CN111994968A - Electrode material precursor and preparation method thereof - Google Patents

Electrode material precursor and preparation method thereof Download PDF

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CN111994968A
CN111994968A CN202010876493.0A CN202010876493A CN111994968A CN 111994968 A CN111994968 A CN 111994968A CN 202010876493 A CN202010876493 A CN 202010876493A CN 111994968 A CN111994968 A CN 111994968A
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metal
salt solution
electrode material
layer
material precursor
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马跃飞
李�权
林予舒
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Xiamen Xiaw New Energy Materials Co Ltd
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    • C01G53/006—
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • C—CHEMISTRY; METALLURGY
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Abstract

A method for preparing an electrode material precursor, comprising: respectively preparing at least one first metal salt solution and at least one second metal salt solution, wherein the first metal is different from the second metal; continuously adding a first metal salt solution and a second metal salt solution into a reaction container at a first flow rate ratio respectively, and mixing the first metal salt solution and the second metal salt solution with a precipitator and a complexing agent for crystallization treatment to form a core layer; respectively adding the first metal salt solution and the second metal salt solution into a reaction vessel at a continuously reduced second flow rate ratio, and carrying out crystallization treatment to form a transition layer on the surface of the core layer, wherein the second flow rate ratio is less than or equal to the first flow rate ratio; and continuously adding the first metal salt solution and the second metal salt solution into the reaction container at a third flow velocity ratio respectively, and carrying out crystallization treatment to form a surface layer on the surface of the transition layer to obtain the electrode material precursor, wherein the third flow velocity ratio is less than or equal to the second flow velocity ratio. The application also provides an electrode material precursor.

Description

Electrode material precursor and preparation method thereof
Technical Field
The application relates to the field of lithium ion batteries, in particular to an electrode material precursor and a preparation method thereof.
Background
With the increasing importance of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), in recent years, the application of multi-electrode materials in the field of Electric vehicles is increasing, and the development of Electric vehicles with high endurance mileage is an era demand, and lithium ion batteries are becoming a development trend.
In practical use, the lithium ion battery needs to simultaneously meet high specific capacity, high safety, high rate performance and high cycle performance, but a single material cannot meet the performances, so that a multi-element gradient material can be adopted to meet the performances, but due to the limitation of a preparation method, the component proportion gradient of the obtained material cannot be controlled, so that the difference of interfaces between different materials is too large, and the performance of the battery in the charging and discharging process cannot be expected.
Disclosure of Invention
In view of the above, it is desirable to provide a method for preparing a gradient-controllable electrode material precursor, so as to solve the above problems.
In addition, the present application also needs to provide an electrode material precursor.
A preparation method of an electrode material precursor comprises the following steps:
respectively preparing at least one first metal salt solution and at least one second metal salt solution, wherein a metal element in the first metal salt solution is a first metal, a metal element in the second metal salt solution is a second metal, and the first metal is different from the second metal;
continuously adding the first metal salt solution and the second metal salt solution into a reaction container at a first flow rate ratio respectively, and mixing with a precipitator and a complexing agent for crystallization treatment to form a core layer;
adding the first metal salt solution and the second metal salt solution into the reaction vessel at a continuously reduced second flow rate ratio, and performing crystallization treatment to form a transition layer on the surface of the core layer, wherein the second flow rate ratio is less than or equal to the first flow rate ratio; and
and continuously adding the first metal salt solution and the second metal salt solution into a reaction container at a third flow velocity ratio respectively, and carrying out crystallization treatment to form a surface layer on the surface of the transition layer to obtain the electrode material precursor, wherein the third flow velocity ratio is less than or equal to the second flow velocity ratio.
Further, the first metal is selected from at least one of nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium and iridium; the second metal is at least one selected from nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium.
Further, the first metal is selected from at least one of nickel, cobalt and aluminum, and the second metal is selected from at least one of cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium and iridium.
Further, the first flow speed ratio is a constant value or a variable value.
Further, the third flow speed ratio is a constant value or a continuously variable value.
An electrode material precursor is granular and sequentially comprises a core layer, a transition layer and a surface layer from inside to outside, wherein the core layer, the transition layer and the surface layer comprise at least one first metal and at least one second metal; the mole percentage of the first metal in the transition layer to the total number of moles of the first metal and the second metal is less than or equal to the mole percentage of the first metal in the core layer, and the mole percentage of the second metal in the transition layer is greater than or equal to the mole percentage of the second metal in the core layer.
Further, a mole percentage of the first metal in the transition layer is less than or equal to a mole percentage of the first metal in the core layer; the mole percentage of the second metal in the transition layer is greater than or equal to the mole percentage of the second metal in the core layer.
Further, the mole percent of the first metal in the skin layer is less than or equal to the mole percent of the first metal in the transition layer; the mole percent of the second metal in the skin layer is greater than or equal to the mole percent of the second metal in the transition layer.
Further, in the core layer, the mole percentage of the first metal to the total moles of the first metal and the second metal is greater than 70%; in the skin layer, the mole percentage of the second metal to the total number of moles of the first metal and the second metal is greater than 30%.
Further, the first metal is selected from at least one of nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium and iridium; the second metal is at least one selected from nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium.
According to the preparation method provided by the application, the pre-designed component distribution in the electrode material precursor can be obtained by respectively preparing different first metal salt solution and second metal salt solution and respectively controlling the feeding speeds of the first metal salt solution and the second metal salt solution, and the preparation method is controllable, simple to operate and suitable for industrial production; in addition, according to the electrode material precursor prepared by the preparation method, the core layer and the surface layer are sequentially connected according to the component ratio of the first metal to the second metal in the transition layer, so that the interface difference between the core layer and the surface layer is reduced, and the material performance transition is prevented from being too fast, so that the influence on proton transfer in the charging and discharging process is avoided, and the performance of the electrode material is not expected.
Drawings
Fig. 1 is a flowchart of a method for preparing an electrode material precursor according to an embodiment of the present disclosure.
Fig. 2 is a scanning electron microscope test chart of the electrode material precursor prepared in example 1 of the present application.
Fig. 3 is an enlarged view of the electrode material precursor shown in fig. 2.
FIG. 4 is a graph of the results of a line scanning electron microscope test along the electrode material precursor shown in FIG. 3.
The following detailed description will further illustrate the present application in conjunction with the above-described figures.
Detailed Description
In order that the above objects, features and advantages of the present application can be more clearly understood, a detailed description of the present application will be given below with reference to the accompanying drawings and detailed description. In addition, the embodiments and features of the embodiments of the present application may be combined with each other without conflict. In the following description, numerous specific details are set forth to provide a thorough understanding of the present application, and the described embodiments are merely a subset of the embodiments of the present application, rather than all embodiments. All other embodiments obtained by a person of ordinary skill in the art without any inventive work based on the embodiments in the present application are within the scope of protection of the present application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes all and any combination of one or more of the associated listed items.
Referring to fig. 1, an embodiment of the present application provides a method for preparing an electrode material precursor, including the following steps:
step S1: respectively preparing at least one first metal salt solution and at least one second metal salt solution, wherein a metal element in the first metal salt solution is a first metal, a metal element in the second metal salt solution is a second metal, and the first metal is different from the second metal.
Wherein, in the same embodiment, when the first metal salt is multiple, each first metal is different; when the second metal salt is plural, each of the second metals is different. And each first metal salt solution and each second metal salt solution are respectively prepared so as to be convenient for subsequently and respectively controlling the amount of the added first metal salt solution and the second metal salt solution, thereby controlling the molar ratio of the first metal to the second metal in the prepared electrode material precursor.
The first metal salt and the second metal salt may each be at least one selected from the group consisting of a nitrate salt, a chloride salt, and a sulfate salt. The molar concentration of the first metal salt is 0.2-2.5 mol/L, and the molar concentration of the second metal salt is 0.2-2.5 mol/L.
Each of the first metal and the second metal may be selected from at least one of nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium. It is understood that in the same embodiment, the first metal is of a different type than the second metal.
Preferably, the first metal may be selected from at least one of nickel, cobalt, and aluminum, and the second metal may be selected from at least one of cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium. The electrode material containing high nickel (nickel accounts for more than 70% of the mole percentage of the metal element) has the characteristic of high discharge capacity, and the electrode material containing high cobalt (cobalt accounts for more than 70% of the mole percentage of the metal element) or high aluminum (aluminum accounts for more than 70% of the mole percentage of the metal element) has the characteristic of high stability, and the types of the first metal and the second metal can be selected according to the electrochemical performance required after the prepared electrode material is assembled into the lithium ion battery. For example, it is desirable to obtain an electrode material with high capacity and high stability, the first metal may include nickel, the second metal may include at least one of cobalt and aluminum; it is desirable to obtain an electrode material with high voltage and high stability, and the first metal may comprise cobalt and the second metal may comprise at least one of titanium or aluminum.
Specifically, different metal salts are selected according to the types of metal elements contained in the electrode material precursor to be formed, metal salt solutions with certain concentrations are prepared respectively, and the different metal salt solutions are placed in different metering pumps respectively so as to control the types and flow rates of the different metal salts to be added respectively.
Step S2: and continuously adding the first metal salt solution and the second metal salt solution into the reaction vessel at a first flow rate ratio respectively to control the molar ratio of the first metal to the second metal to be a first ratio, and mixing the first metal salt solution and the second metal salt solution with a precipitator and a complexing agent for crystallization treatment to form a core layer.
The precipitating agent may be selected from the group consisting of those capable of hydrolyzing to form OH-、CO3 2-Including but not limited to at least one of potassium hydroxide, sodium carbonate, and potassium carbonate. The complexing agent may be selected from ammonia. The precipitant and the complexing agent are used for precipitating the metal elements in the first metal salt and the second metal salt to form the core layer.
The first flow rate ratio is a speed ratio of the first metal salt solution and the second metal salt solution to be respectively added into the reaction container, and the first flow rate ratio can be a constant value or a continuously variable value.
It is understood that the molar ratio of the first metal to the second metal in the core layer is a first ratio, and the first ratio may be a constant value or a continuously variable value. The mole percentage of the first metal to the total moles of the first metal and the second metal is more than 70% to maintain the main performance of the first metal in the prepared electrode material.
When the first ratio is a continuously varying value, the mole percentage of the first metal to the total number of moles of the first metal and the second metal decreases and the mole percentage of the second metal to the total number of moles of the first metal and the second metal increases from the center to the outer layer of the core layer, that is, the feeding speed of the first metal salt solution decreases and the feeding speed of the second metal salt solution increases as time increases during the preparation of the core layer.
Specifically, the flow rates of the first metal salt solution and the second metal salt solution can be respectively controlled by a metering pump, the second metal salt solution and the second metal salt solution are mixed in a centrifugal mixer, the rotating speed in the centrifugal mixer is greater than or equal to 750rmp, and then the mixed solution flows into the reaction vessel in parallel with a complexing agent and a precipitating agent to carry out crystallization reaction.
Step S3: and respectively adding the first metal salt solution and the second metal salt solution into the reaction vessel at a continuously reduced second flow rate ratio for crystallization treatment to form a transition layer on the surface of the core layer.
The second flow rate ratio is the rate ratio of the first metal salt solution and the second metal salt solution which are respectively added into the reaction container. And the second variable flow rate ratio is used for controlling the molar ratio of the first metal to the second metal in the formed transition layer to change in a gradient manner, wherein the second variable flow rate ratio is smaller than or equal to the first variable flow rate ratio.
Specifically, the flow rate of each metal salt is adjusted according to the ratio of the first metal to the second metal in the electrode material precursor to be formed. In the same embodiment, in the process of preparing the transition layer, the feeding rate of the first metal salt solution is decreased and the feeding rate of the second metal salt solution is increased with the increase of time, so that the values of the first metal and the second metal in the transition layer are continuously changed, from the center to the outer layer of the core layer, the mole percentage of the first metal to the total mole number of the first metal and the second metal is decreased, and the mole percentage of the second metal to the total mole number of the first metal and the second metal is increased.
The mole percentage of the first metal in the transition layer is less than or equal to the mole percentage of the first metal in the core layer, and the mole percentage of the second metal in the transition layer is greater than or equal to the mole percentage of the second metal in the core layer.
Step S4: and continuously adding the first metal salt solution and the second metal salt solution into a reaction container at a third flow velocity ratio respectively to control the molar ratio of the first metal to the second metal to be a second ratio, and performing crystallization treatment to form a surface layer on the surface of the transition layer to obtain the electrode material precursor.
The third flow speed ratio is a speed ratio of the first metal salt solution and the second metal salt solution which are respectively added into the reaction container, the third flow speed ratio can be a constant value or a continuously variable value, and the third flow speed ratio is smaller than or equal to the second flow speed ratio.
It is understood that the molar ratio of the first metal to the second metal in the surface layer is a second ratio, which may be a constant value or a continuously varying value. The second metal in the surface layer accounts for more than 30 percent of the total mole number of the first metal and the second metal, so that the electrode material prepared has the main performance of the second metal and can maintain the main performance of the first metal.
When the second ratio is a continuously varying value, the mole percentage of the first metal decreases and the mole percentage of the second metal increases from the surface of the skin layer adjacent to the transition layer to the surface of the skin layer facing away from the transition layer, i.e., the feed rate of the first metal salt solution decreases and the feed rate of the second metal salt solution increases with time during the preparation of the skin layer.
The electrode material precursor needs to be further processed to obtain an electrode material capable of being used as an active material of a lithium ion battery, wherein the electrode material also comprises the core layer, the transition layer and the surface layer.
In a specific embodiment, the electrode material precursor is subjected to washing and drying steps, and then mixed with a lithium salt according to a certain proportion and then calcined to obtain the electrode material, wherein the electrode material is used for assembling a lithium ion battery. Wherein, the drying is carried out in vacuum, the drying temperature is less than or equal to 100 ℃, and the drying time is greater than or equal to 5 h.
The application also provides an electrode material precursor, the electrode material precursor is granular and sequentially comprises a core layer, a transition layer and a surface layer from inside to outside, and the core layer, the transition layer and the surface layer comprise at least one first metal and at least one second metal.
The first metal may be selected from at least one of nickel, cobalt, and aluminum, and the second metal may be selected from at least one of cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium. In the same embodiment, the first metal in the core layer, the transition layer and the skin layer is the same kind, and the second metal in the core layer, the transition layer and the skin layer is the same kind.
The molar ratio of the first metal to the second metal in the core layer is a first ratio, and the first ratio may be a constant value or a continuously variable value. The mole percent of the first metal in the core layer to the total moles of the first metal and the second metal is greater than 70%.
When the first ratio is a continuously varying value, the mole percentage of the first metal to the total moles of the first metal and the second metal decreases and the mole percentage of the second metal to the total moles of the first metal and the second metal increases from the center of the core layer to the outer layer.
The mole percentage of the first metal in the transition layer is less than or equal to the mole percentage of the first metal in the core layer, and the mole percentage of the second metal in the transition layer is greater than or equal to the mole percentage of the second metal in the core layer.
In the surface layer, the molar ratio of the first metal to the second metal in the surface layer is a second ratio, and the second ratio may be a constant value or a continuously changing value. The second metal in the skin layer accounts for more than 30% of the total number of moles of the first metal and the second metal.
When the second ratio is a continuously varying value, the mole percentage of the first metal decreases and the mole percentage of the second metal increases from the surface of the skin layer adjacent to the transition layer to the surface of the skin layer facing away from the transition layer.
The mole percent of the first metal in the skin layer is less than or equal to the mole percent of the first metal in the transition layer; the mole percent of the second metal in the skin layer is greater than or equal to the mole percent of the second metal in the transition layer.
Maintaining a primary property of a first metal by providing a high mole percentage of the first metal in a core layer; then, arranging a second metal different from the first metal and having a higher mole percentage in the surface layer, so as to ensure that the electrode material has the main performance of the second metal and also maintain the main performance of the first metal on the basis of ensuring that the electrode material has the main performance of the second metal; and by arranging the transition layer with the components in gradient change, the contents of the first metal and the second metal in the transition layer are in gradient connection, so that the difference between the core layer and the surface layer interface is reduced, and the material performance transition is prevented from being too fast, thereby avoiding influencing proton transmission in the charging and discharging process to cause the performance of the electrode material to be beyond expectation.
The present application will be described below with reference to specific examples.
Example 1
Respectively preparing a nickel salt solution with the concentration of 2mol/L, a cobalt salt solution with the concentration of 2mol/L and a manganese salt solution with the concentration of 2mol/L, and respectively placing the nickel salt solution, the cobalt salt solution and the manganese salt solution in different metering pumps.
In a reaction container with a proper amount of sodium hydroxide solution and ammonia water, the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution are respectively controlled by the metering pump, the flow rate of the nickel salt solution is 4L/h, the flow rate of the cobalt salt solution is 0.5L/h, the flow rate of the manganese salt solution is 0.5L/h, the flow rate ratio of the nickel salt solution to the cobalt salt solution to the manganese salt solution is 8:1:1, the adding time of the nickel salt solution to the cobalt salt solution to the manganese salt solution is 10h, the rotating speed during mixing is controlled to be 900rmp, and crystallization parameters are controlled to form a core layer, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the core layer is 8:1: 1.
And then adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, wherein the flow rate of the nickel salt solution is uniformly adjusted from 4L/h to 2.5L/h, the flow rate of the cobalt salt solution is uniformly adjusted from 0.5L/h to 1L/h, the flow rate of the manganese salt solution is uniformly adjusted from 0.5L/h to 1.5L/h, the adjustment time is 60h, and during the period, the crystallization condition is controlled to form a transition layer and coat the transition layer on the surface of the core layer.
And after the transition layer is formed, stopping adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, namely feeding the nickel salt solution, the cobalt salt solution and the manganese salt solution for 10 hours at constant flow rates of 2.5L/h, 1L/h and 1.5L/h respectively, controlling crystallization conditions during the feeding, forming a surface layer and coating the surface of the transition layer to obtain an electrode material precursor, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the surface layer is 5:2: 3.
And (3) drying the electrode material precursor in vacuum at 80 ℃, mixing the dried electrode material precursor with lithium salt, and calcining to obtain the electrode material.
Example 2
Respectively preparing a nickel salt solution with the concentration of 2mol/L, a cobalt salt solution with the concentration of 2mol/L and a manganese salt solution with the concentration of 2mol/L, and respectively placing the nickel salt solution, the cobalt salt solution and the manganese salt solution in different metering pumps.
In a reaction container with a proper amount of sodium hydroxide solution and ammonia water, the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution are respectively controlled by the metering pump, the flow rate of the nickel salt solution is 4.5L/h, the flow rate of the cobalt salt solution is 0.35L/h, the flow rate of the manganese salt solution is 0.15L/h, so that the flow rate ratio of the nickel salt solution to the cobalt salt solution to the manganese salt solution is 90:7:3, the adding time of the nickel salt solution to the cobalt salt solution to the manganese salt solution is 20h, the rotating speed during mixing is controlled to be 800rmp, and crystallization parameters are controlled to form a core layer, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the core layer is 90:7: 3.
And then adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, wherein the flow rate of the nickel salt solution is uniformly adjusted from 4.5L/h to 2.5L/h, the flow rate of the cobalt salt solution is uniformly adjusted from 0.35L/h to 1L/h, the flow rate of the manganese salt solution is uniformly adjusted from 0.15L/h to 1.5L/h, the adjustment time is 70h, and during the period, the crystallization condition is controlled to form a transition layer and coat the transition layer on the surface of the core layer.
And after the transition layer is formed, stopping adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, namely feeding the nickel salt solution, the cobalt salt solution and the manganese salt solution for 10 hours at constant flow rates of 2.5L/h, 1L/h and 1.5L/h respectively, controlling crystallization conditions during the feeding, forming a surface layer and coating the surface of the transition layer to obtain an electrode material precursor, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the surface layer is 5:2: 3.
And (3) drying the electrode material precursor in vacuum at 80 ℃, mixing the dried electrode material precursor with lithium salt, and calcining to obtain the electrode material.
Example 3
Respectively preparing a nickel salt solution with the concentration of 2mol/L, a cobalt salt solution with the concentration of 2mol/L and a manganese salt solution with the concentration of 2mol/L, and respectively placing the nickel salt solution, the cobalt salt solution and the manganese salt solution in different metering pumps.
In a reaction container with a proper amount of sodium hydroxide solution and ammonia water, flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution are respectively controlled by the metering pump, the flow rate of the nickel salt solution is 5L/h, the flow rate of the cobalt salt solution and the manganese salt solution is 0, so that the flow rate ratio of the nickel salt solution, the cobalt salt solution and the manganese salt solution is 1:0:0, the adding time of the nickel salt solution, the cobalt salt solution and the manganese salt solution is controlled to be 10h, crystallization parameters are controlled, the rotation speed during mixing is controlled to be 1000rmp, a core layer is formed, and the molar ratio of metal elements of nickel, cobalt and manganese in the core layer is 1:0: 0.
And then adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, wherein the flow rate of the nickel salt solution is uniformly adjusted from 5L/h to 1.67L/h, the flow rate of the cobalt salt solution is uniformly adjusted from 0 to 1.67L/h, the flow rate of the manganese salt solution is uniformly adjusted from 0 to 1.67L/h, and the adjustment time is 80h, and during the period, the crystallization condition is controlled to form a transition layer and coat the transition layer on the surface of the core layer.
After the transition layer is formed, stopping adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, namely feeding the nickel salt solution, the cobalt salt solution and the manganese salt solution at constant flow rates of 1.67L/h, 1.67L/h and 1.67L/h for 10h, controlling crystallization conditions during the period, forming a surface layer and coating the surface of the transition layer to obtain an electrode material precursor, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the surface layer is 5:2: 3.
And (3) drying the electrode material precursor in vacuum at 80 ℃, mixing the dried electrode material precursor with lithium salt, and calcining to obtain the electrode material.
Example 4
Respectively preparing a nickel salt solution with the concentration of 2mol/L, a cobalt salt solution with the concentration of 2mol/L and an aluminum salt solution with the concentration of 2mol/L, and respectively placing the nickel salt solution, the cobalt salt solution and the aluminum salt solution in different metering pumps.
In a reaction container with proper amount of sodium hydroxide solution and ammonia water, the flow rates of the nickel salt solution, the cobalt salt solution and the aluminum salt solution are respectively controlled by the metering pump, the flow rate of the nickel salt solution is 4.15L/h, the flow rate of the cobalt salt solution is 0.6L/h, the flow rate of the aluminum salt solution is 0.25L/h, the flow rate ratio of the nickel salt solution, the cobalt salt solution and the aluminum salt solution is 83:12:5, the adding time of the nickel salt solution, the cobalt salt solution and the aluminum salt solution is 20h, the rotating speed during mixing is 1100rmp, and crystallization parameters are controlled to form a core layer, wherein the molar ratio of the metal elements of nickel, cobalt and aluminum in the core layer is 83:12: 5.
And then adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the aluminum salt solution, wherein the flow rate of the nickel salt solution is uniformly adjusted from 4.15L/h to 3L/h, the flow rate of the cobalt salt solution is uniformly adjusted from 0.6L/h to 1.75L/h, the flow rate of the aluminum salt solution is kept constant at 0.25L/h, the adjustment time is 40h, and during the period, the crystallization condition is controlled to form a transition layer and coat the transition layer on the surface of the core layer.
After the transition layer is formed, stopping adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the aluminum salt solution, namely feeding the nickel salt solution, the cobalt salt solution and the aluminum salt solution at constant flow rates of 3L/h, 1.75L/h and 0.25L/h for 20h, controlling crystallization conditions during the period, forming a surface layer and coating the surface of the transition layer to obtain an electrode material precursor, wherein the molar ratio of metal elements of nickel, cobalt and aluminum in the surface layer is 5:2: 3.
And (3) drying the electrode material precursor in vacuum at 80 ℃, mixing the dried electrode material precursor with lithium salt, and calcining to obtain the electrode material.
Example 5
Respectively preparing a nickel salt solution with the concentration of 2mol/L, a cobalt salt solution with the concentration of 2mol/L and a manganese salt solution with the concentration of 2mol/L, and respectively placing the nickel salt solution, the cobalt salt solution and the manganese salt solution in different metering pumps.
In a reaction container with a proper amount of sodium hydroxide solution and ammonia water, the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution are respectively controlled by the metering pump, the flow rate of the nickel salt solution is 4.5L/h, the flow rate of the cobalt salt solution is 0.35L/h, the flow rate of the manganese salt solution is 0.15L/h, so that the flow rate ratio of the nickel salt solution to the cobalt salt solution to the manganese salt solution is 90:7:3, the adding time of the nickel salt solution to the cobalt salt solution to the manganese salt solution is 50h, the rotation speed during mixing is controlled to be 1000rmp, and crystallization parameters are controlled to form a core layer, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the core layer is 90:7: 3.
And then adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, wherein the flow rate of the nickel salt solution is uniformly adjusted from 4.5L/h to 1.67L/h, the flow rate of the cobalt salt solution is uniformly adjusted from 0.35L/h to 1.67L/h, the flow rate of the manganese salt solution is uniformly adjusted from 0.15L/h to 1.67L/h, the adjustment time is 30h, and during the period, the crystallization condition is controlled to form a transition layer and coat the transition layer on the surface of the core layer.
After the transition layer is formed, stopping adjusting the flow rates of the nickel salt solution, the cobalt salt solution and the manganese salt solution, namely feeding the nickel salt solution, the cobalt salt solution and the manganese salt solution at constant flow rates of 1.67L/h, 1.67L/h and 1.67L/h for 20h, controlling crystallization conditions during the period, forming a surface layer and coating the surface of the transition layer to obtain an electrode material precursor, wherein the molar ratio of metal elements of nickel, cobalt and manganese in the surface layer is 1:1: 1.
And (3) drying the electrode material precursor in vacuum at 80 ℃, mixing the dried electrode material precursor with lithium salt, and calcining to obtain the electrode material.
Please refer to table 1, which is a summary of the main different preparation conditions of examples 1 to 5.
TABLE 1
Kind of metal element Mole percent of core layer Mole percent of surface layer
Example 1 Nickel, cobalt, manganese 8:1:1 5:2:3
Example 2 Nickel, cobalt, manganese 90:7:3 5:2:3
Example 3 Nickel, cobalt, manganese 1:0:0 1:1:1
Example 4 Nickel, cobalt, aluminium 83:12:5 12:7:1
Example 5 Nickel, cobalt, manganese 90:7:3 1:1:1
Referring to table 2, table 2 shows the physical properties of the electrode materials prepared in examples 1 to 5, including the volume fractions of the core layer, the transition layer, and the surface layer of the electrode materials, D50 of the electrode materials, and the tap densities, and it can be seen from the results in table 2 that the tap densities of the electrode materials obtained in examples 1 to 5 are all high.
Referring to fig. 2 and 3, fig. 2 is a scanning electron microscope test chart of the electrode material precursor prepared in example 1, and fig. 3 is an enlarged view of fig. 2, which shows that the electrode material precursor is in a granular form. Please refer to fig. 4, which is a graph showing a relationship between the mass percentages of the nickel, cobalt, and manganese metal elements and the distances from the scanning start point to the scanning end point of the electrode material particles in the test chart of the scanning electron microscope shown in fig. 3, wherein the distances are 0 μm to 1 μm belonging to a curve (without practical significance) outside the electrode material particles, the region corresponding to 1 μm is the outer surface (i.e., the surface layer) of the electrode material, the interval of 1 μm to 3 μm corresponds to the mass percentages of the nickel, cobalt, and manganese metal elements on the surface layer of the electrode material, and the molar ratio of nickel, cobalt, and manganese is calculated to be approximately 5:2: 3; the range of 3-9 μm corresponds to the mass percentage content of the nickel, cobalt and manganese metal elements of the transition layer of the electrode material, and the content of the nickel, cobalt and manganese is distributed in a gradient manner; the interval of 9-12 μm corresponds to the mass percentage of the nickel, cobalt and manganese metal elements in the inner core layer of the electrode material, and the molar ratio of the nickel, the cobalt and the manganese is approximately 8:1: 1.
TABLE 2
Figure BDA0002649930260000151
Figure BDA0002649930260000161
The electrode materials prepared in examples 1 to 5 were assembled into a lithium ion battery, and electrochemical performance tests were performed, please refer to table 3, and table 3 shows electrochemical performance test results of the electrode materials prepared in examples 1 to 5 at different current densities. From the test results in table 3, it can be seen that the gram discharge capacity of examples 1 to 5 is high, and at the same time, the capacity retention rate is high after many cycles, indicating that the stability of the electrode material is good.
TABLE 3
Capacity of discharge gram Capacity retention rate
Example 1 3C is 198mAh/g 87 percent after 800 weeks
Example 2 1C is 215mAh/g 90 percent after 800 weeks
Example 3 0.1C is 220mAh/g 89% after 1000 weeks
Example 4 0.1C is 190mAh/g After 1000 weeks, the content is 92%
Example 5 0.1C is 220mAh/g 93 percent after 1000 weeks
According to the preparation method provided by the application, the pre-designed component distribution in the electrode material precursor can be obtained by respectively preparing different first metal salt solution and second metal salt solution and respectively controlling the feeding speeds of the first metal salt solution and the second metal salt solution, and the preparation method is controllable, simple to operate and suitable for industrial production; in addition, according to the electrode material precursor prepared by the preparation method, the core layer and the surface layer are sequentially connected according to the component ratio of the first metal to the second metal in the transition layer, so that the interface difference between the core layer and the surface layer is reduced, and the material performance transition is prevented from being too fast, so that the influence on proton transfer in the charging and discharging process is avoided, and the performance of the electrode material is not expected.
Although the present application has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the present application.

Claims (10)

1. A preparation method of an electrode material precursor is characterized by comprising the following steps:
respectively preparing at least one first metal salt solution and at least one second metal salt solution, wherein a metal element in the first metal salt solution is a first metal, a metal element in the second metal salt solution is a second metal, and the first metal is different from the second metal;
continuously adding the first metal salt solution and the second metal salt solution into a reaction container at a first flow rate ratio respectively, and mixing with a precipitator and a complexing agent for crystallization treatment to form a core layer;
adding the first metal salt solution and the second metal salt solution into the reaction vessel at a continuously reduced second flow rate ratio, and performing crystallization treatment to form a transition layer on the surface of the core layer, wherein the second flow rate ratio is less than or equal to the first flow rate ratio; and
and continuously adding the first metal salt solution and the second metal salt solution into a reaction container at a third flow velocity ratio respectively, and carrying out crystallization treatment to form a surface layer on the surface of the transition layer to obtain the electrode material precursor, wherein the third flow velocity ratio is less than or equal to the second flow velocity ratio.
2. The method for producing an electrode material precursor according to claim 1, wherein the first metal is at least one selected from the group consisting of nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium; the second metal is at least one selected from nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium.
3. The method for producing an electrode material precursor according to claim 2, wherein the first metal is at least one selected from the group consisting of nickel, cobalt, and aluminum, and the second metal is at least one selected from the group consisting of cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium.
4. The method for producing an electrode material precursor according to claim 1, wherein the first flow rate ratio is a constant value or a variable value.
5. The method for producing an electrode material precursor according to claim 1, wherein the third flow rate ratio is a constant value or a continuously variable value.
6. An electrode material precursor is characterized in that the electrode material precursor is granular and sequentially comprises a core layer, a transition layer and a surface layer from inside to outside, wherein the core layer, the transition layer and the surface layer respectively comprise at least one first metal and at least one second metal; the mole percentage of the first metal in the transition layer to the total number of moles of the first metal and the second metal is less than or equal to the mole percentage of the first metal in the core layer, and the mole percentage of the second metal in the transition layer is greater than or equal to the mole percentage of the second metal in the core layer.
7. The electrode material precursor of claim 6, wherein the mole percentage of the first metal in the transition layer is less than or equal to the mole percentage of the first metal in the core layer; the mole percentage of the second metal in the transition layer is greater than or equal to the mole percentage of the second metal in the core layer.
8. The electrode material precursor of claim 6, wherein a mole percentage of the first metal in the surface layer is less than or equal to a mole percentage of the first metal in the transition layer; the mole percent of the second metal in the skin layer is greater than or equal to the mole percent of the second metal in the transition layer.
9. The electrode material precursor of claim 6, wherein the mole percent of the first metal in the core layer based on the total moles of the first metal and the second metal is greater than 70%; in the skin layer, the mole percentage of the second metal to the total number of moles of the first metal and the second metal is greater than 30%.
10. The electrode material precursor according to claim 6, wherein the first metal is selected from at least one of nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium; the second metal is at least one selected from nickel, cobalt, manganese, aluminum, zirconium, magnesium, tungsten, titanium, and iridium.
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US20170317344A1 (en) * 2014-10-30 2017-11-02 Institute Of Process Engineering, Chinese Academy Of Sciences Nickel lithium ion battery positive electrode material having concentration gradient, and preparation method therefor
CN105609755A (en) * 2016-02-29 2016-05-25 深圳市贝特瑞新能源材料股份有限公司 Preparation method for positive electrode active material, and positive electrode active material
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