A p2 phase nickel-manganese-based positive electrode sheet and a processing method and application thereof

Abstract

The application provides a treatment method of a P2-phase nickel-manganese-based positive electrode sheet, comprising the following steps: step S1, mixing P2-phase nickel-manganese-based positive electrode active material, conductive agent, binder and dispersion solvent to prepare positive electrode slurry, coating the positive electrode slurry on the surface of an aluminum foil, and punching the positive electrode sheet after drying treatment; step S2, placing the positive electrode sheet prepared in step S1 in a surface modification solvent in an inert atmosphere, and placing for 0.5-8 hours to obtain a surface-modified P2-phase nickel-manganese-based positive electrode sheet; wherein the surface modification solvent is a reduced ether organic solvent. The positive electrode sheet obtained by the treatment method of the P2-phase nickel-manganese-based positive electrode sheet of the application is applied to a sodium ion battery, so that the side reaction on the positive electrode-electrolyte interface under the working condition of a wide voltage range is inhibited, and the cycle stability of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a P2 phase nickel-manganese based positive electrode sheet, its processing method, and its application. Background Technology

[0002] The ever-growing demand in the energy storage market is placing new requirements on rechargeable batteries. Sodium-ion batteries, as an important supplement to lithium-ion batteries, possess resource advantages. P2-phase nickel-manganese-based oxide cathode materials are considered promising cathode materials for sodium-ion batteries due to their high operating voltage, good safety, and low cost. However, the electrochemical performance of P2-phase nickel-manganese-based oxide cathode materials is not ideal over a wide voltage range (lower limit below 2V, upper limit above 4V). During charge-discharge cycles, the surface of the oxide cathode material undergoes side reactions with the electrolyte, leading to continuous erosion and surface cracks. The electrolyte penetration along grain boundaries and surface cracks intensifies the reaction between the active material and the electrolyte, resulting in deterioration of cycle stability and rate performance.

[0003] Current technology primarily improves the performance of cathode materials through elemental doping. Elemental doping enhances the structural stability of oxide cathode materials to a certain extent, thereby improving their electrochemical performance over a wide voltage range. However, during battery charge-discharge cycles, the active materials are still directly exposed to the electrolyte, and side reactions between the active materials and the electrolyte still occur.

[0004] Therefore, it is necessary to provide a new process to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a method for processing P2 phase nickel-manganese-based positive electrode sheets. When the obtained positive electrode sheets are applied to sodium-ion batteries, side reactions at the positive electrode-electrolyte interface can be suppressed under a wide voltage range of operating conditions, thereby improving the cycle stability of the battery.

[0006] The technical solution of the present invention is as follows:

[0007] A method for processing a P2 phase nickel-manganese-based positive electrode sheet includes the following steps:

[0008] Step S1: Mix the P2 phase nickel-manganese-based positive electrode active material, conductive agent, binder and dispersing solvent to prepare a positive electrode slurry, coat the positive electrode slurry onto the surface of aluminum foil, and after drying, punch it into a positive electrode sheet.

[0009] Step S2: Under an inert atmosphere, the positive electrode sheet prepared in step S1 is placed in a surface-modifying solvent and left for 0.5-8 hours to obtain a surface-modified P2 phase nickel-manganese-based positive electrode sheet; wherein, the surface-modifying solvent is a reducing ether organic solvent.

[0010] Furthermore, the surface-modifying solvent is selected from one or more of ethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0011] Furthermore, in step S2, the inert gas is selected from either argon or nitrogen.

[0012] Furthermore, the P2 phase nickel-manganese-based positive electrode active material has the general chemical formula: Na 0.67 M x+y Ni 0.33-x Mn 0.67- y O2, M includes one or more of B, Mg, Al, Ti, Cr, Fe, Co, Cu, and Zn, where 0≤x≤0.33 and 0≤y≤0.67, and the stoichiometric ratio satisfies the principle of electroneutrality.

[0013] Furthermore, the conductive agent is selected from one or more of acetylene black, Super P, and Ketjen black; the adhesive is selected from one or more of polyvinylidene fluoride and sodium carboxymethyl cellulose; and the dispersing solvent is selected from one or more of N-methylpyrrolidone, water, and alcohol.

[0014] Furthermore, in the positive electrode slurry, the mass ratio of P2 phase nickel-manganese-based positive electrode active material, conductive agent, and binder is 70-95:5-20:0.5-10.

[0015] The present invention also provides a P2 phase nickel-manganese-based positive electrode sheet, which is prepared by the processing method of the P2 phase nickel-manganese-based positive electrode sheet.

[0016] The present invention also provides a sodium-ion secondary battery, comprising a P2 phase nickel-manganese-based positive electrode sheet prepared by the above method.

[0017] The sodium-ion secondary battery provided by this invention can be used in energy storage devices for solar power generation, wind power generation, tidal power generation, smart grid peak shaving, or distributed power stations.

[0018] Compared with the prior art, the processing method of P2 phase nickel-manganese based positive electrode sheet provided by the present invention has the following advantages:

[0019] The method for processing P2 phase nickel-manganese-based cathode sheets provided by this invention uses reducing ether-based organic solvents as surface modifiers for the cathode sheets. The highly oxidized oxide cathode material and the reducing organic solvent can spontaneously undergo charge transfer and mass transfer. Simultaneously, the surface of the oxide cathode material is converted into a conformal modification layer, and the surface reactivity of the oxide cathode material decreases. The solid-liquid contact reaction between the oxide cathode material and the reducing ether-based organic solvent forms an artificial interface layer on the surface of the active material, promoting the formation of a thin and uniform cathode-electrolyte interface film, suppressing interfacial side reactions during charge-discharge cycles, and improving the cycle stability of the oxide cathode material after optimization. At the same time, the artificial interface layer can effectively prevent the electrolyte from eroding the cathode surface, thereby hindering the dissolution of metal cations in the cathode material and ensuring stable battery performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 These are the X-ray diffraction patterns of the positive electrode plates provided in Comparative Example 1 and Example 1 of this invention;

[0022] Figure 2 These are scanning electron micrographs of the surface of the positive electrode sheet provided in Comparative Example 1 and Example 1 of this invention;

[0023] Figure 3 These are high-resolution transmission electron micrographs of the positive electrode plates provided in Comparative Example 1 and Example 1 of this invention;

[0024] Figure 4 This is a comparison chart of the cycle performance of sodium-ion secondary batteries assembled with the positive electrode sheets provided in Comparative Example 1 and Example 1 of this invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] A method for processing a P2 phase nickel-manganese-based positive electrode sheet includes the following steps:

[0028] Step S1: Mix the P2 phase nickel-manganese-based positive electrode active material, conductive agent, binder and dispersing solvent to prepare a positive electrode slurry, coat the positive electrode slurry onto the surface of aluminum foil, and after drying, punch it into a positive electrode sheet.

[0029] The P2 phase nickel-manganese-based positive electrode active material has the following general chemical formula: Na 0.67 M x+y Ni 0.33-x Mn 0.67-y O2, M includes one or more of B, Mg, Al, Ti, Cr, Fe, Co, Cu, and Zn, where 0≤x≤0.33 and 0≤y≤0.67, and the stoichiometric ratio satisfies the principle of electroneutrality;

[0030] The conductive agent is selected from one or more of acetylene black, Super P, and Ketjen black; the adhesive is selected from one or more of polyvinylidene fluoride and sodium carboxymethyl cellulose; the dispersing solvent is selected from one or more of N-methylpyrrolidone, water, and alcohol.

[0031] In the positive electrode slurry, the mass ratio of P2 phase nickel-manganese-based positive electrode active material, conductive agent, and binder is 70-95:5-20:0.5-10, such as 70:20:10, 95:10:5, 75:5:0.5, 80:15:3, or 85:12:8, or other ratios within this range;

[0032] The drying temperature is 80-120℃.

[0033] Step S2: Under an inert atmosphere, the positive electrode sheet prepared in step S1 is placed in a surface-modifying solvent and left for 0.5-8 hours to obtain a surface-modified P2 phase nickel-manganese-based positive electrode sheet; wherein, the surface-modifying solvent is a reducing ether organic solvent, preferably one or more of ethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether;

[0034] The inert gas is either argon or nitrogen, and the placement time can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h, or other values ​​within this range.

[0035] The following detailed description of the processing method of the P2 phase nickel-manganese based positive electrode sheet provided by the present invention is illustrated through specific embodiments.

[0036] Example 1

[0037] A positive electrode slurry is prepared by mixing P2-phase nickel-manganese-based positive electrode active material, conductive agent, binder, and dispersing solvent. The positive electrode slurry is coated onto aluminum foil, dried, and then punched into positive electrode sheets. By weight, the positive electrode active material is 70 parts, the conductive agent is 20 parts, and the binder is 10 parts.

[0038] The positive electrode active material is selected from Na. 0.67 Ni 0.33 Mn 0.67 O2; the conductive agent is selected from Super P; the binder is selected from polyvinylidene fluoride; the dispersing solvent is selected from N-methylpyrrolidone;

[0039] Under an argon atmosphere (water content less than 0.1 mg / L, oxygen content less than 0.1 mg / L), the prepared positive electrode sheet is placed in tetrahydrofuran and stored for 5 hours. The positive electrode sheet is then removed and prepared for battery assembly.

[0040] Example 2

[0041] A positive electrode slurry is prepared by mixing P2-phase nickel-manganese-based positive electrode active material, conductive agent, binder, and dispersing solvent. The positive electrode slurry is coated onto aluminum foil, dried, and then punched into positive electrode sheets. By weight, the positive electrode active material is 70 parts, the conductive agent is 20 parts, and the binder is 10 parts.

[0042] The positive electrode active material is selected from Na. 0.67 Ni 0.33 Mn 0.67 O2; the conductive agent is selected from Super P; the binder is selected from polyvinylidene fluoride; the dispersing solvent is selected from N-methylpyrrolidone;

[0043] Under an argon atmosphere (water content less than 0.1 mg / L, oxygen content less than 0.1 mg / L), the prepared positive electrode sheet is placed in ethylene glycol dimethyl ether and stored for 5 hours. The positive electrode sheet is then removed and prepared for battery assembly.

[0044] Example 3

[0045] A positive electrode slurry is prepared by mixing P2-phase nickel-manganese-based positive electrode active material, conductive agent, binder, and dispersing solvent. The positive electrode slurry is coated onto aluminum foil, dried, and then punched into positive electrode sheets. By weight, the positive electrode active material is 70 parts, the conductive agent is 20 parts, and the binder is 10 parts.

[0046] The positive electrode active material is selected from Na. 0.67 Mg 0.05 Ni 0.28 Mn 0.67 O2; the conductive agent is selected from Super P; the binder is selected from polyvinylidene fluoride; the dispersing solvent is selected from N-methylpyrrolidone;

[0047] Under an argon atmosphere (water content less than 0.1 mg / L, oxygen content less than 0.1 mg / L), the prepared positive electrode sheet is placed in tetrahydrofuran and stored for 5 hours. The positive electrode sheet is then removed and prepared for battery assembly.

[0048] Example 4

[0049] A positive electrode slurry is prepared by mixing P2-phase nickel-manganese-based positive electrode active material, conductive agent, binder, and dispersing solvent. The positive electrode slurry is coated onto aluminum foil, dried, and then punched into positive electrode sheets. By weight, the positive electrode active material is 70 parts, the conductive agent is 20 parts, and the binder is 10 parts.

[0050] The positive electrode active material is selected from Na. 0.67 Ti 0.17 Ni 0.33 Mn 0.5 O2; the conductive agent is selected from Super P; the binder is selected from polyvinylidene fluoride; the dispersing solvent is selected from N-methylpyrrolidone;

[0051] Under an argon atmosphere (water content less than 0.1 mg / L, oxygen content less than 0.1 mg / L), the prepared positive electrode sheet is placed in tetrahydrofuran and stored for 5 hours. The positive electrode sheet is then removed and prepared for battery assembly.

[0052] Comparative Example 1

[0053] A positive electrode slurry is prepared by mixing P2-phase nickel-manganese-based positive electrode active material, conductive agent, binder, and dispersing solvent. The positive electrode slurry is coated onto aluminum foil, dried, and then punched into positive electrode sheets. By weight, the positive electrode active material is 70 parts, the conductive agent is 20 parts, and the binder is 10 parts.

[0054] The positive electrode active material is selected from Na. 0.67 Ni 0.33 Mn 0.67O2; the conductive agent is selected from Super P; the binder is selected from polyvinylidene fluoride; the dispersing solvent is selected from N-methylpyrrolidone.

[0055] The sodium-ion battery was assembled in a glove box under an argon atmosphere, using a metallic sodium sheet as the negative electrode and a 1M NaClO4 carbonate solution as the electrolyte (the solvent was a mixture of 95 parts by volume of propylene carbonate and 5 parts by volume of fluoropropylene carbonate). The positive electrode sheet from the above embodiment was used to assemble the CR2025 coin cell.

[0056] The test was conducted using a constant current charge-discharge mode, with a discharge cutoff voltage of 1.5V and a charge cutoff voltage of 4.0V, at a current density of 50mA / g. Please refer to [link / reference]. Figure 1 , Figure 2 and Figure 3 ,in Figure 1 These are the X-ray diffraction patterns of the positive electrode plates provided in Comparative Example 1 and Example 1 of this invention. Figure 1 (a) shows the X-ray diffraction pattern of Comparative Example 1. Figure 1 (b) shows the X-ray diffraction lines of Example 1; Figure 2 These are scanning electron micrographs of the surface of the positive electrode provided in Comparative Example 1 and Example 1 of this invention. Figure 2 (a) shows a scanning electron microscope image of Comparative Example 1. Figure 2 (b) shows a scanning electron microscope image of Example 1; Figure 3 These are high-resolution transmission electron micrographs of the positive electrode plates provided in Comparative Example 1 and Example 1 of this invention. Figure 3 (a) shows a high-resolution transmission electron microscope image of Comparative Example 1. Figure 3 (b) shows a high-resolution transmission electron micrograph of Example 1. Figure 1 , Figure 2 , Figure 3 It can be seen that the surface modification treatment does not change the bulk structure of the P2 phase nickel-manganese-based positive electrode active material, and forms an artificial interface layer on the surface of the active material.

[0057] Please see Figure 4 This is a comparison chart of the cycle performance of sodium-ion secondary batteries assembled with the positive electrode sheets provided in Comparative Example 1 and Example 1 of this invention. Figure 4 It can be seen that, compared with Comparative Example 1, the sodium-ion secondary battery with the surface-modified positive electrode has a better capacity retention rate. After surface modification of the positive electrode material in Example 1, the specific capacity of the corresponding sodium-ion secondary battery in the first cycle discharge is 150 mAh / g, and the specific capacity decreases to 102 mAh / g after 200 cycles.

[0058] The sodium-ion secondary battery provided by this invention can be used as a large-scale energy storage device for solar power generation, wind power generation, tidal power generation, smart grid peak shaving, or distributed power stations.

[0059] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for processing a P2 phase nickel-manganese-based positive electrode sheet, characterized in that, Includes the following steps: Step S1: A positive electrode slurry is prepared by mixing the P2 phase nickel-manganese-based positive electrode active material, conductive agent, binder, and dispersing solvent. The positive electrode slurry is coated onto the surface of aluminum foil, dried, and then punched into a positive electrode sheet. The P2 phase nickel-manganese-based positive electrode active material has the general chemical formula: Na... 0.67 M x+y Ni 0.33-x Mn 0.67-y O2, M includes one or more of B, Mg, Al, Ti, Cr, Fe, Co, Cu, and Zn, where 0≤x≤0.33 and 0≤y≤0.67, and the stoichiometric ratio satisfies the principle of electroneutrality; Step S2: Under an argon atmosphere, the water content is less than 0.1 mg / L and the oxygen content is less than 0.1 mg / L; the positive electrode sheet prepared in step S1 is placed in a surface-modifying solvent and left for 0.5-8 hours to obtain a surface-modified P2 phase nickel-manganese-based positive electrode sheet; wherein, the surface-modifying solvent is tetrahydrofuran, and the oxide on the surface of the positive electrode sheet reacts with the tetrahydrofuran solid-liquid contact to form an artificial interface layer.

2. The method for processing the P2 phase nickel-manganese based positive electrode sheet according to claim 1, characterized in that, The conductive agent is selected from one or more of acetylene black, Super P, and Ketjen black; the binder is selected from one or more of polyvinylidene fluoride and sodium carboxymethyl cellulose; and the dispersing solvent is selected from one or more of N-methylpyrrolidone, water, and alcohol.

3. The method for processing the P2 phase nickel-manganese-based positive electrode sheet according to any one of claims 1-2, characterized in that, In the positive electrode slurry, the mass ratio of P2 phase nickel-manganese-based positive electrode active material, conductive agent, and binder is 70-95 : 5-20 : 0.5-10.

4. A P2 phase nickel-manganese based positive electrode, characterized in that, It is prepared by the processing method of any one of claims 1-3 for the P2 phase nickel-manganese based positive electrode sheet.

5. A sodium-ion secondary battery, characterized in that, Including the P2 phase nickel-manganese based positive electrode sheet as described in claim 4.

6. The application of the sodium-ion secondary battery of claim 5 in energy storage devices for solar power generation, wind power generation, tidal power generation, smart grid peak shaving, or distributed power stations.

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