Modified polymer solid electrolyte and preparation method thereof

Abstract

The invention relates to the technical field of electrolytes, and provides a modified polymer solid electrolyte and a preparation method thereof. The modified polymer solid electrolyte is obtained by modifying a polymer electrolyte material mixed with lithium salt with ethyl acetate and triethylamine cyanoacetate, the raw materials of the polymer electrolyte material mixed with the lithium salt comprise a polymer electrolyte material and the lithium salt; the triethylamine cyanoacetate salt is prepared from the following raw materials: cyanoacetic acid and triethylamine; the ionic conductivity of the modified polymer solid electrolyte is more than 0.24 mS / cm, the lithium ion transference number is more than 0.32, and the tensile strength is more than 1.8 MPa. According to the technical scheme, the problems of poor ionic conductivity and poor structural stability of the polymer solid electrolyte in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolyte, in particular to a modified polymer solid-state electrolyte and a preparation method thereof. BACKGROUND

[0002] As a frontier energy storage technology, the core innovation of solid-state lithium battery lies in the use of solid-state electrolyte with high ionic conductivity and chemical stability to replace the traditional liquid or gel electrolyte system. This technology significantly improves the safety performance of the battery, while effectively improving the energy density and cycle stability. The core function of solid-state electrolyte is to realize the directional transmission of lithium ions between the positive and negative electrodes, and its material system can be divided into inorganic and polymer categories. Among them, inorganic solid-state electrolyte (such as oxide, sulfide and phosphate, etc.) is highly concerned due to its excellent ion conduction ability and chemical stability, but its high processing difficulty and cost limit its application. In comparison, polymer electrolyte has higher safety, lightness and easy processing, etc., and is more suitable for industrial production.

[0003] Polymer solid-state electrolyte has unique advantages such as flexibility, easy processing and good interface contact, and is one of the commonly used solid-state electrolytes in all-solid-state batteries. It can be closely connected with the electrode and can adapt to the expansion and contraction of the electrode volume. However, polymer solid-state electrolyte usually has high crystallinity at room temperature, and lithium ion transmission generally only occurs in amorphous regions. The crystal region limits the movement of chain segments, making it difficult for lithium ions to migrate, thereby significantly reducing the conductivity of polymer solid-state electrolyte. In addition, polymer solid-state electrolyte has poor contact wettability, which easily produces large interface impedance, affecting the overall performance of the solid-state battery. SUMMARY

[0004] The present application provides a modified polymer solid-state electrolyte and a preparation method thereof, which solves the problems of poor ionic conductivity and poor structural stability of the polymer solid-state electrolyte in the related art.

[0005] The technical scheme of the present application is as follows: The present application provides a modified polymer solid-state electrolyte, which is obtained by modifying a mixed lithium salt polymer electrolyte material with ethyl acetate and triethylamine cyanacetate; The raw materials of the mixed lithium salt polymer electrolyte material include a polymer electrolyte material and a lithium salt; The raw materials of the triethylamine cyanacetate include cyanacetic acid and triethylamine; The ionic conductivity of the modified polymer solid-state electrolyte is above 0.24 mS / cm, the lithium ion transference number is above 0.32, and the tensile strength is above 1.8 MPa.

[0006] As a further technical solution, the addition amount of the lithium salt is 6% to 10% of the mass of the polymer electrolyte material, for example, it can be 6%, 7%, 8%, 9%, 10%, preferably 6%, 8%, 10%, more preferably 8%.

[0007] As a further technical solution, the addition amount of the ethyl acetate is 10% to 15% of the mass of the polymer electrolyte material, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, preferably 10%, 12%, 15%, more preferably 12%.

[0008] As a further technical solution, the addition amount of the triethylamine cyanacetic acid salt is 3% to 5% of the mass of the polymer electrolyte material, for example, it can be 3%, 3.5%, 4%, 4.5%, 5%, preferably 3%, 4%, 5%, more preferably 4%.

[0009] As a further technical solution, the polymer electrolyte material comprises one or more of polyethylene oxide, polyvinylidene fluoride, polymethyl methacrylate, preferably polyethylene oxide.

[0010] As a further technical solution, the lithium salt comprises one of lithium perchlorate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethylsulfonyl)imide, preferably lithium bis(trifluoromethylsulfonyl)imide.

[0011] As a further technical solution, the molar ratio of the cyanacetic acid and triethylamine is 1 to 3:1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, preferably 1:1, 3:1, more preferably 1:1.

[0012] The present application proposes a preparation method of a modified polymer solid-state electrolyte, for preparing the modified polymer solid-state electrolyte, comprising the following steps: S1, mixing and reacting cyanacetic acid and triethylamine to obtain triethylamine cyanacetic acid salt; S2, mixing the polymer electrolyte material and the organic solvent once, adding lithium salt, and mixing twice to obtain a polymer electrolyte material solution mixed with lithium salt; S3, adding the triethylamine cyanacetic acid salt to the polymer electrolyte material solution mixed with lithium salt, dissolving, adding ethyl acetate, and mixing to obtain a mixed solution; S4, casting and drying the mixed solution to obtain a modified polymer solid-state electrolyte.

[0013] As a further technical solution, the cyanacetic acid is cyanacetic acid dried by molecular sieves, the polymer electrolyte material is polymer electrolyte material dried by vacuum, the lithium salt is lithium salt dried by vacuum, and the ethyl acetate is ethyl acetate purified by distillation. The drying temperature is independently 50-80℃, for example, 50℃, 60℃, 70℃, 80℃, preferably 60℃, and the drying time is independently 12-36h, for example, 12h, 15h, 18h, 20h, 22h, 24h, 25h, 30h, 32h, 34h, 36h, preferably 24h.

[0014] As a further technical solution, when the polymer electrolyte material is polyethylene oxide, the molecular weight of the polyethylene oxide is 400000-1000000, for example, 400000, 600000, 800000, 1000000, preferably 600000.

[0015] As a further technical solution, the organic solvent includes one of diethyl ether, methanol, ethanol, preferably diethyl ether.

[0016] As a further technical solution, in step S2, the temperature during the first mixing is 30-50℃, for example, 30℃, 40℃, 50℃, preferably 40℃, and the stirring time is 3-6h, for example, 3h, 4h, 5h, 6h, preferably 4h. The second mixing continues stirring for 3-6h based on the temperature of the first mixing.

[0017] As a further technical solution, in step S3, the temperature during the dissolving is 50-70℃, for example, 50℃, 55℃, 60℃, 65℃, 70℃, preferably 60℃, and the stirring time is 1-3h, for example, 1h, 2h, 3h, preferably 2h. The temperature during the continued stirring is 30-50℃, for example, 30℃, 40℃, 50℃, preferably 30℃, and the stirring time is 1-3h, for example, 1h, 2h, 3h, preferably 2h.

[0018] As a further technical solution, in step S4, the drying is divided into pre-film forming drying and post-film forming drying. The pre-film forming drying is first dried at 30℃ for 4-6h, for example, 4h, 5h, 6h, preferably 5h, then dried at 50℃ for 4-6h, for example, 4h, 5h, 6h, preferably 5h, and then dried at 70℃ for 4-6h, for example, 4h, 5h, 6h, preferably 5h. The vacuum drying is carried out when the film is dried, the temperature of the vacuum drying is 50-70 DEG C, for example, it can be 50 DEG C, 55 DEG C, 60 DEG C, 65 DEG C, 70 DEG C, preferably 60 DEG C, and the drying time is 12-36h, for example, it can be 12h, 15h, 18h, 20h, 22h, 24h, 25h, 30h, 32h, 34h, 36h, preferably 24h.

[0019] The working principle and beneficial effects of the present application are as follows: In the present application, the modified polymer solid electrolyte is obtained by modifying the polymer electrolyte material mixed with lithium salt by ethyl acetate and triethylamine cyanacetate, wherein the raw material of the triethylamine cyanacetate includes cyanacetic acid and triethylamine, after the formation of the triethylamine cyanacetate from the cyanacetic acid and the triethylamine, the cyano group in the triethylamine cyanacetate is a strong polar group, which can form a hydrogen bond with the polymer electrolyte material, thereby effectively inhibiting the formation of a crystalline region, and the cyano group in the triethylamine cyanacetate has a high dielectric constant, enhances local polarization, and promotes lithium ion hopping conduction; the ethyl acetate as a small molecule solvent initially penetrates into the molecular chain of the polymer electrolyte material, reduces the glass transition temperature of the material, can increase the activity of the chain segment, and the carbonyl group of the ethyl acetate can weaken the coordination of lithium ions, thereby reducing the migration energy barrier, and then the ethyl acetate is preferentially reduced when the modified polymer solid electrolyte contacts the battery negative electrode, and the reduction product can participate in the formation of an organic solid electrolyte interface on the negative electrode surface, and then the ethyl acetate is thermally decomposed in the long-term cycle, which can also form a porous structure to increase the interface contact; by using the ethyl acetate and the triethylamine cyanacetate together, the ionic conductivity of the polymer solid electrolyte can be synergistically improved, and the cyano group in the triethylamine cyanacetate forms an inorganic solid electrolyte interface containing lithium hydride on the surface of the lithium negative electrode, and the reduction product of the ethyl acetate in the modified polymer solid electrolyte when contacting the battery negative electrode can participate in the formation of an organic solid electrolyte interface on the negative electrode surface, and the inorganic solid electrolyte interface and the organic solid electrolyte interface form a multilayer protection structure, thereby finally enhancing the structural stability of the polymer solid electrolyte. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor also fall within the scope of protection of the present application.

[0021] In the following examples and comparative examples, the weight average molecular weight of the polyethylene oxide is 600000; the cyanoacetic acid is cyanoacetic acid dried by molecular sieve, wherein the molecular sieve is 4A molecular sieve with a particle size of 3-5 mm; the polyethylene oxide is polyethylene oxide dried in vacuum at 60℃ for 24h; the lithium bis(trifluoromethylsulfonyl)imide is lithium bis(trifluoromethylsulfonyl)imide dried in vacuum at 60℃ for 24h; and the ethyl acetate is ethyl acetate purified by distillation.

[0022] Example 1 A method for preparing a modified polymer solid-state electrolyte, comprising the following steps: S1, mixing cyanoacetic acid and triethylamine in a molar ratio of 1:1, and reacting to obtain cyanoacetic acid triethylamine salt; S2, stirring and mixing 2.4g of polyethylene oxide and 50mL of ether at 40℃ for 4h, then adding 0.192g of lithium bis(trifluoromethylsulfonyl)imide, and continuing to stir at 40℃ for 4h to obtain a mixed lithium salt polymer electrolyte material solution; S3, adding 0.096g of cyanoacetic acid triethylamine salt to the mixed lithium salt polymer electrolyte material solution, stirring at 60℃ for 2h, adding 0.288g of ethyl acetate, and stirring at 30℃ for 2h to obtain a mixed solution; S4, casting the mixed solution on a polytetrafluoroethylene mold, drying at 30℃ for 5h first, then drying at 50℃ for 5h, and then drying at 70℃ for 5h, and vacuum drying the film at 60℃ for 24h to obtain a modified polymer solid-state electrolyte.

[0023] Example 2 A method for preparing a modified polymer solid-state electrolyte, comprising the following steps: S1, mixing cyanoacetic acid and triethylamine in a molar ratio of 3:1, and reacting to obtain cyanoacetic acid triethylamine salt; S2, stirring and mixing 2.4g of polyethylene oxide and 50mL of ether at 40℃ for 4h, then adding 0.144g of lithium bis(trifluoromethylsulfonyl)imide, and continuing to stir at 40℃ for 4h to obtain a mixed lithium salt polymer electrolyte material solution; S3, adding 0.072g of cyanoacetic acid triethylamine salt to the mixed lithium salt polymer electrolyte material solution, stirring at 60℃ for 2h, adding 0.24g of ethyl acetate, and stirring at 30℃ for 2h to obtain a mixed solution; S4, casting the mixed solution on a polytetrafluoroethylene mold, drying at 30℃ for 4h first, then drying at 50℃ for 4h, and then drying at 70℃ for 4h, and vacuum drying the film at 50℃ for 36h to obtain a modified polymer solid-state electrolyte.

[0024] Example 3 A method for preparing a modified polymer solid electrolyte, comprising the following steps: S1, cyanacetic acid and triethylamine are mixed according to a molar ratio of 1:1, reacted, and cyanacetic acid triethylamine salt is obtained; S2, 2.4g of polyethylene oxide is mixed with 50mL of ether at 40℃ for 4h, then 0.24g of lithium bis-trifluoromethyl sulfonimide is added, and stirring is continued at 40℃ for 4h to obtain a mixed lithium salt polymer electrolyte material solution; S3, 0.12g of cyanacetic acid triethylamine salt is added to the mixed lithium salt polymer electrolyte material solution, stirring is carried out at 60℃ for 2h, 0.36g of ethyl acetate is added, and stirring is carried out at 30℃ for 2h to obtain a mixed solution; S4, the mixed solution is cast on a polytetrafluoroethylene mold, dried at 30℃ for 6h, then dried at 50℃ for 6h, and then dried at 70℃ for 6h, after film formation, vacuum drying is carried out at 70℃ for 12h to obtain a modified polymer solid electrolyte.

[0025] Example 4 The difference between this example and example 1 is that in this example, the addition sequence of cyanacetic acid triethylamine salt and ethyl acetate is different, and the method for preparing a modified polymer solid electrolyte is specifically as follows: S1, cyanacetic acid and triethylamine are mixed according to a molar ratio of 1:1, reacted, and cyanacetic acid triethylamine salt is obtained; S2, 2.4g of polyethylene oxide is mixed with 50mL of ether at 40℃ for 4h, then 0.192g of lithium bis-trifluoromethyl sulfonimide is added, and stirring is continued at 40℃ for 4h to obtain a mixed lithium salt polymer electrolyte material solution; S3, 0.288g of ethyl acetate is added to the mixed lithium salt polymer electrolyte material solution, stirring is carried out at 30℃ for 2h, 0.096g of cyanacetic acid triethylamine salt is added, and stirring is carried out at 60℃ for 2h to obtain a mixed solution; S4, the mixed solution is cast on a polytetrafluoroethylene mold, dried at 30℃ for 5h, then dried at 50℃ for 5h, and then dried at 70℃ for 5h, after film formation, vacuum drying is carried out at 60℃ for 24h to obtain a modified polymer solid electrolyte.

[0026] Comparative Example 1 The difference between this example and example 1 is that in this example, the addition sequence of cyanacetic acid triethylamine salt and ethyl acetate is different, and the method for preparing a modified polymer solid electrolyte is specifically as follows: S1, cyanacetic acid and triethylamine are mixed according to a molar ratio of 1:1, reacted, and cyanacetic acid triethylamine salt is obtained; S2, 0.288 g of ethyl acetate was added to the above mixed lithium salt polymer electrolyte material solution, stirred at 30℃ for 2h to obtain a mixed solution; S3, the above mixed solution was cast on a polytetrafluoroethylene mold, first dried at 30℃ for 5h, then dried at 50℃ for 5h, and then dried at 70℃ for 5h, and after film formation, vacuum dried at 60℃ for 24h to obtain a modified polymer solid electrolyte.

[0027] Comparative Example 2 The difference between this comparative example and Example 1 is only that in this comparative example, no ethyl acetate is added, and the preparation method of the modified polymer solid electrolyte is specifically as follows: S1, cyanacetic acid and triethylamine were mixed according to a molar ratio of 1:1, reacted to obtain a cyanacetic acid triethylamine salt; S2, 2.4g of polyethylene oxide was mixed with 50mL of ether at 40℃ for 4h, then 0.192g of lithium bis(trifluoromethylsulfonyl)imide was added and stirred at 40℃ for 4h to obtain a mixed lithium salt polymer electrolyte material solution; S3, 0.096g of cyanacetic acid triethylamine salt was added to the above mixed lithium salt polymer electrolyte material solution, stirred at 60℃ for 2h to obtain a mixed solution; S4, the above mixed solution was cast on a polytetrafluoroethylene mold, first dried at 30℃ for 5h, then dried at 50℃ for 5h, and then dried at 70℃ for 5h, and after film formation, vacuum dried at 60℃ for 24h to obtain a modified polymer solid electrolyte.

[0028] Comparative Example 3 The difference between this comparative example and Example 1 is only that in this comparative example, neither cyanacetic acid triethylamine salt nor ethyl acetate is added, and the preparation method of the modified polymer solid electrolyte is specifically as follows: A preparation method of a modified polymer solid electrolyte, comprising the following steps: S1, 2.4g of polyethylene oxide was mixed with 50mL of ether at 40℃ for 4h, then 0.192g of lithium bis(trifluoromethylsulfonyl)imide was added and stirred at 40℃ for 4h to obtain a mixed lithium salt polymer electrolyte material solution; S2, the above mixed lithium salt polymer electrolyte material solution was cast on a polytetrafluoroethylene mold, first dried at 30℃ for 5h, then dried at 50℃ for 5h, and then dried at 70℃ for 5h, and after film formation, vacuum dried at 60℃ for 24h to obtain a modified polymer solid electrolyte.

[0029] Experimental Example The modified polymer solid electrolytes prepared in Examples 1-4 and Comparative Examples 1-3 were tested for the following properties: ① Ionic conductivity test: A stainless steel sheet is used to sandwich the punched modified polymer solid electrolyte sample film in the middle, and a button cell is assembled for testing. The frequency range is from 1Hz to 10Hz. The bulk resistance R of the modified polymer solid electrolyte is read from the intersection of the tail line and the real axis in the AC impedance spectrum. The electrode area A of the test cell and the thickness d of the modified polymer solid electrolyte sample film are measured. The conductivity is calculated according to the formula σ=d / (R×A), where σ is the ionic conductivity and the thickness d is 80μm. ② Ion transport number test: The changes in current and interfacial resistance after the interface stabilizes are measured by DC polarization + AC impedance, and t is calculated. Li+ :t Li+ =I ss (ΔV-I0R0) / I0(ΔV-I) ss R ss ), where I0 is the initial current (A), I ss R is the steady-state current (A), R0 is the initial interface resistance (Ω), R ss Let ΔV be the steady-state interface resistance (Ω) and ΔV be the applied DC bias voltage (V). A coin cell was assembled by sandwiching a punched modified polymer solid electrolyte sample membrane between two stainless steel sheets for testing. First, conductivity was measured, and a Nyquist plot was output to fit the initial total resistance R0. Then, constant potential polarization was performed using the chronoamperometry method, with a polarization voltage ΔV of 20mV and a polarization time ≥2h. The current-time curve was output, and the initial current I0 and steady-state current I were extracted. ss Immediately after polarization, ionic conductivity was measured, and the steady-state interfacial resistance R was fitted. ss ; ③ Electrochemical window test: The test voltage range is set to 0V to 7V, and the scan rate is 5mV / s. As the scan voltage increases, the current-voltage change curve is recorded. The voltage value corresponding to the inflection point where the current suddenly increases sharply is the decomposition voltage of the electrolyte. The difference between this voltage value and the initial voltage is the electrochemical window of the modified polymer solid electrolyte sample. ④ Tensile strength test: The modified polymer solid electrolyte sample membrane was tested for tensile strength in accordance with ASTM D638 standard; ⑤ Cycle stability test: The modified polymer solid electrolyte and positive electrode were assembled into a solid-state battery, with lithium metal as the negative electrode. The battery was tested at 40℃ within a working voltage range of 2.8~4.4V (vs. Li). + Cycle life testing was conducted at a rate of 0.1C within the range of / Li); The test results are shown in Table 1: Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-3

[0030] Compared with Comparative Examples 1-3, the modified polymer solid electrolytes in Examples 1-3 exhibited ionic conductivity exceeding 0.28 mS / cm, lithium-ion transference number exceeding 0.37, electrochemical window exceeding 4.98 V, tensile strength exceeding 2.1 MPa, and cycle life exceeding 700 h. This indicates that the triethylamine cyanoacetate salt and ethyl acetate obtained from the reaction of cyanoacetic acid and triethylamine in the modified polymer solid electrolyte have a synergistic effect, facilitating lithium-ion migration and effectively improving the ionic conductivity of the modified polymer solid electrolyte. Furthermore, the combined use of triethylamine cyanoacetate salt and ethyl acetate also enhances the structural stability of the modified polymer solid electrolyte, resulting in good tensile strength and cycle life. In addition, in Examples 1-3, by adjusting the amount of triethylamine cyanoacetate and ethyl acetate added, the modified polymer solid electrolyte exhibited the best performance when the amount of triethylamine cyanoacetate added was 4% of the mass of polyethylene oxide and the amount of ethyl acetate added was 12% of the mass of polyethylene oxide. At this content, the strongly polar groups (-CN and -COOH) contained in triethylamine cyanoacetate better combine with the ether oxygen bond (-COC-) of polyethylene oxide, forming hydrogen bonds or dipole interactions, further disrupting the crystalline region of polyethylene oxide. Its acidic groups (-COOH) can also interact with lithium salt anions, promoting lithium salt dissociation. Ethyl acetate can effectively penetrate into the polyethylene oxide chain segments, weakening the hydrogen bonds and van der Waals forces between polyethylene oxide molecular chains, improving chain segment mobility, and promoting lithium ion migration.

[0031] Furthermore, comparing Example 1 with Comparative Example 1, the performance of the modified polymer solid electrolyte decreased without the addition of triethylamine cyanoacetate, indicating that the chemical action of the cyano group can directionally regulate the ionic environment, while ethyl acetate is volatile and has poor long-term stability. Comparing Example 1 with Comparative Example 2, the performance of the modified polymer solid electrolyte decreased without the addition of ethyl acetate, indicating that ethyl acetate can regulate lithium salt dissociation and increase the concentration of free lithium ions. Comparing Example 1 with Comparative Example 3, the performance of the modified polymer solid electrolyte decreased significantly without the addition of either triethylamine cyanoacetate or ethyl acetate, indicating that the synergistic effect of triethylamine cyanoacetate and ethyl acetate has a significant impact on the performance of the modified polymer solid electrolyte. Comparing Example 1 with Example 4, Example 4 changed the order of addition of triethylamine cyanoacetate and ethyl acetate, and the performance of the modified polymer solid electrolyte also decreased to a certain extent, indicating that when ethyl acetate is added first, it will hinder the crosslinking reaction and affect the grafting modification effect of triethylamine cyanoacetate on polyethylene oxide.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified polymer solid electrolyte, characterized in that, It is obtained by modifying a polymer electrolyte material containing mixed lithium salts with ethyl acetate and triethylamine cyanoacetate; The raw materials of the polymer electrolyte material containing the mixed lithium salt include polymer electrolyte material and lithium salt; The raw materials for the triethylamine cyanoacetate salt include cyanoacetic acid and triethylamine; The modified polymer solid electrolyte has an ionic conductivity of ≥0.24 mS / cm, a lithium-ion transference number of ≥0.32, and a tensile strength of ≥1.8 MPa.

2. The modified polymer solid electrolyte according to claim 1, characterized in that, The amount of lithium salt added is 6% to 10% of the mass of the polymer electrolyte material.

3. The modified polymer solid electrolyte according to claim 1, characterized in that, The amount of ethyl acetate added is 10% to 15% of the mass of the polymer electrolyte material.

4. The modified polymer solid electrolyte according to claim 1, characterized in that, The amount of triethylamine cyanoacetate added is 3% to 5% of the mass of the polymer electrolyte material.

5. The modified polymer solid electrolyte according to claim 1, characterized in that, The polymer electrolyte material includes one or more of polyethylene oxide, polyvinylidene fluoride, and polymethyl methacrylate.

6. The modified polymer solid electrolyte according to claim 1, characterized in that, The lithium salt includes one of lithium perchlorate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

7. The modified polymer solid electrolyte according to claim 1, characterized in that, The molar ratio of cyanoacetic acid to triethylamine is 1~3:

1.

8. A method for preparing a modified polymer solid electrolyte, used to prepare a modified polymer solid electrolyte as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Mix cyanoacetic acid with triethylamine and react to obtain triethylamine cyanoacetate; S2. Mix the polymer electrolyte material with the organic solvent once, add lithium salt, and mix a second time to obtain a polymer electrolyte material solution containing mixed lithium salt. S3. Add the triethylamine cyanoacetate salt to the polymer electrolyte material solution of the mixed lithium salt, dissolve it, add ethyl acetate, mix, and obtain a mixed solution; S4. Cast the mixed solution and dry it to obtain the modified polymer solid electrolyte.

9. The method for preparing a modified polymer solid electrolyte according to claim 8, characterized in that, The organic solvent includes one of diethyl ether, methanol, and ethanol.

10. The method for preparing a modified polymer solid electrolyte according to claim 8, characterized in that, In step S4, the drying process is divided into pre-film-forming drying and post-film-forming drying. During the pre-film drying process, the film is first dried at 30°C for 4-6 hours, then dried at 50°C for 4-6 hours, and finally dried at 70°C for 4-6 hours. The film is dried under vacuum at a temperature of 50-70°C for 12-36 hours.

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