Polymer-based electrolyte and preparation method and application thereof

Abstract

The present invention relates to a polymer-based electrolyte comprising: 100 parts by weight of a porous polymer; 30-60 parts by weight of an alkali ion battery electrolyte, preferably 40-50 parts by weight; 5 to 25 parts by weight of polyethylene glycol, preferably 10 to 20 parts by weight; wherein the porous polymer is prepared from melamine and terephthalaldehyde. According to the polymer-based electrolyte, raw materials are easy to obtain, toxicity is low, and the preparation process is simple, low in cost and easy to implement. The polymer-based electrolyte prepared by the invention has the advantages of wide use conditions, high mechanical strength, good cycle performance, stable electrochemical performance, excellent thermal stability and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of battery materials, and particularly relates to a polymer-based electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Sodium-ion batteries are accelerating development into an important alternative system of lithium-ion batteries due to their significant crust abundance (2.36%), cost advantage and intrinsic safety. Current research mainly focuses on the development and optimization of electrode materials. As the core medium for ion transmission in batteries, electrolyte system research has also received high attention. Electrolyte plays a key role in building a stable sodium ion transmission channel, and its physical and chemical properties directly affect the interface stability, rate performance and cycle life of the battery. The use of solid-state electrolyte instead of traditional flammable liquid system not only fundamentally solves the safety hazards caused by electrolyte leakage, but also effectively inhibits the uncontrollable growth of sodium dendrites, reduces the risk of internal short circuit of the battery and improves the cycle stability of the battery. Therefore, the research and development of new sodium-ion solid-state electrolyte has become a core technology to promote high safety and long life sodium-ion batteries.

[0003] Among the many solid-state electrolyte systems, polymer electrolyte (SPE) is highly regarded due to its light weight, excellent flexibility and scalable processing advantages. However, the existing SPE system has significant defects: limited thermal stability, insufficient mechanical strength and low room temperature ionic conductivity, which leads to poor cycle performance and low capacity retention rate of sodium-ion batteries based on SPE. These technical bottlenecks seriously restrict the practical application of solid-state sodium batteries in high-energy-density energy storage fields, and performance breakthroughs are urgently needed through material innovation and structural design. SUMMARY

[0004] Therefore, the present application aims to provide a polymer-based electrolyte and a preparation method and application thereof.

[0005] The first aspect of the present application relates to providing a polymer-based electrolyte, which comprises: 100 parts by weight of a porous polymer; 30-60 parts by weight, preferably 40-50 parts by weight, of an alkali-ion battery electrolyte; and 5-25 parts by weight, preferably 10-20 parts by weight, of polyethylene glycol; wherein the porous polymer is prepared from melamine and p-phenylenediamine.

[0006] The second aspect of the present application relates to providing a method for preparing the polymer-based electrolyte of the present application, the method comprising the following steps: i) dissolving melamine and p-xylylene in dimethyl sulfoxide, stirring under the condition of a hot water bath ultrasonic until the solution is clear, to obtain a mixed solution; heating the mixed solution under an inert atmosphere to carry out the reaction, then cooling to room temperature, then filtering, and washing the obtained filtrate to obtain a porous polymer; ii) adding polyethylene glycol into the alkali-ion battery electrolyte and mixing uniformly to obtain an alkali-ion battery electrolyte mixture; iii) mixing the porous polymer and the alkali-ion battery electrolyte mixture and grinding uniformly to obtain the polymer-based electrolyte; wherein, in terms of weight parts, the method satisfies the following relationship: porous polymer: alkali-ion battery electrolyte: polyethylene glycol = 100: (30-60): (5-25), preferably 100: (40-50): (10-20).

[0007] The third aspect of the present application relates to providing an application of the polymer-based electrolyte of the present application in a secondary battery.

[0008] The present application has the following beneficial effects:

[0009] The present application provides a polymer-based electrolyte comprising a porous polymer, an alkali-ion battery electrolyte and polyethylene glycol. The porous polymer is prepared from melamine and p-xylylene. In the electrolyte, the porous polymer is designed by aldehyde amine condensation, and the porous polymer itself structure directly bears the electrolyte skeleton function. The polyethylene glycol is filled in the skeleton to play a bridge role for the migration of ions in the porous material. The polymer-based electrolyte of the present application avoids the dependence on the traditional polymer matrix, improves the mechanical strength of the polymer matrix, and constructs a more simple and efficient electrolyte material system. By premixing the alkali-ion battery electrolyte and the polyethylene glycol, the adsorption of the porous material to the organic molecules in the mixed solution of the alkali-ion battery electrolyte is effectively played, the movement of the anion groups in the electrolyte is limited, the negative influence on the migration of the cations is reduced, and the cation migration number is improved. The polymer-based electrolyte of the present application has the advantages of easy availability of raw materials, low toxicity, simple preparation process, low cost and easy implementation. The polymer-based electrolyte prepared by the present application has the advantages of wide use conditions, high mechanical strength, good cycle performance, stable electrochemical performance, excellent thermal stability and the like. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 The micro-morphology diagram of the polymer-based electrolyte of Example 1;

[0011] Figure 2 The nitrogen isothermal adsorption-desorption curve of the porous polymer of Example 1;

[0012] Figure 3Pore size distribution plot for the porous polymer of Example 1;

[0013] Figure 4 DSC plot for the porous polymer of Example 1;

[0014] Figure 5 TG-DSC plot for the polymer-based electrolyte of Example 1;

[0015] Figure 6 Cyclic voltammetry scan test result plot for the test cell of the polymer-based electrolyte of Example 1;

[0016] Figure 7 Impedance plot for the test cell of the polymer-based electrolyte of Example 1;

[0017] Figure 8 Cycle performance test result plot for the test cell of the polymer-based electrolyte of Example 1;

[0018] Figure 9 Microscopic morphology plot for the polymer-based electrolyte of Example 2;

[0019] Figure 10 Nitrogen isothermal adsorption-desorption plot for the porous polymer of Example 2;

[0020] Figure 11 Pore size distribution plot for the porous polymer of Example 2;

[0021] Figure 12 Cyclic voltammetry scan test result plot for the test cell of the polymer-based electrolyte of Example 2;

[0022] Figure 13 Impedance plot for the test cell of the polymer-based electrolyte of Example 2;

[0023] Figure 14 Cycle performance test result plot for the test cell of the polymer-based electrolyte of Example 2;

[0024] Figure 15 Cycle performance test result plot for the test cell of the polymer-based electrolyte of Example 3. DETAILED DESCRIPTION

[0025] Hereinafter, the present application will be described in more detail.

[0026] The term "comprise", and its synonyms "comprising" and "containing", as used herein, have the meaning in the art of "including but not limited to", and are not intended to (and do not) exclude, for example, other additives, components, integers or steps.

[0027] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, wherein any statement of a range can be modified by the use of "substantially," "about" or "approximately." The use of "substantially" or "approximately" in connection with a range applies to both ends of the range. Thus, "substantially 60-120" means "about 60-120" or "approximately 60-120," and "substantially 60 to 120" means "about 60 to 120" or "approximately 60 to 120," and "60 to substantially 120" means "about 60 to about 120" or "approximately 60 to approximately 120."

[0028] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specified otherwise.

[0029] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not specified otherwise.

[0030] All steps of the present application can be performed in sequence, randomly or simultaneously, if not specified otherwise. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence, or steps (a) and (b) performed simultaneously. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any sequence. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0031] If not specified otherwise, the meaning of the terms mentioned in the present application is the same as the meaning generally understood by those skilled in the art.

[0032] If not specified otherwise, the operations mentioned in the present application are performed at room temperature and under normal pressure.

[0033] If not specified otherwise, the operations mentioned in the present application can be performed by means known to those skilled in the art.

[0034] If not specified otherwise, the equipment, devices, instruments, parts, materials, reagents, etc. mentioned in the present application can be obtained by means known to those skilled in the art.

[0035] If not specified otherwise, the indexes mentioned in the present application, such as specific surface area, pore size, etc. can be measured by means known to those skilled in the art.

[0036] According to one aspect of the present application, the present application provides a polymer-based electrolyte, comprising: 100 parts by weight of a porous polymer; 30-60 parts by weight, preferably 40-50 parts by weight, of an alkali-ion battery electrolyte; and 5-25 parts by weight, preferably 10-20 parts by weight, of polyethylene glycol; wherein the porous polymer is prepared from melamine and p-phenylenediamine.

[0037] In any embodiment, the polymer-based electrolyte of the present application consists only of: 100 parts by weight of a porous polymer; 30-60 parts by weight, preferably 40-50 parts by weight, of an alkali-ion battery electrolyte; and 5-25 parts by weight, preferably 10-20 parts by weight, of polyethylene glycol; wherein the porous polymer is prepared from melamine and p-phenylenediamine.

[0038] In any embodiment, the porous polymer is prepared from melamine and p-phenylenediamine at a weight ratio of 1:(2-5), preferably 1:(2-3).

[0039] Without being bound by any theory, the inventors have unexpectedly found that by designing a porous polymer through aldehyde-amine condensation, the porous polymer itself structure directly undertakes the function of electrolyte skeleton, and filling polyethylene glycol inside the skeleton can play a bridge role for ion migration in the porous material. By premixing the alkali-ion battery electrolyte and polyethylene glycol, the porous material effectively plays the adsorption role of organic molecules in the mixed solution of the alkali-ion battery electrolyte, limits the movement of anion groups in the electrolyte, reduces the negative impact of interfering with the migration of cations, and improves the cation migration number. Moreover, the weight ratio between the porous polymer, the alkali-ion battery electrolyte, and the polyethylene glycol is conducive to balancing the solid-liquid system of the polymer-based electrolyte of the present application, thereby improving and balancing the mechanical properties, electrochemical properties, and thermal stability.

[0040] Specifically, the porous polymer of the present application provides mechanical strength, specific surface area, pore size, and thermal stability suitable for the present application. The inventors have unexpectedly found that in the case of the alkali-ion battery electrolyte of the present application being higher than a certain proportion, the mechanical strength of the polymer-based electrolyte will decrease; and in the case of the alkali-ion battery electrolyte being lower than a certain proportion, the number of migratable sodium ions in the polymer-based electrolyte will be too small, thereby causing the electrochemical properties of the polymer-based electrolyte to decrease. Meanwhile, in the case of the polyethylene glycol of the present application being lower than a certain proportion, the mechanical strength of the polymer-based electrolyte will decrease; and in the case of the polyethylene glycol being higher than a certain proportion, the electrochemical properties of the polymer-based electrolyte will decrease. Based on the above factors, the inventors have unexpectedly found that in the weight ratio of the present application, the polymer-based electrolyte can advantageously provide balanced mechanical properties, electrochemical properties, and thermal stability.

[0041] In any embodiment, the specific surface area of ​​the porous polymer of the present invention is 800 to 1100 m 2 / g, preferably 900-1000m 2 / g, more preferably 900 to 950 m 2 / g; pore diameter is 3-6nm, preferably 4-5nm, more preferably 4.5-5nm. The above range is conducive to balancing the mechanical strength of the porous polymer as the electrolyte skeleton and the filling capacity inside the skeleton, thereby improving and balancing the mechanical strength and electrochemical performance of the polymer-based electrolyte as a whole.

[0042] In any embodiment, the melting temperature T m It is 400-500°C, preferably 440-480°C. Since the porous polymer of the present invention is an amorphous polymer material, it has a cross-linked network structure and the weight-average molecular weight cannot be determined. Therefore, its melting temperature reflects the molecular weight range of the porous polymer to a certain extent. The inventors unexpectedly found that the molecular weight range is also related to mechanical properties and electrochemical properties: the larger the molecular weight, the greater the mechanical strength and the lower the ionic conductivity; the smaller the molecular weight, the smaller the mechanical strength and the higher the ionic conductivity. Therefore, the inventors further found that by adopting the above range, it is beneficial to provide a porous polymer with mechanical strength and thermal stability suitable for the needs of the present invention, thereby improving and balancing the mechanical strength and thermal stability capabilities of the porous polymer as an electrolyte skeleton.

[0043] In any embodiment, the weight-average molecular weight of the polyethylene glycol used in the present invention is 300 g / mol to 200,000 g / mol, preferably 1,000 g / mol to 10,000 g / mol, and more preferably 1,000 g / mol to 5,000 g / mol. The inventors unexpectedly discovered that the weight-average molecular weight of the polyethylene glycol is correlated with the viscosity of a mixed solution of the polyethylene glycol and an alkaline ion battery electrolyte. Specifically, a greater weight-average molecular weight of the polyethylene glycol results in a greater viscosity of the mixed solution; a smaller weight-average molecular weight results in a smaller viscosity of the mixed solution. Furthermore, the weight-average molecular weight of the polyethylene glycol is also correlated with electrochemical performance. Specifically, a greater molecular weight results in a lower ionic conductivity; a smaller molecular weight results in a higher ionic conductivity. Therefore, the inventors further discovered that the above range is conducive to balancing the viscosity and ionic conductivity of the mixed solution of polyethylene glycol and alkaline ion battery electrolyte, meeting the viscosity requirements and ionic conductivity requirements of the mixed solution filled into the porous polymer serving as the electrolyte skeleton, thereby improving and balancing the overall mechanical strength and electrochemical properties of the polymer-based electrolyte.

[0044] The base ion battery electrolyte used in the present application can be classified in various ways, for example, according to the type of battery to be applied, the base ion battery electrolyte can include lithium ion battery electrolyte, sodium ion battery electrolyte and potassium ion battery electrolyte. In an embodiment of the present application, the base ion battery electrolyte of the present application can be selected from lithium ion battery electrolyte, sodium ion battery electrolyte and potassium ion battery electrolyte. Among them, the lithium ion battery electrolyte can be selected from, for example, lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonimide (LiFSI) and lithium bis-trifluoromethanesulfonimide (LiTFSI) solution; the sodium ion battery electrolyte can be selected from, for example, sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4) and sodium bisfluorosulfonimide (NaFSI) solution; the potassium ion battery electrolyte can be selected from, for example, potassium hexafluorophosphate (KPF6), potassium bisfluorosulfonimide (KFSI) and potassium bis-trifluoromethanesulfonimide (KTFSI) solution. The solvent of the base ion battery electrolyte of the present application can be selected from, for example, carbonates, ethers and mixtures thereof, the carbonates can include, for example, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC) and the like; the ethers can include, for example, ethylene glycol dimethyl ether (DME) and diethylene glycol dimethyl ether (DEGDME or DIGLYME) and the like. The base ion battery electrolyte of the present application can also include additives, such as film-forming aids, flame retardants and overcharge protection agents and the like.

[0045] In any embodiment, the base ion battery electrolyte used in the present application is selected from sodium ion battery electrolyte. Among them, the solute of the sodium ion battery electrolyte is selected from sodium perchlorate, sodium hexafluorophosphate and sodium trifluoromethyl sulfonate and mixtures thereof, the solvent of the sodium ion battery electrolyte is selected from propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), diethylene glycol dimethyl ether (DEGDME or DIGLYME) and mixtures thereof, preferably selected from ethylene carbonate (EC), diethyl carbonate (DEC), diethylene glycol dimethyl ether (DEGDME or DIGLYME) and mixtures thereof. Preferably, the solvent of the sodium ion battery electrolyte is a mixture of ethylene carbonate and diethyl carbonate or diethylene glycol dimethyl ether, further preferably, the volume ratio of ethylene carbonate and diethyl carbonate in the mixture is 1:1. In this way, better cycle performance and electrochemical performance can be obtained, and thus better balance of excellent forming performance, high mechanical strength, good cycle performance and stable electrochemical performance and other properties.

[0046] In any embodiment, the alkali-ion battery electrolyte employed in the present application can be obtained in a commercially available form, for example, from Suzhou Dodd Chemical Technology Co., Ltd., under a trade name such as NP-001 (composition: 1 M NaPF6 in DEC:EC = 1:1 Vol%), NC-008 (composition: 1 M NaClO4 in DEC:EC = 1:1 Vol%), or NS-001 (composition: 1 M NaCF3SO3 in DIGLYME = 100 Vol%).

[0047] According to another aspect of the present application, the present application also provides a method for preparing the polymer-based electrolyte of the present application, the method comprising the following steps:

[0048] i) dissolving melamine and p-xylylene in dimethyl sulfoxide, stirring under the condition of a hot water bath ultrasonic until the solution is clear, to obtain a mixed solution; heating the mixed solution under an inert atmosphere to perform a reaction, then cooling to room temperature, followed by filtering, and washing the obtained filter, to obtain a porous polymer;

[0049] ii) adding polyethylene glycol into the alkali-ion battery electrolyte and mixing uniformly, to obtain an alkali-ion battery electrolyte mixture;

[0050] iii) mixing the porous polymer and the alkali-ion battery electrolyte mixture and grinding uniformly, to obtain the polymer-based electrolyte;

[0051] wherein,

[0052] The method satisfies the following relationship: porous polymer: alkali-ion battery electrolyte: polyethylene glycol = 100: (30-60): (5-25) by weight, preferably 100: (40-50): (10-20).

[0053] In any embodiment, the method of the present application satisfies the following relationship: melamine: p-xylylene = 1: (2-5) by weight, preferably 1: (2-3). Thereby, it is beneficial to obtain a better porous polymer, and thus it is beneficial to subsequently obtain better cycle performance and electrochemical performance, and further better balance the properties of excellent forming performance, high mechanical strength, good cycle performance, and stable electrochemical performance, etc.

[0054] In any embodiment, the method satisfies the following relationship: melamine: p-xylylene: dimethyl sulfoxide = 1: (2-5): (50-100) by weight, preferably 1: (2-3): (70-100). Thereby, it is beneficial to obtain a better porous polymer, and thus it is beneficial to subsequently obtain better cycle performance and electrochemical performance, and further better balance the properties of excellent forming performance, high mechanical strength, good cycle performance, and stable electrochemical performance, etc.

[0055] The polyethylene glycol used in the present application is as described above.

[0056] The alkali ion battery electrolyte used in the present application is as described above.

[0057] In any embodiment, in step i) of the present application, the hot water bath ultrasonic condition is, for example, ultrasonic wave at a frequency of 35-45 KHz under a hot water bath at 50-70℃; the inert atmosphere is, for example, nitrogen or argon; the heating can be, for example, a solvothermal method or a microwave heating method, wherein the solvothermal method can be, for example, transferring the mixed solution into a high-pressure reactor with a polytetrafluoroethylene lining, sealing and heating at 150-200℃ for 10-20 hours, and the microwave heating method can be, for example, placing the mixed solution in a microwave reactor for reaction at a frequency of 2.4-2.5 GHz for 5-15 minutes; the washing can be, for example, washing with excess acetone or dichloromethane. Step i) of the present application can further comprise drying after washing the obtained filtrate, and the drying can be, for example, vacuum drying, and the condition can be, for example, drying at 70-90℃ for 8-16 hours under a pressure of less than or equal to -0.1 MPa. In this way, it is beneficial to obtain a better porous polymer, thereby facilitating subsequent better cycle performance and electrochemical performance, and further better balancing of excellent forming performance, high mechanical strength, good cycle performance and stable electrochemical performance, etc.

[0058] According to another aspect of the present application, the present application also provides a use of the polymer-based electrolyte of the present application in a secondary battery.

[0059] Examples

[0060] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0061] The reagents or instruments used are not marked with the manufacturer, and are all conventional commercial products commonly used in the art, or can be prepared by those skilled in the art. In the examples of the present application, unless otherwise specified, all operations can be carried out in a manner known to those skilled in the art. In the examples of the present application, unless otherwise specified, all operations are carried out at room temperature and under normal pressure. Unless otherwise specified, the content and percentage in the context of the present application are based on weight.

[0062] Preparation of the polymer-based electrolyte of the present application

[0063] Example 1

[0064] Step i) Synthesis of mesoporous polymer (MTP) by solvothermal method. First, 0.5 g of melamine and 1 g of terephthaldehyde were dissolved in 35 g of dimethyl sulfoxide (DMSO) and stirred completely under the condition of ultrasonic in hot water bath (temperature of hot water bath 60 °C, frequency of ultrasonic 40 KHz) for 2 h until the solution was clear, obtaining a mixed solution. Then the mixed solution was transferred into the inner liner of a high-pressure reactor made of polytetrafluoroethylene and sealed, heated at 180 °C for 14 h under an inert atmosphere (nitrogen), and then cooled. After the reaction was cooled to room temperature, it was filtered, and then washed with excess acetone and dichloromethane for several times, finally obtaining a white solid powder. The obtained white solid powder was placed in a vacuum drying oven to be dried at 80 °C under a pressure of -0.1 MPa for 10 h, obtaining sample MTP.

[0065] Step ii) 0.1 g of polyethylene glycol (PEG) with an average molecular weight of 2000 was added to 0.5 g of a commercial sodium-ion battery electrolyte (1 M NaPF6 in DEC:EC = 1:1 Vol%, Suzhou Duoduo Chemical Technology Co., Ltd., product name NP-001), and stirred until completely dissolved, obtaining an alkali-ion battery electrolyte mixture.

[0066] Step iii) 1 g of MTP was added to the alkali-ion battery electrolyte mixture, and ground uniformly into a paste, which was then placed in a mold and cold-pressed into a film, obtaining a film-shaped polymer-based electrolyte of the application.

[0067] Example 2

[0068] Step i) Synthesis of mesoporous polymer (MTP) by microwave heating method. First, 1 g of melamine and 3 g of terephthaldehyde were dissolved in 100 g of dimethyl sulfoxide (DMSO) and stirred completely under the condition of ultrasonic in hot water bath (temperature of hot water bath 60 °C, frequency of ultrasonic 40 KHz) for 2 h until the solution was clear, obtaining a mixed solution. Then the mixed solution was transferred into a glass flask, placed in a microwave reactor under an inert atmosphere (nitrogen), and the frequency was adjusted to 2.5 GHz, and reacted for 10 minutes, and then cooled. After the reaction was cooled to room temperature, it was filtered, and then washed with excess acetone and dichloromethane for several times, finally obtaining a white solid powder. The obtained white solid powder was placed in a vacuum drying oven to be dried at 80 °C under a pressure of -0.1 MPa for 10 h, obtaining sample MTP.

[0069] Step ii) 0.25 g of polyethylene glycol (PEG) with an average molecular weight of 8000 was added to 1 g of a commercial sodium-ion battery electrolyte (1 M NaClO4 in DEC:EC = 1:1 Vol%, Suzhou Duoduo Chemical Technology Co., Ltd., product name NC-008), and stirred until completely dissolved, obtaining an alkali-ion battery electrolyte mixture.

[0070] Step iii) 2.5 g of MTP was added to the alkali-ion battery electrolyte mixture and grinded uniformly to a mud-like state before being put into a mold to be cold-pressed into a film to obtain a film-shaped polymer-based electrolyte of the present application.

[0071] Example 3

[0072] Step i) The porous polymer (MTP) was synthesized by a microwave heating method. First, 1 g of melamine and 2.5 g of p-phenylenedimethylene were dissolved in 100 g of dimethyl sulfoxide (DMSO), and the solution was completely stirred under the condition of a hot water bath ultrasonic (hot water bath temperature 60 °C, ultrasonic frequency 40 KHz) for 2 h until the solution was clear to obtain a mixed solution. Subsequently, the mixed solution was transferred to a glass flask, and placed in a microwave reactor under an inert atmosphere (nitrogen), and the frequency was adjusted to 2.5 GHz for 10 minutes, and then cooled. After the reaction was cooled to room temperature, the reaction was filtered, and then washed with excess acetone and dichloromethane for several times to finally obtain a white solid powder. The obtained white solid powder was placed in a vacuum drying oven to be dried at 80 °C under a pressure of -0.1 MPa for 10 h to obtain a sample MTP.

[0073] Step ii) 0.25 g of polyethylene glycol (PEG) with an average molecular weight of 4000 was added to 1 g of a commercial sodium-ion battery electrolyte (1 M NaCF3SO3 in DIGLYME = 100 Vol%, Suzhou Duoduo Chemical Technology Co., Ltd., product name NS-001), and stirred until completely dissolved to obtain an alkali-ion battery electrolyte mixture.

[0074] Step iii) 2.5 g of MTP was added to the alkali-ion battery electrolyte mixture and grinded uniformly to a mud-like state before being put into a mold to be cold-pressed into a film to obtain a film-shaped polymer-based electrolyte of the present application.

[0075] Test 1. SEM image characterization

[0076] Test of Example 1

[0077] The polymer-based electrolyte prepared in Example 1 was characterized using a scanning electron microscope (SEM), and the micro-morphology thereof is shown in Figure 1 .

[0078] Test of Example 2

[0079] The polymer-based electrolyte prepared in Example 2 was characterized using a scanning electron microscope (SEM), and the micro-morphology thereof is shown in Figure 9 .

[0080] Figure 1 and Figure 9The SEM image of the polymer-based electrolyte of the present application is shown, from which it can be clearly observed that the material of the present application presents a large-area uniformly distributed porous structure, which is beneficial to the subsequent penetration and liquid retention of the electrolyte. Due to the rich polar functional groups on the surface and the high roughness, it is helpful to enhance the interaction between the electrolyte.

[0081] Test 2. Nitrogen adsorption-desorption test

[0082] Test of Example 1

[0083] The porous polymer (MTP) prepared in Example 1 was subjected to nitrogen adsorption-desorption test, and the test results are shown in Figure 2 and Figure 3 , and the specific surface area was measured to be 937 m 2 / g; the pore size was 4.98 nm.

[0084] Test of Example 2

[0085] The porous polymer (MTP) prepared in Example 2 was subjected to nitrogen adsorption-desorption test, and the test results are shown in Figure 10 and Figure 11 , and the specific surface area was measured to be 981 m 2 / g; the pore size was 4.17 nm.

[0086] Test 3. Dynamic differential scanning calorimetry (DSC) test

[0087] Test of Example 1

[0088] The porous polymer (MTP) prepared in Example 1 was subjected to dynamic differential scanning calorimetry (DSC) test, and the test conditions were as follows: the test temperature range was 50-500℃, the heating rate was 10℃ / min, the atmosphere condition was nitrogen, and the gas flow rate was 40 ml / min. The test results are shown in Figure 4 , and the melting temperature T m was measured to be 460℃.

[0089] As can be seen from Figure 4 , the porous polymer does not have a sharp exothermic and endothermic reaction at 400℃, indicating that the material has good thermal stability.

[0090] Test 4. Simultaneous thermogravimetric differential thermal analysis test

[0091] Test of Example 1

[0092] The polymer-based electrolyte (MTP@PEG) prepared in Example 1 was subjected to simultaneous thermogravimetric differential thermal analysis (TG-DSC) test, and the test conditions were as follows: the test temperature range was 50-500℃, the heating rate was 10℃ / min, the atmosphere condition was nitrogen, and the gas flow rate was 40 ml / min. The test results are shown in Figure 5 .​

[0093] It can be seen from Figure 5 that the decomposition temperature of MTP@PEG all starts from about 180℃, indicating that the material has excellent thermal stability, which can ensure the safety of battery operation; at the same time, its TG curve shows that the mass loss of MTP@PEG is 75% at 400℃, indicating that the MTP material itself has good thermal stability.

[0094] Test 5. Cyclic voltammetry test

[0095] Test of Example 1

[0096] The polymer-based electrolyte of Example 1 was used as the electrolyte, sodium metal was used as the negative electrode, and stainless steel was used as the positive electrode to assemble a test battery. The test battery was subjected to cyclic voltammetry test at room temperature by using CHI600E electrochemical workstation, and the test conditions were: the voltage test interval was -1-4V, and the scanning speed was 1mV / s. The test results are shown in Figure 6 .

[0097] Test of Example 2

[0098] The polymer-based electrolyte of Example 2 was used as the electrolyte, sodium metal was used as the negative electrode, and stainless steel was used as the positive electrode to assemble a test battery. The test battery was subjected to cyclic voltammetry test at room temperature by using CHI600E electrochemical workstation, and the test conditions were: the voltage test interval was -1-4V, and the scanning speed was 1mV / s. The test results are shown in Figure 12 .

[0099] Figure 6 and Figure 12 The CV curve of the sodium-steel sheet test battery assembled by the electrolyte of the application. The CV curve in the figure indicates the stability of the electrolyte in the sodium deposition / stripping process. The results show that in the voltage range of -2V to 4.5V, due to the deposition / stripping of sodium, redox peaks appear near -1V to 1V, and no other peaks are shown in addition, indicating the stability of the electrolyte in the deposition / stripping process. At the same time, the current peak value remains consistent in multiple cycles, proving the high reversibility of sodium deposition / stripping in the quasi-solid-state electrolyte, and having strong cycle stability.

[0100] Test 6. AC impedance test

[0101] Test of Example 1

[0102] The polymer-based electrolyte of Example 1 was used as the electrolyte and stainless steel was used as the symmetrical electrode to assemble a test cell. The AC impedance test of the test cell was performed at room temperature using a CHI600E electrochemical workstation. The test conditions were: frequency 0.1 Hz to 10 kHz, voltage mode 10 mV amplitude. The test results are shown in Figure 2. Figure 7 shown.

[0103] Figure 7 The AC impedance diagram of the steel sheet symmetrical battery assembled with the electrolyte of Example 1 at different temperatures, where the ionic conductivity at 30°C can reach 1.70×10 -4 S cm -1 , indicating excellent ionic conductivity.

[0104] Test of Example 2

[0105] The polymer-based electrolyte of Example 2 was used as the electrolyte and stainless steel was used as the symmetrical electrode to assemble a test cell. The AC impedance test of the test cell was performed at room temperature using a CHI600E electrochemical workstation. The test conditions were: frequency 0.1 Hz to 10 kHz, voltage mode 10 mV amplitude. The test results are shown in Figure 2. Figure 13 shown.

[0106] Figure 13 The AC impedance diagram of the steel sheet symmetrical battery assembled with the electrolyte of Example 2 at different temperatures, where the ionic conductivity at 30°C can reach 0.73×10 -4 S cm -1 , indicating excellent ionic conductivity.

[0107] Test 7. Constant current charge and discharge test

[0108] Test of Example 1

[0109] The polymer-based electrolyte of Example 1 was used as the electrolyte, sodium vanadium phosphate as the positive electrode, and sodium as the negative electrode to assemble a CR2032 type button test battery. The test battery was subjected to constant current charge and discharge tests at room temperature using a LAND battery test system. The test conditions were: voltage test range 2.5-4V, current density 2C (236mA / g). The test results are shown in Figure 8 .

[0110] Figure 8 The long cycle performance and charge-discharge curve of the electrolyte used in Example 1 in Na||NVP half-cell at a current density of 2C. As can be seen from the figure, the battery's first cycle discharge capacity is 99 mAh g -1, and the capacity retention rate of the battery was 93.4% in the first 800 cycles. At the 500th cycle, the capacity retention rate of the battery was 95%, and the coulombic efficiency was 100%. After 800 cycles, the coulombic efficiency of the battery slowly decreased from 98.4% to 92% and then gradually stabilized, and the specific discharge capacity of the battery did not decrease.

[0111] Test of Example 2

[0112] A CR2032 type button test battery was assembled using the polymer-based electrolyte of Example 2 as the electrolyte, sodium vanadium phosphate as the positive electrode, and sodium as the negative electrode. The test battery was subjected to constant current charge and discharge test at room temperature using a LAND battery test system, and the test conditions were: the voltage test interval was 2.5-4V, and the current density was 2C (236mA / g). The test results are shown in Figure 14 .

[0113] Figure 14 The electrolyte of Example 2 was used in a Na||NVP half-cell for long cycle performance at a current density of 2C, and the charge and discharge curves. As can be seen from the figure, the battery can maintain stable reversible capacity. Figure 14 (b-d) show the charge and discharge curves at the 1st, 200th and 500th cycles, respectively, and it can be seen that as the cycle progresses, an obvious voltage platform is shown at about 3.3V, which can be maintained stable, which proves that the reaction has high reversibility. At the 500th cycle, the capacity retention rate of the battery was 78.4, and the coulombic efficiency was 100%.

[0114] Test of Example 3

[0115] A CR2032 type button test battery was assembled using the polymer-based electrolyte of Example 3 as the electrolyte, and metal sodium as the positive and negative electrodes. The test battery was subjected to constant current charge and discharge test at room temperature using a LAND battery test system, and the test conditions were: the protection voltage was -5-5V, the current density was 0.05mA / cm 2 , the plating time was 1h, and the stripping time was 1h. The test results are shown in Figure 15 .

[0116] As can be seen from Figure 15 (a), under the condition of a current density of 0.05mA·cm -2 , after a period of activation, the interface between MTP@PEG and the sodium negative electrode gradually stabilized, and the polarization voltage rapidly decreased from 273mV and stabilized at about 120mV, as shown in Figure 15(b-d). On the one hand, the porous structure framework of MTP can provide stable ion channels for the transmission of sodium ions, improving the ion transport efficiency, on the other hand, the SEI film formed by MTP containing PEG also changes, and the interface impedance of the sodium electrode is reduced, thereby showing a lower polarization voltage. As Figure 15 (d), then MTP can maintain stable 500 hours of cycle and maintain the polarization voltage within 200 mV and no short circuit phenomenon, showing that MTP has excellent interface, cycle stability.

[0117] In summary: the polymer-based electrolyte prepared by the present application has easy-to-obtain raw materials and lower toxicity, and the preparation process of the present application is simple, low in cost and easy to realize. The polymer-based electrolyte prepared by the present application has the advantages of wide use condition, high mechanical strength, good cycle performance, stable electrochemical performance, excellent thermal stability and the like, and can be applied in secondary solid-state sodium ion batteries.

[0118] Please note that the technical features of the above embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application. The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be interpreted as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A polymer-based electrolyte, characterized in that The polymer-based electrolyte comprises: 100 parts by weight of porous polymer; 30 to 60 parts by weight, preferably 40 to 50 parts by weight, of an alkaline ion battery electrolyte; 5 to 25 parts by weight of polyethylene glycol, preferably 10 to 20 parts by weight; Wherein, the porous polymer is prepared from melamine and terephthalaldehyde.

2. The polymer-based electrolyte according to claim 1, characterized in that The specific surface area of ​​the porous polymer is 800 to 1100 m 2 / g, preferably 900-1000m 2 / g; pore diameter is 3 to 6 nm, preferably 4 to 5 nm.

3. The polymer-based electrolyte according to claim 1, characterized in that The melting temperature T of the porous polymer m The temperature is 400-500°C, preferably 440-480°C.

4. The polymer-based electrolyte according to claim 1, characterized in that The average molecular weight of the polyethylene glycol is 300 g / mol to 200,000 g / mol, preferably 1,000 g / mol to 10,000 g / mol, and more preferably 1,000 g / mol to 5,000 g / mol.

5. The polymer-based electrolyte according to claim 1, characterized in that The alkaline ion battery electrolyte is a sodium ion battery electrolyte, and the solute of the sodium ion battery electrolyte is selected from sodium perchlorate, sodium hexafluorophosphate and sodium trifluoromethanesulfonate and mixtures thereof; the solvent of the sodium ion battery electrolyte is selected from propylene carbonate, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, diethylene glycol dimethyl ether and mixtures thereof, preferably selected from ethylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether and mixtures thereof.

6. A method for preparing the polymer-based electrolyte according to claim 1, characterized in that: The method comprises the following steps: i) dissolving melamine and terephthalaldehyde in dimethyl sulfoxide, stirring under ultrasonic conditions in a hot water bath until the solution is clear to obtain a mixed solution; heating the mixed solution under an inert atmosphere to react, then cooling to room temperature, filtering, and washing the filtrate to obtain a porous polymer; ii) adding polyethylene glycol to the alkali ion battery electrolyte and mixing uniformly to obtain an alkali ion battery electrolyte mixture; iii) mixing the porous polymer and the alkali ion battery electrolyte mixture and grinding them uniformly to obtain the polymer-based electrolyte; in, In parts by weight, the method satisfies the following relationship: porous polymer: alkaline ion battery electrolyte: polyethylene glycol = 100: (30-60): (5-25), preferably 100: (40-50): (10-20).

7. The method according to claim 6, characterized in that In parts by weight, the method satisfies the following relationship: melamine: terephthalaldehyde = 1: (2 to 5), preferably 1: (2 to 3); Preferably, the method satisfies the following relationship in parts by weight: melamine: terephthalaldehyde: dimethyl sulfoxide = 1: (2-5): (50-100), preferably 1: (2-3): (70-100).

8. The method according to claim 6, characterized in that The average molecular weight of the polyethylene glycol is 300 g / mol to 200,000 g / mol, preferably 1,000 g / mol to 10,000 g / mol, and more preferably 1,000 g / mol to 5,000 g / mol.

9. The method according to claim 6, characterized in that The alkaline ion battery electrolyte is a sodium ion battery electrolyte, and the solute of the sodium ion battery electrolyte is selected from sodium perchlorate, sodium hexafluorophosphate and sodium trifluoromethanesulfonate and mixtures thereof; the solvent of the sodium ion battery electrolyte is selected from propylene carbonate, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, diethylene glycol dimethyl ether and mixtures thereof, preferably selected from ethylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether and mixtures thereof.

10. Use of the polymer-based electrolyte according to claim 1 in a secondary battery.

Images