Anode Interface Regulation And Electrochemical Performance Investigation In Sodium-Based Batteries

Sodium-based batteries due to the advantages of abundant sodium resources,low cost and environmental friendliness,show great potential in electric vehicles and largescale energy storage devices.However,the development and application of anode materials for sodium-based batteries are limited by the poor cycle life and other problems.Sodium metal possesses a high theoretical specific capacity(1166 mAh g-1)and it is the most ideal anode material for sodium-based batteries.However,the development of sodium-based batteries is severely restricted by the high reactivity,volume expansion and dendrite growth seriously on sodium metal anode.As the most practical anode material for sodium-based batteries,hard carbon is entitled to the advantages of abundant resources and friendly environment,while its reversible capacity and cycling stability are difficult to meet requirements of practical applications.To solve the above problems,this work constructs artificial solid electrolyte interface(SEI)to inhibit the growth and volume expansion of sodium dendrites,thus boosting stability of sodium metal anode.The surface selemnization modification of carbonized cotton can effectively improve its sodium storage kinetics reversible specific capacity and stability of the battery.The main content is as follows:(1)The Na2Se-rich artificial SEI is constructed by electrochemical activation of FeSe2 and PTFE composite films to stabilize sodium metal anode.Na2Se-rich artificial SEI film can not only inhibit the side reaction and dendrite growth between the sodium metal anode and electrolyte,but also promote rapid transport of sodium ion.Stable cycling under a lower overpotential for a long time(～600 h)can be achieved in Na2Se/Na‖Na2Se/Na symmetric batteries,Na2Se/Na‖NVP full cells exhibit a reversible capacity of 110 mAh g-1 after 100 cycles at 0.5 C with excellent cyclic stability.This strategy based on selenide stabilizing sodium metal anode provides a new way to implement high energy density sodium metal batteries.(2)Through the calcination,selenium is combined with carbonized cotton to prepare selenide carbonized cotton,thus supplying more active sites to amend the sodium storage kinetics of carbonized cotton.Selenized carbonized cotton can still provide a reversible specific capacity of 350 mAh g-1 after 50 cycles at 0.5 C,while carbonized cotton can only show obviously lower capacity at the same condition.At the same time,selenized carbonized cotton also manifests excellent rate performance.This simple surface modification method provides a new way for other electrodes modification.