Co < 3 + >-doped lithium nickel manganese oxide binary positive electrode material and preparation method thereof

Abstract

The invention discloses a Co < 3 + >-doped lithium nickel manganese oxide binary positive electrode material and a preparation method thereof, the molecular formula of the Co < 3 + >-doped lithium nickel manganese oxide binary positive electrode material is LiNi < 0.5 > Mn < 1.5-x > CoxO4, and x is 0.01-0.05. The preparation method comprises the following steps: (1) adding a lithium source, a nickel source, a manganese source and a cobalt source into a ball milling tank according to a stoichiometric ratio, adding ethanol, carrying out ball milling, and drying a sample after ball milling; (2) grinding the ball-milled powder in a mortar to obtain precursor powder; and (3) transferring the precursor powder into a muffle furnace, heating to 500 DEG C, presintering at the temperature, then heating to 900 DEG C, sintering, and cooling to room temperature after sintering to obtain the cobalt-doped lithium nickel manganese oxide binary positive electrode material. The content of disordered phases in a bulk phase is increased by doping Co < 3 + >, so that the high-temperature thermal stability is improved, the cycling stability and the rate capability are improved, and the long-cycle performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium nickel manganese oxide binary cathode materials, and specifically relates to a Co 3+ lithium nickel manganese oxide binary cathode material and a preparation method thereof. Background Art

[0002] With the wide use of electric vehicles, portable electronic devices and energy storage systems, lithium-ion batteries (LIBs) have become a key technology in the global energy storage field, and the electrochemical performance of the cathode material largely determines the performance of LIBs. Currently, lithium cobalt oxide, lithium nickel cobalt manganese oxide and lithium iron phosphate are the main lithium-ion battery cathode materials on the market. Lithium cobalt oxide has significant advantages in high specific capacity and kinetics, but its thermal stability is poor. Lithium nickel cobalt manganese oxide has a high energy density, but its safety performance is low. Lithium iron phosphate has high safety and a long cycle life, but its energy density is low and cannot meet the current market demand. Spinel-type LiNi 0.5 Mn 1.5 O4 (LNMO) cathode materials are considered to be promising cathode materials for next-generation lithium-ion batteries due to their high working voltage (4.7V vs. Li / Li + ), high energy density (650 Wh kg -1 ), fast three-dimensional lithium-ion diffusion channels and low cost. Research shows that the space group structure of the LNMO material changes with the change of the Ni / Mn arrangement, mainly showing two space group structures, namely the ordered P4332 and the disordered Fd-3m. The disordered LNMO material exhibits excellent electrochemical performance, which can be attributed to: (1) the presence of Mn 3+ enhances the ionic conductivity; (2) the disordered LNMO structure provides more diffusion channels for lithium ions, which is beneficial to the insertion and extraction of lithium ions. However, the current LNMO material has the following problems to be solved: (1) the low thermal stability of the LNMO material, especially at high temperatures; (2) the distortion caused by the Jahn-Teller effect is not conducive to the crystal structure stability, thus deteriorating the long cycle performance; (3) the excessive content of Mn 3+ is easy to dissolve the transition metal atoms in the material. Summary of the Invention

[0003] Aiming at the above technical problems, the first object of the present invention is to provide a Co 3+ -doped lithium nickel manganese oxide binary cathode material, and the second object is to provide a preparation method thereof.

[0004] To achieve the above first object, the present invention provides a Co 3+ -doped lithium nickel manganese oxide binary cathode material, which is characterized in that the molecular formula is: LiNi 0.5 Mn1.5-x Co x O4, where x is 0.01 - 0.05.

[0005] In the above solution: the x is 0.03.

[0006] In order to achieve the above second object, the technical solution of the present invention is: a preparation method of the above-mentioned Co 3+ doped lithium nickel manganese oxide binary cathode material, characterized in that it is prepared according to the following method:

[0007] (1) According to the stoichiometric ratio, add lithium source, nickel source, manganese source and cobalt source into the ball milling tank, where the addition amount of the lithium source is excessive, add ethanol, ball mill, and dry the sample after ball milling;

[0008] (2) Grind the powder after ball milling in a mortar to obtain precursor powder;

[0009] (3) Transfer the precursor powder to a muffle furnace, heat it to 500 °C, and pre-sinter at this temperature. Subsequently, raise the temperature to 900 °C, sinter, and after sintering is completed, cool to room temperature to obtain the cobalt-doped lithium nickel manganese oxide binary cathode material.

[0010] In the above solution: the lithium source is selected from at least one of lithium hydroxide, lithium chloride, lithium sulfate, lithium nitrate and lithium acetate.

[0011] In the above solution: the manganese source is selected from one of manganese dioxide, manganese sulfate, manganese nitrate, manganese oxalate and manganese acetate.

[0012] In the above solution: the nickel source is selected from nano nickel oxide.

[0013] In the above solution: the cobalt source is selected from Co2O3.

[0014] In the above solution: the lithium source is 5% excessive to compensate for the loss of lithium during calcination.

[0015] In the above solution: the ball milling speed is 500 - 600 revolutions / min, the ball milling time is 6 - 7 h. Grind for 20 min.

[0016] In the above solution: in the muffle furnace, the heating rate of pre-sintering and sintering is both 3 °C / min, the pre-sintering time is 5 - 6 h, and the sintering time is 10 - 12 h.

[0017] Beneficial effects:

[0018] The present invention uses the solid-phase method to prepare spinel-type LiNi 0.5 Mn 1.5 O4 (LNMO) material. Introduce Co 3+To adjust the ratio of disordered / ordered phases in LNMO, thereby improving its electrochemical performance. The results of X-ray diffraction (XRD) refinement showed that doping with Co 3+ samples had larger lattice parameters and unit cell volumes, which was beneficial for Li + diffusion and increased the lithium diffusion rate. In addition, Fourier transform infrared spectroscopy (FT-IR) and Raman results further confirmed that Mn-3Co had the optimal ratio of disordered phases, corresponding to the best electrochemical performance. Cyclic voltammetry (CV) results showed that the Mn-3Co sample had the smallest electrochemical polarization, and the rate performance test showed that this sample could still maintain a capacity of 85.15 mAh g -1 at a high current of 20C. In addition, after 500 cycles at a 1C rate, the LNMO sample maintained a capacity of 91.63 mAh g -1 (capacity retention rate of 77.30%), while the Mn-3Co sample showed a discharge capacity of 114.46 mAh g -1 (capacity retention rate of 89%).

[0019] Samples doped with Co 3+ showed excellent high-temperature performance. After 150 cycles at a 5C rate and 60 °C, the LNMO sample maintained a capacity of 12.83 mAh g -1 (capacity retention rate of 11.11%), while the Mn-3Co sample maintained a capacity of 110.31 mAh g -1 (capacity retention rate of 88.51%).

[0020] The modified spinel-type LNMO material exhibited excellent structural and thermal stability, making it a strong candidate for advanced lithium-ion battery cathode materials. Description of the Drawings

[0021] Figure 1 In (a) are the XRD patterns of four samples; (b)-(d) are the refined patterns of LNMO, Mn-1Co, Mn-3Co, and Mn-Co samples.

[0022] Figure 2 are the Fourier transform infrared spectroscopy (FT-IR) curves of (a) all samples and (b) Raman spectroscopy curves.

[0023] Figure 3 are SEM images of four samples. From left to right, the first column is LNMO, the second column is Mn-1Co, the third column is Mn-3Co, and the fourth column is Mn-5Co. The difference lies in the different magnification factors during the SEM test.

[0024] Figure 4 are the XPS spectra of four samples.

[0025] Figure 5 CV curves and rate curves for four samples.

[0026] Figure 6 Long cycle diagrams for four samples.

[0027] Figure 7 Are (a) high-temperature performance, (b) charge-discharge curves of LNMO and (c) Mn-3Co, and (d)-(g′) scanning electron microscope (SEM) images of all samples after high-temperature cycling.

[0028] Figure 8 Impedance diagrams for four samples. Detailed implementation mode

[0029] The present invention will be further described below through embodiments in conjunction with the accompanying drawings:

[0030] Example 1

[0031] According to stoichiometry, respectively in accordance with LiNi 0.5 Mn 1.49 Co 0.01 O4, LiNi 0.5 Mn 1.47 Co 0.03 O4, LiNi 0.5 Mn 1.45 Co 0.05The ratio of O4 is to weigh LiOH (98%, Macklin brand), nano-NiO (99.5%, Macklin brand), MnO2 (99.0%, Macklin brand) and Co2O2 (99.7%, Macklin brand), and an additional 5% lithium source by mass (5% excess lithium source) is added to compensate for lithium loss during calcination. Ethanol is added to the mixture, which is then transferred to a nylon ball milling jar and milled in a planetary ball mill (YXQM-2L, 500-600 revolutions per minute) for 6 hours. The ball-milled sample is vacuum dried at 80 °C for 12 hours and then milled in a mortar for 20 minutes to obtain a dry precursor powder. Subsequently, the mixture is transferred to a muffle furnace, heated to 500 °C at a rate of 3 °C per minute, and held at this temperature for 5 hours for pre-sintering. Then, it is further heated to 900 °C at the same rate and held for 10 hours. After cooling, cobalt-doped LNMO powder (active material) is obtained, labeled Mn-1Co, Mn-3Co, and Mn-5Co respectively. For comparison, undoped LNMO powder is also prepared using the same procedure. The prepared doped and undoped LNMO, conductive agent (Super-P), and polymer binder (polyvinylidene fluoride, PVDF) are mixed into a slurry in a weight ratio of 8:1:1. The slurry is coated on carbon-coated aluminum foil to make an electrode, and the resulting electrode is dried in a vacuum oven at 120 °C for 12 hours and then cut into 12-mm circular pieces as working electrodes. A CR2032 coin cell uses metallic lithium as the reference electrode and counter electrode. The battery is assembled in a glove box filled with argon, and an electrolyte is used that consists of 1.2 M LiPF6 (0.3 mL) dissolved in a solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixed in a volume ratio of 3:7.

[0032] X-ray diffraction (XRD; Bruker D8 Advance) technology is used, with a scanning rate of 10° per minute, in the 2θ range from 10° to 80°, using Cu Kα radiation The crystal structures of LNMO and cobalt-doped samples were analyzed. The XRD data were further refined using GSAS II software. Raman spectrometer (Horiba LabRAM HR Evolution) with a laser wavelength of 455 nm, Fourier transform infrared (FT-IR; Nicolet 670) spectrometer, and X-ray photoelectron spectrometer (XPS; ESCALab 250, Thermo VG) with C-C bond calibration at 284.8 eV were used to analyze the crystal structure, molecular structure, and elemental composition, respectively. Scanning electron microscope (SEM, ZEISS Gemini 300) and high-resolution transmission electron microscope (HRTEM, FEI Talos F200x) were used to examine the morphology and microstructure of the materials, and the lattice fringe was used to determine the unit cell volume change parameter.

[0033] Table 1: Lattice parameters, unit cell volume, and (111) plane spacing calculated by Rietveld refinement analysis

[0034]

[0035] Figure 1 The X-ray diffraction (XRD) patterns of the pristine LNMO sample and cobalt-doped LNMO samples (Mn-1Co, Mn-3Co, and Mn-5Co) are shown. The main diffraction peaks of all samples are consistent with the standard JCPDS card number 80-2162. It can be inferred that the spinel structure of these four samples is mainly represented by the Fd-3m space group rather than the P4332 space group, and cobalt doping does not change the main crystal structure of LNMO. With the incorporation of cobalt, the (111) diffraction peak begins to shift towards lower angles, which can be attributed to the successful incorporation of Co 3+ into the spinel lattice, indicating lattice expansion. When the calcination temperature exceeds 700 °C, the spinel cathode material will undergo thermal decomposition, resulting in oxygen loss and the formation of oxygen vacancies. This will lead to the appearance of Li x Ni 1-x O impurity phase (marked with ). It can be observed from the enlarged view that Li x Ni 1-x O impurity phase exists in all samples, and the impurity phase content of the Mn-3Co sample is the lowest. The X-ray diffraction (XRD) data were refined using GSAS II software, and Figure 1 shows the Rietveld refinement patterns of all samples. In addition, the lattice parameters and unit cell volume of all samples were obtained through Rietveld refinement of GSAS II software, as shown in Table 1. The lattice parameters of the samples are and It can be concluded that Co 3+ was successfully incorporated into the lattice, and with the increase of Co3+ With the increase in concentration, the lattice parameter increases, resulting in lattice expansion. The increase in the lattice parameter will expand the three-dimensional diffusion channels of Li + , thereby improving the ion diffusion rate.

[0036] To further explore the change in the space group of the material, Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy techniques were used to examine the space group arrangements of LNMO, Mn-1Co, Mn-3Co, and Mn-5Co samples, as Figure 2 shown. These four samples showed five infrared absorption peaks at 623 cm -1 , 584 cm -1 , 554 cm -1 , 503 cm -1 , and 471 cm -1 , indicating that these four samples mainly adopt the Fd-3m space group. In addition, the intensity ratio of the absorption peaks at 623 cm -1 and 584 cm -1 in the FT-IR spectrum can be used as an indicator of the content of the disordered phase in LNMO, where a higher I(623) / I(584) ratio indicates a higher proportion of the disordered phase. The figure clearly shows that the Mn-3Co sample has the highest I(623) / I(584) ratio, suggesting a higher content of the disordered phase. Generally speaking, since the electronegativity of cobalt is higher than that of manganese, the bond energy of the Co-O bond is stronger than that of the Mn-O bond, so the Co-O bond is more stable. Therefore, the introduction of Co 3+ effectively inhibits the oxygen escape in the matrix material during the cycling process, thereby improving the cycling stability and rate performance. The Raman spectra of all samples are shown in Fig. 2(b). The Raman peak at 635 cm -1 corresponds to the symmetric Mn-O vibration of the MnO6 octahedron, while the characteristic peak at 497 cm -1 corresponds to the stretching vibration of the Ni-O bond. These two characteristic peaks are related to the Fd-3m space group. In contrast, the Raman peaks at 167 cm -1 , 226 cm -1 , 396 cm -1 , and 595 cm -1 correspond to the P4332 space group. Therefore, all samples contain both ordered and disordered phases. The characteristic peaks at 167 cm -1 and 396 cm -1 indicate that the Mn-3Co sample has the highest content of the disordered phase, which is consistent with the FT-IR results.

[0037] The surface morphologies of all materials were characterized by scanning electron microscopy (SEM), and the influence of the introduction of Co 3+ on the morphology was analyzed, as Figure 3。The particle morphologies before and after doping are generally similar, and all samples exhibit a regular octahedral structure, confirming the successful synthesis of the spinel-type lithium nickel manganese oxide cathode material. The spinel structure has sharp and clear edges, indicating that the LNMO, Mn-1Co, Mn-3Co, and Mn-5Co samples all have high crystallinity, which is beneficial to the structural stability of the material. In addition, small crystal particles were detected on the surface of the samples, which may have been generated during the calcination process. Given that these materials were prepared by the traditional solid-state method, some particles may not have fully grown during the calcination process and subsequently adhered to the spinel surface.

[0038] X-ray photoelectron spectroscopy (XPS) measurements were further used to study the surface elemental composition and valence states of LNMO and its modified samples, Figure 4 showing the XPS spectra of all samples. The six peaks observed at 855.08 eV, 780.1 eV, 643.08 eV, 530.08 eV, 285.12 eV, and 51.23 eV correspond to Ni 2p, Co 3d, Mn 2p, O 1s, C 1s, and Li 1s, respectively. In the LNMO, Mn-1Co, Mn-3Co, and Mn-5Co samples, the ratio of Mn 4+ / Mn 3+ is 60.93% / 39.07%, 43.04% / 56.96%, 33.77% / 66.23%, and 31.78% / 68.22%, respectively. This figure indicates that as the Co content increases, the Mn 3+ content gradually increases. An appropriate amount of Mn 3+ can improve the ionic conductivity of the LiNi0.5Mn1.5O4 cathode material. According to relevant reports, the content of the disordered phase increases with the increase of Mn 3+ , which is consistent with the previous Fourier transform infrared spectroscopy (FT-IR) and Raman analysis results.

[0039] Table II: Anode Peak and cathode Potential difference (D value) between peaks

[0040]

[0041] Cyclic voltammetry is often used to study the redox process on the electrode, such as Figure 5As shown. We calculated the D values of LNMO, Mn-1Co, Mn-3Co, and Mn-5Co samples, which are 0.147, 0.119, 0.100, and 0.162 respectively, as shown in Table II. Among them, the Mn-3Co sample has the lowest D value, corresponding to the smallest electrochemical polarization, indicating that Mn-3Co has the best cycling stability. Charge-discharge tests were carried out on the four samples at different rates (0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C), and the results are as Figure 5 shown. Among them, Mn-3Co exhibits excellent rate performance. At a high current rate of 20C, the discharge capacity of the Mn-3Co sample is 85.15 mAh g -1 , and the capacity retention rate is 67.12%, while the discharge capacity of LNMO is 64.53 mAh g -1 , and the capacity retention rate is 54.87%. In addition, it was observed that when the discharge current returned to 1C, the discharge capacities of all four samples almost recovered to the initial values, indicating that they have good structural stability and reversibility. The above results can be attributed to: (1) the increase in Mn 3+ concentration enhances the disorder of the LNMO material, thus improving the ionic conductivity; (2) the incorporation of Co 3+ into the lattice expands the unit cell, thus increasing the diffusion rate of Li + .

[0042] Table III Long-cycle data of all samples

[0043]

[0044] Long-cycle charge-discharge tests are an important method for evaluating battery performance. Figure 6 shows the long-cycle performance curves of all samples, and Table III lists the capacity and capacity retention rate of each sample before and after cycling. The figure shows that the initial discharge capacities of LNMO, Mn-1Co, Mn-3Co, and Mn-5Co are 118.54 mAh g -1 , 122.26 mAh g -1 , 128.61 mAh g -1 and 107.27 mAh g -1 respectively. After 500 cycles at a rate of 1C, the capacities are 91.63 mAh g -1 , 101.89 mAh g -1 , 114.46 mAh g -1 and 87.42 mAh g -1 respectively, and the capacity retention rates are 77.30%, 83.34%, 89.00%, and 81.49% respectively. Therefore, Co 3+The introduction of [X] improves the structural stability of the material. After 500 cycles, the Mn-3Co sample exhibits the highest capacity and capacity retention rate. This can be attributed to Co 3+ The introduction of [X] enhances the disorder of the material, thereby improving the ionic conductivity. In addition, the increase in the unit cell volume also expands the diffusion channels of Li + .

[0045] At a 5C rate and 60 °C high temperature, the discharge specific capacity and capacity retention rate of the four samples after 150 cycles were compared, as Figure 7 shown. After 150 cycles, the discharge specific capacity of the LNMO sample remained at 12.83 mAh g -1 (capacity retention rate of 11.11%), while the Mn-3Co sample exhibited a significantly higher discharge specific capacity of 110.31 mAh g -1 (capacity retention rate of 88.51%), confirming its superior high-temperature performance. The capacity of the LNMO sample decreased sharply at high temperature, which was due to the degradation of the crystal structure of the material leading to structural collapse. In contrast, Mn-3Co maintained a stable capacity at high temperature. This can be attributed to the increased disorder, which stabilized the structure and prevented its collapse. In addition, the Co-O bond is less likely to break at high temperature, contributing to enhanced structural stability and thus improved high-temperature performance. Figures 7(b, c) show the charge-discharge curves of the LNMO and Mn-3Co samples at high temperature, further confirming the superior high-temperature performance of Mn-3Co. Figure 7 (d)-(g') of [X] shows the scanning electron microscope (SEM) images of the four samples after high-temperature cycling. The observed flocculent substance has been identified as the conductive agent Super-P. The surface of the LNMO sample is severely corroded, accompanied by the formation of a large amount of by-products, resulting in the destruction of the spinel structure. In contrast, the Mn-3Co sample has clear edges, a smooth surface, and a complete visible spinel structure, indicating its superior high-temperature cycling stability.

[0046] The Nyquist plots of the four samples are composed of a semicircle and a straight line: the semicircle corresponds to the high-frequency region and represents the interfacial impedance between the material and the electrolyte; while the straight line in the low-frequency region represents the Warburg impedance, Figure 8 and the equivalent circuit diagram is shown in the lower right corner. The charge transfer resistances (Rct) of LNMO, Mn-1Co, Mn-3Co, and Mn-5Co are 329.50 Ω, 271.10 Ω, 40.84 Ω, and 116.30 Ω, respectively. The results show that there are significant interfacial side reactions in the LNMO sample, resulting in a higher impedance, while the interfacial impedance of Mn-3Co is smaller. This improvement can be attributed to the introduction of Co 3+ , which not only expands the unit cell but also broadens the diffusion channels of Li +In addition, the increase in disorder also helps to improve ionic conductivity.

[0047] Example 2

[0048] According to the stoichiometry, LiNi 0.5 Mn 1.47 Co 0.03 Lithium chloride, nano-NiO (99.5%, McLean brand), manganese nitrate (99.0%) and Co2O3 (99.7%, McLean brand) were weighed in a ratio of 1:1 and 2:1, and an additional 5% lithium source (5% excess lithium source) was added by mass to compensate for the loss of lithium during calcination. Ethanol was added to the mixture, which was then transferred to a nylon ball mill and ground in a planetary ball mill (YXQM-2L, 500-600 rpm) for 7 hours. The ball-milled sample was vacuum dried at 80°C for 12 hours and then ground in a mortar for 20 minutes to obtain a dry precursor powder. Next, the mixture was transferred to a muffle furnace, heated to 500°C at a rate of 3°C / min, and kept at this temperature for 6 hours for pre-sintering. Thereafter, it was further heated to 900°C at the same rate and kept for 12 hours. After cooling, cobalt-doped LNMO powder (active material) was obtained.

[0049] The present invention is not limited to the above embodiments, and the lithium source is also selected from at least one of lithium sulfate, lithium nitrate and lithium acetate. The manganese source is selected from one of manganese dioxide, manganese sulfate, manganese nitrate, manganese oxalate and manganese acetate. The prepared product has the same effect. It can be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purpose of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A kind of Co 3+ Doped nickel-manganese-oxide binary positive electrode material, characterized in that: Molecular formula: LiNi 0.5 Mn 1.5-x Co x O4, x is 0.01-0.

05.

2. According to claim 1, Co 3+ Doped nickel-manganese-oxide binary positive electrode material, characterized in that: The x is 0.

03.

3. A Co according to any one of claims 1 to 2 3+ The method for preparing a doped nickel-manganese-oxide binary positive electrode material is characterized in that: Prepared as follows: (1) adding a lithium source, a nickel source, a manganese source and a cobalt source into a ball mill according to a stoichiometric ratio, wherein the amount of the lithium source added is excessive, adding ethanol, ball milling, and drying the sample after ball milling; (2) grinding the ball-milled powder in a mortar to obtain a precursor powder; (3) The precursor powder is transferred to a muffle furnace, heated to 500° C., and pre-sintered at this temperature. Subsequently, the temperature is raised to 900° C. and sintered. After the sintering is completed, the powder is cooled to room temperature to obtain a cobalt-doped lithium nickel manganese oxide binary positive electrode material.

4. According to claim 3, Co 3+ The preparation method of doped nickel manganese oxide binary positive electrode material is characterized by: The lithium source is selected from at least one of lithium hydroxide, lithium chloride, lithium sulfate, lithium nitrate and lithium acetate.

5. Co according to claim 4 3+ The preparation method of doped nickel manganese oxide binary positive electrode material is characterized by: The manganese source is selected from one of manganese dioxide, manganese sulfate, manganese nitrate, manganese oxalate and manganese acetate.

6. Co according to claim 5 3+ The method for preparing a doped nickel-manganese-oxide binary positive electrode material is characterized by: The nickel source is selected from nano nickel oxide.

7. The Co according to claim 6 3+ The method for preparing a doped nickel-manganese-oxide binary positive electrode material is characterized by: The cobalt source is selected from Co2O3.

8. Co according to any one of claims 3 to 7 3+ The method for preparing a doped nickel-manganese-oxide binary positive electrode material is characterized by: The lithium source is in excess of 5%.

9. Co according to claim 8 3+ The preparation method of doped nickel manganese oxide binary positive electrode material is characterized by: The ball milling speed is 500-600 rpm and the ball milling time is 6-7h.

10. The Co according to claim 9 3+ The preparation method of doped nickel manganese oxide binary positive electrode material is characterized by: In the muffle furnace, the heating rates of pre-sintering and sintering are both 3°C / min, the pre-sintering time is 5-6h, and the sintering time is 10-12h.

Images