CN113277843A

CN113277843A - Method for improving ionic conductivity of sodium-based solid electrolyte

Info

Publication number: CN113277843A
Application number: CN202110567120.XA
Authority: CN
Inventors: 乐士儒; 李昀隆; 迟大钊; 张乃庆; 温艳迪; 闫宝泽西
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2021-05-24
Filing date: 2021-05-24
Publication date: 2021-08-20

Abstract

The invention discloses a method for improving the ionic conductivity of a sodium-based solid electrolyte, which comprises the following steps: firstly, carrying out ball milling on sodium carbonate, ammonium dihydrogen phosphate, silicon dioxide, zirconium dioxide and magnesium oxide according to a required stoichiometric ratio; secondly, drying the mixture subjected to ball milling until the absolute ethyl alcohol is completely volatilized; grinding the dried powder, and then calcining to obtain precursor powder; fourthly, adding the calcined precursor powder into a sintering aid for ball milling; fifthly, drying the mixture after ball milling until the absolute ethyl alcohol is completely volatilized; sixthly, putting the dried powder into the containerPressing in a tablet press; seventhly, calcining the pressed wafer to obtain Na with improved ionic conductivity₃Zr₂Si₂PO₁₂A solid electrolyte sheet. In the method, a sintering aid Bi₂O₃Doping Na with magnesium ion₃Zr₂Si₂PO₁₂The solid electrolyte can obviously improve the ionic conductivity.

Description

Method for improving ionic conductivity of sodium-based solid electrolyte

Technical Field

The invention belongs to the field of sodium batteries in electrochemistry, and relates to a method for improving Na content₃Zr₂Si₂PO₁₂A method of ion conductivity based solid state electrolytes.

Background

Due to the rapid development of the electric automobile industry such as hybrid electric vehicles and electric vehicles, the demand for lithium ion batteries is increasing, and thus lithium resources are limited by price increases and resource shortages. Sodium Ion Batteries (SIBs) have made significant progress over the past few years and are at the edge of commercial applications. All-solid-state sodium batteries are ideal candidates for next-generation energy storage with exceptional safety, reliability and stability. The NASICON type solid electrolyte in the sodium ion battery has more advantages than other materials at present. The NASICON type material has a structure of Na_1+xZr₂Si_xP_3-xO₁₂(x is more than or equal to 0 and less than or equal to 3), has excellent ionic conductivity at room temperature, remarkable chemical stability and good thermal stability, and is one of the most potential solid electrolytes. Wherein Na₃Zr₂Si₂PO₁₂The ionic conductivity can reach 10 at room temperature^-4 S·cm^-1The conductivity can reach 10 at 300 DEG C^-1 S·cm^-1beta-Al at the same temperature₂O₃And (4) the equivalent. Therefore, most of the studies on modified NASICON materials were based on Na₃Zr₂Si₂PO₁₂. At present Na₃Zr₂Si₂PO₁₂The solid electrolyte can improve the conductivity of the solid electrolyte by: (1) changing the concentration of carriers by aliovalent substitution; (2) by taking with appropriate ionsDesigning the size of an ion transmission channel instead of skeleton ions; (3) the degree of densification of the ceramic is increased by adding a flux, and the grain boundary resistance is reduced.

CN110581312A discloses a high ionic conductivity solid electrolyte with NASICON structure, and preparation and application thereof, tin oxyfluoride can be used as a sintering additive of the sodium ion solid electrolyte with NASICON structure, but the patent does not mention that Bi can be used₂O₃The sodium ion solid electrolyte is used as a sintering aid of a sodium ion solid electrolyte with a NASICON structure. Article Na₃Zr₂(SiO₄)₂(PO₄) Preparation by A Solution-Assisted Solid State Reaction (-2017, 302: -83-91) mentions the use of Sc³⁺Doping with Na₃Zr₂Si₂PO₁₂Based on solid electrolytes, but Mg is not mentioned²⁺Doping with Na₃Zr₂Si₂PO₁₂Based on a solid electrolyte.

Disclosure of Invention

The invention aims to provide a method for improving the ionic conductivity of a sodium-based solid electrolyte, which adopts a sintering aid Bi₂O₃Doping Na with magnesium ion₃Zr₂Si₂PO₁₂The solid electrolyte can obviously improve the ionic conductivity.

The purpose of the invention is realized by the following technical scheme:

a method for improving the ionic conductivity of a sodium-based solid electrolyte comprises the following steps:

step one, anhydrous sodium carbonate powder, ammonium dihydrogen phosphate powder, silicon dioxide powder, zirconium dioxide powder and magnesium oxide powder are mixed according to the required stoichiometric ratio (Na)_3.6Zr_1.7Mg_0.3Si₂PO₁₂) Adding into a ball milling tank (NaCO is volatilized due to high temperature₃、NH₄H₂PO₄The raw materials need to be excessive by 10 percent), and then absolute ethyl alcohol and zirconia microspheres are added for ball milling, wherein: the ball milling speed is 400 revolutions per minute, and the time is 18-30 h;

and step two, drying the ball-milled mixture in a drying oven until the absolute ethyl alcohol is completely volatilized, wherein: the drying temperature is 80-100 ℃, and the drying time is 12-18 h;

step three, grinding the dried powder, then placing the powder into a muffle furnace for calcining, volatilizing the impurity N, H, C element in the powder in a gas form, and obtaining precursor powder Na_3+yMg_xZr_2-xSi₂PO₁₂(x = 0.1-0.6, y is more than or equal to 0.2 and less than or equal to 1.2), wherein: the temperature rise rate of calcination is 1-3 ℃/min, the calcination temperature is 800-1000 ℃, and the calcination time is 12-20 h;

step four, adding the calcined precursor powder into a sintering aid for ball milling, wherein: the ball milling time is 24-40 h, and the sintering aid is Bi₂O₃The content is 0 wt% -6 wt% of the precursor powder;

and step five, drying the ball-milled mixture in a drying oven until the absolute ethyl alcohol is completely volatilized, wherein: the drying temperature is 80-100 ℃, and the drying time is 12-20 h;

step six, putting the dried powder into a tablet press for pressing to prepare a wafer, wherein the specific pressing steps are as follows: (1) pressing for 5-10 min under the pressure of 10-15 MPa, and taking out and grinding; (2) pressing for 5-10 min at the pressure of 15-20 MPa to prepare a wafer;

step seven, calcining the pressed wafer in a muffle furnace to obtain Na with improved ionic conductivity₃Zr₂Si₂PO₁₂Solid electrolyte sheet (i.e., Na)_3+yMg_xZr_2-xSi₂PO₁₂(x is more than or equal to 0.1 and less than or equal to 0.6, and y is more than or equal to 0.2 and less than or equal to 1.2) a solid electrolyte sheet), wherein: the temperature rise rate of sintering is 1-3 ℃/min, the sintering temperature is 1150-1300 ℃, and the sintering time is 8-12 h.

Na produced by the above method_3+yMg_xZr_2-xSi₂PO₁₂(x is more than or equal to 0.1 and less than or equal to 0.6, and y is more than or equal to 0.2 and less than or equal to 1.2) the solid electrolyte sheet can be applied to a solid sodium battery, and the specific method is as follows: and (3) taking NZSP electrolyte and sodium metal (Na) as a working electrode and a counter electrode, dropwise adding 4 mu l of liquid electrolyte to wet an interface between the electrode and the solid electrolyte, and assembling the Na/NZSP/Na symmetrical battery. Then the battery is chargedConstant current charging and discharging are carried out. Alternately circulating with constant current charging for 0.5 h and constant current discharging for 0.5 h, and setting current density at 0.05mA cm^-2. At 0.05mA cm^-2Under the current density, the Na/NZSP/Na symmetrical battery runs very stably, the inside of the electrolyte still keeps intact after the battery runs stably for 1000 hours, and no short circuit occurs.

Compared with the prior art, the invention has the following advantages:

1. the invention relates to a sintering aid Bi₂O₃Doping Na with magnesium ion₃Zr₂Si₂PO₁₂Solid electrolyte, sintering at 1180 deg.C for 8 hr to obtain solid electrolyte sheet with improved ion conductivity when Mg²⁺The doping amount is 0.3 (Na)_3.6Zr_1.7Mg_0.3Si₂PO₁₂) And 5wt.% of Bi is added₂O₃The ionic conductivity of the composite electrolyte prepared by using the composite electrolyte as a sintering aid is 3.97 multiplied by 10^-4The S/cm is improved to 9.74 multiplied by 10^-4S/cm, about Na₃Zr₂Si₂PO₁₂2.45 times the ionic conductivity of the solid electrolyte.

2. The method is simple and effective, and can obtain Na with high ionic conductivity under the condition of low sintering temperature₃Zr₂Si₂PO₁₂The solid electrolyte saves energy, is suitable for large-scale popularization, meets the environmental protection requirement, has the characteristics of no toxicity and no pollution, and is suitable for the field of solid sodium batteries.

Drawings

FIG. 1 shows different Bi contents₂O₃Doping with Na₃Zr₂Si₂PO₁₂A posterior impedance profile;

FIG. 2 is a 5wt.% Bi doping₂O₃Front and rear Na₃Zr₂Si₂PO₁₂Scanning an electron microscope image;

FIG. 3 shows different Bi contents at room temperature₂O₃Doping with Na₃Zr₂Si₂PO₁₂The obtained density and ionic conductivity;

FIG. 4 shows different Bi contents₂O₃Doping with Na₃Zr₂Si₂PO₁₂The posterior arrhenius curve;

FIG. 5 shows different contents of Mg-doped Na₃Zr₂Si₂PO₁₂A posterior impedance profile;

FIG. 6 shows different contents of Mg-doped Na₃Zr₂Si₂PO₁₂The later ionic conductivity;

FIG. 7 is a Mg-doped Na₃Zr₂Si₂PO₁₂Analyzing the X-ray energy spectrum of the sample;

FIG. 8 is a modified Na doping₃Zr₂Si₂PO₁₂With undoped Na₃Zr₂Si₂PO₁₂An impedance map of (a);

fig. 9 is a charge and discharge diagram of a Na | NZNSP | Na symmetric cell doped with a modified NZSP electrolyte sheet.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings, but not limited thereto, and any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

The invention provides a method for increasing Na₃Zr₂Si₂PO₁₂A method of ion conductivity of a solid state electrolyte, the method comprising the steps of:

step one, anhydrous sodium carbonate powder, ammonium dihydrogen phosphate powder, silicon dioxide powder, zirconium dioxide powder and magnesium oxide powder are mixed according to the required stoichiometric ratio (Na)_3.6Zr_1.7Mg_0.3Si₂PO₁₂) Adding into a ball milling tank, adding absolute ethyl alcohol as a solvent, and wet-milling at the rotating speed of 400 r/min for 24 h.

And step two, drying the mixture after wet grinding in a drying oven at 80 ℃ for 12 h.

And step three, grinding the dried powder, then putting the powder into a muffle furnace, raising the temperature to 800 ℃ at the heating rate of 2 ℃/min, and calcining for 12 h.

Step four, calcining the precursorAdding sintering aid Bi into the powder in a ball milling tank₂O₃Wet milling was carried out for 24 h.

And step five, drying the mixture after wet grinding in a drying oven at 80 ℃ for 12 h.

Step six, putting the dried precursor powder into a tablet press for pressing to prepare a wafer, wherein the specific pressing step is as follows: (1) pressing under 10 MPa for 5 min, taking out, and grinding; (2) pressing under 15 MPa for 10min to obtain round sheet.

Step seven, calcining the pressed wafer in a muffle furnace, wherein the temperature rise rate of sintering is 2 ℃/min, the sintering temperature is 1180 ℃, and the sintering time is 8 h to obtain Na with enhanced ionic conductivity₃Zr₂Si₂PO₁₂A solid electrolyte wafer.

And step eight, assembling the Na/NZSP/Na symmetrical battery by using the NZSP electrolyte and sodium metal (Na) as a working electrode and a counter electrode. And then, carrying out constant current charging and discharging on the battery. Alternately circulating with constant current charging for 0.5 h and constant current discharging for 0.5 h, and setting current density at 0.03 mA cm^-2。

Results of the experiment

(1) Sintering aid Bi with different contents₂O₃Doping with Na₃Zr₂Si₂PO₁₂

Undoped Bi₂O₃When it is Na₃Zr₂Si₂PO₁₂Has an ionic conductivity of 4.07X 10^-4S/cm, the density is 82.1 percent, and the activation energy of Arrhenius is 0.36 eV;

1wt.%Bi₂O₃doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity was 5.27X 10^-4S/cm, the density is 83.8 percent, and the activation energy of Arrhenius is 0.34 eV;

2wt.%Bi₂O₃doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity was 5.77X 10^-4S/cm, the density is 86.2 percent, and the activation energy of Arrhenius is 0.34 eV;

3wt.%Bi₂O₃doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity was 6.53X 10^-4S/cm, the density is 87.4 percent, and the activation energy of Arrhenius is 0.3328 eV;

4wt.%Bi₂O₃doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity was 6.86X 10^-4S/cm, the density is 89.2%, and the activation energy of Arrhenius is 0.31 eV;

5wt.%Bi₂O₃doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity was 7.27X 10^-4S/cm, the density is 90.5%, and the activation energy of Arrhenius is 0.3022 eV;

6wt.%Bi₂O₃doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity was 6.59X 10^-4S/cm, the density is 88.4 percent, and the activation energy of Arrhenius is 0.31 eV.

In total, 5wt.% Bi₂O₃Doping with Na₃Zr₂Si₂PO₁₂The ionic conductivity is 7.27X 10 at most^-4S/cm, about undoped Bi₂O₃Na of (2)₃Zr₂Si₂PO₁₂1.8 times of the ionic conductivity, the highest density of 90.5 percent and undoped Bi₂O₃Na of (2)₃Zr₂Si₂PO₁₂Compared with the prior art, the compactness is improved by 8.4 percent.

(2) Different amounts of Mg doped with Na₃Zr₂Si₂PO₁₂Electrolyte (Na)_3+yMg_xZr_2-xSi₂PO₁₂（x=0.1、0.2、0.3、0.4、0.5、0.6））

Based on the above exploration on the optimal amount of the sintering aid doping, 5wt.% of Bi is directly selected₂O₃Doping with Na_3+yMg_xZr_2-xSi₂PO₁₂（x=0.1、0.2、0.3、0.4、0.5、0.6）。

x =0.1, i.e. Na_3.2Zr_1.9Mg_0.1Si₂PO₁₂The ionic conductivity was 8.15X 10^-4S/cm；

x =0.2, i.e. Na_3.4Zr_1.8Mg_0.2Si₂PO₁₂The ionic conductivity was 8.73X 10^-4S/cm；

x =0.3, i.e. Na_3.6Zr_1.7Mg_0.3Si₂PO₁₂The ionic conductivity was 9.74X 10^-4S/cm；

x =0.4, i.e. Na_3.8Zr_1.6Mg_0.4Si₂PO₁₂The ionic conductivity was 9.42X 10^-4S/cm；

x =0.5, i.e. Na₄Zr_1.5Mg_0.5Si₂PO₁₂The ionic conductivity was 8.60X 10^-4S/cm；

x =0.6, i.e. Na_4.2Zr_1.6Mg_0.6Si₂PO₁₂The ionic conductivity was 7.84X 10^-4S/cm。

Taken together, Bi was doped in an amount of 5wt.%₂O₃In combination with Mg²⁺When the doping amount of (A) is 0.3 (Na)_3.6Zr_1.7Mg_0.3Si₂PO₁₂) Has the highest ion conductivity, and is calculated to be 9.74 multiplied by 10^-4S/cm, about undoped pure phase Na₃Zr₂Si₂PO₁₂2.4 times (0.407 mS/cm).

Performance detection

FIG. 1 shows different Bi contents₂O₃Doping with Na₃Zr₂Si ₂PO ₁₂The impedance map of the following can be seen from the figure: sintering aid Bi₂O₃When the doping content is 5wt.%, Na₃Zr₂Si₂PO₁₂The total impedance of the electrolyte is minimal.

FIG. 2 is a 5wt.% Bi doping₂O₃Front and rear Na₃Zr₂Si₂PO₁₂Scanning electron microscope picture, from which can be seen: doping with 5wt.% Bi₂O₃The density of the electrolyte sheet is obviously increased.

FIG. 3 shows different Bi contents at room temperature₂O₃Doping with Na₃Zr₂Si₂PO₁₂The density and the ionic conductivity obtained after the above process are shown in the figure: the ion conductivity is approximately positively correlated with the relative compactness.

FIG. 4 shows different Bi contents₂O₃Doping with Na₃Zr₂Si₂PO₁₂The latter arrhenius curve, as can be seen from the figure: sintering aid Bi₂O₃At a doping level of 5wt.%, the slope is lowest, indicating that the activation energy of arrhenius is lowest.

FIG. 5 shows different contents of Mg-doped Na₃Zr₂Si₂PO₁₂The impedance map of the following can be seen from the figure: mg (magnesium)²⁺Na when the doping content is 0.3₃Zr₂Si₂PO₁₂The total impedance of the electrolyte is minimal.

FIG. 6 shows different contents of Mg-doped Na₃Zr₂Si₂PO₁₂The latter ionic conductivity, as can be seen from the figure: the ionic conductivity is up to 9.74X 10^-4S/cm。

FIG. 7 is a Mg-doped Na₃Zr₂Si ₂PO ₁₂Analysis of the X-ray spectra after the sample, it can be seen from the figure that: mg (magnesium)²⁺Uniformly doped with Na₃Zr₂Si₂PO₁₂In the electrolyte.

FIG. 8 is a modified Na doping₃Zr₂Si₂PO₁₂With undoped Na₃Zr₂Si₂PO₁₂The impedance spectrum of (2) can be seen from the figure: by the sintering aid Bi₂O₃With Mg²⁺Under the effect of co-doping, Na₃Zr₂Si₂PO₁₂The total resistance of the base electrolyte is significantly reduced.

Fig. 9 is a Na | NZNSP | Na symmetrical battery charge-discharge diagram doped with a modified NZSP electrolyte sheet, and 4 μ L of liquid electrolyte is added dropwise to wet the interface when the battery is mounted due to poor contact between the electrolyte and the electrode interface. As can be seen from the figure: at 0.03 mA cm^-2The operation of the symmetrical battery is very stable under the current density, the stable operation exceeds 1000 h, and no short circuit occurs.

Claims

1. A method for improving the ionic conductivity of a sodium-based solid electrolyte, characterized in that the method comprises the following steps:

adding anhydrous sodium carbonate powder, ammonium dihydrogen phosphate powder, silicon dioxide powder, zirconium dioxide powder and magnesium oxide powder into a ball-milling tank according to a required stoichiometric ratio, and then adding anhydrous ethanol and zirconium oxide microspheres for ball milling;

step two, drying the ball-milled mixture in a drying oven until the absolute ethyl alcohol is completely volatilized;

grinding the dried powder, and then putting the ground powder into a muffle furnace for calcining to obtain precursor powder;

step four, adding the calcined precursor powder into a sintering aid for ball milling;

step five, drying the ball-milled mixture in a drying oven until the absolute ethyl alcohol is completely volatilized;

sixthly, putting the dried powder into a tablet press for pressing to prepare a wafer;

step seven, calcining the pressed wafer in a muffle furnace to obtain Na_3+yMg_xZr_2-xSi₂PO₁₂A solid electrolyte sheet, wherein: x is more than or equal to 0.1 and less than or equal to 0.6, and y is more than or equal to 0.2 and less than or equal to 1.2.

2. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the first step, the ball milling rotation speed is 400 rpm, and the time is 18-30 h.

3. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the second step, the drying temperature is 80-100 ℃ and the drying time is 12-18 h.

4. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the third step, the temperature rise rate of calcination is 1-3 ℃/min, the calcination temperature is 800-1000 ℃, and the calcination time is 12-20 h.

5. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the fourth step, the ball milling time is 24-40 h; the sintering aid is Bi₂O₃And adding the precursor powder in an amount of 0-6 wt.%.

6. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the fifth step, the drying temperature is 80-100 ℃ and the drying time is 12-20 hours.

7. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the sixth step, the specific pressing step is as follows: (1) pressing for 5-10 min under the pressure of 10-15 Mpa, and taking out and grinding; (2) pressing the mixture for 5 to 10min under the pressure of 15 to 20 MPa to prepare the wafer.

8. The method for improving the ionic conductivity of the sodium-based solid electrolyte according to claim 1, wherein in the seventh step, the temperature rise rate of sintering is 1-3 ℃/min, the sintering temperature is 1150-1300 ℃, and the sintering time is 8-12 h.

9. Na produced by the process of any one of claims 1 to 8_3+yMg_xZr_2-xSi₂PO₁₂A solid electrolyte sheet.

10. Na produced by the process of any one of claims 1 to 9_3+yMg_xZr_2-xSi₂PO₁₂Use of a solid electrolyte sheet in a solid sodium cell.