Slight Zinc Doping by an Ultrafast Electrodeposition Process Boosts the Cycling Performance of Layered Double Hydroxides for Ultralong-Life-Span Supercapacitors

Abstract

Layered double hydroxides (LDHs) have attracted much attention in supercapacitors because of the high specific surface area and theoretical capacitance. However, the bad cycling stability has always been their Achilles' heel that restrains their further application. In this paper, a small amount of unactive and single-valence element zinc, which has no contribution to the capacitance of electrodes, was first doped into NiCo-LDHs through two consecutive electrodeposition processes only within 30 min. With a polyaniline (PANI) nanolayer as the interlayer, an ultrathin NiCoZn-LDH nanoplate network was well-anchored on the carbon cloth surface. The slight Zn²⁺ doping dramatically enhanced the cycling performance of LDHs with little capacitance decay. Zn²⁺ doping enhanced the cyclic structural stability of NiCoZn-LDHs, while the PANI layer strengthened the interface interaction between LDHs and the current collector. By controlling the doping content of Zn²⁺ at 2.9%, the composite electrode achieved the best performance with a high specific capacitance of 1749 F g^-1 and an ultralong life span with 89% capacitance retention after 40,000 charge-discharge cycles. This work offers a novel strategy to fast build LDH-based supercapacitors with both high specific capacitance and cycling performance.