Positive electrode active material, preparation method thereof and aqueous zinc-iodine battery based on eight-electron conversion reaction

Abstract

The invention provides a positive active material, a preparation method thereof and an aqueous zinc-iodine battery based on eight-electron conversion reaction, and belongs to the technical field of energy storage devices. A positive electrode of the aqueous zinc-iodine battery contains a positive electrode active material. According to the invention, an iodine source is designed to be loaded in a thiazole-connected covalent organic framework (TZ-COFs) to serve as an aqueous zinc-iodine battery positive electrode material, so that 8-electron iodine conversion from I <-> to IO4 <-> / IO65 <-> is realized, and the 8-electron iodine reversible oxidation-reduction conversion reaction mechanism of the iodine source is disclosed. The C = N / C-S group of the thiazole unit in the TZ-COFs can reduce the reaction activation energy, accelerate the iodine redox conversion reaction kinetics, and catalyze the novel reversible iodine conversion reaction process from IO3-to IO4- / IO65-. The work opens up a new way for constructing a high-performance aqueous zinc-iodine battery based on a novel oxidation-reduction conversion reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage devices, and in particular relates to a positive electrode active material and a preparation method thereof, and an aqueous zinc-iodine battery based on an eight-electron conversion reaction. Background Art

[0002] In recent years, due to the growing market demand for electric vehicles and electronic products, there is an urgent need to develop high-energy density batteries to meet the needs of modern life. Aqueous zinc-iodine batteries have attracted widespread attention from researchers due to their low cost, inherent safety of aqueous electrolytes, and relatively high theoretical capacities of zinc and iodine. 2 The battery is based on a two-electron I - / I 2 The redox couple conversion reaction has a relatively low working voltage (0.54 V vs. SHE) and storage capacity (211 mAh / g). 2 Batteries have attracted greater interest from researchers. The Chinese invention patent application number 202010392522.6, "An aqueous zinc-iodine battery based on a four-electron conversion reaction and its electrolyte", activates the four-electron conversion reaction by 2 Highly reversible I activation using ICl subhalogen in aqueous electrolytes 2 / I + The capacity of the pair reaches that of the conventional Zn-I 2 The capacity of the battery is twice as high. It is well known that iodine has a variety of valence states, and by activating different conversion reactions between them, the possibility of high output voltage can be achieved. Giving these conversion systems a higher output voltage will hopefully achieve high energy density in batteries, but this may require new redox reaction mechanisms. Theoretically, the I + The above high-valence iodine redox couples may provide multi-electron transfer. In 2024, the team of Professor Liang Xiao of Hunan University followed the four-electron conversion of Zn-I 2 After the battery, through the 0.1MH 2 SO 4 Add 0.1M KBr to the electrolyte and use I - / IO 3 - The couple realizes twelve electron transfer and obtains a high specific capacity of 1200mAh / g@1A / g [1] Although its capacity has made a significant breakthrough, the battery can only be cycled 70 times, resulting in the high specific capacity Zn-I 2 An important reason for the low cycle life of the battery may be the generation of intermediate substances polyiodide ions (I 3 - ) and the final product iodate (IO 3- ), the unrestricted dissolution and diffusion of these soluble iodide-containing intermediates will lead to various undesirable side effects, resulting in poor cycle life of the battery. So far, polyiodides have been mainly confined by carbon materials with good porosity and high specific surface area, such as amorphous carbon nanotubes, carbon cloth and graphene. Although these support materials can constrain iodine species within the cathode support by physical adsorption, the relatively weak physical interaction is still not enough to effectively solve the shuttle effect, especially in long cycle processes. Recently, covalent organic frameworks (COFs) have emerged in the field of batteries as a new type of porous materials with advantages including easily manipulated organic functional groups, tunable structures and high specific surface area. Like carbon materials, COFs also have a lightweight skeleton and superior stability. Inspired by the successful application of functionalized COFs in battery applications, thiazolyl COFs may be a promising candidate for Zn-I 2 Excellent candidate for battery positive electrode support material. Theoretically, it involves I + The above high-valence iodine redox couple may provide multiple electron transfer. Theoretically, I 5+ is not the highest oxidation state of iodine species. At higher potentials, it can produce more reaction electrons through electrochemical oxidation, which means higher energy density. However, hypervalent iodine (I 5+ and I 7+ ) is hampered by sluggish kinetics and unstable intermediates, which limits the possibility of further exploring multi-electron iodine electrochemistry in the field of energy storage.

[0003] [1]Nature Communications,2021,12(1):70 Summary of the invention

[0004] The present invention is made to solve the above problems, and aims to provide a positive electrode active material and a preparation method thereof, and an aqueous zinc-iodine battery based on an eight-electron conversion reaction.

[0005] The present invention provides a method for preparing a positive electrode active material, which has the following characteristics and comprises the following steps: S10, dissolving trimesic acid, 2,6-naphthalenediamine, sulfur and an oxidant in a solvent to obtain a mixed solution; S20, freezing the mixed solution and placing it in a vacuum environment, and then heating it to obtain a brown solid; S30, separating the brown solid from the reaction system, washing and drying it to obtain a thiazole-connected covalent organic framework having a structural formula of S40, mixing and grinding the covalent organic framework and the iodine source, and heating under vacuum conditions to obtain a positive electrode active material, wherein the iodine source is an iodine source that is easy to expose polarity I - Center, can be with H 2 The oxygen in O combines to form high-valent IO 3- of organic iodine.

[0006] The method for preparing the positive electrode active material provided by the present invention may also have the following characteristics: wherein, in step S10, the mass ratio of trimesaldehyde, 2,6-naphthalenediamine and sulfur is 1:(1.2-2.0):(1.2-5.0).

[0007] The method for preparing the positive electrode active material provided by the present invention may also have the following characteristics: wherein, in step S10, the oxidant is a mixture of acetic acid (aq) and dimethyl sulfoxide, and the solvent is a mixed solvent of N,N-dimethylacetamide and 1,3,5-trichlorobenzene.

[0008] In the preparation method of the positive electrode active material provided by the present invention, it can also have the following characteristics: wherein the volume ratio of acetic acid (aq), dimethyl sulfoxide, N,N-dimethylacetamide and 1,3,5-trichlorobenzene is (0.10-0.50):(0.05-0.10):(0.45-0.60):(0.50-1.00), and the concentration of acetic acid (aq) is 6 mol / L.

[0009] The method for preparing the positive electrode active material provided by the present invention may also have the following characteristics: wherein, in step S20, the freezing method is liquid nitrogen bath freezing, and the heating method is: heating to room temperature and then heating in an oven at 120°C to 180°C for 3 days.

[0010] The method for preparing the positive electrode active material provided by the present invention may also have the following characteristics: wherein, in step S30, the separation method is centrifugal separation, the washing method is washing three times with tetrahydrofuran and ethanol, and the drying method is drying in an oven at 90° C. for 12 hours.

[0011] The method for preparing the positive electrode active material provided by the present invention may also have the following characteristics: wherein, in step S40, the mass ratio of the covalent organic framework to the iodine source is (1.0-1.3):(2.0-5.0), and the heating method is to maintain a constant temperature in an oven at 120°C for 12 hours.

[0012] In the preparation method of the positive electrode active material provided by the present invention, it can also have the following characteristics: wherein the iodine source includes any one or more of trimethylsulfur iodide, 2-iodoterephthalic acid, 1-methyl-3-propylimidazole iodide, tri(4-iodophenyl)amine, 1,2-diiodobenzene, (iodomethyl)triphenylphosphonium iodide, elemental iodine or potassium iodide.

[0013] The present invention also provides a positive electrode active material having the following characteristics, which is prepared by any one of the above-mentioned methods for preparing a positive electrode active material.

[0014] The present invention also provides an aqueous zinc-iodine battery based on an eight-electron conversion reaction, which has the following characteristics: wherein the electrolyte of the aqueous zinc-iodine battery is Zn 2+ (aq), the positive electrode of the aqueous zinc-iodine battery contains positive electrode active materials.

[0015] Functions and Effects of the Invention

[0016] The positive electrode of the zinc-iodine battery of the present invention contains positive electrode active materials. When working, the working electrode is in a mild Zn 2+ A novel redox pathway for 8-electron I in (aq) electrolytes - / I 2 / IO 3 - / IO 4 - / IO 6 5- The redox process overcomes the capacity and voltage limitations in the iodine redox reaction. The thiazole unit in TZ-COFs can enhance the adsorption and conversion of iodine species through chemical interactions and inhibit the shuttle effect. At the same time, the C=N / CS group in the thiazole unit in TZ-COFs reduces the energy barrier and improves the conversion kinetics.

[0017] The present invention designs an iodine source loaded in a thiazole-connected covalent organic framework (TZ-COFs) as a positive electrode material for an aqueous zinc-iodine battery, thereby realizing the conversion of I - To IO 4 - / IO 6 5- The 8-electron iodine conversion of iodine is revealed, revealing the 8-electron iodine reversible redox conversion reaction mechanism of iodine source. The C=N / CS group of the thiazole unit in TZ-COFs can reduce the reaction activation energy, accelerate the iodine redox conversion reaction kinetics, and catalyze IO 3 - To IO 4 - / IO 6 5- This work opens up a new path for building high-performance aqueous zinc-iodine batteries based on new redox conversion reactions. - / IO 3 - / IO 4 - / IO 6 5- The electrochemical reaction of the redox couple is shown in the following reaction formula:

[0018]

[0019] The main raw materials used in the present invention are widely available, low in cost and environmentally friendly. The entire system electrode preparation process is carried out at room temperature and pressure, and the operation is simple, safe and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flowchart of a method for preparing a positive electrode active material according to an embodiment of the present invention;

[0021] Figure 2 is a SEM image of a covalent organic framework of an embodiment of the present invention;

[0022] Figure 3 is a TEM image of a covalent organic framework of an embodiment of the present invention;

[0023] Figure 4 The structure diagram and SEM diagram of trimethylsulfur iodide in the embodiment of the present invention;

[0024] Figure 5 1 is an electrochemical performance diagram of an aqueous zinc-iodine battery according to an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of the electrochemical reaction of the iodine-iodate redox couple in the aqueous zinc-iodine battery of an embodiment of the present invention;

[0026] Figure 7 is the CV curve of the zinc-iodine battery of Comparative Example 1 of the present invention;

[0027] Figure 8 is the Zn||TZ-COFs / C in the embodiment of the present invention 3 H 9 IS battery, Zn||COFs / C in comparative example 2 3 H 9 IS battery and Zn||AC / C in comparative example 2 3 H 9 Comparison of electrochemical performance of IS batteries. DETAILED DESCRIPTION

[0028] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments and the accompanying drawings specifically describe a positive electrode active material and a preparation method thereof and an aqueous zinc-iodine battery based on an eight-electron conversion reaction of the present invention.

[0029] <Example>

[0030] This embodiment provides a positive electrode active material.

[0031] Figure 1 1 is a flowchart of a method for preparing a positive electrode active material according to an embodiment of the present invention. Figure 1As shown, the positive electrode active material in this embodiment is prepared by the following steps:

[0032] S10, trimesaldehyde (structural formula: )、2,6-naphthalenediamine (structural formula is ) and sulfur (structural formula ) as a substrate is added into a 10 mL high temperature and pressure resistant glass tube, followed by the addition of 0.1 mL to 0.5 mL of 6 M acetic acid (aq) and 0.05 mL to 0.10 mL of dimethyl sulfoxide as an oxidant, and the addition of 0.45 mL to 0.60 mL of N,N-dimethylacetamide and 0.5 mL to 1.0 mL of 1,3,5-trichlorobenzene as solvents to completely dissolve the aforementioned substances to obtain a mixed solution.

[0033] S20, the high temperature and pressure resistant glass tube is rapidly frozen in a liquid nitrogen bath, evacuated to an internal pressure of 0.5 mbar and flame sealed, and the total length is reduced by about 10 cm. The sealed glass tube is taken out, heated to room temperature, and placed in an oven at 120°C to 180°C for 3 days to produce a brown solid.

[0034] S30, the neck of the sealed glass tube was broken, the brown solid was separated by centrifugation, and finally washed three times with tetrahydrofuran and ethanol, the powder was collected, and dried in an oven at 90°C for 12h to obtain a thiazole-linked covalent organic framework (TZ-COFs material), the structural formula of which is

[0035]

[0036] Figure 2 is a SEM image of a covalent organic framework according to an embodiment of the present invention.

[0037] like Figure 2 As shown, the covalent organic framework prepared in this step exhibits a tightly interwoven rod-like structure.

[0038] Figure 3 is a TEM image of a covalent organic framework according to an embodiment of the present invention.

[0039] like Figure 3 As shown, the covalent organic framework prepared in this step has a jagged edge and a diameter of about 100 nm. The high-magnification TEM image of the covalent organic framework (TZ-COFs material) shows obvious lattice fringes, indicating that the covalent organic framework (TZ-COFs material) has good crystallinity.

[0040] like Figure 2 and 3 As shown, TZ-COFs with thiazole units were successfully prepared in this example.

[0041] S40, the covalent organic framework (TZ-COFs material) and trimethylsulfur iodide (C 3 H 9 IS) were mixed in a mass ratio of 1:3, ground for 30 min, and then placed in a high temperature and pressure resistant glass tube. The glass tube was evacuated three times under a nitrogen atmosphere to ensure that no air remained. The glass tube was then placed in an oven at 120°C for 12 h to obtain TZ-COFs / C 3 H 9 IS composite material, that is, positive electrode active material.

[0042] In this step, trimethylsulfur iodide (C 3 H 9 IS) structure diagram and SEM diagram Figure 4 As shown, Figure 4 1 is a structural diagram and SEM image of trimethylsulfur iodide in an embodiment of the present invention.

[0043] This embodiment also provides an aqueous zinc-iodine battery based on an eight-electron conversion reaction.

[0044] The preparation process of the aqueous zinc-iodine battery based on the eight-electron conversion reaction in this embodiment is as follows: First, the positive electrode active material (TZ-COFs / C 3 H 9 IS composite material), activated carbon (AC) and polytetrafluoroethylene (PTFE) were mixed in a mass ratio of 8:1:1, added to ethanol and ground into a slurry, which was dried at 30 °C and pressed onto a stainless steel mesh to obtain a positive working electrode (i.e., TZ-COFs / C 3 H 9 IS positive electrode); then, a CR2032 button-type battery shell was selected, the prepared working electrode was used as the positive electrode, a metal zinc sheet (purity ≥ 99.00%) was used as the negative electrode, a GE-Whatman glass fiber separator, and a 3M ZnSO 4 (aq) is the electrolyte, and an aqueous zinc-iodine battery based on an eight-electron conversion reaction is assembled.

[0045] In this embodiment, the electrochemical performance test of the aqueous zinc-iodine battery is carried out as follows: the device energy storage performance is tested by CHI660E electrochemical workstation at room temperature. The cycle and rate performance tests are carried out on LAND CT2001A battery test system. The voltage window is 0.1V~1.8V.

[0046] Figure 5 1 is an electrochemical performance diagram of an aqueous zinc-iodine battery according to an embodiment of the present invention; Figure 6 It is a schematic diagram of the electrochemical reaction of the iodine-iodate redox couple in the aqueous zinc-iodine battery of an embodiment of the present invention.

[0047] like Figure 5 and 6 As shown, Zn||TZ-COFs / C 3 H 9 The CV curve of the IS battery shows four pairs of obvious redox peaks at 0.54 / 0.53V, 1.16 / 1.26V, 1.32 / 1.34V and 1.54 / 1.65V, respectively. Figure 5 Figure a). It can be clearly seen from the GCD curve that TZ-COFs / C 3 H 9 IS positive electrode starts at 1.16 / 1.26V with 6 electrons I - / IO 3 - The conversion yields an ultra-high capacity of 1248 mAh / g. 3 - To IO 4 - / IO 6 5- The 2-electron reversible conversion reaction provides an additional capacity of 124 mAh / g ( Figure 5 In addition, at 1.32 / 1.34V and 1.54 / 1.65V, IO 3 - / IO 4 - and IO 3 - / IO 6 5- The redox reaction converts Zn-I 2 System Zn||TZ-COFs / C 3 H 9 The discharge potential of the IS battery was increased to 1.3 V. Therefore, Zn||TZ-COFs / C 3 H 9 The IS battery has achieved ultra-high capacity (1372mAh / g) and extremely excellent energy density (1738Wh / kg).

[0048] <Comparative Example 1>

[0049] This comparative example refers to the positive electrode active material and the preparation process of the aqueous zinc-iodine battery in the embodiment to prepare TZ-COFs / I 2 Zinc-iodine battery with composite material as positive electrode.

[0050] Figure 7 It is the CV curve of the zinc-iodine battery of Comparative Example 1 of the present invention.

[0051] like Figure 7As shown, Zn||TZ-COFs / I 2 The CV curve of the battery only shows a pair of redox peaks at 1.47 / 1.33V, corresponding to I 3 - / I - From the GCD curve, it can be seen that TZ-COFs / I 2 The electrode only provided a capacity of 182 mAh / g.

[0052] <Comparative Example 2>

[0053] This comparative example refers to steps S10 to S40 in the preparation method of the positive electrode active material in the embodiment to prepare the comparative electrode 1. The difference is that sulfur is not added during the preparation of the comparative electrode 1. The comparative electrode 1 is a COFs / C 3 H 9 IS composite electrode.

[0054] This comparative example also refers to step S40 in the method for preparing the positive electrode active material in the embodiment to prepare AC / C 3 H 9 IS composite electrode, denoted as comparative electrode 2.

[0055] Subsequently, referring to the preparation process of the aqueous zinc-iodine battery in the embodiment, comparative electrode 1 and comparative electrode 2 were used as the positive electrode of the working electrode to prepare Zn||COFs / C 3 H 9 IS battery and Zn||AC / C 3 H 9 IS battery. After the battery is assembled, the cycle performance is tested at a current density of 1A / g.

[0056] Figure 8 is the Zn||TZ-COFs / C in the embodiment of the present invention 3 H 9 IS battery, Zn||COFs / C in comparative example 2 3 H 9 IS battery and Zn||AC / C in comparative example 2 3 H 9 Comparison of electrochemical performance of IS batteries.

[0057] like Figure 8 As shown, Zn||TZ-COFs / C 3 H 9 The IS battery has a reversible discharge capacity of 1375 mAh / g at 1 A / g and retains 74% of its initial capacity after 420 cycles, which is better than that of Zn||AC / C 3 H 9IS battery (1200mAh / g, 30%) and Zn||COFs / C 3 H 9 The performance of IS battery (1116mAh / g, 10%) is comparable to that of TZ-COFs / C 3 H 9 Compared with the IS positive electrode cycle performance, AC / C 3 H 9 IS and COFs / C 3 H 9 The rapid capacity decay of the IS cathode during battery cycling further indicates that TZ-COFs not only promote the redox chemistry of iodine but also effectively inhibit the shuttle effect of iodine, thereby improving the cycle life of the battery.

[0058] Functions and Effects of the Embodiments

[0059] According to the embodiment and comparative example 1, the zinc-iodine battery constructed in this embodiment achieves 1 - To IO 4 - / IO 6 5- The 8-electron iodine conversion is reversible, so it can have excellent electrochemical performance with a discharge capacity of 1372mAh / g and an energy density of 1738Wh / kg. Therefore, only the zinc-iodine battery assembled by using the zinc-iodine battery electrolyte prepared by the present invention and the zinc-iodine battery positive electrode can obtain excellent electrochemical performance.

[0060] In this embodiment, trimethylsulfur iodide (C 3 H 9 IS) is loaded in thiazole-linked covalent organic frameworks (TZ-COFs) as the positive electrode material for aqueous zinc-iodine batteries, in order to achieve the goal of - To IO 4 - / IO 6 5- The 8 electrons of iodine are converted.

[0061] This embodiment is to achieve I - To IO 4 - / IO 6 5- The reversible transformation of covalent organic frameworks (TZ-COFs) is used as the cathode carrier of aqueous zinc-iodine batteries. The C=N / CS group of the thiazole unit in TZ-COFs can reduce the reaction activation energy, accelerate the kinetics of iodine redox conversion, and catalyze IO 3 - To IO 4 - / IO 65- A novel reversible iodine conversion reaction process. 3 H 9 IS positive electrode starts at 1.16 / 1.26V with 6 electrons I - / IO 3 - conversion, obtaining an ultra-high capacity of 1248 mAh / g, and then proceeding from IO 3 - To IO 4 - / IO 6 5- The two-electron reversible conversion reaction provides an additional capacity of 124 mAh / g. In addition, at 1.32 / 1.34 V and 1.54 / 1.65 V, IO 3 - / IO 4 - and IO 3 - / IO 6 5- The redox reaction of Zn||TZ-COFs / C 3 H 9 The discharge potential of the IS battery is increased to 1.3V, which gives the battery an ultra-high capacity (1372mAh / g) and an extremely excellent energy density (1738Wh / kg).

[0062] The main raw materials used in this embodiment are widely available, low-cost and environmentally friendly. The entire system electrode preparation process is carried out at room temperature and pressure, and the operation is simple, safe and pollution-free.

[0063] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, which are within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a positive electrode active material, characterized in that: The following steps are involved: S10, dissolving trimesaldehyde, 2,6-naphthalenediamine, sulfur and an oxidant in a solvent to obtain a mixed solution; S20, freezing the mixed solution and placing it in a vacuum environment, and then heating it to obtain a brown solid; S30, separating the brown solid from the reaction system, washing and drying to obtain a thiazole-linked covalent organic framework, the structural formula of which is S40, mixing and grinding the covalent organic framework and the iodine source, and heating under vacuum conditions to obtain a positive electrode active material, Wherein, the iodine source is easily exposed to polarity I - center, which can combine with oxygen in H2O to form high-valent IO3 - of organic iodine.

2. The method for preparing a positive electrode active material according to claim 1, characterized in that: in, In step S10, the mass ratio of trimesaldehyde, 2,6-naphthalenediamine and sulfur is 1:(1.2-2.0):(1.2-5.0).

3. The method for preparing the positive electrode active material according to claim 1, characterized in that: in, In step S10, the oxidant is a mixture of acetic acid (aq) and dimethyl sulfoxide, The solvent is a mixed solvent of N,N-dimethylacetamide and 1,3,5-trichlorobenzene.

4. The method for preparing the positive electrode active material according to claim 3, characterized in that: in, The volume ratio of acetic acid (aq), dimethyl sulfoxide, N,N-dimethylacetamide and 1,3,5-trichlorobenzene is (0.10-0.50):(0.05-0.10):(0.45-0.60):(0.50-1.00), The concentration of acetic acid (aq) is 6 mol / L.

5. The method for preparing a positive electrode active material according to claim 1, characterized in that: in, In step S20, the freezing method is liquid nitrogen bath freezing. The heating method is: heating to room temperature and then heating in an oven at 120°C to 180°C for 3 days.

6. The method for preparing a positive electrode active material according to claim 1, characterized in that: in, In step S30, the separation method is centrifugal separation. The washing method is to use tetrahydrofuran and ethanol to wash three times. The drying method is to place it in an oven at 90°C for 12 hours.

7. The method for preparing a positive electrode active material according to claim 1, characterized in that: in, In step S40, the mass ratio of the covalent organic framework to the iodine source is (1.0-1.3):(2.0-5.0), The heating method is to keep the temperature in an oven at 120°C for 12 hours.

8. The method for preparing a positive electrode active material according to claim 1, characterized in that: in, The iodine source includes any one or more of trimethylsulfur iodide, 2-iodoterephthalic acid, 1-methyl-3-propylimidazole iodide, tri(4-iodophenyl)amine, 1,2-diiodobenzene, (iodomethyl)triphenylphosphonium iodide, elemental iodine or potassium iodide.

9. A positive electrode active material, characterized in that: The positive electrode active material is prepared by the method for preparing the positive electrode active material according to any one of claims 1 to 8.

10. An aqueous zinc-iodine battery based on an eight-electron conversion reaction, characterized in that: in: The electrolyte of the aqueous zinc-iodine battery is Zn 2+ (aq), The positive electrode of the aqueous zinc-iodine battery contains the positive electrode active material according to claim 9.

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