A P2 phase sodium ion battery positive electrode material, preparation method and use

Abstract

The present invention relates to a P2 phase sodium ion battery positive electrode material, a preparation method and a use thereof, belonging to the technical field of sodium ion batteries. Its chemical formula is: Na x Mg y Mn 1‑y‑z Ru z O2; wherein x, y, and z are all atomic numbers. 0.67 Mg 0.28 Mn 0.72 Doping Ru elements at the Mn sites of the transition metal layer in the O2 material system significantly improves the reversibility of the oxygen redox reaction and optimizes the cycle performance of the material. At the same time, the problems of voltage attenuation and slow kinetics are significantly improved.

Description

Technical Field

[0001] The invention relates to a P2 phase sodium ion battery positive electrode material, a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. Background Art

[0002] Sodium-ion batteries have broad application prospects in new large-scale energy storage systems and smart grids due to their abundant raw materials and low cost. The research and development of high-performance electrode material systems plays a vital role in the application of sodium-ion batteries. Among the many positive electrode materials for sodium-ion batteries, layered transition metal oxides have attracted widespread attention due to their simple synthesis methods, controllable composition and structure. The development of science and technology has increasingly demanded high specific capacity, making the capacity limitation of traditional cationic redox reaction mechanism a bottleneck. To address this problem, the researchers successfully introduced Li into the transition metal layer. + / Mg 2+ / Zn 2+ / Cu 2+ / vacancies, prompting the anions to undergo redox reactions, further increasing the specific capacity of the positive electrode.

[0003] The introduction of anionic redox mechanism has significantly improved the material capacity, but there are problems such as low reaction reversibility, rapid voltage decay and slow kinetics. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the conventional P2 phase layered transition metal oxide sodium ion battery positive electrode has the problems of low reaction reversibility and fast voltage decay.

[0005] The present invention is achieved by 0.67 Mg 0.28 Mn 0.72 O 2 Doping Ru elements at the Mn sites of the transition metal layer in the material system significantly improves the reversibility of the oxygen redox reaction and optimizes the cycle performance of the material. At the same time, the problems of voltage attenuation and slow kinetics are significantly improved.

[0006] A P2 phase sodium ion battery positive electrode material, the chemical formula of which is: Na x Mg y Mn 1-y-z Ru z O 2 ; where x, y, and z are the atomic numbers.

[0007] In one embodiment, 0.6 <x<0.7,0.2<y<0.3,0.05<z<0.0.15。

[0008] In one embodiment, the chemical formula is: Na 0.67 Mg 0.28 Mn 0.6 Ru 0.12 O 2 .

[0009] The above-mentioned method for preparing the P2 phase sodium ion battery positive electrode material is to prepare it by a sol-gel method or a solid phase sintering method.

[0010] The steps of the solid phase sintering method include: taking Na 2 CO 3 ,MgO,RuO 2 and Mn 2 O 3 , mixed and ball-milled, pressed, and then calcined to obtain the positive electrode material.

[0011] In one embodiment, the ball milling process is performed at a rotation speed of 100-1000 rpm.

[0012] In one embodiment, ethanol is used as a grinding aid during the ball milling process, and the ball milling time is 1-16 hours.

[0013] In one embodiment, the heating rate during the calcination process is 1-105° C. / min.

[0014] In one embodiment, the calcination process is calcination at 900-1000° C. for 5-20 hours.

[0015] Application of the above-mentioned P2 phase sodium ion battery positive electrode material in sodium ion batteries.

[0016] Beneficial Effects

[0017] The present invention is achieved by 0.67 Mg 0.28 Mn 0.72 O 2 Doping Ru elements at the Mn sites of the transition metal layer in the material system significantly improves the reversibility of the oxygen redox reaction and optimizes the cycle performance of the material. At the same time, the problems of voltage attenuation and slow kinetics are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 X-ray powder diffraction spectrum of the material

[0019] Figure 2 SEM images of materials

[0020] Figure 3 High-resolution transmission electron microscopy image of the material

[0021] Figure 4 Transmission electron microscope element scanning of the material

[0022] Figure 5 In-situ X-ray diffraction pattern of the material and the corresponding charge and discharge curve

[0023] Figure 6 The charge and discharge curves of the material in the first three cycles at a current density of 20 mA / g

[0024] Figure 7 Charge and discharge curves of materials at different current densities

[0025] Figure 8 Cycling performance of materials at different current densities

[0026] Fig. 9 Long cycle performance curve of the material at a current density of 0.2A / g DETAILED DESCRIPTION

[0027] Example 1

[0028] The material of the present invention is prepared by high temperature solid phase sintering method, and the raw material is Na 2 CO 3 ,MgO,RuO 2 and Mn 2 O 3 According to the corresponding molar ratio, the ball milling was carried out at 300 rpm for 5 h, the wet grinding aid was anhydrous ethanol, and the precursor powder was dried at 100 ° C. The precursor powder was pressed into a 16 mm die and calcined in a muffle furnace. The process was 5 ° C / min heating, calcined at 950 ° C for 10 h, and then naturally cooled to obtain the positive electrode material Na 0.67 Mg 0.28 Mn 0.6 Ru 0.12 O 2 (NMMRO).

[0029] Comparison Example

[0030] The difference from Example 1 is that RuO is not used. 2 .

[0031] The material of the present invention is prepared by high temperature solid phase sintering method, and the raw material is Na 2 CO 3 ,MgO and Mn 2 O 3 According to the corresponding molar ratio, the ball milling was carried out at 300 rpm for 5 h, the wet grinding aid was anhydrous ethanol, and the precursor powder was dried at 100 ° C. The precursor powder was pressed into a 16 mm die and calcined in a muffle furnace. The process was 5 ° C / min heating, calcined at 950 ° C for 10 h, and then naturally cooled to obtain the positive electrode material Na 0.67 Mg 0.28 Mn0.72 O 2 (NMMO).

[0032] Characterization of materials

[0033] 1. XRD characterization

[0034] The X-ray powder diffraction test results of the material are as follows Figure 1 , the space group is P63 / mmc, and no impurity peaks appear, thus Ru is successfully incorporated into the crystal structure.

[0035] 2. SEM Characterization

[0036] The scanning electron microscopy images of the synthesized materials are shown in Figure 2 The morphology of NMMRO positive electrode material is irregular layered particles with a particle size of approximately 2 microns.

[0037] 3. HRTEM Characterization

[0038] High-resolution transmission electron microscopy images of NMMRO cathode materials Figure 3 Obvious lattice fringes can be clearly observed, with the interlayer spacing of 0.56 nm corresponding to the (002) crystal plane of the P2 structure.

[0039] 4. Characterization of element distribution

[0040] The spectrometer test results are as follows Figure 4 As shown, the distribution diagrams of sodium, oxygen, magnesium, manganese and ruthenium in the material particles are shown. Each element is evenly distributed in the material particles.

[0041] 5. Charge and discharge curve test

[0042] The structural change mechanism of NMMRO material was tested by in situ X-ray diffraction. Figure 5 As shown. In the voltage range of 2-4V, the material was charged and discharged. According to the X-ray diffraction test results, the characteristic peaks corresponding to the (004), (102) and (104) crystal planes of the P2 phase disappeared, and the (002) peak became broadened and right-shifted, indicating that there was a process of P2→Z phase during the charging process, and this phase change process is reversible.

[0043] 6. Electrochemical performance test

[0044] The electrochemical performance of the material was tested. The active material: conductive agent (acetylene black): binder (polyvinylidene fluoride PVDF) = 7:2:1 was used and N-methylpyrrolidone was used as solvent to mix evenly, coated on aluminum foil, and cut into 12mm diameter discs as positive electrodes after drying. Metallic sodium was used as the negative electrode, glass fiber membrane as the diaphragm, 1.0MNaClO4PC+5%FEC as the electrolyte, and assembled into button cells in an argon protection glove box. Figure 6, which is the charge and discharge curve of the material at a current density of 20mA / g, the voltage window is 1.5-4.5V, and the reversible specific capacity can reach 222.0mAh / g.

[0045] The charge and discharge curves of the material at different current densities are as follows: Figure 7 As shown, under the test conditions of current density 0.02, 0.05, 0.1, 0.2, 0.5 and 1A / g, the discharge specific capacity is 222, 205.5, 192.0, 177.8, 159.5 and 144.6 mAh g respectively. -1 , with excellent rate performance.

[0046] The material was cycled 10 times at different current densities, and its capacity was significantly higher than that of the control sample 1. After 60 cycles, at a current of 0.02A / g, the discharge capacity could reach 204.5mAh / g, and the retention rate of the discharge capacity in the first cycle was as high as 91.9%.

[0047] like Fig. 9 The NMMRO positive electrode material of Example 1 is 0.2A g -1 The long cycle performance under current density is that the capacity retention rate is 84.4% after 100 cycles, which is much higher than the 43.6% of the control sample, and the discharge specific capacity retention rate is 73.5% after 150 cycles.

Claims

1. A method for preparing a P2 phase sodium ion battery positive electrode material having no impurity peaks in an X-ray powder diffraction spectrum, It is characterized in that The chemical formula of the positive electrode material of P2 phase sodium ion battery is: Na 0.67 Mg 0.28 Mn 0.6 Ru 0.12 O 2 The space group of the P2 phase sodium ion battery positive electrode material is P63 / mmc, and it is prepared by a solid phase sintering method. The steps in the solid phase sintering method include: the raw material is Na 2 CO 3 ,MgO,RuO 2 and Mn 2 O 3 According to the corresponding molar ratio, ball milling was performed at 300 rpm for 5 h. The wet grinding aid was anhydrous ethanol. The precursor powder was dried at 100 °C to obtain the precursor powder. The precursor powder was pressed into a tablet through a 16 mm mold and calcined in a muffle furnace. The process was heated at 5 °C / min, calcined at 950 °C for 10 h, and then naturally cooled to obtain the positive electrode material.

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