Nickel-cobalt lithium aluminate / carbon composite positive electrode material with core-shell structure and spray drying process of nickel-cobalt lithium aluminate / carbon composite positive electrode material

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium nickel cobalt aluminate / carbon composite positive electrode material with a core-shell structure and a spray drying process thereof, the lithium nickel cobalt aluminate / carbon composite positive electrode material comprises the following raw materials: a lithium source, an iron source, a phosphorus source, a carbon source and a solvent; the method specifically comprises the following steps: S1, dissolving a lithium source, an iron source, a phosphorus source and a carbon source in a solvent, mixing according to a stoichiometric ratio, adjusting the pH value by using ammonia water or citric acid, and adding a binder to adjust the viscosity to obtain a precursor solution; s2, atomizing the precursor solution into tiny liquid drops by a centrifugal or pressure type spray dryer through a nozzle or a centrifugal disc, and staying the liquid drops in a tower for 4-10 seconds to obtain a dried microsphere precursor; s3, presintering the dried microsphere precursor in an inert atmosphere at 300-400 DEG C through a firing device, and removing volatile components; and S4, cooling the pre-sintered and dried microsphere precursor, and calcining in the firing device again to form crystals.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof. Background Art

[0002] As the positive electrode material of lithium-ion batteries, lithium iron phosphate has the advantages of abundant raw material sources, low price, green environmental protection, high theoretical specific capacity (about 170mAh / g), long life, safety and good thermal stability. It is currently the preferred positive electrode material for commercial automotive power batteries.

[0003] Currently, the preparation of lithium iron phosphate materials primarily utilizes high-energy wet grinding equipment to grind and pulverize iron orthophosphate and lithium salts to achieve nano-sizing of the lithium iron phosphate material. However, this preparation method is subject to high production costs, which restricts its development. Specifically, 1) the raw materials are finely processed products in specific fields, rather than bulk products in non-chemical applications, resulting in high raw material costs; 2) the existing wet grinding method for preparing lithium iron phosphate materials consumes high energy but has relatively low production capacity; 3) the equipment and auxiliary materials required for the existing wet grinding process are consumables and consumables, resulting in high production investment. In view of this, we propose a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite cathode material and its spray drying process. Summary of the Invention

[0004] The object of the present invention is to provide a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof to solve the problems raised in the above background technology.

[0005] In view of this, the present invention provides a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof, the specific method comprising the following steps:

[0006] Step S1, accurately weighing a certain proportion of nickel source, cobalt source, and aluminum source, dissolving them in an appropriate amount of deionized water to prepare a mixed metal salt solution, adding a lithium source after obtaining the metal salt solution, pre-treating it to make its particle size reach an appropriate range, adding a carbon source, dissolving it in deionized water to prepare a carbon source solution, and then adjusting the pH with ammonia or citric acid, and adding a binder to adjust the viscosity to obtain a precursor solution;

[0007] Step S2: Atomizing the pretreated solution using a dual-fluid atomizing nozzle. Compressed air and the mixed precursor solution are introduced into the dual-fluid atomizing nozzle separately. The compressed air pressure is 0.3-0.6 MPa, and the feed flow rate of the solution is 50-150 mL / min. By controlling the ratio and flow rate of compressed air to solution, uniform atomization is achieved to form tiny droplets.

[0008] The inlet temperature of the drying tower is controlled at 200-300℃, and the outlet temperature is controlled at 80-120℃. The hot air in the drying tower adopts a recycling system, which recovers the heat of the hot air through the heat exchanger and uses it to preheat the fresh air entering the drying tower, thereby improving energy utilization efficiency and reducing energy consumption.

[0009] A rotary flash evaporation device is installed in the drying tower. The device is driven by a motor with a rotation speed of 1000-3000 rpm. The rotary flash evaporation device can make the droplets form a spiral motion trajectory in the drying tower, increasing the contact time and contact area between the droplets and the hot air, further improving the drying efficiency, and at the same time helping to evenly disperse the carbon material in the droplets;

[0010] Step S3: The spray-dried particles are collected by a cyclone separator and a bag dust collector with a collection efficiency of more than 99%, and pre-fired at 300-400° C. in an inert atmosphere by a firing device to remove volatile components;

[0011] Step S4: After the pre-fired dried microsphere precursor cools, it is placed in the firing device again for secondary calcination to form crystals. At the same time, the carbon source is pyrolyzed to form an amorphous carbon coating layer, further removing residual solvent and impurities on the particle surface, and promoting the bonding between the carbon material and lithium nickel cobalt aluminum oxide, thereby improving the performance of the material and obtaining a particle raw material;

[0012] Step S5: crushing the granular raw material obtained in step S4 by a crusher, sieving the crushed raw material to obtain uniform particles, and obtaining a lithium iron phosphate / carbon composite material.

[0013] In the above technical solution, further, in step S1, the stoichiometric ratio of the lithium source, the iron source and the phosphorus source is 1:1:1, and the amount of the carbon source added is usually 5 to 15 wt%.

[0014] In the above technical solution, further, in step S1, the lithium source is lithium hydroxide monohydrate or lithium carbonate, the iron source is ferrous sulfate heptahydrate or ferric nitrate, and the phosphorus source is ammonium dihydrogen phosphate or phosphoric acid.

[0015] In the above technical solution, further, in step S1, the carbon source is glucose, sucrose, citric acid or conductive carbon, and the solvent is deionized water or ethanol.

[0016] In the above technical solution, further, in step S2, the particle size of the tiny droplets is 10 to 50 μm.

[0017] In the above technical solution, further, in step 2, the hot air inlet temperature of the centrifugal or pressure spray dryer is 200-300°C, and the outlet temperature of the centrifugal or pressure spray dryer is 100-150°C.

[0018] In the above technical solution, further, in step S4, the calcination time is 6 to 12 hours, and the calcination temperature is 600 to 800°C. When preparing the lithium iron phosphate / carbon composite material, the calcination temperature of 600 to 800°C and the calcination time of 6 to 12 hours are key parameters affecting the material's crystallinity, particle morphology, and electrochemical performance, promoting the repair of crystal defects and improving purity.

[0019] In the above technical solution, further, the firing device placed in step S4 and step S5 is one of a tube furnace, a rotary furnace or a box furnace.

[0020] Tube furnace:

[0021] Applicable scenarios: laboratory or small-scale production characteristics;

[0022] Atmosphere control: N2 / Ar can be introduced, with good sealing to avoid oxidation;

[0023] Temperature uniformity: The temperature fluctuation in the constant temperature zone is within ±5°C, suitable for precise temperature control.

[0024] Box furnace:

[0025] Applicable scenarios: pilot or large-scale production;

[0026] Features:

[0027] Large capacity: can handle kilogram-level materials;

[0028] Low cost: Equipment investment is less than that of a tube furnace.

[0029] Rotary kiln

[0030] Applicable scenarios: continuous large-scale production;

[0031] Features:

[0032] Continuous feeding: The precursor powder is dynamically heated in the rotating furnace, which improves uniformity;

[0033] Atmosphere control: N2 / Ar can be passed, suitable for industrial processes.

[0034] In the above technical solution, further, in step S5, the screening accuracy is 500-800 meshes.

[0035] In this technical solution,

[0036] The beneficial effects of the present invention are:

[0037] 1. This core-shell structured lithium nickel cobalt aluminum oxide carbon composite cathode material and its spray drying process produce lithium iron phosphate with small particle size and narrow particle size distribution, which reduces the ion diffusion path, helps overcome the disadvantage of low ion diffusion rate, and improves electrical performance. The product has high capacity retention and good rate performance.

[0038] 2. The core-shell structured nickel cobalt aluminum oxide carbon composite cathode material and its spray drying process have good crystal structure, few impurities, uniform particle size, and excellent electrochemical properties. The preparation process is simple and practical, and the raw materials are widely available and low in cost. The raw materials involved are all low-cost bulk chemical products.

[0039] 3. This core-shell structured lithium nickel cobalt aluminum oxide carbon composite cathode material and its spray drying process use a dual-fluid atomization nozzle combined with a solution pretreatment step. By reducing the solution viscosity and precisely controlling the atomization parameters, uniform atomization of the mixed precursor solution is achieved, resulting in a narrow particle size distribution after drying and improved material consistency. Impurities are effectively removed through filtration and secondary heat treatment, ensuring product purity. The precise particle size screening process ensures that the product particle size meets the requirements, further improving product quality. The prepared lithium nickel cobalt aluminum oxide carbon material has excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Example 1:

[0045] See also Figure 1 As shown, this embodiment provides a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process.

[0046] The specific method includes the following steps:

[0047] Step S1, accurately weighing a certain proportion of nickel source, cobalt source, and aluminum source, dissolving them in an appropriate amount of deionized water to prepare a mixed metal salt solution, adding a lithium source after obtaining the metal salt solution, pre-treating it to make its particle size reach an appropriate range, adding a carbon source, dissolving it in deionized water to prepare a carbon source solution, and then adjusting the pH with ammonia or citric acid, and adding a binder to adjust the viscosity to obtain a precursor solution;

[0048] Step S2: Atomizing the pretreated solution using a dual-fluid atomizing nozzle. Compressed air and the mixed precursor solution are introduced into the dual-fluid atomizing nozzle separately. The compressed air pressure is 0.3-0.6 MPa, and the feed flow rate of the solution is 50-150 mL / min. By controlling the ratio and flow rate of compressed air to solution, uniform atomization is achieved to form tiny droplets.

[0049] The inlet temperature of the drying tower is controlled at 200-300℃, and the outlet temperature is controlled at 80-120℃. The hot air in the drying tower adopts a recycling system, which recovers the heat of the hot air through the heat exchanger and uses it to preheat the fresh air entering the drying tower, thereby improving energy utilization efficiency and reducing energy consumption.

[0050] A rotary flash evaporation device is installed in the drying tower. The device is driven by a motor with a rotation speed of 1000-3000 rpm. The rotary flash evaporation device can make the droplets form a spiral motion trajectory in the drying tower, increasing the contact time and contact area between the droplets and the hot air, further improving the drying efficiency, and at the same time helping to evenly disperse the carbon material in the droplets;

[0051] Step S3: The spray-dried particles are collected by a cyclone separator and a bag dust collector with a collection efficiency of more than 99%, and pre-fired at 300-400° C. in an inert atmosphere by a firing device to remove volatile components;

[0052] Step S4: After the pre-fired dried microsphere precursor cools, it is placed in the firing device again for secondary calcination to form crystals. At the same time, the carbon source is pyrolyzed to form an amorphous carbon coating layer, further removing residual solvent and impurities on the particle surface, and promoting the bonding between the carbon material and lithium nickel cobalt aluminum oxide, thereby improving the performance of the material and obtaining a particle raw material;

[0053] Step S5: crushing the granular raw material obtained in step S4 by a crusher, sieving the crushed raw material to obtain uniform particles, and obtaining a lithium iron phosphate / carbon composite material.

[0054] Example 2:

[0055] This embodiment provides a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof. In addition to the technical solutions of the above embodiments, it also has the following technical features.

[0056] In step S1 , the stoichiometric ratio of the lithium source, the iron source, and the phosphorus source is 1:1:1, and the amount of the carbon source added is usually 5 to 15 wt %.

[0057] Wherein, in step S1, the lithium source is lithium hydroxide monohydrate or lithium carbonate, the iron source is ferrous sulfate heptahydrate or ferric nitrate, and the phosphorus source is ammonium dihydrogen phosphate or phosphoric acid.

[0058] Wherein, in step S1, the carbon source is glucose, sucrose, citric acid or conductive carbon, and the solvent is deionized water or ethanol.

[0059] Wherein, in step S2, the particle size of the tiny droplets is 10 to 50 μm.

[0060] Example 3:

[0061] This embodiment provides a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof. In addition to the technical solutions of the above embodiments, it also has the following technical features.

[0062] Wherein, in step 2, the hot air inlet temperature of the centrifugal or pressure spray dryer is 200-300°C, and the outlet temperature of the centrifugal or pressure spray dryer is 100-150°C.

[0063] In step S4, the calcination time is 6 to 12 hours, and the calcination temperature is 600 to 800°C. When preparing the lithium iron phosphate / carbon composite material, the calcination temperature of 600 to 800°C and the calcination time of 6 to 12 hours are key parameters that affect the material's crystallinity, particle morphology, and electrochemical performance, promoting the repair of crystal defects and improving purity.

[0064] Example 4:

[0065] This embodiment provides a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof. In addition to the technical solutions of the above embodiments, it also has the following technical features.

[0066] The firing device in step S4 and step S5 is a tube furnace, a rotary furnace or a box furnace.

[0067] Tube furnace:

[0068] Applicable scenarios: laboratory or small-scale production characteristics;

[0069] Atmosphere control: N2 / Ar can be introduced, with good sealing to avoid oxidation;

[0070] Temperature uniformity: The temperature fluctuation in the constant temperature zone is within ±5°C, suitable for precise temperature control.

[0071] Box furnace:

[0072] Applicable scenarios: pilot or large-scale production;

[0073] Features:

[0074] Large capacity: can handle kilogram-level materials;

[0075] Low cost: Equipment investment is less than that of a tube furnace.

[0076] Rotary kiln

[0077] Applicable scenarios: continuous large-scale production;

[0078] Features:

[0079] Continuous feeding: The precursor powder is dynamically heated in the rotating furnace, which improves uniformity;

[0080] Atmosphere control: N2 / Ar can be passed, suitable for industrial processes.

[0081] Example 5:

[0082] This embodiment provides a core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and a spray drying process thereof. In addition to the technical solutions of the above embodiments, it also has the following technical features.

[0083] Wherein, in step S5, the screening accuracy is 500-800 meshes.

[0084] During use, a lithium source, an iron source, a phosphorus source and a carbon source are dissolved in a solvent and mixed in a stoichiometric ratio, the pH is adjusted with ammonia or citric acid, and a binder is added to adjust the viscosity to obtain a precursor solution; the precursor solution is atomized into tiny droplets through a nozzle or a centrifugal disk by a centrifugal or pressure spray dryer, and the droplets stay in the tower for 4 to 10 seconds to obtain a dry microsphere precursor; the dried microsphere precursor is pre-fired at 300 to 400° C. in an inert atmosphere by a firing device to remove volatile components; after the pre-fired dried microsphere precursor is cooled, it is placed in the firing device again for calcination to form crystals, and at the same time, the carbon source is pyrolyzed to generate an amorphous carbon coating layer to obtain a granular raw material; the obtained granular raw material is crushed by a crusher, and the crushed raw material is sieved to obtain uniform particles to obtain a lithium iron phosphate / carbon composite material;

[0085] The lithium iron phosphate prepared by this method has a small particle size and a narrow particle size distribution, which reduces the path of ion diffusion, helps to overcome the disadvantage of low ion diffusion rate and improves electrical performance. The product has a high capacity retention rate and good rate performance;

[0086] The product has good crystal structure, few impurities, uniform particle size, excellent electrochemical properties, simple and practical preparation process, wide source of raw materials and low cost. The raw materials involved are all low-cost bulk chemical products.

[0087] 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 core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process, characterized in that: The specific method includes the following steps: Step S1, accurately weighing a certain proportion of nickel source, cobalt source, and aluminum source, dissolving them in an appropriate amount of deionized water to prepare a mixed metal salt solution, adding a lithium source after obtaining the metal salt solution, pre-treating it to make its particle size reach an appropriate range, adding a carbon source, dissolving it in deionized water to prepare a carbon source solution, and then adjusting the pH with ammonia or citric acid, and adding a binder to adjust the viscosity to obtain a precursor solution; Step S2: Atomizing the pretreated solution using a dual-fluid atomizing nozzle. Compressed air and the mixed precursor solution are introduced into the dual-fluid atomizing nozzle separately. The compressed air pressure is 0.3-0.6 MPa, and the feed flow rate of the solution is 50-150 mL / min. By controlling the ratio and flow rate of compressed air to solution, uniform atomization is achieved to form tiny droplets. The inlet temperature of the drying tower is controlled at 200-300℃, and the outlet temperature is controlled at 80-120℃. The hot air in the drying tower adopts a recycling system, which recovers the heat of the hot air through the heat exchanger and uses it to preheat the fresh air entering the drying tower, thereby improving energy utilization efficiency and reducing energy consumption. A rotary flash evaporation device is installed in the drying tower. The device is driven by a motor with a rotation speed of 1000-3000 rpm. The rotary flash evaporation device can make the droplets form a spiral motion trajectory in the drying tower, increasing the contact time and contact area between the droplets and the hot air, further improving the drying efficiency, and at the same time helping to evenly disperse the carbon material in the droplets; Step S3: The spray-dried particles are collected by a cyclone separator and a bag dust collector with a collection efficiency of more than 99%, and pre-fired at 300-400° C. in an inert atmosphere by a firing device to remove volatile components; Step S4: After the pre-fired dried microsphere precursor cools, it is placed in the firing device again for secondary calcination to form crystals. At the same time, the carbon source is pyrolyzed to form an amorphous carbon coating layer, further removing residual solvent and impurities on the particle surface, and promoting the bonding between the carbon material and lithium nickel cobalt aluminum oxide, thereby improving the performance of the material and obtaining a particle raw material; Step S5: crushing the granular raw material obtained in step S4 by a crusher, sieving the crushed raw material to obtain uniform particles, and obtaining a lithium iron phosphate / carbon composite material.

2. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: In step S1, the stoichiometric ratio of the lithium source, the iron source, and the phosphorus source is 1:1:1, and the amount of the carbon source added is generally 5-15 wt%.

3. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: In step S1, the lithium source is lithium hydroxide monohydrate or lithium carbonate, the iron source is ferrous sulfate heptahydrate or ferric nitrate, and the phosphorus source is ammonium dihydrogen phosphate or phosphoric acid.

4. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: In step S1, the carbon source is glucose, sucrose, citric acid or conductive carbon, and the solvent is deionized water or ethanol.

5. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: In step S2, the particle size of the tiny droplets is 10 to 50 μm.

6. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: In step S4, the calcination time is 6 to 12 hours, and the calcination temperature is 600 to 800°C.

7. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: The firing device in step S4 is a tube furnace, a rotary kiln or a box furnace.

8. The core-shell structured lithium nickel cobalt aluminum oxide / carbon composite positive electrode material and its spray drying process according to claim 1, characterized in that: In step S5, the screening accuracy is 500-800 meshes.

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