Lithium Ion Conducting Solid Electrolytes for Aqueous Lithium-air Batteries

Abstract

This article summarizes our research on solid electrolytes for rechargeable aqueous lithium-air batteries. Aqueous lithium-air batteries have potential application as a power source for electric vehicles, because of their high specific energy density. A water-stable lithium ion conducting solid electrolyte is the key material for lithium-air batteries to use lithium metal in aqueous circumstance. In this article, two types of lithium ion conducting solid electrolytes, NASICON-type Li 1+x A x Ti 2−x−y Ge y (PO 4 ) 3 (A = Al, Fe) and garnet-type Li 7−x La 3 Zr 2−x A x O 12 (A = Nb, Ta) are introduced, and the conductivity behavior of these solid electrolytes by elemental substitution, their chemical stabilities in water and electrochemical stabilities with lithium metal are discussed. Lithium ion conductivities of 1.3 × 10 −3 and 5.2 × 10 −4 S cm −1 at 25°C were observed in Li

Ion-conducting glass-ceramics for energy-storage applications

“…Such applications include lithium/water, 55 lithium/air, 56 and all-solid-state lithium batteries. 57 NASICON ceramics are used commercially as ion-conducting separator membranes in lithium/air batteries currently touted as promising high-energy storage devices because of their theoretical energy density of 11,140 Wh/kg, 58 which is one order of magnitude higher than currently used storage devices. These batteries use highly corrosive LiCl and LiOH liquid electrolytes.…”

Aqueous Stability of Alkali Superionic Conductors from First-Principles Calculations

“…At anodic voltages <−1 V (SHE), hydrides of Li, Zr, and La are formed. Like LTAP, garnet SICEs have been explored for the role of a separator in aqueous electrolytes with Li metal anodes (Imanishi et al, 2014). Similar to the NASICONs, we find that the acidity of the aqueous medium does not significantly alter the products formed.…”

“…One potential strategy of addressing both issues is to use a separator to protect the alkali metal, as well as act as a barrier against dendrite formation. Indeed, the two common SICEs explored for this purpose, LiTi2(PO4)3 and garnet LLZO (Zhang et al, 2008;Imanishi et al, 2014), are predicted to have relatively good stability in aqueous media. The garnet LLZO, in particular, is remarkable for its relative lack of reactivity across wide voltage and pH ranges, and low driving forces for decomposition.…”

“…In particular, separators are necessary when Li metal is used as an anode, for example, in Li-air systems (Visco and Chu, 2000;Liu et al, 2015), as Li reduces most electrolytes on contact. Separators in such (Zhang et al, 2008;Imanishi et al, 2014). Determination of the aqueous stability of solid electrolytes has thus far been predominantly based on experimental observations.…”

“…Such experiments take anywhere between a week to a month (Fuentes et al, 2001), where the electrolyte is immersed in an aqueous solution, sometimes with LiOH, LiCl, etc. (Hasegawa et al, 2009;Imanishi et al, 2014), and tested for changes in surface morphology, chemistry, and ionic conductivity. These experiments are time-consuming as well as limited in the set of environmental elements that can be tested.…”