A preparation process of a halide blended peo-based electrolyte and its application in solid-state sodium batteries

Abstract

The application provides a preparation process of a halide blended PEO-based electrolyte and application thereof in a solid-state sodium battery; the process selects a polymer, a sodium salt and an inorganic halide additive as solutes, and deionized water as a solvent; compared with the prior art, the application introduces the inorganic halide additive into the PEO-based electrolyte, realizes the improvement of the rate performance and stability of the corresponding battery system through the regulation of the bulk phase aggregate structure and the construction of the interface stable layer, compared with the traditional non-homogeneous blending film preparation process, the application uses deionized water to replace the traditional organic solvent, realizes the effective dispersion of the inorganic halide additive in the electrolyte bulk phase through the homogeneous solution blending or in-situ precipitation blending process, improves the additive effect, greatly shortens the film preparation time, and reduces the pollution; the application is favorable for improving the electrode-electrolyte interface and improving the electrochemical performance of the all-solid-state sodium ion battery.

Description

TECHNICAL FIELD

[0001] The application relates to the field of sodium ion batteries, in particular to a preparation process of a halide blended PEO-based electrolyte and application of the halide blended PEO-based electrolyte in a solid-state sodium battery. BACKGROUND

[0002] The exhaustion of fossil energy promotes the continuous development of renewable clean energy such as wind energy, solar energy and geothermal energy, and it is urgent to develop a matching energy storage system. Among the many developed energy storage systems, electrochemical energy storage has the advantages of high efficiency and convenient maintenance, and therefore has the most potential. With the large-scale application of electric vehicles, the demand for lithium increases, while the reserves of lithium resources are limited and unevenly distributed in the earth's crust (about 70% of lithium is concentrated in the South American region). The price of lithium carbonate has risen from 40,000 yuan / ton at the beginning of 2015 to 160,000 yuan / ton at the beginning of 2016, and the current price is about 150,000 yuan / ton. Therefore, lithium ion batteries are difficult to support the development of both the electric vehicle and the grid energy storage industries.

[0003] In recent years, the research and development of sodium ion batteries have been rapidly developed; the main advantage is that the reserves of sodium resources are abundant and widely distributed, so the price is low, and it has a similar working principle as lithium ion batteries, which can be used as a beneficial supplement to lithium ion batteries in the low-speed electric vehicle and large-scale energy storage fields.

[0004] Due to the flammable and unsafe problems of electrolyte, solid-state sodium batteries may have certain potential in the future large-scale energy storage field. However, the basic scientific problems and preparation process of solid-state sodium batteries are still in the initial stage. Many factors need to be considered in the development of solid-state sodium batteries, including interface, energy and power density, safety problems, etc. At present, there are two methods to solve the interface problem, namely electrode material coating and additive control interface, among which the electrolyte additive is simple to process and low in cost, and is the preferred solution. The inorganic halide selected in the application has been widely used in electrochemical energy storage, such as sodium metal negative electrode protection, interface coating and solid-state electrolyte modification, etc., but it is difficult to dissolve in the currently commonly used organic solvents, which makes the dosage of the additive cannot be accurately controlled.

[0005] In view of this problem, the application uses deionized water to replace the traditional organic solvent to prepare a halide blended PEO-based electrolyte, which simplifies the preparation process and can more effectively disperse the inorganic halide additive. SUMMARY

[0006] The application aims to overcome the current situation that full solid-state sodium ion batteries cannot achieve high charge-discharge specific capacity, and common organic solvents cannot well disperse inorganic halide additives, and provides a preparation process of halide blended PEO-based electrolyte and application thereof in solid-state sodium batteries.

[0007] In a first aspect, a preparation process of halide blended PEO-based electrolyte is provided, which is prepared by using a homogeneous dissolution blending process or an in-situ precipitation blending process, wherein deionized water is used as a solvent, and polyether polymer, sodium salt and inorganic halide are used as solutes.

[0008] Preferably, the inorganic halide additive is selected from one or more of fluoride, bromide and iodide; wherein the fluoride is selected from one or more of AlF3, LiF, NaF and KF, the bromide is selected from one or more of AlBr3, LiBr, NaBr and KBr, and the iodide is selected from one or more of AlI3, LiI, NaI and KI.

[0009] Preferably, the content of the inorganic halide additive in the electrolyte is 0-10 %.

[0010] Preferably, the sodium salt is selected from one or more of sodium triflate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonylimide) and sodium perchlorate.

[0011] Preferably, the content of the sodium salt in the electrolyte is EO: Na = 20: (1-4).

[0012] Preferably, the inorganic halide additive with good water solubility is prepared by using the homogeneous dissolution blending process; for the inorganic halide additive with poor water solubility, such as AlF3, the film preparation process of the halide blended PEO-based electrolyte is optimized by using the in-situ co-precipitation method to improve the poor water solubility of the inorganic halide additive.

[0013] Preferably, the homogeneous dissolution blending process comprises the following steps:

[0014] The inorganic halide, sodium salt and deionized water solvent are uniformly mixed at 25 DEG C and under the condition of 20-40 % relative humidity to obtain the halide blended PEO-based electrolyte.

[0015] In a second aspect, the halide blended PEO-based electrolyte prepared by the above preparation process of halide blended PEO-based electrolyte, and the full solid-state sodium battery comprising the halide blended PEO-based electrolyte all belong to the protection scope of the application.

[0016] The application has the following beneficial effects:

[0017] 1. Unlike other electrolyte additives, the electrolyte additive components in this invention can effectively regulate the electrode-electrolyte interface and participate in the reaction to form part of the SEI layer, forming a more stable and dense SEI layer, effectively preventing dendrites from piercing the electrolyte.

[0018] 2. Unlike conventional electrolytes, the sodium salt component of the electrolyte in this invention is relatively stable in deionized water solvent, is not easily hydrolyzed but is easily soluble, which is conducive to the rapid transport of sodium ions in the system and improves the ionic conductivity and sodium ion transference number of the electrolyte.

[0019] 3. Unlike commonly used organic solvents, the solvent in this invention can effectively improve the shortcomings of inorganic halides being difficult to dissolve and disperse in traditional organic solvents, allowing water-soluble inorganic halides to be better dispersed in the system.

[0020] 4. Unlike inorganic halides that are more water-soluble, the present invention generates the additives during the preparation process through in-situ co-precipitation, thereby solving the problem that some halide additives are difficult to dissolve in water.

[0021] 5. Compared with existing electrolytes, the inorganic additives in this invention are inexpensive and have no special requirements for the usage environment.

[0022] 6. Compared with existing electrolytes, the deionized water solvent in this invention is inexpensive, environmentally friendly, and has no special requirements for the usage environment. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0024] Figure 1 These are comparison graphs showing the charge-discharge performance of electrolyte membranes using different solvents in Examples 1-4 and Comparative Example 1;

[0025] Figure 2 These are comparison graphs showing the charge-discharge performance of the electrolyte membranes prepared in Examples 5 and 17;

[0026] Figure 3 This is a comparison chart of the charge-discharge performance of Comparative Example 2 and its electrolyte membrane with added LiF and NaF, matched with hard carbon. Detailed Implementation

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings.

[0028] The present application first provides a halide blended PEO-based electrolyte, which is composed of a polymer, a sodium salt and an inorganic halide additive, wherein the solvent is deionized water.

[0029] The preparation method is to add one or more inorganic halide additives into the deionized water solvent under the condition of a temperature of 25°C and a relative humidity of 20-40%; the inorganic halide is selected from one or more of fluoride, bromide and iodide, wherein the fluoride is selected from one or more of AlF3, LiF, NaF and KF, the bromide is selected from one or more of AlBr3, LiBr, NaBr and KBr, and the iodide is selected from one or more of AlI3, LiI, NaI and KI; the additive mass fraction is 0-10 wt.%; the sodium salt is selected from one or more of sodium triflate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide and sodium perchlorate.

[0030] The specific embodiment is as follows:

[0031] Comparative Example 1:

[0032] In this comparative example, an electrolyte film without inorganic halide added using acetonitrile as the solvent is assembled into a 2032 button cell, the positive electrode material is sodium vanadium phosphate, and the negative electrode material is metal sodium.

[0033] The electrolyte preparation process is as follows:

[0034] Prepare 920 mg of PEO for use (Mw=600 000);

[0035] According to the ratio of EO: Na = 20: 1, weigh 180 mg of sodium triflate (98%) and dissolve it in 10 g of acetonitrile solvent, and ultrasonically stir for 3 h at room temperature to make it fully dispersed;

[0036] Add the 920 mg of PEO prepared in step 1 to the 2 solution, and stir at room temperature for 12 h to make it fully mixed and uniform, to obtain a PEO-sodium salt mixed slurry;

[0037] Pour the mixed slurry obtained in step 3 into a polytetrafluoroethylene round table mold, and volatilize the acetonitrile solvent in the glove box at low temperature for 24 h;

[0038] Transfer the PEO-based electrolyte film in step 4 which has been completely volatilized to a 60°C vacuum drying oven, and dry for 16 h to fully remove the residual acetonitrile solvent.

[0039] The charge-discharge performance was tested using a Neware tester, and the results are shown in Figure 1

[0040] Comparative Example 2

[0041] In this comparative example, an electrolyte film using deionized water as a solvent without the addition of inorganic halides was assembled into a 2032 button cell, with hard carbon as the positive electrode material and metal sodium as the negative electrode material.

[0042] The electrolyte preparation process:

[0043] Prepare 920 mg of PEO for use (Mw=600 000);

[0044] According to the ratio of EO: Na = 20: 1, weigh 180 mg of sodium triflate (98%) and dissolve it in 12 g of deionized water solvent, and ultrasonically stir for 3 h at room temperature to fully disperse;

[0045] Add the 920 mg of PEO prepared in step 1 to the 2 solution and stir at room temperature for 12 h to fully mix and uniform, obtaining a PEO-sodium salt mixed slurry;

[0046] Pour the mixed slurry obtained in step 3 into a polytetrafluoroethylene round table mold, and volatilize the deionized water solvent at low temperature in a fume hood for 24 h;

[0047] Transfer the PEO-based electrolyte film with complete volatilization in step 4 to a 60°C vacuum drying oven and dry for 24 h to fully remove the residual deionized water solvent.

[0048] The charge-discharge performance was tested using a Neware tester, and the results are shown in Figure 3

[0049] Example 1

[0050] A halide blended PEO-based electrolyte was provided:

[0051] Prepare 920 mg of PEO for use (Mw=600 000);

[0052] According to the ratio of EO: Na = 20: 1, weigh 180 mg of sodium triflate (98%) and dissolve it in 12 g of deionized water solvent, and ultrasonically stir for 3 h at room temperature to fully disperse;

[0053] Add the 920 mg of PEO prepared in step 1 to the 2 solution and stir at room temperature for 12 h to fully mix and uniform, obtaining a PEO-sodium salt mixed slurry;

[0054] ​​The mixed slurry obtained in step 3 is cast in a polytetrafluoroethylene round table mold, and the deionized water solvent is volatilized at low temperature in a fume hood for 24 h;

[0055] The PEO-based electrolyte film completely volatilized in step 4 is transferred to a 60°C vacuum drying oven and dried for 24 h to fully remove the residual deionized water solvent.

[0056] Example 2:

[0057] A halide blended PEO-based electrolyte is provided:

[0058] Different from example 1, the sodium salt added in this example is changed to sodium bis(trifluoromethylsulfonyl)imide, and the rest of the process and process parameters are the same as those in example 1, which will not be repeated here.

[0059] Example 3:

[0060] A halide blended PEO-based electrolyte is provided:

[0061] Different from example 1, the sodium salt added in this example is changed to sodium bis(fluorosulfonylimide), and the rest of the process and process parameters are the same as those in example 1, which will not be repeated here.

[0062] Example 4:

[0063] A halide blended PEO-based electrolyte is provided:

[0064] Different from example 1, the sodium salt added in this example is changed to sodium perchlorate, and the rest of the process and process parameters are the same as those in example 1, which will not be repeated here.

[0065] Example 5:

[0066] A halide blended PEO-based electrolyte is provided:

[0067] Different from example 1, 55 mg of inorganic additive AlF3 is added at the same time as the sodium salt in this example, and the rest of the process and process parameters are the same as those in example 1, which will not be repeated here.

[0068] Example 6:

[0069] A halide blended PEO-based electrolyte is provided:

[0070] Different from example 5, the inorganic additive added in this example is changed to LiF, and the rest of the process and process parameters are the same as those in example 5, which will not be repeated here.

[0071] Example 7:

[0072] A halide blended PEO-based electrolyte is provided:

[0073] The difference between this embodiment and Example 5 is that the inorganic additive added in this embodiment is changed to NaF, and the rest of the process and process parameters are the same as those of Example 5, which will not be repeated here.

[0074] Example 8:

[0075] A halide blended PEO-based electrolyte is provided:

[0076] The difference between this embodiment and Example 2 is that 55 mg of inorganic additive AlF3 is added at the same time as the sodium salt is added, and the rest of the process and process parameters are the same as those of Example 2, which will not be repeated here.

[0077] Example 9:

[0078] A halide blended PEO-based electrolyte is provided:

[0079] The difference between this embodiment and Example 8 is that the inorganic additive added in this embodiment is changed to LiF, and the rest of the process and process parameters are the same as those of Example 8, which will not be repeated here.

[0080] Example 10:

[0081] A halide blended PEO-based electrolyte is provided:

[0082] The difference between this embodiment and Example 8 is that the inorganic additive added in this embodiment is changed to NaF, and the rest of the process and process parameters are the same as those of Example 8, which will not be repeated here.

[0083] Example 11:

[0084] A halide blended PEO-based electrolyte is provided:

[0085] The difference between this embodiment and Example 3 is that 55 mg of inorganic additive AlF3 is added at the same time as the sodium salt is added, and the rest of the process and process parameters are the same as those of Example 3, which will not be repeated here.

[0086] Example 12:

[0087] A halide blended PEO-based electrolyte is provided:

[0088] The difference between this embodiment and Example 11 is that the inorganic additive added in this embodiment is changed to LiF, and the rest of the process and process parameters are the same as those of Example 11, which will not be repeated here.

[0089] Example 13:

[0090] A halide blended PEO-based electrolyte is provided:

[0091] The difference between this example and example 11 is that the inorganic additive added in this example is changed to NaF, and the rest of the process and process parameters are the same as those in example 11, which will not be repeated here.

[0092] Example 14:

[0093] A halide blended PEO-based electrolyte is provided:

[0094] The difference between this example and example 4 is that 55 mg of inorganic additive AlF3 is added at the same time as the sodium salt, and the rest of the process and process parameters are the same as those in example 4, which will not be repeated here.

[0095] Example 15:

[0096] A halide blended PEO-based electrolyte is provided:

[0097] The difference between this example and example 14 is that the inorganic additive added in this example is changed to LiF, and the rest of the process and process parameters are the same as those in example 14, which will not be repeated here.

[0098] Example 16:

[0099] A halide blended PEO-based electrolyte is provided:

[0100] The difference between this example and example 14 is that the inorganic additive added in this example is changed to NaF, and the rest of the process and process parameters are the same as those in example 14, which will not be repeated here.

[0101] Example 17:

[0102] A halide blended PEO-based electrolyte is provided:

[0103] (1) 920 mg of PEO (Mw=600 000) and 10 g of deionized water were added to a serum bottle and stirred uniformly at room temperature;

[0104] (2) 158.2 mg of AlCl3·6H2O and 82.5 mg of NaF were sequentially added to 1, and stirred uniformly at room temperature;

[0105] (3) The slurry obtained in step 2 was placed in a dialysis bag, and the dialysis bag was placed in a beaker containing ultrapure water, and stirred for 48 h;

[0106] (4) The mixed slurry obtained in step 3 was poured into a polytetrafluoroethylene round table mold, and placed in a freeze dryer for 48 h to obtain a freeze-dried product;

[0107] (5) 180 mg of sodium triflate (98%) was weighed according to the ratio of EO: Na = 20: 1, dissolved in 15 g of deionized water solvent, and ultrasonically stirred at room temperature for 3 h to make it fully dispersed;

[0108] (6) The freeze-dried product obtained in step 4 was added to the solution of step 5, and stirred at room temperature for 12 h to make it fully mixed and uniform, obtaining a PEO-sodium salt mixed slurry;

[0109] (7) The mixed slurry obtained in step 6 was cast in a polytetrafluoroethylene round table mold, and volatilized in a fume hood at low temperature for 24 h, and the deionized water solvent was naturally volatilized;

[0110] (8) The PEO-based electrolyte film in step 7 was transferred to a 60°C vacuum drying oven, and dried for 24 h to fully remove the residual deionized water solvent.

[0111] The above only discloses the preferred embodiments of the present application, and of course cannot limit the scope of the right of the present application, so the equivalent changes made according to the claims of the present application still belong to the scope covered by the present application.

Claims

1. A process for the preparation of a halide-blended PEO-based electrolyte, characterized in that: Prepared by homogeneous solution blending process or in-situ precipitation blending process, wherein deionized water is used as solvent, PEO, sodium salt, inorganic halide are used as solute; The inorganic halide additive is selected from one or more of fluoride, bromide and iodide; wherein the fluoride is selected from one or more of AlF3, LiF, NaF, KF, the bromide is selected from one or more of AlBr3, LiBr, NaBr, KBr, and the iodide is selected from one or more of AlI3, LiI, NaI, KI; The content of the inorganic halide additive in the electrolyte is (0, 10] wt.%; The sodium salt is selected from one or more of sodium triflate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium perchlorate; The molar content of the sodium salt in the electrolyte is EO:Na = 20:(1-4); The inorganic halide additive with good water solubility is prepared by homogeneous solution blending process, and the inorganic halide additive with poor water solubility is prepared by in-situ precipitation blending process; The homogeneous solution blending process comprises the following steps: At room temperature, the PEO, inorganic halide, sodium salt and deionized water solvent are mixed uniformly under the condition of relative humidity of 20-40%, to obtain a PEO-sodium salt mixed slurry, the obtained mixed slurry is poured into a mold, heated and deionized water solvent is volatilized in a fume hood, after volatilization, it is transferred to a vacuum drying oven for drying, and finally a halide blended PEO-based electrolyte is obtained.

2. The halide blended PEO-based electrolyte prepared by the preparation process of the halide blended PEO-based electrolyte according to claim 1.

3. An all-solid-state sodium battery comprising the halide blended PEO-based electrolyte according to claim 2.

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