High-yielding preparation of hierarchically branched carbon nanotubes derived from zeolitic imidazolate frameworks for enhanced electrochemical K + storage.

Branched carbon nanotubes are regarded as very promising anode materials of K-ion batteries, while the high-yielding preparation still remains challenging. We here demonstrate a facile approach for synthesizing N-doped branched carbon nanotubes (br-CNTs) in macroscopic quantity, via one-step carbonization of ZnCo-containing zeolitic imidazolate framework (ZnCo-ZIF) nanotubes. At a high current density of 2 A g -1 , the as-synthesized br-CNTs could exhibit 147.2 mA h g -1 specific capacity and retain 84.5% of the initial value after 1300 cycles for electrochemical K + storage, which is better than commercial carbon nanotubes and other carbon counterparts derived from ZnCo-ZIF particles and ZnCo-BTC nanowires. The excellent K + storage performance of ZnCo-ZIF-derived br-CNTs actually results from the unique branched architecture and N doping, by taking advantage of more active sites and desired electrochemical kinetics as well as structural integrity. Our proposed approach would give a significant example for the scalable preparation of other complex nanostructures, and the prepared br-CNT is expected to be a very competitive candidate for high-efficiency electrochemical K + storage.