Bulk-Type All-Solid-State Lithium Batteries Using Complex Hydrides Containing Cluster-Anions

Abstract

In this study, we incorporated fast lithium ion conducting complex hydrides containing cluster anions, namely icosahedral dodecahydro-closo-dodecaborate anions, [B 12 H 12 ] 2− , into a bulk-type all-solid-state battery. Li 2 B 12 H 12 , TiS 2 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, non ammable solid-state electrolyte would ensure the safety, which is currently problematic for the conventional lithium rechargeable battery that uses organic liquid electrolyte. Li 2 B 12 H 12 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 TiS 2 /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 . Li 2 B 12 H 12 exhibits higher oxidative stability. Thus, our battery realized high coulombic ef ciencies of over 92% during the battery operation. This information will be bene cial for the further development of novel complex hydride-based electrolyte to have high-performance bulk-type all-solid-state batteries.

Phase Stability and Fast Ion Conductivity in the Hexagonal LiBH4–LiBr–LiCl Solid Solution

“…13,14 Recently, also complex hydrides were suggested as solid-state electrolytes. [15][16][17][18] LiBH 4 is lightweight material (0.666 g/cm 3 ) and, although used as a strong reducing agent it has a large electrochemical window, being electrochemically stable up to 5 V vs. Li + /Li. 15 It shows a polymorphic transition from an orthorhombic unit cell at room temperature, space group (s.g.) Pnma, to an the hexagonal unit cell, s.g. P6 3 mc, 19 above 110 °C.…”

Borohydride‐Scaffolded Li/Na/Mg Fast Ionic Conductors for Promising Solid‐State Electrolytes

“…Apart from SSEs with BH 4 − groups, the feasibility of polyhedral borohydride SSEs paired with a TiS 2 electrode was also probed. Unemoto et al assembled ASSBs in 2TiS 2 –3Li 2 B 12 H 12 (‐A)|Li 2 B 12 H 12 (‐A)|Li and 2TiS 2 –3Li 2 B 12 H 12 (‐B)|Li 2 B 12 H 12 (‐B)|Li configurations, which utilized ball‐milled Li 2 B 12 H 12 , labeled as Li 2 B 12 H 12 (‐A), and anhydrous commercial Li 2 B 12 H 12 , labeled as Li 2 B 12 H 12 (‐B), respectively . The ASSB with the configuration of 2TiS 2 –3Li 2 B 12 H 12 (‐A)|Li 2 B 12 H 12 (‐A)|Li was operated at 393 K with an initial discharge capacity of 207 mA h g −1 at 0.2C and further yielded a retained discharge capacity of 190 mA h g −1 at 0.2C after 10 cycles.…”

Comparative Molecular Dynamics Study of the Roles of Anion– Cation and Cation–Cation Correlation in Cation Diffusion in Li2B12H12 and LiCB11H12

“…Recently, significant progress has been made in development of ASSBs, 6 where high ionic conductivity is one of the inevitable prerequisites for the electrode and electrolyte. The electrolytes in ASSBs are largely based on Li + ion-conducting materials, [7][8][9][10][11][12][13][14][15][16] such as Li10GeP2S12 (LISICON-like), 8 Li6PS5Br (argyrodite), 17,18 LiBH4, 19 Li2B12H12, 20 Li6.55La3Zr2Ga0.15O12 (garnet), 21,22 Li1.2Al0.2Ti1.8(PO4)3 (NASICON-type), 23 and Li0.34La0.51TiO2.4 (perovskites), 24,25 in which the ionic conductivity is comparable with those of present days liquid electrolytes. However, the current state of the art is not at the level to meet all of the challenges of ASSBs.…”