An organic-inorganic composite solid-state electrolyte, a preparation method and application thereof

Abstract

The present application relates to a kind of organic-inorganic composite solid electrolyte and its preparation method and application, raw material includes polymer monomer, sodium salt, crosslinking agent, plasticizer and sodium silicate, the mole ratio of Na in polymer monomer and sodium salt + It is (8-20):1, the amount of crosslinking agent is 1-10% of the mass of polymer monomer, the amount of plasticizer is 10-20% of the mass of polymer monomer;The amount of sodium silicate is 1-10% of the total mass of polymer monomer, sodium salt, crosslinking agent and plasticizer.The composite solid electrolyte of the present application not only has the flexibility and easy processing of polymer electrolyte, but also has the excellent chemical stability of inorganic electrolyte, wide electrochemical window, shows good interface stability and kinetic performance in full battery.Sodium silicate has high rigidity, so it can inhibit the penetration of sodium dendrite to polymer electrolyte in solid-state sodium ion battery, avoid battery short circuit, thereby improving the safety performance of battery.

Description

Technical Field

[0001] This invention relates to the field of batteries, and specifically to an organic-inorganic composite solid electrolyte, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries have advantages such as abundant resources and low cost, and have broad application prospects in large-scale energy storage and other fields. However, traditional sodium-ion batteries use liquid electrolytes, which pose safety hazards such as flammability and explosion. Therefore, the development of high-safety solid-state batteries has become the research focus of the next generation of sodium-ion batteries.

[0003] Solid-state batteries utilize solid electrolytes, primarily inorganic and polymer solid-state electrolytes, which effectively suppress sodium dendrite growth and improve battery energy density. Polymer solid-state electrolytes offer advantages such as good processability and high sodium stability, but generally suffer from low ionic conductivity. Inorganic solid-state electrolytes exhibit high ionic conductivity and a wide electrochemical window, but their mechanical properties are relatively poor. Organic-inorganic composite solid-state electrolytes combine the advantages of both, achieving a balance between processability, mechanical properties, ionic conductivity, and electrochemical stability, thus effectively improving the overall performance of solid sodium-ion electrolytes. For example, patent CN108232293A mixes lithium salt, fast lithium-ion conductors, and acrylate materials to obtain an organic-inorganic composite solid-state electrolyte; this composite electrolyte, when used in solid-state lithium batteries, exhibits low impedance and high capacity utilization. Patent CN201910284401.7 invents an aramid nanofiber / polymer matrix / lithium (sodium) salt composite solid-state electrolyte, which can be used in lithium / sodium-ion batteries.

[0004] Currently, inorganic sodium-ion solid electrolytes mainly include Al2O3, NASICON materials, sulfides, and silicon dioxide. However, these materials either require high-temperature solid-phase synthesis, resulting in high processing costs, or exhibit low ionic conductivity at room temperature, thus affecting the ionic conductivity of the composite material. Therefore, it is necessary to develop a novel organic-inorganic composite solid electrolyte. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide an organic-inorganic composite solid electrolyte, its preparation method and application, thereby solving the technical problems of high cost of inorganic sodium ion solid electrolyte materials and low ionic conductivity of the resulting electrolyte in existing organic-inorganic composite solid electrolytes.

[0006] To achieve the above-mentioned technical objectives, the present invention provides an organic-inorganic composite solid electrolyte:

[0007] The raw materials include polymer monomers, sodium salts, crosslinking agents, plasticizers, and sodium silicate. Among these, the polymer monomers and sodium salts contain Na...+ The molar ratio is (8-20):1, the amount of crosslinking agent is 1-10% of the polymer monomer mass, the amount of plasticizer is 10-20% of the polymer monomer mass, and the amount of sodium hydroxylite is 1-10% of the total mass of polymer monomer, sodium salt, crosslinking agent and plasticizer.

[0008] Furthermore, the polymer monomer is ethylene oxide.

[0009] Furthermore, the sodium salt is NaClO4, NaPF6, NaClO3, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, or sodium bis(trifluoromethanesulfonyl)imide.

[0010] Furthermore, the crosslinking agent is polyvinylpyrrolidone, polyvinyl chloride, or polyaniline; the plasticizer is ethylene carbonate, propylene carbonate, N,N-dimethylformamide, polyethylene glycol, or succinic acid.

[0011] Furthermore, sodium hydroxysilicate was synthesized using a hydrothermal method.

[0012] The technical solution for preparing the above-mentioned organic-inorganic composite solid electrolyte includes the following steps:

[0013] The polymer monomer and sodium salt are dissolved in a solvent, and then a crosslinking agent, plasticizer and sodium silicate are added and mixed evenly to obtain a mixed solution. The mixed solution is then cast and dried to obtain an organic-inorganic composite solid electrolyte.

[0014] Furthermore, the solvent is water or acetonitrile.

[0015] Furthermore, the mixed solution is poured onto a rigid support material, which is made of polytetrafluoroethylene, polyethylene, glass, or porous ZrO2 cloth.

[0016] Furthermore, the drying temperature is 75–85°C.

[0017] The above describes the application of organic-inorganic composite solid electrolytes in solid sodium-ion batteries.

[0018] Compared with the prior art, the beneficial effects of the present invention include:

[0019] The organic-inorganic composite solid electrolyte of this invention is composed of a polymer and layered sodium hydroxyl silicate, with a thickness of 10-200 micrometers, and an ionic conductivity of 2.2-2.42 × 10⁻⁶ at 25°C. -3With a flux ratio (S / cm) and an electrochemical window greater than 4.6V, it not only possesses the flexibility and processability of polymer electrolytes but also the excellent chemical stability and wide electrochemical window of inorganic electrolytes, thus exhibiting good interfacial stability and kinetic performance in full cells. Furthermore, the layered sodium hydroxyl silicate exhibits high rigidity, which, when used in solid-state sodium-ion batteries, can suppress sodium dendrites from piercing the polymer electrolyte, preventing short circuits and improving battery safety. Attached Figure Description

[0020] Figure 1 This is the XRD pattern of sodium hydroxysilicate synthesized hydrothermally in Example 1 of this invention;

[0021] Figure 2 This is a SEM image of sodium hydroxysilicate synthesized hydrothermally in Example 1 of this invention;

[0022] Figure 3 This is a photograph of the PEO / sodium silicate composite electrolyte obtained in Example 1 of the present invention;

[0023] Figure 4 These are bending photographs of the PEO / sodium silicate composite electrolyte obtained in Example 1 of this invention;

[0024] Figure 5 These are the symmetrical battery cycle curves of the PEO / sodium silicate composite electrolytes obtained in Example 1 and Comparative Example 1 of this invention.

[0025] Figure 6 The charge-discharge curves (1C=170 mA / g) of the Prussian blue / sodium metal batteries assembled with PEO / sodium silicate and PEO / SiO2 composite electrolytes in Example 1 and Comparative Example 2 of this invention are shown.

[0026] Figure 7 These are the charge-discharge curves (1C=170 mA / g) of the Prussian blue / sodium metal batteries assembled with PEO / sodium silicate and PEO / SiO2 composite electrolytes in Example 1 and Comparative Example 2 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] The method for preparing the organic-inorganic composite solid electrolyte of the present invention includes the following steps:

[0029] S1: Sodium hydroxysilicate was synthesized using a hydrothermal method.

[0030] S2: Dissolve ethylene oxide (EO) material and sodium salt in a solvent to obtain solution A.

[0031] The preferred sodium salts are NaClO4, NaPF6, NaClO3, sodium trifluoromethanesulfonate (NaTf), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), etc.; the solvent is water or acetonitrile, etc. EO and Na... + The preferred molar ratio is 8:1 to 20:1.

[0032] S3: Add crosslinking agent and plasticizer to the above solution A, stir evenly to obtain solution B.

[0033] The preferred crosslinking agent is polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyaniline (PANI), etc.; the preferred plasticizer is ethylene carbonate (EC), propylene carbonate (PC), N,N-dimethylformamide (DMF), polyethylene glycol (PEG), succinic anhydride, etc. The preferred mass ratio of the crosslinking agent in the EO is 1-10%; the preferred mass ratio of the plasticizer in the EO is 10-20%.

[0034] S4: Add sodium silicate (Na2Si) to the above solution B. 14 O 29 The mass ratio of EO in the solid electrolyte raw material is 1-10%, and it is dispersed evenly by ultrasonication or stirring to obtain solution C. Among them, the solid electrolyte raw material refers to EO, sodium salt, crosslinking agent and plasticizer, that is, sodium hydroxyl silicate accounts for 1-10% of the total mass of the above four raw materials.

[0035] S5: The above solution C is poured onto a rigid support material, and the solvent is dried by heating at 75-85℃ to obtain the organic-inorganic composite solid electrolyte. Rigid support materials include polytetrafluoroethylene, polyethylene, glass, porous ZrO2 cloth, etc.

[0036] The battery assembly method of the present invention includes the following steps:

[0037] The above-mentioned organic-inorganic composite solid electrolyte is assembled with a positive electrode and a negative electrode to form a sodium-ion solid-state battery. The assembly structure consists of a negative electrode, an organic-inorganic composite solid electrolyte, and a positive electrode stacked sequentially.

[0038] Preferably, the positive electrode includes a positive electrode current collector, a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes sodium vanadium phosphate, Prussian blue, sodium vanadium fluorophosphate, and layered transition metal oxides such as Na. x MeO2 (Me represents transition metal), etc.

[0039] Preferably, the negative electrode includes a negative electrode current collector, a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes hard carbon, sodium metal, sodium titanium phosphate, or one or more of these.

[0040] This invention provides a novel sodium ion conductor based on malathion and its application in polymer solid-state sodium-ion batteries. By combining layered malathion with polymer solid-state electrolyte, a fast sodium ion channel can be introduced into the polymer solid-state electrolyte, thereby effectively improving the room temperature ionic conductivity of the sodium-ion battery solid-state electrolyte.

[0041] To avoid redundancy, the battery testing methods in the following embodiments and comparative examples of this invention are as follows:

[0042] Na||Na battery: The organic-inorganic composite solid electrolyte has 8mm diameter sodium metal sheets on both sides, at 1 mAcm -2 1 mAh cm -2 Cyclic testing was conducted under the specified conditions.

[0043] Na||PB battery: This battery uses PB and sodium metal sheets as the positive and negative electrode active materials, respectively, and an organic-inorganic composite solid electrolyte as the electrolyte. The positive electrode is prepared as follows: The positive electrode active material, conductive agent Super P, conductive agent Ketjen Black, and binder PVDF are mixed in a mass ratio of 7:1:1:1, with a certain amount of N-methylpyrrolidone (NMP) added as a solvent, and ground into a uniform slurry. The slurry is then uniformly coated onto aluminum foil and baked at 70℃ for 24 hours. Finally, it is cut into small circular pieces with a diameter of 8 mm, and the electrode loading is 1.6-2.4 mg / cm³. 2 Between. The battery is set to charge / discharge voltage of 2.0 V-4.2 V. In cycle performance testing, at 0.2 C and 5 C (1 C = 170 mA g). -1 The multiplier was tested.

[0044] All battery assembly processes were conducted in an argon-filled glove box, with water and oxygen levels strictly controlled to below 0.05 ppm. The battery casings used were CR2032 standard button cells, and electrochemical testing was performed using a Land CT2001D instrument at a constant temperature of 25 °C.

[0045] The present invention will be further described in detail below through specific embodiments.

[0046] Example 1

[0047] S1: Sodium hydroxysilicate was synthesized by a hydrothermal method. The raw materials were weighed and mixed and stirred for 15 min, with the molar ratio of the raw materials being SiO2:(NaOH+Na2CO3):H2O=7:1:100 (the molar ratio of NaOH to Na2CO3 was 1 / 2). The mixture was then transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted at 150℃ for 48 h. After the reactor cooled to room temperature, the product was filtered, washed with water until the pH reached 7-8, dried at 80℃ for 4 h, and then heated at 200℃ under an inert atmosphere for 10 h to remove water.

[0048] S2: Dissolve ethylene oxide (EO) material and NaClO4 in acetonitrile solvent, wherein the molar ratio of EO to NaClO4 is 10:1, to obtain solution A.

[0049] S3: Add a crosslinking agent and a plasticizer to the above solution A, and stir until homogeneous to obtain solution B. The crosslinking agent is PVP, with a mass ratio of 1% in EO; the plasticizer is succinic anionyl nitrile, with a mass ratio of 10% in EO.

[0050] S4: Add 10wt% sodium hydroxylite, which is the solid electrolyte raw material, to the above solution B, and sonicate or stir to disperse it evenly to obtain solution C.

[0051] S5: The above solution C is poured into a polytetrafluoroethylene mold and the solvent is dried by heating at 80°C to obtain an organic-inorganic composite solid electrolyte, wherein EO is polymerized to form polyethylene oxide (PEO).

[0052] S6: Assemble the above organic-inorganic composite solid electrolyte with the positive and negative electrodes to form a sodium-ion solid battery, wherein the positive electrode active material is Prussian blue and the negative electrode active material is sodium metal.

[0053] Comparative Example 1

[0054] The other conditions were the same as in Example 1, except that sodium hydroxylite was not added.

[0055] Comparative Example 2

[0056] Other conditions are the same as in Example 1, except that sodium silicate is replaced with nano-SiO2. Specific steps include:

[0057] S1: Dissolve ethylene oxide (EO) material and NaClO4 in acetonitrile solvent, wherein the molar ratio of EO to NaClO4 is 10:1.

[0058] S2: Add a crosslinking agent and a plasticizer to the above solution and stir until homogeneous. The crosslinking agent is PVP, with a mass ratio of 1% in EO; the plasticizer is succinic anionyl nitrile, with a mass ratio of 10% in EO.

[0059] S3: Add 10wt% nano-SiO2, which accounts for the solid electrolyte raw material, to the above solution and disperse it evenly by ultrasonication or stirring.

[0060] S4: The above solution is poured into a polytetrafluoroethylene mold and the solvent is dried by heating at 80°C to obtain an organic-inorganic composite solid electrolyte.

[0061] S5: Assemble the above organic-inorganic composite solid electrolyte with the positive and negative electrodes to form a sodium-ion solid battery, wherein the positive electrode is Prussian blue and the negative electrode is sodium metal.

[0062] The relevant products of Example 1 and Comparative Examples 1-2 were tested, and the results are as follows: Figures 1 to 7 As shown.

[0063] Depend on Figure 1 XRD results show that the product synthesized by hydrothermal synthesis in Example 1 is pure-phase sodium maloxysilane.

[0064] Figure 2 The SEM images show that the sodium hydroxylite obtained in Example 1 has a micron-sized and flake-like morphology.

[0065] Figure 3 and Figure 4 The composite solid electrolyte prepared in Example 1 can be molded into a dense sheet and exhibits good flexibility. Testing showed that its thickness was 20 micrometers and its ionic conductivity at 25°C was 2.2 × 10⁻⁶. -3 S / cm, electrochemical window greater than 4.6 V.

[0066] Figure 5 The cycling curves of sodium symmetric batteries assembled with composite solid electrolytes are shown. In Example 1, the symmetric battery assembled with a composite solid electrolyte containing sodium malolite can cycle effectively for more than 430 hours, while the symmetric battery assembled with a PEO electrolyte without sodium malolite in Comparative Example 1 has very poor cycling performance, with polarization continuously increasing and a short circuit occurring after 250 hours.

[0067] Figure 6 and Figure 7 The table shows the first charge-discharge curves and cycle curves when Prussian blue is assembled with iron-based Prussian blue cathode material into a sodium-ion battery. In Example 1, the capacity of Prussian blue reaches 162 mAh / g at 0.2C (the theoretical specific capacity of Prussian blue is 170 mAh / g), and the capacity at 2C current density is 140 mAh / g. In contrast, in Comparative Example 2, when using a PEO / SiO2 composite electrolyte, the capacity of Prussian blue is 141 mAh / g at 0.2C, and the capacity at 2C current density is 129 mAh / g. The specific comparison is shown in Table 1 below.

[0068] Table 1. Battery current density of Example 1 and Comparative Example 2 of the present invention.

[0069]

[0070] As shown in Table 1, sodium hydroxylite has a layered structure, allowing sodium ions to diffuse rapidly between its layers, making it an excellent sodium ion conductor. When combined with PEO electrolyte, it significantly improves sodium ion conductivity, electrochemical kinetics, and mechanical properties, thus enabling the Prussian blue cathode to exhibit excellent sodium storage performance.

[0071] Example 2

[0072] S1: Dissolve ethylene oxide (EO) material and NaClO4 in acetonitrile solvent, wherein the molar ratio of EO to NaClO4 is 15:1.

[0073] S2: Add a crosslinking agent and a plasticizer to the above solution and stir until homogeneous. The crosslinking agent is PVP, with a mass ratio of 10% in the EO; the plasticizer is succinic anionyl nitrile, with a mass ratio of 20% in the EO.

[0074] S3: Add 1 wt% sodium hydroxylite, which is the solid electrolyte raw material, to the above solution and sonicate or stir to disperse it evenly.

[0075] S4: The above solution is poured into a polytetrafluoroethylene mold and the solvent is dried by heating at 80°C to obtain an organic-inorganic composite solid electrolyte.

[0076] S5: Assemble the above-mentioned organic-inorganic composite solid electrolyte with a positive electrode and a negative electrode to form a sodium-ion solid-state battery. The positive electrode is sodium vanadium phosphate, and the negative electrode is hard carbon.

[0077] After testing, its thickness was found to be 26 micrometers, and its ionic conductivity at 25℃ was 8.1 × 10⁻⁶. -4 The electrochemical window is greater than 4.6V, and the capacity of sodium vanadium phosphate can reach 107 mAh / g when assembled into a sodium-ion battery (the theoretical specific capacity of sodium vanadium phosphate is 117 mAh / g). This demonstrates that adding only a small amount of sodium malathion to PEO can effectively enhance its ionic conductivity at room temperature, resulting in a battery with excellent capacity performance.

[0078] Example 3

[0079] The difference from Example 1 is that the molar ratio of EO to NaClO4 is 5:1, 8:1 and 30:1; the other steps and conditions are the same as in Example 1.

[0080] The performance of the obtained sodium-ion solid-state battery after testing is shown in Table 1 below.

[0081] Table 2 Performance of assembled batteries with organic-inorganic composite solid electrolytes prepared with different raw material ratios

[0082]

[0083] As shown in Table 2, if the molar ratio of EO to NaClO4 in this invention is too low, the sodium salt content will be relatively high. While the changes in ionic conductivity and electrochemical window are not significant, the strength of the prepared electrolyte is poor, resulting in poor positive electrode capacity after assembly into a solid-state battery. If the molar ratio of EO to NaClO4 is too high, the ionic conductivity will decrease significantly. Therefore, the preferred molar ratio of EO to NaClO4 in this invention is (8–20):1, and more preferably 10:1.

[0084] In this invention, the amount of sodium silicate used should not be too much, otherwise the strength will also decrease.

[0085] Comparative Example 3

[0086] Replace EO with EG (ethylene glycol), and follow the same steps and conditions as in Example 1.

[0087] The results showed that it was difficult to form a film when preparing solid electrolytes. Therefore, EO is preferably used as the organic monomer in this invention.

[0088] The sodium hydroxysilicate used in this invention is a layered nano-silicate material, whose structure allows for rapid diffusion of sodium ions between its layers. This invention combines polyethylene oxide and sodium hydroxysilicate to form an organic-inorganic composite solid electrolyte. Sodium hydroxysilicate can be synthesized via a hydrothermal method, resulting in a simple and low-cost preparation process. The resulting composite solid electrolyte has a thickness of 10-200 micrometers, and its ionic conductivity at 25°C is approximately 2.2–2.42 × 10⁻⁶. -3 The electrolyte exhibits a flux ratio (S / cm) and an electrochemical window greater than 4.6V. It possesses not only the flexibility and processability of polymer electrolytes but also the excellent chemical stability and wide electrochemical window of inorganic electrolytes. Therefore, it demonstrates good interfacial stability and kinetic performance in full cells. Furthermore, the layered sodium hydroxyl silicate exhibits high rigidity, which, when used in sodium-ion batteries, can suppress sodium dendrites from piercing the polymer electrolyte, preventing short circuits and thus improving battery safety. In particular, Example 1 of this invention yields an electrolyte with relatively high ionic conductivity and strength (high ionic conductivity is beneficial for capacity utilization, but not a strictly proportional relationship), high capacity, and optimal overall performance.

[0089] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an organic-inorganic composite solid electrolyte, characterized in that, The raw materials for the organic-inorganic composite solid electrolyte include polymer monomers, sodium salts, crosslinking agents, plasticizers, and sodium silicate, wherein the polymer monomers and sodium salts contain Na... + The molar ratio is (8-20):1, the amount of crosslinking agent is 1-10% of the polymer monomer mass, the amount of plasticizer is 10-20% of the polymer monomer mass; the amount of sodium hydroxyl silicate is 1-10% of the total mass of polymer monomer, sodium salt, crosslinking agent and plasticizer. The polymer monomer is ethylene oxide; The preparation method includes the following steps: The polymer monomer and sodium salt are dissolved in a solvent, and then crosslinking agent, plasticizer and sodium hydroxylite are added and mixed evenly to obtain a mixed solution. The mixed solution is then cast and dried to obtain an organic-inorganic composite solid electrolyte. The crosslinking agent is polyvinylpyrrolidone, polyvinyl chloride, or polyaniline; the plasticizer is ethylene carbonate, propylene carbonate, N,N-dimethylformamide, polyethylene glycol, or succinic acid.

2. The method for preparing the organic-inorganic composite solid electrolyte according to claim 1, characterized in that, The sodium salt is NaClO4, NaPF6, NaClO3, sodium trifluoromethanesulfonate, sodium difluorosulfonamide, or sodium difluoromethanesulfonamide.

3. The method for preparing the organic-inorganic composite solid electrolyte according to claim 1, characterized in that, Sodium hydroxysilicate is synthesized using a hydrothermal method.

4. The method for preparing the organic-inorganic composite solid electrolyte according to claim 1, characterized in that, The solvent is water or acetonitrile.

5. The method for preparing the organic-inorganic composite solid electrolyte according to claim 1, characterized in that, The mixed solution is poured onto a rigid support material, which is made of polytetrafluoroethylene, polyethylene, glass, or porous ZrO2 cloth.

6. The method for preparing the organic-inorganic composite solid electrolyte according to claim 1, characterized in that, The drying temperature is 75-85℃.

7. The organic-inorganic composite solid electrolyte prepared by the preparation method according to any one of claims 1-6.

8. The application of the organic-inorganic composite solid electrolyte as described in claim 7 in solid sodium-ion batteries.

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