Sub-nanometer-scale fine regulation of interlayer distance in Ni-Co layered double hydroxides leading to high-rate supercapacitors

Ni-Co layered double hydroxides (LDHs) have high theoretical capacities for energy storage by ion intercalation/release but suffer from the sluggish charge transport kinetics, hence are unsuitable for high-power super -capacitors nowadays. Herein, by intercalating the guest multi-carboxylic anions with straight-chain or conjugated-plane configurations, we have realized the sub-nanometer-scale fine regulation of the interlayer distance in Ni-Co LDHs for tuning the charge (ions and electrons) transport kinetics. With increasing the interlayer distance, the equivalent series resistance (RESR) shows the inverted-volcano evolution, which is first demonstrated for the anion-intercalated LDHs. With the smallest RESR, the LDH pillared by the conjugated 1,4-benzenedicarboxylic anion achieves the best matching between ion diffusion and electron transfer, and thus presents a high capacitance of 2115 F g(-1) at 1 A g(-1) and a record-high rate capability for the powder-like LDHs with the capacitance of 410 F g(-1) at an ultrahigh current density of 150 A g(-1). The corresponding hybrid supercapacitor coupled with activated carbon presents the high energy density of 11.2 Wh kg(-1) at the ultrahigh power density of 30.7 kW kg(-1), ranking at the top level for the supercapacitors based on the powder-like LDHs active materials. The minimal RESR from the inverted-volcano evolution could provide a feasible criterion to explore the high-rate LDH electrodes.