Bulk-type all-solid-state lithium batteries using complex hydrides containing cluster-anions

In this study, we incorporated fast lithium ion conducting complex hydrides containing cluster anions, namely icosahedral dodecahydro-closo-dodecaborate anions, [B12H12]2-, into a bulk-type all-solid-state battery. Li2B12H12, TiS2 and Li were used as an electrolyte, a positive electrode active material and a negative electrolyte, respectively, for a battery assembly to investigate its battery performance. "Bulk-type" battery contains high quantity of electrode active materials in the electrode layer, and thereby the enhanced energy-storage density is expected. In addition, nonflammable solid-state electrolyte would ensure the safety, which is currently problematic for the conventional lithium rechargeable battery that uses organic liquid electrolyte. Li2B12H12 has a high lithium ionic conductivity of log(σ/S cm-1)= -2.6 at 393 K. It exhibits a relatively higher conductivity of log(σ/S cm-1)= -3.5 at reduced temperatures such as 333 K. These high lithium ionic conductivity allows for the repeated operation of the bulk-type all-solid-state TiS2/Li battery for at least 10 cycles at not only 393 K but also 333 K with the discharge capacities higher than 190 mAh g-1. Li2B12H12 exhibits higher oxidative stability. Thus, our battery realized high coulombic efficiencies of over 92% during the battery operation. This information will be beneficial for the further development of novel complex hydride-based electrolyte to have high-performance bulk-type all-solid-state batteries.