Lithium-rich manganese-based positive electrode material precursor, preparation method and application thereof

Abstract

This invention belongs to the field of lithium-ion battery materials, and discloses a precursor of a lithium-rich manganese-based cathode material, its preparation method, and its application. The precursor includes a core and a coating layer covering at least a portion of the surface of the core, wherein the core is Mn2O. y Where 2≤y≤3; the coating layer is MnX2O4, where X is any one or more of Fe, Co, and Zn. The precursor is lithiated and sintered to generate a lithium-rich manganese-based cathode material coated with Li2XMn3O8. Li2XMn3O8 has a spinel structure, which perfectly integrates with the layered structure of the lithium-rich manganese-based cathode material, giving the cathode material good structural stability and high-voltage resistance, and effectively improving the electrochemical stability of the lithium-rich cathode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium ion battery materials, and relates to a lithium-rich manganese-based positive electrode material, in particular to a precursor of a lithium-rich manganese-based positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] The lithium-rich manganese-based material has extremely high specific capacity, and the theoretical specific capacity thereof is as high as 300 mAh / g, which is much higher than the discharge specific capacity of the current commercial lithium iron phosphate and ternary material, and is almost twice the capacity of the existing commercial positive electrode material. In addition, the cost advantage of the lithium-rich manganese-based material is significant, and the lithium-rich manganese-based material has become a research hotspot at present.

[0003] However, when the lithium-rich manganese-based positive electrode material works at a high voltage, in addition to the redox reaction of transition metals thereof, the anion-oxygen negative ion in the structure thereof will also produce activity at a high voltage, so that the redox reaction occurs. Therefore, the lithium-rich manganese-based positive electrode material has poor structural stability at a high voltage, which affects the development and application prospect thereof. SUMMARY

[0004] In view of the defects and deficiencies of the prior art, in a first aspect, the application provides a precursor of a lithium-rich manganese-based positive electrode material; in a second aspect, the application provides a preparation method of the precursor of the lithium-rich manganese-based positive electrode material; in a third aspect, a lithium-rich manganese-based positive electrode material; in a fourth aspect, the application provides a preparation method of the lithium-rich manganese-based positive electrode material; and in a fifth aspect, the application provides a battery.

[0005] In a first aspect, the application provides a precursor of a lithium-rich manganese-based positive electrode material, which comprises a core and a coating layer coated on at least part of the surface of the core, the core is Mn2O y , and 2≤y≤3; the coating layer is MnX2O4, wherein X is any one or two or more of Fe, Co and Zn.

[0006] Preferably, the molar ratio of manganese elements and X elements in the precursor of the lithium-rich manganese-based positive electrode material is 1:0.025-0.06.

[0007] In a second aspect, the application provides a preparation method of the precursor of the lithium-rich manganese-based positive electrode material, which comprises: grinding and mixing manganese oxide and transition metal oxide to obtain a mixed powder, and sintering the mixed powder to obtain the precursor of the lithium-rich manganese-based positive electrode material; wherein the transition metal in the transition metal oxide is any one or two or more of Fe, Co and Zn.

[0008] Preferably, the molar ratio of manganese elements and transition metal elements in the transition metal oxide is 1:0.05-0.12.

[0009] Preferably, the transition metal oxide is any one or more of FeO, Fe2O3, ZnO, CoO, Co2O3.

[0010] Preferably, the sintering is performed in an oxygen-containing atmosphere, the sintering temperature is 700-1000℃, and the sintering time is 2-12h.

[0011] In a third aspect, the present application provides a lithium-rich manganese-based positive electrode material, comprising a substrate and a coating layer coated on at least part of the surface of the substrate, wherein the substrate has a molecular formula of Li 1+m Mn 1-m O2, wherein 0.1≤m≤0.5; and the coating layer has a molecular formula of Li2XMn3O8, wherein X is any one or more of Fe, Co, and Zn.

[0012] Preferably, the molar ratio of manganese and X in the lithium-rich manganese-based positive electrode material is 1:0.025-0.06.

[0013] In a fourth aspect, the present application provides a preparation method of a lithium-rich manganese-based positive electrode material, comprising: grinding and mixing a precursor of the lithium-rich manganese-based positive electrode material and a lithium source, and sintering to obtain a solid particle, which is the lithium-rich manganese-based positive electrode material.

[0014] Preferably, the molar ratio of lithium in the lithium source and the lithium-rich manganese-based positive electrode material precursor is 1:1.23-3.

[0015] Preferably, the lithium source is any one or more of lithium hydroxide, lithium oxide, lithium carbonate, and lithium nitrate.

[0016] Preferably, the sintering is performed in an oxygen-containing atmosphere, the sintering temperature is 900-1100℃, and the sintering time is 10-30h.

[0017] In a fifth aspect, the present application provides a battery comprising the lithium-rich manganese-based positive electrode material or the lithium-rich manganese-based positive electrode material prepared by the preparation method.

[0018] Compared with the prior art, the present application has at least one of the following beneficial effects:

[0019] (1) The present application directly prepares a lithium-rich manganese-based precursor material with an inner Mn2O y O4 and an outer MnX2O4 through a one-step solid-phase method; and then the lithium-rich manganese-based positive electrode material coated with Li2XMn3O8 is generated through further lithiumization sintering, Li2XMn3O8 has a spinel structure and perfectly connects with the layered structure of the lithium-rich manganese-based positive electrode material, so that the positive electrode material has good structural stability and high-pressure resistance, and can effectively improve the electrochemical stability of the lithium-rich positive electrode material.

[0020] (2) The preparation process is simple, easy to operate and suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 HRTEM image of the precursor prepared for step 1 of Example 1;

[0022] Figure 2 HRTEM image of the positive electrode material prepared for Example 1;

[0023] Figure 3 Cycle performance diagram of the battery assembled by the positive electrode material prepared for Examples 1-5 and Comparative Example 1. DETAILED DESCRIPTION

[0024] The present application provides the following specific technical solutions.

[0025] In a first aspect, the present application provides a lithium-rich manganese-based positive electrode material precursor, comprising a core and a coating layer coated on at least part of the surface of the core, wherein the core is Mn2O y , and 2≤y≤3; the coating layer is MnX2O4, wherein X is any one or two or more of Fe, Co and Zn.

[0026] Preferably, the molar ratio of manganese element and X element in the lithium-rich manganese-based positive electrode material precursor is 1:0.025-0.06.

[0027] In specific embodiments of the present application, the molar ratio of manganese element and X element in the lithium-rich manganese-based positive electrode material precursor can be 1:0.025, 1:0.03, 1:0.04, 1:0.05 or 1:0.06.

[0028] In a second aspect, the present application provides a preparation method of a lithium-rich manganese-based positive electrode material precursor, comprising: grinding and mixing manganese oxide and transition metal oxide to obtain a mixed powder, and sintering the mixed powder to obtain the lithium-rich manganese-based positive electrode material precursor; wherein the transition metal in the transition metal oxide is any one or two or more of Fe, Co and Zn.

[0029] The inventors have found that, when preparing the precursor, manganese oxide is the main phase and the transition metal oxide is a small amount of doped phase. During the sintering process, manganese atoms in the manganese oxide lattice move into the transition metal oxide to form MnX2O4 coating material. The precursor material with the core of Mn2O y and the coating layer of MnX2O4 can be prepared by a one-step solid-phase method, which is simple, easy to operate and conducive to popularization and industrialization.

[0030] Preferably, the molar ratio of manganese oxide and transition metal element in the transition metal oxide is 1:0.05-0.12.

[0031] The inventors discovered through research that the reaction mainly occurs in the coating layer. The content of transition metal elements is relatively low compared to manganese. During the reaction process, the transition metal elements in the coating layer have not yet moved before reacting with the manganese elements that have moved from the core to the coating layer to form MnX2O4 coating material.

[0032] Preferably, the transition metal oxide is any one or more of FeO, Fe2O3, ZnO, CoO, and Co2O3.

[0033] The inventors discovered through research that the ionic radii of Fe, Zn, and Co are similar to those of Mn, resulting in a more stable composite structure that is beneficial for further improving the electrochemical performance of the cathode material.

[0034] Preferably, the sintering of the mixed powder is carried out in an oxygen-containing atmosphere, the sintering temperature is 700-1000℃, and the sintering time is 2-12h.

[0035] The sintering temperature of 700-1000℃ and the sintering time of 2-12h are only preferred ranges provided by the inventors. In practical applications, the sintering temperature and sintering time can be adjusted according to the situation. In specific embodiments of the present invention, the sintering temperature can be 700℃, 800℃, 900℃ and 1000℃, and the sintering time can be 2h, 4h, 6h, 8h, 10h and 12h.

[0036] Thirdly, the present invention provides a lithium-rich manganese-based cathode material, comprising a matrix and a coating layer covering at least a portion of the surface of the matrix, wherein the molecular formula of the matrix is ​​Li. 1+m Mn 1-m O2, where 0.1≤m≤0.5; the molecular formula of the coating layer is Li2XMn3O8, where X is any one or more of Fe, Co, and Zn.

[0037] Existing lithium-rich manganese-based cathode materials exhibit poor structural stability under high voltage, affecting their electrochemical performance. However, the Li2XMn3O8 coating layer proposed in this invention has a spinel structure, which can perfectly connect with the layered structure of lithium-rich manganese-based cathode materials, improving the structural stability and high voltage resistance of the cathode materials and effectively enhancing the electrochemical stability of lithium-rich cathode materials.

[0038] Preferably, the molar ratio of manganese to X in the lithium-rich manganese-based cathode material is 1:0.025-0.06.

[0039] Fourthly, the present invention provides a method for preparing a lithium-rich manganese-based cathode material, comprising: grinding and mixing the precursor and lithium source of the above-mentioned lithium-rich manganese-based cathode material, sintering, and obtaining solid particles as the lithium-rich manganese-based cathode material.

[0040] The target cathode material can be prepared by lithiation sintering the above precursor materials. The process is simple, easy to control, and conducive to promotion and industrialization.

[0041] Preferably, the molar ratio of lithium in the precursor material and the lithium source is 1:1.23-3.

[0042] In practical applications, when mixing and calcining precursor materials and lithium sources, an excess of lithium source is required to improve the lithiation effect. The molar ratio of lithium in the precursor material and lithium source of 1:1.23-3 is only a preferred range given by the inventors. In practical applications, the molar ratio of lithium in the precursor material and lithium source can be adjusted according to the situation. In specific embodiments of the present invention, the molar ratio of lithium in the precursor material and lithium source is 1:1.23, 1:1.5, 1:2, 1:2.5, and 1:3.

[0043] Preferably, the lithium source is any one or more of lithium hydroxide, lithium oxide, lithium carbonate, and lithium nitrate.

[0044] Preferably, sintering is carried out in an oxygen-containing atmosphere, with a sintering temperature of 900-1100℃ and a sintering time of 10-30h.

[0045] The sintering temperature of 900-1100℃ and the sintering time of 10-30h during lithiation roasting are only preferred ranges given by the inventors. In practical applications, the sintering temperature and sintering time can be adjusted according to the situation. In specific embodiments of the present invention, the sintering temperature can be 900℃, 950℃, 1000℃, 1050℃, or 1100℃; and the sintering time can be 10h, 15h, 20h, 25h, or 30h.

[0046] Through research, the inventors discovered that sintering the mixed precursor and lithium source within the above-mentioned preferred range is beneficial for the complete lithiation of the material, improving the conversion rate of lithium-rich manganese-based materials; reducing the possibility of lithium defects in the main structure, which is beneficial for further improving the electrochemical performance of the cathode material.

[0047] Fifthly, the present invention provides a battery comprising the above-described lithium-rich manganese-based cathode material or the lithium-rich manganese-based cathode material prepared by the above-described preparation method.

[0048] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0049] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] Example 1:

[0052] A method for preparing a lithium-rich manganese-based cathode material includes the following steps:

[0053] Step 1: Solid-phase mechanical mixing of 0.1 mol MnO and 5 mmol Fe2O3 to obtain mixed powder. The mixed powder is then transferred to a muffle furnace and sintered at 900℃ for 4 hours in air atmosphere to obtain a precursor with Mn2O3 core and MnFe2O4 coating layer.

[0054] Step 2: Take 0.1 mol of the precursor obtained in Step 1 and mechanically mix it with 0.07 mol of Li2O. Then transfer it to a muffle furnace and sinter it at 980℃ for 20 h in an air atmosphere to obtain lithium-rich manganese-based cathode material.

[0055] Figure 1 The HRTEM image of the precursor obtained in step 1 of Example 1 is shown below. Figure 1 The lattice spacing in the sample indicates that the core of the material is Mn2O3, and the surface of the core is coated with a layer of MnFe2O4.

[0056] Figure 2 The image shown is an HRTEM image of the cathode material prepared in Example 1. Figure 1 The lattice spacing in the matrix can be determined to be Li. 1.2 Mn 0.8 O2, with a coating layer of Li2FeMn3O8.

[0057] Comparative Example 1:

[0058] A method for preparing a lithium-rich manganese-based cathode material includes: mechanically mixing 0.1 mol MnO and 0.07 mol Li2O, and then sintering them at 980°C for 20 h in an air atmosphere in a muffle furnace to obtain the lithium-rich manganese-based cathode material.

[0059] Example 2:

[0060] A method for preparing a lithium-rich manganese-based cathode material includes the following steps:

[0061] Step 1: Solid-phase mechanical mixing of 0.1 mol MnO and 8 mmol ZnO to obtain mixed powder. The mixed powder is then transferred to a muffle furnace and sintered at 700℃ for 12 h in air atmosphere to obtain a precursor with a core of Mn2O3 and a coating layer of MnZn2O4.

[0062] Step 2: Take 0.1 mol of the precursor obtained in Step 1 and mechanically mix it with 0.062 mol of Li2CO3, and then transfer it to a muffle furnace for high-temperature sintering at 900℃ for 30 h in air atmosphere to obtain lithium-rich manganese-based cathode material.

[0063] Example 3:

[0064] A method for preparing a lithium-rich manganese-based cathode material includes the following steps:

[0065] Step 1: Solid-phase mechanical mixing of 0.1 mol MnO and 12 mmol CoO to obtain mixed powder. The mixed powder is then transferred to a muffle furnace and sintered at 1000℃ for 2 hours in air atmosphere to obtain a precursor with Mn2O3 core and MnCo2O4 coating layer.

[0066] Step 2: Take 0.1 mol of the precursor obtained in Step 1 and mechanically mix it with 0.3 mol of LiOH, then transfer it to a muffle furnace and sinter it at 1100℃ in air atmosphere for 10 h to obtain lithium-rich manganese-based cathode material.

[0067] Example 4:

[0068] A method for preparing a lithium-rich manganese-based cathode material includes the following steps:

[0069] Step 1: Solid-phase mechanical mixing of 0.1 mol MnO and 4 mmol Co2O3 to obtain mixed powder. The mixed powder is then transferred to a muffle furnace and sintered at 800℃ for 10 h in air atmosphere to obtain a precursor with Mn2O3 core and MnCo2O4 coating layer.

[0070] Step 2: Take 0.1 mol of the precursor obtained in Step 1 and mechanically mix it with 0.08 mol of Li2O. Then transfer it to a muffle furnace and sinter it at 900℃ for 30 h in an air atmosphere to obtain lithium-rich manganese-based cathode material.

[0071] Example 5:

[0072] A method for preparing a lithium-rich manganese-based cathode material includes the following steps:

[0073] Step 1: Solid-phase mechanical mixing of 0.1 mol MnO and 5 mmol FeO to obtain mixed powder. The mixed powder is then transferred to a muffle furnace and sintered at 850°C for 8 hours in air atmosphere to obtain a precursor with a core of Mn2O3 and a coating layer of MnFe2O4.

[0074] Step 2: Take 0.1 mol of the precursor obtained in Step 1 and mechanically mix it with 0.08 mol of Li2O. Then transfer it to a muffle furnace and sinter it at 1050℃ in air atmosphere for 12 h to obtain lithium-rich manganese-based cathode material.

[0075] The cathode materials obtained in Examples 1-5 and Comparative Example 1 were assembled into batteries using the following method:

[0076] The materials prepared in Examples 1-5 and Comparative Example 1 were used as positive electrode materials, and were mixed with conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. N-methylpyrrolidone (NMP) was used as solvent, and the mixture was stirred at 800 r / min for 2 h to obtain a slurry. The slurry was coated onto the current collector aluminum foil using an automatic coating machine, laid flat on tempered glass, and dried in a vacuum drying oven at 85°C for 4 hours. After being punched into electrodes with a diameter of 12 mm, the electrodes were dried in a vacuum drying oven at 105°C for 4 hours. The electrodes were then placed in a glove box filled with argon atmosphere with a water and oxygen content of less than 0.1 ppm to reduce the moisture adsorbed by the electrodes during the transfer process. Pure lithium metal sheets with a diameter of 16 mm and a thickness of 0.5 mm were used as the negative electrode, and a porous polyethylene membrane of model Celgard2300 with a diameter of 18 mm was used as the separator. The electrodes were assembled into CR2032 coin cells in the glove box.

[0077] After battery assembly, it was aged for 12 hours, then activated for 3 cycles at a voltage of 2~4.8V and a current density of 0.1C, followed by 100 cycles at a current density of 2C. Figure 3 This is a schematic diagram illustrating the cycle performance of batteries assembled from the positive electrode materials obtained in Examples 1-5 and Comparative Example 1. Figure 3 It can be seen that the cathode material provided by the present invention has superior cycle performance under high pressure.

[0078] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, It includes a matrix and a coating layer covering at least a portion of the surface of the matrix, wherein the molecular formula of the matrix is ​​Li. 1+m Mn 1-m O2, where 0.1≤m≤0.5; the molecular formula of the coating layer is Li2XMn3O8, where X is any one or more of Fe, Co, and Zn.

2. The lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The molar ratio of manganese to X in the lithium-rich manganese-based cathode material is 2:0.05-0.

12.

3. The method for preparing the lithium-rich manganese-based cathode material according to any one of claims 1 or 2, characterized in that, Includes the following steps: Step 1: Grind and mix manganese oxide and transition metal oxide to obtain mixed powder, and sinter the mixed powder to obtain the precursor material; wherein the transition metal in the transition metal oxide is any one or more of Fe, Co, and Zn. Step 2: Grind and mix the precursor and lithium source, sinter, and the resulting solid particles are lithium-rich manganese-based cathode materials.

4. The method for preparing the lithium-rich manganese-based cathode material as described in claim 3, characterized in that, In step 1, the molar ratio of manganese oxide and transition metal elements in transition metal oxides is 1:0.05-0.

12.

5. The method for preparing the lithium-rich manganese-based cathode material as described in claim 3, characterized in that, In step 1, the transition metal oxide is any one or more of FeO, Fe2O3, ZnO, CoO, and Co2O3; the sintering of the mixed powder is carried out in an oxygen-containing atmosphere, the sintering temperature is 700-1000℃, and the sintering time is 2-12h.

6. The method for preparing the lithium-rich manganese-based cathode material as described in claim 3, characterized in that, In step 1, the precursor material obtained includes a core and a coating layer covering at least a portion of the surface of the core, wherein the core is Mn2O. y , where 2≤y≤3; the coating layer is MnX2O4, where X is any one or more of Fe, Co, and Zn.

7. The method for preparing the lithium-rich manganese-based cathode material as described in claim 6, characterized in that, The molar ratio of manganese to X in the precursor of the lithium-rich manganese-based cathode material is 1:0.025-0.

06.

8. The method for preparing the lithium-rich manganese-based cathode material as described in claim 3, characterized in that, In step 2, the molar ratio of lithium in the precursor material and the lithium source is 1:1.23-3; the lithium source is any one or more of lithium hydroxide, lithium oxide, lithium carbonate, and lithium nitrate; sintering is carried out in an oxygen-containing atmosphere, the sintering temperature is 900-1100℃, and the sintering time is 10-30h.

9. A battery, characterized in that, Includes the lithium-rich manganese-based cathode material as described in any one of claims 1 or 2.

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