Changes in Electronic Structure between Cobalt and Oxide Ions of Lithium Cobalt Phosphate as 4.8-V Positive Electrode Material

Abstract

Insight into electron exchange in LiCoPO4 electrodes for high-voltage lithium ion battery is presented using X-ray absorption spectroscopy (XAS). Despite the formation of the isolated valence electrons around the Co ion, O K-edge XAS reveals clear evidence that the hybridized orbital between Co and O plays an important role in the electron exchange arising from the electrochemical Li extraction.

Carbon coated lithium cobalt phosphate for Li-ion batteries: Comparison of three coating techniques

“…The calculated pattern matches the observed one quite well, implying the reliability of the refinement. The refinement reveals lattice parameters of a ¼ 1.0201 (2) nm, b ¼ 0.5923 (1) nm, c ¼ 0.4700 (5) nm, and accordingly V ¼ 284.01 nm 3 for LCPdeposition, in good agreement with previous reports [4,7,12]. The other two samples exhibit rather similar lattice parameters, signifying that carbon coatings exert little impact on the olivine structure.…”

Preparation and characterization of carbon foams–LiCoPO4 composites

“…However, studies on LiCoPO 4 are scarce because the existing preferred nonaqueous electrolytes are found to be unstable in the high-voltage range (≥4.8 V) where cobalt reduction/oxidation reactions can occur. Efforts toward improving nonaqueous electrolytes have made LiCoPO 4 an attractive cathode to explore in the high charge voltage regime, up to 5 V. Although the reversibility of lithium extraction-insertion from/into LiCoPO 4 was demonstrated in a few reports [9][10][11][12], a severe capacity fading during cycling has limited the use of this material in practical applications. As result, less attention has been paid toward the development of LiCoPO 4 cathode in lithium batteries using nonaqueous electrolytes.…”

Li-ion diffusion kinetics in LiCoPO4 thin films deposited on NASICON-type glass ceramic electrolytes by magnetron sputtering

“…However, the XRD results showed that the crystalline phase was only a lithiumpoor phase; no "CoPO 4 " phase was identified even though LiCoPO 4 was fully charged. In addition, two successive voltage plateaus were often observed during the charge of LiCoPO 4 [5,[11][12][13][14]. Nakayama et al [13] proved that it was not related to the irreversible side reactions and suggested that it might be due to an increase in electrochemical polarization around x = 0.3 in Li 1−x CoPO 4 .…”

“…In addition, two successive voltage plateaus were often observed during the charge of LiCoPO 4 [5,[11][12][13][14]. Nakayama et al [13] proved that it was not related to the irreversible side reactions and suggested that it might be due to an increase in electrochemical polarization around x = 0.3 in Li 1−x CoPO 4 . Nevertheless, the exact mechanism for the two-plateau charge profile is still controversial, and in other cases, a one-plateau charge profile was reported [15][16][17].…”