Fig. 2: Synthesis and characterization of BHNC.
a, Synthesis procedures of bidirectionally aligned and hierarchically structured nanocomposites mainly include bidirectional freezing assembly, freeze drying, cross linking and salt loading. The vertically oriented and radially oriented hierarchical structures are formed enabled by two temperature gradients: vertical temperature gradient (∆TV) for driving ice growth from the bottom copper base to the top of the graphene oxide and sodium alginate (GO-SA) solution and radial temperature gradient (∆TR) for driving ice growth from the copper pillars to the circumferential GO-SA solution. b, SEM images of BPGHM from the top view. c, SEM images of BPGHM from a cross-sectional view. d, SEM images of BHNC after Ca2+ cross linking and LiCl loading, showing nano-size LiCl crystals are evenly distributed on the surface of BPGHM as salt coating. e, Pore size distributions of BPGHM and BHNC. f, Digital photograph of scalable BHNC block with the size of 45 mm (L) × 45 mm (W) × 40 mm (H).
