A method of making, products and applications of a modified polymer electrolyte

Abstract

The application discloses a preparation method of a modified polymer electrolyte, comprising the following steps: (1) mixing a modifier solution and a polymer matrix solvent uniformly to obtain a slurry, coating the slurry on a diaphragm, and obtaining a modified polymer film after drying; the modifier is selected from one or more of lithium ferrocyanide, lithium ferricyanide, lithium cuprocyanide and lithium cobalt cyanide; the polymer matrix is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol and polymethacrylate; (2) immersing the modified polymer film into an electrolyte, and obtaining the modified polymer electrolyte after drying. The prepared modified polymer electrolyte has the advantages of a wide electrochemical window, a high lithium ion transference number and high ionic conductivity; and a solid battery assembled by using the modified polymer electrolyte has the advantages of high capacity, high initial efficiency and high stability.

Description

Technical Field

[0001] This invention relates to the technical field of polymer electrolytes, and more particularly to a method for preparing a modified polymer electrolyte, a product thereof, and its application in solid-state batteries. Background Technology

[0002] Polymer electrolytes not only have good chemical stability, thermal stability and flexibility, but also have advantages such as low cost, easy processing and environmental friendliness. Although the research prospects of all-solid-state batteries prepared by polymer electrolytes are promising, their electrochemical performance in room temperature and low temperature environments is not satisfactory, which seriously restricts their commercial development. The main reasons are as follows: (1) It is impossible to design polymer electrolytes that have both high room temperature ionic conductivity and good mechanical strength;

[0003] (2) The electrochemical voltage window is narrow, making it difficult to match with 4V-level high-voltage cathode materials; (3) Li + The migration number is low, and severe concentration polarization occurs inside the polymer electrolyte during battery operation, which has an adverse effect on the battery, such as generating lithium dendrites and limiting battery output power; (4) The electrochemical stability of the interface between the polymer electrolyte and the electrode is poor.

[0004] Introducing inorganic fillers, such as silica, alumina, aluminosilicates, and titanium dioxide, into the polymer electrolyte matrix can improve both the room-temperature ionic conductivity and mechanical strength of the polymer electrolyte to some extent. However, these modification methods also have limitations. Typically, in all-solid-state batteries assembled with these modified polymer electrolytes, interfacial instability exists between the electrodes and the electrolyte, leading to high interfacial impedance, severe electrochemical polarization, lithium dendrite growth, and the accumulation of dead lithium.

[0005] Lithium salts are the main components of lithium-ion battery electrolytes. Using high-performance lithium salts is key to obtaining lithium-ion secondary batteries with high energy density, wide electrochemical window, long cycle life, and good safety performance. An ideal lithium salt should have the following characteristics: (1) inexpensive, easy to prepare, and environmentally friendly; (2) easily dissociates in organic solvents and has excellent ionic conductivity; (3) good thermal and chemical stability, wide electrochemical stability window, and wide operating temperature range; (4) good matching and compatibility with positive and negative electrode materials and current collectors.

[0006] Traditional polymer lithium salts, such as lithium bis(trifluoromethanesulfonate)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalateborate), and lithium hexafluorophosphate, are unstable in air, easily absorb water and deteriorate, are difficult to store, and are expensive and have complex synthesis processes, making them difficult to industrialize. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention discloses a method for preparing a modified polymer electrolyte. This method uses a special lithium salt as a modifier, which is inexpensive, has undemanding synthesis conditions, and can be synthesized and stably stored in air. This modifier enables efficient modification of the polymer electrolyte, improving interfacial stability and reducing interfacial resistance growth. The resulting modified polymer electrolyte possesses a wide electrochemical window, high lithium-ion transference number, and excellent ionic conductivity. Solid-state batteries assembled from this electrolyte exhibit high capacity, high initial efficiency, and high stability.

[0008] The specific technical solution is as follows:

[0009] A method for preparing a modified polymer electrolyte includes the following steps:

[0010] (1) The modifier solution and the polymer matrix solvent are mixed evenly to obtain a slurry, which is then coated on the substrate and dried to obtain a modified polymer film.

[0011] The modifier is selected from one or more of lithium ferrocyanide, lithium ferrocyanide, lithium copper cyanide, and lithium cobalt cyanide;

[0012] The polymer matrix is ​​selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, and polymethacrylate;

[0013] (2) Immerse the modified polymer membrane in the electrolyte to obtain the modified polymer electrolyte.

[0014] In step (1):

[0015] The modifier solution is obtained by dissolving the modifier in organic solvent A, wherein organic solvent A is selected from one or more of ethanol, diethyl ether, acetonitrile, toluene, acetone, phenol, methanol, and dimethylformamide;

[0016] The concentration of the modifier solution is 5–30 wt%.

[0017] The polymer matrix solvent is obtained by dissolving the polymer matrix in organic solvent B, wherein organic solvent B is selected from one or more of ethanol, diethyl ether, acetonitrile, toluene, acetone, phenol, methanol, and dimethylformamide;

[0018] The concentration of the polymer matrix solvent is 5–30 wt%.

[0019] Organic solvent A and organic solvent B can be the same or different.

[0020] The preparation method disclosed in this invention uses one or more of lithium ferrocyanide, lithium ferricyanide, lithium copper cyanide, and lithium cobalt cyanide as modifiers, and mixes them with a polymer matrix of one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, and polymethacrylate to prepare a modified polymer electrolyte, which can significantly improve the electrochemical window, lithium ion transference number, and ionic conductivity of the modified polymer electrolyte.

[0021] Experiments have shown that there is a certain compatibility between the modifier and the polymer matrix. When the polymer matrix is ​​unsuitable, such as replacing it with polyvinylpyrrolidone or polyphosphazene, or replacing the modifier with a common lithium salt, such as lithium hexafluorophosphate, it will lead to a significant deterioration in performance.

[0022] Preferred:

[0023] In step (1), the mass ratio of the modifier to the polymer matrix is ​​1:1 to 6. Experiments have shown that the modified polymer electrolyte prepared using the above mass ratio has a higher electrochemical window, lithium ion transference number, and ionic conductivity.

[0024] Further optimization:

[0025] The polymer matrix is ​​selected from polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, and polyacrylonitrile;

[0026] The mass ratio of modifier to polymer matrix is ​​1:1.5 to 3.0.

[0027] Better:

[0028] The modifier is selected from lithium ferrocyanide;

[0029] The polymer matrix is ​​selected from polyvinylidene fluoride-hexafluoropropylene;

[0030] The mass ratio of modifier to polymer matrix is ​​1:1.5.

[0031] Experiments have shown that with the continuous optimization of the above raw materials and their amounts, the electrochemical window, lithium-ion transference number, and ionic conductivity of the prepared modified polymer electrolyte are continuously improved.

[0032] The substrate is selected from materials that are easy to demold, such as polytetrafluoroethylene, etc.

[0033] In step (1), the modifier is prepared as follows:

[0034] Metal cyanide, water, and concentrated acid are thoroughly mixed under ice bath conditions. Diethyl ether is added and stirring is continued for a period of time. The precipitate is collected by filtration, washed, and dried to obtain an intermediate product. The intermediate product, water, and lithium hydroxide are thoroughly mixed to obtain a solution. The pH of the solution is adjusted to neutral, and then placed in an oven at 50–100°C for 10–24 hours to obtain the modifier.

[0035] The metal cyanide salt is selected from one or more of potassium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, sodium ferrocyanide, potassium copper cyanide, sodium copper cyanide, potassium cobalt cyanide, and sodium cobalt cyanide.

[0036] The concentrated acid is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, concentrated nitric acid, and concentrated phosphoric acid.

[0037] Preferably, the temperature at which the ether is added is 5–15°C, and the stirring time after adding the ether is 2–5 hours.

[0038] Preferred:

[0039] The mass ratio of metal cyanide salt, water, and concentrated acid is 5–10:50–80:10–30;

[0040] The mass ratio of concentrated acid to diethyl ether is 30–70:30–70;

[0041] The mass ratio of intermediate product, water, and lithium hydroxide is 5–20: 50–80: 10–40.

[0042] The method for preparing the modifier uses inexpensive raw materials, has mild synthesis conditions, and can be synthesized and stably stored in air.

[0043] In step (2):

[0044] The electrolyte comprises a solvent and a lithium salt;

[0045] The solvent is selected from one or more of the following: fluoroethylene carbonate, vinylene carbonate, methylene disulfonate, 1,3-propane sulfonyl lactone, 1,4-butane sulfonyl lactone, 1,3-propene sulfonate lactone, ethylene sulfate, propylene sulfate, sulfone, and polyethersulfone.

[0046] The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate phosphate, lithium bis(fluorosulfonyl)imide, lithium methanesulfonate, lithium bis(oxalate borate), and lithium perchlorate.

[0047] The concentration of lithium salt in the electrolyte is 0.5–3 mol / L, more preferably 1 mol / L.

[0048] The present invention also discloses a modified polymer electrolyte prepared according to the above method and its application in solid-state batteries.

[0049] Experiments have shown that solid-state batteries assembled with this modified polymer electrolyte have high capacity and high coulombic efficiency.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] This invention discloses a method for preparing a modified polymer electrolyte. Using a special modifier and a specific type of polymer matrix as raw materials, the prepared modified polymer electrolyte has the advantages of a wide electrochemical window, high lithium-ion transference number, and excellent ionic conductivity. The process can be carried out in an air environment, and the experimental conditions are not harsh.

[0052] This invention also discloses the application of the modified polymer electrolyte in the preparation of solid-state batteries, and the assembled solid-state batteries have high capacity, high initial efficiency and high stability. Attached Figure Description

[0053] Figure 1 The image shows the SEM image of the modified polymer electrolyte prepared in Example 1.

[0054] Figure 2 EIS of the modified polymer electrolyte prepared in Example 1;

[0055] Figure 3 The SEM image of the modified polymer electrolyte prepared in Example 2;

[0056] Figure 4 This is a diagram showing the electrochemical stability window of the modified polymer electrolyte prepared in Example 2;

[0057] Figure 5 EIS of the modified polymer electrolyte prepared in Example 2;

[0058] Figure 6 Battery performance of the modified polymer electrolyte prepared in Example 2;

[0059] Figure 7 EIS of the modified polymer electrolyte prepared in Example 3;

[0060] Figure 8 The image shows the SEM image of the modified polymer electrolyte prepared in Example 4. Detailed Implementation

[0061] The specific implementation methods of the present invention will be further described below with reference to examples. It should be noted that the specific implementation methods described herein are only for illustration and explanation of the present invention and are not intended to limit the scope of protection of the present invention.

[0062] Example 1

[0063] (1) Preparation of the modifier: 10g potassium ferrocyanide, 70g water and 20g concentrated hydrochloric acid were thoroughly mixed by magnetic stirring under ice bath conditions. 10g of 5℃ diethyl ether was added and stirring was continued for 2h. The precipitate was collected by filtration and then washed clean again with water and diethyl ether. The precipitate was dried in a vacuum oven at 45℃ for 24h to obtain an intermediate product. 10g of the intermediate product, 50g of water and 40g of lithium hydroxide were thoroughly mixed, the pH of the solution was adjusted to neutral, and the solution was placed in an oven at 60℃ for 24h to obtain a novel lithium ferrocyanide.

[0064] (2) Dissolve 30g of synthesized lithium ferrocyanide in 70g of methanol solvent, and simultaneously dissolve 30g of polyvinylidene fluoride-hexafluoropropylene in 70g of dimethylformamide solvent. Stir the two solutions thoroughly for 2h to obtain a slurry, coat it onto a polytetrafluoroethylene substrate, and place it in an oven at 60℃ for 24h to form a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film;

[0065] (3) Cut the polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film into 16 mm round pieces and place them in a vacuum oven at 60 °C for 12 h. Then immerse them in an electrolyte (ethylene carbonate: methyl ethyl carbonate = 1:1 volume ratio, 1 mol / L lithium hexafluorophosphate) for 12 h. The amount of electrolyte used is 10 mL. After drying, the modified polymer electrolyte is obtained.

[0066] Figure 1 This is a SEM image of the modified polymer electrolyte prepared in this embodiment. Observation of this image reveals that the modified polymer electrolyte is in the form of a film. The pore size uniformity of this nanofilm is slightly poor, and there is a certain degree of polymer matrix aggregation, which may hinder the transport of lithium ions.

[0067] Tests showed that the modified polymer electrolyte prepared in this embodiment has an electrochemical stability window of 5V and a lithium-ion transference number of 0.42.

[0068] Figure 2 To obtain the EIS of the modified polymer electrolyte prepared in this embodiment using electron blocking battery testing, the ionic conductivity of the modified polymer electrolyte prepared in this embodiment was calculated to be 2.63 × 10⁻⁶. -4 S·cm -1 .

[0069] A solid-state battery was assembled using lithium iron phosphate as the positive electrode and lithium foil as the negative electrode. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of this solid-state battery was 105.2 mAh·g. -1 The coulomb efficiency is 91.31%.

[0070] Example 2

[0071] The preparation process is basically the same as in Example 1, except for step (2):

[0072] 20g of lithium ferrocyanide was dissolved in 80g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0073] Figure 3 This is a SEM image of the modified polymer electrolyte prepared in this embodiment. Observing this image, it can be seen that the pore size in the nanofilm formed by the modified polymer electrolyte is uniform and the polymer matrix is ​​evenly dispersed.

[0074] The modified polymer electrolyte prepared in this embodiment has an electrochemical stability window of 6V and a lithium-ion transference number of 0.53, as shown in the electrochemical stability window diagram. Figure 4 As shown.

[0075] Figure 5 The EIS of the modified polymer electrolyte prepared in this embodiment using an electron-blocking battery was calculated to be 3.11 × 10⁻⁶. -4 S·cm -1 .

[0076] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Figure 6 The above figure shows the charge-discharge curves at different cycle numbers for the solid-state battery assembled in this embodiment. Under 1C high-current charge-discharge conditions, the discharge capacity of the solid-state battery is 119.1 mAh·g. -1 The coulombic efficiency is 97.24%. The figure below shows the long-cycle performance of the solid-state battery at a current density of 1C. The discharge capacity of the solid-state battery after 179 cycles is 135.7 mAh·g. -1 The coulomb efficiency is 99.35%.

[0077] Example 3

[0078] The preparation process is basically the same as in Example 1, except for step (2):

[0079] 10g of lithium ferrocyanide was dissolved in 90g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed thoroughly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0080] Characterization showed that the SEM images of the modified polymer electrolyte prepared in this example were similar to those in Example 2.

[0081] Tests showed that the modified polymer electrolyte prepared in this embodiment has an electrochemical stability window of 5V and a lithium-ion transference number of 0.44.

[0082] Figure 7 The EIS of the modified polymer electrolyte prepared in this embodiment using an electron-blocking battery was calculated to be 2.51 × 10⁻⁶. -4 S·cm -1 .

[0083] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 110.21 mAh·g. -1 The coulomb efficiency is 93.12%.

[0084] Example 4

[0085] The preparation process is basically the same as in Example 1, except for step (2):

[0086] 5g of lithium ferrocyanide was dissolved in 95g of methanol, and 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0087] Figure 8 This is a SEM image of the modified polymer electrolyte prepared in this embodiment. Observation of this image reveals that the pore size in the nanofilm formed by the modified polymer electrolyte is relatively large and the uniformity is poor. More lithium ions can pass through, but this also leads to the transport of other anions, affecting the transport performance of lithium ions inside and causing a slight decrease in ionic conductivity.

[0088] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.57, and an ionic conductivity of 2.03 × 10⁻⁶. -4 S·cm -1 .

[0089] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 91.27 mAh·g. -1 The coulomb efficiency is 90.32%.

[0090] Example 5

[0091] (1) Preparation of the modifier: 10g potassium ferricyanide, 70g water and 20g concentrated hydrochloric acid were thoroughly mixed by magnetic stirring under ice bath conditions. 10g diethyl ether at 5℃ was added and stirring was continued for 2h. The precipitate was collected by filtration and then washed again with water and diethyl ether. The precipitate was dried in a vacuum oven at 45℃ for 24h to obtain an intermediate product. 10g of the intermediate product, 50g water and 40g lithium hydroxide were thoroughly mixed, the pH of the solution was adjusted to neutral, and the solution was placed in an oven at 60℃ for 24h to obtain a novel lithium ferricyanide.

[0092] Steps (2) to (3) are basically the same as in Example 1, except that lithium ferrocyanide is replaced with lithium ferrocyanide of equal mass.

[0093] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.39, and an ionic conductivity of 2.82 × 10⁻⁶. -4 S·cm -1 .

[0094] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 103.55 mAh·g. -1 The coulomb efficiency is 83.57%.

[0095] Example 6

[0096] The preparation process is basically the same as in Example 5, except for step (2):

[0097] 20g of lithium ferricyanide was dissolved in 80g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0098] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.43, and an ionic conductivity of 2.98 × 10⁻⁶. -4 S·cm -1 .

[0099] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 108.85 mAh·g. -1 The coulomb efficiency is 90.21%.

[0100] Example 7

[0101] The preparation process is basically the same as in Example 5, except for step (2):

[0102] 10g of lithium ferricyanide was dissolved in 90g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferricyanide polymer film.

[0103] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.47, and an ionic conductivity of 2.35 × 10⁻⁶. -4 S·cm -1 .

[0104] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 95.2 mAh·g. -1 The coulomb efficiency is 91.03%.

[0105] Example 8

[0106] The preparation process is basically the same as in Example 5, except for step (2):

[0107] 5g of lithium ferricyanide was dissolved in 95g of methanol, and 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferricyanide polymer film.

[0108] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.48, and an ionic conductivity of 2.41 × 10⁻⁶. -4 S·cm -1 .

[0109] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 90.8 mAh·g. -1 The coulomb efficiency is 88.9%.

[0110] Example 9

[0111] (1) Preparation of the modifier: 10g of potassium copper cyanide, 70g of water and 20g of concentrated hydrochloric acid were thoroughly mixed by magnetic stirring under ice bath conditions. 10g of diethyl ether at 5℃ was added and stirring was continued for 2h. The precipitate was collected by filtration and then washed again with water and diethyl ether. The precipitate was dried in a vacuum oven at 45℃ for 24h to obtain an intermediate product. 10g of the intermediate product, 50g of water and 40g of lithium hydroxide were thoroughly mixed, the pH of the solution was adjusted to neutral, and the solution was placed in an oven at 60℃ for 24h to obtain a novel lithium copper cyanide.

[0112] Steps (2) to (3) are basically the same as in Example 1, except that lithium ferrocyanide is replaced with an equal mass of lithium copper cyanide.

[0113] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.45, and an ionic conductivity of 2.97 × 10⁻⁶. -4 S·cm -1 .

[0114] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 92.76 mAh·g. -1 The coulomb efficiency is 89.32%.

[0115] Example 10

[0116] The preparation process is basically the same as in Example 9, except for step (2):

[0117] 20g of lithium copper cyanide was dissolved in 80g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0118] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.47, and an ionic conductivity of 3.06 × 10⁻⁶. -4 S·cm -1 .

[0119] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 116.57 mAh·g. -1 The coulomb efficiency is 95.79%.

[0120] Example 11

[0121] The preparation process is basically the same as in Example 9, except for step (2):

[0122] 10g of lithium copper cyanide was dissolved in 90g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0123] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.49, and an ionic conductivity of 2.37 × 10⁻⁶. -4 S·cm -1 .

[0124] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 109.52 mAh·g. -1 The coulomb efficiency is 85.82%.

[0125] Example 12

[0126] The preparation process is basically the same as in Example 9, except for step (2):

[0127] 5g of lithium copper cyanide was dissolved in 95g of methanol, and 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two were mixed evenly and coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0128] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.43, and an ionic conductivity of 2.37 × 10⁻⁶. -4 S·cm -1 .

[0129] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 106.52 mAh·g. -1 The coulomb efficiency is 90.58%.

[0130] Example 13

[0131] (1) Preparation of the modifier: 10g potassium cobalt cyanide, 70g water and 20g concentrated hydrochloric acid were thoroughly mixed by magnetic stirring under ice bath conditions. 10g of diethyl ether at 5℃ was added and stirring was continued for 2h. The precipitate was collected by filtration and then washed again with water and diethyl ether. The precipitate was dried in a vacuum oven at 45℃ for 24h to obtain an intermediate product. 10g of the intermediate product, 50g of water and 40g of lithium hydroxide were thoroughly mixed. The pH of the solution was adjusted to neutral. The solution was placed in an oven at 60℃ for 24h to obtain a novel lithium cobalt cyanide.

[0132] Steps (2) to (3) are basically the same as in Example 1, except that lithium ferrocyanide is replaced with an equal mass of lithium cobalt cyanide.

[0133] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.36, and an ionic conductivity of 1.87 × 10⁻⁶. -4 S·cm -1 .

[0134] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 98.6 mAh·g. -1 The coulomb efficiency is 90.63%.

[0135] Example 14

[0136] The preparation process is basically the same as in Example 13, except for step (2):

[0137] 20g of lithium cobalt cyanide was dissolved in 80g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0138] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.35, and an ionic conductivity of 1.81 × 10⁻⁶. -4 S·cm -1 .

[0139] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 107.6 mAh·g. -1 The coulomb efficiency is 93.35%.

[0140] Example 15

[0141] The preparation process is basically the same as in Example 13, except for step (2):

[0142] 10g of lithium cobalt cyanide was dissolved in 90g of methanol, while 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two solutions were mixed evenly and then coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0143] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.33, and an ionic conductivity of 1.76 × 10⁻⁶. -4 S·cm -1 .

[0144] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 102.8 mAh·g. -1 The coulomb efficiency is 91.22%.

[0145] Example 16

[0146] The preparation process is basically the same as in Example 13, except for step (2):

[0147] 5g of lithium cobalt cyanide was dissolved in 95g of methanol, and 30g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 70g of dimethylformamide. The two were mixed evenly and coated to prepare a polyvinylidene fluoride-hexafluoropropylene / lithium ferrocyanide polymer film.

[0148] The modified polymer electrolyte prepared in this embodiment was tested and found to have an electrochemical stability window of 5V, a lithium-ion transference number of 0.31, and an ionic conductivity of 1.66 × 10⁻⁶. -4 S·cm -1 .

[0149] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 87.5 mAh·g. -1 The coulomb efficiency is 90.38%.

[0150] Example 17

[0151] The preparation process is basically the same as in Example 2, except that in step (2), polyvinylidene fluoride-hexafluoropropylene is replaced with an equal mass of polyethylene oxide.

[0152] Testing showed that the modified polymer electrolyte prepared in this embodiment has an electrochemical temperature window of 5V, a lithium-ion transference number of 0.38, and an ionic conductivity of 2.15 × 10⁻⁶. -4 S·cm -1 .

[0153] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 108 mAh·g. -1 The coulomb efficiency is 92.57%.

[0154] Example 18

[0155] The preparation process is basically the same as in Example 2, except that in step (2), polyvinylidene fluoride-hexafluoropropylene is replaced with an equal mass of polyvinylidene fluoride.

[0156] Testing showed that the modified polymer electrolyte prepared in this embodiment has an electrochemical temperature window of 5V, a lithium-ion transference number of 0.35, and an ionic conductivity of 2.21 × 10⁻⁶. -4 S·cm -1 .

[0157] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 102.8 mAh·g. -1 The coulomb efficiency is 93.61%.

[0158] Example 19

[0159] The preparation process is basically the same as in Example 2, except that in step (2), polyvinylidene fluoride-hexafluoropropylene is replaced with an equal mass of polyacrylonitrile.

[0160] Testing showed that the modified polymer electrolyte prepared in this embodiment has an electrochemical temperature window of 5V, a lithium-ion transference number of 0.32, and an ionic conductivity of 2.08 × 10⁻⁶. -4 S·cm -1 .

[0161] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 105.6 mAh·g. -1 The coulomb efficiency is 94.11%.

[0162] Comparative Example 1

[0163] (1) Dissolve 30g of polyvinylidene fluoride-hexafluoropropylene in 70g of dimethylformamide solvent, stir thoroughly for 2h to obtain slurry, coat it on a polytetrafluoroethylene template, and place it in an oven at 60℃ for 24h to form a polyvinylidene fluoride-hexafluoropropylene polymer film.

[0164] (2) Cut the polyvinylidene fluoride-hexafluoropropylene polymer film into 16 mm round pieces and place them in a vacuum oven at 60 °C for 12 h. Then immerse them in an electrolyte (ethylene carbonate: methyl ethyl carbonate = 1:1 volume ratio, 1 mol / L lithium hexafluorophosphate) for 12 h. The electrolyte volume is 10 mL. After drying, the polymer electrolyte is obtained.

[0165] Tests showed that the modified polymer electrolyte prepared in this embodiment has an electrochemical temperature window of 5V, a lithium-ion transference number of 0, and an ionic conductivity of 0.

[0166] The modified polymer electrolyte prepared in this example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large battery charge-discharge conditions, the discharge capacity of the solid-state battery was 0 mAh·g-1 and the coulombic efficiency was 0.

[0167] Comparative Example 2

[0168] The preparation process is basically the same as in Example 2, except that in step (2), polyvinylidene fluoride-hexafluoropropylene is replaced with an equal mass of polyvinylpyrrolidone. The modified polymer electrolyte prepared in this comparative example was tested and found to have an electrochemical stability window of 2V, a lithium-ion transference number of 0.11, and an ionic conductivity of 3.59 × 10⁻⁶. -10 S·cm -1 .

[0169] The modified polymer electrolyte prepared in this comparative example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 28.3 mAh·g. -1 The coulomb efficiency is 60.32%.

[0170] Comparative Example 3

[0171] The preparation process is basically the same as in Example 2, except that in step (2), polyvinylidene fluoride-hexafluoropropylene is replaced with an equal mass of polyphosphazene.

[0172] The modified polymer electrolyte prepared in this comparative example was tested and found to have an electrochemical stability window of 1.5 V, a lithium-ion transference number of 0.25, and an ionic conductivity of 5.78 × 10⁻⁶. -10 S·cm -1 .

[0173] The modified polymer electrolyte prepared in this comparative example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 53.11 mAh·g. -1 The coulomb efficiency is 59.68%.

[0174] Comparative Example 4

[0175] The preparation process is basically the same as in Example 2, except that in step (2), lithium ferrocyanide is replaced with an equal mass of lithium hexafluorophosphate.

[0176] The modified polymer electrolyte prepared in this comparative example was tested and found to have an electrochemical stability window of 3V, a lithium-ion transference number of 0.17, and an ionic conductivity of 5.81 × 10⁻⁶. -12 S·cm -1 .

[0177] The modified polymer electrolyte prepared in this comparative example was assembled into a solid-state battery using the same method as in Example 1. Under 1C large-scale battery charge-discharge conditions, the discharge capacity of the solid-state battery was 30.85 mAh·g. -1 The coulomb efficiency is 85.39%.

[0178] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The specific examples used above to illustrate the present invention are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Those skilled in the art to which this invention pertains can make several simple deductions, modifications, substitutions, or combinations based on the concept of the present invention. These deductions, modifications, substitutions, or combinations also fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a modified polymer electrolyte, characterized in that, Includes the following steps: (1) The modifier solution and the polymer matrix solvent are mixed evenly to obtain a slurry, which is then coated on the substrate and dried to obtain a modified polymer film; The modifier solution is obtained by dissolving the modifier in organic solvent A; The modifier is selected from one or more of lithium ferrocyanide, lithium ferrocyanide, lithium copper cyanide, and lithium cobalt cyanide; The polymer matrix solvent is obtained by dissolving the polymer matrix in organic solvent B; The polymer matrix is ​​selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, and polymethacrylate; (2) The modified polymer membrane is immersed in the electrolyte and dried to obtain the modified polymer electrolyte.

2. The method for preparing the modified polymer electrolyte according to claim 1, characterized in that, In step (1): Organic solvent A is selected from one or more of ethanol, diethyl ether, acetonitrile, toluene, acetone, phenol, methanol, and dimethylformamide; The concentration of the modifier solution is 5-30 wt%; Organic solvent B is selected from one or more of ethanol, diethyl ether, acetonitrile, toluene, acetone, phenol, methanol, and dimethylformamide; The concentration of the polymer matrix solvent is 5-30 wt%; Organic solvent A may be the same as or different from organic solvent B.

3. The method for preparing the modified polymer electrolyte according to claim 1, characterized in that, In step (1), the mass ratio of the modifier to the polymer matrix is ​​1:1~6.

4. The method for preparing the modified polymer electrolyte according to claim 1, characterized in that, In step (1): The polymer matrix is ​​selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, and polyacrylonitrile; The mass ratio of modifier to polymer matrix is ​​1:1.5~3.

0.

5. The method for preparing the modified polymer electrolyte according to claim 4, characterized in that, In step (1): The modifier is selected from lithium ferrocyanide; The polymer matrix is ​​selected from polyvinylidene fluoride-hexafluoropropylene.

6. The method for preparing the modified polymer electrolyte according to claim 1, characterized in that, In step (1), the modifier is prepared as follows: Metal cyanide, water and concentrated acid were thoroughly mixed under ice bath conditions. After adding diethyl ether and stirring for a period of time, the precipitate was collected by filtration and then washed and dried to obtain the intermediate product. The intermediate product, water, and lithium hydroxide are thoroughly mixed to obtain a solution. The pH of the solution is adjusted to neutral, and then placed in an oven at 50-100°C for 10-24 hours to obtain the modifier. The metal cyanide salt is selected from one or more of potassium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, sodium ferrocyanide, potassium copper cyanide, sodium copper cyanide, potassium cobalt cyanide, and sodium cobalt cyanide. The concentrated acid is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, concentrated nitric acid, and concentrated phosphoric acid.

7. The method for preparing the modified polymer electrolyte according to claim 6, characterized in that: The mass ratio of metal cyanide salt, water and concentrated acid is 5~10:50~80:10~30; The mass ratio of concentrated acid to diethyl ether is 30~70:30~70; The mass ratio of intermediate product, water and lithium hydroxide is 5~20:50~80:10~40.

8. The method for preparing the modified polymer electrolyte according to claim 1, characterized in that, In step (2): The electrolyte comprises a solvent and a lithium salt; The solvent is selected from one or more of the following: fluoroethylene carbonate, vinylene carbonate, methylene disulfonate, 1,3-propane sulfonyl lactone, 1,4-butane sulfonyl lactone, 1,3-propene sulfonate lactone, ethylene sulfate, propylene sulfate, sulfone, and polyethersulfone. The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate phosphate, lithium bis(fluorosulfonyl)imide, lithium methanesulfonate, lithium bis(oxalate borate), and lithium perchlorate. The concentration of lithium salt in the electrolyte is 0.5~3.0 mol / L.

9. A modified polymer electrolyte prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the modified polymer electrolyte according to claim 9 in a solid-state battery.

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