Preparation method of O / P core-shell type layered manganese-based sodium-ion battery positive electrode material

Abstract

The invention relates to a preparation method of an O / P core-shell type layered manganese-based sodium-ion battery positive electrode material, and belongs to the technical field of sodium-ion battery materials. The proportion of the content of metal ions to the content of sodium ions is regulated and controlled in the preparation process, the O3-at-P2 core-shell type high-capacity sodium ion battery positive electrode material NaaMnxNiyCozO2 is constructed in a high-temperature sintering and microwave-assisted staged sodium treatment mode, x is larger than or equal to 00.25 and smaller than or equal to 0.65, y is larger than or equal to 0.13 and smaller than or equal to 0.43, z is larger than or equal to 0.02 and smaller than or equal to 0.30, x + y + z is larger than or equal to 0.5 and smaller than or equal to 0.8, and a is larger than or equal to 0.57 and smaller than or equal to 0.87. The O / P core-shell type layered manganese-based sodium ion battery positive electrode material disclosed by the invention has relatively high specific capacity, the specific capacity of the Na < 0.77 > Mn054Ni < 0.13 > Co < 0.13 > O2 material under the charge-discharge rate of 0.1 C is up to 232.5 mAh.g <-1 >, the specific capacity of the Na < 0.77 > Mn054Ni < 0.13 > Co < 0.13 > O2 material after 200 cycles under the charge-discharge rate of 1C is up to 146 mAh.g <-1 >, and the capacity retention ratio is greater than 80%.

Description

Technical Field

[0001] The invention relates to a method for preparing an O / P core-shell layered manganese-based sodium ion battery positive electrode material, belonging to the technical field of sodium ion battery materials. Background Art

[0002] As the core component of sodium-ion batteries (SIBs), cathode materials are crucial determinants of their electrochemical performance and energy density, and thus significantly influence the application of SIBS. Currently, research on cathode materials focuses primarily on layered oxides, polyanionic compounds, and Prussian blue. Layered transition metal oxides, with their advantages of simple synthesis, good crystallinity, and low-cost raw materials, have attracted widespread attention and are considered one of the most promising cathode oxides for SIBs. Layered NaXTMO2 metal oxides are classified into P-type (prismatic) and O-type (octahedral) structures, depending on the chemical environment surrounding the sodium ions and the coordination mechanism between sodium and oxygen ions. In P-type materials, sodium ions and oxygen atoms form triangular prisms, while in O-type materials, sodium ions and oxygen atoms form octahedral structures. O3-type materials offer high initial capacity but poor structural stability, while P2-type materials offer improved rate capability and cycle life. Current research focuses on constructing O3@P2 core-shell structures that combine the advantages of both. However, the traditional high-temperature solid-phase method has problems such as high energy consumption and interpenetration leading to blurred interfaces, making it difficult to accurately control the formation of core-shell structures. Summary of the Invention

[0003] In view of the poor cycle stability and low energy density in the application process of existing sodium ion batteries, and the high energy consumption, mutual penetration leading to interface blurring, and difficulty in precise control of the core-shell structure in the preparation method of O3@P2 core-shell structure sodium ion battery positive electrode materials, the present invention proposes a preparation method of O / P core-shell layered manganese-based sodium ion battery positive electrode materials. The present invention adopts a staged microwave-assisted pre-sodium treatment, which can accurately induce the structural evolution of the O3 core and P2 shell. By setting the microwave power and temperature at different stages, the O3 core can be kept intact and the reconstruction of the surface P2 phase can be promoted at the same time, significantly improving the clarity and interface stability of the core-shell structure.

[0004] A method for preparing an O / P core-shell layered manganese-based sodium ion battery cathode material, comprising the following steps: (1) According to the chemical formula of O / P core-shell layered manganese-based sodium ion battery cathode material Na a Mn x Ni y Co zdissolving a manganese salt, a nickel salt, and a cobalt salt in deionized water in a stoichiometric ratio of 0.25≤x≤0.65, 0.13≤y≤0.43, 0.02≤z≤0.30, 0.5≤x+y+z≤0.8, and 0.57≤a≤0.87 to obtain a transition metal salt mixed solution; stirring and mixing the transition metal salt mixed solution, the complexing agent solution, and the excess precipitant solution, adjusting the pH to 7.5-9.5, and aging the mixture to obtain a manganese-based precursor (manganese-based carbonate precursor); (2) placing the manganese-based precursor in a tube furnace, introducing air or oxygen, and calcining at a temperature of 400-700°C for 4-12 hours to obtain an O3-type oxide core (manganese-based oxide); (3) The O3-type oxide core and the Na source are mixed uniformly and then subjected to microwave stage treatment to obtain a composite precursor; (4) The composite precursor is placed in a tubular furnace, air or oxygen is introduced, the temperature is uniformly raised to 700-1000°C and kept warm for 10-15 hours, uniformly cooled to room temperature, and ground to obtain an O / P core-shell layered manganese-based sodium ion battery positive electrode material.

[0005] Preferably, the total molar concentration of the transition metal salt in the transition metal salt mixed solution is 2-4 mol / L.

[0006] Preferably, in step (1), the complexing agent is ammonium bicarbonate, ammonia water or sodium citrate, and the concentration of the complexing agent solution is 0.1-0.2 mol / L; the precipitant is ammonium carbonate, sodium carbonate or sodium hydroxide, and the concentration of the precipitant solution is 1-2 mol / L.

[0007] Preferably, the volume ratio of the transition metal salt mixed solution to the complexing agent solution in step (1) is 4-10:1.

[0008] Preferably, the aging treatment in step (1) is performed at a temperature of 40-90° C. and for a time of 5-30 hours.

[0009] Preferably, in step (2), the air introduction rate is 50-200 sccm / min, and the oxygen introduction rate is 50-200 sccm / min.

[0010] Preferably, the Na source in step (3) is Na2CO3, CH3COONa or Na2SO4, and the molar ratio of the O3-type oxide core to the Na source is 1:0.5-0.9.

[0011] Preferably, the specific method of microwave treatment in step (3) is: The first stage: the temperature is 280~450℃, the microwave frequency is 2.45GHz, and the power is 400~900W for 5~20min to achieve the initial doping of sodium ions and maintain the O3 core; The second stage: treating at a temperature of 500-750°C, a microwave frequency of 2.45 GHz, and a power of 400-900 W for 5-20 minutes to induce the growth of a P2 shell on the outside of the O3-type oxide core.

[0012] Preferably, in step (4), the air introduction rate is 50-200 sccm / min, the oxygen introduction rate is 50-200 sccm / min; the uniform heating rate is 3-10°C / min, and the uniform cooling rate is 3-10°C / min.

[0013] Preferably, the particle size of the O / P core-shell layered manganese-based sodium ion battery positive electrode material is 300-600 nm, and the thickness of the P2 shell is 20-80 nm.

[0014] The beneficial effects of the present invention are: (1) Based on the characteristics of rapid, uniform and selective heating of microwave-assisted treatment, the present invention uses microwaves to rapidly induce the rearrangement of the surface layer of the material in the medium and low temperature range, prompting the formation of a P2-type outer shell layer on the surface while maintaining the core O3-type structure from collapsing. This successfully realizes the construction of O3@P2 core-shell cathode materials, which can solve the problems of low capacity of P2 structure and unstable cycle of O3 structure in the prior art. (2) The present invention precisely constructs a composite structure of an O3 core and a P2 shell, thereby retaining high capacity while improving structural stability and rate performance; (3) The microwave staged treatment strategy of the present invention can effectively avoid the problems of uneven Na diffusion and blurred core-shell interface in the traditional high-temperature sodiumization process, thereby improving the structural clarity, stability and cycle life of the material; (4) The method of the present invention is simple and efficient. The O / P core-shell layered manganese-based sodium ion battery cathode material prepared in a short time has a high specific capacity. 0.77 Mn 054 Ni 0.13 Co 0.13 The specific capacity of the O2 material is as high as 232.5 mAh g at a charge and discharge rate of 0.1C. -1 The specific capacity is as high as 146 mAh g after 200 cycles at a 1C charge and discharge rate. -1 , the capacity retention rate is greater than 80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 XRD patterns of cathode materials prepared by two-stage microwave-assisted sodium treatment with different Na contents; Figure 2 for Na 0.57 Mn 0.54 Ni 0.13 Co 0.13 Charge and discharge curve of O2 material at 0.1C rate; Figure 3 for Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 Charge and discharge curve of O2 material at 0.1C rate; Figure 4 for Na 0.77 Mn 0.54 Ni 0.13 Co 0.13 The first charge and discharge curve of O2 material at 0.1C charge and discharge rate; Figure 5 for Na 0.77 Mn 0.54 Ni 0.13 Co 0.13 Cycling stability of O2 materials at 1C charge and discharge rate; Figure 6 for Na 0.87 Mn 0.54 Ni 0.13 Co 0.13 Charge and discharge curves of O2 material at 0.1C rate. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0017] Example 1: The positive electrode material of the O / P core-shell layered manganese-based sodium ion battery in this embodiment is Na 0.57 Mn 0.54 Ni 0.13 Co 0.13 O2; A method for preparing an O / P core-shell layered manganese-based sodium ion battery cathode material, comprising the following steps: (1) According to the chemical formula of O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.57 Mn 0.54 Ni 0.13 Co 0.13The stoichiometric ratio of O2 is 0.5:1, manganese sulfate, nickel sulfate and cobalt sulfate are dissolved in deionized water to obtain a transition metal salt mixed solution; the transition metal salt mixed solution, a complexing agent solution (a sodium carbonate solution with a concentration of 2 mol / L) and an excess precipitant solution (a 0.15 mol / L ammonia solution) are added dropwise into a reactor, stirred and mixed at a temperature of 50°C and a stirring speed of 800 r / min, and the pH is adjusted to 7.9. The mixture is aged at a temperature of 40°C for 8 h, filtered, washed with deionized water, and dried at a temperature of 80°C for 24 h to obtain a manganese-based precursor (a spherical manganese-based carbonate precursor); the total molar concentration of the transition metal salt in the transition metal salt mixed solution is 2 mol / L, and the volume ratio of the transition metal salt mixed solution to the complexing agent solution is 10:1; (2) The manganese-based precursor was placed in a tube furnace, air was continuously introduced at a rate of 60 sccm / min, and calcined at a temperature of 400°C for 5 h to obtain an O3-type oxide core (manganese-based oxide); (3) Adding the O3 type oxide core and the Na source (sodium carbonate) into deionized water, stirring and mixing, evaporating and drying to obtain a mixture, and subjecting the mixture to a microwave stage treatment to obtain a composite precursor; the molar ratio of the O3 type oxide core to the Na source is 1:0.59 (5% sodium source is used to supplement the loss of Na at high temperature), and the specific method of the microwave stage treatment is: The first stage: treatment at a temperature of 300 ° C, a microwave frequency of 2.45 GHz, and a power of 400 W for 20 min to achieve preliminary sodium ion doping and maintain O3 cores; The second stage: treatment at a temperature of 550 ° C, a microwave frequency of 2.45 GHz, and a power of 500 W for 15 minutes to induce the growth of a P2 shell on the outside of the O3-type oxide core; (4) The composite precursor was placed in a tube furnace, air was continuously introduced at a rate of 60 sccm / min, the temperature was uniformly raised to 900 °C at a rate of 5 °C / min and kept at this temperature for 12 h, and the composite precursor was uniformly cooled to room temperature at a rate of 5 °C / min, and ground to obtain the O / P core-shell layered manganese-based sodium ion battery positive electrode material Na 0.57 Mn 0.54 Ni 0.13 Co 0.13 O2; The O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.57 Mn 0.54 Ni 0.13 Co 0.13 The XRD pattern of O2 is shown in Figure 1 ,from Figure 1 It can be seen that the prepared cathode material has a diffraction peak consistent with the P2-type layered structure, and the sharp diffraction peak indicates good crystallinity of the material; Weigh the positive electrode materials (Na 0.57 Mn 0.54 Ni 0.13 Co 0.13 O2), conductive agent (SuperP), binder (PVDF) in a weighing bottle, after magnetic stirring at 400r / min for 10min, add 1ml mono-methylpyrrolidone (NMP) solution, and magnetic stirring at 400r / min for 5h again, and then apply the coating with a coating thickness of 100μm. After blowing and vacuum drying for 10h, the positive electrode material electrode is obtained after punching. In a glove box, a sodium sheet is used as the counter electrode and the above-mentioned positive electrode sheet is used as the working electrode. A 2032 type button battery is assembled in a glove box. After standing for 10h, the electrochemical performance test is carried out on a Xinwei tester, such as the charge and discharge curve at a rate of 0.1C. Figure 2 As shown in the figure, it can be seen that the discharge capacity of the material is 140.3 mAh g -1 , the Coulombic efficiency is 95.4%.

[0018] Example 2: The positive electrode material of the O / P core-shell layered manganese-based sodium ion battery in this embodiment is Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 O2; A method for preparing an O / P core-shell layered manganese-based sodium ion battery cathode material, comprising the following steps: (1) According to the chemical formula of O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 O2 in a stoichiometric ratio, manganese sulfate, nickel sulfate and cobalt sulfate are dissolved in deionized water to obtain a transition metal salt mixed solution; the transition metal salt mixed solution, a complexing agent solution (a 30 ml / L ammonia solution) and an excess precipitant solution (a 1 mol / L sodium bicarbonate solution) are added dropwise into a reactor, stirred and mixed at a temperature of 65°C and a stirring speed of 400 r / min, and the pH is adjusted to 8.5. The mixture is aged at a temperature of 65°C for 21 hours, filtered, washed with deionized water, and dried at a temperature of 80°C for 12 hours to obtain a manganese-based precursor (a spherical manganese-based carbonate precursor); the total molar concentration of the transition metal salt in the transition metal salt mixed solution is 3 mol / L, and the volume ratio of the transition metal salt mixed solution to the complexing agent solution is 8:1; (2) The manganese-based precursor was placed in a tube furnace, air was continuously introduced at a rate of 100 sccm / min, and the precursor was calcined at 600°C for 4 h to obtain an O3-type oxide core (manganese-based oxide); (3) Adding the O3 type oxide core and the Na source (sodium sulfate) into deionized water, stirring and mixing, evaporating and drying to obtain a mixture, and subjecting the mixture to a microwave stage treatment to obtain a composite precursor; the molar ratio of the O3 type oxide core to the Na source is 1:0.7035 (5% sodium source is used to supplement the loss of Na at high temperature), and the specific method of the microwave stage treatment is: The first stage: treatment at a temperature of 300 ° C, a microwave frequency of 2.45 GHz, and a power of 800 W for 11 minutes to achieve preliminary sodium ion doping and maintain O3 cores; The second stage: treatment at a temperature of 680 ° C, a microwave frequency of 2.45 GHz, and a power of 550 W for 13 minutes to induce the growth of a P2 shell on the outside of the O3-type oxide core; (4) The composite precursor was placed in a tube furnace, air was continuously introduced at a rate of 60 sccm / min, the temperature was uniformly raised to 800 °C at a rate of 3 °C / min and kept at this temperature for 12 h, and the composite precursor was uniformly cooled to room temperature at a rate of 3 °C / min, and ground to obtain the O / P core-shell layered manganese-based sodium ion battery positive electrode material Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 O2; The O / P core-shell layered manganese-based sodium ion battery positive electrode material Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 The XRD pattern of O2 is shown in Figure 1 ,from Figure 1 It can be seen that the prepared cathode material has a diffraction peak consistent with the P2-type layered structure, and the sharp diffraction peak indicates good crystallinity of the material; Weigh the positive electrode materials (Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 O2), conductive agent (SuperP), binder (PVDF) in a weighing bottle, after magnetic stirring at 400r / min for 10min, add 1ml mono-methylpyrrolidone (NMP) solution, and magnetic stirring at 400r / min for 5h again, and then apply the coating with a coating thickness of 100μm. After blowing and vacuum drying for 10h, the positive electrode material electrode is obtained after punching. In a glove box, a sodium sheet is used as the counter electrode and the above-mentioned positive electrode sheet is used as the working electrode. A 2032 type button battery is assembled in a glove box. After standing for 10h, the electrochemical performance test is carried out on a Xinwei tester, such as the charge and discharge curve at a rate of 0.1C. Figure 3 As shown in the figure, it can be seen that the discharge capacity of the material is 154.3 mAh g -1 , the Coulombic efficiency is 81%.

[0019] Example 3: The positive electrode material of the O / P core-shell layered manganese-based sodium ion battery in this embodiment is Na 0.77 Mn 0.54 Ni 0.13 Co 0.13 O2; A method for preparing an O / P core-shell layered manganese-based sodium ion battery cathode material, comprising the following steps: (1) According to the chemical formula of O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.57 Mn 0.54 Ni 0.13 Co 0.13 The stoichiometric ratio of manganese sulfate, nickel sulfate and cobalt sulfate is 0.5:1 to 1.0, and manganese sulfate, nickel sulfate and cobalt sulfate are dissolved in deionized water to obtain a transition metal salt mixed solution; the transition metal salt mixed solution, a complexing agent solution (a sodium citrate solution with a concentration of 0.15 mol / L) and an excess precipitant solution (a sodium hydroxide solution with a concentration of 2 mol / L) are added dropwise into a reactor, stirred and mixed at a temperature of 85°C and a stirring speed of 400 r / min, and the pH is adjusted to 9.0. The mixture is aged at a temperature of 85°C for 21 hours, filtered, washed with deionized water, and dried at a temperature of 80°C for 12 hours to obtain a manganese-based precursor (a spherical manganese-based carbonate precursor); the total molar concentration of the transition metal salt in the transition metal salt mixed solution is 3.5 mol / L, and the volume ratio of the transition metal salt mixed solution to the complexing agent solution is 7:1; (2) The manganese-based precursor was placed in a tube furnace, oxygen was continuously introduced at a rate of 60 sccm / min, and calcined at a temperature of 650°C for 4 h to obtain an O3-type oxide core (manganese-based oxide); (3) Adding the O3 type oxide core and the Na source (sodium acetate) into deionized water, stirring and mixing, evaporating and drying to obtain a mixture, and subjecting the mixture to a microwave stage treatment to obtain a composite precursor; the molar ratio of the O3 type oxide core to the Na source is 1:0.81 (5% sodium source is used to supplement the loss of Na at high temperature), and the specific method of the microwave stage treatment is: The first stage: treatment at a temperature of 420 ° C, a microwave frequency of 2.45 GHz, and a power of 850 W for 7 minutes to achieve preliminary sodium ion doping and maintain O3 cores; The second stage: treatment at a temperature of 550 ° C, a microwave frequency of 2.45 GHz, and a power of 600 W for 20 min to induce the growth of a P2 shell on the outside of the O3-type oxide core; (4) The composite precursor was placed in a tube furnace, oxygen was continuously introduced at a rate of 150 sccm / min, the temperature was uniformly raised to 950 °C at a rate of 3 °C / min and kept at this temperature for 12 h, and then uniformly cooled to room temperature at a rate of 3 °C / min. The O / P core-shell layered manganese-based sodium ion battery positive electrode material Na was obtained by grinding. 0.77 Mn0.54 Ni 0.13 Co 0.13 O2; The O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.77 Mn 0.54 Ni 0.13 Co 0.13 The XRD pattern of O2 is shown in Figure 1 ,from Figure 1 It can be seen that from Figure 1 It can be seen that the prepared cathode material has a diffraction peak consistent with the P2-type layered structure, and the sharp diffraction peak indicates good crystallinity of the material; Weigh the positive electrode materials (Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 O2), conductive agent (SuperP), binder (PVDF) in a weighing bottle, after magnetic stirring at 400r / min for 10min, add 1ml of mono-methylpyrrolidone (NMP) solution, and magnetically stir again at 400r / min for 5h before coating with a coating thickness of 100μm. After blowing and vacuum drying for 10h, the positive electrode material electrode is obtained by punching. In a glove box, a sodium sheet is used as the counter electrode and the above-mentioned positive electrode sheet is used as the working electrode to assemble a 2032 type button battery in a glove box. After standing for 10h, the electrochemical performance test is carried out on a Xinwei tester, such as the charge and discharge curve at a rate of 0.1C and the cycle performance at a rate of 1C. Figure 4 and Figure 5 As shown in the figure, it can be seen that the discharge capacity of the material is and the coulomb efficiency is Na 0.77 Mn 054 Ni 0.13 Co 0.13 The specific capacity of the O2 material is as high as 231.9 mAh g at a charge and discharge rate of 0.1C. -1 The coulombic efficiency is as high as 96%, and the specific capacity is as high as 156.7 mAh g after 200 cycles at a 1C charge and discharge rate. -1 , the capacity retention rate is about 97%.

[0020] Example 4: The positive electrode material of the O / P core-shell layered manganese-based sodium ion battery in this embodiment is Na 0.87 Mn 0.54 Ni 0.13 Co 0.13 O2; A method for preparing an O / P core-shell layered manganese-based sodium ion battery cathode material, comprising the following steps: (1) According to the chemical formula of O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.57 Mn0.54 Ni 0.13 Co 0.13 The stoichiometric ratio of O2 is 2: 1, manganese sulfate, nickel sulfate and cobalt sulfate are dissolved in deionized water to obtain a transition metal salt mixed solution; the transition metal salt mixed solution, a complexing agent solution (a mixed solution of sodium citrate and ammonia water with a concentration of 0.2 mol / L) and an excess precipitant solution (a mixed solution of sodium carbonate and sodium hydroxide with a concentration of 1.5 mol / L) are added dropwise into a reactor, stirred and mixed at a temperature of 90°C and a stirring speed of 400 r / min, and the pH is adjusted to 9.5. The mixture is aged at a temperature of 90°C for 21 hours, filtered, washed with deionized water, and dried at a temperature of 80°C for 12 hours to obtain a manganese-based precursor (a spherical manganese-based carbonate precursor); the total molar concentration of the transition metal salt in the transition metal salt mixed solution is 4 mol / L, and the volume ratio of the transition metal salt mixed solution to the complexing agent solution is 4:1; (2) The manganese-based precursor was placed in a tube furnace, oxygen was continuously introduced at a rate of 180 sccm / min, and calcined at 800°C for 12 h to obtain an O3-type oxide core (manganese-based oxide); (3) Adding the O3 type oxide core and the Na source (sodium acetate and sodium carbonate mixed in a mass ratio of 1:1) into deionized water, stirring and mixing, evaporating and drying to obtain a mixture, and subjecting the mixture to a microwave stage treatment to obtain a composite precursor; the molar ratio of the O3 type oxide core to the Na source is 1:0.9135 (5% sodium source is used to supplement the loss of Na at high temperature), and the specific method of the microwave stage treatment is: The first stage: treatment at a temperature of 450 ° C, a microwave frequency of 2.45 GHz, and a power of 900 W for 5 minutes to achieve preliminary sodium ion doping and maintain O3 cores; The second stage: treatment at 750 ° C, microwave frequency 2.45 GHz, power 900 W for 8 minutes to induce the growth of P2 shell on the outside of the O3 type oxide core; (4) The composite precursor was placed in a tube furnace, oxygen was continuously introduced at a rate of 180 sccm / min, the temperature was uniformly raised to 1000 °C at a rate of 3 °C / min and kept warm for 12 h, and then uniformly cooled to room temperature at a rate of 3 °C / min. The O / P core-shell layered manganese-based sodium ion battery positive electrode material Na was obtained by grinding. 0.87 Mn 0.54 Ni 0.13 Co 0.13 O2; The O / P core-shell layered manganese-based sodium ion battery cathode material Na 0.87 Mn 0.54 Ni 0.13 Co 0.13 The XRD pattern of O2 is shown in Figure 1 ,from Figure 1It can be seen that from Figure 1 It can be seen that the prepared cathode material has a diffraction peak consistent with the P2-type layered structure, and the sharp diffraction peak indicates good crystallinity of the material; Weigh the positive electrode materials (Na 0.67 Mn 0.54 Ni 0.13 Co 0.13 O2), conductive agent (SuperP), binder (PVDF) in a weighing bottle, after magnetic stirring at 400r / min for 10min, add 1ml mono-methylpyrrolidone (NMP) solution, and magnetic stirring at 400r / min for 5h again, and then apply the coating with a coating thickness of 100μm. After blowing and vacuum drying for 10h, the positive electrode material electrode is obtained after punching. In a glove box, a sodium sheet is used as the counter electrode and the above-mentioned positive electrode sheet is used as the working electrode. A 2032 type button battery is assembled in a glove box. After standing for 10h, the electrochemical performance test is carried out on a Xinwei tester, such as the charge and discharge curve at a rate of 0.1C. Figure 6 As shown in the figure, it can be seen that the discharge capacity of the material is 205.6 mAh g -1 , the Coulombic efficiency is as high as 93.6%.

[0021] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing an O / P core-shell layered manganese-based sodium ion battery cathode material, characterized in that: The specific steps are as follows: (1) According to the chemical formula of O / P core-shell layered manganese-based sodium ion battery cathode material Na a Mn x Ni y Co z dissolving a manganese salt, a nickel salt, and a cobalt salt in deionized water in a stoichiometric ratio of 0.25≤x≤0.65, 0.13≤y≤0.43, 0.02≤z≤0.30, 0.5≤x+y+z≤0.8, and 0.57≤a≤0.87 to obtain a transition metal salt mixed solution; stirring and mixing the transition metal salt mixed solution, the complexing agent solution, and the excess precipitant solution, adjusting the pH to 7.5-9.5, and aging the mixture to obtain a manganese-based precursor; (2) placing the manganese-based precursor in a tube furnace, introducing air or oxygen, and calcining at a temperature of 400-700°C for 4-12 hours to obtain an O3-type oxide core; (3) The O3-type oxide core and the Na source are mixed uniformly and then subjected to microwave stage treatment to obtain a composite precursor; (4) The composite precursor is placed in a tubular furnace, air or oxygen is introduced, the temperature is uniformly raised to 700-1000°C and kept warm for 10-15 hours, uniformly cooled to room temperature, and ground to obtain an O / P core-shell layered manganese-based sodium ion battery positive electrode material.

2. The method for preparing the O / P core-shell layered manganese-based sodium ion battery positive electrode material according to claim 1, characterized in that: The total molar concentration of the transition metal salt in the transition metal salt mixed solution is 2-4 mol / L.

3. The method for preparing the O / P core-shell layered manganese-based sodium ion battery positive electrode material according to claim 1, characterized in that: In step (1), the complexing agent is ammonium bicarbonate, ammonia water or sodium citrate, and the concentration of the complexing agent solution is 0.1-0.2 mol / L; the precipitating agent is ammonium carbonate, sodium carbonate or sodium hydroxide, and the concentration of the precipitating agent solution is 1-2 mol / L.

4. The method for preparing the O / P core-shell layered manganese-based sodium ion battery positive electrode material according to claim 3, characterized in that: In step (1), the volume ratio of the transition metal salt mixed solution to the complexing agent solution is 4 to 10:

1.

5. The method for preparing the O / P core-shell layered manganese-based sodium ion battery positive electrode material according to claim 1, characterized in that: The temperature of the aging treatment in step (1) is 40-90°C and the time is 5-30 hours.

6. The method for preparing the O / P core-shell layered manganese-based sodium ion battery cathode material according to claim 1, characterized in that: In step (2), the air introduction rate is 50-200 sccm / min, and the oxygen introduction rate is 50-200 sccm / min.

7. The method for preparing the O / P core-shell layered manganese-based sodium ion battery cathode material according to claim 1, characterized in that: In step (3), the Na source is Na2CO3, CH3COONa or Na2SO4, and the molar ratio of the O3-type oxide core to the Na source is 1:0.5~0.

9.

8. The method for preparing the O / P core-shell layered manganese-based sodium ion battery cathode material according to claim 1 or 7, characterized in that: The specific method of microwave treatment in step (3) is as follows: The first stage: treatment at a temperature of 280-450°C, a microwave frequency of 2.45 GHz, and a power of 400-900 W for 5-20 minutes; The second stage: treating at a temperature of 500-750°C, a microwave frequency of 2.45 GHz, and a power of 400-900 W for 5-20 minutes to induce the growth of a P2 shell on the outside of the O3-type oxide core.

9. The method for preparing the O / P core-shell layered manganese-based sodium ion battery cathode material according to claim 1, characterized in that: In step (4), the air introduction rate is 50~200sccm / min, and the oxygen introduction rate is 50~200sccm / min; the uniform heating rate is 3~10℃ / min, and the uniform cooling rate is 3~10℃ / min.

10. The method for preparing the O / P core-shell layered manganese-based sodium ion battery cathode material according to claim 1, characterized in that: The particle size of the O / P core-shell layered manganese-based sodium ion battery positive electrode material is 300~600nm, and the P2 shell thickness is 20~80nm.

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