Preparation method and application of a hydrotalcite / MXene chloride ion battery positive electrode material

Abstract

The application provides a preparation method and application of a hydrotalcite / MXene positive electrode material of a chlorine ion battery; the hydrotalcite is first obtained by intercalating nitrate; the hydrotalcite dispersion solution is obtained by delaminating the hydrotalcite in a formamide solution; then MXene is added into the formamide to obtain an MXene dispersion solution; finally, the two dispersion solutions are dropped into a high-concentration sodium chloride solution to react, and the hydrotalcite / MXene superlattice heterostructure with high-order arrangement characteristics and intercalated chlorine anions is obtained as the positive electrode material of the chlorine ion battery based on the delamination strategy from top to bottom, the charge density difference is used to drive the colloidal co-assembly technology, the hydrotalcite / MXene superlattice heterostructure has high-order arrangement characteristics in the ab plane and the like, and the material has the advantages of high chlorine storage capacity, excellent rate characteristics, long cycle life and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chloride ion battery energy; in particular to a preparation method and application of a hydrotalcite / MXene chloride ion battery positive electrode material. BACKGROUND

[0002] One of the most commonly used electrochemical energy storage technologies today is batteries. The performance of rechargeable lithium ion batteries (LIBs) has steadily improved over the past two decades, and as the related technologies approach their limits, the rate of development is slowing year by year. In addition, lithium and cobalt, which are commonly used in LIBs, are non-renewable resources and are very limited in the earth's crust. As a large amount of lithium is consumed, the high cost of lithium hinders the large-scale use of LIBs in the future. Based on this, anion shuttle batteries based on Cl - , F - have become the mainstream of today's battery development.

[0003] Chloride ion batteries have many advantages, including: (1) low cost and sustainability of the chlorine source; (2) the theoretical capacity based on the total electrode is as high as 2500Wh L -1 , comparable to lithium-sulfur batteries. (3) Improved safety due to the dendrite-free performance of its metal negative electrode during cycling. All of these functions are conducive to the sustainability of potential large-scale energy storage applications.

[0004] Hydrotalcite is one of the few intercalation structure materials with interlayer anions, and the type of interlayer anions and the interlayer spacing are highly adjustable. The adjustable interlayer space provides a two-dimensional diffusion channel for the loaded anions, which makes hydrotalcite have anion intercalation / deintercalation characteristics, meeting the primary prerequisite for its use as a positive electrode material for anion batteries. However, the poor conductivity of hydrotalcite powder and the instability of the structure during long-term cycling inhibit the improvement of the battery energy density and other electrochemical properties.

[0005] MXene is a new member of the two-dimensional (2D) material family first reported in 2011, which has excellent properties, including electrical conductivity, flexible structure, hydrophilicity and mechanical stability, which makes it increasingly attractive as an electrode material for electrochemical devices. However, there is currently no report on the application of MXene as an electrode material in chloride ion batteries. SUMMARY

[0006] The purpose of the present application is to provide a preparation method and application of a hydrotalcite / MXene chloride ion battery positive electrode material.

[0007] The present application is realized by the following technical solutions:

[0008] The present application relates to a preparation method of a hydrotalcite / MXene chloride ion battery positive electrode material, comprising the following steps:

[0009] Step 1, soluble inorganic salt M1, soluble inorganic salt M2 are mixed into a mixed metal salt solution in deionized water, sodium hydroxide is added into a sodium hydroxide solution in deionized water, which is slowly dropped into the mixed metal salt solution, the pH of the solution is adjusted to 9, the solution is loaded into a high-pressure reaction kettle, dried in a blast drying oven at 100-130 DEG C for 16-24 h, the reacted solution is washed with deionized water and ethanol to pH 7, dried at 60 DEG C for 24 h, and the carbonated intercalated hydrotalcite is obtained; the carbonated intercalated hydrotalcite sample is dispersed into deionized water, 1-5 M sodium nitrate and a small amount of hydrochloric acid are added, and stirred for 15-25 hours under inert gas protection, then washed with deionized water to neutral, and vacuum dried at 60 DEG C for 10-20 hours to obtain nitrate intercalated hydrotalcite;

[0010] Step 2, the nitrate intercalated hydrotalcite is added into formamide to configure a hydrotalcite dispersion liquid, and the delamination is carried out by continuous stirring for more than 48 h, and the supernatant is taken; the MXene is added into formamide and stirred to obtain a MXene solution;

[0011] Step 3, the supernatant and the MXene solution are dropped into a round-bottom flask containing a high-concentration sodium chloride solution, inert gas is introduced into the round-bottom flask, stirring is continued for 2 h after titration, centrifugation is carried out, and the product is washed with deionized water and alcohol, and freeze-dried to obtain a hydrotalcite / MXene chloride ion battery positive electrode material.

[0012] Preferably, in step 1, M1 in the soluble inorganic salt M1 is any one or several of Ni 2+ , Co 2+ , Ti 2+ , Cr 2+ or Zn 2+ ; M2 in the soluble inorganic salt M2 is any one or several of Fe 3+ , Mn 3+ , Ti 3+ , Cr 3+ or Co 3+ .

[0013] Preferably, in step 1, the concentration of the soluble inorganic salt M1 is 0.001-0.5 mol / L, and the concentration of the soluble inorganic salt M2 is 0.001-0.5 mol / L.

[0014] Preferably, in step 2, the concentration of the dispersion liquid is 1 mg / mL.

[0015] Preferably, in step 2, the concentration of the MXene solution is 1 mg / mL.

[0016] Preferably, in step 2, the MXene is any one or several of Ti3C2 MXene, Ti2C MXene, TiVC MXene, Ti3CN MXene.

[0017] The application also relates to the application of the aforementioned hydrotalcite / MXene chloride ion battery positive electrode material, and the application of the hydrotalcite / MXene chloride ion battery positive electrode material in preparing a positive electrode sheet of a chloride ion battery.

[0018] The hydrotalcite / MXene chloride ion battery positive electrode material is mixed with conductive carbon black Super P and polyvinylidene fluoride binder PVDF (mixed at a mass ratio of 6:3:1) for grinding and mixing, and is dropped into a solvent N-methyl pyrrolidone NMP for sufficient grinding to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on a graphite paper (the graphite paper has a thickness of 50 mu m, and the coating thickness is 75 mu m) by using a doctor blade, and is vacuum dried at 90-120 DEG C for 24-48 h to cut into a circular electrode sheet with a diameter of 12 mm as the positive electrode to obtain the positive electrode sheet of the chloride ion battery.

[0019] The application has the following advantages:

[0020] (1) The application obtains two kinds of ultra-thin two-dimensional nanosheet building blocks of hydrotalcite (sigma+) and MXene (sigma-) based on a "top-down" delamination strategy, and uses a charge density difference driven colloidal co-assembly technology to prepare a hydrotalcite / MXene superlattice heterostructure with highly ordered arrangement characteristics in the ab plane as a positive electrode material of a chloride ion battery, and the material has the advantages of high chlorine storage capacity, excellent rate characteristics and long cycle life.

[0021] (2) The chloride ion battery material prepared by the application is used as a positive electrode material, a metal lithium sheet is used as a negative electrode material, 1-butyl-1-methylpyrrolidinium chloride ionic liquid dissolved in polycarbonate is used as an electrolyte of the chloride ion battery, and a new type of chloride ion battery with the hydrotalcite / MXene superlattice heterostructure electrode material as the positive electrode is constructed. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 It is an X-ray diffraction pattern of the NiFe LDH / MXene in Example 1.

[0023] Fig. 2 It is a scanning electron microscope image of the NiFe LDH / MXene in Example 1.

[0024] Fig. 3 It is a charge-discharge curve of the NiFe LDH / MXene / C electrode material in Example 1. DETAILED DESCRIPTION

[0025] The application will be described in detail below with specific examples. It should be pointed out that the following examples are only further illustrations of the application, and the protection scope of the application is not limited to the following examples.

[0026] Example 1

[0027] This example relates to a preparation method of a hydrotalcite / MXene chloride ion battery positive electrode material, comprising the following steps:

[0028] Step 1: 6.98 g of Ni(NO3)2·6H2O and 3.33 g of Fe(NO3)3·9H2O are added to 150 ml of deionized water to prepare a mixed metal salt solution; 6 g of sodium hydroxide is added to 100 ml of deionized water to prepare a sodium hydroxide solution, which is slowly added to the mixed metal salt, and the pH of the solution is adjusted to 9. The solution is loaded into a high-pressure reaction kettle, and the temperature is kept at 100-130°C in a blast drying oven for 16-24 hours. The reacted solution is washed with deionized water and ethanol until the pH is 7, and then dried at 60°C for 24 hours to obtain a carbonated NiFe LDH;

[0029] 0.1-1.0 g of the carbonated NiFe LDH sample is dispersed in 100-500 ml of deionized water, 1-5 M sodium nitrate and a small amount of hydrochloric acid are added, and stirring is carried out under inert gas protection for 15-25 hours. After reaction, the solution is washed with deionized water until neutral, and then vacuum dried at 60°C for 10-20 hours to obtain a nitrate-intercalated NiFe LDH;

[0030] Step 2: The nitrate-intercalated NiFe LDH is added to formamide to prepare a dispersion solution with a concentration of 1 mg / mL, and the layer is peeled off by continuous stirring for more than 48 hours. The supernatant is taken; MXene is added to formamide and stirred well to obtain a MXene solution with a concentration of 1 mg / mL;

[0031] Step 3: The supernatant and the MXene solution with a concentration of 1 mg / mL are added dropwise into a round-bottom flask containing a high-concentration sodium chloride solution. Inert gas is introduced into the round-bottom flask, and stirring is continued for 2 hours after the titration is completed. The mixed solution is centrifuged, washed with deionized water and alcohol, and then freeze-dried to obtain a NiFe LDH / MXene positive electrode material that can be used for a chloride ion battery;

[0032] This example also relates to a method for preparing a chloride ion battery positive electrode sheet from the NiFe LDH / MXene positive electrode material prepared above, which specifically comprises:

[0033] Take 40 mg of NiFe LDH / MXene positive electrode material, mix it with Super P and binder PVDF (mass ratio of the three is 6:3:1), drop into solvent NMP and grind thoroughly to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on a graphite paper (graphite paper thickness is 50 μm, coating thickness is 75 μm) by a doctor blade. After vacuum drying at 90-120℃ for 24-48h, the positive electrode is cut into a circular electrode with a diameter of 12 mm to obtain a chloride battery positive electrode.

[0034] The embodiment also relates to the preparation of a chloride battery, specifically:

[0035] Take the above-prepared chloride battery positive electrode, and use a high-purity lithium sheet as the battery negative electrode, glass fiber paper (GF / D, Whatman) as the separator, and 0.5M 1-butyl-1-methylpiperidinium chloride as the electrolyte to assemble a chloride battery.

[0036] See Figs. 1-3 As shown in the figure, the chloride battery energy storage mechanism of the hydrotalcite / MXene positive electrode material of the chloride battery is studied using X-ray diffraction and scanning electron microscopy. The electrochemical performance of the battery, such as constant current charge-discharge behavior and cycle stability, is tested. The maximum discharge capacity reaches 232.6 mAh / g, and the capacity can be maintained at 122 mAh / g after 500 charge-discharge cycles. It is further proved that the application obtains hydrotalcite (σ+) and MXene (σ-) two kinds of ultra-thin two-dimensional nanosheet building blocks based on the "top-down" delamination strategy, uses the charge density difference to drive the colloidal co-assembly technology, and prepares a hydrotalcite / MXene superlattice heterostructure with highly ordered arrangement characteristics in the ab plane as the positive electrode material of the chloride battery. The material has high chloride storage capacity, excellent rate characteristics, long cycle life and other advantages.

[0037] The specific embodiments of the application are described above. It should be understood that the application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or changes within the scope of the claims, which does not affect the essence of the application.

Claims

1. An application of a hydrotalcite / MXene cathode material for chloride ion batteries, characterized in that, The hydrotalcite / MXene cathode material is used to prepare cathode sheets for chloride-ion batteries, and the specific method is as follows: Hydrotalcite / MXene chloride-ion battery positive electrode material, conductive carbon black, and polyvinylidene fluoride were ground and mixed. N-methylpyrrolidone solvent was added dropwise and the mixture was ground thoroughly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto graphite paper with a scraper and vacuum dried at 90–120°C for 24–48 hours. The slurry was then cut into circular electrode sheets with a diameter of 12 mm to obtain the positive electrode sheet for the chloride-ion battery. The ratio of hydrotalcite / MXene chloride ion battery cathode material, conductive carbon black, and polyvinylidene fluoride is 6:3:1; the drying temperature is 90-120℃ and the drying time is 24-48h. The preparation method of the hydrotalcite / MXene chloride-ion battery cathode material includes the following steps: Step 1: Prepare a mixed metal salt solution by adding soluble inorganic salts M1 and M2 to deionized water. Prepare a sodium hydroxide solution by adding sodium hydroxide to deionized water. Slowly add the sodium hydroxide solution dropwise to the mixed metal salt solution to adjust the pH of the solution to 9. Place the solution into a high-pressure reactor and dry it in a forced-air drying oven at 100℃~130℃ for 16~24h. Wash the reacted solution with deionized water and ethanol until the pH reaches 7, and dry it at 60℃ for 24h to obtain carbonate-intercalated hydrotalcite. Disperse the carbonate-intercalated hydrotalcite sample in deionized water, add 1~5M sodium nitrate and a trace amount of hydrochloric acid, and stir under inert gas protection for 15~25h. After the reaction, wash with decarbonated water until neutral, and vacuum dry at 60℃ for 10~20h to obtain nitrate-intercalated hydrotalcite. Step 2: Add nitrate-intercalated hydrotalcite to formamide to prepare a hydrotalcite dispersion. Stir continuously for more than 48 hours to remove the layers and take the supernatant. Add MXene to formamide and stir thoroughly to obtain an MXene solution. Step 3: Drop the supernatant and MXene solution into a round-bottom flask containing a high concentration of sodium chloride solution. Inert gas is introduced into the round-bottom flask. After titration, continue stirring for 2 hours, centrifuge, wash with decarbohydrate and alcohol, freeze dry, and obtain hydrotalc / MXene chloride ion battery cathode material. In step 1, M1 in the soluble inorganic salt M1 is Ni. 2+ Co 2+ Ti 2+ Cr 2+ or Zn 2+ Any one or more of the following; the M2 of the soluble inorganic salt M2 is Fe. 3+ Mn 3+ Ti 3+ Cr 3+ or Co 3+ The soluble inorganic salt M1 has a concentration of 0.001–0.5 mol / L, and the molar ratio of M1 to M2 is 1–5. The amount of carbonate-intercalated hydrotalcite sample to deionized water is 0.1–1.0 g: 100–500 ml. In step 2, the concentration of the hydrotalcite dispersion is 1 mg / mL, the concentration of the MXene solution is 1 mg / mL, and the MXene is any one or more of Ti3C2 MXene, Ti2C MXene, TiVC MXene, and Ti3CN MXene.

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