A pio solid electrolyte membrane, a preparation method thereof and a lithium symmetric battery

Abstract

The application provides a PEO solid-state electrolyte film and a preparation method and a lithium symmetrical battery, and comprises the following steps: step S1, weighing PEO, nano-Al2O3 and LiTFSI under a protective atmosphere; step S2, weighing water-absorbing resin SAP or LiH2PO4 under a protective atmosphere; step S3, dissolving all raw materials of steps S1 and S2 into super-dry acetonitrile under a protective atmosphere and heating and stirring; step S4, standing for one hour after sufficient stirring; step S5, dropping the PEO solution onto a PTFE plate under a protective atmosphere after standing and standing for one hour; and step S6, heating and evaporating the acetonitrile solvent under a protective atmosphere after standing to obtain the PEO solid-state electrolyte film. By adding the water-absorbing resin SAP or LiH2PO4 into the PEO solid-state electrolyte, the interface impedance between the PEO solid-state electrolyte and the lithium metal negative electrode is effectively reduced. The method for improving the interface stability of the PEO solid-state electrolyte to the lithium negative electrode is simple in process, convenient in operation and low in cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid-state lithium metal batteries, and particularly relates to a PEO solid-state electrolyte film, a preparation method thereof and a lithium symmetric battery. BACKGROUND

[0002] Under the dual pressures of energy security and environmental protection, clean energy such as wind energy and solar energy has achieved a leap-forward development. Due to the strong dependence of clean energy on the outside weather, lithium-ion batteries have also made great progress. The vigorous development of electric vehicles has also greatly promoted the development of lithium-ion batteries. Due to the use of flammable and flowable organic electrolyte, the current commercialized lithium-ion battery has safety hazards such as fire and explosion. Solid-state lithium metal battery is considered as an ideal next-generation electrochemical energy storage system. Solid-state electrolyte is the core in the research of solid-state lithium metal battery. Among many solid-state electrolytes, PEO (polyethylene oxide) based solid-state electrolyte has the characteristics of good flexibility, easy preparation and good chemical stability.

[0003] However, the PEO-based solid-state electrolyte is unstable to the lithium metal negative electrode, and an interface layer is generated when used with the lithium metal negative electrode. The impedance value of the interface layer is often several times or even dozens of times of that of the PEO solid-state electrolyte, which will seriously affect the rate performance of the solid-state lithium metal battery. Related research has attracted the attention of researchers and has achieved certain research results. For example, adding LiNO3 and black phosphorus in PEO can improve the stability of PEO solid-state electrolyte to the lithium negative electrode. However, LiNO3 is an explosive chemical agent, and black phosphorus is too expensive. Therefore, it is necessary to develop a new method for improving the interface stability of PEO to the lithium negative electrode. SUMMARY

[0004] In view of the above technical problems, the present application provides a PEO solid-state electrolyte film and a preparation method thereof, which can improve the stability of PEO solid-state electrolyte to the lithium negative electrode. By adding water-absorbing resin SAP or LiH2PO4 in the PEO solid-state electrolyte, the interface impedance between the PEO solid-state electrolyte and the lithium metal negative electrode can be effectively reduced. The added water-absorbing resin SAP or LiH2PO4 does not have obvious adverse effects on the ionic conductivity of the PEO solid-state electrolyte. The method for improving the interface stability of PEO solid-state electrolyte to the lithium negative electrode has the characteristics of simple process, convenient operation and low cost.

[0005] The present application also provides a lithium symmetric battery assembled by using the PEO solid-state electrolyte film.

[0006] Note that the description of these objects does not hinder the existence of other objects. One embodiment of the present application does not need to achieve all the above-mentioned objects. The objects other than the above-mentioned objects can be extracted from the description, drawings and claims.

[0007] The present application is achieved by the following technical means to realize the above technical purposes.

[0008] A preparation method of a PEO solid-state electrolyte film, comprising the following steps:

[0009] Step S1, weighing PEO (polyethylene oxide), nano-Al2O3 and LiTFSI (lithium bis-trifluoromethyl sulfonamide) under a protective atmosphere for standby;

[0010] Step S2, weighing water-absorbing resin SAP or LiH2PO4 under a protective atmosphere for standby;

[0011] Step S3, dissolving all raw materials of steps S1 and S2 into super-dry acetonitrile under a protective atmosphere and heating and stirring;

[0012] Step S4, standing for one hour after sufficient stirring;

[0013] Step S5, after standing under a protective atmosphere, dropping the PEO solution onto a PTFE plate and standing for one hour;

[0014] Step S6, after standing, heating and evaporating the acetonitrile solvent under a protective atmosphere to obtain a PEO solid-state electrolyte film.

[0015] In the above scheme, the mass ratio of PEO, nano-Al2O3 and LiTFSI in step S1 is 100:(1-10):(1-81)

[0016] Further, the mass ratio of PEO, nano-Al2O3 and LiTFSI is 60:3:16.

[0017] In the above scheme, the molecular weight of PEO in step S1 is 600000.

[0018] In the above scheme, in step S2, the amount of water-absorbing resin SAP and LiH2PO4 is 1%-8.2% of the total mass of PEO, nano-Al2O3 and LiTFSI in step S1, respectively.

[0019] In the above scheme, in step S3, the heating temperature is 70℃ and the heating time is 10h.

[0020] In the above scheme, in step S6, the heating temperature is 80℃ and the heating time is 10h.

[0021] In the above scheme, the protective atmosphere is argon.

[0022] A PEO solid-state electrolyte film prepared according to the preparation method of the PEO solid-state electrolyte film.

[0023] A lithium symmetric cell is assembled using the PEO solid electrolyte film.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application effectively reduces the interface impedance between the PEO solid electrolyte and the lithium metal negative electrode by adding the water-absorbing resin SAP and LiH2PO4, improves the interface condition between the PEO solid electrolyte and the lithium metal electrode, and improves the stability of the PEO solid electrolyte to the lithium negative electrode. The selected additives, water-absorbing resin SAP and LiH2PO4, have the characteristics of low cost and high safety.

[0026] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present application does not necessarily have all the above-mentioned effects. Effects other than the above-mentioned effects can be clearly seen and extracted from the description, drawings, claims, etc. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the room temperature impedance spectrum of Li / PEO / Li.

[0028] Figure 2 is the room temperature impedance spectrum of the lithium symmetric cell of the PEO solid electrolyte added with LiH2PO4.

[0029] Figure 3 is the interface resistance of the lithium metal negative electrode of the PEO solid electrolyte added with LiH2PO4.

[0030] Figure 4 is the room temperature impedance spectrum of the lithium symmetric cell of the PEO solid electrolyte added with water-absorbing resin SAP.

[0031] Figure 5 is the interface resistance of the lithium metal negative electrode of the PEO solid electrolyte added with water-absorbing resin SAP. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in 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 a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application. The present application will be further described below with reference to the embodiments. Embodiments 3-6 and 9-11 are preferred embodiments of the present application.

[0033] Embodiment 1

[0034] Embodiment 1 is a preparation method of a PEO solid electrolyte film, comprising the following steps:

[0035] Step S1, 0.6g PEO, 0.16g LiTFSI and 0.03g nano-Al2O3 were weighed in the glove box;

[0036] Step S2, SAP and LiH2PO4 were not weighed;

[0037] Step S3, all raw materials were dissolved into super-dry acetonitrile in the glove box and heated and stirred, and the heating temperature was 70°C;

[0038] Step S4, after stirring for 10h, it was left for one hour;

[0039] Step S5, the PEO solution was dropped onto a PTFE plate in the glove box and left for one hour;

[0040] Step S6, after standing, the PEO solid electrolyte film was obtained by heating at 80°C for 10h in the glove box to evaporate the acetonitrile solvent. Then a Li / PEO / Li symmetric battery was assembled in the glove box and the impedance was tested and the PEO / Li interface resistance was calculated, and the test temperature was 60°C.

[0041] The impedance test results of the obtained PEO solid electrolyte film after assembling a lithium symmetric battery are shown in Figure 1 The interface impedance between the PEO solid electrolyte and the lithium negative electrode can be obtained from the curve in the impedance spectrum, as shown in Figure 3 The interface impedance between the PEO in Example 1 and the lithium metal negative electrode was 61.2Ω.

[0042] Examples 2-7

[0043] A preparation method of a PEO solid electrolyte film, comprising the following steps:

[0044] Step S1, 0.6g PEO, 0.16g LiTFSI and 0.03g nano-Al2O3 were weighed in the glove box;

[0045] Step S2, LiH2PO4 was weighed;

[0046] Step S3, all raw materials were dissolved into super-dry acetonitrile in the glove box and heated and stirred, and the heating temperature was 70°C;

[0047] Step S4, after stirring for 10h, it was left for one hour;

[0048] Step S5, the PEO solution was dropped onto a PTFE plate in the glove box and left for one hour;

[0049] Step S6, after standing, heat in the glove box at 80℃ for 10h to evaporate the acetonitrile solvent to obtain the PEO solid-state electrolyte film. Then assemble the Li / PEO / Li symmetric battery in the glove box and test the impedance and calculate the PEO / Li interface resistance, the test temperature is 60℃.

[0050] The difference between Example 2-Example 7 is that the LiH2PO4 weighed in step S2 is respectively 0.008g, 0.016g, 0.024g, 0.032g, 0.04g, 0.048g.

[0051] The obtained PEO solid-state electrolyte film added with LiH2PO4 is assembled into a lithium symmetric battery and the impedance test results are shown in Figure 2 The interface impedance between the PEO solid-state electrolyte added with LiH2PO4 and the lithium negative electrode can be obtained from the curve in the impedance spectrum, and the results are shown in Figure 3 The interface impedance between the PEO and the lithium metal negative electrode in Example 2-7 is respectively 30.5Ω, 20.5Ω, 17.1Ω, 13.8Ω, 19Ω and 31Ω.

[0052] Example 8-15

[0053] A method for preparing a PEO solid-state electrolyte film, comprising the following steps:

[0054] Step S1, weigh 0.6g PEO, 0.16g LiTFSI and 0.03g nano-Al2O3 in the glove box;

[0055] Step S2, weigh the water-absorbing resin SAP;

[0056] Step S3, dissolve all raw materials into ultra-dry acetonitrile in the glove box and heat and stir, the heating temperature is 70℃;

[0057] Step S4, after stirring for 10h, stand for one hour;

[0058] Step S5, drop the PEO solution onto the PTFE plate in the glove box and stand for one hour;

[0059] Step S6, after standing, heat in the glove box at 80℃ for 10h to evaporate the acetonitrile solvent to obtain the PEO solid-state electrolyte film. Then assemble the Li / PEO / Li symmetric battery in the glove box and test the impedance and calculate the PEO / Li interface resistance, the test temperature is 60℃.

[0060] The difference between Example 8-Example 15 is that the water-absorbing resin SAP weighed in step S2 is respectively 0.008g, 0.016g, 0.024g, 0.032g, 0.04g, 0.048g, 0.056g, 0.064g.

[0061] The obtained PEO solid electrolyte film added with water-absorbing resin SAP is assembled into a lithium symmetrical battery, and then the impedance results are tested Figure 4 As shown in the curve in the impedance spectrum, the interface impedance between the PEO solid electrolyte added with water-absorbing resin SAP and the lithium negative electrode can be obtained, and the results are shown in Figure 5 The interface impedance between the PEO in examples 8-15 and the lithium metal negative electrode is 52.6Ω, 39.6Ω, 32.3Ω, 44.7Ω, 46.6Ω, 50.2Ω, 53.5Ω and 59.5Ω, respectively.

[0062] The present application effectively reduces the interface impedance between the PEO solid electrolyte and the lithium metal negative electrode by adding water-absorbing resin SAP and LiH2PO4, improves the interface condition between the PEO solid electrolyte and the lithium metal electrode, and improves the stability of the PEO solid electrolyte to the lithium negative electrode. The selected additives, water-absorbing resin SAP and LiH2PO4, have the characteristics of low cost and high safety. Examples 3-6 and 9-11 are preferred embodiments of the present application.

[0063] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application.

Claims

1. A method for preparing a PEO solid-state electrolyte film, characterized by, The method comprises the following steps: Step S1, weighing PEO, nano-Al2O3 and LiTFSI under a protective atmosphere; Step S2, weighing water-absorbing resin SAP or LiH2PO4 under a protective atmosphere; Step S3, dissolving all raw materials of steps S1 and S2 into ultradry acetonitrile under a protective atmosphere and heating and stirring; Step S4, standing for one hour after sufficient stirring; Step S5, dropping the PEO solution onto a PTFE plate after standing under a protective atmosphere and standing for one hour; Step S6, heating and evaporating the acetonitrile solvent to obtain a PEO solid-state electrolyte film under a protective atmosphere after standing.

2. The method of claim 1, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The mass ratio of PEO, nano-Al2O3 and LiTFSI in step S1 is 100:(1-10):(1-81).

3. The method of claim 2, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The mass ratio of PEO, nano-Al2O3 and LiTFSI is 60:3:

16.

4. The method of claim 1, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The molecular weight of PEO in step S1 is 600000.

5. The method of claim 1, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The amount of water-absorbing resin SAP or LiH2PO4 in step S2 is 1%-8.2% of the total mass of PEO, nano-Al2O3 and LiTFSI in step S1.

6. The method of claim 1, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The heating temperature in step S3 is 70℃, and the heating time is 10h.

7. The method of claim 1, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The heating temperature in step S6 is 80℃, and the heating time is 10h.

8. The method of claim 1, wherein the PEO solid-state electrolyte film is prepared by a process comprising: The protective atmosphere is argon.

9. A PEO solid-state electrolyte film, characterized by, The PEO solid-state electrolyte film is prepared according to the preparation method of any one of claims 1-8.

10. A lithium symmetric battery, characterized by, The PEO solid-state electrolyte film is assembled according to claim 9.

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