Preparation method of double-element anion-cation doped sodium ion battery layered oxide

Abstract

The invention discloses a preparation method of a double-element anion-cation doped sodium ion battery layered oxide. The chemical formula of the positive electrode material is NaxMnyMzO2-nQ2n, x is more than or equal to 0.67 and less than or equal to 1, and y + z is equal to 1, 0lt; n is less than or equal to 0.5, the metal cation M is Cu, Zn, Cr or Zr, and the halogen anion Q is F, Cl, Br or I. The preparation method comprises the following steps: preparing a sodium-ion battery precursor MnyMz (OH) 2 by adopting a precursor preparation process, then uniformly mixing a sodium source, halogen sodium salt and the precursor under the action of sol-gel, and finally synthesizing the halogen anion doped sodium-ion battery positive electrode material by adopting a high-temperature solid-phase method. The first coulombic efficiency of the sodium ion battery is improved by doping halogen anions, the influence of structural collapse and capacity fading caused by a Jahn-Taller effect is reduced, and the structural stability and electrochemical performance of the positive electrode material are improved. The preparation method is simple and low in cost, and a new idea is provided for preparation of the sodium ion battery positive electrode material.

Claims

1. A dual-element anion and cation doped layered oxide for sodium ion batteries, characterized in that: The chemical formula of the positive electrode material is Na x Mn y M z O 2-n Q 2n , where 0.67 ≤ x ≤ 1, y + z = 1, 0 < n ≤ 0.5, the metal cation M is Cu, Zn, Cr or Zr, and the halogen anion Q is F, Cl, Br or I.

2. A method for preparing a dual-element anion-cation doped sodium ion battery layered oxide according to claim 1, characterized in that: The following steps are included: (1) Sodium ion battery precursor Mn y M z Preparation of (OH)2: a. A certain molar ratio of Mn and M soluble salts is mixed uniformly in pure water as a mixed salt solution A, and a certain concentration of a precipitant NaOH solution and a complexing agent NH3·H2O solution is prepared; b. Add the prepared mixed salt solution A, NaOH solution and NH3·H2O solution into the reactor and stir continuously to carry out coprecipitation reaction. After a period of reaction, a solid-liquid mixed slurry is obtained. The slurry is washed, filtered, dried and other steps to obtain Mn y M z (OH)2 coprecipitated particles; (2) Preparation of halogen anion-doped layered oxides for sodium ion batteries: a. Add a soluble sodium source, a sodium halogen salt and the resulting precursor Mn into deionized water in a certain proportion. y M z (OH)2 co-precipitated particles, while adding sol-gel materials, stirring continuously at a certain temperature to make the raw materials evenly distributed to form a sol; b. Drying the sol under certain conditions to form a dry gel, and then calcining the dry gel under specific conditions to melt the halogen elements into a halogen anion-doped sodium ion battery layered oxide.

3. The method for preparing a dual-element anion-cation doped sodium ion battery layered oxide according to claim 2, characterized in that: The step (1) of preparing the sodium ion battery precursor Mn y M z In the preparation of (OH)2, Mn comes from manganese sulfate; the concentration of the soluble salts of Mn and M in the mixed salt solution A is 2-16 mol / L and the concentration ratio of the two is 1:1, the concentration of the precipitant NaOH solution is 2-20 mol / L, and the concentration of the complexing agent NH3·H2O solution is 6-30 mol / L.

4. The method for preparing a dual-element anion-cation doped sodium ion battery layered oxide according to claim 2, characterized in that: The step (1) of preparing the sodium ion battery precursor Mn y M z In the preparation of (OH)2, the stirring speed is 400-800 rpm / min, the pH value of the reaction liquid of the coprecipitation reaction is 8.8-13.9, the ammonia value is 10-26 g / L, the reaction temperature is 50-100°C, and argon or nitrogen is continuously introduced during the reaction.

5. The method for preparing a dual-element anion-cation doped sodium ion battery layered oxide according to claim 2, characterized in that: In the step (2) of preparing the halogen anion-doped sodium ion battery layered oxide, the sol-gel material is citric acid, and the amount of citric acid added is 1-5 times the amount of the positive electrode material. The soluble sodium source is one or more of sodium carbonate, sodium bicarbonate, and sodium oxalate. The amount of sodium element in the soluble sodium source is 1.01 to 1.10 times that of the precursor. The halogen sodium salt is one or more of sodium fluoride and sodium bromide.

6. The method for preparing a dual-element anion-cation doped sodium ion battery layered oxide according to claim 2, characterized in that: In the step (2) of preparing the halogen anion-doped sodium ion battery layered oxide, the preparation temperature of the sol is 75-95° C., the drying temperature of the dry gel is 100-150° C., and the drying time is 12-15 hours.

7. The method for preparing a dual-element anion-cation doped sodium ion battery layered oxide according to claim 2, characterized in that: In the preparation of the halogen anion-doped sodium ion battery layered oxide in step (2), the calcination conditions are calcination at 300-450° C. for 4-8 hours, then calcination at 700-1000° C. for 10-24 hours, and finally cooling to room temperature to obtain the halogen anion-doped sodium ion battery layered oxide.

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