PNNL

Abstract

Herein, we report on a new dual-ion battery (DIB) concept based on an aqueous/non-aqueous electrolyte combining a high safety and improved sustainability in form of a non-flammable water-in-salt electrolyte, a high cathodic stability by forming a protective interphase on the negative electrode (non-aqueous solvent) and by using a sustainable graphite-based positive electrode material. Far beyond the anodic potential limit of water, the formation of a stage-2 acceptor-type graphite intercalation compound (GIC) of bis(trifluoromethanesulfonyl) imide (TFSI) anions from an aqueous-based electrolyte, as confirmed by ex situ X-Ray diffraction, is achieved for the first time. The choice of the negative electrode material shows huge impact on the performance of the novel DIB cell chemistry, i.e., discharge capacities up to 40 mAh g-1 were achieved even at high specific currents of 200 mA g-1. In particular, lithium titanium posphate (LiTi2(PO4)3; LTP) and lithium titanium oxide (Li4Ti5O12; LTO) are evaluated, exhibiting specific advantages for this DIB setup. In this work, we establish a new DIB concept combining an evironmentally friendly, transistion-metal free, abundant graphite positive electrode material and a non-flammable water-based electrolyte, thus, paving the path towards a sustainable and safe alternative energy storage technology.