High-performance halogen-based aqueous dual-ion battery with graphite fluoride as positive electrode

Abstract

The invention discloses a high-performance halogen-based aqueous dual-ion battery with graphite fluoride as a positive electrode, and belongs to the technical field of aqueous secondary batteries. The halogen-based aqueous dual-ion battery comprises a graphite fluoride positive electrode, a water-in-salt electrolyte, a negative electrode and a diaphragm. According to the halogen-based aqueous dual-ion battery designed by taking the carbon monofluoride (CFx) as the positive electrode, the cycling stability of the battery is greatly improved on the premise of not sacrificing the rate capability and the cost advantage. The halogen-based aqueous dual-ion battery is simple in preparation process, low in production cost and suitable for large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of aqueous secondary battery technology, and more specifically relates to a high-performance halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode. Background Technology

[0002] Commercial lithium-ion batteries mostly use flammable organic electrolytes, which are complex to manufacture, difficult to operate, and pose safety hazards. While aqueous secondary batteries use non-flammable electrolyte solutions and offer advantages such as high conductivity, high safety, and low cost, their operating voltage is limited by the electrochemical hydrogen / oxygen evolution potential of the aqueous solution, often not exceeding 1.23V. With the introduction of the "salt-in-water" electrolyte strategy, halogen-based aqueous dual-ion batteries with high operating voltages have attracted widespread attention.

[0003] Halogen-based aqueous dual-ion batteries use graphite as the positive electrode material and halide anions as charge carriers. Through the insertion / extraction of anions in graphite, a positive electrode potential of 1.3V (vs. SHE) can be achieved. When paired with a low-potential negative electrode material such as Zn (-0.78V vs. SHE), operating voltages exceeding 2V and discharge specific capacities exceeding 200mAh / g can be achieved. These dual-ion batteries often employ mixed halogen electrolyte systems, improving electrode reaction stability by forming interhalogen compounds. For example, the positive electrode working mechanism of the Br / Cl electrolyte system can be represented as follows: During charging, Br... - First, it is oxidized to a near-zero state (Br). 0 And embedded in the graphite layer to form C n [Br], then Cl - Oxidized and embedded in C n C is formed in [Br]. n [BrCl]; During discharge, Cl 0 and Br 0 The ions are successively deintercalated and reduced from the graphite interlayer to form halides. However, due to the high reactivity of halide ions and the high conductivity of graphite materials, serious side reactions occur in the graphite cathode, reducing the energy conversion efficiency of the battery and accelerating the performance degradation of the electrode materials. The stability of the cathode reaction is a key issue currently facing aqueous dual-ion batteries.

[0004] This invention is proposed against this background. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode, to solve the problems existing in the prior art. This invention is based on the special working mechanism of halogen anion storage, and utilizes mass-produced fluorinated graphite material (CF2) without sacrificing battery rate performance. xAs the positive electrode, it greatly improves the cycle stability of halogen-based aqueous dual-ion batteries.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is to provide the application of fluorinated graphite in the preparation of halogen-based aqueous dual-ion batteries.

[0008] The second technical solution of the present invention provides a halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode, the halogen-based aqueous dual-ion battery comprising: fluorinated graphite positive electrode, salt-in-water electrolyte, negative electrode and separator.

[0009] Preferably, the preparation steps of the fluorinated graphite cathode include:

[0010] Fluorographite (CF) x The conductive agent, binder and solvent are mixed to obtain an electrode slurry; the electrode slurry is coated on a Ti foil and dried to obtain the fluorinated graphite cathode.

[0011] Preferably, the molar ratio of fluorine to carbon in the fluorinated graphite is 0.1 to 0.99:1.

[0012] Preferably, the conductive agent includes Super-P or acetylene black; the binder includes sodium carboxymethyl cellulose, polyvinylidene fluoride, or polytetrafluoroethylene.

[0013] Preferably, the mass ratio of the fluorinated graphite, conductive agent, and binder is 3–8:1:1; and the coating thickness of the electrode paste is 30–40 μm.

[0014] Preferably, the salt-in-water electrolyte is composed of an aqueous solution of one or more of ZnCl2, ZnBr2, and ZnI2. The concentration of one of the salts in the salt-in-water electrolyte must be sufficiently high to form a "salt-in-water" structure. More preferably, the concentrations are: 13.5 mol / kg ZnI2, 19.5 mol / kg ZnBr2, 20 mol / kg ZnCl2, 2 mol / kg ZnBr2 + 27 mol / kg ZnCl2, or 3 mol / kg ZnI2 + 27 mol / kg ZnCl2.

[0015] Preferably, the material of the negative electrode includes Zn, Cu, Ti, or stainless steel.

[0016] Preferably, the diaphragm comprises glass fiber filter paper, polyethylene diaphragm, or polypropylene diaphragm.

[0017] The third technical solution of the present invention provides a method for preparing the above-mentioned halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode, comprising the following steps:

[0018] The fluorinated graphite positive electrode, the salt-in-water electrolyte, the negative electrode, and the separator are assembled to obtain the halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode.

[0019] The fourth technical solution of the present invention provides a method for improving the cycle stability of halogen-based aqueous dual-ion batteries without sacrificing rate performance, wherein halogen-based aqueous dual-ion batteries are prepared using fluorinated graphite as the positive electrode.

[0020] The technical principle of this invention is as follows:

[0021] Using CF x Halogen anions are fixed by interlayer F atoms, effectively reducing the occurrence of side reactions; through CF x The material's naturally wide interlayer spacing enables highly efficient halide anion transport. Among them, CF... x The molar ratio of fluorine to carbon in the positive electrode is crucial. The fluorine content (x) affects the interlayer spacing and conductivity of the material, which in turn affects the rate performance and the degree of side reactions of the battery. Too high or too low x will have an adverse effect on the battery. The concentration of salt in the salt-in-water electrolyte is critical. It is necessary to ensure that the concentration of one of the salts is high enough to form a "salt-in-water" structure to ensure the stability of the electrolyte. The combination of different halogens in the salt-in-water electrolyte and the proportion of different halogen combinations also have a great impact on battery performance.

[0022] In the salt-in-water electrolyte of the present invention, the salt concentrations are as follows: ZnI2 is 2-13.5 mol / kg, ZnBr2 is 2-19.5 mol / kg, and ZnCl2 is 2-27 mol / kg; the halogens in the salt-in-water electrolyte include I, Br, and Cl.

[0023] This invention, through the synergistic effect of the aforementioned factors, creatively proposes the use of fluorinated graphite in the preparation of halogen-based aqueous dual-ion batteries. By combining fluorine with halogens to form stable [BrF] and [ClF] compounds, the generation of side reactions is reduced. This is achieved through CF... x The material's naturally wide interlayer spacing enables highly efficient halogen anion transport. Therefore, without sacrificing the battery's rate performance, it significantly improves the cycle stability of halogen-based aqueous dual-ion batteries.

[0024] The present invention discloses the following technical effects:

[0025] This invention uses CF x The halogen-based aqueous dual-ion battery designed for the positive electrode greatly improves the cycle stability of the battery without sacrificing rate performance and cost advantages.

[0026] The halogen-based aqueous dual-ion battery described in this invention has a simple preparation process, low production cost, and is suitable for large-scale application. Attached Figure Description

[0027] Figure 1 (-)Zn|13.5mol / kg ZnI2|CF 0.56 (+) Constant current charge-discharge curves (a) and CF of the dual-ion battery 0.56 Cyclic voltammetry curve of the positive electrode (b);

[0028] Figure 2 (-)Zn|19.5mol / kg ZnBr2|CF 0.56 (+) Constant current charge-discharge curves (a) and CF of the dual-ion battery 0.56 Cyclic voltammetry curve of the positive electrode (b);

[0029] Figure 3 (-)Zn|20mol / kg ZnCl2|CF 0.56 (+) Constant current charge-discharge curves (a) and CF of the dual-ion battery 0.56 Cyclic voltammetry curve of the positive electrode (b);

[0030] Figure 4 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) Constant current charge-discharge curve of dual-ion battery;

[0031] Figure 5 For CF 0.56 In-situ Raman spectrum of the positive electrode in a 2 mol / kg ZnBr2 + 27 mol / kg ZnCl2 solution;

[0032] Figure 6 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) Long-cycle performance diagram of dual-ion batteries;

[0033] Figure 7 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.99 (+) Constant current charge-discharge curve of dual-ion battery;

[0034] Figure 8 (-)Zn|8mol / kgZnBr2|CF 0.56 (+) Constant current charge-discharge curves of dual-ion batteries (a) and (-) Zn|12mol / kgZnBr2|CF 0.56 (+) Constant current charge-discharge curve of dual-ion battery (b);

[0035] Figure 9The constant current charge-discharge curves (a) and (b) of the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|g-C3N4(+) dual-ion battery are shown.

[0036] Figure 10 The constant current charge-discharge curves (a) and (b) of the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|Natural Graphite (NG)(+) dual-ion battery are shown.

[0037] Figure 11 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 Photographs of the separator when fully charged: (+) dual-ion battery (a), (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|natural graphite (NG) (+) dual-ion battery (b), and (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG-ZnF2 (+) dual-ion battery (c). Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0044] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0045] The fluorinated graphite used in this embodiment of the invention was purchased from Shanghai McLean Biochemical Technology Co., Ltd.

[0046] Example 1

[0047] (-)Zn|13.5mol / kg ZnI2|CF 0.56 The preparation steps of the (+) dual-ion battery are as follows:

[0048] (1)CF x Positive electrode: Weigh out fluorinated graphite (CF3) with a fluorine / carbon molar ratio of 0.56:1. 0.56 0.4g of sodium carboxymethyl cellulose (CCMC), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) were placed in a beaker, and an appropriate amount of deionized water was added and stirred until homogeneous to obtain an electrode slurry. The prepared slurry was coated onto a Ti foil, then spread evenly using a scraper (40μm thick). This was then dried in a 50℃ oven for 12 hours and cut into φ=14mm round pieces to obtain CF. 0.56 positive electrode.

[0049] (2) Electrolyte: Weigh 43.06g of anhydrous ZnI2 and dissolve it in 10mL of deionized water. Stir well to obtain a 13.5mol / kg ZnI2 electrolyte.

[0050] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0051] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0052] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled according to the following steps: Zn negative electrode, separator (2 pieces, soaked in 280μL electrolyte), CF x Sequential assembly of the positive electrode yields (-)Zn|13.5mol / kg ZnI2|CF 0.56 (+) Dual-ion battery.

[0053] Performance testing:

[0054] The (-)Zn|13.5mol / kgZnI2|CF assembled in Example 1 0.56 (+) The dual-ion battery was left to stand at 25℃ for 3 hours, followed by constant current charge-discharge and cyclic voltammetry tests. The constant current charge-discharge test conditions were: 0.75 A / g; positive electrode specific capacity at charge cutoff ≥ 300 mAh / g; discharge cutoff voltage ≤ 1 V. The cyclic voltammetry test conditions were: scan rate 0.1 mV / s, voltage range 0.8–1.35 V (vs. Zn / Zn). 2+ ).

[0055] Figure 1 (-)Zn|13.5mol / kg ZnI2|CF 0.56 (+) Constant current charge-discharge curves (a) and CF of the dual-ion battery 0.56 Cyclic voltammetry curve of the positive electrode (b).

[0056] The results of constant current charge and discharge are as follows Figure 1 As shown in (a): CF 0.56 The positive electrode has a set of potential plateaus, corresponding to I. - During the insertion / deintercalation process, the charging platform is 1.15–1.17V (vs. Zn / Zn). 2+ The discharge plateau is 1.05–1V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 75 mAh / g. This proves that... - Able to CF 0.56 Positive electrode reversible storage.

[0057] Cyclic voltammetry results are as follows Figure 1As shown in (b): CF 0.56 The positive electrode has a pair of redox peaks, with the oxidation peak at 1.29V (vs. Zn / Zn). 2+ The reduction peak is 1.02V (vs. Zn / Zn). 2+ This is consistent with the GCD results, proving that I - In fluorinated graphite CF 0.56 The reaction at the electrode is reversible.

[0058] Example 2

[0059] (-)Zn|19.5mol / kgZnBr2|CF 0.56 The preparation steps of the (+) dual-ion battery are as follows:

[0060] (1)CF x Positive electrode: Weigh out fluorinated graphite (CF3) with a fluorine / carbon molar ratio of 0.56:1. 0.56 0.4g of sodium carboxymethyl cellulose (CCMC), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) were placed in a beaker, and an appropriate amount of deionized water was added and stirred until homogeneous to obtain an electrode slurry. The prepared slurry was coated onto a Ti foil, then spread evenly using a scraper (40μm thick). This was then dried in a 50℃ oven for 12 hours and cut into φ=14mm round pieces to obtain CF. 0.56 positive electrode.

[0061] (2) Electrolyte: Weigh 43.92g of anhydrous ZnBr2 and dissolve it in 10mL of deionized water. Stir well to obtain a 19.5mol / kg ZnBr2 electrolyte.

[0062] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0063] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0064] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled according to the following steps: Zn negative electrode, separator (2 pieces, soaked in 280μL electrolyte), CF x Sequential assembly of the positive electrode yields (-)Zn|19.5mol / kg ZnBr2|CF 0.56 (+) Dual-ion battery.

[0065] Performance testing:

[0066] The (-)Zn|19.5mol / kg ZnBr2|CF assembled in Example 2 0.56(+) The dual-ion battery was left to stand at 25℃ for 3 hours, followed by constant current charge-discharge and cyclic voltammetry tests. The constant current charge-discharge test conditions were: 0.75 A / g; positive electrode specific capacity at charge cutoff ≥ 300 mAh / g; discharge cutoff voltage ≤ 1 V. The cyclic voltammetry test conditions were: scan rate 0.1 mV / s, voltage range 1–1.8 V (vs. Zn / Zn). 2+ ).

[0067] Figure 2 (-)Zn|19.5mol / kg ZnBr2|CF 0.56 (+) Constant current charge-discharge curves (a) and CF of the dual-ion battery 0.56 Cyclic voltammetry curve of the positive electrode (b).

[0068] The results of constant current charge and discharge are as follows Figure 2 As shown in (a): CF 0.56 The positive electrode has a distinct potential plateau, corresponding to Br - During the insertion / deintercalation process, the charging platform is 1.65–1.75V (vs. Zn / Zn). 2+ The discharge plateau is 1.55–1.45V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 150 mAh / g. This demonstrates that Br... - Able to CF 0.56 Positive electrode reversible storage.

[0069] Cyclic voltammetry results are as follows Figure 2 As shown in (b): During the charging process, CF 0.56 The positive electrode is at 1.8V (vs. Zn / Zn) 2+ There is a sharp oxidation peak at 1.5V (vs. Zn / Zn). 2+ This indicates that Br - In CF 0.56 The reaction at the electrode is reversible, consistent with the results of constant current charge and discharge.

[0070] Example 3

[0071] (-)Zn|20mol / kg ZnCl2|CF 0.56 (+) Dual-ion battery, the steps are as follows:

[0072] (1)CF x Positive electrode: Weigh out fluorinated graphite (CF3) with a fluorine / carbon molar ratio of 0.56:1. 0.560.4g of sodium carboxymethyl cellulose (CCMC), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) were placed in a beaker, and an appropriate amount of deionized water was added and stirred until homogeneous to obtain an electrode slurry. The prepared slurry was coated onto a Ti foil, then spread evenly using a scraper (40μm thick). This was then dried in a 50℃ oven for 12 hours and cut into φ=14mm round pieces to obtain CF. 0.56 positive electrode.

[0073] (2) Electrolyte: Weigh 27.26g of anhydrous ZnCl2 and dissolve it in 10mL of deionized water. Stir well to obtain a 20mol / kg ZnCl2 electrolyte.

[0074] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0075] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0076] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled according to the following steps: Zn negative electrode, separator (2 pieces, soaked in 280μL electrolyte), CF x Sequential assembly of the positive electrode yields (-)Zn|20mol / kgZnCl2|CF 0.56 (+) Dual-ion battery.

[0077] Performance testing:

[0078] The (-)Zn|20mol / kgZnCl2|CF assembled in Example 3 0.56 (+) The dual-ion battery was left to stand at 25℃ for 3 hours, followed by constant current charge-discharge and cyclic voltammetry tests. The constant current charge-discharge test conditions were: 0.75 A / g; positive electrode specific capacity at charge cutoff ≥ 300 mAh / g; discharge cutoff voltage ≤ 1 V. The cyclic voltammetry test conditions were: scan rate 0.1 mV / s, voltage range 1–2.8 V (vs. Zn / Zn). 2+ ).

[0079] Figure 3 (-)Zn|20mol / kg ZnCl2|CF 0.56 (+) Constant current charge-discharge curves (a) and CF of the dual-ion battery 0.56 Cyclic voltammetry curve of the positive electrode (b).

[0080] The results of constant current charge and discharge are as follows Figure 3 As shown in (a): CF 0.56 The positive electrode has a distinct potential plateau, corresponding to Cl. -During the insertion / deintercalation process, the charging platform is 2.2–2.3V (vs. Zn / Zn). 2+ The discharge plateau is 1.7–1.55V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 50 mAh / g. This proves that Cl... - Able to CF 0.56 Positive electrode reversible storage.

[0081] Cyclic voltammetry results are as follows Figure 3 As shown in (b): CF 0.56 The positive electrode only shows an oxidation peak, with no reduction peak. This indicates that Cl... - In CF 0.56 Non-decomposable products were formed on the electrodes. Based on the constant current charge-discharge results, it is inferred that Cl... - In CF 0.56 The reaction at the electrode is divided into two parts, one part Cl - Reversible insertion / de-insertion, another part Cl - It produced non-decomposable products.

[0082] Example 4

[0083] (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 The preparation steps of the (+) dual-ion battery are as follows:

[0084] (1)CF x Positive electrode: Weigh out fluorinated graphite (CF3) with a fluorine / carbon molar ratio of 0.56:1. 0.56 0.4g of sodium carboxymethyl cellulose (CCMC), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) were placed in a beaker, and an appropriate amount of deionized water was added and stirred until homogeneous to obtain an electrode slurry. The prepared slurry was coated onto a Ti foil, then spread evenly using a scraper (40μm thick). This was then dried in a 50℃ oven for 12 hours and cut into φ=14mm round pieces to obtain CF. 0.56 positive electrode.

[0085] (2) Electrolyte: Weigh 4.5g of anhydrous ZnBr2 and 36.8g of anhydrous ZnCl2 and dissolve them in 10.00mL of deionized water. Stir well to obtain an electrolyte of 2mol / kg ZnBr2 + 27mol / kg ZnCl2.

[0086] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0087] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0088] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled according to the following steps: Zn negative electrode, separator (2 pieces, soaked in 280μL electrolyte), CF x Sequential assembly of the positive electrode yields (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) Dual-ion battery.

[0089] Performance testing:

[0090] The (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF assembled in Example 4 0.56 The (+) dual-ion battery was left to stand at 25℃ for 3 hours, and then subjected to constant current charge-discharge testing. The constant current charge-discharge test conditions were: 0.75A / g and 1.5A / g; charging cut-off voltage ≥2V; discharging cut-off voltage ≤1V.

[0091] Figure 4 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) Constant current charge-discharge curves of dual-ion batteries.

[0092] The results of constant current charge and discharge are as follows Figure 4 As shown: at a current density of 0.75 A / g, CF 0.56 The positive electrode exhibits a charging plateau of 1.78–2V (vs. Zn / Zn). 2+ The discharge process has two continuous plateaus, ranging from 1.6 to 1.55 V (vs. Zn / Zn). 2+ ) and 1.55~1.4V (vs. Zn / Zn 2+ The discharge specific capacity is approximately 200 mAh / g. Similarly, at a current density of 1.5 A / g, CF... 0.56 The positive electrode exhibits a charging plateau of 1.78–2V (vs. Zn / Zn). 2+ The discharge process has two continuous plateaus, at 1.66–1.55V (vs. Zn / Zn). 2+ ) and 1.55~1.44V (vs. Zn / Zn 2+ The discharge specific capacity is approximately 196 mAh / g. This demonstrates the effectiveness of using a mixed halogen electrolyte in Zn / CF42O4. 0.56 The battery offers superior electrochemical performance compared to single halogen electrolytes. Furthermore, this dual-ion battery exhibits essentially the same specific capacity at both current densities, indicating that CF... 0.56 The positive electrode has good rate performance.

[0093] For (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) The dual-ion battery underwent Raman spectroscopy and long-cycle performance testing. The long-cycle performance testing conditions were: 0.75 A / g; charging cut-off voltage ≥ 2V; discharging cut-off voltage ≤ 1V.

[0094] (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) The in-situ Raman spectrum results of the dual-ion battery are as follows: Figure 5 As shown.

[0095] Figure 5 For CF 0.56 The in-situ Raman spectrum of the positive electrode in a 2 mol / kg ZnBr2 + 27 mol / kg ZnCl2 solution, by Figure 5 It can be known that: CF 0.56 In the initial state, the positive electrode has a 290cm diameter. -1 1326cm -1 and 1594cm -1 The signal peaks belong to [ZnCl4]. 2- The amorphous carbon structure exhibits D-band vibration and graphite sheet layer vibration G-band vibration. During charging, at 300 cm⁻¹... -1 The Raman signal (intercalated [BrCl]), D-band, and G-band signal peaks gradually increase. When charged to 2V, the peak signal of intercalated [BrCl] gradually decreases, and a 320cm peak appears. -1 (Laminated [BrF]) and 640cm -1 (Plug-in [ClF]) Two new peak signals; during discharge, 320cm -1 and 640cm -1 The two new peak signals gradually weakened and eventually disappeared. This confirmed the CF signal. 0.56 Halogens are stored in a multi-ion intercalation form, namely Br. - and Cl - It is simultaneously embedded in CF, and produces relatively stable [BrF] and [ClF] compounds.

[0096] (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) The long-cycle performance results of the dual-ion battery are shown in the figure. Figure 6 As shown.

[0097] Figure 6 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 (+) Long-cycle performance diagram of dual-ion batteries, from Figure 6 It can be seen that after 300 cycles, the coulombic efficiency remains above 80%, and the discharge specific capacity is 150–250 mAh / g. After 500 cycles, the discharge specific capacity gradually decreases, reaching 50 mAh / g after 1000 cycles. This indicates that CF 0.56 The positive electrode exhibits good stability and has the potential for large-scale application.

[0098] Comparative Example 1 (Impact of Fluorine Content x on Battery Performance)

[0099] (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.99 The preparation steps of the (+) dual-ion battery are as follows:

[0100] (1)CF x Positive electrode: Weigh out fluorinated graphite (CF3) with a fluorine / carbon molar ratio of 0.99:1. 0.99 0.4g of sodium carboxymethyl cellulose (CCMC), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) were placed in a beaker, and an appropriate amount of deionized water was added and stirred until homogeneous to obtain an electrode slurry. The prepared slurry was coated onto a Ti foil, then spread evenly using a scraper (40μm thick). This was then dried in a 50℃ oven for 12 hours and cut into φ=14mm round pieces to obtain CF. 0.99 positive electrode.

[0101] (2) Electrolyte: Weigh 4.5g of anhydrous ZnBr2 and 36.8g of anhydrous ZnCl2 and dissolve them in 10.00mL of deionized water. Stir well to obtain an electrolyte of 2mol / kg ZnBr2 + 27mol / kg ZnCl2.

[0102] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0103] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0104] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled according to the following steps: Zn negative electrode, separator (2 pieces, soaked in 280μL electrolyte), CF x Sequential assembly of the positive electrode yields (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.99 (+) Dual-ion battery.

[0105] Performance testing:

[0106] The assembled (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF from Comparative Example 1 was used to... 0.99 (+) The dual-ion battery was left to stand at 25℃ for 3 hours, and then subjected to constant current charge-discharge test. The constant current charge-discharge test conditions were: 0.25A / g and 0.75A / g; the positive electrode specific capacity at the charging cutoff was ≥300mAh / g or the charging cutoff voltage was ≥2V; and the discharge cutoff voltage was ≤1V.

[0107] Figure 7 is (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.99 (+) Constant current charge-discharge curves of dual-ion batteries.

[0108] The results of constant current charge and discharge are as follows Figure 7 As shown: at a current density of 0.25 A / g, CF 0.99 The positive electrode has a potential plateau, with a charging plateau of 1.73–1.84 V (vs. Zn / Zn). 2+ The discharge plateau is 1.67–1.47V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 192 mAh / g. Similarly, at a current density of 0.75 A / g, CF... 0.99 The positive electrode has a potential plateau, with a charging plateau of 1.83–2V (vs. Zn / Zn). 2+ The discharge plateau is 1.59–1.39V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 120 mAh / g. This demonstrates that CF... x The performance of CF is closely related to its fluorine content; CF with a higher fluorine content... 0.99 The battery's operating voltage and discharge specific capacity are significantly affected by current density; performance decreases significantly as current density increases.

[0109] Comparative Example 2 (The effect of salt concentration in the electrolyte on battery performance)

[0110] (-)Zn|8mol / kgZnBr2|CF 0.56 (+) dual-ion battery and (-)Zn|12mol / kgZnBr2|CF 0.56 The preparation steps of the (+) dual-ion battery are as follows:

[0111] (1)CF x Positive electrode: Weigh out fluorinated graphite (CF3) with a fluorine / carbon molar ratio of 0.56:1. 0.560.4g of sodium carboxymethyl cellulose (CCMC), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) were placed in a beaker, and an appropriate amount of deionized water was added and stirred until homogeneous to obtain an electrode slurry. The prepared slurry was coated onto a Ti foil, then spread evenly using a scraper (40μm thick). This was then dried in a 50℃ oven for 12 hours and cut into φ=14mm round pieces to obtain CF. 0.56 positive electrode.

[0112] (2) Electrolyte: Weigh 18.02g of anhydrous ZnBr2 and dissolve it in 10mL of deionized water. Stir well to obtain an 8mol / kg ZnBr2 electrolyte; weigh 27.03g of anhydrous ZnBr2 and dissolve it in 10mL of deionized water. Stir well to obtain a 12mol / kg ZnBr2 electrolyte.

[0113] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0114] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0115] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled according to the following steps: Zn negative electrode, separator (2 pieces, soaked in 280μL electrolyte), CF x Sequential assembly of the positive electrode yields (-)Zn|8mol / kgZnBr2|CF 0.56 (+) dual-ion battery and (-)Zn|12mol / kgZnBr2|CF 0.56 (+) Dual-ion battery.

[0116] Performance testing:

[0117] The assembled (-)Zn|8mol / kg ZnBr2|CF from Comparative Example 2 0.56 (+) dual-ion battery and (-)Zn|12mol / kgZnBr2|CF 0.56 (+) The dual-ion battery was left to stand at 25℃ for 3 hours, and then subjected to constant current charge-discharge test. The constant current charge-discharge test conditions were: 0.75A / g; charging cut-off positive electrode specific capacity ≥300mAh / g; discharge cut-off voltage ≤1V.

[0118] Figure 8 (-)Zn|8mol / kgZnBr2|CF 0.56 (+) Constant current charge-discharge curves of dual-ion batteries (a) and (-) Zn|12mol / kgZnBr2|CF 0.56 (+) Constant current charge-discharge curve of dual-ion battery (b).

[0119] The results of constant current charge and discharge are as follows Figure 8 As shown in (a): CF 0.56 The positive electrode has a distinct potential plateau, corresponding to Br - During the insertion / deintercalation process, the charging platform is 1.7–1.73V (vs. Zn / Zn). 2+ The discharge plateau is 1.63–1.58V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 34 mAh / g. Similarly, as... Figure 8 As shown in (b): CF 0.56 The positive electrode has a distinct potential plateau, corresponding to Br - During the insertion / deintercalation process, the charging platform is 1.65–1.68V (vs. Zn / Zn). 2+ The discharge plateau is 1.59–1.52V (vs. Zn / Zn). 2 + The discharge specific capacity is approximately 66 mAh / g. This result demonstrates that the Br₂ content in batteries using 8 mol / kg ZnBr₂ and 12 mol / kg ZnBr₂ electrolytes is relatively high. - Able to CF 0.56 Positive electrode reversible storage, but due to the low electrolyte concentration, it is insufficient to form a water-in-salt structure, CF 0.56 The positive electrode capacity is very small, the battery coulombic efficiency is less than 25%, and the specific capacity increases with the increase of ZnBr2 concentration.

[0120] Comparative Example 3 (The Influence of Cathode Materials on Battery Performance)

[0121] The preparation steps of the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|g-C3N4(+) dual-ion battery and the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|h-BN(+) dual-ion battery are as follows:

[0122] (1) g-C3N4 cathode: Weigh 0.4 g of graphitic carbon nitride (g-C3N4, carbon / nitrogen molar ratio 3:4), 0.05 g of conductive agent (Super-P), and 0.05 g of binder (sodium carboxymethyl cellulose) into a beaker, add an appropriate amount of deionized water and stir evenly to obtain an electrode slurry. Coat the prepared slurry onto a Ti foil, then use a scraper (thickness 40 μm) to spread it evenly, and then dry it in a 50℃ oven for 12 h and cut it into φ = 14 mm round pieces to obtain the g-C3N4 cathode. Prepare hexagonal boron nitride (h-BN) cathodes according to the above method.

[0123] (2) Electrolyte: Weigh 4.5g of anhydrous ZnBr2 and 36.8g of anhydrous ZnCl2 and dissolve them in 10.00mL of deionized water. Stir well to obtain an electrolyte of 2mol / kg ZnBr2 + 27mol / kg ZnCl2.

[0124] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0125] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0126] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled in the order of Zn negative electrode, separator (2 pieces, soaked in 280 μL electrolyte) and g-C3N4 positive electrode to obtain (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|g-C3N4(+) dual-ion battery; and (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|h-BN(+) dual-ion battery is assembled according to the above method.

[0127] Performance testing:

[0128] The assembled (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|g-C3N4(+) dual-ion batteries and (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|h-BN(+) dual-ion batteries from Comparative Example 3 were allowed to stand at 25℃ for 3 hours, and then constant current charge-discharge tests were performed. The constant current charge-discharge test conditions were: 0.75A / g; charging cutoff voltage ≥2V; discharging cutoff voltage ≤1V.

[0129] Figure 9 The constant current charge-discharge curves (a) and (b) of the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|g-C3N4(+) dual-ion battery are shown.

[0130] The results of constant current charge and discharge are as follows Figure 9 As shown in (a): the positive electrode of g-C3N4 has a distinct potential plateau, with a charging plateau of 1.9–2V (vs. Zn / Zn). 2+ The discharge plateau is 1.47–1.2V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 109 mAh / g. For example... Figure 9As shown in (b): the h-BN positive electrode has a distinct potential plateau, with a charging plateau of 1.93–2V (vs. Zn / Zn). 2+ The discharge plateau is 1.42–1.24V (vs. Zn / Zn). 2+ The discharge specific capacity is approximately 56 mAh / g. This demonstrates that even using the same electrolyte (2 mol / kg ZnBr2 + 27 mol / kg ZnCl2), if materials with layered structures such as g-C3N4 and h-BN are used as the positive electrode, the battery discharge specific capacity is very low and the discharge voltage plateau is <1.5V, indicating significant battery polarization. This illustrates CF 0.56 As the cathode material for halogen-based aqueous dual-ion batteries, this material exhibits greater specific capacity and higher energy density compared to conventional layered cathode materials such as g-C3N4 and h-BN.

[0131] Comparative Example 4 (The Influence of Cathode Materials on Battery Performance)

[0132] The preparation steps of (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG(+) dual-ion batteries and (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG-ZnF2(+) dual-ion batteries are as follows:

[0133] (1) NG cathode: Weigh 0.4g of natural graphite (NG), 0.05g of conductive agent (Super-P), and 0.05g of binder (sodium carboxymethyl cellulose) into a beaker, add an appropriate amount of deionized water and stir evenly to obtain an electrode slurry. Coat the prepared slurry onto a Ti foil, then use a scraper (40μm thick) to spread it evenly, and then transfer it to a 50℃ oven to dry for 12h and cut it into φ=14mm round pieces to obtain the NG cathode.

[0134] NG-ZnF2 cathode: Weigh 0.2g of natural graphite (NG), 0.2g of zinc fluoride (ZnF2), 0.05g of conductive agent (Super-P), and 0.05g of binder (polyvinylidene fluoride) into a beaker, add an appropriate amount of N-methylpyrrolidone, and stir until homogeneous to obtain an electrode slurry. Coat the prepared slurry onto a Ti foil, then use a scraper (40μm thick) to spread it evenly, and then dry it in a 50℃ oven for 12h. Cut it into φ=14mm round pieces to obtain the NG-ZnF2 cathode.

[0135] (2) Electrolyte: Weigh 4.5g of anhydrous ZnBr2 and 36.8g of anhydrous ZnCl2 and dissolve them in 10.00mL of deionized water. Stir well to obtain an electrolyte of 2mol / kg ZnBr2 + 27mol / kg ZnCl2.

[0136] (3) Zn anode: Cut high-purity Zn foil (purity > 99.9%, thickness 0.15 mm) into φ = 15 mm round pieces to obtain Zn anode.

[0137] (4) Diaphragm: Cut glass fiber filter paper (GA-100) into circular pieces with a diameter of φ=16mm to obtain a diaphragm.

[0138] (5) Battery assembly: The materials obtained in steps (1) to (4) are assembled in the order of Zn negative electrode, separator (2 pieces, soaked in 280 μL electrolyte), and NG positive electrode to obtain (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG(+) dual-ion battery. Similarly, (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG-ZnF2(+) dual-ion battery can be obtained.

[0139] Performance testing:

[0140] The assembled (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG(+) dual-ion batteries and (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG-ZnF2(+) dual-ion batteries from Comparative Example 4 were allowed to stand at 25℃ for 3 hours, and then constant current charge-discharge tests were performed. The constant current charge-discharge test conditions were: 0.75A / g and 1.5A / g; charging cutoff voltage ≥2V; discharging cutoff voltage ≤1V.

[0141] Figure 10 The constant current charge-discharge curves (a) of the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG(+) dual-ion battery and (b) of the (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|NG-ZnF2(+) dual-ion battery are shown.

[0142] The results of constant current charge and discharge are as follows Figure 10 As shown in (a): at a current density of 0.75 A / g, the NG cathode exhibits two distinct potential plateaus, with charging plateaus ranging from 1.72 to 1.83 V (vs. Zn / Zn). 2+ ) and 1.83~2V (vs. Zn / Zn 2+ The discharge plateaus were 1.77–1.64 V (vs. Zn / Zn). 2+ ) and 1.64~1.47V (vs. Zn / Zn 2+ The discharge specific capacity is approximately 269 mAh / g; at a current density of 1.5 A / g, the charging platform of the NG cathode is 1.74–1.81 V (vs. Zn / Zn). 2+) and 1.81~2V (vs. Zn / Zn 2+ The discharge plateau is 1.75–1.62V (vs. Zn / Zn). 2+ ) and 1.62~1.52V (vs. Zn / Zn 2+ The discharge specific capacity decreased significantly, to only 114 mAh / g. For example... Figure 10 As shown in (b): at a current density of 0.75 A / g, the NG-ZnF2 cathode exhibits only one distinct potential plateau, with a charging plateau of 1.87–2 V (vs. Zn / Zn). 2+ The discharge plateau is 1.6–1.43V (vs. Zn / Zn). 2 + The discharge specific capacity is approximately 195 mAh / g; however, when the current density increases to 1.5 A / g, the discharge specific capacity is essentially zero. These results indicate that while the NG material exhibits considerable performance at lower current densities (0.75 A / g), its performance deteriorates significantly after the current density increases to 1.5 A / g, and its rate capability is far inferior to that of CF. 0.56 Materials; in addition, with NG and CF 0.56 In contrast, NG-ZnF2 has almost no capacity at high current density, indicating that the fluorine element in the graphite sheets improves the rate performance of the battery, while simple physical mixing of fluorine-containing materials is actually detrimental to battery performance.

[0143] (-)Zn|2mol / kg ZnBr2+27mol / kg ZnCl2|CF 0.56 Photographs of the separators at full charge of the (+) dual-ion battery, the (-)Zn|2mol / kgZnBr2+27mol / kgZnCl2|NG(+) dual-ion battery, and the (-)Zn|2mol / kgZnBr2+27mol / kgZnCl2|NG-ZnF2(+) dual-ion battery are shown below. Figure 11 As shown.

[0144] Depend on Figure 11 It can be seen that: in a fully charged state, with CF 0.56 The membrane color of the dual-ion battery with NG as the positive electrode remained unchanged upon full charging, indicating no Br2 elemental formation. However, the membrane of the dual-ion battery with NG as the positive electrode turned yellowish-brown upon full charging, indicating a large amount of Br2 elemental formation. Furthermore, the membrane of the dual-ion battery with NG-ZnF2 as the positive electrode turned light yellow upon full charging, indicating a small amount of Br2 elemental formation. These results demonstrate that compared to fluorine-free NG and NG-ZnF2 containing mixed fluorine materials, the presence of F element within the membrane effectively reduces Br2 elemental formation. 0.56 The positive electrode reaction process is very stable.

[0145] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0146] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of fluorinated graphite in the preparation of halogen-based aqueous dual-ion batteries.

2. A halogen-based aqueous dual-ion battery using fluorinated graphite as the positive electrode, characterized in that, The halogen-based aqueous dual-ion battery includes: a fluorinated graphite positive electrode, a salt-in-water electrolyte, a negative electrode, and a separator.

3. The halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to claim 2, characterized in that, The preparation steps of the fluorinated graphite cathode include: Fluorinated graphite, a conductive agent, a binder, and a solvent are mixed to obtain an electrode slurry; the electrode slurry is coated onto a Ti foil and dried to obtain the fluorinated graphite cathode.

4. The halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to claim 3, characterized in that, The molar ratio of fluorine to carbon in the fluorinated graphite is 0.1 to 0.99:1; the conductive agent includes Super-P or acetylene black; the binder includes sodium carboxymethyl cellulose, polyvinylidene fluoride, or polytetrafluoroethylene.

5. The halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to claim 3, characterized in that, The mass ratio of the fluorinated graphite, conductive agent, and binder is 3–8:1:1; the coating thickness of the electrode paste is 30–40 μm.

6. The halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to claim 2, characterized in that, The salt-in-water electrolyte is composed of an aqueous solution containing one or more of ZnCl2, ZnBr2, and ZnI2.

7. The halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to claim 2, characterized in that, The negative electrode material includes Zn, Cu, Ti, or stainless steel.

8. The halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to claim 2, characterized in that, The diaphragm includes glass fiber filter paper, polyethylene diaphragm, or polypropylene diaphragm.

9. The method for preparing a halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode according to any one of claims 2 to 8, characterized in that, Includes the following steps: The fluorinated graphite positive electrode, the salt-in-water electrolyte, the negative electrode, and the separator are assembled to obtain the halogen-based aqueous dual-ion battery with fluorinated graphite as the positive electrode.

10. A method for improving the cycle stability of a halogen-based aqueous dual-ion battery without sacrificing rate performance, characterized in that, Halogen-based aqueous dual-ion batteries were prepared using fluorinated graphite as the positive electrode.

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