Li2O2 Oxidation Research Articles

Metal-Organic Framework with Dual Excitation Pathways as Efficient Bifunctional Catalyst for Photo-assisted Li-O2 Batteries.

Li-O2 batteries (LOBs) have sparked significant interest due to their fascinating high theoretical energy density. However, the large overpotential for the formation and oxidation of Li2O2 during charge and discharge process seriously hinders the further development and application of LOBs. In this work, metal-organic frameworks (MOFs) with different metal clusters (Fe, Ti, Zr) are successfully synthesized, and they are employed as the photoelectrodes for the photo-assisted LOBs. The special dual excitation pathways of Fe-MOF under illumination and the superior separation efficiency of photocarriers, which significantly enhance the activation of O2/Li2O2, improving the catalytic activity of oxygen reduction reaction and oxygen evolution reaction. Moreover, compared to traditional inorganic semiconductor crystals, Fe-MOF exhibits large specific surface area and excellent O2 adsorption ability. Therefore, the LOB with Fe-MOF as the cathode exhibits large specific capacity, ultralow charge/discharge overpotential of 0.22V at 0.05mA cm-2 and excellent stability of 195 cycles under illumination. This study provides an environmentally friendly and highly efficient photocatalyst for LOBs, and a new strategy for designing photoelectrodes.

Revisiting Li-CO2/O2 battery chemistry through the spatial distributions of discharge products and their oxidation behaviors

Li-CO2/O2 batteries present a promising strategy for CO2 conversion and energy storage, yet the complexity of discharge products poses challenges for revealing their oxidation. Here, we simulate the influences of various properties of Li2CO3 and/or Li2O2 on the decomposition pathway by comprehensively analyzing the singlet O2 (1O2) and gas components (O2 and CO2) generated during electrochemical oxidation. Our results show that no matter Li2CO3 or Li2O2, the decomposition of samples with small size and poor crystallinity produces less 1O2 and more gas product. Especially, small and poorly crystalline Li2CO3 triggers the concurrent decomposition of Li2CO3 and C, while large and highly crystalline Li2CO3 favors the solo decomposition pathway. Furthermore, the 1O2 yield can be most inhibited at a Li2CO3/Li2O2 ratio of 50 %. After clarifying the nature of Li2CO3 and/or Li2O2 oxidation, the spatial distributions of the oxygen discharge product in Li-CO2/O2 batteries were observed by scanning transmission X-ray microscopy (STXM). Li2CO3 is mainly distributed in the interior of large aggregates with high crystallinity. Poorly crystalline Li2O2 appears as small particles or coats on the surface of Li2CO3. Combined with multi-dimensional information of the discharge products and simulation results, the oxidation behaviors of the discharge products in Li-CO2/O2 batteries are reacquainted.

A Tetramethylurea-Electrolyte-Based Lithium-Oxygen Battery with High Performance and Alternative Mechanism

The electrolyte is a critical component in electrochemical energy storage devices as it creates the reaction environment for the electrode process. In lithium–oxygen (Li–O2) batteries, the oxygen electrode reaction involves a complex multiphase transition (e.g., gas, liquid, solid) and a variety of intermediates (e.g., O2 –, O2 2–, 1O2), making the role of the electrolyte system more prominent. As an ideal electrolyte for Li–O2 batteries, it should not only resist the attack of superoxide intermediate, but also provide a kinetically favorable O2 redox reaction mechanism. However, currently, no electrolyte solvent is perfectly suitable for Li–O2 batteries, which greatly limited their practical applications. Here, we present a new electrolyte solvent, 1,1,3,3-tetramethylurea, for Li–O2 batteries that exhibits high performance and an alternative mechanism. Specifically, it enables a kinetically favorable one-electron Li2O2 oxidation pathway upon charging. Furthermore, due to the absence of alpha-hydrogen atoms in its molecular structure, it also exhibits good stability in the presence of superoxide intermediates, significantly suppressing the related hydrogen extraction side reactions. Consequently, Li–O2 batteries utilizing this electrolyte show a much lower charge overpotential and a four-fold longer cycle life compared to those with the benchmark electrolyte. Acknowledgments X.L. acknowledges financial support from the Marie Skłodowska-Curie Actions (grant agreement No. 101064286) for his postdoctoral fellowship.

Insights into the LiI Redox Mediation in Aprotic Li-O2 Batteries: Solvation Effects and Singlet Oxygen Evolution.

Lithium-oxygen aprotic batteries (aLOBs) are highly promising next-generation secondary batteries due to their high theoretical energy density. However, the practical implementation of these batteries is hindered by parasitic reactions that negatively impact their reversibility and cycle life. One of the challenges lies in the oxidation of Li2O2, which requires large overpotentials if not catalyzed. To address this issue, redox mediators (RMs) have been proposed to reduce the oxygen evolution reaction (OER) overpotentials. In this study, we focus on a lithium iodide RM and investigate its role on the degradation chemistry and the release of singlet oxygen in aLOBs, in different solvent environments. Specifically, we compare the impact of a polar solvent, dimethyl sulfoxide (DMSO), and a low polarity solvent, tetraglyme (G4). We demonstrate a strong interplay between solvation, degradation, and redox mediation in OER by LiI in aLOBs. The results show that LiI in DMSO-based electrolytes leads to extensive degradation and to 1O2 release, affecting the cell performance, while in G4-based electrolytes, the release of 1O2 appears to be suppressed, resulting in better cyclability.

A Computational Study on Halogen/Halide Redox Mediators and Their Role in 1O2 Release in Aprotic Li-O2 Batteries.

We present a computational study on the redox reactions of small clusters of Li superoxide and peroxide in the presence of halogen/halide redox mediators. The study is based on DFT calculations with a double hybrid functional and an implicit solvent model. It shows that iodine is less effective than bromine in the oxidation of Li2O2 to oxygen. On the basis of our thermodynamic data, in solvents with a low dielectric constant, iodine does not spontaneously promote either the oxidation of Li2O2 or the release of singlet oxygen, while bromine could spontaneously trigger both events. When a solvent with a large dielectric constant is used, both halogens appear to be able, at least on the basis of thermodynamics, to react spontaneously with the oxides, and the ensuing reaction sequence turned out to be strongly exoergic, thereby providing a route for the release of significant amounts of singlet oxygen. The role of spin-orbit coupling in providing a mechanism for singlet-triplet intersystem crossing has also been assessed.

Rational Design of Benzo‐Crown Ether Electrolyte Additives for High‐Performance Li‐O2 Batteries

AbstractDespite theoretical predictions of exceptional gravimetric energy densities in Li‐O2 batteries (LOBs), the current research forefront faces challenges, including high charge overpotential, cathode clogging, parasitic reactions, and Li anode corrosion. Herein, benzo‐crown ethers (BCEs) with varying cavity sizes are used as electrolyte additives to exploit their strong binding toward Li+ and promote the solution growth of Li2O2 with reduced particle size. Notably, the cell with benzo‐18‐crown‐6 ether (B18C6) enables the largest discharge capacity of 14948 mAh g−1. Upon charging, these additives accelerate Li2O2 oxidation through the strong binding with Li+ and the extended electrolyte/Li2O2 interface, resulting in improved reversibility, reduced charge overpotential, and prolonged cycle life. Besides, these additives also stabilize the Li anode by regulating Li+ migration and electron exchange, reducing dendritic growth and anode corrosion. This work presents insights into the rational design of BCEs as additives for high‐performance LOBs.

Oxygen Radical Anion Substituted Iron Phthalocyanine as an Effective Redox Mediator for Li-O2 Batteries.

Transition metal phthalocyanines are potential soluble redox mediators for Li-O2 batteries. In this work, effective strategies to control the redox potentials and activities of iron phthalocyanine (FePc) based redox mediators are designed by the introduction of electron-withdrawing or electron-donating groups. Substituted electron-donating groups can shift the oxidation potential of FePc to a higher energy level, consequently reducing the charging voltage of Li-O2 batteries. Especially, oxygen radical anion (-O-) modified FePc (FePc-O-) shows the most significant improvement to the oxygen reduction and evolution reactions of Li-O2 batteries. Electronic analysis indicates that -O- substitution can break the symmetry of electronic structures of FePc which further tunes the reduction of O2 and the oxidation of Li2O2. Detailed reaction mechanisms of (FePc-O-)-mediated Li-O2 batteries are proposed based on first-principles molecular dynamics simulations and thermodynamic free energy calculations.

New Insights on Singlet Oxygen Release from Li-Air Battery Cathode: Periodic DFT Versus CASPT2 Embedded Cluster Calculations.

Li-air batteries are a promising energy storage technology for large-scale applications, but the release of highly reactive singlet oxygen (1O2) during battery operation represents a main concern that sensibly limits their effective deployment. An in-depth understanding of the reaction mechanisms underlying the 1O2 formation is crucial to prevent its detrimental reactions with the electrolyte species. However, describing the elusive chemistry of highly correlated species such as singlet oxygen represents a challenging task for state-of-the-art theoretical tools based on density functional theory. Thus, in this study, we apply an embedded cluster approach, based on CASPT2 and effective point charges, to address the evolution of 1O2 at the Li2O2 surface during oxidation, i.e., the battery charging process. Based on recent hypothesis, we depict a feasible O22-/O2-/O2 mechanisms occurring from the (112̅0)-Li2O2 surface termination. Our highly accurate calculations allow for the identification of a stable superoxide as local minimum along the potential energy surface (PES) for 1O2 release, which is not detected by periodic DFT. We find that 1O2 release proceeds via a superoxide intermediate in a two-step one-electron process or another still accessible pathway featuring a one-step two-electron mechanism. In both cases, it represents a feasible product of Li2O2 oxidation upon battery charging. Thus, tuning the relative stability of the intermediate superoxide species can enable key strategies aiming at controlling the detrimental development of 1O2 for new and highly performing Li-air batteries.

Why charging Li-air batteries with current low-voltage mediators is slow and singlet oxygen does not explain degradation.

Although Li-air rechargeable batteries offer higher energy densities than lithium-ion batteries, the insulating Li2O2 formed during discharge hinders rapid, efficient re-charging. Redox mediators are used to facilitate Li2O2 oxidation; however, fast kinetics at a low charging voltage are necessary for practical applications and are yet to be achieved. We investigate the mechanism of Li2O2 oxidation by redox mediators. The rate-limiting step is the outer-sphere one-electron oxidation of Li2O2 to LiO2, which follows Marcus theory. The second step is dominated by LiO2 disproportionation, forming mostly triplet-state O2. The yield of singlet-state O2 depends on the redox potential of the mediator in a way that does not correlate with electrolyte degradation, in contrast to earlier views. Our mechanistic understanding explains why current low-voltage mediators (<+3.3 V) fail to deliver high rates (the maximum rate is at +3.74 V) and suggests important mediator design strategies to deliver sufficiently high rates for fast charging at potentials closer to the thermodynamic potential of Li2O2 oxidation (+2.96 V).

Efficient Li2O2 oxidation kinetics of perovskite-type lanthanum chromium-based oxide by promoter interface formation for lithium-oxygen batteries

The development of oxygen evolution reaction (OER) catalysts for the decomposition of discharge products, Li2O2, is important in terms of energy efficiency because of the significant overpotentials during the charging process. In this study, the perovskite, ABO3, has been synthesized as an important functional material that exhibits various stoichiometries and crystal structures. They can accommodate metals entirely or partially at the A and/or B sites without destroying the crystal structure owing to their structural features. Therefore, perovskites provide a way to correlate solid-state chemistry with catalytic properties. Herein, we design a series of La0.8Sr0.2CrOx as practical OER catalysts by controlling the oxidation states and ionic/electron conductivities using the crystallization modulation method. In-situ Raman spectroscopy confirms that the perovskite-type La0.8Sr0.2CrO3 nanowires actively oxidize Li2O2 and increases the OER activity. The La0.8Sr0.2CrO3 nanowires exhibit OER activity by providing an electron acceptor or donor (Cr3+–Cr6+) that is modulated as an OER–active site (Li2CrO4) capable of favorable interaction with Li–deficient solid solution (Li2-xO2) during the charging process. This study provides fundamental insights into OER mechanisms and understanding of OER catalysts properties. These are essential for designing effective electrodes with high–energy efficiency, which is one of the key challenges for rechargeable Li–O2 batteries.

Single-Atomic Zn/Co-Nx Sites Boost Solid-Soluble Synergistic Catalysis for Lithium-Oxygen Batteries.

Lithium-oxygen batteries have attracted widespread attention owing to their superior theoretical energy density. However, they are obstructed by sluggish oxygen reduction (ORR) and evolution reaction (OER) kinetics at air cathodes. Herein, different from using single solid or soluble catalysts, solid-soluble synergistic catalysis is proposed to conjointly enhance ORR/OER performances. During discharge, single-atomic zinc/cobalt embedded in nitrogen-doped carbon (Zn, Co-N/C) is judiciously engineered as a solid catalyst to regulate the growth pathway of Li2O2 and promote ORR kinetics. During charge, a typical redox mediator (RM, LiI) is added as a soluble catalyst to permit efficient oxidation of Li2O2. Of note is that the atomic Zn/Co-Nx sites can chemically adsorb oxidized iodine (I2) and accelerate OER kinetics, which plays a decisive role in eliminating the shuttle effect of I3-/I2 to the Li anode. Coupling a single-atomic catalyst with restricted oxidized iodine offers an exceptional discharge capacity, remarkably low polarization, and superior long-term cycling stability.

High‐Performance Lithium–Oxygen Batteries Using a Urea‐Based Electrolyte with Kinetically Favorable One‐Electron Li2O2 Oxidation Pathways

Glymes are the most widely used electrolyte solvents in lithium-oxygen batteries (LOBs) due to their relatively high stability. However, their associated LOBs have long been plagued by large charge overpotential, which is closely related to the sluggish two-electron Li2 O2 oxidation mechanism. Here, we report a new electrolyte solvent-1,1,3,3-tetramethylurea (TMU) for LOBs with high performance and an alternative mechanism, where a kinetically favorable one-electron Li2 O2 oxidation pathway can happen in the urea electrolyte system, thus leading to a much lower charge overpotential (≈0.51 V) compared to the tetraglyme-based LOBs (≈1.27 V). Besides, TMU also exhibits good stability since it does not contain any α-hydrogen atoms that are vulnerable to be attacked by superoxide species, thus suppressing the hydrogen abstraction side reactions. Consequently, the TMU-based LOBs can stably work for more than 135 cycles, which is four times that of the tetraglyme-based LOBs (≈28 cycles).

High‐Performance Lithium–Oxygen Batteries Using a Urea‐Based Electrolyte with Kinetically Favorable One‐Electron Li2O2 Oxidation Pathways

AbstractGlymes are the most widely used electrolyte solvents in lithium–oxygen batteries (LOBs) due to their relatively high stability. However, their associated LOBs have long been plagued by large charge overpotential, which is closely related to the sluggish two‐electron Li2O2 oxidation mechanism. Here, we report a new electrolyte solvent—1,1,3,3‐tetramethylurea (TMU) for LOBs with high performance and an alternative mechanism, where a kinetically favorable one‐electron Li2O2 oxidation pathway can happen in the urea electrolyte system, thus leading to a much lower charge overpotential (≈0.51 V) compared to the tetraglyme‐based LOBs (≈1.27 V). Besides, TMU also exhibits good stability since it does not contain any α‐hydrogen atoms that are vulnerable to be attacked by superoxide species, thus suppressing the hydrogen abstraction side reactions. Consequently, the TMU‐based LOBs can stably work for more than 135 cycles, which is four times that of the tetraglyme‐based LOBs (≈28 cycles).

Redox Mediator with the Function of Intramolecularly Disproportionating Superoxide Intermediate Enabled High‐Performance Li–O2 Batteries

AbstractThe large charge overpotential and poor cycling stability triggered by sluggish Li2O2 oxidation kinetics and severe superoxide‐related side reactions greatly restrict the development and application of lithium–oxygen batteries. Finding out high‐efficiency catalysts that can effectively facilitate a highly reversible formation/decomposition of lithium peroxide is still a crucial challenge in the field of Li–O2 batteries. Herein, a soluble catalyst of 2,2'‐Azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS) that can promote highly reversible formation and decomposition of Li2O2 during discharge and charge processes is reported for the first time. During discharge, it can capture and couple two LiO2 intermediates via its sulfonate and ammonium ions, and induce the intramolecular disproportionation reaction to produce Li2O2 through ionic microenvironment, which not only prompts the solution‐phase growth of Li2O2, but also restricts the reactivity of LiO2 intermediate, thus significantly alleviating the electrode surface passivation issue and suppressing the superoxide‐related side reactions. During charge, it can quickly transport electrons between the electrode and Li2O2 by serving as a new kind of redox mediator (RM), thus greatly facilitating the Li2O2 oxidation kinetics. As a result, the Li–O2 batteries that incorporate ABTS exhibit outstanding electrochemical performance, low charge overpotential, high discharge capacity, and high cycling stability.

A TEMPO-grafted multi-functional cathode with strong anchoring ability towards redox mediators for high energy efficiency Li-O2 batteries

Soluble redox mediators (RMs) with favorable contact interface are considered to be an effective approach for high efficient lithium-oxygen (Li-O2) batteries. However, the shuttling effect of oxidized RMs from the cathode would lead to the degradation of the RMs’ functionality and poor cycling stability. Herein, TEMPO was anchored into three-dimensional porous ZnO@C/NF conductive substrate (ZnO@C@PPy-TEMPO/NF) and directly utilized as a self-supporting cathode for Li-O2 battery. This novel cathode serves multiple functions as redox mediator, abundant reaction center for lithium ion, as well as electron conduction matrix. The battery perform with a high discharge specific capacity of 6.9 mAh cm−2 and a low overpotential of 0.6 V similar with 4-OH-TEMPO in the electrolyte. The detailed catalysis mechanism of the immobilized TEMPO in improving the electrochemical performance has also been studied. During discharging, the cation-π effect between the conductive polypyrrole and lithium ions helps to realize the "isomorphic growth" of Li2O2. During charging, the TEMPO-immobilized electrochemical oxidation to TEMPO+ provides more direct contact with the discharge products, resulting in rapid chemical oxidation of Li2O2. The ingenious design and in-depth mechanism study provide a new avenue to address the shuttle effect of RMs and design an advanced cathode for Li-O2 batteries.

Satisfying both sides: Novel low-cost soluble redox mediator ethoxyquin for high capacity and low overpotential Li-O2 batteries

Due to cathode passivation caused by the insulating discharged products and by-products, Li-O2 batteries sustain some obstacles encompassing poor discharge capacity and high overpotential. Herein, we introduce 6-Ethoxy-2,2,4-trimethylquinoline (EQ) as a bifunctional redox mediator into electrolyte and investigate its influence on the electrochemical performance of Li-O2 batteries. Strikingly, the discharge process is promoted in the solution phase by the solvated Li+ with EQ, and the correlative capacity exhibits more than a 30-fold increase than pristine Li–O2 battery at the current density of 3000 mA g−1carbon. DFT calculations further clarify the working mechanism of oxygen reduction reaction (ORR) induced by EQ. Furthermore, the surface electrostatic potential diagram shows that N and O atoms in EQ are electron-rich, which is prone to donate electrons to get its desirable oxidation state and effectively catalyze the oxidation of Li2O2, resulting in the extremely low charge plateau at 3.08 V and longtime stable cyclability (150 cycles at a current density of 500 mA g−1carbon with a fixed capacity of 1000 mAh g−1carbon).

Mechanism for Preserving Volatile Nitrogen Dioxide and Sustainable Redox Mediation in the Nonaqueous Lithium–Oxygen Battery

Excessive overpotential during charging is a major hurdle in lithium-oxygen (Li-O2) battery technology. NO2-/NO2 redox mediation is an efficient way to substantially reduce the overpotential and to enhance oxygen efficiency and cycle life by suppressing parasitic reactions. Considering that nitrogen dioxide (NO2) is a gas, it is quite surprising that NO2-/NO2 redox reactions can be sustained for a long cycle life in Li-O2 batteries with such an open structure. A detailed study with in situ differential electrochemical mass spectrometry (DEMS) elucidated that NO2 could follow three reaction pathways during charging: (1) oxidation of Li2O2 to evolve oxygen, (2) vaporization, and (3) conversion into NO3-. Among the pathways, Li2O2 oxidation occurs exclusively in the presence of Li2O2, which suggests that NO2 has high reactivity to Li2O2. At the end of the charging process, most of the volatile oxidized couple (NO2) is stored by conversion to a stable third species (NO3-), which is then reused for producing the reduced couple (NO2-) in the next cycle. The dominant reaction of Li2O2 oxidation involves the temporary storage of NO2 as a stable third species during charging, which is an innovative way for preserving the volatile redox couple, resulting in a sustainable redox mediation for a high-performance Li-O2 battery.

Semiconducting Metal-Organic Polymer Nanosheets for a Photoinvolved Li-O2 Battery under Visible Light.

Li-O2 batteries are considered the ultimate energy storage technology for their potential to store large amounts of electrical energy in a cost-effective and simple platform. Large overpotentials for the formation and oxidation of Li2O2 during discharging and charging have thus far confined this technology to a scientific curiosity. Herein, we consider the role of catalytic intervention in the reversibility of the cathode reactions and find that semiconducting metal-organic polymer nanosheets composed of cobalt-tetramino-benzoquinone (Co-TABQ) function as a bifunctional catalyst that facilitates the kinetics of the cathode reactions under visible light. Upon discharging, we report that O2 is first adsorbed on the Co atoms of Co-TABQ and accepts electrons under illumination from the dz2 and dxz orbitals of Co atoms in the π2p* orbitals, which facilitates reduction to LiO2. The LiO2 is further shown to undergo a second reduction to the discharge product of Li2O2. In the reverse charge, the holes generated in the dz2 orbitals of Co are mobilized under the action of the applied voltage to enable the fast decomposition of Li2O2 to O2 and Li+. Under illumination, the Li-O2 battery exhibits respective discharge and charge voltages of 3.12 and 3.32 V for a round-trip efficiency of 94.0%. Our findings imply that the orbital interaction of metal ions with ligands in Co-TABQ nanosheets dictates the light harvesting and oxygen electrocatalysis for the Li-O2 battery.

(Invited) Challenges in Reversible Electrodeposition and Stripping of Lithium Peroxide for Li-Air Batteries

Thanks to a high theoretical energy density combined to a relatively high operation voltage around 3 Volts versus Li+/Li, the non-aqueous Li-Air battery is a good candidate for future electric cars with an increased driving range. In principle, this battery relies on the reversible electrochemical reaction between the metallic Li and the gaseous O2 in presence of a non-aqueous electrolyte where Li+ ions and dissolved O2 molecules diffuse and react to form the ideal discharge product lithium peroxide Li2O2. However, this apparently simple reaction process appears to be more complicated when put into practice.Considering the Li-O2 discharge process, there are two main models proposed in the literature to explain the Oxygen Reduction Reaction which were unified in a single mechanism process where Li2O2 formation goes through a surface reaction or/and a solution reaction1, depending on system parameters such as the applied potential or the solvent properties. Using an electrochemical quartz crystal microbalance (EQCM) we studied the products formed in discharge as well as the reversibility of the reactions from a mass point of view during cycling.2 Regarding the Li-O2 charge process, the Li2O2 decomposition occurring is a rather sluggish and incomplete process. A lot of efforts was made in this area by the research community, and several approaches were proposed to facilitate and fasten the Li2O2 decomposition: the use of solid state catalyst of several kind (doped carbon, non-precious materials...) or soluble catalysts also called redox mediators, such as for example TTF3 (tetrathiafulvalene), TEMPO4 (2,2,6,6-tetramethylpiperidinyloxyl), Cobalt Bis(terpyridine)5, lithium iodide6 (LiI). The mobile redox mediators, electron-hole transfer agents, aid the oxidation of Li2O2 as has been reported previously. In our EQCM study we activated in situ the TTF and confirms its usefulness on the mass reversibility of the deposition/dissolution of Li2O2 during cycling2. Later on, we performed a detailed study of the effect of LiI redox mediator on the formation and decomposition of Li2O2.7 We showed that the solvent could drastically change the mechanism of decomposition during charge8. Finally, we will discuss the parameters able to influence the most the deposition and stripping of Li2O2 in a non-aqueous medium. Reference s : 1 L. Johnson, C. Li, Z. Liu, Y. Chen, S. A. Freunberger, J. M. Tarascon, P. C. Ashok, B. B. Praveen, K. Dholakia, P. G. Bruce, Nature Chemistry, 6, 1091 – 1099 (2014). 2 S. Schaltin, G. Vanhoutte, M. Wu, F. Bardé, J. Fransaer, Phys. Chem. Chem. Phys. , 17, 12575 – 12586 (2015). 3 Y. Chen, S. A. Freunberger, Z. Peng, O. Fontaine, and P. G. Bruce, Nature Chemistry, 5, 489 – 494 (2013). 4 Y. Hase, J. Seki, T. Shiga, F. Mizuno, H. Nishikoori, H. Iba, K. Takechi, Chem. Commun., 52, 12151 – 12154 (2016). 5 Koffi P.C. Yao, J. T. Frith, S. Youssef Sayed, F. Bardé, J. R. Owen, Y. Shao-Horn, N. Garcia-Araez, J. Phys. Chem. C, 120 (30), 16290 – 16297 (2016). 6 Y. Qiao, S. Wu, Y. Sun, S. Guo, J. Yi, P. He, H. Zhou, ACS Energy Letters, 2, 8, 1869 – 1878 (2017). 7 M. Tulodziecki, G.M. Leverick, C.V; Amanchukwu, Y. Katayama, D.G. Kwabi, F. Bardé, P. Hammond, Y. Shao-Horn, Energy Environ. Sci., 10, 1828, (2017). 8 G. Leverick, M. Tułodziecki, R. Tatara, F. Bardé, Y. Shao-Horn, Joule, Vol. 3, Issue 4, 1106-1126, (2019).

LiOH: A “double-edged” effect toward electrochemical oxidation of Li2O2

During the electro-oxidation of LiOH-doped Li 2 O 2 , the higher conductivity of LiOH brings the reduced overpotential during the first charging step while the yield OH • prompts the CO 2 rather than O 2 release in the second step.