Fast Ionic Migration from Bulk to Interface in the Li(NH₃)_xBH₄@SiO₂ Composite

Abstract

Lithium borohydride (LiBH 4 ), with high compatibility to lithium anode, low grain boundary resistance, and light mass, is regarded as a promising solid-state electrolyte. However, poor ionic conductivity at room temperature limits its practical application in all-solid-state lithium-ion batteries (ASSLBs). In the present study, Li(NH 3 ) x BH 4 @SiO 2 (0 ≤ x ≤ 0.5) composites were obtained by ammonia absorption and simple ball-milling. Among them, Li(NH 3 ) 0.5 BH 4 @ SiO 2 exhibits a high ionic conductivity of 3.95 × 10 −2 S cm −1 at 60 °C, with a lithium transference number up to 0.9999 at 30 °C. More importantly, the experimental results and density functional theory (DFT) calculations show that the skeleton and interfacial interaction of silica can effectively improve the electrochemical performance of the full cell. All-solid-state lithium−sulfur batteries exhibit a specific discharge capacity of 1221.7 mAh g −1 after 10 cycles. Reversible capacities of 1589, 1381, 1176, 969, and 695 mAh g −1 could be achieved at 0.1, 0.2, 0.3, 0.5, and 1C, respectively. These findings prove that Li(NH 3 ) x BH 4 @SiO 2 is an attractive electrolyte for next-generation ASSLBs.

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning

“…In recent studies, the impact of nanoconfinement of LiBH 4 within ordered mesoporous SiO 2 scaffolds has been extensively investigated. 195,196 DFT calculations have provided valuable insights into the behavior of ions within the confined space of the composite electrolytes. As illustrated in Fig.…”

LiBH4 as a Solid-State Electrolyte for Li and Li-Ion Batteries: A Review

“…Carbon and silicon-based materials such as fullerene [41,42], silicon oxide [43][44][45], and mesoporous silica [46,47], which were eventually added with lithium iodide [48,49], were also employed. Low molecular weight molecules including water [50] and ammonia [51][52][53], which were eventually added with silicon oxide [54], lithium amide [55,56], ammonia borane [57], mono-methylamine [58], oxygen [59], magnesium oxide [60], lithium tetrafluoro borate [61], and lithium thiophosphate [62] were also used to increase the conductivity of the hydride at lower temperatures.…”

“…During the process, LiBH 4 xNH 3 transforms into an amorphous material and the ionic conductivity at 20 • C rises to 5.4 × 10 −4 S cm −1 . Composites of LiBH 4 containing ammonia and silicon oxide were also prepared [54]. Composites of formula Li(NH 3 ) x BH 4 @SiO 2 (0 ≤ x ≤ 0.5) were prepared by absorbing ammonia into LiBH 4 and incorporating silicon oxide by ball milling.…”

Enhanced Li-ion conductivity in LiBH4–ZrO2 nanocomposites and nanoscale Li imaging by energy-filtered transmission electron microscopy

“…The formation of B-O species was also confirmed in other LiBH 4 -oxide nanocomposites. 11,17 Moreover, a peak at À1.2 ppm was observed in the 6 Li MAS spectra for pristine LiBH 4 , which corresponded to the chemical bonding states of LiBH 4 . 14 In addition, a broad peak around À0.3 ppm was observed.…”

“…12 Direct observation of nanoscale LiBH 4 by transmission electron microscopy (TEM) may confirm the previous measurements or provide further insights, and thus, several studies have conducted TEM analysis. 11,17 However, it was difficult to visualize Li in the composite with a high-magnification image. Lithium is a light element, which means its atomic scattering factor is low.…”