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(a) Schematic illustration of rechargeable aprotic Li-O2 battery system. (b) Proposed mechanisms for Li2O2 growth in Li-O2 batteries. (c) In situ SERS during O2 reduction and re-oxidation on Au positive electrode. (d) Proposed solvent-controlled Li2O2 decomposition mechanism. (b) Reproduced with permission from Ref. [25], copyright 2016, Nature Publishing Group. (c) Reproduced with permission from Ref. [26], copyright 2011, Wiley-VCH. (d) Reproduced with permission from Ref. [34], copyright 2018, Elsevier.
Source publication
Rechargeable aprotic lithium-oxygen (Li-O2) batteries have attracted significant interest in recent years owing to their ultrahigh theoretical capacity, low cost, and environmental friendliness. However, the further development of Li-O2 batteries is hindered by some ineluctable issues, such as severe parasitic reactions, low energy efficiency, poor...
Contexts in source publication
Context 1
... illustrated in Figure 1a, a rechargeable aprotic Li-O2 battery usually consists of a lithium metal negative electrode, aprotic electrolyte, a separator and a porous catalyzed positive electrode, where the following reversible electrochemical reactions occur [10]: ...
Context 2
... are two different growth modes of the discharge product Li2O2 [21]. As schematically shown in Figure 1b, in the first step, the solvated O2 molecule is reduced by one electron, forming a solvated O2 − intermediate. While divergence occurs in the second step, if the adsorption toward the intermediate is strong enough, the solvated O2 − intermediate can be adsorbed on the electrode surface, attracting a Li + to neutralize the negative charge, and being further reduced or undergoing a disproportionation on the electrode surface to form Li2O2 in the surface pathway. ...
Context 3
... with the help of in-situ surface-enhanced Raman spectroscopy (SERS), Bruce's group [26] directly detected the existence of LiO2 during the discharging progress. As shown in Figure 1c, in the very beginning period of discharging, peak with short lifetime arose at 1137 cm −1 which was associated with the O-O bond vibration in LiO2. Such a result directly proved the formation of unstable LiO2 discharge intermediate which underwent a quick disproportionation to form the final discharge product Li2O2. ...
Context 4
... on, Lu et al. [34] proposed that the oxidation mechanism of Li2O2 is closely related to the DN of electrolyte solvent. Through rotating ring-disk electrode (RRDE) and X-ray absorption near-edge structure, they confirmed the different OER mechanisms of Li-O2 batteries using different solvent varied in DN as described in Figure 1d. In a high DN solvent, the oxidation of Li2O2 followed a solution way with the formation of soluble LiO2 intermediate (e.g., dimethyl sulfoxide, 1-methylimidazole), while for the low DN solvent (e.g., acetonitrile (ACN), tetraethylene glycol dimethyl ether (TEGDME)), the oxidation of Li2O2 proceeded by way of solid delithiation, pretty similar to the behavior of the positive electrode in LIBs under charging. ...
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The effect of carbon nanotube (CNT) surface modification by oxygen– and nitrogen–containing groups on the activity of Pt–containing catalysts supported on these CNT (Pt/CNT and PtCo/CNT) studied in the oxygen reaction in aprotic electrolyte containing lithiumсations. It is shown, that modification of the CNT surface by oxygen– and nitrogen–containing groups enhances the polarization capacity of the material that characterizes the value of the electrochemically active surface area and lowers the overpotential of the oxygen reduction reaction (ORR). Synthesis of platinum or its alloy (PtCo) on modified CNT allowed establishing the relationship between the activity of these catalysts in the oxygen reaction in aprotic electrolyte and the synthesis conditions and CNT pretreatment. The catalytic effect of modification by platinum consists in a decrease in the ORR overpotential with formation of Li2O2 and its further anodic decomposition and in an increase in the reversibility degree. It is shown that the sites on which Pt nanoparticles are fixed on the CNT surface are oxygen–containing groups. The most probable result of synthesis of PtCo alloy on CNT is the binding of cobalt to nitrogen in nitrogen–containing groups and then to platinum (N–Co–Pt).
Rechargeable Li-O2 batteries (LOBs) have been receiving intensive attention because of their ultra-high theoretical energy density close to the gasoline. Herein, Ag modified urchin-like α-MnO2 (Ag-MnO2) material with hierarchical porous structure is obtained by a facile one-step hydrothermal method. Ag-MnO2 possesses thick nanowires and presents hierarchical porous structure of mesopores and macropores. The unique structure can expose more active sites, and provide continuous pathways for O2 and discharge products as well. The doping of Ag leads to the change of electronic distribution in a-MnO2 (i.e., more oxygen vacancies), which play important roles in improving their intrinsic catalytic activity and conductivity. As a result, LOBs with Ag-MnO2 catalysts exhibit lower overpotential, higher discharge specific capacity and much better cycle stability compared to pure α-MnO2. LOBs with Ag-MnO2 catalysts exhibit a superior discharge specific capacity of 13,131 mAhg−1 at a current density of 200 mAg−1, a good cycle stability of 500 cycles at the capacity of 500 mAhg−1. When current density is increased to 400 mAg−1, LOBs still retain a long lifespan of 170 cycles at a limited capacity of 1,000 mAhg−1.
