CN108054443A - Water system sodium ion secondary battery - Google Patents

Abstract

The invention discloses a water system sodium ion secondary battery. The battery includes a positive electrode, a negative electrode, a diaphragm and an electrolyte, the active material of the positive electrode is Prussian blue compound Zn ₃ [Fe(CN) ₆ ] ₂ , the active material of the negative electrode is sodium titanium phosphate, and the solute of the electrolyte is sodium perchlorate and polyethylene glycol. The present invention not only maintains the advantage of high ion mobility in the aqueous electrolyte, but also greatly improves the stable working voltage window of the electrolyte and improves the stability of the electrode material by adding polyethylene glycol to the aqueous electrolyte. The aqueous sodium ion secondary battery of the present invention has electrochemical performance of high voltage, high rate and high stability, and the charging and discharging performance test is carried out under the current of 1C=60mA/g, the working voltage is 1.6V～1.65V, and the rate can be Reaching above 40C and hundreds of cycles, its coulombic efficiency is close to 100%, and its capacity retention rate is greater than 90%.

Description

Aqueous sodium ion secondary battery

technical field

The invention belongs to the technical field of batteries, and relates to a water-based sodium ion secondary battery.

Background technique

Aqueous ion batteries have attracted much attention due to their safety and promise of fast charging and discharging. Its working principle is similar to secondary lithium-ion batteries. Compared with the current organic secondary ion batteries, aqueous ion batteries have the advantages of low cost, high safety, environmental friendliness and high ion mobility.

Lithium-ion secondary batteries are widely used because of their high energy density and long service life, especially in high-tech electronic products such as notebook computers, mobile phones, and cameras, which promote the miniaturization of electronic equipment. However, because the organic solution is used as the electrolyte, the migration rate of ions is much lower than that of the aqueous electrolyte, which limits the rapid charge and discharge of the battery. In addition, organic electrolytes are generally poisonous and easy to burn at high temperatures, which brings great safety hazards to the environment and people. According to different ion types, aqueous ion secondary batteries can be divided into alkali metal ion batteries (Li ⁺ , Na ⁺ and K ^+, etc.) and high-valent metal ion batteries (Mg ²⁺ , Zn ²⁺ and Al ³⁺ , etc.). Due to the activity and charge density of high-valent metal ions, it is difficult to insert and extract them in electrode materials, and it is difficult to find suitable electrode materials. Therefore, current research is mainly on aqueous alkali metal ion batteries. Compared with aqueous lithium-ion batteries, aqueous sodium-ion batteries are expected to reduce costs due to their rich sodium resources (crust abundance 2.74%). For large-scale, stationary energy storage applications, aqueous sodium-ion batteries are considered to be an alternative to aqueous lithium batteries. Ion batteries are ideal candidates for next-generation energy storage power sources. Currently known aqueous sodium-ion batteries mainly include NaMn ₂ (CN) ₆ /Na ₂ CuFe(CN) ₆ (M.Pasta, etal.Commun.2014, 5, 3007), K _0.27 MnO ₂ /NaTi ₂ (PO ₄ ) ₃ (L.Yang, et al, AcsAppl.Mater.Interfaces.2016, 8, 14564-14571), Na ₃ MnTi(PO ₄ ) ₃ /Na ₃ MnTi(PO ₄ ) ₃ (H.Gao, JBGoodenough, Angew .Chem.Int.Ed.2016, 55, 12768-12772) and PPy/KCuFe(CN) ₆ (M.Pasta, et al.Commun.2012,3, 1149), etc. But they all have the problems of low working voltage (<1.5V) and short life.

Contents of the invention

The purpose of the present invention is to provide a water system sodium ion secondary battery with high working voltage, good rate and long cycle life.

The technical scheme that realizes the object of the present invention is as follows:

Aqueous sodium ion secondary battery, including positive pole, negative pole, diaphragm and electrolyte, the active material of the positive pole is Prussian blue compound Zn ₃ [Fe(CN) ₆ ] ₂ , the active material of the negative pole is sodium titanium phosphate , the solute of the electrolyte is sodium perchlorate and polyethylene glycol.

Preferably, the molar ratio of sodium perchlorate to polyethylene glycol is 5-7:2-4.

Preferably, the molar concentration of the sodium perchlorate is 9mol/L˜10mol/L.

The Prussian blue compound Zn ₃ [Fe(CN) ₆ ] ₂ , the active material of the positive electrode, is prepared by the following steps: first react sodium oxalate and zinc salt, after the reaction is completed, slowly add cyanide salt, wash and dry , that is, Zn ₃ [Fe(CN) ₆ ] ₂ .

The zinc salt is selected from ZnSO ₄ , Zn(NO ₃ ) ₂ or ZnCl ₂ , and the concentration is 0.06mol/L˜1mol/L.

The cyanide salt is selected from K ₃ [Fe(CN) ₆ ], Na ₃ [Fe(CN) ₆ ], K ₄ [Fe(CN) ₆ ] or Na ₄ [Fe(CN) ₆ ], most preferably It is K ₃ [Fe(CN) ₆ ], Na ₃ [Fe(CN) ₆ ], the concentration is 0.05mol/L～0.1mol/L.

The reaction time of the sodium oxalate and the zinc salt is 1.5 hours to 5 hours.

The reaction temperature is 25°C to 35°C.

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

(1) In the aqueous electrolyte, by adding polyethylene glycol, it not only maintains the advantages of high ion mobility in the aqueous electrolyte, but also greatly improves the stable working voltage window of the electrolyte; Stability also has a certain promotion effect;

(2) The aqueous sodium-ion secondary battery of the present invention has electrochemical properties of high voltage, high rate and high stability, and the charge and discharge performance test is carried out under the current of 1C=60mA/g, and the working voltage is 1.6V～1.65V , the rate can reach more than 40C and hundreds of cycles, its coulombic efficiency is close to 100%, and the capacity retention rate is greater than 90%.

Description of drawings

FIG. 1 is a scanning electron micrograph of Zn ₃ [Fe(CN) ₆ ] ₂ particles synthesized in Example 1.

Fig. 2 is a charge-discharge curve diagram of Zn ₃ [Fe(CN) ₆ ] ₂ synthesized in Example 1.

FIG. 3 is a graph of the rate performance of the aqueous secondary battery constructed in Example 1. FIG.

4 is a graph showing the relationship between cycle performance and Coulombic efficiency of the aqueous secondary battery constructed in Example 1.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings. Unless otherwise specified in the present invention, conventional methods well known in the art are adopted.

Example 1

Weigh 1.08g of zinc sulfate heptahydrate, 5.36g of sodium oxalate and 1.65g of potassium ferricyanide; they are successively prepared into aqueous solutions with a concentration of 0.075mol/L, 0.2mol/L and 0.005mol/L; zinc sulfate and oxalic acid The sodium aqueous solution is first added to deionized water, and after the reaction is complete, slowly add potassium ferricyanide aqueous solution, and after standing and aging for 2 hours, the reaction product can be obtained; then the obtained reaction product is repeatedly washed with deionized water for many times , and finally dried at 100°C for 12 hours to obtain Zn ₃ [Fe(CN) ₆ ] ₂ solid.

The prepared Zn ₃ [Fe(CN) ₆ ] ₂ solid is shown in Figure 1. From the scanning electron microscope, it can be seen that the ZnHCF particles have a cubic shape and good uniformity; the particle size distribution is uniform, and at 1 -2μm or so. In such highly crystalline particles, the migration of sodium ions and the stability of the material are more favorable.

Using N-methylpyrrolidone as a dispersant, mix and stir 0.8g of Zn ₃ [Fe(CN) ₆ ] ₂ prepared above, 0.1g of acetylene black and 0.1g of polyvinylidene fluoride evenly, and then coat it on a surface with a diameter of 1.3 cm circular titanium mesh, at 80 ℃, drying made zinc ferricyanide electrode sheet.

Using N-methylpyrrolidone as a dispersant, mix 0.8g of sodium titanium phosphate, 0.1g of acetylene black, and 0.1g of polyvinylidene fluoride prepared above, mix and stir evenly, and then coat them on a circular titanium mesh with a diameter of 1.3cm. Dry at 80°C to prepare sodium titanium phosphate electrode sheet.

The formula of the electrolyte: Weigh sodium perchlorate and polyethylene glycol (molar ratio is 5:2) into deionized water respectively, wherein the molar concentration of sodium perchlorate is 10mol/L, stir until it becomes colorless until clear liquid.

It can be seen from Figure 2 that the Zn ₃ [Fe(CN) ₆ ] ₂ material synthesized by the above method exhibited a higher voltage plateau (0.95V vs.Ag/AgCl) and a reversible capacity (66mAh/g ). It shows that Zn ₃ [Fe(CN) ₆ ] ₂ has excellent electrochemical performance.

The zinc ferricyanide electrode sheet prepared above is used as the positive electrode, the sodium titanium phosphate electrode sheet is used as the negative electrode, the aqueous solution of sodium perchlorate and polyethylene glycol is used as the electrolyte, and the glass fiber membrane is used as the diaphragm, and the water-based sodium ion di secondary battery.

The assembled aqueous sodium-ion secondary battery was charged and discharged at a constant current of 1C, and the working voltage of the battery was as high as 1.6V.

It can be seen from Figure 3 that the aqueous sodium-ion battery constructed in this way was tested at a rate up to 40C, and its capacity remained at about 75% of the 1C capacity, indicating that the aqueous battery has excellent rate performance.

It can be seen from Figure 4 that the aqueous sodium-ion secondary battery constructed in this way has a capacity retention rate of over 90% and a Coulombic efficiency close to 100% after 100 cycles of charging and discharging tests, indicating that the aqueous battery has good stability. .

Example 2

This example is basically the same as Example 1, except that the molar concentration of sodium perchlorate in the electrolyte is 9 mol/L, and a water-based sodium-ion battery is constructed by the method of Example 1. The assembled aqueous sodium-ion secondary battery was charged and discharged at a constant current of 1C, and the working voltage of the battery was as high as 1.6V. After 100 cycles of charging and discharging tests, the constructed aqueous sodium-ion secondary battery has a capacity retention rate of about 91%, and a Coulombic efficiency close to 100%, indicating that the aqueous battery has good stability. The constructed aqueous Na-ion battery was charged and discharged at a rate up to 40C, and its capacity remained above 74% of the 1C capacity, indicating that the aqueous battery has excellent rate performance.

Comparative example 1

This comparative example is basically the same as Example 1, except that there is no polyethylene glycol additive in the electrolyte, and a water-based sodium-ion battery is constructed by the method of Example 1. The working voltage of the assembled aqueous secondary battery is as high as about 1.6V. After 100 cycles of charging and discharging tests, the capacity retention rate is 74%, and the Coulombic efficiency is 96%. It can be seen from this comparative example that without the polyethylene glycol additive, the cycle performance of the battery has been greatly reduced.

Comparative example 2

This comparative example is the same as Example 1, except that the molar concentration of sodium perchlorate in the electrolyte is 5 mol/L, and a water-based sodium-ion battery is constructed by the method of Example 1. The operating voltage of the assembled aqueous secondary battery is as high as about 1.5V. After 100 cycles of charge and discharge tests, the capacity retention rate is 83%, and the Coulombic efficiency is 96%. It can be seen from this comparative example that in a high-concentration sodium ion electrolyte, it is beneficial to improve the voltage and cycle stability of the battery.

Comparative example 3

This comparative example is the same as Example 1, except that the molar concentration of sodium perchlorate is 12mol/L.

A water-based sodium-ion battery was constructed by the method of Example 1. The operating voltage of the assembled aqueous secondary battery is as high as about 1.6V; the charge and discharge test is carried out at a rate as high as 40C, and its capacity remains at 68% of the 1C capacity. It can be seen from this comparative example that in a higher concentration sodium ion electrolyte, it is not conducive to the migration of sodium ions, which reduces the rate performance of the battery.

Claims (8)

1. Aqueous sodium ion secondary battery, comprising positive pole, negative pole, diaphragm and electrolyte, it is characterized in that, the active material of described positive pole is Prussian blue compound Zn ₃ [Fe(CN) ₆ ] ₂ , the negative pole of described The active material is sodium titanium phosphate, and the solute of the electrolyte is sodium perchlorate and polyethylene glycol. 2. The aqueous sodium ion secondary battery according to claim 1, characterized in that the molar ratio of sodium perchlorate to polyethylene glycol is 5-7:2-4. 3 . The aqueous sodium ion secondary battery according to claim 1 , wherein the molar concentration of the sodium perchlorate is 9 mol/L˜10 mol/L. 4 . 4. Aqueous sodium-ion secondary battery according to claim 1, characterized in that, the active material Prussian blue compound Zn ₃ [Fe(CN) ₆ ] ₂ of the positive electrode is prepared by the following steps: first sodium oxalate React with zinc salt. After the reaction is over, slowly add cyanide salt, wash and dry to obtain Zn ₃ [Fe(CN) ₆ ] ₂ . 5. The aqueous sodium-ion secondary battery according to claim 1, wherein the zinc salt is selected from ZnSO ₄ , Zn(NO ₃ ) ₂ or ZnCl ₂ , with a concentration of 0.06mol/L-1mol/L . 6. The aqueous sodium ion secondary battery according to claim 1, wherein the cyanide salt is selected from K ₃ [Fe(CN) ₆ ], Na ₃ [Fe(CN) ₆ ], K ₄ [Fe(CN) ₆ ] or Na ₄ [Fe(CN) ₆ ], most preferably K ₃ [Fe(CN) ₆ ], Na ₃ [Fe(CN) ₆ ], the concentration is 0.05mol/L～0.1mol /L. 7 . The aqueous sodium ion secondary battery according to claim 1 , wherein the reaction time between the sodium oxalate and the zinc salt is 1.5 hours to 5 hours. 8 . The aqueous sodium ion secondary battery according to claim 1 , wherein the reaction temperature is 25° C. to 35° C.