Precursor of positive electrode material and preparation method thereof, preparation method of positive electrode material, lithium ion battery

Abstract

The application provides a precursor of a positive electrode material, a preparation method of the precursor, a preparation method of the positive electrode material, and a lithium ion battery, so as to reduce small particles in the positive electrode material and improve the electrochemical performance of the positive electrode material. The precursor of the positive electrode material comprises lithium hydroxide, and a molecular expression formula of the precursor is kLi a Ni x Co y Mn z M w O@(1‑k)LiOH; wherein, 0.3≤k<1.0, 0<a≤1.1, 0<x<1, 0<y≤0.3, 0<z<1, 0<w<0.05, and x+y+z+w=1, and M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery cathode materials, and in particular to a cathode material precursor, a preparation method thereof, a preparation method of a cathode material, and a lithium ion battery. BACKGROUND

[0002] Currently, in the preparation method of lithium ion battery cathode materials, the co-precipitation-calcination method is commonly used. Generally, the precursor prepared by co-precipitation lacks lithium ion diffusion channels, so it exhibits problems such as uneven diffusion and slow diffusion speed during the (high-temperature) calcination stage, resulting in poor electrochemical performance of the final product, the cathode material.

[0003] Therefore, the precursor obtained by co-precipitation is subjected to wet lithium intercalation under high temperature and high pressure, and then the oxide obtained by wet lithium intercalation is calcined, so that lithium can be mixed with other elements at an atomic level in the bulk phase during the wet lithium intercalation process, thereby promoting the uniform diffusion of lithium ions during the high-temperature calcination stage, and further improving the rate performance and the first coulomb efficiency of the final product, the cathode material.

[0004] However, in the process of sintering the oxide under high temperature and high pressure as a precursor to prepare a cathode material, the mass transfer and diffusion of lithium in the oxide in the liquid phase are not uniform, so that the cathode material prepared based on the precursor is prone to small particles, and these small particles adhere to the surface of the cathode material, reducing the performance of the cathode material. Therefore, the performance of the lithium ion battery cathode material is currently restricted by the aforementioned small particles. SUMMARY

[0005] The present application provides a cathode material precursor, a preparation method thereof, a preparation method of a cathode material, and a lithium ion battery, to reduce small particles in the cathode material and improve the electrochemical performance of the cathode material, and to avoid the problem that small particles are prone to occur in the cathode material prepared based on the precursor in the prior art.

[0006] In a first aspect, the present application provides a cathode material precursor, comprising lithium hydroxide, and the molecular expression formula of the precursor is kLi a Ni x Co y Mn z M w O@(1-k)LiOH;

[0007] wherein, 0.3≤k<1.0, 0<a≤1.1, 0<x<1, 0<y≤0.3, 0<z<1, 0<w<0.05, and x+y+z+w=1, M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B.

[0008] In a possible implementation, 0.5≤k≤1.0.

[0009] In a possible implementation, the precursor of the positive electrode material is a secondary particle, a cross section of the secondary particle contains a crack, and a lithium hydroxide content in a target region on the cross section is greater than 0.

[0010] The cross section is a cross section passing through a geometric center of the secondary particle, the target region is a preset-width annulus with the geometric center as a center on the cross section, and an outer circle of the annulus passes through the end point.

[0011] In a second aspect, an embodiment of the present application provides a method for preparing the precursor of the positive electrode material according to the first aspect and any possible implementation, comprising:

[0012] Under the condition of 10-100 ℃ and atmospheric pressure, an oxide containing Ni p Co q Mn e M f and OOH is subjected to an ion exchange reaction with lithium ions in a lithium-containing solution in a liquid phase environment to obtain a slurry containing the precursor of the positive electrode material; wherein 0

[0013] The slurry is filtered, and a filter cake obtained by filtering is dried to obtain the precursor of the positive electrode material.

[0014] In a possible implementation, the oxide containing Ni p Co q Mn e M f and OOH is obtained by dispersing Ni p Co q Mn e M f OH in an alkaline environment.

[0015] In a possible implementation, the drying of the filter cake obtained by filtering to obtain the precursor of the positive electrode material comprises:

[0016] Under the condition of 60-200 ℃, the filter cake is dynamically dried, or is statically dried and then stirred to obtain the precursor of the positive electrode material.

[0017] In a third aspect, an embodiment of the present application provides a method for preparing a positive electrode material based on the precursor of the positive electrode material according to the first aspect and any possible implementation, comprising:

[0018] sintering the precursor of the cathode material, or the mixture containing lithium source and the precursor of the cathode material, at a temperature not more than 900 ℃, to obtain the cathode material Li b Ni c Co d Mn e M w O;wherein, 1.0≤b<1.4, 0

[0019] In a possible implementation, the sintering of the precursor of the cathode material, or the mixture containing lithium source and the precursor of the cathode material, at a temperature not more than 900 ℃, to obtain the cathode material, comprises:

[0020] sintering the precursor of the cathode material, or the mixture, for N times; wherein, N is a positive integer greater than or equal to 1, the sintering temperature increases successively in the N times of sintering, the sintering temperature of the 1st to (N-1)th times of sintering is 400-800 ℃, and the sintering temperature of the Nth time of sintering is 700-900 ℃.

[0021] In a possible implementation, the sintering temperature of the 1st to (N-1)th times of sintering is 500-700 ℃, and the sintering temperature of the Nth time of sintering is 700-800 ℃.

[0022] In a possible implementation, the sintering condition further comprises that the oxygen content in the sintering atmosphere is less than or equal to 50%.

[0023] In a third aspect, the embodiments of the present application provide a lithium ion battery, comprising:

[0024] The cathode material prepared by the method in the third aspect and any one of the implementation forms.

[0025] The one or more technical solutions provided by the embodiments of the present application have at least the following beneficial effects:

[0026] First, the precursor of the cathode material provided by the embodiments of the present application has a suitable content of lithium hydroxide, and the lithium hydroxide is distributed on the surface and inside the lithium metal oxide secondary particles, so that the lithium hydroxide is relatively uniformly distributed in the lithium metal oxide secondary particles. This can promote the recombination and dispersion of the lithium metal oxide in the further lithium intercalation process by means of the conversion of the hydroxide into a molten state in the heating stage of preparing the cathode material, significantly promote the single crystallization of the final product cathode material, and significantly reduce the small particles in the cathode material. Accordingly, the electrochemical performance is also stably improved.

[0027] Secondly, the method for preparing the precursor of the cathode material at normal temperature and pressure provided by the embodiments of the present application significantly reduces the production requirements (including the oxygen content in the sintering process), so that the production cost and the production energy consumption are significantly reduced. Moreover, the reduction of the production cost and the production energy consumption is not at the expense of the quality of the product (i.e. the intermediate product for preparing the cathode material, which is the precursor of the cathode material in the embodiments of the present application); on the contrary, the precursor of the cathode material prepared by the method significantly reduces the small particles in the cathode material, so that the method actually overcomes the technical prejudice.

[0028] Thirdly, when the precursor of the cathode material provided by the embodiments of the present application is used to prepare the cathode material, the energy consumption (including temperature, time and oxygen content) in the sintering stage is reduced by 40%-60%. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 SEM image of the raw material (oxide) for preparing the precursor of the cathode material in Example 1 provided by the embodiments of the present application;

[0030] Figure 2 SEM image of the precursor of the cathode material in Example 1 provided by the embodiments of the present application;

[0031] Figure 3 SEM image of the secondary particle section of the precursor of the cathode material in Example 1 provided by the embodiments of the present application;

[0032] Figure 4 SEM image of the cathode material prepared based on the precursor of the cathode material in Example 1 provided by the embodiments of the present application;

[0033] Figure 5 SEM image of the cathode material prepared based on the precursor of the cathode material in Comparative Example 2 provided by the embodiments of the present application;

[0034] Figure 6 XRD spectrum of the precursor, the first filter cake and the precursor of the cathode material in Example 1 provided by the embodiments of the present application. DETAILED DESCRIPTION

[0035] To solve the problem that it is difficult to monocrystallize and the content of small particles is high in the positive electrode material directly sintered from the existing lithium-embedded product by wet method, the embodiment of the present application provides a precursor of a positive electrode material for preparing a positive electrode material. The precursor of the positive electrode material comprises a lithium metal oxide and lithium hydroxide. When the precursor of the positive electrode material is in a high-temperature sintering process, the lithium hydroxide therein is converted into a molten state in the heating stage, which can effectively promote the recombination and dispersion of the lithium metal oxide in the oxidation process, so as to achieve the purpose of effectively promoting the monocrystallization of the positive electrode material, and can significantly reduce the content of small particles in the positive electrode material prepared by the precursor of the positive electrode material. In this way, even without changing the preparation method, the electrochemical performance (for example, rate performance, initial coulombic efficiency, etc.) of the positive electrode material sintered based on the precursor of the positive electrode material is also significantly improved.

[0036] It should be noted that, unless otherwise specified, the small particles in the positive electrode material described in the embodiments of the present application are microparticles attached to the secondary particles of the positive electrode material (or located between the primary particles and the primary particles).

[0037] The precursor of the positive electrode material and the preparation method thereof, the method for preparing the positive electrode material, and the lithium ion battery provided by the embodiments of the present application are described in detail below. It should be noted that the embodiments described below are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, other embodiments obtained by a person of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0038] The embodiments of the present application first provide a precursor of a positive electrode material, which comprises lithium hydroxide, and the molecular expression of the precursor is kLi a Ni x Co y Mn z M w O@(1-k)LiOH;

[0039] wherein, 0.3≤k<1.0, 0<a≤1.1, 0<x<1, 0<y≤0.3, 0<z<1, 0<w<0.05, and x+y+z+w=1, M is a doping element, and M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B.

[0040] In the above molecular expression, each subscript can be understood as the atomic index of the corresponding atom. The atoms a, x, y, z, and w respectively represent the relative content of Li, Ni, Co, and Mn atoms in the molecule.

[0041] In some embodiments, 0.5≤k≤1.0. For example, k=0.9, k=0.4, or k=0.8.

[0042] The precursor of the positive electrode material is a mixture of the composition of the secondary particles, and the secondary particles are composed of primary particles.

[0043] In the XRD (X-Ray Diffraction) spectrum of the precursor of the positive electrode material, the intensity of the (003) characteristic peak at a diffraction angle of 18.3-19.5° is 2700-5000, the intensity of the (101) characteristic peak at a diffraction angle of 36.1-37.1° is 1000-3000, and the intensity of the (104) characteristic peak at a diffraction angle of 44.0-44.9° is 1000-3000. Due to the presence of lithium hydroxide, the intensity of the above characteristic peaks, especially the (003) characteristic peak, is low.

[0044] Further, the cross section of the secondary particle of the precursor of the positive electrode material contains a crack. In combination with the fact that the precursor contains lithium hydroxide, it can be determined that the lithium hydroxide content in the target region on the cross section is greater than 0. Figure 6 It can be determined that the precursor contains lithium hydroxide in the surface and the interior due to the intercalation of lithium. a Ni x Co y Mn z M w O, and the main peak is obviously shifted to the left compared with oxides and hydroxides. Therefore, it can be determined that the lithium hydroxide content in the target region on the cross section is greater than 0.

[0045] The cross section is a cross section passing through the geometric center of the secondary particle. The target region is a circular ring with a preset width and the geometric center as the center of the circle. The outer circle of the circular ring passes through the end point of the crack. The crack here can be understood as a continuous and unbroken gap on the cross section, and the end point of the crack can be understood as the point on the crack closest to the edge of the cross section, which is also the point on the crack farthest from the geometric center.

[0046] That is, when determining the target region on the cross section, the outer circle can be determined according to the end point of the crack, and then the inner circle can be further determined according to the preset width, so as to obtain the target region. The preset width may, for example, be 10 nm.

[0047] In some embodiments, the crack on the cross section is distributed radially along the geometric center of the secondary particle.

[0048] Based on the same inventive concept, the embodiments of the present application also provide a method for preparing the precursor of the positive electrode material, which comprises:

[0049] Step 101: under the conditions of 10-100°C and atmospheric pressure, making a mixture containing Ni p Co q Mn e M fThe oxide of OOH and lithium ions in the lithium-containing solution undergo ion exchange reaction in a liquid phase environment to obtain a slurry containing the precursor of the positive electrode material.

[0050] The liquid-solid ratio between the above lithium-containing solution and the oxide is 3-5 mL / g.

[0051] The above molecular expression Ni p Co q Mn e M f The atomic indices in OOH are consistent with the content of corresponding elements (Ni, Co, Mn, M) in lithium metal hydroxide in the precursor of the positive electrode material. Therefore, the range of the atomic indices in the hydroxyl oxide is: 0

[0052] The cation in the above lithium salt is Li. The liquid phase environment is alkaline.

[0053] In some embodiments, the lithium salt is introduced into the reaction device in the form of a solution, and the liquid phase environment in the reaction device is a lithium-containing salt solution. The content of Li in the lithium-containing salt solution is 0.1-0.5 mol / L. + The concentration is 5-10 mol / L.

[0054] In some embodiments, the liquid-solid ratio of the liquid phase environment in which the ion exchange reaction occurs is 2-6 mL / g. Preferably, it is 3-5 mL / g.

[0055] In some embodiments, the above lithium salt is at least one of lithium hydroxide, lithium carbonate, lithium sulfate, lithium chloride, and lithium acetate, etc.

[0056] To facilitate the ion exchange reaction, the molar ratio of the lithium salt to Ni p Co q Mn e M f OOH is greater than or equal to 2. Specifically, the chemical reaction equation corresponding to the ion exchange reaction is as follows:

[0057] MeOOH+Li + +OH - =LiMeO2+H2O.

[0058] The above atmospheric pressure is about 0.1 MPa, which slightly fluctuates according to different regions.

[0059] Further, the pH of the liquid phase environment tends to decrease as the ion exchange reaction proceeds. In some embodiments, the pH of the liquid phase environment in the reaction device (e.g., a reaction kettle) is decreased to a target value as the end point of the ion exchange reaction, so as to control the Li / Me of the precursor of the positive electrode material prepared in each batch, and thus stabilize the Li / Me of the precursor of the positive electrode material from batch to batch. In this way, the problem of unstable Li / Me from batch to batch caused by determining the median particle size of the particulate matter in the slurry as the end point of the reaction in the prior art can be avoided. The target value can be dynamically monitored by a pH monitoring and prompting system for the pH of the liquid phase environment in the reaction device (e.g., a reaction kettle) to achieve a sensitive response. The pH monitoring and prompting system has a test range of -1-14, a temperature of 0-110°C, and a measurement accuracy of less than or equal to 0.001.

[0060] In some embodiments, the oxide containing Ni p Co q Mn e M f OOH is subjected to an ion exchange reaction with a lithium salt in a liquid phase environment at a first pH value until the pH of the liquid phase environment decreases from the first pH value to a second pH value, to obtain a slurry containing the precursor of the positive electrode material. The second pH value is greater than or equal to 9.

[0061] In some embodiments, the first pH value is less than or equal to 13.646, and the second pH value is greater than or equal to the first pH value. Accordingly, the Li / Me of the precursor of the positive electrode material is 0.7-1.1.

[0062] In some embodiments, the ion exchange reaction is performed for 2-24 hours, and the stirring rate of the reaction device during the reaction is 100-900 r / min.

[0063] Further, the following is described for the oxide containing Ni p Co q Mn e M f OOH:

[0064] The oxide can be a compound Ni p Co q Mn e M f OOH, and a mixture containing Ni p Co q Mn e M f OOH and Ni p Co q Mn e M f OH.

[0065] When the oxide is a mixture, it is actually a mixture of Ni p Co q Mn e M f OH which is not 100% oxidized. Specifically, the oxidized Ni p Co q Mn e M f OH is a mixture of Ni p Co q Mn e M f OH and Ni p Co q Mn e M f OH. p Co q Mn e M f OOH and Ni p Co q Mn e M f OH.

[0066] And Ni p Co q Mn e M f OOH, and a mixture of Ni p Co q Mn e M f OOH and Ni p Co q Mn e M f OH all appear as secondary particles, and any secondary particle contains a crack.

[0067] Since the secondary particle is composed of primary particles, the crack is not obvious when viewed from the surface of the secondary particle. However, when any cross section passing through the geometric center of the secondary particle is observed, please refer to Figure 3 , the cross section contains a crack corresponding to the crack.

[0068] Thus, the ion exchange reaction described in step 101 is a reaction between Ni p Coq Mn e M f The secondary particle surface of LiOH also occurs along the aforementioned cracks, so that in the precursor secondary particles provided by the embodiments of the present application, lithium hydroxide is distributed not only on the secondary particle surface, but also along the cracks (i.e. the cracks in the section) in the secondary particles.

[0069] Step 102: filtering the slurry containing the aforementioned positive electrode material precursor, and drying the filter cake obtained by filtering to obtain the positive electrode material precursor.

[0070] Specifically, the drying temperature is 60-200°C, and the drying time is 5-24h.

[0071] The specific drying method is dynamic drying, or stirring immediately after static drying (i.e. before cooling down after the end of static drying) to ensure that the final positive electrode material precursor obtained does not have uneven distribution of lithium hydroxide on the surface of the positive electrode material precursor located in the upper layer and the positive electrode material precursor located in the lower layer due to volatilization of LiOH during the drying process.

[0072] In some embodiments, the static drying equipment can be a blast oven or a vacuum oven.

[0073] In some embodiments, the dynamic drying equipment is a rotary evaporation drying, vacuum double-cone drying, or vacuum pear knife drying, etc. vacuum drying equipment with stirring function.

[0074] The method described in steps 101-102 above can significantly save energy consumption and cost in the preparation of the precursor. In particular, the incomplete oxidation reaction at room temperature and pressure can make the lithium metal oxide secondary particles prepared finally also include lithium hydroxide, which further promotes the relatively uniform distribution of lithium hydroxide in the lithium metal oxide secondary particles. And it can also ensure that the lithium metal oxide secondary particles in the positive electrode material precursor have uniform morphology, avoiding the problem that the secondary particle morphology in the positive electrode material precursor prepared under high pressure and / or high temperature conditions (such as the first embodiment) is easily broken.

[0075] 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 positive electrode material precursor, which comprises:

[0076] sintering the aforementioned positive electrode material precursor, or a mixture containing a lithium source and the positive electrode material precursor, at a temperature of not more than 900°C to obtain the positive electrode material Li b Ni c Co d Mn e M wO; wherein 1.0≤b<1.4, 0

[0077] The lithium source is provided for supplementing lithium to the precursor of the positive electrode material in order to obtain the target lithium content of the positive electrode material. Therefore, the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amounts of the main elements Ni, Co and Mn in the precursor of the positive electrode material is 1.01:1-1.4:1. Correspondingly, when the lithium content in the precursor of the positive electrode material is sufficient, lithium supplement is not necessary, i.e., the precursor of the positive electrode material is directly sintered.

[0078] In some embodiments, the oxygen content in the sintering device is less than or equal to 50%.

[0079] The sintering of the mixture is N-stage sintering, wherein N is an integer greater than or equal to 1.

[0080] In some embodiments, N=1. The sintering conditions include a temperature of 700-900°C, preferably 700-800°C. The temperature rising rate is 2-10°C / min. The sintering time is 3-24h, preferably 6-12h.

[0081] In some embodiments, N≥2. For example, it can be 2-stage or 3-stage sintering. The temperature rising rate of any stage is 2-10°C / min. Specifically, in the multi-stage sintering, the sintering temperature is increased in sequence, and the sintering temperature in any intermediate stage, i.e., the first stage to the (N-1)th stage, is 400-800°C; preferably 500-700°C; and the sintering time is 0.5-24h. The sintering temperature of the Nth stage is 700-900°C, preferably 700-800°C; and the sintering time is 1-24h, preferably 6-12h.

[0082] It is worth mentioning that, when the positive electrode material is prepared based on the precursor of the positive electrode material provided in the embodiments of the present application, since the precursor of the positive electrode material is a lithium-embedded oxide, the lithium metal oxide has completed the transition of the metal from a low valence state to a high valence state, and the lithium ion has also been embedded in the lattice sites consistent with the lithium in the positive electrode material in the bulk phase, so that the solid-phase diffusion energy barrier of the lithium ion is significantly reduced in the sintering process for preparing the positive electrode material. This further promotes the preparation of the positive electrode material to be completed at a lower temperature, in a shorter time, and under a lower oxygen content. On this basis, in addition to the lithium metal oxide in the secondary particles, there is also lithium hydroxide on the surface of the secondary particles and in the internal cracks that participates in the high-temperature sintering. The lithium hydroxide can promote the recombination of the secondary particles in a molten state at a lower temperature stage (during temperature rising), and promote the completion of the single crystallization of the positive electrode material with higher quality, avoiding the generation of small particles in the positive electrode material.

[0083] The following is described by specific examples.

[0084] Example 1

[0085] S1, put 100g of hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)2 into 400mL of sodium hydroxide solution and stir to obtain a first slurry.

[0086] The concentration of the sodium hydroxide solution is 5mol / L. The SEM images of the precursor secondary particles are shown in Figure 1 .

[0087] S2, heat the slurry to 40℃, and continuously pass the sodium hypochlorite solution into the slurry at a flow rate of 5mL / min while stirring to start the reaction. After the addition is complete, oxidize for 8h. Filter and wash the reaction slurry obtained by reaction with water (50℃ deionized water) three times to obtain a first filter cake.

[0088] The sodium hypochlorite solution is obtained by dissolving 1.5 times the theoretical amount of sodium hypochlorite in 500mL of deionized water.

[0089] S3, mix the lithium hydroxide solution and the first filter cake at a liquid-solid ratio of 3mL / g, then heat to 80℃, and stir at an atmospheric pressure and a stirring rate of 300r / min. Use a PH online monitoring system to dynamically monitor the PH value of the reaction slurry. In this reaction system, the initial PH is 13.736. When the PH value of the reaction slurry drops to 13.462, start discharging and suction filtration to obtain a second filter cake.

[0090] The concentration of the lithium hydroxide solution is 6mol / L.

[0091] S4, rotary evaporation drying is used for the second filter cake: dry at 100℃ for 12h to obtain a precursor of the positive electrode material.

[0092] The SEM images of the precursor secondary particles and the cross section of the precursor of the positive electrode material are shown in Figure 2 、 Figure 3 The XRD patterns of the precursor, the first filter cake (i.e. the intermediate product after oxidation), and the product after lithium intercalation (i.e. the precursor of the positive electrode material) are shown in Figure 6 .

[0093] Example 2

[0094] S1, put 100g of hydroxide Ni 0.8 Co 0.1 Mn 0.1 (OH)2 into 400mL of sodium hydroxide solution and stir to obtain a first slurry.

[0095] The concentration of the sodium hydroxide solution is 5 mol / L.

[0096] S2, the slurry is heated to 65℃, and the sodium hypochlorite solution is continuously introduced into the slurry at a flow rate of 5 mL / min while stirring to start the reaction. After the addition is completed, the oxidation reaction is carried out for 10 h. The reaction slurry obtained is filtered and washed with water (50℃ deionized water) three times to obtain a first filter cake.

[0097] The sodium hypochlorite solution is obtained by dissolving 1.1 times the theoretical amount of sodium hypochlorite in 500 mL of deionized water.

[0098] S3, the lithium hydroxide solution and the first filter cake are mixed at a liquid-solid ratio of 5 mL / g, and then heated to 60℃. Under atmospheric pressure, stirring is carried out at a stirring speed of 300 r / min. The PH value in the reaction slurry is dynamically monitored by using a PH online monitoring system. In this reaction system, the initial PH is 13.791. When the PH value of the reaction slurry decreases to 13.643, the product is discharged and filtered to obtain a second filter cake.

[0099] The concentration of the lithium hydroxide solution is 6.5 mol / L.

[0100] S4, the second filter cake is dried by rotary evaporation: dried at 100℃ for 12 h to obtain a precursor of the positive electrode material.

[0101] Example 3

[0102] S1, 100g of the hydroxide Ni 0.9 Co 0.05 Mn 0.05 (OH)2 is stirred in 400 mL of a sodium hydroxide solution to obtain a first slurry.

[0103] The concentration of the sodium hydroxide solution is 5 mol / L.

[0104] S2, the slurry is heated to 60℃, and the sodium hypochlorite solution is continuously introduced into the slurry at a flow rate of 5 mL / min while stirring to start the reaction. After the addition is completed, the oxidation reaction is carried out for 10 h. The reaction slurry obtained is filtered and washed with water (50℃ deionized water) three times to obtain a first filter cake.

[0105] The sodium hypochlorite solution is obtained by dissolving 1.1 times the theoretical amount of sodium hypochlorite in 500 mL of deionized water.

[0106] S3, mixing the lithium hydroxide solution and the first filter cake with a liquid-solid ratio of 3 mL / g, then heating to 85°C, stirring at 300 r / min under atmospheric pressure, and dynamically monitoring the pH value of the reaction slurry by using a pH online monitoring system. Under the reaction system, the initial pH is 13.881, and when the pH value of the reaction slurry decreases to 13.641, the discharge and suction filtration are started to obtain the second filter cake.

[0107] The concentration of the lithium hydroxide solution is 8 mol / L.

[0108] S4, rotary evaporation drying is performed on the second filter cake: drying at 100°C for 12 h to obtain the precursor of the positive electrode material.

[0109] Example 4

[0110] S1, 100 g of the hydroxide Ni 0.8 Co 0.1 Mn 0.1 (OH)2 is stirred in 400 mL of a sodium hydroxide solution to obtain a first slurry.

[0111] The concentration of the sodium hydroxide solution is 5 mol / L.

[0112] S2, heating the slurry to 60°C, continuously feeding hydrogen peroxide into the slurry at a flow rate of 3 mL / min while stirring to start the reaction, and after the feeding is completed, oxidizing for 7 h. The reaction slurry obtained by the reaction is filtered and washed with water (60°C deionized water) three times to obtain a first filter cake.

[0113] The hydrogen peroxide is obtained by dissolving 1.5 times the theoretical amount of hydrogen peroxide in 500 mL of deionized water.

[0114] S3, mixing the lithium hydroxide solution and the first filter cake with a liquid-solid ratio of 3 mL / g, then heating to 85°C, stirring at 300 r / min under atmospheric pressure, and dynamically monitoring the pH value of the reaction slurry by using a pH online monitoring system. Under the reaction system, the initial pH is 13.881, and when the pH value of the reaction slurry decreases to 13.641, the discharge and suction filtration are started to obtain the second filter cake.

[0115] The concentration of the lithium hydroxide solution is 8 mol / L.

[0116] S4, rotary evaporation drying is performed on the second filter cake: drying at 100°C for 12 h to obtain the precursor of the positive electrode material.

[0117] Example 5

[0118] S1, 100 g of the hydroxide Ni 033 Co 0.33 Mn0.33 The (OH)2was stirred in 400 mL of sodium hydroxide solution to obtain a first slurry.

[0119] The concentration of the sodium hydroxide solution was 5 mol / L.

[0120] S2, the slurry was heated to 60°C, and the potassium permanganate solution was continuously fed into the slurry at a flow rate of 3 mL / min while stirring to start the reaction. After the feeding was completed, the oxidation reaction was carried out for 10 h. The reaction slurry obtained in the reaction was filtered and washed with water (55°C deionized water) three times to obtain a first filter cake.

[0121] The potassium permanganate solution was obtained by dissolving 1.5 times the theoretical amount of potassium permanganate in 400 mL of deionized water.

[0122] S3, the lithium hydroxide solution and the first filter cake were mixed at a liquid-solid ratio of 3 mL / g, and then heated to 75°C. Under atmospheric pressure, stirring was carried out at a stirring speed of 300 r / min. The PH value in the reaction slurry was dynamically monitored by using a PH online monitoring system. In this reaction system, the initial PH was 13.882. When the PH value of the reaction slurry decreased to 13.642, the product was discharged and filtered to obtain a second filter cake.

[0123] The concentration of the lithium hydroxide solution was 8 mol / L.

[0124] S4, the second filter cake was dried by a micro vacuum double-cone dryer at 100°C for 12 h to obtain a precursor of the positive electrode material.

[0125] Example 6

[0126] S1, 100 g of hydroxide Ni 0.8 Co 0.1 Mn 0.1 The (OH)2was stirred in 400 mL of sodium hydroxide solution to obtain a first slurry.

[0127] The concentration of the sodium hydroxide solution was 5 mol / L.

[0128] S2, the slurry was heated to 55°C, and the sodium persulfate solution was continuously fed into the slurry at a flow rate of 5 mL / min while stirring to start the reaction. After the feeding was completed, the oxidation reaction was carried out for 8 h. The reaction slurry obtained in the reaction was filtered and washed with water (60°C deionized water) three times to obtain a first filter cake.

[0129] The sodium persulfate solution was obtained by dissolving 1.1 times the theoretical amount of sodium persulfate in 400 mL of deionized water.

[0130] S3, mixing the lithium hydroxide solution and the first filter cake with a liquid-solid ratio of 3 mL / g, then heating to 65°C, stirring at an atmospheric pressure and a stirring rate of 300 r / min, and dynamically monitoring the pH value of the reaction slurry by using a pH online monitoring system; in the reaction system, the initial pH is 13.883, and when the pH value of the reaction slurry decreases to 13.641, the reaction slurry is discharged and filtered to obtain a second filter cake.

[0131] The concentration of the lithium hydroxide solution is 8 mol / L.

[0132] S4, drying the second filter cake by using a micro vacuum double-cone dryer at 100°C for 12 h to obtain a precursor of the positive electrode material.

[0133] Example 7

[0134] S1, putting 100 g of a hydroxide Ni 0.125 Co 0.125 Mn 0.75 (OH)2 into 500 mL of a sodium hydroxide solution to obtain a first slurry.

[0135] The concentration of the sodium hydroxide solution is 1.5 mol / L.

[0136] S2, heating the slurry to 60°C, continuously feeding a hydrogen peroxide solution into the slurry at a flow rate of 5 mL / min to start the reaction, and oxidizing the reaction slurry for 10 h after the feeding is completed; the reaction slurry is filtered and washed with water (60°C deionized water) three times to obtain a first filter cake.

[0137] The hydrogen peroxide solution is obtained by dissolving 1.2 times the theoretical amount of hydrogen peroxide in 400 mL of deionized water.

[0138] S3, mixing the lithium hydroxide solution and the first filter cake with a liquid-solid ratio of 3 mL / g, then heating to 45°C, stirring at an atmospheric pressure and a stirring rate of 300 r / min, and dynamically monitoring the pH value of the reaction slurry by using a pH online monitoring system; in the reaction system, the initial pH is 13.895, and when the pH value of the reaction slurry decreases to 13.635, the reaction slurry is discharged and filtered to obtain a second filter cake.

[0139] The concentration of the lithium hydroxide solution is 9 mol / L.

[0140] S4, drying the second filter cake by using a micro vacuum double-cone dryer at 100°C for 12 h to obtain a precursor of the positive electrode material.

[0141] Example 8

[0142] S1, putting 100 g of a hydroxide Ni 0.25 Mn 0.75The (OH)2was stirred in 500 mL of sodium hydroxide solution to obtain a first slurry.

[0143] The concentration of the sodium hydroxide solution was 5 mol / L.

[0144] S2, the slurry was heated to 60°C, and the potassium perchlorate solution was continuously fed into the slurry at a flow rate of 5 mL / min while stirring to start the reaction. After the feeding was completed, the oxidation reaction was carried out for 10 h. The reaction slurry obtained in the reaction was filtered and washed with water (60°C deionized water) three times to obtain a first filter cake.

[0145] The potassium perchlorate solution was obtained by dissolving 1.3 times the theoretical amount of potassium perchlorate in 500 mL of deionized water.

[0146] S3, the lithium hydroxide solution and the first filter cake were mixed at a liquid-solid ratio of 3 mL / g, and then heated to 50°C. Stirring was carried out at an atmospheric pressure and a stirring speed of 300 r / min. The PH value in the reaction slurry was dynamically monitored by using a PH online monitoring system. In this reaction system, the initial PH was 13.778. When the PH value of the reaction slurry decreased to 13.637, the product was discharged and filtered to obtain a second filter cake.

[0147] The concentration of the lithium hydroxide solution was 6 mol / L.

[0148] S4, the second filter cake was dried by a micro vacuum double-cone dryer at 100°C for 12 h to obtain a precursor of the positive electrode material.

[0149] Example 9

[0150] S1, 100 g of the hydroxide Ni 0.8 Co 0.1 Mn 0.05 Al 0.05 The (OH)2was stirred in 500 mL of sodium hydroxide solution to obtain a first slurry.

[0151] The concentration of the sodium hydroxide solution was 5 mol / L.

[0152] S2, the slurry was heated to 70°C, and the sodium hydroxide solution was continuously fed into the slurry at a flow rate of 5 mL / min while stirring to start the reaction. After the feeding was completed, the oxidation reaction was carried out for 10 h. The reaction slurry obtained in the reaction was filtered and washed with water (60°C deionized water) three times to obtain a first filter cake.

[0153] The potassium perchlorate solution was obtained by dissolving 1.3 times the theoretical amount of potassium perchlorate in 500 mL of deionized water.

[0154] S3, mixing the lithium hydroxide solution and the first filter cake at a liquid-solid ratio of 3 mL / g, then warming to 20°C, stirring at 300 r / min under atmospheric pressure, and dynamically monitoring the pH value of the reaction slurry by using a pH online monitoring system; under the reaction system, the initial pH is 13.869, and when the pH value of the reaction slurry decreases to 13.642, start discharging and suction filtration to obtain a second filter cake.

[0155] The concentration of the lithium hydroxide solution is 7.5 mol / L.

[0156] S4, the second filter cake is subjected to micro vacuum double-cone drying: drying at 100°C for 12 h to obtain a precursor of the positive electrode material.

[0157] Example 10

[0158] S1, 100g of a hydroxide Ni 0.8 Co 0.1 Mn 0.1 (OH)2, and 9.62g of ZrOCl2 are put into 400mL of a sodium hydroxide solution and stirred to obtain a first slurry.

[0159] The concentration of the sodium hydroxide solution is 5 mol / L.

[0160] S2, the slurry is warmed to 65°C, sodium persulfate solution is continuously introduced into the slurry at a flow rate of 5 mL / min to start the reaction, and after the feeding is completed, the oxidation reaction is carried out for 10 h; the reaction slurry obtained by the reaction is filtered and washed with water (50°C deionized water) three times to obtain a first filter cake.

[0161] The sodium persulfate solution is obtained by dissolving 176g of sodium persulfate in 500mL of deionized water.

[0162] S3, mixing the lithium hydroxide solution and the first filter cake at a liquid-solid ratio of 5 mL / g, then warming to 70°C, stirring at 300 r / min under atmospheric pressure, and dynamically monitoring the pH value of the reaction slurry by using a pH online monitoring system; under the reaction system, the initial pH is 13.805, and when the pH value of the reaction slurry decreases to 13.642, start discharging and suction filtration to obtain a second filter cake.

[0163] The concentration of the lithium hydroxide solution is 6.5 mol / L.

[0164] S4, the second filter cake is subjected to rotary evaporation: drying at 100°C for 12 h to obtain a precursor of the positive electrode material.

[0165] Example 11

[0166] S1, 100g of a hydroxide Ni 0.6 Co0.1 Mn 0.3 S1, 100g of the hydroxide Ni

[0167] The concentration of the sodium hydroxide solution is 5 mol / L.

[0168] S2, the slurry was warmed to 40°C, and while stirring, sodium persulfate solution was continuously introduced into the slurry at a flow rate of 5 mL / min for 8 h of oxidation reaction. The reaction slurry obtained was filtered and washed with water (deionized water) three times to obtain a first filter cake.

[0169] The sodium persulfate solution was obtained by dissolving 1.6 times the theoretical amount of sodium persulfate in 500 mL of deionized water.

[0170] S3, the lithium hydroxide solution and the first filter cake were mixed at a liquid-solid ratio of 3 mL / g, and then warmed to 80°C. Stirring was performed at an atmospheric pressure and a stirring rate of 300 r / min for 10 h, after which the slurry was filtered to obtain a second filter cake.

[0171] The concentration of the lithium hydroxide solution was 6 mol / L.

[0172] S4, the second filter cake was vacuum double-cone dried at 120°C for 12 h to obtain a precursor of the positive electrode material.

[0173] Comparative Example 1

[0174] S1, 100g of the hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)2was used as a raw material, and a constant amount of LiOH and lithium metal oxide was mixed according to a ratio of Li:Me = 1.02. Then, the temperature was increased to 600°C at a rate of 2°C / min, and the temperature was maintained for 10 h to obtain a positive electrode material LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0175] Comparative Example 2

[0176] S1, 100g of the hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)2was used as a raw material, and a constant amount of LiOH and lithium metal oxide was mixed according to a ratio of Li:Me = 1.02. Then, the temperature was increased to 600°C at a rate of 2°C / min, and the temperature was maintained for 10 h to obtain a positive electrode material LiNi 0.6 Co 0.1 Mn 0.3 (OH)2was stirred in 300 mL of a sodium hydroxide solution to obtain a first slurry.

[0177] The concentration of the sodium hydroxide solution was 5 mol / L.

[0178] S2, the slurry is heated to 40°C, and sodium persulfate solution is continuously introduced into the slurry at a flow rate of 5 mL / min while stirring for 8 h of oxidation reaction. The reaction slurry obtained by the reaction is filtered and washed with water (deionized water) three times to obtain a first filter cake.

[0179] The sodium persulfate solution is obtained by dissolving 1.6 times the theoretical amount of sodium persulfate in 500 mL of deionized water.

[0180] S3, the lithium hydroxide solution and the first filter cake are mixed at a liquid-solid ratio of 3 mL / g, and then heated to 80°C, pressurized to 20 MPa, and stirred at a stirring rate of 300 r / min. After 10 h of reaction, the slurry is filtered to obtain a second filter cake.

[0181] The concentration of the lithium hydroxide solution is 6 mol / L.

[0182] S4, the second filter cake is dried in a vacuum double-cone dryer at 120°C for 12 h to obtain a precursor of the positive electrode material.

[0183] The foregoing steps are repeated 5 times to prepare 5 batches of precursors of the positive electrode material.

[0184] The amount of lithium Li embedded in each batch of the precursor of the positive electrode material is tested by ICP (Inductive Coupled Plasma Emission Spectrometer). Me represents elements in the precursor of the positive electrode material other than Li, O, and H. The test data are shown in Table 1.

[0185] Table 1

[0186] Li / Me test results First batch Second batch Third batch Fourth batch Fifth batch Example 1 0.98 0.98 0.98 0.97 0.98 Example 2 0.90 0.90 0.90 0.90 0.90 Example 3 1.06 1.06 1.05 1.06 1.06 Example 4 0.98 0.98 0.98 0.98 0.98 Example 5 0.99 0.99 0.99 0.99 0.99 Example 6 1.06 1.06 1.06 1.05 1.06 Example 7 1.50 1.50 1.51 1.50 1.50 Example 8 1.40 1.41 1.40 1.40 1.40 Example 9 0.95 0.94 0.95 0.95 0.95 Example 10 0.96 0.96 0.96 0.96 0.96 Comparative Example 3 0.91 0.97 0.95 0.87 1.09 Comparative Example 1 / / / / / Comparative Example 2 1.02 0.96 0.89 0.98 1.06

[0187] As shown in Table 1, the amount of lithium embedded in the batches of Example 1-10 is more stable than that of Example 9. It can be seen that taking the pH value as the reaction endpoint of the ion exchange reaction makes the amount of lithium embedded in each batch of the precursor of the positive electrode material stable.

[0188] The content of LiOH in each batch of the precursor of the positive electrode material is determined by testing the moisture content of the filter cake and the concentration of lithium hydroxide in the filtrate. The content of lithium hydroxide is determined according to the following formula:

[0189]

[0190] N: the proportion of physical lithium hydroxide in the lithium-containing metal oxide (mass proportion);

[0191] α: the moisture content of the lithium-containing metal oxide wet filter cake (mass proportion);

[0192] c: concentration of lithium hydroxide in the filtrate mother liquor, mol / L.

[0193] The test data are shown in Table 2.

[0194] Table 2

[0195] Physical LiOH content (%) First batch Second batch Third batch Fourth batch Fifth batch Example 1 17.13％ 16.82％ 14.31％ 15.63％ 14.25％ Example 2 15.23％ 17.52％ 17.78％ 19.48％ 22.23％ Example 3 7.57％ 5.38％ 4.26％ 9.75％ 8.38％ Example 4 8.67％ 7.12％ 5.47％ 4.47％ 2.25％ Example 5 10.55％ 10.17％ 9.27％ 8.79％ 11.28％ Example 6 12.56％ 13.79％ 15.14％ 11.28％ 10.97％ Example 7 21.56％ 23.79％ 19.32％ 17.28％ 14.39％ Example 8 18.35％ 18.57％ 15.39％ 13.28％ 14.36％ Example 9 50.46％ 48.27％ 46.35％ 47.28％ 43.27％ Example 10 9.24％ 8.37％ 7.29％ 9.59％ 10.24％ Example 11 0.91％ 0.97％ 0.95％ 0.87％ 1.09％ Comparative Example 1 / / / / / Comparative Example 2 1.21％ 1.30％ 0.92％ 2.12％ 0.13％

[0196] Although the lithium hydroxide is mainly distributed on the surface of the precursor of the positive electrode material, and the content of the lithium hydroxide on the crack decreases as the distance from the surface is farther, since the content of the lithium hydroxide in Table 2 is calculated based on the moisture content of the filter cake and the concentration of the lithium hydroxide in the filtrate, the actual content of the lithium hydroxide in the tested precursor of the positive electrode material is slightly higher than the test data in Table 2.

[0197] Further, in order to prepare the positive electrode material with the content of the Li element being 1 mol per mole of the positive electrode material, the lithium is supplemented for each of the examples and the comparative examples. The sintering parameters and conditions are described as follows:

[0198] Example 1: The lithium source is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of the main elements Ni, Co and Mn in the precursor of the positive electrode material being 1.02:1. After mixing, the temperature is raised to 600 at a rate of 2 ℃ / min under the condition of the oxygen content being 40% and the rest being nitrogen, and the temperature is kept for 3 h; then the temperature is continuously raised to 850 ℃ at a rate of 2 ℃ / min, and the temperature is kept for 10 h, to obtain the positive electrode material LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0199] Example 2: The lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of the main elements Ni, Co and Mn in the precursor of the positive electrode material being 1.02:1. After mixing, the temperature is raised to 500 at a rate of 2 ℃ / min under the condition of the oxygen content being 50%, and the temperature is kept for 5 h; then the temperature is continuously raised to 700 ℃ at a rate of 2 ℃ / min, and the temperature is kept for 6 h, to obtain the positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0200] Example 3: The lithium is not supplemented; the temperature is raised to 500 at a rate of 3 ℃ / min under the condition of the oxygen content being 35% and the rest being nitrogen, and the temperature is kept for 3 h; then the temperature is continuously raised to 650 ℃ at a rate of 3 ℃ / min, and the temperature is kept for 5 h, to obtain the positive electrode material LiNi 0.9 Co 0.05 Mn 0.05O2.

[0201] Example 4: Lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of main elements Ni, Co, Mn in the precursor of the positive electrode material is 1.03:1. After mixing, under the condition of 45% oxygen and the rest nitrogen, the temperature is raised to 500 at a rate of 2℃ / min and kept for 3h; then the temperature is continuously raised to 650℃ at a rate of 2℃ / min and kept for 5h, to obtain the positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0202] Example 5: Lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of main elements Ni, Co, Mn in the precursor of the positive electrode material is 1.03:1. After mixing, under the condition of 40% oxygen and the rest nitrogen, the temperature is raised to 700 at a rate of 2℃ / min and kept for 4h, to obtain the positive electrode material LiNi 0.33 Co 0.33 Mn 0.33 O2.

[0203] Example 6: Without lithium supplement, directly raise the temperature to 750℃ at a rate of 4℃ / min under the condition of 10% oxygen and the rest nitrogen and keep for 6h, to obtain the positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0204] Example 7: Without lithium supplement, directly raise the temperature to 500 at a rate of 2℃ / min under the condition of 30% oxygen and the rest nitrogen and keep for 7h; then continuously raise the temperature to 800℃ at a rate of 2℃ / min and keep for 6h, to obtain the positive electrode material Li 1.2 Ni 0.125 Co 0.125 Mn 0.75 O2.

[0205] Example 8: Without lithium supplement, directly raise the temperature to 500 at a rate of 2℃ / min under the condition of nitrogen and keep for 7h; then continuously raise the temperature to 800℃ at a rate of 2℃ / min and keep for 6h, to obtain the positive electrode material Li 1.2 Ni 0.25 Mn 0.75 O2.

[0206] Example 9: Lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of main elements Ni, Co, Mn elements in the precursor of the positive electrode material is 1.03:1. After mixing, under the condition of 30% oxygen and the rest is nitrogen, the temperature is raised to 600 at a rate of 2°C / min and kept for 3h; then continue to raise the temperature to 750°C at a rate of 2°C / min and keep for 5h, to obtain the positive electrode material LiNi 0.8 Co 0.1 Mn 0.05 Al 0.05 O2.

[0207] Example 10: Lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of main elements Ni, Co, Mn elements in the precursor of the positive electrode material is 1.02:1. After mixing, under the condition of 40% oxygen and the rest is nitrogen, the temperature is raised to 500 at a rate of 2°C / min and kept for 5h; then continue to raise the temperature to 700°C at a rate of 2°C / min and keep for 6h, to obtain the positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2@0.05LiZrO2.

[0208] Example 11: Lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of main elements Ni, Co, Mn elements in the precursor of the positive electrode material is 1.02:1. After mixing, under the condition of 50% oxygen and the rest is nitrogen, the temperature is raised to 600 at a rate of 2°C / min and kept for 10h, to obtain the positive electrode material LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0209] Comparative Example 1: Lithium hydroxide is supplemented according to the ratio of the sum of the molar amount of lithium in the lithium source and the molar amount of lithium in the precursor of the positive electrode material to the sum of the molar amount of main elements Ni, Co, Mn elements in the precursor of the positive electrode material is 1.02:1. After mixing, under the condition of 90% oxygen and the rest is nitrogen, the temperature is raised to 600 at a rate of 2°C / min and kept for 10h, to obtain the positive electrode material LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0210] Comparative Example 2: Lithium hydroxide was supplemented according to the ratio of the molar amount of lithium in the lithium source to the sum of the molar amount of lithium in the precursor of the cathode material to the sum of the molar amount of the main elements Ni, Co, Mn in the precursor of the cathode material of 1.02:1. After mixing, the temperature was raised to 600°C at a rate of 2°C / min under conditions of 70% oxygen and the rest nitrogen, and held for 10 h; then the temperature was further raised to 850°C at a rate of 2°C / min and held for 10 h to obtain the cathode material LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0211] The lithium ion batteries using the products in the foregoing examples and comparative examples as cathode materials were subjected to electrochemical tests to determine the electrochemical performance of each cathode material. First, the preparation of the lithium ion batteries is described as follows:

[0212] First, the ternary cathode material, acetylene black, and polyvinylidene fluoride (PVDF) were mixed uniformly at a mass ratio of 94:3:3, N-methyl pyrrolidone (NMP) was added and stirred for 2 hours to obtain a viscous slurry.

[0213] Then, the viscous slurry was coated on an aluminum foil, which was baked under vacuum at 80°C, then pressed and cut into a circular sheet with a diameter of 16 mm.

[0214] Finally, the circular sheet was used as a positive electrode sheet, a pure lithium sheet with a diameter of 16 mm was used as a negative electrode sheet, a solution (1 mol / L) obtained by mixing LiPF6 and DEC / EC (volume ratio 1:1) was used as an electrolyte, and a polypropylene microporous membrane was used as a separator. A coin cell was assembled in an argon-filled glove box.

[0215] The relevant test parameters are as follows:

[0216] Charging-discharging at 0.2C in the range of 3-4.3V was used to determine the specific capacity and initial efficiency of the lithium ion battery in the first cycle;

[0217] Cyclic charging-discharging at 5C in the range of 3-4.3V was used to determine the 5C discharge capacity of the lithium ion battery.

[0218] The cycle performance of the lithium ion battery was tested at 25°C by charging at 0.5C and discharging at 1C in the range of 3-4.3V for 100 cycles, and the capacity retention rate after 100 cycles was calculated according to the following formula: capacity retention rate = discharge specific capacity in the 100th cycle / initial discharge capacity * 100%.

[0219] The test data are shown in Table 3.

[0220] Table 3

[0221]

[0222] Comparison Figure 4 - Figure 5 It can be seen that the small particles in the positive electrode material prepared in the examples are significantly reduced. Further combined with Table 3, it can be seen that the positive electrode material prepared from the precursor of the positive electrode material in the examples contains almost no small particles, and thus has better electrochemical performance than the comparative examples.

[0223] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Thus, it is intended that the present application cover the modifications and changes as long as they come within the scope of the claims of the present application and their equivalents.

Claims

1. A precursor of a positive electrode material, characterized by, including lithium hydroxide, the molecular expression of the precursor is kLi a Ni x Co y Mn z M w O@(1-k)LiOH; wherein 0.3≤k<1.0, 0 The surface and the interior of the precursor contain lithium hydroxide; The precursor of the positive electrode material is a secondary particle, a cross section of the secondary particle contains a crack, and a lithium hydroxide content in a target region on the cross section is greater than 0; The cross section is a cross section passing through a geometric center of the secondary particle, the target region is a preset-width annulus with the geometric center as a center on the cross section, and an outer circle of the annulus passes through an end point of the crack.

2. The precursor of claim 1, wherein, 0.5≤k≤1.0。 3. A method for preparing a precursor of the positive electrode material according to claim 1 or 2, characterized in that, The method comprises: The oxide containing Ni p Co q Mn e M f The oxide containing OOH and lithium ions in a lithium-containing solution undergo ion exchange reaction in a liquid phase environment to obtain a slurry containing a precursor of the positive electrode material; wherein 0 The liquid-solid ratio between the lithium-containing solution and the oxide is 3-5 mL / g. filtering the slurry, and drying a filter cake obtained by filtering to obtain the precursor of the positive electrode material.

4. The method of claim 3, wherein, The Ni p Co q Mn e M f OH of the oxide of OOOH is obtained by dispersing Ni p Co q Mn e M f OH in an alkaline environment.

5. The method of claim 3 or 4, wherein, The drying of the filter cake to obtain the precursor of the positive electrode material comprises: dynamically drying the filter cake at 60-200℃, or stirring after static drying to obtain the precursor of the positive electrode material.

6. A method for preparing a cathode material based on the precursor of claim 1 or 2, characterized in that, The method comprises: sintering the precursor of the cathode material, or the mixture of the lithium source and the precursor of the cathode material, at a temperature not more than 900 ℃, to obtain the cathode material Li b Ni c Co d Mn e M w O; wherein, 1.0≤b<1.4, 0 c+d+e+w=1.

7. The method of claim 6, wherein, The sintering of the precursor of the positive electrode material or the mixture of the lithium-containing source and the precursor of the positive electrode material at a temperature not higher than 900℃ to obtain the positive electrode material comprises: The precursor of the positive electrode material or the mixture is subjected to N-stage sintering, wherein N is a positive integer greater than or equal to 1, sintering temperatures in the N-stage sintering are sequentially increased, the sintering temperature of the first stage to the (N-1)th stage is 400-800℃, and the sintering temperature of the Nth stage is 700-900℃.

8. The method of claim 6 or 7, wherein, The sintering condition further comprises that an oxygen content in a sintering atmosphere is less than or equal to 50%.

9. A lithium-ion battery, characterized by The method comprises: The positive electrode material obtained by the method of any one of claims 6-8.

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