Application of metal phthalocyanine in polymer solid electrolyte and all-solid-state lithium / sodium battery

Abstract

The invention discloses application of metal phthalocyanine in polymer solid electrolyte and an all-solid-state lithium / sodium battery. Metal phthalocyanine is adopted to prepare a PVDF-based polymer solid electrolyte, and then the PVDF-based polymer solid electrolyte is used as a positive electrode component to be used in a polymer all-solid-state sodium battery, or metal phthalocyanine is adopted to prepare a PEO-based polymer solid electrolyte, and then the PEO-based polymer solid electrolyte is used as a negative electrode component to be used in an all-solid-state lithium battery. And the preparation of the high-performance polymer all-solid-state lithium / sodium battery at room temperature can be realized. A metal phthalocyanine network with a plane pi-conjugated structure is introduced into a PVDF or PEO matrix, metal in metal phthalocyanine is Zn, Co or Fe, preparation of the all-solid-state sodium / lithium metal battery is achieved, and the prepared all-solid-state sodium / lithium metal battery has high cycling stability.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and particularly relates to the application of metal phthalocyanine in polymer solid electrolytes and all-solid-state lithium / sodium batteries. Background Art

[0002] Currently, both liquid lithium-ion batteries and sodium-ion batteries have been commercialized. However, liquid electrolytes have safety hazards of being flammable due to thermal runaway. Manufacturing solid-state batteries using solid electrolytes is a key technological direction in the field of secondary batteries. Solid-state batteries not only have high safety but also have the potential to use lithium metal or sodium metal anodes with higher energy density, thereby manufacturing batteries with higher energy density. Solid polymer electrolytes (SPEs) stand out among numerous solid-state electrolytes (SSEs) due to their excellent flexibility and easy processability, becoming one of the most promising solid-state battery materials. Polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF) are two classic polymer electrolytes, which are widely popular due to their excellent heat resistance (>80 °C), electrochemical stability (>4.0 V), and strong mechanical properties. However, the relatively slow ionic conductivity (10 -6 ~10 -4 S cm -1 ) at room temperature becomes a major obstacle to the practical application of SPEs. Therefore, a large amount of research is devoted to developing SPEs with high ionic conductivity by increasing free volume and constructing efficient ion transport channels, such as using covalent organic framework-based polymers, sodium-ion conductive polymers, cross-linked polymer networks, and adding plasticizers. It is worth noting that the introduction of active fillers, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), has also attracted extensive attention. These materials are known for their unique functionalization ability, which can restrict anion migration, ensure uniform electric field distribution, and mitigate concentration polarization.

[0003] Metal phthalocyanine (M-Pc) has classical weak out-of-plane π-π stacking characteristics. Its extended π-π conjugate structure can improve electron transfer ability and enhance the electrochemical redox kinetics of electrolytes. In addition, the dense metal centers in M-Pc have stronger polarity than hydrogen atoms, endowing it with strong chemical adsorption ability for anions in electrolyte salts. Moreover, from the perspective of trial use and cost, phthalocyanine molecules are cheaper than organic additives such as MOFs or COFs and are a kind of molecule that has been commercially available on a large scale. Summary of the Invention

[0004] The purpose of the present invention is to provide the application of metal phthalocyanine in polymer solid electrolytes and to prepare room-temperature high-performance polymer all-solid-state lithium / sodium batteries through metal phthalocyanine molecular additives.

[0005] The present invention first provides the application of metal phthalocyanine (M-Pc) in polymer solid electrolytes, including PVDF-based polymer solid electrolytes and PEO-based polymer solid electrolytes. The metal in the metal phthalocyanine is Zn, Co or Fe.

[0006] (1) Metal phthalocyanine is used to prepare PVDF-based polymer solid electrolytes

[0007] PVDF, NaClO4 and β-Al2O3 are dissolved in N,N-dimethylformamide (DMF) at a mass ratio of 0.8-1.1:0.06-0.1:0.8-1.2, and then stirred at 55-65 °C for 10-14 hours to obtain a homogeneous solution. 0.8-1.2 wt.% of metal phthalocyanine (M-Pc) additive is added to the above solution, degassed under vacuum for 30-40 minutes, and then the solution is cast onto aluminum foil and dried under vacuum at 45-55 °C, thereby forming a PVDF-based polymer solid electrolyte (PVDF-MPc).

[0008] (2) Metal phthalocyanine is used to prepare PEO-based polymer solid electrolytes

[0009] The weighed LiTFSI is dissolved in anhydrous acetonitrile and stirred thoroughly to completely dissolve it to obtain a solution; PEO, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP) and metal phthalocyanine (M-Pc) are added to the above solution. The mass ratio of PEO to LiTFSI is 1:0.4-0.5. The resulting mixed solution is mechanically stirred for 10-14 hours, and then degassed under vacuum for 30-40 minutes to thoroughly remove the bubbles in the solution. The treated solution is evenly cast onto a polytetrafluoroethylene plate and dried in a vacuum environment at 55-65 °C, thereby forming a PEO-based polymer solid electrolyte (PEO-MPc).

[0010] The present invention also provides the application of metal phthalocyanine in polymer all-solid-state lithium / sodium batteries

[0011] (1) Assembly of solid-state sodium batteries: Na3V2(PO4)3 is used as the cathode material, and sodium metal is used as the anode and encapsulated in a CR2025 coin cell. The NVP cathode composition consists of 80 wt.% NVP, 10 wt.% PVDF-MPc and 10 wt.% carbon black, and the loading range is 1.5-2.5 mg·cm -2 . The battery assembly is carried out in a glove box under argon protection (both the oxygen and moisture content are less than 1 ppm). Constant current charge and discharge tests are carried out in the voltage range of 2.2-3.6 V.

[0012] (2) Assembly of solid-state lithium batteries: The solid electrolyte PEO-MPc, LFP as the cathode material, and lithium metal as the anode are encapsulated in a CR2025 button battery. The cathode material contains 80 wt% LFP, 10 wt% PEO-MPc, and 10 wt% carbon black, and the mass loading ranges from 1.5 to 2.5 mg·cm -2 .

[0013] With the above technical solutions, the present invention realizes the preparation of all-solid-state sodium / lithium metal batteries by introducing a metal phthalocyanine (M-Pc, M = Zn, Co, Fe) network with a planar π-conjugated structure into a PVDF or PEO matrix. The prepared all-solid-state sodium / lithium metal batteries have strong cycle stability. The capacity retention rate of the NVP|PVDF-ZnPc|Na full battery is 80% after 700 cycles at a current density of 1C. The capacity retention rate of the LFP|PEO-ZnPC|Li battery is 80% after 400 cycles at 0.5C. Description of the Drawings

[0014] Figure 1 XRD patterns of different substances (a) and XRD patterns of different SPEs (b).

[0015] Figure 2 2D WAXS patterns of PVDF (a) and PVDF-ZnPc film (b).

[0016] Figure 3 SEM images of different SPEs.

[0017] Figure 4 Optical images of different SPE films during stress-strain measurement.

[0018] Figure 5 Discharge and charge curves of NVP|PVDF|Na and NVP|PVDF-ZnPc|Na batteries (a), rate capabilities at different rates from 0.1 to 5C (b), and cycle stability at 1C rate (c).

[0019] Figure 6 Rate capabilities of LFP|PEO|Li and LFP|PEO-ZnPC|Li full batteries at different rates from 0.1 to 2C (a), discharge and charge curves of LFP|PEO-ZnPc|Li battery at different cycles (b), and cycle stability at 0.5C rate (c). Detailed Embodiments

[0020] In the embodiments, the metal phthalocyanine (M-Pc, where M = Zn, Co, and Fe) additives are purchased from Aladdin Company.

[0021] Example 1

[0022] Metal phthalocyanine (Zn-Pc) is used to prepare a PVDF-based polymer solid electrolyte

[0023] PVDF, NaClO4 and β-Al2O3 are dissolved in DMF at a mass ratio of 1.0:0.08:1.0, and then stirred at 60 °C for 12 hours to obtain a homogeneous solution.

[0024] 1.0 wt.% of metal phthalocyanine (Zn-Pc) additive is added to the above solution, degassed under vacuum for 35 minutes, and then the solution is cast onto aluminum foil and dried under vacuum at 50 °C to form a PVDF-based polymer solid electrolyte (PVDF-ZnPc).

[0025] Example 2

[0026] Metal phthalocyanine (Co-Pc) is used to prepare a PVDF-based polymer solid electrolyte

[0027] PVDF, NaClO4 and β-Al2O3 are dissolved in DMF at a mass ratio of 1.0:0.08:1.0, and then stirred at 60 °C for 12 hours to obtain a homogeneous solution.

[0028] 1.0 wt.% of metal phthalocyanine (Zn-Pc) additive is added to the above solution, degassed under vacuum for 35 minutes, and then the solution is cast onto aluminum foil and dried under vacuum at 50 °C to form a PVDF-based polymer solid electrolyte (PVDF-CoPc).

[0029] Example 3

[0030] Metal phthalocyanine (Fe-Pc) is used to prepare a PVDF-based polymer solid electrolyte

[0031] PVDF, NaClO4 and β-Al2O3 are dissolved in DMF at a mass ratio of 1.0:0.08:1.0, and then stirred at 60 °C for 12 hours to obtain a homogeneous solution.

[0032] 1.0 wt.% of metal phthalocyanine (Zn-Pc) additive is added to the above solution, degassed under vacuum for 35 minutes, and then the solution is cast onto aluminum foil and dried under vacuum at 50 °C to form a PVDF-based polymer solid electrolyte (PVDF-FePc).

[0033] Example 4

[0034] Metal phthalocyanine (Zn-Pc) is used to prepare a PEO-based polymer solid electrolyte

[0035] Dissolve the weighed LiTFSI in anhydrous acetonitrile, stir well to completely dissolve it to obtain a solution; add PEO, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Zn-Pc with a mass ratio of 10:1.0:1.1 to the above solution. The mass ratio of PEO to LiTFSI is 1:0.45. Mechanically stir the resulting mixed solution for 12 hours, then degas it under vacuum conditions for 35 minutes to completely remove the bubbles in the solution. Pour the treated solution evenly onto a polytetrafluoroethylene plate and dry it in a vacuum environment at 60 °C to form a PEO-based polymer solid electrolyte (PEO-ZnPc).

[0036] Example 5

[0037] Metal phthalocyanine (Co-Pc) is used to prepare a PEO-based polymer solid electrolyte

[0038] Dissolve the weighed LiTFSI in anhydrous acetonitrile, stir well to completely dissolve it to obtain a solution; add PEO, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Zn-Pc with a mass ratio of 10:0.9:1 to the above solution. The mass ratio of PEO to LiTFSI is 1:0.4. Mechanically stir the resulting mixed solution for 10 hours, then degas it under vacuum conditions for 30 minutes to completely remove the bubbles in the solution. Pour the treated solution evenly onto a polytetrafluoroethylene plate and dry it in a vacuum environment at 55 °C to form a PEO-based polymer solid electrolyte (PEO-CoPc).

[0039] Example 6

[0040] Metal phthalocyanine (Fe-Pc) is used to prepare a PEO-based polymer solid electrolyte

[0041] Dissolve the weighed LiTFSI in anhydrous acetonitrile, stir well to completely dissolve it to obtain a solution; add PEO, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Zn-Pc with a mass ratio of 10:.1.1:1.2 to the above solution. The mass ratio of PEO to LiTFSI is 1:0.5. Mechanically stir the resulting mixed solution for 14 hours, then degas it under vacuum conditions for 35 minutes to completely remove the bubbles in the solution. Pour the treated solution evenly onto a polytetrafluoroethylene plate and dry it in a vacuum environment at 65 °C to form a PEO-based polymer solid electrolyte (PEO-FePc).

[0042] Example 7

[0043] Application of the solid electrolytes prepared based on Examples 1 and 4 in polymer all-solid-state lithium / sodium batteries

[0044] (1) Assembly of solid-state sodium batteries: Na3V2(PO4)3 was used as the cathode material, and sodium metal was used as the anode and encapsulated in a CR2025 button battery. The NVP cathode composition consisted of 80 wt.% NVP, 10 wt.% PVDF-ZnPc, and 10 wt.% carbon black, with a loading range of 1.5 - 2.5 mg·cm -2 . The battery assembly was carried out in a glove box under argon protection (both the oxygen and moisture contents were less than 1 ppm). Constant current charge-discharge tests were performed in the voltage range of 2.2 - 3.6 V.

[0045] (2) Structure of solid-state lithium batteries, the solid electrolyte PEO-ZnPc, LiFePO4 as the cathode material, and lithium metal as the anode were encapsulated in a CR2025 button battery. The LiFePO4 cathode composition contained 80 wt% LFP, 10 wt% PEO-ZnPc, and 10 wt% carbon black, with a mass loading range of 1.5 - 2.5 mg·cm -2 .

[0046] Before the experimental tests, the solid-state lithium / sodium batteries were pretreated at 60 - 80 °C for 24 hours.

[0047] As Figure 1 shown, characteristic peaks of M-Pc could be detected in the X-ray diffraction (XRD) patterns of PVDF-MPc (M = Zn, Co, Fe), indicating that the doping had a certain degree of uniformity.

[0048] As Figure 2 shown, through wide-angle X-ray diffraction (WAXD) measurements, we evaluated the structural evolution of PVDF-ZnPc relative to the original PVDF. The 2D-WAXD pattern of PVDF-ZnPc showed a decrease in the intensities of the (100), (020), and (110) crystal planes of PVDF, indicating that the addition of ZnPc restricted the molecular motion in PVDF, thereby inhibiting the highly oriented crystallization of PVDF.

[0049] Figure 3 are scanning electron microscope (SEM) images of different solid polymer electrolytes (SPEs). Compared with the porous PVDF, PVDF-CoPc, and PVDF-FePc membranes, PVDF-ZnPc had fewer pore morphologies, which helped to form a thinner, more uniform, and denser film. The uniform distribution of M-Pc in the SPEs imparted a significant mechanical strengthening effect, which was crucial for alleviating the formation of Na dendrites.

[0050] Figure 4 Optical images of different SPEs membranes during stress-strain measurements. The yield strength of the PVDF membrane is 7.9 MPa. In contrast, the yield strength of PVDF-ZnPc (50.2 MPa) is significantly increased by 535.4% compared to the PVDF membrane. It is worth noting that the elongation at break of PVDF-ZnPc reaches 480.5%, exceeding that of the PVDF membrane (55.3%), PVDF-FePc (388.2%), and PVDF-CoPc (410.4%).

[0051] To investigate the applicability of PVDF-ZnPc in sodium metal batteries, a button-type full cell was assembled using NVP as the cathode, metallic sodium as the anode, and operated at room temperature. Figure 5 a shows the initial charge-discharge curves of NVP|PVDF|Na and NVP|PVDF-ZnPc|Na at a current density of 0.1 C. Compared with the NVP|PVDF|Na cell (about 191 mV), the voltage polarization of the NVP|PVDFZnPc|Na cell (about 26 mV) is significantly reduced. Figure 5 b shows the rate performance of the two full cells with a current density range from 0.1 C to 5 C. Even at high rates, the NVP|PVDF-ZnPc|Na cell still maintains a considerable discharge capacity, reaching about 108.7 mAh g-1 at 0.5 C and 92.2 mAh g-1 at 5 C. These results highlight the excellent interfacial stability between PVDF-ZnPc and the cathode. Figure 5 c illustrates the long-term cycling stability of the NVP|PVDF-ZnPc|Na full cell at room temperature, with a capacity retention rate of 80% after 700 cycles at a current density of 1 C.

[0052] To further verify the universality and excellent performance of the strategy of the present invention, we prepared PEO-ZnPc for solid-state lithium metal batteries using a similar method, and assembled and evaluated the LFP|PEO|Li and LFP|PEO-ZnPC|Li full cells (LFP refers to the commercial lithium iron phosphate cathode). Figure 6 a shows the rate performance of the LFP|PEO|Li and LFP|PEO-ZnPC|Li full cells at different rates of 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C. The LFP|PEO-ZnPC|Li full cell provides 159.7, 148.5, 145.1, 37.4, 21.8 mAh g at different rates respectively -1Discharge capacity. When restored to a 0.5C discharge rate, it exhibits a remarkable capacity retention rate. In contrast, the rate performance of the LFP / SPE / Li battery is poor, and at 0.1C, 0.2C, 0.5C, 1C, and 2C rates, the discharge capacities are 129.9, 54.8, 25.7, 15.4, and 5.1 mAh g -1 . Figure 6 The charge-discharge curves in b show that the voltage plateau periods of the LFP|PEO-ZnPC|Li battery are consistent, indicating a minimum polarization effect. In addition, the LFP|PEO-ZnPC|Li battery exhibits strong cycle stability and can retain 80% of its capacity even after 400 cycles at 0.5C.

Claims

1. Application of metal phthalocyanine in polymer solid electrolyte, wherein the metal in the metal phthalocyanine is Zn, Co or Fe.

2. The application of the metal phthalocyanine in the polymer solid electrolyte according to claim 1, wherein The metal phthalocyanine is used to prepare a PVDF-based polymer solid electrolyte, or the metal phthalocyanine is used to prepare a PEO-based polymer solid electrolyte.

3. The application of the metal phthalocyanine according to claim 2 in the polymer solid electrolyte, characterized in that The preparation method of the PVDF-based polymer solid electrolyte is as follows: Dissolve PVDF, NaClO4 and β-Al2O3 in N,N-dimethylformamide, then stir at 55-65 °C for 10-14 hours to obtain a homogeneous solution. Add 0.8-1.2 wt.% of the metal phthalocyanine additive to the above solution. After degassing under vacuum, cast the solution onto an aluminum foil and perform vacuum drying to form a PVDF-based polymer solid electrolyte, denoted as PVDF-MPc.

4. The application of the metal phthalocyanine according to claim 3 in the polymer solid electrolyte, characterized in that, The mass ratio of PVDF, NaClO4 and β-Al2O3 is 0.8-1.1:0.06-0.1:0.8-1.

2. The degassing time under vacuum is 30-40 minutes, and the vacuum drying temperature is 45-55 °C.

5. The use of the metal phthalocyanine according to claim 2 in a polymer solid electrolyte, characterized in that, The preparation method of the described PEO-based polymer solid electrolyte is as follows: Dissolve LiTFSI in anhydrous acetonitrile and stir well to completely dissolve it to obtain a solution; Add PEO, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and metal phthalocyanine to the above solution, stir the resulting mixed solution for 10 - 14 hours, then degas under vacuum conditions to completely remove the bubbles in the solution, uniformly cast the treated solution onto a polytetrafluoroethylene plate, and dry it in a vacuum environment to form a PEO-based polymer solid electrolyte, denoted as PEO-MPc.

6. The application of the metal phthalocyanine according to claim 5 in a polymer solid electrolyte, characterized in that, The described PEO, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and the metal phthalocyanine have a mass ratio of 10:0.9 - 1.1:1 - 1.2, the mass ratio of PEO to LiTFSI is 1:0.4 - 0.5, the degassing time under vacuum is 30 - 40 minutes, and the vacuum drying temperature is 55 - 65 °C.

7. Application of metal phthalocyanine in polymer all-solid-state sodium batteries, characterized in that, The positive electrode of the battery contains the PVDF-based polymer solid electrolyte prepared with the metal phthalocyanine in claim 3.

8. The application according to claim 7, characterized in that, Using Na3V2(PO4)3 as the cathode material and sodium metal as the anode, they were encapsulated in a CR2025 coin cell. The NVP cathode composition consisted of 80 wt.% NVP, 10 wt.% PVDF-MPc, and 10 wt.% carbon black, with a loading range of 1.5 - 2.5 mg·cm -2 , and the battery assembly was carried out in a glove box under argon protection.

9. Application of metal phthalocyanine in a polymer all-solid-state lithium battery, characterized in that, The negative electrode of the battery contains the PEO-based polymer solid electrolyte prepared with the metal phthalocyanine in claim 5.

10. The application according to claim 9, wherein PEO-MPc and LFP are used as cathode materials, and lithium metal is used as the anode, which are encapsulated in a CR2025 button cell. The cathode material contains 80 wt% LFP, 10 wt% PEO-MPc, and 10 wt% carbon black, and the mass loading ranges from 1.5 to 2.5 mg·cm -2 .

Images