Intermediate mixture for preparing a cathode material and method for preparing the same, method for preparing a cathode material

Abstract

The present application provides an intermediate mixture for preparing a positive electrode material and a preparation method thereof, and a method for preparing a positive electrode material, so as to improve the production capacity of the positive electrode material of a lithium ion battery, simplify the preparation method and reduce the cost of the positive electrode material of the lithium ion battery, thereby improving the preparation efficiency of the lithium ion battery. The intermediate mixture comprises an intermediate Li α Ni a Co b Mn c Al d M 1‑a‑b‑c‑d O2; in the XRD pattern of the intermediate mixture, the peak intensity ratio of the (003) diffraction peak to the (104) diffraction peak is 0.3-0.6; wherein M is at least one of Mg, Zr and Zn, 0.95 a b c d 1-a-b-c-d 0.6 0.4 0.4 0.1 0.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery cathode material, and particularly relates to an intermediate mixture for preparing a cathode material and a preparation method thereof, and a method for preparing a cathode material. BACKGROUND

[0002] With the wide application of lithium ion batteries, higher requirements are put forward for the preparation efficiency and energy consumption of the cathode materials thereof. The current method for preparing a cathode material is to process coarse lithium hydroxide powder into fine lithium hydroxide powder, so that the fine lithium hydroxide powder can be mixed with a precursor into a relatively uniform intermediate mixture. Then, the intermediate mixture is subjected to high-temperature sintering to obtain the cathode material.

[0003] However, because the fine lithium hydroxide powder has problems such as moisture absorption and decomposition, the process requirement for processing the coarse lithium hydroxide powder into the fine lithium hydroxide powder is high, and the corresponding processing process is relatively complex. Moreover, the fine lithium hydroxide powder as the main raw material of the cathode material has the characteristic of low boat loading amount when participating in sintering, thereby causing the problem of low production capacity when the fine lithium hydroxide powder is used as the lithium source to prepare the cathode material. SUMMARY

[0004] The present application provides an intermediate mixture for preparing a cathode material and a preparation method thereof, and a method for preparing a cathode material, so as to improve the production capacity of the cathode material of the lithium ion battery, simplify the preparation method and cost of the cathode material of the lithium ion battery, and thus improve the preparation efficiency of the lithium ion battery.

[0005] In a first aspect, the embodiments of the present application provide an intermediate mixture for preparing a cathode material, the intermediate mixture comprising an intermediate Li α Ni a Co b Mn c Al d M 1-a-b-c-d O2; in the XRD pattern of the intermediate mixture, the peak intensity ratio of the (003) diffraction peak to the (104) diffraction peak is 0.3-0.6; wherein,

[0006] M is at least one of Mg, Zr and Zn, 0.95

[0007] In a possible implementation, the intermediate mixture is obtained by sintering a mixture of a precursor and coarse lithium hydroxide powder;

[0008] The D 50 of the coarse lithium hydroxide powder is greater than or equal to 80 μm; and the precursor is selected from the group consisting of a molecular expression of Nia Co b Mn c Al d M 1-a-b-c-d O of the oxide precursor, the molecular expression is Ni a Co b Mn c Al d M 1-a-b-c-d CO3 of the carbonate precursor, and the molecular expression is Ni a Co b Mn c Al d M 1-a-b-c-d (OH)2 of the hydroxide precursor.

[0009] In a possible implementation, the sintering temperature of the sintering is 450-700°C, and the sintering time is 4-8 hours.

[0010] In a possible implementation, in the mixture of the precursor and the lithium hydroxide coarse powder, the molar ratio between the lithium hydroxide coarse powder and the precursor is (0.95-1.05):1.

[0011] In a possible implementation, the lithium-nickel mixing rate of the intermediate mixture is 0.2-0.45.

[0012] In a possible implementation, the intermediate mixture further includes intermediate lithium hydroxide; the D 50 of the intermediate lithium hydroxide is less than the D 50 of the lithium hydroxide coarse powder in the sintering raw material of the intermediate mixture.

[0013] In a second aspect, the embodiments of the present application provide a method for preparing the intermediate mixture of the first aspect and any possible implementation, comprising:

[0014] sintering the mixture of the lithium hydroxide coarse powder and the precursor under the sintering condition of 450-700°C to obtain the intermediate mixture;

[0015] wherein the D 50 of the lithium hydroxide coarse powder is greater than or equal to 80μm, and the precursor is selected from: the oxide precursor with the molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d O of the oxide precursor, the molecular expression is Ni a Co b Mn c Al d M 1-a-b-c-d CO3 of the carbonate precursor, and the molecular expression is Nia Co b Mn c Al d M 1-a-b-c-d At least one of the hydroxide precursors of (OH)2.

[0016] In one possible implementation, the sintering conditions further include a sintering time of 4-8 hours.

[0017] In one possible implementation, the precursor comprises a polycrystalline precursor, and the mixture of the crude lithium hydroxide powder and the precursor is obtained by mixing the precursor and the crude lithium hydroxide powder at a frequency of less than or equal to 25 Hz.

[0018] Thirdly, embodiments of this application provide a method for preparing a cathode material based on the intermediate mixture described in the first aspect and any possible implementation, comprising:

[0019] The first mixture comprising the aforementioned mixture and finely powdered lithium hydroxide is sintered to produce a product with the molecular formula Li. β Ni a Co e Mn f Al g M 1-a-e-f-g O2 cathode material;

[0020] Wherein, M is at least one of Mg, Zr and Zn, 0.98 < β < 1.02, 0 ≤ e < 0.4, 0 ≤ f < 0.4, 0 ≤ g < 0.1, 1 - aefg ≥ 0, and f and g are not simultaneously 0;

[0021] The D of the fine lithium hydroxide powder 50 The fine lithium hydroxide powder has a particle size of less than or equal to 20 μm, and the molar ratio between the fine lithium hydroxide powder and the precursor is (0.01-0.11):1. The precursor is a raw material for preparing the intermediate mixture. The precursor is selected from: Ni a Co b Mn c Al d M 1-a-b-c-d O oxide precursor, molecular formula is Ni a Co b Mn c Al d M 1-a-b-c-d The carbonate precursor of CO3 and its molecular formula are Ni a Co b Mn c Al d M 1-a-b-c-dat least one of hydroxide precursor of (OH)2; 0.6

[0022] In one possible implementation, the first mixture further includes a dopant corresponding to an oxide and / or hydroxide of at least one of Co, Al and M in the cathode material.

[0023] In one possible implementation, the first mixture including the intermediate mixture and fine powder lithium hydroxide is sintered to generate a cathode material with a molecular expression of Li β Ni a Co e Mn f Al g M 1-a-e-f-g O2.

[0024] The first mixture is sintered at 650-900°C to obtain a sintered product, wherein the sintered product includes the cathode material with a molecular expression of Li β Ni a Co e Mn f Al g M 1-a-e-f-g O2.

[0025] The sintered product is washed with water and dried to make the cathode material with a molecular expression of Li β Ni a Co e Mn f Al g M 1-a-e-f-g O2, wherein the surface residual alkali content of the cathode material is less than or equal to 3500 ppm.

[0026] In one possible implementation, the sintered product is washed with water and dried to make the cathode material with a molecular expression of Li β Ni a Co e Mn f Al g M 1-a-e-f-g O2, wherein the surface residual alkali content of the cathode material is less than or equal to 3500 ppm, and the cathode material further includes:

[0027] The cathode material with the residual alkali content less than or equal to 3500 ppm is mixed with a coating agent to obtain a second mixture, wherein the coating agent includes at least one of Al(OH)3, B(OH)3, H3BO3, TiO2 and Ti(OH)4.

[0028] The second mixture is subjected to a second sintering, so that the positive electrode material surface has a coating layer; wherein the coating layer is a metal oxide corresponding to the coating agent.

[0029] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects:

[0030] In the embodiments of the present application, by providing an intermediate mixture as a raw material for preparing a positive electrode material of a lithium ion battery, the preparation process of the positive electrode material of the lithium ion battery is simplified, and the preparation efficiency of the positive electrode material of the lithium ion battery is improved.

[0031] Furthermore, the intermediate mixture obtained by sintering the coarse lithium hydroxide and the precursor is used to prepare the positive electrode material, which can avoid the problem of low production capacity of the positive electrode material caused by the low sintering boat loading amount due to the low bulk density of the fine lithium hydroxide when the fine lithium hydroxide is mixed and sintered with the precursor. On the other hand, it can avoid the problem of low preparation efficiency and high process cost caused by the complex grinding process of fine lithium hydroxide and the high demand for fine lithium hydroxide when coarse lithium hydroxide needs to be ground into fine lithium hydroxide before being mixed and sintered with the precursor.

[0032] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The SEM image of the intermediate mixture (i.e. pre-sintering product) obtained in Example 1 provided in the embodiments of the present application;

[0034] Figure 2 The SEM image of the positive electrode material in Example 1 provided in the embodiments of the present application;

[0035] Figure 3 The cycle performance test chart of the lithium ion full battery corresponding to Example 1 and Comparative Example 1 provided in the embodiments of the present application. DETAILED DESCRIPTION

[0036] In view of the low production capacity of the current lithium-ion battery cathode material prepared by using fine lithium hydroxide powder as the lithium source, the application provides an intermediate mixture for preparing a cathode material. The intermediate mixture is an intermediate mixture containing intermediate lithium hydroxide and an intermediate, which is obtained by sintering a precursor and coarse lithium hydroxide powder at 450-650°C. Since the intermediate mixture is obtained by sintering the coarse lithium hydroxide powder and the precursor, the bulk density (greater than 1.3 g / cm 3 ) of the mixture of the coarse lithium hydroxide powder and the precursor is significantly higher than the bulk density (less than 0.8 g / cm 3 ) of the mixture of the fine lithium hydroxide powder and the precursor, so that the loading amount of the coarse lithium hydroxide powder and the precursor can be increased, that is, more coarse lithium hydroxide powder and the precursor can be added under the same sintering equipment and sintering parameters. Thus, the problem of low production capacity of the cathode material caused by the low bulk density of the fine lithium hydroxide powder and the low loading amount of the raw materials (mainly the fine lithium hydroxide powder and the precursor) can be effectively avoided.

[0037] It should be noted that in the application, the subscripts in the molecular formula are atomic indices, which are used to represent the relative molar content of the corresponding atoms in the molecule. For example, in the molecular formula of the intermediate Li α Ni a Co b Mn c Al d M 1-a-b-c-d O2, a, b, c, and d are atomic indices, that is, a, b, c, and d represent the relative molar content of Li, Ni, Co, Mn, Al, and the doping element M in the molecule, and a is the molar ratio of Li to the intermediate.

[0038] In addition, in the application, when the elements (such as M) or atomic indices in different substances are the same symbol, it means that the same element is contained in different substances, and the relative molar content of the same element in different substances is equal. For example, in the precursor and the intermediate, the doping element M and the content 1-a-b-c-d of M are equal.

[0039] On the contrary, when the elements or atomic indices in different substances are different symbols, it means that the types of elements contained in different substances can be the same, can not be completely the same, or can be completely the same; and the contents of the elements can be equal or not equal.

[0040] The following provides a detailed description of an intermediate mixture for preparing cathode materials and a method thereof, as well as a method for preparing cathode materials, provided by the present invention. It should be noted that the embodiments described below are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of the present invention.

[0041] The intermediate mixture for preparing the cathode material provided in the embodiments of this application will be described in detail below.

[0042] The intermediate mixture includes intermediate Li α Ni a Co b Mn c Al d M 1-a-b-c-d O2.

[0043] Wherein, M is at least one of Mg, Zr and Zn, 0.95 < α < 1.05, 0.6 < a < 1, 0 ≤ b < 0.4, 0 ≤ c < 0.4, 0 ≤ d < 0.1, 1 - abcd ≥ 0, and c and d are not simultaneously 0.

[0044] Please refer to Figure 1 The intermediate mixture contains particulate matter. Furthermore, in the XRD diffraction pattern of the intermediate mixture, the peak intensity ratio of the (003) diffraction peak to the (104) diffraction peak is 0.3-0.6. This indicates that the intermediate mixture contains a layered phase, therefore the crystal structure of the intermediate is layered. Thus, Figure 1 Medium-sized particles are intermediates.

[0045] Furthermore, the intermediate mixture is obtained by sintering a mixture of precursor and coarse lithium hydroxide powder.

[0046] The sintering temperature is 450-700℃, for example, 650℃. The sintering time is 4-8 hours. The relationship between the sintering time and the sintering temperature is: the higher the sintering temperature, the shorter the sintering time.

[0047] Furthermore, in the above mixture of precursor and crude lithium hydroxide powder, the molar ratio between the crude lithium hydroxide powder and the precursor is (0.95-1.05):1.

[0048] In some embodiments, the mixture of the precursor and the coarse lithium hydroxide powder can be a mixture that is shaken to mix thoroughly. The precursor can be a single-crystal precursor, can be a polycrystal precursor, or can be a mixture of a single-crystal precursor and a polycrystal precursor. Since the polycrystal precursor has a fragile property, when the polycrystal precursor is contained in the precursor, the frequency of shaking during mixing is less than or equal to 25 Hz to avoid the problem of uneven particle size of the precursor caused by breaking of the particles of the precursor, which leads to excessive sintering and insufficient sintering of the positive electrode material.

[0049] The median particle size D50 of the coarse lithium hydroxide powder described above is greater than or equal to 80 μm. 50 The median particle size D50 of the coarse lithium hydroxide powder described above is greater than or equal to 80 μm.

[0050] In some embodiments, the median particle size D50 of the coarse lithium hydroxide powder is 100-500 μm, or 200 μm. 50 The median particle size D50 of the coarse lithium hydroxide powder described above is greater than or equal to 80 μm.

[0051] The precursor described above is selected from at least one of an oxide precursor having a molecular formula of Ni a Co b Mn c Al d M 1-a-b-c-d O, a carbonate precursor having a molecular formula of Ni a Co b Mn c Al d M 1-a-b-c-d CO3, and a hydroxide precursor having a molecular formula of Ni a Co b Mn c Al d M 1-a-b-c-d (OH)2.

[0052] Further, the intermediate mixture described above further includes intermediate lithium hydroxide. Since the intermediate mixture is obtained by sintering the mixture of the precursor and the coarse lithium hydroxide powder at 450-650°C, and the critical point temperature at which lithium hydroxide turns into a molten state is 450°C, the intermediate lithium hydroxide in the intermediate mixture is actually molten lithium hydroxide that, after the coarse lithium hydroxide powder turns into a molten state, fails to continuously react with the intermediate due to the sintering temperature and sintering time, and is obtained after cooling.

[0053] Therefore, the median particle size D50 of the intermediate lithium hydroxide in the intermediate mixture described above is less than the D50 of the coarse lithium hydroxide powder mixed with the precursor. 50 The median particle size D50 of the intermediate lithium hydroxide in the intermediate mixture described above is less than the D50 of the coarse lithium hydroxide powder mixed with the precursor. 50 Further, compared to the degree of mixing uniformity of the mixture of the coarse lithium hydroxide powder and the precursor, the degree of mixing uniformity of the intermediate lithium hydroxide and the intermediate in the intermediate mixture should be more uniform; that is, the intermediate lithium hydroxide is more uniformly distributed on the surface of the intermediate.

[0054] Further, the lithium-nickel mixing rate of the intermediate mixture is 0.2-0.45. Here, the lithium-nickel mixing rate is obtained via XRD refinement.

[0055] Based on the same inventive concept, the present application provides a method for preparing the aforementioned intermediate mixture, which comprises the following implementation steps:

[0056] The mixture of the coarse lithium hydroxide powder and the precursor is sintered under sintering conditions of 450-700°C to obtain the intermediate mixture.

[0057] The D50 of the coarse lithium hydroxide powder is less than or equal to 80μm. 50 For example, it can be 100-500μm.

[0058] The precursor is selected from at least one of: an oxide precursor with a molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d O, an oxide precursor with a molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d CO3, a carbonate precursor, and a hydroxide precursor with a molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d (OH)2.

[0059] The sintering temperature of the aforementioned sintering is preferably 550-645°C. The aforementioned sintering conditions can further comprise a sintering time. In some embodiments, the sintering time is 4-8 hours, i.e., the constant temperature holding time after reaching the sintering temperature is 4-8 hours.

[0060] The aforementioned can be a single crystal precursor, can be a polycrystal precursor, or can be a mixture of a single crystal precursor and a polycrystal precursor. The polycrystal precursor has the characteristics of large particle size (median particle size of about 10μm), low strength, and easy breakage, and the single crystal precursor has the characteristics of relatively small particle size (median particle size of about 3-4μm), high strength, and not easy to break.

[0061] Since the coarse lithium hydroxide powder has the characteristics of large particle size and high strength, and the polycrystal precursor is easy to break, when the precursor contains a polycrystal precursor and the precursor and the coarse lithium hydroxide powder are mixed, if the mechanical strength of the mixing is too high, the coarse lithium hydroxide powder is easy to obtain high kinetic energy, thereby breaking the polycrystal precursor.

[0062] Therefore, the current precursor contains a polycrystal precursor, and the mixing frequency is less than or equal to 25 Hz when the precursor and the lithium hydroxide coarse powder are mixed.

[0063] Since the aforementioned sintering temperature is not lower than the melting temperature of lithium hydroxide, the lithium hydroxide coarse powder turns into a molten state after reaching the melting temperature, and the lithium hydroxide in the molten state actually diffuses on the surface of the precursor or the intermediate and diffuses towards the interior of the precursor and / or the intermediate while participating in the phase formation of the intermediate: reacting with the precursor to generate the intermediate, and at the same time, the oxidation reaction is carried out under the condition of heat preservation or under the condition of continuing to heat to the sintering temperature after reaching the melting temperature. During the cooling stage after heat preservation, the lithium hydroxide in the molten state that is not fully reacted due to agglomeration and the like gradually returns to a solid state, and the diffusion of lithium hydroxide towards the interior of the intermediate gradually slows down until it stops.

[0064] Therefore, when the intermediate mixture contains intermediate lithium hydroxide, the intermediate lithium hydroxide is obtained after the lithium hydroxide coarse powder turns into a molten state for a period of time, and the median particle size D50 of the intermediate lithium hydroxide is less than the D50 of the lithium hydroxide coarse powder. 50 The D50 of the lithium hydroxide coarse powder to be pre-sintered should be less than the D50 of the lithium hydroxide coarse powder. 50 In addition, the intermediate lithium hydroxide should be obtained due to the large particle size of the lithium hydroxide coarse powder, which is manifested as enrichment on the surface of the precursor and failure to diffuse and contact the precursor to cause the oxidation reaction during the pre-sintering stage.

[0065] Based on the same inventive concept, the embodiments of the present application also provide a method for preparing a positive electrode material based on the aforementioned intermediate mixture, to solve the problem of low efficiency of preparation of the positive electrode material caused by the complex process of grinding the lithium hydroxide coarse powder into a fine powder, and to solve the problem of low production capacity of the positive electrode material caused by the low loading amount when co-sintering the mixture containing the fine powder lithium hydroxide and the precursor after the lithium hydroxide coarse powder is ground into a fine powder. The method at least includes the following implementation steps:

[0066] Sintering the first mixture containing the intermediate mixture and the fine powder lithium hydroxide to generate a positive electrode material with a molecular expression of Li β Ni a Co e Mn f Al g M 1-a-e-f-g O2.

[0067] Wherein, 0.98 < β < 1.02, 0 ≤ e < 0.4, 0 ≤ f < 0.4, 0 ≤ g < 0.1, 1-a-e-f-g ≥ 0, and f and g are not zero at the same time.

[0068] The D50 of the fine powder lithium hydroxide should be less than the D50 of the lithium hydroxide coarse powder. 50less than or equal to 20 μm, and the molar ratio between the fine lithium hydroxide powder and the precursor is (0.01-0.11): 1.

[0069] The precursor is a raw material for preparing the intermediate mixture, and the precursor is at least one selected from the group consisting of an oxide precursor with a molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d O, a carbonate precursor with a molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d CO3, and a hydroxide precursor with a molecular expression of Ni a Co b Mn c Al d M 1-a-b-c-d (OH)2; M is at least one selected from the group consisting of Mg, Zr and Zn, 0.6

[0070] In some embodiments, the D 50 is 2.5-20 μm.

[0071] The first mixture can be mixed at a frequency of no less than 30 Hz. For example, the mixing time can be 50 min, and the mixing frequency can be 50 Hz.

[0072] Further, the first mixture can further include a dopant to increase the content of at least one of Co, Al and the doping element M in the positive electrode material; and the dopant is an oxide and / or a hydroxide corresponding to the at least one of Co, Al and the doping element M.

[0073] In some embodiments, the dopant can be at least one of an oxide of Co, a hydroxide of Co, an oxide of Al, a hydroxide of Al, an oxide of the doping element M and a hydroxide of the doping element M.

[0074] In some embodiments, the first mixture can be directly fired to generate the positive electrode material. Details are as follows:

[0075] First, the first mixture is sintered at 650-900 °C to obtain a first firing product. Since the sintering temperature of the first sintering is high, a high content of residual alkali is easily generated on the surface of the first firing product. The residual alkali is LiOH and Li2CO3. Therefore, the first firing product is the positive electrode material Li β Nia Co e Mn f Al g M 1-a-e-f-g O2. That is, the first sintered product includes the positive electrode material with the molecular expression of Li β Ni a Co e Mn f Al g M 1-a-e-f-g O2, and residual alkali on the surface of the positive electrode material.

[0076] Due to the problems of non-conduction and the like caused by the residual alkali, in some embodiments, the residual alkali is removed by water washing to obtain a first sintered product with a residual alkali content less than or equal to 3500 ppm. That is, after the removal of the residual alkali, the content of LiOH on the surface of the first sintered product is less than or equal to 2000 ppm, and the content of Li2CO3 is less than or equal to 1500 ppm.

[0077] The time of the first sintering (i.e. the constant temperature holding time) can be 7-12 hours.

[0078] In some embodiments, the heating rate can be 2-10℃ / min.

[0079] In some embodiments, to further improve the stability and the like electrochemical performance of the positive electrode material, after the first sintering, the positive electrode material can be further coated by second sintering. Specifically, the aforementioned first sintered product with a residual alkali content less than or equal to 3500 ppm can be mixed with a coating agent to obtain a second mixture. The coating agent includes at least one of Al(OH)3, B(OH)3, H3BO3, SiO2, Si(OH)4, TiO2 and Ti(OH)4. Then, the second mixture is subjected to the aforementioned second sintering, so that the positive electrode material has a coating layer on the surface.

[0080] The coating layer is a metal oxide corresponding to the coating agent, i.e. a metal oxide of the metal ion of the coating element in the coating agent.

[0081] In particular, when the coating agent contains an amphoteric substance, for example, the coating element is Al and / or Si, etc., the coating layer also contains a trace amount of lithium metal oxide, for example, lithium aluminate LiAlO2, lithium silicate Li4SiO4.

[0082] The sintering temperature of the second sintering can be 400-700℃. The corresponding sintering time (i.e. the constant temperature holding time) is 7-12 hours.

[0083] Further, the aforementioned sintering can be carried out in a roller kiln or a rotary kiln, etc., so that the sintering object is in a dynamic sintering. However, during the high-temperature sintering process, the kiln is prone to have impurities such as slag mixed into the product.

[0084] Therefore, in some embodiments, the cathode material can be sieved to remove large-particle impurities, and demagnetized to remove magnetic impurities (e.g., iron slag) therein, so as to finally obtain a high-purity ternary cathode material.

[0085] Based on the same inventive concept, the application also provides a lithium ion battery comprising the aforementioned cathode material. That is, the lithium ion battery comprises the aforementioned cathode material sintered from the intermediate mixture.

[0086] The following is described in detail through examples and comparative examples:

[0087] Example 1

[0088] S1, polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50 = 11 pm) and coarse lithium hydroxide powder (D 50 = 250 pm) in a high-speed mixer at a molar ratio of 1:1.02 and a mixing frequency of 25 Hz for 30 minutes to obtain a first mixture.

[0089] S2, the first mixture is placed in a roller hearth kiln for pre-sintering treatment: the pre-sintering temperature is 550°C, and the pre-sintering time is 7 hours.

[0090] The intermediate mixture obtained by pre-sintering is subjected to SEM testing, and the SEM image is shown in FIG. 1. Figure 1

[0091] S3, the pre-sintered product is mixed with fine lithium hydroxide powder (D 50 = 13 pm) at a molar ratio of 1:0.02 (corresponding to a molar ratio between the precursor and the fine lithium hydroxide powder of 1:0.02), and a dopant (magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, zinc oxide) is added into a high-speed mixer and mixed at a frequency of 35 Hz for 50 minutes to obtain a second mixture.

[0092] S4, the second mixture is placed in a roller hearth kiln for first sintering to obtain a first sintered product. The first sintering temperature is 780°C, and the sintering time is 10 hours.

[0093] The loading height is set to 100 mm, and the loading amount is 8 kg during sintering.

[0094] S5, the first sintered product is crushed, sieved, and demagnetized, and then washed with water at a water-to-material ratio of 1:1 for 5 minutes, and then coated with a coating agent B(OH)3, and subjected to second sintering at a sintering temperature of 320°C for 10 hours. The obtained product is sieved and demagnetized to obtain a ternary cathode material LiNi 0.82 Co​0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al, Zn. The SEM image of the positive electrode material is shown in Figure 2 .

[0095] Example 2

[0096] S1, the polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50 = 11 pm) and coarse lithium hydroxide (D 50 = 250 pm) in a molar ratio of 1:1.02 in a high-speed mixer at a mixing frequency of 25 Hz for 30 minutes to obtain a first mixture.

[0097] S2, the first mixture is placed in a roller hearth kiln for pre-sintering treatment: the pre-sintering temperature is 600°C, and the pre-sintering time is 7 hours.

[0098] S3, the pre-sintered product is mixed with fine lithium hydroxide (D 50 = 13 pm) in a molar ratio of 1:0.02 (corresponding to a molar ratio between the precursor and the fine lithium hydroxide of 1:0.02) and a dopant (magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide) in a high-speed mixer: mixed at a frequency of 35 Hz for 50 minutes to obtain a second mixture.

[0099] S4, the second mixture is placed in a roller hearth kiln for first sintering to obtain a first sintered product. The first sintering temperature is 780°C, and the sintering time is 10 hours.

[0100] The loading height is set to 100 mm and the loading amount is 8 kg during sintering.

[0101] S5, after crushing, sieving, and removing the magnetism, the first sintered product is washed with water at a water-to-material ratio of 1:1 for 5 minutes, then a coating agent B(OH)3 is added, and second sintering is performed: the second sintering temperature is 320°C, and the second sintering time is 10 hours. The obtained product is sieved and the magnetism is removed to obtain a ternary positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al.

[0102] Example 3

[0103] S1, the polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50 = 11 pm) and coarse lithium hydroxide (D 50=250μm) were mixed at a molar ratio of 1:1.02 in a high-speed mixer at a mixing frequency of 25Hz for 30 minutes to obtain the first mixture.

[0104] S2. The first mixture is placed in a roller kiln for pre-sintering treatment: the pre-sintering temperature is 645℃ and the pre-sintering time is 7 hours.

[0105] S3. The pre-sintered product is mixed with fine lithium hydroxide powder (D 50 =13μm) were mixed in a high-speed mixer at a molar ratio of 1:0.02 (equivalent to a molar ratio of 1:0.02 between the precursor and fine lithium hydroxide powder), along with dopants (magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, and zinc oxide); the mixture was mixed at a frequency of 35Hz for 50 minutes to obtain a second mixture.

[0106] S4. The second mixture is placed in a roller kiln for the first sintering to obtain the first sintered product. The temperature of the first sintering is 780℃ and the sintering time is 10h.

[0107] During sintering, the boat height is set to 100mm and the boat weight is 8kg.

[0108] S5. The product from the first sintering is crushed, sieved, and demagnetized. After washing with water at a 1:1 water-to-material ratio for 5 minutes, coating agent B(OH)3 is added, and a second sintering is performed. The second sintering temperature is 320℃, and the second sintering time is 10 hours. The resulting product is then sieved and demagnetized to obtain the ternary cathode material LiNi. 0.82 Co 0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al, Zn.

[0109] Example 4

[0110] S1, making the polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50 =11μm) and coarse lithium hydroxide (D 50 =300μm) were mixed at a molar ratio of 1:1.04 in a high-speed mixer at a mixing frequency of 25Hz for 30 minutes to obtain the first mixture.

[0111] S2. The first mixture is placed in a roller kiln for pre-sintering treatment: the pre-sintering temperature is 550℃ and the pre-sintering time is 7 hours.

[0112] S3. The pre-sintered product is mixed with fine lithium hydroxide powder (D 50= 13 μm) in a molar ratio of 1:0.01 (corresponding to a molar ratio between the precursor and the fine lithium hydroxide powder of 1:0.01) and a dopant (magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, zinc oxide) in a high-speed mixer; mixing at a frequency of 35 Hz for 50 minutes to obtain a second mixture.

[0113] S4, placing the second mixture in a roller hearth kiln to perform first sintering to obtain a first sintered product. The first sintering temperature is 780°C, and the sintering time is 10 hours.

[0114] During sintering, the loading height is set to 100 mm, and the loading amount is 8 kg.

[0115] S5, crushing, sieving, and demagnetizing the first sintered product, and then washing the first sintered product with water at a water-material ratio of 1:1 for 5 minutes, adding a coating agent B(OH)3, and performing second sintering: the second sintering temperature is 320°C, and the second sintering time is 10 hours. Sieving and demagnetizing the obtained product to obtain a ternary positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al, or Zn.

[0116] Comparative Example 1

[0117] S1, mixing the polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50 = 11 μm), coarse lithium hydroxide powder (D 50 = 250 μm) in a molar ratio of 1:1.04, and adding a dopant (magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide) into a high-speed mixer, mixing at a frequency of 35 Hz for 50 minutes to obtain a first mixture.

[0118] S2, placing the first mixture in a roller hearth kiln to perform pre-sintering treatment: the pre-sintering temperature is 600°C, and the pre-sintering time is 7 hours.

[0119] S3, placing the pre-sintered product in a roller hearth kiln to perform first sintering to obtain a first sintered product. The first sintering temperature is 780°C, and the sintering time is 10 hours.

[0120] During sintering, the loading height is set to 100 mm, and the loading amount is 8 kg.

[0121] S4, crushing, sieving, and demagnetizing the first sintered product, and then washing the first sintered product with water at a water-material ratio of 1:1 for 5 minutes, adding a coating agent B(OH)3, and performing second sintering: the second sintering temperature is 320°C, and the second sintering time is 10 hours. Sieving and demagnetizing the obtained product to obtain a ternary positive electrode material LiNi0.82 Co 0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al.

[0122] Comparative Example 2

[0123] S1, mixing the polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50 = 11 pm) with coarse lithium hydroxide powder (D 50 = 250 pm) in a high-speed mixer at a molar ratio of 1:0.5 and a mixing frequency of 25 Hz for 30 minutes to obtain a first mixture.

[0124] S2, placing the first mixture in a roller hearth kiln for pre-sintering treatment: the pre-sintering temperature is 550°C, and the pre-sintering time is 7 hours.

[0125] S3, mixing the pre-sintered product with fine lithium hydroxide powder (D 50 = 12 pm) in a high-speed mixer at a molar ratio of 1:0.54 (corresponding to a molar ratio between the precursor and the fine lithium hydroxide powder of 1:0.54) and a frequency of 35 Hz for 50 minutes, and adding a dopant (magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, zinc oxide) to obtain a second mixture.

[0126] S4, placing the second mixture in a roller hearth kiln for first sintering to obtain a first sintered product: the first sintering temperature is 780°C, and the sintering time is 10 hours.

[0127] During sintering, the loading height is set to 100 mm. Due to the large amount of fine lithium hydroxide powder, the loose bulk density is reduced, and the loading amount can only be 6 kg under the same loading height.

[0128] S5, sieving and demagnetizing the first sintered product, washing with water at a water-to-material ratio of 1:1 for 5 minutes, adding a coating agent B(OH)3, and performing second sintering: the second sintering temperature is 320°C, and the sintering time is 10 hours. Sieving and demagnetizing the obtained product to obtain a ternary positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al, Zn.

[0129] Comparative Example 3

[0130] S1, mixing the polycrystalline ternary precursor Ni 0.82 Co 0.12 Mn 0.06 (OH)2(D 50= 11 μm) and coarse lithium hydroxide powder (D 50 = 250 μm) in a high-speed mixer at a mixing frequency of 25 Hz for 30 minutes to obtain a first mixture.

[0131] S2, the first mixture was placed in a roller hearth kiln for pre-sintering treatment: the pre-sintering temperature was 680°C, and the pre-sintering time was 7 hours.

[0132] S3, the pre-sintered product was mixed with fine lithium hydroxide powder (D 50 = 13 μm) in a high-speed mixer at a frequency of 35 Hz for 50 minutes to obtain a second mixture.

[0133] S4, the second mixture was placed in a roller hearth kiln for first sintering to obtain a first sintered product. The first sintering temperature was 780°C, and the sintering time was 10 hours.

[0134] During sintering, the boat loading height was set to 100 mm, and the boat loading amount was 8 kg.

[0135] S5, the first sintered product was crushed, sieved, and demagnetized, and then washed with water at a water-to-material ratio of 1:1 for 5 minutes, and then coated with a coating agent B(OH)3, and then subjected to second sintering: the second sintering temperature was 320°C, and the sintering time was 10 hours. The obtained product was sieved and demagnetized to obtain a ternary positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 MO2@B2O3; M is Mg, Zr, Ti, Al, or Zn.

[0136] To compare the production capacity of the positive electrode materials of Comparative Examples 1-2 and Comparative Examples 1-2, the boat loading amounts with a boat loading height of 100 mm are summarized below, and are shown in Table 1.

[0137] Table 1

[0138] No. Example 1 Example 2 Comparative Example 1 Comparative Example 2 Charge amount (Kg) 8 8 8 6

[0139] Further, the pre-sintered products (i.e., intermediate mixtures) and the positive electrode materials in the examples and comparative examples were subjected to XRD tests, and XRD test patterns were obtained. Through the XRD test patterns, the peak intensity ratios I(003) / I(104) of the (003) diffraction peaks and the (104) diffraction peaks of the pre-sintered products and the positive electrode materials were determined, respectively. Then, based on the XRD pattern refinement, the lithium-nickel mixing rates of the pre-sintered products and the positive electrode materials were determined. The test data are shown in Table 2.

[0140] Table 2

[0141]

[0142]

[0143] Further, lithium ion button cells were prepared using the positive electrode materials of Example 1 and Comparative Examples 1-2, and lithium ion full cells were also prepared using the positive electrode materials of Example 1 and Comparative Examples 1-2, to test the electrochemical performance of the corresponding positive electrode materials. The preparation of the lithium ion button cells and lithium ion full cells is described below, respectively:

[0144] (I) Preparation of lithium ion button cells

[0145] Step S1, the positive electrode material, acetylene black (conductive agent), and polyvinylidene (binder PVDF) were dissolved in 2-methylpyrrolidone (NMP) in a mass ratio of 96.5:1.5:2 to prepare a thick slurry, which was uniformly coated on the surface of an aluminum foil and then dried. The drying environment can be an oven at 135°C (without a vacuum oven), and the drying time is 0.5 hours.

[0146] Step S2, using a punching machine, the dried aluminum foil was cut into circular electrode pieces (the diameter can be 11 mm), and the surface loading of the current collector of each electrode piece was 15 mg / cm 2 and was placed back into a vacuum oven (120°C) for 2 hours to remove trace amounts of moisture, and finally was stored in an argon atmosphere glove box.

[0147] Step S3, the electrode piece stored in the glove box was used as the positive electrode piece, lithium was used as the negative electrode, the positive electrode and the negative electrode were separated by a separator, and 30 microliters of a ternary commercial electrolyte (LiPF6 / EC-DEC-EMC, volume ratio of 1:1:1) was added. The positive electrode shell, positive electrode piece, separator, lithium piece, gasket, and spring were sequentially assembled in order, and finally a sealing machine was used to complete the packaging to obtain a lithium ion button cell.

[0148] (II) Preparation of lithium ion full cells

[0149] The positive active material, conductive carbon Super P, KS6 and polyvinylidene fluoride (HSV900) were mixed in a mass ratio of 94.5%:2%:1%:2.5% and homogenized, then uniformly coated on an aluminum foil and dried, with a surface density controlled at 16 mg / cm2. The positive electrode sheet was rolled into a compacted density of 3.0 g / cm3 using a roll mill, and then the positive electrode sheet was placed in a vacuum drying oven at 120°C for 10 h. The positive electrode sheet, separator and negative electrode sheet were wound into a battery cell, with a nominal capacity of 600 mAh, an NP ratio of 1.12, a liquid injection of 3 g, a separator of PP / PE composite separator, a negative electrode of graphite, and an electrolyte of high-voltage electrolyte (Xinzhongbang LBC502A50), to obtain a lithium ion full battery.

[0150] Further, the first discharge specific capacity and the first coulombic efficiency of the lithium ion button cell were tested under the condition of a voltage range of 2.5-4.25 V and 0.2C. The capacity retention rate of the lithium ion full battery was tested under the condition of 1C and 100 cycles. The test data are shown in Table 3.

[0151] Table 3

[0152] No. Initial discharge specific capacity (mAh / g) Initial coulombic efficiency (%) Capacity retention rate (%) Example 1 210.4 92.5 96.0 Comparative Example 1 210.0 92.4 95.2 Comparative Example 2 210.3 92.4 95.8 Comparative Example 3 209.8 92.0 95.0

[0153] As shown in Table 3 and Figure 3 It can be seen that the electrochemical performance of Example 1 is better than that of the comparative examples.

[0154] In addition, the electrochemical performance of Example 1 is better than that of Comparative Example 2, but the electrochemical performance test data of the two are relatively similar. The reason is that the intermediate mixture obtained by pre-sintering in Comparative Example 2 has too low a ratio of corresponding diffraction peaks due to insufficient pre-sintering of the coarse lithium hydroxide powder, resulting in slightly lower final electrochemical performance than Example 1. However, because a large amount of fine lithium hydroxide powder is added in Comparative Example 2, its electrochemical performance is similar to that of Example 1.

[0155] Comparative Example 1 does not add fine lithium hydroxide powder, and Comparative Example 3 has a too high pre-sintering temperature, resulting in lower final electrochemical performance than Example 1.

[0156] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for preparing a cathode material, characterized in that, include: A first mixture comprising an intermediate mixture and finely powdered lithium hydroxide is sintered to produce a product with the molecular formula Li. β Ni a Co e Mn f Al g M 1-a-e-f-g O2 cathode material; The intermediate mixture includes intermediate Li α Ni a Co b Mn c Al d M 1-a-b-c-d O2; In the XRD pattern of the intermediate mixture, the peak intensity ratio of the (003) diffraction peak to the (104) diffraction peak is 0.3-0.6; wherein, The molecular formula is Li α Ni a Co b Mn c Al d M 1-a-b-c-d M in the intermediate of O2 is at least one of Mg, Zr and Zn, 0.95 < α < 1.05, 0.6 < a < 1, 0 ≤ b < 0.4, 0 ≤ c < 0.4, 0 ≤ d < 0.1, 1-abcd ≥ 0, and c and d are not both 0; The lithium-nickel mixing ratio of the intermediate mixture is 0.2-0.45; the intermediate mixture also includes intermediate lithium hydroxide; The intermediate mixture is obtained by sintering a mixture of a precursor and crude lithium hydroxide powder; wherein, the crude lithium hydroxide powder has a D 50 Greater than or equal to 80 μm; The molecular expression is Li β Ni a Co e Mn f Al g M 1-a-e-f-g In the positive electrode material of O2, M is at least one of Mg, Zr and Zn, 0.98 < β < 1.02, 0 ≤ e < 0.4, 0 ≤ f < 0.4, 0 ≤ g < 0.1, 1 - aefg ≥ 0, and f and g are not simultaneously 0; The D of the fine lithium hydroxide powder 50 The fine lithium hydroxide powder has a particle size of less than or equal to 20 μm, and the molar ratio between the fine lithium hydroxide powder and the precursor is (0.01-0.11):1; the precursor is selected from: the precursor with the molecular formula Ni a Co b Mn c Al d M 1-a-b-c-d O oxide precursor, molecular formula is Ni a Co b Mn c Al d M 1-a-b-c-d The carbonate precursor of CO3 and its molecular formula are Ni a Co b Mn c Al d M 1-a-b-c-d At least one of the hydroxide precursors of (OH)2; 0.6 < a < 1, 0 ≤ b < 0.4, 0 ≤ c < 0.4, 0 ≤ d < 0.1, 1-abcd ≥ 0, and c and d are not simultaneously 0.

2. The method as described in claim 1, characterized in that, The first mixture further includes a dopant, which is an oxide and / or hydroxide corresponding to at least one of Co, Al and M in the cathode material.

3. The method as described in claim 1 or 2, characterized in that, The first mixture, comprising an intermediate mixture and finely powdered lithium hydroxide, is sintered to produce a product with the molecular formula Li. β Ni a Co e Mn f Al g M 1-a-e-f-g The positive electrode materials for O2 include: The first mixture was subjected to a first sintering at 650-900°C to obtain a first-sintered product; wherein, the first-sintered product includes the product with the molecular formula Li. β Ni a Co e Mn f Al g M 1-a-e-f-g O2 cathode material; The calcined product was washed with water and then dried to obtain the molecular formula Li. β Ni a Co e Mn f Al g M 1-a-e-f-g The residual alkali content on the surface of the O2 cathode material is less than or equal to 3500 ppm.

4. The method as described in claim 3, characterized in that, The product is washed with water and then dried so that the molecular formula is Li. β Ni a Co e Mn f Al g M 1-a-e-f-g After the residual alkali content on the surface of the O2 cathode material is less than or equal to 3500 ppm, it also includes: The cathode material with a residual alkali content of less than or equal to 3500 ppm is mixed with a coating agent to obtain a second mixture; wherein the coating agent includes Al(OH)3, B(OH)3, and B At least one of TiO2 and Ti(OH)4; The second mixture is subjected to a second sintering to give the surface of the positive electrode material a coating layer; wherein the coating layer is a metal oxide corresponding to the coating agent.

Images