A kind of double phthalocyanine synergistically modified PVDF-HFP-based organic solid electrolyte and its preparation method

Abstract

The application discloses a kind of double pthalocyanine synergic modified PVDF-HFP base organic solid electrolyte and its preparation method, specifically using double pthalocyanine metal complex (F 16 ZnPc+F 16 CoPc) Synergic modification is combined with low content nano inorganic filler compound, and the technical scheme of DMF / acetone composite solvent system regulation and vacuum gradient temperature drying, high performance PVDFHFP base organic solid electrolyte can be prepared by solution casting method.The prepared electrolyte can reach 5×10 ‑3 S / cm above at 25 DEG C, compared with pure PVDF-HFP significantly improved, and has excellent wide temperature adaptability;Its good ionic conductivity is conducive to improving the rate performance and energy density of battery;At the same time, improved interface contact and electrochemical stability help to improve the cycle stability and safety of battery.

Description

Technical Field

[0001] This application belongs to the technical field of solid-state electrolytes for batteries, and in particular to a PVDF-HFP-based organic solid-state electrolyte modified by diaphthalocyanine and its preparation method. Background Technology

[0002] With the rapid development of portable electronic devices and electric vehicles, the demand for high-energy-density and high-safety energy storage devices is becoming increasingly urgent, and lithium-ion batteries have received widespread attention. Traditional liquid lithium-ion batteries pose serious safety hazards due to their flammability and leakage. Solid electrolytes, with their advantages of being non-flammable and leak-proof, have become a direction for solving this problem. PVDF-HFP copolymers are considered to be a highly promising polymer solid electrolyte matrix due to their excellent flexibility, electrochemical stability, and good compatibility with electrode materials. However, pure PVD-FHFP electrolytes have low ionic conductivity at room temperature and high contact impedance at the electrode interface, making it difficult to meet the requirements of practical applications.

[0003] Currently, common modification methods mostly involve adding inorganic fillers and plasticizers, but these often suffer from problems such as filler agglomeration and decreased mechanical properties. In recent years, phthalocyanine-based metal complexes have been explored for electrolyte modification due to their large π-conjugated structure and good thermal stability. 16 ZnPc and F 16 CoPc are both organometallic compounds with excellent thermal stability, chemical stability, and π-π conjugated structures. 16 CoPc can catalyze the in-situ cracking of lithium bis(trifluoromethanesulfonylimide) to generate lithium fluoride, F 16 ZnPc has Lewis acid sites that can selectively adsorb TFSI. - The anion promotes the dissociation of lithium salts, while its large π-conjugated structure facilitates the construction of organic ion transport channels. Therefore, F... 16 ZnPc and F 16 The introduction of CoPc into PVDF-HFP-based solid electrolytes is expected to synergistically improve the electrolyte's ionic conductivity, mechanical properties, and electrochemical stability, providing a new solution for developing high-performance solid-state lithium batteries.

[0004] However, existing technologies rarely employ the combined use of both phthalocyanines and phthalocyanines in PVDF-HFP solid electrolytes. This is primarily due to several unresolved technical challenges, including poor dispersion and compatibility of phthalocyanine molecules in the polymer matrix, difficulty in precisely controlling the synergistic effect of phthalocyanines, and the unclear mechanism by which the addition of phthalocyanines affects electrolyte performance. Therefore, developing a phthalocyanine-modified PVDF-HFP-based solid electrolyte that can address these technical issues is of great significance for promoting the development of high-performance solid-state lithium batteries. Summary of the Invention

[0005] This invention aims to solve the problems of low ionic conductivity and high interfacial impedance of pure PVDF-HFP electrolyte, and to synergistically improve its mechanical strength. Specifically, it improves ionic conductivity, improves interfacial contact between electrolyte and electrode, and enhances the cycle performance and safety of solid-state batteries by introducing zinc hexadecyl phthalocyanine / cobalt modification.

[0006] This invention proposes a PVDF-HFP-based organic solid electrolyte modified by diazocyanine synergistic modification. The electrolyte is prepared by solution casting with polyvinylidene fluoride-hexafluoropropylene as the matrix, lithium bis(trifluoromethanesulfonylimide) as the lithium salt, zinc hexafluorophthalocyanine and cobalt hexafluorophthalocyanine as synergistic modifiers, and selective addition of nano-Al2O3 as a composite filler.

[0007] Preferably, the mass ratio of PVDF-HFP to LiTFSI is 1:1 to 4:1; the F 16 The amount of ZnPc added is 5% to 30% of the mass of PVDF-HFP, wherein the F 16 The amount of CoPc added is 1-10% of the mass of PVDF-HFP, and F 16 ZnPc and F 16 The mass ratio of CoPc is (1-10):1, and the total mass of the two accounts for 5-40% of the mass of the PVDF-HFP matrix; the amount of Al2O3 added is 1-3% of the mass of PVDF-HFP.

[0008] This invention also provides a method for preparing a PVDF-HFP-based organic solid electrolyte modified by diaphthalocyanine synergistic modification, comprising the following steps:

[0009] S1 Raw Material Preparation: Weigh out PVDF-HFP, LiTFSI, and F according to the specified proportions. 16 ZnPc, F 16 CoPc and Al2O3 are added to an organic solvent and mixed to form a casting solution;

[0010] S2 Mixing and Dispersion: The casting solution is heated and stirred to fully dissolve and uniformly disperse all components;

[0011] S3 Film Formation and Drying: The uniformly mixed casting solution is poured into a clean mold, dried under vacuum, and then peeled off to obtain an electrolyte film.

[0012] Preferably, in step S1, each raw material needs to undergo pretreatment, the process of which is as follows: PVDF-HFP and LiTFSI are placed in an 80℃ vacuum drying oven for 12 hours; F... 16 ZnPc, F 16 CoPc and Al2O3 were treated in a vacuum drying oven at 60℃ for 6 hours.

[0013] Preferably, the organic solvent in step S1 is a composite solvent of N,N-dimethylformamide (DMF) and acetone; wherein the volume ratio of DMF to acetone in the composite solvent is 3:1.

[0014] Preferably, the stirring process in step S2 is as follows: stirring at a temperature of 40-80℃ and a speed of 450-600 r / min for 10-24 hours.

[0015] Preferably, the vacuum drying process in step S3 is as follows: when using a single DMF solvent, drying is carried out at 50-80°C until constant weight is achieved; when using a composite solvent, drying is carried out first at 40°C for 6 hours, then at 60°C for 12 hours, and finally at 70°C for 2 hours.

[0016] Compared with the prior art, the advantages of this application are:

[0017] 1. This application adopts F 16 ZnPc and F 16 CoPc composites, as modifiers, offer complementary advantages: F 16 CoPc can promote the cleavage of LiTFSI, generating nano-LiF in situ. The generated LiF can improve the stability of the electrolyte / electrode interface, thereby effectively reducing interfacial impedance and improving ion transport efficiency; while F 16 The π-π conjugated structure of ZnPc can form organic ion transport channels, creating an organic-inorganic multi-level ion transport network with LiF, thereby further enhancing the ion transport efficiency of LiF. + This improves migration efficiency, thereby solving the problem of limited ion transport channels in existing single modifiers.

[0018] 2. The π-π stacking structure of the phthalocyanine-based materials in this application can adsorb and disperse nano-Al2O3, preventing its aggregation; the Lewis acid sites of nano-Al2O3 can interact with the anions of LiTFSI, promoting Li... + The dissociation of ions is achieved; at the same time, nano-Al2O3 can enhance the mechanical strength of the electrolyte membrane, thereby achieving a synergistic improvement in ionic conductivity and mechanical strength.

[0019] 3. This application employs a 3:1 volume ratio of DMF to acetone composite solvent, combined with a stirring process at 40–80℃ and 450–600 r / min for 10–24 h. The two solvents work synergistically: DMF exhibits good solubility for PVDF-HFP, while acetone reduces the viscosity and surface tension of the casting solution. Under heating and stirring conditions, the uniform dispersion of each component is accelerated. The different boiling points of the two solvents allow for the regulation of the pore size and distribution of the electrolyte membrane. Simultaneously, it further inhibits the formation of regular crystalline regions in PVDF-HFP, increasing the proportion of its amorphous portion, thereby expanding ion transport channels. This fundamentally solves the problems of uneven pore size and high crystallinity in existing single-solvent film formation.

[0020] 4. The gradient temperature drying process used during casting can remove solvents in stages according to the different boiling points of the composite solvents, avoiding problems such as film warping and cracking caused by rapid drying. At the same time, the high temperature can deeply remove residual solvents. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The image shown is a physical diagram of the electrolyte film obtained in Example 1 of this invention;

[0023] Figure 2 The image shown is a SEM image of the electrolyte film obtained in Examples 2 and 4 of this invention. Figure 2 (a) is the pure PVDF-HFP electrolyte film obtained in Example 4. Figure 2 (b) is the PVDF-HFP-based organic solid electrolyte modified by bisphthalocyanine synergistically obtained in Example 2;

[0024] Figure 3 The figure shows the impedance diagrams of the electrolyte films obtained in Examples 4 and 5 of the present invention;

[0025] Figure 4 The figure shows the cycle performance of the LCO solid-state battery assembled with the electrolyte obtained in Example 2 of the present invention at a 2C rate. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] S1 Raw Material Preparation: Weigh out 400mg of dried PVDF-HFP, 400mg of LiTFSI, and F according to the specified proportions. 16 ZnPc 80mg, F 16 20 mg of CoPc was added to 15 ml of DMF-acetone composite solvent to form a casting solution.

[0029] S2 Mixing and Dispersion: Stir the casting solution at 500 r / min at 60℃ for 12 h to ensure that all components are fully dissolved and uniformly dispersed;

[0030] S3 Film Formation and Drying: The uniformly mixed casting solution is poured into a polytetrafluoroethylene petri dish, dried at 40°C for 6 hours, then at 60°C for 12 hours, and finally at 70°C for 2 hours before peeling off to obtain the electrolyte film.

[0031] The ionic conductivity at 25℃ was measured to be 5.2 × 10⁻⁶. -3 With a tensile strength of 15.3 MPa and an interfacial impedance of 4.8 Ω, the full cell assembled at 2C rate retained 92.5% of its capacity after 300 cycles.

[0032] Example 2

[0033] In step S1 of Example 1, “F” 16 ZnPc 80mg, F 16 "CoPc 20mg" should be changed to "F" 16 ZnPc 70mg, F 16 "CoPc 30mg, nano Al2O3 5mg", the rest is the same as in Example 1, and a uniformly distributed electrolyte film is obtained.

[0034] The ionic conductivity was measured to be 5.5 × 10⁻⁶ at 25°C. -3 With a tensile strength of 16.1 MPa and an interfacial impedance of 4.5 Ω, the full cell assembled at 2C rate retained 93.2% of its capacity after 300 cycles.

[0035] Example 3

[0036] In step S1 of Example 1, “F”16 ZnPc 80mg, F 16 "CoPc 20mg" should be changed to "F" 16 ZnPc 75mg, F 16 "25mg CoPc, 10mg nano Al2O3", the rest are the same as in Example 1, and a uniformly distributed electrolyte film is obtained.

[0037] The ionic conductivity was measured to be 5.1 × 10⁻⁶ at 25°C. -3 With a tensile strength of 16.5 MPa and an interfacial impedance of 4.6 Ω, the assembled full cell retained 92.3% of its capacity after 300 cycles at 2C rate.

[0038] Example 4

[0039] The "F" in the raw material of step S1 in Example 1 16 ZnPc 80mg, F 16 20 mg of CoPc was removed, and the rest remained the same as in Example 1, resulting in a uniformly distributed pure PVDF-HFP electrolyte membrane.

[0040] Tests showed that the ionic conductivity at 25℃ was 1×10⁻⁶. -4 With a tensile strength of 8.2 MPa and an interfacial impedance of 142.9 Ω, the full cell assembled at 2C rate retained 76.2% of its capacity after 300 cycles.

[0041] Example 5

[0042] The "F" in the raw material of step S1 in Example 1 16 ZnPc 80mg, F 16 "CoPc 20mg" should be changed to "F" 16 ZnPc 100mg”, the rest is consistent with Example 1, and a uniformly distributed F is obtained. 16 ZnPc-PVDF-HFP electrolyte membrane.

[0043] The ionic conductivity was measured to be 1.2 × 10⁻⁶ at 25°C. -3 With a tensile strength of 12.4 MPa and an interfacial impedance of 11.8 Ω, the full cell assembled at 2C rate retained 87.6% of its capacity after 300 cycles.

[0044] The results from various embodiments show that pure PVDF-HFP electrolyte films have low ionic conductivity, poor mechanical properties, high interfacial impedance, and poor cycle stability; adding F... 16 Modification of ZnPc can slightly improve ionic conductivity and interfacial stability to a certain extent; furthermore, the addition of F...16 When CoPc is synergistically modified, it can significantly improve ionic conductivity and reduce interfacial impedance. On the basis of phthalocyanine modification, the addition of nano-Al2O3 can further enhance the mechanical strength and structural stability of the film, making the electrolyte have the best comprehensive performance in terms of ion transport, mechanical properties, interfacial compatibility and long cycle stability, thus making it more suitable for high safety and long life solid-state lithium-ion batteries.

[0045] This embodiment is merely an illustrative description of the present patent and does not limit its scope of protection. Those skilled in the art may make partial modifications to it. As long as they do not exceed the spirit and essence of the present patent, they shall be regarded as equivalent substitutions to the present patent and shall be within the scope of protection of the present patent.

Claims

1. A PVDF-HFP-based organic solid electrolyte modified by diaphthalocyanine synergistic modification, characterized in that, The electrolyte is prepared by solution casting with polyvinylidene fluoride-hexafluoropropylene as the matrix, lithium bis(trifluoromethanesulfonyl)imide as the lithium salt, zinc hexafluorophthalocyanine and cobalt hexafluorophthalocyanine as synergistic modifiers, and selective addition of nano-Al2O3 as a composite filler.

2. The organic solid electrolyte according to claim 1, characterized in that, The mass ratio of PVDF-HFP to LiTFSI is 1:1 to 4:1; the F 16 The amount of ZnPc added is 5% to 30% of the mass of PVDF-HFP, wherein the F 16 The amount of CoPc added is 1-10% of the mass of PVDF-HFP, and F 16 ZnPc and F 16 The mass ratio of CoPc is (1-10):1, and the total mass of the two accounts for 5-40% of the mass of the PVDF-HFP matrix; the amount of Al2O3 added is 1-3% of the mass of PVDF-HFP.

3. The method for preparing the organic solid electrolyte according to claim 1, characterized in that, Includes the following steps: S1 Raw Material Preparation: Weigh out PVDF-HFP, LiTFSI, and F according to the specified proportions. 16 ZnPc, F 16 CoPc and Al2O3 are added to an organic solvent and mixed to form a casting solution; S2 Mixing and Dispersion: The casting solution is heated and stirred to fully dissolve and uniformly disperse all components; S3 Film Formation and Drying: The uniformly mixed casting solution is poured into a clean mold, dried under vacuum, and then peeled off to obtain an electrolyte film.

4. The method for preparing the organic solid electrolyte according to claim 3, characterized in that, In step S1, each raw material needs to undergo pretreatment. The pretreatment process is as follows: PVDF-HFP and LiTFSI are placed in an 80℃ vacuum drying oven for 12 hours; F... 16 ZnPc, F 16 CoPc and Al2O3 were treated in a vacuum drying oven at 60℃ for 6 hours.

5. The method for preparing the organic solid electrolyte according to claim 3, characterized in that, The organic solvent in step S1 is a composite solvent of N,N-dimethylformamide and acetone; wherein, in the composite solvent, the volume ratio of DMF to acetone is 3:

1.

6. The method for preparing the organic solid electrolyte according to claim 3, characterized in that, The stirring process in step S2 is as follows: stirring at a temperature of 40-80℃ and a speed of 450-600 r / min for 10-24 hours.

7. The method for preparing the organic solid electrolyte according to claim 3, characterized in that, The vacuum drying process in step S3 is as follows: when using a single DMF solvent, dry to constant weight at 50-80℃; when using a composite solvent, first dry at 40℃ for 6 hours, then dry at 60℃ for 12 hours, and finally dry at 70℃ for 2 hours.

Images