High-stability gel polymer electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a high-stability gel polymer electrolyte as well as a preparation method and application thereof, and relates to the technical field of metal batteries. The preparation method comprises the following steps: mixing a metal salt and a solvent to obtain a basic electrolyte; adding butyl acrylate, triallyl isocyanurate, a plasticizer and an initiator into the basic electrolyte to obtain a precursor solution; and carrying out polymerization reaction on the precursor solution to obtain the high-stability gel polymer electrolyte. The prepared gel polymer electrolyte has the characteristics of high ionic conductivity and high strength, and can be applied to a lithium metal battery and a sodium metal battery. The NVP gel polymer electrolyte Na metal battery assembled by adopting a polyanion positive electrode sodium vanadium phosphate (NVP), a sodium metal negative electrode and the gel polymer electrolyte disclosed by the invention can realize long cycle stability under high magnification.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal battery, in particular to a high-stability gel polymer electrolyte and a preparation method and application thereof. BACKGROUND

[0002] The electrolyte of metal battery is usually composed of liquid solvent and salt, although it has high conductivity, but the electrolyte is easy to leak and flammable, which can easily cause fire accidents. The gel polymer electrolyte is between liquid and solid electrolyte, which combines the advantages of the two types of electrolyte, and is expected to have high performance and safety at the same time. However, the gel polymer electrolyte still has some problems to be overcome, such as low ionic conductivity and poor interface stability, which leads to poor high-rate and long cycle performance. At present, the linear polymer used in the gel polymer electrolyte can improve the ionic conductivity, but its poor stability limits its application in high-energy-density metal batteries. In summary, designing and developing a stable and efficient gel polymer electrolyte is one of the keys to realizing high-performance metal batteries, which is of great significance. SUMMARY

[0003] The purpose of the present application is to provide a high-stability gel polymer electrolyte and a preparation method and application thereof to solve the problems existing in the prior art. The high-stability gel polymer electrolyte prepared by the present application has high interface compatibility with the electrode, and can realize stable long-time charge and discharge cycle under high current density.

[0004] To achieve the above purpose, the present application provides the following scheme:

[0005] One of the technical solutions of the present application: a preparation method of a high-stability gel polymer electrolyte, comprising the following steps:

[0006] Mixing metal salt and solvent to obtain a basic electrolyte; adding butyl acrylate (BA), triallyl isocyanurate (TAIC), plasticizer and initiator into the basic electrolyte to obtain a precursor solution; and polymerizing the precursor solution to obtain the high-stability gel polymer electrolyte.

[0007] In the present application, butyl acrylate is used as a monomer, and triallyl isocyanurate is used as a crosslinking agent. The flexible long-chain structure and bulky butyl side group (compared with methyl) of butyl acrylate can provide more free volume for polymer chain segment movement, thereby optimizing the ion transmission performance. At the same time, triallyl isocyanurate can promote the formation of three-dimensional rigid network, thereby inhibiting the occurrence of side reactions and the growth of sodium or lithium dendrites, so that the obtained gel polymer electrolyte has very high interface compatibility. The gel polymer electrolyte prepared by the present application has the characteristics of high ionic conductivity and high strength, and can be applied to lithium metal batteries and sodium metal batteries.

[0008] Further, the metal salt comprises a lithium salt and / or a sodium salt.

[0009] Further, the sodium salt comprises sodium bis(trifluoromethylsulfonyl)imide (NaTFSI).

[0010] Further, the lithium salt comprises lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6) or lithium bis(oxalato)borate (LiBOB).

[0011] Further, the solvent is a mixed solvent of trimethyl phosphate (TMP), fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC).

[0012] TMP, as an efficient organic phosphorus flame-retardant component, can significantly improve safety and reduce the risk of combustion of the battery under thermal runaway and short circuit; FEC can be preferentially reduced and decomposed on the surface of the negative electrode to form a dense, stable and LiF or NaF-rich solid electrolyte interface film (SEI), which greatly improves the cycle life of the battery; and EMC provides excellent basic solvent performance, and its good solubility for metal salts ensures that the electrolyte has sufficient ionic conductivity. The synergistic effect of the three achieves a balance of safety, long life and good conductivity.

[0013] Further, the volume ratio of trimethyl phosphate, fluoroethylene carbonate and ethyl methyl carbonate in the mixed solvent is 1:1:2.

[0014] Further, the volume ratio of the butyl acrylate and the triallyl isocyanurate is 1-12:1.

[0015] Further, the sum of the volumes of the butyl acrylate and the triallyl isocyanurate is 20-50 vol.% of the volume of the solvent.

[0016] Further, the plasticizer comprises succinonitrile (SN).

[0017] SN can improve the ionic conductivity of the gel polymer electrolyte and broaden its electrochemical window through the synergistic effect of its high dielectric property, low melting point and cyano functional group.

[0018] Further, the mass fraction of the plasticizer in the precursor solution is 5-30 wt.%.

[0019] Further, the initiator comprises azobisisobutyronitrile (AIBN).

[0020] Further, the mass of the initiator is 0.5-1.0 wt.% of the sum of the masses of the butyl acrylate and the triallyl isocyanurate.

[0021] Further, the molar concentration of the metal salt in the precursor solution is 0.5-2 mol / L. −1 .

[0022] Preferably, the adding of butyl acrylate, triallyl isocyanurate, plasticizer and initiator into the base electrolyte comprises: adding butyl acrylate and triallyl isocyanurate first, and then adding plasticizer and initiator after stirring evenly.

[0023] Further, the temperature of the polymerization reaction is 60-70 ℃, and the time is 2-6 h.

[0024] The second technical solution of the application is a high-stability gel polymer electrolyte prepared by the above preparation method of high-stability gel polymer electrolyte.

[0025] The third technical solution of the application is the application of the above high-stability gel polymer electrolyte in a sodium metal battery or a lithium metal battery.

[0026] Further, when the high-stability gel polymer electrolyte is used to prepare a sodium metal battery, the metal salt in the high-stability gel polymer electrolyte is a sodium salt; when the high-stability gel polymer electrolyte is used to prepare a lithium metal battery, the metal salt in the high-stability gel polymer electrolyte is a lithium salt.

[0027] Further, the steps of the application comprise: placing a positive electrode sheet in the center of a positive electrode shell in an argon environment, placing glass fiber on the positive electrode sheet, and stacking a negative electrode sheet on the glass fiber; after the three are aligned, injecting the precursor solution in the above preparation method of high-stability gel polymer electrolyte, then packaging the battery, and heating the packaged battery to perform a polymerization reaction. That is, the battery is assembled using the precursor solution first, and then the polymerization reaction is performed after assembly, so as to generate a high-stability gel polymer electrolyte inside the battery.

[0028] The application discloses the following technical effects:

[0029] First, compared with ordinary linear polymers, the high-stability gel polymer obtained after polymerization in the application is a crosslinked polymer, which has a higher Young's modulus and can resist the growth of dendrites. Second, the crosslinked polymer enhances the stability between the electrolyte and the positive and negative electrodes. Third, the crosslinked polymer has a high ionic conductivity, and the crosslinked network structure can effectively inhibit the transmission of anions, thereby improving the ion migration number. In summary of the above points, the gel polymer electrolyte prepared in the application has the characteristics of long cycle stability in a wide temperature range. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to describe the technical solutions of the embodiments of the present application or the prior art more clearly, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without any creative effort based on these drawings.

[0031] Figure 1 1 C cycle performance graph of NVP|pBAT-1 / 8|Na battery assembled by using the gel polymer electrolyte of Example 1.

[0032] Figure 2 1 C cycle performance graph of NVP|pBAT-1 / 12|Na battery assembled by using the gel polymer electrolyte of Example 2.

[0033] Figure 3 1 C cycle performance graph of NVP|pBAT-1 / 4|Na battery assembled by using the gel polymer electrolyte of Example 3.

[0034] Figure 4 1 C cycle performance graph of NVP|pBAT-0|Na battery assembled by using the gel polymer electrolyte of Comparative Example 1.

[0035] Figure 5 5 C cycle performance graph of NVP|pBAT-1 / 8|Na battery assembled by using the gel polymer electrolyte of Example 1.

[0036] Figure 6 Graph of ionic conductivity of the gel polymer electrolytes prepared in Examples 1-3 and Comparative Example 1 at different temperatures.

[0037] Figure 7 Graph of mechanical strength of the gel polymer electrolytes prepared in Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of the present application and should not be construed to limit the present application, and are understood to be a more detailed description of some aspects, features and embodiments of the present application.

[0039] It should be understood that the terms used in the present application merely describe particular embodiments and are not intended to limit the present application. In addition, for the numerical ranges in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range within any stated range or within any stated intermediate value, as well as any other stated value or stated intermediate value within the stated range, is also included within the present application. The upper limit and the lower limit of these smaller ranges can be included or excluded independently.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those of ordinary skill in the art to which the application relates. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification prevails.

[0041] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit or scope of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0042] It is to be understood that the phraseology or terminology employed herein, such as "comprising", "including", "carrying", "containing" or "having" are open-ended terms that specify the presence of stated elements. The use of "comprising", "including", "carrying", "containing" or "having" to describe combinations also contemplates "consisting of", "consisting essentially of" or "substantially comprising".

[0043] It should be noted that the present application does not describe in detail the conventional operation means in the art, and is not the focus of the present application.

[0044] In the following examples and comparative examples of the present application, if the room temperature is mentioned, it specifically refers to 20-30 ℃.

[0045] In the following examples and comparative examples of the present application, each raw material used is an ordinary commercially available product unless otherwise specified.

[0046] Example 1

[0047] A high-stability gel polymer electrolyte, the preparation steps are as follows:

[0048] Step 1, sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) is added to a mixed solvent of trimethyl phosphate (TMP), fluoroethylene carbonate (FEC) and methyl ethyl carbonate (EMC) in a volume ratio of 1:1:2, and stirred uniformly to obtain a basic electrolyte.

[0049] Step 2, butyl acrylate (BA) and triallyl isocyanurate (TAIC) in a volume ratio of 8:1 are added to the basic electrolyte in step 1, and stirred uniformly to obtain a mixed solution, wherein the total volume of BA and TAIC is 30 vol.% of the mixed solvent in step 1.

[0050] Step 3, a plasticizer succinonitrile (SN) and an initiator azobisisobutyronitrile (AIBN) are added to the mixed solution in Step 2, and stirred uniformly to obtain a precursor solution; wherein the added amount of AIBN is 1.0 wt.% of the sum of the mass of BA and TAIC contained in the mixed solution; the molar concentration of NaTFSI in the precursor solution is 1 mol / L −1 , and the mass percentage of SN is 10 wt.%. The above three steps need to be carried out under argon protection.

[0051] Step 4, the precursor solution obtained in Step 3 is placed in an oven at 60°C, so that the precursor solution undergoes a polymerization reaction, and the polymerization reaction time is 2 h, to obtain a gel polymer electrolyte (abbreviated as pBAT-1 / 8).

[0052] Example 2

[0053] A high-stability gel polymer electrolyte, the preparation steps are as follows:

[0054] Step 1, NaTFSI is added to a mixed solvent of TMP, FEC and EMC in a volume ratio of 1:1:2, and stirred uniformly to obtain a base electrolyte.

[0055] Step 2, BA and TAIC with a total volume of 30 vol.% of the mixed solvent in Step 1 are added to the base electrolyte in Step 1, and stirred uniformly to obtain a mixed solution, wherein the volume ratio of BA to TAIC is 12:1.

[0056] Step 3, a plasticizer SN and an initiator AIBN are added to the mixed solution in Step 2, and stirred uniformly to obtain a precursor solution; wherein the added amount of AIBN is 1.0 wt.% of the sum of the mass of BA and TAIC contained in the mixed solution; the molar concentration of NaTFSI in the precursor solution is 1 mol / L −1 , and the mass percentage of SN is 10 wt.%. The above three steps need to be carried out under argon protection.

[0057] Step 4, the precursor solution obtained in Step 3 is placed in an oven at 60°C, so that the precursor solution undergoes a polymerization reaction, and the polymerization reaction time is 2 h, to obtain a gel polymer electrolyte (abbreviated as pBAT-1 / 8).

[0058] Example 3

[0059] A high-stability gel polymer electrolyte, the preparation steps are as follows:

[0060] Step 1, NaTFSI is added to a mixed solvent of TMP, FEC and EMC in a volume ratio of 1:1:2, and stirred uniformly to obtain a base electrolyte.

[0061] Step 2, add BA and TAIC with a total volume of 30 vol.% of the mixed solvent in step 1 to the base electrolyte in step 1, stir uniformly to obtain a mixed solution, wherein the volume ratio of BA to TAIC is 4:1.

[0062] Step 3, add plasticizer SN and initiator AIBN to the mixed solution in step 2, stir uniformly to obtain a precursor solution; wherein the amount of AIBN added is 1.0 wt.% of the sum of the mass of BA and TAIC contained in the mixed solution; the molar concentration of NaTFSI in the precursor solution is 1 mol / L, and the mass percentage of SN is 10 wt.%. The above three steps need to be carried out under argon protection. −1

[0063] Step 4, place the precursor solution obtained in step 3 into a 60°C oven to make the precursor solution undergo a polymerization reaction, and the polymerization reaction time is 2 h to obtain a gel polymer electrolyte (abbreviated as pBAT-1 / 4).

[0064] Comparative Example 1

[0065] A gel polymer electrolyte, the preparation steps are as follows:

[0066] Step 1, add NaTFSI to a mixed solvent of TMP, FEC, and EMC with a volume ratio of 1:1:2, stir uniformly to obtain a base electrolyte.

[0067] Step 2, add BA with a volume of 30 vol.% of the mixed solvent in step 1 to the base electrolyte in step 1, stir uniformly to obtain a mixed solution.

[0068] Step 3, add plasticizer SN and initiator AIBN to the mixed solution in step 2, stir uniformly to obtain a precursor solution; wherein the amount of AIBN added is 1.0 wt.% of the mass of BA contained in the mixed solution; the molar concentration of NaTFSI in the precursor solution is 1 mol / L, and the mass percentage of SN is 10 wt.%. The above three steps need to be carried out under argon protection. −1

[0069] Step 4, place the precursor solution obtained in step 3 into a 60°C oven to make the precursor solution undergo a polymerization reaction, and the polymerization reaction time is 2 h to obtain a gel polymer electrolyte (abbreviated as pBAT-1 / 4).

[0070] Application Example

[0071] ​​A polyanionic compound, sodium vanadium phosphate (Na3V2(PO4)3, abbreviated as NVP), was used as a positive electrode material (i.e., a positive electrode active material), which was coated on the surface of an aluminum foil to obtain a positive electrode. The loading amount of NVP in the positive electrode was 2.8 mg cm -2 . Specifically, the positive electrode was prepared as follows: NVP, carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 8:1:1, and N-methyl pyrrolidone (NMP) solvent was added. After stirring uniformly, the mixture was coated on an aluminum foil. The coated aluminum foil was dried in a vacuum oven at 100 °C for 12 h, and then punched into a positive electrode sheet with a diameter of 10 mm. A metal sodium sheet with a thickness of 100 μm was used as a negative electrode. The specific assembly process of the battery was as follows: in an argon environment, the positive electrode sheet was placed in the center of the positive electrode shell, a GF / D glass fiber was placed on the positive electrode sheet, and the negative electrode sheet was stacked on the GF / D glass fiber; after the three were aligned, the precursor solution prepared in Examples 1-3 and Comparative Example 1 was injected, and finally the battery was packaged to complete the assembly of the NVP|gel polymer electrolyte|Na button CR2023 battery. After the battery was heated (60 °C for 2 h to perform the polymerization reaction), it was taken out and tested for the cycle stability of each battery under 1 C and 5 C charge-discharge conditions. The charge-discharge voltage range was 2.5-4.1 V.

[0072] Figure 1 The 1 C cycle performance chart of the NVP|pBAT-1 / 8|Na battery assembled using the gel polymer electrolyte of Example 1 is shown. It can be seen that, at 1 C, the initial capacity of the battery was 108.7 mAh g -1 , and the capacity after 800 cycles was 106.7 mAh g -1 , with an average coulombic efficiency of 99.87%, and excellent long cycle stability.

[0073] Figure 2 The 1 C cycle performance chart of the NVP|pBAT-1 / 12|Na battery assembled using the gel polymer electrolyte of Example 2 is shown. It can be seen that, at 1 C, the initial capacity of the battery was 104.3 mAh g -1 , and the capacity after 800 cycles was 98.4 mAh g -1 , with an average coulombic efficiency of 99.78%, and excellent cycle stability.

[0074] Figure 3 The 1 C cycle performance chart of the NVP|pBAT-1 / 4|Na battery assembled using the gel polymer electrolyte of Example 3 is shown. It can be seen that, at 1 C, the initial capacity of the battery was 104.7 mAh g -1 , and the capacity after 800 cycles was 104.5 mAh g -1, and the average coulombic efficiency was 99.91%, which had excellent cycle stability.

[0075] Figure 4 The 1 C cycle performance chart of NVP|pBAT-0|Na battery assembled by using the gel polymer electrolyte of Comparative Example 1 is shown. It can be seen that at 1 C, the initial capacity of the battery was 98.2 mAh g -1 , and the capacity after 700 cycles was 59.1 mAh g -1 , and the average coulombic efficiency was 97.68%.

[0076] Figure 5 The 5 C cycle performance chart of NVP|pBAT-1 / 8|Na battery assembled by using the gel polymer electrolyte of Example 1 is shown. It can be seen that at 5 C, the initial capacity of the battery was 90.4 mAh g -1 , and the capacity after 2600 cycles was 92.7 mAh g -1 , and the average coulombic efficiency was 99.90%, indicating that it still had excellent long cycle stability at high rate.

[0077] Figure 6 The ion conductivity charts of the gel polymer electrolytes prepared in Examples 1-3 and Comparative Example 1 at different temperatures are shown. It can be seen from the chart that the ion conductivity of Comparative Example 1 is higher than that of Examples 1-3, but it has the highest activation energy. The ion conductivity of Example 1 is higher than that of Examples 2 and 3, and it has the lowest activation energy.

[0078] Test Example

[0079] Figure 7 The mechanical strength charts of the gel polymer electrolytes prepared in Examples 1-3 and Comparative Example 1 are shown. It can be seen from the chart that with the increase of the amount of TAIC, the Young's modulus of the gel polymer electrolyte is continuously enhanced, which is conducive to inhibiting dendrite growth.

[0080] The above-described examples only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for preparing a high-stability gel polymer electrolyte, characterized by, The method comprises the following steps: mixing a metal salt and a solvent to obtain a base electrolyte; adding butyl acrylate, triallyl isocyanurate, a plasticizer and an initiator into the base electrolyte to obtain a precursor solution; and performing a polymerization reaction on the precursor solution to obtain the high-stability gel polymer electrolyte; the solvent is a mixed solvent of trimethyl phosphate, fluoroethylene carbonate and ethyl methyl carbonate; the volume ratio of trimethyl phosphate, fluoroethylene carbonate and ethyl methyl carbonate in the mixed solvent is 1:1:2; the plasticizer comprises butanedinitrile.

2. The method for preparing a high-stability gel polymer electrolyte according to claim 1, wherein the electrolyte solution is prepared by dissolving the electrolyte salt in the organic solvent, and the organic solvent is added to the polymer solution. the metal salt comprises a lithium salt and / or a sodium salt.

3. The method of claim 2, wherein the high-stability gel polymer electrolyte is prepared by adding the electrolyte solution to the polymer solution, and then stirring the mixture at a temperature of 20 to 30°C for 1 to 3 hours. the sodium salt comprises sodium bis(trifluoromethylsulfonyl)imide; and / or, the lithium salt comprises lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate or lithium bis(oxalato)borate.

4. The method of claim 1, wherein the high-stability gel polymer electrolyte is prepared by adding 0.1 to 10 parts by weight of the electrolyte salt to 100 parts by weight of the polymer. the volume ratio of the butyl acrylate and the triallyl isocyanurate is 1-12:1; and / or, the sum of the volumes of the butyl acrylate and the triallyl isocyanurate is 20-50 vol.% of the volume of the solvent.

5. The method for preparing a high-stability gel polymer electrolyte according to claim 1, wherein: the mass proportion of the plasticizer in the precursor solution is 5-30 wt.%; and / or, the initiator comprises azobisisobutyronitrile; and / or, the mass of the initiator is 0.5-1.0 wt.% of the sum of the masses of the butyl acrylate and the triallyl isocyanurate; and / or the molar concentration of the metal salt in the precursor solution is 0.5-2 mol L -1 .

6. The method for preparing a high-stability gel polymer electrolyte according to claim 1, wherein: the temperature of the polymerization reaction is 60-70 ℃, and the time is 2-6 h.

7. A high-stability gel polymer electrolyte prepared by the preparation method of the high-stability gel polymer electrolyte according to any one of claims 1-6.

8. Application of the high-stability gel polymer electrolyte according to claim 7 in a sodium metal battery or a lithium metal battery.

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