Metal-organophosphine Framework-derived Carbon Supported Single Atomic Metals And Their Sodium Storage Performances

Sodium-ion batteries are considered as one of the most promising secondary electrochemical energy storage devices due to the abundance,uniform distribution and low cost of sodium in the Earth's crust.Amorphous carbon show potential for anodes of sodium ion batteries because of their large interlayer spacing and rich defect sites.It is still a great challenge to improve the sodium storage performances of amorphous carbon.Theoretical studies show that metal dopants are favorable for anchoring alkali metal ions.Nevertheless,there is no relevant experimental research on single atomic metal-doped carbon materials in the field of sodium-ion batteries despite of their popularity in energy storage and conversion fields.Additionally,low single atomic metal loading severely hinders their practical energy storage applications.In this work,a metal-organophosphine framework-derived strategy is developed to successfully synthesize high-content single atomic metals.Cuboid-like carbon supported single atomic copper can be obtained from 1,3,5-triaza-7-phosphaadamantane(PTA)and copper nitrate as raw materials.The single atomic copper is anchored on the carbon matrix via phosphorus coordination,exihibiting Cu-P3 coordination structure.The metal loading can reach 26.3 wt%.The carbon supported single atomic copper has good corrosion resistance in concentrated hydrochloric acid and concentrated nitric acid.Single atomic nickel or cobalt doped carbon materials can be successfully synthesized using similar procedures,confirming the universality of this strategy.When used as anode materials for sodium-ion batteries,the carbon supported single atomic copper shows superior rate performance and cycle stability.At a current density of 5 A g-1,it can deliver a reversible capacity of 107.7 mAh g-1.At 1 A g-1,the capacity can be retained at 123.2 mAh g-1 after 1000 cycles.Single atomic copper can not only improve the conductivity of the materials and enhance the diffusion kinetics of Na ions,it can also alter the sodium storage behaviors of the materials,maintaining the ionic state of Na at fully discharging state,which is conducive to avoid the dendrite formation and mitigate safety risks.This work provides a new perspective for the preparations of carbon supported high content single atomic metals,and further promotes their applications in energy storage and conversion field.