Construction of NiCoAl-layered trimetallic hydroxides@mesoporous carbon core-shell hollow nanospheres for high-performance battery-type supercapacitors

Developing electrode materials with hierarchically porous structure and high electrochemical stability is crucial for improving the energy density of supercapacitors (SCs). Herein, the NiCoAl layered trimetallic hydroxides supported on hollow carbon shells (NCA@HCs LTHs) with various Al doping amounts is synthesized by a simple hydrothermal method. The electrode material with the optimal NCA doping ratio (mass ratio 3:2:0.3) displays a stable layered hydroxides structure and low crystallinity. Additionally, the unique 3D hollow structure not only increases the specific surface area (SSA) but also effectively prevents the agglomeration of LTHs. The synergistic interaction of these two aspects is responsible for the exceptional specific capacity and cycling performance. The optimal N3C2A0.3@HCs LTHs exhibits a high specific capacitance of 792 C g-1 at 1 A g-1. Moreover, the constructed asymmetric supercapacitor (ASC) achieves a coulombic efficiency of 98% and retains 80% of its capacitance after 12000 cycles at 5 A g-1. The above results show that the synergistic strategy of Al doping and hollow structure design provides new insights into improving the electrochemical performance of SCs.