Evolution of Li₂O₂ Growth and Its Effect on Kinetics of Li–O₂ Batteries

Abstract

Lithium peroxide (Li2O2), the solid and intrinsically electronic insulating discharge product of Li-O2 batteries strongly influences the discharge and charge kinetics. In a series of experiments, we investigated the growth of Li2O2 upon discharge and the corresponding reduction and oxidation processes by varying the depth of discharge. The results indicate that insulating Li2O2 particles with a disc-like shape were formed during the initial discharge stage. Afterward, the nucleation and growth of Li2O2 resulted in the formation of conducting Li2O2 shells. When the discharge voltage dropped below 2.65 V, the Li2O2 discs evolved to toroid-shaped particles and defective superoxide-like phase presumably with high conductivity was formed on the rims of Li2O2 toroids. Both Li2O2 and the superoxide-like phase are unstable in ether-based electrolytes resulting in the degradation of the corresponding cells. Nevertheless, by controlling the growth of Li2O2, the chemical reactivity of the discharge product can be suppressed to improve the reversibility of Li-O2 batteries.

Realizing the Embedded Growth of Large Li2O2 Aggregations by Matching Different Metal Oxides for High‐Capacity and High‐Rate Lithium Oxygen Batteries

“…For the influence of electrode morphology, previous studies have reported that carbon nanotubes and granular KB carbon can both produce toroidal Li 2 O 2 . The morphology of electrode material is not the critical factor to determine its discharge characteristic 9, 47. Our recent study also reported that flower‐like Li 2 O 2 assembled by Li 2 O 2 sheets was both produced on Ni/Co 3 O 4 nanowires and Ni/Co 3 O 4 rectangular nanosheet electrodes 48.…”

Non-aqueous Metal–Oxygen Batteries: Past, Present, and Future

“…It has been reported that low current densities and high water concentrations (hundreds to thousands of ppm) both promote the growth of biconcave disks [23,37,[45][46][47]. Similar biconcave disks have also been observed in the precipitation of silicates [48] and corn starch [49], suggesting that there may be a common growth mechanism.…”

“…Similar biconcave disks have also been observed in the precipitation of silicates [48] and corn starch [49], suggesting that there may be a common growth mechanism. It has also been reported that the characteristic size of these particles decreases with increasing current densities, and that at sufficiently high rates the deposit forms a conformal film rather than discrete particles [23,37,45,47]. However, it has been suggested that the putative conformal films produced at high currents are in fact carpets of nano-scale needles [39].…”

Palladium-Filled Carbon Nanotubes Cathode for Improved Electrolyte Stability and Cyclability Performance of Li-O2Batteries

“…A parallel X-ray beam in size of 100 μm diameter was directed on to the samples and diffraction intensities were recorded on large 2D image plate during exposure time. Li 2 O 2 was quantified in the cathodes after discharge using a colorimetric method previously reported by Schwenke et al 39 Briefly, discharged cathodes were first immersed in water then aliquots were taken and added to 2% aqueous solution of TiOSO 4 . Instantaneously a color change occurred and the absorbance spectra of the solutions were collected using a UV-Vis spectrophotometer (Gamry UV/Vis Spectro-115E).…”