High-capacity Mn-rich sodium ion battery positive electrode material and preparation method thereof

Abstract

The molecular formula of the positive electrode material is NaaMnxCuyO2, a is larger than or equal to 0.85 and smaller than or equal to 1.2, x is larger than or equal to 0.9 and smaller than or equal to 0.98, and y is larger than or equal to 0.02 and smaller than or equal to 0.1. The low-cost and high-capacity rich-Mn-based positive electrode material prepared by the method has the discharge capacity of 153.8 mAh / g within the interval of 2-4V, and 80.5% of the original capacity is kept by 50 cycles at the rate of 1C.

Description

Technical Field

[0001] The present invention relates to the field of cathode materials for sodium-ion batteries, and particularly to a high-capacity Mn-rich cathode material for sodium-ion batteries and a preparation method thereof. Background Art

[0002] At present, due to the uneven distribution of Li resources globally and the huge price fluctuations, the development of Li-ion batteries is restricted. Na resources are widely and evenly distributed in the earth's crust and are inexpensive, which makes sodium-ion batteries with the same energy storage mechanism a promising alternative to Li-ion batteries. Considering the characteristics of rich reserves of Mn sources in the earth's crust, stable market prices, and environmental friendliness, the development of high-capacity Mn-rich cathode materials for sodium-ion batteries has great market potential.

[0003] However, the current Mn-based cathode materials for sodium-ion batteries still have the disadvantages of low discharge capacity and low initial Coulombic efficiency. Summary of the Invention

[0004] To solve the above problems, the object of the present invention is to provide a preparation method of a high-capacity Mn-rich cathode material for sodium-ion batteries. Through the ingenious design of the cathode material and the synergistic effect of manganese ions and copper ions, the discharge capacity of the cathode material is improved, and the Na a Mn x Cu y O2 is in a stable β-phase structure, and the initial Coulombic efficiency is improved.

[0005] The present invention is achieved through the following technical solutions:

[0006] A high-capacity Mn-rich cathode material for sodium-ion batteries, the molecular formula of the cathode material is Na a Mn x Cu y O2, where 0.85 ≤ a ≤ 1.2, 0.9 ≤ x ≤ 0.98, 0.02 ≤ y ≤ 0.1. The low-cost, high-capacity Mn-rich cathode material prepared by the method of the present invention has a discharge capacity of 153.8 mAh / g in the 2-4V range and maintains 80.5% of the original capacity after 50 cycles at a 1C rate.

[0007] a = 1, 0.9 ≤ x ≤ 0.98, 0.02 ≤ y ≤ 0.05.

[0008] a = 1, x = 0.95, y = 0.05.

[0009] A cathode sheet is prepared from the cathode material as described above.

[0010] A battery includes the cathode sheet as described above.

[0011] A preparation method of a high-capacity Mn-rich sodium-ion battery cathode material, comprising the following steps: 1) Weigh the precursors of Na source, Mn source, and Cu source according to the molar ratio of each element in the chemical formula of the cathode material and mix them evenly, wherein the precursor of the Mn source is a compound with divalent to tetravalent manganese ions; 2) Grind, dry, and tablet the premixed powder obtained in step 1) and a solvent dispersant; 3) Presinter the sheet mixture obtained in step 2) to 400-600 °C and maintain the temperature for 4 hours; 4) On the basis of step 3), continue to heat up to 850-1000 °C for sintering and maintain the temperature for 14 hours, and then cool to room temperature with the furnace. The precursor of the Mn source is any one or more of manganese dioxide, manganese sesquioxide, manganese tetraoxide, manganese hydroxide, manganese carbonate, manganese acetate, and manganese nitrate.

[0012] The heating rate in step 3) is 2-10 °C / min, and the presintering temperature is 500 °C.

[0013] The sintering temperature in step 4) is 950 °C. The precursor of the sodium source is selected from one or more of sodium oxide, sodium hydroxide, sodium carbonate, sodium nitrate, and sodium oxalate; the precursor of the copper source includes one or more of copper oxide, cuprous oxide, copper hydroxide, copper nitrate, copper sulfate, or copper acetate. The precursor of the Mn source is a divalent compound of manganese ions or a divalent and trivalent mixed compound. Such as divalent MnCO3, trivalent and divalent mixed Mn3O4, etc. In the present invention, Na a Mn x Cu y The precursor of the O2 material is an important step, especially the main skeleton element Mn source. The oxidation of low-valent Mn during the sintering process is also the process of activating its electrochemical performance. In addition, the low-valent Mn source may form more lattice defects, oxygen vacancies, or Mn3+ ions during the sintering process, which is more helpful to improve the conductivity and ion mobility of the material in cooperation with copper ions. It more prominently shows the synergistic effect between manganese ions and copper ions.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0015] The cathode material prepared by the present invention has a high capacity and good cycle stability. In the potential range of 2-4V and at a 0.1C rate, a specific capacity of 153.8 mAh / g can be achieved, which is better than NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 which mainly uses Ni element to provide capacity at present, and has a greater cost advantage. The method adopted by the invention has strong process controllability and convenient precursor mixing. It is suitable for large-scale production of materials. Description of the Drawings

[0016] The accompanying drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0017] Figure 1 It is the XRD test pattern of the sodium manganate cathode material of Embodiment 1 of the present invention.

[0018] Figure 2 It is the SEM test pattern of the sodium manganate cathode material of Embodiment 1 of the present invention.

[0019] Figure 3 It is the charge-discharge curve of the sodium manganate cathode material of Embodiment 1 of the present invention. Detailed implementation manners

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with embodiments and the accompanying drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and do not limit the present invention.

[0021] Embodiment 1

[0022] 1) According to the stoichiometry of NaMn 0.95 Cu 0.05 O2, weigh Na2CO3, MnCO3, and CuO for premixing to obtain a premixed powder;

[0023] 2) Press the mixed powder obtained in step 1), where the pressure is 2000 Pa;

[0024] 3) Pre-sinter the sheet mixture obtained in step 2) in an air atmosphere to 500 °C and maintain the temperature for 4 hours.

[0025] 4) On the basis of step 3), continue to heat up to 950 °C for sintering, maintain the temperature for 14 hours, and then cool down to room temperature with the furnace.

[0026] Using the NaMn 0.95 Cu 0.05 O2 material prepared in this embodiment as the cathode, using metallic sodium as the anode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button battery, with a voltage range of 2 - 4V, select the rate mode for charge-discharge testing. At a rate of 0.1C, the discharge capacity of the cathode material is 153.8 mAh / g, and the initial Coulomb efficiency is 85.6%. Figure 1 Shows the XRD pattern of the sodium manganate cathode material of Embodiment 1 of the present invention. Figure 2 It is the SEM test pattern of the sodium manganate cathode material of Embodiment 1 of the present invention. Figure 3 It is the charge-discharge curve of the sodium manganate cathode material of Embodiment 1 of the present invention.

[0027] Example 2

[0028] According to the stoichiometry of NaMn 0.98 Cu 0.02 O2, weigh out Na2CO3, MnCO3, and CuO. The remaining steps are the same as those in Example 1. Using the material prepared in this example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button battery and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a rate of 0.1C, the discharge capacity of the positive electrode material is 148.2 mAh / g, and the initial Coulombic efficiency is 82.5%.

[0029] Example 3

[0030] According to the stoichiometry of NaMn 0.9 Cu 0.1 O2, weigh out Na2CO3, MnCO3, and CuO. The remaining steps are the same as those in Example 1. Using the material prepared in this example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button battery and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a rate of 0.1C, the discharge capacity of the positive electrode material is 141.3 mAh / g, and the initial Coulombic efficiency is 86.3%.

[0031] Example 4

[0032] According to the stoichiometry of NaMn 0.95 Cu 0.05 O2, weigh out Na2CO3, Mn3O4, and CuO. The remaining steps are the same as those in Example 1. Using the material prepared in this example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button battery and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a rate of 0.1C, the discharge capacity of the positive electrode material is 151.3 mAh / g, and the initial Coulombic efficiency is 84.7%.

[0033] Example 5

[0034] The difference from Example 1 is only that according to the stoichiometry of NaMn 0.95 Cu 0.05For the O2 stoichiometry, change the precursors in step 1) of Example 1 to Na2CO3, Mn2O3, and CuO. Using the material prepared in this example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button cell and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a 0.1C rate, the discharge capacity of the positive electrode material is 140.3 mAh / g, and the initial Coulombic efficiency is 83.2%.

[0035] Example 6

[0036] The difference from Example 1 is only that, according to the NaMn 0.95 Cu 0.05 O2 stoichiometry, change the precursors in step 4) of Example 1 to Na2CO3, MnO2, and CuO. Using the material prepared in this example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button cell and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a 0.1C rate, the discharge capacity of the positive electrode material is 137.2 mAh / g, and the initial Coulombic efficiency is 81.9%.

[0037] Comparative Example 1

[0038] The difference from Example 1 is only that, according to the NaMnO2 stoichiometry, weigh Na2CO3 and MnCO3 and perform steps 1) - 4) in Example 1. Using the material prepared in the comparative example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button cell and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a 0.1C rate, the discharge capacity of the positive electrode material is 132.6 mAh / g, and the initial Coulombic efficiency is 74.2%.

[0039] Comparative Example 2

[0040] The difference from Example 1 is only that, according to the NaMn 0.85 Cu 0.15O2 stoichiometry, change the precursors in step 4) of Example 1 to Na2CO3, NaMnO4, and CuO. Using the material prepared in the comparative example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button battery and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a rate of 0.1C, the discharge capacity of the positive electrode material is 127.5 mAh / g, and the initial Coulombic efficiency is 70.3%.

[0041] Comparative Example 3

[0042] The difference from Example 1 is only that, according to the NaMn 0.95 Cu 0.05 O2 stoichiometry, change the precursors in step 4) of Example 1 to Na2CO3, NaMnO4, and CuO. Using the material prepared in this example as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator, and a 1M NaClO4 PC / FEC (95:5 wt%) solution as the electrolyte, assemble a button battery and conduct charge-discharge tests. The voltage range is 2 - 4V. Select the rate mode for charge-discharge tests. At a rate of 0.1C, the discharge capacity of the positive electrode material is 102 mAh / g, and the initial Coulombic efficiency is 65.8%.

[0043] It can be seen from the above examples and comparative examples that the synergistic effect between manganese ions and copper ions (between the valence of manganese ions and the mass ratio relationship between manganese ions and copper ions) significantly improves the discharge capacity and also significantly improves the initial Coulombic efficiency.

[0044] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-capacity Mn-rich sodium ion battery positive electrode material, characterized in that: The molecular formula of the positive electrode material is Na a Mn x Cu y O2, where 0.85≤a≤1.2, 0.9≤x≤0.98, 0.02≤y≤0.

1.

2. The positive electrode material according to claim 1, characterized in that a=1, 0.9≤x≤0.98, 0.02≤y≤0.

05.

3. The positive electrode material according to claim 1, characterized in that a=1, x=0.95, y=0.

05.

4. A positive electrode sheet, characterized in that: Prepared according to the positive electrode material according to any one of claims 1 to 3.

5. A battery, characterized in that: Comprising the positive electrode sheet as claimed in claim 4.

6. The method for preparing a high-capacity Mn-rich sodium ion battery positive electrode material according to claim 1, characterized in that: The method comprises the following steps: 1) weighing the precursors of the Na source, the Mn source and the Cu source according to the molar ratio of each element in the chemical formula of the positive electrode material and mixing them uniformly, wherein the precursor of the manganese source is a compound in which the manganese ion is divalent to tetravalent; 2) grinding the premixed powder and the solvent dispersant obtained in step 1), drying and tableting; 3) pre-sintering the flaky mixture obtained in step 2) to 400-600° C. and maintaining the temperature for 4 hours; 4) continuing to heat up to 850-1000° C. for sintering on the basis of step 3), maintaining the temperature for 14 hours, and then cooling to room temperature with the furnace.

7. The preparation method according to claim 6, characterized in that: The heating rate in step 3) is 2-10°C / min, and the pre-sintering temperature is 500°C.

8. The preparation method according to claim 6, characterized in that: The sintering temperature in step 4) is 950°C.

9. The preparation method according to claim 6, characterized in that: The precursor of the sodium source is selected from one or more of sodium oxide, sodium hydroxide, sodium carbonate, sodium nitrate, and sodium oxalate; the precursor of the copper source includes one or more of cupric oxide, cuprous oxide, cupric hydroxide, cupric nitrate, cupric sulfate, or cupric acetate.

10. The preparation method according to claim 6, characterized in that: The precursor of the manganese source is a compound in which the manganese ion is divalent or divalent or trivalent.

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