Different metal precursor based rapid synthesis of α-Ni(OH)2-type Ni-Co-Mn layered double hydroxides and its use as electrodes for high performance energy storage devices

Abstract

Improvement in the specific capacity of battery type electrode material is vital for creating hybrid devices with superior electrochemical performance. To accomplish this, mixed metal hydroxides, Ni0.7Co0.2Mn0.1(OH)2, are synthesized via a simple co-precipitation method by rapid pH switching using chloride, nitrate, acetate and sulphate salts of Ni, Co and Mn. P-XRD analysis confirmed the formation of pure and highly crystalline materials stabilized in the α-Ni(OH)2 structure. Finely divided particle type microstructure with sub 100 nm size and homogenous distribution of elements are confirmed by FESEM and EDX analysis, respectively. Among the studied samples, the layered hydroxide synthesized using chloride salts (Ni0.7Co0.2Mn0.1 LDH-Cl) shows the highest specific surface area of 58.8 m2 g−1 and pore volume of 0.083 cc g−1. The compound exhibited a high specific capacity of 978 C g−1 at 1 A g−1. The observed capacity is much higher than all other double hydroxides studied here and those we have come across in the literature reports on similar metal hydroxides. The diffusion dominance (b = 0.55) and quantitative separation of diffusion and capacitive capacity at different scan rates for Ni0.7Co0.2Mn0.1 LDH-Cl is also studied by CV analysis. Nyquist plot equivalent circuit fitting shows low charge transfer resistance (Rct = 17.6 Ω) and Warburg impedance (Zw = 35 Ω) for Ni0.7Co0.2Mn0.1 LDH-Cl. The high-capacity retention of 90 % for 5000 CV cycles at 100 mV sec−1 and 99 % for 1000 GCD cycles at 5 A g−1 for Ni0.7Co0.2Mn0.1 LDH-Cl confirm its potential for use as a battery type electrode material for practical applications.