Modified PEO-based composite solid-state electrolyte and preparation method and application thereof

Abstract

The application belongs to the field of battery materials, and discloses a modified PEO-based composite solid electrolyte and a preparation method and application thereof.The modified PEO-based composite solid electrolyte comprises modified microporous metal oxide, PEO and lithium salt; the modified microporous metal oxide comprises a core, an intermediate layer and a coating layer, the intermediate layer is at least coated on part of the surface of the core, and the coating layer is at least coated on part of the surface of the solid particles formed by the core and the intermediate layer; the chemical formula of the core is ZnO, the chemical formula of the intermediate layer is ZnCo2O4, and the chemical formula of the coating layer is ZnCo x Mn 2‑x O4, wherein the value range of x is 0.5<=x<=1.5.The modified microporous metal oxide comprises multiple metals, avoids the collapse of the microporous structure formed by the single metal oxide phase under the high-temperature pore-forming condition, guarantees the structural stability of the microporous structure, and exhibits excellent mechanical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of battery materials, and relates to a solid electrolyte material, in particular to a modified PEO-based composite solid electrolyte and a preparation method and application thereof. BACKGROUND

[0002] PEO-based solid electrolytes have high energy density and high safety, and are easy to process, so they are widely used. However, the pure PEO-based solid electrolyte still has problems such as low ionic conductivity and high crystallinity, which leads to insufficient ion transmission channels in the amorphous region, thereby limiting its application in high-power devices. Although the addition of lithium salt can improve the ion dissociation degree, too high lithium salt concentration will cause salt precipitation phenomenon, thereby reducing the ion migration rate. The chemical degradation of PEO may be the main factor leading to battery failure. In the prior art, inorganic fillers, structural modification and other methods are usually added to the solid electrolyte to improve the ion transmission performance of the solid-state battery.

[0003] The conventional inorganic fillers have limited effect on improving the ion transmission performance of the solid electrolyte, and researchers use porous inorganic fillers to increase the lithium ion transmission channels, but the porous structure is easy to collapse in the reversible transmission process of lithium ions, and the durability of the surface composite structure is limited. SUMMARY

[0004] In view of the defects and deficiencies in the prior art, in a first aspect, the application provides a modified PEO-based composite solid electrolyte, in a second aspect, the application provides a preparation method of the modified PEO-based composite solid electrolyte, and in a third aspect, the application provides a battery.

[0005] In a first aspect, the application provides a modified PEO-based composite solid electrolyte, which comprises modified microporous metal oxide, PEO and lithium salt; the modified microporous metal oxide comprises a core, an intermediate layer and a coating layer, the intermediate layer is at least coated on part of the surface of the core, and the coating layer is at least coated on part of the surface of the solid particles formed by the core and the intermediate layer; the chemical formula of the core is ZnO, the chemical formula of the intermediate layer is ZnCo2O4, and the chemical formula of the coating layer is ZnCo2O4-x, wherein the value range of x is 0.5≤x≤1.5. x Mn 2- x O4, wherein the value range of x is 0.5≤x≤1.5.

[0006] Preferably, the ratio of the mass of the modified microporous metal oxide to the sum of the mass of the PEO and the lithium salt is 5-15:100; and the molar ratio of EO in the PEO to lithium ions in the lithium salt is 15-20:1.

[0007] In a second aspect, the present application provides a preparation method of a modified PEO-based composite solid electrolyte, comprising the following steps:

[0008] Step 1: adding a zinc source to an organic ligand to perform a first complexation reaction to obtain a mixture A; then adding a zinc source and a cobalt source to the mixture A to perform a second complexation reaction to obtain a mixture B; and then adding a zinc source, a cobalt source and a manganese source to the mixture B to perform a third complexation reaction to obtain a mixture C;

[0009] Step 2: separating and filtering the mixture C, and sintering the obtained solid particles in an inert atmosphere to obtain the modified microporous metal oxide;

[0010] Step 3: ball-milling the modified microporous metal oxide, PEO and lithium salt, then dropping into an organic solvent, and grinding to obtain a slurry;

[0011] Step 4: coating the slurry on a substrate and vacuum drying to obtain the modified PEO-based composite solid electrolyte.

[0012] Preferably, in Step 1, the zinc source is any one or both of zinc acetate and zinc nitrate; the cobalt source is any one or both of cobalt acetate and cobalt nitrate; the manganese source is any one or both of manganese acetate and manganese nitrate; and the organic ligand is any one or more than two of 2-methylimidazole solution, methyl alcohol solution of trimesic acid, and ethyl alcohol solution of terephthalic acid.

[0013] Preferably, in Step 1, the molar ratio of the zinc source to the organic ligand is 1:20-30 in the first complexation reaction; the molar ratio of the zinc source to the cobalt source is 1:2-2.3 in the second complexation reaction; and the molar ratio of the zinc source, the cobalt source and the manganese source is 1:0.5-1.5:0.5-1.5 in the third complexation reaction; and the molar ratio of the zinc source added in the first, second and third complexation reactions is 1:0.3-1:0.1-0.5.

[0014] Preferably, in Step 1, the reaction time of the first complexation reaction is 8-15 h; the reaction time of the second complexation reaction is 6-10 h; and the reaction time of the third complexation reaction is 6-10 h.

[0015] Preferably, in Step 2, the sintering temperature is 400-600℃, and the sintering time is 1-4 h.

[0016] Preferably, in Step 3, the mass ratio of the modified microporous metal oxide to the sum of the mass of the PEO and the lithium salt is 5-15:100; and the molar ratio of EO in the PEO to lithium ions in the lithium salt is 15-20:1.

[0017] Preferably, in Step 3, the organic solvent is any one or more than two of acetonitrile, tetrahydrofuran and N,N-dimethylformamide.

[0018] Preferably, in step 3, the liquid-solid ratio of the slurry is 15-25 mL / g.

[0019] Preferably, in step 4, the drying temperature is 70-90℃, and the drying time is 6-12 h.

[0020] In a third aspect, the present application provides a battery comprising the modified PEO-based composite solid electrolyte or the modified PEO-based composite solid electrolyte prepared by the preparation method.

[0021] Compared with the prior art, the present application has the following obvious beneficial effects:

[0022] (1) The modified microporous metal oxide provided by the present application has a stable microporous structure and exhibits a high specific surface area; and the modified microporous metal oxide comprises multiple metals, which reduces the possibility of collapse of the microporous structure and exhibits excellent mechanical properties.

[0023] (2) The modified microporous metal oxide has different concentration gradients of cations from inside to outside, which can accelerate the transmission effect of lithium ions, and the microporous structure thereof provides a large number of channels for the transmission of lithium ions, so that the mechanical properties and ion transmission properties of the PEO-based solid electrolyte can be improved.

[0024] (3) The preparation method provided by the present application is simple in process and easy to realize large-scale production, which is conducive to commercialization and popularization. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 HRTEM image of the metal oxide prepared in step 2 of Example 1;

[0026] Figure 2 TEM image of the metal oxide prepared in step 2 of Example 1;

[0027] Figure 3 Cycle performance diagram of the battery assembled by the solid electrolyte prepared in Examples 1-3 and Comparative Examples 1-4;

[0028] Figure 4 EIS diagram of the battery assembled by the solid electrolyte prepared in Examples 1-3 and Comparative Examples 1-4. DETAILED DESCRIPTION

[0029] The present application provides the following specific technical solutions.

[0030] In a first aspect, the present application provides a modified PEO-based composite solid electrolyte, comprising a modified microporous metal oxide, PEO and a lithium salt; the modified microporous metal oxide comprises a core, an intermediate layer and a coating layer, the intermediate layer at least coats part of the surface of the core, and the coating layer at least coats part of the surface of the solid particle formed by the core and the intermediate layer; the chemical formula of the core is ZnO, the chemical formula of the intermediate layer is ZnCo2O4, and the chemical formula of the coating layer is ZnCo x Mn 2- x O4, wherein the value of x ranges from 0.5 to 1.5.

[0031] The inventors have found that, in the modified microporous metal oxide, ZnO has good ion affinity, and the oxygen vacancies or defects in the crystal lattice of ZnO can serve as adsorption sites for lithium ions, promoting the migration of lithium ions on the surface of the oxide particle; and the rigid metal oxide particle (especially the ZnO core) as a filler can improve the mechanical strength of the PEO matrix, inhibit the deformation of the electrolyte during high-voltage or lithium deposition, and avoid the risk of short circuit caused by cracking. ZnCo2O4, as a spinel structure oxide, has both ion and electron conduction capabilities, and can form an ion conduction bridge between the core and the coating layer. The multi-metal oxide composition of ZnCo2O4 can further adjust the surface energy and reduce the lithium ion migration barrier; and the metal-oxygen bond energy of ZnCo2O4 is higher than that of a single oxide (ZnO), which can reduce the reactivity with the lithium salt, reduce the generation of interface byproducts, and avoid increasing the interface impedance between the electrolyte and the electrode. The application of the modified microporous metal oxide in the PEO-based composite solid electrolyte can improve the ionic conductivity and structural stability of the battery. x Mn 2-x x Mn 2-x The application of the modified microporous metal oxide in the PEO-based composite solid electrolyte can improve the ionic conductivity and structural stability of the battery.

[0032] Preferably, the ratio of the mass of the modified microporous metal oxide to the sum of the mass of the PEO and the lithium salt is 5-15:100; and the molar ratio of EO in the PEO to lithium ions in the lithium salt is 15-20:1.

[0033] In a second aspect, the present application provides a preparation method of a modified PEO-based composite solid electrolyte, comprising the following steps:

[0034] Step 1: adding a zinc source to an organic ligand to perform a first complexation reaction to obtain a mixture A; then adding a zinc source and a cobalt source to the mixture A to perform a second complexation reaction to obtain a mixture B; and then adding a zinc source, a cobalt source and a manganese source to the mixture B to perform a third complexation reaction to obtain a mixture C;

[0035] ​Step 2, isolate and filter the mixed C, and sinter the obtained solid particles under an inert atmosphere to obtain the modified microporous metal oxide;

[0036] Step 3, ball-mill mix the modified microporous metal oxide, PEO and lithium salt, then drop into an organic solvent, and grind to obtain a slurry;

[0037] Step 4, coat the slurry on a substrate, and vacuum dry to obtain the modified PEO-based composite solid-state electrolyte.

[0038] The inventors have found that the modified microporous metal oxide prepared by the process of complexation and sintering has a stable microporous structure and exhibits a high specific surface area; and the modified microporous metal oxide comprises multiple metals, which avoids the collapse of the microporous structure of a single metal oxide phase and ensures the structural stability of the microporous structure, thereby exhibiting excellent mechanical properties.

[0039] Preferably, in step 1, the zinc source is any one or two or more of zinc acetate and zinc nitrate; the cobalt source is any one or two or more of cobalt acetate and cobalt nitrate; the manganese source is any one or two or more of manganese acetate and manganese nitrate; and the organic ligand is any one or two or more of 2-methylimidazole solution, methyl alcohol solution of trimesic acid, and ethyl alcohol solution of terephthalic acid.

[0040] Preferably, in step 1, the molar ratio of the zinc source to the organic ligand in the first complexation is 1:20-30; the molar ratio of the zinc source to the cobalt source in the second complexation is 1:2-2.3; and the molar ratio of the zinc source, the cobalt source and the manganese source in the third complexation is 1:0.5-1.5:0.5-1.5; wherein the molar ratio of the zinc source added in the first, second and third complexations is 1:0.3-1:0.1-0.5.

[0041] Preferably, in step 1, the reaction time of the first complexation is 8-15 h; the reaction time of the second complexation is 6-10 h; and the reaction time of the third complexation is 6-10 h.

[0042] Preferably, in step 2, the sintering temperature is 400-600°C, and the sintering time is 1-4 h.

[0043] In actual production, in step 2, the gas providing the inert atmosphere is usually nitrogen.

[0044] Preferably, in step 3, the ratio of the mass of the modified microporous metal oxide to the sum of the mass of the PEO and the lithium salt is 5-15:100; and the molar ratio of EO in the PEO to lithium ions in the lithium salt is 15-20:1.

[0045] Preferably, in step 3, the organic solvent is any one or more of acetonitrile, tetrahydrofuran, and N,N-dimethylformamide.

[0046] Preferably, in step 3, the liquid-solid ratio of the slurry is 15-25 mL / g.

[0047] Preferably, in step 4, the drying temperature is 70-90°C, and the drying time is 6-12 h.

[0048] In a third aspect, the present application provides a battery comprising the modified PEO-based composite solid electrolyte or the modified PEO-based composite solid electrolyte prepared by the preparation method.

[0049] To make the technical problems, technical solutions and technical advantages of the present application clearer, specific examples will be described in detail below, but the protection scope of the present application is not limited to the following specific examples.

[0050] Unless otherwise defined, all the professional terms used below have the same meanings as generally understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing specific examples, and are not intended to limit the protection scope of the present application.

[0051] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0052] Example 1:

[0053] A preparation method of a modified PEO-based composite solid electrolyte, comprising the following steps:

[0054] In step 1, 60 mL of zinc acetate solution is added to 750 mL of 2-methylimidazole solution with a concentration of 2 mol / L to perform a first complexation reaction, and the reaction is performed for 10 h to obtain a mixture A, wherein the zinc acetate in the zinc acetate solution is 0.06 mol; then 30 mL of zinc acetate solution and 62 mL of cobalt acetate solution are added to the mixture A to perform a second complexation reaction, wherein the zinc acetate in the zinc acetate solution is 0.03 mol, the cobalt acetate in the cobalt acetate solution is 0.062 mol, and the reaction is performed for 8 h to obtain a mixture B; then 18 mL of zinc acetate solution, 18 mL of cobalt acetate solution, and 18 mL of manganese acetate solution are added to the mixture B to perform a third complexation reaction, wherein the zinc acetate in the zinc acetate solution is 0.018 mol, the cobalt acetate in the cobalt acetate solution is 0.018 mol, and the manganese acetate in the manganese acetate solution is 0.018 mol, and the reaction is performed for 7 h to obtain a mixture C.

[0055] In step 2, the mixture C is separated and filtered, and the obtained solid particles are sintered at 500°C for 2 h under a nitrogen atmosphere to obtain a modified microporous metal oxide.

[0056] Step 3: Take 4g of the modified microporous metal oxide obtained in Step 2 and mix it with 36.7g of PEO and 13.3g of LiTFSI by ball milling. Then add 1000mL of N,N-dimethylformamide and continue grinding to obtain a slurry. Coat the slurry evenly on a polytetrafluoroethylene plate and dry it under vacuum at 80℃ for 10h to obtain the modified PEO-based composite solid electrolyte.

[0057] Figure 1 The image shown is an HRTEM image of the metal oxide obtained in step 2 of Example 1. Figure 1 As can be seen from the data, the metal oxide contains three phases: ZnO, ZnCo2O4, and ZnCoMnO4, which proves that the three-layer microporous metal oxide was successfully prepared.

[0058] Figure 2 This is a TEM image of the metal oxide obtained in step 2 of Example 1. Figure 2 As can be seen, the metal oxide is black, and white spots are evenly distributed on the surface of the metal oxide. These white spots are pores, which proves that the metal oxide has a porous structure.

[0059] Comparative Example 1:

[0060] A method for preparing a PEO-based composite solid electrolyte includes: taking 4g of the modified microporous metal oxide obtained in step 2 and mixing it with 36.7g of PEO and 13.3g of LiTFSI by ball milling, then adding 1000mL of N,N-dimethylformamide dropwise, continuously grinding to obtain a slurry, uniformly coating the slurry onto a polytetrafluoroethylene plate, and drying it under vacuum at 80℃ for 10h to obtain the PEO-based composite solid electrolyte.

[0061] Comparative Example 2:

[0062] A method for preparing a modified PEO-based composite solid electrolyte includes the following steps:

[0063] Step 1: Add 60 mL of zinc acetate solution to 750 mL of 2 mol / L 2-methylimidazole solution to carry out a complexation reaction. The reaction is carried out for 10 h to obtain mixture A, in which the zinc acetate solution contains 0.06 mol of zinc acetate.

[0064] Step 2: Separate and filter mixture A, and sinter the obtained solid particles at 500°C for 2 hours under a nitrogen atmosphere to obtain modified microporous metal oxide.

[0065] Step 3, 4 g of the modified microporous metal oxide prepared in step 2 is mixed with 36.7 g of PEO and 13.3 g of LiTFSI by ball milling, and then 1000 mL of N,N-dimethylformamide is added dropwise, and the slurry is obtained by grinding. The slurry is uniformly coated on a polytetrafluoroethylene plate, and then vacuum dried at 80°C for 10 h to obtain a modified PEO-based composite solid-state electrolyte.

[0066] Comparative Example 3:

[0067] A method for preparing a modified PEO-based composite solid-state electrolyte comprises the following steps:

[0068] Step 1, 60 mL of zinc acetate solution is added to 750 mL of 2-methylimidazole solution with a concentration of 2 mol / L to perform a first complexation reaction, and the reaction is performed for 10 h to obtain a mixture A, and the zinc acetate in the zinc acetate solution is 0.06 mol; then 30 mL of zinc acetate solution and 62 mL of cobalt acetate solution are added to the mixture A to perform a second complexation reaction, and the zinc acetate in the zinc acetate solution is 0.03 mol, and the cobalt acetate in the cobalt acetate solution is 0.062 mol, and the reaction is performed for 8 h to obtain a mixture B.

[0069] Step 2, the mixture B is separated and filtered, and the obtained solid particles are sintered at 500°C for 2 h under a nitrogen atmosphere to obtain a modified microporous metal oxide.

[0070] Step 3, 4 g of the modified microporous metal oxide prepared in step 2 is mixed with 36.7 g of PEO and 13.3 g of LiTFSI by ball milling, and then 1000 mL of N,N-dimethylformamide is added dropwise, and the slurry is obtained by grinding. The slurry is uniformly coated on a polytetrafluoroethylene plate, and then vacuum dried at 80°C for 10 h to obtain a modified PEO-based composite solid-state electrolyte.

[0071] Comparative Example 4:

[0072] A method for preparing a modified PEO-based composite solid-state electrolyte comprises the following steps:

[0073] Step 1, 60 mL of zinc acetate solution is added to 750 mL of 2-methylimidazole solution with a concentration of 2 mol / L to perform a first complexation reaction, and the reaction is performed for 10 h to obtain a mixture A, and the zinc acetate in the zinc acetate solution is 0.06 mol; then 30 mL of zinc acetate solution and 62 mL of cobalt acetate solution are added to the mixture A to perform a second complexation reaction, and the zinc acetate in the zinc acetate solution is 0.03 mol, and the cobalt acetate in the cobalt acetate solution is 0.062 mol, and the reaction is performed for 8 h to obtain a mixture B.

[0074] Step 2, separate and filter the mixture B, and sinter the obtained solid particles at 500 DEG C under nitrogen atmosphere for 2h to obtain the modified microporous metal oxide.

[0075] Step 3, take 4g of the modified microporous metal oxide prepared in step 2, and mix with 36.7g of PEO and 13.3g of LiTFSI by ball milling, then drop 1000ml of N,N-dimethylformamide, and grind constantly to obtain a slurry, and uniformly coat the slurry on a polytetrafluoroethylene plate, and dry at 80 DEG C under vacuum for 10h to obtain the modified PEO-based composite solid-state electrolyte.

[0076] Example 2:

[0077] A preparation method of a modified PEO-based composite solid-state electrolyte comprises the following steps:

[0078] Step 1, add 60ml of zinc nitrate methanol solution to 600ml of 2mol / L methyl alcohol solution of m-benzenetricarboxylic acid to perform a first complexation reaction, and react for 10h to obtain mixture A, wherein the zinc nitrate in the zinc nitrate methanol solution is 0.06mol; then add 18ml of zinc acetate solution and 36ml of cobalt acetate solution to mixture A to perform a second complexation reaction, wherein the zinc acetate in the zinc acetate solution is 0.018mol, the cobalt acetate in the cobalt acetate solution is 0.036mol, and react for 6h to obtain mixture B; then add 6ml of zinc acetate solution, 3ml of cobalt acetate solution and 9ml of manganese acetate solution to mixture B to perform a third complexation reaction, wherein the zinc acetate in the zinc acetate solution is 0.006mol, the cobalt acetate in the cobalt acetate solution is 0.003mol, and the manganese acetate in the manganese acetate solution is 0.009mol, and react for 7h to obtain mixture C.

[0079] Step 2, separate and filter the mixture C, and sinter the obtained solid particles at 400 DEG C under nitrogen atmosphere for 4h to obtain the modified microporous metal oxide.

[0080] Step 3, take 4g of the modified microporous metal oxide prepared in step 2, and mix with 55.8g of PEO and 24.2g of LiTFSI by ball milling, then drop 1260ml of N,N-dimethylformamide, and grind constantly to obtain a slurry, and uniformly coat the slurry on a polytetrafluoroethylene plate, and dry at 70 DEG C under vacuum for 12h to obtain the modified PEO-based composite solid-state electrolyte.

[0081] Example 3:

[0082] A preparation method of a modified PEO-based composite solid-state electrolyte comprises the following steps:

[0083] Step 1, a first complexation reaction was carried out by adding 60 mL of zinc acetate solution to 900 mL of a methanol solution of m-benzenetricarboxylic acid with a concentration of 2 mol / L, and the reaction was carried out for 15 h to obtain a mixture A, and the zinc acetate in the zinc acetate solution was 0.06 mol; then a second complexation reaction was carried out by adding 60 mL of zinc acetate solution and 138 mL of cobalt acetate solution to the mixture A, wherein the zinc acetate in the zinc acetate solution was 0.06 mol, and the cobalt acetate in the cobalt acetate solution was 0.138 mol, and the reaction was carried out for 10 h to obtain a mixture B; then a third complexation reaction was carried out by adding 30 mL of zinc acetate solution, 45 mL of cobalt acetate solution and 15 mL of manganese acetate solution to the mixture B, wherein the zinc acetate in the zinc acetate solution was 0.03 mol, the cobalt acetate in the cobalt acetate solution was 0.045 mol, and the manganese acetate in the manganese acetate solution was 0.015 mol, and the reaction was carried out for 10 h to obtain a mixture C.

[0084] Step 2, the mixture C was separated and filtered, and the obtained solid particles were sintered at 600 ℃ for 1 h under a nitrogen atmosphere to obtain the modified microporous metal oxide.

[0085] Step 3, 4 g of the modified microporous metal oxide prepared in step 2 was ball-milled with 20.06 g of PEO and 6.54 g of LiTFSI, then 765 mL of N,N-dimethylformamide was added dropwise, and the mixture was continuously ground to obtain a slurry, and the slurry was uniformly coated on a polytetrafluoroethylene plate, and then the coated plate was dried in a vacuum drying oven at 70 ℃ for 12 h to obtain a modified PEO-based composite solid-state electrolyte.

[0086] The solid-state electrolytes prepared in Examples 1-3 and Comparative Examples 1-4 were assembled into batteries by the following method:

[0087] The solid-state electrolytes obtained in Examples 1-3 and Comparative Examples 1-4 were used as the solid-state electrolyte component to assemble a button cell, and Li 1.1 Mn 0.9 O2 was used as the positive active material, and the positive material: conductive graphite: PVDF was weighed according to the mass ratio of 8:1:1, then a proper amount of N-methyl pyrrolidone (NMP) was added for continuous grinding and stirring to form a uniform slurry, the slurry was uniformly coated on an aluminum foil using a mold, the coating thickness was 200 μm, and the coated aluminum foil was placed in a drying oven at 90 ℃ for 10 h, then it was cut into a 12 mm diameter disc to obtain a positive electrode sheet. Lithium sheet was used as the negative electrode, and the water content and oxygen content of the glove box were both less than 0.1 ppm, and the glove box was filled with argon atmosphere, and the electrode sheet was placed in the glove box for 4 h to reduce the adsorbed water in the transfer process, and then the CR2032 type button cell was assembled in the glove box.

[0088] After the battery was assembled, it was aged for 12 h, and then the charge and discharge test at different potentials was carried out. The battery was activated for 3 cycles at a current density of 0.1 C under a voltage of 2.7-4.8 V, and then it was cycled for 100 cycles at a current density of 1 C.

[0089] Figure 3 The cycle performance of the batteries assembled by the solid-state electrolytes prepared in Examples 1-3 and Comparative Examples 1-4 is shown in the following figure: Figure 3 It can be seen from the above that the battery assembled by the three-layer microporous metal oxide modified PEO-based composite solid-state electrolyte has the best electrochemical performance, the battery assembled by the single-layer oxide or double-layer oxide modified PEO-based composite solid-state electrolyte has the second best electrochemical performance, and the battery assembled by the unmodified PEO-based composite solid-state electrolyte has the worst electrochemical performance. The reason for the above difference is that the three-layer microporous structure inorganic filler provided by the application has good structural stability and is not easy to collapse in the process of reversible transmission of lithium ions, thereby improving the electrochemical performance of the battery.

[0090] The resistance of the batteries assembled by the solid-state electrolytes prepared in Examples 1-3 and Comparative Examples 1-4 was tested, and the test data is shown in Table 1.

[0091] Table 1 Resistance of the batteries assembled by the solid-state electrolytes prepared in Examples 1-3 and Comparative Examples 1-4

[0092]

[0093] Figure 4 The EIS diagram of the batteries assembled by the solid-state electrolytes prepared in Examples 1-3 and Comparative Examples 1-4 is shown in the following figure, combined with Table 1 and Figure 4 It can be seen from the above that the battery assembled by the modified microporous metal oxide modified PEO-based composite solid-state electrolyte has the smallest impedance value, which indicates that the modified microporous metal oxide modified PEO-based composite solid-state electrolyte has excellent ion transmission performance.

[0094] The above-described examples are only preferred specific embodiments of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can make equivalent substitutions or changes within the technical scope of the application according to the technical solutions and concepts of the application, which should be covered within the protection scope of the application.

Claims

1. A modified PEO-based composite solid-state electrolyte, characterized in that, A modified microporous metal oxide, PEO and a lithium salt; the modified microporous metal oxide comprises a core, an intermediate layer and a coating layer, the intermediate layer at least coats part of the surface of the core, and the coating layer at least coats part of the surface of the solid particles formed by the core and the intermediate layer; the core has a chemical formula of ZnO, the intermediate layer has a chemical formula of ZnCo2O4, and the coating layer has a chemical formula of ZnCo x Mn 2-x O4, wherein the value range of x is 0.5≤x≤1.5; The ratio of the mass of the modified microporous metal oxide to the sum of the mass of the PEO and the lithium salt is (5-15):100; the molar ratio of EO in the PEO to lithium ions in the lithium salt is (15-20):

1.

2. The preparation method of the modified PEO-based composite solid electrolyte as described in claim 1, characterized in that, The method comprises the following steps: Step 1: adding a zinc source to an organic ligand to perform a first complexation reaction to obtain a mixture A; then adding a zinc source and a cobalt source to the mixture A to perform a second complexation reaction to obtain a mixture B; and then adding a zinc source, a cobalt source and a manganese source to the mixture B to perform a third complexation reaction to obtain a mixture C; Step 2: separating and filtering the mixture C, and sintering the obtained solid particles in an inert atmosphere to obtain the modified microporous metal oxide; Step 3: ball-milling the modified microporous metal oxide, the PEO and the lithium salt, then dropping an organic solvent to obtain a slurry; Step 4: coating the slurry on a substrate and vacuum drying to obtain the modified PEO-based composite solid-state electrolyte.

3. The preparation method of the modified PEO-based composite solid electrolyte as described in claim 2, characterized in that, In step 1, the zinc source is any one or both of zinc acetate and zinc nitrate; the cobalt source is any one or both of cobalt acetate and cobalt nitrate; the manganese source is any one or both of manganese acetate and manganese nitrate; and the organic ligand is any one or more than two of 2-methyl imidazole solution, methyl alcohol solution of trimesic acid and ethyl alcohol solution of terephthalic acid. In step 3, the organic solvent is any one or more than two of acetonitrile, tetrahydrofuran and N,N-dimethylformamide.

4. The preparation method of the modified PEO-based composite solid electrolyte as described in claim 2, characterized in that, In the first complexation, the molar ratio of the zinc source to the organic ligand is 1:(20-30); in the second complexation, the molar ratio of the zinc source to the cobalt source is 1:(2-2.3); and in the third complexation, the molar ratio of the zinc source, the cobalt source and the manganese source is 1:(0.5-1.5):(0.5-1.5). The molar ratio of the zinc source added in the first, second and third complexations is 1:(0.3-1):(0.1-0.5).

5. The method for preparing the modified PEO-based composite solid electrolyte as described in claim 2 or 4, characterized in that, In step 1, the reaction time of the first complexation is 8-15 h; the reaction time of the second complexation is 6-10 h; and the reaction time of the third complexation is 6-10 h.

6. The preparation method of the modified PEO-based composite solid electrolyte as described in claim 2, characterized in that, In step 2, the sintering temperature is 400-600 ℃, and the sintering time is 1-4 h.

7. The preparation method of the modified PEO-based composite solid electrolyte as described in claim 2, characterized in that, In step 3, the ratio of the mass of the modified microporous metal oxide to the sum of the mass of the PEO and the lithium salt is (5-15):100; and the molar ratio of EO in the PEO to lithium ions in the lithium salt is (15-20):

1.

8. The preparation method of the modified PEO-based composite solid electrolyte as described in claim 2, characterized in that, In step 3, the liquid-solid ratio of the slurry is 15-25 mL / g; and in step 4, the drying temperature is 70-90 ℃, and the drying time is 6-12 h.

9. A battery, characterized by The modified PEO-based composite solid-state electrolyte prepared by the method of any one of claims 2-8.

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