Phthalonitrile bicontinuous phase solid electrolyte and application thereof

Abstract

The invention discloses a phthalonitrile bicontinuous phase solid electrolyte and an application thereof. The bicontinuous-phase solid electrolyte is obtained by taking a phthalonitrile compound with high temperature resistance, high ionic conductivity and excellent mechanical property as a matrix and carrying out thermocuring cross-linking reaction on the matrix and a liquid electrolyte. The ionic conductivity of the bicontinuous phase solid electrolyte reaches up to 0.674 mS / cm, the contact internal resistance is small due to good contact with the surface of an electrode, and the bicontinuous phase solid electrolyte can be directly polymerized on the surface of the electrode to assemble a structural energy storage composite material. According to the invention, the defects of high-temperature decomposition, low ionic conductivity and poor mechanical property of the traditional solid electrolyte applied to the structural energy storage composite material are overcome, and the solid electrolyte has a wider application prospect in the fields of military industry, aerospace and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer electrolyte preparation and relates to a phthalonitrile dual-continuous phase solid electrolyte and application thereof. Background Art

[0002] As the demand for lightweight and high-strength materials in high-tech fields such as aerospace becomes more and more urgent, structural multifunctional integrated composite materials with both mechanical bearing and energy storage functions have become an important research direction. Compared with traditional energy storage materials, structural-energy storage integrated composite materials have significant advantages in terms of quality, volume, cost, etc. By developing the design potential of composite materials in terms of structure and function, it is expected to integrate the structural components and power supply components of aerospace equipment as a whole to solve the problems of large volume, large mass, and low efficiency of energy storage devices. At present, the average energy storage density of structural-energy storage integrated carbon fiber composite materials is about 20Wh / kg, which is only 1 / 5 of that of ordinary lithium-ion energy storage structures, and its cycle charge and discharge stability is poor; at the same time, due to its poor mechanical properties, it cannot be used as a load-bearing structure, that is, there is currently no structural-energy storage integrated carbon fiber composite material that takes into account both excellent energy storage and bearing capacity.

[0003] From a technical point of view, solid structure electrolyte is a material that is responsible for both lithium ion conduction and the load transfer capacity of the entire multifunctional solid. Therefore, resin solid structure electrolytes with both high ionic conductivity and excellent mechanical properties are the key factors in preparing structural-energy storage integrated composite materials with excellent comprehensive performance. The all-solid polymer electrolytes currently studied have high mechanical properties due to the lack of solvents, but low ionic conductivity; gel polymer electrolytes have ionic conductivity similar to that of liquid electrolytes, but due to the presence of solvents, the electrolytes have poor mechanical properties. In response to the above problems, in 2010, Ji et al. (Ji J, Li B, Zhong WH. Simultaneously enhancing ionicconductivity and mechanical properties of solid polymer electrolytes via acopolymer multi-functional filler [J]. Electrochimica Acta, 2010, 55 (28): 9075-9082.) proposed the concept of dual continuous phase electrolytes, one phase provides mechanical properties and the other phase provides ion transport. However, dual-continuous phase solid electrolytes are basically based on epoxy resin, the resin matrix is ​​of a single type, and the epoxy resin has a low temperature resistance grade, and still cannot meet the requirements of practical applications in terms of mechanical properties and ionic conductivity. Summary of the invention

[0004] To address the above technical problems, the present invention provides a solid electrolyte comprising a phthalonitrile compound and a liquid electrolyte.

[0005] According to an embodiment of the present invention, the mass ratio of the phthalonitrile compound to the liquid electrolyte is 1:(0.1 - 2), exemplified by 1:0.1, 1:0.43, 1:0.67, 1:0.8, 1:1, 1:1.5, 1:2.

[0006] According to an embodiment of the present invention, the liquid electrolyte comprises the following components in parts by weight: 0.3 - 1 part of an ionic liquid, 0.1 - 0.5 part of a lithium salt, and 0.03 - 0.01 part of an organic solvent.

[0007] According to an embodiment of the present invention, in the liquid electrolyte, the weight part of the ionic liquid is 0.3 - 1 part, exemplified by 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.8 part, 1 part.

[0008] According to an embodiment of the present invention, in the liquid electrolyte, the weight part of the lithium salt is 0.1 - 0.5 part, exemplified by 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part.

[0009] According to an embodiment of the present invention, in the liquid electrolyte, the weight part of the organic solvent is 0.03 - 0.01 part, exemplified by 0.01 part, 0.02 part, 0.03 part.

[0010] According to an embodiment of the present invention, the phthalonitrile compound is one or more of the compounds represented by the following structural formula:

[0011]

[0012] wherein, the grafting rate of the phthalonitrile group is greater than 0% and less than 100%, preferably 40 - 80%;

[0013] n is an integer selected from 1 - 8; for example, n = 1, 2, 3, 4, 5, 6, 7, 8;

[0014] R 1 、R 2 、R 3 、R 4 are the same or different, and independently selected from -H, -OH, halogen, substituted or unsubstituted C 1～6 alkyl;

[0015] According to the present invention, the halogen is F, Cl, Br, I.

[0016] In the present invention, the phthalonitrile group The grafting rate refers to the molar percentage of 4-nitrophthalonitrile substituting for phenolic hydroxyl groups.

[0017] Preferably, R 1 , R 2 , R 3 , R 4 are the same or different and independently selected from -H, -OH, -F, -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 , -CH(CH 3 ) 2 , -CF 3 , * represents a connecting bond;

[0018] More preferably, R 1 , R 2 , R 3 , R 4 are the same or different and independently selected from -H, -OH, -F, * represents a connecting bond.

[0019] According to an embodiment of the present invention, the ionic liquid is one or more of imidazole-based, pyrrole-based, and pyrrolidine-based ionic liquid compounds, and can be represented as: A + X - , where:

[0020] A + can be represented by the following structural formula:

[0021]

[0022] Among them, R 1 -R 10 are the same or different and independently selected from -CH 3 OCH 3 , -NH 2 , -SH, -NHCONH 2 , -OH, -SO 3 H, substituted or unsubstituted C 1～6 alkyl;

[0023] X = Cl, Br, I, BF 4 , PF 6 , HSO 4 , SCN, AsF 6 , CF 3 SO 3 , N(CF 3 SO2 ) 2 or N(FSO 2 ) 2 。

[0024] According to an embodiment of the present invention, the lithium salt is one of lithium tetrafluoroborate, lithium bis(difluorophosphate), lithium difluoro(oxalato)borate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide or lithium bis(oxalato)borate.

[0025] According to an embodiment of the present invention, the organic solvent is one of propylene carbonate or ethylene carbonate.

[0026] According to an embodiment of the present invention, the solid electrolyte is a bicontinuous phase solid electrolyte based on a phthalonitrile resin.

[0027] The present invention also provides a method for preparing the above solid electrolyte, which includes mixing a phthalonitrile compound and a liquid electrolyte to obtain the solid electrolyte.

[0028] According to an embodiment of the present invention, the liquid electrolyte is prepared from 0.3 - 1 part of an ionic liquid, 0.1 - 0.5 part of a lithium salt, and 0.03 - 0.01 part of an organic solvent. Preferably, the reaction is carried out under heating conditions. For example, the heating temperature is 60°C - 120°C, exemplarily 60°C, 90°C, 120°C. Also, for example, the heating is carried out in a vacuum environment to avoid the lithium salt absorbing water and affecting the electrochemical performance.

[0029] According to an embodiment of the present invention, the mixing is carried out under heating and stirring conditions. For example, the heating temperature is 100°C - 120°C, exemplarily 100°C, 110°C, 120°C; the stirring time is 0.5h - 2h, and the stirring rate is 200 - 500 rpm.

[0030] According to an embodiment of the present invention, the preparation method further includes vacuum heating the mixed liquid after mixing to remove bubbles and obtain a cyano-(phthalonitrile compound) liquid electrolyte precursor solution. Preferably, the heating temperature is 100°C - 120°C, exemplarily 100°C, 110°C, 120°C; the heating time is 1h - 3h, exemplarily 1h, 2h, 3h.

[0031] According to an embodiment of the present invention, the preparation method further includes pouring the prepared mixed bubble-free cyanide (phthalonitrile compound) liquid electrolyte precursor solution into a mold and heating and curing it to obtain a bicontinuous phase solid electrolyte. For example, the mold is a cylindrical mold with a diameter of 10 cm, and a cylindrical bicontinuous phase solid electrolyte with a diameter of 10 cm is formed after curing. Again, the curing temperature is 150°C - 300°C, and the curing time is 8 - 24 h. Exemplarily, curing is carried out according to a stepped heating program of 175°C / 2 h, 200°C / 6 h, 250°C / 5 h, 280°C / 2 h, and after cooling, it is taken out to obtain a phthalonitrile bicontinuous phase solid electrolyte.

[0032] According to an embodiment of the present invention, the preparation method of the solid electrolyte includes the following steps:

[0033] (1) Heating and dissolving 0.3 - 1 part by mass of an ionic liquid, 0.1 - 0.5 part by mass of a lithium salt, and 0.03 - 0.01 part by mass of an organic solvent to form a liquid electrolyte, heating and stirring and mixing it with 1 part by mass of a phthalonitrile compound, and heating under vacuum and evacuating to remove bubbles;

[0034] (2) Pouring the uniformly mixed and bubble-free cyanide (phthalonitrile compound) liquid electrolyte precursor solution prepared in step (1) into a mold and heating and curing it.

[0035] The present invention also provides the application of the above solid electrolyte in a structure-energy storage integrated composite material.

[0036] The present invention also provides a composite material containing the above solid electrolyte.

[0037] According to an embodiment of the present invention, the composite material further includes a negative electrode, a separator, and a positive electrode, and the above solid electrolyte is coated on the negative electrode, the separator, and the positive electrode.

[0038] According to an embodiment of the present invention, the negative electrode is carbon fiber. For example, the carbon fiber is polyacrylonitrile-based carbon fiber.

[0039] According to an embodiment of the present invention, the positive electrode active material is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese cobaltate, lithium nickel manganese cobalt aluminate, lithium nickel cobaltate, lithium-rich manganese, sodium vanadium phosphate, and sodium fluorovanadium phosphate.

[0040] According to an embodiment of the present invention, the separator is, for example, a glass fiber separator.

[0041] According to an embodiment of the present invention, the composite material can be a single-layer battery or a double-layer battery.

[0042] According to an exemplary embodiment of the present invention, the composite material includes a negative electrode, a separator, and a positive electrode assembled in sequence, and the above-mentioned solid electrolyte is coated on the negative electrode, the separator, and the positive electrode.

[0043] According to an exemplary embodiment of the present invention, the composite material includes a negative electrode, a separator, a positive electrode, a separator, and a negative electrode assembled in sequence, and the above-mentioned solid electrolyte is coated on the negative electrode, the separator, and the positive electrode.

[0044] According to an embodiment of the present invention, the composite material is a structure - energy storage integrated composite material.

[0045] The present invention also provides a method for preparing the above-mentioned composite material, which includes coating the above-mentioned cyanide liquid electrolyte precursor solution on the surfaces of the negative electrode, the glass separator, and the positive electrode active material, and assembling to obtain the composite material.

[0046] According to an embodiment of the present invention, the method for preparing the composite material further includes heating and curing the assembled composite material. Preferably, the curing temperature is 150°C - 300°C, and the curing time is 8 - 24 h. Exemplarily, it is cured according to a step - wise temperature - rising program of 175°C / 2 h, 200°C / 6 h, 250°C / 5 h, 280°C / 2 h, and taken out after cooling to obtain the composite material.

[0047] According to an embodiment of the present invention, the method for preparing the composite material includes the following steps:

[0048] (1) Heating and dissolving 0.3 - 1 part by mass of an ionic liquid, 0.1 - 0.5 part by mass of a lithium salt, and 0.03 - 0.01 part by mass of an organic solvent to form a liquid electrolyte, heating and mechanically stirring it with 1 part by mass of a phthalonitrile - type compound to mix evenly, and putting it into a vacuum drying oven to heat and evacuate to remove bubbles;

[0049] (2) Uniformly coating the bubble - free cyanide liquid electrolyte precursor solution prepared in step (1) on the surfaces of the negative electrode, the separator, and the positive electrode active material, and assembling it into a single - layer battery; and / or assembling the negative electrode, the separator, the positive electrode active material, the separator, and the negative electrode after coating the mixed solution into a double - layer battery to test the mechanical properties;

[0050] (3) Vacuum - encapsulating the structure - energy storage carbon fiber composite material assembled in step (2) and putting it into an oven for curing.

[0051] The beneficial effects of the present invention:

[0052] The double-continuous phase solid electrolyte prepared with phthalonitrile resin as the matrix in the present invention, phthalonitrile resin is a new type of thermosetting resin system, which has many advantages compared with epoxy resin: (1) High dielectric constant. Phthalonitrile resin has high dielectric constant cyano groups, which helps the miscibility of liquid electrolyte and resin, promotes structural uniformity, and can also promote the dissociation of lithium salts, improving ionic conductivity; (2) High heat resistance. Compared with the maximum service temperature of 180 °C of epoxy resin, the service temperature of phthalonitrile resin can reach 300 °C, meeting the use requirements under high temperature conditions; (3) Excellent flame retardancy. Compared with epoxy resin, the excellent flame retardancy of phthalonitrile resin can ensure the safety performance of structural energy storage materials during use. It has the following advantages: (1) Compared with the double-continuous phase solid electrolyte with epoxy resin as the matrix, the present invention has better heat resistance. In non-isothermal thermogravimetry, the T d5％ decomposition temperature in air and nitrogen is above 360 °C, and the T d10％ decomposition temperature is above 380 °C; (2) Cyano is a high dielectric constant group, which can promote the dissociation of lithium salts. When the proportion of liquid electrolyte is 50%, compared with the ionic conductivity of 0.0456 mS / cm and tensile strength of 373 MPa of the epoxy resin-based double-continuous phase solid electrolyte, the ionic conductivity of the phthalonitrile resin-based double-continuous phase solid electrolyte is as high as 0.674 mS / cm, and the tensile modulus is as high as 534 MPa, having high ionic conductivity and excellent mechanical properties. At the same time, the electrolyte of the present invention has good contact with the electrode surface, reducing the contact internal resistance, and can be directly polymerized on the electrode surface to form a structure-energy storage integrated carbon fiber composite with excellent energy storage performance and load-bearing capacity. Description of the Drawings

[0053] Figure 1 Infrared spectra of the phthalonitrile resin material prepared in Comparative Example 1 and the double-continuous phase solid electrolyte 3 prepared with phthalonitrile resin as the matrix in Example 3.

[0054] Figure 2 Differential scanning calorimetry spectra of the phthalonitrile monomer in Comparative Example 1 and the cyano liquid electrolyte precursor solutions in Examples 1, 2, and 3.

[0055] Figure 3 Schematic diagram of the thermogravimetric curve of the double-continuous phase solid electrolyte 3 prepared with phthalonitrile resin as the matrix in Example 3.

[0056] Figure 4 Scanning electron microscope diagrams of the double-continuous phase solid electrolytes 1, 2, and 3 prepared with phthalonitrile resin as the matrix in Examples 1, 2, and 3.

[0057] Figure 5Schematic diagram of the electrochemical impedance of the double-continuous phase solid electrolyte 3 based on phthalonitrile resin prepared in Example 3.

[0058] Figure 6 Comprehensive schematic diagram of the tensile strength and ionic conductivity of the double-continuous phase solid electrolytes 1, 2, 3, and 4 based on phthalonitrile resin prepared in Examples 1, 2, 3, and 4.

[0059] Figure 7 Schematic diagram of the charge-discharge performance of the phthalonitrile double-continuous phase solid electrolyte structure energy storage carbon fiber composite prepared in Example 5. Detailed Description of the Invention

[0060] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only illustrative explanations of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0061] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0062] Example 1: Phthalonitrile Double-Continuous Phase Solid Electrolyte 1

[0063] Add 14.82 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt, 6.46 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.150 g of propylene carbonate to a conical flask. Place the conical flask in a vacuum drying oven and heat it at 90 °C to dissolve and form a colorless and transparent liquid electrolyte. Add 50 g of phthalonitrile monomer to a three-necked flask and heat it in an oil bath at 120 °C. After the phthalonitrile monomer ( R = R = n = 1 or 2) is completely melted, add the prepared liquid electrolyte, and mechanically stir for 1 h at a stirring rate of 350 rpm. After stirring evenly, pour the prepared cyanide liquid electrolyte precursor solution into a cylindrical mold, place it in a vacuum drying oven, and evacuate the air bubbles at 120 °C for 1 h. Transfer it to a forced-air drying oven and cure it according to the stepwise temperature increase program of 175 °C / 2 h, 200 °C / 6 h, 250 °C / 5 h, and 280 °C / 2 h. After cooling, take it out to obtain the phthalonitrile double-continuous phase solid electrolyte 1.

[0064] Example 2: Phthalonitrile Double-Continuous Phase Solid Electrolyte 2

[0065] Example 2 is different from Example 1 in that the mass ratio of the blend in the cyanide liquid electrolyte precursor solution is replaced with: liquid electrolyte: phthalonitrile monomer = 2:3, where the liquid electrolyte is 33.33 g (i.e., 23.05 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 10.05 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.23 g of propylene carbonate), and the phthalonitrile monomer is 50 g.

[0066] Example 3: Phthalonitrile bicontinuous phase solid electrolyte 3

[0067] Example 2 is different from Example 1 in that the mass ratio of the blend in the cyanide liquid electrolyte precursor solution is replaced with: liquid electrolyte: phthalonitrile monomer = 1:1, where the liquid electrolyte is 50 g (i.e., 34.58 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 15.07 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.35 g of propylene carbonate), and the phthalonitrile monomer is 50 g.

[0068] Example 4: Phthalonitrile bicontinuous phase solid electrolyte 4

[0069] Example 2 is different from Example 1 in that the mass ratio of the blend in the cyanide liquid electrolyte precursor solution is replaced with: liquid electrolyte: phthalonitrile monomer = 3:2, where the liquid electrolyte is 75 g (i.e., 51.87 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 22.61 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.52 g of propylene carbonate), and the phthalonitrile monomer is 50 g.

[0070] Example 5: Phthalonitrile bicontinuous phase solid electrolyte structure energy storage carbon fiber composite

[0071] (1) Preparation of phthalonitrile liquid electrolyte precursor solution: Add 34.58 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 15.07 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.349 g of propylene carbonate to a conical flask, and place the conical flask in a vacuum drying oven and heat it at 90 °C to dissolve it to form a colorless and transparent liquid electrolyte. Add 50 g of phthalonitrile monomer to a three-necked flask, heat it in an oil bath at 120 °C, and after the phthalonitrile monomer is completely melted, add the prepared liquid electrolyte, stir mechanically for 1 h, the stirring rate is 350 rpm, and after stirring evenly, pour the prepared cyanide liquid electrolyte precursor solution into a tin foil box mold and place it in a vacuum drying oven, and evacuate the bubbles at 120 °C for 1 h;

[0072] (2) Preparation of the structure energy storage composite electrode; Prepare a carbon fiber sheet 4 cm × 8 cm, and deposit lithium iron phosphate on the surface of 3 cm × 6 cm aluminum foil as the positive electrode sheet (deposition amount: 4 mg / cm 2) Place the carbon fiber in an aging oven at 400 °C for 4 h to completely desize. The prepared nickel strip and aluminum strip (8 mm × 8 cm) are respectively bonded to the positive and negative electrodes with a high-temperature graphite conductive binder (Ausbond / graphite conductive glue of Ausbond, purchased from Shenzhen Ausbond Co., Ltd.) to facilitate subsequent electrochemical tests.

[0073] (3) Assembly of structural energy storage composite materials: Preheat the heating table to 100 °C. The uniformly mixed cyanide liquid electrolyte precursor solution prepared in step (1) is successively and uniformly coated on the surface of the carbon fiber, glass fiber separator (6 cm × 10 cm), and positive lithium iron phosphate placed horizontally on the heating table, with a coating amount of about 2.2 g to 2.3 g. The carbon fiber (Toray T700), glass fiber separator (whatman-GF / A), and positive lithium iron phosphate after coating the cyanide liquid electrolyte precursor solution are assembled into a single-layer battery in this order, and its electrochemical performance is tested. The results are as Figure 7 shown;

[0074] The carbon fiber coated with the cyanide liquid electrolyte precursor solution, glass fiber separator, positive lithium iron phosphate, glass fiber separator, and carbon fiber are assembled into a double-layer battery in this order, and its mechanical performance is tested.

[0075] (4) Vacuum curing: The structural energy storage composite material assembled in step (3) is vacuum packaged using a wet prepreg molding process. After evacuating and placing it for 2 h to check that the vacuum degree remains unchanged, it is placed in a forced-air drying oven and cured according to a stepped temperature increase program of 175 °C / 2 h, 200 °C / 6 h, 250 °C / 5 h, and 280 °C / 2 h. After cooling, it is taken out to obtain a phthalonitrile double-continuous phase solid electrolyte type structural energy storage carbon fiber composite material.

[0076] Comparative Example 1: Preparation of phthalonitrile resin material

[0077] Add 20 g of phthalonitrile-based monomer to a tin foil box mold, place it in a vacuum drying oven and heat at 120 °C. After the phthalonitrile-based monomer is completely melted, start evacuating to remove bubbles for 1 h, transfer it to a forced-air drying oven, and cure according to a stepped temperature increase program of 175 °C / 2 h, 200 °C / 6 h, 250 °C / 5 h, and 280 °C / 2 h. After cooling, it is taken out to obtain a phthalonitrile resin material.

[0078] Figure 1 are the infrared spectra of the phthalonitrile resin material prepared in Comparative Example 1 and the double-continuous phase solid electrolyte 3 with phthalonitrile resin as the matrix prepared in Example 3. The structure in the figure shows that the -CN peak of the phthalonitrile resin material prepared in Comparative Example 1 and the double-continuous phase solid electrolyte with phthalonitrile resin as the matrix prepared in Example 3 significantly weakens at 2230 cm -1 and at 1010 cm-1 、There are phthalocyanine and isoindoline peaks generated at around 1720 cm -1 . This indicates that the addition of the liquid electrolyte has no effect on the crosslinking and curing of the phthalonitrile resin.

[0079] Figure 2 is the differential scanning calorimetry spectrum of the phthalonitrile-based monomer of Comparative Example 1 and the cyanide liquid electrolyte precursor solutions of Examples 1, 2, and 3. The results in the figure show that: compared with Comparative Example 1, the addition of the liquid electrolyte in Examples 1, 2, and 3 shifts the curing peak of the phthalonitrile resin to the left, indicating that the liquid electrolyte has a catalytic effect on the curing of the phthalonitrile resin.

[0080] Figure 3 is the schematic diagram of the thermogravimetric curve of the bicontinuous phase solid electrolyte 3 based on the phthalonitrile resin prepared in Example 3. The results in the figure show that: in non-isothermal thermogravimetry, the T d5％ decomposition temperature of the solid electrolyte 3 in air and nitrogen is above 360 °C, and the T d10％ decomposition temperature is above 380 °C. This indicates that the phthalonitrile bicontinuous phase solid electrolyte prepared in the present invention has excellent thermal stability.

[0081] Figure 4 is the scanning electron microscope schematic diagram of the bicontinuous phase solid electrolytes 1, 2, and 3 based on the phthalonitrile resin prepared in Examples 1, 2, and 3. The results in the figure show that: as the proportion of the liquid electrolyte increases, the porosity of the solid electrolyte increases, the pore diameter increases and the pores gradually become continuous, thus proving the formation of a bicontinuous structure, and the increase of the pores is beneficial to the transmission of the liquid electrolyte, thereby improving the ionic conductivity of the solid electrolyte.

[0082] Figure 5 is the electrochemical impedance schematic diagram of the bicontinuous phase solid electrolyte 3 based on the phthalonitrile resin prepared in Example 3. The test frequency range is 1000 kHz to 0.01 Hz, and the internal inset is the enlarged view of the high-frequency region. The intersection value of the curve of this figure with the abscissa is small, indicating that the solid electrolyte 3 has a small internal resistance. According to the formula, the ionic conductivity is as high as 0.674 mS / cm, indicating that the preparation obtained in the present invention has a high ion transport rate.

[0083] Figure 6 is the comprehensive schematic diagram of the tensile strength and ionic conductivity of the bicontinuous phase solid electrolytes 1, 2, 3, and 4 based on the phthalonitrile resin prepared in Comparative Example 1 and Examples 1, 2, 3, and 4. The results in the figure show that: as the proportion of the liquid electrolyte increases, the mechanical properties of the solid electrolyte decrease, and the ionic conductivity increases. When the proportion of the liquid electrolyte is too large, a three-dimensional skeleton cannot be formed during the curing of the phthalonitrile, resulting in poor mechanical properties.

[0084] Figure 7 Charge-discharge performance graph of the phthalonitrile bicontinuous phase solid electrolyte structure energy storage carbon fiber composite (single-layer battery) prepared in Example 5. The current density is 8.5 μA / mg. The results in the figure show that the charging capacity of the structure energy storage carbon fiber composite is 12.19 mAh / g, and the discharging capacity is 7.47 mAh / g, and normal charge and discharge can be achieved, indicating that the bicontinuous phase solid electrolyte based on phthalonitrile resin can be successfully applied to the structure energy storage carbon fiber composite and has good charge-discharge performance.

[0085] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A solid electrolyte, characterized in that, it comprises a phthalonitrile compound and a liquid electrolyte.

2. The solid electrolyte according to claim 1, characterized in that, the liquid electrolyte comprises the following components in parts by weight: 0.3 - 1 part of an ionic liquid, 0.1 - 0.5 part of a lithium salt, and 0.03 - 0.01 part of an organic solvent. Preferably, the phthalonitrile compound is one or more of the compounds shown in the following structures: Among them, the grafting rate of the phthalonitrile group is greater than 0% and less than 100%, preferably 40-80%; n is an integer between 1 and 8; R 1 、R 2 、R 3 、R 4 are the same or different and are independently selected from -H, -OH, halogen, substituted or unsubstituted C 1～6 alkyl; Preferably, the halogen is F, Cl, Br, I. Preferably, R 1 , R 2 , R 3 , R 4 are the same or different and are each independently selected from -H, -OH, -F, -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 , -CH(CH 3 ), 2 , -CF 3 , * represents a connecting bond.

3. The solid electrolyte according to claim 1, characterized in that, The ionic liquid is one or more of imidazole-based, pyrrole-based, and pyrrolidine-based ionic liquid compounds, and can be represented as: A + X - A + It can be represented by the following structural formula: Among them, R 1 -R 10 are the same or different and are independently selected from -CH 3 OCH 3 , -NH 2 , -SH, -NHCONH 2 , -OH, -SO 3 H, substituted or unsubstituted C 1～6 alkyl; X = Cl, Br, I, BF 4 , PF 6 , HSO 4 , SCN, AsF 6 , CF 3 SO 3 , N(CF 3 SO 2 ) 2 or N(FSO 2 ) 2 .

4. The solid electrolyte according to claim 1, characterized in that, the lithium salt is one of lithium tetrafluoroborate, lithium bis(difluorophosphate), lithium difluoro(oxalato)borate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium bis(oxalato)borate. Preferably, the organic solvent is one of propylene carbonate or ethylene carbonate.

5. A method for preparing the solid electrolyte according to any one of claims 1 - 4, characterized in that, the preparation method comprises mixing the phthalonitrile compound and the liquid electrolyte to prepare the solid electrolyte.

6. The preparation method according to claim 5, characterized in that, the liquid electrolyte is prepared from 0.3 - 1 part of an ionic liquid, 0.1 - 0.5 part of a lithium salt, and 0.03 - 0.01 part of an organic solvent. Preferably, the reaction is carried out under heating conditions. For example, the heating temperature is 60°C - 120°C. Preferably, the mixing is carried out under heating and stirring conditions. For example, the heating temperature is 100°C - 120°C, such as 100°C, 110°C, 120°C; the stirring time is 0.5h - 2h, and the stirring rate is 200 - 500 rpm. Preferably, the preparation method further comprises vacuum heating the mixed solution after mixing to remove bubbles to obtain a cyanide (phthalonitrile compound) liquid electrolyte precursor solution. Preferably, the heating temperature is 100°C - 120°C; the heating time is 1h - 3h. Preferably, the preparation method further comprises pouring the prepared bubble - free cyanide (phthalonitrile compound) liquid electrolyte precursor solution into a mold and heating and curing to obtain a bicontinuous phase solid electrolyte.

7. The preparation method according to claim 5 or 6, characterized in that, it comprises the following steps: (1) Heating and dissolving 0.3 - 1 part of an ionic liquid, 0.1 - 0.5 part of a lithium salt, and 0.03 - 0.01 part of an organic solvent by weight to form a liquid electrolyte, heating and stirring and mixing with 1 part by weight of a phthalonitrile compound, and vacuum heating and evacuating to remove bubbles; (2) Pouring the uniformly mixed and bubble - free cyanide (phthalonitrile compound) liquid electrolyte precursor solution prepared in step (1) into a mold and heating and curing.

8. Use of the solid electrolyte according to any one of claims 1-4 and / or the solid electrolyte prepared by the preparation method according to any one of claims 5-7 in a structure-energy storage integrated composite material.

9. A composite material, characterized in that it contains the solid electrolyte according to any one of claims 1-4 and / or the solid electrolyte prepared by the preparation method according to any one of claims 5-7. Preferably, the composite material further includes a negative electrode, a separator, and a positive electrode, and the above solid electrolyte is coated on the negative electrode, the separator, and the positive electrode. Preferably, the negative electrode is carbon fiber. For example, the carbon fiber is polyacrylonitrile-based carbon fiber. Preferably, the positive electrode active material is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese cobaltate, lithium nickel manganese cobalt aluminate, lithium nickel cobaltate, lithium-rich manganese, sodium vanadium phosphate, and sodium fluorophosphate vanadate. Preferably, the separator is, for example, a glass fiber separator. Preferably, the composite material can be a single-layer battery or a double-layer battery. Preferably, the composite material includes a negative electrode, a separator, and a positive electrode assembled in sequence, and the above solid electrolyte is coated on the negative electrode, the separator, and the positive electrode. Preferably, the composite material includes a negative electrode, a separator, a positive electrode, a separator, and a negative electrode assembled in sequence, and the above solid electrolyte is coated on the negative electrode, the separator, and the positive electrode.

10. A preparation method of the composite material according to claim 9, characterized in that the preparation method includes coating the cyano liquid electrolyte precursor solution according to claim 7 on the surfaces of the negative electrode, the glass separator, and the positive electrode active material, and assembling to obtain the composite material.

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