Nano Co₃O₄ as Anode Material for Li–Ion and Na‐Ion Batteries: An Insight into Surface Morphology

Abstract

Co 3 O 4 is regarded as a competent anode material for lithium and sodium ion batteries having high theoretical capacity of 890 mAh g -1 obtained through metal displacement reaction with Li or Na. Nano Co 3 O 4 consisting of 20-30 nm-sized particles was synthesized through a simple precipitation method and characterized through X-ray diffraction, Fouriertransform infrared spectroscopy, scanning electron microscopy, Transmission electron microscopy and X-ray photoelectron spectroscopy. Electrochemical evaluation of the nano Co 3 O 4 as anode material for Li-ion and Na-ion batteries was performed through cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge cycling studies. Nano Co 3 O 4 delivered high discharge capacity of 423 mAh g -1 at 0.1 C even after 40 cycles as Li-ion battery anode and exhibited stable discharge behaviour up to 130 cycles with high rate capability. Nano Co 3 O 4 in Na-ion configuration delivered discharge capacity of 101 mAh g -1 at 0.1 C rate even after 30 cycles. At higher current rates Co 3 O 4 electrodes exhibited severe capacity fading due to the huge volume change occurred during sodiation / desodiation. Ex-situ SEM and elemental analyses evidenced that disintegration of electrode structure resulting from volume change and continuous decomposition of electrolyte were responsible for the poor electrochemical performance of Co 3 O 4 with Na + ions while in Li-ion configuration nano Co 3 O 4 outshined in cycling performance.[a] Prof.

Solution combustion synthesis of a nanometer-scale Co3O4 anode material for Li-ion batteries

“…The first to fifth charge-discharge cycle profiles measured at a current density of 100 mA•g −1 are shown in Figure 3a. During the first discharge, the profile consists of one long plateau at around 1.0 V, corre-sponding to the formation of metallic cobalt and Li 2 O according to the reversible conversion reaction stated before (Equation 1), and a gradual continuous voltage slope down to 0.01 V, corresponding to electrolyte decomposition and the resulting formation of a solid-electrolyte interface (SEI) layer [14,15,[19][20][21]26,[28][29][30][31][34][35][36][37][38][39][40][41]52]. In turn, the following discharge profiles slightly differ from the initial one.…”

“…This phenomenon might be explained by the growth of the SEI layer, which provides some additional reversible capacity (cf. Figure 3c and [ 25 , 29 ]) and, at the same time, causes a small increase of the impedance.…”

“…Interestingly, the cyclability test performed at 100 mA•g −1 shows that the values of specific capacity consecutively rise over the theoretical capacity value and are maintained at 1060 mAh•g −1 after 100th cycle. This phenomenon is well known for different transition metal oxide electrodes and is usually ascribed to the reversible formation/dissolution of a gellike SEI layer, which provides some additional reversible capacity apart from the reversible conversion reactions occurring on the electrodes [4,15,17,19,21,24,26,29,34,37,40,52]. This additional lithium storage is often referred to as "pseudo capacitive" mechanism [25,29].…”

“…It has been established that the electrochemical performance of Co 3 O 4 materials is improved when they possess either small size or appropriate pore size distribution and morphologies, such as porous or hierarchical structures, or the combination of both these features [3,4]. So far, different syntheses have been proposed including sol-gel methods [4,6,[13][14][15], sol-electrospinning techniques [16][17][18][19], hydrothermal and solvothermal syntheses [20][21][22][23][24][25][26][27][28], precipitation and co-precipitation [29][30][31], chemical thermal decomposition and pyrolysis [32][33][34][35][36][37], and other methods [38][39][40][41]. Co 3 O 4 nanomaterials with various shapes were obtained, such as films [6,16], particles [13,14,32,38], spheres [15,20,28,36], fibers [18,19], wires…”

“…4 nanostructures with various shapes[15,21,[23][24][25][26][27]30,31,34,36]. This capacity fade is usually ascribed to an irreversible electrolyte decomposition, the formation of the SEI layer, and the formation of stable Li 2 O[4,14,15,[19][20][21]26,[28][29][30][31][34][35][36][37][38][39][40][41]. The charge profiles are very similar and they exhibit a voltage plateau at about 2.0 V, which is associated with the re-conversion reaction and the resulting reconstruction of the cobalt oxide electrode.…”