Preparation method of doped and modified high-nickel cathode material

Abstract

The present invention provides a preparation method of a doped and modified high-nickel cathode material. By reacting a high-nickel precursor with an oxidant under certain conditions to form an active hydroxy oxide, and then performing an ion exchange reaction on the active hydroxy oxide with a lithium salt and a doped metal salt to obtain an amorphous high-nickel cathode material, and then through high-temperature crystallization, the required cathode material is obtained. The preparation method of the present invention is simple in operation, high in energy consumption, short in process flow, and can synthesize a uniformly doped high-nickel cathode material, improving the performance of the high-nickel cathode material.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery materials, and particularly relates to a preparation method of a doped and modified high-nickel cathode material. Background Art

[0002] Among numerous electrochemical energy storage systems, lithium-ion batteries (LIBs), as typical representatives of rechargeable batteries (secondary batteries), are considered to be one of the most successful cases of electrochemical energy storage changing the human lifestyle at present. Their applications include portable electronic devices and hybrid / pure electric vehicles (EVs), and are further extended to large-scale energy storage devices. In recent years, battery companies at home and abroad have focused on the ternary cathode material route. In China, power batteries have gradually shifted from lithium iron phosphate batteries to ternary batteries, especially in the passenger vehicle field. Due to the relatively low energy density of lithium iron phosphate batteries, the research and development focus of power lithium batteries in China has shifted to ternary lithium-ion batteries. The synthesis of ternary cathode materials all requires a high-temperature calcination process. Further improving the process conditions and reducing the high-temperature calcination temperature and holding time are the key issues for solving the production cost of ternary cathode materials and an inevitable trend for future development. At the same time, the electrochemical performance of pure-phase high-nickel ternary materials cannot meet the requirements of commercial applications, and generally requires doping for performance modification.

[0003] At present, the preparation of ternary cathode materials in industry is mainly achieved through two processes: coprecipitation and high-temperature calcination: first, the precursor of the ternary cathode material (mainly hydroxide precursor) is synthesized by coprecipitation, and then the lithium source and the ternary precursor are chemically reacted by high-temperature solid phase method, and lithium is embedded in the precursor under high temperature drive to form a ternary cathode material with a layered structure of alternating Li-O layer and TM-O layer. The precursor and lithium source generated by coprecipitation need to be mixed by mechanical methods and then calcined at high temperature. Due to the complex process of solid phase method, especially high temperature and long time, the production process has high energy consumption. In addition, high-nickel ternary cathode materials are restricted by the fact that nickel elements are difficult to completely oxidize from divalent to trivalent. The high-temperature solid phase reaction process has strict control over the oxidizing atmosphere. The processing and storage process of the obtained materials have very stringent requirements on the environment (especially moisture, CO2, etc.), and the preparation cost is relatively high. Doping modification generally involves adding solid-phase additives during the process of mixing the precursor with the lithium source, and achieving doping modification through element migration during high-temperature sintering. This method is difficult to form uniform doping inside the material particles. In order to achieve uniform doping, people began to add doping elements during the precursor synthesis process, and co-precipitated them into the precursor together with the main elements. However, this method has different adaptability to different doping elements, because the complexing ability of the complexing agent to different elements is different, and the solubility product of the precipitate produced by different elements and the precipitant is different, so that some doping elements cannot enter the precursor, and even segregation will occur. At the same time, some doping elements will affect the microscopic morphology, tap density, specific surface area and other indicators of the precursor, thereby limiting the application of the idea of ​​realizing element doping in the precursor production process. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the problems of high energy consumption in synthesizing existing high-nickel positive electrode materials and difficulty in uniform doping, and to provide a method for preparing a doped and modified high-nickel positive electrode material with uniform doping, low energy consumption and short process flow.

[0005] The present invention is based on the principle of structural similarity and proton exchange, through the optimization design of the reaction path, and by controlling the reaction conditions, the high-nickel hydroxide precursor is first oxidized into a high-nickel hydroxide oxide with a similar structure, thereby reducing the difficulty of oxidation of divalent nickel to trivalent nickel in an aqueous solution. At the same time, the lithium element and the doping element are uniformly introduced into the precursor through the principle of ion exchange, which not only has no effect on the precursor synthesis process, but also the subsequent high-temperature process mainly carries out the crystallization process, and the required temperature and time are greatly reduced, which can effectively reduce the energy consumption of the production process and save costs.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a doped and modified high-nickel positive electrode material comprises the following steps:

[0008] (1) Mix a high-nickel precursor and an oxidant in a certain proportion in an aqueous solution medium system, and react for a certain period of time at a certain temperature, pH value, and solid-liquid ratio to obtain a hydroxy oxide;

[0009] (2) Add a lithium salt and a doping metal salt, adjust the reaction parameters, so that the hydrogen sites in the hydroxy oxide undergo ion exchange with lithium ions and doping element ions, and obtain a doped lithium intercalated high-nickel cathode material precursor through filtration, washing, and drying;

[0010] (3) Subject the obtained doped lithium intercalated high-nickel cathode material precursor to high-temperature crystallization to obtain a doped and modified high-nickel cathode material.

[0011] By optimizing the process conditions, it is beneficial to further improve the structure and performance of the doped and modified high-nickel cathode material.

[0012] Preferably, in step (2), the temperature of the ion exchange is 20-250 °C; the pressure of the ion exchange is 0.1-4 MPa; the pH value of the ion exchange is greater than 5; the time of the ion exchange is 1-50 h.

[0013] Preferably, in step (1), the temperature of the reaction is 20-100 °C; the time of the reaction is 1-24 h; the pH value of the reaction is 9-14; the solid-liquid ratio is 0.3-10.

[0014] Preferably, the oxidant is one or more of persulfate, hydrogen peroxide, oxygen, ozone, potassium permanganate, hypochlorite, chlorate, perchlorate.

[0015] Preferably, in step (2), the lithium salt is one or more of lithium hydroxide, lithium carbonate, lithium acetate, lithium sulfate, lithium nitrate, lithium chloride, etc., and the lithium salt is added according to the molar ratio of Li to the metal element in the precursor of 1-1.5:1.

[0016] Preferably, in step (2), the doping metal salt is one or more water-soluble salts of Zr, Mg, Al, Na, K, Zn, Sn, Se, W, Mo, Nb, Ti; and the molar ratio of the doping element of the doping metal salt to the total metal element in the high-nickel precursor is 0-0.1:1, and further preferably 0.01-0.1:1.

[0017] Preferably, in step (1), the molar ratio of the precursor to the oxidant is 1:1-3.

[0018] Preferably, the molecular formula of the high-nickel precursor is Ni a Co b Mn c Al d(OH)2, where 0.6 ≤ a ≤ 1, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.4, and a + b + c + d = 1; the molecular formula of the doped and modified high-nickel cathode material is Li x Ni e Co f Mn g Al h Me y O2,, where 0.6 ≤ e ≤ 1, 0 ≤ f ≤ 0.4, 0 ≤ g ≤ 0.4, 0 ≤ h ≤ 0.4, 0.9 ≤ x ≤ 1.05, 0 ≤ y ≤ 0.1, and e + f + g + h + y = 1.

[0019] Preferably, in step (3), the temperature of the high-temperature crystallization is 600 - 900 °C; the time of the high-temperature crystallization is 5 - 20 h; the atmosphere of the high-temperature crystallization is air, pure oxygen or oxygen-rich air atmosphere.

[0020] Preferably, in step (2), when the lithium salt and the doped metal salt do not react, they can be added simultaneously or step by step; when the lithium salt and the doped metal salt react, they need to be added step by step.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] In the present invention, by allowing lithium elements to enter the interior of the precursor through ion exchange in a wet process system, the intensity of subsequent high-temperature sintering can be reduced, energy can be saved, and at the same time, the prior uniform entry of lithium elements into the interior of the precursor can effectively reduce lithium-nickel mixing. Moreover, the present invention can dope the precursor through ion exchange in the liquid phase, which can not only achieve uniform doping and modification of high-nickel materials, but also does not affect the synthesis process of the precursor, and is not limited by the types of doped elements; and the high-nickel cathode material prepared by the present invention has excellent performance. Description of the Drawings

[0023] Figure 1 SEM pattern of the precursor in Example 1.

[0024] Figure 2 SEM pattern of the ion-exchanged cathode material precursor prepared in Example 1.

[0025] Figure 3 Cycling performance of the cathode material prepared in Example 1.

[0026] Figure 4 XRD pattern of the precursor in Example 1.

[0027] Figure 5 XRD pattern of the hydroxyoxide obtained by oxidizing the precursor in Example 1.

[0028] Figure 6It is the surface scan EDS map of the K-doped lithium intercalation precursor in Example 1. Detailed implementation manners

[0029] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0030] Example 1:

[0031] A preparation method of a doped and modified high-nickel cathode material includes the following steps:

[0032] (1) Dissolve the (Ni 0.8 Co 0.1 Mn 0.1 )(OH)2 precursor and hydrogen peroxide in a molar ratio of 1:3 in a certain amount of deionized water, adjust the pH value of the solution to 9, and heat it in a water bath at 90 °C for 24 h to prepare the Ni 0.8 Co 0.1 Mn 0.1 OOH compound;

[0033] (2) According to the molar ratio of Li to the metal elements in the precursor being 1.03:1, continue to add LiOH to the above system, react at 200 °C and 2 MPa for 20 h to make the H in Ni 0.8 Co 0.1 Mn 0.1 OOH exchange with Li + ; then adjust the pH value of the solution to 7, and then add potassium chloride according to the molar ratio of K to the metal elements in the precursor being 0.05:1, react at 50 °C and 3 Mpa for 10 h, and then cool, filter, wash, and dry to obtain the doped lithium intercalation precursor;

[0034] (3) Sinter the above-mentioned doped lithium intercalation precursor under industrial-grade pure oxygen to obtain a potassium-doped high-nickel cathode material. The sintering system is set as a heating rate of 3 °C / min, a first-stage pre-sintering temperature of 500 °C and holding for 4 hours (in this example, pre-sintering is not necessary, but it is a conventional process of the roasting furnace in the actual production process of ternary cathode materials. In fact, this process can be omitted), and the second-stage crystallization temperature is 800 °C and holding for 8 hours.

[0035] Figure 1 It is the SEM spectrum of the precursor prepared in this example; Figure 2 It is the SEM spectrum of the ion-exchanged cathode material precursor prepared in Example 1; Figure 3 It is the cycle performance of the cathode material prepared in Example 1.

[0036] Figure 4XRD pattern of the precursor in Example 1. It can be seen from the XRD diffraction pattern of the precursor that its main diffraction peaks are in good agreement with the standard card (Ni(OH)2#14-0117), indicating that the precursor obtained by coprecipitation has a similar crystal structure to Ni(OH)2. Figure 5 XRD pattern of the oxyhydroxide obtained by oxidizing the precursor in Example 1.

[0037] Figure 6 EDS surface scan of the K-doped lithium intercalation precursor in Example 1. It can be seen from the figure that the obtained doped lithium intercalation precursor is uniformly distributed with K element, indicating that the K element has been incorporated into the material lattice.

[0038] Example 2:

[0039] A preparation method of a doped and modified high-nickel cathode material, comprising the following steps:

[0040] (1) Dissolve the Ni 0.9 Co 0.05 Al 0.05 (OH)2 precursor and ozone in a molar ratio of 1:2 in a certain amount of deionized water, adjust the pH value of the solution to 11 using LiOH, and heat it in a 90°C water bath for 24 h to prepare Ni 0.9 Co 0.05 Al 0.05 OOH compound;

[0041] (2) According to the molar ratio of Li to the metal elements in the precursor being 1:1 and the molar ratio of Mg to the metal elements in the precursor being 0.1:1, add LiCl and magnesium chloride to the above system, react at 90°C and 0.5 MPa for 24 h, so that the H in Ni 0.9 Co 0.05 Al 0.05 OOH exchanges ions with Mg 2+ and Li + , then cool, filter, wash, and dry to obtain a Mg-doped ion-exchanged lithium intercalation cathode material precursor;

[0042] (3) Sinter the above precursor under industrial-grade pure oxygen to obtain a Mg-doped high-nickel cathode material. The sintering system is set as a heating rate of 3°C / min, a first-stage pre-sintering temperature of 500°C and holding for 4 hours (in this example, pre-sintering is not necessary, but it is a conventional process of the roasting furnace in the actual production process of ternary cathode materials. In fact, this process can be omitted), and the second-stage crystallization temperature is 750°C and holding for 12 hours.

[0043] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of a doped and modified high-nickel cathode material, characterized in that, It includes the following steps: (1) Mix a high-nickel precursor and an oxidant in an aqueous solution medium system and react to obtain a hydroxy oxide; the molecular formula of the high-nickel precursor is Ni a Co b Mn c Al d (OH)2, where 0.6 ≤ a < 1, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.4, and a + b + c + d = 1; the pH value of the reaction is 11; (2) Then, a lithium source and a doping metal salt are added to the reaction system, and the reaction parameters are adjusted to enable ion exchange between the hydrogen in the hydroxyoxide and lithium ions and doping element ions. After filtration, washing, and drying, a doped lithium intercalated high-nickel cathode material precursor is obtained; the molar ratio of the lithium source to the total amount of metal elements in the hydroxyoxide is 1-1.5:1; the doping metal salt is a water-soluble salt of Mg; the temperature of the ion exchange is 90 °C, and the pressure of the ion exchange is 0.5-3 MPa; the lithium source and the doping metal salt are added simultaneously; the lithium source is lithium hydroxide and / or a lithium salt; (3) The obtained doped lithium intercalated high-nickel cathode material precursor is subjected to high-temperature crystallization to obtain a doped and modified high-nickel cathode material.

2. A preparation method of a doped and modified high-nickel cathode material, characterized in that, It includes the following steps: (1) Mix a high-nickel precursor and an oxidant in an aqueous solution medium system and react to obtain a hydroxy oxide; the molecular formula of the high-nickel precursor is Ni a Co b Mn c Al d (OH)2, where 0.6 ≤ a < 1, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.4, and a + b + c + d = 1; the pH value of the reaction is 9; (2)Add the lithium source to the reaction system first and react at 200 °C and 2 MPa to enable the hydrogen in the hydroxy oxide to undergo ion exchange with Li + ; then adjust the pH value of the solution to 7, add the doping metal salt potassium salt, and react at 50 °C and 3 MPa to enable the hydroxy oxide to undergo ion exchange with K ions. After filtration, washing, and drying, a doped lithium-intercalated high-nickel cathode material precursor is obtained; the molar ratio of the lithium source to the total amount of metal elements in the hydroxy oxide is 1-1.5:1; the doping metal salt potassium salt is a water-soluble salt of K; the lithium source is lithium hydroxide and / or lithium salt; (3) The obtained doped lithium intercalated high-nickel cathode material precursor is subjected to high-temperature crystallization to obtain a doped and modified high-nickel cathode material.

3. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, In step (2), the time of the ion exchange is 1-50 h.

4. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, In step (1), the temperature of the reaction is 20-100 °C; the time of the reaction is 1-24 h; the solid-liquid ratio is 0.3-10.

5. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, The oxidant is one or more of persulfate, hydrogen peroxide, oxygen, ozone, potassium permanganate, hypochlorite, chlorate, and perchlorate.

6. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, In step (2), the lithium salt is one or more of lithium acetate, lithium sulfate, lithium nitrate, and lithium chloride.

7. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, In step (2), the molar ratio of the doping element of the doping metal salt to the total metal elements in the high-nickel precursor is 0.01-0.1:

1.

8. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, In step (1), the molar ratio of the high-nickel precursor to the oxidant is 1:1-3.

9. The preparation method of the doped and modified high-nickel cathode material according to claim 1 or 2, characterized in that, In step (3), the temperature of the high-temperature crystallization is 600-900 °C; the time of the high-temperature crystallization is 5-20 h; the atmosphere of the high-temperature crystallization is air, pure oxygen, or an oxygen-rich air atmosphere.

Images