Suppression of Cobalt Dissolution from the LiCoO[sub 2] Cathodes with Various Metal-Oxide Coatings

Abstract

ZrO 2 -coated LiCoO 2 showed negligible capacity loss up to 70 cycles at the cutoff voltage of 4.4 V, while bare LiCoO 2 exhibited ϳ60% of its original capacity after only 30 cycles. The improved electrochemical behavior was caused by the suppression of cobalt dissolution by nanoscale metal-oxide coating. The amount of cobalt dissolution in the electrolyte from the charged LiCoO 2 held at 25 and 90°C, respectively, correlates well with the capacity retention, among coatings of various metal oxides. The trend of the open-circuit voltage reduction is again well correlated with both the cobalt dissolution and capacity retention.

Rapid SECM probing of dissolution of LiCoO2 battery materials in an ionic liquid

“…Interestingly, in this work, the majority of the dissolution of the battery material (LiCoO 2 ) occurred during deep discharge conditions. This is contrary to popular belief of the failure mechanisms of this cathode material in traditional battery electrolytes [1][2][3][4][5][6][7]. The redox state of cobalt should switch between Co 3+ and Co 2+ during discharge.…”

“…Difficulty in monitoring the condition of cathode materials in situ has helped to continue debate over the possible failure modes. The likely causes are: (i) dissolution of cobalt from the LiCoO 2 [1,2]; (ii) damage from strain induced by cation disorder [3][4][5]; (iii) structural instability due to a hexagonal-to-monoclinic phase change at higher voltages [6]; (iv) side reactions involving oxygen loss from the LiCoO 2 [7]. Some of these papers [1,2,6,7] utilise a metal-oxide coating such as Al 2 O 3 or ZrO 2 to reduce the degradation of the electrodes (presumably by limiting contact with the underlying cobalt oxide) and all of them relate the degradation to a high voltage process (i.e.…”

Reversible and High‐Capacity Nanostructured Electrode Materials for Li‐Ion Batteries

“…[112] On the other hand, MgO, SnO 2 , Al 2 O 3 , ZnO, ZrO 2 , and TiO 2 coatings on layered LiCoO 2 and LiNi 1Àx M x O 2 via the sol-gel method have been intensively investigated. [112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127] Among these coating materials, ZrO 2 coating exhibits the best capacity retention at >4.5 V cycling and hightemperature storage at 90 8C. [128] This finding can be supported with the ZrO 2 coating on spinel LiMn 2 O 4 , which shows the lowest capacity fading at 55 8C cycling among the various coating materials.…”

Mg doping and zirconium oxyfluoride coating co-modification to enhance the high-voltage performance of LiCoO2 for lithium ion battery

“…The existence of a small amount of water causes breakdown of the electrolyte accompanying by HF generation. Then the transition metal element dissolution can occur at the charged state especially at high cutoff potential [36]. In order to obtain further evidence for the suppressing degradation in the modified samples, the cells charged to 4.6 V were carefully disassembled in a glove box.…”