Ion Storage Characteristics Of Tungsten Trioxide Nanostructures

With the continuous development of portable equipment and new energy vehicles,it is very necessary to find an energy storage device with high energy density and fast charge and discharge rate.Electrochemical energy storage,as an energy storage method with a long history,under the background of the new era,because of its reliable stability and excellent ion storage performance,it has again received extensive attention from scientific researchers around the world.It is worth noting that the ion storage mechanism of electrochemical energy storage is still unclear,the reason is that the interaction between the ions in the solution and the electrode material is a very complex physical phenomenon.For different electrode materials,this physical phenomenon can show different ion migration processes.Therefore,this article explores this important topic.First,we select tungsten trioxide with different crystal structures as electrode materials,then we use conventional physical characterization and electrochemical tests on the prepared samples,finally,in order to study the changes in the crystal structure during the process of H⁺embedding/migrating out of the crystal,we performed an ex-situ XRD test on the tungsten trioxide nanomaterial.The research content is as follows:1.h-WO₃·0.6H₂O nanorods were synthesized by hydrothermal method and characterized by electron microscopy and X-ray diffraction.The results show that the morphology of the tungsten trioxide nanorods is roughly the same,the surface is slightly rough,the length is about a few hundred nanometers,and the width is tens of nanometers.At the same time,the sample matches the hexagonal standard card very well.The sharp diffraction peaks indicate that the sample has good crystallinity.2.In order to obtain tungsten trioxide nanomaterials with different crystal structures,a part of h-WO₃·0.6H₂O nanorod powder was placed in a tube furnace and calcined in the air at 350^oC and 450^oC respectively,and then we also used scanning electron microscopy and X-ray diffraction techniques characterize the material properties of the sample.The results showed that the crystal phase of the sample calcined at 350^oC did not change.Part of the morphology of the sample calcined at 450^oC turned into clusters,this is because some of the nanorods were not uniformly dispersed and piled together,and finally the sample aggregates at high temperature.At the same time,the diffraction image showed that the sample calcined at 450^oC had completely transformed into a monoclinic phase.3.We use electrochemical workstation and ex-situ X-ray diffraction technology to study the ion storage dynamics of h-WO₃·0.6H₂O,m-WO₃,h-WO₃·(0.6-x)H₂O nanomaterials.The results show that h-WO₃·0.6H₂O with a pore structure and crystal water exhibits obvious pseudocapacitance characteristics,not only does H⁺intercalation and desorption are very rapid,but the crystal phase does not change during the electrochemical reaction,the reason for such excellent characteristics is H⁺can migrate in the crystal by bridging oxygen atoms.The electrochemical test results of h-WO₃·(0.6-x)H₂O show that the characteristics of ion diffusion on the crystal surface have not changed,however,the ex-situ XRD test results show that the loss of crystal water leads to a stronger interaction between hydrogen ions and ions in the crystal,which makes the crystal structure change more obvious during the electrochemical reaction.For m-WO₃,its CV image shows that the transition from cathode current to anode current is very slow,which shows that its solid-state structure forms an obvious concentration gradient,which is also the most important feature of the battery mechanism.At the same time,electrochemical kinetic analysis showed that m-WO₃has not only been transformed into a battery-like storage material,but its electrochemical reversibility has also been completely destroyed.