MOF-derived carbon/ZnS nanoparticle composite interwoven with structural and conductive CNT scaffolds for ultradurable K-ion storage

Abstract

This study reports MOF-derived carbon/ZnS nanoparticle composite interwoven with CNT scaffolds for ultradurable K-ion storage. Metal–organic framework (MOF)-derived carbons possess in situ generated metal particles, which are subsequently utilized to prepare metal compounds. In MOF derivatives, the original morphology of MOF is rarely maintained due to the collapse of the framework and pyrolysis of organic ligands at high temperature. Accordingly, metal nodes aggregate, resulting in coarsening and non-uniform distribution of metal particles, which degrades their electrochemical properties. Moreover, the collapse dwindles micropore volume, decreases interparticle porosity and hinders diffusion of ions. Despite the importance in energy storage materials, however, these issues have been largely overlooked in MOF-assisted nanoparticle synthesis. We report a novel strategy for synthesizing robust MOF grown in situ on and interwoven with structural and conductive scaffolds of carbon nanotube networks (MOF-5@ACNT), which effectively stabilize the structure and morphology of the MOFs by preventing them from collapsing, thereby suppressing the aggregation and coarsening of metal particles during carbonization. To synthesize ZnS nanoparticles embedded in MOF-derived carbon (ZnS/C@CNT), MOF-5@ACNT and sulfur are mixed and heat-treated to prepare ZnS/C@CNT, wherein the initial cubic morphology of MOF-5 is retained and ∼15 nm ZnS nanoparticles are uniformly distributed without aggregation. ZnS/C@CNT exhibits a highly reversible conversion–alloying reaction with a high specific capacity (410 mA h g−1) and excellent cycling performance (87 % retention after 1000 cycles). The intimate contact between the ZnS nanoparticles and carbon through chemical interactions and structural and morphological stability make ZnS/C@CNT a promising anode material for KIBs.