| Excessive development and utilization of fossil energy will lead to environmental damage,so the demand for new energy is increasing,and the flow battery appears.As a representative of new energy storage technology,zinc-bromine flow battery has excellent power performance and low cost.However,in the process of running,cathode?zinc-side electrode?in zinc bromine flow battery is easy to form zinc dendrites(Zn2++2e-=Zn).With the continuous growth of dendrites,it is easy to puncture the diaphragm to cause mixed flow of anode and cathode electrolyte,causing serious battery self-discharge;on the other hand,the broken diaphragm destroys the integrity and airtightness of the battery structure,causing zinc bromide Leakage of the solution,while bromine is a volatile,toxic liquid,and the bromine vapor is corrosive,which destroys the surrounding soil and affects vegetation growth.Therefore,the problem of handling zinc dendrites has two practical significances for environmental protection:one is to improve energy storage efficiency to solve energy problems;the other is to solve the problem of environmental pollution caused by electrolyte leakage,thereby promoting the construction of an environment-friendly society.Carbon felt has excellent performances such as high temperature resistance and chemical resistance.It is widely used in energy storage industry and chemical environmental protection.Because of its low price,large porosity and good chemical stability,it has become the electrode material of choice for flow batteries.However,its electrochemical activity and hydrophilicity cannot fully meet the requirements of flow batteries.Therefore,research on the modification of carbon felt is particularly important.In this paper,the carbon felt electrode was used as the substrate to modify the treatment to produce the cathode and the anode to inhibit the formation of zinc dendrites in the zinc-bromine flow battery.?1?A mixed gas of acetylene and nitrogen is introduced into the high-temperature furnace,and acetylene is cracked at a high temperature to form acetylene carbon black attached to the surface defect of the carbon felt electrode,and a pyrolytic carbon felt electrode is prepared as a cathode.The optimum preparation conditions obtained from the electrochemical test results were as follows:temperature was 600°C,time was 4 h,and acetylene concentration was 35%.The NOP value of this electrode is only 51 mV,and the deposition current at E=-1.1 V is as high as 29.2mA.The results of SEM show that the surface of the electrode is smooth,zinc is uniformly deposited on the surface,and no zinc dendrite is formed.The deposition model of zinc also approaches the instantaneous nucleation,indicating that the pyrolytic carbon felt electrode can effectively improve the polarization of the electrode and inhibit the formation of zinc dendrites.?2?Anode is prepared by doping multi-walled carbon nanotubes on a carbon felt electrode.Through the electrochemical test and chemical characterization results,the optimal carbon nanotube doping amount was 2.5 mg,and the carbon nanotubes were uniformly dispersed on the carbon felt.According to the calculation results of the kinetics,the reaction rate has the largest value of 1.15×10-7 cm s-1,and the consumption rate of the cathode zinc deposit is as high as 81.8%.It is indicated that the doping of carbon nanotubes increases the reaction rate of the anode,promotes the consumption of the galvanized layer at the protrusions of the cathode,and thereby inhibits the formation of zinc dendrites.?3?Investigate and test the effect of the synergistic effect of two modified carbon felt electrodes on battery performance.Charge and discharge at a current density of 40mA cm-2,the coulombic efficiency,voltage efficiency and energy efficiency of the unmodified zinc-bromine flow cell were only 83.7%,67.5%and 56.5%,respectively;and the modified coulombic efficiency The voltage efficiency and energy efficiency are as high as 98.6%,82.5%and 81.3%,respectively.Even at 80 mA cm-2 current density,the energy efficiency is as high as 69.8%,which is close to the best level reported in the literature.Moreover,there was no reduction in battery performance during the 50 charge and discharge cycles.It is indicated that the modification treatment of the carbon felt electrode can not only improve the performance and stability of the battery,but also effectively inhibit the formation of zinc dendrites. |
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