Method for preparing precursor seed crystal of high-sphericity multi-element positive electrode material through regulation and control of surfactant

Abstract

The invention provides a method for preparing a precursor seed crystal of a high-sphericity-degree multi-element positive electrode material through regulation and control of a surfactant, which comprises the following steps of: in a nitrogen atmosphere, taking nickel-based inorganic salt or nickel-based organic salt as a raw material, and reacting in a backing material containing the surfactant by adopting a nitrogen-containing complexing agent to prepare a hydroxide seed crystal; primary particles of the seed crystal are of a nanorod-shaped structure, secondary particles of the seed crystal are of a sea urchin-shaped structure, the prepared high-sphericity-degree hydroxide seed crystal serves as a base material, a co-precipitation reaction is carried out in a proper oxidation environment, and a nickel-based layered multi-element positive electrode material precursor is prepared. The multi-element positive electrode material precursor prepared by the preparation method disclosed by the invention is relatively good in quality, relatively high in specific surface area and relatively high in degree of sphericity of secondary particles.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery positive electrode materials, and in particular to a method for preparing high-sphericity multi-component positive electrode material precursor seed crystals by regulating and controlling a surfactant. Background Art

[0002] With the rapid development of the new energy vehicle industry, the demand for lithium-ion secondary batteries has shown a rapid growth, which in turn has led to a surge in the demand for positive electrode materials. Nickel-cobalt-manganese, nickel-cobalt-aluminum and nickel-cobalt-manganese-aluminum layered multi-element positive electrode materials have become the most sought-after types of positive electrode materials on the market due to their high energy density, excellent safety performance and relatively low cost advantages. It is well known that the appearance morphology of multi-element layered positive electrode materials mainly inherits the appearance morphology of multi-element layered positive electrode precursors, and this inheritance directly affects the electrochemical properties of positive electrode materials. An ideal precursor should have a regular particle shape, uniform particle size distribution and a suitable crystal structure, which helps to improve the charge and discharge performance, rate performance and cycle life of the positive electrode material. For example, a precursor with a regular morphology can ensure the uniformity of the material during the subsequent high-temperature sintering process, reduce internal stress concentration, and thus improve the structural stability and electrochemical performance of the material. In the preparation process of the precursor, the preparation of the seed is very important, because the morphology, size and thickness of the primary particle of the seed have a great influence on the subsequent growth process. In the traditional seed preparation process system, the prepared seed primary particles present a typical flaky microstructure. From the microscopic level, the building unit size of this flaky structure is large. During the self-assembly kinetics, the contact interface between the two layers is large, and there is a significant kinetic barrier to the angle adjustment at the connection between the layers. During the self-assembly process of the seed, the presence of flaky structure particles will seriously interfere with the overall sphericity formation mechanism of the seed. Due to the anisotropic characteristics of the flaky structure, it is difficult to form a regular spherical configuration during the spatial stacking process, which makes it difficult to prepare seeds with high sphericity. Using this seed as a raw material, the precursor prepared in the subsequent reaction often has a denser surface, a relatively small specific surface area, and poor sphericity. Surfactants, as a substance with a special molecular structure, play an important role in material preparation. By using surfactants, the prepared seed primary particles can present a nanorod-like structure. When the nanorod-like primary particles start the self-assembly process, the fluid shear force creates a specific environment.

[0003] Nanorods rely on their own geometric characteristics and anisotropy, and their two ends become active reaction sites due to unsaturated surface atoms and high surface energy. Under the action of fluid shear force, the nanorods adjust their orientation. When the ends of the rods are close, van der Waals forces, electrostatic interactions, etc. cause them to connect head to head. This connection is affected by both thermodynamics and kinetics, which not only reduces the surface energy of the system and tends to be stable, but also accelerates under the drive of fluid shear force. As the number of connected nanorods increases, they are orderly arranged around the center of the sphere and inserted into the center of the sphere under the combined action of the center of gravity (comprehensive effect of intermolecular forces) and fluid shear force. In this process, the arrangement and interaction of nanorods are precisely regulated, the contact area of ​​the rod ends is small, the structural distortion is reduced, and the negative impact on the sphericity of the seed crystal is reduced, and finally a sea urchin-shaped precursor seed with high sphericity is formed. Using such seeds as raw materials, the precursor prepared by the method of appropriate oxidation in the subsequent reaction process has significant advantages. On the one hand, the sphericity is good; on the other hand, its specific surface area is also high. However, how to prepare highly spherical multi-element cathode material precursor seeds remains a technical challenge. Summary of the invention

[0004] The present invention provides a method for preparing high-sphericity multinary positive electrode material precursor seed crystals by regulating surfactants, so as to solve the problems raised in the background technology and achieve the goal that the prepared multinary positive electrode material precursor has good quality, the multinary positive electrode material precursor has a high specific surface area, and the secondary particles have a high sphericity.

[0005] The present invention provides a method for preparing a multi-element positive electrode material precursor seed with high sphericity by regulating and controlling a surfactant, comprising the following steps:

[0006] Step S1, seed crystal preparation stage: nickel-based inorganic salt or nickel-based organic salt is used as raw material, and a nitrogen-containing complexing agent is used to react in a base material containing a surfactant to prepare a high-sphericity hydroxide seed crystal with a primary particle having a nanorod-like structure and a secondary particle having a sea urchin-like structure, and the surfactant on the seed crystal is washed off with deionized water after filtering;

[0007] Step S2, precursor growth stage: using the high sphericity hydroxide seed crystals obtained in step S1 as the base material for co-precipitation reaction, using nickel-based inorganic salts or nickel-based organic salts as raw materials, and simultaneously using nitrogen-containing complexing agents to react to prepare secondary particles with high sphericity and a nickel-based multi-element positive electrode material precursor with a high specific surface area.

[0008] Preferably, the nitrogen-containing complexing agent is one or a combination of ammonia water, ammonium sulfite, ammonium bisulfite, ammonium sulfate, ammonium bisulfate, ammonium sulfide, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium chloride or ammonium carbonate, and the surfactant is one or a combination of hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyethylene glycol, and polyethylene glycol fatty acid ester.

[0009] Preferably, the nickel-based inorganic salt or nickel-based organic salt in step S1 and step S2 is the same, the nickel-based inorganic salt is nickel-based sulfate, nickel-based nitrate or nickel-based chloride, the nickel-based organic salt is nickel-based acetate, and the nickel base in the nickel-based inorganic salt or nickel-based organic salt is nickel-cobalt, nickel-manganese, nickel-cobalt-manganese, nickel-cobalt-aluminum or nickel-cobalt-manganese-aluminum.

[0010] Preferably, the specific process of step S1 is: under a nitrogen atmosphere, a nickel-based inorganic salt or nickel-based organic salt solution, a NaOH solution, and a nitrogen-containing complexing agent are respectively added to a reactor containing a nitrogen-containing complexing agent and a surfactant as a base material, the pH value in the reactor is controlled to be 11.0-13.0, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.01-2.0 mol / L and the concentration of the surfactant is controlled to be 0.01-3.0 mol / L, and the reaction is carried out at 40-80° C. for 0.1-3 hours to obtain high-sphericity hydroxide seed crystals, and the surfactant on the seed crystals is washed off with deionized water after filtering.

[0011] Preferably, the molar concentration of the nickel-based inorganic salt or nickel-based organic salt solution in step S1 is 1.0-3.0 mol / L, the molar concentration of the NaOH solution is 3.0-10.0 mol / L, the molar concentration of the nitrogen-containing complexing agent is 3.0-12.0 mol / L, the molar concentration of the surfactant is 0.1-3.0 mol / L, the mass ratio of the nickel-based inorganic salt or nickel-based organic salt solution to the NaOH solution is 1.1-3:1, the pH value in the reactor is controlled to be 12.0-13.0, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.2-0.7 mol / L.

[0012] Preferably, the specific process of step S2 is: introducing air into the reactor containing the high-sphericity hydroxide seed crystals, respectively adding a nickel-based inorganic salt or nickel-based organic salt solution, a NaOH solution, and a nitrogen-containing complexing agent, controlling the pH value in the reactor to be 11.0-12.0, and controlling the concentration of ammonia water in the reactor to be 0.1-3.0 mol / L, reacting at 30-80° C. for 30-80 hours to obtain a slurry, and washing and drying the slurry to obtain a nickel-based multi-element positive electrode material precursor;

[0013] The reaction is carried out in a reactor for 30-80 hours to obtain a slurry, and the slurry is washed and dried to obtain a nickel-based multi-element positive electrode material precursor; the nickel-based multi-element material precursor is evenly mixed with a lithium-containing compound and calcined to obtain a crack-free multi-element positive electrode material, and the lithium-containing compound is one or a combination of lithium hydroxide, lithium carbonate, lithium acetate or lithium nitrate.

[0014] Preferably, the oxygen content in the non-solution space in the reactor described in step S2 is 0.002-0.05 mol / L, the molar concentration of the nickel-based inorganic salt or nickel-based organic salt solution is 1.0-3.0 mol / L, the molar concentration of the NaOH solution is 3.0-10.0 mol / L, the molar concentration of the nitrogen-containing complexing agent is 3.0-12.0 mol / L, the feeding mass ratio of the nickel-based inorganic salt or nickel-based organic salt solution to the NaOH solution is 1.1-3:1, the pH value in the reactor is controlled to be 11.2-11.7, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.2-0.7 mol / L.

[0015] Preferably, the calcination comprises the following specific steps: heating to 400-550°C at 2°C / min and keeping the temperature for 4-8 hours; then heating to 700-900°C at 2-7°C / min and keeping the temperature for 8-15 hours.

[0016] Beneficial effects: The present invention adds a surfactant during the seed preparation process, so that the primary particles of the seed prepared are nanorod-like structures, and the secondary particles are sea urchin-like structures. High sphericity precursor seeds, compared with the primary particles of the seed prepared by the traditional method, which are sheet-like structures, the primary particles of the seed prepared by the present invention are nanorod-like. When the nanorod-like primary particles start the self-assembly process, the fluid shear force creates a specific environment. The nanorods rely on their own geometric characteristics and anisotropy, and their two ends become active reaction sites due to unsaturated surface atoms and high surface energy. Under the action of the fluid shear force, the nanorods adjust their orientation, and after the rod ends are close, van der Waals forces, electrostatic interactions, etc. prompt them to connect in a head-to-head manner. This connection is affected by both thermodynamics and kinetics, which not only reduces the surface energy of the system to stabilize, but also accelerates under the drive of fluid shear force. As the number of connected nanorods increases, they are orderly arranged around the center of the sphere and inserted into the center of the sphere under the combined action of the center of gravity (comprehensive effect of intermolecular forces) and the fluid shear force. In this process, the arrangement and interaction of the nanorods are precisely controlled, the contact area of ​​the rod ends is small, the structural distortion is reduced, and the negative impact on the sphericity of the seed crystal is reduced, and finally a sea urchin-like structure precursor seed with high sphericity is formed. The seed crystal is then used to further grow into a layered multi-element cathode material precursor with good secondary particle sphericity and high specific surface area through appropriate oxidation.

[0017] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a SEM image of the seed crystal prepared in Example 1 of the present invention;

[0020] Figure 2 This is a SEM image of the precursor prepared in Example 1 of the present invention;

[0021] Figure 3 This is a SEM image of the seed crystal prepared in Comparative Example 1 of the present invention;

[0022] Figure 4 This is the SEM image of the precursor prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase "embodiments" in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive of other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0025] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings.

[0026] The present invention provides a method for preparing a multi-element positive electrode material precursor seed with high sphericity by regulating and controlling a surfactant, comprising the following steps:

[0027] Step S1, seed crystal preparation stage: nickel-based inorganic salt or nickel-based organic salt is used as raw material, and a nitrogen-containing complexing agent is used to react in a base material containing a surfactant to prepare a high-sphericity hydroxide seed crystal with a primary particle having a nanorod-like structure and a secondary particle having a sea urchin-like structure, and the surfactant on the seed crystal is washed off with deionized water after filtering;

[0028] Step S2, precursor growth stage: using the high sphericity hydroxide seed crystal obtained in step S1 as the base material for coprecipitation reaction, using nickel-based inorganic salt or nickel-based organic salt as the raw material, and using nitrogen-containing complexing agent to react to prepare a nickel-based multi-element positive electrode material precursor with high sphericity of secondary particles and high specific surface area. The reaction is carried out in the reactor for 30-80 hours to obtain a slurry, and the slurry is washed and dried to obtain a nickel-based multi-element positive electrode material precursor; the nickel-based multi-element positive electrode material precursor is evenly mixed with a lithium-containing compound and calcined to obtain a crack-free multi-element positive electrode material, and the lithium-containing compound is one or a combination of lithium hydroxide, lithium carbonate, lithium acetate or lithium nitrate. Calcination includes the following specific steps: heating to 400-550°C at 2°C / min, keeping warm for 4-8 hours; then heating to 700-900°C at 2-7°C / min, keeping warm for 8-15 hours.

[0029] Among them, the nitrogen-containing complexing agent is one or a combination of ammonia water, ammonium sulfite, ammonium bisulfite, ammonium sulfate, ammonium bisulfate, ammonium sulfide, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium chloride or ammonium carbonate, and the surfactant is one or a combination of hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyethylene glycol, and polyethylene glycol fatty acid ester.

[0030] In the present invention, the nickel-based inorganic salt or nickel-based organic salt in step S1 and step S2 is the same, the nickel-based inorganic salt is nickel-based sulfate, nickel-based nitrate or nickel-based chloride, the nickel-based organic salt is nickel-based acetate, and the nickel base in the nickel-based inorganic salt or nickel-based organic salt is nickel-cobalt, nickel-manganese, nickel-cobalt-manganese, nickel-cobalt-aluminum or nickel-cobalt-manganese-aluminum.

[0031] In the present invention, the specific process of step S1 is: under a nitrogen atmosphere, a nickel-based inorganic salt or nickel-based organic salt solution, a NaOH solution, and a nitrogen-containing complexing agent are respectively added to a reactor containing a nitrogen-containing complexing agent and a surfactant as a base material, the pH value in the reactor is controlled to be 11.0-13.0, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.01-2.0 mol / L and the concentration of the surfactant is controlled to be 0.01-3.0 mol / L, and the reaction is carried out at 40-80° C. for 0.1-3 hours to obtain a high-sphericity hydroxide seed crystal, and the surfactant on the seed crystal is washed off with deionized water after filtering.

[0032] In the present invention, the molar concentration of the nickel-based inorganic salt or nickel-based organic salt solution described in step S1 is 1.0-3.0 mol / L, the molar concentration of the NaOH solution is 3.0-10.0 mol / L, the molar concentration of the nitrogen-containing complexing agent is 3.0-12.0 mol / L, the molar concentration of the surfactant is 0.1-3.0 mol / L, the feeding mass ratio of the nickel-based inorganic salt or nickel-based organic salt solution to the NaOH solution is 1.1-3:1, the pH value in the reactor is controlled to be 12.0-13.0, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.2-0.7 mol / L.

[0033] In the present invention, the specific process of step S2 is: introducing air into the reactor containing the high sphericity hydroxide seed crystals, respectively adding a nickel-based inorganic salt or nickel-based organic salt solution, a NaOH solution, and a nitrogen-containing complexing agent, controlling the pH value in the reactor to be 11.0-12.0, and controlling the concentration of ammonia water in the reactor to be 0.1-3.0 mol / L, reacting at 30-80° C. for 30-80 hours to obtain a slurry, washing and drying the slurry to obtain a nickel-based multi-element positive electrode material precursor; the non-solution space in the reactor described in step S2 The oxygen content is 0.002-0.05 mol / L, the molar concentration of the nickel-based inorganic salt or nickel-based organic salt solution is 1.0-3.0 mol / L, the molar concentration of the NaOH solution is 3.0-10.0 mol / L, the molar concentration of the nitrogen-containing complexing agent is 3.0-12.0 mol / L, the feeding mass ratio of the nickel-based inorganic salt or nickel-based organic salt solution to the NaOH solution is 1.1-3:1, the pH value in the reactor is controlled to be 11.2-11.7, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.2-0.7 mol / L.

[0034] Example 1

[0035] 1) Hydroxide seed preparation stage: Under nitrogen atmosphere, 2.0 mol / L MSO4 (M = Ni, Co, Mn, wherein the molar ratio of Ni: Co: Mn is 0.9: 0.05: 0.05) solution, 8.0 mol / L NaOH solution, 10.0 mol / L ammonia solution, are added to a reactor containing 0.5 mol / L ammonia water and 0.8 mol / L polyethylene glycol as bottom water, wherein the feeding rate of MSO4 solution is 30 mL / min, the feeding rate of NaOH solution is about 18 mL / min, the pH value of the coprecipitation reaction is controlled to be 12.5, the coprecipitation reaction temperature is controlled to be 60°C, the ammonia concentration in the coprecipitation reactor is controlled to be about 0.5 mol / L, and the feeding is continued. After 1.5 hours of reaction, Ni with high sphericity is obtained. 0.9 Co 0.05 Mn 0.05 (OH)2 seed crystals, filtered and washed with deionized water to remove the polyethylene glycol attached to the seed crystals. Figure 1 As shown, the seed crystal is a sea urchin-like structure with high sphericity, composed of nanorods, with a rod-shaped primary particle diameter of about 0.2 μm and a secondary particle diameter of 1 μm.

[0036] 2) Multi-element cathode material precursor growth stage: Air was introduced into the reactor to adjust the oxygen content in the non-solution space in the reactor to 0.008 mol / L. 0.9 Co 0.05 Mn 0.05 (OH)2 seed crystals were used as base material, 2 mol / L MSO4 (M=Ni, Co, Mn, wherein the molar ratio of Ni: Co: Mn was 0.9: 0.05: 0.05) solution, 8.0 mol / L NaOH solution, 10.0 mol / L ammonia solution, and solution containing 0.5 mol / L ammonia water were added, wherein the feeding rate of MSO4 solution was 100 mL / min, the feeding rate of NaOH solution was about 62 mL / min, the pH value of the coprecipitation reaction was controlled to be 11.5, the coprecipitation reaction temperature was controlled to be 60°C, the ammonia concentration in the coprecipitation reactor was controlled to be about 0.5 mol / L, the feeding was continued, and Ni was obtained after 80 hours of reaction. 0.9 Co 0.05 Mn 0.05 (OH)2 slurry, washing and drying the slurry to obtain secondary particles with high sphericity Ni 0.9 Co 0.05 Mn 0.05 (OH)2 precursors, such as Figure 2 As shown, it has high sphericity and high specific surface area.

[0037] 3) Using Ni from step 2) 0.9 Co 0.05 Mn0.05 The (OH)2 precursor seed was mixed with LiOH·H2O and then placed in a tube furnace. The temperature was raised to 450°C at a heating rate of 2°C / min and then kept at that temperature for 6 hours. The temperature was then raised to 750°C at a heating rate of 5°C / min and then kept at that temperature for 12 hours to obtain LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material.

[0038] 4) Using the LiNi prepared above 0.9 Co 0.05 Mn 0.05 After the O2 positive electrode material was washed and coated for modification, the electrode was prepared and assembled into a CR2032 button battery. The electrochemical performance was tested. The first coulombic efficiency was 93.8%, the 0.1C cycle capacity was as high as 225mAh / g, and after 100 cycles at 0.1C, the capacity retention rate was as high as 98.2%.

[0039] Example 2

[0040] 1) Hydroxide seed preparation stage: Under nitrogen atmosphere, 2.0 mol / L MSO4 (M = Ni, Co, Mn, wherein the molar ratio of Ni: Co: Mn is 0.96: 0.02: 0.02) solution, 10.0 mol / L NaOH solution, 12.0 mol / L ammonia solution, are added to a reactor containing 0.2 mol / L ammonia solution and 0.3 mol / L sodium dodecyl sulfate solution as bottom water, wherein the feeding rate of MSO4 solution is 60 mL / min, the feeding rate of NaOH solution is about 38 mL / min, the pH value of the coprecipitation reaction is controlled to be 12.3, the coprecipitation reaction temperature is controlled to be 55°C, the ammonia concentration in the coprecipitation reactor is controlled to be about 0.2 mol / L, the feeding is continued, and Ni with high sphericity is obtained after 1 hour of reaction. 0.96 Co 0.02 Mn 0.02 (OH)2 seed crystals, filter and wash away the sodium dodecyl sulfate attached to the seed crystals with deionized water.

[0041] 2) Precursor growth stage: Air was introduced into the reactor to adjust the oxygen content in the non-solution space of the reactor to 0.006 mol / L. 0.96 Co 0.02 Mn 0.02(OH)2 seed crystals were used as base material, 2.0 mol / L MSO4 (M=Ni, Co, Mn, wherein the molar ratio of Ni:Co:Mn is 0.96:0.0.02:0.0.02) solution, 10.0 mol / L NaOH solution, 12.0 mol / L ammonia solution, and solution were added into a reactor containing 0.2 mol / L ammonia water as base water, wherein the feeding rate of MSO4 solution was 120 mL / min, the feeding rate of NaOH solution was about 75 mL / min, the pH value of the coprecipitation reaction was controlled to be 11.3, the temperature of the coprecipitation reaction was controlled to be 55°C, the concentration of ammonia water in the coprecipitation reactor was controlled to be about 0.2 mol / L, the feeding was continued, and Ni was obtained after 60 hours of reaction. 0.96 Co 0.0.02 Mn 0.0.02 (OH)2 slurry, the slurry is washed and dried to obtain secondary particles with high sphericity and high specific surface area Ni 0.96 Co 0.02 Mn 0.02 (OH)2 precursor.

[0042] 3) Using Ni from step 2) 0.96 Co 0.02 Mn 0.02 The (OH)2 precursor seed was mixed with LiOH·H2O and then placed in a tube furnace. The temperature was raised to 420°C at a heating rate of 2°C / min and then kept at this temperature for 8 hours. The temperature was then raised to 720°C at a heating rate of 7°C / min and then kept at this temperature for 10 hours to obtain LiNi 0.96 Co 0.02 Mn 0.02 O2 positive electrode material.

[0043] 4) Using the LiNi prepared above 0.96 Co 0.02 Mn 0.02 After the O2 positive electrode material was washed and coated for modification, the electrode was prepared and assembled into a CR2032 button battery. The electrochemical performance was tested. The first coulombic efficiency was 94%, the 0.1C cycle capacity was as high as 240mAh / g, and after 100 cycles at 0.1C, the capacity retention rate was as high as 97.8%.

[0044] Example 3

[0045] 1) Hydroxide seed preparation stage: Under nitrogen atmosphere, 1.5 mol / L MSO4 (M = Ni, Co, Mn, wherein the molar ratio of Ni: Co: Mnl is 0.8: 0.1: 0.1) solution, 6.0 mol / L NaOH solution, 9 mol / L ammonia solution, are added to a reactor containing 0.3 mol / L ammonia solution and 0.5 mol / L hexadecyltrimethylammonium chloride solution as bottom water, wherein the feeding rate of MSO4 solution is 80 mL / min, the feeding rate of NaOH solution is about 50 mL / min, the pH value of the coprecipitation reaction is controlled to be 12.6, the coprecipitation reaction temperature is controlled to be 50°C, the ammonia concentration in the coprecipitation reactor is controlled to be about 0.3 mol / L, the feeding is continued, and Ni with high sphericity is obtained after the reaction for 0.5 hours. 0.8 Co 0.1 Mn 0.1 (OH)2 seed crystals. After filtering, use deionized water to wash away the hexadecyltrimethylammonium chloride attached to the seed crystals.

[0046] 2) Precursor growth stage: Air was introduced into the reactor to adjust the oxygen content in the non-solution space of the reactor to 0.005 mol / L. 0.8 Co 0.1 Mn 0.1 (OH)2 seed crystals were used as base material, 1.5 mol / L MSO4 (M=Ni, Co, Mn, wherein the molar ratio of Ni:Co:Mn was 0.8:0.1:0.1) solution, 6.0 mol / L NaOH solution, and 9.0 mol / L ammonia solution were added into a reactor containing 0.3 mol / L ammonia water as base water, wherein the feeding rate of MSO4 solution was 150 mL / min, and the feeding rate of NaOH solution was about 90 mL / min, the pH value of the coprecipitation reaction was controlled to be 11.7, the coprecipitation reaction temperature was controlled to be 50°C, and the ammonia concentration in the coprecipitation reactor was controlled to be about 0.3 mol / L, and the feeding was continued. After 50 hours of reaction, Ni 0.8 Co 0.1 Mn 0.1 (OH)2 slurry, washing and drying the slurry to obtain secondary particles of Ni0.8Co0.1Mn0.1(OH)2 precursor with high sphericity and high specific surface area.

[0047] 3) Using Ni from step 2) 0.88 Co 0.06 Mn 0.06 The (OH)2 precursor seed was mixed with LiOH·H2O and then placed in a tube furnace. The temperature was raised to 480°C at a heating rate of 2°C / min and then kept at this temperature for 5 hours. The temperature was then raised to 780°C at a heating rate of 5°C / min and then kept at this temperature for 12 hours to obtain LiNi0.88 Co 0.06 Mn 0.06 O2 positive electrode material.

[0048] 4) Using the LiNi prepared above 0.88 Co 0.06 Mn 0.06 After the O2 positive electrode material was washed and coated for modification, the electrode was prepared and assembled into a CR2032 button battery. The electrochemical performance was tested. The first coulombic efficiency was 93.5%, the 0.1C cycle capacity was as high as 220mAh / g, and after 100 cycles at 0.1C, the capacity retention rate was as high as 98.5%.

[0049] Comparative Example 1

[0050] 1) Hydroxide seed crystal preparation stage: Under nitrogen atmosphere, 2.0 mol / L MSO4 (M = Ni, Co, Mn, wherein the molar ratio of Ni: Co: Mn is 0.9: 0.05: 0.05) solution, 8.0 mol / L NaOH solution, and 10.0 mol / L ammonia solution are added to a reactor containing 0.5 mol / L ammonia water as bottom water, wherein the feeding rate of MSO4 solution is 30 mL / min, and the feeding rate of NaOH solution is about 18 mL / min, the pH value of the coprecipitation reaction is controlled to be 12.5, the coprecipitation reaction temperature is controlled to be 60°C, and the ammonia concentration in the coprecipitation reactor is controlled to be about 0.3 mol / L, and the feeding is continued for 1.5 hours to obtain Ni 0.9 Co 0.05 Mn 0.05 (OH)2 seeds, such as Figure 3 As shown, the seed crystal is severely agglomerated and has poor sphericity. It is composed of flaky primary particles with a width of about 0.8 μm and a secondary particle diameter of about 1.7 μm.

[0051] 2) Precursor growth stage: In a nitrogen atmosphere, the Ni prepared in step 1) 0.9 Co 0.05 Mn 0.05 (OH)2 seed crystals were used as base material, 2 mol / L MSO4 (M=Ni, Co, Mn, wherein the molar ratio of Ni:Co:Mn was 0.9:0.05:0.05) solution, 8 mol / L NaOH solution, and 10.0 mol / L ammonia solution were added to a reactor containing 0.5 mol / L ammonia water as base water, wherein the feeding rate of MSO4 solution was 100 mL / min, and the feeding rate of NaOH solution was about 62 mL / min, the pH value of the coprecipitation reaction was controlled to be 11.5, the coprecipitation reaction temperature was controlled to be 60°C, and the ammonia concentration in the coprecipitation reactor was controlled to be about 0.5 mol / L, and the feeding was continued. After 80 hours of reaction, Ni0.9 Co 0.05 Mn 0.05 (OH)2 slurry, the slurry is washed and dried to obtain secondary particles of spherical Ni 0.9 Co 0.05 Mn 0.05 (OH)2 precursor. Figure 4 As shown, the sphericity is poor and the specific surface area is low.

[0052] 3) Using Ni from step 2) 0.9 Co 0.05 Mn 0.05 The (OH)2 precursor seed was mixed with LiOH·H2O and then placed in a tube furnace. The temperature was raised to 450°C at a heating rate of 2°C / min and then kept at that temperature for 6 hours. The temperature was then raised to 750°C at a heating rate of 5°C / min and then kept at that temperature for 12 hours to obtain LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material.

[0053] 4) Using the LiNi prepared above 0.9 Co 0.05 Mn 0.05 After the O2 positive electrode material was washed and coated for modification, the electrode was prepared and assembled into a CR2032 button battery. The electrochemical performance was tested. The first coulombic efficiency was 86%, the 0.1C cycle capacity was as high as 210mAh / g, and after 100 cycles at 0.1C, the capacity retention rate could reach 88%.

[0054] It can be seen from the comparison of multiple embodiments and comparative examples, as shown in Table 1:

[0055]

[0056] Table 1

[0057] The lithium ion battery positive electrode materials A1, A2, A3 prepared according to the above method in the above Examples 1, 2, 3 and Comparative Example 1 and A4 provided in the comparative example are assembled into button cells according to the following method: the positive electrode material, conductive carbon and polyvinylidene fluoride (PVDF) are added to N-methyl-2-pyrrolidone (NMP) in a mass ratio of 92.5:5:2.5, and the mixture is evenly mixed to form a positive electrode slurry, which is then coated on the positive electrode current collector and vacuum dried to form a positive electrode. The lithium sheet is used as the negative electrode and assembled into a 2025 button cell in a glove box.

[0058] The button cell assembled from A1, A2, A3 and A4 was tested using the CT2001A battery testing system of Wuhan Blue Electric Electronics Co., Ltd., as shown in Table 2.

[0059] Discharge capacity (mAh / g) Example 1 Example 2 Example 3 Comparative Example 1 0.2C / 0.2C, 2.8-4.3v 220 235 215 206 0.2C / 0.2C, 2.8-4.5v 223 238 218 208 2C / 2C, 2.8-4.3v 218 233 213 204 2C / 2C,2.8-4.5v 219 234 214 205 5C / 5C,2.8-4.3v 214 230 209 195 5C / 5C,2.8-4.5v 216 231 211 198

[0060] Table 2

[0061] The particle size distribution and specific surface area of ​​the various embodiments and comparative examples are shown in Table 3:

[0062] Group D10(μm) D50(μm) D90(μm) <![CDATA[BET(m 2 / g))]]> Example 1 1.943 3.007 4.254 15.2 Example 2 1.919 2.924 4.160 15.6 Example 3 1.965 3.012 4.256 15.0 Comparative Example 1 1.840 2.941 4.874 9.8

[0063] Table 3

[0064] Comparing Example 1 and Comparative Example 1, a surfactant is added to Example 1. The surfactant can be used to prepare a multinary precursor seed with high sphericity, in which the primary particles are nanorod-like structures and the secondary particles are sea urchin-like structures. The seed crystals are used as a base material, and then an appropriate amount of oxidation is performed to grow the secondary particles into a multinary precursor with high sphericity and a high specific surface area.

[0065] The present invention adopts nitrogen-containing complexing agent and surfactant simultaneously in the process of preparing hydroxide seed crystals, utilizes ammonium radical in nitrogen-containing complexing agent and nickel, cobalt and manganese ions in nickel-based inorganic salt or nickel-based organic salt to form relatively stable complex, can slow down the nucleation speed of hydroxide, and utilizes surfactant to make its primary particles into nanorod structure, and prepares high sphericity precursor seed crystals with secondary particles into sea urchin-like structure through unique connection mode of nanorods; and then adopts the seed crystals to further grow into layered multi-element positive electrode material precursor with secondary particles of high sphericity and high specific surface area through proper oxidation.

[0066] In summary, the present invention adds a surfactant during the seed preparation process, so that the primary particles of the seed prepared are nanorod-like structures, and the secondary particles are sea urchin-like structures with high sphericity precursor seeds. Compared with the primary particles of the seed prepared by the traditional method, which are sheet-like structures, the seeds prepared by the present invention are nanorod-like in shape. When the nanorod-like primary particles start the self-assembly process, the fluid shear force creates a specific environment. The nanorods rely on their own geometric characteristics and anisotropy, and their two ends become active reaction sites due to unsaturated surface atoms and high surface energy. Under the action of the fluid shear force, the nanorods adjust their orientation, and after the rod ends are close, van der Waals forces, electrostatic interactions, etc. prompt them to connect in a head-to-head manner. This connection is affected by both thermodynamics and kinetics, which not only reduces the surface energy of the system to stabilize, but also accelerates under the drive of fluid shear force. As the number of connected nanorods increases, they are arranged in order around the center of the ball and inserted into the center of the ball under the combined action of the center of the ball gravity (comprehensive effect of intermolecular forces) and the fluid shear force. In this process, the arrangement and interaction of the nanorods are precisely controlled, the contact area of ​​the rod ends is small, the structural distortion is reduced, and the negative impact on the sphericity of the seed crystal is reduced, and finally a sea urchin-like structure precursor seed with high sphericity is formed. The seed crystal is then used to further grow into a layered multi-element cathode material precursor with good secondary particle sphericity and high specific surface area through appropriate oxidation.

[0067] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high sphericity multi-element cathode material precursor seed crystals by surfactant regulation, characterized in that: The steps include: Step S1, seed crystal preparation stage: nickel-based inorganic salt or nickel-based organic salt is used as raw material, and a nitrogen-containing complexing agent is used to react in a base material containing a surfactant to prepare a high-sphericity hydroxide seed crystal with a primary particle having a nanorod-like structure and a secondary particle having a sea urchin-like structure, and the surfactant on the seed crystal is washed off with deionized water after filtering; Step S2, precursor growth stage: using the high sphericity hydroxide seed crystals obtained in step S1 as the base material for co-precipitation reaction, using nickel-based inorganic salts or nickel-based organic salts as raw materials, and simultaneously using nitrogen-containing complexing agents to react to prepare secondary particles with high sphericity and a nickel-based multi-element positive electrode material precursor with a high specific surface area.

2. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 1, characterized in that: The nitrogen-containing complexing agent is one or a combination of ammonia water, ammonium sulfite, ammonium bisulfite, ammonium sulfate, ammonium bisulfate, ammonium sulfide, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium chloride or ammonium carbonate; the surfactant is one or a combination of hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyethylene glycol, and polyethylene glycol fatty acid ester.

3. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 1, characterized in that: The nickel-based inorganic salt or nickel-based organic salt in step S1 and step S2 is the same, the nickel-based inorganic salt is nickel-based sulfate, nickel-based nitrate or nickel-based chloride, the nickel-based organic salt is nickel-based acetate, and the nickel base in the nickel-based inorganic salt or nickel-based organic salt is nickel-cobalt, nickel-manganese, nickel-cobalt-manganese, nickel-cobalt-aluminum or nickel-cobalt-manganese-aluminum.

4. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 1, characterized in that: The specific process of step S1 is: under a nitrogen atmosphere, a nickel-based inorganic salt or nickel-based organic salt solution, a NaOH solution, and a nitrogen-containing complexing agent are respectively added to a reactor containing a nitrogen-containing complexing agent and a surfactant as a base material, the pH value in the reactor is controlled to be 11.0-13.0, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.01-2.0 mol / L and the concentration of the surfactant is controlled to be 0.01-3.0 mol / L, and the reaction is carried out at 40-80° C. for 0.1-3 hours to obtain a high-sphericity hydroxide seed crystal, and the surfactant on the seed crystal is washed off with deionized water after filtering.

5. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 1, characterized in that: The molar concentration of the nickel-based inorganic salt or nickel-based organic salt solution in step S1 is 1.0-3.0 mol / L, the molar concentration of the NaOH solution is 3.0-10.0 mol / L, the molar concentration of the nitrogen-containing complexing agent is 3.0-12.0 mol / L, the molar concentration of the surfactant is 0.1-3.0 mol / L, the mass ratio of the nickel-based inorganic salt or nickel-based organic salt solution to the NaOH solution is 1.1-3:1, the pH value in the reactor is controlled to be 12.0-13.0, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.2-0.7 mol / L.

6. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 1, characterized in that: The specific process of step S2 is: introducing air into the reactor containing the high-sphericity hydroxide seed crystals, respectively adding a nickel-based inorganic salt or nickel-based organic salt solution, a NaOH solution, and a nitrogen-containing complexing agent, controlling the pH value in the reactor to be 11.0-12.0, and controlling the concentration of ammonia water in the reactor to be 0.1-3.0 mol / L, reacting at 30-80° C. for 30-80 hours to obtain a slurry, and washing and drying the slurry to obtain a nickel-based multi-element positive electrode material precursor; The reaction is carried out in a reactor for 30-80 hours to obtain a slurry, and the slurry is washed and dried to obtain a nickel-based multi-element positive electrode material precursor; the nickel-based multi-element material precursor is evenly mixed with a lithium-containing compound and calcined to obtain a crack-free multi-element positive electrode material, and the lithium-containing compound is one or a combination of lithium hydroxide, lithium carbonate, lithium acetate or lithium nitrate.

7. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 1, characterized in that: The oxygen content in the non-solution space in the reactor described in step S2 is 0.002-0.05 mol / L, the molar concentration of the nickel-based inorganic salt or nickel-based organic salt solution is 1.0-3.0 mol / L, the molar concentration of the NaOH solution is 3.0-10.0 mol / L, the molar concentration of the nitrogen-containing complexing agent is 3.0-12.0 mol / L, the feeding mass ratio of the nickel-based inorganic salt or nickel-based organic salt solution to the NaOH solution is 1.1-3:1, the pH value in the reactor is controlled to be 11.2-11.7, and the concentration of the nitrogen-containing complexing agent in the reactor is controlled to be 0.2-0.7 mol / L.

8. The method for preparing high sphericity multi-component positive electrode material precursor seed crystals by surfactant regulation according to claim 6, characterized in that: The calcination comprises the following specific steps: heating to 400-550°C at 2°C / min, and keeping the temperature for 4-8 hours; and then heating to 700-900°C at 2-7°C / min, and keeping the temperature for 8-15 hours.

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