Water-Induced Surface Reconstruction of Co₃O₄ on the (111) Plane for High-Efficiency Li–O₂ Batteries in a Hybrid Electrolyte

Abstract

The crystal plane effect of cobalt oxide has attracted much attention in Li–O2 batteries (LOBs) and other electrocatalytic fields. However, boosting the catalytic activity of a specific plane still faces significant challenges. Herein, a strategy of adding water into the electrolyte is developed to construct a LiOH-based Li–O2 battery system using the (111) plane-exposed Co3O4 as a cathode catalyst. The electrochemical performance shows that on the (111) plane, in the presence of water, the overpotential is largely reduced from 1.5 to 1.0 V and the cycling performance is enhanced. It is confirmed that during the discharge process, water reacts to form LiOH and induce the phase transformation of Co3O4 to amorphous CoO x (OH) y . At the recharge stage, LiOH is first decomposed and then CoO x (OH) y is reduced to Co3O4. Compared with pristine (111), the newly formed Co3O4 surface exhibits more active sites, which accelerates the following oxygen reduction and oxygen evolution processes. This work not only reveals the reaction mechanism of water-induced reaction on the (111) plane of Co3O4 but also provides a new perspective for further design of hybrid Li–O2 batteries with a low polarization and a longer cycle life.

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“…Moreover, the observed peak intensities are increased significantly with the increasing CoPc content, implying the improved crystallinity of the Co 3 O 4 @NHCS materials . In the case of Co 3 O 4 @NHCS-2, a peak shift (111) toward a higher angle with enhanced intensity was observed, indicating that the average loading of the Co precursor improved the crystallinity due to effective anchoring of Co 3 O 4 on the carbon surface under the carbonization process. , In addition, two peaks located at ∼26.0 and ∼42.8° can be indexed to the (002) and (100) planes of graphitic carbon, respectively. , …”

“…44 In the case of Co 3 O 4 @NHCS-2, a peak shift (111) toward a higher angle with enhanced intensity was observed, indicating that the average loading of the Co precursor improved the crystallinity due to effective anchoring of Co 3 O 4 on the carbon surface under the carbonization process. 45,46 In addition, two peaks located at ∼26.0 and ∼42.8°can be indexed to the (002) and (100) planes of graphitic carbon, respectively. 47,48 The surface area and pore structure of Co 3 O 4 @NHCS samples were investigated with a nitrogen adsorption− desorption isotherm, and both type II and IV isotherms were observed, indicating the abundant mesoporous and microporous nature of samples (Figure S1A).…”

RuO2-Incorporated Co3O4 Nanoneedles Grown on Carbon Cloth as Binder-Free Integrated Cathodes for Tuning Favorable Li2O2 Formation

“…Figure e shows the high-resolution spectrum of Co 2p. The two major peaks at 779.9 and 794.9 eV along with the two satellite peaks can be ascribed to the Co 2p 3/2 and Co 2p 1/2 states, ,, respectively. After fitting with Gaussian-Lorentzian functions, each peak can be resolved to two separate parts of Co 3+ and Co 2+ .…”

“…The result image (Figure 1c) from an SEM displayed the microstructure of the synthetic cathode. Compared with the initial smooth CC fiber (Figure 1b), Co 3 O 4 nanoneedles stood like countless "grasses", growing on the CC skeleton densely 23,49 and (101) plane of RuO 2 , 33 respectively. The selected area electron diffraction (SAED) pattern (Figure 2c) indicated several typical planes of ( 111), ( 022), ( 222), ( 024), (115), and (135) of Co 3 O 4 .…”

“…The formation of mesoporous structure further increases the specific surface. The high-resolution TEM image (Figure b) showed clear interplanar spacings of 0.23, 0.29, 0.46, and 0.255 nm, corresponding to the (222), (220), and (111) planes of the Co 3 O 4 crystal , and (101) plane of RuO 2 , respectively. The selected area electron diffraction (SAED) pattern (Figure c) indicated several typical planes of (111), (022), (222), (024), (115), and (135) of Co 3 O 4 . ,, Elemental mapping (Figure S1) illustrated that Co, O, and Ru elements were homogeneously distributed in RuO 2 -Co 3 O 4 @CC.…”