Preparation and application of organic-inorganic composite solid electrolyte

Abstract

The application relates to preparation and application of an organic-inorganic composite solid electrolyte and belongs to the technical field of lithium ion battery electrolytes. The organic-inorganic composite solid electrolyte is prepared by compounding a carbonate-based polymer, a conductive lithium salt, a porous support material and functionalized inorganic nanoparticles. The polycarbonate-based polymer electrolyte has high ionic conductivity and excellent mechanical properties; the functionalized inorganic nanoparticles can improve the ionic transference number of the polymer electrolyte and broaden the electrochemical window of the polymer electrolyte through intermolecular interaction, improve the interface contact between the solid electrolyte and the positive and negative electrodes, and thus improve the charge-discharge performance of the lithium ion battery. The composite solid electrolyte has a thickness of 5-500 mu m, excellent interface stability, a wide electrochemical window (>5.5V), a wide working temperature range (-20-50 DEG C), high ionic conductivity (>1*10 ‑3 S / cm) and is suitable for lithium ion solid-state batteries of high-voltage positive electrode materials.

Description

Technical Field

[0001] This invention relates to solid electrolytes for lithium-ion batteries, and in particular to the preparation and application of an organic-inorganic composite solid electrolyte, belonging to the field of lithium-ion battery electrolyte technology. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and reliability, are widely used energy storage devices. To date, most commercially available lithium-ion batteries use conventional organic liquid electrolytes, such as ethylene carbonate and propylene carbonate. However, lithium-ion batteries using organic liquid electrolytes present significant safety issues, severely hindering their further popularization and wider application. This is mainly because organic electrolytes typically possess high chemical activity, volatility, flammability, and explosiveness. Therefore, using solid-state electrolytes instead of traditional organic electrolytes is one effective way to solve these safety problems. Furthermore, solid-state electrolytes offer advantages such as high ionic conductivity, a wide electrochemical window, a wide operating temperature range, and the ability to be custom-designed and modified.

[0003] Currently, solid electrolytes mainly include inorganic solid electrolytes such as oxide solid electrolytes, sulfide solid electrolytes, and halide solid electrolytes, polymer solid electrolytes, and organic-inorganic composite electrolytes. Inorganic solid electrolytes have advantages such as high mechanical strength and high room temperature ionic conductivity. Patent No. CN 105932327 A discloses a method for preparing a cubic phase lithium lanthanum zirconium oxide solid electrolyte with a room temperature conductivity of 2.9 × 10⁻⁶. -4 S / cm. Meanwhile, inorganic solid-state electrolytes also face significant challenges, such as high material density, high rigidity, poor interfacial compatibility, and high interfacial impedance with electrodes. Organic polymer electrolytes have been widely studied due to their advantages, including good compatibility with lithium metal, high thermal stability, simple preparation process, good flexibility, and adjustable shape and size. Organic-inorganic composite solid electrolytes are obtained by hybridizing organic and inorganic materials. These electrolytes, through the complementary advantages of organic and inorganic components, significantly improve ionic conductivity, electrochemical window, and mechanical strength, solving problems that cannot be addressed by single components. CN 106785009A discloses an organic-inorganic all-solid-state composite electrolyte and its preparation. This organic-inorganic composite all-solid-state electrolyte uses an inorganic fast lithium-ion conductor to form a highly ordered three-dimensional interconnected network framework, with polymer polymers and lithium salts filling the three-dimensional interconnected network. This electrolyte exhibits good mechanical properties and stability to metallic lithium, but its ionic conductivity is much lower than that of liquid electrolytes, and its electrochemical window is low, which cannot meet the requirements for high-voltage cathode materials.

[0004] In all-solid-state batteries, the low ionic conductivity and narrow electrochemical window of the electrolyte, as well as the severe interface problems between the electrolyte and electrode materials, prevent all-solid-state batteries from being matched with high-voltage cathode materials, resulting in poor cycle performance and low power density, which limits their application to some extent. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing and applying an organic-inorganic composite solid electrolyte, and uses this electrolyte to construct a lithium-ion secondary all-solid-state battery.

[0006] The technical solution of this invention is as follows:

[0007] A method for preparing an organic-inorganic composite solid electrolyte includes the following steps: mixing a monomer corresponding to a carbonate-based polymer with a conductive lithium salt, adding an organic solvent or not adding an organic solvent to prepare a solution, then mixing an initiator or catalyst with functionalized inorganic nanoparticles and stirring to obtain a liquid mixture; immersing a porous support material in the liquid mixture or coating the liquid mixture onto the porous support material for permeation, and then curing it to prepare the composite solid electrolyte by utilizing intermolecular interactions.

[0008] The carbonate-based polymer monomers account for 50-90% of the total mass of carbonate-based polymer monomers and conductive lithium salts, the inorganic nanoparticles account for 1-20% of the total mass of carbonate-based polymer monomers and conductive lithium salts, and the initiator or catalyst accounts for 0.5-1‰ of the total mass of carbonate-based polymer monomers and conductive lithium salts.

[0009] The electrolyte is coated or immersed in a polytetrafluoroethylene mold containing a porous support material and then heated and cured at 60-120°C for 2-12 hours to form a film.

[0010] Carbonate-based polymer monomers include one or more of the following: carbonates, ethylene carbonate, ethylene ethylene carbonate, allyl methyl carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate.

[0011] The functionalized inorganic nanoparticles are mainly produced through surface treatment according to different needs, enabling them to contain vacancies or specific functional groups (such as hydroxyl, carboxyl, cyano, amino, benzyl, amide, nitro, etc.; specific functional groups can form intermolecular interactions with lithium salts and / or carbonate-based polymers). The inorganic nanoparticles include one or more of the following: montmorillonite, nano-silica, nano-zirconium dioxide, nano-calcium carbonate, nano-alumina, nano-titanium dioxide, nano-silicon carbide, nano-barium titanate, sulfide solid electrolyte nanoparticles, halide solid electrolyte nanoparticles, and Li7La3Zr2O. 12 Li 10 GeP2S12 , Li₃OCl 0.5 Br 0.5 , Li 3x La (2 / 3) -ₓTiO₃ with 0.04 < x < 0.14, Li₅La₃M₂O₁₂ where M = Ta / Nb, Li₃N-LiX where X = Cl, Br or I, Li 14 ₁₄Zn(GeO₄)₄, LiZr₂(PO₄)₃, LiPON.

[0012] The selected conductive lithium salt is one or more of the following: the conductive lithium salt is one or more selected from the group consisting of lithium hexafluorophosphate (LiPF₆), lithium perchlorate (LiClO₄), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(trifluoromethanesulfonyl)methide [LiC(SO₂CF₃)₃].

[0013] The selected organic solvent is one or more of the following: N-methylpyrrolidone (NMP), ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylene glycol carbonate, ethyl methyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, 1,2-dimethoxyethane, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl sulfoxide;

[0014] The initiator or catalyst is one selected from the following: dibutyltin dilaurate, dibutyltin bis(acetylacetonate), azobisisoheptonitrile (ABVN), azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate (AIBME), benzoyl peroxide (BPO), platinum water (Pt).

[0015] The porous support material is one or more selected from the group consisting of cellulose non-woven fabric, polyethylene non-woven fabric, polypropylene non-woven fabric, glass fiber non-woven fabric, and polytetrafluoroethylene non-woven fabric.

[0016] The electrochemical stability of the organic-inorganic composite electrolyte is improved through intermolecular interactions, and the intermolecular interactions include one or more of positive vacancy interaction, dipole-dipole interaction, hydrogen bond interaction and other intermolecular interactions.

[0017] The thickness of the composite solid electrolyte is 5-500μm; the ionic conductivity is greater than 10 -3 S / cm; the working temperature is -20-50°C, the electrochemical window is greater than 5.5V (vs. Li + / Li), and the ion transference number is greater than 0.62.

[0018] A lithium ion secondary all-solid-state battery, characterized in that:

[0019] The positive electrode active material of lithium-ion batteries is one or more of lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium fluorophosphate, lithium manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium lithium rich materials (LLOs), lithium iron manganese phosphate, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide, lithium iron phosphate (LiFeO4), and lithium vanadium phosphate (Li3V2(PO4)3); the negative electrode active material is one or more of lithium metal, lithium metal alloy, graphite, hard carbon, lithium metal nitride, antimony oxide, carbon germanium composite material, carbon silicon composite material, lithium titanate, and lithium titanium oxide.

[0020] The preparation of positive electrode materials for lithium-ion batteries includes the following steps: grinding and mixing 50-90% by mass of positive electrode active material and 5-30% by mass of conductive agent acetylene black; adding 1-15% by mass of polyvinylidene fluoride (PVDF), 1-15% by mass of polycarbonate-based organic-inorganic composite solid electrolyte, and 1-methyl-2-pyrrolidone (NMP) and grinding and mixing; coating the mixture onto the surface of aluminum foil and drying it; lithium metal and lithium metal alloys can be directly used as the corresponding negative electrode materials. The preparation of other negative electrode materials includes the following steps: grinding and mixing 50-90% by mass of negative electrode active material and 5-30% by mass of conductive agent acetylene black; adding 5-20% by mass of polyvinylidene fluoride (PVDF) and 1-methyl-2-pyrrolidone (NMP) and grinding and mixing; coating the mixture onto the surface of copper foil and drying it.

[0021] Lithium-ion battery assembly includes coin cells and pouch cells. The internal stacking order of solid-state batteries is positive electrode - organic-inorganic composite solid electrolyte membrane - negative electrode. Furthermore, the assembled solid-state battery with lithium-rich positive electrode can operate normally at a high voltage of 4.8V.

[0022] The innovation and practicality of this invention lie in:

[0023] 1. Using polycarbonate-based polymers, which have high ionic conductivity, the composite solid electrolyte exhibits excellent ion transport capabilities and thermal stability.

[0024] 2. Functionalized inorganic nanoparticles can significantly increase the ion transference number and broaden the electrochemical window of the composite solid electrolyte by generating intermolecular interactions with other components of the composite electrolyte, thereby improving the interfacial contact of the solid lithium-ion battery and enhancing its charge-discharge performance.

[0025] 3. The raw materials for this organic-inorganic composite solid electrolyte are easy to sample, the preparation process is simple, and it can be mass-produced. Detailed Implementation

[0026] The present invention will be illustrated below with specific embodiments. These embodiments are provided to better understand the present invention and are not intended to limit the scope of the present invention.

[0027] Electrolyte preparation:

[0028] Example 1

[0029] Ethylene carbonate (VEC) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed in a ratio of 7.69:2.31 to obtain solution A, which was stirred at room temperature until completely dissolved. Azobisisobutyronitrile (AIB) was added at 0.5-1‰ of the mass of solution A and stirred uniformly for 2 hours. Then, hydroxyl-rich functionalized nano-silica (SiO2) was mixed with solution A in a ratio of 0.5:9.5, stirred at room temperature for 1 hour, followed by sonication for 2 hours, and then stirring for another 4 hours to allow for sufficient bonding and intermolecular interactions. The uniformly stirred mixture was then coated onto both sides of a polytetrafluoroethylene (PTFE) mold using a Whatman glass fiber membrane as a porous support framework. The mixture was then cured in a vacuum drying oven at 80°C for 10 hours to form a film.

[0030] Example 2

[0031] Ethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed and stirred at a ratio of 7.69:2.31 (B). 50% (by weight) of N-methylpyrrolidone (NMP) was added to the mixture and stirred at room temperature until completely dissolved. Based on the mass of solution B, 0.5-1‰ (by weight) of azobisisobutyronitrile was added and stirred uniformly for 2 hours. Then, functionalized nano-alumina was added and mixed at a ratio of 0.5:9.5 (to solution B), stirred for 1 hour, then sonicated for 2 hours, and stirred for another 4 hours to allow for sufficient reaction and intermolecular interactions. Using a Whatman glass fiber membrane as a porous support framework, the uniformly stirred mixture was coated onto both sides of a polytetrafluoroethylene mold. The mixture was then cured in a vacuum drying oven at 80°C for 10 hours to form a film.

[0032] Example 3

[0033] Ethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved and mixed in a ratio of 7.69:2.31 (C). A certain amount of N-methylpyrrolidone (NMP) was added and stirred at room temperature until completely dissolved. Based on the mass of solution C, 0.5-1‰ of azobisisobutyronitrile (AIBN) was added and stirred uniformly for 2 hours. Then, nano-sized (solid electrolyte Li) was added. 6.4 Ga 0.2 La3Zr2O 12The solution (C) was mixed in a ratio of 0.5:9.5, stirred for 1 hour, then sonicated for 2 hours, and stirred for another 4 hours to allow it to fully react and generate intermolecular interactions. The mixture was then coated onto both sides of the polytetrafluoroethylene mold using a Whatman membrane as a porous support framework. The mixture was then cured into a film by heating at 80°C in a vacuum drying oven for 10 hours.

[0034] Example 4

[0035] Ethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved and mixed in a ratio of 7.69:2.31 and stirred until completely dissolved (D). A certain amount of N-methylpyrrolidone (NMP) was added and stirred at room temperature until completely dissolved. Based on the mass of solution D, 0.5-1‰ of azobisisobutyronitrile was added and stirred uniformly for 2 hours. Then, functionalized nano-solid electrolytes (Li...) were added. 1.3 Al 0.3 Ti 1.7 The mixture of (PO4)3 and (solution D) in a ratio of 0.5:9.5 was stirred for 1 hour, then sonicated for 2 hours, and stirred for another 4 hours to allow for a full reaction and intermolecular interaction. The mixture was then coated onto both sides of the polytetrafluoroethylene mold using a Whatman membrane as a porous support framework. The mixture was then cured in a vacuum drying oven at 80°C for 10 hours.

[0036] Example 5

[0037] Ethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved and mixed in a ratio of 7.69:2.31 and stirred for E. A certain amount of N-methylpyrrolidone (NMP) was added and stirred at room temperature until completely dissolved. According to the mass of solution E, 0.5-1‰ of azobisisobutyronitrile was added and stirred evenly for 2 hours. Then, functionalized (mesoporous SiO2 powder): (solution E) was added and mixed in a ratio of 0.5:9.5, stirred for 1 hour, then sonicated for 2 hours, and stirred for another 4 hours to allow for sufficient reaction and intermolecular interactions. On a polytetrafluoroethylene mold, using a Whatman membrane as a porous support framework, the uniformly stirred mixture was coated onto both sides of the Whatman membrane. The membrane was then cured in a vacuum drying oven at 80°C for 10 hours to form a film.

[0038] Example 6

[0039] Ethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved and mixed in a ratio of 7.69:2.31 and stirred (F). A certain amount of N-methylpyrrolidone (NMP) was added and stirred at room temperature until completely dissolved. Based on the mass of solution F, 0.5-1‰ of azobisisobutyronitrile was added and stirred uniformly for 2 hours. The mixture was poured onto a functionalized mesoporous SiO2 membrane in a polytetrafluoroethylene mold and heated in a vacuum drying oven at 80°C for 10 hours to allow for sufficient reaction and intermolecular interactions, thus solidifying the membrane.

[0040] Example 7

[0041] Allyl methyl carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved and mixed in a ratio of 7.69:2.31 to obtain solution G. The mixture was stirred at room temperature until completely dissolved. Based on the mass of the solution, 0.5-1‰ of azobisisobutyronitrile was added and stirred uniformly for 2 hours. Then, hydroxyl-rich functionalized (mesoporous titanium dioxide) was mixed with (solution G) in a ratio of 0.5:9.5 and stirred for 1 hour. The mixture was then sonicated for 2 hours and stirred for another 4 hours to allow for sufficient reaction and intermolecular interactions. Using a Whatman glass fiber membrane as a porous support framework, the uniformly stirred mixture was coated onto both sides of a polytetrafluoroethylene mold. The mixture was then cured in a vacuum drying oven at 80°C for 10 hours to form a film.

[0042] Electrolyte thickness: The thickness of the block polymer electrolyte was measured using a micrometer (accuracy 0.01 mm). Three points on the membrane were randomly selected for measurement, and the average value was calculated.

[0043] Ionic conductivity: The impedance of an R2032 coin cell was measured using two stainless steel gaskets sandwiching the polymer electrolyte, according to the formula... Where L is the thickness of the polymer electrolyte, S is the area of ​​the stainless steel gasket, and R is the measured impedance value.

[0044] Electrochemical window: A 2032 coin cell was assembled by sandwiching the polymer electrolyte with stainless steel and lithium sheet, and linear voltammetry (LSV) was performed. The starting voltage was 2.8V, the highest potential was 6.5V, and the scan rate was 1mV / s.

[0045] Example 8

[0046] 240 mg of lithium-rich manganese-based layered oxide positive electrode and 45 mg of conductive agent acetylene black were uniformly ground for 40 min; 15 mg of binder polyvinylidene fluoride, 15 mg of electrolyte mixture and 150 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; the mixture was then coated onto the surface of aluminum foil and dried at 80 °C under vacuum for 8 h; the electrode was cut into circular pieces with R = 12 mm, and a solid-state lithium-ion battery was assembled using the organic-inorganic composite electrolyte from Example 1 as the electrolyte and metallic lithium as the negative electrode. The assembled solid-state battery can be charged to 4.6 V, and can stably cycle 200 times at a charging cutoff voltage of 4.5 V at room temperature, with a capacity retention of over 94%.

[0047] Table 1

[0048]

Claims

1. A method for preparing an organic-inorganic composite solid electrolyte, characterized in that, Includes the following steps: A solution is prepared by mixing monomers corresponding to carbonate-based polymers and conductive lithium salts, with or without the addition of organic solvents. Then, an initiator or catalyst and functionalized inorganic nanoparticles are stirred and mixed evenly to obtain a liquid mixture. A porous support material is immersed in the liquid mixture or the liquid mixture is coated onto the porous support material for permeation, and then cured. A composite solid electrolyte is prepared by utilizing intermolecular interactions. The mass ratio of the monomers ethylene carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in the carbonate-based polymer is 7.69:2.

31. The inorganic nanoparticles account for 5% of the total mass fraction of the carbonate-based polymer monomers and conductive lithium salts. The initiator or catalyst accounts for 0.5-1‰ of the total mass fraction of the carbonate-based polymer monomers and conductive lithium salts. The above liquid mixture is coated or immersed in a polytetrafluoroethylene mold containing a porous support material and cured at 60-120°C for 2-12 hours to form a film. The functionalized inorganic nanoparticles are mesoporous SiO2 powder and mesoporous titanium dioxide. The functionalized inorganic nanoparticles are surface-treated according to different needs to make the inorganic nanoparticles contain vacancies or specific functional groups. The specific functional groups are one or more of hydroxyl, carboxyl, cyano, amino, benzyl, amide, and nitro groups. The specific functional groups form intermolecular interactions with lithium salts and / or carbonate-based polymers. The intermolecular interactions include one or more of positive vacancy interactions, dipole-dipole interactions, and hydrogen bonding interactions. The composite solid electrolyte has a thickness of 5-500 μm and an ionic conductivity >10. -3 S cm -1 Operating temperature: -20-50℃; Electrochemical window: >6V vs. Li + / Li, ion transference number greater than 0.

65.

2. The method for preparing an organic-inorganic composite solid electrolyte according to claim 1, characterized in that, The initiator or catalyst is one of the following: dibutyltin dilaurate, bis(acetylacetonate) dibutyltin, azobisisoheptanenitrile (ABVN), azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate (AIBME), benzoyl peroxide (BPO), or platinum solution.

3. The method for preparing an organic-inorganic composite solid electrolyte according to claim 1, characterized in that, The selected organic solvent is one or more of the following: N-methylpyrrolidone (NMP), ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, 1,2-dimethoxyethylene, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and dimethyl sulfoxide; The porous support material is one or more of the following: cellulose nonwoven fabric, polyethylene nonwoven fabric, polypropylene nonwoven fabric, glass fiber nonwoven fabric, and polytetrafluoroethylene nonwoven fabric.

4. An organic-inorganic composite solid electrolyte membrane prepared according to any one of claims 1-3.

5. A lithium-ion rechargeable all-solid-state battery, characterized in that: This includes an organic-inorganic composite solid electrolyte membrane prepared by the method described in any one of claims 1-3; The positive electrode active material of the lithium-ion battery is one or more of lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium fluorophosphate, lithium manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich materials (LLOs), lithium iron manganese phosphate, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide, lithium iron phosphate (LiFeO4), and lithium vanadium phosphate (Li3V2(PO4)3); the negative electrode active material is one or more of lithium metal, lithium metal alloy, graphite, hard carbon, lithium metal nitride, antimony oxide, carbon germanium composite material, carbon silicon composite material, lithium titanate, and lithium titanium oxide. The preparation of positive electrode materials for lithium-ion batteries includes the following steps: grinding and mixing 50-90% by mass of positive electrode active material and 5-30% by mass of conductive agent acetylene black; adding 1-15% by mass of polyvinylidene fluoride (PVDF), 1-15% by mass of polycarbonate-based organic-inorganic composite solid electrolyte, and 1-methyl-2-pyrrolidone (NMP) and grinding and mixing; coating the mixture onto the surface of aluminum foil and drying it; lithium metal and lithium metal alloys can be directly used as the corresponding negative electrode materials. The preparation of other negative electrode materials includes the following steps: grinding and mixing 50-90% by mass of negative electrode active material and 5-30% by mass of conductive agent acetylene black; adding 5-20% by mass of polyvinylidene fluoride (PVDF) and 1-methyl-2-pyrrolidone (NMP) and grinding and mixing; coating the mixture onto the surface of copper foil and drying it; Lithium-ion battery assembly includes coin cells and pouch cells. The internal stacking order of solid-state batteries is positive electrode - organic-inorganic composite solid electrolyte membrane - negative electrode.

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