Effect of Transition Metal Oxide Cathodes on the Oxygen Evolution Reaction in Li–O₂ Batteries

Abstract

Li–oxygen batteries could provide energy density that is up to five times greater than that of state-of-the-art Li-ion batteries. However, Li–oxygen cell rechargeability is limited by cathode passivation due to nonconductive discharge products. Despite efforts to efficiently oxidize these products, oxygen recovery remains poor at potentials where cell constituents are stable. Transition metal oxide (TMO) cathodes have shown low charging potentials, but a correspondence to improved oxygen evolution efficiency is debated. This is because the deposition of electrically insulating Li2O2 during the battery discharge could passivate the TMO surfaces and render them inactive for catalyzing oxygen evolution during charge. Contrary to this, we show that TMOs enable charging at low overpotentials without compromising the oxygen evolution efficiency. Charge potentials are lowered by 130–400 mV in batteries employing TMO-based cathodes compared to carbon-only cathodes. By a combination of current-sensing atomic force microscopy and differential electrochemical mass spectrometry, we show that Li2O2 has a greater propensity for deposition on carbon surfaces and only sparingly covers the RuO2 surfaces. Our results suggest that chemically heterogeneous cathodes containing (1) surfaces that favor Li2O2 growth and (2) surfaces that are catalytically active but do not promote Li2O2 deposition can decrease charge overpotentials without decreasing oxygen evolution efficiency.

Green Synthesis of a Reduced‐Graphene‐Oxide Wrapped Nickel Oxide Nano‐Composite as an Anode For High‐Performance Lithium‐Ion Batteries

“…A long voltage plateau appeared at 0.6 V vs. Li/Li + in case of NiO and GO‐NiO electrodes while the RGO‐NiO electrode exhibited a long voltage plateau at 1.1 V vs. Li/Li + . This is because of the reduction reaction of NiO to Ni and the formation of SEI [25–31] . In the charge cycle for all the electrodes, two voltage plateaus were observed, corresponding to the partial dissolution of SEI layer and the oxidation of Ni [15–30] .…”

“…[16][17][18][19][20][21][22][23][24][25] The sharp peaks in the XRD patterns corresponded to NiO phases that are matched with JCPDF number 071-1179 for cubic NiO. [25] No other peaks were present in the XRD patterns, indicating the formation of the composites with phase pure NiO.…”

“…Significant volume of researches have been carried out since last decade on graphene and its derivatives with TMOs as composite anode materials in LIBs [1,13–37] . However, most of these studies involve the synthesis of graphene to fabricate composites either by chemical method (oxidation of graphite followed by reduction) or chemical vapour deposition (CVD) route [13–37] . Sophisticated experimental setup, use of inflammable gases, substrate selectivity and high cost are the major challenges for bulk scale production of graphene in CVD process, limiting it to academic interest only.…”

Rational design of porous Ru‐doped CuO nanoarray on carbon cloth: Toward reversible catalyst layer for efficient Li‐O 2 batteries

“…Therefore, cost-effective transition metal oxides (TMO) have been studied as alternative catalyst materials. [7][8][9][10] To improve the catalyst performance to be applicable to Li-O 2 batteries, it is important to control their shape Heewon Yoo and Gwang-Hee Lee contributed equally to this work. and surface composition of the TMO catalysts.…”

“…are recognized as high active oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts but, they are also not suitable for commercialization due to their rarity and high price. Therefore, cost‐effective transition metal oxides (TMO) have been studied as alternative catalyst materials 7‐10 …”