Synergistic doping of La and Sc in nickel-cobalt layered double hydroxides for high capacity and long lifespan supercapacitor

Layered double hydroxides (LDHs) are attractive candidates for hybrid supercapacitor cathodes due to their high theoretical capacitance. However, their practical application is hindered by insufficient achievable capacity and compromised cycling stability caused by irreversible phase transitions. Herein, we developed a quaternary NiCoScLa-LDH via a one-pot hydrothermal method by co-doping scandium (Sc) and lanthanum (La) into NiCo-LDHs. Systematic investigation of trimetallic NiCoLa-LDH revealed that single La doping effectively increases specific capacity (745.2 C g −1 at 1 A g −1 ), while its large ionic radius induces structural instability, leading to rapid capacity decay (50 % capacity retention after 1500 cycles). First-principles calculations demonstrate that Sc doping clearly suppresses the deformation of the hexagonal structure of NiCoLa-LDH. Furthermore, La and Sc co-doping synergistically modulates the chemical coordination environments of Ni/Co and reduces the bandgap, thereby facilitating electrochemical reaction kinetics. The optimized NiCoScLa-LDH exhibits superior electrochemical performance, delivering a high specific capacitance of 744.2 C g −1 at 1 A g −1 , remarkable rate capability (75 % capacitance retention at 10 A g −1 ), and long-term durability (82 % capacity retention after 15,000 cycles). When assembled into a hybrid supercapacitor, the material achieves a maximum energy density of 45.6 Wh kg −1 at 410 W kg −1 and outstanding cycling stability (100 % capacitance retention after 45,000 cycles). This work provides fundamental insights into rational multi-element doping strategies for designing high-performance LDH-based supercapacitor cathodes.