PEO solid electrolyte membrane, preparation method thereof and lithium symmetric battery

Abstract

The invention provides a PEO solid electrolyte membrane, a preparation method thereof and a lithium symmetric battery. The preparation method comprises the following steps: S1, weighing PEO, nano Al2O3 and LiTFSI in a protective atmosphere for later use; step S2, weighing water-absorbent resin SAP or LiH2PO4 under a protective atmosphere for later use; s3, dissolving all the raw materials in the step S1 and the step S2 into ultra-dry acetonitrile in a protective atmosphere, and heating and stirring; s4, fully stirring, and standing for 1 hour; s5, standing under a protective atmosphere, dripping the PEO solution on a PTFE plate, and standing for 1 hour; and step S6, after standing, heating and evaporating the acetonitrile solvent to dryness in a protective atmosphere to obtain the PEO solid electrolyte membrane. The water-absorbent resin SAP or LiH2PO4 is added into the PEO solid electrolyte, so that the interface impedance between the PEO solid electrolyte and the lithium metal negative electrode is effectively reduced. The method for improving the stability of the PEO solid electrolyte to the lithium negative electrode interface improves the stability of the PEO solid electrolyte to the lithium negative electrode, and has the characteristics of simple process, convenience in operation and low cost.

Description

Technical Field

[0001] The invention belongs to the field of solid-state lithium metal batteries, and in particular relates to a PEO solid-state electrolyte membrane and a preparation method thereof, and a lithium symmetrical battery. Background Art

[0002] Under the dual pressure of energy security and environmental protection, clean energy such as wind power and solar energy has achieved leapfrog development. Since clean energy is highly dependent on external weather and exhibits strong instability, lithium-ion batteries have also achieved rapid development. The vigorous development of electric vehicles has also greatly promoted the development of lithium-ion batteries. Due to the use of flammable and easy-to-flow organic electrolytes, current commercial lithium-ion batteries have safety hazards such as fire and explosion. Solid-state lithium metal batteries are considered to be the ideal next-generation electrochemical energy storage system. Solid-state electrolytes are the core of solid-state lithium metal battery research. Among many solid-state electrolytes, PEO (polyethylene oxide)-based solid electrolytes have the characteristics of good flexibility, easy preparation, and good chemical stability.

[0003] However, PEO-based solid electrolytes are unstable to lithium metal negative electrodes. When used with lithium metal negative electrodes, an interface layer will be generated. The impedance value of the interface layer is often several times or even dozens of times that of the PEO solid electrolyte, which will seriously affect the rate performance of solid-state lithium metal batteries. Related research has attracted the attention of researchers and has achieved certain research results. For example, adding LiNO 3 Both black phosphorus and PEO solid electrolyte can improve the stability of lithium anode. 3 PEO is an explosive chemical, while black phosphorus is too expensive. New methods to improve the interface of PEO with the lithium negative electrode are necessary. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a PEO solid electrolyte membrane and a preparation method thereof, which improves the stability of the PEO solid electrolyte to the lithium negative electrode, and adds a water-absorbing resin SAP or LiH 2 PO 4 , can effectively reduce the interface impedance between PEO solid electrolyte and lithium metal negative electrode, the added water-absorbing resin SAP or LiH 2 PO 4 There is no obvious adverse effect on the ionic conductivity of the PEO solid electrolyte. The method of improving the interfacial stability of the PEO solid electrolyte to the lithium negative electrode of the present invention has the characteristics of simple process, convenient operation and low cost.

[0005] The present invention also provides a lithium symmetrical battery assembled using the PEO solid electrolyte membrane.

[0006] Note that the description of these objectives does not prevent the existence of other objectives. One embodiment of the present invention does not need to achieve all of the above objectives. Objectives other than the above objectives can be extracted from the description of the specification, drawings, and claims.

[0007] The present invention achieves the above technical objectives through the following technical means.

[0008] A method for preparing a PEO solid electrolyte membrane comprises the following steps:

[0009] Step S1, weighing PEO (polyethylene oxide), nano-Al 2 O 3 and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) for standby use;

[0010] Step S2: weighing the water-absorbing resin SAP or LiH 2 PO 4 spare;

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

[0012] Step S4, stirring thoroughly and letting stand for one hour;

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

[0014] Step S6, after standing, heating in a protective atmosphere to evaporate the acetonitrile solvent to obtain a PEO solid electrolyte membrane.

[0015] In the above scheme, in step S1, PEO, nano-Al 2 O 3 The mass ratio of LiTFSI is 100:(1-10):(1-81)

[0016] Furthermore, the PEO, nano-Al 2 O 3 The mass ratio of LiTFSI to LiTFSI is 60:3:16.

[0017] In the above scheme, the molecular weight of PEO in step S1 is 600,000.

[0018] In the above scheme, in step S2, the water-absorbing resin SAP, LiH 2 PO 4 The amounts of PEO and nano-Al in step S1 are 2 O 3 and 1%-8.2% of the total mass of LiTFSI.

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

[0020] In the above scheme, in step S6, the heating temperature is 80° C. and the heating time is 10 hours.

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

[0022] A PEO solid electrolyte membrane is prepared according to the preparation method of the PEO solid electrolyte membrane.

[0023] A lithium symmetrical battery is assembled using the PEO solid electrolyte membrane.

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

[0025] The present invention utilizes water-absorbing resin SAP, LiH 2 PO 4 The addition of PEO effectively reduces the interface impedance between PEO solid electrolyte and lithium metal negative electrode, improves the interface between PEO solid electrolyte and lithium metal electrode, and enhances the stability of PEO solid electrolyte to lithium negative electrode. 2 PO 4 It has the characteristics of low cost and high safety.

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

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

[0028] Figure 2 Add LiH 2 PO 4 Room temperature impedance spectrum of lithium symmetric battery with PEO solid electrolyte.

[0029] Figure 3 Add LiH 2 PO 4 Interfacial resistance of PEO solid electrolyte to lithium metal anode.

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

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

[0032] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, rather than all the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The present invention is further described below in conjunction with the embodiments. Among them, embodiments 3-6, 9-11 are preferred embodiments of the present invention.

[0033] Example 1

[0034] Example 1 is a comparative example, a method for preparing a PEO solid electrolyte membrane, comprising the following steps:

[0035] Step S1: weigh 0.6 g PEO, 0.16 g LiTFSI and 0.03 g nano-Al in the glove phase. 2 O 3 ;

[0036] Step S2: Do not weigh SAP and LiH 2 PO 4 ;

[0037] Step S3, dissolving all raw materials into ultra-dry acetonitrile in a glove box and heating with stirring at a heating temperature of 70° C.;

[0038] Step S4, stirring for 10 hours and then standing for one hour;

[0039] Step S5, dripping the PEO solution onto the PTFE plate in a glove box and letting it stand for one hour;

[0040] Step S6: After standing, heat at 80°C for 10 hours in a glove box to evaporate the acetonitrile solvent to obtain a PEO solid electrolyte membrane. Then assemble a Li / PEO / Li symmetric battery in the glove box, test the impedance, and calculate the PEO / Li interface resistance. The test temperature is 60°C.

[0041] The impedance results of the PEO solid electrolyte membrane assembled lithium symmetric battery are as follows Figure 1 As shown, the interface impedance between the PEO solid electrolyte and the lithium negative electrode can be obtained from the curve in the impedance spectrum, such as Figure 3 As shown, the interface impedance between PEO and the lithium metal negative electrode in Example 1 is 61.2Ω.

[0042] Embodiment 2-7

[0043] A method for preparing a PEO solid electrolyte membrane comprises the following steps:

[0044] Step S1: weigh 0.6 g PEO, 0.16 g LiTFSI and 0.03 g nano-Al in a glove box. 2 O 3 ;

[0045] Step S2: weighing LiH 2 PO 4 ;

[0046] Step S3, dissolving all raw materials into ultra-dry acetonitrile in a glove box and heating with stirring at a heating temperature of 70° C.;

[0047] Step S4, stirring for 10 hours and then standing for one hour;

[0048] Step S5, dripping the PEO solution onto the PTFE plate in a glove box and letting it stand for one hour;

[0049] Step S6: After standing, heat at 80°C for 10 hours in a glove box to evaporate the acetonitrile solvent to obtain a PEO solid electrolyte membrane. Then assemble a Li / PEO / Li symmetric battery in the glove box, test the impedance, and calculate the PEO / Li interface resistance. The test temperature is 60°C.

[0050] The difference between Example 2 and Example 7 is that in step S2, LiH 2 PO 4 The weighings were 0.008g, 0.016g, 0.024g, 0.032g, 0.04g and 0.048g respectively.

[0051] The obtained LiH 2 PO 4 The impedance results of the lithium symmetric battery assembled with PEO solid electrolyte membrane are as follows Figure 2 As shown, from the curve in the impedance spectrum, it can be obtained that adding LiH 2 PO 4 The interfacial impedance between the PEO solid electrolyte and the lithium negative electrode is shown in Figure 3 As shown, the interface impedance between PEO and the lithium metal negative electrode in Examples 2-7 is 30.5Ω, 20.5Ω, 17.1Ω, 13.8Ω, 19Ω and 31Ω, respectively.

[0052] Embodiment 8-15

[0053] A method for preparing a PEO solid electrolyte membrane comprises the following steps:

[0054] Step S1: weigh 0.6 g PEO, 0.16 g LiTFSI and 0.03 g nano-Al in a glove box. 2 O 3 ;

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

[0056] Step S3, dissolving all raw materials into ultra-dry acetonitrile in a glove box and heating with stirring at a heating temperature of 70° C.;

[0057] Step S4, stirring for 10 hours and then standing for one hour;

[0058] Step S5, dripping the PEO solution onto the PTFE plate in the glove phase and letting it stand for one hour;

[0059] Step S6: After standing, heat at 80°C for 10 hours in a glove box to evaporate the acetonitrile solvent to obtain a PEO solid electrolyte membrane. Then assemble a Li / PEO / Li symmetric battery in the glove box, test the impedance, and calculate the PEO / Li interface resistance. The test temperature is 60°C.

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

[0061] The impedance results of the lithium symmetric battery assembled with the PEO solid electrolyte membrane with added water-absorbing resin SAP are as follows: Figure 4 As shown, the interface impedance between the PEO solid electrolyte with added water-absorbing resin SAP and the lithium negative electrode can be obtained from the curve in the impedance spectrum. Figure 5 As shown, the interface impedance between PEO and the lithium metal negative electrode in Examples 8-15 is 52.6Ω, 39.6Ω, 32.3Ω, 44.7Ω, 46.6Ω, 50.2Ω, 53.5Ω and 59.5Ω, respectively.

[0062] The present invention utilizes water-absorbing resin SAP, LiH 2 PO 4 The addition of PEO effectively reduces the interface impedance between PEO solid electrolyte and lithium metal negative electrode, improves the interface between PEO solid electrolyte and lithium metal electrode, and enhances the stability of PEO solid electrolyte to lithium negative electrode. 2 PO 4 It has the characteristics of low cost and high safety, among which embodiments 3-6 and 9-11 are preferred embodiments of the present invention.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. 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 invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a PEO solid electrolyte membrane, characterized in that: The following steps are involved: Step S1, weighing PEO, nano-Al2O3 and LiTFSI in a protective atmosphere for later use; Step S2, weighing water-absorbing resin SAP or LiH2PO4 under a protective atmosphere for standby use; Step S3, dissolving all raw materials of steps S1 and S2 in ultra-dry acetonitrile under a protective atmosphere and heating and stirring; Step S4, stirring thoroughly and letting stand for one hour; Step S5, after standing under a protective atmosphere, dripping the PEO solution onto the PTFE plate and standing for one hour; Step S6, after standing, heating in a protective atmosphere to evaporate the acetonitrile solvent to obtain a PEO solid electrolyte membrane.

2. The method for preparing a PEO solid electrolyte membrane according to claim 1, characterized in that: In the step S1, the mass ratio of PEO, nano-Al2O3 and LiTFSI is 100:(1-10):(1-81).

3. The method for preparing a PEO solid electrolyte membrane according to claim 2, characterized in that: The mass ratio of PEO, nano-Al2O3 and LiTFSI is 60:3:

16.

4. The method for preparing a PEO solid electrolyte membrane according to claim 1, characterized in that: The molecular weight of PEO in step S1 is 600,000.

5. The method for preparing a PEO solid electrolyte membrane according to claim 1, characterized in that: In the step S2, the amount of the water-absorbing resin SAP and LiH2PO4 is 1%-8.2% of the total mass of PEO, nano-Al2O3 and LiTFSI in step S1.

6. The method for preparing a PEO solid electrolyte membrane according to claim 1, characterized in that: In step S3, the heating temperature is 70° C. and the heating time is 10 h.

7. The method for preparing a PEO solid electrolyte membrane according to claim 1, characterized in that: In step S6, the heating temperature is 80° C. and the heating time is 10 h.

8. The method for preparing a PEO solid electrolyte membrane according to claim 1, characterized in that: The protective atmosphere was argon.

9. A PEO solid electrolyte membrane, characterized in that: It is prepared according to the method for preparing a PEO solid electrolyte membrane according to any one of claims 1 to 8.

10. A lithium symmetrical battery, characterized in that: Obtained by assembling the PEO solid electrolyte membrane described in claim 9.

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