Design and Preparation of NiCoMn Ternary Layered Double Hydroxides with a Hollow Dodecahedral Structure for High-Performance Asymmetric Supercapacitors

Layered double hydroxides (LDHs) are prospective cathode materials for supercapacitors because of their outstanding theoretical specific capacitance and unique layered structure. However, the finite electroactive sites and cation species confine their practical application in supercapacitors. In this work, a hollow polyhedral ternary metallic Ni2CoMn1-LDH is prepared using zeolitic imidazolate framework-67 (ZIF-67) as the template. It has been found that the hollow dodecahedral structure constructed by thin nanosheets endows the Ni2CoMn1-LDH sample with abundant specific area and more ion-/electron-transport channels, which facilitate ion/electron transfer. Meanwhile, Ni2CoMn1-LDH can achieve the maximum synergistic effect of the different transition metals due to its optimal composition and content, which is conducive to improving the electrochemical behavior of supercapacitors. Benefiting from the advantages of their structure and composition, the as-prepared Ni2CoMn1-LDH electrode presents an excellent capacitance performance of 1634.4 F g(-1) at 0.5 A g(-1). Moreover, an asymmetric supercapacitor fabricated with a Ni2CoMn1-LDH cathode and an activated carbon (AC) anode reveals a good specific capacitance of 123.4 F g(-1) at 1 A g(-1) and a maximum energy density of 43.9 Wh kg(-1) at a power density of 800 W kg(-1). Therefore, constructing ternary LDHs with a unique hollow structure and optimal element composition has a promising prospect in the industrial application of supercapacitors and large-scale energy-storage devices.