Enhancement of lithium storage performance of carbon microflowers by achieving a high surface area.

High-surface-area, nitrogen-doped carbon microflowers (A-NCFs-4) assembled from porous nanosheets are prepared in a three-step process: soft-templating self-assembly, thermal decomposition, and KOH activation. The hydrazine hydrate used in our experiment serves not only as a structure-directing agent, but also as a nitrogen source. The resultant A-NCFs-4 has a hierarchical porous structure and its specific surface area is as high as 2309 m(2)  g(-1). When used as anode, it exhibits a reversible capacity as high as 807 mAh g(-1) at 300 mA g(-1) after 100 cycles, and an excellent rate capability of 200 mAh g(-1) at a high current density of 8 A g(-1). Compared with unactivated counterpart, A-NCFs-4 exhibits a significantly improved lithium storage capacity and rate capability; this can be attributed to its unique structural characteristics and high surface area. The hierarchical micro-/mesopore structure, high surface area, and nitrogen doping of A-NCFs-4 could guarantee fast mass transport for lithium species, enhance the A-NCFs-4/electrolyte contact area, shorten the lithium-ion diffusion length, and accommodate strain induced by volume changes during the electrochemical reaction. The results indicate that the as-prepared A-NCFs-4 could be a promising candidate as a high-performance anode for lithium-ion batteries.