A method for controlling doping sites in high-nickel layered cathode materials
By employing a co-precipitation method and precise control of magnesium doping sites, the problems of insufficient cycle stability and electrochemical performance of high-nickel layered cathode materials have been solved, achieving improvements in high capacity and high stability, making them suitable for the industrial production of high-energy-density lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANKAI UNIV
- Filing Date
- 2026-02-09
- Publication Date
- 2026-05-26
AI Technical Summary
Existing high-nickel layered cathode materials have shortcomings in terms of cycle stability and electrochemical performance, especially the capacity decay problem during cycling, and the doping sites are difficult to determine accurately, resulting in unstable doping effects.
Dense spherical secondary particle precursors were prepared by co-precipitation, and magnesium salts were introduced during the co-precipitation and lithiation stages to precisely control the doping sites of magnesium in the high-nickel layered cathode material, forming co-doped or single-doped transition metal sites and lithium sites, thereby improving the structural stability and electrochemical performance of the material.
It significantly improves the cycle stability and electrochemical performance of high-nickel layered cathode materials, greatly reduces the capacity decay rate after long-term cycling, and significantly improves the voltage retention rate, solving the problem that traditional modification methods cannot achieve both high capacity and high stability.
Smart Images
Figure CN122079259A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy material preparation technology, specifically to a method for controlling the doping sites of high-nickel layered cathode materials. Background Technology
[0002] With the rapid development of 3C electronic products and the rapid rise of new energy electric vehicles, the rate of improvement in energy density and power density of lithium-ion batteries can no longer meet the current needs of industrial development. In response to this situation, many countries have proposed development plans to achieve a single-cell energy density of 500 Wh / kg for lithium-ion batteries. Among the existing inorganic cathode materials for lithium-ion batteries, high-nickel layered cathode materials have become one of the key candidate materials for achieving this technical target due to their high specific capacity potential.
[0003] Despite the significant advantages of high-nickel layered cathode materials in terms of energy density, their practical application still faces numerous challenges, primarily including: 1) low initial coulombic efficiency, leading to insufficient initial energy utilization efficiency; 2) poor rate performance, making it difficult to meet the charging and discharging requirements of high-power scenarios; and 3) poor cycle stability, resulting in significant capacity decay after long-term use. Among these, the capacity decay problem during cycling is the most prominent and difficult to solve, severely limiting the industrial application of high-nickel layered cathode materials.
[0004] Currently, one of the most effective modification methods for high-nickel layered cathode materials internationally is elemental doping (such as Mg, Al, Ti, etc.). However, this method has significant drawbacks in practical applications: during elemental doping, the doping sites are difficult to determine precisely, leading to unstable doping effects and failing to fully leverage the optimization effects of elemental doping on the material's structure and performance. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a method for controlling the doping sites of high-nickel layered cathode materials. This method achieves direct atomic-scale observation of the precise sites of doped atoms in high-nickel layered cathode materials by precisely controlling the bulk atomic structure of the materials. It clarifies the site occupancy rules of different doping elements (such as lithium sites and transition metal sites) and the influence of doping amount on site occupancy, thereby improving the cycle stability and comprehensive electrochemical performance of the materials and promoting the industrialization of high-nickel layered cathode materials.
[0006] To achieve the objectives of this invention, the method for controlling the doping sites of high-nickel layered cathode materials utilizes a co-precipitation method. Primary particles with a diameter between 10-20 nm are aggregated into dense spherical secondary particles with a diameter of 8-10 μm, yielding a precursor. Then, using a lithiation method, the precursor and a lithium salt in a specific stoichiometric ratio are ground and mixed uniformly. After pre-calcination and calcination, a high-nickel layered cathode material is obtained, consisting of microspheres with a diameter of 8-10 μm and a tap density of 1.5-2 g / cm³. 3 The doping sites of magnesium in high-nickel layered cathode materials are controlled by introducing magnesium salts during the co-precipitation and lithiation stages. The specific method includes the following steps: (1) Prepare salt solution: Dissolve nickel salt, cobalt salt and magnesium salt in water according to the molar ratio of a(1-x):b(1-x):x to obtain a mixed salt solution of metal ions, where 0.9≤a≤0.95, b=1-a, 0≤x≤0.02, so that the total molar concentration of metal ions is 2-3 mol / L, and set aside for later use; (2) Prepare a precipitant (the precipitant can be a sodium hydroxide solution, which is sodium hydroxide dissolved in distilled water), and set aside; (3) Prepare a complexing agent (the complexing agent can be ammonia water, or NH3·H2O dissolved in distilled water), and set aside; (4) Add distilled water to the reactor as the base liquid, set the reaction temperature of the reactor to 50-60 ℃, stir, and then add alkaline reagent to adjust the pH (specifically, add NH3·H2O to maintain the pH value at 10.5-11.0), set the pumping rate of the salt solution pump and the complexing agent pump to 1.2-1.5 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable and carry out the reaction. (5) After the reaction is complete, the mother liquor is aged, filtered, washed and dried to obtain precursor powder; (6) The obtained precursor powder is thoroughly ground and mixed with lithium salt and magnesium salt in a molar ratio of (1-y):1-1.10:y, where y=0.02-x. After pre-calcination, the temperature is raised to 700-740 ℃ to obtain the target product.
[0007] Depending on the stage of magnesium salt addition, the magnesium doping sites in high-nickel layered cathode materials are different. Introducing magnesium salt in the co-precipitation stage can achieve high-nickel layered cathode materials with co-doped transition metal sites and lithium sites, while introducing magnesium salt in the lithiation stage can achieve high-nickel layered cathode materials with single-doped transition metal sites.
[0008] Furthermore, in some embodiments of the present invention, the nickel salt is at least one of NiSO4, NiSO4·6H2O, Ni(NO3)2 or Ni(CH3COO)2; the cobalt salt is at least one of CoSO4, CoSO4·7H2O, Co(NO3)2 or Co(CH3COO)2; and the magnesium salt is at least one of MgSO4, Mg(NO3)2 or Mg(CH3COO)2.
[0009] Furthermore, in some embodiments of the present invention, the molar concentration of the precipitant is 4-6 mol / L.
[0010] Furthermore, in some embodiments of the present invention, the molar concentration of the complexing agent is 0.4-0.6 mol / L.
[0011] Furthermore, in some embodiments of the present invention, the amount of distilled water added in step (4) is 8%-12% of the volume of the reaction vessel.
[0012] Furthermore, in some embodiments of the present invention, the stirring in step (4) is carried out at a rate of 800-1000 rad / min.
[0013] Furthermore, in some embodiments of the present invention, the reaction in step (4) lasts for 12-24 hours.
[0014] Furthermore, in some embodiments of the present invention, the reaction in step (5) is carried out for 8-10 hours after completion.
[0015] Furthermore, in some embodiments of the present invention, the washing in step (5) is performed using ultrapure water and ethanol, respectively.
[0016] Furthermore, in some embodiments of the present invention, the drying in step (5) is vacuum drying at 80-100 °C; preferably, the drying time is 8-10 hours.
[0017] Furthermore, in some embodiments of the present invention, the lithium salt in step (6) is one or both of Li2CO3 and LiOH·H2O.
[0018] Furthermore, in some embodiments of the present invention, the pre-calcination and calcination in step (6) are carried out in an oxygen atmosphere.
[0019] Furthermore, in some embodiments of the present invention, in step (6), the temperature is raised and calcined after pre-firing at 400-600 °C; preferably, the pre-firing time is 4-6 hours.
[0020] Furthermore, in some embodiments of the present invention, the calcination time in step (6) is 10-14 hours.
[0021] Compared with the prior art, the advantages of the present invention are as follows: (1) The present invention introduces doping elements at fixed points in the internal lattice of the high-nickel layered cathode material. The doping elements form stronger metal-oxygen bonds with oxygen, which effectively inhibits the loss of lattice oxygen during charge-discharge cycles and avoids the collapse of the layered structure caused by the loss of lattice oxygen. At the same time, the doping elements fix the lattice position, reduce ion dislocation, delay the occurrence of phase transition, stabilize the layered crystal structure of the material, and fundamentally alleviate the capacity decay problem.
[0022] (2) The high-nickel layered cathode material modified by the method of the present invention has significantly improved its electrochemical performance: it not only maintains a high discharge specific capacity and meets the requirements of high energy density, but also has excellent cycle stability. After long-term cycling, the capacity decay rate is greatly reduced and the voltage retention rate is significantly improved, which effectively solves the problem that traditional modification methods cannot take into account both high capacity and high stability. Attached Figure Description
[0023] Figure 1 This is a scanning electron microscope image of the precursor prepared by coprecipitation reaction in Example 1; Figure 2 This is a scanning electron microscope image of the high-nickel layered cathode material from Example 1; Figure 3 The XRD pattern of the high-nickel layered cathode material in Example 1 is shown. Figure 4 This is a transmission electron microscope (TEM) image of the high-nickel layered cathode material from Example 1. Figure 5 This is a scanning electron microscope image of the high-nickel layered cathode material from Example 2; Figure 6 The XRD pattern of the high-nickel layered cathode material in Example 2 is shown. Figure 7 This is a transmission electron microscope (TEM) image of the high-nickel layered cathode material from Example 2. Figure 8 The cycling performance curves of the coin cells assembled in Examples 1, 2, 3 and Comparative Example 1 at 1C are shown. Detailed Implementation
[0024] The core innovation of this invention lies in the controllable preparation of doping sites. By introducing magnesium salts in stages, the occupancy behavior of magnesium in the layered structure is precisely controlled. This method not only significantly improves the structural stability and cycle life of the material, but also provides experimental evidence for understanding the structure-property relationship between doping behavior and electrochemical performance. Furthermore, the preparation method of this invention is simple, requires no complex equipment or harsh reaction conditions, is convenient to operate, and has controllable costs, facilitating large-scale production and widespread application. This is of great significance for promoting the development of high-energy-density lithium-ion batteries.
[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.
[0026] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.
[0027] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.
[0028] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.
[0029] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.
[0030] Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.
[0031] Example 1 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0032] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 720 °C for 12 hours to obtain the target product. Figure 1 The image shows a scanning electron microscope (SEM) image of the precursor prepared by coprecipitation reaction. The image shows that primary particles with a particle size between 10 and 20 nm aggregate into dense spherical secondary particles with a diameter of 8 to 10 μm.
[0033] Figure 2 The image shows a scanning electron microscope (SEM) image of a high-nickel layered cathode material prepared by a high-temperature solid-state method. The image shows that the morphology of the prepared high-nickel layered cathode material is basically consistent with that of the precursor.
[0034] Figure 3 The image shows the XRD pattern of the high-nickel layered cathode material prepared by the high-temperature solid-state method. It indicates that the prepared high-nickel layered cathode material has good high-nickel characteristic peaks and maintains a good layered structure.
[0035] Figure 4 EELS mapping characterization of bulk magnesium in high-nickel layered cathode materials shows that magnesium occupies transition metal sites and lithium sites in high-nickel layered cathode materials.
[0036] Example 2 In this embodiment, the precursor is Ni. 0.95 Co 0.05 (OH)2, the lithium salt is LiOH·H2O, and the magnesium salt introduced during the lithiation stage is MgSO4.
[0037] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O and CoSO4·7H2O in a molar ratio of 0.95:0.05 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder, LiOH·H2O and magnesium sulfate are ground and mixed thoroughly in a molar ratio of 0.98:1.05:0.02. The mixture is then pre-calcined at 400 °C for 5 hours in an oxygen atmosphere using a tube furnace, and then calcined at 720 °C for 12 hours to obtain the target product. Figure 5The image shows a scanning electron microscope (SEM) image of a high-nickel layered cathode material prepared by a high-temperature solid-state method. The image shows that the morphology of the prepared high-nickel layered cathode material is basically consistent with that of the high-nickel layered cathode material prepared in Example 1 of this invention.
[0038] Figure 6 The image shows the XRD pattern of the high-nickel layered cathode material prepared by the high-temperature solid-state method. It indicates that the prepared high-nickel layered cathode material has good high-nickel characteristic peaks and maintains a good layered structure.
[0039] Figure 7 The EELS mapping characterization of the bulk magnesium element in the high-nickel layered cathode material shows that magnesium occupies the transition metal sites in the high-nickel layered cathode material.
[0040] Example 3 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.99 Mg 0.01 (OH)2, the lithium salt is LiOH·H2O, and the magnesium salt introduced during the lithiation stage is MgSO4.
[0041] (1) Prepare a 2M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.9405:0.0495:0.01 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder and LiOH·H2O are thoroughly ground and mixed in a molar ratio of 0.99:1.05:0.01. The mixture is then pre-calcined at 400 °C for 5 hours in an oxygen atmosphere using a tube furnace, and then calcined at 720 °C for 12 hours to obtain the target product. Comparative Example 1 In this comparative example, the precursor is Ni. 0.95 Co 0.05 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the co-precipitation and lithiation stages.
[0042] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O and CoSO4·7H2O in a molar ratio of 0.95:0.05 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 720 °C for 12 hours to obtain the target product. Figure 8 The cycling performance curves of the coin cells assembled in Examples 1, 2, 3 and Comparative Example 1 at 1C are shown.
[0043] Example 4 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0044] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 700 °C for 12 hours to obtain the target product.
[0045] The morphology of the prepared high-nickel layered cathode material is basically the same as that of Example 1, and it also has a good layered structure. The assembled coin cell can achieve a capacity retention rate of 85.7% after 100 cycles at 1C.
[0046] Example 5 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0047] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 740 °C for 12 hours to obtain the target product.
[0048] The morphology of the prepared high-nickel layered cathode material is basically the same as that of Example 1, and it also has a good layered structure. The assembled coin cell can achieve a capacity retention rate of 86.3% after 100 cycles at 1C.
[0049] Comparative Example 2 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0050] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 640 °C for 12 hours to obtain the target product.
[0051] The morphology of the prepared high-nickel layered cathode material is basically the same as that of Example 1, with a good layered structure. The assembled coin cell can only achieve a capacity retention rate of 73.5% after 100 cycles at 1C.
[0052] Comparative Example 3 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0053] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 680 °C for 12 hours to obtain the target product.
[0054] The morphology of the prepared high-nickel layered cathode material is basically the same as that of Example 1, with a good layered structure. The assembled coin cell can only achieve a capacity retention rate of 75.5% after 100 cycles at 1C.
[0055] Comparative Example 4 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02 (OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0056] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 760 °C for 12 hours to obtain the target product.
[0057] The morphology of the prepared high-nickel layered cathode material is basically the same as that of Example 1, with a good layered structure. The assembled coin cell can only achieve a capacity retention rate of 82.3% after 100 cycles at 1C.
[0058] Comparative Example 5 In this embodiment, the precursor is (Ni 0.95 Co 0.05 ) 0.98 Mg 0.02(OH)2, the lithium salt is LiOH·H2O, and no magnesium salt is introduced during the lithiation stage.
[0059] (1) Prepare a 2 M sulfate solution by mixing NiSO4·6H2O, CoSO4·7H2O and MgSO4 in a molar ratio of 0.931:0.049:0.02 to obtain a mixed solution of metal ions for later use; (2) The precipitant is sodium hydroxide solution. Sodium hydroxide is dissolved in water to make a molar concentration of 4 mol / L for later use. (3) The complexing agent is ammonia water. Dissolve NH3·H2O in distilled water to make the molar concentration 0.4 mol / L, and set aside. (4) Use a 10 L coprecipitation reactor, set the reaction temperature of the reactor to 55 °C, add 1 L of distilled water as the base liquid, stir at a rate of 800 rad / min, then add a certain amount of NH3·H2O to maintain the pH value at 10.7, set the pumping rate of the salt solution pump and the complexing agent pump to 1.25 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable at 10.7, and the reaction lasts for 16 hours; (5) After the reaction is completed, the mother liquor is aged for 8 hours, then filtered and washed with ultrapure water and ethanol respectively. The green precursor powder is obtained by vacuum drying at 100 °C for 8 hours. (6) The obtained green precursor powder is thoroughly ground and mixed with LiOH·H2O at a molar ratio of 1:1.05. In an oxygen atmosphere, it is pre-calcined at 400 °C for 5 hours in a tube furnace, and then calcined at 800 °C for 12 hours to obtain the target product.
[0060] The morphology of the prepared high-nickel layered cathode material is basically the same as that of Example 1, with a good layered structure. The assembled coin cell can only achieve a capacity retention rate of 80.6% after 100 cycles at 1C.
[0061] from Figure 1-8 It can be seen that by controlling the introduction stage of magnesium salt, the present invention can achieve in-situ regulation of the occupancy of magnesium element in high-nickel layered cathode material, and the obtained high-nickel layered cathode material can have high specific capacity and capacity retention during cycling. Moreover, the preparation method described in the present invention is simple to operate and suitable for industrial production, which is of great significance for the development of high-energy-density power batteries.
[0062] Those skilled in the art will readily understand that the above description is merely a partial example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for controlling the doping sites of high-nickel layered cathode materials, characterized in that, The method includes the following steps: (1) Prepare salt solution: Dissolve nickel salt, cobalt salt and magnesium salt in water according to the molar ratio of a(1-x):b(1-x):x to obtain a mixed salt solution of metal ions, where 0.9≤a≤0.95, b=1-a, 0≤x≤0.02, so that the total molar concentration of metal ions is 2-3 mol / L, and set aside for later use; (2) Prepare the precipitant and set aside; (3) Prepare the complexing agent and set aside; (4) Add distilled water to the reactor as the base liquid, set the reaction temperature of the reactor to 50-60 ℃, stir, then add alkaline reagent to adjust the pH, set the pumping rate of the salt solution pump and complexing agent pump to 1.2-1.5 mL / min, and set the pumping rate of the precipitant pump to automatic, so as to keep the pH of the solution in the reactor stable and carry out the reaction. (5) After the reaction is complete, the mother liquor is aged, filtered, washed and dried to obtain precursor powder; (6) The obtained precursor powder is thoroughly ground and mixed with lithium salt and magnesium salt in a molar ratio of (1-y):1-1.10:y, where y=0.02-x. After pre-calcination, the temperature is raised to 700-740 ℃ to obtain the target product.
2. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, The nickel salt is at least one of NiSO4, NiSO4·6H2O, Ni(NO3)2 or Ni(CH3COO)2; the cobalt salt is at least one of CoSO4, CoSO4·7H2O, Co(NO3)2 or Co(CH3COO)2; and the magnesium salt is at least one of MgSO4, Mg(NO3)2 or Mg(CH3COO)2.
3. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, In step (2), the precipitant is a sodium hydroxide solution, which is dissolved in distilled water, and the molar concentration of the precipitant is 4-6 mol / L; in step (2), the complexing agent is ammonia water, which is dissolved in distilled water, and the molar concentration of the complexing agent is 0.4-0.6 mol / L.
4. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, In step (4), the amount of distilled water added is 8%-12% of the volume of the reactor; in step (4), the stirring is carried out at a rate of 800-1000 rad / min; in step (4), the reaction lasts for 12-24 hours.
5. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, After the reaction in step (5) is completed, the mixture is aged for 8-10 hours; the washing in step (5) is performed using ultrapure water and ethanol respectively.
6. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, In step (5), the drying is carried out under vacuum at 80-100 ℃; the drying time is 8-10 hours.
7. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, In step (6), the lithium salt is one or both of Li2CO3 and LiOH·H2O.
8. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, In step (6), the pre-calcination and calcination are carried out in an oxygen atmosphere.
9. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, In step (6), the temperature is increased to calcined after pre-firing at 400-600 ℃.
10. The method for controlling doping sites in high-nickel layered cathode materials according to claim 1, characterized in that, The pre-calcination time is 4-6 hours; the calcination time in step (6) is 10-14 hours.