Carbonaceous photonic crystals as ultralong cycling anodes for lithium and sodium batteries

Via carbonization of butterfly wings, carbonaceous photonic crystals (CPCs) were derived as anode materials for lithium and sodium ion batteries (LIB and NIB) with ultralong cycling stability. Owing to the CPC's inheritance of the wing's unique photonic structure, the periodically interconnected ridges and ribs serve as perfect channels for electron transportation and allow the presence of cross-linked macropores for facile electrolyte access and ion diffusion. The carbonization-induced micro- and mesopores in the ridges and ribs can further facilitate electrolyte penetration and thus shorten the ion diffusion distances. Moreover, depending on the carbonization temperature, rich contents of O and N heteroatoms on the carbon surfaces can offer extra sites for reversible Li+/Na+ adsorption and enhance the electrochemical reactivity and electronic conductivity. For LIB/NIB applications, the derived CPC (CPC800) by carbonization at 800 degrees C delivers the best performances. CPC800 offers high specific capacities of 590 mA h g(-1) (LIB) and 235 mA h g(-1) (NIB) with similar to 100% coulombic efficiencies at 0.05 A g(-1). More impressively, CPC800 displays ultralong cycling stability for LIB and NIB applications, sustaining more than 10 000 cycles at 5 A g(-1) (LIB) and 1 A g(-1) (NIB) with no evident observation of the fading of capacity and similar to 100% coulombic efficiencies.