Preparation method and application of iron-doped molybdenum disulfide / polymer-based composite solid electrolyte

Abstract

The invention discloses a preparation method and application of an iron-doped molybdenum disulfide / polymer-based composite solid-state electrolyte, and relates to the technical field of solid-state batteries. After the iron element is doped, defects are introduced into the structure of the modified molybdenum disulfide, phase change is induced, dissociation of the lithium salt is promoted through synergism of the modified molybdenum disulfide and the iron element, and more free lithium ions are released; and meanwhile, the proportion of an amorphous region of the polymer electrolyte is increased, so that the ionic conductivity is improved, and the oxidation resistance is enhanced. In addition, the iron-doped molybdenum disulfide can effectively catalyze decomposition of lithium salt anions, and construction of a uniform and stable solid electrolyte interface (SEI) layer on the surface of the electrode is facilitated. The all-solid-state lithium metal battery assembled based on the modified solid electrolyte shows excellent electrochemical performance.

Description

A method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte and its application. Technical Field

[0001] This invention belongs to the technical field of solid-state batteries, and relates to a method for preparing a composite solid-state electrolyte containing iron-doped molybdenum disulfide and its application, specifically a method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid-state electrolyte and its application. Background Technology

[0002] In recent years, solid-state batteries have attracted much attention due to their high energy density and good safety. Among various solid electrolytes, polymer-based solid electrolytes have shown considerable application potential due to their lower cost and better processing flexibility. These electrolytes have good solubility for lithium salts and good compatibility with electrode interfaces, but they still have problems such as low ionic conductivity and narrow electrochemical stability window, which restrict their further development and practical application.

[0003] To address the aforementioned issues, researchers both domestically and internationally have undertaken extensive modification work. For instance, Professor Zhou's research team proposed a method to incorporate modified tungsten disulfide into a PVDF-HFP / LiFSI matrix, and prepared a composite solid electrolyte film using a solution casting process (Adv. Mater. 2025, 2419271).

[0004] Transition metal chalcogenides have been proven to effectively enhance ion transport performance in polymer electrolytes. Among them, molybdenum disulfide (MoD) possesses tunable electronic structure and high catalytic activity, showing broad application prospects in the energy and catalysis fields. Iron doping can further optimize the performance of MoD, promoting lithium salt dissociation, releasing more free lithium ions, increasing the proportion of amorphous regions in the polymer matrix, thereby improving lithium ion mobility and enhancing the polymer's antioxidant capacity. Simultaneously, the defects and phase transitions introduced by doping can effectively catalyze the decomposition of lithium salt anions, contributing to the formation of a uniform and stable solid electrolyte interphase (SEI) layer on the electrode surface. Summary of the Invention

[0005] To address the problems in existing polymer-based solid electrolytes, such as poor ionic conductivity due to high crystallinity at room temperature affecting ion transport and the formation of lithium dendrites on the electrode surface piercing the electrolyte membrane, resulting in poor cycle performance and limited practical applications, this invention proposes a method for preparing an iron-doped molybdenum disulfide composite solid electrolyte. Specifically, it provides a method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte and its application. On the one hand, iron doping can induce lattice distortion and defects within molybdenum disulfide, promoting lithium salt dissociation. On the other hand, iron doping can induce a phase transition, accelerating the catalytic decomposition of anion ions and promoting the formation of a uniform SEI layer.

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

[0007] The present invention discloses a method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, comprising: treating a mixed solution of ammonium molybdate tetrahydrate and an iron compound solution; mixing the treated precursor with a sulfur source for a hydrothermal reaction to prepare iron-doped molybdenum disulfide; subsequently introducing it as a filler into a polymer-based electrolyte; and then drying it to obtain the composite solid electrolyte.

[0008] Specifically, the process involves treating a mixed solution of ammonium molybdate tetrahydrate and an iron compound solution, then mixing the treated precursor with a sulfur source for a hydrothermal reaction to obtain iron-doped molybdenum disulfide. The iron-doped molybdenum disulfide is then mixed with an electrolyte precursor slurry to obtain a composite electrolyte slurry, which is then dried to obtain a composite solid electrolyte membrane. Finally, this membrane is assembled with the positive and negative electrodes to form a battery.

[0009] Iron-doped molybdenum disulfide promotes the dissociation of lithium salts, releasing more free lithium ions, improving the lithium ion mobility in the amorphous region of the polymer, and enhancing the polymer's antioxidant capacity. Furthermore, the defects and phase transitions introduced by the doping effectively promote the decomposition of lithium salt anions, forming a uniform and stable SEI layer on the electrode surface. The resulting all-solid-state lithium metal battery with a solid electrolyte exhibits excellent electrochemical performance.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, comprising the following steps:

[0012] S1. Iron-containing compounds are reacted with ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 The precursor product was obtained by mixing and dissolving ·4H2O) with deionized water, heating and stirring, cooling, filtering, and recrystallizing.

[0013] S2. After mixing and dissolving the precursor product, thiourea, and deionized water, the mixture is transferred to the inner liner of the reactor for hydrothermal reaction. After cooling, the product is washed and centrifuged multiple times, and then dried in a vacuum drying oven to obtain iron-doped molybdenum disulfide (Fe-MoS2).

[0014] S3. Fe-MoS2 is introduced as a filler into the polymer-based electrolyte slurry, and then dried to obtain a composite solid electrolyte.

[0015] Furthermore, the iron-containing compound mentioned in S1 is at least one of Fe2(SO4)3, Fe(NO3)3, and FePO4.

[0016] Furthermore, the heating and stirring described in S1 are carried out at a temperature of 90-100 ℃ for 30-90 min, with a volume of deionized water of 80-120 mL; the recrystallization described in S1 is carried out at a temperature of 80-90 ℃.

[0017] Furthermore, in the mixed dissolution described in S2, the mass ratio of the precursor to thiourea is 1:1.5-2, and the volume of deionized water is 35-50 mL.

[0018] Furthermore, the hydrothermal reaction described in S2 is carried out at a temperature of 180 ℃-220 ℃ and a reaction time of 18 h-30 h. After cooling, the mixture is washed and centrifuged multiple times with deionized water and an organic solvent, wherein the organic reagent is either acetone or ethanol. The centrifugation speed is 3500-8000 r / min and the centrifugation time is 5-10 min. The temperature of the vacuum drying oven is 60-80 ℃.

[0019] Furthermore, the polymer matrix material described in S3 is at least one of PEO, PVC, PEG, PMA, PVDF, PVDF-HFP, PAN-PVA, and PAN-PEG.

[0020] The molar ratio of repeating units in the polymer matrix to lithium in the conductive lithium salt within the solid electrolyte is 10:1, wherein the conductive lithium salt is at least one of LiTFSI, LiFSI, LiPF6, LiBF4, and LiDFOB.

[0021] The iron-doped molybdenum disulfide is 1%-10% of the polymer matrix mass, preferably 5%.

[0022] Furthermore, in the slurry described in S3, the organic solvent is a solvent capable of dissolving the polymer matrix, including but not limited to at least one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; the mass ratio of the organic solvent to the polymer matrix is ​​10-20:1.

[0023] Furthermore, the drying process described in S3 is carried out at a temperature of 50℃-70℃ for a time of 12h-24h.

[0024] This invention also relates to an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, obtained according to the above-mentioned preparation method of the iron-doped molybdenum disulfide / polymer-based composite solid electrolyte. This composite solid electrolyte has the following properties:

[0025] At room temperature, the ionic conductivity is 4.92.4 × 10⁻⁴. -5 ~6.18×10 -5 S cm -1 The battery assembled with LiFePO4 as the positive electrode exhibits a capacity of 143.5 mAh / g at 1C. - The initial discharge specific capacity¹, after 700 cycles, showed a reversible discharge capacity of 116.09 mAh g⁻¹. - ¹, with a capacity retention rate of 80.89%, while the coulombic efficiency remains stable at 99.9%.

[0026] This invention also relates to the application of the aforementioned iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, which is assembled into an all-solid-state battery, including a positive electrode, a negative electrode, and an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte membrane.

[0027] Furthermore, the cathode material includes lithium iron phosphate (LiFePO4) and ternary materials (LiNi). x Co y Mn 1-y O2, 0≤x≤1, 0≤y≤1).

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention discloses a method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte. Through a two-step hydrothermal method, iron-doped molybdenum disulfide nanospheres are obtained. The defects and phase transitions contained therein can effectively adsorb polymers and lithium salts; enhance electron transfer, promote the decomposition of lithium salt anions, and form a uniform SEI layer.

[0030] 2. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to the present invention involves mixing iron-doped molybdenum disulfide and an electrolyte precursor slurry to prepare the composite solid electrolyte. This reduces the crystallinity of the polymer matrix, promotes polymer chain movement and ion migration, and its Li + Uniform deposition on the surface of lithium metal electrode improves the ionic conductivity of the electrolyte and forms a uniform and stable SEI layer on the electrode surface.

[0031] 3. The present invention prepares an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte. After battery assembly and modification, the electrolyte suppresses the formation of lithium dendrites, thereby improving the cycle stability and safety of the all-solid-state battery. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 is a process flow diagram of a method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to Example 1 of the present invention.

[0034] Figure 2 is a SEM image of the iron-doped molybdenum disulfide prepared in Example 1 of the present invention;

[0035] Figure 3 is the XRD pattern of iron-doped molybdenum disulfide prepared in Example 1 of the present invention;

[0036] Figure 4 is an EPR diagram of iron-doped molybdenum disulfide prepared in Example 1 of the present invention;

[0037] Figure 5 is an impedance diagram of the composite solid electrolyte prepared in Example 1 of the present invention;

[0038] Figure 6 is a calculated ionic conductivity diagram of the composite solid electrolyte prepared in Example 1 of the present invention;

[0039] Figure 7 is the XRD diffraction pattern of the composite solid electrolyte prepared in Example 1 of the present invention;

[0040] Figure 8 shows the cycle performance test results of the composite solid electrolyte prepared in Example 1 of this invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0042] Example 1:

[0043] A method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, as shown in Figure 1, includes the following steps:

[0044] Preparation of precursor: 5.19 g of (NH4)6Mo7O 24• 4H2O was dissolved in 80 mL of deionized water and heated to 100℃. 3.5 mmol of Fe2(SO4)3 was dissolved in 20 mL of deionized water and added to the above mixture. After stirring for 60 min, the mixture was evaporated, cooled, filtered, and recrystallized to obtain the precursor product.

[0045] Preparation of iron-doped molybdenum disulfide: 0.12 g of precursor and 0.2 g of thiourea were dissolved in 35 mL of deionized water. After stirring and dissolving, the solution was transferred to the lining of a high-pressure reactor. The reaction vessel was heated to 200 °C and kept at that temperature for 24 h. After cooling, the product was collected and washed with a centrifuge using deionized water and ethanol as washing solvents. Finally, the product was placed in a vacuum drying oven and dried at 60 °C for 24 h.

[0046] The morphology of iron-doped molybdenum disulfide is shown in Figure 2, which is in the form of nanospheres;

[0047] Figure 3 shows the XRD diffraction of iron-doped molybdenum disulfide, which demonstrates the successful doping of iron and the generation of the molybdenum disulfide phase transition.

[0048] Figure 4 shows the defects in iron-doped molybdenum disulfide;

[0049] Synthesis of electrolyte slurry: LiTFSI was added to acetonitrile, and the obtained iron-doped molybdenum disulfide was mixed and stirred at 5% of the mass of PEO for 30 min. Then PEO powder was added and mixed evenly. The mixture was stirred at room temperature for 16 h to obtain a uniform electrolyte slurry, wherein the molar ratio of repeating units in PEO to lithium in LiTFSI was 10:1.

[0050] Preparation of solid electrolyte membrane: The obtained composite electrolyte slurry was first sonicated for 30 min, and then coated on a glass plate bound with non-woven fabric in two coats. The first coat was thinner, and then air bubbles were removed in a vacuum drying oven. After the air bubbles were removed, the membrane was left to stand in a cool and dry place for 50 min-70 min, and then the second coating was performed. The second coating was slightly larger than the first coating, and then the air bubbles were removed a second time. After the air bubbles were removed, the membrane was left to stand until the acetonitrile evaporated to a semi-dry state on the membrane surface. The membrane was then placed in an oven and vacuum dried at 60 ℃ for 24 h to obtain a composite solid electrolyte membrane containing iron-doped molybdenum disulfide.

[0051] The composite solid electrolyte membrane prepared above was assembled into a battery. The positive and negative electrodes of the battery were connected to an electrochemical workstation, and the AC impedance of the battery at 30℃-60℃ was measured to obtain the AC impedance diagram of the electrolyte, as shown in Figure 5.

[0052] Figure 6 shows the lithium-ion conductivity calculated using the following formula:

[0053]

[0054] Where σ (S cm) -1 The figure represents the ionic conductivity, L (cm) represents the thickness of the solid polymer electrolyte membrane, and S (cm) represents the ionic conductivity. 2 The area represents the working electrode area of ​​the battery (referring to the area of ​​the positive electrode or the negative electrode), which is 1.91 cm² in this embodiment. 2 R represents the resistance value of the electrolyte.

[0055] As shown in Figure 6, the above formula yields the following result: Under the test environment, when the external temperature of the iron-doped molybdenum disulfide polymer electrolyte battery is 30℃, its ionic conductivity is 6.18 × 10⁻⁶. -5 S cm -2 When the external temperature of the battery is 60 ℃, the ionic conductivity is 4.12 × 10⁻⁶. -4 S cm -2 The ionic conductivity of the MoS2 polymer electrolyte battery containing powder is 3.82 × 10⁻⁶ when the external temperature is 30 °C. -5 S cm -2 When the external temperature of the battery is 60 ℃, the ionic conductivity is 2.52 × 10⁻⁶. -4 S cm -2 .

[0056] Furthermore, XRD diffraction experiments confirmed that adding iron doping to the PEO matrix reduced the crystallinity of the polymer solid electrolyte, as shown in Figure 7.

[0057] All-solid-state batteries were assembled in an argon-filled vacuum glove box with a water and oxygen content below 0.01 ppm. A coin cell was constructed using the iron-doped molybdenum disulfide composite solid electrolyte prepared above, with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode. The lithium iron phosphate loading was 1.9 mg cm⁻¹. -2 -2.6 mg cm -2 The electrochemical performance was then tested, and the cycling performance is shown in Figure 8. Under the test conditions of 60 °C and 1 C, the initial capacity was 143.5 mAh g⁻¹. -1 After 700 cycles, the battery capacity is 116.09 mAhg. -1 The capacity retention rate was 80.89%.

[0058] It can be seen that the present invention can realize a polymer solid electrolyte lithium metal battery with high ionic conductivity and excellent cycle stability, which can meet the needs of actual production and application.

[0059] Example 2:

[0060] The difference between Example 2 and Example 1 is that the mass of iron-doped molybdenum disulfide added is different. Specifically, in the synthesis of the composite electrolyte slurry, iron-doped molybdenum disulfide is mixed and stirred at 3% of the mass of PEO for 30 min, while the rest is the same as in Example 1.

[0061] The prepared composite solid electrolyte has the following properties:

[0062] At room temperature, the ionic conductivity is 5.57 × 10⁻⁶. -5 S cm - ¹.

[0063] The results showed that the addition of too little iron-doped molybdenum disulfide in Example 2 resulted in a relatively low ionic conductivity.

[0064] Example 3:

[0065] The difference between Example 3 and Example 1 is that the mass of iron-doped molybdenum disulfide added is different. Specifically, in the synthesis of the composite electrolyte slurry, iron-doped molybdenum disulfide is mixed and stirred at 7% of the mass of PEO for 30 min. The rest is the same as in Example 1.

[0066] The prepared composite solid electrolyte has the following properties:

[0067] At room temperature, the ionic conductivity is 4.92 × 10⁻⁶. -5 S cm -1 .

[0068] The results showed that in Example 3, the addition of too much iron-doped molybdenum disulfide caused the filler to agglomerate, resulting in a relatively low ionic conductivity.

[0069] Example 4:

[0070] The difference between Example 4 and Example 1 is the use of MoS2 powder. Specifically, in the synthesis of the composite electrolyte slurry, MoS2 powder is mixed and stirred at 5% of the mass of PEO for 30 min, while the rest is the same as in Example 1.

[0071] The prepared composite solid electrolyte has the following properties:

[0072] At room temperature, the ionic conductivity is 3.82 × 10⁻⁶. -5 S cm -1 Under test conditions of 60 °C and 1 C, the initial capacity was 140.81 mAhg. -1 After 700 cycles, the battery capacity is 94.96 mAhg. -1 The capacity retention rate was only 67.44%.

[0073] The results showed that the MoS2 powder added in Example 4 failed to effectively promote the dissociation of LiTFSI.

[0074] Example 5:

[0075] The difference between Example 5 and Example 1 is that only conductive lithium salt and PEO are added. Specifically, LiTFSI and PEO are mixed and stirred for 30 min, while the rest is the same as in Example 1.

[0076] The prepared composite solid electrolyte has the following properties:

[0077] At room temperature, the ionic conductivity is 5.08 × 10⁻⁶. -6 S cm -1 .

[0078] The results show that the performance of the unmodified PEO-based solid electrolyte is poor.

[0079] Results and Discussion:

[0080] Iron-doped molybdenum disulfide can increase the room temperature ionic conductivity of solid electrolytes from 5.08×10⁻⁶ to 6.18×10⁻⁵ and effectively improve cycle stability, maintaining 80% capacity retention after 700 cycles at 1C rate.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, characterized in that, Includes the following steps: S1. Iron-containing compounds are reacted with ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 After mixing and dissolving 4H2O and deionized water, the mixture is heated and stirred, evaporated, cooled, filtered, and recrystallized to obtain the precursor product; S2, the precursor product, thiourea, and deionized water are mixed and dissolved, and then transferred to the inner liner of the reactor for hydrothermal reaction. After cooling, the product is washed and centrifuged multiple times, and then dried in a vacuum drying oven to obtain iron-doped molybdenum disulfide (Fe-MoS2); S3, Fe-MoS2 is introduced as a filler into the polymer-based electrolyte slurry, and then dried to obtain a composite solid electrolyte.

2. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 1, characterized in that, The iron-containing compound mentioned in S1 is at least one of Fe2(SO4)3, Fe(NO3)3, and FePO4.

3. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 1, characterized in that, The heating and stirring described in S1 are carried out at a temperature of 90-100 ℃ for 30-90 min, with a volume of deionized water of 80-120 mL; the recrystallization described in S1 is carried out at a temperature of 80-90 ℃.

4. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 1, characterized in that, The mixing and dissolution described in S2 involves a precursor to thiourea mass ratio of 1:1.5-2 and a deionized water volume of 35-50 mL.

5. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 1, characterized in that, The hydrothermal reaction described in S2 is carried out at a temperature of 180 ℃-220 ℃ for 18 h-30 h. After cooling, the mixture is washed and centrifuged multiple times with deionized water and an organic solvent, wherein the organic reagent is either acetone or ethanol. The centrifugation speed is 3500-8000 r / min and the centrifugation time is 5-10 min. The temperature of the vacuum drying oven is 60-80 ℃ and the drying time is 12-24 h.

6. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 1, characterized in that, The polymer matrix described in S3 is at least one of PEO, PVC, PEG, PMA, PVDF, PVDF-HFP, PAN-PVA, and PAN-PEG; the molar ratio of the repeating unit of the polymer matrix to lithium in the conductive lithium salt in the solid electrolyte is 10:1, and the conductive lithium salt is at least one of LiTFSI, LiFSI, LiPF6, LiBF4, and LiDFOB; the iron-doped molybdenum disulfide is 1%-10% of the polymer matrix mass.

7. The method for preparing an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 1, characterized in that, The slurry described in S3 contains an organic solvent that is at least one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; the mass ratio of the organic solvent to the polymer matrix is ​​10-20:1; the drying process described in S3 is carried out at a temperature of 50℃-70℃ for 12h-24h.

8. An iron-doped molybdenum disulfide / polymer-based composite solid electrolyte, characterized in that, The iron-doped molybdenum disulfide / polymer-based composite solid electrolyte is prepared according to any one of claims 1-7, and the composite solid electrolyte has the following properties: at room temperature, the ionic conductivity is 4.9-2.4 × 10⁻⁶. -5 ~6.18×10 -5 S cm -1 The battery assembled with LiFePO4 as the positive electrode exhibits a capacity of 143.5 mAh / g at 1C. - The initial discharge specific capacity¹, after 700 cycles, showed a reversible discharge capacity of 116.09 mAh g⁻¹. - ¹, with a capacity retention rate of 80.89%, while the coulombic efficiency remains stable at 99.9%.

9. The application of the iron-doped molybdenum disulfide / polymer-based composite solid electrolyte as described in claim 8, characterized in that, They are assembled into an all-solid-state battery, including a positive electrode, a negative electrode, and an iron-doped molybdenum disulfide / polymer-based composite solid electrolyte membrane.

10. The application of the iron-doped molybdenum disulfide / polymer-based composite solid electrolyte according to claim 9, characterized in that, The cathode material mentioned above includes LiFePO4 and LiNi. x Co y Mn 1-y O2, 0≤x≤1, 0≤y≤1.

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