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Origin of the Overpotential for the Oxygen Evolution Reaction on a Well-defined Graphene Electrode Probed by in situ Sum Frequency Generation Vibrational Spectroscopy
摘要： To develop an efficient material for the cathode of the lithium-oxygen (Li-O2) secondary battery, the oxygen reduction and evolution reactions (ORR and OER) on a well-defined graphene monolayer have been investigated in a typical organic solvent, dimethyl sulfoxide (DMSO). The adsorption and desorption behaviors of the solvents on the graphene electrode surface were evaluated by an intrinsically surface-selective vibrational spectroscopy of sum frequency generation (SFG) during the ORR and OER. After the initial ORR depositing lithium peroxide (Li2O2) on the graphene electrode surface in a LiClO4/DMSO solution, the SFG spectroscopy revealed that the subsequent OER oxidizing the Li2O2 preferentially proceeds at the interface between the Li2O2 and graphene rather than that between the Li2O2 and bulk solution. Therefore, the OER tends to reduce the electric conductivity between the Li2O2 and graphene by decreasing their contact area before a large part of the deposited Li2O2 was oxidized, which elucidates the origin of the high overpotential for the OER.
关键词： oxygen reduction reaction,lithium-oxygen battery,oxygen evolution reaction,sum frequency generation vibrational spectroscopy,graphene electrode
更新于2025-09-23 15:21:01
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Ultrasensitive Field‐Effect Biosensors Enabled by the Unique Electronic Properties of Graphene
摘要： Using Li metal-free anodes for lithium-ion oxygen and lithium-ion sulfur batteries is considered as a promising solution to resolve the hazard of Li metal anode. Although Si anode exhibits high capacity and low electrochemical potential, it cannot match with oxygen (or sulfur) cathode, because both lack cycleable lithium ions. In this work, a free-standing and fibrous Si/C anode is prepared by electrospinning and its simple but effective lithiation is proposed. When assembling the cells, the free-standing Si/C anode was put between mass-controlled lithium metal foil and separator, and then the Si/C anode could be lithiated after adding electrolytes. By optimizing a LiFSI based ether electrolyte, the Si/C anode could achieve good cycleablity comparable to that in carbonate electrolytes. The lithiated SieO2 cells exhibit better cycling stability than the lithium oxygen cells with gel polymer electrolye. Moreover, because both Si anode and S@pPAN cathode are compatible with carbonate electrolytes, exceptional cycling performance has been achieved for the lithiated SieS cells. This simple method could pave the way to commercial applications of lithium-ion oxygen and lithium-ion sulfur batteries.
关键词： Lithium-sulfur battery,Lithium-oxygen battery,LieSi alloy anode,In-situ lithiation,Fibrous Si/C anode
更新于2025-09-19 17:13:59