Seawater Power Source Based On Coordination Crystal And Its Derivative Materials

With the development of the marine economy and the continuous development and utilization of marine resources,underwater equipment represented by underwater sensor networks and underwater vehicles have been put into use in large quantities,which has led to the increasing demand and market for underwater power supplies.Chemical power supply is an important part of underwater power supply.Among them,seawater batteries use metal anodes to corrode in seawater to provide electrons.Seawater is used as electrolyte and electron acceptors.It can be used in open seawater environments and is an ideal chemical power source for underwater unmanned equipment.However,restricted by the efficiency of electron transfer between solid-liquid and solid-gas phase,seawater batteries are difficult to balance high power density and high energy density,and face difficulties when used as underwater power sources.In this dissertation,aiming at the contradiction between the power density and energy density of seawater batteries,a new electron transfer path is proposed,the change mechanism of the adapted electrode in the electron transfer process is explored,and a new type of seawater power source is constructed.The main contents are as follows:1.The principle verification and prototype device evaluation of high-power seawater power supply based on electron transfer between solid-solid phasesIn this paper,we use the intercalation and extraction of sodium ions in Ni₃[Fe（CN）₆]₂（Ni HCF）crystals,coupled with light metal electrodes,and design the electron transfer path between solid-solid phases,and construct a seawater power source prototype system.X-ray diffraction patterns and scanning electron microscopy imaging techniques confirmed that Ni HCF crystals can exist stably for a long time（more than two months）in seawater without significant structural changes.Ni HCF crystal is used to construct electrode material,which can form a double electrode system with metal electrodes.Cyclic voltammetry test results show that electrons in metal electrodes（aluminum alloys,magnesium alloys）can be transferred to Ni HCF crystals,so that Fe³⁺in Ni HCF can be reduced to Fe²⁺.X-ray photoelectron spectroscopy analysis shows that during this process,sodium ions in the seawater intercalate into the Ni HCF lattice interstitial position to maintain the electrical neutrality of the crystal.During the electron transfer process,the Ni HCF crystal lattice is stable,almost showing the characteristics of zero strain,ensuring stable ion insertion under high-rate conditions,and laying the foundation for further improvement of current density.Based on the electron transfer between metal and Ni HCF crystal,we have constructed a high-power seawater battery.The experimental results show that the output voltage and power of the Mg-Ni HCF system are high.When the current density is 10m A cm^–2,the maximum output voltage of the power supply is 2.09V;when the current density is 130m A cm^–2,the maximum output power of the power supply is161.2m W cm^–2.Under high current density,the seawater power electrode exhibits good cycle stability and can work stably in seawater with a wide temperature range（0-40°C）.After connecting with an electric boat,the system successfully drives a miniature electric boat in seawater,proving the potential of the seawater power supply in unmanned underwater navigation equipment.2.The principle verification and prototype device evaluation of dual-mode seawater power based on electron transfer between solid-solid-gas phaseThe electrical capacity of seawater power sources based on electron transfer between solid and solid phases is restricted by the limited sodium ion storage capacity of Ni HCF crystals.In order to overcome this problem,this paper further constructs a solid-solid-gas phase electron transfer path,using dissolved oxygen molecules in seawater to receive the electrons temporarily stored in the Ni HCF crystal,so that the electrons provided by the metal electrode can completely participate in the electron transfer.Based on the principle of potential matching,we replaced Ni HCF crystals with Na Fe[Fe（CN）₆]（FeHCF）crystals as the transfer warehouse for electrons.The transit warehouse has excellent seawater stability and can exist stably in seawater for more than four months.Studies have shown that electrons from metal electrodes can be spontaneously transferred to FeHCF crystals until the redox sites are consumed.During this process,sodium ions in seawater intercalate into FeHCF crystals and cause chemical composition changes（Na₂Fe[Fe（CN）₆]）and lattice deformation,transforming from a face-centered cubic structure to a rhombohedral structure.After connecting the transit warehouse to the carbon electrode,the electrons in the Transit warehouse can be further transferred to the dissolved oxygen in the seawater.At this time,the sodium ions in the FeHCF crystal are removed,and the capacity is regenerated.When we couple the electron transfer between solid-solid phase and the electron transfer between solid-gas phase,we can build a dual-mode seawater battery system with continuous power supply.Among them,the electron transfer between solid and solid phases ensures the high power of seawater power.The maximum output voltage of the Mg-FeHCF segment is1.80 V,and the maximum output power is 115.7m W cm^–2.The electron transfer between solid and gas phase ensures the high energy density of the system,the maximum energy density is about 4010Wh kg^–1.3.The principle verification and prototype device evaluation of long-life seawater power supply based on electron transfer between solid and liquid phaseAs seawater power sources face severe environmental tests in the deep and open sea environments,under certain extreme conditions,the shortage of dissolved oxygen is unavoidable.In order to respond to emergencies,it is necessary to directly use water molecules to receive electrons and establish an electronic transfer pathway between solid-liquid phase.This article chooses Co₃[Fe（CN）₆]₂（CoHCF）as the initial seawater power electrode.The results show that the trivalent Fe in CoHCF crystals can be used as redox active sites.When the redox active sites are sufficient,sodium ions can be inserted to achieve high-power seawater power.After the active sites of the CoHCF crystal are consumed,the electrons stored in the crystal can be absorbed by water molecules under the catalysis of Co to promote the generation of hydrogen,forming a power supply system similar to a metal/H₂O seawater battery.The X-ray diffraction pattern showed that CoHCF crystals gradually became amorphized during the catalytic process,but the catalytic activity increased slightly with the amorphization,and the electron transfer between solid and liquid was enhanced.The electronic transfer between solid and liquid lays the foundation for the continuous use of seawater power after emergency failure.The experimental results show that the maximum output voltage of the Mg-CoHCF system in the solid-solid electron transfer path is 2.24V,and the maximum output power is 117m W cm^–2;in the solid-liquid electron transfer path,the maximum output voltage is 0.51V,the maximum output power is 7.35m W cm^–2,the working life is more than 100 hours,and the energy density can reach 1130Wh kg^–1.4.Manufacturing and evaluation of integrated electrodes for long-life seawater power sources based on electron transfer between solid and liquid phases The performance of seawater power electrodes needs to take into account mechanical strength,electron transfer catalytic activity and conductivity,resulting in complex preparation processes.This paper develops a manufacturing process from powder to component,which directly converts metal organic powder into a gradient electrode with integrated structure and function through thermochemistry and in-situ vapor deposition.Experiments show that the metal organic powder decomposes to form Co nanoparticles during the heating process,and the particles catalyze the graphitization of organic matter in situ to form carbon particle connectors.During the synthesis process,reactive vapor and Co nanoparticles（uniformly distributed）generated in situ trigger the deposition of carbon nanotubes,forming an array on the electrode surface.The bending test shows that the gradient electrode has good mechanical stability.Hydrogen production electrochemical evaluation shows that the electrode has excellent conductivity and better catalytic activity,and maintains good stability in the electrolyte.Due to its excellent comprehensive performance,the gradient electrode is directly used as a long-life seawater power electrode based on electron transfer between solid and liquid phase.The electrode can exist stably in seawater for more than 7 days,with low overpotential and charge transfer resistance as low as 0.32（?）.The maximum output voltage of the seawater battery assembled by this electrode is 0.60V,and the maximum output power density is 6.14m W cm^–2,which can provide stable power supply for more than 168 hours in seawater.