阅读说明：本技术 钠离子电池用单斜结构正极材料及其制备方法 (Monoclinic structure positive electrode material for sodium-ion battery and preparation method thereof ) 是由 夏晖 朱晓辉 薛亮 郭秋卜 杨梅 于 2018-06-13 设计创作，主要内容包括：本发明公开了一种钠离子电池正极材料及其制备方法,以Mn<Sub>3</Sub>O<Sub>4</Sub>材料为前躯体材料,将其置于钠源水溶液中进行两步水热反应,得到产物经热处理后得到具有单斜结构的NaMnO<Sub>2-y</Sub>(OH)<Sub>2y</Sub>或NaMnO<Sub>2-y-δ</Sub>(OH)<Sub>2y</Sub>材料。本发明公开的钠离子电池正极材料制备工艺简单,能耗较低,制备的钠离子正极材料的比容量、倍率性能、循环稳定性和首次库伦效率等均显示出优良的电化学性能。(The invention discloses a sodium ion battery anode material and a preparation method thereof, and Mn is used 3 O 4 The material is a precursor material, and is placed in a sodium source aqueous solution for two-step hydrothermal reaction to obtain a product, and the product is subjected to heat treatment to obtain NaMnO with a monoclinic structure 2‑y (OH) 2y Or NaMnO 2‑y‑δ (OH) 2y A material. The sodium ion battery anode material disclosed by the invention is simple in preparation process and low in energy consumption, and the prepared sodium ion anode material has excellent electrochemical properties such as specific capacity, rate capability, cycling stability and first coulombic efficiency.)

1. The monoclinic structure anode material is characterized in that the anode material is NaMnO_2-y(OH)_2y(I) The structural formula is as follows:

2. the monoclinic structure anode material is characterized in that the anode material is NaMnO_2-y-δ(OH)_2y(II) having the formula:

3. the method for preparing a monoclinic structure cathode material according to claim 1, characterized in that the method comprises the following steps:

adding Mn₃O₄The material is subjected to low-temperature reaction in a high-concentration sodium source water solution for 6-10 h, then subjected to high-temperature reaction in a low-concentration sodium source water solution for 8-12 h, cooled to room temperature, washed and dried in vacuum to obtain NaMnO_2-y(OH)_2y·nH₂O, and finally treating in the air for 2-12 h to obtain NaMnO with a monocline structure_2-y(OH)_2yAn electrode material.

4. The method for preparing a monoclinic structure cathode material according to claim 2, characterized in that the method comprises the following steps:

adding Mn₃O₄The material is subjected to low-temperature reaction in a high-concentration sodium source water solution for 6-10 h, then subjected to high-temperature reaction in a low-concentration sodium source water solution for 8-12 h, cooled to room temperature, washed and dried in vacuum to obtain NaMnO_2-y(OH)_2y·nH₂O, and finally treating in argon for 2-12 h to obtain NaMnO with an oxygen vacancy monoclinic structure_2-y-δ(OH)_2yAn electrode material.

5. The method according to claim 3 or 4, wherein Mn is present₃O₄The material adopts Mn₃O₄Powder material or Mn₃O₄A film material; wherein Mn is₃O₄The thin film material is Mn grown on a conductive substrate₃O₄The film or the nano array, and the conductive substrate material is stainless steel, Ti, Ni, Au and carbon material.

6. The process of claim 3 or 4, wherein the sodium source is selected from NaOH and NaHCO₃、NaCl、NaNO₃、Na₂SO₄、Na₂CO₃And CH₃COONa.

7. The method according to claim 3 or 4, wherein the molar concentration of sodium in the high-concentration sodium source aqueous solution is 2.0 to 4.0mol/L, and the molar concentration of sodium in the low-concentration sodium source aqueous solution is 0.5 to 1.5 mol/L.

8. The method according to claim 3 or 4, wherein the reaction temperature of the low-temperature reaction is 65 to 90 ℃ and the reaction temperature of the high-temperature reaction is 160 to 200 ℃.

9. The method according to claim 3 or 4, wherein the temperature of the heat treatment in the air atmosphere is 200-300 ℃; the heat treatment temperature under the argon atmosphere is 200-300 ℃.

10. Use of the monoclinic structure positive electrode material as defined in claim 1 or 2 as a positive electrode material for a sodium-ion battery.

Technical Field

The invention belongs to the field of battery materials, and particularly relates to a sodium-ion battery positive electrode material and a preparation method thereof.

Background

Compared with the positive electrode material of a sodium ion battery, such as NaFePO₄、NaCoO₂、Na₂FePO₄F、Na₃V₂(PO4)₃And NaCrO₂Etc. Na_xMnO₂The material has higher theoretical specific capacity, and simultaneously, the manganese element is taken as Na_xMnO₂One of the main raw materials has the advantages of low price, wide source and the like, so Na_xMnO₂The research on the positive electrode material has received a lot of attention, and most researchers will use Na_xMnO₂The research focus of the cathode material is mainly focused on O3-, tunnel (tunnel), and P2-type structures. However, O3-, tunnel-, and P2-Na have been reported so far_xMnO₂The positive electrode material has disadvantages in electrochemical performance. Such as O3-Na_xMnO₂The positive electrode material can provide higher discharge capacity (up to 197mAh/g, Ma XH, et al.J.electrochem.Soc.2011,158, A1307-A1312), but the crystal lattice structure is easy to distort and is converted into a spinel structure in the charge and discharge process due to the crystal structure of the positive electrode material, so that the capacity attenuation is easy to occur (Caballero A, et al.J.solid State chem.,2003,174, 365-); P2-Na_xMnO₂The positive electrode material has a stable structure and good cycling stability, but is difficult to show good rate performance; and tunnel-Na_xMnO₂The positive electrode material can show better cycling stability and rate performance (Cao YL, et al. adv. Mater.2011,23,3155-_xMnO₂The restriction of the content of the medium sodium element cannot exert a high discharge capacity. Therefore, a new synthesis method can be developed to prepare Na with high capacity, better rate capability and cycling stability_xMnO₂A positive electrode material is needed to be solved.

On the other hand, related studies show that: birnessite structured Na_xMnO₂The cathode material has good electrochemical performance, can be used as a cathode material of an aqueous sodium-ion battery (US2009025305A1) and can also be used as a cathode material of a non-aqueous sodium-ion battery (Guo SH, et al. ChemSusChem chem,2014,7,2115-2121), and can show good cycle stability and rate capability. Na of birnessite structure prepared at present_xMnO₂Presence of positive electrode materialThe prepared Birnesselite-Na has obvious defects_xMnO₂The content of sodium element in the material is low (x)<0.65)), which limits Birnessite-Na to a large extent_xMnO₂The capacity of the material is exerted. In addition, consider Birnessite-NaMnO₂The conductivity of the material is poor due to the crystal water between the middle layers, and the crystal water is removed in the charging and discharging process and then undergoes side reaction with the electrolyte, so that the Birnessite-NaMnO needs to be removed₂Crystal water in (1). Based on the related reports, if Birnessite-Na can be further improved_xMnO₂The content of Na in the product is equal to 1 to obtain Birnessite-NaMnO₂The Na storage performance of the composite material can be greatly improved, and the influence of crystal water is eliminated. Theoretically, the positive electrode material of the sodium-ion battery has higher capacity, better rate performance and cycling stability, and no relevant research report exists at present.

Disclosure of Invention

The invention aims to provide a monoclinic structure cathode material with high sodium content and a preparation method thereof.

The technical solution for realizing the purpose of the invention is as follows: the cathode material with the monoclinic structure is NaMnO_2-y(OH)_2y(I) Or NaMnO_2-y-δ(OH)_2y(II) having the following structural formulae:

the preparation method of the monoclinic structure cathode material comprises the step of adding Mn₃O₄The material is subjected to a two-step hydrothermal method and heat treatment in air to obtain NaMnO_2-y(OH)_2yThe material is subjected to heat treatment under argon to obtain NaMnO containing oxygen vacancies_2-y-δ(OH)_2yA material. The method comprises the following specific steps:

adding Mn₃O₄The material is subjected to low-temperature reaction in a high-concentration sodium source water solution for 6-10 h, then subjected to high-temperature reaction in a low-concentration sodium source water solution for 8-12 h, cooled to room temperature, washed and dried in vacuum to obtain NaMnO_2-y(OH)_2y·nH₂O, finally in airObtaining NaMnO with monoclinic structure after conditioning for 2-12 h_2-y(OH)_2yOr treating in argon for 2-12 h to obtain NaMnO with an oxygen vacancy monoclinic structure_2-y-δ(OH)_2yAn electrode material.

Preferably, the Mn is₃O₄The material adopts Mn₃O₄Powder material or Mn₃O₄A film material.

More preferably, the Mn is₃O₄The thin film material is Mn grown on a conductive substrate₃O₄The film or the nano array, and the conductive substrate material is stainless steel, Ti, Ni, Au and carbon material.

Preferably, the sodium source is selected from NaOH and NaHCO₃、NaCl、NaNO₃、Na₂SO₄、Na₂CO₃And CH₃COONa.

Preferably, the molar concentration of sodium in the high-concentration sodium source aqueous solution is 2.0-4.0 mol/L, and the molar concentration of sodium in the low-concentration sodium source aqueous solution is 0.5-1.5 mol/L.

Preferably, the reaction temperature of the low-temperature reaction is 65-90 ℃, and the reaction temperature of the high-temperature reaction is 160-200 ℃.

Preferably, the heat treatment temperature is 200-300 ℃ under the air or argon atmosphere, and the purpose of the treatment under the air or argon atmosphere is to remove NaMnO_2-y(OH)_2y·nH₂Crystal water in the O material improves the conductivity of the material.

NaMnO prepared by the invention_2-y-δ(OH)_2yThe electrode material has excellent charge and discharge performance and can be used as a positive electrode material of a sodium ion battery.

Compared with the prior art, the invention has the beneficial effects that:

(1) the method synthesizes Birnessite-NaMnO with high sodium content by a two-step hydrothermal method_2-y(OH)_2y·nH₂O electrode material, have reaction energy consumption advantage such as being lower; (2) adding Birnessite-NaMnO_2-y(OH)_2y·nH₂O material in air or argonAfter heat treatment in the atmosphere, Monoclinic-NaMnO was obtained_2-y(OH)_2yOr Monoclinic-NaMnO_2-y-δ(OH)_2yThe multiplying power performance is obviously improved; (3) the method is used for preparing Monoclinic-NaMnO_2-y-δ(OH)_2yThe capacity, the first coulombic efficiency, the rate capability, the cycling stability and other electrochemical properties of the electrode material show excellent performances.

Drawings

FIG. 1 shows Mn prepared in example 1 of the present invention₃O₄A/carbon cloth composite material (marked as S1), Birnessite-NaMnO_2-y(OH)_2y·nH₂O/carbon cloth composite (labeled S2) and argon heat treated Monoclinic-NaMnO_2-y-δ(OH)_2yRaman spectra of the/carbon cloth composite (labeled S3).

FIG. 2 shows Mn prepared in example 1 of the present invention₃O₄A/carbon cloth composite material (marked as S1), Birnessite-NaMnO_2-y(OH)_2y·nH₂O/carbon cloth composite material (S2) and Monoclinic-NaMnO treated by argon heat treatment_2-y-δ(OH)_2yX-ray diffraction pattern of the/carbon cloth composite (S3).

FIG. 3 is a Birnessite-NaMnO prepared in example 1 of the present invention_2-y(OH)_2y·nH₂And (3) a field emission scanning electron microscope image of the O/carbon cloth composite material.

FIG. 4 shows Mn prepared in example 1 of the present invention₃O₄/carbon cloth composite material (S1) and Birnessite-NaMnO_2-y(OH)_2y·nH₂O/carbon cloth composite material (S2) and Monoclinic-NaMnO treated by argon heat treatment_2-y-δ(OH)_2yAn X-ray photoelectron spectrum of the/carbon cloth composite material (S3).

FIG. 5 is a Birnessite-NaMnO prepared in example 1 of the present invention_2-y(OH)_2y·nH₂O/carbon cloth composite (S2, panel (A)) and Monoclinic-NaMnO treated with argon_2-y-δ(OH)_2yCharge and discharge curves of the/carbon cloth composite (S3, panel (B)) at 0.2C.

FIG. 6 (A) is Birnessite-NaMnO prepared in example 1 of the present invention_2-y(OH)_2y·nH₂O/carbon cloth composite material (S2) and Monoclinic-NaMnO treated by argon heat treatment_2-y-δ(OH)_2yA discharge capacity test result graph of the/carbon cloth composite material (S3) under different multiplying factors; FIG. B shows Birnessite-NaMnO prepared in example 1 of the present invention_2-y(OH)_2y·nH₂O/carbon cloth composite material (S2) and Monoclinic-NaMnO treated by argon heat treatment_2-y-δ(OH)_2yCycling performance profile of the/carbon cloth composite (S3) at 10C.

FIG. 7 is a Monoclinic-NaMnO solution after argon heat treatment in example 1 of the present invention_2-y-δ(OH)_2yX-ray photoelectron spectroscopy analysis curve of the/carbon cloth composite material (S3).

Detailed Description

The invention is further elucidated with reference to the figures and embodiments. But the content of the invention is not limited thereto.

【Mn₃O₄Preparation of thin film Material

Placing the conductive substrate in a mixed aqueous solution of manganese salt and inorganic sodium salt, and depositing Mn (OH) on the surface of the conductive substrate in a constant potential mode in situ₂Naturally drying the mixture in the air at normal temperature for 12-18 h, washing and then drying the mixture in vacuum to obtain Mn growing on a current collector₃O₄The constant potential deposition potential of the nanosheet array is-1.30 to-1.85V, the electrodeposition time is 5 to 15min, the ratio of the molar weight of manganese in the manganese salt to the molar weight of sodium in the inorganic sodium salt is 1:1-3, the manganese salt is selected from manganese acetate, manganese nitrate or manganese sulfate, and the inorganic sodium salt is selected from sodium sulfate or sodium nitrate. A current collector is used as a working electrode, an Ag/AgCl electrode is used as a reference electrode, a Pt electrode is used as a counter electrode, and a mixed aqueous solution of manganese salt and sodium salt is used as an electrolyte (Xia H, Nanosci. Nanotechnol. Lett.2012,4, 559-.

【Monoclinic-NaMnO_2-y(OH)_2yElectrochemical Performance testing of electrode materials

Firstly, the Monoclinic-NaMnO prepared by the invention_2-y(OH)_2yThe powder, superconducting carbon black (Super P) and polyacrylic acid (PAA) are mixed according to the mass ratio of 8: 1:1, dissolving in N-methylpyrrolidone (NMP) after uniform mixing, andcoating on the surface of an aluminum foil, and drying in a vacuum oven at 120 ℃ for 12h to obtain Monoclinic-NaMnO_2-y(OH)_2yA positive plate; ② the Monoclinic-NaMnO prepared by the invention_2-y(OH)_2yThe film material can be directly used as a positive electrode. Metallic sodium sheet as negative electrode, 1.0mol/L NaClO₄Propylene carbonate as an electrolyte, constituting a half cell in a glove box under an argon atmosphere, and examining Monoclinic-NaMnO of the present invention_2-y(OH)_2yThe capacity, rate capability, cycling stability and first coulombic efficiency of the electrode material are shown, and the test voltage range is 2.0-4.0V.