Efficient synthesis of orthorhombic lithium borate hydroxide micro-rods and their thermal conversion to lithium borate

Uniform orthorhombic Li3B5O8(OH)2 micro-rods were hydrothermally synthesized at 150–210 °C for 6.0–24.0 h, using LiOH·H2O and H3BO3 as the reactants. The resulting Li3B5O8(OH)2 micro-rods had a length of 20–60 μm, an aspect ratio of 6–14, and a high crystallinity. The presence of hexadecyl trimethyl ammonium bromide was favorable for the oriented growth of the Li3B5O8(OH)2 micro-rods. The orthorhombic Li3B5O8(OH)2 was decomposed into Li2B4O7 and α-LiBO2. Pore-free high crystallinity Li2B4O7 with quasi polyhedron morphology can be obtained by NaCl assisted calcination. This enlarged the controllable synthesis of the alkali borates, especially enriched the study on the lithium borates which can be potentially used as a perspective superionic conductor and electrode of lithium ion batteries.

Graphical abstractHigh crystallinity orthorhombic Li3B5O8(OH)2 micro-rods and tetragonal Li3B5O8(OH)2 particles were hydrothermally synthesized, and the flux NaCl assisted thermal decomposition of orthorhombic Li3B5O8(OH)2 led to pore-free quasi polyhedron Li2B4O7.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Controllable synthesis of the alkali borates. ► Hydrothermal synthesis of high crystallinity Li3B5O8(OH)2. ► Thermal decomposition of orthorhombic Li3B5O8(OH)2. ► Pore-free Li2B4O7 with quasi polyhedron morphology.