A well-controlled three-dimensional tree-like core-shell structured electrode for flexible all-solid-state supercapacitors with favorable mechanical and electrochemical durability

Although coupling highly pseudocapacitive species with flexible carbon substrates to fabricate hybrid electrodes holds promise for high-performance flexible supercapacitors, the structural collapse and performance degradation under repeated mechanical deformation remain a bottleneck to be tackled owing to the weak binding force between carbon and electroactive materials. Herein, well-controlled three-dimensional (3D) NS@NCCH tree-like core-shell microarrays grown on flexible and conductive Ni-plated carbon cloth (NPCC) are fabricated, with NiSe (NS) nanorods as the core and NiCo(CO3)(OH)(2) (NCCH) nanosheets as the shell. The dense NS nanorod core in situ grown on NPCC, as a highly conductive and robust support, promotes electron transport as well as hindering the agglomeration of NCCH nanosheets. The NCCH nanosheet shell with a high specific surface area provides a bridge to combine the fast diffusion of electrolyte ions and ionic accessibility to the overall electrode surface. The synergistic contributions from the NPCC substrate and the core-shell NS@NCCH microarrays together with the natural gift of a 3D tree-like architecture enable the NS@NCCH/NPCC electrode to exhibit a high capacity of 6.89 F cm(-2) (1642 F g(-1), 228 mA h g(-1)) at 4 mA cm(-2) and good rate performance. Furthermore, an assembled flexible all-solid-state asymmetric supercapacitor (FASSAS) based on the NS@NCCH/NPCC electrode retains an energy density of 53.8 W h kg(-1) at a high power density of 15 kW kg(-1) and exhibits excellent cycling stability with 91.5% capacitance retention after 5000 cycles. Especially, bending or twisting the FASSAS device to 180 degrees causes negligible electrochemical property attenuation.

Automated summary

A three-dimensional NS@NCCH tree-like core-shell microarray was designed and fabricated for high-performance flexible supercapacitors. The electrode exhibited high capacity and rate performance, as well as excellent cycling stability, attributed to the optimized core-shell structure and substrate material. Moreover, it was assembled into a flexible all-solid-state asymmetric supercapacitor with negligible electrochemical property attenuation even under severe bending or twisting.