Iodine-loaded biomass porous carbon materials, their preparation methods and applications

Abstract

This invention discloses a biomass porous carbon material loaded with iodine, its preparation method, and its application. The preparation method includes: pretreating the biomass material by acid washing followed by water washing until neutral; mixing the biomass material, a pore-forming agent, a nitrogen source, and water until homogeneous, and pre-carbonizing it under a nitrogen or inert gas atmosphere to obtain a yellow powder, wherein the pore-forming agent is potassium oxalate and the nitrogen source is melamine; carbonizing the yellow powder at 600-900℃ under a nitrogen or inert gas atmosphere, cooling it to room temperature to obtain a black powder, washing and drying it to obtain the biomass porous carbon material; mixing the biomass porous carbon material with elemental iodine, heating it in a closed environment to sublimate the elemental iodine and allow the biomass porous carbon material to absorb the iodine, cooling it to room temperature, and then holding it at 50-65℃ in an open environment for at least 12 hours, and finally cooling it to room temperature to obtain the biomass porous carbon material loaded with iodine. Batteries obtained from the biomass porous carbon material loaded with iodine exhibit good cycle life and high capacity retention even at high rates.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a biomass porous carbon material loaded with iodine, its preparation method, and its application. Background Technology

[0002] As fossil fuels are continuously depleted, the need for clean energy is growing. Therefore, developing high-performance, environmentally friendly rechargeable batteries is crucial for alleviating the energy crisis. Among the many commercially available and under-development energy storage battery systems, aqueous zinc-ion batteries, with their high energy density, low cost, and high safety, have attracted increasing attention and are considered a better alternative to lithium-ion batteries. However, existing zinc-ion batteries suffer from several drawbacks, including poor electronic conductivity and zinc-ion conductivity in their electrode materials, complex energy storage mechanisms, and poor reaction kinetics.

[0003] Doping battery materials with iodine (I) is an important research direction for optimizing their performance. Generally speaking, the higher the iodine adsorption, the lower the battery's specific capacity. This is because elemental iodine is a poor conductor of electricity. When the iodine loading is too high, a large amount of iodine cannot form an effective conductive network, which reduces the overall conductivity of the electrodes, hinders electron transport, and leads to a decrease in the battery's specific capacity. If the iodine loading is low, although the battery's specific capacity may increase in the short term, the low loading of iodine as an active material will result in a lower energy density, which is not conducive to the long-term use of the battery. Doping with other elements may be one method, but the introduction of other elements may produce complex side reactions, thereby affecting the battery's performance and lifespan. Yu Zhengtai. Preparation and Electrochemical Performance of Porous Carbon-Iodine Composite Cathode Material for Aqueous Zinc-Iodine Batteries [D]. Tianjin University of Technology [2025-10-15]. Using balsa wood as the carbon source and urea as the nitrogen source, and potassium oxalate and potassium bicarbonate as pore-forming agents, a porous carbon material was prepared. This porous carbon material can efficiently load iodine, with an iodine loading of over 68.9% (mass ratio). However, its performance at high current densities needs improvement (under 10.0C charge-discharge conditions, after 10,000 cycles, the discharge specific capacity is only 125.3 mAh g). -1 (The capacity retention rate is only 82.7%). Therefore, how to prepare electrode materials suitable for aqueous zinc-iodine batteries without introducing other impurity elements and achieve excellent cycle stability at high rates is an urgent problem to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing iodine-loaded biomass porous carbon materials. This method utilizes biomass materials to prepare biomass porous carbon materials with more efficient iodine adsorption capacity. Specifically, it includes: using biomass materials (such as corn stalks) as a carbon source, preparing biomass porous carbon materials (i.e., nitrogen-doped porous carbon) through a two-step process of pre-carbonization and carbonization, and then adsorbing iodine from the prepared biomass porous carbon materials by sublimation to obtain iodine-loaded biomass porous carbon materials, thereby achieving high-value conversion of waste biomass.

[0005] Another object of the present invention is to provide iodine-loaded biomass porous carbon materials obtained by the above preparation method.

[0006] Another object of the present invention is to provide an aqueous zinc-iodine battery.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] A method for preparing iodine-loaded biomass porous carbon material includes the following steps:

[0009] Step 1, pre-treat the biomass material: first acid wash, then water wash until the pH value is neutral;

[0010] Biomass material, pore-forming agent, nitrogen source and water are mixed until uniform, and pre-carbonized at 180~240℃ under nitrogen or inert gas atmosphere to obtain yellow powder. The ratio of biomass material, pore-forming agent and nitrogen source by mass is 3:(7~8):(1~3). Potassium oxalate is the pore-forming agent and melamine is the nitrogen source.

[0011] In step 1, the acid washing in the pretreatment uses sulfuric acid, and the concentration of H2SO4 in the sulfuric acid is 4~8wt%.

[0012] In step 1, the pre-carbonization time is 10~24h.

[0013] In step 1, the biomass material is corn stalks.

[0014] In step 1, the ratio of biomass material to water by mass is 3:(490~510).

[0015] Step 2: Under a nitrogen or inert gas atmosphere, the yellow powder is carbonized at 600~900℃, cooled to room temperature to obtain black powder, washed and dried to obtain biomass porous carbon material.

[0016] In step 2, the carbonization time is 1 to 3 hours.

[0017] In step 2, the washing includes: first acid washing, then rinsing with water until neutral.

[0018] Step 3: Mix the biomass porous carbon material and elemental iodine, heat in a closed environment to sublimate the elemental iodine and allow the biomass porous carbon material to absorb iodine, cool to room temperature, keep warm in an open environment at 50~65℃ for at least 12 hours, and cool to room temperature to obtain iodine-loaded biomass porous carbon material. The ratio of biomass porous carbon material to elemental iodine is 1:(1~3) by mass.

[0019] In step 3, the biomass porous carbon material is kept in a closed environment at 70~100℃ for 12~24 h to allow it to absorb iodine.

[0020] The biomass porous carbon material loaded with iodine obtained by the above preparation method includes: biomass porous carbon material and iodine element loaded in biomass porous carbon material, with the loading amount of iodine element being 49~63wt%.

[0021] The above-mentioned application of iodine-loaded biomass porous carbon materials in improving the specific capacity of aqueous zinc-iodine batteries.

[0022] An aqueous zinc-iodine battery includes: iodine loaded onto the biomass porous carbon material.

[0023] In the above technical solution, the aqueous zinc-iodine battery has an initial discharge specific capacity of 191 mAhg at a 1C current density. - 1 After 4000 cycles, it still has 184.5mAh g. - 1 The discharge specific capacity has a capacity retention rate of 96.5%.

[0024] In the above technical solution, the aqueous zinc-iodine battery has an initial discharge specific capacity of 172.2 mAh g at a 5C current density. - 1 After 10,000 cycles, it still has 171.3 mAh g. - 1 The discharge specific capacity has a capacity retention rate of 99.4%.

[0025] In the above technical solution, the aqueous zinc-iodine battery has an initial discharge specific capacity of 156.6 mAh g at a current density of 10C. - 1 After 10,532 cycles, it still has 144.4 mAh g. - 1 The discharge specific capacity has a capacity retention rate of 92.2%.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. This invention improves the iodine loading capacity of biomass porous carbon materials and suppresses the shuttle effect in aqueous zinc-iodine batteries by selecting a suitable pore-forming agent to achieve a high specific surface area and appropriate pore size distribution. Furthermore, the pore size of the biomass porous carbon material of this invention is mainly distributed around 1 nm, which can effectively anchor iodine molecules, making it less prone to dissolution during charging and discharging, thus suppressing the shuttle effect and significantly improving the battery's specific capacity. Therefore, the aqueous zinc-iodine battery of this invention exhibits a high specific capacity (close to the theoretical specific capacity of iodine (211 mAh / g)) while maintaining a high iodine loading, overcoming the problem in existing technologies where higher iodine adsorption leads to a decrease in battery specific capacity. The battery obtained by loading iodine onto the biomass porous carbon material of this invention still has good cycle life and high capacity retention at high rates, breaking through the performance bottleneck of aqueous zinc-iodine batteries in high-rate applications and laying the foundation for its practical application in fast-charging energy storage, high-power devices, and other scenarios.

[0028] 2. This invention utilizes corn stalks as raw material to prepare iodine-loaded biomass porous carbon materials. The raw materials used are abundant, inexpensive, and environmentally friendly. The process is simple, suitable for large-scale production, and has great potential application value. Attached Figure Description

[0029] Figure 1 This is a SEM image of the biomass porous carbon material prepared in Example 4 at 3000x.

[0030] Figure 2 Here is a SEM image of the biomass porous carbon material prepared in Example 4 at 10000x.

[0031] Figure 3 XRD patterns of the biomass porous carbon material prepared in Example 4 and the biomass porous carbon material prepared in Example 4 loaded with iodine.

[0032] Figure 4 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 1 at a current density of 1C.

[0033] Figure 5 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto a biomass porous carbon material as described in Example 2 at a current density of 1C.

[0034] Figure 6 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 3 at a current density of 1C.

[0035] Figure 7 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto a biomass porous carbon material as described in Example 4 at a current density of 1C.

[0036] Figure 8 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 at a current density of 5C.

[0037] Figure 9 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 at a current density of 10C.

[0038] Figure 10 The graph shows the cycling performance of the aqueous zinc-iodine battery prepared in Comparative Example 3 at a current density of 1C.

[0039] Figure 11 The cycling performance of the aqueous zinc-iodine battery prepared in Comparative Example 3 at a current density of 10C is shown in the figure.

[0040] Figure 12 Cyclic voltammetry curves of an aqueous zinc-iodine battery prepared by loading iodine onto a biomass porous carbon material as described in Example 4;

[0041] Figure 13 Thermogravimetric analysis (TGA) diagrams of the biomass porous carbon material prepared in Example 4 and the biomass porous carbon material loaded with iodine prepared in Example 4 are shown.

[0042] Figure 14 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 5 at a current density of 1C.

[0043] Figure 15 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto a biomass porous carbon material in Comparative Example 1 at a current density of 1C.

[0044] Figure 16 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 6 at a current density of 1C.

[0045] Figure 17 The graph shows the cycling performance of an aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 7 at a current density of 1C.

[0046] Figure 18 The pore size distribution diagram is shown for the biomass porous carbon material prepared in Example 4.

[0047] Figure 19 The pore size distribution diagram is shown for the biomass porous carbon material prepared in Comparative Example 1.

[0048] Figure 20 The rate performance diagram shows the aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4.

[0049] Figure 21 The rate performance diagram is shown for the aqueous zinc-iodine battery prepared in Comparative Example 3. Detailed Implementation

[0050] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0051] Hydrochloric acid was purchased from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; potassium hydroxide, melamine, potassium oxalate, and ammonium carbonate were all purchased from Aladdin Reagent Network; and sulfuric acid was purchased from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd. Corn stalks were purchased from farmers in Dingxi City.

[0052] The instrument information involved in the following embodiments is as follows:

[0053] The electronic analytical balance was purchased from Ohaus International Trading Co., Ltd., the slicing machine from Shenzhen Kejing Zhida Technology Co., Ltd., the tube furnace from Luoyang Huaguan Kiln Equipment Factory, the magnetic stirrer from Gongyi Yuhua Instrument Co., Ltd., and the drying oven from Lichen Technology Bangxi Instrument Technology Co., Ltd.

[0054] Battery performance testing was conducted using the LAND CT3001A battery testing system; the test voltage range was 0.8V to 1.6V, and the test rate was 1C-10C.

[0055] Thermogravimetric test: The material is heated from room temperature to 500℃ at a rate of 5℃ / min.

[0056] Iodine-loaded biomass porous carbon materials and the biomass porous carbon materials synthesized from these materials were subjected to the aforementioned thermogravimetric analysis (TGA) to calculate the iodine loading of the iodine-loaded biomass porous carbon materials. The formula for calculating the iodine loading of the iodine-loaded biomass porous carbon materials is: Iodine loading = (Mass of the biomass porous carbon material at T1℃ to its mass at room temperature) (%) - (Mass of the biomass porous carbon material with iodine loaded at T1℃ to its mass at room temperature) (%). To ensure greater accuracy, the iodine loading was calculated at T1℃ = 300℃, 350℃, 400℃, 450℃, and 500℃, and the average value was taken.

[0057] Examples 1-3

[0058] A method for preparing iodine-loaded biomass porous carbon material includes the following steps:

[0059] Step 1: Use a high-speed blender to pulverize the biomass material to 200 mesh. Mix the pulverized biomass material, pore-forming agent, nitrogen source, and water until uniform. Place the mixture in an oven and pre-carbonize it at 240℃ for 12 hours under an argon atmosphere (heating rate to 240℃ is 5℃ / min) to obtain a yellow powder. The ratio of biomass material, pore-forming agent, and nitrogen source by mass is X. The ratio of biomass material to water by mass is 3:500. The pore-forming agent is potassium oxalate, the nitrogen source is melamine, and the biomass material is corn stalks.

[0060] Step 2: Manually grind the yellow powder for 10 minutes, load it into a ceramic boat and place it in a tube furnace. Carbonize it at Y℃ for 2 hours under an argon atmosphere. Cool it to room temperature to obtain black powder. Wash it and dry it in an oven at 100℃ for 12 hours to obtain biomass porous carbon material. The washing process includes: placing the black powder in a beaker, adding excess hydrochloric acid (HCl concentration of 6M) to the beaker to immerse the black powder in the hydrochloric acid, acid washing under stirring (stirring at 600 r / min for 12 hours), letting it stand for 1 hour, pouring out the upper waste acid liquid, washing it with deionized water until the pH is 7, and finally filtering it.

[0061] Step 3: Mix the biomass porous carbon material and elemental iodine evenly, and absorb iodine in a sealed environment. Specifically, put the biomass porous carbon material and elemental iodine into a black-capped bottle, seal the cap tightly, and keep it in an oven at 70°C for 24 hours to allow the biomass porous carbon material to absorb iodine. Cool to room temperature, put it into a petri dish with a diameter of 90 mm (open environment), and keep it in an oven at 60°C for 12 hours to remove the iodine that was not absorbed into the pores and was attached to the surface of the biomass porous carbon material. Cool to room temperature to obtain iodine-loaded biomass porous carbon material. The ratio of biomass porous carbon material to elemental iodine is 1:2.5 by mass.

[0062] The iodine loading amounts in X, Y, and biomass porous carbon materials are shown in Table 1.

[0063] Table 1

[0064] Example 4

[0065] A method for preparing iodine-loaded biomass porous carbon material includes the following steps:

[0066] Step 1: Use a high-speed blender to grind the biomass material to 200 mesh. Pretreatment: Soak the ground biomass material in excess sulfuric acid (the concentration of H2SO4 in the sulfuric acid is 5wt%), stir at 300r / min for 12h, let stand for 1h, pour off the upper acid liquid, then wash with deionized water until neutral (pH=7), and dry in an oven at 80℃ for 24h.

[0067] The pretreated biomass material, pore-forming agent, nitrogen source, and water were mixed until homogeneous and placed in an oven. The mixture was pre-carbonized at 240℃ for 12 hours under an argon atmosphere (the rate of heating to 240℃ was 5℃ / min) to obtain a yellow powder. The ratio of pretreated biomass material, pore-forming agent, and nitrogen source by mass was 3:8:1, and the ratio of pretreated biomass material to water by mass was 3:500. The pore-forming agent was potassium oxalate, the nitrogen source was melamine, and the biomass material was corn straw.

[0068] Step 2: Manually grind the yellow powder for 10 minutes, load it into a ceramic boat and place it in a tube furnace. Carbonize it at 850℃ for 2 hours under an argon atmosphere. Cool it to room temperature to obtain black powder. Wash it and dry it in an oven at 100℃ for 12 hours to obtain biomass porous carbon material. The washing process includes: placing the black powder in a beaker, adding excess hydrochloric acid (HCl concentration of 6M) to the beaker to immerse the black powder in the hydrochloric acid, acid washing under stirring (stirring at 600 r / min for 12 hours), letting it stand for 1 hour, pouring out the upper waste acid liquid, washing it with deionized water until the pH is 7, and finally filtering it.

[0069] Step 3: Mix the biomass porous carbon material and elemental iodine evenly, and absorb iodine in a sealed environment. Specifically, put the biomass porous carbon material and elemental iodine into a black-capped bottle, seal the cap tightly, and keep it in an oven at 70°C for 24 hours to allow the biomass porous carbon material to absorb iodine. Cool to room temperature, put it into a petri dish with a diameter of 90 mm (open environment), and keep it in an oven at 60°C for 12 hours to remove the iodine that was not absorbed into the pores and was attached to the surface of the biomass porous carbon material. Cool to room temperature to obtain iodine-loaded biomass porous carbon material. The ratio of biomass porous carbon material to elemental iodine is 1:2.5 by mass.

[0070] The iodine loading in the biomass porous carbon material prepared in Example 4 was 62.2 wt%.

[0071] Figure 1 This is a SEM image of the biomass porous carbon material prepared in Example 4 at 3000x. Figure 2 This is a SEM image of the biomass porous carbon material prepared in Example 4 at 10000x. Figure 1 and Figure 2 It can be seen that the surface of the biomass porous carbon material prepared in Example 4 has a large number of pore structures.

[0072] Figure 3 The biomass porous carbon material prepared in Example 4 ( Figure 3 The porous carbon material prepared in Example 4 and the iodine-loaded porous carbon material prepared in Example 4 are both examples of porous carbon materials prepared in Example 4. Figure 3 XRD of the "iodine-carbon complex". Figure 3In the diagram, "PDF#43-0304" is the standard card for I2, and "PDF#26-1079" is the standard card for carbon. Figure 3 As can be seen from the PDF#26-1079 index, the biomass porous carbon material prepared in Example 4 has two broad diffraction peaks at 26° and 44°, and the iodine-loaded biomass porous carbon material prepared in Example 4 also has two broad diffraction peaks at 26° and 44°. This indicates that both the biomass porous carbon material prepared in Example 4 and the iodine-loaded biomass porous carbon material prepared in Example 4 are carbon materials. Compared with the biomass porous carbon material, the diffraction peak intensity of the iodine-loaded biomass porous carbon material prepared in Example 4 is reduced, indicating that its spatial structure has changed. This is attributed to the iodine entering the pores of the biomass porous carbon material.

[0073] Example 5 (for comparison)

[0074] A method for preparing iodine-loaded biomass porous carbon material is basically the same as that in Example 4, except that the phrase "by mass parts, the ratio of pretreated biomass material, pore-forming agent and nitrogen source is 3:8:1" is replaced with "by mass parts, the ratio of pretreated biomass material, pore-forming agent and nitrogen source is 3:6:1".

[0075] The iodine loading in the biomass porous carbon material prepared in Example 5 was 50 wt%.

[0076] Example 6 (for comparison)

[0077] A method for preparing iodine-loaded biomass porous carbon material is basically the same as that in Example 4, except that the only difference is the pretreatment. The "pretreatment" in this example is as follows: the pulverized biomass material is placed in an excess of hydrochloric acid (the concentration of HCl in the hydrochloric acid is 5wt%), stirred at 300r / min for 12h, allowed to stand for 1h, the upper acid layer is poured off, washed with deionized water until neutral (pH=7), and dried in an oven at 80℃ for 24h.

[0078] The iodine loading in the biomass porous carbon material prepared in Example 6 was 55 wt%.

[0079] Example 7 (as a comparison)

[0080] A method for preparing iodine-loaded biomass porous carbon material is basically the same as that in Example 3, except that "the nitrogen source is melamine" is replaced with "the nitrogen source is ammonium carbonate".

[0081] The iodine loading in the biomass porous carbon material prepared in Example 7 was 56 wt%.

[0082] Comparative Example 1

[0083] A method for preparing iodine-loaded biomass porous carbon material is basically the same as that in Example 4, except that "potassium oxalate is the pore-forming agent" is replaced with "potassium hydroxide is the pore-forming agent".

[0084] The iodine loading in the biomass porous carbon material prepared in Comparative Example 1 was 37.5 wt%.

[0085] Examples 8-14 and Comparative Example 2

[0086] An aqueous zinc-iodine battery includes: an electrode, a separator, a zinc sheet, and an electrolyte. The separator is a glass fiber separator, and the electrolyte is an aqueous ZnSO4 solution with a ZnSO4 concentration of 1M. The method for preparing the electrode includes: mixing iodine-loaded biomass porous carbon material with acetylene black, manually grinding in a mortar for 30 min, then mixing with an aqueous carboxymethyl cellulose (CMC) solution, stirring at 600 r / min for 4 h, finally adding styrene-butadiene rubber (SBR), and stirring at 500 r / min for 1 h to obtain a slurry. The slurry is coated onto a titanium sheet, dried at room temperature for 12 h, and cut into small round pieces with a diameter of 12 mm using a cutting machine to obtain the electrode. The iodine loading of the biomass porous carbon material on the electrode is 2 mg / cm³. 2 ~2.5 mg / cm 2 The ratio of sodium carboxymethyl cellulose (CMC) to styrene-butadiene rubber (SBR) in the aqueous solution of iodine-loaded biomass porous carbon material, acetylene black, and sodium carboxymethyl cellulose (CMC) is 320:40:20:20 by mass. The method for obtaining the sodium carboxymethyl cellulose (CMC) aqueous solution includes: placing 20 mg of sodium carboxymethyl cellulose in a beaker, adding 1.2 mL of deionized water to the beaker, and stirring at 900 r / min for 2 h until homogeneous, thus obtaining the sodium carboxymethyl cellulose (CMC) aqueous solution. The iodine-loaded biomass porous carbon material is one of the iodine-loaded biomass porous carbon materials prepared in Examples 1-7 and Comparative Example 1.

[0087] Table 2

[0088] Comparative Example 3

[0089] An aqueous zinc-iodine battery, referred to as “I2@NBPC” in Yu Zhengtai's "Preparation and Electrochemical Performance of Porous Carbon-Iodine Composite Cathode Material for Aqueous Zinc-Iodine Batteries" [D]. Tianjin University of Technology [2025-10-15].

[0090] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 1 was subjected to charge-discharge testing at a 1C current density and cycled 1000 times, as shown below. Figure 4 The cycle performance graph shown is from Figure 4 It can be seen that its initial charging specific capacity is 158mAh g. -1 After 1000 cycles, it still has 122mAh g. - 1 The charging specific capacity has a capacity retention rate of 77.2%.

[0091] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 2 was subjected to charge-discharge testing at a 1C current density and cycled for 510 times, as shown below. Figure 5 The cycle performance graph shown is from Figure 5 It can be seen that its initial charging specific capacity is 180mAh g. - 1 After 510 cycles, it still has 170mAh capacity. - 1 The charging specific capacity has a capacity retention rate of 94.4%.

[0092] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 3 was subjected to charge-discharge testing at a 1C current density and cycled 470 times, yielding the following results: Figure 6 The cycle performance graph shown is from Figure 6 It can be seen that its initial charging specific capacity is 173mAh g. - 1 After 470 cycles, it still has 160mAh capacity. - 1 The charging specific capacity has a capacity retention rate of 92.4%.

[0093] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 was subjected to charge-discharge testing at a 1C current density and cycled 4000 times, as shown below. Figure 7 The cycle performance graph shown is from Figure 7 It can be seen that its initial discharge specific capacity is 191 mAh g. - 1 After 4000 cycles, it still has 184.5mAh g. - 1 The discharge specific capacity has a capacity retention rate of 96.5%.

[0094] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 was subjected to charge-discharge testing at a 5C current density and cycled 10,000 times, as shown below. Figure 8 The cycle performance graph shown is from Figure 8 It can be seen that its initial discharge specific capacity is 172.2 mAh g. - 1 After 10,000 cycles, it still has 171.3 mAh g. - 1 The discharge specific capacity has a capacity retention rate of 99.4%.

[0095] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 was subjected to charge-discharge testing at a current density of 10C and cycled for 10532 times, yielding the following results: Figure 9 The cycle performance graph shown is from Figure 9 It can be seen that its initial discharge specific capacity is 156.6 mAh g. - 1 After 10,532 cycles, it still has 144.4 mAh g. - 1 The discharge specific capacity has a capacity retention rate of 92.2%.

[0096] The aqueous zinc-iodine battery prepared in Comparative Example 3 was subjected to charge-discharge tests at a 1C current density and cycled 3000 times, yielding the following results: Figure 10 The cycle performance graph shown is from Figure 10 It can be seen that its initial discharge specific capacity is 211.1 mAh g. - 1 After 3000 cycles, the discharge specific capacity was 196.6 mAh g. - 1 The capacity retention rate was 93.13%.

[0097] The aqueous zinc-iodine battery prepared in Comparative Example 3 was subjected to charge-discharge tests at a current density of 10C and cycled 10,000 times, as shown below. Figure 11 The cycle performance graph shown is from Figure 11 It can be seen that its initial discharge specific capacity is 146.6 mAh g. - 1 After 10,000 cycles, the discharge specific capacity is 125.3 mAh g. - 1 The capacity retention rate was 85.47%.

[0098] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 was subjected to cyclic voltammetry testing within a voltage window of 0.6V to 1.8V. The voltage-current response data for the first two cycles were recorded, as shown below. Figure 12 The first and second cycle cyclic voltammetry curves shown are as follows: Figure 12 As shown, the voltage corresponding to the reduction peak of the aqueous zinc-iodine battery is 1.25V, and the voltage corresponding to the oxidation peak is 1.35V. The difference between the voltages corresponding to the reduction peak and the oxidation peak is 0.1V, indicating that the battery polarization is very small and the cycle stability is high.

[0099] Figure 13 The ratios of the mass of the biomass porous carbon material at T1°C to its mass at room temperature in Example 4, and the ratios of the mass of the biomass porous carbon material loaded with iodine at T1°C to its mass at room temperature in Example 4, are derived from... Figure 13It can be seen that the biomass porous carbon material prepared in Example 4 has a small mass loss during the process of heating from room temperature to 500°C, while the iodine-loaded biomass porous carbon material prepared in Example 4 has a large mass loss during the process of heating from room temperature to 500°C. This indicates that the iodine in the biomass porous carbon material prepared in Example 4 underwent desorption and sublimation during the heating process, resulting in a large mass loss of the iodine-loaded biomass porous carbon material. According to the calculation formula of "iodine element loading", the iodine content in the iodine-loaded biomass porous carbon material prepared in Example 4 is 62.2 wt%.

[0100] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 5 was subjected to charge-discharge testing at a 1C current density and cycled 350 times, yielding the following results: Figure 14 The cycle performance graph shown is from Figure 14 It can be seen that its initial charging specific capacity is 167mAh g. - 1 After 350 cycles, it still has 158mAh g. - 1 The charging specific capacity has a capacity retention rate of 94.6%.

[0101] The aqueous zinc-iodine battery prepared by loading iodine onto biomass porous carbon material in Comparative Example 1 was subjected to charge-discharge tests at a 1C current density and cycled 1000 times, yielding the following results: Figure 15 The cycle performance graph shown is from Figure 15 It can be seen that its initial charging specific capacity is 129mAh g. -1 After 1000 cycles, it has 80 mAh g. - 1 The charging specific capacity has a capacity retention rate of 62.01%.

[0102] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 6 was subjected to charge-discharge testing at a 1C current density and cycled 100 times, as shown below. Figure 16 The cycle performance graph shown is from Figure 16 It can be seen that its initial charging specific capacity is 100mAh g. - 1 After 100 cycles, it has 95mAh g. - 1 The charging specific capacity has a capacity retention rate of 95%.

[0103] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 7 was subjected to charge-discharge testing at a 1C current density and cycled 100 times, as shown below. Figure 17 The cycle performance graph shown is from Figure 17 It can be seen that its initial charging specific capacity is 138mAh g. - 1 After 100 cycles, it has 99mAh g. - 1 The charging specific capacity has a capacity retention rate of 71.7%.

[0104] Figure 18 This is a pore size distribution diagram of the biomass porous carbon material prepared in Example 4. Figure 18 It can be seen that the biomass porous carbon material prepared in Example 4 is mainly microporous, with micropores mainly distributed at 1 nm, which is compatible with the pore structure of iodine molecules (the kinetic diameter of iodine molecules is approximately 0.535 nm), enabling better iodine loading. This conclusion is further confirmed by the fact that the iodine loading in the biomass porous carbon material prepared in Example 4 is 62.2 wt%. The specific surface area of ​​the biomass porous carbon material prepared in Example 4 was measured to be 2513 m² / m³ by BET testing. 2 / g.

[0105] Figure 19 The image shows the pore size distribution of the biomass porous carbon material prepared in Comparative Example 1. Figure 19 It can be seen that the biomass porous carbon material prepared in Comparative Example 1 is mainly composed of microporous and mesoporous structures. The micropores are mainly distributed at 1.7 nm, and the mesopores are mainly distributed at 2.8 nm and 4.5 nm. The micropores of the biomass porous carbon material prepared in Comparative Example 1 are mainly distributed at 1.7 nm, which is slightly larger and does not match the pore structure of iodine molecules. Therefore, it cannot anchor iodine molecules, and most of the iodine is removed during the iodine removal process. As a result, the iodine loading of the biomass porous carbon material prepared in Comparative Example 1 is very low.

[0106] The aqueous zinc-iodine battery prepared by loading iodine onto the biomass porous carbon material of Example 4 was subjected to charge-discharge tests at different current densities, and the results were as follows: Figure 20 The rate performance diagram shown illustrates the process of cycling five times at each current density, yielding one charge specific capacity and one discharge specific capacity per cycle. The current density increases from 1C, 2C, and 5C to 10C, then sequentially decreases back to 5C, 2C, and 1C. Figure 20 It can be seen that the discharge specific capacity (average value) corresponding to the current density increasing from 1C, 2C, 5C to 10C, and then decreasing back to 5C, 2C, and 1C is 202.8 mAh g. - 1 191.74mAh g - 1 173.92mAh g - 1 152.26mAh g - 1 166.36mAh g - 1 184.3mAh g - 1 193.7mAh g - 1 .

[0107] The aqueous zinc-iodine battery prepared in Comparative Example 3 was subjected to discharge tests at different current densities, and the results were as follows: Figure 21The rate performance graph shown represents the I2@NBPC at current densities of 0.2C, 0.5C, 1.0C, 2.0C, 3.0C, and 5.0C.

[0108] The discharge specific capacity is 210.1 mAh g. -1 192.7mAhg -1 186.5mAhg -1 170.6 mAh g -1 161.6 mAh g -1 and 140.4 mAh g -1 The rate performance of the aqueous zinc-iodine battery prepared in Comparative Example 3 was not as good as that of the aqueous zinc-iodine battery prepared by loading iodine onto biomass porous carbon material in Example 4.

[0109] Although the iodine loading of the biomass porous carbon materials prepared in Examples 6 and 7 was relatively high, the specific capacity and cycle performance of the aqueous zinc-iodine battery prepared from the biomass porous carbon materials prepared in Example 6 and the aqueous zinc-iodine battery prepared from the biomass porous carbon materials prepared in Example 7 were relatively average.

[0110] The aqueous zinc-iodine battery obtained by the present invention using melamine as nitrogen source, potassium oxalate as pore-forming agent and sulfuric acid for pretreatment has the best performance, with both high iodine loading (i.e. high mass energy density, with the highest mass energy density being 0.14941176Wh / kg) and specific capacity.

[0111] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An aqueous zinc-iodine battery, characterized by, include: Iodine-loaded biomass porous carbon materials, the preparation method of iodine-loaded biomass porous carbon materials includes the following steps: Step 1, pretreatment of biomass materials: first acid washing, then water washing until the pH value is neutral; the acid washing in the pretreatment uses sulfuric acid. Biomass material, pore-forming agent, nitrogen source and water are mixed until uniform, and pre-carbonized at 180~240℃ under nitrogen or inert gas atmosphere to obtain yellow powder. The ratio of biomass material, pore-forming agent and nitrogen source by mass is 3:(7~8):(1~3). Potassium oxalate is the pore-forming agent and melamine is the nitrogen source. Step 2: Under a nitrogen or inert gas atmosphere, the yellow powder is carbonized at 600~900℃, cooled to room temperature to obtain black powder, washed and dried to obtain biomass porous carbon material. Step 3: Mix the biomass porous carbon material and elemental iodine, heat in a closed environment to sublimate the elemental iodine and allow the biomass porous carbon material to absorb iodine, cool to room temperature, keep warm in an open environment at 50~65℃ for at least 12 hours, and cool to room temperature to obtain iodine-loaded biomass porous carbon material. The ratio of biomass porous carbon material to elemental iodine is 1:(1~3) by mass. Iodine-loaded biomass porous carbon materials include: biomass porous carbon materials and iodine element loaded in the biomass porous carbon materials, with the iodine element loading amount being 49~63 wt%; The biomass material is corn stalks.

2. The aqueous zinc-iodine battery of claim 1, wherein, In step 1, the pre-carbonization time is 10~24h.

3. The aqueous zinc-iodine battery according to claim 1, characterized in that, In step 2, the carbonization time is 1 to 3 hours.

4. The aqueous zinc-iodine battery according to claim 1, characterized in that, In step 3, the biomass porous carbon material is kept in a closed environment at 70~100℃ for 12~24 h to allow it to absorb iodine.

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