A core-shell doped cobalt tetroxide and its preparation method and application

Abstract

The present invention provides a cobalt tetroxide with a core-shell doping configuration and a preparation method and application thereof. The cobalt tetroxide with a core-shell doping configuration comprises a core body and a shell layer, the core body comprises cobalt tetroxide doped with a first element, and the shell layer comprises cobalt tetroxide doped with a second element; the first element comprises Mg and / or a transition metal, and the second element comprises Al; the cobalt tetroxide with a core-shell doping configuration of the present invention has a core-shell doping structure, can effectively avoid problems such as surface segregation and morphology cracking, and can also accelerate the lithium ion transmission speed of a positive electrode material, improve capacity, alleviate electrolyte corrosion, and improve cycle and rate performance.

Description

Technical Field

[0001] The invention belongs to the technical field of positive electrode material precursors and relates to cobalt tetroxide with a core-shell doping structure and a preparation method and application thereof. Background Art

[0002] Lithium cobalt oxide is widely used in 3C digital electronic products. With the diversification of portable device functions and usage scenarios, the market has higher and higher requirements for the energy density of lithium cobalt oxide batteries. At present, the common industrial process is to increase the charging voltage of lithium cobalt oxide positive electrode materials by doping elements such as Al, thereby increasing the energy density of the battery. For example, CN 114368792A discloses a method for preparing aluminum-doped cobalt oxide particles. In the disclosed method, a certain concentration of cobalt salt solution, ammonium bicarbonate solution and sodium aluminate solution are first prepared respectively; then the above solution is added to a reactor with a certain amount of bottom liquid in advance by a peristaltic pump in a parallel flow manner, and the reaction is carried out, and the reaction temperature is controlled to be 35-60°C, and the pH value of the reaction system is 7-7.6; finally, the obtained product is calcined, the calcination temperature is 200-900°C, and the calcination time is 4-15h, and finally aluminum-doped cobalt oxide particles are obtained.

[0003] Although Al doping can improve the performance of the material to a certain extent, as the amount of Al doping increases, the uniformity of Al distribution becomes more difficult to ensure, and during the reaction process, washing and calcination, the particle surface will partially show flaky segregation and calcination cracking problems. Most of the existing technologies reduce the surface morphology during the growth rate by improving the surface morphology or increasing the reaction temperature to make it more dense, thereby inhibiting Al segregation, but there will be problems such as poor sphericity and aggravated particle cracking during calcination. In addition, heating can also alleviate Al segregation to a certain extent, but whether the temperature is increased in the early or late stages, it will first cause the problem of nuclear explosion, and secondly, it will aggravate the difference in precipitation rate between Co and Al, resulting in a more uneven Al distribution; although doping with other elements can theoretically improve the functionality of the material, due to the inconsistent precipitation rates of different elements and the great impact on the distribution of Al, the actual effect of doping with other elements is not good.

[0004] Based on the above research, it is necessary to provide a cobalt tetroxide with a core-shell doping configuration, which can avoid the problems caused by a high Al doping amount, effectively prevent the positive electrode material from being corroded by the electrolyte, thereby improving the electrochemical performance of the lithium cobalt oxide positive electrode material. Summary of the invention

[0005] The object of the present invention is to provide a cobalt oxide with a core-shell doping configuration and a preparation method and application thereof. The cobalt oxide with a core-shell doping configuration has a core-shell doping structure, which can effectively avoid problems such as surface segregation and morphology cracking, and can also accelerate the lithium ion transmission speed of the positive electrode material, increase the capacity, alleviate electrolyte corrosion, and improve the cycle and rate performance.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a cobalt oxide with a core-shell doping configuration, wherein the cobalt oxide with a core-shell doping configuration comprises a core body and a shell layer, wherein the core body comprises cobalt oxide doped with a first element, and the shell layer comprises cobalt oxide doped with a second element;

[0008] The first element includes Mg and / or a transition metal, and the second element includes Al.

[0009] The cobalt tetroxide described in the present invention is a core-shell type of doping method, with the first element Mg and / or transition metal doped inside and the Al element doped on the surface. Compared with the overall single Al doping process, the core is replaced by a specific element to replace the Al element, which can greatly reduce the doping amount of Al without electrochemical activity, and simplify the uniformity control process of Al distribution on the surface, thereby overcoming the defects caused by excessive Al doping, that is, reducing the process difficulty and improving the performance of the material.

[0010] Preferably, the core body comprises a core and a subcore layer on the surface of the core.

[0011] Preferably, the sub-nuclear layer in the core body includes the second element, and the content of the second element in the sub-nuclear layer gradually decreases from the surface layer of the core body to the inside.

[0012] Preferably, the shell layer further includes a first element, and the content of the first element in the shell layer gradually decreases from the boundary between the shell layer and the core body toward the outside.

[0013] The doping described in the present invention is not only of the core-shell type, but also of double gradient doping, in which the doping elements in the shell and the core body diffuse with each other, so that the first element in the core body is also doped in the shell layer, and the content gradually decreases from the inside of the shell layer to the outer surface, and the second element in the surface layer is also doped in the core body, and the content gradually decreases from the surface of the core body to the inside, thereby making the core body divided into an inner core including only the first element, and a sub-core layer including the first element and the second element, and the second element in the sub-core layer is obtained by diffusion of the second element in the shell layer; at the same time, the double gradient doping method described in the present invention not only effectively prevents the problems caused by high Al doping, effectively avoids surface segregation and morphology cracking, but also effectively prevents the positive electrode material from being corroded by the electrolyte.

[0014] Preferably, the distance from the core of the core body to the surface of the core body is 6.5-8.5 μm, for example, 6.5 μm, 6.75 μm, 8.0 μm, 8.25 μm or 8.5 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the thickness of the shell layer is 2-4 μm, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] In order to match the diffusion effect of double gradient doping and to improve the doping effect of the first element and the second element, the shell thickness is preferably within the above range, so as to obtain a material with better performance.

[0017] Preferably, in the core-shell doped cobalt tetroxide, the content of the first element is 3000-6000 ppm, for example, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm or 6000 ppm, and the content of the second element is 7000-9000 ppm, for example, 7000 ppm, 7500 ppm, 8000 ppm, 8500 ppm or 9000 ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0018] The doping amounts of the first element and the second element in the present invention are within a reasonable range, which can further improve the doping effect. If the doping amount of the first element is too high, the material capacity will be greatly reduced. If the doping amount of the first doping element is too low, the difference between the internal and external doping amounts is too large, resulting in internal and external stress differences, which makes the unit cell prone to dislocation, thereby causing the particles to crack. If the doping amount of the second element is too high, the material capacity will be greatly reduced. If the doping amount of the second element is too low, the high voltage resistance will deteriorate.

[0019] Preferably, the transition metal includes any one of Ni, Mn, Ti or Zr or a combination of at least two thereof. Typical but non-limiting combinations include a combination of Ni and Mn, or a combination of Ti and Zr.

[0020] In a second aspect, the present invention provides a method for preparing cobalt oxide of the core-shell doping configuration as described in the first aspect, the preparation method comprising the following steps:

[0021] (1) feeding solution A, solution B and solution C into a bottom solution for reaction, wherein solution A comprises a cobalt salt solution, solution B comprises a Mg and / or transition metal salt solution, and solution C comprises a precipitant solution;

[0022] (2) replacing the solution B in step (1) with solution D, continuing the reaction, stopping the feeding after the reaction is completed, and then aging to obtain cobalt carbonate;

[0023] The solution D comprises an Al salt solution;

[0024] (3) calcining the cobalt carbonate described in step (2) to obtain the cobaltous oxide of the core-shell doping structure.

[0025] The present invention first reacts a cobalt salt solution, a precipitant solution and a first element salt solution to achieve doping of the first element in the core body, and then replaces the first element salt solution with a second element salt solution to achieve doping of the shell Al element, thereby simplifying the process flow and reducing the process difficulty.

[0026] Preferably, the reaction in step (1) is carried out until the median particle size of the particles is 2-4 μm, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm, and the solution B in step (1) is replaced with solution D.

[0027] Preferably, the feeding method of step (1) is that solution A, solution B and solution C are fed simultaneously in parallel.

[0028] The present invention can improve the uniformity of doping element distribution by feeding in a parallel flow manner.

[0029] Preferably, the reaction temperature in step (1) is 35-55°C, for example, 35°C, 40°C, 45°C, 50°C or 55°C, the pH is 7.2-7.6, for example, 7.2, 7.3, 7.4, 7.5 or 7.6, and the rotation speed is 100-300r / min, for example, 100r / min, 150r / min, 200r / min, 250r / min or 300r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the concentration of solution A in step (1) is 90-130 g / L, for example, 90 g / L, 100 g / L, 110 g / L, 120 g / L or 130 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the concentration of solution B in step (1) is 1.0-2.0 g / L, for example, 1.0 g / L, 1.2 g / L, 1.4 g / L, 1.6 g / L, 1.8 g / L or 2.0 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the concentration of solution C in step (1) is 220-260 g / L, for example, 220 g / L, 230 g / L, 240 g / L, 250 g / L or 260 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the concentration of the base solution in step (1) is 0-50 g / L, but does not include 0 g / L. For example, it can be 1 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L or 50 g / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the cobalt salt solution in step (1) comprises CoCl 2 and / or CoSO 4 .

[0035] Preferably, the base liquid in step (1) comprises ammonium carbonate solution.

[0036] Preferably, the precipitant solution in step (1) comprises ammonium carbonate solution.

[0037] Preferably, after replacing solution B with solution D in step (2), solution A, solution C and solution D are fed simultaneously in parallel.

[0038] Preferably, the concentration of solution D in step (2) is 0.2-1 g / L, for example, 0.2 g / L, 0.4 g / L, 0.6 g / L, 0.8 g / L or 1 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the Al salt solution in step (2) comprises Al 2 (SO 4 ) 3 and / or AlCl 3 .

[0040] Preferably, the aging time in step (2) is 1-2 hours, for example, 1 hour, 1.5 hours or 2 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the aging in step (2) is followed by washing and drying.

[0042] Preferably, the calcination temperature in step (3) is 600-800°C, for example, 600°C, 700°C or 800°C, and the calcination time is 2-4h, for example, 2h, 3h or 4h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0044] (1) feeding solution A with a concentration of 90-130 g / L, solution B with a concentration of 1.0-2.0 g / L, and solution C with a concentration of 220-260 g / L into the bottom liquid in a parallel flow manner, and reacting at a pH of 7.2-7.6, a rotation speed of 100-300 r / min, and a temperature of 35-55° C.;

[0045] The solution A comprises a cobalt salt solution, the solution B comprises a Mg and / or transition metal salt solution, the solution C comprises a precipitant solution, and the concentration of the base solution is 0-50 g / L, but does not include 0 g / L;

[0046] (2) When the reaction in step (1) is carried out until the median particle size of the particles is 2-4 μm after stopping the reaction, the solution B in step (1) is replaced with solution D, and then solution A, solution C and solution D are fed simultaneously in parallel to continue the reaction. After the reaction is completed, the feeding is stopped, and then the mixture is aged for 1-2 hours, and then washed and dried to obtain cobalt carbonate;

[0047] The solution D has a concentration of 0.2-1 g / L and includes an Al salt solution;

[0048] (3) calcining the cobalt carbonate in step (2) at a temperature of 600-800° C. for 2-4 hours to obtain the cobalt tetroxide with the core-shell doping structure.

[0049] In a third aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises a lithium cobalt oxide positive electrode material, wherein the lithium cobalt oxide positive electrode material is prepared using the cobalt oxide of the core-shell doping configuration as described in the first aspect as a raw material.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention adopts a core-shell type doping method to dope different types of elements inside and on the surface of cobalt tetroxide, thereby reducing the doping amount of the Al element and ensuring the uniformity of Al distribution, overcoming the defect caused by excessively high Al doping amount, that is, reducing the process difficulty and improving the performance of the material; at the same time, the present invention is a double-gradient doping, and the doping elements in the shell and the core body diffuse with each other, so that the content of the first element in the core body gradually decreases from the inside of the shell to the outer surface, and the content of the second element in the surface layer gradually decreases from the surface of the core body to the inside, effectively avoiding surface segregation and morphology cracking, so that the multifunctional surface doping layer accelerates the Li ion transmission speed of the positive electrode material, improves the capacity, alleviates the corrosion of the electrolyte, and improves the cycle and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a SEM image of the cobalt tetroxide described in Example 1 of the present invention;

[0053] Figure 2 This is an EDS cross-sectional line scan of the cobalt oxide described in Example 1 of the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] Example 1

[0056] This embodiment provides a cobalt tetroxide with a core-shell doping configuration, wherein the cobalt tetroxide with a core-shell doping configuration includes a core body and a shell layer, wherein the core body includes cobalt tetroxide doped with Ni and Mn, and the shell layer includes cobalt tetroxide doped with Al;

[0057] The core body includes an inner core and a sub-core layer on the surface of the inner core, the sub-core layer in the core body includes Al, and the content of Al in the sub-core layer gradually decreases from the surface of the core body to the inside, and the shell layer also includes Ni and Mn, and the content of Ni and Mn in the shell layer gradually decreases from the junction of the shell layer and the core body to the outside;

[0058] The distance from the core of the core body to the surface of the core body is 7.5 μm, and the thickness of the shell layer is 4 μm; in the cobalt tetroxide of the core-shell doping configuration, the content of Ni is 2000 ppm, the content of Mn is 2000 ppm, and the content of Al is 9000 ppm;

[0059] The method for preparing the core-shell doped cobalt oxide comprises the following steps:

[0060] (1) feeding solution A with a concentration of 130 g / L, solution B with a concentration of 2.0 g / L, and solution C with a concentration of 260 g / L into the bottom liquid in a parallel flow manner, and reacting at a pH of 7.4, a rotation speed of 200 r / min, and a temperature of 45° C.;

[0061] The solution A is CoCl 2 solution, solution B is NiCl 2 and MnCl 2 A mixed solution, solution C includes an ammonium carbonate solution, and the base solution is an ammonium carbonate solution with a concentration of 30 g / L;

[0062] (2) When the reaction in step (1) is carried out until the median particle size of the particles is 4 μm after stopping the reaction, the solution B in step (1) is replaced with solution D, and then solution A, solution C and solution D are fed simultaneously in parallel to continue the reaction. After the reaction is completed, the feeding is stopped, and then the mixture is aged for 2 hours, and then washed and dried to obtain cobalt carbonate;

[0063] The solution D is AlCl with a concentration of 1 g / L 3 Solution;

[0064] (3) calcining the cobalt carbonate in step (2) at 700° C. for 3 h to obtain the cobalt oxide with core-shell doping structure;

[0065] The SEM image of the core-shell doped cobalt oxide is as follows: Figure 1 As shown, the EDS profile line scan is shown in Figure 2 shown.

[0066] Example 2

[0067] This embodiment provides a cobalt tetroxide with a core-shell doping configuration, wherein the cobalt tetroxide with a core-shell doping configuration includes a core body and a shell layer, wherein the core body includes cobalt tetroxide doped with Ni and Mn, and the shell layer includes cobalt tetroxide doped with Al;

[0068] The core body includes an inner core and a sub-core layer on the surface of the inner core, the sub-core layer in the core body includes Al, and the content of Al in the sub-core layer gradually decreases from the surface of the core body to the inside, and the shell layer also includes Ni and Mn, and the content of Ni and Mn in the shell layer gradually decreases from the junction of the shell layer and the core body to the outside;

[0069] The distance from the core of the core to the surface of the core is 6.5 μm, and the thickness of the shell is 3 μm; in the cobalt tetroxide of the core-shell doping configuration, the content of Ni is 1500 ppm, the content of Mn is 1500 ppm, and the content of Al is 7000 ppm;

[0070] The method for preparing the core-shell doped cobalt oxide comprises the following steps:

[0071] (1) feeding solution A with a concentration of 100 g / L, solution B with a concentration of 1.5 g / L, and solution C with a concentration of 240 g / L into the bottom liquid in a parallel flow manner, and reacting at a pH of 7.2, a rotation speed of 300 r / min, and a temperature of 55° C.;

[0072] The solution A is CoCl 2 solution, solution B is NiCl 2 and MnCl 2A mixed solution, solution C includes an ammonium carbonate solution, and the base solution is an ammonium carbonate solution with a concentration of 50 g / L;

[0073] (2) When the reaction in step (1) is carried out until the median particle size of the particles is 3 μm after stopping the reaction, the solution B in step (1) is replaced with solution D, and then solution A, solution C and solution D are fed simultaneously in parallel to continue the reaction. After the reaction is completed, the feeding is stopped, and then the mixture is aged for 1.5 hours, and then washed and dried to obtain cobalt carbonate;

[0074] The solution D is AlCl with a concentration of 0.5 g / L 3 Solution;

[0075] (3) calcining the cobalt carbonate in step (2) at a temperature of 600° C. for 4 hours to obtain the cobalt tetroxide with the core-shell doping structure.

[0076] Example 3

[0077] This embodiment provides a cobalt tetroxide with a core-shell doping configuration, wherein the cobalt tetroxide with a core-shell doping configuration includes a core body and a shell layer, wherein the core body includes cobalt tetroxide doped with Mn, and the shell layer includes cobalt tetroxide doped with Al;

[0078] The core body includes an inner core and a sub-core layer on the surface of the inner core, the sub-core layer in the core body includes Al, and the content of Al in the sub-core layer gradually decreases from the surface layer of the core body to the inside, and the shell layer also includes Mn, and the content of Mn in the shell layer gradually decreases from the junction of the shell layer and the core body to the outside;

[0079] The distance from the core to the surface of the core is 8.5 μm, and the thickness of the shell is 2 μm; the content of Mn in the cobalt tetroxide of the core-shell doping configuration is 6000 ppm, and the content of Al is 9000 ppm;

[0080] The method for preparing the core-shell doped cobalt oxide comprises the following steps:

[0081] (1) feeding solution A with a concentration of 90 g / L, solution B with a concentration of 1.0 g / L, and solution C with a concentration of 220 g / L into the bottom liquid in a parallel flow manner, and reacting at a pH of 7.6, a rotation speed of 1000 r / min, and a temperature of 35° C.;

[0082] The solution A is CoSO 4 solution, solution B is a mixed solution of MnSO4, solution C includes an ammonium carbonate solution, and the base solution is an ammonium carbonate solution with a concentration of 5 g / L;

[0083] (2) When the reaction in step (1) is carried out until the median particle size of the particles is 2 μm after stopping the reaction, the solution B in step (1) is replaced with solution D, and then solution A, solution C and solution D are fed simultaneously in parallel to continue the reaction. After the reaction is completed, the feeding is stopped, and then the mixture is aged for 1 hour, and then washed and dried to obtain cobalt carbonate;

[0084] The solution D is AlCl with a concentration of 0.2 g / L 3 Solution;

[0085] (3) calcining the cobalt carbonate in step (2) at 800° C. for 2 h to obtain the cobalt oxide with the core-shell doping structure.

[0086] Example 4

[0087] This embodiment provides a cobalt oxide with a core-shell doping configuration, wherein the cobalt oxide with a core-shell doping configuration is the same as that of Embodiment 1 except that the thickness of the shell layer is 1 μm;

[0088] The method for preparing the core-shell doped cobalt tetroxide is the same as that of Example 1, except that when the reaction in step (1) is carried out until the median particle size of the particles is 1 μm, the solution B in step (1) is replaced by solution D.

[0089] Example 5

[0090] This embodiment provides a cobalt oxide with a core-shell doping configuration. The cobalt oxide with a core-shell doping configuration is the same as that of Embodiment 1 except that the thickness of the shell layer is 5 μm.

[0091] The method for preparing the core-shell doped cobalt tetroxide is the same as that of Example 1, except that when the reaction in step (1) is carried out until the median particle size of the particles is 5 μm, the solution B in step (1) is replaced by solution D.

[0092] Example 6

[0093] This embodiment provides a core-shell doped cobalt tetroxide, wherein the core-shell doped cobalt tetroxide is the same as that of Embodiment 1 except that the Ni content is 1000 ppm and the Mn content is 1000 ppm;

[0094] The method for preparing the core-shell doped cobalt oxide is the same as that of Example 1 except that the concentration of the solution B in step (1) is adaptively changed.

[0095] Example 7

[0096] This embodiment provides a core-shell doped cobalt tetroxide, wherein the core-shell doped cobalt tetroxide is the same as that of Embodiment 1 except that the Ni content is 4000 ppm and the Mn content is 4000 ppm;

[0097] The method for preparing the core-shell doped cobalt oxide is the same as that of Example 1 except that the concentration of the solution B in step (1) is adaptively changed.

[0098] Example 8

[0099] This embodiment provides a core-shell doped cobalt tetroxide, which is the same as that of Embodiment 1 except that the Al content is 6000 ppm.

[0100] The method for preparing the core-shell doped cobalt oxide is the same as that of Example 1 except that the concentration of the solution D in step (1) is adaptively changed.

[0101] Example 9

[0102] This embodiment provides a core-shell doped cobalt oxide, which is the same as that of Embodiment 1 except that the Al content is 10000 ppm.

[0103] The method for preparing the core-shell doped cobalt oxide is the same as that of Example 1 except that the concentration of the solution D in step (1) is adaptively changed.

[0104] Comparative Example 1

[0105] This comparative example provides a core-shell doped cobalt tetroxide, which is the same as Example 1 except that the first element is replaced by the second element in equal amounts, and the core-shell doped cobalt tetroxide is doped with only 13000 ppm of Al;

[0106] The method for preparing the core-shell doped cobalt tetroxide is the same as that of Example 1 except that solution B is replaced with solution D in equal concentration.

[0107] Comparative Example 2

[0108] This comparative example provides a core-shell doped cobalt tetroxide, which is the same as Example 1 except that the second element is replaced by the first element in equal amounts and the core-shell doped cobalt tetroxide is doped with 6500 ppm of Ni and 6500 ppm of Mn;

[0109] The method for preparing the core-shell doped cobalt tetroxide is the same as that of Example 1 except that solution D is replaced with solution B at an equal concentration.

[0110] Comparative Example 3

[0111] This comparative example provides a cobalt oxide with a core-shell doping configuration, wherein the cobalt oxide with a core-shell doping configuration comprises a core body and a shell layer, wherein the core body comprises cobalt oxide doped with Al, and the shell layer comprises cobalt oxide doped with Ni and Mn;

[0112] The core body includes an inner core and a sub-core layer on the surface of the inner core, the sub-core layer in the core body includes Ni and Mn, and the content of Ni and Mn in the sub-core layer gradually decreases from the surface layer of the core body to the inside, and the shell layer also includes Al, and the content of Al in the shell layer gradually decreases from the junction of the shell layer and the core body to the outside;

[0113] The distance from the core of the core body to the surface of the core body is 7.5 μm, and the thickness of the shell layer is 4 μm; in the cobalt tetroxide of the core-shell doping configuration, the content of Al is 9000 ppm, the content of Ni is 2000 ppm, and the content of Mn is 2000 ppm;

[0114] The method for preparing the core-shell doped cobalt tetroxide is as follows: except that solution B is AlCl with a concentration of 1 g / L 3 Solution D is NiCl with a concentration of 2.0 g / L 2 and MnCl 2 Except for the mixed solution, the rest are the same as in Example 1.

[0115] The cobalt oxide of the core-shell doped configuration described in the above embodiments and comparative examples is mixed with lithium carbonate according to the formula amount, and then sintered at 1000°C for 10 hours to obtain a lithium cobalt oxide material. The lithium cobalt oxide material is prepared into a positive electrode sheet, and then prepared into a battery with a lithium sheet. Then, under the condition of 0.5C / 1C, the capacity of the battery, the capacity retention rate of 100 cycles and the capacity retention rate of 0.5C / 2C are tested.

[0116] The test results are shown in Table 1:

[0117] Table 1

[0118]

[0119]

[0120] From Table 1 we can see that:

[0121] The cobalt tetroxide of the core-shell doping configuration described in the present invention can accelerate the lithium ion transmission speed of the positive electrode material, increase the capacity, alleviate the electrolyte corrosion, and improve the cycle and rate performance; it can be seen from Example 1 and Comparative Example 1 that when only Al element is doped, element segregation and cracking problems will occur, thereby reducing the performance of the material; it can be seen from Example 1 and Comparative Example 2 that when only the first element such as Ni and Mn is doped, the material cannot be effectively prevented from being corroded by the electrolyte, thereby reducing the performance of the material; it can be seen from Example 1 and Comparative Example 3 that when Al is doped in the core and Ni and Mn are doped in the shell, the doping matching effect is reduced. Compared with the present application, the surface layer is not doped with Al, the high voltage resistance will deteriorate, and the performance of the material is reduced; it can be seen from Example 1 and Examples 4-9 that the thickness of the shell, the doping content of the first element and the doping content of the second element are within a reasonable range, which can further improve the electrochemical properties of the material.

[0122] In summary, the present invention provides a core-shell doped cobalt tetroxide and a preparation method and application thereof. The core-shell doped cobalt tetroxide has a core-shell doping structure, which can effectively avoid problems such as surface segregation and morphology cracking, and can also accelerate the lithium ion transmission speed of the positive electrode material, increase the capacity, alleviate electrolyte corrosion, and improve the cycle and rate performance.

[0123] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A cobalt oxide with a core-shell doping structure, characterized in that: The cobalt oxide of the core-shell doping configuration comprises a core body and a shell layer, wherein the core body comprises cobalt oxide doped with a first element, and the shell layer comprises cobalt oxide doped with a second element; The first element includes a transition metal, and the second element includes Al; Wherein, the nuclear body includes the inner core and the subnuclear layer on the surface of the inner core; The subnuclear layer in the nuclear body includes a second element, and the content of the second element in the subnuclear layer gradually decreases from the surface layer of the nuclear body to the inside; The shell layer also includes a first element, and the content of the first element in the shell layer gradually decreases from the boundary between the shell layer and the core body to the outside.

2. The core-shell doped cobalt tetroxide according to claim 1, characterized in that: The distance from the core of the core body to the surface of the core body is 6.5-8.5 μm.

3. The core-shell doped cobalt tetroxide according to claim 1, characterized in that: The thickness of the shell layer is 2-4 μm.

4. The core-shell doped cobalt tetroxide according to claim 1, characterized in that: In the cobalt tetroxide of the core-shell doping structure, the content of the first element is 3000-6000 ppm, and the content of the second element is 7000-9000 ppm.

5. The core-shell doped cobalt tetroxide according to claim 1, characterized in that: The transition metal includes any one of Ni, Mn, Ti or Zr or a combination of at least two thereof.

6. A method for preparing cobalt oxide with a core-shell doping structure as claimed in any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) feeding solution A, solution B and solution C into a bottom solution for reaction, wherein solution A comprises a cobalt salt solution, solution B comprises a transition metal salt solution, and solution C comprises a precipitant solution; (2) replacing the solution B in step (1) with solution D, continuing the reaction, stopping the feeding after the reaction is completed, and then aging to obtain cobalt carbonate; The solution D comprises an Al salt solution; (3) calcining the cobalt carbonate described in step (2) to obtain the cobaltous oxide of the core-shell doping structure.

7. The preparation method according to claim 6, characterized in that: When the reaction in step (1) is carried out until the median particle size of the particles is still 2-4 μm after the reaction is stopped, the solution B in step (1) is replaced with solution D.

8. The preparation method according to claim 6, characterized in that: The feeding method of step (1) is that solution A, solution B and solution C are fed simultaneously in a parallel flow manner.

9. The preparation method according to claim 6, characterized in that: The reaction temperature in step (1) is 35-55° C., the pH is 7.2-7.6, and the rotation speed is 100-300 r / min.

10. The preparation method according to claim 6, characterized in that: The concentration of solution A in step (1) is 90-130 g / L.

11. The preparation method according to claim 6, characterized in that: The concentration of solution B in step (1) is 1.0-2.0 g / L.

12. The preparation method according to claim 6, characterized in that: The concentration of solution C in step (1) is 220-260 g / L.

13. The preparation method according to claim 6, characterized in that: The concentration of the base solution in step (1) is 0-50 g / L, but does not include 0 g / L.

14. The preparation method according to claim 6, characterized in that: The cobalt salt solution in step (1) includes CoCl2 and / or CoSO4.

15. The preparation method according to claim 6, characterized in that: The base liquid in step (1) comprises ammonium carbonate solution.

16. The preparation method according to claim 6, characterized in that: The precipitant solution in step (1) comprises ammonium carbonate solution.

17. The preparation method according to claim 6, characterized in that: After the solution B is replaced by the solution D in step (2), the solution A, the solution C and the solution D are fed simultaneously in a parallel flow manner.

18. The preparation method according to claim 6, characterized in that: The concentration of solution D in step (2) is 0.2-1 g / L.

19. The preparation method according to claim 6, characterized in that: The Al salt solution in step (2) includes Al2(SO4)3 and / or AlCl3.

20. The preparation method according to claim 6, characterized in that: The aging time in step (2) is 1-2 hours.

21. The preparation method according to claim 6, characterized in that: After the aging in step (2), washing and drying steps are also performed.

22. The preparation method according to claim 6, characterized in that: The calcination temperature in step (3) is 600-800°C and the calcination time is 2-4h.

23. The preparation method according to claim 6, comprising the following steps: (1) feeding solution A with a concentration of 90-130 g / L, solution B with a concentration of 1.0-2.0 g / L, and solution C with a concentration of 220-260 g / L into the bottom liquid in a parallel flow manner, and reacting at a pH of 7.2-7.6, a rotation speed of 100-300 r / min, and a temperature of 35-55° C.; The solution A comprises a cobalt salt solution, the solution B comprises a transition metal salt solution, the solution C comprises a precipitant solution, and the concentration of the base solution is 0-50 g / L, but does not include 0 g / L; (2) When the reaction in step (1) is carried out until the median particle size of the particles is 2-4 μm after stopping the reaction, the solution B in step (1) is replaced with solution D, and then solution A, solution C and solution D are fed simultaneously in parallel to continue the reaction. After the reaction is completed, the feeding is stopped, and then the mixture is aged for 1-2 hours, and then washed and dried to obtain cobalt carbonate; The solution D has a concentration of 0.2-1 g / L and includes an Al salt solution; (3) calcining the cobalt carbonate in step (2) at a temperature of 600-800° C. for 2-4 hours to obtain the cobalt tetroxide with the core-shell doping structure.

24. A lithium ion battery, characterized in that: The lithium-ion battery comprises a lithium cobalt oxide positive electrode material, and the lithium cobalt oxide positive electrode material is prepared using the core-shell doped cobalt tetroxide as described in any one of claims 1 to 5 as a raw material.

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