Simple Synthesis of K₄Nb₆O/C Nanosheets for High-Power Lithium-Ion Batteries with Good Stability.

In this work, a series of two-dimensional (2D) large-size nanosheets were prepared through one-step exfoliation of the huge K₄Nb₆O crystals. The K₄Nb₆O nanosheets with the thickness of about 2 nm was used as the templates of dopamine polymerization and was then carbonized to form C-doped K₄Nb₆O nanosheets. More importantly, the C-doped K₄Nb₆O nanosheets exhibited excellent electrochemical performance with high specific capacity (381 mA h g at 0.05 A g, 0.5⁻3.0 V vs. Li/Li⁺) and stable cyclability at high current density (remarkably, preserved a capacity of discharge approximately 90 mA h g at 5 A g after 1000 cycles). The good electrochemical performances of the C-doped K₄Nb₆O nanosheets can be attributed to the outstanding 2D structure and large specific surface, which afforded the short transport route for ion and electron. These noteworthy results demonstrated that the new 2D nanomaterials might be potential candidates for the high-performance, environmentally friendly, and low-cost electrochemical energy storage equipment.