Template-controlled in-situ growing of NiCo-MOF nanosheets on Ni foam with mixed linkers for high performance asymmetric supercapacitors

High mass loading metal–organic frameworks (MOFs) exhibit great potentials as electrode materials in energy storage, benefiting from their massive exposed reactive sites. Keeping high mass loadings while maintaining ultra-fine morphology of MOFs is very technically demanding. Herein, high mass loading binder-free NiCo-MOFs with mixed organic linkers (1,3,5-benzenetricarboxylate, BTC and p-benzenedicarboxylate, PTA) have been in-situ grown on Ni foam (NF) using Co(OH)2 as the template. The designed NiCo-(PTA)0.8(BTC)0.2 nanosheets achieved an areal capacitance of 5.84 F cm−2 (2.92 C cm−2) at a current density of 1 mA cm−2. The origin of the excellent electrochemical performances is carefully explained. The fabricated asymmetric supercapacitor (ASC) using NiCo-(PTA)0.8(BTC)0.2 nanosheets and reduced graphene oxide (rGO) as the positive and negative electrodes presented an excellent specific capacitance of 113 F g−1 at 1 A g−1. Besides, an outstanding energy density of 40 Wh kg−1 was achieved at the power density of 800 W kg−1. The assembled ASC device can retain as high as 97.7% of the original capacitance after 10,000 cycles, manifesting an excellent cycle stability. This work may provide a strategy for the preparation of high mass loading dual metal MOFs electrodes with ultra-fine morphology for high-performance supercapacitors.