Synthesis and Cathodic Properties of LiCo[sub 1−y]Rh[sub y]O[sub 2] (0≤y≤0.2) and LiRhO[sub 2]

Compounds of the formula and have been synthesized by high temperature solid-state reaction and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and infrared spectroscopy. Single-phase materials were obtained for and as observed by XRD. However, IR and electrochemical data indicate that the true solid solubility may be Their cathodic behavior in coin cells with Li metal as anode and a liquid electrolyte has been examined. Cyclic voltammograms and galvanostatic charge/discharge curves show that for the phase transformation occurring at in is suppressed and the deintercalation voltage is decreased. The compositions with and 0.10 show improved cathodic behavior and discharge capacity retention compared to at 0.14C rate in the voltage range 2.7-4.3 V up to 18 cycles. Electrochemical studies on show that phase transitions occur on charge/discharge cycling (varying x in in the voltage window 3.2-3.7 V and these are reversible. This compound shows an initial charge capacity of 162 mAh/g when charged to 4.0 V ( vs. Li metal), corresponding to in After an initial loss of 40 mAh/g in capacity, the discharge capacity retention corresponds to 90% after 18 cycles with respect to the initial discharge capacity in the voltage window, 2.7-4.0 V. © 2001 The Electrochemical Society. All rights reserved.