Precursor of lithium-rich manganese-based positive electrode material as well as preparation method and application of precursor

Abstract

The invention belongs to the field of lithium ion battery materials, and discloses a precursor of a lithium-rich manganese-based positive electrode material and a preparation method and application thereof.The precursor comprises a core and a coating layer coating at least part of the surface of the core, the core is Mn2Oy, and y is larger than or equal to 2 and smaller than or equal to 3; the coating layer is MnX2O4, and X is any one or more than two of Fe, Co and Zn. The Li2XMn3O8 coated lithium-rich manganese-based positive electrode material is generated by lithiating and sintering the precursor, and the Li2XMn3O8 has a spinel structure and is perfectly connected with a layered structure of the lithium-rich manganese-based positive electrode material, so that the positive electrode material has good structural stability and high voltage resistance, and the electrochemical stability of the lithium-rich positive electrode material can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery materials and relates to lithium-rich manganese-based positive electrode materials, and specifically to a precursor of the lithium-rich manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-rich manganese-based materials have extremely high specific capacity, with a theoretical specific capacity of up to 300mAh / g, which is much higher than the discharge specific capacity of currently commercial lithium iron phosphate and ternary materials, and almost twice the capacity of existing commercial positive electrode materials. In addition, its significant cost advantage has made it a current research hotspot.

[0003] However, when lithium-rich manganese-based positive electrode materials work under high voltage, in addition to the redox reaction of their own transition metals, the anions - oxygen anions in their structure will also become active under high voltage, thereby undergoing redox reactions. Therefore, the structural stability of lithium-rich manganese-based positive electrode materials is poor under high voltage, which affects their development and application prospects. Summary of the invention

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

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

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

[0007] In a second aspect, the present invention provides a method for preparing a precursor of a lithium-rich manganese-based positive electrode material, comprising: 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 more of Fe, Co, and Zn.

[0008] Preferably, the molar ratio of manganese oxide to the transition metal element 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, and Co2O3.

[0010] Preferably, the mixed powder is sintered in an oxygen-containing atmosphere, the sintering temperature is 700-1000° C., and the sintering time is 2-12 hours.

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

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

[0013] In a fourth aspect, the present invention provides a method for preparing 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, and the obtained solid particles are the lithium-rich manganese-based positive electrode material.

[0014] Preferably, the molar ratio of the precursor of the lithium-rich manganese-based positive electrode material to the lithium element in the lithium source 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 carried out in an oxygen-containing atmosphere, the sintering temperature is 900-1100° C., and the sintering time is 10-30 hours.

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

[0018] Compared with the prior art, the present invention has at least one of the following beneficial effects: (1) The present invention directly prepares the internal Mn2O by a one-step solid phase method. y , a lithium-rich manganese-based precursor material with an outer layer of MnX2O4; and then further lithiation and sintering to generate a lithium-rich manganese-based positive electrode material coated with Li2XMn3O8. Li2XMn3O8 has a spinel structure, which is perfectly connected 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-voltage resistance, and can effectively improve the electrochemical stability of the lithium-rich positive electrode material.

[0019] (2) The preparation process of the present invention is simple, easy to operate, and easy to scale up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 HRTEM image of the precursor prepared in step 1 of Example 1; Figure 2 HRTEM image of the positive electrode material prepared in Example 1; Figure 3 Schematic diagram of the cycle performance of batteries assembled from the positive electrode materials prepared in Examples 1 to 5 and Comparative Example 1. DETAILED DESCRIPTION

[0021] The present invention provides the following specific technical solutions.

[0022] In a first aspect, the present invention provides a precursor of a lithium-rich manganese-based positive electrode material, comprising a core and a coating layer coated on at least a portion of the surface of the core, wherein the core is Mn2O y , wherein 2≤y≤3; the coating layer is MnX2O4, wherein X is any one or more of Fe, Co, and Zn.

[0023] Preferably, the molar ratio of manganese element to X element in the precursor of the lithium-rich manganese-based positive electrode material is 1:0.025-0.06.

[0024] In a specific embodiment of the present invention, the molar ratio of manganese element to X element in the precursor of the lithium-rich manganese-based positive electrode material can be 1:0.025, 1:0.03, 1:0.04, 1:0.05, or 1:0.06.

[0025] In a second aspect, the present invention provides a method for preparing a precursor of a lithium-rich manganese-based positive electrode material, comprising: 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 more of Fe, Co, and Zn.

[0026] The inventors have found that when preparing the precursor, manganese oxide is the main phase and transition metal oxide is a small amount of doping phase. During the sintering process, the manganese atoms in the manganese oxide lattice move into the transition metal oxide to form a MnX2O4 coating material. y The coating layer is the precursor material of MnX2O4, the process is simple, easy to operate, and is conducive to promotion and industrialization.

[0027] Preferably, the molar ratio of manganese oxide to the transition metal element in the transition metal oxide is 1:0.05-0.12.

[0028] The inventors have found through research that the reaction mainly occurs in the coating layer, and the content of transition metal elements is lower than that of manganese elements. During the reaction, the transition metal elements in the coating layer have not yet moved to react with the manganese elements that move from the core to the coating layer to form MnX2O4 coating material.

[0029] Preferably, the transition metal oxide is any one or more of FeO, Fe2O3, ZnO, CoO, and Co2O3.

[0030] The inventors have found through research that the ionic radius of the three elements Fe, Zn and Co is similar to the ionic radius of the Mn element, and the structure of the formed composite is more stable, which is beneficial to further improve the electrochemical performance of the positive electrode material.

[0031] Preferably, the mixed powder is sintered in an oxygen-containing atmosphere, the sintering temperature is 700-1000° C., and the sintering time is 2-12 hours.

[0032] The sintering temperature of 700-1000°C and the sintering time of 2-12h are only the preferred ranges provided by the inventor. In practical applications, the sintering temperature and sintering time can be adjusted according to the situation. In a specific embodiment of the present invention, the sintering temperature can be 700°C, 800°C, 900°C and 1000°C, and the sintering time can be 2h, 4h, 6h, 8h, 10h and 12h.

[0033] In a third aspect, the present invention provides a lithium-rich manganese-based positive electrode material, comprising a substrate and a coating layer coated on at least a portion of the surface of the substrate, wherein the molecular formula of the substrate is Li 1+m Mn 1-m O2, wherein 0.1≤m≤0.5; the molecular formula of the coating layer is Li2XMn3O8, wherein X is any one or more of Fe, Co, and Zn.

[0034] The lithium-rich manganese-based positive electrode materials in the prior art have poor structural stability under high voltage, which affects their electrochemical performance. The coating layer Li2XMn3O8 proposed in the present invention has a spinel structure, which can be perfectly connected with the layered structure of the lithium-rich manganese-based positive electrode material, thereby improving the structural stability and high-voltage resistance of the positive electrode material, and can effectively improve the electrochemical stability of the lithium-rich positive electrode material.

[0035] Preferably, the molar ratio of manganese element to X element in the lithium-rich manganese-based positive electrode material is 1:0.025-0.06.

[0036] In a fourth aspect, the present invention provides a method for preparing 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, and the obtained solid particles are the lithium-rich manganese-based positive electrode material.

[0037] The target positive electrode material can be obtained by lithiation sintering the above-mentioned precursor materials. The process is simple, easy to control, and conducive to promotion and industrialization.

[0038] Preferably, the molar ratio of the precursor material to the lithium element in the lithium source is 1:1.23-3.

[0039] In practical applications, when the precursor material and the lithium source are mixed and calcined, the lithium source participating in the reaction needs to be excessive to improve the lithiation effect. The molar ratio of the lithium element in the precursor material and the lithium source is 1:1.23-3, which is only the preferred range given by the inventor. In practical applications, the molar ratio of the lithium element in the precursor material and the lithium source can be adjusted according to the situation. In the specific embodiment of the present invention, the molar ratio of the lithium element in the precursor material and the lithium source is 1:1.23, 1:1.5, 1:2, 1:2.5, 1:3.

[0040] Preferably, the lithium source is any one or more of lithium hydroxide, lithium oxide, lithium carbonate and lithium nitrate.

[0041] Preferably, the sintering is carried out in an oxygen-containing atmosphere, the sintering temperature is 900-1100° C., and the sintering time is 10-30 hours.

[0042] During lithium calcination, the sintering temperature of 900-1100°C and the sintering time of 10-30h are only the preferred ranges given by the inventor. In practical applications, the sintering temperature and sintering time can be adjusted according to the situation. In a specific embodiment of the present invention, the sintering temperature can be 900°C, 950°C, 1000°C, 1050°C, 1100°C; the sintering time can be 10h, 15h, 20h, 25h, 30h.

[0043] After research, the inventors found that mixing the precursor and the lithium source and sintering them within the above-mentioned preferred range is conducive to complete lithiation of the material and improving the conversion rate of lithium-rich manganese-based materials; reducing the possibility of lithium defects in the main structure, which is conducive to further improving the electrochemical performance of the positive electrode material.

[0044] In a fifth aspect, the present invention provides a battery, comprising the above-mentioned lithium-rich manganese-based positive electrode material or the lithium-rich manganese-based positive electrode material prepared by the above-mentioned preparation method.

[0045] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention more clear, they will be described in detail below with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0047] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0048] Embodiment 1: A method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps: Step 1, solid phase mechanically mix 0.1 mol MnO and 5 mmol Fe2O3 to obtain a mixed powder, transfer the mixed powder to a muffle furnace and sinter at 900° C. for 4 hours in an air atmosphere to obtain a precursor with a core of Mn2O3 and a coating of MnFe2O4.

[0049] Step 2: Take 0.1 mol of the precursor prepared 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° C. in an air atmosphere for 20 hours to obtain a lithium-rich manganese-based positive electrode material.

[0050] Figure 1 This is the HRTEM image of the precursor obtained in step 1 of Example 1. Figure 1 The lattice spacing in the material can determine that the core of the material is Mn2O3, and the surface of the core is covered with a layer of MnFe2O4.

[0051] Figure 2 HRTEM image of the positive electrode material prepared in Example 1. Figure 1 The lattice spacing in can be determined to be Li 1.2 Mn 0.8 O2, and the coating layer is Li2FeMn3O8.

[0052] Comparative Example 1: A method for preparing a lithium-rich manganese-based positive electrode material comprises: taking 0.1 mol MnO and 0.07 mol Li2O, mechanically mixing them, placing them in a muffle furnace and sintering them at 980° C. for 20 hours in an air atmosphere to obtain the lithium-rich manganese-based positive electrode material.

[0053] Embodiment 2: A method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps: Step 1, solid phase mechanically mix 0.1 mol MnO and 8 mmol ZnO to obtain a mixed powder, transfer the mixed powder to a muffle furnace and sinter at 700° C. for 12 h in an air atmosphere to obtain a precursor with a core of Mn2O3 and a coating of MnZn2O4.

[0054] Step 2, take 0.1 mol of the precursor prepared in step 1 and mechanically mix it with 0.062 mol of Li2CO3, then transfer it to a muffle furnace and sinter it at 900°C in an air atmosphere for 30 hours to obtain a lithium-rich manganese-based positive electrode material.

[0055] Embodiment 3: A method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps: Step 1: solid phase mechanically mix 0.1 mol MnO and 12 mmol CoO to obtain a mixed powder, transfer the mixed powder to a muffle furnace and sinter at 1000° C. for 2 h in an air atmosphere to obtain a precursor with a core of Mn2O3 and a coating of MnCo2O4.

[0056] Step 2, taking 0.1 mol of the precursor prepared in step 1 and mechanically mixing it with 0.3 mol of LiOH, and then transferring it to a muffle furnace and sintering it at 1100° C. for 10 hours in an air atmosphere to obtain a lithium-rich manganese-based positive electrode material.

[0057] Embodiment 4: A method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps: Step 1, solid phase mechanically mix 0.1 mol MnO and 4 mmol Co2O3 to obtain a mixed powder, transfer the mixed powder to a muffle furnace and sinter at 800° C. for 10 h in an air atmosphere to obtain a precursor with a core of Mn2O3 and a coating of MnCo2O4.

[0058] Step 2: Take 0.1 mol of the precursor prepared 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° C. for 30 hours in an air atmosphere to obtain a lithium-rich manganese-based positive electrode material.

[0059] Embodiment 5: A method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps: Step 1, solid phase mechanically mix 0.1 mol MnO and 5 mmol FeO to obtain a mixed powder, transfer the mixed powder to a muffle furnace and sinter at 850° C. for 8 h in an air atmosphere to obtain a precursor with a core of Mn2O3 and a coating of MnFe2O4.

[0060] Step 2: Take 0.1 mol of the precursor prepared 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° C. for 12 hours in an air atmosphere to obtain a lithium-rich manganese-based positive electrode material.

[0061] The positive electrode materials prepared in Examples 1 to 5 and Comparative Example 1 were assembled into batteries by the following method: The materials prepared in Examples 1 to 5 and Comparative Example 1 were used as positive electrode materials respectively, and were mixed with a conductive agent, acetylene black (AB), and a binder, polyvinylidene fluoride (PVDF), in a mass ratio of 8:1:1. N-methylpyrrolidone (NMP) was used as a solvent. The mixture was placed in a small beaker and stirred at a speed of 800 r / min for 2 h to obtain a slurry. The slurry was coated on the current collector aluminum foil using an automatic coating machine, placed flat on tempered glass and transferred to a vacuum drying oven at 85°C for drying for 4 hours. After punching into a pole piece with a diameter of 12 mm, the pole piece was dried at 105°C in a vacuum drying oven for 4 hours. The pole piece was placed in a glove box filled with argon atmosphere with a water content and oxygen content both lower than 0.1 ppm for 4 hours to reduce the moisture adsorbed by the pole piece during the transfer process. A pure metal lithium sheet with a diameter of 16 mm and a thickness of 0.5 mm was used as the negative electrode, and a porous polyethylene film of model Celgard2300 with a diameter of 18 mm was used as the separator. The CR2032 button battery was assembled in the glove box.

[0062] After the battery is assembled, it is aged for 12 hours, then activated for 3 cycles at a voltage of 2~4.8V and a current density of 0.1C, and then cycled for 100 cycles at a current density of 2C. Figure 3 Schematic diagram of the cycle performance of the battery assembled from the positive electrode materials prepared in Examples 1 to 5 and Comparative Example 1, Figure 3 It can be seen that the positive electrode material provided by the present invention has more excellent cycle performance under high pressure.

[0063] The embodiments described above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A precursor of a lithium-rich manganese-based positive electrode material, characterized in that: The invention comprises a core and a coating layer coated on at least a part of the surface of the core, wherein the core is Mn2O y , wherein 2≤y≤3; the coating layer is MnX2O4, wherein X is any one or more of Fe, Co, and Zn.

2. The precursor of the lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The molar ratio of manganese element to X element in the precursor of the lithium-rich manganese-based positive electrode material is 1:0.025-0.

06.

3. A method for preparing a precursor of a lithium-rich manganese-based positive electrode material, characterized in that: include: Grinding and mixing manganese oxide and transition metal oxide to obtain mixed powder, and sintering the mixed powder to obtain a precursor material; The transition metal in the transition metal oxide is any one or more of Fe, Co and Zn.

4. The method for preparing a precursor of a lithium-rich manganese-based positive electrode material according to claim 3, characterized in that: The molar ratio of manganese oxide to the transition metal element in the transition metal oxide is 1:0.05-0.

12.

5. The method for preparing a precursor of a lithium-rich manganese-based positive electrode material according to claim 3 or 4, characterized in that: The transition metal oxide is any one or more of FeO, Fe2O3, ZnO, CoO and Co2O3; the mixed powder is sintered in an oxygen-containing atmosphere, the sintering temperature is 700-1000°C, and the sintering time is 2-12h.

6. A lithium-rich manganese-based positive electrode material, characterized in that: It comprises a substrate and a coating layer coated on at least a portion of the surface of the substrate, wherein the molecular formula of the substrate is Li 1+m Mn 1-m O2, wherein 0.1≤m≤0.5; the molecular formula of the coating layer is Li2XMn3O8, wherein X is any one or more of Fe, Co, and Zn.

7. The lithium-rich manganese-based positive electrode material according to claim 6, characterized in that: The molar ratio of manganese element to X element in the lithium-rich manganese-based positive electrode material is 2:0.05-0.

12.

8. A method for preparing a lithium-rich manganese-based positive electrode material, characterized in that: include: The solid particles obtained by grinding and mixing the precursor of the lithium-rich manganese-based positive electrode material described in any one of claims 1 to 2 or the precursor of the lithium-rich manganese-based positive electrode material prepared by the preparation method described in any one of claims 3 to 5 and a lithium source, and sintering them are the lithium-rich manganese-based positive electrode materials.

9. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 8, characterized in that: The molar ratio of lithium element 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; the sintering is carried out in an oxygen-containing atmosphere, the sintering temperature is 900-1100°C, and the sintering time is 10-30h.

10. A battery, characterized in that: It includes the lithium-rich manganese-based positive electrode material described in any one of claims 6 to 7 or the lithium-rich manganese-based positive electrode material prepared by the preparation method described in any one of claims 8 to 9.

Images