Polymer aqueous aluminum-ion battery and preparation method thereof

Abstract

The application discloses a polymer aqueous aluminum ion battery and a preparation method thereof, and relates to the field of aluminum ion batteries, and is characterized in that the aluminum ion battery comprises a positive electrode, a negative electrode, an aqueous electrolyte, and a diaphragm linking the positive electrode and the negative electrode, the battery positive electrode is a PTMA polymer, the negative electrode is an aluminum foil, and the electrolyte is an aluminum trifluoromethanesulfonate electrolyte; the nitrogen-oxygen free radical material is applied to the aluminum ion battery system for the first time, which adds a new type of organic compound to the aqueous aluminum ion battery positive electrode material, meanwhile, the aqueous electrolyte is used, the battery system becomes safer, the solubility of the organic electrode material is greatly reduced, the battery system is more stable, the polymer aqueous aluminum ion battery prepared by the application has the advantages of cycle stability, high energy density, high safety, low cost, cleanness, environmental protection, simple preparation process and the like, and has great potential to be applied to large-scale energy storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aluminum ion batteries, in particular to a polymer aqueous aluminum ion battery and a preparation method thereof. BACKGROUND

[0002] With the continuous consumption of fossil fuels and the increasingly severe global climate, there is an urgent need to develop new energy storage structures. At present, renewable energy sources such as solar, wind and tidal energy are attracting much attention, but these renewable energy sources are intermittent and difficult to provide continuous power supply, so the integration of renewable resources and energy storage systems is imperative. Lithium ion batteries are one of the most mature and efficient energy storage systems. However, limited lithium resource reserves, inherent safety risks and high costs hinder the application of lithium ion batteries in large-scale energy storage. At present, due to the high theoretical capacity of aluminum ion batteries (mass specific capacity: 2980 mAh / g, volume specific capacity: 8056 mAh / cm 3 ), inherent high safety, low cost and abundant reserves, aluminum ion batteries are expected to become the next generation of practical battery systems to supplement the deficiencies of lithium ion batteries in large-scale energy storage.

[0003] Most of the inorganic materials currently studied have the problem of poor reversibility due to Al 3+ The strong electrostatic interaction between the positive electrode main body usually leads to kinetic lag and high overpotential during intercalation / deintercalation, and even causes serious structural collapse of the material. Compared with inorganic materials, organic positive electrode materials have multiple advantages: (1) unique coordination reaction mechanism avoids high electrostatic repulsion caused by Al 3+ insertion, improving the reaction kinetics. (2) The structure of organic compounds is highly adjustable and designed, which can improve the electrochemical performance of electrode materials by introducing substituents and functional groups. (3) Organic electrode materials are mainly composed of sustainable elements such as C, H, O and N, and do not rely on limited mineral resources. (4) The synthesis of organic electrode materials does not require high-temperature sintering, which can effectively reduce energy consumption and greenhouse gas emissions. (5) Compared with various transition metal inorganic materials, organic compounds are easier to handle and recycle. Based on the above analysis, it is crucial to develop aluminum ion battery cathodes that are resource renewable, low cost and environmentally friendly in preparation conditions.

[0004] Although the organic positive electrode material has many advantages, its high solubility in the electrolyte is fatal. Therefore, it is essential to develop an organic water-based aluminum ion battery system to improve the cycle stability of the organic electrode material. The most widely used electrolyte in the current aluminum ion battery is the room temperature ionic liquid prepared by aluminum chloride and 1-ethyl-3-methylimidazole (EMIC) and the ionic liquid prepared by aluminum chloride and urea. However, both of these two organic electrode materials are easily dissolved in these two electrolytes, the ionic liquid has a high cost, the urea-based electrolyte has a narrow electrochemical window, and the electrolyte has a high viscosity, which is not conducive to ion migration. While aqueous solution has a high ion migration rate, and water-based electrolyte has the advantages of non-flammability, low cost and environmental friendliness, and most importantly, it greatly reduces the dissolution of the organic electrode material, which is of great significance for realizing renewable large-scale energy storage.

[0005] So far there has been no report on the use of nitroxyl radical materials in aluminum ion batteries. SUMMARY

[0006] The first aspect of the present application aims to provide a polymer water-based aluminum ion battery with excellent electrochemical performance.

[0007] The technical solutions adopted by the present application are as follows:

[0008] A polymer water-based aluminum ion battery, characterized in that: the aluminum ion battery comprises a positive electrode, a negative electrode, a water-based electrolyte, and a separator separating the positive electrode and the negative electrode, the positive electrode of the battery is a nitroxyl radical functionalized methacrylate polymer (PTMA), the negative electrode is an aluminum foil, and the electrolyte is an aluminum triflate water-based electrolyte.

[0009] The polymer water-based aluminum ion battery of the present application uses a water-based electrolyte for the electrolyte, which greatly reduces the dissolution of the positive electrode material, and the positive electrode material polymerizes small molecules into macromolecular polymer PTMA, further improving the stability of the positive electrode material and the cycle life of the aluminum ion battery. This electrode material can realize the increase of the proportion of active material PTMA to ninety percent without adhesion, and can successfully construct a water-based soft package battery, which provides a foundation for the commercialization of the water-based aluminum ion battery system.

[0010] The second aspect of the present application is to provide a preparation method of a polymer water-based aluminum ion battery, characterized in that it comprises the following steps:

[0011] (1) Preparation of positive electrode sheet:

[0012] The active material PTMA and carbon nanotubes CNT are placed in a mortar according to a certain mass ratio, a solvent is added, and grinding is performed for 2-3 h. The solvent is volatilized to near dryness, and then the prepared electrode material is soaked in an aluminum trifluoromethanesulfonate electrolyte for 8-15 h, and then dried to prepare a positive electrode sheet.

[0013] (2) Preparation of a water-based aluminum ion battery:

[0014] The prepared positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte are assembled into a Swagelok type mold battery or a soft package battery.

[0015] Further, in step (1):

[0016] In the active material PTMA and carbon nanotubes CNT, the mass content of PTMA is 10%-90%.

[0017] A binder is further added to the active material PTMA and carbon nanotubes CNT.

[0018] The binder is PVDF, and the optimal mass ratio of the active material PTMA, carbon nanotubes CNT, and the binder PVDF is 3:6:1.

[0019] The polymer PTMA is prepared by the following method: 2,2,6,6-tetramethylpiperidine functionalized methacrylate monomer is dissolved in N,N-dimethylformamide, an azobisisobutyronitrile initiator is added to the solution, the solution is purged with N2 for 20 minutes, the reaction liquid is reacted at 70°C for 24 hours, the reaction is terminated by ice water bath cooling, the product is diluted with DMC, precipitated with n-hexane for 3 times, and vacuum dried to obtain a precursor polymer. The precursor polymer is dissolved in 80 ml of a methanol solvent, and then oxidized with 5 ml of H2O2 in the presence of Na2WO4 for 48 hours to obtain the product PTMA.

[0020] In step (1), the prepared electrode material is soaked in a 1 mol / L aluminum trifluoromethanesulfonate aqueous solution for 12 h, and the soaking temperature is 25°C.

[0021] In step (2):

[0022] The negative electrode sheet is an aluminum foil, the electrolyte is a 1 mol / L aluminum trifluoromethanesulfonate aqueous solution, and the separator is GF / A.

[0023] In step (2), the positive electrode sheet is cyclically activated for 50-100 cycles at a 2C charging rate and a 0.5C discharging rate.

[0024] In step (2), the polymer aqueous aluminum ion soft package battery is prepared, wherein the positive carbon paper current collector and the negative aluminum foil are both square with a size of 1.5*1.5 cm, the separator is square with a size of 2*2 cm, the electrolyte is 3 mol / L aluminum triflate aqueous solution, the positive tab is selected from a molybdenum sheet with a thickness of 200 microns, and the negative tab is selected from an aluminum sheet with a thickness of 200 microns.

[0025] Preferably, the assembled soft package battery needs to be subjected to a pressure of 50-80 N.

[0026] The beneficial effects of the present application are as follows:

[0027] (1) The present application provides a novel aqueous aluminum ion battery construction method. The nitroxyl radical material (PTMA) is applied to the aluminum ion battery system for the first time, which adds a new type of organic compound to the positive electrode material of the aqueous aluminum ion battery. Thanks to the fast redox kinetics of the nitroxyl radical material, the problem of slow ion migration and poor kinetics of most aluminum ion batteries at present is well solved. In addition, the use of aqueous electrolyte makes the battery system safer, and to a great extent, reduces the solubility of organic electrode materials, making the battery system more stable.

[0028] (2) Experiments have proved that the aluminum ion battery system prepared by the present application has excellent cycle stability, high specific capacity, good flame retardant performance and safety performance.

[0029] (3) The nitroxyl radical material of the present application is applied to the aluminum ion battery system, which can be used to prepare Swagelok type mold batteries and polymer aqueous aluminum ion soft package batteries. In summary, the polymer aqueous aluminum ion battery prepared by the present application has the advantages of cycle stability, high energy density, high safety, low cost, clean and environmentally friendly, simple preparation process, etc., and has great potential to be applied to large-scale energy storage.

[0030] The present application will be described in detail below in combination with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The scanning electron microscope (SEM) image of the positive electrode sheet of Example 1 without activation by charging and discharging.

[0032] Figure 2 The scanning electron microscope (SEM) image of the positive electrode sheet of Example 2 after activation by charging and discharging.

[0033] Figure 3 The electrochemical impedance (EIS) test graph of the three different Swagelok type mold batteries prepared in Example 1, Alternative Example 1 and Alternative Example 2.

[0034] Figure 4 Charge-discharge cycle plot of Swagelok type cell prepared for Example 2 at 0.5C.

[0035] Figure 5 Charge-discharge cycle plot of Swagelok type cell prepared for Example 2 at 0.5C.

[0036] Figure 6 Charge-discharge specific capacity comparison plot of Swagelok type cell prepared for Example 2 with different active material ratio at 10mA g-1. -1

[0037] Figure 7 Charge-discharge specific capacity comparison plot of Swagelok type cell prepared for Example 2 with different active material ratio at 10mA g-1. -1

[0038] Figure 8 Charge-discharge cycle plot of soft pack cell prepared for Example 3 at charge rate 2C, discharge rate 0.25C.

[0039] Figure 9 Charge-discharge cycle plot of soft pack cell prepared for Example 3 at charge rate 2C, discharge rate 0.25C.

[0040] Figure 10 Flame retardant performance test plot of soft pack cell prepared for Example 3.

[0041] Figure 11 Stability test plot of soft pack cell prepared for Example 3 in open environment. DETAILED DESCRIPTION

[0042] In the following examples of the present application, the active material used is PTMA.

[0043] The specific synthesis process of polymer PTMA is as follows: in a 25ml round bottom flask, 2,2,6,6-tetramethylpiperidine functionalized methacrylate monomer (2.0g, 8.88mmol) is dissolved in 4.0ml N,N-dimethylformamide (DMF). AIBN (0.91mg, 5.55μmol) is added to the solution, the monomer / AIBN ratio is 1600. The solution is purged with N2for 20 minutes. The reaction solution is reacted at 70℃ for 24 hours. The reaction is terminated by ice water bath cooling, the product is diluted with DMC, precipitated with n-hexane for 3 times, vacuum dried, and 2.1g of product is obtained, the yield is 84%.

[0044] ​​The product (precursor polymer) prepared above 2.0 g was dissolved in 80 ml of methanol solvent, and then oxidized with 5 ml of H2O2 under the catalysis of Na2WO4 for 48 hours. The product PTMA was automatically precipitated as the oxidation proceeded. The red polymer was washed with water and dried in a vacuum oven overnight to obtain 1.64 g of PTMA, with a yield of 82%. SEC characterization showed that the number average molar mass Mn was 405.4 kg / mol, the weight average molar mass Mw was 949.2 kg / mol, and the dispersity was 1.94.

[0045] Example 1:

[0046] PTMA, multi-walled carbon nanotubes, and binder PVDF were mixed in a mortar at a mass ratio of 3 / 6 / 1, and a solvent NMP was added and ground for 3 h until the slurry became viscous. The slurry was uniformly coated on a circular carbon paper current collector with a diameter of 8 mm, and was placed in a vacuum oven at 60°C for drying for 12 h, and was soaked in an aluminum trifluoromethanesulfonate electrolyte environment for 12 h at a soaking temperature of 25°C, thereby completing the preparation of the positive electrode sheet.

[0047] An aluminum sheet with a diameter of 10 mm was washed with dilute hydrochloric acid for three times, and was then dried in a nitrogen atmosphere, thereby completing the preparation of the negative electrode sheet.

[0048] In this example, the separator was a glass fiber separator GF / A.

[0049] The prepared positive electrode, separator, and negative electrode were sequentially placed in a cylindrical battery mold, and then 60 μl of 1 mol / L aluminum trifluoromethanesulfonate electrolyte was injected, and finally the battery was sealed, thereby obtaining a Swagelok type mold battery (diameter 10 mm).

[0050] Alternative Example 1:

[0051] The preparation method was the same as in Example 1, except that the step of “drying the electrode sheet and soaking it in 1 mol / L aluminum trifluoromethanesulfonate electrolyte for 12 h” described in Example 1 was omitted. The prepared battery was marked as a Swagelok type mold battery (without electrolyte balancing).

[0052] Alternative Example 2:

[0053] The preparation method was the same as in Example 1, except that the Swagelok type mold battery prepared by the method described in Example 1 was subjected to activation treatment. The prepared battery was marked as a Swagelok type mold battery (with electrolyte balancing and charge-discharge activation).

[0054] The activation process is as follows: the assembled Swagelok type mold battery is placed on the blue test system to activate the positive electrode sheet, the voltage range is 0.8-1.7V, the charging process current density is adjusted to 222mA g -1 , the discharging process current density is 55.5mA g -1 , and the cycle is about 50 cycles.

[0055] Performance test:

[0056] The performance of the three different positive electrode sheets of Example 1, Alternative Example 1, and Alternative Example 2 is compared as shown in Figures 1-5 .

[0057] First, the unactivated positive electrode sheet of Example 1 is compared with the activated (i.e. after charging and discharging cycles) positive electrode sheet of Alternative Example 2 as shown in Figure 1 , Figure 2 . From the SEM images of Figure 1 and Figure 2 , we can see that the carbon nanotubes and PTMA are not uniformly mixed compared to the unactivated electrode sheet, while in the activated electrode sheet, it is clear that PTMA is very uniformly attached to the carbon nanotubes, which significantly improves the conductivity of the electrode material, enhances the ion migration speed in the electrode material, reduces the resistance of the entire battery system, and enhances the electrochemical performance.

[0058] The three batteries prepared by Example 1, Alternative Example 1, and Alternative Example 2, i.e. the Swagelok type mold battery prepared by Example 1 (electrolyte balancing), the Swagelok type mold battery prepared by Alternative Example 1 (without electrolyte balancing), and the Swagelok type mold battery prepared by Alternative Example 2 (electrolyte balancing and charging and discharging activation), are respectively subjected to electrochemical impedance (EIS) test comparison as shown in Figure 3 . From the electrochemical impedance spectrum (EIS) of Figure 3 , we can see that the charge transfer resistance (R ct ) value of the battery assembled by the electrode sheet without electrolyte treatment is as high as 100000Ω, while the R ct value of the electrode sheet soaked in electrolyte is 10000Ω, and the R ct value after electrolyte soaking and activation (charging and discharging cycles) is only 4000Ω.

[0059] The Swagelok type mold battery prepared by Alternative Example 2 (electrolyte balancing and charging and discharging activation) is subjected to normal charging and discharging cycle test under the test conditions of current density of 55.5mA g -1 and voltage range of 0.8-1.7V as shown in Figures 4-5 . From the cycle testFigure 4 and charge-discharge curves Figure 5 It can be seen that the initial discharge specific capacity is as high as 140mAh g -1 After 290 cycles, the discharge specific capacity remains at 105mAh g -1 The capacity loss rate per cycle is only 0.086%. And after 290 cycles, the charge-discharge platform is still very stable.

[0060] Example 2:

[0061] In this embodiment, the charge-discharge performance of the battery system under different PTMA proportions is mainly tested.

[0062] The battery assembly and test system are the same as in Example 2, except that:

[0063] (1) In this embodiment, the positive electrode sheet of the aluminum ion battery system does not contain a binder. The preparation method of the positive electrode sheet is as follows: PTMA and multi-walled carbon nanotubes are placed in a mortar in a mass ratio of 5 / 5, 8 / 2, and 9 / 1, respectively, isopropanol is added and ground into an electrode slurry, isopropanol is volatilized to near dryness, the material is rolled into a 100μm thick sheet on carbon paper with a glass rod and cut into 8mm diameter circular electrodes, then soaked in 1mol / L aluminum triflate electrolyte for 12h, and then dried in a vacuum oven at 80℃. The preparation of the positive electrode sheet is completed.

[0064] (2) The activation current density is 10mA g -1 , and the current density during testing is 10mA g -1 .

[0065] Performance test:

[0066] From the cycle test Figure 6 and charge-discharge curves Figure 7 It can be seen that the battery system has a discharge specific capacity of more than 90mAh g -1 when the proportion of PTMA is 50%. Although the proportion of PTMA is increased to 90%, the aluminum ion battery of the present application still has a discharge specific capacity of about 60mAh g -1 , and maintains a stable charge-discharge platform, which makes the aluminum ion battery system of the present application have a high energy density.

[0067] Example 3:

[0068] This embodiment is to prepare a soft package battery.

[0069] The preparation method of the electrode slurry of the embodiment is as follows: PTMA, multi-walled carbon nanotubes and binder PVDF are mixed in a mortar at a mass ratio of 3 / 6 / 1, and a solvent NMP is added for grinding for 3h until the slurry becomes viscous.

[0070] The carbon paper with a size of 1.5cm*1.5cm is used as the current collector in this embodiment.

[0071] The size of the positive current collector carbon paper and the negative aluminum sheet of the soft package battery is 1.5*1.5cm, the electrolyte is 3mol / L aluminum triflate aqueous solution, the separator is 2*2cm glass fiber GF / A, the positive tab is selected from a molybdenum sheet with a thickness of 200μm, and the negative tab is selected from an aluminum sheet with a thickness of 200μm. Finally, the soft package battery is packaged with an aluminum plastic film, the electrolyte is injected, the air is discharged, and the package is sealed with a heat sealing machine.

[0072] Performance test:

[0073] The prepared soft package battery is subjected to cycle test, charge-discharge test, and flame retardancy and safety test, respectively, and the results are shown in Figures 8-11 The test voltage range of the soft package battery prepared in this embodiment is 0.8-1.55V, the charge current density is 222mA g -1 , and the discharge current density is 27.75mA g -1 .

[0074] From the cycle test Figure 8 and the charge-discharge curve Figure 9 , it can be seen that the polymer aqueous aluminum ion soft package battery constructed by PTMA in the application still has excellent cycle stability, and the specific capacity remains at 94mAh g -1 during the charge-discharge process of 300 cycles, and maintains a good charge-discharge platform during the entire charge-discharge process. From the flame retardancy test of Figure 10 and the safety test of Figure 11 , it can be seen that the aqueous aluminum ion battery constructed by the application has extremely high safety.

Claims

1. A polymer-based aqueous aluminum-ion battery, characterized in that: The aluminum-ion battery includes a positive electrode, a negative electrode, an aqueous electrolyte, and a separator separating the positive and negative electrodes. The positive electrode is a nitrogen oxide radical-functionalized methacrylate polymer (PTMA) and carbon nanotubes (CNTs). In the active materials PTMA and CNTs, the mass content of PTMA is 10% to 90%. The negative electrode is aluminum foil, and the electrolyte is an aqueous electrolyte of aluminum trifluoromethanesulfonate.

2. A method for preparing the polymer-based aqueous aluminum-ion battery according to claim 1, characterized in that, Includes the following steps: (1) Preparation of positive electrode sheet: The active material PTMA and carbon nanotubes (CNTs) are placed in a mortar at a certain mass ratio, a solvent is added, and the mixture is ground for 2-3 hours. The solvent is then evaporated until it is nearly dry. The prepared electrode material is then immersed in aluminum trifluoromethanesulfonate electrolyte for 8-15 hours and then dried to obtain the positive electrode sheet. (2) Preparation of aqueous aluminum-ion batteries: The positive electrode sheet, negative electrode sheet, separator, and electrolyte prepared above are assembled into a Swagelok-type mold battery or a pouch battery.

3. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 2, characterized in that: A binder is also added to the active material PTMA and carbon nanotubes (CNTs).

4. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 3, characterized in that: The binder is PVDF, and the mass ratio of active material PTMA, carbon nanotubes (CNTs) to binder PVDF is 3:6:

1.

5. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 2, characterized in that: The polymer PTMA was prepared by the following method: 2,2,6,6-tetramethylpiperidine-functionalized methacrylate monomer was dissolved in N,N-dimethylformamide, azobisisobutyronitrile initiator was added to the solution, the solution was purged with N2 for 20 minutes, the reaction solution was reacted at 70°C for 24 hours, the reaction was terminated by cooling in an ice-water bath, the product was diluted with DMC, precipitated three times with n-hexane, and dried under vacuum to obtain the precursor polymer. The precursor polymer was dissolved in 80 ml of methanol solvent, and then oxidized with 5 ml of H2O2 in the presence of Na2WO4 for 48 hours to obtain the product PTMA.

6. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 2, characterized in that: In step (1): the prepared electrode material is immersed in a 1 mol / L aluminum trifluoromethanesulfonate aqueous solution for 12 h at a immersion temperature of 25 °C.

7. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 2, characterized in that, In step (2): the negative electrode sheet is aluminum foil, the electrolyte is 1 mol / L aluminum trifluoromethanesulfonate aqueous solution, and the diaphragm is GF / A.

8. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 2, characterized in that, In step (2): the positive electrode plate is cycled and activated for 50 to 100 cycles at a charging rate of 2C and a discharging rate of 0.5C.

9. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 2, characterized in that, In step (2): a polymer aqueous aluminum-ion soft-pack battery is prepared, wherein: the positive electrode carbon paper current collector and the negative electrode aluminum foil are both square with a size of 1.5*1.5cm, the separator is a square with a size of 2*2cm, the electrolyte is a 3 mol / L aluminum trifluoromethanesulfonate aqueous solution, the positive electrode tab is a 200μm thick molybdenum sheet, and the negative electrode tab is a 200μm thick aluminum sheet.

10. The method for preparing a polymer-based aqueous aluminum-ion battery according to claim 9, characterized in that: The assembled pouch cell needs to be subjected to a pressure of 50-80N.

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