Exceeding 50 000 Cycle Durability of Layered Hydroxide-Based Hybrid Supercapacitor Through Scandium Doping-Induced Superlong Activation Process

Layered double hydroxides (LDHs) are a class of promising cathode materials for supercapacitors. However, the bad cycling performance has always been the Achilles’ heel of LDHs-based supercapacitors. In this contribution, a nonelectrochemical active element Scandium (Sc) is doped into NiCo-LDHs to greatly improve the intrinsic cycling performance of active materials. The trimetallic NiCoSc-LDHs exhibit an ultralong cycle lifespan with 40 000 charge–discharge cycles (exceeding 50 days) and a high specific capacity of 196 mAh g −1 (1695 F g −1 ). Sc doping greatly changes the degradation mode of NiCo-LDHs from rapid decay in thousands of cycles to a two-stage performance evolution, which consists of a superlong activation process of about 10 000 cycles and then extremely slow degradation. Moreover, Sc doping enhances the electrochemical activity of Ni 3+ , so as to not only avoid its Jahn–Teller distortion, but also perform as a structural stabilizer to alleviate the local strain of host layer. The assembled asymmetric supercapacitor delivers an ultralong cycling lifespan with 101% capacity retention even after 50 000 cycles. This work presents a new pathway to significantly improve the electrochemical performance, especially the cycling stability of LDH-based electrodes for high-performance supercapacitors.