Methylamine Lithium Borohydride as Electrolyte for All‐Solid‐State Batteries

Abstract

Fast Li-ion conductivity at room temperature is a major challenge for utilization of all-solid-state Li batteries. Metal borohydrides with neutral ligands are a new emerging class of solid-state ionic conductors, and here we report the discovery of a new mono-methylamine lithium borohydride with very fast Li + conductivity at room temperature. LiBH 4 •CH 3 NH 2 crystallizes in the monoclinic space group P2 1 /c, forming a twodimensional unique layered structure. The layers are separated by hydrophobic À CH 3 moieties, and contain large voids, allowing for fast Li-ionic conduction in the interlayers, σ(Li + ) = 1.24 × 10 À 3 S cm À 1 at room temperature. The electronic conductivity is negligible, and the electrochemical stability is � 2.1 V vs Li. The first allsolid-state battery using a lithium borohydride with a neutral ligand as the electrolyte, Li-metal as the anode and TiS 2 as the cathode is demonstrated.

Trinuclear Magnesium Imidazolate Borohydride Complex

“…The title system in the form of acetonitrile solvate was inspected also by 1 H, 11 B, and 13 C solid-state NMR spectroscopy (Figure 2). The carbon NMR spectrum is the most informative.…”

“…Solid-state NMR spectra of the title system in the acetonitrile solvate form were measured on a 600 MHz Varian VNMRS spectrometer, equipped with a 1.6 mm HXY CPMAS probe. Larmor frequencies for 1 H, 11 B, and 13 C nuclei were 599. 51, 192.34, and 150.76 MHz, respectively.…”

“…GIPAW calculations yielded isotropic chemical shielding σ iso , from which the isotropic chemical shift was obtained as δ CS iso = σ ref − σ iso . Here σ ref was 168 ppm for 13 C and 30 ppm for 1 H nuclei. Agreement between the calculated and the experimentally determined chemical shifts was slightly better for structural models, in which only variation of atomic coordinates was allowed.…”

“…The 1 H MAS NMR spectrum was obtained at a sample rotation frequency of 40 kHz, using a 90°excitation pulse of 1.4 μs and repetition delay of 10 s. 11 B MAS NMR measurement employed a short 0.8 μs excitation pulse and high-power XiX proton decoupling during acquisition; 128 scans were collected, and the delay between the scans was 10 s. 1 H− 13 C LG-CPMAS experiment used Lee− Goldburg cross-polarization scheme with duration of 100 μs and highpower proton decoupling; the repetition delay was 2 s, and the number of scans was 4800. In both 2D HETCOR experiments spectral width and number of increments in the indirect dimension were 20 kHz and 20, respectively, XiX decoupling was used, and repetition delay was 2 s. For the measurement of the 1 H− 11 B HETCOR spectrum, a constant-amplitude cross-polarization block of 80 μs was used and the number of scans was 40; for the 1 H− 13 C HETCOR spectrum, a ramped-amplitude cross-polarization block of 2 ms was employed (ramp on the proton channel) and the number of scans was 800. Chemical shifts of 1 H and 13 C nuclei were reported relative to the corresponding signals of tetramethylsilane, whereas the 11 B chemical shift axis was set using a 1 M solution of H 3 BO 3 in water as a secondary reference ( 11 B nuclei resonate at 19.6 ppm).…”

“…In both 2D HETCOR experiments spectral width and number of increments in the indirect dimension were 20 kHz and 20, respectively, XiX decoupling was used, and repetition delay was 2 s. For the measurement of the 1 H− 11 B HETCOR spectrum, a constant-amplitude cross-polarization block of 80 μs was used and the number of scans was 40; for the 1 H− 13 C HETCOR spectrum, a ramped-amplitude cross-polarization block of 2 ms was employed (ramp on the proton channel) and the number of scans was 800. Chemical shifts of 1 H and 13 C nuclei were reported relative to the corresponding signals of tetramethylsilane, whereas the 11 B chemical shift axis was set using a 1 M solution of H 3 BO 3 in water as a secondary reference ( 11 B nuclei resonate at 19.6 ppm).…”