Nitrogen-rich triazine polymer iodine-loaded positive electrode material and preparation method thereof
By combining nitrogen-rich triazine polymers with elemental iodine to form a porous structure, and combining it with a three-dimensional porous carbon cloth current collector, the problems of iodine shuttle effect and structural instability in aqueous zinc-iodine batteries were solved, achieving efficient electrochemical reaction and long cycle life.
Patent Information
- Application Number
- CN202511135825.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-14
- Publication Date
- 2025-11-21
AI Technical Summary
Existing aqueous zinc-iodine batteries suffer from low coulombic efficiency and short cycle life due to the iodine shuttle effect, slow reaction kinetics, and structural instability.
A nitrogen-rich triazine polymer was used as a carrier to form a porous structure with elemental iodine. Iodine species were fixed through a combination of chemical anchoring and physical confinement. An electronic conductive network was constructed by combining the three-dimensional porous carbon cloth current collector, thus optimizing the electrode structure.
It significantly improves the coulombic efficiency and cycle stability of the battery, enhances the electrochemical reaction kinetics of the electrodes, and extends the cycle life of the battery.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of electrochemical energy storage, in particular to a nitrogen-rich triazine polymer loaded with iodine as a positive electrode material and a preparation method thereof. BACKGROUND
[0002] With the increasing demand for sustainable energy worldwide, developing electrochemical energy storage systems with high safety, low cost and environmental friendliness has become an important research direction. Among them, water-based rechargeable batteries, especially water-based zinc ion batteries, have attracted much attention due to their inherent high safety, abundant zinc resources, low cost and high theoretical capacity. Among the many positive electrode materials, iodine has a high theoretical specific capacity (211 mAh g -1 ), a suitable redox potential and fast reaction kinetics, which makes it have great application potential in the field of water-based zinc batteries.
[0003] In the existing technical solutions, in order to overcome the problems of low conductivity and easy solubility of elemental iodine in water-based electrolyte, porous carbon materials are usually used as conductive matrix and physical carrier to carry iodine active material. Specifically, elemental iodine is usually melt-composited with active carbon, carbon nanotubes or graphene and other carbon materials to prepare iodine-carbon composite positive electrode materials. Then, the composite positive electrode material is mixed with a conductive agent and a binder to form a slurry, which is coated on a conventional two-dimensional planar current collector (such as carbon paper or aluminum foil) to prepare a positive electrode sheet, which together with the zinc negative electrode forms a water-based zinc-iodine battery.
[0004] Although the existing technology provides a certain technical basis for the development of water-based zinc-iodine batteries by loading iodine on carbon materials to construct a positive electrode, it still has some deficiencies in practical application. First, the loss and shuttle effect of active materials are still serious. The fundamental reason is that the intermediate product polyiodide anion (such as I3 - , I5 - ) generated in the charging and discharging process has a high solubility in the water-based electrolyte. The conventional carbon carrier mainly binds iodine species through weak physical adsorption such as van der Waals force. This non-specific weak interaction force is not enough to effectively anchor the dissolved polyiodide anion, which inevitably diffuses from the positive electrode side and shuttles to the negative electrode, causing self-discharge and irreversible capacity decay, thereby seriously reducing the coulombic efficiency and cycle life of the battery.
[0005] Secondly, the electrochemical reaction kinetics of existing positive electrode materials needs to be improved, resulting in poor rate performance. On the one hand, the pore size distribution of the conventional carbon carrier is often not optimized, and part of the micropore may limit the effective infiltration of the electrolyte and the rapid transmission of ions, increasing the concentration polarization. On the other hand, when the positive electrode slurry is coated on the two-dimensional planar current collector, especially in the high-load thick electrode required by the pursuit of high energy density, the transmission path of electrons and ions becomes tortuous and long, resulting in an increase in the internal resistance of the electrode as a whole, and the performance decay is particularly obvious at high current density.
[0006] In addition, the structural stability of the electrode also faces challenges in long-term cycling. Iodine is accompanied by significant phase change and volume change during charging and discharging. This repeated volume expansion and contraction generates huge mechanical stress inside the active material layer. For the active layer attached to the two-dimensional planar current collector, this stress easily leads to the agglomeration, pulverization of active material particles, and even peeling off from the surface of the current collector, ultimately causing the destruction of the electrode structure and the continuous degradation of the battery performance. SUMMARY
[0007] In view of the deficiencies of the prior art, the present application provides a nitrogen-rich triazine polymer iodine-loaded positive electrode material and a preparation method thereof, solving the problems of low coulomb efficiency and short cycle life of aqueous zinc-iodine batteries caused by iodine shuttling effect, slow reaction kinetics and unstable structure in the prior art.
[0008] To achieve the above object, the technical scheme is as follows: The first aspect of the present application provides a nitrogen-rich triazine polymer iodine-loaded positive electrode material.
[0009] The positive electrode material is a composite material composed of a specific positive electrode material, a conductive agent, a binder and a three-dimensional porous carbon cloth current collector. Its specific composition is: the positive electrode material 90-110 parts by weight; the conductive agent 45-55 parts by weight; the binder 13-18 parts by weight; the three-dimensional porous carbon cloth current collector 70-90 parts by weight.
[0010] Among them, the positive electrode material is the core of the technical scheme, which is composed of 30-35 parts by weight of porous nitrogen-rich triazine polymer carrier and 65-70 parts by weight of elemental iodine. The porous nitrogen-rich triazine polymer carrier is a specially designed iodine carrier, which is synthesized by using 3,5-diaminobenzonitrile and cyclohexanehexaketone hydrate as reaction monomers. In the polymer skeleton formed by this specific monomer combination, there are naturally rich triazine ring structures and nitrile functional groups. These structures provide high-density and space-configuration-determined Lewis basic sites, which can coordinate with iodine molecules and polyiodide anions (such as I3 - , I5 -between the iodine species and the polymer carrier, i.e. chemical anchoring. This chemical anchoring firmly binds the iodine species to the carrier skeleton, fundamentally inhibiting its dissolution and migration in the electrolyte.
[0011] Meanwhile, the multi-level pore structure formed in the polymer carrier after high-temperature activation treatment provides physical accommodation space for the iodine species, realizing physical confinement. Through the dual synergistic effect of chemical anchoring and physical confinement, the loss of active substances is significantly reduced.
[0012] The conductive agent in the present solution is used to build a continuous electron conduction network inside the positive electrode material, reducing the contact resistance and charge transfer resistance of the electrode. The binder is used to tightly bond the positive electrode material and the conductive agent particles, and to ensure that the overall active layer is firmly attached to the surface of the current collector, thereby maintaining the structural integrity of the electrode during charging and discharging cycles.
[0013] The three-dimensional porous carbon cloth current collector has multiple functions: first, as a current collector, it provides an excellent electron collection and transmission path for the electrode; second, its three-dimensional network structure provides a secondary physical confinement space for the positive electrode active material, further preventing the active material from falling off the electrode; third, its porous structure is conducive to the infiltration of electrolyte and the rapid transmission of ions, reducing the ion diffusion resistance.
[0014] The second aspect of the present application provides a preparation method of a nitrogen-rich triazine polymer carrier iodine positive electrode material.
[0015] The method is used for preparing the positive electrode material described above, and comprises the following steps: Step S1: synthesis of polymer precursor. Cyclohexanehexone hydrate and 3,5-diaminobenzonitrile are used as reaction monomers for polymerization. Specifically, the two reaction monomers are placed in an acetic acid solvent, and heated at a temperature of 140-150℃ for 46-50 hours. This process ensures that the monomers undergo sufficient condensation polymerization to form a polymer skeleton rich in triazine rings and nitrile functional groups.
[0016] Step S2: preparation of porous carrier. The polymer precursor obtained in step S1 is mixed with zinc chloride and then activated at high temperature, and then the zinc chloride is removed. Specifically, the polymer precursor and zinc chloride are uniformly mixed in a mass ratio of 1:(3.5-4.5), and then calcined at a high temperature of 380-420℃ under the protection of an inert atmosphere. In this process, zinc chloride acts as a template agent and an activator, etching a large number of microporous and mesoporous structures on the polymer skeleton. After calcination, an acid solution is used for cleaning to completely remove the zinc chloride as a template agent, thereby exposing the multi-level pores inside the carrier.
[0017] Step S3: iodine loading process. The porous nitrogen-rich triazine polymer support obtained in step S2 is reacted with elemental iodine under vacuum-sealed conditions to obtain a positive electrode material. Specifically, the mixture is placed in a sealed container, vacuumed and sealed to exclude moisture and oxygen in the air from interfering with the reaction. Then the reaction is heated at a temperature of 100-110°C for 4.5-5.5 hours. The temperature is higher than the sublimation point of iodine, so that iodine uniformly and deeply penetrates into the porous structure of the support in the form of vapor, and fully chemically anchors with the nitrogen-containing sites.
[0018] Step S4: preparation of slurry. The positive electrode material obtained in step S3, the conductive agent and the binder are mixed in N-methylpyrrolidone solvent to form a uniform slurry. To ensure the high uniformity of the slurry, the above-mentioned solid powders are first pre-mixed by dry method for 10-15 minutes. Then, the total amount of 120-150 parts by weight of N-methylpyrrolidone solvent is added in 2-4 batches during continuous grinding, and the continuous grinding is maintained until the total grinding time reaches 45-75 minutes. This method can effectively avoid particle agglomeration and obtain a uniformly dispersed and suitable viscosity electrode slurry.
[0019] Step S5: preparation of electrode sheet. The slurry prepared in step S4 is uniformly coated on a three-dimensional porous carbon cloth current collector to obtain a final nitrogen-rich triazine polymer iodine-loaded positive electrode material. Specifically, a coating machine is used for coating, and the wet film thickness is controlled to be 100-150 μm to ensure the consistency of the electrode surface density. The drying process adopts a two-step method: first, pre-drying at 60-70°C for 30-45 minutes to gently remove most of the solvent and prevent the coating from cracking; then, final drying under vacuum conditions at 50-60°C for 10-14 hours to completely remove the residual solvent and obtain a structurally stable positive electrode sheet.
[0020] The present application provides a nitrogen-rich triazine polymer iodine-loaded positive electrode material and a preparation method thereof. The present application has the following beneficial effects: 1. The porous nitrogen-rich triazine polymer synthesized by using specific monomers (cyclohexanehexaketone hydrate and 3,5-diaminobenzonitrile) as the carrier of iodine fundamentally suppresses the shuttle effect of polyiodide. The triazine ring and nitrile group functional groups rich in the carrier skeleton provide a high density of Lewis basic sites, which can form strong chemical anchoring with iodine and polyiodide anions; at the same time, the multi-level pore structure of the carrier forms physical confinement for the active material. The dual effects of chemical anchoring and physical confinement firmly bind the active material to the positive electrode side, greatly reducing its dissolution and migration in the electrolyte, thereby significantly improving the coulombic efficiency and cycle stability of the battery.
[0021] 2、The positive electrode material of the application has optimized electrochemical reaction kinetics. On the one hand, the high specific surface area and porous structure of the porous nitrogen-rich triazine polymer carrier ensure sufficient infiltration of the electrolyte and shorten the ion diffusion path; on the other hand, the three-dimensional porous carbon cloth used as the current collector constructs an efficient three-dimensional electron conduction network throughout the thickness of the electrode. The simultaneous optimization of electron transport and ion diffusion path effectively reduces the charge transfer resistance and concentration polarization of the electrode, so that the positive electrode material can achieve high rate performance and capacity utilization.
[0022] 3、The positive electrode material provided by the application has excellent structural stability and high loading capacity. The three-dimensional porous carbon cloth current collector is not only a conductive network, but also a mechanical support skeleton that can effectively buffer the volume change of iodine active materials during charging and discharging. Combined with the optimized slurry preparation and coating process, it ensures that the active material layer can be uniformly and firmly attached to the current collector skeleton, effectively preventing the electrode from pulverizing and falling off during long-term cycling, and ensuring the long cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS
[0023] Figure 1 is the schematic diagram of the electrochemical test of the application; Figure 2 is the schematic diagram of the constant current charge and discharge test of the application; Figure 3 is the test schematic diagram of the Gitt and diffusion coefficient of the application. DETAILED DESCRIPTION
[0024] The technical solutions in the embodiments of the application will be described below in conjunction with the drawings in the specification of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.
[0025] Please refer to the drawings in the specification of the application Figure 1 - the drawings Figure 3 : Example 1 Material selection and range: The positive electrode material prepared in this embodiment is composed of the following components by weight fraction: positive electrode material: 90 parts; conductive agent (acetylene black): 45 parts; binder (PVDF): 13 parts; three-dimensional porous carbon cloth current collector: 70 parts; Among them, the positive electrode material is made of the following components by weight fraction: Porous nitrogen-rich triazine polymer carrier: 30 parts; elemental iodine: 65 parts.
[0026] Product preparation method: Preparation of polymer precursor (S1): Cyclohexanehexone hydrate and 3,5-diaminobenzonitrile as reaction monomers were placed in an ice acetic acid solvent. The reaction system was heated at a temperature of 140℃ for 46 hours. After the reaction was completed, the polymer precursor powder was obtained after purification and drying.
[0027] Preparation of porous nitrogen-rich triazine polymer carrier (S2): The polymer precursor obtained in step 1 was uniformly mixed with zinc chloride powder at a mass ratio of 1:3.5. The mixture was subjected to high-temperature activation treatment at 380℃ under a nitrogen atmosphere. After the treatment was completed, the product was washed with a hydrochloric acid solution to completely remove the zinc chloride template, and finally washed and dried to obtain the porous nitrogen-rich triazine polymer carrier.
[0028] Preparation of positive electrode material (S3): The porous nitrogen-rich triazine polymer carrier obtained in step 2 was mixed with elemental iodine and placed in a quartz ampoule. The ampoule was vacuum sealed after being vacuumed, and then heated at a temperature of 100℃ for 4.5 hours. After cooling, the positive electrode material was obtained.
[0029] Preparation of slurry (S4): 90 parts of positive electrode material, 45 parts of conductive agent, and 13 parts of binder were dry-premixed in a mortar for 10 minutes. Then, 120 parts of N-methylpyrrolidone solvent was added in two batches while continuously grinding, and the continuous grinding was maintained until the total grinding time reached 45 minutes, forming a uniform slurry.
[0030] Preparation of positive electrode sheet (S5): The slurry prepared in step 4 was uniformly coated on 70 parts of three-dimensional porous carbon cloth current collector using a coating machine, and the wet film thickness was controlled to be 100μm. The coated electrode sheet was pre-dried at 60℃ for 30 minutes, and then transferred to a vacuum oven at 50℃ for final drying for 10 hours, thereby obtaining the positive electrode material of the present embodiment.
[0031] Example 2: Material selection and range: The positive electrode material prepared in this embodiment is composed of the following components in weight parts: Positive electrode material: 100 parts; conductive agent (acetylene black): 50 parts; binder (PVDF): 15 parts; three-dimensional porous carbon cloth current collector: 80 parts; Among them, the positive electrode material is made of the following components in weight parts: Porous nitrogen-rich triazine polymer carrier: 33 parts; elemental iodine: 67 parts.
[0032] Product preparation method: Preparation of polymer precursor (S1): cyclohexanehexaketone hydrate and 3,5-diaminobenzonitrile as reaction monomers were placed in glacial acetic acid solvent. The reaction system was heated at a temperature of 145℃ for 48 hours to obtain the polymer precursor.
[0033] Preparation of porous nitrogen-rich triazine polymer carrier (S2): the polymer precursor obtained in step 1 was mixed with zinc chloride at a mass ratio of 1:4.0, high-temperature activation was carried out at 400℃ under a nitrogen atmosphere, and then the template was removed by washing with an acid solution to obtain the carrier.
[0034] Preparation of positive electrode material (S3): the carrier obtained in step 2 was mixed with elemental iodine, and heated at a temperature of 105℃ for 5.0 hours under vacuum sealing to obtain the positive electrode material.
[0035] Preparation of slurry (S4): 100 parts of the positive electrode material, 50 parts of the conductive agent, and 15 parts of the binder were dry-premixed for 12 minutes. Then, the total amount of 135 parts of N-methyl pyrrolidone solvent was added in three batches under continuous grinding, and the total grinding time was 60 minutes to form a uniform slurry.
[0036] Preparation of positive electrode sheet (S5): the slurry of step 4 was uniformly coated on 80 parts of three-dimensional porous carbon cloth current collector, and the wet film thickness was controlled to be 125μm. The electrode sheet was pre-dried at 65℃ for 38 minutes, and then finally dried at 55℃ under vacuum for 12 hours.
[0037] Example 3: Material selection and range: The positive electrode material prepared in this example is composed of the following components in weight fraction: Positive electrode material: 110 parts; conductive agent (acetylene black): 55 parts; binder (PVDF): 18 parts; three-dimensional porous carbon cloth current collector: 90 parts; Among them, the positive electrode material is made of the following components in weight fraction: Porous nitrogen-rich triazine polymer carrier: 35 parts; elemental iodine: 70 parts.
[0038] Product preparation method: Preparation of polymer precursor (S1): cyclohexanehexaketone hydrate and 3,5-diaminobenzonitrile as reaction monomers were placed in glacial acetic acid solvent and heated at 150℃ for 50 hours to obtain the polymer precursor.
[0039] Preparation of porous nitrogen-rich triazine polymer carrier (S2): the polymer precursor was mixed with zinc chloride at a mass ratio of 1:4.5, high-temperature activation was carried out at 420℃ under a nitrogen atmosphere, and then the template was removed by washing with an acid solution to obtain the carrier.
[0040] Preparation of positive material (S3): The carrier was mixed with elemental iodine, and heated at a temperature of 110°C for 5.5 hours under vacuum sealing condition to obtain the positive material.
[0041] Preparation of slurry (S4): 110 parts of the positive material, 55 parts of the conductive agent and 18 parts of the binder were dry-premixed for 15 minutes. Subsequently, 150 parts of N-methyl pyrrolidone solvent was added in 4 batches under continuous grinding, and the total grinding time was 75 minutes to form a uniform slurry.
[0042] Preparation of positive electrode sheet (S5): The slurry was uniformly coated on 90 parts of the three-dimensional porous carbon cloth current collector, and the wet film thickness was controlled to be 150 μm. The electrode sheet was pre-dried at 70°C for 45 minutes, and then finally dried at 60°C under vacuum condition for 14 hours.
[0043] Comparative Example 1: Compared with Example 2, the difference lies in that, in the preparation process of the positive material, the commercially available ordinary activated carbon is used to replace the "porous nitrogen-rich triazine polymer carrier" prepared in step 2 as the carrier of iodine. All other component proportions, preparation steps and process parameters are exactly the same as those of Example 2.
[0044] Comparative Example 2: Compared with Example 2, the difference lies in that, in the preparation process of the porous nitrogen-rich triazine polymer carrier, the step of mixing with zinc chloride and high-temperature activation in step 2 is omitted, i.e. the "polymer precursor" prepared in step 1 is directly used as the carrier of iodine. All other component proportions, preparation steps and process parameters are exactly the same as those of Example 2.
[0045] Comparative Example 3: Compared with Example 2, the difference lies in that, in the preparation step (S5) of the positive electrode sheet, the conventional flat aluminum foil is used to replace the "three-dimensional porous carbon cloth current collector" as the coating substrate of the slurry. All other component proportions, preparation steps and process parameters are exactly the same as those of Example 2.
[0046] Test Example 1: In order to evaluate the electrochemical performance of the positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-3, the following tests were carried out.
[0047] Battery assembly: The positive electrode sheets prepared in Examples 1-3 and Comparative Examples 1-3 were used as the working electrode, high-purity zinc foil was used as the counter electrode and reference electrode, glass fiber filter paper was used as the separator, and 2M zinc sulfate aqueous solution was used as the electrolyte. Under ambient temperature and atmospheric pressure, the above-mentioned components were assembled into CR2032 type button cells. All the assembled batteries were allowed to stand for 12 hours before electrochemical testing, so as to ensure that the electrolyte was completely soaked into the electrode.
[0048] Electrochemical performance test: All tests were performed on an electrochemical workstation, and the test voltage range was 0.8 V to 1.6 V.
[0049] First cycle coulombic efficiency and discharge specific capacity test: After standing, each group of batteries was subjected to a first charge-discharge cycle at a current density of 0.1 C (1 C = 211 mAh / g, based on the theoretical capacity of iodine). The first discharge specific capacity was recorded, and the first coulombic efficiency was calculated (first charge capacity / first discharge capacity x 100%).
[0050] Cycle stability test: After completing the first cycle, each group of batteries was subjected to continuous charge-discharge cycle tests at a current density of 1.0 C, for a total of 500 times. The discharge specific capacity after the 500th cycle was recorded, and the capacity retention rate relative to the first discharge specific capacity was calculated.
[0051] Rate performance test: For each newly assembled group of batteries, 5 charge-discharge cycles were performed at current densities of 0.1 C, 0.2 C, 0.5 C, 1.0 C, and 2.0 C, respectively. The stable discharge specific capacities of each battery at the 5th cycle at different current densities were recorded and compared.
[0052] The experimental data is shown in Table 1.
[0053] Table of electrochemical performance test results of examples and comparative examples From Table 1, it can be seen that: The positive electrode materials prepared in Examples 1-3 showed significant differences in coulombic efficiency, cycle stability, and rate performance compared to Comparative Examples 1-3. The positive electrode material prepared in Example 2 had a first discharge specific capacity of 195.4 mAh / g, a first coulombic efficiency of 99.5%, and a capacity retention rate of 92.3% after 500 cycles at 1.0 C. In comparison, the first coulombic efficiency of Comparative Example 1 (using a conventional activated carbon carrier) was only 85.3%, and the capacity retention rate was only 45.1%. This difference is attributed to the use of the porous nitrogen-rich triazine polymer carrier in the present technical solution. The triazine ring and nitrile functional groups in the carrier skeleton provide abundant Lewis base sites, which firmly anchor iodine and polyiodide anions through chemical interaction forces; at the same time, the multi-level pore structure of the carrier provides physical confinement for the active material. The synergistic effect of chemical anchoring and physical confinement effectively inhibits the dissolution and shuttling of active materials in the electrolyte, thereby reducing self-discharge and irreversible capacity loss.
[0054] The discharge specific capacity of Example 2 was 153.8 mAh / g at a large current density of 2.0 C, which was much higher than that of Comparative Example 2 (98.4 mAh / g). This was because the carrier formed abundant hierarchical pores after high-temperature activation treatment, greatly increasing the specific surface area and providing low-resistance channels for the infiltration of electrolyte and the rapid transmission of ions. Combined with the efficient electron transmission network constructed by the three-dimensional porous carbon cloth current collector itself, the charge transfer and mass transfer processes inside the electrode were optimized, the polarization of the electrochemical reaction was reduced, and thus excellent rate performance was achieved.
[0055] As can be seen from the test results of Comparative Example 2 and Comparative Example 3 (using a conventional two-dimensional aluminum foil current collector), although the initial capacity and efficiency of the two were similar, the capacity retention rate of Example 2 (92.3%) was much higher than that of Comparative Example 3 (70.2%) after 500 cycles. This result shows that the three-dimensional porous carbon cloth current collector as a mechanical support skeleton of the active material layer can effectively buffer the volume change of iodine during charging and discharging, and firmly fix the active material particles through its three-dimensional network structure to prevent them from being pulverized or falling off from the surface of the current collector in long-term cycling. This structural stability ensures that the electrode can maintain its structural integrity in long-term operation, thereby achieving a longer cycle life.
[0056] Test Example 2: To study the electrochemical reaction characteristics of the positive electrode material of the application, the final positive electrode material (PT-I2) prepared in Example 2 and the intermediate product pure carrier (PT) were subjected to cyclic voltammetry test. The test was carried out in a CR2032 type button cell, and the cell was assembled in the same way as in Test Example 1. An electrochemical workstation was used to test in a voltage window of 0.5 V to 1.6 V (vs. Zn 2＋ / Zn) at a scan rate of 0.2 mVs -1 , to record its electrochemical response. The results of this test are shown in the accompanying Figure 1 .
[0057] Referring to the accompanying Figure 1 , the figure shows the CV curves of the pure carrier PT and the final positive electrode material PT-I2. As shown in the figure, the CV curve of the pure carrier PT does not show obvious redox peaks in the set voltage interval, indicating that its own electrochemical activity is low. In contrast, the CV curve of the PT-I2 positive electrode material shows a pair of clear and symmetrical redox peaks in the interval of about 1.2 V to 1.3 V, which corresponds to the multi-step reversible conversion reaction of iodine species in the electrochemical process.
[0058] The comparison results prove that the electrochemical energy storage function in the technical solution is provided by the loaded elemental iodine, and the porous nitrogen-rich triazine polymer (PT) itself mainly serves as a matrix for carrying and stabilizing the active material. The triazine ring and the nitrile group and other nitrogen-containing functional groups contained in the carrier skeleton provide chemical anchoring sites for iodine species, but they do not participate in the redox reaction within the working voltage window, thereby ensuring the specificity and stability of the electrochemical reaction.
[0059] The symmetry and reversibility of the peak shape preliminarily indicate that the electrochemical reaction of iodine in the specific carrier has good reversibility. This reversibility is achieved based on the effective binding of the carrier to iodine and its polyiodide. Through the dual action of chemical anchoring and physical confinement, the active material is fixed inside the electrode, avoiding its dissolution and loss in the electrolyte, thereby ensuring that the active material can efficiently participate in the reaction in each charge and discharge cycle, which is the basis for achieving high coulombic efficiency and long cycle stability.
[0060] Test Example 3: To evaluate the long-term cycle stability of the positive electrode material at high rates, the PT-I2 positive electrode sheet prepared in Example 2 was assembled into a coin cell, and the battery assembly method was the same as that in Test Example 1. Using a battery test system, constant current charge and discharge cycle tests were carried out at a high current density of 5 Ag -1 , a total of 10,000 times, to evaluate its performance retention ability under high intensity working conditions. The results of this test are shown in the accompanying Figure 2 .
[0061] Referring to the accompanying Figure 2 , the figure shows the long cycle performance of the PT-I2 positive electrode material at a current density of 5 Ag -1 . As shown in the figure, the initial specific discharge capacity of the positive electrode material is 165 mAhg -1 . After 10,000 consecutive charge and discharge cycles, the specific discharge capacity can still be maintained at 154 mAhg -1 , with a capacity retention rate of up to 93%. At the same time, its coulombic efficiency remained at a level close to 100% throughout the cycle.
[0062] The high cycle stability and near 100% coulombic efficiency exhibited by the positive electrode material are directly attributed to the effective fixation of the active material by the porous nitrogen-rich triazine polymer carrier. The inherent triazine ring and nitrile group and other nitrogen-containing structures in the carrier skeleton provide a high density of Lewis base sites, anchoring iodine and polyiodide anions generated in the electrochemical reaction through strong chemical interaction forces. This chemical binding fundamentally suppresses the dissolution of the active material in the electrolyte and its migration to the negative electrode, thereby reducing the irreversible capacity loss to a very low level.
[0063] The physical structural integrity of the electrode is another key factor for achieving long cycle life. The three-dimensional porous carbon cloth current collector used in the present technical solution builds a mechanical support network throughout the whole electrode. This network can effectively buffer and adapt to the volume change of the iodine active material during charge and discharge cycles, preventing cracking, pulverization or falling off from the current collector caused by stress concentration in the active layer. The porous structure of the carrier itself also provides internal buffer space for volume change, both of which work together to ensure the structural stability of the electrode during long-term, high-intensity cycling.
[0064] It can maintain high capacity and high stability at a high current density of 5 Ag -1 , indicating that the positive electrode material has excellent reaction kinetics. This characteristic is due to the efficient internal electron and ion transmission network. The conductive agent and the three-dimensional carbon cloth current collector together build a smooth electron transmission path; at the same time, the multi-level pore structure formed by the porous nitrogen-rich triazine polymer carrier itself provides a low-resistance channel for the full infiltration of the electrolyte and the rapid diffusion of zinc ions. Fast charge transfer and mass transfer process effectively reduces the electrochemical polarization at high rate, ensuring the depth and efficiency of the electrochemical reaction.
[0065] Test Example 4: To study the transport kinetics of zinc ions in the positive electrode material of the present application, a constant current intermittent titration technique (GITT) was used for testing. The PT-I2 positive electrode prepared in Example 2 was assembled into a button cell, and the cell was assembled in the same way as in Test Example 1. During the whole charging and discharging process, a series of short constant current pulses were applied, and a long relaxation time was recorded after each pulse. Based on the voltage response data, the diffusion coefficient (D) of zinc ions in the electrode material was calculated. The results of this test are shown in Figure 3 .
[0066] Referring to the Figure 3 , the figure is the GITT test result of the PT-I2 positive electrode material. The left subgraph shows the voltage-time step curve during the GITT test, and the right subgraph shows the change of the diffusion coefficient (D) of zinc ions with voltage calculated from the curve. The results show that the diffusion coefficient of zinc ions maintains in the range of 10 -12 to 10 -8 cm 2 s -1 at the main voltage platform of charging and discharging. This result shows that in the structure of the positive electrode material of the present application, the ion can realize fast intercalation and deintercalation.
[0067] Such rapid ion transport characteristics are derived from the specific structure of the porous nitrogen-rich triazine polymer carrier in the technical solution. The abundant hierarchical pores formed after high-temperature activation not only provide sufficient wetting interface for the electrolyte, but also constitute a through and low tortuosity ion transport network. This structure significantly shortens the diffusion path of zinc ions in the solid phase matrix, thereby reducing the mass transfer resistance, which is one of the bases for achieving high rate performance.
[0068] Optimized ion diffusion kinetics and efficient electron transport path work together to ensure that electrochemical reactions can be quickly and uniformly carried out throughout the entire electrode volume. The conductive agent and the three-dimensional carbon cloth current collector jointly construct a smooth electron conduction network. Even at a high current density of 5 Ag -1 , the polarization effect of the electrode is effectively inhibited, so that the utilization rate of the active material can be maintained at a high level. Therefore, the good reaction kinetics exhibited by the material is an indispensable technical feature for achieving high capacity and long cycle life at high rates.
[0069] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.
Claims
1. A nitrogen-rich triazine polymer-supported iodine cathode material, characterized in that, The positive electrode material is composed of the following components in parts by weight: The positive electrode material: 90-110 parts; Conductive agent: 45-55 parts; Adhesive: 13-18 parts; Three-dimensional porous carbon cloth current collector: 70-90 parts.
2. The nitrogen-rich triazine polymer-supported iodine cathode material according to claim 1, characterized in that, The positive electrode material is made of the following components in parts by weight: Porous nitrogen-rich triazine polymer carrier: 30-35 parts; Elemental iodine: 65-70 parts, wherein the reactive monomers in the porous nitrogen-rich triazine polymer carrier are 3,5-diaminobenzonitrile and cyclohexanehexanone hydrate.
3. A method for preparing a nitrogen-rich triazine polymer-supported iodine cathode material, characterized in that, The preparation of the nitrogen-rich triazine polymer-supported iodine cathode material according to claim 1 includes the following steps: S1. Cyclohexanehexane hydrate and 3,5-diaminobenzonitrile were used as monomers to carry out a polymerization reaction to obtain a polymer precursor. S2. The polymer precursor is mixed with zinc chloride and then subjected to high-temperature activation treatment, and then the zinc chloride template is removed to obtain the porous nitrogen-rich triazine polymer carrier. S3. The obtained porous nitrogen-rich triazine polymer support is heated and reacted with elemental iodine under vacuum sealing conditions to obtain the positive electrode material; S4. Mix the positive electrode material, conductive agent and binder in N-methylpyrrolidone solvent and grind to form a uniform slurry; S5. The prepared slurry is uniformly coated onto a three-dimensional porous carbon cloth current collector, and the cathode material is obtained after drying.
4. The method for preparing a nitrogen-rich triazine polymer-supported iodine cathode material according to claim 3, characterized in that, The process of obtaining the polymer precursor includes the following steps: Cyclohexane hexaone hydrate and 3,5-diaminobenzonitrile were used as monomers and reacted in glacial acetic acid solvent at 140-150°C for 46-50 hours to obtain a polymer precursor.
5. The method for preparing a nitrogen-rich triazine polymer-supported iodine cathode material according to claim 3, characterized in that, The step of obtaining the porous nitrogen-rich triazine polymer support includes: The obtained polymer precursor was mixed with zinc chloride at a ratio of 1:3.5-4.5 and activated at high temperature of 380-420°C under an inert atmosphere. Then, it was washed with acid solution to remove the zinc chloride template, thus obtaining the porous nitrogen-rich triazine polymer support.
6. The method for preparing a nitrogen-rich triazine polymer-supported iodine cathode material according to claim 3, characterized in that, The steps for obtaining the positive electrode material include: The porous nitrogen-rich triazine polymer carrier was mixed with elemental iodine and placed in a sealed container. After being evacuated and sealed, it was heated at 100-110°C for 4.5-5.5 hours.
7. The method for preparing a nitrogen-rich triazine polymer-supported iodine cathode material according to claim 3, characterized in that, The step of mixing the positive electrode material, conductive agent, and binder in N-methylpyrrolidone solvent and grinding them to form a uniform slurry includes: The positive electrode material, conductive agent and binder are dry premixed for 10-15 minutes; During the continuous grinding process, N-methylpyrrolidone solvent, with a total amount of 120-150 parts, is added to the premixed material in 2-4 batches. Continue grinding until the total grinding time reaches 45-75 minutes to form a uniform slurry with moderate viscosity and no grainy texture.
8. The method for preparing a nitrogen-rich triazine polymer-supported iodine cathode material according to claim 3, characterized in that, The step of uniformly coating the prepared slurry onto a three-dimensional porous carbon cloth current collector and drying it to obtain the cathode material includes: The slurry was uniformly coated onto the three-dimensional porous carbon cloth current collector using a coating machine, and the wet film thickness was controlled to be 100-150 μm. The coated electrode sheet is pre-dried at 60-70℃ for 30-45 minutes; Subsequently, the pre-dried electrode sheets are subjected to final drying under vacuum conditions at 50-60°C for 10-14 hours.