Phase Transitions Occurring upon Lithium Insertion−Extraction of LiCoPO₄

Abstract

In situ synchrotron diffraction revealed a stepwise appearance of two new phases upon electrochemical lithium extraction from LiCoPO 4 . These phases were demonstrated to have the same olivine-like structure as the pristine compound. The lithium-deficient phases were proposed to be Li 0.7 CoPO 4 and CoPO 4 . The completely delithiated phase appears to be unstable in air and undergoes amorphization. The phase transitions are reversible, but a slow kinetics of the initial delithiation was identified by in situ synchrotron diffraction and the potentiostatic intermittent titration technique. We demonstrated that the electrochemical extraction of lithium is accompanied by significant electrolyte decomposition, contributing to the capacity loss upon cycling. The galvanostatic intermittent titration technique combined with impedance spectroscopy revealed self-discharge of the cell in the charged state. This study argues different mechanisms of lithium extraction from LiCoPO 4 in comparison with LiFePO 4 and LiMnPO 4 .

Carbonate anion controlled growth of LiCoPO4/C nanorods and its improved electrochemical behavior

“…A c c e p t e d M a n u s c r i p t 4 studied LiMPO 4 (M = Fe, Co, Mn, Ni) cathodes [9][10][11][12]. Despite these advantages, there are challenges associated with the practical application of LiCoPO 4 [9,10,[13][14][15][16] such as poor conductivity and slow lithium transport kinetics.…”

“…Despite these advantages, there are challenges associated with the practical application of LiCoPO 4 [9,10,[13][14][15][16] such as poor conductivity and slow lithium transport kinetics. These must be improved if LiCoPO 4 is to be a suitable cathode material alternative.…”

Synthesis and characterization of olivine LiNiPO4 for aqueous rechargeable battery

“…Comparative studies of the LiMPO 4 family [12][13] reported that it was difficult to deintercalate Li + from Co and Ni phosphate within the voltage stability window of existing non-aqueous electrolyte; for the high potential value of the redox couples Co 3+ / 2+ and Ni 3+ / 2+ [12]. However, efforts in improving the electrolyte have recently made it possible to explore the LiCoPO 4 compound to about 5 V [9,13] [14][15][16] due to the difficulty in obtaining a pure phase of lithium nickel phosphate.…”

“…However, efforts in improving the electrolyte have recently made it possible to explore the LiCoPO 4 compound to about 5 V [9,13] [14][15][16] due to the difficulty in obtaining a pure phase of lithium nickel phosphate. It is reported [17][18] that stringent synthesis conditions are required to synthesis LiNiPO 4 .…”

Synthesis of Crystalline LiCoPO4 by a Solvo-thermal Method

“…It belongs to olivine lattice [6] and the triphylite lithium orthophosphates: the lattice constants, and also the synthetic procedure followed in its preparation [4]. At present, the main synthetic routes include solid-state, wet chemistry, sol-gel, hydrothermal, co-precipitation, micro-wave heating and other method [6][7][8][9][10]. In order to obtain well formed, highly crystalline and pure LCP particles, here we report the synthesis at low temperature by a solvo-thermal route and subsequent sintering under N 2 atmosphere [3].…”