A solid polymer electrolyte, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a solid polymer electrolyte and its preparation method and application, relating to the technical field of lithium metal batteries. The solid polymer electrolyte of the present invention comprises poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical), poly(vinylidene fluoride-hexafluoropropylene) and a lithium salt. By controlling the contents of the three components and selecting the lithium salt, a solid polymer electrolyte with good compatibility with the electrode interface, high lithium ion transference number, good mechanical properties and high conductivity is prepared. The solid polymer electrolyte is particularly suitable for all-solid-state batteries. The lithium ion transference number of the all-solid-state battery assembled therewith is 0.53 or above, the ionic conductivity is 2.6×10 ‑3 S / cm or above, the capacity retention rate is 90.3% or above, and the tensile strength is 2.1 MPa or above.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium metal batteries, and more specifically, to a solid polymer electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries have high energy density, power density, and good cycling performance. However, currently commercial lithium-ion batteries use organic electrolytes, which will decompose and leak when the battery temperature rises, and are prone to catching fire or even exploding when encountering oxygen. At low temperatures, the viscosity of the liquid electrolyte is large, and the ion migration rate decreases, resulting in an increase in the internal resistance of the battery, seriously affecting the performance of the battery. Incombustible solid electrolytes have good safety and mechanical properties, and have a wide electrochemical stability window, can match high-voltage cathode materials, and improve the energy density of the battery. Therefore, replacing traditional liquid electrolytes with solid electrolytes can fundamentally solve the safety problems of lithium-ion batteries and improve the energy density of the system.

[0003] However, solid electrolytes generally have poor interfacial contact with metallic lithium, resulting in the growth of lithium dendrites, an increase in cross-sectional impedance, hindered lithium-ion conduction, low room-temperature ionic conductivity, and poor cycling performance of the battery.

[0004] The prior art discloses a polyvinylidene fluoride-hexafluoropropylene lithium sulfonate composite polymer solid polymer electrolyte membrane for lithium batteries and a preparation method thereof. Based on the SPVDF-HFPLi composite polymer solid electrolyte membrane, SO3 - is grafted onto the PVDF-HFP main chain, and the sulfonate groups at its ends can combine with lithium ions to form a single-ion polymer electrolyte. This electrolyte fixes anions in the polymer backbone and only allows cations to migrate, which improves the ionic conductivity to a certain extent. The highest ionic conductivity of the solid polymer electrolyte at room temperature reaches 5×10 -4 S / cm. However, the interfacial compatibility between metallic lithium and the electrolyte and the lithium-ion transference number are still problems that need to be improved in solid polymer electrolytes, and the ionic conductivity also needs to be further improved. Summary of the Invention

[0005] In view of the defects and deficiencies of the prior art, the present invention provides a solid polymer electrolyte, which provides a transmission channel for lithium ions by adding poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical), improves the interfacial compatibility between the electrolyte and metallic lithium and the lithium-ion transference number, and further improves the ionic conductivity of the electrolyte.

[0006] Another object of the present invention is to provide a preparation method of a solid polymer electrolyte.

[0007] Another object of the present invention is to provide an application of a solid polymer electrolyte in all-solid-state lithium-ion batteries.

[0008] The above object of the present invention is achieved by the following technical solutions:

[0009] A solid polymer electrolyte, comprising the following components in parts by weight: 10-20 parts of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl), 20-45 parts of poly(vinylidene fluoride-hexafluoropropylene), and 15-35 parts of a lithium salt.

[0010] It should be noted that:

[0011] Poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl) is added to the solid polymer electrolyte of the present invention. The oxygen atom in this polymer has lone pair electrons, which will form a Coulomb force with lithium ions and can provide a channel for ion transport. By controlling the proportions of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl), poly(vinylidene fluoride-hexafluoropropylene), and the lithium salt, the compatibility of the three can be ensured, stably providing a channel for the transport of lithium ions, avoiding the hindrance of lithium ion conduction, not only improving the interfacial compatibility between the electrode and the electrolyte, increasing the lithium ion transference number, but also increasing the ionic conductivity of the electrolyte.

[0012] In addition, poly(vinylidene fluoride-hexafluoropropylene) plays a role in mechanical support in the electrolyte. By adjusting the addition amounts of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl), poly(vinylidene fluoride-hexafluoropropylene), and the lithium salt, the mechanical properties of the solid polymer electrolyte can be significantly improved, and it is not easily broken due to the extrusion of the positive and negative electrodes during the preparation of the solid-state battery, resulting in a short circuit.

[0013] Preferably, the weight fraction of poly(vinylidene fluoride-hexafluoropropylene) in the solid polymer is 20-30 parts, and the weight fraction of the lithium salt is 15-20 parts.

[0014] Preferably, the molecular weight of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl) in the solid polymer is 200,000, and the molecular weight of poly(vinylidene fluoride-hexafluoropropylene) is 450,000.

[0015] When the molecular weight of the polymer is too low, the mechanical properties of the solid polymer electrolyte are poor, and cracks are easily formed due to external forces such as extrusion, affecting its service life and conductivity. However, when the molecular weight of the polymer is too high, the compatibility between poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl) and poly(vinylidene fluoride-hexafluoropropylene) becomes poor, and the interfacial compatibility between the electrode and the electrolyte also deteriorates. Therefore, by controlling the molecular weight of the polymer, the compatibility of the solid polymer electrolyte can be adjusted.

[0016] Preferably, the lithium salt is one or more of lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0017] The solid polymer electrolyte of the present invention incorporates poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical), which effectively reduces the problem of hindered lithium ion conduction while improving the interfacial compatibility between the electrode and the electrolyte, enhances the ionic conductivity of the electrolyte, and has good mechanical properties.

[0018] The present invention specifically protects a method for preparing a solid polymer electrolyte, which includes the following steps:

[0019] S1. Dissolve a mixture of poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical), poly(vinylidene fluoride-hexafluoropropylene), and a lithium salt in an organic solvent at a temperature of 30 to 80 °C, and obtain a mixed solution after mixing evenly. Among them, the mass-volume ratio of the mixture to the organic solvent is 1 g:(9 to 11) mL; the above operations are all carried out in a dry gas environment;

[0020] S2. Drop the mixed solution in S1 onto a mold, let it stand at room temperature for 1 to 2 h, and then dry it at 50 to 80 °C for a drying time of ≥24 h to obtain a solid polymer electrolyte.

[0021] The inventors found that too low a dissolution temperature in S1 would result in slow dissolution or even insoluble poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical) and poly(vinylidene fluoride-hexafluoropropylene), while when the dissolution temperature is too high, the organic solvent volatilizes quickly, and pore structures are likely to appear in the electrolyte, affecting the transport of lithium ions. On the other hand, when the temperature is relatively high, the structure of the polymer is also prone to change, affecting the mechanical properties and electrochemical properties of the solid polymer electrolyte.

[0022] Since the lithium salt is prone to absorb water, the operations in S1 need to be carried out in a dry gas environment.

[0023] In addition, the mass-volume ratio of the mixture to the organic solvent in S1 is preferably 1 g:10 mL.

[0024] After the mixed solution in S2 is dropped into the mold, if it is directly dried at 50-80°C, the solvent will volatilize too fast, resulting in the appearance of bubbles in the prepared electrolyte, and then pore structures will be generated, affecting ion transport. Therefore, before drying, the mixed solution needs to be left standing at room temperature to allow most of the solvent to volatilize at room temperature first. If the standing time is too short at this time, the effect of volatilizing most of the solvent cannot be achieved, and if the time is too long, the lithium salt will absorb water and affect the electrochemical performance of the electrolyte. The drying temperature and time will affect the solvent residue. When the drying temperature is low or the drying time is short, the organic solvent cannot be completely removed and remains in the electrolyte, and a fully solid polymer electrolyte cannot be obtained, and the performance and lifespan of the electrolyte will be affected. When the drying temperature is too high, the structure of the polymer will change, and then the structure of the electrolyte will be damaged.

[0025] In addition, the preparation method of the solid polymer electrolyte provided by the present invention is simple and easy to be industrialized and promoted.

[0026] Preferably, the mass ratio of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) to poly(vinylidene fluoride-hexafluoropropylene) in S1 is 1:(1-3), and more preferably 1:2.

[0027] Preferably, the mass ratio of the total amount of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) and poly(vinylidene fluoride-hexafluoropropylene) to the lithium salt in S1 is 1:(0.25-1.2), and more preferably 1:0.5.

[0028] By controlling the ratio between polymers and the ratio between polymers and the lithium salt, the compatibility of the solid polymer electrolyte can be controlled.

[0029] Preferably, the organic solvent in S1 is a mixed solvent of acetone and a non-volatile organic solvent.

[0030] Acetone is an organic solvent that volatilizes extremely easily. After adding a non-volatile organic solvent, on the one hand, it reduces the impact of the easy volatilization of acetone on the electrochemical performance of the solid polymer electrolyte, and on the other hand, due to the presence of acetone, it also reduces the volatilization time of the organic solvent during drying and avoids the residue of the organic solvent in the solid polymer electrolyte. Further, the mass ratio of acetone to the non-volatile organic solvent is 3:7-1:1.

[0031] More preferably, the non-volatile organic solvent is one or more of N-methylpyrrolidone (NMP), dimethylacetamide (DMAC), and N,N-dimethylformamide (DMF).

[0032] The solid polymer electrolyte of the present invention has high ionic conductivity and high lithium ion transference number, and has good interfacial compatibility with the electrode. In particular, it is only applicable to all-solid-state lithium ion batteries. Since the lithium ion transference number of the solid polymer electrolyte of the present invention is high, the concentration polarization problem between the electrodes of the lithium ion battery can be effectively reduced, and a large overpotential can be avoided to reduce the energy density of the battery. In addition, based on the good compatibility of the solid polymer electrolyte with the electrode interface, the assembled all-solid-state battery has good cycle stability.

[0033] The present invention particularly protects an all-solid-state battery, comprising a positive electrode, a negative electrode and an electrolyte, and the electrolyte is the solid polymer electrolyte of the present invention.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] By adding poly(4-methylacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) and adjusting the contents of the polymer and the lithium salt, the present invention obtains a solid polymer electrolyte with good interfacial compatibility with the lithium metal electrode, high lithium ion transference number and high ionic conductivity, and the electrolyte also has good mechanical properties.

[0036] The solid polymer electrolyte is particularly applicable to all-solid-state electrical appliances. The assembled all-solid-state battery has both high ion transport performance and cycle stability. Its lithium ion transference number is 0.53 or more, the ionic conductivity is 2.6×10 -3 S / cm or more, the capacity retention rate is 90.3% or more, and the tensile strength is 2.1 MPa or more. Description of the Drawings

[0037] Figure 1 is the solid polymer electrolyte membrane prepared in Example 1.

[0038] Figure 2 is the AC impedance diagram of the lithium-lithium symmetric battery prepared from the solid polymer electrolytes of Example 1 and Comparative Example 1.

[0039] Figure 3 is the cycle performance test diagram of the all-solid-state battery prepared from the solid polymer electrolytes in Example 1 and Comparative Example 1.

[0040] Figure 4 is the test diagram of the lithium-lithium symmetric battery prepared from the solid polymer electrolytes in Example 1 and Comparative Example 1.

[0041] Figure 5 is the tensile strength test diagram of the solid polymer electrolyte membranes of Example 1 and Comparative Example 1. Detailed Embodiments

[0042] The preparation method of PTMA used in the embodiments and comparative examples of the present invention is as follows:

[0043] Weigh 2.25 g of 2,2,6,6-tetramethyl-4-piperidyl methacrylate (MTMP) monomer and 0.04 g of azobisisobutyronitrile respectively, then add them into 6 mL of acetic acid solvent, heat to 70 °C under a nitrogen atmosphere, react for 12 h, and obtain the product PMTMP (1.8 g, yield about 80%) after purification. Dissolve PMTMP in a mixed solution of 20 ml of water and 20 ml of ethanol, then add 0.3 g of NaWO4 and 0.2 g of ethylenediaminetetraacetic acid in sequence, and then dropwise add 2 mL of H2O2. The obtained mixed solution reacts at 60 °C for 40 h, and PTMA is obtained after purification. The molecular weight of the obtained PTMA is 200,000;

[0044] The PVDF-HFP used was purchased from the Macklin official website, and its molecular weight is 450,000;

[0045] All the lithium salts used were purchased from the Macklin official website.

[0046] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form.

[0047] Examples 1 to 12

[0048] A solid polymer electrolyte includes poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) (PTMA), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and a lithium salt. For the detailed component parameters, please refer to Table 1.

[0049] Table 1. Parameter table of the solid polymer electrolyte of Examples 1 to 12

[0050] Amount of PTMA Amount of PVDF-HFP Amount of lithium salt Type of lithium salt Example 1 20 40 30 LiTFSI Example 2 15 20 15 LiTFSI Example 3 20 20 15 LiTFSI Example 4 15 30 15 LiTFSI Example 5 15 40 15 LiTFSI Example 6 15 45 15 LiTFSI Example 7 10 20 20 LiTFSI Example 8 10 20 25 LiTFSI Example 9 10 20 30 LiTFSI Example 10 10 20 35 LiTFSI Example 11 20 40 30 <![CDATA[LiClO4]]> Example 12 20 40 30 LiFSI

[0051] The preparation method of the above solid polymer electrolyte includes the following steps:

[0052] S1. Dissolve the mixture of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical), poly(vinylidene fluoride-hexafluoropropylene) and a lithium salt in a mixed organic solvent of acetone and DMF at a temperature of 50 °C, and obtain a mixed solution after mixing evenly. Among them, the mass ratio of acetone to DMF in the mixed organic solvent is 3:7, and the mass-volume ratio of the mixture to the mixed organic solvent is 1 g:10 mL; all the above operations are carried out in a dry gas environment;

[0053] S2. Drop the mixed solution in S1 onto a mold, let it stand at room temperature for 1 h, and then place it at 60 °C for drying. The drying time is ≥24 h to obtain the solid polymer electrolyte.

[0054] Comparative Examples 1 - 8

[0055] A solid polymer electrolyte, the preparation method is the same as that of Examples 1 - 12, and the differences are shown in Table 2.

[0056] Table 2. Parameter Table of Solid Polymer Electrolytes in Comparative Examples 1 - 8

[0057] Amount of PTMA Amount of PVDF-HFP Amount of LiTFSI Standing time Comparative Example 1 4 20 15 1h Comparative Example 2 26 20 15 1h Comparative Example 3 15 15 15 1h Comparative Example 4 15 50 15 1h Comparative Example 5 10 20 10 1h Comparative Example 6 10 20 45 1h Comparative Example 7 20 40 30 0.5h Comparative Example 8 20 40 30 2.5h

[0058] Comparative Example 9

[0059] A polyvinylidene fluoride - lithium hexafluoropropene sulfonate composite polymer solid polymer electrolyte membrane for lithium batteries, the preparation method includes the following steps:

[0060] S1. Take a PVDF - HFP sample and dry it under vacuum at 60 °C for 48 h. Weigh 3.00 g of PVDF - HFP into a 100 ml flask, and dropwise add 20 ml of chlorosulfonic acid under stirring in an oil bath at 60 °C for 7 hours until all of the PVDF - HFP is dissolved. Drop the mixed solution cooled to room temperature into 1,2 - dichloroethane, let the polymer obtained from the reaction stand for 24 h for precipitation separation, continue to wash it 2 times with 1,2 - dichloroethane, pour off the supernatant, centrifuge the lower - layer mixed solution, and the obtained polymer is dried under vacuum at 60 °C for 24 h to obtain SPVDF - HFP.

[0061] S2. Immerse the SPVDF - HFP powder obtained in S1 in a 1.00 mol / L aqueous LiOH solution at 60 °C for 24 h, precipitate and centrifuge to obtain the polymer, wash it with deionized water until neutral, and dry it in a forced - air drying oven for 24 h to obtain SPVDF - HFPLi.

[0062] S3. Weigh 0.40 g of the SPVDF - HFPLi solid powder obtained in S2 and dissolve it in 10 ml of NMP solution. Weigh another 0.60 g of PVDF - HFP and 0.40 g of TFSILi and dissolve them in 20 ml of NMP solution. Stir each solution in a glove box for 12 h until completely dissolved, and then continue to mix and stir the two obtained solutions for 8 h to obtain a PVDF - HFP / SPVDF - HFPLi mixed solution.

[0063] S4. Pour the mixed solution obtained in S3 onto a polytetrafluoroethylene plate and dry it under vacuum at 60 °C for 24 hours to obtain a PVDF - HFP / SPVDF - HFPLi single - ion composite polymer solid polymer electrolyte membrane.

[0064] Result Detection

[0065] The electrolyte membranes obtained from the examples and comparative examples were used to assemble LiFePO4 / Li all-solid-state batteries, and the AC impedance spectra of the batteries were tested; the charge-discharge cycle performance was tested at a voltage range of 3.0 - 4.2 V and a rate of 0.5C at 60 °C, and was expressed as the capacity retention rate after 150 cycles.

[0066] A lithium-lithium symmetric battery was assembled to obtain a deposition-stripping curve to illustrate the compatibility of the solid polymer electrolyte with lithium metal.

[0067] The test method for the ionic conductivity of the solid polymer electrolytes prepared in the examples and comparative examples is as follows:

[0068] An SS / polymer electrolyte / SS symmetric battery was assembled (SS is a stainless steel electrode). At 60 °C, the impedance value R was obtained by AC impedance testing. The thickness of the electrolyte was L, and S was the area of the stainless steel electrode. The ionic conductivity was calculated according to the following formula:

[0069]

[0070] The test method for the lithium ion transference number is as follows:

[0071] A lithium foil / polymer electrolyte / lithium foil symmetric battery was assembled. At 60 °C, first, the impedance before polarization of the battery, R0, was obtained by AC impedance testing. Then, a chronoamperometry test was carried out. A polarization voltage (ΔV) of 10 mV was applied, and the current before polarization of the battery, I0, and the steady-state current I were measured. ss Finally, an AC impedance test was carried out again to obtain the impedance after polarization, R. ss . The lithium ion transference number can be calculated according to the following formula:

[0072]

[0073] Table 3. Test results of the performance of solid polymer electrolytes

[0074]

[0075]

[0076] As can be seen from the data in Table 3, the lithium ion transference numbers of the solid polymer electrolytes prepared in Examples 1 - 12 are above 0.53, the conductivities are above 2.6×10 -3 S / cm, the capacity retention rates are above 90.3%, and the tensile strengths are above 2.1 MPa. For the solid polymer electrolytes in Comparative Examples 1 - 6 with excessive or insufficient weight fractions of PTMA, PVDF-HFP, and lithium salt, their electrochemical and mechanical properties are significantly poor, and the ionic conductivities are lower than 1.7×10 -3S / cm, the lithium ion transference number is less than 0.48. Comparative example 7 is a solid polymer electrolyte obtained by too short standing time in preparation method S2. Since most of the solvent has not volatilized, the solid polymer electrolyte has a porous structure, and its electrochemical performance is greatly reduced. Comparative example 8 is a solid polymer electrolyte obtained by too long standing time in preparation method S2. Since the lithium salt is easy to absorb water, the preparation fails. Comparative example 9 is a solid polymer electrolyte membrane obtained by the preparation method disclosed in the prior art, with a conductivity of 5×10 - 4 S / cm, the lithium ion transference number is 0.31, which is significantly lower than the solid polymer electrolytes prepared in Examples 1 to 12.

[0077] Figure 2 Fig. is the AC impedance diagram of the lithium-lithium symmetric battery prepared with the solid polymer electrolytes of Example 1 and Comparative Example 1. According to the numerical value corresponding to the abscissa of the first semicircle in the test image, the contact situation between the solid polymer electrolyte and the lithium metal interface can be judged. The smaller the abscissa of the first semicircle, the better the contact effect between the solid polymer electrolyte and the lithium metal. It can be seen that the contact effect between the solid polymer electrolyte of Example 1 and the lithium metal is significantly better than that of Comparative Example 1.

[0078] Figure 3 Fig. is the cycle performance test diagram of the all-solid-state battery prepared with the solid polymer electrolytes in Example 1 and Comparative Example 1. The initial discharge specific capacity and capacity retention rate of the battery can be obtained from the figure. It can be seen that the initial specific capacity and capacity retention rate of the all-solid-state battery corresponding to the solid polymer electrolyte of Example 1 are better than those of Comparative Example 1, indicating that the all-solid-state battery prepared with the solid polymer electrolyte of the present invention has a high capacity retention rate.

[0079] Figure 4 Fig. is the test diagram of the lithium-lithium symmetric battery prepared with the solid polymer electrolytes in Example 1 and Comparative Example 1. According to the numerical value of the voltage on the ordinate of the image and the test time, the compatibility between the solid polymer electrolyte and the lithium metal can be judged. The results show that the effect of the solid polymer electrolyte of Example 1 is better than that of Comparative Example 1, indicating that the solid polymer electrolyte prepared by the present invention has good compatibility with the lithium metal interface.

[0080] Figure 5 Fig. is the tensile strength test diagram of the solid polymer electrolyte membrane. It can be seen that the maximum tensile strength of the solid polymer electrolyte membrane of Example 1 is 4 MPa, which is significantly higher than the maximum tensile strength (1.7 MPa) of the solid polymer electrolyte membrane of Comparative Example 1.

[0081] It should be noted that although the remaining embodiments do not provide corresponding drawings to illustrate the compatibility between the solid polymer electrolyte and the electrode, their properties are quite similar, that is, the corresponding interfaces between the solid polymer electrolyte and the electrode all have good compatibility.

[0082] Obviously, the above embodiments of the present invention are merely examples given for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a solid polymer electrolyte, characterized in that, It includes the following steps: S1. Dissolve a mixture of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical), poly(vinylidene fluoride-hexafluoropropylene), and a lithium salt in an organic solvent at a temperature of 30~80 °C. After mixing evenly, a mixed solution is obtained. Among them, the mass-volume ratio of the mixture to the organic solvent is 1 g:(9~11) mL; the above operations are all carried out in a dry gas environment. S2. Drop the mixed solution in S1 onto a mold, let it stand at room temperature for 1~2 h, and then place it at 50~80 °C for drying. The drying time is ≥24 h to obtain a solid polymer electrolyte. The solid polymer electrolyte includes the following components by weight: 10~20 parts of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical), 20~30 parts of poly(vinylidene fluoride-hexafluoropropylene), and 15~20 parts of a lithium salt. In the solid polymer, the molecular weight of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) is 200,000, and the molecular weight of poly(vinylidene fluoride-hexafluoropropylene) is 450,000. The lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. In S1, the mass ratio of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) to poly(vinylidene fluoride-hexafluoropropylene) is 1:(1~3). In S1, the mass ratio of the total amount of poly(4-methacrylic acid-2,2,6,6-tetramethylpiperidine-1-oxyl radical) and poly(vinylidene fluoride-hexafluoropropylene) to the lithium salt is 1:(0.25~1.2). The organic solvent in S1 is a mixed solvent of acetone and a non-volatile organic solvent. The non-volatile organic solvent is one or more of N-methylpyrrolidone, dimethylacetamide, and N,N-dimethylformamide.

2. A all-solid-state battery, comprising a positive electrode, a negative electrode and an electrolyte, characterized in that, The electrolyte is the solid polymer electrolyte prepared by the preparation method described in claim 1.

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