MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method
Through MOF-ionic liquid composite solid polymer electrolyte, the safety hazards and energy density improvement problems of lithium metal batteries in traditional electrolytes are solved, and a high-performance solid lithium metal battery is achieved.
Patent Information
- Application Number
- CN202510151384.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-11
- Publication Date
- 2025-05-13
AI Technical Summary
Traditional lithium-ion batteries have encountered theoretical limits in improving energy density, and lithium dendrites are easily formed when lithium metal comes into contact with liquid electrolytes, resulting in safety hazards. Solid polymer electrolytes have insufficient ionic conductivity, poor mechanical properties and limited interface stability at room temperature, which limit their large-scale applications.
Using MOF-ionic liquid composite solid polymer electrolyte, Lewis acid-base action occurs by introducing unsaturated metal sites and anions of lithium salts into MOF, binding the anions and releasing free lithium ions, and using ionic liquid to fill the holes of MOF to promote the rapid transmission of lithium ions.
It improves lithium ion conductivity, lithium ion migration number, electrochemical stability window, mechanical strength, interface stability and high temperature stability, significantly inhibits the growth of lithium dendrites, and improves the safety and energy density of lithium metal batteries.
Smart Images
Figure CN119994208A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of solid polymer batteries, and specifically relates to a MOF-ionic liquid composite solid polymer electrolyte, a battery and a preparation method thereof. Background Art
[0002] Lithium-ion batteries are rechargeable batteries that are widely used in consumer electronics, electric vehicles, and energy storage systems. However, traditional lithium-ion batteries usually use graphite anodes, and their energy density has been close to the theoretical limit, which makes it difficult to meet the market's urgent demand for lithium batteries with higher energy density. In recent years, lithium metal has been considered an ideal alternative material to traditional graphite anodes, which can meet the market's demand for high-energy-density lithium batteries. This is mainly due to the ultra-high theoretical specific capacity of lithium metal (3860mA hg -1 ) and extremely low electrochemical potential (-3.04 V vs. H + / H2). However, due to its highly active chemical properties, lithium metal is prone to form lithium dendrites when in contact with liquid electrolytes, which can cause safety hazards and lead to serious problems such as battery short circuits. To address these challenges, solid electrolytes (SSEs) have attracted widespread attention as alternatives to liquid electrolytes. They can not only significantly improve the safety of lithium metal batteries, but also have the potential to further increase energy density. Among them, solid polymer electrolytes have become a research hotspot due to their advantages such as good flexibility, easy processing, excellent interface compatibility, low cost and light weight. However, the current problems of such electrolytes at room temperature, such as insufficient ionic conductivity, poor mechanical properties and limited interface stability, are still the main obstacles to their large-scale application.
[0003] Ionic liquids (ILs) are widely used as plasticizers for solid polymer electrolytes due to their superior chemical stability, non-flammability, low volatility, and high ionic conductivity. Adding ionic liquids to solid electrolytes can reduce the crystallinity of the polymer matrix and effectively improve the ionic conductivity of solid polymer electrolytes. Although ionic liquids can effectively improve the ionic conductivity of solid polymer electrolytes, they still have some defects: (1) the incompatibility between polymers and ionic liquids may lead to battery capacity decay; (2) the addition of ionic liquids may reduce the migration number (t Li+ ); (3) It may also reduce the mechanical strength of the polymer matrix, making it unable to resist the growth of dendrites and eventually lead to battery short circuit.
[0004] The combination of metal organic framework materials (MOF) and ionic liquids (IL) can not only make up for the above shortcomings of ionic liquids, but also further improve the ionic conductivity, mechanical strength, interface stability and resistance to dendrites of solid polymer electrolytes. The unsaturated metal sites of MOF react with the anions of lithium salts through Lewis acid-base reactions, firmly binding the anions in MOF and releasing free lithium ions. IL fills the pores of MOF to promote the rapid transmission of lithium ions. The synergistic effect of MOF and IL can even out the lithium ion flux and promote the uniform deposition of lithium ions, thereby reducing the formation of lithium dendrites and increasing interface stability. In addition, the addition of MOF can improve the mechanical properties of solid polymer electrolytes, which can further inhibit the growth of lithium dendrites. Summary of the invention
[0005] The purpose of the present invention is to provide a MOF-ionic liquid composite solid polymer electrolyte, a battery and a preparation method in view of the defects of the background technology. The prepared solid polymer electrolyte has high lithium ion conductivity, high lithium ion migration number, wide electrochemical stability window, good mechanical strength, good interface stability, good high temperature stability and excellent ability to inhibit lithium dendrite growth, and a battery using the solid polymer electrolyte and a preparation method of the battery.
[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:
[0007] Step 1: Preparation of NiCo-MOF: Dissolve cobalt salt, nickel salt and organic ligand uniformly in an organic solvent, then conduct a hydrothermal reaction, and obtain NiCo-MOF powder by filtering, washing and drying.
[0008] Step 2: Preparation of MOF-ionic liquid composite solid polymer electrolyte: Py 14 TFSI, lithium salt (LiTFSI) and PVDF-HFP are dissolved in an appropriate amount of NMP, DMF or acetone solution, and are evenly mixed by magnetic stirring to form a polymer dispersion. The ground NiCo-MOF is dissolved in a small amount of NMP solvent and ultrasonically dispersed to form a NiCo-MOF dispersion. The NiCo-MOF dispersion is added to the polymer dispersion and magnetically stirred to form a solid polymer electrolyte precursor. The precursor is poured into a polytetrafluoroethylene tank, and vacuum heated and dried to obtain a MOF-ionic liquid composite solid electrolyte.
[0009] Step 3, preparing a battery: assembling the MOF-ionic liquid composite solid polymer electrolyte of step 2 with positive and negative electrode materials into a button-type or soft-pack lithium metal battery.
[0010] Furthermore, in step 1, the cobalt salt is one or both of cobalt nitrate hexahydrate and cobalt chloride hexahydrate; the nickel salt is one or both of nickel nitrate hexahydrate and nickel chloride hexahydrate; and the mass ratio of the cobalt salt to the nickel salt is 1:(0.1-1).
[0011] Furthermore, in step 1, the organic ligand is one or two of terephthalic acid and trimesic acid mixed in any proportion; the mass ratio of cobalt salt, nickel salt and organic ligand is 1:(0.1-1):1.
[0012] Furthermore, in step 1, the hydrothermal reaction temperature is 110-190°C, the time is 10-17.5h, the cleaning solvent is one of methanol or ethanol, the number of cleaning times is 5-7 times, and the drying temperature is 50-85°C.
[0013] Furthermore, in step 2, the mass ratio of the ionic liquid, LiTFSI and PVDF-HFP is (1-3):(2-9):6, the addition amount of NiCo-MOF is 5-15% of the total mass of LiTFSI, PVDF-HFP and ionic liquid, and the film thickness of the MOF-ionic liquid composite solid electrolyte is 50 μm to 300 μm.
[0014] Furthermore, in step 2, the vacuum degree of the vacuum heating and drying is 0.01-0.08 MPa, and the drying temperature is 70-100°C.
[0015] Furthermore, in step 3, the active material of the positive electrode is one or more combinations of lithium cobalt oxide, lithium iron phosphate, and lithium nickel cobalt manganese oxide; and the active material of the negative electrode is metallic lithium.
[0016] Furthermore, in step 3, the size of the soft-pack lithium metal battery is (5-10)×(6-12) cm, and the soft-pack battery is assembled in the order of positive electrode-solid polymer electrolyte-negative electrode, and the assembled soft-pack lithium metal battery is pressed at a pressure of 3-10 MPa for 10-30 min.
[0017] Furthermore, in step 3, after the button-type and soft-pack lithium metal batteries are assembled, they are placed in an oven at 50 to 80° C. for 10 to 24 hours.
[0018] Compared with the prior art, the present invention has the following beneficial effects: The MOF-ionic liquid composite solid polymer electrolyte of the present invention has excellent performance, and the ionic conductivity is as high as 6.8×10 -4 S cm -1, the lithium ion migration number is 0.49, and the electrochemical window is 4.8V. After being assembled into a solid-state lithium metal battery, it exhibits excellent electrochemical performance. At a charge and discharge rate of 0.5C, the Li / / LiFePO4 battery has a charge and discharge capacity of 158.5mAh g -1 The discharge specific capacity of the battery is 1.57W, and it has good cycle stability. After 800 cycles at room temperature, the capacity retention rate is as high as 92.7%. In addition, the Li / / LiFePO4 button battery prepared by this method has good high-temperature stability. At 100°C and 3C current, it can stably cycle 600 times, and the capacity retention rate is 85.7%. The Li / / LiFePO4 soft-pack battery prepared by this method has high safety performance and can withstand tests in extreme environments such as folding, puncture, and cutting. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a scanning electron microscope (SEM) photo of NiCo-MOF;
[0020] Figure 2 a, b and c are pure PVDF-HFP, Py 14 TFSI / PVDF-HFP, Py 14 SEM image of TFSI / NiCo-MOF / PVDF-HFP solid polymer electrolyte;
[0021] Figure 3 For Py 14 Physical picture of TFSI / NiCo-MOF / PVDF-HFP solid polymer electrolyte;
[0022] Figure 4 The middle is a comparison chart of the ionic conductivity of three different solid electrolytes;
[0023] Figure 5 A comparison chart of the rate performance of solid-state lithium metal batteries assembled with three different solid electrolytes using LiFePO4 as the positive electrode and lithium sheet as the negative electrode;
[0024] Figure 6 A comparison of the cycling performance of solid-state lithium metal batteries assembled with three different solid electrolytes, using LiFePO4 as the positive electrode and lithium sheet as the negative electrode at room temperature and 0.5C;
[0025] Figure 7 Py 14 Cycling performance diagram of solid lithium metal battery assembled with TFSI / NiCo-MOF / PVDF-HFP solid electrolyte with LiFePO4 as positive electrode and lithium sheet as negative electrode at 100℃ and 3C.
[0026] Figure 8 Py 14Safety performance test diagram of a solid-state soft-pack lithium metal battery assembled with TFSI / NiCo-MOF / PVDF-HFP solid electrolyte, using LiFePO4 as the positive electrode and lithium sheet as the negative electrode. DETAILED DESCRIPTION
[0027] The present invention is further described in detail below in conjunction with the accompanying drawings, embodiments and comparative examples. However, the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0028] Example 1 A MOF-ionic liquid composite solid electrolyte, the solid electrolyte comprising a polymer, MOF and an ionic liquid, the polymer being PVDF-HFP, the MOF being NiCo-MOF, and the ionic liquid being 1-butyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide (Py 14 TFSI).
[0029] A MOF-ionic liquid composite solid polymer electrolyte, a battery and a preparation method, comprising the following steps:
[0030] Step 1, preparation of NiCo-MOF: 0.59 g of cobalt nitrate hexahydrate, 0.24 g of nickel chloride hexahydrate and 0.63 g of trimesic acid were uniformly dissolved in 80 mL of ethanol, and then hydrothermally reacted at 150 ° C for 15 h, and then filtered and washed with methanol three times, and finally dried in an oven at 60 ° C for 12 h to obtain NiCo-MOF powder. The SEM photo of the NiCo-MOF is shown in Figure 1 ,from Figure 1 It can be seen that its morphology is a three-dimensional nanoflower morphology composed of two-dimensional nanosheets;
[0031] Step 2: Preparation of MOF-ionic liquid composite solid polymer electrolyte: 0.6 g Py 14 TFSI, 0.4g lithium salt (LiTFSI) and 0.6g PVDF-HFP were dissolved in 4g NMP, and magnetically stirred and mixed at a speed of 2000 rpm to form a polymer dispersion. The ground 0.05g NiCo-MOF powder was dissolved in 1g NMP solvent and ultrasonically dispersed to form a NiCo-MOF dispersion. The NiCo-MOF dispersion was added to the polymer dispersion, and magnetically stirred at a speed of 2000 rpm to form a solid polymer electrolyte precursor. The precursor was poured into a polytetrafluoroethylene tank, and then placed in a vacuum drying oven, the vacuum degree was drawn to 0.08MPa, the temperature was set to 70°C, the heating time was 12 to 48h, and the MOF-ionic liquid composite solid electrolyte, i.e., Py 14TFSI / NiCo-MOF / PVDF-HFP composite solid electrolyte, denoted as MOF-PISE. The SEM photo of the MOF-PISE composite solid electrolyte is shown in Figure 3 ,from Figure 3 It can be seen that it has a light purple color;
[0032] Step 3, prepare the battery: assemble the MOF-ionic liquid composite solid polymer electrolyte of step 2 with the positive and negative electrode materials into a button or soft-pack lithium metal battery. The positive electrode material used for assembling button or soft-pack lithium metal batteries is lithium iron phosphate (LiFePO4), and the negative electrode material used is metal lithium foil. The prepared button lithium metal battery uses a CR2032 button battery shell and is assembled in the order of positive electrode-solid polymer electrolyte-negative electrode. The prepared soft-pack lithium metal battery uses an aluminum plastic film as a battery shell, and the pole piece size is 5×6cm. It is assembled in the order of positive electrode-solid polymer electrolyte-negative electrode, and the assembled soft-pack lithium metal battery is pressed at a pressure of 6MPa for 20min. In addition, after the prepared button and soft-pack lithium metal batteries are assembled, they are left to stand in an oven at 60°C for 12h.
[0033] Comparative Example 1
[0034] The difference between Comparative Example 1 and Example 1 is that Py 14 TFSI ionic liquid and NiCo-MOF, namely pure PVDF-HFP solid polymer electrolyte, denoted as PSE.
[0035] Comparative Example 2
[0036] Comparative Example 2 is different from Example 2 in that: NiCo-MOF is not added in step 2, i.e., Py 14 TFSI / PVDF-HFP composite solid polymer electrolyte, denoted as PISE.
[0037] Figure 2 a, b, and c are surface SEM images of three solid electrolytes: PSE, PISE, and MOF-PISE. 14 The PISE of TFSI showed smaller particles and fewer pores than the PSE. Apparently, when NiCo-MOF was further added, a denser solid electrolyte membrane with smaller grains was formed, indicating that NiCo-MOF can further regulate the crystallinity of the polymer matrix.
[0038] Figure 4 are the ionic conductivities of the three solid electrolytes at different temperatures. At room temperature, the ionic conductivities of PSE, PISE, and MOF-PISE are: 4.70×10 -5 S cm -1 , 2.2×10-4 S cm -1 , 6.8×10 -4 S cm -1 By comparison, it can be seen that PSE has the lowest ionic conductivity. 14 The ionic conductivity was improved after adding TFSI ionic liquid, and the MOF-PISE solid electrolyte with further addition of NiCo-MOF showed the highest ionic conductivity.
[0039] Figure 5 Figure 2 shows the rate performance of LiFePO4 / / Li button cells assembled with three solid electrolytes at room temperature. The LiFePO4 / MOF-PISE / Li battery exhibited 158.5, 150.6, 135.8, 124.4, 117.3 and 96.2 mAh g at 0.1, 0.2, 0.5, 0.8, 1 and 2C, respectively. -1 The discharge capacity of LFP / MOF-PISE / Li was 0.2C, indicating its excellent rate performance. In addition, when the rate was restored to 0.2C, the capacity of LFP / MOF-PISE / Li was almost not lost and immediately recovered to the initial value, indicating its excellent reversibility. However, the discharge capacity and rate performance of PISE and PSE were lower than those of MOF-PISE. Figure 5 Description, P 14 TFSI is able to improve the specific capacity and rate performance of the solid polymer electrolyte, which is attributed to the enhanced ionic conductivity of PISE. In addition, the incorporation of NiCo-MOF further improves the electrochemical performance of the solid polymer electrolyte.
[0040] Figure 6 The cycling performance of LiFePO4 / / Li button cells assembled with three solid electrolytes at room temperature and 0.5C. The initial discharge capacities of LiFePO4 / / Li based on PSE, PISE and MOF-PISE are 97.9, 109.2 and 131.1 mAh g, respectively. -1 After 800 cycles, the discharge capacities of PSE and PISE only retained 74.8% and 82% of their initial values, respectively. In contrast, LFP / MOF-PISE / Li still had a discharge capacity of 121.6 mAh g after 800 cycles. -1 The capacity of the battery was 2.377W, which maintained 92.7% of the initial capacity, and the average coulombic efficiency exceeded 99.9%. This shows that the lithium metal battery based on the MOF-PISE composite solid electrolyte has excellent cyclability.
[0041] Figure 7The cycling performance of LiFePO4 / / Li button cells assembled with three solid electrolytes at 100°C and 3C. The LFP / MOF-PISE / Li battery was cycled at 100°C and maintained 85.7% of its capacity after 600 cycles at 3C. The excellent electrochemical performance of LFP / MOF-PISE / Li at high temperatures indicates that the MOF-PISE composite solid electrolyte has excellent ionic conductivity and a stable interface between the solid electrolyte and the electrode at high temperatures.
[0042] Figure 8 To test the safety performance of LiFePO4 / / Li soft-pack batteries assembled with MOF-PISE as solid-state electrolyte, the soft-pack batteries were able to ignite a small light bulb after being bent, punctured, cut, and other tests in the air, demonstrating their high safety. This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.
Claims
1. A MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method, characterized in that: The following steps are involved: Step 1: Preparation of NiCo-MOF: Dissolve cobalt salt, nickel salt and organic ligand uniformly in an organic solvent, then conduct a hydrothermal reaction, and obtain NiCo-MOF powder by filtering, washing and drying. Step 2: Preparation of MOF-ionic liquid composite solid polymer electrolyte: Py 14 TFSI, lithium salt (LiTFSI) and PVDF-HFP are dissolved in an appropriate amount of NMP, DMF or acetone solution, and are evenly mixed by magnetic stirring to form a polymer dispersion. The ground NiCo-MOF is dissolved in a small amount of NMP solvent and ultrasonically dispersed to form a NiCo-MOF dispersion. The NiCo-MOF dispersion is added to the polymer dispersion and magnetically stirred to form a solid polymer electrolyte precursor. The precursor is poured into a polytetrafluoroethylene tank, and vacuum heated and dried to obtain a MOF-ionic liquid composite solid electrolyte. Step 3, preparing a battery: assembling the MOF-ionic liquid composite solid polymer electrolyte of step 2 with positive and negative electrode materials into a button-type or soft-pack lithium metal battery.
2. A MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 1, the cobalt salt is one or both of cobalt nitrate hexahydrate and cobalt chloride hexahydrate; the nickel salt is one or both of nickel nitrate hexahydrate and nickel chloride hexahydrate; and the mass ratio of the cobalt salt to the nickel salt is 1:(0.1-1).
3. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 1, the organic ligand is one or two of terephthalic acid and trimesic acid mixed in any proportion; the mass ratio of cobalt salt, nickel salt and organic ligand is 1:(0.1-1):
1.
4. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 1, the hydrothermal reaction temperature is 110-190°C, the time is 10-17.5h, the cleaning solvent is one of methanol or ethanol, the number of cleaning times is 5-7 times, and the drying temperature is 50-85°C.
5. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 2, the mass ratio of the ionic liquid, LiTFSI and PVDF-HFP is (1-3):(2-9):6, the addition amount of NiCo-MOF is 5-15% of the total mass of LiTFSI, PVDF-HFP and ionic liquid, and the film thickness of the MOF-ionic liquid composite solid electrolyte is 50μm-300μm.
6. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 2, the vacuum degree of the vacuum heating and drying is 0.01-0.08 MPa, the drying temperature is 70-100° C., and the time is 12-48 hours.
7. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 3, the active material of the positive electrode is one or more combinations of lithium cobalt oxide, lithium iron phosphate, and lithium nickel cobalt manganese oxide; and the active material of the negative electrode is metallic lithium.
8. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 3, the size of the soft-pack lithium metal battery is (5-10)×(6-12) cm, and the soft-pack battery is assembled in the order of positive electrode-solid polymer electrolyte-negative electrode. The assembled soft-pack lithium metal battery is pressed at a pressure of 3-10 MPa for 10-30 min.
9. The MOF-ionic liquid composite solid polymer electrolyte, battery and preparation method according to claim 1, characterized in that: In step 3, after the button-type and soft-pack lithium metal batteries are assembled, they are placed in an oven at 50 to 80° C. for 10 to 24 hours.