A novel hybrid positive electrode with liquid-solid redox couples having high-capacity for lithium battery

We demonstrate a novel rechargeable energy storage system having a metallic lithium negative electrode and a liquidsolid hybrid positive electrode of Fe3+/Fe2+/Fe in N,N-Dimethylformamide, which are separated by an impermeable NASICON-type Li1.4Al0.4Ge0.2Ti1.4(PO4)(3)-epoxy resin composite film with a lithium ion conductivity of ca. 5.0 x 10(-4) S cm(-1). The discharge curve for the battery shows two plateaus. The first plateau corresponds to Li + FeCl3 = LiCl + FeCl2, while the second one is associated with 2 Li + FeCl2 = 2 LiCl + Fe. In the process of reduction of Fe3+ to Fe2+, it delivers a stable discharge capacity of ca. 110 mAh g(FeCl3)(-1) with a Coulombic efficiency higher than 95% and is capable of enduring over 60 circles at a high current density of 1.0 mA cm(-2) without any catalyst. Furthermore, a stable discharge capacity up to ca. 455 mAh g(FeCl3)(-1) is achieved for conversion of FeCl3/FeCl2/Fe with a three-electron reaction. This work demonstrates a proof of feasibility of hybrid liquid-solid hybrid positive electrode, since these reactions are reversible confirmed by x-ray diffraction patterns and EDX mapping test.