Sodium-ion hybrid electrolyte battery for sustainable energy storage applications

Sustainable, safe, and low-cost energy storage systems are essential for large-scale electrical energy storage. Herein, we report a sodium (Na)-ion hybrid electrolyte battery with a replaceable cathode system, which is separated from the Na metal anode by a Na superionic conducting ceramic. By using a fast Na-ion-intercalating nickel hexacyanoferrate (NiHCF) cathode along with an eco-friendly seawater catholyte, we demonstrate good cycling performance with an average discharge voltage of 3.4 V and capacity retention >80% over '100 cycles and >60% over 200 cycle. Remarkably, such high capacity retention is observed for both the initial as well as replaced cathodes. Moreover, a Na-metal-free hybrid electrolyte battery containing hard carbon as the anode exhibits an energy density of similar to 146 Wh kg(-1) at a current density of 10 mA g(-1), which is comparable to that of lead-acid batteries and much higher than that of conventional aqueous Na-ion batteries, These results pave the way for further advances in sustainable energy storage technology. (C) 2016 Elsevier B.V. All rights reserved.