Interfacial integration and roll forming of quasi-solid-state Li–O2 battery through solidification and gelation of ionic liquid

Abstract

The development of solid-state lithium-oxygen batteries is currently limited primarily by the high solid-solid interfacial resistance and the lack of efficient assembly of electrolyte and electrode. In this work, noncovalent interactions between the cations of an ammonium ionic liquid and both solid electrolytes and carbon air cathodes are introduced. The ionic liquid-based electrolytes (ILE) are solidified on Li6·40La3Zr1·40Ta0·60O12 (LLZTO) nanoparticles and gelated by multi-wall carbon nanotubes (MWCNTs), respectively, to construct LLZTO@ILE quasi-solid-state electrolyte (QSSE) and MWCNTs-LLZTO/ILE gel cathode (GC). The QSSE exhibits a high ionic conductivity of 1.71 × 10−3 S cm−1 at 60 °C, high Li-ion transference number of 0.56, broad electrochemical window of ~4.8 V and good thermal stability. The GC shows outstanding compatibility with QSSE. Quasi-solid-state Li–O2 batteries are assembled by integrating QSSE and GC films with a facile roll forming method, showing a low total interfacial resistance (~87 Ω cm2), and excellent reversible cycles (70 cycles) with low charge overpotential (<0.44 V) and quite high electrical energy efficiency (>70%) at 60 °C and 200 mA g−1. A 0.12 Ah pouch-type Li–O2 battery was achieved by this method. These results suggest that the noncovalent interactions initiated by IL cations could be an effective approach to solve the solid-solid interface issue and achieve high discharge capacity in solid-state energy storage devices.