The Application And Mechanism Investigation Of Polyoxometalates In Electrochemical Energy Storage System

Electrochemical energy storage system has been widely used in production and life of human beings,because it is cheap and efficient.Polyoxometalates(POMs)have open nano cluster structure,multi-electron redox activity,stability,adsorbability and catalytic activity.As a result,POMs are suitable using in electrochemical energy storage system as active materials or catalysts.In this paper,we investigate about the applications of POMs in electrochemical energy storage system including symmetry lithium-ion batteries,sodium-ion batteries and lithium-sulfur batteires,which are shown below:1.A new Li7[V15O36(CO3)]based symmetry batteries system is constructed.The vanadium centers in Li7[V15O36(CO3)]have different valence state,which permits symmetric lithium-ion batteries with the same cluster Li7[V15O36(CO3)]as both cathode and anode to be created.This kind of devices exhibit battery-like energy density and supercapacitor-like power density.An ultrahigh specific power density of 51.5 kW kg-1 at 100 A g-1 and a specific energy density of 125 W h kg-1 can be achieved,along with a long cycling life(>500 cycles).Combining with the analysis of Li-diffusion coefficient,electronic conductivity and morphology,the good electrochemical performance can be attributed to the property of this material including open cluster nanostructure,multi-electron redox activity,and stability.2.Investigations of Li7[V15O36(CO3)]based sodium ion batteries cathode are reported.Electrochemical and DFT theoretical studies reveal that {V15O36(CO3)} also allows the transport of large cations,like Na+.As a result.Li7[V15O36(CO3)]can serve as the cathode material for rechargeable sodium-ion batteries with a high specific capacity of 240 mA h g-1for a half-cell and a specific energy of 390 W h kg-1 for a full battery.3.The K3[H3Ag1PW11O39]/S composites are firstly prepared.The Ag(I)substituted Keggin K3[H3Ag1PW11O39]can serve as a bifunctional Lewis acidic and basic catalyst.As a result,this kind of POMs materials not only can stabilize Li2Sn,but also improve the redox reactions reversibility of the active materials.The K3[H3AgIPW11O39]/S composites were used as Li-S batteries cathode with a very high S utilization of 94%,a specific capacity of 1580 mAh g-1,and highly stability at high rates(1050 and 810 mAh g-1 at 1C and 2C over 100 to 300 cycles,respectively).4.The recycling of POMs materials:the POMs material from these electrochemical energy storage devices can be easily extracted from used electrodes by simple treatment with water,realizing efficient and clean recycling.