Electrochemical Properties of Low Temperature Crystallized LiCoO2

Abstract

Electrochemical properties of low temperature (LT) crystallized LiCoO, are investigated. LT LiCoO, was obtained by a precipitation process in aqueous solution and a final heat-treatment at 400°C in air. Potentiometric, voltammetric, and ac impedance experiments are performed as well as x-ray diffraction measurements on electrochemically delithiated compounds. LT LiCoO2 shows electrochemical and structural properties quite different from that exhibited by the high temperature (lIT) LiCoO,. The main differences appear in terms of practical voltage, reversibility, Li transport in oxide, and structural changes as Li is deintercalated. This work clearly proves the 3D character of LT LiCoO2 (spinel-like structure). In spite of a lower working potential and a satisfactory capacity (zx = 0.5), the LT LiCoO, is highly reactive toward the electrolyte and is characterized by a slower Li transport than in layered HT LiCoO,.

Chemical Synthesis and Properties of Spinel Li1−xCo2O4−δ

“…All the lithium could be completely extracted from the layered HT-LiCoO 2 to give CoO 2Àd with a HTLiCoO 2 :NO 2 BF 4 molar ratio of 1:1.5 in the reaction mixture (13,14). The difficulty in removing all the lithium from the LT-LiCoO 2 , attests to the fact that it is structurally different from the conventionally prepared HT-LiCoO 2 , as has been found before (15)(16)(17)(18)(19)(20)(21). The removal of lithium from the 8a tetrahedral sites of the spinel lattice (Li 1Àx ) 8a [Co 2 ]O 4Àd obtained from LT-LiCoO 2 (see below) requires higher energy than that from the 16c octahedral sites of the spinel structure or 3a sites of the layer structure.…”

“…LiCoO 2 synthesized at low temperatures (TE4001C) is known to adopt a structure that is different from that synthesized at 9001C and it has been designated as LTLiCoO 2 (15)(16)(17)(18)(19)(20)(21). LT-LiCoO 2 has been shown from X-ray 1 To whom correspondence should be addressed.…”

Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions

“…Figure 1a shows the X-ray diffraction patterns of LT-LiCoO 2 , HT-LiCoO 2 and Co 3 O 4 . While the LT-LiCoO 2 synthesized at 400°C shows a single reflection around 2yE63°corresponding to the {440} plane of the cubic lithiated spinel (Fd3m), it splits into the (108) and (110) reflections of the layered HT-LiCoO 2 structure (R 3m) on heating to 800°C [27][28][29][30] . Also, the (220) reflection present in Co 3 O 4 is absent in LT-LiCoO 2 due to the absence of ions with high scattering power in the 8a tetrahedral sites of the spinel lattice in LTLiCoO 2 .…”

“…2), but the second peak is much weaker even at a slow scan rate of 5 mV s À 1 . This is because the lithium diffusion rate is much slower in LT-LiCoO 2 , which has a lithiated spinel structure formed at low temperatures, possibly with defects, compared with that in HT-LiCoO 2 that has a well-formed, well-ordered layered structure 30,34 . In addition, LT-LiCoO 2 may also undergo structural transformations at deep lithium extraction, involving possibly proton insertion, due to the instability at high Co 4 þ contents.…”

Nanotechnology for Energy Storage

“…The wet-chemical techniques could be classified in four groups according the salts and complexing agent used (Table 12.1). They are namely sol-gel [9,10], co-precipitation [11,12], combustion [13], pyrolysis [14], polyol [15], Pechini process [16,17], etc. ; they were employed for the preparation of nanostructured metal oxides devoted to electrodes for Li-ion batteries.…”