintained at 300 / min for the first 6 hours, and then reduced to 250r / min until the particle size grows to 7μm.

[0121] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 10μm;

[0122] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 14μm;

[0123] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6% / h of the available volume of the reactor, maintain the stirring speed at 150 r / min for the first 6 hours, and then reduce it to 100 r / min until the particle size grows to 16.0 μm; the cobalt carbonate doped with aluminum, nickel and manganese of Example 2 was prepared.

[0124] The scanning electron microscope morphology of the cobalt carbonate particles of Example 2 is shown in Figure 6 The cobalt carbonate of Example 2 was tested and found to have a specific surface area of ​​45 m 2 / g, average pore diameter is 1.57nm, pore volume is 0.04cm 3 / g.

[0125] 3. After centrifugal washing, the cobalt carbonate was sintered, with a preheating temperature of 350°C, a residence time of 30 min, a high-temperature sintering temperature of 850°C, a sintering time of 3 h, a rotary kiln tube rotation frequency of 0.5 r / min, and a material layer thickness of <6 cm. The cobalt tetraoxide doped with aluminum, nickel, and manganese of Example 2 was prepared.

[0126] The scanning electron microscope morphology of the cobalt oxide of Example 2 is shown in Figure 7The scanning electron microscope morphology of the cross section is shown in Figure 8 The median particle size D50 of the cobalt oxide in Example 2 is 14.52 μm, and the specific surface area is 1.5 m 2 / g, average pore diameter is 1.82nm, pore volume is 0.0019cm 3 / g, tap density is 2.60g / cm 3 , porosity distribution fitting degree R 2 The value is 0.902. The Ni and Mn components of the cobalt oxide in Example 2 were analyzed by electron probe analysis. The results are as follows: Fig. 9 and 10 As shown, Ni and Mn elements are evenly distributed.

[0127] The cobalt trioxide obtained in Example 2 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1030° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 2.

[0128] Example 3

[0129] 1. A cobalt chloride solution and an aluminum sulfate solution and a magnesium sulfate solution are mixed to prepare a cobalt salt solution doped with aluminum and magnesium, wherein the cobalt concentration in the solution is 120 g / L, and the molar ratio of aluminum, magnesium and cobalt in the solution is: Co:Al:Mg=1:0.0083:0.0056, and a sodium carbonate solution with a mass concentration of 190 g / L is prepared as a precipitant solution; a sodium carbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0130] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base liquid at the same time to react. The flow rate of the cobalt salt solution is 3% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9.5μm;

[0131] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm;

[0132] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 17μm;

[0133] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6% / h of the available volume of the reactor, maintain the stirring speed at 150 r / min for the first 6 hours, and then reduce it to 100 r / min until the particle size grows to 22.0 μm; and the aluminum- and magnesium-doped cobalt carbonate of Example 3 was prepared.

[0134] During the growth process of cobalt carbonate in Example 3, the specific surface area, pore size and pore volume were measured at particle sizes of 5 μm, 10 μm, 15 μm and 22 μm, respectively. The results are shown in Table 1, indicating that the particle size and pore distribution of cobalt carbonate are uniform.

[0135] Table 1 Specific table, pore size, pore volume of cobalt carbonate growth process of Example 3

[0136] Particle size μm <![CDATA[Specific surface area m 2 / g]]> Average pore size nm <![CDATA[Pore volume cm 3 / g]]> 5 115 2.02 0.09 10 103 2.05 0.09 15 110 2.10 0.08 22 125 2.26 0.08

[0137] The scanning electron microscope morphology of the cobalt carbonate particles obtained in Example 3 is shown in Fig.11 The scanning electron microscope morphology of the cross section is shown in Fig.12 .

[0138] 3. After centrifugal washing, the cobalt carbonate is sintered, with a preheating temperature of 300°C, a residence time of 45 min, a high-temperature sintering temperature of 700°C, a sintering time of 3 h, a rotary kiln tube rotation frequency of 1.0 r / min, and a material layer thickness of 16 cm to prepare cobalt tetroxide doped with aluminum and magnesium.

[0139] The scanning electron microscope morphology of cobalt tetraoxide in Example 3 is shown in Fig.13 The median particle size D50 of the cobalt oxide in Example 3 is 18.81 μm, and the specific surface area is 5.3 m 2 / g, average pore diameter is 2.51nm, pore volume is 0.0013cm 3 / g, tap density is 2.95g / cm 3 , porosity distribution fitting degree R 2 The value is 0.993.

[0140] Porosity distribution fitting degree R 2 The calculation method of the value is as follows: take the cobalt tetroxide of Example 3, cut it into sections and take electron microscope photos, and divide the section into four areas ①②③④, such as Fig.14 As shown in Table 2, PS and IPP software were used to analyze the cross-sectional electron microscope image processing (void grayscale 1-100, total area 1-256), and the relative porosity of the corresponding area was calculated, as shown in Table 2. R was calculated by the correlation coefficient between the area and the pore area. 2 =0.993>0.98, such as Fig.15 As shown, it indicates that the porosity distribution of the sample is uniform.

[0141] Table 2 Porosity of cobalt tetroxide in Example 3

[0142] area Pore ​​area Pore ​​area Calculate porosity % ① 42111 11651 28 ② 126331 41542 33 ③ 210552 80215 38 ④ 294773 119855 41 ①+② 168442 53193 32 ①+②+③ 378994 133408 35 ①+②+③+④ 673767 249621 37

[0143] The Al and Mg components of the cobalt oxide in Example 3 were analyzed by electron probe analysis. The results were as follows: Fig.16 and 17 As shown, Al and Mg elements are evenly distributed.

[0144] The cobalt trioxide obtained in Example 3 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1020° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 3.

[0145] Example 4

[0146] 1. Cobalt sulfate solution and zirconium sulfate and lanthanum sulfate solutions are mixed to prepare a cobalt salt solution doped with Zr and La, wherein the cobalt concentration in the solution is 130 g / L, and the ratio of Zr, La and cobalt in the solution is: Co:Zr:La=1:0.0111:0.0056, and an ammonium bicarbonate solution with a mass concentration of 190 g / L is prepared as a precipitant solution; an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0147] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base liquid at the same time to react. The flow rate of the cobalt salt solution is 3% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9.5μm;

[0148] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of cobalt liquid to 4% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm.

[0149] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of cobalt liquid to 5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 17μm.

[0150] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt liquid to 6% / h of the available volume of the reactor, and the stirring speed was maintained at 150 r / min for the first 6 hours, and then reduced to 100 r / min until the particle size grew to 21.0 μm; the cobalt carbonate doped with Zr and La of Example 4 was prepared.

[0151] The scanning electron microscope morphology of the cobalt carbonate particles of Example 4 is shown in Fig.18 The cobalt carbonate of Example 4 was tested and found to have a specific surface area of ​​121 m 2 / g, average pore diameter is 3.9nm, pore volume is 0.09cm 3 / g.

[0152] 3. After centrifugal washing, the cobalt carbonate is sintered, with a preheating temperature of 200°C, a residence time of 60 min in the preheating stage, a high-temperature sintering temperature of 780°C, a sintering time of 3 h, a rotary kiln tube rotation frequency of 1.5 r / min, and a material layer thickness of 10 cm to prepare cobalt tetroxide doped with Zr and La.

[0153] The scanning electron microscope morphology of the cobalt tetraoxide of Example 4 is shown in Fig.19 The scanning electron microscope morphology of the cross section is shown in Fig. 20 The median particle size D50 of the cobalt oxide in Example 4 is 17.50 μm, and the specific surface area is 3.1 m 2 / g, the average pore diameter is 4.23nm, and the pore volume is 0.0020cm 3 / g, tap density is 2.78g / cm 3 , porosity distribution fitting degree R 2 The value is 0.964.

[0154] The Al composition of the cobalt oxide in Example 4 was analyzed by electron probe analysis. Fig.21 As shown, the Al element is evenly distributed.

[0155] The cobalt trioxide obtained in Example 4 was mixed evenly with lithium carbonate at a Li / Me molar ratio of 1.05:1, and calcined at 1010° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 4.

[0156] Example 5

[0157] 1. Prepare a cobalt sulfate solution with a cobalt concentration of 90 g / L, and prepare an ammonium bicarbonate solution with a mass concentration of 190 g / L as a precipitant solution; prepare an ammonium bicarbonate solution with a mass concentration of 10 g / L as a base solution.

[0158] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base solution at the same time to react. The flow rate of the cobalt salt solution is 3% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9μm;

[0159] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm;

[0160] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 17μm;

[0161] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6% / h of the available volume of the reactor, and the stirring speed was maintained at 150 r / min for the first 6 hours, and then reduced to 100 r / min until the particle size grew to 20.5 μm; and the cobalt carbonate without doping elements of Example 5 was prepared.

[0162] The cobalt carbonate of Example 5 was tested and found to have a specific surface area of ​​101 m 2 / g, average pore diameter is 1.97nm, pore volume is 0.06cm 3 / g.

[0163] 4. After centrifugal washing, the cobalt carbonate was sintered, with a preheating temperature of 500° C., a residence time of 20 min, a high-temperature sintering temperature of 790° C., and a sintering time of 3 h to prepare cobalt tetroxide without doping elements of Example 5.

[0164] The median particle size D50 of the cobalt oxide in Example 5 is 17.50 μm, and the specific surface area is 2.8 m 2 / g, average pore diameter is 1.87nm, pore volume is 0.0015cm 3 / g, tap density is 2.75g / cm 3 , porosity distribution fitting degree R 2 The value is 0.923, and the porosity distribution fitting degree R 2 The calculation method of the value is shown in Example 3.

[0165] The cobalt trioxide obtained in Example 5 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1020° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 5.

[0166] Example 6

[0167] 1. A cobalt sulfate solution and an aluminum sulfate solution are mixed to prepare an aluminum-doped cobalt salt solution, wherein the cobalt concentration in the solution is 100 g / L, and the molar ratio of cobalt to aluminum in the solution is: Co:Al=1:0.0139, and an ammonium bicarbonate solution with a mass concentration of 200 g / L is prepared as a precipitant solution; and an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0168] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base solution at the same time to react. The flow rate of the cobalt salt solution is 3% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9μm;

[0169] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm;

[0170] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 17μm;

[0171] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6% / h of the available volume of the reactor, maintain the stirring speed at 150 r / min for the first 6 hours, and then reduce it to 100 r / min until the particle size grows to 20.5 μm; the aluminum-doped cobalt carbonate of Example 6 was prepared, and its performance parameters are shown in Table 3.

[0172] 3. After centrifugal washing, the cobalt carbonate was sintered, with a preheating temperature of 300°C, a preheating residence time of 45 min, a high-temperature sintering temperature of 800°C, and a sintering time of 3 h to prepare aluminum-doped cobalt tetroxide of Example 6, whose performance parameters are shown in Table 4.

[0173] The cobalt trioxide obtained in Example 6 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1060° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 1.

[0174] Example 7

[0175] 1. A cobalt sulfate solution and an aluminum sulfate solution are mixed to prepare an aluminum-doped cobalt salt solution, wherein the cobalt concentration in the solution is 100 g / L, and the molar ratio of cobalt to aluminum in the solution is: Co:Al=1:0.0139, and an ammonium bicarbonate solution with a mass concentration of 200 g / L is prepared as a precipitant solution; and an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0176] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base solution at the same time to react. The flow rate of the cobalt salt solution is 3.5% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9μm;

[0177] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4.5% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm;

[0178] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5.5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 17μm;

[0179] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6.5% / h of the available volume of the reactor, maintain the stirring speed at 150 r / min for the first 6 hours, and then reduce it to 100 r / min until the particle size grows to 20.6 μm; the aluminum-doped cobalt carbonate of Example 7 was prepared, and its performance parameters are shown in Table 3.

[0180] 3. After centrifugal washing, the cobalt carbonate was sintered, with a preheating temperature of 250°C, a preheating residence time of 60 min, a high-temperature sintering temperature of 810°C, and a sintering time of 3 h to prepare aluminum-doped cobalt tetroxide of Example 7, whose performance parameters are shown in Table 4.

[0181] The cobalt trioxide obtained in Example 7 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1060° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 7.

[0182] Example 8

[0183] 1. A cobalt sulfate solution and an aluminum sulfate solution are mixed to prepare an aluminum-doped cobalt salt solution, wherein the cobalt concentration in the solution is 100 g / L, and the molar ratio of cobalt to aluminum in the solution is: Co:Al=1:0.0139, and an ammonium bicarbonate solution with a mass concentration of 200 g / L is prepared as a precipitant solution; and an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0184] 2. Add the prepared cobalt salt solution and precipitant solution to the reactor containing the base solution at the same time to react. The flow rate of the cobalt salt solution is 3.5% / h of the available volume of the reactor. The stirring speed is maintained at 300r / min for the first 6h, and then reduced to 250r / min until the particle size grows to 9μm;

[0185] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 4.5% / h of the available volume of the reactor, and the stirring speed was maintained at 250r / min for the first 6 hours, and then reduced to 200r / min until the particle size grew to 13μm;

[0186] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 5.5% / h of the available volume of the reactor, and the stirring speed was maintained at 200r / min for the first 6 hours, and then reduced to 150r / min until the particle size grew to 17μm;

[0187] Half of the materials in the reactor were separated and the reaction was continued for 2 hours according to the above process. The process was changed to increase the flow rate of the cobalt salt solution to 6.5% / h of the available volume of the reactor, and the stirring speed was maintained at 150 r / min for the first 6 hours, and then reduced to 110 r / min until the particle size grew to 20.5 μm; the aluminum-doped cobalt carbonate of Example 8 was prepared, and its performance parameters are shown in Table 3.

[0188] 3. After centrifugal washing, the cobalt carbonate was sintered, with a preheating temperature of 260°C, a preheating residence time of 60 min, a high-temperature sintering temperature of 710°C, and a sintering time of 3 h to prepare aluminum-doped cobalt tetroxide of Example 8, whose performance parameters are shown in Table 4.

[0189] The cobalt trioxide obtained in Example 8 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1050° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Example 8.

[0190] Comparative Example 1

[0191] 1. A cobalt sulfate solution and an aluminum sulfate solution are mixed to prepare an aluminum-doped cobalt salt solution, wherein the cobalt concentration in the solution is 120 g / L, and the ratio of aluminum to cobalt in the solution is: Co:Al=1:0.0139, and an ammonium bicarbonate solution with a mass concentration of 190 g / L is prepared as a precipitant solution; and an ammonium bicarbonate solution with a mass concentration of 10 g / L is prepared as a base solution.

[0192] 2. The prepared cobalt salt solution and precipitant solution are added to the reactor containing the base liquid at the same time to carry out the reaction. The flow rate of the cobalt salt solution is 4% / h of the available volume of the reactor, the stirring speed is 150 r / min, and the particle size grows to 18.0 μm to prepare the aluminum-doped cobalt carbonate of Comparative Example 1.

[0193] The scanning electron microscope morphology of the cobalt carbonate particles of Comparative Example 1 is shown in Fig. 22 The cobalt carbonate of comparative example 1 was tested and found to have a specific surface area of ​​4 m 2 / g, average pore diameter is 9.70nm, pore volume is 0.005cm 3 / g.

[0194] 3. After centrifugal washing, the cobalt carbonate was sintered at a temperature of 750° C. for 1.5 h to prepare the aluminum-doped cobalt tetroxide of Comparative Example 1.

[0195] The scanning electron microscope morphology of the cobalt tetraoxide of Comparative Example 1 is shown in Fig.23 The scanning electron microscope morphology of the cross section is shown in Fig.24 The median particle size D50 of the cobalt oxide in Comparative Example 1 is 17.10 μm, and the specific surface area is 2.0 m 2 / g, the average pore diameter is 6.12nm, and the pore volume is 0.0021cm 3 / g, tap density is 2.50g / cm 3 , porosity distribution fitting degree R 2 The value is 0.812.

[0196] The cobalt trioxide obtained in Comparative Example 1 and lithium carbonate were uniformly mixed at a Li / Me molar ratio of 1.05:1, and calcined at 1020° C. for 24 h to prepare the lithium cobalt oxide positive electrode material of Comparative Example 1.

[0197] The indicators of the cobalt carbonate of each embodiment and comparative example are shown in Table 3. According to Table 3, in the process of the cobalt carbonate preparation method of Comparative Example 1, the flow rate of the cobalt salt solution does not increase with the increase of the material particle size, and the stirring speed of the reactor does not decrease with the increase of the material particle size. The same flow rate and the same stirring speed are used throughout the process, and the obtained cobalt carbonate has a large average pore size, a small specific surface area, and a small pore volume.

[0198] Table 3 Indexes of cobalt carbonate in various embodiments and comparative examples

[0199]

[0200]

[0201] The indicators of the cobalt tetroxide of each embodiment and comparative example are shown in Table 4, wherein embodiments 1 to 5 are cobalt tetroxides with different doping elements and doping contents, respectively, and the sintering processes of embodiments 6 to 8 are different from those of embodiment 1. The cobalt tetroxide of comparative example 1 has a larger average pore size, and the porosity distribution fitting degree R 2 The value is less than 0.9.

[0202] Table 4 Indexes of cobalt tetraoxide in various embodiments and comparative examples

[0203]

[0204] Test example

[0205] The positive electrode materials of the above-mentioned embodiments and comparative examples were respectively dissolved in NMP solvent with conductive carbon black and polyvinylidene fluoride at a mass ratio of 85:10:5 under vacuum conditions to prepare a positive electrode slurry with a weight solid content of 80%. The positive electrode discs were then prepared by coating, drying, and punching. A lithium battery was then prepared in the order of positive electrode shell-positive electrode sheet-diaphragm-negative electrode sheet-stainless steel sheet-spring sheet-negative electrode shell. The electrolyte was 1 mol / LLiPF with 10% (volume fraction) fluoroethylene carbonate (FEC) added. 6 / EC:DMC (volume ratio is 1:1), the separator is a polypropylene microporous membrane, and the batteries of Examples 1 to 8 and Comparative Example 1 are prepared respectively. The battery performances of each Example and Comparative Example are shown in Table 5.

[0206] Table 5 Battery performance of each embodiment and comparative example

[0207]

[0208] According to Table 5, compared with the comparative example, the batteries of Examples 1 to 8 can improve the discharge capacity and cycle performance. The positive electrode material of Example 5 has no doping elements, so the cycle performance of the battery is relatively poor compared with other examples. Among them, compared with Example 1, the pore distribution of cobalt tetroxide in Example 6 is more uniform, and the capacity and cycle performance of the battery are improved. Compared with Example 1, the pore volume of cobalt tetroxide in Example 7 is larger, the tap density is smaller, and the battery capacity is reduced; but the pores are more uniform, so the cycle performance is better.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A cobalt tetraoxide, It is characterized in that The interior of the cobalt oxide is porous, the pore distribution of the cobalt oxide is uniform, and the porosity distribution of the cobalt oxide is fitted by R 2 Value>0.9; The porosity distribution fitting R 2 The steps for validating the value are as follows: Step 1: Treat a single cobalt oxide particle as a sphere, calculate based on the cross-section circle of the sphere, and divide the circle into n concentric circles, n ≥ 3; Step 2: Calculate the area of ​​each concentric circle and the difference between the areas of adjacent concentric circles, as well as the pore area of ​​the corresponding area; Step 3: Calculate the change x of the cross-sectional area in different regions and the change y of the pore area in the corresponding region; Step 4: Establish a linear relationship between x and y and calculate the correlation coefficient R 2 .

2. The cobalt tetraoxide according to claim 1, It is characterized in that The pore diameter of the cobalt trioxide is 1.0-4.5 nm.

3. The cobalt tetraoxide according to claim 1, It is characterized in that The specific surface area of ​​the cobalt tetraoxide is 1 to 5 m 2 / g.

4. The cobalt tetraoxide according to claim 1, It is characterized in that The tap density of the cobalt oxide is 2.6 to 3.0 g / cm 3 .

5. The cobalt tetraoxide according to claim 1, It is characterized in that The median particle size of the cobalt trioxide is 14-19 μm.

6. The cobalt tetraoxide according to claim 1, It is characterized in that The pore volume of the cobalt oxide is 0.0010 to 0.0090 cm 3 / g.

7. The cobalt tetraoxide according to any one of claims 1 to 6, It is characterized in that The cobalt oxide includes a doping element, and the doping element is selected from one or more of Al, Mg, Ni, Mn, La, Zr, Ti, and W.

8. The cobalt tetraoxide according to claim 7, It is characterized in that The doping mass contents of the doping elements are respectively: Al: 0.40-1.20%, Mg: 0.08-0.50%, Ni: 0.10-3.00%, Mn: 0.10-3.00%, La: 0.05-0.30%, Zr: 0.10-0.30%, Ti: 0.05-0.30%, W: 0.10-0.50%.

9. The cobalt tetraoxide according to claim 8, It is characterized in that The pore volume of the cobalt tetraoxide is 0.0013 to 0.0020 cm 3 / g.

10. A cobalt carbonate, It is characterized in that For preparing the cobalt trioxide according to any one of claims 1 to 9, the cobalt carbonate has a uniform internal pore size and a uniform pore distribution, and the pore volume of the cobalt carbonate is 0.01 to 0.10 cm 3 / g.

11. The cobalt carbonate according to claim 10, It is characterized in that The pore size of the cobalt carbonate is 1.0 to 4.0 nm; the specific surface area of ​​the cobalt carbonate is 40 to 130 m 2 / g.

12. The cobalt carbonate according to claim 11, It is characterized in that The tap density of the cobalt carbonate is 1.4 to 2.0 g / cm 3 ; The median particle size of the cobalt carbonate is 16 to 22 μm.

13. A method for preparing cobalt carbonate according to any one of claims 10 to 12, It is characterized in that include: Adding a cobalt salt solution and a precipitant solution into a reactor containing a base liquid to react, wherein the flow rate of the cobalt salt solution increases with the increase of the particle size of the material, and the stirring speed of the reactor decreases with the increase of the particle size of the material, and the reaction is continued until the target particle size is reached to obtain a cobalt carbonate slurry; Centrifugally washing the cobalt carbonate slurry to obtain the cobalt carbonate; The base solution concentration is 5 to 50 g / L; The flow rate of the cobalt salt solution is in the range of 2-6% / h of the available volume of the reactor, and the stirring speed of the reactor is in the range of 300-100 r / min.

14. The preparation method according to claim 13, It is characterized in that The cobalt salt solution is selected from cobalt sulfate solution and / or cobalt chloride solution; the precipitant solution is selected from ammonium bicarbonate solution and / or sodium carbonate solution; and the base solution is selected from ammonium bicarbonate solution and / or sodium carbonate solution.

15. The preparation method according to claim 13, It is characterized in that The cobalt concentration in the cobalt salt solution is 90-130 g / L, and the concentration of the precipitant solution is 190-230 g / L.

16. The preparation method according to claim 13, It is characterized in that The cobalt salt solution includes a doping element, and the doping element is selected from one or more of Al, Mg, Ni, Mn, La, Zr, Ti, and W.

17. The preparation method according to claim 16, It is characterized in that The doping mass contents of the doping elements in the cobalt carbonate are respectively: Al: 0.26~0.70%, Mg: 0.05~0.33%, Ni: 0.06~2.00%, Mn: 0.06~2.00%, La: 0.03~0.20%, Zr: 0.06~0.20%, Ti: 0.03~0.20%, W: 0.06~0.33%.

18. The preparation method according to claim 13, It is characterized in that The target particle size of the cobalt carbonate is 16 to 22 μm.

19. A method for preparing cobalt trioxide according to any one of claims 1 to 9, It is characterized in that include: Providing the cobalt carbonate according to any one of claims 10 to 12; The cobalt carbonate is sintered to obtain cobalt tetroxide.

20. The preparation method according to claim 19, It is characterized in that The sintering temperature is 700-850°C.

21. The preparation method according to claim 19, It is characterized in that Before sintering the cobalt carbonate, the cobalt carbonate is preheated, the preheating temperature is 200-500° C., and the preheating time is 20 min-60 min.

22. The preparation method according to claim 19, It is characterized in that When a rotary kiln is used for sintering, the rotation frequency of the rotary kiln tube is 0.5-1.5 r / min, and the material layer thickness is ≤16 cm.

23. A positive electrode material, It is characterized in that Lithium cobalt oxide obtained by calcining the cobalt trioxide according to any one of claims 1 to 9 and a lithium source.

24. The positive electrode material according to claim 23, It is characterized in that The molar ratio of the lithium source to the cobalt tetroxide is 1 to 1.

05.

25. The positive electrode material according to claim 23, It is characterized in that The calcination temperature is 900-1200° C., and the calcination time is 20-30 hours.

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