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

Abstract

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° causes negligible electrochemical property attenuation.