Substantially boosted energy density of NiCoMn layered double hydroxides with nanocrystalline-amorphous domains

Abstract

To promote the energy density (E) of the hybrid asymmetric supercapacitance (ASC) device, both anode and cathode materials are crucial. The multi-component layered double hydroxides (LDH) as anode materials boost a surprisingly supercapacitance, while the functions of dual-phase nanodomains induced by multi-constituents on the electrochemical reactions are still puzzled and need to be explored. In this work, Ni1Co1Mnx (Ni/Co/Mn = 1/1/x) LDH microspheres are developed, characterizing by quantum-sized nanocrystals embedded in amorphous matrix modulated via Mn doping. The specific capacities (C) of Ni1Co1Mn1.5 reach up to 5750 at 1 A g−1 and 5300 F g−1 at 10 A g−1, exceeding four times of 1367 (1 A g−1) and 1133 F g−1 (10 A g−1) of the Ni1Co1Mn0 counterpart. To break through the upper limit of the traditional active cardon cathode, bamboo-derived porous carbon (BPC) powders are produced from green raw resource by two stages calcination to increase the C. The assembled ASC cell with Ni1Co1Mn1.5 as an anode and BPC as a cathode possesses a large E of 97.8 Wh kg−1 at a power density (P) of 749.2 W kg−1. An exceptional sustainability of Ni1Co1Mn1.5//BPC device is attained with 91.4 % retention after 8000 cycles at a large charging current of 10 A g−1. The insights of Mn-regulated transition of nanocrystal-amorphous microstructure and the enhanced energy storage performance are explored.