A high-nickel cobalt-free positive electrode material and a preparation method and application thereof

Abstract

The application relates to a high-nickel cobalt-free positive electrode material and a preparation method and application thereof. 1‑x‑y Fe x Mn y O2‑Ce&Cr@CeO2; the high-nickel cobalt-free positive electrode material comprises a positive electrode material LiNi 1‑x‑y Fe x Mn y O2 and a surface-coated CeO2 layer; wherein 1-x-y>0.8, 0.05<=x<=0.15, 0.05<=y<=0.15; the doping concentration of Ce and Cr elements is independently 0.5mol%-3mol%. The prepared high-nickel cobalt-free positive electrode material is applied to the field of lithium ion batteries, enhances lithium ion storage capacity and structural stability, reduces transition metal dissolution, reduces internal polarization resistance of the material, and exhibits excellent cycle stability and rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a high-nickel, cobalt-free cathode material, its preparation method, and its application. Background Technology

[0002] Today, with the depletion of traditional fossil fuels and the increasing demand for renewable energy, energy storage devices are developing rapidly. In particular, lithium-ion batteries (LiBs) have become a key factor in large-scale applications due to their high energy density and long cycle life, finding use in various products including laptops, smartphones, iPads, cameras, and electric vehicles. (LiNi, a type of layered structure, is mentioned as an example.) 1-x-y Co x Mn y O2 materials, as cathode materials, have been extensively studied and applied.

[0003] However, due to the scarcity of cobalt resources and the ecological and environmental damage caused by large-scale cobalt mining, battery manufacturers and users face inconvenience. The current global supply chain is fragile. If the current positive electrode formulation remains unchanged, electric vehicle production is expected to increase at least tenfold. Therefore, to reduce overall costs, the cost of the cathode material, which constitutes the largest proportion, should be reduced. Among the current components of ternary materials, cobalt has the highest price and the greatest volatility. Nickel, manganese, and aluminum are cheaper. Furthermore, the cost of cobalt significantly impacts the technology strategy, raw material costs, and selling price of electric vehicles. Considering all factors, reducing the cobalt content in lithium-ion battery cathode materials is beneficial to the rapid development of electric vehicles.

[0004] Metal oxides are an extremely important class of materials. Different preparation methods have made the bulk and nanoscale preparation of metal oxides a significant research area. Preparation methods for metal oxides include sol-gel methods, hydrothermal methods, reflux methods, and ball milling methods. However, all of these methods have significant limitations, such as being unsuitable for large-scale production, being expensive, time-consuming, and containing toxic substances. In addition to these limitations, a common problem with all the above preparation methods is that the synthesis process causes environmental pollution. In metal oxide preparation experiments, the contaminated solvent exposed to the surrounding environment will cause environmental pollution. Since metal oxides are used in applications such as heavy metal ion removal, dye degradation, energy storage devices, and solar cells, the preparation methods themselves should not harm the environment. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-nickel, cobalt-free cathode material, its preparation method, and its applications. The high-nickel, cobalt-free cathode material obtained by this invention improves the cycle stability and initial coulombic efficiency of cobalt-free, nickel-rich ternary cathode materials.

[0006] The first objective of this invention is to provide a high-nickel, cobalt-free cathode material, wherein the general chemical formula of the high-nickel, cobalt-free cathode material is: LiNi 1-x-y Fe x Mn y O2-Ce&Cr@CeO2; the high-nickel cobalt-free cathode material includes LiNi cathode material doped with Ce and Cr elements. 1-x-y Fe x Mn y O2 core and CeO2 layer covering the surface;

[0007] Where 1-xy>0.8, 0.05≤x≤0.15, and 0.05≤y≤0.15;

[0008] The doping concentrations of Ce and Cr elements are independently between 0.5 mol% and 3 mol%.

[0009] In one embodiment of the present invention, the doping concentration of Ce element is 1.5 mol% to 3 mol%, and the doping concentration of Cr element is 0.05 mol% to 1 mol%. Excessive Ce doping will form a CeO2 coating layer on the surface of the particles.

[0010] The second objective of this invention is to provide a method for preparing a high-nickel, cobalt-free cathode material, comprising the following steps:

[0011] An aqueous solution of a metal salt is provided, wherein the metal salt in the aqueous solution includes lithium salt, nickel salt, iron salt, and manganese salt;

[0012] Provide aqueous solutions of cerium salts and chromium salts;

[0013] Add aqueous solutions of cerium salt and chromium salt to the aqueous solution of metal salt, mix thoroughly to obtain a mixed salt solution;

[0014] Acid is added to a mixed salt solution to obtain a mixed solution;

[0015] The resulting mixed solution was subjected to ultrasonic vibration and heated to form a rheotype, resulting in a viscous slurry.

[0016] The resulting viscous slurry was calcined to obtain a cathode material with a CeO2 coating on its surface.

[0017] In one embodiment of the present invention, the cerium salt in the aqueous solution of lithium salt, nickel salt, iron salt, manganese salt, and cerium salt, and the chromium salt in the aqueous solution of chromium salt, are independently one or more of acetate, nitrate, and sulfate.

[0018] In one embodiment of the invention, the acid is selected from acetic acid and / or phosphoric acid. It primarily functions as a dispersant, allowing for more thorough dispersion and mixing of the metal ions.

[0019] In one embodiment of the present invention, the concentration of the acid is 40 wt% to 80 wt%.

[0020] In one embodiment of the present invention, the heating temperature is 60-90°C and the heating time is 4-8 hours.

[0021] In one embodiment of the present invention, the calcination temperature is 720-780°C, the time is 12-16 hours, and the heating rate is 2-6°C / min.

[0022] In one embodiment of the present invention, the high-nickel cobalt-free cathode material further includes a crushing and sieving process, wherein the sieve mesh is 300-400 mesh.

[0023] A third objective of this invention is to provide a positive electrode sheet comprising the aforementioned high-nickel cobalt-free positive electrode material and the high-nickel cobalt-free positive electrode material obtained by the above-described preparation method.

[0024] A fourth objective of the present invention is to provide a lithium-ion battery comprising the above-described positive electrode.

[0025] The technical solution of the present invention has the following advantages compared with the prior art:

[0026] Compared with existing cobalt-free high-nickel ternary materials, this invention provides a one-step calcination process for synthesizing Ce, Cr co-doped and CeO2-coated high-nickel cobalt-free cathode materials. This incorporates Ce... 4+ Cr 3+ Doping and CeO2 coating are used to optimize the overall material properties. CeO2 coating on the inner surface... 4+ Cr 3+ Doping can make Ni 2+ Converted to Ni 3+ Reduce Li + / Ni 2+ The mixing of ions forms strong Ce-O bonds, increasing the overall thermal stability of the material. Excess Ce... 4+ Coating the surface of the cathode material with a CeO2 layer prevents the cathode from being corroded by the electrolyte during battery operation, thus ensuring the overall electrical performance of the battery. As a cathode material for lithium-ion batteries, it exhibits excellent capacity stability and superior rate performance.

[0027] This invention is achieved through a simple mixing-heating-sintering process. The preparation process is relatively simple, highly controllable, requires no advanced instruments, is low in cost, and is suitable for industrial production.

[0028] The cobalt-free cathode material prepared by this invention, when applied in the field of lithium-ion batteries, enhances lithium-ion storage capacity and structural stability, reduces the dissolution of transition metal elements, and lowers the internal polarization resistance of the material. It exhibits excellent cycle stability. Attached Figure Description

[0029] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0030] Figure 1 The image shows the SEM image of the cobalt-free high-nickel ternary cathode material co-doped with cerium and chromium in Example 2 of this invention: the doping concentrations of Ce and Cr are 2 mol% and 0.5 mol%, respectively. Detailed Implementation

[0031] In order to solve the technical problems pointed out in the background art, the present invention proposes a positive electrode material, its preparation method and application.

[0032] This invention provides a high-nickel, cobalt-free cathode material, the chemical formula of which is: LiNi 1-x-y Fe x Mn y O2-Ce&Cr@CeO2; the high-nickel cobalt-free cathode material includes LiNi cathode material doped with Ce and Cr elements. 1-x-y Fe x Mn y The O2 core and the CeO2 layer covering the surface.

[0033] Where 1-xy>0.8, 0.05≤x≤0.15, and 0.05≤y≤0.15;

[0034] The doping concentrations of Ce and Cr elements are independently between 0.5 mol% and 3 mol%.

[0035] In a specific embodiment, the doping concentration of Ce is preferably 1.5 mol% to 3 mol%, and the doping concentration of Cr is 0.05 mol% to 1 mol%. Excessive Ce doping will form a CeO2 coating layer on the surface of the particles; when the Ce doping concentration is less than 1.5 mol%, a CeO2 layer cannot be formed. Without the coating layer, the interface of the cathode material will not be modified, and the interface condition will directly affect the cycle performance of the cathode.

[0036] This invention also provides a method for preparing a high-nickel, cobalt-free cathode material, comprising the following steps:

[0037] An aqueous solution of a metal salt is provided, wherein the metal salt in the aqueous solution includes lithium salt, nickel salt, iron salt, and manganese salt;

[0038] Provide aqueous solutions of cerium salts and chromium salts;

[0039] Add aqueous solutions of cerium salt and chromium salt to the aqueous solution of metal salt, mix thoroughly to obtain a mixed salt solution;

[0040] Acid is added to a mixed salt solution to obtain a mixed solution;

[0041] The resulting mixed solution was subjected to ultrasonic vibration and heated to form a rheotype, resulting in a viscous slurry.

[0042] The resulting viscous slurry was calcined to obtain a cathode material with a CeO2 coating on its surface.

[0043] In a specific embodiment, the lithium salt, nickel salt, iron salt, manganese salt, cerium salt, and chromium salt are independently one or more of acetate, nitrate, and sulfate.

[0044] In a specific embodiment, the amount of the metal salt is mixed according to the stoichiometric ratio of the required components determined by the chemical formula of the high-nickel cobalt-free cathode material.

[0045] In a specific embodiment, the acid is selected from acetic acid and / or phosphoric acid.

[0046] In a specific embodiment, the concentration of the acid is 40 wt% to 80 wt%.

[0047] In a specific embodiment, the heating temperature is 60–90°C, and the heating time is 4–8 hours.

[0048] In a specific embodiment, the calcination temperature is 680–780°C, the time is 12–16 h, and the heating rate is 2–6°C / min. If the calcination temperature is too low, the material will not have sufficient bonding reaction, resulting in more impurities and numerous side reactions during battery operation; if the calcination temperature is too high, it will damage the crystallinity of the material and affect its activity.

[0049] In a specific embodiment, the high-nickel cobalt-free cathode material further includes a crushing and sieving process, with the sieve mesh being 300-400 mesh.

[0050] The present invention also provides a positive electrode sheet, comprising the high-nickel cobalt-free positive electrode material and the high-nickel cobalt-free positive electrode material obtained by the above preparation method.

[0051] The present invention provides a lithium-ion battery comprising the above-mentioned positive electrode sheet.

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0053] Example 1

[0054] This embodiment provides a cobalt-free high-nickel LiNi0.9 Fe 0.05 Mn 0.05 O2:Ce, Cr (Ce and Cr doping concentrations are 1.5 mol% and 0.5 mol%, respectively) cathode material and its preparation method, including the following steps:

[0055] S1. Soluble lithium acetate, nickel acetate, manganese acetate, and iron acetate are mixed in the corresponding stoichiometric ratios of the required components as determined by the chemical formula of the cobalt-free high-nickel material (where lithium acetate needs to be in excess by 5 wt%); a certain amount of deionized water is added to prepare a metal salt solution.

[0056] S2. Dissolve soluble cerium nitrate and chromium nitrate in deionized water at molar amounts of 1.5 mol% and 0.5 mol% of the metal moles in solution S1, respectively. Then slowly pour the solutions into the metal salt solution and mix thoroughly.

[0057] S3. Slowly add acetic acid with a concentration of 30wt% to the solution in step S2 while stirring to form a clear solution;

[0058] S4. After ultrasonically agitating the clear solution obtained in step S4 for 30 minutes, place it in an oil bath at 80°C for 1.5 hours to generate a rheological phase. Continue stirring until a viscous slurry is formed to obtain a gel-like substance.

[0059] S5. The gel-like material obtained in step S4 is calcined in a muffle furnace at 750°C for 16 hours. The calcined powder is then pulverized and sieved through a 400-mesh sieve to obtain LiNi. 0.9 Fe 0.05 Mn 0.05 O2:Ce,Cr cathode material.

[0060] Example 2

[0061] This embodiment provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2:Ce,Cr (Ce and Cr doping concentrations of 2 mol% and 0.5 mol% respectively) cathode material and its preparation method, including the following steps:

[0062] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, manganese acetate, and iron acetate, and in step S2, cerium nitrate and chromium nitrate, are mixed in the corresponding stoichiometric proportions of the required components as determined by the chemical formula of the cobalt-free high-nickel material; the structural characterization diagram of the resulting cathode material is shown in [image missing]. Figure 1 .

[0063] Example 3

[0064] This embodiment provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2:Ce,Cr (Ce and Cr doping concentrations of 3 mol% and 0.5 mol% respectively) cathode material and its preparation method, including the following steps:

[0065] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, manganese acetate, and iron acetate, and in step S2, cerium nitrate and chromium nitrate, are mixed in the corresponding stoichiometric proportions of the required components as determined by the chemical formula of the cobalt-free high-nickel material.

[0066] Example 4

[0067] This embodiment provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2:Ce, Cr (Ce and Cr doping concentrations are 0.5 mol% and 0.5 mol%, respectively) cathode material and its preparation method, including the following steps:

[0068] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, iron acetate, and manganese acetate are mixed in the required stoichiometric proportions according to the chemical formula of the cobalt-free high-nickel material, and in step S2, cerium nitrate and chromium nitrate are mixed in the required stoichiometric proportions.

[0069] Example 5

[0070] This embodiment provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2:Ce, Cr (Ce and Cr doping concentrations are 1 mol% and 0.5 mol%, respectively) cathode material and its preparation method, including the following steps:

[0071] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, manganese acetate, and iron acetate, and in step S2, cerium nitrate and chromium nitrate, are mixed in the corresponding stoichiometric proportions of the required components as determined by the chemical formula of the cobalt-free high-nickel material.

[0072] Comparative Example 1

[0073] This comparative example provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2 (undoped Ce and Cr) cathode material and its preparation method, including the following steps:

[0074] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, manganese acetate, and iron acetate are mixed in the required stoichiometric proportions according to the chemical formula of the cobalt-free high-nickel material. Step S2 is omitted.

[0075] Comparative Example 2

[0076] This comparative example provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2:Ce,Cr (Ce and Cr doping concentrations of 0 mol% and 3 mol% respectively) cathode material and its preparation method, including the following steps:

[0077] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, manganese acetate, and iron acetate, and in step S2, cerium nitrate and chromium nitrate, are mixed in the corresponding stoichiometric proportions of the required components as determined by the chemical formula of the cobalt-free high-nickel material.

[0078] Comparative Example 3

[0079] This comparative example provides a cobalt-free high-nickel LiNi 0.9 Fe 0.05 Mn 0.05 O2:Ce,Cr (Ce and Cr doping concentrations of 3 mol% and 0 mol% respectively) cathode material and its preparation method, including the following steps:

[0080] The difference from Example 1 is that in step S1, lithium acetate, nickel acetate, manganese acetate, and iron acetate, and in step S2, cerium nitrate and chromium nitrate, are mixed in the corresponding stoichiometric proportions of the required components as determined by the chemical formula of the cobalt-free high-nickel material.

[0081] Performance testing

[0082] 1. Battery Assembly: The positive electrode sheet was prepared using a slurry consisting of 92 wt% of the positive electrode material prepared in the examples or comparative examples, 6 wt% polyvinylidene fluoride (PVDF) binder, and 4 wt% acetylene black. The slurry was coated onto aluminum cloth, dried, and rolled to obtain the positive electrode sheet. The obtained positive electrode sheet was then punched to obtain a circular sheet with a diameter of 1.2 cm. All experimental materials were placed in a 60°C oven for 12 hours of drying. Subsequently, CR2032 coin cells were assembled in an argon-protected glove box, with the negative electrode being a purchased lithium metal sheet. The electrolyte was a 1 mol / L LiPF6 solution dissolved in a mixture of ethylene carbonate (EC), dimethyl carbonate (DEC), and ethyl methyl carbonate (EMC) (volume ratio 1:1:1). The battery assembly sequence was: negative electrode shell - lithium metal - separator - positive electrode sheet - gasket - spring contact - positive electrode shell. The voltage was set to 2.5–4.25V. After the battery was assembled and aged for 12 hours, charge and discharge tests were conducted at different potentials.

[0083] 2. The initial coulombic efficiency and discharge specific capacity after 200 cycles were tested at voltages of 2.5–4.25V and current densities of 1C, as well as the discharge capacity retention rate. The results are shown in Table 1.

[0084] Table 1. Electrical performance test results of batteries assembled from the materials obtained in Examples 1-5 and Comparative Examples 1-3.

[0085]

[0086] As shown in Table 1, the cathode materials obtained in the examples exhibit good initial efficiency and capacity retention. Among the cathode materials prepared using the method of this application, the optimal doping ratio is 2 mol% Ce and 0.5 mol% Cr in the nickel-rich iron-manganese cathode material. This is because the CeO2 coating effectively prevents contact between the cathode material and the electrolyte, reducing side reactions at the solid-liquid interface. Simultaneously, the CeO2 coating effectively promotes electron transport. Furthermore, cerium and chromium can replace some lithium and transition metals, and the CeO2 coating on the inner surface... 4+ Cr 3+ Doping can make Ni 2+ Converted to Ni 3+ Reduce Li + / Ni 2+ The mixing of ions forms strong Ce-O bonds, increasing the overall stability of the material.

[0087] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-nickel, cobalt-free cathode material, characterized in that, The general chemical formula of the high-nickel cobalt-free cathode material is: LiNi 1-x-y Fe x Mn y O2-Ce&Cr@CeO2; the high-nickel cobalt-free cathode material includes LiNi cathode material doped with Ce and Cr elements. 1-x-y Fe x Mn y O2 core and CeO2 layer covering the surface; Where 1-xy>0.8, 0.05≤x≤0.15, and 0.05≤y≤0.15; The doping concentration of Cr is 0.5 mol% to 3 mol%; the doping concentration of Ce is 1.5 mol% to 3 mol%. The preparation method includes the following steps: An aqueous solution of a metal salt is provided, wherein the metal salt in the aqueous solution includes lithium salt, nickel salt, iron salt, and manganese salt; Provide aqueous solutions of cerium salts and chromium salts; Add aqueous solutions of cerium salt and chromium salt to the aqueous solution of metal salt, mix thoroughly to obtain a mixed salt solution; Acid is added to a mixed salt solution to obtain a mixed solution; The resulting mixed solution was subjected to ultrasonic vibration and heated to form a rheotype, resulting in a viscous slurry. The resulting viscous slurry was calcined to obtain a cathode material with a CeO2 coating on its surface.

2. The method for preparing the high-nickel cobalt-free cathode material according to claim 1, characterized in that, The Cr doping concentration is 0.5 mol% to 1 mol%.

3. The method for preparing the high-nickel cobalt-free cathode material according to claim 1, characterized in that, The lithium salt, nickel salt, iron salt, manganese salt, cerium salt, and chromium salt are independently one or more of acetate, nitrate, and sulfate.

4. The method for preparing the high-nickel cobalt-free cathode material according to claim 1, characterized in that, The concentration of the acid is 40 wt% to 80 wt%.

5. The method for preparing the high-nickel cobalt-free cathode material according to claim 1, characterized in that, The heating temperature is 60–90°C, and the heating time is 4–8 hours.

6. The method for preparing the high-nickel cobalt-free cathode material according to claim 1, characterized in that, The calcination temperature is 720–780℃, the time is 12–16 h, and the heating rate is 2–6℃ / min.

7. The method for preparing the high-nickel cobalt-free cathode material according to claim 1, characterized in that, The positive electrode material also includes a crushing and sieving process, with the sieve mesh being 300-400 mesh.

8. A positive electrode plate, characterized in that, The cathode material comprises the high-nickel cobalt-free cathode material obtained by the preparation method according to any one of claims 1-7.

9. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 8.

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