In situ vertically growth of 2D NiCo-BTC nanosheet arrays for binder-free flexible wearable energy storage devices

Metal-organic frameworks (MOFs) with high performance are hopeful materials for miniaturization and flexi-bility of energy storage devices for demands in development of modern electronic products. Thus, in this work, bimetallic MOFs composite with ultrahigh specific capacity and excellent cycling stability is acquired by a facile one-step solvothermal method. The regulated nickel-cobalt bimetallic MOFs (NiCo-BTC) nanosheet array with the linker of 1,3,5-Benzenetricarboxylic acid (H3BTC) was in situ constructed on carbon cloth (CC), and directly served as electrode for supercapacitor without any addition of binder. Through the precisely controlled growth of NiCo-BTC nanosheets on CC, the unique composite structure allows an ultrahigh specific capacity of 644.4C g-1 at the current density of 0.5 A g-1, which is about 11.8 and 4.1 times than that of single metallic Co-BTC (54.6C g-1) and Ni-BTC (157.5C g-1), respectively. Moreover, the actually assembled flexible device based on NiCo-BTC and active carbon (AC) displays a high energy density of 32.4 Wh kg- 1 (at the power density of 346 W kg -1) and an ultra-long cyclic life with a capacity retention of 91.2 % after 8000 cycles. This binder-free NiCo-BTC nanosheet electrode is also benefit for simple preparation process for flexible and all-solid supercapacitor in practical energy storage applications.

Automated summary

A bimetallic metal-organic frameworks (MOFs) composite with ultrahigh specific capacity and excellent cycling stability was prepared using a one-step solvothermal method. The composite electrode, which consists of regulated nickel-cobalt MOFs nanosheet array on carbon cloth, achieved an ultrahigh specific capacity of 644.4C g-1 at a current density of 0.5 A g-1. The flexible device based on this binder-free NiCo-BTC nanosheet electrode and active carbon displayed a high energy density of 32.4 Wh kg-1 and an ultra-long cyclic life with a capacity retention of 91.2% after 8000 cycles.