Biomimetic mineralization is a powerful approach for the synthesis of advanced materials with complex shape, hierarchical organization and controlled size, shape and polymorph under ambient conditions in aqueous environments. Increased understanding of biomineralization mechanisms has greatly enhanced the possibilities of biomimetic mineralization approaches. This overview tries to capture the concepts and recent progress in this rapidly developing field.

Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.

Facile fabrication of well-aligned Li₄Ti₅O₁₂ (LTO) nanosheet arrays grown directly on conductive Ti foil was achieved by hydrothermal growth in LiOH solution. The reaction between Ti foil and LiOH led to the growth of vertically aligned, rectangular lithium titanate oxide hydrate (H-LTO) nanosheet arrays, which could be converted into LTO nanosheet arrays through topotactic transformation via thermal decomposition. An appropriate LiOH concentration was essential for the formation of densely aligned H-LTO nanosheet arrays on the substrate. It was proposed that the formation of the H-LTO nanosheet arrays was through kinetics-controlled growth during the hydrothermal metal corrosion process. When used as a binder-free anode for LIBs, the self-supported LTO nanosheet arrays standing on Ti foil exhibited an excellent rate capability (a reversible capacity of 163 mA h g⁻¹ and 78 mA h g⁻¹ at 20 C and 200 C, respectively) and an outstanding cycling performance (a capacity retention of 124 mA h g⁻¹ after 3000 cycles at 50 C). Furthermore, a flexible lithium ion battery, which could be fully recharged within 30 s and was able to light an LED, was assembled by using the LTO nanosheet arrays as the anode.