Chemical and Morphological Changes of Li–O₂ Battery Electrodes upon Cycling

Abstract

We report considerable chemical and morphological changes of reaction products in binder-free, vertically-aligned carbon nanotube (VACNT) electrodes during Li-O 2 battery cycling with a 1,2-dimethoxyethane (DME)-based electrolyte. X-ray absorption near edge structure (XANES) of discharged oxygen electrodes shows direct evidence for the formation of Li 2 CO 3 -like species at the interface between VACNTs and Li 2 O 2 , but not significantly on the Li 2 O 2 surfaces exposed to the electrolyte. Although Li 2 O 2 and Li 2 CO 3 -like species were largely removed upon first charge, the oxidation kinetics became increasingly difficult during Li-O 2 cycling, which is accompanied by the accumulation of Li 2 CO 3 in the discharged and charged electrodes as evidenced by selected area electron diffraction (SAED) and transmission electron microscopy (TEM). Together, these results indicate that the irreversibility during Li-O 2 cycling in DME can be attributed largely to the growth of Li 2 CO 3 -like species associated with the reactivity between carbon and Li 2 O 2 or other reaction intermediates.

Long life rechargeable Li-O2 batteries enabled by enhanced charge transfer in nanocable-like Fe@N-doped carbon nanotube catalyst

“…Some other weak bumps are also observed in XRD spectrum of the recharged cathode possibly due to the formation of a small amount of side reaction products such as Li2CO3, HCO2Li and other Li-based organic compounds during cycling, as suggested by FTIR analysis (Fig. S4) [8,9,44]. FESEM examination reveals the formation of toroidal-aggregates of Li2O2 on the surface of CNTs or carbon black electrode after discharge (Fig.…”

“…Heteroatom doping or hybridization with metal species represents an efficient way to enhance the activity of carbon-based catalysts towards oxygen reduction reaction (ORR)/OER reactions [39][40][41][42]. The presence of heteroatoms (e.g., N) and metal species not only reduces the local work function on carbon surface for better O2 adsorption, but also changes the charge density on the carbon surface via electron transfer effect [16,[43][44][45][46][47][48][49][50][51]. Nevertheless, the understanding on the origin of their activity and the chemical nature of the reaction pathways is still quite limited, which hinders the development of high-performance cathode catalysts.…”

Rate-Dependent Morphology of Li2O2 Growth in Li–O2 Batteries

“…1). This has since been confirmed on different carbon substrates at low surface specific rates [7,9,11,22,23]. Although the disc-like particles reach 100 nm sizes, toroid-like particles can grow much larger, and the electron transport path and growth mechanisms are just beginning to be understood [10].…”

“…An evolution from singlecrystalline disc to complex toroid-like morphologies during discharge was first observed in nano-structured electrodes with large surface areas [9,11] (Fig. 1).…”

Enhanced electrocatalytic performance of Co3O4/Ketjen-black cathodes for Li–O2 batteries

“…Different from the intercalation mechanism in LIBs, Li-O 2 batteries are based on an electrocatalytic mechanism for both ORR and OER processes, where "electro" emphasizes the essentially smooth transportation for electrons, and "catalytic" indicates the necessity of catalysts with intrinsically high activity. A well-known discharge reaction in a stable Li-O 2 battery is the formation of lithium peroxide on the surface of cathode where oxygen reacts with lithium ions and electrons, 2Li + +O 2 +2e -→Li 2 O 2 [11][12][13][14].…”