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 Ni³⁺, 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.