A facet-sharing layered structure lithium-ion battery positive electrode layered oxide and its preparation method and application

Abstract

The present invention discloses a facet-sharing layered structure for a positive electrode of a lithium-ion battery, as well as a preparation method and application thereof, belonging to the technical field of positive electrode materials for lithium-ion batteries. The present invention synthesizes a sodium- or potassium-containing layered oxide precursor by high-temperature calcination, which is then immersed in a lithium salt solution and a nano-layered oxide ion exchange aid is added to perform liquid-phase ion exchange. During the ion exchange process, the nano-layered oxide is adsorbed on the surface of the precursor, reducing the reaction activation energy and improving the uniformity and consistency of the exchange process. After filtration, washing, and drying, a facet-sharing layered structure is finally obtained. The method includes high-temperature calcination and ion exchange steps, and specifically provides raw materials and operating conditions. The obtained material has a facet-sharing layered structure of lithium oxygen octahedrons and cobalt oxygen octahedrons, has uniform particles, controllable particle size, high material capacity, and excellent cycle performance, and can be widely used in the electronic products and power vehicle markets.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery positive electrode materials, and in particular relates to a facet-sharing layered structure lithium-ion battery positive electrode layered oxide, and a preparation method and application thereof. Background Art

[0002] In recent years, high-energy-density lithium-ion batteries have played a vital role in driving the development of electric vehicles, electronic devices, and large-scale energy storage, among other applications. The development of lithium-ion batteries with even higher energy density has been a persistent pursuit. Among the main components of lithium-ion batteries, the cathode material has become a key factor limiting the improvement of energy density. Therefore, the development of cathode materials plays a crucial role in the success of lithium-ion batteries.

[0003] Layered oxide cathode materials, such as lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (Li(Ni,Co,Mn)O2), have attracted widespread attention in the lithium-ion battery field in recent years due to their high discharge voltage and large discharge capacity. Specifically, as traditional cathode materials, layered oxide cathode materials have high theoretical capacity and a high voltage platform, which gives them a significant advantage in improving battery energy density. For cobalt-free lithium-manganese-based layered oxide cathode materials, their advantages lie not only in their high discharge capacity, but also in their relatively abundant raw material resources and relatively low cost, which makes them have great potential in low-cost, long-life battery applications.

[0004] However, the crystal structure of currently mainstream layered oxide cathode materials features an edge-sharing arrangement of lithium oxygen (LiO6) octahedra and transition metal oxygen (TMO6) octahedra. During electrochemical cycling, this crystal structure is prone to interlayer slip, which not only significantly alters the crystal structure but also creates lattice defects, further increasing the mechanical stress in the material. This structural change blocks lithium ion diffusion pathways, affecting the efficiency of lithium ion insertion and deintercalation, leading to poor battery cycling stability and a sharp drop in capacity. Layered oxide materials with facet-sharing structures, where one side of the LiO6 octahedron is coplanar with the TMO6 octahedron, create significant steric hindrance for transition metal ion migration after lithium ion deintercalation. This facet-sharing structure effectively hinders metal ion migration, resulting in excellent structural stability and electrochemical performance. However, the current synthesis of these materials presents numerous challenges. Their metastable structure significantly increases the difficulty of synthesis, imposes stringent raw material requirements, and makes the synthesis reaction control extremely complex. Furthermore, microstructural manipulation presents challenges. Although the currently widely used ion exchange method can obtain facet-sharing structures, it is difficult to achieve sufficient ion exchange during the exchange process, and the purity of the obtained facet structure is not high. It is urgent to further optimize the synthesis method to obtain high-purity facet-sharing structures. Summary of the Invention

[0005] To overcome the shortcomings of the prior art described above, the present invention aims to provide a facet-sharing layered structure for lithium-ion battery cathodes, as well as a preparation method and application thereof. These methods address the technical issues inherent in existing preparation methods, such as complex reaction control and poor micromorphology control, which compromise the stability and electrochemical performance of the layered oxide structure. Furthermore, they hinder sufficient ion exchange during the exchange process, resulting in low purity of the resulting facet-sharing structure. The present method effectively improves the ion exchange rate, yielding a high-purity facet-sharing layered structure for lithium-ion battery cathodes.

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

[0007] The present invention discloses a facet-sharing layered structure and a preparation method thereof. The invention is that an ion exchange auxiliary agent is used to assist the liquid phase Li + / AM + (AM = Na + or K + ) Ion exchange, methods include:

[0008] First, alkaline earth metal-containing layered oxide AM was synthesized by high-temperature calcination. m [Li x Ni y Co z Mn 1-x-y-z ]O2 (where AM = Na + or K + The synthesized layered oxide is immersed in a solution containing a lithium salt for liquid-phase ion exchange, during which an ion exchange aid is added. Finally, the product is filtered, washed, and dried to produce a facet-sharing layered structure.

[0009] Among them, 0.50≤ m ≤1.00,0.00≤ x ≤0.33; 0.00≤ y ≤1.00; 0.00≤ z ≤1.00.

[0010] The present invention discloses a method for preparing a facet-sharing layered structure, comprising the following steps:

[0011] 1) High temperature calcination

[0012] According to the chemical formula AM m [Li x Ni y Co z Mn 1-x-y-z]O2, weigh the sodium source (or potassium source), lithium source, nickel source, cobalt source, and manganese source respectively and mix them thoroughly. Then, pre-sinter them at 500-600℃ for 3-8 hours, and then calcine them at 700-1000℃ for 5-20 hours. After calcination, let it cool naturally to room temperature to obtain the sodium or potassium layered oxide precursor AM. m [Li x Ni y Co z Mn 1-x-y-z ]O2. AM represents Na or K, 0.50≤ m ≤1.00,0.00≤ x ≤0.33,0.00≤ y ≤1.00,0.00≤ z ≤1.00;

[0013] 2) Ion exchange

[0014] The precursor oxide AM prepared in step 1) m [Li x Ni y Co z Mn 1-x-y-z ]O2 is mixed with a lithium salt solution with a concentration in the range of 0.5-5 mol / L, and a liquid phase ion exchange treatment is carried out with the aid of an ion exchange agent at a reaction temperature of 120-280°C for 0.5-8 hours. After that, it is centrifuged, washed and dried, and the collected product is a lithium-ion battery positive electrode layered oxide with a facet-sharing layered structure. m [Li x Ni y Co z Mn 1-x-y-z ]O2.

[0015] Preferably, in step 1), it is characterized in that, in step 1), the sodium source is sodium carbonate (Na2CO3) or sodium hydroxide (NaOH); the potassium source is sodium carbonate (K2CO3) or sodium hydroxide (KOH); the lithium source is lithium carbonate (Li2CO3) or lithium hydroxide monohydrate (LiOH·H2O) or lithium nitrate (LiNO3) or lithium acetate (LiCH3COO); the nickel source is nickel oxide (NiO), nickel oxalate (NiC2O4) or nickel carbonate (NiCO3); the cobalt source is cobalt oxalate (CoC2O4), cobalt tetroxide (Co3O4), cobalt trioxide (Co2O3) or cobalt carbonate (CoCO3); the manganese source is manganese oxalate (MnC2O4), manganese monoxide (MnO), manganese dioxide (MnO2) or manganese carbonate (MnCO3).

[0016] Preferably, in step 1), the sintering temperature is increased at a heating rate of 0.2-5°C / min.

[0017] Preferably, in step 2), the lithium salt is lithium nitrate (LiNO3), lithium chloride (LiCl), lithium hydroxide monohydrate (LiOH·H2O) or lithium acetate (LiCH3COO).

[0018] Preferably, in step 2), the solvent of the lithium salt solution is deionized water.

[0019] Preferably, in step 2), the ion exchange aid is a lithium-intercalated nano-layered oxide (Li x CoO2、Li x MnO2、Li x NiO2、Li x TiO2、Li x VO2 or Li x AlO2), where 0.3≤ x ≤0.8.

[0020] Further preferably, in step 2), the amount of the ion exchange aid used is 0.1-10% by mass relative to the precursor.

[0021] Further preferably, the precursor oxide AM m [Li x Ni y Co z Mn 1-x-y-z ]The dosage ratio of O2 to lithium salt solution is 1 mg: (5-200) μL.

[0022] The invention also discloses a material with a facet-sharing layered structure prepared by the method.

[0023] The arrangement of interlayer polyhedrons in the crystal structure of this layered structure material has been effectively regulated, with a face-sharing structure of lithium oxygen octahedron and cobalt oxygen octahedron.

[0024] Preferably, the added ion exchange additive is lithium-intercalated nano-layered oxide (Li x CoO2、Li x MnO2、Li x NiO2、Li x TiO2、Li x VO2 or Li x AlO2, where 0.30≤ x ≤0.80), and its addition amount is 0.1%-10% of the mass of the layered oxide material for potassium ion batteries. With its assistance, ion exchange treatment is carried out to obtain a layered lithium battery positive electrode material with a facet sharing structure.

[0025] Preferably, the added ion exchange additive is lithium-intercalated nano-layered oxide (Li x CoO2、Li x MnO2、Li x NiO2、Li x TiO2、Li x VO2 or Li x AlO2, where 0.30≤ x ≤0.80), and its addition amount is 0.1%-10% of the mass of the layered oxide material for sodium ion batteries. With its assistance, ion exchange treatment is carried out to obtain a layered lithium battery positive electrode material with a facet-sharing structure.

[0026] Preferably, the layered lithium battery positive electrode material with the facet-sharing structure is composed of micron-sized particles, the grain size of which is within the range of 1-20 microns, and the particle size is controllable.

[0027] The present invention also discloses the application of the layered lithium battery positive electrode material with the facet-sharing structure in the preparation of lithium ion batteries.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The core invention of the method for preparing the facet-sharing layered structure lithium-ion battery positive electrode layered oxide is that during the preparation process, an ion exchange auxiliary agent is used to assist the liquid phase Li + / AM + (AM =Na + or K + ) for ion exchange. On the one hand, directly through the high-temperature solid-phase method and liquid-phase ion exchange method, an environment with highly controllable temperature, time and ion concentration is provided, the ion diffusion effect is good, the exchange process is fast, uniform and sufficient, the equipment is cheap and universal, the process is simple and mature, and there are advantages such as energy saving, emission reduction, cost reduction and efficiency improvement; on the other hand, the ion exchange process is assisted by the use of nano-layered oxide ion exchange additives. The nano-layered oxide is adsorbed on the surface of the precursor, and its role is similar to that of a catalyst, adsorbing sodium in the bulk phase of the precursor to the surface, while allowing lithium in the lithium salt solvent to enter the interior of the precursor structure. This reduces the reaction activation energy, enhances the ion transfer efficiency, ensures the uniformity and consistency of the exchange process, and promotes the full progress of ion exchange. The layered positive electrode material prepared by this method has excellent electrochemical performance, uniform particle distribution, controllable particle size, and good batch uniformity. In addition, the method is simple in process, easy to operate, and the material structure is stable and reliable.

[0030] The facet-sharing layered structure lithium-ion battery positive electrode layered oxide prepared by the method of the present invention has excellent cycle performance. Under the conditions of 3.0-4.6V and 1C, the capacity retention rate of the material is still as high as more than 84% after 100 cycles. Therefore, it can be used to prepare lithium-ion batteries and can be widely used in the electronic products and power vehicle markets. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the auxiliary mechanism of the ion exchange process using nano-layered oxide ion exchange additives in the present invention;

[0032] Figure 2 A schematic diagram of the crystal structure of the facet-sharing layered structure prepared in the present invention;

[0033] Figure 3 This is an X-ray diffraction spectrum of the lithium cobalt oxide positive electrode material with a facet-sharing layered structure prepared in Example 1 of the present invention;

[0034] Figure 4 This is a scanning electron microscope image of the lithium cobalt oxide positive electrode material with a facet-sharing layered structure prepared in Example 1 of the present invention;

[0035] Figure 5 The charge-discharge curve of the lithium cobalt oxide positive electrode material with a facet-sharing layered structure prepared in Example 1 of the present invention at 0.1C;

[0036] Figure 6 The cycling performance of the lithium cobalt oxide positive electrode material with facet-sharing layered structure prepared in Example 1 of the present invention at a 1C rate;

[0037] Figure 7 This is an X-ray diffraction spectrum of the lithium cobalt oxide positive electrode material with a partially faceted shared layered structure prepared in Comparative Example 1 of the present invention;

[0038] Figure 8 This is an X-ray diffraction spectrum of the lithium cobalt oxide positive electrode material with a facet-sharing layered structure prepared in Example 2 of the present invention;

[0039] Figure 9 This is a scanning electron microscope image of the lithium cobalt oxide positive electrode material with a facet-sharing layered structure prepared in Example 2 of the present invention;

[0040] Figure 10 The charge-discharge curve of the lithium cobalt oxide positive electrode material with facet-sharing layered structure prepared in Example 2 of the present invention at 1C;

[0041] Figure 11 This is an X-ray diffraction spectrum of the lithium-rich manganese-based positive electrode material with a partially faceted shared layered structure prepared in Example 3 of the present invention;

[0042] Figure 12 This is a scanning electron microscope image of the lithium-rich manganese-based positive electrode material with a facet-sharing layered structure prepared in Example 3 of the present invention;

[0043] Figure 13 This is the charge-discharge curve of the lithium-rich manganese-based positive electrode material with a facet-sharing layered structure prepared in Example 3 of the present invention at 0.1C. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] The present invention is described in further detail below with reference to the accompanying drawings:

[0047] See also Figure 1 The method for preparing the facet-sharing layered structure disclosed in the present invention uses liquid phase Li + / AM + (AM = Na + or K + ) ion exchange method. First, directly prepare the sodium or potassium layered oxide precursor AM by high temperature solid phase sintering and calcination. m [Li x Ni y Co z Mn 1-x-y-z ]O2, and then put it into the solution together with the lithium salt solution, add the ion exchange agent, mix it thoroughly and then carry out liquid phase ion exchange treatment. After filtering, washing and drying, the facet-shared layered oxide Li m [Lix Ni y Co z Mn 1-x-y-z ]O2.

[0048] The facet-sharing layered oxide Li prepared by the present invention m [Li x Ni y Co z Mn 1-x-y-z ]O2 crystal structure diagram Figure 2 The oxide material has a layered structure with facets shared by lithium oxygen octahedrons and cobalt oxygen octahedrons, and has uniform particles and controllable particle size.

[0049] Example 1

[0050] The precursor used in this embodiment is a potassium ion battery layered oxide KCoO2, and the prepared positive electrode material is LiCoO2. Specifically, the method for preparing a facet-sharing layered structure lithium ion battery LiCoO2 positive electrode material includes the following steps:

[0051] Step 1. High temperature calcination:

[0052] According to the chemical formula KCoO2, the molar ratio of potassium and cobalt elements is 1.0:1.0, and the corresponding KCO3 and Co2O3 are weighed respectively. The two are placed in a ball mill and mixed thoroughly, and then the mixture is placed in a muffle furnace. Under air atmosphere conditions, the furnace temperature is raised to 500°C at a heating rate of 5°C / min, and pre-burned at this temperature for 6 hours. Subsequently, the temperature is continued to be raised at a heating rate of 5°C / min until the temperature reaches 850°C, and then calcined at this temperature for 18 hours. After calcination is completed, the material is allowed to cool naturally to room temperature, thereby obtaining a precursor material, that is, a potassium ion layered oxide precursor KCoO2 with triangular prisms and octahedrons sharing edges;

[0053] Step 2. Ion exchange:

[0054] The potassium ion layered oxide precursor KCoO2 obtained in step 1 was immersed in a 1 mol / L LiOH·H2O aqueous solution, wherein the ratio of potassium ion layered oxide precursor to LiOH·H2O solution was 1:5 mg / μL, and then added to the reactor. At the same time, an ion exchange additive Li 0.7 MnO2 was subjected to liquid-phase ion exchange treatment at a reaction temperature of 150°C for 2 hours. After the treatment, the mixture was centrifuged and washed three times with ethanol. The resulting product was collected after drying. This product is the positive electrode layered oxide LiCoO2 for lithium-ion batteries with a facet-sharing layered structure.

[0055] The XRD pattern of LiCoO2 prepared in this example is shown in FIG. Figure 3 From the XRD pattern, we can see that all the diffraction peaks belong to the facet-sharing layered structure, and the space group is P6 3 mc , belonging to the hexagonal system. The SEM image of the lithium ion layered oxide with facet-sharing layered structure prepared in this embodiment is shown in FIG. Figure 4 The particle size is about 5 μm.

[0056] The charge and discharge performance test process of the positive electrode material prepared in this embodiment is as follows:

[0057] The positive electrode material prepared in this example was used as the active material, acetylene black as the conductive agent, and polyvinylidene fluoride as the binder. The mixture was uniformly mixed in a mass ratio of 8:1:1 between the active material, the conductive agent, and the binder. Next, 30 times the mass of nitrogen-methyl pyrrolidone as the binder was added dropwise and stirred to form a slurry. The slurry was evenly applied to aluminum foil and then dried in a 120°C constant-temperature drying oven for 12 hours. After drying to constant weight, a sheet puncher was used to punch out small discs with a diameter of 12 mm. This served as the positive working electrode. The small discs were placed in an argon-filled glove box, ensuring the absence of water. A lithium sheet was used as the counter and reference electrodes, a polypropylene film Celgard 2400 was used as the separator, and a 1M LiPF6 / EC + DEC (volume ratio 1:1) electrolyte was used. Finally, the cells were assembled in the glove box into CR2023 button cells.

[0058] Charge and discharge performance test: The facet-sharing layered structure positive electrode material LiCoO2 prepared in this embodiment was tested at 25°C, in the voltage range of 3.0-4.65V, and 0.1C. The initial charge and discharge capacities were 257.5mAh / g and 253.9mAh / g, respectively. Figure 5 When the electrochemical cycle is carried out in the voltage range of 3.0-4.6V and 1C, the capacity retention rate after 100 cycles is 84%, as shown in Figure 2. Figure 6 shown.

[0059] Example 2

[0060] The precursor used in this embodiment is a potassium ion battery layered oxide KCoO2, and the prepared positive electrode material is LiCoO2. Specifically, the method for preparing a lithium ion battery LiCoO2 positive electrode material with a partially faceted shared layered structure includes the following steps:

[0061] Step 1. High temperature calcination:

[0062] According to the chemical formula KCoO2, the molar ratio of potassium and cobalt elements is 1.0:1.0, and the corresponding KCO3 and Co2O3 are weighed respectively. The two are placed in a ball mill and mixed thoroughly, and then the mixture is placed in a muffle furnace. Under air atmosphere conditions, the furnace temperature is raised to 500°C at a heating rate of 3°C / min, and pre-burned at this temperature for 6 hours. Subsequently, the temperature is continued to be raised at a heating rate of 1°C / min until the temperature reaches 850°C, and then calcined at this temperature for 18 hours. After the calcination is completed, the material is allowed to cool naturally to room temperature, thereby obtaining a precursor material, that is, a potassium ion layered oxide precursor KCoO2 with triangular prisms and octahedrons sharing edges;

[0063] Step 2. Ion exchange:

[0064] The potassium ion layered oxide precursor KCoO2 obtained in step 1 was immersed in a 1 mol / L LiOH·H2O aqueous solution, wherein the ratio of potassium ion layered oxide precursor to LiOH·H2O solution was 1:5 mg / μL, and then added to the reactor. At the same time, an ion exchange additive Li was added at a mass percentage of 1% relative to KCoO2. 0.3 VO2 was subjected to liquid-phase ion exchange treatment at a reaction temperature of 250°C for 2 hours. After the treatment, the mixture was centrifuged and washed three times with deionized water. The resulting product was collected after drying. This product is the positive electrode layered oxide LiCoO2 for lithium-ion batteries with a facet-sharing layered structure.

[0065] The XRD pattern of LiCoO2 with partially faceted shared layered structure prepared in this example is shown in Figure 2. Figure 7 From the XRD diagram, we can see that some diffraction peaks belong to the facet-shared layered structure. P6 3 mc Space group.

[0066] Example 3

[0067] The precursor used in this embodiment is sodium ion layered oxide NaCoO2, and the positive electrode material prepared is LiCoO2. Specifically, the method for preparing the facet-sharing layered structure LiCoO2 positive electrode material for lithium-ion batteries includes the following steps:

[0068] Step 1. High temperature calcination:

[0069] According to the chemical formula NaCoO2, the molar ratio of sodium and cobalt elements is 1.0:1.0, and the corresponding Na2CO3 and Co2O3 are weighed respectively. The two are placed in a ball mill and mixed thoroughly, and then the mixture is placed in a muffle furnace. Under air atmosphere conditions, the furnace temperature is raised to 500°C at a heating rate of 5°C / min, and pre-burned at this temperature for 6 hours. Subsequently, the temperature is continued to be raised at a heating rate of 3°C / min until the temperature reaches 850°C, and then calcined at this temperature for 18 hours. After the calcination is completed, the material is allowed to cool naturally to room temperature, thereby obtaining a precursor material, that is, a potassium ion layered oxide precursor NaCoO2 with triangular prisms and octahedrons sharing edges;

[0070] Step 2. Ion exchange:

[0071] The sodium ion layered oxide precursor NaCoO2 obtained in step 1 was immersed in a 1 mol / L LiOH·H2O aqueous solution, wherein the ratio of the sodium ion layered oxide precursor to the LiOH·H2O solution was 1:5 mg / μL, and then added to the reactor. At the same time, an ion exchange additive Li 0.5 CoO2 was subjected to liquid phase ion exchange treatment at a reaction temperature of 120°C for 8 hours. After the treatment, it was centrifuged and washed with ethanol three times. The resulting product was collected after drying. This product is the positive electrode layered oxide LiCoO2 of lithium-ion batteries with a facet-sharing layered structure.

[0072] The XRD pattern of LiCoO2 prepared in this example is shown in FIG. Figure 8 From the XRD pattern, we can see that all the diffraction peaks belong to the facet-sharing layered structure, and the space group is P6 3 mc , belonging to the hexagonal system. The SEM image of the lithium ion layered oxide with facet-sharing layered structure prepared in this embodiment is shown in FIG. Figure 9 , the particle size is about 5μm.

[0073] Charge and discharge performance test: The test method is the same as that of Example 1. The results show that the first charge and discharge capacities of the LiCoO2 positive electrode material with facet-sharing layered structure prepared in this example are 254.7 mAh / g and 249.3 mAh / g at a test temperature of 45°C, a voltage range of 3.0-4.6 V, and 1C, respectively. Figure 10 .

[0074] Example 4

[0075] The precursor used in this embodiment is the sodium ion battery layered oxide Na[Li 0.15 Ni 0.25 Mn 0.6 ]O2, the cathode material prepared in this embodiment is Li[Li0.15 Ni 0.25 Mn 0.6 Specifically, the method for preparing a positive electrode material for a lithium-ion battery with a facet-sharing layered structure comprises the following steps:

[0076] Step 1. High temperature calcination:

[0077] According to the chemical formula Na[Li 0.15 Ni 0.25 Mn 0.6 ]O2 ingredients, the molar ratio of sodium, lithium, nickel and manganese elements is 1.0:0.15:0.25:0.60, and the corresponding Na2CO3, Li2CO3, NiO and MnO are weighed respectively. Place them in a ball mill and mix them thoroughly, then put the mixture into a muffle furnace. Under air atmosphere conditions, the furnace temperature is raised to 500°C at a heating rate of 5°C / min, and pre-burned at this temperature for 6h. Subsequently, the temperature is continued to rise at a heating rate of 0.2°C / min until the temperature reaches 1000°C, and then calcined at this temperature for 18h. After calcination, the material is allowed to cool naturally to room temperature, thereby obtaining a precursor material, that is, a sodium ion layered oxide Na[Li 0.15 Ni 0.25 Mn 0.6 ]O2;

[0078] Step 2. Ion exchange:

[0079] The sodium ion layered oxide precursor Na[Li 0.15 Ni 0.25 Mn 0.6 ]O2 was immersed in a 2mol / L LiOH·H2O aqueous solution, wherein the ratio of sodium ion layered oxide precursor to LiOH·H2O solution was 1:25mg / μL, and then added to the reactor. At the same time, the mass percentage of Na[Li 0.15 Ni 0.25 Mn 0.6 ]O2 is 2% of the ion exchange auxiliary agent LiMnO2, and the liquid phase ion exchange treatment is carried out at a reaction temperature of 280℃ for 8 hours. After the treatment, it is centrifuged and washed with deionized water three times. The resulting product is collected after drying. This product is the lithium-ion battery positive electrode layered oxide Li[Li 0.15 Ni 0.25 Mn 0.6 ]O2.

[0080] The Li[Li 0.15 Ni 0.25 Mn 0.6 ]O2 XRD Figure 11From the XRD pattern, we can see that all the diffraction peaks belong to the facet-sharing layered structure, and the space group is P6 3 mc , belonging to the hexagonal system. The SEM image of the lithium ion layered oxide with facet-sharing layered structure prepared in this embodiment is shown in FIG. Figure 12 , the particle size is about 2-5μm.

[0081] The electrochemical performance test of the battery was carried out at 25°C, in the voltage range of 2.0-4.8V, and 0.1C. The results showed that the positive electrode material Li[Li 0.15 Ni 0.25 Mn 0.6 ]O2 has the first charge and discharge capacities of 256.8mAh / g and 205.4mAh / g at a rate of 0.1C. Figure 13 shown.

[0082] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a layered oxide having a facet-sharing layered structure for a positive electrode of a lithium-ion battery, characterized in that: include: The metal salt raw materials are uniformly mixed and calcined at high temperature to synthesize a sodium or potassium-containing layered oxide precursor; the sodium or potassium-containing layered oxide precursor is immersed in a solution containing a lithium salt, and a lithium-intercalated nano-layered oxide is added as an ion exchange aid to perform a liquid phase ion exchange treatment; The treated reaction system is filtered, washed and dried to obtain a facet-sharing layered structure lithium-ion battery positive electrode layered oxide.

2. The method for preparing a positive electrode layered oxide for lithium-ion batteries with a facet-sharing layered structure according to claim 1, characterized in that: The following steps are involved: 1) According to the chemical formula AM m [Li x Ni y Co z Mn 1-x-y-z ]O2 ratio, respectively weigh the metal salt raw materials sodium source or potassium source, lithium source, nickel source, cobalt source and manganese source, mix them thoroughly, then pre-sinter them at 500-600℃, then calcine them at 700-1000℃, and then cool them to obtain a layered oxide precursor, which is expressed as AM m [Li x Ni y Co z Mn 1-x-y-z ]O2; AM represents Na or K, 0.50≤ m ≤1.00,0.00≤ x ≤0.33,0.00≤ y ≤1.00,0.00≤ z ≤1.00; 2) The prepared layered oxide precursor is mixed with a lithium salt solution, and then lithium-intercalated nano-layered oxide is added as an ion exchange aid to perform ion exchange treatment at 120-280°C. The reaction system is then centrifuged, washed, and dried to obtain a facet-sharing layered structure lithium-ion battery positive electrode layered oxide, the composition of which is Li m [Li x Ni y Co z Mn 1-x-y-z ]O2.

3. The method for preparing a positive electrode layered oxide for lithium-ion batteries with a facet-sharing layered structure according to claim 2, characterized in that: In step 1), the pre-sintering treatment time is 3-8 hours, and the high-temperature sintering treatment time is 5-20 hours. The high-temperature sintering is performed at a heating rate of 0.2-5°C / min starting from the pre-sintering temperature.

4. The method for preparing a positive electrode layered oxide for lithium-ion batteries with a facet-sharing layered structure according to claim 2, characterized in that: In step 1), the sodium source is sodium carbonate or sodium hydroxide; the potassium source is potassium carbonate or potassium hydroxide; the lithium source is lithium carbonate, lithium hydroxide monohydrate, lithium nitrate or lithium acetate; the nickel source is nickel oxide, nickel oxalate or nickel carbonate; the cobalt source is cobalt oxalate, cobalt tetroxide, cobalt trioxide or cobalt carbonate; and the manganese source is manganese oxalate, manganous oxide, manganese dioxide or manganese carbonate.

5. The method for preparing a positive electrode layered oxide for lithium-ion batteries with a facet-sharing layered structure according to claim 2, wherein: In step 2), the lithium salt solution is prepared using lithium nitrate, lithium chloride, lithium hydroxide monohydrate or lithium acetate, with a concentration of 0.5-5 mol / L; the dosage ratio of the layered oxide precursor to the lithium salt solution is 1 mg: (5-200) μL.

6. The method for preparing a positive electrode layered oxide for lithium-ion batteries with a facet-sharing layered structure according to claim 2, characterized in that: In step 2), the ion exchange additive is a lithium-intercalated nano-layered oxide, including Li x CoO2、Li x MnO2、Li x NiO2、Li x TiO2、Li x VO2 or Li x AlO2, where 0.3 ≤ x ≤0.

8.

7. The method for preparing a positive electrode layered oxide for lithium-ion batteries with a facet-sharing layered structure according to claim 2, characterized in that: In step 2), the amount of the ion exchange additive is 0.1%-10% of the mass of the layered oxide precursor.

8. A layered oxide for positive electrode of lithium ion battery with facet-sharing layered structure prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The facet-sharing layered structure lithium-ion battery positive electrode layered oxide is composed of micron-sized particles, the grain size is distributed in the range of 1-20 microns, and the particle size is controllable.

9. The facet-sharing layered structure lithium-ion battery positive electrode layered oxide according to claim 8, characterized in that: The facet-sharing layered structure lithium-ion battery positive electrode layered oxide has a thermodynamically metastable layered structure and belongs to P6 3 mc Space group.

10. Use of the facet-sharing layered structure lithium ion battery positive electrode layered oxide according to claim 8 or 9 in the preparation of lithium ion batteries.

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