An organic-inorganic composite polymer solid electrolyte and its preparation method and application

Abstract

The present invention belongs to the field of lithium-ion batteries, and particularly relates to an organic-inorganic composite polymer solid electrolyte and a preparation method and application thereof. The solid electrolyte includes polyethylene oxide, a lithium salt, an active filler, and an organic additive, and the organic additive is an amidine compound, and the amidine compound contains one or more of a halogen, a phenyl group, a nitro group, a naphthyl group, or a thiophene group. The present invention introduces an amidine group with strong basicity, which can provide a large number of electron pairs and combine with the electron-withdrawing groups in the polymer group; promote the mobility of the polymer segments and the acidity and alkalinity inside the solid electrolyte, thereby converting the fixed lithium ions inside the polymer solid electrolyte into free states, greatly reducing the migration energy barrier of lithium ions inside the polymer, and thus promoting the rapid and efficient transport of lithium ions in the PEO-based organic-inorganic composite solid electrolyte at room temperature and improving the mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and particularly to an organic-inorganic composite polymer solid electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as various electric vehicles, military, and aerospace fields. As an important component of lithium-ion batteries, the electrolyte affects and even determines various macroscopic electrochemical properties of the battery, such as specific energy, lifespan, and safety performance. Currently, the electrolyte has developed from liquid electrolytes to solid electrolytes. Solid electrolytes have higher chemical and thermal stabilities, which can improve the safety performance of the battery. Polymer solid electrolytes are light in weight, flexible, have high thermal stability, and good contact with the electrode interface, and have good application prospects. Poly(ethylene oxide) (PEO) polymer solid electrolyte is the most widely studied and the most promising polymer electrolyte system for large-scale production so far.

[0003] However, the existing poly(ethylene oxide)-based (PEO) polymer organic-inorganic composite solid electrolytes have deficiencies such as low conductivity, large interfacial impedance, and low critical current density. To solve the above problems, common methods include adding inorganic active materials for modification, adding ionic plastic crystals to improve their lithium-ion conductivity, and constructing composite solid electrolytes, etc.

[0004] Chinese patent document CN117352833A discloses an organic-inorganic composite polymer solid electrolyte, which adjusts its conductivity by adding different proportions of poly(vinylidene fluoride) (PVDF) and lithium salt to PEO, and further improves the performance of the battery by adding active fillers and fluorobenzene compounds to the PEO-based organic-inorganic composite polymer solid electrolyte. However, its conductivity, battery capacity retention rate, and mechanical properties are still not ideal, and fluorobenzene compounds have certain toxicity, which is not conducive to environmental protection. Chinese patent document CN116806221A discloses the preparation of an ionic plastic crystal and its application in electrolytes. The plastic crystal contains at least one delocalized anion paired with at least one cation derived from an organic superbase such as guanidine, amidine, or phosphazene. The structure of the organic superbase is mainly alkane groups and ester groups, which has certain limitations on the improvement of lithium-ion conductivity. This patent first synthesizes the plastic crystal and then uses the plastic crystal to prepare an organic-inorganic polymer solid electrolyte, and the preparation method is complex. Summary of the Invention

[0005] To solve the problems of low lithium-ion conductivity, poor interfacial stability, and poor mechanical properties of solid electrolytes, the present invention provides an organic-inorganic composite polymer solid electrolyte, a preparation method thereof, and an application thereof. Introducing an amidino group with strong basicity can provide a large number of electron pairs and combine with the electron-withdrawing groups in the polymer group; promoting the peristalsis of the polymer segments and the acidity and alkalinity inside the solid electrolyte, thereby converting the fixed lithium ions inside the polymer solid electrolyte into free states, greatly reducing the migration energy barrier of lithium ions inside the polymer, and thus promoting the rapid and efficient transport of lithium ions in the PEO-based organic-inorganic composite solid electrolyte at room temperature and improving the mechanical properties.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] An organic-inorganic composite polymer solid electrolyte, comprising polyethylene oxide, a lithium salt, an active filler, and an organic additive, wherein the organic additive is an amidino compound, and the amidino compound contains one or more of a halogen, a phenyl group, a nitro group, a naphthyl group, or a thiophene group; the molar ratio of the polyethylene oxide to the lithium salt is (4 to 30):1 in terms of EO:Li, the mass ratio of the total mass of the polyethylene oxide and the lithium salt to the mass of the active filler is (2 to 40):1, and the mass ratio of the total mass of the polyethylene oxide and the lithium salt to the mass of the organic additive is (1.5 to 15):1.

[0008] Preferably, the amidino compound includes one or more of 3,4-dimethylbenzamidine, 2-(4-fluorobenzylsulfonyl)hydroxyacetamidine, 2-pyrazinecarboximidamide hydrochloride, N-hydroxy-6-chloroindolecarboximidamide, N-[3-(aminomethyl)benzyl]acetamidine, methyl-[5-(N-methyl-N-phenylamino)-2,4-pentadienyl]phenylammonium chloride, isethionate, pentafluoropropylamidine, N'-hydroxy-2-naphthamidine, heptafluorobutyrylamidine, 2-(2-thienyl)hydroxyacetamidine, propamidine, 4-methylsulfonylbenzamidine, 2-N-BOC-aminoethylamidine, 4-benzylpiperazine-1-carboxamidine, 4-nitrobenzamidine.

[0009] More preferably, the amidino compound is selected from at least one of 2-pyrazinecarboximidamide hydrochloride, N-hydroxy-6-chloroindolecarboximidamide, methyl-[5-(N-methyl-N-phenylamino)-2,4-pentadienyl]phenylammonium chloride, 4-methylsulfonylbenzamidine.

[0010] Preferably, the lithium salt includes one or more of LiFSI, LiTFSI, LiBOB, LiODFB, LiPF6, LiClO4, LiNO3. More preferably LiODFB, and the combined use of the lithium salt and the organic additive can effectively improve the lithium-ion conductivity of the solid electrolyte and reduce the interfacial impedance.

[0011] Preferably, the active filler includes lithium lanthanum zirconium tantalum oxide (Li 6.5 La3Zr 1.5 Ta 0.5 O 12 , LLZTO), lithium indium chloride (Li3InCl6), lithium aluminum titanium phosphate (Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LATP), lithium aluminum germanium phosphate (Li 1.5 Al 0.5 Ge 1.5 (PO4)3, LAGP) and lithium phosphorus sulfur chloride (Li6PS5Cl, LPSCl), or one or more of them.

[0012] Preferably, the polyethylene oxide and the lithium salt are in a molar ratio of EO:Li of (7-9):1, the total mass ratio of the polyethylene oxide and the lithium salt to the mass of the active filler is (9-11):1, and the total mass ratio of the polyethylene oxide and the lithium salt to the mass of the organic additive is (6-7):1.

[0013] The organic-inorganic composite polymer solid electrolyte provided by the present invention has ultra-high lithium ion conductivity and high mechanical strength. The reasons are as follows: First, the strong basicity of the amidine group can promote the dissociation of the lithium salt, thereby effectively improving the lithium ion conductivity. Second, the linking group interacts with the dissociated lithium ions, thereby forming an interfacial layer with high lithium ion conductivity and high interfacial stability on the interface, thus effectively improving the interface stability. Finally, the added amidine organic additive improves the bonding environment of the solid electrolyte, greatly improving the mechanical strength of the solid electrolyte.

[0014] The present invention also provides a preparation method of an organic-inorganic composite polymer solid electrolyte, including the following steps: weighing each component, adding an organic solvent, heating and stirring to obtain a uniformly mixed slurry, and then casting and vacuum drying to obtain a polymer solid electrolyte.

[0015] Preferably, the solid content of the slurry is 20%-40%. Preferably, the polyethylene oxide is dried before use, the drying temperature is 20-180°C, and the drying time is 2-60h; more preferably, the drying temperature is 45-120°C, and the drying time is 2-24h.

[0016] Preferably, the organic solvents used include acetonitrile, dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and N,N-dimethylformamide, or one or more of them.

[0017] Preferably, the temperature for heating and stirring is 20-150°C, more preferably 20-80°C.

[0018] Preferably, the heating and stirring time is 8 - 60 h, more preferably 10 - 24 h.

[0019] Preferably, the temperature for vacuum drying is 20 - 100 °C, more preferably 60 - 100 °C.

[0020] Preferably, the vacuum drying time is 2 - 48 h, more preferably 8 - 36 h.

[0021] The present invention also provides an application of the organic - inorganic composite polymer solid electrolyte in the preparation of lithium - ion batteries.

[0022] The present invention has the following advantages:

[0023] In the PEO - based polymer solid electrolyte of the present invention, amidine compounds with special groups (halogen groups, nitro groups, phenyl groups, amino groups, etc.) are introduced, which interact with lithium salts, promote the dissociation of lithium salts, and form a high - lithium - ion - conductivity interface rich in LiX (X = F, Cl, Br, I, etc.) phenyl lithium and lithium nitrate on the interface, thereby improving the stability of the interface. It can effectively improve the ionic conductivity of the PEO - based organic - inorganic composite solid electrolyte at room temperature (up to 8.1×10 -4 S cm -1 ). By introducing amidine groups with strong basicity, a large number of electron pairs can be provided, which combine with the electron - withdrawing groups in the polymer groups; promoting the mobility of polymer segments and the acidity and basicity inside the solid electrolyte, thereby converting the fixed lithium ions inside the polymer solid electrolyte into free states, greatly reducing the migration energy barrier of lithium ions inside the polymer, and thus promoting the rapid and efficient transport of lithium ions in the PEO - based organic - inorganic composite solid electrolyte at room temperature and improving the mechanical properties. Description of the Drawings

[0024] Figure 1 Lithium - ion conductivity diagram of the PEO - based organic - inorganic composite polymer electrolyte membrane obtained in Comparative Example 1;

[0025] Figure 2 Interface impedance diagram of the PEO - based organic - inorganic composite polymer electrolyte membrane obtained in Comparative Example 1;

[0026] Figure 3 Cycling performance test diagram of the full battery of the PEO - based organic - inorganic composite polymer electrolyte membrane obtained in Comparative Example 1;

[0027] Figure 4 Lithium - ion conductivity diagram of the PEO - based organic - inorganic composite polymer electrolyte membrane obtained in Example 1;

[0028] Figure 5It is the interfacial impedance diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 1;

[0029] Figure 6 It is the lithium-ion conductivity diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 2;

[0030] Figure 7 It is the interfacial impedance diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 2;

[0031] Figure 8 It is the lithium-ion conductivity diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 3;

[0032] Figure 9 It is the interfacial impedance diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 3;

[0033] Figure 10 It is the lithium-ion conductivity diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 4;

[0034] Figure 11 It is the interfacial impedance diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 4;

[0035] Figure 12 It is the lithium-ion conductivity diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 5;

[0036] Figure 13 It is the interfacial impedance diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 5;

[0037] Figure 14 It is the cyclic performance test diagram of the full cell of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Example 5;

[0038] Figure 15 It is the lithium-ion conductivity diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Comparative Example 2;

[0039] Figure 16 It is the interfacial impedance diagram of the PEO-based organic-inorganic composite polymer electrolyte membrane obtained in Comparative Example 2. Detailed implementation manners

[0040] The present invention will be described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments are only further descriptions of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0041] In the following examples, unless otherwise specified, the raw materials, reagents, and equipment used can all be obtained commercially or by known existing methods. The number-average molecular weight of PEO is 600,000. Before use, PEO is vacuum-dried at 45 °C for 12 h to remove moisture.

[0042] The lithium-ion conductivity and interfacial impedance are tested using an electrochemical workstation at a test temperature of room temperature (25 °C). The battery cycling performance is tested using a battery charge-discharge tester at a test temperature of room temperature (25 °C).

[0043] Example 1

[0044] A method for preparing an organic-inorganic composite polymer solid electrolyte is as follows:

[0045] Weigh 6.72 g of PEO and 2.87 g of LiTFSI respectively according to the molar ratio EO:Li = 16:1. Then add 4.795 g of LLZTO powder and 1.918 g of 2-pyrazinecarboximidamide hydrochloride. Add acetonitrile as the solvent, heat and stir at 20 °C for 12 h to obtain a uniformly mixed slurry. Then pour and cast it in a polytetrafluoroethylene mold and vacuum-dry it at 60 °C for 24 h to obtain a PEO-based organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium-ion conductivity, and its lithium-ion conductivity is 3.6×10 - 4 S / cm( Figure 4 ) and the interfacial impedance is 113.2 Ω( Figure 5 ). Test its elastic modulus to be 2.2 MPa.

[0046] It can be seen from Example 1 and Comparative Example 1 that the addition of 2-pyrazinecarboximidamide hydrochloride effectively improves the lithium-ion conductivity and mechanical strength of the solid-state battery, and also improves the interfacial performance.

[0047] Example 2

[0048] A method for preparing an organic-inorganic composite polymer solid electrolyte is as follows:

[0049] Weigh 3.36 g of PEO and 1.435 g of LiBOB respectively according to the molar ratio EO:Li = 16:1. Then add 0.12 g of Li3InCl6 powder and 1.59 g of 2-pyrazinecarboximidamide hydrochloride. Add NMP as the solvent, heat and stir at 30 °C for 10 h to obtain a uniformly mixed slurry. Then pour and cast it in a polytetrafluoroethylene mold and vacuum-dry it at 80 °C for 10 h to obtain an organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium-ion conductivity, and its lithium-ion conductivity is 3.9×10 -4 S / cm( Figure 6 ) and the interfacial impedance is 162.5 Ω( Figure 7), and its elastic modulus was tested to be 2.4 MPa.

[0050] Example 3

[0051] A preparation method of an organic-inorganic composite polymer solid electrolyte is as follows:

[0052] Weigh 12.6 g of PEO and 1.87 g of LiFSI respectively according to the molar ratio EO:Li = 30:1, then add 1.447 g of LATP powder and 0.965 g of N-hydroxy-6-chloroindole formamidine. Add DMAC as the solvent, heat and stir at 60 °C for 18 h to obtain a uniformly mixed slurry, then cast and spread it in a polytetrafluoroethylene mold, and vacuum dry it at 60 °C for 36 h to obtain an organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium ion conductivity, and its lithium ion conductivity is 5.7×10 -4 S / cm( Figure 8 ), the interfacial impedance is 241.5 Ω( Figure 9 ), and its elastic modulus was tested to be 2.8 MPa.

[0053] Example 4

[0054] A preparation method of an organic-inorganic composite polymer solid electrolyte is as follows:

[0055] Weigh 1.68 g of PEO and 1.52 g of LiPF6 respectively according to the molar ratio EO:Li = 4:1, then add 0.1144 g of LAGP powder and 1.716 g of methyl-[5-(N-methyl-N-phenylamino)-2,4-pentadienyl]phenyl ammonium chloride. Add NMP as the solvent, heat and stir at 80 °C for 24 h to obtain a uniformly mixed slurry, then cast and spread it in a polytetrafluoroethylene mold, and vacuum dry it at 90 °C for 8 h to obtain an organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium ion conductivity, and its lithium ion conductivity is 6.6×10 -4 S / cm( Figure 10 ), the interfacial impedance is 113.2 Ω( Figure 11 ), and its elastic modulus was tested to be 3.4 MPa.

[0056] Example 5

[0057] A preparation method of an organic-inorganic composite polymer solid electrolyte is as follows:

[0058] Weigh 3.36 g of PEO and 1.06 g of LiODFB respectively according to the molar ratio EO:Li = 8:1. Then add 0.442 g of LSPCl powder and 0.663 g of 4-methylsulfonylphenylamidine. Add NMP as the solvent, heat and stir at 80 °C for 24 h to obtain a uniformly mixed slurry. Then cast and spread it in a polytetrafluoroethylene mold, and vacuum dry it at 100 °C for 8 h to obtain an organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium-ion conductivity, and its lithium-ion conductivity is 8.1×10 -4 S / cm( Figure 12 ), the interfacial impedance is 92.4 Ω( Figure 13 ), and test its elastic modulus to be 4.2 MPa. It is cycled 100 times at 0.5 C, and the discharge specific capacity can reach 145 mAh / g, and the capacity retention rate is close to 100%( Figure 14 ).

[0059] Comparative Example 1

[0060] A preparation method of an organic-inorganic composite polymer solid electrolyte is as follows:

[0061] Weigh 6.72 g of PEO and 2.87 g of LiTFSI respectively according to the molar ratio EO:Li = 16:1. Then add 0.959 g of LLZTO powder. Add acetonitrile as the solvent, heat and stir at 20 °C for 12 h to obtain a uniformly mixed slurry. Then cast and spread it in a polytetrafluoroethylene mold, and vacuum dry it at 60 °C for 24 h to obtain a PEO-based organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium-ion conductivity, and its lithium-ion conductivity is 2.1×10 -6 S / cm( Figure 1 ), the interfacial impedance is 829.5 Ω( Figure 2 ), and test its elastic modulus to be 1.2 MPa. It is cycled 40 times at 0.5 C, and the capacity basically drops to 0( Figure 3 ).

[0062] Comparative Example 2

[0063] Weigh 6.72 PEO and 2.87 LiTFSI respectively according to the molar ratio EO:Li = 16:1. Then add 0.95 LLZTO powder and 0.1918 DBU. Add acetonitrile as the solvent, heat and stir at 20 °C for 12 h to obtain a uniformly mixed slurry. Then cast and spread it in a polytetrafluoroethylene mold, and vacuum dry it at 60 °C for 24 h to obtain an organic-inorganic composite polymer electrolyte membrane. After cutting, test its lithium-ion conductivity, 8.2×10 -6 S / cm( Figure 15 ), the interfacial impedance is 350.2 Ω( Figure 16 ), and test its elastic modulus to be 1.8 MPa.

[0064] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. An organic-inorganic composite polymer solid electrolyte, characterized in that, It includes polyethylene oxide, a lithium salt, an active filler, and an organic additive. The organic additive is an amidine compound, and the amidine compound contains one or more of a halogen group, a phenyl group, a nitro group, a naphthyl group, or a thiophene group; the polyethylene oxide and the lithium salt have a molar ratio of EO:Li of (4 to 30):1, the total mass of the polyethylene oxide and the lithium salt and the mass of the active filler have a ratio of (2 to 40):1, and the total mass of the polyethylene oxide and the lithium salt and the mass of the organic additive have a ratio of (1.5 to 15):

1.

2. The organic-inorganic composite polymer solid electrolyte according to claim 1, wherein The amidine compound includes one or more of 3,4-dimethylbenzamidine, 2-(4-fluorobenzylsulfonyl)hydroxyacetamidine, 2-pyrazinecarboximidamide hydrochloride, N-hydroxy-6-chloroindolecarboximidamide, N-[3-(aminomethyl)benzyl]acetamidine, isethibenzamide, pentafluoropropylamidine, N'-hydroxy-2-naphthamidine, heptafluorobutyramidine, 2-(2-thienyl)hydroxyacetamidine, propamidine, 4-methylsulfonylbenzamidine, 2-N-BOC-aminoethylamidine, 4-benzylpiperazine-1-carboxamidine, 4-nitrobenzamidine.

3. The organic-inorganic composite polymer solid electrolyte according to claim 1, wherein The amidine compound is selected from at least one of 2-pyrazinecarboximidamide hydrochloride, N-hydroxy-6-chloroindolecarboximidamide, and 4-methylsulfonylbenzamidine.

4. The organic-inorganic composite polymer solid electrolyte according to claim 1, characterized in that, The lithium salt includes one or more of LiFSI, LiTFSI, LiBOB, LiODFB, LiPF6, LiClO4, LiNO3.

5. The organic-inorganic composite polymer solid electrolyte according to claim 1, wherein The active filler includes one or more of lithium lanthanum zirconium tantalum oxide, lithium indium chloride, lithium aluminum titanium phosphorus, lithium aluminum germanium phosphorus, and lithium phosphorus sulfur chloride.

6. The organic-inorganic composite polymer solid electrolyte according to claim 1, wherein The polyethylene oxide and the lithium salt have a molar ratio of EO:Li of (7 to 9):1, the total mass of the polyethylene oxide and the lithium salt and the mass of the active filler have a ratio of (9 to 11):1, and the total mass of the polyethylene oxide and the lithium salt and the mass of the organic additive have a ratio of (6 to 7):

1.

7. The preparation method of the organic-inorganic composite polymer solid electrolyte according to any one of claims 1-6, characterized in that, It includes the following steps: Weigh each component, add an organic solvent, heat and stir to obtain a uniformly mixed slurry, and then cast and vacuum dry to obtain a polymer solid electrolyte.

8. The preparation method according to claim 7, wherein The organic solvent includes one or more of acetonitrile, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide; the temperature for heating and stirring is 20 to 150 °C, and the time is 8 to 60 h; the temperature for vacuum drying is 20 to 100 °C, and the time is 2 to 48 h.

9. The preparation method according to claim 8, characterized in that, The temperature for heating and stirring is 20 to 80 °C, and the time is 10 to 24 h; the temperature for vacuum drying is 60 to 100 °C, and the time is 8 to 36 h.

10. Use of the organic-inorganic composite polymer solid electrolyte according to any one of claims 1-6 or the organic-inorganic composite polymer solid electrolyte prepared by the method according to any one of claims 7-9 in the preparation of a lithium electronic battery.

Images