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

Abstract

The application belongs to the field of battery materials, and discloses a PEO-based composite solid electrolyte and a preparation method and application thereof. The PEO-based composite solid electrolyte comprises MS2 / NiFe-LDH, PEO and a lithium salt, wherein M is any one or two or more of Mo, V and W. The MS2 in the modified nickel-iron bimetallic hydroxide provides a smooth channel for the transmission of ions and electrons, which can effectively promote the transmission of lithium ions. The modified nickel-iron bimetallic hydroxide is introduced into the PEO-based composite solid electrolyte, and the unique nanostructure characteristics, interface effect and ion conduction mechanism thereof can significantly improve the comprehensive performance of the electrolyte.

Description

Technical Field

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

[0002] Combinations of polymers (such as polyethers, polyesters, and polyamines) and metal lithium salts can be used as electrolytes in lithium batteries. These electrolytes typically need to meet the following requirements: ion conductivity without electronic conductivity, high room-temperature conductivity, a high ion transference number, good chemical stability, and good flexibility and processability of the resulting solid electrolyte membrane. Polyethylene oxide (PEO)-based polymer electrolytes, gel polymer electrolytes, porous polymer electrolytes, and solid polymer electrolytes (SPEs) are currently the focus of research.

[0003] The application of PEO-based SPEs often involves research on improving electrical conductivity. In existing technologies, this performance improvement is typically achieved by adding functional inorganic fillers to the SPE. Commonly used inorganic fillers include active lithium-containing fillers and inert lithium-free fillers. When combined with polymer electrolytes, these inorganic fillers can combine the advantages of high ionic conductivity and mechanical stability of inorganic electrolytes with the flexibility and low interfacial impedance of polymer electrolytes. However, some inorganic fillers are prone to irreversible structural changes during the material preparation process and subsequent electrochemical processes, thereby affecting the electrochemical performance of the battery. Summary of the Invention

[0004] In view of the defects and shortcomings of the existing technology, in the first aspect, the present invention provides a PEO-based composite solid electrolyte; in the second aspect, the present invention provides a method for preparing a PEO-based composite solid electrolyte; in the third aspect, the present invention provides a battery.

[0005] In a first aspect, the present invention provides a PEO-based composite solid electrolyte, comprising MS2 / NiFe-LDH, PEO and a lithium salt, wherein M is any one or more of Mo, V and W.

[0006] Preferably, the ratio of the mass of the MS2 / NiFe-LDH to the sum of the masses of the PEO and the lithium salt is 5-15:100; and the molar ratio of the EO in the PEO to the lithium element in the lithium salt is 15-20:1.

[0007] Preferably, the lithium salt is any one or more of LiTFSI, LiPF6, and LiBF4.

[0008] In a second aspect, the present invention provides a method for preparing a modified nickel-iron double hydroxide, comprising the following steps:

[0009] Step 1: adding nickel salt, iron salt, sulfur-containing organic sodium salt, and organic amine source into deionized water to obtain solution A, heating solution A in an oil bath, and reacting for a certain period of time to obtain solid particles, namely, talc-like NiFe-LDH nanosheets;

[0010] Step 2: dispersing the metal sulfide in deionized water to obtain a suspension B, dispersing the talc-like NiFe-LDH nanosheets in deionized water to obtain a suspension C, mixing the suspension B and the suspension C, stirring, centrifuging, and drying to obtain MS2 / NiFe-LDH;

[0011] Step 3, mixing MS2 / NiFe-LDH, PEO and lithium salt and ball milling to obtain a mixed powder;

[0012] Step 4: adding an organic solvent dropwise to the mixed powder and grinding again to obtain a slurry;

[0013] Step 5: coating the slurry on a substrate and then vacuum drying the substrate to obtain a film-like substance, which is the PEO-based composite solid electrolyte.

[0014] Preferably, in step 1, when preparing solution A, the specific steps are: dissolving nickel salt and iron salt in water, then adding sulfur-containing organic sodium salt, stirring evenly, and then adding organic ammonia source dropwise until the pH value of the reaction system is 10-11.

[0015] Preferably, the metal sulfide is any one or more of MoS2, VS2, and WS2.

[0016] Preferably, the nickel salt is any one or more of acetate, sulfate and chloride.

[0017] Preferably, the iron salt is any one or more of acetate, sulfate and chloride.

[0018] Preferably, the sulfur-containing organic sodium salt is any one or more of sodium lauryl sulfate, sodium anthraquinone-2-sulfonate monohydrate, and sodium p-toluenesulfonate.

[0019] Preferably, the organic ammonia source is any one or more of hexamethylenetetramine, azodicarbonamide, triethylenetetramine, and tetraethylenepentamine.

[0020] Preferably, in step 1, the nickel ion concentration in the solution A is 1-3 mol / L; the molar ratio of the nickel salt, the iron salt, the sulfur-containing organic sodium salt, and the organic amine source in the solution A is 2-4:1:3.1-6:3.1-6.

[0021] Preferably, in step 1, the temperature of the oil bath heating is 50-80° C., and the time of the oil bath heating is 8-15 hours.

[0022] Preferably, in step 2, the mass ratio of the metal sulfide to the talc-like NiFe-LDH nanosheets in the suspension B is 1:1-2.

[0023] Preferably, the lithium salt is any one or more of LiTFSI, LiPF6, and LiBF4.

[0024] Preferably, in step 3, the ratio of the mass of the MS2 / NiFe-LDH to the sum of the masses of the PEO and the lithium salt is 5-15:100; and the molar ratio of the EO in the PEO to the lithium element in the lithium salt is 15-20:1.

[0025] Preferably, the organic solvent is any one or more of acetonitrile, tetrahydrofuran or N,N-dimethylformamide.

[0026] Preferably, in step 4, the liquid-to-solid ratio of the slurry is 10-30 mL / g.

[0027] Preferably, in step 5, the vacuum drying temperature is 70-90° C., and the vacuum drying time is 6-12 h.

[0028] In a third aspect, the present invention provides a battery comprising the above-mentioned PEO-based composite solid electrolyte or the PEO-based composite solid electrolyte prepared by the above-mentioned preparation method.

[0029] Compared with the prior art, the present invention has the following obvious beneficial effects:

[0030] (1) The present invention introduces modified nickel-iron double hydroxide into a PEO-based composite solid electrolyte, utilizing its unique nanostructure characteristics, interface effect and ion conduction mechanism to improve the cycle stability and ion conductivity of the battery.

[0031] (2) The modified nickel-iron double hydroxide prepared by the preparation method provided by the invention is a talc-like nanosheet with a layered structure and uniform particle size. MS2 and NiFe-LDH are evenly distributed therein, providing a smooth channel for the transmission of ions and electrons, thereby effectively promoting the transmission of lithium ions.

[0032] (3) Modified nickel-iron double hydroxide is synthesized by the oil bath method, composited with metal sulfide, and then freeze-dried to obtain metal sulfide-composite nickel-iron double hydroxide nanosheets. This process is simple and the product is stable, which is conducive to promotion and industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is an SEM image of the modified nickel-iron double hydroxide prepared in step 2 of Example 1 of the present invention;

[0034] Figure 2 This is a SEM image of the PEO-based composite solid electrolyte membrane prepared in step 3 of Example 1 of the present invention;

[0035] Figure 3 This is a SEM image of the electrolyte membrane of a battery assembled with the solid electrolyte membrane prepared in Example 1 after 100 cycles;

[0036] Figure 4 This is a SEM image of the electrolyte membrane of a battery assembled with the solid electrolyte membrane prepared in Comparative Example 1 after 100 cycles;

[0037] Figure 5 EIS graphs of batteries assembled with the solid electrolyte membranes prepared in Example 1 and Comparative Example 1;

[0038] Figure 6 The electrochemical cycle performance test diagram of the battery assembled with the solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0039] The present invention provides the following specific technical solutions.

[0040] In a first aspect, the present invention provides a PEO-based composite solid electrolyte, comprising MS2 / NiFe-LDH, PEO and a lithium salt, wherein M is any one or more of Mo, V and W.

[0041] The inventors have found that the introduction of modified nickel-iron double hydroxide into PEO-based composite solid electrolyte can significantly improve the comprehensive performance of the electrolyte through its unique nanostructure characteristics, interface effect and ion conduction mechanism. First, the layered structure of NiFe-LDH contains exchangeable anions (such as sulfonate), and the Li + It can quickly migrate through the interlayer channel to form an additional ion conduction path, thereby increasing the Li +Migration number; polarized charge exists at the heterogeneous interface between MS2 and LDH, which can attract Li⁺ through Coulomb interaction and reduce its migration activation energy, thereby improving ionic conductivity. Second, it can improve the mechanical strength and stability of the solid electrolyte. The two-dimensional sheet structure of LDH nanosheets can serve as a physical crosslinking point, entangled with PEO chains through van der Waals forces or hydrogen bonds, forming a "nanofiller-polymer" interpenetrating network, which reduces the electrolyte's elongation at break but increases its tensile strength, resisting volume expansion during battery charging and discharging. The sheet structure of MS2 has lubricity. When the electrolyte is subjected to external force, controllable slip can occur between the MS2 and LDH layers, avoiding brittle fracture by dissipating energy and improving toughness. The sulfate ester / sulfate groups on the LDH surface are both lithium-philic and organic-philic, which can improve the interfacial compatibility between inorganic fillers and PEO polymers and reduce mechanical weaknesses caused by filler agglomeration. Third, it can inhibit the growth of lithium dendrites. The size of the LDH interlayer channel can selectively allow Li⁺ to pass through, while hindering the migration of larger anions, thereby reducing concentration polarization, making Li⁺ uniformly deposited at the electrolyte / electrode interface, and inhibiting the growth of dendrite tips; the transition metal sites in NiFe-LDH (Ni 2 ⁺、Fe 3 ⁺) It can catalyze the decomposition of lithium salts and form a stable and uniform SEI film at the lithium metal interface. This film has high ionic conductivity and low electronic conductivity, effectively preventing dendrite penetration.

[0042] Preferably, the ratio of the mass of the MS2 / NiFe-LDH to the sum of the masses of the PEO and the lithium salt is 5-15:100; and the molar ratio of the EO in the PEO to the lithium element in the lithium salt is 15-20:1.

[0043] Preferably, the lithium salt is any one or more of LiTFSI, LiPF6, and LiBF4.

[0044] In a second aspect, the present invention provides a method for preparing a modified nickel-iron double hydroxide, comprising the following steps:

[0045] Step 1: adding nickel salt, iron salt, sulfur-containing organic sodium salt, and organic amine source into deionized water to obtain solution A, heating solution A in an oil bath, and reacting for a certain period of time to obtain solid particles, namely, talc-like NiFe-LDH nanosheets;

[0046] Step 2: dispersing the metal sulfide in deionized water to obtain a suspension B, dispersing the talc-like NiFe-LDH nanosheets in deionized water to obtain a suspension C, mixing the suspension B and the suspension C, stirring, centrifuging, and drying to obtain MS2 / NiFe-LDH;

[0047] Step 3, mixing MS2 / NiFe-LDH, PEO and lithium salt and ball milling to obtain a mixed powder;

[0048] Step 4: adding an organic solvent dropwise to the mixed powder and grinding again to obtain a slurry;

[0049] Step 5: coating the slurry on a substrate and then vacuum drying the substrate to obtain a film-like substance, which is the PEO-based composite solid electrolyte.

[0050] The inventors discovered that the sulfur vacancies or metal sites in nickel-iron double hydroxides and metal sulfides form a heterogeneous interface, triggering electron rearrangement and optimizing active sites. The layered structure of nickel-iron double hydroxides can serve as a supporting framework to prevent the aggregation of metal sulfide nanoparticles. Furthermore, it can provide a highly dispersed carrier for sulfides, exposing more interfacial active sites. Finally, the hydrophilicity of nickel-iron double hydroxides combined with the hydrophobicity of sulfides promotes contact between the organic and inorganic phases, facilitates the transmission of ions and electrons, and ultimately synergistically promotes the electrical conductivity and ion-conducting properties of PEO-based electrolytes.

[0051] The preparation method provided by this invention allows the metal sulfide (MS2) and NiFe-LDH to combine through electrostatic interactions or chemical bonds, forming a "sandwich" multilayer structure. The LDH layer provides abundant active sites (such as hydroxyl groups and metal sites), enhancing ion exchange capacity. The MS2 layer enhances conductivity and structural stability, widens the interlayer spacing, and facilitates the diffusion of guest molecules. Furthermore, the two-dimensional and multilayered structure of the nanosheets significantly increases the specific surface area and enhances the reactant adsorption capacity. Application of this nanosheet in solid-state electrolytes can significantly improve the cycling performance of batteries.

[0052] Preferably, the metal sulfide is any one or more of MoS2, VS2, and WS2.

[0053] Preferably, the nickel salt is any one or more of acetate, sulfate and chloride.

[0054] Preferably, the iron salt is any one or more of acetate, sulfate and chloride.

[0055] Preferably, the sulfur-containing organic sodium salt is any one or more of sodium lauryl sulfate, sodium anthraquinone-2-sulfonate monohydrate, and sodium p-toluenesulfonate.

[0056] The inventors have found that the introduction of sulfate groups / sulfate groups can effectively inhibit the excessive size of particles. Its core function is to regulate the crystal nucleation and growth process through electrostatic repulsion, growth guidance and template effect, forming nano-scale uniformly dispersed LDH particles. On the one hand, sulfate groups / sulfate groups have strong negative charges and can be adsorbed on metal ions (such as Ni 2+ 、Fe 3+) or the surface of LDH nanocrystals, forming a negatively charged double layer. The particles are repelled by like charges and are difficult to aggregate and grow, thus limiting the particle size and promoting uniform dispersion at the nanoscale. Secondly, sulfate ester / sulfate groups act as structure-directing agents, adsorbing on specific LDH crystal faces through coordination or electrostatic effects, inhibiting the growth rate of these faces and forcing the crystals to grow in other directions (such as the transverse direction), forming thin flake-like nanosheets rather than large particles. Thirdly, the weak coordination between sulfate ester / sulfate groups and metal ions can slightly reduce the solubility of metal hydroxides, slowing the nucleation rate and keeping the solution at a low supersaturation, promoting uniform nucleation rather than rapid aggregation and growth.

[0057] Preferably, the organic ammonia source is any one or more of hexamethylenetetramine, azodicarbonamide, triethylenetetramine, and tetraethylenepentamine.

[0058] After research, the inventors found that an organic amine source, as a pH regulator and donor of interlayer anions, can partially exchange the organic sulfonate anions in the talc-like layered material to form a double-anionic talc-like layered material, which exhibits acid-base dual functionality and enhances the corrosion resistance of the electrode, making it resistant to byproducts HF, LiOH phase or other lithium-containing alkaline substances.

[0059] Preferably, in step 1, the nickel ion concentration in the solution A is 1-3 mol / L; the molar ratio of the nickel salt, the iron salt, the sulfur-containing organic sodium salt, and the organic amine source in the solution A is 2-4:1:3.1-6:3.1-6.

[0060] In practical applications, a slight excess of sulfur-containing organic sodium salt and organic amine source can ensure the complete formation of talc-like layered structure materials.

[0061] Preferably, in step 1, the temperature of the oil bath heating is 50-80° C., and the time of the oil bath heating is 8-15 hours.

[0062] Preferably, in step 2, the mass ratio of the metal sulfide to the talc-like NiFe-LDH nanosheets in the suspension B is 1:1-2.

[0063] Preferably, the lithium salt is any one or more of LiTFSI, LiPF6, and LiBF4.

[0064] Preferably, in step 3, the ratio of the mass of the MS2 / NiFe-LDH to the sum of the masses of the PEO and the lithium salt is 5-15:100; and the molar ratio of the EO in the PEO to the lithium element in the lithium salt is 15-20:1.

[0065] In a specific embodiment of the present invention, PEO is polyethylene oxide, the monomer EO is C2H4O, and the molar ratio of EO in PEO to the lithium element in the lithium salt is the molar ratio of C2H4O constituting polyethylene oxide to the lithium element in the lithium salt.

[0066] Preferably, the organic solvent is any one or more of acetonitrile, tetrahydrofuran or N,N-dimethylformamide.

[0067] Preferably, in step 4, the liquid-to-solid ratio of the slurry is 10-30 mL / g.

[0068] Preferably, in step 5, the vacuum drying temperature is 70-90° C., and the vacuum drying time is 6-12 h.

[0069] In a third aspect, the present invention provides a battery comprising the above-mentioned PEO-based composite solid electrolyte or the PEO-based composite solid electrolyte prepared by the above-mentioned preparation method.

[0070] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention clearer, they will be described in detail below with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0071] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0072] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0073] Example 1:

[0074] A method for preparing a PEO-based composite solid electrolyte comprises the following steps:

[0075] Step 1: 0.4 mol nickel chloride and 0.15 mol ferric chloride are dissolved in 250 mL deionized water and stirred evenly. Then, 0.6 mol sodium dodecyl sulfate is added to the solution and stirred evenly. Then, 0.6 mol hexamethylenetetramine is added dropwise for coprecipitation reaction. The pH value of the solution is controlled at 10-11 to obtain solution A. Solution A is then placed in an oil bath at 60° C. for 10 h. After centrifugation, washing with water, washing with alcohol, and drying, talc-like NiFe-LDH nanosheets are obtained.

[0076] Step 2: Take 10g of talc-like NiFe-LDH nanosheets and disperse them in 100mL of deionized water to form a suspension A, disperse 8g of MoS2 in 100mL of deionized water to form a suspension B, add the suspension B dropwise into the suspension A and mix evenly, stirring vigorously, then centrifuge and freeze-dry at -35°C for 16h to obtain the modified nickel-iron double hydroxide.

[0077] Step 3: Take 4 g of modified nickel-iron double hydroxide, 36.61 g of PEO and 13.39 g of LiTFSI and mix them evenly by ball milling. Then, add 1000 mL of N,N-dimethylformamide and continue grinding to make it evenly dispersed into a slurry. Then, apply it evenly on a polytetrafluoroethylene plate and vacuum dry it at 80 ° C for 10 h to obtain a PEO-based composite solid electrolyte membrane.

[0078] Figure 1 The SEM image of the modified nickel-iron double hydroxide obtained in step 2 of Example 1 of the present invention is shown in FIG. Figure 1 It can be seen that the modified nickel-iron double hydroxide prepared in the present invention is talc-like, has a layered structure, and has uniform particle size.

[0079] Figure 2 This is a SEM image of the PEO-based composite solid electrolyte membrane prepared in step 3 of Example 1 of the present invention. It can be seen from the image that the electrolyte membrane is evenly dispersed without agglomeration.

[0080] Comparative Example 1:

[0081] A method for preparing a PEO-based composite solid electrolyte comprises: taking 36.61g of PEO and 13.39g of LiTFSI and mixing them uniformly by ball milling, then dropping N,N-dimethylformamide into the mixture, continuously grinding the mixture to uniformly disperse it into a slurry, uniformly coating the mixture on a polytetrafluoroethylene plate, and vacuum drying the mixture at 80°C for 10 hours to obtain a PEO-based composite solid electrolyte membrane.

[0082] Comparative Example 2:

[0083] A method for preparing a PEO-based composite solid electrolyte comprises the following steps:

[0084] Step 1: 0.4 mol nickel chloride and 0.15 mol ferric chloride are dissolved in 250 mL deionized water and stirred evenly. Then, 0.6 mol sodium dodecyl sulfate is added to the solution and stirred evenly. Then, 0.6 mol hexamethylenetetramine is added dropwise for coprecipitation reaction. The pH value of the solution is controlled at 10-11 to obtain solution A. Solution A is then placed in an oil bath at 60° C. for 10 h. After centrifugation, washing with water, washing with alcohol, and drying, talc-like NiFe-LDH nanosheets are obtained.

[0085] Step 2: 4 g of talc-like NiFe-LDH nanosheets, 36.61 g of PEO, and 13.39 g of LiTFSI were ball-milled and evenly mixed. 1000 mL of N,N-dimethylformamide was then added dropwise and continuously ground to uniformly disperse the mixture into a slurry. The mixture was evenly coated on a polytetrafluoroethylene plate and vacuum-dried at 80°C for 10 h to obtain a PEO-based composite solid electrolyte membrane.

[0086] Example 2:

[0087] A method for preparing a PEO-based composite solid electrolyte comprises the following steps:

[0088] Step 1: 0.4 mol nickel acetate and 0.1 mol ferric acetate are dissolved in 250 mL deionized water and stirred evenly. Then, 0.6 mol sodium anthraquinone-2-sulfonate monohydrate is added to the solution. After stirring evenly, 0.6 mol azodicarbonamide is added dropwise for coprecipitation reaction. The pH value of the solution is controlled at 10-11 to obtain solution A. Solution A is then placed in an oil bath at 50° C. for 15 hours. After centrifugation, washing with water, washing with alcohol, and drying, talc-like NiFe-LDH nanosheets are obtained.

[0089] Step 2: 10 g of talc-like NiFe-LDH nanosheets were dispersed in 100 mL of deionized water to form a suspension A, 8 g of VS2 was dispersed in 100 mL of deionized water to form a suspension B, and the suspension B was added dropwise to the suspension A and mixed evenly, and stirred vigorously. The mixture was then centrifuged and freeze-dried at -30°C for 20 h to obtain the modified nickel-iron double hydroxide.

[0090] Step 3: Take 4g of modified nickel-iron double hydroxide, 67.2g of PEO and 12.8g of LiPF6 and mix them evenly by ball milling. Then, add 840mL of acetonitrile and grind them continuously to make them evenly dispersed into a slurry. Then, apply it evenly on a polytetrafluoroethylene plate and dry it in vacuum at 70°C for 12h to obtain a PEO-based composite solid electrolyte membrane.

[0091] Example 3:

[0092] A method for preparing a PEO-based composite solid electrolyte comprises the following steps:

[0093] Step 1: 0.4 mol nickel sulfate and 0.2 mol ferric sulfate are dissolved in 250 mL deionized water and stirred evenly. Then, 0.62 mol sodium dodecyl sulfate is added to the solution and stirred evenly. Then, 0.62 mol hexamethylenetetramine is added dropwise for coprecipitation reaction. The pH value of the solution is controlled at 10-11 to obtain solution A. Solution A is then placed in an oil bath at 80° C. for 8 h. After centrifugation, water washing, alcohol washing, and drying, talc-like NiFe-LDH nanosheets are obtained.

[0094] Step 2, 10 g of talc-like NiFe-LDH nanosheets were dispersed in 100 mL of deionized water to form a suspension A, 10 g of WS2 was dispersed in 100 mL of deionized water to form a suspension B, the suspension B was added dropwise into the suspension A and uniformly mixed, and was continuously stirred, then was centrifuged, and was freeze-dried at -40℃ for 10 h to obtain the modified nickel-iron bimetallic hydroxide.

[0095] Step 3, 3 g of the modified nickel-iron bimetallic hydroxide, 18.8 g of PEO and 1.92 g of LiBF4 were uniformly ball-milled and mixed, then were dropped into 690 mL of tetrahydrofuran, and were continuously ground to be uniformly dispersed into a slurry, and were uniformly coated on a polytetrafluoroethylene plate, and were vacuum dried at 90℃ for 6 h to obtain the PEO-based composite solid-state electrolyte film.

[0096] Table 1 is the specific surface area of the nickel-iron bimetallic hydroxide prepared in Examples 1-3 and Comparative Example 2.

[0097] The specific surface area of the nickel-iron bimetallic hydroxide prepared in Examples 1-3 and Comparative Example 2

[0098]

[0099] It can be seen from Table 1 that the modified nickel-iron bimetallic hydroxide prepared by the preparation method provided by the present application has a larger specific surface area.

[0100] Figure 3 The SEM image of the electrolyte film of the battery assembled by the solid-state electrolyte film prepared in Example 1 after 100 cycles, from Figure 3 It can be seen that the surface of the electrolyte after the cycle is smooth, which proves that the electrolyte film still maintains good stability after the cycle.

[0101] Figure 4 The SEM image of the electrolyte film of the battery assembled by the solid-state electrolyte film prepared in Comparative Example 1 after 100 cycles, from Figure 4 It can be seen that cracks appear on the surface of the electrolyte after the cycle, indicating that the structure of the electrolyte film is unstable.

[0102] Comparison Figure 3 and Figure 4 , it can be further illustrated that the solid-state electrolyte film provided by the present application has more excellent structural stability, which is beneficial to improve the battery life.

[0103] Figure 5 The EIS image of the battery assembled by the solid-state electrolyte film prepared in Example 1 and Comparative Example 1, from Figure 5 It can be seen that the battery assembled by the solid-state electrolyte film prepared in Example 1 has smaller impedance, which further illustrates that the solid-state electrolyte film prepared in Example 1 has more excellent conductivity.

[0104] The modified PEO-based composite solid electrolyte membrane obtained in Examples 1 to 3 and Comparative Examples 1 to 2 was assembled into a button cell as a solid electrolyte component. The positive electrode active material was LiFePO4, and the lithium sheet was used as the negative electrode. The cells were placed in a glove box filled with argon atmosphere with a water content and an oxygen content both lower than 0.1 ppm for 4 hours to reduce the moisture adsorbed by the electrode during the transfer process. The cells were then assembled into CR2032 button cells in the glove box.

[0105] After aging for 12 hours, the assembled batteries were subjected to charge and discharge tests at different potentials. The batteries were activated at a current density of 0.1C for three cycles at a voltage of 2.7 to 4.8V, and then cycled at a current density of 1C for 100 cycles.

[0106] Figure 6 The electrochemical cycle performance test diagram of the solid electrolyte prepared in Examples 1 to 3 and Comparative Examples 1 to 2 is shown in FIG. Figure 6 As can be seen from the data, compared with PEO-based composite solid electrolyte membranes and nickel-iron double hydroxide-modified PEO-based composite solid electrolytes, the sulfide-modified nickel-iron double hydroxide-modified PEO-based composite solid electrolyte membrane provided by the present invention can effectively improve the electrochemical cycle stability of the battery. This further proves that the uniform distribution of MS2 and NiFe-LDH phases as raw materials for the solid electrolyte can provide unobstructed channels for the transmission of ions and electrons during battery operation, effectively promoting the transmission of lithium ions, thereby improving the electrochemical performance of the battery.

[0107] The embodiments described above are only preferred specific implementation methods of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and concepts of the present invention within the technical scope of the present invention, and they should be covered by the scope of protection of the present invention.

Claims

1. A PEO-based composite solid electrolyte, characterized in that: The PEO-based composite solid electrolyte comprises MS2 / NiFe-LDH, PEO and lithium salt, wherein M is any one or more of Mo, V and W; The ratio of the mass of the MS2 / NiFe-LDH to the sum of the mass of the PEO and the lithium salt is (5-15):100; the molar ratio of the EO in the PEO to the lithium element in the lithium salt is (15-20):1; The preparation method of the PEO-based composite solid-state electrolysis comprises the following steps: Step 1: adding nickel salt, iron salt, sulfur-containing organic sodium salt, and organic amine source into deionized water to obtain solution A, heating solution A in an oil bath, and reacting for a certain period of time to obtain solid particles, namely, talc-like NiFe-LDH nanosheets; Step 2: dispersing the metal sulfide MS2 in deionized water to obtain a suspension B, dispersing the talc-like NiFe-LDH nanosheets in deionized water to obtain a suspension C, mixing the suspension B and the suspension C, stirring, centrifuging, and drying to obtain MS2 / NiFe-LDH; Step 3, mixing MS2 / NiFe-LDH, PEO and lithium salt and ball milling to obtain a mixed powder; Step 4: adding an organic solvent dropwise to the mixed powder and grinding again to obtain a slurry; Step 5: coating the slurry on a substrate and then vacuum drying the substrate to obtain a film-like substance, which is the PEO-based composite solid electrolyte.

2. The PEO-based composite solid electrolyte according to claim 1, wherein The lithium salt is any one or more of LiTFSI, LiPF6, and LiBF4.

3. The PEO-based composite solid electrolyte according to claim 1, wherein The nickel salt is any one or more of acetate, sulfate, and chloride; the iron salt is any one or more of acetate, sulfate, and chloride; the sulfur-containing organic sodium salt is any one or more of sodium dodecyl sulfate, sodium anthraquinone-2-sulfonate monohydrate, and sodium p-toluenesulfonate; the organic amine source is any one or more of hexamethylenetetramine, azodicarbonamide, triethylenetetramine, and tetraethylenepentamine; the metal sulfide MS2 is any one or more of MoS2, VS2, and WS2; the lithium salt is any one or more of LiTFSI, LiPF6, and LiBF4; and the organic solvent is any one or more of acetonitrile, tetrahydrofuran, or N,N-dimethylformamide.

4. The PEO-based composite solid electrolyte according to claim 1 or 3, wherein In step 1, when preparing solution A, the specific steps are: dissolving nickel salt and iron salt in deionized water, then adding sulfur-containing organic sodium salt, stirring evenly, and then adding organic amine source dropwise until the pH value of the reaction system is 10-11.

5. The PEO-based composite solid electrolyte according to claim 1, wherein In step 1, the nickel ion concentration in the solution A is 1-3 mol / L; the molar ratio of the nickel salt, the iron salt, the sulfur-containing organic sodium salt, and the organic amine source in the solution A is (2-4):1:(3.1-6):(3.1-6).

6. The PEO-based composite solid electrolyte according to claim 1, wherein: In step 2, the mass ratio of the metal sulfide and the talc-like NiFe-LDH nanosheets in the suspension B is 1:(1-2); in step 3, the ratio of the mass of the MS2 / NiFe-LDH to the sum of the masses of the PEO and the lithium salt is (5-15):100; and the molar ratio of the EO in the PEO to the lithium element in the lithium salt is (15-20):

1.

7. The PEO-based composite solid electrolyte according to claim 1 or 6, wherein: In step 4, the liquid-to-solid ratio of the slurry is 10-30 mL / g.

8. A battery, characterized in that: The invention comprises the PEO-based composite solid electrolyte according to any one of claims 1 to 7.

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