Doped nickel cobalt lithium manganate and preparation method thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to doped nickel cobalt lithium manganate and a preparation method thereof.The preparation method comprises the following steps that S1, a nickel source, a cobalt source, a manganese source and a lithium source are dissolved in deionized water according to the molar ratio of (0.4-1): (0.4-1): (0.4-1): 1, ethylene glycol is added into an aqueous solution, mixing is conducted through a reactor, and a mixed solution is obtained; respectively continuously adding the prepared solution into a reactor with a stirring function by using a metering pump, controlling the concentration of NH4 < + > in the reaction solution to be 0.1-0.5 mol / L, controlling the reaction temperature to be 50-60 DEG C and the stirring speed to be 600-1000 r / min, and naturally overflowing and discharging the generated precursor material from an overflow port in the reactor to obtain a mixed solution A; a two-stage calcination process is adopted, a precursor and a lithium source can be subjected to primary reaction in a pre-calcination stage, part of lithium compounds are formed, and the reaction time and energy consumption in a high-temperature calcination stage are reduced; the material can form a complete crystal structure in the high-temperature calcination stage, and the crystallinity and the electrochemical performance of the material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a doped lithium nickel-cobalt manganese oxide and a preparation method thereof. Background Art

[0002] With the continuous introduction of environmental policies and increasingly stringent law enforcement in my country, the environmental protection industry has entered a period of rapid development. The development of new energy materials, especially electric vehicles, carries the mission of responding to green environmental protection policies and achieving a leapfrogging of the automotive industry. As the country vigorously promotes the development of new energy vehicles and the production and sales of electric vehicles have also experienced explosive growth, the market for electric vehicle lithium-ion batteries has increasingly stringent requirements for energy density, cycle performance, charge and discharge efficiency, and safety performance. The research and development of high-performance materials that match electric vehicle lithium-ion batteries will have broad application prospects.

[0003] Liquid lithium-ion batteries (LIBs) are widely used in mobile electronic devices due to their high energy density. Recently, their applications have diversified to larger systems such as electric vehicles and energy storage systems. The rapid growth of the LIB industry has generated a continuous demand for improved performance. In particular, increased energy storage capacity is a top priority for achieving longer battery life, and the development of high-capacity cathode materials is a key requirement. Thermal and structural stability, lifespan, and suppression of side reactions with electrolytes are also necessary for the development of improved cathode materials. In view of this, we propose a doped lithium nickel cobalt manganese oxide and its preparation method. Summary of the Invention

[0004] The object of the present invention is to provide a doped lithium nickel cobalt manganese oxide and a preparation method thereof to solve the problems raised in the above background technology.

[0005] In view of this, the present invention provides a doped lithium nickel cobalt manganese oxide and a preparation method thereof.

[0006] In this technical solution, the following steps are included:

[0007] Step S1, dissolving a nickel source, a cobalt source, a manganese source and a lithium source in deionized water at a molar ratio of (0.4-1): (0.4-1): (0.4-1): 1, adding ethylene glycol to the aqueous solution, mixing through a reactor, and continuously adding the prepared solutions to a stirred reactor using a metering pump, controlling the concentration of NH4+ in the reaction solution to be between 0.1 mol / L and 0.5 mol / L, controlling the reaction temperature to be 50°C to 60°C, and stirring at a speed of 600 to 1000 rpm, and the generated precursor material naturally overflowing and discharged from the overflow port in the reactor to obtain a mixed solution A;

[0008] Step S2: adding a doping element precursor to the mixed solution A obtained in step S1, controlling the doping amount, to obtain a mixed solution B;

[0009] Step S3, adding a precipitant to the mixed solution B, and performing a coprecipitation reaction at a temperature of 50-80° C. and a pH of 10-12 for 2-4 hours. The precipitant is sodium hydroxide, potassium hydroxide, or ammonia water, and the concentration of the precipitant is 1-3 mol / L. The reaction temperature is controlled at 50-80° C., the reaction time is 2-5 hours, and the pH value of the solution is controlled at 9-11. Stirring is continued during the reaction, and nitrogen is introduced to prevent oxidation of metal ions, thereby obtaining a precursor.

[0010] Step S4: The precursor obtained in step S3 is quickly filtered using a Buchner funnel or a filter press to avoid long-term soaking that may cause dissolution or agglomeration of particles, and then washed with deionized water until neutral, and dried to obtain a doped hydroxide precursor;

[0011] Step S5: preheating the precursor obtained after drying. The preheating process is to increase the temperature from room temperature to 480°C to 550°C at a heating rate of 2°C to 5°C / min and keep the temperature for 4 to 6 hours.

[0012] Step S6, mixing the precursor and the lithium source in a stoichiometric ratio, mixing the doped hydroxide precursor and the lithium salt in a stoichiometric ratio, and performing high-temperature sintering in an oxygen atmosphere. The sintering is divided into two stages. The sintering temperature in the first stage is 500-600°C, and the sintering time is 3-5 hours. The sintering temperature in the second stage is 800-900°C, and the sintering time is 8-12 hours. After the sintering is completed, evaporation crystals are formed, which are washed with water and ethanol, evaporated and crystallized, and then ball milled in a ball mill for 3-4 hours to obtain a lithium nickel cobalt manganese oxide product, thereby obtaining a doped lithium nickel cobalt manganese oxide material.

[0013] In the above technical solution, further, the stirring time in step S1 is 10-20 minutes. The most important role of stirring in the coprecipitation reaction is to promote the mixed metal salt solution and the dopant solution to fully contact with the precipitant, avoiding local uneven concentrations, so that the metal ions and dopant ions can be uniformly precipitated to form a uniform precursor. Secondly, the stirring speed will affect the size and dispersibility of the particles. The appropriate stirring speed can prevent the particles from agglomerating and form a finer precipitate, which is beneficial to the subsequent calcination process. In addition, uniform mixing helps to improve the utilization rate of the doping element and ensure uniform doping.

[0014] In the above technical solution, further, in step S3, the pH value is controlled to be 10-12, and the doping amount is 1%-5% atomic ratio.

[0015] In the above technical solution, the precipitant in step S3 is one or a mixture of sodium hydroxide and ammonia. The core function of the precipitant is to create an alkaline environment in the reaction system by releasing hydroxide ions. Under these conditions, nickel, cobalt, manganese, and dopant metal ions will combine with OH- to form corresponding hydroxide precipitates. This process is the basis of the coprecipitation reaction, ensuring that all metal ions are simultaneously converted into solid precipitates, laying the foundation for the subsequent formation of a uniform precursor powder.

[0016] In the above technical solution, further, the pore size of the filter membrane in step S4 is 0.1 to 0.45 μm.

[0017] In the above technical solution, further, the complexing agent in step S2 is a mixture of one or more of citric acid, oxalic acid, acetic acid, etc. The complexing agent is a type of chemical substance that can form a stable cyclic complex with metal ions. Its molecular structure contains multiple coordinating atoms (such as O, N, S, etc.), which significantly improves the solubility and stability of metal ions through the chelating effect.

[0018] In the above technical solution, further, in step S4, the temperature of the deionized water is 60-80°C / h, and a countercurrent washing tower or a belt filter is used for washing. Controlling the temperature of the deionized water at 60-80°C can significantly improve the cleaning effect while taking into account safety and economy.

[0019] In the above technical solution, further, in step S4, a dispersant is added during washing.

[0020] Three major functions of dispersants:

[0021] Steric hindrance effect:

[0022] Long-chain molecules adsorb on the surface of particles, forming a physical isolation layer that prevents particles from contacting;

[0023] Electrostatic repulsion:

[0024] Ionic dispersants give the particles the same charge on their surfaces, causing them to repel each other through Coulomb forces;

[0025] Wetting effect:

[0026] Reduce the liquid-solid interfacial tension and help the washing liquid penetrate into the gaps between particles.

[0027] High-purity deionized water (conductivity <1μS / cm) replaces impurity ions adsorbed on the particle surface through ion exchange

[0028] In the above technical solution, further, in step S5, the high-temperature calcination degree is 750-900°C, and the high-temperature calcination time is 10 to 15 hours. The high-temperature calcination degree of 750-900°C can provide sufficient energy to drive atomic diffusion, so that the amorphous precursor is fully converted into the target crystal phase. The longer calcination time allows moderate grain growth, avoids uneven grain size or defect accumulation caused by excessively rapid temperature increase, and balances strength and activity.

[0029] In the above technical solution, further, the nickel source is nickel acetate, nickel chloride or nickel sulfate, the cobalt source is cobalt acetate, cobalt chloride or cobalt sulfate, the manganese source is manganese acetate, manganese chloride or manganese sulfate, the lithium source is lithium hydroxide, and the amount of deionized water used is 100-200 mL.

[0030] The beneficial effects of the present invention are:

[0031] 1. The doped lithium nickel cobalt manganese oxide and its preparation method include dissolving soluble salts of nickel, cobalt, and manganese in deionized water at a target ratio, stirring and mixing with a stirring device to obtain a mixed solution A; adding a doping element precursor to the mixed solution A, controlling the doping amount, to obtain a mixed solution B; simultaneously dripping the mixed solution B, a precipitant, and a complexing agent into a reactor, controlling the pH, temperature, and stirring speed to generate a precursor; quickly filtering the obtained precursor using a Buchner funnel or a filter press to avoid long-term immersion that may cause dissolution or agglomeration of particles, washing with deionized water to neutrality, and drying to obtain the precursor; mixing the precursor with a lithium source in a stoichiometric ratio, calcining at high temperature in an air or oxygen atmosphere to form a layered oxide, and obtaining a doped lithium nickel cobalt manganese oxide material.

[0032] 2. The doped lithium nickel cobalt manganese oxide and its preparation method can quickly obtain doped lithium nickel cobalt manganese oxide material through five steps. The process is simple, the degree of automation is high, the product quality is stable, and mass production can be achieved. It has broad application prospects.

[0033] 2. The doped lithium nickel cobalt manganese oxide and its preparation method adopt a two-stage calcination process. The pre-calcination stage allows the precursor to react with the lithium source to form some lithium compounds, reducing the reaction time and energy consumption of the high-temperature calcination stage; the high-temperature calcination stage allows the material to form a complete crystal structure, improving the material's crystallinity and electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0036] In the description of this application, it should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0037] It should be noted that, in the present application, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0038] Example 1:

[0039] See also Figure 1 As shown, this embodiment provides a doped lithium nickel cobalt manganese oxide and a preparation method thereof.

[0040] The following steps are involved:

[0041] Step S1, dissolving a nickel source, a cobalt source, a manganese source and a lithium source in deionized water at a molar ratio of (0.4-1): (0.4-1): (0.4-1): 1, adding ethylene glycol to the aqueous solution, mixing through a reactor, and continuously adding the prepared solutions to a stirred reactor using a metering pump, controlling the concentration of NH4+ in the reaction solution to be between 0.1 mol / L and 0.5 mol / L, controlling the reaction temperature to be 50°C to 60°C, and stirring at a speed of 600 to 1000 rpm, and the generated precursor material naturally overflowing and discharged from the overflow port in the reactor to obtain a mixed solution A;

[0042] Step S2: adding a doping element precursor to the mixed solution A obtained in step S1, controlling the doping amount, to obtain a mixed solution B;

[0043] Step S3, adding a precipitant to the mixed solution B, and performing a coprecipitation reaction at a temperature of 50-80° C. and a pH of 10-12 for 2-4 hours. The precipitant is sodium hydroxide, potassium hydroxide, or ammonia water, and the concentration of the precipitant is 1-3 mol / L. The reaction temperature is controlled at 50-80° C., the reaction time is 2-5 hours, and the pH value of the solution is controlled at 9-11. Stirring is continued during the reaction, and nitrogen is introduced to prevent oxidation of metal ions, thereby obtaining a precursor.

[0044] Step S4: The precursor obtained in step S3 is quickly filtered using a Buchner funnel or a filter press to avoid long-term soaking that may cause dissolution or agglomeration of particles, and then washed with deionized water until neutral, and dried to obtain a doped hydroxide precursor;

[0045] Step S5: preheating the precursor obtained after drying. The preheating process is to increase the temperature from room temperature to 480°C to 550°C at a heating rate of 2°C to 5°C / min and keep the temperature for 4 to 6 hours.

[0046] Step S6, mixing the precursor and the lithium source in a stoichiometric ratio, mixing the doped hydroxide precursor and the lithium salt in a stoichiometric ratio, and performing high-temperature sintering in an oxygen atmosphere. The sintering is divided into two stages. The sintering temperature in the first stage is 500-600°C, and the sintering time is 3-5 hours. The sintering temperature in the second stage is 800-900°C, and the sintering time is 8-12 hours. After the sintering is completed, evaporation crystals are formed, which are washed with water and ethanol, evaporated and crystallized, and then ball milled in a ball mill for 3-4 hours to obtain a lithium nickel cobalt manganese oxide product, thereby obtaining a doped lithium nickel cobalt manganese oxide material.

[0047] Example 2:

[0048] This embodiment provides a doped lithium nickel cobalt manganese oxide and a preparation method thereof, which, in addition to the technical solutions of the above embodiments, also has the following technical features.

[0049] Among them, the stirring time in step S1 is 10-20 minutes. The most important role of stirring in the coprecipitation reaction is to promote the full contact between the mixed metal salt solution and the dopant solution and the precipitant, avoiding local uneven concentrations, so that the metal ions and dopant ions can be uniformly precipitated to form a uniform precursor. Secondly, the stirring speed will affect the size and dispersibility of the particles. The appropriate stirring speed can prevent the particles from agglomerating and form a finer precipitate, which is beneficial to the subsequent calcination process. In addition, uniform mixing helps to improve the utilization rate of the doping element and ensure uniform doping.

[0050] In step S3, the pH value is controlled to be 10-12, and the doping amount is 1%-5% atomic ratio.

[0051] In step S3, the precipitant is either sodium hydroxide or ammonia, or a mixture thereof. The core function of the precipitant is to create an alkaline environment in the reaction system by releasing hydroxide ions. Under these conditions, nickel, cobalt, manganese, and dopant metal ions combine with OH- to form corresponding hydroxide precipitates. This process is the basis of the coprecipitation reaction, ensuring that all metal ions are simultaneously converted into solid precipitates, laying the foundation for the subsequent formation of a uniform precursor powder.

[0052] Wherein, the pore size of the filter membrane in step S4 is 0.1-0.45 μm.

[0053] Among them, the high-temperature calcination degree in step S5 is 750-900°C, and the high-temperature calcination time is 10-15 hours. The high-temperature calcination degree of 750-900°C can provide sufficient energy to drive atomic diffusion, so that the amorphous precursor is fully converted into the target crystal phase. The longer calcination time allows moderate grain growth, avoids uneven grain size or defect accumulation caused by excessively rapid temperature increase, and balances strength and activity.

[0054] Example 3:

[0055] This embodiment provides a doped lithium nickel cobalt manganese oxide and a preparation method thereof, which, in addition to the technical solutions of the above embodiments, also has the following technical features.

[0056] Among them, the complexing agent in step S2 is a mixture of one or more of citric acid, oxalic acid, acetic acid, etc. The complexing agent is a type of chemical substance that can form a stable cyclic complex with metal ions. Its molecular structure contains multiple coordinating atoms (such as O, N, S, etc.), which significantly improves the solubility and stability of metal ions through the chelating effect.

[0057] Example 4:

[0058] This embodiment provides a doped lithium nickel cobalt manganese oxide and a preparation method thereof, which, in addition to the technical solutions of the above embodiments, also has the following technical features.

[0059] Among them, the temperature of deionized water in step S4 is 60-80℃h, and a countercurrent washing tower or belt filter is used for washing. Controlling the temperature of deionized water at 60-80℃ can significantly improve the cleaning effect while taking into account safety and economy. High temperature (60-80℃) increases the diffusion coefficient of impurity ions and increases the washing efficiency by 3-5 times.

[0060] Wherein, in step S4, a dispersant is added during washing.

[0061] Three major functions of dispersants:

[0062] Steric hindrance effect:

[0063] Long-chain molecules adsorb on the surface of particles, forming a physical isolation layer that prevents particles from contacting;

[0064] Electrostatic repulsion:

[0065] Ionic dispersants give the particles the same charge on their surfaces, causing them to repel each other through Coulomb forces;

[0066] Wetting effect:

[0067] Reduce the liquid-solid interfacial tension and help the washing liquid penetrate into the gaps between particles.

[0068] High-purity deionized water (conductivity <1μS / cm) replaces impurity ions adsorbed on the particle surface through ion exchange.

[0069] Among them, the nickel source is nickel acetate, nickel chloride or nickel sulfate, the cobalt source is cobalt acetate, cobalt chloride or cobalt sulfate, the manganese source is manganese acetate, manganese chloride or manganese sulfate, the lithium source is lithium hydroxide, and the amount of deionized water used is 100-200 mL

[0070] During use: dissolve soluble salts of nickel, cobalt and manganese in deionized water in a target proportion, stir and mix by a stirring device to obtain a mixed solution A; add a doping element precursor to the mixed solution A, control the doping amount, and obtain a mixed solution B; drop the mixed solution B, precipitant and complexing agent into the reactor at the same time, control the pH, temperature and stirring speed to generate a precursor; quickly filter the obtained precursor with a Buchner funnel or filter press to avoid long-term soaking that may cause dissolution or agglomeration of particles, wash with deionized water to neutrality, and obtain a precursor after drying; mix the precursor with a lithium source in a stoichiometric ratio, calcine at high temperature, and form a layered oxide in an air or oxygen atmosphere to obtain a doped nickel cobalt manganese oxide material. The doped nickel cobalt manganese oxide material can be quickly obtained through five steps. The process is simple, the degree of automation is high, the product quality is stable, and mass production can be achieved. It has broad application prospects.

[0071] The embodiments of the present application are described above in conjunction with the accompanying drawings. Unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A doped lithium nickel cobalt manganese oxide and a preparation method thereof, characterized in that: The following steps are involved: Step S1, dissolving a nickel source, a cobalt source, a manganese source and a lithium source in deionized water at a molar ratio of (0.4-1): (0.4-1): (0.4-1): 1, adding ethylene glycol to the aqueous solution, mixing through a reactor, and continuously adding the prepared solutions to a stirred reactor using a metering pump, controlling the concentration of NH4+ in the reaction solution to be between 0.1 mol / L and 0.5 mol / L, controlling the reaction temperature to be 50°C to 60°C, and stirring at a speed of 600 to 1000 rpm, and the generated precursor material naturally overflowing and discharged from the overflow port in the reactor to obtain a mixed solution A; Step S2: adding a doping element precursor to the mixed solution A obtained in step S1, controlling the doping amount, to obtain a mixed solution B; Step S3, adding a precipitant to the mixed solution B, and performing a coprecipitation reaction at a temperature of 50-80° C. and a pH of 10-12 for 2-4 hours. The precipitant is sodium hydroxide, potassium hydroxide, or ammonia water, and the concentration of the precipitant is 1-3 mol / L. The reaction temperature is controlled at 50-80° C., the reaction time is 2-5 hours, and the pH value of the solution is controlled at 9-11. Stirring is continued during the reaction, and nitrogen is introduced to prevent oxidation of metal ions, thereby obtaining a precursor. Step S4: The precursor obtained in step S3 is quickly filtered using a Buchner funnel or a filter press to avoid long-term soaking that may cause dissolution or agglomeration of particles, and then washed with deionized water until neutral, and dried to obtain a doped hydroxide precursor; Step S5: preheating the precursor obtained after drying. The preheating process is to increase the temperature from room temperature to 480°C to 550°C at a heating rate of 2°C to 5°C / min and keep the temperature for 4 to 6 hours. Step S6, mixing the precursor and the lithium source in a stoichiometric ratio, mixing the doped hydroxide precursor and the lithium salt in a stoichiometric ratio, and performing high-temperature sintering in an oxygen atmosphere. The sintering is divided into two stages. The sintering temperature in the first stage is 500-600°C, and the sintering time is 3-5 hours. The sintering temperature in the second stage is 800-900°C, and the sintering time is 8-12 hours. After the sintering is completed, evaporation crystals are formed, which are washed with water and ethanol, evaporated and crystallized, and then ball milled in a ball mill for 3-4 hours to obtain a lithium nickel cobalt manganese oxide product, thereby obtaining a doped lithium nickel cobalt manganese oxide material.

2. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: The stirring time in step S1 is 10-20 minutes.

3. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: In step S3, the pH value is controlled to be 10-12, the doping amount is controlled to be 1%-5% atomic ratio, and the temperature is controlled to be 60° C.-70° C.

4. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: The precipitant in step S3 is sodium hydroxide and ammonia water or a mixture of the two.

5. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: The pore size of the filter membrane in step S4 is 0.1-0.45 μm.

6. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: In step S2, the complexing agent is one of citric acid, oxalic acid, acetic acid, or a mixture of more than one of the above.

7. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: In step S4, the temperature of the deionized water is 60-80° C. / h, and a countercurrent washing tower or a belt filter is used for washing.

8. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: In the step S4, a dispersant is added during washing.

9. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: In step S5, the high-temperature calcination temperature is 750-900° C., and the high-temperature calcination time is 10-15 hours.

10. The doped lithium nickel cobalt manganese oxide and the preparation method thereof according to claim 1, characterized in that: The nickel source is nickel acetate, nickel chloride or nickel sulfate, the cobalt source is cobalt acetate, cobalt chloride or cobalt sulfate, the manganese source is manganese acetate, manganese chloride or manganese sulfate, the lithium source is lithium hydroxide, and the amount of deionized water used is 100-200 mL.

Images