Significantly improved performance of red phosphorus sodium-ion anodes with the addition of iron

Sodium-ion battery is the most promising alternative to lithium-ion battery for the similar chemical properties to lithium and low cost due to the earth abundance of sodium. Red phosphorus (RP) is regarded as a potential candidate for sodium-ion batteries because it has the highest theoretical capacity (-2600 mA h/g), but commercially available RP is electrochemical inactivity with sodium as a result of the insulating nature. Among the P-based anodes for SIBs, they were all in the form of carbon-P composites. Herein, we report that commercial RP mixed with appropriate amount of iron developed by high-energy ball milling can deliver a reversible capacity of 1642 mA h g(-1) over 30 cycles. EIS measurement results indicated that Fe content composites has higher sodium diffusion coefficient. When utilized as a sodium ion battery anode, 9.1% Fe-adding RP composites exhibited the best electrochemical performance achieved 1582, 1419, 884 and 676 mA h g(-1) specific desodiation capacity at 0.2, 0.6, 1, 6 and 10 A g(-1) current density in rate capability tests. This study opens a new approach to activate the sodium-ion storage of phosphorus, which will enable phosphorus-related materials to be used in more innovative energy storage systems. (c) 2017 Elsevier Ltd. All rights reserved.