Zinc-iodine battery positive electrode material based on corn straw derived porous carbon and preparation method of zinc-iodine battery positive electrode material

Abstract

The invention discloses a zinc-iodine battery positive electrode material based on corn straw shell derived porous carbon and a preparation method of the zinc-iodine battery positive electrode material. According to the material, corn straw shells serve as the sole carbon source, an indigenous nitrogen-doped biomass charcoal carrier with a hierarchical pore structure is prepared through pre-carbonization and KOH activation processes, and the material is characterized in that the specific surface area is larger than or equal to 1500 m < 2 > / g, and the micropore proportion is larger than 90%. The iodine is loaded on the carrier (the iodine content is greater than or equal to 45wt%) through a vacuum sublimation method to form the indigenous nitrogen-doped biomass charcoal / iodine composite material. According to the positive electrode material, through the synergistic effect of physical confinement and pyridine nitrogen chemical adsorption, the multi-iodide shuttle effect is effectively inhibited, so that the capacity retention rate of the zinc-iodine battery is greater than or equal to 93% after 40000 cycles under the current density of 2A g <-1 >, and the capacity retention rate is greater than 45% under the rate of 10A / g. The method has double benefits of agricultural waste resource utilization and high-performance energy storage device development.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage materials, and in particular to a nitrogen-doped porous carbon / iodine composite material prepared using corn stalk husk as a precursor and its application in the positive electrode of a zinc-iodine battery. Background Art

[0002] Zinc-iodine batteries have attracted considerable attention due to their high theoretical capacity, excellent safety, and low cost. However, their development is hampered by short cycle life and poor rate performance caused by the multi-iodide shuttle effect. While existing carbon support materials (such as graphene and carbon nanotubes) can partially alleviate this problem, they suffer from complex preparation processes and high costs. Corn stover, an agricultural waste, has a huge annual output but low utilization rate, and its incineration causes severe environmental pollution.

[0003] Although biomass carbon materials have been used in the field of energy storage, there have been no reports on the preparation of zinc-iodine battery positive electrodes using corn straw husks as raw materials through a site-specific carbonization-activation-indigenous nitrogen doping synergistic mechanism. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides an intrinsic nitrogen-doped biochar / iodine integrated electrode material and its preparation method and application, which solve the problems of poor conductivity of electrode materials in the positive electrode of zinc-iodine batteries, low active iodine loading, and multiple iodide ion shuttle effect.

[0005] The electrode material includes an intrinsic nitrogen-doped biomass carbon carrier and elemental iodine, wherein the intrinsic nitrogen-doped biomass carbon carrier carries the elemental iodine, and the iodine in the elemental iodine exists in an amorphous form in the intrinsic nitrogen-doped biomass carbon carrier. The biomass carbon carrier has a hierarchical porous structure, and the elemental iodine is loaded in the microchannels of the biomass carbon carrier. The intrinsic nitrogen atoms on the biomass carbon carrier exist in the form of pyridinic nitrogen and pyrrolic nitrogen at the same time.

[0006] Furthermore, the biochar has a specific surface area greater than 1500 m 2 / g; Furthermore, the volume proportion of micropores in the biochar is ≥ 90%; Furthermore, the iodine loading of the electrode material is ≥ 45 wt%.

[0007] The method for preparing the electrode material of the present invention comprises the following steps: 1) The biomass waste is pulverized with a grinder, washed, dried, and sieved, and then carbonized in an inert atmosphere in a tube furnace to obtain a precursor; wherein the washing is performed with deionized water and the precursor is soaked for 8-12 hours; wherein the precursor is dried in a forced air oven at a drying temperature of 90-110°C and a drying time of 12-36 hours; wherein the sieve mesh size is 50-100 mesh; wherein the inert atmosphere is nitrogen; wherein the carbonization temperature is 250-350°C, the holding time is 1.5-2.5 hours, and the heating rate is 1-3°C / min.

[0008] 2) The precursor is mixed with KOH and activated in a tube furnace under an inert atmosphere. After activation, the mixture is washed, centrifuged, and dried to obtain the native nitrogen-doped biomass carbon carrier; the mixing method is as follows: the precursor and KOH are mixed in a mass ratio of 1:3 and placed in a beaker, and then an appropriate amount of deionized water is added and stirred until the KOH is completely dissolved, and the mixture is transferred to a 100°C forced air drying oven and kept warm for 48 hours to ensure that the moisture is completely removed; the inert atmosphere is nitrogen; the spark temperature is 600-800°C, the activation time is 1.5-2.5 hours, the heating rate is 1-3°C / min, and the temperature is kept warm for 2 hours; the washing step includes first washing with 0.1 M HCl until neutral, then washing with deionized water three times, and washing with anhydrous ethanol three times.

[0009] 3) The native nitrogen-doped biomass carbon support and elemental iodine are mixed, ground, and then transferred into a sealed autoclave. The mixture is then heated to sublime the iodine and loaded into the carbon support. After natural cooling, the mixture is transferred to a muffle furnace for heating to remove residual elemental iodine on the surface, thereby obtaining the positive electrode material. The carbon support and elemental iodine are mixed in a ratio of 1:1 by mass to lithium. The autoclave is heated at 80-100°C for 3-5 hours, and the muffle furnace is heated at 120-140°C for 3 hours.

[0010] The present invention has the following beneficial effects compared to the prior art: 1) To address the problems existing in zinc-iodine batteries, the present invention designs a biomass carbon carrier with a hierarchical porous structure and native nitrogen doping, which can improve the conductivity and iodine loading of the zinc-iodine battery cathode. At the same time, under the synergistic effect of physical confinement and chemical adsorption, it can effectively inhibit the shuttle effect in the operation of the zinc-iodine battery and improve the cycle life of the battery.

[0011] 2) The preparation process of the native nitrogen-doped biomass carbon carrier of the present invention is simple, green and environmentally friendly. The blade coating film-forming method adopted is easy to operate, can be scaled up, and is conducive to industrial production.

[0012] 3) The present invention uses straw husks as raw materials, which is low-cost, can improve battery cycle stability, and can effectively alleviate the impact of straw burning on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the nitrogen adsorption-desorption curve of the native nitrogen-doped biomass carbon support prepared in an embodiment of the present invention.

[0014] Figure 2 This is the pore size distribution diagram of the native nitrogen-doped biomass carbon carrier prepared in an embodiment of the present invention.

[0015] Figure 3 This is the XRD curve of the zinc-iodine battery positive electrode material prepared in an embodiment of the present invention.

[0016] Figure 4 This is the thermogravimetric curve of the zinc-iodine battery positive electrode material prepared in an embodiment of the present invention.

[0017] Figure 5 This is the element distribution diagram corresponding to the zinc-iodine battery positive electrode material prepared in an embodiment of the present invention.

[0018] Figure 6 The charge and discharge curves of the zinc-iodine battery assembled with the zinc-iodine battery positive electrode material prepared in the embodiment of the present invention at a current density of 0.1 A / g.

[0019] Figure 7 The cycling performance of a zinc-iodine battery assembled with the zinc-iodine battery positive electrode material prepared according to the embodiment of the present invention at a current density of 0.1 A / g.

[0020] Figure 8 The zinc-iodine battery positive electrode material prepared in accordance with the embodiment of the present invention has a rate performance at a current density of 0.1 A / g to 10 A / g for the zinc-iodine battery assembled.

[0021] Figure 9 The long cycle performance of the zinc-iodine battery assembled with the zinc-iodine battery positive electrode material prepared in the embodiment of the present invention at a current density of 2 A / g. DETAILED DESCRIPTION

[0022] The present invention is further described below with reference to the examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally based on conventional conditions in the art or the conditions recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection claimed in the present invention.

[0023] Example 1 This embodiment provides a method for preparing a positive electrode material for a zinc-iodine battery. First, corn stalk husks were pulverized using a grinder, then washed and soaked in deionized water for 12 hours. The husks were then dried in a forced-air drying oven at 100°C for 24 hours before use. The husks were ground into a powder, passed through a 100-mesh sieve, and the resulting powder was collected. The powder sample was heated in a tube furnace at 300°C for 2 hours under a nitrogen atmosphere at a heating rate of 2°C / min. After cooling naturally, the sample was removed and ground into a finer powder to obtain a pre-carbonized precursor sample.

[0024] Then, the precursor sample and KOH were mixed in a beaker at a mass ratio of 1:3, and then an appropriate amount of deionized water was injected into the beaker and stirred thoroughly until all the KOH was dissolved. The mixed slurry was then cooled to room temperature and transferred to a 100 °C forced drying oven, kept warm for 48 hours to ensure that the moisture was completely removed and set aside. The above samples were placed in a tubular furnace under a nitrogen atmosphere and activated at a temperature of 700 °C with a heating rate of 2 °C / min and kept warm for 2 hours. Then, it was washed with 0.1 M HCl until neutral, first washed with deionized water 3 times, and then washed with anhydrous ethanol 3 times. The activated product was placed at 80 o C drying oven, and kept warm for 24 h to obtain the native nitrogen-doped biochar.

[0025] The native nitrogen-doped biochar / iodine composite was prepared using the iodine sublimation method. First, 0.5 g of iodine and 0.5 g of the biochar were ground and thoroughly mixed. The mixed powder was transferred and sealed in a 50 ml autoclave and heated in a 90°C forced air drying oven for 4 hours. After cooling naturally, the composite was transferred to a 130°C forced air drying oven and heated for 3 hours to remove any iodine residue on the surface. This resulted in the cathode material.

[0026] The obtained positive electrode material is mixed with Super P and polyvinylidene fluoride in a ratio of 7:2:1, and N-methylpyrrolidone solvent is added dropwise while grinding; the obtained positive electrode slurry is coated on a titanium foil, dried, and cut into pieces to finally obtain a zinc-iodine battery positive electrode sheet.

Claims

1. A corn straw-based zinc-iodine battery positive electrode material, characterized in that: Nitrogen-doped porous carbon derived from corn stalk husks is composited with iodine, wherein the porous carbon has the following characteristics: Specific surface area ≥ 1500 m 2 / g; Porous carbon has a hierarchical pore structure, with micropore volume accounting for ≥ 90%; Iodine loading ≥ 45 wt%.

2. The positive electrode material according to claim 1, characterized in that The preparation method comprises the following steps: (1) crushing, washing and drying the corn stalk husk; (2) In an inert atmosphere, heat the sample to 280-320°C at a rate of 1-3°C / min and hold for 1-3 hours. (3) Mix the pre-carbonized product with KOH in a mass ratio of 1:(2.5-3.5), heat to 680-720 °C at 2 °C / min in a nitrogen atmosphere, and keep warm for 1-3 h; (4) washing with 0.1-0.5 M HCl until neutral and drying the porous carbon support; (5) The porous carbon and iodine are sealed in a reactor at a mass ratio of 1:(0.9-1.1), kept at 90-100 °C for 3-5 h, and then calcined at 120-140 °C to remove the surface iodine residue.

3. A zinc-iodine battery positive electrode material prepared by the preparation method according to any one of claims 1-2, characterized in that: The working electrode is used to prepare a battery working electrode and the mass proportion of the positive electrode material is ≥ 70%.

4. A zinc-iodine battery positive electrode material prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The working electrode is used for manufacturing zinc-iodine batteries.

Images