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Liu et al. Energy Mater 2023;3:300011 https://dx.doi.org/10.20517/energymater.2022.68 Page 7 of 10

Figure 5. SEM images of the Ru/TiO /CNTs at different discharge stages: (A) fresh; (B) after first discharge; (C) after first recharge;
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(D) after 30 cycles; (E) after 60 cycles; (F) after 100 cycles; (G) High-resolution XPS spectra of Li 1s of Ru/TiO /CNTs after first
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discharged, recharge and 30 cycles; (H) XRD patterns of the Ru/TiO /CNTs cathode at different discharge/charge stages;
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(I) Schematic illustration of the feature structure of the Ru/TiO /CNTs after Li O formation.
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decomposition and carbon oxidation caused by the unique system, can be well solved. The XPS result
showed a strong obvious Li 1s peak at 54.68 eV ascribing Li O after the first discharge and the peak
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disappeared after recharge [Figure 5G], demonstrating that the as-prepared Ru/TiO /CNTs material could
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function as a bifunctional catalyst for Li-O battery. One should note that there was no Li O signal except a
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poor peak at 55.52 eV assigning to Li CO appeared on the XPS spectra after 30 cycles. XRD measurements
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on the cathode at different cycling states were also conducted [Figure 5H]. It showed that the primary
discharge product was Li O and the reaction was based on the formation and decomposition of Li O . The
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XRD pattern of the cathode after 30th charge showed overlapped diffraction peaks (36.9°) of Li CO and
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TiO . Li CO is rooted in the decomposition of the ether-based electrolyte and it would accumulate on the
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electrode surface. XRD pattern of the electrode after 60 cycles of charging showed the co-existence of LiOH
and Li CO . The former might come from the reaction of Li O and a trace amount of H O, while the latter
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came from the gradual accumulation of Li CO 3 [35-37] . A concise schematic diagram [Figure 5I] illustrated the
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